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High-density nitrogen plasma was produced using a high-power pulsed power modulator to sputter titanium targets for the preparation of titanium nitride film. The high-power pulsed sputtering discharge unit consisted of two targets facing each other with the same electrical potential. The titanium target plates were used as target materials with dimensions of 60 mm length, 20 mm height, and 5 mm thickness. The gap length was set to be 10 mm. The magnetic field was created with a permanent magnet array behind the targets. The magnetic field strength at the gap between the target plates was 70 mT. The electrons were trapped by the magnetic and electric fields to enhance the ionization in the gap. The nitrogen and argon gases were injected into the chamber with 4 Pa gas pressure. The applied voltage to the target plates had an amplitude from −600 V to −1000 V with 600 μs in pulse width. The target current was approximately 10 A with the consumed power of 13 kW. The discharge sustaining voltage was almost constant and independent of the applied voltage, in the same manner as the conventional normal glow discharge. The ion density and electron temperature at the surface of the ionization region were obtained as 1.7 × 1019 m−3 and 3.4 eV, respectively, by the double probe measurements. The vertical distribution of ion density and electron temperature ranged from 1.1 × 1017 m−3 (at 6 cm from the target edge) to 1.7 × 1019 m−3 and from 2.4 eV (at 6 cm from the target edge) to 3.4 eV, respectively. From the emission spectra, the intensities of titanium atoms (Ti I), titanium ions (Ti II), and nitrogen ions (N2+) increased with increasing input power. However, the intensities ratio of Ti II to Ti I was not affected by the intensities from N2+. [ABSTRACT FROM AUTHOR]

The effects of an AC electric field on ice nucleation temperature and nucleation rate were investigated by freezing distilled water while exposing it to varied AC electric field strengths and frequencies. To eliminate the influence of ion injections and electric field concentrations at a metal electrode surface on ice nucleation, distilled water filled in resin cuvettes are used as samples. The samples are exposed to AC electric field induced by parallel plate electrodes placed outside of the cuvettes. The cuvettes and parallel plate electrodes placed in a freezer with an inside temperature fixed at −15°C. The electric field strength in the sample is 2 or 7.5 kV/m and frequency varies from 50 Hz to 10 kHz. The ice nucleation temperature and the nucleation rate of distilled water increase with increasing the electric field strength and the frequency. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Summary: Spotted mackerel were stored at 5 °C for 0–5 days. To reveal changes in freshness and provide the fundamental knowledge of sarcoplasmic reticulum (SR), structural and biochemical changes were investigated by optical microscope, transmission electron microscopy and biochemical detection, including pH, myosin Ca2+‐ATPase activity, adenosine 5′‐triphosphate (ATP) content, SR recovery field and SR Ca2+‐ATPase (SERCA) activity. The result exhibited that SR swelled on day 1 and ruptured after 2 days. Muscle structure showed significant changes from day 0 to day 5. SERCA activity and SR recovery field were 0.46 μm Pi/min/mg and 1.05 mg/g at day 0 and 0.106 μm Pi/min/mg and 0.109 mg/g at day 2, respectively, highly corresponding to the decline of pH, myosin Ca2+‐ATPase activity and ATP content with a significant difference from day 0 to days 1 and 2. The biochemical properties of SERCA exhibited the maximum activity at pH 6.8–7.0 (0.408 μmol Pi/min/mg). Treated at pH 5.5 for 80 min or incubated at 35 °C for 40 min inactivated SERCA of 80%. Therefore, keeping at a freezing temperature of 5 °C and maintaining SR functionality was essential to delay freshness decrease. [ABSTRACT FROM AUTHOR]

The gel is an important factor in 3D printability of Pennahia argentata surimi. While surimi gel is sensitive to temperature and influenced by chemical bonds changes. Hence, preheating effects on printing and material properties of surimi were investigated. Results shown hydrogen bonds and ionic bonds contents in surimi under different heating conditions decreased about 20%–90%. Meanwhile, hydrophobic force and disulfide bonds increased about 0.2–6 times. These changes formed more gel, as well as 6.5% at most immovable water transferred into free water which enhanced texture properties and made solid properties of rheology in surimi dominant. This phenomenon occurred significantly in temperature range of gel formation (35–40°C, 90°C) while became extinct at 45°C with 10–30 min due to gel degradation. These made surimi by heating exhibit strong mechanical strength, which is conducive to forming process when printing after extrusion. However, if they occurred before extrusion, these could increase extrusion difficulty to make filamentous materials be broken easily after extrusion, weakening printing effect. Hence, preheating of surimi before extrusion was not suitable for 3D printing. While short‐time heating during or after extrusion might be more appropriate for printed surimi, promoting the application of surimi in 3D printing technology. Practical Applications: 3D printing is a new technology in food processing that refers the process of connecting or curing materials to form 3D objects by continuously adding layers of materials. Surimi is one of the suitable materials which can promote the process of printing. While the material properties of surimi are affected by temperature that influences the printing effects. The purpose of this study was to investigate the effects of different temperatures on the material properties of Pennahia argentata surimi, and determine the suitable heating process of printed surimi products. These results could promote the application of 3D printing technology in surimi processing. [ABSTRACT FROM AUTHOR]

The quality changes of shelled Pacific oysters (Crassostrea gigas) were examined in relation to the effects of superchilling storage at −1 °C for 28 d by measuring changes in biochemical properties (microbial analysis, adenosine triphosphate (ATP)-related compounds, pH, free amino acids) and sensory evaluations in this study. The results indicated that microorganism growth was significantly inhibited during superchilling storage. Adenosine diphosphate (ADP) and adenosine monophosphate (AMP) accumulated while ATP rapidly decreased in the adductor muscle. ATP and ADP were the primary components in the other 3 tissues including mantle, gill, and body trunk of oysters, and they remained -relatively stable over time. The pH and adenylate energy charge in the adductor muscle could be utilized as freshness indicators for shelled oysters. However, there were no significant differences (P >0.05) among the free amino acids during whole storage. According to the sensory evaluations, oysters could be alive and tolerated up to 21 d at −1 °C storage. The study demonstrated that superchilling storage at −1 °C could better maintain the eating quality of shelled oysters and the shelf life was extended to 21 d. [ABSTRACT FROM AUTHOR]

