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To find the optimal system-level design of hybrid electric vehicles (HEVs), component models are used in simulations to evaluate a large number of different designs within a high dimensional design space. As the electrical machine (EM) represents a key component of the HEV powertrain in terms of energy consumption, models require scalability and sufficient accuracy with manageable computational effort. This paper presents a novel approach for the development of scalable EM models based on Neural Networks (NN). The models are trained with data derived by a Finite Element Analysis (FEA) based scaling procedure and capable to represent the characteristics of a wide range of EM designs without the incorporation of further details. Once a model is trained, it can be directly used in system-level design optimization. The practicality of the model is proven within an exemplary simulation study and its goodness of fit to the training data is validated by a statistical analysis. This approach can help to reduce the computational effort of EM efficiency maps calculation, since only a small number of time-consuming FEA based scaling simulations must be performed prior to the optimization.
Polymer materials that regulate the relative humidity in their environment are relevant for applications in the packaging and building sectors. By integration of salts in polymer structures, such materials are able to absorb and desorb high amounts of water vapor. In this study, films of polylactic acid and polypropylene with dispersed calcium chloride (2 and 4 wt %) were produced and biaxially stretched to induce the formation of cavities. The resulting cavities in these films account up to 10 vol % and are able to contain emerging calcium chloride solution formed by water vapor absorption. These films absorb reversibly up to 15 wt % water vapor at 75% relative humidity at 23 °C. This absorption behavior is described by effective diffusion and effective sorption coefficients. Using a simple model, the effective water vapor diffusion coefficient of these films can be estimated from the permeation coefficient of the polymer and the sorption coefficient of the absorber.
Dieser Beitrag behandelt ein erweitertes analytisches Berechnungsmodell zum mechanischen Verhalten von beliebig rechtwinklig berandeten Mehrschraubenverbindungen (MV). Es werden die Modellvoraussetzungen, -einschränkungen, Theorie und Ergebnisgüte vorgestellt. Dazu werden die Ergebnisse des analytischen Berechnungsmodells den Ergebnissen der numerischen Untersuchungen gegenübergestellt.
Die mechanischen Eigenschaften additiv gefertigter Bauteile lassen sich nicht nur durch bessere Verfahrens- und Anlagentechnik steigern. Vor allem beim Lasersintern lohnt sich ein genauer Blick auf das eingesetzte Polymerpulver. Eine umfangreiche Untersuchung zeigt, warum und wie sich eine spezifische Pulverqualifizierung auswirkt.
The mechanical properties of additively produced components can only be increased by means of improved processing and plant technology. Particularly with laser sintering, a closer look at the polymer powder used is worthwhile. A comprehensive investigation shows why and how such a specific powder qualification has an effect.
Polymer powders for laser sintering must exhibit special intrinsic and extrinsic properties. A new concept for the characterization and evaluation of laser sintering powders permits conclusions to be drawn about aging as well as the suitability of novel powder systems – even before the first build job.
Um konkrete Kundenanforderungen beim Vertrieb neuer Fahrzeuge zuverlässig berücksichtigen zu können, wurde ein Verfahren erarbeitet, mit dem sich Straßen aus Sicht wesentlicher Einsatzparameter wie z.B. die Straßengüte, der Straßentyp sowie die Längs- und Querdynamik aus Sicht der Beanspruchung bewerten und kategorisieren lassen. Das Belastungs- und Beanspruchungsgeschehen lässt sich weitgehend fahrzeugunabhängig nach Höhe, Häufigkeit und Frequenz anhand erfasster Beschleunigungen zutreffend beschreiben. So können Straßen aus Sicht der Beanspruchung bewertet und in Wort und Bild beschriebenen Straßenqualitäts-klassen zugeordnet werden. Umgekehrt erlauben geeignete Kunden-Abfragen mittels eines Anforderungs- und Einsatzkataloges zu Straßenqualität und Einsatzparametern, die kundengerechte Konfiguration von Fahrzeugen.
Eine Möglichkeit zum verstärkten Schutz kühlpflichtiger Molkereiprodukte gegenüber den in der Logistikkette auftretenden mechanischen Belastungen besteht in der räumlichen Trennung von Lebensmitteln und Temperierelementen innerhalb der Versandverpackung. Je nach Art der Isolierverpackung kann das Temperaturhaltevermögen durch die optimierte Anordnung der Temperierelemente deutlich gesteigert werden.
Der Versand kühlpflichtiger Molkereiprodukten muss unter Einhaltung eines definierten Temperaturbereichs erfolgen. Die systematische Analyse auftretender Wärmetransportprozesse an Isolierverpackungen verdeutlicht deren Aufbau und Wirkungsprinzip und signalisiert ergebnisrelevante Einflussgrößen auf das Temperaturhaltevermögen.
Die rasant voranschreitende Digitalisierung treibt die Vermarktung und den Vertrieb von Lebensmitteln via Internet voran. Allerdings weisen die meisten Molkereiprodukte eine enorme Empfindlichkeit gegenüber den in der Logistikkette typisch auftretenden Belastungsarten auf. Die Sicherstellung eines hohen Qualitätsniveaus fordert deren verstärkten Schutz durch eine geeignete Versandverpackung.
