Showing papers by "American University in Cairo published in 2009"

Fabrication and properties of dispersed carbon nanotube–aluminum composites

Abstract: Powder metallurgy techniques have emerged as promising routes for the fabrication of carbon nanotube (CNT) reinforced metal matrix composites. In this work, planetary ball milling was used to disperse 2 wt% MWCNT in aluminum (Al) powder. Despite the success of ball milling in dispersing CNTs in Al powder, it is often accompanied with considerable strain hardening of the Al powder, which may have implications on the final properties of the composite. Both un-annealed and annealed Al–2 wt% CNT composites were investigated. It was found that, ball-milled and extruded (un-annealed) samples of Al–2 wt% CNT demonstrated high notch-sensitivity and consistently fractured outside the gauge length during tensile testing. In contrast, extruded samples annealed at 400 and at 500 °C for 10 h prior to testing, exhibited more ductile behavior and no notch sensitivity. Under the present investigated processing conditions, ball milling for 3 h followed by hot extrusion and annealing at 500 °C resulted in enhancements of around 21% in tensile strength compared with pure aluminum with the same process history. The ball-milling conditions used were found to result in the creation of a nanostructure in all samples produced, as shown by XRD and TEM analysis. Such nanostructure was retained after prolonged exposures to temperatures up to 500 °C. The tensile testing fracture surfaces showed uniform dispersion and alignment of the CNTs in the aluminum matrix but also showed CNTs acting as nucleation sites for void formation during tensile testing. This has contributed to the observation of CNT pull-out due to the poor bond between the CNTs and the matrix.

Gold nanoparticles for molecular diagnostics

Abstract: Gold nanoparticles (AuNPs) exhibit a unique phenomenon, known as surface plasmon resonance, which is responsible for their large absorption and scattering cross-sections, which are four to five orders of magnitude larger than those of conventional dyes. In addition, their optical properties can be controlled by varying their sizes, shapes and compositions. AuNPs can be easily synthesized and functionalized with different biomolecules including oligonucleotides. Numerous methods have been utilized for detecting AuNPs such as colorimetric, scanometric, fluorescence, surface-enhanced Raman scattering and electrochemical techniques. These unique aspects have permitted the development of novel AuNP-based assays for molecular diagnostics which promise increased sensitivity and specificity, multiplexing capability, and short turnaround times. AuNP-based colorimetric assays in particular show great potential in point-of-care testing assays. This review discusses properties of AuNPs and their utilization for the development of novel molecular assays.

Detection of outliers

Abstract: We present an overview of the major developments in the area of detection of outliers These include projection pursuit approaches as well as Mahalanobis distance-based procedures We also discuss principal component-based methods, since these are most applicable to the large datasets that have become more prevalent in recent years The major algorithms within each category are briefly discussed, together with current challenges and possible directions of future research Copyright © 2009 John Wiley & Sons, Inc For further resources related to this article, please visit the WIREs website

Customer and non‐customer perspectives for examining corporate reputation

Abstract: Purpose – Several studies on corporate reputation have proposed a customer‐based approach for assessing corporate reputation. Other studies proposed examining corporate reputation from the perspective of other primary stakeholder groups such as employees, investors or suppliers. Hence this paper aims to examine corporate reputation by considering both the customer's and the non‐customer's views.Design/methodology/approach – This study was applied to the US wireless telecommunications industry. A random sample of 1,088 respondents composed of 518 customers and 570 representing the non‐customers, was generated for this study. The sample was randomly distributed by age, gender, income, education and geographic location.Findings – The findings of this study revealed that the formation of perceptions about corporate reputation differ between customers and non‐customers. The dimension of emotional appeal is specific to the customer group and the dimension of vision and leadership is specific to the non‐customer...

Linking customer‐based brand equity with brand market performance: a managerial approach

Abstract: Purpose – The purpose of this paper is to attempt to bridge a gap in literature by defining and operationalizing specific brand equity constructs, and testing the relationships between customer‐based brand equity and brand market performance. Current literature has focused on building and conceptualizing brand equity, there is no consensus on how it should be measured and what constructs should be included in the measurement process.Design/methodology/approach – This study was conducted in two phases: a consumer‐level analysis; and a brand‐level analysis. A total of 6,410 observations have been identified (sample size consists of 5,598 usable observations). The second phase involved analyzing the data at the aggregate brand level. Analysis included testing hypotheses on the correlations between customer‐based brand equity constructs and brand market performance. finally, detailed market and country‐of‐origin analyses are presented for managerial considerations.Findings – Results from the consumer dataset ...

