• Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
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• 2001.06a
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• pp.1041-1041
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• 2001

Removal of variability in spectra data before the application of chemometric modeling will generally result in simpler (and presumably more robust) models. Particularly for sparsely sampled data, such as typically encountered in diode array instruments, the use of Savitzky-Golay (S-G) derivatives offers an effective method to remove effects of shifting baselines and sloping or curving apparent baselines often observed with scattering samples. The application of these convolution functions is equivalent to fitting a selected polynomial to a number of points in the spectrum, usually 5 to 25 points. The value of the polynomial evaluated at its mid-point, or its derivative, is taken as the (smoothed) spectrum or its derivative at the mid-point of the wavelength window. The process is continued for successive windows along the spectrum. The original paper, published in 1964 [1] presented these convolution functions as integers to be used as multipliers for the spectral values at equal intervals in the window, with a normalization integer to divide the sum of the products, to determine the result for each point. Steinier et al. [2] published corrections to errors in the original presentation [1], and a vector formulation for obtaining the coefficients. The actual selection of the degree of polynomial and number of points in the window determines whether closely situated bands and shoulders are resolved in the derivatives. Furthermore, the actual noise reduction in the derivatives may be estimated from the square root of the sums of the coefficients, divided by the NORM value. A simple technique to evaluate the actual convolution factors employed in the calculation by the software will be presented. It has been found that some software packages do not properly account for the sampling interval of the spectral data (Equation Ⅶ in [1]). While this is not a problem in the construction and implementation of chemometric models, it may be noticed in comparing models at differing spectral resolutions. Also, the effects on parameters of PLS models of choosing various polynomials and numbers of points in the window will be presented.

• Journal of the Earthquake Engineering Society of Korea
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• v.25 no.5
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• pp.223-232
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• 2021

The spatial variation characteristics of seismic motions at the nuclear power plant's site and structures were analyzed using earthquake records obtained at the Fukushima nuclear power plant during the Great East Japan Earthquake. The ground responses amplified as they approached the soil surface from the lower rock surface, and the amplification occurred intensively at about 50 m near the ground. Due to the soil layer's nonlinear characteristics caused by the strong seismic motion, the ground's natural frequency derived from the response spectrum ratio appeared to be smaller than that calculated from the shear wave velocity profile. The spatial variation of the peak ground acceleration at the ground surface of the power plant site showed a significant difference of about 0.6 g at the maximum. As a result of comparing the response spectrums at the basement of the structure with the design response spectrum, there was a large variability by each power plant unit. The difference was more significant in the Fukushima Daiichi site record, which showed larger peak ground acceleration at the surface. The earthquake motions input to the basement of the structure amplified according to the structure's height. The natural frequency obtained from the recorded results was lower than that indicated in the previous research. Also, the floor response spectrum change according to the location at the same height was investigated. The vertical response on the foundation surface showed a significant difference in spectral acceleration depending on the location. The amplified response in the structure showed a different variability depending on the type of structure and the target frequency.

• Journal of Digital Contents Society
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• v.19 no.1
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• pp.103-112
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• 2018

In this paper, we propose a method of recognizing emotions using PPG sensor which measures blood flow according to emotion. From the existing PPG signal, we use a method of determining positive emotions and negative emotions in the frequency domain through PSD (Power Spectrum Density). Based on James R. Russell's two-dimensional prototype model, we classify emotions as joy, sadness, irritability, and calmness and examine their association with the magnitude of energy in the frequency domain. It is significant that this study used the same PPG sensor used in wearable devices to measure the top four kinds of emotions in the frequency domain through image experiments. Through the questionnaire, the accuracy, the immersion level according to the individual, the emotional change, and the biofeedback for the image were collected. The proposed method is expected to be various development such as commercial application service using PPG and mobile application prediction service by merging with context information of existing smart phone.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.2
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• pp.33.1-33.1
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• 2016

