Search

To address the issue of the in-phase state of charge(SOC) unbalancing in a cascaded H-bridge battery energy storage system, this paper proposes a novel control strategy based on nearest level modulation(NLM). Through NLM, this paper first calculates the number of sub-modules needed, then adjusts the priority of sub-modules in different SOC by the charging state, so that the sub-modules with larger SOC deviation converge to the average value. Considering that sub-modules with a large SOC deviation participating in charging or discharging may bring distortion of the PCS output, limiting the number of sub-modules with large deviations during the charging or discharging is needed, so that the sub-modules with large SOC deviation and sub-modules close to average SOC cooperate in charging/discharging process to reduce the distortion of PCS output. The simulation result verified the correctness of the strategy.

LiDAR has the advantages of small size, high imaging accuracy, high resolution, all-day survey, and strong adaptability to complex environments. With the continuous improvement of technical performance, LiDAR is widely used in aerospace, mapping, military, and civil fields. In this study, the principle of LiDAR survey technology was introduced, and the key technology and application method of using LiDAR to measure the initial section of rocket launch were discussed in detail; a LiDAR survey system was designed on this basis. Afterward, the feasibility and rationality of the survey system and survey method were verified by rocket launch tests. The results show that compared with the traditional survey methods, LiDAR survey technology has obvious advantages in terms of survey accuracy, automation, and real-time visualization of survey data, and it can greatly reduce labor intensity and improves work efficiency, which provides an important reference for the design and application mode of LiDAR survey system in space launch sites.

We propose an extended BCS–Hubbard model and investigate its ground state phase diagram in an external magnetic field. By mapping the model onto a model of spinless fermions coupled with conserving Z 2 variables which are mimicked by pseudospins, the model is shown to be exactly solvable along the symmetric lines for an arbitrary on-site Hubbard interaction on the bipartite lattice. In the zero field limit, the ground states exhibit an antiferromagnetic order of pseudospins. In the large field limit, on the other hand, the pseudospins are fully polarized ordered. With the increase of the applied field, a first-order phase transition occurs between these kinds of phases when the on-site Coulomb interaction is less than a critical value U c. Above this critical U c, a novel intermediate phase emerges between the fully polarized and antiferromagnetic phases. The ground states in this phase are macroscopically degenerate, like in a spin ice, and the corresponding entropy scales linearly with the lattice size at zero temperature.

Machine learning provides a way to use only portions of the variables of a spatiotemporal system to predict its subsequent evolution and consequently avoids the curse of dimensionality. The learning machines employed for this purpose, in essence, are time-delayed recurrent neural networks with multiple input neurons and multiple output neurons. We show in this paper that such kinds of learning machines have a poor generalization ability to variables that have not been trained with. We then present a one-dimensional time-delayed recurrent neural network for the same aim of model-free prediction. It can be trained on different spatial variables in the training stage but initiated by the time series of only one spatial variable, and consequently possess an excellent generalization ability to new variables that have not been trained on. This network presents a new methodology to achieve fine-grained predictions from a learning machine trained on coarse-grained data, and thus provides a new strategy for certain applications such as weather forecasting. Numerical verifications are performed on the Kuramoto coupled oscillators and the Barrio−Varea−Aragon−Maini model.

For many structures, their service environment is very strict, and the requirements for the impact resistance of materials are very high. Therefore, the dynamic testing method has important scientific significance and application value for practical engineering. Split Hopkinson pressure bar (SHPB) is one of the most common experimental methods for obtaining dynamic mechanical properties of materials. However, there is no uniform standard for the size of the bars and specimens used in the test. Theoretically, the size has little influence on the experimental results, but it has not been proved by experiments. This paper mainly studies the influence of device/specimen sizes of split Hopkinson pressure bar through experiments, it is demonstrated that the sizes of bars and specimen have little effect on experimental results.

