• 설비공학논문집
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• 제3권5호
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• pp.365-375
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• 1991

Confined natural convection due to lateral temperature difference in rectangular enclosures was studied numerically and experimentally for the insulated and the constant temperature enclosures. In the case of insulated enclosure, the flow pattern and heat transfer modes are rather simple depending mainly upon Rayleigh number. In the case of isothermal enclosure, however, the phenomena of flow and heat transfer are somewhat complex and interesting due to the stable thermal gradients and various circumstances resulted from four wall temperature conditions. As a dimensionless variable, to describe properly the flow and heat transfer phenomena in the isothermal enclosure, temperature difference ratio ${\Delta}T_v/{\Delta}T_H$ is newly introduced and this parameter seems to be appropriate in the analysis of results on the effect of stabilizing thermal gradient.

• Journal of Applied Biological Chemistry
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• 제62권1호
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• pp.31-38
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• 2019

Scutellaria baicalensis Georgi (Scutellariae Radix)는 이뇨제, 고지혈증, 항박테리아, 항알레르기, 항염증제 및 항암제와 같은 건강보조식 및 전통 생약으로도 널리 사용되어 왔다. 본 연구에서 복잡한 S. baicalensis 추출물에서 지표 물질 또는 유효화합물들을 분리하는 것은 신원 확인 및 생리활성 평가를 위한 필수적인 단계다. 8개의 성분들로 구성된 타겟 분획물을 두개의 gradient elution를 사용하여 고성능 액체 크로마토 그래피에서 분석하였다. 중압 액체크로마토그래피 및 개방형칼럼으로 분취를 시뮬레이션함으로 예비실험에서 충분히 분리가 되도록 용리 조건을 결정할 수 있었다. 최적 분취방법으로 확보된 표준유효분획물로부터 8개의 지표성분들이 포함된 것을 확인하였다. 또한, 분획물은 UPLC-QTof-MS 비교 분석으로 MS, UV, HRESIMS 결과를 확인할 수 있었다. 따라서, 스케일 업 실험법은 S. baicalensis 추출물에 성공적으로 적용될 수 있었다.

• 한국동물학회:학술대회논문집
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• 한국동물학회 2001년도 공동 춘계학술대회
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• pp.78-78
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• 2001

No Abstract, See Full Text

• Bulletin of the Korean Chemical Society
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• 제26권1호
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• pp.77-84
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• 2005

We prepared the new nonlinear optical chromophores that show fairly high microscopic nonlinearity through intramolecular charge transfer. Phenothiazine and carbazole units played an important role to contribute high electron donability and connect the resonance pathway via conjugative effect in the cyclized ring beside the aromatic ring. Theoretical calculation, electrochemical analysis, and absorption spectroscopic study gave us useful information about the energy states and microscopic nonlinearities of two serial chromophores. We compared the microscopic nonlinearities of four chromophores with the conjugation length and electron donability in the push-pull type NLO chromophores. The effect of gradient donability and lengthening the conjugation were investigated on the electronic state and microscopic nonlinearity.

• Advances in nano research
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• 제8권1호
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• pp.49-58
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• 2020

This paper investigates the vibration characteristics of flexoelectric nanobeams resting on viscoelastic foundation and subjected to magneto-electro-viscoelastic-hygro-thermal (MEVHT) loading. In this regard, the Nonlocal strain gradient elasticity theory (NSGET) is employed. The proposed formulation accommodates the nonlocal stress and strain gradient parameter along with the flexoelectric coefficient to accurately predict the frequencies. Further, with the aid of Hamilton's principle the governing differential equations are derived which are then solved through Galerkin-based approach. The variation of the natural frequency of MEVHT nanobeams under the influence of various parameters such as the nonlocal strain gradient parameter, different field loads, power-law exponent and slenderness ratio are also investigated.

• Structural Engineering and Mechanics
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• 제88권4호
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• pp.335-354
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• 2023

In this study, analysis of wave propagation characteristics for functionally graded carbon nanotube-reinforced composite (FG-CNTRC) nanoplates is performed using first-order shear deformation theory (FSDT) and nonlocal strain gradient theory. Uniform distribution (UD) and three types of functionally graded distributions of carbon nanotubes (CNTs) are assumed. The effective mechanical properties of the FG-CNTRC nanoplate are assumed to vary continuously in the thickness direction and are approximated based on the rule of mixture. Also, the governing equations of motion are derived via the extended Hamilton's principle. In numerical examples, the effects of nonlocal parameter, wavenumber, angle of wave propagation, volume fractions, and carbon nanotube distributions on the wave propagation characteristics of the FG-CNTRC nanoplate are studied. As represented in the results, it is clear that the internal length-scale parameter has a remarkable effect on the wave propagation characteristics resulting in significant changes in phase velocity and natural frequency. Furthermore, it is observed that the strain gradient theory yields a higher phase velocity and frequency compared to those obtained by the nonlocal strain gradient theory and classic theory.

