检索结果-南通市图书馆

Frequent item sets mining from high-dimensional dataset based on a novel binary particle swarm optimization

在线全文

学校读者我要写书评

暂无评论

Journal of Central South University 2016年第7期23卷 1700-1708页

作者：张中杰黄健卫莹 College of Mechatronics Engineering and Automation National University of Defense Technology

A novel binary particle swarm optimization for frequent item sets mining from high-dimensional dataset(BPSO-HD) was proposed, where two improvements were joined. Firstly, the dimensionality reduction of initial particles was designed to ensure the reasonable initial fitness, and then, the dynamically dimensionality cutting of dataset was built to decrease the search space. Based on four high-dimensional datasets, BPSO-HD was compared with Apriori to test its reliability, and was compared with the ordinary BPSO and quantum swarm evolutionary(QSE) to prove its advantages. The experiments show that the results given by BPSO-HD is reliable and better than the results generated by BPSO and QSE.

关键词： data mining frequent item sets particle swarm optimization

Recent progress on photoactive nonprecious transition-metal complexes

在线全文

学校读者我要写书评

暂无评论

Science China Chemistry 2025年第1期68卷 46-95页

作者： zhong-Liang Gong Hong-jie zhang Yan Cheng Jianxun Liu Yuhan Ai Yaqin Li Zhihui Feng Qiong zhang Shaolong Gong Yong Chen Chang-Jiang Yao Yuan-Yuan Zhu Liang-Jin Xu Yu-Wu zhong CAS Key Laboratory of Photochemistry Institute of Chemistry Chinese Academy of Sciences State Key Laboratory of Structural Cemistry Fujian Institute of Research on the Structure of Matter Chinese Academy of Sciences School of Chemistry and Chemical Engineering Anhui Key Laboratory of Advanced Catalytic Materials and Reaction EngineeringHefei University of Technology State Key Laboratory of Explosion Science and Safety Protection School of Mechatronical Engineering Beijing Institute of Technology College of Chemistry and Molecular Sciences Hubei Key Lab on Organic and Polymeric Optoelectronic Materials Wuhan University School of Chemistry and Chemical Engineering Anhui University Key Laboratory of Photochemical Conversion and Optoelectronic Materials & CAS-HKU Joint Laboratory on New Materials Technical Institute of Physics and Chemistry Chinese Academy of Sciences

Photoactive complexes of nonprecious transition metals, mainly including those in the first-row and partially the second-row of the Periodic table of elements, have received increasing attention in view of their low cost and long-term sustainability. They are recognized as promising alternatives to noble transition metal complex congeners that have been extensively studied in optoelectronic devices, artificial photosynthesis, photocatalysis, biodiagnostics, and therapeutics, etc. This review is devoted to a comprehensive summary on the classical and recent advances on photoactive nonprecious transition metal complexes, including photoactive Zr, V, Cr, Mo, and W complexes, Mn complexes and hybrids, Fe, Co, Ni, and Cu complexes, and Zn and Cd complexes and hybrids. A particular focus is given on the molecular design, modulation of photophysical and photochemical properties, and applications of the representative and lately-developed nonprecious metal complexes. In addition, a perspective on the future development in this field is provided at the end of this review.

关键词： photoactive metal complexes earth-abundant metals nonprecious metal complexes luminescence photochemistry

Seismic wavefield modeling in media with fluid-filled fractures and surface topography

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Seismic wavefield modeling in media with fluid-filled fractu...

横向各向同性(VTI)介质中非线性地震波场模拟

中国科学院地质与地球物理研究所2012年度（第12届）学术年会

作者： Lan Hai-Qiang zhang zhong-jie State Key Laboratory of Lithospheric Evolution Institute of Geology and GeophysicsChinese Academy of Sciences Graduate School of Chinese Academy of Sciences

We present a finite difference(FD) method for the simulation of seismic wave fields in fractured medium with an irregular(non-flat) free surface which is beneficial for interpreting exploration data acquired in mountainous *** are introduced through the Coates-Schoenberg approach into the FD scheme which leads to local anisotropic properties of the media where fractures are *** implement surface topography,we take advantage of the boundary-conforming grid and map a rectangular grid onto a curved *** use a stable and explicit second-order accurate finite difference scheme to discretize the elastic wave equations(in a curvilinear coordinate system) in a 2D heterogeneous transversely isotropic medium with a horizontal axis of symmetry(HTI).Efficiency tests performed by different numerical experiments clearly illustrate the influence of an irregular free surface on seismic wave propagation in fractured media which may be significant to mountain seismic *** tests also illustrate that the scattered waves induced by the tips of the fracture are re-scaltered by the features of the free surface *** scattered waves provoked by the topography are re-scattered by the fractures,especially Rayleigh wave scattering whose amplitudes are much larger than others and making it very difficult to identify effective information from the fractures.

