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Determination of Young's modulus by nanoindentation

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Science china(Technological Sciences) 2004年第4期47卷 398-408页

作者： MA Dejun1, Chung Wo Ong2, liu Jianmin1 & HE Jiawen3.1. Surface Engineering Research Institute, CMES, beijing 100072, china 2. {3. of applied Physics and Materials Research Center, The Hong Kong Polytechnic University, Hong Kong, china 3. State Key Laboratory for Mechanical Behavior of Materials, Xian Jiaotong University, Xian 710049, china Surface Engineering Research Institute CMES Beijing China department of applied Physics and Materials Research Center The Hong Kong Polytechnic University Hong Kong China State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong University Xi’an China

A methodology for determining Youngs modulus of materials by non-ideally sharp indentation has been developed. According to the principle of the same area-to-depth ratio, a non-ideally pyramidal indenter like a Berkovich one can be approximated by a non-ideally conical indenter with a spherical cap at the tip. By applying dimensional and finite element analysis to the non-ideally conical indentation, a set of approximate one-to-one relationships between the ratio of nominal hardness/reduced Youngs modulus and the ratio of elastic work/total work, which correspond to different tip bluntness, have been revealed. The nominal hardness is defined as the maximum indentation load divided by the cross-section area of the conical indenter specified at the maximum indentation depth. As a consequence, Youngs modulus can be determined from a nanoindentation test only using the maximum indentation load and depth, and the work done during loading and unloading processes. The new method for determining Youngs modulus is referred to as pure energy method. The validity of the method was examined by performing indentation tests on five materials. The experimental results and the standard reference values are in good agreement, indicating that the proposed pure energy method is a promising substitution for the most widely used analysis models at present.

关键词： Young's modulus, nanoindentation, nominal hardness, indentation work.

Low-intensity pulsed ultrasound reduces alveolar bone resorption during orthodontic treatment via Lamin A/C-Yes-associated protein axis in stem cells

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World Journal of Stem Cells 2024年第3期16卷 267-286页

作者： tong Wu Fu Zheng Hong-Yi Tang Hua-Zhi Li Xin-Yu Cui Shuai Ding Duo liu Cui-Ying Li Jiu-Hui Jiang Rui-Li Yang department of Orthodontics Peking University School and Hospital of StomatologyNational Engineering Laboratory for Digital and Material Technology of StomatologyBeijing Key Laboratory of Digital StomatologyBeijing 100081China department of Central Laboratory Peking University School and Hospital of StomatologyNational Clinical Research Center for Oral Diseases&National Engineering Laboratory for Digital and Material Technology of StomatologyBeijing Key Laboratory of Digital StomatologyBeijing 100081China

BACKGROUND The bone remodeling during orthodontic treatment for malocclusion often requires a long duration of around two to three years,which also may lead to some complications such as alveolar bone resorption or tooth root ***-intensity pulsed ultrasound(LIPUS),a noninvasive physical therapy,has been shown to promote bone fracture *** is also reported that LIPUS could reduce the duration of orthodontic treatment;however,how LIPUS regulates the bone metabolism during the orthodontic treatment process is still *** To investigate the effects of LIPUS on bone remodeling in an orthodontic tooth movement(OTM)model and explore the underlying *** A rat model of OTM was established,and alveolar bone remodeling and tooth movement rate were evaluated via micro-computed tomography and staining of tissue *** vitro,human bone marrow mesenchymal stem cells(hBMSCs)were isolated to detect their osteogenic differentiation potential under compression and LIPUS stimulation by quantitative reverse transcription-polymerase chain reaction,Western blot,alkaline phosphatase(ALP)staining,and Alizarin red *** expression of Yes-associated protein(YAP1),the actin cytoskeleton,and the Lamin A/C nucleoskeleton were detected with or without YAP1 small interfering RNA(siRNA)application via *** The force treatment inhibited the osteogenic differentiation potential of hBMSCs;moreover,the expression of osteogenesis markers,such as type 1 collagen(COL1),runt-related transcription factor 2,ALP,and osteocalcin(OCN),*** could rescue the osteogenic differentiation of hBMSCs with increased expression of osteogenic marker inhibited by ***,the expression of LaminA/C,F-actin,and YAP1 was downregulated after force treatment,which could be rescued by ***,the osteogenic differentiation of hBMSCs increased by LIPUS could be attenuated by YAP siRNA ***,LIPUS increased alveolar

关键词： Low-intensity pulsed ultrasound Bone resorption Osteogenesis Cytoskeleton-Lamin A/C-Yes-associated protein axis Bone marrow mesenchymal stem cells Orthodontic tooth movement

