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A polypropylene (PP) film is usually employed as the main insulation of the peaking capacitor, which is important in an electromagnetic pulse simulator to generate high-amplitude nanosecond pulse. The flashover voltage of PP films under nanosecond pulse limits the highest working voltage of a peaking capacitor. Surface fluorination was employed to increase the flashover voltage of PP. The flashover voltages of PP samples with different fluorination times (0, 4, and 6 h) were tested in an oven with nanosecond pulse voltage. The results showed that the flashover voltage of the PP film with 6-h surface fluorination was increased about 15% than the untreated film in the air. To clarify the influential mechanism, the physicochemical properties of PP film samples were tested and characterized. The results of thermally stimulated depolarization current (TSDC) showed that the trap density of the PP film increased obviously after fluorination treatment. With the increase in treatment time, the trap depth and density were increased obviously. The surface conductivity of PP films slightly decreased with the increase in fluorination time. The mechanism of surface fluorination on the influence of the flashover performance of the PP film under nanosecond pulse is discussed. It is concluded that surface fluorination significantly increases the carbon–fluorine (C–F) bond of the PP film, resulting in the increase in the depth and density of the surface trap, and then, a large amount of homocharges trapped in the surface trap reduces the electric field near the electrode. [ABSTRACT FROM AUTHOR]

Megavolt-class pulsed gas switches play an important role in large pulsers as transfer switches. This article analyzes the breakdown process and characteristics of a megavolt self-triggered preionized switch under 100-ns pulses based on the optical diagnosis. It is discovered that the triggering spark illumination targeting the main cathode or anode can separately preionize the main gap. The discharge channel is likely to first form between trigger electrodes and the main anode. Based on the above deduction, the streamer velocity is calculated to be $0.54 \times 10^{6}$ – $2.34 \times 10^{6}$ m/s, proportional to the electric field. Also, parameters of the empirical formula for calculating the gas heating time are amended. Influence mechanisms of the switch jitter are also studied. Under pulsed preionization mode, the trigger gap breaks down when the main gap electric field is high enough, and the switch jitter is mainly determined by the self-triggering jitter. Nonetheless, the self-triggering jitter can be partly offset during the breakdown process if the changing rate of mean reduced electric field $d(E/p)$ / dt at the self-triggering time is higher than 1.0 $1.0\left(\mathrm{kV} \cdot \mathrm{ns}^{-1} \cdot \mathrm{cm}^{-1} \cdot \mathrm{MPa}^{-1}\right)$. Under sustaining preionization mode, the trigger gap breaks down prematurely, and the continuous arcing driven by switch leak current preionizes the main gap. Therefore, the influence of the self-triggering jitter on the switch jitter can be eliminated. [ABSTRACT FROM AUTHOR]

Numerical simulation of discharge mechanism under nanosecond pulse voltage assists in the insulation performance optimization of N2-insulated switches that are widely used in the pulse power devices. This article presents a fluid dynamic model for the positive streamer propagation in N2 based on a needle-plate discharge system. The effects of the operating conditions, such as voltage amplitude, rising edge, gap width, and needle radius, are studied. Simulating results indicate that the streamer might be evoked only when the maximum electric field exceeds the critical value that is closely influenced by the needle radius and gap width, e.g., $1.3\times 10^{7}$ V/m based on a needle-to-plate electrode configuration with a 0.4-mm tip radius and 5-mm gap. The maximum electric field occurs at the head of streamer and it drops suddenly by nearly two orders of magnitude in the back of the head, which makes the streamer moves forward rapidly. Certainly, it needs a high enough voltage to ensure continuous propagation of the streamer, for example, more than 20 kV needed as the tip radius and gap set to 0.4 and 5 mm, and the electric field strength and migration speed increase with the increasing voltage amplitude. The radius of the discharge region is smaller when the rising edge time increases from 10 to 40 ns. However, if the rising edge time is too low (e.g., 2 ns), the streamer will cease before it propagates to the plate electrode and the radius of the discharge region shrink at the same time. In addition, the peak electric field and the averaged electron energy at the same position away from the needle decrease slightly with the gap width. Finally, there is an obvious decrease of the initial peak electric field as the needle radius increases. [ABSTRACT FROM AUTHOR]