Summary: 3D printing, as an emerging intelligent additive manufacturing processing technology, has been widely used in materials, aerospace, construction, medicine and other fields. Moreover, 3D printing technology has gradually emerged in field of food processing because of its characteristics of moulding without moulds and saving materials. The materials properties have a great influence on 3D‐printed food, especially mechanical strength and viscosity which affect accuracy and moulding ability of printed food. Moreover, the combination of materials also could change viscosity and rheology of printable materials (protein, starch, fat and hydrogel) and enhance the printing effect of not‐easy‐printable materials (cellulose). Additionally, the mixing of functional compounds and printing materials had great potential which was beneficial to personally customise functional nutritious foods to meet different people. This manuscript lays a foundation for the development and application of 3D printing technology in food processing. [ABSTRACT FROM AUTHOR]

The changes of sensory and biochemical characteristics on the fresh and frozen‐thawed scallop adductor muscle during storage at 4°C were discussed in this study. The Quality Index Method (QIM) scheme for evaluating scallop adductor muscle as raw materials for sashimi was proposed for the first time. The results of sensory evaluation showed that frozen‐thawed scallop adductor muscle within zero to one day of refrigeration can be happily accepted by consumers, indicating the superiority of freezing for long‐distance transportation, although the triangle test confirmed that there are still sensorial differences between fresh and frozen‐thawed scallop adductor muscle. The microscopic observation of myofibrils extracted from scallop adductor muscle suggested that the myofibrillar protein which constitutes myofibrils has suffered some extent change due to freezing and thawing, even though the head region of myosin remained stable judging by the fact that there was no significant difference in Ca2+‐ATPase activity (p > 0.05). The changes of adenosine triphosphate (ATP) and its related compounds, and pH value during storage can be regarded as indicators to differentiate fresh and frozen‐thawed scallop adductor muscle. The changes of Mg2+‐ATPase activity indicated that the interaction between myosin and actin was weakened by the freezing and thawing process. Practical Application: The QIM scheme can be used to evaluate the scallop adductor muscle as raw materials for sashimi. The mechanism of quality changes in the frozen‐thawed scallop adductor muscle was discussed in combination with the destruction of myofibrils, ATP degradation and the decrease of pH value. This study has positive significance for improving the quality of frozen‐thawed scallop adductor muscle by combining the changes of sensory and biochemical characteristics. [ABSTRACT FROM AUTHOR]

High-voltage pulsed electric fields (PEF) and pulsed discharge plasmas have received a great deal of attention in the fields of biochemistry, medicine, agriculture and food industry. The destruction phenomenon of cell membranes has been confirmed by PEF and discharge plasma, and it can be used for inactivating microorganisms and extracting cell contents. In recent years, it has been reported that PEF changes the activity of proteins such as enzymes. This review describes how PEF and pulsed discharge plasma function in enzyme activity change and permeabilization in food processing. It is thought that PEF affects the three-dimensional structure of proteins, and research is underway. Here, we will introduce the latest research results on the mechanism of enzyme activity change by PEF. In addition, we will introduce the latest research on changes in cell permeability using shock waves caused by the pulsed discharge plasma. [ABSTRACT FROM AUTHOR]

A compact inductive energy storage (IES) pulsed-power generator that is driven by a novel 13 kV silicon carbide (SiC)-MOSFET is developed and molded into a compact modified TO-268. In this article, the switching characteristics required for IES pulsed-power generator development are evaluated. The maximum slew rates at MOSFET turn-on and turn-off are 157 and 129 kV/μs, respectively, at an input voltage of 10 kV. The maximum current flow from the drain to the source terminal is limited to 128 A during short-circuit switching. The on-resistance between the drain and source terminals increases during the SiC-MOSFET's on state. It increases with the voltage and its minimum value is 1.07 Ω. These characteristics show that the device is suitable for use as an opening switch because of its low on-resistance and rapid large-current cutoff at high operating voltages. The characteristics of an IES pulsed-power generator composed of a SiC-MOSFET, a capacitor, and a pulsed transformer with a turn ratio of 5:15 are also evaluated. The output voltage peak and full width at half maximum reach 31.4 kV and 55 ns, respectively, at a charging voltage of 1100 V. The maximum energy transfer efficiency is 50.2% of the input energy with a load resistance of 2.5 kΩ. The results show that the MOSFET has excellent potential to support the development of a compact plasma generation system that offers better performance pulsed-power generators driven by semiconductor devices. [ABSTRACT FROM AUTHOR]

A high-power pulsed sputtering (HPPS) discharge source was evaluated experimentally as the ion source for droplet-free plasma processes. The basic configuration of the HPPS source consisted of a hollow cathode arrangement. A rectangular pulse voltage with an amplitude ranging from −330 to −1200 V and a pulse width of 600 μs was applied. The magnetic field used to reduce electron losses at the gap between the target was 0.2 T and was parallel to the electric field in the ion sheath. The current density on the target with the magnets (HPPS) was approximately 15 kA m−2 and was one order of magnitude higher than that without the magnets [hollow-cathode discharge (HCD)]. The ion density of the HPPS discharge was approximately 3.4 × 1018 m−3 at 30 mm apart from the electrode edge and decreased to 2.2 × 1017 m−3 by changing from an HPPS discharge to an HCD. [ABSTRACT FROM AUTHOR]

