Software Engineering

One of the most critical problems in distributed systems is Leader Failure. Distributed network becomes unstable without leadership. To solve this problem Leader Election algorithm is executed to give the leadership to other processor. The election process starts when one or more processor discovers that leader has failed, and it terminates when the remaining processors know who the new leader is. Election process use ID number to choose the new leader. In this study we propose distributed leader election algorithm to solve leader failure in hypercube network when ID number is not distinguished. Performance is evaluated and analyzed. In a network of N nodes connected by a Hypercube network the proposed algorithm uses O(N ) messages to elect a new leader in O(log N) time steps.

during the past four decades, new software development approaches were presented to going with new trends of the software development companies and developers. Nowadays most software companies search to customise short period and minimal costs to produce valuable software products. These productions are within unstable, changing environments. Agile Methodologies were thus introduced to achieve the new requirements of the software development companies.  Agile development invented for handling change. The key benefit of agile methodology is used to simplify the change-oriented software engineering process, but agile methodology needs to take more consideration to user point of view. Although the weaknesses of prototyping approach have, it can be used effectively by end users to describe requirements that developers may not have considered.  This paper presents a proposed framework based on merge prototyping and agile approaches not only to cure the weaknesses of agile development and...

Leader election is a very important algorithm in wired and wireless networks. It is used to solve the single point failure in distributed systems when one process which called leader is responsible to coordinate and manage the whole network. The leader election algorithms (LEA's) solve the instability problem in the network, which caused by leader failure. The research work reported here is concerned with building and designing a dynamic leader election algorithm, to contribute in solving leader crash problem in three dimensional torus networks. The algorithm solves leader failure despite the existing of intermittent links failure. Algorithm performance was evaluated by calculating the number of messages and time steps overall the algorithm. In a network of N nodes connected by a three dimensional torus network, the performance is evaluated, when leader failure is detected by a (N-1) node and algorithm faces F link failure. The number of messages is O(N+F) in ) ( 3 F N O  time ...

With the huge volume of digital data, clustering algorithms are providing efficient tools for data organizing and analyzing. Clustering algorithms are used in various domains such as bioinformatics, speech recognition, and information retrieval. Clustering is an automatic technique that divides a set of data objects into smaller groups such that the objects within a group are similar to each other and dissimilar to objects in other groups as much as possible. This paper reviews and discusses different clustering algorithms, their concepts, advantages, and limitations. A comparison among clustering algorithms will also be represented based on certain criteria.

Leader election algorithms solve the instability problem in the network which is caused by leader failure .In this paper, we propose a new leader election algorithm in two dimensional torus networks. The algorithm aims to elect one node to be a new leader. The new leader is identified by some characteristics not in the other nodes in the network. When the process is terminated, the network is returned to a stable state with one node as leader where other nodes are aware of this leader. The new algorithm solves this problem despite the existence of one link failure. In a network of N nodes connected by two dimensional torus network, the new algorithm uses O(N) messages to elect a new leader in O( N ) time steps. These results are valid for both cases: simple case (when the leader failure is detected by one node) and in the worst case (when the failure is discovered by up to N-1 nodes).

Every year, more than two millions of Muslims went to the Holy city of Makah for pilgrimage “Hajj”. There are a lot of activities that should be done during pilgrimage. One of the rituals performed by Muslim pilgrims during pilgrimage in al-Jamarat area in Mina, adjacent to Makah, is throwing stones at a pillar target. This activity is a symbol of stoning the devil "Throwing Jamarat " as done by Prophet Ibrahim. Throwing stones in mina during "aladha " eid is the most bottle neck ceremony. It caused a death of many Muslims last few years. This study suggests multi-solutions to solve the problem by using simulation program. Solutions include add more bridges; increase the radius of al-jamrat circles or using gates and semaphores. The suggested simulation presents any combination of the three solutions. The results of the study encourage adopting these solutions.

