• 콘크리트학회지
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• 제10권5호
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• pp.189-195
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• 1998

콘크리트 구조물이 초기재령에서 외기에 노출될 때, 수부확산으로 인하여 수분의 이동이 일어나고, 또한 자체건조도 발생한다. 이러한 콘크리트 내부의 수분확산과 자체건조에 의하여 콘크리트의 위치에 따라 상대습도가 변호한다. 특히 고강도 콘크리트의 경우에 단위 시멘트량을 많이 사용하기 때문에 , 초기재령에서 콘크리트 단면의 수분분포는 자체건조에 의하여 큰 영향을 받는다. 본 연구에서는 초기재령에서 외기에 노출된 콘크리트 내부의 여러 위치에서 상대습도를 측정하였다. 또한 자체건조로 인한 콘크리트의 상대습도 변화를 측정하여 초기재령에서 수분확산과 자체건조가 콘크리트 내부의 각 위치에서 상대습도에 미치는 영향을 검코하였다. 그리고 수분확산 이론에 의하여 해석결과와 실험결과를 비교하여 \ulcorner재령에서 수분확산 이론의 타당성을 검증하였다. 저강도 콘크리트 단면의 수분분포는 주로 수분확산에 의하여 영향을 받았으며, 자체건조의 영향은 매우 작게 나타났다. 그렇지만 고강도 콘크리트는 수분확산 뿐만 아니라 자체건조에 의하여도 영향을 받았다. 또한 수분확산 이론에 의한 해석결과는 실험결과를 잘 예측하였다.

• Macromolecular Research
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• 제8권2호
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• pp.59-65
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• 2000

We simulated the conformational changes of polymethacrylates which have side chains with different lengths (methyl and butyl) by molecular dynamics simulation technique. Bulk states of atactic amorphous polymers relaxed at a higher temperature were generated. The chain behaviors of polymethacrylates were investigated upon varying temperatures. Molecular structural information was then obtained by characterizing radial distribution function(RDF), mean square displacement, self diffusion constant, and Connolly surfaces, among others. The estimated self diffusion constants and RDF values of PMMA and PBMA were found to be in good agreement with our expectation in view of the chain flexibility.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제15권2호
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• pp.137-142
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• 2011

In this paper we formulate a predator-prey system in two patches in which the per capita migration rate of each species is influenced only by its own density, i.e. there is no response to the density of the other one. Numerical studies show that at a critical value of the bifurcation parameter the system undergoes a Turing bifurcation, i. e. the stable constant steady state loses its stability and spatially non-constant stationary solutions, a pattern emerge.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.352.2-352.2
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• 2014

In this present work, we report a Cu-Mn alloy as a materials for the self-forming barrier process. And we investigated diffusion barrier properties of self-formed layer on low-k dielectrics with or without UV curing treatment. Cu alloy films were directly deposited onto low-k dielectrics by co-sputtering, followed by annealing at various temperatures. X-ray diffraction revealed Cu (111), Cu (200) and Cu (220) peaks for both of Cu alloys. The self-formed layers were investigated by transmission electron microscopy. In order to compare barrier properties between Mn-based interlayer interlayer, thermal stability was measured with various low-k dielectrics. X-ray photoelectron spectroscopy analysis showed that chemical compositions of self-formed layer. The compositions of the Mn based self-formed barriers after annealing were determined by the C concentration in the dielectric layers.

• 패션비즈니스
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• 제19권6호
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• pp.112-126
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• 2015

In social environments, hashtags have been widely adopted and have become a new form of language for users. The current study attempts to enhance our understanding of users and their motivations to use hashtags when posting fashion-related information. Specifically, this study examines whether user characteristics (fashion leadership, conspicuousness) influence their motivations to use hashtags (curation, self-presentation, information diffusion), which then leads to behavioral intentions to continue to use hashtags and recommend the same to others. An online survey was administered to test our research questions. A total of 136 consumers in their 20s, 30s, and 40s living in Korea were used for data analysis. Structural equation modeling was conducted, which revealed that fashion leadership and conspicuousness had a positive impact on users' motivations of curation, self-presentation, and information diffusion. Motivations of self-presentation and information diffusions were found to affect users' behavioral intentions while curation had no significant impact. Practical implications are presented.

• Restorative Dentistry and Endodontics
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• 제39권1호
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• pp.32-38
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• 2014

Objectives: In this study, we evaluated the antibacterial activity of self-etching adhesive systems against Streptococcus mutans using the agar diffusion method. Materials and Methods: Three 2-step systems, Clearfil SE Bond (SE, Kuraray), Contax (CT, DMG), and Unifil Bond (UnB, GC), and three 1-step systems, Easy Bond (EB, 3M ESPE), U-Bond (UB, Vericom), and All Bond SE (AB, BISCO) were used. 0.12% chlorhexidine (CHX, Bukwang) and 37% phosphoric acid gel (PA, Vericom) were used as positive controls. Results: The antibacterial activity of CHX and PA was stronger than that of the other groups, except SE. After light activation, the inhibition zone was reduced in the case of all 2-step systems except CT. However, all 1-step systems did not exhibit any inhibition zone upon the light activation. Conclusions: SE may be better than CT or UnB among the 2-step systems with respect to antibacterial activity, however, 1-step systems do not exhibit any antibacterial activity after light curing.

