• 한국분말재료학회지
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• 제11권2호
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• pp.137-142
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• 2004

In this study, chemical solution mixing and hydrogen reduction method was used to fabricate nanostructured $Fe_xCo_{1-x}$ alloy powders. Fe-Co chloride mixture, FeCl$_2$ and COCI$_2$ with 99.9％ purity, were reduced in hydrogen atmosphere. Nanostructured Fe-Co alloy powders with a grain size of 50 nm were successfully fabricated. Magnetic properties of fabricated $Fe_xCo_{1-x}$(x=0, 10, 30, 50, 70, 100) alloy powders with the same grain size were measured because size factor can affect magnetic properties. Coercivity of Fe-Co alloy powders were increased with increasing Co contents. Maximum value of coercivity in various Co contented Fe-Co alloy powders with similar grain size was 125 Oe at Fe$_{100}$. Saturation magnetization value at Fe$_{70}$Co$_{30}$ composition showed maximum value of 219 emu/g and saturation magnetization value decreased with increasing Co contents and minimum value of 155 emu/g was observed at Co$_{100}$.

• KIEAE Journal
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• 제12권3호
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• pp.53-60
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• 2012

This research is an illustrative research to verify the thermo environmental change created after introduction of indoor pond through abridged model test and simulation analysis. Especially, temperature and comfort level are analyzed by adjusting factors like size of water space, distance length, and location. Summary of the research is as follows. First, the most effective size of water space is 7% of the indoor size, from southern side. Temperature reduction effect is about $1.6^{\circ}C$(5.5%), and for the comfort level, it is found that pmv index increases 8%. Second, based on the simulation of distance length with the sphere, it is more effective as it is close to the surface. If distance length is more than 0.5m, there is no effect on reduction of temperature and comfort level of indoor environment. Lastly, for the analysis by location of the introduced water space, simulation is undertaken by dividing the water space (14% of the indoor size) with front, side, rear and center types. Temperature reduction effect is found to be : front type ($-1.53^{\circ}C$), side type ($-0.82^{\circ}C$), rear type ($-0.44^{\circ}C$), center type ($-0.28^{\circ}C$), respectively. The indoor environment change data by introduction of water space, found in this research, is at initial phase, but it is deemed to be a basic data to refer when planning actual water space.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.464-465
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• 2006

Monodispersed and nano-sized Cu powders were synthesized from copper sulfate pentahydrate $(CuSO_4{\cdot}5H_2O)$ inside a nonionic polymer matrix by using wet chemical reduction process. The sucrose was used as a nonionic polymer network source. The influences of a nonionic polymer matrix on the particle size of the prepared Cu powders were characterized by means of X-ray diffraction), scanning electron microscopy), and particle size analysis). The smallen Cu powders with size of approximately 100 nm was obtained with adding of 0.04M sucrose at reaction temperature of $60\;^{\circ}C$. The particle size of the Cu powders prepared by the reduction inside polymer network was strongly dependent of the sucrose content and reaction temperature.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2009년도 추계학술대회
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• pp.401-404
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• 2009

본 논문에서는 ROM의 크기를 줄여 전력 소모를 줄일 수 있는 DDFS를 제안하였다. 새롭게 제안된 병렬 ROM 방식은 두 개의 ROM을 사용하여 원하는 주파수를 합성함으로써 전체적인 ROM들의 크기를 줄여준다. 표본화된 사인파의 양자화 값은 양자화 ROM과 차동 ROM에 저장된다. ROM 크기를 줄이기 위해 사인파를 양자화 할 때 일련의 차동 양자화 기술을 응용, 변형하여 두 개의 병렬 ROM을 사용한 압축방식을 제안한다. 이를 사용함으로써 최대 67.5%의 ROM 크기를 감소시켜 전력소모를 줄일 수 있다.

