Study on Surface Optimization by Ion Beams

Preliminary tribo-mechanical properties of IBED filmsof GCr15 bearing steels have been studied in this paperalong with the comparison between IBED films and PVDfilms as well as non-implanted surface in wear resis-tance,micro-hardness,friction and surface morpholo-gy.Experiments gave a consistent picture and statedclearly that TIN films can really improve the tribo-me-chanical properties of materials and have practical usesin a certain sense.However,further theoretical and ex-perimental studies must be performed in respect thatthere are some defects on IBED films.     

Innovation and practice of TD-LTE for intelligent transportation systems (ITS)

Intelligent transportation system (ITS) has become a popular research topic to meet the increased demands of transportation safety,traffic efficiency,comfort in the journey and environment protection,etc. ITS applications impose higher requirements on wireless communication systems. For example,safety-related ITS services must always be low latency and entertainment-related ITS services need high data rate. The ITS dedicated short range communications (DSRC) technology to support the safetyrelated application is still under development, while long term evolution (LTE),as the next generation mobile communication systems,offers an efficient communication platform for ITS information exchange , which can meet most ITS services requirements of latency,data rate as well as communication range. In this paper,based on the time-division duplex (TDD) mode of LTE,i.e. TD-LTE,an enhanced TD-LTE network architecture is introduced to better support safety-related ITS application with low latency requirement,and some enhanced access schemes of TD-LTE are proposed to improve the performance of supporting the high-speed IP-based ITS applications in hotspots. At last,two practical application scenarios of enhanced TD-LTE systems are given.     

Director of Editorial Development, ISI, Visits Tsinghua University

Dr. James Testa, Director of Editorial Development of ISI (Institute for Scientific Information), visited Tsinghua on October 17, 2005. Tsinghua Vice President Kang Kejun had a talk with Dr. Testa. On behalf of the university, Vice President Kang welcomed Testa to Tsinghua, noting that as a world-famous institute, ISI has contributed a lot to scientific research. Vice President Kang emphasized the importance of international exchange of research and gave an outline of Tsinghua’s r…     

翻译能力与翻译教学(英文)

Through an analysis of the features of Translation Teaching(TT) of China,the author tries to propose a new viewpoint on Translation Competence(TC).Traditionally,the TC focuses on practical TC.To the author translation teaching should put stress on not only practical TC of students,as they do now,but also on their theoretical TC.     

An efficient format-preserving encryption mode for practical domains

Format-preserving encryption (FPE), which makes sure that ciphertext has the same format as plaintext, has been widely used in protecting sensitive data in a database. Aiming at efficiently solving the FPE problem on a collection of practical domains, we propose the RREM (random reference-based encryption mode), which constructs bijection between the original domain and integer set through distance computation. If an appropriate distance function is predefined, the proposed mode can solve the FPE problem on linear equidistance domain in a more efficient way than previous methods. Furthermore, we make a classification on various types of domains, show the application of RREM in some practical domains, and specify RREM’s capability of solving the FPE problem on frequently-used fields in database quite efficiently.     

Synthetic security assessment based on variable consistency dominance-based rough set approach

<正> Security assessment can help understand the security conditions of an information system and yieldresults highly conducive to the solution of security problems in it.Taking the computer networks in a certainuniversity as samples,this paper,with the information system security assessment model as its foundation,proposes a multi-attribute group decision-making (MAGDM) security assessment method based ona variable consistency dominance-based rough set approach (VC-DRSA).This assessment method combinesVC-DRSA with the analytic hierarchy process (AHP),uncovers the inherent information hidden indata via the quality of sorting (QoS),and makes a synthetic security assessment of the information systemafter determining the security attribute weight.The sample findings show that this methoil can effectivelyremove the bottleneck of MAGDM,thus assuming practical significance in information system security assessment.     

A usable selection range standard based on test suite reduction algorithms

In this paper, we analyze the features and distinction of 6 classical algorithms: greedy algorithm (G), greedy evolution algorithm (GE), heuristics algorithm (H), greedy heuristic G (GRE), integer linear programming algorithm (ILP) and genetic algorithm (GA) to ensure the main influencing factors-the performance of algorithms and the running time of algorithms. What's more, we would not only present a research design that aims at gaining deeper understanding about the algorithm classification and its function as well as their distinction, but also make an empirical study in order to obtain a practical range standard that can guide the selection of reduction algorithms. When the size of a test object (product of test requirements and test cases) is smaller than 2000×2000, G algorithm is the commonly recommended algorithm. With the growth of test size, the usage of GE and GRE becomes more general.     

