• Investigative Magnetic Resonance Imaging
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• v.5 no.2
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• pp.116-122
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• 2001

Purpose : To find sensitivity of MRI imaging methods to slow flow phantom study was performed with conventional Spin-Echo, gradient echo based Phase Contrast, fast GRASS, and heavily T2-weighted Fast Spin Echo pulse sequences. Materials and Methods : A siphon driven flow phantom was constructed with a ventriculo-peritoneal shunt catheter and a GE phantom to achieve continuous variable flow. Four different pulse sequences including Spin-Echo, Phase Contrast, GRASS and Heavily T2-weighted Fast Spin Echo were evaluated to depict slow flow in the range from 0.08 ml/min to 1.7 ml/min and to compare signal intensities between static fluid and flowing fluid. Results : In the slow flow above 0.17 ml/min conventional Spin-Echo showed superior apparent contrast between static and flowing fluid while GRASS was more sensitive to the very slow flow below 0.17 ml/mim. It was not accurate to calculate flow and velocity below 0.1 ml/min with a modified PC imaging. Conclusion : Four different MR pulse sequences demonstrated different sensitivity to the range of slow flow from 0.08 ml/min to 1.7 ml/min. This finding may be clinically useful to measure CSF shunt flow or detecting CSF collection and thrombosis.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.9
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• pp.143-147
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• 2016

Recently, digital tomosynthesis system (DTS) has been developed to reduce overlap using conventional X-ray and to overcome high patient dose problem using computed tomography (CT). The purpose of this study was to develop image reconstruction algorithm and to evaluate image characteristics and dose with chest digital tomosynthesis (CDT) system. Image reconstruction was used for filtered back-projection (FBP) methods and system geometry was constructed ${\pm}10^{\circ}$, ${\pm}15^{\circ}$, ${\pm}20^{\circ}$, and ${\pm}30^{\circ}$ angular range for acquiring phantom images. Image characteristics carried out root mean square error (RMSE) and signal difference-to-noise ratio (SDNR), and dose is evaluated effective dose with ${\pm}20^{\circ}$ angular range. According to the results, the phantom image with slice thickness filter has superb RMSE and SDNR, and effective dose was 0.166 mSv. In conclusion, we demonstrated usefulness of developed CDT image reconstruction algorithm and we constructed CDT basic output data with measuring effective dose.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.12 no.2
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• pp.19-28
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• 2009

Echinosophora koreensis (Nakai) Nakai (Leguminosae) is one of the threatened plant growing in secondary forest with sparse pine forest. The aim of this research is to investigate current status in a habitat of E. koreensis population, and obtain knowledge for conservation of the population. The flora of vascular plants and vegetation were investigated in the habitat E. koreensis in Mt. Bibong, Gangweon Province. Investigation were carried out in August 2003 and May 2008 at the three different habitats. As a result, a total 40 species 7 varieties of 28 family were recorded in whole area. The vegetation of investigated area was typical northern-temperate Pinus forest, humidity of soil was low and located at a slope area. These investigated area is very important for conservation of rare plant, E. koreensis. Therefore, sustainable conservation strategy such as designation of conservation area should be prepared urgently by the results of long-term monitoring studies.

• The Journal of the Korea Contents Association
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• v.16 no.3
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• pp.219-231
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• 2016

$^{99m}Tc$-DMSA planar scan that can analyze the functions of kidney quantitatively provides less information on a lesion than tomography scanning. Therefore, this study applied a high sensitivity all-purpose collimator that is sensitive to photonic signals to $^{99m}Tc$-DMSA and carried out a clinical scan with single photon emission computed tomography (SPECT). And diagnostic accuracy and time requirement of were analyzed to know the clinical usefulness of the applied scanning method. 10 subjects were intravenously injected with radiopharmaceutical product (1.0-1.2 MBq/kg) and scanned by a gamma camera with planar scanner (high resolution (HR)-mode, $256{\times}256$, 50 kcts/view, 4 image) and SPECT (HR / high sensitive (HS)-mode, $128{\times}128$, step and shoot, $180^{\circ}$, variable sec/angle, total 64 frame, OSEM reconstruction), respectively. The collected data was compared with an analysis program. The results showed that HS-mode SPECT detected total counts 1.8-5.6 times more than planar scan. Relative renal function evaluated based on the counts was not significantly different by two scanning methods (p=0.96) and it turned out that test time was shortened by 39% when HS-mode SPECT was used. Therefore, SPECT using HR, HS-mode collimator could analyze renal function more quantitatively than using planar scan and the former could diagnose the location information of a lesion more accurately than the latter as well as shortened test time requirement, which demonstrated the clinical usefulness of $^{99m}Tc$-DMSA renal SPECT using high sensitivity all purpose collimator.

