• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.556-559
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• 2006

We successfully developed a high performance and highly reliable blazed GxL device with a high optical efficiency and a high contrast ratio. The device demonstrated superior resistance against a high power laser, which is suitable for a large-area laser projector. We operated the world's largest laser projection screen using this device at the 2005 World Exposition in Aichi, Japan, problem free.

• Nuclear Engineering and Technology
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• v.56 no.6
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• pp.2019-2028
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• 2024

Advanced nuclear reactors, especially the newly developed small and micro-reactors have complex neutron spectrum, which makes the deterministic reactor core calculations sensitive to the energy group structure of few-group cross-sections. To avoid significantly increasing the cost of energy discretization in the core calculation, two energy group structures with 31 groups and 33 groups were adopted for typical thermal and fast reactor cores, respectively. Then, an adaptive scheme of group division for reactor cores with a medium neutron spectrum was proposed. The works were based on the full spectrum nuclear reactor analysis code SARAX/TULIP. An equivalent one-dimensional model of the core was proposed to capture the key neutron spectrum features of the reactor core. Such features were used to adaptively determine a few-group structure for the following reactor core calculations. Then, the neutron spectrum in different zones with more details was calculated. With this spectrum, the cross-sections were condensed into the determined energy groups. Three tests based on different neutron spectrum were calculated to verify the schemes. The results show that using the adaptive energy group division scheme, the following core calculation can meet the accuracy requirement of different reactors with different neutron spectra.

• Journal of Technologic Dentistry
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• v.32 no.4
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• pp.351-356
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• 2010

Purpose: The purpose of this study was to evaluate the fracture strength between the core and veneering ceramic according to 2 core materials, In-Ceram Alumina and In-Ceram Zirconia, fabricated by electro ceramic layering technique. 2 different fixed partial denture cores of three units were veneered by veneering ceramic(Ceranion, Noritake) (n=10). Methods: The fracture strengths between the core and veneering ceramic were measured through the 3 point bending test. The interfaces between the core and veneering ceramic were observed with the X-ray dot mapping of EPMA. Results: The result of fracture strength was observed that IZP group, In-Ceram Zirconia core, had higher fracture strength. IPA group, In-Ceram Alumina core, had fracture strength of 359.9(${\pm}$86.2) N. IZP group, In-Ceram Zirconia core, had fracture strength of 823.2(${\pm}$243.0) N. X-ray dot mapping observation showed that a major element in the core and veneering ceramic of IPA group was alumina and silica, respectively. No binder was observed in interfaces between the core and veneering ceramic, and no ion diffusion or transition was observed between the core and veneering ceramic. However, apparent ion diffusion or transition was observed between the core and veneering ceramic of IZP group.

• Restorative Dentistry and Endodontics
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• v.40 no.3
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• pp.229-235
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• 2015

Objectives: To determine and compare the fracture resistance of endodontically treated maxillary central incisors restored with different posts and cores. Materials and Methods: Forty-eight upper central incisors were randomly divided into four groups: cast post and core (group 1), fiber-reinforced composite (FRC) post and composite core (group 2), composite post and core (group 3), and controls (group 4). Mesio-distal and bucco-lingual dimensions at 7 and 14 mm from the apex were compared to ensure standardization among the groups. Twelve teeth were prepared for crown restoration (group 4). Teeth in other groups were endodontically treated, decoronated at 14 mm from the apex, and prepared for posts and cores. Resin-based materials were used for cementation in groups 1 and 2. In group 3, composite was used directly to fill the post space and for core build-up. All samples were restored by standard metal crowns using glass ionomer cement, mounted at $135^{\circ}$ vertical angle, subjected to thermo-mechanical aging, and then fractured using a universal testing machine. Kruskal-Wallis and Mann-Whitney U tests were used to analyze the data. Results: Fracture resistance of the groups was as follows: Control (group 4) > cast post and core (group 1) > fiber post and composite core (group 2) > composite post and core (group 3). All samples in groups 2 and 3 fractured in restorable patterns, whereas most (58%) in group 1 were non-restorable. Conclusions: Within the limitations of this study, FRC posts showed acceptable fracture resistance with favorable fracture patterns for reconstruction of upper central incisors.

