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Abstract Photocatalytic oxidative coupling of methane with oxygen is promising to obtain valuable muti-carbon products, yet suffering low reactivity. Here, we apply cerium modifications on zinc oxide-supported gold catalysts based on the electronic asymmetry design of lattice oxygen to improve the coupling activity. The methane conversion rate exceeds 16000 μmol g−1 h−1 with muti-carbon selectivity of 94.9% and catalytic durability of 3 days, and it can increase to 34000 μmol g−1 h−1 under more thermal assistance, with a turnover frequency of 507 h−1 for ethane and an apparent quantum efficiency of 33.7% at 350 nm. According to systematic characterizations and theoretical analysis, cerium dopants not only can boost the formation of reactive oxygen species but also intervene in the vivacity of lattice oxygen by manipulating metal-oxygen bond strength, thereby leading to favorable methyl desorption to form ethane and quick water release. This work provides insight into the rational design of efficient photocatalysts for aerobic methane-to-ethane conversion.

Abstract Graphene as a lubricating additive holds great potential for industrial lubrication. However, its poor dispersity and compatibility with base oils and grease hinder maximizing performance. Here, the influence of graphene dispersion on the thickening effect and lubrication function is considered. A well-dispersed lubricant additive was obtained via trihexyl tetradecyl phosphonium bis(2-ethylhexyl) phosphate modified graphene ([P66614][DEHP]-G). Then lithium complex grease was prepared by saponification with 12-OH stearic acid, sebacic acid, and lithium hydroxide, using polyalphaolefin (PAO20) as base oil and the modified-graphene as lubricating additive, with the original graphene as a comparison. The physicochemical properties and lubrication performance of the as-prepared greases were evaluated in detail. The results show that the as-prepared greases have high dropping point and colloidal stability. Furthermore, modified-graphene lithium complex grease offered the best friction reduction and anti-wear abilities, manifesting the reduction of friction coefficient and wear volume up to 18.84% and 67.34%, respectively. With base oil overflow and afflux, well-dispersed [P66614][DEHP]-G was readily adsorbed to the worn surfaces, resulting in the formation of a continuous and dense graphene deposition film. The synergy of deposited graphene-film, spilled oil, and adhesive grease greatly improves the lubrication function of grease. This research paves the way for modulating high-performance lithium complex grease to reduce the friction and wear of movable machinery.

Abstract Designing novel lubricants with easily customized structures, devisable compositions, and simple and economic synthesis over traditional lubricants is critical to fulfilling complex applications, prolonging machine lifetime, and saving energy. Deep eutectic solvents (DESs), which show tunable composition, adjustable structure, easy fabrication, and environmental friendliness, are promising candidates for variable and complicated lubricants applications. To promote the use of DESs as lubricants, a series of PEG200-based DESs with active heteroatoms were fabricated to tailor the tribological performance via tribo-chemistry. Thereinto, PEG200/boric acid (BA) DES shows optimal lubrication performance by forming tribo-chemical reaction film composited of B2O3, iron oxides, and FeOOH, and PEG200/thiourea (TU) DES displays abrasive wear-reducing property by producing FeS tribo-chemical film. Given the excellent abrasive wear-resistance of PEG200/TU DES and friction reduction of PEG200/BA DES, ternary PEG200/BA/TU DESs, composited of PEG200/TU DES and PEG200/BA DES, are first exploited. The ternary DESs possess superior wettability and thermal stability, which render them potential lubricants. Tribological tests of the ternary DESs demonstrate that synergistic lubrication is achieved by forming a transfer film consisting of Fe x B y , BN, B2O3, and FeS. Wherein Fe x B y , BN, and B2O3 increase load bearing of the film, and FeS mitigates severe abrasive wear. The proposed design philosophy of novel DESs as lubricants opens up a unique realm that is unattainable by traditional DESs lubrication mechanisms and provides a platform to design next-generation DESs lubrication systems.

Abstract By simply switching the electrical circuit installed on steel/steel contact, the tribological behaviors of nanofluids (NFs) can be regulated in real time, thereby achieving the desired performance of friction reduction and wear resistance. Herein, solvent-free carbon spherical nanofluids (C-NFs) were successfully prepared for intelligent lubrication regulation. C-NFs with excellent lubrication performance can immediately reduce the coefficient of friction (COF) despite applying a weak electric potential (1.5 V). Moreover, polyethylene glycol 400 (PEG400) containing 5.0 wt% C-NFs remained responsive to electrical stimulation under the intermittent voltage application with an average coefficient of friction (ACOF) reduction of 20.8% over PEG400. Such intelligent lubrication regulation of C-NFs under an external electric field (EEF) mainly depends on the orderly arranged double-electric adsorption film of ion canopy-adsorbed carbon spheres (CSs). The intermittent electrical application can continuously reinforce the adsorption film and its durability for real-time controlling the sliding interfaces. Electrical-stimulation-responsive intelligent lubricants provide a new technical support for realizing intelligent stepless control of devices.

