检索结果-南通市图书馆

Adaptive sparse and dense hybrid representation with nonconvex optimization

Frontiers of Computer Science 2020年第4期14卷 65-78页

作者： Xuejun wang Feilong CAO wenjian wang School of Computer Science and Technology Shanxi UniversityTaiyuan030006China School of Science China Jiliang UniversityHangzhou310018China Key Laboratory of Computational Intelligence and Chinese Information Processing of Ministry of Education Taiyuan030006China

Sparse representation has been widely used in signal processing,pattern recognition and computer vision *** achievements have been made in both theoretical researches and practical ***,there are two limitations on the application of *** is that sufficient training samples are required for each class,and the other is that samples should be *** order to alleviate above problems,a sparse and dense hybrid representation(SDR)framework has been proposed,where the training dictionary is decomposed into a class-specific dictionary and a non-class-specific *** putsℓ1 constraint on the coefficients of class-specific ***,it over-emphasizes the sparsity and overlooks the correlation information in class-specific dictionary,which may lead to poor classification *** overcome this disadvantage,an adaptive sparse and dense hybrid representation with non-convex optimization(ASDR-NO)is proposed in this *** trace norm is adopted in class-specific dictionary,which is different from general *** doing so,the dictionary structure becomes adaptive and the representation ability of the dictionary will be ***,a non-convex surrogate is used to approximate the rank function in dictionary decomposition in order to avoid a suboptimal solution of the original rank minimization,which can be solved by iteratively reweighted nuclear norm(IRNN)*** experiments conducted on benchmark data sets have verified the effectiveness and advancement of the proposed algorithm compared with the state-of-the-art sparse representation methods.

关键词： sparse representation trace norm nonconvex optimization low rank matrix recovery iteratively reweighted nuclear norm

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Experimental Study on Wear and Spalling Behaviors of Railway Wheel

引用

Chinese Journal of Mechanical Engineering 2013年第6期26卷 1243-1249页

作者： wang wenjian GUO Jun LIU Qiyue Tribology Research Institute Southwest Jiaotong University

The current researches of the wear and spalling behaviors of wheel/rail materials focus on the field investigation rather than the mechanism. However, it is necessary and significant for clarifying the mechanism and relationship between the wear and spalling damage of railway wheel to test and reproduce the wheel damages in laboratory. The objective of this paper is to investigate the wear and spalling damage behaviors of railway wheel using a JD-1 wheel/rail simulation facility, which consists of a small wheel serving as rolling stock wheel, and a larger wheel serving as rail. The damage process of wheel roller is explored in terms of the creep ratio, axle load, and carbon content by means of various microscopic examinations. The experimental results show that the wear volume growth of wheel roller is proved to be proportional to the increase of the creep ratio and normal load between simulating wheel and rail. The increase of carbon content of wheel material causes a linear reduction in the wear volume. The microscopic examinations indicate that the rolling wear mechanism transfers from abrasive wear to adhesive and fatigue wear with an increase of tangential friction force, which results in the initiation of fatigue crack, and then aggravates spalling damage on the wheel roller surface. The surface hardness of material depends strongly upon its carbon content. The decrease of the carbon content of wheel material may alleviate spalling damage, but can cause a significant growth in the wear volume of wheel roller. Therefore, there is a competitive relationship between the wear and spalling damage of wheel material. This research proposes an important measure for alleviating or preventing the wear and spalling damage of railway wheel material.

