• Journal of Welding and Joining
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• v.15 no.6
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• pp.32-40
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• 1997

Solid state diffusion bonding is the joining process performed by creep and diffusion, which is accelerated by heating below melting temperature and proper pressing, in vacuum or shielding gas atmosphere. By this process we can obtain sufficient joint which can't be expected from the fusion welding. For Ti-6Al-4V alloy, the optimum solid state diffusion bonding condition and mechanical properties of the joint were found, and micro void morphology at bond interface was observed by SEM. The results of tensile test showed sufficient joint, whose mechanical properties are similar to that of base metal. 850$^{\circ}$C, 3MPa is considered as the optimum bonding condition. Void morphology at interface is long and flat at the initial stage. As the percentage of bonded area increases, however, small and round voids are found. Variation of void shape can be explained as follows. As for the void shrinkage mechanism, at the initial stage, power law creep is the dominant, but diffusion mechanism is dominant when the percentage of bonded area is increased.

• Proceedings of the KIEE Conference
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• 1998.07a
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• pp.164-166
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• 1998

This paper presents the results of the measured pressure-rise and the analyzed results of the cold gas flow-field in a 72.5kV 20kA gas circuit breaker for the electrical railway system. The analysis of cold gas flow field and the calculation of electric field strength have been performed in 3 types of interrupters and the low current interruption capability has been estimated for each of the gas circuit breaker considering the opening speed, the nozzle shape and the stroke length.

• Proceedings of the Optical Society of Korea Conference
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• 2003.07a
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• pp.220-221
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• 2003

We optimized the structure of a fully depleted optical thyristor (DOT) to achieve the faster switching speed and the lower power consumption by the depletion of charge at the lower negative voltage. The fabricated optical thyristor shows sufficient nonlinear s-shape I-V characteristics with the switching voltage of 2.85 V and the complete depletion voltage of -8.73 V. In this paper, using a finite difference method (FDM), we calculate the effects of parameters such as doping concentration and thickness of each layer to determine the optimized structure in the view of the fast and low-power-consuming operation.

• Journal of the Korean Physical Society
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• v.73 no.11
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• pp.1612-1618
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• 2018

In this work, the ground-state properties of an interacting electron gas confined in a two-dimensional quantum dot system with the Gaussian potential ${\upsilon}(r)=V_0(1-{\exp}(-r^2/p))$, where $V_0$ and p are confinement parameters, are determined numerically by using the Thomas-Fermi approximation. The shape of the potential is modified by changing the $V_0$ and the p values, and the influence of the confining potential on the system's properties, such as the chemical energy, the density profile, the kinetic energy, the confining energy, etc., is analyzed for both the non-interacting and the interacting cases. The results are compared with those calculated for a harmonic potential, and excellent agreement is obtained in the limit of high p values for both the non-interacting and the interacting cases.

• Journal of the Korean Society of Radiology
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• v.17 no.2
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• pp.175-184
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• 2023

Based on the actual shape of the detector and the data provided by the manufacturer, the shape of the detector was implemented through Penelope simulation and applied to the appropriate four-layer thickness based on the efficiency obtained from the measurements. Efficiency calculations to determine the effect of the simulated number of Full Energy Peak Efficiency(FEPE) channels in the detector and the outside contact layer in the crystal on the Full Energy Peak Efficiency were performed for various four-layer thicknesses of 0.3, 0.5, 0.7, 1.0, 1.2, and 1.4 mm using the Penelope Code. When the thickness of the external contact layer was increased by 5 times, the Full Energy Peak Efficiency decreased by about 36% for 59.50 keV, and the Full Energy Peak Efficiency decreased by 10% for 1836. In addition, as it increased by 10 times, the Full Energy Peak Efficiency decreased by about 20% for 59.54 keV, and 7% for 1836.01 keV. The Penelope simulated Full Energy Peak Efficiency channel decreases exponentially with the increase in the four layers. In addition, it was confirmed that the total effect curve was well matched with a relative difference of less than 3.5% in the 0.3-1.4 mm dead layer thickness region. However, it was found that the inhomogeneous dead layer is still a parameter in the Monte Carlo model.

