• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.9
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• pp.1163-1171
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• 1999

Superdiffusive transport motions of passive scalars are numerically considered for various advection velocity fields. Calculated exponents ${\alpha}$ in the superdiffusion-defining relation ${\sigma}^2(t){\sim}t^{\alpha}$ for model flow fields agree to the theoretically predicted values. Simulation results show that the superdiffusion takes place as the tracers' motion become less random, compared to their motion at the pure molecular diffusion. Whether the flow field is random or not, degrees of superdiffusion are directly related to the velocity autocorrelation functions along the tracers Lagrangian trajectories that characterize degrees of randomness of the tracers' motion.

• Proceedings of the Korean Information Science Society Conference
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• 2002.10d
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• pp.397-399
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• 2002

가상교육이 활성화됨에 따라 많은 가상대학이 진행되고 있다. 이러한 가상대학운영에서 몇몇의 문제점이 제기되고 있는 것 중에서 학습자의 학습도를 평가하는 평가방법이 중요한 문제로 부각되고 있다. 이런 문제를 보완하고자 본 논문에서는 평가에서 나타날 수 있는 문제를 분석하고 오답 일치율, 신상정보 유사도, IP주소 유사도, 시험시간 유사도 등을 이용하여 담합 여부를 파악하고, 담합 행위를 방지하기 위하여 무작위 문항 제시에 의한 온라인 시험 방법으로 이를 개선하려는 시스템을 구현하였다. 그 결과 Threshold 간을 조절함으로 학습자의 담합 행위를 검출할 수 있었으며 무작위 문항 제시 방법에 적절한 시간 설정값을 조절함으로 기존 평가에서의 담합 행위를 80%정도 방지할 수 있었다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.10 no.4
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• pp.53-66
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• 1990

Rainfall is a phenomenon that shows a high variability both in space and time, Hy drologists are usually interested in the description of spatial distribution of rainfall over watershed. The theory of Kriging, generalized covariance technique using nonstationary mean in the regions under orographic effect, was chosen to construct random surface of total storm depth. For the constructed random surface, the double Fourier analysis of the total storm depths was performed, and the principal harmonics of storm were determined. The local component, or storm residuals was obtained by subtracting the periodic component of the storm from total storm depths. It is assumed that the residuals are a sample function of a homogeneous random field. This random field can be characterized by an isotropic one dimensional autocorrelation function or its corresponding spectral density function. Under this assumption, this study proposed a theorectical model for spectral density function adapted to two watersheds.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.11 no.1
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• pp.109-116
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• 1991

In recent years, hydrologists have been interested in the radial spectrum and its estimation in two dimensional storm field to construct simulation model of the rainfall. This paper deals with the problem of transformation from the spectrum or isotropic covariance function to two dimensional random field. The extended turning band method for the generation of random field is applied to the problem using the line generation method of one dimensional stochastic process by G.Matheron. Examples of this generation is chosen in the random components of the multidimensional rainfall model suggested by Bras and are given with a comparison between theoretical and sample statistics. In this numerical experiments it is observed that first and second order statistics can be conserved. Also the example of moving storm simulation through Bras model is presented with the appropriate parameters and sample size.

• Journal of Korea Society of Industrial Information Systems
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• v.27 no.1
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• pp.49-62
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• 2022

Online customer review data can be easily collected on the Internet and also they describe sentimental evaluation of a product in different aspects. Previous sentiment analysis studies evaluate the degree of sentiment with review data, which may have multiple sentences describing different product aspects. Since different aspects of a product can be described in a sentence, the proposed method suggested analyzing a sentence to build a pair of a product aspect terms and sentimental terms. Bidirectional LSTM and CRF algorithms were used in this paper. A pair of aspect terms and sentimental terms are evaluated by pre-defined evaluation rules. The paper suggested using the result of evaulation as inputs of QFD, so that the quantified customer voices effect on the requirements of a new product. Online reviews for a hair dryer were used as an example showing that the proposed approach can derive reasonable sentiment analysis results.

