• Journal of Dairy Science and Biotechnology
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• 제18권1호
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• pp.1-8
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• 2000

본 실험은 산양유 casein의 조성 및 분별 그리고 이화학적 성질에 관하여 연구하고자 산양유의 일반성분을 분석하고 초유와 정상유로 산 casein을 제조하였으며 chymosin 작용과 전기영동에 의한 분리특성 및 DEAE-cellulose column chromatography에 의한 분별을 실시하였다. 그 결과, 산양 정상유의 단백질, 지방, 유당 함량은 각각 2.70${\pm}$0.27%, 3.82${\pm}$0.51% 및 4.10${\pm}$0.29%이었으며 정상유 casein보다 초유 casein에서chymosin처리에 의해 더 많은 NPN 함량이 유리되었다. 우유 및 산양유 casein을 chymosin 처리하여 전기영동을 실시한 결과 casein 조성이 서로 다르게 나타났으며 그 분리양상 또한 차이를 보였다. 산양 정상유 casein을 0.03${\sim}$0.25 M NaCl linear gradient로 DEAE-cellulose column chromatography를 실시한 결과 명확히 분별되지 않아 농도 기울기를 달리한 0.08${\sim}$0.18 M NaCl linear gradient로 column chromatography를 실시한 결과 5개의 Peak로 분리되었고 그 비율은 각각 5.27%, 26.07%, 25.97%, 30.40%및 12.29%이었다. 또한, 순수한 동정, 특히 n-casein 분획을 확인하기 위하여 chymosin을 처리한 산양 정상유 casein을 동일한 조건에서column chromatography를 실시한 결과 6개의peak로 분리되었으며 그 비율은 각각 17.06%, 9.10%, 17.85%, 20.11%, 27.03% 및 8.85%로 나타났다.

• Journal of Microbiology
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• 제42권1호
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• pp.1-8
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• 2004

Changes in the bacterial populations of a 5-stage biological nutrient removal (BNR) process, with a step feed system for wastewater treatment, were monitored by denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S ribosomal DNA fragments. DGGE analysis indicated seasonal community changes were observed, however, community profiles of the total bacteria of each reactor showed only minor differences in the samples obtained from the same season. The number of major bands was higher in the summer samples, and decreased during the winter period, indicating that the microbial community structure became simpler at low temperatures. Since the nitrogen and phosphate removal efficiencies were highly maintained throughout the winter operation period, the bacteria which still remaining in the winter sample can be considered important, playing a key role in the present 5-stage BNR sludge. The prominent DGGE bands were excised, and sequenced to gain insight into the identities of the predominant bacterial populations present, and most were found to not be closely related to previously characterized bacteria. These data suggest the importance of culture-independent methods for the quality control of wastewater treatment.

• Carbon letters
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• 제8권1호
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• pp.25-29
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• 2007

The carbon brake discs were manufactured by densification the carbon fiber preform using PG-CVI technology with Propene as a carbon precursor gas and Nitrogen as a carrier gas. The densities of carbon brake discs were tested at different densification time. The results indicate that the densification rate is more rapid before 100 hrs than after 200 hrs. The CTscanning image and the SEM technology were used to observe the inner subtle structure. CT-images show the density distribution in the carbon brake disc clearly. The carbon brake disk made by PG-CVI is not very uniform. There is a density gradient in the bulk. The high-density part in the carbon brake is really located in the friction surface, especially in the part of inner circle. This density distribution is most suitable for the stator disc.

• 생태와환경
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• 제46권1호
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• pp.18-24
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• 2013

