• Structural Engineering and Mechanics
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• 제65권5호
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• pp.573-585
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• 2018

This article presents strain gradient elasticity-based procedures for static bending, free vibration and buckling analyses of functionally graded rectangular micro-plates. The developed method allows consideration of smooth spatial variations of length scale parameters of strain gradient elasticity. Governing partial differential equations and boundary conditions are derived by following the variational approach and applying Hamilton's principle. Displacement field is expressed in a unified way to produce numerical results in accordance with Kirchhoff, Mindlin, and third order shear deformation theories. All material properties, including the length scale parameters, are assumed to be functions of the plate thickness coordinate in the derivations. Developed equations are solved numerically by means of differential quadrature method. Proposed procedures are verified through comparisons made to the results available in the literature for certain limiting cases. Further numerical results are provided to illustrate the effects of material and geometric parameters on bending, free vibrations, and buckling. The results generated by Kirchhoff and third order shear deformation theories are in very good agreement, whereas Mindlin plate theory slightly overestimates static deflection and underestimates natural frequency. A rise in the length scale parameter ratio, which identifies the degree of spatial variations, leads to a drop in dimensionless maximum deflection, and increases in dimensionless vibration frequency and buckling load. Size effect is shown to play a more significant role as the plate thickness becomes smaller compared to the length scale parameter. Numerical results indicate that consideration of length scale parameter variation is required for accurate modelling of graded rectangular micro-plates.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권10호
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• pp.4060-4079
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• 2020

Blur is an important type of image distortion. How to evaluate the quality of blurred image accurately and efficiently is a research hotspot in the field of image processing in recent years. Inspired by the multi-scale perceptual characteristics of the human visual system (HVS), this paper presents a no-reference image blur/sharpness assessment method based on multi-scale local features in the spatial domain. First, considering various content has different sensitivity to blur distortion, the image is divided into smooth, edge, and texture regions in blocks. Then, the Gaussian scale space of the image is constructed, and the categorized contrast features between the original image and the Gaussian scale space images are calculated to express the blur degree of different image contents. To simulate the impact of viewing distance on blur distortion, the distribution characteristics of local maximum gradient of multi-resolution images were also calculated in the spatial domain. Finally, the image blur assessment model is obtained by fusing all features and learning the mapping from features to quality scores by support vector regression (SVR). Performance of the proposed method is evaluated on four synthetically blurred databases and one real blurred database. The experimental results demonstrate that our method can produce quality scores more consistent with subjective evaluations than other methods, especially for real burred images.

• 한국수자원학회논문집
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• 제31권5호
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• pp.553-564
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• 1998

지하저장공동의 적절한 설계와관리를 위해서는 공동주위의 지하수 흐름이 분석되어야 한다. 지하수 흐름은 수리전도도의 공간적인 변동성에 의해 영향을 받게 되므로 본 연구에서는 이러한 영향분석을 위해 추계학적 개념을 도입한 2차원 유한요소모형을 개발하였다. 추계학적으로 정의된 불균일 매질에서의 2차원 정류흐름에 대한 근사해를 얻기 위해 Monte carlo 방법을 이용하엿으며, 이를 위해 알려진 평균과 표준편차를 가진 수리전도도를 발생시켰다. 모형을 통한 예측결과의 불확실성은 수리전도도의 불균일성 뿐 아니라 수막시설이나 경계조건과 같은 흐름계의 성질에도 좌우되는 것으로 나타났다. 따라서 수두와 동수경사의 예측에 대한 불확실성은 평균동수경사가 상대적으로 큰 공동직상부에서 크고, 경계로부터 멀수록 커지는 것으로 확인되었다. 본 연구에서는 특히 동수경사의 불확실성을 널리 안려진 기밀조건식과 관계시켜 분석하였다.

• 대한원격탐사학회지
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• 제26권5호
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• pp.581-591
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• 2010

본 연구에서는 주파수 및 공간 도메인 상에서 선호 분석에 장점이 있는 웨이블릿 기반의 영상 융합 알고리듬을 제안하였다. 개발된 알고리듬은 레이더 영상 신호와 광학 영상 신호의 상대적인 크기를 비교하여 상대적으로 신호 크기가 큰 경우에는 레이더 영상 신호를 융합 영상에 할당하고 크기가 작은 경우에는 레이더 영상 신호와 광학 영상 선호의 가중치 합으로 융합 영상 신호를 결정한다. 사용되는 융합 규칙은 두 영상 신호의 상대적인 신호 비(ratio) 영상 그레디언트, 로컬 영역의 분산 특성을 동시에 고려한다. Ikonos 위성 영상과 TerraSAR-X 위성 영상을 이용한 실험에서 상대적으로 신호 크기가 큰 레이더 신호 만을 융합 영상에 할당하는 기존 방법에 비해 entropy, image clarity, spatial frequency, speckle index 측면에서 우수한 융합 결과를 얻었다.

• 환경영향평가
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• 제18권3호
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• pp.161-170
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• 2009

As urban growth continues, the earth ecosystem is increasingly dependent on the patterns of urban growth. The impact intensity from urban growth is expected to change predictably with distance from the urban center. However we can't fully understand yet how urban development pattern affects urban ecosystem. In researches about urban ecosystem, it is important to relate the spatial pattern of urbanization to ecological processes. So we used gradient analysis with time data; 1980's, 1990's and 2000's. We attempted to quantify the urban spatiotemporal impacts in Daejeon-city and Cheonan-city, Korea, along a 75km long and 3km wide transect. Through the results, we found the impacts range of urbanization with urban development process of two cities. When the urban growth was concentrated on in both cities, the impacts intensity and range were much stronger and wider. As a result, in urban planning or green space planning, we have to consider suitable urban development forms with surrounding areas, and make legal clauses which limits landuse change. This quantifying the urban gradient is an important step in understanding urban ecology.

