Distributed computing for carbon footprint reduction by exploiting low-footprint energy availability

Low carbon footprint energy sources such as solar and wind power typically suffer from unpredictable or limited availability. By globally distributing a number of these renewable sources, these effects can largely be compensated for. We look at the feasibility of this approach for powering already distributed data centers in order to operate at a reduced total carbon footprint. From our study we show that carbon footprint reductions are possible, but that these are highly dependent on the approach and parameters involved. Especially the manufacturing footprint and the geographical region are critical parameters to consider. Deploying additional data centers can help in reducing the total carbon footprint, but substantial reductions can be achieved when data centers with nominal capacity well below maximum capacity redistribute processing to sites based on renewable energy availability.     

无线应变测量节点的精度与功耗综合分析

在无线传感器网络中,一般采用电池供电,如何取得精度和功耗的平衡十分重要.应变片功耗与其他传感器相比大得多,直接决定无线节点总功耗.系统设计时,不但要考虑电路参数和器件噪声对精度的影响,功耗分析也很必要.从无线节点整体框架出发,系统分析了模拟和数字电路中精度和功耗的影响机理,建立了完整的理论模型.精度和功耗同时受电桥电压影响,电桥电压越高,精度越高,但功耗也越大,精度与功耗相互制约.以电桥电压和器件参数为影响因素,提出了在保证测量精度的同时,减小电路功耗的方法.在设计无线应变测量节点时,该研究可以为实现系统精度和功耗的平衡提供理论指导.     

A note on models for non-probabilistic analysis of packet switching networks

We consider two models commonly used in the literature to model adversarial injection of packets into a packet switching network. We establish the relation between these two types of models, and between them and the set of sequences of packets that allow stability. We also consider the adaptive setting in which packets are injected with only their source and destination but without a prescribed path to follow.     

包交换网络中调度方法进展：扩展性分析

1.引言现在Internet主要提供无服务质量(QoS)保证的尽力服务(best effort)。随着Internet朝着提供包括数据、声音、视频等多服务统一的多媒体通讯平台发展,传统的Internet已经不能满足不同的应用在吞吐率、延迟、延迟抖动、丢失率等方面的不同要求。服务质量控制作为网络提供保证服务的手段在近十多年的时间里得到了广泛的研究。传统的服务质量研究主要基于集成服务(Intserv/RSVP)模型。这种模型的基本思想是为每一个流提供端到端的服务质量控制,它的实     

一种融合电路交换与分组交换的方法

提出了基于TCP交换技术的电路交换与分组交换融合的新方法,分析了TCP交换需要解决的主要问题,较详细的讨论了TCP交换中由IP路由协议创建与撤销电路链路的过程,边界路由器与核心路由交换机所需完成的主要功能与任务以及实现TCP交换所必须研究的关键技术。     

Competitive On-Line Switching Policies

Abstract. Consider the following problem. A switch connecting n input channels to a single output channel must deliver all incoming messages through this channel. Messages are composed of packets , and in each time slot the switch can deliver a single packet from one of the input queues to the output channel. In order to prevent packet loss, a buffer is maintained for each input channel. The goal of a switching policy is to minimize the maximum buffer size. The setting is on-line; decisions must be made based on the current state without knowledge of future events. This general scenario models multiplexing tasks in various systems such as communication networks, cable modem systems, and traffic control. Traditionally, researchers analyzed the performance of a given policy assuming some distribution on the arrival rates of messages at the input queues, or assuming that the service rate is at least the aggregate of all the input rates. We use competitive analysis, avoiding any prior assumptions on the input. We show O(log n )-competitive switching policies for the problem and demonstrate matching lower bounds.     

一种输入排队交换结构的自适应包切分策略

针对传统的输入排队交换结构的数据包切分策略带宽利用率低、灵活性差等缺点,提出一种自适应包切分策略。新策略利用集中式调度的同步特性,在调度过程中通过输入端的队列状态来确定切分单元的大小,并动态调整算法匹配时间,有效地减少了填充字节和系统所需加速比。仿真分析表明,与现有的包切分策略相比,采用自适应策略的交换结构更能适应实际网络环境,且具有良好的时延性能。     

新型航天飞行器20kW级空间电源设计

具有升压、降压,能量双向流动的空间电源成为新型航天飞行器的研究热点和关键技术。本文设计一种20kW级多路双向半桥结构的空间电源,具有以下功能和特点：拓扑结构简单,采用PWM闭环控制,利用Boost电路升压,Buck电路降压,不仅能够实现能量双向流动,而且可适应不同工况,不同输入电压下可选择不同电压恒压输出,电压精度高,电流纹波较小,系统效率高,体积和重量小,具有故障保护功能,可靠性高。     

Maximizing throughput in multi-queue switches

We study a basic problem in Multi-Queue switches. A switch connectsm input ports to a single output port. Each input port is equipped with an incoming FIFO queue with bounded capacityB. A switch serves its input queues by transmitting packets arriving at these queues, one packet per time unit. Since the arrival rate can be higher than the transmission rate and each queue has limited capacity, packet loss may occur as a result of insufficient queue space. The goal is to maximize the number of transmitted packets. This general scenario models most current networks (e.g. IP networks) which only support a “best effort” service in which all packet streams are treated equally. A 2-competitive algorithm for this problem was designed in [5] for arbitraryB. Recently, a (17/9 ≈ 1.89)-competitive algorithm was presented forB>1 in [3]. Our main result in this paper shows that forB which is not too small our algorithm can do better than 1.89, and approach a competitive ratio ofe/(e − 1) ≈ 1.58. The research of Yossi Azar was supported in part by the Israeli Ministry of Industry and Trade and by the Israel Science Foundation.     