The aft-body mounted inlet of a hypersonic vehicle has garnered attention for its potential to shorten the propulsion system. This study aims to explore the influence of compression direction on the performance of the hypersonic inlet attached to the vehicle’s aft body. To achieve this objective, a simplified, integrated model of the body and two-dimensional inlet was developed and evaluated using numerical simulation techniques. The study conducted a comparative analysis of the overall and starting performance between inverted and normal inlet layouts while ensuring uniformity in inlet configuration and installation location. The results indicated that the inverted layout surpassed the normal layout in terms of airflow capture capabilities, with an 8.24% higher mass flow rate. However, the inverted inlet layout exhibited an 11.46% reduction in total pressure recovery performance compared to the normal layout. Additionally, the study found that the inverted inlet layout demonstrated a self-starting Mach number 1.62 lower than that of the normal inlet layout. This difference stemmed primarily from the pressure gradient on the body surface induced by the incident shock wave of the inverted inlet, which enhanced starting performance by eliminating low-energy flow near the wall.

The mechanical properties and toughness of phase change materials are often weakened by defects which affect the application of matrix in tribology, and considering the hybridization of nanomaterials is able to increase the upper limit of materials’ performance. In this study, the in-situ polymerization of isopropylacrylamide was used on the surface of graphene and MXene to prepare a phase change two-dimensional composite with reversible phase change under specific temperatures. The composites were dispersed in epoxy resin matrix by KH550 (γ-Aminopropyl triethoxysilane) to realize phase change modulation of tribological properties. The results showed that the tribological properties of the modified epoxy resin coating realized friction reduction and anti-wear functions, and exhibited different tribological properties at different temperatures. The friction coefficient and wear rate of the composite coatings can be reduced to 0.1 % and 82.2 %, respectively, which is mainly attributed to the two-dimensional structure and physical characteristics of graphene and MXene, as well as the mechanical enhancement of the phase change homopolymer and their synergistic effects.

Compressor characteristic evaluation is a critical step in design and optimization. Corrected characteristic curves are typically derived via experimental testing or CFD computation which is typically executed through manual manipulation. For compressors necessitating extensive characteristic computation across multiple speeds and operational conditions, the involved process is inherently complex. This paper introduces an automation approach, employing dichotomy and optimization algorithms aligned with a 3D numerical solver, to streamline the derivation of compressor characteristic curves. Initially, the paper delineated the procedural frameworks for two methodologies and validated them using a single-stage transonic compressor. Both methods achieved the automated resolution of the characteristic lines. The result indicates that the volume of the iterative computations hinges on the granularity of the space searching step and the precision in identifying the stall boundary point. Pertaining to the subject investigated herein, the dichotomy method entailed fewer iterations relative to the optimization algorithm. Subsequent adjustments to the optimization algorithmic process revealed that direct optimization mitigated computational demands substantially by reducing a cycle, thereby attesting to its superior efficacy. In summary, when simulating compressor characteristic curves, the dichotomy method proves more efficient when the interval value of the stall boundary range can be approximated. Conversely, direct optimization is preferable when the estimation of the compressor’s stall boundary is imprecise. The proposed methodologies contribute to compressor research and expedite the progression of compressor development and performance advancement.

Intense shock boundary-layer interaction may lead to multiple unstart modes existing in a hypersonic inlet. Thus, self-start problems become complex and cannot be explained using the classical double-solution theory of air inlet. The essence of the self-start process of a hypersonic inlet is the vanishment of separations near or in the inlet. To clarify self-start characteristics, experiments were conducted on three distinct types of unstart mode: the flow mode of small separation on body (SSB), large separation on body (LSB), and dual separations on both body and lip (DSBL); researchers recently discovered these as the unstart modes of hypersonic inlet. The results from the current experiment are as follows: (1) The SSB vanishes by raising the angle of attack (alpha). Before the vanishing point is reached, there is a dwindling process for this separation. (2) The LSB vanishes through acceleration or a decreasing alpha. (3) DSBL are difficult to vanish directly, which results in poor self-start performance. However, the DSBL flow mode may convert to LSB unstart form—which is easier to self-start—by decreasing the alpha. The Flow Field Reconstruction Method was designed to improve the self-start of the DSBL flow mode, and it was validated through experiments. Analysis of the flow mechanism revealed the reason for the poor self-start performance of the DSBL unstart mode: large-scale separation on the lip side cannot be promoted to vanish through broadwise spillage due to the resistance of sideboards. The results of this study could greatly enrich the existing theory of start problems for hypersonic inlets.

