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941.
K. K. Poornesh Sang-kyo Lee Chongdu Cho Kyu-won Choi 《International Journal of Precision Engineering and Manufacturing》2010,11(4):583-588
In polymer electrolyte fuel cell (PEFC) system, ideal structural integrity design takes into account the end-to-end load transfer
mechanism. Hence, structural durability of cell is dependent of individual layers response to the external clamp loading.
Since failure modes of each layer differ from another, multidisciplinary approach is needed to innovative designs. Bipolar
plate (BPP) of PEFC is multi-functional layer that has a significant potential for research to avoid its structural failure
as well as neighboring layers. To this end, present work investigates the effect of BPP materials on the stress transfer as
well as distribution in cell layers based on theoretical investigation for clamping load. Gas-diffusion layer (GDL) / BPP
interface has drawn considerable interest among researchers due to its susceptibility for damage failure and other related
losses. Hence, investigating the interfacial behavior and relating this to the electrical contact resistance is the key feature
in proposed investigation. 相似文献
942.
Chang-Ho Jeong Gwi Nam Choi Ji Hye Kim Ji Hyun Kwak Dae Ok Kim Young Jun Kim Ho Jin Heo 《Food chemistry》2010,118(2):669-282
In order to obtain basic data necessary for the utilisation of aerial parts from Platycodon grandiflorum as a functional substance in Korea, the antioxidant activities of solvent fractions from the ethanol extract of P. grandiflorum aerial parts were examined. The butanol fraction from P. grandiflorum showed the most potent antioxidant activities in each assay, showing 91.31% in the DPPH radical scavenging method, 99.62% in the ABTS radical scavenging method, 7.84% in the reducing power method, and 1.29% in the FRAP method at a concentration of 10 mg/ml. The DPPH, ABTS, reducing power, and FRAP assay indicated that the butanol fraction of aerial parts of P. grandiflorum was the most potent radical-scavengers and reducing agents compared to the other two extracts. Therefore, our study verified that the butanol fraction has strong antioxidant activities which are correlated with its high level of phenolics, particularly luteolin-7-O-glucoside and apigenin-7-O-glucoside. This extract of P. grandiflorum aerial parts can be utilised as an effective and safe source of functional food materials such as natural antioxidants. 相似文献
943.
944.
Jaewoo Lee Chang Han Je Sungweon Kang Chang-Auck Choi 《Microwave Theory and Techniques》2005,53(11):3335-3344
A low-loss single-pole six-throw (SP6T) switch using very compact metal-contact RF microelectromechanical system (MEMS) series switches is presented. The metal-contact MEMS switch has an extremely compact active area of 0.4 mm /spl times/ 0.3 mm, thus permitting the formation of an SP6T MEMS switch into the RF switch with a total area of 1 mm/sup 2/. The MEMS switch shows an effective spring constant of 746 N/m and an actuation time of 8.0 /spl mu/s. It has an isolation loss from -64.4 to -30.6dB and an insertion loss of 0.08-0.19 dB at 0.5-20 GHz. Furthermore, in order to evaluate RF performances of the SP6T MEMS switch, as well as those of the single-pole single-throw RF MEMS series switch, we have performed small-signal modeling based on a parameter-extraction method. Accurate agreement between the measured and modeled RF performances demonstrates the validity of the small-signal model. The SP6T switch performed well with an isolation loss from -62.4 to -39.1dB and an insertion loss of 0.19-0.70 dB from dc to 6 GHz between the input port and each output port. 相似文献
945.
Young Chul Choi Ho-Young Cha Eastman L.F. Spencer M.G. 《Electron Devices, IEEE Transactions on》2005,52(9):1940-1948
A novel silicon carbide (SiC) normally off lateral channel vertical junction field-effect transistor (LC-VJFET), namely a source-inserted double-gate structure with a supplementary highly doped region (SHDR), was proposed for achieving extremely low power losses in high-power switching applications. The proposed architecture was based on the combination of an additional source electrode inserted between two adjacent surface gate electrodes and a unique SHDR in the vertical channel region. Two-dimensional numerical simulations for the static and resistive switching characteristics were performed to analyze and optimize the SiC LC-VJFET structures for this purpose. Based on the simulation results, the excellent performance of the proposed structure was compared with optimized conventional structures with regard to total power losses. Finally, the proposed structure showed about a 20% reduction in on-state loss (P/sub on/) compared to the conventional structures, due to the effective suppression of the JFET effect. Furthermore, the switching loss (P/sub sw/) of the proposed structure was found to be much lower than the results of the conventional structures, about a 75% /spl sim/ 95% reduction, by significantly reducing both input capacitance (C/sub iss/) and reverse transfer capacitance (C/sub rss/) of the device. 相似文献
946.
