• 대한지하수환경학회지
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• 제1권1호
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• pp.6-9
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• 1994

지하수의 Ar/$N_2$가스의 비율은 탈질화(denitrification)의 정도를 측정하는 하나의 방법으로 사용된다. (Barnes et al., 1975; Vogel et al., 1981; Mariotti et al., 1988) 그 비율 측정은 일반적으로 질량분석기 (Mass Spectrometer)를 사용한다. 본 실험에서 사용한 Mass Spectrometer는 일반적인 Static Mass Spectrometer가 아닌 Ar과 $N_2$을 시간적으로 동시에 측정하여 오차를 줄일 수 있는 VG Optima isotope ratio Mass Spectrometer를 사용하였다. 두 지역 지하수의 Ar/$N_2$가스의 비율을 측정한 결과 Site 1(Grand Island, NE)의 경우 대기가스가 포화된 증류수의 Ar/$N_2$가스 비율인 0.026보다 낮은 0.015-0.018로서 탈질이 일어났음을 알 수 있으며, Site 2(Shelton, NE)의 경우 0.023-0.02로서 탈질이 일어나지 않음을 알 수 있다. 본 실험의 목적은 지하수에 응해되어 있는 Ar/Nitrogen의 비율을 정확히 측정하는 방법을 개발하므로서 탈질의 정도를 정확히 측정하며 탈질의 전개 과정을 관찰하기 위한 것이다.

• 한국수산과학회지
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• 제51권6호
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• pp.632-639
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• 2018

To develop the high-value added seafood products from a regional speciality seafood, the seasoned dried pen shell Atrina pectinata adductor (SDPA) and seasoned smoke-dried pen shell adductor (SSPA) samples were prepared, and their optimal processing conditions, quality metrics, and shelf-life characteristics were examined. SDPA and SSPA samples were produced by thawing of frozen pen shell adductor, and cutting it into 6-7 mm slices, hot-air drying ($60^{\circ}C$, 20 min) or smoking ($110^{\circ}C$, 20 min), seasoning ($4^{\circ}C$, 12 h) with seasoning powder (60% sorbitol, 15% sucrose, 16% salt and 9.0% monosodium glutamate), hot-air drying ($60^{\circ}C$, 3 h), torching, vacuum-packaging in a laminated plastic film bag, heat treating with hot-water ($85^{\circ}C$, 15 min), and cooling. The moisture content of SDPA and SSPA samples was 44.5 and 43.0%, respectively, and the water activity was 0.845 and 0.842. The total amino acids in SDPA and SSPA samples were 20,986.8 and 21,312.4 mg/100 g, respectively, and the major amino acids in both products were aspartic acid, serine, glutamic acid, proline, glycine, alanine, valine, leucine, phenylalanine, lysine and arginine. The primary minerals were Na, S, K and P. Incubating tests indicated that the quality of SDPA and SSPA samples was maintained for 30 days of storage.

• Journal of Microbiology and Biotechnology
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• 제25권5호
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• pp.709-717
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• 2015

Airborne bacteria from hog farms may have detrimental impacts on human health, particularly in terms of antibiotic resistance and pathogen zoonosis. Despite human health risks, very little is known about the composition and diversity of airborne bacteria from hog farms and hog-related spray fields. We used pyrosequencing analysis of 16S rRNA genes to compare airborne bacterial communities in a North Carolina hog farm and lagoon spray field. In addition, we isolated and identified antibiotic-resistant bacteria from both air samples. Based on 16S rRNA gene pyrosequence analysis, Actinobacteria, Bacteroidetes, Firmicutes, and Proteobacteria were the dominant phyla in airborne bacterial communities from both hog farm and spray field sites. Within the Firmicutes genera, Clostridium spp. were more abundant in the hog farm, whereas Staphylococcus spp. were higher in the spray field. The presence of opportunitic pathogens, including several Staphylococcus species and Propionibacterium acnes, was detected in both bioaerosol communities based on phylogenetic analysis. The isolation and identification of antibiotic-resistant bacteria from air samples also showed similar results with dominance of Actinobacteria and Proteobacteria in both hog farm and spray field air. Thus, the existence of opportunistic pathogens and antibiotic resistant bacteria in airborne communities evidences potential health risks to farmers and other residents from swine bioaerosol exposure.

