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High-voltage pulse power supplies are key power input devices for the study and application of discharge plasma. A high-voltage pulse current power supply (HV-PCPS) with an energy storage pulse transformer based on flyback topology can output microsecond pulsewidths with high-power, ultrahigh voltage, and high reliability, which are suitable for most dielectric barrier discharge (DBD) plasma applications. However, during the process of DBD driven by an HV-PCPS based on an energy storage pulse transformer, the output pulse voltage waveform quality is poor, making it not suitable for stable discharge long-term operation. This article aims to solve the aforementioned problem and proposes a novel resistor–diode–diode (RDD) shaping method. Not only can this novel method solve the problem of poor quality of the output pulse power from the HV-PCPS, guaranteeing stable discharge for various DBD electrodes, it can also limit the maximum output voltage amplitude. This prevents overvoltage breakdown when the output terminal is in an open state or a light load state because the HV-PCPS is acting as a current source. This article also analyzes the effectiveness of an RDD branch when solving the problem in theory, and gives a detailed parameter design method. Finally, a 30-kV HV-PCPS prototype is built to verify the effectiveness of the proposed RDD pulse shaping method. The average pulse power output of the whole prototype is greatly improved, and it can achieve an average pulse power output of 1 kW. Furthermore, the electrode loads of different DBD reactors can be driven by this technology. [ABSTRACT FROM AUTHOR]

A novel 24/17-pole 3-phase stator wound field flux switching (SWFFS) machine with the combination of overlapping armature winding (OAW) and asymmetric stator poles (ASP) is proposed for higher torque density in this article. First, the air-gap modulation principle of the 24/17-pole OAW-SWFFS machine is analyzed to better understand its torque production mechanism. Second, since the torque capacity will be greatly restricted by the serious magnetic saturation which is introduced by the OAW configuration, two effective measures are proposed from two perspectives in this article to solve this problem. The first measure is to reduce the magnetic saturation directly by optimizing the area ratio of armature slot and excitation slot, and thus, the torque density can be improved effectively. The second measure is to further enhance the open circuit flux linkages, back electromotive force (EMF), and thus, the torque density by adopting the proposed ASP structure. Furthermore, the accurate ASP distances which are corresponding to the largest back EMF can be obtained effectively based on the air-gap field modulation theory. Finally, the proposed design is validated experimentally by a prototype machine. The simulated and experimental results show that about 25.7% higher torque density can be obtained when compared with 24/14-pole SWFFS machine. [ABSTRACT FROM AUTHOR]

Active disturbance rejection control using extended state observer (ESO) is less dependent on the knowledge of the system. It has proved to be an excellent scheme for speed control of electrical drives. However, for time-varying disturbance, the observation precision of conventional ESO is undesired, which limits the speed tracking accuracy. Accordingly, this article proposes an enhanced speed controller for electrical drives based on adaptive switching high-order ESO (ASHESO). First, the critical parameters affecting the steady-state performance of ASHESO are determined according to frequency analytical results. Then, optimized observer gain is obtained by modifying a part of pole locations, which weakens the influence of noise on estimated state. Finally, an adaptive switching gain mechanism is proposed according to the closed-loop tracking error and the swiftness of dynamic response is maintained. The proposed speed controller has achieved high estimation accuracy for disturbance and strong immunity to measurement noise. The feasibility and effectiveness of the strategy is verified on a laboratory permanent magnet synchronous motor (PMSM) drive system. [ABSTRACT FROM AUTHOR]

