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In pulsed power engineering, the modification of dielectric surfaces is a potential method in order to increase the flashover strength of solid insulation. In this work, dielectric materials are subjected to a knurled finish, where small indentations are machined on to the surface resulting in quick consistent modification. These flashover voltages from the knurled dielectric spacers have been compared to spacers with a ‘smooth’ machined finish. The three materials which have been tested are HDPE (High Density Polyethylene), Delrin (Polyoxymethylene) and Ultem (Polyetherimide). The materials were tested under a 100/700 ns impulse voltage. Cylindrical spacers made of these materials were located in the center of a parallel-plane electrode setup in air, which provided a quasi-uniform field distribution. Breakdown tests published in this work were performed in a sealed container at air pressures of −0.5, 0 and 0.5 bar gauge, with relative humidity levels of 90% RH.

Within the pulsed power industry, a key factor determining the achievable output voltage of a HV system is the flashover voltage of the insulating parts. Statistical analysis of the breakdown voltages associated with solid-gas interfaces can reveal useful information to aid system designers in the selection of solid materials. However, it is important to test the applicability of the distribution being applied, to ensure that the fitting parameters obtained are truly representative of the distribution of the data. Normal, lognormal, 2-parameter Weibull and 3-parameter Weibull cumulative distribution functions (CDF) were plotted, to enable extraction of the specific fitting parameters associated with each distribution. The CDF for each statistical method has been plotted alongside the empirical cumulative distribution function (ECDF), found from the flashover voltages recorded during experimental testing. The distribution of best fit was then analysed by using the Kolmogorov-Smirnov (K-S) test, in order to determine the CDF that best represented the ECDF. Maximum values have been compared to the α = 0.05, K-S critical value, in order to reject or accept the null hypothesis based on how the data fits the specified distributions. This will facilitate a comparison between different statistical distributions, applied to experimental data on breakdown/flashover voltages of gas-solid interfaces, generated at a fixed pressure, and different levels of RH

Considerable amount of research work has been focused on investigation and optimization of strong acoustic waves generated by spark discharges in water. There are several methods to achieve and to stimulate underwater spark breakdowns, including free-discharges, wire-guided and gas-bubble stimulated discharges. In the present work, air bubbles are injected into water in order to achieve spark discharges in relatively long inter-electrode gaps. This paper reports on hydrodynamic and acoustic characteristics of spark discharges stimulated by air bubbles and presents the functional relationships between the hydrodynamic and electrical parameters of such discharges, including breakdown voltage, spark plasma resistance and energy available in the discharge. A hydrodynamic analytical model has been developed and used to calculate the acoustic efficiency of the underwater spark discharges.

The installation of a lightning protection system for wind turbine blades has been adapted from other industries (i.e. building, aircraft) where a lightning down conductor is installed internally so as to preserve the aerodynamic performance of the blade. Having the down conductor internally within the blades would indeed preserve their aerodynamic performance. However the blades are, as a consequence, vulnerable to damage and burn resulting from lightning strikes. Owing to that, the authors believe that by having the down conductor on the external surface of the blade, the incidence of blade damage would be reduced. The authors have not found any literature in the public domain that quantifies the effect of having an external down conductor on the aerodynamic property. Hence, this aspect is being undertaken. Previous studies conducted by the authors were on two different arrangements. In one arrangement, a single 1 mm thick conductor was placed at 1m from the leading edge on the upper and lower parts of the blade. In the other arrangement, multiple conductors were placed at 1m intervals. The results from previous studies indicated that external down conductors affect the aerodynamic performance significantly but the first conductor (as encountered by the wind flow) appear to have the maximum influence. Hence, this paper addresses the question whether a single external down conductor could be deployed in an optimal position for least effect on the aerodynamic performance. The results show that the degradation on aerodynamic property is least at the trailing edge or the leading edge of the blade and these indicate that the installation of external down conductors may be viable in that region.

In general, there are three components making up a lightning protection system for wind turbines. These are the receptors, the down conductor and the grounding grid. Receptors and down conductors are usually found in the more recent wind turbine blades and where the down conductors are normally installed on the internal side of the blade. Consequently, the blades are vulnerable to damage and burn resulting from lightning strikes. The authors believe that a system with an external down conductor is likely to reduce the risk of damage when compared to the system having an internal down conductor. One could envisage an external down conductor would look similar to the one installed on a building or an aircraft. However, external down conductors may compromise the aerodynamic performance of the turbine blades. This paper reports the effect of external down conductors on the pressure coefficient distribution around the turbine blade. The blade profile (aerofoil) used is according to NACA 4418. Numerical simulations, using computational fluid dynamics (CFD), were conducted on an aerofoil without and with external down conductors of 1mm thickness. The k-ɛ turbulence model that is incorporated in COMSOL Multiphysics (CFD Module) was used for the simulation and the wind speed and angle of attack used was 5 m/s and 5˚ respectively. The preliminary results show that the degradation on aerodynamic properties may not be too significant and these indicate that external down conductor arrangement could be considered.