High-voltage and plasma applications to keep the freshness and quality of agricultural produce are described focusing on functions of plasma in each application of a post-harvest stage. The high voltage and the plasma are used for decontamination of airborne bacteria in a storage house and a transport container of agricultural produce. The working mechanisms of the decontamination are mainly caused by inactivation through the oxidization process with reactive oxygen species and the collection of airborne bacteria as an electric precipitating process. The plasma is also used to maintain a freshness by decomposition of the agricultural produce exhausting gases such as ethylene, which works as a plant hormone and accelerates ripening of some kind produces in a mix-loading container. The decomposition of the ethylene is mainly an oxidization process by the atomic oxygen in dry gas condition. The ethylene is also decomposed by hydroxyl radical under the humid air condition. [ABSTRACT FROM AUTHOR]

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The influence of waveforms of the applied voltage on hydrogen production from methane reforming using dielectric barrier discharge (DBD) is investigated. Three types of high voltage power generators with different pulse shape with widths of $50~\mu \text{s}$ –250 ns and voltage rise speeds of $7.6\times \,\,10^{4}$ – $5.2\times 10^{10}$ V/s of sinusoidal, bipolar pulses, and a nanosecond pulse voltage are used to control the waveform. The energy efficiency for hydrogen production in the case of nanosecond pulse is approximately 0.9 g/kW $\cdot \text{h}$ , much higher than those of sinusoidal and bipolar pulses, with approximately 0.5 g/kW $\cdot \text{h}$. This is due to that the voltage rise speed by the short pulse is much higher than those using the sine wave and the bipolar pulse, and so the discharge by the short pulse is uniformly generated. The hydrogen production increases and the energy efficiency decreases slightly with increasing pulse repetition rate. The hydrogen production efficiency is independent of the gas pressure within the ranges from 0.12 to 0.16 MPa. [ABSTRACT FROM AUTHOR]

Ethylene gas was decomposed using a dielectric barrier discharge (DBD) plasma reactor for the long-term preservation of fruits and vegetables with a focus on the influence of humidity on ethylene decomposition efficiency. DBD is actively used to produce nonthermal plasma, which is effective in converting C2H4 into CO2 and H2O, through an oxidization process with a high reaction rate because the nonthermal plasma in air contains a large number of chemically active species such as atomic oxygen radicals (O) and hydroxyl radicals (OH). This production of radicals depends on the level of humidity in the air. During the experiment, C2H4 gas was diluted by 200 ppm with an N2 and O2 gas mixture and was fed into the DBD reactor at a 3 L/min gas flow rate. The relative humidity (RH) of the gas was adjusted by the bubbling gas through water. The gas temperature was fixed at 25 °C. The experimental results showed that C2H4 decomposition efficiency was almost independent of RH. [ABSTRACT FROM AUTHOR]

In the microplasma generated by dielectric barrier discharge (DBD), a huge variety of discharge patterns are generated by self-organization. In this study, we experimentally observed variation in the hexagonal structures in capacity-coupled microgap DBD using a helium (He)/argon (Ar) mixture. The spatial distribution of the self-organized structure was revealed via a discharge experiment in which the equivalent barrier capacitance was continuously changed within the range of 56–1500 pF. The results demonstrate that the lattice spacing of the patterns can be continuously controlled within the range of 1.22–1.59 mm for an equivalent barrier capacitance of 56–172 pF. It is likely that an increase in external capacitance increases the discharge cell voltage. In contrast, the lattice constant remained unchanged with an increase in barrier capacitance within a range of 172–1500 pF. The lattice spacing of the patterns could be continuously controlled within a range of 0.66–0.74 mm for all He/Ar gas mixing ratios. [ABSTRACT FROM AUTHOR]

A silicon wafer etching using a burst pulse high-power inductively coupled plasma (ICP) is investigated. A 200 μs wide burst of a 157 kHz power supply is employed to generate ICP with a repetition rate of 50 Hz. A rectangular pulsed voltage synchronized with the burst power supply is applied upto 1 kV at the wafer. Mixed gas of argon (Ar) and tetrafluoromethane (CF4) is supplied into the vacuum chamber. The plasma density and electron temperature are 1019 m−3 and 2.8 eV where the wafer is, respectively. In the case of Ar plasma, the silicon etching rate is 0.01 μm min−1 with 1000 V negative bias. The etching rate increases to 0.23 μm min−1 by adding CF4 into Ar and increases linearly with increasing the bias voltage. The target current and emission intensity of Ar+ and F* are depended on bias voltage from −300 to −1000 V. The etching rate sharply increases by increasing CF4 content from 0% to 10%, and it becomes almost constant at 10%. The dependency of emission intensity of F* on CF4 content is similar to the dependency the etching rate. [ABSTRACT FROM AUTHOR]

Decomposition process of volatile organic compound dissolved into water by discharge plasma inside bubble is investigated. The experiment is conducted on decomposition of dichloromethane (DCM). Argon or oxygen gas is injected into the water through a vertically positioned glass tube, in which high-voltage wire electrode is placed to generate plasmas at low applied voltage. The nanosecond pulsed high voltage generated by an inductive energy storage system pulsed power generator is applied to the tungsten wire to generate streamer discharge. Total organic carbon decreases and chloride ion concentration increases by the discharge treatment. To clarify the decomposition process, DCM and indigo carmine (IC) mixed solution is employed as specimen. The amount of IC decomposition decreases with increasing the DCM concentration. On the other hands, the amount of DCM decomposition is almost independent of IC concentration. These results show that DCM is quickly volatilized into the bubble, which is decomposed by hydroxyl radical produced by the discharge in gas phase inside bubble. [ABSTRACT FROM AUTHOR]

