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81.
Charlotte T.M. Kwok Author VitaeAuthor Vitae Edmund G. Seebauer Author Vitae Author Vitae 《Automatica》2008,44(9):2241-2247
Self-diffusion in crystalline silicon is controlled by a network of elementary steps whose activation energies are important to know in a variety of applications in microelectronic fabrication. The present work employs maximum a posteriori (MAP) estimation to improve existing values for these activation energies, based on self-diffusion data collected at different values of the loss rates for interstitial atoms to the surface. Parameter sensitivity analysis shows that for high surface loss fluxes, the energy for exchange between an interstitial and the lattice plays the leading role in determining the shape of diffusion profiles. At low surface loss fluxes, the dissociation energy of large-atom clusters plays a more important role. Subsequent MAP analysis provides significantly improved values for these parameters. 相似文献
82.
It is by now familiar that in the deployment of solar photovoltaic (PV) systems, the cost dynamics of major system component like solar cell/module is subjected to experience curve effects driven by production learning and research and development at the supplier side. What is less clear, however, is the economics of system integration or system deployment that takes place locally close to the user, involving other market players, in the downstream solar PV value chain. Experts have agreed that suppliers of solar PV system must customize their flexible characteristics to address local unique users’ and applications requirements and compete on price/performance basis. A lack of understanding of the drivers of the economics of system customization therefore is a deficiency in our understanding of the overall economics of this renewable energy technology option. 相似文献
83.
Fang B. Leung C.H. Tang Y.Y. Kwok P.C.K. Tse K.W. Wong Y.K. 《Vision, Image and Signal Processing, IEE Proceedings -》2002,149(2):85-90
It is often difficult to obtain sufficient signature samples to train up a signature verification system. An elastic matching method to generate additional samples is proposed to expand the limited training set so that a better estimate of the statistical variations can be obtained. The method differs from existing ones in that it is more suitable for the generation of signature samples. Besides this, a set of peripheral features, which is useful in describing both the internal and external structures of signatures, is employed to represent the signatures in the verification process. Results showed that the additional samples generated by the proposed method could reduce the error rate from 15.6% to 11.4%. It also outperformed another existing method which estimates the class covariance matrix through optimisation techniques. Results also demonstrated that the peripheral features are useful for signature verification. 相似文献
84.
Baoqing Zhang Julia Shuk‐Ping Wong Richard Ching‐Man Yam Robert Kwok‐Yiu Li 《Polymer Engineering and Science》2010,50(5):900-910
A new approach for improving the wear performances of nylon 6 (PA6)/clay nanocomposites was examined in this study. Two hybrid nanocomposites were prepared by melt blending a thermotropic liquid crystalline polymer (TLCP) and a well‐dispersed PA6/clay nanocomposite, but with and without the incorporation of maleic‐anhydride grafted polypropylene (MAPP) as compatibilizer. The addition of MAPP improved the compatibility between TLCP and matrix and thus enhanced the fibrillation of dispersed TLCP phase. Wear‐testing results revealed that the wear resistance of the compatibilized hybrid nanocomposite could be improved effectively, as indicated by the low values of specific wear rate and frictional coefficient, especially under high‐normal load (i.e., 80 N). Based on the characterization on the worn damage and the debris, it was suggested that abrasive wear was the main‐damage mechanism for all the materials under investigation, except for the compatibilized hybrid nanocomposite. For this system, the wear damage was caused by a combination of abrasive and adhesive wearing because of the formation of transfer film on the counter pin surface from the wear debris. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers 相似文献
85.
In this paper, we investigate bit-error-rate (BER) performance of a minimum mean-squared error (MMSE) multiuser receiver for
asynchronous band-limited direct- sequence code-division multiple-access (DS-CDMA) systems. We focus on the BER performance
in the presence of multitone jamming (MTJ) over frequency-selective multipath fading channels. We consider the generalized-K fading model in our analysis, as it can model a large spectrum of fading-channel characteristics. We also analyze the effects
of band- limited pulse shape on the BER performance of the system. Multipath diversity based on the maximal-ratio combining
(MRC) scheme is employed to combat fading effects. Our analytical expressions are valid for arbitrary diversity levels and
fading parameters. Spectrum raised cosine (SRC) and Beaulieu–Tan–Damen (BTD) pulse shapes are employed for numerical analysis.
