• Structural Engineering and Mechanics
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• 제83권6호
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• pp.709-727
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• 2022

Fastening systems have a significant role in the response of railway slab track systems. Although experimental tests indicate nonlinear behavior of fastening systems, they have been simulated as a linear spring-dashpot element in the available literature. In this paper, the influence of the nonlinear behavior of fastening systems on the slab track response was investigated. In this regard, a nonlinear model of vehicle/slab track interaction, including two commonly used fastening systems (i.e., RFFS and RWFS), was developed. The time history of excitation frequency of the fastening system was derived using the short time Fourier transform. The model was validated, using the results of a comprehensive field test carried out in this study. The frequency response of the track was studied to evaluate the effect of excitation frequency on the railway track response. The results obtained from the model were compared with those of the conventional linear model of vehicle/slab track interaction. The effects of vehicle speed, axle load, pad stiffness, fastening preload on the difference between the outputs obtained from the linear and nonlinear models were investigated through a parametric study. It was shown that the difference between the results obtained from linear and nonlinear models is up to 38 and 18 percent for RWFS and RFFS, respectively. Based on the outcomes obtained, a nonlinear to linear correction factor as a function of vehicle speed, vehicle axle load, pad stiffness and preload was derived. It was shown that consideration of the correction factor compensates the errors caused by the assumption of linear behavior for the fastening systems in the currently used vehicle track interaction models.

• 대한기계학회논문집
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• 제11권5호
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• pp.846-855
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• 1987

본 연구에서는 실용적 설계및 이론해석에 필요한 동적 거동에 관한 현상규명 및 기초자료를 제공하기위해, 기하학적 형상변화에 따른 맥동연소의 안정성 및 흡입공 기량의 측정을 통한당량비의 범위를 관찰하고, 연소실과 배기관, 공기유입관, 연료노 즐실에서의 압력을 각각 동시측정해서 동적거동에 관해 고찰하고, 작동주파수에 관한 간단한 실험식의 확립과 추력성능에 관한 실험을 행했다.

• International Journal of Human Ecology
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• 제5권2호
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• pp.81-91
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• 2004

The purpose of this study is to evaluate consumer use of unit price information introduced in Korea 1999. A total of 571 observations were analyzed by frequency, percent, and paired t-test using SPSS. The main findings are (1) consumers use unit price information to make better purchase decisions, (2) consumers with higher than average attentiveness in purchase behavior utilize unit price information to make better buying decisions, and (3) consumers with higher than average knowledge utilize unit price information to make better buying decisions. (4) Also if either attentiveness in purchase behavior or consumer knowledge is lower than average, unit price information helped consumers make better purchase decisions. (5) However, there was no difference among those consumers with below average or above average attentiveness and knowledge.

• Wind and Structures
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• 제30권2호
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• pp.133-140
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• 2020

In this paper, critical fluid velocity and frequency of laminated pipe conveying fluid are presented. Each layer of the pipe is reinforced by functionally graded carbon nanotubes (FG-CNTs). The internal fluid is assumed turbulent and the induced forces are calculated by momentum equations. The pipe is resting on viscoelastic foundation with spring, shear and damping constants. The motion equations are derived based on classical shell theory and energy method. Differential quadrature method (DQM) is used for solution and obtaining the critical fluid velocity. The effects of volume percent and distribution of CNT, boundary condition, lamina layer number, length to radius ration of pipe, viscoelastic medium and fluid velocity are shown on the critical fluid velocity. Results show that with increasing the lamina layer number, the critical fluid velocity increases.

• 자원환경지질
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• 제21권2호
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• pp.165-169
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• 1988

2차원 구조에 대한 음수의 분도분극 반응을 차분법을 이용한 2차원 모델링 기술로 검토하였다. 유도분극 변수로서는 섭동방법으로 효율적으로 계산이 가능한 주파수 효과를 사용하였다. 전도성이면서 분극성인 얇은 표토층은 가상단면도상에서 뚜렷한 음수의 유도분극 반응을 일으킨다. 이는 분극성 표토층하에 존재하는 저항성인 부극체에 의한 반응이 단지 비저항분포의 함수만으로 음폐되는 것을 뜻한다. 그러나, 분극성 표토층하의 저항성인 비 분극체는 음수의 반응으로 발견될 수 있다.

• 대한조선학회지
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• 제20권1호
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• pp.29-33
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• 1983

The loading condition, of a ship, especially a multi-purpose cargo carrier, in service, is often changed. Then, the prediction of natural frequency changes is necessary to provide measures for prevention of ship vibrations. In this paper a simplified method for the above purpose is presented. The bases of the method are analytical solutions for the lateral vibrations of uniform Timoshenko beams carrying a concentrated mass and the Dunkerley's formula. In this method a ship in the standard ballast condition is reduced to a uniform Timoshenko beam having same system parameters as those of the midship section. To investigate the validity of the proposed method, numerical calculations are carried out for a 46,000 DWT bulk carrier and compared with detailed calculations based on the finite difference method. Even in cases those the cargoes in a hold, length of which is about 13% of the ship's length, are reduced to a concentrated mass, the proposed method gives results of several percent differences from the detailed calculations up to the six-noded mode.

