A scanning aperture-type terahertz near-field imaging system is developed to perform precise nondestructive testing on packaged aluminum etched antenna arrays, and surface imaging of a flexible gold electrode array, to obtain subsurface imaging and surface imaging. The resolution of subsurface imaging is 110 μm and 500 μm when the packaging (polyethylene terephthalate) thickness is 50 μm and 200 μm respectively, and the surface imaging resolution is 6 μm at 0.11 THz. An adaptive threshold segmentation algorithm of Hilbert scan combined with wavelet transform were employed to successfully suppress the noise of the imaging results due to the change of near-field distance. We also proposed a derivative filtering extremum threshold segmentation algorithm to effectively suppress severely uneven threshold distribution of the packaged aluminum etched antenna arrays.

Distributed interactive applications such as multiplayer games will become increasingly popular in wide area distributed systems. To provide the response time desired by users despite high and unpredictable communication latency in such systems, shared objects will be replicated or cached by clients that participate in the applications. Any updates to the shared objects will have to be disseminated to clients that actually use the objects to maintain consistency. We address the problem of efficient and scalable update dissemination in an environment where client interests can change dynamically and the number of multicast channels available for update dissemination is limited. We present a heuristic based algorithm that can group objects and clients in a way that it handles limited bandwidth resources. We show that our algorithm can produce better results than several algorithms that have been developed in the past for update dissemination.

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Value-added content resiliency services help to migrate the burden of resiliency provisioning and maintenance from service users, especially home users and small/medium organizations, who have difficulty in handling correlated failures that impact large areas. For service providers to achieve business success, however, the cost-effectiveness of their resiliency strategies is critical: while the content resiliency requirements specified by the end users have to be satisfied, excessive preventive operation costs caused by the over-reaction to potential risks should be avoided. In this paper, we study the problem of cost-effective configuration in content resiliency service networks under both independent and geographically correlated failures. We propose a new approach to modeling correlated failures in a representable, quantifiable and consistent way, which allows for both quantified availability guarantees and aggressive prevention cost optimization. We then formulate the costeffective configuration problem in content resiliency services and develop both real optimal and heuristic-based algorithms for solving the problem. Our experiments show that with the help of good models for correlated failures, the operation cost of the services can be significantly reduced without impairing the user-specified content resiliency.

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