본 연구는 바다새 서식지 복원 및 식생복원을 위해 2011년 4월부터 12월까지 전라남도 신안군 칠발도와 소구굴도지역에 대한 식물군락 및 환경구배에 따른 바닷새 번식지 토양환경 요인을 분석하였다. 토양요인을 분석한 결과 칠발도는 닭의장풀군락이 수분함량, 유기물함량, 염분농도, 총질소가 높게 나타났으며, 쇠무릎 군락은 낮게 나타났다. 또한, 바닷새 서식처로 이용되는 밀사초 군락은 토양환경요인 분포범위가 넓고 유입종인 쇠무릎군락과 쑥군락은 좁게 나타났다. 소구굴도 밀사초군락 토양pH는 3.14로 가장 낮았고, 갯기름나물군락은 3.84 가장 높게 나타났다. 수분함량과 유기물함량은 갯기름나물군락에서 가장 높게 나타났으며, 쇠무릎군락이 35.9%로 가장 낮게 분석되었다. 염분농도와 총질소는 밀사초군락이 가장 높게 나타났다. 고도에 따른 토양환경특성에서는 칠발도의 경우 고도가 높아질수록 수분함량, 유기물함량, 염분농도 및 총질소가 낮아지는 유의성을 보였다. 소구굴도 토양수분함량은 평균 35.73%, 유기물함량 16.38%, pH 3.34로 전체적으로 산성토양이었다. 토양산성화는 조류분비물에 의해 영향을 받았을 것으로 판단된다. 염분농도는 평균 2.11 ppt, 총질소는 평균 $6.43mg\;g^{-1}$로 분석되었다. 소구굴도는 섬면적이 좁고, 고도가 낮아 전체적으로 토양환경요인의 분석결과는 크게 차이가 나타나지 않았으나, 수분함량은 환경구배에 대해 고도에 의한 유의성을 보였다.

• 천문학회지
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• 제16권1호
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• pp.1-5
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• 1983

Four HII regions of the Sd galaxy NGC 7793 were observed using AAT/IPCS. From these spectra we determined abundances of the elements using observed emission lines and electron temperatures. The calculated abundances show that this galaxy does not show any significant radial abundance gradient. The mean oxygen abundance is very much like the Orion nebulae and the nitrogen abundance is similar to the late type barred spiral galaxy NGC 1313.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2007년도 제34회 KOSCO SYMPOSIUM 논문집
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• pp.13-18
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• 2007

When triple flames propagated in a diverging channel, the effects of fuel dilution on the lift-off characteristics of triple flames were investigated. A multi-slot burner was used to stabilize the lift-off flame especially at weak fuel concentration gradients. It was reported that there is a maximum propagation velocity at a critical concentration gradient in an open jet regardless of fuel dilution. The enhancement of a diffusion flame affected to increase the propagation velocity around critical concentration gradients. However, the influence of a confined channel on the structure of triple flames according to fuel dilution needs to be investigated compared with an open jet case. This study aimed to examine the effect of a confined channel on the structure and the propagation velocity of the triple flames according to fuel dilution. Lift-off height and propagation velocity of triple flames were investigated by employing three kinds of fuel compositions diluted by nitrogen (0%, 25%, 50% $N_2$), Fuel dilution reduced the propagation velocity of triple flame in a confined channel mainly due to the decrease of flame temperature in premixed branch. Despite the difference in fuel dilution, the propagation velocity has a maximum value at a specific fuel concentration gradient even though the critical concentration gradient increases with fuel dilution. And the critical concentration gradient in a confined channel is larger than that in an open jet due to enhancement of convective diffusion.

• Journal of Microbiology and Biotechnology
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• 제25권10호
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• pp.1670-1679
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• 2015

Two hollow fiber membrane biofilm reactors (HF-MBfRs) were operated for autotrophic nitrification and hydrogenotrophic denitrification for over 300 days. Oxygen and hydrogen were supplied through the hollow fiber membrane for nitrification and denitrification, respectively. During the period, the nitrogen was removed with the efficiency of 82-97% for ammonium and 87-97% for nitrate and with the nitrogen removal load of 0.09-0.26 kg NH₄⁺-N/m³/d and 0.10-0.21 kg NO₃^--N/m³/d, depending on hydraulic retention time variation by the two HF-MBfRs for autotrophic nitrification and hydrogenotrophic denitrification, respectively. Biofilms were collected from diverse topological positions in the reactors, each at different nitrogen loading rates, and the microbial communities were analyzed with partial 16S rRNA gene sequences in denaturing gradient gel electrophoresis (DGGE). Detected DGGE band sequences in the reactors were correlated with nitrification or denitrification. The profile of the DGGE bands depended on the NH₄⁺ or NO₃^- loading rate, but it was hard to find a major strain affecting the nitrogen removal efficiency. Nitrospira-related phylum was detected in all biofilm samples from the nitrification reactors. Paracoccus sp. and Aquaspirillum sp., which are an autohydrogenotrophic bacterium and an oligotrophic denitrifier, respectively, were observed in the denitrification reactors. The distribution of microbial communities was relatively stable at different nitrogen loading rates, and DGGE analysis based on 16S rRNA (341f /534r) could successfully detect nitrate-oxidizing and hydrogen-oxidizing bacteria but not ammonium-oxidizing bacteria in the HF-MBfRs.