The polymer film dielectric has been widely used in high voltage equipment for bulk insulation owing to the excellent insulation performance. Martin’s empirical formula for bulk breakdown is frequently used to predict the breakdown field strength of multilayer thin film with different electrode areas. In this article, based on the academic consensus that the cumulative breakdown probability of single-layer film obeys the Weibull distribution, the relationship between the cumulative breakdown probability of film dielectric under different electrode areas and the applied electrical field is deduced. Moreover, the relationship between the cumulative breakdown probability of film dielectric with various numbers of film layers and the applied electrical field is obtained and simplified. On these bases, combined with the experimental results of the average breakdown field of film dielectric with smaller electrode areas and fewer layers, a prediction model of the average breakdown field strength of film dielectric with different electrode areas and film layers is established. To obtain the solution of the prediction model concerning the number of film layer, an effective approximate solution method is proposed to solve the calculation problem with ultralarge and ultrasmall data, which significantly reduces the complexity of the solution process. A coaxial film capacitor is developed and tested to verify the prediction model with the “Chenguang” accelerator. The experimental breakdown field strength of 54 layers of 15 $\mu \text{m}$ biaxially oriented polypropylene (BOPP) film with an electrode area of 218.1 cm2 is 355.6 V/ $\mu \text{m}$ , which is comparable to the predicted result of 374 V/ $\mu \text{m}$. The prediction model presented in this article is of certain reference significance for the insulation design of film dielectrics. [ABSTRACT FROM AUTHOR]

Avalanche transistor (AT)-based repetitive nanosecond pulse generators with high amplitude, fast rise time, narrow pulse width, and low jitter have been widely developed and applied in numerous fields. However, relatively little research has been carried out on the positive nanosecond pulse generation with high flexibility in a wide range of output voltage amplitude. In this article, a novel AT-based Marx circuit (MC) topology adopting base-triggering method is proposed to avoid the formation of current filamentation inside the transistors and resolve the contradiction between high-voltage output and high repetition rate operation. A $6\times 10$ -stage MC prototype is implemented with optimized parameters to validate the feasibility of the proposed topology. The conduction processes of transistors show that, with the injection of additional base current, the switched-ON modes are transformed, which contributes to reliable conduction of transistors even without sufficient overvoltage ramp. With the adoption of inner triggering loops, the minimum working voltage of the prototype is extended to 1150 V. The operation characteristics of the generator in the whole operation range are investigated in depth. Experimental results illustrate that, at the 75- $\Omega $ match-ended coaxial cable, the prototype is capable of generating positive pulses with an adjustable voltage amplitude in the range of 6.50 to 12.39 kV, a basically consistent rise time of 3.6 ns and pulse width of 19.5 ns. Over 107 successive pulses are generated at a maximum repetition rate of 1 kHz without any device failure. [ABSTRACT FROM AUTHOR]

N × N filter operations are frequently used in various image processing algorithms in display driver circuits. The implementation of the N × N filter requires a storage element to temporarily retain N or N-1 lines of display data. The traditional approach for this temporary storage element for N × N image filter is either by using N blocks of memory to store N lines of display data with single-port six-transistor (6T) SRAM bit-cells or by using N-1 blocks of memory to store N-1 lines of display data with dual-port eight-transistor (8T) SRAM bit-cells. In this paper, a pseudo multi-port SRAM circuit is proposed for N × N filter in image processing in a display driver integrated circuit (IC). By using pre-read mechanism and word-line/column selection signal forwarding technique, the proposed approach only stores N-1 lines of display 3 × 3 filter application, the proposed approach reduces the overall layout area by 50.3% and 30.2% compared to the traditional dual-port 8T and single-port 6T memory implementations, respectively, in an industrial 0.18-μm CMOS technology. Furthermore, the power used to perform a 3 × 3 filter operation is reduced by 47% and 30.8% with the proposed approach as compared to the traditional dual-port 8T and signal-port 6T memory circuits, respectively, with slight degradation of the access speed. [ABSTRACT FROM AUTHOR]

