• Imaging Science in Dentistry
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• v.49 no.2
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• pp.131-137
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• 2019

Purpose: This study was designed to investigate the effects of voxel size, the oversampling technique, and the direction and area of measurement on modulation transfer function (MTF) values to identify the optimal method of MTF measurement. Materials and Methods: Images of the wire inserts of the SedentexCT IQ phantom were acquired, and MTF values were calculated under different conditions(voxel size of 0.1, 0.2, and 0.3 mm; 5 oversampling techniques; simulated pixel location errors; and different directions and areas of measurement). The differences in the MTF values across various conditions were evaluated. Results: The MTF 10 values showed smaller standard deviations than the MTF 50 values. Stable and accurate MTF values were obtained in the 0.1-mm voxel images. In the 0.3-mm voxel images, oversampling techniques of 11 lines or more did not show significant differences in MTF values depending on the presence of simulated location errors. MTF 10 values showed significant differences according to the direction and area of the measurement. Conclusion: To measure more accurate and stable MTF values, it is better to measure MTF 10 values in small-voxel images. In large-voxel images, the proper oversampling technique is required. MTF values from the radial and tangential directions may be different, and MTF values vary depending on the measured area.

• Progress in Medical Physics
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• v.32 no.2
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• pp.50-58
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• 2021

Purpose: In this study, we investigated the relationship between the noise characteristics and the number of projected images in tomosynthesis using a digital phantom. Methods: The digital phantom consisted of a columnar phantom in the center of the image and a spherical phantom with a diameter of 80 pixels. A virtual scan was performed, and 128 projected images (Tomo_w/o) of the phantoms were obtained. The image noise according to the Poisson distribution was added to the projected images (Tomo_×1). Furthermore, another projected image with additional noise was prepared (Tomo_×1/2). For each dataset, we created datasets with 64 (half) and 32 (quarter) projections by removing the even-numbered images twice from the 128 (fully) projected images. Tomosynthesis images were reconstructed by filtered back projection (FBP). The modulation transfer function (MTF) was estimated using the sphere method, and the noise power spectrum (NPS) was estimated using the two-dimensional Fourier transform method. Results: The MTFs did not change between datasets, and the NPSs improved as the number of projected images increased. The noise characteristics of the Tomo_×1_half images were the same as those of the Tomo_×1/2_full. Conclusions: To achieve a reduction in the patient dose in tomosynthesis acquisition, we recommend reducing the number of projected images rather than reducing the dose per projection.

• Korean Journal of Remote Sensing
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• v.39 no.4
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• pp.395-407
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• 2023

Super-resolution (SR) has great significance in image processing because it enables downstream vision tasks with high spatial resolution. Recently, SR studies have adopted deep learning networks and achieved remarkable SR performance compared to conventional example-based methods. Deep-learning-based SR models generally require low-resolution (LR) images and the corresponding high-resolution (HR) images as training dataset. Due to the difficulties in obtaining real-world LR-HR datasets, most SR models have used only HR images and generated LR images with predefined degradation such as bicubic downsampling. However, SR models trained on simple image degradation do not reflect the properties of the images and often result in deteriorated SR qualities when applied to real-world images. In this study, we propose an image degradation model for HR satellite images based on the modulation transfer function (MTF) of an imaging sensor. Because the proposed method determines the image degradation based on the sensor properties, it is more suitable for training SR models on remote sensing images. Experimental results on HR satellite image datasets demonstrated the effectiveness of applying MTF-based filters to construct a more realistic LR-HR training dataset.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.05a
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• pp.787-789
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• 2017

Edge detection is used in many applications such as image analysis, pattern recognition and computer vision. Existing edge detection methods, there is such Sobel, Prewitt, Roberts, and LoG(Laplacian of Gaussian). In the conventional edge detection method, edge detection is insufficient because the change of the pixel brightness is small when the original image is in low illumination. Therefore, in this paper, we proposed a function to convert the pixel brightness of low illumination image to solve this problem. And it was compared by applying the conventional methods Sobel, Prewitt, Roberts, LoG(Laplacian of Gaussian) to determine the performance of the pixel brightness transform function.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.366-370
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• 2003

This paper is on weighted model reduction using structurally balanced truncation. For a given weighted(single or double-sided) transfer function, a state space realization with the linear fractional transformation form is obtained. Then we prove that two block diagonal LMI(linear matrix inequality) solutions always exist, and it is possible to get a reduced order model with guaranteed stability and a priori error bound. Finally, two examples are used to show the validity of proposed weighted reduction method, and the method is compared with other existing methods.

