• 항공우주기술
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• 제9권2호
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• pp.51-56
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• 2010

통신해양기상위성의 정상임무 수행시 자세제어계에 대한 중요한 지상국 소프트웨어에는 궤도위치 유지와 휠오프로딩이 있는데, 본 논문에서는 외팔보 태양전지판 형상으로 인해 E3000 heritage로부터 설계 변경을 수행하여 해석을 수행한 휠오프로딩 임무에 대한 지상국 소프트웨어 검증시험을 정리하여 기술하였다. 휠오프로딩 지상국 소프트웨어는 크게 2가지로 구분되는데, 하나는 휠오프로딩을 위한 추력기 조합 변경 시기에서의 변수 변경이고 다른 하나는 위성으로 전달해야 하는 모멘텀기준값 변경이다.

• 산업기술연구
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• 제37권1호
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• pp.5-11
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• 2017

The purpose of this research is to propose an efficient loop line operation plan for customer transportation in a new theme park. Based on the expected customer arrivals, customer loading/unloading methods, and scheduled/non-scheduled departure schemes, movement time between stations etc., we have performed indepth analyses and derived the best optimal policy. Our results show that, over all, the operation with separate loading/unloading doors and scheduled departure is preferred to the other options. We then derived the optimal number of trains and cars meeting minimal customer unsatisfaction with low cost for each season.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1998년도 춘계학술발표회논문집(2)
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• pp.837-843
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• 1998

This paper presents the thermomechanical and fracture mechanics evaluation procedure of thermal striping damage on the secondary piping of LMFR using Green's function method and standard FEM. The thermohydraulic loading conditions used in the present analysis are simplified sinusoidal thermal loads and the random type data thermal load. The thermomechainical fatigue damage was evaluated according to ASME code subsectionNH. The analysis results of fatigue for the sinusoidal and random load cases show that fatigue failure would occur at a geometrically discontinuous location during 90,000 hours of operation The fracture mechanics analysis showed that the crack would be initiated at an early stage of the operation. The fatigue crack was evaluated to propagate up to 5 ㎜ along the thickness direction during the first 944 and 1083 hours of operation for the sinusoidal and the random loading cases, respectively.

• Industrial Engineering and Management Systems
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• 제9권1호
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• pp.28-40
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• 2010

One of the most important objectives of the schedules in a container terminal is to minimize the ship operation time, which consists of discharging and loading operation times. Recently, dual cycling techniques have been used for improving terminal operations, especially for reducing the total empty trips of handling equipment. The main focus of this study is to reduce the empty trip times of yard trucks with minimum delays for ship operations. A heuristic algorithm, modified from a previous algorithm, is proposed to solve this problem. A simulation study is conducted to evaluate the effect of different types of discharging and loading schedules and different locating methods for discharging containers in terms of the performance of the system, including the percentage of the dual cycle operations of yard trucks.

• 대한교통학회지
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• 제22권4호
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• pp.19-30
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• 2004

현재 국내에서는 물류시설의 부족, 물류시설의 비효율적 운영, 복잡한 유통구조, 물류산업의 낙후, 폐쇄적 정보 이용 등으로 인하여 필요 이상의 물류비용이 발생하고 있다. 이런 문제들을 해결하기 위해서는 물류구조의 전반적인 개선 및 물류시설의 확충 등이 필요하다. 하지만, 이러한 노력들이 기존의 원단위식 규모예측으로 이루어진다면 차량의 하역특성을 세밀히 고려하지 못하게 되고, 또한 향후 하역작업의 기계화 및 자동화 등으로 인한 작업능률의 향상을 반영하지 못 할 우려가 있다. 따라서 본 연구는 화물터미널에서의 화물차량의 이용현황을 기초로 대기행렬이론(queueing theory)을 적용함으로써 화물차량의 하역특성이 고려된 화물터미널의 최적규모산정법을 제시하였다. 또한, 현재의 하역시스템에서 이루어지는 작업들이 기계화 및 자동화, 정보화되었을 경우에는 화물터미널의 최적규모에 어떠한 영향을 미치는가에 대해 분석하였다. 분석결과, 하역시간의 규칙성 증가가 화물터미널의 규모변화에 미치는 영향은 크지 않은 것으로 나타났으며, 하역속도 및 서비스율의 향상은 화물터미널의 규모변화에 매우 큰 영향을 미치는 것으로 나타났다.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume I
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• pp.290-293
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• 2006

COMS (Communication, Ocean and Meteorological Satellite) shall be operated with two remote sensing payloads, MI (Meteorological Imager) and GOCI (Geostationary Ocean Color Imager). Since both payloads have rotating mechanisms, the dynamic coupling between two payloads is very important considering the pointing stability during GOCI operation. In addition, COMS adopts a single solar wing to improve the image quality, which leads to the unbalanced solar pressure torque in COMS. As a result, the off-loading of the wheel momentum needs to be performed regularly (2 times per day). Since the frequent off-loading could affect MI/GOCI imaging performance, another suboptimal off-loading time needs to be considered to meet the AOCS design requirements of COMS while having margin enough in the number of thruster actuations. In this paper, preliminary analysis results on the pointing stability and the wheel off-loading time selection with respect to MI/GOCI operations are presented.

