检索结果-南通市图书馆

Multi-scale finite element simulation on large deformation behavior of wood under axial and transverse compression conditions

引用

Acta Mechanica Sinica 2021年第7期37卷 1136-1151,I0002页

作者： Weizhou zhong Zexiong Zhang Xiaowei Chen Qiang Wei gang Chen Xicheng Huang Institute of Systems Engineering China Academy of Engineering PhysicsMianyang Sichuan621999China Shock and Vibration of Engineering Materials and Structures Key Laboratory of Sichuan Province Mianyang 621999China College of Engineering Science University of Science and Technology of ChinaHefei 230026China Advanced Research Institute for Multidisciplinary Science Beijing Institute of TechnologyBeijing100081China The State Key Lab of Explosion Science and Technology Beijing Institute of TechnologyBeijing100081China

Multi-scale finite element method is adopted to simulate wood compression behavior under axial and transverse loading. Representative volume elements (RVE) of wood microfibril and cell are proposed to analyze orthotropic mechanical behavior. Lignin, hemicellulose and crystalline-amorphous cellulose core of spruce are concerned in spruce nanoscale model. The equivalent elastic modulus and yield strength of the microfibril are gained by the RVE simulation. The anisotropism of the crystalline-amorphous cellulose core brings the microfibril buckling deformation during compression loading. The failure mechanism of the cell-wall under axial compression is related to the distribution of amorphous cellulose and crystalline cellulose. According to the spruce cell observation by scanning electron microscope, numerical model of spruce cell is established using simplified circular hole and regular hexagon arrangement respectively. Axial and transverse compression loadings are taken into account in the numerical simulations. It indicates that the compression stress-strain curves of the numerical simulation are consistent with the experimental results. The wood microstructure arrangement has an important effect on the stress plateau during compression process. Cell-wall buckling in axial compression induces the stress value drops rapidly. The wide stress plateau duration means wood is with large energy dissipation under a low stress level. The numerical results show that loading velocity affects greatly wood microstructure failure modes in axial loading. For low velocity axial compression, shear sliding is the main failure mode. For high velocity axial compression, wood occur fold and collapse. In transverse compression, wood deformation is gradual and uniform, which brings stable stress plateau.

关键词： Multi-scale model Representative volume element Spruce Energy dissipation Wood cell

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

Interharmonic Analysis Model of Photovoltaic Grid-connected System with Extended Dynamic Phasors

引用

Journal of Modern Power Systems and Clean Energy 2021年第6期9卷 1540-1547页

作者： Qing zhong Yangxin Qiu Yuming Zhao Haifeng Li gang Wang Fushuan Wen School of Electric Power South China University of Technology Shenzhen Power Supply Bureau Co. Ltd. School of Electrical Engineering Zhejiang University

The interactions between randomly fluctuating power outputs from photovoltaic(PV) at the DC side and background voltage distortions at the AC side could generate interharmonics in the PV grid-connected system(PVGS). There is no universal method that can reveal the transmission mechanism of interharmonics and realize accurate calculation in different scenarios where interharmonics exist in the PVGS. Therefore, extended dynamic phasors(EDPs) and EDP sequence components(EDPSCs) are employed in the interharmonic analysis of the PVGS. First, the dynamic phasors(DPs) and dynamic phasor sequence components(DPSCs) are extended into EDPs and EDPSCs by selecting a suitable fundamental frequency other than the power frequency. Second, an interharmonic analysis model of the PVGS is formulated as a set of state space equations. Third, with the decoupling characteristics of EDPSCs,generation principles and interactions among the interharmonics in the PVGS are presented by the sequence components,and its correctness is verified by simulation and *** presented model can be used to accurately calculate the interharmonics generated in the PVGS both at the AC and DC sides. Because of the decoupling among the EDPSCs, the set of state space equations can effectively describe the principle.

关键词： Dynamic phasor sequence component(DPSC) harmonic interharmonic photovoltaic grid-connected system(PVGS) power quality

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

Precise, Long-Time Displacement Self-Sensing of Piezoelectric Cantilever Actuators Based on Charge Measurement Using the Sawyer–Tower Circuit

引用

Chinese Physics Letters 2018年第10期35卷 81-84页

作者： Qiang-zhong Wang gang Wang Fa-xin Li LTCS and College of Engineering Peking UniversityBeijing 100871 Center for Applied Physics and Technology Peking UniversityBeijing 100871

Previous studies show that near linearity exists between displacement and charge of piezoelectric actuators, while studies under higher fields are lacking and long-time displacement self-sensing is still a challenge. Here we indicate that precise, long-time displacement self-sensing can be accomplished using the Sawyer–Tower circuit, where a high-impedance electrometer and a non-leaky capacitor are used to measure the charge. Calibrating the results on a piezoelectric unimorph cantilever shows that the displacement resolution of charge self-sensing is ~3 nm, much better than that of ~40 nm for the calibrating laser sensor. Testing results under a unipolar field up to 2 kV/mm with different periods indicate that a direct proportional relationship holds between charge and displacement with the maximum error of 4.65%. The self-sensing time can be over 20 min or even longer if a higher-impedance electrometer is used.

