• Journal of the Optical Society of Korea
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• v.17 no.1
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• pp.103-108
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• 2013

The operation of a Doppler wind LIDAR in a mobile environment is very sensitive to shocks and vibrations, which can cause critical failures such as misalignment of the optical path and damage to optical components. To be able to stabilize the LIDAR and to perform wind field measurements in motion, a shock absorption and vibration isolation system was designed and implemented. The performance of the vehicle-mounted Doppler wind LIDAR was tested in motion, first in a circular test route with a diameter of about 30 m and later in regular expressway traffic. The vibration isolation efficiency of the system was found to be higher than 82% in the main vibration area and shock dynamic deflection was smaller than maximal deflection of the isolator. The stability of the laser locking frequency in the same mobile environment before and after the vibration isolation system installation was also found to be greatly improved. The reliability of the vibration isolation system was confirmed by good results of the analysis of the LIDAR data, in particular the plane position indicator of the line of sight velocity and the wind profile.

• Journal of Korean Society for Quality Management
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• v.49 no.4
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• pp.527-537
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• 2021

Purpose: The purpose of this study was to suggest an improved version of Proof-of-Nonce (PoN) algorithm, which is a distributed consensus algorithm used for block chain system. Methods: First, we used response surface method for design of experiment that is to generate experimental points considering non-linear relationship among variables. Then, we employed overlapped contour plots for visualizing the impact of control variables to performance target. Results: First, we modified the consensus procedure of the existing PoN algorithm by diminishing the content of the exchanged message. Then, we verified the performance improvement of the new PoN algorithm by performing a numerical experiment and paired t-test. Finally, we established new regression models for consensus time and Transactions per second (TPS) and proposed a method for optimizing control variables for obtaining performance target. Conclusion: We could improve the performance of the previous version of PoN algorithm by modifying the content of the exchanged message during 4-steps of consensus procedure, which might be a stepping stone for designing an efficient and effective consensus algorithm for blockchain system with dynamic operation environment.

• Journal of the Korea Institute of Military Science and Technology
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• v.22 no.3
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• pp.392-400
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• 2019

This paper provides a fin actuation system of missile based on electromagnetic-spring mechanism to miniaturize the system and lower the cost. Compared with proportional electro-mechanical actuators, the output of Electromagnetic-Spring Actuators(EMSA) has two or three discrete states, but the mechanical configuration of EMSA is simple since it does not need power trains like gears. The simple mechanism of EMSA makes it easy to build small size, low cost, and relatively high torque actuators. However, fast response time is required to improve the dynamic performance and accuracy of missiles since bang-off-bang operation of EMSA affects the flight performance of missile. In this paper the development of EMSA including parameter optimization and mathematical modeling is described. The simulation results using Simulink and experimental test results of prototype EMSAs are presented.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.14 no.4
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• pp.53-60
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• 2018

This study was conducted for analysis of a heat pump system using waste heat in an enclosed space such as a green house. The model was developed with mathematical equations in literature and Engineering Equation Solver (EES) was used to get the solution of the developed equations. The simulation results have 5% of reliability comparing the results with actual test data of heat pump system's dynamic operation. The operating performance of the system was calculated with variation of working fluid temperature in the thermal storage tank such as $25^{\circ}C$, $35^{\circ}C$, $45^{\circ}C$ and $55^{\circ}C$. As a result, the system's the highest total heating capacity shows 280 kWh and the storage tank's operating time decreased as the starting storage tank's temperature was high.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.6
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• pp.1291-1298
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• 2023

Surveillance reconnaissance sensor network is used for surveillance in wartime and area of operation. In this paper, we propose a target localization method using the detection signal strength of seismic sensors. Relay equipment calculates the target location using coordinate information and detection signal strength of the seismic sensors. Target localization error deviation due to environmental factors was minimized by subtracting the dynamic offset when calculating the target location. Field test shows improvement of target localization through reduction of errors. The average error was decreased to 3.62m. Up to 62% improved result was obtained compared to weighted centroid localization method.

• Journal of Drive and Control
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• v.20 no.4
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• pp.17-26
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• 2023

A forklift is an industrial vehicle that lifts or transports heavy objects using a hydraulically operated fork, and is equipped with an automatic transmission for the convenience of repetitive transportation, loading, and unloading work. The Transmission Control Unit (TCU) is a key component in charge of the shift control function of an automatic transmission. It consists of an electric circuit with an input/output signal interface function and firmware running on a microcontroller. To develop TCU firmware, the development process of shifting algorithm design, firmware programming, verification test, and performance improvement must be repeated. A simulator is a device that simulates a mechanical system having dynamic characteristics in real time and simulates various sensor signals installed in the system. The embedded transmission simulator is a simulator that is embedded in the TCU firmware. information related to the mechanical system that is necessary for TCU normal operation. In this study, an embedded transmission simulator applied to the originally developed forklift TCU firmware was designed and used to verify various forklift shift control algorithms.

