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Wet-operated stirred media mills are commonly used in the field of fine and ultra-fine grinding. Depending on the application, there are different mill geometries, sizes and mill equipment materials of which the grinding chamber lining and the stirrer are made. Increasing energy prices demand an energy-efficient mill operation for a desired product, which can be achieved with mechanistic stress models. Here, besides the mill geometry and volume, the process parameters and various energy-transfer-coefficients are of importance. In this work, the impact of different mill equipment materials affecting the mill-related-energy-transfer-coefficients on performance prediction and scale-up using the advanced stress model are investigated. It was found that the mill-related-energy-transfer-coefficients as well as the improved grinding-media-energy-transfer-coefficients have a significant effect on the prediction precision of the comminution times and specific energies for chosen target particle sizes.
Embedded permanent magnets are widely used for electrical machines with interior-rotor. This provides better protection of the magnets and enables the use of an additional reluctance torque for torque density improvements. For external rotors, the use of surface-mounted permanent magnets is common. The following paper analyses the application of inserted magnets at exterior-rotors with segmentation to achieve an increase in torque density.High pole electrical machines are often designed with a fractional-slot concentrated winding which leads to field harmonics. Therefore, an analytical method for qualitative comparison of different winding configurations for using reluctance torque with consideration of stator field harmonics is applied. Besides rotor saliency, the magnetic flux concentration is a positive effect of interior permanent magnets. Here, the flux leakage along mechanical necessary iron bridges is crucial. With the segmented rotor geometry, these iron bridges can be avoided for interior placed magnets. This allows a flux concentration for electrical machines with a high number of pole-pairs. The paper presents a simplified geometry-based approach to describe these improvements. The method is validated with a finite element analysis (FEA) and a prototype with a segmented rotor is built.
Because of the absence of rare earth magnets, the reluctance synchronous machine has a more favourable sustainability balance compared to the permanent magnet synchronous machine with NdFeB magnets. Additional advantages include the absence of copper in the rotor and the ease of manufacture of the non modified rotor. A clear disadvantage of the reluctance synchronous machine is the relatively high torque ripple if no measures such as skewing are taken. Therefore, the machine is mainly used in applications such as fans where the torque ripple is not critical for the operation. The paper makes a contribution to addressing the problem of torque pulsation. For the reduction of torque harmonics, the usage of various rotor designs as well as asymmetric rotor geometry are presented. In addition, the aspect of torque harmonics, which is predicted by the finite element analysis is discussed and possibilities of torque ripple reduction for further investigations are shown. The description of a reluctance network of the machine is addressed with a semi-analytical approach for this purpose. Finally, the results of the preliminary calculation are validated by finite element analysis (FEA) and the quantities are verified with measurements on a device under test. The deviations between the methods are shown and discussed.
This paper presents a current control approach for permanent magnet synchronous machines (PMSMs) using the deep reinforcement learning algorithm deep deterministic policy gradient (DDPG). The proposed method is designed by examining different training setups regarding the reward function, the observation vector, and the actor neural network. In doing so, the impact of the different design factors on the steady-state and dynamic behavior of the system is assessed, thus facilitating the selection of the setup that results in the most favorable performance. Moreover, to provide the necessary insight into the controller design, the entire path from training the agent in simulation, through testing the control in a controller-in-the-loop (CIL) environment, to deployment on the test bench is described. Subsequently, experimental results are provided, which show the efficacy of the presented algorithm over a wide range of operating points. Finally, in an attempt to promote open science and expedite the use of deep reinforcement learning in power electronic systems, the trained agents, including the CIL model, are rendered openly available and accessible such that reproducibility of the presented approach is possible.
In this paper, the influence of temperatures up to
250 °C on core losses and magnetization demand of electrical
steel sheets is illustrated. Therefore, measurements are made
using an adopted high-temperature Epstein frame and a stator
core as a ring probe. Three different electrical steel sheet grades,
M330-50A, M530-50A and NO20-15, and a stator core are
tested. Magnetic property measurements are performed at
various frequencies from DC to 1.2 kHz with a defined
sinusoidal waveform of magnetic polarization. This covers a
wide range of electric motor applications from industrial drives
to electric vehicle drives. With increasing temperature,
magnetization demand rises significantly in medium
polarization range. For specific core losses, a loss separation is
performed using the Jordan approach, separating specific
hysteresis and specific eddy current losses to determine the
temperature influence on each loss component. The
temperature behavior of the specific electrical resistivity of
electrical steel sheets is measured and used to calculate the
physical specific eddy current losses. After separation, specific
hysteresis losses also show a significant temperature influence.
Control of multi-phase machines is a challenging topic due to the high number of controlled variables. Conventional control methods, such as field-oriented control (FOC), address this issue by introducing more control loops. This, however, increases the controller design complexity, while the tuning process can become cumbersome. To tackle the above, this paper proposes a deep deterministic policy gradient algorithm based controller that fulfills all the control objectives in one computational stage. More specifically, the proposed approach aims to learn a suitable current control policy for six-phase permanent magnet synchronous machines to simplify the commissioning of the drive system. In doing so, physical limitations of the drive system can be accounted for, while the compensation of imbalances between the two three-phase subsystems is rendered possible. After validating the training results in a controller-in-the-loop environment, test bench measurements are provided to demonstrate the effectiveness of the proposed controller. As shown, favorable steady-state and dynamic performance is achieved that is comparable to that of FOC. Therefore, as indicated by the presented results, reinforcement learning-based control approaches for multi-phase machines is a promising research area.
A novel modeling strategy is proposed which allows high-accuracy predictions of aerodynamic and aeroacoustic target values for a low-pressure axial fan, equipped with serrated leading edges. Inspired by machine learning processes, the sampling of the experimental space is realized by use of a Latin hypercube design plus a factorial design, providing highly diverse information on the analyzed system. The effects of four influencing parameters (IP) are tested, characterizing the inflow conditions as well as the serration geometry. A total of 65 target values in the time and frequency domains are defined and can be approximated with high accuracy by individual artificial neural networks. Furthermore, the validation of the model against fully independent test points within the experimental space yields a remarkable fit, even for the spectral distribution in 1/3-octave bands, proving the ability of the model to generalize. A metaheuristic multi-objective optimization approach provides two-dimensional Pareto optimal solutions for selected pairs of target values. This is particularly important for reconciling opposing trends, such as the noise reduction capability and aerodynamic performance. The chosen optimization strategy also allows for a customized design of serrated leading edges, tailored to the specific operating conditions of the axial fan.
With a special focus on the industrial feasibility and the manufacturability, a recently proposed novel approach to centrifugal impeller blade inclination is adopted and investigated through extensive CFD analysis. The fan blades, originally aligned perpendicular to the impeller backplate, are inclined in either forward or backward direction. For the presented study, an industrially proven fan design is chosen for testing. Compared to the original design, the inclined fan blades possess an increased total blade area and at the same time providing variable inflow angles at the leading edges of the blades. These two factors are expected to alter the fan characteristic curves in providing an increased range of optimum performance while maintaining high aerodynamic efficiency. The results obtained show a clear trend in aerodynamic performance with the degree of inclination, where the characteristic curves rotate at about the design point, allowing local improvements either at overload conditions or part-load conditions of the fan. Moreover, the trends obtained show the tendency to agree well with the rudimentary models published in previous studies, even though it appears to be affected by the fan volute and the point of operation as well.
Passive air-jet blowing is an effective yet simple technique to control flow-induced noise due to vortex shedding of bluff bodies. The current study investigates the effect of the specific slot angles of passive jets in connection with the suppression capabilities of vortex shedding and the byproduct of vortex-induced noise in the wake region of a circular cylinder. Aeroacoustic tests for a baseline case and 10 different slotted cases with slot angles of 80°≤𝜃≤125° are performed for Reynolds numbers 6.6×103≤R≤3.3×104. This is supplemented by numerical computational fluid dynamics (CFD) analyses to identify the underlying aerodynamic mechanisms. The results obtained reveal that using the current passive control method results in a significant reduction of the vortex shedding tonal noise for slot angles of 90°≤𝜃≤125° and high Reynolds numbers. The numerical results showed good agreement with a remarkably reduced kinetic energy for slot-end angles of 115°≤𝜃≤125°. At low Reynolds numbers, however, the identified aeroacoustic benefits tend to cease.
Aerodynamic and aeroacoustic performance experiments were carried out on four- and eight bladed, 1.542 m diameter, axial flow cooling fans, with constant solidity and hub-to-tip ratio. Tests were conducted in an ISO5801, Type A Fan Test facility. The tip gap (TG) was reduced from 4 mm (0.26% fan diameter) to 2 mm (0.13% fan diameter), to 0 mm, for both fan configurations. The noise profile of each fan configuration at the same TG over the whole volumetric flow rate spectrum was compared to each other. The 4 mm (0.26%) TG is used as a baseline to measure the nett increase or decrease in sound levels. Noise emissions decreased as the TG was reduced. It is discovered that the four bladed fan configuration had lower noise emissions than the eight bladed fan configuration at all blade tip clearances at design flow rate. It is concluded that reducing the TG and number of blades, at constant solidity, reduces sound emissions. The 0 mm TG for the four bladed fan produced the greatest reduction in noise emissions. An increase in fan total-to-static performance is observed when reducing the TG for both fan configurations.
Extensive research efforts in the aeroacoustics community have firmly established the benefits of porous trailing edges to achieve low-noise radiation. However, most studies of porous treatment are based on the use of very complex, open-cell structures to manipulate turbulent flow. Although this implementation has been shown to improve the aeroacoustics performance, the exact physical mechanisms that can be drawn from such a geometry are limited due to their complex topology. This study aims to draw from previous works and to develop an optimised experimental method that utilises a 3D-printed array of rectilinear, structured permeable trailing edges on a NACA-0012 aerofoil based on a Box-Behnken experimental design. The essence of the work is to isolate individual porous parameters, and investigate the interdependencies of these parameters on target values such as the overall sound power level, the Strouhal number of the maximum noise reduction and many other characteristics of the far field. Twenty-eight porous trailing edges were produced based on the initial experimental design. Each is unique with the combination of streamwise and spanwise separation distance between the pores, pore size and porous coverage. The experiment was conducted over various angles of attack and Reynolds numbers. The results show that many of these trailing edges can indeed achieve low-noise radiation, and acceptable prediction accuracies are obtained for all the response variables except the total sound power reduction, ΔOAPWL, and the lower Strouhal limit of the noise reduction. This paper will establish the findings, discuss the results and detail the next stage of the experiment for the improvement of the statistical model.
