• 한국분말재료학회지
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• 제10권3호
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• pp.168-171
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• 2003

Interpenetrating phase composites of $TiB_2$-Cu system were produced via Spark-Plasma Sintering (SPS) oi nanocomposite powders. Under simultaneous action of pressure, temperature and electric current titanium diboride nanoparticles distributed in copper matrix move, agglomerate and form a fine-grained skeleton. Increasing SPS-temperature and he]ding time promote densification due to local melting of copper matrix When copper melting is avoided the compacts contain 17-20% porosity but titanium diboride skeleton is still formed representing the feature of SPS . High degree of densification and formation of titanium diboride network result in increased hardness of high-temperature SPS-compacts.

• 식품과학과 산업
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• 제51권2호
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• pp.114-126
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• 2018

The production of high quality oil to meet new standard needs a 'next generation' innovative oil refining tool in paradigm shift. 'Nanoneutralization' using controlled hydrodynamic cavitation-assisted Nanoreactor is successfully being introduced and commercialized into edible oil industry and it plays a key driver for sustainable development of food processing. This emerging technology using bubble dynamics as a consequence of Bernoulli's principle by hydrodynamic cavitation in Venturi-designed multi-flow through cell is radically changing the conventionally chemical-oriented neutralization. Nanoneutralization derived by the creation of nanometer-sized bubbles formed through scientifically structured geometric channels under high pressure has been proven to improve mass transfer and reaction rate so substantially reduce the chemicals required for refined vegetable oil and to increase oil yield while even improving oil quality. More researches on science behind this revolutionary technology will help usto better understand the principle and process hence makes its potential applications expandable in extraction, refining and modification of fats and oils processing.

• 소성∙가공
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• 제31권3호
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• pp.143-150
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• 2022

The purpose of this study was to investigate an innovative hydroforming process for the cost-effective manufacturing of double layered tube with circumferentially corrugated patterns. Conventional double pipe heat exchanger has relatively poor heat transfer efficiency because of the limited contact area resulting from the concentrically arranged simple cylindrical structure. As a promising alternative to enhance heat transfer efficiency, double layered tube with corrugated internal pattern was considered in this study. To fabricate corrugated inner tube, innovative tube hydroforming system was developed. The customized loading paths were established using the simulated forming pressure and contracting stroke at various bar diameters. Experimentally obtained cross-sectional profiles were analyzed to evaluate the reliability and applicability of the hydroformed tube with various patterns. The results demonstrate that the proposed hydroforming process can be a feasible alternative for manufacturing high-performance double-tube heat exchangers.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 추계학술대회 논문집
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• pp.394-397
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• 2008

In this research, the fine-structure TiO2+Ti bulks have been fabricated by the combined application of magnetic pulsed compaction (MPC) and subsequent sintering, and their densification behavior was investigated. The obtained density of $TiO_2$+Ti bulk prepared by the combined processes was increased with increasing MPC pressure from 0.7 to 1.7 GPa. Relatively higher density (88%) in the MPCed specimen at 0.7Gpa was attributed to the decreasing of the inter-particle distance of pre-compacted component. High pressure and rapid compaction by Magnetic Pulsed Compaction could reduce shrinkage rate (about 10%) of the sintered bulks compared to that of general processing (about 20%). Mixing conditions of PVA, water, Ti and $TiO_2$ nano powder for compaction of $TiO_2$ nano powder did not affect on density and shrinkage of the sintered bulks due to high pressure of MPC.

• 소성∙가공
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• 제18권8호
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• pp.633-639
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• 2009

Remarkable progress had been made in both technology and production of optical elements including aspheric lens. In the past, precision optical glass lenses were produced through multiple processes such as grinding and polishing, but mass production of aspheric lenses requiring high accuracy and having complex profile was rather difficult. Against such a background, the high-precision optical GMP process was developed with an eye on mass production of precision optical glass pasts by molding press. This GMP process can produce with precision and good repeatability special form lenses such as for cameras, video cameras, aspheric lenses for optical items. In this study, Design Of Experiment(Taguchi method) was adopted to find a tendency of molding conditions that influence formability. Three main factors for molding conditions were selected based on pressure at pressing stage and temperature, pressure at cooling stage. Also, the DOE was carried out and the interference patterns were measured to evaluate the formability of GMP process. From the results, it was found that the cooling pressure is the most sensitive parameter for progressive GMP process.

