• Tribology and Lubricants
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• 제34권6호
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• pp.209-216
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• 2018

Sapphire is a substrate material that is widely used in optical and electronic devices. However, the processing of sapphire into a substrate takes a long time owing to its high hardness and chemical inertness. In order to process the sapphire ingot into a substrate, ingot growth, multiwire sawing, lapping, and polishing are required. The lap grinding process using pellets is known as one of the ways to improve the efficiency of sapphire substrate processing. The lap grinding process ensures high processing efficiency while utilizing two-body abrasion, unlike the lapping process which utilizes three-body abrasion by particles. However, the lap grinding process has a high material removal rate (MRR), while its weakness is in obtaining the required surface roughness for the final polishing process. In this study, we examine the effects of free abrasives in lap grinding on the material removal characteristics of sapphire substrate. Before conducting the lap grinding experiments, it was confirmed that the addition of free abrasives changed the friction force through the pin-on-disk wear test. The MRR and roughness reduction rate are experimentally studied to verify the effects of free abrasive concentration on deionized water. The addition of free abrasives (colloidal silica) in the lap grinding process can improve surface roughness by three-body abrasion along with two-body abrasion by diamond grits.

• Korea-Australia Rheology Journal
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• 제21권2호
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• pp.83-89
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• 2009

Coating process plays an important role in information technology such as display, battery, chip manufacturing and so on. However, due to complexity of coating material and fast deformation of the coating flow, the process is hard to control and it is difficult to maintain the desired quality of the products. Moreover, it is hard to measure the coating process because of severe processing conditions such as high drying temperature, high deformation coating flow, and sensitivity to the processing variables etc. In this article, the coating process is to be re-illuminated from the rheological perspectives. The practical approach to analyze and quantify the coating process is discussed with respect to coating materials, coating flow and drying process. The ideas on the rheology control of coating materials, pressure and wet thickness control in patch coating process, and stress measurement during drying process will be discussed.

• 한국인지과학회:학술대회논문집
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• 한국인지과학회 2010년도 춘계학술대회
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• pp.42-47
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• 2010

Speech shares acoustic features with other sound-based processing, which makes it difficult to distinguish phonological process from acoustic process in speech processing. In this study, we examined the difference between acoustic process and phonological process during repetition tasks. By contrasting various stimuli in different lengths, we localized neural correlates of acoustic process within bilateral superior temporal gyrus, which was consistent with the previous studies. The activated patterns were widely overlapped between words and pseudowords, i.e., contents-free. In contrast, phonological process showed left-lateralized activation in middle temporal gyrus located at anterior temporal areas. It implies that phonological process is contents-specific as shown in our previous study, and at the same time, more language-specific. Thus, we suggest that phonological process is distinguished from acoustic process in that it is always accompanied with the obligatory access to available phonological codes, which can be an entry of the mental lexicon.

• 대한전자공학회논문지
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• 제27권4호
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• pp.571-579
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• 1990

A dynamic relocation algorithm for non-deterministic process graph in distributed computer systems is proposed. A method is represented for determining the optimal policy for processing a process tree. A general database query request is modelled by a process tree which represent a set of subprocesses together with their precedence relationship. The process allocation model is based on operating cost which is a function fo selection of site for processing operation, data reduction function and file size. By using expected values of parameters for non-deterministic process tree, the process graph and optimal policy that yield minimum operating cost are determined. As process is relocated according to threshold value and new information of parameters after the execution of low level process for non-deterministic process graph, the assigned state that approximate to optiaml solution is obtained. The proposed algorihtm is heuristic By performing algorithm for sample problems, it is shown that the proposed algorithm is good in obtaining optimal solution.

