• 소성∙가공
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• 제12권6호
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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.

• 디지털산업정보학회논문지
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• 제7권4호
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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.

• Bulletin of the Korean Chemical Society
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• 제34권2호
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• pp.505-509
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• 2013

A low temperature ($65^{\circ}C$) thermal deposition process was developed for depositing a silver coating on thermally sensitive polymeric substrates. This low temperature deposition was achieved by chemical reduction of a silver alkylcarbamate complex with latent reducing agent. The effects of acetol as a latent reducing agent for the silver 2-ethylhexylcarbamate (Ag-EHCB) complex and their blend solutions were investigated in terms of reducing mechanism, and the size and shape of silver nanoparticles (Ag-NPs) as a function of reduced temperature and time, and PVP stabilizer concentration were determined. Low temperature deposition was achieved by combining chemical reduction with thermal heating at $65^{\circ}C$. A range of polymer film, sheet and molding product was coated with silver at thicknesses of 100 nm. The effect of process parameters and heat treatment on the properties of silver coatings was investigated.

• KIEE International Transactions on Power Engineering
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• 제12A권1호
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• pp.1-5
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• 2002

This paper presents the procedure to construct equivalent model of large power system based on nonlinear time simulation responses. It consists of coherency identification, generator aggregation and network reduction. Coherency index that can be directly implemented to this procedure is proposed. Generator aggregation based on detailed model is performed. This procedure can be used to construct equivalent model in PSS/E. It is also possible to reduce the large power system directly from the nonlinear time responses. This procedure is applied to the transient stability analysis of Korea power system that now experiences rapid changes. The equivalent model is compared with the original model in its size, accuracy, speed and performance. This paper shows that the developed equivalent model is a good estimate of the original system.

• 대한전기학회논문지:시스템및제어부문D
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• 제53권5호
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• pp.368-373
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• 2004

Surface visualization can be useful, particularly for internet-based education and simulation system. Since the mesh data size directly affects the downloading and operational performance, the problem that should be solved for efficient surface visualization is to reduce the total number of polygons, constituting the surface geometry as much as Possible. In this paper, an efficient polygon reduction algorithm based on Stokes＇ theorem, and topology preservation to delete several adjacent vertices simultaneously for past polygon reduction is proposed. The algorithm is irrespective of the shape of polygon, and the number of the polygon. It can also reduce the number of polygons to the minimum number at one time. The performance and the usefulness for medical imaging application was demonstrated using synthesized geometrical objects including plane. cube. cylinder. and sphere. as well as a real human data.

• 정보저장시스템학회논문집
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• 제10권2호
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• pp.55-60
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• 2014

Laser projector has many advantages of high brightness, high resolution and small size, but the huge drawback of image degradation called speckle which generated by coherence of laser and roughness of surface interrupts their general use. There are many methods to reduce speckle pattern, but they need effective optical systems to realize display to the far field with huge volume. We designed speckle reduction element by using microlens with controlled curvature to reduce spatial coherence. Vibration element was also applied to reduce temporal coherence which considered response time of eye. Designed element was fabricated by simple reflow method and imprinting method. From the results, the fabricated element performed 48.33% of speckle reduction efficiency and 41.29% of optical efficiency with a single doublet lens.

• 한국분말재료학회지
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• 제11권3호
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• pp.242-246
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• 2004

FePt nanoparticles for high-density magnetic recording media were synthesized by the simultaneous chemical reduction of Fe(acac) $_2$ and Pt(acac) $_2$ with 1,2-hexadecanediol as the reducing reagent. TEM images showed that the shape of as-synthesized FePt nanoparticle was spherical and average particle size was 3 nm. Also, SAD pattern showed that crystal structure was disordered FCC (face centered cubic). These FCC structured nanoparticles were transformed FCT (face centered tetragonal) structure by annealing at 55$0^{\circ}C$ for 30 min in Ar atmosphere. XRD analysis revealed that as-synthesized FePt nanoparticles were transformed from disordered FCC to ordered FCT. Finally, the coercivity of 2 kOe for FePt nanoparticles with FCT structure was obtained by VSM measurement.

• Bulletin of the Korean Chemical Society
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• 제16권1호
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• pp.37-42
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• 1995

Reactions of alkenes and alkynes with the recently discovered isopinocampheylhaloborane-methyl sulfide (IpcBHX·SMe2, X=Cl, Br, I) were investigated in detail in order to establish their usefulness as hydroborating agents. The reagents readily hydroborated alkenes at 50 ℃ and alkynes at 25 ℃ with excellent regioselectivity in placing the boron atom exclusively at the less hindered carbon atom. Especially, the selectivity achieved by the iodo derivative reaches essentially 100%. In addition to that, IpcBHX·SMe2 was applied to the reduction of cyclic ketones to examine its stereoselectivity. The halogen substituent in these reagents plays an important role in the stereoselective reduction. The stereoselectivity increased dramatically with increasing steric size of the substituent. Finally, the iodo derivative achieved highly stereoselective reduction, such selectivity being comparable to that previously achieved with trialkylborohydrides.

• 대한금속재료학회지
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• 제50권11호
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• pp.823-828
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• 2012

Direct reduction of $Ta_2O_5$ using liquid calcium was investigated. The experiment was conducted in a closed stainless steel chamber in an Ar atmosphere for 5-120 minutes. Most of $Ta_2O_5$ was reduced to ${\alpha}-Ta$ in 30 minutes above 1173 K and at a molar ratio of Ca and $Ta_2O_5$ above 10. The particles size increased with the reaction temperature, but it did not change much above 1223 K. The oxygen content of metal Ta was about 1 wt%.

• Bulletin of the Korean Chemical Society
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• 제15권6호
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• pp.478-483
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• 1994

Reactions of alkenes and alkynes with thexylhaloborane-methyl sulfide (ThxBHX${\cdot}$SMe$_2$, X= Cl, Br, I) were investigated in detail in order to elucidate the effect of halogen substituent in thexylborane and hence establish their usefulness as hydroborating agent. The reagents readily hydroborated alkenes at $50^{circ}C$and alkynes at $25^{circ}C$ in exceptional regioselectivity. Especially, the selectivity achieved by the bromo and iodo derivative reaches essentially 100%. In addition to that, $ThxBHX{\cdot}SMe_2$ was applied to the reduction of cyclic ketones to examine its stereoselectivity. The halogen substituent in thexylborane plays an important role in the stereoselective reduction. The stereoselectivity increased dramatically with increasing steric size of the substituent. Finally, the iodo derivative achieved highly stereoselective reduction, such selectivity being comparable to that previously achieved with trialkylborohydrides.