• 대한공간정보학회지
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• 제10권2호
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• pp.67-75
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• 2002

최근 GIS는 수자원 분야에서 활발하게 연구되고 있다. 이는 GIS가 수문해석을 하는데 있어서 설계자의 주관적인 요소를 객관적으로 발진시킬 수 있는 방안이라 해석되기 때문이다. 최근의 많은 개발사업들은 토사 발생을 유발시켜 재해의 원인이 되고 있기 때문에, 이러한 재해를 사전에 대처하기 위하여 재해영향평가를 시행을 하고 있다. 따라서, 본 연구에서는 재해영향평가에 따른 토사유출 산정시 LS인자의 값을 DEM자료를 통하여 얻고, 격자의 크기에 따른 경사도의 영향과 토사유출량의 변화가 어떠한 관계가 있는지를 비교 분석하였다. 그 결과, 격자의 크기가 커짐에 따라 경사도가 감소하는 경향을 보였고, 수치지형도의 축척이 작아짐에 따라서도 경사도가 감소함을 알 수 있었다.

• 천문학회보
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• 제41권2호
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• pp.30.1-30.1
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• 2016

We have estimated a metallicity map of the Large Magellanic Cloud (LMC) using the Magellanic Cloud Photometric Survey (MCPS) and Optical Gravitational Lensing Experiment (OGLE III) photometric data. This is a first of its kind, high-spatial resolution map of metallicity up to a radius of $4^{\circ}-5^{\circ}$, derived using large area photometric data and calibrated using spectroscopic data of Red Giant Branch (RGB) stars. The RGB is identified in the V, (V - I) colour- magnitude diagrams of small subregions of varying sizes in both data sets. The slope of the RGB is used as an indicator of the mean metallicity of a subregion, and it is calibrated to metallicity using spectroscopic data for field and cluster red giants in selected subregions. The mean metallicity of the LMC is found to be [Fe/H] = -0.37 dex (${\sigma}[Fe/H]=0.12$) from MCPS data, and [Fe/H] = -0.39 dex (${\sigma}[Fe/H]=0.10$) from OGLE III data. The bar is found to have an uniform and higher metallicity compared to the disk, and is indicative of an active bar in the past. Both the data sets suggest a shallow radial metallicity gradient up to a radius of 4 kpc ($-0.049{\pm}0.002$ dex kpc-1 to $-0.066{\pm}0.006$ dex kpc-1). This metallicity gradient of the LMC disk, though shallow, resembles the gradient seen in spiral galaxies, and similar to that found in our Galaxy.

• 한국지능시스템학회논문지
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• 제15권7호
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• pp.852-857
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• 2005

본 논문은 지능형 로봇 시스템을 위한 인간 몸의 하이브리드 실루엣 추출 기법을 제안한다. 지능형 로봇은 내부적인 진동과 낮은 해상도로 인해 강인한 실루엣 추출을 필요로 한다. 이를 극복하기 위해서 본 논문에서는 하이브리드 실루엣 추출 기법을 제안하였다. 하이브리드 실루엣은 영상간의 공간차 및 시간차 정보를 고려 생성되며 움직임 영역 모델을 통해 두 정보간의 중요성에 가중치를 준다. 최종적으로 실험결과를 통해 제안된 기법의 우수성을 확인하였다.

• 말소리와 음성과학
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• 제12권2호
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• pp.17-27
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• 2020

This paper examines kinematic characteristics of /pk/ clusters, as compared to /kk/ and /pp/ with varying vowel contexts and speech rate. The results of EMMA data from eight Seoul-Korean speakers indicate as follows. Firstly, comparing /pk/ to /pp/ sequences, lips closing movement was faster and spatially greater in the /a/-to-/a/ context while temporally longer in the /i/-to-/i/ context. It was smaller in spatial displacement and shorter in temporal duration in /pk/ sequences. Peak velocity did not vary. Secondly, comparing /pk/ with /pp/ and /kk/ controls, lip aperture was less constricted in the /a/-to-/a/ context than /i/-to-/i/, but the maximum contact between the upper and lower lips was invariant across different vocalic contexts within /pk/ sequences (/apka/=/ipki/). Categorical reduction of C1 in /pk/ sequences fell in with the low-vowel and fast-rate conditions with across-/within-speaker variability. Gradient reduction of C1 was observed in all C1C2 types, being more frequent in fast rate. Lastly, the jaw articulator was a stable indicator of rate effects. The implication of the current study is that gestural reduction occurs with categorical reduction and general spatiotemporal weakening in the assimilating contexts, while quantitative properties of gestures may be a reason for gradient reduction, not necessarily confined to place assimilation.

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 2005년도 추계학술대회 학술발표 논문집 제15권 제2호
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• pp.257-260
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• 2005

This paper discusses a human body extraction method for mobile robot system. The skeleton features are used to analyze human motion and pose estimation. The intelligent robot system requires more robust silhouette extraction method because it has internal vibration and low resolution. The new hybrid silhouette extraction method is proposed to overcome this constrained environment. Finally, the experimental results show the superiority of the Proposed method.