• Investigative Magnetic Resonance Imaging
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• v.8 no.1
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• pp.1-8
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• 2004

Purpose : Information about electrical activity inside the brain during fMRl scans is very useful in monitoring physiological function of the patient or locating the spatial position of the activated region in the brain. However, many additional noises appear in the EEG signal acquired during the MRI scan. Gradient induced noise is the biggest one among the noises. In this work, we propose a gradient noise reduction method using the independent component analysis (ICA) method. Materials and Methods : We used a 29-channel MR-compatible EEG measurement system and a 3.0 Tesla MRI system. We measured EEG signals on a subject lying inside the magnet during EPI scans. We selectively removed the gradient noise from the measured EEG signal using the ICA method. We compared the results with the ones obtained with conventional averaging method and PCA method. Results : All the noise reduction methods including the averaging and PCA methods were effective in removing the noise in some extent. However, the proposed ICA method was found to be superior to the other methods. Conclusion : Gradient noise in EEG signals acquired during fMRI scans can be effectively reduced by the ICA method. The noise-reduced EEG signal can be used in fMRI studies of epileptic patients or combinatory studies of fMRI and EEG.

• Progress in Superconductivity
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• v.3 no.1
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• pp.65-69
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• 2001

We measured the transport properties of$ YBa_2$$Cu_3$$O_{x}$ ramp-edge junction fabricated with interface-engineered barrier. The current-voltage characteristics show a typical resistively-shunted junction like behavior Voltage noise measurement revealed that the main source of the 1/f noise is the critical current and resistance fluctuations. The analysis of the noise data showed that the critical current fluctuations increase with temperature, whereas the resistance fluctuations are almost constant, and both fluctuations are almost correlated. The smaller magnitude of the critical current and resistance fluctuations seems to result from the columnar-deflects.s.

• Journal of Sensor Science and Technology
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• v.26 no.1
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• pp.60-65
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• 2017

This paper describes the low noise and low power IC using the opamp sharing technique for the capacitive micro-sensor sensing platform. The proposed IC reduces noise using correlated double sampling (CDS) and reduces power consumption using the opamp sharing technique. The IC is designed to be fully programmable, and can be digitally controlled by serial peripheral interface (SPI). The power consumption and the integrated input referred noise are 1.02 mW from a 3.3 V supply voltage and $0.164aF_{RMS}$ with a bandwidth of 400 Hz. The capacitive sensitivity, the input-output linearity and the figure of merits (FoM) are 2.5 mV/fF, 2.46 %FSO, and 8.4, respectively.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.10
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• pp.1890-1896
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• 2008

In this paper, the Si vertical Hall devices ale fabricated by using standard bipolar process and investigated in terms of the opeating and noise properties. The sensitivity of device with P+ isolation dam(type B) has been increased up to about 1.2 times compared to that device without the dam also noise has been increased. With the condition of f=I[KHz], band-width 1[Hz], the resolution of magnetic-field detection were about $0.97[{\mu}T]$/ type B and $1.25[{\mu}T]$/ type A, respectively, thus we must consider correlation the low noise or good resolution and high sensitivity in the situation for device geometry design or even for the materials.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.32 no.2
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• pp.64-74
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• 2021

Background and Objectives This study was to investigate the voice quality and articulation effects of laryngeal massage on muscle tension dysphonia (MTD). Materials and Method A systematic review of articles published between January 2000 and December 2020 in Cochrane, PubMed, ScienceDirect, SpingerLink, ERIC, and Naver Academic was conducted. From the total of 2094 articles identified, 10 peer-reviewed articles were included in a meta-analysis. Mean effect sizes of the variables related to voice quality (jitter, shimmer, harmonic to noise ratio or noise to harmonic ratio, high-F0, low-I, cepstral peak prominence) and articulation (F1, F2, F1 slope, F2 slope) were calculated by Hedges'g. Results Meta-analysis of the selected articles showed that laryngeal massage had medium to large effects on all variables of voice quality and articulation except F0-high and F1 slope in the MTD patients. Conclusion This study provided comprehensive clinical evidence that it is highly desirable to apply laryngeal massage to MTD patients.

