• Journal of Korean Society of Transportation
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• v.22 no.5
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• pp.89-97
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• 2004

The Korea Air Force(KAF) has operated freight flights based on the prefixed time and route schedule, which is adjusted once in a month. The major purpose of the operation of freight flights in the KAF is to distribute necessary supplies from the home air base to other air bases. The secondary purpose is to train the young pilots to get more experiences in navigation. Each freight flight starts from and returned to the home air base everyday except holidays, while it visits several other air bases to accomplish its missions. The study aims to forecast freight demand at each base by using time series analysis, and then it tried to optimize the cost of operating flights by solving vehicle routing problem. For more specifically, first, several constraints in operating cargos were defined by reviewing the Korea Air Force manuals and regulation. With such constraints, an integer programming problem was formulated for this specific routing problem allowing several visits in a tour with limitation of maximum number of visits. Then, an algorithm to solve the routing problem was developed. Second, the time series analysis method was applied to find out the freight demand at each air base from the mother air base in the next month. With the forecasted demands and the developed solution algorithm, the oprimum routes are calculated for each flight. Finally, the study compared the solved routing system by the developed algorithm with the existing routing system of the Korea Air Force. Through this comparison, the study proved that the proposed method can provide more (economically) efficient routing system than the existing system in terms of computing and monetary cost. In summary, the study suggested objective criteria for air routing plan in the KAF. It also developed the methods which could forecast properly the freight demands at each bases by using time series analysis and which could find the optimum routing which minimizes number of cargo needed. Finally, the study showed the economical savings with the optimized routing system by using real case example.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2004.04a
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• pp.39-44
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• 2004

In this thesis, two test flights were conducted in Gwacheon and Suwon area to evaluate the performance of accuracy and efficiency through the analysis of results among the three photogrammetric methods, that is, traditional photogrammetry, GPS -Photogrammetry and GPS/INS-Photogrammetry. Test results shows that a large variety of advantages of GPS-Photogrammetry and GPS/INS-Photogrammetry against traditional photogrammetry is to be verified. Especially, the number of ground control points for the exterior orientation could be saved more than 70-80%, and the cost for map production 30-50%, respectively. In addition, it was convinced that the large reduction of control points has not any effect on the block accuracy. It was also proved that the number of required ground control points for GPS/INS-Photogrammetry, is similar to that of GPS-Photogrammetry. Therefore it should be noted that GPS -Photogrammetry is more efficient in the aspect of reduction of mapping cost against GPS/INS-Photogrammetry, installing only an existing GPS receiver on survey aircraft to avoid high economic burden of procurement for integrated GPS/INS equipment.

• Journal of the Korean Society of Industry Convergence
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• v.26 no.5
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• pp.953-965
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• 2023

The stratospheric drones are developed to perform missions such as weather observation, communication relay, surveillance, and reconnaissance at 18km to 20km, where climate change is minimal and there is no worry about a collision with aircraft. It uses solar panels for daytime flights and energy stored in batteries for night flights, providing many advantages over existing satellites. The electrical and power systems essential for stratospheric drone flight must ensure reliability, efficiency, and lightness by selecting the optimal circuit topology. Therefore, it is necessary to analyze the circuit topology of various types of multi-level inverters with high redundancy that can ensure the reliability and efficiency of the motor driving power required for stable long-term flight of stratospheric drones. By quantifying the switch element voltage drop and the number and weight of inverter components for each topology, we evaluate efficiency and lightness and propose the most suitable circuit topology for stratospheric drones.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.28 no.2
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• pp.53-62
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• 2020

This study is to evaluate the accuracy of the meteorological information provided for the aircraft operating at low altitude. At first, it is necessary to identify crucial elements of weather information closely related to flight safety during low altitude flights. The study conducted a survey of pilots of low altitude aircraft, divided into pre-flight and in-flight phases, and reached an opinion that wind direction, wind speed, cloud coverage and ceiling and visibility are important items. Related to these items, we compared and calculated the accuracy of TAFs and METARs from Taean Airfield, Seosan Airport and Gunsan Airport because of their high number of domestic low-altitude flights. Accuracy analysis evaluated the accuracy of two numerical variables, Mean Absolute Error(MAE) and Root Mean Square Error(RMSE), and the cloud coverage which is categorical variable was calculated and compared by accuracy. For numeric variables, one-way ANOVA, which is a parameter-test, was approached to identify differences between actual forecast values and observations based on absolute errors for each item derived from the results of MAE and RMSE accuracy analyses. To determine the satisfaction of both normality assumptions and equivalence variability assumptions, the Shapiro-Wilk test was performed to verify that they do not have a normality distribution for numerical variables, and for the non-parametric test, Kruscal-Wallis test was conducted to determine whether or not they are satisfied.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.05a
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• pp.207-210
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• 2008

