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Turboprop aircraft plays an important role in the field of regional airliners and military transport. During take-off or landing, turboprop aircrafts frequently encounter bird flocks that can be ingested into the engine inlet, thereby posing a significant threat to flight safety. Consequently, the aerodynamic characteristics and bird ingestion characteristics of turboprop inlet are investigated in this article. An unsteady computational fluid dynamics (CFD) approach has been proposed to calculate bird ingestion characteristics in a turboprop inlet with different bulge heights under propeller interference by combining a self-developed collision-rebound model with the overset mesh method and 6-degree of freedom (6-DOF) motion method. Considering the characteristics of bird strikes, a parameterized controlled bulge of turboprop inlet with a scavenge duct has been designed. Moreover, the trajectory characteristics of the bird, bird-inlet coupling flowfield characteristics and the aerodynamic characteristics are analyzed in depth. The bulge of the inlet plays a positive role in preventing the bird object from entering the engine duct at a 23° incidence angle. The bird rebounds from the upper bulge and is discharged through the scavenge duct at Ma AIP =0.45. The results show that the growth of inlet bulge height has the minimal influence on the total pressure recovery coefficient σ, with only approximately 0.3% variation within the bulge height range of interest. However, it significantly affects the total pressure distortion DC60 with an increase up to 84%. [ABSTRACT FROM AUTHOR]

A green approach of using supercritical CO 2 in a silica-packed column via adsorption and desorption steps has been developed to enrich β-carotene in the 10% β-carotene concentrate made from crude palm oil. In the adsorption stage, the yield of the β-carotene poor fraction with the content of 3% was 82.2% when the pressure, temperature, CO 2 flow rate and the time were 25 MPa, 60 ℃, 3 kg/h, and 180 min, respectively. The rich β-carotene fraction adsorbed in the column was thoroughly extracted out by supercritical CO 2 when the pressure, temperature, flow rate and time were 35 MPa, 70 ℃, 3 kg/h, and 120 min, respectively, in which the β-carotene content reached 27% and the yield reached 22.3%. This two-step process is an efficient way to prepare natural β-carotene with high content and has potential applications in the concentration of value-added components. [ABSTRACT FROM AUTHOR]

It is highly desirable to develop industrially scalable methods to produce defect-free graphene to meet the requirement of graphene from lab to commercial applications. In this paper, a ball-milling in series with a shear-mixing exfoliation technique in supercritical CO 2 was developed. Graphite was pretreated by ball-milling in supercritical CO 2 , and the exfoliated sheets with smaller lateral sizes and numerous crevices on their edges were elutriated into a shear-mixing vessel by supercritical CO 2 simultaneously to inhibit over crushing. Whereafter, the freshly exfoliated sheets with crevices were further exfoliated into few-layer graphene without aggregation. 90% of the obtained graphene was less than five layers, and the processing capacity of 40 g for one batch increased 40–100 times compared with the previously reported method. The electrical conductivity of 3.25 × 105 S/m of the flexible graphene film on PVDF substrate demonstrates the excellent electrical performance of the obtained graphene. [Display omitted] • Continuous graphene exfoliation system via ball-milling and shear-mixing in SC-CO 2. • SC-CO 2 ball-milling pretreatment producing numerous crevices on graphite edges. • CO 2 elutriation separation inhibits over crushing and promoting exfoliation. • High-quality graphene was produced continuously with a single batch output of 40 g. • Obtained graphene showed excellent electrical conductivity of 3.25 × 105 S/m. [ABSTRACT FROM AUTHOR]

Three-dimensional and three-components (3D-3C) measurement of flow velocity vector is important for the investigation of mechanism underlying flow structure. Light-field particle imaging velocimetry (LF-PIV) is a newly emerged technique for flow velocity measurement. However, LF-PIV suffers low axial resolution, prohibiting it for high fidelity imaging. To overcome this limitation, we proposed to employ color-depth-encoded illumination in light-field PIV (Code LF-PIV) to refine the particle's axial location with the color-depth information of the illumination beam. Code LF-PIV is the first system that integrates the snapshot acquisition of light-field acquisition and the high resolution capability of color coded illumination. Compared to conventional light-field PIV, Code LF-PIV can achieve much higher axial resolution due to the new illumination strategy. Compared to traditional coded illumination PIV, such as Rainbow PIV, Code LF-PIV has higher flexibility for variant imaging applications because of the elimination of customized diffractive optical element. We demonstrated the superiority of our system by imaging fixed particle, randomly distributed cavities inside crystal cube, and the square lid-driven cavity flow, where our Code LF system has increased the axial resolution by a factor of 23 when compared to the conventional LF system, and has achieved a comparable axial resolution as the depth super-resolved Rainbow PIV. Comprehensive evaluation of the imaging results demonstrated that Code LF-PIV combines the advantages of the high resolution of color-depth coded method with the convenient volumetric imaging of light-field camera, making Code LF-PIV a useful technique for high-resolution and large-scale flow measurement. [ABSTRACT FROM AUTHOR]

