检索结果-南通市图书馆

INFLUENcES OF DENSITY AND DIMENSION OF cARBON NANOTUBES ON THEIR FIELD EMISSION

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2003年第4期16卷 302-308页

作者： Y.B.Zhu w.L.wang c.G.Hu DepartmentofPhysics JiangsuNormalUniversitySuzhou221009ChinaManuscriptreceived25November2002 DepartmentofAppliedPhysics ChongqingUniversityChongqing400044China

The influences of density and dimension of carbon nanotubes on their electron emission from arrays are studied. The tip electric field of nanotubes, electric field enhancement factor, and optimum nanotube density are expressed by analytic equations. The theoretical analyses show that the field enhancement factor is sensitive to nanotube density, and can be sharply improved at a specific and optimum density. Some experiments have demonstrated these. Owning to electrostatic screening effect, the length of carbon nanotubes has little effect on their emission. A uniformly-distributed carbon nanotube array model is set up, and applied to analysis of carbon nanotube arrays. The results obtained here are in good agreement with the experimental data.

关键词： carbon nanotube array field emission optimum density

Prostate cancer metastasis-driving genes： hurdles and potential approaches in their identification

在线全文

学校读者我要写书评

暂无评论

Asian Journal of Andrology 2014年第4期16卷 545-548页

作者： Yan Ting chiang Peter w Gout colin c collins Yuzhuo wang The Vancouver Prostate centre Vancouver General Hospital and Department of Urologic Sciences the University of British Columbia Department of Experimental Therapeutics British Columbia Cancer Agency Vancouver British Columbia Canada.

Metastatic prostate cancer is currently incurable. Metastasis is thoughtto result from changes in the expression of specific metastasis-driving genes in nonmetastatic prostate cancer tissue, leading to a cascade of activated downstream genes that set the metastatic process in motion. Such genes could potentially serve as effective therapeutic targets for improved management of the disease. They could be identified by comparative analysis of gene expression profiles of patient-derived metastatic and nonmetastatic prostate cancer tissues to pinpoint genes showing altered expression,

关键词： @@

comparing material wastage levels between conventional in-situ and prefabrication construction in Hong Kong

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

Journal of Harbin Institute of Technology(New Series) 2004年第5期11卷 548-551页

作者： Vivian w YTam c M Tam L Y Shen Dept. of Building and construction City University of Hong Kong Hong Kong ChinaDept. of Building and Construction City University of Hong Kong Hong Kong ChinaDept. of Building and Construction City University of Hong Kong Hong Kong China

Generation of construction wastes constitutes a major impact to the environment. Studies have been directed toward reducing wastes of the various construction processes. However, contractors in Hong Kong are rather conservative and lack motivation to develop new technology for waste minimization. This paper examines the benefits of using prefabrication in reducing material wastage levels for some traditional in-situ trades such as concreting, rebar fixing, bricklaying, drywall, plastering, screeding and tiling in Hong Kong. By measuring thirty construction projects, it is been found that waste levels of all major construction trades can be effectively reduced. This is particularly significant in the trade of plastering where 100% saving can be achieved after adopting prefabrication. The standardized design of the building can also be useful in the adoption of prefabrication for private housing projects.

关键词： prefabrication conventional in-situ trades material wastage environment

Integration of piezoelectric transducers(PZT and PVDF)within polymer-matrix composites for structural health monitoring applications:new success and challenges

在线全文

学校读者我要写书评

暂无评论

International Journal of Smart and Nano Materials 2020年第4期11卷 343-369页

作者： c.Tuloup w.Harizi Z.Aboura Y.Meyer Roberval(Mechanics Energy and Electricity)Universitéde Technologie de CompiègneCNRSCentre de Recherche RoyallieuCompiègne CedexFrance Savoie SYMME Systems Laboratory Mechatronics and MaterialsUniversitéSavoie Mont-BlancChambéryFrance

