Papers by Keyword: Bimodal Distribution

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Authors: Chang Chun Ge, Jun Yu, Wei Ping Shen, Cheng Cheng, Guo Hua Ni, Lu Lu Meng, Ming Li, Cheng Xu Zhang, Yue Dong Meng
Abstract: Superfine and nano-sized Fe powders were prepared by a spark plasma discharge process in deionized water. The powders were characterized by Field Emission Scanning Electron Microscope (FESEM) with Oxford Inca EDX, and X-ray diffraction (XRD). The experimental results indicate that the powders prepared by the process have a bimodal size distribution, high purity, single phase, good spherical shape and high yield.
Authors: Ming Chun Li, Jin Zhang, Zi Yao Yuan
Abstract: The evolution characteristics of pore structure during the decomposition of limestone were experimental measured with nitrogen adsorption method. As a result, the pore structure of calcined limestone has a characteristic of bimodal distribution and the most probable pore sizes are about 3.8nm and 45nm. The probability ratio between the front and following humps decreases at first with the solid fractional conversion and then increases in the later stage of decomposition, and the corresponding inflection point of solid fractional conversion is about η=0.56 under the condition of calcination temperature 1133K. A probability density function with bimodal distribution for pore volume was established to construct the pore structure parameters model. As the average pore size decreased from 38.2nm to14.9nm, the effective diffusion coefficient of gaseous product through the porous solid product layer reduced from 0.0088cm2.s-1 to 0.0017cm2.s-1, which leads to an increase in the pore diffusion resistance affecting the decomposition mechanisms of limestone.
Authors: Freddy J. Arenas G., E. Montoya, M. Cabezas, Joaquín Lira-Olivares
Authors: Li Da Shen, Zong Jun Tian, Y.H. Huang, Guo Ran Hua
Abstract: Reconstituted nanostructured partially stabilized zirconia (PSZ) feedstock powders were laser sintered under a range of laser processing parameters. Scanning electron microscopy (SEM) was applied to analyze the microstructure of the powders and sintered bulk. Microhardness of the samples was also tested by Vickers Microhardness tester. These results demonstrated that the microstructure of the samples exhibits a bimodal distribution which comprises molten and non-molten feedstock particles. It was found that feedstock maintained some of its nanostructure during laser sintering with relatively low laser power; whereas feedstock lost most of its initial characters with high laser power. It was also observed that Microhardness values have respect to the proportion of non-molten feedstock in those samples.
Authors: Ying Guang Liu, Shi Bing Zhang, Zhong He Han, Xiao Yan Zhu
Abstract: Nanostructured Cu-Ag alloys with bimodal grain size distribution were prepared and their tensile deformation behaviors were studied. The alloys were processed by hot isostatic pressing of blends of nanoand micrometer-sized powder particles. The microstructure of the alloys consisted of nanograins with an average grain size of 40 nm and coarse-grains with an average grain size of 30 um. The bimodal structured alloy exhibited high tensile strengths 522 MPa and a large plastic strain to failure approximately 30%. Simultaneously, Their tensile stress-strain curves displayed a long work-hardening region, and their tensile ductility increased with increasing coarse-grained volume fraction. The high strength primarily results from the contribution of nanograins, while the enhanced ductility may be attributed to the improved strain hardening capability by the presence of coarse grains.
Authors: Tao Wang, Wan Shui Han, Yan Wei Li
Abstract: Nowadays, with the rapid development of the traffic infrastructure construction and the growing of the traffic flowing and speed, the vehicle-bridge coupling vibration research has become the focus of the bridge engineering study. The dynamic response of the bridge under the traffic flowing is one of the vital parameters for the vehicle-bridge coupling vibration analysis. In this paper, a methodology, employing the speed radar gun, the video recorder, and the dynamic strain tester in combination with manually recording is used to continuously and detailed investigate the traffic loads on the expressway bridge within 24 hours a day. With this approach introduced by this paper, all the critical parameters, such as the vehicle type, speed, traffic lane, the arriving time of the traffic and the bridge-vehicle dynamic interaction are all recorded. In this investigation, firstly the dynamic responses of 8 pieces of girders of the bridge under 5650 individual vehicles driving through the bridge are recorded, then in conjunction with the investigated traffic flowing samples, in terms of the vehicle type, some detailed statistics study is conducted on the collected records, and finally the space-time distribution laws of the dynamic response of the bridge under the traffic flowing are studied extensively. The result of this study could provide helpful theoretic guidance and supporting data for the vehicle-bridge coupling vibration research.
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