• Nuclear Engineering and Technology
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• 제49권8호
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• pp.1758-1771
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• 2017

In this study, to determine the most effective alloy for shielding against gamma-rays, the gamma-ray shielding parameters of six types of cerrobend alloys have been investigated. Gamma-ray interaction with the cerrobend alloys has been discussed mainly in terms of total mass attenuation coefficient (${\mu}_t$), half value layer (HVL), tenth value layer (TVL), effective atomic number ($Z_{eff}$), and effective electron density ($N_{eff}$). These parameters have been calculated by theoretical approach using the ParShield program in a photon energy range between 0.1 MeV and 100 GeV. The dependence of these parameters on the incident photon energy and chemical composition of the cerrobend alloys has been studied.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2016년도 자성 및 자성재료 국제학술대회
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• pp.11-11
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• 2016

• Smart Structures and Systems
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• 제21권4호
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• pp.397-405
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• 2018

In this paper, a novel simple shear deformation theory for buckling analysis of single layer graphene sheet is formulated using the nonlocal differential constitutive relations of Eringen. The present theory involves only three unknown and three governing equation as in the classical plate theory, but it is capable of accurately capturing shear deformation effects, instead of five as in the well-known first shear deformation theory (FSDT) and higher-order shear deformation theory (HSDT). A shear correction factor is, therefore, not required. Nonlocal elasticity theory is employed to investigate effects of small scale on buckling of the rectangular nano-plate. The equations of motion of the nonlocal theories are derived and solved via Navier's procedure for all edges simply supported boundary conditions. The results are verified with the known results in the literature. The influences played by Effects of nonlocal parameter, length, thickness of the graphene sheets and shear deformation effect on the critical buckling load are studied. Verification studies show that the proposed theory is not only accurate and simple in solving the buckling nanoplates, but also comparable with the other higher-order shear deformation theories which contain more number of unknowns.

• Smart Structures and Systems
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• 제19권2호
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• pp.115-126
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• 2017

In this paper, size dependent bending and free flexural vibration behaviors of functionally graded (FG) nanobeams are investigated using a nonlocal quasi-3D theory in which both shear deformation and thickness stretching effects are introduced. The nonlocal elastic behavior is described by the differential constitutive model of Eringen, which enables the present model to become effective in the analysis and design of nanostructures. The present theory incorporates the length scale parameter (nonlocal parameter) which can capture the small scale effect, and furthermore accounts for both shear deformation and thickness stretching effects by virtue of a hyperbolic variation of all displacements through the thickness without using shear correction factor. The material properties of FG nanobeams are assumed to vary through the thickness according to a power law. The neutral surface position for such FG nanobeams is determined and the present theory based on exact neutral surface position is employed here. The governing equations are derived using the principal of minimum total potential energy. The effects of nonlocal parameter, aspect ratio and various material compositions on the static and dynamic responses of the FG nanobeam are discussed in detail. A detailed numerical study is carried out to examine the effect of material gradient index, the nonlocal parameter, the beam aspect ratio on the global response of the FG nanobeam. These findings are important in mechanical design considerations of devices that use carbon nanotubes.

• Advances in nano research
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• 제7권6호
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• pp.443-457
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• 2019

In this investigation, dynamic and bending behaviors of isolated protein microtubules are analyzed. Microtubules (MTs) can be considered as bio-composite structures that are elements of the cytoskeleton in eukaryotic cells and posses considerable roles in cellular activities. They have higher mechanical characteristics such as superior flexibility and stiffness. In the modeling purpose of microtubules according to a hollow beam element, a novel single variable sinusoidal beam model is proposed with the conjunction of modified strain gradient theory. The advantage of this model is found in its new displacement field involving only one unknown as the Euler-Bernoulli beam theory, which is even less than the Timoshenko beam theory. The equations of motion are constructed by considering Hamilton's principle. The obtained results are validated by comparing them with those given based on higher shear deformation beam theory containing a higher number of variables. A parametric investigation is established to examine the impacts of shear deformation, length scale coefficient, aspect ratio and shear modulus ratio on dynamic and bending behaviors of microtubules. It is remarked that when length scale coefficients are almost identical of the outer diameter of MTs, microstructure-dependent behavior becomes more important.

• 한국체육학회지인문사회과학편
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• 제55권2호
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• pp.657-667
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• 2016

본 연구의 목적은 지체장애인의 생활체육 참여도가 자립생활도 및 사회적 체형불안에 미치는 영향관계를 규명하고자 하였다. 연구의 목적을 달성하기 위하여 2015년도 B시, K도, U시에 생활체육대회 참가자와 생활체육에 참여하고 있는 지체장애인 311명을 대상으로 설문조사를 실시하였으며, 자료처리는 SPSS 21.0 프로그램을 이용하여 빈도분석, 신뢰도 분석, 타당도 분석, 단순회귀분석을 사용하였다. 이상과 같은 연구방법 및 자료분석의 결과를 통해 도출된 결론은 다음과 같다. 첫째, 지체장애인의 생활체육 참여도가 자립생활도 하위변인인 사회적 자립, 심리적 자립, 신체적 자립, 전체적인 자립생활도에 정적 영향을 미치는 것으로 나타났다. 둘째, 지체장애인의 생활체육 참여도가 사회적 체형불안에 부적 영향을 미치는 것으로 나타났다. 셋째, 지체장애인의 자립생활도 하위변인인 신체적 자립, 전체적인 자립생활도가 사회적 체형불안에 부적 영향을 미치는 것으로 나타났으며, 반면에 사회적 자립, 심리적 자립은 사회적 체형불안에 유의한 영향을 미치지 않는 것으로 나타났다.

