• Journal of Korean Society of Environmental Engineers
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• v.27 no.8
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• pp.877-885
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• 2005

The Froude scaling between the prototype and the model was tried to estimate the necessary ventilation rate for non-isothermal concentrated fume from the semi-closed inner space. Based on the non-dimensional similitude equations derived from the Zukoski plume rise analysis, the scaling experiments were done to verify the relationship of the non-dimensional energy release rate and the non-dimensional mass flow rate by using two different scaled volume models, model A ($1\;m{\times}1\;m{\times}1\;m$) and model B ($0.5\;m{\times}0.5\;m{\times}0.5\;m$). The experimental results showed that the theoretical similitude between the models is acceptable for the prediction of ventilation rate of the concentrated fume. The maximum energy release rate used for the experiments was $20\;kW/m^3$. In the experimental range, the similitude between the energy release rate and the ventilation mass flow rate was well defined and the necessary ventilation rates were 20-30% higher than the stoichiometric ventilation mass flow rate. Based on results of current study, the design of the local air ventilation system can be improved by correcting the effects of buoyancy and diffusion of the non-isothermal concentrated fume.

• Journal of the Architectural Institute of Korea Planning & Design
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• v.34 no.6
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• pp.3-14
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• 2018

The aim of this study is to propose a method for calculating the weight of walking energy in ERAM model by calculating it for the analysis of vertical and horizontal spaces in a building. Conventional theories on the space analysis in the field of architectural planning predict the pedestrian volume of network spaces in urban street or in two-dimensional plane within a building, however, for vertical and horizontal spaces in a building, estimates of the pedestrian volume by those theories are limited. Because in the spatial syntax and ERAM model have been applied weights such as the spatial depth, adjacent angles, and physical distances available only to the two-dimensional same layer or plane. Therefore, the following basic assumptions and analysis conditions in this study were established for deriving a predictor of pedestrian volume in vertical and horizontal spaces of a building. The basic premise of space analysis is not to address the relationship between the pedestrian volume and the spatial structure itself but to the properties of spatial structure connection that human beings experience. The analysis conditions in three-dimensional spaces are as follows : 1) Measurement units should be standardized on the same scale, and 2) The connection characteristics between spaces should influence the accessibility of human beings. In this regard, a factor of walking energy has the attributes to analyze the connection of vertical and horizontal spaces and satisfies the analysis conditions presented in this study. This study has two implications. First, this study has shown how to quantitatively calculate the walking energy after a factor of walking energy was derived to predict the pedestrian volume in vertical and horizontal spaces. Second, the method of calculating the walking energy can be applied to the weights of the ERAM model, which provided the theoretical basis for future studies to predict the pedestrian volume of vertical and horizontal spaces in a building.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.1D
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• pp.111-120
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• 2009

Restructuring urban land use patterns from the motor-oriented to transit-oriented ones is a contemporary trend in urban planning and transportation. It is expected that transforming urban land use patterns to be transit and walking friendly would resolve various urban problems such as heavy energy consumptions, air pollutions, and traffic congestions. Korean cities have much potentials for developing transit-oriented urban environments in terms of its density and civil service levels, but the level of transit usage levels and the environmental quality of cities are not good enough for supporting such transition. The purpose of this study is to analyze the urban transit center areas and identify the problems to be solved to create transit-oriented urban environments. Case studies of four urban transit center areas in Seoul Metropolitan region were conducted to examine the spatial characteristics of urban transit center areas and identify their problems. Development density, land use diversity, walk-ability and transit connectivity were the primary feature of interests.

• Journal of the Korean Society for Marine Environment & Energy
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• v.12 no.1
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• pp.15-22
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• 2009

Auto-navigation algorithm have been studied to avoid collision and grounding of a ship due to human error. There have been many research on collision avoidance algorithms but they have been validated little on the real coastal traffic situation. In this study, a Collision Avoidance algorithm is developed by using Fuzzy algorithm and the concept of Changeable Action Space Searching (CAS). In the first step, on a basis of collision risk calculated from fuzzy algorithm in the current time(t=to), alternative Action Space for collision avoidance is planned. In the second step, next alternative Action Space for collision avoidance in the future($t=to+{\Delta}t$) is corrected and re-planned with re-evaluated collision risk. In the third step, the safest and most effective course among Action Space is selected by using optimization method in real time. In this paper, the main features of the developed collision avoidance algorithm (CAS) are introduced. CAS is implemented in the ship-handling simulator of MOERI. The performance of CAS is tested on the situation of open sea with 3 traffic ships, whose position is assumed to be informed from AIS. Own-ship is fully autonomously navigated by autopilot including the collision avoidance algorithm, CAS. Experimental results show that own-ship can successfully avoid the collision against traffic ships and the calculated courses from CAS are reasonable.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.6
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• pp.751-760
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• 2014

The unmanned underwater vehicle(UUV) requires the highly dense energy source because of its limited space. Especially, for the UUV designed for long-term operation, it should be reviewed first whether it is possible to install the energy source against required total power. Therefore, this study identifies whether it is possible to install the energy source for the energy requirement of the UUV. And fuel and oxidizer requirement for the fuel cell system are calculated to determine its location and layout inside of the vehicle. Finally, we design the closed type 1kW polymer-electrolytic fuel cell system and check the applicability to underwater operations with UUV.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.129.1-129.1
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• 2010

