Ion bridges in microfluidic systems

Recently many microfluidic systems are increasingly equipped with functional units for ionic controls for various applications. In this review article, we define an ion bridge as a structure that controls current or distribution of ions in a microfluidic system, and summarize the ion bridges in the literature in terms of characteristics, fabrication methods, advantages and disadvantages. The ion bridges play two basic roles, namely to ensure electrical contact in a microfluidic network and mechanically separate a liquid phase from another. More interestingly, the charged surfaces of ion bridges, which can be chemically modified, create new characteristics such as permselectivity and concentration polarization. Asymmetric ion transport as well as ionic conductivity through the ion bridges suggests a variety of applications including sample preconcentration, electroosmotic pump, electrospray ionization, electrically driven valve and many others. This review categorizes the ion bridges into several classes and describes the structures, materials, fundamental functions and applications. In Perspectives, new opportunities of microfluidics and nanofluidics provided by the ion bridges are discussed.     

Potential cyberterrorism via a multimedia smart phone based on a web 2.0 application via ubiquitous Wi-Fi access points and the corresponding digital forensics

Cyberterrorism has become a hotly debated research issue in the past decades because of the convergence of mobile computing powers and the fledging multimedia communication computing capabilities. Cyberterrorism is the exploitation of computer network tools to incur malfunction or shut down critical infrastructures with several keyboard punches, which is dramatically different from traditional terrorism. Due to the ubiquitous multimedia communication tools, they have radically transformed the ways concerning data transmission. Unfortunately, it also incurs unprecedented opportunities for committing cyber crimes that we were not able to foresee two decades ago. Undoubtedly, the mushrooming proliferation of mobile phones spectacularly triggers the information security leakage while most people heavily rely on mobile phones for daily communication. As cybercrime or cyberterrorism surges, digital forensics (DF) of mobile communication devices still enormously lags behind than computer forensics. Hence, in this research paper, we provide a hypothetical case review concerning the DF of a potential cyberterrorist attack that was triggered by a mobile multimedia smart phone utilizing a popular web 2.0 application program via ubiquitous Wi-Fi access points. The corresponding DF of the mobile device was conducted in a step-by-step manner as well as the crime scene reconstruction based on the digital evidence collected, analyzed, and preserved.     

结合信源特性与网络拥塞控制的可靠性视频传输算法

提出了一种用于在无线网络中传输视频的结合信源特性及网络拥塞控制的鲁棒性算法.通过场景建模以及特性分析,将分级编码产生的所有码流层划分成不同的类型,并根据它们对网络拥塞控制的贡献以及对重建图像质量的贡献不同,将其分成两个不同的队列.系统根据不同的网络丢包状态(即丢包是由网络拥塞引起还是由无线信道的不可靠传输引起)动态地调整信源速率、不等错误保护强度以及拥塞控制策略.仿真结果表明,该方法与MPEG-4信源编码加固定速率Turbo码方法以及动态调整信源、信道编码速率加选择性丢I,B,P包的网络拥塞控制方法相比,能够提供更好的性能.     

虚拟化技术在实验教学中的应用

介绍虚拟化技术的优势,以VMware Workstation的应用为例,阐述构建虚拟网络的几种模式;通过实验教学中的典型案例,指出采用虚拟化技术构建实验教学环境,可增加学生动手练习的机会,方便教师演示实验教学内容,大大增进教学效果,提高机房的利用率。     

Optimal switch location in mobile communication networks using hybrid genetic algorithms

The optimal positioning of switches in a mobile communication network is an important task, which can save costs and improve the performance of the network. In this paper we propose a model for establishing which are the best nodes of the network for allocating the available switches, and several hybrid genetic algorithms to solve the problem. The proposed model is based on the so-called capacitated p-median problem, which have been previously tackled in the literature. This problem can be split in two subproblems: the selection of the best set of switches, and a terminal assignment problem to evaluate each selection of switches. The hybrid genetic algorithms for solving the problem are formed by a conventional genetic algorithm, with a restricted search, and several local search heuristics. In this work we also develop novel heuristics for solving the terminal assignment problem in a fast and accurate way. Finally, we show that our novel approaches, hybridized with the genetic algorithm, outperform existing algorithms in the literature for the p-median problem.     

