Steeper Rate Research Articles

Study on discharge characteristics of low-temperature sub-atmospheric pressure under steep change rate voltage

Study on discharge characteristics of low-temperature sub-atmospheric pressure under steep change rate voltage

Convection-permitting climate model representation of severe convective wind gusts and future changes in southeastern Australia

Abstract. Previous research has suggested that the frequency and intensity of surface hazards associated with thunderstorms and convection, such as severe convective winds (SCWs), could potentially change in a future climate due to global warming. However, because of the small spatial scales associated with SCWs, they are unresolved in global climate models, and future climate projections are uncertain. Here, we evaluate the representation of SCW events in a convection-permitting climate model (Bureau of Meteorology Atmospheric Regional Projections for Australia, BARPAC-M) run over southeastern Australia for the months of December–February. We also assess changes in SCW event frequency in a projected future climate for the year 2050 and compare this with an approach based on identifying large-scale environments favourable for SCWs from a regional parent model (BARPA-R). This is done for three different types of SCW events that have been identified in this region, based on clustering of the large-scale environment. Results show that BARPAC-M representation of the extreme daily maximum wind gust distribution is improved relative to the gust distribution simulated by the regional parent model. This is due to the high spatial resolution of BARPAC-M output, as well as partly resolving strong and short-lived gusts associated with convection. However, BARPAC-M significantly overestimates the frequency of simulated SCW events, particularly in environments having steep low-level temperature lapse rates. A future decrease in SCW frequency under conditions with steep lapse rates is projected by BARPAC-M, along with less frequent favourable large-scale environments. In contrast, an increase in SCW frequency is projected under conditions of high surface moisture, with more frequent favourable large-scale environments. Therefore, overall changes in SCWs for this region remain uncertain, due to different responses between event types, combined with historical model biases.

Unveiling the Pivotal Influence of Sea Spray Heat Fluxes on Hurricane Rapid Intensification

Abstract Predicting rapid hurricane intensification remains a challenge, partially due to neglected factors like sea spray-mediated heat flux. To shed light on the specific roles of spray-mediated sensible and latent heat fluxes, we conducted sensitivity experiments with heat flux parameterizations. Our results demonstrate that the inclusion and variation of the spray-mediated sensible heat significantly reduce model errors when compared against dropsonde data. These findings uniquely quantify the pivotal role of spray-mediated sensible heat flux in accurately predicting hurricane rapid intensification compared to previous studies. Without sea spray processes, ocean-coupled model simulations could not reproduce the steep intensification rate observed in multi-case studies of four high-impact hurricanes. This study also highlights that dropsonde data, as well as directly observed flux, is useful in minimizing uncertainty in the flux parameterization used for hurricane simulations. In this paper, we show how spray-mediated heat flux affects hurricane energetics through turbulent heat exchange and subsequent humid air inflow through primary and secondary circulations. Our findings provide new insights into the transformative role of sea spray in turbulent heat exchange that drives rapid hurricane intensification.

A Modified High-Selective Frequency Selective Surface Designed by Multilevel Green’s Function Interpolation Method

A compact high-selective band-pass frequency selective surface (FSS) with the unit cell less than λ/7 is presented. For the simulation of the structure, the multilevel Green’s function interpolation method (MLGFIM) using Floquet theory is adopted to accelerate the calculation of the complex unit cell. The radial basis function (RBF)-QR method is used in the interpolation, which makes the shape parameter in the RBF function not required to be retested for different periodicity. In this design, with an aperture coupling structure between the top and bottom layers patterned by triangular patches and meander lines, the FSS has two transmission zeros (TZs) on both sides of the pass-band and achieves a steep roll-off rate of 192 dB/GHz. Consequently, the FSS has high selectivity and out-of-band suppression, besides profiting from the low profile and symmetric geometry, this FSS exhibits good angular and polarization stabilities. The prototype of the proposed FSS is fabricated and good performance is obtained.

