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The numerical simulation of the damage characteristics of CFRP under high-speed impact is of great significance for the lightweight design of the fan case of the new aero turbofan engine. The refined solid model of CFRP laminates was established by TexGen. Based on ABAQUS/Explicit and the secondary development of the VUMAT user subroutine, the failure process of CFRP laminates caused by the ballistic impact experiment was numerically simulated. The failure process of Ti-6Al-4V alloy flake impact on CFRP laminates at high-speed, and the dynamic stress-strain distribution, energy absorption mechanism and fiber failure mode of CFRP laminates were carried out. The CFRP laminates was impacted by Ti-6Al-4V alloy flake ( simulated fragments of engine blade due to fatigue ) at the speed of 156.9~297 m∙s-1 by a light gas gun. Based on the images collected by high-speed cameras and the three-dimensional digital image correlation technology ( 3D-DIC ), the macroscopic damage characteristics such as damage morphology and strain of CFRP laminates were obtained. The reliability of the numerical simulation was verified by comparing the experimental results, such as fracture morphology and microstructure obtained by SEM with the damage element morphology and dynamic strain response near the target of CFRP laminates in numerical simulation. The damage characteristics of CFRP laminates were described. The results show that the deformation process of CFRP, such as matrix cracking, fiber pull-out and delamination, absorbs most of the initial kinetic energy of Ti-6Al-4V alloy flake, and plays a certain role in energy absorption and protection. Under the experimental conditions given in this paper, combined with the deformation characteristics and energy absorption mechanism of ballistic impact laminates, a reliable numerical simulation method for the damage characteristics of Ti-6Al-4V alloy flake penetrating CFRP laminates is given

Recently, van der Waals heterojunctions (vdWHs) constructed from two two-dimensional materials have attracted considerable attention. In particular, vdWHs based on black phosphorus (BP) have shown excellent photoelectric properties. In this work, we construct a BP/GeTe vdWH and investigate its electronic and optical properties. We find that the BP/GeTe vdWH has a type-II band alignment. Its optical absorption exhibits a red shift compared to the freestanding BP and GeTe monolayers. The electric field and strain effects on the BP/GeTe vdWH are also investigated. The band offsets can be modulated by the electric field and the strain. The BP/GeTe vdWH will convert from type-II to type-I when applying an electric field and to type-III under strain, which will expand the application of BP/GeTe vdWHs in transistor devices. Furthermore, the strain can significantly enhance the optical absorption and induce the red shift of the absorption edge, which indicates the broad applications of the BP/GeTe vdWH in photodetector devices.

Metal nanogaps can confine electromagnetic field into extremely small volumes, exhibiting strong surface plasmon resonance effect. Therefore, metal nanogaps show great prospects in enhancing light–matter interaction. However, it is still challenging to fabricate large-scale (centimeter scale) nanogaps with precise control of gap size at nanoscale, limiting the practical applications of metal nanogaps. In this work, we proposed a facile and economic strategy to fabricate large-scale sub-10 nm Ag nanogaps by the combination of atomic layer deposition (ALD) and mechanical rolling. The plasmonic nanogaps can be formed in the compacted Ag film by the sacrificial Al2O3 deposited via ALD. The size of nanogaps are determined by the twice thickness of Al2O3 with nanometric control. Raman results show that SERS activity depends closely on the nanogap size, and 4 nm Ag nanogaps exhibit the best SERS activity. By combining with other porous metal substrates, various sub-10 nm metal nanogaps can be fabricated over large scale. Therefore, this strategy will have significant implications for the preparation of nanogaps and enhanced spectroscopy.

To develop high performance computing methods for compressible flow calculation, a GPU-accelerated compressible flow solver is developed with Compute Unified Device Architecture (CUDA). The WENO5 scheme is adopted for spatial discretization, and the third-order Runge-Kutta scheme is used for time discretization. According to the algorithm and programming model, the heterogeneous computing method of the solver is designed. Different kernels are designed to implement different computing functions, and shared memory is used for time-advanced computations. The solver is verified by the one-dimensional shock tube case, and a good acceleration effect is obtained with the increase of the grid size. And the impact of execution configuration on kernel performance was investigated. When the block size is reduced under different grid sizes, the speedup changes in the same way, but the performance parameters change differently.

