检索结果-南通市图书馆

Pronounced impact of size and shape effects on creep rupture life of a K439B superalloy combustion chamber casting simulator

在线全文

学校读者我要写书评

暂无评论

China Foundry 2025年

作者： Wen-tong Liu Yi-dong Wu Lei Gao Jing-yang Chen cheng-bo xiao Xi-dong Hui State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing Science and Technology on Advanced High Temperature Structural Materials Laboratory Beijing Institute of Aeronautical Materials

The size and shape effect(SSE) of components has become a critical issue for mechanical properties, application reliability, and processing. In this study, the creep rupture life(CRL) of components with different wall thicknesses and positions in a combustion chamber casing simulator made of K439B superalloy was investigated. The intrinsic mechanisms of the SSE were explored from the dendrite structure, volume fraction and size of the γ' phase, and element segregation, etc. It is shown that this casting exhibits a strong SSE of creep rupture life, characterized by a significant difference in the CRL values up to 60% with the variation of wall thickness and position in the casing. In terms of casting technology, the influence of SSE on CRL is actually determined by the cooling rate. The SSE on the creep rupture life originates from the dendrite structure(such as the secondary dendrite arm spacing), volume fraction size of the γ' phase in the dendrite trunk, and elements segregation rate. This work may have implications for the design and application of engineering components with large sizes and complex structures.

关键词：

Structural and Operational Optimization of A Flapping Fin Used as A Self-Propulsor for AUV Propulsion

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

China Ocean Engineering 2022年第1期36卷 86-99页

作者： FAN Shuang-shuang CI xiao-han Neil BOSE cheng xiao School of Marine Sciences Sun Yat-sen UniversityZhuhai 519082China Southern Laboratory of Ocean Science and Engineering Zhuhai 519000China Department of Ocean and Naval Architectural Engineering Memorial University of NewfoundlandSt.John’sNL A1C 5S7Canada School of Geospatial Engineering and Science Sun Yat-sen UniversityZhuhai 519082China

Marine mammals could directly harvest energy from waves and obtain propulsive force through oscillating flapping fins or horizontal tail flukes,which in many cases have been observed and proved to be *** propulsion generated by the flapping fin has been analyzed by many researchers from both the theoretical and experimental prospects;however,the structural and operational optimization of a flapping fin for the optimal propulsion performance has been less studied,such as the investigation of the effects of the phase difference between heave and pitch motion,maximum oscillation angle,fin shape,oscillation centre of the fin and the operating sea state on the generated *** this paper,the flapping fin is used as a self-propulsor to propel an autonomous underwater vehicle(AUV)for propulsion *** the optimization design of the flapping fin,its propulsion effect is numerically investigated with different structural parameters and under various operation conditions using computational fluid dynamics(CFD)*** and validation study have been implemented to quantify the numerical uncertainties and evaluate the accuracy of the proposed CFD ***,a series of case studies are thoroughly conducted to investigate the effects of different structural parameters and operational conditions on the generated propulsion of a flapping fin by CFD *** simulation results demonstrate that different structural parameters and operation conditions would significantly impact the magnitude and distribution state of the fluid pressure around the flapping fin surface,thus,affect the propulsion performance of the *** findings in this study will provide guidelines for the structural and operational optimization design of a flapping fin for self-propulsion of mobile platforms.

关键词： autonomous underwater vehicle(AUV) flapping fin self-propulsion computational fluid dynamics(CFD) optimization design

Synthesis and Mesophase Properties of Intraanular Functionized Shape-persistent Macrocycles Containing Dibenzo[fg,op]naphthacenes

在线全文

学校读者我要写书评

暂无评论

Chemical Research in Chinese Universities 2007年第1期23卷 35-43页

作者： cheng xiao-hong HOEGER Sigurd Key Laboratory of Medicinal Chemistry for Natural Resource Ministry of Education School of Chemistry and Material Engineering Yunnan University Kunming 650091 P. R. China University Karlsruhe Institute for Technic Chemistry and Polymer Chemistry Engesserstr. 18 76131 Karlsruhe Germany

