基于人工智能的全自动化一站式CT血流储备分数在冠心病患者中的诊断与预后价值

Currently,clinically available coronary CT angiography(CCTA)derived fractional flow reserve(CT-FFR)is time-consuming and complex.We propose a novel artificial intelligence-based fully-automated,on-site CT-FFR technology,which combines the automated coronary plaque segmentation and luminal extraction model with reduced order 3 dimentional(3D)computational fluid dynamics.A total of 463 consecutive patients with 600 vessels from the updated China CT-FFR study in Cohort 1 undergoing both CCTA and invasive fractional flow reserve(FFR)within 90 d were collected for diagnostic performance evaluation.For Cohort 2,a total of 901 chronic coronary syndromes patients with index CT-FFR and clinical outcomes at 3-year follow-up were retrospectively analyzed.In Cohort 3,the association between index CT-FFR from triple-rule-out CTA and major adverse cardiac events in patients with acute chest pain from the emergency department was further evaluated.The diagnostic accuracy of this CT-FFR in Cohort 1 was 0.82 with an area under the curve of 0.82 on a per-patient level.Compared with the manually dependent CT-FFR techniques,the operation time of this technique was substantially shortened by 3 times and the number of clicks from about 60 to 1.This CT-FFR technique has a highly successful(>99%)calculation rate and also provides superior prediction value for major adverse cardiac events than CCTA alone both in patients with chronic coronary syndromes and acute chest pain.Thus,the novel artificial intelligencebased fully automated,on-site CT-FFR technique can function as an objective and convenient tool for coronary stenosis functional evaluation in the real-world clinical setting.

Thermochemical non-equilibrium flow characteristics of high Mach number inlet in a wide operation range

The high-temperature non-equilibrium effect is a novel and significant issue in the flows over a high Mach number(above Mach 8)air-breathing vehicle.Thus,this study attempts to investigate the high-temperature non-equilibrium flows of a curved compression two-dimensional scramjet inlet at Mach 8 to 12 utilizing the two-dimensional non-equilibrium RANS calculations.Notably,the thermochemical non-equilibrium gas model can predict the actual high-temperature flows,and the numerical results of the other four thermochemical gas models are only used for comparative analysis.Firstly,the thermochemical non-equilibrium flow fields and work performance of the inlet at Mach 8 to 12 are analyzed.Then,the influences of high-temperature non-equilibrium effects on the starting characteristics of the inlet are investigated.The results reveal that a large separation bubble caused by the cowl shock/lower wall boundary layer interaction appears upstream of the shoulder,at Mach 8.The separation zone size is smaller,and its location is closer to the downstream area while the thermal process changes from frozen to non-equilibrium and then to equilibrium.With the increase of inflow Mach number,the thermochemical non-equilibrium effects in the whole inlet flow field gradually strengthen,so their influences on the overall work performance of the high Mach number inlet are more obvious.The vibrational relaxation or thermal non-equilibrium effects can yield more visible influences on the inlet performance than the chemical non-equilibrium reactions.The inlet in the thermochemical non-equilibrium flow can restart more easily than that in the thermochemical frozen flow.This work should provide a basis for the design and starting ability prediction of the high Mach number inlet in the wide operation range.

Effect of high-pressure detonation products on fuel injection and propagation characteristics of detonation wave

The effect of high-pressure detonation products on fuel injection and propagation characteristics of detonation wave has been investigated in the form of ion voltage by varying the equivalence ratio(ER),air mass flux,and operation duration with hydrogen-air mixtures.It has been shown experimentally that the ion voltage decays gradually during the initial stage of rotating detonation wave(RDW).The attenuation of ion voltage is a general phenomenon,and the decay rate of ion voltage and its peak value of the trough state are related to the equivalence ratio and air mass flux.The analysis of interaction between the combustor and hydrogen plenum indicates that the feedback of high-pressure detonation products leads to the attenuation of ion voltage.In addition,the long-duration tests show that the ion voltage will recover to a steady state with the extension of reaction time,when the purgation(products leaving plenums)of detonation products is greater than feedback(products entering plenums)of detonation products in the hydrogen plenum.The recovery of ion voltage starts earlier at the higher equivalence ratio and air mass flux,and the peak value of ion voltage in the steady state also increases with the increase of equivalence ratio and air mass flux.A low frequency oscillation about 10 e12 Hz occurs in the RDW at some operation conditions.This low frequency oscillation is related to the interaction between the combustor and hydrogen plenum,and can be eliminated by either increasing the equivalence ratio or decreasing the air mass flux.

Investigation on C_(2)H_(4)-Air combustion mode in a non-premixed rotating detonation combustor

Based on the working characteristics of the rotating detonation combustor,the combustion mode of C_(2)H_(4)-Air under non-premixed injection conditions is experimentally studied in this paper.By changing the equivalence ratio,we observed the acoustic deflagration mode,fast deflagration mode,stable detonation mode,and weak detonation mode in the combustor.The velocity and pressure of the shock wave increase gradually as the equivalence ratio increases from 0.6 to 1.8.The stable detonation region appears near the stoichiometric ratio and the velocity of the detonation wave is relatively stable.When the equivalence ratio of the mixture is larger than 1.32,the stable detonation wave will suddenly extinguish,forming a weak detonation mode until the end of the combustor operation.The combustion mode of weak detonation is greatly affected by the fuel injection pressure ratio,and the release rate of energy is the main reason for the formation of deflagration mode or detonation mode.