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排序方式: 共有4654条查询结果,搜索用时 31 毫秒
161.
C. Lämmel M. Schneider M. Weiser A. Michaelis 《Materialwissenschaft und Werkstofftechnik》2013,44(7):641-649
A comparison between various methods for determining the capacitance and resistance of electrochemical double layer capacitors (EDLC) with cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), galvanostatic charge‐discharge methods and cell voltage jump experiments are presented. Therefore, a commercially available electrochemical double layer capacitor was used. For the validation of the screw cell measurements the electrode foils were isolated and extracted from the commercial capacitor. The results support the adequacy of the screw cell tests for electrode materials on a laboratory scale. The comparison of methods shows in part strong differences. The reasons will therefore be discussed. Consequently, the determination of specific values requires methods which respect the influence of the actual tests or measurement frequency and exhibit the importance of an internationally accepted specification for electrochemical double layer capacitors material investigation. 相似文献
162.
Kerim Isik Gregory Gerstein Thomas Schneider Robert Schulte Daniel Rosenbusch Till Clausmeyer Florian Nürnberger Milan Vucetic Sergej Koch Sven Hübner Bernd-Arno Behrens A. Erman Tekkaya Marion Merklein 《Production Engineering》2016,10(1):5-15
Sheet-bulk metal forming processes combine conventional sheet forming processes with bulk forming of sheet semi-finished parts. In these processes the sheets undergo complex forming histories. Due to in- and out-of-plane material flow and large accumulated plastic strains, the conventional failure prediction methods for sheet metal forming such as forming limit curve fall short. As a remedy, damage models can be applied to model damage evolution during those processes. In this study, damage evolution during the production of two different toothed components from DC04 steel is investigated. In both setups, a deep drawn cup is upset to form a circumferential gearing. However, the two final products have different dimensions and forming histories. Due to combined deep drawing and upsetting processes, the material flow on the cup walls is three-dimensional and non-proportional. In this study, the numerical and experimental investigations for those parts are presented and compared. Damage evolution in the process chains is simulated with a Lemaitre damage criterion. Microstructural analysis by scanning electron microscopy is performed in the regions with high mechanical loading. It is observed that the evolution of voids in terms of void volume fraction is strongly dependent on the deformation path. The comparison of simulation results with microstructural data shows that the void volume fraction decreases in the upsetting stage after an initial increase in the drawing stage. Moreover, the concurrent numerical and microstructural analysis provides evidence that the void volume fraction decreases during compression in sheet-bulk metal forming. 相似文献
163.
Osmar Franca Siebel Marcio Cherem Schneider Carlos Galup-Montoro 《Microelectronics Journal》2012,43(5):329-336
This paper exploits a universal current-based definition of the threshold voltage (VT) and discusses some direct methods to measure it. The consistency, accuracy, and sensitivity of the extraction procedures to second-order effects are examined through numerical simulations and experimental measurements. In addition to three procedures based on dc current measurements we propose an automatic VT-extractor circuit which allows the direct determination of the threshold voltage with minimum influence of second-order effects. 相似文献
164.
165.
Hydrogenation of liquid organic hydrogen carriers is usually carried out in liquid phase. To measure the kinetics of this hydrogenation, an experimental setup using in situ Raman spectroscopy for analysis of the reaction mixture is proposed. With this setup it is possible to perform hydrogenation reactions at temperatures of up to 573 K and pressures up to 25 MPa. For validation of the experimental setup the hydrogenation of 1‐octene was measured in liquid phase. The reaction progress can be monitored in detail by Raman spectroscopy. To determine kinetic parameters from the experimental data, two modeling approaches were applied: a classic kinetic model and a thermodynamic kinetic model. The results were compared to literature data. 相似文献
166.
167.
Incorporation of Alpha‐Linolenic Acid and Enhancement of n‐3 Fatty Acids in Nile Tilapia: a Factorial Design 下载免费PDF全文
Vanessa Vivian Almeida Schneider Fabiana Carbonera Paula Fernandes Montanher Ana Paula Lopes Makoto Matsushita Jesuí Vergílio Visentainer 《Journal of the American Oil Chemists' Society》2015,92(5):693-700
A 22 factorial design (two factors at two levels, in triplicate) was performed to investigate the influence of factors A (time of treatment, 15 and 30 days) and B (chia oil content in a supplemented diet, at 2.1 and 4.2 %) in three responses of interest referring to: (a) the incorporation of alpha‐linolenic acid (LNA) in lipids of Nile tilapia fillet; (b) the enhancement of n‐3 fatty acids; and (c) the decrease in the omega‐6/omega3 (n‐6/n‐3) ratio in fish. Factors A and B were significant in the three regression models obtained and the interaction AB was a significant contributor to the LNA and n‐6/n‐3 ratio. Analysis of variance suggested three significant and predictive mathematical models. Response surfaces analyses from designs indicated higher LNA and n‐3 contents and a lower n‐6/n‐3 ratio using both factors A and B in the higher levels (30 days of treatment and 4.2 % of chia oil in the diet for fish) chosen for this study. 相似文献
168.
169.
N. Schneider D. Schwerdt U. Wuttke M. Oechsner 《Materialwissenschaft und Werkstofftechnik》2015,46(9):931-941
A significant proportion of machinery and equipment is operated up to a number of cycles greater 108, which is in the range of conventionally fatigue limit design. For materials with a face‐centred cubic crystal lattice and for high‐strength steels with a body‐centred cubic crystal lattice fatigue failures were observed even in the Very High Cycle Fatigue (VHCF) regime of load‐cycles greater N = 107. To reduce the testing time in the VHCF regime, one possibility is to perform the tests at a higher frequency. In addition to the typical servo‐hydraulic testing machines or resonant fatigue testing machine with test frequencies up to f = 400 Hz, ultrasonic fatigue testing machines with frequencies up to f = 20 kHz were used. In different comparative investigations it was shown that the testing method has a significant influence on fatigue life and fatigue strength. In this paper the influence of the testing method and test frequency on fatigue behaviour in the VHCF regime is presented using the example of steels and aluminium alloys and different hypotheses for the decrease in fatigue strength in this area are discussed. 相似文献
170.