Surface activated bonding (SAB) based on argon ion beam irradiation was used to directly bond Si and Si wafers at room temperature, and the effects of the surface activation time on the Si-Si bonding were investigated. The experimental results show that the surface activation treatment with a proper duration is beneficial to the reduction of surface roughness of Si wafers and the realization of high bonding strength. The Si-Si wafers bonded after the surface activation of 420 s has an extremely low percentage of area covered by voids (0.08%) and a high bonding strength (9.45 MPa). Meanwhile, the annealing at 500 °C does not lead to a significant change in the percentage of area covered by voids for Si-Si bonding. Besides, the transmission electron microscope characterization indicates that the argon ion beam irradiation of 180 s can result in the formation of an amorphous Si layer with a thickness of approximately 10.6 nm at the Si-Si bonding interface, and the whole cross-section structure of the Si-Si bonding consists of a Si substrate, an amorphous Si layer and a Si substrate.

Microfluidic droplet technique is a novel technology developed on the basis of microfluidics to study the formation, manipulation and application of microdroplets of a few micrometers size. It drastically enhances the advantages in terms of low consumption, automation and high throughput and is widely used in chemical, microelectronics, materials science, biology and biomedical engineering etc. Nevertheless, there are still a series of problems about the formation and control of droplet. To generate the given droplets and control their size, a micro-vibrator based cross-junction microfluidic system is designed and implemented, where the size of droplet can be dynamically adjusted via the flow rates of two phase fluids and the vibrant frequency of micro-vibrator. Moreover, a closed-loop control framework with certain special mothold, i.e., iterative learning control (ILC), is discussed to assist the formation of droplets. The experimental results confirm the feasibility of proposed scheme.

In order to improve the nutrient absorption effect of cotton in the process of simultaneous application of water and fertiliser, this paper studied the effect of injecting magnetised water and fertiliser on cotton nutrient absorption under the production conditions of drip irrigation. In the process of integrated water and fertiliser management of cotton, the study adopted the method of magnetisation treatment—After the water-fertiliser fusion liquid is magnetised by a magnetisation device, it is dripped on the cotton field through the drip irrigation pipe network. In this work, the water and fertiliser magnetisation device was designed, and it was combined with the drip irrigation pipe network as a test device. The nutrient absorption test of the water-fertiliser fusion liquid applied to cotton under different magnetic fields was conducted. The accumulation, absorption and distribution of cotton biomass and N, P and K elements were studied respectively. As a result of the research, we found that the magnetised water and fertiliser treatment can promote cotton nutrient absorption to varying degrees. A method of drip irrigation under a magnetised water and fertiliser film to improve the nutrient absorption effect of cotton was proposed.

The sample was extracted under the ultrasonic assistance and purified through the solid-phase extraction, and then the residual tylosin in soil was detected via the high-performance liquid chromatography (HPLC). Acetonitrile-aqueous solution was used as the extracting agent in the ultrasound-assisted extraction. The HLB solid-phase extraction column was activated using 5 mL of methanol and 5 mL of ultrapure water, leached with 5 mL of water and 5 mL of 2% ammonium hydroxide + 5% methanol solution, and eluted with 5 mL of methanol in the end. The determination was implemented using the HPLC method, where the detected wavelength λ value was 290 nm, the sample size was 20μL, and the column temperature was 30°C. Acetonitrile -0.01 mol/L monopotassium phosphate solution (pH=2.5) = 60:40 (V: V) was taken as the mobile phase in the detection of response degree to tylosin in soil. The detection results were as follows: LOD was 0.019mg/kg, LOQ was 0.062mg/kg, the coefficient of variation of intra-day precision was smaller than 10%, and that of inter-day precision was smaller than 15%.

The 110kV dry type epoxy casting transformer had the characteristics of high voltage grade, great difficulty and uncertainty in research. Especially in the field strength control under lightning impulse, higher requirements were put forward for its insulation structure design. In this paper, an equivalent circuit model was built based on the heap winding structure, and the voltage distribution of winding nodes under lightning impulse was calculated. According to the actual drawing, a two-dimensional transformer model was established, and the E-field distribution of transformer under lightning impulse was obtained by simulation. The results showed that the maximum field strength at sampling point 1 was 4.1kV/mm, appearing around 65μs and 157μs. From the simulation results, the insulation performance of the pile winding did not meet the safety requirements. The research results in this paper could provide an important basis for the design of 110kV dry type transformer and technical support for the product development and safe operation of large capacity dry type transformer.

