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排序方式: 共有6934条查询结果,搜索用时 15 毫秒
41.
Yue-long Bai) Jun Xu) Zhi-feng Zhang) Wei-min Mao) Hong Xu) ) General Research Institute for Non-ferrous Metals Beijing China ) School of Materials Science Engineering University of Science Technology Beijing Beijing China ) Research Center for Foundry Engineering North University of China Taiyuan China 《北京科技大学学报(英文版)》2009,16(4):422-426
The effect of injection pressure, piston velocity, and the forming temperature of semisolid slurry on the filling behavior of the semi-solid A356 aluminum alloy was investigated by simulation methods. The simulation results show that these processing parameters have an important effect on the filling behavior of the semi-solid A356 aluminum alloy. The slurry flows steadily in the cavity when the injection pressure, the piston velocity, and the forming temperature are low, but it is prone to turbulent flow w... 相似文献
42.
Guo-jun Wang ) Bai-qing Xiong) Yong-an Zhang) Zhi-hui Li) Pei-yue Li) ) State Key Laboratory for Fabrication Processing of Nonferrous Metals General Research Institute for Nonferrous Metals Beijing China ) Northeast Light Alloy Co. Ltd. Harbin China 《北京科技大学学报(英文版)》2009,16(4):427-431
The microstructure of the as-cast 2D70 aluminum alloy and its evolution during homogenization were investigated by means of optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and differential scanning calorimetry (DSC) analysis. The results indicate that the microstructure of the as-cast 2D70 aluminum alloy mainly consists of the dendritic network of aluminum solid solution and intermetallic compounds (Al2CuMg, Al2Cu, Al9FeNi, Cu2FeAl7... 相似文献
43.
Shuang Kuang) Yong-lin Kang) Hao Yu) Ren-dong Liu) ) School of Materials Science Engineering University of Science Technology Beijing Beijing China ) Technology Center Anshan Iron & Steel Group Corporation Anshan China 《北京科技大学学报(英文版)》2009,16(4):393-398
A more accurate estimation of stress-strain relationships for martensite and ferrite was developed, and the modified law of mixture was used to investigate the stress-strain partitioning of constituent phases in dual phase (DP) steels with two different martensite volume fractions. The results show that there exist great differences in the stress-strain contribution of martensite and ferrite to DP steel. The stress-strain partitioning coefficient is not constant in the whole strain range, but decreases with... 相似文献
44.
Comprehensive assessment on dynamic roof instability under fractured rock mass conditions in the excavation disturbed zone 总被引:3,自引:0,他引:3
Xing-ping Lai ) Fen-hua Ren) Yong-ping Wu Mei-feng Cai) ) Energy School Xi’an University of Science & Technology Xi’an China ) School of Civil Environmental Engineering University of Science Technology Beijing Beijing China ) Key Laboratory of Western Mine & Hazard Prevention China Ministry of Education China 《北京科技大学学报(英文版)》2009,16(1):12-18
The damage process of fractured rock mass showed that the fracture in rocks induced roof collapse in Yangchangwan Coal Mine,China.The rock mass was particularly weak and fractured.There occurred 6 large-scale dynamical roof falls in the excavation disturbed zone (EDZ) with the collapsing volume of 216 m3.First,the field detailed geological environment,regional seismic dy-namics,and dynamic instability of roadways were generally investigated.Second,the field multiple-index monitoring measurements for detecting the deep delamination of the roof,convergence deformation,bolt-cable load,acoustic emission (AE) characteristic pa-rameters,total AE events,AE energy-releasing rate,rock mass fracture,and damage were arranged.Finally,according to the time-space-strength relations,a quantitative assessment of the influence of rock-mass damage on the dynamic roof instability was accomplished. 相似文献
45.
Di-feng Wu) Shu-sen Cheng) Zi-jian Cheng) ) School of Metallurgical Ecological Engineering University of Science Technology Beijing Beijing China ) Steelmaking Plant Jiuquan Iron Steel Co. Ltd. Jiayuguan China 《北京科技大学学报(英文版)》2009,16(1):25-31
The key to reduce shell breakout in the continuous casting process is to control shell thickness in the mold.A numerical simulation on the turbulent flow and heat transfer coupled with solidification in the slab mold using the volume of fluid (VOF) model and the enthalpy-porosity scheme was conducted and the emphasis was put upon the flow effect on the shell thickness profiles in longitudinal and transverse directions.The results show that the jet acts a stronger impingement on the shell of narrow face,which causes a zero-increase of shell thickness in a certain range near the impingement point.The thinnest shell on the slab cross-section locates primarily in the center of the narrow face,and secondly near the comer of the wide face.Nozzle optimization can obviously increase the shell thickness and make it more uniform. 相似文献
46.
