双辊铸轧高速钢薄带的晶粒细化

主要介绍了W9Mo3Cr4V高速钢在双辊铸轧过程中的晶粒细化。薄带钢在铸轧过程中的冷却时间仅为0．2—0．3s，冷却速度很快，冷却速度已达到100—1000℃／s，因此，在快速凝固的过程中，液体金属获得了较大的过冷度，晶核的临界半径随过冷度的增加而减小，晶粒必然细化。另外，过冷度增大，晶核形核功减小,形核几率增大，也使晶粒细化。     

双辊铸轧高速钢薄带的晶粒细化

主要介绍了W9Mo3Cr4V高速钢在双辊铸轧过程中的晶粒细化.薄带钢在铸轧过程中的冷却时间仅为0.2-0.3 s,冷却速度很快,冷却速度已达到100-1000℃/s,因此,在快速凝固的过程中,液体金属获得了较大的过冷度,晶核的临界半径随过冷度的增加而减小,晶粒必然细化.另外,过冷度增大,晶核形核功减小,形核几率增大,也使晶粒细化.     

双辊铸轧高速钢薄带的晶粒细化

主要介绍了W9Mo3Cr4V高速钢在双辊铸轧过程中的晶粒细化.薄带钢在铸轧过程中的冷却时间仅为0.2-0.3 s,冷却速度很快,冷却速度已达到100-1000℃/s,因此,在快速凝固的过程中,液体金属获得了较大的过冷度,晶核的临界半径随过冷度的增加而减小,晶粒必然细化.另外,过冷度增大,晶核形核功减小,形核几率增大,也使晶粒细化.     

Al-5Ti-0.2C细化剂对7085铝合金形核及过冷度的影响

在7085铝合金凝固过程中添加不同质量分数的Al-5Ti-0.2C细化剂,对比其铸锭凝固组织,并用DSC测定其凝固过程熔体过冷度,探讨Al-5Ti-0.2C细化剂对铝熔体形核与过冷度的影响。研究结果表明:Al-5Ti-0.2C细化剂能够明显细化晶粒,当细化剂质量分数为0.5%时细化效果最好;细化剂质量分数的差异对DSC曲线中的熔化曲线影响较小,而凝固曲线有明显差异;在凝固过程中增大细化剂质量分数,铝熔体形核过冷度与最大过冷度都呈递减趋势,当细化剂质量分数超过0.5%时,过冷度不再有明显递减趋势;Ti C颗粒是铝熔体异质形核的核心,凝固过程中Ti C颗粒的发生团聚,从而增大形核基底颗粒粒度,减小润湿角与临界形核能,最终减小熔体中形核所需过冷度。     

深过冷金属熔体中单晶形成的临界条件

将形核率和晶体生长速度对过冷金属结晶晶粒数的影响用过冷度统一起来，建立了过冷金属结晶晶粒数随金属热力学过冷度变化的理论关系。结果表明：过冷金属的结晶晶粒数随金属热力学过冷度的增大而减小，过冷度增大到一临界值后，过冷金属的结晶晶粒数减小到１；所得到的在过冷金属熔体中形成单晶的理论判据与有关实验结果完全吻合。     

基于均匀形核的金属液滴凝固过程

研究了均匀形核的金属液滴凝固过程,应用渐近分析法求得金属液滴内晶核生长数学模型的渐近解,分析了表面张力、界面动力学参数、初始晶核尺寸和过冷度对晶核界面生长速度、晶核半径以及液滴凝固时间的影响。在一定的过冷条件下,表面张力和界面动力学参数显著减缓了晶核界面生长速度。在凝固开始的很短时间内晶核界面生长速度迅速上升,当速度上升到最大值后,随着晶核半径的增大,界面生长速度逐渐减慢,表面张力和界面动力学参数对晶核生长速度的作用也逐渐减小。过冷度越大,液滴凝固时间越短。经过在开始的瞬变凝固阶段之后,温度场从设定的初始分布迅速地调整为由过冷度、表面张力、界面动力学参数等所确定的特定温度分布。     

基于均匀形核的金属液滴凝固过程

研究了均匀形核的金属液滴凝固过程,应用渐近分析法求得金属液滴内晶核生长数学模型的渐近解,分析了表面张力、界面动力学参数、初始晶核尺寸和过冷度对晶核界面生长速度、晶核半径以及液滴凝固时间的影响.在一定的过冷条件下,表面张力和界面动力学参数显著减缓了晶核界面生长速度.在凝固开始的很短时间内晶核界面生长速度迅速上升,当速度上升到最大值后,随着晶核半径的增大,界面生长速度逐渐减慢,表面张力和界面动力学参数对晶核生长速度的作用也逐渐减小.过冷度越大,液滴凝固时间越短.经过在开始的瞬变凝固阶段之后,温度场从设定的初始分布迅速地调整为由过冷度、表面张力、界面动力学参数等所确定的特定温度分布.     

