排序方式: 共有178条查询结果,搜索用时 109 毫秒
31.
WANG Wei MA YuZhen FENG ZhaoDong MENG HongWei SANG YanLi & ZHAI XinWei Key Laboratory of Western China’s Environmental Systems Ministry of Education of China & College of Earth Environmental Sciences Lanzhou University Lanzhou China Key Laboratory of Environmental Change Natural Disaster Ministry of Education of China & State Key Laboratory of Earth Surface Processes Resource Ecology Beijing Normal University Beijing Department of Geology Baylor U... 《科学通报(英文版)》2009,54(9):1579-1589
Based on modern pollen studies and reliable chronology of nine AMS 14C dates, a detailed history of vegetation and climate changes during the past 8660 cal. a BP was reconstructed by a high-resolution pollen record from Ugii Nuur in central Mongolia. Poaceae-steppe dominated the study area and the climate was mild and semi-humid before 7800 cal. a BP with a noticeable cool and humid interval at 8350―8250 cal. a BP. Xerophytic plant increased and the climate became warm and dry gradually since 7800 cal. a BP... 相似文献
32.
基于高斯混合模型的EM学习算法 总被引:7,自引:0,他引:7
本文研究了一类基于无监督聚类学习的算法——EM算法的算法实现.EM算法通常用于存在隐含变量时的聚类学习,由于引入了隐含变量,导致算法难以保证收敛和达到极优值.本文通过将该算法应用于高斯混合模型的学习,引入重叠度分析的方法改进EM算法的约束条件,从而能够确保EM算法的正确学习. 相似文献
33.
Waste heat recovery from the flue gas of gasfired boilers was studied experimentally by measuring the flow and heat transfer of air and water through six kinds of packing with saturated humid air as the simulated flue gas.The experiments measured the effects of inlet air temperature, inlet air velocity and circulating water flow rate on the flow and heat transfer. The results show that higher inlet air temperatures and lower inlet air velocities lower the flow resistance and increase the heat transfer coefficient. The stainless steel packing had better surface wettability and larger thermal conductivity than the plastic packing, which enhanced the heat transfer between the water and the saturated moist air. When both the flow resistance reduction and the heat transfer enhancement were considered, the experimental results gave an optimal packing-specific surface area. A packed heat exchanger tower was designed for waste heat recovery from the flue gas of gas-fired boilers based on the experimental results which had better flow and heat transfer characteristics with lower pump and fan power consumption, more stable system operation and less thermal fluctuations compared with a non-packed heat transfer system with atomized water. 相似文献
34.
Characteristics of dry friction backward whirl-A self-excited oscillation in rotor-to-stator contact systems 下载免费PDF全文
JIANG Jun SHANG ZhiYong & HONG Ling MOE Key Laboratory of Strength Vibration Xi’an Jiaotong University Xi’an China 《中国科学:技术科学》2010,(2)
In this paper, the response characteristics of dry friction backward whirl of a general rotor/stator model, which accounts for both the dynamics of the rotor and the stator as well as the friction and the deformation at the contact surfaces, are investigated. The existence boundaries and the whirl frequencies of the dry friction backward whirl are determined analytically. It is found that there are two or three existence boundaries of the dry friction backward whirl that usually form two existence regions, ... 相似文献
35.
XU ShengXian WU XueFei WU QingYin & YAN WenFu Department of Chemistry Zhejiang University Hangzhou China School of Chemistry Chemical Engineering Jiangxi Science Technology Teachers’ College Nanchang State Key Laboratory of Inorganic Synthesis Preparative Chemistry Jilin University Changchun China Received October accepted January 《科学通报(英文版)》2011,56(25):2679-2682
The ruthenium-substituted polyoxometallic acid H6 [Ru(H2O)FeW 11O39 ]·18H2O was synthesized by stepwise acidification and stepwise addition of solutions of the component elements, and an ion-exchange-cooling method. The product was characterized using inductively coupled plasma spectrometry (ICP), Infrared Spectroscopy (IR), Ultraviolet Spectroscopy (UV), and X-ray diffraction (XRD). The results show that this complex has the Keggin structure. The determination of the thermal stability and proton conductivi... 相似文献
36.
