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In this work, the influence of the electrode surface roughness on the self-breakdown gas switch is investigated by physical analysis, computer simulation and experiment. Cu-W electrodes of different surface roughness were tested under the conditions of a pulse repetitive frequency of 50 Hz, self-breakdown voltage of ∼30 kV, and peak current of ∼2 kA for ∼93000 shots (the total charge transferred was ∼15 C). The coefficients of variation of the self-breakdown voltage of Cu-W 0.8, Cu-W 3.2 and Cu-W 12.5 electrodes were ∼2.95%, ∼1.62% and ∼1.16%, respectively. With the increase of electrode roughness, the erosion area decreased continuously, indicating that the breakdown positions were more stable and the coefficient of variation of breakdown voltage decreased. The method showed that decreasing the coefficient of variation of the self-breakdown voltage by increasing the surface roughness of electrode greatly improves the stability of the self-breakdown switch, which is significant for their application in compact high-power pulse power devices over a long time with stable operation.

As an effective and reliable method of obtaining extremely high magnetic fields, rare-earth barium copper oxide (REBCO) magnets have contributed significantly to the development of condensed matter physics, chemistry, life sciences, and materials research. However, large screening currents in REBCO magnets can significantly degrade the magnetic field quality. Recent experiments on the inner insert of a 30 T superconducting magnet at the Institute of Electrical Engineering, Chinese Academy of Sciences showed that the measured magnetic field is highly asymmetric single-peaked field instead of the designed saddle-shaped fields, and it differs significantly from the values calculated based on the commonly-used uniform and symmetric screening current model. Therefore, a simulation model based on the T–A formulation with consideration of accurate dimensions and critical currents was developed. The simulation results with this new developed model indicate that the angle dependence can cause more than an 8.3% difference in the critical currents of the symmetrically located double pancake (DP) coils of the magnet. The average relative error between the measured and calculated magnetic field values was sharply reduced by a maximum of 44.4% after considering the non-uniform critical currents. In consideration of manufacturing uncertainties and non-uniform critical currents, better magnetic field quality of REBCO magnets can be achieved by arranging the location of each DP with this model.

The bandstructure of a material, playing an important role in its electron transport property, is usually governed by the lattice configuration. Materials with a field-effect tunable band, such as bilayer [1] and rhombohedral trilayer graphene [2, 3], are more flexible for electronic applications. Here, on dual-gated twisted double bilayer graphene (TDBG) samples with small twist angle around 1∘, we observe vertical electric-field-tunable bandstructures at multiple moiré fillings with bandgap values continuously varying from zero to tens of mili-electron volts. Moreover, within the first moiré filling on both electron and hole sides, the carrier transport deviates from Fermi liquid behavior, with measured resistivity exhibiting linear temperature dependence between 1.5 K and 50 K. Furthermore, under a vertical magnetic field, the coupling between the two bilayer graphene layers can also be turned on and off by a displacement field. Our results suggest TDBG with small twist angle is a platform for studying the evolution of multiple electric field tunable moiré bands and the resulting emergent correlated electronic phases.

In this work, the theoretical and experimental study on vibration transmission in quasi-periodic impedance layered structures built by magnetorheological (MR) fluid is conducted. Based on the MR effect of MR fluid, the quasi-periodic layered structures formed by low and high impedance layers following Fibonacci, Thue–Morse and multiperiodic sequences are constructed, respectively. These different quasi-periodic patterns can be flexibly obtained by controlling the arrangement style and magnetic field strength of electromagnets outside the MR fluid. The vibration transfer model is established based on the transfer matrix method and the trends of vibration level difference with different parameters are analyzed. Furthermore, experiments are performed to estimate the vibration transmissivity of the proposed structures. It indicates that the developed quasi-periodic impedance layered structures can exhibit greater damping effect on vibrations by appropriately increasing the magnetic field strength and thickness ratio of low to high impedance layers. Moreover, there exist quasi-periodic impedance patterns whose attenuation effect on vibration is better than that of periodic pattern in the frequency range studied in this paper (20–200 Hz). This means that the introducing of the particular quasi-periodicity increases the transmission loss of vibrations in a certain frequency range. This investigation is conducive to further expand the application of MR materials and quasi-periodic structures in the field of vibration control.

