• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -3
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• pp.1827-1830
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• 2002

A matrix pencil method for source separation 〔3〕was shown to be an unbiased signal extractor in the presence of temporally white noise. Its efficiency and robustness lies in the fact that the method in 〔3〕 employs only time-delayed correlation matrices of the observation data, In this paper we stress out that the matrix pencil method might suffer from a numerical instability problem, be- cause the symmetric-definite pencil was not exploited. Moreover we present a simple method of constructing a symmetric-definite pencil so that the matrix pencil method is numerically stable.

• 한국음향학회:학술대회논문집
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• 한국음향학회 2002년도 하계학술발표대회 논문집 제21권 1호
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• pp.41-44
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• 2002

Blind source separation (BSS) is a fundamental problem that is encountered in many practical applications. In most existing methods, stationary sources are considered higher-order statistics is necessary either explicitly or implicitly. But, many natural signals are nonstationary, and it is possible to perform BSS using only second-order statistics. Our method is based on only second order statistics. The algorithms are developed using the gradient descent method in orthogonality constraint and their performance is confirmed by numerical experiments.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2004년도 가을 학술발표논문집 Vol.31 No.2 (1)
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• pp.25-27
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• 2004

독립적인 여러 개의 음원의 convoultive mixture로부터 blind source separation(BSS)을 수행하는 것은 수년간 활발히 연구되어 오고있다. 그러나 많은 BSS 알고리즘이 존재함에도 불구하고, 직접적으로 하드웨어를 구현할 수 있는 알고리즘은 실제로 매우 드물다. 이 논문의 목표는 FPGA를 이용하여 실시간으로 효과적인 구현이 가능한 BSS 구조를 소개하는 것이다.

• 한국안전학회지
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• 제17권3호
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• pp.61-65
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• 2002

A study on the characteristics of electric shock in fresh water due to the leakage of submerged electric facility is conducted by using a reduced scale model at a scale of 1:10 in laboratory. Electric potential as a function of distance from leakage source, type of the leakage source, magnitude of the source voltage, submerged depth and diameter of a copper rod electrode is measured. On the basis of safety standard, separation for guarantee of safety is determined by the measured potential. Also supposing that body resistance is 500［$\Omega$］, the human reaction was estimated by calculating body current for some shock duration. Thus, in this paper, the hazard of the electric shock is assessed by introducing representative safety factors, body voltage and body current due to leakage source.

• 대한기계학회논문집B
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• 제20권2호
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• pp.741-751
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• 1996

The coupled conduction and convection heat transfer from the protruding heat source in a vertical channel is numerically investigated. Conjugate solution of the two-dimensional energy equation is obtained for the incompressible air flow over the rectangular block with local heat source. It was found that several recirculation zones and separation bubble near the block were related to Re and Gr. And the results show that fractions of the heat transfer through each of the block face, maximum temperature of the block and the relative effect of each parameter on the maximum temperature and heat transfer.

• 상하수도학회지
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• 제27권5호
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• pp.621-629
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• 2013

Since algae had been issued an environmental problem, water blooms, deepened due to increase of retention water basin in Korea as well as a biomass resource for producing biofuel, this study conducted a series of experiments for Spirulina platensis using the flotation process with micro-bubble. To elevate utilization of collected-algae, this study focused on omitting or minimizing coagulant's doses as changing a cultivation period and condition affected on physical property change of algae. Two coagulants, PAC and Chitosan, were used to test the collecting rate of algae and the result found no difference between two rates. For flotation experiments without adding the coagulant, dried algae weight (passing 14 days after cultivation for 20 days) detected high separation efficiency 98.2 % and it (passing 7 days after long-term cultivation for 28 days) presented good separation efficiency 91.9 %. Chlorophyll's separation efficiency showed a similar tendency with the case of the dried algae weight. In endogeny conditions, a light source and a carbon source were not considerably affected on the flotation separation efficiency. Thus, this study confirms that algae biomass may be collected without the coagulant during the endogeny condition period after enough cultivation time, 3 weeks.

• 한국초전도ㆍ저온공학회논문지
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• 제24권3호
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• pp.12-18
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• 2022

In recent years, the impact of microplastics (MPs) on ecosystems is a serious problem. Since MPs are difficult to recover once they are dispersed into the environment, it is important to remove them at the source. We proposed a magnetic separation of primary MPs (plastics manufactured in minute sizes) sized 10-100 ㎛ that has not been removed in the sewage process, based on the magnetic seeding process. In this study, we used magnetite as a magnetic seeding agent, and conducted magnetic separation experiments in the continuous process using a superconducting solenoidal magnet to investigate the feasibility of practical magnetic separation system of MPs. As a result, 85% separation rate was obtained by continuous separation using high gradient magnetic separation (HGMS) with hydrophobically treated magnetite as a magnetic seeding agent.

