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Free vibration analysis of FG plates under thermal environment via a simple 4-unknown HSDT
Amina Attia,Amina Tahar Berrabah,Abdelmoumen Anis Bousahla,Fouad Bourada,Abdelouahed Tounsi,S. R. Mahmoud 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.41 No.6
A 4-unknown shear deformation theory is applied to investigate the vibration of functionally graded plates under thermal environment. The plate is fabricated from a functionally graded material mixed of ceramic and metal with continuously varying material properties through the plate thickness. Three types of thermal loadings, uniform, linear and nonlinear temperature rises along the plate thickness are taken into account. The present theory contains four unknown functions as against five or more in other higher order shear deformation theories. The through-the-thickness distributions of transverse shear stresses of the plate are considered to vary parabolically and vanish at upper and lower surfaces. The present model does not require any problem dependent shear correction factor. Analytical solutions for the free vibration analysis are derived based on Fourier series that satisfy the boundary conditions (Navier's method). Benchmark solutions are firstly considered to evaluate the accuracy of the proposed model. Comparisons with the solutions available in literature revealed the good capabilities of the present model for the simulations of vibration responses of FG plates. Some parametric studies are carried out for the frequency analysis by varying the volume fraction profile and the temperature distribution across the plate thickness.
Amina Hassini,Khalifa Trimeche 강원경기수학회 2020 한국수학논문집 Vol.28 No.4
In this paper we give the harmonic analysis associated with the Cherednik operators, next we define and study the Cherednik wavelets and the Cherednik windowed transforms on $\mathbb{R}^d$, in the W-invariant case, and we prove for these transforms Plancherel and inversion formulas. As application we give these results for the Gaussian Cherednik wavelets and the Gaussian Cherednik windowed transform on $\mathbb{R}^d$ in the W-invariant case.
Amina Attia,Abdelmoumen Anis Bousahla,Abdelouahed Tounsi,S. R. Mahmoud,Afaf S. Alwabli 국제구조공학회 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.65 No.4
In this paper, an efficient higher-order shear deformation theory is presented to analyze thermomechanical bending of temperature-dependent functionally graded (FG) plates resting on an elastic foundation. Further simplifying supposition are made to the conventional HSDT so that the number of unknowns is reduced, significantly facilitating engineering analysis. These theory account for hyperbolic distributions of the transverse shear strains and satisfy the zero traction boundary conditions on the surfaces of the plate without using shear correction factors. Power law material properties and linear steady-state thermal loads are assumed to be graded along the thickness. Nonlinear thermal conditions are imposed at the upper and lower surface for simply supported FG plates. Equations of motion are derived from the principle of virtual displacements. Analytical solutions for the thermomechanical bending analysis are obtained based on Fourier series that satisfy the boundary conditions (Navier’s method). Non-dimensional results are compared for temperature-dependent FG plates and validated with those of other shear deformation theories. Numerical investigation is conducted to show the effect of material composition, plate geometry, and temperature field on the thermomechanical bending characteristics. It can be concluded that the present theory is not only accurate but also simple in predicting the thermomechanical bending responses of temperature-dependent FG plates.
Sorption of Pb2+ Ions on to Activated Carbons Prepared from Olive Stones
Amina. A. Attia,Mona. A. Shouman,Th. El-Nabarawy 한국탄소학회 2005 Carbon Letters Vol.6 No.3
The carbon sample "O", phosphoric acid-activated carbon "OP", zinc chloride-activated carbon "OZ", and two steam activated carbons "OS" and "OS2" with different burn-off of 25% and 58% respectively, were prepared from olive stones. The textural properties were determined from the results of nitrogen adsorption at 77 K and by analyzing these results through the application of different adsorption models. The chemistry of the carbon surfaces was determined from the base neutralization capacities, acid neutralization capacity and surface pH. The sorption of Pb2+ ions on to the carbons prepared was followed under dynamic and equilibrium conditions. The differences between the values of the textural parameters were attributed to the inapplicability of some adsorption models and to the heterogeneity of the microporous carbons. The sorption of Pb2+ ions is favored on carbon and activated carbons. However, chemically activated carbons are more effective compared with steam-activated ones. The sorption of Pb2+ ions were related to the chemistry of the surface rather than to the textural properties.
