• The Journal of Korean Academy of Prosthodontics
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• v.45 no.3
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• pp.389-400
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• 2007

Statement of problem. Use of the conventional dental impression procedure is problematic in patients who have difficulty opening their mouth, difficulty breathing through their nose or tendency to gag. Purpose. It is necessary to make individual trays more comfortable for patients during impression taking procedure. It was reported at the KAP Annual Meeting 2001 Seoul that an improved impression technique was suitable for this purpose. In this study, the accuracy of the improved dental impression method for implant was compared with the conventional dental impression method. Material and methods. An oral simulator was made from clear acrylic resin block which had similar form of edentulous ridge. For setting up the standard, five fixtures were installed on it. Study casts were made using two kinds of impression techniques. One was the conventional method that was taken using silicone impression material and an individual resin tray under connection of inter-fixture relation. The other was the improved method in which was the connection of the impression coping and the thermoformed polymethyl methacrylate tray. In addition, two different study casts were made from the improved impression body. The coordinates of the fixture on the study model were measured by three-dimensional coordinate measuring equipment. Then the distances between each fixture were calculated and compared with that of oral simulator. Accuracy of the each impression method was also assessed. Results. The differences of inter-fixture dimension between study casts and simulator in the improved impression technique showed $0.014{\pm}0.016mm$ and $0.017{\pm}0.022mm$, respectively and that of the conventional method was $0.017{\pm}0.014mm$. There was no significant difference between the improved impression technique and conventional method. Conclusion. The improved impression technique is useful for multiple support implants.

• Journal of The Korean Association For Science Education
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• v.31 no.6
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• pp.998-1008
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• 2011

The purpose of this study is to develop the criteria for measuring the observation abilities of elementary school students. Object, viewpoint and mental demand constitute the evaluation criteria of observation abilities. Object domain was classified into two- and three-dimensional figures, while viewpoint was classified into constancy and variety of views. Mental demand covered 2 through 5. The assesment tool based on the threedimensional criteria was developed for the lower, middle and upper grades of 166 elementary school students. Results from this study were as follows. These students' scores were significantly different in the classification by each dimension and distinguishable between the grades. They scored high on two-dimensional figures, constancy of view and lower mental demand, and the upper grade students' scores were higher than the lower ones in all dimensions. Therefore, the evaluation criteria developed in this study can be used effectively for measuring the observation abilities of elementary school students. Implication for this study was determined to be the development of a valid and reliable test for observation abilities of elementary school students.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.36.2-37
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• 2016

We study the long-term radio variability of 43 radio bright AGNs by exploiting the data base of the University of Michigan Radio Astronomy Observatory (UMRAO) monitoring program. The UMRAO database provides high quality lightcurves spanning 25 - 32 years in time at three observing frequencies, 4.8, 8, and 14.5 GHz. We model the periodograms (temporal power spectra) of the observed lightcurves as simple power-law noise (red noise, spectral power $P(f){\propto}f^{-{\beta}}$ using Monte Carlo simulations, taking into account windowing effects (red-noise leak, aliasing). The power spectra of 39 (out of 43) sources are in good agreement with the models, yielding a range in power spectral index (${\beta}$) from ${\approx}1$ to ${\approx}3$. We find a strong anti-correlation between ${\beta}$ and the fractal dimension of the lightcurves, which provides an independent check of the quality of our modelling of power spectra. We fit a Gaussian function to each flare in a given lightcurve to obtain the flare duration. We discover a correlation between ${\beta}$ and the median duration of the flares. We use the derivative of a lightcurve to obtain a characteristic variability timescale which does not depend on the assumed functional form of the flares, incomplete fitting, and so on. We find that, once the effects of relativistic Doppler boosting on the observed timescales are corrected, the variability timescales of our sources are proportional to the black hole mass to the power of ${\alpha}=1.70{\pm}0.49$. We see an indication for AGNs in different regimes of accretion rate, flat spectrum radio quasars and BL Lac objects, having different scaling relations with ${\alpha}{\approx}1$ and ${\approx}2$, respectively. We find that modelling the periodograms of four of our sources requires the assumption of broken powerlaw spectra. From simulating lightcurves as superpositions of exponential flares we conclude that strong overlap of flares leads to featureless simple power-law periodograms of AGNs at radio wavelengths in most cases (The paper is about to be submitted to ApJ).

• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.41.2-41.2
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• 2016

The follow-up BVRI photometric observations of NSVS 1461538, which was discovered as an $Algol/{\beta}$ Lyr eclipsing variable by Hoffman, Harrison & McNamara (2009), were performed for three years from 2011 to 2013 by using the 61-cm telescope and CCD cameras of Sobaeksan Optical Astronomy Observatory (SOAO). New light curves have deep depths both of the primary and secondary eclipses, rounded shapes outside eclipses and a strong O'Connell effect, indicating that NSVS 1461538 is a typical W UMa close binary system rather than an $Algol/{\beta}$ Lyr type binary star. A period study with all the timings shows that the orbital period may vary in a sinusoidal way with a period of about 5.6 yr and a small semi-amplitude of about 0.008 d. The cyclical period variation was interpreted as a light-time effect due to a tertiary body with a minimum mass of $0.66M{\odot}$. The first photometric solution with the Wilson-Devinney binary model shows that the system is a W-subtype contact binary with the mass ratio ($q=m_c/m_h$) of 3.46, orbit inclination of 85.6 deg and fill-out factor of 30%. From the existing empirical relationship between parameters, the absolute dimension was estimated. The masses and radii of the component stars are $0.28M{\odot}$ and $0.71R{\odot}$ for the less massive but hotter primary star, respectively, and $0.96M{\odot}$ and $1.21R{\odot}$ for the more massive secondary, respectively. Possible evolution of the system is discussed in the mass-radius and the mass-luminosity planes.

• Journal of the Korean Institute of Navigation
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• v.18 no.2
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• pp.91-109
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• 1994

Technological and organisational changes in transport system have introduced new dimension into port system development and inter-port competition. The quality of service now required by the customer is costly and not easily provided by small shipping companies and small ports. It has been suggested that in the future container shipping may be concentrated by space-sharing arrangements or actual mergers into the hands of a few mega-operators with the investment potential to provide total logistics networks. In order to compete effectively, high load factors will be essential and port concentration inevitable. A fa-voured few ports will become the load centres and other ports will assume a secondary feeder role. In this study, three questions are raised and attempts are made to answer them : (a) what is the new role of ports today ; (b) why should ports be engaged in this new role ; and (c) how can ports play this new role. In short, a modern port should be a service centre and a logistic platform for international trade and transport-a third generation port. Ports, in particular, have to make every effort to be competitive in the cost and quality of services and to make the port a transport and distribution service centre. For most ports, this is not an option but a must ; an essential requirement for survival in this win or lose situation. The best way to win is to maintain a close contact with port users, listen to them, discuss with them, help them and satisfy them. That is port marketing. Starting from the findings of port marketing, it is es-sential to work out appropriate development plans and marketing targets and to improve port competitive-ness. As an alternative method, a port competitiveness model is suggested, which may help port managers to make appropriate improvements.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.6
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• pp.490-496
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• 2014

The thickness of knee joint cartilage causes most diseases of knee. Therefore, an articular cartilage segmentation of knee magnetic resonance imaging (MRI) is required to diagnose a knee diagnosis correctly. In particular, fully automatic segmentation method of knee joint cartilage enables an effective diagnosis of knee disease. In this paper, we analyze a well-known level-set based segmentation method in brain MRI, and apply that method to knee MRI with solving some problems from different image characteristics. The proposed method, a fully automatic segmentation in whole process, enables to process faster than previous semi-automatic segmentation methods. Also it can make a three-dimension visualization which provides a specialist with an assistance for the diagnosis of knee disease. In addition, the proposed method provides more accurate results than the existing methods of articular cartilage segmentation in knee MRI through experiments.

