基于代理的虚拟实验室系统

为了克服传统虚拟实验室由于访问接口不统一而造成的访问成本较高的缺陷,本文提出了基于代理的虚拟实验室的概念,统一了资源的访问.并且,本文给出了一个基于代理的虚拟实验室的设计方案,通过容器代理、视图代理、通信代理、服务代理、资源代理、仿真代理,使得系统能够有效集成和管理现有的资源,且具有良好的可扩展性.通过统一的公共接口,使不同的资源甚至是没有任何公共特征的资源都能够通过同一个虚拟实验室服务器而被共享.     

Digital access,choice and agency in remote Sarawak

Internet use and access to digital devices continues to increase even in remote regions around the world, but users do not participate equally or engage in the same practices online. This leads to inequalities in the outcomes different groups of users can generate as a result of their online practices. Drawing from recent literature on digital divides and using a theoretical framework focused on user choice and agency, we present data from a study of internet and device use in remote villages in Sarawak, a state of Malaysia on the island of Borneo. These villages lack most basic infrastructure such as paved roads or grid electricity, but some have mobile phone and mobile internet access installed under Malaysia’s Universal Service Provision. We discuss qualitative and quantitative data collected between 2015 and 2017 to point to the opportunities as well as obstacles users in remote communities encounter in their engagements with digital devices and the internet. We argue that while remote areas seem to lag behind urban areas in terms of users’ internet skills and practices, people choose to engage with these technologies in ways that are appropriate to their needs and to the local low-bandwidth environment. To enable these communities to tap into additional potential benefits of internet use, however, faster and more reliable access is a prerequisite.     

How variation in internet access,digital skills,and media use are related to rural student outcomes: GPA,SAT, and educational aspirations

Some have pointed to divides in the availability of fixed home broadband Internet access as a contributor to rural students’ lower levels of educational attainment. Based on standardized exams (SAT Suite) and a survey of rural Michigan students in grades 8–11, we find that rural students with broadband home Internet access are more interested in school and leave homework incomplete less often. However, the relationship to classroom grades (GPA) is relatively trivial. Yet, we find that students who are not dependent on a cell phone for Internet access and those with higher digital skills, especially social media skills, rank considerably higher on the SAT. Rural students with broadband Internet access are able to participate in a more diverse array of online media activities, which supports building digital skills. Any negative relationship between time spent on social media, video games, other digital media and educational outcomes is outweighed by the benefit to digital skills. However, aspects of rural culture; including the emphasis on activities such as sports, as a path to postsecondary schooling and upward, social mobility; may be stunting the positive relationship between access, digital skills, and educational aspirations. Whereas extra-curricular sports have no direct relationship to SAT performance, students who spend more time on sports receive higher grades and have higher educational aspirations than those with more digital skills. We discuss the implications for rural students’ access to human capital and how the unequal relationship between digital skills and performance in the classroom and on the SAT may perpetuate inequalities.     

基于AT89S52的多功能智能小车设计

采用AT89S52单片机为主控制芯片,结合直流电机、多种传感器、红外遥控及其他外围电路,设计实现了一种沿黑色轨迹行走的智能循迹小车,同时还能自动避障,并在遥控的作用下完成小车行走的控制。实验证明整个系统设计灵巧、控制准确、工作稳定、使用效果良好。     

SenseWeb: An Infrastructure for Shared Sensing

Peer-produced systems can achieve what might be infeasible for stand-alone systems developed by a single entity. The SenseWeb's goal is to enable these kinds of capabilities. Using SenseWeb, applications can initiate and access sensor data streams from shared sensors across the entire Internet. The SenseWeb infrastructure helps ensure optimal sensor selection for each application and efficient sharing of sensor streams among multiple applications.     

