• Advances in nano research
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• 제6권1호
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• pp.1-19
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• 2018

Iron oxide nanoparticles excite researcher interest in biomedical applications due to their low cost, biocompatibility and superparamagnetism properties. Magnetic iron oxide especially magnetite ($Fe_3O_4$) possessed a superparamagnetic behaviour at certain nanosize which beneficial for drug and gene delivery, diagnosis and imaging. The properties of nanoparticles mainly depend on their synthesis procedure. There has been a massive effort in developing the best synthetic strategies to yield appropriate physico-chemical properties namely co-precipitation, thermal decomposition, microemulsions, hydrothermal and sol-gel. In this review, it is discovered that magnetite nanoparticles are best yielded by co-precipitation method owing to their simplicity and large production. However, its magnetic saturation is within range of 70-80 emu/g which is lower than thermal decomposition and hydrothermal methods (80-90 emu/g) at 100 nm. Dimension wise, less than 100 nm is produced by co-precipitation method at $70^{\circ}C-80^{\circ}C$ while thermal decomposition and hydrothermal methods could produce less than 50 nm but at very high temperature ranging between $200^{\circ}C$ and $300^{\circ}C$. Thus, co-precipitation is the optimum method for pre-compliance magnetite nanoparticles preparation (e.g., 100 nm is fit enough for biomedical applications) since thermal decomposition and hydrothermal required more sophisticated facilities.

• 물과 미래
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• 제10권2호
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• pp.101-111
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• 1977

The analysis performed here is aimed to increase the familiarity of hydrologic process especially for the small basins which are densely gaged. Kyung An and Mu Shim river basins are selected as a represectative basin according to the criteria which UNESCO has establisheed back in 1964 and being operated under the auspice of Ministry of Construction. The data exerted from these basins is utilized for the determination of the characteristics of precipitation and runoff phenomena for the small basin, which is considerred as a typical Korean samll watershed. The methodology developed by Soil Conservation Service, USA for determination of runoff value from precipitation is applied to find the suitability of the method to Korean River Basin. The soil cover complex number or runoff curve number was determined by considering the type of soil, soil cover, land use and other factor such as antecent moisture content. The averag values of CN for Kyung An and Mushim river basins were found to be 63.9 and 63.1 under AMC II, however, the values obtained from soil cover complex was less than those from total precipitation and effective precicpitation by 10-30%. It may be worth to note that an attention has to be paid in the application of SCS method lo Korean river basin by adjusting 10-30% increase to the value obtained from soil cover complex. Finally, the design flood hydrograph was consturcted by employing unit hydrograph technique to the dimensionless mass curve. Also a stepwise multiple regression was performed to find the relationship between runoff and API, evapotranspiration rate, 5 days antecedent precipitation and daily temperature.

• 농업과학연구
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• 제46권4호
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• pp.999-1006
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• 2019

Recently, the quantitative management of agricultural water supply, which is the main source for water consumption in Korea, has become more important due to the effective water management organization of the Korean government. In this study, the estimation method for irrigation supply based on agricultural reservoir storage data was improved compared to previous research, in which drought year selection was unclear, and the outlier data for the rainfall-irrigation supply were not eliminated in the regression analysis. In this study, the drought year was selected by the ratio of annual precipitation to mean annual precipitation and the storage rate observed before the start of irrigation. The outlier data for the rainfall-irrigation supply were eliminated by the Grubbs & Beck test. The proposed method was applied to nine agricultural reservoirs for validation. As a result, the ratio of annual precipitation to mean annual precipitation is less than 53% and the storage rate observed before the start of irrigation is less than 55% it was judged to be the drought year. In addition, the drought supply factor, K, was found to be 0.70 on average, showing closer results to the observed reservoir rates. This shows that water management at the real is appling drought year practice. It was shown that the performance of the proposed method was satisfactory with NSE (Nash-Sutcliffe model efficiency coefficient) and R² (coefficient of determiniation) except for a few cases.

• 한국분말재료학회지
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• 제20권3호
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• pp.180-185
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• 2013

The iron oxides nanoparticles and iron oxide with other compounds are of importance in fields including biomedicine, clinical and bio-sensing applications, corrosion resistance, and magnetic properties of materials, catalyst, and geochemical processes etc. In this work we describe the preparation and investigation of the properties of coated magnetic nanoparticles consisting of the iron oxide core and organic modification of the residue. These fine iron oxide nanoparticles were prepared in air environment by the co-precipitation method using of $Fe^{2+}$: $Fe^{3+}$ where chemical precipitation was achieved by adding ammonia aqueous solution with vigorous stirring. During the synthesis of nanoparticles with a narrow size distribution, the techniques of separation and powdering of nanoparticles into rather monodisperse fractions are observed. This is done using controlled precipitation of particles from surfactant stabilized solutions in the form organic components. It is desirable to maintain the particle size within pH range, temperature, solution ratio wherein the particle growth is held at a minimum. The iron oxide nanoparticles can be well dispersed in an aqueous solution were prepared by the mentioned co-precipitation method. Besides the iron oxide nanowires were prepared by using similar method. These iron oxide nanoparticles and nanowires have controlled average size and the obtained products were investigated by X-ray diffraction, FESEM and other methods.

