• Journal of the Mineralogical Society of Korea
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• v.24 no.4
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• pp.301-312
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• 2011

The study on the atomic structure of iron-bearing silicate glasses has significant geological implications for both diverse igneous processes on Earth surface and ultra-low velocity zones at the core-mantle boundary. Here, we report experimental results on the effect of iron content on the atomic structure in iron-bearing alkali silicate glasses ($Na_2O-Fe_2O_3-SiO_2$ glasses, up to 16.07 wt% $Fe_2O_3$) using $^{29}Si$ and $^{17}O$ solid-state NMR spectroscopy. $^{29}Si$ spin-lattice ($T_1$) relaxation time for the glasses decreases with increasing iron content due to an enhanced interaction between nuclear spin and unpaired electron in iron. $^{29}Si$ MAS NMR spectra for the glasses show a decrease in signal intensity and an increase in peak width with increasing iron content. However, the heterogeneous peak broa-dening in $^{29}Si$ MAS NMR spectra suggests the heterogeneous distribution of $Q^n$ species around iron in iron-bearing silicate glasses. While nonbridging oxygen ($Na-O-Si$) and bridging oxygen (Si-O-Si) peaks are partially resolved in $^{17}O$ MAS NMR spectrum for iron-free silicate glass, it is difficult to distinguish the oxygen clusters in iron-bearing silicate glass. The Lorentzian peak shape for $^{29}Si$ and $^{17}O$ MAS NMR spectra may reflect life-time broadening due to spin-electron interaction. These results demonstrate that solid-state NMR can be an effective probe of the detailed structure in iron-bearing silicate glasses.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.7
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• pp.115-124
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• 2017

The objective of study was to investigate the optimal echo phase for mouse brain enhancement scan using fast low angle shot (FLASH) sequence of 9.4T magnetic resonance imaging (MRI). For quantification based on this method, an MR phantom experiment and clinical research were done. The phantom experiment was conducted by fabricating three phantoms with different molar concentration of gadolinium to create changes in echo phase of 9.4T FLASH sequence used in mouse brain scans. In the phantom experiment, SSI was 25~27 [arbitrary units, a.u.] in each of 33 phases from $6{\pi}$ to $28{\pi}$, while RSP was 30~100 mmol. MPSI was 47~52 [a.u], while MPP, where MPSI is seen, was 0.8~9 mmol. EPMS was 80.8~108.0%, while ASIMP was formed between 21.1 and 31.8 [a.u]. In the clinical research, Finally, the occurrence rate of artifact that expressed -1 nd +1. The present study was able to quantify the degree of enhancement at FLASH sequence of 9.4T MRI, as well as identify the optimal echo phase during mouse brain enhancement scan.

• Journal of Yeungnam Medical Science
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• v.22 no.2
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• pp.191-198
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• 2005

Background: Computed tomography (CT) is commonly used to evaluate the degree of sinus involvement in cases of inverted papilloma (IP). However, CT cannot differentiate tumor from adjacent inflammatory mucosa or retained secretions. By contrast, magnetic resonance imaging (MRI) has been reported to be useful in distinguishing IP from paranasal sinusitis. This study investigated whether preoperative assessment with MRI and CT accurately predict the extent of IP.1) Materials and methods: CT and MRI were retrospectively reviewed in 9 cases of IP. Patients were categorized into stages based on CT and MRI findings, according to the staging system proposed by Krouse. The involvement of IP in each sinus was also assessed. Results: Differentiation of IP from inflammatory disease may be more successful in routine cases where the inflammatory mucosa has low signal intensity on T1-weighted images and very high signal intensity on T2-weighted images. CT imaging could not differentiate tumor from adjacent inflammatory mucosa or retained secretions. Conclusion: Preoperative MRI of IP can predict the location and extent of the tumor involvement in the paranasal sinuses and sometimes predicts malignant changes.

• Journal of the Korean Society of Radiology
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• v.14 no.5
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• pp.715-723
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• 2020

Cross-talk artifacts occur in two adjacent groups of axial imaging of lesions lumbar 4-5 and sacrum 1 in lumbar spine MRI. This causes problems in reading lesions in areas corresponding to the posterior vertebra. In this study, we are going to completely remove the cross-talk artifacts through optimal concatenation TR. The region of interested were measured by averaging them into fat (ROI1), erector spinal muscle(lateral tract: iliocostalis lumborum muscle) (ROI2), erector spinal muscle(lateral tract: longissimus muscle) (ROI3), and spinous process (ROI4). The mean signal intensity (SI) was 163.43 ± 25.08 at C4 for ROI1, ROI 2 and ROI 3 at C6, 67.89 ± 11.75 and 69.99 ± 10.91 and ROI4 at C5, respectively (p<0.000). The mean signal to noise ratio (SNR) was 135.45 ± 35.90, 56.92 ± 15.90, 58.77 ± 15.59, and 54.91 ± 118.95 for SNR 1, 2, 3 and 4 (p<0.000). The contrast-to-noise ratio (CNR) was CNR1 78.52 ± 24.11, CNR2 was 76.67 ± 24.38 and CNR3 was 80.54 ± 26.33 in concatenation 6, respectively (p<0.000). The SNR, CNR, and the most efficient concatenation TR value over time are 6, and it is considered to help reduce cross-talk artifact if this is applied to T1 axial images.

