• Progress in Medical Physics
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• v.12 no.1
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• pp.51-58
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• 2001

Synchrotron radiation (SR) has several advantages over convetional x-rays, including its phase, collimation, and high flux. A synchrotron radiation beamline 5C1 at Pohang Light Source (PLS) was recently built for imaging applications. We have shown that a SR imaging system is useful in imaging microscopic structures. SR with broad-band energy spectrum were adjusted to an object by Si wafers and their energy were approximately ranging from 6 keV to 30 keV. SR were passed through an object and finally transformed into visible lights by CdWO$_4$ scintillator screen. The visible lights which were reflected at an angle of 90 degrees by gold plated mirror were detected by a CCD camera and the image data were acquired using image acquisition system. A high-resolution phantom, capacitor, adult tooth, child tooth, cancerous breast tissue, and mouse lumbar vertebra were imaged with SR imaging system. The Objects were rotated within the field of view of the CCD detector, and their projection image data were obtained at 250 steps over 180 degrees rotation. Image reconstructions were carried out in a PC by using IDLTM(Research systems, Inc., US) program. The spatial resolution of the images acquired by the SR imaging system was measured with a high-resolution chart manufactured for several micrometer resolution. The specimens were also imaged with conventional x-ray radiography system to compare the image quality of radiography obtained with the SR imaging system. The results showed more structural details and high contrast images with SR imaging system than conventional x-ray radiography system. The SR imaging system may have a potential for imaging in biological researches, material applications, and clinical radiography.

• Journal of Embryo Transfer
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• v.20 no.3
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• pp.271-277
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• 2005

This study was undertaken to determine the normal appearance of the postpartum uterine involution. Postpartum changes in uterine shape, architecture, echogenicity and diameter were monitored with ultrasonography in 8 Cocker spaniel bitches. The excretory period of vaginal discharges in 8 normal bitches of uterine involution was finished completely at 23.20$\pm$2.77 days (Mean$\pm$SD) postpartum. The short axis shape of the uterus was varied from polygonal to circular. This lasted until 1600$\pm$2.12 days Postpartum, during which time the short axis uterine shape gradually changed to circular. Also, the long axis shape of the uterus was created a beaded appearance of the horns until 25.60$\pm$2.51 days postpartum. The uterine diameter was decreased not only in the placental sites from 24.20$\pm$2.06mm at 1 day to 13.18$\pm$0.84mm at 7 days postpartum, but also in the interplacental sites 14.26$\pm$2.22mm at 1 day, 9.81$\pm$0.7mm at 7 days postpartum. There was a general trend of decreasing uterine diameter, which occurred more rapidly at the placental sites. In conclusion, normal postpartum uterine involution in Cocker spainel bitches appeared to be completed around 68 days postpartum by gross findings such as vaginal discharges, and by ultrasongraphic findings, uterine shape and echogenicity.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.21 no.2
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• pp.131-136
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• 1985

The calculation of the resulting fluid motion is an important problem of ship hydrodynamics. For a partially immersed body the condition of constant pressure at the free surface can be linearized. The resulting linear boundary-value problem for the velocity potential is the Neumann-Kelvin problem. The two-dimensional Neumann-Kelvin problem is studied for the half-immersed circular cylinder by Ursell. Maruo introduced a slender body approach to simplify the Neumann-Kelvin problem in such a way that the integral equation which determines the singularity distribution over the hull surface can be solved by a marching procedure of step by step integration starting at bow. In the present pater for the two-dimensional Neumann-Kelvin problem, it has been suggested that any solution of the problem must have singularities in the corners between the body surface and free surface. There can be infinitely many solutions depending on the singularities in the coroners.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.17 no.5
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• pp.423-435
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• 1984

The reproductive cycle of the small filefish, Rudarius ercodes was investigated based on the annual variations of gonadosomatic index(GSI) and hepatosomatic index(HSI) by electronic and photic microscophy. The specimens used were collected at the coastal area of Benden island, Sizuokagen, Japan, from September 1982 to August 1983. GSI began to increase from March, starting season of longer daylength and higher water temperature, and reached the maximum value between June and August. It began to decrease from September with the lowest value appearing between November and February without any evident variation. The annual variations of HSI were not distinct in male filefish and were negatively related to GSI in female : HSI decreased in the summer season when the ovary was getting mature and reached the maximum in the winter season when the ovary was getting retrogressive. The ovary consisted of a pair of saccular structure with numerous ovarian sacs branched toward the median cavity. Oogonia divided and proliferated along the germinal epithelium of the ovarian sac. Young oocytes with basophile cytoplasm showed several scattering nucleoli along the nuclear membrane. when the oocytes growing to about 300 ${\mu}m$, nuclear membrane to disappear with nucleus migrating toward the animal pole. The regions of protoplasm were extremely confined within the animal hemisphere in which most of cytoplasms were filled with yolk materials and oil drops. After ovulation, residual follicles and growing oocytes remaining in the ovarian sacs degenerated. But perinucleatic young oocytes without follicles formed were not degenerated, and growing continuously still in the next year. Mitochondria and endoplasmic reticula in the cytoplasm remarkably increased with oocytes maturing and yolk accumulating. Those were considered to be functionally related to the yolk accumulation. Five or six layers of possible vitellogenin, oval-shaped disc structures with high electron density, appeared in the apex of follicular processes stretching to the microvilli pits of mature oocytes. Testis consisting of a pair of lobular structures in the right and left were united in the posterior seminal vesicle, Cortex of testis was composed of several seminiferous tubules, and medulla consisting of many sperm ducts connected with tubules. Steroid hormone-secreting cells with numerous endoplasmic reticula and large mitochondria of well developed cristae were recognized in the interstitial cells of the growing testis. Axial filament of spermatozoon invaginated deeply in the central cavity of the nucleus and the head formed U-shape with acrosome severely lacking, mitochondria formed large globular paranuclei at the posterior head, and microtubular axoneme of the tail represented 9+9+2 type. The annual reproductive cycles could be divided into five successive stages : growth(March to July), maturation(May to September), Spawning(mid May to early October) and resting stages(October to February). The spawning peak occurred from June to August.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.44 no.3
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• pp.407-416
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• 2024

