Measurement of Opening and Closing Angles of Aortic Valve Prostheses In Vivo Using Dual-Source Computed Tomography: Comparison with Those of Manufacturers’ in 10 Different Types

서영주,김영진,홍유진,이혜정,허진,임동진,김윤정,최병욱 대한영상의학회 2015 Korean Journal of Radiology Vol.16 No.5

The aims of this study were to compare opening and closing angles of normally functioning mechanical aortic valves measured on dual-source computed tomography (CT) with the manufacturers’ values and to compare CT-measured opening angles according to valve function. A total of 140 patients with 10 different types of mechanical aortic valves, who underwent dualsource cardiac CT, were included. Opening and closing angles were measured on CT images. Agreement between angles in normally functioning valves and the manufacturer values was assessed using the interclass coefficient and the Bland-Altman method. CT-measured opening angles were compared between normal functioning valves and suspected dysfunctioning valves. The CT-measured opening angles of normally functioning valves and manufacturers’ values showed excellent agreement for seven valve types (intraclass coefficient [ICC], 0.977; 95% confidence interval [CI], 0.962–0.987). The mean differences in opening angles between the CT measurements and the manufacturers’ values were 1.2° in seven types of valves, 11.0° in On-X valves, and 15.5° in ATS valves. The manufacturers’ closing angles and those measured by CT showed excellent agreement for all valve types (ICC, 0.953; 95% CI, 0.920–0.972). Among valves with suspected dysfunction, those with limitation of motion (LOM) and an increased pressure gradient (PG) had smaller opening angles than those with LOM only (p < 0.05). Dual-source cardiac CT accurately measures opening and closing angles in most types of mechanical aortic valves, compared with the manufacturers’ values. Opening angles on CT differ according to the type of valve dysfunction and a decreased opening angle may suggest an elevated PG.

Numerical study on the effects of intake valve timing on performance of a natural gas-diesel dual-fuel engine and multi-objective Pareto optimization

Jung, Jaehwan,Song, Soonho,Hur, Kwang Beom Pergamon 2017 Applied thermal engineering Vol. No.

<P><B>Abstract</B></P> <P>A natural gas-diesel dual-fuel engine is considered an attractive option for reducing the emissions of a diesel engine while maintaining high thermal efficiency. However, it is important to investigate and optimize the parameters of such an engine in dual-fuel mode. Intake valve timing is a major parameter affecting the air/fuel (A/F) ratio, which is an important factor in dual-fuel combustion characteristics. Here, a numerical study was performed to investigate the fundamentals of dual-fuel combustion and the effects of intake valve closure (IVC) changes in dual-fuel mode using a 1D engine simulation. As the natural gas energy proportion (NGP) increased, brake power decreased and nitrogen oxide (NO<SUB>x</SUB>) emissions decreased because of low combustion efficiency and a lower temperature in the cylinder. At each NGP, a change in IVC could increase combustion efficiency and affect NO<SUB>x</SUB> emissions by controlling the A/F ratio. Additionally, the start of diesel injection (SOI), a major parameter in a dual-fuel engine, and the IVC were selected as independent variables. Latin hypercube sampling (LHS) was used with these variables and a multi-objective Pareto optimization (MOP) was performed to optimize high thermal efficiency and low NO<SUB>x</SUB> emissions. As a result, optimal Pareto solutions were obtained.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The dual-fuel engine was established by using GT-POWER 1D engine simulation. </LI> <LI> The effects of a natural gas-diesel dual-fuel combustion were investigated in a heavy duty engine. </LI> <LI> The effects of IVC were investigated for a natural gas-diesel dual-fuel engine. </LI> <LI> A multi-objective pareto optimization was performed to optimize brake power and NO<SUB>x</SUB> concentration. </LI> </UL> </P>

HIGH-LOAD EXPANSION BY VARYING EFFECTIVE COMPRESSION RATIO USING VARIABLE VALVE DURATION SYSTEM UNDER DUAL-FUEL PREMIXED COMPRESSION IGNITION

민경덕,김기홍,임동현,신형진,추상현,이정우 한국자동차공학회 2022 International journal of automotive technology Vol.23 No.3

In this study, a high-load expansion strategy was investigated by varying the effective compression ratio (CR) using the variable valve duration (VVD) method during combustion in a gasoline/diesel dual-fuel premixed compression ignition engine. The effective CR was varied from 15.0 to 10.6 via the retardation of the intake valve closing timing (IVC) at 1,500 rpm. With respect to optimization, the diesel injection timing, fuel ratio, and exhaust gas recirculation (EGR) rate were adjusted for each optimized condition. The limitations were the maximum pressure rise rate (below 10 bar/deg) and in-cylinder pressure (below 150 bar) with NOx < 40 ppm and soot < 0.2 FSN. The results emphasized that when the effective CR was 12.7, the maximum load increased by 10.5 % (gIMEP from 13.3 to 14.7 bar) compared with that at a CR of 15.0. Although the decrease in CR resulted in a gross thermal efficiency loss, the difference was negligible (from 45.9 to 45.5 %). The main reason for high-load expansion was the increase in intake air volume under the same intake pressure upon lowering the CR and the margin for the maximum in-cylinder pressure. From this result, it can be concluded that the Miller cycle is useful for the expansion of high load ranges in premixed combustion systems.