A mechatronics educational laboratory – Programmable logic controllers and material handling experiments

The integration of robotics, conveyors, sensors, and programmable logic controllers into manufacturing and material handling processes requires engineers with technical skills and expertise in these systems. The coordination of assembly operations and supervisory control demands familiarity with mechanical and electrical design, instrumentation, actuators, and computer programming for successful system development. This paper presents an educational mechatronics laboratory that encourages multi-disciplinary hands-on engineering discovery within team settings. Three focused progressive experiments are reviewed that allow students to program and operate a programmable logic controller, a traditional conveyor system, and a distributed servo-motor based conveyor. The students also program and implement two robotic arms for material handling applications. The equipment, learning objectives, and experimental methodology for each laboratory are discussed to offer insight. A collaborative design project case study is presented in which student teams create a smart material handling system. Overall, engineering graduates have generally been required to learn material handling and other multi-disciplinary concepts in the field, and therefore, a well-rounded engineering curriculum should incorporate mechatronics in both the classroom and laboratory.     

虚拟专用网接入设备的设计

虚拟专用网通过在公共网传输介质上建立加密信道,在连接分布在不同地区的网络和个人用户形成专用网络。根据虚拟专用网用户三种没的接入方法,文章给出了ＶＰＮ接入设备的设计方案、数据处理流程及内部算法。     

DefSim: A Remote Laboratory for Studying Physical Defects in CMOS Digital Circuits

This paper describes a unique remote laboratory for studying CMOS physical defects that is meant to be used in advanced courses in the scope of microelectronic design and test. Both the measurement equipment and the remote access mechanism were custom developed in the frame of the European Union project REASON. The core of the equipment is an educational chip that contains different manufacturing defects physically implemented into standard digital cells and small logic circuits on the layout level. The chip is supplied with a dedicated plug-and-play measurement box, which provides an interface between the chip and the training software. This measurement kit offers a glimpse into the silicon reality, revealing behavior of the most common defects and their influence on the circuits' operations. Students can choose between approximately 500 different defects, which can be classified into different groups by studying their properties, and find differences or similarities. The remote server-based version of the laboratory is accessible over the Internet, thereby supporting distance learning and e-learning modes of training. A personal version of the training software is also available.     

Design and implementation of a wireless internet remote access platform

Recently, mobile networks and internet technologies have been widely developed for the voice communication and information retrieval services all over the world. Compared with the wire‐line internet environment, mobile networks have lower bandwidth, longer transmission latency and unreliable connection, and the capability of mobile terminals is restricted by the limited memory size, lower CPU computation capability and inconvenient I/O interface. These limitations restrict the development of the wireless internet applications. In this paper, we design and implement a ‘wireless internet remote access platform’ (WIRAP). The WIRAP platform interconnects the wireless network and internet to provide mobile users a remote centralized storage and computation environment. A mobile user can store large volume of data and execute complex computations on WIRAP instead of on the mobile terminals. WIRAP supports different network interfaces (e.g. short message service (SMS), wireless markup language (WML) and hyper text markup language (HTML) and users may use terminals (with different network capabilities) to access WIRAP. Copyright © 2006 John Wiley & Sons, Ltd.     

Narrowband and broadband infrastructure design for wirelessnetworks

There has been an explosion in the number of wireless subscribers. A number of air interface technologies, such as GSM, TDMA and CDMA, are available to wireless service providers for offering wireless services. In addition, a variety of networking technologies, such as STM, ATM and frame relay, are available to the wireless services provider for designing their infrastructure networks. The abundant choice of technologies, and their associated capabilities and costs, creates a need for network design tools which can help vendors and wireless service providers to understand the economics of investing in different technologies. This article is concerned with the design of narrowband and broadband infrastructure networks for wireless access. The article first describes the different technology alternatives and tariff structures and their impact on wireless infrastructure network design. The general infrastructure design problem is then stated and a solution methodology outlined. Examples of the economic trade-offs involved in narrowband and broadband networking technologies are also presented     

Secure remote access to an Internet Web server

We address the problem of secure remote access to a site's internal Web server from outside the firewall. The goal is to give authorized users access to sensitive information, while protecting the information from others. We implemented our solution using a one-time password scheme for client authentication and secure socket layer (SSL) for confidentiality. Our main design considerations were security, performance, ease of use, availability, and scale. We were further constrained by the desire to leave our firewall and local infrastructure unchanged     

