Cooling Load Density Analysis and Optimization for an Endoreversible Air Refrigerator

The performance analysis and optimization of an endoreversible air refrigerator is carried out by taking the cooling load density, which is defined as the ratio of cooling load to the maximum specific volume in the cycle, as the optimization objective in this paper. The results obtained are different from those with the cooling load objective. Numerical examples show the effects of pressure ratio and allocation of heat exchanger inventory on the cooling load density of the refrigerator.     

Power Density Optimization for an Irreversible Closed Brayton Cycle

In this paper, the power density, defined as the ratio of power output to the maximum specific volume in the cycle, is taken as objective for performance optimization of an irreversible closed Brayton cycle coupled to constant-temperature heat reservoirs in the viewpoint of finite time thermodynamics (FTT) or entropy generation minimization (EGM). The analytical formulas about the relations between power density and pressure ratio are derived with the heat resistance losses in the hot- and cold-side heat exchangers and the irreversible compression and expansion losses in the compressor and turbine. The maximum power density optimization is performed by searching the optimum heat conductance distribution corresponding to the optimum power density of the hot- and cold- side heat exchangers for the fixed heat exchanger inventory. The influence of some design parameters on the optimum heat conductance distribution, the maximum power density, and the optimum pressure ratio corresponding to the maximum power density are provided. The power plant design with optimization leads to a higher efficiency and smaller size including the compressor, turbine, and the hot- and cold-side heat exchangers.     

Ecological Optimization Performance of An Irreversible Quantum Otto Cycle Working with an Ideal Fermi Gas

The model of an irreversible Otto cycle using an ideal Fermi gas as the working fluid, which is called as the irreversible Fermi Otto cycle, is established in this paper. Based on the equation of state of an ideal Fermi gas, the ecological optimization performance of an irreversible Fermi Otto cycle is examined by taking an ecological optimization criterion as the objective, which consists of maximizing a function representing the best compromise between the exergy output and exergy loss (entropy production) of the cycle. The relationship between the ecological function E and the efficiency η is studied. Three special cases are discussed in detail. The results obtained herein may reveal the general performance characteristics of the irreversible Fermi Otto cycle.     

基于GRNN的冰蓄冷空调逐时冷负荷预测

冷负荷动态预测对冰蓄冷空调最优化控制来说是不可或缺的.建立了基于广义回归神经网络(GRNN)和遗传算法(GA)的逐时冷负荷预测模型,建模时以前一日已知的24小时室外干球温度为输入,以次日逐时冷负荷为输出.为提高预测精度及改善鲁棒性,以均方差(MSE)最小构造适应度函数,应用遗传算法寻优广义回归神经网络的平滑因子.通过预测负荷与实际负荷的比较分析验证了模型的可靠性和鲁棒性.     

基于现状负荷成熟度校验的负荷密度指标选取方法研究

传统的基于用地仿真法的空间负荷预测方法对各种环境因素的考虑并不完善,而且对于这些环境因素,评价的指标越多,模糊规则也就越多、越复杂,已经不能够满足电力规划实际需求。本文提出了一种规范化的可以直接考虑各种实际地块建设状态要素的饱和负荷密度指标选取新方法。该方法提出了“负荷成熟度”、“负荷达成率”及“建成投产率”的概念,考虑城市发展和改造的不确定性,把区域负荷指标与区域发展定位及市政建设进度情况相结合,指标选取紧密关联现状实际情况。据此,进一步形成负荷指标的评价优选模型,以模型方法对城市地块饱和负荷指标值进行迭代计算,并对异常指标进行负荷指标修正,最终得到最符合全区实际发展远景的饱和负荷预测指标值。     

Optimization Zone on the Performance of a Generalized Irreversible Magnetic Stirling Cryocooler

Finite time thermodynamic performance of a generalized irreversible magnetic Stirling cryocooler coupled to constant-temperature heat reservoirs has been analyzed in this paper. The relationship between the optimal cooling load and the coefficient of performance for the magnetic Stirling cryocooler is derived. The optimization zone on the performance of the cryocooler is obtained. The results obtained here will be useful for the further understanding and the selection of the optimal operating conditions for a magnetic Stirling cooler.     

