• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.341-348
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• 2009

Various types of micro cone penetrometers have been developed by using strain gages for the layered soil detection. Strain gages, however, are affected by several factors such as temperature, self heating and lead wire length. In this study, micro cone penetrometers with 3~7mm in diameter, are developed by using FBG sensor to overcome the defects of the strain gage, and compensate the effect of temperature during penetration. In order to verifiy the accuracy and reliability of the developed FBG cone, the cone penetration test is performed on the layered soil. The tip resistance of FBG snesor shows excellent sensitivity, and can detect the interface of the layered soils with higher resolution. In addition, the 3mm micro cone penetrometer which is impossible cone diameter by using strain gages presents much higher sensitivity than the 7mm cone penetrometer. This study suggests that FBG sensor is a useful sensor for manufaturing the ultra small sized cone, and effectively detects the interface of the layered soil.

• Journal of the Korean Geotechnical Society
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• v.24 no.2
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• pp.77-86
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• 2008

The disturbance zone and measured values are affected by the size of the penetrometer. The local value may be measured by the smaller penetrometer. An ultra small Micro-Cone penetrometer (5mm in outer diameter) is designed and manufactured to characterize soil properties with minimum disturbance during penetration tests. The tip resistance is measured by using stain gauges attached near the Micro-Cone. In addition, the friction sleeve is adopted to effectively remove the skin friction from the tip resistance. Design concern includes the installation of stain gauges, circuits, penetration systems, penetration rate, sampling rate, operating temperature, and calibration. Application tests show that the clay interface, and the soil layers consisting of clay and sand are clearly detected by the Micro-Cone. Furthermore, the cone tip resistances measured by the Micro-Cone and the miniature cone (16mm in outer diameter) are similar. Note the resolution is much higher in the Micro-Cone. This study shows that the Micro-Cone may effectively detect the soil interface with high resolution, and with minimum disturbance.

• Restorative Dentistry and Endodontics
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• v.43 no.3
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• pp.30.1-30.12
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• 2018

Objectives: To evaluate sealing ability of root canals obturated with bioceramic-impregnated gutta percha cone (BCC) or gutta percha (GP), with bioceramic sealer (BCS) or AH Plus (AH; Dentsply-Maillefer), in roundly-prepared canals using matched single-cone technique, based on bacterial leakage test, and to analyze obturation quality using micro-computed tomography (CT) analysis. Materials and Methods: Ninety-two distobuccal roots of maxillary molars were prepared using nickel-titanium files to apical size 40/0.06. The roots were divided into 4 groups (n = 20) that were obturated with a master cone and sealer: GP/AH, BCC/AH, GP/BCS, and BCC/BCS. Bacterial leakage model using Enterococcus faecalis was used to evaluate sealing ability for 60-day period. Obturated samples from each group (n = 4) were analyzed using micro-CT. Results: All groups showed bacterial leakage at 20%-45% of samples with mean leakage times of 42-52 days. There were no significant differences in bacterial leakage among the groups. Micro-CT showed minimal gaps and voids in all groups at less than 1%. Conclusions: In roundly-prepared canals, the single cone obturation with BCC/BCS was comparable to GP/AH for bacterial leakage at 60 days.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.1052-1055
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• 2001

In micro-drilling of brittle materials including glass, cracks occur at the exit surface. In drilling glass, the main type of crack is cone crack. Cone crack is generated by thrust force acting at the bottom surface of the workpiece. Cone crack size could be reduced by changing cutting conditions, but cone crack still existed. Two methods were proposed to prevent crack formation and perfect hole shapes were obtained. One method is attaching two glass plates with water and the other method is constraining two glass plates. The proposed methods eliminated tensile stress acting on the exit surface of glass and prevented crack propagation.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.117-125
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• 2008

The detection of thin-layered soil is important in soft soils to evaluate the soil behavior. The smaller diameter cone penetrometer have been commonly used to detect the layer with increasing sensitivity. The objective of this study is to detect the thin-layered soil using cone resistance and electrical resistance. The cone resistivity penetration test (CRPT) is developed to evaluate the cone tip resistance and electrical resistance at the tip. The CRPT is a micro-cone which has a $0.78cm^2$ in projected area. The application test is conducted in a laboratory large-scale consolidometer (calibration chamber). The kaolinite, sand and water are mixed to make the specimen at the liquid limit of 46% using a slurry mixer. It takes two months for the consolidation of the specimen. After consolidation, the CRPT test is carried out. Furthermore the standard CPT results are compared with the electrical resistance measured at the tip in the field. This study suggests that the CRPT may be a useful tool for detecting thin-layers in soft soils.

