WiMAX技术及其在电力系统通信的应用

WiMAX具有容量大、可靠性高、传输距离长等特点,在电力系统通信中有一定的应用潜力。文章从物理层、链路层、大覆盖范围、QoS性能等4个方面,对WiMAX的技术展开分析,并结合电力行业的特点,阐述了WiMAX在无线城域网、变电站接入备用通信方式、应急通信、配网自动化等方面的应用,表明了WiMAX可以作为下一代宽带无限接入技术应用于未来的电力系统通信。     

世界化纤工业现状和发展

阐述了当前世界化纤工业的状况和特点,介绍了近年开发的新化纤,对我国化纤工业的进步发展具有重要的指导意义。     

移动多跳中继网络中的混合式认证延时性能分析

首先分析了在移动多跳中继(Mobile Multihop Relay,MMR)WiMAX网络中,新的移动中继(Relay Station,RS)节点在进入网络之前存在的两种认证方案:集中式和分布式接入认证方案。接着在这两种接入认证方式的基础上,提出了一种新的混合式认证方案。然后使用排队论对集中式和混合式认证方案在不同中继节点分布下的认证延时性能进行了分析。最后数值分析结果表明,混合式认证方案相较于集中式认证方案在认证延时性能方面具有更大的优势。     

The effects of cultural dimension on ICT innovation: Empirical analysis of mobile phone services

ICT Innovation is one of the major forces for socioeconomic development. It is the key element to spur growth of the economy of a nation. Several studies have shown that culture is a crucial determinant of innovations. This study examines the effect of socio-cultural factors on ICT innovation with specific focus on the mobile banking services. Research was conducted on 220 respondents from sampled population in South Africa. The questionnaire used in this study was developed based on previous studies that have proven validity. The findings indicate that culture is an appropriate concept to describe how innovation in information and communication technology can be influenced by human behavior.     

A reliable model for global planning of mobile networks

In this paper, we propose a global model for WiMAX networks planning. This model represents the network planning problem and helps to solve it entirely without dividing it into several subproblems. The objective of the model is to minimize the cost of the network while maximizing its survivability. The model has been compared to a sequential model with the same constraints, which consists in solving the subproblems sequentially, and to a global model without reliability constraints. The results show that the proposed model performs on an average 25% better than the other models.     

2004年世界空调器的发展(上)

本文综述2004年世界空调器的生产、销售规模和产品的发展趋势.     

CYCLOPS: A mobile robotic platform for testing and validating image processing and autonomous navigation algorithms in support of artificial vision prostheses

While artificial vision prostheses are quickly becoming a reality, actual testing time with visual prosthesis carriers is at a premium. Moreover, it is helpful to have a more realistic functional approximation of a blind subject. Instead of a normal subject with a healthy retina looking at a low-resolution (pixelated) image on a computer monitor or head-mounted display, a more realistic approximation is achieved by employing a subject-independent mobile robotic platform that uses a pixelated view as its sole visual input for navigation purposes. We introduce CYCLOPS: an AWD, remote controllable, mobile robotic platform that serves as a testbed for real-time image processing and autonomous navigation systems for the purpose of enhancing the visual experience afforded by visual prosthesis carriers. Complete with wireless Internet connectivity and a fully articulated digital camera with wireless video link, CYCLOPS supports both interactive tele-commanding via joystick, and autonomous self-commanding. Due to its onboard computing capabilities and extended battery life, CYCLOPS can perform complex and numerically intensive calculations, such as image processing and autonomous navigation algorithms, in addition to interfacing to additional sensors. Its Internet connectivity renders CYCLOPS a worldwide accessible testbed for researchers in the field of artificial vision systems. CYCLOPS enables subject-independent evaluation and validation of image processing and autonomous navigation systems with respect to the utility and efficiency of supporting and enhancing visual prostheses, while potentially reducing to a necessary minimum the need for valuable testing time with actual visual prosthesis carriers.     

WiMAX认证方案研究

WiMAX安全要实现两大目标:一是为整个无线网络提供机密性保护;二是提供网络接入控制功能。IEEE802.16的安全子层采用了认证客户端/服务器密钥管理协议,在该协议中基站(即服务器)能够对分发给客户端SS的密钥进行控制。本文首先分析了WiMAX网络物理层和MAC层面临的安全威胁,然后给出了WiMAX网络安全体系架构。最后,对散列消息认证码(HMAC)、X.509证书和可扩展认证协议(EAP)进行了详细的介绍。     

An econometrics view of worldwide fossil fuel consumption and the role of US

Crude oil, coal and gas, known as fossil fuels, play a crucial role in the global economy. This paper proposes new econometrics modelling to demonstrate the trend of fossil fuels consumption. The main variables affecting consumption trends are: world reserves, the price of fossil fuels, US production and US net imports. All variables have been analysed individually for more than half a century. The research found that while the consumption of fossil fuels worldwide has increased trends in the US production and net imports have been dependent on the type of fossil fuels. Most of the US coal and gas production has been for domestic use, which is why it does not have a strong influence on worldwide fossil fuel prices. Moreover, the reserves of fossil fuels have not shown any diminution during the last couple of decades and predictions that they were about to run out are not substantiated. The nominal and real price of fossil fuels was found to change depending on the type. Finally, estimates of three econometric models for the consumption of fossil fuels from 1949 to 2006 are presented which identify the effects of significant variables.