• Wind and Structures
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• 제25권3호
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• pp.261-282
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• 2017

The probabilistic information of directional extreme wind speeds is important for precisely estimating the design wind loads on structures. A new joint probability distribution model of directional extreme wind speeds is established based on observed wind-speed data using multivariate extreme value theory with the t-Copula function in the present study. At first, the theoretical deficiencies of the Gaussian-Copula and Gumbel-Copula models proposed by previous researchers for the joint probability distribution of directional extreme wind speeds are analysed. Then, the t-Copula model is adopted to solve this deficiency. Next, these three types of Copula models are discussed and evaluated with Spearman's rho, the parametric bootstrap test and the selection criteria based on the empirical Copula. Finally, the extreme wind speeds for a given return period are predicted by the t-Copula model with observed wind-speed records from several areas and the influence of dependence among directional extreme wind speeds on the predicted results is discussed.

• 벤처창업연구
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• 제8권4호
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• pp.25-35
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• 2013

본 연구는 벤처기업의 웹사이트에 대한 신뢰의 선행요인과 결과요인의 구조적 관계를 확인하고 웹사이트에 대한 신뢰, 만족도 및 행동의도에 영향을 주는 선행변수를 밝히고자 하였다. 이를 위해 대학생 123명을 대상으로 3개의 벤처기업의 웹사이트에 대한 과제 수행을 하도록 한 후 방문 웹사이트에 대한 지각을 측정하였다. 그 결과 첫째, 벤처기업의 웹사이트의 특성을 측정하기 위한 문항들에 대한 요인분석결과, 웹사이트의 디자인, 비즈니스 기능의 지원, 인터페이스, 기술, 커뮤니티, 콘텐츠의 6개 요인이 추출되었다. 둘째, 벤처기업의 웹사이트 특성 6개 요인을 선행변수로, 웹사이트의 신뢰도, 만족도 및 행동의도 의 3개 요인을 내생요인으로 한 모형을 구성하여 관계구조 모형에 대한 검증을 시도하였다. 공분산 구조분석 결과, 전반적 부합지수들은 비교적 양호하게 나타났으며, 경로도형에서는 웹사이트의 디자인, 인터페이스, 기술 및 커뮤니티의 요인들이 웹사이트의 만족도로 가는 경로가, 그리고 디자인과 콘텐츠가 웹사이트의 신뢰도로 가는 경로에서 유의하게 나타났다. 내생요인간의 경로는, 만족도는 행동의도에 영향을 주는 것으로 나타났으나 웹사이트의 신뢰도는 만족도의 매개역할을 통해 행동의도에 영향을 주는 것으로 나타났다. 이러한 결과를 기초로 쇼핑몰 운영에 있어서의 시사점을 논의하였다.

• Structural Engineering and Mechanics
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• 제85권5호
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• pp.679-691
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• 2023

Many codes allow designers to use the bending moment diagram computed by elastic analysis and modify it by a certain amount of moment redistribution (MR) to account for plastic behaviour of continuous beams. However, several researchers indicated that the MR at the ultimate limit state (𝛽_u) for some beams deviate significantly from the specified values of various codes. This paper examines the applicability of the provisions on 𝛽_u in ACI 318-19 and Eurocode 2 through numerical investigations and comprehensively explores the influencing factors. The results show that some parameters not considered in those codes influence 𝛽_u to a certain extent, where the ratio of tensile reinforcement ratio at intermediate support to tensile reinforcement ratio at midspan (𝜌_s1/𝜌_s2) and load type are crucial parameters to consider. The specific combination of these two parameters may make the codes overestimate or significantly underestimate the 𝛽_u. On the other hand, the yield state of both critical sections is found to have an important influence on the influence degree of each parameter on 𝛽_u. The yield conditions are investigated, and an empirical judgment equation is proposed. In addition, the influence laws of the critical parameters on 𝛽_u have been further proved by theoretical derivation. Finally, due to 𝜀_t is found to have a better linear correlation with 𝛽_u than x_u/d, equations as a function of 𝜀_t for predicting the 𝛽_u of continuous beams under the two loads are proposed, respectively.

