检索结果-南通市图书馆

Acoustic emission characterization of microcracking in laboratory-scale hydraulic fracturing tests

Journal of Rock Mechanics and Geotechnical engineering 2018年第5期10卷 805-817页

作者： Jesse Hampton Marte Gutierrez Luis Matzar Dandan Hu Luke Frash Department of Civil & Environmental engineering Colorado School of Mines Golden CO 80401 USA New England Research Inc. White River Junction VT 03766 USA Halliburton Houston TX 77032 USA Los Alamos National Laboratory Los Alamos NM 87545 USA

Understanding microcracking near coalesced fracture generation is critically important for hydrocarbon and geothermal reservoir characterization as well as damage evaluation in civil engineering structures. Dense and sometimes random microcracking near coalesced fracture formation alters the mechanical properties of the nearby virgin material. Individual microcrack characterization is also significant in quantifying the material changes near the fracture faces （i.e. damage）. Acoustic emission （AE） monitoring and analysis provide unique information regarding the microcracking process temporally, and infor- mation concerning the source characterization of individual microcracks can be extracted. In this context, laboratory hydraulic fracture tests were carried out while monitoring the AEs from several piezoelectric transducers. In-depth post-processing of the AE event data was performed for the purpose of under- standing the individual source mechanisms. Several source characterization techniques including moment tensor inversion, event parametric analysis, and volumetric deformation analysis were adopted. Post-test fracture characterization through coring, slicing and micro-computed tomographic imaging was performed to determine the coalesced fracture location and structure. Distinct differences in fracture characteristics were found spatially in relation to the openhole injection interval. Individual microcrack AE analysis showed substantial energy reduction emanating spatially from the injection interval. It was quantitatively observed that the recorded AE signals provided sufficient information to generalize the damage radiating spatially away from the injection wellbore.

关键词： Acoustic emission (AE) Microcracking Hydraulic fracturing Laboratory-scale testing Moment tensor analysis Fracture coalescence Computed tomography (CT) imaging

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

A fiber bundle structure with uniform transmission characteristics for high-density astronomical optical cables

引用

Research in Astronomy and Astrophysics 2019年第8期19卷 131-142页

作者： Qi Yan Tao Geng Hang Jiang Chuang Zhao Ying-Hua Zhang An-Zhi Wang Jia-Bin Wang Xi-Ren Jin Xu-Dong Chen Chun-Lian Lu Liang Wang Zhi-Xin Huang Jing-Dong Zhuang Song Wang Wei-Min Sun Xiang-Qun Cui Key Lab of In-fiber Integrated Optics Ministry Education of ChinaHarbin Engineering UniversityHarbin150001China Yangtze Optical Fibre and Cable Joint Stock Limited Company Wuhan430073China Nanjing Institute of Astronomical Optics and Technology National Astronomical ObservatoriesChinese Academy ofSciencesNanjing210042China

Transmission efficiency(TE) and focal ratio degradation(FRD) are two important parameters for evaluating the quality of an optical fiber system used for astronomy. Compared to TE, the focal ratio is more easily influenced by external factors, such as bending or stress. Optical cables are widely implemented for multi-object telescopes and integral field units(IFUs). The design and fabrication process of traditional optical cables seldom considers the requirements of astronomical applications. In this paper, we describe a fiber bundle structure as the basic unit for miniaturized high-density FASOT-IFU optical cables,instead of the micro-tube structure in stranded cables. Seven fibers with hexagonal arrangement were accurately positioned by ultraviolet(UV)-curing acrylate to form the bundle. The coating diameter of a fiber is0.125 mm, and the outer diameter of the bundle is 0.58 mm. Compared with the 0.8 mm micro-tube structure of a traditional stranded cable, the outer diameter of the fiber bundle was reduced by 27.5%. Fiber paste was filled into the bundle to reduce stress between the fibers. We tested the output focal ratio(OFR) in95% of the encircled energy(EE95) of the fibers in the bundle under different conditions. With the incident focal ratio F/8, the maximum difference of OFR is 0.6. In particular, when the incident focal ratio is F/5,the maximum difference of OFR is only 0.1. The jacket formed by the UV-curing acrylate can withstand a certain stress of less than 1.38 N mm-1. The fiber bundle can maintain uniform emitting characteristics with a bending radius of 7.5 cm and with tension less than 6 N. The test results show that the structure of the fiber bundle can be used as a basic unit for miniaturized high-density astronomical optical cables.

