• 한국농공학회논문집
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• 제52권3호
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• pp.113-120
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• 2010

Reduction factor for installation damage required to calculate design strength of geogrid used in MSEW(mechanically stabilized earth wall) design is usually obtained in the field test simulating real construction condition. However, damages occurred in geogrid during backfill work are influenced by many factors such as polymer types, unit weight per area, backfill construction method and gradation of backfill material and field test considering these factors demand lots of time and costs. In this study, factors affecting installation damage are analyzed and empirical method to evaluate reduction factor for installation damage using maximum particle size in backfill material is suggested.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 춘계 학술발표회
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• pp.518-525
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• 2009

The bi-directional high pressure pile load test(BDH PLT) which is a kind of pile load tests was conducted to find out a reasonable design procedure of large-diameter drilled shafts of large-size building structures. The behaviors of bearing capacity and settlement of the large-diameter drilled shafts were analyzed and the results obtained from BDH PLT were also compared with those obtained from the equations suggested in the specification. In case of the reasonable design procedure adopted, the construction cost could be saved at least 15 ~ 28%. It could be concluded that BDH PLT should be needed for the foundation construction cost reduction of the high-rise building structures.

• 소성∙가공
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• 제25권5호
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• pp.306-312
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• 2016

Effects of manufacturing conditions, such as austenitizing temperature, patenting temperature and carbon content in steels, on mechanical properties, especially on reduction of area (RA), of hyper-eutectoid steel wires were investigated. RA increased and then decreased with transformation temperature. This was attributed to the presence of abnormal structures in steels transformed at low transformation temperatures and the occurrence of shear cracking during tensile testing of steels transformed at high transformation temperatures. The increase of austenitizing temperature resulted in the increased austenite grain size and consequently the decrease of RA. The decrease of RA with increasing the carbon content in steels was attributed to the increased fraction of cleavage fracture in tensile fractured surfaces.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.120-121
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• 2006

Magnetic properties of nanostructured materials are affected by the microstructures such as grain size (or particle size), internal strain and crystal structure. Thus, it is necessary to study the synthesis of nanostructured materials to make significant improvements in their magnetic properties. In this study, nanostructured Fe-20at.%Co and Fe-50at.%Co alloy powders were prepared by hydrogen reduction from the two oxide powder mixtures, $Fe_2O_3$ and $Co_3O_4$. Furthermore, the effect of microstructure on the magnetic properties of hydrogen reduced Fe-Co alloy powders was examined using XRD, SEM, TEM, and VSM.

• 한국감성과학회:학술대회논문집
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• 한국감성과학회 1999년도 추계학술대회 논문집
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• pp.53-58
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• 1999

Recently, the size and complexity of the system we have to develop and to deal with are expanding quickly. Because of the great size of causally related network in itself, such a system will be very difficult to deal with based on the typical reduction model. One of alternatives for this is to adopt emergence-based paradigm instead of reduction-based paradigm. The first is based on the low level causality and the latter on the high level emergence. In this paper we proposed an emergence-based object model realizable in terms of engineering. It is the abstracted one from original object model using of such concepts as performance function, interest function and emotional layer. The suggested model allows us to emerge some important concepts which might be useful for implementing the complex system which can hardly be available by reduction paradigm.

• 한국강구조학회 논문집
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• 제16권3호통권70호
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• pp.333-344
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• 2004

복합재료는 건설공학 분야의 해석, 설계, 제작, 건설, 품질 제어 등에서 경제적이고 효율적인 재료로 사용될 수 있다. 많은 교량 구조물중 거더, 가로보로 이루어진 콘크리트 상판은 특별직교이방성판으로 거동한다. 이러한 경계조건을 갖는 단면 혹은 불규칙한 단면을 갖는 시스템은 해석적인 해를 구하기가 매우 어렵다. 이러한 문제에 대한 해석을 위해서 유한차분법이 이용되었다. 본 논문에서는 인장강도 감소율을 적용하여 파괴강도 해석을 수행하였다. 또한 이러한 경우에 대한 수치해석을 수행하였다. 응력영역에 대한 Tasi-Wu의 파괴기준을 적용하였다.

• 한국환경과학회지
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• 제22권11호
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• pp.1481-1498
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• 2013

The SCR (selective catalytic reduction) system is highly-effective technique for NOx reduction from exhaust gases. In this study, the effects of the direction and size of nozzle and the ammonia injection concentration on the performance of SCR system are analyzed by using the computational fluid dynamics method. When the nozzle is arranged in zigzaged direction which is normal to exhausted gas flow, it is shown that the uniformity of gas flow and the NH3/NO molar ratio is improved remarkably. With the change of the ammonia injection concentration from 0.2 vol%(wet) to 1.0 vol%(wet), the uniformity of gas flow shows a good results. As the size of nozzle diameter changes from 6 mm to 12 mm, the uniformity of gas flow is maintained well. It is shown that the uniformity of the $NH_3/NO$ molar ratio becomes better with decreasing the ammonia injection concentration and the size of nozzle diameter.

• 전자공학회논문지
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• 제52권5호
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• pp.66-73
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• 2015

OFDM 기반 통신시스템에서 IFFT는 중요한 핵심 컴포넌트 중의 하나이다. 본 논문에서는 OFDM 기반 통신시스템을 위한 메모리가 효율적인 새로운 IFFT 설계 방법을 제안한다. OFDM 기반 통신시스템에서 사용되는 IFFT의 입력신호는 데이터 변조신호, 파일럿과 널(null) 신호로 구성된다. 제안한 방법은 IFFT 입력신호의 매핑을 통해 IFFT에서 가장 큰 메모리를 차지하는 비트리버스의 메모리를 감소시키는 데 초점을 둔다. 비트리버스의 메모리 크기를 감소시키기 위해 DIT기반 구조에 적합한 선택 매핑기법을 제안한다. 시뮬레이션을 통해 제안한 방법이 기존 방법과 비교하여 약 50%의 메모리가 감소됨을 보인다.

• 한국재료학회지
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• 제12권6호
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• pp.488-492
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• 2002

Magnetic properties of nanostructured materials are affected in complicated manner by their microstructure such as grain size, internal strain and crystal structure. Thus, studies on the synthesis of nanostructured materials with controlled microstructure are necessary for a significant improvement in magnetic properties. It is well known that when Fe-Co alloy undergoes ordering transformation, soft magnetic properties could be obtained. There are many reports that the magnetic properties of the materials can be changed with variation of grain size. In the present work, nanostructured Fe-50at.%Co alloy powder produced by hydrogen reduction process (HRP) starting with two oxide powder mixtures of $Fe_2O_3\;and\; Co_3O_4$. The mean grain size of the HRP powders was about 40 nm and coercivity of the: powders was about 43 Oe.

• 한국세라믹학회지
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• 제47권6호
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• pp.534-539
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• 2010

$HfB_2$-HfC composites were prepared by reactive hot pressing using Hf and $B_4C$ at temperatures of 1800 and $1900^{\circ}C$ for 60 min under 32 MPa in an Ar atmosphere. The reaction sequences of the $HfB_2$-HfC composite were studied through series of pressureless heat treatments ranging from 800 to $1600^{\circ}C$. The effect of size reduction of the starting powders on densification was investigated by vibration milling. Fully dense $HfB_2$-HfC composites were obtained by size reduction of the starting powders via vibration milling. The oxidation behaviour of the $HfB_2$-HfC composites at $1500^{\circ}C$ in air showed formation of a non-protective $HfO_2$ scale with linear mass gain. Examination of the mechanical properties showed that particle size reduction via vibration milling also led to improved flexural strength, hardness and fracture toughness.