• 대한금속재료학회지
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• 제48권12호
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• pp.1047-1055
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• 2010

The objective of this study is to investigate the ballistic properties of Zr-based amorphous alloy surface composites fabricated by high-energy electron-beam irradiation. The mixture of Zr-based amorphous powders and $LiF+MgF_2$ flux powders was deposited on a pure Ti substrate, and then an electron beam irradiated this powder mixture to fabricate a one-layer surface composite. A four-layer surface composite, in which the composite layer thickness was larger than 3 mm, was also fabricated by irradiating the deposited powder mixture by an electron beam three times on the one-layer surface composite. The microstructural analysis results indicated that a small amount of fine crystalline particles were homogeneously distributed in the amorphous matrix of the surface composite layer. According to the ballistic impact test results, the surface composite layers effectively blocked a fast traveling projectile, while many cracks were formed at the composite layers, and thus the surface composite plates were not perforated. The surface composite layer containing ductile ${\beta}$ dendritic phases showed a better ballistic performance than the one without dendrites because dendritic phases hindered the propagation of shear bands or cracks.

• 대한토목학회논문집
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• 제39권1호
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• pp.219-225
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• 2019

겨울철 발생하는 아스팔트 혼합물의 저온균열의 정량적 분석 및 평가를 위해서는 해당 아스팔트 혼합물의 저온응력이 반드시 계산되어야 하며, 이는 현재 대한민국, 미국 북부 및 캐나다 지역에서 포장 유지관리, 설계에 있어서 매우 중요한 사항 중 하나이다. 일반적으로 아스팔트 혼합물의 저온응력은 크리프 시험과 시간중첩이론을 바탕으로 계산되며 전통적으로 두 수학적 단계를 통해 계산된다. 우선 수학적, 수치적 변환과정(홉킨스-해밍 알고리즘)을 통해 크리프-강성응력에서 이완응력이 계산된다. 다음으로 이완응력 지배곡선을 구현한 후 회선적분의 수치해석적 접근을 통해 아스팔트 혼합물의 저온응력이 최종적으로 계산된다. 상기의 과정은 복잡하며, 시간이 오래 걸리는 단점이 있다. 이번 논문에서는 보다 간편한 라플라스 변환을 통해 해당 아스팔트 혼합물의 저온응력을 계산하였으며, 이의 결과를 전통적 계산 기법과 비교, 분석하였다. 결론적으로 새로이 제안된 라플라스 변환 기법은 보다 아스팔트 혼합물의 저온응력을 효과적, 효율적으로 계산할 수 있음이 발견되었다.

• 분석과학
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• 제20권6호
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• pp.502-507
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• 2007

X 선 회절법은 물질 내부에 원자의 배열 상태를 연구하는데 널리 사용되는 실험 방법으로써 넓은 응용 범위를 가지고 있다. 특히 분말 X 선 회절법은 비파괴적으로 다양한 형태의 시료에 대한 측정이 가능하기 때문에 결정의 배향성, 결정의 크기, 결정 내부의 응력 측정 등에 널리 이용되고 있다. 분말 X 선 회절 방법을 이용하여 혼합물의 성분을 정량적으로 측정하기 위해서는 시료를 구성하고 있는 source 스펙트럼을 도출하고 혼합된 시료의 XRD 스펙트럼에 회귀식을 적합시켜 혼합물 구성비를 얻는 방법이 제안된 바 있다. 그러나 구성성분의 특성상 스펙트럼의 피이크가 폭이 좁고 민감한 경우에는 노이즈의 영향을 받아 도출된 source 스펙트럼이 원래의 순수성분의 형태와 달리 나타날 수 있다. 특히 순수성분 시료를 구할 수 없거나 측정이 불가능한 경우 혼합물 구성비 측정에 어려움이 있다. 본 연구에서는 노이즈 간섭에 의한 source 스펙트럼 도출의 문제를 해결하는 방안으로 비음독립성분분석을 이용하여 혼합된 미지시료로부터 순수한 성분에 해당하는 스펙트럼을 분리해내는 방법을 제안하고자 한다.

• 한국건설순환자원학회논문집
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• 제2권1호
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• pp.113-119
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• 2006

최근 콘크리트용 골재의 활용실무는 골재의 품질 및 공급상의 문제점들로 인하여 장기적으로 2종류 이상의 골재를 혼합하여 사용하는 것이 유리할 것으로 판단된다. 그러나 2종류 이상의 골재를 혼합사용하는 것에 대한 연구는 미흡하고, 그에 따른 최적배합 평가 방법의 도입도 요구된다. 따라서 본 연구에서는 천연잔골재, 부순잔골재, 재생잔골재의 3종의 혼합모래를 혼합율 변화에 따른 시멘트 모르터의 굳지 않은 상태와 경화 상태의 제반 물성실험을 통하여 최적배합평가 방법에 대해 검토하였다. 실험결과, 플로우는 천연잔골재와 부순잔골재의 혼합 비율이 클수록 높게 나타났으며, 압축강도 및 휨강도도 천연잔골재와 부순잔골재를 일정 비율로 혼합한 경우는 부순잔골재와 유사한 강도를 나타내지만, 재생잔골재가 혼합된 배함에서는 강도가 조금씩 저하되었다. 건조수축은 재생잔골재만을 사용한 경우가 건조수축율이 가장 큰 것으로 나타났다. 단, 본 연구에서는 정량적 수치의 표현은 아니지만 3종류의 잔골재를 사용할 경우의 최적배합 표현방법을 3차원적으로 나타내어 최적배합을 쉽게 알아볼 수 있도록 도상화 수법을 제안하였다.

