扩散热阻对FR4/AlN复合材料导热性能的影响

首先,将AlN陶瓷表面金属化后分别切割成10 mm×10 mm×1.0mm、12 mm×12 mm×1.0 mm及15 mm×15 mm×1.0mm的方块,嵌入环氧树脂中制备成FR4/AlN复合材料;然后,利用SMT工艺将同款LED灯珠与上述内置三种不同尺寸AlN的复合基板材料组装成LED模组;最后,利用结温测试仪与半导体制冷温控台对三种LED模组分别进行了结温测试.同时,结合热仿真手段对复合材料水平面的温度分布情况进行了模拟研究.结果表明:上述三种尺寸陶瓷片对应LED的结温分别为96.95、92.94与91.81℃.热仿真结果显示,陶瓷片尺寸通过界面热阻对扩散热阻产生影响,增大陶瓷片尺寸有助于降低扩散热阻,进而改善FR4/AlN复合材料的整体散热性能.     

关于生物安全实验室送、回风口上下位置问题的探讨

介绍上送下回、上送上回、下送上回这三种气流组织的优缺点。从回风口速度场、送风口速度场、跟随速度、速度的合成等方面加以分析,认为这些气流组织用于生物安全实验室中,只有上送下回才能把产生的污染迅速压向呼吸带以下,其他两种方式对室内污染的排除均不利。     

A Tale of Two Cities: Physical Form and Neighborhood Satisfaction in Metropolitan Portland and Charlotte

Problem: Literature advocating compact development and mixed uses frequently claims that this form of development supports a higher quality of life, yet the empirical basis for this claim is weak.

Purpose: I assess the relationship between physical form and quality of life using neighborhood satisfaction as an empirical definition of quality of life.

Methods: I examine the effects of block and neighborhood housing density, land use mix, the mix of housing structure types, and street network connectivity on residents' ratings of neighborhood satisfaction. Using a multilevel dataset that combines individual household information with neighborhood contextual variables, I compare the Charlotte, North Carolina and Portland, Oregon metropolitan statistical areas (MSAs), which have very different development patterns and land use policies.

Results and conclusions: At the neighborhood level, I find density and mixed land uses to be associated with higher neighborhood satisfaction in Portland, but lower neighborhood satisfaction in Charlotte. At the block level, however, I find blocks that are exclusively single family detached housing to be associated with higher neighborhood satisfaction in both MSAs. These findings suggest that the influence of compact development and mixed uses on residents' quality of life depends upon the context, and may be sensitive to the spatial scales at which urban form is examined.

Takeaway for practice: Planners should understand that strategies promoting compact development and mixed uses will have different consequences in different contexts, and should pay careful attention to the appropriate spatial scale for implementing such policies. I conclude that compact growth and mixed uses improve quality of life by contributing to higher levels of neighborhood satisfaction, though they may not succeed in low density metropolitan areas. I conclude that in considering such development, planners should: rely on evidence to identify appropriate strategies; learn how to create conditions that foster urban amenities and discourage urban problems; pay attention to factors that complement the appeal of compact and mixed environments; and consider the possibility that the market will not tolerate mixing different housing types at a fine grain for the purpose of achieving higher density and diversity.

Research support: This research was supported by a dissertation research grant from the Department of Housing and Urban Development and the Department of City and Regional Planning, Cornell University.     

废白土制备有机膨润土处理炼油碱渣废水

采用十六烷基三甲基溴化铵( CTAB)对废白土进行改性,制成了有机改性膨润土,研究了其对炼油碱渣废水的处理效果.结果表明:所制得的有机改性膨润土可显著吸附炼油碱渣废水中的有机污染物,使废水的COD值从14173.2 mg/L降到3300 mg/L,COD去除率达到76.72 %.     

国家标准《食品工业洁净用房建筑技术规范》编制说明

阐述了以良好生产规范、卫生标准操作程序、危害分析和关键控制点为基础的食品生产环境安全体系。介绍了该规范的编制背景、编制原则、适用范围、内容安排和主要特点等,以便读者更好地理解和执行。     

一种内阻辨识控制的热电变流系统

针对热电转换系统提出了一种四管升降压式变换器。该电路可以工作在升压、降压和升降压3种工作模式。通过对热电模块的热阻进行辨识,实现了新型最大功率点跟踪(maximum power point tracking,MPPT)和功率匹配(power matching,PM)的控制方法。分析了电路的工作原理,给出了电路控制算法及流程图,并分析了系统模型。最后以20 V电压为输入,12 V蓄电池为负载,建立了该系统实验装置。结果表明:该算法能有效实现电路所需工作模式,证明了该算法的准确、高效。     

用于污染控制的回风口净化装置的三个必要条件——空调净化系统污染控制与节能关系系列研讨之三

提出把空气净化装置主要设于回风口以拒尘、菌的主动式污染控制理念和方法,得出这样的装置必需具备三个必要条件:初阻力不大于20Pa,滤菌效率不小于90%,除尘计重效率不小于95%(或对于粒径大于等于0.5μm微粒的计数效率不小于70%)。     

AC Impedance of Li(Ni1/3Co1/3Mn1/3)O2/graphite cell as UPS

以Li（Ni_1/3Co_1/3Mn_1/3）O₂/graphite动力电池为研究对象,在模拟备用电源工况下对动力电池进行交流阻抗测试。通过建立等效电路来研究欧姆阻抗R_s、电荷传递阻抗R_ct和扩散阻抗CPE_W随不同搁置时间、荷电状态（state of charge,SOC）的变化规律,研究Li（Ni_1/3Co_1/3Mn_1/3）O₂/graphite动力电池在备用电源工况下,容量和阻抗的变化趋势。结果表明：随着搁置时间的增加,电池容量衰减1.7%左右。随着搁置时间的增加,不同SOC下的欧姆阻抗R_s具有相同的变化趋势,电荷传递阻抗明显增加。随着SOC的降低,由双电层产生的电荷传递阻抗在逐渐增加。在SOC=0%时,扩散阻抗随搁置时间的增加而增加,在SOC=100%、50%的扩散阻抗有细微的增加。容量衰退和阻抗结果显示出Li（Ni_1/3Co_1/3Mn_1/3）O₂/graphite动力电池可以很好地在备用电源工况上使用。     

高压水除鳞技术的研究

简要介绍除鳞技术的研究发展历史和国内外应用概况,重点说明高压水除鳞技术的发展过程及侧重于节能方面研究和应用现状,总结分析了目前高压水除鳞技术的不足之处,并提出了除鳞技术未来主要研究方向。     

基于广义塑性模型的高心墙堆石坝反演计算分析

高堆石坝工程在填筑、蓄水和运行过程中,堆石料常经历复杂多变的应力路径,它所表现出的各向异性和颗粒破碎对其力学特性有明显的影响。采用现有的方法计算高堆石坝变形误差大,其主要原因是目前本构模型在反映堆石料的本质特性方面有待完善。本文构造了各向异性状态参量,定义了参考各向异性状态参数替代基于固定临界状态线的状态参数,可将各向异性、颗粒破碎、复杂应力路径的影响综合考虑到与参考状态线的相对空间位置中。基于参考各向异性状态参数,发展了考虑各向异性和颗粒破碎的堆石料弹塑性本构模型。最后,采用所发展的堆石料广义塑性模型MPZR对已建的糯扎渡高心墙堆石坝进行了应力变形有限元计算分析,并与堆石体内测点的监测值进行对比,验证了模型的可靠性和实用性。