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SMath with Maxima
(2023)
Untersuchung der Rotorfestigkeit von permanenterregten Synchronmaschinen mit vergrabenen Magneten
(2023)
Diese Projektarbeit behandelt die mechanische Simulation der Rotoren von permanenterregten Synchronmaschinen für den Festigkeitsnachweis. Hierzu wird die Finite-Elemente-Methode mit dem Programm CalculiX verwendet. Als Beispiel wird der Elektromotor des Toyota Prius II im Detail betrachtet. Hierbei werden die unterschiedlichen Lasten modelliert, dazu zählen neben der Zentrifugalkraft auch der Innendruck durch eine Presspassung sowie die elektromagnetischen Kräfte. Für die Modellierung von Kräften auf der Rotoroberfläche wird eine Methodik zur Umsetzung in CalculiX entwickelt und anhand eines Beispielmodells demonstriert. Der angestrebte Festigkeitsnachweis kann im Rahmen dieser Arbeit erbracht werden. Weiterhin wird gezeigt, dass der Einfluss der elektromagnetischen Kräfte im Arbeitspunkt mit der höchsten Drehzahl sehr gering ausfällt. Insgesamt bietet diese Arbeit die Grundlagen für mechanische Modellierungen von Rotoren unter Berücksichtigung aller Kräfte. Dies kann direkt auf andere Elektromotoren angewendet werden.
Der Erwartungswert einer Zufallsgröße kann generell am Graphen ihrer Verteilungsfunktion durch eine naheliegende Gleichheit zweier Flächeninhalte festgelegt werden. Äquivalent dazu lässt er sich mit zwei uneigentlichen Riemann-Integralen darstellen. Davon ausgehend werden die Tschebyschow-Ungleichung und ihre Modifikation mit strikten Ungleichheitszeichen hergeleitet.
A sample set of calculations is presented in this supplemental document to analytically estimate joint distortion for gas metal arc lap joining of aluminum and steel thin sheets following the published article "Analytical Estimation of Thermomechanical Distortion and Interface Layer Thickness for Gas Metal Arc Lap Joining of Dissimilar Sheets"
Large three-dimensional metallic parts can be printed layer-by-layer using gas metal arc directed energy deposition (GMA-DED) process at a high deposition rate and with little or no material wastage. Fast responsive real-time monitoring of GMA-DED process signatures and their transient variations is required for printing of dimensionally accurate and structurally sound parts. A systematic experimental investigation is presented here on multi-layer GMA-DED with two different scanning strategies using a high strength low alloy (HSLA) filler wire. The dynamic metal transfer, melt pool temperature field and its longitudinal cross-section, and arc voltage and current are monitored synchronously. The transient arc heat input and the melt pool solidification cooling rate are estimated from the monitored signals. The layer-wise variations of the melt pool dimension, surface temperature profile, thermal cycles, and solidification cooling rate are examined for different scanning strategies. It is comprehended that the part defects can be minimized, and the mass production of zero-defect parts can be achieved in GMA-DED process with synchronized monitoring and assessment of the real-time process signatures.
An approach for analyzing business process execution complexity based on textual data and event log
(2023)
With the advent of digital transformation, organizations increasingly rely on various information systems to support their business processes (BPs). Recorded data, including textual data and event log, expand exponentially, complicating decision-making and posing new challenges for BP complexity analysis in Business Process Management (BPM). Herein, Process Mining (PM) serves to derive insights based on historic BP execution data, called event log. However, in PM, textual data is often neglected or limited to BP descriptions. Therefore, in this study, we propose a novel approach for analyzing BP execution complexity by combining textual data serving as an input at the BP start and event log. The approach is aimed at studying the connection between complexities obtained from these two data types. For textual data-based complexity, the approach employs a set of linguistic features. In our previous work, we have explored the design of linguistic features favorable for BP execution complexity prediction. Accordingly, we adapt and incorporate them into the proposed approach. Using these features, various machine learning techniques are applied to predict textual data-based complexity. Moreover, in this prediction, we show the adequacy of our linguistic features, which outperformed the linguistic features of a widely-used text analysis technique. To calculate event log-based complexity, the event log and relevant complexity metrics are used. Afterward, a correlation analysis of two complexities and an analysis of the significant differences in correlations are performed. The results serve to derive recommendations and insights for BP improvement. We apply the approach in the IT ticket handling process of the IT department of an academic institution. Our findings show that the suggested approach enables a comprehensive identification of BP redesign and improvement opportunities.
