• 비파괴검사학회지
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• 제33권5호
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• pp.415-421
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• 2013

CGI는 주철보다 큰 강도 또는 작은 무게가 요구되는 응용에서 인기를 얻고 있다. 최근, 강화흑연강은 디젤 엔진 블록, 터보 하우징 및 배기 매니폴드에 사용된다. 이 논문은 873~1173 K에서 1~24 시간 동안 열화된 CGI340의 기계적 성질의 변화에 따른 음향방출 특성을 평가하였다. 연필심 파괴시험 결과에서, 탁월주파수 및 모재의 속도는 각각 97 kHz와 5,490 m/s이었다. 인장시험에서 모재는 상대적으로 높은 탁월주파수를 얻었다. 그러나 열처리된 재료, 열처리 시간이 길고, 열처리 온도가 높을수록, 낮은 주파수의 영역에서 얻어졌다. 이러한 현상은 장기간의 사용에 의해 나타난다.

• 한국추진공학회지
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• 제17권1호
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• pp.1-8
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• 2013

단일액체추진제 하이드라진 추력기는 간단한 구조, 우수한 추진제 저장성, 깨끗한 반응생성물 기체 등과 같은 장점으로 수많은 우주비행체의 궤도 및 자세제어시스템으로 적용되고 있다. 우주발사체의 자세제어시스템에 적용하기 위한 중형급 하이드라진 추력기가 설계 제작되었으며, 성능검증을 위해 수행된 개발모델 추력기의 지상연소시험 결과를 추력, 임펄스 비트, 그리고 엔진 구성품별 온도 및 압력 등을 통하여 제시한다. 개발모델 엔진은 매우 우수한 추력 응답성과 재현성을 보였고, 그 추력성능 효율은 이론설계치 대비 93% 이상임을 확인할 수 있었다.

• 한국항행학회논문지
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• 제21권3호
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• pp.300-305
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• 2017

주행중인 차량내의 컴퓨터 시스템과 통신을 효과적으로 연계해서 언제, 어디서나 각종 데이터의 검색이나 수정 등이 가능하고, 제한적인 플랫폼에서 원활한 동작을 하기 위해 장비를 적절히 제어할 수 있도록 주행차량에 맞게 시스템이 구축되어야 한다. 또한 시스템 엔진 정보 추출을 위해 차량 CAN 통신을 이용하고, 이러한 정보 전송을 위해 ZigBee을 이용하여 데이터를 전송한다. 따라서 차량 CAN을 위해 차량에서 자체 제공되는 OBD-II 프로토콜을 사용하여 차량의 각종 센서 정보 및 O2 센서 값을 이용하여 차량 상태 정보와 배기 가스양을 구하고 ZigBee 메인 컨트롤 시스템에 전송한다. 본 연구는 저전력 차량용 임베디드 시스템으로 전력 사용량을 최대로 줄여서 배터리 부하의 데미지를 최대한으로 감소시키고, ZigBee 통신을 통한 차량의 내부 상태 모니터링을 할 수 있는 시스템을 구현하였다.

• Journal of Advanced Marine Engineering and Technology
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• 제40권6호
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• pp.499-503
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• 2016

배기가스의 배출을 현저하게 저감시켜 강화된 환경규제에 적합한 DF 엔진의 고압 가연성 가스를 공급하기 위한 이중관 가스 벨로우즈의 연구개발에 대한 필요성이 대두되고 있다. 본 연구에서는 최적화된 이중관 벨로우즈의 개발을 위한 것으로, 내식성재료인 오스테나이트계 스테인리스강에 대하여 이중관으로 벨로우즈화하는 성형방법과 최적화된 용접 조건을 도출하여 다양한 성능평가를 통해 생산된 시제품의 신뢰성을 확보하기 위한 연구를 수행하였다. 본 연구의 제1보에서는 최적화된 벨로우즈를 설계하기 위하여 구조설계, 좌굴해석 및 응력해석을 통해 좌굴 발생 하중 및 벨로우즈 응력을 해석하였다. 그 결과 엠보싱 형상을 가진 벨로우즈의 경우 좌굴 발생 하중이 약 1.6배 증가하였으며, 최대 설계압력보다 2배인 30.0 bar에서 어떠한 좌굴 및 스컴이 발생하지 않는다는 것을 확인하였다.

