检索结果-南通市图书馆

在线全文

学校读者我要写书评

暂无评论

混凝土声发射规律的协同学研究及可视化模拟

青岛建筑工程学院学报 2005年第4期26卷 1-5,16页

作者：于广明魏晔潘永战刘文锋祝英杰刘福顺青岛理工大学土木工程学院青岛266033 山东建筑工程学院设计院济南250014

混凝土破裂过程中声发射现象能够很好地揭示混凝土破裂机理.首次利用协同学的基本原理,对混凝土破裂过程中声发射现象进行了探索性研究,并通过混凝土破裂过程中内部结构状态变化(损伤演化)和声发射特征的对应关系,从更深层次上认识混凝... 详细信息

混凝土破裂过程中声发射现象能够很好地揭示混凝土破裂机理.首次利用协同学的基本原理,对混凝土破裂过程中声发射现象进行了探索性研究,并通过混凝土破裂过程中内部结构状态变化(损伤演化)和声发射特征的对应关系,从更深层次上认识混凝土的破裂机理.首先分析了混凝土声发射参数与损伤演化的关系,并以声发射事件计数率作为混凝土破坏过程的序参量,建立了混凝土声发射序参量的演化方程,求出了其定态和非定态解,并分析了其科学意义,对混凝土声发射的协同特征进行了全面描述.最后,应用RFPA软件对混凝土声发射进行模拟,首次应用数值模拟的方法验证了混凝土声发射的协同效应,从而进一步证实了研究结果的准确性和利用协同学研究混凝土声发射的可行性,为混凝土声发射技术的工程应用提供理论依据;同时,所做的数值模拟工作,也为混凝土破裂机理研究提供了新的手段,即数值试验手段.

关键词：混凝土破裂声发射协同学数值模拟协同效应数值试验

The influence of nano-particle tracers on the slip length measurements by microPTV

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2013年第3期29卷 411-419页

作者： Xu Zheng Gao-pan Kong zhan-Hua Silber-Li State Key Laboratory of Nonlinear Mechanics Institute of MechanicsCAS

Direct measurement of slip length is based on the measured fluid velocity near solid boundary. However, previous micro particle image velocimetry/particle tracking velocimetry （microPIV/PTV） measurements have reported surprisingly large measured near-wall velocities of pressure-driven flow in apparent contradiction with the no-slip hy-pothesis and experimental results from other techniques. To better interpret the measured results of the microPIV/PTV, we performed velocity profile measurements near a hy-drophilic wall （z = 0.25-1.5 μm） with two sizes of tracer particles （φ 50 nm and φ200 nm）. The experimental results indicate that, at less than 1 μm from the wall, the deviations between the measured velocities and no-slip theoretical values obviously decrease from 93% of φ200 nm particles to 48% of φ50 nm particles. The Boltzmann-like exponential measured particle concentrations near wall were found. Based on the non linear Boltzmann distribution of particle concentration and the effective focus plane thickness, we illustrated the reason of the apparent velocity increase near wall and proposed a method to correct the measured velocity profile. By this method, the deviations between the corrected measured velocities and the no-slip theoretical velocity decrease from 45.8% to 10%, and the measured slip length on hy-drophilic glass is revised from 75 nm to 16 nm. These results indicated that the particle size and the biased particle concentration distribution can significantly affect near wall velocity measurement via microPIV/PTV, and result in larger measured velocity and slip length close to wall.

关键词： MicroPIV/PTV · Slip length · Nano-particle tracer · Particle concentration distribution · Boltzmann distribution

管棚注浆预支护技术在富水砂层地铁施工中的应用

在线全文

学校读者我要写书评

暂无评论

青岛理工大学学报 2015年第2期36卷 19-24,58页

作者：许德龙郭宗河张海波潘永战于广明霍兵兵青岛理工大学土木工程学院青岛266033 蓝色经济区工程建设与安全协同创新中心青岛266033 青岛市市政工程管理处青岛266011

管棚注浆法是地下结构工程浅埋暗挖时通常采用的一种超前支护方法.以青岛地铁一期(3号线)土建10标段河西站—河东站区间工程暗挖隧道所处的富水砂层地质条件为例,应用MIDAS/GTS有限元软件分别模拟分析了不采用和采用管棚注浆时围岩的位... 详细信息