Longitudinal Trajectories of Stress and Positive Aspects of Dementia Caregiving: Findings From the IDEAL Programme.

Understanding what influences changes over time in caregiver well-being is important for the development of effective support. This study explores differences in trajectories of caregiver stress and positive aspects of caregiving (PAC). Caregivers of community-dwelling individuals with mild-to-moderate dementia at baseline from the IDEAL cohort were interviewed at baseline (n = 1,203), 12 months (n = 917), and 24 months (n = 699). Growth mixture models identified multiple growth trajectories of caregiver stress and PAC in the caregiver population. Associations between study measures and trajectory classes were examined using multinomial logistic regression and mixed-effects models. Mean stress scores increased over time. A 4-class solution was identified: a "high" stable class (8.3%) with high levels of stress, a "middle" class (46.1%) with slightly increasing levels of stress, a "low" class (39.5%) with initial low levels of stress which slightly increased over time, and a small "increasing" class (6.1%) where stress level started low but increased at a steeper rate. Mean PAC scores remained stable over time. A 5-class solution was identified: 3 stable classes ("high," 15.2%; "middle," 67.6%; "low" 9.3%), a small "increasing" (3.4%) class, and 1 "decreasing" class (4.5%). For stable classes, positive ratings on study measures tended to be associated with lower stress or higher PAC trajectories and vice versa. Those with "increasing" stress also had worsening trajectories of several study measures including depression, relationship quality, competence, and ability to cope. The findings highlight the importance of identifying caregivers at risk of increased stress and declining PAC and offering them targeted support.

“A Trial Like No Other in Ljubljana”: The Financial Affair of Terezija Aristoteles in 1874

The contribution presents the financial affair of a wood merchant’s wife, Terezija Aristoteles, in Ljubljana in the 1870s. Aristoteles took a loan from one of Ljubljana’s female brokers who, for steep interest rates, mediated the borrowing of money obtained from moneylenders. In doing so, Aristoteles got heavily into debt and resorted to fraud to keep borrowing increasing sums of money. Once her actions were revealed, a high-profile trial at the Ljubljana Court followed in February 1874, attracting a lot of interest not only from the Ljubljana citizens but also from the Slovenian and Austrian press, mainly because most of the perpetrators and victims involved were female. The public opinion did not favour either Aristoteles or the aggrieved moneylenders, who were seen as exploiters preying on those in need. Aristoteles and her broker were sentenced to two years in prison.

Climatology of the Elevated Mixed Layer over the Contiguous United States and Northern Mexico Using ERA5: 1979–2021

Abstract Elevated mixed layers (EMLs) influence the severe convective storm climatology in the contiguous United States (CONUS), playing an important role in the initiation, sustenance, and suppression of storms. This study creates a high-resolution climatology of the EML to analyze variability and potential changes in EML frequency and characteristics for the first time. An objective algorithm is applied to ERA5 to detect EMLs, defined in part as layers of steep lapse rates (≥8.0°C km−1) at least 200 hPa thick, in the CONUS and northern Mexico from 1979 to 2021. EMLs are most frequent over the Great Plains in spring and summer, with a standard deviation of 4–10 EML days per year highlighting sizable interannual variability. Mean convective inhibition associated with the EML’s capping inversion suggests many EMLs prohibit convection, although—like nearly all EML characteristics—there is considerable spread and notable seasonal variability. In the High Plains, statistically significant increases in EML days (4–5 more days per decade) coincide with warmer EML bases and steeper EML lapse rates, driven by warming and drying in the low levels of the western CONUS during the study period. Additionally, increases in EML base temperatures result in significantly more EML-related convective inhibition over the Great Plains, which may continue to have implications for convective storm frequency, intensity, severe perils, and precipitation if this trend persists. Significance Statement Elevated mixed layers (EMLs) play a role in the spatiotemporal frequency of severe convective storms and precipitation across the contiguous United States and northern Mexico. This research creates a detailed EML climatology from a modern reanalysis dataset to uncover patterns and potential changes in EML frequency and associated meteorological characteristics. EMLs are most common over the Great Plains in spring and summer, but show significant variability year-to-year. Robust increases in the number of days with EMLs have occurred since 1979 across the High Plains. Lapse rates associated with EMLs have trended steeper, in part due to warmer EML base temperatures. This has resulted in increasing EML convective inhibition, which has important implications for regional climate.

