Cooperative Access in Cognitive Radio Networks: Stable Throughput and Delay Tradeoffs

In this paper, we study and analyze fundamental throughput-delay tradeoffs in cooperative multiple access for cognitive radio systems. We focus on the class of randomized cooperative policies, whereby the secondary user (SU) serves either the queue of its own data or the queue of the primary user (PU) relayed data with certain service probabilities. The proposed policy opens room for trading the PU delay for enhanced SU delay. Towards this objective, stability conditions for the queues involved in the system are derived. Furthermore, a moment generating function approach is employed to derive closed-form expressions for the average delay encountered by the packets of both users. Results reveal that cooperation expands the stable throughput region of the system and significantly reduces the delay at both users. Moreover, we quantify the gain obtained in terms of the SU delay under the proposed policy, over conventional relaying that gives strict priority to the relay queue.Comment: accepted for publication in IEEE 12th Intl. Symposium on Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks (WiOpt), 201

Leagile strategies for optimizing the delivery of prefabricated house building projects

Australian housing supply has not been responded at a rate commensurate with its growing demand. Residential housing sector is facing this serious shortage issue by actively developing and effectively using new construction material, processes and practices for sustaining its competitive advantage over other construction sectors in the Australian context. The Construction 2020 report confirmed prefabrication/off-site manufacturing (OSM) as a critical vision for the Australian construction industry’s future, as OSM provides opportunities for not only increased productivity and safety, but also decreased cost. It also has the capability of meeting the growing housing demand within the extant level of skilled labour. By combining lean and agile concepts, OSM’s supply responsiveness and efficiency can be intensified. The current research studies the association between demand–supply housing imbalance factors using mixed methods from literature and interviews. Literature has documented four main factors that drive this imbalance: (1) housing completion time; (2) cost of a finished house; (3) customer preferences and (4) level of skilled labour. Interviews with 13 industry professionals identified the four main leagile strategies used to deliver prefabricated building projects. Literature and interview findings supported the development and validation of multicriteria decision-making (MCDM) model comprising and incorporating these factors (and subfactors) and the four leagile strategies. The choice of the appropriate strategy to address the studied factors within the Australian context was optimized using analytic hierarchy process (AHP). The results from the AHP model show the suitability of applying each strategy at different degrees as influenced by the tested factors

BARRIERS TO IMPLEMENTATION OF BUILDING INFORMATION MODELLING (BIM) IN THE PALESTINIAN CONSTRUCTION INDUSTRY

The objective of this study is to determine potential barriers faced by the implementation of BIM in the Palestinian construction industry. The data collection was obtained using a questionnaire-based survey of 270 professionals in the construction industry. The results obtained from the factor analysis clustered the BIM barriers in four components, namely: the lack of interest in BIM, the organization's resistance to change workflows, the lack of BIM knowledge, and the cost implementation and cultural barriers towards adopting new technology and training requirements. The main reason given for not using BIM in the construction industry in the Gaza Strip is due to the fact that the clients and other contracting parties did not require the use of BIM. This study adds to the current body of knowledge on BIM in developing countries, especially in Palestine. The contributed knowledge establishes a good platform for future

Factors affecting the bid/no bid decision in the Palestinian construction industry

Purpose – The purpose of this paper is to identify and rank the factors that affect the bid/no bid decision according to their relative importance from the perspective of the contracting parties operating in the Gaza Strip, Palestine. Design/methodology/approach – The objectives of this research were investigated through a postal questionnaire, which covered a randomly selected sample of 63 contractors, 29 clients and 13 consultants operating in the construction industry in the Gaza strip. The questionnaire was structured based on related literature, the pilot study and actual factors affecting bidders' decisions to bid or not that arise from special conditions in the Gaza Strip. A total of 78 factors that affect the bid/no bid decision were identified. These factors were then ranked according to their relative importance to contracting parties operating in the Gaza Strip, Palestine. Findings – The results illustrate that the financial

Evaluating the In vivo Efficacy of Copper-Chitosan Nanocomposition for Treating Vascular Wilt Disease in Date Palm

Date palm, Phoenix dactylifera, as one of the most important fruit crops in Egypt and many other countries, can be affected by many fungal diseases, among which the vascular wilt disease, caused by the fungal pathogen Fusarium oxysporum, is considered the most deteriorating one. This study aims at evaluating the efficiency of Copper-Chitosan Nanopcomposition for treating the vascular wilt disease in date palm. The study relies mainly on beleaguering the disease via the double-role functionality of copper-chitosan nanocomposition, i.e. its potential antifungal effect on the fungal pathogen, besides its capability to enhance the immune responses of the infected plant. In this regard, chitosan nanoparticles were prepared according to the ionic gelation method, whereas copper nanoparticles were prepared according to the chemical reduction method. Physicochemical characterization of both chitosan and copper nanoparticles was performed using dynamic light scattering (DLS), transmission electron microscopy (TEM), fourier transform infrared spectroscopy (FTIR) and x-ray diffraction (XRD). Copper-chitosan nanocomposition could significantly reduce the vascular wilt disease severity; this means that the nanocomposition can be used in the future for developing new nano-fungicides to control such pathogens

Assessment of Fences as Noise Barriers: A Case Study in New Cairo, Egypt

Noise levels in Egypt exceed acceptable thresholds due to high population and lack of mandatory sound regulations. According to noise measurements done by “The National Network for Noise Level Measurement in Greater Cairo” most of the areas examined ( main squares, industrial areas, main roads, residential areas, commercial and administrative areas in Cairo governorate)  had shown that noise levels exceeded the standard permissible levels that are identified by the Environmental Law 4/1994 and its executive regulations. Noise levels reached up to 75-85 decibels (dB), which is considered unacceptable as noise levels should not exceed 65 dB during daytime and 55 dB during night due to law number 4/1994. On the other hand, fences are considered a common feature within the Egyptian urban context and are mainly constructed for safety and privacy reasons. This research assesses the effectiveness of existing fences as noise barriers and specifies factors that reduce noise levels. Site measurements and photographs were taken for the fence of a residential compound in new Cairo, where noises arising from surrounding places cause annoyance. MEP services were the main sources of disturbing continuous noise along with social activities and traffic noises. Measurements were performed using TM-102 digital sound level meter. Readings were recorded at various time intervals in front and behind of the fence and noise reduction levels were calculated. Measurements revealed that the fence acts as a good noise barrier and that combined configuration of the fence resulted in the attenuation of noise to acceptable levels

Factors affecting bid/no bid decision in the Gaza Strip–contractorsperspectives

To bid or not to bid for a certain project is considered to be a crucial decision for contractors' survival. The objective of this paper is to identify and rank the factors that affect the bid/no bid decision according to their relative importance from the perspective of the local contractors operating in the Gaza Strip, Palestine. A total of seventy-eight factors were identified through a comprehensive literature review to evaluate the most important factors that affect the contractors' decisions to bid or not in the Gaza strip. A survey was conducted on a sample of seventy three contractors classified under the building category, and sixty five of them responded with response rate 89%. The results illustrate that, the financial capability of the contractors, the reputation of the clients, the financial capability of the clients, the financial values of the project, the availability of construction raw materials in the local markets, and the stability of the construction industry were the most critical factors affecting the contractors bid-no bid decisions. This study suggests that contractors and clients should improve their financial systems and capabilities in order to stay in business