This article investigates the interest of using in-situ piezoelectric(PZT and PVDF)disks to perform real-time Structural Health Monitoring(SHM)of glass fiber-reinforced polymer composites submitted to var-ious tensile *** goal is to evaluate the working range and SHM potential of such embedded transducers for relatively simple mechanical loadings,with the long-term aim of using them to monitor complete 3D structures submitted to more complex *** is performed acquiring the electrical capacitance variation of the embedded *** study the potential links between the insitu capacitance signal and the global response of the loaded host specimens,a multi-instrumentation composed of external Nondestructive Testing techniques was implemented on the surfaces of the specimens to search for multi-physical couplings between these external measurements and the capacitance *** confirmed the non-intrusiveness of the embedded transducers,and allowed estimating their working *** capacitance signal follows well the mechanical loadings,but the piezoceramic transducer gets damaged after a determined relatively low strain level due to its *** limits of this working domain are extended by using a stretchable PolyVinylidene Fluoride(PVDF)polymer transducer,allowing this one to perform in-situ and real-time SHM of its host tensile specimens until failure.

关键词： Polymer-matrix composites(PMcs) in-situ piezoelectric transducer structural health monitoring nondestructive testing tensile loading PZT PVDF

westerly moisture transport to the middle of Himalayas revealed from the high deuterium excess

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

chinese Science Bulletin 2005年第10期50卷 1026-1030页

作者： TIANLide YAOTandong J.w.c.white YUwusheng wANGNinglian LaboratoryofIcecoreandcoldRegionsEnvironment InstituteofTibetanPlateauResearchChineseAcademyofSciencesBeijing100085China InstituteofArcticandAlpineResearch UniversityofColoradoBoulderUSA LaboratoryofIcecoreandcoldRegionsEnvironment ColdandAridRegionsEnvironmentalandEngineeringResearchInstituteChineseAcademyofSciencesLanzhou730000China LaboratoryofIcecoreandcoldRegionsEnvironment ColdandAridRegionsEnvironmentalandEngineeringResearchInstituteChineseAcademyofSciencesLanzhou730000China

Previous studies found extremely high d-excess in both ice core and glacial melt water in Dasuopu glacier, Xixiabangma, middle of Himalayas. These values are much higher than the global average and those measured in southwest monsoon precipitation. The d-excess variation in over one year at Nyalam station will clarify this phenomenon. Studies show that the high d-excess is related to the seasonal variation of moisture transport to this region. The d-excess values are low during the southwest monsoon active periods, when moisture originated from the humid ocean surface. The d-excess values are higher in non-monsoon months, when moisture is derived from westerly transport. winter and spring precipitation accounts for a substantial portion of the annual precipitation, resulting in higher d-excess in the yearly precipitation in the middle of Himalayas than other parts of the southern Tibetan Plateau. This finding reveals that the precipitation in the middle of Himalayas is not purely from southwest monsoon, but a large portion from the westerly transport, which is very important for ice core study in this area.

关键词：喜马拉雅山湿气传送器氘过剩

Maneuvering Modeling and Simulation of AUV Dynamic Systems with Euler-Rodriguez Quaternion Method

在线全文

学校读者我要写书评

暂无评论

china Ocean Engineering 2013年第3期27卷 403-416页

作者： c.w.chen J.S.Kouh J.F.Tsai Department of Science Engineering and Ocean Engineering National Taiwan University

The purpose of this study is to develop maneuvering models and systems of a simulator to improve the motion performance of autonomous underwater vehicles （AUVs） at the preliminary design stages in advance. The AUVs simulation systems based on the standard submarine equations of motion in six-degree-of-freedom （6-DOF） integrated with the Euler-Rodriguez quaternion method for representing singularity-free AUV attitude and time-saving calculation, and with a nonlinear control model for maneuvering and depth control simulations, time-marching in the fourth-order Runge-Kutta scheme. For validation of the simulation codes, results of the ISiMI AUV open-loop tests including turning test and zigzag test as well as an AUV simulator on the basis of Euler-angle method were used to compare with the quaternion-based AUV simulator. The computational results from the proposed simulator agree well with those from both the ISiMI AUV experiments and the Euler-angle based simulations. Additionally, a new maneuvering procedure, namely ＂put-out＂ was implemented to test directional stability for a large-scale AUV in the proposed AUV simulator that can be considered for vehicles in space as well as in constrained planes.

