• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2001년도 제34회 추계학술대회 개최
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• pp.364-373
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• 2001

This paper describes the variation of lubricant's temperature effects on elastohydrodynamic lubrication. The Newton-Raphson technique was used to solve the simultaneous system of Reynolds and elasticity equations. To show effects of lubricant's temperature, average temperature across the oil film was calculated using the energy equation. Pressure distribution, film shape, and temperature distribution were obtained for fully flooded conjunctions, and various dimensionless speed parameters while load and material parameters were held constant. Minimum film thickness were obtained for various material properties while load and velocity were held constant. It is drawn that the thermal effects have a strong influence on a minimum film thickness under high rolling velocity and slip ratio.

• 대한기계학회논문집A
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• 제20권4호
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• pp.1356-1362
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• 1996

Fracture toughness of heterogeneous brittle materials such as poly crystalline ceramics used to present the size (thickness) effect as well as statistically distributed results. There is belief that both(size effect and scatter) must be associated with each other. However, no generally accepted theory has been established so far. Using statistical approach, a probabilistic modeling for the fracture toughness which describes the thickness effect was attempted in this paper, Weibull distribution of specific fracture energy(SFE)at local areas and Griffith criterion are applied to the model. In addition, the newly developed model was verified with experimental results of alumina.

• Structural Engineering and Mechanics
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• 제20권4호
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• pp.435-450
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• 2005

Here, the dynamic instability characteristics of aero-thermo-mechanically stressed functionally graded plates are investigated using finite element procedure. Temperature field is assumed to be a uniform distribution over the plate surface and varied in thickness direction only. Material properties are assumed to be temperature dependent and graded in the thickness direction according to simple power law distribution. For the numerical illustrations, silicon nitride/stainless steel is considered as functionally graded material. The aerodynamic pressure is evaluated based on first-order high Mach number approximation to the linear potential flow theory. The boundaries of the instability region are obtained using the principle of Bolotin's method and are conveniently represented in the non-dimensional excitation frequency-load amplitude plane. The variation dynamic instability width is highlighted considering various parameters such as gradient index, temperature, aerodynamic and mechanical loads, thickness and aspect ratios, and boundary condition.

• Geomechanics and Engineering
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• 제29권6호
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• pp.667-681
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• 2022

This paper presents a thermoelastic analysis of variable thickness plates made of functionally graded materials (FGM) subjected to mechanical and thermal loads. The thermal load is applied to the plate as a temperature difference between the top and bottom surfaces. Temperature distribution in the plate is obtained using the steady-state heat equation. Except for Poisson's ratio, all mechanical properties of the plate are assumed to vary linearly along the thickness direction based on the volume fractions of ceramic and metal. The plate is resting on an elastic foundation modeled based on the Winkler foundation model. The governing equations are derived based on the third-order shear deformation theory (TSDT) and are solved numerically for various boundary conditions using the differential quadrature method (DQM). The effects of various parameters on the stress distribution and deflection of the plate are investigated such as the value of thermal and mechanical loads, volume fractions of ceramic and metal, and the stiffness coefficients of the foundation.

• Steel and Composite Structures
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• 제42권5호
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• pp.711-722
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• 2022

In this paper, hyperbolic shear deformation plate theory is developed for thermal buckling of functionally graded plates with porosity by dividing transverse displacement into bending and shear parts. The present theory is variationally consistent, and accounts for a quadratic variation of the transverse shearstrains across the thickness and satisfies the zero traction boundary conditions on the top and bottom surfaces of the plate without using shear correction factors. Three different patterns of porosity distributions (including even and uneven distribution patterns, and the logarithmic-uneven pattern) are considered. The logarithmic-uneven porosities for first time is mentioned. Equilibrium and stability equations are derived based on the present theory. The non-linear governing equations are solved for plates subjected to simply supported boundary conditions. The thermal loads are assumed to be uniform, linear and non-linear distribution through-the-thickness. A comprehensive parametric study is carried out to assess the effects of volume fraction index, porosity fraction index, aspect ratio and side-to-thickness ratio on the buckling temperature difference of imperfect FG plates.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.162-162
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• 2012

ZnPc and CuPc molecules stacked similar way in the film, but showed different growth modes in thermal evaporation. The distribution of CuPc crystals did not change by the film thickness, whereas the distribution of ZnPc became random as the increase of the film thickness. The disc type nanograins of CuPc were quite regularly distributed at the initial growth regime and the regular distribution of nanograins was kept during the film growth. On the other hand, ZnPc consisted in ellipsoid shaped nanograins and the distribution of nanograins was not regular in the initial growth regime. The irregular distribution of nanograins changed to the regular mode at the later growth regime by showing structure factor in GISAXS measurement. The different initial nanograin distribution in ZnPc and CuPc was related to the different nanostructure in the mixed layer with C60 to form the bulk heterojunction.

