• Journal of the Korean Data and Information Science Society
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• v.28 no.1
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• pp.143-152
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• 2017

Restriction of completely randomization within a block can be handled by a split plot factorial design splitted by several plots. $3{\times}3$ split plot factorial design with two fixed main factors and one fixed block shows that powers of the rank transformed statistic for testing whole plot factorial effect and split plot factorial effect are superior to those of the parametric statistic when existing effect size is small or the remaining effect size is relatively smaller than the testing factorial effect size. Powers of the rank transformed statistic show relatively high level for exponential and double exponential distributions, whereas powers of the parametric and rank transformed statistic maintain similar level for normal and uniform distributions. Powers of the parametric and rank transformed statistic with two fixed main factors and one random block are respectively lower than those with all fixed factors. Powers of the parametric andrank transformed statistic for testing split plot factorial effect with two fixed main factors and one random block are slightly lower than those for testing whole plot factorial effect, but powers of the rank transformed statistic show comparative advantage over those of the parametric statistic.

• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.3
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• pp.224-236
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• 2002

In this paper, a comparative study on the performance of two-phase and three-phase randomized pulse position PWM scheme for mitigation of audible switching acoustic noise in motor drives is done. In the randomized Pulse Position PW, each of two-Phase or three-phase PWM Pulses is located randomly in each switching interval. Simulation and experimental efforts were executed to investigate the spread effects of Power spectra of inverter output voltage, waveforms of ripple current and audible switching acoustic noise. As results, two-phase RP% scheme is more effective from the viewpoint of switching loss and ease of implementation while the three-phase RPWM scheme is more effective from the viewpoint of the spread effects of power spectra. Also, from the view point of the audible switching acoustic noise in motor drives, two-phase and three-phase RPW schemes are nearly the same.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.2
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• pp.151-164
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• 2003

In this paper, induction motor drives with low switching acoustic noise based on the 2 phase modulated RLL(Random Lead-Lag) PWM is proposed and implemented. The proposed switching method is much bettor than 3 phase modulated RLL-PWM from the standpoint of the broadening effect of the acoustic noise spectrum. Along with the randomization of PWM Pulses, SVM(Space Vector Modulation) is executed in the TMS320C31 DSP(Digital Signal Processor). To verify the validity of the proposed RPWM(Random PWM), the experimental study was tried. The experimental results show that the performance of the proposed method and the 3 phase center-aligned SVM / conventional RLL-PWM are nearly the same from the viewpoint of the constant v/f centrel. But, in case of the proposed 2 phase modulated RLL-PWM, the spectrum characteristics of the voltage and the switching acoustic noise are shown to have better broadening effect than 3 phase modulated one.

• Journal of the Korea Society of Computer and Information
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• v.17 no.10
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• pp.79-88
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• 2012

In this paper, we design a mutual authentication protocol which divided sessions from an authenticated session are updated periodically. And in order to minimize the traffic overhead for session authentication, we also introduce dynamic session management according to sampling rate of medical sensor type. And randomize the divided session time. This model has the effect of blocking the integrity and confidentiality intrusion of rogue gateway. Moreover, efficiency is provided through medical data to be transmitted have different sampling rate. In order to evaluate this model, it was embodied and experimented in TinyOS 2.1 environment. The result, we got an overall validity from three types of experiment.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.1
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• pp.61-67
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• 2016

Opportunistic incremental relaying (OIR) system effectively overcomes the degradations caused by the fading of the wireless channel, and efficiently utilizes the wireless resources. Most of the OIR studies, however, assume spatially fixed relays. The user terminals which are usually served as relays move continuously, the assumption that the relays are fixed is not realistic. In this paper, the location of the spatially random user terminals are modeled by the Poisson point process, and the performance of an OIR system is derived. We noticed that the performance of the OIR system improves with the spatially random relays as well as with the fixed relays. Also the intensity of the relays and the transmitting directions toward the destination affect the performances. The performances of the maximal ratio combining (MRC) and the selection combining (SC) at the destination are compared.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.3
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• pp.48-55
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• 2015

