Sequential Discharge Research Articles

Discussion on the reverse recovery characteristics and protection methods of high-power silicon stack in electromagnetic railgun pulse forming network

Abstract In response to the problem of adverse effects on circuit elements caused by the reverse recovery characteristics of electromagnetic railgun freewheeling silicon stack during the sequential discharge process of pulse forming network, this paper uses the existing diode reverse recovery model and simulates the I-t and U-t change curves during the diode reverse recovery process through numerical calculation methods, obtaining results that are consistent with expectations. And through the pulse forming network composed of two modules in parallel, the changes in load voltage during the PFN timing discharge process were analyzed, and the impact of the reverse recovery process of the freewheeling diode on the power module was analyzed. Explored the influence of storage time and recovery time on the peak reverse current and maximum current change rate during reverse recovery process, and verified the correctness of the theory that if the reverse recovery time is too short, it can also cause damage to semiconductor components in the circuit.

Development of a New Lightweight Multi-Channel Micro-Pipette Device

In this study, to improve the efficiency of the pipetting workstation and reduce the impact of the pipetting device on the stability performance of the workstation, a novel fully automatic pipetting method is proposed. Based on this method, a lightweight, multifunctional, and quantitative twelve-channel pipetting device was designed. This device can achieve simultaneous quantitative liquid absorption for twelve channels and sequential interval liquid discharge for each channel. Initially, the overall functional requirements were determined, and with the aim of a lightweight design, the total weight of the device was controlled to be within 580 g through a reasonable structural design, material selection, and choice of driving source. The device’s overall dimensions are 170 mm × 70 mm × 180 mm (length × width × height), with a micropipetting volume ranging between 1.3 μL and 1.4 μL. Subsequently, factors affecting liquid suction stability were experimentally analyzed, and appropriate pipetting parameters were selected. The stability performance of this pipetting method during prolonged operation was investigated. Finally, the twelve-channel pipetting device was validated through experiments, demonstrating results that meet the national standards for the stability of a pipetting device. In summary, the device designed in this study exhibits novel design features, low cost, and modularity, thus demonstrating promising potential for applications in high-speed micro-volume pipetting.

Automatic Characterization of WEDM Single Craters Through AI Based Object Detection

Wire electrical discharge machining (WEDM) is a process that removes material from conductive workpieces by using sequential electrical discharges. The morphology of the craters formed by these discharges is influenced by various process parameters and affects the quality and efficiency of the machining. To understand and optimize the WEDM process, it is essential to identify and characterize single craters from microscopy images. However, manual labeling of craters is tedious and prone to errors. This paper presents a novel approach to detect and segment single craters using state-of-the-art computer vision techniques. The YOLOv8 model, a convolutional neural network-based object detection technique, is fine-tuned on a custom dataset of WEDM craters to locate and enclose them with tight bounding boxes. The segment anything model, a vision transformer-based instance segmentation technique, is applied to the cropped images of individual craters to delineate their shape and size. Geometric analysis of the segmented craters reveals significant variations in their contour and area depending on the energy setting, while the wire diameter has minimal influence.

Ecological succession and community assembly of mixed microbial culture polyhydroxyalkanoate production systems: Drivers of polyhydroxyalkanoate synthesis and Bdellovibrio predation

The production of polyhydroxyalkanoate (PHA) by mixed microbial culture (MMC) can reduce the pollution of plastics. Ecophysiological study of the microbial community assembly and succession is helpful for comprehensive understanding the MMC PHA production process. The operation mode of sequential aerobic dynamic discharge - aerobic dynamic feeding (ADD-ADF) was applied and the operation can be divided into acclimation phase and maturation phase. Deterministic process caused by selective pressure dominated the community assembly throughout the operation. In the acclimation phase, the physical selective pressure recovered the settling capacity of the system, and settling ability of the MMC was closely related to function of PHA synthesis. However, in the maturation phase, stochastic process caused sludge bulking, making the settling ability and PHA synthesis function of the MMC independent on each other. Stochastic process led to the succession of the dominant PHA-producing bacteria, for example, the predation of Paracoccus and Thauera by Bdellovibrio.

