换热管直径对换热器(火用)效率影响的探讨

本文通过换热管直径对换热器(火用)效率影响的分析,提出了换热器设计及改造时,减小(火用)损失的一条途径.     

社区尺度居民楼内涝淹没过程精细化模拟及室内财产损失评估

以西安一小区居民楼为研究对象,构建了高精度城市雨洪模型,并通过实测暴雨内涝监测数据验证了模型的可靠性;利用构建的模型模拟了6种设计降雨重现期下的居民楼室内动态淹没过程,并以西安市中等收入家庭的房屋配置为计算单元,分析了各类居民室内财产的淹没水深阈值,依此拟合得到了室内财产淹没水深-损失率关系曲线,结合居民楼在不同降雨重现期下的淹没水深,计算得到了各居民楼在不同降雨重现期下的内涝淹没财产损失数据。结果表明：不同降雨重现期下,同一居民楼一层居民房屋室内进水淹没水深随降雨重现期的增大而增大;同一降雨重现期下,各栋居民楼因高程不一致导致内涝淹没过程及最大淹没水深不一样。     

Development of an index based on fish,macroinvertebrates, phytoplankton,and physicochemical properties to assess urban aquatic ecosystems in Jinan,China

Because of the rapid growth in urbanization over recent decades, urban aquatic ecosystems have been subjected to unprecedented threats and challenges. In this study, we visited 48 sites, of which 14 were reservoir sites, in water bodies in Jinan, China, on six occasions in May, August, and October of 2014 and 2015. We sampled fish, macroinvertebrates, and phytoplankton assemblages and physicochemical factors at each site. We used the richness and diversity of fish, macroinvertebrates, and phytoplankton to evaluate the condition of the aquatic ecosystems of the river sites. We also evaluated the water quality of the reservoir sites using the physicochemical factors of the State Environmental Protection Administration of China. We classified the results into five levels—excellent, good, moderate, poor, and bad—with the comprehensive evaluation index (CEI). More than 40% of the sampling sites were in either poor or bad condition. Nearly half of the excellent or good sites were in the south of Jinan. The CEI was significantly different between the reference and impaired sites; it was significantly and positively correlated with the qualitative habitat evaluation index and was significantly and negatively correlated with conductivity, total alkalinity, and ammonia nitrogen.     

基于梯度的重叠式层次社区检测

社区检测(community detection)任务一直是数据挖掘领域的一个研究热点,近年来,深度学习和图链接数据呈现出多样化和复杂化的发展趋势,层次(Hierarchical)社区检测逐渐成为研究的焦点.层次社区检测任务的目标是,在将同质图中相似的节点聚集到社区中的同时,学习社区之间的层次结构关系,以更好的理解图数据结构.社区间层次关系的引入给社区检测算法带来了更复杂的建模挑战.针对该任务,已经有一些有效的启发式的方法被提出,但是受限于社区分布形态的简单假设和离散的优化学习方式,它们无法描述更复杂的图链路数据,也无法和其它有效的连续优化算法组合获得更好的结果.为了解决这个问题,本文首次尝试建模复杂的重叠式(overlapping)层次社区结构,提出简洁的节点嵌入和社区检测双任务优化模型,通过梯度更新的方式来灵活地探索节点和重叠式层次社区的隶属关系.在学习过程中,我们可以分别获得节点和社区的嵌入表示,以应用于丰富的下游任务.     

西藏牛皮消的化学成分研究

从西藏牛皮消(Cynanchum saccatum)乙醇提取物的乙酸乙酯萃取部位分离出13个化合物,通过理化性质和波谱分析,分别鉴定为对羟基苯乙酮(1)、3,4-二羟基苯乙酮(2)、2,4-二羟基苯乙酮(3)、2,5-二羟基苯乙酮(4)、白首乌二苯酮(5)、3,5-二羟基苯甲酸甲酯(6)、对羟基苯甲酸(7)、2,5-二羟基苯甲酸甲酯(8)、3,3'-二甲氧基-4,9,9'-三羟基-苯并呋喃木脂素-7'-烯-9-O-β-D-吡喃葡萄糖苷(9)、加加明3-O-β-D-加拿大麻吡喃糖基-(1→4)-β-D-夹竹桃吡喃糖基-(1→4)-β-D-夹竹桃吡喃糖苷(10)、青阳参苷元3-O-β-D-加拿大麻吡喃糖基-(1→4)-β-D-加拿大麻吡喃糖基-(1→4)-β-D-夹竹桃吡喃糖基-(1→4)-β-D-加拿大麻吡喃糖苷(11)、β-谷甾醇(12)和β-胡萝卜苷(13).其中化合物9为首次从鹅绒藤属中分离得到,化合物1--3、5--8、10、11、13为首次从该植物中分离得到.     

