• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.346-346
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• 2006

Several types of dynamic atomic force microscopy such as tapping-mode, force modulation-mode are commonly cooperated by phase-contrast imaging techniques, which were interpreted as elastic contrast by mistake in the past and are nowadays regarded as the representation of energy dissipative processes. However, as theoretically reported, the situation is not so simple when the strong adhesive interaction is involved. Furthermore, elastic and viscous contributions are not easily divided in the case of polymeric systems. Thus, the interpretation of image contrast for them must be very carefully treated. In this study, we will demonstrate how such contrast mechanisms are complicated, using several miscible and immiscible polymer blend systems as model samples.

• 한국세라믹학회지
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• 제30권11호
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• pp.919-924
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• 1993

Domain structure and the spatial arrangement of tetragonal and rhombohedral phases in PZT ceramics at MPB composition were investigated with a transmission electron microscope. Fringe Contrast and doublet spot splitting were observed in the image mode and the selected area diffraction pattern, respectively. Besides, triplet spot splitting was also observed in the other part of the specimen. These observations indicate that both the single phase regions and the regions which are comosed of alternatively arranged tetragonal and rhombohedral domains coexist in a PZT ceramics at the MPB composition.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권3호
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• pp.1670-1683
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• 2017

Mitotic event recognition is a crucial and challenging task in biomedical applications. In this paper, we introduce the slow feature analysis and propose a fully-automated mitotic event recognition method for cell populations imaged with time-lapse phase contrast microscopy. The method includes three steps. First, a candidate sequence extraction method is utilized to exclude most of the sequences not containing mitosis. Next, slow feature is learned from the candidate sequences using slow feature analysis. Finally, a hidden conditional random field (HCRF) model is applied for the classification of the sequences. We use a supervised SFA learning strategy to learn the slow feature function because the strategy brings image content and discriminative information together to get a better encoding. Besides, the HCRF model is more suitable to describe the temporal structure of image sequences than nonsequential SVM approaches. In our experiment, the proposed recognition method achieved 0.93 area under curve (AUC) and 91% accuracy on a very challenging phase contrast microscopy dataset named C2C12.

• Applied Microscopy
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• 제38권1호
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• pp.63-72
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• 2008

Allen et al. (2004)에 의해 개발된 IWFR 방법에 대해서 응용성에 관심을 가지고 고찰되었다. 이 고찰에는 문헌에 보고된 GaAs, $YBa_2CuO_7$ 및 $Al_2CuMg$의 재료에 대한 HRTEM 연구물들이 이용되었다. 이 고찰 과정에서 이 방법의 타당성에 대한 이론적 근거, 제한조건 및 정보한계들을 명확히 제시되었다. IWFR 방법을 통해 얻은 결정 밑 표면에 전자 파동함수의 상(phase)-영상은 구면수차에 의한 영상 왜곡이 교정된 정보한계 범위 내에서 원자분해상을 나타낼 뿐만 아니라 결정의 구성원자의 원자번호에 대체적으로 비례하는 강도 분포를 나타내는 강한 경향이 있음이 특히 주목되었다.

• Journal of the Optical Society of Korea
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• 제20권4호
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• pp.510-514
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• 2016

The conventional liquid crystal displays (LCDs) have been using optically uniaxial liquid crystal (LC) medium and this often causes a significant image change at oblique viewing angles. We simulated the viewing angle properties of the biaxial nematic (N_b) phase of a bent-core liquid crystal (BLC) and compared the results with the vertically aligned (VA)- and the in-plane switching (IPS)-LCDs. The N_b phase of the BLC showed a smaller transmittance at the dark state as well as a greater contrast ratio at wide viewing angle. The viewing angle property of the N_b-mode without any compensation film was slightly superior to the IPS-mode with the compensation films eliminating the decross of the polarizers at oblique viewing angle.

• 정보학연구
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• 제4권2호
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• pp.129-136
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• 2001

초음파현미경은 대부분 단순히 시료로부터 반사된 신호의 진폭만을 이용하여 초음파영상을 구성하였다. 그러나 이 방법은 미세한 변화를 가지는 시료에 대해서는 반사신호의 진폭변화가 민감하지 않음으로 인하여 영상의 질을 저하 시켰다. 본 연구에서는 초음파 반사신호의 진폭과 위상을 동시에 측정할 수 있는 초음파현미경 시스템을 구성하고 샘플로서 500원 주화와 내부에 원형결함이 존재하는 알루미늄 시료에 대해 진폭영상과 위상영상을 획득하고 이들을 상호 비교분석하였다. 실험결과, 위상영상은 미세한 높이변화에 대해서는 진폭영상에 비하여 민감한 반응을 보였고 콘트라스트가 좋은 영상을 얻을 수 있었다. 이와같은 실험결과로 위상영상은 미세변화를 갖는 시료에 대한 비파괴검사시 진폭영상으로 얻어진 영상의 모호성을 개선하는 보조도구로서 활용이 기대된다.