• Earthquakes and Structures
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• 제3권3_4호
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• pp.495-506
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• 2012

An elasto-dynamic model for pile-soil-pile interaction together with a simple plate model is used in this study to assess the effect of flexible foundation slabs on the dynamic response of pile groups. To this end, different pile configurations with various slab thicknessesare considered in two soil media with low and high elastic moduli. The analyses include dynamic impedances and seismic responses of pile-group foundations. The presented results indicate that the stiffness and damping of pile foundations increase with thickness of the foundation slab; however, the results approach those for rigid slab as the slab thickness approaches twice the pile diameter for the cases considered in this study. The results also reveal that pile foundations with flexible slabs may amplify the earthquake motions by as much as 10 percent in the low to intermediate frequency ranges.

• 한국식품과학회지
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• 제12권3호
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• pp.165-169
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• 1980

실험실(實驗室) 소비자(消費者) 파넬을 대상으로 시판(市販) 우유에 대한 기호(嗜好) 조사(調査) 시험(試驗)을 실시하여 다음과 같은 결과(結果)를 얻었다. 1. 시판(市販) A 우유와 각종 우유 사이에 대한 2점(點) 기호(嗜好) 조사(調査) 시험(試驗) 결과(結果), 소비자(消費者) 기호(嗜好) 선택(選擇)에 있어서 5% 수준(水準)에서 유의적(有意的)인 차이(差異)가 인정(認定)되지 않았다. 2. 시판(市販) 우유에 대한 기호(嗜好) 척도(尺度) 시험(試驗) 결과(結果), 시료간(試料間)이나 파넬원 간(間) 모두가 5% 수준(水準)에서 유의적(有意約)인 차이(差累)가 인정(認定)되지 않았다. 3. 시판(市販) 우유에 대한 기호(嗜好) 빈도(頻度) 시험(試驗) 결과(結果) ‘기회만 있으면 언제나 먹겠다’가 39%로 가장 높았다. 4. 우유의 시음(試飮) 온도(溫度)에 따른 우유 풍미(風味)에 관한 기호성(嗜好性)을 조사(調査)한 결과(結果), $20^{\circ}C$에서 마실 때가 가장 높았다. 5. 전보(前報)(한국식품과학회지, 12 (3), 150 및 158(1980))에서 행한 차이(差異) 식별(識別) 시험(試驗)이나 묘사(描寫) 시험(試驗)에서는 시판(市販) 5개(個) 회사(會社) 제품별(製品別) 우유 풍미(風味)에 대한 차이(差異)가 인정(認定)되었으나 순위(順位) 시험(試驗)이나 기호(嗜好) 선택(選擇) 및 기호(嗜好) 척도(尺度) 시험(試驗)에서는 유의적(有意的)인 차이(差異)를 나타내지 않음을 알 수 있는데, 이것은 순위(順位) 시험(試驗)이나 기호(嗜好) 선택(選擇) 및 척도(尺度) 시험(試驗)이 파넬원들간의 기호성(嗜好性)의 차이(差異), 품질(品質) 기준(基準)의 차이(差異) 등(等)에 의하여 많은 영향을 받는다는 사실을 시사하는 것으로 고려된다.

• 대한가정학회지
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• 제48권2호
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• pp.121-134
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• 2010

This study was performed to develop the semi-quantitative food frequency questionnaire (SQFFQ) for assessing the usual dietary intake of Korean adolescents. For that, we used 24 hour recall data from the 2005 NHANES(the Third Korean National Health and Nutrition Examination Survey). The cumulative percent contribution and cumulative multiple regression coefficients of 17 nutrients(energy, protein, fat, carbohydrate, fiber, calcium, phosphorus, iron, sodium, potassium, vitamin A, retinol, ${\beta}$-carotene, thiamin, riboflavin, niacin, vitamin C) of each food were computed. Among 687 food items, 265 food items were selected and grouped depending on similarities in ingredients, nutrient profiles, and/or culinary usage and re-added food items which were excluded for seasonal effect. Finally, total 19 food groups, 87 food items, were included in SQFFQ. Food intake frequency was quantified using nine categories. The portion size was classified depending on the average size of each selected food item. Each portion size was then categorized as one of three amounts: small (0.5 times), medium (1 times), and large (1.5 times). The SQFFQ covered 91.9% of the intake of 17 nutrients in 2005 NHANES and 86.6% in 2001 NHANES. Therefore, by testing the validity of developed SQFFQ using nutrient intakes, this list was valid to evaluate the usual daily intake in Korean adolescents.

• 한국도로학회논문집
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• 제14권6호
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• pp.103-110
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• 2012

PURPOSES : In Korea, over 70 percent of the land consists of mountainous and rolling area. Thus, tunnels continue its upward trend as road network are extended. In these circumstances, the importance of tunnel has been increased nowadays and then its safety investigation and research should be performed. This study is focus on confirming and improving the safety of tunnel. On tunnel hood, sunglare effect can irritate driver's behavior instantly and this can result in incident. METHODS : The study of this phenomenon is rarely conducted in domestic and foreign papers, so there is no proper measure for this. This study analyzes the driving environment of the effect of sunglare effect on tunnel hood. RESULTS : Traffic accidents stem from complex set of factors. This study build the Traffic Accident Prediction Models to find out the effect of sunglare effect on tunnel's hood. The independent variables are traffic volume, geometric design of road, length of tunnel and road side environment. Using these variables, this model estimates accident frequency on tunnel hood by Poisson regression model and Negative binomial regression model. Although Poisson regression model have more proper goodness of fit than Negative binomial regression model, Poisson regression model has overdipersion problem. So the Negative binomial regression model is used in this analysis. CONCLUSIONS : Consequently, the model shows that sunglare effect can play a role in driving safety on tunnel hood. As a result, the information of sunglare effect should be noticed ahead of tunnel hood so this can prevent drivers from being in hazard situation.