Quantifying streamflow properties using a calculus‐based differential approach

AbstractThis research quantifies streamflow temporal configuration and demonstrates the advantages of examining the hydrologic record on a day‐to‐day basis, heretofore unavailable with statistical‐based index parameters. The streamflow chronological structure represents a previously untapped wealth of information that would benefit ecohydrology allowing alternate lines of investigation, re‐evaluating past research in a new light and expanding analysis options for ecohydrologists. Innovative approaches are introduced to quantify this important but overlooked hydrologic property. To accomplish this, a non‐index calculus‐based differential approach has been developed using the lag(1) temporal autocorrelation signature of streamflow. The techniques for quantifying discharge (Q), day‐to‐day discharge change (dQ/dt), rate of day‐to‐day discharge change (d2Q/dt2) and sequential discharge summations are explained and presented using updated data visualization methods. A dam release river impact case study for the Colorado River at Lees Ferry, Arizona, demonstrates this novel way of analyzing and comparing discharge datasets. A set of highly customizable tools for this new approach can be used as a stand‐alone analysis or to complement other existing techniques. The result is a better understanding of the hydrologic regime, permitting more focused research and more effective management planning.

TIME BEHAVIOR OF THE Hα SPECTRAL LINE AND THE MOLECULAR HYDROGEN SPECTRAL LINE IN HYDROGEN PLASMA IN THE URAGAN-2M STELLARATOR

The studies of the scenario of hydrogen plasma creation with two sequential RF discharges during one pulse were carried out for the Uragan-2M stellarator. The first-stage discharge initiated the hydrogen pre-ionization at the generator anode voltage of 4 kV. The second-stage discharge was performed at the generator anode voltage selected from 6 to 9 kV. As result, plasma with an electron density up to 3.9·1018 m-3 was produced in a confinement volume. An increase of voltage resulted in an earlier appearance of signals of electron density, the intensity of the Hα spectral line, and the intensity of the molecular hydrogen spectral line. The increase of the time-dependent intensities of these signals was also registered.

Divergent gunshot residues and characterization of the memory effect in a .22 caliber revolver and pistol

BackgroundThe forms and compositions of primer gunshot residue (GSR) in shooting cases have been routinely analyzed in many crime labs by scanning electron microscope/energy-dispersive X-ray spectroscopy (SEM/EDS). Gunshot residue studies over the last 30 years have identified a contribution by residual GSR from surfaces within the firearm to GSR (the “memory effect”). In this study, we first focus on the GSR compositional differences between target, bore, and cylinder gap for a .22 caliber revolver which has received little attention in the literature. Secondly, we examine the behavior of elements involved in the residual contribution to GSR for a .22 caliber pistol.ResultsThe compositions of target, bore, and cylinder gap GSRs from a .22 caliber revolver were determined for 11 discharge series. Breech GSR compositions from a .22 caliber pistol changed in sequential discharges revealing behavior of individual primer and bullet elements. The target GSR forms from some .22 caliber ammunitions were not spherical.ConclusionsFor the revolver, GSR compositions from the target, bore, and cylinder gap are divergent. Analysis of the pistol’s breech GSRs indicated mixing with the previously deposited GSRs resulting in a sequential contribution or loss of elements and redeposition of the new composition. Aluminum did not contribute to the residual GSR. The GSR composition of a discharge and its contribution to residual GSR on the internal parts of the firearm represents a complex process which likely involves a number of variables including, but not restricted to firearm design, primer composition, pressure and temperature of the discharge gas, and bullet surface composition.

ASSOCIATIONS OF THE SERUM ALBUMIN CONCENTRATION AND SEQUENTIAL ORGAN FAILURE ASSESSMENT SCORE AT DISCHARGE WITH 1-YEAR MORTALITY IN SEPSIS SURVIVORS: A RETROSPECTIVE COHORT STUDY.

