• 한국의학물리학회지:의학물리
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• 제7권2호
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• pp.79-90
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• 1996

본 논문에서는 2 차원 심초음파도의 경계선 유사 영역에 대해 베이즈 추정기를 사용하여 경계선 검출을 위한 자동문턱 결정방법을 제안하고자 한다. 경계선 유사영역은 전처리과 정에서 흐려진 영상을 명확히 하는데 사용할 열비등방성 확산 방법의 전도계수로부터 얻어진다, 이러한 경계선 유사 영역에 대해 최적 문턱치를 선택하기 위해 베이즈 추정기가 사용되었다. 이 문턱치를 사용하여 영상을 이진화함으로서 심초음파도의 경계선을 자동 적으로 검출하게 된다. 마지막으로 본래의 심초음파도에 위에서 얻어진 경계선을 덧씌움으로써 경계선이 강조된 심초음파도를 얻을 수 있게 된다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 신호처리소사이어티 추계학술대회 논문집
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• pp.461-464
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• 2003

This paper proposes the multi-level vector error diffusion for smear artifact reduction in the boundary regions. Smear artifact mainly results from a large accumulation of quantization error. Accordingly, to reduce these artifacts, the proposed method excludes the large quantization error in the error diffusion process by comparing the magnitude of the error vector with predetermined first threshold. In addition, if the vector norm of the difference between the error adjusted input vector and the primary co]or that has minimum vector norm for the error adjusted input vector is larger than second threshold, the error is excluded. As a result, the proposed method reduce smear artifact in the boundary region and produces visually pleasing halftone pattern.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1994년도 추계학술대회
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• pp.9-13
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• 1994

The Heat Anisotropic Diffusion Method has shown very effective for the contour detection of 2-D echocardiogram. To implement this algorithm, we have to choose the parameter C, K, and the threshold level. The choice of C and K are not very sensitive for the good edge detection of the echocardiogram, however the choice of the threshold level is very critical. Until now the threshold level is chosen by the trial and error method. In this paper, we present an automatic threshold decision method from the histogram of the gradient of boundary-like pixels.

• 한국정밀공학회지
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• 제16권5호통권98호
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• pp.48-57
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• 1999

Applications of thresholding technique are based on the assumption that object and background pixels in a digital image can be distinguished by their gray level values. For the segmentation of more complex images, it is necessary to resort to multiple threshold selection techniques. This paper describes a new method for multiple threshold selection of gray level images which are not clearly distinguishable from the background. The proposed method consists of three main stages. In the first stage, a probability distribution function for a gray level histogram of an image is derived. Cluster points are defined according to the probability distribution function. In the second stage, fuzzy partition matrix of the probability distribution function is generated through the fuzzy clustering process. Finally, elements of the fuzzy partition matrix are classified as clusters according to gray level values by using max-membership method. Boundary values of classified clusters are selected as multiple threshold. In order to verify the performance of the developed algorithm, automatic inspection process of ball grid array is presented.

• 대한기계학회논문집
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• 제19권9호
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• pp.2105-2113
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• 1995

The compressive tests under impact conditions were performed to establish a design guide for impact damage tolerance. The composition of layup was selected for the real cases of composite aircraft structure. The energy level of visible of visible damage threshold was determined as 7 Joules. It was found that the normalized bending stiffnesses in the direction of closely fixed boundary affected the area of damage. Graphite/epoxy used in the tests exhibited 60% reduction in compression strength at the energy level of visible damage threshold. Wet-conditioned specimens represented 9% reduction in residual compressive strength in comparison with room temperature ambient specimens. In this study, a design factor of 2.1 was proposed for the low velocity impact damage.

• 대한의용생체공학회:의공학회지
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• 제11권2호
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• pp.217-226
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• 1990

This paper presents a new algorithm that extracted lung region in X-ray and enhanced the region. With a lung region that was extracted by histogram threshold value, it was diffi cult to detect perfect lung boundary. Therefore we presented perfect lung boundary detection method using apex detection and apex region restoration. Also, by applying modified equalization algorithm and presented function to inside of lung region, we want to give help to automatic diagnosis In X-ray chest image. Presented main line trace algorithm gave good result in detection of lung boundary And, as apex detection method using lung row and column gray level average value found more correct place of lung than the rpethod of prior algorithm, we succeeded perfect lung region detection, Also, presented function that had lung region's gray level distribution characteristic was very effective to image enhancement.

