• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.09a
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• pp.98-106
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• 2003

To construct pile-supported wharf structures that must support heavy horizontal loads, both vertical piles and batter piles are used. Batter piles are used to secure the bearing capacity against the horizontal loads. However, past case histories have shown that the heads of batter piles are vulnerable because these heads are subjected to excessive axial loads during earthquakes. Therefore, the aseismatic reinforcement method must be developed to prevent batter pile heads from breaking due to excessive seismic loads. Two different connecting methods of either inserting rubber or ball-bearing between batter pile head and upper plate were proposed to improve the aseismatic efficiency. Three large-scale pile head models(rubber type model, ball-bearing type model, and fixed type model) were manufactured and horizontal loading tests were peformed for these models. The results showed that the force-displacement relationship of the fixed type model was linear, but that of the rubber type model and the ball-bearing type model was bilinear. The increase in the horizontal displacement led to the increase in the horizontal stiffness of the rubber type models and the decrease in that of the ball-bearing type model. Compared with the values for fixed type model, the damping ratios of the rubber type model and the ball-bearing type model increased about 33~185％ and 263~269％, respectively.

• Geomechanics and Engineering
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• v.13 no.5
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• pp.881-892
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• 2017

Design and management of concrete slabs in concrete-faced rock-fill dams are crucial issues for stability and overall dam safety since cracks in the concrete face induced by stress, shrinkage, and deterioration can cause severe leakage from the reservoir into the dam. Especially, the increase of dam height to a certain level to enhance the storage capacity and to improve hydraulic stability can lead to undesirable deformation behavior and stress distribution in the existing dam body and in the concrete slabs. In such conditions, simulation of a concrete slab with a numerical method should involve the use of an interface element because the behavior of the concrete slab does not follow the behavior of the dam body when the dam body settles due to the increase of dam height. However, the interfacial properties between the dam body and the concrete slab have yet to be clearly defined. In this study, construction sequence of a 125 m high CFRD in South Korea is simulated with commercial FDM software. The proper interfacial properties of the concrete slab are estimated based on a comparison to monitored vertical displacement history obtained from the concrete slab. Possibility of shear strength failure under the critical condition is investigated based on the simplified model. Results present the significance of the interfacial properties of the concrete slab.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.4
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• pp.761-768
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• 2019

In this paper, the aim is to develop plasma heater products combining the sterilization and purification functions of low-temperature plasma lamp method with the function of vertical heating system using wavelengths of vacuum magnetic (VU). Through this process, the government aims to improve the cultivation environment of crops in greenhouses or facility houses and to increase their storage capacity by increasing the freshness of stored crops such as free-temperature storage. In addition, real-time monitoring technologies will be incorporated that will enable users to identify and respond to changes within greenhouses in real time by utilizing ICT technologies.

• Computers and Concrete
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• v.26 no.6
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• pp.515-531
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• 2020

Due to the construction difficulties of steel reinforced concrete (SRC), a new composite structure of steel and steel fiber reinforced concrete (SSFRC) is proposed for solving construction problems of SRC. This paper aims to investigate the bond properties and composition of interfacial bond stress between steel and steel fiber reinforced concrete. Considering the design parameters of section type, steel fiber ratio, interface embedded length and concrete cover thickness, a total of 36 specimens were fabricated. The bond properties of specimens were studied, and three different methods of calculating interfacial bond stress were analyzed. The results show: relative slip first occurs at the free end; Bearing capacity of specimens increases with the increase of interface embedded length. While the larger interface embedded length is, the smaller the average bond strength is. The average bond strength increases with the increase of concrete cover thickness and steel fiber ratio. And calculation method 3 proposed in this paper can not only reasonably explain the hardening stage after the loading end curve yielding, but also can be applied to steel reinforced high-strength concrete (SRHC) and steel reinforced recycled coarse aggregate concrete (SRRAC).

• Clean Technology
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• v.18 no.2
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• pp.177-182
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• 2012

Mesoporous anatase $TiO_2$ nanoparticles have been synthesized by a hydrothermal method using a tri-block copolymer as a soft template. The resulting $TiO_2$ materials have a high specific surface area of $230\;m^2/g$, a predominant pore size of 6.8 nm and a pore volume of 0.404 mL/g. The electrochemical properties of mesoporous anatase $TiO_2$ for lithium ion battery (LIB) anode materials have been investigated by typical coin cell tests. The initial discharge capacity of these materials is 240 mAh/g, significantly higher than the theoretical capacity (175 mAh/g) of LTO ($Li_4Ti_5O_{12}$). Although the discharge capacity decreases with the C-rate increase, the mesoporous $TiO_2$ is very promising for LIB anode because the surface for the Li insertion is presented significantly with mesopores. Nitrogen doping has a certain effect to control the capacity decrease by improving the electron transport in $TiO_2$ framework.

