• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.8
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• pp.4809-4814
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• 2014

The aim of the present study was to estimate the prediction performance of a FDS (Fire Dynamic Simulator) to simulate the fire behaviors and suppression characteristics by operating a water-mist. Rosin-Rammler/log-normal distribution function was used to determine the initial droplet distribution of water-mist and the effects of its model constant were considered. In addition, the simulation models were validated by a comparison of the predicted fire suppression characteristics with water-mist injection pressures to the previous experiments, and the thermal flow behaviors and gaseous concentration variations were analyzed. The results showed that water-mists with the same mean diameter were affected by the characteristics of the droplet size distribution, which have different size and velocity distributions at the downstream location. The fire simulations conducted in this study determine the initial droplet size distribution tuned to the base of the spray characteristics measured by previous experiments. The simulation results showed good agreement with the previous measurements for temperature variations and fire suppression characteristics. In addition, it was confirmed that the FDS simulation with a water-mist operation supplies useful details on estimations of the thermal flow fields and gaseous concentration under water mist operation conditions.

• Journal of the Korea Society for Simulation
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• v.15 no.1
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• pp.87-95
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• 2006

We need to check into when a security system is newly developed, we against cyber attack which is expected in real network. However it is impossible to check it under the environment of a large-scale distributive network. So it is need to simulate it under the virtual network environment. SSFNet is a event-driven simulator which can be represent a large-scale network. Unfortunately, it doesn't have the module to simulate security functions. In this paper, we added the IDS module to SSFNet. We implement the IDS module by modeling a key functions of Snort. In addition, we developed some useful functions using Java language which can manipulate easily a packet for network simulation. Finally, we performed the simulation to verify the function if our developed IDS and Packets Manipulation. The simulation shows that our expanded SSFNet can be used to further large-scale security system simulator.

• Journal of Digital Convergence
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• v.11 no.1
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• pp.283-288
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• 2013

In this study, we introduce a 3D micro-cell simulator for radio wave propagation analysis in indoor environments. Previous studies treat only the path loss between the transmitter and receiver in 2D geometry. We provide the simulation results of indoor propagation prediction based on various ITU-R Recommendations. Simulation results described here indicate that the low and high frequency bands give quite different characteristics in presented indoor geometry. The propagation loss as a function of distance has two distinct regions. It is similar to that occurring in free space within 5-20m of the transmitter, however, increases significantly as the electromagnetic waves become obstructed by the walls at distances further away in the next region.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.10a
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• pp.219-220
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• 2016

A power management system (PMS) has been an important part in a ship integrated control system. To evaluate a PMS for a liquefied natural gas carrier (LNGC), this research proposes a real-time hardware-in-the-loop simulation (HILS), which is composed of major component models such as turbine generator, diesel generator, governor, circuit breaker, and 3-phase loads on MATLAB/Simulink. In addition, FPGA based control console and main switchboard (MSBD) are constructed in order to develop an efficient control and a similar real environment in an LNGC PMS. A comparative study on the performance evaluation of PMS functions is conducted using two test cases for sharing electric power to consumers in an LNGC. The result shows that the proposed system has a high verification capability for the operating function and failure insertion evaluation as a PMS simulator.

• Journal of the Korea Society of Computer and Information
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• v.27 no.1
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• pp.51-59
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• 2022

As the weapon system's dependence on software functions increased, software became a key factor in controlling the weapon system. In addition, as software development becomes more important domestically and internationally, software verification becomes an issue. The recent defense market has recognized this point and is demanding a plan for weapon system software maintenance. In this paper, we propose a weapon system software maintenance plan using Automatic Test Equipment. The specific method is to use a simulator to check the software function and identify failure cases. This is an effective way for developers to reduce the Total Corrective Maintenance Time(TCM) of the weapon system by reducing the time it takes to identify failure cases. It has been proven that the proposed Automatic Test Equipment can achieve software maintenance and excellent Maintainability and Operational Availability compared to the existing ones.

• Korean Journal of Acupuncture
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• v.38 no.4
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• pp.267-274
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• 2021

Objectives : Acupoints education is important in that it can determine the clinical competency of Korean Medicine Doctors (KMDs). Accordingly, we aimed to develop a practical simulator for acupoints education, acupoints training, acupoints practice, and acupoints evaluation. Methods : Korean Medicine (KM) SMART Table can be divided into hardware, server and components, and is organically linked. We develop KM SMART Table that combines the hardware of a human-sized table with a UHD display capable of multi-touch in two cases and software that can teach acupoints. We make Augmented Reality (AR) contents linked with KM SMART Table contents and develop applications that can use contents using mobile devices. By developing an AR image tracking module to react with KM SMART Table, it enables acupoint learning according to the mobile device platform and human anatomy. Results : The current system is a prototype where some 3D technology has been implemented, but the AR function will be produced later. New learning using 3D and AR will be required during acupoints education and acupoints practice. It will be used a lot in OSCE (Objective Structured Clinical Examination) practices for strengthening the competency of KMDs, and it will be of great help not only in KM education as a unique simulator of KM, but also in the practice of acupuncture and chuna for musculoskeletal diseases. Conclusions : The KM SMART Table is a technology that combines 3D and AR to learn acupoints, and to conduct acupoints OSCE practice, and we suggest that it can be usefully used for educational evaluation.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.2
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• pp.75.2-76
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• 2021

