• Steel and Composite Structures
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• 제49권3호
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• pp.281-291
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• 2023

Due to the fact that the nonlinear low-velocity impact response of graphene platelets reinforced metal foams (GPLRMF) doubly curved shells have not been investigated in the existing works, this paper aims to solve this issue. Using Reddy's high-order shear deformation theory (HSDT), the nonlinear governing equations of GPLRMF doubly curved shells are obtained by Euler-Lagrange method, discretized by Galerkin principle, and solved by the fourth-order Runge-Kutta method to obtain the impact force and central deflection. The nonlinear Hertz contact law is applied to determine the contact force. Finally, the impacts of graphene platelets (GPLs) distribution pattern, porosity distribution form, porosity coefficient, damping coefficient, impact parameters (radius and initial velocity), GPLs weight fraction, pre-stressing force and different shell types on the low-velocity impact curves are analyzed. It can be found that, among the four shell structures, the impact resistance of spherical shell is the best, while that of cylindrical shell is the worst.

• Spatial Information Research
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• 제16권3호
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• pp.359-372
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• 2008

본 연구에서는 우리나라 소나무의 공간분포를 추정하고, 소나무 공간분포와 출현패턴을 효과적으로 설명할 수 있는 최적의 격자크기를 제안하였다. 다음으로 최적 격자크기에서 지형인자에 따른 소나무의 출현빈도를 분석하고, 지형인자가 소나무 분포에 미치는 영향력을 비교함으로써 소나무 공간분포를 지형학적으로 분석하고자 하였다. 그 결과 1m 격자크기의 DEM은 방위를 동, 서, 남, 북으로 세밀하게 구분하고 소나무도 모든 방위에 분포한 한 반면, 격자크기가 증가함에 따라 주능선에 의해 방위를 동, 서, 남 또는 동, 남과 같이 단순화시켜서 구분할 수 있었으며 소나무 또한 특정 방위에 주로 분포하는 특징을 보였다. 소나무 출현빈도 분석결과 격자크기가 100m일 때 소나무 공간분포 특징을 설명할 수 있었으며, 방위, 경사, TWI가 소나무 공간분포에 미치는 영향력 비교를 통해서는 방위의 영향력이 경사의 영향력보다 크고 경사와 TWI 사이의 영향력 차이는 크지 않은 것을 확인하였다.

• 한국산학기술학회논문지
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• 제10권9호
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• pp.2236-2245
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• 2009

본 논문은 최근 북미 지역을 중심으로 상용화에 대한 기대가 높아지고 있는 플러그인 하이브리드 전기자동차가 배터리의 충전을 위해 전기에너지 배전망에 직접 접속될 때 나타날 수 있는 설비의 과부하 및 전압문제 등에 대한 평가방법을 제안하고 실제 계통에 대한 평가결과를 분석한다. 플러그인 하이브리드 전기자동차가 일반 가정에서 충전되기 시작할 경우 전기에너지 배전계통은 가정에서 사용되어 오던 기존의 전기제품보다 훨씬 많은 전력을 소모하는 새로운 부하에 전력을 공급하게 되는 만큼 이를 배전계통의 설비계획에 반영하기 위한 모델링과 절차가 요구된다. 본 논문에서는 미국 전력연구소에서 북미지역의 전력회사들과 함께 수행하고 있는 관련 연구 과제를 소개하며 OpenDSS 프로그램을 통해 배전계통과 플러그인 전기자동차의 충전부하를 모델링하고 충전시각과 전기자동차 배터리 형태에 따른 다양한 시나리오를 적용하여 배전계통에 대한 플러그인 전기자동차 충전부하의 영향을 분석한다.

• 소성∙가공
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• 제21권3호
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• pp.172-178
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• 2012

We performed a shot peening test and used a 2-D finite element model which predicts the compressive residual stress distribution below the material's surface. In this study, the concept of 'impact cycle' is introduced to account for the irregularity in the shot's impact position during testing. The impact cycle was imbedded in the finite element model. In the shot peening test, shot bombarded a type-A Almen strip surface with different impact velocities. To verify the proposed finite element model, we compared the deformed cross sectional shape of the Almen strips with the shapes computed by the proposed finite element model. Good agreement was noted between measurements and the finite element model predictions. With the verified finite element model, a series of finite element simulations was conducted to compute the residual stress distribution below the material's surface and the characteristics of these distributions are discussed.