Similarity laws (SLs) are useful for correlation and prediction of plasma parameters at different scales, which have been verified for geometrically symmetric capacitive radio-frequency (rf) discharges in nonlocal kinetic regimes. In this work, we demonstrate the applicability of SLs to dual-frequency rf discharges and confirm that similarity relations still hold considering the electrical asymmetry effect (EAE). By simultaneously tuning the control parameters (the gas pressure p, discharge gap d, and driving frequency f), we examine the similarity relations in rf plasmas via fully kinetic particle-in-cell simulations with the external circuits coupled and solved self-consistently. The validity of the SL scalings in dual-frequency rf plasmas with the EAE is confirmed for parameters such as the electron/ion density, ion flux, dc self-bias, ion energy distribution function, and power absorption. Although adjusted by the EAE, the dc self-bias and ion energy distribution functions are identified as similarity invariants under similar discharge conditions. Furthermore, the plasma series resonance phenomenon, filamentation of power depositions of electrons and ions in bulk plasma, and electric field reversal are observed in dual-frequency discharges with the EAE, which can also be exactly replicated under similar discharge conditions. The results further extend the application of SL scaling to dual-frequency rf plasmas, providing a more comprehensive understanding of the scaling characteristics in rf plasmas.

Two-dimensional materials have a wide range of applications in many aspects due to their unique properties. Here we carry out a detailed structural search and design of the BP2 using the first principles method, and find a new PMM2 sheet. The analysis of the phonon dispersive curves shows that the 2D PMM2 is dynamic stable. The study of molecular dynamics shows that the 2D PMM2 can be stable under high temperature, even at 600 K. Most importantly, when a suitable strain is applied, the structure can exhibit other electronic properties such as direct band gap semiconductor. In addition, the small strain can tune the band gap value of the PMM2 structure to around 1.4 eV, which is very close to the ideal band gap of solar materials. Therefore, the 2D PMM2 may have potential applications in the field of photovoltaic materials.

The complementary resistive switching (CRS) memristor has originally been proposed for use as the storage element or artificial synapse in large-scale crossbar array with the capability of solving the sneak path problem, but its usage has mainly been hampered by the inherent destructiveness of the read operation (switching ‘1’ state to ‘ON’ or ‘0’ state). Taking a different perspective on this ‘undesired’ property, we here report on the inherent behavioral similarity between the CRS memristor and a leaky integrate-and-fire (LIF) neuron which is another basic neural computing element, in addition to synapse. In particular, the mechanism behind the undesired read destructiveness for storage element and artificial synapse can be exploited to naturally realize the LIF and the ensuing spontaneous repolarization processes, followed by a refractory period. By means of this biological similarity, we demonstrate a Pt/Ta2O5−x /TaO y /Ta CRS memristor that can exhibit these neuronal behaviors and perform various fundamental neuronal operations, including additive/subtractive operations and coincidence detection. These results suggest that the CRS neuron, with its bio-interpretability, is a useful addition to the family of memristive neurons.

The initial stage of the gas breakdown with the generation of runaway electrons was investigated using particle-in-cell/Monte Carlo collision simulations. The parameters of the solved problem are a 1 mm long atmospheric air gap between tip-plane electrodes applied with a nanosecond pulse voltage. The pulse is 5.2 ns in rising time (10%–90%), 10 ns in pulse width (FWHM) and 40 kV in amplitude. The cathode is a cone-shaped electrode, the tip of which is defined by the elliptic equation (the major axis is 4 mm and the minor axis is 1 mm), and the minimum radius of curvature is 0.125 mm. As it is found in the simulation that the development of the discharge channel from the cathode to the anode only takes about tens to hundreds of picoseconds, especially at high overvoltages with runaway electrons, it is assumed that the gap voltage applied in such a short time is nearly constant. Depending on the voltage at the breakdown, different behavior of the energetic electrons is observed. When the voltage is low, about 12 kV, energetic electrons are only produced in the tip cathode layer, where the electric field is the highest; no runaway electrons leading the discharge channel are observed. When the voltage is higher, about 15 kV, the energetic electrons begin to run away at the head of the discharge channel, where the electric field is high enough. When the voltage is even higher, the energetic electrons run away, even at the beginning of the discharge, and from the cathode to the anode. Pre-ionization of the gas ahead of the discharge channel by the runaway electrons is observed, which may play an important role in the fast breakdown of the gas under the nanosecond short pulse.

