• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.6A
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• pp.425-433
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• 2011

In this study, in order to investigate the wave-induced buoyancy effects, experimental studies were conducted on pontoon-type floating structures. A series of small-scale tests with various wave cases were performed on the pontoon models. A total of four small-scale pontoon models with different lateral shapes and bottom details were fabricated and tested under the five different wave cases. Six hydraulic pressure gauges were attached to the bottom surfaces of the pontoon models and the wave-induced hydraulic pressure was measured during the tests. Finally, hydraulic pressures subjected to the bottoms of the pontoon models were compared with each other. As the results of this study, it was found that whereas the waffled bottom shape hardly influenced the wave-induced hydraulic pressure, the hybrid lateral shape significantly influenced the wave-induced hydraulic pressure subjected on the bottoms of floating structures. The air gap effects of the hybrid shape contribute to decreasing the wave-induced hydraulic pressure due to absorption of wave impact energy. Compared with box type, the hydraulic pressures of the hybrid type were about 83% at the bow, 74% at the middle, and 53% at the stern.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.1
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• pp.36-41
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• 2000

We studied the exchange anisotropy of Ni-Fe/Co-Fe/Mn-Ir/Cu/buffer/Si multilayers using D.C magnetron sputtering technique. Generally, Ni-Fe/Mn-Ir/buffer(Cu)/Si multilayers cannot pin the ferromagnetic layer for the lower exchange biased field. We got $H_{ex}$ ex/ increased by two times, after using Cu/Ta as buffer layer to get larger grain size of Mn-Ir layer and inserting very thin Co-Fe layer between the Ni-Fe layer and the Mn-Ir layer to get improved grain-to-grain epitaxy relation at the interface between Ni-Fe layer and Mn-Ir layer. The variation of $H_{ex}$ by thickness of Mn-Ir layer in ferromagnete/Mn-Ir/buffer/Si multilayers is different to that in Mn-Ir/ferromagnete/buffer/Si multilayers, because the volume distribution of grain size of Mn-Ir layer and the exchange energy at the interface between the Mn-Ir and the ferromagnetic layers is different for stacking sequence.

• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.1
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• pp.15-22
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• 1998

The goal of this paper is to propose analyzing and evaluating method of power parameters for motor drive system with various experimental graphic screens and numerical results and to develop the proposed system. A developed system is made up 586-PC and DSP board, motor drive system, power parameters analyzing and evaluating software for windows. Power parameters are analyzed using correlation signal processing techniques based on the correlation between voltage and current waveforms. Analysis results are visualized by 3-D current coordinates, and it is compared and evaluated with conventional time/ frequency domain. To verify the validity of the proposed system, capacitor run type single phase induction motor and thyristor speed controller is used for analyzing. Power and harmonic parameters of motor drive system is analyzed and verified, with varying fire angle of thyristor speed controller, and the proposed approach is to confirm validity.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.1B
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• pp.95-105
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• 2010

IEEE 802.15.4 is the one of the protocols for radio communication in a personal area network. Since it aims to provide low cost and low power communication for ubiquitous communication, it requires high level of optimization in implementation. Recently, there have been many studies on the performance evaluation of IEEE 802.15.4 MAC protocol. According to the results of the studies, it is tendency that the transceiver is implemented to SoC type. On the implementation, the specific functions of MAC like CSMA-CA and MAC frame handling is designed to hardwired functions. In this paper, we implemented the protocol with hardwired low MAC (HL-MAC) and its state machine for the optimization from the physical layer and MAC layer. it has the characteristics of the small code size and the enhanced power consumption.

• Journal of the Korea Institute of Building Construction
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• v.16 no.4
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• pp.359-365
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• 2016

With the government's support using new and renewable energy, photovoltaic equipment has been rapidly supplied. However, compared to supply rate, maintenance has not supported enough and relevant research has not much conducted. Even though large power plant facilities have been maintained well, small equipment for detached houses has been rarely maintained. Therefore, the purpose of this study is to analyze maintenance effectiveness of photovoltaic equipment for detached houses. It was analyzed that photovoltaic equipments were merely maintained. What is the most important in maintenance effectiveness is increase of power generation. It was estimated that if photovoltaic equipment for detached houses is maintained well, power generation increases by 6.5% at least. That produces the same effect as the additional supply of photovoltaic equipment to 9,700 households. As a result, it is necessary to maximize the effectiveness of the government's budget investment through well maintenance of photovoltaic equipments.

