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In this paper, computational fluid dynamic (CFD) analysis and experiments have been carried out to study the effect of nozzle pressure ratio, i.e. the ratio of inlet pressure to atmospheric pressure, and the pitch circle diameter of the control jets to regulate the base pressure. The variables considered for the analysis as well as the experiments are the nozzle pressure ratio (NPR), the Mach number (M) and the pitch circle diameter (PCD) of the control jets. The area ratio considered for the study is kept constant at 4.84 while the length to diameter (L/D) ratio of an enlarged duct is set constant at 5. The inertia parameter considered for the study is Mach number. The Mach numbers considered for study are 1.5, 2.0, and 2.5. The nozzle pressure ratio considered for study are 2, 5 and 8. Three different pitch circle diameters of control jets considered for study are 13.1 mm, 16.2 mm and 19.3 mm. From the numerical simulations and the results of the experimental tests, it is found that the control jets are very beneficial to increase the base pressure at higher NPR when the jets issuing from the nozzles are under-expanded. The control jets were able to increase the base pressure value from 160% to 400% at nozzle pressure ratio 8. It is concluded that the parameter D3 is the most effective pitch circle diameter of the control jets to increase the base pressure.

This research presents the effectiveness of sonic air tabs positioned at varying distances from the nozzle exit in a Mach 2.1 supersonic jet, focusing on their impact on aerodynamic mixing efficiency. The study involved placing the air tabs at two locations: directly at the nozzle exit (0D) and 0.5D downstream from the nozzle exit. The Injection Pressure Ratio (IPR) was adjusted between 3 and 6 while maintaining a constant Nozzle Pressure Ratio (NPR) of 6. Core length measurements of the jet were conducted using pitot pressure measurements and shadowgraph techniques, comparing controlled and uncontrolled jet conditions. The findings revealed that under an NPR of 6 at 0D, the maximum reduction in core length reached 56.4% for IPR 6 and at 0.5D the maximum reduction was 31.4% for IPR 6. As the IPR increased from 3 to 6, the core length reduction rate increased proportionally at both air tab locations. However, the reduction rate was consistently higher when the air tabs were positioned at the nozzle exit compared to the 0.5D location. The results from shadowgraph images aligned with those derived from pitot pressure measurements. In conclusion, for an NPR of 6 positioning sonic air tabs directly at the nozzle exit (0D) proved more efficient than placing them at 0.5D.

The use of fluid injection in supersonic jet control techniques provides several benefits, including thrust augmentation and mixing enhancement. This study aimed to investigate the effect of air tabs on a Mach 2.1 supersonic jet by varying the injection pressure ratio (IPR) from 3 to 7 for fixed nozzle pressure ratios (NPR) of 4 and 7. The core length of the jet with and without air tabs was quantified by analyzing shadowgraph images under controlled conditions. The results showed that increasing the IPR from the air tabs at the nozzle exit (0D) led to a reduction in core length for the fixed NPRs of 4 and 7. The rate of core length reduction increased with increasing IPRs from 3 to 7. For NPR 4, the maximum and minimum core length reduction rates were found to be 32% and 8% for IPRs 7 and 3, respectively. Similarly, for NPR 7, the core length reduction rate was highest for IPR 7 (38%) and lowest for IPR 3 (8%). The results demonstrate that the use of air tabs induces stream-wise vortices, leading to mixing enhancement and a reduction in core length.

Lift system plays key role to Air Cushion Vehcile overall performance, whose design includes cushion flow demanding analysis, lift fan design, airflow distribution and pressure control. The method to calculate cushion flow exit velocity variation with craft speed was firstly presented based on cushion induced wave. Through application development in CATIA, a full solution was presented to check if craft keeps in safety flight boundary at maximum calm water speed. Through analysis, current cushion flow demanding method based on statistic former ACVs seems conservative for particular ACV with super high cushion density, which was adviced to decrease by 10%∼15%. New double discharge lift fan for polar hovercraft was developed through CFD simulation, model test, full-scale utilizing. To reach designed bag-cushion pressure ratio, polar ACV model skirt feed holes was added by 1/3 more than simple geometrical scale. Larger bag feed holes and lower bag-cushion pressure ratio are effective means to lower lift power.

