Repetitively pulsed gas volume and dielectric surface discharges have gained growing attention because of peculiar and exciting physics phenomena, high efficiency, high reactivity, and potential to ...obtain conventionally unachievable plasma properties. Nevertheless, incomplete understanding of fundamental mechanisms renders the repetitively pulsed discharge far less predictable and controllable, where the inherent memory effect and the discharge mode transition are universal challenges. In this topical review, the authors will explore the macroscopic characteristics of the gas gap breakdown and the surface flashover, state-of-the-art mechanisms and dominant agents of discharge memory effects, operation regimes and transitions of the discharge mode, and how waveform parameters affect the pulsed discharge properties. Challenges and potential approaches for further understanding the memory effect and the discharge mode transition in the repetitively pulsed discharge are discussed.
Benchmarking the quality of river discharge data and understanding its information content for hydrological analyses is an important task for hydrologic science. There is a wide variety of techniques ...to assess discharge uncertainty. However, few studies have developed generalized approaches to quantify discharge uncertainty. This study presents a generalized framework for estimating discharge uncertainty at many gauging stations with different errors in the stage‐discharge relationship. The methodology utilizes a nonparametric LOWESS regression within a novel framework that accounts for uncertainty in the stage‐discharge measurements, scatter in the stage‐discharge data and multisection rating curves. The framework was applied to 500 gauging stations in England and Wales and we evaluated the magnitude of discharge uncertainty at low, mean and high flow points on the rating curve. The framework was shown to be robust, versatile and able to capture place‐specific uncertainties for a number of different examples. Our study revealed a wide range of discharge uncertainties (10–397% discharge uncertainty interval widths), but the majority of the gauging stations (over 80%) had mean and high flow uncertainty intervals of less than 40%. We identified some regional differences in the stage‐discharge relationships, however the results show that local conditions dominated in determining the magnitude of discharge uncertainty at a gauging station. This highlights the importance of estimating discharge uncertainty for each gauging station prior to using those data in hydrological analyses.
Key Points:
A generalized framework for discharge uncertainty estimation is presented
Allows estimation of place‐specific discharge uncertainties for many catchments
Local conditions dominate in determining discharge uncertainty magnitudes
Shifts in water fluxes and chemical heterogeneity through catchments combine to dictate stream solute export from the Critical Zone. The ways in which these factors emerge in resultant ...concentration‐discharge (C‐Q) relationships remain obscure, particularly at the timescale of individual precipitation and discharge events. Here we take advantage of a new high‐frequency, multi‐element and multi‐event stream C‐Q data set. The stream solute concentrations of seven major ions were recorded every 40 min over five flood events spanning one hydrologic year in a French agricultural watershed (Orgeval) using a lab‐in‐the‐field deployment we refer to as a “River Lab.” We focus attention on the recession periods of these events to consider how geochemical heterogeneity within the catchment translates into dynamic stream solute concentrations during shifts in water storage. We first show that for C‐Q relationships resulting from data acquisition over multiple flood events, lumping all trends together can lead to biases in characteristic C‐Q parameters. We then reframe C‐Q relationships using a simple recession curve analysis to consider how hydrological processes produce chemical mixing of distinct solute pools immediately following discharge events. We find three distinct classes of behavior among the major solutes, none of which can be interpreted based on water storage changes alone. The shape of C‐Q relationships for each solute can then be related to their vertical zonation in the subsurface of Orgeval, and to the capacity for subcomponents of these distributions to be readily mobilized during a discharge event.
Key Points
We combine high‐frequency (every 40 min) stream chemistry data and stream discharge recession analysis
We propose a conceptual model for the relationship between water storage and solute export at the Orgeval Critical Zone Observatory (CZO), France
Three classes of solute behavior are identified at the Orgeval CZO, related to the role of rock dissolution and amendments in their budget
In this paper, the positive corona discharge in rod-plane gap was measured by non-inductive resistance, photomultiplier and ultraviolet imager. With the increase of applied voltage, different ...positive corona discharge modes are distinguished according to the difference of optical and electrical characteristics. The positive corona discharge develops from streamer discharge to glow discharge at low humidity, and the discharge of water molecules in air can be detected before streamer discharge when the relative humidity is higher than 80%. Humidity has little effect on the inception voltage of streamer discharge, while the inception voltage of glow discharge increases with the humidity. As for the positive corona discharge in salty air, the streamer discharge will never develops into the glow discharge but develops directly to a spark if the air humidity is somewhat high. The physical mechanism of positive streamer discharge and glow discharge are analyzed, and the evolution of space charge distribution during positive corona discharge are obtained by simulation. The glow discharge is characterized by the presence of negative ion sheath around the anode. The increase of humidity and salinity in air reduces the migration rate of negative ions, which is not conducive to the establishment of glow discharge.
