• Advances in materials Research
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• 제9권3호
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• pp.219-231
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• 2020

The aim of this study is to investigate the durability of fly ash based geopolymer mortar with and without protective coatings in aggressive chemical environments. The source materials for geopolymer are Fly ash and Ground Granulated Blast furnace Slag (GGBS) and they are considered in the combination of 80% & 20% respectively. Two Molarities of NaOH solution were considered such as 8M and 10M. The ratio of binder to sand and Sodium silicate to Sodium hydroxide solution (Na₂SiO₃/NaOH) are taken as 1:2 and 2 respectively. The alkaline liquid to binder ratio is 0.4. Compressive strength tests were conducted at various ages of the mortar specimens. In order to evaluate the performance of coatings on geopolymer mortar under aggressive chemical environment, the mortar specimens were coated with two different types of coatings such as epoxy and Acrylic. They were then subjected to different chemical environments by immersing them in 10% standard solutions of each ammonium nitrate, sodium chloride and sulphuric acid. Drop in compressive strength as a result of chemical exposure was considered as a measure of chemical attack and the drop in compressive strength was measured after 30 and 60 days of chemical exposure. The compressive strength results following chemical exposure indicated that the specimens containing the acrylic coating proved to be more resistant to chemical attacks. The control specimen without coating showed a much greater degree of deterioration. Therefore, the application of acrylic coating was invariably much more effective in improving the compressive strength as well as the resistance of mortar against chemical attacks. The results also indicated that among all the aggressive attacks, the sulphate environment has the most adverse effect in terms of lowering the strength.

• ALGAE
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• 제24권3호
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• pp.139-147
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• 2009

Microalgae using a submersible fluorescence probe in water column (up to 100 m) were measured during the austral summer of 2006 (February) in Prydz Bay, East Antarctica (triangular-shaped embayment in the Indian sector of Southern Ocean). Concurrently, environmental parameters such as temperature, salinity and nitrogen (nitrate, ammonium, urea) uptake rates were measured. The concentration of phytoplankton is relatively high due to availability of high nutrients and low sea surface temperature. Phytoplankton community is dominated by diatoms whereas cryptophytes are in low concentration. The maximum concentration of total chlorophyll is 14.87 ${\mu}g\;L^{-1}$ and is attributed to upwelled subsurface winter water due to local wind forcing, availability of micro-nutrients and increased attenuation of photosynthetically available radiation (PAR). Concentration of blue-green algae is low compared to that of green algae because of low temperature. Comparatively high concentration of yellow substances is due to the influence of Antarctic melt-water whereas cryptophytes are low due to high salinity and mixed water column. Varied concentrations of phytoplankton at different times of Fluoroprobe measurements suggest that the coastal waters of Prydz Bay are influenced by changing sub-surface water temperature and salinity due to subsurface upwelling induced by local winds as also melting/freezing processes in late summer. The productivity is high in coastal water due to the input of macro as well as micro-nutrients.

• 한국재료학회지
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• 제21권8호
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• pp.444-449
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• 2011

Nano-sized $Y_2O_3$ powders were prepared via a sol-gel method starting with $Y(NO_3)_3{\cdot}6H_2O$ (Yttrium(III) nitrate hexahydrate) and water with ethanol as a cosolvent. $Y_2O_3$ is an important rare earth oxide and has been considered for use in nuclear applications, such as ceramic materials, due to its excellent optical and refractory characteristics. It has been used as a chemically stable substrate, a crucible material for melting reactive metals, and a nozzle material for jet casting molten rare earth-iron magnetic alloys. Oxalic acid ($C_2H_2O_4$) has been adopted as a chelating agent in order to control the rate of hydrolysis and polycondensation, and ammonia was added in order to adjust the base condition. The synthesized $Y_2O_3$ powder was characterized using TG/DTA, XRD, FE-SEM, BET and Impedance Analyzer analyses. The powder changed its properties in accordance with the pH conditions of the catalyst. As the pH increases according to the FE-SEM, the grain grew and it showed that the pore size decreased while confirming the effect of the grain size. The nano-material $Y_2O_3$ powders demonstrated that the surface area was improved with the addition of oxalic acid with ammonium hydroxide.

• KSBB Journal
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• 제25권1호
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• pp.85-90
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• 2010

