18,713 research outputs found
Peng (Stephen) Xue
No full text1 b&w photograph.Excellent condition photograph.Head shot of Peng (Stephen) Xue, commerce student and co-op member at SMU.Written on back: 'Peng (Stephen) Xue came all the way from Beijing, China to attend Saint Mary's commerce program'; 'Peng (Stephen) Xue'; 'Nov/94'; '800.3'Date Catalogued: Apr. 12/1
Self-Sustained Turn-OFF Oscillation of Cascode GaN HEMTs:Occurrence Mechanism, Instability Analysis, and Oscillation Suppression
Full text linkThis article presents a comprehensive study on the occurrence mechanism, instability analysis, and suppression methods of self-sustained turn-off oscillation, which occurs on cascode gallium nitride high electron mobility transistors (cascode GaN HEMTs). In the beginning, the oscillation waveforms are analyzed, which indicate that the occurrence of the oscillation is determined by test circuit instability. Based on the double pulse test, the impact of the load current I_L, dc bus voltage V-{text{DC}} and gate resistance R-{G} on the self-sustained oscillation is identified. To investigate the instability of the resonant circuit, a small-signal ac model of the resonant circuit is derived. Based on the model, the influences of various parameters on the self-sustained oscillation are analyzed. The analyses reveal the possible methods which can suppress the oscillation. The effectiveness of the proposed methods is validated by the experimental data and simulation results in the end. </p
Ferrite Beads Design to Improve Turn-off Characteristics of Cascode GaN HEMTs:An Optimum Design Method
Full text linkIn this article, an optimum ferrite beads design method is proposed to suppress the self-sustained turn-off oscillation of cascode gallium nitride high-electron-mobility transistors (GaN HEMTs). At first, the impacts of gate loop beads and power loop beads on the turn-off oscillation of cascode GaN HEMTs are analyzed. The analysis reveals the weak damping effect of gate loop beads on the turn-off oscillation. Next, an analytical method is proposed to design the power loop beads that can achieve maximum effective damping on the turn-off oscillation. The power loop beads introduce extra stray inductance in the power loop, which can induce high-voltage overshoot. To tackle the problem, an optimum design method is proposed, so that the power loop beads can suppress the oscillation while mitigating the voltage overshoot. The accuracy of the proposed model is validated by the experimental data in the end.</p
Effective Resistances in Non-Expander Graphs
Full text linkEffective resistances are ubiquitous in graph algorithms and network analysis. For an undirected graph G, its effective resistance R_G(s,t) between two vertices s and t is defined as the equivalent resistance between s and t if G is thought of as an electrical network with unit resistance on each edge. If we use L_G to denote the Laplacian matrix of G and L_G^† to denote its pseudo-inverse, we have R_G(s,t) = (_s-_t)^⊤ L^† (_s-_t) such that classical Laplacian solvers [Daniel A. Spielman and Shang{-}Hua Teng, 2014] provide almost-linear time algorithms to approximate R_G(s,t).
In this work, we study sublinear time algorithms to approximate the effective resistance of an adjacent pair s and t. We consider the classical adjacency list model [Ron, 2019] for local algorithms. While recent works [Andoni et al., 2018; Peng et al., 2021; Li and Sachdeva, 2023] have provided sublinear time algorithms for expander graphs, we prove several lower bounds for general graphs of n vertices and m edges:
1) It needs Ω(n) queries to obtain 1.01-approximations of the effective resistance of an adjacent pair s and t, even for graphs of degree at most 3 except s and t.
2) For graphs of degree at most d and any parameter , it needs Ω(m/) queries to obtain c ⋅ min{d,}-approximations where c > 0 is a universal constant. Moreover, we supplement the first lower bound by providing a sublinear time (1+ε)-approximation algorithm for graphs of degree 2 except the pair s and t.
