• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1995년도 가을 학술발표회 논문집
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• pp.187-192
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• 1995

Four types of experiments were performed to check the similitude of member behavior between prototype and 1/10 scale models:(1) Test of slender columns with P- effect, (2)Test of short columns with and without confinement steel, (3)Test of simple beams without stirrups, and (4)T-beam test. Based on the results of experiments, the conclusions were made as follows : (1) The P- effect of slender columns can be almost exactly represented by 1/10 acale model. (2)The effect of confinement on short columns by the hoop steel can also roughly simulated by 1/10 scale model. (3)The failure modes of simple beams models were the yielding of tension steel followed by large diagonal tension cracking+compressive concrete failure. (4)The behaviors of prototype and 1/10 scale model in T-beams appear very similar.

• Journal of Mechanical Science and Technology
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• 제18권8호
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• pp.1479-1489
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• 2004

The effect of fluctuation of Equivalence Ratio (ER) in a turbulent reactive field has been studied in order to check the global combustion characteristics induced by the local fluctuation. When the flow is premixed on a large scale, closer examination on a small scale reveals that local fluctuations of ER exist in an imperfectly premixed mixture, and that these fluctuations must be considered to correctly estimate the mean reaction rate. The fluctuation effect is analyzed with DNS by considering the joint PDF of reactive scalar and ER, followed by modeling study where an extension of stochastic mixing models accounting for the ER fluctuation is reviewed and tested. It was found that models prediction capability as well as its potential is in favor to this case accounting the local ER fluctuation. However, the effect of local fluctuation did not show any notable changes on the mean global characteristics of combustion when statistical independence between the reactive scalar and ER field is imposed, though it greatly influenced the joint PDF distribution. The importance of taking into account the statistical dependency between ER and combustible at the initial phase is demonstrated by testing the modeled reaction rate.

• 대한화학회지
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• 제51권5호
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• pp.433-446
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• 2007

이 연구의 목적은 Small-Scale Chemistry 실험수업이 고등학교 2학년 자연계열 학생의 학업적 자기 효능감 및 과학 관련 정의적 특성에 미치는 영향을 알아보는 것이다. 7차 교육과정 고등학교 화학 I 교과서를 분석하여 SSC 화학 실험 프로그램을 개발하였고, 실험집단은 SSC 실험수업을 실시하고 비교집단은 전통적인 실험수업을 실시하였다. 학생들의 사전 과학성취도 점수를 이용하여 상하 수준으로 나눈 후 이를 구획변인으 로 하는 이원 공변량(2-way ANCOVA) 분석을 통해 두 집단 간의 차이를 알아보았다. 연구 결과 SSC 실험 프 로그램은 전통적 Large-Scale 실험에 비해 학업적 자기효능감의 향상에 유의미한 효과가 있었다. 또한 과학에 대한 정의적 특성 중에서 과학에 대한 직업적 흥미와 창의성 등에서 SSC 실험 집단의 점수가 유의미하게 높 은 것으로 나타났다. SSC 실험수업에 대한 학생들의 인식 조사 결과 대부분의 학생들은 SSC 실험이 편리하 고, 효과적이며 흥미로운 방법이라고 생각하고 있었다.

• Structural Engineering and Mechanics
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• 제73권5호
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• pp.565-584
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• 2020

The nonlinear thermo-electro-elastic buckling behavior of viscoelastic nanoplates under magnetic field is investigated based on nonlocal elasticity theory. Employing nonlinear strain-displacement relations, the geometrical nonlinearity is modeled while governing equations are derived through Hamilton's principle and they are solved applying semi-analytical generalized differential quadrature (GDQ) method. Eringen's nonlocal elasticity theory considers the effect of small size, which enables the present model to become effective in the analysis and design of nano-sensors and nano actuators. Based on Kelvin-Voigt model, the influence of the viscoelastic coefficient is also discussed. It is demonstrated that the GDQ method has high precision and computational efficiency in the buckling analysis of viscoelastic nanoplates. The good agreement between the results of this article and those available in literature validated the presented approach. The detailed mathematical derivations are presented and numerical investigations are performed while the emphasis is placed on investigating the effect of the several parameters such as electric voltage, small scale effects, elastomeric medium, magnetic field, temperature effects, the viscidity and aspect ratio of the nanoplate on its nonlinear buckling characteristics. It is explicitly shown that the thermo-electro-elastic nonlinear buckling behavior of viscoelastic nanoplates is significantly influenced by these effects. Numerical results are presented to serve as benchmarks for future analyses of viscoelastic nanoplates as fundamental elements in nanoelectromechanical systems.