管棚注浆法是地下结构工程浅埋暗挖时通常采用的一种超前支护方法.以青岛地铁一期(3号线)土建10标段河西站—河东站区间工程暗挖隧道所处的富水砂层地质条件为例,应用MIDAS/GTS有限元软件分别模拟分析了不采用和采用管棚注浆时围岩的位移场情况,说明采用管棚注浆法能显著抑制富水砂层的变形,减少隧道支护结构的变形,避免浅埋流砂层开挖中塌方现象的产生.

关键词：富水砂层暗挖隧道管棚注浆数值模拟

脑血管病急性期血尿酸/血肌酐比值与脑血管事件复发及死亡的关系:一项前瞻性队列研究

在线全文

学校读者我要写书评

暂无评论

中国全科医学 2025年第2期28卷 175-182,192页

作者：任小乔王盼吴昊纪勇石志鸿天津医科大学神经内外科及神经康复临床学院天津市300070 天津市环湖医院 300350

背景脑卒中在世界各地有较高的死亡率和复发率。血尿酸(SUA)是嘌呤代谢的产物,已被认为是心脑血管病的危险因素。血尿酸/血肌酐比值(SUA/Scr)是代表肾功能标准化的SUA,目前有关SUA/Scr在急性脑血管病中的作用仍有争议。目的探讨脑血管... 详细信息

背景脑卒中在世界各地有较高的死亡率和复发率。血尿酸(SUA)是嘌呤代谢的产物,已被认为是心脑血管病的危险因素。血尿酸/血肌酐比值(SUA/Scr)是代表肾功能标准化的SUA,目前有关SUA/Scr在急性脑血管病中的作用仍有争议。目的探讨脑血管病急性期SUA/Scr与脑血管事件复发和死亡的关系。方法本研究为前瞻性队列研究,选取2006年9月—2019年9月天津市环湖医院连续收治的首次发生脑血管事件的13313例患者为研究队列,并对患者进行随访,随访截至2020年9月。随访方式为门诊及电话相结合。随访主要终点事件为全因死亡,次要终点事件为脑血管事件复发、心血管事件复发、其他血管事件发生(如下肢动静脉栓塞)。采用Cox比例风险回归模型探究SUA/Scr与脑血管事件复发与死亡的关系。结果根据脑血管病急性期SUA/Scr四分位数,将患者分为Q1组(SUA/Scr≤3.16,n=3520)、Q2组(3.164.92,n=3243)。截至随访结束,774例(5.8%)患者死亡,2064例(15.5%)患者复发脑血管事件。脑血管病急性期SUA/Scr位于Q1~Q4的患者中,男性复发脑血管病的例数依次为302、375、408、337例,女性依次为99、125、169、249例;男性复发脑梗死的例数依次为261、314、345、283例,女性依次为90、101、142、205例;男性复发大动脉粥样硬化型脑梗死的例数依次为154、191、214、183例,女性依次为58、52、45、31例;男性全因死亡的例数依次为165、128、131、88例,女性依次为57、63、62、80例;男性因脑梗死死亡的例数依次为93、72、70、46例,女性依次为31、33、36、44例;男性因大动脉粥样硬化型脑梗死死亡的例数依次为58、52、45、31例,女性依次为17、18、27、24例。调整多项混杂因素后,SUA/Scr位于Q4相较于Q1是男性急性脑梗死复发的影响因素(HR=0.690,95%CI=0.500~0.953,P=0.026);SUA/Scr位于Q4相较于Q1是男性脑梗死亚组患者大动脉粥样硬化型脑梗死复发的影响因素(HR=0.740,95%CI=0.578~0.947,P=0.017)。SUA/Scr位于Q4相较于Q1是男性全因死亡、因脑梗死死亡的影响因素(HR=0.575,95%CI=0.368~0.901,P=0.003;HR=0.610,95%CI=0.353~0.814,P=0.011)。SUA/Scr位于Q3、Q4相较于Q1是男性出院后死亡的影响因素(HR=0.656,95%CI=0.476~0.904,P=0.010;HR=0.582,95%CI=0.409~0.829,P=0.001)。SUA/Scr位于Q4相较于Q1是男性脑梗死亚组患者因大动脉粥样硬化型脑梗死死亡的影响因素(HR=0.580,95%CI=0.386~0.873,P=0.007)。结论一定范围内,脑血管病急性期SUA/Scr升高对男性患者脑血管事件复发及死亡有一定的保护作用,低SUA/Scr与男性大动脉粥样硬化型脑梗死的死亡和复发风险升高有关,但与小动脉闭塞型脑梗死和心源性卒中复发和死亡无关。在女性患者中没有观察到SUA/Scr与脑血管事件复发及死亡的关系。

