Catálogo de publicaciones - libros

Quadratic/Analytical placement methods have been widely used in the latest IC design process. This kind of placement needs a powerful detailed placement method for large-scale mixed macro and standard cell placement. An efficient and effective ulti-tage terative detailed lacement (MSIP) algorithm is proposed in this paper. It combines a better initial placement based on combinatorial optimization method with a deterministic local search for post optimization. Various strategies are used for saving computation time. Experimental results show that it can get an average of 22% wire length improvement comparing to PAFLO [6] in comparable runtime.

A simple algorithm is presented in this paper to preserve the feature of the mesh while the mesh is smoothed. In this algorithm, the bilateral filter is modified to incorporate local first-order properties of the mesh to enhance the effectiveness of the filter in preserving features. The smoothing process is error-bounded to avoid over-smoothing the mesh. Several examples are given to demonstrate the effectiveness of this algorithm in preserving the feature while removing noise from the mesh.

In the distributed object computing systems a set of server objects are made available over the network for computations on behalf of remote clients. In a typical distributed system setting the existing load balancing algorithms usually do not consider the global system state. In this paper we propose a new approach for improving the performance of distributed system using fuzzy grouping-based load balancing. It utilizes membership graphs in terms of the amount of CPU time and memory used for inferencing the service priority. Extensive computer simulation reveals that the proposed approach allows consistently higher performance than other approaches in terms of response time and throughput for various number of servers and tasks.

In a peer to peer grid computing environment, volunteers are exposed to failures such as crash and link failures. In addition, since volunteers can dynamically join and leave executions and they are not dedicated only to a peer to peer grid computing, the executions of volunteers are stopped or suspended more frequently than in a grid computing environment. These failures result in the delay and blocking of the executions of tasks and even partial or entire loss of the executions. In addition, these failures make it difficult for a volunteer server to schedule tasks and manage the allocated tasks as well as volunteers. Existing peer to peer grid computing systems, however, do not deal with these failures in scheduling mechanisms. Moreover, since existing scheduling mechanisms are performed only by a volunteer server in a centralized way, there is a high overhead.

To solve these problems, we propose a mobile agent based adaptive scheduling mechanism (MAASM). We implemented MAASM in Korea@Home and ODDUGI mobile agent system. The MAASM reduces the overhead of volunteer server by using mobile agents in scheduling procedure in a distributed way. In addition, it tolerates the various failures(especially, ) which frequently occur in a peer to peer grid computing environment. Consequently, MAASM guarantees reliable and continuous executions in spite of the failures, so it decreases total execution time.

Various global optimization methods are compared in order to find the best strategy to solve realistic drag reduction problems in the automotive industry. All the methods consist in improving classical genetic algorithms, either by coupling them with a deterministic descent method or by incorporating a fast but approximated evaluation process. The efficiency of these methods (called HM and AGA respectively) is shown and compared, first on analytical test functions, then on a drag reduction problem where the computational time of a GA is reduced by a factor up to 7.

Visualization techniques increase the user involvement in the interactive process of data mining and querying of spatio-temporal data. This paper describes a novel geometric approach to clustering and querying of spatio-temporal data. We propose the uniform geometric model based on function representation of solids to cluster and query time-dependent data. Clustering and querying are integrated with visualization techniques in one GUI. First, visual clustering with blobby model allows the user to see the result of clustering on the screen for different time points and/or time intervals and set the appropriate parameters interactively. After that, the user gets the data of clusters for the chosen time frames. Then, the user can visually query the cluster/clusters he/she is interested in with geometric primitive solids which currently are cubes, spheres/ellipsoids, cylinders, etc. Geometric operations of union, intersection and/or subtraction can be performed over the geometric primitive solids to get the final query shape. The user visually clusters spatio-temporal data and queries the clusters with geometric shapes through graphics interface accessing dynamically 3D projections of multidimensional points from database, warehouses or files.With the uniform geometric model of the clustering and querying of spatio-temporal data, 3D visualization tools can be naturally incorporated in one system to allow the user to visualize and query clusters changing over time.

This paper investigates the routing efficiency problem with quality of service (QoS). A solution to this problem is needed to provide real-time communication service to connection-oriented applications, such as video and voice transmissions. We propose a new weight parameter by efficiently combining two independent measures, the cost and the delay. The weight plays on important role in combining the two measures. If the approaches 0, then the path delay is low. Otherwise the path cost is low. Therefore if we decide an , we then find the efficient routing path. A case study shows various routing paths for each . We also use simulations to show the variety of paths for each . When network users have various QoS requirements, the proposed weight parameter is very informative.

Vector quantization (VQ) is an elementary technique for image compression. However, searching for the nearest codeword in a codebook is time-consuming. The existing schemes focus on software-based implementation to reduce the computation. However, such schemes also incur extra computation and limit the improvement. In this paper, we propose a hardware-based scheme “” (PLUT) which could prune possible codewords. The scheme is based on the observation that the minimum one-dimensional distance between the tested vector and its matched codeword is usually small. The observation inspires us to select likely codewords by the one-dimensional distance, which is represented by bitmaps. With the bitmaps containing the positional information to represent the geometric relation within codewords, the hardware implementation can succinctly reduce the required computation of VQ. Simulation results demonstrate that the proposed scheme can eliminate more than 75% computation with an extra storage of 128 Kbytes.

Electronic exchange is widely used in e-commerce systems. This paper mainly discusses abuse-freeness in general item exchange protocol for two parties. Based on convertible signature scheme and adapted designated verifier proof, an efficient item exchange protocol is proposed to satisfy many interesting requirements including fairness, timeliness and .

Aggregate signatures are digital signatures that allow players to sign different messages and all these signatures can be aggregated into a single signature. This single signature enables the verifier to determine whether the players have signed the original messages. Verifiably encrypted signatures are used when Alice wants to sign a message for Bob but does not want Bob to possess her signature on the message until a later date. In this paper, we first propose an identity (ID)-based signature scheme from bilinear pairing and show that such a scheme can be used to generate an ID-based aggregate signature. Then, combining this ID-based signature with the short signature given by Boneh, Lynn and Shacham, we come up with an ID-based verifiably encrypted signature. Due to the nice properties of the bilinear pairing, the proposed signatures are simple, efficient and have short signature size.