• 한국기계가공학회지
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• 제20권8호
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• pp.80-85
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• 2021

This study is to evaluate the structural stability of heavy duty structure of the Complex CNC automatic lathe. The analysis conditions were analyzed by applying the weight and load of the part itself and then applying the weight of the upper assembly unit. As a result of the structural analysis, the values of stress and strain are small and safety factor is high, and as a result of the dynamic analysis, there will be no resonance outside the equipment driving area, so there will be no problem in equipment stability.

• 공업화학전망
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• 제24권4호
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• pp.22-35
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• 2021

현재 수소전기차는 승용 및 상용 등 다양한 모빌리티 분야에서 전 세계적으로 이슈가 되고 있다. 환경규제 강화, 신기후체제 출범 등의 변화의 물결에 따라 자동차산업의 패러다임이 친환경으로 전환되고 있으며, 세계적으로 관련 기술 개발 및 보급을 위한 확대 정책이 발표되고 있다. 1990년 초 수소전기차(Fuel Cell Electric Vehicle, FCEV) 기술 개발이 진행되어 1994년 독일 다임러사가 세계 최초로 NECAR1을 개발하였다. 이후 많은 완성차가 상용화를 위해 기술개발이 진행되었으며, 2013년 국내 현대차가 세계최초로 양산차인 투싼 ix 수소전기차를 출시하였다. 1년 이후 다시 일본 도요타에서 세계 최초로 전용 차체를 적용한 미라이 수소전기차가 출시되면서 초기시장이 형성되었으며, 이후 현대차는 NEXO를 2018년에 발표하였다. 전 세계적으로 가장 많이 팔린 수소전기차에 해당된다. 2021년 미라이 2세대가 더욱 진보된 기술을 바탕으로 출시되었으며, 국내 현대차에서도 2세대 수소전기차 출시를 앞두고 있다. 또한 수소승용차 뿐만 아니라 수소상용차 시장이 뜨겁게 부각되고 있으며, 각국에서 수소상용차 기술개발을 진행하고 있다. 본 기획특집에서는 각국의 수소전기차 기술개발 및 보급 정책을 소개하고 국내 기술개발 및 보급 정책의 타당성을 확인하고자 하였다.

• 융복합기술연구소 논문집
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• 제11권1호
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• pp.19-23
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• 2021

These days, sales of battery electric vehicles have been rapidly increasing due to the strict CO₂ regulations. However, since it take too long to measure the energy economy of electric vehicles, it has been required to improve the procedure of energy economy measurement. In order to improve this problem, the present study analyzed the battery charge/discharge pattern according to the changes in battery SOC (state of charge). In general, the energy economy test is started with a battery SOC charged to 100 %. However, it was identified that when the battery is fully charged, it can actually be charged over the 100 % (e.g., 100.5 %). This can induce errors in the energy economy measurement. Therefore, the present study recommend to start the test at SOC 99.9 %. The regenerative braking was partly restricted for the SOC over 90 %. This made it difficult to estimate the overall energy economy of the electric vehicle. However, it was identified that there was no change in the battery charge/discharge characteristics under the SOC 90 %. Therefore, the energy economy test can be shortened by predicting the overall energy economy through a short mileage test.

• 한국정밀공학회지
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• 제12권5호
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• pp.88-97
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• 1995

The leaf spring is used in the suspension of most buses and trucks due to its compactness, which reduces the shock-force and the vibration from the road, and increases passenger comfortability and carlife. Of the various kinds of leaf springs, the leaf spring without eyes can be found easily in the heavy duty truck, and has different characteristics to the leaf spring with eyes in the case of large free camber. Because of radius change, the leaf without eyes slips on the supports, which makes the deflection. The difference is due to this deflection. In this paper, we show the general method of characteristic analysis, for example, Pandan method, can be no more applicable to these springs. Thus considering the geometry deflection by slip, we have developed the equation of the characteristic of the leaf spring without eyes and prove the effectiveness of this equation by experiment. From the result, at large camber the slip deflection is large and as camber smaller, this is smaller. At the camber behind some value, the effect of slip no longer influence to the characteristic of leaf springs.

• 한국분무공학회지
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• 제29권2호
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• pp.60-67
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• 2024

This study compared exhaust gas recirculation (EGR) and excess air strategies for improving thermal efficiency and emissions of hydrogen combustion engines at low-load operation. The experimental investigation was conducted in a single-cylinder, heavy-duty engine under throttling and wide-open throttle (WOT) conditions. Although both EGR and excess air strategies reduced peak heat release rates and increased combustion durations, the net indicated thermal efficiencies were improved by reducing the pumping losses. Under the constraint of similar nitrogen oxides emissions, the EGR strategy had higher net indicated thermal efficiencies compared to the excess air strategy in throttling operation. However, the difference between their thermal efficiencies was reduced under WOT condition. The trend of reducing nitrogen oxides emissions according to the two strategies was similar.

