• 한국환경복원기술학회지
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• 제5권6호
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• pp.14-23
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• 2002

Daejeon is a large city in Korea and very high-speedly developing city. Recently urban area is expanding and large forest patch is fragmenting into small habitats because of urban sprawl. The fragmentation of large forest patch decreases the size of habitats and increases the loss of biodiversity in urban area. This study is to analysis the connectivity of green space of Daejeon metropolitan city, and suggest the optimum location of greening site and corridor in order to increase the connectivity of green space of Daejeon metropolitan city. The findings of this study are as follows; (1) The result of this study showed that ${\alpha}$ and ${\gamma}$ index are -0.24 and 0.20. A ${\alpha}$ index is very low and a ${\gamma}$ index is relatively low. (2) The dispersion was very high, for urban forest patches were isolated through fragmentation. Therefore, it needed ecological corridors in order to connect the patches. (3) A urban streams were very important in connectivity of urban green space. Urban riparian corridor must be preserved and restored. (4) A urban green space policy and planning must be prepared to increase the connectivity and assessment of alternatives must be accomplished from perspective of connectivity. The results of this study show the practical implications in perspective of green space planning and policy in Daejeon metropolitan city. The suggestions by findings of this study are to connect green space between large forest patch in urban fringe and island green space in inner city. Also, It is required that urban stream is restored to natural feature for use of corridor by wildlife.

• Advances in nano research
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• 제8권4호
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• pp.283-292
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• 2020

In the present research, differential quadrature (DQ) method has been utilized for investigating free vibrations of porous functionally graded (FG) micro/nano beams in thermal environments. The exact location of neutral axis in FG material has been assumed where the material properties are described via porosity-dependent power-law functions. A scale factor related to couple stresses has been employed for describing size effect. The formulation of scale-dependent beam has been presented based upon a refined beam theory needless of shear correction factors. The governing equations and the associated boundary conditions have been established via Hamilton's rule and then they are solved implementing DQ method. Several graphs are provided which emphasis on the role of porosity dispersion type, porosity volume, temperature variation, scale factor and FG material index on free vibrational behavior of small scale beams.

• Journal of the Optical Society of Korea
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• 제8권4호
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• pp.163-167
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• 2004

We propose and demonstrate an external optical modulation method based on TE/TM-mode absorption nulls in a Multiple Quantum Well(MQW) Fabry-Perot laser diode(FP-LD). The center wavelength of the absorption nulls is rapidly shifted to short-wavelength by the small current change(~1mA) in the FP-LD, which can modulate an optical signal with more than 10 dB of extinction ratio(ER). The shift of the center wavelength comes from the refractive index change due to anomalous dispersion and the plasma effect in MQW FP-LD waveguide. Non-inverting and inverting signals are made by TE- and TM-mode absorption nulls at 155.52 Mbps and BERs for the signals are measured.

• Journal of Magnetics
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• 제20권2호
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• pp.110-113
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• 2015

Two kinds of magnetic fluids with different volume fractions are symmetrically filled into the W0.9 photonic crystal waveguide structure. The 2D plane-wave expansion method is used to investigate the slow light properties numerically. The constant group index criterion is employed to evaluate the slow light performance. The wavelength bandwidth ${\Delta}{\lambda}$ centering at ${\lambda}_0=1550nm$ varies from 32.4 to 44.2 nm when the magnetic field factor ${\alpha}_{\parallel}$ changes from 0 to 1. And the corresponding normalized delay bandwidth product can be tuned from 0.221 to 0.258. For comparison and optimization, two infiltration cases are investigated and the more advantageous infiltration scheme is found.

