• Journal of KIISE:Software and Applications
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• v.33 no.1
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• pp.95-104
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• 2006

The Gradient Vector Flow (GVF) snake or active contour model offers the best performance for image segmentation. However, there are problems in classical snake models such as the limited capture range and the slow progress into concavity. This paper presents a new method for enhancing the performance of the GVF snake model by extending the external force fields from the neighboring fields and using a modified smoothing method to regularize them. The results on a simulated U-shaped image showed that the proposed method has larger capture range and makes it possible for the contour to progress into concavity more quickly compared with the conventional GVF snake model.

• Journal of Periodontal and Implant Science
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• v.26 no.1
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• pp.266-275
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• 1996

The purpose of this study was to evaluate the effect of anatomical predisposing factors on the development of furcation involvement. Root trunk length, root divergency angle, buccal root trunk concavity and cervical enamel projection of the mandibular 1st and 2nd molars with(l03 teeth) and without(42 teeth) furcation involvement and enamel projection were classified by Lindhe's degree and Masters's classification, respectively, and buccal root trunk concavity was examined by probing. Statistical analysis was performed by means of ANOVA and CHI-SQUARE test in Microstat. The obtained results were as follows : 1. Root trunk length was longer in teeth without furcation involvement($4.20{\pm}1.05mm$) than teeth with furcation involvement(I : $3.62{\pm}0.68mm$, II : $3.64{\pm}0.86mm$, III: $3.61{\pm}0.74mm$)(p<0.05), but there was fno significant difference among furcation involvement group according to the degree of furcation involvement(p0>.05). 2. The root divergency angle was wider in teeth with furcation involvement(I : $53.14^0{\pm}15.11^0$, II : $44.82^0{\pm}14.26^0$, III : $52.69^0{\pm}16.09^0$) than teeth without furcation involvement($34.81^0{\pm}16.57^0$(p<0.05). 3. The group of teeth without furcation involvement showed significantly hign percentage of teeth without buccal root concavity, and the group of teeth with furcation involvement showed significantly hign percentage of teeth with buccal root concavity(p<0.05) 4. The group of teeth without furcation involvement showed higher percentage of teeth with grade I cervical enamel projection, teeth with furcation involvement I or II defect showed higher percentage of teeth with grade II enamel projection, and teeth with furcation involvement III defect showed higher percentage of teeth with grade III enamel projection(p<0.05) The results suggest that short root trunk length, wide root divergency, buccal root concavity and well-developed enamel projection could affect development and progression of furcation involvement as anatomical predisposing factors of periodontal diseases.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.9 no.5
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• pp.175-181
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• 2009

In this paper, we introduce the implementation of the security system using iris recognition. This system acquires images with infrared camera and extracts the 2D code from a infrared image which uses scale-space filtering and concavity. We examine the system by (i) extract 2D code and (ii) compare the code that stored on the server (iii) mearsure FAR and FRR using pattern matching. Experiment results show that the proposed method is very suitable.

• Journal of the Korean Statistical Society
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• v.24 no.1
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• pp.257-266
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• 1995

Consider a p-variate $(p \geq 4)$ normal distribution with mean $\b{\theta}$ and identity covariance matrix. For estimating $\b{\theta}$ under a quadratic loss we investigate the behavior of risks of Stein-type estimators which shrink the usual estimator toward the mean of observations. By using concavity of the function appearing in the shrinkage factor together with new expectation identities for noncentral chi-squared random variables, a characterization of estimators with nondecreasing risk is obtained.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.09a
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• pp.360-361
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• 2005

• Archives of Craniofacial Surgery
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• v.17 no.1
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• pp.20-24
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• 2016

Background: Midface concavity is a relatively common facial feature in East Asian populations. Paranasal augmentation is becoming an increasingly popular procedure for patients with mild concavity and normal occlusion. In this study, we evaluate clinical outcomes following a series of paranasal augmentation. Methods: A retrospective review was performed for patients with Class I occlusion who had undergone bilateral paranasal augmentation using custom-made silicone implants, between October 2005 and September 2013. Patient charts were reviewed for demographic information, concomitant operations, and postoperative complications. Preoperative and postoperative (1-month) photographs were used to evaluate operative outcome. Results: The review identified a total of 93 patients meeting study criteria. Overall, aesthetic outcomes were satisfactory. Five-millimeter thick silicone implant was used in 81 cases, and the mean augmentation was 4.26 mm for this thickness. Among the 93 patients, 2 patients required immediate implant removal due to discomfort. An additional 3 patients experienced implant migration without any extrusion. Nine patients complained of transient paresthesia, which had resolved by 2 weeks. There were no cases of hematoma or infection. All patients reported improvement in their lateral profile and were pleased at follow-up. Complications that arose postoperatively included 9 cases of numbness in the upper lip and 3 cases of implant migration. All cases yielded satisfactory results without persisting complications. Sensations were fully restored postoperatively after 1 to 2 weeks. Conclusion: Paranasal augmentation with custom-made silicone implants is a simple, safe, and inexpensive method that can readily improve the lateral profile of a patient with normal occlusion. When combined with other aesthetic procedures, paranasal augmentation can synergistically improve outcome and lead to greater patient satisfaction.

