• ETRI Journal
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• v.38 no.2
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• pp.366-375
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• 2016

This paper describes an algorithm to suppress composite noise in a two-microphone speech enhancement system for robust hands-free speech communication. The proposed algorithm has four stages. The first stage estimates the power spectral density of the residual stationary noise, which is based on the detection of nonstationary signal-dominant time-frequency bins (TFBs) at the generalized sidelobe canceller output. Second, speech-dominant TFBs are identified among the previously detected nonstationary signal-dominant TFBs, and power spectral densities of speech and residual nonstationary noise are estimated. In the final stage, the bin-wise output signal-to-noise ratio is obtained with these power estimates and a Wiener post-filter is constructed to attenuate the residual noise. Compared to the conventional beamforming and post-filter algorithms, the proposed speech enhancement algorithm shows significant performance improvement in terms of perceptual evaluation of speech quality.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.6
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• pp.90-96
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• 1998

Helical gear system is widely used to transmit heavy duty power with harmonies and silences between parallel shafts. This paper predicts a life with Weibull distribution and estimates a reliability based on recycle principle of helical gear systems. 2-parameter Weibull distribution is generally adopted to estimate the mechanical life and the reliability of most gear systems, because this Weibull distribution is proper to explain a characteristics or a life of parts of gear systems with linearity of probability density data on weibull data sheet. For a high reliability, this paper estimates a number of overhaul times and a number of needed substitutes (exchange attachment,1 or parts) with following renewal theory, One is make an exchange of whole module include failure attachments/parts and second estimating method is only exchange of a failure attachments / parts.

• Journal of the Korean Society of Safety
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• v.32 no.1
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• pp.21-26
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• 2017

An IoT-based particulate matter (PM2.5) sensing device (PSD) is developed. The PSD consists of a PM2.5 sensor, signal processing circuit, and wi-fi enabled-microprocessor along with temperature and humidity sensors. The PSD estimates PM2.5 density by measuring light scattered by PM2.5. To gauge performance of the PSD, PM2.5 density of open air was measured with the PSD and compared with that of the collocated-government-certified measuring station. Measurements were taken at a sampling frequency of 100 Hz and moving-averaged to remove measurement noise. When compared to the result of the measuring station, average percentile error of PM2.5 density from the PSD is found to be 31%. A correlation coefficient is found to be 0.72 which indicates a strong correlation. Instantaneous variation, however, may far exceed average errors, leading to a conclusion that the PSD is more suitable for estimating average trend of PM2.5 density variations than estimating instantaneous PM2.5 density.

• Communications for Statistical Applications and Methods
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• v.16 no.3
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• pp.479-485
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• 2009

When a part of data is unobserved the marginal likelihood of parameters given the observed data often involves analytically intractable high dimensional integral and hence it is hard to find the maximum likelihood estimate of the parameters. Simulated maximum likelihood(SML) method which estimates the marginal likelihood via Monte Carlo importance sampling and optimize the estimated marginal likelihood has been used in many applications. A key issue in SML is to find a good proposal density from which Monte Carlo samples are generated. The optimal proposal density is the conditional density of the unobserved data given the parameters and the observed data, and attempts have been given to find a good approximation to the optimal proposal density. Algorithms which adaptively improve the proposal density have been widely used due to its simplicity and efficiency. In this paper, we describe a fully adaptive algorithm which has been used by some practitioners but has not been well recognized in statistical literature, and evaluate its estimation performance and robustness via a simulation study. The simulation study shows a great improvement in the order of magnitudes in the mean squared error, compared to non-adaptive or partially adaptive SML methods. Also, it is shown that the fully adaptive SML is robust in a sense that it is insensitive to the starting points in the optimization routine.

• Journal of The Korean Astronomical Society
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• v.22 no.2
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• pp.127-140
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• 1989

Problem of the diffuse radiation (DFR) transfer is solved exactly for pure hydrogen nebulae of uniform density, and accuracies of the on-the-spot (OTS) approximation are critically examined. For different values of density and spectral types of the central star, we have calculated the degree of ionization and the kinetic temperature of electrons as functions of distance from the central star, and compared them with the corresponding results of the OTS approximation. At most locations inside an HII region. the DFR ionizes considerable amount of hydrogen; therefore, the OTS approximation under-estimates the size of ionized regions. The exact treatment of the DFR transfer results in an about 10 to 20 percent increase in the classical $Str{\ddot{o}}mgren$ radius. The OTS approximation overestimates the local heating rate by raising the density of neutral hydogens. Consequently, it predicts higher values for the local electron temperature. The OTS approximation also exaggerates the dependence of electron temperature on density. When the hydrogen density is changed from $10/cm^3$ to $10^3/cm^3$ with an 06.5V star, the OTS approximation shows an about 3,000 K difference in the electron temperature, while the exact treatment of the DFR-transfer reduces the difference to about 1,000 K. The OTS approximation fails to demonstrate the brightening of the electron temperature close to the ionization boundary.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.8
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• pp.1952-1966
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• 1994

