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Al Ain, United Arab Emirates

Janajreh I.,Masdar Institute of Science and Technology | Su L.,Masdar Institute of Science and Technology | Alan F.,UAEU
Renewable Energy | Year: 2013

Annual wind data at Masdar City (24.4202° N, 54.6132° E) has been recorded in attempt to assess wind energy potential. Thereby, accurate wind energy production can be assessed for a given region. The vertical wind profile is inferred and was appropriately fitted with power law profile. The spectrum of the temporal data is obtained which exhibits turbulent type. Investigation of high resolution temporal records also emphasized the turbulence, non-periodicity, and intermittency of the wind data. Consequently, frequency-scale wavelet decomposition is carried out, and intermittency of the data is identified. The measured wind capacity categorized Masdar City as poor wind region. It is followed by fitting the measured wind data with the maximum likelihood Weibull distribution. The power curves of two sizes of horizontal axis wind turbines (HAWTs) are coupled with the Weibull distribution. The annual energy production was found to be 3307.08 MWh and 28.73 MWh at the height of 50 m for the large and small turbine, respectively. Considering the turbine efficiency and the return on the investment for the current case study, results are in favor of small size HAWT deployment, i.e. 3.5 KW Windspot, over the larger size. © 2012. Source

El-Maaddawy T.A.,UAEU | Sherif E.-S.I.,Al Wasl Al Jadeed Consultants AWAJ
Journal of Composites for Construction | Year: 2014

This paper aims to investigate the structural response of concrete corbels reinforced internally with steel rebars and externally with carbon fiber-reinforced polymer (CFRP) composite sheets. Nine specimens were constructed and tested. Test parameters included the amount of internal longitudinal steel rebars and configuration of the external composite sheets. Nine two-dimensional finite-element (FE) models were developed, assuming a perfect bond between the CFRP and concrete. Three additional FE models were developed in which an interfacial bond stress-slip model was adopted between the diagonal CFRP reinforcement and the concrete. The external CFRP composite reinforcement resulted in up to 40% increase in the load capacity. The contribution of the external CFRP reinforcement to the load capacity decreased with an increased amount of internal steel rebars. The addition of primary longitudinal CFRP sheets in a direction parallel to the primary steel rebars reduced the steel strains and increased the yield and ultimate loads. The inclusion of secondary CFRP longitudinal reinforcement at the midheight of the corbels did not result in additional strength gain. The diagonal CFRP reinforcement restricted growth and widening of the shear cracks, and hence, increased the gain in the load capacity. The numerical load capacity was in the range of 10% error band. The numerical crack pattern, deflection response, and steel and CFRP strain responses were in good agreement with those measured experimentally. The integration of the interfacial bond stress-slip model in the FE analysis between the diagonal CFRP reinforcement and concrete resulted in more conservative/accurate predictions for the structural response. © 2013 American Society of Civil Engineers. Source

Santagati P.,UAEU | Beiu V.,UAEU
Lecture Notes of the Institute for Computer Sciences, Social-Informatics and Telecommunications Engineering, LNICST | Year: 2014

The aim of this paper is to investigate how the length of communication links could affect the reliability during operations, by analysing how the Johnson-Nyquist (thermal) noise on the links affects the probability of failure (defined as the probability of switching) of devices/switches scaled to the limit like, e. g., ion channels but also nanoscale CMOS transistors. To this end, we will consider classical CMOS circuits, and base our analysis on statistical considerations. In particular, our aim is to look for the existence of an optimum wire/link length in this context, which would maximize the reliability of the simplest system formed by a communication link (wire) driving a switch (transistor or ion channel). © Institute for Computer Sciences, Social Informatics and Telecommunications Engineering 2014. Source

Khaleel A.,UAEU | Nawaz M.,UAEU | Al-Hadrami S.,UAEU | Greish Y.,UAEU | Saeed T.,FHMS
Microporous and Mesoporous Materials | Year: 2013

Transition-metal-doped γ-alumina with various dopant concentrations was prepared by straightforward template-free sol-gel method. The presence of dopant metal ions, generally, enhanced the gel formation and their behavior was dependent on the nature of the metal ion and its concentration. Certain ions, especially Fe3+, resulted in rapid formation of a transparent gel upon hydrolysis. The prepared doped γ-alumina powders weakly crystalline at low dopant ion concentrations, 2%, and became completely amorphous at a concentration of 10%. The morphology of the particles was also dependent on the dopant concentration. While dopant concentration of 2% resulted in nano-particles with significant amount of inter-particle mesopores, 10% concentration led to significant aggregation into larger particles. The prepared doped γ-Al2O3 as well as the undoped γ-Al2O3 showed high surface areas and pore volumes which were largely dependent on the nature of the dopant metal ions and on their concentrations. While composites with low dopant concentration, 2%, exhibited surface areas and pore volumes comparable to those of undoped γ-alumina, a considerable decrease was associated with higher concentrations. The changes in textural properties were referred to the evident enhanced sintering associated with high dopant concentrations. © 2012 Elsevier Inc. All rights reserved. Source

Powders of xerogel γ-Al2O3 doped with various concentrations of Cr3+ and Cu2+ (M/M + Al molar fraction = 0.75-10%) were prepared via a sol-gel method. Cr3+ and Cu 2+ precursors (acetylacetonate, nitrate or chloride) were added to 0.12 M 2-propanol solution of aluminum tri-sec-butoxide (ASB) and hydrolysis was performed using a H2O/ASB molar ratio of 4.7. The effect of the dopant precursor on structural, textural and morphological properties was studied. Employing acac precursors resulted in unique properties after calcination at 500 °C including high surface areas, as high as 455 m 2/g, homogeneous mesopores, 3-12 nm, and amorphous powders (5-10 nm particles in diameter). On the other hand, the acac precursor enhanced the resistance to sintering mainly at higher metal loads (10%) and elevated temperature (800 °C). Nevertheless, the solids issued from nitrate and chloride precursors exhibited lower surface areas at high metal loads, and lower resistance to sintering. © 2013 Elsevier Ltd. Source

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