1423209
Scalable load balancing on distributed web servers using mobile agents
Distributed web servers on the immensely expanding Internet require high scalability and availability to provide efficient services to millions of clients on the web. To provide rapid responses to enormous number of client requests, load balancing is an important technique to evenly distribute the requests to web servers. In this paper, we propose a framework called Mobile Agent based LoaD balancing (MALD) that uses mobile agents technology to implement scalable load balancing on distributed web servers. The web servers can dispatch mobile agents to collect system-wide load information and accomplish load redistribution on all servers. Various load-balancing policies can be incorporated with versatile mobile agents in the framework. Compared with the traditional message-passing-based load-balancing methods, the mobile-agent-based approaches have the merits of high flexibility, low network traffic and high asynchrony. The performance evaluation demonstrates that the MALD framework provides a foundation to develop efficient load-balancing schemes on wide range of web server systems from cluster to the Internet.
14338621
A distributed object model for solving irregularly structured problems on cluster
This paper presents a distributed object model MOIDE (Multithreaded Object-oriented Infrastructure on Distributed Environment) for solving irregularly structured problems on cluster. The primary appeal of MOIDE is its flexible system structure that is adaptive to heterogeneous architecture of a cluster. MOIDE integrates the object-oriented and multithreaded methodologies to set up a unified computing environment. Both the shared-data access and remote messaging are incorporated in a two-layer communication mechanism for efficient inter-object communication with the common communication interface. MOIDE supports dynamic load balancing by its autonomous load scheduling technique. A runtime support system implements the MOIDE model as a platform-independent infrastructure for developing and executing irregularly structured applications. N-body, ray tracing, and conjugate gradient applications are implemented to illustrate the advantages of MOIDE model.
15800513
ClusterProbe: an open, flexible and scalable cluster monitoring tool
In this paper, we describe the ClusterProbe, an open, flexible, scalable, and Java-based cluster monitoring tool. The tool provides an open environment by developing a multiple-protocol communication interface that can be connected to various types of external accesses from the clients. ClusterProbe is flexible that the monitoring tool can be easily extended to adapt to the resource changes by using the Java-RMI mechanism. In addition, the design of ClusterProbe allows it to scale up to commodious capacity with its cascading hierarchical architecture. Several useful services are implemented based on ClusterProbe, including the visualization of cluster resource information in various form and cluster fault management. The tool has been used to assist the execution of a cluster-based search engine and a distributed N-body application. All experiments demonstrate high efficiency.
14112050
Distributed particle simulation method on adaptive collaborative system
Abstract This paper presents a distributed N-body method based on an adaptive collaborative system model. The collaborative system is formed by the distributed objects on a distributed system. The system can be reconfigured during the computation to fully utilize the computing power of the networked hosts. The method is implemented in Java and RMI to support distributed computing in heterogeneous environment. A distributed tree structure is designed for communication-efficient computation of N-body method. The performance test shows satisfactory speedup and portability of the method on both homogeneous and heterogeneous clusters. The collaborative system model can be used in various applications and it is expandable to wide-area environment.
1335499
Dynamic configuration management in a graph-oriented Distributed Programming Environment
Dynamic configuration is a desirable property of a distributed system where dynamic modification and extension to the system and the applications are required. It allows the system configuration to be specified and changed while the system is executing. This paper describes a software platform that facilitates a novel approach to the dynamically configurable programming of parallel and distributed applications and systems. This platform is based on a graph-oriented model and it provides support for constructing reconfigurable distributed programs. We describe the design and implementation of a dynamic configuration manager for the graph-oriented distributed programming environment. The requirements and services for dynamic reconfiguration are identified. The architectural design of a dynamic configuration manager is presented, and a parallel virtual machine-based prototypical implementation of the manager, on a local area network of workstations, is described.
