• 한국자동차공학회논문집
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• 제21권2호
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• pp.146-153
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• 2013

CNG buses has contributed to improve air quality in cities. But it is difficult to meet the next emission regulations such as EURO-VI without the help of additional post-processing device. Hydorgen has higher flame speed and lower combustion temperature that make it thermal efficiency increase with leaner operation. Using hydrogen natural gas blend (HCNG) fuel is promising technology which can reduce $NO_x$ and $CO_2$ emissions for a natural gas vehicle. However, fuel flow rate of HCNG should be increased since hydrogen's energy density per volume is much smaller than natural gas. In the present study, the characteristics of fuel supply system and its applicability were evaluated in a heavy duty natural gas engine. The results showed that the potential of fuel pressure regulator and fuel metering valve had enough capacity with HCNG. Employed mixer did not affect the distribution characteristics of mixture.

• 전기학회논문지
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• 제66권12호
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• pp.1905-1912
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• 2017

In recent years, Ulaanbaatar, a capital of Mongolia has witnessed major problem that air quality reaches hazardous level during the winter season. Coal combustion for heating of every house in "Ger" district is main reason. One way to reduce the air pollution is mass usage of electric heater. However, there are several difficulties such as overload and degradation of transformers and other equipment used in distribution and transmission systems as well as power shortage occurrence in evening peak period due to residential consumption. This study aims to contribute for solving the air pollution and power shortage problem in Mongolia. One possible solution could be distributed generation (DG) with photovoltaic (PV) penetration. In this study, PV with energy storage (ES) hybrid system to reduce peak load is analyzed. We proposed the suitable structure of PV-ES hybrid for Mongolian household, and suggested several operation scenarios. Optimal operation algorithm is carried out based on a comparison aspect from economical, grid impact and PV penetration possibility. The economic analyse shows annual income of 520USD, and has a payback period of 8 years for selected scenario. The proposed PV-ES system structure is verified by experimentation set on the building rooftop in city center. The suggested scenario is planned to apply for system in further research.

• 한국항해학회지
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• 제14권4호
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• pp.53-70
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• 1990

Much efforts have been made to improve the training education system for last decades. however, it still leaves much room form improving the system. The reason for this is that the have been many changes in given educational conditions, national and international, and that there existed the lack of training facilities on shore and the limits of capacity on the training ship. The existing program adopts a straight-through system of which the course has to be completed at same time, and also forces students to study the course, disregarding their aptitude for sea life. Consequently, the program resulted in frustrating the learning desire of some students and, as a consequence, in deteriorating the quality of the entire training education. This paper aims to develop an efficient training program including curriculla by the literature survey and the teaching and sea experiences on the training ship "HANBADA" and merchant ships, where the authors have been for many years. Compared with the existing one, the new training model suggested in this paper has some advantages as follows : First, the new model adopts multi-state system which consists of various short-term training courses according to each purpose. This system will be helpful for student to find their aptitude for sea life earlier and to understand classes of major subjection shore. Second, the model includes new curriculla which consist of core subjects (for example, navigation, marine operation, marine transportation, watch keeping and nautical English for deck cadets and internal and external combustion engine, auxiliary machinery, electric and electronics and engine maintenance for engine cadets), by incorporating existing 20 subjects in 5 subjects. These curriculla may contribute to embodying the characteristics of training education where the above mentioned subjects must be linked with each other. In order to implement this new training model efficiently and effectively, the following prerequisties must be prepared : $\circled1$ The contents of each subject included in the new model should be systematically developed. $\circled2$ The educational schedule should be adjusted according to the new model.new model.

• 한국연초학회지
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• 제29권1호
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• pp.23-29
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• 2007

The measurement of physical properties such as apparent density and void fraction of tobacco materials, which is so bulky, is a main theme with regard to tobacco process, quality control, cigarette combustion and smoke generation. Except Solution Impregnation Method, there was no alternative method for measuring those properties in the porous material so far. However, experimental processes of that method are so complicated as to cost much time and labor, the main solution such as mercury to apply to the method is usually very hazard. Therefore, we had developed a new method to determine them easily in our other paper by the mathematical equations derived from the Ergun equation for the purpose of it, and then already evaluated our method through applying some basic data from Muramatsu et at. (1979) with regard to our developed equations. Then, we found our method best fit to experimental one (Oh et al., 2001). In this study we tried to establish our method to conveniently determine those physical properties. Especially, we have focused on the development the easy way to measure surface area and the volume of single shred in a tobacco column. As a result of that, we found that the computer image analyzer was best fit for it. Then, we have finally determined apparent density and void fraction for our domestic tobacco shred.