Context awareness is critical for the successful execution of processes. In the abundance of business process management (BPM) research, frameworks exclusively devoted to extracting context from textual process data are scarce. With the deluge of textual data and its increasing value for organizations, it becomes essential to employ relevant text analytics techniques to increase the awareness of process workers, which is important for process execution. The present paper addresses this demand by developing a framework for context awareness based on process executions-related textual data using a well-established layered BPM context model. This framework combines and maps various text analytics techniques to the layers of the context model, aiming to increase the context awareness of process workers and facilitate informed decision-making. The framework is applied in an IT ticket processing case study. The findings show that contextual information obtained using our framework enriches the awareness of process workers regarding the process instance urgency, complexity, and upcoming tasks and assists in making decisions in terms of these aspects.
Ubiquitous Music is an interdisciplinary research area that combines methodologies from music, computer science, education, creativity studies, human sciences and engineering.
The Ubiumus 2023 symposium, held at Ulster University and North West Regional College in Derry~Londonderry, Northern Ireland, included contributions on the following topics:
Rapid Prototyping and Live Environments
Ecological Approaches to Ubiquitous Music
Ubiquitous Music Creative Practices, Tools and Influences
The symposium also included a number of artistic contributions and workshops, which are also discussed in the proceedings volume. A number of events (including all paper presentations, an invited lecture, a panel discussion, and a keynote and associated performance) were also documented via video, with a link available in this Proceedings volume.
Climate change, but also geopolitical circumstances, are moving topics such as energy efficiency and renewable energies more and more into the focus of the population, economy , and politics. As a result, the will to optimize new and existing energy systems extends from private individuals to companies and even entire communities. This work describes the development and usage of a new software called FINEconcepts which creates a digital twin of an energy system. This virtual model can then be used to optimize the energy system based on annual costs, CO2 emissions or other relevant criteria such as self-sufficiency. Because all system components, which include renewable technologies as well, can be added as a building block with chosen but changeable parameters, the software allows the user to explore and awaken interest and understanding of technologies that were previously considered too costly, irrelevant, or unrealistic. Implemented projects in small and large companies as well as in residential areas did prove, that the usage of FINEconcepts leads not only to more efficient energy systems by increasing the use of renewable energy, but also increased knowledge and understanding in terms of energy. Besides economics, ecology and security, understanding is an equally important factor in achieving a sustainable energy supply.
The problem of increasing the efficiency of existing photodetectors and creating their new types attracts much research attention. Among new photodetector types are photosensitive structures based on cascade concentrators, whose operational principle involves the absorption of optical radiation followed by its reemission at a longer wavelength and radiation concentration onto a highly efficient small-area photodetector. The absorption and re-emission spectra of each cascade layer depend on the characteristics of the material used. Сolloidal quantum dots are among the most promising materials for cascade layers due to their manufacturing technology, which provides for accurate control over the photoluminescence maximum position. It seems highly relevant to develop and to study photosensitive structures with cascade concentrators of various shapes based on CdS, CdSe/ZnS, and PbS colloidal quantum dots. Aim . To develop photosensitive structures with a wide-range sensitivity spectrum based on concentrators containing arrays of metal chalcogenide CQDs and to study their characteristics. Materials and methods . Cascade photosensitive structures were manufactured based on layers made of polymethyl methacrylate and layers of colloidal quantum dots embedded in a polystyrene matrix. Results . Three-layer concentrators were manufactured with different colloidal quantum dots in each concentrator layers. A 22 % increase in the output power was observed for a three-layer cascade structure based on different cascade layer materials compared to a similar structure using a single layer concentrator. Conclusion . The conducted studies showed an increase in the efficiency of photosensitive structures with a cascade concentrator based on colloidal quantum dots of various types (CdS, CdSe/ZnS, and PbS) in the cascade layers.
