• Nuclear Engineering and Technology
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• 제47권4호
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• pp.434-442
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• 2015

The advanced passive pressurized water reactor (PWR) is being constructed in China and the passive residual heat removal (PRHR) system was designed to remove the decay heat. During accident scenarios with increase of heat removal from the primary coolant system, the actuation of the PRHR will enhance the cooldown of the primary coolant system. There is a risk of power excursion during the cooldown of the primary coolant system. Therefore, it is necessary to analyze the thermal hydraulic behavior of the reactor coolant system (RCS) at this condition. The advanced passive PWR model, including major components in the RCS, is built by SCDAP/RELAP5 code. The thermal hydraulic behavior of the core is studied for two typical accident sequences with PRHR actuation to investigate the core cooling capability with conservative assumptions, a main steam line break (MSLB) event and inadvertent opening of a steam generator (SG) safety valve event. The results show that the core is ultimately shut down by the boric acid solution delivered by Core Makeup Tank (CMT) injections. The effects of CMT boric acid concentration and the activation delay time on accident consequences are analyzed for MSLB, which shows that there is no consequential damage to the fuel or reactor coolant system in the selected conditions.

• 한국조경학회지
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• 제33권1호
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• pp.10-18
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• 2005

The main concept of social carrying capacity is based on the principle that 'there are limits to the number of users a given recreation site can accommodate in order to provide quality of recreation experience'. The quality of the experience is revealed as user's satisfaction and perceived crowding. In this respect, studies of social carrying capacity have been frequently conducted by measuring perceived crowding and satisfaction. The purpose of this study is to identify the variables affecting perceived crowding, and causality bet-ween satisfaction and perceived crowding. Four hundred seventy six visitors were selected at Naejangsan National park on peak day of autumn excursion through on-site survey. The collected data were applied by factor analysis for categorizing the research variables, and multiple regression for finding the causality among variables. The study results are follows. The expectation of crowding, as a normative variable for perceived crowding, are categorized by three factors; circulation, user facility, and landscape. The circulation factor is the most powerful affecting perceived crowding among three factor. The landscape factor, however, do not have statistical significance on perceived crowding. The causality between satisfaction and perceived crowding is found. Although this relation is significant in statistics, magnitude of the coefficient is very small. It might be interpreted that satisfaction cannot be predicted simply from a user's perception of crowding, but a multi-dimensional concept such as adaptation and coping behavior.

• 한국자동차공학회논문집
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• 제10권4호
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• pp.15-22
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• 2002

As the emission regulations on the automobiles have been increasingly stringent, precise control of air/fuel ration is one of the most important issues on the gasoline engines. Although many researches have been carried out to identify the fuel transport phenomena in the port fuel injection gasolines, mixture preparation in the cylinder has not been fully understood due to the complexity of fuel film behavior, In this paper, the mixture preparation during cold engine start is studied by using a Fast Response Flame ionization Detector.(FRFID) In order to estimate the transportation of injected fuel from the intake port into cylinder, the wall wetting fuel model was used. The two coefficient($\alpha$,$\beta$) of the wall-wetting fuel model was determined from the measured fuel mass that was inducted into the cylinder at the first cycle after injection cut-in. $\alpha$( ratio of directly inducted fuel mass into cylinder from injected fuel mass) and $\beta$ (ratio of indirectly inducted fuel mass into cylinder from wall wetted fuel film on the wall) was increased with increasing cooling water temperature. To reduce a air/fuel ratio fluctuation during cold engine start, the appropriate fuel injection rate was obtained from the wall wetting fuel model. Result of air/fuel ratio control, air/fuel excursion was reduced.

• Structural Engineering and Mechanics
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• 제40권4호
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• pp.517-539
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• 2011

This paper presents the seismic responses of a 1:5-scale five-story reinforced concrete building model, which represents a residential apartment building that has a high irregularity of weak story, soft story, and torsion simultaneously at the ground story. The model was subjected to a series of uni- and bi-directional earthquake simulation tests. Analysis of the test results leads to the following conclusions: (1) The model survived the table excitations simulating the design earthquake with the PGA of 0.187 g without any significant damages, though it was not designed against earthquakes; (2) The fundamental mode was the torsion mode. The second and third orthogonal translational modes acted independently while the torsion mode showed a strong correlation with the predominant translational mode; (3) After a significant excursion into inelastic behavior, this correlation disappeared and the maximum torsion and torsion deformation remained almost constant regardless of the intensity of the two orthogonal excitations; And, (4) the lateral resistance and stiffness of the critical columns and wall increased or decreased significantly with the large variation of acting axial forces caused by the high bi-directional overturning moments and rocking phenomena under the bi-directional excitations.

