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Kim, Jeongjae,Kim, Bong Soo,Lee, Jeong Sub,Woo, Seung Tae,Choi, Guk Myung,Kim, Seung Hyoung,Lee, Ho Kyu,Lee, Mu Sook,Lee, Kyung Ryeol,Park, Joon Hyuk Korean Society of Magnetic Resonance in Medicine 2018 Investigative Magnetic Resonance Imaging Vol.22 No.1
Purpose: This study was designed to optimize the flip angle (FA) and scan timing of the hepatobiliary phase (HBP) using the 3D T1-weighted, gradient-echo (GRE) imaging with controlled aliasing in parallel imaging results in higher acceleration (CAIPIRINHA) technique on gadoxetic acid-enhanced 3T liver MR imaging. Materials and Methods: Sixty-two patients who underwent gadoxetic acid-enhanced 3T liver MR imaging were included in this study. Four 3D T1-weighted GRE imaging studies using the CAIPIRINHA technique and FAs of $9^{\circ}$ and $13^{\circ}$ were acquired during HBP at 15 and 20 min after intravenous injection of gadoxetic acid. Two abdominal radiologists, who were blinded to the FA and the timing of image acquisition, assessed the sharpness of liver edge, hepatic vessel clarity, lesion conspicuity, artifact severity, and overall image quality using a five-point scale. Quantitative analysis was performed by another radiologist to estimate the relative liver enhancement (RLE) and the signal-to-noise ratio (SNR). Statistical analyses were performed using the Wilcoxon signed rank test and one-way analysis of variance. Results: The scores of the HBP with an FA of $13^{\circ}$ during the same delayed time were significantly higher than those of the HBP with an FA of $9^{\circ}$ in all the assessment items (P < 0.01). In terms of the delay time, images at the same FA obtained with a 20-min-HBP showed better quality than those obtained with a 15-min-HBP. There was no significant difference in qualitative scores between the 20-min-HBP and the 15-min-HBP images in the non-liver cirrhosis (LC) group except for the hepatic vessel clarity score with $9^{\circ}$ FA. In the quantitative analysis, a statistically significant difference was found in the degree of RLE in the four HBP images (P = 0.012). However, in the subgroup analysis, no significant difference in RLE was found in the four HBP images in either the LC or the non-LC groups. The SNR did not differ significantly in the four HBP images. In the subgroup analysis, 20-min-HBP imaging with a $13^{\circ}$ FA showed the highest SNR value in the LC-group, whereas 15-min-HBP imaging with a $13^{\circ}$ FA showed the best value of SNR in the non-LC group. Conclusion: The use of a moderately high FA improves the image quality and lesion conspicuity on 3D, T1-weighted GRE imaging using the CAIPIRINHA technique on gadoxetic acid, 3T liver MR imaging. In patients with normal liver function, the 15-min-HBP with a $13^{\circ}$ FA represents a feasible option without a significant decrease in image quality.
The experimental investigation on the response of the Burke–Schumann flame to acoustic excitation
Kim, Taesung,Ahn, Myunggeun,Hwang, Jeongjae,Kim, Seongheon,Yoon, Youngbin Elsevier 2017 Proceedings of the Combustion Institute Vol.36 No.1
<P><B>Abstract</B></P> <P>This paper presents experiments showing the response of a diffusion jet flame to acoustic forcing. The experimental results from the Burke–Schumann flame, which is a special case of the diffusion flame, are compared with the analytical results. The flame response is described by comparing the flame surface, flame length, and heat release oscillation measurements with those from reference papers that have calculated the analytical solution. The flame shape depends on both the forcing frequency and the mean input velocity. The flame shape is divided into three types depending on the forcing frequency. The local stagnation point of the flame propagation and the cutting phenomenon are shown with a low-frequency forcing of the test condition. The flame consists of an undulation form when a high forcing frequency is used as the test condition. At a specific frequency, no flame oscillation is seen, even with acoustic forcing. The forcing frequency also affects the flame length. The mean input velocity affects the magnitude of flame surface oscillations. The heat release ratio oscillation shows that both a premixed flame and a diffusion flame act like low-pass filters. The Peclet number's dependence on the flame surface and the response of the heat release both fit well with the analytical results, whereas the Strouhal number's dependence on the flame surface varies slightly from the analytical solution. The heat release rate oscillation is closely connected to the flame surface oscillations.</P>
Jeongjae Kim,Bong Soo Kim,Jeong Sub Lee,Seung Tae Woo,Guk Myung Choi,Seung Hyoung Kim,Ho Kyu Lee,Mu Sook Lee,Kyung Ryeol Lee,Joon Hyuk Park 대한자기공명의과학회 2018 Investigative Magnetic Resonance Imaging Vol.22 No.1
Purpose: This study was designed to optimize the flip angle (FA) and scan timing of the hepatobiliary phase (HBP) using the 3D T1-weighted, gradient-echo (GRE) imaging with controlled aliasing in parallel imaging results in higher acceleration (CAIPIRINHA) technique on gadoxetic acid-enhanced 3T liver MR imaging. Materials and Methods: Sixty-two patients who underwent gadoxetic acidenhanced 3T liver MR imaging were included in this study. Four 3D T1-weighted GRE imaging studies using the CAIPIRINHA technique and FAs of 9° and 13° were acquired during HBP at 15 and 20 min after intravenous injection of gadoxetic acid. Two abdominal radiologists, who were blinded to the FA and the timing of image acquisition, assessed the sharpness of liver edge, hepatic vessel clarity, lesion conspicuity, artifact severity, and overall image quality using a five-point scale. Quantitative analysis was performed by another radiologist to estimate the relative liver enhancement (RLE) and the signal-to-noise ratio (SNR). Statistical analyses were performed using the Wilcoxon signed rank test and one-way analysis of variance. Results: The scores of the HBP with an FA of 13° during the same delayed time were significantly higher than those of the HBP with an FA of 9° in all the assessment items (P < 0.01). In terms of the delay time, images at the same FA obtained with a 20-min-HBP showed better quality than those obtained with a 15-min-HBP. There was no significant difference in qualitative scores between the 20-min-HBP and the 15-min-HBP images in the non-liver cirrhosis (LC) group except for the hepatic vessel clarity score with 9° FA. In the quantitative analysis, a statistically significant difference was found in the degree of RLE in the four HBP images (P = 0.012). However, in the subgroup analysis, no significant difference in RLE was found in the four HBP images in either the LC or the non-LC groups. The SNR did not differ significantly in the four HBP images. In the subgroup analysis, 20-min-HBP imaging with a 13° FA showed the highest SNR value in the LC-group, whereas 15-min-HBP imaging with a 13° FA showed the best value of SNR in the non-LC group. Conclusion: The use of a moderately high FA improves the image quality and lesion conspicuity on 3D, T1-weighted GRE imaging using the CAIPIRINHA technique on gadoxetic acid, 3T liver MR imaging. In patients with normal liver function, the 15-min-HBP with a 13° FA represents a feasible option without a significant decrease in image quality.
