• 한국정보통신학회논문지
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• 제17권6호
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• pp.1292-1305
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• 2013

자동차에 환경 관련 규제가 강화되고 있으나 대체 에너지 개발 이전에 에너지 절감 기술에 대한 필요성이 대두되어 차량의 공회전 상태 시 엔진 구동을 정지시키는 공회전 방지 시스템에 대한 연구가 자동차 제조사 중심으로 연구되어 왔다. 이와 함께 관심도가 높은 차량용 스마트키 시스템에 공회전 방지 시스템을 융합하여 소비자의 구매 욕구를 높임과 동시에 편의성에 대한 장점을 높이고 에너지도 절약하여 친환경적인 공회전 방지 시스템을 보급하기 위한 움직임도 보이고 있다. 본 논문에서는 하나의 전자제어장치에서 두 개의 상이한 시스템을 제어해 친환경적인 공회전 방지 기능과 지능적인 스마트키 기능을 동시에 사용할 수 있는 OBD-II 인터페이스를 이용한 사후 시장용 스마트키 시스템에서의 공회전 방지 알고리즘을 구현하였다. 구현된 공회전 방지 알고리즘은 차량과의 통신 인터페이스를 표준화함으로써 다양한 차종에 대해 시스템을 실제 차량에 장착하는 시간을 단축하였고, 차량 상태 요청신호에 대한 표준 응답 제한시간을 만족함으로써 시스템 제어 시 통신 응답 지연 시간으로 인한 장애가 발생하지 않음을 확인하였다.

• 대한전자공학회논문지TE
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• 제39권1호
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• pp.71-76
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• 2002

차량의 폭발적 증가로 인해 저속, 서행형태로 주행시간이 점점 늘어나므로, 본 연구에서는 연비향상을 목적으로 정차상태에서는 일부 실린더만으로 일정한 엔진회전수를 유지하고, 주행상태에서는 전 실린더를 이용하는 가변실린더에 대해 실제 하드웨어로 제작하여 실험해 보았다. 과거에 일부 제작되었던 가변실린더 엔진은 정차상태나 저속상태에서 사용하는 실린더 주위에 열이 집중하여 열응력이 발생하고, 사용하지 않는 실린더는 냉각수의 순환으로 인해 주변의 온도가 더욱 떨어지게 되어, 재점화시에 많은 유해가스가 배출되고 연료 소모량도 많아지게 되며, 엔진회전수가 고르지 못하는 문제가 있었다. 이러한 문제점을 극복하고자 정지상태나 저속주행상태에서와 같이 많은 출력을 요하지 않는 운행조건에서는 새로운 점화방식과 밸브 개폐시기를 이용하여 연비를 향상시키는 방안을 제시하고, 그 타당성을 검증하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계 학술대회논문집(수송기계편)
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• pp.208-211
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• 2005

This paper describes the development process of steering system for reduce idle vibration through the data level of frequency and sensitivity. High stiffness and light weight vehicle is a major target in the refinement of passenger cars to meet customers' contradictable requirements between NVH performance and fuel economy. The target frequency of the steering system is set by benchmarking of a competitive vehicle and the vibration mode map is used to separate steering column modes from resonance of body structure and engine idle rpm. This paper descirbes the analysis approach process for high stiffness of steering system and the design guideline is suggested about steering column and support system by using mother car at initial design stage. We used a patent map in order to analyze accurately a technical trend and suggested the design process using dynamic damper of steering system considering sensitivity. And we established techniques of analysis on steering system and evaluated the level of accuracy of analysis through correlating the test and analysis results. It makes possible to design the good NVH performance vehicle at initial design stage and save vehicles to be used in tests. These improvements can lead to shortening the time needed to develop better vehicles.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.110-113
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• 2006

This paper describes the development process of body and full vehicle for reduced idle vibration through the data level of frequency and sensitivity. The vibration mode map is used to separate body structure modes from resonance of engine idle nm and steering system. This paper describes the analysis approach process to reduce the variation of uncertainties for idle vibration performance at initial design stage. The robust design method is performed to increase the stabilization performance under vehicle vibration. It is used to predict the effects of the stiffness deviation according to the spot welding condition of the body structure. The tolerance associated with hood over slam bumper is analyzed for the quality deviation of the moving system in full vehicle. And the glass sealant stiffness and weight difference is considered for the deviation characteristic. The design guideline is suggested considering sensitivity about body and full vehicle by using mother car at initial design stage. It makes possible to design the good NVH performance and save vehicles to be used in tests. These improvements can lead to shortening the time needed to develop better vehicles.

• Journal of applied mathematics & informatics
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• 제28권1_2호
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• pp.531-537
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• 2010

In this paper, some vacation policies are considered, which can be related to the past behavior of the system. The server, after serving all customers, stays idle or to wait for some time before a vacation is taken. General formulas for the waiting time and the amount of work in the system are derived for a vacation policy. Using the analysis on the vacation system, we derived the waiting time in the sequential bottleneck station.

