Heat transfer mechanism of a swirling impinging jet in a stagnation region

Heat transfer characteristics of a swirling impinging jet have been experimentally examined using a combined particle image velocimetry (PIV) and laser‐induced fluorescence (LIF) technique for simultaneous measurement of velocity and temperature fields. The present study shows that the radial width of the jet stretches with increasing swirl intensity, and that the stretching phenomenon contributes to the maximum local heat transfer coefficient. At the stagnation region, the flow near the heated surface is mixed intermittently by reverse flows toward upstream, and spatial distributions of temperature are correlated with instantaneous velocity vector maps. The dynamic behavior of recirculation zones, attributed to swirl number Sw and impinging distance, mainly determines the turbulent heat transfer at the stagnation region. © 2003 Wiley Periodicals, Inc. Heat Trans Asian Res, 32(8): 663–673, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.10120     

How Meta-Analysis Increases Statistical Power.

One of the most frequently cited reasons for conducting a meta-analysis is the increase in statistical power that it affords a reviewer. This article demonstrates that fixed-effects meta-analysis increases statistical power by reducing the standard error of the weighted average effect size (T?.) and, in so doing, shrinks the confidence interval around T?.. Small confidence intervals make it more likely for reviewers to detect nonzero population effects, thereby increasing statistical power. Smaller confidence intervals also represent increased precision of the estimated population effect size. Computational examples are provided for 3 effect-size indices: d (standardized mean difference), Pearson's r, and odds ratios. Random-effects meta-analyses also may show increased statistical power and a smaller standard error of the weighted average effect size. However, the authors demonstrate that increasing the number of studies in a random-effects meta-analysis does not always increase statistical power. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

基于TiNi合金的超弹性对其相关磨损机制的FEM研究

本文在重点考虑TiNi合金高弹性变形量的前提下，采用等向强化模型，对不锈钢和超弹TiNi合金在法向接触载荷作用下的六种模型进行了有限元(FEM)分析。结果表明：在相同载荷条件下，超弹TiNi合金产生的von Mises弹性应变要高于不锈钢，但其von Mises应力和塑性应变却恰恰相反，在同一载荷下该合金发生塑性变形的区域要小于不锈钢；此外，超弹TiNi合金发生塑性变形要比不锈钢困难，所需的临界载荷值随其最大弹性变形量(屈服点处的应变值)的增加而增加。最后，基于本文的有限元计算结果对超弹TiNi合金的蘑粒磨损和疲劳磨损机制进行了讨论。     

煤粉粒度对高炉风口前燃烧性能的影响

安钢炼铁厂在喷吹瘦煤后，将小于0．074mm的比例由70％放宽到30％，使磨煤能力提高了21％。采用自行设计的风口取样器，研究了风口前气体成分和煤粉燃烧率的变化。当煤粉粒度变粗后，风口前循环区变长，放宽煤粉粒度与高富氧、高风温配合，能使高炉得到较好的经济效益。     

Influence of Billet Size on Flow, Solidification and Solute Transport in Continuous Casting

ListofSymbol　　B———Buoyancy ,m·s- 2 ;　　c———Concentrationofsoluteelement ;　　Cμ———Turbulentconstant;　　D———Diffusivityofsoluteelement ,m2 ·s- 1 ;　　fl,fs———Liquidandsolidfraction ;　　fμ———Turbulentcoefficient ;　　h———Enthalpy ,J·kg- 1 ;　　k———Turbulentkineticenergy ,m2 ·s- 2 ;　　kp———Equilibriumpartitioncoefficient;　　Kp———Permeabilityofmushyzone ,m2 ;　　K0 ———Permeabilitycoefficient;　　p———Pressure ,Pa ;　　Pr———Prandtlnumber ;…     

矿用高强度圆环链的热处理

结合矿用高强度圆环链的使用条伯对其不同的热处理方式进行了分析，特别是对中频感应加热淬、回火的规律进行了较详细的测试和分析，分析结果为选用最佳的热处理制度提供了依据。     

套管钻井用套管外表面磨损后剩余强度分析

在分析讨论套管钻井管柱磨损形态的基础上,结合API5C5实物试验尺寸要求,通过有限元计算分析方法,对钻井套管完钻后含有外表面磨损缺陷的套管柱的极限剩余抗挤强度和极限剩余抗拉强度进行了研究,分别获得了均匀磨损和偏磨条件下,套管钻井套管柱外表面磨损缺陷的临界长度尺寸数值,以及不同破坏失效准则条件下的剩余抗挤强度和剩余抗拉强度的计算方程,为套管钻井中套管柱的设计、计算奠定了理论基础。     

Sorption of Acid Green 25 on chitosan: Influence of experimental parameters on uptake kinetics and sorption isotherms

Acid Green 25, which is a diazoic dye bearing two sulfonic groups, is efficiently sorbed on chitosan. The protonation of chitosan may explain the electrostatic attraction of this anionic dye and that its optimum pH is close to 3. Preliminary protonation of amine groups (obtained by contact with a sulfuric acid solution) reduced the variation of solution pH following sorbent addition but significantly reduced sorption performance: the maximum sorption capacity of raw chitosan, 525 mg dye/g (0.84 mmol dye/g), was halved by acidic preconditioning. The acidic conditioning also reduced the kinetic rate—the time necessary to reach equilibrium increased up to threefold depending on the experimental conditions. The size of sorbent particles influenced sorption kinetics and equilibrium because of resistance to intraparticle diffusion, but the sorption appeared to occur not only at the surface of the sorbent but also in the intraparticle network of the polymer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1073–1080, 2003     

尺度目标识别中的若干技术问题

从工程应用的角度阐述了现代鱼雷常用的尺度目标识别原理，讨论了影响识别距离的若干因素和措施，提出了小尺度模拟靶通过亮点延时算法以弥补尺度不足及其试验技术，试验结果表明，该方法可以获得良好效果。     

熔体吹气发泡法制备泡沫铝合金研究

泡沫金属是近年来发展起来的一种新型材料。文章采用熔体吹气发泡法制备出了孔径为5．0—8．3mm，壁厚为0．040—0．076mm，密度为0．19—0．40g／cm^3，孔隙率为85．2％—93．0％的Al—Si泡沫铝合金，并着重讨论了发泡温度、气体流量、SiC粉末体积百分含量对泡沫铝合金形成的孔径和壁厚的影响关系。