The surface flashover characteristics of BOPP (biaxial-oriented polypropylene) films in SF 6 under nanosecond-pulsed voltages are experimentally investigated in this research by using finger electrodes and using the front-edge flashover method. The test factors include the gas pressure, electrode distance, pulse voltage steepness, pulse polarity and applied field direction. The flashover voltage first increases with gas pressure and then saturates at a certain value, such as 0.4 MPa for a 9 mm gap. The more serious the field distortion is, the lower the saturation gas pressure. The increase in the pulse voltage steepness enhances the flashover voltage in general, but a frap phenomenon of the flashover voltage occurs, and the flashover voltages under pulses with steeper fronts are lower at some pressures. Generally, the negative flashover voltage is higher than a positive voltage by using finger-cuboid electrodes, especially at high pressures. The flashover voltage on the film surface with a normal electrical field component is higher than that with a parallel component at low pressures and lower at high pressures. Moreover, a qualitative avalanche model based on the accumulation and emission of surface charges on the films and the field distortion effect of space charge behaviors is employed to explain the above experimental results. [ABSTRACT FROM AUTHOR]

The characteristics, breakdown probability, and statistical distribution of breakdown time delay under different du/dt in hundreds of nanoseconds pulse for millimeter gaps have been investigated by employing the statistical experimental method in this paper. The experimental results indicate that both the breakdown time delay and jitter are essentially decreased as the slope of the pulse voltage- du/dt is increased for 1-, 2-, and 4-mm gaps; in particular, increasing the value of du/dt is useful to obtain the smaller relative deviation of breakdown time delay under the same breakdown electric field. The breakdown probabilities for different gaps have been analyzed and a method of utilizing the Gaussian distribution function has been proposed which can be used for evaluating the statistical distribution of breakdown time delay. When the experimental condition is 100% breakdown probability, the breakdown time delay follows a Gaussian distribution. However, it is unsuitable for the fitting of breakdown time delay utilizing a Gaussian function for 2- and 4-mm gaps from the cumulative probability distributions of breakdown time delay because of the lower du/dt values and breakdown probabilities. [ABSTRACT FROM AUTHOR]

In the practical operation of an electromagnetic pulse (EMP) simulator, the flashover phenomenon on the edge of polypropylene dielectrics dominates the insulation failure mode of a peaking capacitor. To analyze the characteristics of polypropylene film flashover voltage under high-pressure SF6, an experimental platform was established, and the pulse generator could output a pulse with a rise time of approximately 27 ns. The experiments were performed on finger electrodes, and the SF6 pressure was set from 0.1 to 1.0 MPa. The experimental results show that the relationship of flashover voltage and gas pressure could be divided into two regions: in low-pressure regions, the flashover voltage increases with the gas pressure linearly and in high-pressure regions, the growth of flashover voltage gradually slows down and approaches a saturation value. As the gap distance increases, the saturation point of gas pressure decreases, and even when close to 0.4 MPa, with a 9-mm gap distance, this unconventional phenomenon cannot be ignored, particularly in practical EMP simulators. When the high surface resistivity and the charge trap distribution on the polypropylene film are considered, the accumulation and emission of surface charges on the film might be the primary reason for the saturated phenomena. [ABSTRACT FROM AUTHOR]

Due to its low-loss and high dielectric strength, polypropylene is widely used as electrical insulation material in pulse capacitors. In order to study its breakdown characteristics for nanosecond voltage pulses, an experimental setup was designed to generate voltage pulses with a 10%–90% rise time of 38 ns and a full width at half maximum of about 90 ns. Tests of the three polypropylene films with thicknesses of 12, 15, and $18~\mu \text{m}$ were performed. In addition, hundreds of nanoseconds pulse and dc voltage were also applied for comparison. The experimental results reveal that most of the breakdown occurs during the front edge of the pulse for tens of nanoseconds pulse, and the breakdown strengths of the three kinds of polypropylene films are almost identical for different applied voltages, which show a weak correlation between the thickness of the dielectric and the breakdown field. The expected breakdown strength of tens of nanoseconds pulse defined in this paper is not significantly higher than the mean value of the hundreds of nanoseconds pulse and the dc condition, suggesting that the breakdown of a thin polypropylene film is mainly determined by the electrical field but not the voltage-time cumulative effect. All these observations strengthen the conclusion that the breakdown of a thin polypropylene film is an intrinsic phenomenon. [ABSTRACT FROM AUTHOR]