Null Fiber Coupler with Ultra-high Splitting Ratio of 100000∶1 for All-fiber Acousto-optic Switch

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Chinese Journal of Lasers 2000年第6期 40-45页

作者： LI tong PENG Jiangde LI Qun liu Xiaoming (department of Electronics Engineering, {3. University, beijing 100084, china)

A fiber null coupler with very high splitting ratio of 100000∶1 and low excess loss of 0.1 dB is reported. The control of the maximum splitting ratio and loss of the null coupler is studied. Its switching function is... 详细信息

关键词： fiber coupler acousto optic switch

CONSTANT AMPLITUDE FATIGUE STRENGTH AND P-S_a-S_m-N CAMBER FAMILY

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Chinese Journal of Aeronautics 1996年第1期9卷 28-37页

作者： Ni Kan(department of Naval Architecture and Ocean Engineering,Shanghai Jiao tong Universily, Shanghai, china, 20003.)Gao Zentong(department of Flight Vehicle Design and applied Mechanics, beijing University of Aeronautics and Astronautics,beijing, china, Dept. of Nav. Arch. and Ocean Eng. Shanghai Jiao Tong University Shanghai 200030 China Dept. Flight Vehicle Des. Appl. M. Beijing Univ. Aero. and Astronaut. Beijing 100083 China

Functions of the P-Sa-Sm-N camber family in constant amplitude cyclic loading are established by combining the P-S-N curve family and constant life diagrams, which is feasible in engineering application. Meanwhile, the preconditions of mechanics and probability-statistics are clearly presented. According to Weibull's assumptions i.e., monotone decreasing and nonintersecting about individual S-N curves, the relation of isostructural measure preserving transformation (IMPT) between the probability spaces of constant amplitude fatigue life and constant amplitude fatigue strength is proved based on the measure theory. Therefore, an individual specimen possesses the same percentile value in different probability spaces of fatigue life and fatigue strength under constant amplitude loading. The P-Sa -Sm-N cambers of individual, population and sample are also distinguished.

关键词： amplitude camber fatigue life fatigue (materials) strength

TAX EVASION:MODELS WITH SELF-AUDIT

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Journal of Systems Science & Complexity 2008年第4期21卷 487-518页

作者： Kin Keung LAI department of Management Sciences City University of Hong Kong College of Business Management Hunan University

Different from traditional tax audit, supervision with self-audit is a combination of audit by the taxpayer himself and audit by the tax authority. This paper mainly studies a taxpayer＇s optimal policy of tax evasion under supervision with self-audit and its related properties, in order to deduce some effective suggestions and theoretical bases to restrain tax evasion. Assuming that only a certain proportion of evaded tax can be discovered when the audit is executed, the authors first formulate a static model with self-audit. This model is divided into two stages. At the first stage, taxpayers declare their taxes, then the tax authority chooses audit objects, based on a known probability, and announces the result; if the taxpayer is chosen, he will enter the second stage, during which he has a chance to pay the evaded tax and the corresponding late fees and then is audited by the tax authority. The authors show the existence and uniqueness of the optimal amount of tax evasion at the first stage and the optimal proportion to self-expose at the second stage. The authors also discuss the related properties of the interior solution, and do elasticity analyses on some parameters. Besides, the authors extend the static model into the corresponding two-period model, and study the existence and uniqueness of the solution of the extended model. Finally, under the assumption that tax evasion can only be discovered with a certain probability when the audit is executed, the authors formulate another static model with self-audit and investigate its properties.

关键词： Existence and uniqueness of the solution self-audit static model tax evasion two-period model.

A novel neuroprotective method against ischemic stroke by accelerating the drainage of brain interstitial fluid

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Science china(Life Sciences) 2024年第10期67卷 2213-2223页

作者： Jingge Lian liu Yang Hanbo Tan Shaoyi Su Leonor Serrano Lopes Fangxiao Cheng Junhao Yan Yu Fu Wanyi Fu Zhaoheng Xie Jianfei Sun Jicong Zhang Zhiqian tong Yajuan Gao Hongbin Han department of Radiology Peking University Third HospitalBeijing 100191China beijing Key Laboratory of Magnetic Resonance Imaging Technology Beijing 100191China Institute of Medical Technology Peking University Health Science CenterBeijing 100191China department of Informatics Technical University of MunichGarching 80539Germany department of Anatomy and Histology School of Basic Medical SciencesPeking UniversityBeijing 100191China department of Neurology Peking University Third HospitalBeijing 100191China department of Electronic Engineering Tsinghua UniversityBeijing 100084China State Key Laboratory of Bioelectronics School of Biological Science and Medical EngineeringSoutheast UniversityNanjing 210096China School of Biological Science and Medical Engineering Beihang UniversityBeijing 100191China Key Laboratory of Alzheimer’s Disease of Zhejiang Province Institute of AgingSchool of Mental HealthWenzhou Medical UniversityWenzhou 325035China NMPA Key Laboratory for Evaluation of Medical Imaging Equipment and Technique Beijing 100191China

