액체로켓엔진 동특성 해석을 위한 병렬 수치계산

정승채,윤웅섭 한국항공우주학회 2001 한국항공우주학회 학술발표회 논문집 Vol.- No.-

액체추진시스템 성능 천이 예측 프로그램

정승채,김택수,김규홍,최현철,윤웅섭,김영수,박승경 한국추진공학회 2001 한국추진공학회 학술대회논문집 Vol.2001 No.4

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.

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.

A Comparison of the Use of Contrast Media with Different Iodine Concentrations for Multidetector CT of the Kidney

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.

램제트 연소 유동장 수치 해석

정승채,고현,성흥계,윤웅섭 한국항공우주학회 2004 한국항공우주학회 학술발표회 논문집 Vol.- No.-

단일 채널 DPF의 PM 포집과 압력 강하 모델링

정승채(Seung-chai Jung),박종선(Jong-sun Park),윤웅섭(Woong-sup Yoon) 한국자동차공학회 2005 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2005 No.11_1

Prediction of diesel particulate filtration necessitates appropriate models for pressure drop and particulate matter (PM) collection, and the models are not frequently deterministic, thus must be closed with certain parameters of much smaller scales typically determined experimentally. Included are soot cake permeability, soot cake density, soot density in filter wall, and percolation constant. Aiming at elucidating these essential parameters, the present study attempts the enhancement of DPF filtration model with non-linear description of soot cake regression, The model is properly validated with single channel DPF measurements. Effects of these parameters on the pressure drop, a direct measure of filtration quality, are estimates in a parametric manner and discussed in terms of filtration velocity. Conclusively, the extent of percolation constant is controlling pressure drops, and soot density in the filter wall is relatively important in deep-bed filtration regime. Filtration quality of the deep-bed mode is relatively less sensitive to particle size than soot cake regime.

DPF의 열 재생 모델링 및 해석

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.

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.

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.