Design of Multi-Input Multi-Output Non-linear Model Predictive Control for Main Steam Temperature of Super Critical Boiler

Flexible operation of coal-fired power plants is becoming increasingly necessary for successful integration of large-scale renewable power generation into the power grid. The maximum ramp rate and the number of load cycles are generally limited by the thermal stress experienced by the boiler pressure parts, turbine metallurgy and creep and fatigue of critical thick-walled components Main steam temperature is a critical operating parameter that must be controlled within acceptable limits for safe operation. Main steam temperature deviation beyond acceptable limit has impact on boiler pressure parts and turbine material of construction due to creep and fatigue effect. Base load operating units do not require steep ramp rate and hence recommended ramping rates are kept low within the safe operating zone in comparison to the flexible operation of the units with wide range load change width. Thermal stresses are caused by the temperature changes inside the thick-walled components and turbine steam admission parameters. Hence, the quality of main steam temperature control plays a vital role in flexible operation of the coal fired units. Conventional cascaded PID temperature control loop architecture performs well at steady state condition within a limited variation of load change at low ramp rate but it acts slowly and performs poorly at transient operating conditions of flexible operation of the boiler turbine with wide range load variation and load cycle with high ramp rate and remains far from rated conditions. In this paper, a Multi-Input Multi-Output (MIMO) Non-linear Model Predictive Control (MPC) design for regulation of the main steam temperature of a Once-Through supercritical Boiler is proposed. The controller is based on a non-linear dynamic model which incorporates dynamics of the variables of interest. It has the capability to operate effectively across a wide load range while maintaining main steam temperature within acceptable limits. A notable advancement in this design of MPC is the incorporation of coal flow demand and feedwater flow demand as additional control inputs alongside primary and secondary spray flows. In simulation test cases, the MPC controller demonstrates satisfactory performance and computational efficiency.

Helicobacter pylori infection in humans and phytotherapy, probiotics, and emerging therapeutic interventions: a review.

The global prevalence of Helicobacter pylori (H. pylori) infection remains high, indicating a persistent presence of this pathogenic bacterium capable of infecting humans. This review summarizes the population demographics, transmission routes, as well as conventional and novel therapeutic approaches for H. pylori infection. The prevalence of H. pylori infection exceeds 30% in numerous countries worldwide and can be transmitted through interpersonal and zoonotic routes. Cytotoxin-related gene A (CagA) and vacuolar cytotoxin A (VacA) are the main virulence factors of H. pylori, contributing to its steep global infection rate. Preventative measures should be taken from people's living habits and dietary factors to reduce H. pylori infection. Phytotherapy, probiotics therapies and some emerging therapies have emerged as alternative treatments for H. pylori infection, addressing the issue of elevated antibiotic resistance rates. Plant extracts primarily target urease activity and adhesion activity to treat H. pylori, while probiotics prevent H. pylori infection through both immune and non-immune pathways. In the future, the primary research focus will be on combining multiple treatment methods to effectively eradicate H. pylori infection.

