• Corrosion Science and Technology
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• v.11 no.6
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• pp.218-224
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• 2012

Liquid droplet impingement erosion (LDIE) known to be generated in aircraft and turbine blades is recently appeared in nuclear piping. UT thickness measurements with both A-scan and B-scan UT inspection equipments were performed for a component estimated as susceptible to LDIE in feedwater heater vent system. The thickness data measured with B-Scan equipment were compared with those of A-Scan. Thermal hydraulic analysis based on ANSYS FLUENT code was performed to analyze the behavior of liquid droplets inside piping. The wall thinning rate and residual lifetime based on both existing Sanchez-Caldera equation and measuring data were also calculated to identify the applicability of the existing equation to the LDIE management of nuclear piping. Because Sanchez-Caldera equation do not consider the feature of magnetite formed inside piping, droplet size, colliding frequency, the development of new evaluation method urgently needs to manage the pipe wall thinning caused by LDIE.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.969-970
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• 2009

• Journal of the Korean Society of Propulsion Engineers
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• v.16 no.2
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• pp.65-72
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• 2012

A defect analysis program for a composite motor case was developed to apply the ultrasonic signal processing method, based on the ultrasonic pulse-echo method. With the proposed defect analysis program, defects of FRP delamination and FRP/Rubber disbond in the composite motor case could be quantitatively measured. The defects detected in the composite motor case were in good agreement with the results measured with the computed tomography and video microscope. This paper described the development process of the defect analysis program to convert the ultrasonic test data into the C-Scan images.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.393-399
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• 2011

A defect analysis program of the composite motor case was developed to apply the ultrasonic signal processing method on basis of the ultrasonic pulse-echo method and the defects of FRP delamination and FRP/Rubber disbond in the composite motor case could be quantitatively measured. The defects detected in the composite motor case were in agreement with the results measured with the computed tomography and video microscope. This paper was described about the development process of the defect analysis program to convert the ultrasonic test data into the C-Scan image.

• The Korean Journal of Nuclear Medicine Technology
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• v.16 no.1
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• pp.102-107
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• 2012

Purpose : Because of the rapid physical decay of the short half-lived radionuclide, counting of event for image is very limited. In this reason, long scan duration is applied for more accurate quantitative analysis in the relatively low sensitive examination. The aim of this study was to evaluate the difference according to scan duration and investigate the resonable scan duration using the radionuclide of 11C and 18F in PET scan. Materials and Methods : 1994-NEMA Phantom was filled with 11C of $30.08{\pm}4.22MBq$ and 18F of $40.08{\pm}8.29MBq$ diluted with distilled water. Dynamic images were acquired 20frames/1minute and static image was acquired for 20minutes with 11C. And dynamic images were acquired 20frames/2.5minutes and static image was acquired for 50minutes with 18F. All of data were applied with same reconstruction method and time decay correction. Region of interest (ROI) was set on the image, maximum radioactivity concentration (maxRC, kBq/mL) was compared. We compared maxRC with acquired dynamic image which was summed one bye one to increase the total scan duration. Results : maxRC over time of 11C was $3.85{\pm}0.45{\sim}5.15{\pm}0.50kBq/mL$ in dynamic image, and static image was $2.15{\pm}0.26kBq/mL$. In case of 18F, the maxRC was $9.09{\pm}0.42{\sim}9.48{\pm}0.31kBq/mL$ in dynamic image and $7.24{\pm}0.14kBq/mL$ in static. In summed image of 11C, as total scan duration was increased to 5, 10, 15, 20minutes, the maxRC were $2.47{\pm}0.4$, $2.22{\pm}0.37$, $2.08{\pm}0.42$, $1.95{\pm}0.55kBq/mL$ respectively. In case of 18F, the total scan duration was increased to 12.5, 25, 37.5, and 50minutes, the maxRC were $7.89{\pm}0.27$, $7.61{\pm}0.23$, $7.36{\pm}0.21$, $7.31{\pm}0.23kBq/mL$. Conclusion : As elapsed time was increased after completion of injection, the maxRC was increased by 33% and 4% in dynamic study of 11C and 18F respectively. Also the total scan duration was increased, the maxRC was reduced by 50% and 20% in summed image of 11C and 18F respectively. The percentage difference of each result is more larger in study using relatively shorter half-lived radionuclide. It appears that the accuracy of decay correction declined not only increment of scan duration but also increment of elapsed time from a starting point of acquisition. In study using 18F, there was no big difference so it's not necessary to consider error of quantitative evaluation according to elapsed time. It's recommended to apply additional decay correction method considering decay correction the error concerning elapsed time or to set the scan duration of static image less than 5minutes corresponding 25% of half life in study using shorter half-lived radionuclide as 11C.

