• Journal of Information Display
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• v.4 no.1
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• pp.1-8
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• 2003

Recent progress in both low pretilt and high pretilt defect free C1 surface stabilized ferroelectric liquid crystal (SSFLC) devices is reviewed. First, by numerical calculation to investigate the balance between surface azimuthal anchoring energy and bulk elastic energy within the confined chevron layer geometry of C1 and C2, it is possible to achieve a zigzag free C1 state by low azimuthal anchoring alignment with a low pretilt angle. The critical azimuthal anchoring coefficient for defect free C1 state is calculated. Its relationship with elastic constant, chevron angle as well as surface topography effect are also discussed. Second, using $5^{\circ}$ oblique SiO deposition alignment method a defect free, large memory angle, high contrast ratio and bistable C1 SSFLC display, which has potential for electronic paper applications has also been developed. The electrooptical properties and bistability of this device have been investigated. Various aspects of defect control are also discussed.

• Journal of Veterinary Clinics
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• v.34 no.6
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• pp.410-413
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• 2017

Composites of hydroxyapatite (HAp) and chitosan (CS) have been successfully used in bone healing in humans and animals. However, the characteristics of HAp and CS are different. Therefore, the effects of HAp/CS composites on canine bone formation could differ according to their ratio. This study investigated the therapeutic effects of different contents ratios (100, 80:20, 60:40 wt%) on bone defects in a canine model. Thirty intrabony cylindrical defects were created in the humeruses and femurs of 5 beagle dogs, and then the defects were implanted with different composites. The evaluations were performed using radiographs obtained at 10 weeks post-surgery and by histological findings. In radiographic evaluation including the grades of bone filling, periosteal and endosteal reactions, pure hydroxyapatite composite had a significant effect on bone filling, and chitosan containing the composites showed vigorous responses at the periosteum and endosteum. In histological findings, the defect implanted with pure hydroxyapatite had healed completely into mature bony tissue with an obvious osteon structure, and the defect implanted with chitosan containing the composites had the amount of fibrous connective tissue increased significantly within the cortical bone tissue. The results indicate that hydroxyapatite/chitosan composites are therapeutically useful, promoting effective bone healing in defects when the ratio of hydroxyapatite is high and enhanced fibrous connective tissue formation at the periosteum as more chitosan is added.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.5
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• pp.997-1003
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• 2007

In this paper, we propose a global approach for automatic inspection of defects in the polarizer film image. The proposed method does not rely on local feature of the defect. It is based on a global image reconstruction scheme using the singular value decomposition(SVD). SVD is used to decompose the image and then obtain a diagonal matrix of the singular values. Among the singular values, the first singular value is used to reconstruct a image. In reconstructed image, the normal pixels in background region have a different characteristics from the pixels in defect region. It is obtained the ratio of pixels in the reconstructed image to ones in the original image and then the defects are detected based on the the statistical process of the ratio. The experiment results show that the proposed method is efficient for defect inspection of polarizer lam image.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.49 no.1
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• pp.8-11
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• 2012

Automated Vision Inspection (AVI) systems automatically detect any defect feature in a surface image. The performance of the system can be measured under a special circumstances such as ultimate defect detection. In this situation, the defect signal level is similar to noise level and it becomes hard to make a solid decision with AVI systems. In this paper, we propose an effective preprocessing technique to enhance SNR (Signal to Noise Ratio). The method is motivated by some principles of HVS (Human Visual System) and RLC (Run Length Coding) techniques is used for this purpose. The proposed preprocessing technique enhances SNR under ultimate defect conditions and improves overall performance of AVI system.

• Journal of Institute of Control, Robotics and Systems
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• v.4 no.4
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• pp.499-505
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• 1998

In developing an automated surface inspect algorithm, we have designed a hierarchical classifier using neural network. The defects which exist on the surface of cold mill strip have a scattering or singular distribution. We have considered three major problems, that is preprocessing, feature extraction and defect classification. In preprocessing, Top-hit transform, adaptive thresholding, thinning and noise rejection are used Especially, Top-hit transform using local minimax operation diminishes the effect of bad lighting. In feature extraction, geometric, moment, co-occurrence matrix, and histogram ratio features are calculated. The histogram ratio feature is taken from the gray-level image. For defect classification, we suggest a hierarchical structure of which nodes are multilayer neural network classifiers. The proposed algorithm reduced error rate by comparing to one-stage structure.