Chemoresistance causes tumor recurrence and metastasis, resulting in poor clinical outcomes and low survival, and has been considered an obstacle to tumor therapy. The development of novel therapeutic approaches that can effectively kill chemoresistant tumor cells (CRTCs) is therefore critical to overcoming these obstacles. Objective: Here, we introduce an emerging physical feature-based therapeutic approach based on nanosecond pulsed electric fields (nsPEFs). The goal of this study is to investigate the effect of nsPEFs on CRTCs. Methods: The cell viability, ablation effects on a 3D-cultured scaffold, and lethal thresholds of nsPEFs were evaluated according to fluorescence staining assays. Results: nsPEF treatment preferentially affected chemoresistant cells (A549/CDDP) with a higher cell viability inhibition ability/cell death rate, larger ablation area, and lower ablation threshold compared to their respective homologous tumor cells (A549). The experimental and theoretical studies suggested that nsPEFs displayed selective behavior toward intracellular structures. With this selective character, nsPEFs can induce higher electroporation effects (e.g., higher pore number, larger electroporation area, and faster fluorescence dissipation on the nuclear envelope) on CRTCs due to their larger nuclear size and cell membrane capacitance. Conclusion: These findings demonstrated that nsPEFs induced preferential ablation of CRTCs over their respective homologous tumor cells. Significance: This study provides an experimental and theoretical basis for the study of killing CRTCs by electrical treatments and suggests potential applications in the optimization of novel anti-chemoresistance methods. [ABSTRACT FROM AUTHOR]

High-frequency irreversible electroporation (H-FIRE) is a tissue ablation modality employing bursts of electrical pulses in a positive phase–interphase delay (d1)–negative phase–interpulse delay (d2) pattern. Despite accumulating evidence suggesting the significance of these delays, their effects on therapeutic outcomes from clinically-relevant H-FIRE waveforms have not been studied extensively. Objective: We sought to determine whether modifications to the delays within H-FIRE bursts could yield a more desirable clinical outcome in terms of ablation volume versus extent of tissue excitation. Methods: We used a modified spatially extended nonlinear node (SENN) nerve fiber model to evaluate excitation thresholds for H-FIRE bursts with varying delays. We then calculated non-thermal tissue ablation, thermal damage, and excitation in a clinically relevant numerical model. Results: Excitation thresholds were maximized by shortening d1, and extension of d2 up to 1,000 μs increased excitation thresholds by at least 60% versus symmetric bursts. In the ablation model, long interpulse delays lowered the effective frequency of burst waveforms, modulating field redistribution and reducing heat production. Finally, we demonstrate mathematically that variable delays allow for increased voltages and larger ablations with similar extents of excitation as symmetric waveforms. Conclusion: Interphase and interpulse delays play a significant role in outcomes resulting from H-FIRE treatment. Significance: Waveforms with short interphase delays (d1) and extended interpulse delays (d2) may improve therapeutic efficacy of H-FIRE as it emerges as a clinical tissue ablation modality. [ABSTRACT FROM AUTHOR]

Objective: Tissue electroporation is achieved by applying a series of electric pulses to destabilize cell membranes within the target tissue. The treatment volume is dictated by the electric field distribution, which depends on the pulse parameters and tissue type and can be readily predicted using numerical methods. These models require the relevant tissue properties to be known beforehand. This study aims to quantify electrical and thermal properties for three different tissue types relevant to current clinical electroporation. Methods: Pancreatic, brain, and liver tissue were harvested from pigs, then treated with IRE pulses in a parallel-plate configuration. Resulting current and temperature readings were used to calculate the conductivity and its temperature dependence for each tissue type. Finally, a computational model was constructed to examine the impact of differences between tissue types. Results: Baseline conductivity values (mean 0.11, 0.14, and 0.12 S/m) and temperature coefficients of conductivity (mean 2.0, 2.3, and 1.2 % per degree Celsius) were calculated for pancreas, brain, and liver, respectively. The accompanying computational models suggest field distribution and thermal damage volumes are dependent on tissue type. Conclusion: The three tissue types show similar electrical and thermal responses to IRE, though brain tissue exhibits the greatest differences. The results also show that tissue type plays a role in the expected ablation and thermal damage volumes. Significance: The conductivity and its changes due to heating are expected to have a marked impact on the ablation volume. Incorporating these tissue properties aids in the prediction and optimization of electroporation-based therapies. [ABSTRACT FROM AUTHOR]