Enough!: Egypt's Quest for Democracy

Abstract: In 2004-2005, for the first time in more than five decades, Egypt witnessed the rise of a protest movement calling for the end of one-party rule. In 1 year, Egypt witnessed more oppositional demonstrations, rallies, and the organization of nonviolent dissident groups than it has seen in the previous 25 years. However, the outcome of this mobilization in terms of democratic opening remained limited and, some argue, negligible. Using social movement theory, which has been unduly ignored by students of democratic transition in the Middle East, and data from fieldwork, the article analyzes the rise, limitations, and potentials of this prodemocracy movement in Egypt. The article argues that changes in the political opportunity structure and relatively successful cultural framing and mobilizing structures pushed for the rise of this movement, but shortcomings on these same fronts limited the movement's expansion and concomitantly, its direct impact.

Effect of cold work and annealing on the structure and characteristics of NiTi alloy

Abstract: A hot rolled NiTi alloy (50.7 at.% Ni) was subjected to cold rolling with reductions of 20%, 30% and 40%. Some of the 40% cold rolled samples were then annealed at 400 °C, 500 °C, 600 °C and 700 °C. X-ray results and microstructural analysis show that increasing the percent of cold rolling causes an increase in the volume fraction of martensite, which results in an increase in recoverable strain, tensile strength and hardness. On the other hand, this eliminates the superelasticity plateau and results in a reduction in ductility and shape memory recovery. After an initial sharp decrease in superelasticity with cold rolling, further increase in cold rolling results in relative improvement in the superelasticity. Annealing on the other hand causes a significant increase in austenite volume fraction, leading to a decrease in hardness and superelasticity in the temperature range of 400 °C–500 °C. Recrystallization starts at 500 °C and grains grow with annealing at higher temperatures while hardness and superelasticity increase.The results of this work indicate that it is best to use the NiTi alloy in the as hot rolled condition if maximum SME is desired. Cold rolled NiTi would be preferable if high strength, hardness and acceptable recoverable strains are desirable.

Dependence of GaN HEMT Millimeter-Wave Performance on Temperature

Abstract: This paper presents extensive thermal characterization of recently fabricated high-performance millimeter-wave GaN/SiC devices from four sources across temperature (-25°C to + 125°C). The changes with temperature for: output power at millimeter-wave frequencies (Pout), pinchoff voltage (Vp), knee-voltage (Vk), onresistance (Ron), power-added efficiency (PAE), saturated drain current (Idss), power gain (G), and transconductance (gm) are measured, statistics studied, and correlations investigated. Temperature-coefficients are established for Pout, Vp, Vk, Ron, PAE, Idss, G, and gm in GaN technology. The main findings are: 1) Pout's temperature dependence can be negative or positive, opposite of G's and Idss's strong negative temperature dependence, and 2) the pinchoff voltage's dependence on temperature is very weak. The results obtained provide monolithic microwave integrated circuit designers with key information required for meeting performance over a wide temperature range.

Arab Citizen Journalism in Action: Challenging Mainstream Media, Authorities and Media Laws

Abstract: Arab citizens have adopted the blogging technology of the internet to create a venue for alternate viewpoints in a manner similar to their global counterparts. Initially a handful of bloggers, writing mostly in English and reflecting a Western flavour in their content, initiated the Arab blogosphere. They have since been joined by thousands of Arabic blogs. Their impact has been noted, whether directly on politics and media or in their ability to enable civil society by providing instant networking and expanding the space for freedom of expression. They have also created an unexpected challenge to their governments, causing inconsistent reactions. This article analyzes the region’s laws, regulations and the methods used to govern those nationals who choose to join the growing number of global citizen journalists, and how they often learn to defy those rules. The primary focus has been the case of Egypt’s blogs due to their influential role in the regional blogosphere.

Military Spending and Inequality: Panel Granger Causality Test

Abstract: The relationship between military spending and economic inequality is not well documented within the empirical literature, while numerous studies have uncovered the linkages between military spendi...

The Impact of ICT Investments on Economic Development in Egypt

Abstract: Since the mid 1980s, Egypt has realized significant growth in information and communication technology (ICT) usage across different sectors in the economy. However, in today’s global environment, the challenge no longer lies in accommodating the growth of the ICT sector that introduced changes that are arguably the most important since the industrial revolution. The essence is the diffusion of ICT across the society and ensuring that it furthers socioeconomic development. Managing this transformational process requires cooperation and partnerships between different stakeholders in the society to ensure steady and successful progress towards the goal of realizing a fully developed information society. Moreover, in order to generate economic development and growth, ICT need to be transformed into economic activities offering services, applications and content that create new markets, reduce costs and increase productivity. While ICT are generally adaptable; their effectiveness in addressing development issues still depends on their introduction, adoption, diffusion and adaptation within a healthy and encouraging regulatory environment. In that respect, the importance of ICT in socioeconomic development in Egypt was realized since 1999 leading to the allocation of ICT on the government agenda supported by the private sector and the civil society. This article addresses the recent efforts that were exerted in Egypt, as an emerging economy, in terms of building its ICT sector while analyzing the associated investments and their impact on economic development.

