• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.10
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• pp.936-942
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• 2015

This paper suggests the significant strategies and their priority to deal with space transportation market trends. First, market trends related with technical improvement and change in demand are analyzed by the literature research. The three key trends are obtained: 'Increasing Demand of High-Performance Launch Vehicles', 'Rising of Low-Price Launch Vehicles', and 'Rising of Dual/Multi-Launch'. And then, strategies for developing the launch vehicle industry in Korea are selected from several studies about commercialization of Korean launch vehicle. The strategies are evaluated by the experts through pairwise comparison matrix and the criteria for this process is how significantly does the strategy effect on the launch vehicle industry through market assessment. As a result, reliable order of priority among the strategies are obtained. Under the three key trends, strategy to enhance reliability is most important. And, strategy to have price competitiveness has secondary priority to deal with 'Rising of Low-Price Launch Vehicles' trend and 'Rising of Dual/Multi-Launch' trend. On the contrary, strategy of government's support is secondary under 'Increasing Demand of High-Performance Launch Vehicles' trend.

• International Journal of Aeronautical and Space Sciences
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• v.17 no.2
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• pp.260-267
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• 2016

The design process of blended inlet body (BIB) for the preliminary design of a near-space high supersonic unmanned aerial vehicle (HSUAV) is presented. The mass flow rate and cowl area of inlet at a design point are obtained according to the cruise condition of the HSUAV. A mixed-compression axisymmetric supersonic inlet section with a fixed geometry reasonably matching the high supersonic cruise state is created by using the inviscid theory of aerodynamics. The inlet section is optimized and used as a baseline section for the BIB design. Three BIB concepts for the HSUAV are proposed, and their internal aerodynamic characteristics of inlet are evaluated using Euler computational fluid dynamics (Euler CFD) solver. The preferred concept is identified, in which the straight leading edge of the baseline HSUAV configuration is modified into the convex leading edge to accommodate the inlet and meet the requirements of the cowl area to capture the sufficient air flow. The total recovery of inlet for the preferred BIB concept and the aerodynamic characteristics of the modified HSUAV configuration are verified using Navier-Stokes computational fluid dynamics (NS CFD) solver. The validation indicates that the preferred BIB concept can meet both the requirements of the inlet and aerodynamic performance of the HSUAV.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.7
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• pp.962-970
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• 2021

The cause of the majority of vehicle accidents is a safety issue due to the driver's inattention, such as drowsy driving. A forward collision warning system (FCWS) can significantly reduce the number and severity of accidents by detecting the risk of collision with vehicles in front and providing an advanced warning signal to the driver. This paper describes a low power embedded system based FCWS for safety. The algorithm computes time to collision (TTC) through detection, tracking, distance calculation for the vehicle ahead and current vehicle speed information with a single camera. Additionally, in order to operate in real time even in a low-performance embedded system, an optimization technique in the program with high and low levels will be introduced. The system has been tested through the driving video of the vehicle in the embedded system. As a result of using the optimization technique, the execution time was about 170 times faster than that when using the previous non-optimized process.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.8
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• pp.702-708
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• 2013

Underwater TRN (Underwater Terrain Referenced Navigation) estimates an underwater vehicle state by measuring a distance between the vehicle and undersea terrain, and comparing it with the known terrain database. TRN belongs to absolute navigation methods, which are used to compensate a drift error of dead reckoning measurements such as IMU (Inertial Measurement Unit) or DVL (Doppler Velocity Log). However, underwater TRN is different to other absolute methods such as USBL (Ultra-Short Baseline) and LBL (Long Baseline), because TRN is independent of the external environment. As a magnetic-field-based navigation, TRN is a kind of geophysical navigation. This paper develops an EKF (Extended Kalman Filter) formulation for underwater TRN. A filter propagation part is composed by an inertial navigation system, and a filter update is executed with echo-sounder measurement. For large-initial-error cases, an adaptive EKF approach is also presented, to keep the filter be stable. At the end, simulation studies are given to verify the performance of the proposed TRN filter. With simplified sensor and terrain database models, the simulation results show that the underwater TRN could support conventional underwater navigation methods.