Low-energy proton irradiation effects on the optical properties and the molecular structure of phenyl-C61-butyric acid methyl ester (PCBM) are studied in this work. The PCBM films are irradiated by 100-keV proton beams with fluences of 5 × 1012 p/cm2, 5 × 1013 p/cm2, and 5 × 1014 p/cm2, respectively. The photoluminescence (PL) peaks of the post-irradiated PCBM films show a progressive decrease in the peak intensity as the proton fluences increase, which can be attributed to the deep defect levels induced by proton irradiation. Additionally, a slight blue-shift in the PL spectrum is also observed at a proton fluence of 5 × 1014 p/cm2. The underlying mechanism can be traced back to the lift of the lowest unoccupied molecular orbital (LUMO) level, which is caused by the attachment of methoxy radicals on ortho position of the phenyl ring in the post-irradiated PCBM structure. This work is of significance in understanding the radiation hardness and the damage mechanism of the PCBM film in radiation environments, which is essential before it is put into practical application in space.

The traditional radar emitter identification method based on the five parameters of the pulse is difficult to achieve the desired effect in today’s abnormally dense electromagnetic environment. Modern radars often impose intentional modulation in the signal to improve the anti-jamming and low interception performance. Therefore, a radar emitter identification method based on the spectrum resemblance coefficient is proposed in this paper, which reflects the approximation degree between the signal spectrum and various basis functions by calculating the resemblance coefficients between them. Simulation results show that the method proposed in this paper has strong anti-interference capability and can effectively distinguish different types of intra-pulse modulated radar signals.

We study the nonreciprocal properties of transmitted photons in a chiral waveguide quantum electrodynamics (QED) system, including single- and two-photon transmissions and second-order correlations. For the single-photon transmission, the nonreciprocity is induced by the effects of chiral coupling and atomic dissipation in the weak coupling region. It vanishes in the strong coupling regime when the effect of atomic dissipation becomes ignorable. In the case of two-photon transmission, there exist two ways of going through the emitter: independently as plane waves and formation of bound state. Besides the nonreciprocal behavior of plane waves, the bound state that differs in two directions also alters transmission probabilities. In addition, the second-order correlation of transmitted photons depends on the interference between plane wave and bound state. The destructive interference leads to the strong antibunching in the weak coupling region, while the effective formation of bound state leads to the strong bunching in the intermediate coupling region. However, the negligible interactions for left-propagating photons hardly change the statistics of the input coherent state.

Two new photon-modulated spin coherent states (SCSs) are introduced by operating the spin ladder operators J ± on the ordinary SCS in the Holstein–Primakoff realization and the nonclassicality is exhibited via their photon number distribution, second-order correlation function, photocount distribution and negativity of Wigner distribution. Analytical results show that the photocount distribution is a Bernoulli distribution and the Wigner functions are only associated with two-variable Hermite polynomials. Compared with the ordinary SCS, the photon-modulated SCSs exhibit more stronger nonclassicality in certain regions of the photon modulated number k and spin number j, which means that the nonclassicality can be enhanced by selecting suitable parameters.

A rotary optical encoder is an important component in a rotational inertial navigation system (RINS). It is used to form a closed-loop motor control system and calculate the system attitude. The system performance will be affected by the encoder’s error. Ín addition to the installation errors, the working temperature variants can lead to encoder error. Therefore, in this paper we propose a method to calibrate and compensate the temperature errors of rotary optical encoders. First, an independent testing mechanism with position limitation and a rotatable platform is designed and produced to verify the temperature influence on encoders. Then, the temperature error of the rotary optical encoder used in RINS is calculated by a gyroscope whose sensitive axis is parallel to the same motor axis. The method is verified by a self-researched single-axis RINS. According to the experimental results, the measurement accuracy is increased by more than 47.9% compared to the traditional method.

The world’s first database on the effect of stabilizers on the resistivity and thermal conductivity of 20 different commercial REBa2Cu3O7−δ (REBCO) tapes was established. The resistivity and thermal conductivity in the radial and circumferential directions were listed. The charging loss and self-protection ability of 20 different commercial REBCO tapes in the no-insulation coils were evaluated via simulation. By comparing and analyzing the data, the Cu/Ag interface was found to be the most probable primary factor determining the resistivity and thermal conductivity of REBCO tapes. Such a database can support abundant data for the design of the REBCO magnet or even the choice of REBCO switch or current lead. Another goal was to help the REBCO manufacturers find a feasible way to adjust the resistivity and thermal conductivity, thereby meeting different requirements of the REBCO magnet.