• Journal of the Korean Society of Physical Medicine
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• v.8 no.1
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• pp.111-116
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• 2013

연구목적: 본 연구는 흰쥐를 대상으로 정강뼈의 관절연골에 적용한 맥동전자장과 맥동초음파가 HSP70(Heat shock protein 70)의 발현을 통한 연골 형성에 미치는 영향을 알아보고자 실시하였다. 연구방법: 36마리의 200~250g의 Sprague-Dawley 흰쥐를 대조군, 맥동전자장 적용군, 맥동초음파 적용군으로 각 집단별로 12마리씩 무작위 배정하여 실험을 진행하였다. 맥동전자장은 27.12 MHz의 주파수, 5가우스의 강도, 450 W의 출력으로 10분간 적용하였고, 맥동초음파는 20%의 맥동비, 1MHz의 주파수, $1.5W/cm^2$의 강도로 10분간 적용하였다. 연구결과: 맥동전자장 적용군과 맥동초음파 적용군의 관절연골 조직에서 유의한 수준의 HSP70 발현량을 나타냈다. 또한 맥동전자장 적용군과 맥동초음파 적용군에서는 Akt, Erk1, CREB의 높은 활성도를 나타내었고, 맥동초음파 적용군에 비해서 맥동전자장 적용군의 더 높은 수준의 활성도를 보였다. 결론: 맥동전자장과 맥동초음파는 HSP70의 과발현을 유발하고, 이를 통해 연골형성을 증가시키는 것으로 나타나, 향후 관절연골의 손상에 대한 임상적 적용을 위한 추가적인 연구가 진행되어야 할 것으로 생각된다.

• Journal of the Korean earth science society
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• v.25 no.7
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• pp.604-614
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• 2004

Using three-components geomagnetic data from a permanent geomagnetic observatory in Icheon, we have computed the power spectrum of each geomagnetic component, amplitude, phase and estimation error of transfer function for each day in the 6 months period July 2002${\sim}$December 2002. The temporal variation of power spectrum have random appearances with repeating relative strong and weak magnitude, which is considered as solar activities. However, there is no clear long-term trend. In the case of amplitude, phase and error of transfer function, even though there are some random patterns over the periods of 1000 s and under 100 s, they seem to be comparatively stable without manifest temporal changes. Futhermore, we have estimated electrical field by assuming P$_{1}\;^{0}$ spherical harmonics and then calculated the approximated apparent resistivity for each day. As a result, the variations of resistivity depend on the temporal magnitude of spectral power in horizontal magnetic fields rather than hydrological changes in near surface.

• KIPS Transactions on Software and Data Engineering
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• v.5 no.11
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• pp.555-562
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• 2016

Semantic Role Labeling (SRL) is to determine the semantic relation of a predicate and its argu-ments in a sentence. But Korean semantic role labeling has faced on difficulty due to its different language structure compared to English, which makes it very hard to use appropriate approaches developed so far. That means that methods proposed so far could not show a satisfied perfor-mance, compared to English and Chinese. To complement these problems, we focus on suffix information analysis, such as josa (case suffix) and eomi (verbal ending) analysis. Korean lan-guage is one of the agglutinative languages, such as Japanese, which have well defined suffix structure in their words. The agglutinative languages could have free word order due to its de-veloped suffix structure. Also arguments with a single morpheme are then labeled with statistics. In addition, machine learning algorithms such as Support Vector Machine (SVM) and Condi-tional Random Fields (CRF) are used to model SRL problem on arguments that are not labeled at the suffix analysis phase. The proposed method is intended to reduce the range of argument instances to which machine learning approaches should be applied, resulting in uncertain and inaccurate role labeling. In experiments, we use 15,224 arguments and we are able to obtain approximately 83.24% f1-score, increased about 4.85% points compared to the state-of-the-art Korean SRL research.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.8
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• pp.873-877
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• 2010

CAPTCHA is a security tool that prevents the automatic sign-up by a spam or a robot. This CAPTCHA usually depends on the smart readability of humans. However, the common and plain CAPTCHA with text-based system is not difficult to be solved by intelligent web-bot and machine learning tools. In this paper, we propose a new sub-image based CAPTCHA system totally different from the text based system. Our system offers a set of cropped sub-image from a whole digital picture and asks user to identify the correct orientation. Though there are some nice machine learning tools for this job, but they are useless for a cropped sub-images, which was clearly revealed by our experiment. Experiment showed that our sub-image based CAPTCHA is easy to human solver, but very hard to all kinds of machine learning or AI tools. Also our CAPTCHA is easy to be generated automatical without any human intervention.

• Journal of IKEEE
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• v.27 no.1
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• pp.1-11
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• 2023

Path driving tests are necessary for the development of self-driving cars or robots. These tests are being conducted in simulation as well as real environments. In particular, for development using reinforcement learning and deep learning, development through simulators is also being carried out when data of various environments are needed. To this end, it is necessary to utilize not only manually designed paths but also various randomly and automatically designed paths. This test site design can be used for actual construction and manufacturing. In this paper, we introduce a method for randomly generating a driving test path consisting of a combination of arcs and segments. This consists of a method of determining whether there is a collision by obtaining the distance between an arc and a line segment, and an algorithm that deletes part of the path and recreates an appropriate path if it is impossible to continue the path.