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Structure and kinematic analysis of a novel 2.DOF translational parallel robot

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Progress in Natural Science:Materials International 2007年第10期17卷 1213-1219页

作者： Chen Tao1, Wu Chao2.and liu xinjun2.1. School of Application Science and Technology, Harbin University of Science and Technology, Harbin 150080,{2. 2. department of Precision Instruments, Tsinghua University, beijing 100084,{2.) School of Application Science and Technology Harbin University of Science and Technology Harbin 150080 China department of Precision Instruments Tsinghua University Beijing 100084 China

This paper addresses the analysis of a novel parallel robot with 2.translational degrees of freedom (DOFs). The robot can position a rigid body in a plane with constant orientation. The kinematic structure of the robot is first described in detail. Some kinematic problems, such as the inverse and forward kinematics, velocity, and singularity are then analyzed. The working and assembly modes are discussed. Since it is the most important index to design a robot, the workspace of the robot is studied systematically in this paper. Based on the analysis of reachable workspace and singularity, a kind of workspace concept characterizing the region that the end-effector of the robot can reach in practice is defined. The results of this paper will be very useful for the design and application of the robot.

关键词： parallel robot degree of freedom kinematics workspace.

On the periodic solutions of a type of differential-iterative equations

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Chinese Science Bulletin 1998年第3期43卷 204-206页

作者： GE Weigao 1, liu Zhengrong 2.and YU Yuanhong 3 1. department of Applied Mathematics, {2. Institute of Technology, {2. 100081, china 2. department of Mathematics, Yunnan University, Kunming 650091, china 3. Institute of Applied Mathematics, C department of Applied Mathematics Beijing Institute of Technology Beijing China department of Mathematics Yunnan University Kunming China Institute of Applied Mathematics Chinese Academy of Sciences Beijing China

Sufficient conditions for the existence of periodic solutions to a type of nonautonomous differential_iterative equations are given.

关键词： differential_iterative equation periodic solution fixed point.

A Mendelian randomisation,propensity score matching study to investigate causal association between serum homocysteine and intracranial aneurysm

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Stroke & Vascular Neurology 2024年第3期9卷 202-211,I0104-I0109页

作者： Zhuohua Wen xin Feng xin Tong Chao Peng Anqi {2. Haiyan Fan Yiming Bi Wenchao liu Zhenjun Li Shenquan Guo Fa Jin Ran Li Yanchao liu Shixing Su xin Zhang Xifeng Li {2.ying He Aihua liu Chuanzhi Duan Neurosurgery Center Department of Cerebrovascular SurgeryEngineering Technology Research Center of Education Ministry of China on Diagnosis and Treatment of Cerebrovascular DiseaseZhujiang HospitalSouthern Medical UniversityGuangzhouChina beijing Neurosurgical Institute Beijing Tiantan HospitalCapital Medical UniversityBeijingChina department of Neurosurgery Guangdong Provincial People's Hospital(Guangdong Academy of Medical Sciences)Southern Medical UniversityGuangzhouChina

Background and purpose Recent observational studies have reported that serum total homocysteine(tHcy)is associated with intracranial aneurysms(IAs).However,the causal effect of tHcy on IAs is *** leveraged large-scale genetic association and real-world data to investigate the causal effect of tHcy on IA *** We performed a two-sample Mendelian randomisation(MR)using publicly available genome-wide association studies summary statistics to investigate the causal relationship between tHcy and IAs,following the recommendations of the Strengthening the Reporting of Observational Studies in Epidemiology-MR ***,a propensity score matching(PSM)analysis was conducted to evaluate the detailed effects of tHcy on risk of IA formation by utilizing real-world multicentre data,including 9902.patients with and without IAs(1:1 matched).Further interaction and subgroup analyses were performed to elucidate how tHcy affects risk of IA *** MR analyses indicated that genetically determined tHcy was causally associated with IA risk(OR,1.38,95%CI 1.07 to 1.79;p=0.018).This is consistent with the more conservative weighted median analysis(OR,1.41,95%CI 1.03 to 1.93;p=0.039).Further sensitivity analyses showed no evidence of horizontal pleiotropy or heterogeneity of single nucleotide polymorphisms in causal *** to the PSM study,we found that,compared with low tHcy(≤15μmol/L),moderate tHcy(>15-30μmol/L)(OR 2.13,95%CI 1.93 to 2.36)and high tHcy(>30μmol/L)(OR 3.66,95%CI 2.71 to 4.95)were associated with a higher IA risk(p trend2. to 2.01).Conclusion Both large-scale genetic evidence and multicentre real-world data support a causal as

关键词： matching random centre

Analysis on ignition and extinction of n-heptane in homogeneous systems

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Science china(Technological Sciences) 2005年第5期48卷 556-569页