A filtering dense dielectric patch antenna with rectangular silver strips

The filtering dense dielectric patch (DDP) antenna (DDPA) is proposed in this paper. Two pairs of rectangular silver strips are pasted on the top and bottom surfaces of DDP along the y-axis direction. This not only introduces the TM10-like mode, but also independently adjusts the resonant frequency of the TM10-like mode. The rectangular silver strips on the bottom surface of DDP can also make the DDPA obtain a radiation null. By pasting a pair of rectangular silver strips on the top surface of DDP along the x-axis direction, the resonant frequency of TE12 mode can be independently regulated. The resonant frequencies of TM10-like and TE12 modes of DDP form a passband. The proposed filtering DDPA is fabricated and measured to verify this idea. The simulation results are in good agreement with the measured results. The relative bandwidth of the proposed filtering DDPA is 4.64% (4.21–4.41 GHz), with an average gain of 5 dBi. The steep roll-off rates of the two sidebands are 120 and 320 dB/GHz, respectively.

Highly Reproducible Synthesis of Hollow Zirconia Particles via Atmospheric-Pressure Plasma Processing with Inkjet Droplets

Hollow particles have attracted considerable attention owing to their unique properties. In this study, hollow monoclinic zirconia particles were directly synthesized from inkjet droplets of a zirconyl hydroxychloride aqueous solution via atmospheric-pressure plasma processing. Hollow structures with craggy surfaces were obtained in the plasma at gas temperatures above 1000 K. The steep solvent evaporation rate induced by the localized high-energy reaction field of the atmospheric-pressure plasma may have induced solute condensation near the droplet surface and contributed to the formation of hollow particles. The average diameter of the synthesized particles was ~ 3 μm, while their size distribution was narrow (coefficient of variation: 0.06–0.10). The high reproducibility of the synthesized particles was attributed to the small variations in inkjet droplet size. The proposed method enables the rapid synthesis of hollow particles of various inorganic materials, while controlling their number and composition.

Long-Term Observational Characteristics of Different Severe Convective Wind Types around Australia

Abstract Regional understanding of severe surface winds produced by convective processes [severe convective winds (SCWs)] is important for decision-making in several areas of society, including weather forecasting and engineering design. Meteorological studies have demonstrated that SCWs can occur due to a number of different mesoscale and microscale processes, in a range of large-scale atmospheric environments. However, long-term observational studies of SCW characteristics often have not considered this diversity in physical processes, particularly in Australia. Here, a statistical clustering method is used to separate a large dataset of SCW events, measured by automatic weather stations around Australia, into three types, associated with strong background wind, steep lapse rate, and high moisture environments. These different types of SCWs are shown to have different seasonal and spatial variations in their occurrence, as well as different measured wind gust, lightning, and parent-storm characteristics. In addition, various convective diagnostics are tested in their ability to discriminate between measured SCW events and nonsevere events, with significant variations in skill between event types. Differences in environmental conditions and wind gust characteristics between event types suggests potentially different physical processes for SCW production. These findings are intended to improve regional understanding of severe wind characteristics, as well as environmental prediction of SCWs in weather and climate applications, by considering different event types. Significance Statement The purpose of this study is to improve regional understanding of different types of severe wind events in Australia, specifically those associated with atmospheric convection. We did this by constructing a dataset of 413 severe convective wind events, using weather station and radar data within 20 regions around Australia. We then split those events into three different types, based on the environmental conditions that they occur within. We found that each event type tends to occur at different times of the year and in different regions, while also having different wind gust and lightning characteristics. In addition, the atmospheric conditions that are helpful for prediction of severe wind events differs between each type. These results are intended to be useful for prediction of severe wind events associated with convection and assessing their variability, characteristics, and impacts, in both weather forecasting and climate analysis.