• 산경연구논집
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• 제10권9호
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• pp.53-60
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• 2019

Purpose - The objective of this paper is to discover if there exists a relationship between the economic index and distribution industry index in Korean. Because of the distribution industry boom in the recent years, a lot of interest in the relationship between the economic index and distribution industry index in Korean and the economy has been generated. This article examine on the mutual influence between economic index and distribution industry index in Korean. Research design, data, and methodology - For this purpose, we use the vector-auto regression model, impulse response function and variance decomposition of the economic index and distribution industry index, Granger causality test using weekly data on the economic index and distribution industry price index in korea. The sample period is covering from January 2, 2010 to August 31, 2019. The VAR model can also be linked to cointegration analysis. Cointegration Analysis makes possible to find a mechanism causing x and y to move around a long-run equilibrium (Engle and Granger, 1987). This equilibrium means that external shocks may separate the series temporarily at any particular time, but there will be an overall tendency towards some type of long-run equilibrium. If variables are found to have this tendency they are said to be cointegrated and a long-run relationship between these series is established. These econometric tools have been applied widely into economics and business areas to analyze intertemporal linkages between different time series. Results - This research showed following main results. First, from the basic statistic analysis of the economic index and distribution industry index in Korean, the economic index and the distribution industry index in korea have unit roots. Second, there is at least one cointegration between the economic index and distribution industry index in Korean. Finally, the correlation between of the economic index and the distribution industry index in korea is (+) 0.528876. Conclusions - We find that the distribution industry price index Granger cause the economic index in korea. As a consequence, the distribution industry index affect the economic index in Korean. The distribution industry index to the economic index is stronger than that from the economic index to the distribution industry index.

• 감성과학
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• 제17권2호
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• pp.63-76
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• 2014

대부분의 인지적 과제에서 관찰되는 반응시간 자료의 분포는 정적으로 편포되어 나타남에도 불구하고, 반응시간을 종속측정치로 하는 대다수의 연구들은 표본 평균에 근거한 집중경향치 분석에 의존한다. 본 연구에서는 반응시간 자료의 분포특성에 분석의 초점을 맞추어 실험적 처치의 효과를 구체적으로 추론하는 방법을 소개하였다. 평균 반응시간의 변화는 그 분포상 가우시안 및 지수 분포가 혼합된 형태로 나타난다고 가정할 수 있으며, 최대우도 추정법에 근거한 ex-Gaussian 모형 검증을 통해 반응시간 분포 특성을 수치화된 파라미터로 산출하고 확률밀도함수를 구현할 수 있다. 분석 사례를 위해 두 가지 고전적 시각탐색과제에서 얻어진 반응시간 자료를 사용하였으며, ex-Gaussian 함수를 통해 탐색배열의 항목개수의 증가가 초래하는 평균 반응시간의 지연효과에 대한 해석을 시도하였다. 수리적 모형을 통한 반응시간 분포 분석은 고전적 집중경향치 분석의 한계를 넘어 반응시간을 활용한 다양한 이론 및 개인차 연구에서 활용될 수 있을 것으로 기대된다.

• 대한기계학회논문집A
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• 제26권2호
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• pp.380-386
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• 2002

Damage behaviors induced in silicon carbide by an impact of particle having different material and size were investigated. Especially, the influence of the impact velocity of particle on the cone crack shape developed was mainly discussed. The damage induced by spherical impact was different depending on the material and size of particles. Ring cracks on the surface of specimen were multiplied by increasing the impact velocity of particle. The steel particle impact produced larger ring cracks than that of SiC particle. In the case of high velocity impact of SiC particle, radial cracks were produced due to the inelastic deformation at the impact site. In the case of the larger particle impact, the damage morphology developed was similar to the case of smaller particle one, but a percussion cone was farmed from the back surface of specimen when the impact velocity exceeded a critical value. The zenithal angle of cone cracks developed into SiC material decreased monotonically with increasing of the particle impact velocity. The size and material of particle influenced more or less on the extent of cone crack shape. An empirical equation, $\theta$= $\theta$$\sub$st/, v$\sub$p/(90-$\theta$$\sub$st/)/500 R$\^$0.3/($\rho$$_1$/$\rho$$_2$)$\^$$\frac{1}{2}$/, was obtained as a function of impact velocity of the particle, based on the quasi-static zenithal angle of cone crack. It is expected that the empirical equation will be helpful to the computational simulation of residual strength in ceramic components damaged by the particle impact.

• 벤처창업연구
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• 제9권5호
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• pp.115-127
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• 2014

