Continuum modeling of cooperative traffic flow dynamics

This paper presents a continuum approach to model the dynamics of cooperative traffic flow. The cooperation is defined in our model in a way that the equipped vehicle can issue and receive a warning massage when there is downstream congestion. Upon receiving the warning massage, the (up-stream) equipped vehicle will adapt the current desired speed to the speed at the congested area in order to avoid sharp deceleration when approaching the congestion. To model the dynamics of such cooperative systems, a multi-class gas-kinetic theory is extended to capture the adaptation of the desired speed of the equipped vehicle to the speed at the downstream congested traffic. Numerical simulations are carried out to show the influence of the penetration rate of the equipped vehicles on traffic flow stability and capacity in a freeway.     

A new fault-management method using congestion-avoidance routing for optical burst-switched networks

Optical burst switching (OBS) has been proposed as a promising technique to support high-bandwidth, bursty data traffic in the next-generation optical Internet. This study investigates a new fault-management framework for an OBS network. In an OBS network, burst-loss performance is a critical concern. In OBS, the data-burst transmission is delayed by an offset time (relative to its burst control packet (BCP), or header), and the burst follows its header without waiting for an acknowledgment for resource reservation. Thus, a burst may be lost at an intermediate node due to contention, which is generally resolved according to the local routing and bandwidth information. The routing table maintained in each OBS node is generally pre-computed and fixed to forward the data bursts. Such a static forwarding feature might have limited efficiency to resolve contentions. Moreover, a burst may be lost and the network may be congested when a network element (e.g., fiber link) fails. Therefore, for reliable burst transport, we develop dynamic routing approaches for preplanned congestion avoidance. Our goal is to proactively avoid congestion during the route-computation process, and our approach employs wavelength-channel utilization, traffic distribution, and link-distance information in the proposed objective functions for routing. Two update mechanisms for maintaining a dynamic routing table are presented to accommodate bursty data traffic. Based on our routing mechanisms, we also propose a new congestion-avoidance-and-protection (CAP) approach, which employs a primary route and a group of backup routes for each node pair against failures and congestion. The performance of the proposed protection strategy using congestion-avoidance routing is demonstrated to be promising through illustrative numerical examples.

基于群智能和冲突规避策略的基因-基因交互作用检测方法

针对当前检测基因-基因交互作用方法中存在的一些缺陷,提出一种基于群智能和冲突规避策略的基因-基因交互作用检测方法（DEIBSC）.以SNP（single nucleotide polymorphism）为研究对象,从大量SNP中选出具有显著基因-基因交互作用的SNP组.初始化多个SNP组作为初值,同时产生多条搜索路径,利用得分单调递增原则寻找问题的解,通过冲突规避策略和群智能动态调整搜索路径的方向,使得到的解更能反映基因-基因交互作用在基因组范围内分布的情况.在仿真数据和真实数据上的实验证实,本文方法在统计能力上可以和SNPHarvester方法相比,在效率上有明显优势,得到的结果能够更广泛地代表基因-基因交互作用在基因组的分布.     

A full-scale solution to the rectilinear obstacle-avoiding Steiner problem

Routing is one of the important steps in very/ultra large-scale integration (VLSI/ULSI) physical design. Rectilinear Steiner minimal tree (RSMT) construction is an essential part of routing. Macro cells, IP blocks, and pre-routed nets are often regarded as obstacles in the routing phase. Obstacle-avoiding RSMT (OARSMT) algorithms are useful for practical routing applications. However, OARSMT algorithms for multi-terminal net routing still cannot meet the requirements of practical applications. This paper focuses on the OARSMT problem and gives a solution to full-scale nets based on two algorithms, namely An-OARSMan and FORSTer. (1) Based on ant colony optimization (ACO), An-OARSMan can be used for common scale nets with less than 100 terminals in a circuit. An heuristic, greedy obstacle penalty distance (OP-distance), is used in the algorithm and performed on the track graph. (2) FORSTer is a three-step heuristic used for large-scale nets with more than 100 terminals in a circuit. In Step 1, it first partitions all terminals into some subsets in the presence of obstacles. In Step 2, it then connects terminals in each connected graph with one or more trees, respectively. In Step 3, it finally connects the forest consisting of trees constructed in Step 2 into a complete Steiner tree spanning all terminals while avoiding all obstacles. (3) These two graph-based algorithms have been implemented and tested on different kinds of cases. Experimental results show that An-OARSMan can handle both convex and concave polygon obstacles with short wire length. It achieves the optimal solution in the cases with no more than seven terminals. The experimental results also show that FORSTer has short running time, which is suitable for routing large-scale nets among obstacles, even for routing a net with one thousand terminals in the presence of 100 rectangular obstacles.     

