• Journal of the Microelectronics and Packaging Society
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• v.15 no.1
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• pp.59-64
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• 2008

Recently, DC-DC choppers must be increased switching frequency in order to achieve a small size, a light weight and a low noise. However, the switches of chopper are subjected to high switching power losses and switching stresses. As a result of these, the chopper system bring on a low power efficiency. To improved these, this paper is studied on a new DC-DC chopper of high efficiency operated with soft switching(that is, zero current switching and zero voltage switching, ZVCS), of semiconductor switches using in chopper. The soft switching operation is applied to a partial resonant method that the switches operate at zero current of inductor and zero voltage of capacitor in resonant circuit. And the partial resonant circuit makes use of a inductor using step-up and a snubber capacitor, the circuit topology of chopper is simple. Some simulative results on computer and experimental results confirm the validity of analytical results of the DC-DC chopper.

• Journal of the Society of Disaster Information
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• v.19 no.1
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• pp.204-215
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• 2023

Purpose: In this study, it was proposed a plan to build the Continuous Preventive Audit System in the military Organization with the expectation that we will develop an efficient audit method under the rapidly changing audit and work environment in the future. Method: it was examined the realities and problems of the military self-audit, the cases of the Continuous Preventive Audit System currently being used by government departments and institutions and internal control inspection of the information system of the Foreign Audit Office. Result: Government departments, agencies, and foreign auditors have established a Continuous Preventive Audit System to overcome the problems and limitations of their own audits, ensuring accounting accident prevention and audit work efficiency and are focused on auditing internal controls of information systems. Conclusion: In the future, more specific studies on the design of detailed scenarios for each function of defense work and the research and analysis on the improvement of defense information system should be followed for the establishment and settlement of a more specific Continuous Preventive Audit System.

• Journal of Korea Water Resources Association
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• v.46 no.9
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• pp.885-896
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• 2013

SEMMA (Soil Erosion Model for Mountain Areas) should be revised to apply on mountain watershed of large scale. In this study, the basic structure of original SEMMA and methods to calculate main parameters are reviewed and the revised parameters are presented to expand a range of application. SEMMA-Ic is new model revised by a rate of vegetation cover which is substituted for index of vegetation structure to use specially NDVI for large scale areas. The correlation coefficient and the Nash-Sutcliffe simulation efficiency for the revised model decreased rather than those of original model. However the evaluation of the revised model on watershed showed the approximate simulation with measured sediment yield and the underestimated simulation when sediment yield is large. The additional research for channel erosion is needed so that soil erosion model for hillslopes is used to estimate sediment yield from a watershed.

• Journal of Korea Society of Industrial Information Systems
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• v.11 no.5
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• pp.141-149
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• 2006

Ubiquitous computing environment means the computing environment that has taken its position so closely with the ordinary living so much like air or water. In building up the U-Korea, one of the important issues is the social issue from the drasticincrease of senior population. The contemporary society has its distinct trend in increase of senior household following the nuclear family orientation, increase of working parents with the advancement of women in society, unable to support seniors for long distance or short distance of business trip and other reasons that the need of senior welfare has been ever more felt. Accordingly, the Ministry of Government Affairs and Home Administration has developed the wireless paging system to make prompt response system for 119 Rescue when the single senior is encountered with emergency situation that is has been widely provided for the socially neglected people such as single senior, the disabled persons and others. Currently, the wireless paging system is operated as the sub-system for emergency rescue informationsystem, but due to the lack of reliability of product, problems of terminal portable transmitter, receptor and others, rejection of beneficiary and lack of knowledge in use, insufficient management and supervision of managing officers, the efficiency has been declined that there is a need of development for the system. Therefore, this study proposes the context aware information structure of the subject of ubiquitous wireless paging system required forthe development of the wireless paging system model of ubiquitous environment that improved the problems of currently operated wireless paging system.

• Journal of The Korean Society of Agricultural Engineers
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• v.59 no.6
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• pp.101-108
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• 2017

This study attempted to improve the accuracy of streamflow and baseflow prediction of Soil and Water Assessment Tool (SWAT) by applying baselfow recession constants for each sub-watershed. This study set two different scenarios (S1 and S2) to evaluate the impact of application of baseflow recession constants for each sub-watershed on streamflow prediction. In S1, Only the baseflow recession constant obtained from the streamflow station located in the final outlet of study area was applied for whole sub-watersheds. In S2, baseflow recession constants obtained from six different streamflow stations were applied for each sub-watershed. Then, baseflow was separated form the measured streamflow data and the predicted streamflow of S1 and S2 using Web-based Hydrograph Analysis Tool (WHAT). The results showed Nash-Sutcliff efficiency (NSE) and $R^2$ of S2 were a little higher than these of S1 in both streamflow and baseflow prediction results. However, it is important that S2 reflected physical meaning of baseflow recess. Also, recession part of hydrograph in S2 was calibrated better than that of S1 compared to the measured hydrograph.

