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Ductility and inelastic deformation demands of structures
Cheikh Benazouz,Leblouba Moussa,Zerzour Ali 국제구조공학회 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.42 No.5
Current seismic codes require from the seismically designed structures to be capable to withstand inelastic deformation. Many studies dealt with the development of different inelastic spectra with the aim to simplify the evaluation of inelastic deformation and performance of structures. Recently,the concept of inelastic spectra has been adopted in the global scheme of the performance-based seismic design through capacity-spectrum methods. In this paper, the median of the ductility demand ratio for 80 ground motions are presented for different levels of normalized yield strength, defined as the yield strength coefficient divided by the peak ground acceleration (PGA). The influence of the post-to-preyield stiffness ratio on the ductility demand is investigated. For fixed levels of normalized yield strength, the median ductility versus period plots demonstrated that they are independent of the earthquake magnitude and epicentral distance. Determined by regression analysis of the data, two design equations have been developed; one for the ductility demand as function of period, post-to-preyield stiffness ratio, and normalized yield strength, and the other for the inelastic deformation as function of period and peak ground acceleration valid for periods longer than 0.6 seconds. The equations are useful in estimating the ductility and inelastic deformation demands for structures in the preliminary design. It was found that the post-to-preyield stiffness has a negligible effect on the ductility factor if the yield strength coefficient is greater than the PGA of the design ground motion normalized by gravity.
Numerical Simulation of the Process-induced Residual Stress in Composite Materials
Cheikh Cisse,Sang-Woo Kim,In Lee 한국항공우주학회 2012 한국항공우주학회 학술발표회 논문집 Vol.2012 No.11
The pre-existing inner stresses in composite materials should be determined in order to avoid structural failure. Such stresses are accumulated during the manufacturing process. Thus, they are called “process-induced residual stress”. In this paper, the process-induced residual stresses in glass/epoxy composites were predicted by using micro-mechanical model in ABAQUS. Moreover, the effect of parameters such as the fiber volume fraction, cooling rate, and nature of the matrix were investigated. The viscoelastic nature of the epoxy was implemented in a UMAT code by using FORTRAN. The results showed that higher fiber volume fraction induces higher residual stress. However, the increase of the cooling rate slightly changes the residual stress values. Moreover, using elastic solution of the epoxy overestimated the residual stress.
Amani Cheikh,Rym Benkhalifa,Zied Landoulsi,Imen Chatti,Mohamed El Ayeb 대한약학회 2014 Archives of Pharmacal Research Vol.37 No.11
AahG50, the toxic fraction of Androctonus australishector venom, was studied on human Kv3.1 channelsactivation, stably expressed in Xenopus oocytes using the twoelectrodevoltage clamp technique. AahG50 reduced Kv3.1currents in a reversible concentration-dependent manner,withan IC50 value and a Hill coefficient of 40.4 ± 0.2 lg/ml and1.3 ± 0.05, respectively. AahG50 inhibited IKv3.1 withoutmodifying the current activation kinetics. The AahG50-induced inhibition of Kv3.1 channels was voltage-dependent,with a gradual increase at lower concentrations and over thevoltage range of channels opening. However, at higher concentrations,the inhibition exhibited voltage dependence onlyin the first range of channels opening from -20 to ?10 mV,but demonstrates a low degree of voltage-dependence whenchannels are fully activated. In the literature, toxins havepreviously been isolated from AahG50, KAaH1 and KAaH2and were reported not to have any effect on IKv3.1. Thepresent article’s findings suggest that AahG50 may contain apeptidic component active on Kv3.1 channels, which inhibitsIKv3.1 in a selective manner.