This paper proposes an augmented model approach for identification of nonlinear errors-in-variables (EIVs) systems. An EIV model accounts for uncertainties in the observations of both inputs and outputs. As the direct identification of nonlinear functions is difficult, we propose to approximate the nonlinear EIV model using multiple ARX models. To estimate the noise-free input signal, we use a collection of particle filters which run in parallel corresponding to each of the multiple ARX models. The parameters of local models are estimated by applying expectation maximization algorithm, under a maximum likelihood framework, using the input-output data of the nonlinear EIV system. Simulated numerical examples and an experiment study on a multitank system are used to illustrate the efficacy of the proposed approach. [ABSTRACT FROM AUTHOR]

Coaxial magnetically insulated transmission line (MITL) was widely used in high-current pulsed power facilities. It is also an important option in future high-current accelerators based on the linear transformer driver (LTD) technology, in which the output line is usually coaxial to fit the component layout. In one of the schemes for high-current LTD accelerator, tens of coaxial MITLs are connected to conical disk lines in parallel. As a special structure, the coaxial–conical transition is a key component of the system. The feasibility of efficient current transmission under magnetic insulation condition is the precondition for building such a pulsed power facility. In this paper, we report the results of coaxial–conical MITL transition experiment which were conducted on the primary test stand (PTS). At the inner MITL of PTS, four coaxial MITLs were connected, gradually changed to mini-triplate and finally connected two conical MITLs. The total current at the entrance of coaxial lines (input) and at the conical MITL (output) were recorded. It showed that an output–to-input current efficiency of above 96% and of 87% across the transition was achieved with short load connection and open load connection, respectively. The 3-D transient electromagnetic simulation and 3-D particle-in-cell simulations were conducted to check the transmission efficiency, which confirmed very tiny loss when the load was short connected. [ABSTRACT FROM AUTHOR]

Existing view-invariant gait recognition methods encounter difficulties due to limited number of available gait views and varying conditions during training. This paper proposes gait partial similarity matching that assumes a 3D object shares common view surfaces in significantly different views. Detecting such surfaces aids the extraction of gait features from multiple views; 3D parametric body models are morphed by pose and shape deformation from a template model using 2D gait silhouette as observation. The gait pose is estimated by a level set energy cost function from silhouettes including incomplete ones. Body shape deformation is achieved via Laplacian deformation energy function associated with inpainting gait silhouettes. Partial gait silhouettes in different views are extracted by gait partial region of interest elements selection and re-projected onto 2D space to construct partial gait energy images. A synthetic database with destination views and multi-linear subspace classifier fused with majority voting is used to achieve arbitrary view gait recognition that is robust to varying conditions. Experimental results on CMU, CASIA B, TUM-IITKGP, AVAMVG, and KY4D data sets show the efficacy of the propose method. [ABSTRACT FROM PUBLISHER]

Ultraviolet (UV) illumination can effectively shorten the statistical lag and jitter in gas breakdown processes. The spark gap discharge can produce abundant spectrum including UV waveband. In this paper, a simple but reliable spark gap operating with N2 at atmospheric pressure is used to test optical radiation characteristics, such as spectrum intensity, rise time, fall time, and duration of optical pulse, which are adjusted by changing the circuit or configuration parameters. Three UV-illuminated switches with different UV spark gap configurations have been tested. The experimental results approve our assumption. With a uniform electric field UV spark gap, the breakdown voltage standard deviation percentage of the switch is 0.74%. [ABSTRACT FROM PUBLISHER]

Current transmission efficiency in a conical transition magnetically insulated transmission line (MITL) has been studied experimentally on a 1.0-MV linear transformer driver system, which has 10 identical cavities connected in series with MITL. Transmission efficiencies of anode current as high as 98.4% and 93.1% could be achieved when the MITL operates at load-limited and self-limited flows, respectively. As for the cathode current, because of the sufficient length of conical transition MITL, cathode current is also able to sustain high transmission efficiency. But as long as the diode gap is too large, many of the electrons will be launched into the anode–cathode gap and the cathode current near the diode drastically decreases. Particle-in-cell simulations were conducted to validate the conclusions. The simulation results agree with experiments. [ABSTRACT FROM PUBLISHER]

Presents an investigation on the influence of O2-Hb reaction kinetics and the Fahraeus effect on steady state O2 and CO2 transport in cat brain microcirculation using the refined multicompartmental model. Most important model predictions; What results indicated about the maximal difference between O2-Hb saturation; Suggestions drawn on the capillaries.