• 한국산업융합학회 논문집
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• 제24권3호
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• pp.363-371
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• 2021

Forest operations like timber harvesting have already been mechanized to reduce hazards to the worker and increase productivity. However, timber harvesting operations have still been considered potentially dangerous and expensive on steep terrain. Teleoperation, to control the timber harvesting machine at a distance, has the potential to improve the safety, productivity and efficiency of harvesting operations on steep terrain. To verify the effects of teleoperation, an experimental prototype system of a monitor image-based teleoperation was constructed using a real forestry machine. In this study, the productivity of excavator based grapple loader, which is one of the most used mechanized harvesting equipment in the timber production, was analyzed using time-study method. Factors like skill and age of operators, influencing loader productivity in timber loading operation were also evaluated by statistical analysis. Productivity analysis results showed that less experienced operators were more productive than experienced operators for teleoperation through image of monitors in the operator cabin. These results are shown to be unfamiliar to the monitor image and different loading operation pattern by operators. According to the results, the monitor image-based teleoperation system of forestry machine need to improve the resolution and installation position of camera. It was expected that additional studies will be needed for real-time remote control of forestry machine in the future.

• 대한안전경영과학회지
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• 제10권2호
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• pp.95-103
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• 2008

The package loading process of the lumbering industry is an operation that after a pair of workers bind three or six lumbers into one unit and cut both ends of the lumbers, transports the weight cargo of 30-50kg by one meter, pack and load at a height of 1.2 meters. This package loading process causes lots of noise and wood dust when workers carry out the heavy work as the above. Therefore we developed the monolithic both ends cutting package loading equipment in order to prevent from getting musculoskeletal disease. An loading bar working system of this equipment is improved from pneumatic pressure system to oil pressure system, furnished the newly designed flow dividers, and developed the new system that a both end array is loaded identically. Also we developed the safety equipment of loading bar in order to prevent workers mistake and overload from malfunction during the package loading process. The main cause of job evasion on working place could be solved by preventing the musculoskeletal disease and improving the working environments.

• 대한안전경영과학회:학술대회논문집
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• 대한안전경영과학회 2008년도 춘계학술대회
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• pp.135-147
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• 2008

The package loading process of the lumbering industry is an operation that after a pair of workers bind three or six lumbers into one unit and cut both ends of the lumbers, transports the weight cargo of 30-50kg by one meter, pack and load at a height of 1.2 meters. This package loading process causes lots of noise and wood dust when workers carry out the heavy work as the above. Therefore we developed the monolithic both ends cutting package loading equipment in order to prevent from getting musculoskeletal disease. An loading bar working system of this equipment is improved from pneumatic pressure system to oil pressure system, furnished the newly designed flow dividers, and developed the new system that a both end array is loaded identically. Also we developed the safety equipment of loading bar in order to prevent workers mistake and overload from malfunction during the package loading process. The main cause of job evasion on working place could be solved by preventing the musculoskeletal disease and improving the working environments.

• 한국환경과학회지
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• 제16권4호
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• pp.449-458
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• 2007

Research results for the pressure drop variance depending on operation conditions such as change of inlet concentration, pulse interval, and face velocity, etc., in a pulse air jet-type bag filter show that while at $3kg/cm^2$ whose pulse pressure is low, it is good to make an pulse interval longer in order to form the first layer, it may not be applicable to industry because of a rapid increase in pressure. In addition, the change of inlet concentration contributes more to the increase of pressure drop than the pulse interval does. In order to reduce operation costs by minimizing filter drag of a filter bag at pulse pressure $5kg/cm^2$, the dust concentration should be minimized, and when the inlet dust loading is a lower concentration, the pulse interval in the operation should be less than 70 sec, but when inlet dust loading is a higher concentration, the pulse interval should be below 30 sec. In particular, in the case that inlet dust loading is a higher concentration, a high-pressure distribution is observed regardless of pulse pressure. This is because dust is accumulated continuously in the filter bag and makes it thicker as filtration time increases, and thus the pulse interval should be set to below 30 sec. If the equipment is operated at 1m/min of face velocity, while pressure drop is low, the bag filter becomes larger and thus, its economics are very low due to a large initial investment. Therefore, a face velocity of around 1.5 m/min is considered to be the optimal operation condition. At 1.5 m/min considered to be the most economical face velocity, if the pulse interval increases, since the amount of variation in filter drag is large, depending on the amount of inlet dust loading, the operation may be possible at a lower concentration when the pulse interval is 70 sec. However, for a higher concentration, either face velocity or pulse interval should be reduced.