• Magazine of the Korean Society of Agricultural Engineers
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• v.24 no.2
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• pp.76-88
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• 1982

The stream morphological characteristics of a basin have important influence upon the analysis of runoff. In this study, the laws of stream morphology-the law of average stream fall and the law of least rate of potential energy expenditure-which were derived based on the analogy of entropy in thermodynamics are introduced and their validity is analysised with the data taken from the topographic maps covering the whole Geum River system. The first law is the Law of Average Stream Fall which states that under the dynamic equilibrium condition the ratio of average fall between any two different order stream in the same river basin in unity. The second law is the law of least rate of energy expenditure which states that all natural streams are intended to choose their own course of flow such that the rate of potential energy loss per unit mass of water this course is a minimum. The parameters representing the morphological characteristics of 13 tributaries in the Geum River system such as stream bifurcation ratio and stream concavity were Computed from the Horton-Strahler's laws and are used to check the law of average stream fall. The result showed that the law of average stream fall agrees reasonably well with law of Horton-Strahler. Concavity of a river basin is shown to be the determinative factor to the formation of a stream system. Concavity of a river basin is shown to be the determinative factor to the formation of a stream system. Based on Horton's Law and the law of average stream fall, longitudinal stream profiles can be calculated.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.12
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• pp.2761-2768
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• 2010

In this paper, we studied the use of the foreground and background features and SVM classifier to improve the accuracy of offline handwritten numeral recognition. The foreground features are two directional features: directional gradient feature by Kirsch operators and directional stroke feature by projection runlength, and the background feature is concavity feature which is extracted from the convex hull of the numeral, where concavity feature functions as complement to the directional features. During classification of the numeral, these three features are combined to obtain good discrimination power. The efficiency of our feature sets was tested by recognition experiments on the handwritten numeral database CENPARMI, where we used SVM with RBF kernel as a classifier. The experimental results showed that each combination of two or three features gave a better performance than a single feature. This means that each single feature works with a different discriminating power and cooperates with other features to enhance the recognition accuracy. By using the composite feature of the three features, we achieved a recognition rate of 98.90%.

• Journal of the Korean Geographical Society
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• v.42 no.1 s.118
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• pp.27-40
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• 2007

The streams evolve to diverse forms influenced by various factors such as rock resistance tectonic process, sediments and discharge. This study focuses on erosion resistance of rocks among these factors. The morphology of plane and longitudinal profile has been analysed in upper and lower reach of 6 streams using GIS; Yeoryong-cheon, Heungjeong-cheon, Duhak-cheon, Daehwa-cheon, Namcheon-cheon, Guryong-cheon, having distinct bedrock types between upper and lower reach. While the basins of granite have gentle slope, low concavity and wide valley area, those of gneiss form steep slope, high concavity and narrow valley area. However, the basins of sedimentary rock make steep slope and high relief in main channel, the other features show some differences in each stream. Among the various morphological features, the indices on slope and concavity of main channel, drainage density, ratio of valley area, average slope and average relief of the basin which have clear differences between rocks in upper and lower reach are calculated to interpret the erosion resistance of rocks in upper and lower reach. As a result, the upper reaches composed of gneiss have the highest erosion resistance, sedimentary rocks in upper and lower reaches show moderate resistance, and granite reaches generally have the lowest resistance except the upper reaches bordered by sedimentary rock.

• The korean journal of orthodontics
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• v.39 no.1
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• pp.28-35
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• 2009

Objective: The purpose of this study was to investigate the relationship between menarche and cervical vertebral maturation. Methods: Lateral cephalograms of 67 young korean girls within the range of 1 year before or after their menarche were gathered. The concavity of the cervical vertebrae base and the ratio of the base length to the 3rd and 4th cervical vertebrae anterior height were measured and analyzed. Results: The mean measured values were as follows, concavity of the 3rd cervical vertebrae base: 1.27(${\pm}0.18$) mm, concavity of the 4th cervical vertebrae base: 1.06(${\pm}0.15$) mm, ratio of the base length to the 3rd cervical vertebrae anterior height: 0.73(${\pm}0.06$) and ratio of the base length to the 4th cervical vertebrae anterior height: 0.70(${\pm}0.05$). There was a significant increase in the ratio of the base length to the 3rd vertebrae anterior height and the base concavity of the 3rd and 4th cervical vertebrae during the period of 1 year before to 1 year after their menarche. Conclusions: These characteristics of the 3rd and 4th cervical vertebrae on the lateral cephalogram can provide useful clues on evaluating the growth stage.