Assignment schemes for replicated services in Jini

This paper introduces and compares different schemes for assignment of replicated services in Jini - an object oriented middleware architecture for network-centric computing. Each client in Jini has to be assigned a service selected from the pool of available services, which have joined the Jini federation and registered with the lookup service. Both early and delayed assignments are considered as basic options in our evaluation. The information for the system load can be collected at four different levels of detail in order to be used in the process of assignment decisions. In our analysis, we concentrate on the scenario where the requests for service generated by the clients follow independent user-initiated or machine-initiated transactions. The performance evaluation of the assignment schemes follows the queuing systems methodology. The comparisons are done with regard to the mean residence time of the clients in the system as well as the control overhead imposed by the assignment schemes. A case study of the scheme using the lowest information level proves the effectiveness, applicability and limitations of the delayed assignment in comparison to the early one. These results are a first step towards developing a methodology for building large-scale applications for Jini-based distributed systems

Existence of Global Solutions to Supercritical Semilinear Wave Equations

∗The author was partially supported by Alexander von Humboldt Foundation and the Contract MM-516 with the Bulgarian Ministry of Education, Science and Thechnology.In this work we study the existence of global solution to the semilinear wave equation (1.1) (∂2t − ∆)u = F(u), where F(u) = O(|u|^λ) near |u| = 0 and λ > 1. Here and below ∆ denotes the Laplace operator on R^n. The existence of solutions with small initial data, for the case of space dimensions n = 3 was studied by F. John in [13], where he established that for 1 < λ < 1+√2 the solution of (1.1) blows-up in finite time, while for λ > 1 + √2 the solution exists globally in time. Therefore, the value λ0 = 1 + √2 is critical for the semilinear wave equation (1.1)

Model turbulent floods with the Smagorinski large eddy closure

Floods, tides and tsunamis are turbulent, yet conventional models are based upon depth averaging inviscid irrotational flow equations. We propose to change the base of such modelling to the Smagorinksi large eddy closure for turbulence in order to appropriately match the underlying fluid dynamics. Our approach allows for large changes in fluid depth to cater for extreme inundations. The key to the analysis underlying the approach is to choose surface and bed boundary conditions that accommodate a constant turbulent shear as a nearly neutral mode. Analysis supported by slow manifold theory then constructs a model for the coupled dynamics of the fluid depth and the mean turbulent lateral velocity. The model resolves the internal turbulent shear in the flow and thus may be used in further work to rationally predict erosion and transport in turbulent floods

Polysemy in Design Review Conversations

This paper examines the role of polysemy, defined as the quality of having multiple meanings, in design review conversations. It examines the polysemy, particularly of nouns, involved in a dataset of design review conversations with reference to design ideas. The purpose is to determine whether polysemy is related to successful development of design ideas and more creative design outcomes. The results show that the polysemy of nouns involved in the conversations of the finally developed, successful, design ideas exceeds in the most cases the average polysemy involved in the conversations pertaining to the unsuccessful design ideas. Furthermore, the polysemy of these nouns is linked to high overall creativity of the design idea. The paper concludes by discussing issues and directions for further investigation of polysem

Does Atkinson-Wilcox Expansion Converges for any Convex Domain?

2000 Mathematics Subject Classification: 35C10, 35C20, 35P25, 47A40, 58D30, 81U40.The Atkinson-Wilcox theorem claims that any scattered field in the exterior of a sphere can be expanded into a uniformly and absolutely convergent series in inverse powers of the radial variable and that once the leading coefficient of the expansion is known the full series can be recovered uniquely through a recurrence relation. The leading coefficient of the series is known as the scattering amplitude or the far field pattern of the radiating field. In this work we give a simple characterization of the strictly convex domains, such that a reasonable generalization of the AtkinsonWilcox expansion converges uniformly in the corresponding exterior domain. All these strictly convex domains are spheres

A Taxonomy of Essential Services

Communities, countries and alliances cannot be efficient in preparing to meet diverse threats to their security within traditional organizational stovepipes. The boundaries between ‘internal’ and ‘external’ threats are getting fuzzier, and the vulnerabilities of governments, businesses and communities feed on each other, while the comprehensive approach is gaining traction in ever more security fields. The implementation of the comprehensive approach poses a number of methodological challenges. While it clearly requires coordination of various capabilities of a multitude of actors, it is less apparent which is the suitable organising concept. This paper takes as a starting point the concept of ‘essential services’ and suggests a taxonomy, that would allow to treat threats, vulnerabilities and risk in a common comprehensive framework. The taxonomy has been developed with a specific purpose in mind, and thus refers to European Essential Services (EES). We nevertheless reason that it can be replicated to support decision making at other levels, e.g. in national security policy making and planning