Over the past 20 years, there has been a rapid increase in the number and size of subway stations and underground structures worldwide, and the importance of safety for subway users has also continuously grown. Subway stations, due to their structural characteristics, have limited visibility and escape routes in disaster situations, posing a high risk of human casualties and economic losses. Therefore, an analysis of disaster vulnerabilities is essential not only for existing subway systems but also for deep underground facilities like GTX. This paper presents a case study applying a betweenness centrality-based disaster vulnerability analysis framework to the case of Gwanggyo Central Station. The analysis of Gwanggyo Central Station's base model and various disaster scenarios revealed that the betweenness centrality distribution is symmetrical, following the symmetrical spatial structure of the station, with high centrality concentrated in the central areas of basement levels one and two. These areas exhibited values more than 220% above the average, indicating a high likelihood of bottleneck phenomena during evacuation in disaster situations. To mitigate this vulnerability, scenarios were proposed to distribute evacuation flows concentrated in the central areas, enhancing the usability of peripheral areas as evacuation routes by connecting staircases continuously. This modification, when considered, showed a decrease in centrality concentration, confirming that the proposed addition of evacuation paths could effectively contribute to dispersing the flow of evacuation in Gwanggyo Central Station. This case study demonstrates the effectiveness of the proposed framework for assessing evacuation vulnerability in enhancing subway station user safety and can be effectively applied in disaster response and management plans for major underground facilities.

• The Korean Journal of Nuclear Medicine
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• v.39 no.6
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• pp.413-420
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• 2005

Purpose: Neuroreceptor PET studies require 60-120 minutes to complete and head motion of the subject during the PET scan increases the uncertainty in measured activity. In this study, we investigated the effects of the data-driven head mutton correction on the evaluation of endogenous dopamine release (DAR) in the striatum during the motor task which might have caused significant head motion artifact. Materials and Methods: $[^{11}C]raclopride$ PET scans on 4 normal volunteers acquired with bolus plus constant infusion protocol were retrospectively analyzed. Following the 50 min resting period, the participants played a video game with a monetary reward for 40 min. Dynamic frames acquired during the equilibrium condition (pre-task: 30-50 min, task: 70-90 min, post-task: 110-120 min) were realigned to the first frame in pre-task condition. Intra-condition registrations between the frames were performed, and average image for each condition was created and registered to the pre-task image (inter-condition registration). Pre-task PET image was then co-registered to own MRI of each participant and transformation parameters were reapplied to the others. Volumes of interest (VOI) for dorsal putamen (PU) and caudate (CA), ventral striatum (VS), and cerebellum were defined on the MRI. Binding potential (BP) was measured and DAR was calculated as the percent change of BP during and after the task. SPM analyses on the BP parametric images were also performed to explore the regional difference in the effects of head motion on BP and DAR estimation. Results: Changes in position and orientation of the striatum during the PET scans were observed before the head motion correction. BP values at pre-task condition were not changed significantly after the intra-condition registration. However, the BP values during and after the task and DAR were significantly changed after the correction. SPM analysis also showed that the extent and significance of the BP differences were significantly changed by the head motion correction and such changes were prominent in periphery of the striatum. Conclusion: The results suggest that misalignment of MRI-based VOI and the striatum in PET images and incorrect DAR estimation due to the head motion during the PET activation study were significant, but could be remedied by the data-driven head motion correction.

• 한국지구물리탐사학회:학술대회논문집
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• 2002.09a
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• pp.139-162
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• 2002

Since weak zones or geological lineaments are likely to be eroded, weak zones may develop beneath rivers, and a careful evaluation of ground condition is important to construct structures passing through a river. Dc resistivity surveys, however, have seldomly applied to the investigation of water-covered area, possibly because of difficulties in data aquisition and interpretation. The data aquisition having high quality may be the most important factor, and is more difficult than that in land survey, due to the water layer overlying the underground structure to be imaged. Through the numerical modeling and the analysis of case histories, we studied the method of resistivity survey at the water-covered area, starting from the characteristics of measured data, via data acquisition method, to the interpretation method. We unfolded our discussion according to the installed locations of electrodes, ie., floating them on the water surface, and installing at the water bottom, since the methods of data acquisition and interpretation vary depending on the electrode location. Through this study, we could confirm that the dc resistivity method can provide the fairly reasonable subsurface images. It was also shown that installing electrodes at the water bottom can give the subsurface image with much higher resolution than floating them on the water surface. Since the data acquired at the water-covered area have much lower sensitivity to the underground structure than those at the land, and can be contaminated by the higher noise, such as streaming potential, it would be very important to select the acquisition method and electrode array being able to provide the higher signal-to-noise ratio data as well as the high resolving power. The method installing electrodes at the water bottom is suitable to the detailed survey because of much higher resolving power, whereas the method floating them, especially streamer dc resistivity survey, is to the reconnaissance survey owing of very high speed of field work.