• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.5
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• pp.202-206
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• 2010

Single crystals of $ZnWO_4$ were grown successfully in the [100], [010] and [001] directions using the Czochralski method. The growth parameters and the formation of slip plane in $ZnWO_4$ crystals were studied. $ZnWO_4$ crystals had a cleavage plane of (010). The dislocation density on the (010) plane at the center of the crystal was lower than that of the edge region. It was inferred that the high density at the edge of the crystals was caused by the thermal gradient during crystal growth. The etch pit arrangement revealed the (100) slip plane to be most active during crystal growth.

• The Korean Journal of Quaternary Research
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• v.18 no.2 s.23
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• pp.1-2
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• 2004

The Ilkwang Fault is NNE-striking, elongated 40 Km between Ulsan and Haendae-ku, Busan in southeastem part of the Korean Peninsula(Kim, D.H. et al., 1989; Kim, J.S. et al., 2003). This paper is mainly concemed about the ages of the fault activities especially in the Quatemary, infered from classification of geomorphic surface and trench excavation for the construction of Singori nuclear power plant. The geomorphi surfaces are classified into the Beach and the Alluvial plain, the 10 m a.s.l. Marine terrace, the 20 m a.s.l. Marine terrace, the Reworked surface of 45 m a.s.l. Marine terrace and the Low relief erosional surface, from lower to higher altitude. The Beach and the Alluvial plain are elongated to the Holocene terrace(ist terrace, choi, 2003). The 10 m a.s.l. Marine terrace is correlated to 2nd terrace (MIS 5em 125 Ka. y. B.P., Choi, 1998). The 45 m a.s.l. Marine terace is correlated to the Lower marine terrace (MIS 7,220 Ka. y. B.P., Choi, 2003 or MIS 9,320 y. B.P.) to the Gwanganri terrace(Penultimate interglacial age, 200-200 Ka. Y. B.P., Oh, 1981). The Low relief erosional surface is distributed coastal side, the Reworked surface of 45 m a.s.l. Marine terrace inland side by the Ilkwang Fault Line as the boundary line. But the former is above 10 m higher in relative height than the latter. The 20 m a.s.l. Marine terrace on the elongation line of the Ilkwang Fault reveals no dislocation. A site was trenched on the straight contract line with $N30^{\circ}$ E-striking between the 10 m a.s.l. Marine terrace and the 20 m a.s.l. Marine terrace. Fault line or dislocation was not observable in the trench excavation. Accordingly, the straight contact line is inferred as the ancient shoreline of the 10 m a.s.l. Marine terrace. The Ages of the Fault activities are inferred after the formation of the Ichonri Formation - before the formation of the 45 m a.s.l. Marine terrace (220 Ka. y. B.P. or 320 Ka. y. B.P.). The Low relief erosional surface was an island above the sea-level during the formation of the 45 m a.s.l. Marine terrace in the paleogeography.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.7 no.1
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• pp.9-15
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• 1977

The author observed the effect of X-ray irradiation on the secondary palate formation of the rat fetuses. The mothers were exposed to X-radiation on the 10½th, 11½th and 12½th day of gestation with respectively 150, 200, 250, 300 and 350 rads. The fetuses were removed from mothers on 15½h, 16½th and 18½th day of gestation. Morphological changes in palate formation were examined and histochemical preparations were made. 1. In control fetuses, the secondary palates were fully developed on the 15½th to 18½th day of gestation. But in experimental fetuses, many cleft palates were observed in accordance with increase of X-radiation dose. 2. Frequency of incidence of horizontal position of both palated shelves in cleft palate was highest. 3. Accordig to the dislocation of palatal processes, the stain ability of palatal crest was varied. 4. The thickened area of palatal epithelium of palatal crest showed intense methyl green-pyronin and PAS reaction 5. Mesenchymal cell condensation was appeared under the thickened epithelium of palatal process and this mesenchymal tissue showed strong colloidal iron reaction. 6. The stain ability of alizarin red S and alkaline phosphatase reaction of tectal ridge were decreased, in accordance with increase of irradiation doses.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.54-55
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• 2010