In order to be able to reliably take account of specific customer requirements when selling new vehicles, a method has been developed with which roads can be compared from the point of view of essential operational parameters such as, evaluate and categorize the road grade, the type of road and the longitudinal and lateral dynamics in terms of the load. The load and stress conditions can be described largely vehicle-independent according to height, amount and frequency based on detected accelerations. Hence, roads can be assessed in view of stress and combined to street-quality classes described in words and pictures. Conversely, suitable customer queries by means of a requirement catalog for road quality and operational parameters allow a specific configuration of vehicles.
Equations of the form ?[?] = 0, ?: ? ⟶ ?̅ smooth, ?, ?̅ real Banach spaces are investigated with the aim of continuing the basic solution ?[0] = 0 with ? ′ [0] Fredholm operator to a solution curve ?[?(?)] = 0 with the implicit function theorem. If ? ′ [0] is surjective, then the transversality condition of the implicit function theorem can be satisfied in a straightforward way, yielding a regular solution curve, whereas otherwise the equation ?[?] = 0 has to be extended appropriately for reaching a surjective linearization accessible to the implicit function theorem. This extension process, implying in the first step the standard bifurcation theorem of simple bifurcation points, is continued arbitrarily, yielding a sequence of bifurcation results presumably being applicable to bifurcation points with finite degeneracy.
The system of undetermined coefficients of a bifurcation problem
?[?] = 0 in Banach spaces is investigated for proving the existence of families of solution curves by use of the implicit function theorem. The main theorem represents an Artin-Tougeron type result in the sense that approximation of order 2? ensures exact solutions agreeing up to order ? with the approximation
[13], [22]. Alternatively, it may be interpreted as Hensel’s Lemma in Banach spaces. In the spirit of [9] and [18], the required surjectivity condition is interpreted as a direct sum condition of order ? that allows for solving the remainder equation
with respect to graded subspaces derived from an appropriate filtration [24], [25]. In the direction of these subspaces, the determinant can be calculated in a finite dimensional setting, enabling the investigation of secondary global bifurcation phenomena by sign change of Brouwer’s degree [18]. The direct sum
condition seems to be a generalization of the direct sum condition introduced in [9].
The implicit function theorem delivers stability of ? leading coefficients [?̅1 , … , ??̅] with respect to perturbations of order 2? +1 and uniqueness in pointed wedges around the solution curves. Further, denoting by ?̅∞ the subset of arc space ?∞ with [?̅1 , … , ??̅] fixed, ?̅∞ is iteratively approximated by ?̅ 2?+? as ? → ∞. In addition, a lower bound of the Greenberg function ?(?) of a singularity is constructed by use of a step function obtained from ?-degree of different solution curves.
Finally, based on Kouchnirenko’s theorem [17] and an extension in [6], the results are applied to Newton-polygons where it is shown that the Milnor number of a singularity can be calculated by the sum of ?-degrees of corresponding solution curves. Simple ???-singularities are investigated in detail. The main theorem represents a version of strong implicit function theorem in Banach spaces, possibly comparable to theorems in [2]. Moreover, our aim is to extend the direct sum condition of order ? from [9] to certain topics in singularity and approximation theory. Generalizations to modules as well as specializations to polynomials seem to be promising.
A note on an expansion formula with application to nonlinear Differential-Algebraic-Equations
(2019)
In [DL] systems of differential polynomials are investigated with
respect to properties of Artin approximation type. The key tool in [DL] is an extended version of a formula by Hurwitz [Hu] expressing high order derivatives of an expansion by lower ones. The formula is further refined in [VFZ] to deliver sufficient conditions concerning the existence of power series solutions of scalar algebraic differential equations of order?.
In the paper at hand, the main results from [VFZ] are first reproduced and further extended to systems of nonlinear differential algebraic equations. In addition, a simple extension of Tougeron’s implicit function theorem is given in a specific constellation.
The results follow from [S1], [S2] where Artin approximation is treated within a Banach space setting, thereby constructing an expansion formula that expresses accurately the required dependency of low and high order derivatives within the system of undetermined coefficients.
Tougeron’s implicit function theorem and Hensel’s lemma are well known representatives concerning 2?-approximation/?-nondegeneracy implying existence of solutions with identity of order ?. This note aims to extend this
principle to equations ?[?] = 0 in Banach spaces, using ?-transversality concepts, which may geometrically be interpreted as generalized cones spanned by
submanifolds, each characterized by a certain expansion rate.
The number of manifolds in the cone, as well as their expansion rates, is recursively increased until an appropriate desingularization of the cone is build up
with linearization expressed by first ? + 1 derivatives of the singular operator
at the base point.
Along these lines, a well-defined submersion is constructed in the cone with
uniformly bounded inverse when approaching the singularity. The techniques
are restricted to curves, possibly touching by high order the singular locus of ?, but ultimately traversing it, in this way defining an isolated singularity of the
operator family given by the linearization along the curve.