• 한국음향학회지
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• 제38권2호
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• pp.161-167
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• 2019

본 논문은 트랙기반 중작업용 ROV(Remotely Operated underwater Vehicle)에 적용 가능한 어라운드 뷰 소나 및 굴착깊이 측정 소나의 성능 검증에 대한 내용을 다루고 있다. 현재 국산화 개발 중인 중작업용 ROV에 활용 가능한 어라운드 뷰 소나 및 굴착깊이 측정 소나를 장착하여 수조 및 실해역에서 성능 검증 실험을 수행하였다. 어라운드 뷰 소나의 경우 이미지 소나를 ROV 전후좌우 4방향에 장착하고, 굴착깊이 측정 소나는 멀티 빔 음향측심기(Multi Beam Echo Sounder, MBES) 기술로써 ROV 전방에 장착된다. 본 논문에서 개발한 소나를 장착하고 ROV를 실해역에 진수시켜 소나를 운용한 결과 소나 시스템들은 작업 중 발생하는 침전된 부유물이 발생하거나 탁도가 높은 해역에 영향을 거의 받지 않으며 어라운드 뷰 소나의 경우 ROV 전방 30 m 거리에 있는 암반지형, 자갈, 모래톱 등을 확인할 수 있었다. 그리고 굴착깊이 측정 소나의 경우 ROV가 굴착 작업을 수행 후 굴착 깊이를 측정 가능함을 확인하였다. 본 논문에서 제안한 어라운드 뷰 소나와 굴착깊이 측정 소나를 활용함으로써 작업효율성을 높일 수 있음을 입증하였다.

• 의료법학
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• 제9권1호
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• pp.319-382
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• 2008

As a withdrawing care's study, the purpose of this study is searching about withdrawing care's acceptance and circumstances through Bora-mae hospital case(chapter 1). Withdrawing life-sustaining treatment has various forms. Though the meaning of euthanasia, death with dignity, natural death, physician assisted suicide are duplicated, the meaning of those are different slightly. Firstly, this study looks about the difference of the those meaning and acceptance range(condition) by withdrawing care's forms(chapter 2). Bora-mae hospital case sentenced guilty about physician who discharged incompetent patient who was after surgery by patient's wife determination. This Bora-mae case that sentenced guilty about discharge against medical advise(DAMA) that is regarded to custom has brought intensive confliction of legal, social, medical aspect, Bora-mae hospital case has many legal problems. First, as to criminal law rule 250(murder), the problem is whether discharge and withdrawing life-sustaining treatment is commission or omission. this study concluded omission(district court: omission, appeal, supreme court: commission). Because legal denounce point of discharge and medical treatment withdrawing is omission that physician who is obligatory on patient to cure. If physician's act is regarded omission, it is necessary to determine whether he has guardian status and obligation. Without guardian status and obligation, omission crime can't exist. This study decided that physician had guardian status and obligation and foundation of guardian status was pre-action or acceptance of emergency patient. Physician's medical treatment duty finished when patient(or patient's guardian) demands discharge. But when patient death is foreseen and other possible treatment does not exist, his duty of life prolonging treatment does not finish. This originate from physician's social responsibility and public status that limits patient's private liberty. This study regarded physician's action as accomplice about whether physician's discharging action is accomplice or the principal offender(district court: the principal offender, appeal, supreme court: accomplice). Though the principal offender needs criminal determination and action, there is no this common determination and functional action control of physician in Bora-mae case(chapter 3). Bora-mae hospital case partly originated from deficiency of legal, institutive system including medical security system shortage, the instruction is 1. medical security system strengthening, 2. hospital ethical committee's activity strengthening, 3. institutionalization of withdrawing life-sustaining treatment, 4. acceptance of pre-decision making system, 5. sufficient persuasion of physician for patient and faithful writing of medical paper, 6. respect for patients' self-determination and rights, 7. consciousness's changing for withdrawing life-sustaining treatment and persistent education about medical ethics(chapter 4). Considering Bora-mae case, medical sector is not the dead ground of a criminal punishment. Intervention of criminal law in medical sector give rise to ill effect, that is, excess medical examination and treatment, safeguard treatment, delay of discharge from a hospital. Because sufficient guarantee of life becomes mere empty slogan under situation that impose a burden of heavy cost to family or hospital, public and systematic solution should be given(chapter 5).

