检索结果-南通市图书馆

Trajectory Analysis of Fuel Injection into Supersonic Cross Flow Based on Schlieren Method

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2012年第1期25卷 42-50页

作者： YANG Hui li feng sun Baigang School of Jet Propulsion Beihang University Beijing 100191 China

Trajectory analysis of fuel injection into supersonic cross flow is studied in this paper. A directly-connected wind tunnel is constructed to provide stable supersonic freestream. Based on the test rig, the schlieren system is established to reveal the fuel injection process visually. Subsequently, the method of quantitative schlieren is adopted to obtain data of both fuel/air interface and bow shock with the aid of Photoshop and Origin. Finally, the mechanism based on two influential factors of fuel injection angle and fuel injection driven pressure, is researched by vector analysis. A dimensionless model is deduced and analyzed. The curve fitting result is achieved. The relationship between the data and the two influential factors is established. The results provide not only the quantitative characteristics of the fuel injection in supersonic cross flow but also the valuable reference for the future computational simulation.

关键词： fuel injection schlieren supersonic flow injection driven pressure injection angle characteristic velocity

Edge Video CDN： A Wi-Fi Content Hotspot Solution

在线全文

学校读者我要写书评

暂无评论

Journal of Computer Science & Technology 2016年第6期31卷 1072-1086页

作者： Wen Hu Zhi Wang Ming Ma li-feng sun Tsinghua National Laboratory for Information Science and Technology Tsinghua University Beijing 100084 China Department of Computer Science and Technology Tsinghua University Beijing 100084 China Graduate School at Shenzhen Tsinghua University Shenzhen 518055 China

The emergence of smart edge-network content item hotspots, which are equipped with huge storage space （e.g., several GBs）, opens up the opportunity to study the possibility of delivering videos at the edge network. Different from both the conventional content item delivery network （CDN） and the peer-to-peer （P2P） scheme, this new delivery paradigm, namely edge video CDN, requires up to millions of edge hotspots located at users＇ homes/offices to be coordinately managed to serve mobile video content item. Specifically, two challenges are involved in building edge video CDN, including how edge content item hotspots should be organized to serve users, and how content items should be replicated to them at different locations to serve users. To address these challenges, we propose our data-driven design as follows. First, we formulate an edge region partition problem to jointly maximize the quality experienced by users and minimize the replication cost, which is NP-hard in nature, and we design a Voronoi-like partition algorithm to generate optimal service cells. Second, to replicate content items to edge-network content item hotspots, we propose an edge request prediction based replication strategy, which carries out the replication in a server peak offioading manner. We implement our design and use trace-driven experiments to verify its effectiveness. Compared with conventional centralized CDN and popularity-based replication, our design can significantly improve users＇ quality of experience, in terms of users＇ perceived bandwidth and latency, up to 40%.

关键词： video content item delivery network (CDN) edge network content item hotspot

Numerical simulation analysis of covering rock strata as mining steep-inclined coal seam under fault movement

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

中国有色金属学会会刊：英文版 2011年第S3期21卷 556-561页

作者： MA feng-hai, sun li, li Dun College of Civil and Architectural Engineering, Dalian University, Dalian 116622, China College of Civil and Architectural Engineering Dalian University Dalian 116622 China

The fault is one important factor for the stability of overburden strata caused by steeply inclined coal seam. The stress and displacement change of overburden strata caused by steeply-inclined coal seam mining activity under faulting was simulated by FLAC2D finite differential program on the basis of Zhaogezhuang mining example belonging to Kailuan Mining Group. From the results, the stress and displacement clouding image after mining became complex because of the fault, that is, a kind of weak structural plane. The stress concentration region concentrated around the goaf, and also around the fault plane. As the mining depth increases, the stress and displacement within the fault zone change significantly. This movement and deformation characteristic of overburden strata can provide theoretical basis for the similar mining condition.