The fine resolution of the cone by the manifolds represents an improvement
compared to measuring the variation of the nonlinear operator exclusively by
the overall behaviour of the determinant.
In case of finite dimensions, each half-cone is characterized by a constant topological degree that can be used to investigate a solution curve in general position with respect to secondary bifurcation.
The core of all considerations is given by some characteristic patterns, valid in
the system of undetermined coefficients that allow for detailed analysis of the
power series resulting from plugging the power series of the ansatz into the
power series of the nonlinear operator.
Open Source
(2020)
In der IT-Branche hat sich Open-Source-Software (OSS) heute durchgesetzt, führende IT-Konzerne verwenden Open-Source-Code und entwickeln ihn auch selbst. Doch auch für Unternehmen anderer Branchen bietet Open-Source-Software Potenzial. In diesem Beitrag erfahren Sie, dass Open-Source-Software nicht nur ein Schlagwort, sondern genau definiert ist,was es mit den Risiken von Open Source auf sich hat und wie man damit umgeht, welche Vorteile und Potenziale Open-Source-Software auch für Nicht-IT-Firmen bietet.
Im Projekt KWK-Flex untersuchte die Hochschule Kempten innovative Methoden und Anlagenbetriebsstrategien zur flexiblen, stromgeführten Fahrweise von Kraft-Wärme-Kopplungs-(KWK)-Anlagen in Fernwärmeverbundnetzen im Kontext steigender Anteile erneuerbarer Energien. Solche KWK-Anlagenverbunde im Leistungsbereich ab einigen MW werden in Deutschland aufgrund ihrer hohen Brennstoffnutzungsgrade und der daraus folgenden Ressourcen- und Klimafreundlichkeit von mehreren hundert Stadtwerken bzw. Fernwärmeversorgern betrieben.
Bei der Methodenentwicklung und den daraus resultierenden optimierten Anlagenbe-triebsstrategien standen neben den Zielgrößen Dynamik und Flexibilität der Strombe-reitstellung insbesondere die Ressourceneffizienz, d.h. hohe Wirkungsgrade, geringe Emissionen und hohe Wirtschaftlichkeit, sowie eine hohe Versorgungssicherheit im Fokus. Als Schwerpunkte des Forschungsvorhabens wurde Untersuchungen zur in-stationären Prozesssimulation von KWK-Kraftwerken mit dem Ziel der Erhöhung der stromseitigen Anlagendynamik mit dem Einsatz numerischer Methoden zur optimierten Anlageneinsatzplanung der Kraftwerke in KWK-Verbunden kombiniert.
Das Projekt wurde am Institut für Energie- und Antriebstechnik (IEAT) der Hochschule Kempten mit Unterstützung der beiden assoziierten gewerblichen Partner Fernwärme Ulm GmbH (FUG) und ZAK Energie GmbH (ZAK) sowie dem Fernwärmeversorgerdachverband AGFW | Der Energieeffizienzverband für Wärme, Kälte u. KWK e.V. durchgeführt.
Die verstärkte Einbindung fluktuierender erneuerbarer Energien erfordert hochflexible thermische Kraftwerke zur Netzstabilisierung und bedarfsgerechten Abdeckung der verbleibenden Netzlasten. Für einen effizienten Anlageneinsatz spielt dabei die möglichst genaue Kenntnis der zu erwartenden Fernwärmelast eine zentrale Rolle. Für die Fernwärmelastprognose können innovative Verfahren unter Verwendung moderner maschineller Lernverfahren zum Einsatz kommen, die im Folgenden vorgestellt werden.
Silica gel is a well-known desiccant. Through dispersion of silica gel in a polymer, films can be made that absorb and desorb water vapor. The water vapor absorption becomes reversible by exposing such films to a water vapor pressure below that of the water vapor pressure during absorption, or by heating the film. The intention of this study was to achieve a better understanding about the water vapor absorption, permeability (H2O, N2, O2, CO2), and mechanical properties of films with dispersed silica gel. Low-density polyethylene (PE-LD) monolayer films with a nominal silica gel concentration of 0.2, 0.4, and 0.6 g dispersed silica gel per 1 g film (PE-LD) were prepared and they absorbed up to 0.08 g water vapor per 1 g of film. The water vapor absorption as a function of time was described by using effective diffusion coefficients. The steady state (effective) water vapor permeation coefficients of the films with dispersed silica gel were a factor of 2 to 14 (8.4 to 60.2·10−12 mg·cm·(cm2·s·Pa)−1, 23 °C) higher than for pure PE-LD films (4.3·10−12 mg·cm·(cm²·s·Pa)−1, 23 °C). On the other hand, the steady state gas permeabilities for N2, O2, and CO2 were reduced to around one-third of the pure PE-LD films. An important result is that (effective) water vapor permeation coefficients calculated from results of sorption and measured by permeation experiments yielded similar values. It has been found that it is possible to describe the sorption and diffusion behavior of water by knowing the permeability coefficient and the sorption capacity of the film (Peff.≈Seff.⋅Deff.). The tensile stress changed only slightly (values between 10 and 14 N mm−2), while the tensile strain at break was reduced with higher nominal silica gel concentration from 318 length-% (pure PE-LD film) to 5 length-% (PE-LD with 0.6 g dispersed silica gel per 1 g film).