Introduction: This study was performed to investigate the predictors of 1-year mortality at discharge in sepsis survivors. Methods: This study was a retrospective analysis of patients with sepsis and septic shock at a single center. Patients who survived hospitalization for sepsis or septic shock between January 2016 and December 2017 were included in this study. Age, sex, body mass index, laboratory results such as blood cell count, C-reactive protein (CRP) and albumin levels, the Sequential Organ Failure Assessment (SOFA) score at the time of discharge and site of infection were compared between the survivors and nonsurvivors at 1 year postdischarge. Multivariate logistic regression was performed to identify the predictors of 1-year mortality. Results: During the study period, 725 sepsis patients were included in the analysis, 64 (8.8%) of whom died within the first year. The nonsurvivors were older and had a lower body mass index and a higher SOFA score at discharge than the survivors ( P < 0.05). Among the laboratory results at discharge, hemoglobin, platelet counts, and albumin concentrations were lower in the nonsurvivors than in the survivors, whereas CRP was higher in the nonsurvivors than in the survivors. In the multivariate logistic regression analysis, serum albumin <2.5 mg/dL and SOFA score ≥2 at discharge were identified as independent prognostic factors for 1-year mortality (odds ratio, 2.616; 95% confidence interval, 1.437-4.751 for albumin <2.5 mg/dL and 2.106, 1.199-3.801 for SOFA score ≥2, respectively). Conclusions: A low serum albumin concentration of <2.5 mg/dL and a high SOFA score of ≥2 at the time of discharge were prognostic factors for 1-year mortality in survivors of sepsis.

Variable load modes and operation characteristics of closed Brayton cycle pumped thermal electricity storage system with liquid-phase storage

As a new type of large-scale energy storage system, pumped thermal electricity storage (PTES) requires frequent load variation to smooth out grid fluctuations. However, there is a lack of research on the variable load of PTES systems. Therefore, five variable load methods are innovatively proposed in this paper, and the dynamic characteristics of the closed Brayton cycle PTES system with liquid-phase storage are simulated for variable load, separately. The results show that: for the same total air discharge time, during charge process, the rotor speed fluctuation rates of the five modes are “air charge + low-pressure and high-pressure sequential air discharge (CLHS)” (+0.80%), “air charge + low-pressure air discharge (CL)” (+1.07%), “air charge + high-pressure air discharge (CH)” (+1.40%), “air charge + high-pressure and low-pressure sequential air discharge (CHLS)” (+1.51%), “air charge + high-pressure and low-pressure simultaneous air discharge (CHL)” (+2.51%), from small to large. During discharge process, the rotor speed fluctuation rates are “CL” (-3.31%), “CHLS” (-3.96%), “CLHS” (-4.39%), “CH” (-5.61%), “CHL” (-9.83%), from small to large. During both charge and discharge processes, the load regulation ranges are “CHL”, “CLHS”/“CHLS”, “CH”, “CL”, from large to small. It can be seen that the modes with smaller rotor speed fluctuation rates also have smaller load regulation ranges, while the modes with larger load regulation ranges have larger rotor speed fluctuation rates. Therefore, in operation, different variable load modes should be selected according to the actual needs of rotor stability and load regulation range. The results of this study can provide a reference for the actual operation of pumped thermal electricity storage system.

Calcium-dependent subquantal peptide release from single docked lawn-resident vesicles of pituitary lactotrophs

