• 한국산학기술학회논문지
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• 제14권6호
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• pp.2743-2748
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• 2013

비타민은 우리 몸에서 많은 양을 필요로 하지는 않지만 없어서는 안 될 필수 영양성분으로 음식물과 태양광등을 통하여 획득하고 그 농도를 유지하고 있다. 그러나 때로는 어떤 요인에 의하여 농도가 변하는 경우가 있는데 그중 간기능 인자들과 $25OH-VIT.D_3$ 농도값의 영향요인을 분석하고자 실시하였다. 연구 대상은 2012년 8월부터 2012년 12월까지 모대학병원 검진센타에 건강검진을 받은 검체를 대상으로 하여 실험군 검체와 대조군 정상검체 두 군으로 분류한 후 성별, 연령, 비만도, AST, ALT, rGTP와 $25OH-VIT.D_3$의 상관성을 조사하였다. 분석결과로 $25OH-VIT.D_3$농도에 영향을 미치는 요인으로 선정된 변수는 연령과 B형간염역가로 나타났으며 특히 B형간염역가는 역 상관관계를 나타내었다($R^2$=0.40). 이는 간염바이러스에 의한 간기능에 의해 그 농도값에 영향을 줄 수 있으므로 간염 보균자인 경우 간기능 검사와 더불어 $25OH-VIT.D_3$의 영향인자로 관리 되어져야 한다고 사려 된다.

• 한국약용작물학회:학술대회논문집
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• 한국약용작물학회 2012년도 심포지엄 및 춘계학술발표회
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• pp.81-82
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• 2012

• 한국기계가공학회지
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• 제20권8호
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• pp.42-51
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• 2021

Investigations of process parameters are essential when fabricating high-quality parts using additive manufacturing. This study investigates the change in the mechanical characteristics of a SUS316L specimen fabricated using selective laser melting based on the energy density and bead overlap ratio. The SUS316L powder particles were spherical and 35 ㎛ in size. Single-bead and hexahedral shape deposition experiments were performed sequentially. A single bead experiment was performed to obtain the bead overlap ratios for different laser parameters utilizing laser power and scan speed as experimental parameters. A hexahedral shape deposition experiment was also performed to observe the difference in mechanical properties, such as the internal porosity, surface roughness, and hardness, based on the energy density and bead overlap ratio of the three-dimensional printed part. Laser power, scan speed, overlap ratio, and layer thickness were chosen as parameters for the hexahedral shape deposition experiment. Accordingly, the energy density applied for three-dimensional printing, and the experimental parameters were calculated, and the energy density and bead overlap ratio for fabricating parts with good properties have been suggested.

• Korean Journal of Mathematics
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• 제26권2호
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• pp.155-166
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• 2018

Consider FARIMA time series with innovations that have infinite variances. We are interested in the estimation of self-similarities $H_n$ of FARIMA(0, d, 0) by using modified R/S statistic. We can confirm that the $H_n$ converges to Hurst parameter $H=d+\frac{1}{2}$. Finally, we figure out ARMA and minimum variance power spectrum density of FARIMA processes.

• 대한방사선기술학회지:방사선기술과학
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• 제41권1호
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• pp.53-60
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• 2018

The purpose of this study was investigating the effect of 3D printing technology that changes the speed of sound (SOS) and the broadband ultrasound attenuation (BUA) by controlling the density of the media phantom. We used 3D printers which called additive manufacturing (AM) by using material with polylactic acid (PLA). The inside of the medium phantom was filled crossly with 100%, 90%, 80%, 70%, 60%, and 50% of the material. The ultrasonic instrument measured the SOS and the BUA using a 0.55 MHz ultrasound output in opposing mode with a pair of transducers. As a result, the density of the medium phantoms with the SOS showed very high correlation (r = 0.944), but the SOS showed very low correlation (r = 0.500). It is expecting that the manufacturing and measurement method of the medium phantom using 3D printing technology will be used as basic data for ultrasonic bone mineral density.

• 한국재료학회지
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• 제22권9호
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• pp.482-488
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• 2012

To fabricate a precise micro metal mold, the electrochemical etching process has been researched. We investigated the electrochemical etching process numerically and experimentally to determine the etching tendency of the process, focusing on the current density, which is a major parameter of the process. The finite element method, a kind of numerical analysis, was used to determine the current density distribution on the workpiece. Stainless steel(SS304) substrate with various sized square and circular array patterns as an anode and copper(Cu) plate as a cathode were used for the electrochemical experiments. A mixture of $H_2SO_4$, $H_3PO_4$, and DIW was used as an electrolyte. In this paper, comparison of the results from the experiment and the numerical simulation is presented, including the current density distribution and line profile from the simulation, and the etching profile and surface morphology from the experiment. Etching profile and surface morphology were characterized using a 3D-profiler and FE-SEM measurement. From a comparison of the data, it was confirmed that the current density distribution and the line profile of the simulation were similar to the surface morphology and the etching profile of the experiment, respectively. The current density is more concentrated at the vertex of the square pattern and circumference of the circular pattern. And, the depth of the etched area is proportional to the current density.

• 정보저장시스템학회논문집
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• 제4권1호
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• pp.1-5
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• 2008

Super-resolution near-field structure (super-RENS) technology and solid immersion lens (SIL) based near-field (NF) technology have been expected as promising approaches to increase data capacity or areal density of optical disc. Super-RENS technology has been studied until now using mainly numerical aperture (NA) of 0.85 far-field optical system and possibility of tangential data density increment have been presented. NF technology has been studied with NA over 1 and presented demonstration of removable performance. To achieve much higher density, approach to increase NA of super-RENS by NF technology (Near-Field Super-Resolution, NFSR) can be a candidate and we think this technology would be advantageous compared to wavelength reduction or much higher NA increment of NF technology or much smaller effective optical spot size reduction of far-field super-resolution technology. In this paper we present readout result of ROM media having monotone pits using NF optical system with wavelength of 405nm and NA of 1.84 surface type SIL. GeSbTe material was used for super resolution active layer and pit length is 37.5nm which is shorter than resolution limit 55nm. We present the feasibility of NFSR technology by confirming the CNR threshold according to readout power (Pr) and CNR 33dB over threshold Pr.

• 한국약용작물학회:학술대회논문집
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• 한국약용작물학회 2008년도 추계학술발표회
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• pp.187-188
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• 2008

• 한국약용작물학회:학술대회논문집
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• 한국약용작물학회 2008년도 추계학술발표회
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• pp.193-194
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• 2008

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2006년도 6th International Meeting on Information Display
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• pp.505-508
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• 2006

Self-heating induced device degradation and its width/length (W/L) dimension dependence were studied in p-type polycrystalline silicon (poly-Si) thin film transistors (TFTs). Negative channel conductance was observed under high power region of output curve, which was mainly caused by hole trapping into gate oxide and also by trap state generation by self-heating effect. Self-heating effect became aggravated as W/L ratio was increased, which was understood by the differences in heat dissipation capability. By reducing applied power density normalized to TFT area, self-heating induced degradation could be reduced.