This paper investigates the transmission energy minimization problem for the two-user downlink with strictly heterogeneous latency constraints. To cope with the latency constraints and to explicitly specify the trade-off between blocklength (latency) and reliability the normal approximation of the capacity of finite blocklength codes (FBCs) is adopted, in contrast to the classical Shannon capacity formula. We first consider the non-orthogonal multiple access (NOMA) based transmission scheme. However, due to heterogeneous latency constraints and channel conditions at receivers, the conventional successive interference cancellation may be infeasible. We thus study the problem by considering heterogeneous receiver conditions under different interference mitigation schemes and solve the corresponding NOMA design problems. It is shown that, though the energy function is not convex and does not have closed form expression, the studied NOMA problems can be globally solved semi-analytically and with low complexity. Moreover, we propose a hybrid transmission scheme that combines the time division multiple access (TDMA) and NOMA. Specifically, the hybrid scheme can judiciously perform bit and time allocation and take TDMA and NOMA as two special instances. To handle the more challenging hybrid design problem, we propose a concave approximation of the FBC rate/capacity formula, by which we obtain computationally efficient and high-quality solutions. Simulation results show that the hybrid scheme can achieve considerable transmission energy saving compared with both pure NOMA and TDMA schemes. [ABSTRACT FROM AUTHOR]

For irreversible-electroporation (IRE)-based therapies, the underlying electric field distribution in the target tissue is influenced by the electroporation-induced conductivity changes and is important for predicting the treatment zone. Objective: In this study, we characterized the liver tissue conductivity changes during high-frequency irreversible electroporation (H-FIRE) treatments of widths 5 and 10 μs and proposed a method for predicting the ablation zones. Methods: To achieve this, we created a finite-element model of the tissue treated with H-FIRE and IRE pulses based on experiments conducted in an in-vivo rabbit liver study. We performed a parametric sweep on a Heaviside function that captured the tissue conductivity versus electric field behavior to yield a model current close to the experimental current during the first burst/pulse. A temperature module was added to account for the current increase in subsequent bursts/pulses. The evolution of the electric field at the end of the treatment was overlaid on the experimental ablation zones determined from hematoxylin and eosin staining to find the field thresholds of ablation. Results: Dynamic conductivity curves that provided a statistically significant relation between the model and experimental results were determined for H-FIRE. In addition, the field thresholds of ablation were obtained for the tested H-FIRE parameters. Conclusion: The proposed numerical model can simulate the electroporation process during H-FIRE. Significance: The treatment planning method developed in this study can be translated to H-FIRE treatments of different widths and for different tissue types. [ABSTRACT FROM AUTHOR]

Irreversible electroporation (IRE) is an emerging technology for the non-thermal ablation of tumors, but it is challenged due to the unintended induction of muscle contractions, which must be avoided by neuromuscular blockade in clinic. In this study, high frequency irreversible electroporation (H-FIRE), which replaces the monopolar IRE pulses with a burst of bipolar pulses, was used for tissues ablation on rabbit liver through Plate Electrodes. The bursts with different individual pulse durations maintain a constant total energized time (100 μs), burst number (90), and inter-burst delay (1 s). An accelerometer was used to measure the muscle contraction intensity. After the experiments, the tissue sections were made for pathological analysis. The experimental results show that all the cells are intact in the treated tissues that were harvested immediately. The tissues, which were harvested three days after the experiments, have an obvious ablation area, and the necrosis degree is increased with the pulse voltage and individual pulse width of the bursts. The extent of muscle contractions caused by H-FIRE is less than IRE. In addition, the simulations of electric field distribution near the vessels in liver tissues show that with the increase of the frequency and decrease of the pulse duration of the bursts, the electric field distribution will be more uniform. Compared with the lethal thresholds, bursts with larger pulse width can ablate the liver tissues effectively. Integrating into account the ablation effect and muscle contraction, we consider that H-FIRE with the individual pulse durations for 5 μs, electric field intensity for 2000 V/cm, can replace the traditional IRE, which have a good ablation effects and less extent of muscle contractions for animals. [ABSTRACT FROM AUTHOR]