• Archives of Craniofacial Surgery
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• v.22 no.5
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• pp.260-267
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• 2021

Background: Elastic ear cartilage is a good source of tissue for support or augmentation in plastic and reconstructive surgery. However, the amount of ear cartilage is limited and excessive use of cartilage can cause deformation of the auricular framework. This animal study investigated the potential of periosteal chondrogenesis in an ear cartilage defect model. Methods: Twelve New Zealand white rabbits were used in the present study. Four ear cartilage defects were created in both ears of each rabbit, between the central artery and marginal veins. The defects were covered with perichondrium (group 1), periosteum taken from the calvarium (group 2), or periosteum taken from the tibia (group 3). No coverage was performed in a control group (group 4). All animals were sacrificed 6 weeks later, and the ratio of neo-cartilage to defect size was measured. Results: Significant chondrogenesis occurred only in group 1 (cartilage regeneration ratio: mean±standard deviation, 0.97±0.60), whereas the cartilage regeneration ratio was substantially lower in group 2 (0.10±0.11), group 3 (0.08±0.09), and group 4 (0.08±0.14) (p= 0.004). Instead of chondrogenesis, osteogenesis was observed in the periosteal graft groups. No statistically significant differences were found in the amount of osteogenesis or chondrogenesis between groups 2 and 3. Group 4 showed fibrous tissue accumulation in the defect area. Conclusion: Periosteal grafts showed weak chondrogenic potential in an ear cartilage defect model of rabbits; instead, they exhibited osteogenesis, irrespective of their embryological origin.

• Journal of Chest Surgery
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• v.21 no.6
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• pp.1117-1123
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• 1988

Prolapse of the aortic valve is the main cause of insufficiency of the aortic valve as a complication of ventricular septal defect. Aortic insufficiency gets worse by the progress of prolapse of aortic valve due to lack of support of the valve and the hemodynamic effect of blood flow through the ventricular septal defect. This produces typical clinical picture, that may be serious and threatening when it is untreated. Type and timing for the surgical treatment of the ventricular septal defect with aortic insufficiency is considered. Among 113 ventricular septal defect, 9 patients of ventricular septal defect with associated aortic insufficiency were experienced from June. 1983 to June 1988 at the Department of Thoracic and Cardiovascular Surgery, Chon-Buk University Hospital. Male was 6 patients and female was 3 patients. Ages were from 7 years to 24years. 5 patients were from 10 to 19 years age. 3 patients were below 10 years age. The ratio of pulmonary blood flow to systemic f low [Qp/Qs] was 1.53 and in pulmonary vascular resistance, normal or slight increase was 7 patients, moderate 1 patient, and severe 1 patient. Ventricular septal defect was subpulmonic in 5 patients and infracristal in 4 patients. Prolapse of right coronary cusp was 7 patients, right and non coronary cusp 1 patient and non coronary cusp 1 patient. Teflon patch closure of ventricular septal defect was undertaken in 3 patients and primary closure in 1 patient. Among the 4 patients of defect closure alone, one patient performed valve replacement 7 months later due to progressive regurgitation and cardiac failure and the result was good. The other 3 patients were good result. Closure of ventricular septal defect and aortic valvuloplasty performed in 4 patients. 2 patients of these required valve replacement for the sudden intractable cardiac failure and died due to low cardiac output. The cause of intractable cardiac failure was tearing of repaired valve at the fixed site. The other 2 patients were good result. Closure of ventricular septal defect and valve replacement performed in 1 patient with good result.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.11a
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• pp.1-12
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• 2001

In cold forging of piston-pin for automobile parts, the flow defect appears by the dead metal zone. This appearance evidently happens in products with a thin piercing thickness for the dimension accuracy and the decrease of material loss. The best method that can prevent flow defect is removing dead metal zone. The purpose of this study is to investigate the material flow behavior of forward-backward extruded piston-pin through the relative velocity ratio and the stroke control of upper moving punch & container using the flow control forming technique. The finite element simulations are applied to analyse the flow defect, then the results are compared with the plasticine model material experiments. Finally, the model experiment results are in good agreement with the FE simulation ones.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.7
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• pp.1366-1375
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• 2002

In cold forging of piston-pin for automobile parts, the flow defect appears by the dead metal zone. This appearance evidently happens in products with a thin piercing thickness for the dimension accuracy and the decrease of material loss. The best method that can prevent flow defect is removing dead metal zone. The purpose of this study is to investigate the material flow behavior of forward-backward extruded piston-pin through the relative velocity ratio and the stroke control of upper moving punch & container using the flow control forming technique. The finite element simulations are applied to analyse the flow defect, then the results are compared with the plasticine model material experiments. The model experiment results are in good agreement with the FE simulation ones.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.7 no.1
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• pp.27-34
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• 2011

The objective of this study is to classify the geometry of wall-thinning defect that causes a circumferential crack in the pipe elbows subjected to internal pressure. For this objective, first of all a criterion to determine the occurrence of circumferential cracking at wall-thinned area was developed based on finite element simulation for burst tests of pipe elbow specimens that showed axial and circumferential cracking at wall-thinned area. In addition, parametric finite element analysis including various wall-thinning geometries, locations, and pipe geometries was conducted and the wall-thinning geometries that initiate circumferential crack were determined by applying the criterion to the results of parametric analysis. It showed that the circumferential crack occurs at wall-thinning defect, which has a deep, wide, and short geometry. Also, it is indicated that the pipe elbows with larger radius to thickness ratio are more susceptible to circumferential cracking at wall-thinned area.