On the basis of the C-C coupling reactions of dibenzo [ fg, op ] naphthacene bistriflate, which was obtained by the condensation of phenylacetates with 4-aryl-2,6-bis（2-bromo-4-methoxy-phenyl） pyrylium salts followed by palladium-catalyzed dehydrohalogenation, three shape-persistent macrocycles with dibenzonaphthacene corner pieces, a nanometer interior void, and intraanular oligoalkyl side groups were synthesized by the oxidative cyclization of the corresponding bisacetylenes under high-dilution conditions. Their thermotropic liquid crystalline properties were investigated by using polarizing microscopy and differential scanning calorimetry. All the three compounds showed nematic mesophases and belonged to discotic liquid crystals with inverted topology.

关键词： Dibenzo [ fg, op ] naphthacene Macrocycles Liquid crystal C-C coupling

Effects of lanthanum(Ⅲ) on nitrogen metabolism of soybean seedlings under elevated UV-B radiation

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2007年第11期19卷 1361-1366页

作者： CAO Rui HUANG xiao-hua ZHOU Qing cheng xiao-ying The Key Laboratory of Industrial Biotechnology Ministry of Education Southern Yangtze University Wuxi 214036 China College of Chemistry and Environment Science Nanjing Normal University Nanjing 210097 China

The hydroponic culture experiments of soybean bean seedlings were conducted to investigate the effect of lanthanum （La） on nitrogen metabolism under two different levels of elevated UV-B radiation （UV-B, 280-320 nm）. The whole process of nitrogen metabolism involves uptake and transport of nitrate, nitrate assimilation, ammonium assimilation, amino acid biosynthesis, and protein synthesis. Compared with the control, UV-B radiation with the intensity of low level 0.15 W/m^2 and high level 0.45 W/m^2 significantly affected the whole nitrogen metabolism in soybean seedlings （p 〈 0.05）. It restricted uptake and transport of NO3^-, inhibited activity of some key nitrogen-metabolism-related enzymes, such as： nitrate reductase （NR） to the nitrate reduction, glutamine systhetase （GS） and glutamine synthase （GOGAT） to the ammonia assimilation, while it increased the content of free amino acids and decreased that of soluble protein as well. The damage effect of high level of UV-B radiation on nitrogen metabolism was greater than that of low level. And UV-B radiation promoted the activity of the anti-adversity enzyme glutamate dehydrogenase （GDH）, which reduced the toxicity of excess ammonia in plant. After pretreatment with the optimum concentration of La （20 mg/L）, La could increase the activity of NR, GS, GOGAT, and GDH, and ammonia assimilation, but decrease nitrate and ammonia accumulation. In conclusion, La could relieve the damage effect of UV-B radiation on plant by regulating nitrogen metabolism process, and its alleviating effect under low level was better than that under the high one.

关键词： lanthanum(Ⅲ) UV-B radiation soybean seedlings nitrogen metabolism alleviating effect

Iterative methods for a forward-backward heat equation in two-dimension

在线全文

学校读者我要写书评

暂无评论

Applied Mathematics(A Journal of Chinese Universities) 2010年第1期25卷 101-111页

作者： SUN Jie cheng xiao-liang School of Mathematics and Statistics Zhejiang University of Finance and Economics Hangzhou310018 China Department of Mathematics Zhejiang University Hangzhou 310027 China

A finite difference method is introduced to solve the forward-backward heat equation in two space dimensions. In this procedure, the backward and forward difference scheme in two subdomains and a coarse-mesh second-order central difference scheme at the middle interface are used. Maximum norm error estimate for the procedure is derived. Then an iterative method based on domain decomposition is presented for the numerical scheme and the convergence of the given method is established. Then numerical experiments are presented to support the theoretical analysis.

关键词： Forward-backward heat equation coarse mesh iterative method.