关键词：脑血管障碍脑卒中血尿酸/血肌酐比值动脉粥样硬化男性复发死亡队列研究前瞻性研究 Cox比例风险回归模型

维普期刊数据库博看期刊

Parameterization of ocean wave-induced mixing processes for finite water depth

在线全文

学校读者我要写书评

暂无评论

Acta Oceanologica Sinica 2009年第4期28卷 16-22页

作者： YANG yongzeng zhan Run TENG yong First Institute of Oceanography State Oceanic Administration Qingdao 266061 China Key Laboratory of Marine Science and Numerical Modeling State Oceanic Administration Qingdao 266061 China

Three dimensional wave-induced mixing plays an important role in shallow water area. A quite direct approach through the Reynolds average upon characteristic length scale is proposed to parameterize the horizontal and vertical shallow water mixing. Comparison of finite depth case with infinite depth results indicates that the difference of the wave-induced mixing strength is evident. In the shallow water condition, the infinite water depth approximation overestimates the mixing strength in the lower layers. The nonzero horizontal wave-induced mixing presents anisotropic property near the shore. The Prandtl＇s mixing length theory underestimated the wave-induced mixing in the previous studies.

关键词： Reynolds average Characteristic length scale Wave-induced mixing parameter

Preparation of ultrafine WC-Co powder via fluidized bed

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Chemical Engineering 2024年第9期73卷 15-26页

作者： Huijun Shang Hengli Li Weijun Li Feng pan zhan Du State Key Laboratory of Mesoscience and Engineering Institute of Process EngineeringChinese Academy of Sciences(CAS)Beijing 100190China College of Chemistry and Chemical Engineering Shihezi UniversityShihezi 832003China College of Chemical Engineering University of Chinese Academy of SciencesBeijing 100049China Chinalco Environmental Protection and Energy Conservation Group Co. Ltd.Xiong'an 071700China

In this study,the effects of reaction parameters on the deep-reduction and carbonization process of WO_(2)-Co to WC-Co were *** results indicate that the oxygen loss rate of WO_(2) is positively correlated with temperature and methane partial *** partial pressure of methane has no significant effect on the formation rate of *** carbon content and particle size of the product increase with the increase of CH_(4) partial *** synergistically regulating the reaction temperature to 950℃,the CH_(4) partial pressure to 1.25%,and the reaction time to 60 min,ultrafine WC-Co powder without η phase can be *** particle size of the composite powder is 128 nm,with total carbon content of 6.16%,free carbon content of 0.4%,and residual oxygen content of 0.05%,*** growth rate relationship of tungsten carbide is as follows:δ(t)=1.21×10^(-13)exp(-12809.72/T)√t.

关键词： Ultrafine WC-Co powder Gas-solid reaction Fluidization Reaction process regulation Growth rate equation

IBPSO-Based MUSIC Algorithm for Broken Rotor Bars Fault Detection of Induction Motors

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2018年第5期31卷 48-57页

作者： pan-pan Wang Xiao-Xiao Chen yong zhang yong-Jun Hu Chang-Xin Miao School of Electrical and Power Engineering China University of Mining & Technology Xuzhou 221116 China School of Information and Control Engineering China University of Mining & Technology Xuzhou 221116 China

