• The Korean Journal of Nuclear Medicine Technology
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• v.17 no.2
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• pp.72-77
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• 2013

Purpose: Whole-body PET using radiopharmaceutical is one of the imaging study methods for physiological changes of body. High specificity of the PET-CT examination is used to detect an early stages of cancer and metastatic cancer by imaging a physiological changes. During the imaging process, PET image has been characterized by a relatively low image quality due to its low sensitivity and the acquisition of random and scatter coincidences as well as patients figure. Therefore, the image quality as the changes of the acquisition times of patient weight was evaluated in this study. Materials and Methods: Thirty patients who presented to our hospital were enrolled. They were divided to normal, overweight, and obese group using BMI index, respectively. The patients with a liver disease and diabetes were excluded. $^{18}F-FDG$ was administered to the patients as 5.2 MBq per kg. After an hour from an injection, image acquisition was obtained as List mode in a part of liver in 1 bed. SNR (signal-to-noise ratio) of each groups acquisition times were confirmed from the calculated radiation counts and random fractions. The statistical significance of three groups was confirmed through one-way ANOVA test. On the basis of the counts of 2 minutes on normal group, the SNR of overweight group and obese group were compared. Results: The SNR were increased with loger aquisition time in 3 groups. In the condition of same acquisition time, the SNR had a statistical significance (P<0.05). The SNR were decreased to the normal, overweight, and obese, respectively. Liver activity had no significance difference on each group and RF had the significance differences (P<0.05). On the basis of the counts of 2 minutes on normal group, there were no statistical significance in a three minute acquisitions of overweight group and two minute acquisitions of obese group (P=0.150). Conclusion: In this study, the administrated amount of radiation dose did not adjust as the change of the patients weight. Increasing the acquisition time when the administration of the same amount of dose was able to get a good result of SNR. When the Based 2 minute on normal group, if overweight and obese case the increased acquisition time of 3 minute was able to obtain a similar SNR. On the basis of the normal group, the acquisition times of overweight and obese group were increased to 3 minutes per bed and the SNR were similar to the normal group.

• Progress in Medical Physics
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• v.21 no.2
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• pp.232-237
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• 2010

The shielding materials designed for replacement of lead equivalent materials for lighter apron than that of lead in diagnostic photon beams. The absorption characteristics of elements were applied to investigate the lead free material for design the shielding materials through the 50 kVp to 110 kVp x-ray energy in interval of 20 kVp respectively. The idea focused to the effect of K-edge absorption of variable elements excluding the lead material for weight reduction. The designed shielding materials composited of Tin 34.1%, Antimon 33.8% and Iodine 26.8% and Polyisoprene 5.3% gram weight account for 84 percent of weight of lead equivalent of 0.5 mm thickness. The size of lead-free shielder was $200{\times}200{\times}1.5\;mm^3$ and $3.2\;g/cm^3$ of density which is equivalent to 0.42 mm of Pb. The lead equivalent of 0.5 mm thickness generally used for shielding apron of diagnostic X rays which is transmitted 0.1% for 50 kVp, 0.9% for 70 kVp and 3.2% for 90 kVp and 4.8% for 110 kVp in experimental measurements. The experiment of transmittance for lead-free shielder has showed 0.3% for 50 kVp, 0.6% for 70 kVp, 2.0% for 90 kVp and 4.2% for 110 kVp within ${\pm}0.1%$. respectively. Using the attenuation coefficient of experiments for 0.5 mm Pb equivalent of lead-free materials showed 0.1%. 0.3%, 1.0% and 2.4%, respectively. Furthermore, the transmittance of lead-free shielder for scatter rays has showed the 2.4% in operation energy of 50 kVp and 5.9% in energy of 110 kVp against 2.4% and 5.1% for standard lead thickness within ${\pm}0.2%$ discrepancy, respectively. In this experiment shows the designed lead-free shielder is very effective for reduction the apron weight in diagnostic radiation fields.

• Computers and Concrete
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• v.22 no.3
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• pp.337-353
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• 2018

The present study focuses on examining the structural behaviour of steel-fibre-reinforced concrete (SFRC) beams under high rates of loading largely associated with impact problems. Fibres are added to the concrete mix to enhance ductility and energy absorption, which is important for impact-resistant design. A simple, yet practical non-linear finite-element analysis (NLFEA) model was used in the present study. Experimental static and impact tests were also carried out on beams spanning 1.3 meter with weights dropped from heights of 1.5 m and 2.5 m, respectively. The numerical model realistically describes the fully-brittle tensile behaviour of plain concrete as well as the contribution of steel fibres to the post-cracking response (the latter was allowed for by conveniently adjusting the constitutive relations for plain concrete, mainly in uniaxial tension). Suitable material relations (describing compression, tension and shear) were selected for SFRC and incorporated into ABAQUS software Brittle Cracking concrete model. A more complex model (i.e., the Damaged Plasticity concrete model in ABAQUS) was also considered and it was found that the seemingly simple (but fundamental) Brittle Cracking model yielded reliable results. Published data obtained from drop-weight experimental tests on RC and SFRC beams indicates that there is an increase in the maximum load recorded (compared to the corresponding static one) and a reduction in the portion of the beam span reacting to the impact load. However, there is considerable scatter and the specimens were often tested to complete destruction and thus yielding post-failure characteristics of little design value and making it difficult to pinpoint the actual load-carrying capacity and identify the associated true ultimate limit state (ULS). To address this, dynamic NLFEA was employed and the impact load applied was reduced gradually and applied in pulses to pinpoint the actual failure point. Different case studies were considered covering impact loading responses at both the material and structural levels as well as comparisons between RC and SFRC specimens. Steel fibres were found to increase the load-carrying capacity and deformability by offering better control over the cracking process concrete undergoes and allowing the impact energy to be absorbed more effectively compared to conventional RC members. This is useful for impact-resistant design of SFRC beams.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.3
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• pp.671-678
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• 2021

