• Steel and Composite Structures
• /
• 제51권2호
• /
• pp.139-151
• /
• 2024

In this research, a semi-analytical solution is presented for computing mechanical displacements and thermal stresses in rotating thick cylindrical pressure vessels made of functionally graded material (FGM). The modulus of elasticity, linear thermal expansion coefficient, and density of the cylinder are assumed to change along the axial direction as a power-law function. It is also assumed that Poisson's ratio and thermal conductivity are constant. This cylinder was subjected to non-uniform internal pressure and thermal loading. Thermal loading varies in two directions. The governing equations are derived by the first-order shear deformation theory (FSDT). Using the multilayer method, a functionally graded (FG) cylinder with variable thickness is divided into n homogenous disks, and n sets of differential equations are obtained. Applying the boundary conditions and continuity conditions between the layers, the solution of this set of equations is obtained. To the best of the researchers' knowledge, in the literature, there is no study carried out bi-directional thermoelastic analysis of clamped-clamped rotating FGM thick-walled cylindrical pressure vessels under variable pressure in the longitudinal direction.

• Steel and Composite Structures
• /
• 제45권2호
• /
• pp.175-191
• /
• 2022

A review of previous studies shows that although there is a considerable difference between buckling loads of structures under follower and non-follower lateral loads, only the buckling load of FGM elliptical cylindrical shell under non-follower lateral load was investigated in the literature. This study is the first to obtain the buckling load of elliptical FGM cylindrical shells under follower lateral load and also make a comparison between buckling loads of elliptical FGM cylindrical shells under follower and non-follower lateral loads. Moreover, this research is the first one to derive the load potential function of elliptical cylindrical shell. In this regard, the FGM cylindrical elliptical shell was modeled using the semi-analytical finite strip method and based on the First Shear Deformation Theory (FSDT). The shell is discretized by strip elements aligned in the longitudinal direction. The Lagrangian and harmonic shape functions were considered in the circumference and longitudinal directions, respectively. The buckling pressure of the shell under follower and non-follower lateral loads was obtained from eigenvalue problem. The results obtained from the model were compared with those presented in the literature to evaluate the validity of the model. A comparison index was defined to compare the buckling loads of the shell under follower and non-follower lateral load. A parametric study was carried out to investigate the effects of material properties and shell geometry characteristics on the comparison index. For the elliptical cylindrical shells with length-to-radius ratio greater than 16 and major-to-minor axis ratio greater than 0.6, the comparison index reaches to more than 20 percent which is significant. Moreover, the maximum difference is about 30 percent in some cases. The results obtained from the parametric study indicate that the buckling load of long elliptical cylindrical shell under non-follower load is not reliable.

• 재활복지공학회논문지
• /
• 제6권1호
• /
• pp.83-87
• /
• 2012

본 연구는 취업장애인의 보조공학기기 사용형태의 변화에 따른 잠재계층을 분류하고 그에 대한 영향요인을 탐색하는데 그 목적이 있다. 분석에는 장애인고용패널조사 1-3차년도 자료가 사용되었다. 분석방법은 준모수적 집단 중심 접근방법(semi-parametric group based approach)을 적용하였다. 분석모형은 종속변수가 보조공학기기 사용여부를 나타내는 이분형 척도(dichotomous scale)라는 특성을 고려해 로짓모형을 적용하였다. 보조공학기기 사용 변화 형태에 따라 3개의 잠재계층이 도출되었으며 이들은 보조기기 지속사용 집단, 보조기기 중간사용 집단, 보조기기 사용 급감소 집단으로 구분되었다. 다항로짓분석으로 영향요인을 검증한 결과, 학력, 장애유형, ICF, 주관적 사회경제적 지위, 일상생활만족도가 잠재계층을 결정하는 데 유의미한 변수로 나타났다. 마지막으로 분석결과에 따른 시사점을 제시하였다.