In this paper, high strength Cu-Cu interconnections were achieved by sintering the paste of Ag-Sn bimetallic nanoparticles at low temperature. Compared with nano-Ag paste, the outer Sn coatings of the nano-Ag particles were found to be favorable for the densification of the bondline. The microstructures of Ag-Sn bimetallic nanoparticles and the bondlines under different sintereing conditions were studied in detail by x-ray photoelectron spectroscopy (XPS), x-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The Ag-Sn bimetallic nanoparticles bondline exhibit a high shear strength of 35.3 MPa and a low resistivity of 9.5 μΩ cm, when sintered at 260 °C for 20 min under a pressure of 0.5 MPa. The electrochemical migration time of this sintered Ag-Sn bimetallic nanoparticles was prolonged to be ten times of that of sintered nano-Ag. This bonding technology based on Ag-Sn bimetallic nanoparticles was a promising die attach method for high temperature power device packaging.

Elastic scattering of 10Be on a 208Pb target was measured at = 127 MeV, which corresponds to three times the Coulomb barrier. The secondary 10Be beam was produced at the Radioactive Ion Beam Line in Lanzhou of the Heavy-Ion Research Facility in Lanzhou. The angular distribution of elastic scattering in the 10Be + 208Pb system shows a typical Fresnel diffraction peak. Optical model analysis of the angular distribution was performed using the Woods-Saxon, double-folding and global potentials. With the global potential, different density distributions were used. The results indicate that different density distributions for the projectile induce distinct effects in the angular distribution.

In this paper, the effect of the addition of graphene on the as-cast and homogenized annealing microstructure of 7075 aluminum alloy (AlZnMgCu) was studied. The analytical model devised in this study has demonstrated the significant grain refinement of graphene-7075 aluminium matrix composites (G-7075) due to large surface area of graphene. The results showed that the as-cast microstructure of graphene-7075 aluminum matrix composite was refined significantly, which the average grain size of the composite decreased from 78 μm to 45 μm and lattice distortion is more significant. The effect of the dissolution of the non-equilibrium eutectic structure and the secondary phase distribution of the graphene-7075 aluminum matrix composite is better after annealing at 470 °C for 16 hours.

During long-term operation, impurities and moisture in insulation oil would be absorbed by supporting parts in the elevating seat, which would reduce its insulation strength and leaded to partial discharge. In order to analyse the changing effect of the introduction of supporting parts on long oil gap E-field and optimize the insulation structure, based on the 500kV transformer, FEM was used to calculate the distribution of electric field in elevating seat, the equalizing ball shape was designed and optimized, the influence of elevating seat diameter on the lead surface maximum E-field was analysed. The results showed that after structural optimization, the maximum E-field on lead surface near supporting parts decreased from 8.95kV/mm to 7.82kV/mm, and on the equalizing ball surface decreased from 6.20kV/mm to 5.34kV/mm, with a decrease of 12.63% and 13.87% respectively, which improved the safety and reliability of transformer operation.

Developing excellent performance conductors with high strength and electrical conductivity is a key issue in the electrical conductor industries. In this paper, an extruded composites containing trace amounts of Sc,Zr and graphene was prepared. Then all samples were extrusion into round bars with a final diameter of 6.3mm. Research results show that the UTS of one stage aging is 181±2.7MPa and the elongation is 21.4%. The hardness increases rapidly from 25.8HB to 69.8HB within the first 12h when the aging temperature at 280℃. During the secondly stage aging, a peak electrical conductivity of 58.5%IACS, which is obtained after a secondary aging at 380℃ for 48h. A large number of nanocrystalline precipitates with smaller diameter are uniformly distributed throughout the matrix after aging at 280℃ for 24h. As the aging time increases, the size of the precipitated phase increases significantly. This work also provides a good guideline for designing heat-resistant conductors.

