• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2000.11a
• /
• pp.771-776
• /
• 2000

Major noise source in high speed rotating CD-Rom drives arises due to the high-speed airflow produced from the upper and lower surfaces on the rotating disk. The present paper deals with the experimental approach how to identify the noise source based on the fundamental principles of aeroacoustics and to propose a reduction method of the noise source. Experimental studies were carried out in the anechoic wind tunnel with various design modifications, such as tray geometry and window size, to identify and reduce the major aerodynamic noise source and significant reductions of the noise source were obtained.

• Korean Journal of Materials Research
• /
• v.27 no.10
• /
• pp.530-533
• /
• 2017

ZnO micro/nanocrystals with different morphologies were synthesized by thermal evaporation of various zinc source materials in an air atmosphere. Zinc acetate, zinc carbonate and zinc iodide were used as the source materials. No catalysts or substrates were used in the synthesis of the ZnO crystals. The scanning electron microscope(SEM) image showed that the morphology of ZnO crystals was strongly dependent on the source materials, which suggests that source material is one of the key factors in controlling the morphology of the obtained ZnO crystals. Tetrapods, nanogranular shaped crystals, spherical particles and crayon-shaped crystals were obtained using different source materials. The X-ray diffraction(XRD) pattern revealed that the all the ZnO crystals had hexagonal wurtzite crystalline structures. An ultraviolet emission was observed in the cathodoluminescence spectrum of the ZnO crystals prepared via thermal evaporation of Zn powder. However, a strong green emission centered at around 500 nm was observed in the cathodoluminescence spectra of the ZnO crystals prepared using zinc salts as the source materials.

• Journal of Korean Society for Atmospheric Environment
• /
• v.19 no.4
• /
• pp.387-396
• /
• 2003

A field study was conducted during the summer time of 2002 to determine compositions of volatile organic compounds (VOCs) emitted from vehicles and to develop source emission profiles that is applied to CMB model to estimate the source contribution of certain area. Source emission profile is widely used for the estimation of source contribution by the chemical mass balance model and have to be developed applicable for the target area of estimation. This study was aimed to develop source emission profile and estimation of source contribution of VOCs after application of the chemical mass balance (CMB) receptor model. After considering the emission inventory and other research results for the VOCs in Seoul, Korea, the sources like vehicle emission (tunnel), gas station (gasoline, diesel), solvent usage (painting operation, dry cleaning, graphic art), and gas fuels were selected for the major VOCs sources. Furthermore, ambient air samples were simultaneously collected from 09:00 to 11:00 for four days at eight different official air quality monitoring sites as receptors in Seoul during summer of 2001. Source samples were collected by canisters, and then about seventy volatile organic compounds were analyzed by gas chromatography with flame ionization detector (GC/FID). Based on both the developed source profiles and the database of the receptors, CMB model was intensively applied to estimate mass contribution of VOCs sources. Examining the source profile from the vehicle, the portion of alkanes of VOCs was highest, and then the portion of aromatics such toluene, m/p-xylene were followed. In case of gas fuel. they have their own components; the content of butane, propane, ethane was higher than any other component according to the fuel usage. The average of the source apportionment on VOCs for 8 sites showed that the major sources were vehicle emission and gas fuels. The vehicle emission source was revealed as having the highest contribution with an average of 49.6%, and followed by solvent with 21.3%, gas fuel with 16.1%, gasoline with 13.1%.

• Journal of Environmental Science International
• /
• v.14 no.6
• /
• pp.543-553
• /
• 2005

In recent days, photochemical smog due to the rapid industry development and vehicle increasement has become a critical pollutant in the metropolitan area and the number of ozone alarm signal has increased every year. This research was performed to evaluate VOCs emission source characteristics and concentration of VOCs in Daegu. The site average concentration was observed in the following order: industrial area > commercial area > residential area. Most of the VOCs species except toluene showed variations with higher concentration during nighttime, and lower concentration during the daytime. The major VOCs of stationary emission source were BTEX(benzene, toluene, ethylbenzene. xylene) and methylene chloride, trichloroethene and styrene. Also, those of automobile exhaust were toluene and benzene. Also, the major VOCs concentration emited by the vehicle fuel was observed in the following order: gasoline > light oil > liquefied petroleum gas (L.P.G). Correlation coefficients values were estimated between major VOCs such as toluene, ethylbenzene, m,p-xylene, o-xylene. Results showed that correlation coefficient values were significant magnitude above 0.76. Also, there showed highly significant correlations among ethyl benzene, m,p-xylene, and o-xylene concentration(Pearson correlation coefficients, r=0.868-0.982). Calculated correlation coefficients among commercial area,industrial area and residential area were 0.934-0.981, they showed high correlation. There showed highly correlation between stationary emission source and industrial area, compared with commercial area and residential area. Also, calculated correlation coefficients among commercial area, industrial area, residential area and automobile exhaust were 0.732, 0.725, 0.777, respectively.

