三弧抄板

现有转筒烘干机的抄板不能把料撒在整个转筒内 ,而且撒料也不合理 .用力学理论和实验结合得出的三弧抄板克服了这些缺点 ,并且填充率高 (>2 0 % ) .如果用于工业生产 ,必将有显著的节能效果 .     

双合铝箔亮点缺陷产生的条件及机理

研究了双合轧制铝箔产生亮点的工艺条件,运用摩擦,润滑理论阐明了亮点产生的机理,提出了预防这种缺陷的措施。     

钢板组合剪力墙界面脱空的红外热成像法检测

基于传热学理论,利用红外热成像检测技术对钢板组合剪力墙界面脱空问题进行了研究。结果表明,采用主动式热激励和被动式热激励加热两种方式可以有效识别出钢板组合剪力墙界面脱空的缺陷位置和尺寸,当钢板壁厚为1 mm时,可识别1 cm^2以上的缺陷;钢板壁厚为3 mm和5 mm时,可识别4 cm^2以上的缺陷。合理控制热激励功率和时间可以有效减小缺陷尺寸识别的误差率。结合工程实际,红外热成像法可以识别出钢板组合剪力墙界面脱空缺陷及未浇筑区域,便于在浇筑混凝土时进行实时跟踪检测。     

5052铝合金单双道次压缩动态与静态软化行为探讨

实验采用Gleeble-1500D热模拟试验机对5052铝合金进行等温热压缩,研究了该合金动态软化特征和静态软化特征,变形温度330～480℃,应变速0.005～0.05/s。结果表明,5052铝合金在热压缩过程中发生了动态软化和静态软化,首道次压下量显著地影响了道次间的静态软化率。结合流变应力曲线和显微组织分析,揭示了动态软化机制主要为动态回复,而静态软化主要是静态再结晶的结果。     

气液两相流对板式换热器影响的模拟研究

用Fluent软件对人字形板式换热器冷流道中气液两相流的4组不同工况进行了模拟研究,分析了冷流道中两相流体的流动和换热特性以及气体在流道中的分布状况。结果表明,由于气相的扰动作用,使进出口连线一侧传热死区的换热状况有了很大改善;在一定含气率范围内,随着空气体积含气率的增大,增强了板式换热器的换热效果。     

Solder void position and size effects on electro thermal behaviour of MOSFET transistors in forward bias conditions

This research aims to enhance the understanding on position and size effects on the electro thermal behaviour of low voltage power MOSFET transistors in forward bias condition. The numerical simulations are based on a fractional design of experiments (DoE). The performance of a finite elements model is discussed by comparing thermal and electrical measurements to results of finite elements simulation on a module of free void and voided solder. The void in the model is afterwards parameterized on position and size, according to the fractional DoE of the study. The combined functions issued from the parametric simulations and the DoE show the main impact of void size on temperature of the device and on the surface temperature of the bonding wires. From the numerical viewpoint, the most impacting position of void depends highly on the void size. The redistribution of current density and temperature on MOSFET chip and bonding wires due to solder void is also observed. A future experimental study in respect to the same DoE is expected in prospect, in order to fulfil the complementarity for this approach.     

Constant fraction discriminator in pulsed time-of-flight laser rangefinding

Constant fraction discriminator (CFD) is one of theoretic method which can locate timing point at same fraction of echo pulse in pulsed time-of-flight (TOF) laser rangefinding.In this paper,the theory ...     

Quantifying the impacts of landscape heterogeneity and model resolution on dust emissions in the Arabian Peninsula

This study evaluates the spatiotemporal variability of dust emission in the Arabian Peninsula and quantifies the emission sensitivity to the land-cover heterogeneity by using the Community Land Model version 4 (CLM4³) at three different spatial resolutions. The land-cover heterogeneity is represented by the CLM4-default plant function types (PFTs) and the Moderate Resolution Imaging Spectroradiometer (MODIS) land cover types, respectively, at different grids. We area-average surface vegetation data and use the default nearest neighbor method to interpolate meteorological variables. We find that using MODIS data leads to a slightly higher coverage of vegetated land than the default PFT data; the former also gives more dust emission than the latter at 25- and 50-km grids as the default PFT data have more gridcells favoring less dust emission. The research highlights the importance of using proper data-processing methods or dust emission thresholds to preserve the dust emission accuracy in land models.     

Recoilless fraction of cobalt-doped magnetite

Hydrothermally-synthesized Fe_3−xCo_xO₄ (x = 0-0.9) samples were analyzed by transmission Mössbauer spectroscopy in order to determine the recoilless fraction of the tetrahedral (A) and octahedral (B) sites as a function of the cobalt content x. Our results provided direct evidence for the presence of the Co substitution in the B sublattice, which was found to be accompanied by a systematic increase of the hyperfine field at these sites. The recoilless fractions of the two sublattices were determined using our recently-developed dual absorber method. The recoilless fraction of the tetrahedral sites is practically constant, while that of the octahedral sites steadily decreases with increasing the Co content. These results tend to suggest that only the iron lattice participates in the recoilless process.