An ion selective microelectrode (ISME) was fabricated to measure concentrations of ammonium (${NH_4}^+$-N) and nitrate (${NO_3}^-$-N) according to the depth of nitrifying biofilm. The limits of detectability and validity of results were investigated to evaluate the ISME. The electromotive force (EMF) was directly proportional to the ion concentration, and average detection limits of ${NH_4}^+$ and ${NO_3}^-$ ISME were $10^{-5.14}$ and $10^{-5.18}$ M, respectively. The concentrations of ${NH_4}^+ $-N and ${NO_3}^-$-N in various depths on the nitrifying biofilm were measured by the ISME. When a modified Ludzack-Ettinger (MLE) process was operated at an HRT of 6 h, concentration gradients of ${NH_4}^+$-N in the bulk solution and biofilm at depths of $100\;{\mu}m$ decreased by $70\;{\mu}M$, while ${NO_3}^-$-N increased by $101\;{\mu}M$ and remained constant thereafter. At an HRT of 4 h, concentration gradients of ${NH_4}^+$-N at depths of $500\;{\mu}m$ decreased by $160\;{\mu}M$ and ${NO_3}^-$-N increased by $162;{\mu}M$ and remained constant thereafter. As HRT decreased, the concentration gradients of ${NH_4}^+$-N and ${NO_3}^-$-N between bulk solution and biofilm was higher due to the increase of nitrogen load. Also, the concentration gradients of the ${NH_4}^+$-N and ${NO_3}^-$-N of biofilm in the second aerobic tank were lower than those of the first aerobic tank, suggesting differences of nitrogen load and concentrations of DO between the first and second aerobic tank.

• 한국균학회지
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• 제15권3호
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• pp.158-168
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• 1987

1. Cassava 전분(澱粉)을 이용(利用)하여 곰팡이를 $28^{\circ}C$에서 96시간(時間) 액체정치(液體定置) 배양(培養)한 바 배지중(培地中)의 Cassava 전분함량(澱粉含量)이 6%, 72시간(時間)일 때에 균체량(菌體量)이 가장 많았다. 2. Cassava 전분(澱粉)이 6% 함유(含有)된 배지(培地)에서 곰팡이를 배양(培養)하여 얻은 균체단백질량(菌體蛋白質量)은 Rhizopus는 48시간(時間) 배양(培養)하였을때 가장 많았고, Aspergillus niger 및 Aspergillus fumigatus에서는 72시간(時間) 배양(培養)했을 때 균체단백질량(菌體蛋白質量)이 많았다. 3. Cassava 전분량(澱粉量)을 4%, 6% 및 8%되게 변화(變化)시킨 배지(培地)에서 분리균(分離菌)을 접종(接種)하여 96시간(時間) 배양(培養)하면서 24시간(時間)마다 배양여액(培養濾液) 중(中)의 m-amylase의 활성(活性)을 측정(測定)한 바 8% 농도(濃度)에서 Aspergillus niger 및 Aspergillus fumigatus는 72시간(時間)일 때 높은 D.P 값을 얻었고. Rhizopus 는 144시간(時間)일 때 D.P 값이 높았다.

• 환경영향평가
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• 제19권4호
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• pp.421-429
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• 2010

The reliability of the measurement of ambient trace species is an important issue, especially, in background area such as Gosan in Jeju Island. In a previous episodic study, it was suggested that the PM10 measurement result by the gravimetric method(GMM) was not in agreement with the result by the ${\beta}$-ray absorption method(BAM). In this study, a systematic comparison was carried out for the data between 2001 and 2008 at Gosan(GMM and BAM) and Jeju city (BAM) which is near to Gosan. It was found that at Gosan the PM10 concentration by BAM was higher than GMM and the correlation between them was low. The BAM results at Gosan and Jeju city showed similar trend implying the discrepancy at Gosan was not caused by instrumental problem of the BAM at Gosan. Based on the previous studies two probable reasons for the discrepancy are identified; (1) negative measurement error by the evaporation of volatile ambient species at the filter in GMM such as nitrate and ammonium and (2) positive error by the absorption of water vapor during measurement in BAM. There was no heater at the inlet of BAM at Gosan during the sampling period. Based on the size-segregated measurement data, it was identified that the evaporation error was minor, if any. The relationship between the two methods did not vary with the ambient relative humidity. Thus, at present, it is not clear why the discrepancy had been occurring and when using the PM10 data at Gosan, one should be aware the possible errors.

• 한국식품과학회지
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• 제24권5호
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• pp.451-455
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• 1992

Monascus anka albidus 균사를 쌀가루 7%, $NH_4NO_3$ 0.15%, $KH_2PO_4$ 0.05% 및 $MnSO_4$ 0.1%, 조성의 초기 pH 6.0으로 조절한 배지에 접종하여 $30^{\circ}C$에서 5일간 진탕 배양 하였을 때 가장 높은 색소 생산을 보였다. 특히 탄소원으로써 찹쌀가루가 제일 좋았으며 동시에 질소원으로써 $NH_4NO_3$, 인산염으로는 $KH_2PO_4$가 가장 우수하였으며 최적 C : N율은 18 : 1로 나타났다. 상기 조건에서 색소 생산은 플라스크에서 2.6mg/ml을, 그러나 5l 발효조에서 약 70%인 1.8mg/ml을 생산하였다.

