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A Dynamic Sliding Load Balancing Strategy in Distributed Systems

Ahmad Dalal’ah

Computer Science Department, Jordan University of Science and Technology, Jordan

                                               

Abstract: A sliding strategy for load balancing is introduced. The strategy groups a certain number of adjacent nodes to perform a load balancing process. Upon the completion of a given period, the groups are to be rotated by shifting each group one position to the right, thus produces different groups. This strategy (sort of clustering) not only reduces the load balancing overheads, but also it could be utilized as a backbone by any load balancing strategy. The proposed load balancing strategy always converges, and tends to be in a steady state in a negligible processing time. In this paper, the load status and the locations of the nodes regarding the system’s topology are irrelevant to load balancing process. The new algorithm can be always applied to any distributed system, even if it is heavily loaded, since the cost of scheduling is very low due to the highly reduced number of messages. This is achieved by reducing dramatically the overheads incurred from attached information tables, message passing, job thrashing, and response time.

 Keywords: Load balancing, distributed systems, scalability, message passing. 

Received January 10, 2005; accepted March 20, 2005
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Unconstraint Assignment Problem: A Molecular Computing Approach

Ibrahim Zuwairie1&2, Tsuboi Yusei2, Ono Osamu2, and Khalid Marzuki3

1Department of Mechatronics and Robotics, University Technology Malaysia, Malaysia

2Institute of Applied DNA Computing, Meiji University, Japan

3Center for Artificial Intelligence and Robotics (CAIRO), University Technology of Malaysia, Malaysia 

Abstract: Deoxyribonucleic Acid or DNA-based computing is an emerging field that bridging the gap between chemistry, molecular biology, computer science, and mathematics. This research area is a new paradigm whereby the computation can be done by the use of DNA molecules to encode the computational problem. During the massively parallel computation in a test tube, a series of bio-molecular reactions are employed and the output encoded also by DNA molecules can be printed and read out by electrophoretical fluorescent method. Since DNA computing is very suitable for combinatorial problems, in this paper, an idea on DNA-based computing algorithm for solving unconstraint assignment problem is proposed. The proposed approach basically consists of two phases; encoding phase and computational phase. During the encoding phase, a method to encode the computational problem is carried out by introducing four rules. On the other hand, for the computational phase, it is discovered that the complexity of the unconstraint assignment problem can be reduced to a path problem of a graph, and the possibility to solve the unconstraint assignment problem by DNA computing approach is shown in detail. 

Keywords: DNA computing, assignment problem, optimization. 

Received December 25, 2004; accepted March 11, 2005
 
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Performance of the Modified Round Robin Scheduling Algorithm for Input-Queued Switches Under Self-Similar Traffic

Shanmugam Arumugam1 and Shanthi Govindaswamy2

1Bannari Amman Institute of Technology and Science, Coimbatore, India

2ECE Department, PSG College of Technology, Coimbatore, India 

Abstract: The iSLIP algorithm has been proved to be a very efficient, high throughput scheme for scheduling in input-queued switches. In this paper, we discuss a Modified Round Robin (MRR) scheme, which involves less number of arbitration steps in each iteration when compared to iSLIP. We prove through simulation studies, that the MRR algorithm shows a performance equivalent to iSLIP, but requires less number of processing steps. We compare the performance of the two algorithms under different types of traffic, including Bernoulli independent identically distributed (i. i. d) and bursty traffic. We study the load-delay performance for different switch sizes and for traffic of different burst lengths. We also consider several traffic generation models for generating self-similar traffic and study the performance of both the algorithms under this type of traffic. 

Keywords: High-speed packet switches, self-similar traffic, input-queued switches, packet schedulers, scheduling algorithms. 

