• 한국전산유체공학회지
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• 제17권3호
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• pp.59-67
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• 2012

Large Eddy Simulation(LES) of turbulent mass transfer in fully developed turbulent pipe flow has been performed to study the effect of Reynolds number on the concentration fields at $Re_{\tau}=180$, 395, 590 based on friction velocity and pipe radius. Dynamic subgrid-scale models for the turbulent subgrid-scale stresses and mass fluxes were employed to close the governing equations. Fully developed turbulent pipe flows with constant mass flux imposed at the wall are studied for Sc=0.71. The mean concentration profiles and turbulent intensities obtained from the present LES are in good agreement with the previous numerical and experimental results currently available. The effects of Reynolds number on the turbulent mass transfer are identified in the higher-order statistics(Skewness and Flatness factor) and instantaneous concentration fields. The budgets of turbulent mass fluxes and concentration variance were computed and analyzed to elucidate the effect of Reynolds number on turbulent mass transfer. Furthermore, to understand the correlation between near-wall turbulence structure and concentration fluctuation, we present an octant analysis in the vicinity of the pipe wall.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1992년도 춘계학술대회 논문집
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• pp.301-305
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• 1992

A mold plant is characterized by complex processes, frequent schedule changes, and lots of troubles. In order to control the production in mold plant efficiently, huge amount of informations are to be managed in the appropriate way. In this paper, a modular software system for production control is described, which is located between a higher level production planning system and a process control system. It contains the functions such as order processing, operations scheduling and control, tool managemant, NC program managememt including DNC functions, production data acquisition and progress control and statistics.

• Journal of the Korean Statistical Society
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• 제20권1호
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• pp.29-43
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• 1991

Two data-based bandwidth selectors which are optimal in the sense that they achieve n$\^$-$\frac{1}{2}$/ rate of convergence in kernel density estimation are proposed. The proposed bandwidth selectors are constructed by modifying Park and Marron's plug-in method. The first modification is taking Taylor expansion of the mean integrated squared error to two more terms than in the case of plug-in method. The second is estimating more accurately the functionals of the unknown density appeared in the minimizer of the expansion by using higher order kernels. The proposed bandwidth selectors were proved to be optimal in terms of convergence rate. According to small-sample Monte Carlo studies, the proposed bandwidth selectors showed better performance than all the other bandwidth selectors considered in the simulation.

• 천문학회지
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• 제37권5호
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• pp.563-570
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• 2004

Turbulence is a crucial component of dynamics of astrophysical fluids dynamics, including those of ISM, clusters of galaxies and circumstellar regions. Doppler shifted spectral lines provide a unique source of information on turbulent velocities. We discuss Velocity-Channel Analysis (VCA) and its offspring Velocity Coordinate Spectrum (VCS) that are based on the analytical description of the spectral line statistics. Those techniques are well suited for studies of supersonic turbulence. We stress that a great advantage of VCS is that it does not necessary require good spatial resolution. Addressing the studies of mildly supersonic and subsonic turbulence we discuss the criterion that allows to determine whether Velocity Centroids are dominated by density or velocity. We briefly discuss ways of going beyond power spectra by using of higher order correlations as well as genus analysis. We outline the relation between Spectral Correlation Functions and the statistics available through VCA and VCS.

• International Journal of Reliability and Applications
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• 제4권4호
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• pp.191-199
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• 2003

In the present work, a moment inequality is derived for new renewal better (worse) than used in expectation(NRBUE) (NRWUE) distributions. This inequality demonstrates that if the mean life is finite then all higher order moments exist. A new test statistics for testing exponentiality against NRBUE (NRWUE) is introduced based on this inequality. It is shown that the proposed test is simple and has high relative efficiency for some commonly used alternatives. Critical values are tabulated for sample sizes n = 5(1)30. A set of real data is used as an example to elucidate the use of the proposed test statistics for practical reliability analysis.

• 천문학회보
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• 제46권2호
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• pp.72.3-73
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• 2021

Baryon Acoustic Oscillations (BAO) are caused by acoustic density waves in the early universe and act as a standard ruler in the clustering pattern of galaxies in the late Universe. Measuring the BAO feature in the 2-point correlation function of a sample of galaxies allows us to estimate cosmological distances to the galaxies mean redshift, , which is important for testing and constraining the cosmology model. The BAO feature is also expected to appear in the higher order statistics. In this work we measure the generalized spatial N-point point correlation functions up to 4th order. We made measurements of the 2, 3, and 4-point correlation functions in the SDSS-III DR12 CMASS data, comprising of 777,202 galaxies. The errors and covariances matrices were estimated from 500 mock catalogues. We created a theoretical model for these statistics by measuring the N-point functions in halo catalogues produced by the approximate Lagrangian perturbation theory based simulation code, PINOCCHIO. We created simulations using initial conditions with and without the BAO feature. We find that the BAO is detected to high significance up to the 4-point correlation function.