In spectrum analysis of induction motor current, the characteristic components of broken rotor bars（BRB） fault are often submerged by the fundamental component. Although many detection methods have been proposed for this problem, the frequency resolution and accuracy are not high enough so that the reliability of BRB fault detection is a ected. Thus, a new multiple signal classification（MUSIC） algorithm based on particle swarm intelligence search is developed. Since spectrum peak search in MUSIC is a multimodal optimization problem, an improved bare?bones particle swarm optimization algorithm（IBPSO） is proposed first. In the IBPSO, a modified strategy of subpopulation determination is introduced into BPSO for realizing multimodal search. And then, the new MUSIC algorithm, called IBPSO?based MUSIC, is proposed by replacing the fixed?step traversal search with IBPSO. Meanwhile, a simulation signal is used to test the e ectiveness of the proposed algorithm. The simulation results show that its frequency precision reaches 10-5, and the computational cost is only comparable to that of traditional MUSIC with 0.1 search step. Finally, the IBPSO?based MUSIC is applied in BRB fault detection of an induction motor, and the e ectiveness and superiority are proved again. The proposed research provides a modified MUSIC algorithm which has su cient frequency precision to detect BRB fault in induction motors.

关键词： MUSIC Multimodal Bare?bones particle swarm optimization Induction motors Broken rotor bars Fault detection

A novel technique for measuring 3D deformation of adhesively bonded single lap joint

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2016年第1期59卷 58-65页

作者： Bing pan LuJun Ma yong Xia Institute of Solid Mechanics Beihang University State Key Lab of Automotive Safety and Energy Tsinghua University

An easy-to-implement yet practical single-camera microscopic stereo-digital image correlation(stereo-DIC) technique is proposed for surface three-dimensional(3D) deformation measurement of singe lap joint(SLJ) samples subjected to mechanical loads. The basic principles, optical configurations and implementation procedures of the proposed technique are described in detail. Compared with existing single-camera 2D-DIC technique, which has been regularly used for in-plane deformation measurement of a SLJ specimen, the proposed technique offers the special merit of simultaneously determining all the three displacement components by simply adding two additional optical elements to existing single-camera 2D-DIC systems. The accuracy and effectiveness of the proposed technique is demonstrated by measuring the 3D deformation of a SLJ specimen subjected to quasi-static tensile loads.

关键词： digital image correlation single lap joint deformation measurement

SCHEDULING ALGORITHM BASED ON FOLLOW-UP SHARING CHARACTER FOR POST-EVENT RESPONSE RESOURCE DISTRIBUTION IN LARGE-SCAL DISASTERS

在线全文

学校读者我要写书评

暂无评论

Journal of Systems Science and Systems Engineering 2016年第1期25卷 77-101页

作者： yong Ye Nan Liu Guiping Hu Shalei zhan Department of Management College of Humanities and Management Wenzhou Medical University Wenzhou 325035 P.R. China Department of Management Sciences & Engineering School of Management Zhejiang University Hangzhou 310058 P.R. China Industrial and Manufacturing Systems Engineering 3014 Black Engineering Iowa State University Ames IA 50011 School of Computer Science and Information Engineering Zhejiang Gongshang University Hangzhou 310058 P.R. China

Post-event response planners must develop effective and efficient plans for the proper allocation and distribution of resources to impacted areas （IAs） within a critical time window. To determine the effectiveness and efficiency of distribution plans, this study addresses resource allocation effectiveness losses （RAEL, or losses caused by the mismatch between supply and demand in IAs） and emergency logistics time costs （ELTC, or transportation time of logistics processes under emergency conditions）. Moreover, this study examines a follow-up sharing character （FSC） that coordinates resources among different phases. This research proposes an integrated model （IM） based on this character. This model aims to minimize RAEL and ELTC. Furthermore, the IM combines the time dimension model （TDM）, which coordinates the demands and supplies of all phases in the planning horizon, and the space dimension model （SDM）, which generates a specific distribution plan for the first phase. An analytical solution is obtained for the TDM as per the definition of FSC, after which the SDM is solved through a single-objective linear programming model. After solving the IM effectively, we fred that the proposed methodology fits the emergency circumstance well. Insights derived from the model are also presented in the conclusion.）

关键词： Emergency management humanitarian logistics decision-making resource distribution