https://scholarworks.bwise.kr/hanyang/handle/2021.sw.hanyang/215 2026-07-04T09:37:14Z https://scholarworks.bwise.kr/hanyang/handle/2021.sw.hanyang/170096 Title: Numerical Analysis of RF-Induced Heating While Wearing Face Mask at Magnetic Resonance Imaging Authors: Cho, Youngdae; Yoo, Hyoungsuk Abstract: In response to the unprecedented COVID-19 pandemic, wearing face masks in public places and common facilities has been strongly recommended to help prevent the further spread of the virus. However, conductive components of the face mask carry the potential risk of radio-frequency (RF)-induced heating when exposed to an RF electromagnetic field, particularly during magnetic resonance imaging (MRI). In this study, a realistic human head model wearing a face mask exposed to a strong RF electromagnetic field in 1.5 T, 3 T, and 7 T MRI was simulated. A nose wire in contact with the skin and a mask sheet with relatively high electrical conductivity, emulating a silver nanoparticle-coated face mask, was modeled to investigate the worst case of RF-induced heating that could occur during the MRI scan. 24 scenarios were simulated by using finite-difference time-domain (FDTD)-based electromagnetic solver and thermal-transient solver from Sim4Life commercial simulation software. According to the results, a notable enhancement in the specific absorption rate (SAR) and temperature rise was observed in the local region of the skin where the wire contacted the skin around the edge of the high-conductive mask sheet. In particular, a maximum of a 12-fold increase in mass-averaged SAR and a temperature increase of more than 8.0 degrees C occurred because of the conductive face mask at 3 T, compared to the normal polymer-based face mask with low conductivity. Our results confirmed that the degree of RF-induced heating due to the face mask could be completely different depending on the RF frequency of the MRI, location where the nose wire contacted the skin, and conductivity of the mask sheet. To the best of our knowledge, this is the first study to assess the face mask as a factor for RF-induced heating during MRI. These findings are important for providing a safety guide that allows patients to safely undergo MRI while wearing a face mask during the COVID-19 pandemic. 2022-06-01T00:00:00Z https://scholarworks.bwise.kr/hanyang/handle/2021.sw.hanyang/141822 Title: 도심부 제한속도변화에 따른 직접 및 간접 교통안전 효과 분석 Authors: 박준영 2021-11-11T00:00:00Z https://scholarworks.bwise.kr/hanyang/handle/2021.sw.hanyang/140497 Title: Comparative analysis of default mode networks in major psychiatric disorders using resting-state EEG Authors: Choi, Kang-Min; Kim, Jeong-Youn; Kim, Yong-Wook; Han, Jung-Won; Im, Chang-Hwan; Lee, Seung-Hwan Abstract: Default mode network (DMN) is a set of functional brain structures coherently activated when individuals are in resting-state. In this study, we constructed multi-frequency band resting-state EEG-based DMN functional network models for major psychiatric disorders to easily compare their pathophysiological characteristics. Phase-locking values (PLVs) were evaluated to quantify functional connectivity; global and nodal clustering coefficients (CCs) were evaluated to quantify global and local connectivity patterns of DMN nodes, respectively. DMNs of patients with post-traumatic stress disorder (PTSD), obsessive compulsive disorder (OCD), panic disorder, major depressive disorder (MDD), bipolar disorder, schizophrenia (SZ), mild cognitive impairment (MCI), and Alzheimer's disease (AD) were constructed relative to their demographically-matched healthy control groups. Overall DMN patterns were then visualized and compared with each other. In global CCs, SZ and AD showed hyper-clustering in the theta band; OCD, MCI, and AD showed hypo-clustering in the low-alpha band; OCD and MDD showed hypo-clustering and hyper-clustering in low-beta, and high-beta bands, respectively. In local CCs, disease-specific patterns were observed. In the PLVs, lowered theta-band functional connectivity between the left lingual gyrus and the left hippocampus was frequently observed. Our comprehensive comparisons suggest EEG-based DMN as a useful vehicle for understanding altered brain networks of major psychiatric disorders. 2021-11-01T00:00:00Z https://scholarworks.bwise.kr/hanyang/handle/2021.sw.hanyang/140798 Title: Suppression of motion vision during course-changing, but not course-stabilizing, navigational turns Authors: Fenk, Lisa M.; Kim, Anmo J.; Maimon, Gaby Abstract: From mammals to insects, locomotion has been shown to strongly modulate visual-system physiology. Does the manner in which a locomotor act is initiated change the modulation observed? We performed patchclamp recordings from motion-sensitive visual neurons in tethered, flying Drosophila. We observed motorrelated signals in flies performing flight turns in rapid response to looming discs and also during spontaneous turns, but motor-related signals were weak or non-existent in the context of turns made in response to brief pulses of unidirectional visual motion (i.e., optomotor responses). Thus, the act of a locomotor turn is variably associated with modulation of visual processing. These results can be understood via the following principle: suppress visual responses during course-changing, but not course-stabilizing, navigational turns. This principle is likely to apply broadly-even to mammals-whenever visual cells whose activity helps to stabilize a locomotor trajectory or the visual gaze angle are targeted for motor modulation. 2021-10-01T00:00:00Z