• Applied Chemistry for Engineering
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• v.18 no.2
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• pp.111-115
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• 2007

Bimodally porous ${\gamma}$-alumina granules, including mesopores (2~50 nm) and macropores (>50 nm), were prepared by sol-gel and oil-drop method. Mesopores are made from the voids among the alumina crystallites, while macropores are from the space of the decomposed PS particles used as physical templates during the granulation process. The product ${\gamma}$-alumina granules with the average diameter of 2 mm were characterized by FE-SEM, XRD, FT-IR, $N_2$ porosimetry, and universal mechanical testing system.

• Journal of the Korea Concrete Institute
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• v.24 no.3
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• pp.233-240
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• 2012

Hybrid SHCC is being researched actively for its excellent performance in controlling macro and micro cracks using macro and micro fibers, respectively. However, a significant autogenous shrinkage of SHCC is expected since it possesses high unit cement volume in its mix proportion, resulting in autogenous shrinkage cracks. Therefore, this study was performed to evaluate mechanical property of shrinkage-reducing type hybrid SHCC mixed together with steel fiber and PE fiber with excellent micro/macro crack controlling performance. In order to evaluate mechanical property of shrinkage-reducing type hybrid SHCC, replacement ratios of 0% and 10% of expansive admixture and water to binder ratios of 0.45, 0.3, and 0.2 were considered as variables. Then, shrinkage, compressive, flexural, and direct tensile tests were performed. The test results showed that mix proportion with W/B 0.3 significantly improved mechanical performance by using 10% replacement of expansive admixture.

• Journal of Korean Society of Steel Construction
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• v.23 no.4
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• pp.515-522
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• 2011

The purpose of this study was to evaluate the material characteristics of SHN400 steel, which is suitable as a steel material for building structures, using the experimental approach. For this purpose, the chemical composition test, tensile test, macro test, micro test, and charpy notch impact test were conducted with specimens taken from the highest, thickest, and commonly used H-beams for girder or beam members. Each test was conducted under the Korean Standard(KS) test conditions. All the test results satisfied the requirements of KS (KS D 3866) and the steel material for seismic design. The carbon equivalent value (Ceq), which is related to weldability, and the yield ratio, which is related to inelastic behavior, showed especially good results. Thus, SHN400 is definitely suitable as the steel material for building structures.

• Journal of the Korean Geosynthetics Society
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• v.14 no.4
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• pp.105-115
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• 2015

In this study, to understand mechanical characteristic of hybrid reinforced concrete by PVA-fiber 6 mm and PP-fiber 50 mm, which are organic fiber replaced macro-fiber with PP-fiber, four mixed Hybrid Organic Fibers Reinforced Concrete (HFRC) is compared with one mixed plain concrete without fiber reinforcement. Volume portion of the fibers are limited under one percent. The result presents that hybrid reinforcement of the organic fibers cannot maximize stiffness and ductility behavior of the steel fiber reinforcement. however, in comparison to plain concrete, it is confirmed that meaningful relation between toughness index and equivalent flexural strength with advanced ductility behavior. Also, in the case of concrete hybrid reinforced by organic fiber, when the volume portion of the fiber increases, ductility also increases. PP-fiber, which is macro fiber, has more effect on the flexural behavior of concrete than PVA-fiber, which is micro fiber, does. The result also shows that it decrease chloride penetration in chloride penetration test.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.10
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• pp.1463-1470
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• 2010

Microforming, which exploits the advantages of metal forming technology, appears very promising in manufacturing microparts since it enables the production of parts using various materials at a high production rate, it has high material utilization efficiency, and it facilitates the production of parts with excellent mechanical properties. However, the conventional macroscale forming process cannot be simply scaled down to the micro-scale process on the basis of the extensive results and know-how on the macroscale process. This is because a so-called "size effect" occurs as the part size decreases to the microscale. In this paper, we attempt to develop an effective analytical and experimental modeling technique for explaining the effects of the grain size and the specimen size on the behavior of metals in microscale deformation processes. Copper sheet specimens of different thicknesses were prepared and heat-treated to obtain various grain sizes for the experiments. Tensile tests were conducted to investigate the influence of specimen thickness and grain size on the flow stress of the material. In addition, an analytical model was developed on the basis of phenomenological experimental findings to quantify the effects of the grain size and the specimen size on the flow stress of the material in microscale and macroscale forming.