• 한국자동차공학회논문집
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• 제22권2호
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• pp.60-66
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• 2014

A control oriented model of the Lean $NO_x$ trap (LNT) was developed to determine the timing of $NO_x$ regeneration. The LNT model consists of $NO_x$ storage and reduction model. Once $NO_x$ is stored ($NO_x$ storage model), at the right timing $NO_x$ should be released and then reduced ($NO_x$ reduction model) with reductants on the catalyst active sites, called regeneration. The $NO_x$ storage model simulates the degree of stored $NO_x$ in the LNT. It is structured by an instantaneous $NO_x$ storage efficiency and the $NO_x$ storage capacity model. The $NO_x$ storge capacity model was modeled to have a Gaussian distribution with a function of exhaust gas temperature. $NO_x$ release and reduction reactions for the $NO_x$ reduction model were modeled as Arrhenius equations. The parameter identification was optimally performed by the data of the bench flow reactor test results at space velocity 50,000/hr, 80,000/hr, and temperature of $250-500^{\circ}C$. The LNT model state, storage fraction indicates the degree of stored $NO_x$ in the LNT and thus, the timing of the regeneration can be determined based on it. For practical purpose, this model will be verified more completely by engine test data which simulate the NEDC transient mode.

• 한국대기환경학회지
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• 제27권6호
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• pp.663-671
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• 2011

Although a scooter is a convenient transportation means for a short distance traveling with a light package in the congested urban center, it might be one of the significant sources of air pollutants to which many people can easily be exposed during its passing-by. In this paper, we measured concentrations of gases and particles emitted from a scooter at roadside with no other traffic. To understand the characteristics of scooter emissions with respect to driving speed (idling, 30 km/h) at the roadside, total particle number concentration, particle size distribution, average surface area of particles deposited in the alveolar region, and concentrations of black carbon, CO, and $NO_x$ were measured. The concentrations of the particle number, surface area of deposited particles, CO, and $NO_x$ were highly fluctuated in the scooter's idling condition. The trends of particle number concentration, CO, and $NO_x$ generation were similar to one another. When the scooter started to move, all of $NO_x$, CO and particle number concentrations increased and after it passed by at the speed of 30 km/h, the concentration peaks of the particles and gases appeared at the same time. Unimodal size distribution with ~70 and ~93 nm mode diameters was observed for the idling and cruising condition, respectively. From this work, we found that emission from a passing vehicle could be characterized using a roadside monitoring technique.

• 한국자동차공학회논문집
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• 제23권4호
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• pp.410-419
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• 2015

In this study, the roadability, fuel economy and emission characteristics were evaluated for a natural gas converted vehicle. The results are as follows; Not only the shortage of power was observed in stall test, but also large deterioration of acceleration performance was exposed in roadability. Compared to the original LPG system, the acceleration is 76% in start acceleration and 45 ~ 65% in overtaking acceleration, especially the decline became larger when air conditioner is at work. Furthermore, because the mapping data, which controls the injection depending on driving condition, do not match up with injection system, the failure of air-fuel ratio feedback control occurs resulting from the large gap between the required and the really supplied amount of fuel. This failure cause the exhaust gas to emit without catalytic conversion and the fuel economy based on the fuel heat value to get worse 22% in the mode test and 16% in road test respectively. In addition, the existing injection system does not secure enough fuel at the starting so that it may lead to the fail of clod start, the deterioration of hot start and inharmonic of engine at the idle after start.

