Estimates of pollutant temporal and spatial variability in commercial buildings from the joint urban 2003 field experiments

In this paper, we report on the indoor concentrations from a suite of full-scale outdoor tracer-gas point releases conducted in the downtown area of Oklahoma City in 2003. A point release experiment consisted of releases of sulfur hexafluoride (SF₆) in multiple buildings and from different outdoor locations. From the measurements, we are able to estimate the concentration variations indoors for a building operating under “typical” operating conditions. The mean indoor spatial coefficients of variation are 30% to 45% from a daytime outdoor release are around 80% during an outdoor evening release. Having estimates of the spatial coefficient of variation provides stakeholders, including first responders, with the likely range of concentrations in the building when little is known about the building characteristics and operating behavior, such as developing urban-scale hazard and consequence analyses. We show differences in indoor measurements at different distances to the release points, floors of the building, and heating, ventilation, and air conditioning system (HVAC) operation. We also show estimates at different time resolutions. The statistics show that in the studied medium to large commercial buildings, spatial differences would result in peak indoor concentrations in certain parts of the buildings that may be substantially higher than the building average. To our knowledge, very few tracer gas measurements have been conducted in buildings of this scope, particularly with measurements on multiple floors and within a floor. The resulting estimates of spatial variability provide a unique opportunity for hazard assessment, and comparison to multi-zone models.     

李子溪流域水土流失及泥沙输移规律初步研究

为了探讨长江上游流域水土流失及泥沙输移规律，选取嘉陵江中游的支流李子溪为典型流域进行分析研究，在实地调查，野外测验及应用１９６０年－１９９１年实测降雨、径流、输沙资料的基础上，利用单因子相关分析和多因子回归分析，分别建立了输水利沙量、最大输沙率计算方程。在此基础上，参照径流瞬时单位线原理，以线性时不变系统为基础，建立输沙瞬时单位线模型。通过输沙单位线与时段净侵蚀量的卷积得到流域出口断面的输沙率过程     

高能超声处理Al-1Si合金凝固组织分析

采用高能超声处理Al-1Si合金熔体,借助金相显微镜和电子探针进行组织分析,并测定合金的熔化潜热,分析了熔体中超声空化效应和声流效应影响凝固过程的机理。结果表明,试样晶粒平均尺寸由超声处理前的94μm减小到超声处理后的34μm;合金试样的熔化吸热量由263.90J/g降低为159.81J/g,在熔体中施加高能超声显著改善了合金成分的均匀性并细化了晶粒。     

用于较大水平位移测量的电阻应变式位移传感器

针对目前位移传感器很难直接测得木结构或木构件在转动中产生较大绝对水平位移的问题,研制了量程为±500 mm的电阻应变式位移传感器（WD位移传感器）,应用正交试验法分析WD位移传感器的影响因素,并对其进行设计与制作,拟合了传感器在不同量程下应变位移的分段函数关系,通过计算得出了WD位移传感器的6种静态参数指标。试验结果表明,WD位移传感器克服了传统电阻应变式位移传感器量程小的问题,解决了木结构或木构件发生非直线运动很难直接测得绝对水平位移的问题,且各静态参数指标良好。     

电磁场对水平连铸Al-1Si合金线材组织和性能的影响

研究了工频电磁场对水平连铸10 mm的Al-1Si合金键合线铸坯表面质量、凝固组织、溶质偏析和力学性能的影响.试验结果表明,在工频电磁场作用下,铸坯的表面质量得到了改善,当励磁电流达到100 A时,表面粗糙度由未施加电磁场时的40 μm降为20 μm;凝固组织得到了细化,晶粒尺寸均匀;溶质偏析得到了抑制,Si元素在α（Al）基体中的固溶度及其分布的均匀性得到提高;并且力学性能得到了改善,抗拉强度和伸长率分别提高了16.5%和36%.     

钢中非金属夹杂物控制技术发展现状及展望

钢中夹杂物的数量、尺寸、分布规律对钢产品质量有较大影响,因此,控制钢中非金属夹杂物是冶炼高品质洁净钢、提升产品品质的关键。通过对钢中非金属夹杂物性质、来源入手,分析了夹杂物碰撞、聚合长大、上浮及去除机理,同时对气泡吸附、电磁净化、过滤分离等夹杂物控制技术进行了对比分析,并对氧化物冶金技术发展现状进行了介绍。研究表明,气泡法与过滤法是以气泡和过滤器为媒介对钢水中夹杂进行吸附、捕捉并促进其进入渣相;电磁净化法借助电磁场离心力增加夹杂物碰撞、聚集长大的几率,但设备较为复杂,其应用受电力资源供给限制;夹杂物改性技术是将高熔点夹杂变性生成低熔点夹杂,促进夹杂物上浮,其操作简单,但容易造成钢水的二次污染。氧化物冶金技术通过改变夹杂物大小、形状和分布来钉扎和抑制高温下奥氏体晶粒的长大,避免粗大晶粒的形成,从而实现细化组织、提高钢的强度和韧性的目的。氧化物冶金技术为夹杂物的控制提供了新思路,具有重要的应用前景。     