关键词： fault steep-inclined coal seam numerical simulation overburden distortion

Kinetic study on hydrolysis and oxidation of formamidine disulfide in acidic solutions

在线全文

学校读者我要写书评

暂无评论

Science China Chemistry 2012年第2期55卷 235-241页

作者： HU Ying feng JiaMin li YanWei sun YanYan XU li ZHAO YueMin GAO QingYu College of Chemical Engineering China University of Mining and Technology Xuzhou 221008 China

Hydrolysis and oxidation of formamidine disulfide in acidic medium were investigated using high-performance liquid chro- matography （HPLC） and mass spectrometry （MS） at 25 ~C. By controlling the slow reaction rate and choosing appropriate mobile phase, HPLC provides the unique advantages over other methods （UV-Vis, chemical separation） in species tracking and kinetic study. In addition to thiourea and formamidine sulfinic acid, two unreported products were also detected in the hy- drolysis reaction. Mass spectrometry measurement indicates these two products to be formamidine sulfenic acid and thiocyan- ogen with mass weights of 92.28 and 116,36, respectively. In the oxidation of formamidine disulfide by hydrogen peroxide, besides thiourea, formamidine sulfenic acid, formamidine sulfinic acid, thiocyanogen and urea, formamidine sulfonic acid and sulfate could be detected. The oxidation reaction was found to be first order in both forrnamidine disulfide and hydrogen per- oxide. The rate constants of hydrolysis and oxidation reactions were determined in the pH range of 1.5-3.0. It was found both rate constants are increased with the increasing of pH. Experimental curves of different species can be effectively simulated via a mechanism scheme for formamidine disulfide oxidation, including hydrolysis equilibrium of formamidine disulfide and irre- versible hydrolysis of formamidine sulfenic acid.

关键词： formamidine disulfide hydrolysis oxidation HPLC-MS

Effect of SNC19/ST14qene overexpression on invasion of colorectal cancer cells

在线全文

学校读者我要写书评

暂无评论

World Journal of Gastroenterology 2005年第36期11卷 5651-5654页

作者： Ke-feng Ding li-feng sun Wei-Ting Ge Han-Guang Hu Su-Zhan Zhang Shu Zheng Surgery of Oncology The Second Affiliated Hospital School of Medicine Zhejinag UniversityHangzhou 310009 Zhejiang Province China Cancer Institute School of Medicine Zhejinag University Hangzhou310009 Zhejiang Province China

AIM： TO study the effect of SNC19/ST14gene overexpression on invasion in vitro of colorectal cancer cells. METHODS： The adhesion of SlVC19/ST14gene-transfected cells to ECM was measured by MTT assay. The cell movement was evaluated by wound healing assay. Cell invasion and migration were determined by invasion assay in vitro. RESULTS： SNC19/ST14 gene overexpression could enhance invasion of colorectal cancer cells in vitro significantly and influence early cell adherence to ECM, but could not change cell movement significantly. CONCLUSION： SNC19/ST14 gene overexpression increases the local invasion of colorectal cancer cells in vitro. 2005 The WJG Press and Elsevier Inc. All rights reserved.

关键词： Gene SNC19/ST14 Colorectal cancer Invasion

Expression and significance of VEGF and p53 in rat degenerated intervertebral disc tissues

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Asian Pacific Journal of Tropical Medicine 2013年第5期6卷 404-406页

作者： Xiao-Wei liu Jin Kang Xian-Dong Fan li-feng sun Orthopedics Center No.251 Hospital of People's Liberation Army

Objective:To discuss the expression and significance of vascular endothelial growth factor (VEGF) and p53 expression in rat degenerated intervertebral disc(IVD) ***:A total of 78 even-aged Sprague-Dawley(SD) rats(observation group) were chosen to establish a rat IVD degeneration model with anterior limbs and tail-removing *** months after modeling, rats were executed and degenerated IVD tissues were obtained for pathological biopsy so as to observe VEGF and p53 expression ***,IVD tissues from 8 healthy rats were gained for ***:Capillary infiltration was found in 62.8%of cases in observation group. Positive expression of VEGF and p53 was seen in 74.4%and 59.0%of cases respectively with a co-expression rate of 53.8%.VECF and p53 expression in degenerated IVD tissues with capillary infiltration was higher than that in non-infiltration group(P<0.05).Conclasion:A coordinate expression of VEGF and p53 in rat degenerated IVD tissues is demonstrated,indicating that they are both involved in neovascularization and infiltration,which accelerates IVD degeneration.