• 대한조선학회지
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• 제21권3호
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• pp.43-50
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• 1984

A body form, which experiences minimum vertical wave-exciting forces in the vicinity of a prescribed wave frequency in water of finite depth, is obtained by an approximate method. Its configuration has the symmetry with respect to the vertical axis, expressed in terms of exponential functions. By distributing three-dimensional pulsating sources and dipoles on the immersed surface of the body, a velocity potential is determined and subsequently hydrodynamic forces including the 2nd-order time-mean drift forces are calculated. The dynamic behavior of the body moored in irregular waves is investigated numerically by using central difference method. Hereby irregular wave trains are simulated with examining its repeatability by comparing the resulting spectrum with original one. Numerical results indicated that the body form obtained from the present analysis possesses in general a favorable hydrodynamic characteristics in comparison with a spherical buoy and that the maximum excursion of the body can be significantly reduced by setting pre-tension of an appropriate amount in the mooring cable.

• Nuclear Engineering and Technology
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• 제19권1호
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• pp.22-33
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• 1987

원자력 발전소에 있어서 정상가동 상태나 이상동작시에 핵연료 피복관의 건전성 확보와 연관하여 피복재의 항복거동은 중요한 문제이다. 급격한 출력상승 상황에서 이산화 우라늄 소결체와 피복관 사이의 노내 조사거동의 차이는 소결체와 피복관 사이에 Contact Pressure를 야기 시킨다. 만일 이 Contact Pressure가 Zircaloy 피복관의 Yield Pressure에 도달하면 피복관에는 영구변형이 일어난다. 이 변형은 원자로의 출력이 정상상태로 회복되더라도 존재하므로 소결체와 피복관 사이의 Gap을 증대시킨다. 이러한 상황을 묘사하기 위해 본 논문에서는 구리 Mandrel과 Zircaloy사이의 열팽창 차이를 이용하는 Mandrel 팽창 실험을 실행했다. 실험 결과 측정된 Zircaloy 피복관의 외경 팽창치와 본 논문에서 유도된 수학적 관계식들을 이용하여 온도에 따른 Zircaloy 피복관의 내부항복압력과 항복응력, 피복재의 항복에 따른 핵연료 소결체와 피복관 사이의 Gap 증대를 구하고, 항복 거동에 따른 온도의 영향을 보기 위해 항복과정의 활성화 에너지를 구했다. 본 실험과 분석에서 얻어진 이들 결과들은 다른 실험 결과들과 상당히 일치하였으며, 이것으로 볼 때 본 논문에서 유도된 관계식들과 Mandrel 팽창 실험이 Zircaloy 피복관의 항복거동과 Gap Expansion 측정에 신뢰성이 있음을 알 수 있었다.

• 한국환경과학회지
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• 제23권5호
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• pp.943-962
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• 2014

Industrial gas drying, dilute gas mixtures purification, air fractionation, hydrogen production from steam reformers and petroleum refinery off-gases, etc are conducted by using adsorptive separation technology. The pressure swing adsorption (PSA) has certain advantages over the other methods, such as absorption and membrane, that are a low energy requirement and cost-effectiveness. A key component of PSA systems is adsorbents that should be highly selective to a gas being separated from its mixture streams and have isotherms suitable for the operation principle. The six standard types of isotherms have been examined in this review, and among them the best behavior in the adsorption of $CO_2$ as a function of pressure was proposed in aspects of maximizing a working capacity upon excursion between adsorption and desorption cycles. Zeolites and molecular sieves are historically typical adsorbents for such PSA applications in gas and related industries, and their physicochemical features, e.g., framework, channel structure, pore size, Si-to-Al ratio (SAR), and specific surface area, are strongly associated with the extent of $CO_2$ adsorption at given conditions and those points have been extensively described with literature data. A great body of data of $CO_2$ adsorption on the nanoporous zeolitic materials have been collected according to pressure ranges adsorbed, and these isotherms have been discussed to get an insight into a better $CO_2$ adsorbent for PSA processes.

• 한국구조물진단유지관리공학회 논문집
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• 제7권4호
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• pp.191-199
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• 2003

대부분 강구조 및 철근콘크리트 구조물은 탄소성 거동에 의해 극한강도가 지배된다. 비록 평상시에는 탄성 범위를 초과하는 진폭(振幅)이 발생하지 않지만 심각한 폭발이나 지진하중과 같은 극단적인 경우가 발생할 때, 엔지니어는 구조물에 영구적인 손상을 줄 수 있는 상황들을 접하게 된다. 이러한 상태 평가를 위해 본 연구는 폭발 등의 극한하중에 특성에 의해 발생되는 구조물의 동적거동을 분석하였다. 그리고 본 연구는 극한진동 특성을 분석하기 위해 비선형 유한요소프로그램(ATENA2D, FRANC2DL)을 사용하였다. 본 연구의 해석결과, 평상시와 횡하중시의 균열은 발생 위치와 양태가 매우 다르게 나타났다. 또한, 초기 손상균열이 있는 RC라멘의 보에 단면형상과 기하학적 형상비 변화를 고려하여 균열각의 변화를 분석하였으며 이를 통해 동적 횡하중 작용에 의한 피해여부를 판단할 수 있었다.

