• The Journal of the Acoustical Society of Korea
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• v.4 no.1
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• pp.43-54
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• 1985

이 논문에서는 Frequency weighting을 이용하여 선형예측 부호화기의 명료성을 개선하는 방법 을 연구한다. 잡음이 섞이지 않은 음성에 대해서는 음성을 분석하기전에 frequency weighting을 행한다. 또한 잡음이 섞인 음성인 경우에는 잡음성분을 spectral subtraction 방법에 의해서 제거한 다음에 frequency weighting을 준다. 이 때 frequency weighting을 주기 위해서 귀의 특성과 연관되어 잘 알려 진 C- message weighting 함수, flanagan weighting 함수 및 articulation index를 약간 수정한 weighting 함수를 사용했다. 여러 객관적인 distance measure를 사용하여 frequency weighting 방법의 성능을 측정하고 귀로 들어 본 결과, frequency weighting 방법을 사용하여 선형예측 방법에 의한 합성 음의 명료도를 효율적으로 개선할 수 있었다.

• The Korean Journal of Applied Statistics
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• v.30 no.6
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• pp.877-888
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• 2017

Spectral analysis is used to determine the frequency of time series data. We first determine the frequency of the series through the power spectrum or the periodogram and then calculate the period of a cycle that may exist in a time series. Estimating the frequency using a Bayesian technique has been developed and proven to be useful; however, the Bayesian estimator for the frequency cannot be analytically solved through mathematical equations and may be handled numerically or computationally. In this paper, we make an inference on the Bayesian frequency through both resampling a parameter by Markov chain Monte Carlo (MCMC) methods and resampling data by bootstrap methods for a time series. We take the Korean real estate price index as an example for Bayesian frequency estimation. We have found a difference in the periods between the sale price index and the long term rental price index, but the difference is not statistically significant.

• Journal of the Korean Dietetic Association
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• v.18 no.2
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• pp.186-199
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• 2012

The present study was conducted to investigate dietary habits and biochemical indices according to the obesity index of elementary school students visiting a hospital for diagnosis. The subjects of this study were 150 elementary school students and their mothers. The overweight rates of child subjects were 37.5% for males and 40.9% for females, whereas the rates of underweight children were 35.0% for males and 14.5% for females. Children's obesity index significantly decreased with an increase in the average monthly income of children's families. Children's obesity index, mothers' weights, BMI, and percent ideal body weight were all positively correlated. Blood biochemical values in children (hemoglobin, hematocrit, albumin, globulin, glucose, total cholesterol, and triglyceride levels) and their obesity index also showed positive correlation. For the underweight group, the frequency of iron-deficiency anemia was significantly high, whereas for the overweight group, the frequency of dyslipidemia was high. There was a significant increase in children's obesity index and a decrease in frequency of regular exercise with time spent on the TV/computer. The normal weight group recorded the highest total scores for mothers' nutritional knowledge, whereas the overweight group recorded the lowest total scores. Therefore, to maintain healthy weight in children, nutritional education programs for mothers and children should be developed.

• Smart Structures and Systems
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• v.20 no.4
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• pp.427-440
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• 2017

One of the suitable structural damage detection methods using vibrational characteristics are damage-index-based methods. In this study, a damage index for identifying damages in plate structures using frequency response function (FRF) data has been provided. One of the significant challenges of identifying the damages in plate structures is high number of degrees of freedom resulting in decreased damage identifying accuracy. On the other hand, FRF data are of high volume and this dramatically decreases the computing speed and increases the memory necessary to store the data, which makes the use of this method difficult. In this study, FRF data are compressed using two-dimensional principal component analysis (2D-PCA), and then converted into damage index vectors. The damage indices, each of which represents a specific condition of intact or damaged structures are stored in a database. After computing damage index of structure with unknown damage and using algorithm of lookup tables, the structural damage including the severity and location of the damage will be identified. In this study, damage detection accuracy using the proposed damage index in square-shaped structural plates with dimensions of 3, 7 and 10 meters and with boundary conditions of four simply supported edges (4S), three clamped edges (3C), and four clamped edges (4C) under various single and multiple-element damage scenarios have been studied. Furthermore, in order to model uncertainties of measurement, insensitivity of this method to noises in the data measured by applying values of 5, 10, 15 and 20 percent of normal Gaussian noise to FRF values is discussed.

