• 대한지하수환경학회지
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• 제5권2호
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• pp.66-79
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• 1998

본 연구는 제주도 백록담 담수호에서 해안변 용천수에 이르는 고도별로 대표적인 55개 용천수에 대한 지역적 수질특성과 그 진화과정을 연구하였다. 조사지역 55개 용천수의 수질분석 결과 관음사물은 수소이온농도에서, 유수암천, 장수물, 덕지샘물, 신촌큰물, 영천사, 운량천, 하원통물, 동해물, 색달생수, 안덕계곡, 화순곤물, 돗물, 화강물, 정금물은 주변 육상오염원들에 의해서, 삼양제3수원, 신촌큰물, 명법사, 서느렁물, 토산물, 정금물, 곽지물, 애월하물, 고내물, 녹고물은 해수침입에 의해 오염이 진행중인 용천수들로 분류되었다. 용천수내의 전기전도도, pH, 질산성질소, 중탄산이온은 강수량이 많았을 때 그 농도가 증가하였으며, 나트륨, 염소이온, 황산이온은 강수량이 많았을 때 그 농도가 감소하였고, 칼륨과 마그네슘, 칼슘은 영향이 미미하였다. Piper의 삼각다이어그램을 통한 조사지역 용천수의 수질특성을 보면 고산지역은 Sodium or Potassium type과 bicarbonate type의 군을 이루었고, 중산간지 역은 Sodium or Potassium type과 No dominant type의 군을 형성하였으며, 저지대지역은 No dominant type과 Sulfate or Nitrate type의 군을, 해안지역은 Sodium or Potassium type과 Chloride type 및 No dominant type의 복잡한 용천수군을 형성하고 있었다. 즉 제주도 용천수는 해발고도가 높은 고산 및 중산간지역에서는 bicarbonate type이 우세한 수질조성에서 저지대 및 해안지역으로 유동되면서 non-bicarbonate type 형태의 수질로 변질되어가고 있었다.

• 한국토양비료학회지
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• 제18권1호
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• pp.78-88
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• 1985