关键词： autonomous underwater vehicle (.4 UV) Euler-Rodriguez quaternion hydrodynamics maneuvering systemdynamics

Perception of artificial conspecifics by bearded dragons(Pogona vitticeps)

在线全文

学校读者我要写书评

暂无评论

Integrative Zoology 2019年第2期14卷 214-222页

作者： Anna FROHNwIESER Thomas w.PIKE John c.MURRAY Anna wILKINSON School of Life Sciences University of LincolnLincolnUK School of computer Science University of LincolnLincolnUK wildlife Research center Kyoto UniversityKyotoJapan

Artificial animals are increasingly used as conspecific stimuli in animal behavior ***,researchers often have an incomplete understanding of how the species under study perceives conspecifics,and,hence,which features are needed for a stimulus to be perceived *** investigate the features that bearded dragons(Pogona vitticeps)attend to,we measured their lateralized eye use when assessing a successive range of *** ranged through several stages of realism in artificial conspecifics,to see how features such as color,the presence of eyes,body shape and motion influence *** found differences in lateralized eye use depending on the sex of the observing bearded dragon and the artificial conspecific,as well as the artificial conspecific’s ***,this approach can inform the design of robotic animals that elicit biologically-meaningful responses in live animals.

关键词： bearded dragons conspecifics lateralized eye use perception

EVOLUTION OF MIcROSTRUcTURE OF Sn-Ag-cu LEAD-FREE FLIP cHIP SOLDER JOINTS DURING AGING PROcESS

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

Acta Metallurgica Sinica(English Letters) 2006年第4期19卷 301-306页

作者： Y.H. Tian c.Q. wang w.F. Zhou State Key Lab of Advanced welding Production and Technology Harbin Institute of Technology Harbin 150001 China

Flip chip bonding has become a primary technology that has found application in the chip interconnection process in the electronic manufacturing industry in recent years. The solder joints of the flip chip bonding are small and consist of complicated microstructures such as Sn solution, eutectic mixture, and intermetallic compounds （IMcs）, whose mechanical performance is quite different from the original solder bulk. The evolution of microstructure of the flip chip solder joints under thermal aging was analyzed. The results show that with an increase in aging time, coarsening of solder bulk matrix and AuSn4 IMcs occurred within the solder. The IMcs that are formed at the bottom side of the flip chip bond were different from those on the top side during the aging process. （cu, Ni, Au）0Sn5 were formed at the interfaces of both sides, and large complicated （Au,Ni, cu）Sn4 IMcs appeared for some time near the bottom interface after aging, but they disappeared again and thus （cu,Ni, Au ）0Sn5 IMc thickness increased considerably. The influence of reflow times during the flip chip bonding （as-bonded condition） on the characteristics of interfacial IMcs was weakened when subjected to the aging process.

关键词： lead free solder flip chip aging

Optimal Selling Time in Stock Market over a Finite Time Horizon

在线全文

学校读者我要写书评

暂无评论

Acta Mathematicae Applicatae Sinica 2012年第3期28卷 557-570页

作者： S.c.P.YAM S.P.YUNG w.ZHOU The chinese University of Hong Kong China The University of Hong Kong China

In this paper, we examine the best time to sell a stock at a price being as close as possible to its highest price over a finite time horizon [0, T], where the stock price is modelled by a geometric Brownian motion and the ＇closeness＇ is measured by the relative error of the stock price to its highest price over [0, T]. More precisely, we want to optimize the expression：V^＊=sup 0≤τ≤T E[Vτ/MT],where （Vt）t≥0 is a geometric Drownian motion with constant drift α and constant volatility σ 〉 0, Mt = max Vs 0≤a〈t is the running maximum of the stock price, and the supremum is taken over all possible stopping times 0 ≤ τ≤T adapted to the natural filtration （Ft）t≥0 of the stock price. The above problem has been considered by Shiryacv, Xu and Zhou （2008） and Du Toit and Peskir （2009）. In this paper we provide an independent proof that when α=1/ 2 σ^2 , a selling strategy is optimal if and only if it sells the stock either at the terminal time T or at the 1 2 moment when the stock price hits its maximum price so far. Besides, when α 〉1/2σ^2 , selling the stock at the terminal time T is the unique optimal selling strategy. Our approach to the problem is purely probabilistic and has been inspired by relating the notion of dominant stopping pr of a stopping time τ to the optimal stopping strategy arisen in the classical ＂Secretary Problem＂.

关键词： optimal Stopping stock selling buy and hold local time