• Atmosphere
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• v.17 no.4
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• pp.435-453
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• 2007

KEOP (Korea Enhanced Observing Period)-2004 intensive summer observation was carried out from 20 June to 5 July 2004 over the Southwestern part of the Korean peninsula. In this study, the effects of KEOP-2004 intensive observation data on the simulation of precipitation system are investigated using KLAPS (Korea Local Analysis and Prediction System) and PSU/NCAR MM5. Three precipitation cases during the intensive observation are selected for detailed analysis. In addition to the control experiments using the traditional data for its initial and boundary conditions, two sensitivity experiments using KEOP data with and without Jindo radar are performed. Although it is hard to find a clear and consistent improvement in the verification score (threat score), it is found that the KEOP data play a role in improving the position and intensity of the simulated precipitation system. The experiments started at 00 and 12 UTC show more positive effect than those of 06 and 18 UTC. The effect of Jindo radar is dependent on the case. It plays a significant role in the heavy rain cases related to a mesoscale low over Changma front and the landing of a Typhoon. KEOP data produce more strong difference in the 06/18 UTC experiments than in 00/12 UTC, but give more positive effects in 00/12 UTC experiments. One of the possible explanations for this is that : KEOP data could properly correct the atmosphere around them when there are certain amounts of data, while gives excessive effect to the atmospheric field when there are few data. CRA analysis supports this reasoning. According to the CRA (Contiguous Rain Area) analysis, KEOP data in 00/12 UTC experiments improve only the surrounding area, resulting in essentially same precipitation system so the effects remain only in each convective cell rather than the system itself. On the other hand, KEOP data modify the precipitation system itself in 06/18 UTC experiments. Therefore the effects become amplified with time integration.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.4
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• pp.314-320
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• 2011

In this work, optimization of two-stage shock absorption system for lunar lander has been carried out. Because of complexity of impact phenomena of shock absorption system, a 1-D constitutive model is proposed to describe the behavior of shock absorption system. Quadratic polynomial regression meta-model is constructed by using a commercial software ABAQUS with the proposed 1-D constitutive model, and sequential approximate optimization of two-stage shock absorption system has been carried out along with the constructed meta-model. Through the optimization, it is verified that landing impact force on lunar lander can be considerably reduced by changing the cell size and foil thickness of honeycomb structure in two-stage shock absorption system.

• Journal of Hydrogen and New Energy
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• v.23 no.4
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• pp.300-309
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• 2012

Long endurance is a key issue in the application of unmanned aerial vehicles. This study presents feasibility test results when fuel cell system as an alternative to the conventional engine is applied for the power of the UAV after the 150W fuel cell system is developed and packaged to the 1/4 scale super cub airplane. Fuel cell system is operated by dead-end method in the anode part and periodically purged to remove the water droplet in flow field during the operation. Oxygen in the air is supplied to the stack by the two air blowers. And fuel cell stack is water cooled by cooling circuit to dissipate the heat generated during the fuel cell operation. Weight balance is considered to integrate the stack and balance of plant (BOP) in package layout. In flight performance test, we demonstrated 4 times standalone take-off and landing. In the laboratory test simulating the flight condition to quantify the energy flow, the system is analyzed in detail. Sankey diagram shows that electric efficiency of the fuel cell system is 39.2%, heat loss 50.1%, parasitic loss 8.96%, and unreacted purged gas 1.67%, respectively compared to the total hydrogen input energy. Feasibility test results show that fuel cell system is high efficient and appropriate for the power of UAV.

• Journal of Aerospace System Engineering
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• v.15 no.5
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• pp.43-49
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• 2021

This research shows how is designed, and its performance is evaluated on the ground for the VTOL drone before the flight test initiates. The targeted drone weight is approximately 45 kg including battery packs, and 4 motors are utilized to produce thrust and control directions. 30 min flight schedules were simulated to estimate the total power consumptions which result in 2.4 kWh. Then, two packs of 13-cells lithium-polymer battery with operating voltage ranging between 54 V and 44 V with up to 4 C-rate were fabricated to safely operate a VTOL drone. Moreover, the battery management system was installed to prevent over and under-voltage and over-current while running a battery system. To finally verify battery's performance, we conducted a ground evaluation for discharging battery tests at -10 ℃, 25 ℃ and 40 ℃, resulting in satisfying simulated power consumption conditions for flight schedules.

