• 한국구조물진단유지관리공학회 논문집
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• 제28권2호
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• pp.69-76
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• 2024

굳지 않은 콘크리트의 유변특성은 콘크리트의 제조 및 성능에 중요한 영향을 미치지만, 새롭게 개발되는 배합과 제조 공법의 다양화로 인하여 기존의 경험적 방법으로는 유변특성의 정확한 예측에 어려움이 있다. 본 연구에서는 시멘트 입자와 같은 나노 수준에서의 입자간 상호작용부터 잔골재와 같은 마이크로 수준에서의 유변학적 성질을 정량적으로 예측하기 위하여 멀티스케일 기법을 적용한 유변특성 예측 모델을 제안하였으며, 시멘트 페이스트의 항복응력, 모르타르의 항복응력 및 소성점도를 예측하기 위하여 YODEL(Yield stress mODEL), Chateau-Ovarlez-Trung 방정식 및 Krieger-Dougherty 방정식을 적용하였다. 일차적으로 시멘트 페이스트의 물-시멘트비(W/C)를 기준으로 하여 페이스트 스케일의 유변특성을 예측하였으며, 예측 결과를 토대로 동일한 W/C에 시멘트-잔골재 부피비(C/S)를 추가한 모르타르 스케일의 유변특성의 예측을 진행하였다. 시멘트 모르타르에 대한 유변특성 실험을 통하여 예측 결과와 실험 결과의 비교를 진행함으로써 예측 모델의 적용 가능성을 평가하였다.

• Bulletin of the Korean Chemical Society
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• 제34권9호
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• pp.2697-2701
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• 2013

The solvolysis rate constants of piperonyloyl chloride (1) in 27 different solvents are well correlated with the extended Grunwald-Winstein equation, using the $N_T$ solvent nucleophilicity scale, $Y_{Cl}$ solvent ionizing scale, and I aromatic ring parameter with sensitivity values of $0.30{\pm}0.05$, $0.71{\pm}0.02$, and $0.60{\pm}0.04$ for l, m, and h, respectively. The solvent kinetic isotope effect values (SKIE, $k_{MeOH}/k_{MeOD}$ and $k_{50%MeOD-50%D2O}$) of 1.16 and 1.12 were also in accord with the values for the $S_N1$ mechanism and/or the dissociative $S_N2$ mechanism. The product selectivity values (S) for solvolysis of 1 in alcohol/water mixtures were in the range of 0.5 to 1.9, which is also consistent with the proposed unimolecular ionization mechanism.

• 한국축산시설환경학회지
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• 제12권2호
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• pp.85-94
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• 2006

The effects of turning frequency of in-vessel composting on ammonia emissions during composting of separated solids from swine slurry/sawdust mixtures and performance of biofiltration using the chicken manure compost were investigated. Separated solids from swine manure amended with sawdust was composted in a 226 L laboratory-scale in-vessel reactors under various turning frequency and continuous airflow (0.6 L/min.kg.dm) for three weeks. Three laboratory-scale manure compost biofilters were built to treat effluent gas from the composting of separated solid from swine manure amened with sawdust process. These experiments were continued over a period of three weeks. The composting of separated solid swine manure amended with sawdust and manure compost biofiltration system were evaluated to determine the turning frequency type that would be adequate for the rate of decomposition and compost odour reduction. The compost odour cleaning was measured based on ammonia gas concentration before and after passing through the manure compost biofilter. The average ammonia odor reduction in the manure compost biofilter was 96.9 % at R1 (no turning), 99.4 % at R2(once a day turning) and 89.0 % at R3(twice a day turning), respectively. The efficiency of ammonia reduction was mainly influenced by the turning frequency.

