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Quantum confinement effect in β-SiC nanowires

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Frontiers of physics 2018年第4期13卷 117-122页

作者： Gang Peng Xiaoyan Yu yan-lan he Gong-Yi Li Yi-Xing Liu Xinfang Zhang Xue-Ao Zhang college of Science National University of Defense Technology Changsha 410073 China School of Electronic Communication Engineering Guiyang University Guiyang 550005 China

The quantum confinement effect is important in nanoelectronics and optoelectronics applications; however, there is a discrepancy between the theory of quantum confinement, which indicates that band-gap widening occurs only at small sizes, and experimental observations of band-gap widening in large-diameter nanowires （NWs）. This paper reports an obvious blue shift of the absorption edge in the UV-visible absorption spectra of SiC NWs with diameters of 50-300 nm. On the basis of quantum confinement theory and high-resolution transmission electron microscopy images of SiC NWs, band-gap widening in SiC NWs with diameters of up to hundreds of nanometers is fully explained; the results could help to explain similar band-gap widening in other NWs with large diameters.

关键词： quantum confinement effect SiC nanowires (SiC NWs) band gap

Hydroxylation Reaction Mechanism for Nitrosodimethylamine by Oxygen Atom

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Chemical Research in Chinese Universities 2011年第6期27卷 1006-1009页

作者： LI lan LIN Xiao-yan LI Zong-he College of Sciences Shanghai Institute of Technology Shanghai 200235 P. R. China College of Chemistry Beijing Normal University Beijing 100875 P. R. China

The hydroxylation reaction mechanism of nitrosodimethylamine（NDMA） by oxygen atom was theoretically investigated at the B3LYP/6-31G＊＊ level. It has been found that the path of the oxydation of the C―H bond is easier than the path involving a Singlet/Triplet crossing. The study of the potential surface shows that both solvent effect at B3LYP/6-31G＊＊ level and different method at more credible MP2/6-311G＊＊ level in the gas phase have no effect on the hydroxylation reaction mechanism. The oxidation hydroxylation process of NDMA by O is exothermic reaction and easy to occur.

关键词： Nitrosodimethylamine(NDMA) Hydroxylation B3LYP MP2

A Novel Re-weighted CTC Loss for Data Imbalance in Speech Keyword Spotting

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Chinese Journal of Electronics 2023年第3期32卷 465-473页

作者： lan Xiaotian he Qianhua yan Haikang LI yanxiong School of Electronic and Information Engineering South China University of Technology

Speech keyword spotting system is a critical component of human-computer interfaces. And connectionist temporal classifier(CTC) has been proven to be an effective tool for that task. However, the standard training process of speech keyword spotting faces a data imbalance issue where positive samples are usually far less than negative samples. Numerous easy-training negative examples overwhelm the training, resulting in a degenerated model. To deal with it, this paper tries to reshape the standard CTC loss and proposes a novel reweighted CTC loss. It evaluates the sample importance by its number of detection errors during training and automatically down-weights the contribution of easy examples, the majorities of which are negatives, making the training focus on samples deserving more training. The proposed method can alleviate the imbalance naturally and make use of all available data efficiently. Evaluation on several sets of keywords selected from AISheLL-1 and AISheLL-2 achieves 16%–38% relative reductions in false rejection rates over standard CTC loss at 0.5 false alarms per keyword per hour in experiments.

关键词： Training Human computer interaction Task analysis Speech processing Standards Faces

基于SSR标记的澜沧江流域大理茶群体遗传多样性研究

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农业生物技术学报 2025年第1期33卷 68-78页

作者：黄利超陈洪宇罗义菊陶燕蓝蓝增全西南林业大学园林园艺学院西南林业大学古茶树研究中心

大理茶(Camellia taliensis)是茶的重要野生近缘种，是茶资源的重要组成部分，研究大理茶群体的遗传多样性和亲缘关系，对科学保护和合理利用大理茶种质资源至关重要。本研究应用SSR标记技术对澜沧江流域5个州市共45份大理茶种和5份普洱... 详细信息

大理茶(Camellia taliensis)是茶的重要野生近缘种，是茶资源的重要组成部分，研究大理茶群体的遗传多样性和亲缘关系，对科学保护和合理利用大理茶种质资源至关重要。本研究应用SSR标记技术对澜沧江流域5个州市共45份大理茶种和5份普洱茶(C. sinensis var. assamica)种的种质资源进行遗传多样性和亲缘关系分析。结果显示，15对有效引物共检测到55个多态性位点，每对引物平均扩增3.67个位点；大理茶资源的平均期望杂合度(epected heterozygosity, he)为0.346；多态信息含量(polymorphism information content, PIC)变化范围是0.024～0.661，平均值为0.381；香农指数变化范围是0.067～1.321，平均值为0.669；多态性引物比例为60.0%，多态性引物占有效引物的比例为75.0%。聚类分析结果显示，澜沧江流域大理茶树种质分类与地理区域具有相关性，地理位置较远的大理茶树居群间的遗传距离较远，但居群内遗传距离较近。以上结果表明，澜沧江流域大理茶资源具有中等遗传多样性和中等丰富度。本研究为大理茶种质资源的保护开发及遗传图谱构建提供参考。

关键词：大理茶遗传多样性 SSR

Study on folds of monolayer sandwiched-in different thickness terranes

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Journal of Central South University 2001年第3期13卷 203-207页

作者： YE Bai-long YU Ai-nan he yan-lan College of Resources Environment and Civil EngineeringCentral South UniversityChangsha 410083China Department of Applied Physics Defence University of Science and TechnologyChangsha 410073China

The paper discussed the limitation of ’Dominant wavelengt h theory’. The theoretical model and nonhomogeneous differential equation of fold and deformation of a monolayer sandwiched-in limited and different thickn ess terranes are proposed by using mechanics of elasticity. In addition, the ′D ominant wavelength theory’ is proved by the experimental folding in elastic ma terials. The folds of a monolayer sandwiched-in limited and different thickness terranes are studied inside and are explored in the field.

