• KSTLE International Journal
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• 제2권2호
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• pp.114-119
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• 2001

The distribution of magnetic flux density of electro-magnetic chucks may clarify the clamping characteristics, which is strongly related to the machining efficiency and machining accuracy in surface grinding machine. Therefore the distribution of the normal and the tangential components of magnetic flux density have been analyzed theoretically. It appears that the normal component of magnetic flux density increases and the tangential component of magnetic flux density increases as the ratio of the separator width to the pitch, e/p decreases. The results seem to increase the stability and uniformity of normal component of magnetic flux density for the decreased e/p.

• 한국대기환경학회지
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• 제9권3호
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• pp.191-199
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• 1993

This paper describes the results of a systematic study to determine the characteristics of particle generated from various types of asbestos containing material(ACM) and manmade fiber material(MMFM) during operations of cutting and grinding in laboratory and workplace. Tests were conducted with a specially designed glove box which allowed complete sampling of the generated asbestos fibers. Specificially, air measurements were made during ACM and MMFM installation in building. All personal air samples collected were identified by polarized light microscopy(PLM), X-ray diffraction(XRD) and scanning electron microscope with energy dispersive X-ray analysis(SEM/EDXA). Also, the samples were counted by phase contrast microscope(PCM) in order to compare the results with the permissible exposure standard for workplace. Results indicate that the characterisitcs of fibers found in the roofing sheet, the ceiling and the wall insulation boards were identical to those of asbestos, while the characteristics of fibers found in the ceiling insulation board, the floor tile and the sprayed on insulation products in parking area were identical to those of asbestos, while the characteristics of fibers found in the ceiling insulation board, the floor tile and the sprayed on insulation products in parking area were identical to those of rock wool. The concentrations of airborne fibers from various building materials cut by a grinder for 5 minutes were in the ranges of 0.09 $\sim$ 1.71 fibers/cc(f/cc). The highest concentration(1.71f/cc) was found during grinding the wall insulation board which also contains rock wool. The airborne fiber concentrations generated by installing at workplace were ranged from 0.0009 to 0.029 f/cc. All asbestos fibers from the ceiling insulation board at workplace were less than 20$\mu$m in length and more than 20% of them had the average aspect ratio greater than 20. Therefore, for the purpose of decreasing asbestos and man-made fiber concentrations at the workplace, the ceiling and wall board should use strong binding material to increase the binding force with fiber. Also, the permissible exposure standard for workplace(2.0f/cc) in Korea should be constituted below the maximum avaiable concentration measured at glove box.

• 대한안전경영과학회지
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• 제14권1호
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• pp.201-208
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• 2012

Recently the market of the food waste disposer has increased. Therefore, many companies in the development of food garbage disposer has been increasing interest. In this study, we used QFD (Quality Function Development) to find out the quality factors for the development of the food waste disposer reflecting the consumer needs. HOQ (House Of Quality) showing the correlation between consumer characteristic and engineering characteristic was written by investigating the consumer needs based on the consumer complaints and survey. In addition, we generated the CTQ (Critical To Quality) reflecting the weighting of the importance of the parts. As the research result, the important quality factors for the food garbage disposer were the grinding capability, drying, and odor emission features. The crushing motor associated with grinding and dehydration appeared as the most important quality factors among the parts. Second thing was the fan motor associated with odor. The findings will be able to contribute to the development of the food waste disposer reflecting the consumer needs.

• 한국기계가공학회지
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• 제12권5호
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• pp.157-162
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• 2013

To analyze the dynamic acceleration characteristics, it is necessary to identify the acceleration model using some methods that can represent the dynamic properties well. In this sense, fractal methods were used for the verification of characteristics of an acceleration signal. To estimate and analyze the geometry of acceleration signal, a fractal interpolation and its analysis was introduced in this paper. The chaotic nature of acceleration signal was considered in fractal modeling. In this study the fractal signal modeling has brought a focus within the scope of the fractal interpolation and fractal dimension. And a new idea of fractal dimension has been introduced and discussed considering the damping ratio and amplitude for its dynamic properties of the signal. The fractal dimension of acceleration with respect to the scaling factor using fixed data points of 1000 points was calculated and discussed. The acceleration behaviors of this results show some different characteristics. And this fractal analysis can be applied to other signal analysis of several machining such as pendulum type grinding and milling which has many dynamic properties in the signal.

• 한국식품영양과학회지
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• 제46권6호
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• pp.730-738
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• 2017