• 한국전자통신학회논문지
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• 제9권3호
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• pp.393-402
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• 2014

ICT환경에서 통계청이 조사하여 발표한 2012년 가계금융. 복지조사에 따르면 우리나라 전체가구중 금융자산은 24.9%, 부동산은 이보다 약 3배나 많은 69.9%로 조사되었다. 문제는 정보화가 더디고, 소득분위(1~4분위)가 낮은 가구가 상대적으로 높은 비율(78.8%~69%)의 부동산자산을 보유함으로써 세계경제의 불확실성 확대와 저성장과 저소비, 정보화로 인한 재택근무 증가 등과 같은 경제구조의 변화로 부동산 가격하락 리스크에 그대로 노출되어 있어 하우스푸어와 랜트푸어와 같은 현상은 저소득층에게 더 심각한 현상이 될 수밖에 없다. 이에 상관관계가 낮은 복합자산으로 포트폴리오를 구성함으로써 개별자산 위험의 가중평균보다 전체수익은 높이면서 위험은 감소시킬 수 있다는 포트폴리오 원리에 기초하여 지역과 유형별로 상이한 ICT환경에서 부동산가격지수로 구성된 포트폴리오에 상관관계가 낮은 금융자산을 포함시킴으로써 복합자산 포트폴리오의 분산효과를 안정형과 성장형으로 나눠 실증 분석하였다.

• 전자공학회논문지CI
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• 제45권3호
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• pp.149-159
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• 2008

참조 영상을 이용하여 영상의 분위기를 전환하고자 할 때, 영상의 분위기에 영향을 주는 요소 중 하나인 색을 이용하여 영상이 가지는 분위기를 변환한다. 색을 변환할 때, 국부적인 색상의 특징을 반영하기 위해 입력 영상의 화소에 대하여 색인을 하는데 낮은 채도 상에서는 색상의 식별력 저하로 인해 부적절한 색인의 색상 항목으로 색인이 되는 문제가 발생한다. 따라서 본 논문에서는 유채색과 무채색을 분리하여 처리함으로써, 낮은 채도 상에서의 잘못된 색인이 일어나지 않도록 제한하는 기법을 제안한다. 제안하는 기법은 채도의 문턱치를 이용하여 유채색과 무채색을 구분하는 단계, 구분된 화소들을 실린드리컬 거리(Cylindrical metric)를 이용하여 11가지 색상 항목(Index color)으로 색인을 하는 단계, 각 색상 항목의 우선순위 결정하고 평균과 표준편차를 구하는 단계, 마지막으로 Lab 색 공간에서 색을 변환하고 영상의 잡음과 의사 윤곽선(pseudo-contour)을 제거하기 위한 후처리 단계의 4단계로 구성된다. 실험결과를 통해 제안하는 기법은 낮은 채도 상에서도 유채색과 무채색이 잘 분리되어 색인이 되었으며 원본 영상의 색이 참조 영상의 색으로 자연스럽게 변환된 결과를 얻을 수 있음을 확인하였다.

• Advances in concrete construction
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• 제14권3호
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• pp.169-183
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• 2022

In this article, vibrational behavior and wave propagation characteristics in (FG) functionally graded plates resting on Kerr foundation with three parameters is studied using a 2D dimensional (HSDT) higher shear deformation theory. The new 2D higher shear deformation theory has only four variables in field's displacement, which means has few numbers of unknowns compared with others theories. The shape function used in this theory satisfies the nullity conditions of the shear stresses on the two surfaces of the FG plate without using shear correction factors. The FG plates are considered to rest on the Kerr layer, which is interconnected with a Pasternak-Kerr shear layer. The FG plate is materially inhomogeneous. The material properties are supposed to vary smoothly according to the thickness of the plate by a Voigt's power mixing law of the volume fraction. The equations of motion due to the dynamics of the plate resting on a three-parameter foundation are derived using the principle of minimization of energies; which are then solved analytically by the Navier technique to find the vibratory characteristics of a simply supported plate, and the wave propagation results are derived by using the dispersion relations. Perceivable numerical results are fulfilled to evaluate the vibratory and the wave propagation characteristics in functionally graded plates and some parameters such wave number, thickness ratio, power index and foundation parameters are discussed in detail.