• 한국재료학회지
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• 제18권8호
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• pp.411-416
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• 2008

In this research, fine-structure TiO2 bulks were fabricated in a combined application of magnetic pulsed compaction (MPC) and subsequent sintering and their densification behavior was investigated. The obtained density of $TiO_2$ bulk prepared via the combined processes increased as the MPC pressure increased from 0.3 to 0.7 GPa. Relatively higher density (88%) in the MPCed specimen at 0.7 GPa was attributed to the decrease of the inter-particle distance of the pre-compacted component. High pressure and rapid compaction using magnetic pulsed compaction reduced the shrinkage rate (about 10% in this case) of the sintered bulks compared to general processing (about 20%). The mixing conditions of PVA, water, and $TiO_2$ nano powder for the compaction of $TiO_2$ nano powder did not affect the density and shrinkage of the sintered bulks due to the high pressure of the MPC.

• 한국재료학회지
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• 제12권5호
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• pp.363-368
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• 2002

we proposed the use of $Si_2H_ 6/H_2$ chemistry for selective silicon epitaxy growth by low-pressure chemical vapor deposition(LPCVD) in the temperature range $600~710^{\circ}C$ under an ultraclean environment. As a result of ultraclean processing, an incubation period of Si deposition only on $SiO_2$ was found, and low temperature epitaxy selective deposition on Si was achieved without addition of HCI. Total gas flow rate and deposition pressure were 16.6sccm and 3.5mtorr, respectively. In this condition, we selectively obtained high-quality epitaxial Si layers of the 350~1050$\AA$ thickness. In older to extend the selectivity, we kept high pressure $H_2$ environment without $Si_2H_6$ gas for few minutes after first incubation period and then we conformed the existence of second incubation period.

• 비파괴검사학회지
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• 제20권6호
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• pp.562-567
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• 2000

발전 및 산업설비에 사용되는 많은 압력용기는 저합금강을 사용하여 제작되고 있다. 압력용기의 내면은 부식이 미치는 영향을 최소화하기 위하여 오스테나이트계 스테인리스강으로 덧살용접을 하고 있으나, 용접층간의 계면에서 발생하고 있는 박리균열은 압력용기의 신뢰성에 중요한 변수가 되고 있다. 본 연구에서는 DSP를 사용하여 오버레이 용접부를 고속으로 검사할 수 있는 C-scan 시스템을 개발하였다. 본 시스템은 신호 처리부 (오실로스코프, 펄서/리시버, 디지타이저, DSP), 스캐너, 프로그램 및 위치 제어부로 구성되어 있다. 개발된 시스템을 사용하여 실제 오버레이 용접부에 대한 초음파검사를 실시한 결과 고속으로 신뢰성 높은 검사결과를 얻을 수 있었다.

• 한국수소및신에너지학회논문집
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• 제29권2호
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• pp.219-225
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• 2018

This study was carried out to investigate the injection characteristics of 800 kPa compressed natural gas compressed natural gas (CNG) injector developed in Korea. The CNG injector with multi-holes, employed in this experiment, was designed to inject CNG in the manifold at high pressure of 800 kPa. The spray macroscopic visualization test was carried out via Schlieren photography to study fuel-air mixing process. The fundamental spray characteristics, such as spray penetration, spray cone angle and spray velocity, were evaluated in the constant volume combustion chamber (CVCC) with varying the constant back pressure in CVCC from 0 to 1.8 bar. For the safety reason, nitrogen ($N_2$) and an acetone tracer were utilized as a surrogate gas fuel instead of CNG. The surrogate gas fuel pressures were controlled at 3, 5.5, and 8 bar, respectively. Injection durations were set at 5 ms throughout the experiment. The simulating events of the low engine speed were arranged at 1,000 rpm. The spray images were recorded by using a high-speed camera with a frame rate of 10,000 f/s at $512{\times}256pixels$. The spray characteristics were analyzed by using the image processing (Matlab). The results showed the significant difference that higher injection pressure had more effect on the spray shape than the lower injection pressure. When the injection pressure was increased, the longer spray penetration occurred. Moreover, the linear relation between speed and time are dependent on the injection pressure as well.

• 소성∙가공
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• 제16권8호
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• pp.582-589
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• 2007

This paper is related to an analysis on the surface expansion in backward can extrusion process using spherical punches. It is generally known that the backward can extrusion process usually experiences severe normal pressure and heavy surface expansion. This is a reason why the backward can extrusion process is one of most difficult operations among many forging processes. Different punch nose radii have been applied to the simulation to investigate the effect of punch nose radius on the surface expansion, which is a major effort in this study. AA 2024 aluminum alloy is selected as a model material for investigation. Different frictional conditions have also been selected as a process parameter. The pressure applied on the punch has been also investigated since heavy surface expansion as well as high normal pressure on the tool usually leads to severe tribological conditions along the interface between material and tool. The simulation results are summarized in terms of surface expansion at different reduction in height, deformation patterns including strain distributions and maximum pressure exerted on the workpiece and punch, the effect of punch nose radius and the frictional condition on the surface expansion and the location and magnitude of maximum pressure exerted, respectively.