Divergence in land carbon cycle simulation is persistent and widespread. Regardless of model intercomparison project, results from individual models diverge significantly from each other and, in consequence, from reference datasets. Here we link model spread to structure using a 15-member ensemble of land surface models from the Multi-scale synthesis and Terrestrial Model Intercomparison Project (MsTMIP) as a test case. Our analysis uses functional benchmarks and model structure as predicted by model skill in a machine learning framework to isolate discrete aspects of model structure associated with divergence. We also quantify how initial conditions prejudice present-day model outcomes after centennial-scale transient simulations. Overall, the functional benchmark and machine learning exercises emphasize the importance of ecosystem structure in correctly simulating carbon and water cycling, highlight uncertainties in the structure of carbon pools, and advise against hard parametric limits on ecosystem function. We also find that initial conditions explain 90% of variation in global satellite-era values—initial conditions largely predetermine transient endpoints, historical environmental change notwithstanding. As MsTMIP prescribes forcing data and spin-up protocol, the range in initial conditions and high levels of predetermination are also structural. Our results suggest that methodological tools linking divergence to discrete aspects of model structure would complement current community best practices in model development.

Satellite microwave communication transmitters mainly evaluate the transmitted signal quality through EVM indicator. In this paper, we used the mathematical derivation result between phase noise and signal EVM, then proposed a high phase stability transmitter clock domain design scheme, based on the design process of a spaceborne transmitter. After testing, compared with the traditional transmitter clock domain, the new transmitter clock domain achieved an 6% increase in the EVM indicators.

Sharp bending as one of the mechanical properties of double-stranded DNA (dsDNA) on the nanoscale is essential for biological functions and processes. Force sensors with optical readout have been designed to measure the forces inside short, strained loops composed of both dsDNA and single-stranded DNA (ssDNA). Recent FRET single-molecule experiments were carried out based on the same force sensor design, but provided totally contrary results. In the current work, Monte Carlo simulations were performed under three conditions to clarify the discrepancy between the two experiments. The criterion that the work done by the force exerted on dsDNA by ssDNA should be larger than the nearest-neighbor (NN) stacking interaction energy is used to identify the generation of the fork at the junction of dsDNA and ssDNA. When the contour length of dsDNA in the sensor is larger than its critical length, the fork begins to generate at the junction of dsDNA and ssDNA, even with a kink in dsDNA. The forces inferred from simulations under three conditions are consistent with the ones inferred from experiments, including extra large force and can be grouped into two different states, namely, fork states and kink states. The phase diagrams constructed in the phase space of the NN stacking interaction energy and excited energy indicate that the transition between the fork state and kink state is difficult to identify in the phase space with an ultra small or large number of forks, but it can be detected in the phase space with a medium number of forks and kinks.

The molten eutectic Al–Mn alloy, whose eutectic point is about 2.0 wt%, possesses sound fluidity that might satisfy the demands of the thin-wall parts of 3 C products and the auto industry. In this research, the anodic oxide film, fluidity of the melts and tensile property of Al–Mn alloys with additional manganese amounts ranging from 0.6 wt% to 2.7 wt% were studied. The x-ray diffraction test was carried out for the identification of the phases in the fabricated Al–Mn alloys. The commercial ADC12 alloy was selected for comparison of performance. The identical anodic oxidation process and the coloring process were implemented on both the commercial ADC12 alloy and Al–Mn alloys, and the effects on their micro- and macro-structures were observed. According to the results of the spiral fluidity tests, the fluidity length of the molten Al-2.0Mn alloys was close to that of the commercial ADC12 alloy. And the optimal ultimate tensile strength of the Al–Mn alloys was obtained at a manganese content of 2.0 wt%. In addition, analysis on the benchmarks of color difference, film thickness and roughness showed that the appearance quality of anodic oxide film of the Al–Mn alloys was superior to that of the commercial ADC12 alloy. Moreover, as for the Al–Mn alloys, the benchmarks of color difference and roughness of these anodic oxide films were raised with the increase of manganese contents.

