• Steel and Composite Structures
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• v.22 no.4
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• pp.889-913
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• 2016

Vibration analysis of embedded functionally graded (FG)-carbon nanotubes (CNT)-reinforced piezoelectric cylindrical shell subjected to uniform and non-uniform temperature distributions are presented. The structure is subjected to an applied voltage in thickness direction which operates in control of vibration behavior of system. The CNT reinforcement is either uniformly distributed or functionally graded (FG) along the thickness direction indicated with FGV, FGO and FGX. Effective properties of nano-composite structure are estimated through Mixture low. The surrounding elastic foundation is simulated with spring and shear constants. The material properties of shell and elastic medium constants are assumed temperature-dependent. The motion equations are derived using Hamilton's principle applying first order shear deformation theory (FSDT). Based on differential cubature (DC) method, the frequency of nano-composite structure is obtained for different boundary conditions. A detailed parametric study is conducted to elucidate the influences of external applied voltage, elastic medium type, temperature distribution type, boundary conditions, volume percent and distribution type of CNT are shown on the frequency of system. In addition, the mode shapes of shell for the first and second modes are presented for different boundary conditions. Numerical results indicate that applying negative voltage yields to higher frequency. In addition, FGX distribution of CNT is better than other considered cases.

• Steel and Composite Structures
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• v.23 no.6
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• pp.691-714
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• 2017

Rotating fluid induced vibration and instability of embedded piezoelectric nano-composite separators subjected to magnetic and electric fields is the main contribution of present work. The separator is modeled with cylindrical shell element and the structural damping effects are considered by Kelvin-Voigt model. Single-walled carbon nanotubes (SWCNTs) are used as reinforcement and effective material properties are obtained by mixture rule. The perturbation velocity potential in conjunction with the linearized Bernoulli formula is used for describing the rotating fluid motion. The orthotropic surrounding elastic medium is considered by spring, damper and shear constants. The governing equations are derived on the bases of classical shell theory (CST), first order shear deformation theory (FSDT) and sinusoidal shear deformation theory (SSDT). The nonlinear frequency and critical angular fluid velocity are calculated by differential quadrature method (DQM). The detailed parametric study is conducted, focusing on the combined effects of the external voltage, magnetic field, visco-Pasternak foundation, structural damping and volume percent of SWCNTs on the stability of structure. The numerical results are validated with other published works as well as comparing results obtained by three theories. Numerical results indicate that with increasing volume fraction of SWCNTs, the frequency and critical angular fluid velocity are increased.

• Steel and Composite Structures
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• v.34 no.4
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• pp.615-623
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• 2020

In this paper, free vibration analysis of a functionally graded cylindrical nanoshell resting on Pasternak foundation is presented based on the nonlocal elasticity theory. A two-dimensional formulation along the axial and radial directions is presented based on the first-order shear deformation shell theory. Hamilton's principle is employed for derivation of the governing equations of motion. The solution to formulated boundary value problem is obtained based on a harmonic solution and trigonometric functions for various boundary conditions. The numerical results show influence of significant parameters such as small scale parameter, stiffness of Pasternak foundation, mode number, various boundary conditions, and selected dimensionless geometric parameters on natural frequencies of nanoshell.

• Korean Journal of Human Ecology
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• v.15 no.6
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• pp.1073-1081
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• 2006

The development of foundation garment pattern on the typical adult women's body was carried out. By means of the flatted body surface shell, the foundation garment pattern was developed. And its fitting test also performed. The results of this study can be summarized as follows; 1. The investigated Foundation basic pattern was made by the allowing the maximum bust size without any surplus since it was based on the tight-fitted model drawing technique. The investigated the completed pattern was designed in three parts of front and back body, including bust. 2. The result showed by overlapping the torso basic pattern foundation and body surface development selected from body almost the same except for the shift of dart position. 3. The result by overlapping basic pattern 3 existing basic patterns. On the basis of top-bust line showed that the setting up the volume of dart of bust and its waist affect the appearance of model. Especially, it was found that the above result was related to the bust and under bust line. 4. The result of the wearing test of 3 existing basic patterns and basic pattern of this study revealed that the mean values of whole items were higher than average in type P and type E. The fitting & position of under-bust line and extent of wrapping bust showed the high points in the current study and type of P. The result of evaluating the whole appearance in three points(front, side, back) showed different according to the every basic foundation garment pattern.

• International Journal of Industrial Entomology and Biomaterials
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• v.2 no.2
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• pp.111-117
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• 2001

Screening of fifteen bivoltine silkworm breeds of Bombyx mori Linn at a temperature of $31{\pm}1^{\circ}C$ and relative humidity of 85${\pm}$5% resulted in the identification of eight thermo-tolerant breeds. The survival and cocoon shell ratio of the tolerant breeds ranged from 72.7 to 78.7% and 20.0 to 20.1% respectively. The tolerant breeds comprised of four oval breeds and four dumb-bell breeds. Eight foundation crosses prepared by crossing the oval and dumb-bell parents among themselves were screened at a temperature of $31{\pm}1^{\circ}C$ and relative humidity of 85{\pm}5%. The performance of the foundation crosses on 11 economic characters were analysed by employing Multipie Trait Evaluation Index method. Four foundation crosses which scored average index value > 50 were selected as breeding parents and breeding initiated for the evolution of thermo-tolerant bivoltine silkworm breeds. The methodology and the results of the foundation crosses reared both at 31{\pm}1$^{\circ}C$ and at $25{\pm}1^{\circ}C$ temperatures, are discussed.

