Design and verification of an improved experimental platform for stray current in urban rail transit

With the rapid development of urban rail transit,there have been an urgent problem of excessive stray current.Because the stray current distribution is random and difficult to verify in the field,we designed an improved stray current experimental platform by replacing the simulated aqueous solution with a real soil environment and by calculating the transition resistance by measuring the soil resistivity,which makes up for the defects in the previous references.Firstly,the mathematical models of rail-drainage net and rail-drainage netground were established,and the analytical expressions of current and voltage of rail,drainage net and other structures were derived.In addition,the simulation model was built,and the mathematical analysis results were compared with the simulation results.Secondly,the accuracy of the improved stray current experimental platform was verified by comparing the measured and simulation results.Finally,based on the experimental results,the influence factors of stray current were analyzed.The relevant conclusions provide experimental data and theoretical reference for the study of stray current in urban rail transit.

教师话语缺失探因——基于小说《大风起兮》的语料分析

传统制度课程和制度化课堂教学给予教师的是附庸于专家话语的虚假话语权,教育场域中官本位思想极大威胁教师话语的民主化,教师个人话语压抑导致其存在危机,教师应积极参与课改、提升自身素质,有关部门应依《教师法》给予教师参与教育决策的话语交流平台。

Stochastic Air Traffic Flow Management for Demand and Capacity Balancing Under Capacity Uncertainty

This paper introduces an innovative approach to the synchronized demand-capacity balance with special focus on sector capacity uncertainty within a centrally controlled collaborative air traffic flow management(ATFM)framework.Further with previous study,the uncertainty in capacity is considered as a non-negligible issue regarding multiple reasons,like the impact of weather,the strike of air traffic controllers(ATCOs),the military use of airspace and the spatiotemporal distribution of nonscheduled flights,etc.These recessive factors affect the outcome of traffic flow optimization.In this research,the focus is placed on the impact of sector capacity uncertainty on demand and capacity balancing(DCB)optimization and ATFM,and multiple options,such as delay assignment and rerouting,are intended for regulating the traffic flow.A scenario optimization method for sector capacity in the presence of uncertainties is used to find the approximately optimal solution.The results show that the proposed approach can achieve better demand and capacity balancing and determine perfect integer solutions to ATFM problems,solving large-scale instances(24 h on seven capacity scenarios,with 6255 flights and 8949 trajectories)in 5-15 min.To the best of our knowledge,our experiment is the first to tackle large-scale instances of stochastic ATFM problems within the collaborative ATFM framework.

浅谈指导学生课外阅读的几种有效途径

教师通过阅读时间给学生传授几种课外阅读方法,既帮助学生开阔视野、陶冶情操,又有利于培养学生阅读能力和语言表达能力。同时又增强了学生的语文素养。

欢迎订阅《环境技术》双月刊(邮发代号:46-355)

一、杂志简介《环境技术》(双月刊)杂志创刊于1983年,由中国机械工业集团有限公司主管,中国电器科学研究院有限公司主办、中国电工技术学会电工产品环境技术专业委员会、全国电工电子产品环境技术标准化技术委员会等协办,关注于电工电子产品环境适应性与可靠性领域,国内外公开统一发行的国际级权威刊物。二、办刊宗旨《环境技术》旨在充分发挥其专业媒体优势,整合资源,服务行业,打造电工电子产品环境适应性和可靠性领域专业技术交流平台,促进行业的进步与发展。

Changes of Terrestrial Water Storage in River Basins of China Projected by RegCM4

In this study, a historic simulation covering the period from 1951 to 2000 and three projected scenario simulations covering 2001-2050 were conducted em- ploying the regional climate model RegCM4 to detect the changes of terrestrial water storage （TWS） in major river basins of China, using the Intergovernmental Panel on Climate Change （IPCC） Special Report on Emissions Scenarios （SRES）： A1B, A2, and B1. The historic simula- tion revealed that the variations of TWS, which are dominated by precipitation in the basins, rely highly on their climatic features. Compared with the historic simu- lation, the changes of TWS in the scenario simulations showed strong regional differences. However, for all sce- narios, TWS was found to increase most in Northeast China and surrounding mountains around the Tibetan Plateau, and decrease most in eastern regions of China. Unlike the low seasonal variations of TWS in arid areas, the TWS showed strong seasonal variations in eastern monsoon areas, with the maximum changes usually oc- curring in summer, when TWS increases most in a year. Among the three scenario simulations, TWS increased most in Songhua River Basin of B1 scenario, and de- creased most in Pearl River Basin of A2 scenario and Hal River Basin of A1B scenario, accompanied by different annual trends and seasonal variations.

