检索结果-南通市图书馆

Propagation effects of low frequency electromagnetic waves in production well

Petroleum science 2012年第2期9卷 182-191页

作者： Song Xijin Guo Baolong Dang Ruirong Wang Xuelong Institute of Intelligent Control and image Engineering Xidian UniversityShaanxi 710071China Key laboratory of Photoelectric Logging and Detecting of Oil and Gas Ministry of EducationXi'an Shiyou UniversityShaanxi 710065China College of Computer science&technology Shaanxi University of TechnologyShaanxi 710048China

The frequency domain electromagnetic method has already been widely used for tomographic imaging or electromagnetic well logging. However, different from open hole logging, the metal casing existing in production well logging has a strong shielding effect on the electromagnetic waves, thus bringing some difficulties to the application of the frequency domain electromagnetic method in production well logging. According to the relation of the field source geometry to the ring around the mandrel, the general expressions of frequency domain electromagnetic responses in axially symmetrical layered conductive medium are deduced. The propagation effects caused by the low-frequency electromagnetic waves in cased hole are also analyzed. The distribution curves of eddy current density and magnetic flux density along the radial direction in the mandrel indicate that the eddy loss within the mandrel is proportional to the transmission signal frequency and the mandrel conductivity. The secondary field responses of different casing materials show that the transmission frequency has an important effect on the ability of electromagnetic waves penetrating the metal casing. The transmission frequency should be ultra-low in order to enable the electromagnetic signal to penetrate the casing easily. The numerical results of frequency responses for different casing physical parameters show that the casing thickness has a significant impact on the choice of the transmission frequency. It is also found that the effect of the casing radius on the transmission frequency can be neglected.

关键词： Propagation effects eddy current density magnetic flux density production well frequency response

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

UWB monocycle pulse generation based on optical cross-polarization modulation

引用

Chinese Optics Letters 2009年第11期7卷 990-992页

作者：王世光陈宏伟陈明华谢世钟 State Key laboratory on Integrated Optoelectronics Tsinghua National Laboratory for InformationScience and Technology (TNList)Department of Electronic EngineeringTsinghua University

A novel all-optical method for ultra-wideband （UWB） monocycle pulses generation based on cross polarization modulation （CPM） effect in highly nonlinear photonic crystal fiber is proposed and demonstrated. Due to the CPM effect between the probe light and the pump pulse, a pair of polarity-reversed Gaussian pulses is produced. After proper differential delay, an UWB monocycle pulse with 84-ps width and the fractional bandwidth of 153% is generated after photodetection.

关键词： Phase modulation Photonic crystal fibers Photonic crystals Polarization Ultra wideband (UWB) Wireless telecommunication systems

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

Finite element analysis of deformation characteristics in cold helical rolling of bearing steel-balls

引用

Journal of Central South University 2015年第4期22卷 1175-1183页

作者：曹强华林钱东升 School of Materials science and Engineering Wuhan University of Technology Hubei Key laboratory of Advanced technology of Automotive Parts (Wuhan University of technology) School of Automotive Engineering Wuhan University of Technology

Due to the complexity of investigating deformation mechanisms in helical rolling(HR) process with traditional analytical method, it is significant to develop a 3D finite element(FE) model of HR process. The key forming conditions of cold HR of bearing steel-balls were detailedly described. Then, by taking steel-ball rolling elements of the B7008 C angular contact ball bearing as an example, a completed 3D elastic-plastic FE model of cold HR forming process was established under SIMUFACT software environment. Furthermore, the deformation characteristics in HR process were discovered, including the forming process, evolution and distribution laws of strain, stress and damage based on Lemaitre relative damage model. The results reveal that the central loosening and cavity defects in HR process may have a combined effect of large negative hydrostatic pressure(positive mean stress)caused by multi-dimensional tensile stresses, high level transverse tensile stress, and circular-alternating shear stress in cross section.