The purpose of this study was to confirm inosine monophosphate (IMP) generation and to clarify the decomposition pathway of adenosine monophosphate (AMP) by investigating the properties of AMP, IMP, and adenosine (AdR) decomposition enzymes in Japanese scallop (Patinopecten yessoensis). The results showed that IMP accumulated due to AMP decomposition via endogenous enzymes in scallops stored at both 4 °C and 20 °C. The AMP decomposition rate was highest in the supernatant of homogenized scallop adductor muscle, followed by the suspended solution and precipitate, while IMP could not be decomposed in scallop. The results indicated that the activity of AdR deaminase was very high, and this enzyme was involved in an intracellular process in scallop. Moreover, 1 min of heating exerted little influence on the AMP and AdR decomposition rates, while 5 min of heating induced enzyme denaturation. The IMP generation rate increased dramatically in scallop crude enzyme solution containing 5 mM ethylenediaminetetraacetic acid (EDTA). This suggests that the major pathway of AMP decomposition might change with variations in metal ion concentrations in Japanese scallop. Practical Application: IMP generation in Japanese scallop (Patinopecten yessoensis) caused by endogenous enzymes was confirmed. IMP is very important for the umami taste (a pleasant savory taste) of aquatic products. As IMP accumulation might be achieved by changing the concentration of divalent metal ions and no IMP 5'‐nucleotidase activity was detected in scallop, a suitable process to produce good flavor scallops with high IMP contents might be developed. [ABSTRACT FROM AUTHOR]

The influence of the electric parameters, applied voltage, and pulse repetition rate on the energy efficiency for hydroxyl radical production from pulsed discharge inside of a bubble is investigated in this paper, as a possible application for waste water treatment. To evaluate the energy efficiency, indigo carmine, a common dye, is used as a chemical probe of hydroxyl radicals. Argon is injected into water through a vertically positioned glass tube, into which high-voltage wire electrode is placed to generate plasmas at low applied voltage. The energy efficiency increases with the decreasing pulse repetition rate and output voltage with the same indigo carmine concentration. The results show that the energy efficiency for the hydroxyl radical production increases with the decreasing amount of energy input into the solution per unit time because of the decrease in the recombination reaction of the hydroxyl radicals in the solution. The impedance between the electrodes decreases with the increasing output voltage, which increases the ohmic losses in the solution but does not contribute to the production of hydroxyl radicals. [ABSTRACT FROM AUTHOR]

Influence of pulsed electric field (PEF) on the drying rate of foods during the hot air drying process is investigated. Nine kinds of fruits and vegetables and two kinds of marine products are used as the samples, and changes in the weight of these samples during the process are evaluated. PEF is applied to the samples using parallel plate electrodes. The applied voltage ranges from 0.4 to 3 kV, and the input energy of the sample ranges from 1.5 to 115.5 J/g. The samples are dehydrated using a hot air dryer after the PEF treatment. The drying rate of leafy vegetables, apples, and wakame seaweed is accelerated by PEF. The results show that the moisture permeability of membrane can be improved by destroying the cell membrane by PEF. On the other hand, there is no effect on root vegetables because their hard tissues are hard to destroy. © 2020 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

An ac electric field (acEF) application technology has been reported as a principle technique for food preservation. With this method, conformational changes in the protein molecules of food materials may be induced. Conformational changes were experimentally examined using bovine serum albumin (BSA) as a model protein using an acEF technology. The amplitude of acEF was 66.7 kV/m. BSA with acEF (ac-BSA) and BSA without the ac field (n-BSA) were trypsinized under the same conditions. The derived peptides were compared by using sodium dodecyl sulfate polyacrylamide gel electrophoresis patterns. Formation of tryptic peptides was increased in n-BSA, and trypsin digestion was suppressed in ac-BSA. These results indicate that conformational changes in BSA molecules were induced by acEF application. [ABSTRACT FROM PUBLISHER]

SUMMARY Ethylene gas was decomposed using packed-bed type dielectric barrier discharge (PBDBD) plasma reactor to keep freshness of fruits. The ethylene gas was diluted with gas mixture of nitrogen, oxygen, and carbon dioxide as simulated gas in the transportation container. The PBDBD plasma was generated by a pulse switching power supply, which consisted of MOS-FET switching devices, capacitors, and pulse transformers. The Ag nanoparticle-loaded zeolite as catalyst has high activity and good performance for reduction of ozone and oxidizing carbon monoxide at room temperature. The Ag nanoparticle-loaded zeolite pellets enhanced ethylene removal efficiency and reduced ozone and carbon monoxide produced by the plasma treatment. It was confirmed that the carbon monoxide in the gas simulated dry air composition was oxidized using Ag nanoparticle-loaded zeolite with plasma treatment. [ABSTRACT FROM AUTHOR]

SUMMARY An effect of discharge plasma irradiation to the circulating water in hydroponic cultivation system on plant growth rate was evaluated using Brassica rapa var. perviridis as specimen. The discharge plasma produced acids in the solution, which acts as a fertilizer. The Brassica rapa var. perviridis were cultivated in period of 42 days with the hydroponic system. The experimental result indicated that the growth rate of the Brassica rapa var. perviridis is improved drastically with the discharge treatment of the solution of hydroponic system, especially content of leaf blade is significantly increased ( p < 0.01). [ABSTRACT FROM AUTHOR]

Ethylene (C2H4) gas promotes the aging of some kinds of fruits and vegetables such as persimmon, banana, and cucumber. Decomposition of ethylene using nonthermal plasma is effective for keeping freshness of fruits and vegetables in the transportation container. The ethylene was decomposed into gas stream using a dielectric barrier discharge (DBD) reactor driven by dual-polarity pulse generator that consisted of four insulated gate bipolar transistors and a pulse transformer. The output voltage of the pulse generator was 10 kV in amplitude, 1 kilopulse/s in repetition rate, and 50~\mu \texts in rectangular pulsewidth. The 200 ppm ethylene was diluted with dried air and was employed as simulated gas of the transportation container. The gas mixture was fed into the DBD reactor for the evaluation of the decomposition efficiency. The ethylene concentration decreased to less than 1 ppm after the DBD treatment at 30 J/L in input energy. The energy efficiency for ethylene decomposition was around 50 g/kWh and was almost independent of the initial ethylene concentration. The decomposition efficiency increased with increasing oxygen content of the background gas. The byproducts were analyzed by a Fourier transform infrared spectrometer. The results showed that the H2O and CO2 were mainly produced after the decomposition of the ethylene by the DBD plasma. [ABSTRACT FROM PUBLISHER]