Recently, instantaneous wave-free ratio (iFR) has emerged as an alternative to the fractional flow reserve (FFR) for intracoronary physiological assessment. Although all diastolic resting indices are reportedly identical to the iFR, limited data exist on diastolic pressure ratio (dPR) measured using a microcatheter (dPR micro ). This study aimed to evaluate the diagnostic accuracy of dPR micro compared to FFR measured using a microcatheter (FFR micro ) in real-world practice for intracoronary physiological assessment. This was a single-center, retrospective, observational study. We identified 103 consecutive suspected angina pectoris patients (107 lesions) who underwent dPR micro and FFR micro measurement using the Navvus® catheter at Takasaki Heart Hospital from March 2019 to June 2019. A total of 103 lesions in 103 patients were finally included in the study. The mean FFR micro and dPR micro values were 0.80 and 0.88, respectively. With an FFR micro  ≤ 0.80, the dPR micro showed a diagnostic accuracy of 79.6%, sensitivity of 74.6%, specificity of 87.5%, positive predictive value of 90.4%, and negative predictive value of 68.6%. The area under the receiver operating characteristic (ROC) curve was 0.894 (95% confidence interval, 0.833–0.956), and the optimal cut-off value for dPR micro derived from the ROC analysis was 0.90. dPR micro and FFR micro values were discordant in 21/103 cases (20.4%). As a multivariable logistic regression analysis was performed, the male sex (vs. female) had a statistically significant association with a dPR micro -FFR micro discordance (OR 4.91; 95% CI, 1.04–23.0; P  = 0.044). No other factors were found to be significantly associated with the discordance. In conclusion, dPR micro measured using a microcatheter had good diagnostic accuracy and correlation with FFR micro , hence, it can be useful for making revascularization decisions. However, re-studies in larger populations will be needed to better understand the properties of diastolic resting index measured using a microcatheter in clinical settings.

Diverse methods have been proposed for liquefying gases due to their need in different industries. This study examined the precooled Linde–Hampson cycle for liquefying six gases. First, the proposed system is analyzed from a thermodynamic perspective. Then, the effects of pressure ratio on performance parameters such as system required work, heat exchanger-specific heat capacity, number of transfer units, the liquefied gas mass ratio, Coefficient of Performance (COP), and exergy efficiency are examined. The results show that methane at a pressure ratio of 40 has the highest COP (1.606), while argon at a pressure ratio of 220 has the highest exergy efficiency (31.51%). Exergy analysis indicates that the Joule–Thomson valve destroys the most exergy, followed by heat exchanger-3 and compressor-1. Finally, the TOPSIS technique is used as a multi-objective optimization method to optimize the compressor-1 pressure ratio based on two objective functions, COP and exergy efficiency. The results show that in optimal conditions, COP and exergy efficiency are respectively 0.99 and 20.6% for air, 0.93 and 28.35% for argon, 0.97 and 20% for nitrogen, 1.46 and 14.76% for methane, 1.05 and 22.87% for fluorine, and 1.18 and 20.08% for oxygen.

Aim To evaluate the distribution of a generic diastolic pressure ratio (dPR) after angiographically successful percutaneous coronary intervention (PCI) and to assess its association with the 2‑year incidence of target vessel failure (TVF), defined as a composite of cardiac mortality, target vessel revascularisation, target vessel myocardial infarction and stent thrombosis. Methods The dPR SEARCH study is a post hoc analysis of the prospective single-centre FFR-SEARCH registry, in which physiological assessment was performed after angiographically successful PCI in a total of 1000 patients, using a dedicated microcatheter. dPR was calculated offline with recently validated software in a subset of 735 patients. Results Mean post-PCI dPR was 0.95 ± 0.06. Post-PCI dPR was ≤ 0.89 in 15.2% of the patients. The cumulative incidence of TVF at 2‑year follow-up was 9.4% in patients with a final post-PCI dPR ≤ 0.89 as compared to 6.1% in patients with a post-PCI dPR > 0.89 (adjusted hazard ratio [HR] for dPR ≤ 0.89: 1.53; 95% CI 0.74–3.13; p  = 0.249). dPR ≤ 0.89 was associated with significantly higher cardiac mortality at 2 years; adjusted HR 2.40; 95% CI 1.01–5.68; p  = 0.047. Conclusions In a real-world setting, despite optimal angiographic PCI results, 15.2% of the patients had a final post-PCI dPR of ≤ 0.89, which was associated with a higher incidence of TVF and a significantly higher cardiac mortality rate.

