• Imaging Science in Dentistry
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• v.46 no.2
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• pp.93-101
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• 2016

Purpose: The objective of this study was to investigate the effect of varying resolutions of cone-beam computed tomography images on the accuracy of linear measurements of edentulous areas in human cadaver heads. Intact cadaver heads were used to simulate a clinical situation. Materials and Methods: Fiduciary markers were placed in the edentulous areas of 4 intact embalmed cadaver heads. The heads were scanned with two different CBCT units using a large field of view ($13cm{\times}16cm$) and small field of view ($5cm{\times}8cm$) at varying voxel sizes (0.3 mm, 0.2 mm, and 0.16 mm). The ground truth was established with digital caliper measurements. The imaging measurements were then compared with caliper measurements to determine accuracy. Results: The Wilcoxon signed rank test revealed no statistically significant difference between the medians of the physical measurements obtained with calipers and the medians of the CBCT measurements. A comparison of accuracy among the different imaging protocols revealed no significant differences as determined by the Friedman test. The intraclass correlation coefficient was 0.961, indicating excellent reproducibility. Inter-observer variability was determined graphically with a Bland-Altman plot and by calculating the intraclass correlation coefficient. The Bland-Altman plot indicated very good reproducibility for smaller measurements but larger discrepancies with larger measurements. Conclusion: The CBCT-based linear measurements in the edentulous sites using different voxel sizes and FOVs are accurate compared with the direct caliper measurements of these sites. Higher resolution CBCT images with smaller voxel size did not result in greater accuracy of the linear measurements.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.45 no.6
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• pp.309-315
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• 2019

Objectives: The aim of this study was to evaluate the validity of the existing classification and difficulty index of impacted mandibular third molars in clinical situations and propose a more practical classification system. Materials and Methods: This study included 204 impacted mandibular third molars in 154 patients; panoramic x-ray images were obtained before tooth extraction. Factors including age, sex, and pattern of impaction were investigated. All impacted third molars were classified and scored for spatial relationship (1-5 points), depth (1-4 points), and ramus relationship (1-3 points). All variables were measured twice by the same observer at a minimum interval of one month. Finally, the difficulty index was defined based on the total points scored as slightly difficult (3-4 points), moderately difficult (5-7 points), very difficult (8-10 points), and extremely difficult (11-12 points). Results: The strength of agreement of the total points scored and difficulty index were 0.855 and 0.746, respectively. Most cases were classified as moderately difficult (73.0%). Although only 13 out of 204 cases (6.4%) were classified as extremely difficult, patients classified as extremely difficult were the oldest (P<0.05). Conclusion: For difficulty classification, the authors propose one more difficult category beyond the existing three-step difficulty index: the clinician should consider the patient's age in the difficulty index evaluation.

• Physical Therapy Korea
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• v.14 no.3
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• pp.72-80
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• 2007

The purpose of this study was to verify the effects on fine motor, muscle strength (hand-grip), explosive muscular strength (vertical jump) and muscular endurance (sit-up) after ingesting coffee. Hence this study targeted a sample group of 38 healthy men in their twenties, without cardiac disorders and muscle disorders and none of them were hypersensitive to caffeine with symptoms such as palpitation and dyspnea. Nineteen of them ingested coffee, whereas the other nineteen men ingested decaffeinated coffee at the same amount. The amount of coffee was controlled by weight so as to regulate intake to 6 mg caffeine per kg. Research material was evaluated through O'Conner's finger dexterity test, hand-grip strength test, vertical jump test and sit-up test. The data were analyzed by means of paired t-test and ANCOVA. The material was then, analyzed by means of two-way ANOVA in order to verify the effect of one or two cups of coffee on fine motor and hand-grip strength. All parameters were measured by an independent observer. The results were as follows: There were no significant differences to fine motor, hand-grip strength, vertical jump, sit-up before and after drinking decaffeinated coffee, but there was a difference to those before and after drinking caffeine coffee. There was no significant difference to hand dexterity and hand-grip strength in one or two cups of coffee. Intake of a certain dosage of caffeine effects activation of muscles working in a short period based on the results. As a consequence, intake of certain dosages of caffeine was beneficial to enhance efficiency of activity during exercises, but it is will be difficult to obtain the desired result with only one or two cups of coffee.

• Journal of the Korean Home Economics Association
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• v.29 no.4
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• pp.45-64
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• 1991

Each of us has personal and unique "Mental Images" of environment that are the results of a two-way process between an observer and his environment. By understanding of people's image on their physical settings through cognitive maps, congruent with their design environment. In this context, this study is to fine out the characteristics of the resident's image in apartment housing that are modern housing. This paper is theoretically based on Appleyard's cognitive maps types, Lynch's the components of image, Harrison and Howard's image enhancing factors and Applyard's image enhancing factors of buildings. For the purpose of this study, two-instruments were used. One was sketch mapping, that told of visual aspects of cognitive map. Another was verbal questionnaire, which was composed of nonvisual aspects of image components and image enhancing factors. For the methods of research analysis, Percentage, Frequency, and Chi-square test were used. The results of this study are as follows. Firstly, as for the types of cognitive maps, the rate of sequential maps and spatial maps are nearly same. Secondly, as for the components of images, landmarks and districts are significant elements in apartment housing, and edges, nodes and paths are rare element. Thirdly, with regard to image enhancing factors, landscaping is shown to be most effective at landmarks and districts. And finally, in examing the differences of images between various social groups, significant variables are years of living and housing size. Age and income are the next. In this study of image, we can learn about manner in which individuals come to see, understand, and cope with the environment at a personal level. So, user-oriented approach is useful in environmental design, and particularly, it is useful in the apartment housing of the future life space.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.9B
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• pp.1731-1741
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• 1999

