• Journal of Korean Academy of Oral and Maxillofacial Radiology
• /
• v.25 no.2
• /
• pp.375-387
• /
• 1995

The purpose of this study was to quantitatively evaluated experimental tooth root resorption for digital radiography. For this study, experimentally three root sites were used, and radiograms were taken with standardized apparatus. Digital imaging system were consisted of NEC PC-980l(computer), TRINITRON(monitor), SONY XC-711 CCD camera. The display monitor had a resolution of 512X512 pixels. The obtained results were as follows: 1. In the difference of the four X-ray film of the contrast correction, the contrast difference was one gray scale variation at mean value. 2. Viewing of the view box of the periapical radiographs, experimental tooth root resorption of the periapical area of the first premolar, middle of mesial surface of the first molar mesial root, middle of lingual surface of the first molar distal root were recognized by increased diameter. 3. On the analysis by histogram, the periapical area of the first premolar, the middle of mesial surface of the first molar mesial root were each recognized tooth root resorption of the 5,6,7 pixel, 2,4,5 pixel by increased diameter. 4. On the analysis by histogram, the middle of lingual surface of the first molar distal root was each recognized tooth root resorption of the none, 3,6 pixel by increased diameter.

• Korea-Australia Rheology Journal
• /
• v.17 no.4
• /
• pp.181-190
• /
• 2005

Rheological characterisation of flocculated kaolinite pulps has been undertaken to elucidate particle interactions underpinning the dewatering behaviour induced by flocculation with polyethylene oxide (PEO), anionic polyacrylamide (PAM A) and their blends. Shear yield stress $(\tau_y)$ analysis indicated that polymer mediated particle interactions were markedly amplified upon shear of PEG based pulps. In contrast, PAM A based pulps showed a significant decrease in yield values upon shear. Steady stress measurements analysed using a modified Ellis model indicated subtle differences between the respective linear viscoelastic plateaus of the pulps. Furthermore, modified shear thinning behaviour was evident in PEG based pulps. Estimation of elastic and viscous moduli (G', G') was made using dynamic stress analysis for comparison with values determined from vane measurements. Despite a noticeable difference in the magnitude of G' between the two methods, similar trends indicating sheared PEG-based pulps to be more elastic than PAM based pulps, were observed. Floc microstructural observations obtained in support of rheological properties indicate that PEG flocculant induces significantly more compact particle aggregation within the clay pulps under shear consistent with the yield stress data, in contrast to PAM A, or indeed unsheared PEG based pulps. Consequentially, sheared PEG based pulps show significantly improved dewatering behaviour. The implications of the results, potential benefits and drawbacks of flocculation with PEG and PAM A are discussed with respect to improvements in current dewatering processes used in the minerals industry.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 2002.03a
• /
• pp.93-100
• /
• 2002

In this paper, new simple model is developed to evaluate the variation of the magnitude and the phase contrast of force components with the development of excess pore pressure in backfill soil. Also, Newmark sliding block analysis is performed inputting the calculated total force from new model. The applicability of new simple model and Newmark sliding block model is verified from the analyses of 1g shaking table test results.

• Proceedings of the Korean Vacuum Society Conference
• /
• 1999.07a
• /
• pp.167-167
• /
• 1999

In laser ionisation mass spectrometry (LIMS) atoms and molecules which are desorbed from solid surfaces are ionised by an intense laser beam. The photoions which are created are then mass analysed in a time-of-flight mass spectromenter. In best situations, 10% of the ejected particles can be detected, giving the technique^g , pp b sensitivity. Since the ionisation and desorption steps are separated, matrix effects are minimised, in contrast to competitor techniques like SIMS, so quantitation is improved. The talk will illustrate the application of LIMS to basic studies in sputtering in Sr, Cu3Au(100) and Ni3Al(100) as well as ultratrace analysis of Zr in Si.

• KDI Journal of Economic Policy
• /
• v.46 no.2
• /
• pp.21-43
• /
• 2024

This paper provides a new theoretical rationale for public procurement for innovation (PPI), a unique policy encouraging public procurers to purchase innovative products. In contrast to existing studies that primarily emphasize the advantages of PPI, this paper takes a comprehensive approach, examining both the costs and risks associated with PPI, alongside its benefits. It finds a general condition under which PPI outperforms traditional public procurement. Under this condition, this paper demonstrates that PPI enhances social welfare by facilitating optimal risk-sharing between public procurers and the general economy. Additionally, it draws policy implications from a comparative analysis between the current PPI policy in Korea and an optimal PPI policy.