XU Bin WU ZhenSen WU Jian & XUE Kun School of Science Xidian University Xi’an China State Key Laboratory of Electromagnetic Environment China Research Institute of Radiowave Propagation Beijing 《中国科学E辑(英文版)》2009,52(4):1112-1116
The electron velocity distribution function and the incoherent scatter spectra during ionospheric heating in low ionosphere
region are presented with consideration of the elastic collision between electrons and neural particles and the excitation
of rotation energy level. The effects of pump frequency and electric fields on the spectra are discussed. With the increase
of electric field, the non-Maxwellian feature is enhanced, and with the increase of heating frequency, the non-Maxwellian
feature is weakened. The non-Maxwellian factor will bring a large error in ionosphere parameters, which must be considered
in the inversion.
Supported by the National Natural Science Foundation of China (Grant No. 40310223), the National Key Laboratory of Electromagnetic
Environment (LEME), and National Key Technologies R&D Program of China (Grant No. 2006BAB18B06) 相似文献
47.
Research on indoor experimentation of range SAL imaging system 总被引:1,自引:0,他引:1
GUO Liang XING MengDao ZHANG Long TANG Yu & BAO Zheng State Key Laboratory of Radar Signal Processing Xidian University Xi’an China Xi’an Polytechnic University Xi’an 《中国科学E辑(英文版)》2009,52(10):3098-3104
By means of advantages of both SAR and lidar, the combination of the techniques of (inverse) synthetic aperture and lidar makes it possible to obtain high resolution 2-D image. In this paper, an indoor experimental system of inverse synthetic aperture lidar imaging is given and a processing approach is presented. The given system is in the mode of lidar system with separated receiver and transmitter, which can effectively eliminate the jamming from the lens or/and the intersection between two optic fibers. ... 相似文献
48.
YUAN Jing HE ZhengJia ZI YanYang & LIU Han State Key Laboratory for Manufacturing Systems Engineering School of Mechanical Engineering Xi’an Jiaotong University Xi’an China Shanghai Baosteel Industry Inspection Corporation Baosteel Group Corporation Shanghai 《中国科学E辑(英文版)》2009,52(10):2801-2809
Fault diagnosis of rolling mills, especially the main drive gearbox, is of great importance to the high quality products and long-term safe operation. However, the useful fault information is usually submerged in heavy background noise under the severe condition. Thereby, a novel method based on multiwavelet sliding window neighboring coefficient denoising and optimal blind deconvolution is proposed for gearbox fault diagnosis in rolling mills. The emerging multiwavelets can seize the important signal proce... 相似文献
49.
既有混凝土结构难免存在带有初始材性缺陷的 RC构件,其加固可行性及力学行为与正常混凝土构件不同,当前缺乏针对性研究成果。为此,采用玄武岩纤维(BFRP)布加固了 2根混凝土材性不符合设计要求的 RC梁,另有 1根未加固梁作为对比梁,共计测试了 3根梁。通过试验加载观察缺陷梁在加固前后的受力特征、破坏模式和极限抗弯承载力,分析相应的力学模型,最后根据极限状态下的破坏模式,采用“系杆 -拱”模型推导出缺陷梁加固后极限承载力计算公式。结果表明:随着外荷载和破坏程度的增加,加固梁由正截面抗弯模型进化到“梳状拱”受力模型,再变为极限状态下的“系杆 -拱”模型;梁底 BFRP布加固结合梁端 U型锚固措施可以有效提高缺陷梁的抗弯刚度、屈服荷载和极限承载力;提出的承载力计算公式计算值和试验值吻合良好且适中保守。 相似文献
50.
珊瑚砂热传导性能影响着周围土体的传热过程,是分析地层中能量平衡、热湿迁移规律和土壤温度分布特征等的一个关键因素。为探讨含水率ω、干密度ρd、环境温度T等因素对珊瑚砂颗粒导热系数λ的影响规律,基于热探针法测试了三种不同试验工况下珊瑚砂颗粒的导热系数 λ,分析了导热系数 λ与各影响因素的关系,并解释了各自的影响机理;在此基础上,建立了考虑含水率、干密度、环境温度 3因素影响的珊瑚砂导热系数计算模型。结果表明:(1)珊瑚砂试样的导热系数 λ和含水率 ω成良好线性递增关系;(2)试样导热系数 λ随干密度 ρd的递增而增大;(3)试样导热系数 λ随着环境温度 T的升高而增大,温度对导热系数的影响主要取决于试样内水蒸气的潜热传输效应;(4)对比分析表明提出的导热系数计算模型具有较好的适应性。 相似文献