• 제어로봇시스템학회논문지
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• 제4권5호
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• pp.630-635
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• 1998

The objective of this paper is to propose a new efficient technique for the estimation of time-delay parameters using wavelet theory and third-order cumulants, yielding good performance even in the case of low SNR. In particular, band-limited non-Gaussian signals with non-zero skewness and spatially correlated Gaussian noises are considered here. The approach is based on the fact that the effects of spatially correlated Gaussian noises on time-delay estimation can be reduced by using the projection sequences (based on the redundant wavelet decomposition) of given measurements in the higher-order cumulant domain. Finally, the performance of the proposed approach is demonstrated using simulations.

• Journal of Communications and Networks
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• 제14권1호
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• pp.1-9
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• 2012

We consider a receiving node, located at the origin, and a Poisson point process (PPP) that models the locations of the desired transmitter as well as the interferers. Interference is known to be non-Gaussian in this scenario. The capacity bounds for additive non-Gaussian channels depend not only on the power of interference (i.e., up to second order statistics) but also on its entropy power which is influenced by higher order statistics as well. Therefore, a complete statistical characterization of interference is required to obtain the capacity bounds. While the statistics of sum of signal and interference is known in closed form, the statistics of interference highly depends on the location of the desired transmitter. In this paper, we show that there is a tradeoff between entropy power of interference on the one hand and signal and interference power on the other hand which have conflicting effects on the channel capacity. We obtain closed form results for the cumulants of the interference, when the desired transmitter node is an arbitrary neighbor of the receiver. We show that to find the cumulants, joint statistics of distances in the PPP will be required which we obtain in closed form. Using the cumulants, we approximate the interference entropy power and obtain bounds on the capacity of the channel between an arbitrary transmitter and the receiver. Our results provide insight and shed light on the capacity of links in a Poisson network. In particular, we show that, in a Poisson network, the closest hop is not necessarily the highest capacity link.

• Journal of the Korean Data and Information Science Society
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• 제21권3호
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• pp.427-435
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• 2010

이 논문에서는 응급실 급성 충수염 환자의 치료와 검사 항목에 대한 임상경로를 개발하였다. 임상경로 개발을 위해 먼저 Park과 Kim (2010)에 의해 제시된 처방 선택 방법을 이용하였으며, 그 다음에 이렇게 선택된 처방들을 연관성이 있는 처방끼리 묶어서 그림으로 표시하였다. 구체적으로 사용된 처방 선택 방법은 향상도에 근거하고 있으며 빈도가 높은 처방부터 출발하여 이것과의 향상도가 0.9에 못 미치는 음의 연관성 처방들을 순차적으로 제거하였다. 이렇게 선택된 처방들에 대해 연관성이 있는 처방들을 묶는 방법도 처방 선택 방법과 비슷하다. 구체적으로 선택된 처방 중 빈도가 높은 처방부터 출발하여 순차적으로 이것과의 향상도가 1.1을 넘는 처방들을 연관성 있는 처방으로 고려하여 해당 처방 오른쪽에 표시하였다. 따라서 임상경로 그림에는 제일 왼쪽에는 연관성이 낮은 처방들을 빈도순으로 위에서 아래로 배치하고, 제일 왼쪽에 있는 각 처방의 오른쪽에는 이것과 연관성이 높은 처방들을 왼쪽에서 오른쪽으로 역시 빈도순으로 배치하는 것을 원칙으로 하였다.

• Journal of Contemporary Eastern Asia
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• 제12권1호
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• pp.35-47
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• 2013

During the last a few decades, internationalisation of universities has emerged as an important issue not only in developed countries but in developing countries. South Korea as a fast catch-up country has experienced a remarkable change in its higher education system. This change is largely related to the South Korean government's higher education policy and to economic developmental stages. Against this backdrop, in order to assess the internationalisation of Korean higher education, we focus on international student mobility rather than other criteria such as infrastructure or programmes for international students and faculties. According to the recent statistics, the number of inbound foreign students involved in Korean higher education has increased significantly since 2005. Nevertheless, compared to other OECD and Asian countries, the number of outbound students in Korean higher education is high, whereas the number of inbound foreign students in higher education in Korea is very low. Against these observations, Korean government's recent policies and efforts of Korean universities to improve internationalization are discussed. Finally, some policy implications are put forward.