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This article describes the implementation of fiber Bragg grating (FBG) strings to simultaneously measure pressure, temperature, and terminal shock in a supersonic inlet. For the demanding conditions of wind tunnel testing and the measuring needs of supersonic inlets, together with simulation and experimental research, an FBG-based device for measuring flow field characteristics in supersonic inlets has been developed. The device consists of a bare FBG string for measurement and a steel tube-encapsulated FBG string for temperature compensation. By sensing the changes in flow conditions at multiple points in real time, they are buried by the polymer in slots on the surface of the inlet to measure temperature and pressure variations. The experiments were performed in a wind tunnel at a Mach number of 2.0, and the findings revealed that the pressure data obtained using the FBG-based measuring method suggested in this work were quite similar to that obtained using traditional pressure sensors. The signal measured by FBG had good repeatability and the error was within the tolerance of the supersonic inlet pressure measurement. The position of the terminal shock can be achieved according to the measured pressure distribution. In addition, the temperature could be measured by comparing the signal of the FBG string encapsulated in steel tubes with the signal of the bare FBG string. It was shown that the measuring method was appropriate for supersonic ground-based aerodynamic tests.

The inlet with scavenge duct is an important part of turboprop aircraft engine. This type of inlet normally has a complex shape, of which the design is challenging and directly affects the flow field quality of the engine entrance and thus the engine performance. In this paper, the parametric design method of a turboprop aircraft inlet with scavenge duct is established by extracting and controlling the transition law of the critical characteristic parameters. The inlet’s performance and internal flow characteristics are examined by wind-tunnel experiment and numerical simulation. The results indicate that a flow tendency of winding up on both sides is formed due to the induction of the inlet profile, as well as a vortex pair on the back side of the power output shaft. The vortex pair dominates the pressure distortion index on the Aerodynamic Interface Plane (AIP). In addition, with the increase of freestream angle of attack, the total-pressure recovery coefficient of the inlet increases gradually while the total pressure distortion index decreases slightly. On the basis of the experimental results under different working conditions, the parametric design method proposed in this paper is feasible.

In this study, a solver coupling the level-set and volume-of-fluid methods is developed for interface computation of incompressible two-phase flows on the OpenFOAM platform. It corrects the surface tension, density, and viscosity of the fluids with the level-set function synchronously. To examine the effect of density and viscosity corrections, an intermediate solver that only corrects the surface tension force is also developed. Two test cases, that is, a bubble rising freely in stagnant water and a drop impacting on a liquid surface, are performed to validate and compare the capabilities of the new solvers. It is found that the coupling solver which corrects all the fluids’ properties mentioned above has the best prediction accuracy, especially for Rayleigh jet issues. With the application of this solver, the mechanism for the bubble entrainment in drop impact on a liquid pool is explained.

This study looks at initial results from the Transportation Wallet for Residents of Affordable Housing pilot program launched by the City of Portland’s Bureau of Transportation. The program provides a set of transportation incentives for low-income participants, including a US$308 prepaid Visa card that could be applied to public transit or other transportation services, a free bike share membership, and access to discounted rates on several services. A survey was conducted with the program’s participants (278 total responses) to understand how they used the Transportation Wallet and how the program helped them use different transport modes to get around. The main findings include: (1) The financial support of this program encouraged some participants to use new mobility services (including Uber/Lyft, bike share, and e-scooter) that they had never used before; (2) the program increased access for participants, helping them make more trips and, for some, get to places they otherwise could not have gone; and (3) transportation fairs, where participants could learn about services and talk to providers, promoted both mode sign-up and mode usage, particularly for new mobility services and a reduced fare transit program. The survey results also point to some opportunities to improve the program. Participant feedback suggests that transportation agencies do more to streamline and educate participants on how to use new mobility services and coordinate different service providers to optimize seamless services for participants. The paper provides insights into the implementation and effectiveness of a transportation financial incentive program for low-income populations.