• International Journal of High-Rise Buildings
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• v.7 no.2
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• pp.145-151
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• 2018

Newly-designed high-rise buildings, both in China and abroad, have demonstrated new innovations from the creative concept to the creative method. from the creative concept to the creative method. At the same time, digital technology has enabled more design freedom in the vertical dimension. "Twisting" has gradually become the morphological choice of many city landmark buildings in recent years. The form seems more likely to be driven by the interaction of aesthetics and structural engineering. Environmental performance is often a secondary consideration; it is typically not simulated until the evaluation phase. Based on the research results of "DigitalFUTURE Shanghai 2017 Workshop - Wind Tunnel Visualization", an approach that can be employed by architects to design environmental-performance buildings during the early stages has been explored. The integration of a dynamic form-finding approach (DFFA) and programming transforms the complex relationship between architecture and environment into a dialogue of computer language and dynamic models. It allows the design to focus on the relationship between morphology and the surrounding environment, and is not limited to the envelope form itself. This new concept of DFFA in this research consists of three elements: 1) architectural form; 2) integration of wind tunnel and dynamic models; and 3) environmental response. The concept of wind tunnel testing integrated with a dynamic model fundamentally abandons the functional definition of the traditional static environment simulation analysis. Instead it is driven by integral environmental performance as the basic starting point of morphological generation.

• Journal of Digital Convergence
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• v.12 no.3
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• pp.309-316
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• 2014

The main purpose of this study is to find out how strategy orientation influences to performance in general hospitals, and to analyze the effect of the general hospital structure and its size to the relationship between independence variables and performance variable. To achieve the goal we set 3 sub-dimension, customer orientation, competition orientation and care skill orientation based on comprehensive consideration of related studies, and established 5 hypothesis. Survey data for statistic analysis have been collected from 176 members of 5 general hospitals in Korea from 1July to 13 October, 2013. We found that three dimensions of strategy orientation influence to performance significantly. We also found that moderating effect of general hospital structure and its size is partially supported. General hospital structure and its size moderates only the relationship between competition orientation and performance.

• Composites Research
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• v.29 no.1
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• pp.16-23
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• 2016

In this paper, numerical results of sectional analysis, stress recovery and energy release rate were compared with the results of VABS, 3-D FEM through the blade analysis library. The result of stress recovery analysis for one-dimensional model including the stiffness matrix is compared with stress results of three-dimensional FEM. We discuss the configuration of the blade analysis library and compare verifications of numerical analysis results of VABS. Blade analysis library through dimensional reduction and stress recovery is intended to be utilized in conjunction with pre- and post-processing of the analysis program of the composite blade, high-altitude uav's wing, wind blades and tilt rotor blade.

• Steel and Composite Structures
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• v.34 no.1
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• pp.17-34
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• 2020

This paper investigates the flexural behavior of concrete beams reinforced longitudinally with either steel bars, molded glass-fiber reinforced polymer (GFRP) grating mesh or pultruded glass-fiber reinforced polymer (GFRP) grating mesh, under four-point bending. The variables included in this study were the type of concrete (normal weight concrete, perlite concrete and vermiculite concrete), type of the longitudinal reinforcement (steel bars, molded and pultruded GFRP grating mesh) and the longitudinal reinforcement ratio (between 0.007 and 0.035). The influences of these variables on the load-midspan deflection curves, bending stiffness, energy absorption and failure modes were investigated. A total of fifteen beams with a cross-sectional dimension of 160 mm × 210 mm and an overall length of 2400 mm were cast and divided into three groups. The first group was constructed with normal weight concrete and served as a reference concrete. The second and third groups were constructed with perlite concrete and vermiculite concrete, respectively. An innovative type of stirrup was used as shear reinforcement for all beams. The results showed that the ultimate load of the beams reinforced with pultruded GFRP grating mesh ranged between 19% and 38% higher than the ultimate load of the beams reinforced with steel bars. The bending stiffness of all beams was influenced by the longitudinal reinforcement ratio rather than the type of concrete. Failure occurred within the pure bending region which means that the innovative stirrups showed a significant resistance to shear failure. Good agreement between the experimental and the analytical ultimate load was obtained.