Regulated exocytosis consists of the fusion between vesicles and the plasma membranes, leading to the formation of a narrow fusion pore through which secretions exit the vesicle lumen into the extracellular space. An increase in the cytosolic concentration of free Ca2+ ([Ca2+]i) is considered the stimulus of this process. However, whether this mechanism can be preserved in a simplified system of membrane lawns with docked secretory vesicles, devoid of cellular components, is poorly understood. Here, we studied peptide discharge from individual secretory vesicles docked at the plasma membrane, prepared from primary endocrine pituitary cells (the lactotrophs), releasing hormone prolactin. To label secretory vesicles, we transfected lactotrophs to express the fluorescent atrial natriuretic peptide (ANP.emd), previously shown to be expressed in and released from prolactin-containing vesicles. We used stimulating solutions containing different [Ca2+] to evoke vesicle peptide discharge, which appeared similar in membrane lawns and in intact stimulated lactotrophs. All vesicles examined discharged peptides in a subquantal manner, either exhibiting a unitary or sequential time course. In the membrane lawns, the unitary vesicle peptide discharge was predominant and slightly slower than that recorded in intact cells, but with a shorter delay with respect to the stimulation onset. This study revealed directly that Ca2+ triggers peptide discharge from docked single vesicles in the membrane lawns with a half-maximal response of ∼8 µM [Ca2+], consistent with previous whole-cell patch-clamp studies in endocrine cells where the rapid component of exocytosis, interpreted to represent docked vesicles, was fully activated at <10 µM [Ca2+]. Interestingly, the sequential subquantal peptide vesicle discharge indicates that fluctuations between constricted and dilated fusion pore states are preserved in membrane lawns and that fusion pore regulation appears to be an autonomously controlled process.

Numerical modeling of latent heat thermal energy storage integrated with heat pump for domestic hot water production

A combination of a heat pump and thermal energy storage is an efficient method to utilize variable renewable energy. Phase change materials have the potential to provide higher energy densities for thermal energy storage. Previous thermal energy storages utilizing phase change materials are either limited to sequential charge and discharge cycles or a complicated design that limits the maximum charge and responsiveness. This paper presents a novel integration of a heat pump and a thermal energy storage for a responsive simultaneous consumption and charging of the thermal energy storage up to the maximum charge. This concept is illustrated with a process model which is an essential tool in the dimensioning, design, and analysis of integrated thermal energy storage systems. The concept is demonstrated in domestic hot water with the heat pump operating either constantly, with solar energy, or with cheap electricity. For the daily demand of 138.4 kWh, heat pump outputs of 6.0, 14.0, and 22.8 kW were required with thermal energy storage capacities of 30.5, 54.6, and 130.2 kWh. This demonstrates the applicability of the concept as well as the process model for research and design of thermal energy storage with phase change materials. • Integrated model for a heat pump and a thermal energy storage for Matlab-Simulink environment. • Novel design for using only one heat transfer surface inside the energy storage. • Simultaneous heat production and consumption achieved with the novel design. • Developed process model utilized for case study for production of domestic hot water. • Utilization of variable renewable energy enhanced.

Effects of inter-pulse coupling on nanosecond pulsed high frequency discharge ignition in a flowing mixture

This work numerically investigates the effects of non-equilibrium nanosecond plasma discharge pulse repetition frequency, pulse number, and flow velocity on the critical ignition volume, minimum ignition energy, and chemistry in a plasma-assisted H2/air flow at 300 K and 1 atm using a multi-scale adaptive reduced chemistry solver for plasma assisted combustion (MARCS-PAC). The interactions between discharges/ignition kernels spanning decoupled, partially-coupled and fully-coupled regimes in a pulse train are studied. For a single pulse discharge, increased flow velocity increases the minimum ignition energy required due to the increase of convective heat loss and flame stretch. The results show that the minimum ignition kernel propagation speed at the critical ignition kernel volume increases with the flow velocity. The minimum critical ignition volume decreases with the increase of plasma discharge energy. For sequential two-pulse discharges, ignition fails at both decoupled and partially-coupled regimes even when the total discharge energy is above the minimum ignition energy, but succeeds only in the fully-coupled regime at a shorter inter-pulse time. Overlap of the OH radical pool between the sequential two-pulse discharges and the increase of the chemistry effect due to the increase of reduced electric field in the fully-coupled regime contribute to the ignition enhancement. In addition, for two-pulse discharges in the fully-coupled discharge regime, the mixture can be ignited at a total energy below the minimum ignition energy of a single pulse with the same flow conditions. Moreover, for a given total discharge energy with multiple pulsed discharges, the enhancement of the ignition kernel volume has a non-monotonic dependence on discharge frequency and pulse number. The effective ignition enhancement can be achieved with an optimal pulse repetition frequency and pulse number. This work provides a new understanding of the mechanism for repetitive plasma ignition and insights for the optimization of plasma ignition in a reactive flow.