Objective: To minimize the effect of muscle contractions during irreversible electroporation (IRE), this paper attempts to research the ablation effect and muscle contractions by applying high-frequency IRE (H-FIRE) ablation to liver tissue in vivo. Methods: An insulated needle electrode was produced by painting an insulating coating on the outer surface of the needle electrode tip. A series of experiments were conducted using insulated needle electrodes and traditional needle electrodes to apply H-FIRE pulses and traditional monopolar IRE pulses to rabbit liver tissues. The finite element model of the rabbit liver tissue was established to determine the lethal thresholds of H-FIRE in liver tissues. Muscle contractions were measured by an accelerometer. Results: With increased constitutive pulse width and pulse voltage, the ablation area and muscle contraction strength are also increased, which can be used to optimize the ablation parameters of H-FIRE. Under the same pulse parameters, the ablation areas are similar for the two types of electrodes, and the ablation region has a clear boundary. H-FIRE and insulated needle electrodes can mitigate the extent of muscle contractions. The lethal thresholds of H-FIRE in rabbit liver tissues were determined. Conclusion: This paper describes the relationships between the ablation area, muscle contractions, and pulse parameters; the designed insulated needle electrodes can be used in IRE for reducing muscle contraction. Significance: The study provides guidance for treatment planning and reducing muscle contractions in the clinical application of H-FIRE. [ABSTRACT FROM AUTHOR]

Given its nonthermal property and other advantages, irreversible electroporation (IRE) has quickly translated into clinical applications. An increasing number of clinical cases using IRE have also revealed crucial issues. The uneven distribution of the electric field caused by the heterogeneity of biological tissues has not been completely and effectively addressed to date. The use of high-frequency monopolar pulse bursts (HFMPBs) is expected to solve this problem. The high-frequency content of the HFMPB is used to ensure the uniform distribution of the electric field in the tissue. A temperature increase similar to that of the conventional pulse method does not cause thermal damage and results in a killing effect similar to that of the conventional technique. Meanwhile, the subpulse has a pulse duration of 1– 100~\mu \texts , which remains unexplored and may induce new cell responses. This paper analyzes the HFMPB based on the frequency domain and infers that the cell death pathways under this pulse induce necrosis and other processes, such as apoptosis. The phosphatidylserine externalization rate had a peak value at a different inner frequency of HFMPB when the electric field was 1 kV/cm for melanoma cells. This new type of pulse is expected to solve the problem of the uneven distribution of the electric field without altering the cell killing effect. If this effect is also verified in tissue ablation, these new types of pulses will promote the clinical application of IRE. [ABSTRACT FROM AUTHOR]

Irreversible electroporation (IRE) uses high-intensity electric pulses of ? 100 ?s duration to induce cell death through permanent membrane destruction. In this study, monopolar pulses are replaced by bipolar high repeated frequency pulses (BHRFPs) while maintaining a constant total energized time (100 ?s), burst number (90), and inter-burst delay (1 s). To observe the damage to the cell membrane directly, the fluorescent dye DiI, which has the advantages of a high signal-to-noise ratio, a lack of toxicity in cells, and slow fading, is used to label the cell membrane. This study explores the degree of damage to the stained adherent cell membrane caused by BHRFPs with equal quantities of energy. The experimental results show that the degree of damage to the cell membrane gradually increases with increasing number of bursts, but different changes are observed with different pulse widths. The DiI fluorescence intensity (degree of damage to the cell membrane) decreases from 79% to 54% with an increase in the pulse width from 400 ns (250 ?) to 10 ?s (10 ?). Therefore, a positive relationship exists between the degree of cell membrane damage as we increase the pulse duration from 400 ns (250 pulses) to 10 ?s (10 pulses) at the same electric field strength while delivering the same total energy. The amount of cell membrane damage increases for increasing electric field strengths with sufficiently strong fields ultimately inducing cell lysis. A numerical model of single cell is built to investigate the mechanism considering the effect of electroporation. The simulated results also show that the total pore area increases by applying the electric pulse with a pulse width of 400 ns (250 ?) to 10 ?s (10 ?); an increase in the total pore area means a stronger damage degree, which agrees well with the experimental results. [ABSTRACT FROM PUBLISHER]

To investigate dielectric property variations induced by electric pulses, equivalent doses of conventional irreversible electroporation (IRE) and high-frequency IRE were used to treat potato slices. The dielectric property of the potatoes were measured before and after treatment in the frequency band of 0.1 Hz-10 MHz, and then the Cole-Cole model was used to fit the experimental data in the frequency band of 1 kHz-10 MHz to explain the ? dispersion mechanism. The Cole-Cole model parameters showed that under an equivalent dose, the conventional IRE pulses were more efficient than the high-frequency IRE pulses for electroporation. After treatment with conventional IRE pulses, the DC conductivity greatly increased at time 0 after the pulses and showed little recovery over time. The electroporation effect of the high-frequency IRE pulses improved with increasing pulse duration. This study presents a potential new method for evaluating the effects of IRE during and immediately after the treatment process. [ABSTRACT FROM AUTHOR]

