• The Journal of Korean Academy of Prosthodontics
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• v.24 no.1
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• pp.55-65
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• 1986

An in vitro study was performed to evaluate adaptation of custom direct, custom indirect, and prefabricated post system on 15 extracted upper central incisors. 15 specimens were prepared and equally devided into 3 groups under random sampling. Each group of 5 cast posts was made with custom direct, custom indirect, and prefabricated post core method. Gap between inner wall of the dentin and outer wall of the cast post was measured on electron microphotographic prints at x500 magnification. The result were as follows ; 1. No significant difference of adaptation at cervical portion was found between each method. 2. Prefabricated post core method had poor adaptation compared with other methods. 3. Even distribution of adaptation was found in custom direct method between each portion. 4. Prefabricated post core method showed remarkable difference in adaptation between each portion.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.6
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• pp.1313-1318
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• 2007

When the mold is cooled suddenly to reduce the time for forming work and improve the quality of jar50ml which is different highly at rib thickness by a series of various curvature radii, the poor quality of void, flow and deformation happens. The structure of spiral cooling circuit at cavity and core can control the temperature of inner and outer side sufficiently. And the system can control cooling and heating automatically. These things are applied to Jar mold. and so, the best quality and the effect of productivity improvement can be obtained.

• The Transactions of the Korean Institute of Power Electronics
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• v.15 no.2
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• pp.119-126
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• 2010

An integrated magnetic (IM) transformer is proposed for a phase shifted full bridge (PSFB) converter with zero voltage switching (ZVS). In a proposed IM transformer, the transformer is located on the center leg of E-core and the output inductor is wound on two outer legs with air gap. The proposed IM transformer is analyzed by using the magnetic capacitor model. For reducing the core size, EE core is redesigned. The proposed IM transformer is experimentally verified on a 1.2 kW prototype converter. The converter efficiency with the proposed IM transformer is about 93 % at full load and its volume size can be reduced. It can be expected that the power density can be largely increased with the proposed IM transformer.

• Progress in Superconductivity and Cryogenics
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• v.10 no.4
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• pp.33-37
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• 2008

The main objective of this study is to identify the pressure drop characteristics of coolant flow passages of 154kV/1GVA High Temperature Superconducting (HTS) power cable, experimentally. The passages were consisted of two parts, the one is the circular path with spiral ribs in the core to cool the cable conductor layer and the other is annular path with spirally corrugated outer wall to cool the shield layer. Thus the experiments to acquire the pressure drop data were performed with two types of circular spiral tubes and eight types of the concentric annuli in various range of Reynolds number. The pressure drops in the core tubes and the annuli were much higher than those in the tubes with smooth surface. Therefore, modified correlations to present the experimental results in each flow passage were suggested.

• Bulletin of the Korean Chemical Society
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• v.33 no.8
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• pp.2535-2538
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• 2012

$SnO_2@carbon$ tube-core nanowire was synthesized via a facile self-organized method, which was in situ by one step via Chemical Vapor Deposition. The resulting composite was characterized by scanning electron microscopy, X-ray diffraction and transmission electron microscope. The diameter of the single nanowire is between 5 nm and 60 nm, while the length would be several tens to hundreds of micrometers. Then X-ray diffraction pattern shows that the composition is amorphous carbon and tin dioxide. Transmission electron microscope images indicate that the nanowire consists of two parts, the outer carbon tube and the inner tin dioxide core. Meanwhile, the possible growth mechanism of $SnO_2@carbon$ tube-core nanowire is also discussed.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.191-191
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• 2006

The structures of the mesophases and their subunits of PS-b-P4VP in a toluene solution were studied by using SAXS, TEM and GIFT methods. The hierarchical structures of PS-b-P4VP, such as the individual micelle, the face-centered cubic (fcc) and body-centered cubic (bcc) structures and the lamellar structure, were identified for the first time. The diameter of the micelle core was ${\sim}80\;%$ of the most extended chain length of the core chain, suggesting that the core chains were quite stretched. The stretched chain in the core caused the core of the micelle to be not homogenous with a higher density at the center than at the outer part. As the concentration level increases, the fcc and both fcc and bcc appear for the packing of the micelles of PS(3.3k)-b-P4VP(4.7K) and PS(12K)-b-P4VP(11.8K), respectively. The lamellar structure was also identified, with a further increase in the concentration for PS(3.3k)-b-P4VP(4.7K). These hierarchical structures were also identified via TEM images.

