• Journal of Korea Water Resources Association
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• v.49 no.6
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• pp.495-507
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• 2016

This study aims at hydrologically demonstrating the universality of power law distribution by analyzing runoff aggregation structures of river basins. Power law distribution is fitted to cumulative drainage area of basins of interest by maximum likelihood, which results in the power law exponents. And then those exponents are assessed in terms of the shape of catchment plan-form. As a main result all of the basins in this study have similar distributions of catchment area. The exponents from this study tend to be higher than the ones from previous researches reflecting self-similar property of the catchment plan-forms of interest. Further study is required about the universality of power law distribution by means of the more realistic flow routing scheme within the framework of DEM.

• Journal of Korea Water Resources Association
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• v.50 no.11
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• pp.725-734
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• 2017

The main purpose of this study is to analyze runoff aggregation structure and energy expenditure pattern of Choyang creek basin within the framework of power law distribution. To this end geomorphologic factors of every point in the basin of interest, which define tractive force and stream power as well as drainage area, are extracted based on GIS, and their complementary cumulative distributions are graphically analyzed through fitting them to power law distribution. The results indicate that three distinct behavioral regimes are observed from the complementary cumulative distributions of three geomorphogic factors. Based on the parameter estimation of power law distribution by maximum likelihood drainage area and stream power can be judged as scale invariance factor without finite scale while tractive force as scale dependence factor with finite scale. Furthermore, it is judged that tractive force would not follow power law distribution because it shows limited complex system behaviors only within the small extent of scale. The exponent of power law distribution for drainage area obtained in this study by maximum likelihood is larger than the previous researches due to the difference of parameter estimation methodologies. And the exponent for stream power is smaller than the previous researches due to the scaling property of channel slope for the basin of interest.

• Proceedings of the Korea Technology Innovation Society Conference
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• 2013.10a
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• pp.261-269
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• 2013

• Journal of Korea Water Resources Association
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• v.51 no.3
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• pp.235-246
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• 2018

The main purpose of this study is to suggest a methodology for identifying vulnerable region in Choyang creek basin susceptible to soil losses based on runoff aggregation structure and energy expenditure pattern of natural river basin within the framework of power law distribution. To this end geomorphologic factors of every point in the basin of interest are extracted by using GIS, which define tractive force and stream power as well as drainage area, and then their complementary cumulative distributions are graphically analyzed through fitting them to power law distribution to identify the sensitive points within the basin susceptible to soil losses with respect to scaling regimes of tractive force and stream power. It is observed that the range of vulnerable region by scaling regime of tractive force is much narrower than by scaling regime of stream power. This result seems to be due to the tractive force is a kind of scale dependent factor which does not follow power law distribution and does not adequately reflect energy expenditure pattern of river basins. Therefore, stream power is preferred to be a more reasonable factor for the evaluation of soil losses. The methodology proposed in this study can be validated by visualizing the path of soil losses, which is generated from hill-slope process characterized by local slope, to the valley through fluvial process characterized by drainage area as well as local slope.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.171-171
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• 2017

강우의 시간분포는 다양한 시간규모에 걸쳐 프랙털 또는 멀티프랙털 특성을 가지고 있음이 알려졌다. 기존의 연구는 주로 시간단위 이상의 프랙털 특성에 관한 것이었다. 실제로 극한 홍수를 가져오는 집중호우는 짧은 시간 규모에서 발생함에도, 이것에 대해서는 관측 자료가 제한되어 극소수의 실험적 연구만 가능했다. 본 연구에서는 기상청에서 제공한 고해상도(1분 단위) ASOS(Automated Synoptic Observation System) 자료를 이용하여, 강우 사상 안에서의 프랙털 특성을 분석해보았다. 대부분의 사상에서 단일 멱함수보다는 2개의 멱함수로 나누어지는 것이 밝혀졌으며, 나뉘는 시간 규모(T*)는 $3{\times}10$ 분으로 파악되었다. 이 시간 규모는 한 단위의 집중호우를 가져올 수 있는 구름크기의 물리적 상한과 관련이 있는 것으로 보인다. T*보다 작은 시간 규모에서의 멱함수 지수는 그 이후의 값보다 대체로 작은 것으로 나타났다. 이는 호우가 집중되는 기간의 변동성이, 강수가 물리적 한계에 도달한 이후보다 훨씬 작기 때문으로 보인다. 구체적인 멱함수의 지수는 강수의 발생과정과도 관련이 있을 것으로 추정된다.

