• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.05a
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• pp.601-604
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• 2012

Recently, there have been many attempts to monitor the equipment's condition or the input devices in sensors remotely by using cable and wireless communications. Also, the research and development on this matter has been actively carried on. In this paper, we developed the monitoring system which will eliminate the errors of manual reading by humans and therefore will secure reliability between tenants and the building management office. Through the system, the private telecommunication network can be connected between the building management office and the households. This enables the control office to remotely read the electric meter and exact energy consumption of each household even when the tenants are absent.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.52 no.7
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• pp.421-428
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• 2003

After the cable is installed, many geometric factors, such as bowing types of the cable and the length difference of the cable between each minor section will cause the impedance unbalance between cables. The impedance unbalance will increase or decrease the sheath circulating currents, which are critical to human safety and sustaining the capabilities of electric power. Accordingly, in this paper, a new method is also proposed to reduce the sheath circulating currents and an reduction equipment according to the theory of the new method is developed. The reduction equipment is tested when the cable is on service. The test results show that it can reduce the sheath circulating currents by up to 97.8［%］. This confirms the validation of the new method and the reduction equipment, and assures the safe operation of the transmission cables. In order to illustrate the safe operation of the cable with new current reduction equipment at transient state due to lightning and single line-to-ground fault, extensive simulations have been made. Then the protection scheme of sheath circulating currents reduction equipment is proposed by adopting the new device of RDP(Reduction Device Protector).

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.3
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• pp.519-527
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• 1997

AISI 316 steel has been used extensively for heater and boiler tube of the structural plants such as power, chemical and petroleum plants under severe operating conditions. Usually, material degradation due to microcrack or precipitation of carbides and segregation of impurity elements, is occured by damage accumulated for long-term service at high temperature in this material. In this study, the effect of aging time on fracture toughness was investigated to evaluate the measurement of material degradation. The elastic-plastic fracture toughness behaviour of AISI 316 steel pipe aged at $550^{\circ}C$for 1h-10000h (the aged material) was characterized using the single specimen J-R curve technique and eletric potential drop method at normal loading rate(load-line displacement speed of 0.2mm/min) in room temperature and air environment. The fracture toughness data from above experiments is compared with the $J_{in}$ obtained from predicted values of crack initiation point using potential drop method.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.1
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• pp.142-147
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• 2018

Private electrical facilities are judged whether it is suitable for the insulation aging condition of their incoming underground cables using DC leakage current test method. In the case where the service point of utility is the secondary side of cut out switch installed in the electric pole, there is a problem that it is difficult to separate the lightning arresters(LA) because of their high position of the pole. Therefore, the field test voltage is applied at value lower than DC 30 kV, which are stated in the inspection guideline. However, this test could reduced the insulation performance of the LA by accelerating the electrical stress of the metal oxide varistor element in the pre-breakdown region. In this study, we analyzed the relationship between the DC test voltage and the leakage current using the non-destructive DC high voltage equipment with leakage current measurement function. The results show that the leakage current increases sharply above the specified test voltage. As a consequence, it could be contributed to improve insulation aging inspection method by selecting the possible test area on the VI characteristic curve of the pre-breakdown area of the LA.

• Journal of the Korean Society of Safety
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• v.27 no.1
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• pp.14-19
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• 2012

This study proposes to suggest a direction hereafter which is the most suitable operating system of electrical safety management agency for electrical facilities to enhance electrical safety considering our domestic conditions. It was designed to prevent electrical disasters which are increasing due to environmental changes in the electrical industry, and the diversification and complication of the electrical facilities. And the strategy of this research is based on conditions of safety management agency for the electrical facilities, with the analysis on conditions of electrical disasters, and with a questionnaire investigation for owner of electrical facilities, safety management agency. Results of this research are expected to be used to prevent electric fires and shocks effectively by reinforcing the electrical safety management agency of electrical facilities having danger of large-scaled accidents. It is expected to enhance the nation's competing power against foreign countries by reducing the human and physical loss, resulted from the development of reasonable operating system for electrical safety management agency.