The ionization rate of sputtered carbon species in magnetron sputtering glow plasmas is low because of a low sputtering yield, a high ionization energy and a low reaction rate between the carbon and electron in the plasma. In this paper, efficient ionization of sputtered carbon species is realized in high-power impulse magnetron sputtering (HiPIMS) glow plasma. The arrangement of the permanent magnet placed at the back of the target can recover the above issues, which enables a power consumption as high as over 100 kW with a pulse duration as short as 5.5 \mus at a source voltage as high as 2200 V. The magnet arrangement affects the production zone of the HiPIMS glow plasma on the target; the plasma moves outward to the radial direction of the target with an increased number of the inner magnets. When the plasma has a larger diameter on the target, a glow easily transits to an arc discharge even at a lower voltage compared with the case of the small-diameter plasma production, because the distance between the plasma and the grounded plate becomes short. Both the highest target voltage without an arc transition and the highest glow current are obtained at n=1, the least number of the inner magnet. In this case, a source voltage of 2200 V brings into the highest instantaneous power of about 144 kW. It is confirmed that higher the source voltage, higher the intensity of the optical emission spectrometry spectrum of carbon ions is. The high power consumption contributes to the high-density argon plasma production. Hence, the least number of the inner magnet results in a higher acceleration energy to bombard the target to efficiently sputter carbon species and a high ion flux bombarding to the target. The longer pulse duration such as 30 \mus results in an arc transition at the source voltage as low as 1200 V. Thus, the highest emission intensity of the carbon optical emission obtained for n=1 at 2200 V with 5.5-\mus pulse duration. It is observed that the intensities of the optical emission from argon and carbon ions are proportional to the power consumed in the plasma. [ABSTRACT FROM PUBLISHER]

A compact magnetically expanding plasma source having a strong magnetic field is developed, where a pulsed solenoid current is provided by an insulated gate bipolar transistor switching circuit. The field strength is successfully increased up to ∼6 kG. The 13.56 MHz radio-frequency power with a pulse width of 28 ms and the operating argon pressure are maintained at 600 W and 3 mTorr, respectively. When the magnetic field strength is increased, the plasma density downstream of the source cavity increases due to the inhibition of cross-field diffusion and appears to saturate above ∼3.5 kG, while maintaining a plasma density of 5 × 1012 cm−3 within the source cavity. [ABSTRACT FROM AUTHOR]

Spatial distributions of charged particles diffusing from a double dc corona discharge ionizer operated in air and nitrogen atmospheres are 2-D measured. It is experimentally demonstrated that static electricity on a silicon wafer downstream side of the ionizer is eliminated only in the area where the local net charge flux becomes zero. The 2-D profiles of the local net ion current clearly show that the spatial profile of the local net ion current can be controlled by a balance between the positive and negative discharge voltages. Hence, it is demonstrated that the balance can yield the control of the charge elimination area. [ABSTRACT FROM AUTHOR]

Silicon carbide (SiC) is one of the most promising materials for next-generation power electronic devices, owing to its superior physical properties. Among existing SiC power devices, the SiC junction field-effect transistor (JFET) (SiC-JFET) has excellent performance. A high-power discrete package of a SiC-JFET was developed with the aim of being applied to the High Energy Accelerator Research Organization (KEK) digital accelerator. The device was assembled on a 58 mm \times 36 mm copper base plate and with a height of 7 mm. The size of the die was 4.16 mm \times 4.16 mm. The device was tested using a pulse discharge circuit and successfully operated at 1 MHz, 1 kV, and 27 A. The power dissipation and the thermal resistance were estimated at 235 W and 0.56 K/W. [ABSTRACT FROM PUBLISHER]

Shunting discharge plasmas are metal plasmas that can be generated around a conductive rod at a reduced pressure on the order of 0.1–100 Pa. Even at atmospheric pressure, a plasma can be generated because the rod is heated to emit metal vapor so as to generate gas breakdown around the rod. When the temporally increasing voltage across the rod matches the plasma ignition voltage, a shunting plasma is ignited. The plasma ignition is triggerless and, thus, does not require an external signal. There are two types of shunting plasmas: glow and arc discharges, with sustenance voltages of approximately 100 and 60 V, respectively. The plasma results in an arc discharge via a glow state. When a pulsed-power source with a controlled pulse duration is used to obtain a glow plasma only, a stable steady-state glow can be obtained under a suppressed current with a duration of over 10 \mu\s and a consumed power of several tens of kilowatts. A shunting glow plasma can be realized by controlling the pulse duration. In this paper, optical emission spectra from the shunting glow and shunting arc are observed. Singly charged carbon ions were found to be produced by the glow plasma. Carbon emission was significant in a nitrogen gas environment, as compared with an argon environment. In the case of a shunting arc, the optical emission is broad in wavelength, and doubly ionized carbon species also arise. A preliminary test of diamond-like carbon (DLC) film deposition was carried out, where the DLC was deposited on a substrate set near a plasma source. The DLC state was determined using Raman spectroscopy, and no macroparticles were found on the deposited film, which had a clean surface. The rod holder used as an electrode showed no damage. In contrast, in the case of a shunting arc, many macroparticles were found on the deposited films, and serious damage to the electrode also occurred. [ABSTRACT FROM PUBLISHER]

Effects of the radius of a coaxial pulse corona reactor and the polarity of an applied voltage on \NOx (nitrogen oxide) removal are investigated for industrial applications of the \NOx removal technology. Three radii of the pulse corona reactors (10, 30, and 50 mm) were chosen in the experiments of ozone generation and \NOx removal, and their energy efficiencies were measured. The 50-mm-radius reactor with the positive pulsed voltage was found to be suitable for the removal of large amount of \NOx and ozone generation. On the other hand, it was clarified that the 10-mm-radius reactor with the negative pulsed voltage is effective for the removal of small amount of \NOx and ozone generation. In the case of the 30-mm-radius reactor, energy efficiencies versus ozone concentration characteristics became a single curve at both the positive and negative polarities. For the purpose of the industrial application, a parallel reactor system and a reactor having a dielectric barrier were also tested experimentally. Through these experiments, the value of the energy efficiency of the parallel reactor system was confirmed to keep almost the same value as that of the single-reactor system. The reactor with the dielectric barrier on the outer electrode had higher energy efficiency than that without one. [ABSTRACT FROM AUTHOR]

