Wave propagation in functionally graded plates with porosities using various higher-order shear deformation plate theories

Yahia, Sihame Ait,Atmane, Hassen Ait,Houari, Mohammed Sid Ahmed,Tounsi, Abdelouahed Techno-Press 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.53 No.6

In this work, various higher-order shear deformation plate theories for wave propagation in functionally graded plates are developed. Due to porosities, possibly occurring inside functionally graded materials (FGMs) during fabrication, it is therefore necessary to consider the wave propagation in plates having porosities in this study. The developed refined plate theories have fewer number of unknowns and equations of motion than the first-order shear deformation theory, but accounts for the transverse shear deformation effects without requiring shear correction factors. The rule of mixture is modified to describe and approximate material properties of the functionally graded plates with porosity phases. The governing equations of the wave propagation in the functionally graded plate are derived by employing the Hamilton's principle. The analytic dispersion relation of the functionally graded plate is obtained by solving an eigenvalue problem. The effects of the volume fraction distributions and porosity volume fraction on wave propagation of functionally graded plate are discussed in detail. The results carried out can be used in the ultrasonic inspection techniques and structural health monitoring.

Neutron diffraction studies of the Na-ion battery electrode materials NaCoCr₂(PO₄)₃, NaNiCr₂(PO₄)₃, and Na₂Ni₂Cr(PO₄)₃

Yahia, H.B.,Essehli, R.,Avdeev, M.,Park, J.B.,Sun, Y.K.,Al-Maadeed, M.A.,Belharouak, I. Academic Press 2016 Journal of solid state chemistry Vol.238 No.-

<P>The new compounds NaCoCr2(PO4)(3), NaNiCr2(PO4)(3), and Na2Ni2Cr(PO4)(3) were synthesized by sol-gel method and their crystal structures were determined by using neutron powder diffraction data. These compounds were characterized by galvanometric cycling and cyclic voltammetry. NaCoCr2(PO4)(3), NaNiCr2(PO4)(3), and Na2Ni2Cr(PO4)(3) crystallize with a stuffed alpha-CrPO4-type structure. The structure consists of a 3D-framework made of octahedra and tetrahedra that are sharing corners and/or edges generating channels along [100] and [010], in which the sodium atoms are located. Of significance, in the structures of NaNiCr2(PO4)(3), and Na2Ni2Cr(PO4)(3) a statistical disorder Ni2+/Cr3+ was observed on both the 8g and 4a atomic positions, whereas in NaCoCr2(PO4)(3) the statistical disorder Co2+/Cr3+ was only observed on the 8g atomic position. When tested as negative electrode materials, NaCoCr2(PO4)(3), NaNiCr2(PO4)(3), and Na2Ni2Cr(PO4)(3) delivered specific capacities of 352, 385, and 368 mA h g(-1), respectively, which attests to the electrochemical activity of sodium in these compounds. (C) 2016 Elsevier Inc. All rights reserved.</P>

A Kinetic Study of Fatty Acid Composition of Embryos, Oviductal and Uterine Fluids in the Rabbit

Yahia Khandoker, M.A.M.,Tsujii, H.,Karasawa, D. Asian Australasian Association of Animal Productio 1998 Animal Bioscience Vol.11 No.1

The different developmental stage embryos and oviductal and uterine fluids of rabbit were analyzed by gas chromatography. Myristic (C 14:0), palmitic (C 16:0), palmitoleic (C 16:1), stearic (C 18:0), oleic (C 18:1), linoleic (C 18:2), linolenic (C 18:3), arachidic (C 20:0), arachidonic (C 20:4), docosahexaenoic (C 22:6) and lignoceric (C 24:0) acids were the common fatty acid constituents with little exception. In most of the samples palmitic, oleic, linoleic and arachidonic acids were observed in high concentration. Moreover, linoleic, linolenic and arachidonic acids were the three poly-unsaturated fatty acids in both type sample except day-1 oviductal fluids. Similarly, in both day-1 and day-2 oviductal and uterine fluids myristic, palmitoleic, stearic, linolenic, arachidic and docosahexaenoic acids were in less composition or undetected.