Received December 4, 2004; accepted June 29, 2005  

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Operator Decomposition of Graphs

Ruzayn Quaddoura

Computer Science Department, Zarqa Private University, Jordan 

Abstract: In this paper we introduce a new form of decomposition of graphs, the (P, Q)-decomposition. We first give an optimal algorithm for finding the 1-decomposition of a graph which is a special case of the (P, Q)-decomposition which was first introduced in [21]. We then examine the connections between the 1-decomposition and well known forms of decomposition of graphs, namely, modular and homogeneous decomposition. The characterization of graphs totally decomposable by 1-decomposition is also given. The last part of our paper is devoted to a generalization of the 1-decomposition. We first show that some basic properties of modular decomposition can be extended in a new form of decomposition of graphs that we called operator decomposition. We introduce the notion of a (P, Q)-module, where P and Q are hereditary graph-theoretic properties, the notion of a (P, Q)-split graph and the closed hereditary class (P, Q) of graphs (P and Q are closed under the operations of join of graphs and disjoint union of graphs, respectively). On this base, we construct a special case of the operator decomposition that is called (P, Q)-decomposition. Such decomposition is uniquely determined by an arbitrary minimal nontrivial (P, Q)-module in G. In particular, if G Ï (P, Q), then G has the unique canonical (P, Q)-decomposition.

Keywords: Graph decomposition, hereditary class, split graph. 

Received October 28, 2004; accepted August 8, 2005
 
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Alternative Learning Approaches for Electronic Learning Environments in Smart Schools: Survey Results

Kemalatha Krishnasamy1, Sai Peck Lee1, and Ananda Kumar Palaniappan2

1Faculty of Computer Science and Information Technology, University of Malaya, Malaysia

2Faculty of Education, University of Malaya, Malaysia

 

Abstract: Learning styles have been studied for many years; however, studies focusing on learning styles based on multiple intelligences theory for electronic learning are very limited. Knowledge of learning styles is important and may be useful in the development and conduct of e-learning in higher learning institutions and schools. The purpose of this study was to establish baseline information regarding the distribution of learning styles among lower secondary students at selected smart schools in Malaysia. A secondary purpose was to establish for these same individuals their stated preferred learning mode for learning online. A purposive sample (judgment sampling) was developed with permission from Ministry of Education and Education Departments in Malaysia. The learning style for each respondent was determined using the multiple intelligences inventory. The results of the study showed that, web-based instruction in its present form was more preferred by students whose intelligences were visual/spatial and interpersonal. Verbal/linguistic and logical/mathematical students reported less benefit from e-learning, perhaps because these students were more oriented towards traditional classroom learning.

Keywords: E-learning, online teaching and learning, multiple intelligences, effective design. 

Received November 5, 2004; accepted February 21, 2005
 
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Protocols for Committing Mobile Transactions

Nadia Nouali1&2, Habiba Drias2&3, and Anne Doucet4

1Mobile Computing Department, CERIST, Algeria

2Faculté du Génie Electrique, Université Houari Boumediene, Algeria

3Institut National d’Informatique, Algeria

4LIP6 Laboratory, Université Pierre et Marie Curie, France  

 

Abstract: Mobile computing has attracted attention of intensive researches during the recent years. Many papers revisit the conventional implementation of distributed computing paradigms for use in this new environment. A key paradigm of the transaction processing is the transaction commitment. A commitment mechanism such as Two Phases Commit (2PC) protocol, a fundamental asset of transactional technology (and its variants), ensures consistent effects of a distributed transaction. This paper surveys the solutions proposed for mobile transaction commitment and outlines how the conventional commit protocols are revisited in order to fit the needs of a mobile environment. The different approaches try to deal with the slow and unreliable wireless links, the lightweight devices and their limited resources, the frequent disconnections and the movement of mobile devices. 

Keywords: Mobile transaction commitment, disconnection, mobility, resources constraints, wireless communication.  

Received November 3, 2004; accepted February 21, 2005 
 
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Ad Hoc Networks Routing Protocols and Mobility

Djamel Djenouri1, Abdelouahid Derhab1, and Nadjib Badache2

1Basic Software Laboratory, CERIST Research Center, Algeria

2Computer Science Department, USTHB University, Algeria

Abstract: An ad hoc network is a temporary infrastructureless network, formed dynamically by mobile devices without turning to any existing centralized administration. To send packets to remote nodes, a node uses other intermediate nodes as relays, and ask them to forward its packets. For this purpose, a distributed routing protocol is required. Because the devices used are mobile, the network topology is unpredictable, and it may change at any time. These topology changes along with other intrinsic features related to mobile devices, such as the energy resource limitation, make ad hoc networks challenging to implement efficient routing protocols. In this paper, we drive a GloMoSim based simulation study, to investigate the mobility effects on the performance of several mobile ad hoc routing protocols.

Keywords: Ad hoc mobile networks, wireless networks, routing protocols, simulation, GloMoSim. 