关键词： wear spalling content carbon railway wheel wear mechanism

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Effect of Curing Age on Chloride Diffusion Coefficient of Recycled Aggregate Concrete Subjected to Compressive Stresses

引用

Transactions of Nanjing University of Aeronautics and Astronautics 2018年第2期35卷 326-333页

作者： Tang Jinzhi Wu Jin wang wenjian wang Zhe Wu Guanzheng College of Aerospace Engineering Nanjing University of Aeronautics and Astronautics

The effect of curing age on chloride diffusion coefficient of recycled aggregate concrete subjected to different compressive stresses was investigated.A compression loading setup was both designed and *** chloride diffusion coefficients of recycled aggregate concrete under compressive stresses were measured by the rapid chloride ion migration(RCM)*** experimental results show that the chloride diffusion coefficients of recycled aggregate concrete(RAC)under different compressive stress ratios generally decrease with the increase of curing *** RAC subjected to the same compressive stress ratios,the chloride diffusion coefficients approximately have power functions with curing ages and the relationship models are ***,the influence of curing age on chloride diffusion coefficient firstly decreases and then increases as the compressive stress ratio increases.

关键词： recycled aggregate concrete(RAC) chloride diffusion coefficient curing age compressive stress ratio rapid chlorideion migration(RCM) method

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Dynamic analysis of preferential orientation of aragonite crystals in nacre from mollusk shell

引用

Chinese Science Bulletin 2007年第24期52卷 3452-3456页

作者： ZHANG XueAo WU wenjian wang JianFang College of Aerospace and Material Engineering National University of Defense Technology Changsha 410073 China

Based on the scanning electron microscope (SEM) observations, it is confirmed that the nacre is composed of aragonite crystals and organic matrix with interlaced arrangement, showing ordered "brick-mortar" structure. The dynamic analysis of preferential orientation of aragonite crystals in the nacre from the abalone (Haliotis diverscolor supertexta) with different shell ages is systematically investigated using X-ray diffraction (XRD) and high resolution transmission electron microscope (HRTEM). Experiments reveal that, in the nacre from the juvenile mollusk shell, there exist three kinds of orientations of aragonite crystals: (113), (002) and (012). However, along with the growing of the mollusk shell, the intensity of (012) and (113) becomes weak, and the (002) becomes the preferred crystal orientation of aragonite in the nacre from the adult mollusk shell, which means that the c axis of aragonite crystals is perpendicular to the nacreous layers. The results obtained show that the nacre possesses a highly ordered structure at the micrometer/nanometer multiscale levels.

关键词：珠母贝霰石晶体优先定位动态分析软体动物

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Preparation of Porous NiO-Ce_(0.8)Sm_(0.2)O_(1.9) Ceramics for Anode-supported Low-temperature Solid Oxide Fuel Cells

引用

Journal of Materials Science & Technology 2010年第6期26卷 523-528页

作者： Han Chen Kui Cheng Zhicheng wang wenjian Weng Ge Shen Piyi Du Gaorong Han Department of Materials Science and Engineering State Key Laboratory of Silicon Materials Zhejiang UniversityHangzhou 310027 China

Porous NiO-Ce0.8Sm0.2O1.9（NiO-SDC） ceramics with homogeneous pore distribution were prepared using polystyrene （PS） spheres as pore templates. NiO-SDC powders were synthesized by a glycine-nitrate method, ultrasonically mixed with PS spheres in ethanol, dried and then pressed into green pellets. The pellets were sintered to yield porous NiO-SDC ceramics. The effects of the sintering temperature on the microstructure and mechanical strength of the ceramics were investigated. NiO-SDC ceramics sintered at 1200 and 1350℃ have interconnected pore structures and high compression strength. When single cells were fabricated using porous NiO-SDC ceramics as anode-supported layers, the peak power density of the cells at 600℃ was 333 and 353 ***-2 for ceramics sintered at 1200 and 1350℃, respectively. The results indicated that these porous ceramic materials are promising for anode substrates for solid oxide fuel cells.