Ce3+/Tb3+-coactived NaMgBO3 phosphors toward versatile applications in white LED,FED, and optical anti-counterfeiting

Ce³⁺/Tb³⁺ co-doped NaMgBO₃ phosphors were successfully synthesized by solid-state method. Under 381 nm excitation, the cyan emission owing to the 5d → 4f of Ce³⁺ ions and green emissions arising from the ⁵D₄ → ⁷F_J (J = 6, 5, 4, and 3) transitions of Tb³⁺ ions were seen in all the phosphors. Through theoretical analysis, one knows that the energy transfer from Ce³⁺ to Tb³⁺ ions with high efficiency of 83.74% was contributed by dipole–dipole transition. Furthermore, the internal quantum efficiency of NaMgBO₃:0.01Ce³⁺,0.03Tb³⁺ phosphor was 54.28%. Compared with that of at 303 K, the emission intensity of the developed products at 423 K still kept 73%, revealing the splendid thermal stability of the studied phosphors. Through utilizing the resultant phosphors as cyan-green components, the fabricated white-LED device exhibited an excellent correlated color temperature of 2785 K, high color-rendering index of 85.73, suitable luminance efficiency of 25.00 lm/W, and appropriate color coordinate of (0.4279, 0.3617). Aside from the superior photoluminescence, the synthesized phosphors also exhibited excellent cathode-luminescence properties which were sensitive to the current and accelerating voltage. Furthermore, the NaMgBO₃:0.01Ce³⁺,0.03Tb³⁺ phosphors with multi-mode emissions were promising candidates for optical anti-counterfeiting. All the results indicated that the Ce³⁺/Tb³⁺ co-doped NaMgBO₃ phosphors were potential multi-platforms toward white-LED, field emission displays, and optical anti-counterfeiting applications.     

Structure and properties of bio-based polyurethane coatings for controlled-release fertilizer

Two kinds of bio-based polyurethane coatings for controlled-release urea were prepared by in-situ polymerization used castor oil and liquefied starch as raw materials, respectively. Scanning electron microscopy (SEM) showed that the section morphology of castor oil based polyurethane (Castor-PU) coating was uniform and dense, and that of liquefied starch based polyurethane (Starch-PU) coating had certain proportion of microporous. Infrared spectroscopy (IR) showed that the two coatings had typical urethane characteristic structure, but the difference was that the Starch-PU had obvious unreacted isocyanate structure. Differential scanning calorimetry (DSC) showed that the glass transition temperature of the two coatings was around 58°C, but the Castor-PU had a crystallization domain with obvious crystallization melting peak at 130°C. Thermogravimetric analysis (TG) showed that the thermal stability of Castor-PU was significantly higher than that of Starch-PU. The controlled-release property test showed that when the coating ratio was 2.8%, the nutrient release longevity of urea coated with Castor-PU was 49 days and that of urea coated with Starch-PU was 14 days. The reasons for the poor controlled-release performance of Starch-PU were analyzed, which probably caused by concentrated sulfuric acid and hydrophilic dispersant added in the liquefied starch.     

Study on improvement of conductivity of Cu-Cr-Zr alloys

The influence of alloying, heat treatment, and plastic working on the performance of Cu-Cr-Zr alloys was investigated. The precipitated phases were characterized as Cr, Cu51Zr14 and Cu5Zr. Cu-Cr-Zr alloys demonstrate combination properties of high strength and high conductivity after solution treatment, aging treatment, and plastic deformation. Precipitation course of Cr is the main factor that influences the conductivity of Cu-Cr-Zr alloys, while adding Zr in the alloys adjusts the orientation relationship between Cr and matrix, and tends to increase the conductivity of aged Cu-Cr-Zr alloys after deformation.     

基于FPGA与LabVIEW的DDS任意信号发生器设计

实现了一种基于FPGA与LabVIEW平台的任意波形发生器。通过FPGA搭建硬件平台,与LabVIEW上位机软件实现串口通信,实时调整FPGA内部波形数据,可实现正弦波、方波、锯齿波、三角波、高斯白噪声、叠加正弦波、自定义公式等常规波形,同时也可以手动绘制任意波形,充分发挥了软件的灵活性。通过参数的设定,可方便地设计各种复杂波形。本设计在EP4CE15F17C8芯片上实现,与LabVIEW上位机软件协同工作,经测试系统具有良好的稳定性、灵活性。     

基于指向路径分次删剪的移动Agent通信算法

基于移动agent环境,在应用程序的开发时agent的移动为应用程序找到一种好的通信处理方式。因此通讯算法要面对更多的挑战,最主要的就是agent移动和消息传递之问的异步性而带来的通信不可靠问题。由于目前解决此类问题的算法和机制都有不足之处,本文就针对此类问题来介绍一种新的agent通信算法,即S-COMP算法,它综合了多种手段,主要有:集中同步、指向路径分次删剪、途经节点转发、Home寻址等,能够满足各种不同需求的agent的通信特点,既可以保证适应性和效率,同时也具有可靠性。