• Title/Summary/Keyword: Simulation-X$^{(R)}$

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Tests of Hypotheses in Multiple Samples based on Penalized Disparities

  • Park, Chanseok;Ayanendranath Basu;Ian R. Harris
    • Journal of the Korean Statistical Society
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    • v.30 no.3
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    • pp.347-366
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    • 2001
  • Robust analogues of the likelihood ratio test are considered for testing of hypotheses involving multiple discrete distributions. The test statistics are generalizations of the Hellinger deviance test of Simpson(1989) and disparity tests of Lindsay(1994), obtained by looking at a 'penalized' version of the distances; harris and Basu (1994) suggest that the penalty be based on reweighting the empty cells. The results show that often the tests based on the ordinary and penalized distances enjoy better robustness properties than the likelihood ratio test. Also, the tests based on the penalized distances are improvements over those based on the ordinary distances in that they are much closer to the likelihood ratio tests at the null and their convergence to the x$^2$ distribution appears to be dramatically faster; extensive simulation results show that the improvement in performance of the tests due to the penalty is often substantial in small samples.

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Power Comparison of Independence Test for the Farlie-Gumbel-Morgenstern Family

  • Amini, M.;Jabbari, H.;Mohtashami Borzadaran, G.R.;Azadbakhsh, M.
    • Communications for Statistical Applications and Methods
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    • v.17 no.4
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    • pp.493-505
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    • 2010
  • Developing a test for independence of random variables X and Y against the alternative has an important role in statistical inference. Kochar and Gupta (1987) proposed a class of tests in view of Block and Basu (1974) model and compared the powers for sample sizes n = 8, 12. In this paper, we evaluate Kochar and Gupta (1987) class of tests for testing independence against quadrant dependence in absolutely continuous bivariate Farlie-Gambel-Morgenstern distribution, via a simulation study for sample sizes n = 6, 8, 10, 12, 16 and 20. Furthermore, we compare the power of the tests with that proposed by G$\ddot{u}$uven and Kotz (2008) based on the asymptotic distribution of the test statistics.

Analysis of Design Parameter Characteristics for Automobile Passive Dampers (승용차용 Passive Damper의 설계변수에 관한 특성 분석)

  • Noh, DaeKyung;Jang, JooSup;Seo, WonJin
    • Tribology and Lubricants
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    • v.30 no.1
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    • pp.46-51
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    • 2014
  • In this study, we attempted to characterize the physical meaning of the design parameters used for automobile passive dampers by considering the slit, disc, and hole, which influence the pressure characteristics. We also analyzed the change in the pressure characteristics when mixing various slits and discs. Finally, we used a computer simulation to implement lag according to nitrogen gas and analyzed the dependence of frequency on the nitrogen gas pressure.

CMS: Application Layer Cooperative Congestion Control for Safety Messages in Vehicular Networks

  • Lee, Kyu-haeng
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.12 no.3
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    • pp.1152-1167
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    • 2018
  • In this paper, I propose an application layer cooperative congestion control scheme for safety message broadcast in vehicular networks, called CMS, that adaptively controls a vehicle's safety message rate and transmit timing based on the channel congestion state. Motivated by the fact that all vehicles should transmit and receive an application layer safety message in a periodic manner, I directly exploit the message itself as a means of estimating the channel congestion state. In particular, vehicles can determine wider network conditions by appending their local channel estimation result onto safety message transmissions and sharing them with each other. In result CMS realizes cooperative congestion control without any modification of the existing MAC protocol. I present extensive NS-3 simulation results which show that CMS outperforms conventional congestion control schemes in terms of the packet collision rate and throughput, especially in a high-density traffic environment.

Design of a generator control system for small nuclear distributed generation

  • Yoon, Dong-Hee;Jang, Gil-Soo
    • Journal of Electrical Engineering and Technology
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    • v.6 no.3
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    • pp.311-318
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    • 2011
  • Small-scale reactors have recently attracted attention as a potential power generation source for the future. The Regional Energy Research Institute for Next Generation is currently developing a small-scale reactor called Regional Energy rX 10 MVA (REX-10). The current paper deals with a power system to be used with small-scale reactors for multi-purpose regional energy systems. This small nuclear system can supply electric and thermal energy like a co-generation system. The electrical model of the REX-10 has been developed as a part of the SCADA system. REX-10's dynamic and electromagnetic performance on the power system is analyzed. Simulations are carried out on a test system based on Ulleung Island's power system to validate REX-10 availability on a power system. RSCAD/RTDS and PSS/E software tools are used for the simulation.

Comparison of Operating Characteristics for DFIG and FSIG wind Turbine Systems with Respect to Variable Interconnecting Line Conditions (연계선로의 조건 변화에 따른 DFIG와 FSIG 풍력발전시스템의 운전특성 비교)

  • Ro, Kyoung-Soo;Kim, Tae-Ho
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.24 no.9
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    • pp.8-15
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    • 2010
  • This paper analyzes the steady-state output characteristics of variable-speed wind turbine systems using doubly-fed induction generators(DFIG) compared with fixed-speed induction generator(FSIG) wind turbine systems. It also presents simulations of a grid-connected wind turbine generation system for dynamics analysis on MATLAB/Simulink and compares the responses between DFIG and FSIG wind turbine systems with respect to wind speed variation, impedance changes and X/R ratio changes of interconnecting circuits. Simulation results show the variation of generator's active output, terminal voltage and fault currents at the interconnecting point. Case studies demonstrate that DFIG wind turbine systems illustrate better performance to 3-phase fault than FSIG's.

