Design studies for a 10 MW superconducting wind generator have been performed for offshore wind turbine applications. Electromagnetic, mechanical and thermal analyses are performed by taking into account the characteristic properties of the superconducting and non-superconducting materials. The investigations use enhanced YBCO (Yttrium Barium Copper Oxide) second generation (2G) high temperature superconducting (HTS) wire under development in a research program sponsored by the U.S. Department of Energy.

In this paper we present K-VAC -- a key-value access control model for modern non-relational data stores. This model supports specification and enforcement of access control policies at different levels of resource hierarchy, such as a column family, a row, or a column. The policies can be based on contents of the key-value store and they may also include context information. Through a case-study example we demonstrate the capabilities of this system.

This paper details the design and development work for fabricating a modular and configurable multi-megawatt power amplifier. The impetus for creating the amplifier was to enable electric grid code standards testing for interconnection of large wind turbines. However, the flexible nature of the amplifier topology and control readily enables its use as a multipurpose power interconnect converter.

We present a programming framework based on the paradigm of generative application development for building context-aware collaborative applications. In this approach, context-aware applications are implemented using a domain-specific design model, and their execution environment is generated and maintained by the middleware. The key features of this design model include support for context-based service discovery and binding, context-based access control, context-based multiuser coordination, and context-triggered automated task executions. The middleware uses the technique of policy-based specialization for generating application-specific middleware components from the generic middleware components. Through a case-study example, we demonstrate this approach and present the evaluations of the design model and the middleware.

In this paper, we present a forward recovery model for programming robust context-aware applications. The mechanisms devised as part of this model fall into two categories: asynchronous event handling and synchronous exception handling. These mechanisms enable designing recovery actions to handle different kinds of failure conditions arising in context-aware applications. These include service discovery failures, service binding failures, exceptions raised by a service, and context invalidations. This model is integrated in the high-level programming framework that we have designed for building context-aware collaborative (CSCW) applications. In this paper, we demonstrate the capabilities of this model for programming various kinds of recovery patterns in context-aware applications.

In this paper we present the design and evaluation of a system for deploying highly available and migratable services in shared infrastructures, such as the PlanetLab, where the available resource capacities at a node can fluctuate significantly. A migratable service can monitor its operating conditions and autonomously relocate itself to another node when the available resource capacities at the current node fall below certain acceptable limits. We utilize the autonomous mobile agent paradigm for building such migratable services. Such agents can monitor their operating conditions and follow various migration policies. We investigate here the mechanisms for service relocation, and client-side protocols to access migratory services. The "blackout periods'', i.e. the time during which the clients are unable to access a migrating service, need to be minimized and kept within some tolerable limits for services required to be highly available. We first present the design of a migratable service implemented using a mobile agent, and evaluate its performance in terms of the blackout periods and the service agent's abilities to autonomously migrate in the network. We replicate service agents to reduce the blackout periods, and develop the coordination protocols for autonomous agent migration in a group of service agents. We also present here our work for monitoring PlanetLab nodes for their available resource capacities in order to assist a migratory service in selecting a target node for relocation.

In this paper we present a context-aware RBAC (CARBAC) model for pervasive computing applications. The design of this model has been guided by the context-based access control requirements of such applications. These requirements are related to users' memberships in roles, permission executions by role members, and context-based dynamic integration of services in the environment with an application. Context information is used in role admission policies, in policies related to permission executions by role members, and in policies related to accessing of dynamically interfaced services by role members. The dynamic nature of context information requires model-level support for revocations of role memberships and permission activations when certain context conditions fail to hold. Based on this model we present a programming framework for building context-aware applications, providing mechanisms for specifying and enforcing context-based access control requirements.

We identify here various kinds of failure conditions and robustness issues that arise in context-aware pervasive computing applications. Such conditions are related to failures in an application's interactions with ambient services, failures in resource discovery and binding, and invalidation of context conditions during the execution of an application task. In this paper we present an exception handling model for integrating forward error recovery mechanisms in the designs of such applications. This model is integrated in a role-based framework and supported by a programming environment for construction of such applications.

Abstract In this paper we present a framework for building policy‐based autonomic distributed agent systems. The autonomic mechanisms of configuration and recovery are supported through a distributed event processing model and a set of policy enforcement mechanisms embedded in an agent framework. Policies are event‐driven rules derived from the system's functional and non‐functional requirements. Agents in the network monitor the system state for policy violation conditions, generate appropriate events, and communicate them to other agents for cooperative filtering, aggregation, and handling. A set of agents perform policy enforcement actions whenever events signifying any policy violation conditions occur. Policies are defined using a specification framework based on XML. The policy enforcement agents interpret the policies given in XML. We illustrate the utility of this framework in the context of an agent‐based distributed network monitoring application. We also present an experimental evaluation of our approach. Copyright © 2006 John Wiley & Sons, Ltd.