Trajectories for children and young people who experience out of home care: Examining the influences of pre-care characteristics on later wellbeing and placement stability

BackgroundInterplay of risk and protective factors influence longer-term outcomes for children in out-of-home care. Participants and settingPathways of Care Longitudinal Study (POCLS) data were used to explore how child and birth family factors interact to influence wellbeing and placement stability over time. MethodsCluster analysis identified three groups of children differentiated on demographic characteristics on entry in care. Latent growth curve modelling was used to compare changes in children's cognitive functioning, socio-emotional wellbeing, and health over time. ResultsThere were cluster differences in trajectories for cognitive and socio-emotional outcomes, but not for health. Children who were older at entry to care (mean 7.6 years) showed the poorest socio-emotional and cognitive functioning at Wave 2, and despite improvements by Wave 4, the poor starting point may explain why their cognitive functioning scores never catch up to children entering care younger (mean 1.5 years). Younger on entry children who also tended to come from less socio-economically disadvantaged backgrounds showed the most positive cognitive and socio-emotional functioning over study waves, and cognitive functioning for these children improved at a steeper rate than the other clusters. Children with multiple characteristics associated with risk of poorer outcomes showed little improvement in cognitive functioning over time, and the poorest socio-emotional wellbeing by Wave 4. Placement changes between waves were lowest for children who entered care younger. ConclusionsThis study explicates the role of early risk and protective factors on subsequent trajectories for children in care. Understanding how early risk and protective factors impact longer term wellbeing may help to better target placement and support for cohorts of children with different presentations at entry to care.

Newly Developed Method for Liquid Thin Film Thickness Measurement Using Optical Fiber–Based Reflective Probe

A new ray-tracing–based calibration method for an Optical-fiber-based Reflective Probe (ORP) was developed. This technique enables thickness measurement in micrometers in wavy thin liquid film flow, which is simpler and quicker than other liquid film measurements. First, the relationship between the film thickness and ORP signal was calculated through the ray-tracing simulator. The signal trend showed a steep rate of change within a few-hundred-micron thicknesses, thanks to the emission nature of the step index multimode fiber. The ray-tracing–based calibration was established using the calculated relationship. Second, the calibration method was validated under quiescent conditions. The calibrated ORP measured the thickness and then was compared to visualization. Good agreement was confirmed between the two results at a maximum difference of 20% under 1000 μm in thickness. Finally, thickness measurement for the wavy thin film flow was performed. Airflow (jG = 40 to 75 m/s) was introduced into the rectangle test section, and a small amount of tap water (Q = 30 to 90 mL/min) was injected into the channel plate. The difference in the measured thickness between ORP and high-speed visualization was around 20%. The effectiveness of the new calibration method and ORP measurement including its uncertainty will be discussed.

Repeated Traumatic Brain Injury is Associated with Neurotoxic Plasma Autoantibodies Directed against the Serotonin 2A and Alpha 1 Adrenergic Receptors.

Traumatic brain injury (TBI) was associated with increased plasma agonist autoantibodies targeting the serotonin 2A receptor. Repeated TBI exposure is associated with high risk for neurodegenerative and neuropsychiatric complications. Here we tested a hypothesis that repeated TBI is associated with plasma agonist autoantibodies targeting more than one kind of catecholamine G-protein coupled receptor. Protein-A affinity chromatography was used to isolate the IgG fraction of plasma in forty-two middle-aged and older adults who had experienced one or more TBI exposures. The Ig (1/40th dilution=7.5 ug/mL) were tested for neurotoxicity in mouse neuroblastoma cells using an acute neurite retraction assay indicative of Gq11/IP3/Ca2+ and RhoA/Rho kinase signaling pathways' activation. Three different linear synthetic peptides corresponding to the second extracellular loop of the alpha 1A, alpha 2A or serotonin 2A receptors were used as target antigen in different enzyme-linked immunoassays. The second extracellular loop receptor peptides themselves (alpha 1A, alpha 2A) or a fragment (serotonin 2A) were tested for ability to prevent Ig-induced neurite retraction. Patients who had experienced either repeated TBI (N=10) or a single TBI with a co-morbid autoimmune disease (N=5) were significantly more likely to harbor neurotoxic plasma autoantibodies targeting both alpha 1 adrenergic and serotonin 2A receptors vs. patients having only a single TBI. Ig-induced neurotoxicity was significantly prevented by co-incubation with either 850 nM prazosin (alpha 1 adrenergic receptor) and/or 500 nM M100907 (serotonin 2A receptor) antagonists. Alpha 1 adrenergic receptor and serotonin 2A receptor Ig immunoreactive level and titer were significantly increased in repeated TBI and single TBI/autoimmune patients (N=7-8) compared to age-matched TBI patients without neurotoxic plasma Ig (N=4). SN.8, a linear synthetic peptide corresponding to a conserved region of the second extracellular loop (ECL) of the serotonin 2A receptor completely prevented neurite retraction induced by repeated TBI plasma Ig. A repeated TBI patient harboring alpha adrenergic receptor AAB alone experienced prospective steep decline in cognitive function over two years. Repeated TBI and TBI with associated autoimmunity harbored more than one kind of neurotoxic catecholaminergic agonist GPCR autoantibody each associated with high risk for steep rate of cognitive decline. Specific immunoassays using the second extracellular receptor loop as target antigen are needed to detect each specific different GPCR autoantibody. A fragment of the second ECL of the serotonin 2A receptor (SN.8) neutralized Ig-induced neurotoxicity in repeated TBI or TBI with associated systemic autoimmunity.