• 한국약용작물학회지
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• 제7권1호
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• pp.1-6
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• 1999

지황(Rehmannja glutjnosa)에서 종근 저장시 나타나는 병원균의 오염을 배제하면서 종묘를 대량 증식시키는 방법을 개발하기 위하여 액체 배양을 통해 직접 체세포배를 형성하고자 할 때 요구되는 배지, 질소원, 탄소원 및 pH와 배양 기간 중 배지의 성분 변화를 조사하였다. 줄기나 엽병을 접종조직으로 할 경우, 배지내 질소원인 $NH_4NO_3$ 와 $KNO_3$의 적정비율은 825 mg/1 : 1900 mg/l 이었고, 탄소원으로는 자당이 적합하였으며, 적정 농도는 3% 이었다. 배지로는 1X MS 배지가 적합하였고, 적정 BA 농도는 2.0 mg/l 였는데, NAA와 조합하였을 경우에는 BA 1 mg/l에 NAA를 0.5 mg/l 를 조합한 배지 와 BA 2.0 mg/l 에 NAA를 0.1 mg/l로 첨가한 배지가 체세포배 발생에 효과적이었다. 멸균 전에 pH를 5.7로 조정한 경우에 직접 체세포배의 형성에 효과적이었다. 배양기간 중 배지 내 $Ca^{++}$와 $Mg^{++}$이온은 거의 변화가 없었으나, $K^{+}$이온은 많이 흡수되었다. 배양 3주 째에 자당은 거의 고갈되었고, 과당과 포도당은 3주 째부터 흡수되기 시작하였다.

• 기술사
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• 제16권3호
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• pp.5-23
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• 1983

On the Seoul Metropolitan Subway Construction of No. 3, 4 Line, the total length is 57 Km and it is now undergoing almost 55％ progress. The working method is classified into Open Cut of 70% and the rest of 30% tunnelling method in the 48 job site. Above tunnelling method is execute by American Steel Support System and the rest of 10 job site carried out by New Austria Tunnelling Method. This paper describes Blasting Standardizations works on the above Tunnelling ' Open Cut Method under big slogan, first safety, second execution. As a superintendent, I strived standardization of works with Better powder, Better Drills ' Better Pattern. Geological structure of Seoul area is composed by Jurassic Granite and also the above rockgroup are over burden by Alluviums as a Unconformity. First of all, I carried out the standard amount of powder and burden through experimental standard blasting by each powder as following Blasting works in the subway construction is surrounding shop Building, under pass the city river and also under pass highest building basement floor. I made allowable Blasting Vibration Value by West-Germany Vornorm DIN 4150, Teil 3 and should measure each blasting works as fellows all of powder is used basically Low-Gravity and Low Velocity such as Slurry, Ammonium Nitrate ' Finex I, II. for Smooth Blasting Instead of Gelatin Dynamite. Electric Detonation Cap is used basically M/S Delay Cup instead of Electric delay ' Simultaneous cap. I applied following formula V=KW3/4 $D^{-2}$ V=Particle Velocity (Cm/sec) K=Ginh Huh's Value W=Delay Charge (Kg) D=Distance(m) In the Open Cut, within 1m distance from H-pile I made to use the Concrete breaker, as following V=7W/$^{0.5}$V/$^{-1.75}$ On the Concentrate Building area, I advise to use Light class drill ø36m Bit and advance 1.1m per round blasting the three boom jumbo drill over ø45mm used only suburb of city.e Light class drill ø36m Bit and advance 1.1m per round blasting the three boom jumbo drill over ø45mm used only suburb of city.

• Journal of Plant Biotechnology
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• 제33권2호
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• pp.147-152
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• 2006

This work was carried out to establish adventitious root culture system in three Panax species (wild-grown P. ginseng, P. quinquefolium, and P. japonicum) to analyze their ginsenoside productivity. Adventitious roots were induced directly from segments of seedlings after cultured on MS(Murashige andSkoog 1962) solid medium containing 3.0 mg/l IBA. Omission of $NH_4NO_3$ from the medium greatly enhanced both the frequency of adventitious root formation and number of roots per explants in all the three Panax species. However, elongation of post-induced adventitious roots was enhanced on medium with $NH_4NO_3$. Two-step culture protocol: $NH_4NO_3$-free medium for first two weeks of culture, followed by $NH_4NO_3$ containing medium for further 4 weeks, greatly enhanced the fresh weight increase of adventitious roots in all the three ginseng species. The fresh weight of adventitious roots was high in P. quinquefolium and low in P. ginseng, followed by P. japonioum regardless of the composition of medium. Pattern and content of ginsenosides in adventitious roots differed among the three Panax species. Total ginsenoside content of adventitious roots in P. quinquefolium, P. ginseng, and p. japonicum was 8.03, 15.7 and 1.2 mg/g dry weight, respectively. Among the three speices, adventitious roots in P. quinquefolium produced hig-hamount of ginsenosides. The pattern of ginsenoside fractions between P. ginseng and P. quinquefolium was similar but the amount of ginsenoside differed between the two, While, in P japonicum, total ginsenoside content was very low and some ginsenosides such as ginsenoside Rb2 and Rf were not detected. Conclusively, we demonstrate that same culture condition was required for induction and elongation of adventitious roots of three ginseng species but growth of adventitious roots and their ginsenoside production were different among them.