• 한국분무공학회지
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• 제18권3호
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• pp.126-131
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• 2013

This paper describes the effect of ultrasonic frequency(f) on the atomization and deformation characteristics of single water droplet in an acoustic levitation field. To achieve this, the ultrasonic levitator that can control sound pressure and velocity amplitude by changing frequency was installed, and visualization of single water droplet was conducted with high resolution ICCD and CCD camera. At the same time, atomization and deformation characteristics of single water droplet was studied in terms of normalized droplet diameter($d/d_0$), droplet diameter(d) variation and droplet volume(V) variation under different ultrasonic frequency(f) conditions. It was revealed that increase of ultrasonic frequency reduces the droplet diameter. Therefore, it is able to levitate with low sound pressure level. It also induces the wide oscillation range, large diameter and volume variation of water droplet. In conclusion, the increase of ultrasonic frequency(f) can enhance the atomization performance of single water droplet.

• 한국추진공학회지
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• 제7권4호
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• pp.1-9
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• 2003

액체 로켓 시스템에 있어서 주 구조물과 연료 공급 장치의 상호작용 효과에 기인하여 발생하는 POGO라 불리는 축방향 동적 불안정 현상을 억제하기 위하여 몇 가지 종류의 PSD라 불리는 장치가 연구되고 있다. 본 연구에서는 기존에 사용된 PSD의 형태를 살펴보았다. PSD 장치는 수동적 PSD와 능동적 PSD 두 가지 그룹으로 분류할 수 있다. 수동적 PSD는 다시 컴플라이언스의 분포 방식에 따라 집중형과 분산형의 두 가지로 세분할 수 있다 현재까지 개발된 PSD 장치에 대한 포괄적인 검토를 통해, 기체 채움 수위조절 방식의 완충기가 연료 공급 장치의 성능을 저하시키지 않고 POGO 불안정성을 억제할 수 있는 최적의 PSD임을 잠정적으로 제안하였다.

• Toxicological Research
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• 제24권2호
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• pp.113-117
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• 2008

Chronic exposure to ethanol induces cumulative damage to the liver starting from fatty infiltration to cirrhosis depending on the dose and duration of exposure. The whole process leading to the development of alcoholic liver disease is very complex and the mechanisms involved are not fully understood. Among many experimental animal models, Lieber-DeCarli liquid diet provides moderate to severe pathophysiological outcome depending on the compositional changes. In the present study, we investigated the temporal changes in the early phase hepatic disease in rats fed with standard Lieber-DeCarli diet. Male Wistar rats were fed with Lieber-Decarli ethanol diet for 6 weeks and the liver samples were obtained after 2, 4 and 6 weeks. Mild fatty infiltration was observed in 2 weeks of feeding and it became evident in 4 and 6 week samples. The level of hepatic triglyceride showed a good agreement with the data obtained in the pathological analysis. Feeding mice with ethanol diet resulted in the maturation and translocation of SREBP-1 to nucleus in the liver. Western blot analysis of the pooled liver sample of control and ethanol fed animals showed a clear-cut time-dependent increase in the expression of nSREBP-1. These data provide important information for selecting proper time point in experimental intervention study in the field of drug development for alcoholic liver disease.

• 한국건축시공학회지
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• 제10권5호
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• pp.137-143
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• 2010

본 연구는 거푸집에 부착하는 코팅재료에 따른 콘크리트 표면광택도 비교 분석으로서 시멘트모르터로 제작한 시험체의 광택도를 분석하고 유동화제를 혼합한 콘크리트와 혼합하지 않은 콘크리트의 노출콘크리트 표면 광택의 특성을 분석한 것이다. 시멘트모르터를 이용한 코팅재료별 광택도 분석에서 광택도가 가장 높게 나타난 코팅재료는 7번 재료로 액체포장재의 일부이며 2번째는 3번 재료로 투명필름을 이용한 재료이다. 코팅필름의 소재에 따라 광택도가 다르게 나타난 것으로 미루어 소재의 표면입자 상태와 화학적 구성요소의 따라 다른 것으로 판단된다. 콘크리트의 표면상태를 매끄럽게 하기 위해서는 불투수성이며 매우 밀실한 표면을 가진 코팅재료를 사용하는 것이 효과적이다.

• 한국추진공학회지
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• 제12권3호
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• pp.24-33
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• 2008

진공 작동 조건에서 50 Newton 추력 레벨을 가지는 과산화수소 단일추진제 추력기를 개발하였다. 축소형 추력기를 제작하여 제조한 촉매의 추진제 분해 성능을 평가하였다. 축소형 추력기의 성능 평가 결과로부터 50 Newton 추력을 위한 추진제 유량을 완전히 촉매 분해시키기 위해 필요한 반응기를 설계하였다. 스케일 업을 통해 제작된 추력기는 34.8 g/s의 추진제 유량에서 98%의 특성속도 효율을, 대기압 조건에서 42 Newton의 추력, 123 sec의 비추력 결과를 보임으로써 반응기 스케일 업 과정이 적절함을 확인하였다.

