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Microstructural evolution of titanium matrix composite coatings reinforced by in situ synthesized TiB and TiC by laser cladding

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International Journal of Minerals,Metallurgy and Materials 2010年第4期17卷 481-488页

作者： Jun Li Zhi-shui yu Hui-ping wang Man-ping Li School of Materials Engineering Shanghai University of Engineering Science Shanghai 201620 China

Titanium-based composite coatings reinforced by in situ synthesized TiB and TiC particles were successfully fabricated on Ti6Al4V by laser cladding using Ti-B_4C-Al or Ti-B_4C-C-Al powders as the precursor *** microstructural and metallographic analyses were made by X-ray diffraction（XRD）,optical microscope（OM）,scanning electron microscopy（SEM）,and electron probe microanalysis （EPMA）.The results show that the coatings are mainly composed ofα-Ti cellular dendrites and a eutectic transformation product in which a large number of coarse and fine needle-shaped TiB and a few equiaxial TiC particles are homogeneously embedded.A thin dilution zone with a thickness of about 100μm is present at the interface,and it consists of a few TiB and TiC reinforcements and a large number of lamella grains growing parallel to the heat flux direction in which a thin needle-shaped microstructure exists due to the martensitic transformation. The microstructural evolution can be divided into four stages：precipitation and growth of primaryβ-Ti phase,formation of the binary eutecticumβ-Ti＋TiB,formation of the ternary eutecticumβ-Ti＋TiB＋TiC,and solid transformation fromβ-Ti toα-Ti.

关键词： coating laser cladding in-situ synthesis microstructure

The inverse problem for differential pencils on a star-shaped graph with mixed spectral data

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Science China Mathematics 2020年第8期63卷 1559-1570页

作者： yu ping wang Natalia Bondarenko Chung Tsun Shieh Department of Applied Mathematics Nanjing Forestry UniversityNanjing 210037China Department of Applied Mathematics and Physics Samara National Research UniversitySamara 443086Russia Department of Mathematics Tamkang UniversityNew Taipei City 25137China

The partial inverse problem for differential pencils on a star-shaped graph is studied from mixed spectral *** precisely,we show that if the potentials on all edges on the star-shaped graph but one are known a priori then the unknown potential on the remaining edge can be uniquely determined by partial information on the potential and a part of eigenvalues.

关键词： inverse spectral problem differential pencils potential star-shaped graph

A Trace Formula for Integro-differential Operators on the Finite Interval

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Acta Mathematicae Applicatae Sinica 2017年第1期33卷 141-146页

作者： yu-ping wang Hikmet Koyunbakan Chuan-fu YANG Department of Applied Mathematics Nanjing Forestry University Department of Mathematics Firat University Department of Applied Mathematics Nanjing University of Science and Technology

In this paper, we consider the eigenvalue problem for integro-differential operators with separated boundary conditions on the finite interval and find a trace formula for the integro-differential operator.

关键词： trace formula integro-differential operator eigenvalue

Up-Regulation of Trem2 Inhibits Hippocampal Neuronal Apoptosis and Alleviates Oxidative Stress in Epilepsy via the PI3K/Akt Pathway in Mice

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Neuroscience Bulletin 2019年第3期35卷 471-485页

作者： Ai-Hua Liu Min Chu yu-ping wang Department of Neurology Xuanwu Hospital Capital Medical University

Epilepsy is a chronic and severe neurological disorder that has negative effects on the autonomous activities of patients. Functionally, Trem2(triggering receptor expressed on myeloid cells-2) is an immunoglobulin receptor that affects neurological and psychiatric genetic diseases. Based on this rationale, we aimed to assess the potential role of Trem2 integration with the PI3 K/Akt pathway in epilepsy. We used microarray-based gene expression profiling to identify epilepsy-related differentially-expressed genes. In a mouse hippocampal neuron model of epilepsy, neurons were treated with lowMg^2+ extracellular fluid, and the protein and mRNA expression of Trem2 were determined. Using a gain-offunction approach with Trem2, neuronal apoptosis and its related factors were assessed by flow cytometry, RT-qPCR,and Western blot analysis. In a pilocarpine-induced epileptic mouse model, the malondialdehyde(MDA) and8-hydroxy-20-deoxyguanosine(8-OHdG) content and superoxide dismutase(SOD) and glutathione-peroxidase(GSH-Px) activity in the hippocampus were determined,and the protein expression of Trem2 was measured. In addition, the regulatory effect of Trem2 on the PI3 K/Akt pathway was analyzed by inhibiting this pathway in both the cell and mouse models of epilepsy. Trem2 was found to occupy a core position and was correlated with ***2 was decreased in the hippocampus of epileptic miceand epileptic hippocampal neurons. Of crucial importance,overexpression of Trem2 activated the PI3 K/Akt pathway to inhibit neuronal apoptosis. Moreover, activation of the PI3 K/Akt pathway through over-expression of Trem2 alleviated oxidative stress, as shown by the increased expression of SOD and GSH-Px and the decreased expression of MDA and 8-OHdG. The current study defines the potential role of Trem2 in inhibiting the development of epilepsy, indicating that Trem2 up-regulation alleviates hippocampal neuronal injury and oxidative stress, and inhibits neuronal apoptosis in epilepsy