Illuminated bridges have become important assets to navigable aquatic systems. However, if artificial light at night (ALAN) from illuminated bridges reaches aquatic habitats, such as rivers, it can threaten the river's natural heterogeneity and alter the behavioural responses of migratory fish. Here, via a pilot study, we quantified levels of ALAN at illuminated bridges that cross a river and, propose a conceptual model to estimate its potential implications on two migrating fish species with contrasting life histories. Night-time light measurements on the river Spree in Berlin were performed continuously along a transect and in detail at seven illuminated bridges. Photometric data of the pilot study showed rapidly increased and decreased light levels at several illuminated bridges from which we derived several model illumination scenarios. These illumination scenarios and their potential effect on migrating Atlantic salmon smolts (Salmo salar) and European silver eel (Anguilla anguilla) are presented as a conceptual model, considering illuminated bridges as behavioural barriers to fish migration. ALAN's adverse effects on freshwater habitats must be better researched, understood, managed, and properly communicated to develop future sustainable lighting practices and policies that preserve riverscapes and their biodiversity.
So weit das Auge trägt
(2023)
Sichtweiten in der Atmosphäre reichen von wenigen Metern im Nebel bis zu einigen hundert Kilometern bei extrem guten Fernsichtbedingungen. Die zugrundeliegende Physik geht vom Wahrnehmungskontrast aus. Dieser ändert sich mit der Entfernung entlang der Sichtlinie zwischen Objekt und Auge aufgrund von Lichtstreuung und Absorption an den Bestandteilen der Atmosphäre. Dazu kommt bei der Fernsicht die Refraktion, die es erlaubt, auch über den durch die Kugelform der Erde geometrisch bedingten Horizont hinaus zu sehen.
In this study, we have investigated the form of velocity and pressure functions of a fluid oscillating between two parallel glass sheets that form a circular Hele-Shaw cell. The flow has been considered to be radial, incompressible and laminar. The time-dependent Navier-Stokes equation has been solved in cylindrical coordinates using Fourier transform, and the oscillating flow velocity across the thickness of the cell has been obtained at different times. The flow velocity function in the unsteady state is related to the vertical component of the coordinates in the form of parabolic functions and also to the inverse of the radial component. The time dependence appears as a simple harmonic with a frequency equal to the oscillation frequency. The velocity of the flow is maximum at the middle of the cell along its height and gradually decreases from the middle towards the top or bottom plane and reaches zero. Pressure does not depend on the height and changes logarithmically with the radius. The dependence of pressure on time is also a simple harmonic with the external frequency, but it has a phase shift with respect to the velocity.
The Patellostabilometer: A New Device for Quantification of Mediolateral Patella Displacement
(2023)
Mediolateral patella displacement is of interest for diagnostics and clinically relevant
research questions. Apart from manual testing, no standardized method is currently available. Proper
quantification of patella mobility is necessary to better understand pathologies at the patellofemoral
joint. Patella mobility was assessed in 25 healthy individuals using a Patellostabilometer, a new
prototype instrument for quantification of the mediolateral patella displacement. The participants
underwent measurements of the mediolateral displacement three times using the Patellostabilome-
ter. A maximal force of 10 N was applied for patella movement. Additionally, leg length and
circumference of the knee, upper- and lower-leg were measured. Lateral patella displacement of
18.27 ± 3.76 mm (range 15.85–20.64 mm, interquartile range (IQR) of 4.79) was measured. The medial
patella displacement showed 24.47 ± 6.59 mm (range 19.29–29.76 mm, IQR of 10.47). The test–retest
measurement error was 2.32 ± 1.76 mm (IQR of 2.38 mm), with five outliers. There was greater
test–retest variability between the measurements of the medial displacement compared to the lateral
one. The test–retest variability reached 7% of the patella displacement. Other parameters provided no
significant correlations. Based on the natural patellofemoral mobility, a precise and clinically relevant
quantification of patella mobility is allowed.