• Journal of Korean Physical Therapy Science
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• v.29 no.4
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• pp.96-111
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• 2022

Background: This study aims to evaluate the effect of core stabilization exercise on the dynamic balance and horizontal rotation of the trunk in young adult men. Through this study, it is expected that various core stabilization exercises will prevent and treat musculoskeletal disease. Design: Randomized Controlled Trial. Methods: The study subjects were recruited from young adult men in their 20s and 30s living in Seoul, and after the randomized controlled trial, it was divided into an experimental group training core stabilization exercise(n=15) and a control group(n=15). The evaluation methods of this study were modified Star Excursion Balance Test(mSEBT), Functional Reach Test(FRT), and Trunk Rotation Test(TRT). The experimental group performed three sets of crunches and deadbug exercises twice a week for eight weeks, and the control group did not perform any exercises similar to core stabilization exercise during the experimental period. Results: The result of the experiment, the experimental group showed significant improvement in mSEBT(p<.05), FRT(p<.05) and TRT(p<.05). Conclusion: In conclusion, core stabilization exercises improved dynamic balance and horizontal rotation of the trunk. As a result of this study, core stabilization exercise can prevent and treat musculoskeletal diseases even in healthy people.

• The Journal of Advanced Prosthodontics
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• v.4 no.1
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• pp.37-42
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• 2012

PURPOSE. The influence of the modified process in the fiber-reinforced post and resin core foundation treatment on the fracture resistance and failure pattern of premolar was tested in this study. MATERIALS AND METHODS. Thirty-six human mandibular premolars were divided into 4 groups (n = 9). In group DCT, the quartz fibre post (D.T. Light-post) was cemented with resin cement (DUO-LINK) and a core foundation was formed with composite resin (LIGHT-CORE). In group DMO and DMT, resin cement (DUO-LINK) was used for post (D.T. Lightpost) cementation and core foundation; in group DMO, these procedures were performed simultaneously in one step, while DMT group was accomplished in separated two steps. In group LCT, the glass fiber post (LuxaPost) cementation and core foundation was accomplished with composite resin (LuxaCore-Dual) in separated procedures. Tooth were prepared with 2 mm ferrule and restored with nickel-chromium crowns. A static loading test was carried out and loads were applied to the buccal surface of the buccal cusp at a 45 degree inclination to the long axis of the tooth until failure occurred. The data were analyzed with MANOVA (${\alpha}$= .05). The failure pattern was observed and classified as either favorable (allowing repair) or unfavorable (not allowing repair). RESULTS. The mean fracture strength was highest in group DCT followed in descending order by groups DMO, DMT, and LCT. However, there were no significant differences in fracture strength between the groups. A higher prevalence of favorable fractures was detected in group DMT but there were no significant differences between the groups. CONCLUSION. The change of post or core foundation method does not appear to influence the fracture strength and failure patterns.

• Proceedings of the SAREK Conference
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• 2004.06a
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• pp.202-202
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• 2004

• The Journal of Korean Academy of Prosthodontics
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• v.40 no.5
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• pp.493-506
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• 2002