Polymers with dispersed desiccants are relevant for various packaging applications to protect packaged goods from water vapor. The intention of this study was to analyze and to describe a relevant system. Therefore, films with calcium oxide (CaO) were investigated, because such materials are hardly described in scientific literature. Monolayer films with 0.14 to 0.51 g dispersed CaO per 1 g film (PE‐LD) were prepared and they absorbed up to 0.2 g water vapor per 1 g of film. The water vapor absorption was described by effective diffusion coefficients. By the use of effective diffusion coefficients and the absorption capacity, the absorption behavior of layers with various thicknesses can be estimated. The steady state (effective) water vapor permeation coefficients of the films with dispersed CaO were a factor of 2 to 24 (8.4 to 101.5 mg cm [cm2 s Pa]–1 × 1012, at 23 °C) higher than for pure PE‐LD films (4.26 mg cm [cm2 s Pa]−1 × 1012, 23 °C). The tensile stress changed only slightly (pure PE‐LD: 9.5 N mm−2; PE‐LD with 0.14 g dispersed CaO per 1 g film: 8.1 N mm−2; PE‐LD with 0.51 g dispersed CaO per 1 g film: 10.5 N mm−2), while the tensile strain at break was reduced with higher CaO concentration from 318% (pure PE‐LD) to 10% (PE‐LD with 0.51 g dispersed CaO per 1 g film). © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47460.
Packaging materials containing certain salts can regulate the humidity of packaged products. This study investigated whether thermoforming of foamed monolayer PP films with dispersed NaCl increases the water vapour sorption capacity and rate. Foamed monolayer PP-films (thickness 630 μm, porosity 0.28) with 6 (g/100 g) dispersed NaCl crystals were thermoformed to cups with depths up to 90 mm. By thermoforming the porosity increased up to 0.63 and the effective water vapour diffusion coefficient elevated by one order of magnitude from 10−11 to 10−10 cm²∙s−1. Therefore, such films absorb and desorb water vapour with a higher rate and they can bind more salt solution which is formed from solid salt crystals by water vapour absorption. Our results are important for packaging producers who thermoform films to cups and trays. This study addresses markets for fresh produce and other products with a high water activity.
Der moderne Karosseriebau ist geprägt durch den Wunsch nach einer schlanken Prozesskette, die sich durch hohe Prozesssicherheit auszeichnet. Im Umfeld der Fügetechnik rücken zur Erreichung dieses Ziels vermehrt sogenannte „unmittelbare Verbindungen“ in den Vordergrund. Hierbei handelt es sich um Fügeverbindungen, zu deren Erzeugung keine zusätzlichen Verbindungsmittel wie Schrauben oder Niete bereitgestellt werden müssen. Daher werden spezielle Schnappelemente für den Karosseriebau entwickelt, die als integraler Bestandteil aus dem Fügeteil ausgeformt werden. Durch den Einsatz derartiger Schnappelemente lässt sich die Teilevielfalt signifikant reduzieren. Das Fügen derartiger Teile erfolgt hierbei mit geringstem Zeitaufwand und nur mit der ohnehin zur Zuführung des Fügeteils benötigten Handhabungsvorrichtung.
Die assistierte Querführung wie das Spurhalteassistenzsystem ist ein Schlüssel zur erfolgreichen Einführung des hochautomatisierten Fahrens. Was empfindet der Kunde beim Einsatz von Spurhalteassistenzsystemen, und welche psychischen und physischen Belastungen lösen die verschiedenen Fahrsituationen aus? Welche Erwartungen hat er an das Fahrerlebnis? Was wird als angenehm und unangenehm empfunden, was wird akzeptiert, und welche Attribute sind inakzeptabel? Die Hochschule Kempten und MdynamiX sind diesen Fragen in breit angelegten Studien mit insgesamt 120 Probanden im Realeinsatz nachgegangen.
Support prospect of success in mathematics for first-year students in engineering by early feedback
(2020)
Providing students with the necessary mathematical skills is a growing challenge in German engineering degree courses. This is due to manifold mostly pre-university reasons, for example, inadequate or heterogeneous secondary education in Germany. Preparatory courses, a common remedy offered by many universities, often turn out to lack the expected effect. However, implying an early, mandatory test that scans the basic mathematical skills defined as entrance standard, showed positive results, as it detects the individual knowledge gaps of first-year students and motivates them to take action. For this purpose, we coupled the test with detailed, individual feedback and a cluster of affiliated support offers - preparatory to the test as well as attendant to the first year. Being mandatory, the test already pushes more students in our preparatory math courses. Whereas its detailed, individual feedback enables students to choose among the subsequent support offers and to cope with remaining gaps. The support offers range from transition workshops, co-learning tutorials, an online exercise platform, video tutorials up to conventional worksheets and consultation hours. This setup of mandatory test, early and detailed feedback and versatile supporting offers, tackling the missing skills, significantly increased the success in the basic mathematics and mathematics dependent modules of our engineering bachelor courses. In the process, this setup generates several additional, statistical outcomes, like a rating of the different German pre-university school systems, which helps to further work on measures dealing with the decreasing skills of beginners.