• 한국식물병리학회지
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• 제14권5호
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• pp.376-381
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• 1998

Xanthomonas campestris pv. glycines 8ra causes bacterial pustule disease on susceptible soybean leaves and produces a bacteriocin, named glycinecin, against related bacteria such as Xanthomonas campestris pv. vesicatoria. The antimicrobial activity of the glycinecin was effective to most tested Xanthomonas species. X. c. pv. glycines 8ra was able to produce the glycinecin in liquid media as well as solid media. Maximal productivity of glycinecin was obtained at 3$0^{\circ}C$ in the early stationary phase of growth of the X. c. pv. glycines 8ra. The production of glycinecin was not dependent on the initial inoculum level but on cell density. Glycinecin was very sensitive to proteolytic enzymes such as trypsin and proteinase K but resistant to DNase and RNase. The culture supernatant of X. c. pv. glycines 8ra retained some of its antimicrobial activity after 15 min at 6$0^{\circ}C$. It is stable at wide range of pH. The glycinecin showed the bactericidal activity after the adsorption of the glycinecin to the sensitive bacterial cell.

• 식물조직배양학회지
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• 제24권6호
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• pp.341-344
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• 1997

알팔파의 자엽과 하배축을 배양하여 캘러스를 유기하고 이들을 glyphosate첨가 액체배지에서 배양하여 glyphosate에 대한 생장억제 반응을 검사하였으며 10 mM glyphosate에 저항성인 세포주를 선발하고 EPSPS 활성을 조사 하였던 바 캘러스 유기율은 2,4-D 1 mg/L, kinetin 0.5 mg/L에서 가장 높았고 자엽보다 하배축이 캘러스 유기율이 높았으며, glyphosate 농도에 대한 ID$_{50}$은 0.1 mM과 0.2 mM사이에 있었다. A49-10G와 A58-10G는 대조세포주에 비해 각각 8.0배 와 9.1배의 높은 EPSPS 활성을 보였다.

• 한국산업보건학회지
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• 제26권4호
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• pp.396-403
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• 2016

Objectives: The study is to evaluate biological monitoring and risk assessment for epichlorohydrin-bisphenol A resin exposed from waterproofing or finishing work in the apartment building construction. Methods: Subjected workers were working on spray-painting and waterproofing work for 8 hours per day every 20 days. The urine samples were collected at the end of 20 days working period. For urinary bisphenol A as metabolite from epichlorohydrin-bisphenol A exposure, urine samples were analyzed with liquid chromatography mass-mass spectrometry(HPLC-MS/MS). Results: Geometric means of urinary bisphenol A(BPA) with no hydrolysis and with enzymic hydrolysis(BPA-EH) in the workers were $1.10{\mu}g/L$ and $2.90{\mu}g/L$. BPA-EH was 4 times higher than that of control group. The factors for working period and ages did not affect the variation of BPA and BPA-EH. The levels for BPA and BPA-EH were not higher than 95th percentile for exposure on human-life environment. Conclusions: The BPA and BPA-EH were therefore effective biological markers for epichlorohydrin-bisphenol A exposure workers, but not seem to hazardous exposure level. Waterproofing work in construction workshop is required to measuring work environment and health care management for the workers.

• International Journal of Aeronautical and Space Sciences
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• 제14권4호
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• pp.398-407
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• 2013

Optical tomography was used to measure the pattern of spray cross-section. The maximum-likelihood estimation (MLE) algorithm was used to reconstruct the spray cross-section from the measured transmission rate of the spray. A swirl-type injector was used to form an optically dense spray, and the test was carried out in a high-pressure chamber, to control the pressure condition of the test site. Before the experiment, the reliability of the MLE-based reconstruction algorithm was verified, by comparing it with a conventional filtered back projection reconstruction (FBP) method. The MLE algorithm showed superior reconstruction of the image. In the spray patternation experiment, the results of the optical tomography and optical line patternator, which uses Mie scattering signal information, were compared. While measuring the cross-section of optically dense spray, the intensity of the scattering signal had attenuated to an uncorrectable level, which led to incorrect spray pattern measurement by the optical line patternator. However, reliable results were obtained by optical tomography, under the same condition. Finally, the pattern of the optically dense spray was measured at various chamber pressures, of up to 3 MPa. As the chamber pressure increased, the hollow cone-shaped swirl spray shrank, and the attenuation coefficient value of the inner region increased.

• 대한치과보철학회지
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• 제34권4호
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• pp.816-822
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• 1996

The purpose of this study was to determine whether there was any difference in the mean porosity of denture base resin cured by microwave energy, when the liquid monomers of denture resin(K-33 : methyl methacrylate for conventional water bath curing or Acron MC : special monomer for microwave curing) and/or the thicknesses of denture base($5{\times}10{\times}60mm\;or\;10{\times}10{\times}60mm$) were varied. The mean porosities of k-33 specimens cured in water bath with two different thicknesses were used as control. The results were as follows : 1. Regardless of specimen thickness, Acron MC cured by microwave energy showed the least mean porosity, followed by K-33 cured by water bath heat, and K-33 cured by microwave energy showed the highest level of mean porosity(P<0.05). 2. In both K-33 and Acron MC cured by microwave energy the mean porosities of 5mm thickness groups were lower than those of 10mm thickness groups(P<0.05). But no significant difference was found in mean porosity between 5mm thickness and 10mm thickness of water bath heat cured groups made of K-33(P>0.05).