• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.8
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• pp.637-648
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• 2021

This paper aims to propose new reentry guidance for Korean Space plane (KSP). Similar to the Space Shuttle guidance concept, a reference drag profile is first determined to satisfy several flight path constraints and boundary conditions, and the proposed guidance commands are realized in a way to track the predetermined reference drag profile. To this end, the drag dynamics is examined. The investigation uncovers that the dynamics characteristics of the drag and the flight path angle are considerably different. Based on this fact, the proposed guidance commands are determined using the time-scale separation technique and the feedback linearization methodology. The key feature of the proposed guidance lies in its simple structure and a clear working mechanism. Therefore, the proposed method is simple to implement compared to existing methods. Numerical simulations are performed to investigate the performance of the proposed method.

• Proceedings of the Korea Contents Association Conference
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• 2012.05a
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• pp.81-82
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• 2012

대리운전업은 서비스업으로 세무서에 신고만 하면 사업자 등록을 하고 사업을 할 수 있고, 설사 신고를 하지 않고 영업을 하더라도 규제할 방법이 마땅치 않아 진입장벽이 없는 상태이며 대리운전업에 대한 규제법은 전무한 상태이다. 이들이 법적 관리로부터 방치되어 있는 결과 대리운전행위의 사회적 편익에도 불구하고 요금시비 등 서비스의 질, 생계형 운전미숙자의 진입, 주로 야간에 다수의 낮선 차량을 운전하여야 하고 겸업이 47.3%에 이르러, 과중한 노동으로 인한 피로누적, 주의력 산만, 과속경쟁 등 대리운전의 속성상 교통사고 발생위험, 사고발생시 피해보상책임, 절도나 성폭력행위와 같은 범죄유발 등 여러 가지 문제가 끊이지 않고 있다. 관련업계나 일부 단체에서는 대리운전업 종사자가 15만 명을 넘어섰다고 주장하며 당당한 직업으로 인정해 달라고 요구하고 있고, 근로형태나 조건 등 사업자 내부의 문제도 제기된다. 본고(本稿)에서는 대리운전으로 발생하는 범죄의 현황과 대책을 개괄적으로 조망하고자 한다.

• TTA Journal
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• s.41
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• pp.81-112
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• 1995

최근 전기통신시장의 단일화가 추구되면서 그동안 각국이 자국의 실정에 맞게 운영해 오던 단말장치의 형식승인제도가 범 세계적 흐름인 통신정책의 규제 완화 및 각국간의 원활한 무역을 위한 불필요한 기술장벽 해소라는 변화된 환경속에서 자국의 통신시장 보호수단으로 활용되고 있으며, 한편으로는 지역간/국가간의 형식승인 상호인정을 통한 효율적인 운영 제도의 조화로 무역확대를 꾀하고 있다. 이에 본 고는 세계 각국이 보다 유리한 통신시장의 진입조건을 확보하기 위해 각국의 형식승인제도에 대한 운영 현황에 관한 정보를 파악하는 것을 급선무로 여기고 있는 현실을 감안하여, 미국, 일본, 호주, 캐나다, 영국 및 우리나라에 대한 형식승인제도 현황을 분석하였다. 또한, 이러한 형식승인제도가 어떠한 방법으로 지역간/국가간의 형식승인 상호인정 추진과 맥락을 같이 하는지 살펴보았다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.4
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• pp.350-358
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• 2009

This paper describes a result of the guidance and control for re-entry vehicle during TAEM phase. TAEM phase (Terminal Aerial Energy Management phase) has many conditions, such as density, velocity, and so on. Under these conditions, we have optimized trajectory and other states for guidance in TAEM phase. The optimized states consist of 7 variables, down-range, cross range, altitude, velocity, flight path angle, vehicle's azimuth and flight range. We obtained the optimized reference trajectory by DIDO tool, and used feedback linearization with neural network for control re-entry vehicle. By back propagation algorithm, vehicle dynamics is approximated to real one. New command can be decided using the approximated dynamics, delayed command input and plant output, NARMA-L2. The result by this control law shows a good performance of tracking onto the reference trajectory.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.153-153
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• 2017