• 농촌의학ㆍ지역보건
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• 제21권1호
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• pp.21-45
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• 1996

The purpose of this study is to compare the health status of Korean and Chosun-Jok elementary children. To accurately achieve the purpose, a survey was conducted in Yanbian area in China and Kojae in Korea during the period of June 15 to July in 1995. This survey was performed by using two survey methods. The first was the parents' survey method. It asked structured questions about their children. The second method focused on the actual health of the children. It used the collection of children's physical records in school. Guided by the school teachers, each child distributed the questionnaires to their parents. We used stratified-cluster sampling method to determine subjects. 1,083 questionnaires of 1,749 were used to analyze the data (666 questionnaires were incomplete and were not used in the analysis). Each questionnaire matched the data of their physical record. : Body Weight, Body Height, Chest-Circumstance, Eyesight, Dental Health. Using the data, we compared the BMI(Body Mass Index) the Koreans and Chosun-Jok in China. The results of this study were as follows : Comparing the general average physique of contained body height, body weight and chest circumstance of Korean and Chosun-Jok, the general physique of Chosun-Jok is inferior to that of Korean regardless of age and sex. Meanwhile, the average physical constitution of Korean compared the Chosun-Jok (i.e. eyesight and dental hygiene), revealed that the physical constitution of Chosun-Jok is superior to that of Korean without concern of age and sex. Average BMI of Chosun-Jok is lower than that of Koreans. But, it seemed that most of the students in both groups maintain an adequate health level. In the case of children from 10 to 12 years old, females are superior to males through all data contained of the body weight, the chest circumstance, and the body height. It seems that females and males have a different maximum growth age. Most of the parents preferred a good physique as a good health condition for their children. The physique of each child was affected with some variables, including the number of family members, and the educational level of the parents. According to the above results, the students' physique in Korea is superior to that of Chosun-Jok in China. But, Koreans are inferior to Ethnic Koreans in China in the students' physical constitution. In conclusion, we consider Chosun-Jok in China to maintain an adequate health level in their physique and physical constitution.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2007년도 The 1st International Symposium on Advanced Magnetic Materials
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• pp.11.2-11.2
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• 2007

• Journal of Nutrition and Health
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• 제2권1호
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• pp.9-17
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• 1969

For the purpose of finding out the differences between urban and rural primary school children aged from 7 to 12 in their physipue, 1146 (578 boys and 567 girls) urban children and 1378 (693 boys and 635 girls) rural children were obserbed by the author during 2 months period from September, 1968 to October, 1968. Following were the findings obtained from this study. 1. Physique In general, urban children showed superiority than rural children if their physique, There could be seen significant differences in their height, weight and chest-girth specially in the age group of 11 and 12. 2. Physique indices In the physique indices based on the height, the value of urban children showed superiority than rural children in relative weight but in relative chest-girth it was the other way around and there were no significant differences between these two groups in relative sitting height. The Kaup index showed higher value in urban children and the Vervaeck index in the rural children and there were no significant differences between these two groups in the Rohrer's index. 3. Comparing these figures with the Korean Standard Value, urban children showed superiority and rural children showed inferiority. Our children were inferior than the Japanese children in their physiques.

• Advances in nano research
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• 제4권4호
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• pp.251-264
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• 2016

In this paper, a simple and refined nonlocal hyperbolic higher-order beam theory is proposed for bending and vibration response of nanoscale beams. The present formulation incorporates the nonlocal scale parameter which can capture the small scale effect, and it considers both shear deformation and thickness stretching effects by a hyperbolic variation of all displacements across the thickness without employing shear correction factor. The highlight of this formulation is that, in addition to modeling the displacement field with only two unknowns, the thickness stretching effect (${\varepsilon}_z{\neq}0$) is also included in the present model. By utilizing the Hamilton's principle and the nonlocal differential constitutive relations of Eringen, the equations of motion of the nanoscale beam are reformulated. Verification studies demonstrate that the developed theory is not only more accurate than the refined nonlocal beam theory, but also comparable with the higher-order shear deformation theories which contain more number of unknowns. The theoretical formulation proposed herein may serve as a reference for nonlocal theories as applied to the static and dynamic responses of complex-nanobeam-system such as complex carbon nanotube system.