• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.101-106
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• 2004

In this paper, a blood vessel in an angiographic image, which plays an importance role in the diagnose diseases including in the eyes, brain and heart, is enhanced by using a directed diffusion technique. A fundamental component of the angiographic analysis is vessel segmentation that the proposed method provides a preprocessing of the image into a form suitable for human analysis, or more importantly, for machine analysis such the segmentation. Vessel enhancement is a challenging problem due to the complex nature of vascular trees and to imaging imperfections. Some parts of the inherent imperfections in angiography are the intensity inhomogeneity between the larger and smaller vessels, and another imperfection is the leakage of contrast agent into the background tissue that provides to low contrast between vessels and tissue. In the proposed scheme, the directed diffusion solves the problem by formulating a local geometric structure, which consists of direction and scale of the blood vessels. The diffusion process uses the local structure to enhance by a diffusivity tensor. The proposed algorithm can be applied to maintain sharpness and coherence-smooth the intra-regions into homogeneity better than traditional diffusion methods, which are Gaussian regulation and coherence enhancing diffusion.

• Journal of Information Processing Systems
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• 제18권1호
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• pp.59-74
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• 2022

During the last decade, the security of digital images has received considerable attention in various multimedia transmission schemes. However, many current cryptosystems tend to adopt a single-layer permutation or diffusion algorithm, resulting in inadequate security. A hierarchical bilateral diffusion architecture for color image encryption is proposed in response to this issue, based on a hyperchaotic system and DNA sequence operation. Primarily, two hyperchaotic systems are adopted and combined with cipher matrixes generation algorithm to overcome exhaustive attacks. Further, the proposed architecture involves designing pixelpermutation, pixel-diffusion, and DNA (deoxyribonucleic acid) based block-diffusion algorithm, considering system security and transmission efficiency. The pixel-permutation aims to reduce the correlation of adjacent pixels and provide excellent initial conditions for subsequent diffusion procedures, while the diffusion architecture confuses the image matrix in a bilateral direction with ultra-low power consumption. The proposed system achieves preferable number of pixel change rate (NPCR) and unified average changing intensity (UACI) of 99.61% and 33.46%, and a lower encryption time of 3.30 seconds, which performs better than some current image encryption algorithms. The simulated results and security analysis demonstrate that the proposed mechanism can resist various potential attacks with comparatively low computational time consumption.

• Computers and Concrete
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• 제34권2호
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• pp.169-178
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• 2024

To circumvent the constraints of time-consuming experimental methods, numerical simulation can be one of the most effective approaches to investigating chloride diffusion behaviors in concrete. However, except for the effect of the external environments, the transport direction of the chloride cannot be neglected when the concrete is exposed to the marine tidal zone, especially in certain areas of concrete members. In this study, based on Fick's second law, considering the effects of timevarying, chloride binding capacity, concrete stress state, ambient temperature, and relative humidity on chloride diffusion coefficient, the modified one-dimensional, two-dimensional, and three-dimensional novel modified chloride diffusion theoretical models were established through defining the current boundary conditions. The simulated results based on the novel modified multi-dimensional model were compared with the experimental results obtained from some previous pieces of literature. The comparing results showed that the modified multi-dimensional model was well-fitted with experimental data, confirming the high accuracy of the novel modified model. The experimental results in literature showed that the chloride diffusion in the corner area of the concrete structure cannot be simulated by a simple one-dimensional diffusion model, where it is necessary to select a suitable multi-dimensional chloride diffusion model for simulation calculation. Therefore, the novel modified multi-dimensional model established in this study has a stronger applicability for practical engineering.

• 한국기후변화학회지
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• 제8권2호
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• pp.81-89
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• 2017

In this study CALPUFF was used to estimate the influence of temperature rise, according to the observation value of temperature rise based RCP scenario, on meteorological elements (wind direction, wind speed, mixing height) and the change of pollutant diffusion. According to the result. applying estimated value of year 2050 temperature rise, the mixing height is increased as per the temperature rise, so the range of atmospheric diffusion is widened. In summer case, by applying temperature rise of $4^{\circ}C$ and comparing with before applying temperature rise, there was change of diffusion range as per the change of temperature between 10 AM to 11 PM. And the range of diffusion was wider than that of before temperature rise. In winter case, by applying estimated value of temperature rise, $2.3^{\circ}C$, diffusion range has been changed between 8 AM to 4 PM, showing different diffusion aspect from summer. Also, according to the result of air pollution level assessment with temperature rise, it was proved that the ratio of area with increasing air pollution level has been getting higher by increase of temperature.

• 한국대기환경학회지
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• 제16권4호
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• pp.339-350
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• 2000

The three-dimensional new corrdinate system over a single hill double hills and complex terrain with a single hill and a rectangular obstacle was generated using a body-fitted coordinate system. Control of the coordinate line distribution in the field was executed by generalizing the elliptic generating system to Poisson equation. ▽2ξ=P. The new coordinate system was well fitted to the surface boundary of single hill and double hills. But in the case of complex terrain with hill and rectangular obstacle there was smoothing tendency around the rectangular obstacle. In order to show the validity of the body-fitted coordinate system the heat diffusion equation was transformed and the temperature distribution was calculated over the various terrain. The results showed the temperature distribution was very symmetrical and stable around hills and obstacle. As a result the couple of a body-fitted coordinate system and the heat diffusion equation were executed successfully. Wind field over complex terrain with hill and rectangular obstacle which represent urban area was simulated stably in body-fitted coordinate system. The qualitative result show the enhancement of wind speed at the upwind direction of a hill and a rectangular obstacle and the recirculation zone at the downwind direction.