• Nuclear Engineering and Technology
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• v.56 no.9
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• pp.3512-3527
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• 2024

Seismic quantification of nonstructural components like electrical cabinets is essential to ensure the uninterrupted operation of nuclear facilities during earthquake events. This process requires experimental tests, which can be expensive, time-consuming, and limited by safety concerns and precision. As an alternative to that, numerical simulations should be done in such a way that they are capable of capturing the global dynamic behavior with minimum computational efforts. However, in the case of complex interconnected cabinets, the simplification of numerical models often poses difficulties in illustrating the real-time behavior of combined cabinet systems. On the other hand, detailed three-dimensional (3D) numerical models require lengthy time and sophisticated computational setup, indicating their expensive computational efforts. To resolve this issue, a simplified and efficient 3D modeling approach has been proposed in this study. The accuracy of the results from the new model showed an excellent match with that obtained from the responses of the experimental test. After the validation and observation of the numerical efficiency, a practical application is implemented by considering the impacts of earthquake frequency contents on the behavior of cabinet systems. From the outcomes, it is evident that this proposed modeling methodology has the potential to replace the complex combined nuclear cabinet models for earthquake evaluation.

• Applied Chemistry for Engineering
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• v.4 no.4
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• pp.753-759
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• 1993

The research and motor octane numbers (RON & MON, respectively) of a gasoline are dynamic measures of its quality of performance as a fuel. ASTM standard engine test methods (RON:ASTM D-2699, MON:ASTM D-2700) have been used for determining the octane numbers (RON,MON)of gasolines. But these methods have been widely criticized because their repeatability and reproducibility of the test method are very poor. In addition to these objections, the cost and operation time involved in measuring by the standard method led to searches for "non -engine" methods (Gas Chromatographic method, Nuclear Magnetic Resonance Spectroscopic method). In this study, we determined the carbon type structural compositions of the gasolines by $^{13}C-NMR$ spectroscopy and predicted the octane number (RON & MON) with good accuracy. we presented an assessment of the effects of molecular structural composition on octane numbers.

• Wind and Structures
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• v.20 no.3
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• pp.449-468
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• 2015

Current wind-resistance designs of large-scale indirect dry cooling towers (IDCTs) exclude an important factor: the influence of the ventilation rate for radiator shutter on wind loads on the outer surfaces of the tower shell. More seemingly overlooked aspects are the effects of various ventilation rates on the wind pressure distribution on the tower surfaces of two IDCTs, and the feature of the flow field around them. In order to investigate the effects of the radiator shutter ventilation rates on the aerodynamic interference between IDCTs, this paper established the numerical wind tunnel model based on the Computational Fluid Dynamic (CFD) technology, and analyzed the influences of various radiator shutter ventilation rates on the aerodynamic loads acting upon a single and two extra-large IDCTs during building, installation, and operation stages. Through the comparison with the results of physical wind tunnel test and different design codes, the results indicated that: the influence of the ventilation rate on the flow field and shape coefficients on the outer surface of a single IDCT is weak, and the curve of mean shape coefficients is close to the reference curve provided by the current design code. In a two-tower combination, the ventilation rate significantly affects the downwind surface of the front tower and the upwind surface of the back tower, and the larger positive pressure shifts down along the upwind surface of the back tower as the ventilation rate increases. The ventilation rate significantly influences the drag force coefficient of the back tower in a two-tower combination, the drag force coefficient increases with the ventilation rate and reaches the maximum in a building status of full ventilation, and the maximum drag coefficient is 11% greater than that with complete closure.

• Geotechnical Engineering
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• v.13 no.5
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• pp.145-154
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• 1997

Though the static pile load tests gives the mosts accurate estimation on the load carrying capacity of tested pile, it appears time-consuming and not economical. Many test methods using equipments, such as Pile Driving Analyzer(PDA), STATNAMIC, and Osterberg cell, have been introduced in Korea, and pile best using PDA has been gaining popularity because of iris fast and simple operation. Static and dynamic tests results on the piles installed in the granular coils were analyzed to investigate the effect of geometrical damping on the estimated load carrying capacity. It was found that the CAPWAP analysis without considering geometrical damping effect underestimates the pile capacity by 30~60% under certain conditions. It was observed that the underestimation of pile capacity by CAPWAP occurs on the piles installed in the water-borne granular boils by SIP methods. When Smith skin damping value(SSkn) greater than 1.0 sec/m is obtained in CAPWAP analysis, it may reflect the large possibility of underestimation of pile capacity. The introduction of the geometircal damping option in CAPWAP analysis gives reasonable pile capacity, compared with the static pile load test results, and reduces the SSb value under 0.7 sec/m.