关键词： Porous ceramic NiO-Ce0.8Sm0.2O1.9 (NiO-SDC) Polystyrene spheres Microstructure Anode-supported solid oxide fuel cells

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

An ISGW Filtering Antenna with Spurious Modes and Surface Wave Suppression for Millimeter Wave Communications

引用

China Communications 2023年第11期20卷 1-12页

作者： Lihui wang Dongya Shen Qiuhua Lin Zhiyong Luo wenjian wang Jianpei Chen Zhao Gao Wei Zhang School of Electronics and Communication Engineering Sun Yat-sen UniversityShenzhen 518107China School of Information Science and Engineering Yunnan UniversityKunming 650091China Kuang-Chi Institute of Advanced Technology&State Key Laboratory of Meta-RF Electromagnetic Modulation Technology ShenzhenChina School of Electrics and Information Engineering Yunnan Minzu UniversityKunmingChina Institute of Telecommunication and Navigation Satellites China Academy of Space TechnologyBeijing 100094

In this paper,an integrated substrate gap waveguide(ISGW)filtering antenna is proposed at millimeter wave band,whose surface wave and spurious modes are simultaneously suppressed.A secondorder filtering response is obtained through a coupling feeding scheme using one uniform impedance resonator(UIR)and two stepped-impedance resonators(SIRs).To increase the stopband width of the antenna,the spurious modes are suppressed by selecting the appropriate sizes of the ISGW unit ***,the ISGW is implemented to improve the radiation performance of the antenna by alleviating the propagation of surface *** an equivalent circuit is investigated to reveal the working principle of *** demonstrate this methodology,an ISGW filtering antenna operating at a center frequency of 25 GHz is designed,fabricated,and *** results show that the antenna achieves a stopband width of 1.6f0(center frequency),an out-of-band suppression level of 21 dB,and a peak realized gain of 8.5 dBi.

关键词： filtering antenna integrated substrate gap waveguide millimeter wave communications spurious modes suppression surface wave suppression

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Effects of solid friction modifier on friction and rolling contact fatigue damage of wheel-rail surfaces

引用

Friction 2022年第4期10卷 597-607页

作者： Jingdong SONG Lubing SHI Haohao DING Radovan GALAS Milan OMASTA wenjian wang Jun GUO Qiyue LIU Martin HARTL Tribology Research Institute State Key Laboratory of Traction PowerSouthwest Jiaotong UniversityChengdu 610031China School of Mechanical Engineering Xi’an Jiaotong UniversityXi’an 710049China Faculty of Mechanical Engineering Brno University of TechnologyBrno 61669Czech Republic

In railway network,friction is an important factor to consider in terms of the service behaviors of wheel-rail *** objective of this study was to investigate the effect of a solid friction modifier(FM)in a railway *** was achieved by studying the friction,wear,and rolling contact fatigue(RCF)damage on the wheel-rail materials at different slip *** results showed that when a solid FM was applied,the friction coefficient *** the solid FM was separated from the wheel-rail interface,the friction coefficient gradually increased to its original *** the application of the solid FM,the wear rates of the wheel-rail *** addition,the thickness and hardness of the plastic deformation layers of the wheel-rail materials were *** worn surfaces of the wheel-rail were dominated by pits and RCF *** the FM,RCF cracks ranged from 84 to 120μm,and subsurface cracks were ***,with the FM,RCF cracks ranged from 17 to 97μm and no subsurface cracks were *** findings indicate possible methods of improving the performance of railway rolling stock by managing friction,and reducing wear and permanent RCF damage affecting both the wheels and rails.

关键词： wheel-rail solid friction modifier(FM) friction wear rolling contact fatigue(RCF)damage

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Gaps,challenges and possible solution for prediction of wheel-rail rolling contact fatigue crack initiation

引用

Railway Engineering Science 2023年第3期31卷 207-232页

作者： Shuyue Zhang Qiyue Liu Maksym Spiryagin Qing Wu Haohao Ding Zefeng Wen wenjian wang State Key Laboratory of Traction Power Tribology Research InstituteSouthwest Jiaotong UniversityChengdu 610031China Centre for Railway Engineering Central Queensland UniversityRockhamptonQLDAustralia

