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Sang‑Wook Kim,Hyeon‑Woo Son,Taek‑Kyun Jung,Young‑Bum Chun,Yi‑Hyun Park,Ji‑Woon Lee,Soong‑Keun Hyun 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.4
The hot deformation behavior of advanced reduced-activation alloy (ARAA) was investigated using hot torsion tests. Thefl ow stress decreased as deformation temperature increased and as strain rate decreased. The fl ow behavior demonstratedthe typical dynamic recrystallization (DRX). Based on the constitutive analysis of peak stress, the activation energy for hotdeformation was found to be 330.3 kJ mol −1 . Peak stress was analyzed as a function of the Zener–Hollomon parameter, andcalculated and experimental values were in good agreement. A DRX kinetic model for ARAA was derived with deformationconditions based on the Avrami-type model. It was confi rmed that the volume fraction of dynamically recrystallized grainsincreased as deformation temperature increased and as strain rate decreased. The necklace structure and grain boundarybulging were observed in the deformed microstructure of ARAA. The suggested DRX mechanism for ARAA during hotworking is discontinuous DRX.
Multiple Buck-Chopper using Partial Resonant Switching
Sang-Pil Mun,Ki-Young Suh,Hyun-Woo Lee,Jung-Ham Chun 전력전자학회 2001 ICPE(ISPE)논문집 Vol.2001 No.10
This paper proposed that an AC-DC converter system using multiple buck-chopper operates with four choppers connecting to a number of parallel circuits, To improve these, a large number of soft switching topologies included a resonant circuit have been proposed And, some simulative results on computer are included to confirm the validity of th e analytical results The partial resonant circuit makes use of an inductor using step-down and a condenser of loss-less snubber The result is that the switching loss is very low and the efficiency of system is high And the snubber condenser used in a partial resonant circuit makes charging energy regenerated at input power source for resonant operation The proposed conversion system is deemed the most suitable for high power applications where the power switching devices are used.<br/>
Hyun-Ju Kim(Hyun-Ju Kim),Minji Bang(Minji Bang),Chun Il Park(Chun Il Park),Chongwon Pae(Chongwon Pae),Sang-Hyuk Lee(Sang-Hyuk Lee) 대한신경정신의학회 2023 PSYCHIATRY INVESTIGATION Vol.20 No.3
Objective Mental health problems such as anxiety, panic, and depression have been exacerbated by the coronavirus disease-2019 (COVID-19). This study aimed to compare the symptom severities and overall function before and during the COVID-19 pandemic among patients with panic disorder (PD) seeking treatment compared to healthy controls (HCs). Methods Baseline data were collected from the two groups (patients with PD and HCs) in two separate periods: before COVID-19 (Jan 2016-Dec 2019) and during COVID-19 (Mar 2020-Jul 2022). A total 453 participants (before COVID-19: 246 [139 patients with PD and 107 HCs], during COVID-19: 207 [86 patients with PD and 121 HCs]) was included. Scales for panic and depressive symptoms and overall function were administered. Additionally, network analyses were performed to compare the two groups within the patients with PD. Results The results of two-way analysis of variance analyses showed that patients with PD enrolled during COVID-19 showed higher levels of interoceptive fear and lower overall functioning. In addition, a network comparison test revealed that a significantly high strength and expected influence for agoraphobia and avoidance in patients with PD during COVID-19. Conclusion This study suggested that the overall function could have worsened, and the importance of agoraphobia and avoidance as a central symptom may have increased in patients with PD seeking treatment during COVID-19.