Vacancy defects in graphene can be created by electron or ion irradiation and those induce ripples which can change the electronic properties of graphene. Recently, the formation of defect structures such as vacancy defects and non-hexagonal rings has been reported in the high resolution transmission electron microscope (HR-TEM) of reduced graphene oxide [1]. In those HR-TEM images, it is noticed that the dislocations with pentagon-heptagon (5-7) pairs are formed and diffuses. Interestingly, it is also observed that two 5-7 pairs are separated and diffuse far away from each other. The separation of 5-7 pairs has been known to be due to their self-diffusion. However, from our tight-binding molecular dynamics simulation, it is found that the separation of 5-7 pairs is due to the diffusion of single vacancy defects and coalescence with 5-7 pairs. The diffusion and coalescence of single vacancy defects is too fast to be observed even in HR-TEM. We also implemented Van der Waals interaction in our tight-binding carbon model to describe correctly bi-layer and multi-layer graphene. The compressibility of graphite along c-axis in our tight-binding calculation is found to be in excellent agreement with experiment. We also discuss the difference between single layer and bi-layer graphene about vacancy diffusion and reconstruction.

• Applied Microscopy
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• v.46 no.1
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• pp.45-50
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• 2016

Iron containing a high amount of chromium is known to be inferior to ductility due to ${\sigma}$ phase formation so that it is generally difficult to apply the plastic deformation process although the alloy possesses a superior characteristics of an excellent corrosion resistance. In this study, Fe-50mass%Cr alloy was melted using high purity powder and the deformation behavior has been investigated by cold rolling and tensile test. The tensile test yielded that the alloy revealed a serration at an early stage of tensile deformation and then the serrated flow vanished to change to a normal work hardening flow at the later stage. The former was governed by twin formation process, the latter by dislocation multiplication one, bringing about a high ductility of 20% or over. The reduction ratio in cold rolling was attained as high as 90%, thus the high corrosion-resistant alloy is able to possess a high ductility.

• Journal of Biomedical Engineering Research
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• v.41 no.4
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• pp.165-171
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• 2020

In this study, it focuses on the development of radiographic devices for patellar imaging. On the previous X-ray examination of patella and patellofemoral joint, it analyzed the problems which could affect the results: unstable patients' pose, radiation exposure, and deterioration of image quality. The purpose of the research is to propose a future use of a developed device with an explanation of the process, function, and advantage of the device including the methods. The device is developed to focus on the diagnosis of the longitudinal and longitudinal fractures of the patella and patella/femoral joint, displacement such as dislocation, bone formation, stenosis of the patella/femorla joint, and cartilage wear. Due to the patient's anxious posture, it caused a shaking image, overlapping structures, and etcs, these factors challenge to diagnose accurately. In addition, the existing Settegast method and Hughston method, which are most frequently performed in the hospital field, are not suitable for the presence or absence of features or dislocation due to the heavy load on the patella of the patient. The developed device requires patients in a lying position and placing only their leg on the device, it increases the conveniences of the examination and decreases unnecessary radiation exposure of the patient except the patellar examination area. Moreover, one of the systems in the device fixes the detector, where the patients no longer need to hold the detector nor be in unstable posture, but describes the structure of the patella/femoral joint more clearly. Hoping the device will apply to more patients.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.2
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• pp.45-50
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• 2005

During oxidation process, several type of defects are formed on the surface of the silicon crystal which was damaged mechanically before oxidation. As the size of abrasive particle increases multiple dislocation loops are produced favorably over oxidation-induced stacking faults, which are dominantly produced when ground with finer abrasive particle. These defects are not related with the crystal growth process like Czochralski or directional solidification. During directional solidification process, twins and stacking faults are the two major defects observed in the bulk of the silicon crystal. On the other hand, slip dislocations produced by the thermal stress are not observed. Thus, not only in single crystalline silicon crystal but also in multi-crystalline silicon, extrinsic gettering process with programmed production of surface defects might be highly applicable to silicon wafers for purification.

