• Journal of Aerospace System Engineering
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• v.11 no.4
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• pp.36-43
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• 2017

Blade design optimization of QTP-UAV prop-rotor was conducted using ModelCenter(R). Performance efficiency of the blade in hover and forward flight were adopted as the multi-objective function. Required power and pitch link force applied to constraint in each flight mode and limited lower than the value of the baseline blade. Design variables of root chord length of the blade, taper ratio, twist slope, twist angle at 0.5R of the blade, anhedral angle, parabolic coefficient of a tip shape and location of airfoil were used to generate the blade planform. CAMRAD-II, the comprehensive analysis program of rotorcraft, was used for performance analysis of prop-rotor blade in design process. Performance of the optimized blade improved 1.6% of figure of merit in hover and 13.6% of propulsive efficiency in forward flight. Pitch link force also reduced approximately 30% less than that of the baseline blade.

• Journal of the Society of Naval Architects of Korea
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• v.55 no.6
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• pp.490-496
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• 2018

The consistency of the initially designed waves in the domain is essential for accurate calculation of the added resistance in waves through CFD. In particular, unwanted reflected waves at domain boundaries can cause incorrect numerical solutions due to the superposition with initially designed waves. Euler Overlay Method(EOM) is one of the methods for reducing wave reflections by adding an additional source term to momentum and phase conservation equations, respectively. In this study, we apply the Euler Overlay Method(EOM) to the open-source CFD library, OpenFOAM(R), to simulate the accurate free-surface waves in the domain and the parametric study is performed for efficient implementation of Euler Overlay Method(EOM). Considering that the damping efficiency depends on the selection of the overlay parameter in the added source terms, the size of overlay zone and the wave steepness, the influences of these factors are tested through the wave elevation measured at constant time intervals in the 2D numerical wave tank. Through this process, guidelines for selection of optimal overlay parameter and overlay zone size that can be applied according to the scaling law are finally presented.

• Land and Housing Review
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• v.14 no.4
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• pp.103-110
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• 2023

People who spend most of their day indoors are continuously exposed to internally and externally generated indoor pollutants. According to a 2022 report from the World Health Organization (WHO), air pollution is the cause of more than 7 million deaths annually worldwide, emphasizing the seriousness of indoor air pollutants. Air pollutants include nitrogen oxides (NOx), formaldehyde (HCHO), and volatile organic compounds (VOCs), which have serious effects on the human body. Photocatalyst is a material that can remove these indoor air pollutants. Photocatalysts not only have the ability to remove dust precursors, but also have antibacterial, sterilizing, and deodorizing functions, making them effective in improving indoor air quality. This study suggests areas and methods in which photocatalysts can be applied to buildings. Fields of application include interior and exterior construction materials such as concrete, as well as organic paints and ventilation devices. If appropriate utilization plans are developed, it may be possible to improve the built environment through reduced indoor and outdoor pollutant levels.

• Fire Science and Engineering
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• v.26 no.3
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• pp.106-111
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• 2012

In this study, EIFS (Exterior insulation finish system) of exterior cladding was applied Cone calorimeter test to confirm the effect of flame retardant. As a results, the initial ignition points in accordance with the coated form and concentration of the flame retardant was delayed. But flame resistant treatment of EIFS cladding to control the fire will not affect confirmed that. In addition, EIFS that uses high-density and low-density due to difference in the density of the impact of the fire was no difference. The exterior of the ignition experiment occurred before and after 40 seconds, heat release rate to 100 seconds appears to occur about 90 % compared with the other exterior wall materials, the initial fire spread very fast was confirmed. EIFS cladding in order to prevent the spread of fire in the application of EIFS legally use is limited by the use of the building. And flame spread can be prevented, such as a vertical outer wall compartment measures are urgently needed.

• Journal of KIISE:Software and Applications
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• v.31 no.12
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• pp.1637-1648
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• 2004

When digital libraries are developed by the traditional client/sever system using a single agent on the distributed environment, several problems occur. First, as the search method is one dimensional, the search results have little relationship to each other. Second, the results do not reflect the user's preference. Third, whenever a client connects to the server, users have to receive the certification. Therefore, the retrieval of documents is less efficient causing dissatisfaction with the system. I propose a new platform of mobile multiagents for a personal digital library to overcome these problems. To develop this new platform I combine the existing DECAF multiagents platform with the Voyager mobile ORB and propose a new negotiation algorithm and scheduling algorithm. Although there has been some research for a personal digital library, I believe there have been few studies on their integration and systemization. For searches of related information, the proposed platform could increase the relationship of search results by subdividing the related documents, which are classified by a supervised neural network. For the user's preference, as some modular clients are applied to a neural network, the search results are optimized. By combining a mobile and multiagents platform a new mobile, multiagents platform is developed in order to decrease a network burden. Furthermore, a new negotiation algorithm and a scheduling algorithm are activated for the effectiveness of PDS. The results of the simulation demonstrate that as the number of servers and agents are increased, the search time for PDS decreases while the degree of the user's satisfaction is four times greater than with the C/S model.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.5
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• pp.675-682
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• 2021