In this study, one type of ramjet intake were designed for the flight condition of Mach number 4 and numerical analysis was performed. In order to widen the flight envelope range (Mach number $2{\sim}6$), movable intake concept was applied. The central body was designed so that the capture area ratio which is one of most important factors of ramjet intake design could be adjusted. And various types of cowl and movable insert part of shell were designed in order to control throat area which could increase total pressure recovery. The numerical results showed that the designed ramjet intake could be applied in various flights Mach number.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.706-709
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• 1997

Extruders are the heart of the polymer processing industry. The single most important mechanical element of a screw extruder is the screw. The proper design of the geometriy of the extruder screw is of crucial importance to the proper functioning of the extruder. If material transport instabilities occur as a result of improper screw geometry, even the most sophisticated computerized control system cannot solve the problem. For this purpose, characteristics design on helix angle of the extruder screw. This paper presents strength of the screw flight, optimum helix angle versus dimensionless down channel pressure gradient, optimum helix angle versus the power law index in simultaneous optimization, volumetric efficiency versus helix angle at various number of flights and power consumption versus helix angle in the barrel of screw extruder.

• Journal of Ginseng Research
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• v.13 no.1
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• pp.119-122
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• 1989

phenological study on the oviposition, emergence, and flight activity of the African mole cricket adult has been made to obtain basic information for management of pest populations in ginseng fields. The flight activity, as monitored by the blarklight trap, seemed to be initiated depending on the sunset time and lasted about 2-2.5 hours. The trap data (1984-1988) showed that the adult flight of the species occurred twice a year, from early May to late June(Spring flight) and from late August to mid October(Fall flight) during which usually more crickets were trapped than during the former period. The number of females trapped was greater than that of males regardless to the flight period, i.e., females comprised 72.2%, 83.9%, and 73.3% of the total catches in 1984, 1985, and 1986, respectively. Adults emerged from late August to mid October and laid eggs from mid May to mid July the next year, indicating that the spring and fall flights correspond to the oviposition and emergence period, respectively.

• Journal of Aerospace System Engineering
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• v.14 no.4
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• pp.32-39
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• 2020

A technological review and analysis were performed on thermal cracking of aviation hydrocarbon fuels that circulate as coolants in regenerative cooling systems of hypersonic flights. Liquid hydrocarbons decompose into low-carbon-number hydrocarbons when they absorb a considerable amount of energy at extremely high temperatures, and these thermal cracking behaviors are represented by heat sink capacity, conversion ratio, reaction products, and coking propensity. These parameters are closely interrelated, and thus, they must be considered for optimum performance in terms of the overall heat absorption in the regenerative cooling system and supersonic combustion in the scramjet engine.

• 한국연소학회:학술대회논문집
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• 2015.12a
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• pp.251-255
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• 2015

Unsteady Shock-Induced Combustion has been studied for the past few decades since it is considered as one of the potential ways to reach supersonic flights. Experimental observations of Unsteady SIC were observed as early as 1960's. But Lehr was the first to report in detail the mechanisms of Shock-Induced Combustion experimentally. Numerical Studies on SIC were helpful in explaining the insight into the oscillatory behaviour in the mid 90's to early 2000's. Detailed reaction mechanisms is required to prediction the SIC flowfield more in detail. However at that time, very few reaction mechanisms on hydrogen-oxidation were reported. In the last decade, various number of hydrogen reaction mechanisms were reported. In this study, an attempt has been made to analyze the effect of various reaction mechanisms in an unsteady mode of Shock-Induced Combustion.

• Journal of the Korea Safety Management & Science
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• v.4 no.4
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• pp.129-136
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• 2002

Utilization rate for the restrictive gate and required time and walking distance to board are to be a measure for the gate management and passenger's convenience estimation. So, the main purpose of the gate management are maximization of utilization rate and increment of airport terminal user's convenience through the efficient gate management. This study intends to maximize the utilization rate on usable gates and minimize the passenger's working distance in terminal by concerning about layout, terminal configuration, local passenger of the airport and formulate the gate assignment problem with integer linear programming problem. Then we obtained solution using optimization software LINGO and analyzed that maximize the number of assignment flights and minimize the passenger's walking distance.