• Journal of radiological science and technology
• /
• v.39 no.1
• /
• pp.59-69
• /
• 2016

The objective of this study was to analyze the factors influencing integrated bolus peak timing in contrast-enhanced computed tomographic angiography (CTA) and to determine a method of calculating personal peak time. The optimal time was calculated by performing multiple linear regression analysis, after finding the influence factors through correlation analysis between integrated peak time of contrast medium and personal measured value by monitoring CTA scans. The radiation exposure dose in CTA was $716.53mGy{\cdot}cm$ and the radiation exposure dose in monitoring scan was 15.52 mGy (2 - 34 mGy). The results were statistically significant (p < .01). Regression analysis revealed, a -0.160 times decrease with a one-step increase in heart rate in male, and -0.004, -0.174, and 0.006 times decrease with one-step in DBP, heart rate, and blood sugar, respectively, in female. In a consistency test of peak time by calculating measured peak time and peak time by using the regression equation, the consistency was determined to be very high for male and female. This study could prevent unnecessary dose exposure by encouraging in clinic calculation of personal integrated peak time of contrast medium prior to examination.

• Journal of the Korean Society of Radiology
• /
• v.14 no.5
• /
• pp.669-676
• /
• 2020

The purpose of this study was to analyze the changes in the values of Hounsfield Unit (HU) according to the changes in monoenergy (keV) and dilution ratio of the contrast agent, using the spectral CT. Spectral CT was used as the testing device, while 20 cc syringe phantom was used to set a total of six dilution ratios of the contrast agent: 8:2, 7:3, 6:4, 5:5, 4:6, and 3:7. Here, the non-ionic iodine solution (350 mg/ml) was used as a contrast agent. The syringe axial image was reconstructed by adjusting the obtained data on nine MonoE levels; 40 keV, 45 keV, 50 keV, 55 keV, 60 keV, 65 keV, 70 keV, 75 keV, and 80 keV. The HU values were measured at the three points of the reconstructed syringe axial image. The measurements were taken 1,620 times in total. In the analysis of the HU values according to the changes in keV and dilution ratio of the contrast agent, the highest and lowest HU values were obtained from dilution ratio 8:2 and dilution ratio 3:7, respectively, across every MonoE in the comparison of HU according to dilution ratio per MonoE (p<0.05), while the highest and lowest HU values were obtained from 40 keV and 80 keV, respectively, across all dilution ratios in the comparison of HU according to MonoE per dilution ratio (p<0.05). For the correlation per each parameter, a negative correlation of -15.014 ± 0.298 was found for HU per keV (R²=0.519) and a negative correlation of -61.372 ± 3.608 was found for HU per dilution ratio (R²=0.152) (p<0.05). To conclude, an increase in keV or dilution ratio of the contrast agent was shown to decrease the HU, and the findings in this study are anticipated to serve as the basic data in the research of HU-related parameters in Spectral CT.

• Journal of the Korean Society of Radiology
• /
• v.5 no.1
• /
• pp.37-49
• /
• 2011

To examine the possible changes in the SNRs, CNRs, and ADC values for lumbar spines with metastasis based on the DW images before and after contrast agent injection taken from metastatic spinal cancer patients using a 1.5 T MR machine. The quantitative analysis revealed that in case of spinal cancer subjects, both SNRs and CNRs at all of those assessed locations significantly increased on the DWI after contrast agent injection compared to before, while on the ADC map images, SNRs significantly decreased. On the other hand, significantly decreased ADC values at all the assessed locations were found on the ADC map images. With reference to the normal group, significantly increased SNRs were found at all of the assessed locations on the DWI image after injection compared to before, while significantly decreased SNRs were found on the ADC map images. Also, significantly decreased ADC values at all the assessed locations were found on the ADC map images. For the qualitative analysis, after contrast agent injection, significantly increased signal intensities were found at the locations with spinal cancer on the DWI. In contrast, significantly decreased signal intensities were found on the ADC map images. The implication from the results showing that SNR and CNR significantly increased while ADC value significantly decreased at, above, and below the location of metastatic spinal cancer on DWI after contrast agent injection is that DWI obtained after contrast agent injection can be made available for wider application to vertebral disorders.