• 한국자동차공학회논문집
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• 제15권4호
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• pp.101-107
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• 2007

This study investigated the wear of the valve and seat insert seating faces. A tester, an exhaust valve and a seat insert were used. Test variables were cycle numbers ($2{\times}10^6,\;4{\times}10^6,\;6{\times}10^6\;and\;8{\times}10^6$) and Hz (10Hz and 25Hz). The other test conditions such as temperature ($350^{\circ}C$), fuel (LPG) and load (1960N) were fixed. The 10Hz tests indicated that the average Rmax of the valve increased at the rate of $7.76{\mu}m/10^6$ cycles starting from $29.42{\mu}m$ at the $2{\times}10^6$ cycles and that of the seat insert increased at the rate of $8.57{\mu}m/10^6$ cycles starting from $34.19{\mu}m$ at the $2{\times}10^6$ cycles. The 25Hz tests indicated that the average Rmax of the valve increased at the rate of $1.58{\mu}m/10^6$ cycles starting from $74.2{\mu}m$ at the $2{\times}10^6$ cycles and that of the seat insert increased at the rate of $1.25{\mu}m/10^6$ cycles starting from $83.95{\mu}m$ at the $2{\times}10^6$ cycles. The tribochemical reaction product covered the two seating faces, preventing the wear of the seating faces. As cycle numbers became greater, the average Rmax of the seating faces became greater, but the increase rate varied significantly depending on the Hz. The wear mechanism of the two faces was investigated through the tribochemical reaction.

• Journal of Biosystems Engineering
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• 제39권1호
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• pp.21-33
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• 2014

Background: Significant technological development and changes happened in the tractor industries. Contrariwise, the test procedures of the major standard development organizations (SDO's) remained unchanged or with a little modification over the years, demanding new tractor test standards or improvement of existing ones for tractor performance, safety, and comfort. Purpose: This study focuses on reviewing the research trends regarding performance, safety and comfort evaluation of agricultural tractors. Based on this review, few recommendations were proposed to revise or improve the current test standards. Review: Tractor power take-off power test using the DC electric dynamometer reduced human error in the testing process and increased the accuracy of the test results. GPS signals were used to determine acceleration and converted into torque. High capacity double extended octagonal ring dynamometer has been designed to measure drawbar forces. Numerical optimization methodology has been used to design three-point hitch. Numerous technologies, driving strategies, and transmission characteristics are being considered for reducing emissions of gaseous and particulate pollutants. Engine emission control technology standards need to be revised to meet the exhaust regulations for agricultural tractors. Finite Element Analysis (FEA) program has been used to design Roll-Over Protective Structures (ROPS). Program and methodology has been presented for testing tractor brake systems. Whole-body vibration emission levels have been found to be very dependent upon the nature of field operation performed, and the test track techniques required development/adaptation to improve their suitability during standardized assessment. Emphasizes should be given to improve visibility and thermal environment inside the cab for tractor operator. Tractors need to be evaluated under electromagnetic compatibility test conditions due to large growing of electronic devices. Research trends reviewed in this paper can be considered for possible revision or improvement of tractor performance, safety, and comfort test standards.

• Safety and Health at Work
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• 제8권1호
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• pp.29-35
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• 2017

Background: Despite our knowledge of the causes of cancer, millions of workers are involuntarily exposed to a wide range of known and suspected carcinogens in the workplace. To address this issue from a policy perspective, we developed a policy framework based on a prospective health policy analysis. Use of the framework was demonstrated for developing policies to prevent cancers associated with diesel engine exhaust (DEE), asbestos, and shift work, three occupational carcinogens with global reach and large cancer impact. Methods: An environmental scan of existing prospective health policy analyses was conducted to select and describe our framework parameters. These parameters were augmented by considerations unique to occupational cancer. Policy-related resources, predominantly from Canada, were used to demonstrate how the framework can be applied to cancers associated with DEE, asbestos, and shift work. Results: The parameters of the framework were: problem statement, context, jurisdictional evidence, primary prevention policy options, and key policy players and their attributes. Applying the framework to the three selected carcinogens illustrated multiple avenues for primary prevention, including establishing an occupational exposure limit for DEE, banning asbestos, and improving shift schedules. The framework emphasized the need for leadership by employers and government. Conclusion: To our knowledge, this is the first proposal for a comprehensive policy framework dedicated to the primary prevention of occupational cancer. The framework can be adapted and applied by key policy players in Canada and other countries as a guide of what parameters to consider when developing policies to protect workers' health.