• 한국분말재료학회지
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• 제21권2호
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• pp.142-146
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• 2014

Fundamental experiences have been studied for development of pre-treatment process of Sn by-products such as solders. Dry and wet separation/recovery processes were considered by the differences of physical properties. The by-products, which are analyzed by solder metal and oxides. The metal and oxide were simply separated by dry ball-milling process for 12 hours, after that recovery metal powder might be reusable as lead or lead-free solders. In terms of wet separation process, samples were dissolved in $HNO_3+H_2O_2$ and the precipitation were analyzed by $SnO_2$. Overall efficiency of recovery might be increasing via developing simple pre-treatment process.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.1085-1088
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• 2001

The process of styrofoam pattern that has been used for material of press die pattern depends chiefly on handwork. Laser manufacturing system developed to increase precision and efficiency of process that is also able to convert the design easily. Applying the RP(rapid prototyping) concept reversely, the unnecessary part of section is vapored away by heat source of laser beam after converting 3-D CAD model into cross-sectional shape information. Laser beam is line-scanned in plane specimens to measure the depth and width of cut, surface roughness, cross-sectional shape as converting laser power, scanning speed, cutting gas pressure. With these basic data, plane surface, inclined surface, hole, outer contour trimming process is experimented and optimum condition are obtained. In plane and inclined surface experiments, 15W laser power and 50mm/s scanning speed make superior processing property and 30W, 10mm/s make processing efficiency increase in trimming process. With these results, simple patterns were manufactured and the possibility of applying laser manufacturing system to styrofoam pattern was convinced.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.569-572
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• 2003

In VLM-ST process, the fine detailed shape processing process is needed due to the use of thick sheets for layers. The developed process perform the fine detailed shape processing in VLM-ST parts using non-contact hot tool. To predict the heat-affected zone and temperature distribution of VLM-ST parts in detailed shaping, the heat flux from the tool to the surface was calculated for the finite element analysis by modeling the tool as a heat source of radiation. The dominant process parameters such as the radiated heat input, the tool speed, and the gap between the tool tip and the foam sheet (tool height) were considered in the analysis. The results showed a good agreement with the experiments.

• 한국표면공학회지
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• 제29권6호
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• pp.760-765
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• 1996

Silicon oxide thin films are prepared by plasma-enhanced CVD (PECVD) using 100kHz and 13.56MHz generators. Source gases are two sorts of mixture, tetramethoxysilane (TMOS) and oxygen, and tetramethylsilane (TMS) and oxygen. We investigate the effect of frequency on film properties of deposited films including mechanical properties. 100kHz PECVD process can deposit silicon oxide films at $23^{\circ}C$ at the power of 20W. X-ray photoelectron spectroscopy (XPS), infrared spectroscopy (IR) and ellipsometric measurements reveal that the structural quality of the films prepared both by 100kHz process and by 13.56MHz process are very like silicon dioxide. The 100kHz process is adequate for low temperature deposition of SiOx films.

• 한국전기전자재료학회논문지
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• 제28권12호
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• pp.771-775
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• 2015

In this paper, we designed and fabricated low cost imprinting process for micro patterning on FCCL (flexible copper clad laminate). Compared to conventional imprinting process, developed fabrication method processing imprint and UV photolithography step simultaneously and it does not require resin etch process and it can also reduce the fabrication cost and processing time. Based on proposed method, patterns with $10{\mu}m$ linewidth are fabricated on $180mm{\times}180mm$ FCCL. Compared to conventional methods using LDI (laser direct imaging) equipment that showed minimum line with $10{\sim}20{\mu}m$, proposed method shows comparable pattern resolution with very competitive price and shorter processing time. In terms of mass production, it can be applied to fabrication of large-area low cost applications including FPCB.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.826-827
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• 2006

Copper infiltration is demonstrated as a viable solution to achieve higher mechanical properties by filling the interconnected porosities of a ferrous structure with copper infiltrant. This paper will present the results of a design of experiments study based on the selected processing variables in the copper infiltration process. The variables are the following: Infiltrating temperatures, infiltrating time at pre-heat zone and hot zone, the green density of iron part, the migration of copper into the iron part at different processing conditions. The results show the flexibility of the infiltration process to attain certain mechanical properties by changing the processing conditions.