• 한국환경과학회지
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• 제19권4호
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• pp.509-516
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• 2010

This study was investigated the characteristics of indoor air concentration of fiber particles in 30 public facilities and 245 schools by PCM (phase contrast microscopy). Also SEM/EDX (scanning electron microscope / energy dispersive using X-ray analysis) was used to obtain physicochemical information of asbestos fiber and to classify asbestos and non-asbestos of fiber particles. The airborne concentrations of fiber particles were $0.0009\pm0.0009$ counts/mL in public facilities and $0.0012\pm0.0006$ counts/mL in schools by PCM. All the samples were satisfied with the IAQ (indoor air quality) level of 0.01 counts/mL. In classification of 4 type shapes, over 80% of the fiber particles were identified as single fiber type. And this study analysed airborne fiber particles in 4 sites for identifying asbestos of by SEM/EDX. The asbestos fibers in most samples could not be found.

• 한국대기환경학회지
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• 제13권5호
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• pp.397-410
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• 1997

An annular denuder filter pack sampling system (ADS) was used to collect acidic air pollutants in Pusan. During the study period (from June 1995 to November 1995), forty eight samples were collected every 12 hours starting from 6:00 in the morning. These samples were devided into two sets of data for day (6:00 a.m.-6:00 p.m.) and night (6:00 p.m.-6:00 a.m.). The chemical species were analyzed for HN $O_3$, HN $O_2$, S $O_2$ and N $H_3$ in the gas Phase, and N $O_3$$^{[-10]}$ , S $O_4$$^{2-}$ and N $H_4$$^{+}$ in the particulate phase. The mean concentrations measured from this study were 0.24, 1.91, 30.07 and 4.24 $\mu\textrm{g}$/㎥ for HN $O_3$, HN $O_2$, S $O_2$ and N $H_3$, respectively. The mean concentrations of N $O_3$$^{[-10]}$ , S $O_4$$^{2-}$ and N $H_4$$^+{\ulcorner}$ were 1.95, 7.36 and 3.48 $\mu\textrm{g}$/㎥, respectively. The mean concentrations of gaseous species except for HN $O_2$ were higher in daytime than in nighttime, but the reverse was true in the particulates except for N $H_4$$^{+}$. +/..

• Asian Journal of Atmospheric Environment
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• 제11권1호
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• pp.54-60
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• 2017

Quantifying the trace elements in infinitesimal ambient liquid samples (e.g., single raindrop, cloud/fog water, and the soluble fraction extracted from the particles collected for a short time) is an important task for understanding formation processes, heating/cooling rates, and their health hazards. The purpose of this study is to employ an in-air micro PIXE system for quantitative analysis of the trace elements in a thimbleful of reference liquid sample. The bag type liquid sample holder originally designed with $10{\mu}m$ thick $Mylar^{(R)}$ film retained the original shape without any film perforation and apparent peaks of film blank by the end of the analysis. As one of tasks to be solved, the homogeneity of the elemental distribution in liquid reference species was verified by the X-ray line profiles for several references. It was possible to resolve the significant peaks for whole target elements corresponding to the channel number of micro-PIXE spectrum. The calibration curves for the six target elements (Si, S, Cl, Fe, Ni, and Zn) in standard solutions were successfully plotted by concentration (ppm) and ROI of interest net counts/dose (nC).

