• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.3
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• pp.649-660
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• 2017

In electronic warfare, the pulse amplitude, one of information of a pulse signal emitted by an enemy, is used for estimating distance from the source and for deinterleaving mixed source signals. An estimate of pulse amplitude is conventionally determined as the maximum magnitude of a Fourier transformed signal within its pulse width which is estimated pre-step in an electronic warfare receiver. However, when frequency modulated signals are received, it is difficult to estimate their pulse amplitudes with this conventional method because the energy of signals is dispersed in frequency domain. In order to overcome this limitation, this paper proposes an enhanced pulse amplitude estimation method which calculates the average power of the received pulse signal in time domain and removes the noise power of the receiver. Simulation results show that even in case the frequency modulated signal is received, the proposed method has the same performance as estimating the pulse amplitude when unmodulated signal is received. In addition, the proposed method is shown to be more robust to an estimation error of pulse width, which affects the estimation performance of pulse amplitude, than the conventional method.

• The Journal of the Acoustical Society of Korea
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• v.32 no.1
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• pp.22-31
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• 2013

In this paper, we propose a method that estimates the channel response from underwater communication signals with MMSE (Minimun Mean Squared Error) and detects dominant components automatically based on power of response components using CFAR (Constant False Alarm Rate). Statistical characteristics are analyzed with variation of magnitude and phase and time coherence via experimental data obtained by drifting transmitter and receiver. We show that bit error rate has small difference, 1.2 times, compared with the case using every channel information estimated within data period when estimation and equalization is performed with extracted characteristic obtained by the proposed method.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.42 no.1
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• pp.101-108
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• 2005

Adaptive constant false alarm rate(CFAR) algorithm is used for good detection probability as well as constant false alarm rate in clutter background. Especially, filtering technique adaptive to spatial variation is necessary for improving detection quality in non stationary clutter environment which has spatial correlation and large magnitude deviation. In this paper, we propose a two-dimensional block interpolation(TBI) adaptive CFAR algorithm that calculates the node estimate in the fred two dimensional region and subsequently determines the final estimate for each resolution cell by two-dimensional interpolation. The proposed method is efficient for filtering abnormal ejection by adopting distribution median in fixed region and also has advantage of reducing required memory space by using estimation method which gets final values after calculating the block node values. Through simulations, we show that the proposed method is superior to the traditional adaptive CFAR algorithms which are transversal or recursive in aspect of the detection performance and required memory space.

• Journal of Biomedical Engineering Research
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• v.30 no.1
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• pp.56-65
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• 2009

Compton imaging is often recognized as a potentially more valuable 3-D technique in nuclear medicine than conventional emission tomography. Due to inherent computational limitations, however, it has been of a difficult problem to reconstruct images with good accuracy. In this work we show that the row-action maximum likelihood algorithm (RAMLA), which have proven useful for conventional tomographic reconstruction, can also be applied to the problem of 3-D reconstruction of cone-beam projections from Compton scattered data. The major advantage of RAMLA is that it converges to a true maximum likelihood solution at an order of magnitude faster than the standard expectation maximiation (EM) algorithm. For our simulations, we first model a Compton camera system consisting of the three pairs of scatterer and absorber detectors placed at x-, y- and z-axes, and generate conical projection data using a software phantom. We then compare the quantitative performance of RAMLA and EM reconstructions in terms of the percentage error. The net conclusion based on our experimental results is that the RAMLA applied to Compton camera reconstruction significantly outperforms the EM algorithm in convergence rate; while computational costs of one iteration of RAMLA and EM are about the same, one iteration of RAMLA performs as well as 128 iterations of EM.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.5
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• pp.623-628
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• 2007

The accurate peak response estimation of a seismically excited structure with frictional damping system(FDS) is very difficult since the structure with FDS shows nonlinear behavior dependent on the structural period, loading characteristics, and relative magnitude between the frictional force and the excitation load. Previous studies have estimated that by replacing a nonlinear system with an equivalent linear one or by employing the response spectrum obtained based on nonlinear time history and statistical analysis. In the case that an earthquake load is defined with probabilistic characteristics, the corresponding response of the structure with FDS has probabilistic distribution. In this study, nonlinear time history analyses were performed for the structure with FDS subjected to artificial earthquake loads generated using Kanai-Tajimi filter. An equation for the probability density function (PDF) of the displacement response is proposed by adapting the PDF of the normal distribution. Finally, coefficients of the proposed PDF are obtained by regression analysis of the statistical distribution of the time history responses. Finally the correlation between PDFs and statistical response distribution is presented.