关键词： Piezoelectric actuators

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

Introducing an antibiotic stewardship program in a pediatric center in China

引用

World Journal of Pediatrics 2018年第3期14卷 274-279页

作者： Zhi-gang Zhang Fei Chen Jian-zhong Chen Department of Pharmacology Liaocheng People's Hospital of Shandong ProvinceLiaocheng 252000China

Background This study aimed to investigate the eff ect of antibiotic stewardship programs (ASP) on reducing antimicrobial resistance rate, antibiotics consumption and multi-drug resistance bacterial infections in the pediatric patients. Methods This study was carried out in the Pediatric Center of a tertiary hospital of Shandong Province, China. The study duration was separated into two periods according to introduction of ASP (began from April 2011). Before intervention: from April 2009 to March 2011;after intervention: from April 2012 to March 2014. The consumption of antibiotics, defi ned daily dose (DDD), isolation of multidrug-resistant organisms (MDRO) and resistance rate of antibiotics were analyzed and compared between the two study periods. Results Total antibiotics consumption (DDDs) reduced from 56,725 in 2011 to 31,380 in 2014;antibiotic use density (AUD) reduced from 93.8 to 43.5;mean (± SD) antibiotic costs per patient (per quarter) decreased from 637 (± 29) RMB to 462 (± 49) RMB;and the mean total drug consumption (g)/DDD (DDDs) for inpatients decreased from 90.4 (± 3.3) to 56.4 (± 9.5). Multidrug-resistant microorganisms isolation reduced signifi cantly from 463 (20.0) to 216 (6.9%). Resistance rate of general spectrum antibiotics reduced remarkably after intervention. The proportion of patients colonized or infected with Carbapenems-resistantAcinetobacter baumannii was correlated with DDDs of carbapenem. Conclusions Implementation of ASP leads to reduced medical expense, decrease of improper and abuse of antibiotics, and reduced antibiotics resistance rate and MDRO isolation. Continuous eff orts to improve antibiotic use are required.

关键词： Antimicrobial resistance Antibiotic stewardship program (ASP) Defined daily dose (DDD) Isolation of multidrug-resistant organisms (MDRO)

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

BaTiO_(3)-based ceramics with high energy storage density

引用

Rare Metals 2023年第4期42卷 1261-1273页

作者： Yang Li Ming-Yang Tang zhong-gang Zhang Qi Li Jing-Lei Li Zhuo Xu gang Liu Fei Li Electronic Materials Research Lab Key Lab of Education Ministry and State Key Laboratory for Mechanical Behavior of MaterialsSchool of Electronic Science and EngineeringXi’an Jiaotong UniversityXi’an710049China Laboratory of Micro/Nano Systems for Aerospace Ministry of EducationNorthwestern Polytechnical UniversityXi’an710072China School of Materials and Energy Southwest UniversityChongqing400715China

BaTiO_(3)ceramics are difficult to withstand high electric fields,so the energy storage density is relatively low,inhabiting their applications for miniaturized and lightweight power electronic *** address this issue,we added Sr_(0.7)Bi_(0.2)TiO_(3)(SBT)into BaTiO_(3)(BT)to destroy the long-range ferroelectric ***^(2+)was introduced into BT-SBT in the form of CaTiO_(3)(CT),which has the effect of inhibiting the movement of A-site defects to reduce dielectric loss and refining the grains to increase the breakdown field *** addition,we have increased the density and grain uniformity of ceramics by repeated rolling of the green samples through the viscous polymer processing(VPP),to further increase the breakdown electric *** BT-SBT-CT ceramics exhibit the high recoverable energy storage density of 4.0 J·cm^(-3)under electric field of 480 kV·cm^(-1).Its recoverable energy storage density varies by less than 8%in the temperature range of 30-150℃,indicating good temperature stability of the energy storage *** this work,the energy storage performance of barium titanate-based ceramics was greatly improved by transforming ferroelectrics into relaxor ferroelectrics and VPP method,which can bring new inspiration for the research of energy storage ceramics.

关键词： Barium titanate Energy storage Viscous polymer processing(VPP)

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 New Angiosperm Genus from the Lower Cretaceous Yixian Formation, Western Liaoning, China

引用

Acta Geologica Sinica(English Edition) 2013年第4期87卷 916-925页

作者： HAN gang FU Xiao-ping LIU zhong-jian WANG Xin Palaeontological Center Bohai University Fairylake Botanical Garden Shenzhen Municipality and Chinese Academy of Sciences Shenzhen Key Laboratory for Orchid Conservation and Utilization the National Orchid Conservation Center of China and Orchid Conservation & Research Center of Shenzhen State Key Laboratory of Palaeobiology and Stratigraphy Nanjing Institute of Geology and Palaeontology

The abundant fossils of early angiosperms found in the Yixian Formation （125 Ma, Early Cretaceous） have demonstrated unexpectedly high diversity and various reproductive strategies, and thus have shed new light on early angiosperm evolution. Here, using light microscope and scanning electron microscope, we document several fructifications of Baicarpus gen. nov. from Liaoning province, China. Each fructification of the new taxon includes several apocarpous carpels/fruits attached in an urn-formed gynobase. Each fruit/carpel has a persistent straight style and an ovary enclosing a single seed. These fossil plants demonstrate a new floral organization and thus enhance our understanding of the diversity of angiosperms in the Yixian Formation. Together with previously reported ones, this fossil angiosperm suggests an origin time for angiosperms earlier than widely accepted.

