• Proceedings of the Korean Nuclear Society Conference
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• 1997.05a
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• pp.166-171
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• 1997

LPMS(Loose Part Monitoring System)는 원자로 및 냉각재계통내에서 발생하는 금속파편의 검출 및 분석을 위하여 사용되는 진단 장비이다. 본 논문에서는 RPV(Reactor Pressure Vessel)의 상부헤드(closure head)와 하부헤드(lower head)에서의 금속파편의 충격위치를 평가하는 LPMS를 위한 새로운 기법을 제안하고, Mock-up에서의 실험을 통하여 그 효용성을 검증하였다. 즉, 수정된 원교차법을 제안하고, 이를 반구로 모델링된 RPV의 상ㆍ하부헤드에 존재하는 금속파편의 위치평가에 적용하므로써 정확한 충격위치를 찾을 수 있음을 보였다. 이들 결과는 충격물질의 질량이나 에너지를 계산하는데 정확한 정보를 제공해 줄 수가 있다.

• Proceedings of the Korean Magnestics Society Conference
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• 2007.05a
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• pp.253.2-253.2
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• 2007

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 2004.08a
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• pp.160-163
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• 2004

• International Journal of Fluid Machinery and Systems
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• v.9 no.2
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• pp.107-118
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• 2016

This paper focuses on the single stage and multistage performance characteristics of centrifugal mixed flow submersible borewell pump. This study reveals that the performance of single stage pump is higher than that of multistage pumps. The head, input power and efficiency of single stage pump are higher than the per stage head, per stage input power and efficiency of multistage pumps. This study is divided into three parts. In the first part, five prototype pumps were made in single stage and multistage construction and the performance tests were conducted. In the second part, numerical validation has been done for different turbulence models and grid sizes. k-Omega SST model has been selected for the performance simulation and was validated with the performance of the test pump with static pressure tappings. In the third part, single and three stage pump performance were simulated numerically and compared with experimental results. The detailed analysis of pressure and velocity distributions reveals the difference in performance of single and three stage pump, due to non-uniform flow and difference in averaged flow velocities at the subsequent impeller inlets except the 1st stage impeller inlet.

• Journal of the Society of Naval Architects of Korea
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• v.37 no.1
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• pp.91-98
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• 2000

The present paper is Part 2 of three-part paper for an experimental study on breaking waves generated by a submerged cylinder. Measurements of velocity and head loss profiles at the wakes of cylinder and breaker as well as the turbulent intensities in breaking region were made to elucidate the viscous aspects of breaking waves. Their mutual correlation is also investigated. It is found that the head loss profile is an excellent indicator of the strength and extent of breaker. Very high turbulent intensities measured at and just downstream of the breaker indicate the consequence of energy transfer of wave breaking into turbulence.

• Journal of the Korean Society for Railway
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• v.2 no.2
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• pp.21-30
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• 1999

This study proposes the analysis and evaluation method of time series ultrasonic signal using the phase space-frequency domain. Features extracted from time series signal analyze quantitatively characteristics of weld defects. For this purpose, analysis objectives in this study are features of time domain and frequency domain. Trajectory changes in the attractor indicated a substantial difference in fractal characteristics resulting from distance shifts such as parts of head and flange even though the types of defects are identified. These differences in characteristics of weld defects enables the evaluation of unique characteristics of defects in the weld zone. In quantitative fractal feature extraction, feature values of 3.848 in the case of part of head(crack) and 4.102 in the case of part of web(side hole) and 3.711 in the case of part of flange(crack) were proposed on the basis of fractal dimension. Proposed phase space-frequency domain method in this study can integrity evaluation for defect signals of rail weld zone such as side hole and crack.

• Nuclear Engineering and Technology
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• v.52 no.4
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• pp.776-783
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• 2020

As the refueling of a sodium-cooled fast reactor is conducted by rotating part of the reactor head without opening it, the monitoring of existing obstacles that can disturb the rotation of the reactor head is one of the most important issues. This paper deals with the ultrasonic ranging technique that directly monitors the existence of possible obstacles located in a lateral gap between the upper internal structure and the reactor core in a prototype generation IV sodium-cooled fast reactor (PGSFR). A 10 m long plate-type ultrasonic waveguide sensor, whose feasibility has been successfully demonstrated through preliminary tests, was employed for the ultrasonic ranging technique. The design of the sensor's wave radiating section was modified to improve the radiation performance, and the radiated field was investigated through beam profile measurements. A test facility simulating the lower part of the upper internal structure and the upper part of the reactor core with the same shapes and sizes as those in the PGSFR was newly constructed. Several under-water performance tests were then carried out at room temperature to investigate the applicability of the developed ranging technique using the plate-type ultrasonic waveguide sensor with the actual geometry of the PGSFR's internal structures.