• Journal of the Korean Society of Safety
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• v.35 no.5
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• pp.59-65
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• 2020

For monitoring the status of industrial accidents, many statistical indexes have been developed and applied such as fatal rate, frequency rate, and severity rate. These accident indexes are measured by frequency and loss time according to the accidents in the individual industry level. However, it is less considered to use the index of identifying the industrial concentration of accidents in the holistic view. Thus, this study aims to suggest the accident concentration level among domestic industries through index analysis. The concentration level of industrial accidents is calculated by the accident composition of sub-industries. This concentration level shows whether an industry is comprised of a few sub-industries generating more accidents or an industry consists of sub-industries having the similar number of accidents. To this end, the concentration rate (CR) and concentration index (CI) are proposed to take a look at the industry composition of accidents by embracing the concept of market concentration indexes such as Hirschman-Herfindahl Index. As for the case study, four industries of mining, manufacturing, transportation, and other business (usually service) are analyzed in terms of indexes of accident rate, death(fatality) rate, and CR and CI of accident and death. Finally, we illustrate the positioning map that the accident concentration level is compared with the traditional accident frequency level among industries.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.59-63
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• 2003

Modal properties of guided waves along circular dispersive double negative (DNG) index metamaterial rod waveguides are numerically investigated. Identical forms of dispersive dielectric and magnetic material constants are used for simplicity. For degenerated azimuthally symmetric mode, a multimode region, a single mode region, a band gap region and a forbidden region are found which cannot be observed in the case of the conventional dielectric rod waveguide. As the normalized frequency goes down, discrete guided modes are continuously generated, which is a reverse property of conventional dielectric rod waveguide. Also, there are high-frequency cutoffs, which have been generally examined in dispersive circular geometries such as a plasma column or a plasma Goubau line. In the single mode region, both the low- and high-frequency cutoffs are existed where the propagation constants are continued between the guided oscillating and surface modes.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.240-240
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• 2000

This paper presents two algorithms based on the concept of the frequency domain adaptive filter(FDAF). First the frequency domain recursive least squares(FRLS) algorithm with the overlap-save filtering technique is introduced. This minimizes the sum of exponentially weighted square errors in the frequency domain. To eliminate discrepancies between the linear convolution and the circular convolution, the overlap-save method is utilized. Second, the sliding method of data blocks is studied Co overcome processing delays and complexity roads of the FRLS algorithm. The size of the extended data block is twice as long as the filter tap length. It is possible to slide the data block variously by the adjustable hopping index. By selecting the hopping index appropriately, we can take a trade-off between the convergence rate and the computational complexity. When the input signal is highly correlated and the length of the target FIR filter is huge, the FRLS algorithm based on the block processing technique has good performances in the convergence rate and the computational complexity.

• Magazine of the Korean Society of Agricultural Engineers
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• v.41 no.5
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• pp.43-52
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• 1999

In an effort to identify quantitatively historical drought conditions, and to evaluate their temporal and spatial variability , two commonly used drougth indices, the standardized precipitation index, SPI by Mckee and the Palmer drought severity index. PDSI were calculated from 54 meteorological stations, SPI was evaluated for different time scales, 3 to 48 months. As the compjtational spans for SPI increase from 3 to 48 months the frequency and intensity of drought decrease, but the duration of drought increase. When monthly and ten-day PDSIs were compared, the frequency and duratin of drought were almost equal and the intensity of drought differ slightly. The three month SPI has the advatage to detect the drought resulting from short-term shortage of rainfall, while PDSI had the advantage to detect the state of drought resulting from cumulated shortage of rainfall. The period-frequency spectrum analyses at Kangnung statino showed that the maximum value of relative frequency was 24.4% when the period was 5.2months, and the 6month SPI has most similar trends to PDSI.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.922-926
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• 2001

This paper deals with sensing ability of smart sensor that has a sensing ability to distinguish materials according to frequency changing. We have developed a new signal processing method that can distinguish among different materials. The smart sensor was developed for recognition of materials. We estimated the sensing ability of smart sensor with the $R_{SAI}$ method according to frequency changing. Experiments and analysis were executed to estimate the ability to recognize objects according to frequency changing. Sensing ability of smart sensors was evaluated relatively through a new $R_{SAI}$ method. Applications of smart sensors are for finding abnormal conditions of objects (auto-manufacturing), feeling of objects (medical product), robotics, safety diagnosis of structure, etc.etc.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.6
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• pp.1078-1086
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• 2009

This paper presents a Fourier based algorithm for estimating the parameters of the low frequency oscillating modes. The proposed methods estimates various parameters(frequency, damping factor, mode magnitude, phase) by fitting Fourier spectrum and phase with a damped exponential cosine function. Dominant frequency is selected by taking frequency corresponding to the peak spectrum, and damping factor is estimated using the left/right spectra of Fourier spectrum. In addition, mode magnitude is calculated by the normalized peak spectrum, and phase is estimated from spectrum phase. Also, we introduce an accuracy index in order to determine the accuracy of the estimated parameters, and the index is calculated using the deviations of the peak spectrum and the left/right spectra. The parameter estimation methods proposed in this paper include very simple arithmetical processes, so the algorithms are simple and the calculation speed is very fast. The proposed methods are applied to test functions with two dominant modes. The results show that the proposed methods are highly applicable to low frequency parameter estimation.