본 연구에서는 농작업지내 모서리 점을 이용하여 자율주행 트랙터의 경로점을 생성하는 알고리즘을 개발하였다. 작업지는 직사각형의 형태에서 거리가 긴 방향으로 직선주행 경로로 하고, 직선경로의 수는 작업폭에 의해 결정되며 홀수 또는 짝수 개일 수 있다. 또한 TM좌표계에서 직선주행 경로의 기울기는 양수 또는 음수 일 수 있으며, 선회시 전체적으로 좌회전 또는 우회전하는 경우로 구분하여, 즉 총 8가지의 경우에 대하여 조건이 주어지면 경로점을 구할 수 있도록 프로그램하였다. 선회를 위한 곡선경로 생성에는 트랙터의 최소 회전반경 데이터를 사용하였으며, 이때 새로 진입할 다음 경로가 충분히 떨어져 있는 경우에는 선회 구간에서도 직선 경로 구간이 생길 수 있음을 고려하였다. 한 주기의 경로점은 직선 경로 구간의 시작점과 끝점, 선회 구간의 시작점과 끝점, 다음 직선경로로 진입을 위해 선회하기 직전까지의 직선 구간에 대한 시작점과 끝점 등 6가지의 경우로 구분할 수 있다. 이때 어떤 끝점 경로점은 다음 조작 구간의 시작점 경로점이 되므로 최종적인 경로점 데이터는 4개가 된다. 여기서, 첫 번째 경로점 생성에서는 직선구간 진입을 위한 선회구간의 시작점과 끝점은 제외하였으며, 작업지로 진입할 수 있는 입구와 출구는 동일한 것으로 가정하여, 작업이 완료되는 지점에서 선회하여 다시 출발점으로 돌아올 수 있도록 추가 구성하였다. 실제 상황에서는 직선주행 경로의 수가 정수가 되지 않을 수 있으며, 이때는 작업 구간이 약간씩 오버랩되도록 작업폭을 조정하여 경로의 수가 항상 정수가 되도록 하였다. 알고리즘 평가에 사용된 작업 패턴은 관행적인 방법으로서 작업 포장을 반으로 나누어 8자형 패턴을 이용하였다.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.9 no.6
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• pp.83-93
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• 2010

The roundabout is a green transportation system which reduces the accident, the congestion cost and greenhouse effect. The purpose of the study is to analyze the multi-legged roundabout's efficiency. In pursuing the above, this study gives particular attention to building the optimal network of multi-legged roundabout and intersections, developing the scenarios for analysis reflected by the proportion of entering traffic volume of main and minor roads, and comparatively analyzing the average delay per car using VISSIM. The main results are as follows. First, when the entering traffic volume are less than 3,500pcph, the 5-legged single and double-lane roundabout are all analyzed to be more effective than intersection. Second, when the entering traffic volume are less than 3,600pcph, the 6-legged single-lane roundabout is analyzed to be more effective than intersection. The 6-legged double-lane roundabout is analyzed to be more effective than intersection. The 6-legged double-lane roundabout is analyzed to be more effective than intersection in all cases of entering volume.

• Journal of the Korean Society for Railway
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• v.16 no.6
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• pp.454-459
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• 2013

Pressure waves are generated and propagate in a tunnel when train enters tunnel high speed. A compression wave due to the entry of train head propagates along the tunnel and is reflected at tunnel exit as an expansion wave. An expansion wave due to the entry of the train tail propagates along the tunnel and is reflected at tunnel exit as a compression wave. These pressure waves are repeatedly propagated and reflected at the tunnel entrance and exit. Severe pressure changes causes ear-discomfort for passengers in the cabin and micro pressure waves around the tunnel exit. It is necessary to analyze the transient pressure phenomena in tunnels qualitatively and quantitatively, because pressure change rate is considered as one of the major design parameters for optimal tunnel cross sectional area and repeated fatigue force on car body. In this study, we developed a characteristics method based on a fixed mesh system and boundary conditions for crossing trains and analyzed this system using an X-t diagram. The results of the simulation show that offsetting of pressure waves occurs for special entry conditions of a crossing train.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.15 no.1
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• pp.247-257
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• 2020