12578633
High-level abstractions for message-passing parallel programming
61852216
Cross-Evaluation: A new model for information system evaluation
In this article, we introduce a new information system evaluation method and report on its application to a collaborative information seeking system, AntWorld. The key innovation of the new method is to use precisely the same group of users who work with the system as judges, a system we call Cross-Evaluation. In the new method, we also propose to assess the system at the level of task completion. The obvious potential limitation of this method is that individuals may be inclined to think more highly of the materials that they themselves have found and are almost certain to think more highly of their own work product than they do of the products built by others. The keys to neutralizing this problem are careful design and a corresponding analytical model based on analysis of variance. We model the several measures of task completion with a linear model of five effects, describing the users who interact with the system, the system used to finish the task, the task itself, the behavior of individuals as judges, and the self-judgment bias. Our analytical method successfully isolates the effect of each variable. This approach provides a successful model to make concrete the “three-realities” paradigm, which calls for “real tasks,” “real users,” and “real systems.” © 2006 Wiley Periodicals, Inc.
7719537
Measuring Fingertip Forces by Imaging the Fingernail
This paper presents an external camera method for measuring fingertip forces by imaging the fingernail and surrounding skin. This method is an alternative to the photoplethysmograph sensor originally developed by one of the authors. A 3D model of the fingernail surface and skin is obtained with a stereo camera and laser striping system. Subsequent images from a single camera are registered to the 3D model by adding fiducial markings to the fingernail. Calibration results with a force sensor show that the measurement range depends on the region of the fingernail and skin. A Bayesian method is developed to predict fingertip force given coloration changes. Preliminary accuracy results for normal and shear force measurement are presented. In comparison to the results using the photoplethysmograph fingernail sensor, our results are more accurate and double the range of forces that can be transduced, all the way up to the saturation level.
4666459
Synchronous and asynchronous multiple object rate control for MPEG-4 video coding
Video scenes containing multiple objects can potentially achieve higher degree of compression and better visual quality with individual coding for each object. Video objects are not always synchronous, implying each object may have a separate temporal resolution. This paper proposes a rate control algorithm for multiple video object encoding. Using a novel bit allocation strategy, the algorithm achieves accurate target bit rate, provides good visual quality, and decreases buffer overflow/underflow. Experimental results for both synchronous and asynchronous multiple video object encoding demonstrate that, when compared with the existing rate control scheme recommended by the MPEG-4 standard, the proposed algorithm provide better temporal-spatial tradeoff with more accurate rate regulation.
17387040
Automated judgment of document qualities
The authors report on a series of experiments to automate the assessment of document qualities such as depth and objectivity. The primary purpose is to develop a quality-sensitive functionality, orthogonal to relevance, to select documents for an interactive question-answering system. The study consisted of two stages. In the classifier construction stage, nine document qualities deemed important by information professionals were identified and classifiers were developed to predict their values. In the confirmative evaluation stage, the performance of the developed methods was checked using a different document collection. The quality prediction methods worked well in the second stage. The results strongly suggest that the best way to predict document qualities automatically is to construct classifiers on a person-by-person basis.
16523105
Region-based rate control and bit allocation for wireless video transmission
In this paper, we propose a joint source-channel region-based rate control algorithm for real-time video transmissions over wireless systems. During the video transmission, the channel throughput available to the video encoder in the wireless systems is inherently variable, due to the retransmission of the error packets using the automatic repeat request (ARQ) error control. The variable data rate of the wireless system is characterized by the packet-level Gilbert two-state Markov Model, the parameters of which are extracted from the statistical properties of the channel information obtained from the wireless channel simulator. The proposed algorithm adopts a fast but effective block-based segmentation method to extract the regions of interest. Unlike traditional bit allocation methods used in the region/content-based rate control, the algorithm exploits the most effective criteria "coding qualities" as quantitative factors to directly control bit allocation among different regions so as to achieve better visual quality in the regions of interest. The computational complexity of the algorithm is low making it suitable for real-time applications. Compared with the MPEG-4 rate control algorithm, our algorithm can effectively enhance the perceptual quality for the regions of interest and significantly reduce the number of frame skipping; thereby, improve the smoothness of the video.