We report on the development and analysis of a new torque-actuated dissipative spring loaded inverted pendulum model with rolling contact (TDR-SLIP), which is a successor to the previously developed spring loaded inverted pendulum model with rolling contact (R-SLIP) model. The stability properties of the models were analyzed numerically via steps-to-fall analysis and return map analysis, wherein the dimensionless parameters are varied to analyze their effects on the dynamic performance of the model, including torque, damping constant, spring constant, touchdown angle, touchdown speed, and landing angle. Because the involvement of torque and damping in the TDR-SLIP model is similar to other recently developed torque-actuated dissipative spring loaded inverted pendulum studies, their performance was compared so that the unique features of the TDR-SLIP model, such as rolling contact, could be investigated. To undertake the comparison, a method for yielding parameter equivalency between these two models is also reported. In addition to its analytical role, the TDR-SLIP model served as a template to initiate the stable running behavior of the empirical robot acted as the anchor. Two sets of legs were evaluated-the original compliant half-circular leg of the robot and the new mechanical legs, which resemble the morphology of the TDR-SLIP model. Two types of control strategies were tested-position-based control and hybrid control. The experimental results reveals that the low-damped compliant half-circular leg and the mechanical leg match the behaviors of the R-SLIP model and the TDR-SLIP model, respectively, and the robot with hybrid control performs more stably and more closely to the model profile. In addition, when the robot's motion follows the template's stable dynamics, the energy cost of the leg in stance can be significantly lower than that in flight.

In this paper, aerodynamic actuation characteristics of radio-frequency(RF) discharge plasma are studied and a method is proposed for shock wave control based on RF discharge. Under the static condition, a RF diffuse glow discharge can be observed; under the supersonic inflow, the plasma is blown downstream but remains continuous and stable.Time-resolved schlieren is used for flow field visualization. It is found that RF discharge not only leads to continuous energy deposition on the electrode surface but also induces a compression wave. Under the supersonic inflow condition, a weak oblique shock wave is induced by discharge. Experimental results of the shock wave control indicate that the applied actuation can disperse the bottom structure of the ramp-induced oblique shock wave, which is also observed in the extracted shock wave structure after image processing. More importantly, this control effect can be maintained steadily due to the continuous high-frequency(MHz) discharge. Finally, correlations for schlieren images and numerical simulations are employed to further explore the flow control mechanism. It is observed that the vortex in the boundary layer increases after the application of actuation, meaning that the boundary layer in the downstream of the actuation position is thickened. This is equivalent to covering a layer of low-density smooth wall around the compression corner and on the ramp surface, thereby weakening the compressibility at the compression corner. Our results demonstrate the ability of RF plasma aerodynamic actuation to control the supersonic airflow.

In the competition with high-speed railway, the Logit Competition Model was built according to the theory of utility maximization to maximize the airline ticket revenue. Taking the six routes centre of Zhengzhou city as an example, the probability of choosing plane or the high-speed railway under different discounts was predicted. Based on the relationship between probability and ticket price, the optimal discount rate and ticket price when selecting different routes was calculated. The results show that the Zhengzhou to Dalian route has the most optimal revenue and the minimum discount pressure, while the Zhengzhou to Beijing route has the least optimal revenue and the maximum discount pressure.

Dynamical heterogeneities of 2D liquid dusty plasmas at different temperatures are investigated systematically using Langevin dynamical simulations. From the simulated trajectories, various heterogeneity measures have been calculated, such as the distance matrix, the averaged squared displacement, the non-Gaussian parameter, and the four-point susceptibility. It is found that, for 2D Yukawa liquids, both spatial and temporal heterogeneities in dynamics are more severe at a lower temperature near the melting point. For various temperatures, the calculated non-Gaussian parameter of 2D Yukawa liquids contains two peaks at different times, indicating the most heterogeneous dynamics, which are attributed to the transition of different motions and the α relaxation time, respectively. In the diffusive motion, the most heterogeneous dynamics for a colder Yukawa liquid happen more slowly, as indicated by both the non-Gaussian parameter and the four-point susceptibility.

