• 한국세라믹학회지
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• 제25권3호
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• pp.243-250
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• 1988

전자 전도체 이온 결합 화합물, $A_{1-\delta}O_\mu$에서 전자의 흐름과 이온의 흐름 사이에서 일어나는 간섭 현상을 비가역 열역학적으로 분석하였다. 이 계를 가역 전극 사이에 두고 전기를 흘리면 주된 전하 나르게인 전자의 흐름에 의하여 잘 움직이는 양이온 빈자리들의 알짜 흐름이 유발되며, 이 반자리의 흐름은 Fick 좌표계를 실험실 좌표계에 대하여 상대적으로 움직이게 한다는 것이 드러났다. 따라서 이 상대속도는 전자와 이온의 흐름간 간섭효과의 크기와 방향을 결정하는 양이온 유효전하의 척도가 되는 것이다. 이 상대속도를 측정하는 두 가지의 실험을 고안하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1876-1881
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• 2003

When a projectile travels at high speed underwater, supercavitating flow arises, in which a huge cavity is generated behind the projectile so that only the nose, i.e., the cavitator, of the projectile is wetted, while the rest of it should be surrounded by the cavity. In that case, the projectile can achieve very high speed due to the reduced drag. Furthermore if the nose of the body is shaped properly, the attendant pressure drag can be maintained at a very low value, so that the overall drag is also reduced dramatically. In this study, shape optimization technique is employed to determine the optimum cavitator shape for minimum drag, given certain operating conditions. Shape optimization technique is also used to solve the potential flow problem for any given cavitator, which is a free boundary value problem having the cavity shape as unknown a priori. Analytical sensitivities are derived for various shape parameters in order to implement a gradient-based optimization algorithm. Simultaneous optimization technique is proposed for efficient cavitator shape optimization, in which the cavity and cavitator shape are determined in a single optimization routine.

• KSBB Journal
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• 제23권1호
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• pp.96-100
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• 2008

한국산 녹차로부터 HPLC On-line $ABTS^{+}$ screening기법을 사용하여 catechin compounds의 특성중의 하나인 항산화활성을 빠르게 분석하였으며 녹차로부터 catechin compound의 추출을 다양한 온도와 시간의 추출방법을 적용하였다. 전 처리한 추출액에 포함된 catechin compounds을 분석하고 최적의 추출조건을 실험적으로 모색하였다. 실험결과에 의하면 추출온도 $60^{\circ}C$, 추출시간 3분으로 추출한 시료가 항산화활성이 가장 우수하였다.

• 농약과학회지
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• 제2권1호
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• pp.1-11
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• 1998

The generally accepted idea for carbohydrate translocation in plants is an osmotic pressure flow hypothesis. According to the hypothesis, a high concentration of carbohydrate in the phloem of carbohydrate synthesis regions (source) causes a water influx into the phloem. The generated osmotic potential in the phloem is responsible for long distance carbohydrate transport through the positive hydrostatic pressure. In regions of carbohydrate utilization and storage (sink), translocated carbohydrates are continuously metabolized and compartmentalized, generating a concentration gradient between source and sinks. In this system, carbohydrates load into the phloem (phloem loading) and unload out of the phloem (phloem unloading). Phloem-mobile herbicides that are applied to plants are also translocated from the source to sinks. However, some experimental results reveal that the patterns of phloem translocation between carbohydrates and herbicides are different. The differences are due, in part, to the physico-chemical properties of herbicides and to the absence/presence of specific carrier(s) in the phloem.

• Natural Product Sciences
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• 제19권1호
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• pp.15-19
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• 2013

Analysis of flavonoid contents in the fruits of Acanthopanax species (A. chiisanensis, A. divaricatus, A. koreanum, A. senticosus, and A. sessiliflorus) was conducted by high performance liquid chromatography. A Discovery$^{(R)}$ C18 ($4.6{\times}250$ mm, 5 ${\mu}m$) column was used with a gradient mobile phase of water and acetonitrile (90 : 10 to 60 : 40 for 60 min) and UV detection was conducted at 350 nm. The contents of rutin, hyperin, quercetin, afzelin, and kaempferol were 0.063~0.540, 0.494~7.480, 0.584~0.704, 0.388~0.567, 0.190~0.471 mg/g, respectively, in the fruits of Acanthopanax species. Total content of flavonoids in the fruits of Acanthopanax species was highest in those of A. chiisanensis. Furthermore, hyperin was the most abundant compound in the fruits of Acanthopanax species. Consequently, our results demonstrate that the fruits of Acanthopanax species containing flavonoids have promising potential as a new income source of agriculture and industry in medicinal natural products, health supplements, and beverages.