• Tribology and Lubricants
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• 제20권2호
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• pp.51-57
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• 2004

Micro/nano adhesion and friction properties of mixed self-assembled monolayer (SAM) with different chain length for MEMS application were experimentally studied. Many kinds of SAM having different spacer chains(C6, C10 and C18) and their mixtures (1:1) were deposited onto Si-wafer, where the deposited SAM resulted in the hydrophobic nature. The adhesion and friction properties between tip and SAM surfaces under nano scale applied load were measured using an atomic force microscope (AFM) and under micro scale applied load were measured using ball-on-flat type micro-tribotester. Surface roughness and water contact angles were measured with SPM (scanning probe microscope) and contact anglemeter. Results showed that water contact angles of mixed SAMs were similar to those of pure SAMs. The morphology of coating surface was roughened as mixing of SAM. Nano adhesion and nano friction decreased as increasing of the spacer chain length and mixing of SAM. Micro friction was decreased as increasing of the spacer chain length, but micro friction of mixed SAM showed the value between pure SAMs. Nano adhesion and friction mechanism of mixed SAM was proposed in a view of stiffness of spacer chain modified chemically and topographically.

• Journal of the Korean Data and Information Science Society
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• 제22권3호
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• pp.459-466
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• 2011

본 논문은 독립적으로 수행된 연구결과를 합쳐서 일반적인 결론을 도출하는 메타분석을 위한 로버스트 계층적 베이지안 모형을 고려한다. 사전정보가 정규분포를 따른다는 가정 대신 정규분포의 척도혼합을 사용하여 정규분포보다 더 두꺼운 꼬리를 가지는 사전분포를 사용한다. 나아가 개별 분석의 분산이 알려져 있지 않은 경우를 계층적 베이지안 모형에 포함하여 메타분석을 수행하고자 한다. 깁스 표집을 사용하여 추정값을 계산하고, 실제 자료를 사용하여 제안된 방법을 예시한다.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2003년도 학술대회지
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• pp.56-63
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• 2003

Micro/nano adhesion and friction properties of mixed self-assembled monolayer (SAM) with different chain length for MEMS application were experimentally studied. Many kinds of SAM having different spacer chains(C6, C10 and C18) and their mixtures (1:1) were deposited onto Si-wafer, where the deposited SAM resulted in the hydrophobic nature. The adhesion and friction properties between tip and SAM surfaces under nano scale applied load were measured using an atomic force microscope (AFM) and micro scale applied load were measured using ball-on-flat type micro-tribotester. Surface roughness and water wetting angles were measured with SPM (scanning probe microscope) and contact anglemeter. Results showed that wetting angles of mixed SAMs showed the similar value of pure SAMs. The coating surface morphology was increased as mixing of SAM. Nano adhesion and nano friction decreased as increasing of the spacer chain length and mixing of SAM. Micro friction was decreased as increasing of the spacer chain, but micro friction of mixed SAM showed the value between pure SAMs. Nano adhesion and friction mechanism of mixed SAM was proposed in a view of stiffness of spacer chain modified chemically and topographically.

• Bulletin of the Korean Chemical Society
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• 제33권12호
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• pp.4117-4121
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• 2012

The solvolysis rate constants of allyl chloroformate ($CH_2=CHCH_2OCOCl$, 3) in 30 different solvents are well correlated with the extended Grunwald-Winstein equation, using the $N_T$ solvent nucleophilicity scale and $Y_{Cl}$ solvent ionizing scale, with the sensitivity values of $0.93{\pm}0.05$ and $0.41{\pm}0.02$ for l and m, respectively. These l and m values can be considered to support a $S_N2$ reaction pathway. The activation enthalpies (${\Delta}H^{\neq}$) were 12.5 to 13.4 $kcal{\cdot}mol^{-1}$ and the activation entropies (${\Delta}S^{\neq}$) were -34.4 to -37.3 $cal{\cdot}mol^{-1}{\cdot}K^{-1}$, which is also consistent with the proposed bimolecular reaction mechanism. The solvent kinetic isotope effect (SKIE, $k_{MeOH}/k_{MeOD}$) of 2.16 was also in accord with the $S_N2$ mechanism. The values of product selectivity (S) for the solvolyses of 3 in alcohol/water mixtures was 1.3 to 3.9, which is also consistent with the proposed bimolecular reaction mechanism.

