Thermal buckling response of functionally graded sandwich plates with clamped boundary conditions

Zohra Abdelhak,Lazreg Hadji,T. Hassaine Daouadji,E.A. Adda Bedia 국제구조공학회 2016 Smart Structures and Systems, An International Jou Vol.18 No.2

In this research work, an exact analytical solution for thermal buckling analysis of functionally graded material (FGM) sandwich plates with clamped boundary condition subjected to uniform, linear, and non-linear temperature rises across the thickness direction is developed. Unlike any other theory, the number of unknown functions involved is only four, as against five in case of other shear deformation theories. The theory accounts for parabolic distribution of the transverse shear strains, and satisfies the zero traction boundary conditions on the surfaces of the plate without using shear correction factor. A power law distribution is used to describe the variation of volume fraction of material compositions. Equilibrium and stability equations are derived based on the present refined theory. The non-linear governing equations are solved for plates subjected to simply supported and clamped boundary conditions. The thermal loads are assumed to be uniform, linear and non-linear distribution through-the-thickness. The effects of aspect and thickness ratios, gradient index, on the critical buckling are all discussed.

Buildings Vulnerability Assessment and Damage Seismic Scenarios at Urban Scale: Application to Chlef City (Algeria)

Zohra Boutaraa,Caterina Negulescu,Ahmed Arab,Olivier Sedan 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.10

Seismic scenarios are tools used to assess seismic risk at the city level. This allows the assessment of the vulnerability of exposed elements to risk (buildings, bridges, etc.). In the case of Chlef city (formerly El Asnam), this evaluation type proves to be useful given the seismic hazard to which it is exposed and the building park size. This city has been shaken in the past by several earthquakes including that of the El Asnam 1980 (Ms = 7.3), which caused hundreds of casualties and destroyed 70% of the city. In this paper, a seismic vulnerability assessment at urban scale and three seismic damage scenarios are simulated using the “RISK-UE” methodology. First, a recreation of the El Asnam 1980 earthquake, considering the urban conditions of the 1980s, is done. A difference of about 12% between observed and simulated damage is observed. Secondly, two senarios considering the current urban conditions are simulated then, vulnerabilty curves are developed. The simulations purpose is to detect the most vulnerable typologies and districts in the event of a similar earthquake and to provide decision support elements to the local seismic risk manager. The results show a structural damage decrease compared to the 1980 urban conditions.

Dynamic analysis of steel frames with semi-rigid connections

Zohra, Djouaher Fatma,Nacer, Ihaddoudene Touati Abd Techno-Press 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.65 No.3

In the steel structures design, beam-to-column connections are usually considered either rigid or pinned, while their actual behavior lies between these two ideal cases. This consideration has a major influence on the results of the local and the global behavior of steel structures. This influence is noticed in the case of a static analysis, and has an important effect in the case of a dynamic analysis. In fact, pinned and rigid nodes can be considered as two specific cases of a semi-rigid behavior. To study the efficiency of the classification adopted in Eurocode 3, a numerical simulation of semi-rigid nodes has been carried out using the software ANSYS. In the aim to validate this simulation, the numerical results are compared to those of an analytical approach. After that, the validated numerical simulation has been used, to evaluate the efficiency of the classification adopted by the Eurocode 3, regarding semi-rigid connections. Finally, a new method is proposed to define a more accurate evaluation about semi-rigid connections.

Analysis on the buckling of imperfect functionally graded sandwich plates using new modified power-law formulations

Abdelhak Zohra,Rabia Benferhat,Hassaine Daouadji Tahar,Abdelouahed Tounsi 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.77 No.6

A new simple solution for critical buckling of FG sandwich plates under axial and biaxial loads is presented using new modified power-law formulations. Both even and uneven distributions of porosity are taken into account in this study. Material properties of the sandwich plate faces are assumed to be graded in the thickness direction according to a modified power-law distribution in terms of the volume fractions of the constituents. Equilibrium and stability equations of FG sandwich plate with various boundary conditions are derived using the higher-order shear deformation plate theory. The results reveal that the distribution shape of the porosity, the gradient index, loading type and functionally graded layers thickness have significant influence on the buckling response of functionally graded sandwich plates.

Study of Hydrodynamic-Magnetic-Thermal Coupling in a Linear Induction MHD Pump

Fatima Zohra Kadid,Said Drid,Rachid Abdessemed 대한전기학회 2009 Journal of Electrical Engineering & Technology Vol.4 No.2

This article deals with the analysis of a coupling between stationary Maxwell’s equations, the transient state Navier-Stokes and thermal equations. The resolution of these equations is obtained by introducing the magnetic vector potential A , the vorticity ξ , the stream function ψ and the temperature T. The flux density, the electromagnetic thrust, the electric power density, the velocity, the pressure and the temperature are graphically visualized. Also, the influence of the frequency is presented.