Leading edge serrations are well known for their ability to reduce turbulence-induced noise of single aerofoils while also providing aerodynamic advantages under certain operating conditions. Continuatively, applying leading edge serrations to rotating machinery such as axial fans proved the validity to generally transfer the obtained aeroacoustic benefits of single aerofoils. However, for the rotating applications the noise reduction potential highly depends on the point of operation. The current work aims at assessing the aeroacoustic effects of serrated leading edges under the increased geometrical complexity of the fan blades through blade skew. Therefore, the question is whether combining two potentially effective noise-reducing treatments through blade skew and leading edge serrations results in leveraging or obstructing effects. By varying the skew angle from 0 deg to 38 deg, four different prototypes of the fan impeller are tested experimentally in a test rig according to ISO 5136 and ISO 5801. All configurations are tested with original blades of straight leading edges plus five sets of serrations each, parameterised by the serration amplitude and the serrations wavelength. The intensity of the incoming turbulence ranges from 2.6% to 12.1%. The results obtained show the skewed blades to improve both the aerodynamic performance and the noise radiation after exceeding an initial skew angle, complemented by a significant onset of stall. Moreover, no contraindication between blade skew and serrated leading edges is encountered, showing the potential to further extend the noise reduction capabilities by combining effects of blade skew and leading edge treatment.
Potential and Evolution of Miniatures Compressed Air Energy Storage Plants Based on Impulse Turbine
(2022)
This paper describes the work carried out to develop an impulse turbine for miniatures compressed air system. This study hypothesizes the question; what is the effect of combining an impulse turbine loss model into a compressed air energy storage system analysis? The miniatures power system has lower mass flow rates which lead to a small turbine size. The miniature impulse turbine has relatively low efficiency and is highly sensitive to operating conditions at a low mass flow rate due to all losses in terms of passage, trailing edge, incidence, and clearance becoming higher amounts compared to the total losses of the percentage foundation.
The development of a novel impulse turbine configuration is presented based on one-dimensional design and three-dimensional simulations. The impulse turbine in single-stage configuration was designed and analyzed for a range of operating conditions in terms of pressures, temperatures, mass flow rate, and rotational speeds. The simulations results showed that the maximum efficiency and power were 65.93% and 4.019 kW respectively with a mass flow rate of 0.2 kg/s. The energy analysis revealed that the system efficiency was 10.3%. The miniature compressed air energy storage system driven by an impulse turbine can be used to generate electricity for small power applications.
Heavy-duty centrifugal fans require high reliability and first-class performance. Besides, extreme conditions and harsh environments are often encountered, such as in the papermaking process, in steel or cement plants or the chemical and petrochemical industry. Therefore, the design of high-performance heavy-duty industrial fans requires robust yet efficient solutions. The previous work indicates a high aerodynamic and aeroacoustic sensitivity concerning the specific position of the volute cutoff (tongue). This effect will be further investigated, not by directly changing the orientation of the cutoff, but by varying the position of the impeller relative to a fixed volute casing. The initial evaluation is done through a numerical study of three influencing parameters, which allow the aerodynamic dependencies to be modeled using low-layer artificial networks. Subsequently, extensive experimental studies were carried out to validate the aerodynamic dependencies and also to incorporate information on the aeroacoustic performance. The obtained results show that the operating point represents the key factor in determining the optimal positioning, with qualitatively comparable dependencies found for both tested fans. From an aeroacoustic point of view, the determined optimal configuration does not necessarily coincide with the observed aerodynamic desires, so careful analysis and a reasonable compromise are required, motivating for a multi-objective optimization process.
Previous as well as ongoing studies have shown that bioinspired modifications of the leading edge of axial fans, so-called leading edge serrations, have beneficial effects on sound radiation in rotating systems such as a broadband noise reduction. The objective of this study is to elaborate on the comparability of two geometrically similar low-pressure axial fans that differ in fan diameters. For this purpose, a fan design based on the geometric characteristics of an existing fan, which had been tested in previous studies, was developed with and without leading edge serrations at a scale of 1:3. Extensive experiments were carried out to gather detailed data on the aerodynamic and aeroacoustic performance of the specimen. Similarity laws and non-dimensional parameters are used to investigate whether a transferability comparison of the aerodynamic and aeroacoustic experimental results of these geometrically similar axial fans is possible. The latter also includes an analysis of the spectral range. The results prove that it is possible to derive a comparability of the aerodynamic parameter of the flow coefficient and thus of the flow rate of the fans. Furthermore, a correlation between the noise reduction potential of the two models can be established through spectral Strouhal number normalization. The proposed aerodynamic and aeroacoustic coherences ensure transferability from the model fan to an upscaled fan and thus allow generalized statements to accurately transfer the aeroacoustic potential of leading edge serrations for different geometrically similar fan applications.
In this article we show how fashion brands communicate with their follower on Instagram. We use a continuously update dataset of 68 brands, more than 300,000 posts and more than 40,000,000 comments. Starting with descriptive statistics, we uncover different behavior and success of the various brands. It turns out that there are patterns specific to luxury, mass-market and sportswear brands. Posting volume is extremely brand dependent as is the number of comments and the engagement of the community. Having understood the statistics, we turn to machine learning techniques to measure the response of the community via comments. Topic models help us understand the structure of their respective community and uncover insights regarding the response to campaigns. Having up-to-date content is essential for this kind of analysis, as the market is highly volatile. Furthermore, automatic data analysis is crucial to measure the success of campaigns and adjust them accordingly for maximum effect.
Using Mask R-CNN for Image-Based Wear Classification of Solid Carbide Milling and Drilling Tools
(2020)
In order to ensure high productivity and quality in industrial production, early identification of tool wear is needed. Within the context of Industry 4.0, we integrate wear monitoring of solid carbide milling and drilling cutters automatically into the production process. Therefore, we propose to analyze wear types with image instance segmentation using Mask R-CNN with feature pyramid and bounding box regression. Our approach is able to recognize the five most important wear types: flank wear, crater wear, fracture, built-up edge and plastic deformation. While other methods use image classification and classify only one wear type for each image, our model is able to detect multiple wear types. Over 35 models with different hyperparameter settings were trained on 5,000 labeled images to establish a reliable classifier. The results show up to 82.03% accuracy and benefit for overlapping wear types, which is crucial for using the model in production.
Heterogeneous catalysis, a process in which the reaction of gaseous or liquid chemical reagents is facilitated at the surface of a solid material, is responsible for the majority of industrial-scale chemical and fuel production reactions. The energy required to drive these reactions has historically been derived from the combustion of non-renewable fossil fuels and carries an unavoidably large carbon footprint. More recently, the development of environmentally responsible and sustainable chemical industries is increasingly motivated by greenhouse gas-induced climate change, thus creating demand for eco-friendly heterogeneous catalytic processes. This includes innovative approaches enabled by renewable forms of energy, such as the electrification of chemical and petrochemical processes, utilization of CO2 as a feedstock and the incorporation of light into catalytic reactions. Herein we review the conversion of solar energy to chemical energy using CO2, and describe how the photophysical and photochemical properties of nanostructured metal oxide photocatalysts have been engineered to efficiently incorporate light into heterogeneous gas–solid CO2 hydrogenation reactions. Realizing high photonic and energy efficiencies in these systems has demanded innovation in not only photocatalyst engineering, but also photoreactor and process engineering. Rather than exclusively providing an in-depth discussion of the chemistry and science within each individual study, this Tutorial Review highlights the multidisciplinary character of photocatalysis studies by covering the four essential components of a typical research work in this field (materials engineering, theoretical modelling, reactor engineering and process development) via case studies of the archetypal indium oxide catalyst materials. Through advances in these four components, progress has been made towards the ultimate goal of industrializing the production of CO2-derived chemicals and fuels.
Im Forschungsvorhaben „+EQ-Net II“ wird der Betrieb eines gemischt genutzten Gebäudes über ein mehrjähriges Monitoring wissenschaftlich analysiert. Ziel ist es, Betriebsoptimierungspotenziale an der Anlagentechnik inklusive einer Großkollektoranlage zu heben. Aufgrund der Messdaten konnten bereits erhebliche Einsparpotenziale in der Wärmeverteilung aufgezeigt werden.
This paper reports on the successful synthesis of visible light photoactive N–TiO2 nanolayers and the investigation of charge carrier dynamics in dependence on N-doping and irradiation wavelengths. Grazing incidence X-ray diffractometry exhibited that N-doping supports the formation of an anatase phase with a higher crystallinity than observed for undoped TiO2. Photoelectrochemical measurements gave evidence that N–TiO2 is characterized by a significantly higher incident photon conversion efficiency (IPCE) upon both UV and visible light irradiation. Photoelectrochemical impedance spectroscopy revealed that the higher IPCE of N–TiO2 in UV can be explained by a lowered charge transfer resistance, probably due to its higher crystallinity. The higher photoactivity in the visible can be explained by the incorporation of intrabandgap states upon N-doping. This is supported by X-ray photoelectron spectroscopy indicating the incorporation of N atoms in the titania layer, the observed bandgap narrowing by at least 250 meV as measured by ultraviolet–visible absorption spectroscopy, and the decrease of the work function by 50 meV, as derived from scanning Kelvin probe microscopy. Intensity-modulated photocurrent/photovoltage spectroscopy proved that the generally lower quantum yield at visible light is caused not only by the generation of less photoexcited charge carriers, but also by a higher surface hole recombination rate and hence lower hole charge transport efficiency.
Ethylene is a phytohormone that is responsible of fruit and vegetable ripening. TiO2 has been studied as a possible solution to slowing down unwanted ripening processes, due to its photocatalytic capacity which enables it to remove ethylene. Thus, the objective of this study was to develop nanocomposites based on two types of eco-friendly materials: Mater-Bi® (MB) and poly(lactic acid) (PLA) combined with nano-TiO2 for ethylene removal and to determine their ethylene-removal capacity. First, a physical–chemical characterization of nano-TiO2 of different particle sizes (15, 21, 40 and 100 nm) was done through structural and morphological analysis (DRX, FTIR and TEM). Then, its photocatalytic activity and the ethylene-removal capacity were determined, evaluating the effects of time and the type of light irradiation. With respect to the analysis of TiO2 nanoparticles, the whole samples had an anatase structure. According to the photocatalytic activity, nanoparticles of 21 nm showed the highest activity against ethylene (~73%). The results also showed significant differences in ethylene-removal activity when comparing particle size and type and radiation time. Thus, 21 nm nano-TiO2 was used to produce nanocomposites through the melt-extrusion process to simulate industrial processing conditions. With respect to the nanocomposites’ ethylene-removing properties, there were significant differences between TiO2 concentrations, with samples with 5% of active showed the highest activity (~57%). The results obtained are promising and new studies are needed to focus on changes in material format and the evaluation in ethylene-sensitive fruits.