• 한국학교보건학회지
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• 제23권1호
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• pp.63-70
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• 2010

Purpose: To identify the need to reform in the crisis response of Health Teacher, School Nurse, in elementary school during epidemic outbreak of influenza H1N1. Methods: 139 elementary health teachers, school nurse, in seoul elementary school responded in the questionnaire, and we analysed by using frequency and percent, t-test, and paired t-test. Results: The Job status became 121% more 'during influenza H1N1 (flu) outbreak' than Job status of 'before outbreak'. The proportion of the flu-related duty among their daily workload was up to 77.5%. The administration-related workload of the flu-related duty was 30.8%. and students' health assessment including temperature measurement 18.7%. Furthermore, an impediment of usual daily work due to an increaed flu-related workload was 95.7%, and no alternative plan such as disposition of assistant labor force was 86.1%. Especially, an impediment of health education was 61.0%, so the major concern was the loss of health education. We compared average scores (a five-point Likert scale) of health teachers' work motivation, exhaustion, work relationship and Job management of 'during' with 'before' flu-outbreak. The difference range of 'during' minus 'before' work motivation score was from -0.4 points to -0.9; work exhaustion range from 1.8 to 1.9; the difficulty of relationship between students, school personnel, parents of students, and health teachers from 1.4 points to 1.3 points; and the consideration of changing Job, taking time off from the Job and retirement from 1.4 to 1.6 points. Conclusion: The health teachers had a heavy workload due to flu-outbreak. They also experienced the impediment of usual work implementation. However, there was a shortage of alternative plan such as disposition of an assistant labor force. Under their Job status like this, the health teachers' motivation score was decreased and work exhaustion was increased. Furthermore, they had a lot of relation difficulty with students and school personnel. Therefore, we suggested that in contrast to the usual Job status, there is a need to have a prepared response during school crisis like flu-outbreak such as improved response system in seoul metropolitan education office, simplification or dispersion of administrative work, and temporary call-center for simple inquiries or advices.

• 한국자동차공학회논문집
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• 제22권3호
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• pp.171-178
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• 2014

From now on, in order to meet more stringer diesel emission standard, diesel vehicle should be equipped with emission after-treatment devices as NOx reduction catalyst and particulate filters. Urea-SCR is being developed as the most efficient method of reducing NOx emissions in the after-treatment devices of diesel engines, and recent studies have begun to mount the urea-SCR device for diesel passenger cars and light duty vehicles. That is because their operational characteristics are quite different from heavy duty vehicles, urea solution injection should be changed with other conditions. Therefore, the number and diameter of the nozzle, injection directions, mounting positions in front of the catalytic converter are important design factors. In this study, major design parameters concerning urea solution injection in front of SCR are optimized by using a CFD analysis and Taguchi method. The computational prediction of internal flow and spray characteristics in front of SCR was carried out by using STAR-CCM+7.06 code that used to evaluate $NH_3$ uniformity index($NH_3$ UI). The design parameters are optimized by using the $L_{16}$ orthogonal array and small-the-better characteristics of the Taguchi method. As a result, the optimal values are confirmed to be valid in 95% confidence and 5% significance level through analysis of variance(ANOVA). The compared maximize $NH_3$ UI and activation time($NH_3$ UI 0.82) are numerically confirmed that the optimal model provides better conversion efficiency of $NH_3$. In addition, we propose a method to minimize wall-wetting around the urea injector in order to prevent injector blocks caused by solid urea loading. Consequently, the thickness reduction of fluid film in front of mixer is numerically confirmed through the mounting mixer and correcting injection direction by using the trial and error method.

• 한국대기환경학회지
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• 제24권1호
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• pp.72-82
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• 2008

Benzene is a very harmful and toxic compound known as human carcinogen by all routes of exposure. Owing to the risky feature of benzene, several countries such as Japan, UK and EU have established the ambient air quality standard and protect from that risk of it. Korea also has designated it as one of the criteria air pollutants and established the concentration limit ($5\;{\mu}g/m^3$) in the air and is going to apply the standard from 2010. Benzene is emitted from various sources such as combustion plants, production processes, waste treatment facilities and also automobiles. Mobile source is known as one of the major emission sources of benzene. In this study, we estimated the domestic emissions of benzene from mobile source and compared the results with those of advanced countries. Mobile source was divided into 2 categories, Le., on-road source and non-road source. The total emissions of benzene from mobile source were estimated as 3,106 tons/yr and 1,612 tons/yr was emitted from on-road source and 1,494 tons/yr was from non-road source. Emission ratio of benzene from on-road source showed that 80.0% was from passenger cars, 10.1% was from taxis, 7.2% was from light-duty vehicles, 2.5% was from heavy-duty vehicles and 0.2% was from buses. In the case of non-road source, the distribution showed that 66.3% was from construction machineries, 14.5% was from locomotives, 11.7% was from ships, 7.1% was from agriculture equipments and 0.5% was from aircrafts. The cold-start emissions were estimated as 942 tons/yr and this value was almost 1.5 times greater than that for hot engine emissions (608 tons/yr). In addition, the fuel-based distribution was 65.9%, 31.1% and 2.8% from gasoline, LPG and diesel vehicles, respectively. The emission ratio from mobile source occupied 65% and 30% of total benzene emissions in USA and UK, respectively. In case of Korea, the emission ratio of benzene from mobile source occupied 29% (15% from on-road source, 14% from non-road source) which showed similar value with UK.