• 한국해안·해양공학회논문집
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• 제20권1호
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• pp.62-72
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• 2008

본 연구에서는 흐름에 수직한 방향으로 급격한 수심 변화가 존재하는 해역에서 점열원에 의한 열오염 분포를 예측할 수 있는 해석 모델을 개발하였다. 개발된 모델을 이용하여 열오염 분포에 있어 수심 변화와 흐름효과를 검토하였다. 계산 결과 흐름에 수직한 방향으로 수심 변화가 존재할 경우 수평 확산 플럭스의 증감으로 인해 수심 변화 경계를 가로지르는 열의 이동이 증가하거나 감소하는 것으로 나타났다. 조류와 동시에 잔차류 성분을 포함할 경우에는 이류에 의한 열오염 수송 효과가 증가하여 수심 변화 경계를 가로지르는 수평 확산은 상대적으로 감소하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 추계학술대회 논문집
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• pp.464-467
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• 1999

The undoped-InSe and Sn-doped InSe single crystals were grown by vertical Bridgman method and their properties were invesigated. The orientations and the crystallinites of these crystals were identified by X-ray diffraction(XRD), double crystal rocking curve(DCRC) and etch-pit density(EPD) measurements. From the Raman spectrum at room temperature, TO, LO modes and together with their overtones and combinations were observed. Optical properties were inves ated by PL at 12K and direct band gap of these crystals obtained from optical absorption spectrum. Compared with undo&-InSe, electrical properties of Sn-doped InSe were increased and the electrical conductivity type were n-type. But electrical properties along growth direction of crystals and radial direction of wafer showed nearly uniform distribution. The Zn diffusion mechanism in InSe could be explained by interstitial-substitutional and vacancy complex models and the activation energy of 1.15-3.01eV were needed for diffusion.fusion.

• 대한교통학회지
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• 제28권5호
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• pp.55-64
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• 2010

지하역사 미세먼지의 효율적 저감방안 마련을 위하여 서울지하철 5호선 개화산역 대합실, 승강장, 본선터널 3곳의 미세먼지 농도를 동시간대에 30분 단위로 측정하고, 각 위치에서 측정한 미세먼지농도 변화패턴 사이의 상관관계 분석을 통하여 지하역사에서의 미세먼지 확산방향과 확산속도를 추정하였다. 지하역사의 미세먼지 농도는 본선터널이 가장 높고, 승강장, 대합실 순으로 낮아진다. 본선터널과 승강장, 대합실의 미세 먼지농도는 열차운행이 많은 혼잡시간대에는 증가하고 비 혼잡시간대에는 감소하는 패턴을 보인다. 위치에 따른 미세먼지농도의 상대적인 크기와 변화패턴에 대한 통계적 분석결과 본선터널의 높은 미세먼지농도가 승강장으로 확산되고, 승강장의 미세먼지 중 일부가 대합실로 확산되는 것으로 나타났다. 따라서 지하역사의 미세먼지를 효율적으로 감소시키기 위해서는 본선터널 내 미세먼지 집중발생지점과 발생원, 확산경로, 확산수단 등을 정확하게 파악하여 발생원을 제거하거나 발생량을 저감시키는 것이 중요하며, 환기시스템 가동을 위치별로 미세먼지농도가 높아지는 시간대에 맞추어 가동시킴으로써 전력사용량과 피크전력을 줄일 수 있다.

• 패션비즈니스
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• 제20권6호
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• pp.66-78
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• 2016

Hygroscopic knitted cotton fabric was found to spontaneously absorb water showing a significantly wide concentration gradient in the absorption direction. A semi-empirical diffusion model was introduced to describe how the wicking behavior compared to the classical capillary model (Washburn's equation), which has been widely used in the textiles industry. The capillary sorption curve and the permeability coefficient, which are key variables for the model equations, were measured using an electronic balance. The concentration profile as a function of the wicking distance and the elapsed time was derived, based on the diffusion model. From the concentration profile, the wicking distance detectable by the human eye or a digital camera with the aid of an image-analysis system, could be described realistically as a function of the time. The classical capillary model could be modified by introducing the tortuous correction factor to match the diffusion model. Wicking models and data-processing techniques in the work could provide useful tools for objectively evaluating the textile's wicking performances.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 하계학술대회 논문집
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• pp.187-190
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• 1991

The analytical model to investigate the effects of the drift and diffusion carrier transport upon the Hall effect is presented and applied to the general PN junction structure. The diffusion current effect on the Hall coefficient can not be considered in the conventional model, which produces the conversion of the direction of the induced Hall field between measured and calculated values. The proposed analytical model which considers the diffusion current effect provides the coincident results with the previous experimental results.