The body segment parameters of twelve young male Korean were measured to compare with the results of foreign cadaver studies. A human body was assumed to have fourteen body segments. The mass of each segment was measured with a water immersion test and the mass center of a segment was determined on the balance platform by changing postures. In the case of Korean, because of the difference in body proportion, the mass center of whole-body is located further from the distal end of head(Korean : 44.9% vs. Caucasian : 41.2%), and the mass center of each segment also located in different proportional locations. The existing regression equations, which can estimate segment mass based upon the anthropometric dimensions, estimates segment mass (the mass of shank) for Korean with 13% error. Therefore, it is not recommended to estimate the mass, and the moment of inertia of body segment of Korean based on the existing equations. However, the density information of body constituents was similar enough to apply it to Korean density. It was validated by the comparison between the results of the direct immersion method and 3-dimensional volume reconstruction of segment form the cross sectional images of CT-scan. The average body density measured form twelve subjects was $1.035{\;}kg/m^3$ and showed deceasing trendency.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.114.1-114.1
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• 2012

To measure the magnetic field strength in the solar corona, we examined 10 fast (>1000 km/s) limb coronal mass ejections (CMEs) that show clear shock structures in Solar and Heliospheric Observatory/Large Angle and Spectrometric Coronagraph images. By applying the piston-shock relationship to the observed CME's standoff distance and electron density compression ratio, we estimated the Mach number, Alfven speed, and magnetic field strength in the height range 3-15 solar radii (Rs). The main results from this study are as follows: (1) the standoff distance observed in the solar corona is consistent with those from a magnetohydrodynamic model and near-Earth observations; (2) the Mach number as a shock strength is in the range 1.49-3.43 from the standoff distance ratio, but when we use the density compression ratio, the Mach number is in the range 1.47-1.90, implying that the measured density compression ratio is likely to be underestimated owing to observational limits; (3) the Alfven speed ranges from 259 to 982 km/s and the magnetic field strength is in the range 6-105 mG when the standoff distance is used; (4) if we multiply the density compression ratio by a factor of two, the Alfven speeds and the magnetic field strengths are consistent in both methods; and (5) the magnetic field strengths derived from the shock parameters are similar to those of empirical models and previous estimates.

• Asian-Australasian Journal of Animal Sciences
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• v.32 no.1
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• pp.58-62
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• 2019

Objective: The oxidized low density lipoprotein receptor 1 (OLR1) gene plays an important role in the degradation of oxidized low-density lipoprotein and adipocyte proliferation in mammals. For this reason, we aimed at investigating the association of OLR1 gene polymorphisms with carcass quality traits in Chinese Qinchuan cattle. Methods: The single nucleotide polymorphism (SNP) was identified in the 3' untranslated region of bovine OLR1 gene by DNA sequencing. In addition, the haplotype frequency and linkage disequilibrium estimates of three SNPs were evaluated in 520 individuals. Results: Results indicated that the studied three SNPs were within the range of moderate genetic diversity (0.25< polymorphism information content<0.5). Haplotype analysis of three SNPs showed that ten different haplotypes were identified, but only five haplotypes were listed as those with a frequency of <0.05 were excluded. The Hap3 ($-G_1T_2C_3-$) had the highest haplotype frequency (42.10%). Linkage disequilibrium analysis showed that the three SNPs had a low linkage ($r^2<0.001$). The T10588C and C10647T were significantly associated with backfat thickness and intramuscular fat content in Qinchuan cattle. Conclusion: Based on our results, we believe that the OLR1 gene could be a strong candidate gene for influencing carcass quality traits in Qinchuan cattle.

• Journal of Korean Society of Forest Science
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• v.88 no.4
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• pp.446-453
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• 1999

In this study, the effects of stand planting density on parameters of stand height and basal area growth models were investigated. We used the Korf equation as the base model in estimating the parameters of the growth models for cryptomeria plantation forest stands. Then, in order to investigate the effects of the change in plantation density on the parameter estimates, the "extra sums of square" principle, which provided a reasonable statistical procedure for a performance test, was used. The results of the test coincide with the understandings that stand height growth is not affected significantly by the planting density and the growth curves of stand basal area approaches a common asymptote regardless of the stand density for a given site. However, the shapes of the basal area growth curves were affected significantly by the planting density. Based on the results of the test, we developed a basal area growth model to account for the effects of initial planting density in cryptomeria plantation forest stands.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1D
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• pp.49-58
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• 2006

The purpose of this study is to develop transportation-sensitive land use densities in a metropolitan context. It analyses traffic impacts according to 20 different development density scenarios in the downtown Seoul, and estimates the density ceiling. The results identify that the transportation-wise sustainable density in the downtown can be extended up to the FAR level of 460% with an option of 2,000 won congestion charge levied on the downtown area. It also finds that the region-wide sustainability measured by congestion level can be improving as the level of congestion charge increases. Without the congestion charge, however, the density ceiling slides down to 430%. It is recommended that, in order to bring in higher density developments in the region, transportation demand management (TDM) measures are indispensible.