• 대한치과기공학회지
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• 제12권1호
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• pp.23-45
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• 1990

This study aimed at inquiring into the basic theory on co-operative education, grasping and analyzing the present situation of the junior health college, the present condition of co-operative education and into problem. and seeking to find a solution to activate the co-operative edcation of the junior health colleges. For this purpose this study compared the co-operative education system in our country with that of foreign countries revolving around the related literature to co-operative education, analyzed it, and the pointed out its problem. And this study classified into the solution of establishing co-operative education system, the solution of consolidating the on-the-spot training system, the solution to activate the co-operative education of the junior health college. First this study suggested three methods as a part of establishing co-operative education system as below. 1. The need to set up the ideology concerning co-operative education. 2. The construction of the advisory committee for co-operative education. 3. The establishment of an agency for co-operative education. And this study suggested nine methods as the method of consolidating the on-the-spot training as below. 1. The execution of the basic research for the on-the-spot training. 2. The reorganization of the existing curriculum into the curriculum the industrial organization requires. 3. The establishing of the system in a closer cooperation with the industrial organization for the on-the-spot training. 4. The participation in solving commonly the problems of the industrial organization and in education. 5. The establishing of the guidance system assuming exclusive charge of the on-the-spot training. 6. The submission of the evaluation sheet for the on-the-spot training. 7. The extension of the period of the on-the-spot training and the reorganization of an educational system. 8. The persistent support for the on-the-spot training at the governmental dimension. 9. The securing of the educational dost spent on the on-the-spot training and the imposition of benefits on the industrial organization.

• Imaging Science in Dentistry
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• 제42권4호
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• pp.231-235
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• 2012

Purpose: This study was performed to evaluate the trabecular pattern on panoramic radiographs to predict age-related osteoporosis in postmenopausal women. Materials and Methods: Thirty-one postmenopausal osteoporotic women and 25 postmenopausal healthy women between the ages of 50 and 88 were enrolled in this study. The bone mineral density (BMD) of the lumbar vertebrae and femur were calculated using dual-energy X-ray absorptiometry (DXA), and panoramic radiographs were obtained. Fractal dimension (FD) was measured using the box counting method from 560 regions of interest ($51{\times}51$ pixels) in 6 sites on the panoramic radiographs. The relationships between age and BMD and between FD and BMD were assessed, and the intraobserver agreement was determined. Results: There was a significant difference in the FD values between the osteoporotic and normal groups (p<0.05). There was a significant difference in the FD values at three sites in the jaws (p<0.05). Age was significantly correlated with the BMD measurements, with an odds ratio of 1.25. However, the FD values were not significantly correlated with the BMD measurements, with an odds ratio of 0.000. The intraobserver agreement showed relatively higher correlation coefficients at the upper premolar, lower premolar, and lower anterior regions than the other sites. Conclusion: Age was an important risk factor for predicting the presence of osteoporosis in postmenopausal women. The lower premolar region was the most appropriate site for evaluating the FD value on panoramic radiographs. However, further investigation might be needed to predict osteoporosis using an FD value on panoramic radiographs.

• 대한치과보철학회지
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• 제39권3호
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• pp.282-296
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• 2001

The accuracy of master cast reproduction by a polyvinylsiloxane impression material using two visible-light curing resin and autopolymerizing polymethyl methacrylate resin custom tray material was investigated. Custom trays were fabricated from a master cast that had three index points marked on both inner and outer vestibules and then poured in yellow stone. The distance between the reproduced index points were measured to be ${\pm}0.001mm$ with a measuring microscope and the algebraic norms calculated for each tray material. No differences were found in the algebraic norms of inner and outer dimensions for upper tray impressions by ANOVA(p>0.05). However, T-test revealed that there were differences between upper and lower impressions and Tukey's hsd test revealed that in lower tray impressions, the Palatray in inner, the Lightplast in outer dimensions respectively were different from other materials. The index points reproduced on the casts compared with the master cast, were closer together for upper tray impressions. All four tray materials produced acceptable casts, 1. Algebraic norms of inner and outer dimensions of the test casts for upper trays were not statistically different irrespective of materials.(P>0.05) 2. T-test showed that there were differences between means with upper and lower trays especially in outer dimension.(P>0.05) 3. But, algebraic norms of inner and outer dimensions of the test casts for lower trays were statistically different between materials. 4. Palatray XL in inner, Lightplast-platten in outer dimensions respectively for lower trays were different from other materials, but, the nearest to the original model.