• Smart Structures and Systems
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• 제13권2호
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• pp.257-280
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• 2014

In this paper, a novel PARAllel FACtor (PARAFAC) decomposition based Blind Source Separation (BSS) algorithm is proposed for modal identification of structures equipped with tuned mass dampers. Tuned mass dampers (TMDs) are extremely effective vibration absorbers in tall flexible structures, but prone to get de-tuned due to accidental changes in structural properties, alteration in operating conditions, and incorrect design forecasts. Presence of closely spaced modes in structures coupled with TMDs renders output-only modal identification difficult. Over the last decade, second-order BSS algorithms have shown significant promise in the area of ambient modal identification. These methods employ joint diagonalization of covariance matrices of measurements to estimate the mixing matrix (mode shape coefficients) and sources (modal responses). Recently, PARAFAC BSS model has evolved as a powerful multi-linear algebra tool for decomposing an $n^{th}$ order tensor into a number of rank-1 tensors. This method is utilized in the context of modal identification in the present study. Covariance matrices of measurements at several lags are used to form a $3^{rd}$ order tensor and then PARAFAC decomposition is employed to obtain the desired number of components, comprising of modal responses and the mixing matrix. The strong uniqueness properties of PARAFAC models enable direct source separation with fine spectral resolution even in cases where the number of sensor observations is less compared to the number of target modes, i.e., the underdetermined case. This capability is exploited to separate closely spaced modes of the TMDs using partial measurements, and subsequently to estimate modal parameters. The proposed method is validated using extensive numerical studies comprising of multi-degree-of-freedom simulation models equipped with TMDs, as well as with an experimental set-up.

• 한국정보과학회논문지:소프트웨어및응용
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• 제36권3호
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• pp.179-186
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• 2009

본 논문에서는 학습이 가능한 특정화자의 발화음성이 있는 경우, 잡음과 반향이 있는 실 환경에서의 스테레오 마이크로폰을 이용한 특정화자 음성복원 알고리즘을 제안한다. 이를 위해 반향이 있는 환경에서 음원들을 분리하는 다중경로 암묵음원분리(convolutive blind source separation, CBSS)와 이의 후처리 방법을 결합함으로써, 잡음이 섞인 다중경로 신호로부터 잡음과 반향을 제거하고 특정화자의 음성만을 복원하는 시스템을 제시한다. 즉, 비음수 행렬분해(non-negative matrix factorization, NMF) 방법을 이용하여 특정화자의 학습음성으로부터 주파수 특성을 보존하는 기저벡터들을 학습하고, 이 기저벡터들에 기반 한 두 단계의 후처리 기법들을 제안한다. 먼저 본 시스템의 중간단계인 CBSS가 다중경로 신호를 입력받아 독립음원들을(두 채널) 출력하고, 이 두 채널 중 특정화자의 음성에 보다 가까운 채널을 자동적으로 선택한다(채널선택 단계). 이후 앞서 선택된 채널의 신호에 남아있는 잡음과 다른 방해음원(interference source)을 제거하여 특정화자의 음성만을 복원, 최종적으로 잡음과 반향이 제거된 특정화자의 음성을 복원한다(복원 단계). 이 두 후처리 단계 모두 특정화자 음성으로부터 학습한 기저벡터들을 이용하여 동작하므로 특정화자의 음성이 가지는 고유의 주파수 특성 정보를 효율적으로 음성복원에 이용 할 수 있다. 이로써 본 논문은 CBSS에 음원의 사전정보를 결합하는 방법을 제시하고 기존의 CBSS의 분리 결과를 향상시키는 동시에 특정화자만의 음성을 복원하는 시스템을 제안한다. 실험을 통하여 본 제안 방법이 잡음과 반향 환경에서 특정화자의 음성을 성공적으로 복원함을 확인할 수 있다.

• 한국초전도ㆍ저온공학회논문지
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• 제21권2호
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• pp.10-14
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• 2019

In order to improve resource value, separation of nonferrous metals obtained from crushed materials of home appliances is required. In this study, we aimed to develop a continuous separation system by magneto-Archimedes method using magnetic fluid as a medium and the permanent magnet as a magnetic field source. Firstly, the separation conditions were examined in which only copper is settled and the difference in levitation positions between aluminum and other metals are over 1 cm. Based on the results, levitation experiment of each metal and separation experiment from the mixture of nonferrous metals were confirmed. The separation experiment showed that the continuous separation of copper and aluminum from a mixture of nonferrous metals is possible.