• The Journal of Korean Academy of Prosthodontics
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• v.36 no.1
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• pp.64-80
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• 1998

The risk of cross-contamination in dental clinic is very high. Those who are engaged in dental clinic are exposed to various microorganisms in saliva and blood of patient. Potential possibility of cross-contamination of patient to patient, patient to dentist, dentist to laboratory technician always exist, which is important in the view of public health. It is well known that microorganisms may cause cross-contamination by suck-back of microorganisms into the water supply line or air supply line of dental unit and sprayed back into the next patient's oral cavity. The majority of microorganisms coming from dental unit are water microorganisms from the main water supply which have colonized the tube within the units and multiplied in the relatively warm and stagnant conditions. The purpose of this study is to measure the extent of microbial contamination of dental unit and ultrasonic scaler, to evaluate that dental unit water supply is suitable for drinking water, and to assess the effect of flushing on reduction of microbial contamination of dental unit and ultrasonic scaler. In the first experiment, water samples(50ml) from 20 dental units and 10 ultrasonic scalers in Seoul National Univ. Hosp. were tested for the presence of coliform. The samples were filtered by membrane filtration technique.(Microfil system, Millipore Co. U. S. A.) The filter was then placed onto MacConkey agar plate and the plates with filter on it were incubated aerobically at $37^{\circ}C$ for 5 days. The colors and shapes of colonies were examined if those were coliform. To verify the presence of coliform, the colonies were inoculated into phenol red lactose broth and incubated aerobically at $37^{\circ}C$ for 2 days. The fomation of gas was observed. In the second experiment, water samples from 20 handpieces, 10 ultrasonic scalers and 30 A/W syringes after 0, 2, 4, 6 min. flushing respectively were taken. $200{\mu}l$ water samples were spreaded on Brain Heart Infusion agar plate and the plates were incubated aerobically at $37^{\circ}C$ for 5 days. The number of colony was counted. The results obtained were summarized as follows 1. The water from dental unit and ultrasonic scaler was not suitable for drinking water. 2. No coliform was founded in dental unit and ultrasonic scaler water supply. 3. The number of colony of dental unit and ultrasonic scaler was highest in the group of o min. flushing(p<0.05). 4. There was no statistically significant difference in the extent of microbial contamination among handpiece, ultrasonic scaler and A/W syringe (p>0.05). 5. The number of colony was lowest in the group of 4 min. flushing, but there was no statistically significant difference among 2, 4, 6 min. flushing groups.(p>0.05) 6. It is recommended to flush dental unit water line for 4 min. after use on each patient.

• Journal of Aerospace System Engineering
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• v.16 no.5
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• pp.94-101
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• 2022

In this paper, we have obtained the acceleration coefficient of the IMU (Inertial Measurement Unit) to prove reliability by analyzing the characteristic of the MEMS IMU installed in guided weapon systems for overseas export and the operating environment of the guided weapon system. Additionally, based on designed life testing, we performed life tests on three the IMUs and demonstrated a target lifetime of 12 years.

• Korean Institute of Interior Design Journal
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• v.13 no.5
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• pp.90-97
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• 2004

The purpose of this study is to grasp the spatial characteristic of the unit plan for a Super-High-Rise-Residence. This study is focused on the open air contact sides for a tower type Super-High-Rise-Residence. A tower type Super-High-Rise-Residence which has open air contacts from 1 to 3.5 sides differed in spatial characteristics of the unit plan for other apartment units. The current study analyzed 188 unit plans for the size of 40 pyong or larger in Seoul and the metropolitan areas which have been built since 1990. Open air contact side was classified as under 2 sides, 2 sides, and over 2 sides. The unit plan which belong to each open air contact side was Investigated according to the location of public area, the relationship between livingroom and master bedroom, and a method of entry to the master bedroom. The results of this study are as follow: According to increase open air contact sides is changed the location of public area in unit plan from an typical arrangement to various arrangement. Also the relationship between livingroom and master bedroom becomes loose and in a method of entry to the master bedroom increase an indirect approach through other room.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1998.05a
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• pp.271-277
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• 1998

1. Why Wind Power\ulcorner Advantages of Wind Energy : free cost, non-pollutant, free waste large unit is possible Disadvantages : intermittent of energy density limited sites Unit Capacity of various Power Plant Solar PP : 10 - 500㎾ Wind PP : 200 - 2000 ㎾ Nuclear PP 700 - 1000 MW Installation Cost of Power Plants Nuclear PP : $ 2,500/㎾ Solar PP : $ 6,000/㎾ Wind PP : $ 1.000 /kw.

• Bulletin of the Korean Mathematical Society
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• v.33 no.4
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• pp.497-501
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• 1996

Let B denote the unit ball in $C^n(n \geq 1)$, and $\upsilon$ the 2n-dimensional Lebesgue measure on B normalized so that $\upsilon(B) = 1$, while $\sigma$ is the normalized surface measure on the boundary S of B.

