检索结果-南通市图书馆

Application of inverse method to estimation of boundary conditions during investment casting simulation

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2009年第6期22卷 429-434页

作者： Haipeng JIN Jiarong LI dong pan National Key Laboratory of Advanced High Temperature Structural Materials Institute of AeronauticalMaterials Beijing 100095 China Key Lab for Advanced Materials Processing Technology MOE Department of Mechanical EngineeringTsinghua University Beijing 100084 China

Inverse method was used in single crystal superalloy DD6 processing simulation during solidification. Numerical modeling coupled with experiments has been used to estimate the interface heat transfer coefficient （IHTC） between the surface of slab casting and inner mold. Calculated temperature dependent values of IHTC were obtained from a numerical solution. The calculated temperatures agreed well with the measurement of cooling profile.

关键词： Numerical simulation Single crystal Inverse method Boundary conditions

A State Space Boundary Element Method with Analytical Formulas for Nearly Singular Integrals

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Solida Sinica 2018年第4期31卷 433-444页

作者： Changzheng Cheng dong pan ZhiUn Han Meng Wu Zhongrong Niu School of Civil Engineering Hefei University of Technology Hefei 230009 China Department of Civil Environmental and Geo-Engineering University of Minnesota Minneapolis MN 55455 USA School of Mathematics Hefei University of Technology Hefei 230009 China

A new method named the state space boundary element method （SSBEM） is estab- lished, in which the problem domain is divided into two parts. One is the boundary element domain which includes the interested inner point, and the other is the state space domain. The boundary integral equation and the state space equation are combined together based on the interfacial continuity condition to form the system equation of the SSBEM. The SSBEM synthe- sizes both advantages of the boundary element method and the state space method. However, it can give inaccurate results when being used to evaluate the mechanical quantity of a point very close to the boundary element, because the Gaussian quadrature fails to calculate the nearly singular integrals. The analytical formulas were developed by part of the authors before intro- duced to deal with the nearly singular integrals. Thus, the SSBEM can yield accurate physical quantities for the points very close to the boundary element. The SSBEM results agree well with those of the finite element method （FEM）, while the discretized elements are far fewer than those of the FEM. Meanwhile, the SSBEM can analyze very thin coating, while the FEM fails due to the limitation of tolerance for Boolean operations.

关键词： Boundary element method State space method Nearly singular integral Analytical formulation

Progress on modeling and simulation of directional solidification of superalloy turbine blade casting

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

China Foundry 2012年第1期9卷 69-77页

作者： Xu Qingyan Liu Baicheng pan dong Yu Jing Key Laboratory for Advanced Materials Processing Technology MOEDepartment of Mechanical EngineeringTsinghua UniversityBeijing 100084China

Directional solidified turbine blades of Ni-based superalloy are widely used as key parts of the gas turbine *** mechanical properties of the blade are greatly influenced by the final microstructure and the grain orientation determined directly by the grain selector geometry of the *** this paper,mathematical models were proposed for three dimensional simulation of the grain growth and microstructure evolution in directional solidification of turbine blade ***-tracing method was applied to calculate the temperature variation of the *** on the thermo model of heat transfer,the competitive grain growth within the starter block and the spiral of the grain selector,the grain growth in the blade and the microstructure evolution were simulated via a modified Cellular Automaton *** experiments were carried out,and the measured results were compared quantitatively with the predicted *** simulated cooling curves and microstructures corresponded well with the experimental *** proposed models could be used to predict the grain morphology and the competitive grain evolution during directional solidification.

关键词： Ni-based superalloy microstructure directional solidification modeling

Numerical simulation of microstructure evolution during directional solidification process in directional solidified (DS) turbine blades

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2011年第12期54卷 3191-3202页

作者： ZHANG Hang XU QingYan TANG Ning pan dong LIU BaiCheng Key Laboratory for Advanced Materials Processing Technology Ministry of Education Department of Mechanical Engineering Tsinghua University Beijing 100084 China

Directional solidified(DS) turbine blades are widely used in advanced gas turbine engine. The size and orientation of columnar grains have great influence on the high temperature property and performance of the turbine blade. Numerical simulation of the directional solidification process is an effective way to investigate the grain's growth and morphology,and hence to optimize the process. In this paper,a mathematical model was presented to study the directional solidified microstructures at different withdrawal rates. Ray-tracing method was applied to calculate the temperature variation of the blade. By using a Modified Cellular Automation(MCA) method and a simple linear interpolation method,the mushy zone and the microstructure evolution were studied in detail. Experimental validations were carried out at different withdrawal rates. The calculated cooling curves and microstructure agreed well with those experimental. It is indicated that the withdrawal rate affects the temperature distribution and growth rate of the grain directly,which determines the final size and morphology of the columnar grain. A moderate withdrawal rate can lead to high quality DS turbine blades for industrial application.