Church bells are exposed to severe loading conditions during ringing, which results in different damage modes due to material wear, fatigue loading, material deficiencies, different clapper-to-bell layouts, etc. As part of the activities of an EU-funded project called Maintenance and Protection of Bells (PROBELL), experimental investigations and finite-element simulations of the local contact between the clapper and the bell were carried out to study the wear-related damage to bells. First a simplified model was built to assess under the laboratory-controlled conditions the consequences of the repetitive impacts between a spherical body made from steel and a flat block made from bronze. After the results of the finite-element simulations for a simplified model were in reasonable agreement with the measured data a full-scale finite-element model for simulating the repetitive clapper-to-bell strokes was built. The simulations with the full-scale model were performed for variations of the parameters that influence the structural behaviour of the bell and the clapper: the clapper material, the clapper mass, the relative impact velocity of the clapper, the shape of the clapper, the clapper's pin support, the clapper's impact angle, the clapper's guide accuracy, the bell's sound-burp thickness and the coefficient of friction between the clapper and the bell. The agreement between the simulated and the measured results and the relation between the local stress–strain state and the damage to the bell in the contact area are discussed.
To investigate the combustion and emission behavior of straight vegetable oils (SVO), jatropha oil, soybean oil, and diesel fuel were tested. For this research, a 2.2L common-rail engine with a two-stage turbocharging concept was equipped with a cylinder pressure indication system, an exhaust-gas analyzer, an AVL Micro Soot sensor and a Scanning Mobility Particle Sizer 3936 (SMPS) device to detect the particle-size-distribution (PSD). At a low- and mid-load engine-operating point (EOP), the thermodynamic and emissions were investigated under various exhaust gas recirculation (EGR) rates with respect to the PSD. Moreover, the injection behavior of the three test fuels was analyzed separately using an injection rate analyzer. This procedure facilitates the thermodynamic investigations of the engine process and allows the calculation of the hydraulic delay (HD) as well as the ignition delay (ID). The ID of the SVO fuels compared to diesel fuel was found to be lower at all engine-operating modes, while jatropha oil always showed the shortest ID. In the particulate-nitrogen oxide (NOX) trade-off, the SVO fuels showed higher particulate matter (PM) emissions at the low-load EOP, whereas the PM emissions of diesel fuel overtop the SVO fuels at a higher engine load. With increased EGR-rates, a rise in the particle size was observed for all fuels. At the low-load EOP, the SVO fuels showed larger particles for high EGR-rates. This effect also changed by increasing the engine-load to the mid-load EOP, wherein the particle size of the diesel fuel emissions is higher by applying elevated EGR-rates.
A scanning Kerr microscope with a temporal resolution of <230 fs and a spatial resolution of 210 nm is presented. Equipped with a large temporal and spatial scanning range of 8 ns and 320 μm, respectively, the microscope allows studying nonuniform magnetization dynamics on many different time scales over a large area. For demonstration, we study the magnetization dynamics in Fe/Gd multilayer dot arrays exhibiting a spin reorientation transition (SRT) on three different time scales, namely, femtosecond, picosecond, and nanosecond scales. The dynamics on all time scales varies from one dot to another. This is attributed to the high sensitivity of the SRT to the variations of the layer thicknesses and the Fe/Gd interface structure.
The oxygen permeability of films is relevant for packaging related and technical applications. An increasingly used test method for the measurement of oxygen permeability is the optical test method, because it allows a simple and cost-efficient measurement setup. This method is based on optical chemical sensors. However, not much is known about its validity. Therefore, method validation is necessary which is subject of this study. The optical method is compared with the carrier gas method for a variety of film samples. In the tested permeability range of 0.5–2500 cm3 (STP)·(m2 d bar)−1 both methods deviated less than 20% for zero and 50% relative humidity.
Oxygen scavengers are used in food packaging to protect oxygen-sensitive food products. A mixture of gallic acid (GA) and sodium carbonate was used as an oxygen scavenger (OSc) in bio-based multilayer packaging films produced in a three-step process: compounding, flat film extrusion, and lamination. We investigated the film surface color as well as oxygen absorption at different relative humidities (RHs) and temperatures, and compared the oxygen absorption of OSc powder, monolayer films, and multilayer films. The films were initially brownish-red in color but changed to greenish-black during oxygen absorption under humid conditions. We observed a maximum absorption capacity of 447 mg O2/g GA at 21 °C and 100% RH. The incorporation of GA into a polymer matrix reduced the rate of oxygen absorption compared to the GA powder because the polymer acted as a barrier to oxygen and water vapor diffusion. As expected, the temperature had a significant effect on the initial absorption rate of the multilayer films; the corresponding activation energy was 75.4 kJ/mol. Higher RH significantly increased the oxygen absorption rate. These results demonstrate for the first time the production and the properties of a bio-based multilayer packaging film with GA as the oxygen scavenger. Potential applications include the packaging of food products with high water activity (aw > 0.86).