We present simultaneous broad-band radio observations on the abnormal emission mode from PSR B1859+07 using the Five-hundred-meter Aperture Spherical radio Telescope (FAST). This pulsar shows peculiar emission, which takes the form of occasional shifts of emission to an early rotational phase and mode change of emission at the normal phase. We confirm all these three emission modes with our data sets, including the B (burst) and Q (quiet) modes of the non-shifted pulses and the emission shift mode with a quasi-periodicity of 155 pulses. We also identify a new type of emission shift event, which has emission at the normal phase during the event. We studied polarization properties of these emission modes in detail, and found that they all have similar polarization angle curve, indicating the emissions of all these three modes are from the same emission height.

In order to make the output flow of the valveless micropump larger and obtain continuous pumping capacity, a valveless piezoelectric micropump with a combination of V-shaped structure inlet and Y-shaped structure outlet is designed, which saves the design and installation of microvalve and makes the structure relatively simple and easy to process. In this paper, first, the operating principle of the valveless piezoelectric micro pump is analyzed; secondly, COMSOL simulation software was used to perform modal analysis on the drive and the appropriate vibration mode was obtained. The displacement trend of the piezoelectric vibrator was simulated and tested at the frequency of 40 Hz and different voltages; finally, 3D printing technology was used to produce an experimental prototype of the micro-pump, and t the specific size of the micro pump is 20 mm×20 mm×6 mm. The test results show that, driven by AC voltage, the discharge liquid of the valveless piezoelectric micropump can reach 658.8μl/min.

The uniformity of electric current distribution in a wire array and its unstable behavior during the process of underwater electrical explosion have been investigated. Two exploding wires in parallel were used in the experiments and the current waveforms flowing through each wire were obtained using two self-integrating coils. Significant differences in the current waveforms of the two wires were observed near the melting point, which was attributed to the non-simultaneity of heating and phase transition. Unbalanced current distribution caused by the deviations of wire dimensions was analyzed based on a magneto-hydrodynamic model, and the simulation results show that thermodynamic state difference between two wires is present throughout the entire electrical explosion process. It is also found that the initial stored energy of pulse generator will affect the thermodynamic state evolution of exploding wires, resulting in different behaviors of current distribution after the explosion time. The slightly different heating rate caused by unbalanced current distribution in a wire array can break the symmetry of converging shock waves and lower the pressure peak in the vicinity of implosion axis, which was discussed based on the two-dimensional hydrodynamic simulations.

Similarity laws (SL) are essential for correlating the characteristics of plasmas at different dimensional scales, which have been validated for radio frequency (rf) discharges at low pressure but under limited conditions. In this work, we evaluate the effects of nonlinear collisions (e.g. stepwise ionization) on the similarity properties in capacitive rf discharges in argon across a wide range of pressure regimes via fully kinetic particle-in-cell simulations. The SL scalings of fundamental discharge parameters, e.g. the electron power absorption and electron energy probability function, are examined with and without nonlinear collisions, respectively. Without the nonlinear collisions, the similarity scalings are found to be rigorously valid. When the nonlinear collisions are considered, the similarity properties in rf discharges still exist approximately, which indicates that the violations caused by the nonlinear collisions are still minor in the studied cases. The reasons for the effectiveness of SL scalings with nonlinear collision processes are also discussed. The results from this study confirmed the validity of similarity transformations with more complex reaction kinetics, which may promote the applicability of the SL scalings for the design and fabrications of plasma devices.

In view of the current situation of tight teaching resources, the intelligent scheduling system alleviates this problem to a certain extent, and the advantages and disadvantages of the scheduling method determine the performance of the scheduling system. a method based on Case-based reasoning is presented in this paper to solve the course scheduling problem. Using graph theory, a case representation model is built for the course scheduling problem, a measure is established for case similarity, and a case retrieval method based on maximum common subgraph selection is brought forward. Finally, the validity of the proposed method for solving course scheduling problem based on case-based reasoning is verified through an experiment.

