Development of efficient and accurate skeletal mechanisms for hydrocarbon fuels and kerosene surrogate

In this paper,the methodology of the directed relation graph with error propagation and sensitivity analysis(DRGEPSA),proposed by Niemeyer et al.(Combust Flame 157:1760-1770.2010).and its differences to the original directed relation graph method are described.Using DRGEPSA,the detailed mechanism of ethylene containing 71 species and 395 reaction steps is reduced to several skeletal mechanisms with different error thresholds.The 25-species and 131-step mechanism and the 24-species and115-step mechanism are found to be accurate for the predictions of ignition delay time and laminar flame speed.Although further reduction leads to a smaller skeletal mechanism with 19 species and 68 steps,it is no longer able to represent the correct reaction processes.With the DRGEPSA method,a detailed mechanism for n-dodecane considering low-temperature chemistry and containing 2115 species and8157 steps is reduced to a much smaller mechanism with249 species and 910 steps while retaining good accuracy.If considering only high-temperature(higher than 1000 K)applications,the detailed mechanism can be simplified to even smaller mechanisms with 65 species and 340 steps or48 species and 220 steps.Furthermore,a detailed mechanism for a kerosene surrogate having 207 species and 1592 steps is reduced with various error thresholds and the results show that the 72-species and 429-step mechanism and the66-species and 392-step mechanism are capable of predicting correct combustion properties compared to those of the detailed mechanism.It is well recognized that kinetic mechanisms can be effectively used in computations only after they are reduced to an acceptable size level for computation capacity and at the same time retaining accuracy.Thus,the skeletal mechanisms generated from the present work are expected to be useful for the application of kinetic mechanisms of hydrocarbons to numerical simulations of turbulent or supersonic combustion.     

Regulating Phase Junction and Oxygen Vacancies of TiO2 Nanoarrays for Boosted Photoelectrochemical Water Oxidation

In this study, we have provided a facile solution to synthesize well-aligned titanium dioxide nanorods by using hydrothermal reaction. By calcining the materials under different atmospheres and temperatures, a batch of titanium dioxides with excellent oxygen evolution reaction(OER) catalytic efficiency were obtained. This new structured TiO₂ photoanode material yields a high photocurrent density of 5.69 mA/cm² at 1.23 V vs. reversible hydrogen electrode(RHE) under simulated solar light(100 mW/cm²). Surface photovoltage techniques and other measurements were carried out to confirm that the enhanced photoelectrochemical performances were attributed to the synergistic effect of the phase junction and a certain content of surface states, which accelerate the separation and transmission of the photogenerated charges. This material with phase junction and surface states promises a potential application in the field of photoelectric catalysis under solar light.     

Spreading of Oil Droplets Containing Surfactants and Pesticides on Water Surface Based on the Marangoni Effect

Oil droplets containing surfactants and pesticides are expected to spread on a water surface, under the Marangoni effect, depending on the surfactant. Pesticides are transported into water through this phenomenon. A high-speed video camera was used to measure the movement of Marangoni ridges. Gas chromatography with an electron capture detector was used to analyze the concentration of the pesticide in water at different times. Oil droplets containing the surfactant and pesticide spread quickly on the water surface by Marangoni flow, forming an oil film and promoting emulsification of the oil–water interface, which enabled even transport of the pesticide into water, where it was then absorbed by weeds. Surfactants can decrease the surface tension of the water subphase after deposition, thereby enhancing the Marangoni effect in pesticide-containing oil droplets. The time and labor required for applying pesticides in rice fields can be greatly reduced by using the Marangoni effect to transport pesticides to the target.     

Ring Airy-Like Beams along Predesigned Parabolic Trajectories

By phase-modulating ring Airy Gaussian beams, ring Airy-like beams propagating along predesigned parabolic trajectories are presented which combine the properties of accelerating beams and abruptly autofocusing beams analytically and numerically for the first time. The enhancement of the quadratic term ratio α shortens the autofocus distance and increases the slope of the beams after autofocusing. Interestingly, the main lobe tends to break into pieces as α increases and the possible reasons have been discussed. Furthermore, the distribution factor β and the radius of the primary r₀ can prominently affect the autofocus distance and the intensity at the focal point but do not change the slope of the beams after the autofocusing. In addition, the self-healing properties are validated to be retainable while RAiG beams via predesigned parabolic trajectories with various α.     

