• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.8
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• pp.1612-1620
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• 2003

This papers describes a nonlinear transfer function modelling of designed GaAs FET power amplifier by measured and simulated values of designed PA amplifier for multi­carrier transmission system, With the results of PA nonlinearity characteristic, we can estimates AM­AM and AM­PM of designed PA. According to the estimated nonlinear characteristics, we can analysis the ACPR of PA for spectral regrowth, the error vector measurement(EVM) of constallation signals and bit error rate of QPSK and 64­QAM. The suggested nonlinear modelling results are used to get an accurate estimate of digital characteristics between PA amplifier and wireless multi­carrier transmission system using OFDM.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.7 no.5
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• pp.90-96
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• 2008

This paper presents an algorithm of a single chip acoustic speech enhancement for telematics device. The algorithm consists of two stages, i.e. noise reduction and echo cancellation. An adaptive filter based on cross spectral estimation is used to cancel echo. The external background noise is eliminated and the clear speech is estimated by using MMSE log-spectral magnitude estimation. To be suitable for use in consumer electronics, we also design a low cost, high speed and flexible hardware architecture. The performance of the proposed speech enhancement algorithms were measured both by the signal-to-noise ratio(SNR) and recognition accuracy of an automatic speech recognition(ASR) and yields better results compared with the conventional methods.

• Bulletin of the Korean Chemical Society
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• v.20 no.1
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• pp.35-41
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• 1999

Stability characteristics of hyperbolic reaction-diffusion equations with a reversible Brusselator model are investigated as an extension of the previous work. Intensive stability analysis is performed for three important parameters, Nrd, β and Dx, where Nrd is the reaction-diffusion number which is a measure of hyperbolicity, β is a measure of reversibility of autocatalytic reaction and Dx is a diffusion coefficient of intermediate X. Especially, the dependence on Nrd of stability exhibits some interesting features, such as hyperbolicity in the small Nrd region and parabolicity in the large Nrd region. The hyperbolic reaction-diffusion equations are solved numerically by a spectral method which is modified and adjusted to hyperbolic partial differential equations. The numerical method gives good accuracy and efficiency even in a stiff region in the case of small Nrd, and it can be extended to a two-dimensional system. Four types of solution, spatially homogeneous, spatially oscillatory, spatio-temporally oscillatory and chaotic can be obtained. Entropy productions for reaction are also calculated to get some crucial information related to the bifurcation of the system. At the bifurcation point, entropy production changes discontinuously and it shows that different structures of the system have different modes in the dissipative process required to maintain the structure of the system. But it appears that magnitude of entropy production in each structure give no important information related for states of system itself.

• Bulletin of the Korean Chemical Society
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• v.15 no.7
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• pp.553-559
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• 1994

Dynamics of $CH_2CI$ group in ${\alpha},2,6$-trichlorotoluene dissolved in $CDCl_3$ was studied by observing various relaxation modes for $^{13}C$ under proton undecoupled condition. Partially relaxed $^{13}C$ spectra were obtained at $34^{\circ}C$ as a function of evolution time after applying various designed pulse sequences to this $AX_2$ spin system. It was found that nonlinear regression analysis of the relaxation data for these magnetization modes could provide the information about dipolar and spin-rotational auto-correlation and cross-correlation spectral densities for fluctuation of the $^{13}C-^1H$ internuclear vector in $CH_2Cl$ group. The results show that the effect of cross-correlation is comparable in magnitude to that of auto-correlation and the relaxation in this spin system is dominated by dipolar mechanism rather than spin-rotational one. From the resulting spectral density data we could calculate the bond angle ${\angle}HCH\;(105.1$^{\circ}$) and elements of the rotational diffusion tensor for $CH_2Cl$ group.

• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.5
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• pp.23-29
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• 2009

On December 13, 1996, an earthquake with local magnitude (M$_L$) 4.5 occurred in the Yeongwol area of South Korea. The epicenter was 37.2545$^{\circ}$N and 128.7277$^{\circ}$E, which is located inside the Okcheon Fold Belt. The waveform inversion analysis was carried out to estimate source parameters of the event according to the filtering bandwidth of seismic data. Using 0.02$\sim$0.2 Hz filtering bandwidth, focal depth and seismic moment were estimated to be 6 km and 1.3$\times$10$^{16}$ N$\cdot$m, respectively. This seismic moment corresponds to the moment magnitude (M$_W$) 4.7. The focal mechanism by the waveform inversion and P wave first motion polarity analysis is a strike slip faulting including a small thrust component, and the direction of P-axis is ENE-WSW. The moment magnitude estimated by spectral analysis was 4.8, which is similar to that estimated by waveform inversion. Average stress drop was estimated to be 14.3 MPa.

• Korean Journal of Applied Biomechanics
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• v.27 no.4
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• pp.263-268
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• 2017

Objective: The purpose of this study was to show differences in impact variables between treadmills with (treadmills B, C, and D) and treadmills without a shock-absorbing function (treadmill A) to propose the development of a treadmill with improved or added shock-absorbing function to reduce impact shock. Method: Thirteen male students in their twenties who had habitual rear foot strike during running ran on four treadmills at 2.67 m/sec while ankle and neck acceleration data were collected. The magnitude of the ankle and neck acceleration peaks and peak positive ankle acceleration were calculated. The power spectral density of each signal was calculated to transform the ankle and neck accelerations in the frequency domain. Results: The peak positive ankle acceleration on treadmill B was significantly lesser than that on treadmills A and D, and that on treadmill C was significantly less than that on treadmill A (p < .01). Peak positive neck acceleration was not statistically different between the treadmills. The frequencies of the peak power of the ankle and neck acceleration signal within the lower and higher frequency ranges were not statistically different between the treadmills. The signal power magnitude of the ankle in higher frequency ranges on treadmill B was significantly less than that on treadmills A, C, and D (p < .01). The signal power magnitude of the ankle in higher frequency ranges was not statistically different between the treadmills. The signal power magnitudes of the neck acceleration signal within the lower and higher frequency ranges were not statistically significantly different between the treadmills. Conclusion: Our results indicate that the shock-absorbing function of a treadmill plays a role in reducing impact shock. Therefore, in future treadmill development, shock-absorbing function should be improved or incorporated to reduce impact shock to the body.

• Journal of Biosystems Engineering
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• v.24 no.2
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• pp.115-122
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• 1999

Because of their small mass, volume, solid state construction and long life, light-emitting diodes(LEDs) hold promises as a lighting source for intensive plant production system. Spectral characteristics and light intensity of LEDs were tested to investigate their feasibility as artificial lighting sources for growth and morphogenesis control in transplant production system. Blue, green, and red LEDs had a peak-emission wavelength at 442nm, 522nm, and 673nm, respectively. Their half width defined as the difference between upper and lower wavelength in the intensity equivalent to 50% of the maximum intensity showed 26nm, 41nm, and 74nm, respectively. Photosynthetic photon flux(PPE) at the distance of 9cm under the LEDs array was measured as $235{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$ for red, $109{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$ for green, and $75{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$ for blue LEDs. At the same distance, green LEDs had the illuminance of 13,0001x, nine to ten times higher than those of red and blue LEDs. Red, green, and blue LEDs at a distance of 9cm had the irradiance of $46W{\cdot}m^{-2},\;19W{\cdot}m^{-2},\;8W{\cdot}m^{-2}$, respectively. Light intensity of blue, green, and red LEDs increased linearly in proportion to the magnitude of the current applied to the operating circuit. Thus the light intensity of LEDs was controlled by the applied current in operating circuit.