This paper evaluates the capability of a silicon carbide junction field-effect transistor for an induction synchrotron. The device was operated with a repetition rate of 1 MHz, a drain–source voltage of 1 kV, and a drain current of 50 A in burst mode. Based on the results, the feasibility of continuous-mode operation from the point of view of maximum junction temperature is evaluated. If the total thermal resistance is smaller than 0.7 ^\circ\C/W, the device has potential to be applied in an induction synchrotron. [ABSTRACT FROM AUTHOR]

Water purification by streamer discharge using pulsed-power generator under a high-conductivity water containing pollutants has been investigated. A gas–liquid separated reactor was developed to treat highly conductive solution. A wire electrode was placed in the gas phase and a plane electrode was immersed in the water. A pulsed high voltage generated by six stacked Blumlein lines was applied to the wire electrode to generate streamer discharge in the gas phase, which propagated into the air bubble injected into the water. Indigo carmine solution was employed as a specimen. Natrium chloride was used to adjust the solution conductivity in the range from 10 to 30 000 \mu\S/cm. A solution with 30 000- \mu\S/cm conductivity was successfully decolorized with energy efficiency of 75 \mg/\W\cdot\h. Some species of gas such as air, oxygen, nitrogen, and argon were injected to clarify dominant reactions of the decolorization. The result showed that the ozone produced by gas-phase discharges mainly contributed to the decolorization of the solution. The decolorization rate depended on the chloride ion supplied from the natrium chloride by scavenging of hydroxyl radical and on the copper ion eluted from the plane electrode by redox reactions such as Fenton reactions. [ABSTRACT FROM PUBLISHER]

To meet the needs of the hungry population, it is critical to boost agricultural product production while minimizing contaminated waste. The use of two nonthermal technologies, pulsed electric field (PEF) and nonthermal plasma (NTP), is increasing every day. As both PEF and NTP are relatively newer areas, there is limited knowledge about these two technologies and their modes of action. Studies showed that PEF treatment on the plant seeds helps germination and seedling growth. The positive impact of PEF intensity is highly dependent on the seed coat type and plant species. Another nonthermal technology, NTP, affects seed germination, seedling growth, yield, and resilience to abiotic stress when generated at varying pressures with and without different feed gases. Early germination, germination rate, and germination percentage were all improved when the seedlings were treated with NTP. Similarly to the PEF treatment, NTP had a negative or no effect on germination. This review examined the effects of PEF and NTP on seed germination and analyzed the situation and mechanism behind the positive or negative effect. Deactivation of proteins and enzymes to extend the shelf life of beverages is another prominent application of PEF and NTP. The interaction of PEF and NTP with proteins aids in understanding the microscopic mechanism of these technologies. Therefore, we covered in this review the potential structural and functional changes in proteins/enzymes as a result of PEF and NTP, as well as a comparison of the benefits and drawbacks of these two technologies. [ABSTRACT FROM AUTHOR]

Disinfection and sterilization against cold-tolerant microorganisms are very important for enhancing food safety and hygiene management under refrigeration conditions. We isolated Exiguobacterium sp. and Pantoea sp. from an immersion solution of packed tofu and evaluated their growth properties and sensitivities to various bactericidal methods. These microorganisms were classified as psychrotrophic bacteria, according to their ability to grow at 4 °C, with an optimum growth temperature of 30 °C. Exiguobacterium sp. and Pantoea sp. were more sensitive to heat and sodium hypochlorite than Escherichia coli (E. coli). Exiguobacterium sp. was sensitive to acetic acid and citric acid, while Pantoea sp. was relatively insensitive and E. coli was insensitive to these organic acids. All microorganisms used in this study were resistant to sodium hydroxide solution (pH 8.00). Exiguobacterium sp. showed resistance to ozonated water and UV; therefore, particular attention should be paid to the contamination of this microorganism in food factories. Both Exiguobacterium sp. and Pantoea sp. were inactivated by pulsed electric field (PEF) treatment that did not cause lethal damage to E. coli. The results obtained in this study suggest that the bactericidal methods targeting the fragile cell membrane with high permeability are effective for the inactivation of cold-tolerant microorganisms. [ABSTRACT FROM AUTHOR]

Bacillus velezensis is a kind of beneficial bacteria that is widely used in agriculture industry. Bacillus velezensis was irradiated with corona discharge generated by a needle-array high-voltage electrode. The results showed an improvement of activity of Bacillus velezensis by the corona discharge treatment was confirmed at an optimum input energy. Mutation of the Bacillus velezensis by the corona discharge treatment was also confirmed through an rRNA sequence alignment analysis. The enzyme activity of the mutated bacteria was greatly improved, which was a positive effect that can meet the production demand. [ABSTRACT FROM AUTHOR]

Ion extraction from a magnetically driven shunting arc plasma and the plasma density at the sheath boundary are described in this paper. The plasma density is obtained using current and voltage waveforms for a target which is immersed in the plasma to extract the carbon ions. A 40-mm-long carbon rod which is 2 mm in diameter is employed as a solid-state plasma source. A large current of more than 1 kA is supplied from a charged-up 20-µF capacitor to heat the carbon rod and to vaporize the rod materials. The shunting arc plasma generated along the rod surface is driven by the Lorenz force and is accelerated toward the muzzle of a plasma launcher which consists of a pair of 100-mm-long carbon plates. A 64-mm-diameter brass disk is placed 100 mm away from the carbon rod and is used as the target. A 10-µs-wide negative pulse bias voltage is applied to the target for the extraction of the carbon ions from the shunting arc plasma. The ion density near the sheath boundary around the target is obtained using two procedures: utilization of the stationary target current to determine the ion current and/or utilization of the target bias voltage waveforms. The ion density is obtained as 1.1×1015m-3 at µs after the arc ignition using the target current. The density is larger than the density of 5.1×1014m-3 obtained using the waveform of the target voltage. The plasma density is also predicted using a Bohm equation and a momentum conservation equation. The plasma density is 1.6×1015m-3 at 100 µs after the arc ignition. The density decreases as the time from arc ignition increases. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 162(2): 1– 9, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20553 [ABSTRACT FROM AUTHOR]

