检索结果-南通市图书馆

Nonlinear dynamic analysis of a rotor/bearing/seal system

在线全文

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2011年第1期12卷 46-55页

作者： Wei LI Yi YANG De-ren sheng Jian-hong chen Yong-qiang CHE Department of Energy Engineering Zhejiang University Hangzhou 310027 China

In this study a new dynamic model of a rotor system is established based on the Hamilton principle and the finite element method (FEM). We analyze the dynamic behavior of the rotor system with the coupled effects of the nonlinear oil film force, the nonlinear seal force, and the mass eccentricity of the disk. The equations of the motion are solved effectively using the fourth order Runge-Kutta method in MATLAB. The dynamic behavior of the system is illustrated by bifurcation diagrams, largest Lyapunov exponents, phase trajectory diagrams, and Poincaré maps. The numerical results show that the rotational speed of the rotor, the pressure drop in the seal, the seal length, the seal clearance, and the mass eccentricity of the disk are the key parameters that significantly affect the dynamic characteristics of the rotor system. The motion of the rotor system exhibits complex types of periodic, quasi-periodic, double-periodic, multi-periodic, and chaotic vibrations. This analysis can be used to guide the design of seal parameters and to diagnose the vibration of rotor/bearing/seal systems.

关键词： Nonlinear Rotor system Hamilton principle Dynamic Finite element method (FEM)

Corrosion Behavior of B_4C/6061Al Neutron Absorber Composite in Different H_3BO_3 Concentration Solutions

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2016年第11期29卷 1037-1046页

作者： Yu-Li Li Wen-Xian Wang hong-sheng chen Jun Zhou Qiao-Chu Wu School of Materials Science and Engineering Taiyuan University of Technology Key Laboratory of Interface Science and Engineering in Advanced Materials Ministry of Education Taiyuan University of Technology Department of Mechanical Engineering Pennsylvania State University Erie The Behrend College

In this study, electrochemical corrosion tests, full-soak corrosion tests and associated microstructure analysis were conducted to investigate the corrosion behaviors of B4C/6061Al neutron absorber composites（NACs） manufactured by powder metallurgy method in solutions having different boric acid（H3BO3） concentrations（500, 2500 and 10,000 ppm）. In electrochemical corrosion tests, B4C/6061Al NACs demonstrate the highest（short-term） corrosion resistance in the 2500 ppm H3BO3 solution. While for full-soak corrosion tests, the B4C/6061Al NACs show the highest（long-term） corrosion resistance in the 500 ppm H3BO3 solution. This difference is found to be mainly due to the formation of different surface morphologies during these two different corrosion tests. As noticed, a layer of Al（OH）3was formed on the composite surface during full-soak corrosion tests, but it cannot be found in the electrochemical corrosion tests. The full-soak corrosion mechanism of the B4C/6061Al NACs in the H3BO3 solution is found to be primarily determined by the dynamic balance between the formation and dissolution rates of the oxide film, which is mainly controlled by the density of H~＋ ions in the solution.

关键词： B4C/6061Al NACs Powder metallurgy Electrochemical corrosion Full-soak corrosion

Identification of optimal solid solution temperature for Sm_(2)Co_(17)-type permanent magnets with different Fe contents

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2021年第12期40卷 3567-3574页

作者： Shuai Wang hong-sheng chen Yi-Kun Fang Chao Wang Lei Wang Ming-Gang Zhu Wei Li Division of Functional Materials Research Central Iron and Steel Research InstituteBeijing 100081China

It is confirmed that the solid solution temperature range to obtain optimal magnetic properties is different for the magnets with different Fe contents,and the correlation between magnetic properties and microstructures influenced by solid solution temperature(Ts)has been systematically *** optimal solid solution temperature range is 1413-1463 K for the Sm(Co_(bal)Fe_(0.213)Cu_(0.073)Zr_(0.024))_(7.6)magnet,which is higher than that of the Sm(Co_(bal)Fe_(0.262)Cu_(0.073)Zr_(0.024))_(7.6)magnet(1403-1453 K),and the optimal T_s range is about 50 K for both of the *** solid solution temperature range shifting toward relatively high temperature is due to the increase in a phase transition *** magnet solution-treated at proper temperature exhibits 1:7 H single phase,and intact cell structure and high Cu concentration(23.12 at%)in the cell boundary are found after aging process,which makes the magnet shows high intrinsic coercivity(H_(cj))and magnetic field at knee-point(H_(knee)).At a lower solid solution temperature,the 2:17 H,1:5 H and Zr-rich precipitation phases appear,which affects the cell structure,density of lamellar phase and Cu concentration in the cell boundary,leading to the reduced magnetic ***,at a higher solid solution temperature,there exist obviously light gray and dark regions with different Sm,Cu and Fe contents in scanning electron microscopy observation,and the magnet shows low pinning field in the two regions and incomplete cell structure,resulting in an inferior H_(cj)and H_(knee).