关键词： directional solidified (DS) turbine blade Cellular Automation (CA) numerical modeling and simulation

Protective effect of selenium-enriched lactobacilluson CCI_4-induced liver injury in mice and its possible mechanisms

在线全文

学校读者我要写书评

暂无评论

World Journal of Gastroenterology 2005年第37期11卷 5795-5800页

作者： Long Chen Dao-dong pan Juan Zhou Ying-Zi Jiang College of Life Sciences Nanjing Normal University Jiangsu Engineering Research Center for Bio-Medical Function Materials Nanjing 210097 Jiangsu Province China Department of Food Sciences Nanjing Normal University Nanjing 110097 Jiangsu Province China

AIM： To study the protective effects and mechanisms of Se-enriched lactobacillus on liver injury caused by carbon tetrachloride （CCl4） in mice. METHODS： Seventy-two ICR mice were randomly divided into four groups： normal group, CCl4-induced model group, low Se-enriched lactobacillus treatment group （L-Se group）, and high Se-enriched lactobacillus treatment group （H-Se group）. During a 3-wk experimental period, the common complete diet was orally provided daily for normal group and model group, and the mice in L-Se and H-Se groups were given a diet with 2 and 4 mg of organoselenium from Se-enriched lactobacillus per kg feed, respectively. From the 2nd wk of experiment, the model group, L-Se group, and H-Se group received abdominal cavity injection of olive oil solution containing 500 mL/L CCl4 （0.07 mL/100 g body mass） to induce liver injury, and the normal group was given olive oil on every other day for over 2 wk. In the first 2 wk post injection with CCl4, mice in each group were killed. The specimens of blood, liver tissue, and macrophages in abdominal cavity fluid were taken. Then the activities of the following liver tissue injury-associated enzymes including glutathione peroxidase （GSH-Px）, superoxide dismutase （SOD）, alanine aminotransferase （ALT） and aspartate aminotransferase （AST） as well as malondialdehyde （MDA） content were assayed. Changes of phagocytic rate and phagocytic index in macrophages were observed with Wright-Giemsa stain. Plasma TNF-α level was measured by radioimmunoassay. The level of intracellular free Ca^2＋（[Ca^2＋]i） in hepatocytes was detected under a laser scanning confocal microscope. RESULTS： During the entire experimental period, the AST and ALT activities in liver were greatly enhanced by CCl4 and completely blunted by both low and high doses of Se-enriched lactobacillus. The Se-enriched lactobacillus- protected liver homogenate GSH-Px and SOD activities were higher or significantly higher than those in model group and were close t

关键词： Se-enriched lactobacillus Liver injury Carbon tetrachloride Macrophage Ca^2+

Local curve fitting based Lagrange multiplier selection for Id-slice in multi-view video coding

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

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2009年第6期10卷 778-785页

作者： Shi-fang XU Guo-bin CHEN Hua-dong pan Ji-lin LIU Department of Information Science and Electronic Engineering Zhejiang University Hangzhou 31002 7 China

The rate and distortion of Id-slice do not fit the globally linear relationship on a logarithmic scale. Lagrange multiplier selection methods based on the globally linear approximate relationship are neither efficient nor optimal for multi-view video coding (MVC). To improve the coding efficiency of MVC, a local curve fitting based Lagrange multiplier selection method is proposed in this paper, where Lagrange multipliers are selected according to the local slopes of the approximate curves. Experi-mental results showed that the proposed method improves the coding efficiency. Up to 2.5 dB gain was achieved at low bitrates.