In order to solve the problem that the development of self-built logistics cannot meet the development of fresh e-commerce, a coordinated distribution strategy of self-built logistics and third-party logistics is proposed. The tasks assigned by third-party logistics are used to determine the price discount ratio. Third-party distribution outsourcing cost function, customer satisfaction function, and freshness function of fresh produce. Aiming at the goal of minimum delivery cost, maximum customer satisfaction, and maximum freshness of fresh produce, a collaborative delivery optimization model was established, and a corresponding genetic algorithm was designed with examples. Simulation results show that: collaborative distribution can effectively reduce the cost of distribution, when the proportion of price discount increases, the cost of collaborative distribution decreases. It has a certain reference value for the optimization of fresh e-commerce enterprises’ distribution mode.

Zinc ferrite precursors are prepared by coprecipitation method using zinc nitrate and ferric nitrate as reactants, monohydrate ammonia and citric acid as precipitants and dispersants respectively. And zinc ferrite precursors are calcined at high temperature to obtain zinc ferrite photocatalysts at different temperatures(350°C, 450°C, 550°C). Methylene blue is used as substrates. The quality of the catalyst, the type of catalyst and the temperature of calcining are measured to study the photocatalytic performance. The results show that the preparation of zinc ferrite under 450°C has an optimal effect on the degradation of methylene blue dye. Compared with iron oxide and zinc oxide, the photocatalytic properties of zinc ferrite are superior to that of single oxide.

With simple three-step method, a new symmetrical metal free organic diphenylpyran dye containing dual rhodamine-3-acetic acid anchors was successfully synthesized, characterized and applied to dye-sensitized solar cells (DSSC). The dye has saturated methylene in its acceptor part, which makes the electron withdrawing group and the anchor group cannot be conjugated well. In addition, the exhibits lower molar extinction coefficients of the dye and its blue-shifted absorption spectrum also influenced the light capture ability. The resulting weaker intramolecular charge transfer and the electron coupling effect of the dye hindered the dye charge injection and shorten the electron lifetime, leading to an average power conversion efficiency of 0.65 % (Jsc = 2.32 mA cm−2, Voc = 448 mV and FF = 0.63). Further design of an efficient dye molecule needs efficient conjugation between the electron-withdrawing group and anchoring group, as well as an effective light harvest capability.

We investigate the performance of the hybrid energy consistent/WENOCU4 scheme compared to the classical WENOCU4 scheme. It is borne out that the hybrid scheme preserves excellent shock-capturing ability without numerical oscillations. In the meantime, the hybrid scheme can achieve more accurate representations of smooth flow features which indicates its low-dissipation capacities. Moreover, hybrid scheme significantly outperforms WENOCU4 for its superior computational efficiency. Therefore, employing hybrid scheme is a much more cost-effective choice for the simulation of shock/turbulence interaction.

The dependence of the carrier-induced degradation on the temperature and irradiance is studied. The stability of samples after accelerated degradation and regeneration at different temperature and irradiance are studied also. Minority carrier lifetime and normalized defect density are used to characterize the degradation and regeneration kinetics. The mechanism of temperature and irradiance on degradation is studied and discussed.

Bipolar charge transport model has been widely used to simulate the behavior of space charge. In order to reduce the splitting error three-order flux limiter is adopted to solve the advection-reaction equations. The simulation results are compared with experimental results and simulation results of Le Roy et al, validating the feasibility of the numerical scheme. Recombination rates and charge densities during polarization and depolarization are deeply analyzed for polyethylene at 40kV/mm. The effect of electric field on charge transport are also presented. It is found that the net charge density during polarization increases with the increase of the electric field. Negative charges are observed in the vicinity of the cathode, which disagrees with the experimental results.

In order to study the effect of flexural stiffness on the mechanical properties of single conductor under wind load, a configuration function of the conductor considering stiffness is established in this paper. Based on the configuration function, the finite element model is established, and the effects of suspension point angle, span on the mechanical properties of down lead conductor under wind load are studied. The results show that, compared with the catenary model, the model in this paper is more consistent with the experimental fitting formula. The angle of the suspension point has obvious influence on the tension of down lead conductor. With the increase of the angle of the suspension point from 0°to 80°, the tension decreases by nearly one third. The bending moment is affected by the alignment, and the reverse sign appears with the increase of suspension point angle. When the redundancy rate is the same, the span increases from 2 m to 4 m, and the tension of the conductor decreases by 18%.