Owing to the influence of the viscosity of the flow field, the strength of the shedding vortex decreases gradually in the process of backward propagation. Large-scale vortexes constantly break up, forming smaller vortexes. In engineering, when numerical simulation of vortex evolution process is carried out, a large grid is needed to be arranged in the area of outflow field far from the boundary layer in order to ensure the calculation efficiency. As a result, small scale vortexes at the far end of the flow field cannot be captured by the sparse grid in this region, resulting in the dissipation or even disappearance of vortexes. In this paper, the effect of grid scale is quantified and compared with the viscous effect through theoretical derivation. The theoretical relationship between the mesh viscosity and the original viscosity of the flow field is established, and the viscosity term in the turbulence model is modified. This method proves to be able to effectively improve the intensity of small-scale shedding vortexes at the far end of the flow field under the condition of sparse grid. The error between the simulation results and the results obtained by using fine mesh is greatly reduced, the calculation time is shortened, and the high-precision and efficient simulation of the flow field is realized.

The concentration of intracellular zinc ions is a significant clinical parameter for diagnosis. However, it is still a challenge for direct visual detection of zinc ions in cells at single-cell level. To address this issue, herein, water-soluble amino-rich polydopamine carbon quantum dots (PDA-CQDs) were successfully synthesized, with strong blue-green fluorescence as the probes for zinc ions detection in cells. The structure and properties of PDA-CQDs were confirmed by transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transformed infrared (FT-IR), UV–visible spectrophotometry (UV–vis), and fluorescence spectroscopy. Importantly, by successfully linking salicylaldehyde (SA) to PDA-CQDs via nucleophilic reaction, the FL quenching and Zn ions induced FL-recovering system was built up, thus offering a signal-on platform for the detection of zinc ions. This PDA-CQDs-SA nanoprobe can be applied for the detection of Zn2+ with a detection limit of 0.09 μM, with good biocompatibility confirmed using cytotoxicity assay. Of significance, the results of fluorescence bioimaging showed that PDA-CQDs-SA is able to detect Zn2+ in single-cell visually, with the detection limit of Zn ions in cells as low as 0.11 μM per cell, which was confirmed using flow cytometry. Therefore, this work offers a potential probe for Zn2+ detection in cells at single-cell level, towards the precise diagnosis of zinc ions related diseases.

Gas-solid two phase flow widely lies in industry process, while its parameters measurement (flow velocity, the mass flowrate, particle sizes, et al.) is very difficult. This paper mainly studies the solid phase flow velocity measurement questions of gas-solid two phase flow with the ring electrostatic sensor. During the flow velocity measurement study, a new mathematical model of the electrostatic sensor is established, and by simulating the obtained model the spatial filter characteristics of the electrostatic sensor are obtained. By the spatial filter characteristics analysis of the ring electrostatic sensor, a new flow velocity measurement method is obtained in this paper. At last, some experiments are accomplished in the laboratory with line sand. The new method of measuring flow velocity is effective in these experiments. The flow velocity obtained with the new measuring method is calibrated with the cross-correlation velocity. When the line sand velocity is less than 7m/s, the repeatability error of the measured velocity is less than ± 10%.

In this study, by combining the equal spacing rule with recent observations of and baryons, we predict the spectrum of the low-lying -mode -wave excited states. Furthermore, their strong decay properties are predicted using the chiral quark model and the nature of is investigated by analyzing the invariant mass spectrum. The structure observed in the mass spectrum was found to potentially arise from two overlapping -wave resonances, and . These resonances have similar decay widths of MeV and predominantly decay into the channel. The state is likely to be a very narrow state with a width of MeV, with its decays almost saturated by the channel. Additionally, evidence of the resonance as a very narrow peak may be seen in the invariant mass spectrum. The other two -wave states, and , are relatively narrow states with similar widths of MeV and predominantly decay into and , respectively. This study can provide useful references for discovering these low-lying -wave states in forthcoming experiments.