Heterogeneous thermal catalytic processes are vital for industrial production of fuels, fertilizers, and other chemicals necessary for sustaining human life. However, these processes are highly energy-intensive, requiring a vast consumption of fossil fuels. An emerging class of heterogeneous catalysts that are thermally driven but also exhibit a photochemically enhanced rate can potentially reduce process energy intensity by partially substituting conventional heat (where fossil fuels are needed) with solar energy. Such catalyst systems have yet to be practically utilized. Here, we demonstrate a compact electrically heated photo- and thermal annular reactor module to reduce CO2 to CO, via the reverse water gas shift reaction. A first-principles-based design approach was taken in developing a SiO2 on an Al photo- and thermal catalyst system for the model photo- and thermal indium oxide hydroxide (In2O3–x(OH)y) catalysts. A 5-fold light enhancement in the CO production rate and over 70 h of stable CO production were achieved. This represents the highest light enhancement effect reported for this model photocatalyst to date. The reactor presented herein allows continuous operation and a significant reduction of 31% in heater power consumption when provided with an additional 2 suns of irradiation, demonstrating the strong photo- and thermal-harvesting performances of the catalyst system developed in this work.
Here we report the enhanced light penetration and mass transfer efficiency of photocatalytic foams to convert CO2 to CO. The viability of utilizing a metallic foam as a model photocatalyst support is used to evaluate the photochemical and thermochemical reverse water gas shift reaction catalyzed by photoactive indium oxide hydroxide nanorods uniformly coated on nickel foams. A light-enhanced CO production rate up to 130% higher than the dark CO production was achieved through enhanced light penetration. A remarkably high thermo-
chemical CO production rate of 0.75 mmol gcat 1 h 1 was achieved at 295 ◦C. Whilst several approaches to optimization of photocatalyst morphology at the nanoscale have been successful in extending electron hole-pair lifetime and modifying the site of reactions, these advantages cannot be significantly realized unless microscale to macroscale structuring efforts, that shorten the path length for diffusion of the reactant gas molecule and lengthen photon penetration to these catalytic sites are integrated. The superior catalytic performance of the indium oxide hydroxide nanorods on an optimized coated foam configuration compared to the performance of packed bed and thin film configurations demonstrates the critical importance of using structured supports in scale up of future photocatalytic processes.
Low-Noise Design of Axial Fans Through Optimized Spanwise Application of Leading Edge Serrations
(2023)
Recent studies have shown that leading edge serrations can effectively reduce broadband noise in axial fans and expand their operational range. However, additional aerodynamic losses have to be considered alongside the benefits of improved acoustic performance. The majority of studies focused on applying leading edge serrations along the entire span of the rotor blades regardless of local differences in radial inflow angles, deflection effects, and blade loading. In this regard, local and spanwise varying applications of leading edge serrations are considered crucial to reconciling maximum aeroacoustic and aerodynamic performance. In making these applications, a fan blade span is divided into five sub-segments. Each segment can then be equipped with either an acoustic or aerodynamic optimum as well as a baseline straight leading edge. Through testing at three different inflow turbulence levels along the full characteristic curve, an extensive statistical experimental design is executed. Ultimately, a simplified statistical model is derived. The model provides information on the optimum spanwise shape of a serration design. The results indicate significant effects of the local spanwise selection of varying serration designs. Discrepancies between aerodynamic and aeroacoustic optimum solutions can be satisfactorily resolved where, primarily, a significant extension of the working area is observed. Moreover, an extended potential in the delay of stall entry and the associated improvement of total pressure as well as a significant reduction of aeroacoustic signature is found. The underlying mechanisms are attributed to the compartmentalization effects of the serrations which restrict separation phenomena to local cells of finite spanwise extension. Furthermore, the spanwise geometrical parametrization of the serration segments correlates well with radial blade loading as well as respective flow conditions. By taking the radial distribution of aerodynamic quantities into account, an individual design of locally applied leading edge serrations can be integrated into the fan design process, enabling improved balancing between aeroacoustic benefits while maximizing aerodynamic performance.
The ineffectiveness of many gamification projects can be attributed to wrong decisions made during the conceptual design phase, especially in the selection of game design elements. This paper introduces a data driven method of creating a gamification pattern language similar to software design patterns to help gamification designers select such elements. Thanks to modern machine learning technologies such a pattern language can be based on a comprehensive empirical analysis to assess the actual use of game design elements in games. This paper is the first report on an ongoing research project that has been carried out since the beginning of 2017 in cooperation with the German Games Archive to extract game design elements from more than 30,000 board games using machine learning techniques. Initial tests based on support vector classification and 4,000 games show that game design elements can be reliably identified with accuracy rates between 80 and 90%.
High-Performance, Scalable, and Low-Cost Copper Hydroxyapatite for Photothermal CO2 Reduction
(2020)
Urea, an agricultural fertilizer, nourishes humanity. The century‐old Bosch–Meiser process provides the world's urea. It is multi‐step, consumes enormous amounts of non‐renewable energy, and has a large CO2 footprint. Thus, developing an eco‐friendly synthesis for urea is a priority. Herein we report a single‐step Pd/LTA‐3A catalyzed synthesis of urea from CO2 and NH3 under ambient conditions powered solely by solar energy. Pd nanoparticles serve the dual function of catalyzing the dissociation of NH3 and providing the photothermal driving force for urea formation, while the absorption capacity of LTA‐3A removes by‐product H2O to shift the equilibrium towards urea production. The solar urea conversion rate from NH3 and CO2 is 87 μmol g−1 h−1. This advance represents a first step towards the use of solar energy in urea production. It provides insights into green fertilizer production, and inspires the vision of sustainable, modular plants for distributed production of urea on farms.
An essential element for sustainable use of renewable resources is an efficient comminution process for which the relation between energy input and size reduction is of great importance. Fine comminution of beech, oak, and spruce wood chips in cutting and hammer mills at different moisture content levels is investigated. The influence of the different process parameters as well as the size reduction performed by the hammer and cutting mill on the specific comminution energy is reported and the particulate properties of the comminution products are reported. Considering the energy requirements, functional relations were derived from the experimental results, which describe the relation between comminution energy and size reduction.
A novel jet dispersion technique was developed and investigated which enabled excellent carbon nanotube (CNT) dispersion by high exfoliation at even very low pressure drops. Suitable procedures were developed for the characterization of agglomerate size and fraction of individual CNTs. The appropriate characterization enabled the definition of a dimensionless dispersing parameter and the development of a kinetic model that describes CNT dispersion in dependence of the volumetric energy input. The rheological behavior of CNT suspensions in steady‐shear flows was investigated and demonstrated how the agglomerate fracture and CNT individualization influence the suspension viscosity.
Influence of the Temperature on Coccolith‐Containing Systems from Emiliania huxleyi Cultivations
(2020)
Thermogravimetric analysis of a coccolith‐containing biogenic broth showed a three‐step degradation process. According to this system behavior, the biogenic broth was heated to specific temperatures and characterized in terms of its morphology, surface chemistry, and crystallinity. The elemental and organic composition of the treated samples was also evaluated and compared to the reference material. The presented results were acquired in an effort to exploit pretreatment scenarios for such a biogenic system that would improve and support a separation process.
Die Digitalisierung des Lehrens und Lernens wird häufig zu einseitig von den technischen Möglichkeiten angetrieben. Das Potenzial der Digitalisierung bleibt dadurch unerschlossen. Statt sich neue Möglichkeitsräume zu erschließen, verbleiben Hochschulen bei einer digitalen Kopie ihrer selbst. Wir beschreiben in diesem Beitrag ein systematisches Vorgehen, um sich von festgefahrenen Denkweisen zu lösen und stattdessen eine spielerische Haltung einzunehmen. Denn eine digitale Transformation, die sich Spiele zum Vorbild nimmt, könnte das Studieren nicht nur zeit- und ortsunabhängig machen, sondern auch Motor für die Gestaltung motivierender Lern- und Arbeitsgemeinschaften sein.
Herausforderungen bei der Etablierung einer Circular Economy von carbonfaservertärkten Kunststoffen (CFK) ergeben sich insbesondere durch die nötige, jedoch problematische Trennung des Faser‐Matrix‐Verbunds. Das Pyrolyseverfahren stellt eine mögliche, bereits industriell umgesetzte, Technologie zur Verbundtrennung dar. Eine Weiterentwicklung ist die mikrowellenunterstütze Pyrolyse, bei der das CFK‐Material durch die Mikrowellen aufgeheizt und so die Faser freigelegt wird. Prozessgrundlagen und Einflüsse auf die Faser‐Matrix‐Trennung werden im vorliegenden Beitrag betrachtet.
Aufgrund steigender energetischer Anforderungen an Gebäude, werden Wärmedämmverbundsysteme (WDVS) seit den 1970 Jahren zur Dämmung von Gebäudefassaden verwendet. Angesichts der Langlebigkeit dieser Kompositmaterialien fallen seit den letzten Jahren vermehrt WDVS‐Abfälle an. Eine werkstoffliche Verwertung dieser Systeme existiert aktuell noch nicht, wodurch ein enormes Ressourceneffizienzpotenzial verloren geht. Aufgrund der Komplexität dieser Kompositmaterialien wurden im Rahmen dieser Arbeit Wärmedämmverbundsysteme durch verfahrenstechnische Prozessschritte aufbereitet.
Die elektrischen Eigenschaften von Partikeln insbesondere der Durchgangswiderstand von Partikelschüttungen haben in vielen verfahrenstechnischen Prozessen, bei der Produktqualifizierung oder dem Brand‐ und Explosionsschutz eine entscheidende Bedeutung. Da sich der Ladungstransport in einem dispersen System von dem in einem homogenen Festkörper unterscheidet, ist der Durchgangswiderstand entscheidend von den Produkteigenschaften der Partikel und des Fluids abhängig. Im Rahmen dieser Arbeit wurde die Abhängigkeit des Durchgangswiderstandes von der inneren Struktur der Schüttung, der relativen Feuchtigkeit, der Konditionierungszeit bei unterschiedlichem Klima und der mittleren Partikelgröße in einer konzentrischen Messzelle untersucht.