• Journal of Korea Multimedia Society
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• v.9 no.3
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• pp.333-341
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• 2006

Recently, Random Constant worm is increasing The worm retards the availability of the overall network by exhausting resources such as CPU resource and network bandwidth, and damages to an uninfected system as well as an infected system. This paper analyzes the Power-Law network which possesses the preferential characteristics to restrain the worm from spreading. Moreover, this paper suggests the model which dynamically controls the spread of the worm using information about depth distribution of the delivery node which can be seen commonly in such network. It has also verified that the load for each node was minimized at the optimal depth to effectively restrain the spread of the worm by a simulation.

• Journal of Korean Library and Information Science Society
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• v.44 no.4
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• pp.399-419
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• 2013

This paper conducted the empirical analysis of the behaviors revealed in the eight size distributions of the public libraries in Korea. As a result, the behaviors of complex system appeared in all eight size factors. This means that the sizes of public libraries in Korea were highly polarized. Especially, the zipf's law were found in the size factors such as gross area, number of staffs, volume of books, total budget. And the highly uneven distributions were occurred in the size factors such as membership, number of users, number of borrowers, number of borrowed books. This research outcomes show that a new policy of public libraries is needed to resolve the polarization revealed in the sizes of public libraries in Korea.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.1
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• pp.181-190
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• 2016

Improvements in disaster management has become a global necessity because the magnitude of disasters is intensifying in parallel with the increased disaster damage. The disaster risk in Korea is also increasing due to the emergence of new types of disaster; such as the Middle East respiratory syndrome coronavirus, the increase of complex disasters, and the heightened probability of a catastrophic event due to climate change. This paper aimed to identify the disaster loss-frequency relationship from 1948 to 2014 in Korea by using four types of variables. In addition, this paper found major disasters that resulted in the reformation of disaster response organizations, and inputted the deaths and economic loss attributed to those disasters into the disaster loss-frequency graph. The research result substantiated that the disaster loss-frequency relationship in Korea follows the Power Law and found the coefficients of each Power Function. Additionally, this paper found that most of the reformations of disaster response organizations happened after major disasters that concentrated societies attention and anger due to the high human and economic impact; such events are labelled as "focusing events." These focusing events, with the characteristics of a low probability and high impact, are located in the long tail of the Power Law Distribution. This paper suggests that the effective public policy for disaster response needs to be developed by paying attention to 'low probability and high impact' focusing events that are located in the long tail of the Power Law Distribution.

• Journal of Korea Water Resources Association
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• v.54 no.5
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• pp.335-345
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• 2021

The one-dimensional solute transport models have been developed for recent decades to predict behavior and fate of solutes in rivers. Transient storage model (TSM) is the most popular model because of its simple conceptualization to consider the complexity of natural rivers. However, the TSM is highly dependent on its parameters which cannot be directly measured. In addition, the TSM interprets the late-time behavior of concentration curves in the shape of an exponential function, which has been evaluated as not suitable for actual solute behavior in natural rivers. In this study, we suggested a stochastic approach to the solute transport analysis. We delineated the model development and model application to a natural river, and compared the results of the proposed model to those of the TSM. To validate the proposed model, a tracer test was carried out in the 4.85 km reach of Gam Creek, one of the first-order tributaries of Nakdong River, South Korea. As a result of comparing the power-law slope of the tail of breakthrough curves, the simulation results from the stochastic storage model yielded the average error rate of 0.24, which is more accurate than the 14.03 and 1.87 from advection-dispersion model and TSM, respectively. This study demonstrated the appropriateness of the power-law residence time distribution to the hyporheic zone of the Gam Creek.

• The Korean Journal of Applied Statistics
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• v.28 no.3
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• pp.511-527
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• 2015

For time series analysis, power transformation (especially log-transformation) is widely used for variance stabilization or normalization for stationary ARMA(p, q) model. A simple and naive back transformed forecast is obtained by taking the inverse function of expectation. However, this back transformed forecast has a bias. Under the assumption that the log-transformed data is normally distributed. The unbiased back transformed forecast can be obtained by the expectation of log-normal distribution; consequently, the property of this back transformation was studied by Granger and Newbold (1976). We investigate the sensitivity of back transformed forecasts under several different underlying distributions using simulation studies.