关键词： Sm_(2)co_(17)-type magnets Magnetic properties Solid solution treatment Iron content Microstructures

Study on the clogging mechanism of punching screen in sand control by the punching structure parameters

在线全文

学校读者我要写书评

暂无评论

Petroleum Science 2024年第1期21卷 609-620页

作者： Fu-cheng Deng Fu-Lin Gui Bai-Tao Fan Lei Wen sheng-hong chen Ning Gong Yun-chen Xiao Zhi-Hui Xu Yangtze University Jingzhou434023HubeiChina CNOOC Research Institute Ltd. Beijing100028China CNOOC Ener Tech-Drilling&Production Co. Tianjin300457China Tianjin Branch of CNOOC Ltd. Tianjin300459China

As an independent sand control unit or a common protective shell of a high-quality screen,the punching screen is the outermost sand retaining unit of the sand control pipe which is used in geothermal well or oil and gas ***,most screens only consider the influence of the internal sand retaining medium parameters in the sand control performance design while ignoring the influence of the plugging of the punching screen on the overall sand retaining performance of the *** explore the clogging mechanism of the punching screen,this paper established the clogging mechanism calculation model of a single punching screen sand control unit by using the computational fluid mechanics-discrete element method(CFD-DEM)combined *** to the combined motion of particles and fluids,the influence of the internal flow state on particle motion and accumulation was *** results showed that(1)the clogging process of the punching sand control unit is divided into three stages:initial clogging,aggravation of clogging and stability of *** the initial stage of blockage,coarse particles form a loose bridge structure,and blockage often occurs preferentially at the streamline gathering place below chamfering inside the sand control *** the stage of blockage intensification,the particle mass develops into a relatively complete sand bridge,which develops from both ends of the opening to the center of the *** the stable plugging stage,the sand deposits show a“fan shape”and form a“V-shaped”gully inside the punching slot element.(2)Under a certain reservoir particle-size distribution,The slit length and opening height have a large influence on the permeability and blockage rate,while the slit width size has little influence on the permeability and blockage *** microscopic clogging mechanism and its law of the punching screen prevention unit are proposed in this study,which has some field guidance significance for the design of punching screen

关键词： Punching screen Plugging CFD-DEM Size parameter Sand control

Microstructure and Dynamic Compression Properties of PM Al6061/B_4C Composite

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2015年第10期28卷 1214-1221页

作者： hong-sheng chen Wen-Xian Wang Hui-Hui Nie Yu-Li Li Qiao-Chu Wu Peng Zhang College of Materials Science and Engineering Taiyuan University of Technology Key Laboratory of Interface Science and Engineering in Advanced Materials Ministry of Education Taiyuan University of Technology Shanxi Key Laboratory of Advanced Magnesium-Based Materials Taiyuan University of Technology

Aluminum 6061 matrix composite reinforced by 35 wt% B4 C particle was fabricated by power metallurgy method. Then, the as-deformed composite was tested by quasi-static（0.001 s-1） and dynamic（760-1150 s-1） compression experiments. The Johnson-Cook plasticity model was employed to model the flow behavior. The damage mechanism of composite was analyzed through the microstructure observations. The results showed that the B4 C particles exhibited uniform distribution and no deleterious reaction product Al4C3 was found in the composite. Al6061/B4 C composite showed high yield strength, moderate strain rate sensitivity and strain hardening under the dynamic loading, and a constitutive model under dynamic compression was established based on Johnson-Cook model, and accorded well with experimental results. The microstructure damage was dominated by particle fracture and interface debonding, and the dislocation was observed in the composite at a higher strain rate.

关键词： Power metallurgy Dynamic compression Johnson-Cook model AI6061/B4C composite

Expression of Obesity Hormone Leptin in Human Colorectal Cancer

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Cancer Research 2009年第2期21卷 142-146页

作者： Jin-chun Cong Xian-wei Dai Ming-yang Shen Jun-jiang Wang Chun-sheng chen hong Zhang Lei Qiao Department of Colorectal Surgery Shengjing Hospital China Medical University Shenyang 110004 China

