Received 26 November 2011 Accepted 10 November 2012 Abstract The purpose of the present study was... more Received 26 November 2011 Accepted 10 November 2012 Abstract The purpose of the present study was to investigate levels of nickel in feathers of the Western Reef Heron Egretta gularis (N=15) and Siberian Gull Larus heuglini (N=15). Bird samples were collected from November to December 2010 in Hara Biosphere Reserve. Assaying nickel by using Shimadzu AA 680 flame atomic absorption spectrophotometer, the results were given as micrograms per gram of dry weight. The results of the current study showed that the amount of nickel in feathers of the Siberian Gull (a migratory species) was higher than in feathers of the Western Reef Heron (a resident species). The concentration of nickel was found to follow the order of female/juvenile> female/adult> male/adult in Western Reef Heron and male/adult> female/juvenile> female/adult> male/juvenile in Siberian Gull. The results also indicated that the nickel concentration level in female Western Reef Herons was higher than in males ...
Background: Nowadays, an accumulation of heavy metals in the environment is one the most importan... more Background: Nowadays, an accumulation of heavy metals in the environment is one the most important consideration in the world. Heavy metals due to their chemical stability, low flexibility and power of bioaccumulation in the body organism are becoming quickly toxic pollutants. This study was carried out to determine the heavy metals (e.g. Cadmium, Copper, Zinc and Lead) in the water and sediments of Amirkolayeh wetland in Guilan from Winter 2010 to Spring 2011 then they were compared to global scales. Materials and Methods: Sampling was done at the three stations in Amir kolayeh wetland during Winter and Spring. At first, samples were dried by the wet methods and mixed acid then the chemical annualized were done. Concentrations of the heavy metals were determined by a flame atomic absorption spectrophotometer (FAAS). Results: Results showed that the mean concentrations of heavy metals in water for Cu, Pb, Cd and Zn were 0.394±0.078, 0.03±0.007, 0.011±0.003 and 0.517±0.09mg/l and in ...
Abstract This paper presents a theoretical analysis for the frequency response of thermally pre/p... more Abstract This paper presents a theoretical analysis for the frequency response of thermally pre/post buckled composite pipes reinforced with carbon nanotubes (CNTs). The vibrational behavior of the uniformly heated nanocomposite pipe surrounded by a nonlinear elastic foundation is analytically studied. The nanocomposite media is introduced using a refined rule of mixtures that is calibrated with the available data on the basis of molecular dynamics simulations. Distribution of CNTs across the radius of composite pipes can be uniform or functionally graded (FG) and properties are considered to be temperature-dependent. A higher-order shear deformation model and the von Karman assumption are employed to extract the nonlinear equations of motion. The system of partial differential equations is established by means of Hamilton’s principle. A two-step perturbation method is utilized to carry out closed-form solutions for these nonlinear equations. The natural frequencies are obtained for the immovable simply-supported boundary conditions. A comparison study is provided for the case of isotropic homogeneous pipes in which good agreement is obtained. The novel numerical results are presented to show the influences of geometric characteristics, CNT distribution pattern, foundation stiffness, and the CNT volume fraction upon the frequency response of the nanocomposite pipe subjected to uniform temperature rise loading.
A nonlocal strain gradient model is developed in this research to analyse the nonlinear frequenci... more A nonlocal strain gradient model is developed in this research to analyse the nonlinear frequencies of functionally graded porous curved nanotubes. It is assumed that the curved nanotube is in contact with a two-parameter nonlinear elastic foundation and is also subjected to the uniform temperature rise. The non-classical theory presented for curved nanotubes contains a nonlocal parameter and a material length scale parameter which can capture the size effect. A power law distribution function is used to describe the graded properties through the thickness direction of curved nanotubes. The even dispersion pattern is used to model the porosities distribution. The high-order shear deformation theory and the von Karman type of geometric non-linearity are utilized to obtain the nonlinear governing equations of the structure. The size-dependent equations of motion for the large amplitude vibrations of curved nanotubes are obtained by employing Hamilton’s principle. The analytical solutions are extracted for the curved nanotube with immovable hinged-hinged boundary conditions. Size-dependent frequencies of the curved nanotube exposed to thermal field are obtained using the two-step perturbation technique and Galerkin procedure. The effects of important parameters such as nonlocal and length scale parameters, temperature field, elastic foundation, porosity, power law index and geometrical parameters are studied in detail.