Water loss, gain or transfer results in a decline in the overall quality of food. The aim of this study was to form a uniform layer of sodium alginate-based edible coating (1.25% sodium alginate, 2% glycerol, 0.2% sunflower oil, 1% span 80, 0.2% tween 80, (w/w)) and investigate the effects on the water barrier characteristics of fresh-cut cantaloupe and strawberries. To this end, a uniform and continuous edible film formation was achieved (0.187 ± 0.076 mm and 0.235 ± 0.077 mm for cantaloupe and strawberries, respectively) with an additional immersion step into a calcium solution at the very beginning of the coating process. The coating application was effective in significantly reducing the water loss (%) of the cantaloupe pieces. However, no significant effect was observed in water vapor resistance results and weight change measurements in a climate chamber (80%→60% relative humidity (RH) at 10 °C). External packaging conditions (i.e., closed, perforated, and open) were not significantly effective on water activity (aw) values of cantaloupe, but were effective for strawberry values. In general, the coating application promoted the water loss of strawberry samples. Additionally, the water vapor transmission rate of stand-alone films was determined (2131 g·100 µm/(m2·d·bar) under constant environmental conditions (23 °C, 100%→50% RH) due to the ability to also evaluate the efficacy in ideal conditions.
Achieving high quality of a coated food product is mostly dependent on the characteristics of the food material to be coated, the properties of the components in the coating solution, and the obtained coating material. In the present study, usability and effectiveness of various components as well as their concentrations were assessed to produce an effective coating material. For this purpose, different concentrations of gelling agent (sodium alginate 0–3.5%, w/w), plasticizers (glycerol and sorbitol (0–20%, w/w), surfactants (tween 40, tween 80, span 60, span 80, lecithin (0–5%, w/w), and vegetable oils (sunflower oil, olive oil, rapeseed oil (0–5%, w/w) were used to prepare edible coating solutions. Formulations were built gradually, and characteristics of coatings were evaluated by analyzing surface tension values and its polar and dispersive components, emulsion droplet size, and optical appearance in microscopic scale. The results obtained showed that 1.25% sodium alginate, 2% glycerol, 0.2% sunflower oil, 1% span 80, and 0.2% tween 40 or tween 80 can be used in formulation to obtain an effective coating for hydrophobic food surfaces. Three formulations were designed, and their stability (emulsion droplet size, optical characteristics, and creaming index) and wettability tests on strawberry showed that they could be successfully used in coating applications
The water vapour transmission rate (WVTR) of packaging materials and edible coatings is one of their critical parameters for the shelf life of many food products. The water vapour transmission rates of flat bodies such as films are determined by permeation measurements which are a steady-state method. Another method is based on water vapour sorption measurements which is a non-steady-state method. It can be used only for mono-material flat bodies. It allows using smaller sample areas compared to permeation measurements. However, not much is known about how well both methods correlate with each other. Therefore, the aim of this study was to compare the WVTR results of different materials determined by both methods. The results of both methods differed by up to factor of three, measured at identical samples. In a few cases the difference was up to factor five. The exact reasons for these differences are unknown. Nonetheless, the water vapour sorption method is a suitable method to determine the magnitue of order of the water vapour transmission rate but not its exact value.
For “on board” diagnosis purposes of the injected fuel quantity flow sensitive elements based on the thermo-resistive measurement principle were integrated into finished Common Rail injection nozzles of valve-covered orifice (VCO) or mini-sac hole (MSH) class. Electron-discharge machining as well as electron beam welding technique are key technologies for a reliable integration procedure. To demonstrate negligible influence on the hydraulic performance of the nozzle after modification an optical measurement set-up is used to record temporally resolved the propagation of the spray patterns ejected from the six injection holes simultaneously. From these investigations the impact on the structural distortion of the valve caused by the welding seam is proved as its position can be directly linked to any chances in spray performance of each individual injection hole. Reducing the energy input during the electron beam welding lowers substantially the asymmetry in spray patterns from hole to hole as the needle uncovers the six injection holes more symmetrically. Besides this important finding, the numerical calculations indicate that the implementation of the sensor chip slightly amplifies the asymmetry induced by the welding process due to an additional weakening of the nozzle body which is confirmed experimentally. Despite these challenges, however, it is demonstrated that appropriate parameters for the integration procedure can be found affecting the hydraulic performance negligible compared to the original state.
Alginate is a naturally occurring polysaccharide used in the bio industry. It is mainly derived from brown algae species. Alginate-based edible coatings and films attract interest for improving/maintaining quality and extending the shelf-life of fruit, vegetable, meat, poultry, seafood, and cheese by reducing dehydration (as sacrificial moisture agent), controlling respiration, enhancing product appearance, improving mechanical properties, etc. This paper reviews the most recent essential information about alginate-based edible coatings. The categorization of alginate-based coatings/film in food packaging concept is formed gradually with the explanation of the most important titles. Emphasis will be placed on active ingredients incorporated into alginate-based formulations, edible coating/film application methods, research and development studies of coated food products and mass transfer and barrier characteristics of the alginate-based coatings/films. Future trends are also reviewed to identify research gaps and recommend new research areas. The summarized information presented in this article will enable researchers to thoroughly understand the fundamentals of the coating process and to develop alginate-based edible films and coatings more readily.