关键词： Trem2 Epilepsy Neuronal apoptosis PI3K/Akt pathway Oxidative stress

Synthesizing Robot Programs with Interactive Tutor Mode

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International Journal of Automation and computing 2019年第4期16卷 462-474页

作者： Hao Li yu-ping wang Tai-Jiang Mu Tsinghua National Laboratory for Information Science and Technology(TNList) Department of Computer Science and TechnologyTsinghua University

With the rapid development of the robotic industry, domestic robots have become increasingly popular. As domestic robots are expected to be personal assistants, it is important to develop a natural language-based human-robot interactive system for end-users who do not necessarily have much programming knowledge. To build such a system, we developed an interactive tutoring framework, named " Holert”, which can translate task descriptions in natural language to machine-interpretable logical forms automatically. Compared to previous works, Holert allows users to teach the robot by further explaining their intentions in an interactive tutor mode. Furthermore, Holert introduces a semantic dependency model to enable the robot to " understand” similar task descriptions. We have deployed Holert on an open-source robot platform, Turtlebot 2. Experimental results show that the system accuracy could be significantly improved by 163.9% with the support of the tutor mode. This system is also efficient. Even the longest task session with 10 sentences can be handled within 0.7 s.

关键词： Human-robot interaction semantic parsing program synthesis intelligent robotic systems natural language unders-tanding

Realizing high thermoelectric properties in p-type polycrystalline SnSe by inducing DOS distortion

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Rare Metals 2021年第10期40卷 2819-2828页

作者： yu-ping wang Bing-Chao Qin Dong-Yang wang Tao Hong Xiang Gao Li-Dong Zhao School of Materials Science and Engineering Beihang UniversityBeijing 100191China Center for High Pressure Science and Technology Advanced Research(HPSTAR) Beijing 100094China

SnSe crystals have been discovered as one of the most efficient thermoelectric materials due to their remarkable thermal and electrical transports. But the polycrystalline SnSe possesses much lower performance especially for the low carrier mobility and electrical conductivity. We firstly attempted to explain and verify the difference in the electrical conductivity as a function of temperature between p-type crystalline and polycrystalline SnSe by considering the grain boundary effects in the polycrystalline samples. On the basis of 2% Na doping to optimize the carrier concentration, the carrier mobility is improved by further introducing In, leading to enhanced carrier mobility from 3 to 9 cm2·V^(-1)·s^(-1) in polycrystalline SnSe. Moreover, In doping introduces extra resonant levels in SnSe, which increases the density of states near Fermi level and leads to an enhanced band effective mass. Large Seebeck coefficient of ~205 l V·K^(-1) at 300 K and maximum power factor of ~7.5 l W·cm^(-1)·K^(-2) at 773 K can be obtained in the Sn_(0.975)Na_(0.02)In_(0.005) Se sample,leading to a competitively high dimensionless figure of merit(ZT) value exceeding 1.1 at 773 K.

