264 research outputs found
Asymmetrische Polanordnung als fertigungsoptimierte Methode der Nutrastmomentreduzierung am Beispiel eines permanentmagnetisch erregten Synchrongenerators fĂŒr Kleinwindenergieanlagen
In diesem Beitrag wird eine fertigungsoptimierte Methode der Nutrastmomentreduzierung durch Magnetverschiebung am Beispiel eines Synchrongenerators fĂŒr Kleinwindenergieanlagen mit in die LĂ€uferoberflĂ€che eingelassenen Permanentmagneten vorgestellt. Auf Grundlage der Drehfeldtheorie wird ein analytisches Berechnungsmodell unter Einbezug der Magnetverschiebung zur Bestimmung des Nutrastmoments entwickelt und mit FEM-Simulationen verifiziert. Durch experimentelle Untersuchung eines gefertigten Prototyps wird der optimierende Effekt der Magnetverschiebung nachgewiesen und mit einem ReferenzlĂ€ufer mit ungeschrĂ€gt, symmetrisch verteilten Polen verglichen. AbschlieĂend werden mögliche Ursachen fĂŒr die verbleibenden Abweichungen identifiziert und AnsĂ€tze fĂŒr die weiteren Betrachtungen abgeleitet.A production-optimized method of reducing cogging torque by magnet shifting using the example of a synchronous generator for small wind turbines with a rotor with inset surface magnets is proposed in this paper. On the basis of rotating field theory an analytical calculation model is developed taking into account the magnet shifting for determination of cogging torque. The analytical results are verified with FEM simulations. By experimental investigation of a manufactured prototype, the optimizing effect of magnet shifting is verified and compared to a rotor with symmetrically distributed poles. Finally, possible reasons for remaining discrepancies are identified and approaches for further considerations are presented
Influence of the Triglyceride Composition, Surfactant Concentration and TimeâTemperature Conditions on the Particle Morphology in Dispersions
Many applications for crystalline triglyceride-in-water dispersions exist in the life sciences and pharmaceutical industries. The main dispersion structures influencing product properties are the particle morphology and size distribution. These can be set by the formulation and process parameters, but temperature fluctuations may alter them afterwards. As the dispersed phase often consists of complex fats, there are many formulation variables influencing these product properties. In this study, we aimed to gain a better understanding of the influence of the dispersed-phase composition on the crystallization and melting behavior of these systems. We found that different particle morphologies can be obtained by varying the dispersed-phase composition. Droplets smaller than 1 ”m were obtained after melting due to self-emulsification (SE), but these changes and coalescence events were only partly influenced by the melting range of the fat. With increasing surfactant concentration, the SE tendency increased. The smallest x50,3 of 3 ”m was obtained with a surfactant concentration of 0.5 wt%. We attributed this to different mechanisms leading to the dropletsâ breakup during melting, which we observed via thermo-optical microscopy. In addition, SE and coalescence are a function of the cooling and heating profiles. With slow heating (0.5 K/min), both phenomena are more pronounced, as the particles have more time to undergo the required mechanisms
Fission of Multiply Charged Cesium and Potassium Clusters in Helium Droplets - Approaching the Rayleigh Limit
Electron ionization of helium droplets doped with sodium, potassium or cesium results in doubly and, for cesium, triply charged cluster ions. The smallest observable doubly charged clusters are Na92+, K112+, and Cs92+; they are a factor two to three smaller than reported previously. The size of sodium and potassium dications approaches the Rayleigh limit nRay for which the fission barrier is calculated to vanish, i.e. their fissilities are close to 1. Cesium dications are even smaller than nRay, implying that their fissilities have been significantly overestimated. Triply charged cesium clusters as small as Cs193+ are observed; they are a factor 2.6 smaller than previously reported. Mechanisms that may be responsible for enhanced formation of clusters with high fissilities are discussed
The overshoot phenomenon as a function of internal resistance in microbial fuel cells
A method for assessing the performance of microbial fuel cells (MFCs) is the polarisation sweep where different external resistances are applied at set intervals (sample rates). The resulting power curves often exhibit an overshoot where both power and current decrease concomitantly. To investigate these phenomena, small-scale (1. mL volume) MFCs operated in continuous flow were subjected to polarisation sweeps under various conditions. At shorter sample rates the overshoot was more exaggerated and power generation was overestimated; sampling at 30. s produced 23% higher maximum power than at 3. min. MFCs with an immature anodic biofilm (5. days) exhibited a double overshoot effect, which disappeared after a sufficient adjustment period (5. weeks). Mature MFCs were subject to overshoot when the anode was fed weak (1. mM acetate) feedstock with low conductivity (1500 ΌS). MFCs developed in a pH neutral environment produced overshoot after the anode had been exposed to acidic (pH 3) conditions for 24. h. In contrast, changes to the cathode both in terms of pH and varying catholyte conductivity, although affecting power output did not result in overshoot suggesting that this is an anodic phenomenon. © 2011 Elsevier B.V