질소(窒素)의 형태(形態)가 상이(相異)한 몇가지 비종(肥種)이 수도(水稻)의 생육(生育) 및 수량(收量)에 미치는 영향(影響)을 구명(究明)코자 진주(眞珠)벼를 공시품종(供試品種)로 하여 4가지 질소형태(窒素形態)와 7종(種)의 비종(肥種)으로 질소(窒素) 시비량(施肥量)을 달리하여 Pot시험(試驗)한 결과(結果)를 요약(要約)하면 다음과 같다. 1. 토양중(土壤中) pH는 $NH_4-N$인 Ammonium Sulfate의 시용량(施用量)이 증대(增大)할수록 낮아졌으며 $NO_3-N$의 경우 부성분(副成分)이 없는 Nitric Acid구(區)는 시간이 경과함에 따라 pH가 높아졌으나 부성분(副成分)이 있는 $NO_3-N$ 비료(肥料)는 변화(變化)가 적었다. 2. 토양중(土壤中) $NH_4{^+}$ 함량(含量)은 N 15kg/10a구(區)에서는 비료형태(肥料形態)나 비종(肥種)에 관계없이 이앙후(移秧後) 14일(日)에 가장 낮았다. N 30kg/10a구(區)에서는 $NH_4-N$, Urea-N 등(等)은 17~24일(日)에 함량(含量)이 가장 낮았으나 $NO_3-N$는 31일(日)까지 계속 감소(減少)하였다. 3. 생육상황(生育狀況)은 질소시용량간(窒素施用量間)에 다소(多少) 차이(差異)가 있지만 간장(稈長), 고중(藁重) 등(等) 지상부(地上部)의 생육(生育)은 질소형태별(窒素形態別)로는 $NH_4-N$인 인산(燐酸)을 함유(含有)한 Ammonium Phosphate구(區)와 유황(硫黃)을 함유(含有)한 Ammonium Sulfate구(區), 그리고 Urea-N인 Urea구(區)에서 양호(良好)하였고 지하부(地下部) 뿌리의 생육(生育)은 $NO_3-N$인 질산구(窒酸區), Potassium Nitrate구(區) 및 Calcium Nitrate구(區)에서 양호(良好)하였다. 4. 수도(水稻)의 수량(收量)은 질소형태별(窒素形態別)로는 질소시용량간(窒素施用量間)에 다소(多少) 차이(差異)가 있으나 $NH_4-N$인 Ammonium Sulfate구(區), Ammonium Phosphates구(區)가 수량(收量)이 많았으며 $NO_3-N$인 Calcium Nitrate구(區) Potassium Nitrate구(區), Nitric Acid구(區)는 수량(收量)이 낮았다. 5. 식물체(植物體) 경엽중(莖葉中)에 N, P, Mg 및 Mn등(等) 무기성분(無機成分) 함량(含量)은 $NH_4-N$비료(肥料)에서 많았으며 Urea-N $NH_4-N+NO_3-N$의 순(順)로 적었다. 또한 $NO_3-N$ 비료(肥料)는 대체로 K, Ca 및 $SiO_2$ 등(等)의 무기성분(無機成分) 함량(含量)이 많았으나 N, P와 Mg, Mn, Fe 및 Mn등(等)의 함량(含量)이 적었다. 6. 식물체(植物體) 경엽중(莖葉中) 질소흡수(窒素吸收)의 증가(增加)는 인산흡수(燐酸吸收)를 증진(增進)시키는 상조작용(相助作用)이 있어 생육(生育) 및 수량증가(收量增加)에 기여하는 것으로 보였다. 반면(反面)에 $NO_3-N$ 비료(肥料) 중(中) K가 첨가(添加)된 비료구(肥料區)에서는 N, P, Ca 및 Mg, 그리고 Ca가 첨가(添加)된 비료구(肥料區)는 P, K 및 Mg 또한 $NO_3$-시용구(施用區)는 N, P, Mg흡수(吸收)를 감소(減少)시켰으며 N, P, Mg 및 Ca등(等)은 생육(生育) 및 수량증가(水量增加)에 크게 기여하는 것으로 보였다. 7. 수확기(收穫期) 벼 뿌리중 $SiO_2$, Zn, Fe 함량(含量)은 경엽(莖葉)에 비하여 많았고 N, P, Mg, Mn, Zn 및 Fe함량(含量)는 $NH_4-N$, Urea-N시용구(施用區)에서 많았고 K, Ca, $SiO_2$함량(含量)는 $NO_3-N$시용구(施用區)에서 많았다.

• 한국세라믹학회지
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• 제55권6호
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• pp.597-607
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• 2018

In this study, a wet chemical method was used to synthesize nanostructured hydroxyapatite for biomedical applications. Diammonium hydrogen phosphate and calcium nitrate 4-hydrate were used as starting materials with a sodium hydroxide solution as an agent for pH adjustment. Scanning electron microscopy, transmission electron microscopy, Fourier-transform infrared spectroscopy, differential thermal analysis, thermal gravimetric analysis, atomic absorption spectroscopy, and ethylenediaminetetraacetic acid (EDTA) titration analysis were used to characterize the synthesized powders. Having been uniaxially pressed, the powders formed a disk-like shape. The sinterability and electrical properties of the samples were examined, and the three-point bending test allowed for the measurement of their mechanical properties. Sedimentation analysis was used to analyze the slurry ability of hydroxyapatite. As in-vitro biological properties of the samples, biocompatibility and cytotoxicity were assessed using osteoblast-like cells and the L929 cell line, respectively. Solubility was assessed by employing a simulated body fluid.

• International Journal of Concrete Structures and Materials
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• 제8권1호
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• pp.15-26
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• 2014

