Search

The research object in this paper is an industrial HTL gasifier in a plant. A three-dimensional model is built. The chemical percolation devolatilization (CPD) model is used to calculate the pyrolysis reaction. Considering the gas diffusion in the inner pores of the particle and the evolution of pore structure, the random pore model (RPM) was used to simulate the chemical reaction on the particle surface, and the gasification reaction kinetic parameter of char was measured by high-pressure thermogravimetry analysis. The slag model was constructed to describe the formation process and distribution of slag. Through the coupling of the above models, a simulation method that combines several submodels for the entrained flow gasifier is built, and the results from simulation are in good agreement with the industrial data. Furthermore, the effect of the uniformity of pulverized coal injection was analyzed by this method. The simulation results reflect that the asymmetric feed of coal will affect gas-solid mixing and reduce carbon conversion, and it leads to a higher local wall temperature and a lower ratio of crude slag to fine slag.

Aiming at the dry pulverized biochar fuel refined by thermochemical conversion technology, its properties were obtained through experiment. By blending 5% additives to improve the ash fusion characteristics of biomass particles and considering the viscosity-temperature characteristics and the matching principle of CO2 reaction activity, the entrained flow gasification technology scheme of biomass particles was formulated. Based on the gasification reaction kinetics of dry pulverized biochar, a numerical simulation model was established to predict the flow characteristics, syngas composition, and particle conversion process in the gasifier. The results show that under the swirling entrainment and centrifugal force, the oxidizing reaction of particles is completed in the upper part of the gasifier quickly after mixing with oxygen. And the gasification reduction reaction occurs in the recirculating area and the pipe flow area. These effectively complete the conversion of char. The simulation results are in good agreement with the equilibrium calculation values, which proves the feasibility and rationality of the biomass particle entrained flow gasification technology scheme based on the HT-L.

Given the high power consumption rate of large venues with high power consumption, excessive carbon emissions, and severe environmental pollution, this paper proposes a low-carbon operation mode for large venues with high power consumption based on big data mining technology. The DEA model of high-power consumption venues is constructed by linear programming. Then the preliminary indicators of low-carbon operation mode are selected based on big data mining technology. Finally, the selected indicators are used to set up the operation system. Through experimental analysis, it is found that the low-carbon operation mode of large venues with high power consumption can reduce 2 million kg of carbon emissions on the basis of the initial value of carbon emissions. This mode can effectively reduce the carbon emissions of high-power consumption venues and play a great role in curbing environmental pollution and improving the social benefits of venues.

Effects of the incident shear flow on operational performance of a drag-type hydrokinetic rotor were investigated numerically. A flow visualization experiment was conducted to validate the numerical method. Energy conversion ability of the rotor under different incident shear flow conditions were analysed. The effects of the tip speed ratio were also taken into consideration. The results show that under the incident shear flow conditions, the upstream flow inclines downward and the velocity magnitudes at the upper and lower side of the rotor are significantly different, which affects the operation of the rotor. As the shear coefficient increases, the azimuthal angle range corresponding to the negative torque coefficient reduces and the fluctuation of the torque coefficient with the azimuthal angle appears delay phenomenon. The tip speed ratio has a great effect on the flow patterns around the rotor. The shape and position of the flow structures downstream of the rotor vary obviously with the tip speed ratio. The results are anticipated to provide sound support on the design and optimization of the drag-type hydrokinetic rotor in actual condition.

At present, the environmental problems in the water are becoming more and more prominent, and many teams are working on the research of the automation of garbage collection at sea. In order to a ready-made sea on the garbage recycling equipment automation, intelligent recognition for all white plastic and in identifying regional planning the path of the recycling of recycling equipment, aiming at different times during the day under the sea lighting situation, puts forward a visual processing and multi-step sea boundary identification method. After the image is processed by using two peak method normalized Canny boundary scan and other methods, the vertical and horizontal scanning and boundary recognition are carried out to obtain the closed Marine garbage main body area. Finally, Zigzag algorithm is used to carry out recovery path planning in the scanned area, and the results under different search radii are compared and analysed. The experimental results show that this method is applicable to a wide range of applications and has high accuracy and practicability, and the recognition results are satisfactory.

For a molecule irradiated by an intense laser field, the sudden excitation or removal of an electron will trigger ultrafast electronic and nuclear dynamics, of which the timescales are usually several orders different and can be separately treated according to the Born-Oppenheimer approximation. However, the electrons and nuclei are intrinsically coupled in a molecule and should be considered on an equal footing in strong laser fields. In this paper, we review the recent progresses made on the correlated electron-nuclear dynamics of molecules exposed to strong laser fields, in particular, the multiphoton energy absorption and deposition in molecular dissociative ionization. Moreover, the electron-nuclear correlation offers an alternative visual angle to capture the fascinating strong-field molecular dynamics, including the photon-number-resolved asymmetric dissociative single ionization, high-order above-threshold dissociation, and Rydberg states excitation in dissociative frustrated ionization of molecules, which cannot be revealed if only the electrons or nuclear fragments are measured independently.