An odyssey: the way Chinese catalysis towards the world

The 16^th International Catalysis Congress (16th ICC) was successfully held in China in July 2016. This paper reviewed the development of catalytic science and technology of China from scratch to small then to large under the efforts of several generations. In 1950s, catalysis discipline was first set up to train early catalytic professionals in Jilin University, Peking University and Xiamen University. Subsequently, a large research team was formed in colleges and universities, the Academy of Sciences, the Enterprise Research Institute to carry out a large number of catalytic researches. Along with the Chinese reform and opening-up, the spring of science came, and the state started to emphasize and strongly support scientific research. Chinese catalytic researchers began to enter the international catalytic academic exchange platform. Famous foreign scientists are invited to visit China and a large number of visiting scholars and foreign students have been sent to the United States, Europe and Japan, many of them have become well-known professors, and grown into catalytic academic elites. The first China-Japan-USA Symposium on Catalysis was held in Dalian in 1982, and it was expanded to become the Asian-Pacific Congress on Catalysis (APCAT), one of the three regional catalytic conferences in the world. After several generations of bidding for the organization of the International Catalytic Congress three times, China won the right to host the 16th ICC. It has effectively promoted the Chinese catalytic academic circles to the international academic ones and improved the influence of catalysis communities in China significantly. The great development in catalytic research and technology has condensed the efforts of several generations of catalysts. To make China a catalytically strong country, there is still a long way to go. We hope that the contemporary scientists can accomplish this historical task.

Research on General Financial Message Standards and Their Application

New challenges have been posed to the infornmtion exchange and interconn,u;fion in financial industry with the innovalion of financial business and the development of infarmation techtinlogy. From the perspective of financial message standardization. ISO 20022 puts forward a set of sohaions and ideas for information exchange, which have been recognized in financiat industry all around the world. Considering the variety of financial message standards and message exchange modes, it is essential to strengthen the development and application of general message standards for financial industry and build：up the general m^sage exchange platform, which wild play a significant role in guiding lhe slandardized developmenl of industry, implementing financial s/andardizalion slralegies, and enhancing the level of inlerconneclion.

A two-stage short-term traffic flow prediction method based on AVL and AKNN techniques

Short-term traffic flow prediction is one of the essential issues in intelligent transportation systems(ITS). A new two-stage traffic flow prediction method named AKNN-AVL method is presented, which combines an advanced k-nearest neighbor(AKNN)method and balanced binary tree(AVL) data structure to improve the prediction accuracy. The AKNN method uses pattern recognition two times in the searching process, which considers the previous sequences of traffic flow to forecast the future traffic state. Clustering method and balanced binary tree technique are introduced to build case database to reduce the searching time. To illustrate the effects of these developments, the accuracies performance of AKNN-AVL method, k-nearest neighbor(KNN) method and the auto-regressive and moving average(ARMA) method are compared. These methods are calibrated and evaluated by the real-time data from a freeway traffic detector near North 3rd Ring Road in Beijing under both normal and incident traffic conditions.The comparisons show that the AKNN-AVL method with the optimal neighbor and pattern size outperforms both KNN method and ARMA method under both normal and incident traffic conditions. In addition, the combinations of clustering method and balanced binary tree technique to the prediction method can increase the searching speed and respond rapidly to case database fluctuations.

A Feasibility Study for New Transport Connections between Italy and Algeria

The present study is part of the Executive Scientific Project 2 in the ItalMed Project which aims to elaborate a feasibility study for new transport connections between Italy and Algeria. The main objectives of the study are to increase the degree of economic integration between the two countries and improve commercial exchanges and direct investments in Algeria by Italian private companies. Moreover, the study tries to promote Italy＇s role as logistic platform for Mediterranean Countries along the east-west and north-south corridors and to improve the capacity of Italian regions to manage international cooperation programs on transport and logistics, finally, to support regional entrepreneurship in the foreign services sector.

Macro modeling and analysis of traffic flow with road width

The macro modeling and the solution of traffic flow with road width were investigated.Firstly,a new macro model with the consideration of road width was proposed.Secondly,the effects of road width on uniform flow and small perturbation were studied.The analytical and numerical results show that widening (shrinking) road can enhance (reduce) the equilibrium speed and flow,and the increments (decrements) will increase with the absolute value of road width gradient.In addition,the numerical results illustrate that the new model can describe the effects of road width on the evolutions of uniform flow and small perturbation.

Packaging

CCPIT Packaging Industry Office mainly provides services in the following aspects:communi- cating among CCPIT and de- partments and sub-committees of China Packaging Federation,and coordinating working relations among departments of Packaging Industry Office,and

Hybrid Supply for-Automotive Application Using Supercapacitors

In this article, the replacement of the car battery by a hybrid supply is proposed. The specific power of the supercapacitor makes it very attractive for the startup of the car. This component has very high lifetime （1 million of cycles） which can improve the lifetime of the supply （for starter or starter-alternator）. After the identification of the internal combustion engine torque developed at the startup, the validation of the hybrid supply interest is proved by the simulation of the system using Matlab-Simulink software. Finally, a test bench is developed in the laboratory to validate the simulation results.