A nonlocal strain gradient theory is developed in this paper to study the large amplitude vibrati... more A nonlocal strain gradient theory is developed in this paper to study the large amplitude vibrations of arches made of functionally graded (FG) porous material. The case of shallow arches resting on nonlinear elastic foundation is modeled via a general higher-order shear deformation theory. The third-order model of Reddy, the first-order model of Timoshenko, and the classical model of Euler–Bernoulli are analyzed. Thermomechanical properties of the arch exposed to the uniform thermal field are assumed to be temperature dependent. The nonlinear motion equations of the arch are established by employing Hamilton’s principle and the von Kármán type of geometric nonlinearity. The two-step perturbation technique and the Galerkin method are utilized to solve the nonlinear governing equations. The size-dependent linear and nonlinear frequencies of the arch are obtained for the immovable pinned-pinned boundary conditions. The comparison studies are performed to verify the present solution method with the provided data in the literature, and a good agreement is observed. The novel parametric studies covered in this research include the effects of several parameters such as elastic foundation, nonlocal and length scale parameters, porosity, temperature field, power law index, and geometrical parameters on the frequencies of FG porous arches in detail.
This research deals with the stability analysis of shallow segments of the toroidal shell made of... more This research deals with the stability analysis of shallow segments of the toroidal shell made of saturated porous functionally graded (FG) material. The nonhomogeneous material properties of porous shell are assumed to be functionally graded as a function of the thickness and porosity parameters. The porous toroidal shell segments with positive and negative Gaussian curvatures and nonuniform distributed porosity are considered. The nonlinear equilibrium equations of the porous shell are derived via the total potential energy of the system. The governing equations are obtained on the basis of classical thin shell theory and the assumptions of Biot's poroelasticity theory. The equations are a set of the coupled partial differential equations. The analytical method including the Airy stress function is used to solve the stability equations of porous shell under mechanical loads in three cases. Porous toroidal shell segments subjected to lateral pressure, axial compression, and hyd...
Iranian Journal of Science and Technology, Transactions of Mechanical Engineering, 2020
The present research deals with the small and large amplitude free vibrations of thick functional... more The present research deals with the small and large amplitude free vibrations of thick functionally graded material (FGM) beams. Beams are resting on an elastic foundation which consists of the Winkler layer, shear layer and nonlinear springs. The effect of uniform temperature elevation is also included into the formulation. A third-order shear deformation beam theory is adopted as the basic assumption of the formulation which satisfies the traction-free boundary conditions on the top and bottom surfaces. Using two different formulations, i.e. the mid-surface-based formulation and the neutral surfacebased formulation, the governing equations of motion are established. For the case of beams with immovable edges in inplane direction and simply supported in flexure, the governing equations are given in a new presentation. These equations are solved using the two-step perturbation technique. Closed-form expressions are provided to obtain the small and large amplitude natural frequencies of the FGM beam resting on nonlinear elastic foundation and operating in thermal environment. Numerical results are given to discuss the effects of thermal environment, elastic foundation parameters, different formulations, and the geometrical parameters.
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Present investigation deals with the geometrically non-linear bending response of functionally gr... more Present investigation deals with the geometrically non-linear bending response of functionally graded carbon nanotube reinforced composite (FG-CNTRC) beams. It is assumed that beam is resting on a three parameter elastic foundation. Uniform thermal field is also included into the formulation and properties are considered as temperature dependent. Distribution of CNTs in the beam may be uniform or functionally graded according to linear distribution of volume fraction of CNTs across the thickness. The equivalent properties of the composite media are obtained with the aid of the refined rule of mixtures approach which
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
International Journal of Mechanical Sciences, 2020
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Mechanics Based Design of Structures and Machines, 2020
Analysis of nonlinear response of thick FGM beams subjected to either thermal or mechanical load ... more Analysis of nonlinear response of thick FGM beams subjected to either thermal or mechanical load is performed. Beam is in contact with a threeparameter elastic foundation. Nonlinear component of the foundation may be of the hardening or softening type. Equilibrium equations of the clamped beam are obtained within the framework of von Karman assumptions and third-order shear deformation theory and solved using the twostep perturbation technique. It is shown that when the FGM beam is in contact with a sufficiently soft foundation, the post-buckling path of the heated/compressed FGM beam is unstable and therefore, the structure is imperfection sensitive.