• 대한의용생체공학회:의공학회지
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• 제33권2호
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• pp.72-77
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• 2012

Phase Contrast MR Angiography(PC MRA) is excellent MRA technique for measuring the velocity of vessels in the human body. PC MRA need to at least four images for angiogram reconstruction and it caused longer scan time. Therefore, we used keyhole imaging combined PC MRA to reduce the scan time. However, keyhole imaging can lead the erroneous effects as loss of phase information or frequency discontinuous. In this study, we applied the keyhole imaging combined 2D PC MRA for improving the temporal resolution and also measured the velocity to evaluate the accuracy of phase information. We used 0.32T MRI scanner(Magfinder II, Scimedix, Korea). Using the 2D PC MRA pulse sequence, the vascular images for a human brain targeted on the Superior Sagittal Sinus(SSS) were obtained. We applied tukey window function for keyhole images to minimize the ringing artifact and erroneous factors that are induced frequency discontinuous and phase information loss. We also applied zero-padded algorithm to peripheral missing k-space lines to compare keyhole imaging results and the artifact power(AP) value was measured on the complex difference images to validate the image quality. Consider as based on our results, heavy image distortions and artifacts were shown until using at least 50% keyhole factor. Using above the 50% keyhole factors are shown well reconstructed and matched for magnitude images and velocity information measurements. In conclusion, we confirmed the image quality and velocity information of keyhole technique combined 2D PC MRA. Especially, measured velocity information through the keyhole imaging combination was similar to the velocity information of full sampled k-space image despite of frequency discontinuous and phase information loss in the keyhole imaging reconstruction process. Consequently, the keyhole imaging combined 2D PC MRA will give some clinical usefulness and advantages as improving the temporal resolution and measuring the velocity information via selecting the appropriate keyhole factor at low tesla MRI system.

• 대한자기공명의과학회:학술대회논문집
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• 대한자기공명의과학회 2001년도 제6차 학술대회 초록집
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• pp.140-140
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• 2001

We present two cases of surgically proven focal nodular hyperplasia whou underwent tri contrast-enhance MR imaging using gadolinium chelates, mangafodipir trisodium, and ferumoxides After the unehanced MR images were obtained, dynamic gadolinium-enhanced T1-weighted imagi were performed, then mangafodipir enhanced and ferumoxides-enhanced images were obtained. In one case, the mass was isointense on both T1- and T2-weighted images on the unehanced M images, iso and slightly hyperintense on ferumoxides-enhanced FSE and GRE images, strong hyperintense on the mangafodipir enhanced and gadolinium enhanced arterial phase images. In th other case, the mass was isointense on T2-weighted and hypointense on T1-weighted image isointense on ferumoxides-enhanced images, and hyperintense on mangafodipir enhanced an gadolinium enhanced arterial phase images. Triple contrast enhanced MR images were useful correctly diagnose these two cases preoperatively.

• Investigative Magnetic Resonance Imaging
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• 제19권3호
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• pp.200-204
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• 2015

Image findings of hepatic lymphoma have been reported as variable, ranging from single or multiple small nodules to diffuse infiltrative patterns. On MRI, most hepatic lymphomas show T1 low signal intensity, T2 high signal intensity. Dynamic imaging reveals a hypointense appearance in the arterial phase, followed by delayed enhancement in the portal venous and transitional phase. In the hepatobiliary phase using a hepatocyte-specific contrast agent (which have recently aided in increasing the access to the focal liver lesions), hepatic lymphoma is known to exhibit low signal intensity. We report a case of hepatic lymphoma, which shows iso-signal intensity on hepatobiliary phase, using gadoxetic acid (Gd-EOB-DTPA).

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 추계종합학술대회 논문집(2)
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• pp.321-324
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• 2000

In this paper, we proposed a new visual cryptography scheme based on optical interference which improves the contrast and SNR of reconstructed images comparing with conventional visual cryptography method. We divided an binary image to be encrypted into n slides. To encrypt them, (n-1) random independent keys and one another random key by XOR process between four random keys were prepared. XOR between each divided image and each random key makes encrypted n encrypted images. From these images, encrypted binary phase masks can be made. For decryption all of phase masks should be placed together in the interferometer such as Mach-Zehnder interferometer.