An Intelligent Similarity Model between Generalized Trapezoidal Fuzzy Numbers in Large Scale
Mohamedou Cheikh Tourad,Abdelmounaim Abdali 한국지능시스템학회 2018 INTERNATIONAL JOURNAL of FUZZY LOGIC and INTELLIGE Vol.18 No.4
The rapid expansion of data published on the web has given rise to the similarity problem on a large scale, a very important subject for scientific research in the field of computer science. Several methods have been developed for this. In this paper, we propose the first mathematical model to find the similarity value between generalized trapezoidal fuzzy numbers (GTFNs). This model employs fuzzy inference systems to find the value of an effective weighting, the weights to be associated to different kinds of methods that can handle an important scale of the data. This model will allow us to develop intelligent systems. A comparative study based on 21 sets of GTFNs has been carried out to demonstrate the difference between our approach and existing methods. This study shows that our model is more reasonable than existing methods
Ductility and inelastic deformation demands of structures
Benazouz, Cheikh,Moussa, Leblouba,Ali, Zerzour Techno-Press 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.42 No.5
Current seismic codes require from the seismically designed structures to be capable to withstand inelastic deformation. Many studies dealt with the development of different inelastic spectra with the aim to simplify the evaluation of inelastic deformation and performance of structures. Recently, the concept of inelastic spectra has been adopted in the global scheme of the performance-based seismic design through capacity-spectrum methods. In this paper, the median of the ductility demand ratio for 80 ground motions are presented for different levels of normalized yield strength, defined as the yield strength coefficient divided by the peak ground acceleration (PGA). The influence of the post-to-preyield stiffness ratio on the ductility demand is investigated. For fixed levels of normalized yield strength, the median ductility versus period plots demonstrated that they are independent of the earthquake magnitude and epicentral distance. Determined by regression analysis of the data, two design equations have been developed; one for the ductility demand as function of period, post-to-preyield stiffness ratio, and normalized yield strength, and the other for the inelastic deformation as function of period and peak ground acceleration valid for periods longer than 0.6 seconds. The equations are useful in estimating the ductility and inelastic deformation demands for structures in the preliminary design. It was found that the post-to-preyield stiffness has a negligible effect on the ductility factor if the yield strength coefficient is greater than the PGA of the design ground motion normalized by gravity.
Nonlinear Exchange Rate Pass-Through : Does Business Cycle Matter?
( Nidhaleddine Ben Cheikh ),( Younes Ben Zaied ),( Houssam Bouzgarrou ),( Pascal Nguyen ) 세종대학교 경제통합연구소 2018 Journal of Economic Integration Vol.33 No.2
This paper investigates the nonlinear dynamics in the Exchange Rate Pass-Through of the Euro area. We implement the class of logistic smooth transition models to explore the role of the business cycle in driving nonlinearity. Using quarterly data over the period of January 1980 ~ April 2015, our results provide strong evidence of nonlinearity in 7 out of 10 Eurozone countries. We show that the exchange rate transmission to inflation respond to the economic activity in the nonlinear manner, that is, exchange rate pass-through is higher during expansion than recession periods. By monitoring the different patterns of growth and exchange rate pass-through, European monetary authorities could enhance inflation convergence within the Euro area.
Ali Ben-Cheikh,Aymen Bali,Fatma Z Guerfali,Chiraz Atri,Hanène Attia,Dhafer Laouini 대한기생충학ㆍ열대의학회 2022 The Korean Journal of Parasitology Vol.60 No.5
Hypoxia-inducible factor-1 alpha (HIF-1α) is one of the master regulators of immune and metabolic cellular functions. HIF-1α, a transcriptional factor whose activity is closely related to oxygen levels, is a target for understanding infectious disease control. Several studies have demonstrated that HIF-1α plays an important role during the infectious process, while its role in relation to parasite virulence has not been addressed. In this work, we studied the expression levels of HIF-1α and related angiogenic vascular endothelial growth factor A (VEGF-A) in human macrophages infected with promastigotes of hypo- or hyper-virulent Leishmania major human isolates. L. major parasites readily subverted host macrophage functions for their survival and induced local oxygen consumption at the site of infection. In contrast to hypo-virulent parasites that induce high HIF-1α expression levels, hyper-virulent L. major reduced HIF-1α expression in macrophages under normoxic or hypoxic conditions, and consequently impeded the expression of VEGF-A mRNA. HIF-1α may play a key role during control of disease chronicity, severity, or outcome.