Atmospheric pressure non-thermal plasma is of interest for industrial applications. In this study, polypropylene (PP) films are modified by a dielectric barrier discharge (DBD) with a non-uniform magnetic field in air at atmospheric pressure. The surface properties of the PP films before and after a DBD treatment are studied by using contact angle measurement, atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The effect of treatment time on the surface modification with and without a magnetic field is investigated. It is found that the hydrophilic improvement depends on the treatment time and magnetic field. It is also found that surface roughness and oxygen-containing groups are introduced onto the PP film surface after the DBD treatment. Surface roughness and oxygen-containing polar functional groups of the PP films increase with the magnetic induction density. The functional groups are identified as C-O, C=O and O-C=O by using XPS analysis. It is concluded that the hydrophilic improvement of PP films treated with a magnetic field is due to a greater surface roughness and more oxygen-containing groups.

A dielectric barrier discharge in a 2 mm air gap was studied. The experiments show that the mesh electrode and PET film really make the discharge looking homogeneous. The breakdown onset voltage in the case of a mesh electrode and PET film is 6.4 kV, considerably lower than 8 kV, the breakdown voltage in the usual case using two spherical electrodes. The field calculations show that even with this much lower voltage the gap field in the region very close to the PET film is enhanced to a value near the breakdown field in the usual case. It may be this field enhancement that initiates a corona discharge which provides seed electrons, leading to the breakdown of the whole air gap at a lower voltage. A lower voltage applied to the gap means a lower averaged field over the gap. Because the development of an electron avalanche is very sensitive to the electric field, a small decrease in the field will depress the avalanche significantly, preventing a homogeneous discharge from transiting to filament discharge. This may be the reason why a mesh electrode and PET film make the discharge look homogeneous.

A small neon gas-puff z-pinch device was constructed, and the plasma implosion and its radiation characteristics were studied experimentally. The plasma implosion was investigated using a three-frame Mach–Zehnder interferometer (TFMZI) that is capable of taking three pictures (5 ns exposure and 13 ns interpicture delay) within a single z-pinch shot. Thermopiles were also used in the experiments with the TFMZI to study the correlation between the total energy of x-ray emission and the plasma implosion. The ion beams from the z-pinch plasma were analysed using a compact Thomson spectrometer. Based on the experiments, the imploding velocity and electron density of the plasma shell were obtained, a conclusion that a nearly uniform and symmetric imploding plasma shell would emit a higher x-ray yield than an asymmetric one was drawn and the charge state resolved energy spectra of ion beams emitted from the z-pinch plasma were plotted.

Experiments were performed on an atmospheric pressure glow discharge (APGD) in an air gap between two dielectric barrier electrodes. While it is possible to get an APGD in a 2 mm air gap, it is possible to get only a filament discharge in a 5 mm air gap. The development of an electron avalanche in such a gap was numerically simulated. It was found that the critical applied field for a 5 mm electron avalanche to transit to a streamer is equal to 35.07 kV cm−1. This calculated critical applied field is in good agreement with the experimental one. The experimental and theoretical results confirm that only a filament discharge, rather than a glow discharge, can be produced in an atmospheric pressure air gap that is not less than 5 mm if it is not possible to lower the breakdown field of air. A resistive barrier discharge (RBD) was theoretically analysed and the development of RBD was numerically simulated. If a kilohertz discharge is required, the parameters of the resistive layer should be in the range ρer = (109–1011) Ω cm. APGD in a helium gap was realized using 50 Hz line power with a suitably fabricated resistive layer.

The glow discharges in the gaps geometrically similar to that used in glow discharge cleaning of the International Thermonuclear Experimental Reactor (ITER) were numerically simulated based on a two-dimensional fluid model in which the linear dimensions of gap A are two times that of gap B and the pressure of gap A is half that of gap B. Under an applied voltage of 1000 V, the physical parameters at the corresponding point pz in these two gaps were compared. It was found that the electric potential U(pz), the reduced field E(pz)/p and the electron temperature Te(pz) are equal in values for these two gaps, but the electron density ne(pz) and ion density ni(pz) for gap B are four times that of gap A. All these parameter ratios are the same as that defined by similarity law, which confirmed that the similarity law is valid for the glow discharges in non-plane-parallel gaps.