A review of mainly the past two years is undertaken of the industrial applications of pulsed power. Repetitively operated pulsed power generators with a moderate peak power have been developed for industrial applications. These generators are reliable and have low maintenance. Development of the pulsed power generators helps promote industrial applications of pulsed power for such things as food processing, medical treatment, water treatment, exhaust gas treatment, ozone generation, engine ignition, ion implantation and others. Here, industrial applications of pulsed power are classified by application for biological effects, for pulsed streamer discharges in gases, for pulsed discharges in liquid or liquid-mixture, and for material processing. [ABSTRACT FROM AUTHOR]

The recent trend in thin film deposition is to prepare ceramic films capable of enduring violent environments, such as corrosive pollutant gases with high temperatures. Different kinds of plasma species existing in the same space are advantageous in order to facilitate a reactive deposition between the gaseous and metallic species. In this paper, we study a carbon shunting arc that triggers a gas discharge using a positively biased electrode. An electrode with a positive voltage of up to 500 V was set nearby the carbon shunting arc source. Nitrogen, methane, or argon was used as an ambient gas. The induced plasma was generated with a time delay from the moment of the generation of the shunting arc. The electrical and optical characteristics of the discharge were studied. The onset time of the induced plasma as a function of the ambient gas pressure has a Paschen-like V-shaped characteristic. The generated plasma includes both carbon and gaseous species. At the surface of the positively biased electrode, both spectrum emissions of carbon and gaseous species are observed, by which the plasma is confirmed to be mixed. This is based on the spectrum observation in addition to the change in the color of the plasma. A shunting arc is an easy method used in generating a hybrid plasma consisting of metallic (including carbon) and gaseous species. This method promises to efficiently prepare ceramic films by reactive deposition. This method is simple, and both plasma species, i.e., those of metal and gas particles, are easily mixed. The carbon shunting arc plasma plays both the roles of supplying the ca/'bon species and triggering a gaseous plasma as an induced plasma. [ABSTRACT FROM AUTHOR]

A capacitor discharge joining technique used to fabricate an alumina-(Al2O3) tile-titanium-foil-Al2O3-tile joint was investigated to clarify the influence of titanium foil width on bonding strength. A several-kiloampere pulse current was supplied from an 8.28-μF storage capacitor to the titanium foil while simultaneously applying a pressure of 8.3 MPa to the joint. The temperature of the foil rapidly increases owing to ohmic heating with a large current. As a result, the titanium foil melts and vaporizes in a short time. The Al2O3 tiles were successfully bonded when the charged voltage in the capacitor was almost the same value as the energy required for vaporization of the titanium foils. The bonding strength increases with the energy input to the foil. The attainable bonding also increases with increasing shear strength from 150 to 300 kg, which in turn increases with increasing foil width from 1 to 7.5 mm for a 50-μm-thick foil. The main reason of the shear-strength improvement was the increase of the joined area that was measured with image analysis of the joint surface. [ABSTRACT FROM AUTHOR]

Shunting arc discharge is a pulsed plasma source of metals and semimetal materials and is ignited without any trigger sources at a wide range of gas pressures, from vacuum to atmospheric pressure under identical discharge conditions. In this paper, an ion extraction from magnetically driven carbon shunting arc discharge and a criterion of the arc ignition are described. A carbon rod with a diameter of 2 mm and a length of 40 mm was employed for arc ignition. The carbon rod was set in the vacuum and was initially heated up with a pulsed current supplied by a charged capacitor with a capacitance of 20 μF, followed by self-ignition. The heating energy is almost independent of the charging voltage of the capacitor and changes with the rod position on the rail. The ions are extracted from the arc plasma by applying a negative pulse voltage to a target. The target current has a sharp peak at the initial stage, followed by a stationary state. The stationary current decreases with increasing the distance to the target from a muzzle of the shunting arc plasma gun. Under the assumption of a collisionless ion sheath, the ion density at a 20-mm target–muzzle distance is estimated as 1 × 108 and 2 × 108 cm-3 for the delay times of 250 and 1000 μs, respectively. The density at a 250-μs delay time decreases from 1 × 108 to 0.8 × 108 cm-3 by increasing the distance from 20 to 140 mm. The ion density increases as the charging voltage of the capacitor for arc generation is increased. [ABSTRACT FROM AUTHOR]

We performed measurements of the radio frequency power and temperature of electrodes and plasma parameters of rf discharge. The purpose of this research is to check the accuracy of the measurement of energy consumed in plasmas. The heat energy in plasma was obtained by heat flux that was calculated from substrate temperature. The temperature was measured by a laser interferometer using LiNbO3 crystals. In the case of electrode spacings of 2, 3, and 4 cm, the heat energy toward electrodes was 7.7, 5.4, and 4.0 W, respectively. The current and voltage measurement was made at the driven electrode. The input power was 8.2, 5.1, and 7.7 W for electrode spacings of 2, 3, and 4 cm, respectively. The heat energy calculation based on the electron density distribution measured was conducted by estimating the Bohm flux and ambipolar diffusion flux. It was found that the heat energy toward electrodes was 1.4, 1.8, and 1.5 W for electrode spacings of 2, 3, and 4 cm, respectively, and the heat toward the wall was negligible. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 155(1): 1–8, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20295 [ABSTRACT FROM AUTHOR]