Work, Refuge, Transit: An Emerging Pattern of Irregular Immigration South and East of the Mediterranean.

Abstract: Southern and Eastern Mediterranean (SEM) countries have recently turned into receivers of migrants, but they have neither the institutions nor the policies that would allow them to integrate migrants. Therefore, most migrants in SEM countries found themselves in irregular situation. Using a variety of statistical sources, official and non-official, the article establishes that out of 5.6 million immigrants living in SEM countries in the mid-2000s, a minimum of 3.6 would be in irregular situation. They belong to three categories: approximately 2 million migrant workers attracted by SEM labour markets where they are employed in the informal sector with no work permit, 1.5 million de facto refugees who cannot obtain the status of refugee and are waiting for resettlement in a third country or return to their homes, and less than 200,000 transit migrants initially bound for Europe, which they are unable to reach for lack of visa. While their reasons to be stranded in the SEM differ, these three categories share the same vulnerable conditions, with no legal access to work, services, or protection.

Hybrid Time-Cost Optimization of Nonserial Repetitive Construction Projects

Abstract: Time-cost trade-off analysis represents a challenging task because the activity duration and cost have uncertainty associated with them, which should be considered when performing schedule optimization. This study proposes a hybrid technique that combines genetic algorithms (GAs) with dynamic programming to solve construction projects time-cost trade-off problems under uncertainty. The technique is formulated to apply to project schedules with repetitive nonserial subprojects that are common in the construction industry such as multiunit housing projects and retail network development projects. A generalized mathematical model is derived to account for factors affecting cost and duration relationships at both the activity and project levels. First, a genetic algorithm is utilized to find optimum and near optimum solutions from the complicated hyperplane formed by the coding system. Then, a dynamic programming procedure is utilized to search the vicinity of each of the near optima found by the GA, and converges on the global optima. The entire optimization process is conducted using a custom developed computer code. The validation and implementation of the proposed techniques is done over three axes. Mathematical correctness is validated through function optimization of test functions with known optima. Applicability to scheduling problems is validated through optimization of a 14 activity miniproject found in the literature for results comparison. Finally implementation to a case study is done over a gas station development program to produce optimum schedules and corresponding trade-off curves. Results show that genetic algorithms can be integrated with dynamic programming techniques to provide an effective means of solving for optimal project schedules in an enhanced realistic approach.

Ontology learning from domain specific web documents

Abstract: Ontologies play a vital role in many web- and internet-related applications. This work presents a system for accelerating the ontology building process via semi-automatically learning a hierarchal ontology given a set of domain-specific web documents and a set of seed concepts. The methods are tested with web documents in the domain of agriculture. The ontology is constructed through the use of two complementary approaches. The presented system has been used to build an ontology in the agricultural domain using a set of Arabic extension documents and evaluated against a modified version of the AGROVOC ontology.

Contested Sudan : The Political Economy of War and Reconstruction

Abstract: Part One: Historical and Theoretical Foundation. Chapter 1: Introduction: The Making of Sudan: A history of Incomplete Processes. Chapter 2: War and the Transformative Potential: Towards an Alternative Conceptual Framework for Analyzing Post-Civil Wars. Part Two: The Unmaking of Sudan Chapter 3: The Failed Modernity I: The early Phase of the crisis (Post-colonial to 1989). Chapter 4: The Failed Modernity II: The Crony Capitalism of Political Islam (1989-2004). Part Three: Re-Negotiating a Sudan. Chapter 5: Sudan's War Produced Economy and Society: The Case for Transformative Potential. Chapter 6: From Addis to Nivasha war-Fatigue Driven Peace Agreement: Sources of Fragility and Challenges of Governance. Chapter 7: Post-Nivasha: Challenges of re-building war-produced economy. Part Four: Potential Scenarios: Conclusion. Chapter 8: Conclusion.

Hopf-Ranãda linked and knotted light beam solution viewed as a null electromagnetic field.

Abstract: The Hopf-Ranada linked and knotted light beam solution, which has been interpreted physically and extended analytically by Irvine and Bouwmeester recently, is viewed in this Letter as a null electromagnetic field. It is shown, in particular, that the Hopf-Ranada solution is a variant of a luminal null electromagnetic wave due originally to Robinson and Troutman and reported by Bialynicki-Birula recently. This analogy is motivated by means of a method due to Whittaker and Bateman, and a relationship to well-known scalar luminal localized waves is examined.