Es wird eine neue Trennfunktion T(x, α′, β) für den stationären Siebprozesses vorgestellt. Sie ist eine Funktion der Partikelgröße x, der Trennschärfe α′ und der neue eingeführten Trenneffizienz β. Mit der neuen Trennfunktion kann der Siebklassierprozess sehr gut beschrieben werden, insb. im Fein‐ und Grobgutbereich ist eine sehr gute Übereinstimmung mit den Messwerten zu beobachten. Ein Vergleich der Trennfunktionen berechnet mit dem Trennschärfeparameter α′ und der Trenneffizienz β zu den Trennfunktionen, die nur mit α′ ermittelt wurden, zeigt, dass durch T(x, α′, β) eine wesentliche Verbesserung der Charakterisierung des stationären Siebklassierprozesses möglich ist. Das neue Modell der Trennfunktion T(x, α′, β) liefert eine wesentlich bessere Übereinstimmung mit den Messwerten als andere Modelle und ist somit zur Beschreibung einer Trennfunktion für den stationären Siebprozess sehr gut geeignet ist.
Austernschalen stellen als Abfallprodukt eine große Umweltbelastung dar und die Wiederverwendung des Materials gewinnt zunehmend an Bedeutung. Da der Zerkleinerungsprozess beim Recycling von Sekundärrohstoffen die Eigenschaften des Materials definiert, wurden Austernschalen mit einer Planetenkugelmühle und einer Schlagradmühle zerkleinert und die gewonnenen Fraktionen in Bezug auf Größe und Form analysiert und miteinander verglichen. Ein Zerkleinerungsmaterial der Schlagradmühle wurde für eine Reihe von Benetzungsversuchen verwendet, die dazu beitrugen, die freie Oberflächenenergie des Materials nachzuweisen.
Rotorblätter von Windkraftanlagen stellen nicht nur durch die eingesetzten Verbundwerkstoffe eine Herausforderung für das Recycling dar, sondern bei der Demontage auch durch ihre großvolumige Bauweise. In dem Beitrag wird ein neuer Ansatz zur Zerlegung von Verbundbauteilen mit energetischen Materialien aufgezeigt. Die Ergebnisse verdeutlichen die unterschiedliche Demontagewirkung von Sprengschnüren und Schneidladungen sowie die Abhängigkeit von den Materialfraktionen, der Materialdicke, dem Lagenaufbau oder auch der Faserarchitektur.
In den vergangenen Jahrzehnten ist aufgrund der energetischen Anforderung der Anteil an verbauten Wärmedämmverbundsystemen (WDVS) in der Bundesrepublik Deutschland deutlich angestiegen. Aktuell kommt es zu einem signifikanten Anstieg von WDVS‐Abfällen, für die noch keine etablierte Recyclingstrategie existiert. Aus diesem Grund wurden in dieser Arbeit WDVS‐Abfälle im Sinne der Kreislaufwirtschaft aufbereitet, um die erhaltenen Sekundärrohstoffe industriell nutzbar zu machen. Um eine zielgerichtete Wiederverwertung zu ermöglichen und den Stoffkreislauf von WDVS langfristig zu schließen, wurden partikuläre Eigenschaften wie der Zerkleinerungsgrad, Sphärizität, Dispersität sowie die Fließfähigkeit und Kompressibilität der Rezyklate untersucht.
Charakterisierung und Störstoffanalyse von rückgewonnenen Stoffströmen aus Wärmedämmverbundsystemen
(2021)
Aufgrund steigender energetischer Anforderungen ist der Anteil an verbauten Wärmedämmverbundsystemen (WDVS) in den vergangenen 50 Jahren deutlich gestiegen. Trotz der Langlebigkeit dieser Systeme fallen zunehmend WDVS‐Abfälle an, deren Nutzungsphase beendet ist. Aufgrund der komplexen Bauweise sowie einer Vielzahl an unterschiedlich verbauten Materialien der vergangenen Generationen bestehen viele Unsicherheiten und Probleme bei der sortenreinen und schadstoffarmen Aufbereitung solcher Systeme. Im Rahmen der vorliegenden Arbeit wurde ein Aufbereitungsverfahren für WDVS entwickelt. Damit gelingt eine weitestgehende Rückgewinnung verwertbarer Werkstofffraktionen. Diese wurden auf etwaige Stör‐ und Schadstoffe wie Flammschutzmittel sowie auf deren Reinheit untersucht.
As a result of the development of innovative technologies for use of renewable materials, these materials are increasingly used for the production of precursors and basic chemicals for the chemical industry. The upstream process of comminution is a key element in the use of renewable raw materials, which impacts the consecutive disintegration of the materials, which means the separation of the three main components cellulose, hemicellulose and lignin as well as the handling. Energy efficiency of the comminution process is of utmost importance to make renewable resources more competitive with petrochemical products. The key parameters to increased energy efficiency are, besides the mill type and the mill operation parameters, the species of the renewable resource, in terms of moisture content and the mechanical properties. A better understanding of these interdependencies can help to improve the adjustment of particle size distribution and particle shape as well as the energy demand for the comminution process, which impacts the overall efficiency of the supply chain process, disintegration as well as the conversion. This work focuses on the comminution of lignocellulosic biomass in a cutting mill and a hammer mill and how the specific comminution energy and particulate properties are affected by the type of mill, the species of wood, the archived size reduction as well as the moisture content. Therefore two spices of hardwood, common beech (F. sylvatica L.) and oak (Q. robur L.), and one species of coniferous wood common, spruce (P. abies L.), where comminuted under variation of different process parameters. The specific comminution energies were determined and the comminution products were characterized by dynamic image analysis. This work describes the influence of the process parameters, internal classifying screen, type of stress and moisture content, on the comminution products and the specific comminution energy. From the results of the experiments, functions were determined which can describe the influence of the type of mill, the moisture content, the type of wood and the comminution ratio on the specific comminution energy.
Coccoliths are micro-structured biomineral particles found in cell protective covering layers of coccolithophore species. They are mainly composed of CaCO3 and their individual crystal entities are arranged in such a way that they construct complex and unique structures. This complexity is found down to the individual particle level and appears to have promising properties to offer. This study focuses on the essential step prior to any kind of implementation, which is the recovery of the material. It summarizes cleaning protocols found in literature, compares them for the first time for the same freshly cultivated material and addresses challenges that still need to be overcome. Further, it highlight the advantages and disadvantages of the best cleaning protocols, suggests optimizations with promising results and uses size distribution measurements to analyse the recovery efficiency. To that end, further characterization techniques, new for coccoliths, are introduced and used to improve our current knowledge of the particles behaviour.
Due to concerns about the very high primary raw material consumption and CO2 emissions of the economically important construction sector, the demand for “green” binders is growing. One option that is receiving particular attention is the material class of “geopolymers”, which could be used as a substitute for Portland cement. This new group of binders not only exhibits improved mechanical properties, but is also characterized by particularly low carbon dioxide emissions in the course of its production. This work focuses on the influence of concrete rubble on the setting behavior and microstructural properties of fly ash-based geopolymers. In the course of the investigations, the manufactured geopolymer samples are examined for the material parameters relevant to building materials, namely compressive strength, raw density and thermal conductivity. The setting behavior and the forming structures are investigated by infrared spectroscopy, X-ray diffraction analysis and scanning electron microscopy. The present work is intended to contribute to the development of a suitable recycling strategy for the material recycling of concrete rubble in novel substitute construction materials, the geopolymers.
The increasing number of new construction projects requiring high-quality building products, which, in turn, emit enormous amounts of CO2, runs counter to European and global climate goals. The increasing occupation of valuable landfill space is also an ecological problem. To meet these challenges without having to lower living standards, more ecological building materials should be used in the future. Geopolymers or alkali-activated materials, which, unlike conventional building materials, can be produced and used without a prior burning or calcination process, offer a comparatively low-CO2 alternative. Significant CO2 emissions can already be saved by using this technology. The aim of this work is to investigate whether geopolymers can also be produced from construction and demolition residuals generated by the construction industry in order to counteract the problem of the increasing use of landfill space and, at the same time, to further reduce greenhouse gas emissions in the production of building materials. For this purpose, various residual materials from the construction and demolition industry are investigated by means of XRF, XRD, and IR spectroscopy for their setting behavior by alkaline activation. At the same time, the characteristic values of compressive strength, flexural strength, bulk density, and thermal conductivity, which are important for building materials, are determined in order to test the possible applications of the resulting materials as building materials.
Good management requires proper measurement, yet little is known about anthropogenic climate effects of agriculture. To remedy this, a precise measurement of negative externalities is urgently needed. Therefore, the authors of this article describe the heterogeneity of results from previous studies on climate effects and – focusing on the agricultural sector – identify reasons for this phenomenon. The authors conduct a meta-regression analysis, based on 53 primary studies that cover the period between 1951 and 2015. All countries or country groups are included in the 1345 reported results on emitted amounts of CO2e and SO2e. Our findings confirm the well-known result that an increase in livestock quantities corresponds with a significant increase in emission levels. By integrating culture-related country data, the authors conclude that the level of “humane orientation” and the amounts of emissions follow opposite courses. Furthermore, studies conducted while the first author of this study was working for an NGO, report significantly higher emissions. Based on an adaptation of a meta-regression analysis to the field of environmental performance measurement, we are able to provide new insights about the influence of the change of individual drivers on the emission level. Examples of these insights include a one-third increase in cattle stock is associated with an increase in emissions of 29.45 t/km2. We also find that publications where the first author works for an NGO reported an emission level 87.04 t/km2 higher than other publications. These findings enable the identification of the main drivers of emissions, while helping to explain the heterogeneity of existing studies. Based on the findings of this study, companies can take reliable measures to reduce the external climate effects of their products.