Optimized k-shortest-paths algorithm for facility restoration

The problem of finding shortest paths arises in many contexts; testing restoration algorithms and developing design packages for large telecommunications networks are two cases where the simple task of finding sets of restoration paths can consume up to 95 per cent of the execution time of an application program. This paper presents experimental studies of several well-known shortest-paths algorithms adapted to the task of finding the k-successively-shortest link-disjoint replacement paths for restoration in a telecommunications network with n nodes. The implementations range in complexity from O(kn²) when based on Dijkstra's original method, through several improvements to an efficient implementation of O(kn[v+longn]) complexity, and finally to an O(kn) implementation for the special case of edge-sparse graphs with small integer edge weights. Here v is the maximum degree of a node in the network. Several alternatives were tested during the course of these studies, particularly with a view to minimizing the number of heap updates, These alternatives are possible because we are searching for several paths between a given pair of nodes, rather than just one path between one or more pairs of nodes. Two fairly straightforward changes yield a decrease in execution time, whereas a more complex heap management strategy consumes as much time in the added code as it releases from the main routine. Experimental results confirm the theoretical complexity of q k n log n) and demonstrate a speed-up of nearly an order of magnitude over the simpler O(kn²) implementation in the largest networks tested. The optimized implementation is recommended for planning and operational applications of k-shortest paths rerouting for telecommunications network restoration and restorable network design. If hop counts or small integer link weights can be used to measure distances, then the qkn) implementation is recommended, as typical telecommunications networks are edge-sparse.     

A neural network model of a communication network with information servers

This paper models information flow in a communication network. The network consists of nodes that communicate with each other, and information servers that have a predominantly one-way communication to their customers. A neural network is used as a model for the communication network. The existence of multiple equilibria in the communication network is established. The network operator observes only one equilibrium, but if he knows the other equilibria, he can influence the free parameters, for example by providing extra bandwidth, so that the network settles in another equilibrium that is more profitable for the operator. The influence of several network parameters on the dynamics is studied both by simulation and by theoretical methods.The author was with the Intelligent Systems Unit, BT Laboratories, Martlesham Heath, Ipswich IP5 7RE, UK.     

使用动态网络提高分布应用的性能

动态网络允许应用程序将用户特制的程序注入网络节点,从而使得配置新的网络协议更加容易,协议的升级也更快。该文主要讨论引入动态协议对分布的端-端应用性能的影响。文章首先介绍一些提供novell网络服务的动态协议,并讨论其对端-端应用性能的潜在影响。接下来,具体介绍一个利用网络主干内的缓存处理来降低服务器和主干路由负载的动态协议,并定量分析其性能。     

Complete analysis of configuration rules to guarantee reliable network security policies

The use of different network security components, such as firewalls and network intrusion detection systems (NIDSs), is the dominant method to monitor and guarantee the security policy in current corporate networks. To properly configure these components, it is necessary to use several sets of security rules. Nevertheless, the existence of anomalies between those rules, particularly in distributed multi-component scenarios, is very likely to degrade the network security policy. The discovery and removal of these anomalies is a serious and complex problem to solve. In this paper, we present a complete set of mechanisms for such a management.     

A network visualization of stable matching in the stable marriage problem

The stable marriage problem (SMP) seeks matchings between n women and n men which would result in stability, and not lead to divorce or extramarital affairs. We have introduced a network consisting of nodes which represent matchings, and links between nodes which attain stability by exchanging a partner between two pairs. The network is depicted with nodes laid out to involve several coordinates which indicate either women’s satisfaction or men’s or both. With the network visualization, regularity and symmetry can be made conspicuous in specific instances of the SMP such as the Latin SMP.     

Constructive approximation to real function by wavelet neural networks

We present a type of single-hidden layer feed-forward wavelet neural networks. First, we give a new and quantitative proof of the fact that a single-hidden layer wavelet neural network with n + 1 hidden neurons can interpolate n + 1 distinct samples with zero error. Then, without training, we constructed a wavelet neural network X _a (x, A), which can approximately interpolate, with arbitrary precision, any set of distinct data in one or several dimensions. The given wavelet neural network can uniformly approximate any continuous function of one variable.     