• 한국식품위생안전성학회지
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• 제4권1호
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• pp.29-36
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• 1989

In order to investigate the Storage time of chicken eggs, several physico-chemical tests from chicken eggs store at 5, 13 and 27$^{\circ}C$ were examined. Egg samples were collected from six poultry farms. Egg stored at 5$^{\circ}C$ based on the depth of air cell and specific gravity, were all acceptable until 17 days ; on the egg yolk coefficient and pH of the egg white and egg yolk until about 10 days. Egg stored at 13$^{\circ}C$, based on the depth of air cell. were acceptable by about 10 days of storage, but on the other physico-chemical tests by about 7 days. Egg samples stored at room temperature(about 27$^{\circ}C$) base on the depth of air cell, were acceptable by about 5 days of storage ; on the specific gravity by 4 days ; and on the egg yolk coefficient and pH of the egg yolk and egg white by 3 days. The results of this study showed that egg stored at 5$^{\circ}C$ were considered acceptable by 10 days of storage ; at 13$^{\circ}C$ by 7 days ; at room temperature (27$^{\circ}C$) by 3 days.

• 설비공학논문집
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• 제30권3호
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• pp.116-122
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• 2018

The purpose of this study was to confirm the effects of flush-out in the reduction of formaldehyde concentration in newly built residential buildings. The field measurements were conducted on two complexes of multi-residential buildings which are located in the suburban area of Seoul. About eight samples of residential buildings were selected to measure the changes in formaldehyde concentrations after flush-out from the two apartment complexes. The concentration of formaldehyde was measured using DNPH cartridge and HPLC. From the results of the field measurements, it was established that indoor formaldehyde concentration decreases 27.6~54.2% in the samples after flush-out. The number of days that the flush-out were conducted was noted to have no significant influence on the reduction rate of formaldehyde concentration when the flush-out continued more than 7 days. The comparison with Bake-out showed that flush-out also can reduce formaldehyde in newly built buildings as same levels of it.

• 설비공학논문집
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• 제29권3호
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• pp.142-147
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• 2017

Improvement of the enthalpy exchange element's energy efficiency is of current interest from anenergy-saving viewpoint. In this study, a LiCl-impregnated spacer was devised as a means to improve the performance of the enthalpy exchange element. Two samples were tested : one with and one without impregnated spacers of $338{\times}338{\times}380mm$ sizes with 2.0 mm channel spacing. The results showed that the temperature efficiencies of the two samples were approximately the same. The humidity efficiency, however, was strongly affected by the LiCl impregnation. The impregnated sample yielded a 9% higher humidity efficiency under cooling and the difference increased to 14% under aheating condition. It was anticipated that more moisture would beadsorbed on the LiCl-impregnated spacers, which was delivered to their roots and eventually to the air in neighboring channels. Separate moisture adsorption tests revealed that both the adsorption rate and the amount of the adsorbed moisture are higher for the LiCl-impregnated specimen.

• 대한치과기공학회지
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• 제11권1호
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• pp.83-88
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• 1989

This investigation was performed to evaluate the effect of four different preteatment techniques on the bond strength of porcelain to non-precious metal alloy. Samples of total of 40 were divided into 4 groups according to the 4 variables which included the 50$\mu$alumina oxide air abrasion, method, the as retention bead method, the L-retention bead method, the Etching method. The completed metal-porcelain samples were compressed in Instron loading machine until gross fracture occured to examine the effect of the complex variables on the bond strength of porcelain to non precious metal alloy. The result obtained were as follows : 1. The difference of bond strength according to four different pretreatment techniques was statistically significant(p<0.01). 2. The difference of bond strength between the ss-retention bead method and the L-retention bead method was not significant statistically(p>0.05) 3. The difference of bond strength between the retention bead method and the etching method was statistically significant(p<0.01). 4. The difference of bond strength between the retention bead method and the 50$\mu$alumina oxide air abrasion method was statistically significant(p<0.01). 5. The difference of bond strength between the etching method and the 50$\mu$alumina oxide air abrasion method was statistically significant(p<0.01).