A subwavelength asymmetric grating refractive index (RI) sensor based on quasi-bound states in the continuum (q-BIC) with temperature self-compensation was proposed. The sensor structure consisted of a prism/asymmetric grating/analytes, where the grating layers were periodically arranged asymmetric silicon (Si) and polydimethylsiloxane. The asymmetry of the structure led to the fact that the tangential field component and the radiative field component in the grating layer were no longer in a fully decoupled state at the resonance position, creating two extremely narrow q-BIC resonance peaks, which gave the sensor a high figure of merit (FOM) and a low detection limit (DL). In addition, the thermo-optical coefficient of the materials made one of the resonance peaks more sensitive to temperature changes, realizing the temperature self-compensation of RI detection and thus improving the detection accuracy. From the results, reducing the asymmetry of the structure by modifying the parameters could theoretically make FOM > 5.1 × 106 RIU−1 and DL < 9.8 × 10−9 RIU. For the RI sensor with temperature self-compensation, FOM = 3057.85 RIU−1 and DL = 1.64 × 10−5 RIU for the RI, FOM = 0.88 °C−1 and DL = 0.057 °C for the temperature. These findings could effectively improve the temperature interference resistance of the sensor and thus the accuracy of trace substance detection.

Rotational structure properties along the yrast line for 766 observed even–even nuclei with Z ≥ 20 in the nuclide chart have been systematically studied by means of the approach of pairing-deformation self-consistent total Routhian surface calculations in three-dimensional deformation space (β 2, γ, β 4). Typical two-dimensional maps of the total nuclear energy are presented as functions of rotational frequency ℏ ω. Various types of physical quantities (including nuclear shapes, aligned angular momenta, pairing gaps and excitation energies) are presented in the (Z, N) plane, indicating the overall characteristics. The ground-state deformations are compared with experimental data and other theoretical results. The present investigation shows that the Coriolis coupling may affect the overall properties systematically, for instance, enforcing regular drifts of the different deformation ‘islands’. We believe that the synthetic presentation will be helpful when planning high-spin experiments, especially in the data-scarce drip-line or superheavy regions. Moreover, such systematic and large-scale calculation and analysis can help overcoming and eliminating the bias among different theoretical models and be useful for checking and developing them.

Oxygen evolution reaction (OER) is an important half-cell reaction of the electrical water splitting, for its high overpotential associated with sluggish OER kinetics. Therefore, it is critical to develop highly active and durable electrocatalysts to reduce the overpotential. Herein, ultra-small RuO2 nanoparticles (NPs) supported on onion-like carbon (OLC) and carbon nanotube (CNT) are successfully synthesized by means of wet impregnation combined with annealing treatment, respectively. The microstructure characterization results showed OLC perfect graphitic carbon layer structure, and the RuO2 NPs supported on the OLC possess larger particle size compared with the RuO2 NPs supported on the CNT. Moreover, the electronic structure of Ru in RuO2/OLC was also optimized by the OLC support to be beneficial for the OER. The OER performance of the catalysts were investigated in 1 M KOH solution. The results show RuO2/OLC has a comparable OER activity to the commercial RuO2, but a significantly higher mass activity than the commercial RuO2. When compared with the RuO2/CNT, RuO2/OLC not only exhibits lower overpotential and Tafel slop, but also owns more active sites and higher TOF value, indicating the OLC support improved the OER activity of RuO2/OLC. Moreover, RuO2/OLC showed a superior stability compared with RuO2/CNT, which can be attributed to the excellent electrochemical oxidation-resistance of the OLC.

Semiconductor mode-locked lasers (MLLs) with extremely high repetition rates are promising optical frequency comb (OFC) sources for their usage as compact, high-efficiency, and low-cost light sources in high-speed dense wavelength-division multiplexing transmissions. The fully exploited conventional C- and L- bands require the research on O-band to fulfil the transmission capacity of the current photonic networks. In this work, we present a passive two-section InAs/InGaAs quantum-dot (QD) MLL-based OFC with a fundamental repetition rate of ∼100 GHz operating at O-band wavelength range. The specially designed device favours the generation of nearly Fourier-transform-limited pulses in the entire test range by only pumping the gain section while with the absorber unbiased. The typical integrated relative intensity noise of the whole spectrum and a single tone are −152 and −137 dB Hz−1 in the range of 100 MHz–10 GHz, respectively. Back-to-back data transmissions for seven selected tones have been realised by employing a 64 Gbaud four-level pulse amplitude modulation format. The demonstrated performance shows the feasibility of the InAs QD MLLs as a simple structure, easy operation, and low power consumption OFC sources for high-speed fibre-optic communications.

