检索结果-南通市图书馆

A method to model the effect of pre-existing cracks on P-wave velocity in rocks

在线全文

学校读者我要写书评

暂无评论

Journal of Rock Mechanics and Geotechnical Engineering 2020年第3期12卷 493-506页

作者： Haimeng Shen xiaying li Qi li Haibin Wang State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan430071China University of Chinese Academy of Sciences Beijing100049China

Crack closure is one of the reasons inducing changes of P-wave velocity of rocks under *** this context,a method is proposed to investigate the relationships among P-wave velocity,pre-existing cracks,and confining pressure based on the discrete element method(DEM).Pre-existing open cracks inside the rocks are generated by the initial gap of the flat-joint *** validity of the method is evaluated by comparing the P-wave velocity tested on a sandstone specimen with numerical *** the crack size is determined by the diameter of particles,the effects of three factors,***,aspect ratio,and orientation of cracks on the P-wave velocity are *** results show that P-wave velocity is controlled by the(***) of open micro-cracks,while the closure pressure is determined by the aspect ratio of *** reason accounting for the anisotropy of P-wave velocity is the difference in crack number in measurement *** of the number and aspect ratio of cracks can affect the responses of P-wave velocity to the applied confining *** confining pressure,the number of open cracks inside rocks will dominate the lowest P-wave velocity,and the P-wave velocity of the rock containing narrower cracks is more sensitive to the confining *** this sense,crack density is difficult to be back-calculated merely by P-wave *** proposed method offers a means to analyze the effect of pre-existing cracks on P-wave velocity.

关键词： Pre-existing cracks P-wave velocity Discrete element method(DEM) Anisotropic rock

Influence of bedding structure on stress-induced elastic wave anisotropy in tight sandstones

在线全文

学校读者我要写书评

暂无评论

Journal of Rock Mechanics and Geotechnical Engineering 2021年第1期13卷 98-113页

作者： xiaying li Xinglin Lei Qi li Dianguo Chen State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan430071China University of Chinese Academy of Sciences Beijing100049China National Institute of Advanced Industrial Science and Technology(AIST) Tsukuba305-8567Japan Chongqing Dizhiyuan Geology and Engineering Testing Co. LtdChongqing401329China

To understand the evolution of stress-induced elastic wave anisotropy,three triaxial experiments were performed on sandstone specimens with bedding orientations parallel,perpendicular,and oblique to the maximum principal stress.P-wave velocities along 64 different directions on each specimen were monitored frequently to understand the anisotropy change at various stress levels by fitting Thomsen’s anisotropy *** results show that the elastic wave anisotropy is very sensitive to mechanical *** hydrostatic loading,the magnitude of anisotropy is reduced in all three ***,under deviatoric stress loading,the evolution of anisotropic characteristics(magnitude and orientation of the symmetry axis)is bedding orientation *** reversal occurs in specimens with bedding normal/oblique to the maximum principal stress.P-wave anisotropyε0 is linearly related to volumetric strain Sv and dilatancy,indicating that stress-induced redistribution of microcracks has a significant effect on P-wave velocity *** closure of initial cracks and pores aligned in the bedding direction contributes to the decrease of the ***,opening of new cracks,aligned in the maximum principal direction,accounts for the increase of the *** experimental results provide some insights into the microstructural behavior under loading and provide an experimental basis for seismic data interpretation and parameter selection in engineering applications.

关键词： Elastic wave anisotropy Stress-induced anisotropy Anisotropy reversal Bedding orientation Microstructure Tight sandstone

An effective method for laboratory acoustic emission detection and location using template matching

在线全文

学校读者我要写书评

暂无评论

Journal of Rock Mechanics and Geotechnical Engineering 2022年第5期14卷 1642-1651页

作者： Xinglin Lei Tomohiro Ohuchi Manami Kitamura xiaying li Qi li National Institute of Advanced Industrial Science and Technology(AIST) Tsukuba305-8567Japan Geodynamics Research Center Ehime UniversityMatsuyama790-8577Japan State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan430071China University of Chinese Academy of Sciences Beijing100049China

In this paper, a template matching and location method, which has been rapidly adopted in microseismic research in recent years, is applied to laboratory acoustic emission(AE) monitoring. First, we used traditional methods to detect P-wave first motions and locate AE hypocenters in three dimensions. In addition, we selected events located with sufficient accuracy(normally corresponding AE events of relatively larger energy, showing clear P-wave first motion and a higher signal-to-noise ratio in most channels) as template events. Then, the template events were used to scan and match other poorly located events in triggered event records or weak events in continuous records. Through crosscorrelation of the multi-channel waveforms between the template and the event to be detected, the weak signal was detected and located using a grid-searching algorithm(with the grid centered at the template hypocenter). In order to examine the performance of the approach, we calibrated the proposed method using experimental data of different rocks and different types of experiments. The results show that the proposed method can significantly improve the detection capability and location accuracy, and can be applied to various laboratory and in situ experiments, which use multi-channel AE monitoring with waveforms recorded in either triggering or continuous mode.