• Korean Journal of Food Science and Technology
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• v.41 no.5
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• pp.597-601
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• 2009

Activation of hepatic stellate cells (HSCs) is known to be responsible for hepatic fibrosis and cirrhosis. When round-shape quiescent HSCs go to activation by liver injury, production of extracellular matrix is increased, and its shape becomes myofibroblast-like shape. The activated HSCs are characterized by the high rate of proliferation and the increased production of extracellular matrix. One way of the regeneration of activated HSCs is an apoptosis induction followed by removing the activated myofibroblast-like cells. The effect of extract of Terminalia chebula Retz. (TCE) on cytotoxicity was evaluated using the rat primary hepatocyte, HepG2 and T-HSC/Cl-6 by incubating these cells with TCE up to the dose of $1,000{\mu}g/mL$. At the maximum dose of TCE, no cytotoxicity was found on primary hepatocyte and HepG2, but cytotoxic effect of TCE was found on activated HSCs, and T-HSC/Cl-6 in a U-shaped dose-response manner with the highest effect at $500{\mu}g/mL$ of TCE. Finally, we confirmed the occurrence of apoptotic cell death by annexin-V/PI double staining. The population of annexin-V positive cells was increased in a dose dependent manner.

• Applied Microscopy
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• v.12 no.2
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• pp.55-68
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• 1982

The study on the nerve cells in the pars intercerebralis(IP) of 5-day-old cabbage butterfly Pieris rapae L. was performed to observe their ultrastructures and classify them on the basis. of the differences in size, shape and relative distribution cf cell organelles. The brain-subesophageal ganglion complex was fixed in 1% paraformaldehyde-1% gluaraldehyde mixture and embedded in araldite mixture. The transverse thin sections of IP were stained with uranyl acetate and lead citrate and examined by Hitachi 500 and ]EM 100B electron microscope. Five distinct types. of nerve cells are recognized and are arbitrarily designated as Type I, Type II Type III, Type IV and Type V. Type I neurone: These neurones are neurosecretory cells. Several neurosecretory cells are. recognized in the pars intercerebralis. They are roughly round or peach-shaped cells measuring $13{\sim}25{\mu}m$ in diameter. The rounded nucleus shows about $5{\sim}10{\mu}m$ in diameter. The chromatin is predominantly diffused with only occasional dense patches. The perikaryon contains numerous. mitochondria, free polyribosomes and neurosecretory granules. The neurosecretory granules are relatively uniform in electron density, and each one is about $100{\sim}400{\mu}m$ in diameter and surrounded by a single membrane. The granules are also observed mostly as in groups. In one group of neurones the cisternae of endoplasmic reticulum are distended or in other group of neurones are not distended. Golgi saccules are slightly dilated at their lateral extremities and contains. frequenty dense rounded materials. Type II neurone: Thes have the largest soma in the pars intercerebralis about $30{\sim}35{\mu}m$ in diameter. They also show roughly polygonal in shape. The nucleus is elongated or sickle-shaped. The chromatin is mainly in the euchromatin form. The perikarya in these cells are well populated with populated with free ribosomes and contain numerous mitochondria and Golgi bodies. The cisternae of granular endoplasmic reticulum are also well distributed. Type III neurone: They are oval or spindle-shaped and also medium-sized. neurones approximately $15{\sim}17{\mu}m$ in length. The nucleus is oval or slightly elongated in shape and $8{\sim}9{\mu}m$ in length. The chromatin occurs in diffused form. The cytoplasm contains many filamentous or oval mitochondria. The perikaryon has also numerous free polyribosomes and cisternae of granular endoplasmic reticulum. Type VI neurone: They are roughly polygonal in shape probably due to the close approximation of the adjacent cells. The soma is about $7{\sim}8{\mu}m$ in diameter. The nucleus is round or oval in shape and $5.0{\sim}5.8{\mu}m$ in diameter. The necleus also occupies a large proprion of the cell body. The perikaryon is well populated with free ribosomes and contains several mitochondria and cistenae of granular endoplasmic reticulum. Type V neurone: These neurones are similar to Type VI neurones in various respects such as cell size and cell inclusion, but they differ from Type IV neurones in shape. The soma is oval or slightly elongated. The cell body contains several filamentous and oval mitochondria.

• The Journal of Korean Academy of Prosthodontics
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• v.43 no.2
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• pp.191-203
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• 2005