Edible coating based on sodium alginate solution was applied to fresh‐cut cantaloupe melon by dipping and vacuum impregnation coating methods. One aim of this work is to produce more technical information concerning these conventional and novel coating processes. For this purpose, the effect of various coating parameters (dipping time, draining time, time length of the vacuum period, vacuum pressure, atmospheric restoration time) with several levels on physical quality parameters (percentage of weight gain, color, and texture) of noncoated and coated samples were determined in order to define adequate coating process parameters to achieve a successful coating application. Additionally, the effects of dipping and vacuum impregnation processes were compared. Both processes improved the firmness of the melon pieces. However, vacuum impregnation application had higher firmness and weight gain results, and had significant effect (P < 0.05) on color (lower luminosity, higher redness, yellowness, and chroma values). Experimental results affirm that vacuum impregnation method can be used successively to improve mechanical and structural properties of food products.
Friction surfacing offers a means of producing coatings between dissimilar materials through a solid state process; a union that would otherwise be classed as incompatible for liquid state coating processes. A method of using a rotating consumable friction rod supplemented by inductive heating was employed to produce conditions necessary for a sound bond between a stainless steel coating and an aluminium substrate. The rotational speed of and load on the coating rod influenced the bond strength significantly with low rotational speeds and high load values producing a good bond quality; however, cavitations at the coating-substrate interface showed a detrimental effect on the bond quality. Mechanical interlocking could be identified from images of longitudinal cross-sectional slices which were recorded using optical microscopy. An image recognition software tool was used to generate an interfacial roughness profile graph which described the coating-substrate interface. Additional filtering of the profile graph showed the depth of mechanical interlocking of the stainless steel coating into the aluminium substrate with the degree of this interlocking quantified by roughness values calculated from the profile graph. Large roughness values can be related to high coating push-off strengths (up to 107 MPa), and also were a result of low rotational speeds and high load values during friction surfacing. Dovetail shaped mechanical interlocks identified in the profile produced both high push-off and shear strength when compared with wedge-shaped interlocks; which, overall, provided good shear strengths up to 126 MPa.
Inductive heating effects on friction surfacing of stainless steel onto an aluminium substrate
(2015)
An experimental setup was designed to compare the principal process parametric relationships with the classical approach to friction surfacing with the addition of inductive heating. The production of the flash is described quantitatively and its influence on coating geometry and mass is presented. It was found that the coating mass and thickness decreased for an increase in the rotational speed of the consumable rod; the amount of flash produced by the consumable rod also increased. However, the effect of an increase in this rod contact pressure on the coating thickness is insignificant, whilst the coating mass decreases with rising pressure and the coating width increases coupled with an increase in flash production. Cross sections showed good bonding quality and mechanical interlocking at the bond interface. The substrate-coating interface showed a varying degree of mechanical interlocking and the presence of cavitations. Bond strength values applying shear and push-off testing of up to 106 MPa and 96 MPa, respectively, could be identified.
Friction surfaced specimens produced by the application of inductive heating and utilising a flash-reducing tool were compared with those obtained through the classical approach. It was found that the use of inductive heating resulted in an increased consumption of the coating material; however, the push-off strength could be more than doubled when compared with the classical process with high shear strength values of up to 111 MPa. The application of the flash-reducing tool reduced the flash to less than 0.05% of the material deposited as a coating and manifested itself in the form of small chips. High push-off strength values of up to 135 MPa were observed, accompanied by an increased coating thickness, coating width and bonding area. Temperature measurements with thermocouples taken during the coating process showed that the melting temperature of the aluminium substrate was reached at the substrate–coating interface. Mixed mode failure was evident at the fractured surfaces of the push-off test specimens and mechanical interlocking appears to be a main bonding mechanism. The presence of cavities were shown to have a detrimental effect on the bonding integrity, but could be reduced in size and number by the application of the flash-reducing tool.
High fogging is a power augmentation device where water is sprayed upstream of the compressor inlet with higher mass flow than that which would be needed to saturate the intake air. The main focus of this paper is on applications of high fogging on the ALSTOM gas turbine engines of the family GT24/GT26. Engine operation and performance are illustrated based on test results obtained from four different engines that have meanwhile accumulated more than 12,000 operating hours (OH) in commercial operation with ALSTOM’s ALFog® high fogging system. The effect of internal cooling (water evaporation inside the compressor) is investigated considering actual compressor boundaries matched within the complete engine. Changes in the secondary air system (SAS) and corresponding movement of the engine operating line have been taken into account. Power output gain as high as 7.1% was experimentally demonstrated for injected water mass fraction (f=mH2O∕mair) equal to 1% and considering internal cooling effects only. Higher figures can be obtained for operation at low ambient relative humidity and partial evaporation upstream of the compressor inlet.
