• Archives of Craniofacial Surgery
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• v.17 no.3
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• pp.162-164
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• 2016

Stafne bone cavity is a rare mandibular defect that was first reported by Edward C. Stafne in 1942. It commonly presents with a well-demarcated, asymptomatic, unilateral radiolucency that indicates lingual invagination of the cortical bone. A 52-year-old female patient who with nasal bone fracture, visited the hospital. During facial bone computed tomography (CT) for facial area evaluation, a well-shaped cystic lesion was accidentally detected on the right side of the mandible. Compared to the left side, no swelling or deformity was observed in the right side of the oral lesion, and no signs of deformity caused by mucosal inflammation. 3D CT scans, and mandible series x-rays were performed, which showed a well-ossified radiolucent oval lesion. Axial CT image revealed a cortical defect containing soft tissue lesion, which has similar density as the submandibular gland on the lingual surface of the mandible. The fact that Stafne cavity is completely surrounded by the bone is the evidence to support the hypothesis that embryonic salivary gland is entrapped by the bone. In most cases, Stafne bone cavity does not require surgical treatment. We believe that the mechanical pressure from the salivary gland could have caused the defect.

• Journal of the Korean Geotechnical Society
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• v.19 no.5
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• pp.59-67
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• 2003

In this study, the change in hydraulic conductivity according to the changes in the contact area, aperture, confining pressure and temperature was observed to improve the reliability of the analysis of underground water flow. Also, the mechanical and thermal properties of domestic crystalline rocks in a great depth were obtained. It was found that the averaged intial aperture ranged from 544.33${\mu}{\textrm}{m}$ to 898.62${\mu}{\textrm}{m}$ and it followed a log-normal distribution. The hydraulic conductivity decreased with the increase of normal stress on the fracture surface and the hydraulic conductivity decreased as temperature increased. The change in hydraulic conductivity was strongly correlated with the change in contact area. It was verified by experiments that hydraulic conductivity was inversely proportional to the contact area. The measured mechanical and thermal properties were very close to the existing typical properties of domestic granites.

• Transactions of the Korean hydrogen and new energy society
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• v.26 no.2
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• pp.120-126
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• 2015

Recently, the ever-increasing use of fossil fuels for rapid industrial development and population significantly caused an environment pollution and global warming such as climate change. So research and development of sustainable and eco-friendly energy have been performed. Especially the interest in nuclear fusion fuel was significantly increased from the developed countries. The system of fusion energy production was tritium separation, storage and delivery, and purification. Republic of Korea is in charge of Storage and Delivery System (SDS) in the International Thermonuclear Experimental Reactor (ITER). Welding part of the SDS bottles for storing the tritium is known to be susceptible to hydrogen embrittlement. In this study, conducted a study for the relaxation of the stability and hydrogen embrittlement of the weld area. The hydrogen heat treatment was processed through the Pressure-Composition-Temperature (PCT) device according to the time variation. Also mechanical properties such as impact test and hardness test according to using the alkaline cleaning liquid for hydrogen embrittlement relief and the fracture was observed by scanning electron microscopy (SEM) after the mechanical properties evaluation.

• Transactions of the Korean hydrogen and new energy society
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• v.26 no.2
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• pp.114-119
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• 2015

Nowdays, fossil fuels have been used as an important resource in development of industry. But it is limited and caused climate change such as pollution and global warming. So nuclear fusion research is being issued with tritium to develop eco-friendly and sustainable energy. Republic of Korea is in charge of Storage and Delivery System (SDS) in the International Thermonuclear Experimental Reactor (ITER), weld present in the SDS bottles are easily exposed to the hydrogen embrittlement of special characteristics of the hydrogen in hydrogen atmosphere, When the hydrogen embrittlement is rapidly progresses, the cracking is generated in the weld zone. Due to this cracking, the risk of leakage of tritium into the atmosphere occurs. In this study, hydrogen heat treatment was processed through the Pressure-Composition-Temperature (PCT) device according to the time variation. Also mechanical properties such as rupture strength test, three point bend test and hardness test in accordance with the respective time have been conducted and the fracture was observed by scanning electron microscopy(SEM) after the mechanical properties evaluation.