The prediction of wheel/rail rolling contact fatigue(RCF)crack initiation during railway operations is an important *** RCF crack evolution is influenced by many factors,its prediction process is *** paper reviews the existing approaches to predict RCF crack *** crack initiation region is predicted by the shakedown *** combining the shakedown map with various initiation criteria and the critical plane method,the crack initiation life is *** classification,methodologies,theories and applications of these approaches are included in this *** advantages and limitations of these methods are analyzed to provide recommendation for RCF crack initiation *** review highlights that wheel/rail dynamic characteristic,complex working conditions,surface defects and wear all affect the RCF crack *** optimal selection of criteria is essential in the crack initiation *** on the research gap regarding the challenging process of crack initiation prediction detailed in this review,a proposed prediction process of RCF crack initiation is proposed to achieve a more accurate result.

关键词： RCF Crack initiation prediction Shakedown map Criteria Wheel-rail contact

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Unique fluorophilic pores engineering within porous aromatic frameworks for trace perfluorooctanoic acid removal

引用

National Science Review 2023年第10期10卷 106-113页

作者： Chi Zhang Junchao Dong Panpan Zhang Lei Sun Liu Yang wenjian wang Xiaoqin Zou Yunning Chen Qingkun Shang Danyang Feng Guangshan Zhu Faculty of Chemistry Northeast Normal University Institute of Molecular Sciences and Engineering Institute of Frontier and Interdisciplinary Science Shandong University

Perfluorooctanoic acid(PFOA),a representative of per/polyfluorinated alkyl substances,has become a persistent water pollutant of widespread concern due to its biological toxicity and refractory *** this work,we design and synthesize two porous aromatic frameworks(PAF) of PAF-CF3and PAF-C2F5using fluorine-containing alkyl based monomers in tetrahedral *** PAFs exhibit nanosized pores(～1.0 nm) of high surface areas(over 800 m2g-1) and good *** adsorption capacity(>740 mg g-1) and superior efficiency(>24 g mg-1h-1) are achieved toward the removal of PFOA with 1μg L-1concentration owing to unique C-F…F-C *** particular,PAF-CF3and PAF-C2F5are able to reduce the PFOA concentration in water to 37.9 ng L-1and 43.3 ng L-1,below EPA regulations(70 ng L-1).The reusability and high efficiency give both PAFs a great potential for sewage treatment.

关键词： porous aromatic frameworks fluorophilicity perfluorooctanoic acid adsorption removal halogen interactions

来源：

同方期刊数据库评论

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

CTAB Assisted Synthesis of CuS Microcrystals:Synthesis,Mechanism,and Electrical Properties

引用

Journal of Materials Science & Technology 2013年第11期29卷 1047-1052页

作者： Chunyan Wu Guofang Zhou Dun Mao Zihan Zhang Yiliang Wu wenjian wang Linbao Luo Li wang Yongqiang Yu Jigang Hu Zhifeng Zhu Yan Zhang Jiansheng Jie School of Electronic Science and Applied Physics Hefei University of Technology Institute of Functional Nano & Soft Materials(FUNSOM) and Jiangsu Key Laboratory for Carbon-Based Functional Materials &Devices Soochow University

CuS microcrystals were successfully prepared through a mild solvothermal reaction in ethylene glycol （EG） with the assistance of cationic surfactant cetyltrimethylammonium bromide （CTAB）. An interesting morphology evolution from flower-like microspheres to hollow microspheres, and finally to smooth nanoflakes was observed when increasing the amount of CTAB. The products were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, and UV-vis spectroscopy. It was found that the amount of CTAB played an important role in determining the morphology of the CuS microcrystals. Electrical measurement reveals that the as-prepared CuS microspheres were of high conductivity, which might favor their device applications. It is expected that CuS microcrystals with controlled morphologies and structures will have important applications in solar cells. This simple but effective method could also be extended to the controlled growth of other inorganic microcrystals.

关键词： Copper sulfide Microcrystals Solvothermal Cationic surfactant cetyltrimethylammonium bromide (CTAB) Electrical conductivity

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：