The flow response hysteresis in a mixed-compression supersonic inlet's throttling/unthrottling process is unconducive to its practical engineering applications. To suppress such hysteresis, herein, a flow control method based on a distributed bleed system in the inlet's internal contraction part was proposed and applied to a rectangular supersonic inlet with a designed Mach number of 4.0 and an internal contraction ratio of 1.5. All tests were conducted in a supersonic wind tunnel at a freestream Mach number of 2.9, and the relevant test data were obtained using the high-speed schlieren and dynamic pressure measurement systems. The results indicate that the distributed bleed system improved the uncontrolled inlet's unstart throttling ratio from 43.8% to 47.3% and the restart throttling ratio from 29.4% to 47.1%, and it essentially eliminated the flow response hysteresis during the throttling/unthrottling process. Moreover, the hysteresis mechanism of the uncontrolled inlet, dominated by the separation-induced flow structures in the internal contraction part, was investigated to help elucidate the targeted control mechanism of the bleed system that suppresses the hysteresis. Finally, the specific flow phenomena in the oscillation of the controlled inlet were examined to study the bleed system's impact on the unsteady flowfield, including the coupled flow of the mainstream with the bleed system and complex wave motion structures. • Flow response hysteresis in a mixed-compression supersonic inlet's downstream throttling/unthrottling process is experimentally investigated. • An effective hysteresis suppression method based on a distributed bleed system is proposed. • New flow phenomena in the oscillation of the inlet under bleed control were examined. [ABSTRACT FROM AUTHOR]

In this study, high-aspect-ratio (~1250) curved copper nanowires (CuNWs) composed of formate (FA) as the surface passivation layer were synthesized by the solvothermal method using sodium formate (HCOONa). Experimental data and density functional theory (DFT) simulations suggest that the growth of CuNWs-FA was due to the high chemisorption energy of FA on the [100] plane of Cu. The relative resistance ratio of CuNWs-FA increased by 1.67 and 1.72 after aging at 25 °C for 60 days and 60 °C for 5 days, showing FA passivation greatly improved the oxidation resistance of CuNWs. The transparent conductive electrodes (TCEs) fabricated from CuNWs-FA showed high transmittance (89.19%), low sheet resistance (R s = 44.54 Ω sq−1), and excellent mechanical stability against 10,000 bending cycles. The TCEs-based transparent flexible heaters (TFHs) exerted a fast heating rate and a uniform temperature distribution within the 20 s response time, which is a testament to the CuNWs-FA in applications such as electrochromic and optoelectronic devices. This passivation approach sheds light on solving the major drawback of CuNWs oxidation and promotes its use in flexible electronic devices. • CuNWs coated with FA was synthesized by a straightforward synthesis method. • HCOONa acted as the mild reducing and surface coordinating agent. • CuNWs-FA presented superb resistance against oxidation. • CuNWs-FA based TCEs possessed promising optoelectronic performance. • TCEs-based TFHs showed high saturation temperature with short response times. [ABSTRACT FROM AUTHOR]

• Supercritical CO 2 elutriation coupled with the membrane was used to sort the AgNWs. • Almost 100 % purity of AgNWs were obtained from the initially synthesized mixture. • AgNWs-based TCEs displayed a transmittance of 99.6 %, with a low haze of 0.56 %. • The flexible electrode shows well-bending performance. Silver nanowires (AgNWs) are promising materials to fabricate flexible transparent conductive electrodes (TCEs) widely used in next-generation electronic devices. However, the impurity silver particles generated during synthesis severely deteriorated the optical transmission of AgNWs meshes. Isolating AgNWs from its reacted mixture is a vexing and challenging issue but highly desirable. In this work, a facile approach of using supercritical carbon dioxide elutriation coupled with a membrane was developed to purify the AgNWs from its synthesized mixture. Almost 100 % of purified AgNWs with the yield of 56 % was obtained, from which the AgNWs-based electrodes with excellent flexibility, conductivity, and transparency were fabricated. The AgNWs-based TCEs displayed a transmittance of 99.6 % with the haze of 0.56 % at the sheet resistance of 248 Ω·sq−1 or transmittance of 96.7 % with the haze of 1.36 % at the sheet resistance of 32.5 Ω·sq−1. The sheet resistance remained almost constant after bending in 1000 cycles. [ABSTRACT FROM AUTHOR]