Service Specific Overlay Networks (SSONs) have recently attracted a great interest, and have been extensively investigated in the context of multimedia delivery over the internet. SSONs are virtual networks constructed on top of the underlying network and they have been proposed to provide and improve services not provided by other traditional networks to the end users. The increased complexity and heterogeneity of these networks in addition to ever changing conditions in the network and the different types of fault that may occur make their control and management by human administrators more difficult. Therefore, self-healing concept was introduced to handle these changes and assuring highly reliable and dependable network system performance. Self-healing aims at ensuring that the service will continue to work regardless of defects that might occur in the network. This paper introduces literature in the area of self-healing overlay networks, presents their basic concepts, requireme...

Despite the deleterious effects associated with elevated carbon dioxide (CO(2)) or hypercapnia, it has been hypothesized that CO(2) can protect the lung from injury. However, the effects of chronic hypercapnia on the neonatal lung are unknown. Hence, we investigated the effect of chronic hypercapnia on neonatal mouse lung to identify genes that could potentially contribute to hypercapnia-mediated lung protection. Newborn mouse litters were exposed to 8% CO(2), 12% CO(2), or room air for 2 wk. Lungs were excised and analyzed for morphometric alterations. The alveolar walls of CO(2)-exposed mice appeared thinner than those of controls. Analyses of gene expression differences by microarrays revealed that genes from a variety of functional categories were differentially expressed following hypercapnia treatment, including those encoding growth factors, chemokines, cytokines, and endopeptidases. In particular and of major interest, the expression level of genes encoding surfactant proteins A and D, as well as chloride channel calcium-activated 3, were significantly increased, but the expression of WNT1-inducible signaling pathway protein 2 was significantly decreased. The significant changes in gene expression occurred mostly at 8% CO(2), but only a few at 12% CO(2). Our results lead us to conclude that 1) there are a number of gene families that may contribute to hypercapnia-mediated lung protection; 2) the upregulation of surfactant proteins A and D may play a role as anti-inflammatory or antioxidant agents; and 3) the effects of CO(2) seem to depend on the level to which the lung is exposed.

Breathing-disordered states, such as in obstructive sleep apnea, which are cyclical in nature, have been postulated to induce neurocognitive morbidity in both pediatric and adult populations. The oscillatory nature of intermittent hypoxia, especially when chronic, may mimic the paradigm of ischemia-reperfusion in that tissues and cells are exposed to episodes of low and high O(2) and this may lead to oxidant stress. Therefore, we decided to explore the potential contribution of oxidant stress in our intermittent hypoxia/hypercapnia animal model and the role that mitochondria might play in this stress. Neonatal mice were exposed to intermittent hypoxia/hypercapnia for 10 days and 2 wk. Combined intermittent hypoxia/hypercapnia led to a marked increase in apoptotic cell death in the cerebral cortex. Oxygen consumption studies in isolated mitochondria from intermittent hypoxia/hypercapnia-exposed brains demonstrated significant reductions in both state 4 and state 3 respiratory activities by approximately 60% and 75%, respectively. Electron paramagnetic resonance spectroscopy registered a significant increase in superoxide production during nonphosphorylating state 4 by 37%, although superoxide leakage during state 3 did not increase upon treatment. Neuronal superoxide-specific dihydroethidium oxidation was also greater in exposed animals. These studies indicate that intermittent hypoxia/hypercapnia leads to oxidative stress due to mitochondrial response within the mouse central nervous system.