We report detection of short-term flux variability in multi-epoch observations and intraday variability in polarized emission at millimeter-wavelength from S5 0716+714 using Korean VLBI Network (KVN) radio telescopes. Over the whole observation epochs, the source shows significant inter-month variations at K- and Q-band with modulation indices of 19% at K-band and 36% at Q-band. In each epoch, the source shows monotonic flux increase in Epoch 1 and 3, and monotonic flux decrease in Epoch 2 and 4. We found an inverted spectrum with mean spectral indices of -0.57 in Epoch 1 and -0.15 in Epoch. On the contrary, we found relatively steep indices of 0.24 and 0.17 in Epoch 2 and Epoch 4, respectively. In the study of intraday variability of polarization, we found significant variations in the degree of linear polarization at 86 GHz, and in polarization angle at 43 and 86 GHz during ~10 h. The spectrum of the source is quite flat with spectral indices of -0.07 to 0.07 at 22-43 GHz and -0.23 to 0.04 at 43-86 GHz. The measured degree of the linear polarization ranges from 2.3% to 3.3 % at 22 GHz, from 0.9% to 2.2 % at 43 GHz and from 0.4 % to 4.0 % at 86 GHz, yielding prominent variations at 86 GHz over 4-5 h. The linear polarization angle is in the range of 4 to $12^{\circ}$ at 22 GHz, -39 to $81^{\circ}$ at 43 GHz, and 66 to 119 at 86 GHz with a maximum rotation of $110^{\circ}$ at 43 GHz over ~4 h. We estimated the Faraday rotation measures (RM) ranging from -9200 to 6300 rad m-2 between 22 and 43 GHz, and from -71000 to 7300 rad m-2 between 43 and 86 GHz, respectively. The frequency dependency of RM was investigated, yielding a mean power-law index, a, of 2.0. This implies that the polarized emission from S5 0716+714 at 22-86 GHz moves through a Faraday screen in or near the jet of the source.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.36.2-37
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• 2016

We study the long-term radio variability of 43 radio bright AGNs by exploiting the data base of the University of Michigan Radio Astronomy Observatory (UMRAO) monitoring program. The UMRAO database provides high quality lightcurves spanning 25 - 32 years in time at three observing frequencies, 4.8, 8, and 14.5 GHz. We model the periodograms (temporal power spectra) of the observed lightcurves as simple power-law noise (red noise, spectral power $P(f){\propto}f^{-{\beta}}$ using Monte Carlo simulations, taking into account windowing effects (red-noise leak, aliasing). The power spectra of 39 (out of 43) sources are in good agreement with the models, yielding a range in power spectral index (${\beta}$) from ${\approx}1$ to ${\approx}3$. We find a strong anti-correlation between ${\beta}$ and the fractal dimension of the lightcurves, which provides an independent check of the quality of our modelling of power spectra. We fit a Gaussian function to each flare in a given lightcurve to obtain the flare duration. We discover a correlation between ${\beta}$ and the median duration of the flares. We use the derivative of a lightcurve to obtain a characteristic variability timescale which does not depend on the assumed functional form of the flares, incomplete fitting, and so on. We find that, once the effects of relativistic Doppler boosting on the observed timescales are corrected, the variability timescales of our sources are proportional to the black hole mass to the power of ${\alpha}=1.70{\pm}0.49$. We see an indication for AGNs in different regimes of accretion rate, flat spectrum radio quasars and BL Lac objects, having different scaling relations with ${\alpha}{\approx}1$ and ${\approx}2$, respectively. We find that modelling the periodograms of four of our sources requires the assumption of broken powerlaw spectra. From simulating lightcurves as superpositions of exponential flares we conclude that strong overlap of flares leads to featureless simple power-law periodograms of AGNs at radio wavelengths in most cases (The paper is about to be submitted to ApJ).

• Journal of Acupuncture Research
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• v.21 no.5
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• pp.227-239
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• 2004

Objectives : The purpose of this study was to assess the effect of acupuncture for reducing mental stress using power spectrum analysis of the heart rate variability. Methods : 5 healthy volunteers participated in this study. After instrumentation and 5-minute rest period, mental stress was provided for 5-minute. HRV was recorded before and after the mental stress. Acupuncture was put on the HT8, and needle was removed after 15min. Than 2nd mental stress was given for 5-minute with same method. For the control, same process was repeated to same subject except for acupuncture. Results : After mental stress, LF and LF/HF ratio is significantly increased. After acupuncture treatment, LF/HF ratio is significantly decreased, and LF do not significantly changed despite of mental stress. Conclusions : The result suggest that acupuncture treatment can regulate and prevent the alteration of autonomic nerve system due to mental stress.