关键词： instrumentation:spectrographs techniques:imaging spectroscopy techniques:spectroscopic methods:miscellaneous

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

Probing electron and lattice dynamics by ultrafast electron microscopy: Principles and applications

引用

International Journal of Mechanical System Dynamics 2023年第3期3卷 192-212页

作者： Yiling Lian Jingya Sun Lan Jiang Laser Micro/Nano Fabrication Laboratory School of Mechanical EngineeringBeijing Institute of TechnologyBeijingP.R.China Yangtze Delta Region Academy of Beijing Institute of Technology JiaxingP.R.China Chongqing Innovation Center Beijing Institute of TechnologyChongqingP.R.China

Microscale charge and energy transfer is an ultrafast process that can determine the photoelectrochemical performance of ***,nonlinear and nonequilibrium properties hinder our understanding of ultrafast processes;thus,the direct imaging strategy has become an effective means to uncover ultrafast charge and energy transfer *** to diffraction limits of optical imaging,the obtained optical image has insufficient spatial ***,electron beam imaging combined with a pulse laser showing high spatial–temporal resolution has become a popular area of research,and numerous breakthroughs have been achieved in recent *** this review,we cover three typical ultrafast electron beam imaging techniques,namely,time-resolved photoemission electron microscopy,scanning ultrafast electron microscopy,and ultrafast transmission electron microscopy,in addition to the principles and characteristics of these three *** outstanding results related to photon–electron interactions,charge carrier transport and relaxation,electron–lattice coupling,and lattice oscillation are also *** summary,ultrafast electron beam imaging with high spatial–temporal resolution and multidimensional imaging abilities can promote the fundamental under-standing of physics,chemistry,and optics,as well as guide the development of advanced semiconductors and electronics.

关键词： ultrafast electron imaging charge transfer time-resolved photoemission electron microscopy scanning ultrafast electron microscopy ultrafast transmission electron microscopy

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

Encapsulation-Induced Conformational Conversion and Emission Enhancement in Eu(Ⅲ)-based Host-Guest Complexes

Encapsulation-Induced Conformational Conversion and Emission...

引用

中国稀土学会2020学术年会暨江西(赣州)稀土资源绿色开发与高效利用大会

作者：吴尧蒋选丰 Key Laboratory of Green Preparation and Application for Functional Materials Ministry of Education Hubei Key Laboratory of Polymer Science School of Materials Science and Engineering Hubei University

Host-guest inclusion was widely employed as a powerful tool to create supramolecular assembles with multicomponent *** designed and synthesized an emissive tripodal ligand L with two tunable conformers (boat and chair shape).Two host-guest complexes 1 (HL@2OHˉ)and 2 (L@[Eu(NO)·HO·2CHOH]) were controllably self-assembled via host-guest *** this host-guest inclusion systems,a reversible structure transformation between two complexes 1 and 2 can be controlled exactly via sequentially changing different guest molecules (hydroxides and solvated lanthanide ions).In this reversible process,the ligand conformational motion,Eu emission enhancement and red-blue photo-switching behaviors were also observed and fully *** the structural features of host-guest complexes were directly determined by X-ray crystallography,***,the reversible conversion process was successfully monitored by fluorescence spectrometer and on-line mass *** calculation revealed the conversion energy (ΔG) of two ligand conformations when free ligand encapsulated hydroxides and solvated lanthanide ions,***,such Eu-based host-guest complex shown a good luminescence and can be used as a potential imaging regent in living cell.

