• 대한수의학회지
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• 제4권1호
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• pp.19-22
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• 1964

The alcohol precipitation test(APT) is widely used in the inspection of cow milk, whereas the APT in goat milk inspection is not specifically known. The APT is used to determine the precipitating ability of milk by heat used in sterilization and evaporating process at the milk plant. The APT may also be used to detect abnormal milks such as acid milk, colostrum, and any milk in which the salt balance is disturbed so that it may be more subject to precipitation than normal milk. In the experiments the applicability of the APT of goat milk was studied. The results obtained by using 87 sample of goat milk are as follows: 1. As all the fresh samples(100%) were APT positive by using 70% ethanol which is used in the practice of cow milk and 3 out of 87 samples(3.7%) were positive by using 45% ethanol, it is suggested that 45% ethanol may be applied in the APT of goat milk. 2. The distribution of natural acidity (apparent acidity) was between 0.12%-0.30% and the amount of natural acidity did not significantly affect the precipitating ability of goat milk by APT. 3. The freshness of goat milk cannot be detected sharply by APT even though 45% ethanol is applied.

• Journal of Microbiology and Biotechnology
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• 제20권11호
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• pp.1571-1576
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• 2010

Two bacterial strains designated as CT2 and CT5 were isolated from highly alkaline cement samples using the enrichment culture technique. On the basis of various physiological tests and 16S rRNA sequence analysis, the bacteria were identified as Bacillus species. The urease production was 575.87 U/ml and 670.71 U/ml for CT2 and CT5, respectively. Calcite constituted 27.6% and 31% of the total weight of sand samples plugged by CT2 and CT5, respectively. Scanning electron micrography analysis revealed the direct involvement of these isolates in calcite precipitation. This is the first report of the isolation and identification of Bacillus species from cement. Based on the ability of these bacteria to tolerate the extreme environment of cement, they have potential to be used in remediating the cracks and fissures in various building or concrete structures.

• 한국재료학회지
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• 제31권11호
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• pp.642-648
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• 2021

The precipitation effect of Al-6%Si-0.4%Mg-0.9%Cu-(Ti) alloy (in wt.%) after various heat treatments was studied using a laser flash device (LFA) and differential scanning calorimetry (DSC). Solid solution treatment was performed at 535 ℃ for 6 h, followed by water cooling, and samples were artificially aged in air at 180 ℃ and 220 ℃ for 5 h. The titanium-free alloy Al-6%Si-0.4%Mg-0.9%Cu showed higher thermal diffusivity than did the Al-6%Si-0.4%Mg-0.9%Cu-0.2%Ti alloy over the entire temperature range. In the temperature ranges below 200 ℃ and above 300 ℃, the value of thermal diffusivity decreased with increasing temperature. As the sample temperature increased between 200 ℃ and 400 ℃, phase precipitation occurred. From the results of DSC analysis, the temperature dependence of the change in thermal diffusivity in the temperature range between 200 ℃ and 400 ℃ was strongly influenced by the precipitation of θ'-Al₂Cu, β'-Mg₂Si, and Si phases. The most important factor in the temperature dependence of thermal diffusivity was Si precipitation.

• 한국환경과학회지
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• 제7권5호
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• pp.707-716
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• 1998

The chemical characteristics of precipitation was investigated in Pusan area. Samples were collected from January to November in 1996 at 4 sites, and analyzed pH, major soluble ionic components(C $l^{[-10]}$ , N $O_3$$^{[-10]}$ , S $O_4$$^{2-}$, N $a^{+}$, $K^{+}$, N $H_4$$^{+}$, $Mg^{2+}$, $Ca^{2+}$). The order of anion and cation concentrations for the initial precipitation were C $l^{[-10]}$ ＞ S $O_4$$^{2-}$ ＞ N $O_3$$^{[-10]}$ , and $Ca^{2+}$ ＞ N $a^{+}$ ＞ N $H_4$$^{+}$ ＞ $Mg^{2+}$ ＞ $K^{+}$, respectively. At coastal sites(P1 and P2) C $l^{[-10]}$ and N $a^{+}$ of maritime sources (seasalt) were high, but at inland sites(P3 and P4) nss-C $a^{2+}$ and nss-S $O_4$$^{2-}$ were high. Calcium ion for the initial precipitation showed high value of enrichement factor(EF) relative to seawater composition. The contribution of seasalt to the composition of precipitation was higher at bite P1 (53.5%) than those of the other sites. Throughout the year the concentrations of major ions for the initial precipitation were low in the heavy rain season. The mean pH for the initial precipitation was 5.4 and showed the negative relationship with the precipitaion amount. The S $O_4$$^{2-}$ and N $O_3$$^{[-10]}$ do not play an important role in rain acidification due to the high(97%) neutralizing effect of amonia and calcium species.and calcium species.