• 유통과학연구
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• 제16권12호
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• pp.5-11
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• 2018

Purpose - We investigate the relationship between economic policy uncertainty (EPU) of the US and China and housing distribution economy in Korea using EPU indexes of two countries and the economic indicators in Korea. Research design, data, and methodology - We use the data such as the Korean housing price stability index (HPSI), housing purchase price index (HPPI), housing lease price index (HLPI), banking stock index (BSI), and consumer price index (CPI) with EPU indexes from January 1999 to December 2017. As an empirical methodology, we select the vector error correction model (VECM) due to the existence of cointegration. Result - As results of the impulse response function, the impact of the US EPU index has initially a negative response on the Korean HPSI, HPPI, and HLPI referring the housing distribution market including the economic variables, BSI, and CPI. Likewise, the impact of index in China has initially a negative response on economic indicators except the BSI in Korea. Conclusions - This study shows that the EPU index of the US has significantly negative relationships on all economic indicators in Korea. In this study, we reveal EPU of the US and China has dynamic impact on housing distribution economy returns in Korea.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2008년도 Asian Magnetics Conference
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• pp.133.2-133.2
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• 2008

• 대한안전경영과학회지
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• 제18권2호
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• pp.65-71
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• 2016

This study was aimed to demonstrate how the analysis of the impact on confidence in the safety-conscious organizations target the clothing distribution center employees and organizational commitment. Safety awareness of employees of the clothing distribution center safety rules, safety education, road safety interests, divided into risk handling and trusted organization with the emotional trust and cognitive trust, organizational commitment was divided into affective, cognitive and normative commitment. Data collection was surveyed 185 people clothing distribution center workers, tested the hypothesis through regression analysis. The results are safety conscious exerts a positive effect on organizational trust, organizational trust was found to have a positive impact on organizational commitment.

• 아시안잔디학회지
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• 제10권3호
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• pp.231-246
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• 1996

In order to elucidate the human impact on the distribution of cellular slime molds, samples were collected from 3 types of forest ; natural forests(Mt. Deogyu and Mt. Tsukuba), semi-natural forests(Seoul Great Zoo and Tama Zoo), artificial forests(Seoul National University and Tokyo Gakugei University) .The distribution of cellular slime molds in mountains was different from that of zoo and universities. In mountains, endemic species was occurred and species diversity was higher than in zoo and universities. In zoo and universities disturbed by human, Dictyostelium sphaerocephalum was occurred with higher importance value than in mountains. 6 species were selected to investigate the effect of temperature on froctification; Polysphondylium canlidum, D. delicatum. D. firmibasis, D. sphaerocephalum P. violaceum, D. purpureum. P. violaceum and D. purpureum had an optimum temperature for fructification around 25~3O˚C but the others around 22~23˚C. The degree of sensitivity to temperature was as follows; P. candidum >D. lelicatum > D. firmibasis > D. sphaerocephalum > P. violaceum > D. purpureum. Key words: Human impact, Cellular slime molds, Occurrence and distribution, fructification, Dictylostelium delicatum. Dictyostelium sphaerocephalum.

• 유통과학연구
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• 제12권5호
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• pp.15-26
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• 2014

Purpose - This study addresses an acquisition's impact on a firm's strategic relationship based on findings of existing academic studies and theoretical assertions. Through examining existing research results and theoretical grounds for an acquisition's impact on various stakeholders, this study indirectly approaches the impact on stakeholders including alliance partners. Research design, data, and methodology - This research identified a variety of related theoretical foundations and empirical studies. Research objectives of prior studies mainly focused on merging firms and direct participants of acquisition activity. In addition, academic attention on the impact on rival firms has recently been growing. However, little research on alliance partners was found. Prior studies simultaneously employed event study methodology and cross-sectional analysis to make further theoretical contributions. Results and Conclusions - Based on the findings of prior studies, this research proposed a complementary research model for future academic inquiry into the impact of an acquisition on an alliance partner's return and for predicting an acquisition announcement's effect on alliance partners.

• 한국소음진동공학회논문집
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• 제12권8호
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• pp.639-647
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• 2002

The nonlinear vibration of the thin perforated plate is analyzed in consideration of the V-shaped tension distribution and the effect of wire impact damping. The reduced order FEM model of the tension plate is obtained from dynamic condensation for the mass and stiffness matrices. Tension wire is modeled using the lumped parameter method to effectively describe its contact interactions with the plate. The nonlinear contact-impact model is composed of spring and damper elements, of which parameters are determined from the Hertzian contact theory and the restitution coefficient, respectively. From the evaluation of the computational accuracy and computation time for the deduced impact stiffness and damping coefficient, we determined proper values for the simulation works, accounting for the computational accuracy as well as the computational efficiency. Finally we discussed the results of nonlinear nitration analysis for variations of their design parameters.