• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.3
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• pp.19-26
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• 1999

The detectability of pipes buried in dry sand is investigated by using the GPR with self-designed bow-tie antenna. The antennas are covered with shielding structures to reduce the direct-coupling between the transmitting and receiving antennas. The ringing, due to finite length of the antenna, is decreased by performing resistive termination at the ends of the antennas. It is shown that without additional signal processing, the presence of various buried targets can be found by discriminating hyperbolic pattern in B-scan data.

• Nuclear Engineering and Technology
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• v.4 no.3
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• pp.223-228
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• 1972

In the radiography, of thick materials the scattered rays from an object are one of major causes to reduce the quality of the radiographic image on the film. To determine the rate of scattering of incident gamma rays by an objective specimen, film blacknesses are measured for various slit widths. For each measurement, the changes of a penetrameter's sensitivity are also evaluated. It is observed that the fault-detectability can be improved by reducing the slit width when the fault detectability deteriorates due to the increase in scattered gamma rays by thicker samples. This experiment has been carried out with the iron specimens and $^{60}$ Co source.

• Korean Journal of Remote Sensing
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• v.34 no.4
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• pp.591-600
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• 2018

Recent SAR systems provide fully polarimetric SAR data, which is known to be useful in a variety of applications such as disaster monitoring, target recognition, and land cover classification. The objective of this study is to evaluate the performance of polarization SAR data for landslide detection. The detectability of different SAR parameters was investigated based on the supervised classification approach. The classifier used in this study is the Adaptive Boosting algorithms. A fully polarimetric L-band PALSAR-2 data was used to examine landslides caused by the 2016 Kumamoto earthquake in Kyushu, Japan. Experimental results show that fully polarimetric features from the target decomposition technique can provide improved detectability of landslide site with significant reduction of false alarms as compared with the single polarimetric observables.

• Nuclear Engineering and Technology
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• v.30 no.4
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• pp.377-385
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• 1998

Many nuclear power plants have experienced unscheduled shutdown due to the leakage of steam generator tubes. The leakages are normally due to the crack, possibly stress corrosion cracking (SCC) near the tube expansion at the top of tubesheet or at the tangential point of the row-1 U-bend region. The conventional eddy current technique, which makes use of a differential bobbin coil, has been found to be inadequate for the early detection of SCC. During the in-service inspection, therefore, it is a general practice that the rotating pancake coil (RPC) is used for detecting the cracks. Even in using RPC, however, it is difficult to determine the depth of the cracks quantitatively. This paper attempts to determine the detectability and sizing ability of RPC technique for axial or circumferential cracks at the tube expansion region. The simulated cracks with various dimensions were fabricated by electro-discharge machining (EDM) method. Experimental results are discussed with theoretical calculations.

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.4
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• pp.473-479
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• 1999

The two-microphone sound-intensity technique has been used for the detection of defects in ra-ally loaded ball bearings. The difference in the sound-intensity levels measured for bearings with no defect and for those with intentionally introduced defects of different sizes n heir elements under various operating conditions of loads and speeds is demonstrated. The results show that of an inner-race or ball defect. It is difficult to detect defects at lower speeds. Sound-pressure measurements were also performed for comparison and it shown that the detectability of defects by sound-intensity measurements is better than that by sound-pressure measurements.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.05a
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• pp.222-228
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• 1999

The two-microphone sound-intensity technique has been used for the detection of defects in radially loaded ball bearings. The difference in the sound-intensity levels measured for bearings with no defect and for those with intentionally introduced defects of different sizes in their elements under various operating conditions of loads and speeds is demonstrated. A change in the intensity frequency spectrum because of the defects is observed. The results show that the detectability of an outer-race defect is much better than that of on inner-race or ball defect. It is difficult to detect defects at lower speeds. Sound-pressure measurements were also performed fur comparison, and it is shown that the detectability of defects by sound-intensity measurements is better than that by sound-pressure measurements.