Good management requires proper measurement, yet little is known about anthropogenic climate effects of agriculture. To remedy this, a precise measurement of negative externalities is urgently needed. Therefore, the authors of this article describe the heterogeneity of results from previous studies on climate effects and – focusing on the agricultural sector – identify reasons for this phenomenon. The authors conduct a meta-regression analysis, based on 53 primary studies that cover the period between 1951 and 2015. All countries or country groups are included in the 1345 reported results on emitted amounts of CO2e and SO2e. Our findings confirm the well-known result that an increase in livestock quantities corresponds with a significant increase in emission levels. By integrating culture-related country data, the authors conclude that the level of “humane orientation” and the amounts of emissions follow opposite courses. Furthermore, studies conducted while the first author of this study was working for an NGO, report significantly higher emissions. Based on an adaptation of a meta-regression analysis to the field of environmental performance measurement, we are able to provide new insights about the influence of the change of individual drivers on the emission level. Examples of these insights include a one-third increase in cattle stock is associated with an increase in emissions of 29.45 t/km2. We also find that publications where the first author works for an NGO reported an emission level 87.04 t/km2 higher than other publications. These findings enable the identification of the main drivers of emissions, while helping to explain the heterogeneity of existing studies. Based on the findings of this study, companies can take reliable measures to reduce the external climate effects of their products.
Bestimmung der Prozessparameter von Zerkleinerungsprozessen für dämmstoffhaltige Kompositmaterialien
(2021)
Ein wesentlicher Aspekt in der Aufbereitungstechnik ist der Zerkleinerungs-prozess, der auch einen der energieaufwendigsten Prozessschritte darstellt. Durch mangelnde Aufbereitungstechnologien zur selektiven Zerkleinerung von dämmstoffhaltigen Kompositmaterialien wie Wärmedämmverbundsystemen (WDVS) geht aktuell ein erhebliches Ressourceneffizienzpotenzial verloren. Im Rahmen dieser Arbeit wurden WDVS mit unterschiedlichen Dämmstoffmaterialien zerkleinert und der Einfluss von relevanten Prozessparametern sowie die in den Mühlen vorherrschende Beanspruchungsart am Komposit untersucht und ein erstes Zerkleinerungsmodell erstellt. Durch die Methode der dynamischen Bildanalyse konnten die individuellen Zerkleinerungsprodukte charakterisiert und somit der Prozess quantifiziert werden.
Oyster shells are an important bioresource that causes serious environmental problems and is currently only partially repurposed. Its versatile nature is reflected in the manifold studies already proposed for the material. In this study, we add to this effort by first grinding the material with a hammer mill, beater disc mill, pin mill and wet media mill, treating part of it in a muffle furnace, noting the shift in its properties such as particle size, morphology, surface free energy, specific surface area and choosing a fraction to incorporate in a particle stabilized emulsion. The particle stabilized emulsions were prepared with oyster shells grinded by the agitated wet media mill at 2000 rpm for 30 min, with a media at x50 = 0.79 μm, a SSA at 17.16 m2/g, a SFE at 32.53 mN/m and with particles resembling a spherical shape. The emulsion was studied in terms of particle concentration, ranging from 2 to 10 wt% with the 8 wt% showing the best stability. The 8 wt% oyster shell formulation was tested and compared with a formulation using 2 wt% Aerosil particles and a surfactant store-bought product. The oyster shell particle formulation exhibited minor viscosity changes in the studied period of 8 weeks, a constant LVE range and promising behaviour in the proposed application.
SafeML: Safety Monitoring of Machine Learning Classifiers Through Statistical Difference Measures
(2020)
AbstractIn the present study, a new separation function T(x,α’,β) for the steady‐state screening process is presented. This new grade efficiency T(x,α’,β) presented here is a function of particle size x, separation sharpness α’, and the newly introduced separation efficiency β. With this new efficiency function, the screening classification process can be described exactly. Especially in the fine and coarse material ranges, a very good correlation of the calculated function with the measured values can be observed. A comparison of the grade efficiency function with separation sharpness α’, separation efficiency β, and only with the measure for separation efficiency has shown that the new grade efficiency T(x,α’,β) allows a significant improvement in the characterization of the stationary screen classification process. When compared with other models, the new model of the grade efficiency T(x,α’,β) shows a significantly higher correlation with the measured values and is therefore very well suited to describe a grade efficiency for the stationary screening process.
Security cannot be implemented into a system retrospectively without considerable effort, so security must be taken into consideration already at the beginning of the system development. The engineering of automotive software is by no means an exception to this rule. For addressing automotive security, the AUTOSAR and EAST-ADL standards for domain-specific system and component modeling provide the central foundation as a start. The EASTADL extension SAM enables fully integrated security modeling for traditional feature-targeted attacks. Due to the COVID-19 pandemic, the number of cyber-attacks has increased tremendously and of these, about 98 percent are based on social engineering attacks. These social engineering attacks exploit vulnerabilities in human behaviors, rather than vulnerabilities in a system, to inflict damage. And these social engineering attacks also play a relevant but nonetheless regularly neglected role for automotive software. The contribution of this paper is a novel modeling concept for social engineering attacks and their criticality assessment integrated into a general automotive software security modeling approach. This makes it possible to relate social engineering exploits with feature-related attacks. To elevate the practical usage, we implemented an integration of this concept into the established, domain-specific modeling tool MetaEdit+. The tool support enables collaboration between stakeholders, calculates vulnerability scores, and enables the specification of security objectives and measures to eliminate vulnerabilities.
Large-Scale Geothermal Collector Systems for 5th Generation District Heating and Cooling Networks
(2021)
Low temperature district heating and cooling networks (5GDHC) in combination with very shallow geothermal energy potentials enable the complete renewable heating and cooling supply of settlements up to entire city districts. With the help of 5GDHC, heating and cooling can be distributed at a low temperature level with almost no distribution losses and made useable to consumers via decentralized heat pumps (HP). Numerous renewable heat sources, from wastewater heat exchangers and low-temperature industrial waste heat to borehole heat exchangers and large-scale geothermal collector systems (LSC), can be used for these networks. The use of large-scale geothermal collector systems also offers the opportunity to shift heating and cooling loads seasonally, contributing to flexibility in the heating network. In addition, the soil can be cooled below freezing point due to the strong regeneration caused by the solar irradiation. Multilayer geothermal collector systems can be used to deliberately generate excessive cooling of individual areas in order to provide cooling energy for residential buildings, office complexes or industrial applications. Planning these systems requires expertise and understanding regarding the interaction of these technologies in the overall system. This paper provides a summary of experience in planning 5GDHC with large-scale geothermal collector systems as well as other renewable heat sources.
The fourth and fifth generation of district heating (GDH) networks are among the key elements for the energy optimization of districts. Low heat losses in the distribution lines as well as bidirectional heat flow and the use of low-temperature waste heat can lead to new business models for energy suppliers. Despite the continuous development of heat networks, significant heat losses still occur in conventional networks, despite well insulated pipelines, with fluid temperatures at 60-100 °C. Therefore, a study was conducted to investigate heat losses and gains in hot water heating (3GDH), low temperature heating (4GDH) and district heating and cooling networks (5GDHC) based on numerous simulations. The main purpose of the investigations is to determine the main factors influencing the heat transfer characteristics of underground heat networks. The derived results serve as a basis for the development of future planning tools to determine the heat losses and gains of local heating networks quickly and costefficiently.
Dieses Projekt stellt die Frage, wie die COVID-19-Pandemie Prozesse der sozialen Inklusion und Exklusion von wohnungslosen Jugendlichen beeinflusst. Anhand von drei internationalen Fallstudien soll das Verständnis dafür verbessert werden, wie Pandemien die Risiken und die zugänglichen wohlfahrtsstaatlichen Ressourcen für junge Menschen mit Wohnungslosigkeits-erfahrung prägen. Das Wissen, das in dieser vergleichenden Studie entwickelt wird, kann dazu beitragen, die Art und Weise zu verbessern, wie Organisationen der Wohnungslosenhilfe auf neue, veränderte oder verstärkte Probleme und Bedürfnisse von jungen wohnungslosen Menschen reagieren.
In dem an der Technischen Hochschule Nürnberg Georg Simon Ohm angesiedelten Forschungsprojekt „Securing Housing. Wohnen, Wohnraumverluste und Wohnungslosigkeit in Nürnberg und Wien“ wird die Wirkungsweise wohnraumsichernder Instrumente in einem Städtevergleich untersucht. Während sich die Situation auf einigen ohnehin schon angespannten urbanen Wohnungsmärkten zuungunsten ärmerer Bevölkerungsteile zunehmend zuspitzt, und es vermehrt zu Verdrängungen und zur Verknappung leistbaren Wohnraumes kommt, bleiben Unterstützungsangebote, die Wohnraumverluste abwenden oder die Folgen verringern könnten, teilweise ungenutzt oder werden erst sehr spät genutzt. Um die (Nicht‑)Akzeptanz und (Nicht‑)Wirkung besser verstehen zu können, werden die den Interventionsversuchen zu Grunde liegenden Wissensvorräte, Deutungsmuster, Kollektivsymboliken und Normalitätsvorstellungen analysiert. Es wird also untersucht, welchen Einfluss die Wahrnehmung, Interpretation und normative Beurteilung von Wohnungslosigkeit und Wohnraumverlusten durch die Beteiligten auf die Akzeptanz und Reichweite wohnungspolitischer, sozialpolitischer und sozialpädagogischer Regulierungsversuche haben.
Energy-saving potential for centrifugal pump storage operation using optimized control schemes
(2021)
AbstractIn this paper, we present the energy-saving potential of using optimized control for centrifugal pump–driven water storages. For this purpose, a Simulink pump-pipe-storage model is used. The equations and transfer function for steady-state and transient system behavior are presented and verified. Two different control strategies — optimum constant flow rate and level guided speed control — are compared to an allegedly optimal-driven pump with constant rotational speed. Twelve centrifugal pumps between 1 and 120 kW nominal power are evaluated to analyze the influence of different system parameters. The system characteristics, which are the static head, dynamic head factor, and maximum filling head, are varied 25 times for each pump in consideration of the pump’s best efficiency point. Thus, 300 different systems are optimized for each control strategy and compared to the constant speed control. The results are analyzed and the relevant system’s parameters, which have the most significant impact on energy savings, are shown. This theoretical energy–saving potential is verified with measurements, which show the high impact of the part load losses of the frequency converter and the electric motor. A law for identifying and estimation potential energy savings is developed using this information. Four use cases are analyzed with this law. It is shown that for a cost-minimal operation, not only the savings potential but also the operating time is decisive.
In laboratory practicals (labs), students actively investigate technical and scientific phenomena and thus experience autonomy, competence, and social embedding, factors that promote motivation. However, labs mostly rely on highly structured and instructive concepts and often require costly equipment. Therefore, the research question in this paper is: How can learner-centered teaching methods and learning formats be improved by rethinking the digitization of lab practicals?