关键词： dominant wavelength theory monolayer fold simulation ex periment

Composite Polyphosphazene Membranes Doped with Phosphotungstic Acid and Silica

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Chinese Journal of Polymer Science 2014年第8期32卷 996-1002页

作者： Feng-yan Fu 徐虎林 Min-lan he yan Dong Peng Liu Xin Hao 朱长进 Department of Applied Chemistry Beijing Institute of Technology Beijing Qintian Science & Technology Development Co. Ltd

Poly（bis（phenoxy）phosphazene）（SPBPP）/phosphotungstic acid （PWA）/silica composite membranes for fuel cells were prepared. The composite membranes were characterized by using FTIR, TGA and SEM techniquies. Incorporation of PWA particles and silica particles into the SPBPP polymer matrix and a specific interaction between them were confirmed by FTIR spectra. TGA results showed that the composite membranes had high thermal stability. Homogeneous distribution of PWA and silica particles within the SPBPP matrix was verified by SEM micrographs. The doped membranes showed increased water uptake and proton conductivity.

关键词： Sulfonated polyphosphazene Composite membrane Proton conductivity.

Enantioselective Resolution Copolymerization of Racemic 2,3-Disubstituted cis-Epoxides with CO_(2) Mediated by Binuclear Cobalt(Ⅲ)Catalyst

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Chinese Journal of Chemistry 2021年第9期39卷 2386-2390页

作者： yan-lan Liu Guang-Hui he Ye Liu Xiao-Bing Lu State Key Laboratory of Fine Chemicals Dalian University of TechnologyDalianLiaoning 116024China

Enan tioselective resoluti on copolymerization of racemic internal epoxides with carb on dioxide(CO_(2))is a challe nging issue because of their poor reactivity and complicated regio/***,we describe the first enantioselective resolution copolymeriza-tion of racemic aromatic 2,3-disubstituted c/s-epoxides and CO_(2) using enantiopure dinuclear cobalt(lll)complexes as catalyst under mild conditions,affordi ng the corresp on ding polycarbonates with completely alter nating structure and good enantioselectivity in the range of 70% to 97%*** isotactic polycarb on ate from/3-methylstyre ne oxide is a typical semicrystalli ne material,possessi ng a melting point of 241℃;while other isotactic-enriched copolymers from 2,3-disubstituted c/s-epoxides bearing a substitute group on the aromatic ring are amorphous,having glass transition temperatures between 86℃ and 124℃.Interestingly,the copolymer selectivity is correlated well with the Hammett substituent constant,and the highest polymer selectivity of 98%was found in the system using the epoxides bearing an electron-donating group on the benzene ring.

关键词： Asymmetric catalysis Internal c/s-epoxides Carbon dioxide fixation Polymerization Hammett constant

Oxygen as an oxidant in rhodium(III) catalyzed oxidative C–H/C–H cross-coupling between indoles and oxazoles

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Science China Chemistry 2018年第2期61卷 200-205页

作者： yan Wang Jingbo lan Key Laboratory of Green Chemistry and Technology of Ministry of Education College of Chemistry Sichuan University

A Rh(III)-catalyzed oxidative C–H/C–H cross-coupling between indoles and oxazoles with molecular oxygen as an oxidant has been developed to construct a variety of 2-(indol-2-yl)oxazoles. The chelation-assisted strategy endows this catalytic system with an excellent C2-site selectivity by introducing a pyrimidyl directing group. In addition, polycyclic pyridinium salts are also obtained via Rh(III)-catalyzed C–H activation/cyclization of 2-(indol-2-yl)oxazoles with alkynes.

关键词： rhodium catalyzed molecular oxygen C–H/C–H cross-coupling chelation-assisted strategy

Robust Stability Criteria for Neutral Systems with Interval Time-Varying Delays and Nonlinear Perturbations

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Journal of Harbin Institute of Technology(New Series) 2014年第2期21卷 68-74页

作者： Mao Wang yan-Ling Wei Zhao-lan he Le Xiao Space Control and Inertial Technology Research Center Harbin Institute of Technology School of Automation Harbin University of Science and Technology

This paper investigates the problem of delay-dependent robust stability analysis for a class of neutral systems with interval time-varying delays and nonlinear perturbations. Such nonlinear perturbations are with time-varying but norm-bounded characteristics. Based on a new Lyapunov-Krasovskii functional, together ,sith a free-weighting matrices technique, improved delay-dependent stability criteria are established. It is shown that less conservative results can be obtained in terms of linear matrix inequalities （LMIs）. Numerical examples are provided to demonstrate the effectiveness and less conservatism of the proposed approach.

关键词： neutral systems interval time-varying delays nonlinear perturbations robust matrix inequality