• Proceedings of the KOSOMBE Conference
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• v.1995 no.05
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• pp.23-26
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• 1995

The objectives of the present study are 1)to find the effect of the diameter of transpedicular screws on their fixational strength in pedicles under static pull-out loading, 2)to determine the biomechanical correlation between the pedicle diameter and the screw diameter, and 3)to find the effects of other factors in the screw design, such as materials, screw pitch, thread height and shape on their fixational strength. Biomechanical tests (Test I) were performed to evaluate the effect of the screw diameter on pull-out strength by using 60 porcine pedicls and six groups of custom-made pedicle screws with different diameters (the major and the minor diameter of the screws used in the testing varied from 4mm upto 9mm and from 3mm upto 8mm, respectively) while all other factors (materials, screw pitch, thread height and shape etc.) were fixed. In Test II, by using 61 porcine pedicles, the relationship between the ratio of the pedicle diameter and the screw diameter(=aspect ratio) of the custum-made screw and the pull-out strength of the screw was investigated. Test III was performed with 94 porcine pedicles and 8 different types of the commercial screws from 6 major productors in order to determine the effect of the screw diameter, pitch and the thread shape on the pull-out strength of the screw, respectively. The results of Test I showed that the axial pull-out resistance of the screw could be increased prportionaly to the screw diameter(P<0.05). But this increase in the pull-out resistance did not found when the screws of 4mm or 9mm in the diameter were employed. It was found from the results of Test II that the screws had its maximum pull-out resistant force when the aspect ratio ranging 40 - 69% (P<0.05). based on the results for the major diameter against the minor diameter of screw, the maximal pull-out resistance was found at 60-65% (P<0.05). According to these biomechanical testing results, it seems that the screw with a moderately large pitch is more desirable and the buttress-shaped screw can provide stronger fixation than the V-shape one can, if other designal factor and conditions were fixed.

• Journal of the Korean Association of Geographic Information Studies
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• v.16 no.4
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• pp.91-105
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• 2013

This study performed an assessment of wave power potential in the Kangwon and Dongnam regions encompassing the East Sea and part of South Sea. Annual electricity production and economic effects of 28 wave energy converters with 750kW capacity were analyzed using significant wave height and peak wave period data(created from the NOAA's NWW3 model) and InVEST software(developed by Stanford University and University of Minnesota). Annual electricity production was estimated to be up to 1,207MWh/year and at least 163MWh/year. The spatial pattern of annual electricity production showed that the sea far from land has higher wave power potential than the sea near coast. The net present value(NPV) of 28 wave energy converters was calculated by considering an operation period of 25 years. When assuming that the electricity produced from wave energy converters is transferred to onshore power plants through underwater cables, the NPV was estimated to be up to 5,883USD(6,600,000KRW) and at least -63,494USD(-71,000,000KRW). In contrast, the NPV increased up to 28,095 USD(31,600,000KRW) when assuming that the electricity is utilized in the Ulleungdo and Dokdo. In addition, it was found that the break-even line of NPV in the East Sea becomes closer towards the land according to the increment of electricity price. The NPV of wave energy converters near the Ulleungdo and Dokdo will be 88,158 USD(99,000,000KRW) if the increment of electricity price is 100KRW.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.1
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• pp.36.2-36.2
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• 2013

The SPICA (SPace Infrared Telescope for Cosmology & Astrophysics) project is a next-generation infrared space telescope optimized for mid- and far-infrared observation with a cryogenically cooled 3m-class telescope. The focal plane instruments onboard SPICA will enable us to resolve many astronomical key issues from the formation and evolution of galaxies to the planetary formation. The FPC-S (Focal Plane Camera - Sciecne) is a near-infrared instrument proposed by Korea as an international collaboration. Owing to the capability of both low-resolution imaging spectroscopy and wide-band imaging with a field of view of $5^{\prime}{\times}5^{\prime}$, it has large throughput as well as high sensitivity for diffuse light compared with JWST. In order to strengthen advantages of the FPC-S, we propose the studies of probing population III stars by the measurement of cosmic near-infrared background radiation and the star formation history at high redshift by the discoveries of active star-forming galaxies. In addition to the major scientific targets, to survey large area opens a new parameter space to investigate the deep Universe. The good survey capability in the parallel imaging mode allows us to study the rare, bright objects such as quasars, bright star-forming galaxies in the early Universe as a way to understand the formation of the first objects in the Universe, and ultra-cool brown dwarfs. Observations in the warm mission will give us a unique chance to detect high-z supernovae, ices in young stellar objects (YSOs) even with low mass, the $3.3{\mu}$ feature of shocked circumstance in supernova remnants. Here, we report the current status of SPICA/FPC project and its extragalactic sciences.