• 대한치과보철학회지
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• 제45권6호
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• pp.787-794
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• 2007

Statement of problem. Surface microgrooves on Ti substrata have been shown to alter the expression of genes responsible for various biological activities of cultured fibroblasts. However, their effect on enhancing cell proliferation is not yet clear. Purpose. The purpose of this study was to determine the dimension of surface microgrooves on Ti substrata that enhances proliferation and alters gene expression of cultured human gingival fibroblasts. Material and methods. Commercially pure Ti discs with surface microgrooves of monotonous $3.5{\mu}m$ in depth and respective 15 and $30{\mu}m$ in width were fabricated using photolithography and used as the culture substrata in the two experimental groups in this study (TiD15 and TiD30), whereas the smooth Ti was used as the control substrata (smooth Ti group). Human gingival fibroblasts were cultured on the three groups of titanium substrata and the proliferation, DNA synthesis, and gene expression of theses cells were analyzed and compared between all groups using XTT assay, BrdU assay, and reverse transcriptase-polymerase chain reaction (RT-PCR), respectively. Results. From the XTT assay at 48 h incubation, the proliferation of human gingival fibroblasts in TiD30 was significantly enhanced compared to that in smooth Ti and TiD15. The results from the BrdU assay showed that, at 24 h incubation, the DNA synthesis was significantly enhanced in TiD30 compared to that in smooth Ti. In RT-PCR, increase in the expression of PCR transcripts of fibronectin, CDK6, $p21^{cip1}$ genes was noted at 48h incubation. Conclusion. Surface microgrooves $30{\mu}m$ in width and $3.5{\mu}m$ in depth on Ti substrata enhance proliferation and alter gene expression of cultured human gingival fibroblasts.

• 대한치과보철학회지
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• 제45권3호
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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.

• 한국과학교육학회지
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• 제31권6호
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• pp.998-1008
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• 2011

이 연구는 초등학생의 관찰능력 측정준거를 개발하는 데 목적이 있다. 본 연구에서는 관찰능력의 측정준거를 관찰대상, 관찰관점 및 요구정신용량으로 설정하였다. 관찰대상은 평면모양과 입체모양, 관찰관점은 고정과 변화로 구분하고, 요구정신용량은 2부터 5까지로 하여, 관찰능력 측정 준거의 삼차원틀을 개발하였다. 측정 준거의 타당성을 검증하기 위해 삼차원틀에 따라 조사도구를 개발하였고, 초등학교 저 중 고학년 166명에게 투입하였다. 연구결과, 관찰대상, 관찰관점 및 요구정신용량의 세 가지 준거에 따라 관찰능력 검사점수에 의미 있는 차이가 나타났고, 학년에 따라 의미 있는 차이가 있었다. 관찰대상에서는 평면모양, 관찰관점에서는 관점고정, 요구정신용량이 작을수록 관찰능력 점수가 높게 나타났고, 저학년에서 고학년으로 갈수록 관찰능력 점수가 높았다. 따라서, 본 연구에서 개발한 관찰능력 측정 준거는 초등학생들의 관찰능력을 의미있게 파악하고 변별할 수 있으며, 신뢰롭고 타당한 초등학생의 관찰능력 측정도구를 개발하는데 기초자료를 제공할 수 있을 것으로 기대한다.

• 천문학회보
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• 제41권1호
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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).

• 천문학회보
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• 제41권1호
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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.

• 한국항해학회지
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• 제18권2호
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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.

• 한국통신학회논문지
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• 제39C권6호
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• pp.490-496
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• 2014

무릎 관절 연골은 두께가 얇아 대부분 무릎 질환의 원인이 되고 있다. 그러므로 무릎 자기공명영상에서 관절 연골 분할은 무릎 질환의 정확한 진단을 위한 필수조건이다. 특히 수동이 아닌 전자동 방식으로 무릎 관절 연골을 분할하여야만 효과적인 무릎 질환 진단을 할 수 있다. 본 논문에서는 뇌 자기공명영상에서 대표적으로 사용되는 레벨 셋 기반의 영상 분할 기법을 분석하여 무릎 자기공명영상에 적용 시 문제점을 파악하고 이를 해결함으로써, 무릎 자기공명영상에 레벨 셋 기반 영상분할 방식을 적용하였다. 이는 본 논문에서 제안하는 분할기법을 사용할 경우 무릎 관절 연골 분할에 대한 모든 과정이 전자동화 되어 기존 반자동화 방식보다 빠른 처리가 가능하며, 3차원 형상화를 통해 보다 정확한 진단에 도움을 줄 수 있다. 또한 우리는 제안하고 있는 분할기법이 기존 대표적인 무릎 관절 분할보다 더 높은 정확도를 갖는 것을 실험을 통해 확인할 수 있었다.