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Seshadri constants and the spaces of curves with prescribed singularities and positions

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Science China Mathematics 2011年第8期54卷 1611-1620页

作者： GAO Yun tan sheng-Li Department of Mathematics Shanghai Jiao Tong UniversityShanghai 200240China Department of Mathematics East China Normal UniversityShanghai 200241China

We will give optimal bounds for Seshadri constants of an ample line bundle at multiple points on a complex projective surface *** also present a solution to the long-studied classical problem on the existence of curves on X with given topological singularities at r arbitrary points p1,...,***,we obtain a universal lower bound on the degree of curves for the *** is independent of the position of the singular points.

关键词： Seshadri constant topological type curve singularities k-very ample

Calculating the Fundamental Group of Galois Cover of the(2, 3)-embedding of CP^1× T

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Acta Mathematica Sinica,English Series 2020年第3期36卷 273-291页

作者： Meirav AMRAM sheng Li tan Wan Yuan XU Michael YOSHPE Department of Mathematics Shamoon College of EngineeringAshdodIsrael School of Mathematical Sciences Shanghai Key Laboratory of PMMPEast China Normal UniversityShanghai 200241P.R.China Department of Mathematics Shanghai Normal UniversityShanghai 200234P.R.China

As known to all,it is quite difficult to compute the fundamental group of a surface of general *** this paper,applying Moishezon-Teicher’s algorithm,we investigate the fundamental group of a special surface of general type with zero topological index,namely,the Galois cover of the(2,3)-embedding of CP^1×*** the full presentation of the group is very complicated,we compute its special quotient and get an interesting result about its structure.

关键词： Fundamental groups Galois cover braid monodromy factorization

Power Adjusting Algorithm： A New Cross-Layer Power Saving Mechanism for Mobile Ad-Hoc Networks

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Journal of Computer Science & Technology 2013年第1期28卷 42-53页

作者： Jin-Tao Meng Jian-Rui Yuan sheng-Zhong Feng Lian-sheng tan Shenzhen Institutes of Advanced Technology Chinese Academy of Sciences Shenzhen 518055 China Institute of Computing Technology Chinese Academy of Sciences Beijing 100190 China Graduate University of Chinese Academy of Sciences Beijing 100049 China Central South University Changsha 410083 China School of Information Science and Engineering Central China Normal University Wuhan 430079 China

Power saving is one of the key issues in Mobile Ad-Hoc Networks （MANETs）. It can be realized in Medium Access Control （MAC） layer and network layer. However, previous attentions were mainly paid to MAC layer or network layer with the aim of improving the channel utilization by adopting variable-range transmission power control. In this paper we focus on the power saving in both MAC layer and network layer, and propose a Power Adjusting Algorithm （PAA）. In the presence of host＇s mobility, PAA is designed to conserve energy by adjusting the transmission power to maintain the route＇s connectivity and restarting the route discovery periodically to find a new route with better energy efficiency dynamically. After analyzing the operations of PAA, we find that the length of route discovery restarting period is a critical argument which will affect power saving, and an energy consumption model is abstracted to find the optimal value of the restarting period by analyzing the energy consumption of this algorithm. PAA can handle the mobility of MANET by adjusting the transmission power and in the meantime save energy by restarting route discovery periodically to balance the energy consumption on route discovery and packet delivering. Simulation results show that, PAA saves nearly 40% energy compared with Dynamic Source Routing protocol when the maximum speed of mobile hosts is larger than 8 m/s.

关键词： mobile ad-hoc networks mobility control power control power efficiency

The influence of radial entrance width of the circular cavity on incident shock wave focusing

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Propulsion and Power Research 2018年第2期7卷 120-128页

作者： Xin Chen Chuan Wang sheng tan Liming He Qiang Zhang Aeronautics and Astronautics Engineering College Air Force Engineering UniversityXi’an 710038China Aerospace Science and Engineering College National University of Defense TechnologyChangsha 410071China

Despite the achievement of shock wave focusing with certain reflectors,the influence of the radial entrance width of a circular cavity on the flow field has yet to be *** this study,we systematically investigated the effects of the shock wave focusing process in a cavity based on the radial entrance *** experimental system was installed to research the evolution of the flow field under conditions with different radial entrance widths of 3.0,11.1,19.5,and 33.0 mm.A schlieren system was used to photograph the structures of the flow field in the cavity,and a data acquisition system was used to record the dynamic pressure histories of different points.A numerical simulation was carried out to investigate greater details of the shock wave focusing process.A third-order strong stability-preserving Runge-Kutta method,third-order weighed essential non-oscillation scheme,and an adaptive mesh refinement algorithm were adopted to simulate the shock wave reflection,diffraction,and focus *** agreement between the experimental and numerical results was *** comparing the evolution process of the flow field under the conditions of four different entrance cavity widths,we found that when the entrance width was 19.5 mm,there was the stronger intensity of the shock wave focusing in the focal region,and the larger pressure value at the apex of the cavity than the other three entrance widths,*** study improves our understanding of shock wave focusing.