A simulation-based fault-injection methodology for validating fault-tolerant microprocessor architectures is described. The approach uses mixed-mode simulation (electrical/logic analysis), and injects transient errors in run-time to assess the resulting fault-impact. To exemplify the methodology, a fault-tolerant architecture which models the digital aspects of a dual-channel, real-time jet-engine controller is used. The level of effectiveness of the dual configuration with respect to single and multiple transients is measured. The results indicate 100% coverage of single transients. Approximately 12% of the multiple transients affect both channels; none result in controller failure since two additional levels of redundancy exist 相似文献
947.
Jinseong Choi Swaminathan M. Nhon Do Master R. 《Electromagnetic Compatibility, IEEE Transactions on》2005,47(3):424-439
In this paper, a multilayered on-chip power distribution network consisting of two million passive elements has been modeled using the finite-difference time-domain (FDTD) method. In this method, a branch capacitor has been used. The use of the branch capacitor is important for simulating multilayered power grids. In addition, a method for including the CMOS inverter characteristics into the FDTD simulation has been presented. As an example of the application of this method, an H-tree clock network was simulated to compute the power supply noise distribution across an entire chip. Various scenarios with varying decoupling capacitances, load capacitances, number of clock buffers, and rise times have been analyzed to demonstrate the importance of circuit nonlinearity on power supply noise. Also, a method has been presented for analyzing package and board planes. Based on the methods presented, the interaction between chip and package has been discussed for capturing the resonant behavior that is otherwise absent when each section of the system is analyzed separately. 相似文献
948.
Seung-Hwan Seo Se-Woon Kim Jang-Uk Lee Gu-Cheol Kang Kang-Seob Roh Kwan-Young Kim Soon-Young Lee Chang-Min Choi Kwan-Jae Song So-Ra Park Jun-Hyun Park Ki-Chan Jeon Dong Myong Kim Dae Hwan Kim Hyungcheol Shin Jong Duk Lee Byung-Gook Park 《Solid-state electronics》2008,52(6):844-848
The channel width dependence of hot electron injection program/hot hole erase cycling behavior in silicon-oxide-nitride-oxide-silicon (SONOS) memories is investigated. While the trapped charge profile-dependent overerasure is observed in 10-μm-wide device, it is suppressed in 0.22-μm-wide device. Both the overerasure suppression and gradual positive threshold voltage shift in narrow device are explained as an elevated hot hole injection efficiency followed by more pronounced redistribution of the hole profile in the channel-center and the suppression of the lateral migration of injected holes in the channel-edge, by combining the measured endurance characteristics and TCAD simulation results. Main physical mechanisms are three-dimensional distribution of the electric field by gate/drain voltage, increasing interface states, and their trapped charge with cycling in the channel-edge. 相似文献
949.
Effect of salt concentration and temperature of storage water on the physicochemical properties of fish proteins 总被引:1,自引:0,他引:1
Biochemical and physical properties of fish proteins from damaged (filleted and skinned) and undamaged (free of trauma or broken skin) Pacific whiting were investigated during chilling in various salt concentrations at 0.7 to ?1.1 °C. The increase of pH and moisture content were suppressed when chilling water contained higher concentration of NaCl. Conductivities of damaged fish were maximal after 24 h storage, but those of undamaged fish continuously increased throughout 72 h. K-values increased, but rapidly increased at lower salt concentrations. Puncture force and deformation were very low when chilled water contained higher concentration of salt (2–3 g/100 ml). Gel colors were also negatively affected as the concentration of salt increased for chilling water. Our study suggest Pacific whiting may be stored at 0–2 °C, but at 0–1 g/100 ml salt concentration. 相似文献
950.
A numerical method to model the surface of a reflowed square micro- lens is proposed to improve the simulation accuracy of photosensitivity for an image sensor. To verify the proposed method, a reflowed square microlens with base size of 4.8 x 4.8 mum and sag height of 1.55 mum was fabricated and the modelling accuracy was compared and analysed. 相似文献