• 한국재료학회:학술대회논문집
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• 한국재료학회 2012년도 춘계학술발표대회
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• pp.81.2-81.2
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• 2012

To fabricate a metal mold for injection molding, hot-embossing and imprinting process, mechanical machining, electro discharge machining (EDM), electrochemical machining (ECM), laser process and wet etching ($FeCl_3$ process) have been widely used. However it is hard to get precise structure with these processes. Electrochemical etching has been also employed to fabricate a micro structure in metal mold. A through mask electrochemical micro machining (TMEMM) is one of the electrochemical etching processes which can obtain finely precise structure. In this process, many parameters such as current density, process time, temperature of electrolyte and distance between electrodes should be controlled. Therefore, it is difficult to predict the result because it has low reliability and reproducibility. To improve it, we investigated this process numerically and experimentally. To search the relation between processing parameters and the results, we used finite element simulation and the commercial finite element method (FEM) software ANSYS was used to analyze the electric field. In this study, it was supposed that the anodic dissolution process is predicted depending on the current density which is one of major parameters with finite element method. In experiment, we used stainless steel (SS304) substrate with various sized square and circular array patterns as an anode and copper (Cu) plate as a cathode. A mixture of $H_2SO_4$, $H_3PO_4$ and DIW was used as an electrolyte. After electrochemical etching process, we compared the results of experiment and simulation. As a result, we got the current distribution in the electrolyte and line profile of current density of the patterns from simulation. And etching profile and surface morphologies were characterized by 3D-profiler(${\mu}$-surf, Nanofocus, Germany) and FE-SEM(S-4800, Hitachi, Japan) measurement. From comparison of these data, it was confirmed that current distribution and line profile of the patterns from simulation are similar to surface morphology and etching profile of the sample from the process, respectively. Then we concluded that current density is more concentrated at the edge of pattern and the depth of etched area is proportional to current density.

• 한국재료학회지
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• 제27권12호
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• pp.705-709
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• 2017

The electronic and optical characteristics of molybdenum disulphide ($MoS_2$) film significantly vary with its thickness, and thus a rapid and accurate estimation of the number of $MoS_2$ layers is critical in practical applications as well as in basic researches. Various existing methods are currently available for the thickness measurement, but each has drawbacks. Transmission electron microscopy allows actual counting of the $MoS_2$ layers, but is very complicated and requires destructive processing of the sample to the point where it will no longer be useable after characterization. Atomic force microscopy, particularly when operated in the tapping mode, is likewise time-consuming and suffers from certain anomalies caused by an improperly chosen set point, that is, free amplitude in air for the cantilever. Raman spectroscopy is a quick characterization method for identifying one to a few layers, but the laser irradiation causes structural degradation of the $MoS_2$. Optical microscopy works only when $MoS_2$ is on a silicon substrate covered with $SiO_2$ of 100~300 nm thickness. The last two optical methods are commonly limited in resolution to the micrometer range due to the diffraction limits of light. We report here a method of measuring the distribution of the number of $MoS_2$ layers using a low voltage field emission electron microscope with acceleration voltages no greater than 1 kV. We found a linear relationship between the FESEM contrast and the number of $MoS_2$ layers. This method can be used to characterize $MoS_2$ samples at nanometer-level spatial resolution, which is below the limits of other methods.

• Design & Manufacturing
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• 제13권2호
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• pp.17-21
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• 2019

In this study, selective laser sintered 3D printing mold core and metal core were used to investigate the difference of the thickness shrinkage from the gate of the injection molded part at a constant interval. SLS 3D printing mold core was made of nylon-based PA2200 powder and the metal core was manufactured by conventional machining method. As the PA2200 powder material has low strength, thermal conductivity and high specific heat characteristics compared with metal, molding conditions were set with the consideration of molten temperature and injection pressure. Crystalline resin(PP) and amorphous resin(PS) with low melting temperature and viscosity were selected for the injection molding experiment. Cooling time for processing condition was selected by checking the temperature change of the cores with a cavity temperature sensor. The cooling time of the 3D printing core was required a longer time than that of the metal core. The thickness shrinkage of the molded part compared to the core depth was measured from the gate by a constant interval. It was shown that the thickness shrinkage of the 3D printing core was 2.02 ~ 4.34% larger than that of metal core. In additions, in the case of metal core, thickness shrinkage was increased with distance from the gate, on the contrary, in the case of polymer core showed reversed aspect.

• 동아시아식생활학회지
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• 제17권4호
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• pp.554-562
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• 2007

본 연구는 식이 습관병 예방을 위한 건강식품을 개발하기 위한 기초 연구로써 계획되어 선행 연구와 문헌상의 기록을 바탕으로 한 천마의 여러 기능 중 혈류 개선 효과에 중점을 두고 그 기능을 과학적으로 확인하여 보고자 하였다 즉, 쌀뜨물을 주로하여 소화 흡수 및 면역력의 증강을 기대할 수 있고 독성 성분을 제거할 수 있으며, 더불어 활혈(活血) 및 청열량혈(靑熱凉血)기능을 가지는 천궁과 이수(利水) 및 안신(安神)작용을 하는 복령을 포제에 함께 이용하여 뇌혈류와심혈관 기능을 증진시키고자 하였다. 따라서 흰쥐를 대상으로 Laser-Doppler flowmeter system(LDF)을 이용하여 천마가 국소 뇌혈류량과 혈압에 미치는 효과를 관찰한 결과는 다음과 같다. 1. 천마를 0.1mg/kg, 1.0mg/kg 및 10.0 mg/kg 농도로 주사 시 농도 의존적으로 국소 뇌혈류량이 증가되었다. 2. 천마가 국소 뇌혈류량을 증가시키는 기전을 확인하기 위해 propranolol, atropine, methylene blue, indomethacin으로 전처리한 후 천마를 주사했을 때는 국소뇌혈류량에 유의한 변화를 관찰할 수 없었으나, anti-nitric oxide synthetase를 전처리한 후 천마를 주사했을 때는 국소 뇌혈류량이 유의적으로 증가함을 관찰할 수 있었다. 3. 천마를 0.1 mg/kg, 1.0 mg/kg 및 10.0 mg/kg 농도로 주사 시 농도 의존적으로 혈압이 저하되었다. 4. 천마가 어떤 기전으로 혈압의 변화를 초래하는지를 확인하기 위해 propranolol, atropine, methylene blue, indomethacin으로 전처리한 후 천마를 주사했을 때는 혈압에 유의한 변화를 관찰할 수 없었으나 anti-nitric oxide synthetase로 전처리한 후 천마를 주사했을 때에는 혈압이 유의적으로 저하되는 변화가 나타났다. 이상의 결과에서 포제 천마는 뇌혈류량을 증가시키고 혈압을 강하시키는 작용이 있음을 확인하였고, 그 기전은 nitric oxide 생성과 관련되어 나타나는 결과로 판단된다. 따라서 혈관 질환을 포함한 식이 습관병과 관계된 질환의 예방 및 치료의 보조 식이물로써 활용이 가능하다고 판단되며, 향후 포제 천마를 이용한 건강식품을 개발하고 완제품에 대한 유효성에 대한 연구를 수행할 때 기초 자료가 될 수 있을 것으로 사료된다.