• 대한기계학회논문집B
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• 제21권3호
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• pp.427-435
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• 1997

Conditional sampling techniques are utilized to investigate the relation between the wall skin-friction and stream wise velocity fluctuations in a turbulent boundary layer. Conditionally averaged results using a peak detection and the VITA (variable-interval time-averaging) technique show that a high skin friction is associated with high frequency components of the wall skin-friction fluctuations. The conditionally averaged wall skin-friction fluctuations obtained by using the VITA technique have a positively-skewed characteristics compared with the conditionally averaged stream wise velocity fluctuations. It is confirmed that there exists a phase shift between the wall skin-friction and stream wise velocity fluctuations, which was also found from the long-time averaged space-time correlations. The amount of phase shift between the wall skin-friction and stream wise velocity fluctuations is the same as that from the long-time averaged space-time correlations and does not change despite the variation of the detection threshold.

• 한국정보통신학회논문지
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• 제14권8호
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• pp.1819-1826
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• 2010

본 논문은 어류영상 검색을 위해 어류영상에서 어류객체를 추출하기 위한 영상분할 알고리즘을 제안하고 있다. 명암 유사도를 이용한 기존 알고리즘은 객체와 배경의 명암이 유사한 경계 영역에서 잘못된 영상분할 결과를 초래한다. 제안된 알고리즘은 대비가 약한 경계영역에 대응하기 위해 강화된 에지와 적응적 블록단위의 임계값을 사용하고, 대비가 없는 경계 영역에서 침식 혹은 단절된 객체를 개선하기 위해 가상 객체를 사용하고 있다. 모의실험 결과는 시각적으로 좋은 어류객체를 추출하는 비율이 기존 알고리즘에서는 90% 이하인 반면 제안된 알고리즘에서는 97.7%인 것을 보여주고 있다.

• 한국지능시스템학회논문지
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• 제13권6호
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• pp.704-709
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• 2003

디지털 영상은 전송 중에 잡음과 시스템의 다른 요소에 의해 입력 요소가 왜곡된다. 이는 영상객체의 분할시 경계면의 모호함이 발생시키고, 특히 입력 영상 경계 부분은 패턴인식의 분할 및 검출 요소를 결정하기 때문에 매우 중요하다. 따라서 그 경계 부분을 정확하게 분할ㆍ검출하는 최적의 에지 검출 방법을 제안하였다. 본 논문에서는 입력 영상의 임계값에 따른 적응적 형상학을 이용하여 영상의 경계면을 부각시킨 후, 이 영상을 Meyer 웨이브렛-CNN 알고리즘에 적용한 후 최적의 에지를 검출하였다. 제안된 알고리즘이 기존의 영상 에지 검출 알고리즘인 Sobel 에지 검출과 기존의 다른 에지 검출보다 우수함을 확인하였다. 특히 에지와 에지의 부분이 가까운 곳과 완만한 곡선을 가지고 있는 부분에서 더 우수한 결과 에지를 얻을 수 있음을 시뮬레이션에 의해 확인하였다.

• 한국환경보건학회지
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• 제43권4호
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• pp.247-256
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• 2017

Objectives: The deaths of Korean victims exposed to the disinfectant CMIT/MIT have remained unresolved. This is mainly due to a lack of concordance between the few available toxicity tests and the abundant epidemiological data, making it difficult to establish a cause-and-effect relationship. Therefore, this study was carried out to investigate any potential associations between CMIT/MIT exposure and death. Methods: Groups of experimental and control C57BL/6 mice were instilled (in the trachea) with chloromethylisothiazolinone/methylisothiazolinone (CMIT/MIT) using a visual instillobot. CMIT/MIT was instilled over a period of three days and eight weeks, respectively, to achieve acute and chronic exposures. A threshold dose-response model was applied for estimating the threshold level as one line of evidence for a causal association between CMIT/MIT and death. Results: An acute exposure of 1.2 mg ai/kg/day of CMIT/MIT was estimated to reflect the threshold for death. The dose-response curve with this threshold showed a very steep slope and a narrow range of CMIT/MIT exposures. The narrow range of CMIT/MIT exposures, in particular, indicated an evident boundary between survival and death, thus implicating a strong causal association. A similar threshold dose-response relationship observed following acute exposure was also seen following chronic exposure to CMIT/MIT. Airborne disinfectant exposure was visible as minimal or mild lung damage with no fibrosis, as shown by histopathological tests. However, many observations are considered to be functional respiratory tract or lung failure due to death, as observed in necropsies of the mice that died due to CMIT/MIT exposures. Conclusions: There are two strong lines of evidence for a causal association between death and CMIT/MIT exposure: 1) The threshold dose-response curve, with a very steep slope and a narrow range of CMIT/MIT exposures showing a visible boundary between survival and death; and 2) many cases of functional respiratory or lung failure.