• Journal of the Korean Society for Nondestructive Testing
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• v.14 no.2
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• pp.112-121
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• 1994

This paper discusses the feasibility of ultrasonic C-scan technique for nondestructive evaluation of spot weld quality. Ultrasonic evaluation for spot weld quality was performed by immersion method with the mechanical and the electronic scanning of point-focussed ultrasonic beam(25 MHz). For the sake of the approach to the quantitative measurement of nugget diameter and the discrimination of the corona bond from nugget, preliminary infinitesimal gap experiment by newton ring is tried in order to set up the optimum ultrasonic test condition. Ultrasonic image data obtained were confirmed and compared by optical microscope and SAM(Scanning Acoustic Microscope) observation of the spot-weld cross section. The results show that the nugget diameter can be measured with the accuracy of 1.0mm, and voids included in nugget can be detected to $10{\mu}m$ extent with simplicity and accuracy. Finally, it was found that it is necessary to make a profound study of definite discrimination of corona bond from nugget and the approach of quantitative evaluation of nugget diameter by utilizing the various image processing techniques.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.06a
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• pp.969-970
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• 2008

• 대한핵의학회:학술대회논문집
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• 1966.11a
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• pp.96.2-96.2
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• 1966

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.6
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• pp.482-489
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• 2014

This paper suggests the new network scanning algorithm that makes use of measurement pilot of IEEE 802.11k. The purpose of suggesting this algorithm is to improve the existing network scanning schemes. After introducing new algorithm, this paper shows the difference of time property and energy property between former scanning schemes and new scheme with simulation results. Passive scan has a merit of low-power consumption but it takes too long time to fulfill whole scanning. On the contrary, an advantage of active scan is speed but it consumes more battery power than passive scan. By using measurement pilot's smaller interval than beacon interval, the suggested algorithm can consume less power than active scan does, and also make shorter scanning delay than passive scan does.

• The Journal of Korean Society for Radiation Therapy
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• v.20 no.1
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• pp.17-23
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• 2008

Purpose: Cone-beam CT using linear accelerator attached to on-board imager is a image guided therapy equipment. Because it is to check the patient's set-up error, correction, organ and target movement. but imaging dose should be cause of the secondary cancer when taking a image. The aim of this study is investigation of appropriate cone beam CT scan mode to compare and estimate the image quality and skin dose. Materials and Methods: Measurement by Thermoluminescence dosimeter (TLD-100, Harshaw) with using the Rando phantom are placed on each eight sites in seperately H&N, thoracic, abdominal section. each 4 methods of scan modes of are measured the for skin dose in three time. Subsequently, obtained average value. Following image quality QA protocol of equipment manufacturers using the catphan 504 phantom, image quality of each scan mode is compared and analyzed. Results: The results of the measured skin dose are described in here. The skin dose of Head & Neck are measured mode A: 8.96 cGy, mode B: 4.59 cGy, mode C: 3.46 cGy mode D: 1.76 cGy and thoracic mode A: 9.42 cGy, mode B: 4.58 cGy, mode C: 3.65 cGy, mode D: 1.85 cGy, and abdominal mode A: 9.97 cGy, mode B: 5.12 cGy, mode C: 4.03 cGy, mode D: 2.21 cGy. Approximately, dose of mode B are reduced 50%, mode C are reduced 60%, mode D are reduced 80% a point of reference dose of mode A. the results of analyzed HU reproducibility, low contrast resolution, spatial resolution (high contrast resolution), HU uniformity in evaluation item of image quality are within the tolerance value by recommended equipment manufacturer in all scan mode. Conclusion: Maintaining the image quality as well as reducing the image dose are very important in cone beam CT. In the result of this study, we are considered when to take mode A when interested in soft tissue. And we are considered to take mode D when interested in bone scan and we are considered to take mode B, C when standard scan. Increasing secondary cancer risk due to cone beam CT scan should be reduced by low mAs technique.