Development of Power System Impedance Analyzer on the Electric Railway (전기철도 급전계통 임피던스 분석장치 개발)

  • Lee, Chang-Mu;Chang, Sang-Hoon;Han, Moon-Seob;Oh, Kwang-Hae
    • Proceedings of the KIEE Conference
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    • 1998.07a
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    • pp.387-389
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    • 1998
  • For the continuous and exact measurement of load impedance of AC power system on the electric railway, this paper presents a method to show the load area to resistance(R)-reactance(X) plane of impedance plane. The load area is presented in terms of impedance which is in the ratio of voltage and current continuously measured and impedance plane indicates the protection area of fault locator. The proposed method is verified its reasonability by computer simulation, and using this method we will develop the power system impedance analyser which is available actual application.

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Neural Network Application to the Bad Data Detection Using Autoregressive filter in Power System (AR 필터에 의한 전력계통의 불량데이타검출에서 신경회로망의 응용)

  • Lee, H.S.;Yang, S.O.;Park, J.H.
    • Proceedings of the KIEE Conference
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    • 1993.07a
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    • pp.131-133
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    • 1993
  • In the power system state estimation, the J(x)-index test and normalized residuals $r_N$ have been used to detect the presence of bad measurements and identify their location. But, these methods require the complete re-estimation of system states whenever bad data is identified. This paper presents back-propagation neural network model using autoregressive filter for identification of bad measurements. The performances of neural network method are compared with those of conventional methods and simulation results show the good performance in the bad data identification based on the neural network under sample power system.

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A combination method to generate fluctuating boundary conditions for large eddy simulation

  • Wang, Dayang;Yu, X.J.;Zhou, Y.;Tse, K.T.
    • Wind and Structures
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    • v.20 no.4
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    • pp.579-607
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    • 2015
  • A Combination Random Flow Generation (CRFG) technique for obtaining the fluctuating inflow boundary conditions for Large Eddy Simulation (LES) is proposed. The CRFG technique was developed by combining the typical RFG technique with a novel calculation of k and ${\varepsilon}$ to estimate the length- and time-scales (l, ${\tau}$) of the target fluctuating turbulence field used as the inflow boundary conditions. Through comparatively analyzing the CRFG technique and other existing numerical/experimental results, the CRFG technique was verified for the generation of turbulent wind velocity fields with prescribed turbulent statistics. Using the turbulent velocity fluctuations generated by the CRFG technique, a series of LESs were conducted to investigate the wind flow around S-, R-, L- and U-shaped building models. As the pressures of the models were also measured in wind tunnel tests, the validity of the LES, and the effectiveness of the inflow boundary generated by the CRFG techniques were evaluated through comparing the simulation results to the wind tunnel measurements. The comparison showed that the LES accurately and reliably simulates the wind-induced pressure distributions on the building surfaces, which indirectly validates the CRFG technique in generating realistic fluctuating wind velocities for use in the LES. In addition to the pressure distribution, the LES results were investigated in terms of wind velocity profiles around the building models to reveal the wind flow dynamics around bluff bodies. The LES results quantitatively showed the decay of the bluff body influence when the flow moves away from the building model.

Numerical Simulajtions of Non-ergodic Solute Transport in Strongly Heterogeneous Aquiferss (불균질도가 높은 대수층내에서의 비에르고딕 용질이동에 관한 수치 시뮬레이션)

  • Seo Byong-Min
    • The Journal of Engineering Geology
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    • v.15 no.3
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    • pp.245-255
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    • 2005
  • Three dimensional Monte-Carlo simulations of non-ergodic transport of a non-reactive solute plume by steady-state groundwater flow under a uniform mean velocity in isotropic heterogeneous aquifers were conducted. The log-normally distributed hydraulic conductivity, K(x), is modeled as a random field. Significant efforts are made to reduce the simulation uncertainties. Ensemble averages of the second spatial moments of the plume, $$lt;S_{ij}'(t',l')$gt;$ and plume centroid variances, $$lt;R_{ij}'(t',l')$gt;$ were simulated with 3200 Monte Carlo runs for three variances of log K, $\omega^2_y1.0,,2.5,$ and 5.0, and three dimensionless lengths of line plume sources ( l=,5 and 10) normal to the mean velocity. The simulated second spatial moment and the plume centroid variance in longitudinal direction fit well to the first order theoretical results while the simulated transverse moments are not fit well with the first order results. The first order theoretical results definitely underestimated the simulated transverse second spatial moments for the aquifers of large u: and small initial plume sources. The ergodic condition for the second spatial moments is far from reaching, and the first order theoretical results of the transverse second spatial moment of the ergodic plume slightly underestimated the simulated moments.