• Journal of Electrical Engineering and Technology
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• v.12 no.2
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• pp.576-585
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• 2017

Dynamic thermal rating (DTR) of overhead transmission lines can provide a significant increase in transmission capacity compared to the static thermal rating. However, the DTR are usually estimated by the traditional thermal model of overhead conductor that is highly dependent on the solar, wind speed and wind direction data. Consequently, the estimated DTR would be unreliable and the safety of transmission lines would be reduced when the solar and wind sensors are out of function. To address this issue, this study proposed a novel thermal model of overhead conductor based on the thermal-electric analogy theory and Markov chain. Using this thermal model, the random variation of conductor temperature can be simulated with any specific current level and ambient temperature, even if the solar and wind sensors are out of function or uninstalled. On this basis, an estimation method was proposed to determine the DTR in the form of probability. The laboratory experiments prove that the proposed method can estimate the DTR reliably without measured solar and wind data.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.8
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• pp.623-628
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• 2000

Video-on-demand system in which users can request any video through the network at any time is made possible by rapid increase in network bandwidth and capacity of the media server. However true video-on-demand system cannot support all requests since bandwidth requirement is still too demanding. Therefore efficient bandwidth reduction algorithm is necessary. both the piggybacking method and the batching method are novel solutions that can provide more logical number of streams than the physical system can support. Of course each of them has its pros and cons. hence piggybacking with batching-by-size can take advantage of both the schemes. Some parameters such as the size of batch and the size of the catch-up window should be adjusted and order to maximize the bandwidth reduction for piggybacking with batching-by-size method. One of the most important parameters is decided optimally in this paper. Simulation shows that the optimized parameter can achieve considerable reductionand consequently remarkable enhancement in performance.

• Journal of the Korea Safety Management & Science
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• v.9 no.3
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• pp.95-102
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• 2007

Nowadays, globally high-grade companies have done their best for increasing their competitive power through a many kinds of method in incisive competition for making certain of a pacesetting position. Among the rest, Six Sigma have been the best methodology of improving process and have proven to be effective by the result of improving process in many of manufacturing business, however, it has not obtained excellent results in the transaction business. In transaction business, a $30\sim50%$ costs in total costs is generated by slow-speed working and reworking. The slow processes decrease the quality and increase the cost, which decreases customer satisfaction, and finally the income is decreased. All of them are so called wastes in processes. For this, adopting of lean six sigma methodology in process management can eliminate the wastes and reduce the variation. This study focuses on distribution with the domains like capacity, layout, amount of location, assignment of product, operation procedure and operation rule in order to improve these domains, we make a further application of eight analysis ways based on DMAIC method for improving operation of processes of distribution center as the third profit source. The goal of this study is to trace an approach that can easily adopt of Lean Six Sigma in operational management of distribution center by a kind of data, analysis method and template.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.10
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• pp.1454-1459
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• 2017

In spite of continuous increase of electric power demand and new generation plants, it is very difficult to install new transmission line. Therefore, it comes to be difficult to operate the power system stable, so it is required to find another way to get new transmission capacity. Because HVDC transmission system installation is the one of the best option for us, we have undertake the HVDC project in mainland. Buckdangjin-Goduck HVDC project(500kV, 3GW) is currently under construction and Eastern Power HVDC project(500kV, 8GW) is under the study for technical specification. Both of them have the Run-up SPS function for taking action of 765kV Transmission line fault. The Run-up SPS function increases the active power output of the HVDC rapidly when the transmission line between the power plant and network is tripped, thereby preventing the generator from overspeed and improving the power system stability. In this paper, we propose MEAC(Modified Equal Area Criteria) method based on traditional EAC method to quantitatively evaluate the effect of the HVDC run-up SPS function on the power system stability improvement.

• Journal of the Korean Society for Advanced Composite Structures
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• v.4 no.4
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• pp.1-8
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• 2013

Pile foundations constructed by the fiber reinforced polymer plastic piles have been used in coastal and oceanic regions in many countries. Generally, fiber reinforced polymer plastic piles are consisted of filament winding FRP which is used to wrap the outside of concrete pile to increase the axial load carrying capacity or pultruded FRP which is located in the core concrete to resist the bending moment arising due to eccentric loading. In this paper, the analytical procedures of hybrid concrete filled FRP tube flexural members are suggested based on the CFT design method. Moreover, the analytical results are compared with the experimental results to obtained by the previous researches. The results of comparison analyses are performed to estimate the accuracy of the analytical procedure for hybrid FRP-concrete composite compression test, members under eccentrical loading.