In a previous study, technology protection levels were set on a qualitative basis. That study lacked quantitative standards, so here, we conduct a study to complement the previous study and to present an objective standard. This paper provides a method of setting a technical protection level that applies statistical analysis. To set the technology protection level, statistical analysis of six technical survey items is performed first. Second, the technical survey items are analyzed by AHP to quantify the opinions of experts in order to derive weights for each technical survey item. Finally, by using the normal distribution scatter map and median calculation method, the technology protection level is selected in three stages using the final detailed factor technology score reflecting the weight. The technology protection level methodology developed through this study is the first methodology with objectivity that can evaluate defense technology by level. If this methodology is applied in practice, it is believed that it will provide a scientific and quantitative technology value judgment criterion when setting the technology protection level in the future.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.50 no.spc1
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• pp.161-166
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• 2005

Objectives of this study were to select inbred lines which have a good eating quality and desirable segregates during inbreeding of waxy corn. The 64 inbred lines showed a large variance in their kernel shape and weight. 100-kernel weight, pericarp thickness, kernel length, kernel width, and kernel thickness ranged $11.7\~37.3g,\;11\~77{\mu}m,\;5.8\~9.6mm,\;6.5\~10.0mm$, and $4.1\~6.8mm$, respectively. The physicochemical analysis of 64 waxy corn inbred lines showed crude protein, crude fat, free sugar, and amylopectin content ranging $8.7\~15.8\%,\;2.3\~5.8\%,\;1.1\~11.0\%,\;and\;78.5\~93.8\%$, respectively. The texture property analysis of 64 inbred lines by texture analyzer showed a big difference. Gumminess, hardness, and chewiness of 64 inbred lines ranged $91\~383,\;181\~394,\;and\;73\~370$, respectively. The principal component analysis for 14 characteristics related to kernel quality showed that $73.1\%$ of the total variation could be attributed to the first five principal components. Biological meaning of the principal component was explained clearly by the correlation coefficient between principal components and characters. The first principal component appeared to correspond to small kernel and bad eating quality, The second principal component appeared to correspond to large kernel and good eating quality. The 64 inbred lines were classified into 8 groups by the cluster analysis using the first and second principal component. Among the groups, group VII and VIII included inbred lines with good eating quality that had thin pericarp thickness, low protein content, large kernel, and soft tenderness.

• The Korean Journal of Nuclear Medicine Technology
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• v.15 no.2
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• pp.36-40
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• 2011

Purpose: $^{18}F$-FDG injected dose to the patient is quite different between the recommended dose from manufacturer and the actual dose applied to each of hospitals. injection of inappropriate $^{18}F$-FDG dose may not only increase the exposed dose to patients but also reduce the image quality. we thus evaluated the proper $^{18}F$-FDG injected dose to decrease the exposed dose to patients considering the image quality. Materials And Methods: NEMA Nu2-1994 phantom was filled with $^{18}F$-FDG increasing hot cylinder radioactivity concentration to 1, 3, 5, 7, 9 MBq/kg based on the ratio of 4:1 between the hot cylinder and background activity. after completing the transmission scan using ct, emission scan was acquired in 3D mode for 2 minutes 30 seconds/bed. ROI was set up on hot cylinder and background radioactivity region. after measuring $SUV_{max}$ those regions, then analyzed SNR at the points. clinical experiment has been conducted the object of patients who have came to smc from november 2009 to august 2010, 97 patients without having a hepatic lesions were selected. ROI was set up in the liver and thigh area. after measuring $SUV_{max}$, the image quality was compared following the injected dose. Results: in phantom study, as the injected radioactivity concentration per unit mass was 1, 3, 5, 7, 9 MBq/kg, $SUV_{max}$ was 23.1, 24.1, 24.3, 22.8, 23.6 and SNR was shown 0.48, 0.54, 0.56, 0.55, 0.55. according to increment of the injected dose, $SUV_{max}$ and SNR was increased under 5 MBq/kg but they were decreased over 7 MBq/kg. in case of clinical experiment, as increased the injected radioactivity concentration per unit mass was 4.72, 5.34, 6.16, 7.41, 8.68 MBq/kg, $SUV_{max}$ was 2.68, 2.67, 2.26, 1.88, 1.95 and SNR was shown 0.52, 0.53, 0.46, 0.46, 0.44. if the injected dose exceeds 5 MBq/kg, showed a decrease pattern as phantom study. Conclusion: increasing $^{18}F$-FDG injected dose considered patient's body weight improve image quality within a certain range. if it exceeds the range, it can be reduced image quality due to random and scatter coincidences. this study indicates that the optimal injected dose was 5 MBq/kg per unit mass the injected radioactivity concentration in 3d wb pet/ct.