In this paper, the corona discharge in rod-plane air gap under AC-DC composite voltages was measured by non-inductive resistance and MPD 600 partial discharge measurement system. The characteristics ...of corona discharge pulses under AC-DC composite voltages were interpreted by phase resolved partial discharge (PRPD) patterns. The corona discharge inception voltage of rod-plane air gap under AC-DC composite voltages were measured and predicted theoretically. The charge of positive corona discharge is much larger than that of negative corona discharge, and the repetition rate of positive corona discharge is much smaller than that of negative corona discharge, which is due to the difference in the production mechanism of initial electron. The repetition rate and phase distribution range of discharge pulses decrease with the increase of AC component when the amplitude of AC-DC composite voltage is a constant. The weighted pulse sequence analysis (WPSA) was used to analyze the corona discharge pulses under different applied voltages. The WPSA plots of positive corona discharge and negative corona discharge have different characteristics, and the WPSA plots under AC-DC composite voltage have greater dispersion than that under DC voltage. This work provides a new perspective for the analysis of corona discharge pulses under AC-DC composite voltages, which will be helpful to the location and identification of equipment defects under AC-DC composite voltages.
In this paper, an experimental system is established to characterize the internal, surface, and corona partial discharge (PD) properties of polypropylene films under a magnetic field. With the ...increase of the magnetic flux density, the PD inception voltage in various defects is reduced by 5-12%. At the same time, the number of dischrages under the magnetic field increases by 126, 183, and 61% respectively. The magnetic field changes the charge moving direction and reshapes the charge distribution through the Lorentz force. The influence of magnetic field on internal discharge in the negative half cycle is more significant, by exciting electrons and distorting the electric field. The proportion of PD in the negative half cycles increases from 58.4 to 71.8%. The change of discharge characteristics on the surface is mainly reflected in the broadening of discharge phase, which is due to the recombination of bipolar charges separated by the magnetic field and accumulated on the surface of the sample. The corona discharge ratio in the positive half voltage cycles increases from 9.50 to 22.1%, although it is still far less than that in the negative half voltage cycles. The trajectory of electrons in the air is changed by the magnetic field, which enhances the electric field near the high voltage electrode in the positive half cycles.
Surface contamination on the disc-spacers is one of the main threats to the safe operation of gas insulated switchgear (GIS) insulation. The authors’ research has confirmed the phenomena of ...intermittent discharge of such defects under AC constant voltage and concluded that long-intermittent discharge may be the cause of sudden flashover failure of GIS. To explore the characteristics of the process from the partial discharge (PD) inception to the breakdown of surface discharge under constant AC voltage, a 126 kV GIS test platform was built and long-term uninterrupted detection was carried out in this study. By processing the discharge data of the entire process, distribution characteristics of phase-resolved PD and N–V spectra and the trend of discharge repetition rate, discharge amplitude (maximum, mean, standard deviation) and discharge time interval (maximum, mean, standard deviation) were obtained. The results indicate that: there are two typical stages in the entire process of surface discharge under constant voltage and both discharge characteristics and risk of breakdown of those two stages are different obviously. Furthermore, based on the electro-chemical aging theory and space charge effects, the long-intermittent characteristics of solid insulation discharge are explained.
Sharing information about hospital care with primary care in the form of a discharge summary is essential to patient safety. In the United Kingdom, although discharge summary targets on timeliness ...have been achieved, the quality of discharge summaries' content remains variable.
Mixed methods study in West Midlands, England with three parts: 1. General Practitioners (GPs) sampling discharge summaries they assessed to be "successful" or "unsuccessful" exemplars, 2. GPs commenting on the reasons for their letter assessment, and 3. surveying the hospital clinicians who wrote the sampled letters for their views. Letters were examined using content analysis; we coded 15 features (e.g. "diagnosis", "GP plan") based on relevant guidelines and standards. Free text comments were analysed using corpus linguistics, and survey data were analysed using descriptive statistics.
Fifty-three GPs participated in selecting discharge letters; 46 clinicians responded to the hospital survey. There were statistically significant differences between "successful" and "unsuccessful" inpatient letters (n = 375) in relation to inclusion of the following elements: reason for admission (99.1% vs 86.5%); diagnosis (97.4% vs 74.5%), medication changes (61.5% vs 48.9%); reasons for medication changes (32.1% vs 18.4%); hospital plan/actions (70.5% vs 50.4%); GP plan (69.7% vs 53.2%); information to patient (38.5% vs 24.8%); tests/procedures performed (97.0% vs 74.5%), and test/examination results (96.2% vs 77.3%). Unexplained acronyms and jargon were identified in the majority of the sample (≥70% of letters). Analysis of GP comments highlighted that the overall clarity of discharge letters is important for effective and safe care transitions and that they should be relevant, concise, and comprehensible. Hospital clinicians identified several barriers to producing "successful" letters, including: juniors writing letters, time limitations, writing letters retrospectively from patient notes, and template restrictions.
The failure to uniformly implement national discharge letter guidance into practice is continuing to contribute to unsuccessful communication between hospital and general practice. While the study highlighted barriers to producing high quality discharge summaries which may be addressed through training and organisational initiatives, it also indicates a need for ongoing audit to ensure the quality of letters and so reduce patient risk at the point of hospital discharge.
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