국내의 창업 정책은 글로벌 경제위기와 청년층 실업이 심각하게 증가하는 문제를 해결하기 위한 하나의 방안으로 대학생 또는 청년창업을 다양하게 지원하고 있다. 하지만 대부분의 청년창업은 기업경영에 관한 사전지식과 경험 부족 상태에서 이루어지기 때문에 성공보다는 실패사례가 많아 청년 예비창업자들은 이러한 실패에 대한 두려움 등으로 창업을 주저하거나 포기하는 경우가 많다. 현재 예비창업자들을 위해 여러 가지 창업교육들이 진행되고 있으며, 예비창업자들을 위한 창업 멘토링 프로그램도 마련되어 있다. 특히, 창업 멘토링 프로그램은 새로운 것에 대한 도전과 그로 인해 겪을 수 있는 실패에 대한 두려움과 같이 창업자들의 두려움과 불안감을 완화하는 데 그 중요성이 인정되어 그 비중과 프로그램의 내용이 강화되고 있다. 이에 본 연구에서는 창업 멘토링기능이 청년창업자의 창업역랑 향상에 미치는 영향을 규명하고, 멘토링기능과 창업역랑 사이에 창업예비기간과 창업희망기간의 조절효과를 검증하여 멘토링기능이 창업을 원하는 우수한 기술 또는 아이디어를 가진 청년창업자에게 미치는 영향을 알아보고자 한다. 본 연구의 회귀 분석 결과 멘토링기능은 창업역량인 기술적 역량과 창의적 역량에 유의적인 정(+)의 영향을 미치며, 창업예비기간과 창업희망기간의 조절효과는 멘토링 기능과 기술적 역량 사이에는 유의하지 않지만, 창의적 역량 사이에는 유의하게 영향을 미쳐지는 것을 알 수 있었다. 다만, 멘토링 기능별로 창업역량에 미치는 조절효과를 살펴본 결과 창업예비기간만이 창업역량에 유의적인 영향을 미치고, 창업 희망기간은 창업역량에 조절효과를 미치지 않는 다는 것을 알 수 있었다. 따라서 창업 교육 중 멘토링 관련 프로그램은 창업자의 창의성역량을 강화하는 프로그램에 중점적으로 활용되어야하며, 멘토링 프로그램 참여 시 예비창업자들의 창업 준비정도를 반영하여 창업자 눈높이에 적합한 맞춤형 멘토링기능을 제공하도록 하여야 한다.

• Geomechanics and Engineering
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• 제21권5호
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• pp.423-432
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• 2020

Hydraulic conductivity is one of the engineering properties of soil. This study focusses on the influence of cement content on the hydraulic conductivity of cemented sand, which is investigated based on the results from numerical analysis and laboratory testing. For numerical analysis the cemented samples were scanned using X-ray Computed Tomography (CT) while laboratory testing was carried out using a triaxial setup. Numerical analysis enables us to simulate flow through the sample and provides insight to the microstructure. It quantifies the pore volume, proportion of interconnected voids and pore size distribution in both cemented and uncemented samples, which could be computed only through empirical equations in case of laboratory testing. With reduction in global voids, the interconnecting voids within the samples also reduce with cement content. Gamma cumulative distribution function is used to predict the percentage of voids lesser than a given pore volume. Finally, the results obtained from both numerical analysis and laboratory testing are compared.

• Journal of Nutrition and Health
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• 제15권4호
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• pp.290-300
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• 1982

The study deals with the empirical research on the condition of nutrient intake of low income class which be represented by urban slum and rural area, with the analysis of the factors which might influence on the prevalent condition of nutrient- intake. The method of the research was based on the spot-survey with questionaires. The result is that the levels of nutrient-intake are below the standard requirement level of nutrients in both of urban slum and rural area. The level of nutrient intake in urban slum lies in approximately 50% of the standard requirement level and 80% of the standard requirement level in rural area. The extent of malnutrition was explained in terms of the amount of calorie, protein, calcium and iron. More than half of the population in the community are below the standard requirement level of the nutrient- intake. The problem of malnutrition was serious in urban slum than in rural areas, which made a good contrast with the result of Peru study. Deficiency in calcium was most serious. The factor analysis of the prevalent condition of malnutrition in low class suggests that 1) The function of local market in supplying food is not so effective in the sense that the quality of the foods purchased id the local market is poor. 2) Low level of knowledge, the consequent ignorance and the indifference to the nutrition and the low income led to malnutrition. The level of income and the education were significantly correlated to the nutrient-intake.

• Tribology and Lubricants
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• 제24권1호
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• pp.1-6
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• 2008

An experimental study was conducted to evaluate the viscosity characteristics of multi-grade engine oils in which contain diesel fuels. Unused engine oils of SAE 5W40, 10W40 and 15W40 were blended with a diesel fuel ratio of 5%, 10%, and 15%. The viscosity of a diluted engine oil was measured with temperature variation ranging from $-20^{\circ}C$ to $120^{\circ}C$ using a rotary viscometer. The diluted engine oil in which is blended to a diesel fuel plays an important role for decreasing an engine oil viscosity, which may decrease the oil film thickness and a load-carrying capacity. Test results show that the viscosity tends to fall for the increased temperature when engine oil is mixed with a diesel fuel. Especially, the viscosity at a low temperature zone is radically decreased compared with a high temperature zone. Based on the experimental results, the empirical equation that can predict the viscosity of diluted engine oil is expressed in the exponential function with the variation of the temperature and a fuel ratio of diluted engine oil. This equation may be possible to predict the limitation of the oil-fuel dilution rate at the concept design stage of the CDPF system, which doesn't affect the influence of the tribological components.