Pulsed electric fields have recently been the focus of considerable attention because of their potential application in biomedicine. However, their practical clinical applications are limited by poor understanding of the interaction mechanism between pulsed electric fields and cells, particularly in the process of electroporation and its effect on parameter selection. This paper established a multishelled dielectric model based on finite elements to simulate and analyze the processes involved in electroporation. In particular, the processes include the dynamic development of the pore radius and electroporation region: the distribution of recoverable, nonrecoverable, and nonelectroporation areas on the cell; and the influence of pulse parameters on varying degrees of electroporation. Results showed that membrane conductivity, pore density, transmembrane potential, and distribution of pore radii are functions of time and position on the cell. The electroporation areas were divided into recoverable, nonrecoverable, and no-electroporation pores. For 10~\mu \texts , 1.5-kV/cm pulse was observed in the regions exposed to sufficiently high transmembrane voltage (1 V), electroporation occurred, membrane conductivity and pore density (up to 10^\mathrm 16/\textm^\mathrm 2) rapidly increased with time, and electroporation areas increased gradually and were mainly distributed in the range 0°–70° (recoverable pore [0°, 35°], nonrecoverable pore [35°, 70°], and no-electroporation pore [70°, 90°]). Electric field strength was the major factor that induced electroporation, particularly in the recoverable pore, but it had minimal effect on pore expansion. However, pulse duration affects the nonrecoverable pore, such that the high-intensity wide pulse is more useful in the field of irreversible electroporation. The high-intensity short pulse can increase permeability and maintain cell viability. [ABSTRACT FROM AUTHOR]

High-frequency pulses constitute a new method for tumor treatment and have been proposed to solve the problems of muscle contraction and tumor recurrence caused by the nonuniform distribution of the electric field. However, the killing mechanism of high-frequency pulses remains unclear. Different pulse parameters have varying influences on the killing effect on cells. We studied the influence of the pulse duty cycle and the interval between pulses on the cellular response, including the transmembrane potential (TMP), pore radii, and the pore density, using finite-element simulation. Results showed that, given a pulse duration of 5~\mu \texts , the pulse duty cycle has an insignificant effect on the cellular response, and the cellular responses under monopolar pulses and bipolar pulses are similar. Given a bipolar pulse duration of 300 ns, the TMP and the pulse radii become larger if the interval between pulses is longer under bipolar pulses. Given a pulse duration of 300 ns, the TMP and pore radii under the monopolar pulse are larger than those under the bipolar pulse. Normal human epidermal cells (Hacat) and tumor cells (Gll19) are used to verify the simulation results, which show that the duty has an insignificant effect on cell killing. The simulation with the duration of 300 ns is verified using an experiment reported in the literature. [ABSTRACT FROM AUTHOR]

Applying high-frequency pulses to animals for tissue ablation can reduce the number and intensity of muscle contractions. Hence, developing a composite pulse generator is necessary to investigate the mechanism of tumor ablation under high-frequency composite pulses. In this study, a high-frequency and high-voltage composite pulse generator is proposed for such application. This generator combines the technology of full-bridge soft-switching circuit, MOSFET series, and RCD equalization circuit. This generator has the capability of producing composite pulses, in which the center frequencies of the bursts are up to 2 MHz, the inter-burst delay is 0.1?10 s, the pulse width is from 100 ns to 100 μs, the pulse amplitude is ±3 kV, and the rise time is around 30 ns. The parameters satisfy the requirements of the experiments for studying muscle contraction under high-frequency pulses and tumor ablation. The details of the generator?s production of high-frequency composite pulses are provided. An all-solid-state modular design makes the generator compact and reliable. Initial experiments are then conducted to verify the performances of the proposed generator. [ABSTRACT FROM PUBLISHER]