• Sleep Medicine and Psychophysiology
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• v.6 no.1
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• pp.46-51
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• 1999

Objectives: Patients with premenstrual dysphoric disorder(or PMDD) have impairments of the social, occupational or academic function due to psychological or somatic symptoms, which have the characteristic pattern of symptom exacerbation in the week before menses begin and remission shortly after the onset of menses. In the chronobiological view, many researchers have assumed that the etiology of PMDD is the advanced circadian rhythm. It has been suggested that light has a therapeutic effect on PMDD, because evening light results in phase delay of circadian rhythm through the biochemical changes including melatonin. Methods: The authors investigated the therapeutic effect of light therapy on four patients with prospectively diagnosed PMDD by DSM-IV criteria using clinical psychiatric interview, Premenstrual Assessment Form(PAF) and Daily Rating Form(or DRF). In the evening(6:30pm-8:00pm), the 2,500 lux light administered for seven consecutive days during the symptomatic late luteal phase of menstrual cycle. Beck Depression Inventory(or BDI), Hamilton Rating Scale for Depression(or HAM-D), Spielberg State Anxiety Inventory(or SA), and DRF were evaluated before and after seven days of light therapy. Results: Premenstrual symptoms of PMDD could be effectively treated with the evening bright light therapy, especially in PMDD patients with atypical symptoms. In addition, the light therapy seemed to more effective on the psychologic symptoms than the somatic symptoms of PMDD. There was no significant side-effect of light therapy, except the transient and mild eye-strain in one case. Conclusions: In spite of the results of limited data from our clinical trial, the authors suggest that the potential use of light therapy as an alternative to the pharmacological management of patients with PMDD.

• BMB Reports
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• v.37 no.4
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• pp.454-459
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• 2004

Experimental hyperoxia represents a suitable in vitro model to study some pathogenic mechanisms related to oxidative stress. Moreover, it allows the investigation of the molecular pathophysiology underlying oxygen therapy and toxicity. In this study, a modified experimental set up was adopted to accomplish a model of moderate hyperoxia (50% $O_2$, 96 h culture) to induce oxidative stress in the human leukemia cell line, U-937. Spectrophotometric measurements of mitochondrial respiratory enzyme activities, NMR spectroscopy of culture media, determination of antioxidant enzyme activities, and cell proliferation and differentiation assays were performed. The data showed that moderate hyperoxia in this myeloid cell line causes: i) intriguing alterations in the mitochondrial activities at the levels of succinate dehydrogenase and succinate-cytochrome c reductase; ii) induction of metabolic compensatory adaptations, with significant shift to glycolysis; iii) induction of different antioxidant enzyme activities; iv) significant cell growth inhibition and v) no significant apoptosis. This work will permit better characterization the mitochondrial damage induced by hyperoxia. In particular, the data showed a large increase in the succinate cytochrome c reductase activity, which could be a fundamental pathogenic mechanism at the basis of oxygen toxicity.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.8 no.3
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• pp.97-111
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• 2013

This study reviews preceding research for detailed factors to establish development strategies for Korean Hidden Champion firms and classifies strategy factors into internal ones and external ones through specialists' opinions to draw strengths, weaknesses, opportunities and threats of each factor. It also sets hierarchical model to draw up a survey, distributes the survey to groups of specialists and enterprises respectively and then examines consistency ratio. Fifty-four copies of survey whose reliability on responses is secured through examining the consistency ratio are evaluated with their relative importance in factors by using SWOT/AHP technique and their order of priority is determined. Based on their results, development strategies for Korean Hidden Champion firms are established. SWOT/AHP analyses results show that external factors are with the opportunity of industry growth and the threat of intensified competition and market uncertainty and internal factors are with the strength in order of technological competence, construction competence in customer relation and marketing competence. The weakness in the lack of funds, lack of brand awareness in order. This result suggests that external environments of enterprises that more emphasis should be put on the industry growth and aggressive strategies cannot help but be adopted even in a global competition getting fiercer every day are seen more important. Then, it also seems to be thought that the technological competence including R&D and specialization, construction competence in customer relation and marketing competence should internally chosen for strategies to support strategies. The order of priority in development strategies for Korean Hidden Champion firms is drawn as; (i) aggressive S/O strategy which utilizes opportunities by taking advantage of strengths, (ii) W/O strategy which utilizes opportunities by supplementing weaknesses, (iii) diversified S/T strategy which utilizes strengths to make up for threats and (iv) defensive W/T strategy which supplements weaknesses to overcome threats.