[Display omitted] •The effect of geological and tunnel permeability parameters on tunnel drainage capacity were studied through model tests.•The evolution of the tunnel discharge and tunnel external water pressure under varying conditions were obtained.•The evaluation of the tunnel water pressure spatial distribution was studied. Effective control of the tunnel seepage field is crucial in water-abundant regions to ensure the safety and stability of underground structures. Therefore, it is imperative to investigate the effects of the geological factors and tunnel permeability parameters on the drainage capacities of such structures. The Tongzi Tunnel was subjected to model tests using a self-developed testing apparatus to investigate the spatial distribution of tunnel seepage under varying conditions of sand permeability, number of primary support layers, and number of primary support openings. Subsequently, numerical models were developed to validate the observed tunnel seepage field based on experimental conditions. On this basis, an effective water pressure ratio η is proposed to evaluate the hydraulic safety of the tunnel spatial distribution. The results indicated a positive correlation between the tunnel water discharge and sand permeability, primary support layers, and primary support openings. Among these factors, the primary support openings exhibited the highest sensitivity to tunnel water discharge, whereas the impact of the primary support layers was relatively low. Additionally, the external water pressure in the tunnel exhibited a negative correlation with sand permeability, primary support layers, and primary support openings. The sensitivity ranking of the structural water pressure fluctuations to the parameters is as follows: primary support openings > sand permeability > primary support layers. Furthermore, the longitudinal water pressure values in the tunnel gradually increase from Section A (circular drainage section) to Section B (middle circular drainage section). Model tests and numerical simulations were performed to demonstrate the data reliability. Finally, with the increase of sand permeability and the number of primary support openings, the effective drainage area (η < 0.6) around the tunnel spatial gradually expands. Besides, the tunnel longitudinal effective drainage interval progressively degrades from the vault (A1 area) to the tunnel bottom (A7 area), and even the tunnel bottom areas are not effectively drained (η > 0.6).

This paper presents the concrete tunnel-sand-pile interaction (TSPI) phenomenon in liquefiable sand considering various relative densities and seismic excitations. The novel shake table test for the TSPI model was performed to evaluate the excess pore pressure ratio (EPPR) surrounding the tunnel body and interactive tunnel and pile moments. The relative densities are taken to be 27, 41, and 55% in the local sand of Bangladesh. Similarly, the peak ground acceleration (PGA) of the Kobe and Loma Prieta earthquakes are considered to be 0.05, 0.10, 0.15, and 0.20 g. The shake table was calibrated based on similar variations of the input and output PGA. The 3D finite element concrete TSPI model has been performed by Plaxis considering the UBC3D-PLM (two yield surfaces consisting of kinematic hardening rules) constitutive model of sand. Therefore, experimental and numerical results vary closely, which may inform the possibility of the application of the concrete TSPI model on a large scale. The maximum SRSS (Square Root Sum of Squares) tunnel moment has been found to be 18.7 kN-m from the experimental results for 27% relative density of the Kobe earthquake with a PGA of 0.15 g. Also, the maximum SRSS moments of front and rear piles vary (0.10–0.14) % of the tunnel moment. So, the tunnel moment always shows a higher value in liquefiable ground based on the experimental results because of the larger volume and stiffness than a series of piles. However, the present study may be enhanced in the future by varying geometric properties.