Statement of problem. In Korea, the preliminary impression trays for dental and edentulous maxillae are manufactured on the base of the statistical value of Westerners. There had been less study on the dental and edentulous arches of Koreans. Purpose. The purpose of this study was to evaluate an average dental cast, preliminary impression trays, three-dimensional relation of dental and edentulous maxilla of Koreans Material and methods. The subjects for this study were 173 dental casts of maxilla (dental: 52, edentulous : 146) with ages $18\{\sim}60$ years old. Each of the master casts was measured 69 measuring points on the dental cast or maxilla, and 46 measuring points on the edentulous cast of maxilla with three-dimensional digital measuring machine. Each measuring points were analysed and were overlapped, that three dimensional dental graphic manufactured by CAD/CAM system. Results. 1. A standard of distribution to alveolar bone were width between left and right buccal border lines of the standard 3/4 line. The mean value of dental and edentulous casts were 67.27mm, 63.49mm respectively. 2. Morphological classification of dental casts were divided into three groups or V-shape, O-shape, U-shape, that proportion of distribution were 17%, 16%, 67%, respectively. Dimensional classification of the dental casts were divided into five groups of less than 63mm, 63 up to 65mm, 65 up to 67mm. 67 up to 69mm, more than 69mm, respectively. 3. Morphological classification of edentulous casts were divided into three groups or V-shape, O-shape, U-shape, that proportion of distribution were 18%, 17%, 65%, respectively Dimensional classification of the edentulous casts were divided into five groups of less than 57mm, 57 up to 61mm, 61 up to 65mm, 65 up to 69mm, more than 69mm, respectively. 4. Mean dental and edentulous cast of maxilla were overlapped, the proportion of bone resorption to alveolar bone is higher than that of palatal bone, its difference were higher anterior 2/4 area than posterior 3/4 area. Conclusion. It obtains information of preliminary impression trays for dental and edentulous maxilla of Koreans.

• Computers and Concrete
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• v.26 no.6
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• pp.565-576
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• 2020

Experimental and discrete element methods were used to investigate the effects of angle of Y shape non-persistent joint on the tensile behaviour of joint's bridge area under brazilian test. concrete samples with diameter of 100 mm and thikness of 40 mm were prepared. Within the specimen, two Y shape non-persistent notches were provided. The large notch lengths were 6 cm, 4 cm and 2 cm. the small notch lengths were 3 cm, 2 cm and 1 cm. The angle of larger notch related to horizontal axis was 0°, 30°, 60°, 90°. Totally, 12 different configuration systems were prepared for Y shape non-persistent joints. Also, 18 models with different Y shape non-persistent notch angle and notch length were prepared in numerical model. The large notch lengths were 6 cm, 4 cm and 2 cm. the small notch lengths were 3 cm, 2 cm and 1 cm. The angle of larger notch related to horizontal axis was 0, 30, 60, 90, 120 and 150. Tensile strength of model materil was 1 MPa. The axial load was applied to the model by rate of 0.02 mm/sec. This testing showed that the failure process was mostly governed by the Y shape non-persistent joint angle and joint length. The tensile strengths of the specimens were related to the fracture pattern and failure mechanism of the discontinuities. It was shown that the tensile behaviour of discontinuities is related to the number of the induced tensile cracks which are increased by increasing the joint length and joint angle. The minimum tensile strength occurs when the angle of larger joint related to horizontal axis was 60°. Also, the maximum compressive strength occurs when the angle of larger joint related to horizontal axis was 90°. The tensile strength was decreased by increasing the notch length. The failure pattern and failure strength are similar in both methods i.e. the experimental testing and the numerical simulation methods.

• Computers and Concrete
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• v.29 no.1
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• pp.31-45
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• 2022

Experimental and numerical simulation were used to investigate the effects of angle and number of T shape non-persistent crack on the shear behaviour of crack's bridge area under uniaxial compressive test. concrete samples with dimension of 150 mm×150 mm×40 mm were prepared. Within the specimen, T shape non-persistent notches were provided. 16 different configuration systems were prepared for T shape non-persistent crack based on two and three cracks. In these configurations, the length of cracks were taken as 4 cm and 2 cm based on the cracks configuration systems. The angle of larger crack related to horizontal axis was 0°, 30°, 60° and 90°. Similar to cracks configuration systems in the experimental tests, 28 models with different T shape non-persistent crack angle were prepared in numerical model. The length of cracks were taken as 4 cm and 2 cm based on the cracks configuration systems. The angle of larger crack related to horizontal axis was 0°, 15°, 30°, 45°, 60°, 75° and 90°. Tensile strength of concrete was 1 MPa. The axial load was applied to the model. Displacement loading rate was controlled to 0.005 mm/s. Results indicated that the failure process was significantly controled by the T shape non-persistent crack angle and crack number. The compressive strengths of the specimens were related to the fracture pattern and failure mechanism of the discontinuities. Furthermore, it was shown that the compressive behaviour of discontinuities is related to the number of the induced tensile cracks which are increased by increasing the crack number and crack angle. The strength of samples decreased by increasing the crack number. In addition, the failure pattern and failure strength are similar in both methods i.e. the experimental testing and the numerical simulation methods (PFC2D).