• 한국유기농업학회지
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• 제25권3호
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• pp.643-651
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• 2017

본 연구는 HACCP 제도를 적용하고 있는 소규모, 중규모, 대규모 양돈농장의 HACCP 제도 도입 목적, 효과, 그리고 문제점 등을 비교분석하기 위한 목적으로 실시하였다. 소규모와 중규모 양돈농장은 HACCP 도입 목적의 1순위를 정부의 예산을 지원받기 위함이라고 하였으나 대규모 농장은 농장의 경쟁력 향상이라고 답하였다. HACCP 적용 효과는 소규모 농장의 경우 체계적인 농장관리를 1순위로 응답하였으나 중규모와 대규모 농장은 농장의 위생관리 수준 향상이라고 답하였다. 아울러 HACCP 적용에 따라 발생되는 가장 큰 문제점으로는 직원의 의식향상의 어려움(소규모 농장)과 HACCP 도입에 따른 기록관리(중규모, 대규모 농장)인 것으로 조사되었다. 이러한 문제점을 개선하기 위해서는 양돈농장 HACCP 평가항목 수의 조정과 종업원을 대상으로 HACCP 교육을 실시할 필요성이 있을 것으로 판단된다.

• Structural Engineering and Mechanics
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• 제70권3호
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• pp.269-277
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• 2019

Using the non-local elasticity theory, Timoshenko beam model is developed to study the non- local buckling of Triple-walled carbon nanotubes (TWCNTs) embedded in an elastic medium under axial compression. The chirality and small scale effects are considered. The effects of the surrounding elastic medium based on a Winkler model and van der Waals' (vdW) forces between the inner and middle, also between the middle and outer nanotubes are taken into account. Considering the small-scale effects, the governing equilibrium equations are derived and the critical buckling loads under axial compression are obtained. The results show that the critical buckling load can be overestimated by the local beam model if the small-scale effect is overlooked for long nanotubes. In addition, significant dependence of the critical buckling loads on the chirality of zigzag carbon nanotube is confirmed. Furthermore, in order to estimate the impact of elastic medium on the non-local critical buckling load of TWCNTs under axial compression, the use of these findings are important in mechanical design considerations, improve and reinforcement of devices that use carbon nanotubes.

• Advanced Composite Materials
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• 제17권4호
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• pp.343-358
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• 2008

This present study provides the structural design and analysis of main wing, horizontal tail and control surface of a small scale WIG (Wing-in-Ground Effect) craft which has been developed as a future high speed maritime transportation system of Korea. Weight saving as well as structural stability could be achieved by using the skin.spar.foam sandwich and carbon/epoxy composite material. Through sequential design modifications and numerical structural analysis using commercial FEM code PATRAN/NASTRAN, the final design structural features to meet the final design goal such as the system target weight, structural safety and stability were obtained. In addition, joint structures such as insert bolts for joining the wing with the fuselage and lugs for joining the control surface to the wing were designed by considering easy assembling as well as more than 20 years service life.

• Advances in materials Research
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• 제7권1호
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• pp.1-16
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• 2018

Thermal bifurcation buckling behavior of fully clamped Euler-Bernoulli nanobeam built of a through thickness functionally graded material is explored for the first time in the present paper. The variation of material properties of the FG nanobeam are graded along the thickness by a power-law form. Temperature dependency of the material constituents is also taken into consideration. Eringen's nonlocal elasticity model is employed to define the small-scale effects and long-range connections between the particles. The stability equations of the thermally induced FG nanobeam are derived via the principal of the minimum total potential energy and solved analytically for clamped boundary conditions, which lead for more accurate results. Moreover, the obtained buckling loads of FG nanobeam are validated with those existing works. Parametric studies are performed to examine the influences of various parameters such as power-law exponent, small scale effects and beam thickness on the critical thermal buckling load of the temperature-dependent FG nanobeams.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.1110-1115
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• 2002

The purpose of this study is to analyze the effects of the parameters of the suspension system in railway rolling-stock for KT-23 type passenger vehicle. According to the results of simulation and the small scale vehicle test. Optimal condition was obtained for the stiffness ratio of the primary spring and secondary spring of the suspension system. When the stiffness ratio was Increased, the vortical vibration was increased on the car body for empty and weight car. The result of this study are stable to use of the optimum parameter of the ride duality of KT-23 type vehicle. Also, it is usefull to development of full scale vehicle dynamomer

• 천문학회보
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• 제43권2호
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• pp.41.3-42
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• 2018

Redshift space distortion (RSD) is known as a powerful cosmological probe. The large-scale RSD has been detected by various redshift surveys and continues to be a major target of ongoing surveys. On the other hand, the small-scale RSD, called finger-of-god (FoG) effect, also has cosmological information, because different cosmological parameters cause different halo mass functions and viriarized velocities. We define the "length" of FoG and examine its dependence on cosmological parameters using the Multiverse simulation. We also use the SDSS DR7 data to see how strong constraints current data sets could provide. It is found that the volume-limited subsample D5, consisting of ~100,000 galaxies at z~0.08, yields $\Delta \Omega_m ~ 0.02$.