• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.588-593
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• 2006

자연하천은 일반적으로 만곡수로나 사행수로 형태를 보이고 있으며, 직선수로에서와 달리 원심력에 기인한 이차류 영향을 받게 된다. 이차류에 의해서 수면에서는 만곡부 바깥쪽으로, 하상에서는 만곡부 안쪽으로의 흐름특성을 보이게 된다. 만곡부 안쪽으로 가해지는 하상 전단응력에 기인하여 하상에서의 입자가 만곡부 안쪽으로 이송되며, 결과적으로 만곡부 안쪽에는 점사주가, 바깥쪽에는 소(pool)가 생성된다. 또한 지형경사의 생성으로 입자에 가해지는 중력효과도 변화된다. 따라서 이와 같은 자연하천의 흐름과 하상변동을 수치모의 하기 위해서는 만곡부 이차류 특성을 고려한 모형이 필요하다. 본 연구에서는 수심 적분된 흐름방정식과 하상토 보존방정식 (Exner equation)을 이용한 하상변동을 위한 비연계 수치모형을 위해서 하상토 보존방정식의 유한요소 알고리즘을 개발하였다. 하상토 보존방정식은 흐름 특성에 따른 평형 유사량의 공간변화율을 이용하여 일정 기간 동안의 하상 변화량을 계산한다. 이 때 이차류에 의한 하상 전단응력의 편각 및 지형경사 변화에 따른 실제 입자의 이송방향을 보정하여 평형 유사량이 계산된다. 이러한 보정식을 적용시키기 위해서는 유속성분의 공간변화량 및 지형경사의 공간성분이 필요하다. 유한요소법은 연속성 변수를 이산화시켜 근사해를 구하는 수치기법의 일종이기 때문에, 요소망이 불규칙적으로 구성되었을 경우 임의의 절점에서 연속성을 지닌 변수의 공간변화율을 계산하는데 어려움이 있다. 따라서 본 연구에서는 평형 유사량 계산 시에 절점이 아닌 요소 내부에서 평형 유사량을 계산하는, 하상토 보존방정식의 새로운 유한요소 알고리즘을 개발하고, 새로운 알고리즘을 적용시킨 수치모형의 검증을 행하였다. 경계조건 알고리즘의 검증으로 위해서 Soni 등 (1980)이 행한 상류 유입 유사량에 따른 하상변동을 수치 모의하고 실험치와 비교하였으며, Sutmuller와 Glerum (1980)이 수행한 만곡수로에서의 하상변동을 모의하고 실험과 비교하였다. 새로운 알고리즘을 적용시킨 하상토 보존방정식의 유한요소 수치모형의 결과는 매우 안정적이며, 실험과 매우 유사한 결과를 얻을 수 있었다. 본 수치모델은 현재 균일한 입자의 하상토만을 고려하므로, 입자분급이나 하상 장갑화 현상 등은 무시한다.

• The Journal of Engineering Geology
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• v.25 no.2
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• pp.299-304
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• 2015

Slope stability analysis of unsaturated soil slopes due to rainfall infiltration is an important issue in evaluating landslide analysis and stability assessment. The purpose of this study is to establish the critical depth considering weathered soil of parent rock and rainfall intensity at main scarp in national landslide. Based on the analytical results, it is found that as rainfall duration and Slope angle increased, the critical depth of gneiss-weathered soil increased from 3.00 m to 3.77 m, the critical depth of granite weathered-soil increased from 1.75 m to 2.40 m, and the critical depth of mudstone-weathered soil increased from 3.00 m to 4.15 m, respectively. The critical depth of granite-weathered soil with low cohesion and high internal friction angle is much lower than those of other soils. It is interestingly shown that a decrease in the safety factor is highly significant, much affected by the slope increase rather than the rainfall intensity.

• Journal of Internet Computing and Services
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• v.13 no.3
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• pp.61-73
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• 2012

This paper proposes a histogram specification based image enhancement method, which uses the brightness mean and variance of an image to maximize the entropy of the image. In our histogram specification step, the Gaussian distribution is used to fit the input histogram as well as produce the target histogram. Specifically, the input histogram is fitted with the Gaussian distribution whose mean and variance are equal to the brightness mean(${\mu}$) and variance(${\sigma}2$) of the input image, respectively; and the target Gaussian distribution also has the mean of the value ${\mu}$, but takes as the variance the value which is determined such that the output image has the maximum entropy. Experimental results show that compared to the existing methods, the proposed method preserves the mean brightness well and generates more natural looking images.

• Journal of Intelligence and Information Systems
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• v.10 no.1
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• pp.1-11
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• 2004

It is very important part of pre-processing for get better results by image processing that get emphasized image by processing of source image. Emphasized image is not only good looking image but clear and sharp image. Emphasized images are used very useful data at contour extraction and image recognition in image processing. It have different image recognition by how much represent a origin scene in row quality image. Present algorithms that get emphasized premier image do not get clear picture of degree that want in various kind of images and there is shortcoming that need much process times being proportional size of picture quality or accumulation degree of histogram. In this paper, we propose method to change distribution chart that pixels occupy in histogram as subsequentness in reflex of various kinds as well as that picture quality reflex method to emphasize so that is suitable in practical use purpose originally of premier. Proposed algorithm re-allot histogram distribution by reverse tracking histogram. Experimental images are same result and take less processing time than histogram equalization.