关键词： cold helical rolling finite element(FE) simulation rotary forming bearing steel-balls

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

High-Q factor photonic crystal cavities with cut air holes [Invited]

引用

Chinese Optics Letters 2020年第6期18卷 86-92页

作者： Liang Fang Xuetao Gan Jianlin Zhao Key laboratory of Space Applied Physics and Chemistry Ministry of Educationand Shaanxi Key Laboratory of Optical Information TechnologySchool of Physical Science and TechnologyNorthwestern Polytechnical UniversityXi’an 710129China

Planar photonic crystal(PPC)cavities with high quality(Q)factors were currently designed by missing or moving air ***,we propose that cutting air holes in PPC into semicircles could be considered as another strategy to realize and optimize cavities,presenting superiorities over cavities with missed or moved air holes in a higher Q factor and a smaller mode volume(Vmode).Examples are demonstrated:(1)in a PPC lattice,cutting two adjacent air holes promises a cavity mode with a Q exceeding 200,500 and an ultrasmall mode volume Vmode<0.329(λ/2 n)^3;(2)in a PPC waveguide,cutting two air holes on opposite sides of the waveguide supports a cavity mode with a Q exceeding 104,600 and a Vmode<1.22(λ/2 n)^3;(3)cutting the two air holes at the edges of an L3-type PPC cavity,the Q factor is optimized from 5500 to 124,700,with an almost constant *** concept of cutting air holes to introduce defects in PPC also promises the design of PPC also waveguides with an engineered transmission loss and dispersion.

关键词： photonic crystal cavity quality factor mode volume

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 grain size on gas bubble evolution in nuclear fuel:Phase-field investigations

引用

Chinese Physics B 2024年第1期33卷 563-572页

作者：孙丹杨青峰赵家珺高士鑫辛勇周毅尹春雨陈平赵纪军王园园 science and technology on Reactor System Design technology laboratory Nuclear Power Institute of ChinaChengdu 610213China Key laboratory of Materials Modification by Laser Ionand Electron BeamsDalian University of TechnologyDalian 116024China

Numerous irradiation-induced gas bubbles are created in the nuclear fuel during irradiation, leading to the change of microstructure and the degradation of mechanical and thermal properties. The grain size of fuel is one of the important factors affecting bubble evolution. In current study, we first predict the thermodynamic behaviors of point defects as well as the interplay between vacancy and gas atom in both UO_(2) and U_(3)Si_(2) according to ab initio approach. Then, we establish the irradiation-induced bubble phase-field model to investigate the formation and evolution of intra-and inter-granular gas bubbles. The effects of fission rate and temperature on the evolutions of bubble morphologies in UO_(2) and U_(3)Si_(2) have been revealed. Especially, a comparison of porosities under different grain sizes is examined and analyzed. To understand the thermal conductivity as functions of grain size and porosity, the heat transfer capability of U_(3)Si_(2) is evaluated.

关键词： grain size point defects fission gas bubble

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

Synthesis and Electrochemical Properties of Porous α-Co（OH）2 and Co3O4 Microspheres

引用

Progress in Natural science:Materials International 2017年第2期27卷 197-202页

作者： Yingying Xu Zhiyuan Liu Di Chen Yuanjun Song Rongming Wang Beijing Key laboratory for Magneto-Photoelectrical Composite and Interface science School of Mathematics and PhysicsUniversity of Science and Technology Beijing

Both α-Co（OH）2and Co3O4porous microspheres have been synthesized by the simple solvothermal process as well as subsequent treatment. The morphologies and structures of the as-synthesized products were characterized by X-ray diffraction（XRD）, scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, and X-ray photoelectron spectroscopy（XPS）. Both samples have spherical structures consisting of nanosheets, with similar crystallinity. The electrochemical properties of both samples were further investigated. Both samples show excellent electrochemical performances including high specific capacity, good cycling stability and rate capability. All results show that these microspheres exhibit potential applications in energy storage field.

关键词： α-Co(OH)2 microspheres Co3O4 porous microspheres Supercapacitor Cycling stability Rate capability

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

IBEA-SVM: An Indicator-based Evolutionary Algorithm Based on Pre-selection with Classification Guided by SVM

引用

Applied Mathematics(A Journal of Chinese Universities) 2019年第1期34卷 1-26页

作者： LI Hao-ran HE Fa-zhi YAN Xiao-hu School of Computer science and technology Wuhan University State Key laboratory of Digital Manufacturing Equipment and technology Huazhong University

