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- 저자 : Rasha M. Mohamed (검색결과 5 건)
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A semi-analytical study on the nonlinear pull-in instability of FGM nanoactuators
Mohamed A. Attia,Rasha M. Abo-Bakr 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.76 No.4
In this paper, a new semi-analytical solution for estimating the pull-in parameters of electrically actuated functionally graded (FG) nanobeams is proposed. All the bulk and surface material properties of the FG nanoactuator vary continuously in thickness direction according to power law distribution. Here, the modified couple stress theory (MCST) and Gurtin-Murdoch surface elasticity theory (SET) are jointly employed to capture the size effects of the nanoscale beam in the context of Euler-Bernoulli beam theory. According to the MCST and SET and accounting for the mid-plane stretching, axial residual stress, electrostatic actuation, fringing field, and dispersion (Casimir or/and van der Waals) forces, the nonlinear nonclassical equation of motion and boundary conditions are obtained derived using Hamilton principle. The proposed semi-analytical solution is derived by employing Galerkin method in conjunction with the Particle Swarm Optimization (PSO) method. The proposed solution approach is validated with the available literature. The freestanding behavior of nanoactuators is also investigated. A parametric study is conducted to illustrate the effects of different material and geometrical parameters on the pull-in response of cantilever and doubly-clamped FG nanoactuators. This model and proposed solution are helpful especially in mechanical design of micro/nanoactuators made of FGMs.
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Radiation induced modification of NBR and SBR montmorillonite nanocomposites
Rasha M. Mohamed 한국공업화학회 2013 Journal of Industrial and Engineering Chemistry Vol.19 No.1
Nanocomposites of two different kinds of rubber (acrylonitrile-butadiene rubber NBR and styrene butadiene rubber SBR)/organo-montmorillonite nanocomposites modified by hexadecyltrimethyl ammonium bromide were prepared by the reactive mixing intercalation method in the presence of trimethylolpropane trimethylmethacrylate (TMPTMA). The influence of gamma irradiation on the morphology and properties of the rubber nanocomposites was investigated. Intercalated polar or unsaturated matrices (e.g., NBR and SBR)/OMMT nanocomposites can be obtained, which was confirmed by X-ray diffraction (XRD). The clay layers could be uniformly dispersed in the rubber matrix on the nanometer level. Mechanical tests showed that the nanocomposites had good mechanical properties as compared to the neat composites. The results also showed that the irradiated NBR/OMMT nanocomposites had higher thermal stabilities than irradiated SBR/OMMT nanocomposites.
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Metabolic Effects of Honey in Type 1 Diabetes Mellitus: A Randomized Crossover Pilot Study
Mamdouh M. Abdulrhman,Mohamed H. El-Hefnawy,Rasha H. Aly,Rania H. Shatla,Rasha M. Mamdouh,Doaa M. Mahmoud,Waheed S. Mohamed 한국식품영양과학회 2013 Journal of medicinal food Vol.16 No.1
The aim of this study was to evaluate the metabolic effects of 12-week honey consumption on patients suffering from type 1 diabetes mellitus (DM). This was a randomized crossover clinical trial done in the National Institute for Diabetes and Endocrinology, Cairo, Egypt. Twenty patients of both sexes aged 4–18 years with type 1 DM and HbA1C<10% participated in the study. They were randomized into two equal groups (intervention to control and control to intervention). The dietary intervention was 12-week honey consumption in a dose of 0.5 mL/kg body weight per day. The main outcome measures were serum glucose, lipids, and C-peptide, and anthropometric measurements. None of participants were lost in follow-up. The intervention resulted in significant decreases in subscapular skin fold thickness (SSFT; P=.002), fasting serum glucose (FSG; P=.001), total cholesterol (P=.0001), serum triglycerides (TG; P=.0001), and low-density lipoprotein (P=.0009), and significant increases in fasting C-peptide (FCP; P=.0004) and 2-h postprandial C-peptide (PCP; P=.002). As possible long-term effects of honey after its withdrawal, statistically significant reductions in midarm circumference (P=.000), triceps skin fold thickness (P=.006), SSFT (P=.003), FSG (P=.005), 2-h postprandial serum glucose (P=.000), TG (P=.003), and HbA1C (P=.043), and significant increases in FCP (P=.002) and PCP (P=.003) were observed. This small clinical trial suggests that long-term consumption of honey might have positive effects on the metabolic derangements of type 1 DM.
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Characterization of electron beam irradiated natural rubber/modified starch composites
Magdy M. Senna,Rasha M. Mohamed,Amira N. Shehab-Eldin,Sabrnal El-Hamouly 한국공업화학회 2012 Journal of Industrial and Engineering Chemistry Vol.18 No.5
The effects of electron beam irradiation on thermal, mechanical and morphological properties of natural rubber/starch blends were investigated. The results of thermogravimetric analysis indicated that the thermal stability of natural rubber was improved by the addition of modified starch and by irradiation. On the other hand, thermal stability of irradiated natural rubber and natural rubber/unmodified starch blends is lower than that of pure natural rubber. The tensile strength of natural rubber (2.01 MPa) was improved to 3.82 MPa with the addition of 5 phr unmodified starch. There was a further increase from 2.01 MPa to 6.44 MPa when 5 phr modified starch was used.
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3-아미노-1H-피라졸-4-카르복실산 에틸의 디아조화와 결합반응;피라졸로아진의 합성
Youssef, Ayman M.S.,Faty, Rasha A.M.,Youssef, Mohamed M. 대한화학회 2001 대한화학회지 Vol.45 No.5
피라졸로아진은 농업이나 의약품에서 매우 유용한 화합물등이다. 본 논문에서는 몇 가지 새로운 피라졸로아진의 합성을 보고하고자 한다. 표제 화합물인 3-아미노-1H-피라졸-4-카복실산 에틸을 다이아조화한 후 활성화된 메틸렌 화합물들과 반응시키고 고리화하여 피라졸로[5,1-c][1,2,4]트라이아진 유도체들을 합성하였다. 또한 표제 화합물을 $\alpha$-치환된 신남나이트릴과 반응시켜 피라졸로[1,5-a]피리미딘 유도체들을 합성하였다. 새로 합성된 화합물들의 구조는 화학적 방법과 분광학적 방법을 사용하여 확립하였다. Pyrazoloazines are extremely useful in agriculture and medicine. The main objective of this article is to synthesize some new pyrazoloazines. Ethyl 3-amino-1H-pyrazole-4-carboxylate undergoes diazotization, couples with activated methylene compounds and cyclizes to form pyrazolo[5,1-c][1,2,4]tri-azine derivatives. The title compound also reacts with $\alpha$-substituted cinnamonitriles to produce pyrazolo[1,5-a]pyrimidine derivatives. Structures of newly synthesized compounds are established via chemical and spectral methods.
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