Hexagonal boron nitride ceramic (h-BN) based on the nitridation of B powders was obtained by reaction sintering method. The dynamic compressive response was investigated using a Split Hopkinson pressure bar tester at high strain rates in a range of 0.8×103−1.6×103s−1. By increasing the strain rate, the dynamic strength and the failure strain increased continuously. The compressive stress–strain curves exhibited universal three deformation regions, including inelastic deformation region, rapid loading region and failure region. The failure mode of the h-BN ceramic depended upon the strain rate.

We experimentally investigate the dissociative frustrated double ionization of N2Ar dimers exposed to strong laser fields by measuring the ejected charged and excited neutral Rydberg fragments in coincidence. The results show that the tunneled electron is more likely to be recaptured by the argon atomic ion than the nitrogen molecular ion to form the neutral Rydberg fragment in the dissociative frustrated double ionization of N2Ar dimers. It is attributed to the T-shaped molecular structure and the electron-localization-assisted enhanced ionization of the N2Ar dimer.

We experimentally investigate Coulomb exploded directional double ionization of N2O molecules in elliptically polarized femtosecond laser pulses. The denitrogenation and deoxygenation channels are accessed via various pathways. It leads to distinct asymmetries in directional breaking of the doubly ionized N2O molecules versus the instantaneous laser field vector, which is revealed by tracing the sum-momentum spectra of the ionic fragments as a recoil of the ejected electrons. Our results demonstrate that the accessibility of the Coulomb exploded double ionization channels of N2O molecules are ruled by the detailed potential energy curves, and the directional emission of the fragments are governed by the joint effects of the electron localization-assisted enhanced ionization of the stretched molecules and the profiles of the molecular orbitals.

The congestion state models are established for three traffic modes of city railway hubs. According to visual and psychological characteristics of passengers, a new dynamic guidance sign system is designed to release transfer information. The identification and continuity level of information on guidance signs are evaluated to make the design more reasonable. The research would provide a new design and evaluation method for transfer information guidance system in city railway hubs.

The performance of the electric field sensing unit determines the sensitivity, linearity and range of the electric field sensor. In this paper, a kind of alternating electric field sensing unit based on parallel capacitance was been introduced. And it analyzed the measurement principle of the parallel capacitive sensing unit. The structure parameters of the electric field sensing unit with equipotential ring were been designed by simulation, which reduced the influence of edge effect on the performance of the sensing unit. According to the measurement standard of power frequency electric field, the designed sensing units were tested under uniform electric field. And the influence of the sampling capacitances on the static characteristics of the sensing unit was been analyzed. The sensing unit with the best performance had a linearity of 1.6025% and a sensitivity of 248 mV/(kV/m). Its sensing unit had the characteristics of small volume, low production cost and it was easy to integrate and have mass production.

We experimentally investigate symmetric dissociative double ionization of acetylene in femtosecond laser pulses of various ellipticities. Two dissociative ionization pathways with kinetic energy release of 4.8 and 6.0 eV, denoted as the low- and high-EN pathways, are observed in the spectrum of the ejected fragment ions. The relative yield of the high-E N gradually increases as compared to the low-E N when the polarization of the driving laser field is adjusted from linear to circular with increasing ellipticity. The low and high-E N fragment ions exhibit distinct angular distributions for various field ellipticities. It is attributed to the releasing of electrons from orbitals of different symmetries in producing the low- and high-E N pathways.

This study investigates the multi-objective optimization of quality characteristics for a T300/epoxy prepreg tape-wound cylinder. The method integrates the Taguchi method, grey relational analysis (GRA) and response surface methodology, and is adopted to improve tensile strength and reduce residual stress. In the winding process, the main process parameters involving winding tension, pressure, temperature and speed are selected to evaluate the parametric influences on tensile strength and residual stress. Experiments are conducted using the Box–Behnken design. Based on principal component analysis, the grey relational grades are properly established to convert multi-responses into an individual objective problem. Then the response surface method is used to build a second-order model of grey relational grade and predict the optimum parameters. The predictive accuracy of the developed model is proved by two test experiments with a low prediction error of less than 7%. The following process parameters, namely winding tension 124.29 N, pressure 2000 N, temperature 40 °C and speed 10.65 rpm, have the highest grey relational grade and give better quality characteristics in terms of tensile strength and residual stress. The confirmation experiment shows that better results are obtained with GRA improved by the proposed method than with ordinary GRA. The proposed method is proved to be feasible and can be applied to optimize the multi-objective problem in the filament winding process.

