• Iberoamérica
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• v.21 no.1
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• pp.127-158
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• 2019

In this paper, the variation in coda /ɾ/ is analyzed in the Spanish of the Tupe district in Peru. The work was carried out on the corpus of 24 semi-structured interviews. Four variants of /-ɾ/ were distinguished and 1920 tokens were analyzed. Praat was used to recognize and describe the variants and two statistical analysis were carried out: descriptive analysis and probabilistic analysis using the statistical program Goldvarb X. The results obtained from the analysis show that the assibilated variant is favored in the prepausal position and before homorganic consonants. The frequency of occurrence was very low before other consonants. Regarding the social factor that contributes to the assimilated variant, the young and middle-aged men (from 20 to 60), those who did not live more than a year on the Peruvian coast and male speakers favor it.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.8
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• pp.1464-1469
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• 2008

A CMOS Gm-C filter with variable cutoff frequency applicable for using in the direct conversion receiver is designed. The designed filter comprises the CMOS differential transconductors, and the gm of the transconductor is controlled by the bias voltage. This configuration can compensate variant of the cutoff frequency which could be generated by external noises, and also be used in multiband receiver. As a results of HSPICE simulation, the control range of the cutoff frequency is $1.5MHz{\sim}3.5MHz$ and the gain control range is $-2.8dB{\sim}2.6dB$. The layout of the designed 5th-order Elliptic low-pass filter is performed to fabricate a chip using $2.5V-0.25{\mu}m$ CMOS processing parameter.

• Korean Journal of Optics and Photonics
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• v.34 no.2
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• pp.76-83
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• 2023

In this paper, the results of analyzing the frequency lock-in breaking characteristics of a ring laser gyroscope with random dithering through numerical experiments are presented. By observing the variant features in the frequency lock-in characteristics according to the dithering amplitude noise, it was possible to analyze the minimum noise condition that causes the frequency lock-in to be broken. It was confirmed that the result is closely related to the relative difference between the dynamic frequency lock-in corresponding to the average dithering amplitude and the frequency determined by the Sagnac effect corresponding to an input rotational angular velocity.

• Journal of the Korean Vacuum Society
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• v.12 no.S1
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• pp.83-87
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• 2003

Zirconium oxide films have been synthesized by radio-frequency magnetron sputtering deposition on n-Si(001) substrate with metal zirconium target at variant $O_2$ partial pressures. The influences of $O_2$ partial pressures of the morphology, deposition rate, microstructure, and the dielectric constant of $ZrO_2$ have been discussed. The results show that deposition rate of $ZrO_2$ films decreases, the roughness, and the thickness of the native $SiO_2$ interlayer increases with the increase of $O_2$ partial pressure. $ZrO_2$ films synthesized at low $O_2$ partial pressure are amorphous and monoclinic polycrystalline in nanometer scale at low $O_2$ partial pressure. The relative dielectrics of $ZrO_2$ films are in the range of 12 to 25.

• Journal of electromagnetic engineering and science
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• v.7 no.4
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• pp.195-200
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• 2007

Doubly-selective channel estimator for orthogonal frequency division multiplexing(OFDM) systems is proposed in this paper. Based on the generalized complex exponential basis expansion model(GCE-BEM), we describe the time-variant channel with time-invariant coefficients over multiple OFDM blocks. The time variation of the channel destroys the orthogonality between subcarriers, and the resulting channel matrix in the frequency domain is no longer diagonal, but the main interference comes from the near subcarriers. Based on this, we propose a channel estimator with low pilot ratio. We first develop a least-square(LS) estimator under the assumption that only the maximum Doppler frequency and the channel order are known at the receiver, and then verify that the correlation matrix of inter-channel interference(ICI) is a scaled identity matrix based on which we derive an optimal pilot insertion scheme for the LS estimator in the sense of minimum mean square error. The proposed estimator has the advantages of low pilot ratio and robustness against inter-carrier interference.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.5
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• pp.798-805
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• 2006

I evaluate the BER performance of downlink OFDMA systems in time variant Rayleigh Doppler fading channel, considering the carrier frequency offset and the nonlinear high power amplifier. I obtain the required output back-off of the nonlinear amplifier and value of frequency offset for good BER performance. And I also analyze the BER degradation upon Doppler fading channel.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.49 no.6
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• pp.289-297
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• 2000

This paper presents a comparison on the resistance and characteristics of transient response of grounding systems under surge currents using frequency domain electromagnetic field analysis software package and field test. Analysis is done by computer model, based on electromagnetic field theory approach, that accurately takes into account frequency dependent characteristics of the system. The transient performance of three grounding systems is analyzed by comparison of frequency dependent impedance and the maximal transient GPR. A double exponential lighting surge current is injected at one corner of the grounding systems. The transient GPRs a rod grounding systems are higher than mesh or electrolytic grounding systems. Af field test, the results of resistance measurement and time-variant of ground resistance slightly reduce electorlytic grounding systems less than rod and mesh grounding systems.

• Proceedings of the KIEE Conference
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• 2001.10a
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• pp.150-156
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• 2001

This paper describes an implementation of the DSP(Digital Signal Processor) based triangular carrier frequency modulated RPWM inverter drive system. The power spectrum of the noise emitted from the induction motor was measured in the anechoic chamber. The analysis of the sources for the acoustic noise and the effects of the noise reduction are confirmed by the measured spectra of the noise. Real-time RPWM along with the speed control was achieved by high speed DSP. By changing the center frequency and the bandwidth of the carrier, the proposed real-time RPWM scheme can be used as an efficient switching frequency band acoustic noise reduction method for the inverter drive system with variant load conditions.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.12
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• pp.2391-2397
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• 2007

I evaluate the BER performance of uplink OFDMA systems in time variant Rayleigh Doppler fading channel, considering the carrier frequency offset and the nonlinear high power amplifier. I obtain the required output back-off of the nonlinear amplifier and value of frequency offset for good BER performance. And I also analyze the BER degradation upon Doppler fading channel.

• Korean Journal of Clinical Laboratory Science
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• v.37 no.2
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• pp.71-77
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• 2005

We experienced the specimen that contains a hemoglobin variant known as interference from HbAS in October 2003. It was the first case of Hb variants since Samsung Medical Center began conducting glycohemoglobin College of American Pathologists surveys in 1997. The purpose of this study is to share our experience with the specimen and promote the understanding of Hb variants & derivatives. We've performed cross checks to examine HbA1c by using two pieces of equipment; the TOSHOH G7 and BIO-RAD VARIANT-T(turbo), and Automatic High Performance Liquid Chromatography(HPLC) as an analytic measurement method. HPLC provides different fractional information of hemoglobin with a two-dimensional graph as well as numeric results. We have been performing a "Systematic Checking Process". Three specimen suspicious of Hb variants & derivatives were found through this process. College of American Pathologists notified that it is important for users to be aware of the limitation of their glycohemoglobin method to avoid reporting incorrect results due to interference from hemoglobin variants or hemoglobin adducts. Therefore, laboratory findings of Hb variants & derivatives are very important. The experience of qualified technicians with professional knowledge in Hb variants is the most important aspect in finding Hb variants. Korea is homogeneous in race and is not in an area with a higher finding rate of Hb variants. While 1,024 cases of Hb variants have been found in Japan, we do not have specific data on how many cases of Hb variants have been found in Korea. Considering Hb variant cases in Japan, which is geographically close to us, it is presumed that there must be various Hb variant cases in Korea. If domestic laboratories set a systemic protocol and build a network to share our experience in Hb variants, I expect the Korean Hb variants could also be listed on the world's Hb variant list.