基于BFC模型的ATM网络拥塞控制器的设计

为充分提高ATM网络性能，设计一个高效的拥塞控制系统是关键。自适应比特(ABR)业务的流量控制正是ATM网络中一种有效的拥塞控制机制和流量管理手段。在二进制ABR流反馈控制方案中，信元速率和队列的大幅度振荡降低了链路利用率，但它的简洁性对设计高性能交换机又极具吸引力。为此，该文基于流体理论给出了二进制反馈控制的分析模型，并基于该模型。提出了传统PID和智能拥塞控制器的设计方案。然后，该文在相同条件下对两类控制方法进行了仿真，并比较分析了他们的优缺点。最后，该文提出了拥塞控制器的改进方法及下一步研究的课题和思路。     

NUMERICAL STUDY ON 3-D FLUID FLOW WITHIN THE MOLTEN POOL DURING UNEQUAL DIAMETER TWIN ROLL STRIP CAST-ROLLING

1.IntroductionNearNetShapeContinuousCasting(NNSCC)isoneofthemootadvancedteclmologiesinMaterialandMetallurgyinthe1990s.Meanwhile,thetechniqueoftWinrollStripCast--ROllingco~sfirst.Stripcast-rollingwhichcastsmoltenst.eeldirectlyilltostrip,eliminatingtheintermediatehot-stripmilloperation,hasformany}rearsbeenacherisheddreamofsteelengineerssincetheintreniionsofSirHenryBesseme.[1],Withtheplogressofsteelmakinganditsperipheraltechnologies,homelier,thedreanlisbeillgreallied.AsshowninPig.1,unequ…     

锅炉炉膛负压测量装置的改造

分析燃煤机组锅炉炉膛负压取样管堵灰的原因,提出了彻底解决该问题的改造方案。     

适体坐标下二维差分网格自动剖分的研究

开展了适体坐标系(Body-Fitted Coordinates,BFC)网格自动生成技术的研究,弥补了有限差分法在笛卡尔直角坐标系下模拟结果连续性差、对不规则区域边界适应性差等不足。采用椭圆型偏微分方程法生成适体坐标网格,并在对DXF文件解析的基础上,针对二维单连域规则图形及二维双连域任意图形开发了适体网格生成系统。结果表明,程序通用性好,能够对大多数复杂区域实现自动剖分,生成的网格能够很好地适应物理区域的曲率变化,物理区域内部的网格分布也比较合理。     

底吹钢包内掷入合金的运动

应用边界适体坐标(BFC)技术计算底吹钢包内的三维流场,该计算无需在未知流场内设置内边界,而使流动及运动的合金可顺利跨越圆心轴.在计算合金运动轨迹时,修正了合金在气液两相区内运动模型的参数.最后分析了若干因素对合金运动轨迹的影响.     

Designing for an Earlier Age

While the need for suitable housing to accommodate burgeoning numbers of elderly citizens is undeniably great worldwide, Jayne Merkel puts the case that the necessity for affordable housing among young adults is arguably even greater, at least in the US and the UK, and particularly in New York, London and Los Angeles. The relationship between the demands of these two very different age groups is direct, since young people tend not to have children until they can find suitable housing. Forestalled childbearing means fewer members of later generations to financially support growing numbers of aged over time.¹ And young people without suitable housing tend to move back in with ageing parents or drain their financial resources.     

Development of a Numerical Analysis Method for Cross-sectional Void Fraction Distribution in Subchannels of Nuclear Fuel Assemblies

Detailed information about the void fraction distribution in fuel assemblies is increasingly important with the development of high burn-up fuels. A numerical method has been developed for the steady cross-sectional void fraction profile in fuel assemblies using a marching method in the axial direction, considering cross-flows due to lift forces, void diffusion and momentum balance. Uniform pressure in a cross section was assumed under the dominant vertical flow and the secondary lateral flow condition in each subchannel. The merit of this simplified method is its high-performance computation using many BFC meshes for expression of complex void fraction and velocity distributions inside the subchannels. The calculated results were compared with the observed void distributions obtained with X-ray computed tomography in the NUPEC tests of full-scale advanced BWR fuels. The comparison showed the capability of this method for predictions of overall void fraction distributions inside the subchannels. This method will provide a good tool for void fraction profile prediction in high burn-up fuels, while future studies for reliable correlations of lift forces are required over a wide range of flow conditions.     

美国的自行车友好社区及其启示

美国大力推广自行车友好社区（BFC），并且有具体的评估内容。自行车的推广对促进社区发展，改善城市生态环境．改善城市交通状况以及对公众的健康等方面都有积极的作用。自行车友好社区的活动对我国有借鉴意义。它对于我国城市发展政策的制定和城市人居环境的改善有重要参考价值。     

焙烧多功能机组除尘系统滤袋的选择

滤袋是焙烧多功能机组除尘系统的主要部件。本文通过膨体微孔薄膜复合滤袋与普通滤袋的对比,说明了选择膨体微孔薄膜复合滤袋的正确性。     

适体坐标系下充型流动模拟的计算方法

介绍了一种基于适体坐标系（BFC）的充型过程模拟方法。在网格剖分、控制方程转换、控制方程离散和自由表面处理等方面进行了介绍和讨论。通过算例比较了BFC方法与基于笛卡尔正交网格方法的各自特点。通过对模拟结果进行比较，表明在相同网格密度下，BFC方法可以获得更高的计算精度，并在网格系统、计算时间和内存消耗综合水平上均比传统的基于笛卡尔正交网格的模拟方法优越。