• 자원환경지질
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• 제30권6호
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• pp.587-601
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• 1997

This study had three purposes: (1) to investigate the enrichment levels and dispersion patterns of potentially toxic elements in the rock-soil-plant system; (2) to evaluate the uptake ratios of heavy metals from soils into plants and (3) to assess the chemical speciation of heavy metals in soils. Rock, surface soil and plant samples were collected in the Boeun area underlain by black shales of the Okchon Zone. These samples were analyzed for multi-elements using INAA, ICP-AES and AAS. The maximum abundance of U in black shales is 16 mg/kg and radioactivity counts up to 300 cpm. In particular, Mo, V, Ba, Cd, Pb and U are enriched in black shales. Most of soils derived from black shales show high concentrations of U, As, Mo, Ba, Cu, Cd, Pb, Zn and mean concentrations of As and Mo in soils (20 mg/kg of As and 6.6 mg/kg of Mo) are higher than the permissible level suggested by Kloke (1979). Enrichment index values of soils are calculated and higher than 1.0 in the black shale area with the highest value of 6.4. Mean concentration of Cd in plants is higher than those of Cu, Pb and Zn. The concentration of Cd in plant species decreases in the order of Chinese cabbage > red pepper > soybean=sesame > rice stalk > com > rice grain. The biological absorption coefficients (BAC) in plants are in the order of Cd > Zn=Cu > Pb, which suggests that Cd is more bioavailable to plants than Cu, Pb and Zn. From the results of sequential extraction analysis of soils, relatively high proportion of Cu, Pb and Zn are present as residual fractions whereas that of Cd as non-residual fractions. Cadmuim occurs predominantly as exchangeable/water-acid soluble phase in soils, and Cd is more mobile and bioavailable than Cu, Pb and Zn.

• 한국광학회지
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• 제15권2호
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• pp.89-99
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• 2004

금속에서의 흥미로운 광학적 특성들은 주로 표면 폴라리톤(surface polaritons: SP)의 기여에 의해 나타난다. 물질상수(유전율과 투자율)가 모두 음수인 왼손잡이 물질(left-handed materials: LHM)의 표면에서도 두 종류의 SP인 표면 전기-폴라리톤(surface electric-polariton: SEP), 또는, 표면 자기-폴라리톤(surface magnetic-polariton: SMP)이 형성되어 군속도와 위상속도가 서로 반전되는 경우가 발생한다. 본 논문에서는 금속물질과 LHM와 같은 메타물질(metamaterials)의 경계면에서 발생하는 SP의 전파특성을 분산관계를 통하여 분석하였다. 임의의 물질상수를 갖는 두 매질의 경계면에서 SEP와 SMP가 생성될 수 있는 일반화된 조건을 도출하였으며, 양쪽 매질을 통해 전파하는 에너지 비율의 차이에 의해 군속도와 위상속도가 반전된다는 물리적인 원인을 제안하였다. 도출된 SP 생성조건을 이용하여 금속물질과 메타물질의 경계면에서 전파하는 SEP와 SMP의 분산관계를 구하고, 주파수에 따라 다양한 SP의 전파특성이 나타날 수 있음을 보였다. SEP 및 SMP 분산관계로부터 구한 정량화 된 전파특성은 SP가 존재하기 위한 매질의 일반화된 조건과 에너지 전파 비율의 계산으로부터 얻은 결과와 일치함을 확인하였다. 특히, 두 매질 중 어느 한 매질이 LHM이 아니더라도 SP은 위상속도와 군속도가 반전되어 전파될 수 있음을 밝혀내었다.

• 한국세라믹학회지
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• 제54권1호
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• pp.49-54
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• 2017

In this study, based on hydrolysis and condensation via $St{\ddot{o}}ber$ process of sol-gel method, synthesis of mono-dispersed silica nanoparticles was carried out with hydrophilic solvent. This operation was expected to be a more simplified process than that with organic solvent. Based on the sol-gel method, which involves simply controlling the particle size, the particle size of the synthesized silica specimens were ranged from 30 to 300 nm by controlling the composition of tetraethylorthosilicate (TEOS), DI water and ammonia solution, and by varying the stirring speeds while maintaining a fixed amount of ethanol. Increasing the content of DI water and decreasing the content of ammonia caused the particle size to decrease, while controlling the stirring speed at a high level of RPMs enabled a decrease of the particle size. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) were utilized to investigate the success factors for synthesizing process; Field emission scanning electron microscopy (FE-SEM) was used to study the effects of the size and morphology of the synthesized particles. To analyze the dispersion properties, zeta potential and particle size distribution (PSD) analyses were utilized.