This paper studies how to solve a problem caused by M2M terminals sending a few data based on $3^{rd}$ Generation Partnership Project(3GPP) Long Term Evolution-Advanced(LTE-A) system and then it is analyzed, proposed, and introduced into the techniques. Especially, it is introduced solution for the lack of Random Access Channel and an increasing number of latency caused by countless M2M devices. It is proposed the technology for M2M grouping as well as allowable access probability according to user type. As it decreases the number of terminal by grouping M2M devices to try random access at PRACH, it can be reduced collision between Cellular users and M2M devices. So, it is proved that the proposed mechanism can solve the increasing average latency of random access on system coexisting Cellular users and M2M devices through simulations.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.12A
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• pp.1267-1275
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• 2007

An improved backoff algorithm for retransmission randomization for OFDMA/CDMA/slotted ALOHA used in the ranging subchannel of IEEE 802.16 network is proposed. Exploiting the fact that a base station coordinates channel access using UL-/DL-MAP in the IEEE 802.16 networks, we propose a minor modification of the existing IEEE 802.16 in order to increase throughput, decrease delay variation and achieve a graceful performance degradation in case of overload channel condition of the random access protocol. The algorithm basically estimates the number of backlogged users and arrival rate using which, the BS calculates retransmission probability for the subscriber stations involved in a collision. Computer simulation is performed to demonstrate the effectiveness of the proposed algorithm and to compare the performance with existing binary exponential backoff algorithm.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.3
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• pp.356-360
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• 2010

Recently, there have been many research efforts on privacy-preserving data mining. In privacy-preserving data mining, accuracy preservation of mining results is as important as privacy preservation. Random perturbation privacy-preserving data mining technique is known to well preserve privacy. However, it has a problem that it destroys distance orders among time-series. In this paper, we propose a notion of the noise averaging effect of piecewise aggregate approximation(PAA), which can be preserved the clustering accuracy as high as possible in time-series data clustering. Based on the noise averaging effect, we define the PAA distance in computing distance. And, we show that our PAA distance can alleviate the problem of destroying distance orders in random perturbing time series.

• Journal of the Korean Geotechnical Society
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• v.25 no.12
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• pp.13-25
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• 2009

In this paper, a numerical procedure of probabilistic slope stability analysis that considers the spatial variability of soil properties is presented. The procedure extends the deterministic analysis based on the limit equilibrium method of slices to a probabilistic approach that accounts for the uncertainties and spatial variation of the soil parameters. Making no a priori assumptions about the critical failure surface like the Random Finite Element Method (RFEM), the approach saves the amount of solution time required to perform the analysis. Two-dimensional random fields are generated based on a Karhunen-Lo$\grave{e}$ve expansion in a fashion consistent with a specified marginal distribution function and an autocorrelation function. A Monte Carlo simulation is then used to determine the statistical response based on the random fields. A series of analyses were performed to verify the application potential of the proposed method and to study the effects of uncertainty caused by the spatial heterogeneity on the stability of slope. The results show that the proposed method can efficiently consider the various failure mechanisms caused by the spatial variability of soil property in the probabilistic slope stability assessment.

• Journal of the Korean Geotechnical Society
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• v.24 no.8
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• pp.111-123
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• 2008

Geotechnical engineering problems are characterized by many sources of uncertainty. Some of these sources are connected to the uncertainties of soil properties involved in the analysis. In this paper, a numerical procedure for a probabilistic analysis that considers the spatial variability of soil properties is presented to study the response of spatially random soil. The approach integrates a commercial finite difference method and random field theory into the framework of a probabilistic analysis. Two-dimensional non-Gaussian random fields are generated based on a Karhunen-$Lo{\grave{e}}ve$ expansion in a fashion consistent with a specified marginal distribution function and an autocorrelation function. A Monte Carlo simulation is then used to determine the statistical response based on the random fields. A series of analyses were performed to study the effects of uncertainty due to the spatial heterogeneity on the settlement and bearing capacity of a rough strip footing. The simulations provide insight into the application of uncertainty treatment to the geotechnical problem and show the importance of the spatial variability of soil properties with regard to the outcome of a probabilistic assessment.