• Convergence Security Journal
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• v.16 no.6_1
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• pp.43-50
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• 2016

As North Korea has a sufficient ability to attack our society's vulnerable computer network, various large-scale cyber attacks are expected to be tried. North Korea's cyber military strength is known a world-class level. The number of its cyber agents is increasing consistently. Recently North Korea's cyber attack has been made regardless of trick and target. But up to now North Korea's cyber attack is more of an exploration than a real attack. Its purpose was to check how fast Korea found a problem and recovered from it. In future, cyber attack that damages substantially is highly probable. In case of an attack against national infrastructure like traffic, financial and energy services, the extent of the damage will be great beyond imagination. In this paper, characteristics of recent North Korea's cyber attack is addressed in depth and countermeasures such as the enactment of cyber terror prevention law, simulation training enforcement, private and public cooperation system construction, cyber security infrastructure expansion, etc. are proposed.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.6
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• pp.1479-1485
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• 2012

The parking management system can increase driver's convenience with detailed parking information service in the parking lot. At the same time, parking management system consumes non-negligible electrical energy with large amount of sensors, displays and control modules. With the increase in the demand for green and sustainable building design all over the world, it becomes a meaningful issue for parking management system to reduce operating power. This paper presents the preliminary design and estimated results of a parking management system which is optimized to reduce the power consumption mainly on detectors and displays. The system design is based on pre-developed wireless parking detectors, Park Tile and Park Disk. The system has a number of parking space detectors, vehicle count detectors, information displays, guidance terminals and other control units. We have performed system architecture design, communication network design, parking information service scenario planning, battery life regulation and at last operating power estimation. The estimated operating power was 0.93KW per parking-slot, which is 20% of traditional systems. The estimated annual maintenance cost was 18% of traditional systems.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.2
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• pp.169-187
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• 2008

Performance-based approaches as an alternative method of the existing force-based approach have gradually become recognized tools for the seismic design and evaluation. The maximum inelastic displacement response using capacity spectrum method (CSM) with elastic response spectrum is estimated from seismic response of equivalent linear system converted from nonlinear system. The purpose of this paper is to evaluate accuracy of capacity spectrum method using the equivalent SDOF methods of 4 types and the equivalent damping methods of 5 types for RC wall structure. In order to evaluate accuracy of capacity spectrum analysis, the shaking table test results for RC wall structures are compared with those by the capacity spectrum analysis. Also, the effect of bilinear capacity curves by two bilinear approximation methods for capacity spectrum analysis is compared.

• Journal of Digital Convergence
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• v.11 no.11
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• pp.767-774
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• 2013

The electricity demand and supply could be off balance if several electric vehicles(EVs) were charged at the same time or at peak load times. Therefore, smart grids are necessary to flatten the EVs' electricity demand and to enable EVs to be used as distributed storage devices as electricity demand from EV-charging increases. There are still few quantitative studies on the impact of smart grids on managing EVs' electrical loads. In this study, we analyzed the quantitative impact of smart grids on managing EVs' electrical loads and suggested policy implications. As a result, it is identified that smart grids can manage effectively EVs' impact on electrical grids. The electricity market structure and regulatory framework should support the demonstration and commercialization of smart grid technologies.

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.5
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• pp.71-81
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• 2007

For the design of composite bridge piers, detail requirements for the reinforcements is not clear to satisfy the required seismic performance. Composite bridge piers were suggested to reduce the sectional dimensions and to enhance the ductility of the columns under earthquake loadings. In this paper, five specimens of concrete encased composite columns of 400mm diameter with single core steel were fabricated to investigate the seismic performance of the composite columns. Shaking table tests and a Pseudo-Dynamic test were carried out and structural behavior of small-scaled models considering near-fault motions was evaluated. Test parameters were the pace of the transverse reinforcement, lap splice of longitudinal reinforcement and encased steel member sections. The displacement ductility from shaking table tests was lower than that from the pseudo-dynamic test. Limited ductile design and 50% lap splice of longitudinal reinforcement reduced the displacement ductility. Steel ratio showed significant effect on the ultimate strength. Lap splice and low transverse reinforcements reduced the displacement capacity. The energy dissipation capacity of composite columns did not show significant difference according to details.