Received 26 November 2011 Accepted 10 November 2012 Abstract The purpose of the present study was... more Received 26 November 2011 Accepted 10 November 2012 Abstract The purpose of the present study was to investigate levels of nickel in feathers of the Western Reef Heron Egretta gularis (N=15) and Siberian Gull Larus heuglini (N=15). Bird samples were collected from November to December 2010 in Hara Biosphere Reserve. Assaying nickel by using Shimadzu AA 680 flame atomic absorption spectrophotometer, the results were given as micrograms per gram of dry weight. The results of the current study showed that the amount of nickel in feathers of the Siberian Gull (a migratory species) was higher than in feathers of the Western Reef Heron (a resident species). The concentration of nickel was found to follow the order of female/juvenile> female/adult> male/adult in Western Reef Heron and male/adult> female/juvenile> female/adult> male/juvenile in Siberian Gull. The results also indicated that the nickel concentration level in female Western Reef Herons was higher than in males ...
Background: Nowadays, an accumulation of heavy metals in the environment is one the most importan... more Background: Nowadays, an accumulation of heavy metals in the environment is one the most important consideration in the world. Heavy metals due to their chemical stability, low flexibility and power of bioaccumulation in the body organism are becoming quickly toxic pollutants. This study was carried out to determine the heavy metals (e.g. Cadmium, Copper, Zinc and Lead) in the water and sediments of Amirkolayeh wetland in Guilan from Winter 2010 to Spring 2011 then they were compared to global scales. Materials and Methods: Sampling was done at the three stations in Amir kolayeh wetland during Winter and Spring. At first, samples were dried by the wet methods and mixed acid then the chemical annualized were done. Concentrations of the heavy metals were determined by a flame atomic absorption spectrophotometer (FAAS). Results: Results showed that the mean concentrations of heavy metals in water for Cu, Pb, Cd and Zn were 0.394±0.078, 0.03±0.007, 0.011±0.003 and 0.517±0.09mg/l and in ...
Abstract This paper presents a theoretical analysis for the frequency response of thermally pre/p... more Abstract This paper presents a theoretical analysis for the frequency response of thermally pre/post buckled composite pipes reinforced with carbon nanotubes (CNTs). The vibrational behavior of the uniformly heated nanocomposite pipe surrounded by a nonlinear elastic foundation is analytically studied. The nanocomposite media is introduced using a refined rule of mixtures that is calibrated with the available data on the basis of molecular dynamics simulations. Distribution of CNTs across the radius of composite pipes can be uniform or functionally graded (FG) and properties are considered to be temperature-dependent. A higher-order shear deformation model and the von Karman assumption are employed to extract the nonlinear equations of motion. The system of partial differential equations is established by means of Hamilton’s principle. A two-step perturbation method is utilized to carry out closed-form solutions for these nonlinear equations. The natural frequencies are obtained for the immovable simply-supported boundary conditions. A comparison study is provided for the case of isotropic homogeneous pipes in which good agreement is obtained. The novel numerical results are presented to show the influences of geometric characteristics, CNT distribution pattern, foundation stiffness, and the CNT volume fraction upon the frequency response of the nanocomposite pipe subjected to uniform temperature rise loading.
A nonlocal strain gradient model is developed in this research to analyse the nonlinear frequenci... more A nonlocal strain gradient model is developed in this research to analyse the nonlinear frequencies of functionally graded porous curved nanotubes. It is assumed that the curved nanotube is in contact with a two-parameter nonlinear elastic foundation and is also subjected to the uniform temperature rise. The non-classical theory presented for curved nanotubes contains a nonlocal parameter and a material length scale parameter which can capture the size effect. A power law distribution function is used to describe the graded properties through the thickness direction of curved nanotubes. The even dispersion pattern is used to model the porosities distribution. The high-order shear deformation theory and the von Karman type of geometric non-linearity are utilized to obtain the nonlinear governing equations of the structure. The size-dependent equations of motion for the large amplitude vibrations of curved nanotubes are obtained by employing Hamilton’s principle. The analytical solutions are extracted for the curved nanotube with immovable hinged-hinged boundary conditions. Size-dependent frequencies of the curved nanotube exposed to thermal field are obtained using the two-step perturbation technique and Galerkin procedure. The effects of important parameters such as nonlocal and length scale parameters, temperature field, elastic foundation, porosity, power law index and geometrical parameters are studied in detail.