• Journal of Advanced Navigation Technology
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• v.22 no.2
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• pp.96-104
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• 2018

NOTAM is an announcement that is distributed to flight attendants with status information related to aviation. ICAO, the International Civilian Aviation Organization, recommends that a NOTAM service be provided for the SBAS service in order to use the SBAS signal-based access procedure. To comply with ICAO recommendation, KASS must provide NOTAM service to all aircraft landing using SBAS signal in order to provide APV-I SoL service. Therefore, it is necessary to develop KASS NOTAM system to provide KASS NOTAM service. In this paper, we analyzed the regulations related to NOTAM in Korea and abroad and analyzed the present state of NOTAM service in Korea. Based on this, we propose a method of providing KASS NOTAM service. We analyzed the NOTAM system of WAAS in the US and EGNOS in Europe and analyzed the main functional requirements of the KASS NOTAM system.

• Journal of Advanced Navigation Technology
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• v.25 no.3
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• pp.242-247
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• 2021

Major countries in space field such as the United States, China and Russia have not only general ground-based space capabilities, but also maritime-based space capabilities. Maritime-based space systems include a maritime-based space surveillance system, a maritime-based space launch vehicle, and a maritime-based space information transmission system, and these maritime-based systems complement the ground-based space systems. Therefore, in this paper, we analyze the maritime-based space capabilities of major countries, and propose the future direction for south Korea's maritime-based space capabilities. The maritime-based space system is essential due to the geographical characteristics of south Korea, which has three sides of the ocean, and it is considered an one of important strategic element to become the seven major country in the space field.

• Journal of Advanced Navigation Technology
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• v.26 no.6
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• pp.448-455
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• 2022

In this study, when establishing a UTM(UAS Traffic Management) system, a corridor must be set to separate the flight distance between unmanned aerial vehicles, and the size of the corridor was calculated in consideration of TSE(Total System Error). The flight data of the straight section and the turning section were collected using a hybrid vertical take-off and landing unmanned aerial vehicle. The flight data were derived from the TSE using the SQSM(Scalar Quantity Summation Method) method, and the impact on the straight and turning sections was analyzed by calculating in detail by NSE(Navigation System Error) and FTE(Flight Technical Error). The corridor size was calculated by referring to the TSE analysis results and PBN (Performance-based Navigation) manual.

• Journal of Advanced Navigation Technology
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• v.18 no.4
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• pp.288-295
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• 2014

Current ILS is difficult for the many aircraft to access to the system at the same time because of it's system. And the equipments should be installed at the direction of every runway. Also, There is limitation that landing procedures must be have of only ILS single course when the aircraft land on the ground. hereupon, The more air traffic exist, the longer delay time of flight be. GBAS using the GNSS has been developed to overcome those limitations. Before flight test in Teean airport, this paper compares the taean approach procedure and curved approach procedure by using the simulator. Comparison study shows that curved approach procedure takes less flight time, low fuel consumpsion and make it possible to avoid noise airspace more than original procedure.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.1
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• pp.49-61
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• 2015

Ground Based Augmentation System(GBAS) is a system that offers an aircraft within 23 NM radius from the airport precision positioning service and precision approach service using the concept of Differential Global Positioning System(DGPS). After GBAS ground equipment installing at the airport, functionalities and performances of GBAS should be verified through the GBAS ground and flight testing. This paper describes the methods and results for GBAS flight test using the flight inspection aircraft at Gimpo International Airport. From the test results, we confirmed that the VDB data was received without misleading within the VDB coverage of Gimpo International Airport, and VDB field strength, protection level, and course alignment accuracy met the evaluation's criteria.

• Journal of Practical Engineering Education
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• v.8 no.1
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• pp.63-68
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• 2016

As job mismatch intensifies in the employment market, the work based learning has emerged as a solution to this social problem. The so called Korean dual education system is expected to raise jobseekers equipped with knowledge and skills demanded by industry. This study intends to recommend an effective operational model for contracted education programs at higher institutions in order to support soft landing of Korean dual education system. Students of contracted education programs are adults graduated from vocational high schools and working for companies during weekdays. In consideration of the difficulties experienced by employee students, more flexible operation of academic affairs is required. To address these challenges, the recommended contracted education model includes such beneficial features as S-OJT courses, standard curriculum based on National Competency Standard, recognition of prior learning, flipped classroom, and tutoring system. In the last part, several directions for implementing the new contracted education model are discussed.