Most amorphous carbon (a-C) applications require films with ultra-thin thicknesses; however, the electronic structure and opto-electronic characteristics of such films remain unclear so far. To address this issue, we developed a theoretical model based on the density functional theory and molecular dynamic simulations, in order to calculate the electronic structure and opto-electronic characteristics of the ultra-thin a-C films at different densities and temperatures. Temperature was found to have a weak influence over the resulting electronic structure and opto-electronic characteristics, whereas density had a significant influence on these aspects. The volume fraction of sp3 bonding increased with density, whereas that of sp2 bonding initially increased, reached a peak value of 2.52 g/cm3, and then decreased rapidly. Moreover, the extinction coefficients of the ultra-thin a-C films were found to be density-sensitive in the long-wavelength regime. This implies that switching the volume ratio of sp2 to sp3 bonding can effectively alter the transmittances of ultra-thin a-C films, and this can serve as a novel approach toward photonic memory applications. Nevertheless, the electrical resistivity of the ultra-thin a-C films appeared independent of temperature. This implicitly indicates that the electrical switching behavior of a-C films previously utilized for non-volatile storage applications is likely due to an electrically induced effect and not a purely thermal consequence.

The reduced graphene oxide/silver selenide nanowire (rGO/Ag2Se NW) composite powders were fabricated via a wet chemical approach, and then flexible rGO/Ag2Se NW composite film was prepared by a facile vacuum filtration method combined with cold-pressing treatment. A highest power factor of 228.88 μW·m−1·K−2 was obtained at 331 K for the cold-pressed rGO/Ag2Se NW composite film with 0.01 wt% rGO. The rGO/Ag2Se NW composite film revealed superior flexibility as the power factor retained 94.62% after bending for 500 times with a bending radius of 4 mm, which might be due to the interwoven network structures of Ag2Se NWs and pliability of rGO as well as nylon membrane. These results demonstrated that the GO/Ag2Se NW composite film has a potential for preparation of flexible thermoelectric devices.

Various requirements for the repair of complex bone defects have motivated to development of scaffolds with adjustable degradation rates and biological functions. Tricalcium phosphate (TCP) and calcium sulfate are the most commonly used bone repair materials in the clinic, how to better combine TCP and calcium sulfate and play their greatest advantages in the repair of osteoporotic bone defect is the focus of our research. In this study, a series of scaffolds with multistage-controlled degradation properties composed of strontium-doped calcium sulfate (SrCSH) and strontium-doped tricalcium phosphate (Sr-TCP) microspheres scaffolds were prepared, and their osteogenic activity, in vivo degradation and bone regeneration ability in tibia of osteoporotic rats were evaluated. In vitro studies revealed that different components of SrCSH/Sr-TCP scaffolds significantly promoted the proliferation and differentiation of MC3T3-E1 cells, which showed a good osteogenic induction activity. In vivo degradation results showed that the degradation time of composite scaffolds could be controlled in a large range (6–12 months) by controlling the porosity and phase composition of Sr-TCP microspheres. The results of osteoporotic femoral defect repair showed that when the degradation rate of scaffold matched with the growth rate of new bone, the parameters such as bone mineral density, bone volume/total volume ratio, trabecular thickness, angiogenesis marker platelet endothelial cell adhesion molecule-1 and new bone formation marker osteocalcin expression were higher, which promoted the rapid repair of osteoporotic bone defects. On the contrary, the slow degradation rate of scaffolds hindered the growth of new bone to a certain extent. This study elucidates the importance of the degradation rate of scaffolds for the repair of osteoporotic bone defects, and the design considerations can be extended to other bone repair materials, which is expected to provide new ideas for the development of tissue engineering materials in the future.

This paper presents a novel Nb superconducting joint with an ultralow resistance of 7.9 × 10−16 Ω, fabricated using the electron beam welding (EBW) method. After the EBW process, the two Nb filaments formed a single joint with a much larger grain size and smaller grain misorientation. More importantly, the resistance of the EBW Nb joint was nearly one magnitude lower than that of most conventional pressing joint. The ultralow resistance is essential for superconducting gravimeters, which require an extremely low drift rate. The EBW Nb joint allowed the superconducting gravimeter to have a much better performance when applied in the field of structural geology, geodesy, microgravity, and metrology. We believe that the EBW method could be one of the most promising joint fabrication methods for achieving maximum stability (less than 1 μgal yr−1).

