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Transient analysis of monopile foundations partially embedded in liquefied soil
Barari, Amin,Bayat, Mehdi,Saadati, Meysam,Ibsen, Lars Bo,Vabbersgaard, Lars Andersen Techno-Press 2015 Geomechanics & engineering Vol.8 No.2
In this study, the authors present a coupled fluid-structures-seabed interaction analysis of a monopile type of wind turbine foundations in liquefiable soils. A two dimensional analysis is performed with a nonlinear stiffness degradation model incorporated in the finite difference program Fast Lagrangian Analysis of Continua (FLAC), which captured the fundamental mechanisms of the monopiles in saturated granular soil. The effects of inertia and the kinematic flow of soil are investigated separately, to highlight the importance of considering the combined effect of these phenomena on the seismic design of offshore monopiles. Different seismic loads, such as those experienced in the Kobe, Santa Cruz, Loma Prieta, Kocaeli, and Morgan Hill earthquakes, are analyzed. The pore water pressure development, relative displacements, soil skeleton deformation and monopile bending moment are obtained for different predominant frequencies and peak accelerations. The findings are verified with results in the liter.
QoSCM: QoS-aware Coded Multicast Approach for Wireless Networks
Mohajer, Amin,Barari, Morteza,Zarrabi, Houman Korean Society for Internet Information 2016 KSII Transactions on Internet and Information Syst Vol.10 No.12
It is essential to satisfy class-specific QoS constraints to provide broadband services for new generation networks. The present study proposes a QoS-driven multicast scheme for wireless networks in which the transmission rate and end-to-end delay are assumed to be bounded during a multiple multicast session. A distributed algorithm was used to identify a cost-efficient sub-graph between the source and destination which can satisfy QoS constraints of a multicast session. The model was then modified as to be applied for wireless networks in which satisfying interference constraints is the main challenge. A discrete power control scheme was also applied for the QoS-aware multicast model to accommodate the effect of transmission power level based on link capacity requirements. We also proposed random power allocation (RPA) and gradient power allocation (GPA) algorithms to efficient resource distribution each of which has different time complexity and optimality levels. Experimental results confirm that the proposed power allocation techniques decrease the number of unavailable links between intermediate nodes in the sub-graph and considerably increase the chance of finding an optimal solution.
QoSCM: QoS-aware Coded Multicast Approach for Wireless Networks
( Amin Mohajer ),( Morteza Barari ),( Houman Zarrabi ) 한국인터넷정보학회 2016 KSII Transactions on Internet and Information Syst Vol.10 No.12
It is essential to satisfy class-specific QoS constraints to provide broadband services for new generation networks. The present study proposes a QoS-driven multicast scheme for wireless networks in which the transmission rate and end-to-end delay are assumed to be bounded during a multiple multicast session. A distributed algorithm was used to identify a cost-efficient sub-graph between the source and destination which can satisfy QoS constraints of a multicast session. The model was then modified as to be applied for wireless networks in which satisfying interference constraints is the main challenge. A discrete power control scheme was also applied for the QoS-aware multicast model to accommodate the effect of transmission power level based on link capacity requirements. We also proposed random power allocation (RPA) and gradient power allocation (GPA) algorithms to efficient resource distribution each of which has different time complexity and optimality levels. Experimental results confirm that the proposed power allocation techniques decrease the number of unavailable links between intermediate nodes in the sub-graph and considerably increase the chance of finding an optimal solution.
Monotonic loading of circular surface footings on clay
Lars Bo Ibsen,Amin Barari 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.12
Appropriate modeling of offshore foundations under monotonic loading is a significant challenge in geotechnical engineering. This paper reports experimental and numerical analyses, specifically investigating the response of circular surface footings during monotonic loading and elastoplastic behavior during reloading. By using the findings presented in this paper, it is possible to extend the model to simulate the vertical-load displacement response of offshore bucket foundations.
HEAVY VEHICLES BRAKE DRUMS – AN ACCURATE EVALUATION ON THERMAL LOADS IN SEVERE SERVICE CONDITIONS
Eduardo Umaras,Ahmad Barari,Sales Guerra Tsuzuki 한국자동차공학회 2021 International journal of automotive technology Vol.22 No.2
Heavy vehicles service brakes are subject to severe loading conditions that can exceed the design conditions of safe operating performance in critical situations. Materials are prone to lose their design properties at high temperatures. Since the function of brakes is to convert the vehicle kinetic energy into heat by friction, temperature is the main variable to be considered, due to the fade of the linings composite material and cast iron drum deformation. The intent of this work is to evaluate the thermal loads of brake drums, when subjected to severe service conditions, in order to allow further analyses, mainly related to their dimensional and form variation. A case study is described, showing the possibility of the development of high temperatures and consequent risk of accidents in a real long downhill descent. Experimental data were preferably used to assure higher accuracy to the analysis. In the authors’ further work, a FEA simulation will be conducted with the data supplied in the present paper.
Kalantar, Enayatollah,Assadi, Mojan,Pormazaheri, Helen,Hatami, Shiva,Barari, Maryam Agha,Asgari, Esfandiar,Mahmoudi, Elaheh,Kabir, Kourosh,Marashi, Seyed Mahmoud Amin Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.24
Background: Many scientists have reported Candida species to be of great concern because of the high frequency that they colonize and infect human hosts, particularly cancer patients. Moreover, in the last decades Candida species have developed resistance to many antifungal agents. Based on this, we aimed to identify and determine the prevalence of Candida spp from blood culture bottles among cancer patients and their antifungal resistance pattern. Materials and Methods: From the blood culture bottles isolation and identification of the Candida spp were performed by conventional microbiological techniques. The in vitro antibiotic resistance pattern of the isolates was determined by CLSI guidelines. Genomic DNA was isolated and amplified. Each gene was separated by agar gel electrophoresis. Results: Identification of Candida spp was based on the presence of yeast cells in direct examination, culture and DNA extraction. Of the 68 blood samples collected during the study period (April 2013 to October 2013), five (7.35%) were positive for the presence of Candida spp, 2 (40%) of which were identified as Candida albicans and 3 (60%) were Candida non-albicans. Conclusions: High resistance to amphotricin B was observed among all the Candida non-albicans isolates. Regular investigations into antifungal resistance will help us to get an updated knowledge about their antibiotic resistance pattern which may help the physician in selecting the antibiotics for empirical therapy.