• Proceedings of the KIEE Conference
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• 1992.07a
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• pp.299-301
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• 1992

The adaptive active noise control algorithm for duct noise attenuation is considered. A new algorithm to estimate the secondary path transfer function using multiple models is presented. The computational burden of the proposed algorithm is much smaller than the existing methods, so it could be applied to the multi-channel cases. Computer simulations were done to show the effectiveness of the proposed algorithm in a duct case.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.724-727
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• 1999

The previous LQ-servo PI design methods have some serious design problems happened from the frequency matching of the maximum and minimum singular values of loop transfer function at both low and high frequency regions on the Bode plot. To solve these problems, this paper proposes a new design technique based on the inverse-optimal control and convex optimization.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.05a
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• pp.629-634
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• 2000

This System is developed for the estimation of the Camera Lens Resolution. Signal data proportional to light intensity is obtained and sampled from the 2D CCD. Based on the measured signal. the MTF charateristcs of a camera lens are measured. We could measure the sagittal and tangential MTF in the on and off-axis at the same time. The automatic measurig methods for optimal image plane, magnification, and best marginal direction of test lens are presented.

• Clinics in Shoulder and Elbow
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• v.22 no.1
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• pp.9-15
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• 2019

Background: Latissimus dorsi (LD) tendon transfer is used as a treatment option for massive irreparable posterosuperior rotator cuff tears, and recently, an arthroscopic-assisted technique was introduced. This study was undertaken to evaluate the clinical and radiological outcomes of arthroscopic-assisted LD tendon transfer for the management of irreparable rotator cuff tears in active middle-aged patients. Methods: The records of five patients (two males) with irreparable tears involving the supraspinatus and infraspinatus tendons managed by arthroscopic-assisted LD tendon transfer were retrospectively reviewed. Clinical outcomes were assessed using the visual analogue scale (VAS) pain scale, American Shoulder and Elbow Surgeon's (ASES) scores, the University of California Los Angeles (UCLA) scale, and ranges of motion. Postoperative integrities of transferred tendon were evaluated by magnetic resonance imaging in 4 patients and by ultrasound in one. Results: Mean patient age was 55 years (range, 48-61 years), and mean follow-up period was 20 months (range, 12.0-27.2 months). Mean VAS score significantly improved from $6.6{\pm}2.6$ preoperatively to $1.8{\pm}2.5$ postoperatively (p=0.009), mean ASES score increased from $67.6{\pm}9.2$ to $84.6{\pm}15.1$, and mean UCLA score from $18.0{\pm}1.4$ to $28.8{\pm}8.5$ (all p<0.001). Postoperative imaging of the transferred LD tendon showed intact repair in 4 patients. The remaining patient experienced LD transfer rupture and a poor outcome. Conclusions: Arthroscopic-assisted LD tendon transfer improved shoulder pain and function in patients with massive, irreparable rotator cuff tears, and may be an option for this condition, especially in physically active patients.

• The Journal of Korean Physical Therapy
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• v.27 no.6
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• pp.425-429
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• 2015

Purpose: This study was to identify the whether there is any correlation between Gross Motor Function Measures (GMFM) and Functional independence Measurement for children (WeeFIM) in order to identify a relevance of daily life motor with gross motor function of children with cerebral palsy. Methods: Subjects were instructed to evaluated by an occupational therapist using WeeFIM (reliability 0.83-0.99) and by a physical therapist using GMFM (reliability 0.93). 10 male children and 13 female children among 23 children being diagnosed as cerebral palsy were targeted for this study. A correlation between GMFM and WeeFIM was analyzed with Kendall correlation. Results: Participants showed significant correlation between GMFM and WeeFIM in all categories, except in the GMFM's walking running jumping category, standing category of GMFM and self care, sphincter control, communication category of WeeFIM. Lying rolling and sitting and crawling kneeling area of GMFM showed a significant correlation with self care(r=0.35, 0.39, 0.4), sphincter control (r=0.45, 0.43, 0.61), mobility transfer (r=0.44, 0.36, 0.64), locomotion (r=0.41, 0.35, 0.74), communication (r=0.4, 0.44, 0.51), and social cognition (r=0.43, 0.51, 0.64) area of WeeFIM (p<0.05). Standing of GMFM and mobility transfer (r=0.74), locomotion (r=0.47) and social cognition (r=0.4) area of WeeFIM showed a significant correlation (p<0.05). Conclusion: These findings indicated significant correlation between activity of daily living (ADL) and gross motor function of children with cerebral palsy. However, because there are a few results that are not significant, both assessment tools should be used for evaluations so that treatment can be achieved with an accurate assessment and establish a therapeutic plan.