Exposure to chronic constant or intermittent hypoxia (CCH or CIH) may have different effects on growth and development in early life. In this work, we exposed postnatal day 2 (P2) CD1 mice to CCH or CIH (11% O2) for 4 weeks and examined the effect of hypoxia on body and organ growth until P30. Regression analysis showed that weight increased in control, CCH and CIH cohorts with age with r2 values of 0.99, 0.97, and 0.94, respectively. Between days 2 and 30, slopes were 0.93 ± 0.057, 0.76 ± 0.108, and 0.63 ± 0.061 (g/day, means ± SEM) for control, CIH, and CCH, respectively and significantly different from each other (P < 0.001). The slopes between P2 and P16 were 0.78 ± 0.012, 0.46 ± 0.002, and 0.47 ± 0.019 for control, CCH and CIH, respectively. From P16 to 30, slopes were 1.12 ± 0.033, 1.09 ± 0.143, and 0.82 ± 0.08 for control, CIH, and CCH, respectively with no significant difference from each other, suggesting a catch-up growth in the latter part of the hypoxic period. Slower weight gain resulted in a 12% and 23% lower body weight in CIH and CCH mice (P < 0.001) by P30. Lung/body ratios were 0.010, 0.015, 0.015 for control, CIH, and CCH at P30, respectively. The decrease in liver, kidney, and brain weight were greater in CCH than CIH. Smaller liver weight was shown to be due to a reduction in cell size and cell number. Liver in CIH and CCH mice showed a 5% and 10% reduction in cell size (P < 0.05) and a reduction of 28% in cell number (P < 0.001) at P30. In contrast, CCH and CIH heart weight was 13% and 33% greater than control at P30 (P < 0.05), respectively. This increase in the heart weight was due to an increase in the size of cardiomyocytes which showed an increase of 12% and 14% (P < 0.001) for CIH and CCH, respectively as compared to control. Brain weight was 0.48 and 0.46 g for CIH and CCH, respectively (95% and 92% of normal). We concluded that (a) CIH and CCH follow different body and organ growth patterns; (b) mostly with CCH, the liver and kidneys are reduced in size in a proportionate way to body size but heart, lung, and brain are either spared or increased in size compared to body weight; and (c) the decrease in liver is secondary mostly to a decrease in cell number. Pediatr Pulmonol. 2008; 43:20–28. © 2007 Wiley-Liss, Inc.

Several pulmonary and neurological conditions, both in the newborn and adult, result in hypercapnia. This leads to disturbances in normal pH homeostasis. Most mammalian cells maintain tight control of intracellular pH (pH(i)) using a group of transmembrane proteins that specialize in acid-base transport. These acid-base transporters are important in adjusting pH(i) during acidosis arising from hypoventilation. We hypothesized that exposure to chronic hypercapnia induces changes in the expression of acid-base transporters. Neonatal and adult CD-1 mice were exposed to either 8% or 12% CO(2) for 2 wk. We used Western blot analysis of membrane protein fractions from heart, kidney, and various brain regions to study the response of specific acid-base transporters to CO(2). Chronic CO(2) increased the expression of the sodium hydrogen exchanger 1 (NHE1) and electroneutral sodium bicarbonate cotransporter (NBCn1) in the cerebral cortex, heart, and kidney of neonatal but not adult mice. CO(2) increased the expression of electrogenic NBC (NBCe1) in the neonatal but not the adult mouse heart and kidney. Hypercapnia decreased the expression of anion exchanger 3 (AE3) in both the neonatal and adult brain but increased AE3 expression in the neonatal heart. We conclude that: 1) chronic hypercapnia increases the expression of the acid extruders NHE1, NBCe1 and NBCn1 and decreases the expression of the acid loader AE3, possibly improving the capacity of the cell to maintain pH(i) in the face of acidosis; and 2) the heterogeneous response of tissues to hypercapnia depends on the level of CO(2) and development.

—University web portals are considered one of the main access gateways for universities. Typically, they have a large candidate audience among the current students, employees, and faculty members aside from previous and future students, employees, and faculty members. Web accessibility is the concept of providing web content universal access to different machines and people with different ages, skills, education levels, and abilities. Several web accessibility metrics have been proposed in previous years to measure web accessibility. We integrated and extracted common web accessibility metrics from the different accessibility tools used in this study. This study evaluates web accessibility metrics for 36 Jordanian universities and educational institute websites. We analyze the level of web accessibility using a number of available evaluation tools against the standard guidelines for web accessibility. Receiver operating characteristic quality measurements is used to evaluate the effectiveness of the integrated accessibility metrics.