• Journal of Korea Water Resources Association
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• v.40 no.10
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• pp.801-810
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• 2007

In this study, validity and limitation of the estimation of roughness coefficient using the measured field data are investigated and the errors of the calculated roughness coefficient are analyzed. The assumption of uniform flow led to much difference of the computed results in low flow, and this is due to change of the cross-section informations such as flow area and hydraulic radius rather than the difference of velocity head. From the comparison between the estimations of average roughness coefficient in the reach which is relatively long, the calculation using the modified Newton-Raphson method is very efficient and accurate. In the measured roughness coefficient, the errors of measured flow and stage are included and the lower flow is, the larger the magnitude of error of measured roughness coefficient is. But the error of depth and velocity associated with uncertainty of roughness coefficient is less than about 5% in the both of low and high flow, and it shows the validity of measured roughness coefficient.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.2
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• pp.379-387
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• 2017

As the average load factor of High-Speed Rail (HSR) trains increased up to 98%, it caused uncomfortable crowdedness in the cabin and deteriorated the level of service to the HSR users. In this paper, we estimated the willingness-to-pay (WTP) of the HSR users for mitigating the crowdedness in the cabin. The contingent valuation method based on the stated preference data was used and the tobit model was applied for the estimation of WTP. It can be concluded that WTP for mitigating the crowdedness in the HSR trains is proportional to the congestion level of train and income level of user. Males, first-class users, not-assigned ticket users, and monthly pass users have relatively higher WTPs, while homemakers, travelers in weekends, commuters and leisure travelers have relatively lower values. The results can provide the fundamental information to estimate the benefits of mitigating crowdedness or the magnitude of governmental subsidy to railway operators for additional introduction of HSR trains.

• Water for future
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• v.19 no.1
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• pp.75-86
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• 1986

This study aims at the analysis and application of PMP(Probable Maximum Precipitation)for the determination of design flood in the river basin planning and design of major hydraulic structures. PMP was estimated by hydro-meterological method statistical method and envelope curve method. PMF(Probable Maximum Flood)was then estimated from this PMP by synthetic unit hydrograph method and chow method. From the comparison of three methods for PMP estimation of magnitude of PMP in order of statistical, hydro-metrological, envelope curve method. Among PMP results estimated by each method it is believed that the hydro-meteorological method gave the best proper value in comparison with historical maximum rainfall because of this method reflected upon all meterological factor. From the comparison of PMP with probable rainfall and flood, it was shown that estimated value by statistical method and hydro-metrological method were nearly equivalent to the value of return period 100 years and its value of envelope curve method was equivalent to return period 200 to 500 year. It was found that PMF estimated from would be more safe for the design of major hydraulic structures in the consideration.

• Proceedings of the Korea Water Resources Association Conference
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• 1986.07a
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• pp.93-101
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• 1986

This study aims at analysis and application of PMP(Probable Maximum Precipitation) for the determination of design of major hydraulic structures. PMP was estimated by hydro-meteorolgical method and envelope curve method. PMF(Probable Maximum Flood) was then estimated from this PMP by synthetic unit hydrograph method and chow method. From the comparison of three methods for PMP estimation of magnitude of PMP in order of statistical, hydro-meteorlogical, envelope curve method. Amon PMP results estimated by each method it is believed that the hydro-meteorological method gave the best proper value in comparison with historical maximum rainfall because of this method reflected upon all meteorological factor. From the comparison of PMP with probable rainfall and flood, it was shown that estimated value by statistical method and hydro-metelogical method were nearly equivalent to the value of return period 200 to 500 year. It was found that PMF estimated from would be more safe for the design of major hydraulic structures in the consinderation.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.17 no.5
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• pp.29-38
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• 2018

This study aims to propose a method for the estimation of operational delay cost using transportation card data in bus accidents. Average operational delay time from bus accidents was surveyed among 12 bus companies through an interview method. Then, the operational delay cost was estimated using actual traffic accident data and transportation card data. Results showed that average loss time per bus accident was found to be 45 minutes. In addition, total occupancy of 659 was estimated for the accidents investigated using transportation card data, resulting a total loss time of 494.25 hours. An estimated operational delay cost was 186.9 thousand won per accident, which was 6.37% of social agency cost. The magnitude of this number implied that operational delay cost may have a significant impact on traffic accident cost if included.