This paper presents an experimental and numerical study of the aerodynamics of a moderate-scale rotor hovering in the Extreme Ground Effect (EGE) where rotor height-off-ground is below half the rotor radius. The tip vortex field was visualized by using the PIV technique. The aerodynamic performance, tip vortex trajectory, wall jet characteristics, surface pressure and velocity fields were measured and analyzed. To explore more deeply the flow mechanisms of the extreme ground effect, Detached Eddy Simulation (DES) was conducted on completely structured meshes. The results showed significant deviations of the rotor performance in EGE from that in Regular Ground Effect (RGE) with the rotor heights of more than half the rotor radius. Moreover, the flow structures of the rotor in EGE are considerably complex, such as the wall jet and groundwash flow separation. The rotor wake flow and tip vortices impact the ground more frequently, resulting in distinctive characteristics of the surface pressure and velocity fields in EGE.

The study presents an experimental exploration into the mode transition of an over-under TBCC (Turbine-Based Combined Cycle) inlet, with a specific emphasis on the flow characteristics at off-design transition Mach number. A systematic investigation was undertaken into the mode transition characteristics in both unthrottled and throttled conditions within a high-speed duct, employing high speed Schlieren and dynamic pressure acquisition systems. The results show that the high-speed duct faced flow oscillations primarily dictated by the separation bubble near the duct entrance during the downward rotation of splitter, leading to the duct's unstart under the unthrottled condition. During the splitter's reverse rotation, a notable hysteresis of unstart/restart of the high-speed duct was observed. Conversely, hysteresis vanishes when the initial flowfield nears the critical state owing to downstream throttling. Moreover, the oscillatory diversity, a distinctive characteristic of the high-speed duct, was firstly observed during the mode transition induced by throttling. The flow evolution was divided into four stages: an initial instability stage characterized by low-frequency oscillations below 255 Hz induced by shock train self-excitation oscillation and high-frequency oscillations around 1367 Hz caused by the movement of separation bubble. This stage is succeeded by the “big buzz” phase, comprised of pressure accumulation/release within the overflow-free duct and shock motion outside the duct to retain dynamic flow balance. The dominant frequency escalated with the increase of the internal contraction ratio in the range of 280 Hz to 400 Hz. This was followed by a high-frequency oscillation stage around 453 Hz dominated by a large internal contraction ratio with low pulsating energy, accompanied by a continuous supersonic overflow. Lastly, as the splitter gradually intersected the boundary layer of the first-stage compression surface, the capture area and the turbulence intensity of the incoming flow underwent a sudden shift, leading to a more diverse flow oscillation within the duct, manifested as various forms of mixed buzz.

The ultrathin silver nanowires (UT-AgNWs) with high aspect ratios are considered as a promising alternative to indium tin oxide for modern optoelectronic devices. Therefore, the cost-effective preparation of ultrathin AgNWs with a high aspect ratio on a large scale is highly desired. In this work, we demonstrated that the Maillard reaction in the polyol system was able to control the growth of silver crystal nuclei, thus forming UT-AgNWs with a high aspect ratio, which is a cost-effective, green, and simple approach. Accordingly, transparent conductive electrodes (TCEs) were fabricated by the obtained UT-AgNWs. It had a sheet resistance of only 18 Ω/sq at a transmittance of 95% and a haze of less than 2.0%. Also, it had excellent flexibility. Its sheet resistance did not change, even after bending up to 1000 cycles. This approach paves a way to synthesize TCE-orientated UT-AgNWs massively and to boost its pragmatic application.

This review concentrates on significant development in an important biomacromolecule, nucleic acid, especially deoxyribonucleic acid (DNA), and its biomedical application in cell uptake, drug delivery, gene regulation, and therapeutics. Herein, DNA molecules as nanomaterials are coarsely categorized into linear DNA, DNA aptamer, and programmable DNA origami structures, both of which are easily conjugated with other popular nanomaterial, i.e., carbon nanotube, metallic nanoparticles, quantum dots, proteins, etc., viaπ-π stacking, base-pair hybridization or chemical modification. This review not only provides mechanism and perspective on biomedical applications using hybrids of DNA-based nanocomposites, but also integrates an ideal strategy on designing and inventing the state-of-the-art targeted drug delivery systems.