• Proceedings of the KWS Conference
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• 2000.04a
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• pp.279-282
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• 2000

• Imaging Science in Dentistry
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• v.33 no.3
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• pp.187-193
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• 2003

Purpose: To compare the measurements of the mandible and the detectability of the mandibular canal on reformatted images using a newly developed 3-dimensional implant simulation program with traditionally used CT multiplanar reconstruction program and true measurements. Materials and Methods: Ten dry dog mandibles were used in this study. Occlusal templates for CT examination were fabricated and marked with gutta perch a at ten sites. Axial CT scans were taken and reconstructed using DentaScan (D group) and Vimplant program (V group), and each mandible was sectioned at the previously marked sites (R group). Maximum vertical height (H) and maximum width (W) of the mandible, the distances from buccal border of the mandibular canal to the most buccal aspect of the mandible (X), and the distance from the superior border of the mandibular canal to the alveolar crest (Y) were measured, and the mandibular measurements in each group were compared. Detectability of mandibular canal was evaluated using a 3-point scale in both V and D groups by three oral radiologists and compared. Results: H in the V group was slightly greater than that in the D group, and Wand X in the V group was slightly less than those in the D group. H in the V group was less than that in the R group, and Wand X in the V group was larger than those in the R group. The detectability of the mandibular canal did not show statistically significant differences between V and D groups. Conclusion: The results of the experiment show that the newly developed, inexpensive Vimplant/TM/ simulation program can be used as an alternative to the traditionally used, and more expensive CT multiplanar reconstruction program.

• Imaging Science in Dentistry
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• v.35 no.3
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• pp.157-165
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• 2005

Purpose : To find out the proper compression ratios without degrading image quality and affecting lesion detectability on diagnostic images used in dentistry compressed with JPEG 2000 algorithm. Materials and Methods : Sixty Digora periapical images, sixty panoramic computed radiographic (CR) images, sixty computed tomographic (CT) images, and sixty magnetic resonance (MR) images were compressed into JPEG 2000 with ratios of 10 levels from 5:1 to 50:1. To evaluate the lesion detectability, the images were graded with 5 levels (1 : definitely absent; 2: probably absent; 3: equivocal; 4: probably present; 5: definitely present), and then receiver operating characteristic analysis was performed using the original image as a gold standard. Also to evaluate subjectively the image quality, the images were graded with 5 levels (1 definitely unacceptable; 2: probably unacceptable; 3: equivocal, 4: probably acceptable; 5· definitely acceptable), and then paired t-test was performed. Results : In Digora, CR panoramic and CT images, compressed images up to ratios of 15 : 1 showed nearly the same lesion detectability as original images, and in MR images, compressed images did up to ratios of 25 : 1. In Digora and CR panoramic Images, compressed images up to ratios of 5 : 1 showed little difference between the original and reconstructed images in subjective assessment of image quality In CT images, compressed images did up to ratios of 10: 1 and in MR images up to ratios of 15 : 1 Conclusion : We considered compression ratios up to 5 : 1 in Digora and CR panoramic images, up to 10 : 1 in CT images, up to 15 : 1 in MR images as clinically applicable compression ratios.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.28 no.2
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• pp.461-470
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• 1998

The comparative detectability of the artificial periapical defects among Ektaspeed Plus film. digitized and digora images was evaluated. The artifical defects were made in the cancellous bone and cancellous-cortical junction with the size of 1.0×0.8mm², 1.4×1.1mm² and 2.8×2.2mm². The defects in cancellous-cortical junction extended into cortical bone with the depth of 0, 0.5 and 1.0 mm. The results were as follows : 1. In junctional defects Ektaspeed Plus film for 2.8×12.2mm² defect showed the highest detectability. But significant difference were only found between Ektaspeed Plus films and digitized images (p<0.05). 2. Almost all defects within cacellous bone were not detected except a few digitized and Digora images for the size of 2.8×2.2mm². Digora images for them showed significant differences with Ektaspeed Plus films and digitized images (p<0.05). 3. The sensitinity of all imaging modalities were 0.9 or 1.0 in junctional defects for the size of 1.4×2.2mm² and 2.8×2.2mm². For cancellous defects, Digora image showed the highest sensitivity of 0.6 for the size of 2.8×2.2mm². 4. Significant differences for change of exposure time were found in most group of Ektaspeed Plus films and digitized images (p<0.05) . But there was no significant differences in Digora images for cacellous defects.