• Journal of Powder Materials
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• v.13 no.6 s.59
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• pp.432-438
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• 2006

Aluminum nitride (AlN) nanopowders with low degree of agglomeration and uniform particle size were synthesized by carbothermal reduction of alumina and subsequent direct nitridization. Boehmite powder was homogeneously admixed with carbon black nanopowders by ball milling. The powder mixture was treated under ammonia atmosphere to synthesize AlN powder at lour temperature. The effect of process variables such as boehmite/carbon black powder ratio, reaction temperature and reaction time on the synthesis of AlN nanopowder was investigated.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2006.04a
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• pp.123-126
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• 2006

Reduction kinetics and intermediates behaviour of three high explosives (HMX, RDX, and TNT) were studies in batch reactors using either nano or micro size zero valent iron(ZVI) as reducing agent. The kinetics constants normalize to the mass of iron($k_M$) or to the surface area ($k_{SA}$) were measured and compared along with the changes of intermediate concentrations of each explosive. Results showed that $k_M$ and $k_{SA}$ values neither correlated each other nor explained the behaviour of intermediates of each high explosive in the batch reactor, in which initial intermediates decreased rapidly with nano ZVI treatment whereas the intermediates accumulated and stayed longer in the micro ZVI treated reactor.

• Journal of the Korean Society of Industry Convergence
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• v.12 no.3
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• pp.143-147
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• 2009

The enantioselective reduction of representative prochiral alkyl-aryl ketones with a new chiral alkoxy-amine-aluminum derivatives from aluminum hydride and ${\alpha},{\alpha}$-diphenyl-${\beta}$-amino alcohols, such as (S)-(-)-2-amino-3-methyl-1,1-diphenylbutan-1-ol(AMDPB) and (S)-(-)-2-(diphenylhydroxy-methyl)pyrrolidine(DPHMP), in THF at $0^{\circ}C$ was studied. In the reduction of alkoxy-amine-aluminum derivatives, acetophenone, propiophenone, isopropiophenone, and butyrophenone are reduced to corresponding aromatic secoundary alcohols with 34~60 % enantiomeric excess of (S)-isomers. For such ketones, the optical induction was enhanced by increasing a size of alkyl groups.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.9
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• pp.1227-1236
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• 2001

A systematic analysis is made of suboptimal control for drag reduction. The influence of the amplitude of actuation (A) and the time scale of actuation ($\Delta$t(sub)a(sup)+) is evaluated. Two wall sensing variables are employed (∂w/∂y│(sub)w and ∂p/∂z│(sub)w) with two wall actuations (${\Phi}$$_2$and ${\Phi}$$_3$). To test the suboptimal control, direct numerical simulations of turbulent channel flow at Re(sub)$\tau$=100 are performed in a spectral domain. It is found that the effect of A and $\Delta$t(sub)a(sup)+∼1. The near-wall behaviors of flow structure are analyzed to characterize the drag reduction. The size effect of the sensor/actuator is examined.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.134-137
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• 2014

The noise reduction performance of a passive facility is dependent on the its length or volume. In other words, this means that the larger the size of passive facility is, the better the noise reduction performance is. The sound directivity control has been proposed as an alternative for the noise reduction without a passive facility. The purpose of this study is to investigate the correlation between the flange attached to inclined exit of the tube and sound directivity when the sound radiates from the tube to the outside. As a result, the sound radiated from flanged tube had weak sound directivity in the wide angle. Also as the flange was bigger, the sound pressure level was lower in the behind the flange.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.28B no.5
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• pp.318-326
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• 1991

A Quantizer reconstruction level control method for block artifact reduction in DCT image coding is described. In our scheme, quantizer reconstruction level control is obtained by adding quantization level step size to the optimum quantization level in the direction of reducing the block artifact by minimizing the mean square error(MSE) and error difference(EDF) distribution in boundary without the other additional bits. In simulation results, although the performance in terms of signal to noise ratio is degraded by a little amount, mean square of error difference at block boundary and mean square error having relation block artifact is greatly reduced. Subjective image qualities are improved compared with other block artifact reduction method such as postprocessing by filtering and trasform coding by block overlapping. But the addition calculations of 1-dimensional DCT become to be more necessary to coding process for determining the reconstruction level.

• Journal of the Korean Ceramic Society
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• v.43 no.4 s.287
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• pp.224-229
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• 2006

Ag-Pd alloy nanoparticles were prepared by a chemical reduction method using hydrazine $(N_2H_4)$ as a reductant in $AgNO_3\;and\;Pd(NO_3)_2$ aqueous solutions. Characterization of these particles by X-ray powder diffraction revealed a bimetallic and crystalline silver-palladium alloy. The average size of the particles was influenced not by the reductant $(N_2H_4)$ concentration, but the concentration of the starting materials $(AgNO_3\;and\;Pd(NO_3)_2)$.

• Journal of the Korea Safety Management & Science
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• v.15 no.1
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• pp.177-182
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• 2013

More and more medium and small enterprises do business across the world according to generalization of online shopping mall such as eBay and Amazon. But high export and import transportation cost make weak the price competitive power of medium and small enterprises products. Then this paper deals with the development of new business model which can reduce the transportation cost for global logistics through efficiently overcoming the constraints as length, size, and weight of product. We explain this model with application for company which export the automobile parts. We can expect the transportation cost reduction by 50%.

• Transactions of Materials Processing
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• v.12 no.6
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• pp.558-565
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• 2003

Rotary swaging is one of the incremental forming process which is a chipless metal forming process for the reduction of cross-sections of bars, tubes and wires. In the present work, the rotary swaging machine and dies were designed to investigate the formability of TDS(Tube Drive Shaft) used in automotive industry. The process variables such as the speed of forming, the shape of the formed materials and the reduction of area were also estimated to study experimental analyses of rotary swaging process using the materials of 34Mn5 and S45C. From experimental results, it was found that the process variables affected the quality of TDS in terms of hardness, the precision of products and the surface roughness. The hardness after swaging approved to be Increased with the increase in the reduction of diameter. And it was found that the grain size became smaller and the elongated grains were formed in the axis direction.

• Journal of Korea Society of Digital Industry and Information Management
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• v.7 no.4
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• pp.133-139
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• 2011

In this paper, we propose a hybrid filter for noise reduction. The proposed method adjusts rational filtering direction according to an edge in the image using median filtered data. Rational filter modulates the coefficients of a linear lowpass filter to limit its action in presence of image details. By the ratio of polynomials in the input variables, rational filter reduces noise adaptively. Median filter is widely used to reduce impulse noise, but removes some details for highly corrupted images. Also, desirable details are removed when the window size is large. Our proposed algorithm combines rational filter and median filter. Thus, proposed method not only preserves edge, but also reduces noise in uniform region. Experimental results show that our proposed method has better quality than those by existing median and rational filtering methods.