• 사회복지연구
• /
• 제39호
• /
• pp.5-28
• /
• 2008

본 연구의 목적은 한국청소년패널조사(KYPS) 자료를 활용하여 청소년기 흡연의 상이한 발달궤적 변화에 영향 미치는 예측요인들을 분석하는 것이다. 준모수적 집단중심모형(Semi-parametric group-based modeling)을 통해 청소년기 흡연에는 점증형 흡연집단(escalator), 실험형 흡연집단(experimenter), 후발형 흡연집단(late onsetter), 비흡연집단(non initiator) 등 4가지 발달궤적이 존재하는 것으로 밝혀졌다. 비행, 음주 등 다른 영역의 발달궤적과 달리 흡연에는 중단형 집단이 없는 것으로 나타났다. 또한 다항 로지스틱 회귀분석을 통해 사회발달모형(social development model) 내의 위험요인과 보호요인을 중심으로 흡연집단들을 구분하는 요인을 살펴본 결과, 모든 발달영역의 위험요인과 보호요인 대부분이 13세 시기에 흡연하지 않았던 청소년 중 계속해서 비흡연하는 집단과 이후 흡연을 늦게 시작한 집단을 구분하는 것으로 나타났다. 반면 13세에 이미 흡연하고 있었던 청소년 중 계속해서 흡연을 증가시키는 집단과 점차 흡연을 감소시키는 집단을 구분하는 요인은 자아존중감, 학업성취 등 소수로 나타났다. 흡연집단을 구분하는 위험요인과 보호요인들은 발달적으로 적절하고 효과적인 예방프로그램의 구성요소를 발견할 수 있도록 도와준다. 본 연구의 결과를 통해 13세에 흡연하고 있지 않은 집단은 물론 이미 흡연을 시작한 집단까지도 원조할 수 있는 중학교 시기 금연프로그램을 개발할 수 있는 단초를 마련하였다.

• Journal of Preventive Medicine and Public Health
• /
• 제20권1호
• /
• pp.97-113
• /
• 1987

This study was carried out to know physical growth and development, physical and nutritional indices and body fat weight and so forth by semi-longitudinal research method to measure body height, body weight, chest girth and sitting height of 260 of general high school and 306 of vocational high school 3rd grade students who are living in Seoul and born from 1966 March 1st to 1967 Feb.28th. The results are as follows: 1) Physical growth and development Growth in terms of body height showed one step straight linear development, andthat of body weight showed two step straight linear development in each section in high school. The age of cross over between two sexes of general high school students was between 10.6 to 12. 3 years in body height, between 10.8 to 13 years in body weight, between 11.2 to 14.6 years in chest girth and between 10 to 13 years in sitting height. The age of cross over between two sexes of vocational high school students was between 10.5 to 12.5 years in body height, between 10.5 to 12.5 years in body weight, between 10.5 to 12.5 years in chest girth and between 10.5 to 12.5 years in sitting height. In this periods, female group was superior to male group and after that male group was superior to female group again. The growth of vocational school students was superior to that of general school students in both sexes in terms of body height and body weight significantly. 2) Physical growth and nutritional indices In all cases of relative body weight, relative chest girth and relative sitting height, it was found to be increasing thereafter with advancing ages. In cases of $R{\"{o}}hrer$ index and Kaup index, it was found to be reaching to normal state thereafter with advancing ages. In each case of Vervaeck and Pelidisi index, it was found to be increasing and reaching to normal state thereafter with advancing ages. 3) Total body fat by vital measuring method Average values of body surface area, body volume and body density are measured indirectly by using the body height and body weight as Table 12, 13 and 14. The rate of body fat weight of general high school students was from minimum $11.96{\pm}3.53%(3.33{\pm}1.10kg$) to maximum $18.25{\pm}6.46%(9.08{\pm}2.01kg$) in male and from $25.88{\pm}3.62%(7.96{\pm}0.78kg$) to $43.00{\pm}7.22%(12.91{\pm}1.21kg$) in female. The rate of body fat weight of vocational high school students was from minimum $11.20{\pm}2.88%(3.32{\pm}1.13kg$) to maximum $17.16{\pm}5.88(10.83{\pm}3.16kg$) in male and from minimum $25.11{\pm}2.26%(7.91{\pm}0.89kg$) to maximum $42.16{\pm}7.96%(13.22{\pm}1.75kg$) in female.

• 패션비즈니스
• /
• 제11권3호
• /
• pp.35-45
• /
• 2007

This study examined how to create 2D basic pattern of individuals by means of 3-D body figure, which is to develop a flat of individual basic pattern directly from the 3-D body scan data of each subject using that of the upper body of a male adult. In terms of methodology, this study adopted 3D body scan data on system and body to make examinations in the following steps: 1. Standard point and line were set on human body, along with 3-D definition points(feature points). 2. PB was created by modifying horizontal and longitudinal section of scan data. 3. Ways to set reserve were established in the findings of PB planar development. Respective developed flat patterns were compared with pattern findings in previous studies by means of sensory evaluation. As a result, it was found that both system and body model are basic pattern and belong to appropriate pattern as semi-tight-fit basic pattern with overall appropriate tolerances. Thus, this study came to a conclusion that it is feasible and valid to develop theories for flat development as considered herein.