The Management and Use of Social Network Sites in a Government Department

In this paper we report findings from a study of social network site use in a UK Government department. We have investigated this from a managerial, organisational perspective. We found at the study site that there are already several social network technologies in use, and that these: misalign with and problematize organisational boundaries; blur boundaries between working and social lives; present differing opportunities for control; have different visibilities; have overlapping functionality with each other and with other information technologies; that they evolve and change over time; and that their uptake is conditioned by existing infrastructure and availability. We find the organisational complexity that social technologies are often hoped to cut across is, in reality, something that shapes their uptake and use. We argue the idea of a single, central social network site for supporting cooperative work within an organisation will hit the same problems as any effort of centralisation in organisations. Fostering collective intelligence in organisations is therefore not a problem of designing the right technology but of supporting work across multiple technologies. We argue that while there is still plenty of scope for design and innovation in this area, an important challenge now is in supporting organisations in managing what can best be referred to as a social network site ‘ecosystem’.     

Trust Prediction in Online Communities Employing Neurofuzzy Approach

Exploiting the opportunities provided by Web 2.0 technologies has led to the appearance of social web applications, which allow users to interact and collaborate with each other, thereby sharing experience in an online environment. Establishing a trust mechanism is vital in order to identify the trustful sources of information on the social web. Trust prediction can be a useful tool for identifying the potential trust relationships among users in an online community. Thereby, reliable participants can be recommended to users; this increases social interaction among users and makes the trust network denser. The main contribution of this study is to investigate the effectiveness of soft computing and neurofuzzy techniques within the context of trust prediction. Therefore, an adaptive neurofuzzy inference system (ANFIS) as a representative of neurofuzzy techniques is compared with the widely used classification techniques including C4.5 decision tree, artificial neural network (ANN), logistic regression, and Bayesian network. All methods are applied on a portion of data obtained from the Epinions network. The results of empirical experiments indicate that ANFIS achieves the best performance in terms of area under ROC (AUC) among all other methods. Furthermore, ANFIS follows closely a C4.5 algorithm concerning F-measure. Overall, the results of experiments indicate that AFNIS can be a suitable candidate for prediction of unknown trust relationships in an online community.     

无线Mesh网中编码感知组播路由协议CAMR

网络编码是一种能够提高网络吞吐量的新技术,将网络编码应用于无线Mesh网组播对Mesh网络进一步实用化有重要意义.编码感知路由是一种能够充分识别和利用网络中的编码机会的路由.虽然已有若干个基于网络编码的单播路由协议,但无线网络中编码机会并没有被充分利用,到目前为止还没有无线Mesh网络中的编码感知组播路由协议.提出一个编码感知组播路由协议CAMR(coding-aware multicast routing).CAMR协议利用了一个新奇的编码感知路由度量CAM(coding-awarerouting metric),可以度量无线Mesh网络中节点的实际编码机会和编码能力的大小.基于CAM设计的CAMR协议可以充分利用无线Mesh网络中节点的编码机会,提高了无线Mesh网络组播的吞吐量.模拟实验验证了CAMR协议的优势及其有效性.     

Improving IPS by network processors

Many present applications usually require high communication throughputs. Multiprocessor nodes and multicore architectures, as well as programmable NICs (Network Interface Cards) provide new opportunities to take advantage of the available multigigabits per second link bandwidths. Nevertheless, to achieve adequate communication performance levels efficient parallel processing of network tasks and interfaces should be considered. In this paper, we leverage network processors as heterogeneous microarchitectures with several cores that implement multithreading and are suited for packet processing, to investigate on the use of parallel processing to accelerate the network interface, and thus the network applications developed above it. More specifically, we have implemented an intrusion prevention system (IPS) with such a network processor. We describe the IPS we have developed that after its offloaded implementation allows faster packet processing of both normal and corrupted traffic. The benefits from placing the IPS close to the network, by using specialized network processors, give many times lower latency and higher bandwidth available to the legitimate traffic.     

一种利用信道侦听的IEEE 802.11自适应优化算法

提出一种适用于DCF(distributed coordination function)机制的自适应优化算法.该算法基于网络节点侦听信道得到的网络状态信息进行相关参数的自适应调整以获得最优的网络性能,称为CSB(channel sensing backoff)算法.算法采用了对节点的信道接入请求以概率参数P_T进行过滤的方法控制节点竞争接入信道的激烈程度.不同于已有的DCF机制优化方法,CSB算法的特点在于,在优化调整过程中不需要进行计算复杂的网络节点数量估计,并且可以在不同网络状态下始终围绕确定的优化目标进行参数优化调整.仿真实验结果表明,算法能够针对网络节点数量和分组大小改变等网络状态变化作出自适应的网络优化调整,并获得了系统吞吐量、碰撞概率、延迟、延迟抖动、公平性等多方面的性能改善.     