Endowing Mg alloy surface with superhydrophobicity solves its poor corrosion resistance for broadening the wide application fields. However, the superhydrophobicity is vulnerable to failure under service environments due to the exfoliation and degradation of surface material. Hence, a bilayer composite coating composed of microarc oxidation layer and superhydrophobic layer was fabricated to protect Mg alloys by modulating superhydrophobic coating/substrate interface. The bilayer coating with a water contact angle of 158.3° possesses excellent water-repellent, and self-cleaning properties. In addition, the bilayer coating consistently remains superhydrophobicity in acid, alkaline, high/low temperature, and ultraviolet radiation environments, indicating the excellent environmental stability. Notedly, the lowest-frequency impedance value of bilayer coating (6.78 × 106 Ω·cm) increases five orders of magnitude compared with that of Mg alloy (60.2 Ω·cm), and the inhibition efficiency is calculated to be 99.99 %. The excellent corrosion resistance of coating is attributed to the synergistic barrier protection of microarc oxidation layer and superhydrophobic layer, implying that it provides effective protection for Mg alloy. Therefore, the as-prepared bilayer coating has great application prospects in corrosion protection of Mg alloys toward different service environments.

Electrochemical exfoliation of graphene is an environmentally friendly method, which enables mass production. Herein, three ionic liquids (ILs) with the same imidazole cation were used to exfoliate graphite into functionalized graphene, as a lubricant additive in an acetonitrile solution. Chemical and structural characterization revealed the relationship between the functionalization density of graphene and the concentration of IL, showing higher concentrations with higher densities. The exfoliated graphene hybrid oil displayed good dispersion because of a high functionalization density. More importantly, the different anions affected the tribological properties of the exfoliated graphene. Among them, the exfoliated graphene with 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIm][PF6]) possessed the best tribological performance, and the average friction coefficient and wear volume were reduced by 32% and 39%, respectively. Through the characterization of worn surfaces and wear debris, the lubrication mechanism and structural evolution of the functionalized graphene were illustrated in detail. The good lubrication function was attributed to the formation of a tribo-film and the disorder transformation of the graphene structure. The simultaneous exfoliation and functionalization of graphene offers a promising advanced lubricant for industrial fabrication.

Experiments were conducted in this study to reveal the flow characteristics of a variable cross-section S-shaped isolator, when applying the steady-state back pressure at the isolator outlet. The self-excited oscillation characteristics of the shock train generated under the influence of steady-state back pressure at an incoming flow speed of Mach 2, were also studied. The findings suggest that pressure oscillation within the area affected by the shock train’s flow field was significantly more potent than outside the affected area. Moreover, the forward movement velocity of the shock train in the variable cross-section S-shaped isolator was not uniform. The forward movement speed was slower when encountering sharp turns and faster during gentle turns. In the shock train flow field, high-frequency pressure oscillations, which mainly stemmed from the oscillations of the separated shock legs, propagated more readily within the flow field than low-frequency pressure oscillations. The significant separation of the shock train flow field will switch between the top and bottom walls, and the frequency of pressure oscillation in the large separation region is low. On another note, the closer the distance between two points is in the shock flow field, the stronger the coherence of pressure oscillations will be. In the distance upstream of the shock train flow field, the turbulent boundary layer (TBL) determines pressure oscillations instead of the shock train flow field, so the coherence was very high.

Abstract In this study, lithium complex grease (LCG) and polyurea grease (PUG) were synthesized using mineral oil (500SN) and polyalphaolefin (PAO40) as base oil, adsorbed onto lithium complex soap and polyurea as thickeners, respectively. The effects of grease formulation (thickener and base oil with different amounts (80, 85, and 90 wt%) on the corrosion resistance and lubrication function were investigated in detail. The results have verified that the as-prepared greases have good anti-corrosion ability, ascribed to good salt-spray resistance and sealing function. Furthermore, the increase in the amount of base oil reduces the friction of the contact interface to some extent, whereas the wear resistance of these greases is not consistent with the friction reduction, because the thickener has a significant influence on the tribological property of greases, especially load-carrying capacity. PUG displays better physicochemical performance and lubrication function than LCG under the same conditions, mainly depending on the component/structure of polyurea thickener. The polyurea grease with 90 wt% PAO displays the best wear resistance owing to the synergistic lubrication of grease-film and tribochemical film, composed of Fe2O3, FeO(OH), and nitrogen oxide.

