• The Transactions of The Korean Institute of Electrical Engineers
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• v.68 no.1
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• pp.129-139
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• 2019

In order for a gun-launched guided projectile to glide to the maximum range, when to deploy the fin and start flight with guidance and control should be considered in range optimization process. This study suggests a solution to the optimal guidance problem for flight range maximization of the flight model of a guided projectile in vertical plane considering the aerodynamic properties. After converting the nonlinear Multi-Phase Optimal Control Problem to Two-Point Boundary Value Problem, the optimized guidance command and the best fin deployment timing are calculated by the proposed numerical method. The optimization results of the multiple flight rounds with various initial velocity and launch angle indicate that determining specific launch condition incorporated with the guidance scheme is of importance in terms of mechanical energy consumption.

• Journal of the Korean Society of Systems Engineering
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• v.16 no.2
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• pp.131-140
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• 2020

The characteristics of ballistic missiles are changing rapidly but studies have mostly focused on fragmentary flight trajectory analysis estimating the changing characteristics of some types, while there is a lack of research on comprehensive and efficient ballistic search, detection and prediction for missiles including the new types that have been gaining attention lately. This paper analyzes the flight trajectory characteristics of ballistic missiles at various ranges considering flight path angle adjustment, specific impulse and drag force with altitude based on the optimized equations of motion reflecting the parameters of North Korea's general and new types of ballistic missiles. The flight trajectory characteristics of representative ranges for each ballistic missile were analyzed by adjusting the flight path angle in the minimum energy method, lofted method, and depressed method. In addition, High value target can attacked by ballistic missiles considering flight path angle adjustment at various points. It's expected to be used to Threat Evaluation and Weapon Allocation, and deployment of defense systems by interpreting the analysis of the latest Iskander-class ballistic missiles and the new multiple rocket launcher.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.9
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• pp.851-858
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• 2008

In this paper, the wrinkling behavior of vertically creased corner-loaded square membranes was studied using geometrically nonlinear post-buckling analysis. The membranes were modeled using shell elements, and the meshes were seeded with semi-random geometrical imperfection to instigate the buckling deformation. A pristine and creased membranes with various initial deployment angles were considered in the analyses and the results were compared. Results showed that local wrinkles initiated near the corner where the higher load was applied, which grew to form a single diagonal global wrinkle as the load ratio increased. It was also found that the local wrinkle initiation and the global wrinkle formation were significantly dependent on the initial deployment angles.

• Journal of Electrical Engineering and Technology
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• v.13 no.5
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• pp.1769-1777
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• 2018

This paper proposes a method for optimal placement of Phasor Measurement Units (PMUs) considering system configuration and its attributes during the planning phase of PMU deployment. Each bus of the system is assessed on four diverse attributes; namely, redundancy of measurements, rotor angle and frequency monitoring of generator buses, reactive power deficiency, and maximum loading limit under transmission line outage contingency, and a consolidated 'degree of criticality' is determined using Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS). The major contribution of the proposed work is the development of modified objective function which incorporates values of the degree of criticality of buses. The problem is formulated as maximization of the aggregate degree of criticality of the system. The resultant PMU configuration extends complete observability of the system and majority of the PMUs are located on critical buses. As budgetary restrictions on utilities may not allow installation PMUs even at optimal locations in a single phase, multi-horizon deployment of PMUs is also addressed. The proposed approach is tested on IEEE 14-bus, IEEE 30-bus, New England (NE) 39-bus, IEEE 57-bus and IEEE 118-bus systems and compared with some existing methods.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.4
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• pp.509-517
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• 2020

This study evaluated the importance of technical characteristics in manufacturing street furniture using 3D printing technology to suggest the direction of development of high priority 3D printing technology. The importance was analyzed by the QFD, quantified by scores and the priority of the items was summarized. As a result, the 'output size', 'shrinkage of material', and 'output angle' were derived as technical elements that should be prioritized in development and research. For verification, the design of atypical street furniture was made into a large 3D printed output and the development direction was suggested by applying the technical elements of priority during the manufacturing process. Street furniture should be designed based on functionality and stability, as well as economic efficiency, productivity, and aesthetics. Therefore, the 'output size' ensured stability by minimizing the division of parts, and the 'contractability of materials' satisfied the aesthetic and productivity by minimizing the error of form. Finally, the 'output angle' was verified by improving the quality of the output and selecting an angle with efficient and structural stability through various output angles.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.9
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• pp.681-689
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• 2020