Received October 20, 2004; accepted March 12, 2005   

 

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Two Methods for Analysis of Dynamic Scintigraphic Images of the Heart

Kamel Hamrouni and Nawrès Khlifa

Ecole Nationale d’Ingénieurs de Tunis (ENIT, Tunisia)

Abstract: Dynamic scintigraphic images allow functional exploration of the considered organ and thus a good comprehension of the pathological phenomenon. There are two different approaches to analyse such images series; by following the activity of a region of interest or by computing parametric images. Both approaches may require the detection of an area of interest. This paper presents two methods of analysis of synchronised dynamic scintigraphic images of the heart based on an automatic detection of the left ventricle. The first method follows the time activity of the left ventricle and computes the ventricular ejection fraction. The second method computes a parametric image called “covariance image” where each pixel represents a covariance coefficient that indicates if the corresponding point in the heart and the reference area evolve or not in the same direction. The results of the application of the two methods on several dynamic images are presented and discussed.  .

Keywords: Image processing, segmentation, scintigraphic image, covariance, time activity curve 

Received November 10, 2004; accepted February 19, 2005 

 

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Evolution of Agent-Oriented Distributed Model for Software Testing: A Layered Approach

Dhavachelvan Ponnurangam1 and Uma Anbarasan2

1 Department of Information Technology, Sri Manakula Vinayagar Engineering College, India

2Department of Computer Science and Engineering, Anna University, India 

 

Abstract: As new requirements arise, on one hand, from the increasing complexity of modern software systems and, on the other hand, from the distribution of today’s information economies, it has been recognized that the modularity and reusability provided by existing techniques and approaches are insufficient. Although, each paradigm has its own contribution in the software engineering field on the support of their proficiencies, due to the exceptional growth of the software industry, researchers continue to strive for more efficient and powerful techniques. Agents are being advocated as a next generation model for engineering complex and distributed systems. They facilitate the automated software testing by virtue of their high-level decomposition, independency and parallel activation. Here, we address a set of more specific characteristics of agent-based approach (modularity, independency and parallel activation) and its efficacy in software testing. In this paper, we did not only describe the claims for agent-based approach in software testing, but also developed a multi‑agent system for software testing with agent qualities. The multi‑agent system illustrated here is on the basis of few basic operational real-world testing techniques, as an attempt to describe how to practice Agent-Oriented Software Testing (AOST) which has not previously done. 

Keywords: Software testing agent, distributed testing framework, AOST, multi‑agents. 

Received October 4, 2004; accepted April 30, 2005 
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Image Segmentation Based on Watershed and Edge Detection Techniques

Nassir Salman

 

Computer Science Department, Zarqa Private University, Jordan

Abstract: A combination of K-means, watershed segmentation method, and Difference In Strength (DIS) map was used to perform image segmentation and edge detection tasks. We obtained an initial segmentation based on K-means clustering technique.  Starting from this, we used two techniques; the first is watershed technique with new merging procedures based on mean intensity value to segment the image regions and to detect their boundaries.  The second is edge strength technique to obtain an accurate edge maps of our images without using watershed method. In this paper: We solved the problem of undesirable oversegmentation results produced by the watershed algorithm, when used directly with raw data images. Also, the edge maps we obtained have no broken lines on entire image and the final edge detection result is one closed boundary per actual region in the image.

Keywords: Watershed, difference in strength map, K-means, edge detection, image segmentation. 

Received September 30, 2004; accepted February 13, 2005 
 
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An XML-Based Security Management Model for Multilevel Security Databases

Awad Awadelkarim and Norbik Idris

Faculty of Computer Science and Information System, University Technology Malaysia, Malaysia

Abstract: This paper proposes a universal architecture of Security Management Model (SMM) for integrating security features namely low-level access control at row and column level of relational legacy databases using XML as an integration medium. The proposed model integrates and then rearranges, controls, and manages the new and inherent low-level access control attributes based on Rule-Based Algorithm (RBA) and Global Security Policies (GSP) of the integrated environment. In addition, the paper shows how Public-Key Cryptography Scheme (PKCS) can be adapted by the SMM to provide a consistent security management at the global level.

Keywords: Database security, integration of databases, legacy databases, access control, PKCS, XML.

Received September 25, 2004; accepted February 23, 2005 
 
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