关键词： Acoustic emission Template matching and location Waveform cross-correlation Grid search

Hydromechanical behaviors of andesite under different stress states during fluid injection

在线全文

学校读者我要写书评

暂无评论

Journal of Rock Mechanics and Geotechnical Engineering 2021年第4期13卷 727-744页

作者： Miao He Qi li xiaying li liang Xu Michael Kühn State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan430071China University of Chinese Academy of Sciences Beijing100049China Fluid Systems Modelling Section GFZ German Research Centre for GeosciencesPotsdamGermany Institute of Earth and Environmental Science University of PotsdamPotsdamGermany

Water reinjection into the formation is an indispensable operation in many energy engineering *** operation involves a complex hydromechanical(HM)coupling process and sometimes even causes unpredictable disasters,such as induced *** is acknowledged that the relative magnitude and direction of the principal stresses significantly influence the HM behaviors of rocks during ***,due to the limitations of current testing techniques,it is still difficult to comprehensively conduct laboratory injection tests under various stress conditions,such as in triaxial extension stress *** this end,a numerical study of HM changes in rocks during injection under different stress states is *** this model,the saturated rock is first loaded to the target stress state under drainage conditions,and then the stress state is maintained and water is injected from the top to simulate the formation injection *** attention is given to the difference in HM changes under triaxial compression and extension *** includes the differences in the pore pressure propagation,mean effective stress,volumetric strain,and stress-induced *** numerical results demonstrate that the differential stress will significantly affect the HM behaviors of rocks,but the degree of influence is different under the two triaxial stress *** HM changes caused by the triaxial compression stress states are generally greater than those of extension,but the differences decrease with increasing differential stress,indicating that the increase in the differential stress will weaken the impact of the stress state on the HM *** addition,the shear failure potential of fracture planes with various inclination angles is analyzed and summarized under different stress *** is recommended that engineers could design suitable injection schemes according to different tectonic stress fields versus fault occurrence to reduce the risk of

关键词： Water reinjection Stress state Hydromechanical(HM)coupling Injection-induced seismicity Numerical modeling

Comparison of Five Endogenous Reference Genes for Specific PCR Detection and Quantification of Rice

在线全文

学校读者我要写书评

暂无评论

Rice science 2019年第4期26卷 248-256,I0006,I0007页

作者： ZHANG Xiujie JIN Wujun XU Wentao li xiaying SHANG Ying li Sha OUYANG Hongsheng College of Animal Sciences Jilin University Changchun 130062 China Development Center of Science and Technology Ministry of Agriculture and Rural Affairs Beijing 100176 China Biotechnology Research Institute Chinese Academy of Agricultural Sciences Beijing 100081China College of Food Science and Nutritional Engineering China Agricultural University Beijing 100083China

Endogenous reference genes (ERGs) provide vital information regarding genetically modified organisms (GMOs). The successful detection of ERGs can identity GMOs and the source of genes, verify stability and reliability of the detection system, and calculate the level of genetically modified (GM) ingredients in mixtures. The reported ERGs in rice include sucrose-phosphate synthase (SPS), phospholipase D (PLD), RBE4 and rice root-specific GOS9 genes. Based on the characteristics of ERGs, a new ERG gene, phosphoenolpyruvate carboxylase (PEPC), was selected, and further compared with the four existing genes. A total of 18 rice varieties and 29 non-rice crops were used to verify the interspecies specificity, intraspecies consistency, sensitivity, stability and reliability of these five ERGs using qualitative and quantitative PCR. Qualitative detection indicated that SPS and PEPC displayed sufficient specificity, and the detection sensitivity was 0.05% and 0.005%, respectively. Although the specificity of both RBE4 and GOS9 were adequate, the amplicons were small and easily confused with primer dimers. Non-specific amplification of the PLD gene was present in maize and potato. Real-time quantitative PCR detection indicated that PLD, SPS and PEPC displayed good specificity, with R2 of the standard curve greater than 0.98, while the amplification efficiency ranged between 90% and 110%. Both the detection sensitivities of PLD and PEPC were five copies and that of SPS was ten copies. RBE4 showed typical amplification in maize, beet and Arabidopsis, while GOS9 was found in maize, tobacco and oats. PEPC exhibited excellent detection sensitivity and species specificity, which made it a potentially useful application in GM-rice supervision and administration. Additionally, SPS and PLD are also suitable for GM-rice detection. This study effectively established a foundation for GMO detection, which not only provides vital technical support for GMO identification, but also is of grea

关键词： endogenous reference gene rice genetically modified crop phosphoenolpyruvate carboxylase gene sucrose-phosphate synthase gene phospholipase D gene starch branching enzyme 4 gene rice root-specific GOS9 gene

基于SCL-90的青少年和成人抑郁症状对比分析

在线全文

学校读者我要写书评

暂无评论

重庆医学 2024年第5期53卷 754-759,765页

作者：胡冰洪素杨天宇黄凯欣李夏颖程丹丹况利重庆医科大学附属第一医院精神科重庆400016 重庆医科大学附属大学城医院精神科重庆401331

目的探讨青少年和成人抑郁症状的差别,为早期发现青少年抑郁提供可能的依据。方法选取2021年7月至2022年6月重庆医科大学附属第一医院精神科门诊以“抑郁情绪”就诊的4096例患者为研究对象,根据年龄分为青少年组(n=2439)和成人组(n=165... 详细信息