Directed cell migration requires a spatially polarized distribution of polymerized actin. We develop and treat a mechanical model of cell polarization based on polymerization and depolymerization of actin filaments at the two ends of a cell, modulated by forces at either end that are coupled by the cell membrane. We solve this model using both a simulation approach that treats filament nucleation, polymerization, and depolymerization stochastically, and a rate-equation approach based on key properties such as the number of filaments N and the number of polymerized subunits F at either end of the cell. The rate-equation approach agrees closely with the stochastic approach at steady state and, when appropriately generalized, also predicts the dynamic behavior accurately. The calculated transitions from symmetric to polarized states show that polarization is enhanced by a high free-actin concentration, a large pointed-end off-rate, a small barbed-end off-rate, and a small spontaneous nucleation rate. The rate-equation approach allows us to perform a linear-stability analysis to pin down the key interactions that drive the polarization. The polarization is driven by a positive-feedback loop having two interactions. First, an increase in F at one side of the cell lengthens the filaments and thus reduces the decay rate of N (increasing N); second, increasing N enhances F because the force per growing filament tip is reduced. We find that the transitions induced by changing system properties result from supercritical pitchfork bifurcations. The filament lifetime depends strongly on the average filament length, and this effect is crucial for obtaining polarization correctly.

The similarity law of gas discharge is not always valid due to the occurrence of some elementary processes, such as the stepwise ionization process, which are defined as the forbidden processes. To research the influence of forbidden processes on the similarity law, physical parameters (i.e., the electric field, electron density, electron temperature) in similar gaps are investigated based on the fluid model of gas discharge. The products of gas pressure p and dimensions are kept to be constant in similar gaps and the discharge model is solved with and without the forbidden processes, respectively. Discharges in similar gaps are identified as glow discharges and the typical similarity relations all are investigated. The results show that the forbidden processes cause significant deviations of similarity relations from the theoretical ones and the deviations are enlarged as the scaled-down factor k increases. If the forbidden processes are excluded from the model, the similarity law will be valid in argon glow discharge at low pressure.

A three-dimensional model containing tungsten electrodes, arc plasma and a weld pool is presented for double electrodes tungsten inert gas welding. The model is validated by available experimental data. The distributions of temperature, velocity and pressure of the coupled arc plasma are investigated. The current density, heat flux and shear stress over the weld pool are highlighted. The weld pool dynamic is described by taking into account buoyance, Lorentz force, surface tension and plasma drag force. The turbulent effect in the weld pool is also considered. It is found that the temperature and velocity distributions of the coupled arc are not rotationally symmetrical. A similar property is also shown by the arc pressure, current density and heat flux at the anode surface. The surface tension gradient is much larger than the plasma drag force and dominates the convective pattern in the weld pool, thus determining the weld penetration. The anodic heat flux and plasma drag force, as well as the surface tension gradient over the weld pool, determine the weld shape and size. In addition, provided the welding current through one electrode increases and that through the other decreases, keeping the total current unchanged, the coupled arc behaviour and weld pool dynamic change significantly, while the weld shape and size show little change. The results demonstrate the necessity of a unified model in the study of the arc plasma and weld pool.

The scalar model of non-uniformly correlated partially coherent pulses is extended to the full electromagnetic domain and the realizability conditions of stochastic electromagnetic non-uniformly correlated partially coherent (SENUC) pulse sources in the frequency domain are derived. It is shown that the evolution properties of the intensity and degree of polarization (DOP) of the SENUC pulse in dispersive media in the frequency domain are much different from those of an SENUC pulse in the temporal domain. And the distribution of the intensity and DOP of the pulse on propagation is dependent on its spectral coherence width, shift parameters of the spectral correlation maximum and second-order dispersion coefficient.

A small electrical explosion of wire (EEW) setup for nanopowder production is constructed. It consists of a low inductance capacitor bank of 2 ?F?4 ?F typically charged to 8 kV?30 kV, a triggered gas switch, and a production chamber housing the exploding wire load and ambient gas. With the EEW device, nanosize powders of titanium oxides, titanium nitrides, copper oxides, and zinc oxides are successfully synthesized. The average particle size of synthesized powders under different experimental conditions is in a range of 20 nm?80 nm. The pressure of ambient gas or wire vapor can strongly affect the average particle size. The lower the pressure, the smaller the particle size is. For wire material with relatively high resistivity, such as titanium, whose deposited energy Wd is often less than sublimation energy Ws due to the flashover breakdown along the wire prematurely ending the Joule heating process, the synthesized particle size of titanium oxides or titanium nitrides increases with overheat coefficient k (k = Wd/Ws) increasing.