Numerical results show that in the presence of MTJ and under various channel conditions, the MMSE based receiver gives better
BER performance than the one without it. Moreover, the system with BTD pulses outperforms the one with SRC pulses. 相似文献
86.
两种大豆胰蛋白酶抑制剂的抑制活性及二级结构分析比较 总被引:2,自引:0,他引:2
研究了I型Kunitz大豆胰蛋白酶抑制剂(I-KSTI)和Bowman-Birk大豆胰蛋白酶抑制剂(BBTI)对胰蛋白酶的抑制活性及其二级结构的组成差异。发现I-KSTI及 BBTI对胰蛋白酶的抑制曲线分为两部分:活性急剧下降部分和缓慢下降部分。使胰蛋白酶的活性降为原来的一半时的I-KSTI和BBTI浓度为1.5μg/ml 和1.2μg/ml。使胰蛋白酶活性趋向于零(完全钝化)时的I-KSTI浓度为13.5μg/ml,而BBTI则为9μg/ml。两种抑制剂的存在不改变胰蛋白酶的Km值,但其Vmax随抑制剂浓度的增加而下降。表明其对胰蛋白酶的抑制作用是一种非竞争性抑制作用。远紫外圆二色谱的研究发现I-KSTI和BBTI的单一吸收负峰在200nm波长处,I-KSTI的克分子椭圆度[θ]200nm=-2545deg·cm2/d mol,其二级结构由22.5%β折叠,16.25%β转角和61.4%无规卷曲组成;BBTI的[θ]200nm=-797deg·cm2/d mol,由52.6%β折叠和47.4%无规卷曲组成。 相似文献
87.
Hostile environmental pressure on supply chain management increases emphasis on supply chain agility, integration, and visibility to respond rapidly, effectively and efficiently to changes in the marketplace. There is a need for new methods and tools to visualize the supply chain topologies which captures and recognizes the complexity of the supply chain network. This paper presents a Knowledge-based Customization System for Supply Chain Integration (KCSSI) which is developed based on three core technologies: visualization of topologies, network analysis, and knowledge-based system so as to obtain quantified actionable information and formulating strategies for supply chain configuration leading the long term success. The performance of the system is verified by a series of controlled simulation experiments conducted in a selected reference site. It is verified that the KCSSI improves supply chain visibility by recognizing the structure clustering and interconnection of the supply chain network, quantifying and exploiting holistic supply chain performance to provide measurable insights for the customization of the supply chain configuration leading to long term success. 相似文献
88.
H. S. Kwok J. Chen F. H. Yu H. C. Huang 《Journal of the Society for Information Display》1999,7(2):127-133
Abstract— A generalized mixed twisted-nematic/birefringent-effect mode reflective LCD is presented. This new mode encompasses all previously published reflective nematic LCD modes and is clearly shown on the parameter space diagrams. We also discuss how to obtain operating conditions of this generalized mixed-mode display with large cell gaps, low color dispersion, and high contrast at low voltages. This operating mode is particularly suitable for reflective crystalline-silicon-backplane active-matrix LCDs. 相似文献
89.
The objective of this article is to present the end-to-end broadband service and protocol architecture over DSL that has been adopted for both ADSL and G.Lite (PPP over ATM). G.Lite is a new form of DSL, and its characteristics are discussed. The article then presents a vision for the evolution of an analog modem-based service to G.Lite and ADSL services. The article explains the standardized architecture of PPP over ATM for DSL, and explores how the unique characteristics of G.Lite affect higher-layer protocols (PPP over ATM). Finally, it discusses a vision of how DSL will be deployed together with home networking to provide broadband services to multiple devices in a user-friendly fashion 相似文献
90.
G. W. Crabtree D. Lopez W. K. Kwok H. Safar L. M. Paulius 《Journal of Low Temperature Physics》1999,117(5-6):1313-1322
We describe transport experiments where the spatial gradient of the driving Lorentz force is controlled. The velocity profiles induced by the Lorentz force gradient in the driven liquid and lattice vortex phases are characteristic of hydrodynamic, plastic, and elastic motion. 相似文献