The public sector faces several challenges, such as a number of external and internal demands for change, citizens' dissatisfaction and frustration with public sector organizations, that need to be addressed. An alternative to the traditional top-down development of public services is co-creation of public services. Co-creation promotes collaboration between stakeholders with the aim to create better public services and achieve public values. At the same time, data analytics has been fuelled by the availability of immense amounts of textual data. Whilst both co-creation and TA have been used in the private sector, we study existing works on the application of Text Analytics (TA) techniques on text data to support public service co-creation. We systematically review 75 of the 979 papers that focus directly or indirectly on the application of TA in the context of public service development. In our review, we analyze the TA techniques, the public service they support, public value outcomes, and the co-creation phase they are used in. Our findings indicate that the TA implementation for co-creation is still in its early stages and thus still limited. Our research framework promotes the concept and stimulates the strengthening of the role of Text Analytics techniques to support public sector organisations and their use of co-creation process. From policy-makers' and public administration managers' standpoints, our findings and the proposed research framework can be used as a guideline in developing a strategy for the designing co-created and user-centred public services.
Disclinations or disclination clusters in smectic C freely suspended films with topological charges larger than one are unstable. They disintegrate, preferably in a spatially symmetric fashion, into single defects with individual charges of +1, which is the smallest positive topological charge allowed in polar vector fields. While the opposite process of defect annihilation is well-defined by the initial defect positions, disintegration starts from a singular state and the following scenario including the emerging regular defect patterns must be selected by specific mechanisms. We analyze experimental data and compare them with a simple model where the defect clusters adiabatically pass quasi-equilibrium solutions in one-constant approximation. It is found that the defects arrange in geometrical patterns that correspond very closely to superimposed singular defect solutions, without additional director distortions. The patterns expand by affine transformations where all distances between individual defects scale with the same time-dependent scaling factor proportional to the square-root of time.
We investigate micrometer-sized flat droplets consisting of an isotropic core surrounded by a nematic rim in freely suspended smectic A liquid-crystal films. In contrast to purely isotropic droplets which are characterized by a sharp edge and no long-range interactions, the nematic fringe introduces a continuous film thickness change resulting in long-range mutual attraction of droplets. The coalescence scenario is divided in two phases. The first one consists in the fusion of the nematic regions. The second phase involves the dissolution of a thin nematic film between the two isotropic cores. The latter has many similarities with the rupture of thin liquid films between droplets coalescing in an immiscible viscous liquid.
Coalescence of biphasic droplets in free-standing smectic films is controlled in part by the rupture of a thin nematic membrane separating the isotropic droplet cores.
Fast protein and metabolite liquid chromatography (FPLMC) was introduced years ago to enable the easy separation of high-molecular compounds such as proteins from small molecules and the identification of the low-molecular substances. In this paper, the method is applied for the rapid evaluation of freshness and monitoring the aging of animal meat and fish. A novel chromatographic sensor was developed with a deep UV LED-based photometric detection unit (255–265 nm), an original flow cuvette and registration scheme; the processing of a chromatogram with the sensor takes approximately 15 min. Strict isochronism between the elution of ATP metabolites, mainly hypoxanthine (Hx) and inosine monophosphate (IMP), and the time of maturation of meat or fish, was discovered. A new freshness index H* = [Hx]/[IMP] was introduced, which is proportional to the instrumental delay time in the FPMLC chromatograms: the H* index < 0.5 indicates the presence of inosine monophosphate (IMP) and the high quality of the meat or fish. Reasonably strong correlations were revealed between data obtained by FPMLC and total volatile basic nitrogen TVB-N (for fish) or volatile fatty acids VFA (for meat) content. Moreover, putative nucleotide salvage and an increase in the concentration of IMP were observed in fish after heat treatment using the FPMLC sensor and NMR technique.