A bipolar pulse has been proved to be more advanced in the treatment of tumor because of the elimination of muscle contractions and the effect for ablating nonuniform tissue. In this paper, a new type of modular bipolar pulsed-power generator based on Marx generator with double power charging is proposed. The concept of this generator is charging the two series of capacitors in parallel by two power sources, respectively, and then connecting the capacitors in series through solid-state switches with different control strategies. Utilizing a number of fast solid-state switches, the capacitors can be connected in series with different polarities, so that a positive or negative polarity pulse will be delivered to the load. The simulated models of this generator have been investigated in a PSPICE platform, and a laboratory prototype has been implemented in a laboratory. The simulation and test results verify the operation of the proposed topology in different switching modes. The development of this pulse generator can provide the hardware foundation for the research on biological effect without muscle contraction when the tumors are applied with bipolar pulse electric field. [ABSTRACT FROM AUTHOR]

Seven hundred fifty kilovolt extra-high voltage (EHV) shunt reactors are important power equipment that stabilize the normal operation of an entire 750 kV power grid. Internal winding faults of a reactor could be a difficult issue when the reactor is in service, and result in sudden equipment failure and significant economic losses. To prevent sudden catastrophic failure of equipment, online detection should be implemented to evaluate the state of the reactor properties when requested. In this paper, a noninvasive method based on online impulse frequency analysis was proposed and developed to detect internal winding faults of a 750 kV EHV shunt reactor. Initially, the safe implementation of the online detecting device was verified before field installation. Unlike in previous work, the online detecting device was modified and improved according to the specific situation of shunt reactors. Original fingerprints of 750 kV EHV shunt reactors were obtained and analyzed after site installation and normal operation of the detecting device. A fault simulation test was implemented to validate the method. This paper provides guidance on actual implementation of online impulse frequency response analysis on power equipment. [ABSTRACT FROM AUTHOR]

The measurement of lightning current plays an important role in the identification of lightning strikes fault and location. However, measuring the lightning current directly, accurately, and safely is difficult. This paper presents an improved contactless measuring method by using a differential loop made of a printed circuit board with a numerical integral program. This differential loop is used to obtain the differential signals of the measured lightning current and consists of a planar circular spiral coil, a coaxial fitting, and an aluminous shielding shell. MATLAB numerical integral program is used to integrate the differential signal to reproduce lightning-current waveforms. Measurement theory, equivalent circuit, frequency analysis, and design of this improved contactless measurement are described. In the laboratory, experiments with three types of impact currents (24/42, 8/20, and 7/20 μs) were adopted to calibrate this improved measurement compared with Pearson coil. The results of the experiments show the following: 1) for a certain measuring distance, the differential loop with a numerical integral program can reproduce the waveform of 24/42, 8/20, and 7/20 ?s accurately and completely under an appropriate design; 2) the differential loop retains the advantages of safety, strong anti-interference ability, good linearity and accuracy compared with the differential-integral loop; 3) the improved measurement facilitates the easy unification of stray parameters and breaks the contradiction between sensitivity and low cut-off frequency, which is beneficial in acquiring lightning-current waveforms with low amplitudes. [ABSTRACT FROM PUBLISHER]

The capacity of a multiple-input–multiple-output (MIMO) channel with N transmit and receive antennas for high-speed railways (HSRs) is analyzed based on the 3-D modeling of the line of sight (LOS). The MIMO system utilizes a uniform linear antenna array. Instead of increasing the number of antennas or simply changing the parameters of the antenna array, such as separation and geometry, the capacity gain can be obtained by adjusting the weights of multiantenna array groups, because there are few scatterers in strong LOS environments. On the other hand, it is hard to obtain the array gain of MIMO beamforming for HSRs because of drastic changes in the receiving angle when the train travels across E-UTRAN Node B. Without changing the antenna design of Long-Term Evolution systems, this paper proposes a multiple-group multiple-antenna (MGMA) scheme that makes the columns of such a MIMO channel orthogonal by adjusting the weights among MGMA arrays, and the stable capacity gain can be obtained. The value of weights depends on the practical network topologies of the railway wireless communication system. However, the reasonable scope of group number N is less than 6. In selecting N, one important consideration is the tradeoff between practical benefit and cost of implementation. [ABSTRACT FROM PUBLISHER]