• Biotechnology and Bioprocess Engineering:BBE
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• 제6권3호
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• pp.189-193
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• 2001

Critical cell density (CCD), the maximum cell concentration without mutual shading in algal cultures, can be used as a new operating parameter for high-density algal cultures and for the application of the flashing light effect on illuminated algal cultures. CCD is a function of average cell volume and light illumination area. The CCD is thus proposed as an index of estimation of mutual shading in algal cultures. Where cell densities are below the CCD, all the cells in photobioreactors can undergo photosysnthesis at their maximum rate. At cell densities over CCD, mutual shading will occur and some cells in the illumination chamber cannot grow photoautotrophically. When the cell concentration is higher than the CCD, specific oxygen production rates under flashing light were higher than those under continuous light. The CCD was found to be a useful engineering parameter for the application of flashing light, particularly in high-density algal cultures.

• Asian-Australasian Journal of Animal Sciences
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• 제15권8호
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• pp.1222-1226
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• 2002

Estimates of genetic correlation between direct and maternal effects for weaning weight of beef cattle are often negative in field data. The biological existence of this genetic antagonism has been the point at issue. Some researchers perceived such negative estimate to be an artifact from poor modeling. Recent studies on sources affecting the genetic correlation estimates are reviewed in this article. They focus on heterogeneity of the correlation by sex, selection bias caused from selective reporting, selection bias caused from splitting data by sex, sire by year interaction variance, and sire misidentification and inbreeding depression as factors contributing sire by year interaction variance. A biological justification of the genetic antagonism is also discussed. It is proposed to include the direct-maternal genetic covariance in the analytical models.

• 응용통계연구
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• 제25권4호
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• pp.633-640
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• 2012

Biological methods are described for the assay of certain substances and preparations whose potency cannot be adequately assured by chemical or physical analysis. The principle applied through these assays is of a comparison with a standard preparation to determine how much of the examined substance produces the same biological effects as a given quantity (the Unit) of the standard preparation. In these dilution assays, to estimate the relative potencies of the unknown preparations to the standard preparations, it is necessary to compare dose-response relationships of standard and unknown preparations. The dose-response relationship in the dilution assay is non-linear and sigmoid when a wide range of doses is applied. The parallel line model (applied to the dose region with the steepest slope) is used to estimate the relative potency. In this paper, the statistical theory in the parallel line model is explained with an application to a dilution assay data. The parallel line method is implemented in a SAS program and is available at the author's homepage(http://cafe.daum.net/go.analysis).

• 생물환경조절학회지
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• 제1권2호
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• pp.148-153
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• 1992

본 연구는 생물생산시설의 구조설계 과정에서 초기단계의 고정하중을 합리적으로 추정하기 위한 식을 유도하여 구조설계 기준 설정에 기초자료를 제공하고, 생물생산분야 종사자가 간편하게 구조적 안전성을 진단할 수 있는 방법을 개발할 목적으로 수행하였으며 연구 결과를 요약하면 다음과 같다. 1. 국내의 온실설계자료를 수집하여 실제 하중을 산출, 분석해 본 결과 기존의 일본 시설원예기준 적용치와는 차이가 있었으며, 잠정적으로 국내 시설에의 적용을 위한 추정식을 유도하였다. 2. 지역별 설계하중을 적용하여 구조해석을 실시하고, 발생되는 응력의 크기에 따라서 풍하중 및 설하중 지배지역으로 안전설계 지역구분을 실시하였다.

• 대한의용생체공학회:의공학회지
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• 제15권1호
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• pp.71-76
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• 1994

단일 쌍극자 모델을 이용한 source localization 문제에서 전극의 갯수, 쌍극자의 위치 및 방향 등이 S/N(signal to noise ratio)과 추정 오차사이의 관계에 미치는 영향을 Monte Carlo 시뮬레이션으로 조사했다. forward problem은 3중 구각 모델로 계산했고, simplex 방법으로 쌍극자 파라미터를 최적화시켰다. 전극의 갯수가 많을때, 쌍극자가 뇌 중심(midbrain)보다 대뇌 피질(cortex)부근에 있을 때, 쌍극자가 tangential 방향일 때 추정 오차의 평균과 표준편차가 작아졌다.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1994년도 추계학술대회
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• pp.113-116
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• 1994

Estimation of the evoked potential using the iterated bispectrum and cross-correlation (IBC) has been tried for both simulation and real clinical data. Conventional time average (TA) method suffers from synchronization error when the latency time of the evoked potential is random, which results in poor SNR distortion in the estimation of EP waveform. Instead of EP signal average in time domain, bispectrum is used which is insensitive to time delay. The EP signal is recovered by the inverse transform of the Fourier amplitude and phase obtained from the bispectrum. The distribution of the latency time is calculated using cross-correlation between EP signal estimated by the bispectrum and the acquired signal. For the simulation. EEG noise was added to the known EP signal and the EP signal was estimated by both the conventional technique and bispectrum technique. The proposed bispectrum technique estimates EP signal more accurately than the conventional technique with respect to the maximum amplitude of a signal, full width at half maximum(FWHM). signal-to-noise-ratio, and the position of maximum peak. When applied to the real visual evoked potential(VEP) signal. bispectrum technique was able to estimate EP signal more distinctively. The distribution of the latency time may play an important role in medical diagonosis.

