• Carbon letters
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• 제11권4호
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• pp.304-310
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• 2010

To manufacture a carbon/carbon composite the coal tar pitch was used as the matrix precursor and the PAN (polyacrylonitrile)-based carbon fiber was used as the reinforcing material to weave 3-directional preform. For pressure carbonization HIP equipment was used to produce a maximum temperature of $1000^{\circ}C$ and a maximum pressure of 100 MPa. The carbonization was induced by altering the dwell temperature between $250^{\circ}C$ and $420^{\circ}C$, which is an ideal temperature for the moderate growth of the mesophase nucleus that forms within the molten pitch during the pressure carbonization process. The application of high pressure during the carbonization process inhibits the mesophase growth and leads to the formation of spherical carbon particles that are approximately 30 nm in size. Most particles were spherical, but some particles were irregularly shaped. The spread of the carbon particles was larger on the surface of the carbon fiber than in the interior of the matrix pocket.

• 한국기계가공학회지
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• 제20권10호
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• pp.56-62
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• 2021

In this study, a cavitation occurrence in a piston-pump inlet was investigated by simulating the pressure distribution, according to the inlet shape of a variable-displacement swash-plate piston pump that supplies high-pressure oil to control the hydraulic system of a marine engine. Two types of pump inlets with different shapes were cast into impression models, and the models were reverse-engineered by 3D scanning. Then, the hydraulic-pressure distribution was analyzed through finite-element analysis. The results of the analysis confirmed that cavitation occurs more easily in the inlet with a steeper slope during pump operation because the inlet pressure on the valve plate is lower than that of the other pump with a gentler inlet slope.

• 반도체디스플레이기술학회지
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• 제16권4호
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• pp.63-67
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• 2017

In this study, We developed a simple and low cost capacitive pressure mapping sensor and microcontroller-base lock-in amplifier array. We developed capacitive type pressure mapping sensor by forming the electrode and adhesives on plastic films using only the printing process, and the finishing the process by bonding the two films. Lock-in amplifier array was based on a general purpose microcontroller and had only a charge amplifier as analog circuits. In this study, a $10{\times}10$ capacitive type pressure mapping sensor and lock-in amplifier array was fabricated and its characteristics were analyzed.

• 반도체디스플레이기술학회지
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• 제16권2호
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• pp.89-93
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• 2017

For various process pressures, aluminum doped zinc oxide(AZO) films were deposited by in-line pulsed-DC sputtering. The deposited AZO films were optically and electrically investigated and analyzed for the window layers of CIGS solar cell systems. As the pressure was increased from 9 mtorr to 15 mtorr, the thickness of AZO was decreased as a result of scattering and its sheet resistance was rapidly increased. The transmittance of AZO was slightly decreased as the pressure was increased and the calculation of figure of merit(F.O.M) was dependent on the sheet resistance. The structural characteristics of AZO thin films analyzed by X-ray diffraction(XRD) showed no significant dependency according to the pressure.

• 한국기계가공학회지
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• 제18권7호
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• pp.36-41
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• 2019

The design of pressure plate for automotive clutch also has been improved. The tension of the clutch spring compresses the clutch plate onto the flywheel to deliver the power. In this study, three types of pressure plate for clutch were modelled by using CATIA program, and the structural analyses due to external forces were performed with ANSYS program. It is thought that this study result can be used to verify the stability and strength according to the shape of the pressure plate.

• 한국기계가공학회지
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• 제20권8호
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• pp.107-114
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• 2021

Butterfly valves are used in various industries to control the flow rate, flow direction, pressure, and temperature. These are gaining popularity in the field of plant industry to enable high-differential pressure because of their low maintenance costs and ease of installation. This study presents a numerical analysis method to analyze changes in the flow characteristics of a high-differential pressure control butterfly valve based on the location and shape of the orifice. The numerical analysis was conducted using a commercial CFD program. The analysis results show a correlation between the orifice shape and cavitation phenomenon.

