Modeling and simulation of self-similar variable bit rate compressed video: A unified approach

Variable bit rate (VBR) compressed video is expected to become one of the major loading factors in high-speed packet networks such asATM-based B-ISDN. However, recent measurements based on long empirical traces (complete movies) revealed that VBR video tra c possesses self-similar (or fractal) characteristics, meaning that the dependence in the tra c stream lasts much longer than traditional models can capture. In this paper, we present a uni ed approach which, in addition to accurately modeling the marginal distribution of empirical video records, also models directly both the short and the long-term empirical autocorrelation structures. We also present simulation results using synthetic data and compare with results based on empirical video traces. Furthermore, we extend the application of e cient estimation techniques based on importance sampling that we had used before only for simple fractal processes. We use importance sampling techniques to e ciently estimate low probabilities of packet losses that occur when a multiplexer is fed with synthetic tra c from our self-similar VBR video model.

IoT-B&B: Edge-Based NFV for IoT Devices with CPE Crowdsourcing

For embracing the ubiquitous Internet-of-Things (IoT) devices, edge computing and Network Function Virtualization (NFV) have been enabled in branch offices and homes in the form of virtual Customer-Premises Equipment (vCPE). A Service Provider (SP) deploys vCPE instances as Virtual Network Functions (VNFs) on top of generic physical Customer-Premises Equipment (pCPE) to ease administration. Upon a usage surge of IoT devices at a certain part of the network, vCPU, memory, and other resource limitations of a single pCPE node make it difficult to add new services handling the high demand. In this paper, we present IoT-B&B, a novel architecture featuring resource sharing of pCPE nodes. When a pCPE node has sharable resources available, the SP will utilize its free resources as a "bed-and-breakfast" place to deploy vCPE instances in need. A placement algorithm is also presented to assign vCPE instances to a cost-efficient pCPE node. By keeping vCPE instances at the network edge, their costs of hosting are reduced. Meanwhile, the transmission latencies are maintained at acceptable levels for processing real-time data burst from IoT devices. The traffic load to the remote, centralized cloud can be substantially reduced

Positive and negative intergroup contact and willingness to engage in intergroup interactions among high-status (Han) and low-status (Uyghur) group members in China: The moderating role of social dominance orientation

The present study investigated whether the associations of positive and negative intergroup contact with behavioral intentions (intentions to have contact with the outgroup in the future) are moderated by social dominance orientation (SDO), by considering the perspective of both high- and low-status group members in the context of China. Participants were 325 Han (high-status) and 373 Uyghur (low-status) members, who completed a self-report questionnaire. Results indicated that positive contact was associated with more positive behavioral intentions among high-SDO high-status group members, whereas SDO did not moderate the association between positive contact and behavioral intentions among low-status group members. In addition, negative contact was associated with lower behavioral intentions among high-SDO high-status group members, and among low-SDO low-status group members. This study suggests that attention should be placed simultaneously on positive and negative contact and on individual difference variables relevant to social ideologies, such as SDO

Highly chlorinated PCBs inhibit the human xenobiotic response mediated by the steroid and xenobiotic receptor (SXR).

Polychlorinated biphenyls (PCBs) are a family of persistent organic contaminants suspected to cause adverse effects in wildlife and humans. In rodents, PCBs bind to the aryl hydrocarbon (AhR) and pregnane X receptors (PXR) inducing the expression of catabolic cytochrome p450 enzymes of the CYP1A and 3A families. We found that certain highly chlorinated PCBs are potent activators of rodent PXR but antagonize its human ortholog, the steroid and xenobiotic receptor (SXR), inhibiting target gene induction. Thus, exposure to PCBs may blunt the human xenobiotic response, inhibiting the detoxification of steroids, bioactive dietary compounds, and xenobiotics normally mediated by SXR. The antagonistic PCBs are among the most stable and abundant in human tissues. These findings have important implications for understanding the biologic effects of PCB exposure and the use of animal models to predict the attendant risk

Coordination of preventive, emergency and restoration dispatch against cascading failures for resilience enhancement

Blackout events caused by cascading failures have induced enormous losses in power systems. Good defense strategies are helpful for stopping cascading failures spread, which not only reduces system losses, but also improves the system’s ability to cope with the cascading failures. However, the current studies mostly focus on single-stage defense strategy and lack coordination of preventive, emergency and restoration dispatch (CPERD) against cascading failures. This paper proposes a CPERD methodology to counteract cascading failures for resilience enhancement. We first analyze the propagation mechanism and the prediction method for the propagation paths of cascading failures. Second, we explore the necessity and feasibility of whole-process coordinated dispatch under cascading failures and design a CPERD model framework. Based on this framework, we further analyze the impact of whole-process coordinated dispatch on the propagation path of cascading failures. Third, preventive dispatch, emergency dispatch and restoration dispatch sub-models are separately modeled to minimize the dispatch cost. Since the model has the characteristics of multi-stage and multi-objective, a double-layer optimization framework and an improved particle swarm optimization algorithm are introduced to solve the CPERD problem. Finally, the IEEE 39-bus and IEEE 118-bus test systems are taken as examples for simulation analysis. The results show that whole-process coordinated dispatch can effectively reduce the final load loss and overall dispatch cost, and enhance power system resilience against cascading failures