• Advances in nano research
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• v.16 no.1
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• pp.11-26
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• 2024

In this study, free vibration analysis of FG porous spherical cap reinforced by graphene platelets resting on Winkler-type elastic foundation has been surveyed for the first time. Three different types of porosity patterns are considered for the spherical cap whose two types of porosity patterns in the metal matrix are symmetric and the other one is uniform. Besides, five GPL patterns are assumed for dispersing of GPLs in the metal matrix. Tsai-Halpin and extended rule of the mixture are used to determine the Young modulus and mass density of the shell, respectively. Employing 3D FEM elasticity in conjunction with Hamilton's Principle, the governing motion equations of the structure are obtained and solved. The impact of various parameters including porosity coefficient, various porosity distributions in conjunction with different GPL patterns, the weight fraction of graphene Nano fillers, polar angles and stiffness coefficient of elastic foundation on natural frequencies of FG porous spherical cap reinforced by GPLs have been reported for the first time.

• Korean Journal of Veterinary Research
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• v.42 no.3
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• pp.309-320
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• 2002

Animal bones that were excavated with earthenware at the Jongdal-ri shell mound archaeological site IV on Jeju Island were investigated morpholgically and osteometrically. This archaeological site is estimated to date from the late Tamra period to the unified Shilla Dynasty (A.D. 7C) based on the type of earthenware. The number of animal bones was 3,430 pieces(Quarter B : 758, Quarter C : 2,672). The animal species consisted of Cervus spp., Sus spp., Bos spp and Canivore. The animal bone pieces excavated at Quarter B consisted of those of Cervus(53.3%), Bos(2.8%) and Sus(13.7%). The bones of Cervus(53.3%), Bos(2.8%), Sus(13.7%) and Canivore(4.6%) were found at Quarter C. The greatest number of heads was unearthed as a whole, and the classification according to animal species showed that the heads were more visible than other bones. Forelimbs and hindlimbs were distributed evenly on the part of Cervus. The skeletons from Bos were identified in the order of heads, forelimbs and hindlimbs, while nearly all the Sus bones were found to be heads. These data suggests that Cervus, Sus and Bos are major fauna at the estimated period.

• Structural Engineering and Mechanics
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• v.62 no.5
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• pp.551-565
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• 2017

Based on the strain gradient theory (SGT), vibration analysis of an embedded micro cylindrical shell reinforced with agglomerated carbon nanotubes (CNTs) is investigated. The elastic medium is simulated by the orthotropic Pasternak foundation. The structure is subjected to magnetic field in the axial direction. For obtaining the equivalent material properties of structure and considering agglomeration effects, the Mori-Tanaka model is applied. The motion equations are derived on the basis of Mindlin cylindrical shell theory, energy method and Hamilton's principal. Differential quadrature method (DQM) is proposed to evaluate the frequency of system for different boundary conditions. The effects of different parameters such as CNTs volume percent, agglomeration of CNTs, elastic medium, magnetic field, boundary conditions, length to radius ratio and small scale parameter are shown on the frequency of the structure. The results indicate that the effect of CNTs agglomeration plays an important role in the frequency of system so that considering agglomeration leads to lower frequency. Furthermore, the frequency of structure increases with enhancing the small scale parameter.

• Journal of the Korean Geotechnical Society
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• v.18 no.6
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• pp.103-116
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• 2002

The development of contaminated sites often requires foundation concrete to be placed in contact with soils contaminated with organic compounds. There is a common perception that organic compounds affect the setting and hardening of concrete, giving a reduced long-term strength. In this study, unconfined compressive strength tests for concrete cured in Ethylbenzene were performed. The possibility of byproduct to be used for aggregate of concretes as materials of construction was also evaluated by carring out the investigation of the characteristics of the mixture of concrete and crushed oyster shell which is treated as waste material and often illegally disposed at coastal oyster production site. The transformation of strength characteristics was investigated by varying the blending ratio of fly ash.

• Steel and Composite Structures
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• v.33 no.2
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• pp.195-208
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• 2019

Based on a four-variable shear deformation shell theory, the free vibration analysis of functionally graded graphene platelet-reinforced composite (FGGPRC) doubly-curved shallow shells with different boundary conditions is investigated in this work. The doubly-curved shells are composed of multi nanocomposite layers that are reinforced with graphene platelets. The graphene platelets are uniformly distributed in each individual layer. While, the volume faction of the graphene is graded from layer to other in accordance with a novel distribution law. Based on the suggested distribution law, four types of FGGPRC doubly-curved shells are studied. The present shells are assumed to be rested on elastic foundations. The material properties of each layer are calculated using a micromechanical model. Four equations of motion are deduced utilizing Hamilton's principle and then converted to an eigenvalue problem employing an analytical method. The obtained results are checked by introducing some comparison examples. A detailed parametric investigation is performed to illustrate the influences of the distribution type of volume fraction, shell curvatures, elastic foundation stiffness and boundary conditions on the vibration of FGGPRC doubly-curved shells.