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김덕원,김정래,송철규,김정열,남문현 대한의용생체공학회 1989 의공학회지 Vol.10 No.1
In this study, Rheoencephalography(REG) was designed and constructed. Using the constructed instrument cerebral blood flow(CBF) of left and right brain, CBF change by posture, and reproducibility were studied. Followings are important results. Relative CBF could be measured noninvasively and continuously. Since reproducibility of the constructed REG was found to be quite high (4 %), the accuracy of the instrument itself was proved. REG can be easily applied for testing the effect of drugs for the patients with cerebral vessel diseases since it is quite sensitive to the relative changes of CBF. Various cerebral diseases can be diagnosed by analyzing the REG waveforms. The area of restricted cerebral blood vessels can be located by arranging the electrode configuration. Comparative studies with the standard techniques of measuring CBF are needed to verify the accuracy of REG. Further studies on optimal electrode configuration and various artifacts are also necessary.
자유 음장 조건에서 빔형성 방법을 이용한 수직 및 경사입사 음향 임피던스의 측정
신창우(Chang Woo Shin),선종천(Jong Choen Sun),강연준(Yeon June Kang),백순권(Soon Kwon Paik) 한국자동차공학회 2007 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
The improved Beamforming method is proposed to measure the acoustic impedance and absorption coefficient in a free field. It is possible to estimate the acoustic impedance by separating incident and reflected signals with the Adaptive Nulling Method. The wavelet shrinkage method is applied to reduce the White Gaussian noise. Transfer function vector is used for obtaining better results instead of pressure vector. The proposed method was verified by the comparison of measurement and theoretical method. The results show that the proposed method is efficient to measure acoustic impedance for frequencies higher than 400 ㎐.
김정래,김정열,김덕원,남문현 대한의용생체공학회 1989 의공학회지 Vol.10 No.1
In this paper, principles of Rheoencephalography(REG) was described and REG was designed and developed. Using the developed instrument, REG waveforms of the left and right brain, REG waveform changes by posture, were observed. It was found that REG waveforms could be observed noninvasively. REG can be easily applied for testing the effect of various drugs related to CBF(Cerebral blood flow) since it is quite senaitive to the relative changes of CBF. Various cerebral diseases can be diagnosed by analyzing the REG waveforms. The area of restricted cerebral blood vessels can be located by arranging the appropriate electrode configuration.
최현,박건록,김두훈,이상조 한국소음진동공학회 1997 소음 진동 Vol.7 No.6
Viscoelastic materials have the characteristics of elasticity and viscosity. Unlike the metals which show negligible damping characteristics, the damping characteristic of viscoelastic materials like rubber mounts is very important in the analysis of the dynamic system. So there has been a great interest in measuring the damping characteristics of the material can be measured. One is the resonant method which loss factor can be measured only in the resonant frequency. The other is the nonresonant method. In this paper, the test procedure and the physical meaning of the impedance method are introduced. The impedance test results, the loss factor by the impedance method, are compared to the results of the resonant method including some recommendations in the experimental setup.
공명기를 가진 내연기관 흡기시스템의 최적화를 위한 이론 및 실험적 연구
이재순 건국대학교 산업기술연구원 1996 건국기술연구논문지 Vol.21 No.-
The theoretical and experimental study on the optimization of intake system has been carried out when the resonator is mounted on the intake system of single cylinder diesel engine. For this study, the simulation program for the prediction of volumetric efficiency has been developed and is verified by the experimental work. The study to find the effect of resonator through both the simulation and experimental works showed that the resonator can increase the volumetric efficiency at low engine speed without sacrificing the volumetric efficiency much at the high engine speed. The optimum dimension of the resonator such as resonator volume, its neck length and diameter must be chosen so as to generate the adequate flow loss in the intake pipe. Therefore, the dimension can not be determined by only natural acoustic frequency of resonator, but it is found that the ratio of resonator frequency, ???, to that of intake system for open period of intake valve, f, could be used to estimate the effect of resonator, and the optimum ratio of frequency, ?? / f, is found as 1.1 ∼ 1.2 roughly.
헬름홀츠 공명기들로 구성된 음향 메타물질의 파동전파 특성
권병진(Kwon, Byung-Jin),조충희(Jo, Choonghee),박광춘(Park, Kwang-Chun),오일권(Oh, Il-Kwon) 한국소음진동공학회 2013 한국소음진동공학회 논문집 Vol.23 No.2
The wave propagation characteristics of an acoustic metamaterial composed of periodically repeated one-dimensional Helmholtz resonator array was investigated considering the effects of dimensional changes of the resonator geometry on the transmission coefficient and band gap. The effective impedance and transmission coefficient of the acoustic metamaterials are obtained based on the acoustic transmission line method. The designed acoustic metamaterials exhibit band gaps and negative bulk modulus that are non-existent properties in the nature. The band gap of the acoustic metamaterial is strongly dependent on the geometry parameters of Helmholtz resonators and lattice spacing. Also, a new type of metamaterial that is periodically constructed with two different resonators was designed to open the local resonance band gap without change of Bragg scattering.