• Journal of Energy Engineering
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• v.23 no.3
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• pp.132-145
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• 2014

There is a general agreement that performance of hydrogen fuel cell vehicle(FCV) with respect to cold start, packaging, acceleration, refueling time and range has progressed to the point where vehicles that could be brought to market in 2015_2020 will satisfy customer expectations. However cost, durability and the lack of refueling infrastructure remain significant barriers. Cost have been dramatically reduced and durability has been enhanced over the past decade, yet are still about twice what appears to be needed sustainable market success. Advanced Technologies for the commercialization of hydrogen FCV were reviewed.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.3
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• pp.71-77
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• 2018

This paper suggests how to improve the fatigue strength of an axle shaft, which is the vulnerable part of an axle shaft system for a 3.5-ton commercial vehicle. The axle shaft is composed of a universal joint with a spider and yoke, yoke shaft, and so on. Structural analysis of the initial axle shaft was conducted to select the exact area for structural strength fatigue improvement, and as a result, the inner/outer yoke shaft and spider were selected. Four cases considered design variables, such as length and thickness, to verify the enhanced durability of the axle shaft, and fatigue analysis was conducted. Finally, we suggest that the axle shaft system satisfied the working conditions for a 3.5-ton commercial vehicle.

• Journal of Industrial Technology
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• v.37 no.1
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• pp.1-4
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• 2017

Speeding up of railway vehicles requires weight reduction of the vehicle body. However, when the vehicle body is lighter, the sound insulation performance for blocking the noise from the outside is reduced. Aluminum is an important material used in the bodywork of transportation vehicles such as railway vehicles, aircraft, and automobiles. In this study, the bending stiffness and sound insulation performance of foamed aluminum with sandwich structure are investigated experimentally. The transmission loss is measured in accordance with the international standard ASTM E 2249-02. The mass-law deviation is used to evaluate the sound insulation performance per weight. In order to examine the applicability of the foamed aluminum sandwich panel to railway vehicles, the analysis of bending stiffness and an experimental review are carried out at the same time.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.6
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• pp.751-760
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• 2014

The unmanned underwater vehicle(UUV) requires the highly dense energy source because of its limited space. Especially, for the UUV designed for long-term operation, it should be reviewed first whether it is possible to install the energy source against required total power. Therefore, this study identifies whether it is possible to install the energy source for the energy requirement of the UUV. And fuel and oxidizer requirement for the fuel cell system are calculated to determine its location and layout inside of the vehicle. Finally, we design the closed type 1kW polymer-electrolytic fuel cell system and check the applicability to underwater operations with UUV.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.5
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• pp.96-106
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• 1999

In this study, the advanced shift control algorithm for parallel type hybrid drivetrain system with automated manual transmission(AMT) is proposed. The AMT can be easily realized by mounting the pneumatic actuators and sensors on the clutch and shift levers of the conventional manual transmission. By using the electronic-controlled AMT, engine and induction machine, it is possible to achieve the integrated control of overall system for the efficiency and the performance of the vehicle. Performing the speed control of the induction machine and the engine, the synchronization at gear shifting and the smooth engagement of clutch can be guaranteed. And it enables to reduce the shift shock and shorten the shift time. Hence, it results in the improvement of shift quality and the driving comfort of the vehicle. Dynamometer-based experiments are carried out to prove the validity of the proposed shift control algorithm.

• ETRI Journal
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• v.41 no.6
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• pp.731-738
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• 2019

We proposed a novel electromagnetic band-gap (EBG) cell-embedded antenna structure for reducing the interference that radiates at the antenna edge in wireless access in vehicular environment (WAVE) communication systems for vehicle-to-everything communications. To suppress the radiation of surface waves from the ground plane and vehicle, EBG cells were inserted between micropatch arrays. A simulation was also performed to determine the optimum EBG cell structure located above the ground plane in a conformal linear microstrip patch array antenna. The characteristics such as return loss, peak gain, and radiation patterns obtained using the fabricated EBG cell-embedded antenna were superior to those obtained without the EBG cells. A return loss of 35.14 dB, peak gain of 10.15 dBi at 80°, and improvement of 2.037 dB max at the field of view in the radiation beam patterns were obtained using the proposed WAVE antenna.