基于M-ACO算法的空气污染源反演

为了解决空气污染源反演的盲目性和低效率问题,本文提出了一种基于改进型蚁群算法(modified-ant colony optimization, M-ACO)的空气污染源反演方法.利用点源高斯扩散模型建立污染源反演模型,采取蚁群算法(ant colony optimization, ACO)来求解.针对蚁群算法中存在的缺点,引入遗传算法的选择交叉思想,从而丰富种群的多样性来避免陷入局部极值;同时设计奖惩因子机制,对信息素更新规则进行改进来使算法更快地收敛,进而归纳为M-ACO算法.通过对比实验,证明了M-ACO算法相比于传统ACO算法来说,能够使得污染源的反演结果更准确和高效,为空气污染源反演的实际应用提供了有效的理论支撑.     

基于辐照度测量法的火焰检测研究

火焰检测的核心问题是用于火焰检测中的传感器特性评估.本文提出以黑体标定红外传感器.在一定条件下,将标准火光谱辐射出射度特性传递到电光源,以电光源取代标准火的标定方法,采用标准传感器对被检标准火焰辐照度进行量值传递,构造了火焰测量装置并进行了实验.实验结果表明,采用标准传感器在一定精度下实现对标准火焰光谱辐照度进行量值传递是可行的,所引入的不确定度小于1%,为建立人工电光源提供了基本设计参数.     

端子骚扰电压测量不确定度的评定

对家用电器在500kHz频率点的端子骚扰电压测量中,影响测量结果的不确定度各分量进行了分析,并给出了不确定度评定结果。     

沉积气压对电弧离子镀制备ZnO薄膜的结构和性能影响

采用阴极真空电弧离子镀技术在玻璃衬底上制备出了具有择优取向的透明ZnO薄膜. 利用X射线衍射仪、扫描电子显微镜及紫外-可见吸收光谱仪分别对ZnO薄膜的结构、表面形貌及可见光透过率进行了分析.XRD结果表明,所制备的ZnO薄膜具有六角纤锌矿结构的(002)和(101)两种取向,在沉积气压＞1.0Pa时所制备的ZnO薄膜具有(002)择优取向,并且非常稳定.SEM图表明,ZnO晶粒大小较为均匀,晶粒尺寸随着气压升高而变小.在400～1000nm范围内,ZnO薄膜的可见光透过率超过80%,吸收边在370nm附近,所对应的光学带隙约为3.33～3.40eV,并随着沉积气压上升而变大.     

注氮、注氟SIMOX/NMOS器件辐射加固性能

本文对注N、注F的SIMOX/NMOSFET器件的抗辐射特性进行了研究,发现两者都能减少埋氧层及其界面的空穴陷阱,对辐射加固有所改善,特别是对大剂量辐射的加固更为明显.总体来说,在此能量下,离子注入剂量越大,加固越好.由于注入的剂量对片子本身的阈值电压有很大影响,所以选择对于器件初始特性影响较小的剂量及能量非常重要.     

Photocatalytic H2 evolution from NaCl saltwater over ZnS1−x−0.5yOx(OH)y-ZnO under visible light irradiation

Photocatalytic hydrogen production was investigated over ZnS_1−x−0.5yO_x(OH)_y-ZnO using sulfide ion (Na₂S-Na₂SO₃) as an electron donor from NaCl saltwater. NaCl can affect markedly the activity for photocatalytic hydrogen production, depending on NaCl concentration. When NaCl concentration is lower, the activity is lower than that in pure water, whereas when NaCl concentration is higher, the activity is higher than that in pure water. NaCl decreases not only the surface charge of ZnS_1−x−0.5yO_x(OH)_y-ZnO but also the surface hydration. When ZnS_1−x−0.5yO_x(OH)_y-ZnO was impregnated with the electron donor (Na₂S-Na₂SO₃), ZnO was transformed partly into ZnS. The impregnated ZnS_1−x−0.5yO_x(OH)_y-ZnO exhibits higher activity than the non-impregnated one. The possible mechanisms were discussed.     

Turbulent natural convection in an enclosure with localized heating from below

This study reports the results of a numerical investigation of turbulent natural convection in a square enclosure with localized heating from below and symmetrical cooling from the vertical side walls. The present study simulates the case of an accidental heat generation due to fire in a typical isolated building of a nuclear reactor or electronic components cabin. The source of fire is considered to be centrally located at the bottom wall with different heated widths, which is assumed to be either isothermal or with isoflux. For the purpose of the analysis, the source length is varied from 20 to 80% of the total width of the bottom wall. The top wall and the unheated portion of the bottom wall are considered to be adiabatic, whereas sidewalls are isothermal. Steady as well as transient forms of two-dimensional Reynolds–Averaged-Navier–Stokes equations and conservation equations of mass and energy, coupled with the Boussinesq approximation, are solved by the control volume based discretisation method employing the SIMPLE algorithm for pressure–velocity coupling. Turbulence is modeled using the standard k–ε model. Rayleigh number, Ra, based on the enclosure height is varied from 10⁸ to 10¹². Stream lines and isotherms are presented for various combinations of Ra and the heated width. A double cell flow pattern is observed with marginal loss in symmetry as Ra increases. The results are reported in the form of local and average Nusselt number on the heated floor. Correlations are developed to predict the heat transfer rates from the enclosure as a function of dimensionless heated width of the bottom wall and Ra, by least square linear regression analysis.     

Synthesis and characterization of Li2MnSiO4/C nanocomposite cathode material for lithium ion batteries

A high capacity Li₂MnSiO₄/C nanocomposite cathode material with good rate performance for lithium ion batteries through a solution route has been successfully prepared. The material is able to deliver a reversible capacity of 209 mAh g⁻¹ in the first cycle, i.e. more than one electron exchange can be reversible cycled in the materials. The highly dispersion of nanocrystalline Li₂MnSiO₄ which was surround by a thin film of carbon was attributed to the cause of excellent performance of the materials. Ex situ XRD and IR results show that poor cycling behavior of Li₂MnSiO₄ might be due to an amorphization process of the materials.     

地源热泵的分类及其若干问题的看法

针对地源热泵的分类和名称不很统一的现状，提出了按低温热源的来源统一分类的看法，并据此对目前常用的各种土壤源、水源热泵进一步分类；并提出目前把水环热泵当作水源热泵是不合适的，应该作为空气源热泵的一种。     

Thermal management of lithium‐ion batteries for electric vehicles

Thermal issues associated with electric vehicle battery packs can significantly affect performance and life cycle. Fundamental heat transfer principles and performance characteristics of commercial lithium‐ion battery are used to predict the temperature distributions in a typical battery pack under a range of discharge conditions. Various cooling strategies are implemented to examine the relationship between battery thermal behavior and design parameters. By studying the effect of cooling conditions and pack configuration on battery temperature, information is obtained as to how to maintain operating temperature by designing proper battery configuration and choosing proper cooling systems. It was found that a cooling strategy based on distributed forced convection is an efficient, cost‐effective method which can provide uniform temperature and voltage distributions within the battery pack at various discharge rates. Copyright © 2012 John Wiley & Sons, Ltd.