关键词： Shock wave focusing Radial entrance widths Cavity Schlieren system Weighed essential nonoscillation

SYNTHESIS AND PROPERTIES OF UV-CURABLE POLYSILOXANE METHACRYLATE OBTAINED BY ONE-STEP METHOD

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Chinese Journal of Polymer Science 2013年第2期31卷 363-370页

作者： Zhen Li Dong-sheng tan Qi-lin Ren 傅强 Yan-fen Xu Yun-feng Tao College of Polymer Science and Engineering State Key Laboratory of Polymer Materials EngineeringSichuan University Chengdu Taly Industrial Chemical Co. Ltd of China

In this study, a UV-curable polysiloxane methacrylate （PSMA） was synthesized by a one-step method. The reaction was catalyzed by chloroplatinic acid between polymethylhydrosiloxane （PMHS） and hydroxyethyl methacrylate （HEMA）, as proved by FTIR and ^1H-NMR. The preliminary results indicate that the obtained UV-cured PSMA film has very good thermal stability, excellent transparency and satisfactory tensile strength. Our work provides a simple but efficient way to prepare UV-curable PSMA, which may find potential applications in UV-curing optical fiber, metal and glass coating and other fields.

关键词： Polysiloxane methacrylate UV-curing Synthesis.

Mechanism of thermoviscoelasticity driven solid-liquid interface reducing friction for polymer alloy coating

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Friction 2023年第9期11卷 1606-1623页

作者： sheng tan Yimin LUO Junhua YANG Wei WANG Xia LI Baoguang JIA Zhuangzhu LUO Guangan ZHANG School of Materials Sun Yat-sen UniversityShenzhen 518107China The 14th Research Institute of China Electronics Technology Group Corporation Nanjing 210039China State Key Laboratory of Solid Lubrication Lanzhou Institute of Chemical PhysicsChinese Academy of SciencesLanzhou 730000China

High-temperature ablation is a common failure phenomenon that limits the service life of the transmission parts on heavy-duty machines used in heavy load,high temperature,high shock conditions due to in-sufficient supply of lubricating oil and *** self-lubricating coatings prepared by inorganic,organic or organic-inorganic hybrid methods are prone to be oxidated at high temperatures to lose their friction reducing function,so that it is difficult to meet the engineering requirements of high-temperature *** design viscoelastic polymer coatings by a high-temperature self-lubricating and wear-resistant ***(PTFE,T_(m)=329℃)and polyphenylene sulfide(PPS,T_(g)=84℃,T_(m)=283℃)are used to prepare a PTFE/PPS polymer alloy *** the temperature increases from 25 to 300℃,the PTFE/PPS coating softens from glass state to viscoelastic state and viscous flow state,which is owing to the thermodynamic transformation characteristic of the PPS *** the friction coefficient(μ)decreased from 0.096 to 0.042 with the increasing of temperature from 25 to 300℃.The mechanism of mechanical deformation and surface morphology evolution for the PTFE/PPS coating under the multi-field coupling action of temperature(T),temperature–centrifugal force(T–F_(ω)),temperature–centrifugal force–shearing force(T–F_(ω)–F_(τ))were *** physical model of“thermoviscoelasticity driven solid–liquid interface reducing friction”is proposed to clarify the self-lubricating mechanism determined by the high-temperature viscoelastic properties of *** high-temperature adjusts the viscosity(η)of the coating,increases interface slipping and intensifies shear deformation(τ),reducing the friction *** result is expected to provide a new idea for designing anti-ablation coatings served in high temperature friction and wear conditions.

