Green cell association for multimedia transmission in cognitive heterogeneous networks

With the introduction of low‐powered pico/femto‐base stations and relay nodes into the macro‐cell, recent heterogeneous networks provide an attractive approach for future wireless communication. Although it may achieve better coverage and higher capacity, several problems remain unsolved before practical deployment. For example, how to select the proper cell from neighbor low‐powered cells and then occupy the radio resource without interference on macro‐users is both important and challenging, especially for rigorous multimedia applications. The traditional cell access algorithms and quality‐control parameters such as delay or throughput no longer suit well in this complex environment. An effective approach should be pursued. In this paper, we investigate this interesting cell association problem and propose a complete green resolution on the basis of thorough discussions about the multimedia transmission under these concerns. Cognitive radio is introduced to share spectrum between macro‐cell and low‐powered cells while securing the transmission of authorized macro‐users. We also bring forth the concept of ‘interference balance’ to better manage the overall interference and energy consumption in the network. Restless bandit model is formulated on the basis of channel state, data rate, interference control, and the carefully chosen intra‐refreshing rate for multimedia traffic. Then the cell association scheme is designed to be efficient and practical because of the simple index property of our model output. Simulation results have proven the performance of our proposed resolution compared with existing algorithms on interference constraint, multimedia distortion, and overall network energy consumption balance. Copyright © 2013 John Wiley & Sons, Ltd.     

ATM无源光网络中直流耦合突发模式光接收机分析

本文根据异步传输模式(ATM)无源光网络(APON)的实际要求,对直流耦合突发模式光接收机进行了理论分析,结果表明基于动态峰值检测的突发模式接收机其灵敏度代价和传输容量代价过高,而基于局部峰值检测的突发模式接收机则可较好满足APON的要求.     

Laminar flows of a non-newtonian fluid in mild stenosis

The laminar steady and nonsteady flows of non-Newtonian fluids through a tube whose radius varies slowly in the axial direction are adopted as an approximation of the flows in blood vessels with irregular walls. A perturbation and a numerical method are presented for determining the velocity distribution, the pressure drop along the tube and the wall stress.     

Optimal exchange renewal strategies for local telephone networks

The problem of planning the introduction of multiple digital switching systems with remote concentrator options into a local telephone network essentially consists in finding an optimal network evolution strategy. Such a strategy is defined by the type, location and time of placement of electronic exchanges and remote concentrators, as well as the assignment of remote concentrators to electronic exchanges. Several mathematical formulations of the problem are discussed, and a practical and realistic model is suggested. The model is solved by a heuristic two-level hierarchical optimization procedure, which is computationally efficient and produces good approximate solutions. Computational experiments and practical uses of the model are reported.     

面向主动脉缩窄辅助诊断的神经网络模型设计

为了辅助临床医生更快、更准确地进行主动脉缩窄的术前评估,结合心脏计算机断层扫描图像的三维空间特征,提出一种基于三维卷积神经网络的主动脉缩窄辅助诊断模型。相比于传统主动脉缩窄辅助诊断方法,使用这种新模型可在提高诊断结果可靠性的同时,直接面向图像操作,无需进行繁杂的数据预处理,诊断准确率、查准率和查全率均有显著提高。     

An Effective Cloud Workflow Scheduling Approach Combining PSO and Idle Time Slot-Aware Rules

Workflow scheduling is a key issue and remains a challenging problem in cloud computing.Faced with the large number of virtual machine(VM)types offered by cloud providers,cloud users need to choose the most appropriate VM type for each task.Multiple task scheduling sequences exist in a workflow application.Different task scheduling sequences have a significant impact on the scheduling performance.It is not easy to determine the most appropriate set of VM types for tasks and the best task scheduling sequence.Besides,the idle time slots on VM instances should be used fully to increase resources'utilization and save the execution cost of a workflow.This paper considers these three aspects simultaneously and proposes a cloud workflow scheduling approach which combines particle swarm optimization(PSO)and idle time slot-aware rules,to minimize the execution cost of a workflow application under a deadline constraint.A new particle encoding is devised to represent the VM type required by each task and the scheduling sequence of tasks.An idle time slot-aware decoding procedure is proposed to decode a particle into a scheduling solution.To handle tasks'invalid priorities caused by the randomness of PSO,a repair method is used to repair those priorities to produce valid task scheduling sequences.The proposed approach is compared with state-of-the-art cloud workflow scheduling algorithms.Experiments show that the proposed approach outperforms the comparative algorithms in terms of both of the execution cost and the success rate in meeting the deadline.     

一种新的共享密钥安全协议设计方法

为了设计出具有高安全性的安全协议,提出了一种面向主体的逻辑,可以形式化和系统地设计共享密钥安全协议;根据可以提供的不同安全服务,将密码机制抽象为不同信道,这样在设计安全协议时不必考虑密码机制的实现细节;提出安全协议的转发设计规则,将设计规则作为预防攻击的有效措施;运用该逻辑和设计规则设计了一种新的共享密钥安全协议,该协议能达到相互身份认证和密钥分发目的,并能预防与设计规则相对应的攻击。     

Synthesis of digital optimal reduced-order compensators for asynchronously sampled systems

The synthesis of finite-horizon digital optimal reduced-order compensators is presented, for asynchronous and aperiodically sampled continuous-time systems. The dimensions of the compensator state are a priori fixed and may be time varying. Asynchronous and aperiodic sampling refers to a deterministic sampling scheme where an arbitrary, but a priori known, number of control variables is updated, and/or an arbitrary, but a priori known, number of outputs is sampled, at arbitrary, but a priori known, time instants. This sampling scheme generalizes most deterministic sampling schemes considered in the control literature. Through the use of an integral criterion the intersample behaviour is explicitly considered in the design. As a result, frequent, synchronous and periodic sampling is no longer necessary, which can be highly relevant in practice. Also the synthesis enables comparison of the optimal performance of reduced-order compensators as a function of their dimensions and the sampling scheme. The synthesis is illustrated with a numerical example.     

The rational approximations of the unitary groups

This paper is to investigate the rational approximation of the unitary groups. Specially, based on the Household decomposition we prove that the rational unitary subgroup is dense in the complex unitary group. Moreover, its random approximate property is characterized by the natural Harr measure, which can be used to obtain random unitary matrix. Our simulation shows that these results may be applied to approximate quantum computations.