作者： liu Yongfeng1 & PEI Pucheng2.1. Mechanical and Electrical Engineering {2., beijing Institute of Civil Engineering and Architec-ture, beijing 100044, china 2. State Key Laboratory of Automotive Safety and Energy, Tsinghua University, beijing 100084, china 1. Mechanical and Electrical Engineering department Beijing Institute of Civil Engineering and Architecture 100044 Beijing China 2. State Key Laboratory of Automotive Safety and Energy Tsinghua University 100084 Beijing China

To calculate ignition delay times, the governing equations about species and temperature, which are in a closed volume based on the theory of thermal explosion and in a continuously stirred flow reactor, are deducted. The method referred to steady state assumptions is based on the observation that due to very fast chemical processes in combustion problems many chemical species and reactions are in a quasi-steady state or partial equilibrium. When a species is assumed to be in the steady state, the corresponding differential equation can be replaced by an algebraic relation, which reduces the computational costs. The steady state solution of the reactor equations describes the three ignition temperature regimes and get “S-shaped curve”. The reduced simplified 4-step mechanism for n-heptane from 1011 elementary reactions leads with the steady state assumptions to linear differential equations, which is solved. The simulation results of the 4-step reduced mechanism for n-heptane are fitted well with the experiment data. At last, two important parameters are discussed thoroughly and the temperature perturbation is given. It reduces the computational efforts considerably without losing too much accuracy and further supplies numerical methods for turbulent combustion in the diesel engine.

关键词： ignition delay times, thermal runaway, steady state assumptions, continuously stirred flow reactor.

Dehydration melting of solid amphibolite at 2.0 GPa: Effects of time and temperature

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Science china Earth Sciences 2005年第8期48卷 1120-1133页

作者： ZHOU Wenge1, XIE Hongsen1, liu Yonggang1, ZHENG Xiaogang1, ZHAO Zhidan2.& ZHOU Hui3 1. Laboratory of Material in the Earth’s Interior, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002. china 2. {2. of Geology, china University of Geosciences, beijing 100083, china 3. {2. of Geology, Peking University, beijing 100871, china 1. Laboratory of Material in the Earth’s Interior Institute of Geochemistry Chinese Academy of Sciences 550002 Guiyang China 2. department of Geology China University of Geosciences 100083 Beijing China 3. department of Geology Peking University 100871 Beijing China

Two sets of dehydration-melting with a natural solid amphibolite, collected from North Himalayan structure zone, Tibet, have been carried out in multi-anvil apparatus at 2.0 GPa and 800―1000℃, for 12.2.0 h. One is keeping the pressure at 2.0 GPa and the annealing time of 12.h, changing the temperature (800―1000℃). The other is keeping the pressure at 2.0 GPa and temperature at 850℃, varying the annealing time (12.2.0 h). The products are inspected with microscope and electron probe. The results indicate that at 2.0 GPa, annealing time of 12.h, garnets, melts and clinopyroxenes occur in amphibolite gradually with increasing temperature and the chemical compositions of melt vary from tonalite to granodiorite, and then to tonalite. However, at 2.0 GPa and 850℃, with the annealing time increasing, the garnets, melts and cli-nopyroxenes also occur in amphibolite gradually and the chemical compositions of melt vary from tonalite to granodiorite. In both cases, melts interconnect with each other when the contents of melt are over the 5 vol.%. the viscosities of the melt produced in amphibolite at temperature higher than 850℃ are on a level with 104 Pa·s. The interconnected melt with such a viscosity may segregate from the source rock and form the magma over reasonable geological time. Therefore, it is believed that at the lower part of the overthickened crust, the tonlitic and grano-dioritic magma may be generated through the dehydration melting of amphibolite.

关键词： solid amphibolite, high pressure, high temperature, time, partial melting.

Solvation effects on brain uptakes of isomers of ^(99m)Tc brain imaging agents

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Chinese Science Bulletin 2002年第21期47卷 1786-1791页

作者： JIA Hongmei, MA Xiaohui, WANG Cunxin & liu Boli1. {2. of Chemistry, beijing Normal University, beijing 100875, china 2. Center for Biomedical Engineering, beijing Polytechnic University, beijing 10002., china 1. department of Chemistry Beijing Normal University Beijing 100875 China 2. Center for Biomedical Engineering Beijing Polytechnic University Beijing 100022 China

Analysis of electrostatic hydration free energies of the isomers of the 99mTc-BAT and 99mTc-DADT complexes is carried out using the computer simulation technique. The results show that not only a correlation exists between the logarithm of the brain uptake and the electrostatic hydration free energy for the isomers of 99mTc-brain radiopharmaceu-ticals, but also a linear relationship exists between the logarithm of the ratio of the brain uptake of the syn isomer to that of the anti one and the difference between the electrostatic hydration free energy of the syn-isomer and that of the anti one. Furthermore, the investigation on the important factors influencing the brain uptakes of 99mTc-radiophar-maceuticals and the reasons of the different biodistribution of the isomers of the 99mTc-complexes is explored at the molecular level. The results may provide a reference for the rational drug design of brain imaging agents.

关键词： 99mTc-brain imaging agent isomer brain uptake electro-static hydration free energy.