Non-thermal plasma can produce reactive species such as O, O3 and OH toinduce dye degradation in water. Many chemical reactions are known to occur at the plasma-water interface, but contributions from each reactive species for the degradation are still not clear. This research investigated the discoloration ofmethylene blue using a specially-configured dielectric barrier discharge reactor, where the plasma was injected into the methylene blue solution through micro-holes to initiate the oxidation reactions at different pH values of 2.9, 7.1 and 11. The degradation effects from hydroxyls and ozone were determined separately by using the radical scavenger Tert-butanol. The results demonstratethat methylene blue is degraded by both ozone and reactive hydroxyl radicals,with the latter contributing up to 30% of the discoloration effect depending onsolution pH values. The yield of plasma-produced hydroxyl radicalsup to 4.6 g/kWh was achieved and the efficiency was not affected by solution pH values; the corresponding methylene blue degradation efficiency is 184 g/kWh.

Micro-Electrostatic precipitation uses combining impulses and dc voltage in order to charge and remove fine, sub-micron particles efficiently. Short impulses are expected to increase the precipitation efficiency and to reduce power consumption.

A significant portion of medical devices fail due to acquired infection, with infection rates after arthroplasty surgery between 1-4%, and considerably higher after revision surgery. To reduce the associated costs of infection, a new preventative method is required. High intensity narrow spectrum (HINS) 405 nm light is a new technology shown to have bactericidal effects on a range of medically important bacteria[1]. The effect of HINS-light on osteoblasts and bacteria were investigated to determine the potential of this technology to contribute to infection prevention in operating theatres, during surgery and postoperative dressing changes.

Pulsed electric field (PEF) treatment has been shown to achieve bacterial inactivation in collagen gels whilst retaining the ability of the collagen to function as a biomaterial [1, 2]. Nisin, an antimicrobial peptide, has been used widely as a food preservative and has shown bactericidal action against a number of Gram-positive bacteria [3]. The potential of nisin to increase the efficacy of PEF disinfection of collagen gels to be used for tissue engineering applications was investigated.

There is the need to develop a compatible sterilisation method for hybrid biomaterials. High-intensity blue light in the 405 nm region has been shown to be an effective bacterial decontamination method [1], to cause no noticeable damage to the gross structure of type-I collagen monomer (when treated at 10 mW/cm2) [2], and to have no noticeable effect on 3T3 cell viability, growth rate, redox state or lactate dehydrogenase (LDH) leakage (at 1.0 mW/cm2) [2]. The purpose of this research was to investigate the effect of varying the blue-light intensity on the 3T3 cell response parameters.

A pulsed-plasma gas-discharge (PPGD) system was developed for the novel decontamination of chilled poultry washwater. Treatment of poultry wash water in the plasma generation chamber for up to 24 s at 4C reduced Escherichia coli NCTC 9001, Campylobacter jejuni ATCC 33560, Campylobacter coli ATCC 33559, Listeria monocytogenes NCTC 9863, Salmonella enterica serovar Enteritidis ATCC 4931, and S. enterica serovar Typhimurium ATCC 14028 populations to nondetectable levels (8 log CFU/ml). Although similar PPGD treatments at 4C also produced significant reductions (3 log CFU/ml) in recalcitrant B. cereus NCTC 11145 endospore numbers within 30 s, the level of endospore reduction was dependent on the nature of the sparged gas used in the plasma treatments. Scanning electron microscopy revealed that significant damage occurred at the cellular level in PPGD-treated test organisms. This electrotechnology delivers energy in intense ultrashort bursts, generating products such as ozone, UV light, acoustic and shock waves, and pulsed electric fields that have multiple bactericidal properties. This technology offers an exciting complementary or alternative approach for treating raw poultry wash water and for preventing cross-contamination in processing environments. yes

Aims: To apply scanning electron microscopy, image analysis and a fluorescent viability stain to assess lethal and sublethal injury in food‐borne bacteria exposed to pulsed‐plasma gas discharges (PPGD). Methods and Results: The fluorescent redox probe 5‐cyano‐2,3‐ditolyl tetrazolium chloride (CTC) was used for enumerating actively respiring cells of Campylobacter jejuni, Escherichia coli, Listeria monocytogenes, Staphylococcus aureus and Salmonella enterica serovar Typhimurium that were suspended in sterile water at 4°C and exposed to separate PPGD and heat treatments. While there was good agreement between use of respiratory staining (RS) and direct‐selective agar plate counting (PC) for enumerating untreated bacteria, there were c. 1 and 3 log‐unit differences in surviving cell numbers per millilitre for test organisms subjected to PPGD and heat treatments respectively, when enumerated by these different viability indicators. PPGD‐treated bacteria were markedly altered at the cellular level when examined by scanning electron microscopy. Conclusions: Use of this RS method revealed that substantial subpopulations of test bacteria rendered incapable of forming colonies by separate PPGD and heat treatments may remain metabolically active. yes