低钛铝合金晶粒细化的凝固计算

基于单个晶粒生长所形成的成分过冷为邻近的形核颗粒提供形核所需成分过冷的假设，提出晶粒细化的相关晶粒尺寸(RGS)判据。0．03％TiB2细化不同含钛量的铝合金的试验数据拟和出的形核过冷度与试验测量结果较一致。分析发现成分过冷区初期其形成的速率正比于抑制生长因子Q，成分过冷参数P可作为柱状晶向等轴晶转变的判据。对于使用强形核颗粒合金的晶粒尺寸可用直接使用抑制生长因子Q来衡量，而弱形核颗粒使用RGS可能更准确一些。     

深过冷Fe-30%Co合金的组织演化

采用熔融玻璃净化与循环过热相结合的方法，使原子分数Fe-30%Co合金获得了高达457K的大过冷度.系统考察了合金凝固组织随过冷度的演化规律.发现合金的凝固组织随过冷度的增大存在两次细化和一次粗化过程, 即在小过冷度范围内粗大树枝晶向粒状晶的转变和中等过冷度下局域定向枝晶的细化，而在大过冷度范围内随着亚稳枝晶核数目的增加,存在一个明显晶粒粗化的过程.     

微观组织参数及工艺条件对430不锈钢凝固显微结构的影响

在多元合金CAFE模型的基础上,分析了微观组织参数(形核密度、高斯分解参数、Gibbs-Thomson系数等)与430不锈钢凝固过程中晶粒形貌的复杂关系,以及过热度与冷却强度等工艺参数对凝固组织的影响.研究发现,晶粒尺寸和柱状晶向等轴晶转变不仅与体最大形核过冷度有关,也受体形核密度的影响.高斯分解参数和Gibbs-Thomson系数增大时,一次枝晶间距减小,等轴晶范围增大;但当它们增加至一定范围后,其对显微结构的影响逐渐变得不明显.过热度或冷却强度增大时,等轴晶范围减小,但一次枝晶间距的变化不明显.     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

Perspherical Approaches for Electrons in Atoms and Charged Excitons in Quantum Wells

Instead of following Fock’s expansion,we solve the Schrodinger equation for some quantum mechanical manybody systems such as electrons in atoms and charged excitons in quantum wells in a similar way in hyperspherical coordinates by expanding the wave functions into orthonormal complete basis sets of the hyperspherical hannonics(HHs)of hyperangles and generalized Laguerre polynomials(GLPs)of the hyperradius.This leads the equation to     

Advances in broadband wireless communications under high-mobility scenarios

Future mobile communication systems aim at providing very high data transmission rates, even in high-mobility scenarios such as high-speed wheel-track trains, maglev trains, highway vehicles, airplanes, guided missiles or spacecraft. A particularly important commercial application is the strong and increasing worldwide demand for high- speed broadband wireless communications （up to 574.8 km/ h test speeds or 380 km/h commercial speeds） in railways, providing data, voice and video services for applications such as onboard entertainment services to passengers, train control, train dispatch, train sensor status handling and sur- veillance. In such high-mobility scenarios, there are a number of communication challenges, including fast hand- over, location updating, high-speed channel modeling, estimation and equalization, anti-Doppler spreading tech- niques, fast power control, and dedicated network architec- ture. Because signal transmission in very high-speed scenarios will inevitably experience serious deterioration, it is imperative to develop key broadband mobile communi- cation techniques for such high-speed vehicles.     

Wuhan University Journal of Natural Sciences TOTAL CONTENTS

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海南岛地体及其毗邻陆缘晚中生代—新生代古地磁研究和构造演化

本文叙述了对海南岛及其毗邻大陆边缘白垩纪到第四纪地层岩石进行古地磁研究的全部工作过程。通过分析岩石中剩余磁矢量的磁偏角及磁倾角的变化,提出海南岛白垩纪以来经历的构造演化模式如下:早期伴随顺时针旋转而向南迁移,后期伴随逆时针转动并向北运移。联系该地区及邻区的地质、地球物理资料,对海南岛上述的构造地体运动提出以下认识:北部湾内早期有一拉张作用,主要是该作用使湾内地壳显著伸长减薄,形成北部湾盆地。从而导致了海南岛的早期构造运动,而海南岛后期的构造运动则主要是受南海海底扩张的影响。海南地体运动规律的阐明对于了解北部湾油气盆地的形成演化有重要的理论和实际意义。     

Scale-based spatial data model for GIS

Being the primary media of geographical information and the elementary objects manipulated, almost all of maps adopt the layer-based model to represent geographic information in the existent GIS. However, it is difficult to extend the map represented in layer-based model. Furthermore, in Web-Based GIS, It is slow to transmit the spatial data for map viewing. In this paper, for solving the questions above, we have proposed a new method for representing the spatial data. That is scale-based model. In this model we represent maps in three levels: scale-view, block, and spatial object, and organize the maps in a set of map layers, named Scale-View, which associates some given scales.Lastly, a prototype Web-Based GIS using the proposed spatial data representation is described briefly.     

Exciton Seebeck in Molecular Systems

Various applications relevant to the exciton dynamics,such as the organic solar cell,the large-area organic light-emitting diodes and the thermoelectricity,are operating under temperature gradient.The potential abnormal behavior of the exicton dynamics driven by the temperature difference may affect the efficiency and performance of the corresponding devices.In the above situations,the exciton dynamics under temperature difference is mixed with     

Achieving Unusual States of Matter Under High Pressure

The elongation method,originally proposed by Imamura was further developed for many years in our group.As a method towards O(N)with high efficiency and high accuracy for any dimensional systems.This treatment designed for one-dimensional(ID)polymers is now available for three-dimensional(3D)systems,but geometry optimization is now possible only for 1D-systems.As an approach toward post-Hartree-Fock,it was also extended to