关键词： Thermoelectric p-type polycrystalline SnSe Carrier mobility Resonant effect Band effective mass

Effects of UV-A exposures on longevity and reproduction in Helicoverpa armigera, and on the development of its F1 generation

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Insect Science 2011年第6期18卷 697-702页

作者： Chang-yu Zhang Jian-yu Meng Xiao-ping wang Fen Zhu Chao-Liang Lei Hubei Insect Resources Utilization and Sustainable Pest Management Key Laboratory College of Plant Science and TechnologyHuazhong Agricultural University Wuhan China

Helicoverpa armigera adults display a conspicuous positive phototactic behavior to light stimuli, and are especially sensitive to ultraviolet （UV） light. The effects of UV-A （longwave） exposures on adult longevity and reproduction in H. armigera were investigated, as well as the development of the Ft generation. Paired adults were exposed to UV-A for various time periods （0, 1, 5 and 9 h/day）, until the end of adult life. The results showed that adult longevity decreased with increasing exposure time for both sexes, and a significant decrease was observed after exposure for 5 and 9 h/day. Fecundity increased when adults were exposed for 1 and 5 h/day, and a significant difference was observed in the 5 h/day group. Oviposition rates of females in all treatments were significantly higher than in the control. Exposure to UV-A for longer periods （5 and 9 h/day） caused a decline in cumulative survival of F1 immature stages, but no significant differences were found in egg hatch, pupation and eclosion. The developmental periods of F1 larvae were significantly prolonged after exposure to UV-A for 5 and 9 h/day. UV-A radiation had no significant effects on F1 pupal period.

关键词： development Helicoverpa armigera longevity oxidative stress,reproduction UV-A

Dry-spun Polyimide Fibers with Excellent Thermal Stability,Intrinsic Flame Retardancy and Ultralow Smoke Release

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Chinese Journal of Polymer Science 2022年第11期40卷 1422-1431页

作者： Han Dong yu-ping wang Xiu-Ting Li Xin Zhao Jie Dong Qing-Hua Zhang State Key Laboratory for Modification of Chemical Fibers and Polymer Materials College of Materials Science and EngineeringDonghua UniversityShanghai201620China Jiangsu New Vision Advanced Functional Fiber Innovation Center Co. Ltd.Suzhou215000China

Polymer fiber with an ultrahigh thermal stability,superior flame retardancy and low smoke release during combustion is urgently needed and a crucial challenge for developing advanced fireproof *** this study,a series of high-performance polyimide fibers are synthesized by copolymerizing 4,4'-diaminodiphenylmethane(MDA)into the pyromellitic dianhydride-p-phenylenediamine(PMDA-PDA)backbone for synergistically solving the technical challenge of poor fiber processing ability of these polyimides with a high inherent molecular *** glass transition temperature(Tg)of resultant fibers with the PDA molar ratio over 50 mol%reaches above 420℃ and their 10 wt%weight loss temperature(T10%)is within 543-633℃.For the typical fiber containing 80 mol%of PDA,the limiting oxygen index(LOI)reaches 39%and exhibits a rapid self-extinguishing performance after deviating from the ***,this fiber exhibits the minimum heat release rate of 14.1 kW/m^(2) in a long ignition time of 813 s during combustion,revealing its better flame retardancy than the well-known Nomex fiber with a heat release rate of 140.6 kW/m^(2) during the 120 s ***,the total smoke production of this polyimide fiber is only 1/9 of the Nomex ***,the excellent flame retardancy of polyimide fibers indicating them more attractive as the fireproof materials in the field of emergency protection.

关键词： Polyimide fiber Copolymerization Thermal stability Flame retardancy Smoke release

Coarsening and Age Hardening Behaviors of γ' Particles in GH742 During High Temperature Treatment

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Journal of Iron and Steel Research International 2009年第5期16卷 81-86页

作者： LI Hong-yu SONG Xi-ping wang Yan-li CHEN Guo-liang State Key Lab for Advanced Metals and Materials University of Science and Technology Beijing Beijing 100083 China

The coarsening and ageing hardening behaviors of γ′ particles in superalloy GH742 have been investigated by field emission scanning electron microscopy （FESEM）, coarsening kinetics calculation and microhardness testing when ageing at 1 050, 950 and 900 ℃ for different time. The cube of γ′ particle size and ageing time follows a linear law as predicted by LSW theory. The particle size distributions give better fit to the LSW theoretical distribution. The activation energy for γ′ coarsening is accurately determined to have 245. 06±14.42 kJ/mol when considering the effect of temperature on the solution concentrations in matrix. Based on the activation energy, the coarsening kinetics of γ′ particle is predicted as r^-t^3=7.35×10^15 Ce/T exp -（245060±14420）/RT *** microhardness studies indicate that microhardness decreases rapidly with increasing the ageing temperature and it has a maximum value corresponding to a critical particle size beyond which the microhardness increase stalls with increasing the ageing time.

关键词： superalloy γ′ particle coarsening kinetics activation energy microhardness