• 소성∙가공
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• 제30권6호
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• pp.291-300
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• 2021

Currently, starting with electric vehicles, the application of ultra-high-strength steel sheets and light metals has expanded to improve mileage by reducing vehicle weight. At a time when internal combustion engine vehicles are rapidly changing to electric vehicles, the application of ultra-high-strength steel is expanding to satisfy both weight reductions and the performance safety of the chassis parts. There is an urgent need to improve the quality of parts without defects. It is particularly difficult to estimate the part formability through the finite element method (FEM) in the burring operation, so product design has been based on the hole expansion ratio (HER) and experience. In this study, design of experiment (DOE), analysis of variance (ANOVA), and regression analysis were combined to optimize the formability by adjusting the process variables affecting the burring formability of ultra-high-strength steel parts. The optimal variables were derived by analyzing the influence of variables and the correlation between the variables through FE analysis. Finally, the optimized process parameters were verified by comparing experiment with simulation. As for the main influence of each process variable, the initial hole diameter of the piercing process and the shape height of the preforming process had the greatest effects on burring formability, while the effect of a lower round of punching in the burring process was the least. Moreover, as the diameter of the initial hole increased, the thickness reduction rate in the burring part decreased, and the final burring height increased as the shape height during preforming increased.

• 공업화학
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• 제22권2호
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• pp.155-160
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• 2011

동물성유지는 식물성유지에 비해 산화안정성이 뛰어나며, 높은 발열량과 세탄가를 보여 불완전 연소율이 낮다는 장점을 가지고 있으나 포화지방산의 함량이 높고, 원료유지에 불순물 함량이 높아 정제과정이 필요하다는 단점을 가지고 있다. 본 연구에서는 동물성 유지로 폐돈지를 선정하여 초음파에너지를 이용한 전이에스테르화반응의 최적조건을 설정하고자 하였다. 또한 기존공정의 가열 및 교반을 대체할 수 있는 초음파에너지 효과를 확인함으로써 새로운 바이오디젤 제조공정을 제시하고자 하였다. 기존가열방식을 이용한 폐돈지의 전이에스테르화 반응은 $55^{\circ}C$에서 메탄올과 돈지의 반응몰비 12에서 1 h 반응한 경우 가장 우수한 전환특성을 나타내었다. 전이에스테르화 반응에 초음파에너지를 조사할 경우 최적 초음파 조사세기 500 W에서 반응시간을 30 min으로 크게 단축할 수 있었다. 또한 제조된 바이오디젤의 성능평가 결과 점도는 $0{\sim}70^{\circ}C$ 범위에서 1.3~4.0 cP, 발열량은 40.3 MJ/kg으로 바이오디젤 성능기준을 만족하였다.

• 한국인터넷방송통신학회논문지
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• 제22권1호
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• pp.181-186
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• 2022

세계 전기자동차 분야는 기술적 환경변화를 넘어서 시장 환경에까지 영향을 미치는 단계로 전환하여 완성차업체들은 "기술 우위 → 브랜드 제고 → 기존 내연기관 차량의 판매 확대"라는 기존 전략에서 시장경쟁력 제고라는 전기자동차 시장 자체의 확대로 전환되고 있다. 또한 전기자동차 부품시장은 기존 부품업체들의 사업영역 확대와 신규업체들의 진입으로 경쟁이 심화될 전망이며, 전기자동차 주요 부품의 효율성 향상을 위해 개발 협력도 활발히 진행될 전망이다. 이러한 전망과 함께 전기자동차가 성장할수록 자동차 산업의 전반적인 구조적 변화가 예상됨에 따라 배터리, 파워트레인(모터, 전력관리 제어시스템), 전기차 생산, 충전 인프라 등 전기자동차 Value Chain 전반의 성장이 예상된다. 따라서 본 논문에서는 변화되고 있는 전기자동차 산업의 발맞춰 기업이 원하는 다양한 고급인력을 양성하기 위해 전기자동차의 에너지 및 전기 요소기술을 선도하는 인력양성 알고리즘을 연구한다.