Objective： The obesity hormone, leptin, has been found to participate in the development and proliferation of normal and malignant tissues. The aim of this study was to evaluate the role of leptin in human colorectal cancer. Methods： Serum leptin levels were measured via ABC-ELLSA in 30 colorectal cancers and 24 normal controls. Leptin concentration in colorectal cancer was analyzed in terms of selected clinicopathological features and some oncogenes. Results： The mean concentration of leptin was significantly higher for colorectal cancers（3.54±1.46 ng/ml） than normal controls（2.27±0.99 ng/ml）, no gender difference was observed in this study. Leptin expression in poorly differentiated tumors was obviously lower than those in moderately and well differentiated tumors. There were no statistically significant correlations between leptin and the serum CEA and CA199 in colorectal cancers （P〉0.05）, and between leptin and the expressions of K-RAS, P53, APC, DCC genes in tumor tissues （P〉0.05）. Conclusion： Leptin is overexpressed in human colorectal cancer, which is related to the differentiation degrees of the tumor. There is no correlation between leptin expression and changes of oncogenes in colorectal cancers.

关键词： Colorectal cancer Leptin

Positions and Spectral Energy Distributions of 41 Star Clusters in M33

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Astronomy and Astrophysics 2002年第3期2卷 197-206页

作者： Jun Ma, Xu Zhou, Jian-sheng chen, hong Wu, Zhao-Ji Jiang, Sui-Jian Xue and Jin ZhuNational Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 National Astronomical Observatories Chinese Academy of Sciences Beijing 100012

We present accurate positions and multi-color photometry for 41 star clusters detected by Melnick & D'odorico in the nearby spiral galaxy M33 as a part of the BATC Color Survey of the sky in 13 intermediate-band filters from 3800 to 10 000 A. The coordinates of the clusters are found from the HST Guide Star Catalog. By aperture photometry, we obtain the spectral energy distributions of the clusters. Using the relations between the BATC intermediate-band system and UBVRI broadband system, we derive their V magnitudes and B - V colors and find that most of them are blue, which is consistent with previous findings.

关键词： galaxies: individual (M33) - galaxies: evolution - galaxies: star clusters

A Modified TD-Haar Modeling Technique for Guided-Wave Structure with Anisotropic Materials

在线全文

学校读者我要写书评

暂无评论

A Modified TD-Haar Modeling Technique for Guided-Wave Struct...

Advances in therapies using mesenchymal stem cells and their exosomes for treatment of peripheral nerve injury:state of the art and future perspectives

2002海峡两岸三地无线科技研讨会

作者： chen hong-sheng, chen Kang-sheng Zhejiang University, Hangzhou 310027, China

A modified time domain Haar-wavelet-based modeling technique has been developed and applied to waveguide problems including discontinuities. The main advantages of this technique are that it can be ap

关键词： TD-Haar time domain FDTD method

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

Neural Regeneration Research 2025年第11期20卷 3151-3171页

作者： Fatima Aldali Chunchu Deng Mingbo Nie hong chen Department of Rehabilitation Medicine Tongji HospitalTongji Medical CollegeHuazhong University of Science and TechnologyWuhanHubei ProvinceChina Department of Orthopedics Tongji HospitalTongji Medical CollegeHuazhong University of Science and TechnologyWuhanHubei ProvinceChina

“Peripheral nerve injury”refers to damage or trauma affecting nerves outside the brain and spinal *** nerve injury results in movements or sensation impairments,and represents a serious public health *** severed peripheral nerves have been effectively joined and various therapies have been offered,recovery of sensory or motor functions remains limited,and efficacious therapies for complete repair of a nerve injury remain *** emerging field of mesenchymal stem cells and their exosome-based therapies hold promise for enhancing nerve regeneration and *** stem cells,as large living cells responsive to the environment,secrete various factors and *** latter are nano-sized extracellular vesicles containing bioactive molecules such as proteins,microRNA,and messenger RNA derived from parent mesenchymal stem *** have pivotal roles in cell-to-cell communication and nervous tissue function,offering solutions to changes associated with cell-based *** ongoing investigations,mesenchymal stem cells and mesenchymal stem cell-derived exosome-based therapies are in the exploratory stage.A comprehensive review of the latest preclinical experiments and clinical trials is essential for deep understanding of therapeutic strategies and for facilitating clinical *** review initially explores current investigations of mesenchymal stem cells and mesenchymal stem cell-derived exosomes in peripheral nerve injury,exploring the underlying ***,it provides an overview of the current status of mesenchymal stem cell and exosomebased therapies in clinical trials,followed by a comparative analysis of therapies utilizing mesenchymal stem cells and ***,the review addresses the limitations and challenges associated with use of mesenchymal stem cell-derived exosomes,offering potential solutions and guiding future directions.

关键词： clinical trials exosome extracellular vesicles mesenchymal stem cells nerve regeneration peripheral nerve injury pre-clinical experiments