• 한국재료학회지
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• 제26권1호
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• pp.13-16
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• 2016

Morphology and formation processes of lamellar grain boundaries in titanium rich binary TiAl intermetallics were studied. TiAl alloys containing aluminum content of 44 to 48 at.% were induction-heated to 1723 K followed by helium-gas-quenching at various temperatures. For the Ti-44%Al, few lamellae were observed in samples quenched from higher than 1473 K. Although small peaks of beta phase were detected using X-ray diffraction, only the ordered hexagonal phase (${\alpha}_2$) with clear APB contrast was observed in TEM observation. For the Ti-48 at.%Al alloy, almost no lamellar structure, and straight grain boundaries were observed in samples quenched from higher than 1623 K. The formation of lamellae along grain boundaries was observed in the sample quenched from 1573 K. The fully lamellar microstructures with serrated boundaries were observed in samples quenched from lower than 1473 K. It was found that the formation of ${\gamma}$ platelets took place at higher temperatures in Ti-48 at.%Al than in Ti-44 at.%Al. Although the size of the serration is different, serrated lamellar grain boundaries could be obtained for all alloy compositions employed. The serration appeared to be due to the grain boundary migration induced by precipitation and growth of ${\gamma}$. Differences in transformation characteristics with aluminum content are discussed.

• 한국세라믹학회지
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• 제41권3호
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• pp.190-196
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• 2004

Al 및 Y 질산염 용액에 탄산수소암모늄(NH$_4$HCO$_3$)을 침전제로 사용하여 YAG 분말을 합성하였다. 침전물을 attrition-milling한 결과, $Y_2$O$_3$와 YAG 상이 생성되었으며, 분쇄한 침전물을 110$0^{\circ}C$에서 1시간 하소하여 결정상이 잘 발달된 YAG 단일상 분말을 얻을 수 있었다. 분말의 소결성은 소결조제 SiO$_2$(500ppm Si)의 첨가에 관계없이 매우 우수하였다. 모든 시편은 130$0^{\circ}C$에서 이미 70% 이상의 밀도로 소결되었으며,140$0^{\circ}C$에서도 -83%의 밀도를 나타내었다. SiO$_2$로 도핑한 시편은 도핑하지 않은 시편 보다 치밀화가 약간 향상되었으며, 1$600^{\circ}C$에서 97%의 소결밀도가 얻어졌다.

• 대한자원환경지질학회:학술대회논문집
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• 대한자원환경지질학회 2003년도 춘계 학술발표회 논문집
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• pp.237-237
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• 2003

Preliminary studies on the seasonal variations in abundance of stable isotopes were carried out on the snow and rainwater samples from urban area. Stable isotopes and other geochemical data as a tool for characterizing the seasonality and source of pollutants were examined in study areas, especially to trace the sources of sulfate in precipitation and to distinguish sulfates of natural and anthropogenic origin. (omitted)

• Journal of Korean Society for Atmospheric Environment
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• 제18권E4호
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• pp.191-201
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• 2002

