• 한국자동차공학회논문집
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• 제21권2호
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• pp.154-158
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• 2013

Expansion joint has been utilized in many areas including automotive bellows for exhaust system. Usage of expansion joint has been increased due to its inherent flexibility and excellent anti-vibration property. Simple shape of expansion joint is modeled to understand the behavior of joint system. 27 design cases using 3 design factors with 3 levels are constructed by design of experiment. Each case is simulated to find the most influential design factors. Response for this study, maximum stress in the expansion joint, has been used to determine main design factors of joint. Among the 3 design factors, factor B has affected greatly a response in the formation of optimum shape of joint. Also, interaction factor, $A{\times}B$, has also showed its influence to the response of joint. This study showed that design of experiment combined with finite element analysis could be used in the design decision process effectively in the design of expansion joint.

• 한국시뮬레이션학회논문지
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• 제8권4호
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• pp.25-31
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• 1999

To analyze the impulsive response of a motorcycle helmet, a simulation is performed using the finite element method. Based upon the simulation result, an equivalent one degree of freedom vibrational system is adapted, and transient impulsive responses are analysed to investigate the influence of engineering parameters such as damping, natural frequency, and impact velocity on the impulsive response of the helmet. Maximum gravitational acceleration reduces as the damping factor value increases. When the damping factor value is around 0.6 or larger, the maximum acceleration does not change. With respect to the natural frequency and the impact velocity, it increases linearly. The relationship between head injury criterion(HIC) and maximum gravitational acceleration is also presented. The scheme of this study is expected to be utilized to economize the design process of high quality motorcycle helmets.

• 한국농공학회지
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• 제38권5호
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• pp.74-84
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• 1996

Dynamic loading of structures often causes excursions of stresses well into the inelastic range and the influence of geometric changes on the dynamic response is also significant in many cases. Therefore, both material and geometric nonlinearity effects should be considered in case that a dynamic load acts on the structure. For developing a program to analyze the dynamic response of an axisymmetric shell in this study, the material nonlinearity effect on the dynamic response was formulated by the elasto-viscoplastic model highly corresponding to the real behavior of the material. Also, the geometrically nonlinear behavior is taken into account using a total Lagrangian coordinate system, and the equilibrium equation of motion was numerically solved by a central difference scheme. A complete finite element program has been developed and the results obtained by it are compared with those in the references 1 and 2. The results are in good agreement with each other. As a case study of its application, the developed program was applied to a dynamic response analysis of a nuclear reinforced concrete containment structure. The results obtained from the' numerical examples are summarized as follows : 1. The dynamic magnification factor of the displacement and the stress were unrelated with the concrete strength. 2. As shown by the results that the displacement dynamic magnification factor were form 1.7 to 2.3 and the stress dynamic magnification factor from 1.8 to 2.5, the dynamic magnification factor of stress were larger than that of displacement. 3. The dynamic magnification factor of stress on the exterior surface was larger than that on the interior surface of the structure.

• Structural Engineering and Mechanics
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• 제44권5호
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• pp.681-704
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• 2012

The dynamic response of Euler-Bernoulli beams to resonant harmonic moving loads is analysed. The non-dimensional form of the motion equation of a beam crossed by a moving harmonic load is solved through a perturbation technique based on a two-scale temporal expansion, which permits a straightforward interpretation of the analytical solution. The dynamic response is expressed through a harmonic function slowly modulated in time, and the maximum dynamic response is identified with the maximum of the slow-varying amplitude. In case of ideal Euler-Bernoulli beams with elastic rotational springs at the support points, starting from analytical expressions for eigenfunctions, closed form solutions for the time-history of the dynamic response and for its maximum value are provided. Two dynamic factors are discussed: the Dynamic Amplification Factor, function of the non-dimensional speed parameter and of the structural damping ratio, and the Transition Deamplification Factor, function of the sole ratio between the two non-dimensional parameters. The influence of the involved parameters on the dynamic amplification is discussed within a general framework. The proposed procedure appears effective also in assessing the maximum response of real bridges characterized by numerically-estimated mode shapes, without requiring burdensome step-by-step dynamic analyses.

• Coupled systems mechanics
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• 제3권2호
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• pp.147-170
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• 2014

In the recent times, dimensions of heavy load carrying vehicle have changed significantly incorporating structural flexibility in vehicle body. The present paper outlines a procedure for the estimation of bridge response statistics considering structural bending modes of the vehicle. Bridge deck roughness has been considered to be non homogeneous random process in space. Influence of pre cambering of bridge surface and settlement of approach slab on the dynamic behavior of the bridge has been studied. A parametric study considering vehicle axle spacing, mass, speed, vehicle flexibility, deck unevenness and eccentricity of vehicle path have been conducted. Dynamic amplification factor (DAF) of the bridge response has been obtained for several of combination of bridge-vehicle parameters. The present study reveals that flexible modes of vehicle can reduce dynamic response of the bridge to the extent of 30-37% of that caused by rigid vehicle model. However, sudden change in the bridge surface profile leads to significant amount of increment in the bridge dynamic response even if flexible bending modes remain active. The eccentricity of vehicle path and flexural/torsional rigidity ratios plays a significant role in dynamic amplification of bridge response.