본 연구에서는 커피 분쇄입도 조건에 따라 변화되는 커피의 이화학적 품질특성 및 휘발성 향기성분 변화에 미치는 영향을 조사하기 위하여 분쇄된 원두는 표준체(pore size 850, 600 및 $425{\mu}m$)를 사용하여 입자 크기를 whole bean(Control), $850{\mu}m$ 이상(coarse), $850{\sim}600{\mu}m$(medium), $600{\sim}425{\mu}m$(fine), $425{\mu}m$ 이하(very fine)의 크기가 되도록 사별하여 커피 추출 시료를 제조하였다. 품질특성으로는 pH, 산도, 갈색도, 색도, 총페놀, 카페인, 클로로겐산 함량 및 휘발성 화합물을 비교 분석하였다. pH 및 갈색도는 분쇄입도가 작아질수록 4.84~5.18, 0.257~0.284로 증가하였으나, 산도는 0.31~0.17로 감소하였다. 색도에서 L, a 값은 분쇄입도가 작아질수록 감소하였으나 L 값에서 분쇄입도별 유의적인 차이는 나타나지 않았으며 b 값은 분쇄입도가 제일 작은 very fine size($425{\mu}m$ 이하)에서 15.75로 가장 높은 황색도를 나타내었다. 색차에서 Control과 분쇄 커피분말과의 차이는 11 이상의 색차값을 나타내어 현저한 색의 차이 단계를 나타내었다. 총페놀, 카페인 및 클로로겐산 함량은 분쇄입도가 제일 작은 very fine size 입도($425{\mu}m$ 이하)에서 추출한 커피가 4.54 mg GAE/mL, 733.0 및 $383.7{\mu}g/mL$로 높은 함량을 나타내었고, 휘발성 화합물의 총함량도 100 mg/kg 이상 높게 검출되었다. 따라서 본 연구에서는 커피 추출의 기본 단계라고 할 수 있는 커피 분쇄입도 조건에 따라 변화되는 커피의 이화학적 품질특성을 상호 비교하고 향기성분 특성을 확인함으로써 커피 품질 평가에 관한 기초자료를 제시하였다고 생각된다.

• 펄프종이기술
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• 제44권4호
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• pp.16-24
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• 2012

To characterize the coating structure, diverse methods such as mercury intrusion, nitrogen adsorption and oil absorption methods have been developed and widely employed. These indirect techniques, however, have some limitation to explain the actual coating structure. Recently microscopic observation methods have been tried for analyzing structural characteristics of coating layers. Preparation of the undamaged cross section of a coating layer is essential for obtaining high quality image for analysis. In this study, distortion-free cross-section of the coating layer was prepared using a grinding and polishing technique. The coated paper was embedded in epoxy resin and cured. After curing the resin block it was ground with abrasive papers and then polished with diamond particle suspension and nylon cloth. Polished coating layer was sufficient enough to obtain undamaged cross sectional images with scanning electron microscope under backscattered electron image mode. In addition, the SEM images allowed distinction of the coating layer components. Also S/B latex film formed between pigment particles was visualized by osmium tetroxide staining. Pore size distribution and pore orientation were evaluated by image analysis from SEM cross-sectional images.

• Journal of the Korean Wood Science and Technology
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• 제44권2호
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• pp.166-171
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• 2016

Size reduction is one of the major pre-processing operations in using biomass as a source of energy or raw materials for forest products industry. The grinding characteristics of dried yellow poplar wood chips were investigated using laboratory knife mill with three different screen aperture diameters to provide the basic information for the optimizing of size reduction processes in biomass industry. Average specific energy consumptions were 0.157, 0.137, and 0.093 Wh/g for the screen aperture diameters of 5.0, 7.5, and 9.0 mm, respectively. According to the results of size distribution analysis of ground particles, the sizes of the most of ground particles were much smaller than the aperture diameters of the screens installed on knife mill used in this study.

• KSTLE International Journal
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• 제4권2호
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• pp.66-72
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• 2003

This paper presents the hydrodynamic effect by the journal speed, eccentricity and source positions in order to overcome the defects of air bearing such as low stiffness and damping coefficient. Choosing the two row source position of air bearing is different from existing investigations in the side of pressure distribution of air film because of the high speed of journal and the wedge effects by the eccentricity. These optimal choices of the two row source positions enable us to improve the performance of the film reaction force and loading force as making the high-speed spindle. In this paper, The pressure behavior in theory of air film in high speed region of journal according to the eccentricity of journal and the source positions analyzed. The theoretical analysis has been identified by experiments. The results of investigated characteristics may be applied to precision devices like ultra-precision grinding machine and ultra high-speed milling.

• 한국안전학회지
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• 제25권6호
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• pp.161-168
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• 2010

A series of fatigue tests have been performed on the non-load carrying fillet welded joints in order to quantitatively assess the fatigue characteristics due to the grindings and TIG(Tungsten Inert Gas) welding treatments. From the results of fatigue tests, it has been shown that the fatigue strengths at $2{\times}106$ load cycles were improved in the case of the grinding sand TIG welding treatments, and we could know that it is satisfying fatigue strength prescribed in fatigue design standard in general. Besides, from the results of fracture mechanics approaches, the geometric shape correction factors were the most dominant factors in the initial fatigue crack growth, but as the fatigue crack develops, the finite plate correction factor were became the most dominant factor, and the fatigue life on non-load carrying fillet welded joints could be relatively exactly estimated by using the relations between fatigue crack growth rate and stress intensity factor obtained from finite element analysis and existing proposed formulae.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1992년도 추계학술대회 논문집
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• pp.115-120
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• 1992

Mirror-surface machining is very important machining technology to manufacture optical parts. especially brittle materials. In case of optical plastics, it is produced through both grinding and polishing till now. New machining method which is more efficient and contributed to the protection of the environmental pollution is, therefore, studied. In this , experimental results and an analysis of surface roughness in ultrasonic vibration cutting of optical plastic (CR-39) which is used for optical lens is presented. In results, a comparison of the micro-structure of machined surfaces produced by cutting with ultrasonic vibration and conventional turning is presented by analyzing S.E.M. photograph. Also, wavelength spectrum analysis is performed to investigate the surface-characteristics machined by ultrasonic vibration cutting.