Beneficial Effects of Algerian Green Alga Ulva lactuca and Its Hydroethanolic Extract on Insulin Resistance and Cholesterol Reverse Transport in High-Fat/Streptozotocin Diabetic Rats

Fatima Zohra Labbaci,Farida Ouda Boukortt 한국식품영양과학회 2020 Preventive Nutrition and Food Science Vol.25 No.4

The aim of this study was to evaluate the impact of the green algae Ulva lactuca and its hydroethanolic extract on insulin resistance and cholesterol reverse transport in type 2 diabetic (T2D) rats. Rats had T2D induced by a high-fat diet (HFD) for 5 weeks followed by intraperitoneal injection of streptozotocin. Diabetic rats were divided into three groups and were fed a HFD in the presence or absence of 1% alga (HFD-Alg) or 1% of its hydroethanolic extract (HFD-Ext), for 4 weeks. The control group consumed 20% casein combined with 5% lipids. Hyperglycemia, insulin resistance, hypercholesterolemia, and hypertriglyceridemia were noted in HFD rats vs control rats. Whole alga and its extract decreased these parameters vs the HFD. Moreover, fecal total cholesterol and triacylglycerols levels were lowered in HFD group vs C group, but were increased with HFD-Alg vs HFD. Compared with the Control, the HFD group had decreased lecithin:cholesterol acyltransferase (LCAT) activity, apolipoprotein A-I (ApoA-I), high-density lipoprotein (HDL₃)-phospholipids (PL), and HDL₂-cholesteryl ester (CE) levels, but increased HDL₃-unesterified cholesterol (UC) levels. Furthermore, compared with the HFD group, the HFD-Alg and HFD-Ext groups had increased LCAT activity, ApoA-I, HDL₃-PL, and HDL2-CE levels and decreased HDL₃-UC levels. In addition, in the HFD-Ext group, LCAT activity and ApoA-1 levels were decreased vs the HFD-Alg whereas HDL₃-UC levels were increased. In conclusion, these results indicate that U. lactuca and its hydroethanolic extract have curative effect on T2D. Therefore, this alga could be considered a functional food supplement for the treatment and prevention of diabetes.

The Effects of Mood and Overconfidence on Stock Returns : Evidence from Tehran Stock Exchange

Faizi, Zohra,Kwag, Seung Woog 한국국제경영관리학회 2021 국제경영리뷰 Vol.25 No.4

계절적 정서장애(SAD) 회복 기간과 주말 휴일 직전 거래일(보통 금요일)에 무드와 주식수익률 간의 긍정적인 상관관계는 무드효과 로 잘 알려져 있다. 전자는 4월효과, 후자는 주말효과라고 한다. 더불어 투자자의 자기과신은 투자수익률을 감소시키는 편향으로 주목 받아 왔다. 본 연구는 무드효과와 자기과신편향이 주식수익률에 미치는 직접적, 간접적 영향을 분석하였다. 주식수익률은 2015년 2월 부터 2021년 1월까지 테헤란증권거래소의 TEDPIX 동일 가중지수로부터 산출되었다. 낙관적 무드의 정량적 대리변수로 4월(SAD 회 복 기간)과 수요일(주말효과; 이란에선 수요일이 금요일 해당), 자기과신의 대리변수로 거래회전율이 사용되었다. 세 가지 가설을 다중 회귀분석으로 검증한 결과, SAD 회복으로 인해 낙관적 무드가 지배하는 4월의 평균 주식수익률이 다른 달들의 평균 수익률보다 월등 히 높았다. 또한, 거래회전율(자기과신)이 높을수록 주식수익률은 감소하는 경향이 나타났지만, 자기과신이 무드와 주식수익률 간의 관계를 매개하는 역할(자기과신의 매개효과)은 관찰되지 않았다. 오히려 4월에 자기과신과 주식수익률의 통계적 연관성이 유의한 양의 관계로 바뀌었다. 무드의 조절효과가 작용했다는 의미다. 통계적으로 유의한 주말효과는 관찰되지 않았다. 오히려 한 주를 시작하는 날(보통 월요일; 이란에서는 토요일)의 주식수익률이 다른 요일에 비해 월등히 높았다. 본 연구의 결과는 투자자가 비정상이익을 얻을 수 있는 투자 타이밍을 분별하도록 도울 뿐만 아니라 무드와 자기과신의 부정적 영향으로부터 자유로운 투자 포트폴리오 구성에 이바 지할 것으로 기대된다. Existing research has documented a positive correlation between mood and stock returns during the recovery period from seasonal affective disorder (SAD) and on the last working day before the weekend. These phenomena represent two different types of mood effect known as April effect and weekend effect, respectively. Prior studies have also reported that investor overconfidence negatively influences investment returns. This study aims to analyze the impact of these two major behavioral traits - mood and overconfidence - on stock returns simultaneously. Specifically, we investigate the mediating effect of overconfidence on the good mood-stock return relationship and the moderating effect of mood on the overconfidence-stock return relationship as well as the mood and overconfidence effects. To this end, we develop and test three hypotheses with the multiple regression analysis. Stock returns are computed by using daily index numbers of the TEDPIX equal-weighted index, the Tehran Stock Exchange’s main index from February 2015 to January 2021. April (recovery period from SAD) and Wednesday (weekend mood; Wednesday represents Friday in Iran) are employed as proxies for positive mood, while turnover rate manifests overconfidence. The results show that positive mood elevated during the offset period of SAD (April) has a positive correlation with stock returns. Overconfidence lowers stock returns but the mediating effect of overconfidence is not supported. The negative effect of overconfidence on stock returns, however, turns positive in April. These findings together confirm the expected effects of mood and overconfidence on stock returns and discover unexpected moderating effect of good mood on the overconfidence-stock return relationship. No weekend effect is detected in the Iranian market. Rather, an early-in-the-week effect is observed. The empirical evidence is expected to help investors to form portfolios, which are immune to the influences of mood and overconfidence bias, as well as provide them with an investment strategy to time the market and earn abnormal returns.