• Journal of the korean society of oceanography
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• 제31권2호
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• pp.43-54
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• 1996

Jinhae Bay, one of the largest tidal bays on the southern coast of Korea, is an area with thick accumulations of recent, fine-grained sediments, mainly supplied from the Nakdong River. The preponderance of silt and clay particles reflects the large quantity of sediments transported in suspension. Although the clay mineral assemblage is similar to that derived from the nearby Nakdong River, relatively high concentration (3-9%) of smectite suggests some local input of fine particles from several streams around the bay or some contribution from the offshore water that may be influenced by the Tsushima Current. The content of organic matters in sediments is as high as 12%, and their C/N ratios imply that they are comprised of mixtures derived from marine plankton and terrestrial plants. $^{210}Pb$ excess activity profiles of sediment cores yield an average sedimentation rate (a 100-year time scale) of about 2-5 mm/yr, which coincides well with the long-term sedimentation rate (a 1000-year time scale) estimated from the sediment isopach map. On the basis of sediment bulk density and sedimentation rate, an annual sink of mud in the bay is estimated approximately 1.0 ${\times}$ $10^{6}$ tons per year.

• 한국응용과학기술학회지
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• 제38권5호
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• pp.1219-1228
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• 2021

친환경적 바이오 계면활성제의 하나인 람노리피드(rhamnolipid)의 제조는 Pseudomonas aeruginos 계열의 박테리아가 가장 많이 사용되며, 바이오 공정을 통해 생산된다. 람노리피드의 화학구조는 rhamnose당과 𝛽-hydroxylated fatty acid의 결합으로 이루어져 있으며, 바이오 공정을 통해 동질체 혼합물 형태로 생산된다. 발효(fermentation)공정 중 거품 제어가 수율을 결정하는 가장 중요한 요인으로 알려져 있다. 본 논문에서는, 박테리아 내부에서 일어나는 람노리피드 합성 메카니즘을 소개하였고, 발효공정에서 문제점으로 인식되었던 거품 제어 방법에 대한 최근 시도들을 살펴보았다. 10년 전과 비교하여, 람노리피드 양산화 가능성은 빠르게 높아지고 있다. 특히, 람노리피드와 같은 바이오 계면활성제는 의약품과 같은 고부가가치 제품으로 응용된다면, 시장의 요구가 더 커질 것으로 기대한다.

• Nuclear Engineering and Technology
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• 제55권8호
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• pp.2734-2741
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• 2023

Brachytherapy is a special case of radiotherapy. It should be arranged according to some principles in medical radiation applications and radiation physics. The primary principle is to use as low as reasonably achievable dose in all ionizing radiation applications for diagnostic and therapeutic treatments. Dosimetric distributions are dependent on radioactive source properties and radiation-matter interactions in an absorber medium such as phantom or tissue. In this consideration, the geometrical structure and material of the seed capsule, which surrounds a radioactive material, are directly responsible for isodose profiles and dosimetric functions. In this study, the radiometric properties of capsule material were investigated on dose distribution in a water phantom by changing its nuclear properties using the EGSnrc Monte Carlo (MC) simulation code. Effective atomic numbers of hypothetic mixtures were calculated by using different elements with several fractions for capsule material. Model 6711 brachytherapy seed was modeled by EGSnrc/Dosrcnrc Code and dosimetric functions were calculated. As a result, dosimetric parameters of hypothetic sources have been acquired in large-scale atomic number. Dosimetric deviations between the data of hypothetic seeds and the original one were analyzed. Unit dose (Gy/Particle) distributions belonging to different types of material in seed capsule have remarkably differed from the original capsule's data. Capsule type is major variable to manage the expected dose profile and isodose distribution around a seed. This study shows us systematically varied scale of material type (cross section or effective atomic number dependent) offers selective material usage in production of seed capsules for the expected isodose profile of a specific source.