EFFECT OF SWIRL MOTION ON COMBUSTION AND EMISSIONS CHARACTERISTICS WITH DUAL-FUEL COMBUSTION IN COMPRESSION IGNITION ENGINE

민경덕,임동현,이정우,신형진,김기홍,문선영 한국자동차공학회 2022 International journal of automotive technology Vol.23 No.2

In-cylinder flow motion is important for enhancing combustion in internal combustion engines. There are two major flow motions: tumble and swirl. Tumble enhances the flame propagation speed to spread throughout the entire cylinder. Swirl affects the behavior of diesel spray; an enhanced swirl ratio has been widely used in conventional diesel engines. Because dual-fueled combustion has the characteristics of premixed combustion from background fuels and mixingcontrolled combustion from directly injected fuels such as diesel, understanding the effect of in-cylinder flow motion on combustion characteristics in dual-fuel combustion is critical. In this research, the effect of swirl in gasoline and diesel dualfuel combustion was evaluated with different diesel injection timing conditions. As the dual-fuel combustion engine used in this research was driven by diesel spray, swirl was selected as the main flow motion rather than tumble. The effect of swirl with different diesel injection timings was investigated under low-speed and low-load conditions. The results demonstrate that increasing swirl intensity provokes fast-burning caused by the enhanced air-fuel mixture, decreasing the diesel fraction and allowing more exhaust gas recirculation (EGR) to be used for the reduction of engine-out nitrogen oxides (NOx) and smoke emissions, without reducing thermal efficiency.

Comparative performance investigation of a dual evaporator cycle using an ejector with the conventional cycle using a pressure reducing valve

Sachdeva Gulshan,Jaiswar Ajay,Anuradha Parinam,Jain Vaibhav 대한설비공학회 2023 International Journal of Air-Conditioning and Refr Vol.31 No.1

The performance of a dual evaporator cycle using ejector is compared with a conventional cycle employing pressure reducing valve. In both the systems, high temperature evaporator is considered as a flooded evaporator, thus a separator is employed after the high temperature evaporator. However, low temperature evaporator is a kind of conventional dry evaporator. The comparison of both systems, i.e., conventional and ejector assisted, is done for the same cooling capacities and same dryness fraction at the exit of high temperature evaporator with R134a, R152a, and R1234yf refrigerants. The effects of varying the states of refrigerant at the exit of flooded evaporator, and temperatures of both the evaporators and the condenser are analyzed using Engineering Equation Solver. It is found that the compressor work is reduced in both the cycles with the rise in low temperature evaporator temperature; however, a little variation is observed in the total cooling effect. The cooling effect in high temperature evaporator is increased with the increase in dryness fraction at the exit of the high temperature flooded evaporator, but it is decreased in low temperature evaporator.

Rotation Effect of In-plane FM layer on IrMn Based GMR-SV Film

Purevdorj Khajidmaa,Jong-Gu Choi,Sang-Suk Lee 한국자기학회 2017 Journal of Magnetics Vol.22 No.1

The magnetoresistance (MR) properties of antiferromagnetic (AFM) IrMn based giant magnetoresistance-spin valve (GMR-SV) was investigated in view point of the artificial rotation effect of ferromagnetic (FM) layer in the plane induced by an applied field during the post annealing temperature. The MR curves measured with an azimuthal angle region of φ = 0°-360° are depended on the annealing temperature and the magnetization easy axis of two free NiFe layers and two pinned NiFe layers in dual-type GMR-SV film. Especially, the annealing temperature and sample rotation angle(θ ) maintained to the magnetic sensitivity (MS) of 1.4 %/Oe with an isotropic region angle of 110° are 100 °C and 90°, respectively.

듀얼 클러치 변속기용 저마찰 저누유 유압제어 시스템 개발

양갑진(Kabjin Yang),이창훈(Changhoon Lee),나병철(Byungchul Na) 한국자동차공학회 2014 한국자동차공학회 학술대회 및 전시회 Vol.2014 No.11

Recent improvements in the fuel efficiency of a car, etc. greening policies and emissions reduction, and improved reliability, and improved recycling, particularly in improving fuel economy because it affects most of the world"s automotive technology automotive powertrain (engine + transmission) is a technology for this this development has been actively promoted. Current technologies can be divided into the intelligent car green vehicle technology development direction of the automotive industry. In particular, and for increasingly stricter environmental regulations, laws and regulations to improve fuel economy and reduce emissions CO to respond to global warming, and actively promote the development of eco-friendly cars with this set to achieve emission reduction targets specific fuel consumption of the gas station and around the world pursuing an aggressive technology development and research and development. We believe this will be a burden on infrastructure led to the near future because the market when compared to other greens, such as hybrid cars and electric vehicles, fuel cell vehicles are dual-clutch transmission. Further development is necessary because it is high can be transferred to the transmission for a hybrid vehicle is high and in addition the transmission efficiency of the motor is a dual clutch transmission. Since in the vehicle to improve the overall system in order to improve fuel efficiency and exhaust gas emissions to meet state-of-the-art in the driving system and transmission system, 8% of the width is emphasized the need for improved technological development of high-efficiency transmission is to improve fuel efficiency. In this study, we developed a dual-clutch transmission for low friction for improved fuel efficiency, low leakage, high-efficiency hydraulic control system design, analysis, fabrication, control and evaluation techniques.