The implementation of a reliable vision system for a human-robot environment is a key issue for the collaborative production industry. The core challenge of human-robot collaboration is to ensure safety. Furthermore, a flexible safety system is required for frequently changing applications and work areas. This paper focuses on the development and application of a workspace monitoring system for safeguarding using radar sensors. The human-robot collaboration cell is designed to enable a flexible integration regardless of the work location. This results in higher productivity. Since no separating protective devices are provided for the cell, safety-oriented monitoring and control by suitable safety sensors is required. The methods to minimize the size of the necessary safety distance will be presented. The experimental validation shows that this safety system with radar sensors performs a reliable workspace monitoring system. The high robustness, reactivity and flexibility of the safet y concept makes this system usable for collaborative tasks in a real industrial environment.
Given the lasting positive effects of prenatal and infancy home visiting in the United States on disadvantaged mothers and children at school age, we analyzed the follow-up effects of a German home visiting program (ProKind). We hypothesized improvements in 3 domains at child age 7 years: (1) child development and life satisfaction, (2) maternal mental health and life satisfaction, and (3) adverse parenting, abusive parenting, and neglectful parenting.METHODSWe conducted a randomized controlled trial of home visiting, enrolling 755 pregnant, low-income women with no previous live births. The intervention comprised 32.7 home visits by family midwives and/or social pedagogues until child age 2 years. Assessments were completed on 533 7-year-old firstborn offspring to evaluate 8 primary hypotheses.
We found significant positive effects for 4 of the 8 primary hypotheses. Mothers in the intervention group reported fewer behavioral problems among their children in the Child Behavior Checklist (effect size [ES] = 0.21; 95% confidence interval [CI]: 0.03 to 0.38), less child abusive parenting (ES = 0.19; 95% CI: 0.00 to 0.37), fewer maternal mental health problems (ES = 0.25; 95% CI: 0.07 to 0.43), and higher maternal life satisfaction (ES = 0.25; 95% CI: 0.07 to 0.43). Additional preregistered subgroup analyses regarding child sex revealed larger effects for boys and mothers of boys.CONCLUSIONSThe results suggest that in a western European welfare state, home visiting targeting disadvantaged mothers has lasting effects in important outcome domains. Therefore, home visits also appear to be an effective and efficient public health intervention in European settings.
Home visiting programs constitute an important policy to support vulnerable families with young children. One of their principal aims is to improve infant-parent relationships, so a key measure of their effectiveness is based on observational measures of parent-children interactions. In the present study we provide novel evidence on the effectiveness of home visiting programs in improving mother-child interactions within a randomized controlled trial (RCT) of the Pro Kind program. A major goal of the Pro Kind program is to promote child development by strengthening the intuitive parenting skills of mothers. On this basis, the following research question is addressed in this paper: What is the impact of the Pro Kind home visitation program on the quality of mother-child interaction?
Despite long-term interest in whether welfare benefits motivate fertility, evidence from research has not been consistent. This paper contributes new evidence to this debate by investigating the fertility effect of a German welfare reform. The reform decreased the household income of families on welfare by 18% in the first year after the birth of a baby. Using exclusive access to German social security data on over 460,000 affected women, our analysis finds that the reform leads to a fertility reduction of 6.8%. This result implies that for mothers on welfare, fertility has an income elasticity of 0.38, which is much smaller than that of general populations reported in the literature. Our findings suggest that welfare recipients’ fertility reacts less strongly to financial incentives than the fertility of overall populations.
AbstractThis study examines the immediate and intermediate effects of the COVID-19 pandemic on the well-being of two high school graduation cohorts (2020 and 2021) and how changes in well-being affect students’ educational plans and outcomes. Our unique panel data on 3697 students from 214 schools in 8 German federal states contain prospective survey information on three dimensions of well-being: mental health problems, self-rated health, and life satisfaction. Data is collected several months before (fall 2019), shortly before and soon after (spring 2020) as well as several months after (fall/winter 2020/21) the beginning of the COVID-19 pandemic. Applying difference-in-differences designs, random effect growth curve models, and linear regression models, we find that school closures had a positive immediate effect on students’ well-being. Over the course of the pandemic, however, well-being strongly declined, mainly among the 2021 graduation cohort. We show that a strong decline in mental health is associated with changes in educational and career plans and transition outcomes. As adverse life experiences in adolescence are likely to accumulate over the life course, this study is the first to exhibit potential long-lasting negative effects of the COVID-19 pandemic on education and careers of young individuals.
Im Rahmen der Freibordbemessung an Staudämmen stellt der Wasserübertritt grundsätzlich ein Tabu dar. Mit der Durchführung unabhängiger Untersuchungen erfolgte die Prüfung der Prognosefähigkeit numerischer Verfahren bzgl. des Wellenauflauf- und Wellenumlenkprozesses an Dammböschungen mit und ohne Wellenumlenker. Des Weiteren wurde im Hinblick auf die erforderliche Größe von Wellenumlenkern ein Dimensionierungskonzept entwickelt, welches auf Datensätzen basiert, die mittels kalibrierter hydrodynamisch-numerischer Modelle gewonnen wurden.
Alzheimer’s Disease (AD) results from the progressive loss of neurons in the hippocampus, which affects the capability to produce coherent language. It affects lexical, grammatical, and semantic processes as well as speech fluency. This paper considers the analyses of speech and language for the assessment of AD in the context of the Alzheimer’s Dementia Recognition through Spontaneous Speech (ADReSSo) 2021 challenge. We propose to extract acoustic features such as X-vectors, prosody, and emotional embeddings as well as linguistic features such as perplexity, and word-embeddings. The data consist of speech recordings from AD patients and healthy controls. The transcriptions are obtained using a commercial automatic speech recognition system. We outperform baseline results on the test set, both for the classification and the Mini-Mental State Examination (MMSE) prediction. We achieved a classification accuracy of 80% and an RMSE of 4.56 in the regression. Additionally, we found strong evidence for the influence of the interviewer on classification results. In cross-validation on the training set, we get classification results of 85% accuracy using the combined speech of the interviewer and the participant. Using interviewer speech only we still get an accuracy of 78%. Thus, we provide strong evidence for interviewer influence on classification results.
The “Switchboard benchmark” is a very well-known test set
in automatic speech recognition (ASR) research, establishing
record-setting performance for systems that claim human-level
transcription accuracy. This work highlights lesser-known practical considerations of this evaluation, demonstrating major improvements in word error rate (WER) by correcting the reference transcriptions and deviating from the official scoring
methodology. In this more detailed and reproducible scheme,
even commercial ASR systems can score below 5% WER and
the established record for a research system is lowered to 2.3%.
An alternative metric of transcript precision is proposed, which
does not penalize deletions and appears to be more discriminating for human vs. machine performance. While commercial
ASR systems are still below this threshold, a research system
is shown to clearly surpass the accuracy of commercial human
speech recognition. This work also explores using standardized scoring tools to compute oracle WER by selecting the best
among a list of alternatives. A phrase alternatives representation
is compared to utterance-level N-best lists and word-level data
structures; using dense lattices and adding out-of-vocabulary
words, this achieves an oracle WER of 0.18%.
For dementia screening and monitoring, standardized tests play
a key role in clinical routine since they aim at minimizing subjectivity by measuring performance on a variety of cognitive
tasks. In this paper, we report a study consisting of a semistandardized history taking followed by two standardized neuropsychological tests, namely the SKT and the CERAD-NB.
The tests include basic tasks such as naming objects, learning
word lists, but also widely used tools such as the MMSE. Most
of the tasks are performed verbally and should thus be suitable
for automated scoring based on transcripts. For the first batch
of 30 patients, we analyze the correlation between expert manual evaluations and automatic evaluations based on manual and
automatic transcriptions. For both SKT and CERAD-NB, we
observe high to perfect correlations using manual transcripts;
for certain tasks with lower correlation, the automatic scoring is
stricter than the human reference since it is limited to the audio.
Using automatic transcriptions, correlations drop as expected
and are related to recognition accuracy; however, we still observe high correlations of up to 0.98 (SKT) and 0.85 (CERADNB). We show that using word alternatives helps to mitigate
recognition errors and subsequently improves correlation with
expert scores.
Going Beyond the Cookie Theft Picture Test: Detecting Cognitive Impairments Using Acoustic Features
(2022)
Stuttering is a varied speech disorder that harms an individual’s
communication ability. Persons who stutter (PWS) often use
speech therapy to cope with their condition. Improving speech
recognition systems for people with such non-typical speech or
tracking the effectiveness of speech therapy would require systems that can detect dysfluencies while at the same time being
able to detect speech techniques acquired in therapy.
This paper shows that fine-tuning wav2vec 2.0 [1] for
the classification of stuttering on a sizeable English corpus
containing stuttered speech, in conjunction with multi-task
learning, boosts the effectiveness of the general-purpose
wav2vec 2.0 features for detecting stuttering in speech; both
within and across languages. We evaluate our method on
FluencyBank , [2] and the German therapy-centric Kassel
State of Fluency (KSoF) [3] dataset by training Support Vector
Machine classifiers using features extracted from the finetuned models for six different stuttering-related event types:
blocks, prolongations, sound repetitions, word repetitions,
interjections, and – specific to therapy – speech modifications.
Using embeddings from the fine-tuned models leads to relative classification performance gains up to 27% w.r.t. F1-score.
We are interested in the problem of conversational analysis and
its application to the health domain. Cognitive Behavioral Therapy is a structured approach in psychotherapy, allowing the therapist to help the patient to identify and modify the malicious
thoughts, behavior, or actions. This cooperative effort can be
evaluated using the Working Alliance Inventory Observer-rated
Shortened – a 12 items inventory covering task, goal, and relationship – which has a relevant influence on therapeutic outcomes. In this work, we investigate the relation between this
alliance inventory and the spoken conversations (sessions) between the patient and the psychotherapist. We have delivered
eight weeks of e-therapy, collected their audio and video call
sessions, and manually transcribed them. The spoken conversations have been annotated and evaluated with WAI ratings by
professional therapists. We have investigated speech and language features and their association with WAI items. The feature types include turn dynamics, lexical entrainment, and conversational descriptors extracted from the speech and language
signals. Our findings provide strong evidence that a subset of
these features are strong indicators of working alliance. To the
best of our knowledge, this is the first and a novel study to exploit speech and language for characterising working alliance.