• Advances in nano research
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• 제7권4호
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• pp.249-263
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• 2019

In the current paper, an exact solution method is carried out for analyzing the thermo-mechanical vibration of curved FG nano-beams subjected to uniform thermal environmental conditions, by considering porosity distribution via nonlocal strain gradient beam theory for the first time. Nonlocal strain gradient elasticity theory is adopted to consider the size effects in which the stress for not only the nonlocal stress field but also the strain gradients stress field is considered. It is perceived that during manufacturing of functionally graded materials (FGMs) porosities and micro-voids can be occurred inside the material. Material properties of curved porous FG nanobeam are assumed to be temperature-dependent and are supposed to vary through the thickness direction of beam which modeled via modified power-law rule. Since variation of pores along the thickness direction influences the mechanical and physical properties, porosity play a key role in the mechanical response of curved FG nano-structures. The governing equations and related boundary condition of curved porous FG nanobeam under temperature field are derived via the energy method based on Timoshenko beam theory. An analytical Navier solution procedure is utilized to achieve the natural frequencies of porous FG curved nanobeam supposed to thermal loading. The results for simpler states are confirmed with known data in the literature. The effects of various parameters such as nonlocality parameter, porosity volume fractions, thermal effect, gradient index, opening angle and aspect ratio on the natural frequency of curved FG porous nanobeam are successfully discussed. It is concluded that these parameters play key roles on the dynamic behavior of porous FG curved nanobeam. Presented numerical results can serve as benchmarks for future analyses of curve FG nanobeam with porosity phases.

• 한국환경생물학회:학술대회논문집
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• 한국환경생물학회 2005년도 추계학술대회 초록집
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• pp.85-85
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• 2005

• 생명과학회지
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• 제24권4호
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• pp.393-402
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• 2014

천연염색폐수시설 폐수의 세균 군집분석을 위해 배양 가능한 세균을 분리하는 방법과 비배양 방법인 denaturing gradient gel electrophoresis 방법을 이용하였다. 3개의 폐수 공정단계로부터 분리된 104개(폐수유입수, 48균주; 접촉포기조, 25균주; 침전조, 31균주) 균주들의 16S rRNA 유전자의 염기서열을 분석하였다. 104개의 분리균들은 Proteobacteria 문이 가장 많은 비율을 차지 하였으며, Actinobacteria, Firmicutes 와 Bacteriodetes 등 4개 문에 속했다. DGGE profile중 각 시료의 우점 군집을 대표하는17개의 band를 선택하여 부분 염기서열 분석 결과 분리균과 동일한 4개의 문에 속했다. 배양기법을 이용한 결과와 배양하지 않고 분석하는 방법인 DGGE결과 모두 Proteobacteria 문이 우점하였으며 Alphaproteabacteria강이 높은 비율을 차지하였다. 천연염색 폐수처리시설의 세균 군집들은 인간을 비롯한 동식물의 기생균, 다당류와 난분해성 화합물을 분해하는 세균 그리고 세포외 다당을 형성하는 세균들이 우점하고 있음을 알 수 있었다.

• Structural Engineering and Mechanics
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• 제68권1호
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• pp.103-119
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• 2018

In the present research, an attempt is made to obtain a semi analytical solution for both nonlinear natural frequency and forced vibration of embedded functionally graded double layered nanoplates with all edges simply supported based on nonlocal strain gradient elasticity theory. The interaction of van der Waals forces between adjacent layers is included. For modeling surrounding elastic medium, the nonlinear Winkler-Pasternak foundation model is employed. The governing partial differential equations have been derived based on the Mindlin plate theory utilizing the von Karman strain-displacement relations. Subsequently, using the Galerkin method, the governing equations sets are reduced to nonlinear ordinary differential equations. The semi analytical solution of the nonlinear natural frequencies using the homotopy analysis method and the exact solution of the nonlinear forced vibration through the Harmonic Balance method are then established. The results show that the length scale parameters give nonlinearity of the hardening type in frequency response curve and the increase in material length scale parameter causes to increase in maximum response amplitude, whereas the increase in nonlocal parameter causes to decrease in maximum response amplitude. Increasing the material length scale parameter increases the width of unstable region in the frequency response curve.