• Magazine of the Korea Concrete Institute
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• v.10 no.5
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• pp.159-165
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• 1998

중트럭 통행으로 인한 철근콘크리트 교량바닥판의 열화는 교량구조물을 유지보수하는데 있어 심각한 문제 중 하나이며, 프리캐스트 바닥판을 이용한 교량바닥판의 시공 및 교체 방법이 실용적이며 효과적인 방법으로 인식되고 있다. 본 연구에서는 횡방향 ddusruf부에 종방향 프리스트레싱을 도입한 프리캐스트 바닥판의 모델을 제작하여 바닥판간 횡방향 연결부의 강성 평가 및 연결부의 피로 거동을 파악하기 위해서 피로실험을 수행하여 피로하중하에서의 휨강성의 변화, 균열발생 및 파괴하중 등을 측정하였다. 실험결과를 통해서 피로하중하에서 프리스트레스 프리캐스트 부재의 프리스트레스 효과를 평가하였으며, 현장타설에 의해서 시공되는 일반 RC 부재에 비해서 우수한 구조적 거동을 보여주는 적정량의 종방향 프리스트레스 크기를 결정하였다.

• Journal of Korean Society of Steel Construction
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• v.16 no.1 s.68
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• pp.43-49
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• 2004

With building structures becoming higher and having longer spans, new structural steel with better strength, thicker plate, and performance may be required rather than conventional structural steel. TMC steel is widely used in building structures largely due to its excellent seismic performance, superior weldability, and design strength that is not affected by plate thickness. To make use of TMC steel in pipe structures with large diameter and heavy wall, however, the this study, the degradation of material properties in submerged are welded SM520TMC steel pipes and tubes was evaluated using variable fabrication process and material change. Degradation test results showed that the yield and ultimate strength increased and elongation decreased regardless of the mode of fabrication, i.e., through roll bending or press forming, or steel used, i.e., domestic SM520TMC steel or SM520TMC steel from Japan.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.38 no.4 s.117
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• pp.53-60
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• 2006

Paper materials for long term conservation suffer slowly mechanical and chemical deterioration, the extent of which may depend upon their conservation environment. Those deterioration includes discoloring, low moisture content, acidification, and brittleness. To slow deterioration, washing treatment, deacidification, and polymer reinforcement on paper materials are usually used. One easy and simple method of fixing low moisture content and acidification was an washing method, and we used both distilled and alkali water in washing method in this study. Alkali water is electrolyzed cathode water of high pH, and has no alkali metal ions in it. Experiment showed that washing treatment with both distilled and alkali water gave improvement in raising moisture content, pH, and mechanical strength of paper materials even after severe accelerated aging test. Advantageous effect of alkali water over distilled water on preventing deterioation was also shown clearly.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2011.04a
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• pp.235-241
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• 2011

Effects of thermal aging on color variations of various papers were evaluated. With thermal aging, most of papers showed a special trend in $a^*$-$b^*$ plane: $a^*$ (red-green) values of the samples were reduced at beginning and after a turning point it was increased while $b^*$ (blue-yellow) was kept increased (yellowing of paper). In case of filter paper which consists of chemical pulps, the changes in $a^*$ value was occurred late compared with other samples. In case of the copy paper with optical brightening agent, the turning point in $a^*$ was not observed while a constant increase in $b^*$ was observed. In case of color paper, no specific trends in $a^*$-$b^*$ were found.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.6
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• pp.520-527
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• 2013

In this paper, a joint cell grouping and user association technique proposed for a semi-dynamic grouped network MIMO in a clustered heterogeneous cellular network (HCN). With the conventional macro BSs, small cells are being overlaid to increase a spectral efficiency per area and these small cells are expected to be concentrated to support exponentially increasing data traffic in hot spot areas. The main culprits of performance degradation in the clustered HCN are interference and load imbalance. The proposed scheme jointly handles them to maximize a proportional-fair metric. It is shown that the proposed technique can largely improve user average rate and proportional fairness among users than any other conventional schemes in the clustered HCN.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.46 no.6
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• pp.87-93
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• 2014

Optical brightening agents (OBA) is generally used to improve the optical property of printing paper in the paper industry. However, effects of OBA addition on paper preservability has been not fully understood yet. Therefore, this study was aimed to investigate effects of a OBA on the aging characteristics of paper. The OBA treatment of three different types was performed by dipping a filter paper into each a OBA solutions of different concentrations. The filter papers applied with a OBA were artificially aged at 80oC and 65% RH, and their optical and mechanical properties were evaluated. It was found that application of OBAs influenced the aging characteristics of paper. Especially, after aging, the optical and mechanical properties of the filter paper treated with the tetra-type OBA were more significantly decreased than those of the non-treated filter paper. The more the concentration of the tetra-type OBA increased, the more decreasing rate of optical and mechanical properties of the filter paper. While, in case of di-type OBA and hexa-type OBA, paper optical and mechanical properties were slightly decreased or not changed with a OBA treatment.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.46 no.5
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• pp.35-42
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• 2014

Many historical archives have been deteriorated by aging with time. Various kinds of defects such as worm-hole, yellowing, brittleness are observed and their severity was dependent on raw material type, storage condition, and so on. For a long-term use and storage, a proper preservation treatment is required. Many studies on preservation and conservation have been carried out on hanji which was made from mulberry fiber, but there are few concerns on foreign paper. Therefore, aging and chemical strengthening treatment was done on paper made of bamboo and wood fibers depending on aging condition, the type and pickup weight of chemicals and treatment method. When methyl cellulose was treated with impregnation or brushing, the aged paper was strengthened effectively. The strengthening effect by chemicals was dependent on the aged condition of the paper.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.35-38
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• 2005

The computational fluid dynamic analysis has been conducted for the thermo-chemical flow field in an arcjet thruster with mono-propellant hydrazine ($N_{2}H_4$) as a working fluid. Coupled Reynolds Averaged Navier-Stokes (RANS) equations and Maxwell equations were used to account for the Ohm heating and Lorentz forces. Hydrazine chemistry and thermal radiation were also incorporated to the fluid dynamic equations by assuming infinitely-fast reactions and optically thick media. In addition to the thermo-physical understandings of the flow field inside the arcjet thruster, results shows that performance indices are improved by amount of $20\%$ in thrust and $200\%$ in specific impulse with the 0.6kW are heating.

• 전자공학회논문지 IE
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• v.47 no.1
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• pp.1-5
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• 2010

This paper presents new results of the impact of gate structure on hot-carrier-induced performance degradation in SOI low noise amplifier. Circuit simulations were carried out using the measured S-parameters of H--gate and T-gate SOI MOSFETs and Agilent's Advanced Design System (ADS) to compare the performance of H-gate LNA and T-gate LNA before and after stress. We will discuss the figure of merit for the characterization of low noise amplifier in terms of impedance matching (S11), noise figure, and gain as well as the relation between device degradation and performance degradation of LNA.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.9
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• pp.1063-1070
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• 2014

Currently, The terrestrial MMS(Multi Mode Service) is considering to be adapted in the Korea. The objective and subjective video quality test was carried out to verify the current TV channel's video quality degradation by the MMS. In the objective assessment, MMS system showed better PSNR than current system. In the subjective assesment result, It's hard to find the perceive video quality degradation at overall assesment. Even though, The MMS's video quality will be improved at the documentary and entertainment genre. Comparing with the previous research at 2006 and 2008, It's the time to give the benefit of broadcasting technology to the people.