• 한국기계가공학회지
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• 제18권5호
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• pp.103-109
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• 2019

The pressure reducing valve for water is controlled by the load of the compression spring and the force of the fluid acting on the diaphragm of the stem. Repeated upward and downward reciprocation of the pressure-reducing valve stem damages the diaphragm, resulting in leakage. In this study, we designed a stem without a diaphragm and adjusted the stiffness of the compressing spring. In order to select the spring stiffness, springs offering a stiffness of -20%, -10%, 0%, and 10% with respect to the stiffness of the compression spring attached to the existing pressure reducing valve stiffness. A prototype for the pressure reducing valve was fabricated and the pressure change was evaluated for the target static pressure (6 bar) by testing the pressure characteristics after mounting the modified stem and each compression spring. Evaluation of the pressure characteristics was carried out using ASSE 1003 and KS B 6153. In addition, the flow rates were compared by internal flow analysis of the conventional pressure reducing valve and the pressure reducing valve using the modified stems, and the flow analysis was performed using Solidworks flow simulation 2018. The spring stiffness was constantly discharged at the target static pressure of 3.793 kgf/mm, and the flow rate was increased by about 15% compared with the conventional pressure reducing valve.

• Ocean and Polar Research
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• 제32권2호
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• pp.157-164
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• 2010

A marine alga, Spirulina maxima, was extracted under high pressure and low temperature conditions at 500 MPa and $60^{\circ}C$ for 5 and 10 min. A high pressure of 500 MPa was applied to improve process yields because of low temperature extraction. This method resulted in highest higher extraction yield of 26.1% (w/w) in comparison to those results obtained from conventional extraction methods which produced a yield of 17.6% (w/w) from water. The extracts from this process also showed 19% of low cytotoxicity against human normal fibroblast cells in adding 1.0 mg/ml of the highest concentration. The crude extract significantly reduced the production of Prostaglandin $E_2$ ($PGE_2$) from CCD-986sk cells and increased nitric oxide production by macrophages. These higher activities of enhancing skin immune functions were found to have high antioxidant extract properties, like a 98% increase in DPPH radical scavenging activity. The extracts from the high pressure process showed a higher elution of active components than other processes and generated new compounds based on HPLC analysis. This clearly indicates that the extracts from high pressure and low temperature conditions have higher skin immune activation properties that have not been previously reported.

• 한국주조공학회지
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• 제17권1호
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• pp.58-66
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• 1997

The main aim of the present study is to investigate the effects of several processing parameters on the characteristics of Fe-Al alloy preform manufactured by reactive sintering process. The processing parameters include preform composition of 25, 40, 50, 60 and 75at.%Al, compacting pressure of 10, 20 and $30kg/cm^2$, and mean Al particle size of 29, 66 and $187{\mu}m$. Mean Fe particle size was $39{\mu}m$. The density of preform processed under same compacting pressure was not affected by changing Al composition. The preform with Al compositions of 25, 40, 50 and 60at.% Al swelled after reactive sintering process, thus having lower density than the green compacts. The preform with Al compositions of 75at.%Al, however, shrinked after reactive sintering process, thus having higher density than the green compacts. Ignition temperature increased with increasing compacting pressure, and increased with increasing Al composition at the fixed compacting pressure. And adiabatic temperature decreased with increasing compacting pressure at the fixed Al composition, and increased with increasing Al composition at the fixed compacting pressure. The size of compound particles increased with increasing Al composition. Especially, The size of compound particles increased largely in the case of 75at.%Al. It was observed that 50at.%Al preform have three dimentional network structure having a homogeneous and fine decreasing Al particle size.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.357-357
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• 2012

The doping process of the solar cell has been used by furnace or laser. But these equipment are so expensive as well as those need high maintenance costs and production costs. The atmospheric pressure plasma doping process can enable to the cost reduction. Moreover the atmospheric pressure plasma can do the selective doping, this means is that the atmospheric pressure plasma regulates the junction depth and doping concentration. In this study, we analysis the atmospheric pressure plasma doping compared to the conventional furnace doping. the single crystal silicon wafer doped with dopant forms a P-N junction by using the atmospheric pressure plasma. We use a P type wafer and it is doped by controlling the plasma process time and concentration of dopant and plasma intensity. We measure the wafer's doping concentration and depth by using Secondary Ion Mass Spectrometry (SIMS), and we use the Hall measurement because of investigating the carrier concentration and sheet resistance. We also analysis the composed element of the surface structure by using X-ray photoelectron spectroscopy (XPS), and we confirm the structure of the doped section by using Scanning electron microscope (SEM), we also generally grasp the carrier life time through using microwave detected photoconductive decay (u-PCD). As the result of experiment, we confirm that the electrical character of the atmospheric pressure plasma doping is similar with the electrical character of the conventional furnace doping.