• Journal of Fashion Business
• /
• v.13 no.6
• /
• pp.125-136
• /
• 2009

The main objective of this research was to understand the characteristics of complementary color scheme through the analysis of contemporary women's fashion color coordination as they appear in the 'Collections'. Data collection of 115 was done through review of 'pr$\hat{e}$t-$\grave{a}$-porter Collections' of four cities; Milan, London, New York, Paris. Statistical analysis of frequency and also qualitative interpretation of characteristics of complementary color harmony characteristics which appeared in four collections were completed. The main findings were as followed; (1) Only 115 complementary color schemes out of 4968 two color combinations appeared. Compared the comparative ratios of appearance frequency between the two color combination and the complementary color harmony, London showed the highest, and followed by New York, and Milan and Paris. (2)The combined color type of 'red+green' was the most frequently appeared, and followed by 'violet+yellow' and 'orange+blue'. For the type of tone harmony, the contrast tone showed the most, and followed by the similarity and identity. According to the type of complementary color combination, the type of tone harmony used differently. Some differences showed in the types of color harmony and tone harmony between collections. (3) The complementary color scheme which shown in four collections harmonized two opposite colors mainly through the strong tone contrast and this could cause tension along with interest in the image. The complementary colors intensified and brought out the attributes each other. More details, high contrast of two complementary colors of yellow and violet created a vibrant look especially when used at higher saturation. Sometimes, however, some tone variations of two hues neutralized the strong effect and sometimes enhanced each other. When they used in similarity tones or identity tones in light colors, the tension was reduced and became softened but still presented nice harmony. In the type of 'red+green' color harmony, the various color combinations were demonstrated, mostly through tone manipulation of green color. The similarity tone harmony, which used the most, could effect a better sense of harmony and present more sophisticated looks. When used in contrast tone harmony, some changes in its own color which have only one color of two the excessive intensity led a good harmony. The 'orange+blue' color harmony was shown the least and used three tone harmony almost the same ratio. In this color harmony, blue amplified its energy and brilliance of orange and seemed to work better when one color was at a lower intensity than the other. In harmony with a similarity and an identity tone, this color harmony produces a stable and calm image. (4) The complementary scheme appeared more frequently in the S/S collections than in A/W collections and showed some differences in the types of color harmony and tone harmony between seasons, however, no big differences between collections.

• Korean Journal of Digital Imaging in Medicine
• /
• v.14 no.2
• /
• pp.1-8
• /
• 2012

Purpose : We aim at presenting the optimum radiologic factor through the evaluation of dose variation and of image quality through the use of a grid in Humerus examination and the change of dose because of the change of radiologic factor. Materials and Methods : We divided it in 3 cases: when using a grid or not and when using IP(Image Plate) in a digital system. Also, as fixing kVp to 70kVp it changed mAs, and fixing mAs to 10 it changed kVp, we put up resolution chart and Burger rose phantom on the acrylic phantom of 7cm (the same level of Humerus) to evaluate the dose and image. We used Image J program to evaluate the quantitative resolution of the obtained image, and made the qualitative evaluation and statistical analysis of the image saved in PACS for 20 radiologic technologist with more than 10 years of experience in order of evaluate its contrast. We used SPSS10(SPSS Inc. Chicago, Illinois) for statistical analysis. Results : We observed the analytic result of resolution by the change of kVp that it was $4.539dGycm^2$ in 60kVp and $757.472dGycm^2$ in 75kVp, which increased about 64.6% of dose, while for the resolution it had the pixel value 30.7% better with 851 in 60kVp than 651 in 75kVp. Also, we analyzed the result of resolution by the change of mAs that it was $3.106dGycm^2$ in 5mAs, and $12.470dGycm^2$ in 20mAs, which increased about 400% of dose, while for the resolution DR had 678 in 5mAs, and 724 in 20mAs that increased about 6.8% of resolution. We made the qualitative evaluation of contrast by the change of kVp that DR showed the higher quality than CR, but the contrast by the change of kVp had no special different at the moment of visual evaluation, nor statistically significant difference(P>0.05). We observed the qualitative evaluation of contraste by the change of mAs that the contrast increased as DR increased mAs, and had statistically significant difference(P<0.05). On the other hand, CR had no significant difference for more than 10mAs nor statistically significant difference(P>0.05). Conclusion : In case of some patients with radiographic exposure by the repeated examination such as emergent patient or Follow up patient, they are considered to try to limit the use of a grid, to set kVp under 65kVp in fixed mode, to select less than 10mAs and to reduce the possibility of patient being bombed.