• 한국운동역학회지
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• 제25권2호
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• pp.175-182
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• 2015

Objective : The purpose of this study was to investigate difference in fascicle behavior of the medial gastrocnemius during the locomotion with varying intensities, such as gait and one-legged and two-legged vertical jumping. Methods : Six subjects (3 males and 3 females; age: $27.2{\pm}1.6yrs.$, body mass: $62.8{\pm}9.8kg$, height: $169.6{\pm}8.5cm$) performed normal gait (G) at preferred speed and maximum vertical jumping with one (OJ) and two (TJ) legs. While subjects were performing the given tasks, the hip, knee and ankle joint motion and ground reaction force was monitored using a 8-infrared camera motion analysis system with two forceplates. Simultaneously, electromyography of the triceps surae muscles, and the fascicle length of the medial gastrocnemius were recorded using a real-time ultrasound imaging machine. Results : Comparing to gait, the kinematic and kinetic parameters of TJ and OJ were found to be significantly different. Along with those parameters, change in the medial gastrocnemius (MG) muscle-tendon complex (MTC) length ($50.57{\pm}6.20mm$ for TJ and $44.14{\pm}5.39mm$ for OJ) and changes in the fascicle length of the MG ($18.97{\pm}3.58mm$ for TJ and $20.31{\pm}4.59mm$ for OJ) were observed. Although the total excursion of the MTC and the MG fascicle length during the two types of jump were not significantly different, however the pattern of length changes were found to be different. For TJ, the fascicle length maintained isometric longer during the propulsive phase than OJ. Conclusion : One-legged and two-legged vertical jumping use different muscle-tendon interaction strategies.

• 한국조경학회지
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• 제16권2호
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• pp.43-57
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• 1988

지리산 국립공원의 이용자 행태특성과 과거실태에 대한 이용자의 만족도를 계량적 접근방법으로 제시하고자 5개 조사대상지역 이용자들의 이용전 기대도와 이용후 만족도를 리커트척도에 의하여 조사, 분석하였다. 또한 이용후 만족도 평가결과를 인자 분석 Algorithm을 통하여 행태유형과 지역별 인자점수를 밝혔으며 관리실태에 대한 이용자의 만족도를 다변량분석하여 주요 변수를 밝혔다. 1. 학생과 사무직의 청년층이 친구들과 또는 직장 동료와 3∼10명 정도의 그룹형태로 춘·하·추 계절에 2회 이상 탐방하는 패턴이 비교적 높게 나타난 반면, 사찰지역은 봄·가을에 1일 체류를 주로하는 관광객의 이용빈도가 현저히 높게 나타났다. 2. 각 지역별 공히 암벽등반 및 산속기도가 이용자 이용전의 기대도 보다 체험 후 높은 만족도를 보였고, 여타의 체험 후 평가는 불만족으로 나타났으며 이 결과는 고도의 유의성을 보였다. 3. 조사대상지의 이용후 만족도 평가에 의한 인자 분석 결과 5개의 인자군으로 분류할 수 있었고, 전체의 설명력은 50.85%를 나타냈으며, 학생이 주를 이룬 청년층의 이용행태를 함축하는 변인이 주성분을 나타내는 인자군에서 E.V와 C.V가 각각 높게 나타났다. 인자 II는 이용자의 각 속성과 인자 I은 연령과 직업에 각각 고도의 유의성을 보였다. 4. 인자점수를 이용한 Cluster분석결과 화엄사 및 쌍계사·대성계곡지역은 인자 IV가 중산리 인자 II·V, 백무동·한신계곡지역 인자I·III 및 뱀사골 지역은 인자 I·II가 높은 치를 나타내고 있어 지역에 따라 이들 인자의 주성분을 이룬 행태에 대해서는 비교적 만족한 체험을 보였다. 5. 식생관리에 대한 이용자의 만족도에 지피류 보호 및 인위적 피해의 복구가, 경관보전에서는 사찰 및 야영장 주변의 경관보전이, 시설물 관리 실태에 대해서는 안내판, 산장·야영장 및 쓰레기장 설치와 그 관리실태가, 그리고 공원운영에 대해서는 자연보호홍보 및 행락지도 실태가 각각 긍정적으로 작용하는 주요변수로 나타났다.