Tc trend in high-Tc superconductors

In our previous works, we have shown that most existing ceramic superconductors can be considered to be built of superconductor-semiconductor composite and we have estimated the change in phonon spectrum of the intrinsic superconductor unit if a semiconductor unit is attached to it. Moreover, the proximity effect under the size quantization condition has been examined in the superconductor-semiconductor composite. Each of the stated effects by itself could causeT _c enhancement in general as more semiconductor blocks are added to the system. We extend our study in this paper to analyze the combined actions of phonon spectral change and proximity effect without size quantization condition onT _c variation in members of the Tl₁ series of high-T _c superconductors. Our results indicate that an optimumT _c is obtained if the stated effects are included in the idealized unit cells of the superconductors made up of a superconductor-semiconductor array.     

提高大直径井眼机械钻速的几项措施

随着我国西部地区石油勘探开发的进展，5000－7000m的深探井所钻数量不断增多，套管程序增加，特别是大尺寸井眼所钻深度明显加大。由于国产大尺寸钻头结构单一、型号少，破岩机械能量和水力能量不足，在易斜井段目前尚无可靠的防斜保直措施，以及钻井液性能不适宜等原因，大尺寸井眼的钻这远远低于215．9mm井眼的钻速。据此，提出了几项可以提高大尺寸井眼钻速的措施：增加大尺寸钻头的种类，采用阶梯式扩眼钻头，强化钻井参数和水力参数，选用中速动力钻具，改善钻井液性能以及采用冲击旋转钻具等。     

泥浆制备中工艺改造的研究

根据室条件下粉磨试验结果，发现球磨过程中筛上料变化存在的突变范围，提出两次加料一次加水可改变泥浆颗粒分布，并找出适宜的加料种类与时间。另外给予测粒度分布提供了宝贵的试验基础数据。     

A polydispersed particle system representation of the porosity for non-saturated cementitious materials

In this paper, the porosity of cementitious materials is described in terms of pore size distribution by means of a 3-dimensional overlapping sphere system with polydispersivity in size. On the basis of results established by Lu and Torquato [B. Lu, S. Torquato, Nearest-surface distribution functions for polydispersed particle systems, Phys. Rev. A 45(8) (1992) 5530-5544] and Torquato [S. Torquato, Random Heterogeneous Media: Microstructure and Macroscopic Properties. Springer-Verlag: New York, 2001] providing relations for nearest-neighbor distribution functions, the volume fraction of pores having a radius larger than a prescribed value is explicitly expressed. By adopting an appropriate size distribution function for the sphere system, it is shown that the pore size distribution of cementitious materials as detected for instance by mercury intrusion porosimetry (MIP), which generally points out several pore classes, can be well approached. On the basis of this porosity representation, the evaluation of the capillary pressure in function of the saturation degree is provided. The model is then applied to the simulation of the saturation degree versus relative humidity adsorption curves. The impact of the pore size distribution, the temperature and the thickness of the adsorbed water layer on these parameters are assessed and analyzed for three model materials having different pore characteristics.     

高速钢高温形变诱发析出的研究

本文探讨了高速钢在高温形变过程中碳化物析出的行为及奥氏体组织状态对析出的影响。用透射电镜和扫描电镜分析了不同热处理状态奥氏体的组织结构,分析了高温形变过程中碳化物析出的部位,颗粒尺寸及形态。试验表明, 碳化物主要在奥氏体的缺陷处呈点状和点列状析出,大小为20mμ。处于回复状态的奥氏体缺陷诱发碳化物析出,析出碳化物钉札缺陷阻止再结晶进行。当再结晶驱动力较大时,由于动态再结晶充分发展,使缺陷大量消除,碳化物析出显著地减少。     

用激光粒度分析仪测定二氧化锆粒度

介绍以六偏磷酸钠作为分散剂，采用激光粒度分析仪测量二氧化锆粒度的一种新方法。该方法的测量范围为0．05～300μm。     

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)     

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 ;…     

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。