Multi-objective optimization has many important applications and becomes a challenging issue in applied science. In typical multi-objective optimization algorithms, such as Indicator-based Evolutionary Algorithm(IBEA), all of parents and offspring need to be evaluated in every generation, and then the better solutions of them are selected as the next generation candidates. This leads to a large amount of calculation and slows down convergence rate for IBEA related applications. Our discovery is that the evaluation of evolutionary algorithm is a binary classi?cation in nature and a meaningful preselection method will accelerate the convergence rate. Therefore this paper presents a novel preselection approach to improve the performance of the IBEA, in which a SVM(Support Vector Machine) classi?er is adopted to sort the promising solutions from unpromising solutions and then the newly generated solutions are conversely added as train sample to increase the accuracy of the classi?er. Firstly, we proposed an online and asynchronous training method for SVM model with empirical kernel. The initial population is randomly generated among population size, which is used as initial training. In the process of training, SVM classi?er is modi?ed and perfected to adapt to the evolutionary algorithm sample. Secondly, the classi?er divides all the new generated solutions from the whole solution spaces into promising solutions and unpromising ones. And only the promising ones are forwarded for evaluation. In this way, the evaluation time can be greatly reduced and the solution quality can be obviously improved. Thirdly, the promising and unpromising solutions are labeled as new train samples in next generation to re?ne classi?er model. A number of experiments on benchmark functions validates the proposed approach. The results show that IBEA-SVM can signi?cantly outperform previous works.

关键词： multi-objective optimization SVM IBEA training classification

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

Recent progress in the interaction between energetic particles and tearing modes

引用

National science Review 2022年第11期9卷 240-261页

作者： Huishan Cai Ding Li Chinese Academy of sciences Key laboratory of Geospace Environment School of Nuclear Sciences and TechnologyUniversity of Science and Technology of China Institute of Physics Chinese Academy of Sciences Songshan Lake Materials laboratory

The dynamics of energetic particles and tearing modes and the interactions between them are of great significance for magnetically confined fusion plasmas. In this review, we focus on these issues in the context of tokamak plasmas. The interaction between energetic particles and tearing modes is considered from two perspectives:(i) the influence of energetic particles on tearing modes and(ii) the transport of energetic particles by tearing modes. The influence of energetic particles on tearing modes is described on the basis of a general dispersion relation for tearing modes. The effects of energetic particles are considered separately in the outer region and the island region of a tearing mode. The physics mainly results from the modification of the perturbed parallel current by energetic particles without wave–particle resonance. In addition, the resonance between energetic particles and tearing modes is also reviewed. For the transport of energetic particles, transport of both circulating and trapped energetic particles by tearing mode is reviewed. Our descriptions of physical phenomena here are based on an analytical approach, while the experiments and simulations are used to illustrate and confirm our results. Finally, a number of open issues are discussed.

关键词： magnetically confined plasma energetic particle tearing mode transport confinement tokamak

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

Integrated Ni-P-S nanosheets array as superior electrocatalysts for hydrogen generation

引用

Green Energy & Environment 2017年第2期2卷 112-118页

作者： Haoxuan Zhang Haibo Jiang Yanjie Hu Hao Jiang Chunzhong Li Key laboratory for Ultrafine Materials of Ministry of Education & School of Materials science and Engineering East China University of Science and Technology

Searching for efficient and robust non-noble electrocatalysts for hydrogen generation is extremely desirable for future green energy ***, we present the synthesis of integrated Ni-P-S nanosheets array including Ni_2P and NiS on nickel foam by a simple simultaneous phosphorization and sulfurization strategy. The resultant sample with optimal composition exhibits superior electrocatalytic performance for hydrogen evolution reaction(HER) in a wide pH range. In alkaline media, it can generate current densities of 10, 20 and 100 mA cm^(-2) at low overpotentials of only-101.9,-142.0 and-207.8 mV with robust durability. It still exhibits high electrocatalytic activities even in acid or neutral media. Such superior electrocatalytic performances can be mainly attributed to the synergistic enhancement of the hybrid Ni-P-S nanosheets array with integration microstructure. The kind of catalyst gives a new insight on achieving efficient and robust hydrogen generation.

关键词： Nanosheets array Nickel phosphide Nickel sulfide Overpotential Hydrogen generation

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

On optics of human meridians

引用

science China(Physics,Mechanics & Astronomy) 2009年第4期52卷 502-507页

作者： YANG HongQin XIE ShuSen LI Hui WANG YuHua Institute of Laser and Optoelectronics technology Fujian Provincial Key Laboratory of Photonic TechnologyKey Laboratory of Optoelectronic Science and Technology for Medicine of Ministry of EducationFujian Normal UniversityFuzhou 350007China

A new concept and its methodology for studying human meridians are presented based on rigorous and scientific observation on the objective existence of human meridians in view of biomedical optics. According to this methodology,the infrared radiant characteristics of acupuncture meridians over human body and the optical transport properties of light propagating along the meridian are reported. This study,thus,confirms the existence of acupuncture meridians,sheds new light on an approach to investigation of human meridians and offers a new perspective in understanding the potential meridian functions such as energy and information transfer and physiological regulation.

关键词： fourteen meridians acupuncture points biomedical optics meridian optics

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：