• Progress in Superconductivity
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• v.11 no.1
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• pp.30-35
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• 2009

We have investigated the characteristics of a superconductive Pb shield for hemispherical shape and plate to improving signal-to-noise ratio(SNR) of biomagnetism. We measured the shielding factor for the position of helmet shape Pb and for changing the distance from Pb surface. To make a uniform magnetic field, a $1.5m{\times}1.5m$ set of the helmholtz coils activated at several frequencies. The shielding factor of hemispherical shape Pb was from 20 to 57 dB and of Pb plate was about $6{\sim}26dB$ as a function of distance from the lead surface. The shielding factor was rapidly reduced as increasing the distance from Pb surface. The white noise of superconductive quantum interference device(SQUID) with a superconductive shield was about $12fT/Hz^{1/2}$ at 1 Hz, $7fT/Hz^{1/2}$ at 100 Hz. The white noise was more increased about two times than conventional SQUID system without Pb shielding. An auditory signal was measured by first order gradiometer and magnetometer with Pb superconductive shield and compared the SNR. The SQUID system with Pb shield had better performance at low frequency noise level.

• ETRI Journal
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• v.36 no.3
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• pp.510-513
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• 2014

A Q-band pHEMT image-rejection low-noise amplifier (IR-LNA) is presented using inter-stage tunable resonators. The inter-stage L-C resonators can maximize an image rejection by functioning as inter-stage matching circuits at an operating frequency ($F_{OP}$) and short circuits at an image frequency ($F_{IM}$). In addition, it also brings more wideband image rejection than conventional notch filters. Moreover, tunable varactors in L-C resonators not only compensate for the mismatch of an image frequency induced by the process variation or model error but can also change the image frequency according to a required RF frequency. The implemented pHEMT IR-LNA shows 54.3 dB maximum image rejection ratio (IRR). By changing the varactor bias, the image frequency shifts from 27 GHz to 37 GHz with over 40 dB IRR, a 19.1 dB to 17.6 dB peak gain, and 3.2 dB to 4.3 dB noise figure. To the best of the authors' knowledge, it shows the highest IRR and $F_{IM}/F_{OP}$ of the reported millimeter/quasi-millimeter wave IR-LNAs.

• The Journal of the Korea Contents Association
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• v.9 no.1
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• pp.159-166
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• 2009

In this paper, we analyse the noise robustness of MLPs(Multilayer perceptrons) through deriving the probability density function(p.d.f.) of output nodes with additive input noises and the misclassification ratio with the integral form of the p.d.f. functions. Also, we propose linear preprocessing methods to improve the noise robustness. As a preprocessing stage of MLPs, we consider ICA(independent component analysis) and PCA(principle component analysis). After analyzing the noise reduction effect using PCA or ICA in the viewpoints of SNR(Singal-to-Noise Ratio), we verify the preprocessing effects through the simulations of handwritten-digit recognition problems.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.1
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• pp.94-99
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• 1997

There are several factors that have influence on the phase noise of an oscillator. But one of the major factors is the flicker noise of a transistor, since the phase noise of an oscillator is generated by mixing the carrier with the low frequency noise near the DC having the characteristic of 1/f. In this paper, we have presented a method on reducing the phase noise of an oscillator by using a low-frequency feedback circuit based on an active bias circuit, and have fabricated a DRO for a DBS receiver. Measurement results show that the phase noise is -92 dBc/Hz at the 10 KHz offset frequency, and from these results we have found out that the reduction method is very effective.

• 전자공학회논문지 IE
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• v.45 no.2
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• pp.1-5
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• 2008

In this work, RF performance degradation due to hot carrier effects in SOI MOSFET have been measured and analyzed. The LNA that designed at $V_{GS}=0.8V$, f=2.5GHz, gain is 16.51dB and noise figure is 1.195dB. After stress at SOI, the LNA's gain and noise figure change of 15.3dB and 1.44dB with before stress.