• Journal of the Korean Society for Railway
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• v.14 no.3
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• pp.240-247
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• 2011

Finite element analysis was undertaken to investigate the effect of freezing force of water unexpectedly penetrated into inserts used in railway sleeper on pullout capacity of anchor bolts for fixing base-plate onto concrete sleeper. Based on the in-situ investigation and measurement of geometry of railway sleeper and rail-fastener, the railway sleeper was modeled by 3D solid elements. Nonlinear and fracture properties for the finite element model were assumed according to CEB-FIP 1990 model code. And the pullout maximum load of anchor bolt obtained from the model developed was compared with experimental pullout maximum load presented by KRRI for verification of the model. Using this model, the effect of position of anchor bolt, amount of fastening force applied to the anchor bolt, and compressive strength of concrete on pull-out capacity of anchor bolts installed in railway sleeper was investigated. As a result, it is found that concrete railway sleepers could be damaged by the pressure due to freezing of water penetrated into inserts. And the pullout capacity of anchor bolt close to center of railway is slightly greater than that of the others.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.3
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• pp.233-238
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• 2000

t-$ZrO_2/Al_2O_3$composites having a superior biocompatability and phase stability were prepared by adding 0~4 mol% of $Eu_2O_3$and sintered for 1 h at $1600^{\circ}C$ to evaluate phase stability, chromaticity and mechanical properties of the composites. No tetragonal to monoclinic phase transformation was observed for the composites containing $Eu_2O_3$after heat treatment for 20 h at $180^{\circ}C$ under 3.5 MPa water vapor pressure condition. As $Eu_2O_3$content increased, the color of the composites was changed from a slight white ivory to a light pink. The strength and the fracture toughness of the composites containing $Eu_2O_3$were above 620 MPa and 7.6 MPa.$m^{1/2}$, respectively, when $Eu_2O_3$was added up to 3 mol%.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.49-54
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• 2000

Cr-Mo-V steel is widely used as a material for the turbine structural component in fossil power plants. It is well known that this material shows the various material degradation phenomenons such as temper embrittlement, carbide coarsening. and softening etc. or ins to the severe operation conditions as high temperature and high pressure. These deteriorative factors cause tile change of mechanical properties as reduction of fracture toughness. Therefor it is necessary to evaluate tile extent of degradation damage for Cr-Mo-V steel in life assessment of turbine structural components. In this paper. the electrochemical potentiokinetic reactivation(EPR) test in $50wt%-Ca(NO_3)_2$ solution is performed to develop the newly technique for degradation damage evaluation of Cr-Mo-V steel. The results obtained from the EPR test are compared with those in small punch(SP) tests recommended by semi-nondestructive testing method using miniaturized specimen. The evaluation parameters used in EPR test are tile reactivation current density$(I_R)$ and charge$(Q_{RC})$ reactivation rate$(I_R/I_{Crit},\;Q_R/Q_{Crit})$. The results suggest that $I_R/I_{Crit}$ in these parameters shows a good correlation with SP test results.

• The Journal of Engineering Geology
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• v.6 no.2
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• pp.53-58
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• 1996

In order to investigate the source mechanism of micro cracks through acoustic emission measurement induced by rock fracture, careful calibration of the entire linkage of the detecting system, from the transducers to transient recorder, is an essential requirement prior to testing. Transducers and digitiging system are generally the weakest links in the measurement system because they must translate mechanical motions into digital electric signals. In this study, PAC piezoelectric pressure transducers are calibrated with a standard NBS conical shaped displacement transducer and a DG piezoelectric displacement transducer. The NBS and PAC transducers are insensitive to changes in horizontal impingement angle but sensitive to changes in incident angle. The ray path along the logitudinal axis of the tranducer produced a maximum response while the ray path perpendicular to the transducer axis gave a minimum. And a difference in individual transducers factor for a peak-to-peak amplitude of PAC transducers was within 40%. An average PAC transducer coefficient was determined as 77mv/pm by an absolute calibration test using NBS transducer.

• Journal of the Korean Society of Radiology
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• v.14 no.1
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• pp.31-37
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• 2020

This study was conducted to examine the kinds and the frequency of incorrect outcomes occurring depending examiners' skills, in testing osteoporosis by using Dual Energy X-ray Absorptiometry(DXA) and improve frequently occurring errors by educating them. The results of an analysis show that the outcomes from the test of hips in patients with wrong postures or some regions with pressure fracture and degenerative changes were often included, even though they should be excluded, and that surgical instruments were also included in the analysis, though they should be excluded from resulting values. Of them, the errors most often found were those about patients' postures (n=56, 6 cases for spines and 50 cases for hips), followed by those about analytical processes (n=37, 35 cases for spines and 2 cases for hips), and then those about regions of interest (n=33, 28 cases for spines and 5 cases for hips). There were, however, no errors caused by the defectiveness of quality control.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.3
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• pp.353-358
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• 2013

The ultrasonic characteristics of 2.25Cr-1Mo steel were investigated in relation to the isothermal heat treatment temperature and time. Charpy impact tests and hardness tests were conducted on individual specimens with three different heat treatment conditions. A pulse-echo method with longitudinal waves was used to measure the attenuation and velocity of ultrasonic waves. The FATT (fracture appearance transition temperature) increased with an increase in the isothermal heat treatment time, which implies that the toughness decreased. As the isothermal heat treatment time and temperature increased, the longitudinal wave velocity and ultrasonic attenuation coefficient were raised.