• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.2
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• pp.82-89
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• 2021

This study proposes a DAB two-stage series structure with insulated bidirectional DC-DC converter for two-way power transfer between the renewable energy of high voltages (1 kV and above). The proposed circuit transforms the existing DAB converter into a two-stage series structure to reduce the pressure in the switch. The problem of power imbalance occurring in the design of the DAB converter second-stage series is improved by applying the cell balancing method circuit and the common mode coupled inductor using an external flying capacitor instead of reflecting the existing improvement measures, voltage balance control, and inductor current control. In addition, a no-load supercharging sequence is proposed in high voltages and high-speed switching by using the fixed duty output method. This study presents the analysis results through the structure of the proposed circuit, the principle of improving the power imbalance problem, and simulations. Prototypes were manufactured to meet the specifications of input/output voltage of 1700 V, maximum load of 65 kW, and switching frequency of 51kHz, and the validity of the topology was verified using the experimental results and efficiency data.

• Korean Journal of Construction Engineering and Management
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• v.4 no.2 s.14
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• pp.66-73
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• 2003

Building construction projects are performed by a number of sub-contractors specialized in diverse trades. Therefore information management among these constituents is quite challenging especially due to exponentially increasing manpower and material resources. In recognition of the importance of information management in project sites a number of systems have been suggested, but the application is limited one of the main reason is that general contractors use these systems and sub-contractor's participation understanding and financial ability are limited. Besides other problems such as loss along communication channel, distortion of information due to inefficient input device and tremendous amount of time and labor are required for collection analysis, and management of information to prepare a daily-report. Therefore the Purpose of this study is to improve reporting process through analyzing current daily reporting system. This paper also suggests the direction of the improved daily reporting system to enhance the performance of construction projects through incorporating sub-contractor's participation in daily reporting system.

• Journal of Navigation and Port Research
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• v.29 no.10 s.106
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• pp.859-863
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• 2005

This paper describes the improvement of power control characteristics of ship's emergency lighting power supply(SELPS), by which electric power is controlled extensively, and power ON-OFF is controlled and system parameter monitored in remote distance by PC serial communication. Proposed system is composed of step-down converter(SDC), emergency power supply circuit(EPSC), half bridge(HB) inverter, fluorescent lamp(FL) starting circuit, microprocessor control and multi communication circuit. Experimental works confirm that relative system stops when over current is detected and speedy and stable emergency power is supplied when main power source cut-off, and controls input power up to 35[$\%$] by adjusting pulse frequency of the HB inverter, and ON-OFF control of multiple SELS, real time transmission and monitor of parameters as to voltage, current, and power values are performed appropriately by PC communication.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.1
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• pp.329-332
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• 2012

LEDs are using widely in a field of illumination, LCD LED backlight, mobile signals because they have several merits, such as low power consumption, long lifetime, high brightness, fast response, environment friendly. To achieve high performance LEDs, one needs to enhance output power, reduce operation voltage, and improve device reliability. In this paper, we have proposed that the optimum design and specialized process could improve the performance of LED chip. It was showed an output power of 7cd and input supplied voltage of 3.2V by the insertion technique of current blocking layer. In this paper, GaN-based LED chip which is built on the sapphire epi-wafer by selective MOCVD were designed and developed. After that, their performances were measured. It showed the output power of 7cd more than conventional GaN-based chip. It will be used the lighting source of a medical equipment and LCD LED TV with GaN-based LED chip.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.292-295
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• 2004

The SIT was introduced by Nishizawa. in 1972. When compared with high-voltage, power bipolar junction transistors, SITs have several advantages as power switching devices. They have a higher input impedance than do bipolar transistors and a negative temperature coefficient for the drain current that prevents thermal runaway, thus allowing the coupling of many devices in parallel to increase the current handling capability. Furthermore, the SIT is majority carrier device with a higher inherent switching speed because of the absence of minority carrier recombination, which limits the speed of bipolar transistors. This also eliminates the stringent lifetime control requirements that are essential during the fabrication of high-speed bipolar transistors. This results in a much larger safe operating area(SOA) in comparison to bipolar transistors. In this paper, vertical SIT structures are proposed to improve their electrical characteristics including the blocking voltage. Besides, the two dimensional numerical simulations were carried out using ISE-TCAD to verify the validity of the device and examine the electrical characteristics. A trench gate region oxide power SIT device is proposed to improve forward blocking characteristics. The proposed devices have superior electrical characteristics when compared to conventional device. Consequently, the fabrication of trench oxide power SIT with superior stability and electrical characteristics is simplified.