Exfoliation of graphite has become a popular top-down method of producing graphene. However, it is still a challenging issue to prepare purified graphene because the exfoliated graphene was usually mixed with the un-exfoliated graphite. In this work, we investigated the isolation of the graphene and graphite by using supercritical CO 2 through Computational Fluid Dynamics (CFD) simulation and experimental. The Eulerian multiphase and standard k–ε turbulence models for CFD simulation were used to explore the influences of the pressure and the velocity of supercritical CO 2 , the geometry of the separation column, and the feeding amount of the mixture on the distribution of the graphene and graphite in the column. The isolation experiments were carried out based on the CFD simulation results, and the isolated graphene was characterized by Raman spectroscopy, X-ray diffraction, atomic force microscopy, and transmission electron microscopy. The results indicate that the purified graphene sheets can be obtained by supercritical CO 2 elutriation approach and the optimal experimental conditions were consistent with that obtained by CFD simulation. The graphene was isolated with graphite completely when the volume fraction of the mixture of the graphene and graphite was <20%, the pressure and the flow rate of supercritical CO 2 were 8 MPa and 0.2 m/s, respectively. The obtained graphene sheets mainly consisted of 3–5 layers. The CFD simulation is helpful in scale-up production of purified graphene by supercritical CO 2 elutriation technique. Unlabelled Image • The graphene in the mixture of the graphene and graphite was isolated by supercritical CO 2 elutriation technique. • The influences of process parameters on separation were investigated by CFD simulation and experiment. • The CFD simulation results were consistent with that obtained by experiment. • The purified graphene sheets consisted of 3–5 layers were obtained. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A free-standing PANI/G/MnO 2 paper electrode was constructed with exciting performance. • The electrode has a mass loading of 11.75 mg cm−2 and excellent flexibility stability. • The electrode has a sizeable areal capacitance of 3.5 F cm−2. • The all-solid-state supercapacitor was assembled with the ternary composite paper. • The supercapacitor exhibits a high energy density of 5.2 mW h cm−3 at 8.4 mW cm−3. Abstract Free-standing hierarchical polyaniline/graphene/MnO 2 (PANI/G/MnO 2) paper is well constructed using low-cost printing paper by a simple layer-by-layer in situ growth and vacuum filtration method. The PANI nanofiber was polymerized on cellulose fibers, and then the pristine graphene sheet was introduced to generate the polyaniline/graphene paper, whose surface was subsequently scattered with the formed MnO 2 nanoflowers through oxidation of the cellulose fiber and graphene. The PANI/G/MnO 2 paper possessing a mass loading of 11.75 mg cm−2 is of high flexibility and could serve as a working electrode without using any binder and conductive additives. The electrode shows a sizeable areal capacitance of 3.5 F cm-2 at 5 mA cm−2 and excellent cycling stability of 90% after 1000 bending cycles. All-solid-state supercapacitor assembled with the PANI/G/MnO 2 paper exhibits a high energy density of 5.2 mW h cm-3 at 8.4 mW cm-3. Eight supercapacitors connected in series can light a green light-emitting diode of 3 V. [ABSTRACT FROM AUTHOR]

High-resolution and large-scale three-dimensional measurements of the flow field are essential for us to uncover the underlying fluid mechanism. Currently, the mainstream modalities, such as tomographic particle imaging velocimetry and conventional light-field particle imaging velocimetry (LF-PIV), that can perform volumetric measurement suffer system complexity and low axial resolution, respectively, and cannot realize volumetric imaging at isotropic resolution with only one camera. Here, we proposed a dual-view LF-PIV system that can achieve three-dimensional acquisition at isotropic spatial resolution with only one camera. We comprehensively assessed the feasibility of the system through imaging of sparsely distributed beads, and real vortex flows generated via stir bar. We showed that our dual-view LF-PIV system resolved beads with isotropic resolution, reported lower errors of the divergence, and revealed the three-dimensional vortex field more accurately than the conventional system. To be the first PIV system that can achieve isotropic resolution volumetric imaging without adding extra cost in cameras, data acquisition, and hardware synchronization and scanning, our dual-view LF-PIV should open up avenues for large-scale high-resolution flow dynamics imaging. [ABSTRACT FROM AUTHOR]

• CuNWs-GNs composites with a length-diameter ratio of 1778 were formed in one-step. • The CuNWs-GNs based electrodes showed a low sheet resistance of 0.028 Ω·sq-1. • The electrodes displayed excellent oxidation stability at 25 ℃ and 65 ℃ for 46 days. • The transparent electrode exerted 87% transmittance at a resistance of 81.42 Ω/sq. • The electrodes exhibited excellent flexibility against bending up to 1000 cycles. Copper nanowires (CuNWs) endowed with oxidation stability without impairing their conductivity is highly desirable for their practical applications. This work demonstrates a green and cost-effective method to produce a stable copper nanowires-graphene nanosheets composite (CuNWs-GNs), and the electrodes based on CuNWs-GNs were fabricated. The CuNWs with a high-aspect-ratio of 1778 in-situ grown directly between the high crystalline GNs interlayers, thereby obtained a multilayer protective shield of GNs. The electrodes fabricated by a filtration method possessed high electrical conductivity of 2.77 × 106 S·m−1. The relative resistance ratio of the electrodes increased only 1.27 and 1.92, respectively, after aging at 25 ℃ and 60 ℃ for 46 days, which suggested that the electrodes had excellent oxidation stability. The transparent flexible electrodes (TFEs) fabricated on a polyethylene terephthalate sheet by a spray coating method presented an excellent transmittance of about 89% at an electrical resistance of 81.42 Ω/sq. The TFEs demonstrated impressive mechanical flexibility against 1000 bending cycles and in different radius curvature ranging from 1 mm to 30 mm. This approach sheds light on solving the big issue of the instability of CuNWs and promote their applications in a modern electronic device. [ABSTRACT FROM AUTHOR]