Escaping Low-Level Equilibrium of Urbanization——Institutional Promotion,Social Interaction and Labor Migration

The policies resulting in urban-rural segmentation have not only directly impeded the transfer of labor from rural to urban areas,but also trapped the process of urbanization in a low-level equilibrium,as the negative effects are amplified by interdependencies between interpersonal decisions.This paper finds from the CHIPS2002 data that there is interdependence of rural residents' decision-making on labor migration from rural to urban areas,and the interdependence is strengthened by the exchange of information between rural residents.According to the simulation results of the models in this paper,China's rural-urban labor migration is indeed at a low-level equilibrium.To get rid of the low-level equilibrium,in addition to improving the level of education and promotion of information exchange among rural residents,it is more important to implement "big push " policies to eliminate institutional barriers to labor mobility and accelerate urbanization with the social interaction.

Social Media Use for Information-Sharing Activities Among Youth in Malaysia

Social media are popular among youth for sharing information. This study tries to explore the popularity of the social media sites, the level of use of the social media sites, the types of information-sharing activities involved on the social media sites, to compare youth of various background in relation to information-sharing activities, and to analyze the relationship between the level of social media use and the information-sharing activities among youth. This study employs a quantitative research design, using survey method with questionnaire as the research instrument used for data collection. In this study, youth aged between 17-40 years old nationwide were surveyed. The study was developed based on the user and gratification theory （Blumler ＆ Katz, 1974）. Findings showed that youth always （five to seven days per week） use social media to share information including personal information. Results also showed that youth used the social media more for sharing negatively-oriented information compared to the positively-oriented information. Although there were more items on the positively-oriented information-sharing activities but more youth spent their time on the negatively-oriented information-sharing activities. The results are supported by a strong relationship between frequency of use and the negatively-oriented information-sharing activities.

High Power Density Three-Level Three-Phase AC-DC 48 V Power Supply

International standards impose several constraints concerning the electric power quality and require that the harmonic content of the line current of grid connected equipment is below assigned limits; for this reason, operating of AC-DC converters with high power factor and low line current distortion has become essential. In this paper, the prototypal realization of a three-phase AC-DC 48 V power electronic converter for telecom system supplying is described and experimental testing results are discussed. The main constraints in the power supply design are the required power density of about 900 W per dm3 as well as the absence of the neutral wire in the supply grid. The carried out investigation is focused on three-level power converter configurations which are considered in order to reduce voltage rating of power switches. As a result of the reduced voltage, low on-resistance metal-oxide-semiconductor field effect transistors can be used in the power stage, solution which allows to achieve improved efficiency as well as increased switching frequency with respect to the insulated gate bipolar transistors based two-level topologies.

COMMUNICATION ON-LINE AND THE DEVELOPMENT OF GRAMMATICAL COMPETENCE

It is questioned whether network-based communication aids the development of grammatical competence in teaching English as a foreign language. We studied the on-line communication between students of a Chinese university and a Japanese university and found that network-based communication holds similar potential for the development of grammatical competence as does oral interaction.

FPn-Injective, FPn-Flat Covers and Preenvelopes, and Gorenstein AC-Flat Covers

We prove that, for any n 〉 2, the classes of FPn-injective modules and of FPn-flat modules are both covering and preenveloping over any ring R. This includes the case of FP∞-injective and FP∞-flat modules （i.e., absolutely clean and, respectively, level modules）. Then we consider a generalization of the class of （strongly） Gorenstein flat modules, i.e., the （strongly） Gorenstein AC-flat modules （cycles of exact complexes of flat modules that remain exact when tensored with any absolutely clean module）. We prove that some of the properties of Gorenstein fiat modules extend to the class of Gorenstein AC-flat modules; for example, we show that this class is precovering over any ring R. We also show that （as in the case of Gorenstein flat modules） every Gorenstein AC-flat module is a direct summand of a strongly Gorenstein AC-flat module. When R is such that the class of Gorenstein AC-flat modules is closed under extensions, the converse is also true. Moreover, we prove that if the class of Gorenstein AC-flat modules is closed under extensions, then it is covering.

DESIGN AND STUDY OF SHADOWNET-BASED BICULTURAL COMMUNICATION MODE

A ShadowNet-based communication mode was designed,and some related activities planned and carried out,for an experimental cooperative project between two universities in China and the US.The students' post-survey results from both parties were analyzed and compared and it appeared that the ShadowNet system helped the students improve the following:an awareness of cultural difference,an openness toward cultural diversity,and a deeper appreciation for the significance of cultural identity in language learning and teaching.It also facilitated some direct improvements in the language acquisition of the Chinese ESL learners and the teaching ability of their American counter-parts.