Iranian journal of science and technology. transaction a, science (IRAN J SCI TECHNOL A )


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    ABSTRACT: In this paper, the meshless local Petrov-Galerkin (MLPG) method is used to analyze the dynamic fracture of an isotropic FGM plate containing a center crack. The dynamic stress intensity factors are studied under the influence of various non-homogeneity ratios. Both the moving least square (MLS) and the direct method have been applied to estimate the shape function and to impose the essential boundary conditions. The enriched weight function method is used to simulate the displacement and stress field around the crack tip. Normalized dynamic stress intensity factors (NDSIF) are calculated using the path independent integral, J*, which is formulated for the nonhomogeneous material. To validate the method, the homogenous center cracked plate problem is analyzed. The obtained results show good agreement between the analytical solution and the MLPG results for homogenous material. After validation, a center cracked plate made of FGM with two different material gradations (along and normal to the crack length) and three different lengths of FGM zone under the effect of step load are considered, and the following six distinct problems are studied here.
    Iranian journal of science and technology. transaction a, science 04/2014; 2014(38M1+):181-194.
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    ABSTRACT: Sluice and radial radial gates are common devices used for flow control in hydraulic structures. This paper demonstrates the variation of the contraction coefficient of sluice gates and three types of radial gates (namely, Hard-Rubber, Sharp and Music Note gates) by using Energy and Momentum Equations (EMEs). This paper presents a novel method for estimating the acting force behind these gates under free and submerged flow conditions. A minimum value of the contraction coefficient for sluice gates was obtained under a certain value of relative gate opening. Under a specific condition, Hard-Rubber gates have a larger contraction than Sharp gates, while Music Note gates have the least contraction. It is recognized that the contraction coefficient decreases as the gate lip angle and the gate opening increase. Under submerged flow conditions, the contraction coefficient of sluice and radial gates would be either increased or decreased depending on the level of flow submergence. It is concluded that using the proposed contraction coefficient in estimating the discharge coefficient demonstrates an acceptable accuracy.
    Iranian journal of science and technology. transaction a, science 01/2014;
  • Iranian journal of science and technology. transaction a, science 01/2014; 38(2):95-103.
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    ABSTRACT: Concentrations of elements (As, Co, Cu, Ni, Mo, Pb, V, Cd, Cr and Zn) are studied in the surface sediments of Bakhtegan Lake, northwest of Nyriz City, Iran, to assess metal contamination. The average abundance order of trace elements content in Bakhtegan Lake sediments is Cr>Ni> V> Zn> Cu> Co> As> Pb> Mo>Cd. The comparison of trace elements concentration in Bakhtegan Lake sediments with toxicological reference values, reveal that the average concentration of As, Cr and Ni in the present sediments is higher than threshold effective level (TEL). Ni shows higher concentration than toxic effect threshold (TET) and probable effective level (PEL) values. The results of contamination factor (CF) based on background value reveal that Cr, Cu, Zn, V, Co, Pb, Mo, As and Ni have moderate and Cd has considerable contamination factor. The application of modified degree of contamination values (mC d ) based on background and mean shale values indicate low and very low degree of contamination in sediment samples, respectively. The calculated EF values indicate that Cd in Bakhtegan Lake sediments is enriched compared to the background value. The strong association of Cr, Ni, Zn, Co, Cu, Pb, and V in sediments and high loading of these trace elements with clay, Mn and Fe (PC1) agree with the measured correlation coefficients indicating that Mn and Fe hydroxides and clay content play a significant role in the distribution and sorption of trace elements in sediments. The results of PCA for As and Cd indicate that these elements are influenced by anthropogenic activities. Keywords: Sediment; contamination; Factor analysis; toxicological reference; Bakhtegan Lake; Iran
    Iranian journal of science and technology. transaction a, science 01/2014;
  • Iranian journal of science and technology. transaction a, science 01/2014; 37(C):513-517.
  • Iranian journal of science and technology. transaction a, science 01/2014;
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    ABSTRACT: Let R be a graded ring and M be a graded R-module. We define a topology on graded prime spectrum G-Spec(M) of the graded R-module M which is analogous to that for G-Spec(R), and investigate several properties of the topology.
    Iranian journal of science and technology. transaction a, science 12/2013;
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    ABSTRACT: During a survey of Sindh and Punjab provinces of Pakistan, two dragonfly genera were collected and identified for the first time from the country. Anaciaeshna(Family Aeshnidae) is a genus of large dragonflies. Representatives were collectedfrom Gujjo, District Thatta (Sindh) in August 2008 and were identified as Anaciaeshna jaspidea (Burmeister). The second genus was Epophthalmia (Family Corduliidae), medium to large sized, well-built and very fast flying dragonflies. Epophthalmia vittata vittata Burmeister (Family Corduliidae) was collected from Java Dam, Rawalpindi and Dhok Tallian Dam near Chakwal. Individuals of this genus were found maneuvering near the peripheries of small dams. Some taxonomic notes of the said species are provided. Keywords: Dragonflies; first record of occurrence; Pakistan; taxonomic survey
    Iranian journal of science and technology. transaction a, science 11/2013; IJST (2013) 37A4: 445-448(2013):445-448.

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