• 대한의용생체공학회:의공학회지
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• 제10권2호
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• pp.165-172
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• 1989

본 논문에서는 초음파 반사신호에 내포되어 있는 정량적인 정보로부터 감쇠계수, 전파속도 파라메타를 매개로 조직의 온도특성에 대해 검토하고 이를 기초로 무침습적인 심부 온도추정의 가능성에 대해서 고찰하였다. 실험에 사용한 기초시료는 아크릴과 돼지의 근육, 간, 지방이며 온도분해능이 $0.25^{\circ}C$이하로 조절되는 항은수조를 제작하여 시료의 온도를 변화시켰다. 일련의 실험을 통하여 조직의 온도변화에 따른 초음파 파라메타의 변화가 근시적 선형성을 가짐이 확인되었으며 이는 표준적인 실험조건과 기준치의 설정을 전제로 무침습적 심부 온도추정이 가능함을 시사하는 것이다.

• 대한의용생체공학회:의공학회지
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• 제31권3호
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• pp.177-186
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• 2010

In 3D ultrasound color Doppler imaging (CDI), 8-16 pulse transmissions (ensembles) per each scanline are used for effective clutter rejection and flow estimation, but it yields a low volume acquisition rate. In this paper, we have evaluated three flow estimation methods: autoregression (AR), eigendecomposition (ED), and autocorrelation combined with adaptive clutter rejection (AC-ACR) for a small ensemble size (E=4). The performance of AR, ED and AC-ACR methods was compared using 2D and 3D in vivo data acquired under different clutter conditions (common carotid artery, kidney and liver). To evaluate the effectiveness of three methods, receiver operating characteristic (ROC) curves were generated. For 2D kidney in vivo data, the AC-ACR method outperforms the AR and ED methods in terms of the area under the ROC curve (AUC) (0.852 vs. 0.793 and 0.813, respectively). Similarly, the AC-ACR method shows higher AUC values for 2D liver in vivo data compared to the AR and ED methods (0.855 vs. 0.807 and 0.823, respectively). For the common carotid artery data, the AR provides higher AUC values, but it suffers from biased estimates. For 3D in vivo data acquired from a kidney transplant patient, the AC-ACR with E=4 provides an AUC value of 0.799. These in vivo experiment results indicate that the AC-ACR method can provide more robust flow estimates compared to the AR and ED methods with a small ensemble size.

• 대한기계학회논문집A
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• 제33권11호
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• pp.1202-1208
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• 2009

An inverse finite element (FE) model parameter estimation algorithm can be used to characterize mechanical properties of biological tissues. Using this algorithm, we can consider the influence of material nonlinearity, contact mechanics, complex boundary conditions, and geometrical constraints in the modeling. In this study, biomechanical experiments on macro and micro samples are conducted and characterized with the developed algorithm. Macro scale experiments were performed to measure the force response of porcine livers against mechanical loadings using one-dimensional indentation device. The force response of the human liver cancer cells was also measured by the atomic force microscope (AFM). The mechanical behavior of porcine livers (macro) and human liver cancer cells (micro) were characterized with the algorithm via hyperelastic and linear viscoelastic models. The developed models are suitable for computing accurate reaction force on tools and deformation of biomechanical tissues.

• 대한의용생체공학회:의공학회지
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• 제15권4호
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• pp.447-454
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• 1994

기하학적인 모델을 이용한 좌심실에 대한 단축 2D 심초음파도에서의 심내벽 윤관석의 완전 자동검출방법을 제안하였다. 이 방법은 3단계의 과정에 걸쳐 수행된다. 첫번째 단계는 부표본화된 영상에 초기 중심 추정 알고리듬을 적용하여 초기 중심을 추정한다. 두번째 단계에서는 원 영상에 중심추성 알고리듬을 적용하여 정확한 중심과 타원추정에 필요한 정보를 구한다음, 심내벽에 근사하는 타원모델을 추정한다. 세번째 단계는 추정한 타원모델에 근거한 코스트 함수로서 심내벽 윤관석을 검출한다. 제안된 방법을 조작자의 수동적인 개입없이도 효과적인 결과를 보여준다.