Recently as the esthetic concerns about dental prosthesis have been increased, the nonmetallic post and core systems have been introduced clinically to improve the color and the low optical transmittance of conventional casting metal post and core systems. The purpose of this study was to compare and analyze the optical transmittance and the shade changes of all-ceramic crowns with two nonmetallic post and core systems. The experimental groups were classified as follows : Total 27 specimens(9 samples in each group) were evaluated. Group I : Natural teeth as a control group Group II : CosmoPost and $Empress^{(R)}$ core (Ivoclar-Vivadent, Liechtenstein) Group III : $LIGHT-POST^{TM}$ and $LIGHT-CORE^{TM}$ (Bisco, U.S.A.) In all group, all-ceramic crowns were fabricated with the same shade of IPS $Empress^{(R)}$ II (Ivoclar-Vivadent, Liechtenstein) after abutment preparation, and then two kinds of spectrophotometers, UV 3101 PC (Shimadzu, Japan) and CM 503i (Minolta Co. Ltd. Japan), were used to measure the optical transmittance and the color value. The following results were obtained : 1. The optical transmittance of each group without all-ceramic crowns, was siginificantly decreased in order of Group III, I and II (p<0.05). 2. The optical transmittance of each group with all-ceramic crowns cemented, were siginificantly decreased in order of Group I, II and III (p<0.05). 3. In comparison with the shade of all-ceramic crowns, there were no significant differences between groups regardless of the cementation. 4. In comparison with the shade changes in each group after the cementation of all-ceramic crowns, there were no significant differences between groups. From the above results, it is thought that the selection among materials used in this study doesn't influence greatly the esthetic restoration, because the differences of optical transmittance were so small that those were clinically insignificant.

• Physical Therapy Rehabilitation Science
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• v.12 no.1
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• pp.56-61
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• 2023

Objective: Core training is a key exercise for conditioning and fitness programs, injury prevention, and more. This study aimed to find out the effect of adding dynamic core training, which is frequently prescribed in clinical practice, on dynamic balance and muscle activity compared to conventional static core training. Design: An experimental study Methods: This study is an experimental pilot study of prospective parallel design. Six healthy young adults were allocated to static core training group (SCG; crunch and plank) and blended group (BG; crunch, plank, and dead bug exercise) for two weeks to perform core training. Dynamic balance and muscle activity (erector spinae, rectus abdominis) were measured for all participants before and after core training. Results: All six healthy young adults enrolled completed the study. No significant difference was found before and after 6 sessions of core training in each group (P>0.05). Likewise, no significant difference was found in the results of the difference comparison between groups (P>0.05). Conclusions: In conclusion, in this experimental study, no difference was found when dynamic core training was added. Although the results before and after core training did not show improvement in dynamic balance and muscle activity, a randomized controlled trial is needed considering the results of previous studies and the limitations of this experimental study.

• The Journal of Korean Academy of Prosthodontics
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• v.32 no.2
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• pp.225-233
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• 1994

The restorations of the severely damaged teeth by post core have been increased with the developement of endodontic procedures. But high failure rates of these procedures being reported, various restorative modifications were induced for successful treatments. Cast post-core and prefabricated post with core buildups are choice of treatment. The main causes of failure of the restorations are the fracture of post and core, root fracture, and recurrent caries due to microleakage. Recently, the acid etching technique and the use of dentin bonding agent at tooth surface to reduce the possible microleakage at the tooth-restoration interfaces were introduced. The object of this study was to measure and compare the microleakage by the types and cementation methods of post-core. For this study, forty extracted human anterior teeth were selected for specimen. After cleansing and routine endodontic procedures, anatomic crowns of each specimen were removed at the level of 2mm above the cementoenamel junction. Canals were preparated for post insertion and specimens were divided into four groups randomly. Post-cores were fabricated according to method for each group. Microleakage was measured by length of dye penetration at the tooth-restoration interfaces with measuring microscope at 50 magnification. Oneway ANOVA and t-test were performed for statistical analysis of resulting data. The following results were obtained from this study. 1. There wert significant statistical differences in degree of microleakage between each group (p<0.01). 2. Cast post-core cemented with ZPC (Group I) showed the most severe microleakage pattern$(1.5547{\pm}0.0872mm)$, and cast post-core cemented with adhesive resin cement after tooth surface treatment with dentin bonding agent (Group II) showed the least microleakage $(0.1497{\pm}0.0872mm)$. 3. Group IV revealed less dye penetrations than group III, but no statistical significance was seen between two groups.