• Korean Journal of Radiology
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• v.22 no.6
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• pp.922-930
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• 2021

Objective: It is uncertain why a b-value range of 1500-2000 s/mm² is optimal. This study was aimed at qualitatively and quantitatively analyzing the optimal b-value range of synthetic diffusion-weighted imaging (sDWI) for evaluating prostatic index lesions. Materials and Methods: This retrospective study included 92 patients who underwent DWI and targeted biopsy for magnetic resonance imaging (MRI)-suggested index lesions. We generated sDWI at a b-value range of 1000-3000 s/mm² using dedicated software and true DWI data at b-values of 0, 100, and 1000 s/mm². We hypothesized that lesion conspicuity would be best when the background (i.e., MRI-suggested benign prostatic [bP] and periprostatic [pP] regions) signal intensity (SI) is suppressed and becomes homogeneous. To prove this hypothesis, we performed both qualitative and quantitative analyses. For qualitative analysis, two independent readers analyzed the b-value showing the best visual conspicuity of an MRI-suggested index lesion. For quantitative analysis, the readers assessed the b-value showing the same bP and pP region SI. The 95% confidence interval (CI) or interquartile range of qualitatively and quantitatively selected optimal b-values was assessed, and the mean difference between qualitatively and quantitatively selected b-values was investigated. Results: The 95% CIs of optimal b-values from qualitative and quantitative analyses were 1761-1805 s/mm² and 1640-1771 s/mm² (median, 1790 s/mm² vs. 1705 s/mm²; p = 0.003) for reader 1, and 1835-1895 s/mm² and 1705-1841 s/mm² (median, 1872 s/mm² vs. 1763 s/mm²; p = 0.022) for reader 2, respectively. Interquartile ranges of qualitatively and quantitatively selected optimal b-values were 1735-1873 s/mm² and 1573-1867 s/mm² for reader 1, and 1775-1945 s/mm² and 1591-1955 s/mm² for reader 2, respectively. Bland-Altman plots consistently demonstrated a mean difference of less than 100 s/mm² between qualitatively and quantitatively selected optimal b-values. Conclusion: b-value range showing a homogeneous background signal may be optimal for evaluating prostatic index lesions on sDWI. Our qualitative and quantitative data consistently recommend b-values of 1500-2000 s/mm².

• Investigative Magnetic Resonance Imaging
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• v.15 no.1
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• pp.32-40
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• 2011

Purpose : The purpose of this study was to investigate the microstructural changes according to aging on the thickness and signal intensity (SI) of the cortical gray matter (GM) and white matter (WM) on the T2-, fluid-attenuated inversion recovery (FLAIR) and T1-weighted MR images in normal subjects. Materials and Methods : The 10, 20, 30, 40, 50, 60, 70, 80 and 90 year age groups of men and women (each 10 individuals) who underwent routine brain MRI, including the T2-, FLAIR and T1-weighted images, were selected for this study. We measured the thickness and the SI of the cortical GM and WM at the postcentral gyrus, which has an even thickness at the level of centrum semiovale, on the axial scans and we calculated the mean values of the thickness ratio of the gray/white matter (TRGW) and the signal intensity ratio of the gray/white matter (SRGW), and we compared the ratios of each age group. Results : On the T2-weighted images, the TRGWs were 0.81 and 0.79 at the age of 10 and they were 0.73 and 0.71 at the age of 90 in the men and women, respectively. So, the GM thickness was decreased more than the WM thickness was with aging. On the FLAIR images, the TRGWs were 1.09 and 1.00 at the age of 10 and they were 1.11 and 0.95 at the age of 70 in the men and women, respectively. On the T1-weighted images, the TRGWs were 0.66 and 0.80 at the age of 10, and the ratio was changed to 0.90 and 0.78 at the age of 90 in the men and women, respectively. On the T2-weighted image, the SRGWs were 1.53 and 1.43 at the age of 10, and they were 1.23 and 1.27 at the age of 90 in the men and women, respectively. On the FLAIR images, the SRGWs were 1.23 and 1.25 at the age of 10 and they were 1.06 and 1.05 at the age of 90 in the men and women, respectively. On the T1-weighted images, the SRGWs were 0.86 and 0.85 at the age of 10, and they were 0.90 and 0.87 at the age of 90 in the men and women, respectively. Conclusion : We suggest that the age-related microstructural changes of the thickness and the SI of the cortical GM and WM on the T2-, FLAIR and T1-weighted images are unique, and so this knowledge will be helpful to differentiate neurodegenerative disease from normal aging of the brain.