• 한국물환경학회지
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• 제24권3호
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• pp.273-279
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• 2008

Space separation method that use independent reactor for nitrification and other reactor for denitrification has been commonly used for biological nitrogen removal process like $A^2O$ process. However, this method needs large space and complicate pipelines and time separation method such as SBR process have a difficulty in continuous treatment. Thus biological nitrogen removal process which is capable of continuous treatment, easy opeation and space saving is urgently required. In this research, submerged moving media was used for a biofilm process and suspended sludge was used for biological nitrogen removal at the same time. In particular DO environment by controlling air flow rate was investigated for simultaneous nitrification/denitrification. Total nitrogen removal in aeration rate more than $67L/min{\cdot}m^3$ showed 51~53% and rose to 65%, 70% and 78% in $50L/min{\cdot}m^3$, $58L/min{\cdot}m^3$ and $25L/min{\cdot}m^3$ respectively. Total phosphorus removal was very low about 10~20% more than $67L/min{\cdot}m^3$ aeration rates. But total phosphorus removal roses when reduces aeration rate by $58L/min{\cdot}m^3$ low and it showed total phosphorus removal of 72% in aeration rate $25L/min{\cdot}m^3$.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 1993년도 Proceedings of International Conference for Agricultural Machinery and Process Engineering
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• pp.443-452
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• 1993

Direct freezing tests of soybean seed by liquid nitrogen were carried out at various moisture contents and the following important conclusions were drawn from the results of temperature measurements of soybean seed and photographs of bubbles generated on its surface : 1) Assuming that the temperature gradient in a soybean seed is negligible because of its small seed size and the freezing ratio is followed the Heiss's formula, and a differential equation based on the heat energy balance was introduced . The equation was easily solved by the Runge-Kutta-Gill method and the predicted values of the temperature were in good agreement with the observed data. 2) The photographs of bubble generation during freezing showed the boiling mode was nucleate, and then the most suitable formula on the nucleate boiling heat transfer was introduced from many formulate proposed up to now by fitting the calculated values based on the formula to the observed data. The formula used for the predict on of the seed temperature was as follows: $\frac{{\partial}T_s}{\partial\theta}\;=\;-\frac{{\alpha}(T_s\;-\;T_L)^{3.3}}{W(C_s\;-\;\frac{{\delta}m(CT_s\;+\;{\sigma})}{T_s^2})}$ where C = difference of the specific heat between pure ice and water m=moisture content of soybean seed $T_s$ = seed temperature $T_L$ = Temperature of liquid nitrogen W = mass of soybean seed $\alpha$ = proportional constant $\delta$ = constant depends on variety or the type of seed $\theta$ = time $\sigma$ = latent heat of melting of pure ice This study will give important information in the hydro-freezing technique by liquid nitrogen, available as a new technique of processing agricultural products in the near future.

• Journal of Korean Neurosurgical Society
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• 제30권3호
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• pp.381-383
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• 2001

Neurological symptoms may develope when the blood urea nitrogen is lowered too rapidly by hemodialysis. It is known that these symptoms, known as dialysis disequilibrium are associated with cerebral edema. However, the pathogenesis of brain swelling and neurological deterioration after rapid hemodialysis is controversial. The reverse urea hypothesis suggests that hemodialysis removes urea more slowly from the brain than from the plasma, creating an osmotic gradient that results in cerebral edema. The idiogenic osmole hypothesis proposes that an osmotic gradient between brain and plasma develops during rapid dialysis because of newly formed brain osmoles. Authors report a such case and discuss the possible mechanism and preventive methods.