目的探讨青少年和成人抑郁症状的差别,为早期发现青少年抑郁提供可能的依据。方法选取2021年7月至2022年6月重庆医科大学附属第一医院精神科门诊以“抑郁情绪”就诊的4096例患者为研究对象,根据年龄分为青少年组(n=2439)和成人组(n=1657),收集并分析其抑郁自评量表(SDS)和90项症状清单(SCL-90)结果。结果两组民族、居住地、籍贯、家族史及抑郁程度比较,差异有统计学意义(P<0.05)。青少年组抑郁症状更重,主要表现在消极观念、强迫症状、敌对和人际关系及精神病性症状(P<0.05),而成人组则在睡眠方面表现得更加明显(P<0.05)。结论应针对青少年的消极观念等进行尽早干预。

关键词：青少年成人抑郁抑郁症状对比研究

集束化护理对留置NCC血液透析患者护理效果的影响

同方期刊数据库博看期刊评论

在线全文

学校读者我要写书评

暂无评论

中国基层医药 2024年第8期31卷 1254-1257页

作者：冯文第加美万秀娟李侠英彭保华米欣安徽理工大学第一附属医院肾脏内科淮南232007

目的:探讨集束化护理对采用无隧道和涤纶套的透析导管(NCC)行血液透析患者护理效果的影响。方法:选取2021年3月至2023年11月在安徽理工大学第一附属医院血液净化中心通过超声引导下经皮中心静脉置入NCC行血液透析治疗的患者44例进行回... 详细信息

目的:探讨集束化护理对采用无隧道和涤纶套的透析导管(NCC)行血液透析患者护理效果的影响。方法:选取2021年3月至2023年11月在安徽理工大学第一附属医院血液净化中心通过超声引导下经皮中心静脉置入NCC行血液透析治疗的患者44例进行回顾性分析,根据护理方式不同分为两组,对照组22例采用常规护理,观察组22例采用集束化护理,比较两组患者导管感染、栓塞、脱管等并发症发生率和患者满意度。结果:研究期间对照组发生4例置管口感染,8例栓塞,1例脱管;观察组发生2例栓塞,无其他相关并发症;观察组护理满意度[95.45%(21/22)]高于对照组护理满意度[63.63%(14/22)],差异均有统计学意义(χ^(2)=14.31,P<0.001)。结论:实施集束化护理模式可以增加患者对NCC的认知度,降低NCC并发症的发生率,提高患者护理满意度。

关键词：血液透析滤过血液透析病房医院护理导管感染栓塞病人满意度

Copy number and zygosity determination of transgenic rapeseed by droplet digital PCR

在线全文

学校读者我要写书评

暂无评论

Oil Crop Science 2017年第2期2卷 84-94页

作者： Yuhua Wu Jun li xiaying li Jingang liang Yunjing li Xinhua Zeng Gang Wu Key Laboratory of Biology and Genetic Improvement of Oil Crops Ministry of Agriculture Oil Crops Research InstituteChinese Academy of Agricultural Sciences Wuhan China Science and Technoloty Center of Ministry of Agriculture China

Establishing an accurate and rapid method for copy number and zygosity determination can accelerate genetic engineering research process. In this study, droplet digital PCR (ddPCR), an emerging DNA absolute quantification technology, was used to identify single-copy homozygous transgenic lines from a batch of T0 transgenic rapeseed harboring 11 exogenous elements. Copy number of exogenous gene was evaluated in T0 generation based on calculated ratio between transgene and reference CruA gene, single-copy transformants were selected for selfing followed by subsequent zygosity analysis. Single-copy homozygous transgenic plants were successfully screened out in T1 generation by *** analysis with T2 seedlings verified that identification results of ddPCR were accurate and reliable. This study provides a novel rapid and accurate method for copy number and zygosity determination in transgenic rapeseed which overcomes disadvantages of traditional Southern analysis and recently developed real-time quantitative method.

关键词： droplet digital PCR (ddPCR) copy number zygosity homozygotes transgenic rapeseed

在线全文

学校读者我要写书评

暂无评论

高校实验动物平台管理模式研究

实验技术与管理 2020年第12期37卷 270-272,276页

作者：李夏莹北京大学生命科学学院实验动物中心北京100871

实验动物是现代生命科学研究的重要组成部分,是生物医学科研的基础和重要支撑条件。实验动物平台是进行实验动物饲养、管理、实验研究的重要场所。该文从北京大学实验动物中心平台建设和管理的实际经验出发,对实验动物设施设计及要求、... 详细信息

实验动物是现代生命科学研究的重要组成部分,是生物医学科研的基础和重要支撑条件。实验动物平台是进行实验动物饲养、管理、实验研究的重要场所。该文从北京大学实验动物中心平台建设和管理的实际经验出发,对实验动物设施设计及要求、动物管理、从业人员的职业安全的要点进行了阐述。

关键词：实验动物平台设施设计动物管理人员安全