Ischemic stroke is a leading cause of death and disability *** response after stroke determines the outcome of ischemic injury.A recent study has reported an efficient method,epidural arterial implantation(EAI),for accelerating interstitial fluid(ISF)drainage,which provides a promising strategy to clear pro-inflammatory cytokines in the brain extracellular space(ECS).In this study,the method of EAI was modified(m-EAI)to control its function of accelerating the ISF drainage at different time points following ischemic *** neuroprotective effect of m-EAI on ischemic stroke was evaluated with the transient middle cerebral artery occlusion(tMCAO)rat *** results demonstrated the accumulation of IL-1β,IL-6,and TNF-αwas significantly decreased by activating m-EAI at 7 d before and immediately after ischemic attack in tMCAO rats,accompanied with decreased infarct volume and improved neurological *** study consolidates the hypothesis of exacerbated ischemic damage by inflammatory response and provides a new perspective to treat encephalopathy via brain *** research is essential to investigate whether m-EAI combined with neuroprotective drugs could enhance the therapeutic effect on ischemic stroke.

关键词： ischemic stroke brain extracellular space interstitial fluid modified epidural arterial implantation

Magnetic properties of tin-doped ferrites nanoparticles Sn_xFe_(3.x)O_4

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Rare Metals 2006年第Z1期25卷 493-497页

作者： LU Yanwu OU Yiyu liu Fangxin department of Physics Beijing Jiaotong University Beijing 100044 China Department of Physics Beijing Jiaotong University Beijing 100044 China Department of Astronomy and Applied Physics University of Science & Technology of China Hefei 230026 China

Nanoparticles of tin-doped ferrites SnxFe3.xO4 (x=0, 0.1, 0.2, 0.3. 0.4, 1.0) were prepared by the precipitation exchange method. The particles of all specimens are crystalline with mean diameter in the range of 4-8 nm, and the lattice parameters enlarge with increasing tin content. Magnetization and Mssbauer data indicate that the specimens are paramagnetic. The saturation magnetization decreases, as well as the magnetization and the coercive field increase, with increasing tin-content, the possible causes of which were discussed.

关键词： tin-doped ferrite quantum composition article-size effect paramagnetic properties

Controllable synthesis of well-ordered TiO2 nanotubes in a mixed organic electrolyte for high-efficiency photocatalysis

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中国科学:化学 2012年第11期42卷 1658-1659页

作者： WANG Chao 1,CHEN Da 1,2,PING GuangXing 1,liu Shu 1,HUANG XiaNi 1,HUANG YueXiang 1,SHU KangYing 1 & LI JingHong 2 1 College of Materials Science & Engineering,china Jiliang University,Hangzhou 3.0018,china 2 {3. Key Laboratory for Microanalytical Methods and Instrumentation department of Chemistry,tsinghua University,{3. 100084,china College of Materials Science Engineering china Jiliang University Hangzhou 3.0018 china beijing Key Laboratory for Microanalytical Methods and Instrumentation department of Chemistry tsinghua University{3. china

Well-ordered TiO2 nanotube arrays (TNAs) were fabricated by electrochemical anodization in a mixed organic electrolyte consisting of ethylene glycol and *** morphology,structure,crystalline phase,and photocatalytic properties of TNAs were characterized by using TEM,SEM,XRD and photodegradation of methylene *** was found that the morphology and structure of TNAs could be significantly influenced by the anodization time and applied *** obtained tube length was found to be proportional to anodization time,and the calculated growth rate of nanotubes was 0.6 m/*** microstructure analysis demonstrated that the diameter and thickness of the nanotubes increased with the increase of anodization *** growth mechanism of TNAs was also proposed according to the observed relationship between current density and time during *** expected,the obtained TNAs showed a higher photocatalytic activity than the commercial TiO2 P25 nanoparticles.

关键词： TiO2 nanotube arrays (TNAs) anodization organic electrolytes photocatalysis

The application of EBSP in the research of deformation microstructure of metals

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电子显微学报 2001年第4期20卷 348-349页

作者： WU Qing lan,WU Gui lin,MENG Jun,liu Qing,liu Wei (department of materials science and technology, {3. University,beijing 100084) 清华大学北京 100084

The basic principle and application of EBSP in the research of deformed microstructure are illustrated in this paper. The results suggest that EBSP can be applied in the research of deformation microstructure and crys... 详细信息

关键词： EBSP deformation microstructure crystallography