• Journal of the Korean Geotechnical Society
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• v.27 no.5
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• pp.5-15
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• 2011

Recent increase of large scale construction near costal area has also increased the application of soft ground treatment. As a result, solidification with cement and lime which increases stability and durability of soils, is frequently used for surface layer stabilization in soft ground site. While stabilization of very soft clay with high plasticity and compressibility has widely been studied, studies on silty clay with low plasticity and compressibility are relatively rare. In this study, after stabilizing low plasticity silty clay of Songdo area with cement and lime under various water contents, mixing ratio, and curing time, uniaxial compression test and plate load test were performed. Strength properties from both tests were considerably consistent. And trackability of construction equipment on the treated surface layer of dredged land was estimated. Finally, optimum mixing condition for Songdo silty clay was proposed.

• Spatial Information Research
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• v.19 no.3
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• pp.83-93
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• 2011

Since urban facilities have a signigicant meaning that represents the degree of development of nations and cities, it is very important to effectively manage and operate the facilities. In this paper, we propose a context-awareness system for managing urban underground facilities intelligently and develop its algorithm and prototype. The algorithm of the suggested system includes the period from the point when various sensors set up in USN environments sense abnormal signals and make alarms to the point when the context-awareness system analyzes the alarm and sends the analysis results to integrated platform and related modules. We then implement the prototype of the proposed context awareness system and verify the effectiveness of the system by performing unit tests. Our developed prototype will become the basis of actual system development. We expect that the suggested system will be used as a good reference model of related systems managing various types of urban facilities.

• Journal of the Korean GEO-environmental Society
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• v.21 no.11
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• pp.21-26
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• 2020

Natural soil is composed of particles of various sizes, and the shear behavior which is a kind of mechanical behavior of the soil is affected by the particle size distribution. In addition, since the natural soil contains a large mixture of coarse and fine grained soil, it is difficult to clearly understand the shear behavior of the soil. Therefore, a ring shear test was conducted on sandy soils that has various particle size distribution in order to identify the effect of the distribution on shear characteristics of soils. At this time, sand and silt were used for coarse and fine grained soils, respectively, to make sandy soils by changing the silt content. Also the water was supplied during the test to confirm shear characteristics of sandy soils with various particle size distributions. The result shows that the shear strength increases as the silt content increases, and the strength decreases as the silt content increases over the sand. Besides, residual shear strength gradually decreases because of the silt content when the water is supplied.

• Journal of the Korean Institute of Intelligent Systems
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• v.20 no.1
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• pp.30-35
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• 2010

This paper presents a quality enhancement of images by using a histogram equalization based on the symmetric logistic function. The histogram equalization is a simple and effective spatial processing method that it enhances the quality by adjusting the brightness of image. The logistic function that is a sigmoidal nonlinear transformation function, is applied to non-linearly enhance the brightness of the image according to its intensity level frequency. We propose a flexible and symmetrical logistic function by only using the intensity with maximum frequency in an histogram and the total number of pixels. The proposed function decreases the computation load of an exponential function in the traditional logistic function. The proposed method has been applied for equalizing 5 images with a different resolution and histogram distribution. The experimental results show that the proposed method has the superior enhancement performances compared with the source images and the traditional global histogram equalization, respectively.

• Korean Journal of Medicinal Crop Science
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• v.9 no.1
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• pp.76-82
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• 2001

This study was conducted to find out the optimum ranges of soil physical properties for wasabi growth by the relationship of soil physical properties and plant growth. Soil bulk density and hardness were higher in decomposition of granite and river sand than hydroball. This root distribution of surface layer was higher in decomposition of granite and river sand than hydroball. Growth characteristics and yield were higher in hydroball than decomposition of granite and river sand. In inlet site, the marketable rhizome weight in decompasition of granite, river sand, hydroball were 298kg/10a, 401kg/10a, 766kg/10a, respectively. But outlet, the weight in three soils were 251kg/10a, 256kg/10a, 633kg/10a, respectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.11
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• pp.919-927
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• 2013

In this paper, we present a perception-based tone mapping technique using histogram modification for displaying high dynamic range image. HDR (high dynamic range) tone mapping algorithms are used to display HDR image on LDR (low dynamic rnage) devices. Although perception-based tone mapping methods provides better performance, it dose not always produce good results for a wide variety of images. The proposed method reduces dynamic range by using the perception-based tone mapping function and histogram modification. A derivative of perception-based tone mapping function is used as constraint function of histogram and additional compensation process is performed. This method not only improves contrast by adopting different constraints on each pixel value, but also preserves more visual details. In order to prevent over enhancement, histogram modification technique is applied. Furthermore, it can control the rate of image contrast using control parameters. Subjective and objective evaluations show that proposed algorithm is better than existing algorithms.