• Journal of The Korean Society of Agricultural Engineers
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• v.60 no.3
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• pp.95-105
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• 2018

Understanding the composition of the dam inflow can improve the efficiency of dam operation considering the seasonal characteristics. Hydrograph analysis is one of the methods to identify the characteristics of dam inflow. In addition, baseflow separation on the dam inflow can be affected by anthropogenic influences depending on dam locations. In this regard, the objectives of this study are 1) to analyze yearly and monthly baseflow contribution to the dam inflow and 2) to compare the baseflow contribution to the inflow in dams located upstream and downstream of the watershed. The result shows that the estimated baseflow index was smaller in the upstream dams compared to the downstream dams. Discharge from the upstream water infrastructure including dams and reservoirs can be a part of inflow into the downstream water infrastructure. Based on this scenario, the discharge regulated from the upstream dam could lead to overestimation of baseflow contribution to inflow into the downstream dam. We expect that the results from this study elucidate the role and function of dams and hence, contribute to the efficient operation of dams located in the upstream and the downstream of the watershed.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.171-171
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• 2023

This study investigates the capability of Physics-Informed Neural Networks (PINNs) for solving the solution of partial differential equations. Particularly, the 1D Saint-Venant Equations (SVEs) were considered, which describe the movement of water in a domain with shallow depth compared to its horizontal extent, and are widely adopted in hydrodynamics, river, and coastal engineering. The core contribution of this work is to combine the robustness of neural networks with the physical constraints of the SVEs. The PINNs method utilized a neural network to approximate the solutions of SVEs, while also enforcing the underlying physical principles of the equations. This allows for a more effective and reliable solution, especially in areas with complex geometry and varying bathymetry. To validate the robustness of the PINNs method, numerical experiments were conducted on several benchmark problems. The results show that the PINNs could be achieved high accuracy when compared with the solution from the numerical solution. Overall, this study demonstrates the potential of using PINNs and highlights the benefits of integrating neural network and physics information for improved efficiency and accuracy in solving SVEs.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.980-987
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• 2006

Recently, twin-tunnel is often designed considering the aspects of disaster prevention and economic reasons. However, the design cases and the studies are relatively insufficient. By the twin-tunnel excavation, deviate stresses of pillar between tunnels are increased and the increased stresses induce the instability of the twin-tunnel. In this study, numerical analyses about the twin-tunnel behaviour are conducted while varying ground strength, width of pillar and depth of earth cover and a series of regression analyses are carried out by using the results of numerical analyses for the twin-tunnel. Based on the numerical analyses, an estimation method of derived stresses is suggested though the regression analyses. Also, based on the results of regression analyses, an quantitative estimation method considering the reinforcement effects is also suggested. Then various parametric studies are conducted to be considered the reinforcement type and various design parameters. Finally, the efficiency of the suggested method is verified through the results of parametric studies.

• International Journal of Internet, Broadcasting and Communication
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• v.16 no.2
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• pp.247-254
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• 2024

In this paper, we compare and analyze the evacuation time required at a general hospital using an evacuation simulation program and propose an optimized procedure to improve safety. The paper analyzed the evacuation time of all occupants, including patients who cannot evacuate by themselves. The following four cases were analyzed in order: the width of evacuation stairs is 120cm, 130cm, 140cm, and 150cm. The results of the evacuation simulation showed that the total evacuation time is 1998s, 1796s, 1651s, and 1161s, respectively. For every 10cm increase in the width of the evacuation stairs, the evacuation time decreases by 202s, 145s, and 91s in sequence. The evacuation time decreases as the width of the evacuation stairs increases. However, the rate of reduction in evacuation time decreases. Therefore, simply increasing the width of evacuation stairs cannot significantly improve evacuation efficiency, and it is necessary to choose an appropriate width of evacuation stairs. In addition, all four cases simulations display that after 600 seconds, the evacuees are concentrated in two evacuation stairs, while there are very few evacuees in the other stairs. To solve this problem, it is necessary to disperse the movement route and consider multiple avoidance methods.

• Journal of Korean Society for Geospatial Information Science
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• v.22 no.4
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• pp.159-164
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• 2014

These days, inexpensive and high efficiency UAV of disaster prevention and spatial information has been given more attention. But studies about test of accuracy of UAV were not enough despite high interest. This research produced DSM and ortho photo and estimated accuracy by comparing coordinates with GNSS survey to evaluate outcome of fixed wing UAV. The ortho photo was found to make use of it to update 1/1,000 map. This research investigated spatial information construction using existing terrestrial LiDAR to suggest effectiveness of fixed wing UAV.