• 전자공학회논문지D
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• 제35D권2호
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• pp.1-12
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• 1998

In this paper, an incoherent imaging of a high-contrast cylindrical cavity illuminated by the time-harmonic cylindrical wave is obtained ia the back-projections of he incoherent intensity patterns, which si acquired by averaging out the multi-frequency intensities of the total electric field scattered from this object in the cross-borehole measurement configuration. Multi-freuqncy effect is shown numerically and is intepreted analytically by the mutual coherence function defined in the is frequency domain. This imaging method is validated by imaging high-contrast cylindrical cavidities and the conditions to get better image are investigated.

• 전기학회논문지P
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• 제57권1호
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• pp.14-21
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• 2008

In this paper, we propose an adaptive contrast enhancement method using dynamic range segmentation. Histogram Equalization (HE) method is widely used for contrast enhancement. However, histogram equalization method is not suitable for commercial display because it may cause undesirable artifacts due to the significant change in brightness. The proposed algorithm segments the dynamic range of the histogram and redistributes the pixel intensities by the segment area ratio. The proposed method may cause over compressed effect when intensity distribution of an original image is concentrated in specific narrow region. In order to overcome this problem, we introduce an adaptive scale factor. The experimental results show that the proposed algorithm suppresses the significant change in brightness and provides wide histogram distribution compared with histogram equalization.

• 한국전기전자재료학회논문지
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• 제22권2호
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• pp.169-173
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• 2009

We studied driving characteristics according to the ratio of mass and charging (m/q) value for charged toner particles with black and yellow color in charged particle type display panel. After biasing rectangle pulse to the transparency electrodes of putted panel with toner particles, its response time and contrast ratio are simultaneously measured using a laser as a optical source, photodiode as a detector and reflective system. As a results, contrast ratio is largest at the shortest response time region which is different to the particle because of m/q. We proposed relational equation for response time, m/q, cell gap and biasing voltage. It has not been studied and reported to analyze the relationship of response time, biasing voltage, lumping phenomena, cell gap, and contrast ratio for toner particle type display.

• 한국의류학회지
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• 제30권4호
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• pp.633-643
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• 2006

When women are exposed to images of other attractive women such as media models, it is known that many go through a social comparison process and a contrast effect occurs which results in unfavorable perception and attitudes toward the self. This paper suggests women's perception of control over their appearance as one of the factors that may moderate the contrast effect of a social comparison with attractive media models. An experiment with 211 women was conducted to examine the differential effect of viewing attractive models versus non-human images on the responses of women with high/low perceived control over appearance. A two(Stimuli Type: attractive-model image vs. non-human image) by two(Perceived Control over Appearance: High vs. Low) MANCOVA model was tested with physical appearance anxiety, self-esteem, and body satisfaction as dependent variables and appearance orientation, body mass index, age, years of schooling, ethnicity, and marital status as covariates. A significant Perceived Control main effect on Physical Appearance Anxiety and Self-Esteem and a significant Stimuli Type by Perceived Control interaction effect on Physical Appearance Anxiety and Self-Esteem were found. Those who perceived high control over their appearance were more likely to have higher self-esteem and lower appearance anxiety. However, among those who saw attractive model's images, women perceived low appearance control showed less anxiety and higher body satisfaction than those perceived high appearance control.

• 한국임상약학회지
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• 제22권2호
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• pp.103-112
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• 2012

Performance of coronary angiography for exact diagnosis and treatments of cardiovascular disease have been increased recently and it also brings increase of the contrast-induced nephropathy (CIN) referred from increasing use of radiological contrast agents. The variation of estimated glomerular filtration rate (eGFR) is an indicator of CIN, which is known to increase when renal function is decreased. Therefore, this study was to evaluate the affecting factors including concomitant drug on variation of eGFR of patients who underwent coronary angiography according to the conditions of renal function. Medical records of 66 patients were evaluated retrospectively and the patients underwent coronary angiography or angioplasty with nonionic and isotonic contrast media (iodixanol) at Chungnam national university hospital from 1 Jan 2008 to 30 Jul 2010. Patients group was divided into 2 groups; the patients in stages 3-4 chronic kidney disease (CKD) and the patients in stage 2 CKD. Each group was researched about the effect of concomitant drug and clinical characteristics on eGFR variation. The change of eGFR was compared among baseline and 2 or 3 day after coronary angiography. In results, the eGFR variation in group over age 75 was significantly decreased after radiological contrast agents exposure (p $$\leq_-$$ 0.05). The eGFR variation in anemia was significantly decreased after radiological contrast agents exposure in stage 2 CKD (p > 0.05). The eGFR variation in group under $HbA_{1c}$ 6.5% was significantly decreased after radiological contrast agents exposure in stages 3-4 CKD (p $$\leq_-$$ 0.05). The eGFR variation by taking statins, angiotensin converting enzyme inhibitors, calcium channel blockers and nitroglycerin was increased after radiological contrast agents exposure in stage 2 CKD (p $$\leq_-$$ 0.05). The eGFR variation by using of diuretics was significantly decreased after radiological contrast agents exposure in stages 3-4 CKD (p $$\leq_-$$ 0.05). The eGFR variation by taking statins, nitroglylcerin was increased after radiological contrast agents exposure in stages 3-4 CKD(p > 0.05). The eGFR variation in group over contrast dosage 150 ml was significantly decreased after radiological contrast agents exposure in stages 3-4 CKD (p $$\leq_-$$ 0.05). Therefore, when undergoing coronary angiography, contrast dosage should be minimized less than 150 ml, and diuretics should be restricted as possible in stages 3-4 CKD. Patients over age 75 require special attention to prevent CIN, and if patients undergo coronary angiography in stages 3-4 CKD, $HbA_{1c}$ is also requried to maintain below 6.5% to prevent CIN.