With the continuous development of our economy, the types and quantity of engine bearing are increasing. In order to prevent the bearing moving in the bearing pedestal, one or both ends of the bearing need to make positioning lip for axial positioning. In order to meet the needs of mass bearing production, an auto loading device for positioning lip of bearing is proposed in this paper. The horizontal conveyor belt and loading guide are used to make the blank turn to the required angle, and then the double cylinder valve and push rod motor are used to realize the time-sharing conveying and continuous loading of the blank. During the loading process, there are inclined slideway and blocking plate to avoid the collision between blanks and ensure the reliable loading bearings. Through the actual production verification, the developed device has the advantages of simple structure, low cost, fine working stability, and made great improving in the efficiency and safety for production of bearing.

In this work, neutron irradiation effects on the optical property of multilayer MoS2 have been investigated in depth. Our results display that the intensity of the photoluminescence (PL) spectra of MoS2 flakes tends to slightly decrease after exposed to neutron irradiation with low fluence of 4.0 × 108 n/cm2. An unexpected improvement of PL intensity, however, is observed when the irradiation fluence accumulates to 3.2 × 109 n/cm2. Combined with the experimental results and first-principles calculations, neutron irradiation damage effects of multilayer MoS2 are analyzed deeply. Sulfur vacancy (V S) is found to be responsible for the attenuation of the PL intensity as a major defect. In addition, our results reveal that the adsorbed hydroxyl groups (OH) and oxygen atoms (O) on the surface of MoS2 flakes not only promote the transition from trion excitons to neutral excitons, but also repair the V S in MoS2, both of which contribute to the enhancement of luminescence properties. The detailed evolution process of irradiation-induced defects is discussed to reveal the microscopic mechanism of the significantly difference in luminescence intensity of MoS2 under different irradiation stages. This work has great significance for evaluating the neutron radiation hardness of multilayer MoS2, which is helpful to enrich the fundamental research on neutron irradiation effects.

The tunability in Josephson junctions is foundational to the superconducting classical and quantum applications. Here, we demonstrate the local manipulation of supercurrent realized in a superconducting quantum interference device (SQUID) with two Nb/TiO x /Nb Josephson junctions that is biased at the TiO x layer. Our measurements indicate that the multi-port device allows for an easy and in situ tunability of the supercurrent. The control mechanism can be finely explained by simple yet valid theoretical methods, which take an effective electronic temperature across the SQUID and the self inductive magnetic flux into account. Furthermore, we show that the phase difference and kinetic inductance of this device can be tuned locally via the injection current. Thus, the device provides perspective for several superconducting electronics such as tunable superconducting circuits, sensitive magnetometry, and fast digital elements.

Aiming at the problem that the high classification feature dimensionality of the back propagation neural network (BPNN) leads to slow convergence speed and the initial weight and threshold sensitivity of the BPNN lead to the problem of easy convergence to the local optimum. A novel BPNN optimized by rough set and particle swarm algorithm (RS-PSO-BPNN) for remanufacturing service provider classification and selection is proposed. First, the attribute reduction method of rough set theory is used to preprocess the classification features of remanufacturing service providers, redundant attributes are deleted from the decision table, and the input feature dimension is reduced; then the PSO algorithm is used to optimize the network Initial weight and threshold. Finally, the proposed method is used for the selection and optimization of remanufacturing service providers. The results show that the proposed RS-PSO-BPNN has higher classification accuracy and efficiency for the problem, which provides scientific decision supports for remanufacturing service provider selection.

Based on the data of environmental monitoring stations and meteorological stations in Qinhuangdao from May 2017 to May 2020, the variation characteristics of O3 and precursors (NO2 and CO) as well as their relationship with meteorological elements were analyzed. The results showed that the daily average concentration of O3-8 h in Qinhuangdao increased year by year. The monthly average concentration of O3-8 h was high in summer and low in winter, and the peak appeared in June. The diurnal variation of O3 concentration was unimodal structure, and the concentration increased in the afternoon, but it decreased at night. The concentration of NO2 and CO was inversely correlated with O3, and the peak value of NO2 in March could be related to frequent cold air activity and increased burning of loose coal. The meteorological elements favorable for the occurrence of ozone pollution weather in Chengde were total solar radiation irradiance greater than 1000W/m2, the daily maximum temperature greater than 33 °C, and the daily minimum relative humidity less than 40% and 65%∽80%, southerly wind or southwest wind.