The pH, electric conductivity. and the major ionic components were analyzed for the precipitation samples collected at 1100 Site of Mt. Halla and Jeju city. The quality of analytical data was verified by the comparison of ion balances, conductivities and acid fractions, all of which correlation coefficients were over 0.952. The ionic strengths lower than 10$^{-4}$ M were found in 57 and 28% at 1100 Site and Jeju city respectively. The precipitation in Jeju city was influenced more by the oceanic effect than those in 1100 Site. The acidification of precipitation was caused mostly by S $O_4$$^{2-}$and N $O_3$$^{[-10]}$ in both areas, and the organic acids have contributed to the acidity with only 7~8%. The neutralization factors by N $H_3$ were about 44 and 47％ at the 1100 site and the Jeju city, respectively, whereas those by CaC $O_3$were 21 and 24%, and the free acidity were about 38 and 28％ at two sites. From the investigation of seawater and soil enrichment factors, the S $O_4$$^{2-}$, N $O_3$$^{[-10]}$ and N $E_4$$^{+}$ were immigrated by other sources rather than from the seawater or soil origins. but not in the case of $Mg^{2+}$, C $l^{[-10]}$ , N $a^{+}$, and $K^{+}$. Factor analysis has shown that the precipitation at the 1100 site had been influenced mostly by anthropogenic sources, followed by soil and sea-water sources. On the other hand, the precipitation at the Jeju city was mainly influenced by oceanic sources, followed by anthropogenic and soil sources.urces.

• 자원환경지질
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• 제48권5호
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• pp.371-377
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• 2015

강우의 산소 및 수소안정동위원소는 물순환 연구에서 수분의 이동 및 강우와 지하수계의 상호작용을 이해하는 데에 사용되어 왔다. 종유석 및 빙하의 안정동위원소를 이용하여 과거의 기후 및 기상을 이해하는 데에 이용되고 있으며, 이러한 과거지시자를 설명하기 위한 전지구순환모델의 기초자료로 이용되고 있다. 동위원소 분석기기의 발전으로 인해 이전보다 고해상도 연구가 점차 가능해 지고 있으며, 강우안정동위원소 역시 고해상도 연구에 대한 필요성이 제기되고 있다. 이번 연구에서는 해안에서 강우안정동위원소의 변동을 관찰하기 위하여 자동시료채취장치를 개발하여 강우량에 따라 5-15분 간격으로 강우시료를 채취하였다. 강우동위원소의 변동은 연구기간동안 최대 -5.7(-40.1)‰, 최소 -10.8(-74.3)‰ 값을 보였으며, 연구기간동안 강우안정동위원소의 산소와 수소의 선형관계의 기울기는 6.8이며, 이를 강우사상으로 분리하면 각각 5.1, 4.2, 7.9, 7.7이다. 이는 첫 두 강우가 내리면서 증발이 일어났음을 지시하며, 시간이 갈수록 증발이 더 이상 일어나지 않았음을 의미한다. 이러한 안정동위원소의 분화는 여러 물순환 연구에 시사하는 바가 크며, 앞으로 강우안정동위원소를 이용한 연구를 수행할 때 강우의 고해상도 분석이 필요할 것으로 판단된다.

• Macromolecular Research
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• 제12권2호
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• pp.233-239
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• 2004

We prepared thermally robust fully crosslinked poly(methyl methacrylate-co-divinyl benzene) ［poly(MMA-co-DVB)］microspheres successfully by precipitation polymerization in the absence of a stabilizing agent. The DVB concentration plays a pivotal role not only in the formation of the individually stable microspheres but also in the polymerization characteristics, including the particle size, the uniformity of size, the polymerization yield, and the thermal properties. The number-average diameter of the microspheres increased linearly, from 0.72 to 2.15 $\mu\textrm{m}$, and the particle size distribution became narrower, by elevating the uniformity from 1.35 to 1.12, as the DVB concentration increased from 20 to 75 mol%. In addition, the yield of the polymerization increased, from 73.4 to 98.6%, as the DVB concentration increased. Since the prepared particles possess fully crosslinked microstructures, no glass transition temperatures were observed, but all the samples prepared with DVB concentrations ranging from 20 to 75 mol% possess enhanced thermal properties. Based on the DSC and TGA data, the thermal stability of the mesospheres prepared by the precipitation polymerization is significantly improved as a result of crosslinking with DVB.