JeongJae Kim,Su Yeon Ko 제주대학교 의과학연구소 2023 The Journal of Medicine and Life Science Vol.20 No.2
Multiple studies have reported on unilateral axillary adenopathy following coronavirus disease 2019 (COVID-19) vaccination, which is currently recognized as a common finding. Here, we present a series of eight adult patients with reactive axillary lymphadenopathy following COVID-19 vaccination, in whom the follow-up ultrasonography (US) showed resolution of a previously noted unilateral axillary adenopathy. From March 2021 to March 2022, 2,599 consecutive women underwent breast US in Jeju National University Hospital. We identified 10 patients with unilateral axillary lymphadenopathy following COVID-19 vaccination detected on the breast US. The 10 patients were recommended for follow-up US. Two patients were lost to follow-up, whereas the remaining eight patients underwent follow-up US, in whom resolution of the unilateral axillary lymphadenopathy was noted. Radiologists should be aware of evolving guidelines for evaluating and managing axillary lymphadenopathy to avoid false positive biopsies. Recent studies on lymphadenopathy following COVID-19 vaccination show that a prolonged duration until resolution is often observed. Therefore, a follow-up US examination at least 12 weeks after vaccination may be reasonable. Furthermore, management guidelines should include a risk-stratified approach considering both vaccination timing and the patient’s overall risk of metastatic disease.
Kim, Hongjun,Lee, Sunghwan,Kim, Suran,Oh, Chungik,Ryu, Jeongjae,Kim, Jaegyu,Park, Eugene,Hong, Seungbum,No, Kwangsoo Springer-Verlag 2017 JOURNAL OF MATERIALS SCIENCE - Vol.52 No.5
<P>We report on the effect of the addition of phosphotungstic acid (PWA) in Nafion membrane on ethanol-crossover and the proton conductivity for DEFC application. A set of PWA-Nafion composite membranes (PWA 0, 5, 10, 15, 20 wt%) was prepared by solution casting and their microstructures, diffraction patterns, permeability, and proton conductivity were systematically characterized. The significant reduction in ethanol-crossover is observed with increasing PWA concentration in PWA-Nafion membranes, which is mainly attributed to an improvement in crystallinity of the membrane. PWA provides additional nucleation sites during solidification leading to higher crystallinity, which is supported by the membrane permeability tests. The proton conductivity of the composites is enhanced with PWA concentration until 15 wt% due to an increase in hopping pathways, while higher PWA of 20 wt% leads to a conductivity decrease possibly due to the excessive particle aggregations that limit ion transports. These PWA-Nafion composites were implemented in prototype DEFC devices as a membrane and the maximum power density achieved was 22% higher than that of commercial Nafion-117 device.</P>
Flexible piezoelectric liquid volume sensor
Ryu, Jeongjae,Jeong, Hanbert,Chen, Yugang,Oh, Chungik,Kim, Jaegyu,Kim, Hongjun,Cho, Seongwoo,No, Kwangsoo,Park, Yong-Hwa,Park, Steve,Hong, Seungbum Elsevier 2018 Sensors and actuators. A, Physical Vol.276 No.-
<P><B>Abstract</B></P> <P>We report a non-contact type polyvinylidene fluoride (PVDF)-based liquid volume sensor. When a liquid container vibrates due to an applied impact, our sensor that is attached to the wall of the container detects the resonance frequency of vibration, which shifts as a result of change in liquid volume. The sensitivity of our sensor was enhanced by stacking multiple sensors in series. A PVDF bimorph actuator was also fabricated to demonstrate an integrated actuator-sensor system. We believe that the results presented in this work will pave the way for novel applications in volume sensing.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We developed a contact-free liquid volume sensor based on a flexible PVDF film. </LI> <LI> Resonance frequency of vibration is detected using our sensor when a liquid container vibrates. </LI> <LI> A simulation describes the relationship between resonance frequecy and liquid volume. </LI> <LI> Sensitivity increases with stacked multiple sensors in series. </LI> <LI> An integrated actuator-sensor system is demonstrated. </LI> </UL> </P>