Analysis of Social Interactions Through Mobile Phones

Equipment of mobile phones with various kinds of sensors is transforming these devices from mere capabilities of voice and internet access to devices capable of sensing a number of phenomena pertaining to their users. In this paper we make use of these capabilities of phones to detect social interactions between people and analyze social context by using embedded sensors found in typical smart phones. Work carried out in this area has typically used dedicated hardware to establish social interactions, and we contend on the suitability of mobile phone, since additional devices that user is not familiar with influence natural user behavior and thus their social interaction patterns. Our work shows that two parameters that can be detected through mobile phone sensing, namely interpersonal distance and relative body orientation, provide a solid basis for inferring social interactions. We describe how these factors are acquired using smart phones and describe our analysis. The experiments demonstrate that we can recognize not only whether a social interaction is taking place, but also the type of social interaction, distinguishing between formal and informal social settings.     

An Interactive Network Laboratory for Electronic Engineering Education

The advantage of the network laboratory is the better flexibility of lab experiments by allowing remote control from different locations at a freely chosen time. In engineering education, the work should not only be focused on the technical realization of virtual or remote access experiments, but also on the achievement of its pedagogical goals. In this paper, an interactive laboratory is introduced which is based on the online tutoring system, virtual and remote access experiments. It has been piloted in the Department of Electronic Science and Technology, HUST. Some pedagogical issues for electronic engineering laboratory design, the development of a multi-server- based distributed architecture for the reduction of network latency and implementations of the function module are presented. Finally, the system is proved valid by an experiment.     

Design and Implementation of an Educational Testbed for Experiencing With Industrial Communication Networks

This paper presents the design and implementation of an educational testbed developed for a course on industrial communication networks at the Engineering Faculty, University of Catania. The aim is to realize a platform capable of emulating various network configurations, thus enabling students to find out by themselves through practical experiments how different design choices, parameter settings, network configurations, and algorithms impact on the overall network performance. The testbed comprises a number of basic components (hosts, routers, and access points) implemented on nodes equipped with operating systems and open source software, which together make up a modular system. Each router can be loaded with data flows and monitored over preestablished time windows so as to evaluate its performance in a wide range of operating conditions. The wireless part makes it possible to configure environments with different levels of noise and bandwidth utilization so as to emulate a broad spectrum of real operating environments. The testbed can be used via remote access through a web interface that not only allows the operating conditions to be configured but also permits real-time monitoring. Students can configure the testbed on the basis of the network they are studying and can measure its performance for evaluation purposes.     

Traffic load metrics for multihomed mobile IP and global connectivity

Support for host mobility an essential and necessary feature for roaming users who connect to wireless networks via access points. Access points may have different capabilities, be connected to different networks and be installed by different providers. A mobile host will discover multiple access points in this environment. In such an environment, a mobile host should be able to use the best available connection to communicate with a correspondent host and perhaps use multiple connections for different hosts. In areas with wireless local area network access, pockets with limited or no coverage could exist. Such restricted connectivity could be compensated by neighbor hosts who form an ad hoc network and relay packets until they reach an access point. This paper describes and discusses a proposed solution towards enabling and supporting connectivity in wireless networks. In the proposed solution the network layer software will evaluate and decide which wireless network connections to use. A Running Variance Metric (RVM) and a Relative Network Load(RNL) are used to measure the traffic load of access points in wireless access networks. RVM and RNL can be efficiently used for both infrastructure networks and ad hoc networks. Multihomed Mobile IP (M-MIP) is an extension of Mobile IP that enables mobile hosts to use multiple care-of addresses simultaneously. The extension enhances network connectivity by enabling the mobile host, the home agent and correspondent hosts to evaluate and select the best connection. A proposed gateway architecture using M-MIP that integrates wired IP networks with ad hoc networks is described. The M-MIP and gateway architecture using the RVM and RNL metrics have been validated with simulation studies and results are presented.     