现代计算机冷却系统的优化设计

本文论述了为建立“低（热）阻高效”热传送系统,必须对现代计算机冷却系统进行优化设计的必要性和重要性,以及优化设计的基本思路、过程、要求和方法。     

中压配电网电力空间负荷密度分布仿真

针对传统方法没有考虑到同类负荷分布不均,导致无法为电力预测提供可靠的数据基础的问题,提出一种中压配电网应用电力空间负荷密度特性研究方法。按照中压配电网应用电力空间实际情况,通过元胞生成在应用电力空间中完成土地使用种类的模拟,利用GIS平台得到元胞的空间分布以及涉及属性数据,形成数据表。通过均匀核函数获取核密度计算的一般形式,采用核估计实现中压配电网应用电力空间负荷密度计算,解决负荷分布不均的问题,并确定中压配电网应用电力空间负荷密度及其置信区间。在此基础上运用Logistic曲线对负荷密度指标进行拟合,通过回归模型获取不同产业占比和负荷密度间的关系,得到差异分位数下负荷密度指标和各产业占比间的定量关系,获取负荷密度分布特性。分析实验结果得出,所提方法研究结果和实际结果基本一致,方法可靠。     

The Performance Analysis of a Quantum Brayton Refrigeration Cycle with an Ideal Bose Gas

A Brayton refrigeration cycle using an ideal Bose gas as the working substance is simply referred to as a quantum Brayton refrigeration cycle, which consists of two constant-pressure and two adiabatic processes. The influence of quantum degeneracy on the performance of the cycle is investigated, based on the correction equation of state of an ideal Bose gas. The general expressions of the coefficient of performance, refrigeration load and work input of the cycle are calculated. The lowest temperature of the working substance and the minimum pressure ratio of the two constant-pressure processes for a quantum Brayton refrigeration cycle are determined. The variations of the relative refrigeration load with the temperature of the cooled space and the pressure of the low constant-pressure process are discussed for three special cases. Some curves related to the important performance parameters are given. The results obtained here are compared with those of a classical Brayton refrigeration cycle using an ideal gas as the working substance. Some significant conclusions are obtained.     

基于聚类的对等网络负载优化算法研究

减少系统的资源消耗是对等网络设计的目标之一。该文对基于聚类的对等网络建立了负载的抽象模型,根据实际系统中采集的数据分析了节点的动态特性,并分别在节点能力相同、节点的能力的异构和系统处于动态的情况下,对聚类的数目进行了优化分析,为设计和构造对等网络提供了依据。     

MongoDB负载均衡算法优化研究

随着Web2.0网络应用的兴起和大数据技术的发展,传统的关系型数据库(ORDBMS)已经难以满足海量数据的存储需求。非关系型数据库(NoSQL)因其高扩展性、高伸缩性、高可用性和容错性等特点,得到了越来越多的应用。作为一种新兴的NoSQL数据库,MongoDB数据库因具有模式自由、易于扩展、故障自动恢复、支持自动分片等特点,被广泛应用于大数据处理与分析中。文中首先介绍了MongoDB自动分片架构原理和实现机制,然后分析了MongoDB自带的负载均衡算法,其虽能使各个节点数据量达到平衡,但没有考虑各个节点的负载均衡。为了解决节点的负载平均问题,在原算法基础上提出了一种基于节点实时负载的负载均衡改进算法,改进算法的主要思想是引入节点负载指数作为chunk块迁移的一个判断条件。通过搭建测试环境并进行实验,验证了改进的负载均衡算法可以有效地均衡分片中的数据,提高集群的并发读写性能,从而证明了算法的有效性。     

一种业务部署的负载平衡优化算法

下一代网络(NGN)中业务部署的负载平衡问题不仅要考虑业务本身对资源的使用,还要考虑业务之间的协作。针对以上特性,该文提出了一种基于递归优化的算法,在减少业务协作对通信带宽消耗的同时,使异构系统达到负载平衡。实验证明了该算法的有效性。     

Co-evolution of Density and Topology in a Simple Model of City Formation

We study the influence that population density and the road network have on each others’ growth and evolution. We use a simple model of formation and evolution of city roads which reproduces the most important empirical features of street networks in cities. Within this framework, we explicitly introduce the topology of the road network and analyze how it evolves and interact with the evolution of population density. We show that accessibility issues -pushing individuals to get closer to high centrality nodes- lead to high density regions and the appearance of densely populated centers. In particular, this model reproduces the empirical fact that the density profile decreases exponentially from a core district. In this simplified model, the size of the core district depends on the relative importance of transportation and rent costs.     

