• Bulletin of the Korean Chemical Society
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• 제22권4호
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• pp.337-348
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• 2001

This article gives an overview of a recently developed channel system, frit-inlet asymmetrical flow field-flow fractionation (FI-AFlFFF), which can be applied for the separation of nanoparticles, proteins, and water soluble polymers. A conventiona l asymmetrical flow FFF channel has been modified into a frit-inlet asymmetrical type by introducing a small inlet frit near the injection point and the system operation of the FI-AFlFFF channel can be made with a great convenience. Since sample components injected into the FI-AFlFFF channel are hydrodynamically relaxed, sample injection and separation processes proceed without interruption of the migration flow. Therefore in FI-AFlFFF, there is no requirement for a valve operation to switch the direction of the migration flow that is normally achieved during the focusing/relaxation process in a conventional asymmetrical channel. In this report, principles of the hydrodynamic relaxation in FI-AFlFFF channel are described with equations to predict the retention time and to calculate the complicated flow variations in the developed channel. The retention and resolving power of FI-AFlFFF system are demonstrated with standard nanospheres and protreins. An attempt to elucidate the capability of FI-AFlFFF system for the separation and size characterization of nanoparticles is made with a fumed silica particle sample. In FI-AFlFFF, field programming can be easily applied to improve separation speed and resolution for a highly retaining component (very large MW) by using flow circulation method. Programmed FI-AFlFFF separations are demonstrated with polystyrene sulfonate standards and pululans and the dynamic separation range of molecular weight is successfully expanded.

• 한국음향학회지
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• 제21권4호
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• pp.146-146
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• 2002

We present a new technique for achieving source separation when given only a single channel recording. The main idea is based on exploiting the inherent time structure of sound sources by learning a priori sets of time-domain basis functions that encode the sources in a statistically efficient manner. We derive a learning algorithm using a maximum likelihood approach given the observed single channel data and sets of basis functions. For each time point we infer the source parameters and their contribution factors. This inference is possible due to the prior knowledge of the basis functions and the associated coefficient densities. A flexible model for density estimation allows accurate modeling of the observation, and our experimental results exhibit a high level of separation performance for simulated mixtures as well as real environment recordings employing mixtures of two different sources. We show separation results of two music signals as well as the separation of two voice signals.

• Bulletin of the Korean Chemical Society
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• 제24권9호
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• pp.1333-1338
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• 2003

Hollow Fiber flow field-flow fractionation (HF-FlFFF) has been tested in polyacrylonitrile (PAN) membrane channel in order to compare it with polysulfone (PSf) membrane channel. It has been experimentally shown that the separation time of 0.05-0.304 ${mu}m$ polystyrene latex (PSL) standards in PAN membrane channel is shorter than that in PSf channel by approximately 65%. The optimized separation condition in PAN membrane is ${\dot V}_{out}/{\dot V}_{rad}=1.4/0.12\;mL/min$, which is equal to the condition in PSf membrane channel. In addition both the resolution ($R_s$) and plate height (H) in PAN membrane channel are better than that in PSf membrane channel. The membrane radius was obtained by back calculation with retention time. It shows that the PSf membrane is expanded by swelling and pressure, but the PAN membrane doesn't expand by swelling and pressure.

• 대한음성학회지:말소리
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• 제67호
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• pp.195-216
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• 2008

This paper addresses the problem of single-channel speech separation to extract the speech signal uttered by the speaker of interest from a mixture of speech signals. We propose to apply time-frequency smoothing to the existing statistical single-channel speech separation algorithms: The soft mask and the minimum-mean-square-error (MMSE) algorithms. In the proposed method, we use the two smoothing later. One is the uniform mask filter whose filter length is uniform at the time-Sequency domain, and the other is the met-scale filter whose filter length is met-scaled at the time domain. In our speech separation experiments, the uniform mask filter improves speaker-to-interference ratio (SIR) by 2.1dB and 1dB for the soft mask algorithm and the MMSE algorithm, respectively, whereas the mel-scale filter achieves 1.1dB and 0.8dB for the same algorithms.

• 대한전기학회논문지:시스템및제어부문D
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• 제54권3호
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• pp.198-205
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• 2005

In this paper, we proposed a new algorithm for the separation of fetal ECG from single channel abdominal ECG. The algorithm consists of a stage of demixing vector calculation for initial signal and a stage of fetal beat detection for the rest of signal. The demixing vector was obtained by applying independent component analysis technique to projected signals into time-frequency domain. For the test of this algorithm, simulation signals, De Lathauwer's data and some measured data, which was acquired from 8 healthy volunteers whose pregnant periods ranged from 22 weeks to 35 weeks and whose ages from 27 to 37, were used. For each data, the accuracy of fetal beat detection was $100\%$ and with the location of fetal beats, fetal heart rate variability and morphology could be offered. In conclusion, this proposed algorithm showed the possibility of fetal beat separation with a single channel abdominal ECG and it might be adopted to a fetal health monitoring system, by which a single channel abdominal ECG is acquired.