• Earthquakes and Structures
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• v.7 no.2
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• pp.141-157
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• 2014

The Conditional Mean Spectrum represents a powerful link between the seismic hazard information and the selection of strong ground motion records at a particular site. The scope of the paper is to apply for the city of Bucharest for the first time the method to obtain the Conditional Mean Spectrum (CMS) presented by Baker (2011) and to select, on the basis of the CMS, a suite of strong ground motions for performing elastic and inelastic dynamic analyses of buildings and structures with fundamental periods of vibration in the vicinity of 1.0 s. The major seismic hazard for Bucharest and for most of Southern and Eastern Romania is dominated by the Vrancea subcrustal seismic source. The ground motion prediction equation developed for subduction-type earthquakes and soil conditions by Youngs et al. (1997) is used for the computation of the Uniform Hazard Spectrum (UHS) and the CMS. The disaggregation of seismic hazard is then performed in order to determine the mean causal values of magnitude and source-to-site distance for a particular spectral ordinate (for a spectral period T = 1.0 s in this study). The spectral period of 1.0 s is considered to be representative for the new stock of residential and office reinforced concrete (RC) buildings in Bucharest. The differences between the Uniform Hazard Spectrum (UHS) and the Conditional Mean Spectrum (CMS) are discussed taking into account the scarcity of ground motions recorded in the region of Bucharest and the frequency content characteristics of the recorded data. Moreover, a record selection based on the criteria proposed by Baker and Cornell (2006) and Baker (2011) is performed using a dataset consisting of strong ground motions recorded during seven Vrancea seismic events.

• Geomechanics and Engineering
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• v.16 no.4
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• pp.435-448
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• 2018

In order to make reliable earthquake-resistant design of civil engineering structures, one of the most important considerations in a region with high seismicity is to pay attention to the local soil condition of regions. It is aimed in the current study at specifying dynamic soil characteristics of Kirikkale city center conducting the 1-D equivalent linear and non-linear site response analyses. Due to high vulnerability and seismicity of the city center of Kirikkale surrounded by active many faults, such as the North Anatolian Fault (NAF), the city of Kirikkale is classified as highly earthquake-prone city. The first effort to determine critical site response parameter is to perform the seismic hazard analyses of the region through the earthquake record catalogues. The moment magnitude of the city center is obtained as $M_w=7.0$ according to the recorded probability of exceedance of 10% in the last 50 years. Using the data from site tests, the 1-D equivalent linear (EL) and nonlinear site response analyses (NL) are performed with respect to the shear modulus reduction and damping ratio models proposed in literature. The important engineering parameters of the amplification ratio, predominant site period, peak ground acceleration (PGA) and spectral acceleration values are predicted. Except for the periods between the period of T=0.2-1.0 s, the results from the NL are obtained to be similar to the EL results. Lower spectral acceleration values are estimated in the locations of the city where the higher amplification ratio is attained or vice-versa. Construction of high-rise buildings with modal periods higher than T=1.0 s are obtained to be suitable for the city of Kirikkale. The buildings at the city center are recommended to be assessed with street survey rapid structural evaluation methods so as to mitigate seismic damages. The obtained contour maps in this study are estimated to be effective for visually characterizing the city in terms of the considered parameters.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.2
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• pp.62.1-62.1
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• 2013

We present the Exposure Time Calculator of IGRINS (Immersion Grating Infrared Spectrograph). The noises of IGRINS and the simulated emission line can be calculated from the combination of Telluric background emission and absorptions, the emission and transmission of the telescope and instrument optics, and the dark noise and the read noise of the infrared arrays. For the atmospheric transmissions, we apply the simulated spectra depending on the Precipitable Water Vapor (PWV) values. In case of calculation of noises, the user needs to input the expected target magnitude, the weather conditions, and the desired exposure time. In addition to the simulated emission line, the parameters of rest wavelength, line-flux, Doppler shift and line-width are needed. The output would be the expected signal-to-noise for each spectral resolution element. The source-code of IGRINS-ETC v2.1.1 is available to be downloaded on the World Wide Web.