• Korean Journal of Environment and Ecology
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• v.26 no.4
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• pp.550-558
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• 2012

The naturalized plant species in Gyeongju National Park was summarized as 46 taxa including 14 families 40 genus 45 species 1 varieties. Among them, annual herbaceous species was 17 taxa (37%) which is grouped as the biggest proportion and 16 taxa (34.8%) for perennial herbaceous species and 11 taxa (23.9%) for biannual herbaceous species and 2 taxa(4.3%) for tree species. European origin was the biggest proportion as 17 taxa (37%), and 16% (34.8%) from North America. The degree of naturalization (DoN) was the biggest for Degree III, V as 18 taxa (39.1%). Regarding 321 naturalized plant species, the Urbanization Index in the studied area was 14.3%. The Namsam District showed 8.1% which is the highest DoN in the studied districts within the Gyeongju National Park. As the cultural properties is important in the Gyeongju National Park as a representatives for historical sites in Korea, planting and its management in the cultural properties is important tasks. The naturalized plant species in the studied area should be reasonably management.

• Journal of Periodontal and Implant Science
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• v.36 no.2
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• pp.531-554
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• 2006

Oral implants must fulfill certain criteria arising from special demands of function, which include biocompatibility, adequate mechanical strength, optimum soft and hard tissue integration, and transmission of functional forces to bone within physiological limits. And one of the critical elements influencing the long-term uncompromise functioning of oral implants is load distribution at the implant- bone interface, Factors that affect the load transfer at the bone-implant interface include the type of loading, material properties of the implant and prosthesis, implant geometry, surface structure, quality and quantity of the surrounding bone, and nature of the bone-implant interface. To understand the biomechanical behavior of dental implants, validation of stress and strain measurements is required. The finite element analysis (FEA) has been applied to the dental implant field to predict stress distribution patterns in the implant-bone interface by comparison of various implant designs. This method offers the advantage of solving complex structural problems by dividing them into smaller and simpler interrelated sections by using mathematical techniques. The purpose of this study was to evaluate the stresses induced around the implants in bone using FEA, A 3D FEA computer software (SOLIDWORKS 2004, DASSO SYSTEM, France) was used for the analysis of clinical simulations. Two types (external and internal) of implants of 4.1 mm diameter, 12.0 mm length were buried in 4 types of bone modeled. Vertical and oblique forces of lOON were applied on the center of the abutment, and the values of von Mises equivalent stress at the implant-bone interface were computed. The results showed that von Mises stresses at the marginal. bone were higher under oblique load than under vertical load, and the stresses were higher at the lingual marginal bone than at the buccal marginal bone under oblique load. Under vertical and oblique load, the stress in type I, II, III bone was found to be the highest at the marginal bone and the lowest at the bone around apical portions of implant. Higher stresses occurred at the top of the crestal region and lower stresses occurred near the tip of the implant with greater thickness of the cortical shell while high stresses surrounded the fixture apex for type N. The stresses in the crestal region were higher in Model 2 than in Model 1, the stresses near the tip of the implant were higher in Model 1 than Model 2, and Model 2 showed more effective stress distribution than Model.

• Journal of the korean academy of Pediatric Dentistry
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• v.28 no.4
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• pp.566-574
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• 2001

For decades it has been a clinically accepted requirement, in case of salivary contamination, to re-etch conditioned enamel and dentin to proceed with the adhesive technique. Only a few reports have been so far dealing with the potential of one-bottle adhesive system to bond even when applied after salivary contamination and without re-etching. The purpose of this study was to evaluate the influence of the salivary contamination on the shear bond strength of dentin. The results were as follows: 1. In group II, in which saliva contamination and washing occurred before applying of Prime & Bond NT showed high shear bond strength as in control group. In Group III and IV, in which the cured adhesive was contaminated with saliva, showed significantly lower mean bond strength, 2. Relating long resin tags of $70\sim120{\mu}m$ were observed in samples of all groups under SEM. We could observed hybrid layer, resin tag and many lateral branches in every group. And there were no differences between groups.

• Journal of The Korean Association For Science Education
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• v.21 no.2
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• pp.342-356
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• 2001

Integrated science for high school is required in the present Korean National Sixth Curriculum and the Seventh Curriculum which will be effective in 2002. Currently, most science teachers in secondary school have concerns about teaching integrated science subjects and this continues to raise a significant problem for practical implementation of integrated science education in schools. In this paper, we discuss two reasons for these concerns that our analysis revealed: 1) Science teachers do not understand how to implement integrated science education and 2) there are insufficient teaching-learning materials supporting integrated science. Three different approaches to integration that have been suggested to overcome the problem of implementation are outlined here. They are the knowledge centered, social problem centered, and individual interest centered approaches. Reported here are the first two steps we undertook in preparation for testing the relative effectiveness of these approaches. First, we analyzed the content of the Korean Sixth and Seventh National Science Curricula, seven Korean integrated science text books, the American National Science Education Standards, and the American Association for the Advancement of Science Benchmarks looking for common themes. We identified in the analyzed materials the common themes: energy conservation, energy transformation, energy transport, energy degradation. We then used their energy related content to organize sets of concept structures, one set for each of the three approaches. These concept structures will provide the foundations for the development of integrated teaching-learning energy plans to be used in our research into the effectiveness of the approaches.