• 한국대기환경학회지
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• 제26권5호
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• pp.543-553
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• 2010

Almost five million citizens a day are using subways as a means of traffic communication in the Seoul metropolitan. As the subway system is typically a closed environment, indoor air pollution problems frequently occurs and passengers complain of mal-health impact. Especially $PM_{10}$ is well known as one of the major pollutants in subway indoor environments. The purpose of this study was to compare the indoor air quality in terms of $PM_{10}$ and to quantitatively compare its source contributions in a Seoul subway platform before and after installing platform screen doors (PSD). $PM_{10}$ samples were collected on the J station platform of Subway Line 7 in Seoul metropolitan area from Jun. 12, 2008 to Jan. 12, 2009. The samples collected on membrane filters using $PM_{10}$ mini-volume portable samplers were then analyzed for trace metals and soluble ions. A total of 18 chemical species (Ba, Mn, Cr, Cd, Si, Fe, Ni, Al, Cu, Pb, Ti, $Na^+$, $NH_4^+$, $K^+$, $Mg^{2+}$, $Ca^{2+}$, $Cl^-$, and ${SO_4}^{2-}$) were analyzed by using an ICP-AES and an IC after performing proper pre-treatments of each sample filter. Based on the chemical information, positive matrix factorization (PMF) model was applied to identify the source of particulate matters. $PM_{10}$ for the station was characterized by three sources such as ferrous related source, soil and road dust related source, and fine secondary aerosol source. After installing PSD, the average $PM_{10}$ concentration was decreased by 20.5% during the study periods. Especially the contribution of the ferrous related source emitted during train service in a tunnel route was decreased from 59.1% to 43.8% since both platform and tunnel areas were completely blocked by screen doors. However, the contribution of the fine secondary aerosol source emitted from various outside combustion activities was increased from 14.8% to 29.9% presumably due to ill-managed ventilation system and confined platform space.

• 해양환경안전학회지
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• 제28권4호
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• pp.639-647
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• 2022

선박의 건조공정 중 강재의 절단과 곡 가공, 용접에 있어 화염의 사용은 필수적이다. 현재 조선소의 강재 절단과 가공 과정에서는 아세틸렌이 화염 연료로 가장 많이 사용되고 있지만, 폭발 사고의 위험성과 상대적으로 적은 발열량의 한계로 최근에는 프로판 연료의 활용이 증가하고 있다. 하지만 프로판 연료는 상대적으로 가공 속도가 느리고, 가공 시 슬래그의 발생빈도가 높아 품질이 저하된다. 대체 연료로써 프로필렌이 주목받으며 가공 속도와 품질향상에 대한 기대가 증가하고 있다. 프로필렌은 발열량이 우수한 연료로 강재 가공 간 생산성과 가공 품질의 우수성을 갖추고 있다. 이에 본 논문에서는 프로판, 프로필렌 화염을 이용한 철판 가공 시 각 연료의 연소 특성을 분석 및 비교하였다. 프로필렌 화염을 이용한 철판 가공 시 배출되는 온실가스와 유해가스를 프로판 연료의 배출량과 비교하여 저감효과를 실험적으로 확인하였다. 또한, 가공 연료에 따른 입열량이 선박용 강재의 기계적 강도 변화에 미치는 영향을 알아보기 위해 열 분포실험과 인장시험을 수행하였다. 실험 결과로, 대체 연료인 프로필렌을 사용할 때 프로판 연료에 비해 온도분포가 고르게 나타났다. 기계적 강도 실험 결과로 인장강도의 저하는 관찰되지 않았으나, 변형률은 감소하는 경향을 보였다. 본 연구의 결과를 바탕으로 향후 실제 조선소의 강재가공 및 절단과정에 적용하였을 때, 발생하는 문제점에 대한 분석 및 보완연구를 수행할 예정이다.

• 한국응용과학기술학회지
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• 제39권2호
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• pp.368-376
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• 2022

자연발화 현상은 산업현장 또는 우리 생활 속 어디에서나 발생하며 물질이 대기 중에서 점화원 없이 스스로 발화되는 현상이다. 화학반응 속도가 빨라져 발생하는 열이 증가하게 되어 자연발화의 위험성은 더욱 커진다. 본 연구에서는 식품과 화장품 소재로 이용되는 안전한 원료를 배합하여 다양한 자연발화 현상 중 특히 석탄 자연발화 방지제를 제조하였다. 인도네시아산 저열량, 저급탄에 대한 Lab과 Field Test를 통하여 석탄 자연발화 억제 효과를 확인하였다. 옥외 현장 테스트 결과, 비교군(90일 후 발화)에 비하여 본 연구에서 제조한 발화방지제는 120일 이상 우수한 자연 발화억제 효과를 나타내었으며 실내저탄장에서 50일 동안의 CO의 농도변화를 비교하여 CO 농도 제어 효과를 확인하였다. 비교군인 석탄, 기존의 발화 방지 방법보다 우수한 결과를 확인하였다. 또한, 환경을 고려한 토양 및 수질 시험, 작업 근로자를 고려한 발화방지제의 MSDS, 수질, 안 자극 등의 공인시험을 통하여 환경과 근로자 작업환경의 안전성 등을 연구하여 2024년부터 적용되는 실내저탄장용 석탄 발화방지제의 가능성을 확인할 수 있었다.