关键词： paleobotany fruits Barremian-Aptian Yixian Formation Liaoning province

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

Fully Self-Consistency in Relativistic Random Phase Approximation

引用

Chinese Physics Letters 2012年第11期29卷 40-42页

作者： YANG Ding CAO Li-gang MA zhong-Yu School of Science Communication University of ChinaBeijing 100024 Institute of Modern Physics Chinese Academy of SciencesLanzhou 730000 Center of Theoretical Nuclear Physics National Laboratory of Heavy Ion Accelerator of LanzhouLanzhou 730000 China Institute of Atomic Energy P.O.Box 275(18)Beijing 102413

Fully self-consistent relativistic random phase approximation(RRPA)is built on the relativistic mean field ground state with a non-linear relativistic *** consistency requires that the same effective interaction is adopted to simultaneously describe both the ground states and the excited states of the *** and accurate numerical results of the nuclear giant resonances obtained in the RRPA require fully consistent *** some excitation modes they are extremely sensitive to consistent treatment,e.g.,such as isoscalar giant monopole and dipole resonances(ISGMR and ISGDR).In this work we perform the numerical calculations in the case of ISGDR for ^(208)Pb and check the *** spurious state in the ISGDR vanishes once the full self-consistency is achieved.

关键词： relativistic consistency Approximation

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

Effect of Intergranular Precipitation on the Internal Oxidation Behavior of Cr–Mn–N Austenitic Stainless Steels

引用

Acta Metallurgica Sinica(English Letters) 2015年第8期28卷 1008-1014页

作者： Lei-gang Zheng Xiao-Qiang Hu Xiu-Hong Kang Dian-zhong Li Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences

The effect of intergranular precipitation on the internal oxidation behavior of Cr–Mn–N austenitic steels at 1000 °C in dry air atmosphere was investigated using scanning electron microscope, transmission electron microscope, and X-ray diffraction analysis. The results show that intergranular M23C6 carbide morphologies play an important role on the internal oxidation behavior of Cr–Mn–N steels. During the period of the oxidation, both discontinuous chain-shaped and continuous film-shaped intergranular M23C6 carbides precipitated along the grain boundaries. Internal oxides of silica preferentially intruded into the matrix along grain boundaries with discontinuous M23C6 carbide particles, while silica was obviously restricted at the interfaces between the external scale and matrix on the occasion of continuous film-shaped M23C6 carbides. It is seemed that reasonable microstructure could improve the oxidation resistance of Cr–Mn–N steels.

关键词： M23C6 precipitation Internal oxidation Cr–Mn–N austenitic steel

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 Optoelectronic Properties of Donor-acceptor Molecules Containing Pyromellitic Diimide Chromophore

引用

Chemical Research in Chinese Universities 2013年第6期29卷 1083-1088页

作者： ZHANG Qian LU Xue-feng WANG zhong-sheng ZHOU gang Laboratory of Advanced Materials Department of ChemistryFudan University Shanghai 200438 P.R.China

Three donor-acceptor molecules containing pyromellitic diimide chromophore were designed and synthe- sized. The synthetic route towards the target compounds was systematically investigated and discussed in detail. The resulted organic semiconductors have shown promising optoelectronic properties as further revealed by UV-Vis ab- sorption spectroscopy, cyclic voltammetry, and theoretic calculation.

关键词： Pyromellitic diimide Donor-acceptor Charge transfer

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

Synthesis,Spectroscopic Properties and Crystal Structural Characterization of a Triphenyltin(IV) Complex with 5-Bromonicotinic Acid

引用

Chinese Journal of Structural Chemistry 2006年第10期25卷 1228-1232页

作者： GAO zhong-Jun YIN Han-Dong LI gang XU Hao-Long Department of Chemistry Liaocheng University Liaocheng Shandong 252059 China

A novel organotin complex [Ph3Sn（C2H5OH）（OCOC5H3NBr）SnPh3（OCOC5H3NBr）] has been synthesized by the reaction of 5-bromonicotinic acid with triphenyltin hydroxide in ethanol and characterized by elemental analysis, IR and ^1H NMR. The crystal structure was determined by X-ray single-crystal diffraction. The crystal belongs to the monoclinic system, space group P21/c with a = 15.564（2）, b = 24.975（4）, c = 12.2973（19）°A, β = 92.224（2）°, Z = 4, V = 4776.5（13）°A^3, Dc = 1.596 g/cm^3, μ（MoKα） = 2.765 mm^-1, F（000） = 2264, R = 0.0385 and wR = 0.0667. In the molecular structure of the title complex, the tin atoms are five-coordinated in a trigonal bipyramidal geometry.

关键词： organotin 5-bromonicotinic acid synthesis crystal structure

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：