• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.2
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• pp.623-631
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• 2018

In this study, the degree of deterioration of concrete was investigated in the laboratory under conditions of carbonation and freeze-thaw cycling, which are the major causes of the deterioration of its performance. In this test, the carbonated concrete was subjected to combined freeze-thaw deterioration tests for up to 300 cycles, and its dynamic elastic modulus and compressive strength were measured. The evaluation of the effect of the water-binder ratio on normal concrete subjected to combined carbonization and freezing-thawing showed that its resistibility against such combined deterioration decreased more rapidly in the concrete with a water-binder ratio of 55 % compared with that having a water-binder ratio of 35 %. In the case where the concrete was blended with a mineral admixture consisting of fly ash and blast furnace slag at the same water-binder ratio, it showed an increase of its resistibility against combined deterioration.

• 한국도로학회:학술대회논문집
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• 2005.11a
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• pp.255-258
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• 2005

• Journal of Korean Society of Steel Construction
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• v.28 no.5
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• pp.325-335
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• 2016

To predict service life of coating systems registered in Korean specifications for steel bridge coatings, field deterioration evaluation and accelerated weatherproof test were carried out, and deterioration models were drawn through regression analysis for evaluation results. For the coating systems that have not been used in field, regression analyses were carried out for the virtual evaluation results drawn by applying coordination factor to the field evaluation results for chlorinated rubber and urethane topcoat system. Service life prediction results showed that application of thermal sprayed coating (TSC) could extend service life of coatings to more than twice of general coatings.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.12
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• pp.1585-1590
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• 2012

Engineering plastics are used in instrument panels, interior trim, and other vehicle applications, and the thermomechanical behaviors of plastic materials are strongly influenced by many environmental factors such as temperature, sunlight, and rain. As the material properties change, the mechanical parts create unexpected noise. In this study, the dynamic mechanical property changes of plastics used in automobiles are measured to investigate the temperature effects. Viscoelastic properties such as the glass transition temperature and storage modulus and loss factor under temperature and frequency sweeps were measured. The data were compared with the original ones before aging to analyze the behavior changes. It was found that as the temperature increased, the storage modulus decreased and the loss factor increased slightly.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.8
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• pp.711-718
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• 2011

The thermoelastic behavior of the porous carbon/phenolic composites is studied using the thermomechanical response model of chemically decomposing composites. The model includes thermal dependence of the porous composites, porosity in the pyrolysis process, pore pressure due to decomposing gases, and shrinkage. The poroelastic coefficients are calculated based on representative volume element model and finite element analysis. The internal stress distribution caused by pores and pore pressure, and the overall deformation are verified. The effects of the poroelastic coefficients on the thermoelastic behavior are examined through numerical experiments.

• Tunnel and Underground Space
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• v.23 no.3
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• pp.212-218
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• 2013

Tuff specimens were thermally treated with predetermined temperatures of 200, 400 and $600^{\circ}C$ to construct specimens simulating weathered tuff rocks. Specific gravity, absorption ratio, elastic wave velocity, uniaxial compressive strength, Brazilian tensile strength, Young's modulus, Poisson's ratio and slake-durability index were measured for pre-heated specimens. Heating of rock specimens entailed the degradation of material properties except for slake-durability index. It was found that correlations among P-wave velocity, uniaxial compressive strength, Brazilian tensile strength, Young's modulus and absorption ratio are high. Regression equations which use the P-wave velocity as an independent variable were presented to evaluate uniaxial compressive strength, Brazilian tensile strength, Young's modulus and absorption ratio.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.541-544
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• 2008

Recently, a variety of researches has been carried out to estimate the reliability-based analysis and design method of concrete structures and is attracted by probabilistic-based durability analysis/method of concrete structures subjected to chloride containing environment using MCS (Monte Carlo Simulation). Probabilistic-based durability analysis/method was proposed by lots of researches, but there is the lack of data for degradation factors for the calculation of probability distribution. The reliability based durability analysis method represents that the service life and reliability index varies with the probability distribution and coefficient of variation of each factor. Therefore, in this paper, the importance of experiment data for the degradation factors is confirmed and the study of reliability index in RC structures under chloride attack environments is performed considering the variation coefficient of degradation factors.

• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.565-568
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• 2000

본 논문에서는 data-driven 반향제거기 구조에서 타이밍 지터의 보상 방법을 제안한다. V.90PCM 모뎀환경에서 네트윅 클록에 동기가 되어 동작하는 사용자 터미널 모뎀이 디지털 PLL (DPLL)을 이용하여 타이밍 복원을 하면 타이밍 지터 성분이 반향제거기의 성능을 순간적으로 악화 시키게 된다. 제안된 방법은 두개의 계수세트 들로부터 타이밍 지터 발생시 필요한 계수를 디콘볼루션 알고리듬을 이용하여 FIR 필터링을 통해 구하며 발생하는 지터 성분 의 대부분을 보상 해 준다. 또한 제안 방법은 waveform driven 반향제거기에 비해 약간의 성능열화가 있지만 적은 연산량으로 타이밍 지터보상을 할 수 있는 장점이 있다.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.06c
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• pp.189-192
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• 1998

전화망을 이용한 음성인식 시스팀에서 출력신호의 반향에 의한 입력신호의 음질 열화현상을 막기위해서 적응디지털 필터를 이용한 반향제거기가 필수적이다. 대표적인 적응 필터 알고리즘인 LMS와 NLMS 들을 각각 이용한 적응 반향제거기들과 입/출력신호의 상관계수를 이용한 개선된 적응 필터 알고리즘의 성능을 비교하였다. 개선된 알고리즘의 경우 NLMS 알고리즘의 빠른 수렴특성을 가지면서도 더블톡(double talk)구간에서의 음질왜곡 현상을 LMS보다 개선시켰다.

• Proceedings of the Korean Information Science Society Conference
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• 2003.04a
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• pp.446-448
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• 2003

본 논문은 MPEG 비디오를 위한 양자화된 차분 에너지 워터마킹(QDEW) 알고리즘을 제안한다. 이 알고리즘은 블록의 고주파 성분인 DCT 계수를 선택적으로 제거함으로써 워터마크를 삽입하는 방식이다. 특히 제안된 방벌은 기존의 차분 에너지 워터마킹(DEW)의 단순비교방식과 다르게 양자화단위로 에너지 크기를 비교함으로써 큰 범위의 에너지가 차이날 때 발생되는 다량의 주파수제거 문제를 해결하여 화질의 열화를 방지하고 삽입되는 워터마크의 중량을 증가시켰다. 그리고 DCT계수를 제거하는 것으로만 워터마크를 삽입할 수 있기 때문에 재인코딩 과정없이 MPEG스트림에서 직접 워터마크를 삽입할 수 입는 장점이 있다.