基于光谱和时相特征的夏玉米遥感识别

精确提取作物种植面积一直是农业遥感关注的主要问题之一。综合运用低分辨率的时相变化特征和中分辨率的光谱特征,提出一种夏玉米识别方法。首先基于MODIS NDVI时间序列曲线,分析夏玉米在时相变化上的识别特征,构建识别模型。夏玉米纯像元利用识别模型识别,而耕地和非耕地类型的植被产生的混合像元,则基于像元分解办法获取耕地组分的NDVI时序特征,再利用识别模型判定,然后结合土地利用数据根据空间关系得到中分辨率结果;玉米与其他作物的混合像元则利用中分辨率尺度光谱差异加以区分。研究结果表明,在伊洛河流域主要农业区,识别精度达到90.33%,为作物类型识别提供了新的思路。     

Electrocapacitive Deionization: Mechanisms,Electrodes, and Cell Designs

Capacitive deionization (CDI) is an emerging water desalination technology for removing different ionic species from water, which is based on electric charge compensation by these charged species. CDI is becoming popular because it is more energy-efficient and cost-effective than other technologies, such as reverse osmosis and distillation, specifically in dealing with brackish water having low or moderate salt concentrations. Over the past decade, the CDI research field has witnessed significant advances in the used electrode materials, cell architectures, and associated mechanisms for desalination applications. This review article first discusses ion storage/removal mechanisms in carbon and Faradaic materials aided by advanced in situ analysis techniques and computations. It then summarizes research progress toward electrode materials in terms of structure, surface chemistry, and composition. More still, it discusses CDI cell architectures by highlighting their different cell design concepts. Finally, current challenges and future research directions are summarized to provide guidelines for future CDI research.     

一种基于YOLOv4-TIA的林业害虫实时检测方法

针对现有基于深度学习的林业昆虫图像检测方法存在检测精度低和检测速度慢的问题,提出一种结合改进PANet结构与三分支注意力机制的目标检测方法YOLOv4-TIA。通过对样本数量较少的昆虫类别进行数据增强,实现样本均衡分布。利用三分支注意力机制改进YOLOv4中的CSPDarkNet53骨干网络,同时通过旋转操作和残差变换建立维度间的依存关系,以提高有效的特征通道权重,在PANet结构上增加将跳跃连接与跨尺度连接相结合的特征融合方式,从而获取更丰富的语义信息和位置信息。在此基础上,采用Focal loss函数优化分类损失,解决正负样本不均衡的问题。实验结果表明,该方法的精确率和召回率分别达到85.9%和91.2%,相比SSD、Faster R-CNN、YOLOv4方法,其在保证检测速度的同时,能够有效提高检测精度,且实现对林业害虫的实时精确监测。     

添加Al-5Ti-B和Al-2Zr-Er对铸态铝锌镁合金力学性能的影响

铝锌镁合金以其优异的力学性能广泛应用于航空、航天、交通运输等工业领域,而铝合金的细化一直是铝加工行业的研究重点.为细化晶粒并提高其力学性能,本文将传统细化剂Al-Ti-B与RE复合添加到铝锌镁合金中,借助于XRD、光学显微镜、扫描电镜、拉伸实验等测试方法研究了不同细化剂对Al7Zn2.4Mg合金组织及其力学性能的影响.试验结果表明,合金中加入Al-5Ti-B和Al-Zr-Er后细化效果明显,单独添加Al-Ti-B的细化效果最好,但仍有少部分的晶粒保留的树枝晶形态.随着Al-Ti-B和Al-Zr-Er添加量的增多,合金的晶粒发生明显变化,塑性也随之增加,其中,添加0.4wt.%Al-5Ti-B细化剂对合金的塑性影响最大,而抗拉强度呈先增大后减小的趋势,复合添加0.2wt.%Al-2Zr-Er和0.2wt.%Al-5Ti-B细化剂的合金晶粒圆整且未出现树枝晶,晶界析出物最少平均抗拉强度最高.Al-Ti-B和Al-Zr-Er均可细化铸态铝锌镁合金的晶粒,同时添加两种细化剂更有利于提高合金的综合力学性能.