In order to study the capacities of a new occurrence of Brazilian clay samples as partial replacements of cement, a bentonite sample was selected for utilization in the natural and modified forms for present study. The natural bentonite (BBT) was modified by anchorament of 3-aminopropyltrietoxisilane ($BBT_{APS}$) and 3,2-aminoethylaminopropyltrimetoxisilane (BBTAEAPS) in the surface of component minerals of bentonite sample. The original and organo-bentonite samples were characterized by elemental analysis, scanning electron microscopic and textural analyses. The values of micropore area were varying from $7.2m^2g^{-1}$ for the BBT to $12.3m^2g^{-1}$ for the $BBT_{AEAPS}$. The bentonite samples were characterized by the main variable proportion of bentonite in the natural and intercalated forms (2, 5, 10, 15, 20, 25, 30, and 35 % by weight of cement) in the replacement mode whiles the amount of cementations material. The workability, density of fresh concrete, and absorption of water decreased as the substitution of ordinary Portland cement by perceptual of natural and modified bentonite increased. The results reveal that workability decreased with decrease of the amount of natural bentonite in the concrete, same behavior is observed for bentonite functionalized, varying from 49 to 28 mm. The energetic influence of the interaction of calcium nitrate in the structure of blends was determined through the calorimetric titration procedure.

• Computers and Concrete
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• 제26권3호
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• pp.257-273
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• 2020

Concrete bond strength with steel re-bars depends on multiple factors including concrete-steel interface and mechanical properties of concrete. However, the hydration development of cementitious paste, and in turn the mechanical properties of concrete, are negatively affected by cold weather. This study aimed at exploring the concrete-steel bonding behavior in concrete cast and cured under freezing temperatures. Three concrete mixtures were cast and cured at -10 and -20℃. The mixtures were protected using conventional insulation blankets and a hybrid system consisting of insulation blankets and phase change materials. The mixtures comprised General Use cement, fly ash (20%), nano-silica (6%) and calcium nitrate-nitrite as a cold weather admixture system. The mixtures were tested in terms of internal temperature, compressive, tensile strengths, and modulus of elasticity. In addition, the bond strength between concrete and steel re-bars were evaluated by a pull-out test, while the quality of the interface between concrete and steel was assessed by thermal and microscopy studies. In addition, the internal heat evolution and force-slip relationship were modeled based on energy conservation and stress-strain relationships, respectively using three-dimensional (3D) finite-element software. The results showed the reliability of the proposed models to accurately predict concrete heat evolution as well as bond strength relative to experimental data. The hybrid protection system and nano-modified concrete mixtures produced good quality concrete-steel interface with adequate bond strength, without need for heating operations before casting and during curing under freezing temperatures down to -20℃.

• 한국미생물·생명공학회지
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• 제10권1호
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• pp.45-52
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• 1982

A fungus with the highest protopectinase productivity was selected among 205 strains isolated from the soil and identified as a Verticillium sp. The Verticillium sp. was cultivated on wheat bran and the crude extruct of its culture medium showed the highest protopectinase activity on the following conditions: 3 days of cultivation time, 27$^{\circ}C$ of cultivation temperature, 1.2 $m\ell$/g wheat bran of water content, and reinforcement of ammonium nitrate and calcium chloride at the concentration of 0.5 and 0.02%, respectively. The optimum conditions for pectin production from Citrus peel pulp by the protopectinase were consequently obtained as follows: 20$m\ell$/g of liquid volume-to-pulp weight ratio, 4$0^{\circ}C$ of reaction temperature, and 4 of reaction pH. The higher the enzyme concentration, the better the yield of pectin and the shorter the reaction time. Total 45.6mg of pectin/g peel was produced by 1 hour reaction at the enzyme concentration of 10.5 units/$m\ell$. Molecular weight of the pectin produced by the enzyme was estimated to be about 62,000 by Smit and Bryant's method.

• Journal of Biosystems Engineering
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• 제32권5호
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• pp.348-353
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• 2007

A solid state ion sensor module has been developed and evaluated for hydroponic nutrients analysis. The sensor module consisted of five ion-selective electrodes (ISE) fabricated by screen-printing technology. The electrochemical responses of ion sensors for nitrate, ammonium, potassium, calcium, and pH were measured with specially designed 7-channel low voltage signal transducers. The analytical characteristics of the sensors were comparable with those of conventional ISE sensors. The solid state ion sensors exhibit linear relationships over five concentration decades. Detection limit of the sensors were $5.6{\times}10^{-5}{\sim}1.6{\times}10^{-7}M$ depends on ions. Performance test results showed that relative errors of measured ion concentrations were less than 5% for $NO_3{^-},\;K^+,\;Ca^{2+}$ ion, and pH. The concentration of $NO_3{^-},\;NH_4{^+},\;K^+,\;Ca^{2+}$, and pH ion in standard solution and nutrient solutions could be determined by direct potentiometric measurements without any conditioning before measurements.