Separation,Quantification and Structural Study of (+)‐Catechin and (–)‐Epicatechin by Ion Mobility Mass Spectrometry Combined with Theoretical Algorithms

Two catechin epimers and their non‐covalent complexes with γ‐cyclodextrin were studied by using ion mobility coupled with mass spectrometry (IM‐MS). Rapid separation of complexes was achieved with the peak‐to‐peak resolution reaching 0.86 after optimization of IM condition. Collision cross section (CCS) was measured to explore the structural difference of complexes. A gap of 11.75 Ų between two complexes was found. Molecular modeling and theoretical CCS calculation were adopted to explain the measurement results. Two binding ways of both complexes were found and the calculated CCS corresponds accurately to the measured CCS. Quantification of catechins in mixtures was performed and the relative error was less than 15%, indicating the effectiveness of quantification by IM‐MS.     

Efficient Generation of Atomic Singlet State with Rydberg Blockade and Lie-Transform-Based Pulse Design

A protocol to generate atomic singlet state of three atoms is proposed. The strong Rydberg interactions between atoms mediate the multi-qubit operations and help to simplify the dynamics of the system. The effective Hamiltonian is constructed in the regime of Rydberg blockade and the evolution path is built up from an initial state to the target singlet state via the Lie-transform-based pulse design. Numerical simulations show the protocol can produce atomic singlet state with high fidelity and holds robustness against several types of experimental imperfections. Therefore, it may provide some useful results for the generation of singlet states in atomic system.     

An efficient approach to isoquinoline via AgNO3-promoted 6-endo-dig cyclization followed by oxidative elimination of o-alkynylarylaldimines and its application in fluoride recognition

A novel 6-endo-dig cyclization followed by oxidation/elimination of o-alkynylarylaldimines with 4-hydroxybenzylamine was developed for preparation of isoquinolines. The intermediates of this tandem reaction were monitored by mass spectroscopy (MS) to confirm the reaction pathway. This methodology was further applied to the design and synthesis of a novel ratiometric chemosensor for determination of fluoride.     

Experimental and Numerical Investigation on Effects of the Steam Ingestion on the Aerodynamic Stability of an Axial Compressor

In order to investigate the influence of steam ingestion on the aerodynamic stability of a two-stage low-speed axial-flow compressor, multiphase flow numerical simulation and experiment were carried out. The total pressure ratio and stall margin of the compressor was decreased under steam ingestion. When the compressor worked at 40% and 53% of the nominal speed, the stall margin decreased, respectively, by 1.5% and 6.3%. The ingested steam reduced the inlet Mach number and increased the thickness of the boundary layer on the suction surface of the blade. The low-speed region around the trailing edge of the blade was increased, and the flow separation region of the boundary layer on the suction surface of the blade was expanded; thus, the compressor was more likely to enter the stall state. The higher the rotational speed, the more significant the negative influence of steam ingestion on the compressor stall margin. The entropy and temperature of air were increased by steam. The heat transfer between steam and air was continuous in compressor passages. The entropy of the air in the later stage was higher than that in the first stage; consequently, the flow loss in the second stage was more serious. Under the combined action of steam ingestion and counter-rotating bulk swirl distortion, the compressor stability margin loss was more obvious. When the rotor speed was 40% and 53% of the nominal speed, the stall margin decreased by 6.3% and 12.64%, respectively.     

Morphology control and photocatalytic characterization of WO3 nanofiber bundles

WO₃ nanofiber bundles with high photocatalytic activity have been synthesized through the soluble salt-assisted hydrothermal method.     

Improved Biodegradation of Synthetic Azo Dye by Anionic Cross-Linking of Chloroperoxidase on ZnO/SiO<Subscript>2</Subscript> Nanocomposite Support

A novel ZnO nanowire/macroporous SiO₂ composite was used as a support to immobilize chloroperoxidase (CPO) by in situ cross-linking method. An anionic bi-epoxy compound was synthesized and used as a long-chained anionic cross-linker, and it was adsorbed on the surface of ZnO nanowires through static interaction before reaction with CPO, creating a new approach to change the structure, property, and catalytic performance of the produced cross-linking enzyme aggregates (CLEAs) of CPO. The immobilized CPO showed high activity in the decolorization of three azo dyes. The effect of various conditions such as the loading amount of CPO, solution pH, temperature, and dye concentration was optimized on the decolorization. Under optimized conditions, the decolorization percentage of Acid Blue 113, Direct Black 38, and Acid Black 10 BX reached as high as 95.4, 92.3, and 89.1%, respectively. The immobilized CPO exhibited much better thermostability and resistance to pH inactivation than free CPO. The storage stability and reusability were greatly improved through the immobilization. It was found from the decolorization of Acid Blue 113 that 83.6% of initial activity retained after incubation at 4 °C for 60 days and that 80.9% of decolorization efficiency retained after 12 cycles of reuses.