Concepts, applications, and extensions of value chain analysis to livestock systems in developing countries

Abstract: The analysis of value chains has augmented our knowledge on the complexities, inter-linkages, distributional benefits, and institutional arrangements of production and marketing channels in developing countries. However, the analysis remains relatively qualitative and case-specific, with limited ability to rank or assess the impact of alternative interventions or to analyze sufficiently the complex market dynamics and feedbacks present in livestock systems. This paper offers insights on ways to improve the analytical rigor of the value chain methodology that combines both qualitative and quantitative approaches.

HIV surveillance and epidemic profile in the Middle East and North Africa.

Abstract: HIV infection is the most devastating infection that has emerged in the recent history The risk of being infected can be associated with both individuals knowledge and behavior and community vulnerability influenced by cultural norms laws politics and social practices Despite that the countries in the Middle East and North Africa have succeeded in keeping low the HIV epidemic rates the number of identified infected cases are increasing Since the appearance of the first AIDS cases all the national authorities devoted their efforts to abort the epidemic in its early stages The rate of new HIV infections across the Middle East and North Africa region are not at an alarming level but the need for a concerted effort from nation-states and nongovernmental organizations to stem the spread of the virus across the region is vitalMost countries of the region have put in place better information systems to track the HIV epidemic yet the passive HIV/AIDS reporting remains the cornerstone in the HIV surveillance systems Several countries still believe that their current strategies are optimal to the HIV status within their territories and that their national strategies are appropriate to their low epidemic status that is not expected to grow Additionally these countries fear that establishing an HIV national program to survey risk behaviors may be perceived as an approval of these behaviors that are culturally and religiously unacceptable This background article aims to summarize the HIV surveillance strategies and epidemic profile in 17 Arab countries in the Middle East and North Africa The article also displays the national surveillance system and the epidemic profile in Egypt and Lebanon as models for the region This information aims to provide useful insights that may help the national authorities in finding out the best surveillance strategies that allow merging and collecting biological and risk data which is an integral part of their efforts to fight the HIV epidemic in the region

Effect of processing technique on the dispersion of carbon nanotubes within polypropylene carbon nanotube‐composites and its effect on their mechanical properties

Abstract: Carbon nanotube-reinforced polymer composites are being investigated as promising new materials having enhanced physical and mechanical properties. With regards to mechanical behavior, the enhancements reported thus far by researchers are lower than the theoretical predictions. One of the key requirements to attaining enhanced behavior is a uniform dispersion of the nanotubes within the polymer matrix. Although solvent mixing has been used extensively, there are concerns that any remaining solvent within the composite may degrade its mechanical properties. In this work, a comparison is carried out between solvent and “solvent-free” dry mixing for dispersing multiwall carbon nanotubes in polypropylene before further melt mixing by extrusion. Various weight fractions of carbon nanotubes (CNTs) are added to the polymer and their effect on the mechanical properties of the resulting composites is investigated. Enhancements in yield strength, hardness, and Young's modulus when compared with the neat polymer, processed under similar conditions, are observed. Differences in mechanical properties and strain as a function of the processing technique (solvent or dry) are also clearly noted. In addition, different trends of enhancement of mechanical properties for the solvent and dry-mixed extrudates are observed. Dry mixing produces composites with the highest yield strength, hardness, and modulus at 0.5 wt% CNT, whereas solvent mixing produces the highest mechanical properties at CNT contents of 1 wt%. It is believed that this difference is primarily dependent on the dispersion of CNTs within the polymer matrix which is influenced by the processing technique. Field emission scanning electron microscopy analysis shows the presence of clusters in large wt% CNT samples produced by dry mixing. Samples produced by solvent mixing are found to contain homogeneously distributed CNTs at all CNT wt fractions. CNT pull-out is observed and may explain the limited enhancement in mechanical properties. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers

Quantitative Methods for Design-Build Team Selection

Abstract: Use of design-build (DB) contracting by transportation agencies has been steadily increasing as a project delivery system for large complex highway projects However, moving to DB from traditional design-bid-build procurement can be a challenge One significant barrier is gaining acceptance of a best value selection process in which technical aspects of a proposal are considered separately and then combined with price to determine the winning proposal These technical aspects mostly consist of qualitative criteria, thus making room for human errors or biases Any perceived presence of bias or influence in the selection process can lead to public mistrust and protests by bidders It is important that a rigorous quantitative mathematical analysis of the evaluation process be conducted to determine whether bias exists and to eliminate it The paper discusses two potential sources of bias – the evaluators and the weighting model – in the DB selection process and presents mathematical models to detect and remove biases should they exist A score normalization model deals with biases from the evaluators; then a graphical weight space volume model and a Monte Carlo statistical sampling model are developed to remove biases from the weighting model The models are then tested and demonstrated using results from the DB bridge replacement project for the collapsed Mississippi River bridge of Interstate 35W in Minneapolis, Minnesota