• 한국전자파학회논문지
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• 제17권11호
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• pp.1058-1064
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• 2006

본 논문에서는 3차원 광선 추적법을 이용하여 실내 무선 MIMO 채널에서 공간적 특성들을 해석함으로써 채널 용량을 계산하고, 특정 실내 환경에서 최적화된 다중 안테나의 이격거리를 알아내는 방법을 제안한다. 우선, 가시 영역과 비가시 영역을 갖는 복도 환경에서 3차원 광선 추적법을 이용하여 전파 경로, 전송 손실 및 시간지연 확산 등의 채널 공간적 특성들을 계산하고, 시간 지연 확산 특성을 다이폴 안테나와 네트워크 분석기를 이용하여 측정한 후에 계산 값들과 비교하여 3차원 광선 추적법의 정확성을 검증한다. 그런 다음에 그 실내 환경에 다중 안테나를 갖는 송신기와 수신기를 위치시키고, 수신기 위치별로 송 수신 안테나들의 간격에 따른 전파 경로와 전송 손실을 3차원 광선 추적법을 이용하여 계산하며, 이들 계산 값을 이용하여 채널 용량을 계산한다. 이 계산을 100개의 수신 위치에서 4종류의 안테나 방향 조합을 갖는 조건들에서 안테나 간격에 따른 채널용량을 계산하고, 이들 값들을 평균하여 이 실내 환경에서의 최적의 안테나 이격 거리를 알아내었다.

• The Journal of the Acoustical Society of Korea
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• 제23권2E호
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• pp.56-67
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• 2004

Despite abundant research outcomes of blind source separation (BSS) in many types of simulated environments, their performances are still not satisfactory to be applied to the real environments. The major obstacle may seem the finite filter length of the assumed mixing model and the nonlinear sensor noises. This paper presents a two-step speech enhancement method with multiple microphone inputs. The first step performs a frequency-domain BSS algorithm to produce multiple outputs without any prior knowledge of the mixed source signals. The second step further removes the remaining cross-channel interference by a spectral cancellation approach using a probabilistic source absence/presence detection technique. The desired primary source is detected every frame of the signal, and the secondary source is estimated in the power spectral domain using the other BSS output as a reference interfering source. Then the estimated secondary source is subtracted to reduce the cross-channel interference. Our experimental results show good separation enhancement performances on the real recordings of speech and music signals compared to the conventional BSS methods.

• Bulletin of the Korean Chemical Society
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• 제24권9호
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• pp.1339-1344
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• 2003

Flow field-flow fractionation (FlFFF) is a technology to separate the molecules by size in an open channel. Molecules with different size have different diffusivities and are located vertically in different positions when passing through an open channel. In this study, hollow fiber membranes instead of conventional rectangular channels have been used as materials for the open channel and this change would decrease the cost of manufacturing. FlFFF is a useful technique to characterize the biopolymeric materials. Retention time, diffusion coefficients and Stokes radius of analysis can be calculated from the related simple equations. Hollow-fiber flow field-flow fractionation (HF-FlFFF) has been used for the characterization and separation of protein mixture in a phosphate buffer solution and has demonstrated the potential to be developed into a disposable FlFFF channel. The important indexes for the analytical separation are selectivity, resolution and plate height. The optimized separation condition for protein mixture of Ovalbumin, Alcohol dehydrogenase, Apoferritin and Thyroglobulin is ${\dot V}_{out}/{\dot V}_{rad}=0.65/0.85\;mL/min$.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권5호
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• pp.2434-2453
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• 2019

To improve the separation performance of time-frequency overlapped radar and communication signals from a single channel, this paper proposes an effective separation method based on an improved empirical wavelet transform (EWT) that introduces a fast boundary detection mechanism. The fast boundary detection mechanism can be regarded as a process of searching, difference optimization, and continuity detection of the important local minima in the Fourier spectrum that enables determination of the sub-band boundary and thus allows multiple signal components to be distinguished. An orthogonal empirical wavelet filter bank that was designed for signal adaptive reconstruction is then used to separate the input time-frequency overlapped signals. The experimental results show that if two source components are completely overlapped within the time domain and the spectrum overlap ratio is less than 60%, the average separation performance is improved by approximately 32.3% when compared with the classic EWT; the proposed method also improves the suitability for multiple frequency shift keying (MFSK) and reduces the algorithm complexity.

• 말소리와 음성과학
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• 제5권4호
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• pp.211-216
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• 2013

The IVA(Independent Vector Analysis) is a well-known FD-ICA method used to solve the frequency permutation problem. It generally works quite well for blind source separation problems, but still needs some improvements in the frequency bin permutation problem. This paper proposes a post-processing method which can improve the source separation performance with the IVA by fixing the remaining frequency permutation problem. The proposed method makes use of the correlation coefficient of power ratio between frequency bins for separated signals with the IVA-based 2-channel source separation. Experimental results verified that the proposed method could fix the remaining frequency permutation problem in the IVA and improve the speech quality of the separated signals.