• Journal of the Korea Society of Computer and Information
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• v.4 no.3
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• pp.28-34
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• 1999

In this paper. we propose the method of Scene Change Detection for video sequence using the DC components and the moving vectors in the Macro Blocks in the DCT blocks. The proposed method detects the Scene Change which would not be related with the specific sequences in the compressed MPEG domain. To do this. we define new metrics for Scene Change Detection using the features of picture component and detect the exact Scene Change point of B-pictures using the characteristics of B-picture's sharp response for the moving vectors. In brief, we will detect the cut point using I-picture and the gradual scene changes such as dissolve, fade, wipe, etc. As a results, our proposed method shows good test results for the various MPEG sequences.

• Journal of the Korea Concrete Institute
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• v.19 no.1
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• pp.39-46
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• 2007

In this study, for the establishment of the performance evaluation methods and the quality control standards of durability recovery method, the quantitative exposure data by long term exposure test under the coast and normal atmosphere is accumulated and analyzed. Investigating and evaluating the result of exposure test during 30 months of exposure age under the coastal and normal atmosphere environment, carbonation depth and chloride-ion penetration depth very little penetrated than cover depth. It seems reasonable to conclude that main cause of Corrosion of reinforcing bar are chloride-ion and macro cell from the result of corrosion area and corrosion velocity. Therefore, it is considered to be applied as the fundamental data on the performance evaluation and quality control standards of repair material and method through continuous exposure test in the future.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.10
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• pp.1471-1478
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• 2010

Microforming processes have recently attracted considerable attention from industry and academia since they enable the production of microscale parts using various materials at a high production rate, minimize material loss, and provide parts with excellent mechanical properties. However, for successful development and applications of the microforming process it is critical to take the tribological size effect into consideration because previous studies have shown that traditional friction models for macroscale forming generate significantly erroneous results in the case of microforming. In this paper, we performed scaled ring compression experiments to investigate the tribological size effect of aluminum and brass materials in microforming. The sensitivity of the interfacial friction to the deformation characteristics of the ring was quantitatively analyzed by the finite element analysis. In addition, a friction model based on slip line field and upper boundary techniques was used to theoretically explain the friction mechanism in microforming.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.3
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• pp.277-288
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• 2013

3GPP LTE-Advanced (Third Generation Partnership Project Long Term Evolution-Advanced) as a next generation mobile communication standard introduced small base stations such as femto cells or pico cells, and D2D (Device-to-Device) communications between mobiles in the proximity in order to satisfy the needs of rapidly growing wireless data traffic. A diverse range of topics has been studied to solve various interference situations which may occur within a single cell. In particular, an introduction of a small base station along with D2D communication raises important issues of how to increase the channel capacity and frequency efficiency in HetNets (Heterogeneous Networks). To this end, we propose in this paper methods to manage the interference between the macro cell and other small cells in the HetNet to improve the frequency efficiency. The proposed CCN (Cluster Coordinator Node)-assisted ICI (Inter-Cell Interference) avoidance methods exploit the CCN to control the interference in HetNet comprising of an MeNB (Macro enhanced Node-B) and a large number of small cells. A CCN which is located at the center of a number of small cells serves to avoid the interference between macro cell and small cells. We propose methods of resource allocation to avoid ICI for user equipments within the CCN coverage, and evaluate their performance through system-level computer simulations.

• Journal of Advanced Navigation Technology
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• v.16 no.2
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• pp.278-286
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• 2012

Hardware and software of optical network monitoring system for optical network installed in ship for providing massive information are designed and fabricated. And, we investigated whether the fabricated system will accurately monitoring three events of optical cable extension, macrobanding and ferrule dust, which are related with special situation of ship, or not through the experiment. We used the combined method of chained branch and dark fiber for designing and fabricating hardware of optical network monitoring system for optimal corresponding with network configuration in ship. And, we confirmed that the proposed system excellently trace within 5 m range of event point in all three cases by investigating each event experiments.