A novel approach to exfoliating graphite into graphene using ultrasound coupled with a shear mixer in supercritical CO2is presented in this article. The influence of the ultrasound power and the shearing speed on the exfoliation efficiency was systematically studied, and the optimal processing parameters were achieved. In comparison with either the ultrasound or the shearing method, the coupling approach obtained a higher yield, up to 82.6%, and about 60% of the graphene sheets had fewer than three layers. The electrical conductivity of the film formed by the obtained graphene was up to 1.18 × 106S/m. A synergy exfoliation mechanism was proposed: the ultrasound activated the edges of the graphite, generating the gap between the graphite layers, and the shear mixer peeled off the graphene layer from the gap simultaneously. The coupling approach of ultrasound and the shear mixer enabled the production of the graphene.

•Natural β-carotene was enriched by supercritical CO2in a silica-packed column.•82.2% oil with the β-carotene of 3% was removed in the adsorption stage.•β-carotene of the concentrated fraction and its yield achieved 27% and 22.3%, respectively.

The hysteresis during the throat regulation process of a supersonic variable inlet is unconducive to restart. Hence, detailed experimental studies of such a hysteresis and its control are necessary. A throat variable supersonic inlet was designed at a shock-on-lip Mach number of 4.0 and an Internal Contraction Ratio (ICR) ranging over 1.21–2.94. Meanwhile, a distributed bleed system was proposed to suppress the hysteresis. The wind tunnel tests were conducted at Mach number 2.9. The throat regulation processes were recorded using a high-speed schlieren and dynamic pressure acquisition system. The results indicate that the unstart and restart ICRs during the uncontrolled inlet’s throat regulation process were 1.95 and 1.48, respectively, demonstrating an unstart-restart hysteresis. Four typical flowfields were summarized during the uncontrolled inlet’s restart process. The proposed bleed control increased the unstart and restart ICRs to 2.06 and 1.75, respectively, and the inlet realized the designed state as the ICR was further decreased to 1.67. The controlled inlet’s hysteresis loop was decreased compared to the uncontrolled inlet. Finally, the mechanism of the hysteresis, dominated by the entrance separation-induced wave system, was clarified. The mechanisms of the bleed control to broaden the unstart and restart boundaries and suppress the hysteresis were elucidated.

It is difficult to disperse graphene flakes well in an aqueous solution while maintaining conductivity due to its high hydrophobicity. Herein, we demonstrated that a well-dispersed state of graphene in an aqueous solution was realized by using reduced graphene oxide (rGO) with a suitable content of oxygen-functional groups. A rGO-dispersed graphene (rGO/G) film was fabricated from the graphene dispersion with good conductivity by using rGO with a C/O ratio of 2.48 as the surfactant. Also, the prepared rGO/G aerogel has a broad prospect. Density functional theory calculation revealed that the strong electrostatic repulsion, which was more potent than the van der Waals force and the π–π interaction, was the primary driving force promoting the dispersibility of graphene in an aqueous solution. Furthermore, the repulsion of the rGO/G dispersion decreased with the reduction of the oxygen-functional groups of rGO. Therefore, applying rGO with an appropriate content of oxygen-functional groups is an alternative option to improve the dispersibility of graphene in an aqueous medium while maintaining its original properties, from which many potential applications could be expected.

The variable geometry supersonic inlet tends to decrease the throat area to reduce the Mach number upstream of the terminal shock, so as to reduce the flow loss. However, excessive Internal Contraction Ratio (ICR) exposes the inlet to a greater risk of unstart, which inevitably results in a process of increasing the throat area to aid the inlet restart. In the above throat regulation process, the inlet undergoes the start, unstart, and restart states in turn. In order to reveal the flow structure and mechanism of this process, a two-dimensional unsteady numerical simulation combined with a dynamic mesh technique were employed. The shock-on-lip Mach number of the studied inlet is 4.0 and the flight angle of attack is + 6°. Analysis was focused on the state with a freestream Mach number of 3.0. The results clearly show that the flow response hysteresis appears, and restart is only realized when the throat area is obviously increased as compared to that of unstart due to the historical unstart flow structure. In addition, three typical flow fields were analyzed, and it is found that the separation ahead of the inlet was the key factor affecting the hysteresis. Finally, unstart and restart boundaries of the inlet were discussed, and the factors influencing its deviation from the typical boundaries of dual-solution area were analyzed. The newly predicted unstart and restart boundaries are much closer to the CFD results.