• Progress in Medical Physics
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• v.13 no.2
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• pp.85-89
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• 2002

We authors developed a new small-size birdcage RF coil for animal MR images. And we compared signal-to-noise ratio (SNR) of the new small coil with a conventional knee coil. The dimension of the low-pass type birdcage coil with 12 elements at 37 MRI system are 13 cm outer diameter, 12 cm inner diameter and 20 cm length. For each element, the width of copper tape is 0.05 mm, thickness is 8 mm and length is 20 cm. The small birdcage coil with 12 elements exhibited 7 resonance modes. The isolation of the quadrature channel could be achieved more than 20 ㏈. The coil quality factor (Q value) was 98.6. The SNR of the animal coil was 243.2 on the average and was about twice as high as the conventional knee coil. The present study successfully demonstrated that the small birdcage coil could provide high quality animal MR images with the improved SNR. Therefore, it is expected that the small birdcage coil could be used in the clinical diagnosis and research studies for veterinary medicine in the near future.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.3
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• pp.181-189
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• 2016

An analytical model was developed by Sim to estimate the two-phase damping ratio for upward two-phase flow perpendicular to horizontal tube bundles. The parameters of two-phase flow, such as void fraction and pressure loss evaluated in the model, were calculated based on existing experimental formulations. However, it is necessary to implement a few improvements in the formulations for the case of tube bundles. For the purpose of the improved formulation, we need more information about the two-phase parameters, which can be found through experimental test. An experiment is performed with a typical normal square array of cylinders subjected to the two-phase flow of air-water in the tube bundles, to calculate the two-phase Euler number and the two-phase friction multiplier. The pitch-to-diameter ratio is 1.35 and the diameter of cylinder is 18mm. Pressure loss along the flow direction in the tube bundles is measured with a pressure transducer and data acquisition system to calculate the two-phase Euler number and the two-phase friction multiplier. The void fraction model by Feenstra et al. is used to estimate the void fraction of the two-phase flow in tube bundles. The experimental results of the two phase friction multiplier and two-phase Euler number for homogeneous and non-homogeneous two-phase flows are compared and evaluated against the analytical results given by Sim's model.

• Investigative Magnetic Resonance Imaging
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• v.4 no.2
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• pp.113-119
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• 2000

Purpose : To know the possibility of clinical application of MRI using oxygen inhalation as a perfusion MRI Materials and methods : Two healthy volunteers and three patients of one moyamoya disease, one acute infarction and one meningioma were studied using a 1.5 Tesla MRI unit. Oxygen (15 liters/min) mixed with room air was given using face mask from 8 second to 35 second during the study. Images were acquired 25 times (scan time per study were 1.6 seconds) using susceptibility contrast EPI (echo planar image) sequence. Difference maps were acquired by early (study 12-18), and late (study 19-25) O2 inhalation image groups minus pre-O2 inhalation image group (study 3-9) with a Z-score of 0.7-1.0 using VB31C program of Magneton Vision. The resulting perfusion images were created by superimposition of difference maps on corresponding T1 weighted anatomic images. On moyamoya patient, similar perfusion images were acquired after Gd-DTPA injection, and compared with O2 inhalation perfusion images. Results ; The author can get the perfusion images of the brain by oxygen inhalation with susceptibility contrast EPI sequence at the volunteers, and the patient of moyomoya disease, acute infarction and meningioma. On moyamoya patient, perfusion images with O2 inhalation are similar with perfusion images by Gd-DTPA injection. Conclusion 1 This study has demonstrated that the susceptibility contrast EPI by oxygen inhalation can be used as the clinically useful perfusion MRI technique

• The Korean Journal of Mycology
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• v.19 no.4
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• pp.266-275
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• 1991

The gene CDC70 encoding the${\alpha}-subunit$ of G protein has been known to be a component involved in mating pheromone signalling in the yeast, Saccharomyces cerevisiae. To isolate mutations of the genes involved in the signal transduction, Saccharomyces cerevisiae the strain bearing the cdc70-5 mutation was mutagenized to be forced to recover the ability of colony-formation at restrictive temperature, which means the new mutation can suppress the temperature sensitivity of the cdc70-5 phenotypes. Among these suppressors, $sir^-$ and $mat{\alpha}2^{-}$ mutations are excluded because of no relationship to signal transducer. And the selected suppressors were analyzed for the linkage relationships by the tetrad analysis. Out of fifteen suppressors isolated, twelve were classified into four linkage groups, designated as sga1, sga2, sga3, sga4 by the tetrad analysis. The other three genes were determined for the linkage.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.4C
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• pp.341-348
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• 2009

In this paper, we propose a grouping technique for the SDD(Synchronous Digital Duplexing) based on OFDMA(Orthogonal Frequency Division Multiple Access). The SDD has advantages of increasing data efficiency and flexibility of resource since SDD can transmit uplink signals and downlink signals simultaneously by using mutual time information and mutual channel information, obtained during mutual ranging process. However, the SDD has a disadvantage of requiring additional CS to maintain orthogonality of OFDMA symbols when the sum of mutual time difference and mutual channel length between AP(access point) and SS(subscriber station) or among SSs are larger than CP length. In order to minimize the length of CS for the case of requiring additional CS in SDD, we proposes a grouping technique which controls transmit timing and receive timing of AP and SS in a cell by classifying them into groups. Performances of the proposed grouping technique are evaluated by computer simulation.

• Journal of the Korean Society for Marine Environment & Energy
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• v.19 no.2
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• pp.137-143
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• 2016

The sedimentary environment and sediment were surveyed at the West-Northern site of Chagwi-do nearby Jeju Island for the design of the embedded suction anchor system of 10 MW-class floating wave-offshore wind hybrid power generation system. According to the classification scheme of Chough et al.[2002], the echo type of the seismic profiles using the chirp III was classified. As a results, the center and west-northern area of survey site were proved to be type I-3 where subbottom layer with thickness 5~15 m exists under the flat seafloor. On the other hands, the east-southern area were regarded to be type I-1, I-2 and III-1 where seafloor reflection is much stronger than type I-3. Also, the physical tests (unit weight, moisture content, grain size, liquid limit, specific gravity) were performed with samples taken from 8 fixed locations. It is found that the sand (SP), the sand blended with silt (SM) and the mixture of SP-SM are distributed uniformly on the survey area.