• 한국지진공학회논문집
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• 제8권6호통권40호
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• pp.13-22
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• 2004

연성 계수는 반응수정계수(R)의 핵심구성요소로서 내진설계에서 중요한 역할을 하는 계수이다. 본 연구에서의 연성계수()는 단자유도 구조물의 연성계수()에 다자유도 보정계수()를 곱하여 평가하였다. 단자유도 시스템의 연성계수는 지진하중을 받는 단자유도 구조물의 변위 연성요구도와 주기에 따른 비선형 동적해석으로부터 산정하였다. 다자유도 시스템의 영향을 고려하기 위한 다자유도 보정계수()는 기존의 연구에 근거하여 제시하였다. 철골 연성 모멘트 골조의 연성계수를 평가하기 위하여, 구조물의 층수, 골조시스템(외곽골조, 분배골조), 붕괴 메카니즘(강-기둥 약-보, 약-기둥 강-보), 토질조건 및 지진구역을 변수로 하여 총 108개의 예제 구조물을 설계하였다. 구조물의 층수, 붕괴 메카니즘 및 토질조건은 연성계수에 큰 영향을 미치는 반면, 골조 시스템 및 지진구역은 연성계수에 영향을 미치지 않는 것으로 나타났다.

• 한국항해항만학회지
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• 제36권1호
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• pp.59-67
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• 2012

본 연구에서는 컨테이너 터미널의 물류역량이 서비스 품질과 고객반응에 어떠한 영향을 미치는지 파악하여 향후 컨테이너 터미널의 마케팅 전략 수립에 시사점을 제공하고자 한다. 표본설계는 한국선주협회, 한국선박관리업협회에 등록된 선사 중 부산항 컨테이너 터미널을 이용하고 있는 선사별로 2011년 12월 5일부터 23일까지 5~8부의 설문지를 직접방문을 통하여 배포하고 회수된 설문지 243부를 분석하였다. 실증분석 결과 서비스 품질과 고객반응에 정(+)의 영향을 미치는 물류역량 요인 중 관리역량이 가장 큰 영향을 미치는 것으로 나타났고, 고객반응에 정(+)의 영향을 미치는 서비스품질 요인 중 공감성이 가장 큰 영향을 미치는 것으로 나타났다. 그러므로 컨테이너 터미널에서는 적/양하를 계획할 때 고객의 요구사항을 정확히 파악하여 이를 적극적으로 반영하고 고객에게 최상의 서비스를 제공하여야 할 것이다.

• 한국임상보건과학회지
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• 제8권2호
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• pp.1417-1425
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• 2020

Purpose: The purpose of this study was to check the stress, stress and coping ability of nursing college students and to identify factors that influence college life adjustment. Method: This study was a descriptive research study to confirm the correlation between stress, stress response, coping ability, and college life adaptation of nursing college students, and to analyze the factors that influence college life adjustment. The data collection period was from August 17 to 23, 2020, for one week, the researcher directly explains the purpose and purpose of the study to 221 nursing college students nationwide, and online surveys to those who have agreed to participate in the study. The collected data were analyzed using SPSS Win 20.0 program. Results: Adaptation to college was negatively correlated with stress (r=-.285, p<.001), stress response (r=-.258, p<.001), and coping ability (r=.512, p<.001) had a positive correlation. The most significant factor influencing the study subjects' adaptation to college life was coping ability (β=.473, p<.001), followed by stress (β=-.185, p=.002) in the order of The explanatory power of the factors affecting the subject's adaptation to college life was 28.9%. Conclusion: As a result of this study, it means that nursing students' adaptation to college life has less stress and stress response, and higher coping ability increases college life adaptation. The factor that influenced the adjustment to college life was the most significant factor, followed by stress. In order for nursing students to adjust to college life smoothly, it is thought that coping measures to reduce stress and stress responses and overcome them are necessary.

• Tribology and Lubricants
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• 제35권3호
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• pp.158-168
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• 2019

This paper presents the investigation of two types of rotordynamic modeling issues for 2.2 kW-class, rated speed of 1,800 rpm, squirrel-cage type induction motors. These issues include the lamination structure of rotor cores, and the radial clearance of ball bearings that support the shaft of the motor. Firstly, we focus on identifying the effects of rotor core lamination on the rotordynamic analysis via a 2D prediction model. The influence of lamination is considered as the change in the elastic modulus of the rotor core, which is determined by a modification factor ranging from 0 to 1.0. The analysis results show that the unbalanced response of the rotor-bearing system significantly varies depending on the value of the modification factor. Through modal testing of the system, the modification factor of 0.079 is proven to be appropriate to consider the effects of lamination. Next, we investigate the influence of ball bearing clearance on the rotordynamic analysis by establishing a bearing analysis model based on Hertz's contact theory. The analysis results indicate that negative clearance greatly changes the bearing static behavior. Rotordynamic analysis using predicted bearing stiffness with various clearances from -0.005 mm to 0.010 mm reveals that variations in clearance result in a slight difference in the displacement of the system up to 18.18. Thus, considering lamination in rotordynamic analysis is necessary as it can cause serious analysis errors in unbalanced response. However, considering the effect of the bearing clearance is optional because of its relatively weak impact.

• 시스템엔지니어링학술지
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• 제15권2호
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• pp.87-97
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• 2019

This paper focuses on the SE concept based on the weapon system design, which is the lack of systematic research at the stage of military requirements creation prior to acquisition management phase. Influence factors were derived by focusing on the core issues that were at issue in the process of requirements analysis, requirements verification, and business management in recent years. Next, the impact factor was prioritized using the AHP technique and then alternatives were suggested. As a result, through the hierarchical analysis process, 'substantiation of necessity' was found to be the most important factor in the large category, and 'satisfaction of the operating concept' was the most important factor. In addition, as a result of calculating the final weight for each nutritional factor, it was analyzed in order of 'enemy threat response ability', 'response to operational environment change', 'performance considering operational environment', and 'guaranteed power generation'. The results of this analysis suggest which factors should be focused on, firstly, based on the concept of SE by the military and JCS.