ASYMPTOTICS OF ORTHOGONAL POLYNOMIALS CORRESPONDING TO POLYNOMIAL SZEGŐ MEASURE WITH AN INFINITE DISCRETE PART

Fatima Zohra Benghia,Youcef Belabbaci 충청수학회 2021 충청수학회지 Vol.34 No.3

The asymptotics behavior orthogonal polynomials have been in the spotlight since the result of G. Szegő in 1921. In this paper we study the pointwise asymptotics inside the unit disk for orthogonal polynomials with respect to a polynomial Szegő measure with an infinite masses points.

Synthesis and Characterization of Zn(1-x)NixAl2O4 Spinels as a New Heterogeneous Catalyst of Biginelli’s Reaction

Fatima-Zohra Akika,Nadjib Kihal,Tahir Habila,Ivalina Avramova,Smail Khelili,Bernard Pirotte,Sçefik Suzer 대한화학회 2013 Bulletin of the Korean Chemical Society Vol.34 No.5

Zn(1-x)NixAl2O4 (x = 0.0-1.0) spinels were prepared at 800 °C by co-precipitation method and characterized by infrared spectroscopy, X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy. The specific surface area was determined by BET. SEM image showed nano sized spherical particles. XPS confirmed the valence states of the metals, showing moderate Lewis character for the surface of materials. The powders were successfully used as new heterogeneous catalysts of Biginelli’s reaction, a one-pot threecomponent reaction, leading to some dihydropyrimidinones (DHPMs). These new catalysts that produced good yields of DHPMs, were easily recovered by simple filtration and subsequently reused with persistent activity, and they are non-toxic and environmentally friendly. The optimum amount of catalyst is 20% by weight of benzaldehyde derivatives, while the doping amount has been found optimal for x = 0.1.

Mechanical and thermal buckling analysis of laminated composite plates

Fatima Zohra Kettaf,Mohamed Beguediab,Soumia Benguediab,Mahmoud M. Selim,Abdelouahed Tounsi,Muzamal Hussain 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.40 No.5

The mechanical and thermal buckling analysis of laminated composite plates is presented in this document. Different theories of thick plates taking into account the parabolic distribution of transverse shear stresses and satisfying the condition of zero shear stresses on the top and bottom surfaces without using shear correction factor are presented and a comparison between the results obtained by these theories is also illustrated. The high order nonlinear stress-displacement relation of the plates was taken into consideration. The principle of potential energy is used to obtain the equations of equilibrium. The closed-form solutions of symmetric and antisymmetric cross-ply are obtained using Navier solution. Using math software Maple, the temperatures and the critical loads of buckling are determined. Finally, a parametric study of the influence of the various parameters such as: mode of buckling, the geometrical ratios a / b and a / h, Young's modulus, Coefficient of thermal expansion, loading type, the orientation of the fibers and the number of layers on the critical buckling temperature and the critical buckling charge is shown and discussed. Numerical results indicate that deformation due to transverse shear has a significant effect on both mechanical and thermal behavior of buckling of laminated simply supported plates.