关键词： self-lubricating polymer coating viscoelastic state solid-liquid interface friction reduction hightemperature tribology

Spatial variation of health risk of groundwater for drinking water supply in Mingshan County,Ya'an City,China

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Water Science and Engineering 2010年第4期3卷 454-466页

作者： Fu-quan NI Guo-dong LIU Yao-sheng tan Yu DENG State Key Laboratory of Hydraulics and Mountain River Engineering Sichuan University Chengdu 610065 P. R. China College of Information and Engineering Sichuan Agricultural University Ya ＇an 625014 P. R. China College of Civil Engineering Tianjin University Tianjin 300072 P. R. China Key Laboratory of Sichuan Agricultural Environment Engineering Sichuan Agricultural University Ya ＇an 625014 P. R. China

Rural drinking water safety is a growing concern in China. This study investigated the health risk of pollution of groundwater for the drinking water supply in Mingshan County, Ya＇an City, in Sichuan Province, China, using 46 samples from the years 1991 to 2010. Carcinogenic, non-carcinogenic, and total risks were assessed by the model recommended by the United States Environmental Protection Agency （U.S. EPA）. Thematic maps of the risks caused by single and multiple factors were generated from inverse distance weighting interpolation （IDW） and the geostatistical analysis functions of ArcGIS. The results show that the carcinogenic risks caused by chemicals in groundwater for drinking water supply are low, within the acceptable interval for risk management. However, non-carcinogenic risks are high and the number of sampling sites with risk values exceeding the standards amounted to 29. Non-carcinogenic risks of Cr6＋, nitrate, fluoride, and Fe at sites 43, 46, 50, 64, 67, and 74 were the sources that caused high total health risk. This study reveals the risk level of groundwater quality and orders of treatment of pollutants, and provides a scientific basis for groundwater management in this area.

关键词： groundwater for drinking water supply water safety health risk assessment (HRA) Ya 'an City

How Effective are Decentralized Anti-poverty Programs?

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China & World Economy 2024年第4期32卷 85-113页

作者： Shuai Chen Mingda Cheng Jie-sheng tan-Soo China Academy for Rural Development and School of Public Affairs Zhejiang UniversityChina Jiangxi Caitong Supply Chain Financial Group Co. Ltd.Jiangxi Financial Holding Group Co.Ltd.China Lee Kuan Yew School of Public Policy National University of SingaporeSingapore

This study examines the effectiveness of China's National Poor Counties(NPC)program,a decentralized anti-poverty initiative,by analyzing five rounds of individual-level panel data from 1988 to *** impact of two waves of the NPC program(1994 and 2001)is evaluated utilizing a panel fixed-effects regression *** results indicate substantial positive effects,with residents in NPC counties experiencing a 47 percent income increase,3.1 percent higher employment rates,and a 5.7 percent rise in household expenditure from 1988 to 2008,in comparison with non-NPC ***,the program benefited vulnerable populations,dispelling concerns about"elite capture."The study also reveals that evolving policy focus has played a pivotal role in sustaining the effects of the program over *** 1994 round prioritized low-skilled employment,and the 2001 wave emphasized productivity enhancement through skills *** findings highlight the continued efficacy of decentralized anti-povertyefforts.

关键词： decentralization elite capture National Poor Counties program poverty

Fe_3O_4 Magnetic Nanoparticles Modified Electrode as a Sensor for Determination of Nimesulide

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Chemical Research in Chinese Universities 2011年第4期27卷 566-569页

作者： ZHANG Jin-lei tan Xue-cai ZHAO Dan-dan tan sheng-wei LIU Li WANG Lin HUANG Zeng-wei College of Chemistry and Ecological Engineering Guangxi University for Nationalities Nanning 530006 P. R. China Department of Chemistry and Life Science Baise University Baise 533000 P. R. China

A novel type of Fe3O4 nanoparticles modified glass carbon electrode（Fe3O4/GCE） was constructed and the electrochemical properties of N-（4-nitro-2-phenoxyphenyl）methanesulfonamide（nimesulide） were studied on the Fe3O4/*** 0.4mol/L HAc-NaAc buffer solution（pH=5.0）,the electrode process of nimesulide was irreversible at bare GCE and Fe3O4/*** Fe3O4/GCE exhibited a remarkable catalytic and enhancement effect on the reduction of *** reduction peak potential of nimesulide shifted positively from-0.683 V at bare GCE to-0.625 V at Fe3O4/GCE,and the sensitivity was increased by ca.3 *** experimental conditions were *** linear range between the peak current and the concentration of nimesulide was 2.6×10-6 ＂1.0×10-4mol/L（R=0.993） with a detection limit of 1.3×10-7mol/*** method has been used to determine the content of nimesulide in medical *** recovery was determined to be 96.9% ＂101.9% by means of standard addition *** method is comparable to UV-Vis spectrometry.

关键词： Fe3O4 nanoparticle Modified electrode Nimesulide Determination Electrochemical behavior