• 대한수학회지
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• 제33권4호
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• pp.823-855
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• 1996

We study Dirichlet forms and the associated diffusion processes for the Gibbs measures related to the quantum unbounded spin systems (lattice boson systems) interacting via superstable and regular potentials. This work is a continuation of the author's previous study on the classical systems [LPY] to the quantum cases. In [LPY], we constructed Dirichlet forms and the associated diffusion processes for the Gibbs measures of classical unbounded spin systems. Furthermore, we also showed the essential self-adjointness of the Dirichlet operator and the log-Sobolev inequality for any Gibbs measure under appropriate conditions on the potentials. In this atudy we try to extend the results of the classical systems to the quantum cases. Because of some technical difficulties, we are only able to construct a Dirichlet form and the associated diffusion process for any Gibbs measure of the quantum systems. We utilize the general scheme of the previous work on the theory in infinite dimensional spaces [AH-K1-2, AKR, AR1-2, Kus, MR, Ro, Sch] and the ideas we employed in our study of the calssical systems ]LPY].

• 한국진공학회:학술대회논문집
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• 한국진공학회 2010년도 제39회 하계학술대회 초록집
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• pp.54-55
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• 2010

Vacancy defects in graphene can be created by electron or ion irradiation and those induce ripples which can change the electronic properties of graphene. Recently, the formation of defect structures such as vacancy defects and non-hexagonal rings has been reported in the high resolution transmission electron microscope (HR-TEM) of reduced graphene oxide [1]. In those HR-TEM images, it is noticed that the dislocations with pentagon-heptagon (5-7) pairs are formed and diffuses. Interestingly, it is also observed that two 5-7 pairs are separated and diffuse far away from each other. The separation of 5-7 pairs has been known to be due to their self-diffusion. However, from our tight-binding molecular dynamics simulation, it is found that the separation of 5-7 pairs is due to the diffusion of single vacancy defects and coalescence with 5-7 pairs. The diffusion and coalescence of single vacancy defects is too fast to be observed even in HR-TEM. We also implemented Van der Waals interaction in our tight-binding carbon model to describe correctly bi-layer and multi-layer graphene. The compressibility of graphite along c-axis in our tight-binding calculation is found to be in excellent agreement with experiment. We also discuss the difference between single layer and bi-layer graphene about vacancy diffusion and reconstruction.

• Journal of Electrochemical Science and Technology
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• 제2권2호
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• pp.76-84
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• 2011

Potentiostatic oxidation of Pb-1.7%Sb alloy used in the manufacture of grids of lead-acid batteries over the potential range from -1.0V to 2.3V in 5M $H_2SO_4$ in the absence and the presence of 0.4M $H_3PO_4$ and the self-discharge characteristics of the oxide layer formed is studied by electrochemical impedance spectroscopy (EIS). Depending on the potential value, sharp variations in resistance and capacitance of the alloy are recorded during the oxidation and they can be used for identification of the various substances involved in passive layer. Addition of $H_3PO_4$ is found to deteriorate the insulating properties of the passive layer by the retardation of the formation of $PbSO_4$. $H_3PO_4$ completely inhibits the current and impedance fluctuations recorded in $H_3PO_4$-free solutions in the potential range 0.5 V-1.7 V. These fluctuations are attributed to the occurrence of competitive redox processes that involve the formation of $PbSO_4$, $PbOSO_4$, PbO and $PbO_2$ and the repeated formation and breakdown of the passive layer. Self-discharge experiments indicate that the amount of $PbO_2$ formed in the presence of $H_3PO_4$ is lesser than in the $H_3PO_4$-free solutions. The start of transformation of $PbSO_4$ into $PbO_2$ is greatly shortened. $H_3PO_4$ facilitates the diffusion process of soluble species through the passive layer ($PbSO_4$ and basic $PbSO_4$) but impedes the diffusion process through $PbO_2$.

• 한국응용과학기술학회지
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• 제36권3호
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• pp.813-820
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• 2019

Oleic acid의 분자분절 운동에 대한 cholesterol 유도체들의 영향을 보다 잘 이해하기 위해 소량의 첨가물들이 포함된 oleic acid 시료에 대해 밀도, 점성도, IR, $^1H$ NMR, self-diffusion coefficient를 측정하였다. 이 측정을 통하여 cholesterol, cholestanol, cholestane, cholesteryl oleate, benzene, ethanol 등의 첨가물이 포함된 oleic acid 시료에 이들의 효과가 어떻게 나타나는지 알 수 있었다. OH기와 하나의 이중결합을 갖고 있는 cholesterol은 oleic acid의 점성도는 크게 증가시켰으나, 자체 확산계수, 분자내 운동은 감소시켰다. 다른 첨가물들을 시험한 결과 OH기의 유무, 이중결합의 정도에 따라 영향이 변화하였다. 벤젠과 에탄올의 경우 점성도는 감소하였으나 자체 확산계수와 분자내 운동은 증가하는 현상를 보여주었다. 이들 실험을 바탕으로 oleic acid는 에탄올 뿐 아니라 cholesterol과도 착물을 형성하고 또 착물이 이뤄지는 메카니즘에 대해서도 이해할 수 있었다. 이들 착물 형성과 oleic acid 이합체로 이루어진 집합체의 성질 조사를 바탕으로 oleic acid의 분자분절 운동에 대한 cholesterol의 영향을 알 수 있었다.