• Advances in materials Research
• /
• v.3 no.2
• /
• pp.77-89
• /
• 2014

In the present article, the thermal buckling of zigzag single-walled carbon nanotubes (SWCNTs) is studied using a nonlocal refined shear deformation beam theory and Von-Karman geometric nonlinearity. The model developed simulates both small scale effects and higher-order variation of transverse shear strain through the depth of the nanobeam. Furthermore the present formulation also accommodates stress-free boundary conditions on the top and bottom surfaces of the nanobeam. A shear correction factor, therefore, is not required. The equivalent Young's modulus and shear modulus for zigzag SWCNTs are derived using an energy-equivalent model. The present study illustrates that the thermal buckling properties of SWCNTs are strongly dependent on the scale effect and additionally on the chirality of zigzag carbon nanotube. Some illustrative examples are also presented to verify the present formulation and solutions. Good agreement is observed.

• Structural Engineering and Mechanics
• /
• v.64 no.6
• /
• pp.737-749
• /
• 2017

A new quasi-3D higher shear deformation theory (quasi-3D HSDT) for functionally graded plates is proposed in this article. The theory considers both shear deformation and thickness-stretching influences by a hyperbolic distribution of all displacements within the thickness, and respects the stress-free boundary conditions on the upper and lower surfaces of the plate without using any shear correction factor. The highlight of the proposed theory is that it uses undetermined integral terms in displacement field and involves a smaller number of variables and governing equations than the conventional quasi-3D theories, but its solutions compare well with 3D and quasi-3D solutions. Equations of motion are obtained from the Hamilton principle. Analytical solutions for buckling and dynamic problems are deduced for simply supported plates. Numerical results are presented to prove the accuracy of the proposed theory.

• Wind and Structures
• /
• v.22 no.3
• /
• pp.329-348
• /
• 2016

This work presents a simple hyperbolic shear deformation theory for analysis of functionally graded plates resting on elastic foundation. The proposed model contains fewer number of unknowns and equations of motion than the first-order shear deformation model, but the transverse shear stresses account for a hyperbolic variation and respect the tangential stress-free boundary conditions on the plate boundary surface without introducing shear correction factors. Equations of motion are obtained from Hamilton's principle. The Navier-type analytical solutions for simply-supported plates are compared with the existing solutions to demonstrate the accuracy of the proposed theory.

• Wind and Structures
• /
• v.29 no.6
• /
• pp.371-387
• /
• 2019

In the present paper, a simple refined nth-higher-order shear deformation theory is applied for the free vibration analysis of laminated composite plates. The proposed displacement field is based on a novel kinematic in which include the undetermined integral terms and contains only four unknowns, as against five or more in case of other higher-order theories. The present theory accounts for adequate distribution of the transverse shear strains through the plate thickness and satisfies the shear stress-free boundary conditions on the top and bottom surfaces of the plate, therefore, it does not require problem dependent shear correction factor. The governing equations of motion are derived from Hamilton's principle and solved via Navier-type to obtain closed form solutions. The numerical results of non-dimensional natural frequencies obtained by using the present theory are presented and compared with those of other theories available in the literature to verify the validity of present solutions. It can be concluded that the present refined theory is accurate and efficient in predicting the natural frequencies of isotropic, orthotropic and laminated composite plates.

• Journal of Microbiology and Biotechnology
• /
• v.20 no.12
• /
• pp.1664-1671
• /
• 2010

A new biosurfactant producer was isolated from palm-oil-contaminated soil and later identified through morphology and DNA sequencing as the yeast-like fungus Exophiala dermatitidis. Biosurfactant production was catalyzed by vegetable oil, supplemented with a basal medium. The culture conditions that provided the biosurfactant with the highest surface activity were found to be 5% palm oil with 0.08% $NH_4NO_3$, at a pH of 5.3, with shaking at 200 rpm, and a temperature of $30^{\circ}C$ for a 14-day period of incubation. The biosurfactant was purified, in accordance with surfactant properties, by solvent fractionation using silica gel column chromatography. The chemical structure of the strongest surface-active compound was elucidated through the use of NMR and mass spectroscopy, and noted to be monoolein, which then went on to demonstrate antiproliferative activity against cervical cancer (HeLa) and leukemia (U937) cell lines in a dose-dependent manner. Interestingly, no cytotoxicity was observed with normal cells even when high concentrations were used. Cell and DNA morphological changes, in both cancer cell lines, were observed to be cell shrinkage, membrane blebbling, and DNA fragmentation.