Characteristics of three-electrode pulsed surface dielectric barrier discharge: streamer-to-spark transition and hydrodynamic expansion

Streamer-to-spark transition and hydrodynamic expansion in a three-electrode pulsed surface dielectric barrier discharge are studied under atmospheric-pressure air. Three sequential discharge processes of the primary streamer, transitional streamer and spark phase during a single pulse are observed from the time-resolved plasma morphologies. The primary streamer and transitional streamer phases, with a rising voltage and low current, followed by a spark phase with a rapidly falling pulse and ascending current are characterized. Images of the discharge development show that the transitional streamer is maintained in the ionization channel after the primary streamer bridges the high-voltage electrode and the second grounded electrode. When the transitional streamer develops to a certain level, the streamer discharge transfers into the spark discharge. As a result, two shock waves are induced in the two exposed electrode domains, and then merge into a single ellipse during the process of hydrodynamic expansion. Boltzmann plots indicate that the electron temperature is 4.815 eV in the initial phase of spark discharge and gradually decreases in the spark phase. Stark broadening of the O atomic line shows that the electron density is 7.06 × 1017 cm−3 during the spark phase.

In situ electrochemical nanoindentation of a nickel (111) single crystal: hydrogen effect on pop-in behaviour

Abstract The hydrogen effect on dislocation nucleation in Ni single crystals with (111) surface orientation has been examined with the aid of a specifically designed nanoindentation setup for in situ electrochemical experiments. The effect of the electrochemical potential on the indent load – displacement curve, especially the unstable elastic-plastic transition (pop-in), was studied in detail. The experiments allowed the exclusion of the surface from hydrogen effects. The observations showed a pop-in load drop from an average value of 250 to 100 μN due to in situ hydrogen charging, which is reproducibly observed within sequential hydrogen charging and discharging. Clear evidence is provided that hydrogen atoms facilitate homogeneous dislocation nucleation.

Enhancement Modelling Based on Electrical Discharge Machining Successive Discharges

The surface roughness of Inconel 718 is predicted using a sequential discharge model for electrical discharge machining (EDM). To begin with, the EDM single pulse discharge machining process was accurately simulated using the finite-element method (FEM). The surface topography under various discharge settings, the size, and the characteristic parameters of a single-pulse crater are simulated. Second, the material defines the discharge position as the minimum gap width between the work piece’s starting surface and the electrode in the removal model. The simulation shows that the magnitude of the single-pulse discharge energy influences the crater’s form and size. A difference in discharge energy causes a divergence in the increasing crater radius, depth, and flanging height trends. On the other hand, the ultimate surface morphology of an EDM machined surface is determined by the distribution of discharge locations around the parts in the workpiece; finally, machined surfaces are inspected using the same discharge parameters. The EDM work piece’s surface morphology matches the material removal. Between simulation and experiment, there is a relative error in surface roughness around 8.26%, and there is a relative error in surface roughness.

Comparison of active impurity control between lithium and boron powder real-time injection in EAST

The lithium and boron powder have been successfully real-time injected into Experimental Advanced Superconducting Tokamak (EAST) high-confinement (H−) mode discharges, showing good wall conditioning effects, especially on the impurities control. Both of lithium and boron powder particles are gravitationally accelerated into the upper edge of a upper single null discharge. The lithium powder real-time injection effectively reduced the tungsten impurity content both in the plasma edge and core. Contrary to the lithium injection, the boron injection mainly reduced the impurities content in the plasma core, while the impurities increased in the edge. This mainly due to that there was an edge harmonic mode stimulated by boron injection, providing sufficient particles transport. Moreover, the impurities control through boron injection has much wider operation windows than lithium powder injection. Furthermore, there was accumulative wall conditioning effects after sequential boron powder injection discharges.