Color images are often corrupted by the noise due to noisy sensors or channel transmission errors. Some filters such as vector media and vector $\alpha$-trimmed mean filter have bee used for color noise removal. In this paper, We propose the fuzzy cluster filters based on the possibilistic c-means clustering, because the possibilistic c-means clustering can get robust memberships in noisy environments. Also, we propose weighted vector $\alpha$-trimmed mean filter to improve the conventional vector $\alpha$-trimmed mean filter. In this filter, the central data are more weighted than the outlying data. In this paper, we implemented the color noise generator to evaluate the performance of the proposed filters in the color noise environments. The NCD measure and visual measure by human observer are used for evaluation the performance of the proposed filters. In the experiment, proposed fuzzy cluster filters in the sense of NCD measure gave the best performance over conventional filters in the mixed noise. Simulation results showed that proposed weighted vector $\alpha$-trimmed mean filters better than the conventional vector $\alpha$-trimmed mean filter in any kinds of noise.

• The KIPS Transactions:PartB
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• v.12B no.4 s.100
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• pp.387-394
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• 2005

This paper describes an idea for determining self-localization using visual landmark. The critical geometric dimensions of a pentagon are used here to locate the relative position of the mobile robot with respect to the pattern. This method has the advantages of simplicity and flexibility. This pentagon is also provided nth a unique identification, using invariant features and colors that enable the system to find the absolute location of the patterns. This algorithm determines both the correspondence between observed landmarks and a stored sequence, computes the absolute location of the observer using those correspondences, and calculates relative position from a pentagon using its (ive vortices. The algorithm has been implemented and tested. In several trials it computes location accurate to within 5 centimeters in less than 0.3 second.

• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.5
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• pp.491-497
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• 2004

This paper presents a new rotor position estimation method for brushless DC motors. It is clear that the estimation error of the rotor position provokes the phase shift angle misaligned between the phase current and the back-EMF waveforms, which causes torque ripple in brushless DC motor drives. Such an estimation error can be reduced with the help of the proposed neutral voltage-based estimation method that is structured in the form of a closed loop observer. A neutral voltage appearing during the normal mode of the inverter operation is found to be an observable and controllable measure, which can be dealt with for estimating an exact rotor position. This neutral voltage is obtained from the DC-link current, the switching logic, and the motor speed values. The proposed algorithm, which can be implemented easily by using a single DC-link current and the motor terminal voltage sensors, is verified by simulation and experiment results.

• Communications of Mathematical Education
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• v.31 no.2
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• pp.223-239
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• 2017

In this paper, it is aimed to design the teaching units 'Inquiry into the isoperimetric problem of triangle and quadrilateral' to give elementary gifted students experience of mathematization. For this purpose, the teacher and the class observer (researcher) made a discussion about the design of the teaching unit through the analysis of the class based on the thought processes appearing during the problem solving process of each group of students. The following is a summary of the discussions that can give educational implications. First, it is necessary to use mathematical materials to reduce students' cognitive gap. Second, it is necessary to deeply study the relationship between the concept of side, which is an attribute of the triangle, and the abstract concept of height, which is not an attribute of the triangle. Third, we need a low-level deductive logic to justify reasoning, starting from inductive reasoning. Finally, there is a need to examine conceptual images related to geometric figure.

• Journal of the Korean Institute of Intelligent Systems
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• v.17 no.5
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• pp.582-590
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• 2007

Nonlinear adaptive control of overhead cranes is investigated for anti-sway trajectory tracking with high-speed hoisting motion. The sway dynamics of two dimensional underactuated overhead cranes is heavily coupled with the trolley acceleration, hoisting rope length, and the hoisting velocity which is an obstacle in the design of decoupling control based anti-sway trajectory tracking control law To cope with this obstacle. we propose a fuzzy nonlinear adaptive anti-sway trajectory tracking control law guaranteeing the uniform ultimate boundedness of the sway dynamics even in the presence of uncertainties in such a way that it cancels the effect of the trolley acceleration and hoisting velocity on the sway dynamics. In particular. system uncertainties, including system parameter uncertainty unmodelled dynamics, and external disturbances, are compensated in an adaptive manner by utilizing fuzzy uncertainty observers. Accordingly, the ultimate bound of the tracking errors and the sway angle decrease to zero when the fuzzy approximation errors decrease to zero. Finally, numerical simulations are performed to confirm the effectiveness of the proposed scheme.

• Journal of the Optical Society of Korea
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• v.17 no.4
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• pp.344-349
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• 2013

This paper proposes a simulation algorithm to assess the gradual yellowing vision of the elderly, which refers to the predominance of yellowness in their vision due to aging of the ocular optic media. This algorithm employed the spectral transmittance property of a yellow filter to represent the color appearance perceived by elderly people with yellow vision, and modeled the changes in the color space through a spectrum change in light using the yellow filter effect. The spectral reflectivity data of 1269 Munsell matte color chips were used as reference data. Under the standard conditions of a D65 illuminant and a $10^{\circ}$ observer of 1964 CIE, the spectrum of the 1269 Munsell colors were processed through the yellow filter effect to simulate yellow vision. Various degrees of yellow vision were modeled according to the transmittance percentage of the yellow filter. The color differences before and after the yellow filter effect were calculated using the DE2000 formula, and the color pairs were selected based on the color difference function. These color pairs are distinguishable through normal vision, but the color difference diminishes as the degree of yellow vision increases. Assuming 80% of yellow vision effect, 17 color pairs out of $(1269{\times}1268)/2$ pairs were selected, and for the 90% of yellow vision effect, only 3 color pairs were selected. The result of this study can be utilized for the diagnosis system of gradual yellow vision, making various types of test charts with selected color pairs.