Personal investment in Japan and the U.S.A.: A study of worker motivation,
The Inventory of Personal Investment (IPI) was administered to 522 Japanese and 746 American workers to compare their work motivation and self-concepts. Eleven subscales were formed based on the IPI model and were found through factor analysis to be appropriate for the samples in both countries. Discriminant analyses of scale scores by subjects' nationality, gender, occupational strata, and age are reported. Findings included: (1) Japanese and American workers sampled emphasized different aspects of meaning as they perceive work and self, (2) Japanese and American women sampled exhibited similar profiles to one another, as did the two male subsamples, and (3) motivational profiles for various age groupings differed between the two samples. The results are related to previous research on Japanese and American workers.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30299/1/0000701.pd
Influence of platinum group metal-free catalyst synthesis on microbial fuel cell performance
© 2017 The Authors Platinum group metal-free (PGM-free) ORR catalysts from the Fe-N-C family were synthesized using sacrificial support method (SSM) technique. Six experimental steps were used during the synthesis: 1) mixing the precursor, the metal salt, and the silica template; 2) first pyrolysis in hydrogen rich atmosphere; 3) ball milling; 4) etching the silica template using harsh acids environment; 5) the second pyrolysis in ammonia rich atmosphere; 6) final ball milling. Three independent batches were fabricated following the same procedure. The effect of each synthetic parameters on the surface chemistry and the electrocatalytic performance in neutral media was studied. Rotating ring disk electrode (RRDE) experiment showed an increase in half wave potential and limiting current after the pyrolysis steps. The additional improvement was observed after etching and performing the second pyrolysis. A similar trend was seen in microbial fuel cells (MFCs), in which the power output increased from 167 ± 2 ÎŒW cmâ2 to 214 ± 5 ÎŒW cmâ2. X-ray Photoelectron Spectroscopy (XPS) was used to evaluate surface chemistry of catalysts obtained after each synthetic step. The changes in chemical composition were directly correlated with the improvements in performance. We report outstanding reproducibility in both composition and performance among the three different batches
Pharmacokinetic-Pharmacodynamic Modeling in Pediatric Drug Development, and the Importance of Standardized Scaling of Clearance.
Pharmacokinetic/pharmacodynamic (PKPD) modeling is important in the design and conduct of clinical pharmacology research in children. During drug development, PKPD modeling and simulation should underpin rational trial design and facilitate extrapolation to investigate efficacy and safety. The application of PKPD modeling to optimize dosing recommendations and therapeutic drug monitoring is also increasing, and PKPD model-based dose individualization will become a core feature of personalized medicine. Following extensive progress on pediatric PK modeling, a greater emphasis now needs to be placed on PD modeling to understand age-related changes in drug effects. This paper discusses the principles of PKPD modeling in the context of pediatric drug development, summarizing how important PK parameters, such as clearance (CL), are scaled with size and age, and highlights a standardized method for CL scaling in children. One standard scaling method would facilitate comparison of PK parameters across multiple studies, thus increasing the utility of existing PK models and facilitating optimal design of new studies
Microbial fuel cells: From fundamentals to applications. A review
© 2017 The Author(s) In the past 10â15 years, the microbial fuel cell (MFC) technology has captured the attention of the scientific community for the possibility of transforming organic waste directly into electricity through microbially catalyzed anodic, and microbial/enzymatic/abiotic cathodic electrochemical reactions. In this review, several aspects of the technology are considered. Firstly, a brief history of abiotic to biological fuel cells and subsequently, microbial fuel cells is presented. Secondly, the development of the concept of microbial fuel cell into a wider range of derivative technologies, called bioelectrochemical systems, is described introducing briefly microbial electrolysis cells, microbial desalination cells and microbial electrosynthesis cells. The focus is then shifted to electroactive biofilms and electron transfer mechanisms involved with solid electrodes. Carbonaceous and metallic anode materials are then introduced, followed by an explanation of the electro catalysis of the oxygen reduction reaction and its behavior in neutral media, from recent studies. Cathode catalysts based on carbonaceous, platinum-group metal and platinum-group-metal-free materials are presented, along with membrane materials with a view to future directions. Finally, microbial fuel cell practical implementation, through the utilization of energy output for practical applications, is described
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