20021213
Trust and Privacy in Dissemination Control
Dissemination control is concerned with controlling electronic resources even after they have been delivered to a legitimate recipient. This paper proposes a secure resource dissemination system framework in which resource providers and recipients are interacted mutually in an anonymous, accountable, and trustworthy way, while security constraints on diverse resources can be continuously protected along resource distribution. We specify the three-party context-aware trust management and privacy protection mechanism based on part behavior using Dempster-Shafer (D-S) theory. We also discuss main logic functions and procedures in the resource dissemination and usage transaction process.
1252893
A Configurable Web Service Performance Testing Framework
More and more softwares based on web service technologies are developed. Before their releases on the Internet, it is necessary to evaluate these systems' performance, especially their response time under different workload pressures. However, existing performance testing benchmarks and tools for web service applications are difficult to adapt to various user-specific testing purposes. This paper proposes a configurable web service performance testing framework which contains client module, application server module and database module. Client module, by using the network cooperation method that one central client drives several other clients, adapts to a great number of concurrent customers to request web services. Application server module contains web services under testing and external supporting web services, each of which is configured as a plug-in. The process to realize mixed ratio of web service interactions is similar to dealing cards and adapts to different commercial application characteristics. In database module, the data model including table and attribute dependence can be customized, and the data scale initialization can be resized according to the topology of above dependence. As such, this framework allows testers to dynamically define their data model, customize their scale of database, configure their transaction characteristics, deploy their application strategies and confirm their performance metrics..
62585345
An effective collision resolution mechanism for wireless LAN
Based on the current standardized IEEE 802.11 distributed coordination function (DCF) protocol, this paper proposes a new efficient collision resolution mechanism, called GDCF (gentle DCF). Our main motivation is based on the observation that 802.11 DCF decreases the contention window to the initial value after each success transmission, which essentially assumes that each successful transmission is an indication that the system is under low traffic loading. GDCF takes a more conservative measure by halving the contention window size after c consecutive successful transmissions. This "gentle" decrease lowers the collision probability, especially when the competing node number is large. We compute the optimal value for c, and the numerical results from both analysis and simulation demonstrate that GDCF significantly improve the performance of 802.11 DCF including throughput, fairness, and energy efficiency. In addition, GDCF is flexible for supporting priority access by selecting different values of c for different traffic types; it is fully compatible with the original 802.11 DCF, and simple to implement, as it does not requires changes in control message structure and access procedures in DCF.
10259496
An E-Government Platform Based on Multi-Tier Architecture
With the development of dynamic e-government and the network, the application system becomes more complicated. Traditional e-government system will have an inherent scalability problem as the number of applications increases continuously. To solve this problem, an e-government platform based on multi-tier architecture is presented. By integrating applications, resources and system modules, the platform provides an effective mechanism to reduce the development and communication cost. This paper intensively discusses the design rationale and practical solutions of the platform, including structured data models, a secure data exchange model, uniform interface specifications, a topic based publish/subscribe communication mechanism and an asynchronous execution mechanism. The security of the platform is also evaluated by formal logic method.
18568161
Analysis of locomotion of a planetary rover on a slope
For improvement of planetary rover locomotion, a new type of tracked vehicle was designed for planetary exploration based on the concept of reconfigurability. By applying the planetary wheel principle, the system can give output in different forms under various constraint conditions. As a reconfigurable module, the vehicle can be integrated into a larger system using two basic configurations. As a stand-alone rover, it has two moving modes. The whole design was analyzed by conducting dynamics simulations and experiments.
14401068
Nitrogen and Phosphate Removal by Zeolite-Rare Earth Adsorbents
Zeolite modified by rare earth lanthanum compounds would be an excellent water purification agent that can simultaneously remove both nitrogen and phosphate in aqueous solution. In the context, a novel adsorbent was prepared by loading lanthanum chloride on the zeolite, and the the optimal sorbent was produced at 0.5% La3+ and pH value 10 in the solution. Remove ammonia nitrogen and phosphate synchronously tests result showed that the new sorbent is very effective for ammonia nitrogen and phosphate removal, and the best adsorption capacity is 25mg/g and 50mg/g respectively. Feeding into 10 mg/L NH4+-N and 5mg/L H2PO4- in wastewater, the removal ratio will be over 80% and 90% respectively, and dynamics for the process is accordance to Freundlich adsorption model. The result suggests that the novel rare earth adsorbent will provide a new way for the treatment of ammonia nitrogen and phosphate in wastewater.
31996271
A Method of General Stiffness Modeling for Multi-axis Machine Tool
In this paper, a new method for computing general stiffness model at tool tip for multi-axis machine tool is presented. The formula of general stiffness model at tool tip is derived from virtual-work principle and point transformation matrix method. Point transformation matrix method indicates the transformation relationship of elastic displacement on both ends of flexible axes as well as the transformation relationship of force. By multiplying the point transformation matrix, the final stiffness matrix at tool tip will be obtained efficiently. In this modeling method, the final stiffness matrix is composed of local compliance matrixes according to their contribution to the final stiffness matrix.