This paper empirically investigates the influence of different data splits and splitting strategies on the performance of dysfluency detection systems. For this, we perform experiments using wav2vec 2.0 models with a classification head as well as support vector machines (SVM) in conjunction with the features extracted from the wav2vec 2.0 model to detect dysfluencies. We train and evaluate the systems with different non-speaker-exclusive and speaker-exclusive splits of the Stuttering Events in Podcasts (SEP-28k) dataset to shed some light on the variability of results w.r.t. to the partition method used. Furthermore, we show that the SEP-28k dataset is dominated by only a few speakers, making it difficult to evaluate. To remedy this problem, we created SEP-28k-Extended (SEP-28k-E), containing semi-automatically generated speaker and gender information for the SEP-28k corpus, and suggest different data splits, each useful for evaluating other aspects of methods for dysfluency detection.
Vocal fatigue refers to the feeling of tiredness and weakness of voice due to extended utilization. This paper investigates the effectiveness of neural embeddings for the detection of vocal fatigue. We compare x-vectors, ECAPA-TDNN, and wav2vec 2.0 embeddings on a corpus of academic spoken English. Low-dimensional mappings of the data reveal that neural embeddings capture information about the change in vocal characteristics of a speaker during prolonged voice usage. We show that vocal fatigue can be reliably predicted using all three types of neural embeddings after 40 minutes of continuous speaking when temporal smoothing and normalization are applied to the extracted embeddings. We employ support vector machines for classification and achieve accuracy scores of 81% using x-vectors, 85% using ECAPA-TDNN embeddings, and 82% using wav2vec 2.0 embeddings as input features. We obtain an accuracy score of 76%, when the trained system is applied to a different speaker and recording environment without any adaptation.
Ein- und Durchschlafstörungen, nichterholsamer Schlaf oder erhöhte Tagesmüdigkeit sind unspezifische Symptome von heute ca. 100 unterscheidbaren Störungsbildern, die in der kommenden 11. Revision der Internationalen statistischen Klassifikation der Krankheiten (ICD-11) erstmals als eigenes Kapitel 7 „Schlaf-Wach-Störungen“ zusammengefasst werden. Mit Blick auf den Fachbereich Psychiatrie und Psychotherapie besteht ein bidirektionaler Zusammenhang zwischen Schlaf-Wach-Störungen und psychischen Erkrankungen. Schlaf-Wach-Störungen können einen unabhängigen Risikofaktor für das Entstehen einer psychischen Erkrankung darstellen und den Erkrankungsverlauf ungünstig beeinflussen. Zudem können Schlaf-Wach-Störungen einer psychischen Erkrankung auch als Frühsymptom vorausgehen und damit ein wichtiger Hinweis bei der Früherkennung sein. Zahlreiche Schlaf-Wach-Störungen können anhand der Anamnese und üblicher klinischer Untersuchungen diagnostiziert werden. Bei spezielleren Fragestellungen können die Untersuchung in einem speziali-sierten Schlaflabor und die Behandlung in einem schlafmedizinischen Zentrum im Sinne einer gestuften Versorgung notwendig sein. Hier ist die Polysomnographie die wichtigste Untersuchungsmethode für die Differenzialdiagnostik, für deren Abrechnung über die Kostenträger heute in Deutschland jedoch keine gesetzliche Grundlage im Bereich neuro-psychiatrischer Störungen besteht. Die vorliegende Arbeit fasst die aktuellen Leitlinien hinsichtlich der Kriterien für eine Untersuchung im Schlaflabor aus Sicht des Fachgebiets Psychiatrie und Psychotherapie zusammen und stellt daraus abgeleitet Forderungen für eine leitliniengerechte Diagnostik und Behandlung.
Shiftwork can be a risk factor for a number of different somatic and psychological health conditions, especially sleep disorders. Shiftworkers sleep less than dayworkers, and 20–40% of them suffer from difficulties initiating and maintaining sleep, which result in reduced capacity for work and social life. A common coping strategy might be the use of alcohol, which presents a health and safety hazard as it further impairs sleep quality and exacerbates sleepiness in the workplace. This review aimed to assess the extent of such possible connections.
Der Begriff „Coronasomnia“ beschreibt populärwissenschaftlich Schlafstörungen, die im Zusammenhang mit der COVID-19-Pandemie in Erscheinung treten. Diese können auch im Anschluss der Pandemie einen Teil der Bevölkerung betreffen. Erste wissenschaftliche Hinweise deuten darauf hin, dass durch die Pandemie entstandene Insomniebeschwerden sich nach dem Ende der Pandemie chronifizieren und somit die schlafmedizinische Gemeinschaft weiterhin beschäftigen werden.
Sleep Disorders in Cancer
(2021)
Sleep disorders, especially insomnia, are very common in different kinds of cancers, but their prevalence and incidence are not well-known. Disturbed sleep in cancer is caused by different reasons and usually appears as a comorbid disorder to different somatic and psychiatric diagnoses, psychological disturbances and treatment methods. There can be many different predictors for sleep disturbances in these vulnerable groups, such as pre-existing sleep disorders, caused by the mental status in cancer or as side effect of the cancer treatment. Methods: A systematic literature review of 8073 studies was conducted on the topic of sleep and sleep disorders in cancer patients. The articles were identified though PubMed, PsycInfo and Web of Knowledge, and a total number of 89 publications were qualified for analysis. Results: The identified eighty-nine studies were analyzed on the topic of sleep and sleep disorders in cancer, twenty-six studies on sleep and fatigue in cancer and sixty-one studies on the topic of sleep disorders in cancer. The prevalence of sleep disturbences and/or sleep disorders in cancer was up to 95%. Discussion: Sleep disturbances and sleep disorders (such as insomnia, OSAS, narcolepsy and RLS; REM-SBD) in cancer patients can be associated with different conditions. Side effects of cancer treatment and cancer-related psychological dysfunctions can be instigated by sleep disturbances and sleep disorders in these patients, especially insomnia and OSAS are common. An evidence-based treatment is necessary for concomitant mental and/or physical states.
AbstractActigraphy has been used for more than 60 years to objectively measure sleep–wake rhythms. Improved modern devices are increasingly employed to diagnose sleep medicine disorders in the clinical setting. Although less accurate than polysomnography, the chief advantage of actigraphs lies in the cost-effective collection of objective data over prolonged periods of time under everyday conditions. Since the cost of wrist actigraphy is not currently reimbursed, this method has not enjoyed wide acceptance to date. The present article provides an overview of the main clinical applications of actigraphy, including the recommendations of specialist societies.
BackgroundThere are only limited reports on the prevalence of restless legs syndrome (RLS) in patients with psychiatric disorders. The present study aimed to evaluate the prevalence and clinical correlates in psychiatric inpatients in Germany and Switzerland.MethodsThis is a multicenter cross-sectional study of psychiatric inpatients with an age above 18 years that were diagnosed and evaluated face-to-face using the International RLS Study Group criteria (IRLSSG) and the International RLS severity scale (IRLS). In addition to sociodemographic and biometric data, sleep quality and mood were assessed using the Pittsburgh Sleep Quality Index (PSQI), the Insomnia Severity Index (ISI), the Epworth Sleepiness Scale (ESS), and the Patient Health Questionnaire (PHQ-9). In addition to univariate statistics used to describe and statistically analyze differences in variables of interest between patients with and without RLS, a logistic model was employed to identify predictors for the occurrence of RLS.ResultsThe prevalence of RLS in a sample of 317 psychiatric inpatients was 16.4%, and 76.9% of these were diagnosed with RLS for the first time. RLS severity was moderate to severe (IRLS ± SD: 20.3 ± 8.4). The prevalences in women (p = 0.0036) and in first-degree relatives with RLS (p = 0.0108) as well as the body mass index (BMI, p = 0.0161) were significantly higher among patients with RLS, while alcohol consumption was significantly lower in the RLS group. With the exception of atypical antipsychotics, treatment with psychotropic drugs was not associated with RLS symptoms. Regarding subjective sleep quality and mood, scores of the PSQI (p = 0.0007), ISI (p = 0.0003), and ESS (p = 0.0005) were higher in patients with RLS, while PHQ-9 scores were not different. A logistic regression analysis identified gender (OR 2.67; 95% CI [1.25; 5.72]), first-degree relatives with RLS (OR 3.29; 95% CI [1.11; 9.73], ESS score (OR 1.09; 95% CI [1.01; 1.17]), and rare alcohol consumption (OR 0.45; 95% CI [0.22; 0.94] as predictors for RLS.ConclusionsClinically significant RLS had a high prevalence in psychiatric patients. RLS was associated with higher BMI, impaired sleep quality, and lower alcohol consumption. A systematic assessment of restless legs symptoms might contribute to improve the treatment of psychiatric patients.
IntroductionIt is unclear how internet-delivered cognitive-behavioural therapy for insomnia (CBT-I) can be integrated into healthcare systems, and little is known about the optimal level of therapist guidance. The aim of this study is to investigate three different versions of a stepped care model for insomnia (IG1, IG2, IG3) versus treatment as usual (TAU). IG1, IG2 and IG3 rely on treatment by general practitioners (GPs) in the entry level and differ in the amount of guidance by e-coaches in internet-delivered CBT-I.Methods and analysisIn this randomised controlled trial, 4268 patients meeting International Classification of Diseases, Tenth Revision (ICD-10) criteria for insomnia will be recruited. The study will use cluster randomisation of GPs with an allocation ratio of 3:3:3:1 (IG1, IG2, IG3, TAU). In step 1 of the stepped care model, GPs will deliver psychoeducational treatment; in step 2, an internet-delivered CBT-I programme will be used; in step 3, GPs will refer patients to specialised treatment. Outcomes will be collected at baseline, and 4 weeks, 12 weeks and 6 months after baseline assessment. The primary outcome is insomnia severity at 6 months. An economic evaluation will be conducted and qualitative interviews will be used to explore barriers and facilitators of the stepped care model.Ethics and disseminationThe study protocol was approved by the Ethics Committee of the Medical Centre—University of Freiburg. The results of the study will be published irrespective of the outcome.Trial registration numberDRKS00021503.
COVID-19-Pandemie und Schlaf
(2022)
TU-178. Maladjustment of pressure settings of programmable shunt valves by weak magnetic fields
(2022)
Insomnie und ein reduzierter Schlaf gehören zu den häufigsten Beschwerden, die im Verlauf einer Schwangerschaft auftreten können, vor allem im dritten Trimester. Rund 66–94 % aller Schwangeren geben Schlafprobleme an, die mit negativen physischen und psychischen Konsequenzen für das schwangere Individuum wie auch für das ungeborene Kind verbunden sind.