A compact tunable guided-mode resonant filter (GMRF) in the telecommunication region near the 1550 nm wavelength is proposed in this paper. Particle swarm optimization (PSO) is used to design the GMRF. The tunability of the GMRF is achieved by an MEMS-based physical movement (in the horizontal or vertical direction) combined with an incident angle in a certain range. The results show that the resonant wavelength tuning of 110 nm (140 nm) is obtained by horizontal movement of 168 nm (vertical movement of 435 nm) combined with an about 11° variation of incident angle.

Metal–insulator–metal (MIM) capacitors with atomic-layer-deposited Al2O3–HfO2 laminated and sandwiched dielectrics have been fabricated and electrically compared for analog circuit applications. The experimental results indicate that the laminated dielectrics exhibit much better leakage and breakdown characteristics than the sandwiched ones while maintaining higher capacitance densities and acceptable voltage linearity. In respect of the 1 nm Al2O3 and 10 nm HfO2 laminated dielectric, the resulting capacitor offers an extremely low leakage current of 2.4 × 10−9 A cm−2 at 8 V and a breakdown electric field of ~3.3 MV cm−1 at 125 °C together with a capacitance density of ~3.1 fF µm−2 and voltage coefficients of capacitance of 100 ppm V−2 and −80 ppm V−1 at 100 kHz. The superiority of the laminated dielectrics correlates with inhibition of HfO2 crystallization, discontinuity of the grain boundary channels from the top to the bottom and changes of the dielectric electronic properties due to the bonding and polarization effects at the multi-interfaces.

Cluster calculations employing hybrid density functional theory have been carried out to examine the initial surface reactions in atomic layer deposition (ALD) of TiN thin films on the SiO(2) surface using TiCl(4) and NH(3) as precursors. The potential energy surface (PES) of both half-reactions at different temperatures is presented. The first half-reaction between TiCl(4) with the SiO(2) surface is activated with an activation barrier of 0.78 eV and an exothermicity of 0.38 eV, suggesting that it is thermodynamically favourable. Also, the NH(3) half-reaction begins with the formation of amido complexes by the replacement of Cl atoms by NH(2), which is endothermic by 0.58 eV with a physisorbed HCl state (HCl-PS1). Formation of the amido complexes can be followed by an elimination reaction to form imido complexes, which has a relatively high activation barrier of 2.51 eV. In addition, the effect of the reaction temperature on the Cl impurity concentrations and film growth rate in the ALD process is also discussed.

Hybrid density functional theory has been used to investigate the initial surface reaction mechanism in atomic layer deposition (ALD) of Al2O3 on the hydroxylated GaAs(001)-4 x 2 surface. The precursors for ALD of Al2O3' are trimethylaluminium (TMA) and H2O as the aluminium and oxygen sources. For the first half-reaction between TMA with the GaAs surface the calculated activation barrier is 15.4 kcal mol(-1), and the H2O half-reaction proceeds by a mechanism similar to that of the first half-reaction, resulting in an activation barrier of 27.6 kcal mol(-1). Both half-reactions are thermodynamically favourable, exothermic by 52.0 and 43.6 kcal mol(-1) relative to the reactants, respectively.

We study the low frequency photonic band structures in triangular metallic lattice, displaying Dirac points in the frequency spectrum, and constructed upon the lowest order regular polygonal tiles. We show that, in spite of the unfavourable geometrical conditions intrinsic to the structure symmetry, the lowest frequency photonic bands are formed by resonance modes sustained by local structure patterns, with the corresponding electric fields following a triangular distribution at low structure filling rate and a honeycomb distribution at high filling rate. For both cases, the lowest photonic bands, and thus the plasma gap, can be described in the framework of a tight binding model, and analysed in terms of local resonance modes and their mutual correlations. At high filling rate, the Dirac points and their movement following the structure deformation are described in the same framework, in relation with local structure patterns and their variations, as well as the particularity of the metallic lattice that enhances the topological anisotropy.