• 한국전산유체공학회지
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• 제22권1호
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• pp.37-42
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• 2017

Infrared signals are frequently used to detect objects exposed to wide variety of environmental conditions. Detection by infrared signature is accomplished by distinguishing objects by using the IR radiant contrast between objects and the background. There are several methods of estimating the IR radiant contrast. The inverse distance weighting method, which is one of the IR radiant contrast estimation method using the effect of distance from objects, is known to be an effective way to analyze radiant contrast for complex backgrounds. However this method has a disadvantage of requiring a long calculation time. In this study we propose a statistical method of estimating the IR radiant contrast by using randomly selected pixels of arbitrary number among background pixels to reduce calculation time. Some measured IR images in MWIR and LWIR regions are used to test the applicability of the method proposed and we found that the proposed method is very effective in determining the IR radiant contrast showing very rapid estimation with minar accuracy loss.

• 한국콘텐츠학회논문지
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• 제19권11호
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• pp.445-450
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• 2019

본 연구는 자기공명영상 동적검사 시 자동주입기의 사용에 따라 조영제 역류로 인한 생리식염수의 오염 현상을 실험적으로 증명함으로써, 오염된 실린지 재사용 문제의 심각성을 인식시키고자 하였다. 연구방법은 조영제 주입 전 생리식염수와 주입 후 생리식염수를 각각 채취한 다음, T1 강조영상을 획득하여 신호강도를 측정하여 비교하였다. 생리식염수의 주입 후 신호강도가 주입 전에 비해 523.43% 통계적으로 높게 나타났다(p<0.05). 이는 조영제 주입에 따른 압력에 의해 조영제가 관을 통해 역류하여 압력이 낮은 반대쪽 생리식염수를 오염시킨 것으로 분석되었다. 결론적으로 조영제 주입 시 사용하는 실린지는 조영제 역류로 인해 교차오염이 발생하므로 정량적 분석을 위한 검사 시 동일한 환자의 검사라도 검사순서를 변경하거나 실린지를 교체하여 오류를 방지해야 한다.

• Korean Journal of Radiology
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• 제2권4호
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• pp.197-203
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• 2001

Objective: To compare the clinical utility of contrast-enhanced color Doppler US in the differentiation of retinal detachment (RD) from vitreous membrane (VM) with that of various conventional US modalities, and to analyze the enhancement patterns in cases showing an enhancement effect. Materials and Methods: In 32 eyes examined over a recent two-year period, RD (n=14) and VM (n=18) were confirmed by surgery (n=28) or clinical follow-up (n=4). In all cases, gray-scale, color Doppler, and power Doppler US were performed prior to contrast injection, and after the intravenous injection of Levovist (Schering, Berlin) by hand for 30 seconds at a dose of 2.5 g and a concentration of 300 mg/mL via an antecubital vein, contrast-enhanced color Doppler US was performed. At Doppler US, the diagnostic criterion for RD and VM was whether or not color signals were visualized in membranous structures. Results: Diagnostic accuracy was 78% at gray-scale US, 81% at color Doppler US, 59% at power Doppler US, and 97% at contrast-enhanced color Doppler US. The sensitivity of color Doppler US to color signals in RD increased from 57% to 93% after contrast enhancement. The enhancement patterns observed were signal accentuation (n=3), signal extension (n=2), signal addition (n=3), and new signal visualization (n=5). Conclusion: Contrast-enhanced color Doppler US was the most accurate US modality for differentiating RD from VM, showing a significantly increased signal detection rate in RD.

• 한국산학기술학회논문지
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• 제16권7호
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• pp.4704-4710
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• 2015

본 연구는 가돌리늄 조영제의 T1 shortening effect를 이용하여 말초동맥으로 갈수록 신호강도가 낮아지는 위상영상의 단점을 근본적으로 개선함으로써 진단에 유용한 영상을 획득하고자 하였다. 연구기간은 2014년 10월부터 동년 12월까지 시행하였으며, 심장질환자를 제외한 AVM 환자 30명을 대상으로 하였다. 연구방법은 T1 shortening effect에 따른 신호강도의 차이를 알아보기 위해 가돌리늄 조영제 주입 전 후 자화강조영상을 획득한 다음, 위상영상을 비교평가 하였다. 연구결과, 가돌리늄 조영제 주입 전, 후 뇌실질 내 말초동맥의 신호강도는 가돌리늄 조영제 주입 후가 주입 전에 비해 전두엽 19.45%, 측두엽 23.09%, 두정엽 18.82%, 후두엽 25.45%, 소뇌 20.93%로 증가 하였고 통계적으로 유의하였다. 그러므로 위상영상 획득 시 가돌리늄 조영제의 T1 shortening effect를 이용하면 위상영상의 단점을 보완할 수 있어 진단 및 치료에 유용한 영상을 획득할 수 있으리라 사료된다.

• 한국광학회지
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• 제15권5호
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• pp.461-468
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• 2004

본 논문에서 연구된 정밀모형안은 정시안에서 1.2 시력의 적정한 수차를 가진 모형안임을 확인하였다. 망막의 특성을 생략한 안광학계에 광전달함수를 사용하여 망막에서의 광세기 분포를 조사하여 자각식으로 측정한 임상자료와 비교하였다. 망막의 광학적 특성을 나타내는 안구의 수차, 회절, 망막 대비감도, Stiles-Crawford 효과, 동공크기를 포함한 대비감도함수를 계산하였다. 모형안에 동공직경 1 mm와 8 mm의 범위에서 정시안과 비정시안에 대해 대비감도함수와 변조전달함수를 비교하여 시력을 예측하였다.