• 한국수소및신에너지학회논문집
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• 제19권2호
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• pp.171-181
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• 2008

There are several methods for the gas hydrate production such as spraying water with countercurrent gas flow, stirring water-gas mixture, and flowing water with micro-bubble, etc. These days it has been widely studied for the gas hydrate production method, having low energy consumption and high efficiency. In this paper, patents in the gas hydrate production method were gathered and analyzed. The search range was limited to the open patents of USA, European Union (EP), Japan (JP), and Korea (KR) from 1991 to 2007. Patents were gathered by using keywords searching and filtered by crucial criteria. The trends of the patents were analyzed by the years, countries, companies, and technologies.

• Tribology and Lubricants
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• 제6권1호
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• pp.36-51
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• 1990

A parametric study of the thermal effects of a half-circumferential grooved journal bearings under aligned and misaligned conditions has been carried out by solving numerically the coupled Reynolds and energy equation system. Five different sets of boundary conditions for the energy equation have been used which include mixing between recirculating oil and inlet oil and a contraction ratio for the cavitation region. The effects of changes of the inlet oil temperature and pressure, the wall temperature and the L/D ratio have also been examined. For the range of parameters found in internal combustion engines, the mixing effectiveness at the groove and the resulting final mixture temperature have been found to be as important as the wall temperature and the heat transfer rate. The variability of the temperature, though, has been shown to smooth out the peaks of both pressure and friction during misaligned condition Distributions of friction and pressure in the oil are also examined which may be useful in attempts to reduce friction without reducing load. Results for an axial grooved bearing are also presentsed for comparision purpose.

• Advances in materials Research
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• 제5권1호
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• pp.35-53
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• 2016

Flexural bending analysis of perfect and imperfect functionally graded materials plates under hygro-thermo-mechanical loading are investigated in this present paper. Due to technical problems during FGM fabrication, porosities and micro-voids can be created inside FGM samples which may lead to the reduction in density and strength of materials. In this investigation, the FGM plates are assumed to have even and uneven distributions of porosities over the plate cross-section. The modified rule of mixture is used to approximate material properties of the FGM plates including the porosity volume fraction. In order the elastic coefficients, thermal coefficient and moisture expansion coefficient of the plate are assumed to be graded in the thickness direction. The elastic foundation is modeled as two-parameter Pasternak foundation. The equilibrium equations are given and a number of examples are solved to illustrate bending response of Metal-Ceramic plates subjected to hygro-thermo-mechanical effects and resting on elastic foundations. The influences played by many parameters are investigated.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2004년도 Asia Display / IMID 04
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• pp.465-467
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• 2004

We presented a systematic investigation on the growth of CNTs including SWNTs on nano-catalyst-embedded particles by PECVD. For CNTs growth, the mixture of $C_2H_2$ and $NH_3$ was used. The total pressure and temperature were kept at 3.25 Torr and 650 $^{\circ}C$, respectively. Finally, we measured the field emission property from CNTs grown from nano-catalyst embedded zeolite particles in vacuum chamber (<$10^{-7}$ Torr).

• International Journal of Automotive Technology
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• 제2권4호
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• pp.147-155
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• 2001

Analysis of the thermodynamic cycle of IC engine from the point of view of economy and emissions was carried out. From this analysis potential capability of engine development was derived. This potential capability is lean-burn engine, fuelled with homogeneous mixture with $\lambda \geq$ 1.4. Several different modes of fuelling were proposed and tested on one-cylinder test engine from the point of view of extending lean operating limit of the engine, emissions and fuel economy. Among them were: fuelling with evaporated preheated gasoline, with gas (LPG evaporated) and with liquid butane. From these modes, fuelling with liquid butane injected to inlet port was selected and finally tested. This novel system of fuelling offered better than standard engine performances and emissions at lean operating limit. These results were validated on full-scale two-cylinder engine.

• Computers and Concrete
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• 제25권1호
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• pp.59-65
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• 2020

The premise for the study reflected in this article is the need to dispose of industrial waste, which is increasingly being used in the construction materials industry. Also, dynamically developing building industry demands attention of scientists and a direction of their works on improvement of the technology of carrying out construction works. Thus, the article is devoted to studying the influence of various chemical additives and fine fillers (industrial wastes) available in Kazakhstan on self-compacting concrete (SCC) mixtures and its rheological, physical, and technical properties. According to the studies, revealed the most efficient type of fine-dispersed filler and the most optimal type of chemical additive to enable obtaining a high-quality SCC mixture based on local raw materials. As a result, the use of microsilica in comparison with other industrial wastes resulted in a conglomerate with high compressive strength of SCC at early terms of curing. In terms of economic efficiency and quality improvement, the results of study are of practical value for the manufacturers of ready-mixed concrete operating in Kazakhstan.