• Journal of Physiology & Pathology in Korean Medicine
• /
• v.21 no.6
• /
• pp.1586-1589
• /
• 2007

This study aims to construct Constitution Information Bank to objectification of Sasang Constitution Diagnosis and Treatment. 422 cases clinically confirmed their Constitution by experts are collected retrospectively and 219 cases for constitution-family study are also collected in Constitution Information Bank from Nov. 2006 to Sept. 2007. The information include their physique, appearance, character, temper, symptom and treatment records. Their DNA cell lines also included in Constitution Information Bank for constitution-genome study. Constitution Information Bank is composed of constitution-clinical information -physique, appearance, character, temper, symptom and treatment records- and biological information -DNA genotyping data-. Total of 550 cases are collected in Constitution Information Bank from Nov. 2006 to Sept. 2007. Among these, 219 cases are for constitution-family study, especially, 74 cases are collected from Han's large family.

• Journal of Physiology & Pathology in Korean Medicine
• /
• v.20 no.5
• /
• pp.1111-1116
• /
• 2006

Medical science is an area of study that focuses on maintaining health and treating disease. However, modern medicine focuses on treating disease and neglects methodology of maintaining health. Although the definition of heal this defined by the World Health Organization (WHO) and as the concept of harmonizing Yin and Yang in Korean medicine, there is no specific details regarding the definition. Thus, the following conclusion was obtained after the concept of health is viewed through Yin-Yang(陰陽), Vital Essence(精), Qi(氣), and Healthy Person(平人). Although Yin and Yang have opposite properties, they work very closely, maintaining the overall balance and harmony. Secondly, Vin and Yang would each function by the effects of one another, and the body could maintain normal physiological activities through this function. Thirdly, it maintains normal physiological state through the ascending Kidney-Water and descending Heart-Yang(水升火降). Fourthly, Vital Essence is divided into the congenital Essence(先天之精) and the acquired Essence(後天之精) in which the former is related with reproduction and the latter, nourishing. Fifthly, Qi is resistant to pathogens and related with the physique so that Qi and physique should be balanced. Sixthly, Healthy Person is the state where the exchange of Qi-Blood is active.

• Wind and Structures
• /
• v.27 no.5
• /
• pp.311-324
• /
• 2018

This work examines vibration and bending response of carbon nanotube-reinforced composite plates resting on the Pasternak elastic foundation. Four types of distributions of uni-axially aligned single-walled carbon nanotubes are considered to reinforce the plates. Analytical solutions determined from mathematical formulation based on hyperbolic shear deformation plate theory are presented in this study. An accuracy of the proposed theory is validated numerically by comparing the obtained results with some available ones in the literature. Various considerable parameters of carbon nanotube volume fraction, spring constant factors, plate thickness and aspect ratios, etc. are considered in the present investigation. According to the numerical examples, it is revealed that the vertical displacement of the plates is found to diminish as the increase of foundation parameters; while, the natural frequency increase as the increment of the parameters for every type of plate.

• Geomechanics and Engineering
• /
• v.18 no.2
• /
• pp.161-178
• /
• 2019

In this research, a simple quasi 3D hyperbolic shear deformation model is employed for bending and dynamic behavior of functionally graded (FG) plates resting on visco-Pasternak foundations. The important feature of this theory is that, it includes the thickness stretching effect with considering only 4 unknowns, which less than what is used in the First Order Shear Deformation (FSDT) theory. The visco­Pasternak's foundation is taken into account by adding the influence of damping to the usual foundation model which characterized by the linear Winkler's modulus and Pasternak's foundation modulus. The equations of motion for thick FG plates are obtained in the Hamilton principle. Analytical solutions for the bending and dynamic analysis are determined for simply supported plates resting on visco-Pasternak foundations. Some numerical results are presented to indicate the effects of material index, elastic foundation type, and damping coefficient of the foundation, on the bending and dynamic behavior of rectangular FG plates.

• Wind and Structures
• /
• v.28 no.1
• /
• pp.19-30
• /
• 2019

This article present the free vibration analysis of simply supported perfect and imperfect (porous) FG beams using a high order trigonometric deformation theory. It is assumed that the material properties of the porous beam vary across the thickness. Unlike other theories, the number of unknown is only three. This theory has a parabolic shear deformation distribution across the thickness. So it is useless to use the shear correction factors. The Hamilton's principle will be used herein to determine the equations of motion. Since, the beams are simply supported the Navier's procedure will be retained. To show the precision of this model, several comparisons have been made between the present results and those of existing theories in the literature.