GUO Jie CHEN HuiJuan SUN WeiGuo HAO RuiTing XU YingQiang & NIU ZhiChuan Material School NorthWest Polytechnical University Xi’an China Luoyang Optical Electronics Center Luoyang Institute of Semiconductors Chinese Academy of Sciences Beijing 《中国科学:技术科学》2010,(4)
Type Ⅱ superlattices(SLs) short period InAs(4ML)/GaSb(8ML) were grown by molecular-beam epitaxy on lattice-mismatched GaAs substrates and on GaSb substrates.A smooth GaSb epilayer was formed on GaAs substrates by inserting mulit-buffer layers including an interfacial misfit mode AlSb quantum dot layer and AlSb/GaSb superlattices smooth layer.SLs grown on GaAs substrates(GaAs-based SLs) showed well-resolved satellite peaks in XRD.GaSb-based SLs with better structural quality and smoother surface showed strong photoluminescence at 2.55μm with a full width at half maximum(FWHM) of 20 meV,narrower than 31 meV of GaAs-based SLs.Inferior optical absorption of GaAs-based SL was observed in the range of 2-3μm. Photoresponse of GaSb-based SLs showed the cut-off wavelength at 2.6μm. 相似文献
37.
YAN Dan WEI Li XIAO XiaoHe ZHOU DanLei & HAN YuMei Institute of Chinese Medicine Hospital of People’s Liberation Army Beijing China Chongqing Institute of Technology Chongqing 《科学通报(英文版)》2009,(3)
The inhibitory effect of three berberine alkaloids (BAs) from Coptis chinensis Franch, a traditional Chinese medicinal (TCM) herb, on Bifidobacterium adolescentis growth was investigated by micro- calorimetry. The power-time curves of B. adolescentis with and without BAs were acquired, meanwhile the extent and duration of inhibitory effect on the metabolism were evaluated by the growth rate con- stant (k), half inhibitory ratio (IC50), maximum heat-output power (Pmax), peak time of maximum heat-output power... 相似文献
38.
YAN ZhenLin XIE WenJun GENG DeLu & WEI BingBo * Department of Applied Physics Northwestern Polytechnical University Xi’an China 《科学通报(英文版)》2011,56(31):3284-3288
We report on the ninth-mode sectorial oscillation of acoustically levitated drops excited by actively modulating sound pressure. A numerical computation based on the level set method was performed to model drop shape evolution by solving an incompressible two-phase flow problem. The calculated shapes of the oscillating drop are in good agreement with experimental observations. The relationship between the oscillation frequency and parameters describing the flattened drops is studied both experimentally and numerically. The frequency of the ninth-mode sectorial oscillation decreases with increasing equatorial radius and can be well-described by a modified Rayleigh equation. 相似文献
39.
DONG LingYi JIANG KeWei ZHANG YanBin ZHANG Hui ZHUO HongQing CUI ZhiRong YE YingJiang * & WANG Shan * Department of Gastroenterological Surgery Surgical Oncology Laboratory Peking University People’s Hospital Peking University Beijing China 《科学通报(英文版)》2011,56(23):2444-2449
We previously showed that B cell receptor associated protein 31(BAP31) was significantly upregulated in colorectal cancer compared with normal mucosa epithelia. However, its expression pattern and pathological role in colorectal cancer are not clearly understood. In this study, we investigated whether the expression of BAP31 was associated with the clinicopathological parameters of colorectal cancer. The expression pattern of BAP31 was detected by immunohistochemistry on a tissue microarray in both primary ... 相似文献
40.
拥有信息资源,才能拥抱知识经济时代! 总被引:16,自引:5,他引:11