Preparation of MWNTs/Al_2._3 composites and their mechanical and electrical properties

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Science china(Technological Sciences) 2005年第6期48卷 622-631页

作者： FAN Jinpeng1,2. ZHAO Daqing1,2. xu Zening1,2.& WU Minsheng1,2.1. department of Mechanical Engineering, Tsinghua University, {2. 100084, china 2. Key Laboratory for Advanced Manufacturing by Materials Processing Technology, Tsinghua University, {2. 100084, china 1. department of Mechanical Engineering Tsinghua University 100084 Beijing China 2. Key Laboratory for Advanced Manufacturing by Materials Processing Technology Tsinghua University 100084 Beijing China

The mechanical and electrical properties of MWNTs/Al2.3 composite prepared fabricated by hot pressing are investigated. The relation between properties and microstructure of composites is also discussed. With 4wt% MWNTs as reinforcement, the fracture toughness of composite obtained reaches 5.55 MPa·m1/2. which is 80% higher than that of pure Al2.3 obtained in the same conditions. The main toughening mechanism is CNTs’ pinning alumina grain boundaries, and the pullout of CNTs takes effect also. Through adding 2.t% MWNTs and altering the mix method, the fracture toughness of the composite obtained is 3.97 MPa·m1/2. Furthermore, the electrical resistivity is as low as 8.4×10?3 ?·m, decreasing by 14 orders of magnitude compared with pure alumina ceramics. The function of CNTs in composite is related to the distribution state of CNTs in composite, and the distribution state of CNTs in matrix is dependent on preparation procedures.

关键词： MWNTs, alumina, composite, fracture toughness, electrical properties.

Pole assignment in descriptor periodic systems

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Science china Mathematics 2005年第10期48卷 1309-1332页

作者： FAN Hung-Yuan~1 LIN Wen-Wei~1 & xu Shufang~2.1. department of Mathematics,Tsing Hua University,Hsinchu 30043,{2. 2. LMAM,School of Mathematical Sciences,Peking University,beijing 100871,{2. 1. department of Mathematics Tsing Hua University 30043 Hsinchu China 2. LMAM School of Mathematical Sciences Peking University 100871 Beijing China

In this paper a pole assignment problem is considered for the descriptor linear discrete-time periodic systems, which is using the periodic proportional-derivative feedback to modify a given system such that the closed loop system has a specified selfconjugate set of eigenvalues. It is shown that the complete reachability of an open loop periodic system is equivalent to the possibility of assigning an arbitrary set of the eigenvalues to the system by choosing the suitable periodic proportional-derivative feedback.A computational approach is also proposed to solve the problem, which uses the reliable numerical techniques based on the orthogonal transformations. Numerical examples are presented to illustrate the effectiveness of the proposed approach.

关键词： descriptor linear periodic system, pole assignment, proportional and derivative feedback, numerical method, periodic Schur decomposition.

METTL1 promotes colorectal cancer cell proliferation by attenuating CHEK2.induced G1/S phase arrest

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Genes & Diseases 2024年第2期11卷 579-581页

作者： Houxiang Jiang Ying liu Huibin Song Jinquan Xia Ying Tian Luolin Wang Mingwei Li Zhenyu xu Zheng{2.i xu chang Zou department of Gastrointestinal Surgery The First Affiliated Hospital of Wannan Medical College (Yijishan Hospital of Wannan Medical College)WuhuAnhui 241001China Anhui Province Clinical Research Center for Critical Respiratory Medicine WuhuAnhui 241001China department of Clinical Medical Research Center The Second Clinical Medical College (Shenzhen People's Hospital) of Jinan UniversityThe First Affiliated Hospital of Southern University of Science and TechnologyShenzhenGuangdong 518020China Integrated Chinese and Western Medicine Postdoctoral Research Station Jinan UniversityGuangzhouGuangdong 510632China School of Pharmacy Southwest Medical UniversityLuzhouSichuan 646000China department of Gastroenterology Shenzhen People's Hospital(The Second Clinical Medical CollegeJinan UniversityThe First Affiliated HospitalSouthern University of Science and Technology)ShenzhenGuangdong 518020China Precision Medicine Center The First Affiliated Hospital of Wannan Medical College(Yijishan Hospital of Wannan Medical College)WuhuAnhui 241001China School of Medicine Life and Health SciencesThe Chinese University of Hong KongShenzhenGuangdong 518172China

Colorectal carcinoma(CRC),the third most commonly diagnosed cancer,accounts for 9.7%of all newly diagnosed cancer cases and 9.4%of cancer-related deaths globally.1 Recent studies have demonstrated that post-transcriptional RNA modifications,such as N^(6)-methyladenosine,N^(5)-methylcytosine,and N^(7)-methylguanosine,play critical roles in the regulation of mRNA stability and translation,primary microRNA processing,and lncRNA-protein complex that contributes to the progression of human cancer.

关键词： cancer colorectal globally