Modeling the Human Sinoatrial Node Based on Sequential Discharge Hypothesis

The electrical synchronization of human sinoatrial (SA) node cells for propagating the pacemaker activity has always been an important challenge in literatures. Nevertheless, most literatures, that provide hypotheses for the electrical synchronization of SA node cells, only investigated the activity of a very small group of coupled SA node cells. Therefore, this study proposes a novel SA node model based on the sequential discharge hypothesis to estimate the electrical potential around the SA node, which electrodes measure it. This model consists of a three-dimensional regular network of Hodgkin-Huxley (HH) model modified by time constantthat propagates the action potentials of dominant pacemaker through the gap junctions. The results show that the HH model modified in this study not only has adequate capacity for generating oscillations between 40 and 180 beats per minute (BPM), but also their three-dimensional regular network can provide a suitable estimate from the electrical potential around the SA node. Therefore, this model is a good suggestion for the electrical synchronization of large mammalian SA node cells, especially human.

Electrical discharge propagation between GEM foils

This paper presents the studies of fast sequential discharge formations in neighboring Gas Electron Multiplier foils (so called fast discharge propagations). We report on the characteristics of the time delay between the discharges, which has been shown to be of the order of tens of nanoseconds. This time delay decreases both with increasing voltage on the foil where the secondary discharge occurs as well as with decreasing distance between the neighboring foils. Optical measurements of the discharges in two- and three-stage detector setups show that the propagating discharge does not occur directly below the primary discharge, but is displaced from the shortest line between neighboring foils. This observation, together with Scanning Electron Microscope and Energy Dispersive Spectroscopy analyses of the material deposited below the position of the primary discharge provide valuable information on the time evolution of the fast discharge propagation through the detector and its formation mechanism. In the light of these findings, we propose and discuss a new hypothesis for the occurrence of the secondary discharges.

Interior Ballistic Characteristics of Electromagnetic Rail Launcher Under Continuous Firing

According to the characteristics of an actual electromagnetic rail launcher (EMRL), this article points out defects in the traditional dynamic response model of EMRL, proposes an improved dynamic response model, and analyzes its dynamic and stopping response characteristics. On this basis, it presents a fast and accurate numerical calculation method for three-dimensional transient electromagnetic (EM) force of the EMRL and an order-reduced model of EMRL dynamic response. Furthermore, the second development of commercial software leads to the establishment of an interior ballistic simulation model with EM-structural coupling. The model is used to analyze the interior ballistic characteristics of the EMRL under sequential discharge and continuous firing. The finding is that the dynamic response of the first launching rail will cause a deformation in the second launching rail, in which a greater fluctuation happens. When the time interval between successive launches reaches 1.0 s, the deformation of the second launching rail will no longer be affected by the dynamic response of the first launching rail.

Tomography of the positive-pitch fast-ion velocity distribution in DIII-D plasmas with Alfvén eigenmodes and neoclassical tearing modes

Understanding the effect of Alfvén eigenmodes (AEs) and neoclassical tearing modes (NTMs) on fast ions is highly important for fusion reactors due to potentially strong resonant interactions between the fast ions and the modes. Here, we use the four-view fast-ion D-alpha (FIDA) diagnostic installed in the DIII-D tokamak to reconstruct the fast-ion velocity distribution at two radial positions during two sequential discharges with strong and weak mode activity, respectively. The velocity-space coverage of the diagnostics, however, only allows reliable reconstructions of fast ions with positive pitches. Therefore, we suggest new tomographic inversion methods relying on prior information outside the well-diagnosed region. We find that within the population of fast ions with positive pitches, ions, at all energies, are transported away from the measurement volumes. Comparisons between the reconstructions and kick model simulations, where the mode activity is considered, reveal that low-frequency modes such as the NTMs and low-frequency AEs contribute significantly to the positive-pitch fast-ion transport in the central measurement volume, whereas TAEs and EAEs become important farther out and are responsible for decreased fast-ion confinement.