• 한국항공운항학회지
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• 제28권4호
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• pp.117-124
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• 2020

This study empirically analyzed air transport trade patterns using data for 30 years between Korea and its trading partners in order to identify specific factors that determine the size of Korea's air transport trade. Independent variables were GDP per capita, capital distance between countries, country area data and number of airports. In addition, it reflected whether it is a landlocked country and whether it has joined the OECD, APEC and ASEAN+3. According to the results of the analysis, it was found that the air cargo trade pattern in Korea is proportional to GDP per capita, and the scale increases as the distance is closer. In addition, the national area and the airport capital acted as a factor in increasing air transport trade. However, whether a country is a landlocked country did not show significant results in terms of trade, exports, and imports. The OECD, APEC, and ASEAN+3 variables were found to generally increase air transport trade.

• 한국결정성장학회지
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• 제16권2호
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• pp.53-58
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• 2006

조화용융조성 $LiNbO_3$ 결정에 외부 전계를 인가하였을 때 초기 도메인 생성 및 이동에 관하여 연구하였다. 0.5mm 두께의 $LiNbO_3$ 결정에 23.5, 22.0, 21.0kV/mm의 전계를 인가하였을 때 도메인 벽은 각각 28.70, 16.02, $5.75{\mu}m/sec$의 속도를 나타내었다. 분극 반전 시스템에 전류 제어를 위한 외부저항으로 $1 M{\Omega}$을 사용하였을 시 너무 빠른 도메인 성장으로 인하여 원활한 분극 반전 제어가 이루어지지 않으므로 $10 M{\Omega}$ 외부저항을 사용하여 전하량을 제어하여 50% duty cycle을 가진 주기적 분극 반전 $LiNbO_3$ 결정을 제작하였다.

• 한국세라믹학회지
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• 제42권11호
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• pp.749-752
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• 2005

When an electric field higher than a characteristic coercive field is applied to a ferroelectric such as $LiNbO_3$, the orientation of the spontaneous polarization is reversed, which causes the reversal of the sign of odd-rank tensor properties such as electro-optic and nonlinear optic coefficients. A fabrication process of insulator and periodic external field assisted poling of a z-cut $LiNbO_3$ have been optimized for a periodic $180^{\circ}$ phase inversion along z-axis. The poling jig and the poling control system, fully controlled by a computer, for high quality and reproducible PPLN fabrication have been devised. Periodically polarization reversed PPLN was adjusted based on the fabricated thickness of insulator. The poling structure of PPLN was observed under a microscope after etching PPLN samples by an etching solution ($HF:HNO_3$ = 1 : 2) for about 15 min.

• 한국항공운항학회지
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• 제12권3호
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• pp.25-39
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• 2004

An experimental study was quantitatively carried out in order to investigate the influence of flow conditions on a boundary layer in the near-wake of a flat plate. Tripping wires attached at various positions were selected to change flow conditions of a boundary layer in the vicinity of trailing edge. The flows such as laminar, transitional, and turbulent boundary layer at 0.98C from the leading edge are imposed to investigate the evolution of symmetric and asymmetric wake. Measurements were made at freestream velocity of 6.0m/s, and the corresponding Reynolds number is $2.8{\times}10^5$. An x-type hot-wire probe(55P61) was employed to measure at 8 stations in the near-wake region. Test results show that the near-wake of the flat plate for the case of a laminar and transitional boundary layer is sensitive to mean flow shear generated after separation but for the case of turbulent boundary layer is insensitive.

• 한국항공운항학회지
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• 제15권4호
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• pp.100-107
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• 2007

We proposed the concatenation of logistics' Information to constructing the intelligent logistics city that is to manage efficiently cargo distribution as providing at real-time information of cargo location trace and management through the Telematics/RFID. Case of the Incheon of the "Air Logistics Hub", this area is on an increasing trend on the quantity of cargo transport of the Air & Sea cargo system until 2006. As intelligent project of the Air's and the Sea's field is independently developed at each area, it is a problem on the concatenation of logistics' information such as freight location trace and management, operation management and route information of cargo vehicles. Therefore, we propose the advanced transport service model for the concatenating smoothly of Air & Sea cargo system. In this paper, we only manage the model of Air & Sea cargo system of the advance logistics city.

