• Journal of the Korea Institute of Military Science and Technology
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• v.3 no.2
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• pp.140-148
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• 2000

This paper presents a fault detection and isolation(FDI) method based on Generalized Likelihood Ratio(GLR) test for the tightly coupled SDINS/CPS system. The GLR test is known to have the capability of detecting an assumed change while estimating its occurrence time and magnitude, and isolating the changing part. Once a fault is detected even if we don't know if the fault occurrs at either INS or GPS, multi-hypothesized GLR scheme performs the fault isolation between INS and GPS, and find which satellite malfunctions. However, in the INS faulty case, it turned out to fail to accomodate the fault isolation between accelerometer and gyroscope due to the coupling effects and a poor observability of the system. Hence, to isolate the INS fault, it needs to change the attitude of the vehicle resulting in enhancing the degree of observability.

• Advances in aircraft and spacecraft science
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• v.6 no.5
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• pp.427-442
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• 2019

Small satellites represent an emerging opportunity to realize a wide range of space missions at lower cost and faster delivery, compared to traditional spacecraft. However, small platforms, such as CubeSats, shall increase their actual capabilities. Miniaturized electric propulsion systems can provide the satellite with the key capability of moving in space. The level of readiness of miniaturized electric propulsion systems is low although many concepts have been developed. The present research intends to build a flexible test platform for the assessment of selected small propulsion systems in relevant environment at laboratory level. Main goal of the research is to analyze the mechanical, electrical, magnetic, and chemical interactions of propulsion systems with the modern CubeSat-technology and to assess the performance of the integrated platform. The test platform is a 6U CubeSat hosting electric propulsion systems, providing mechanical, electrical and data interfaces, able to handle a variety of electric propulsion systems, thanks to the ability to regulate and distribute electric power, to exchange data according to several protocols, and to provide different mechanical layouts. The test platform is ready to start the first verification campaign. The paper describes the detailed design of the platform and the main results of the AIV activities.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.1
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• pp.37-46
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• 2014

This paper describes the conceptual design and development test procedure of a unmanned scaled-down personal air vehicle(PAV) with drive and flight dual mode capability. Trade studies on operational requirements led to the suggestion of a quad tilt prop platform which has nacelle tilt capability with multi rotor configuration. Motors for propeller propulsion and driving mechanism were integrated into a single nacelle, then they were implemented by nacelle tilt mechanism for conversion between the drive and the flight modes. Primary design parameters and initial specifications were confirmed through conceptual design, then functional tests were performed with the test platforms for the drive and the flight modes.

• Journal of Korean Institute of Industrial Engineers
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• v.34 no.3
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• pp.362-372
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• 2008

Manufacturers, or vendors, and their customers continue to adopt vendor-managed inventory(VMI) program to improve supply chain performance through collaboration achieved by consolidating replenishment responsibility upstream with vendors. In this paper, we construct a mixed integer linear programming model and propose a genetic algorithm for the integrated inventory and routing problems with lost sales maximizing the total profit in the VMI supply chains which comprise of a single manufacturer and multi-retailer. The proposed GA is compared with the mathematical model on the various sized test problems with respect to the solution quality and computation time. As a result, the GA demonstrates the capability of reaching solutions that are very close to those obtained by the mathematical model for small problems and stay within 3.2% from those obtained by the mathematical model for larger problems, with a much shorter computation time. Finally, we investigate the effects of the cost and operation variables on the total profit of the problem as well as the GA performance through the sensitivity analyses.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.437-441
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• 2008

A non-toxic Post Boost Stage(PBS) with LOX/Ethanol engine was successfully demonstrated at the Tomioka Facility of IHI Aerospace. IHI Aerospace has researched and developed the nontoxic propulsion systems and the LOX/Ethanol is one of the most attractive non-toxic bipropellant candidates. ${\rho}ISP$ of LOX/Ethanol is higher than ${\rho}ISP$ of the other non-toxic bipropellants as LOX/HC or $LOX/LH_2$. The authors studied the combustion characteristics of LOX/Ethanol propellant with the engine designed for LOX/LNG propellant. Also the injector with a built-in igniter was designed and examined its feasibility, ignition and combustion characteristics. We have demonstrated Post Boost Stage with future LOX/Ethanol engines. This propulsion system is targeted for expandable vehicle upper stage to accelerate delta-V to reach the required orbit. PBS Demonstration Model is designed as a test stand to evaluate feed system for integrated propulsion system and also to demonstrate Integrated Vehicle Health Management(IVHM) technique using local valve control and also valve behavior-monitoring capability.