In recent years, the proportion of youth's self-employed is steadily increasing, and government policy also actively encourages youth to become an entrepreneur. However, most of the domestic precedent studies on the self-employed labor market focus on the middle-aged and the elderly, and previous studies on the self-employed labor market of young people are hardly ever studied. Above all, the study that examines the factors of entry into self-employment of young people is not sufficient and researchers usually utilize the study about for all ages to explain the self-employment market of young people. However, because the young and middle-aged people differ in labor market conditions, family backgrounds, and the level of accumulation of human capital, separate explanations and theories are needed. Therefore, this study explored the factors of entry into self-employment by separating the age group from 15~29 years old. The data used in the analysis was the 9th to 20th data of the Korea Labor Panel Survey. The youth unemployment rate and employment rate were referred to the Economically Active Population Survey of Statistics Korea. The analysis subject was limited to young people who are currently performing economic activities, and the analysis method used multi-level logit model. The main results are summarized as follows. First, the lower the unemployment rate and the higher the employment rate, the younger people tend to enter their own businesses on the structural level. Second on the individual level, young people who possess enough financial capital or pursuit personal aptitude or interest tend to enter self-employment. However, there are no statistical effects of human capital and entrepreneur capital.

• Korean Journal of Social Welfare
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• v.52
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• pp.5-32
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• 2003

This paper examines the labor entry of conditional welfare recipients. This paper focuses on two questions. First, what is the percentage of conditional welfare recipients who have labor entry? Second, what are the predictors in the labor entry and the duration to the entry? Using Data about 917 welfare recipients who participated in the self-sufficiency programs of the Offices for Secure Employment in Seoul, this paper attempts to answer the above questions. Logistic regression analysis and survival analysis are adopted to identify variables predicting labor entry of conditional welfare recipients. This paper also utilizes a multiple imputation method to deal with the limitation of data by the missing values in some variables. The major findings are as follows: about 43.8% of the conditional welfare recipients have successful labor entry; and in the labor entry and the duration to the entry, gender, household, information and referral services for employment, health and willingness for self-sufficiency are the predictors that are statistically significant. Among these variables, health and willingness for self-sufficiency are more noticeable; it is recognized that programs to care for health of welfare recipients who want to have the labor entry and counseling programs to strengthen welfare recipients' willingness for labor entry are very important for them to be successful in the labor entry. This paper provides a basic knowledge about realities of the conditional welfare recipients' labor entry, identifies research areas for further research, and develops policy implications for their self-sufficiency.

• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.1
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• pp.40-46
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• 2015

Arctic Ocean has rapidly melted due to global warming, by this, commercial ship has been operating through the area. Reason to develop the Northern Sea Route(NSR) even in extreme conditions, the distance than the existing route is shortened, which bring economic benefits. For these reason, the International Maritime Organization(IMO) established safety standards of the Arctic navigation(Polar Code) in order to ensure safe operation in the Northern Sea Route. In this study, it has been described ice types and safety standards of Artic vessel what officer needs to know for safe navigation on the Arctic Ocean. And It was verified by simulation the theoretical knowledge for the safe operation of the Arctic vessel. As a result, it was found that ship needs to reduce speed and analyze ice for safe operation before enter into the ice, it is necessary to enter at right angle to break ice safety and efficiently. Also according to the result of the simulation of navigation entering in ice channel(Lead), it was difficult to change course, it is believed that require emergency training for passing Vessel. In the future, It shall be analyzed precisely under various conditions of scenario.