Credal networks

This paper presents a complete theory of credal networks, structures that associate convex sets of probability measures with directed acyclic graphs. Credal networks are graphical models for precise/imprecise beliefs. The main contribution of this work is a theory of credal networks that displays as much flexibility and representational power as the theory of standard Bayesian networks. Results in this paper show how to express judgements of irrelevance and independence, and how to compute inferences in credal networks. A credal network admits several extensions—several sets of probability measures comply with the constraints represented by a network. Two types of extensions are investigated. The properties of strong extensions are clarified through a new generalization of d-separation, and exact and approximate inference methods are described for strong extensions. Novel results are presented for natural extensions, and linear fractional programming methods are described for natural extensions. The paper also investigates credal networks that are defined globally through perturbations of a single network.     

A random generator of resource-constrained multi-project network problems

Many scheduling problems in project management, manufacturing, and elsewhere require the generation of activity networks to test proposed solution methods. Single-network generators have been used for the resource-constrained project scheduling problem (RCPSP). Since the first single-network generator was proposed in 1993, several advances have been reported in the literature. However, these generators create only one network or project at a time; they cannot generate multi-project problems to desired specifications. This paper presents the first multi-network problem generator. It is especially useful for investigating the resource-constrained multi-project scheduling problem (RCMPSP), where a controlled set of multi-project test problems is crucial for analyzing the performance of solution methods. In addition to the single-project characteristics handled by existing network generators—such as activity duration, resource types and usage, and network size, shape, and complexity—the proposed generator produces multi-project portfolios with controlled resource distributions and amounts of resource contention. To enable the generation of projects with desired levels of network complexity, we also develop several theoretical insights on the effects of network topology on the probability of successful network generation. Finally, we generate 12,320 test problems for a full-factorial experiment and use analysis of means to conclude that the generator produces “near-strongly random” problems. Fully “strongly random” problems require much greater computational expense.     

Hyperform specification: designing and interacting with self-reconfiguring materials

We are on the verge of realizing a new class of material that need not be machined or molded in order to make things. Rather, the material forms and re-forms itself according to software programmed into its component elements. These self-reconfiguring materials are composed of robotic modules that coordinate with each other locally to produce global behaviors. These robotic materials can be used to realize a new class of artifact: a shape that can change over time, i.e., a four-dimensional shape or a hyperform. Hyperforms present several opportunities: objects such as furniture could exhibit dynamic behaviors, could respond to tangible and gestural input, and end-users could customize their form and behavior. To realize these opportunities, the tangible interaction community must begin to consider how we will create and interact with hyperforms. The behaviors that hyperforms can perform will be constrained by the capabilities of the self-reconfiguring materials they are made of. By considering how we will interact with hyperforms, we can inform the design of these systems. In this paper, we discuss the life cycle of a hyperform and the roles designers and end-users play in interacting with hyperforms at these various stages. We consider the interactions such a system could afford as well as how underlying hardware and software affect this interaction. And we consider the extent to which several current hardware systems, including our own prismatic cubes (Weller et al. in Intelligent Robots and Systems. IEEE, 2009), can support the hyperform interactions we envision.     

Diagnostic neural adaptive control of drifting systems

A hierarchical network of neural network planning and control is employed to successfully accomplish a task such as grasping in a cluttered real world environment. In order for the individual robot joint controllers to follow their specific reference commands, information is shared with other neural network controllers and planners within the hierarchy. Each joint controller is initialized with weights that will acceptably control given a change in any of several crucial parameters across a broad operating range. When increased accuracy is needed as parameters drift, the diagnostic node fuzzy supervisor interprets the controller network's diagnostic outputs and transitions the weights to a closest fit specificchild controller. Future reference commands are in turn influenced by the diagnostic outputs of every robot joint neural network controller. The neural network controller and diagnostics are demonstrated for linear and nonlinear plants.