The water cavitation line as predicted by the TIP4P/2005 model.

The formation of vapor bubbles in a metastable liquid, cavitation, is an activated process due to the free energy cost of having both phases at contact. Such an energetic penalty enables the existence of the liquid beyond its thermodynamic borders. Establishing the stability limits of a liquid as ubiquitous as water has important practical implications and has thereby attracted a lot of attention. Different experimental strategies and theoretical analyses have been employed to measure and predict the cavitation line, or the pressure-temperature kinetic stability border of liquid water. Understanding the location of the cavitation line requires knowing the cavitation rate dependence on pressure and temperature. Such dependency is difficult to obtain in experiments, and we use molecular simulations with the TIP4P/2005 model to fill this gap. By deeply overstretching liquid water below the saturation pressure, we are able to observe and quantify spontaneous cavitation. To deal with a lower overstretching regime, we resort to the Seeding technique, which consists of analyzing simulations of a liquid containing a vapor bubble under the theoretical framework of Classical Nucleation Theory. Combining spontaneous cavitation with Seeding, we get a wide overview of the cavitation rate. We study two different temperatures (450 and 550K) and complement our perspective with the results previously obtained at 296.4K [Menzl et al., Proc. Natl. Acad. Sci. 113, 13582 (2016)] to establish a broad simulation-experiment comparison. We find a good agreement between simulations and both isobaric heating and isochoric cooling experiments using quartz inclusions. We are, however, unable to reconcile simulations with other experimental techniques. Our results predict a decrease in the solid-liquid interfacial free energy as the liquid becomes increasingly overstretched with a temperature independent Tolman length of 0.1nm. Therefore, the capillarity approximation underestimates the nucleation rate. Nonetheless, it provides a fair indication of the location of the cavitation line given the steep rate vs pressure dependence. Overall, our work provides a comprehensive view of the water cavitation phenomenon and sets an efficient strategy to investigate it with molecular simulations.

Trends in Computer-Assisted Surgery for Total Knee Arthroplasty in Germany: An Analysis Based on the Operative Procedure Classification System between 2010 to 2021.