Sustainability in Web server systems

The exponential growth of Internet during the last decade leads us to make more efforts in the researching and developing of sustainable Web servers in order to decrease the global energy demand. In this paper, we cover, as a first step, a proper review of the literature related to the energy efficiency research in Web server systems to depict the state of the art to plan further contributions as more research in sustainable Web systems. We also propose and implement an energy metric that permits to establish a relation between the Quality of Service (QoS) obtained by the system and the power it consumes.     

Cluster Size Optimization in Sensor Networks with Decentralized Cluster-Based Protocols

Network lifetime and energy-efficiency are viewed as the dominating considerations in designing cluster-based communication protocols for wireless sensor networks. This paper analytically provides the optimal cluster size that minimizes the total energy expenditure in such networks, where all sensors communicate data through their elected cluster heads to the base station in a decentralized fashion. LEACH, LEACH-Coverage, and DBS comprise three cluster-based protocols investigated in this paper that do not require any centralized support from a certain node. The analytical outcomes are given in the form of closed-form expressions for various widely-used network configurations. Extensive simulations on different networks are used to confirm the expectations based on the analytical results. To obtain a thorough understanding of the results, cluster number variability problem is identified and inspected from the energy consumption point of view.     

用瞬时电压箝位改进CMOS电路ESD防护

包含倒相器的小的瞬时电压箝位保护电路可能在一个HBM ESD事件期间产生振荡而且使箝位脱离。用0.25μm工艺生产的一个瞬时电压箝位电路可以使问题得到解决,其方法是在最后一个倒相器处增加一个电阻,这样可以提高电路的ESD防护能力。     

全自动化电路板在线检测系统

为了降低检测成本,同时提高电路板的检测效率和准确率,设计了一种全自动化电路板检测系统。该系统在不改变现有生产线的情况下,能轻松对接电路板生产线,实现成品电路板质量检测的全自动化,并且可以接入工厂的FIS系统,实现了对产线的全面改造升级。系统选用工控机和ADLINK PCI-7432 IO卡来构成主控硬件平台;在Qt软件开发环境下完成主控机软件的开发,控制接驳台、机械手和ICT检测箱协调工作,完成对电路板的全自动检测。为了适配不同的电路板生产线,提高系统的通用性,该检测系统允许人工配置产线信息。经过电路板生产厂家的实际应用,该系统运行可靠稳定,与传统的人工检测方法相比自动化检测速度为比人工快1倍,误检率为0.2%,大大提高了生产效率,降低了生产成本。     

磁力轴承功率放大器的研究和设计

在磁力轴承控制器的基础上，设计了一种磁力轴承功率放大器功率电路，对电路进行了过流保护和过压保护。实验表明，采用本文设计的功率电路，可有效降低系统损耗，实现电流的无损开通和关断，极大地提高了功率放大器的稳定性和可靠性。本研究为进一步提高功放寿命，优化功放设计具有一定的参考价值。     

升压直流电能收集充电器

该电能收集充电器采用基于ARM？CortexTM—M3的LM3S1138微控制器,它为嵌入武微控制器应用方案带来了高性能的32位运算能力。该系统主要由硬件来实现,通过boost电路实现直流电压之间的转换和提升并完成直流电源变换器的功能。LM3S1138内置的10位A／D转换器能够实现精确采样以监测电压的微小变化,并通过LCD液晶显示屏显示,其界面友好,性能优良。应用软件则主要完成系统监测和控制。它全部采用C语言编程,实现基本监测、控制和输出功能,并可收集微弱输入电压或通常电压对不同的电池充电,同时还具有超时报警等功能。该系统资源丰富,还可方便地扩展其附加功能。     

一种全双工认知中继网络中实现能量高效的安全传输方法

在“绿色”安全通信背景下,提出了一种保证同时同频全双工认知中继网络物理层安全、不影响主用户性能且能量高效的中继簇功率分配方案,该网络包含两个认知源节点、多个认知中继节点、多个主用户节点以及多个主用户窃听节点。在考虑了自干扰消除率以及中继转发信息的公平性的基础上,分别针对中继节点选择放大转发与译码转发策略的情形,设计协作波束成形向量及人工噪声矩阵,并通过一种结合半定松弛技术的爬山算法来获取最优解。仿真结果与理论分析表明了方案的有效性与合理性,同时表明选择放大转发策略能够获取更高的总能量效率。