• 한국지구과학회지
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• 제35권2호
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• pp.115-130
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• 2014

우리나라에서 악기상으로 인한 재해 유발 가능성이 높아짐으로써, 방재 및 수자원 관리 대책이 필요하다. 국지성 강한 강우에 대한 방재를 위해서는 강우량을 정량적으로 관측 및 예측해야 한다. 본 연구에서는 레이더 강우추정 오차의 지구통계학적 유효반경을 LGC 방법에 적용하여 레이더 추정강우를 조정하는 기법을 개발하였다. 지구통계적 방법을 이용하여 레이더 강우의 실제오차에 대한 유효반경을 결정하였고, LGC 방법을 기반으로 여름철 집중호우 네 사례의 레이더 강우를 조정하였다. 여름철 집중호우 사례의 레이더 1시간 누적강우량과 총누적강우량의 오차는 조정 후 각각 약 40%와 60% 이상 개선효과를 보였다. 그러므로, 여름철 국지적으로 강한 강우 현상의 레이더강우를 예측하는데 있어서 본 연구에서 개발된 조정 알고리즘을 이용하는 것은 적절한 것으로 판단된다.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2018년도 학술발표회
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• pp.310-310
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• 2018

현재 지상에서의 강우관측은 여러기관에 의해 이루어 지고 있다. 국토교통부에서는 홍수 및 갈수예보, 가뭄대응, 하천 유량관리 등 다양한 국가 수자원 관리의 목적으로 강우관측을 포함한 수문조사를 시행중이고, 전국에 424개의 강수량 관측소를 설치하여 운영중이다. 강수량 데이터는 10분단위 자료를 실시간으로 수집하여 각 관할 홍수통제소로 전송되며, 전송된 자료는 최적의 품질을 확보하기 위해 다양한 방법으로 품질관리를 실시하고 있다. 강수량 자료는 다양한 원인에 의해 결측이 발생할 수 있는데, 강수총량은 알지만 결측에 의해 시간 배분 보정을 해야 하는 경우 주변 관측소의 관측자료나 강우레이더의 반사도 등을 활용할 수 있다. 본 연구에서는 국토교통부에서 운영중인 강우레이더를 통해 생산되는 다양한 반사도 자료를 활용하여 결측자료에 대한 시간보정을 수행하는 방법론을 제시하였다. 제안한 방법론의 검증을 위해 낙동강 하류 유역의 50개 강수량 관측소 자료를 이용하였다. 다양한 강우사상의 자료들을 이용하여 반사도를 활용한 강수보정과 실제 관측된 자료와의 일치성을 검토하였고, 제안된 방법론이 결측자료 품질관리를 위한 하나의 방안으로 활용될 수 있음을 확인하였다.

• Bulletin of the Korean Chemical Society
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• 제35권9호
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• pp.2665-2668
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• 2014

Aptamers are oligonucleotides or peptide molecules that are able to bind to their specific target molecules with high affinity via molecular recognition. In this study, we present development of aptamer-based precipitation assays (or simply aptamoprecipitation) for His-tagged proteins and thrombin to compare their purification efficiency with other conventional affinity precipitation methods. A crosslinking method was employed to immobilize thiol-functionalized aptamers onto the surface of polystyrene resins, enabling them to specifically bind to His-tag and to thrombin, respectively. The resulting aptamer-functionalized resins were successfully applied via a one-step experiment to purification of His-tagged proteins from complex E. coli and to thrombin extraction, exhibiting superior or at least comparable purification results to the conventional immobilized metal affinity precipitation or immunoprecipitation.

• 동아시아식생활학회지
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• 제16권6호
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• pp.702-706
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• 2006

The aim of this study was to identify the onuses of abnormal precipitation in buckwheat extracts and to suggest the preventive solutions. Abnormal precipitation was formed by the coagulations of small round droplets, and increased when poor quality or old buckwheat used. It was found that, unlike poor quality buckwheat, extracts made from fresh buckwheat showed almost no saccharifying enzyme activity and a lower number of microorganisms. The addition of branched starch to the extracts restricted the occurrence of abnormal precipitation and microorganisms and imparted stability to the extracts.

• 한국전기전자재료학회논문지
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• 제11권9호
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• pp.705-710
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• 1998

Intrinsic gettering is usually to improve wafer quality, which is an important factor for reliable ULSI devices. In order to generate oxygen precipitation in lightly and heavily boron doped silicon wafers with or without high $^75 As^+$ ion implantation, the 2-step annealing method was adopted. After annealing, the were cleaved and etched with th Wright etchant. The morphology of cross section on samples was inspected by FESEM(field emission scanning electron microscopy). The morphology of unimplanted samples was rater rough than that of the implanted. Oxygen precipitation density observed by an optical microscope in lightly boron doped samples was about 3$\times10^6/cm^3$. However, in heavily boron doped samples, the density of oxygen precipitation was largest at $600^{\circ}C$ in 1st annealing, and decreased abruptly until $800^{\circ}C$, But it increased slightly at $1000^{\circ}C$ and was independent with the implantation.

• 한국세라믹학회지
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• 제25권5호
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• pp.465-472
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• 1988

Alpha alumina powder with fine particle size and narrow particle size distribution was prepared by precipitation method using Al2(SO4)3.18H2O as a starting material. The alpha alumina powder was prepared by calcining aluminum hydroxide which was formed under various pH values. The sinterabilityof alpha alumina powder and the effect of MgO on the sinterability of alpha alumina powder were investigated. The sinterability of alpha alumina powder was the order of pH=10≒pH11>pH=7≒pH9, and alpha alumina obtained from boehmite which was prepared by precipitation method reached to 97.5% of theoretcal density by the pressureless sintering. The effect of MgO on volume shrinkage of alumina was very slight in the initial sintering stage but remarkable in the final sintering stage. It was also found that MgO controlled effectively the grain growth of alumina.