Effect of homogenization models on stress analysis of functionally graded plates

Yahia, Sihame Ait,Amar, Lemya Hanifi Hachemi,Belabed, Zakaria,Tounsi, Abdelouahed Techno-Press 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.67 No.5

In this paper, the effect of homogenization models on stress analysis is presented for functionally graded plates (FGMs). The derivation of the effective elastic proprieties of the FGMs, which are a combination of both ceramic and metallic phase materials, is of most of importance. The majority of studies in the last decade, the Voigt homogenization model explored to derive the effective elastic proprieties of FGMs at macroscopic-scale in order to study their mechanical responses. In this work, various homogenization models were used to derive the effective elastic proprieties of FGMs. The effect of these models on the stress analysis have also been presented and discussed through a comparative study. So as to show this effect, a refined plate theory is formulated and evaluated, the number of unknowns and governing equations were reduced by dividing the transverse displacement into both bending and shear parts. Based on sinusoidal variation of displacement field trough the thickness, the shear stresses on top and bottom surfaces of plate were vanished and the shear correction factor was avoided. Governing equations of equilibrium were derived from the principle of virtual displacements. Analytical solutions of the stress analysis were obtained for simply supported FGM plates. The obtained results of the displacements and stresses were compared with those predicted by other plate theories available in the literature. This study demonstrates the sensitivity of the obtained results to different homogenization models and that the results generated may vary considerably from one theory to another. Finally, this study offers benchmark results for the multi-scale analysis of functionally graded plates.

Fatty Acid Compositions of Oocytes, Follicular, Oviductal and Uterine Fluids of Pig and Cow

Yahia Khandoker, M.A.M.,Tsujii, H.,Karasawa, D. Asian Australasian Association of Animal Productio 1997 Animal Bioscience Vol.10 No.5

The fatty acid compositions of oocytes, follicular, oviductal and uterine fluids of pig and cow were analyzed using gas chromatography. Myristic (C 14: 0), palmitic (C 16: 0), palmitoleic (C 16: 1), stearic (C 18 : 0), oleic (C 18: 1), linoleic (C 18: 2), linolenic (C 18: 3) and arachidonic (C 20: 4) acids were identified as the common fatty acid constituents with little exception. Oleic acid composition was the highest (21.90 to 36.24%) in both pig and cow followed by palmitic (18.61 to 31.90%) and stearic (10.34 to 20.39%) acid. The three polyunsaturated fatty acids like linoleic, linolenic and arachidonic acids were detected in both pig and cow reproductive fluid samples. Myristic acid was not detected in pig oviductal fluid. Similarly, in cow oocytes myristic, palmitoleic and linolenic acids were not detected. Moreover, palmitic, stearic, oleic and linoleic acid comprised about 80% (73.74 to 88.00%) of the total fatty acids in the different samples analyzed in both animals.

Local Knowledge on Trees Utilization and Their Existing Threats in Rashad District of Nuba Mountains, Sudan

Yahia Omar Adam 강원대학교 산림과학연구소 2014 Journal of Forest Science Vol.30 No.4

Rural people of Sudan are endowed with a deep knowledge concerning the utilization of different tree species. However research on the local knowledge related to tree species utilization still lacks adequate attention. The study objectives were to identify the existing local knowledge related to the utilization of the tree species and the existing threats to the availability of the trees. A total of 300 respondents were selected randomly from Rashad district in Nuba Mountains in 2011. Semi-structured interview, direct observation, group discussion, preference ranking and direct matrix ranking were used to collect the data. The study results revealed that people of Nuba Mountains utilize different tree species for food, medicinal purposes, fodder, firewood, construction and cultural ceremonies. The study results also indicated that the availability of trees is negatively influenced by firewood collection, agricultural expansion, drought, overgrazing and charcoal production. The study concluded that local knowledge has crucial role in tree species utilization in Nuba Mountains. Further researches to document and substantiate the local knowledge on useful tree species are highly recommended.

Preparation of activated carbon from fly ash and its application for CO2 capture

Yahia Abobakor Alhamed,Sami Ullah Rather,Ahmad Hasan El-Shazly,Sharif Fakhruz Zaman,Mohammad Abdulrhaman Daous,Abdulrahim Ahmad Al-Zahrani 한국화학공학회 2015 Korean Journal of Chemical Engineering Vol.32 No.4

Power and desalination plants are one of the main anthropogenic sources for CO2 generation, which is oneof the key elements to cause greenhouse gas effect and thus contribute to the global warming. Fly ash (FA) generated indesalination and power plants was converted into activated carbon (AC) treated with KOH at higher temperature andtested for CO2 capturing efficiency. Morphological characteristics of FA such as BET specific surface area (SSA), porevolume, pore diameter, and pore size distribution (PSD) were performed using N2 adsorption isotherm. CO2 adsorptioncapacity and adsorption isotherms of CO2 over AC were measured by performing thermogravimetric analysis atdifferent temperatures. BET SSA of 161m2g−1 and adsorption capacity of 26mg CO2/g AC can be obtained by activationat KOH/FA ratio of 5 at 700 oC and activation time of 2 h. Therefore, great potential exists for producing AC fromFA, which will have the positive effect of reducing the landfill problem and global warming.