Superconducting nanowire single-photon detectors (SNSPDs) are widely used for the detection of visible and near-infrared single photons. Due to the nature of the polarization sensitive absorption of the nanowire, the detection efficiency (DE) of the meander SNSPD is polarization sensitive. In order to obtain a polarization-insensitive device with high DE, we fabricated NbN SNSPDs with spiral structure, which were embedded into an optical cavity. No meaningful current crowding effect was observed in the spiral SNSPDs. The spiral SNSPD showed a maximal system detection efficiency of 52.5% at 1550 nm with a dark count rate of 100 Hz and a polarization extinction ratio of 1.04, due to the combination of a spiral geometry and an optical cavity.

The performance of superconducting nanowire single-photon detectors (SNSPDs) relies on substrate materials. Magnesium fluoride (MgF2) exhibits outstanding optical properties, such as large optical transmission range and low refractive index (n = 1.38), making it an attractive substrate. We present the fabrication and the performance of SNSPDs made of a 4.5 nm thick NbN thin film deposited on MgF2 substrate for the wavelength of 1550 nm. The front-side illuminated SNSPDs without an optical cavity showed a maximal detection efficiency of 12.8% at a system dark count rate (DCR) of 100 Hz, while the backside illuminated SNSPDs with a SiO2/Au optical cavity atop displayed a maximal detection efficiency of 33% at a DCR of 100 Hz.

We experimentally investigate directional bond breaking in dissociative single ionization of H2 driven by circularly polarized two-color ultrashort pulses of counter- and co-rotating laser fields. Trefoil or semilunar patterns of directional proton emission in a two-dimensional space spanned by the laser fields are observed, which can be finely controlled by varying the relative phase of the counter- or co-rotating circularly polarized two-color fields, respectively. Our results open new possibilities to manipulate two-dimensional directional bond breaking of molecules by strong laser fields.

Exploring the role of electrode metals on the resistive switching properties of metal electrode/oxide/metal electrode sandwiched structures provides not only essential information to understand the underlying switching mechanism of the devices, but also useful guidelines for the optimization of the switching performance. A systematic study has been performed to investigate the influence of electrodes on the resistive switching characteristics of zinc oxide (ZnO) films in this contribution, in terms of both the intrinsic and interfacial effects. It has been found that the low-resistance state resistances (Ω(LRS)) of all the investigated devices are below 50 Ω, which can be attributed to the formation of highly conductive channels throughout the ZnO films. On the other hand, the high-resistance state resistances (Ω(HRS)) depend on the electronegativity and ionic size of the employed electrode metals. Devices with electrode metals of high electronegativity and large ionic size possess high Ω(HRS) values, while those with electrode metals of low electronegativity and small ionic size carry low Ω(HRS) values. A similar trend of the set voltages has also been observed, while the reset voltages are all distributed in a narrow range close to ±0.5 V. Moreover, the forming voltages of the switching devices strongly depend on the roughness of the metal/ZnO and/or ZnO/metal interface. The present work provides essential information for better understanding the switching mechanism of zinc oxide based devices, and benefits the rational selection of proper electrode metals for the device performance optimization.

A single cluster covering for the ship tiling of a dodecagonal quasiperiodic structure is obtained via a self-similar transformation, by which a turtle-like cluster, dubbed as a T-cluster, comprising seven squares, twenty regular triangles and two 30°-rhombuses, is changed into twenty scaled-down T-clusters, each centering at a vertex of the original one. Remarkably, there are three types of transformations according to the distinct configuration of the 20 scaled-down T-clusters. Detailed data for the transformations are specified. The results are expected to be helpful for the study of the physical and structural properties of dodecagonal quasicrystals.

The single cluster covering approach provides a plausible mechanism for the formation and stability of octagonal and decagonal quasiperiodic structures. For dodecagonal quasiperiodic patterns, such a single cluster covering scheme is still unavailable. We demonstrate that ship tiling, one of the dodecagonal quasiperiodic structures, can be completely covered by a single cluster. A deflation procedure is devised by assigning proper orientations to different tiles, and nine types of vertex configurations, if the mirror patterns are considered to be identical, have been identified, which fulfill the closure condition under deflation and all result in a T-cluster centered at the vertex.

Pure phase polycrystalline clathrates Sr8Ga16−xGe30−y with Ga/Ge ratios ranging from 0.481 to 0.517 have been prepared by the melting method. The obtained samples exhibit n-type conduction behaviour with carrier concentrations varying from 0.33 × 1020 to 2.81 × 1020 cm−3 as the Ga/Ge ratio changes from 0.517 to 0.481 at room temperature. The relationship between the thermoelectric properties and the Ga/Ge ratio is explored. The electrical conductivities increase and the absolute Seebeck coefficients decrease with a decrease in the Ga/Ge ratio. The power factors increase with a decrease in the Ga/Ge ratios. The thermal conductivities are maintained at the same order, lower than 1 W m−1 K−1 at room temperature. As a result, a maximum ZT value of 0.85 is obtained at 650 K for the lowest Ga/Ge ratio sample of Sr16.86Ga27.01Ge56.13.