One of our technical ingredients is to bound the expansion of a graph in terms of the smallest non-trivial eigenvalue of its Laplacian matrix after removing edges. We discover a new lower bound on the eigenvalues of perturbed graphs (resp. perturbed matrices) by incorporating the effective resistance of the removed edge (resp. the leverage scores of the removed rows), which may be of independent interest
Xin Peng, flute, Tuesday, February 19, 2013
No full textIn partial fulfillment of the requirements for the degree of
Master of Musi
Peng zhen ren zui tu
No full text美院红旗画兵.文字:彭真认罪圖;下款:美院红旗画兵 一九六七年三月十五日繪; 印記: 广州美术学院 红旗画兵 造反兵团.裝裱後高寬: 111 x 48 cm.Mei yuan hong qi hua bing.Wen zi : Peng Zhen ren zui tu; Xia kuan : Mei yuan hong qi hua bing 1967 nian 3 yue 15 ri hui; Yin ji : Guangzhou mei shu xue yuan hong qi hua bing zao fan bing tuan.Zhuang biao hou gao kuan : 111 x 48 cm
Cheng shi xin pin qiong she qun yu fu li san jiao: yi ge she hui pai chi de fen xi.
No full text彭華民.呈交日期: 2005年11月.論文(哲學博士)--香港中文大學, 2006.參考文獻(p. 246-261).Cheng jiao ri qi: 2005 nian 11 yue.Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.Abstracts in Chinese and English.Lun wen (zhe xue bo shi)--Xianggang Zhong wen da xue, 2006.Can kao wen xian (p. 246-261).Peng Huamin
FIGURE 1 in Aspidistra saccata (Asparagaceae), a new species with erect stem from limestone areas in Guangxi, China
No full textFIGURE 1. Aspidistra saccata: A–B. Habit of flowering plant; C. Flowers; D. Top view of flower bud; E. Side view of flower bud; F. Perianth, dissected opened to show pistil and stamens; G. Stems, show leaves attachment; H. Leaves; I. Young fruit. Photos by Xue-Yan Huang, correction and design by Dong-Xin Nong (The plate made from Yu-De Peng et al. 451424211102001LY).Published as part of Huang, Xue-Yan, Peng, Yu-De, Nong, Dong-Xin, Huang, Bao-You & Yu, Li-Ying, 2022, Aspidistra saccata (Asparagaceae), a new species with erect stem from limestone areas in Guangxi, China, pp. 297-300 in Phytotaxa 541 (3) on page 298, DOI: 10.11646/phytotaxa.541.3.10, http://zenodo.org/record/639258
Seasonal transmission dynamics and optimal control strategies for tuberculosis in Jiangsu Province, China
No full textTuberculosis was ranked No. 3 among 29 types of infectious diseases in January 2022 of Jiangsu Province, in the southeast of China, and it has strong seasonality whose incidence rate has been high in springs and low in winters. This comprehensive study extends the spreading dynamics to the control strategies of TB in Jiangsu Province with time-varying transmission rate, which is the first one in this type. The periodic transmission rate is incorporated to the classic SEIR model with susceptible, latent, infectious, and recovered compartments. The analysis shows that when the basic reproduction number (Formula presented.) is less than one, the epidemic will eventually disappear but, if (Formula presented.) is larger than one, the disease may persist with a periodic solution. The (Formula presented.) value of Jiangsu TB is calculated as 1.297. In addition, the model predicts that the epidemic will not disappear over time and there will be a major outbreak after certain years. To eradicate TB, this work introduces three control strategies on susceptible, latent, and infectious populations. It turns out that the optimal control solutions can reduce the incidence rate in 2035 by 90% from 2015, the goal of World Health Organization. Simultaneously, we find that the optimal controls have the same seasonality as the transmission rate. This indicates that Jiangsu Province needs to invest more control efforts in springs than in winters. In addition, the cost of control strategies is analyzed in terms of the unit cost, total cost, and incremental cost-effectiveness. Summarizing all results, we recommend targeting the latent patients, or both latent and infectious individuals, with the transmission rate-synchronized control strength as the most effective control strategy, to mitigate or even eradicate TB disease in Jiangsu Province.</p
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