Two algorithms for two-phase Stefan type problems

在线全文

学校读者我要写书评

暂无评论

Applied Mathematics(A Journal of Chinese Universities) 2009年第3期24卷 298-308页

作者： LIAN xiao-peng cheng xiao-liang HAN Wei-min Dept. of Math. Zhejiang Univ. Hangzhou 310027 China Dept. of Math. University of Iowa Iowa City IA 52242 USA

In this paper,the relaxation algorithm and two Uzawa type algorithms for solving discretized variational inequalities arising from the two-phase Stefan type problem are *** analysis of their convergence is presented and the upper bounds of the convergence rates are *** numerical experiments are shown to demonstrate that for the second Uzawa algorithm which is an improved version of the first Uzawa algorithm,the convergence rate is uniformly bounded away from 1 if τh^-2 is kept bounded,where τ is the time step size and h the space mesh size.

关键词： relaxation method Uzawa algorithm variational inequality two-phase Stefan type problem

Design and preliminary test of the LLRF in C band high-gradient test facility for SXFEL

在线全文

学校读者我要写书评

暂无评论

Nuclear Science and Techniques 2020年第10期31卷 43-54页

作者： cheng-cheng xiao Jun-Qiang Zhang Jian-Hao Tan Wen-cheng Fang Shanghai Advanced Research Institute Chinese Academy of SciencesShanghai 201210China

This paper describes the design and preliminary test of the low-level radio frequency(LLRF)part of the C band high-gradient test facility for the Shanghai Soft X-ray Free-Electron Laser(SXFEL)-Linear Accelerator(LINAC).Before installation,the accelerating structures should be tested and *** the conditioning process,breakdown detection is needed to protect the accelerating structures and klystron from *** PCI extensions for instrumentation-based LLRF system and auto-conditioning algorithm are designed and applied in the LLRF part of the C band high-gradient test *** C band accelerating structures and 1 pulse compressor have completed conditioning and were installed in the SXFEL-LINAC.

关键词： Accelerating structure High gradient C band Breakdown LLRF Conditioning

Adaptive Tracking Control of Uncertain MIMO Nonlinear Systems with Time-varying Delays and Unmodeled Dynamics

在线全文

学校读者我要写书评

暂无评论

International Journal of Automation and computing 2013年第3期10卷 194-201页

作者： xiao-cheng Shi Tian-Ping Zhang Department of Automation College of Information Engineering Yangzhou University

In this paper, adaptive neural tracking control is proposed based on radial basis function neural networks （RBFNNs） for a class of muki-input multi-output （MIMO） nonlinear systems with completely unknown control directions, unknown dynamic disturbances, unmodeled dynamics, and uncertainties with time-varying delay. Using the Nussbaum function properties, the unknown control directions are dealt with. By constructing appropriate Lyapunov-Krasovskii functionals, the unknown upper bound functions of the time-varying delay uncertainties are compensated. The proposed control scheme does not need to calculate the integral of the delayed state functions. Using Young＇s inequality and RBFNNs, the assumption of unmodeled dynamics is relaxed. By theoretical analysis, the closed-loop control system is proved to be semi-globally uniformly ultimately bounded.

关键词： Adaptive control unmodeled dynamics time-varying delays neural networks Nussbaum function

Numerical estimation of the piecewise constant Robin coefficient by identifying its discontinuous points

在线全文

学校读者我要写书评

暂无评论

Applied Mathematics(A Journal of Chinese Universities) 2015年第1期30卷 1-16页

作者： cheng xiao-liang YU Yuan-jie Department of Mathematics Zhejiang University

We propose a new numerical method for estimating the piecewise constant Robin coefficient in two-dimensional elliptic equation from boundary measurements. The Robin in- verse problem is recast into a minimization of an output least-square formulation. A technique based on determining the discontinuous points of the unknown coefficient is suggested, and we investigate the differentiability of the solution and the objective functional with respect to the discontinuous points. Then we apply the Gauss-Newton method for reconstructing the shape of the unknown Robin coefficient. Numerical examples illustrate its efficiency and stability.

关键词： Inverse problem Robin coefficient differentiability the Gauss-Newton method.