关键词： Intervertebral disc Neovascularization Immunohistochemistry VEGF p53 protein

Inclusions and solidification structures of high pure ferritic stainless steels dual stabilized by niobium and titanium

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Rare Metals 2014年第6期33卷 761-766页

作者： Hong-Po Wang li-feng sun Jun-Jie Shi Cheng-Jun liu Mao-Fa Jiang Chi Zhang Key Laboratory for Ecological Metallurgy of Multimetallic Ores(Ministry of Education) Northeastern University

As the raw materials in the post process of rolling and heat treatment, ingots have great effects on the properties of the final products. Inclusions and solidification structures are the most important aspects of the quality of ingots. Niobium and titanium are usually used to react with carbon and nitrogen to improve the properties of ferritic stainless steels. In this research, combined with thermodynamic calculation, effects of niobium and titanium on the inclusions and solidification structures in three kinds of high pure ferritic stainless steels with different titanium additions were investigated by optical microscope（OM）, scanning electron microscope（SEM）, transmission electron microscope（TEM）, and energy disperse spectrometer（EDS）. Results show that Al2O3 and a few（Nb,Ti）N particles form when titanium addition is 0.01 %.Furthermore, inclusions are mainly Ti N and Al2O3–Ti Ox–Ti N duplex inclusions when titanium addition is more than0.10 %. Those two types of inclusions are in well distribution, and can afford nuclei to the solidification ***, the ratio of equiaxed zone increases with the increase of titanium addition. The ratio increases from42.1 % to 64.0 % with the titanium addition increasing from 0.01 % to 0.10 %, and it increases to 85.7 % when the titanium addition reaches 0.34 %.

关键词： High pure ferritic stainless steel Inclusion Solidification structure Equiaxed zone Stabilization element

Applied research of landscape ecology in desertification monitoring and assessment

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2000年第3期12卷 349-354页

作者： li feng, sun Si heng (Academy of Forest Inventory and Planning/China National Desertification Monitoring Center, State Forestry Administration, Beijing 100714, China) Academy of Forest Inventory and Planning/China National Dese 北京 1 0 0 71 4

A preliminary research on landscape ecology in desertification monitoring and assessment was reported. Also, this paper laid stress on the study of landscape diversity, dominance, evenness and Markov Matrix model and their respective landscape ecological meanings in the desertification monitoring and assessment. Concurrently, it took Shazhuyu Experimental Area, Qinghai Province as a specific case study.

关键词： landscape ecology desertification monitoring and assessment Shazhuyu Experimental Area

MicroRNA regulation network in colorectal cancer metastasis

在线全文

学校读者我要写书评

暂无评论

World Journal of Biological Chemistry 2014年第3期5卷 301-307页

作者： Jiao-Jiao Zhou Shu Zheng li-feng sun Lei Zheng Department of Surgical Oncology the Second Affiliated Hospital Zhejiang University College of Medicine The Key Laboratory of Cancer Prevention and Intervention China National Ministry of Education Departments of Oncology Johns Hopkins University School of Medicine Department of Surgery Johns Hopkins University School of Medicine The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins

Colorectal cancer is the third most common cancer worldwide. Metastasis is a major cause of colorectal cancer-related death. Mechanisms of metastasis remain largely obscure. MicroRNA is one of the most important epigenetic regulators by targeting mRNAs posttranscriptionally. Accumulated evidence has supported its significant role in the metastasis of colorectal cancer, including epithelial-mesenchymal transition and angiogenesis. Dissecting microRNAome potentially identifies specific microRNAs as biomarkers of colorectal cancer metastasis. Better understanding of the complex network of microRNAs in colorectal cancer metastasis provide new insights in the biological process of metastasis and in the potential targets for colorectal cancer therapies and for diagnosis of recurrent and metastatic colorectal cancer.

关键词： MicroRNAs Colorectal neoplasms Neoplasm metastasis