• Journal of the Korean Society of Radiology
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• v.6 no.5
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• pp.351-356
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• 2012

Ultrasonic cavitation is a physical phenomenon that generates and collapses microbubbles in media (mainly fluids) under conditions of strong ultrasonic irradiation. In this study, changes in the ultrasonic acoustic characteristics of bubble clouds in relation to ultrasonic irradiation were observed by the quantitative evaluation of cavitation yields. Concave-type single ultrasonic transducers with center frequencies of 500 kHz and 1.1 MHz were used to produce cavitation, and 2.25 MHz interference ultrasonic waves that would traverse any bubble clouds generated were used to analyze the cavitation. The parameters used for the evaluation of cavitation yields (changes in the center frequency, attenuation characteristics, and the propagation time of penetrating waves) were analyzed in relation to the cavitation-generating conditions (irradiation intensity, excitation signal, and center frequency). On the basis of these results, correlations between the changes in the center frequency and irradiation intensity were identified. Although the correlation coefficient was low, notable changes were observed in the center frequency under certain irradiation conditions. Attenuation trends in the interference ultrasonic waves showed high correlations with all the irradiation conditions, and it was noted that these trends were not affected by the forms of cavitation generated. No differences in the propagation time were observed among different irradiation conditions. These findings suggest that bubble yields can be quantitatively evaluated effectively by evaluating the diverse irradiation conditions and that such a quantitative evaluation could be used to study the basic cavitation phenomenon occurring in high-intensity ultrasonic wave treatment.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.4
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• pp.43-48
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• 2006

Recently, many researchers have shown great interest in wind-photovoltaic hybrid generation system which promotes electric power supply safely and progress of energy usage efficiently with complementary cooperation of a wind generation system and photovoltaic generation system. To use this hybrid generation system stably and effectively, we established a system which can acquire, analyse and save data and monitored remotely using internet. We constructed the signal conditioning circuit and used many kinds of converters to measure physical quantities such as wind velocity, intensity of illumination and temperature as well as many kinds of voltage and current for AC and DC. we acquired data from computer with data acquisition board, developed server program and client program which can download data that is monitored and saved in realtime at remote place. We analysed the measured data in relation to many conditions such as time and weather conditions.

• The Journal of the Korean bone and joint tumor society
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• v.9 no.2
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• pp.212-216
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• 2003

A Common peroneal nerve palsy caused by ganglionic cyst is very rare condition but well recognised entities. There have been three previous reports describing the magnetic resonance image (MRI) findings of peroneal nerve entrapment due to a ganglionic cyst. Ultrasonography, MRI, and electromyography (EMG), nerve conduction velocity (NCV), and microscopic examination were taken for diagnosis. A tubular structure near the fibular neck extending longitudinally over several slices with an inferior extension towards the superior tibiofibular joint with high T2 signal intensity was characteristic. The peroneal nerve was exposed and the ganglionic cyst was excised. The nerve was paralysed immediately after operation, but at 4 month after operation, started recovery of the function gradually and has recovered completely at 7 month. MRI is helpful to detect the extent, location, and origin of the cyst. Meticulous surgical excision can provide favorable result.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.03a
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• pp.21-21
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• 2010

(Ba,Sr)$TiO_3$ (BST) thin film with a perovskite structure has potential for the practical application in various functional devices such as nonvolatile-memory components, capacitor, gate insulator of thin-film transistors, and electro-optic devices for display. Normally, the BST thin films derived from sol-gel and sputtering are amorphous or partially crystalline when processed below $600^{\circ}C$. For the purpose of integrating BST thin film directly into a Si-based read-out integrated circuit (ROIC), it is necessary to process the BST film below $400^{\circ}C$. The microstructural and electrical properties of low-temperature crystallized BST film were studied. The BST thin films have been fabricated at $350^{\circ}C$ by UV-assisted rapidly thermal annealing (RTA). The BST films are in a single perovskite phase and have well-defined electrical properties such as high dielectric constant, low dielectric loss, low leakage current density, and high breakdown voltage. Photoexcitation of the organics contained in the sol-gel-derived films by high-intensity UV irradiation facilitates elimination of the organics and formation of the single-crystalline phase films at low temperatures. The amorphous BST thin film was transformed to a highly (h00)-oriented perovskite structure by high oxygen pressure processing (HOPP) at as low as $350^{\circ}C$. The dielectric properties of BST film were comparable to (or even better than) those of the conventionally processed BST films prepared by sputtering or post-annealing at temperature above $600^{\circ}C$. When external pressure was applied to the well-known contractive BST system during annealing, the nucleation energy barrier was reduced; correspondingly, the crystallization temperature decreased. The UV-assisted RTA and HOPP, as compatible with existing MOS technology, let the BST films be integrated into radio-frequency circuit and mixed-signal integrated circuit below the critical temperature of $400^{\circ}C$.