关键词： finite difference modeling fracture irregular free surface curvilinear coordinate

来源： cnki会议评论

在线全文

cnki会议

学校读者我要写书评

暂无评论

地球物理学报 2005年第3期48卷 660-671页

作者：郑海山张中杰中国科学院地质与地球物理研究所北京100029

数值计算方法是考察非线性弹性波在介质中(如岩石)传播特征的重要手段.非线性弹性波的数值模拟存在陡峭间断面(点)、数值振荡以及误差的指数级增长等现象而破坏数值解的稳定性、收敛性,能否消减上述现象的不利影响成为制约数值方法有效... 详细信息

数值计算方法是考察非线性弹性波在介质中(如岩石)传播特征的重要手段.非线性弹性波的数值模拟存在陡峭间断面(点)、数值振荡以及误差的指数级增长等现象而破坏数值解的稳定性、收敛性,能否消减上述现象的不利影响成为制约数值方法有效与否的重要因素.文中同时引入了FCT算子和幅值限制器,采用中心差分格式对具有垂直对称轴的横向各向同性(VTI)介质中的二维非线性弹性波进行数值模拟,从而克服了上述困难;介绍了适用于非线性弹性波的吸收边界条件,给出了差分方程的稳定性条件.在验证了方法的有效性后成功地获取了二维VTI介质中非线性弹性波的三分量地震正演记录,表明非线性波在传播过程中会发生波形畸变等现象.

关键词：非线性地震波 VTI介质 FCT算子幅值限制器合成记录

Dynamic behaviors of graphene platelets-reinforced metal foam piezoelectric beams with velocity feedback control

在线全文

学校读者我要写书评

暂无评论

Applied Mathematics and Mechanics(English Edition) 2025年第1期46卷 63-80页

作者： jie CHEN Xinyue zhang Mingyang FAN School of Mathematics Statistics and Mechanics Beijing University of Technology College of Mechanical & Energy Engineering Beijing University of Technology

Graphene platelets(GPLs)-reinforced metal foam structures enhance the mechanical properties while maintaining the lightweight characteristics of metal foams. Further bonding piezoelectric actuator and sensor layers on the surfaces of GPLs-reinforced metal foam beams enables active vibration control, greatly expanding their applications in the aerospace industry. For the first time, this paper investigates the vibration characteristics and active vibration control of GPLs-reinforced metal foam beams with surfacebonded piezoelectric layers. The constant velocity feedback scheme is used to design the closed-loop controller including piezoelectric actuators and sensors. The effects of the GPLs on the linear and nonlinear free vibrations of the beams are numerically *** Newmark-β method combined with Newton's iteration technique is used to calculate the nonlinear responses of the beams under different load forms including harmonic loads,impact loads, and moving loads. Additionally, special attention is given to the vibration reduction performance of the velocity feedback control on the responses of the beam.

关键词： Piezoelectric actuators

基于介质环形柱结构的二维光子晶体中Dirac点的实现

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

物理学报 2015年第14期64卷 320-328页

作者：张中杰沈义峰赵浩中国矿业大学理学院物理系徐州221116

利用偶然简并方法在二维正方格子介质环形柱结构光子晶体中成功实现了Dirac点,并利用平面波展开法对实现Dirac点的过程进行了研究.研究结果表明,对于二维正方格子介质环形柱结构光子晶体,在一定的外径RO范围内(0.37a1.4),介质环内径RI... 详细信息

利用偶然简并方法在二维正方格子介质环形柱结构光子晶体中成功实现了Dirac点,并利用平面波展开法对实现Dirac点的过程进行了研究.研究结果表明,对于二维正方格子介质环形柱结构光子晶体,在一定的外径RO范围内(0.37a1.4),介质环内径RI与外径RO满足一个不随介质环折射率n变化的恒定关系式.同时,Dirac点对应的光子约化频率f随折射率n及外径RO的增大而减小.利用所得的关系式对特定介质环折射率n条件下能实现Dirac点的环形光子晶体进行了预判设计.