• Journal of Nutrition and Health
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• 제24권3호
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• pp.157-165
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• 1991

The purpose of this study was to investigate differences in body fat distribution between normal and obese subjects and the relationship between risk factors(fasting blood sugar, blood pressure. fasting serum lipids) and obesity. Measurements of height. weight, skinfold thickness. body circumference. percent body fat. blood pressure, fasting blood sugar and serum lipids were made and a dietary survey was performed on 120(Males 61. Females 59) adult subjects. 1) Among the female subjects, the obese group appeared to have significantly higher centrality of body fat than the normal group. Obese groups of both sexes appeared with higher blood pressure than normal groups. No differences in daily average nutrient intake, fasting blood sugar and fasting serum lipids concentrations were observed between obese and normal groups. 2) In males. the serum triglyceride concentration was observed to have a significantly positive correlation to body weight, body mass index and body circumference, additionally concentrations of total cholesterol and LDL-cholesterol were observed to have significantly positive correlations to the skinfold thickness. but the ratio of HDL-cholesterol/total cholesterol was observed to be significantly negatively correlated to the skinfold thickness. 3) In females. the obese group consumed about 47% of total energy intake at lunch. whereas the normal group consumed about 29% . The food habit score of males appeared to be negatively related to body weight, percent ideal body weight. But the food habit score of females appeared to be negatively related to percent body fat(r=-0.32, p<0.05) .

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집C
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• pp.293-298
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• 2001

In this paper, film thickness and temperature distribution are measured in EHL point contact at high roll/slip ratios. Infrared temperature mapping with two band pass filters, proposed by Ausherman (1976), is used to measure temperature distribution. And the optical interferometric method with two filters (red and green filters) is used to measure film thickness. Result of experiment showed that temperature rising at film and ball surface occurred very dramatically in Dimple zone. As slip velocity, roll/slip ratio and load increased, size of Dimple and temperature rising became more large. In addition, position and shape of Dimple were changed by roll/slip ratios, and increasing of Dimple size decreased traction coefficient. In short, it is appointed that the Dimple phenomenon be developed by the effect of viscosity wedge.

• Earthquakes and Structures
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• 제12권2호
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• pp.153-163
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• 2017

The underlying goal of the present paper is to investigate soil and structural uncertainties on impedance functions and structural response of soil-shallow foundation-structure (SSFS) system using Monte Carlo simulations. The impedance functions of a rigid massless circular foundation resting on the surface of a random soil layer underlain by a homogeneous half-space are obtained using 1-D wave propagation in cones with reflection and refraction occurring at the layer-basement interface and free surface. Firstly, two distribution functions (lognormal and gamma) were used to generate random numbers of soil parameters (layer's thickness and shear wave velocity) for both horizontal and rocking modes of vibration with coefficients of variation ranging between 5 and 20%, for each distribution and each parameter. Secondly, the influence of uncertainties of soil parameters (layer's thickness, and shear wave velocity), as well as structural parameters (height of the superstructure, and radius of the foundation) on the response of the coupled system using lognormal distribution was investigated. This study illustrated that uncertainties on soil and structure properties, especially shear wave velocity and thickness of the layer, height of the structure and the foundation radius significantly affect the impedance functions, and in same time the response of the coupled system.

• Steel and Composite Structures
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• 제33권6호
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• pp.865-875
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• 2019

The current article proposed to develop a geometrical model for the analysis and modelling of the uniaxial functionally graded structure using the higher-order displacement kinematics with and without the presence of porosity including the distribution. Additionally, the formulation is capable of modelling three different kinds of grading patterns i.e., Power-law, sigmoid and exponential distribution of the individual constituents through the thickness direction. Also, the model includes the distribution of porosity (even and uneven kind) through the panel thickness. The structural governing equation of the porous graded structure is obtained (Hamilton's principle) and solved mathematically by means of the isoparametric finite element technique. Initially, the linear frequency parameters are obtained for different geometrical configuration via own computer code. The comparison and the corresponding convergence studies are performed for the unidirectional FG structure for the validation purpose. Finally, the impact of different influencing parameters like aspect ratio (O), thickness ratio (S), curvature ratio (R/h), porosity index (λ), type of porosity (even or uneven), power-law exponent (n), boundary condition on the free vibration characteristics are obtained for the FG panel and discussed in details.