A Distributed Design for Minimum 2-Connected m-Dominating Set in Bidirectional Wireless Ad-Hoc Networks

Wireless ad-hoc network is widely used in many fields for its convenience and outstanding suitability. Because of the inherent lack of infrastructure and the nature of wireless channels, people select the k-Connected m-Dominating Set ((k; m)-CDS) in a network as a fault-tolerant virtual backbone to help the routing process, which will save the energy of non-dominators and improve the network performance significantly. Considering the economic cost and efficiency, we choose (2,m)-CDS as the object of this paper, which is helpful enough in practical applications and has a smaller size. We firstly study the existing algorithms for (k,m)- CDS and figure out the problems of these designs. Then we propose a new distributed algorithm named Dominating Set Based Algorithm (DSBA) with three sub-routines: Dominating Set Algorithm (DSA), Connection Algorithm (CA), and Connectivity Expansion Algorithm (CEA). Instead of commonly used Maximal Independent Set (MIS), we pick dominating set directly from the given graph, and then connect them by a two-step ring based connecting strategy to satisfy the 2-connectivity. We also provide the correctness and complexity analysis of DSBA. At last, we compare DSBA with the last construction Distributed Deterministic Algorithm (DDA) by several numerical experiments. The simulation results show that DSBA improves over 30 percent of the performance of DDA, proving that DSBA is more practical for real-world applications.     

Approximation of NURBS Curves and Surfaces Using Adaptive Equidistant Parameterlzatlons

Non-uniform rational B-spline (NURBS) curves and surfaces are very important tools for modelling curves and surfaces. Several important details, such as the choice of the sample points, of the parameterization, and of the termination condition, are however not well described. These details have a great influence on the performance of the approximation algorithm, both in terms of quality as well as time and space usage. This paper described how to sample points, examining two standard parameterizations: equidistant and chordal. A new and local parameterization, namely an adaptive equidistant model, was proposed, which enhances the equidistant model, Localization can also be used to enhance the chordal parameterizatfon, For NURBS surfaces, one must choose which direction will be approximated first and must pay special attention to surfaces of degree 1 which have to be handled as a special case.     

Effective Algorithms to Detect Stepping-Stone Intrusion by Removing Outliers of Packet RTTs

An effective method to detect stepping-stone intrusion(SSI) is to estimate the length of a connection chain.This type of detection method is referred to as a network-based detection approach. Existing network-based SSI detection methods are either ineffective in the context of the Internet because of the presence of outliers in the packet round-trip times(RTTs) or inefficient, as many packets must be captured and processed. Because of the high fluctuation caused by the intermediate routers on th...     

基于本族语和第二语言阅读谈文化差异

本族语阅读与第二语言或外语的阅读之间尽管有许多共同的基本要素,但阅读过程却差异很大。令人感兴趣的问题为是否存在着两个平行发挥作用的认知过程,或着是否存在着对两种语言的处理都适应的策略。着力探讨本族语与第二语言的阅读的异同之处,尤其是在文化方面的差异,如语言文化内容或背景知识认知体系,形式上的(或字面的)认知体系、语言学(或语言)认知体系等。     

Tsinghua University Voted Formal Member of PIM

Tsinghua University was chosen as the 53rd member of PIM (Partnership in International Management) at the 32nd Annual Conference of PIM, held in Prague on Nov. 12, 2005. Professor Zhao Chunjun, former Dean of the School of Economics and Management, Dr. Qi…     

Tsinghua Betters Ties with MIT

BEIJING,Feb.18,2006—Tsinghua University,famed as the“cradle of engineers,”is often dubbed“Chinese MIT(Massachusetts Institute of Technology)”on the Chinese mainland.The recent visit of Dr.Susan Hockfield,presi-dent of MIT,to Tsinghua University broug     

Modeling study on the flow patterns of gas-liquid flow for fast decarburization during the RH process

A water model and a high-speed video camera were utilized in the 300-t RH equipment to study the effect of steel flow patterns in a vacuum chamber on fast decarburization and a superior flow-pattern map was obtained during the practical RH process. There are three flow patterns with different bubbling characteristics and steel surface states in the vacuum chamber:boiling pattern (BP), transition pattern (TP), and wave pattern (WP). The effect of the liquid-steel level and the residence time of the steel in the chamber on flow patterns and decarburization reaction were investigated, respectively. The liquid-steel level significantly affected the flow-pattern transition from BP to WP, and the residence time and reaction area were crucial to evaluate the whole decarburization process rather than the circulation flow rate and mixing time. A superior flow-pattern map during the practical RH process showed that the steel flow pattern changed from BP to TP quickly, and then remained as TP until the end of decarburization.     