• 한국약용작물학회지
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• 제24권1호
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• pp.27-30
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• 2016

Background : This text was conducted to evaluate the distribution, shape characteristics and habitat condition of Crypsinus hastatus in Buyeo Korea. Methods and Results : In Buyeo, Crypsinus hastatus was distributed at an altitude of 31.2 m, a slope of 82.5% and a distance from river water of 27.2 m. The leaf blade was oblong, 2.7 cm long, 1.2 cm wide with a petiole length of 2.3 cm. The total population comprised 2,100 individuals, with the highest proportion being individuals with a leaf blade of length 0.5 - 1 cm. The temperature and light intensity of the growth point were lower, but the humidity higher, than that of growth around. The chemical properties of the soil were as follows: pH 4.42, organic matter 77.99 g/kg, electrical conductivity 0.50 dS/m, nitrate nitrogen 20.50 mg/kg and available phosphate 165.7 mg/kg. Exchangeable cation content of potassium, magnesium, sodium and calcium was 0.35, 0.70, 0.09 and $2.04cmol^+/kg$, respectively. Conclusions : In Buyeo, Crypsinus hastatus was distributed in $5.3m^2$ area of Nakhwaam, Naeseongri and Jeongamri. However, the population of the medicinal resources seemed to decrease owing to the poor environmental conditions of the habitat.

• 한국환경보건학회지
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• 제29권3호
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• pp.91-96
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• 2003

This study was intended as an investigation of characteristics of background site atmospheric respirable particulate matters(RPM), and fine particles(<2.5 ${\mu}{\textrm}{m}$). The particle size distributions during the phenomenon of Yellow Sand(YS) occurs from April, 2001. Atmospheric aerosol particulate matter was directly collected on the Jeju island between 1 to 30, April, 2001 using an eight-stage cascade impacter(particle size range: 0.43-11 ${\mu}{\textrm}{m}$), and cyclone separator(cut size: 2.5, 10 ${\mu}{\textrm}{m}$). The episode of YS observed in background monitoring site, Kosan and appeared 2 times at sampling period. The mass concentrations of fine and coarse particles for YS episode were 34.2 and 59.6 $\mu\textrm{g}$/㎥, respectively, which were significantly increased amounts compared to 13.3 and 13.0 $\mu\textrm{g}$/㎥ for NonYS(NYS). Most size distributions had two peaks, one at 0.43∼.65 ${\mu}{\textrm}{m}$ and the other at 3.3${\mu}{\textrm}{m}$4.7 ${\mu}{\textrm}{m}$. The result of analysis of water-soluble ion component indicated that sulfate was mainly ion component, but nitrate and calcium ion was significantly increased at the YS episode.

• Asian-Australasian Journal of Animal Sciences
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• 제24권3호
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• pp.439-448
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• 2011

Oxalic acid is synthesized by a wide range of plants. A few of them are forage plants that can cause oxalate poisoning in ruminants under certain conditions. In this paper, the role of some agronomic, climatic and genetic factors in minimizing oxalate accumulation in forage plants has been discussed. Research indicates that the content of oxalate in forage can be controlled by fertilizer application. For example, nitrate application resulted in higher contents of soluble and insoluble oxalates than ammonium application. With an increased rate of potassium application, soluble oxalate content showed an increasing trend and insoluble oxalate content showed a decreasing trend. With an increased rate of calcium application, soluble oxalate content showed a decreasing trend and insoluble oxalate content showed a reverse trend. Other agronomic factors such as growing season, harvesting practices, plant maturity, plant species, plant variety and plant parts can also have a large effect on oxalate accumulation. However, the potential benefits of the above approaches for improving forage quality have not been fully exploited. In addition, there is still insufficient information to fully utilize means (e.g. plant nutrients, season and soil moisture) to minimize oxalate accumulation in forage plants. Therefore, more research is required for a better understanding of the interactions between oxalate and the above-mentioned factors in forage plants.