• The Journal of the Korean dental association
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• v.51 no.11
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• pp.595-603
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• 2013

The requirements for the successful treatment of all-ceramic restorations are not so different from the ones of conventional restorations. "The provisional restoration followed by an adequate tooth reduction and the accurately fitting prostheses with corresponding to final impression" can be the examples of them. Nevertheless, the one which all-ceramic restorations are distinguished from conventional restorations is the additional procedure of so called "bonding". In addition to the application of resin cement between "inner surface of restoration and outer surface of abutment", bonding technology can be also applied to the treatment process of "Post and Core" in particular if the abutments are non-vital teeth. Core build-up for all-ceramic crown is conducted with fiber post and tooth colored composite by considering the properties of the restorations transmitting light. We know well that a vital abutment is easier than a non-vital one to get the targeted goals for clinical success in connection with esthetics and structure. The creation of "Post and Core" with bonding technique is a decisive factor for a long-term success if the abutment is non-vital tooth with dentinal collapse. I would like to share my clinical experience about "post & core build-up and all-ceramic restoration bonding" out of several success strategies of all-ceramic crown with this presentation.

• Structural Engineering and Mechanics
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• v.55 no.4
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• pp.719-742
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• 2015

This paper dealt the free vibration analysis of thick truncated conical composite sandwich shells with transversely flexible cores and simply supported boundary conditions based on a new improved and enhanced higher order sandwich shell theory. Geometries were used in the present work for the consideration of different radii curvatures of the face sheets and the core was unique. The coupled governing partial differential equations were derived by the Hamilton's principle. The in-plane circumferential and axial stresses of the core were considered in the new enhanced model. The first order shear deformation theory was used for the inner and outer composite face sheets and for the core, a polynomial description of the displacement fields was assumed based on the second Frostig's model. The effects of types of boundary conditions, conical angles, length to radius ratio, core to shell thickness ratio and core radius to shell thickness ratio on the free vibration analysis of truncated conical composite sandwich shells were also studied. Numerical results are presented and compared with the latest results found in literature. Also, the results were validated with those derived by ABAQUS FE code.

• Nuclear Engineering and Technology
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• v.48 no.1
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• pp.16-25
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• 2016

In severe loss of coolant accidents (LOCA), similar to those experienced at Fukushima Daiichi and Three Mile Island Unit 1, the zirconiumalloy fuel claddingmaterials are rapidlyheateddue to nuclear decay heating and rapid exothermic oxidation of zirconium with steam. This heating causes the cladding to rapidly react with steam, lose strength, burst or collapse, and generate large quantities of hydrogen gas. Although maintaining core cooling remains the highest priority in accident management, an accident tolerant fuel (ATF) design may extend coping and recovery time for operators to restore emergency power, and cooling, and achieve safe shutdown. An ATF is required to possess high resistance to steam oxidation to reduce hydrogen generation and sufficient mechanical strength to maintain fuel rod integrity and core coolability. The initiative undertaken by Electric Power Research Institute (EPRI) is to demonstrate the feasibility of developing an ATF cladding with capability to maintain its integrity in $1,200-1,500^{\circ}C$ steam for at least 24 hours. This ATF cladding utilizes thin-walled Mo-alloys coated with oxidation-resistant surface layers. The basic design consists of a thin-walled Mo alloy structural tube with a metallurgically bonded, oxidation-resistant outer layer. Two options are being investigated: a commercially available iron, chromium, and aluminum alloy with excellent high temperature oxidation resistance, and a Zr alloy with demonstratedcorrosionresistance.Asthese composite claddings will incorporate either no Zr, or thin Zr outer layers, hydrogen generation under severe LOCA conditions will be greatly reduced. Key technical challenges and uncertainties specific to Moalloy fuel cladding include: economic core design, industrial scale fabricability, radiation embrittlement, and corrosion and oxidation resistance during normal operation, transients, and severe accidents. Progress in each aspect has been made and key results are discussed in this document. In addition to assisting plants in meeting Light Water Reactor (LWR) challenges, accident-tolerant Mo-based cladding technologies are expected to be applicable for use in high-temperature helium and molten salt reactor designs, as well as nonnuclear high temperature applications.

• The Journal of the Convergence on Culture Technology
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• v.5 no.1
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• pp.341-346
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• 2019

The study aims to provide a study on the mixing ratios and manufacturing methods of biodegradable PLA sheets for mid - term introduction, A 3-layer process was introduced to produce a multifunctional multi-layer structure sheet having improved heat resistance, impact resistance and transparency while having anti-fogging functionality as a biodegradable PLA sheet used for the purpose of anti-fogging function. Inner layer, core layer and outer layer were mixed and extruded. The inner layer and core layer were studied for a biodegradable PLA multi-layer sheet structure having inner hardness and high heat resistance and outer layer for imparting antifogging function. By applying the results of this study, plastic PLA properties and heat-resistant temperature can be improved to replace and expand plastics.