• Nuclear Engineering and Technology
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• v.54 no.2
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• pp.554-564
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• 2022

The natural circulation phenomena occurring in fully integrated nuclear reactors are associated with a unique formation mechanism. The phenomenon results from a structural feature of these reactors involving upward flow from the core, located in the central-bottom region of a single vessel, and downward flow to the steam generator in the annulus region. In this study, to understand the natural circulation in a single vessel involving a multi-layered flow path, single-phase and two-phase natural circulation tests were performed using the SMART-ITL facility, and validation analysis of the TASS/SMR-S code was performed by comparing the corresponding test results. Three single-phase natural circulation tests were sequentially conducted at 15%, 10%, and 5% of full-scaled core-power without RCP operation, following which a two-phase natural circulation test was successively conducted with an artificial discharge of coolant inventory. The simulation capability of the TASS/SMR-S code with respect to the natural circulation phenomena was validated against the test results, and somewhat conservative but reasonably comparative results in terms of overall thermalhydraulic behavior were shown.

• Journal of Institute of Control, Robotics and Systems
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• v.14 no.5
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• pp.502-510
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• 2008

UAVs(Unmanned Aerial Vehicles) have many applications in military and commercial areas. The flight control system of UAVs is more important than manned aircraft's because the mission of UAVs must be operated without a human pilot. But very heavy and expensive navigation system makes it difficult to develop UAV flight control system. In this research, GPS/IMU integrated navigation filter was developed for light weight/low cost flight control system of small UAVs. With this navigation filter, full flight control system which has real time operating capability has been developed. The performance of the flight control system is basically checked by HILSIM (Hardware In the Loop SIMulation). Finally, the flight control system is verified by showing performance test result under real flight environment.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.9
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• pp.146-155
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• 1994

In this paper, we desribe a new system, called BEST, that is used to develop a macromodel or behavioral model easily. It automatically calculates the component values of macromodel represented by equations to satisfy the given specification. Also, it gives the way to analyze both the behavioral model and transistor level circuit, and then compare the analysis results of them to check the correspondence under specific temperature and bias condition, and BEST optimizes the component values of macromodel. Other feature is to characterize MOSFET as switch model which consists of PWL-RC network. Finally, it is possible to generage multi-level netlist which consists of macro/switch/transistor level circuits, and user can determine the trade-off between simulation speed and accuracy. With the graphic user interface form of macromodel development system described above. BEST enable designers to make macromodel by themselves and to uas it. We applied BEST to develop the macromodel for the test circuit and got the 18.6 times simulation speed up with preserving the accuracy within 10% compared to the conventional transistor level circuit simulation. Also, applicability of optimization capability was verified.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.5
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• pp.361-365
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• 2019

Although there is no strict definition of a power semiconductor device, a general description is a semiconductor that has capability to control more than 1 W of electricity. Integrated gate bipolar transistors (IGBTs), which are power semiconductors, are widely used in voltage ranges above 300 V and are especially popular in high-efficiency, high-speed power systems. In this paper, the size of the gate was adjusted to test the variation in the yield voltage characteristics by measuring the electric field concentration under the trench gate. After the experiment Synopsys' TCAD was used to analyze the efficiency of threshold voltage, on-state voltage drop, and breakdown voltage by measuring the P- region and its size under the gate.

• International conference on construction engineering and project management
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• 2009.05a
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• pp.388-392
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• 2009

Operation of LNG (Liquefied Natural Gas) plants requires an effective maintenance strategy. To this end, the long-term and short-term trend of faults, such as mechanical and electrical troubles, should be identified so as to take proactive approach for ensuring the smooth and productive operation. However, it is not an easy task to predict the fault trend in LNG plants. Many variables and unexpected conditions make it quite difficult for the facility manager to be well prepared for future faulty conditions. This paper presents a model to predict the fault trend in a LNG plant. ARIMA (Auto-Regressive Integrated Moving Average) model is combined with Wavelet Transform to enhance the prediction capability of the proposed model. Test results show the potential of the proposed model for the preventive maintenance strategy.