检索结果-南通市图书馆

Grain boundary characteristics and tensile properties of Ti14 alloy after semi-solid deformation

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

International Journal of Minerals,Metallurgy and materials 2011年第5期18卷 576-581页

作者： yong-nan Chen jian-feng Wei yong-qing Zhao School of materials Science and Engineering Chang＇an University Xi＇an 710064 China State Key Laboratory for Mechanical Behavior of materials Xi＇an Jiaotong University Xi＇an 710049 China Northwest Institute for Nonferrous Metal Research Xi＇an 710016 China

The microstructure and room-temperature tensile properties of Ti14,a new α＋Ti2Cu alloy,were investigated after conventional forging at 950°C and semi-solid forging at 1000 and 1050°C,*** show that coarse grains and grain boundaries are obtained in the semi-solid *** coarse grain boundaries are attributed to Ti2Cu phase precipitations occurred on the grain boundaries during the *** is found that more Ti2Cu phase precipitates on the grain boundaries at a higher semi-solid forging temperature,which forms precipitated zones and coarsens the grain *** tests exhibit high strength and low ductility for the semi-solid forged alloys,especially after forging at 1000°*** analysis reveals the evidence of ductile failure mechanisms for the conventional forged alloy and cleavage fracture mechanisms for the alloy after semi-solid forging at 1050°C.

关键词： titanium alloys semi-solid forging grain boundaries tensile properties fracture

Denitrification potential enhancement by addition of external carbon sources in a pre-denitrification process

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2007年第3期19卷 284-289页

作者： PENG yong-zhen ma yong WANG Shu-ying School of Municipal and Environmental Engineering Harbin Institute of Technology Harbin 150090 China Key Laboratory of Beijing for Water Quality Science and Water Environment Recovery Engineering Beijing University of Technology Beijing 100022 China

The aim of this study is to investigate the denitrification potential enhancement by addition of external carbon sources and to estimate the denitrification potential for the predenitrification system using nitrate utilization rate （NUR） batch tests. It is shown that the denitrification potential can be substantially increased with the addition of three external carbon sources, i.e. methanol, ethanol, and acetate, and the denitrification rates of ethanol, acetate, and methanol reached up to 9.6, 12, and 3.2 mgN/（g VSS.h）, respectively, while that of starch wastewater was only 0.74 mgN/（g VSS,h）. By comparison, ethanol was found to be the best external carbon source. NUR batch tests with starch wastewater and waste ethanol were carried out. The denitfification potential increased from 5.6 to 16.5 mg NO3-N/L owing to waste ethanol addition. By means of NUR tests, the wastewater characteristics and kinetic parameters can be estimated, which are used to determine the denitrification potential of wastewater, to calculate the denitrification potential of the plant and to predict the nitrate effluent quality, as well as provide information for developing carbon dosage control strategy.

关键词： predenitrification process external carbon addition ethanol denitrification potential

Survey of polycyclic aromatic hydrocarbons(PAHs)in arterial street air of Hangzhou

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2001年第1期13卷 8-13页

作者： ZHU Li zhong LIU yong jian Department of Environmental Science Zhejiang UniversityHangzhou 310028China

The presence of particulate and vapor PAHs, SO2 and NOx and other interrelated conditions (temperature, traffic intensity and wind velocity) were investigated in the arterial street air of Hangzhou. The concentration of the nine PAHs in the air was mean to 11.7 μg/m3, and the content of benzo(a) pyrene was up to 0.108 μg/m3. The contents of PAHs in the sampling sites were in good relation to the traffic intensity, and would be also affected by the terrain and meteorological conditions. The occurrences of PAHs in ambient air were mainly affected by their physical, chemical characters and temperature. The three- and four-ring PAHs (MW&le228) mainly existed in the vapor phase and the five-ring PAHs (MW > 228) existed predominately in the particulate phase. The fraction of vapor PAHs in the total nine PAHs was 84.2% in the air of the sampling sites. In the morning and evening, the concentrations of PAHs in the arterial street air were higher than that on the noon and the diurnal variation of PAHs was similar to that of the traffic gas NOx. A conclusion would be drawn that the major source of PAHs in the arterial street air was the traffic. And the results indicated that 75% of BaP would come from traffic source and remaining 25% of BaP would come from non-traffic source.

关键词： polycyclic aromatic hydrocarbons arterial street air pollution

Finding orthogonal latin squares using finite model searching tools

在线全文

学校读者我要写书评

暂无评论

Science China(Information Sciences) 2013年第3期56卷 140-148页

作者： ma FeiFei ZHANG jian State key Laboratory of Computer Science Institute of SoftwareChinese Academy of Sciences

An important class of problems in combinatorics is to find orthogonal latin squares with certain *** search is a promising approach for solving such *** generally its worstcase complexity is *** paper describes how to use a general-purpose model searching program to find orthogonal latin *** techniques for problem representation and symmetry breaking are proposed to increase search efficiency.

关键词： latin squares finite models symmetry

A practical iterative two-view metric reconstruction with uncalibrated cameras

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2007年第10期8卷 1614-1623页

作者： ZHOU yong-jun KOU Xin-jian School of Naval Architecture. Ocean and Civil Engineering Shanghai Jiao Tong University Shanghai 200240 China

This paper presents a practical iterative algorithm for two-view metric reconstruction without any prior knowledge about the scene and motion in a nonsingular geometry configuration. The principal point is assumed to locate at the image center with zero skew and the same aspect ratio, and the interior parameters are fixed, so the self-calibration becomes focal-length cali- bration. Existing focal length calibration methods are direct solutions of a quadric composed of fundamental matrix, which are sensitive to noise. A quaternion-based linear iterative Least-Square Method is proposed in this paper, and one-dimensional searching for optimal focal length in a constrained region instead of solving optimization problems with inequality constraints is applied to simplify the computation complexity, then unique rotational matrix and translate vector are recovered. Experiments with simulation data and real images are given to verify the algorithm.