Based on a Mach-Zehnder interferometer, we report on the first observation of two different modes of wire explosion for nanosized powder production in 5–30 kPa ambient gas, depending on the property of wire material. For wire material with relatively high resistivity, such as titanium, more than one vapor burst was observed. While for wire material with relatively low resistivity, such as copper, the whole wire would explode totally within one single vapor burst.

A dielectric barrier discharge in neon at atmospheric pressure is investigated with electrical measurement and fast photography. It is found that a stable diffuse discharge can be easily generated in a gap with a gap space of 0.5–6 mm and is identified with a glow discharge. The first breakdown voltage of the gap is considerably higher than that of the same gap working in a stable diffuse discharge mode, which indicates that Penning ionization of neon metastables from the previous discharge with inevitable gas impurities plays an important role in the decrease in the breakdown voltage. Discharge patterns are observed in a gap shorter than 1 mm. From the experiments with a wedge-like gap, it is found that the discharge patterns are formed in the area with a higher applied electric field, which suggests that a higher applied electric field may cause a transition from a diffuse glow to discharge patterns.

A dielectric barrier discharge in nitrogen at atmospheric pressure was investigated by means of the electrical measurement, the fast photography and the time-resolved spectroscopy. By addition of a nitrogen flow, a stable homogeneous discharge was produced in a gap not longer than 3 mm and it was identified with a Townsend discharge. It was found that the discharge was extinguished while the voltage of the gas gap continued to increase. This extraordinary manner of discharge extinction was explained by the limited number of trapped electrons on the dielectric surface that could not provide a long-lasting Townsend discharge with sufficient secondary electrons. Due to the 'memory effects' the lowest breakdown voltage for a Townsend discharge in a 2 mm gap is only 4.9 kV in contrast to the streamer breakdown voltage of 8.2 kV. The working domain of the Townsend discharge is dependent on the frequency and the amplitude of the applied voltage. When the flow velocity increases from 0 to 140 cm s−1, the discharge current decreases from 2.9 to 2.3 mA and the breakdown voltage increases from 5.3 to 5.9 kV, which is attributed to the nitrogen pressure in the gap increasing with the flow velocity. With the gas flow, the intensities of the spectral lines from the second positive system of N2 are almost unchanged, whereas those from NOγ systems are significantly reduced. From this phenomenon, it may be inferred that the density of oxygen as impurity in the discharge gap decreases with the gas flow. This result is in agreement with the existing theory that less oxygen leads to more metastables N2(A) surviving to produce more seed electrons for initiating a Townsend discharge in nitrogen at atmospheric pressure.

Results from scanning electron microscopy, Fourier transform infrared spectroscopy and the measurement of thermally stimulated current show that a high density of the physical defects and the chemical defects are introduced into the surface of the silicone rubber plates after they are treated by corona discharge plasma. These defects behave electrically as shallow electron traps, leading to the formation of a uniform discharge in air at higher pressure when the corona-modified silicone rubber is used in dielectric barrier discharge.

Based on the diagnostic techniques of electrical measurement, emission spectroscopy and fast photography, the effects of the helium flow in dielectric barrier discharge of atmospheric helium were investigated. It was shown that the nitrogen molecules as impurity in the discharge gap are reduced by a helium flow through the gap. As nitrogen molecules are very efficient quenchers of helium metastables, the introduction of the helium flow may induce an increase in the density of helium metastables after discharge and thus an enhanced contribution of these metastables to the next breakdown of helium gap at a lower voltage. The area of the higher density of He metastables after discharge moves from upstream to downstream as the flow velocity increases, leading to the area of starting discharge moving from upstream to downstream. It seems that the nitrogen molecules as the impurity in helium play more important roles in influencing the behaviour of helium discharge than the products etched from the dielectric surface by discharge.

The X-ray emission from an X-pinch was measured with diamond photoconducting detectors and a pinhole camera, and the results show that the X-ray source of the X-pinch is extremely small in size and high in brightness. As such, the X-pinch could be considered as an X-ray point source having a high spatial coherence that is required by a simplified scheme of X-ray phase-contrast imaging. The X-pinch was used as X-ray source for the phase-contrast imaging of a weakly X-ray-absorbing mosquito and an image with high contrast was obtained.