A nonlocal strain gradient theory is developed in this paper to study the large amplitude vibrati... more A nonlocal strain gradient theory is developed in this paper to study the large amplitude vibrations of arches made of functionally graded (FG) porous material. The case of shallow arches resting on nonlinear elastic foundation is modeled via a general higher-order shear deformation theory. The third-order model of Reddy, the first-order model of Timoshenko, and the classical model of Euler–Bernoulli are analyzed. Thermomechanical properties of the arch exposed to the uniform thermal field are assumed to be temperature dependent. The nonlinear motion equations of the arch are established by employing Hamilton’s principle and the von Kármán type of geometric nonlinearity. The two-step perturbation technique and the Galerkin method are utilized to solve the nonlinear governing equations. The size-dependent linear and nonlinear frequencies of the arch are obtained for the immovable pinned-pinned boundary conditions. The comparison studies are performed to verify the present solution method with the provided data in the literature, and a good agreement is observed. The novel parametric studies covered in this research include the effects of several parameters such as elastic foundation, nonlocal and length scale parameters, porosity, temperature field, power law index, and geometrical parameters on the frequencies of FG porous arches in detail.
This research deals with the stability analysis of shallow segments of the toroidal shell made of... more This research deals with the stability analysis of shallow segments of the toroidal shell made of saturated porous functionally graded (FG) material. The nonhomogeneous material properties of porous shell are assumed to be functionally graded as a function of the thickness and porosity parameters. The porous toroidal shell segments with positive and negative Gaussian curvatures and nonuniform distributed porosity are considered. The nonlinear equilibrium equations of the porous shell are derived via the total potential energy of the system. The governing equations are obtained on the basis of classical thin shell theory and the assumptions of Biot's poroelasticity theory. The equations are a set of the coupled partial differential equations. The analytical method including the Airy stress function is used to solve the stability equations of porous shell under mechanical loads in three cases. Porous toroidal shell segments subjected to lateral pressure, axial compression, and hyd...
Iranian Journal of Science and Technology, Transactions of Mechanical Engineering, 2020
The present research deals with the small and large amplitude free vibrations of thick functional... more The present research deals with the small and large amplitude free vibrations of thick functionally graded material (FGM) beams. Beams are resting on an elastic foundation which consists of the Winkler layer, shear layer and nonlinear springs. The effect of uniform temperature elevation is also included into the formulation. A third-order shear deformation beam theory is adopted as the basic assumption of the formulation which satisfies the traction-free boundary conditions on the top and bottom surfaces. Using two different formulations, i.e. the mid-surface-based formulation and the neutral surfacebased formulation, the governing equations of motion are established. For the case of beams with immovable edges in inplane direction and simply supported in flexure, the governing equations are given in a new presentation. These equations are solved using the two-step perturbation technique. Closed-form expressions are provided to obtain the small and large amplitude natural frequencies of the FGM beam resting on nonlinear elastic foundation and operating in thermal environment. Numerical results are given to discuss the effects of thermal environment, elastic foundation parameters, different formulations, and the geometrical parameters.
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Present investigation deals with the geometrically non-linear bending response of functionally gr... more Present investigation deals with the geometrically non-linear bending response of functionally graded carbon nanotube reinforced composite (FG-CNTRC) beams. It is assumed that beam is resting on a three parameter elastic foundation. Uniform thermal field is also included into the formulation and properties are considered as temperature dependent. Distribution of CNTs in the beam may be uniform or functionally graded according to linear distribution of volume fraction of CNTs across the thickness. The equivalent properties of the composite media are obtained with the aid of the refined rule of mixtures approach which
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
International Journal of Mechanical Sciences, 2020
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Mechanics Based Design of Structures and Machines, 2020
Analysis of nonlinear response of thick FGM beams subjected to either thermal or mechanical load ... more Analysis of nonlinear response of thick FGM beams subjected to either thermal or mechanical load is performed. Beam is in contact with a threeparameter elastic foundation. Nonlinear component of the foundation may be of the hardening or softening type. Equilibrium equations of the clamped beam are obtained within the framework of von Karman assumptions and third-order shear deformation theory and solved using the twostep perturbation technique. It is shown that when the FGM beam is in contact with a sufficiently soft foundation, the post-buckling path of the heated/compressed FGM beam is unstable and therefore, the structure is imperfection sensitive.
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