Effect of Exogenous Fatty Acids on in vitro Development of Rat Embryos

Yahia Khandoker, M.A.M.,Tsujii, H. Asian Australasian Association of Animal Productio 1999 Animal Bioscience Vol.12 No.2

Studies were made to evaluate the specific and combined effects of different fatty acids on the in vitro development of 8-cell rat embryo in culture media with and without carbohydrate substrate. Palmitic, oleic, linoleic and arachidonic acids were added singly and in combination to media which contained fatty acid-free BSA. Cell numbers in blastocysts cultured in the media were counted and compared with cell numbers in blastocysts at the corresponding stage collected from the uterus. Oleic, linoleic and arachidonic acids promoted the rat embryo development from 8-cell to the blastocysts. especially in the absence of carbohydrate substrates. Among these three, oleic acid was the most effective but embryo development was not accelerated by the addition of palmitic acid in either the presence or the absence of carbohydrate substrates. Addition of the mixture of four fatty acids was more effective for rat embryo development than single treatment with any of fatty acids tested. Cell numbers per blastocyst in the presence and absence of carbohydrate substrate were similar, and did not differ from those for blastocysts obtained from the uterus.

Propagation Measurements and Estimation of Channel Propagation Models in Urban Environment

( Yahia Zakaria ),( Lubomir Ivanek ),( Ivan Glesk ) 한국인터넷정보학회 2017 KSII Transactions on Internet and Information Syst Vol.11 No.5

Wireless communication is a telecommunication technology, which enables wireless transmission between the portable devices to provide wireless access in all types of environments. In this research, the measurements and various empirical models are analysed and compared in order to find out a suitable propagation model to provide guidelines for cell planning of wireless communication systems. The measured data was taken in urban region with low vegetation and some trees at 900 MHz frequency band. Path loss models are useful planning tools, which permit the designers of cellular communication to obtain optimal levels for the base station deployment and meeting the expected service level requirements. Outcomes show that these empirical models tend to overestimate the propagation loss. As one of the key outputs, it was observed that the calculations of Weissberger model fit with the measured data in urban environment.

Flow Instability (FI) for subcooled flow boiling through a narrow rectangular channel under transversely uniform and non-uniform heat flux

Al-Yahia, Omar S.,Kim, Taewoo,Jo, Daeseong Elsevier 2018 INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER - Vol.125 No.-

<P><B>Abstract</B></P> <P>Transversely non-uniform heating enforces high local heat fluxes at a few areas on the heated surface and low local heat fluxes at others. Differences in the heat flux distribution may generate differences in the boiling behavior when compared with that under uniform heating. Thus, the present experiments investigate the influence of transverse heat flux distribution on the flow instability through a narrow rectangular channel (2.35 mm × 54.0 mm × 566 mm). A wide range of experimental operation conditions, such as inlet temperatures (35–65 °C), thermal power (500–6250 W), and mass flow rates (0.03–0.13 kg/s), are applied to the upward flow channel. The working fluid corresponds to demineralized water under atmospheric pressure. The channel is heated from a side, and the other side is a transparent polycarbonate window from which the bubble behavior is visualized by using a high-speed camera. The heating surface is composed of aluminum with a width of 50 mm and a length of 300 mm. The experiments are performed by using two different procedures to achieve the flow instability, namely (1) constant mass flow rate with power increases and (2) constant power with mass flow rate decreases. The results show that the flow instability occurs at similar thermal power and similar mass flow rates for both uniform and non-uniform heating conditions. However, the pressure drop and wall temperature curves exhibit differences in the trends between the two heating conditions, especially after the fluctuation in the inlet pressure. In the uniform case, bubbles are generated uniformly on the whole transverse direction of the heated surface. In the non-uniform case, more bubbles are generated at the higher local heat flux, which disturbs the velocity profile in the transverse direction. The differences in bubble generation in the transverse direction leads to differences in the flow instability in a narrow rectangular channel.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Heat flux distribution has no effect under single-phase flow. </LI> <LI> Heat flux distribution has a high influence on the first bubble generation. </LI> <LI> Pressure drop trend is different between uniformly and non-uniformly heating conditions. </LI> <LI> Inlet pressure fluctuates after significant bubble generation. </LI> <LI> Void fraction oscillation is affected by the heat flux distribution. </LI> </UL> </P>