• 한국조사연구학회지:조사연구
• /
• 제10권3호
• /
• pp.37-58
• /
• 2009

본 연구의 목적은 청소년의 초기 단계에 해당하는 초등학교 고학년 학생들의 공격성 변화에 따라 구분되는 집단(잠재계층)의 수와 그 형태를 알아보고, 각 잠재계층과 성별, 자기통제력, 부모애착, 교사애착, 비행친구 수와의 관련성을 밝히는 것이다. 이를 위하여 한국청소년패널조사의 초등학교 4학년 패널 1, 2, 3차 년도 종단자료에 Nagin(1999)의 준모수적 집단 중심 방법(semi-parametric group-based approach)을 적용하였다. 분석 결과 변화형태에 따라 4개의 잠재계층이 도출되었고, 그 형태에 따라 저수준 집단, 증가 집단, 중간수준 집단, 고수준 집단으로 명명하였다. 다항 로짓분석을 통해 영향요인을 검증한 결과 성별, 자기통제력, 교사애착, 비행친구 수가 잠재계층을 결정하는 데 유의미한 변수로 나타났다. 본 연구는 공격성의 변화에 영향을 줄 수 있는 생태학적 변수들을 바탕으로 잠재계층을 예측하여 공격성으로 인해 범죄를 저지를 가능성이 있는 청소년들을 위한 적절한 대비책을 찾는 데 도움을 줄 것이다. 또한 변화의 형태에 따라 잠재계층을 도출하고 그 잠재계층을 결정짓는 데 미치는 독립변수의 효과들을 검증하는 종단연구 방법은 아직 널리 이용되고 있지 않다는 점에서 연구 방법론적 측면에서도 의의가 있다.

• 한국자동차공학회논문집
• /
• 제13권5호
• /
• pp.134-141
• /
• 2005

Semi-Spherical Continuously Variable Transmission(SS-CVT) is the CVT which transmits power by rolling friction between dry metals, and its outstanding advantage is the ability of realizations of neutral, forward and reverse states without relying on any other devices. A spherical shaped variator transmits power and also changes gear ratio where keeping contact with a output disk. The frictional direction to transmit power and the other direction to change gear ratio are perpendicular to each other, so we can describe that two dimensional rolling friction is occurred in the contact point between the variator and the disk. Since magnitudes or relations of the two forces are completely unknown, they were analyzed by the experiments in this study. We determined the variables related with the friction phenomena by the dimensional analysis, and manufactured the SS-CVT test bench which could measure the related variables. Finally, the empirical formula for evaluating the two friction forces was proposed based on the experimental results.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2003년도 The Fifth Asian Computational Fluid Dynamics Conference
• /
• pp.294-298
• /
• 2003

The complex, unsteady, self-sustained pressure oscillations induced by supersonic flow past a rectangular cavity is investigated using numerical simulations. The present numerical study is performed using a parallel, multiblock solver for the two-dimensional, compressible Navier­Stokes equations. Open cavities with length-to-depth (L / D) ratio in the range 0.5 - 3.3 are considered. This paper sheds light on the cavity physics, cavity oscillatory mechanism, and the organisation of vortical structures inside the cavity. The vortex shedding phenomenon, the shear layer impingement event at the aft wall and the movement of the acoustic/compression wave within the cavity are well predicted. The vortical structures· and the source of the acoustic disturbances are found to be located near the aft wall of the cavity. With the increase in the cavity length, strong recompression of the flow near the aft wall leading to a sudden jump in the cavity form drag is observed. The estimated cavity tones are in good agreement with the available semi­empirical relation. Multiple peaks are noticed in deep and long cavities. For the present free­stream Mach number 1.71, it is observed that around L/D=2.0, the cavity oscillatory mechanism changes from the transverse to longitudinal oscillatory mode. The effects of this transition on various fluid dynamics and acoustic properties are also discussed.

• Nutrition Research and Practice
• /
• 제1권3호
• /
• pp.231-236
• /
• 2007

Underreporting patterns by the level of obesity have not been fully assessed yet. The purpose of this study was to examine the differential underreporting patterns on cardiovascular risk factor, macronutrient, and food group intakes by the level of Body Mass Index (BMI). We analyzed cross-sectional baseline nutritional survey data from the population-based longitudinal study, the Healthy Women Study (HWS) cohort. Study subjects included 538 healthy premenopausal women participating in the HWS. Nutrient and food group intakes were assessed by the one-day 24-hour dietary recall and a semi-quantitative food frequency questionnaire, respectively. The ratio of reported energy intake (EI) to estimated basal metabolic rate (BMR) was used as a measure of relative energy reporting status and categorized into tertiles. Overweight group ($BMI{\geq}25kg/m^2$) had a higher ratio of EI to BMR (EI/BMR) than normal weight group ($BMI<25kg/m^2$). Normal weight and overweight groups showed similar patterns in cardiovascular risk factors, nutrient intake, and food group intake by the EI/BMR. Fat and saturated fat intakes as a nutrient density were positively associated with the EI/BMR. Proportion of women who reported higher consumption (${\geq}4\;times/wk$) of sugar/candy, cream and red meat groups was greater in higher tertiles of the EI/BMR in both BMI groups. Our findings suggest similar patterns of underreporting of cardiovascular risk factors, and macronutrient and food group intakes in both normal and overweight women.