CoFe/Cu/CoFe/PtMn 다층박막의 자기저항 곡선을 이용한 자기 등방성 특성 분석

최종구(Jong-Gu Choi),김수희(Su-Hee Kim),최상헌(Sang-Heon Choi),이상석(Sang-Suk Lee),이장로(Jang-Roh Rhee) 한국자기학회 2017 韓國磁氣學會誌 Vol.27 No.4

The magnetic isotropy property from the magnetoresistance (MR) curve and magnetization (MH) loop for the PtMn based spin valve (SV) multilayer films fabricated with different the bottom structure after post-annealing treatment was investigated. The exchange biased coupling field (H<SUB>ex</SUB>), coercivity (H<SUB>c</SUB>), and MR ratio of Glass/Ta(10 ㎚)/CoFe(6 ㎚)/Cu(2.5 ㎚)/CoFe(3 ㎚)/Ta(4 ㎚) SV multilayer film without antiferromagnetic PtMn layer are 0 Oe, 25 Oe, and 3.3 %, respectively. MR curve for the Glass/Ta(10 ㎚)/CoFe(6 ㎚)/Cu(2.5 ㎚)/CoFe(3 ㎚)/PtMn(6 ㎚)/Ta(4 ㎚) SV multilayer film showed H<SUB>ex</SUB> = 2 Oe, H<SUB>c</SUB> = 316 Oe, and MR (%) = 4.4 % with one butterfly MR curve having by the effect of antiferromagnetic PtMn layer. MR curve for the dualtype Glass/Ta(10 ㎚)/CoFe(6 ㎚)/Cu(2.5 ㎚)/CoFe(3 ㎚)/PtMn(6 ㎚)/CoFe(3 ㎚)/Cu(2.5 ㎚)/CoFe(6 ㎚)/Ta(4 ㎚) SV multilayer film showed H<SUB>c</SUB> = 37.5 Oe and 386 Oe, MR = 3.5 % and 6.5 % with two butterfly MR curves and square-like hysteresis MH loops. The anisotropy property in CoFe spin valve-PtMn multilayer is neglected by the effects of a very small value of H<SUB>ex</SUB> and a very slightly shape magnetic anisotropy. This result is possible to explain the effect of magnetization configuration spin array of the bottom SV film and the top SV film of PtMn layer.

이중구조 거대자기저항-스핀밸브 박막의 자기등방성 영역분포에 관한 연구

카지드마(Purevdorj Khajidmaa),이상석(Sang-Suk Lee) 한국자기학회 2013 韓國磁氣學會誌 Vol.23 No.6

The regional distribution of magnetic isotropy depending on the post annealing condition for the dual-type structure GMR-SV (giant magnetoresistance-spin valve) of NiFe/Cu/NiFe/IrMn/NiFe/Cu/NiFe multilayer was investigated. The rotation of in-plane ferromagnetic layer induced by controlment of the post annealing temperature inside of the vacuum chamber. The magnetoresistive curves of a dual-type IrMn based GMR-SV depending on the direction of the magnetization easy axis of the free layer and the pinned layer are measured by between 0˚ and 360˚ angles for the applied fields. The optimum annealing temperature having a steady and isotropy magnetic sensitivity of 1.52 %/Oe was 107℃ in the rotational section of 0~90˚. By investigating the switching process of magnetization for an arbitrary measuring direction, the in-plane orthogonal magnetization for the dual-type GMR-SV multilayer can be used by a high sensitive biosensor for detection of magnetized micro-beads.

바이오센서용 거대자기저항-스핀밸브 박막이 등방성 자기저항 특성을 갖게 하는 후열처리 조건 연구

카지드마(P. Khajidmaa),박광준(Kwang-Jun Park),이상석(Sang-Suk Lee) 한국자기학회 2013 韓國磁氣學會誌 Vol.23 No.3

The magnetic easy axis of the ferromagnetic layer for the dual-type GMR-SV (giant magnetoresistance-spin valve) having NiFe/Cu/NiFe/IrMn/NiFe/Cu/NiFe multuilayer structure controlled by the post annealing treatment. The magnetoresistive curves of a dual-type IrMn based GMR-SV depending on the direction of the magnetic easy axis of the free and the pinned layers are measured by the different angles for the applied fields. By investigating the switching process of magnetization for an arbitrary measuring direction, the optimum annealing temperature having a steady and isotropy magnetic sensitivity of 2.0 %/Oe was 105 ℃. This result suggests that the in-plane orthogonal magnetization for the dual-type GMR-SV film can be used by a high sensitive biosensor.