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Quasi-static Characteristics in Radial Direction of 100 kWh Class Superconductor Bearing
정세용,박병준,한영희,박병철,이정필,한상철,Jung, S.Y.,Park, B.J.,Han, Y.H.,Park, B.C.,Lee, J.P.,Han, S.C. The Korean Superconductivity Society 2010 Progress in superconductivity Vol.12 No.1
A superconductor flywheel energy storage system (SFES) is an electro-mechanical battery which transforms electrical energy into mechanical energy for storage, and vice versa. Many aspects of the quasi-static behavior of flywheel rotors still need to be studied closely, and the rotors require a stable and highly efficient supporting system such as high temperature superconductor (HTS) bearings, which offer dynamic stability without the use of active control. Quasi-static properties of HTS bearings in the radial direction provide data to solve problems which may occur in a running system. Since stiffness in countering rotor vibration is the main parameter for designing an HTS bearing system, we investigated the quasi-static properties of the magnetic force between permanent magnets(PMs) and HTS bulks in the radial direction. We measured radial stiffness, and discovered that bearing stiffness varied greatly depending on the number of active HTS bulks. This is valuable data for predicting the change in stiffness during partial HTS bearing failure. The quasi-static test results are used for optimal design and performance prediction for the 100 kWh class superconductor bearing.
정세용,한정우,진송이,한승민,김효선,김동석,서창옥,유철주 대한소아혈액종양학회 2014 Clinical Pediatric Hematology-Oncology Vol.21 No.2
Background: Pilocytic astrocytoma (PA) is a low-grade glioma that occurs primarily in children and young adults. The optimal postoperative treatment modality after subtotal resection (STR) of PAs remains to be elucidated. The aim of this study was to compare the efficacies of different post-STR treatment modalities and to examine the risk factors for the progression of PAs. Methods: We reviewed the medical records of 91 pediatric PA patients in a single institute during a 30-year period. Kaplan-Meier analysis was used to assess overall survival (OS) and progression-free survival (PFS), and Cox proportional hazard models were used to calculate hazard ratios. Results: The median age of 91 patients was 8.9 years (range, 0.3-17.9). GTR was perfomed, whenever possible. Patients who underwent STR afterwards received either radiotherapy, chemotherapy, or were observed without further treatment, according to clinician preference. In total group, 10-year OS was 97.4% and 10-year PFS was 57.2%. In GTR group (N=33), 10-year OS and PFS was 100%. In STR group (N=49), 10-year OS was 97.7%, while 10-year PFS was 38.6%. STR group underwent following postoperative (PO) modalities; observation (PO-Obs, N=32), radiotherapy (PO-RT, N=10), chemotherapy (PO-CTx, N=7). The 10-year PFS rate was higher in patients who received postoperative treatment (either PO-RT or PO-CTx) than in patients who received PO-Obs (62.5% vs 27.0%, P=0.039). In multivariate analysis for STR group, PO-CTx (Hazard ratio (HR)=0.20, P=0.035) and PO-RTx (HR=0.13, P=0.008) were superior to observation, respectively. Conclusion: Radiation and chemotherapy are better post-STR treatment modalities than observation for pediatric PA patients.
정세용,이양석,Jung, Se-Yong,Lee, Yang-Suk 한국군사과학기술학회 2009 한국군사과학기술학회지 Vol.12 No.3
The experimental research was conducted to setup a performance prediction logic for the regenerative cooling system on a small scale liquid rocket engine using kerosene and LOX. Total heat flux of the combustion gas side was determined for the flow rate of the coolant, combustion pressure using the calorimeter thrust chamber. Based on the experimental investigation, a performance prediction scheme for the regenerative cooling system is setup in our own way. A performance prediction logic for the regenerative cooling system has been developed by the correction scheme of the combustion gas side. The key parameters determining the temperature limitation of the coolant are the mass flow rate of the coolant and the length of the combustion chamber and the nozzle. And the parameters to control the limitation of the usable wall temperature are the number of channels and wall thickness.
Transcatheter Treatment of Atrial Septal Defect Presenting with Platypnea-Orthodeoxia Syndrome
정세용,김남균,은영민,정조원,최재영 대한심장학회 2015 Korean Circulation Journal Vol.45 No.2
A 29-year-old woman was referred to our institute for symptomatic hypoxemia. Her dyspnea was aggravated while sitting or standingand relieved while in supine position. She did not have any pulmonary disease. Transthoracic echocardiography and heart computed tomographyrevealed an underestimated small atrial septal defect (ASD) with a left-to-right shunt. A cardiac catheterization was performedto evaluate pulmonary hypertension. It revealed a normal pulmonary artery pressure and a large ASD with bidirectional shunt during Valsalvamaneuver by intracardiac echocardiogram. Her arterial oxygen saturation decreased from 93% while supine to 79% while at a 15°sitting position. Thus, the patient was diagnosed with platypnea-orthodeoxia syndrome. The ASD was successfully closed with Amplatzer®(St. Jude Medical) septal occluder and both platypnea and orthodeoxia were resolved immediately after the procedure.
Design and Construction of 10 kWh Class Flywheel Energy Storage System
정세용,한상철,한영희,박병준,배용채,이욱륜,Jung, S.Y.,Han, S.C.,Han, Y.H.,Park, B.J.,Bae, Y.C.,Lee, W.R. The Korean Superconductivity Society 2011 Progress in superconductivity Vol.13 No.1
A superconductor flywheel energy storage system (SFES) is an electro-mechanical battery which transforms electrical energy into mechanical energy for storage, and vice versa. A 10 kWh class flywheel energy storage system (FESS) has been developed to evaluate the feasibility of a 35 kWh class SFES with a flywheel $I_p/I_t$ ratio larger than 1. The 10 kWh class FESS is composed of a main frame, a composite flywheel, active magnetic dampers (AMDs), a permanent magnet bearing, and a motor/generator. The flywheel of the FESS rotates at a very high speed to store energy, while being levitated by a permanent magnetic bearing and a pair of thrust AMDs. The 10 kWh class flywheel is mainly composed of a composite rotor assembly, where most of the energy is stored, two radial and two thrust AMD rotors, which dissipate vibration at critical speeds, a permanent magnet rotor, which supports most of the flywheel weight, a motor rotor, which spins the flywheel, and a central hollow shaft, where the parts are assembled and aligned to. The stators of each of the main components are assembled on to housings, which are assembled and aligned to the main frame. Many factors have been considered while designing each part of the flywheel, stator and frame. In this study, a 10 kWh class flywheel energy storage system has been designed and constructed for test operation.