• Tribology and Lubricants
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• v.11 no.5
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• pp.114-121
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• 1995

An ultrasonic technique using normal-incident compressional waves was used to evaluate the surface and subsurface damage in ceramics produced by Hertzian indentation. Damage was produced by a blunt indenter (tungsten carbide ball) in glass-ceramic, green glass and silicon nitride. The damage was classified into two types; (1) Hertzian cone crack, in green glass and fine grain silicon nitride, and (2) distributed subsurface micro fractures, without surface damage, produced in glass ceramic. The ultrasonic technique was successful in detecting cone craks. The measurement results with the Hertzian cone cracks indicated that cracks perpendicular to the surface could be detected by the normal-incident compressional waws. Also shown is the capability of normal-incident compressional waves in detection distributed micro-sized cracks size of subsurface microfractures.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.9
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• pp.662-664
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• 1999

We fabricated AC-TFEL device having cone-shaped Si micro-tip reflector array based on the process which have been conventionally employed for the Si-tip field emitter array in FED system. As a result, the AC-TFEL device having a new geometrical structure could generate well concentrated visible white-light from 3600 reflectors/pixel under bipolar pulse excitation mode only by edge-emission mechanism.

• Korean Journal of Optics and Photonics
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• v.23 no.3
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• pp.119-123
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• 2012

The structure of an LCD backlight unit (BLU) was simplified by installing a micro reverse-pyramid array (MRPA) or a micro reverse-cone array (MRCA) on the top surface of the light guide panel (LGP) in order to eliminate the conventional diffuser sheet and the prism sheet. The optimum conditions of the MRPA and the MRCA in the new light guide panel were obtained through optical simulation. The change of the luminance and view angle that depend on the side angle, the height, and the length at the top of the MRPA and MRCA were studied. The optimized side angle and the view angle of the MRPA and MRCA were 59 and 57 degrees for the side angles and 68 and 64 degrees for the view angles, respectively.

• Journal of Biomedical Engineering Research
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• v.25 no.2
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• pp.97-102
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• 2004

We developed an x-ray cone-beam micro computed tomography (micro-CT) system for small-animal imaging. The micro-CT system consists of a 2-D flat-panel x-ray detector with a field-of-view (FOV) of 120${\times}$120 mm2, a micro-focus x-ray source, a scan controller and a parallel image reconstruction system. Imaging performances of the micro-CT system have been evaluated in terms of contrast and spatial resolution. The minimum resolvable contrast has been found to be less than 36 CT numbers at the dose of 95 mGy and the spatial resolution about 14 lp/mm. As small animal imaging results, we present high resolution 3-D images of rat organs including a femur, a heart and vessels. We expected that the developed micro-CT system can be greatly used in biomedical studies using small animals.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.4C
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• pp.163-174
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• 2009

Mechanical device using the load cell or strain gage sensor can be influenced by tempearute changes because temperature change can cause a shift in the load cell or straing gage output at zero loading. In this paper, micro cone penetrometers with 1~7mm in diameter, are developed by using an optical fiber sensor (FBG: Fiber Bragg Grating) to compensate the continous temperature change during cone penetration test. Note the temperature compensated method using optical fiber sensor which has hair-size in diameter, and is not affected by environmental conditions because the measured data is the wavelength shifting of the light instead of the intensity of the electric voltage. Temperature effect test shows that the output voltage of strain gage changes and increases with an increase in the temperature. A developed FBG cone penetrometer, however, achieves excellent temperature compensation during penetration, and produces continuous change of underground temperature. In addition, the temperature compensated FBG cone shows the excellent sensitivity and detects the interface of the layered soils with higher resolution. This study demonstrates that the fiber optic sensor renders the possibility of the ultra small size cone and the new fiber optic cone may produce more reliable temperature compensated tip resistance.