UAV-based LoRaWAN flying gateway for the internet of flying things

The Internet of Things (IoT) is one of the paradigms related to the evolution of telecommunication networks which is contributing to the evolution of numerous use cases, such as smart city and smart agriculture. However, the current communication infrastructure and wireless communication technologies are not always able to guarantee a proper service for these IoT scenarios. Smart solutions are needed to overcome current terrestrial network limitations offering a cost-effective way to extend the current terrestrial network coverage. For example, temporary extensions “on-request” of the terrestrial infrastructure may be a viable solution to allow collecting data generated by nodes outside the current network coverage. Flying objects can help achieve this goal. Various studies supported the use of unmanned aerial vehicles (UAVs) as intermediate nodes between IoT devices and the network. However, such solutions have not been exhaustively tested yet in real-case scenarios. This paper proposes an efficient solution to collect data from multiple IoT sensors in rural and remote areas based on UAVs. It describes the implementation of the proposed UAV-based Long RangeWide Area Network (LoRaWAN) flying gateway able to collect data directly from LoRaWAN sensors during its flight, keep them stored in an onboard memory, and forward them at the end of its flying path to a platform where the authorized users can access them. A prototype of the gateway has been developed to assess the proposed solution through both indoor and outdoor tests aiming to test its feasibility both in terms of communication performance and UAV-required hardware resources.     

Architecture of Ubiquitous Mobile Internet

With shortcomings in its original design,the Internet is limited in its capacity to meet increasing demands from ubiquitous mobile users. This paper discusses a new architecture for ubiquitous mobile Internet as well as the models and theories of its two layers. The infrastructure layer allows users to access the Internet anywhere,anytime,and by any means,while the pervasive service layer supports a variety of services. This paper proposes a mobility management mechanism under the new architecture. Experime...     

Achieving distributed user access control in sensor networks

User access control in sensor networks defines a process of granting user an access right to the stored information. It is essential for future real sensor network deployment in which sensors may provide users with different services in terms of data and resource accesses. A centralized access control mechanism requires the base station to be involved whenever a user requests to get authenticated and access the information stored in the sensor node, which is inefficient, not scalable, and is exposed to many potential attacks along long communication paths. In this paper, we propose a distributed user access control under a realistic adversary model in which sensors can be compromised and user may collude. We split the access control into local authentication conducted by a group of sensors physically close to a user, and a light remote authentication based on the endorsement of the local sensors. We implement the access control protocols on a testbed of TelosB motes. Our analysis and experimental results show that our schemes are feasible for real access control requirements.     

A Service-Oriented Educational Laboratory for Electronics

This paper proposes a service-oriented middleware to access heterogeneous remote laboratory equipment and experimental settings through the network. The web service paradigm is used to expose the functionality of the instruments and to compose measurement workflows in a multilevel architecture that enables high flexibility, scalability, and interoperability. The proposed architecture has been applied to the development of a remote laboratory for education on electronics, but the middleware can address a broad range of instrumentation and experimental activities in different fields via the same architectural design.      

Online Competitions: An Open Space to Improve the Learning Process

Experimentation and practical work, which are usually accomplished in a laboratory, are the basics of technological fields. Laboratory activities enable students to acquire methodologies, work habits, knowledge, and experience of equipment operation, in conditions as near as possible to their future professional activities. The evolution of communication and information technologies opens new possibilities in educational methods. This article describes a project that aims to facilitate the use of real robots in an educational laboratory via Web, allowing users to learn different robotics aspects while performing a competition. Students can remotely program several robots to participate in games to accomplish a set of goals in a remote stadium (the RoboStadium). To facilitate the use of robots, the online robot stadium provides a set of training resources. Having these resources, previous knowledge on robotics is not required to use the system. Since robotics is a multidisciplinary field (mechanics, electronics, control, mathematics, computers, etc.), students of different degrees can take advantage of the presented system. Researchers of two Spanish universities are participating in this project, which provides robotics telelaboratories via Web.