This paper presents methods and results of both flight test examining roll angle estimation performance of slowly rolling munition forced to spin in the air, and fabricating a replica of guided munition. Guided munition was deployed from multi rotor type UAV mother ship whose altitude and velocity was conveyed to it as initial state. Flight test scenario is composed of a sequence of munition drop(deployment), munition spin, roll angle estimation and stabilization. Munition was deployed from mother ship at around 200m high with horizontal velocity of 15m/s, and was made spun using internal reaction wheel. Performance analysis on roll angle estimation is provided in comparison with commercial aerospace graded GPS/INS. Moreover, several mechanisms that rotates munition using reaction wheel, and actual product that realizes one of them are introduced.

• Journal of Convergence for Information Technology
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• v.10 no.6
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• pp.14-18
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• 2020

In this paper, when two sets of cross-eye jammer antennas are installed vertically to jam a monopulse radar, the jamming effects according to the jammer's phase difference, amplitude ratio, and radar angle of engagement are analyzed. The phase difference and amplitude ratio of the cross-eye jammer can be adjusted in the jammer, but since the angle of engagement is relatively determined by the radar, it is very important to respond to changes in the angle of engagement. The orthogonally deployed jammer antennas can be considered as a good way to increase the jamming effect while minimizing the hardware configuration, and the jamming effect is analyzed while changing the angle of inclination from 0° to 360°. This jammer greatly improves the jamming effects at the angles of incidence 45°~135° and 225°~315°, compared to a single jammer. And it is expected to be useful in the design of cross-eye jammers for military aircraft and ships.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.5
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• pp.421-426
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• 2010

In this paper, the thickness effect on the wrinkle-crease interaction behavior of corner-loaded creased square membranes was studied using geometrically nonlinear post-buckling analysis. The membranes were modeled using shell elements, and the meshes were seeded with semi-random geometrical imperfection to instigate the buckling deformation. Results indicated that the wrinkle-crease interaction behavior was significantly dependent on the membrane thickness. Both the global and local wrinkles developed earlier as the thickness decreased. It was also found that the wrinkling behavior depended on the initial deployment angle in which the local wrinkle initiation occurred earlier, while the global wrinkle formation was delayed as the angle increased.

• Journal of the Korean Society for Marine Environment & Energy
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• v.4 no.3
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• pp.65-73
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• 2001

Herein, a theoretical method based on the catenary model Is applied to obtain the tension and drag forces acting on the trash curtain which is deployed at river for the prevention of floating debris inflow into the ocean. Under the assumption that fluid drag is perpendicular to the trash curtain, the tension and drag forces are uniform along the trash curtain. As a numerical model, the trash curtain is moored both symmetrically and asymmetrically with respect to the flow. The tension and drag forces on the trash curtain are investigated according to the change of Bap ratio and inclined angle of the trash curtain. Numerical results show that tension parameter is increased as the gap ratio is increased. It is found that tension parameter is reduced as the inclined angle is increased in the case of asymmetric deployment. The numerical model is applied to the specific problem for the trash curtain (200m) deployed at the Tancheon on the Han river. The maximum inflow velocity that anchor system can endure is 2m/sec.

• Ocean Systems Engineering
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• v.9 no.4
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• pp.391-407
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• 2019

Tracking the location (position) of a surface or underwater marine vehicle is important as part of guidance and navigation. While the Global Positioning System (GPS) works well in an open sea environment but its use is limited whenever testing scaled-down models of such vehicles in the laboratory environment. This paper presents the design, development and implementation of a low energy ultrasonic augmented single beacon-based localization technique suitable for such requirements. The strategy consists of applying Extended Kalman Filter (EKF) to achieve location tracking from basic dynamic distance measurements of the moving model from a fixed beacon, while on-board motion sensor measures heading angle and velocity. Iterative application of the Extended Kalman Filter yields x and y co-ordinate positions of the moving model. Tests performed on a free-running ship model in a wave basin facility of dimension 30 m by 30 m by 3 m water depth validate the proposed model. The test results show quick convergence with an error of few centimeters in the estimated position of the ship model. The proposed technique has application in the real field scenario by replacing the ultrasonic sensor with industrial grade long range acoustic modem. As compared with the existing systems such as LBL, SBL, USBL and others localization techniques, the proposed technique can save deployment cost and also cut the cost on number of acoustic modems involved.