Fire accidents on land and at sea can cause serious casualties; specifically, owing to the nature of marine plants and ships, the mortality rate at sea from suffocation in confined spaces is significantly higher than that on land. To prevent such cases of asphyxiation, it is essential to install ventilation fans that can outwardly direct these toxic gases from fires; however, considering the scale of marine fires, the installation of large ventilation fans is not easy owing to the nature of marine structures. Therefore, in this study, we developed a new concept for fire safety technology to control toxic gases generated by fires from applied direct current (DC) electric fields. In the event of a fire, most flames contain large numbers of positive and negative charges from chemi-ionization, which generates an "ionic wind" by Lorentz forces through the applied electric fields. Using these ionic winds, an experimental study was performed to artificially control the fire smoke caused by burning paper and styrofoam, which are commonly used as insulation materials in general buildings and ships. The experiments showed that a fire smoke could be artificially controlled by applying a DC voltage in excess of ±5 kV and that relatively effective control was possible by applying a negative voltage rather than a positive voltage.

• Journal of Korean Port Research
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• v.13 no.1
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• pp.65-78
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• 1999

운송에 필요한 각종 서류와 정보의 효율적 교환은 국제물류시스템의 중요한 일부분이 되었다. 또한 EDI(전자문서교환)는 수출입에 필요한 각종 상거래 서식을 컴퓨터가 읽을 수 있는 표준화된 전자문서의 형태로 바꾸어 교환함으로써 무역절차의 간소화와 운송서류의 신속한 교환을 가능하게 하여 물류 효율성을 증대시키는 것으로 알려져있다. 이러한 맥락에서 세계각국의 항만당국은 자국의 물류혁신을 도모하기 위하여 경쟁력으로 EDI의 도입을 추진해왔다. 그러나 90년대에 들어 EDI의 발전은 처음의 기대와는 달리 저조한 것으로 나타났다. 이는 크게 두가지로 설명된다. 첫째는 EDI 문서의 국제표준을 제정하는 UN/ECE 산하 WP4의 표준제정 미 공표의 비효율성으로 인해 실제 상거래에서 필요한 문서들의 EDI 표준화가 제때에 이루어지지 않았다는 점이다. 두 번째 이유는 대부분의 EDI 사용자가 전자문서의 교환통로로 이용해 왔던 부가가치통신망(VAN)서비스의 고비용적인 구조로 인하여 비용에 민감한 중소규모 화주들의 폭넓은 이용을 저해왔다는 점이다. 따라서 본고에서는 EDI의 확산을 저해했던 두가지 문제점에 입각하여 먼저 효율적 EDI 표준 제공을 위한 국제적 노력의 산물인 CEFACT(Center for Facilitation of Procedures and practices for Administration Commerce and Transport))와 보다 안전하고 신뢰성 있는 전자상거래 솔류션의 마련을 위해 이루어진 각종 국제기구들의 활동 및 결과물들을 소개하고 다음으로 인터넷의 급속한 확산으로 새롭게 개발되고 있는 Web-based EDI, XML/EDI, Simpl-EDI, Form-based EDI 그리고 Lite-EDI의 저비용적 구조 측면을 분석하여 중소규모화주들의 EDI에 대한 인식을 제고시킴으로써 EDI의 전반적인 확산을 도모하고 있다.

• 한국HCI학회:학술대회논문집
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• 2009.02a
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• pp.1109-1113
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• 2009

Exchange of data between users and system is made by users' inputting their information into HTML input forms like when signing up in websites or buying in online shopping malls. If users make a mistake of inputting their information, the system gives an error message in order for users to correct their mistakes. Although ISO recommends immediate feedback, Bargas et al. gave a report that feedback in all after filling forms out is more usable than feedback one by one when inputting data online. We made a comparative experiment on usability under each case of feedback one by one and feedback in all. The result is immediate feedback is more usable and satisfactory. The analysis of data resulted that immediate feedback produced fewer error and gets higher subjective ratings.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.2
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• pp.149-156
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• 2007

The present study provides structural design and analysis of main wing and horizontal tail of a small scale WIG(Wing in Ground Effect) vehicle which has been developed as a part of the high speed maritime transportation system for the future of Korea. Weight saving as well as structural stability could be achieved by skin-spar with foam sandwich design and with wide application of carbon/epoxy composite material. A commercial FEM code, NASTRAN, was utilized to confirm the structural safety and stability through sequential design modifications to meet the final design goal. In addition, each wing and the fuselage were fastened together by eight insert bolts with high strength to accomodate easy assembling and disassembling as well as to guarantee a service life longer than 20 years.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.12
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• pp.1087-1096
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• 2011

The purpose of current study is to develop and verify the newly developed solver for analyzing rotor flow using the open-source code. The algorithm of standard solver, OpenFOAM, is improved to analyze the rotor inflow with and without fuselage. For the calculation of the rotor thrust, the virtual blade method based on the blade element method is employed. The inflow velocities on the rotor disk used to specify the effective angle of attack, have been included in the solver. The results of the current rotor inflow analysis are verified by comparing with other experimental and numerical results. It was confirmed that the modified solver provides satisfactory results for rotor-fuselage interaction problem.