Based on the data of environmental monitoring stations and meteorological stations in typical city in the Bohai Rim region in June 2021 and June 2020. The air quality in June 2021 was better than that in the same period in 2020. Ozone (O3) was the primary pollutant in June 2021 and June 2020. The overall meteorological conditions in May 2021 were relatively favorable. In June 2021, the number of light wind days and wind speed had no significant impact on air quality compared with the same period last year. The dominant wind direction in June 2021 was southeast wind, which was not conducive to the increase of ozone concentration compared with the southwest wind frequency in the same period in 2020; the relative humidity in June 2021 was slightly higher year-on-year, which was slightly conducive to the hygroscopic growth of pollution; the static stability index in June 2021 was lower year-on-year, and the weather conditions for comprehensive pollution diffusion were preferred year-on-year; the height of the mixed layer in June 2021 was lower year-on-year, the vertical diffusion weather conditions were deviated year-on-year; the average temperature, sunshine hours and total radiation in June 2021 were all low, which was not conducive to the generation of ozone.

Modular multilevel converter (MMC) contains a large number of power electronic switching devices. The modeling method based on switching circuit model needs a lot of resources and the simulation speed is slow, so it is difficult to realize large-scale real-time simulation of electromagnetic transient. A MMC electromagnetic transient numerical modeling method based on ideal transformer model (ITM) is presented. Firstly, the MMC system is divided into the main circuit network and the sub module group network by ITM method, and the error caused by decoupling delay in serial and parallel real time simulation is compensated respectively by interpolation prediction and advanced interpolation prediction. Secondly, the capacitor in sub module is discreted respectively by trapezoidal integration method, backward Euler method and Gear-2 method. Based on the above numerical integration, the difference equations of capacitance voltage, capacitance current and output voltage of half bridge and full bridge sub modules are derived. Then, in order to improve the calculation speed, a simplified numerical model of half bridge and full bridge sub module based on switching function is proposed. Finally, the MMC based on switching circuit model runs off-line simulation in the simulation software, and the above MMC numerical modeling method runs real-time simulation in Speedgoat real-time simulator. The off-line and real-time simulation results of the MMC numerical modeling method and the switching circuit model are compared. And the simulation results verify the feasibility and effectiveness of the above MMC numerical modeling method in real time simulation.

China has submitted an application to join the Kigali amendment to the Montreal Protocol. As the second largest hydrofluorocarbons (HFCs) consumer industry in China, the automotive industry is facing enormous pressure to reduce HFCs. This paper analyzes the current situation of HFCs use in the domestic automotive industry, and makes a simulation prediction of HFCs use data in the automotive industry from 2024 to 2030, analyze and evaluate the advantages and disadvantages of different technical routes. The relevant contents of this paper will provide reference for the formulation of HFCs reduction policy.

Nowadays, numerous supervised deep learning models have been applied to bearing fault diagnosis. However, labelling the health states of the bearing vibration data is a time-consuming work and dependent on expert experience. In order to tackle this problem, a novel unsupervised bearing fault diagnosis method named adversarial flow-based model is explored in this paper. Flow-based model is a type of generative models that is proved to be better than other types in many aspects. This paper introduces the flow-based model into the field of machinery fault diagnosis, and designs an appropriate model architecture so as to train the model in unsupervised and adversarial ways. The proposed model contains an autoencoder (AE), a flow-based model, and a classifier. Firstly, the AE maps the vibration data from signal space to latent vector space. Then, the flow-based model aligns the distributions of the latent vectors of different bearing states with specific prior distributions. Finally, the classifier tries to discriminate the aligned latent vectors from the vectors sampled from the prior distributions. With the help of distinguishable prior distributions and the adversarial training mechanism between the classifier and the flow-based model together with the AE, the bearing data with the same health states are clustered into the same areas. The good clustering performance of the adversarial flow-based model is verified by a dataset with 10 health states from a bearing test rig.