Ceramic dielectric material pellet shape effects on the performance of perfluoroethane (C2 F6) gas removal from simulated semiconductor process gas using packed-bed reactor are experimentally investigated. The bench-scale cylindrical shaped (plasma part: 30-mm inner diameter and 20-mm length) plasma reactor consists of two metal mesh electrodes packed with spherical, cylindrical, or hollow cylindrical shaped ferro-electric pellets with various dielectric constants. The 60-Hz ac high voltage was applied to the mesh electrode. The 3000 ppm C2F6 gas diluted with nitrogen was used as simulated gas with flow rate of 30 mL/min. The C2F6 concentration was monitored using Fourier transform Infrared absorption spectroscopy measurements. The results show that the packed-bed plasma reactor with the hollow cylindrical-shaped pellets removed the C2F6 gas with energy efficiency of 3.7 g/kWh. This value was almost 1.5 times higher than the efficiency 2.5 g/kWh in case of the spherical pellets. The discharge characteristics in the reactor were also changed with the pellet shape. The discharge onset voltage decreases by changing the pellets shape from sphere to hollow cylinder. The quantity of charges accumulated with the microdischarge currents increases by changing the pellet shape from sphere to hollow cylinder in spite of fact that the energy consumed in the reactor decreases. [ABSTRACT FROM AUTHOR]

In order to validate a non-thermal plasma model using nitrogen in a ferro-electric packed-bed reactor, the number density of the excited nitrogen molecules has been investigated by spectroscopic measurements. Experiments were conducted at applied voltages from 0 to 20 kV, 60 Hz and gas flow rates from 1 to 5 L/min in pure nitrogen gas. The results show that the number density for excited N2 molecules increases with increasing applied voltage and dielectric constant and agrees qualitatively with the numerical modeling results at lower applied voltage. The vibrational temperature of the C3 IIu (v') state of N2 has been calculated from the light intensity emitted by the 2nd positive band. The vibrational temperature decreases with increasing gas flow rate and no significant effects of the applied voltage and dielectric constant were observed. [ABSTRACT FROM AUTHOR]

Numerical modelling of ferro-electric packed bed non-thermal plasma reactor has been conducted to predict plasma parameters in a pure nitrogen environment. Simplified time averaged one-dimensional physical model based on Poisson's equation for electric field and transport equation for electrons was developed. The mean electron energy was obtained by a swarm relationship from calculated electric field profiles and plasma neutral conditions. For chemical model, N+, N2+, N3+, N4+, N*, N2* and electron were considered where N* and N2* are the total excited atoms and molecules, respectively. The results show that all the plasma parameters increase with increasing applied ac voltage and pellet dielectric constant. The numerical results also show that the dominant ion is N4+ and the metastable molecule density is much higher than radical and the electron densities at atmospheric gas pressure. [ABSTRACT FROM AUTHOR]

An experimental study on nitrogen oxides (NOx) removal from a simulated diesel engine exhaust gas was carried out in geometry of various electrodes for dielectric barrier discharge reactor to improve the removal efficiency. The electrodes employed in the experiment were a plane, a trench, and a multipoint geometry. The right-pyramids, which were used as multipoint, had 45° tip angle and a height of 1-5 mm. The multipoint electrodes have 528-5000 pyramids in an area of 132 cm² (22 × 6 cm). The trench electrode has knife-edge rails with 5-mm height and 45° tip angle. The alumina dielectric barrier coated plane electrode was used as a high-voltage electrode, to which a sinusoidal high voltage was applied with frequency of several tens kilohertz. The N2: O2 = 9: imixedgascontaining200-ppmNOwasusedaS simulated gas with gas flow rate of S L/min. NO removals in case of the plane and the trench electrodes were lower than that in case of multipoint one. NO removal yield drastically decreases with increasing the number of pyramids on the electrode. NO removal efficiency was almost independent of the pyramid projection height under our experimental condition. [ABSTRACT FROM AUTHOR]

Investigates the application of a nonthermal plasma process using a dielectric barrier discharge, in the removal of nitrogen oxides (Nox) from the exhaust gas of a diesel engine generator. Circuit of the pulse modulator used in the experiment; Electrical performance; Effect of electrical energy density on the removal of NOx.

Pulsed electric fields (PEFs), which are generated by pulsed power technologies, are being tested for their applicability in food processing through protein conformational change and the poration of cell membranes. In this article, enzyme activity change and the permeabilization of agricultural products using pulsed power technologies are reviewed as novel, nonthermal food processes. Compact pulsed power systems have been developed with repetitive operation and moderate output power for application in food processing. Firstly, the compact pulsed power systems for the enzyme activity change and permeabilization are outlined. Exposure to electric fields affects hydrogen bonds in the secondary and tertiary structures of proteins; as a result, the protein conformation is induced to be changed. The conformational change induces an activity change in enzymes such as α-amylase and peroxidase. Secondly, the conformational change in proteins and the induced protein functional change are reviewed. The permeabilization of agricultural products is caused through the poration of cell membranes by applying PEFs produced by pulsed discharges. The permeabilization of cell membranes can be used for the extraction of nutrients and health-promoting agents such as polyphenols and vitamins. The electrical poration can also be used as a pre-treatment for food drying and blanching processes. Finally, the permeabilization of cell membranes and its applications in food processing are reviewed. [ABSTRACT FROM AUTHOR]

The high-speed etching of a silicon wafer was experimentally investigated, focusing on the duty factor of 150 kHz band high-power burst inductively coupled plasma. The pulse burst width was varied in the range of 400–1000 µs and the repetition rate was set to 10 Hz. A mixture of argon (Ar) and carbon tetrafluoride (CF4) gas was used as the etching gas and injected into the vacuum chamber. The impedance was changed with time, and the coil voltage and current were changed to follow it. During the discharge, about 3 kW of power was applied. The electron temperature and plasma density were measured by the double probe method. The plasma density in the etching region was 1018–1019 m−3. The target current increased with t burst width. The etching rate of Ar discharge at burst width of 1000 µs was 0.005 µm/min. Adding CF4 into Ar, the etching rate became 0.05 µm/min, which was about 10 times higher. The etching rate increased with burst width. [ABSTRACT FROM AUTHOR]