• 한국가스학회지
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• 제19권5호
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• pp.20-28
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• 2015

탄화수소 선택적 촉매환원공정에서 ${\gamma}$-알루미나에 지지된 금속 산화물 촉매의 크기 및 형태에 따른 질소산화물 ($NO_x$) 저감 특성에 대해 조사하였다. 환원촉매로는 Ag, Cu 및 Ru를 사용하였으며, n-heptane을 환원제로 사용하였다. Ag/${\gamma}$-$Al_2O_3$ 촉매의 경우 온도범위 $250{\sim}400^{\circ}C$에서 20 nm>50 nm>80 nm 순으로 Ag의 크기가 작을수록 $NO_x$ 전환효율이 높게 나타났다. 금속 산화물 촉매의 형태에 따른 영향은 구형과 선형에 대해 살펴보았다. Ag와 Cu는 동일한 조건에서 선형이 구형보다 $NO_x$ 전환효율이 높은 것으로 나타났으나, Ru의 경우에는 형태에 따른 영향이 거의 관찰되지 않았다. 사용된 금속산화물 촉매 중에서 Ag를 사용했을 때 $NO_x$ 저감효율이 가장 높았으며, 선형의 Ag를 사용했을 때 $300^{\circ}C$의 반응온도에서 대부분의 $NO_x$를 제거할 수 있었다. Cu와 Ru 촉매상에서는 NO가 환원되기보다는 $NO_2$로의 산화반응이 우세하여 전체적으로 $NO_x$ 저감효율이 낮게 나타났다.

• 대한금속재료학회지
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• 제48권4호
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• pp.315-319
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• 2010

In this study, the hydrogen reduction behavior of ball-milled NiO nanopowder was investigated depending on the partial pressure of water vapor. The hydrogen reduction behavior was analyzed by thermogravimetry and hygrometry under heating to 873 K in hydrogen. In order to change the partial pressure of the water vapor, the dew point of hydrogen was controlled in the range of 248 K~293 K by passing high-purity hydrogen through a saturator that contained water. Interestingly, with the increase in the dew point of the hydrogen atmosphere, the first step of the hydrogen reduction process decreased and the second step gradually increased. After the first step, a pore volume analysis revealed that the pore size distribution in the condition with a higher water vapor pressure shifted to a larger size, whereas the opposite appearedat a lower pressure. Thus, it was found that the decrease in the pore volume during the chemical reaction controlled process at a dew point of 248 K caused a reduction in retardation in the diffusion controlled process.

• 한국기계연구소 소보
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• 통권12호
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• pp.63-71
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• 1984

A new kind of bulb called Stern-End-Bulb(SEB) for the improvement of the after part of fine hull forms was developed. The reduction of wave resistance and the improvement of the powering performance for the ship with SEB were shown by the ship model tests, At the same time, the characteristics of wave in the vicinity of the stern and the mechanism of the resistance reduction by SEB were investigated. By the systematical variation of the SEB size, the optimum size of SEB was obtained.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2002년도 동계연구발표회 논문개요집
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• pp.17-17
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• 2002

The magnetic effects connected to finite-size of the particles become dominant at transition of particles in region several nanometers and less [1]. At reduction of atom numbers in magnetic cluster (tens or hundreds atoms), along the classical features, essential appear the quantum phenomena resulting in spin transformation of magnetic structure, both with reduction of the size and at applying of an external magnetic field. (omitted)

• Journal of Electrical Engineering and Technology
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• 제11권6호
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• pp.1582-1589
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• 2016

In this paper the integration of Distributed Generation (DG) in radial distribution system is investigated by computing the optimal site and size of DG to be placed. An analytical expression based on equivalent current injection has been derived by utilizing topological structure of radial distribution system to find optimal size of DG to minimize losses. In the presented formulation, the optimal DG placement is obtained without repeatedly computing the load flow. The proposed formulation can be used to find the optimal size of all types of DGs namely Type-I, Type-II, Type-III and Type-IV DGs. The investigations are carried out on IEEE 33-bus and 69-bus radial distribution systems. The optimal DG placement results into reduction in active and reactive power losses and improvement in voltage profile of the buses.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.616-619
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• 2000

The optimum design of a structure requires to determine economical member size and shape of a structure which satisfies the design conditions and functions. In this study, it is attempted to minimize a dead weight of the bogie frame. Therefore, shape optimization is performed for a bolster rib at first and then size optimization for the thickness of top and bottom plate. For the efficient reduction of a weight of a bogie frame, various ellipses centered at a centroid of a bolster rib are made and tried. For the shape optimization, a major axis and an eccentricity of an ellipse are chosen as design variables. From the numerical results of shape and size optimization of a bogie frame, it is known that the weight can be reduced up to 12.476 Y4717.21 kg) with displacement and stress constraints.