CDMA系统寻呼负荷的估算和优化

研究了CDMA寻呼信道的结构,计算了各种消息的寻呼信道占用率,得出了寻呼负荷和忙时用户呼叫尝试次数（BHCA）之间的函数关系。在对郑州的CDMA网络寻呼负荷估算之后,提出了分区域寻呼的解决方案,将系统的寻呼负荷由峰值的65％降低到峰值的 50％左右。     

连铸二冷配水自适应动态优化控制

在常规连铸二冷配水控制方法的基础上,提出了自适应动态配水控制策略,建立了由基础自动控制、 软测量技术和智能控制技术相结合的二级动态配水控制系统．在控制系统中,建立了基于凝固传热理论的软测量模 型,用于实时预测铸坯表面温度;应用基于自整定神经元的多变量PID 控制算法,实现连铸二冷配水动态单元跟踪 控制,使铸坯表面温度保持在目标值范围内．仿真及应用结果表明了所建模型和控制算法的有效性,控制系统对拉 速扰动具有良好的目标温度跟随性能．     

Effect of Heat Transfer Law on the Ecological Optimization of a Generalized Irreversible Carnot Engine

The optimal ecological performance of a irreversible Carnot engine with the losses of heat-resistance, heat leak and internal irreversibility, in which the transfer between the working fluid and the heat reservoirs obeys a generalized heat transfer law Q ∝ δ(Tⁿ), is derived by taking an ecological optimization criterion as the objective, which consists of maximizing a function representing the best compromise between the power and entropy production rate of the heat engine. Some special examples are discusses. A numerical example is given to show the effects of heat transfer law, heat leakage and internal irreversibility on the optimal performance of the generalized irreversible heat engine. The results can provide some theoretical guidance for the designs of practical engine.     

民航客机货舱自动配平优化技术

民航客机配载是飞机勤务关键步骤之一,随着工业互联网发展和航空业对自身服务要求的提高,手工配载操作出现了效率瓶颈,机场各项业务操作必将向自动化、智能化发展,其数字化势在必行.现存的部分算法不能较好地适应民航客机配载的多约束、多变动环境,依赖地勤工作人员进行手动调整.本文将配载环境中涉及到的各种约束条件和配载流程进行结构化...     

Runtime Analysis of a Simple Ant Colony Optimization Algorithm

Ant Colony Optimization (ACO) has become quite popular in recent years. In contrast to many successful applications, the theoretical foundation of this randomized search heuristic is rather weak. Building up such a theory is demanded to understand how these heuristics work as well as to come up with better algorithms for certain problems. Up to now, only convergence results have been achieved showing that optimal solutions can be obtained in finite time. We present the first runtime analysis of an ACO algorithm, which transfers many rigorous results with respect to the runtime of a simple evolutionary algorithm to our algorithm. Moreover, we examine the choice of the evaporation factor, a crucial parameter in ACO algorithms, in detail. By deriving new lower bounds on the tails of sums of independent Poisson trials, we determine the effect of the evaporation factor almost completely and prove a phase transition from exponential to polynomial runtime. A preliminary version of this paper appeared in the Proceedings of the 17th International Symposium on Algorithms and Computation (ISAAC 2006), volume 4288 of LNCS, pp. 618–627, Springer. Financial support for C. Witt by the Deutsche Forschungsgemeinschaft (SFB) in terms of the Collaborative Research Center “Computational Intelligence” (SFB 531) is gratefully acknowledged.     

AquaSee: Predict Load and Cooling System Faults of Supercomputers Using Chilled Water Data

An analysis of real-world operational data of Tianhe-1A(TH-1A)supercomputer system shows that chilled water data not only can reflect the status of a chiller system but also are related to supercomputer load.This study proposes AquaSee,a method that can predict the load and cooling system faults of supercomputers by using chilled water pressure and temperature data.This method is validated on the basis of real-world operational data of the TH-1A supercomputer system at the National Supercomputer Center in Tianjin.Datasets with various compositions are used to construct the prediction model,which is also established using different prediction sequence lengths.Experimental results show that the method that uses a combination of pressure and temperature data performs more effectively than that only consisting of either pressure or temperature data.The best inference sequence length is two points.Furthermore,an anomaly monitoring system is set up by using chilled water data to help engineers detect chiller system anomalies.