The online monitoring network of marine ranching ecological environment is one of the important development directions of marine ranching construction. Traditional marine monitoring systems are large in size, high in power consumption, and expensive. The investment in pasture construction cannot achieve a large amount of investment to form a monitoring network. There is an urgent need for a low-cost marine monitoring method that can afford a large area and high spatial density. This problem cannot be realized in traditional technology. Based on MEMS technology, this paper develops low-cost monitoring small floats that can be deployed in a large number of “swarm bees”, with high spatial and temporal resolution, and take into account environmental and biological population characteristics monitoring. Each small float is connected to a multi-node sensor chain and video monitoring node. The low-cost surface and underwater wireless transmission and wireless communication means are used for networking observation, which proposes a brand-new solution for the construction of the intelligent three-dimensional monitoring of the marine pasture environment.

We fabricated thin film Nb/Au/NbSeaamp;lt;subaamp;gt;2aamp;lt;/subaamp;gt; hybrid Josephson junctions by a dry transfer technique with only a single lithography step in the process. A thin Au layer is deposited on Nb to prevent oxidation during the fabrication process. The superconducting van der Waals (vdW) material NbSe2 is placed on top of the Nb/Au layer. Electrical transport properties are studied in detail and are compared to numerical simulations. The current-voltage characteristics we observe are typical for superconductor-normal metal-superconductor junctions and we do not observe an effect of a potential insulating barrier between NbSe2 and Au. The modulation of the critical current in magnetic fields indicates an inhomogeneous distribution of supercurrent density, presumably caused by the roughness of the Nb/Au interface to NbSe2. Nevertheless, we observe clear integer Shapiro steps, indicating a sinusoidal current phase relation of junctions. We do not see an impact of the anisotropic s-wave and the charge density wave in NbSe2 on the Josephson effects. Our method presents a viable and simple way to fabricate hybrid Josephson junctions between superconducting films and two-dimensional (2D) vdW superconducting materials, which might offer a chance for widespread applications.

This paper investigated the impact of braking intensity of self-driving cars at different initial speeds on straight road sections on drivers’ comfort, with a view to achieving the comfort optimization of adaptive cruise control (ACC). Specifically, the real vehicle test was conducted in an enclosed venue based on the within-subjects design of 3 × 3 × 2, and the data pertaining to electrocardiogram (ECG) and subjective evaluation of 9 subject drivers in 9 sub tests were collected. Besides, the impacts of different motion states on heart rate variability (HRV) parameters were analyzed using the general linear model for repeated measures, and the relationships among drivers’ comfort, decelerations, and standard deviation of NN intervals (SDNN, an index of HRV) were obtained based on subjective and objective analyses. Additionally, a control strategy based on HRV and fuzzy control was formulated to realize the comfort optimization of ACC in case of an abrupt deceleration of the preceding vehicle, the verifications were performed through joint simulation. The results exhibited that the control strategy based on HRV and fuzzy control could shorten the deceleration time in case of an abrupt deceleration of the preceding vehicle, and may improve the comfort in such scenario.

The classical attribute reduction algorithm is not suitable for the neighborhood decision information system of numerical attribute. Since any feature subset in real feature space can be approximated by neighborhood information particles, the concept of knowledge granularity is extended to neighborhood rough set from the perspective of the granularity computation. In this paper, knowledge granularity, attribute importance and heuristic algorithm based on the granularity of knowledge in neighborhood rough set are studied from the point of view of neighborhood relation matrix. The feasibility of heuristic algorithm is analyzed on UCI data sets. Experiments achieve better classification accuracy and lower attribute reduction results than the existing algorithms.

In this study, computer simulation prediction technology was used to establish an interaction model between cyclohexene and protonated small molecules modified uranyl-Salophen. Theoretical simulation research the compounds using Uranyl-Salophen modified by methyl, vinyl and carboxyl-propenyl, with the cyclohexene complexes in vacuum condition, were performed by using density functional theory (DFT) at level with the B3LYP/6-311G*basis set. All of the combination structure is carried out under the same base group, in optimization, infrared spectrum, the binding energy, and the calculation of molecular orbital energy level. The results showed that the capacity and stability of complexes whose Uranyl-Salophen modified by carboxyl-propenyl was strongest, the vinyl followed, and the methyl weakest, and methyl modified even reduce the compounds combining ability.