瞬态热线法导热系数测试中的自然对流影响

基于瞬态热线法导热系数测试原理,试验测量了微细金属丝(Φ=0.06 mm)水平、垂直放置时的空气加热过程,获得了不同加热功率下的空气导热系数。采用了考虑自然对流影响的空气导热系数估算法,对估算法与瞬态热线法计算的导热系数进行对比分析。分析结果表明:金属丝水平放置时两种方法的计算值吻合度好,但与空气导热系数的标准值差别较大。当加热功率较小,垂直放置时两种方法的计算值偏差稍大,基于瞬态热线法计算的空气导热系数准确度较高;而加热功率较大时,两种方法的计算值偏差较小,基于瞬态热线法计算的空气导热系数准确度较低。通过微细金属丝表面自然对流换热强度的理论分析,认为随着金属丝表面温度的升高,水平加热普遍大于垂直加热时的自然对流换热系数,瞬态热线法计算导热系数时,会受到微细金属丝加热表面自然对流换热强度的影响。     

金属泡沫铜/石蜡复合相变材料融化传热特性的实验研究

为了探究不同厚度的金属泡沫铜对石蜡融化过程的影响,设计搭建了可视化相变蓄热实验台,制备了不同厚度的金属泡沫铜复合相变材料,通过实验对比研究了纯相变材料和添加不同厚度金属泡沫铜的复合相变材料的融化界面变化和内部温度分布,分析了不同厚度的金属泡沫铜对换热强度的影响。实验结果表明:在纯相变材料融化过程中自然对流起主导作用,5mm厚的金属泡沫铜促进了上部的石蜡自然对流,10、15、20mm的金属泡沫铜抑制了石蜡的自然对流;金属泡沫铜的厚度越大,导热换热强度越大;对流换热强度和导热换热强度二者呈现出负相关的关系;当金属泡沫铜厚度为14mm时,导热换热强度和对流换热强度相当。     

金属泡沫/石蜡复合相变材料融化传热特性的可视化实验研究

为了探究不同厚度的金属泡沫铜对石蜡融化过程的影响,设计搭建了可视化相变蓄热实验台,制备了不同厚度的金属泡沫铜复合相变材料,通过实验对比研究了纯相变材料和添加不同厚度金属泡沫铜的复合相变材料的融化界面变化和内部温度分布,分析了不同厚度的金属泡沫铜对换热强度的影响。实验结果表明：在纯相变材料融化过程中自然对流起主导作用,5 mm厚的金属泡沫铜促进了上部的石蜡自然对流,10、15、20 mm的金属泡沫铜抑制了石蜡的自然对流;金属泡沫铜的厚度越高,导热强度越大;对流作用强度和导热作用强度二者呈现出负相关的关系;当金属泡沫铜厚度为14 mm时,导热换热强度和对流换热强度相当。     

金属泡沫/石蜡复合相变材料融化传热特性的可视化实验研究

为了探究不同厚度的金属泡沫铜对石蜡融化过程的影响,设计搭建了可视化相变蓄热实验台,制备了不同厚度的金属泡沫铜复合相变材料,通过实验对比研究了纯相变材料和添加不同厚度金属泡沫铜的复合相变材料的融化界面变化和内部温度分布,分析了不同厚度的金属泡沫铜对换热强度的影响。实验结果表明：在纯相变材料融化过程中自然对流起主导作用,5 mm厚的金属泡沫铜促进了上部的石蜡自然对流,10、15、20 mm的金属泡沫铜抑制了石蜡的自然对流;金属泡沫铜的厚度越高,导热强度越大;对流作用强度和导热作用强度二者呈现出负相关的关系;当金属泡沫铜厚度为14 mm时,导热换热强度和对流换热强度相当。     

封闭腔内层流自然对流换热过渡层数值研究

对正方形空腔内的层流自然对流换热进行了数值模拟 ,用SIMPLE算法和乘方格式对该问题 (Ra =1× 10 3～ 1× 10 6)进行了详细的数值计算 .根据计算结果 ,在前人工作的基础上总结出封闭腔内层流自然对流换热的变化规律 ,提出了导热占主导地位的层流流动和导热与对流共时作用的层流流动的分界点 ,同时得出了两个区域的平均努塞尔数的计算公式 ,通过比较 ,表明其精度较以前的计算公式要高 .     

横管表面自然对流传热特性的实验分析和数值模拟

对大空间内管径d=40mm横管表面的自然对流进行了实验分析和数值模拟,通过测出不同位置的壁温计算出横管表面的自然对流换热系数α,并与3种不同经验公式计算值进行了比较,得出大空间内横管径表面自然对流换热系数的最佳经验公式;并用数值计算方法模拟了大空间自然对流换热现象。     

基于保温性能的磷石膏空腔楼盖内空气层研究

空腔模盒内空气层的存在使得磷石膏空腔楼盖具有较大的保温隔热潜力,常规厚度的空气层对于空腔楼盖的保温性能提高不大。通过对磷石膏空腔内空气对流情况进行分析,确定了磷石膏空腔内空气对流的数学模型。根据Ostrach给出的对流临界Ra数,结合贵阳市冬季气候条件,将傅里叶定律运用于平壁,确定了保温条件下常规尺寸的磷石膏空腔模盒内不发生对流换热的最优空气层厚度为0.02 m,改良了磷石膏空腔模盒。最后运用Fluent软件模拟,验证该工况下空腔内对流换热难以展开。     

脉管制冷机内自然对流影响的数值分析

通过对脉管内自然对流的数值模拟,在相同的冷、热端温度条件下,研究重力的方向对脉管内自然对流的流场、温度场及脉管内热交换的影响,并进行了对比分析。采用二维圆柱坐标,引入Boussinesq假设,计算稳态的自然对流。计算表明,冷端在下（冷面朝上）时,自然对流对脉管内的换热有抑制的作用,有利于保持两端的温差,从而使得在冷端与冷端温度相同、热端与热端温度相同的情况下,冷端在下时端部所需的导热量是冷端在上时的31％。这一结论与实验测试结果一致。所做的理论分析对脉管制冷机的良好运行有指导意义。     

水平圆管在大空间内自然对流换热的实验与数值分析

通过实验与数值计算相结合的方法,对大空间水平圆管的自然对流换热过程进行研究.实验得出圆管自然对流换热系数随管壁温度的升高而增大,并拟合了实验条件下的自然对流换热实验关联式.以Fluent为平台,对水平圆管在大空间内的自然对流换热进行数值分析.结果表明,自然对流换热强弱取决于圆管壁面与周围流体温差的大小,温差越大,自然对流流动发展越快,最大流速越大,圆管周围空气在温差产生的浮升力驱动下形成不断上升的气流.     

圆内开缝圆不同开缝方向自然对流换热

采用SIMPLE方法对圆内开缝圆在不同开缝方向时的自然对流换热进行了数值模拟,根据数值结果,分析了开缝圆不同开缝方向的自然对流换热规律和特性.数值结果表明:采用SIMPLE方法的计算结果与已有文献相同工况的实验结果相吻合;同一开缝方向,平均当量导热系数Keqs随着瑞利数Ra的增加而增大.当Ra较小时,Keqs基本不随开缝方向的改变而变化;当Ra继续增大,同一Ra下开缝方向从竖直到水平随角度φ增大Keqs值变小;当Ra超过一个临界值时,Keqs数值结果出现了振荡,且这个临界值与开缝方向相关;研究水平开缝的圆内开缝圆自然对流换热,随着Ra的增加,能够获得稳定解、周期性振荡解及非周期振荡解,最终为混沌.     

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