Approximating the Negative Binomial

This paper presents the results of a numerical investigation of six approximations to the cumulative negative binomial distribution. The approximations studied include two Poissons, Poisson Gram-Charlier, Normal, Normal Gram-Charlier and the Camp-Paulson. Two approximations were found to be extremely good: the Poisson Gram-Charlier when the probability p is large, and the Camp-Paulson almost everywhere.     

Modelling observed California Current mesoscale eddies and the ecosystem response

Satellite and in situ observations are used to test model dynamics for the California Current System (CCS). The model and data are combined to reconstruct the mesoscale ocean structure during a given three-week period. The resulting physical flow field is used to drive a 3D ecosystem model to interpret SeaWiFS and in situ chlorophyll-a (chl-a) variations. With this approach a more complete and consistent picture of the physical and ecosystem processes of the CCS is obtained, providing the basis for addressing fundamental questions about dynamics and predictability of the coastal ocean.     

Dynamics of a viscous thread on a non-planar substrate

We derive a general reduced model for the flow of a slender thread of viscous fluid on a grooved substrate. Specific choices of the substrate topography allow further analytic progress to be made, and we subsequently focus on a convection–diffusion equation governing the evolution of viscous liquid in a wedge geometry. The model equation that arises also appears in the context of foam drainage, and we take the opportunity to review and compare the results from both applications. After summarising the constant mass results, we introduce a time-dependent fluid influx at one end of the wedge. The analytical results are supported by numerical computations.     

Less cyber,more café: Enhancing existing small businesses across the digital divide with ICTs

About 10% of the world has access to information and communication technologies (ICTs). Telecenters and cyber cafés are one prevalent way to increase access. This paper suggests increasing access through currently existing, local businesses where people already gather and where proprietors already posses existing business relationships with suppliers and customers. This paper questions the prevailing emphasis on the “cyber'' characteristics of access, e.g., computing and internet access as is currently known, and attempts to refocus the conversation by considering computing and access in the context of the “café,” e.g., as public life in the sense of Habermas, which permits an in situ evolution of relevant access. This analysis is based on extant literature and direct ethnographic research in several public places in six countries. We offer example design perspectives based on a reflection of “third places” as inspiration for appropriate innovation in the provision of computing and communications. © 2005 Wiley Periodicals, Inc.     

模拟集成促进工厂整合

正模拟和混合信号IC的技术进步促进了前所未有的工厂生产力、效率、质量及安全性整合。这些IC使得系统性能更强、测量精度越来越高、通信更可靠、功耗更低,安全性更高;它们是工业系统的核心,根据大量传感器测量数据快速做出响应,高精度控制材料处理、工业过程的步骤、供电和温度,以及操作的安全性。当计算功能集成到这些模拟与混合信号IC时,工厂可采用分布式的智能管理模型。现在,工厂数据能够更     

Control point policy optimization using genetic algorithms

This paper describes the application of an integrated Genetic Algorithm (GA)/Discrete Event Simulation model for selecting optimum values for Critical Point Policy (CPP) hedging time and buffer size parameters. The CPP is shown to perform well, when compared with the Critical Ratio priority rule, in terms of improving service levels, particularly when subject to conditions where buffer sizes and Takt times are required to be small. The technique developed involves buffer sizes being chosen by a GA according to a constraint on the total storage space available within the system. A method is described for reducing the number of variables that the GA needs to deal with, hence, improving the efficiency of the GA optimization process. The development and application work reported also provides further understanding into how and when the CPP should be applied.