• The Research Journal of the Costume Culture
• /
• v.4 no.2
• /
• pp.157-171
• /
• 1996

The purpose of this study was to find out the effect of fashion information source in the stage of purchase decision-making and difference by stage of purchase decision-making and difference by stage of the effect extend, and to analyze the difference by fashion information source. For this study, the data were collected through the questionnaire distributed to 337 female students from five universities. The results are as follows: 1) There was significant difference among the effect to fashion information source according to the purchase decision-making stage. At the adoption stage, fashion information source have the most effect on clothing purchase. 2) The effect of Impersonal Source in the purchase decision-making stage was gradually decreased fro the initial (awareness, interest) sage to the late stage. 3) The effect of Personal Source in the purchase decision-making stage was gradually increased from the initial (awareness, interest) stage to the late stage. 4) Addition stage was highly influenced by friend and family that was Personal Independent Source than other fashion information source. However the final selection on clothing purchase was not influenced by friend and family. 5. There was significant difference among the effect of fashion information source according to the grade. Low garde students were highly influenced by Personal Source on clothing purchase, but high grade students were highly influenced by Impersonal Sources on clothing purchase. 6) There was significant difference among the effect of fashion information source according to the major. The students a majored clothing & textile-design were highly influenced by Impersional Source. These results suggest that fashion information source was significantly different according to purchase decision-making stage and was influenced by grade and major of subjects.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.23 no.4
• /
• pp.380-384
• /
• 2014

This study focused on identifying the major noise source in a tractor cabin using experimental methods. The noise levels in a tractor cabin for different engine revolution speeds were analyzed to identify the noise source. The results showed that the power steering unit (PSU) was the major noise source in a tractor cabin. The PSU was moved to the outside from the inside of the cabin in order to reduce the noise in the tractor cabin. As a result, the noise levels on the left and right sides of the operator in the tractor cabin were reduced by 6.8 and 3.9 dB, respectively. Finally, the window method was introduced to evaluate the contribution of the transmission noise. The orders of significance in the tractor noise were the front, bottom, and left area, successively.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.24 no.5
• /
• pp.687-693
• /
• 2000

Recently, a scroll compressor is widely used, because a scroll compressor features low noise, due to less pulsation of gas pressure, than that of the rotary compressor. The major source of noise in air-conditioner is a compressor. Therefore, noise reduction in a compressor is quite significant as an element technology in air-conditioner field. For a reduction of noise, the source of noise must be identified. This paper presents detailed analyzes for the major noise source (fluid-borne noise and structure-borne noise) causes in a scroll compressor, which will make possible a low noise and vibration design of a scroll compressor.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.17 no.6 s.123
• /
• pp.477-483
• /
• 2007

Major noise source in high speed rotating optical disk drives (CD and DVD-ROM) arises due to the high-speed airflow produced from the upper and lower surfaces on the rotating disk. The present paper deals with the experimental approach how to identify the noise source based on the fundamental principles of aeroacoustics and to propose a reduction method of the noise source. The CD-ROM device is composed of disk, window tray, motors at the bottom place and electronic circuit plate also located below the window plate. The window is cut in the tray to read the disk information using the optical device located below the tray and moving linearly from the center of the disk through the end of the disk. All components are possible noise generators. Experimental studies were carried out in the anechoic room with various design modifications, such as tray geometry, window size and hole location on tray, to identify the major aerodynamic noise source and significant reductions of the aerodynamic noise were obtained.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2001.05a
• /
• pp.27-33
• /
• 2001

Linear harmonic analysis is a convenient and generally accurate method to use for the acoustic analysis of intake and exhaust silencers for IC engines. The major uncertainty in this form of modelling is the characterisation of the source, which is inherently nonlinear and time-variant. Experimental methods are generally used to determine the source characteristics, and in particular the indirect method is most suitable for an IC-engine source. With reference to an idealised linear time-variant source, it is found that the characteristics of a time-variant source as determined by the indirect method have no physical relevance. The direct method of experimental measurement appears to have some advantage over the indirect method, although in practice it is difficult to apply to an IC engine source. Again, an idealised linear time-variant source can be used to indicate that the characteristics of a time-variant source as determined by the direct method also have no physical relevance. Strangely, these meaningless measured source properties can nevertheless be used to accurately predict the radiated noise from an IC engine and silencer system.

• Journal of Nutrition and Health
• /
• v.30 no.1
• /
• pp.91-99
• /
• 1997

We have studied the major food sources of minerals and vitamin based on the data from the National Nutrition Survey in 1993. The most important food sources was anchovy for calcium, spinach for vitamin A, and kimchi for vitamin C. The primary source of iron, thiamin, riboflavin and niacin was rice. Number of foods providing 90% of individual nutrient intake were 54 items for calcium, 40 items for iron, 20 items for vitamin A, 25 items for thiamin, 29 items for riboflavin, 39 items for niacin and 18 items for vitamin C. Among regions, amount of nutrients from same foods(10 more important food source) didn't show any significant differences (p>0.05) in minerals and vitamins studied. Over all rice was found to be the most important sources of minerals and vitamins.