Management of food-chain systems via Liapunov design control

A general food-chain system involving control is considered. A Liapunov design methodology is used to establish a control growth policy of qualitative nature, aimed to restrict the fluctuations of the size of the chain elements (populations, consumers, resources). The policy is based on the concept of avoidance control.Invited talk at 14 Symposium on Operations Research, Ulm, September 1989.     

Nonequilibrium statistical mechanics of finite classical systems-I

It is pointed out that the fine-grained probability density of statistical mechanics is of interest only through coarse-grained densities—integrals over nonzero volumes of phase space. This suggests the definition of a smoothed probability density: the unsmoothed density convoluted with a kernel having a small spread aroundzero velocity. If this kernel is of Gaussian form, the smoothed density satisfies a closed and exact equation for its evolution differing from the Liouville equation by the addition of one term. This equation is applied to the simple example of a noninteracting system. We need make no assumption about the size of the system in our discussion, though if the system is large enough, the assumption that it is infinite gives the same results. Reduced distribution functions are then discussed, and a treatment of the Landau damping of electron plasma oscillations is given that is free from the usual difficulties occasioned by the breakdown of the linearization.Formerly at Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, England.     

A Distributed Packet Scheduling Scheme with Interference Avoidance for Non Real-Time Applications in CDMA Networks

In this paper, a packet scheduling scheme based on real-time channel conditions and dominant intercell interferer avoidance is proposed, studied and evaluated for reverse links in a time-slotted code division multiple access (CDMA) system. This scheme is implemented by distribution of tags by receivers among transmitters. Each base station issues M(1) tags to M mobile users based on the ranked reverse link gains in every slot. M=1 corresponds to spread-spectrum time division multiplexing mode operation and M1 corresponds to scheduling multiple simultaneous transmissions as in the traditional CDMA systems. The number of issued tags is a system parameter which depends on the expected traffic, the number of cells and the propagation conditions in the network. In the proposed scheme, users who not only have stronger channel gains to their respective home base stations but also cause relatively lower intercell interference are scheduled for transmissions. Different classes of tags can be issued and various scheduling decision rules can be implemented giving flexibility in interference management. Simulation results in shadow and multipath fading environment are presented to show the performance advantage of the proposed scheme.     

State constraints in the linear regulator problem: Case study

In this paper, we consider the problem of minimum-norm control of the double integrator with bilateral inequality constraints for the output. We approximate the constraints by piecewise linear functions and prove that the Langrange multipliers associated with the state constraints of the approximating problem are discrete measures, concentrated in at most two points in every interval of discretization. This allows us to reduce the problem to a convex finite-dimensional optimization problem. An algorithm based on this reduction is proposed and its convergence is examined. Numerical examples illustrate our approach. We also discuss regularity properties of the optimal control for a higher-dimensional state-constrained linear regulator problem.The first author was supported by the National Science Foundation, Grant No. DMS-9404431. The second author was supported by a François-Xavier Bagnoud Doctoral Fellowship and by NSF Grants DMS-9404431 and MSS-9114630.     

一种新的基于网络丢包率的主动队列管理策略

提出了一种新的基于网络丢包率的动态自适应的主动队列管理的改进算法。该算法首先用早期网络的丢包率标记到达的数据包,并作为数据包的丢弃概率。这样使得到达数据包的丢弃概率逼近当前实际网络的丢包率,然后经过自适应调整丢弃概率使得缓冲队列长度保持在一定范围内。通过NS仿真实验表明了该算法可以很好的控制队列长度,降低延迟抖动。     

Understanding publics’ post-crisis social media engagement behaviors: An examination of antecedents and mediators

This study examines the psychological mechanisms underlying the process that enables publics’ individual differences (e.g., the levels of uncertainty avoidance and social media usage) to give rise to varying post-crisis social media engagement intentions (e.g., information seeking, support seeking, and negative word-of-mouth). The study confirms that this process is serially mediated by perceived threat severity, perceived susceptibility, and negative emotions. These psychological mediators, however, function differently between uncertainty avoidance and social media usage. For uncertainty avoidance, a high arousal negative emotion (e.g., anger, fear) is a more essential step to influence engagement intentions than a low arousal emotion (e.g., shame, guilt). For social media usage, however, the type of aroused negative emotions does not matter. Rather, the relationship social media usage has with information seeking is different from that with support seeking and negative word-of-mouth intentions. Social media usage induces information seeking intentions only through publics’ cognitive appraisals of the situation without the activation of negative emotions, while it induces supporting seeking and negative word-of-mouth intentions through both cognitive appraisals and negative emotion arousals.