Amina Potter,Hilana Ceotto,Marcia Giambiagi-deMarval,Kátia Regina Netto dos Santos,Ingolf F. Nes,Maria do Carmo de Freire Bastos 한국미생물학회 2009 The journal of microbiology Vol.47 No.3
This study analyzed ten strains of coagulase-negative staphylococci (CNS) involved in nosocomial infections in three Brazilian hospitals. Their antibiotic susceptibility profile showed that most strains exhibited multiple antibiotic resistance and possessed the mecA gene. The ability of these strains to adhere to polystyrene microtiter plates was also tested and nine of them proved to be biofilm producers at least in one of the three conditions tested: growth in TSB, in TSB supplemented with NaCl, or in TSB supplemented with glucose. The presence of the bap gene, which codes for the biofilm-associated protein (Bap), was investigated in all ten strains by PCR. All strains were bap-positive and DNA sequencing experiments confirmed that the fragments amplified were indeed part of a bap gene. The presence of the icaA gene, one of the genes involved in polysaccharide intercellular adhesin (PIA) formation, was also detected by PCR in eight of the ten strains tested. The two icaA-negative strains were either weak biofilm producer or no biofilm producer, although they were bap-positive. To our knowledge, this is the first report demonstrating the presence of the bap gene in nosocomial isolates of CNS, being also the first report on the presence of this gene in Staphylococcus haemolyticus and S. cohnii.
Amina KhatunEmail author,Mahmudur Rahman,Khaza Nur Uddin,Kamrul Ahsan,Sabequn Nahar Shimu,Khadejatul Kobra,Shamme Akter Shimu,Wahidul Haque,Tobibur Rahman,Tangila Hoque Jessy,Farzana Akhter 경희대학교 융합한의과학연구소 2016 Oriental Pharmacy and Experimental Medicine Vol.31 No.4
Traditional medicinal practitioners or Kavirajes use a variety of medicinal plants for treatment of thrombus ailments-cardiovascular problems. In this study, thrombolytic activity of 36 extracts of different solvents of eight Bangladeshi medicinal plants traditionally used in cardiovascular problems were evaluated to justify their use in folklore medicinal practitice. Extraction was conceded using methanol. Five grams of the concentrated methanol extract of each crude extract were then fractionated to provide n-hexane and carbon tetrachloride fractions. Phytochemically important groups like reducing sugars, tannins, saponins, steroids, gums, flavonoids and alkaloids were tested using standard chromogenic reagents. In vitro thrombolytic potential of extracts was assayed for analyzing the clot lyses by adding the extracts to the pre-clotted blood. The results were compared with the results obtained from streptokinase as standard and water as a negative control. Thrombolytic effect of the extracts ranged from 0.73 ± 2.44 % to 45.81 ± 0.34 % clot lysis whereas the standard streptokinase showed 65.13 ± 0.96 % and the negative control water showed 2.50 ± 0.67 % clot lysis. The highest thrombolytic effect was shown by the crude extract of Melastoma malabathricum leaves and the lowest by the CCl4 fractionate of Litsea glutinosa leaves. Most of the results were found relevant to the traditional use of the plants. Plants traditionally used in thrombus ailments may be an interesting source for further drug development.
Amina Fouad Farag,Dalia Ali Abou-Alnour,Noha Saleh Abu-Taleb 대한영상치의학회 2018 Imaging Science in Dentistry Vol.48 No.4
Purpose: Oral carcinoma cuniculatum is a rare well-differentiated variant of oral squamous cell carcinoma. The purpose was to systematically review its unique features to differentiate it from other variants as verrucous carcinoma, papillary squamous cell carcinoma and well-differentiated squamous cell carcinoma. Materials and Methods: A systematic review was performed using MEDLINE, Dentistry and Oral Sciences Source and PubMed databases and any existing articles related to the research subject missed in the search strategy to screen ones reporting cases occurring exclusively in the oral cavity in English literature. Variables analyzed included clinical, etiologic, imaging, histopatholgical features, treatment, follow-up and survival rates. Results: From 229 hits, 17 articles with 43 cases were included in the systematic review. Clinically it showed a female predilection with pain and/or ulceration of a relatively long duration and exudation being the most common symptoms. Histologically, it showed more endophytic features comprising well-differentiated squamous epithelium with absent or minimal cytological atypia and multiple keratin filled crypts or cuniculus. Inflammatory stromal reaction and discharging abscesses were reported in most of the cases. Bone destruction was predominant in most imaging features. Complete surgical resection with a safety margin was the treatment of choice in most of the cases with few recorded recurrence cases. Conclusion: Apprehensive knowledge of oral carcinoma cuniculatum unique features is essential to avoid its misdiagnosis and provide proper treatment especially for recurrent cases.
Amina Irakoze(아미나 이라코제),Seok So-I(석소이),Kwanho Lee(이관호),Kee Han Kim(김기한) 대한건축학회 2022 대한건축학회 학술발표대회 논문집 Vol.42 No.2
An effective energy upgradation of existing building stock requires classification of buildings based on their thermal characteristics. The purpose of this study is to classify buildings with similar envelop thermal characteristics by applying k-means clustering analysis on building energy consumption data of different granularity (hourly, daily, and monthly energy). Heating energy consumption from 51 building models with varying wall, window, and roof thermal transmittance, window SHGC, and infiltration rate (ac/h) is used. The findings of this study indicate that building classifications obtained from hourly, daily, and monthly heating energy differ especially in the identification of buildings with high window thermal transmittance and infiltration rate.