关键词： Id-slice Lagrange multiplier Local curve fitting Multi-view video coding (MVC)

Myricetin reduces cytotoxicity by suppressing hepcidin expression in MES23.5 cells

在线全文

学校读者我要写书评

暂无评论

Neural Regeneration Research 2021年第6期16卷 1105-1110页

作者： Han Deng Shang Liu dong pan Yi Jia Ze-Gang Ma Department of Physiology School of Basic MedicineQingdao UniversityQingdaoShandong ProvinceChina Institute of Brain Science and Disorders Qingdao UniversityQingdaoShandong ProvinceChina

Multiple studies implicate iron accumulation in the substantia nigra in the degeneration of dopaminergic neurons in Parkinson’s ***,slowing of iron accumulation in cells has been identified as the key point for delaying and treating Parkinson’s *** reportedly plays an important role in anti-oxidation,anti-apoptosis,anti-inflammation,and iron ***,the mechanism underlying its neuroprotection remains *** the present study,MES23.5 cells were treated with 1×10^-6 M myricetin for 1 hour,followed by co-treatment with 400 nM rotenone for 24 hours to establish an in vitro cell model of Parkinson’s *** results revealed that myricetin alleviated rotenone-induced decreases in cell viability,suppressed the production of intracellular reactive oxygen species,and restored mitochondrial transmembrane *** addition,myricetin significantly suppressed rotenone-induced hepcidin gene transcription and partly relieved rotenone-induced inhibition of ferroportin 1 mRNA and protein ***,myricetin inhibited rotenone-induced phosphorylation of STAT3 and SMAD1 in MES23.5 *** findings suggest that myricetin protected rotenone-treated MES23.5 cells by potently inhibiting hepcidin expression to prevent iron accumulation,and this effect was mediated by alteration of STAT3 and SMAD1 signaling pathways.

关键词： factor flavonoid hepcidin in vitro iron Parkinson’s disease pathways rotenone

Generic security analysis framework for quantum secure direct communication

在线全文

学校读者我要写书评

暂无评论

Frontiers of physics 2021年第2期16卷 23-31页

作者： Zhang-dong Ye dong pan Zhen Sun Chun-Guang Du Liu-Guo Yin Gui-Lu Long State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics Tsinghua UniversityBeijing 100084China Frontier Science Center for Quantum Information Beijing 100084China School of Information and Technology Tsinghua UniversityBeijing 100084China Beijing National Research Center for Information Science and Technology Beijing 100084China Beijing Academy of Quantum Information Sciences Beijing 100193China

Quantum secure direct communication provides a direct means of conveying secret information via quantum states among legitimate *** past two decades have witnessed its great strides both theoretically and ***,the security analysis of it still stays in its *** practical problems in this field to be solved urgently,such as detector efficiency mismatch,side-channel effect and source imperfection,are propelling the birth of a more impeccable *** this paper,we establish a new framework of the security analysis driven by numerics where all the practical problems may be taken into account *** apply this framework to several variations of the DL04 protocol considering real-world experimental ***,we propose two optimizing methods to process the numerical part of the framework so as to meet different requirements in *** these properties considered,we predict the robust framework would open up a broad avenue of the development in the field.

关键词： quantum secure direct communication(QSDC) practical security analysis secrecy capacity optimization detectory efficiency mismatch convex optimization

Three-dimensional microstructure simulation of Ni-based superalloy investment castings

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2011年第5期54卷 851-855页

作者： pan dong XU QingYan LIU BaiCheng Key Laboratory for Advanced Materials Processing Technology Ministry of Education Department of Mechanical Engineering Tsinghua University Beijing 100084 China

An integrated macro and micro multi-scale model for the three-dimensional microstructure simulation of Ni-based superalloy investment castings was developed, and applied to industrial castings to investigate grain evolution during solidification. A ray tracing method was used to deal with the complex heat radiation transfer. The rnicrostructure evolution was simulated based on the Modified Cellular Automaton method, which was coupled with three-dimensional nested macro and micro grids. Experi- ments for Ni-based superalloy turbine wheel investment casting were carried out, which showed a good correspondence with the simulated results. It is indicated that the proposed model is able to predict the microstructure of the casting precisely, which provides a tool for the optimizing process.

关键词： microstructure simulation Ni-based superalloy investment casting