• The Journal of Korea Robotics Society
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• v.18 no.3
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• pp.251-259
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• 2023

In the path traveling of differential-drive robots, the steering controller plays an important role in determining the path-following performance. When a robot with a pure-pursuit algorithm is used to continuously drive a right-angled driving path in an unstructured environment without turning in place, the robot cannot accurately follow the right-angled path and stops driving due to the ground and motor load caused by turning. In the case of pure-pursuit, only the current robot position and the steering angle to the current target path point are generated, and the steering component does not reflect the speed plan, which requires improvement for precise path following. In this study, we propose a driving algorithm for differentially driven robots that enables precise path following by planning the driving speed using the radius of curvature and fusing the planned speed with the steering angle of the existing pure-pursuit controller, similar to the Model Predict Control control that reflects speed planning. When speed planning is applied, the robot slows down before entering a right-angle path and returns to the input speed when leaving the right-angle path. The pure-pursuit controller then fuses the steering angle calculated at each path point with the accelerated and decelerated velocity to achieve more precise following of the orthogonal path.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.10
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• pp.6466-6474
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• 2015

The purpose of this study is to indicate the problem and its improvement plan derived from pollution discharge industries inspection, implementation process on overall instruction including record management, and utilization of information about emission. This focuses on analyzing the inspection system of pollution discharge industries and the actual condition of management system with survey and interview from the managers. As a result of examining the administration information system from each of structural and practical perspectives, the users were not able to receive support for inspection through the system because it was designed based on licensing. Also according to results of survey and interview, it was difficult to input checkup data and to maintain the information of emission in a sustainable manner. This problem occurs since the current system is not utilized properly. Thus, this study examines similar systems operated in Korea and suggests measure to make improvements. The measures are considered as constructing simple user interface for systematizing of administrative works, simplifying the input matters, linking systems of inspection and emission information, establishing statistical function of emission information, and managing inspection functions through the mobile system.

• Fire Science and Engineering
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• v.31 no.4
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• pp.80-85
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• 2017

Recently, in Korea, construction of high-rise buildings has been rapidly increasing. Therefore, in order to minimize the loss of life and property in the event of a fire, "performance-based design" which requires performance equal to or better than current regulations is obligatorily required. However, in the field of fire and evacuation simulation, which occupies a large part in the performance-based design, detailed technical guidelines have not yet been established. Therefore, various designers are proceeding with the computer simulation modelling by referring to the design report book previously performed. Especially, in the case of the fire simulation, according to the judgment of a designer the scenario type is selected and the input values is set. Even if the building is used for the same purpose, it is true that the result can be different depending on how and who designed it. Therefore, in this paper, we have investigated the fire scenarios type and scenarios input values by randomly examining 7 preliminary reports of performance-based design in B metropolitan city. We also propose the improvement strategy for fire simulation and lay the groundwork for establishment of technical guidelines for fire simulation for performance-based design.

• Industry Promotion Research
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• v.7 no.2
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• pp.59-73
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• 2022

This paper aims to analyze efficiency of sustainable development of foreign trade in eastern China to reduce the input while maintaining the current output level. This paper adopts relevant input-output indicators of 11 provinces in eastern China from 2016 to 2020 and uses DEA to measure comprehensive efficiency, pure technical efficiency, and scale efficiency from the input perspective. Malmquist index was used to calculate MPI. As a result, from 2016 to 2020, the MPI of all provinces in eastern China was 1.035, higher than 1, and the net technology efficiency was 0.911, lower than 1. Overall, the average technological progress index increased 4.5% to 1.045. It can be seen that the sustainable development efficiency of foreign trade has an overall influence on comprehensive efficiency, net technology efficiency, and scale efficiency. The efficiency of sustainable development of foreign trade in eastern China is mainly limited by its scale. The improvement of MPI in the eastern Region mainly benefits from technological progress. For provinces affected by internal factors, it is suggested to strengthen internal coordination. For provinces affected by external factors, it is suggested to respond appropriately to external factors.

• Journal of the Society of Disaster Information
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• v.16 no.1
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• pp.155-162
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• 2020

Purpose: The purpose of study was to identify problems in disaster recovery resource management and operation through on-site investigation and utilize them as improvement proposal for disaster recovery resources management by local governments. Method: Areas with high natural and social disasters recorded in historical and yearly records of natural and social disasters, related books, and annual reports for 20 years were selected. The DRSS data of the selected local governments were analyzed and the reserve warehouse were selected for field survey. Result: It is analyzed that the current situation in the city hall and district offices is somewhat insufficient due to heavy work by the working-level officials of local governments on the storage of disaster recovery resources. The actual amount of stockpiles and DRSS data are somewhat different or missing because the input method and criteria are not clear at present when inputting the current data. Conclusion: To improve the management of the disaster recovery resource reserve, it is deemed that education of DRSS and training of best practices for the operation of disaster management resources are urgently needed, and that a systematic management of stockpiles using disaster prevention experts will be required.