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정승채,김승협,조정연 대한영상의학회 2011 Korean Journal of Radiology Vol.12 No.6
Objective: To determine the optimal iodine concentration of contrast media for kidney multidetector computed tomography (MDCT) by comparing the degree of renal parenchymal enhancement and the severity of the renal streak artifact with contrast media of different iodine concentrations. Materials and Methods: A 16-row MDCT was performed in 15 sedated rabbits by injection of 2 mL contrast media/kg body weight at a rate of 0.3 mL/sec. Monomeric nonionic contrast media of 250, 300, and 370 mg iodine/mL were injected at 1-week intervals. Mean attenuation values were measured in each renal structure with attenuation differences among the structures. The artifact was evaluated by CT window width/level and three grading methods. The values were compared with iodine concentrations. Results: The 370 mg iodine/mL concentration showed significantly higher cortical enhancement than 250 mg iodine/mL in all phases (p < 0.05). There was however no significant difference in the degree of enhancement between the 300 mg iodine/mL and 370 mg iodine/mL concentrations in all phases. There is a significant difference in attenuation for the cortex-outer medulla between 250 mg iodine/mL and 300 mg iodine/mL (p < 0.05). The artifact was more severe with a medium of 370 mg iodine/mL than with 250 mg iodine/mL by all grading methods (p < 0.05). Conclusion: The 300 mg iodine/mL is considered to be the most appropriate iodine concentration in an aspect of the enhancement and artifact on a kidney MDCT scan. Objective: To determine the optimal iodine concentration of contrast media for kidney multidetector computed tomography (MDCT) by comparing the degree of renal parenchymal enhancement and the severity of the renal streak artifact with contrast media of different iodine concentrations. Materials and Methods: A 16-row MDCT was performed in 15 sedated rabbits by injection of 2 mL contrast media/kg body weight at a rate of 0.3 mL/sec. Monomeric nonionic contrast media of 250, 300, and 370 mg iodine/mL were injected at 1-week intervals. Mean attenuation values were measured in each renal structure with attenuation differences among the structures. The artifact was evaluated by CT window width/level and three grading methods. The values were compared with iodine concentrations. Results: The 370 mg iodine/mL concentration showed significantly higher cortical enhancement than 250 mg iodine/mL in all phases (p < 0.05). There was however no significant difference in the degree of enhancement between the 300 mg iodine/mL and 370 mg iodine/mL concentrations in all phases. There is a significant difference in attenuation for the cortex-outer medulla between 250 mg iodine/mL and 300 mg iodine/mL (p < 0.05). The artifact was more severe with a medium of 370 mg iodine/mL than with 250 mg iodine/mL by all grading methods (p < 0.05). Conclusion: The 300 mg iodine/mL is considered to be the most appropriate iodine concentration in an aspect of the enhancement and artifact on a kidney MDCT scan.
Approximate velocity scale for primary and secondary dual-inlet side-dump flows
정승채,박병훈,고현,윤웅섭 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.3
Effects of the bulk inlet velocity on the characteristics of dual-inlet side-dump flows are numerically investigated. Non-reacting subsonic turbulent flow is solved by a preconditioned Reynolds-averaged Navier-Stokes equation system with low-Reynolds number k −ε turbulence model. The numerical method is properly validated with measured velocity distributions in the head dome and the combustor. With substantial increase in the bulk inlet velocity, general profiles of essential primary and secondary flows normalized by the bulk inlet velocity are quantitatively invariant to the changes in the bulk inlet velocity.
간동맥 화학 색전술 후 빠른 지혈을 위한 새로운 지혈 방법인 Clo-Sur P.A.D. 의 안전성과 유효성
정승채,제환준,김상윤,이활,정진욱,박재형 대한영상의학회 2007 대한영상의학회지 Vol.56 No.4
Purpose: We wanted to evaluate the safety and efficacy of a new hemostatic device, Clo-Sur P.A.D., at an arterial access site after performing femoral arterial catheterization to achieve transcatheter arterial chemoembolization (TACE). Materials and Methods: From August 2002 to March 2005, 113 patients who underwent TACE and agreed on using the Clo-Sur P.A.D. were enrolled in this study. We evaluated the mean time interval from compression to the first movement and also to the first walk. We also evaluated such complications as rebleeding, pseudoaneurysm, vascular occlusion, hematoma, infection and pain. For 92 patients who had previous experiences with manual compression, we evaluated their preference of hemostatic method by asking them. Results: Successful hemostasis was achieved with the Clo-Sur P.A.D. in 105 subjects (92%). The mean time interval from compression to the first movement was 201 minutes, and that to the first walk was 267 minutes. There was no statistical difference between the complicated and the uncomplicated groups for the mean time, prothrombin time, Child-Pugh class and platelet count (p > 0.05). Rebleeding occurred in 3 patients (2.7%) and mild hematoma around puncture site was noted in 5 patients (5.4%). Eighty-seven patients (95%) preferred Clo-Sur P.A.D. to the manual compression method. Conclusion: The Clo-Sur P.A.D. is a safe and effective hemostatic device and it provides early ambulation after TACE.