Joining sheet metal can be problematic using traditional friction welding techniques. Friction crush welding (FCW) offers a high speed process which requires a simple edge preparation and can be applied to out-of-plane geometries. In this work, an implementation of FCW was employed using an additional wire to weld sheets of EN AW5754 H22, DC01, and Cu-DHP. The joint is formed by bringing together two sheet metal parts, introducing a wire into the weld zone and employing a rotating disk which is subject to an external force. The requirements of the welding preparation and the fundamental process variables are shown. Thermal measurements were taken which give evidence about the maximum temperature in the welding center and the temperature in the periphery of the sheet metals being joined. The high welding speed along with a relatively low heat input results in a minimal distortion of the sheet metal and marginal metallurgical changes in the parent material. In the steel specimens, this FCW implementation produces a fine grain microstructure, enhancing mechanical properties in the region of the weld. Aluminum and copper produced mean bond strengths of 77 and 69 pct to that of the parent material, respectively, whilst the steel demonstrated a strength of 98 pct. Using a wire offers the opportunity to use a higher-alloyed additional material and to precisely adjust the additional material volume appropriate for a given material alignment and thickness.
Large arrays of ordered magnetic nanostructures have been fabricated by sputter depositing Fe/Gd multilayers on an array of self-assembled nanospheres. On a planar substrate the system shows an in-plane magnetization whereas a spin reorientation transition (SRT) to out-of-plane orientation occurs on the spherules. This SRT cannot only be explained by the reduction in the shape anisotropy due to patterning of the extended film into nanometer sized islands. In fact, more important is the curved surface of the film on the nanocaps. Micromagnetic simulations of various geometries reveal that the crescent shape of the magnetic film on the spheres is ideal to get small values of the shape anisotropy for all diameters of the spheres, ranging from 1 μm down to 20 nm. The observed SRT enables a simple and cost effective bottom-up approach to produce patterned perpendicular magnetic nanostructures, having a high potential for magnetic data storage and spintronic applications.
For a further optimization of the automotive power train of diesel engines, advanced combustion processes require a highly flexible injection system, provided e.g., by the Common Rail (CR) injection technique. In the past, the feasibility to implement in the injection nozzle injection quantity sensors based on a thermo-resistive measurement principle has been demonstrated up to injection pressures of 135 MPa (1350 bar). Due to a very complex integration procedure a less-costly implementation is realized in the range of the high-pressure pipe connecting each single injector with the common pressure reservoir. The sensor output signals measured at this location of the hydraulic system are compared to those obtained from the nozzle as well as from an injection amount indicator used as standard reference method. Finally, hydraulic simulations on system level are performed showing a good correspondence in respect to the onset of fuel flow and to the period of pressure oscillations generated in the hydraulic system after termination of the drive pulse.
The aim of this study was to evaluate the influence of relative humidity (RH) on the oxygen permeability and water vapour transmission rate (WVTR) of whey protein coated Polyethylene terephthalate (PET) or whey protein monolayer films. Furthermore, the activation energies for the permeability of oxygen, carbon dioxide and nitrogen as well as the permselectivities under different set of temperatures were measured. The results showed that the permeability values through the whey protein coating and whey protein film increased with increasing RH. The water vapour permeability measured at 50% RH of (9.3 ± 0.6)−10 cm3 (STP) cm cm−2 s−1 Pa−1 increased to (16.2 ± 0.9)−10 cm3 (STP) cm cm−2 s−1 Pa−1 at 85% RH. An increase in temperature showed an expected increase of the permeability in both uncoated PET and the whey protein monolayer. The permselectivity of whey protein film was determined and the calculated ratios of the permselectivity (P(N2)/P(O2)/P(CO2):1/(4–6/(34–35)) differed from the simplified ratios given in the literature (P(N2)/P(O2)/P(CO2):1/4/16). Furthermore the calculated activation energy values for whey (51 kJ mol−1) were in agreement with other studies.
This study investigates chemical grafting with fatty acid chlorides as a method for the surface modification of hydrophilic web materials. The resulting changes in the water repellence and barrier properties were studied. For this purpose, different grades of polyvinyl alcohol (PVOH) were coated on regenerated cellulose films (“cellophane”) and paper and then grafted with fatty acid chlorides. The PVOH grades varied in their degree of hydrolysis and average molecular weight. The surface was esterified with two fatty acid chlorides, palmitoyl (C16) and stearoyl chloride (C18), by chemical grafting. The chemical grafting resulted in water-repellent surfaces and reduced water vapor transmission rates by a factor of almost 19. The impact of the surface modification was greater for a higher degree of hydrolysis of the polyvinyl alcohol and for shorter fatty acid chains. Although the water vapor barrier for palmitoyl-grafted PVOH was higher than for stearoyl-grafted PVOH, the contact angle with water was lower. Additionally, it was shown that a higher degree of hydrolysis led to higher water vapor barrier improvement factors after grafting. Furthermore, the oxygen permeability decreased after grafting significantly, due to the fact that the grafting protects the PVOH against humidity when the humidity is applied on the grafted side. It can be concluded that the carbon chain length of the fatty acid chlorides is the limiting factor for water vapor adsorption, but the grafting density is the bottleneck for water diffusing in the polymer.