从文化转换角度谈动物成语的英译

美国著名翻译理论家尤金·奈达曾十分精辟地论述过:What one must determineis the response of the receptor to the translated message.This response musethen be compared with the way in which the original receptor presumablyreacted to the message when it was given in its original setting.(Eugene A.Nida and Charles K.Taber:Theory and Practice of Translation,Leiden:E.J.Brill,1969)(必须确定的是译文接受者对被译信息作出的反应,这种反应随后必须与原文接受者在原始背景中对此信息可能作出的反应方式进行比较。尤金·奈达与查尔斯·泰伯:《翻译理论与实践,1969年,自译。)他近年还进一步指出:The translator mustseek to employ a functionally equivalent set of forms which in so far aspossible will match the meaning of the originai source-language text.(Jande Warrd and Eugene A.Nida:From One Languge to Another,Nashville.     

教育学习工具灵活和有效的瘦客户部署方式

Given today's dynamic and fast paced world of Information Technology(IT),it has become more challenging for an IT manager to provide students with the most flexible and innovative learning environment.The requirement to provide these facilities must be balanced against constraints such as capital spending within budgets,maintenance costs and staffing issues.This paper discusses how a server-centric IT solution,such as thin clients,is capable of meeting these demands in a more efficient manner particularly in relation to Financial Management,Infrastructure Management and Security Management.The flexibility and efficiency of server-centric technology as an education tool is overviewed as experienced by several departments within the Dublin Institute of Technology.     

试从外语教学法的发展谈谈我国外语教材编写中的若干问题

首先,让我们对外语教学法的三种不同主导思想或三个不同发展阶段作一简要叙述。在国外,五十年代前占主导地位的外语教学法是传统的“语法翻译法”(The grammar-translation method或The translation and grammar-rule methods)。两个世纪以前,教会为传播教义,需要翻译古代希腊语、拉丁语宗教文献,促使外语教学发展起来。当时教学的目标是读懂,能够进行两种文字的翻译,教学方法是使用本族语描述外语、背诵语法条文及翻译书面语,这种教学法使学生即使学了许多语法规则及     

Manufacturing Technology Research and Appraisal of Large-Diameter SSAW Pipe Applied to the West-East Pipeline Project

This paper introduced the research and development of large-diameter SSAW pipes applied to West-East Pipeline project as well as domestic acicular ferrite pipeline steel of X70 grade. Its microstructure analysis was performed in comparison with the pipeline steel of a foreign steel plant (SPC). This paper introduced the research of welding procedures prior to SSAW pipe making and some new procedures and technologies used for West-East Pipeline Project, and appraised the practical level of Large-diameter SSAW pipe applied to the West-East Pipeline Project.     

Collagen/Chitosan Electrospun Nanofibrous Membrane for Wound Dressing

Collagen(Col)/chitosan(CS)nanofibrous membrane has great potential to be used as wound dressing.However,current Col/CS nanofibrous membrane produced from electrospinning can not offer sufficient mechanical strength for practical applications.Herein,a novel mixed solvent was used to prepare next-generation high-strength Col/CS nanofibrous membrane.Meanwhile,the optimal Col to CS weight ratio was investigated as well.The asproduced membrane was examined by scanning electron microscopy(SEM),attenuated total reflectance Fourier transform infrared spectroscopy(ATR-FTIR),differential scanning calorimetry(DSC),and XF-1A tester to study its morphological,chemical,thermal and mechanical properties.The preliminary results demonstrated that the mechanical properties of Col/CS nanofibrous membranes were enhanced substantially with the increase of CS weight ratios from 0 to 90%and the optimal Col to CS weight ratio was determined to be 1∶1.A promising way was presented to fabricate Col/CS electrospun nanofibrous membrane with sufficient mechanical strength for practical wound dressing applications.     

Process mineralogy as a key factor affecting the flotation kinetics of copper sulfide minerals

The aim of this study is to apply process mineralogy as a practical tool for further understanding and predicting the flotation kinetics of the copper sulfide minerals. The minerals' composition and association, grain distribution, and liberation within the ore samples were analyzed in the feed, concentrate, and the tailings of the flotation processes with two pulp densities of 25 wt% and 30 wt%. The major copper-bearing minerals identified by microscopic analysis of the concentrate samples included chalcopyrite(56.2 wt%), chalcocite(29.1 wt%),covellite(6.4 wt%), and bornite(4.7 wt%). Pyrite was the main sulfide gangue mineral(3.6 wt%) in the concentrates. A 95% degree of liberation with d_(80) 80 μm was obtained for chalcopyrite as the main copper mineral in the ore sample. The recovery rate and the grade in the concentrates were enhanced with increasing chalcopyrite particle size. Chalcopyrite particles with a d_(80) of approximately 100 μm were recovered at the early stages of the flotation process. The kinetic studies showed that the kinetic second-order rectangular distribution model perfectly fit the flotation test data. Characterization of the kinetic parameters indicated that the optimum granulation distribution range for achieving a maximum flotation rate for chalcopyrite particles was between the sizes 50 and 55 μm.