关键词：环形柱结构光子晶体 Dirac点平面波展开法偶然简并

Color Doppler ultrasonographic examination on the relationship between the gallbladder bed and major branch of the middle hepatic vein

在线全文

学校读者我要写书评

暂无评论

Hepatobiliary & Pancreatic Diseases International 2005年第2期4卷 299-301页

作者： Wei-zhong zhang, jie Shen, Jue-Xing Xie and Hong Zhu Taizhou, China Departments of Surgery and Ultrasonography , Taizhou First People’s Hospital, Taizhou 318020, China Department of Surgery Taizhou First People's Hospital Taizhou 318020 China. zhangweizhong11@***

BACKGROUND: There is a controversy about the risk of injury to the branch of the middle hepatic vein during lapa- roscopic cholecystectomy. This study was conducted to further investigate the relationship between the gallbladder bed and the branch of the middle hepatic vein. METHODS: Color Doppler ultrasound was used to exa- mine the anatomical relationship between the gallbladder bed and the branches of the middle hepatic vein in 143 healthy volunteers. RESULTS: Not all the middle hepatic vein extended close to the gallbladder bed, the branches and gallbladder beds in 23 subjects were not in the same plane during ultrasound scanning. In 21 of the 143 subjects the branch of the middle hepatic vein was completely adherent to the gallbladder bed with a diameter ranging from 1.2 mm to 3.6 mm. In 10 subjects the branches of the middle hepatic vein traversed approximately 1.0 mm from the gallbladder bed with a dia- meter ranging from 1.6 mm to 3.0 mm. CONCLUSIONS: In most subjects the branch of the middle hepatic vein and the gallbladder bed are well separated. Only patients with large branches of the middle hepatic vein close to the gallbladder bed are at risk of hemorrhage during laparoscopic cholecystectomy.

关键词： laparoscopic cholecystectomy color Doppler ultrasound hepatic vein

基于加窗Hilbert变换的复偏振分析方法及其应用

在线全文

学校读者我要写书评

暂无评论

地球物理学报 2005年第4期48卷 889-895页

作者：陈赟张中杰田小波中国科学院地质与地球物理研究所北京100029

考虑到传统Hilbert变换所隐含的无限长序列假设的实际局限性,本文将多窗分析法引入到短时序列Hilbert变换中,通过构建复协方差矩阵和对该矩阵的特征值与特征向量的求解,获得三分量地震记录的时变偏振参数;基于不同波型的偏振特性与实测... 详细信息

考虑到传统Hilbert变换所隐含的无限长序列假设的实际局限性,本文将多窗分析法引入到短时序列Hilbert变换中,通过构建复协方差矩阵和对该矩阵的特征值与特征向量的求解,获得三分量地震记录的时变偏振参数;基于不同波型的偏振特性与实测偏振参数,采用线性_余弦权重函数或高斯权重函数自适应空间滤波,识别与分离具有特定偏振特性的不同地震响应.针对天然地震三分量记录的处理结果表明,该方法在识别、分离具有特定偏振特性的不同地震响应方面具有一定的潜力.

关键词： Hilbert变换多窗分析协方差矩阵偏振分析波场分离

光子晶体中基于有效折射率接近零的光束准直出射

在线全文

学校读者我要写书评

暂无评论

物理学报 2014年第17期63卷 160-164页

作者：赵浩沈义峰张中杰中国矿业大学理学院物理系徐州221116

利用平面波展开法(PWM)和时域有限差分法(FDTD)研究了二维正方格子光子晶体靠近禁带边沿附近频率光波的传输特性.研究发现,若有效折射率接近于零,可出现光束从晶体表面准直出射的现象,且光束的出射方向只与晶体表面的取向有关,而与晶格... 详细信息

利用平面波展开法(PWM)和时域有限差分法(FDTD)研究了二维正方格子光子晶体靠近禁带边沿附近频率光波的传输特性.研究发现,若有效折射率接近于零,可出现光束从晶体表面准直出射的现象,且光束的出射方向只与晶体表面的取向有关,而与晶格取向无关.这种现象与自准直现象有很大不同.

关键词：光子晶体有效折射率准直出射远场角