• Earthquakes and Structures
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• v.14 no.4
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• pp.285-295
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• 2018

In this study, the effect of local site conditions (site class and site amplifications) and structural variability are investigated on fragility functions of typical building structures. The study area is chosen as Eastern Turkey. The fragility functions are developed using site-specific uniform hazard spectrum (UHS). The site-specific UHS is obtained based on simulated ground motions. The implementation of ground motion simulation into seismic hazard assessment has the advantage of investigating detailed local site effects. The typical residential buildings in Erzincan are represented by equivalent single degree of freedom systems (ESDOFs). Predictive equations are accomplished for structural seismic demands of ESDOFs to derive fragility functions in a straightforward manner. To study the sensitivity of fragility curves to site class, two sites on soft and stiff soil are taken into account. Two alternative site amplification functions known as generic and theoretical site amplifications are examined for these two sites. The reinforced concrete frames located on soft soil display larger fragilities than those on stiff soil. Theoretical site amplification mostly leads to larger fragilities than generic site amplification more evidently for reinforced concrete buildings. Additionally, structural variability of ESDOFs is generally observed to increase the fragility especially for rigid structural models.

• Journal of Acupuncture Research
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• v.22 no.6
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• pp.173-180
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• 2005

Objectives : The purpose of this study was to assess the effect auricular acupuncture for acute mental stress using power spectrum analysis of the heart rate variability(HRV). Methods : 10 healthy volunteers participated in this study. After 5 minute rest, the first mental stress was provided for 5 minute. And then subjects rested for 15 minute. The second mental stress was provided for 5 minute. The acupoint, Shin-Mun point of the ear was stimulated for 15 minute. HRV was recorded before and after the first and second mental stress, and after auricular acupuncture stimulation. Results : After mental stress, normalized LF and LF/HF ratio is significantly increased. Before and after simple rest, normalized LF and normalized HF is significantly changed, but LF and LF/HF ratio is not significantly changed. On the other hand, before and after auricular acupuncture treatment, normalized LF, normalized HF is significantly changed, and also LF and LF/HF ratio is significantly decreased. Conclusion : The result suggest that auricular acupuncture can decrease more significantly in cardiac sympathetic activity due to mental stress than simple rest.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 1999.03a
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• pp.243-248
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• 1999

There is substantial evidence that anatomical connections and functional interactions exist between vestibular and autonomic systems. Heart rate variability (HRV) including mean, standard deviation, coefficient of variation (CV), power spectrum was analyzed for evaluation of the physiological role of the vestibular system on control of heart rate in rabbits. In anesthetized rabbits, electrical stimulation of the vagus nerve decreased heart rate and decreased LF/HF by increasing HF. On the cervical sympathetic nerve increased heart rate and increased LF/HF by increasing LF. Atropine, cholinergic blocker, increased heart rate and increased LF/HF by reducing HF, and propranolol, ${\beta}$-adrenergic blocker, decreased heart rate and decreased LF/HF by reducing LF> In unanesthetized rabbits, stimulation of the vestibular system induced by rotation or caloric increased heart rate and increased LF/HF by increasing LF> Also electrical stimulation of the vestibular nerve produced the same of effects as rotation or caloric in anesthetized rabbits. These results suggest that Stimulation of the vestibular system increased heart rate not by inhibiting the parasympathetic nerve but by activating the sympathetic nerve.

• Phonetics and Speech Sciences
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• v.7 no.1
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• pp.125-131
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• 2015

The current study explores whether speaker variability in the fronted articulations of Seoul Korean affricates can be explained by cognitive differences measured by individual autistic traits. The goal was to explore Yu's (2010; 2013) proposal that individual differences in cognitive style can be an important factor in speakers' use of sound variants. The spectral peak frequencies (SPF) of affricates relative to those of fricatives, reported in Kong et al. (2014), were used to acoustically represent the relative degree of anterior place of constriction. When these individual SPFs were related to the scores of Autistic-Spectrum Quotients (Baron-Cohen et al., 2001), a correlation was found for the male speakers, but not for the female speakers, such that speakers of more anterior affricate productions scored low in AQs. Discussion is made with respect to how these findings are in line with Yu's proposal.