• Korean Journal of Materials Research
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• v.27 no.10
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• pp.524-529
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• 2017

The effect of strain aging on the tensile properties of API X70 linepipe steel was investigated in this study. The API X70 linepipe steel was fabricated by controlled rolling and accelerated cooling processes, and the microstructure was analyzed using optical and scanning electron microscopes and electron backscatter diffraction. Strain aging tests consisting of 1 % pre-strain and thermal aging at $200^{\circ}C$ and $250^{\circ}C$ were conducted to simulate U-forming, O-forming, Expansion(UOE) pipe forming and anti-corrosion coating processes. The API X70 linepipe steel was composed of polygonal ferrite, acicular ferrite, granular bainite, and bainitic ferrite whose volume fraction was dependent on the chemical composition and process conditions. As the thermal aging temperature increased, the steel specimens showed more clearly discontinuous type yielding behavior in the tensile stress-strain curve due to the formation of a Cottrell atmosphere. After pre-strain and thermal aging, the yield and tensile strengths increased and the yield-to-tensile strength ratio decreased because yielding and aging behaviors significantly affected work hardening. On the other hand, uniform and total elongations decreased after pre-strain and thermal aging since dislocation gliding was restricted by increased dislocation density after a 1 % pre-strain.

• Journal of the Korean Magnetics Society
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• v.15 no.1
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• pp.25-29
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• 2005

Magnetic properties of YIG films grown by solid phase epitaxy (SPE) was measured as a function of temperature with focus on magneto-crystalline and perpendicular magnetic anisotropy. Perpendicular magnetic anisotropy was not induced in the SPE YIG films annealed at low temperature by relaxing residual stress through formation of dislocation. On the contrary the films annealed at high temperature showed perpendicular magnetic anisotropy which shows very low density of dislocation. Perpendicular magnetic anisotropy field decreased linearly up to a high temperature of $230^{\circ}C$ above which magneto-crystalline anisotropy disappeared. Coercivity also decreased linearly with temperature up 세 $230^{\circ}C$. Magneto-crystalline anisotropy of perpendicular anisotropy induced epitaxial (111) YIG films can be measured using $H_k=4K_1/3M_s$. Temperature behavior of initial susceptibility can be successfully explained by Hopkinson effects. Curie temperature of YIG films grown on GGG substrate with high paramagnetic susceptibility can be easily measured using the results.

• Korean Journal of Materials Research
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• v.25 no.11
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• pp.630-635
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• 2015

The fatigue strength of a nickel-base superalloy was studied. Stress-controlled fatigue tests were carried out at $700^{\circ}C$ and 5 Hz using triangular wave forms. In this study, two kinds of testing procedures were adopted. One is the conventional tension-zero fatigue test(R = 0). The other was a procedure in which the maximum stress was held at 1000 MPa and the minimum stress was diverse from zero to 1000 MPa at 24 and $700^{\circ}C$. The results of the fatigue tests at $700^{\circ}C$ indicate that the fracture mechanism changed according to both the mean stress and the stress range. At a higher stress range, ${\gamma}^{\prime}$ precipitates are sheared by a/2<110> dislocation pairs coupled by APB. Therefore, in a large stress range, the deformation occurred by shearing of ${\gamma}^{\prime}$ by a/2<110> dislocations, which brought about crystallographic shear fracture. As the stress range was decreased, the fracture mode gradually changed from crystallographic shear fracture to gradual growth of fatigue cracks. At an intermediate stress range, as it became more difficult for a/2<110> dislocation pairs to shear ${\gamma}^{\prime}$ particles, cracks started to propagate in the matrix, avoiding the harder ${\gamma}^{\prime}$ particles. High mean stress induced creep deformation, that is, ${\gamma}^{\prime}$ particles were sheared by {111}<112> slip systems, which led to the formation of stacking faults in the precipitates. Thus, the change in fracture mechanism brought about the inversion of the S-N curves.