BackgroundSleep disruption (SD) increases sympathetic activity and cortisol secretion, and delays cognitive functions such as reaction-time (RT). Sympathetic activity of disturbed sleepers, is similar to those of so-called decision-reinvesters. Decision-reinvestment refers to traits in individuals with greater tendency to ruminate and reinvest in their decisions, with significant decrease in both motor-control and cognitive performance. Decision-making quality is a crucial attribute to athletic performance which relies on RT. Consequently, SD affects pitch-performance negatively, particularly in decision-reinvesters. This observational pilot-study examined the relationship between SD and cognitive function, perceived health, as well as reinvestment strategies. The hypothesis was that athletes with lower SD perceive their health better, report lower stress levels, perform better in cognitive tasks, and show lower tendency for decision-reinvestment.MethodsTwenty-one football player recorded their sleep with fit-trackers for 7 nights. Participants self-reported their mental and physical health, decision-reinvestment strategy, sleep behaviour, and perceived stress levels. Athletes then performed a set of cognitive tests to examine memory function (Backwards Corsi), selective attention (STROOP), and cognitive flexibility (Wisconsin Card Sorting Test, WCST). Normality was tested with a Shapiro-Wilk test, and analysed with a Pearson's or Spearman's correlation test.ResultsSignificant correlation appeared between extended sleep-interruptions and Backwards Corsi RT, r = 0.66, p = 0.010, as further in total sleep time and wellbeing r = 0.50, p = 0.029. A negative correlation exist in regard of pain scores and Backwards Corsi scores r = −0.57, p = 0.110. Physical health correlated with error-rates in the WCST, r = 0.69, p ≤ 0.001. Also, reinvestment negatively correlated with physical health, r = −0.80, p ≤ 0.001.ConclusionWellbeing relies on total sleep-time. Athletes with extended sleep-interruptions are slower in recalling memory, and those with greater reported pain have lower memory scores. Participants who rate physical health greater, have more error-rates in the WCST; indicating that cognitive flexibility is enhanced in individuals with inferior perceived health. However, individuals with lower physical health scores also have greater tendency to ruminate and reinvest in decisions, suggesting interrelation between reinvestment and physical health.
In the research project AVerdi the influence of photonic sintering methods on the resulting electrical conductivity, sintering duration and adhesion of digitally printed silver nanoparticle inks was investigated and compared to convective sintering. Conductor paths with film thicknesses below 1 μm were applied on flexible polymer substrates via inkjet printing. Aerosoljet printing was used to generate thicker lines up to 11 μm on injection molded substrates. Photonic sintering was carried out with near infrared emitters or ultraviolet light emitting diodes. For inkjet printed structures on polyimide a conductivity up to 24 % relative to bulk silver was achieved after a sintering duration of 2 s and 5 s for the near infrared and the ultraviolet light source, respectively. Oven sintered samples showed an electrical conductivity of 14 % after 1 h at 200° C. On polyethylene terephthalate a conductivity around 7 % was achieved after irradiation with near infrared light for 1 s, whereas convectively sintered samples showed a conductivity around 4 %. All material combinations sintered by the different methods showed good adhesion. The overall results of long-term behavior after thermal-cycling, regarding electrical conductivity and adhesion, show that the photonically sintered structures achieve similar results compared to the reference. The photonically sintered structures generated with the aerosoljet on polyamide 6 achieved conductivity values up to 19 %, which were comparable to the furnace sintered reference samples. On liquid crystal polymer substrates conductivity values reached up to 35 % after sintering with ultraviolet light emitting diodes for 60 s. Oven sintered samples showed a conductivity around 25 % after 1 h at 150° C. The adhesion of the silver nanoparticle ink on liquid crystal polymer and polyamide 6 substrates is better than with the reference samples. The reliability tests show fewer failures with alternative sintered samples. In this study only the results for inkjet printed structures are presented.
The integration of SMT components is necessary to produce more complex assemblies within the framework of conformable electronics. During High-Pressure-Forming (HPF) and subsequent overmolding electronic components must withstand high amounts of stress. In this study 0402- as well as 0603-sized chip resistors were mounted on different common polymer substrates using conductive adhesive paste followed by electrical and mechanical evaluation. Prior to HPF electronic components were positioned in areas of different local deformation. After HPF the specimen were characterized by shear force testing and electrical resistance measurements. In a similar manner, electronic components were tested to assess the mechanical behavior during injection molding. To examine different melt induced stress scenarios, electronic components were arranged parallel as well as perpendicular to the flow direction of the melt at different positions. Additionally, three different injection speeds were evaluated to assess the influence on the electrical conductivity and functionality of the assemblies. It was found that meandering of conductors is necessary for higher deformations. El. components (without additional nonconductive adhesives) can be placed in areas of up to 15% deformation, smaller package sizes seem to be advantageous for HPF. Regarding overmoulding, it was found that larger components (larger bonding area) is beneficial. Also, placement near the injection point, as well as low injection speeds should be avoided. Overall, el. components should be protected (using globtops / underfills etc.) to withstand consecutive HPF and overmoulding.
In this paper the stress on electronic components for Conformable Electronic applications is evaluated. During High-Pressure-Forming (HPF) and subsequent overmolding (OM) these components have to withstand high amounts of stress. Globtops are used to protect 0402 as well as 0603-sized components mounted on different polymer substrates. The components are placed in different areas of deformation (for HPF) and melt velocities (for OM). The components are afterwards examined by means of electrical resistance measurements and shear force measurements as well as micro-sections. For conductive adhesive, the globtop material positively influenced the resistance change after deformation, soldered assemblies showcased good formability up to 20 %. The shear force drop caused by higher deformations could be mitigated using globtop materials. Soldered components were able to withstand OM when globtops were used. Here, smaller components seem to take less damage from the impacting melt. Components should be placed in areas where the melt has cooled down to prevent damages.
Evaluation of detatchable board-to-board interconnects on screen printed electronic structures
(2021)
Hybrid printed electronics (HPE) combines advantages of conventional electronics manufacturing technologies such as surface mount technology with those of printed electronics in order to realize more complex electronic systems. To realize the final product, such HPE subassemblies have to be connected to higher-level assemblies. So far interconnection techniques for the so-called level 3 interconnection between printed subsystems and standard electronics have not yet been considered adequately in scientific research. In this paper, alternative detachable level 3 interconnection technologies, i.e. spring loaded contact pins, zero insertion force (ZIF) as well as Non-ZIF connectors are investigated systematically regarding their electrical behaviour against the background of printed electronics. Screen-printed silver filled polymer thick film paste is used to realize printed conductor patterns on flexible polymer substrates, which are connected later on with the alternatives mentioned above. Transition resistance is measured using the four wire method as produced, after repeated mating cycles as well as after accelerated aging tests. The various electrical contacts are subjected to thermal stress in temperature cycling testing and during aging at a constant high temperature. As a result it can be stated, that the sping-loaded contact pins used in this investigation show superior behavior compared with the selected connectors in terms of resistance increase after mating cycles. Concerning long-term behavior after thermal cyling and high temperature storage, all investigated alternaives reveal convincing results.
Characterization of Crimp Interconnections for Hybrid Integration of Screen-Printed Electronics
(2021)
In this work, electrical contacts between piercing-crimp terminals and screen-printed silver structures on three different polymeric films are characterized electrically and mechanically before and after accelerated thermal aging tests. Temperature cycling and constant thermal load tests were performed as like as ampacity and resistance measurements and tensile tests. The tensile tests show that the mechanical strength of the crimp connection depends on substrate material, but is independent of the aging state. For all joints, breaking forces of more than 100 N were achieved. Furthermore, some of tested connections can be loaded with more than 2.5 A in unaged state till they heat up by 25 K. Besides that, accelerated thermal aging generally leads to a reduction in electrical resistance in our experiments.
In this work, on different substrate materials thermally cured polymer thick-film (PTF) pastes are connected to surface mount technology resistors using a SnBiAg solder alloy. The effect of substrate pre-treatment with atmospheric plasma and thermal cycling on the shear strength of these interconnections is investigated, and the shear forces obtained are graded using United States Defense Standard / Military Standard (MIL-STD) 883. In particular, the build-up of solder interconnections on conductive structures made of commercially available copper-containing PTF pastes and their mechanical characterization is novel. As well as the mechanical characterization of conductive structures, made of PTF pastes, on plasma-treated substrates and their grading using the MIL-STD 883. In addition, interconnections with silver-containing conductive structures are realized for comparison. Depending on the interconnection system, component mean shear forces of up to 31 N are achieved. While some systems meet the 1.25× criterion of MIL-STD 883, the majority of the systems investigated do not meet the 1.00× criterion. Hereby, the adhesion between the conductive structure and the substrate usually fails. Plasma pre-treatment shows an adhesion-increasing effect only for a proportion of substrate materials used, as does thermal aging. But thermal loads can also impair the adhesive strength.
The vapor pressures of two binary mixtures containing 2-trifluoroethanol (TFE) + 1,3-dimethyl-2-imidazolidinone (DMI) and TFE + 2-pyrrolidone (PYR), were investigated at temperatures T = (274.15 to423.15) K using two different static method installations. Both combinations were modelled using an extended
Clausius-Clapeyron equation with concentration dependent parameters and the NRTL equation with temperature dependent parameters. The best fit was obtained using the NRTL equation.
DIN SPEC 5031-100 and CIE S 026:2018 are regulatory frameworks that are intended to establish health-preserving indoor lighting in Europe. Therefore, they are crucial for the visual environment and its sustainability. The standards are largely congruent. Inconsistencies should now be harmonized with the newly published draft standard DIN/TS 5031-100, for which the objection period ended on 3 June 2020; thus, it can be expected that the standard will soon be put into operation. This publication provides the reader with a detailed technical as well as medical overview of the scope and background information on how the standard came about. Applicable laws, ordinances and standards were compiled across countries, and related studies were reviewed. It is demonstrated that the focus of this new standard, as with previous versions, is on the melanopic sensitivity of ganglion cells. The authors base this on a literature search for projects about ecological lighting design over the past 20 years. However, in practice, the publication of the standard does not yet completely counteract the health effects of inappropriate indoor lighting.
This publication describes an application of a
Truncated Signed Distance Mapping approach for disaster
intervention in underground mine shafts through geometrical
change detection of the shaft walls. The paper describes two
main problems of such an approach (aligning two potentially
huge point clouds and automatic change detection by comparing
the reconstructed volumes) and explains in detail the proposed
solution.