• 제어로봇시스템학회:학술대회논문집
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• 1990.10b
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• pp.1361-1364
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• 1990

In order to tackle global environmental problems such as destruction of the ozone layer or climatic changes due to atmospheric temperature increase, the acquisition of plentiful and precise data is necessary. Therefore, a means of conducting long-lasting high-resolution measurements over broad areas is required. A feasibility study has been made on a high altitude (20km), super-pressured helium-filled PLTA (Powered Ligher-than-Air) vehicle as an ideal platform for environmental observation. It has a long service life and carries a larger payload than an artificial satellite. This PLTA platform uses an electric propulsion system to maintain position in space against wind currents. The thruster is driven by solar power acquired from solar cells. For night use, solar energy is stored in regenerative fuel cells. This study focuses on energy balance and structural analysis of the hull and platform. The platform is capable of conducting high resolution remote sensing as well as having the capability to serve as a telecommunications relay. The platform could replace a number of ground-based telecommunications relay facilities, guaranteeing sufficient radio frequency intensity to secure good quality telecommunication transmittal. The altitude at which the platform resides has the lowest wind flow in the lower stratosphere, and permits viewing from the ground within a 1,000km range. Because this altitude is much lower than that required of an artificial satellite, the measuring resolution is a couple of thousand times higher than with artificial satellites. The platform can also be used to chase typhoons and observe them from their sources in tropical regions.

• International journal of advanced smart convergence
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• v.4 no.2
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• pp.131-137
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• 2015

Home Entertainment system is recently being offered by Home Theater & Smart TV with contents service. Also, console game is being played in the media like in TV. The usage of 4D as the main technology in entertainment industry has mostly been limited in Theme Park, Amuse Park, Theater, and contents for Movie and Animation. Some simulation systems for game has been developed but they were made mostly by using electric or hydraulic motion system which cause high power consumption and have a restriction of place for install. The paper is attempted to build Home Entertainment system which makes users feel realistic contents by developing 4D systems for Home Entertainment rather than before. 4D control S/W in which user can insert and edit 4D effects on contents of all areas such as game, movie, and broadcasting is developed. Also, built-in pneumatic cylinder in 4D system which can be easily controlled and managed in home is developed.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.8
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• pp.443-451
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• 2021

The classification standards for hotels in Vietnam are different from many other hotel classification standards in the world. This study aims to analyze customer reviews on the TripAdvisor website to develop a new algorithm for hotel rating that is independent of Vietnam's hotel classification standards. This method can be applied to individual hotels, or hotels of a region or the whole country, while online booking sites only rate individual hotels. Data was crawled from TripAdvisor with 22,287 reviews of 5 cities in Vietnam. This study used a statistical model to analyze the review dataset and build an algorithm to rate hotels according to aspects or hotel overall. The results have less rating deviation when compared to the TripAdvisor system. This study also supports hotel managers to regularly update the status of their hotels using data from customer reviews, from which, managers can strategize long-term solutions to improve the quality of the hotel in all aspects and attract more travelers to Vietnam. Moreover, this method can be developed into an automatic system to rate hotels and update the status of service quality more quickly, thus, saving time and costs.

• Steel and Composite Structures
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• v.38 no.4
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• pp.365-380
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• 2021

Although traditional steel-concrete composite beams have excellent structural characteristics, it cannot meet the requirement of quick assembly and repair in the engineering. This paper presents a study on static behavior of bolt connected steel-concrete composite beam without post-cast zone. A three-dimensional finite element model was developed with its accuracy and reliability validated by available experimental results. The analysis results show that in the normal service stage, the bolt is basically in the state of unidirectional stress with the loss of pretightening can be ignored. Parametric studies are presented to quantify the effects of the post-cast zone, size and position of splicing gap on the behavior of the beam. Based on the studies, suggested size of gap and installation order were proposed. It is also confirmed that optimized concrete slab in mid-span can reduce the requirement of construction accuracy.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.6
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• pp.1321-1326
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• 2015

The amount of smart phones has increased exponentially. Due to the periodic release of high-performance smart phones and upgraded operating system, new smart phones become out-dated over 1 or 2 years. In order to solve environmental constraints of these smart phones, virtualization technology using Thin-Client terminal has been developed. However, in the case of Virtual Machine(VM), the applications associated with sensors and a GPS device can not run because they are not included. In this paper, by implementing the device driver for Android running in a virtual machine in the x86-based systems, it is to provide Android virtualization capabilities such as using the latest smart phones in the virtual machine environment. It would like to propose a method that the virtual device driver receives sensors and GPS information from the old Android smart phones(Thin-Client) that actually work and run as if the real device exists.