• PNF and Movement
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• v.21 no.2
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• pp.265-272
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• 2023

Purpose: The purpose of this study was to investigate tactile sense perception of the lower extremities according to physical function in children with spastic cerebral palsy. Methods: This study was conducted on 15 children diagnosed with spastic cerebral palsy. Physical function measurement items included dynamic balance ability, gross motor function level, and lower extremity ankle spasticity. The lower extremity tactile sensation uses a monofilament to measure the sole of the first metatarsal head, the sole of the fifth metatarsal head, the heel, the anterior part of the shin midway between the patella and the ankle joint, the kneecap, the upper anterior iliac spine, and the knee. A total of six measurements were taken in the mid-femoral region of the bone. Spearman correlation analysis was performed to determine the degree of body function and lower extremity tactile perception. Results: As the physical function of children with spastic cerebral palsy deteriorated, there was a decrease in tactile sensation in the thigh area corresponding to the proximal lower extremity. (p <.05). Conclusion: Children with spastic cerebral palsy and poor physical function have sensory loss not only in the distal part but also in the proximal part, so a treatment approach that recognizes and improves it is necessary.

• The Korean Journal of Zoology
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• v.29 no.2
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• pp.121-140
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• 1986

The spermiogenesis of Cipangopaludina chinensis malleata began with the changes of nucleus and cytoplasm. The chromatin in the nucleus began to stack and condense around perinuclear envelope. Axonema (doublet microtubules of 9+2) appeared in the cytoplasm. After this process, the cytoplasm was protruded and the bell-shaped nucleus was located on protruding part of it. The electron dense masses were distributed throughout cytoplasm and lysed or secreted by exocytosis of lysosomal vacuoles. Especially, some mitochondria were migrated by the doublet microtubules of axonema toward nucleus. The axoneme was enclosed by electron dense materials after exocytosis of unnecessary materials for the tail formation. The electron dense masses were released and migrated into the each part through microtubules or axonemal doublet microtubules as the granular particles. These granular particles were containing glycogen. Ultimately, the condensed head developed into helical and neck region into cylindrical shape respectively. The mitochondria which have regular lamellar layers at cross axis became to middle piece, and then spermatozoon was completely matured. Thus, these phenomena showed special processes in spermiogenesis, those were as follows; chromatin in the head was condensed, the head was changed into helical shape, and cytoplasmic materials are migrated and transferred into the each part in the tail by mitochondria and microtubules.

• Imaging Science in Dentistry
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• v.37 no.2
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• pp.65-68
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• 2007

Purpose: To compare the leakage and scattered radiation from hand-held dental X-ray unit with radiation from fixed dental X-ray unit. Materials and Methods: For evaluation we used one hand-held dental X-ray unit and Oramatic 558 (Trophy Radiologie, France), a fixed dental X-ray unit. Doses were measured with Unfors Multi-O-Meter 512L at the right and left hand levels of X-ray tube head part for the scattered and leakage radiation when human skull DXTTR III was exposed to both dental X-ray units. And for the leakage radiation only, doses were measured at the immediately right, left, superior and posterior side of the tube head part when air was exposed. Exposure parameters of handheld dental X-ray unit were 70 kVp, 3 mA, 0.1 second, and of fixed X-ray unit 70 kVp, 8 mA, 0.45 second. Results: The mean dose at the hand level when human skull DXTTR III was exposed with portable X-ray unit $6.39{\mu}Gy$, and the mean dose with fixed X-ray unit $3.03{\mu}Gy$ (p<0.001). The mean dose at the immediate side of the tube head part when air was exposed with portable X-ray unit was $2.97{\mu}Gy$ and with fixed X-ray unit the mean dose was $0.68{\mu}Gy$ (p<0.01). Conclusions: The leakage and scattered radiation from hand-held dental radiography was greater than from fixed dental radiography.