• 한국기계가공학회지
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• 제12권2호
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• pp.27-33
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• 2013

In this study we analyzed the on-road driving performance of two parallel-type diesel-hybrid buses which have been driven in Daegu metropolitan area. A real-time on-board data logger was facilitated to measure the vehicle information such as vehicle speed, idle stop, state of charge of battery, and engine operating conditions. These diesel-hybrid buses ran as a commuter at Daegu Exco area and Dalsung industrial complex. The driving pattern in Exco area comprised more frequent idle stop and relatively lower speed than at Dalsung area, where comprised no idle stop. Due to those different driving patterns, the fuel economy at Dalsung showed $3.7\;km/{\ell}$, which is about 8% higher than that of Exco. The main causes of this come from the higher portion of regenerative braking and higher speed which moves to the operating points of diesel engine with a lower fuel consumption.

• 한국콘텐츠학회논문지
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• 제16권2호
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• pp.129-142
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• 2016

본 연구는 유휴공간의 재생에 대한 부문별 효과를 평가하여 주민 삶의 질과 지역경제 활성화에 어떠한 영향 관계 및 구조를 가지고 있는지 알아보기 위한 목적으로 분석하였다. 연구가설 설정에 대한 적합성과 통계적 유의성 분석을 통해 전체 총 11개의 가설 중 8개의 가설을 PLS 구조모형을 통해 검증하였다. 그 결과를 크게 3가지로 요약할 수 있는데 첫째, 유휴공간의 재생을 통해 거주민의 삶의 질과 지역경제 활성화를 동시에 만족하려면 물리적, 사회적, 문화적 차원에 대한 부문을 기본적으로 고려해야 한다. 둘째, 유휴공간 환경적 차원의 재생은 지자체 차원에서 주도해야 하며, 관 민 협업을 통해 유휴공간의 재생에 대한 효과가 지역경제 활성화로 이어질 수 있도록 해야 한다. 마지막으로 유휴공간의 재생을 통해 주민 삶의 질의 향상을 도모하고 이러한 만족이 다시 지역경제 활성화로 이어지는 순환적 효과로 이어지도록 해야 한다. 본 연구를 통해 유휴공간의 재생의 이론적 기반을 마련하고 이에 대한 영향구조모형에 대한 실증연구로 의의가 존재한다.

• 산업경영시스템학회지
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• 제42권4호
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• pp.91-105
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• 2019

Discrete-time Queueing models are frequently utilized to analyze the performance of computing and communication systems. The length of busy period is one of important performance measures for such systems. In this paper, we consider the busy period of the Geo/Geo/1/K queue with a single vacation. We derive the moments of the length of the busy (idle) period, the number of customers who arrive and enter the system during the busy (idle) period and the number of customers who arrive but are lost due to no vacancies in the system for both early arrival system (EAS) and late arrival system (LAS). In order to do this, recursive equations for the joint probability generating function of the busy period of the Geo/Geo/1/K queue starting with n, 1 ≤ n ≤ K, customers, the number of customers who arrive and enter the system, and arrive but are lost during that busy period are constructed. Using the result of the busy period analysis, we also numerically study differences of various performance measures between EAS and LAS. This numerical study shows that the performance gap between EAS and LAS increases as the system capacity K decrease, and the arrival rate (probability) approaches the service rate (probability). This performance gap also decreases as the vacation rate (probability) decrease, but it does not shrink to zero.

• Ocean Systems Engineering
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• 제9권3호
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• pp.329-347
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• 2019

The shipbuilding industry is characterized by order production, and various processes are performed simultaneously in the construction of ships. Therefore, effective management of the production process and productivity improvement form important key factors in the industry. For decades, researchers and process managers have attempted to improve processes by using business process analysis (BPA). However, conventional BPA is time-consuming, expensive, and mainly based on subjective results generated by employees, which may not always correspond to the actual conditions. This paper proposes a method to improve the production process of offshore plant modules by analysing the process mining data obtained from the shipbuilding industry. Process mining uses information accumulated from the system-provided event logs to generate a process model and determine the values hidden within the process. The discovered process is visualized as a process model. Subsequently, alternatives are proposed by brainstorming problems (such as bottlenecks or idle time) in the process. The results of this study can aid in productivity improvement (idle time or bottleneck reduction in the production process) in conjunction with a six-sigma technique or ERP system. In future, it is necessary to study the standardization of the module production processes and development of the process monitoring system.

• International Journal of Reliability and Applications
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• 제3권4호
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• pp.165-171
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• 2002

An optimization of the M/M/1 queue with impatient customers is studied. The impatient customer does not enter the system if his or her virtual waiting time exceeds the threshold K ＞ 0. After assigning three costs to the system, a cost proportional to the virtual waiting time, a penalty to each impatient customer, and also a penalty to each unit of the idle period of the server, we show that there exists a threshold K which minimizes the long-run average cost per unit time.