석탄가스화로부터 얻어진 합성가스는 CO, $H_2$가 주성분으로, 그 자체를 연료로 사용하여 발전을 하거나 또는 적절한 정제, 분리 및 합성을 통해 다양한 원료물질을 생산할 수 있다. 이러한 석탄의 청정 사용 기술은 최근의 에너지 분야에서 많은 관심을 불러일으키고 있는 고유가 현상 및 석유자원 고갈에 대비할 수 있는 현실적인 방법의 하나로 여겨지고 있다. 석유를 대체할 에너지원으로서 석탄을 이용하는 다양한 응용 방법 중의 하나로 가스화 반응을 통해 발생하는 합성가스를 이용한 SNG 제조 공정을 들 수 있는데, 이는 석탄 등의 고체 시료를 이용하여 메탄이 주성분인 연료가스를 생산하는 것이다. SNG(Synthesis Natural Gas 또는Substitute Natural Gas)는 합성천연가스 또는 대체천연가스로 불리어지는데 주로 석탄의 가스화를 통해 얻어진 합성가스(syngas 또는 synthesis gas)인 CO, $H_2$를 촉매에 의한 합성반응을 통해 얻을 수 있다. SNG 합성 반응(메탄화 반응)은 보통 수성가스 전환 공정과 가스 정제 공정을 거친 합성가스를 $CH_4$로 전환하는 것으로 석탄을 이용한 SNG 제조 공정에서 가장 핵심 공정인 메탄화 반응은 높은 발열반응으로 주로 니켈 촉매를 사용하며 $250{\sim}400^{\circ}C$에서 반응이 이루어진다. SNG 합성 반응은 공급되는 합성가스의 조성($H_2$/CO 비), 공급되는 합성가스의 유량과 반응기에 충진된 촉매의 부피와의 관계를 나타낸 공간속도, 반응온도 등의 조건에 따라 반응 특성이 달라질 수 있다. 가스화 반응을 통해 생성되는 합성가스를 이용한 SNG 합성반응(메탄화 반응)의 특성을 파악하기 위하여 Lab-scale 규모의 고정층 반응기를 이용하여 Ni 함량이 다른 2종류의 촉매를 대상으로 반응온도 및 압력에 따른 CO 전환율, $CH_4$ 선택도, $CH_4$ 생산성 변화를 파악하였다. 실험 결과 반응기의 온도가 350도 이상의 조건에서 CO 전환율은 99.8%이상, $CH_4$ 선택도는 90.7%이상으로 나타났으며, 공간속도가 2,000 1/h 이상의 조건에서는 $CH_4$ 생산성이 500 ml/g-cat, h을 만족하였다.

• Journal of Energy Engineering
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• v.19 no.3
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• pp.195-202
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• 2010

A third of primary energy is lost as a waste heat. To improve this inefficient use of energy, systems using chemical reaction have been suggested and studied. In this study, methanol decomposition/synthesis reaction as a chemical reaction was selected for long time heat storage and long distance heat transport system because of safe, cheap and gaseous product. The purpose of this study is to find the optimal conditions in the methanol decomposition and synthesis reactions for long distance heat transport. Several parameters such as reaction temperature, pressure, $H_2$/CO ratio, space velocity, catalyst particle size were tested to find the effects on the reaction rates for the methanol synthesis. And the reaction temperature, space velocity, catalyst particle size were tested to find the effects on the production concentration for the methanol decomposition.

• Journal of the Korean Institute of Intelligent Systems
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• v.21 no.1
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• pp.6-11
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• 2011

In this paper, we propose a gait-based human identification system using eigenfeature regularization and extraction (ERE). First, a gait feature for human identification which is called gait energy image (GEI) is generated from walking sequences acquired from a camera sensor. In training phase, regularized transformation matrix is obtained by applying ERE to the gallery GEI dataset, and the gallery GEI dataset is projected onto the eigenspace to obtain galley features. In testing phase, the probe GEI dataset is projected onto the eigenspace created in training phase and determine the identity by using a nearest neighbor classifier. Experiments are carried out on the CASIA gait dataset A to evaluate the performance of the proposed system. Experimental results show that the proposed system is better than previous works in terms of correct classification rate.

• Journal of Hydrogen and New Energy
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• v.33 no.4
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• pp.267-283
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• 2022

In these day, the environmental issues of climate change have been continuously highlighted and there is an active discussion on the transition from fossil fuel-based energy to eco-friendly energy use. This study considered psychological attitudes as a major influencing factors for successful implementation of a hydrogen society totally based on the use of hydrogen energy, which is regarded as an alternative energy for future. Accordingly, familiarity, risk perception, and acceptability of psychological factors were investigated. In addition, this study identified whether there are differences in psychological factors according to the general characteristics of gender, age, occupation, and housing type. The results showed that awareness of hydrogen cars and fuels is below the average level, and we also have obtained the implication that social knowledge sharing should precede the implementation of hydrogen policy. Although we found that the degree of urban acceptance of hydrogen energy was high, it was also confirmed that the charging infrastructure was generally perceived as having a high risk. Our findings implicate that it is necessary to figure out policy strategies for suitable locating charging infrastructure in order to promote the use of hydrogen energy more.

• Explosives and Blasting
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• v.41 no.4
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• pp.17-28
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• 2023

Recently, the utilization of underground space for research facilities and resource development has been on the rise, expanding development from shallow to deep underground. The establishment of deep underground spaces necessitates a thorough examination of rock stability under conditions of elevated stress and temperature. In instances of greater depth, the stability is influenced not only by the geological structure and discontinuity of rock but also by the propagation of ground vibrations resulting from earthquakes and rock blasting during excavation, causing stress changes in the underground cavity and impacting rock stability. In terms of blasting engineering, empirical regression models and numerical analysis methods are used to predict ground vibration through statistical regression analysis based on measured data. In this study, single-hole blasting was conducted, and the pressure of the blast hole and observation hole and ground vibration were measured. Based on the experimental results, the blast pressure blasting vibration at a distance, and the response characteristics of the tunnel floor, side walls, and ceiling were analyzed.