An experimental study on bubble growth within a narrow space under an interference‐piece

An experimental study was performed on the nucleate boiling of water in the narrow space formed between an interference piece and the heating surface of heat‐proof glass. A past study analyzed the bubble growth due to the conduction of heat through the thinner liquid layer under a growing bubble; however, the thickness of the liquid layer was not shown experimentally. This study investigates the thickness of this thinner layer by the interference method. Almost no change was found on the thickness of the liquid layer under both the interference‐piece and on the heating surface. The experimental results indicate the great contribution of superheating of the test liquid to bubble growth. © 2006 Wiley Periodicals, Inc. Heat Trans Asian Res, 35(2): 165–177, 2006; Published online in Wiley InterScience ( www.interscience. wiley.com ). DOI 10.1002/htj.20100     

Ring Network Design by Lagrangean Based Column Generation

We discuss the problem of designing a telecommunication network with the survivability requirement that the network should be composed of connected rings of links. The network design problem is then to choose links from a given network, and compose them into a number of rings. Furthermore, the rings should be connected at certain transit nodes. The traffic between rings may pass through other rings. Each ring is associated with a certain fixed cost depending on the length of the ring. We describe the problem, modeled as a linear integer programming problem, and a heuristic solution method, based on column generation and Lagrangean relaxation.     

Planning of WDM Ring Networks

The rapid introduction of wavelength division multiplexing (WDM) technology to cope with the increased bandwidth requirements of transmission networks has intensified the need for recovery mechanisms at the optical layer. A first step towards survivable optical networking will be seen through the introduction of optical rings. This paper presents different types of optical rings (dedicated and shared protection WDM rings) and the planning issues associated with these WDM rings. In particular, we give mathematical models as well as solution methods for the ring loading and wavelength assignment problem. We compare the wavelength requirement of dedicated and shared protection rings under scenarios with different demand patterns. We also discuss the influence of the WDM equipment cost, and present a mathematical model for the optimization of hybrid networks with both dedicated and shared protection rings.     

Effective Traffic Grooming Algorithms in SONET/WDM Ring Networks

Much work has focused on traffic grooming in SONET/WDM ring networks. Previous work has considered many aspects of traffic grooming, including minimizing the number of ADMs, minimizing the number of wavelengths, considering different traffic models, using different network architectures, incorporating switching capability and so on. In this work, we study traffic grooming in unidirectional ring networks with no switching capability under both uniform traffic and non-uniform traffic models to reduce electronic multiplexing costs. Based on the clustering notion, we derive a general and tighter lower bound for the number of ADMs required in traffic grooming under the uniform all-to-all traffic model. This bound reduces to special cases obtained in previous work. We also derive general, tighter, and closed form lower bounds for the number of ADMs required under two non-uniform traffic models: the distance-dependent traffic model and the non-uniform symmetric traffic model. Cost-effective multi-phase algorithms that exploit traffic characteristics are then designed and studied to efficiently groom traffic streams under different traffic models. Our numerical and simulation results show that the proposed multi-phase algorithms outperform existing traffic grooming algorithms by using a fewer number of ADMs. Our algorithms in several cases also achieve the lower bounds derived.     

A Novel Dynamic Fault Restoration Mechanism Using a Multiple Ring Approach in WDM Mesh Networks

This work describes a distributed fault restoration algorithm, called the Dynamic Multiple Ring Algorithm (DMRA), for application in WDM mesh networks. This study explores the choice of restoration paths and the assignment of fault-tolerant bandwidth when a link, node, or channel failure occurs according to the change in traffic load, number of nodes, and transmission delay including propagation and switching delays. Accordingly, the primary aim of this work is to use networking segments near faults to share the restoration load throughout a mesh network. Each node searches for restoration paths in their near environment using the proposed DMRA. Nodes use distributed control to search for neighboring nodes and to establish the relationship between them to build numerous logical rings. Nodes can also locate faults in the logical rings. These rings establish the restoration paths. The traffic load over failed links or nodes can be diverted to other paths in the networking segments. The cost of the restoration paths is computed at each node based on both the current capacity and the transmission delay. The selected restoration paths are suitable transmission routes in the network neighborhood. Hence, restoration paths can be identified and wavelength assigned quickly according to network bandwidth and traffic load. Simulation results reveal that the proposed method works extremely quickly and has a high success rate. Consequently, it is very useful for applications in real WDM networks, where the status varies from minute to minute.Corresponding author is presently a guest scientist with the National Institute of Standards and Technology, USA. This research was partially supported by the Grant of National Science Council, ROC (NSC-92-2218-E-155-004 and NSC-93-2917-I-155-001).     

Analysis of failed nuclear plant components

Argonne National Laboratory has conducted analyses of failed components from nuclear power- gener-ating stations since 1974. The considerations involved in working with and analyzing radioactive compo-nents are reviewed here, and the decontamination of these components is discussed. Analyses of four failed components from nuclear plants are then described to illustrate the kinds of failures seen in serv-ice. The failures discussed are (1) intergranular stress- corrosion cracking of core spray injection piping in a boiling water reactor, (2) failure of canopy seal welds in adapter tube assemblies in the control rod drive head of a pressurized water reactor, (3) thermal fatigue of a recirculation pump shaft in a boiling water reactor, and (4) failure of pump seal wear rings by nickel leaching in a boiling water reactor. Work supported by Commonwealth Edison Company under ACK 85026.     

Mn18Cr18N护环钢静态再结晶组织及模型

在Gleeble-1500D热模拟机上,采用双道次热压缩试验研究Mn18Cr18N护环钢高温变形后不同停留时间内的静态软化行为,分析热变形温度、应变速率、变形程度以及初始奥氏体晶粒对静态再结晶行为的影响.通过应力补偿法计算静态再结晶软化率,并结合金相组织作了修正.建立其静态再结晶动力学模型,获得静态再结晶激活能249.3 k J/mol.研究表明:Mn18Cr18N钢静态再结晶软化曲线呈\"S\"形,符合Avrami方程.静态再结晶体积分数随着停留时间延长而增加,热变形温度越高,静态再结晶分数越大,而在较低温度和较小变形程度时,孕育时间较长,主要发生静态回复,将静态再结晶动力学模型的预测结果与实测值进行比较,二者吻合较好,为护环钢后续热镦粗工艺模拟提供更为详尽的模型.     

环Fq+uFq++uk-1Fq上一类重根常循环码

记R=Fq+uFq++uk-1Fq,G=R[x]/,且是R中可逆元。定义了从Gn到Rtn的新的Gray映射,证明了J是G上长为n的线性的x-常循环码当且仅当(J)是R上长为tn的线性的-常循环码。使用有限环理论,获得了环R上长为pe的所有的(u-1)-常循环码的结构及其码字个数。特别地,获得了环F2m+uF上长为2e的(u-1)-常循环码的对偶码的结构及其码字个数。推广了环Z2a根负循环码的若干结果。     

内燃机活塞环调质稀土离子渗氮处理的摩擦磨损性能

通过改善活塞环的磨损、腐蚀抗力来提高其使用寿命.利用相应的仪器和设备,对经调质处理后的活塞环进行了表面稀土离子渗氮处理和金相观察,并将调质后稀土离子渗氮处理的活塞环与表面未经任何处理的活塞环制出3组试样,对不同的载荷及不同时间内的磨损情况进行了对比试验研究.结果表明,采用调质后稀土离子渗氮活塞环的抗磨损性能和腐蚀抗力优于原始环.通过装机试验,经调质后稀土离子渗氮的活塞环耐磨性能明显高于其他措施处理的活塞环.