Alignment strategies for primary total knee arthroplasty (TKA) have changed significantly over time with a shift towards a more individualized alignment goal. At the same time, computer-assisted surgery (CAS) has gained interest for intraoperative control and accuracy in implant positioning and limb alignment. Despite the often discussed benefits and drawbacks of robotics and navigation for TKA, the routine use of these new devices on a day-to-day basis remains obscure. Therefore, nationwide hospital billing data based on the Operation Procedure Classification System (OPS) were retrieved from the Federal Statistical Office of Germany for the period from 2010 to 2021. OPS codes for primary total knee arthroplasty (OPS code: 5-822*) were further analyzed regarding the usage of computer navigation (additional OPS code: 5-988) or robotic devices (additional OPS code: 5-987). Gender and age at the time of surgery were also assessed. The results show a total of 2,226,559 primary TKAs were implanted between 2010 and 2021, of which 2,044,914 were performed conventionally (91.84% of all TKAs). A total of 170,276 TKAs were performed using navigation technique (7.65% of all TKAs) and another 11,369 TKAs were performed using robotics (0.51% of all TKAs). For the period from 2018 to 2021, a substantial increase in robot-assisted TKA (R-TKA) was observed, with an average increase rate of 84.74% per year, while the number of navigated TKAs declined (-3.67% per year). Computer-assisted surgery, and particularly robotics for TKA, are seeing growing popularity and stepwise translation into routine clinical use in Germany, with a steep increase rate of more than 80% per year since 2018. Nevertheless, the majority of TKAs are still performed using manual instrumentation, rendering conventional TKA the currently unchanged gold standard.

Climate Change and the Need for Future Research

Climate Changes have impacted our planet since the beginning of time. These were manifested by cyclic Ice Ages and Warm Periods ever since. The changes were caused by natural forcing such as, continental drift, plate tectonics, major volcanic eruptions, and internal dynamics of earth and oceans interactions with the atmosphere. The present warm period, the “Holocene Epoch”, is not different from other such periods except for the sharp global warming which began at the onset of the industrial revolution. This was proven by scientific research to be due to anthropogenic drives, i.e., increased fossil fuel burning and increased Co2 and other Green House Gases (GHG) emissions into the atmosphere. These gases trap the sun radiation reflected from earth surface and result in higher earth temperature. The steep rate of rise in temperature trend since 1960s is directly linked to the use of much more fossil fuels in power production and transportation. This has led to more research to quantify the changes and their impacts on the environment and humans. This paper gives a brief history of the scientific research carried out hitherto and policy suggestions made so far to combat the negative impacts of the increasing global warming of the world. Needed future scientific research in this field is outlined, while at the same time suggesting the needs of Iraq of such research. This includes among other things, forming a regional scientific panel for the Middle East countries (ME. IPCC) for carrying out research on regional level, fostering research on national level, encouraging academics for climate change-oriented research and providing the necessary funds and facilities for such research.

Electric discharge initiation in water with gas bubbles: A time scale approach

High voltage nanosecond pulse driven electric discharges in de-ionized water with an argon bubble suspended between two electrodes were experimentally investigated. Two electrode configurations were used to temporally resolve the time scales of the discharge from the applied voltage rise time (7 ns), through the end of the first pulse (∼30 ns), and longer (>50 ns). We found that, in positive and negative applied voltage polarities, discharge initiates in the water at the tip of the anode. The discharge in the water rapidly extends (∼104 m/s) to the apex of the bubble and light emitted from inside the bubble begins to form. The steep rate of rise of the applied voltage (dV/dt<4 kV/ns) and the short time for the development of discharge in the water suggest that cavitation is a likely mechanism for discharge initiation and propagation in water. In addition, the short duration of the applied voltage pulse results in only a partial Townsend discharge inside the bubble.

An omnidirectional filtering dielectric resonator antenna based on metal patches

A novel filtering dielectric resonator (DR) antenna (DRA) is designed in this article. By using a single-layer planar feed structure, the TM01δ and TM011+δ modes of a cylindrical DR are excited. The proposed filtering DRA achieves a good omnidirectional radiation performance and a flat gain response. By loading a crossed patch with four shorting pins on the feed structure, the lower edge of the passband obtains a steep roll-off rate. By plating four metal patches on the side wall of the DR, a radiation null (RN) is successfully introduced at the upper sideband of the DRA. The suppression levels of the proposed filtering DRA in the lower and upper stopbands are above 18 dB. Therefore, the proposed filtering DRA achieves filtering function without additional circuits. For demonstration, a prototype DRA is fabricated and measured. The simulated and measured results are basically consistent.