Internal flow numerical simulation of a cross‐flow fan in refrigerant operating condition using user‐defined functions

In the paper, a cross‐flow fan in refrigerant operating condition is systematically simulated using user‐defined functions. Three‐dimensional simulations are acquired with Navier–Stokes equations coupled with k–ε turbulence model, and internal flow characteristics of an indoor split‐type air conditioner are obtained, which is mainly composed of cross‐flow fan and heat exchanger. It has systematically been simulated in the isothermal flow condition that the performance of cross‐flow fan may be reduced easily with dry or humid air, and in the refrigerant operating condition in which user‐defined functions are applied to the humid air, considered as a mixture of dry air and vapor. A density‐modulated function is adopted to deal with the condensation of the vapor at the heat‐transfer region approximately. The results show flow mechanism of the two gas‐phase flow, including phase‐vary process. The distribution of the parameters is not uniform at the inlet of the machine, the intensity and position of pressure and velocity vary along the axial direction of the fan, the distribution of vapor volume fraction and turbulent intensity in heat‐transfer region is obtained, and the external characteristic data of the indoor machine are obtained and analyzed. Compared with the experimental data, the calculated characteristic curves and designed parameters are on target. © British Crown Copyright 2010/MOD. Reproduced with permission. Published by John Wiley & Sons, Ltd.     

一种物理实验教学网络系统

利用网络技术建立了物理实验网络，提高了教学质量。     

准东高碱煤气化过程中碱金属迁移与结渣特性实验研究

利用循环流化床对天池木垒高碱煤进行了气化实验研究,获得了天池木垒高碱煤在循环流化床上的结渣特性及碱金属迁移规律,并对实验中出现的床内颗粒聚团现象进行了分析。结果表明,不同存在形态的碱金属在煤气化过程中的迁移规律不同,水溶钠和醋酸铵溶钠在煤气化过程中以气态形式析出,不溶钠主要存在半焦中;随着气化温度升高,底渣和煤气中钠含量增加,飞灰中钠含量减少;尾部管道温度降低过程中,煤气中钠的冷凝速率明显高于钾;天池木垒高碱煤气化过程中容易引起床内颗粒聚团,床温越高,颗粒聚团现象越明显,床温波动越大;碱金属与灰分中矿物成分及床料中SiO₂反应生成黏性低温共熔物是导致颗粒聚团的关键。     

“禁摩限电”效果综合评价模型

将交通需求级别进行划分后,通过数据包络分析法计算交通需求匹配度和交通运行效率,近乎绝对细化交通运行表现,依据具有时间轴的四维交通状况模拟建立了全新多维度的交通评价体系。此外,利用模糊层次分析法确定道路交通安全评价指标体系中各个指标的权重,同时作出基于差异驱动原理的综合评价。最后,将交通的污染指标提炼为机动车的排放指标和电动车的耗电指标来衡量交通工具对环境的影响。     

Asymptotic tail probability of randomly weighted sums of dependent random variables with dominated variation

This paper investigates the asymptotic behavior of tail probability of randomly weighted sums of dependent and real-valued random variables with dominated variation, where the weights form another sequence of nonnegative random variables. The result we obtain extends the corresponding result of Wang and Tang[7].     

A solution approach for optimizing long- and short-term production scheduling at LKAB’s Kiruna mine

We present a mixed-integer program to schedule long- and short-term production at LKAB’s Kiruna mine, an underground sublevel caving mine located in northern Sweden. The model minimizes deviations from monthly preplanned production quantities while adhering to operational constraints. Because of the mathematical structure of the model and its moderately large size, instances spanning a time horizon of more than a year or two tend to be intractable. We develop an optimization-based decomposition heuristic that, on average, obtains better solutions faster than solving the model directly. We show that for realistic data sets, we can generate solutions with deviations that comprise about 3-6% of total demand in about a third of an hour.     

Control of multi-node mobile communications networks with time-varying channels via stability methods

Consider a communications network consisting of mobiles and random external data processes, each destined to a particular destination. Each mobile can serve as a node in the multi-hop path from source to destination. At each mobile the data is queued according to the source destination pair. The quality of the connecting channels are randomly varying. Time is divided into small scheduling intervals. At the beginning of each interval, the channels are estimated and this information is used for the decisions concerning allocation of transmission power and/or time, bandwidth, and perhaps antennas, in a queue and channel-state dependent way. Under a natural (and “almost” necessary) “average flow” condition, stochastic stability methods are used to develop scheduling policies that assure stability. The policies are readily implementable and allow a range of tradeoffs between current rates and queue lengths, under very weak conditions. Because of the non-Markovian nature of the problem, we use the perturbed Stochastic Liapunov function method. The choice of Liapunov function allows a choice of the effective performance criteria. All essential factors are incorporated into a “mean rate” function, so that the results cover many different systems. Extensions concerning acknowledgments, multicasting, non-unique routes, and others are given to illustrate the versatility of the method, and a useful method for getting the a priori routes is discussed.     

嵌入式实时操作系统VxWorks在惯性导航系统中的应用

详细介绍了嵌入式实时操作系统VxWorks的性能特点，叙述了基于VxWorks操作系统的开发过程和在导航接口机中的应用实例，提出了现行惯导系统软件从汇编语言到OS，高级语言的必要性和可能性，从而在提升软件的可维护性，可测试性和可靠性的同时，充分的发挥导航计算机的性能，以适应日益复杂的导航计算要求。     

Design of a small conversational system

The main features of a time-sharing system for a minicomputer are outlined. An interpretive language LAX plays a central role in the system both as a base for the languages seen by the user and for implementing part of the system. The system is open-ended, new subsystems can be plugged in easily, and a variety of error and interrupt behavior can be obtained.     

Uniform estimate for maximum of randomly weighted sums with applications to insurance risk theory

This paper obtains the uniform estimate for maximum of sums of independent and heavy-tailed random variables with nonnegative random weights,which can be arbi- trarily dependent of each other.Then the applications to ruin probabilities in a discrete time risk model with dependent stochastic returns are considered.