The success of carbon nanotubes (CNTs) as fillers in improving the physicochemical and mechanical properties of polymer is attributed to their unique structure and performance characteristics. The interfacial interaction between fillers and matrix is of significant influence in agglomeration of fillers and mechanical/damping properties of as-prepared composites. Here, polydopamine (PDA), (3-Aminopropyl) triethoxysilane (KH550) and ionic liquid (1-aminoethyl-3methylimidazolium bis ((trifluoromethyl) sulfonyl) imide)) were used to not only functionalize CNTs for suppressing their agglomeration, but also regulate the interfacial interaction between CNTs and carboxylated butadiene nitrile rubber (XNBR) for achieving excellent mechanical properties and better damping properties. The storage modulus of composites rose by 80% (from 1392 to 2488 MPa) with the addition amount of 2.2 wt% CNTs-KH550 and the tensile strength rose by 110% (from 0.32 to 0.68 MPa) with 3.0 wt% CNTs-IL. In addition, the damping degradation of composites caused by the agglomeration of fillers was resolved. The results of molecular dynamics (MD) simulation show that the strong interfacial interaction of CNTs-PDA and CNTs-KH550 is mainly attributed to hydrogen bond interaction, while the interaction of CNTs-IL is determined by hydrogen bond interaction and van der Waals' (vdW) force. The functionalized CNTs with excellent interfacial interaction and dispersion have bright application prospects in the field of composite. Keywords: Functionalized carbon nanotubes, Composite, Molecular dynamics simulation, Mechanical/damping properties

In the hypersonic regime, noncircular missiles have attracted significant attention from researchers. The paper first summarizes the development and present situation of the noncircular missiles at home and abroad. Previous research found that the cross-section shape of missiles has a direct influence on the aerodynamics performance. To find the best cross-section shape in terms of lift-drag-ratio, an efficient and robust shape optimization framework is developed. Class/shape function transformation (CST) method and power-law curve are introduced to complete the parametric modeling of the noncircular missile. The evolutionary algorithm has been utilized to improve the optimization efficiency. A combination of script and journal files is written to automate the CAD loft, mesh generation, and CFD simulations process. Finally, the forebody section of a missile body is chosen as an example to deliver the whole optimization steps. The optimization results show that the lift-to-drag ratio increases from 1.8 to 2.4 when the hypersonic missile forebody cruises at the design condition. The results also demonstrate that the optimized configuration has a better aerodynamic performance than the original one over a wide speed range from Mach 2 to 8 and a wide attack of angle range from 0 to 30.

Pancreatic cancer is an aggressive disease with dismal prognosis. It is of paramount importance to understand the underlying etiological mechanisms and identify novel, consistent, and easy-to-apply prognostic factors for precision therapy. TUSC3 (tumor suppressor candidate 3) was identified as a potential tumor suppressor gene and previous study showed TUSC3 is decreased in pancreatic cancer at mRNA level, but its putative tumor suppressor function remains to be verified. In this study, TUSC3 expression was found to be suppressed both at mRNA and protein levels in cell line models as well as in clinical samples; decreased TUSC3 expression was associated with higher pathological TNM staging and poorer outcome. In three pairs of cell lines with different NF-κB activity, TUSC3 expression was found to be reversely correlated with NF-κB activity. TUSC3-silenced pancreatic cancer cell line exhibited enhanced potential of proliferation, migration and invasion. In an orthotopic implanted mice model, TUSC3 silenced cells exhibited more aggressive phenotype with more liver metastasis. In conclusion, the current study shows that decreased immunological TUSC3 staining is a factor prognostic of poor survival in pancreatic cancer patients and decreased TUSC3 promotes pancreatic cancer cell proliferation, invasion and metastasis. The reverse correlation between NF-κB activity and TUSC3 expression may suggest a novel regulation pattern for this molecule.

Experimental results show that there exist two flow fields in the hypersonic inlets when the forebody waves interact with the lip boundary, which is similar to the shock reflection ion hysteresis phenomenon. In order to improve the performance of the flow field, counterflow is applied to control the shock reflection configuration in the hypersonic inlets. For better understanding of the internal mechanism, inviscid numerical simulation is conducted. And the results demonstrate that it is feasible to realize the transition between the regular reflection configuration and the Mach reflection ion configuration in the hypersonic inlets. That is because the von Neumann criterion and detached criterion play a dominant role, respectively, in these transitions. In addition, the evolution process of Mach reflection ion in the hypersonic inlets can be divided into three stages: transmission of waves, emergence of Mach stem, and stabilization of flow field.