MESSIER is a science satellite project to observe the Low Surface Brightness (LSB) sky at UV and optical wavelengths. The wide-field, optical system of MESSIER is optimized minimizing optical aberrations through the use of a Linear Astigmatism Free - Three Mirror System (LAF-TMS) combined with freeform mirrors. One of the key factors in observations of the LSB is the shape and spatial variability of the Point Spread Function (PSF) produced by scatterings and diffraction effects within the optical system and beyond (baffle). To assess the various factors affecting the PSF in this design, we use PhoSim, the Photon simulator, which is a fast photon Monte Carlo code designed to include all these effects, and also atmospheric effects (for ground-based telescopes) and phenomena occurring inside of the sensor. PhoSim provides very realistic simulations results and is suitable for simulations of very weak signals. Before the application to the MESSIER optics system, PhoSim had not been validated for confocal off-axis reflective optics (LAF-TMS). As a verification study for the LAF-TMS design, we apply Phosim sequentially. First, we use a single parabolic mirror system and compare the PSF results of the central field with the results from Zemax, CODE V, and the theoretical Airy pattern. We then test a confocal off-axis Cassegrain system and check PhoSim through cross-validation with CODE V. At the same time, we describe the shapes of the freeform mirrors with XY and Zernike polynomials. Finally, we will analyze the LAF-TMS design for the MESSIER optical system.

• Design Convergence Study
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• v.17 no.4
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• pp.17-29
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• 2018

In the semi-autonomous vehicle, before reaching a fully autonomous driving stage, it is imperative for the system to issue a take-over request(TOR) that asks a driver to operate manually in a specific situation. The purpose of this study is to compare whether head-up display(HUD) is a better human-vehicle interaction than head-down display(HUD) in the event of TOR. Upon recognition of TOR in the experiment with a driving simulator, participants were prompted to switch over to manual driving after performing a secondart task, that is, playing a game, while in auto-driving mode. The results show that HUD is superior to HDD in 'ease of use' and 'satisfaction' although there is no significant difference in reaction time and subjective workload. Therefore, designing secondary tasks through HUD during autonomous driving situation improves the user experience of the TOR function. The implication of this study lies in the establishing an empirical case for setting up UX design guidelines for autonomous driving context.

• Journal of computational fluids engineering
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• v.20 no.3
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• pp.94-103
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• 2015

The turbulent flow characteristics in the channel flow are investigated using large eddy simulation(LES) of FDS code, built in NIST(USA), in which the near-wall flow is solved by Werner-Wengle wall function. The periodic flow condition is applied in streamwise direction to get the fully developed turbulent flow and symmetric condition is applied in lateral direction. The height of the channel is H=1m, and the length of the channel is 6H, and the lateral length is H. The total grid is $32{\times}32{\times}32$ and $y^+$ is kept above 11 to fulfill the near-wall flow requirement. The Smagorinsky model is used to solve the sub-grid scale stress. Smagorinsky constant $C_s$ is 0.2(default in FDS). Three cases of Reynolds number(10,700, 26,000, 49,000.), based on the channel height, are analyzed. The simulated results are compared with direct numerical simulation(DNS) and particle image velocimetry(PIV) experimental data. The linear low-Re eddy viscosity model of Launder & Sharma and non-linear low-Re eddy viscosity model of Abe-Jang-Leschziner are utilized to compare the results with LES of FDS. Reynolds normal stresses, Reynolds shear stresses, turbulent kinetic energys and mean velocity flows are well compared with DNS and PIV data.

• Journal of Electrical Engineering and Technology
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• v.11 no.1
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• pp.86-92
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• 2016

Upon detecting a frequency event in a power system, the stepwise inertial control (SIC) of a wind turbine generator (WTG) instantly increases the power output for a preset period so as to arrest the frequency drop. Afterwards, SIC rapidly reduces the WTG output to avert over-deceleration (OD). However, such a rapid output reduction may act as a power deficit in the power system, and thereby cause a second frequency dip. In this paper, a hybrid reference function for the stable SIC of a doubly-fed induction generator is proposed to prevent OD while improving the frequency nadir (FN). To achieve this objective, a reference function is separately defined prior to and after the FN. In order to improve the FN when an event is detected, the reference is instantly increased by a constant and then maintained until the FN. This constant is determined by considering the power margin and available kinetic energy. To prevent OD, the reference decays with the rotor speed after the FN. The performance of the proposed scheme was validated under various wind speed conditions and wind power penetration levels using an EMTP-RV simulator. The results clearly demonstrate that the scheme successfully prevents OD while improving the FN at different wind conditions and wind power penetration levels. Furthermore, the scheme is adaptive to the size of a frequency event.