• Tribology and Lubricants
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• 제36권5호
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• pp.290-296
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• 2020

When two layers of carbon nanotube (CNT) arrays are loaded to mate, the free ends of individual CNTs come into contact at the interface of the two layers. This leads to a higher contact resistance due to a smaller contact region. However, when the free CNT ends of one array penetrate into the mating array, the contact region increases, effectively lowering the contact resistance. To explore the penetration of mating CNTs, we perform molecular dynamic simulations of a simple unit cell model, incorporating four CNTs in the lower array layer coupled with a single moving CNT on the upper layer. The interaction with neighboring CNTs is modelled by long-range carbon bond order potential (LCBOP I). The model structure is optimized by energy minimization through the conjugate gradient method. A NVT ensemble is used for maintain a room temperature during simulation. The time integration is performed through the velocity-Verlet algorithm. A significant vibrational motion of CNTs is captured when penetration is not available, resulting in a specific vibration mode with a high frequency. Due to this vibrational behavior, the random behaviors of CNT motion for predicting the penetration are confirmed under the specific gap distances between CNTs. Thus, the probability of penetration is examined according to the gap distance between CNTs in the lower array and the aspect ratio of CNTs. The penetration is significantly affected by the vibration mode due to the van der Waals forces between CNTs.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권11호
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• pp.5583-5604
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• 2016

In this paper, we present a novel image operator to extract textual information in natural scene images. First, a powerful refiner called the Stroke Color Extension, which extends the widely used Stroke Width Transform by incorporating color information of strokes, is proposed to achieve significantly enhanced performance on intra-character connection and non-character removal. Second, a character classifier is trained by using gradient features. The classifier not only eliminates non-character components but also remains a large number of characters. Third, an effective extractor called the Character Color Transform combines color information of characters and geometry features. It is used to extract potential characters which are not correctly extracted in previous steps. Fourth, a Convolutional Neural Network model is used to verify text candidates, improving the performance of text detection. The proposed technique is tested on two public datasets, i.e., ICDAR2011 dataset and ICDAR2013 dataset. The experimental results show that our approach achieves state-of-the-art performance.

• Design & Manufacturing
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• 제12권1호
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• pp.1-6
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• 2018

In this study, we calculated the redistribution of vacancy concentration in metal specimens induced by stress-induced diffusion at a high temperature. To deduce the governing equation, we associated the unit volume change equation of strains with a differential equation of vacancy concentration as a function of stress using the stress-strain relationship. In this governing equation, we considered stress as the only chemical potential parameter to stay in the scope of this study, which provided the vacancy concentration equation as of stress gradient in metals. The equation was then mathematically delineated to derive a analytical solution for a transient, one-dimensional diffusion case. With the help of Korhonen's approximation and the boundary conditions, we successfully deduced a general solution from the governing equation. To visualize the feasibility of our solutions, we applied the solution to two different stress-induced cases - a rod with fixed concentrated stresses at both ends and a rod with varying concentrated stresses at both ends. Although it is necessary to legitimatized the model in the future for improvement, our results showed that the model can be used to interpret the location of structural defects, the formation of vacancy, and furthermore the high temperature behavior of metals.

• Journal of Magnetics
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• 제13권4호
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• pp.124-127
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• 2008

The magnetic and electronic properties of Ni impurity in bcc Fe ($Ni_1Fe_{26}$) are investigated using the full potential linearized augmented plane wave (FLAPW) method based the generalized gradient approximation (GGA). We found that the Ni impurity in bcc Fe increases both the lattice constant and the magnetic moment of bcc Fe. The calculated equilibrium lattice constant of $Ni_1Fe_{26}$ in the ferromagnetic state was 2.84 A, which is slightly larger than that of bcc Fe (2.83 ${\AA}$). The averaged magnetic moment per atom of $Ni_1Fe_{26}$ unit cell was calculated to be $2.24{\mu}_B$, which is greater than that of bcc Fe (2.17 ${\mu}_B$). The enhancement of magnetic moment of $Ni_1Fe_{26}$ is mainly contributed by the nearest neighbor Fe atom of Ni, i.e., Fe1, and this can be explained by the spin flip of Fe1 d states. The density of states shows that Ni impurity forms a virtual bound state (VBS), which is contributed by Ni $e_{g{\downarrow}}$ states. We suggest that the VBS caused by the Ni impurity is responsible for the spin flip of Fe1 d states.

• Journal of Magnetics
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• 제13권4호
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• pp.115-119
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• 2008

The authors predicted that $Co_2HfSi$, a $Co_2$-based full Heusler alloy, is being a half-metallic ferromagnet by first-principles calculations using the all electron full-potential linearized augmented plane wave method which adopts the generalized gradient approximation. The integer value of the calculated total magnetic moment of 2.00 ${\mu}_B$ per formula unit and a spin gap of 0.69 eV in spin down state confirmed the half-metallicity of bulk $Co_2HfSi$. For the $Co_2HfSi$(001) surface, we considered two possible surface terminations, namely, Co terminated and HfSi terminated surfaces. It was found that half-metallicity was retained at the HfSi-terminated surface but not at the Co-terminated surface. The magnetic moment of surface Co atoms in the Co-terminated surface was slightly lower than that of Co atoms in deep inner-layers, whereas the magnetic moments of Hf and Si atoms at the HfSi-terminated surface were almost same as those in deep inner-layers.