关键词： Close-range photogrammetry Computer vision General relative orientation Unit quaternion Metric reconstruction

在线全文

学校读者我要写书评

暂无评论

喷印金属微滴撞击粗糙表面的分子动力学模拟

原子与分子物理学报 2025年第4期42卷 73-80页

作者：苏仁健陈小勇游自浩桂林电子科技大学机电工程学院桂林541004 广西制造系统与先进制造技术重点实验室桂林541004

研究金属微滴撞击固体表面的行为对预测微滴形态和实现高精度的喷印制造具有重要的意义.然而,由于微纳尺度下金属微滴撞击实验的难以开展,目前涉及金属微滴撞击粗糙表面的形态变化和热毛细效应机理尚不清楚.本文采用分子动力学模拟研究... 详细信息

研究金属微滴撞击固体表面的行为对预测微滴形态和实现高精度的喷印制造具有重要的意义.然而,由于微纳尺度下金属微滴撞击实验的难以开展,目前涉及金属微滴撞击粗糙表面的形态变化和热毛细效应机理尚不清楚.本文采用分子动力学模拟研究了镓铟微滴撞击粗糙表面的动态行为,定量分析了撞击速度、粗糙结构和不同温度对微滴撞击行为的影响.结果表明:随着撞击速度的提高,微滴先后呈现沉积、弹跳和破碎飞溅三种模式,且微滴的最大铺展因子与韦伯数呈幂函数关系.此外,通过修饰基底粗糙结构发现,结构间距或高度的变化对微滴的弹跳行为存在不同的影响机制,可以有效促使或抑制微滴的弹跳行为.最后,分析得出随着温度的提高,微滴的铺展直径会变大,产生的黏性耗散也会增大.研究结果对金属微滴撞击行为的有效预测提供了理论基础.

关键词：金属微滴撞击粗糙基底分子动力学

Asymptotic properties of Lasso in high-dimensional partially linear models

同方期刊数据库博看期刊评论

在线全文

学校读者我要写书评

暂无评论

Science China mathematics 2016年第4期59卷 769-788页

作者： ma Chi HUANG jian Department of Applied mathematics Anhui University of Science and Technology School of Statistics and management Shanghai University of Finance and Economics Department of Statistics and Actuarial Science and BiostatisticsUniversity of Iowa

We study the properties of the Lasso in the high-dimensional partially linear model where the number of variables in the linear part can be greater than the sample *** use truncated series expansion based on polynomial splines to approximate the nonparametric component in this *** a sparsity assumption on the regression coefficients of the linear component and some regularity conditions,we derive the oracle inequalities for the prediction risk and the estimation *** also provide sufficient conditions under which the Lasso estimator is selection consistent for the variables in the linear part of the *** addition,we derive the rate of convergence of the estimator of the nonparametric *** conduct simulation studies to evaluate the finite sample performance of variable selection and nonparametric function estimation.

关键词： Lasso irrepresentable condition restricted eigenvalue semiparametric models sparsity

Formation of adiabatic shear band and deformation mechanisms during warm compression of Ti–6Al–4V alloy

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2016年第8期35卷 598-605页

作者： Jiao Luo Lin-Feng Wang Miao-Quan Li Chang-jian Ge Xiao-Xiao ma yong-Ting Yang School of materials Science and Engineering Northwestern Polytechnical UniversityXi'an 710072China

Adiabatic shear band （ASB） was narrow region where softening occurred and concentrated plastic defor- mation took place. In present study, the effects of height reduction and deformation temperature on ASB were investigated by means of optical microscopy （OM） and scanning electron microscopy （SEM）. And the deformation mechanisms within the shear band were discussed thor- oughly with the help of transmission electron microscopy （TEM）. There is a critical strain for the formation of ASB during warm compression of Ti-6AI-4V alloy. The width of ASB increases with height reduction increasing. Elon- gated alpha grains within shear band grow up with defor- mation temperature increasing. Some ultrafine grains that confirm the occurrence of dynamic recrystallization are observed within shear band during warm compression of Ti-6AI-4V alloy.

关键词： Titanium alloy Adiabatic shear band Deformation mechanisms Dynamic recrystallization

Investigation on inductive heating of A356 alloy for thixo-forming

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and materials 2009年第3期16卷 309-313页

作者： Kai-kun Wang jian-lin Sun yong-lin Kang Qi Zhang Lei Yang Chun-mei ma School of materials Science and Engineering University of Science and Technology Beijing 100083 Beijing China East-China Micro-electronic Institute of Technology 230022 Hefei China

To meet the demands of continuous stream-line for component production in the thixo-forming industry, billet heating should be of high quality and in a controllable way. A 4-step inductive heating strategy for aluminum alloy A356 was performed. Thixotropic testing and microstructure analysis showed that a homogenous temperature distribution was achieved after temperature-power-time optimization. Theoretical analysis was given concerning the thermal conductivity and heat capacity of A356 between conventional and semisolid casting microstructures. The experimental results show that the optimized 4-step strategy could be the best strategy for billet heating during the thixo-forming of aluminum alloy A356.

关键词： Thixo-forming aluminum alloys inductive heating temperature distribution