• 한국항공운항학회지
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• 제18권4호
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• pp.86-91
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• 2010

New Design configurations of the fighter aircraft igloo diffuser were studied based on the closed ventilation type in contrast to the conventional open distribution type. To validate the enhanced and safe performance, the exhaust flow patterns of the two igloo diffuser types were simulated by both experimental and computational approaches as design tools. Flow visualizations were conducted to investigate the exhaust flow patterns in experimental approach. In addition, the commercial code called Fluent was used to calculate flow field properties. Computational simulations provided detailed parametric studies that significantly reduced the amount of experimentation necessary to alter the design parameters of the existing fighter igloo diffuser. The closed ventilation type of the igloo diffuser was shown the better results.

• 한국항공운항학회지
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• 제18권4호
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• pp.1-8
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• 2010

In the aerospace field, the study on a morphing-wing is in progress to improve flight performance and perform multi flight mission. There are many concepts of morphing-wing such as camber-change, wing-twist, variable-span, and so on. In this study, the aerodynamic characteristics and flight control of an air vehicle with a variable-span morphing wing (VSMW) have been investigated. VSMW with symmetric span control(SSC) can increase cruising range of aircraft by reducing drag in various flight condition. VSMW with anti-symmetric span control(ASSC) can be used in the roll control of an aircraft. The flight control about pure rolling dynamic system and full dynamic system have been performed about the cruise missile.

• 한국항공운항학회지
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• 제17권1호
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• pp.46-51
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• 2009

This paper presents results from field studies carried out to monitor off-target droplet movement of endosulfan insecticide applied to the Korea chestnut tree area. As a results, mean airborne drift values were recorded 25m as average from downwind of a single flight line(sample line) in mountain terrain and mean effective swath width was recorded 19.5m as average in a plain. In terms of characteristics of geography of Korea aerial application is mainly carried out in mountain terrain. The equipment, weather conditions, and appropriate aerial spray technic are required for effective aerial application. In particular, the pilot can get effective results when he only sprays with consideration of environment factors since there is much turbulence in mountain terrain. Eventually, the most effective factor of droplets drift is to estimate the local weather conditions exactly.

• 한국군사과학기술학회지
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• 제13권6호
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• pp.1099-1105
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• 2010

The purpose of this paper is to propose a methodology that can estimate optimal requirement of attack helicopter Korea army will be operating in future. For estimating optimal requirement, attack helicopter's operation concept, performance, battlefield environment and enemy threat are considered. We use a wargame model, AAsim(Army Aviation simulation), as a analytic simulation model which is used to analyze DOTMLPF and operation in army aviation field. In this paper, we conduct battle experiment for anti armored corps operation which reflects attack helicopter's combat effectiveness very well. As a result of simulation, the destructive rate for enemy armored corps per each attack helicopter can be calculated. In this paper, we propose optimal requirement of attack helicopter using that destructive rate for enemy armored corps.

• 한국항공운항학회지
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• 제17권4호
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• pp.25-31
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• 2009

In development phase of the Aircraft Systems, the reliability prediction of electronic equipments are usually performed using MIL-HDBK-217. The reliability of fielded electronic systems, however, used to be underestimated with MIL-HDBK-217. To solve this problem, some alternatives are suggested and Telcordia SR-332 is among them. In this case study, the reliability of ESU which controls gas turbine engine is predicted using Telcordia SR-332 along with the development test data. The predicted reliabilities of ESU using Telcordia SR-332 and MIL-HDBK-217 are also compared. As a result this case study showed that the predicted reliability using Telcordia SR-332 was better close to field(operation) reliability than MIL-HDBK-217.