关键词： Host-guest supramolecular chemistry reversible conformational conversion emission enhancement

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

Brain Tumor Detection and Classification Using PSO and Convolutional Neural Network

引用

Computers, Materials & Continua 2022年第12期73卷 4501-4518页

作者： Muhammad Ali Jamal Hussain Shah Muhammad Attique Khan Majed Alhaisoni Usman Tariq Tallha Akram Ye Jin Kim Byoungchol Chang Department of Computer Science COMSATS University IslamabadWah CampusPakistan Departmnt of Computer Science HITEC University TaxilaPakistan Computer Sciences Department College of Computer and Information SciencesPrincess Nourah Bint Abdulrahman UniversityRiyadh11671Saudi Arabia College of Computer engineering and Sciences Prince Sattam bin Abdulaziz UniversityAl-KharjSaudi Arabia Department of EE COMSATS University IslamabadWah CampusPakistan Department of Computer Science Hanyang UniversitySeoul04763Korea Center for Computational Social Science Hanyang UniversitySeoul04763Korea

Tumor detection has been an active research topic in recent years due to the high mortality *** vision(CV)and image processing techniques have recently become popular for detecting tumors inMRI *** automated detection process is simpler and takes less time than manual *** addition,the difference in the expanding shape of brain tumor tissues complicates and complicates tumor detection for *** proposed a newframework for tumor detection aswell as tumor classification into relevant categories in this *** tumor segmentation,the proposed framework employs the Particle Swarm Optimization(PSO)algorithm,and for classification,the convolutional neural network(CNN)*** preprocessing techniques such as noise removal,image sharpening,and skull stripping are used at the start of the segmentation ***,PSO-based segmentation is *** the classification step,two pre-trained CNN models,alexnet and inception-V3,are used and trained using transfer *** a serial approach,features are extracted from both trained models and fused features for final *** classification,a variety of machine learning classifiers are *** dice values on datasets BRATS-2018 and BRATS-2017 are 98.11 percent and 98.25 percent,respectively,whereas average jaccard values are 96.30 percent and 96.57%(Segmentation Results).The results were extended on the same datasets for classification and achieved 99.0%accuracy,sensitivity of 0.99,specificity of 0.99,and precision of ***,the proposed method is compared to state-of-the-art existingmethods and outperforms them.

关键词： Magnetic resonance imaging(MRI) tumor segmentation deep learning features extraction classification

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

Underwater Image Enhancement Based on the Dark Channel Prior and Attenuation Compensation

引用

中国海洋大学学报（英文版） 2017年第5期 757-765页

作者： GUO Qingwen XUE Lulu TANG Ruichun GUO Lingrui College of Information Science and engineering Ocean University of China College of Oceanic and Atmospheric Sciences Ocean University of China

Aimed at the two problems of underwater imaging, fog effect and color cast, an Improved Segmentation Dark Channel Prior(ISDCP) defogging method is proposed to solve the fog effects caused by physical properties of water. Due to mass refraction of light in the process of underwater imaging, fog effects would lead to image blurring. And color cast is closely related to different degree of attenuation while light with different wavelengths is traveling in water. The proposed method here integrates the ISDCP and quantitative histogram stretching techniques into the image enhancement procedure. Firstly, the threshold value is set during the refinement process of the transmission maps to identify the original mismatching, and to conduct the differentiated defogging process further. Secondly, a method of judging the propagating distance of light is adopted to get the attenuation degree of energy during the propagation underwater. Finally, the image histogram is stretched quantitatively in Red-Green-Blue channel respectively according to the degree of attenuation in each color channel. The proposed method ISDCP can reduce the computational complexity and improve the efficiency in terms of defogging effect to meet the real-time requirements. Qualitative and quantitative comparison for several different underwater scenes reveals that the proposed method can significantly improve the visibility compared with previous methods.

关键词： dark channel image defogging color cast histogram stretching

来源：评论

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

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

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：