• Korean Chemical Engineering Research
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• v.54 no.6
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• pp.822-829
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• 2016

Our aim was to optimize the production of cellulase-free thermoactive xylanase by Aureobasidium pullulans CBS 135684 with statistical methodology based on experimental designs. Among eleven variables, the nutrient sources that had significant effect on xylanase production were corncob, $(NH_4)_2SO_4$, xylose, $KH_2PO_4$ and tween 80, identified by the initial screening method of Plackett-Burman. The optimum concentrations of these five components were subsequently investigated using response surface methodology. The optimal concentrations ($g{\cdot}l^{-1}$) for maximum production of xylanase were corncob, 39.0; $(NH_4)_2SO_4$, 3.0; xylose, 1.8; $KH_2PO_4$ 1.4; and tween 80, 1.4, respectively. An improved xylanase yield of $8.74{\pm}0.84U{\cdot}ml^{-1}$ was obtained with optimized medium which is 2.1-fold higher production than previously obtained results ($4.10{\pm}0.10U{\cdot}ml^{-1}$) after 48 h of cultivation. In addition, the xylanase production under optimal condition reached $10.09{\pm}0.27U{\cdot}ml^{-1}$ after 72 h of cultivation.

• The Korean Journal of Quaternary Research
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• v.13 no.1
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• pp.79-89
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• 1999

Three deep borings to obtain vertical continuous samples including weathered basement soils (KP-1, KP-2 and KP-3) were carried out in the reclaimed Kimpo tidal flat with purposes to establish late Quaternary stratigraphy. On the basis of detailed observations and descriptions on color, sedimentary structure and textural composition of cored sediments, four lithostratigraphic units are classified. From the stratigraphic top to bottom, they are Holocene tidal sand and muddy deposit (Unit I), early Holocene freshwater marsh muddy deposit (Unit II), late Pleistocene tidal sand and muddy deposit (Unit III) and late Pleistocene basal fluvial gravel deposit (Unit IV). In particular, Unit III is divided into two parts: the upper part-weathered and cryoturbated part during the Last Glacial Maximum (Unit III-a) and the lower part-unweathered tidal sand and muddy deposit (Unit III-b).

• Journal of Environmental Impact Assessment
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• v.19 no.1
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• pp.29-38
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• 2010

At recent the number of livestock is increased and the size of farm has changed to large facilities in Korea. So the livestock facilities have become one of major sources of odor emission. The purpose of this study is to analyze the concentration and assessment of odor unit from livestock facilities for cow, dairy, swine and poultry. The eleven odor pollutants such as $H_2S$, ($CH_3$)SH, $(CH_3)_2S$, $(CH_3)_2S_2$, $CH_3N$, $NH_3$, $(CH_3)_2N$, $(CH_3)_3N$, butyric acid, valeric acid and isovaleric acid, measured for assessment of the odor concentrations from livestock facility. As the results, it is found that the major matters of odor from livestock facilities were $NH_3$ and $H_2S$. The highest concentration of $NH_3$ is measured as 15 ppm at henhouse and $H_2S$ is measured as 858 ppb at penpig facilities. In the comparison of the average odor unit from livestocks, it is found that the highest odor unit was from swine and the lowest odor unit was from cow facility. So odor unit from swine facilities was 12 to 30 times higher than the odor unit from cow facilities.

• Applied Chemistry for Engineering
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• v.2 no.3
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• pp.246-252
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• 1991

Copolyesters (PEHT) of poly (ethylene terephthalate) (PET) and poly (1,4-phenylene terephthalate) (PHT) were synthesized by the solution polymerization with the PHT unit contents of less than 30 mol %, and their physical properties were studied. As the content of PHT unit in PEHT was increased, glass transition temperature, crystallization rate, thermal stability increased, whereas melting temperature decreased. When the PHT unit contents were 16.5 and 24.9 mol%, nematic mesophase was observed. Wide angle X-ray diffraction pattern showed the peaks originated from both PET unit and PHT unit.

• Journal of the Korean housing association
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• v.16 no.1
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• pp.55-63
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• 2005

The purpose of this study is to find a way of solving on parking problems at apartment complex through the trend analysis research of the parking demands according to the housing unit size. The subjects of this study are high-rise apartment complexes in Daegu city which are constructed within 10 years. The parking demand according to the housing unit size at apartment complexes had been surveyed every July for 4 years from 2000 to 2003. Specially, we knew that the parking demand of $85 m^2$ below sized housing unit at apartment complex was exceeded architectural regulation of parking supply, and the parking demand of $85 m^2$ over sized housing unit at apartment complex was kept within architectural regulation of parking supply. And, the estimating formula that can predict the future parking demand by the trend analysis according to the housing unit size at apartment complexes in Daegu city was gotten through this study. But, in order to get more accurate estimating formula, it should be based on data of funker research and investigation about apartment complexes and it should be studied continuously.