Dual-band reflective polarization converter based on metasurface

In this paper, a dual-band and reflective polarization converter based on metasurface is proposed. Its unit cell is composed of two layers of metal plates separated by a dielectric substrate. The simulation results show that the proposed converter is able to convert x- or y-polarized incident waves into cross-polarized waves perfectly in frequency bands of 6.75—10.59 GHz and 17.78—19.61 GHz, and the polarization conversion ratio (PCR) is nearly 100%, which can also convert linearly polarized waves into circularly polarized waves at four frequencies. It can be widely used in applications of radar satellites, antenna design and telecommunication with the function of realizing polarization conversion in two bands and achieving high PCR simultaneously.     

高效能空气净化器评价技术要求国家标准研究

本文论述了编制高效能空气净化器产品评价技术要求国家标准的意义和作用,介绍了标准研制的总体思路和原则,高效能空气净化器的定性和定量评价指标要求,测试、计算和评价方法等,通过国标的研制与实施,将引领并促进高效能空气净化器产品的生产与应用.     

基于神经网络与遗传算法的锅炉系统的优化

传统热工控制系统DCS在锅炉运行中存在多变量之间相关关系难以全面协调以及期望性能指标难以达到的问题。针对参数难以全面协调问题,采用BP神经网络来解决多变量间的非线性关系。针对性能指标的优化,在神经网络预测功能的基础上,采用遗传算法优化锅炉参数间的比值,并将优化后的风煤比在线监测数据作为反馈信号引入锅炉性能优化系统中,改进后的方法优化处理了热工控制系统问题。以青岛市某循环流化床锅炉为例,通过Matlab与C#语言编写的可视化界面曲线得出,预测与优化的综合方法能够将锅炉效率提高0.5%~3%。     

Numerical investigation on flow and convective heat transfer of aviation kerosene at supercritical conditions

In this paper,characteristics of flow and convective heat transfer of China RP-3 kerosene in straight circular pipe were numerically studied.Navier-Stokes equations were solved using RNG k-turbulence model with low Reynolds number correction.The thermophysical and transport properties of the China RP-3 kerosene were calculated with a 10-species surrogate and the extended corresponding state method(ECS) combined with Benedict-Webb-Rubin equation.The independence of grids was first studied and the numerical results were then compared with experimental data for validation.Under flow conditions given in the paper,the results show that deterioration of convective heat transfer occurs when the wall temperature is slightly higher than the pseudo-critical temperature of kerosene for cases with wall heat flux of 1.2 and 0.8 MW/m 2.The degree of the heat transfer deterioration is weakened as the heat flux decreases.The deterioration,however,does not happen when the heat flux on the pipe wall is reduced to 0.5 MW/m 2.Based on the analysis of the near-wall turbulent properties,it is found that the heat transfer deterioration and then the enhancement are attributed partly to the change in the turbulent kinetic energy in the vicinity of pipe wall.The conventional heat transfer relations such as Sieder-Tate and Gnielinski formulas can be used for the estimation of kerosene heat convection under subcritical conditions,but they are not capable of predicting the phenomenon of heat transfer deterioration.The modified Bae-Kim formula can describe the heat transfer deterioration.In addition,the frictional drag would increase dramatically when the fuel transforms to the supercritical state.     

提高立体仓库自动化水平的Flexsim仿真

以自动化立体仓库的现有设备为基础,提出一些可以提高立体仓库自动化水平的优化措施,在满足正常生产需求的条件下达到了减少仓储储位10%的核心目标.Flexsim仿真模型的运行结果表明:采用优化措施之后比当前运作情况下的单体包仓库最大利用率提高12.36%,多体包仓库平均利用率提高5.32%,整板仓库平均利用率提高1.27%,且工厂对安全存货的需求不受影响.     

船用双电源转换控制器的研制

传统双电源开关,多采用继电器方式控制,但在船舶等颠簸环境下使用,继电器有可能发生误触发,因而有工作不可靠的缺点.电子式数字控制双电源具有操作简便、工作可靠、能监控显示电源多种状态、可以远程控制等众多特点.介绍了P89C66x单片机为核心、在传统模拟继电器式双电源的基础上开发的电子式的数字船用双电源转换控制器的结构和软件编程.     

2001年绵阳科学城地区辐射环境监测与质量评价

2001年绵阳科学城地区主要环境介质(大气、河水、土壤和沉降等)中放射性水平与科学城开工前天然本底辐射没有显著性差别。通过对每个核设施烟囱流出物的测量与估算,获得了烟囱排放源项数据。利用该地区的大气扩散模式和多烟囱排放的剂量叠加原理,在评价坐标系中计算了叠加剂量分布。辐射环境质量评价表明80km范围内最大个人有效剂量是公众剂量限值的十万分之四,健康危害是危害约束值的千万分之二。表明环境影响是微弱的,是人们可以接受的。     

关于抽水蓄能电站水库优化调度的研究

针对某抽水蓄能电站水库运行的特点，在满足电力系统调度要求的前提下，以整个调度周期内总发电收益现值最大为目标建立了优化调度模型。通过径流描述以及应用动态规划法进行优化计算，求解抽水蓄能电站水库优化调度方案。在求解寻优的过程中，既兼顾了面临时段和余留时期的效益，又考虑上水库的天然来水和下水库的区间来水，通过分析表明，所提模型与计算方法是可行和实用的。     

Microstructures of laser cladding of intermetallic-ceramic composite coatings

The microstructures of laser cladding of (Ni-24.5%(atom fraction)Al)+5O%(mass haction)WC coatingsbefore and after aging was comparetively studied by using SEM and TEM. It is shown that dissolving of WC and reprecipitating in the forms of WC and W,Coccurred during laser cladding, and intermetallic γ' (Ni3Al) orderly precipitatefrom metastable supersaturant Ni-matrix solid solution after heat treatment. The structures are favorable for coating'sproperties.