정승채(Seung-chai Jung),윤웅섭(Woong-sup Yoon) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Diesel oxidation catalyst (DOC) is a widely used device to reduce harmful species of exhaust gas with less engine back pressure. A one-dimensional model simulating the oxidation of CO, HC and NO was developed to predict the state of gaseous emission exiting a DOC. The model formulation is based on the constraint of conservation of mass, species and energy inside DOC. Kinetics of CO, HC and NO were modeled assuming global reaction using inhibition factor. Steady-state experimental data covering a wide range of operating conditions calibrates the model parameters. The results showed good agreement with the experimental data in a test window of 200℃~500℃ for temperature and 0.1㎥/s~0.7㎥/s for volumetric flowrate.
DOC-DPF-SCR 시스템에 의한 디젤 배기 내 NO<SUB>x</SUB>, 입자상 물질 저감 과정의 일관 모델링 및 성능 예측
정승채(Seung-chai Jung),윤웅섭(Woong-sup Yoon) 한국자동차공학회 2007 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Computer methods employing simplified mathematical models with empirically tuned model parameters can be efficiently practiced into an optimization of a diesel aftertreatment system. Components of prime interests are diesel particulate filter, diesel oxidation catalyst and de-NOx catalytic converter. de-NOx, de-PM, and de-HC processes in each member unit are separately modeled, formulated and then combined into an integrated analysis procedure for a unified prediction of the diesel emission aftertreatment. The unified model is empirically tuned and validated with comprehensive engine and laboratory data. Parametric studies to investigate the effects of emission species and space velocity on the NOx and soot reductions are conducted. A lowered NO₂/NO, ratio after PM oxidation in DPF contributes to promote the NOx reduction by SCR at intermediate gas temperatures. In contrast, NOx reduction is inert to the PM oxidation at high temperatures. Rate of PM accumulation appears to be a strong function of temperature and NOx concentration.
NH₃-SCR 방법에 의한 디젤 배기 내 De-NO<SUB>x</SUB> 과정에서의 DOC에 의한 영향과 거감 성능 변화 해석
정승채(Seung-chai Jung),윤웅섭(Woong-sup Yoon) 한국자동차공학회 2007 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
A positive influence of oxidation precatalyst on the NOx reduction by NH₃-SCR was analytically investigated. Physicochemical processes in regard to NOx reduction by NH₃-SCR and NO-NO₂ conversion by the oxidation catalyst are formulated with proper models for individual physics. A unified model is correctly validated with experimental data in terms of NOx reduction efficiency for SCR and NO-NO₂ conversion efficiency for DOC. The model equipped with rate expressions of Langmuir-Hinshelwood type reaction scheme is deterministic and finds a conversion extent directly. A series of numerical experiments were carried out and parametric analysis of the NOx reduction was conducted. NOx reduction is expedited in proportion to DOC volume at lower temperatures, whereas deactivated with increasing DOC volume when the space velocity is lower at intermediate temperature regime. At intermediate temperatures, NOx conversion is proportionally increasing with the space velocity. NOx conversion is a weak function of the space velocity and DOC volume at higher exhaust temperatures. In DOC-SCR system, the NOx reduction efficiency is gradually increasing with NH₃/NOx ratios.
정승채(Seung-chai Jung),윤웅섭(Woong-sup Yoon) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Particulate filter system has been developed to cope with tight diesel PM emission regulations. One of the major issue for DPF system is developing safe and effective thermal regeneration strategy because any PM oxidation methods without additional heat source do not ensure lasting permissible back-pressure level under all engine operation condition. In the present study, thermal regeneration process of wall-flow DPF has been studied using one-dimensional model. Regeneration model consists of mass, momentum and energy conservation equation. Heat generation by particulate matter oxidation was modeled through heterogeneous global carbon reaction. This model can produce spatio-temporal evolution of filter temperature, distribution of particulate layer thickness and mass of PM remained in the filter during regeneration. Simulation results were compared to three different experimental data and showed good agreement, therefore this model can be used to develop thermal regeneration strategy.