Alternative Voltage Research Articles

A nonlinear analysis of electrically forced vibrations of piezoelectric plates with viscous damping near the thickness-shear mode

Based on the theory of nonlinear piezoelectricity, an approximate solution for electrically forced nonlinear thickness-shear vibrations of piezoelectric plates is introduced. The model considers an infinite piezoelectric plate subjected to an alternative voltage, incorporating 3rd-order and 4th-order elastic constants and viscous damping under finite deformation. The system's differential equations for steady-state forced vibrations are derived from the nonlinear pure thickness-shear vibration problem, and transformed so that the new electrical boundary conditions are free. After the application of Galerkin's method, the transformed differential equations lead to a cubic equation, capturing the nonlinear current-frequency curves of AT-cut quartz plates without the need of the quality factor Q, due to the introduced viscous damping. When the damping effect is ignored, the frequency response curves of the AT-cut quartz plate under a specific voltage are confirmed with the existing literature. The study emphasizes the presence of the critical voltage and the importance of the fourth-order elastic constant (c6666) in the stability, revealing lower c6666 values correspond to improved stability. Additionally, a proposed algorithm efficiently determines critical voltages for resonator stability.

Dynamic voltage mapping of the ventricular tachycardia substrate

Abstract Background Substrate mapping techniques that predict ventricular tachycardia (VT) isthmus components in sinus or paced rhythm are necessary as mapping during VT is often not possible. Voltage maps lack accuracy in differentiating scar, traditionally displayed as tissue <0.50mV, from bordering arrhythmogenic substrate. We developed a practical technique aiming to improve the utility of a voltage map during VT ablation, termed ‘Dynamic Voltage Mapping’ (DVM). Methods Consecutive patients with post-infarct VT at our centre underwent left ventricle (LV) voltage mapping (mean 4762 points) with Carto3 v.7® and a PentaRay®, or Ensite X® and a HD Grid mapping catheter. Both mapping systems offer algorithms that allow substrate activation maps to be superimposed and analysed on the surface of a voltage display (i.e. Carto Ripple Maps, or Ensite X activation vectors). DVM is a process that sequentially adjusts the voltage display to highlight scar tissue in areas devoid of Ripple bars, or in areas where activation vectors point in multiple unfathomable directions (‘vector disarray’). This approach is summarised in Figures 1 & 2 and was retrospectively performed in all cases. This alternative scar voltage limit was termed the ‘DVM scar threshold’ (mV). Tissue below this threshold was termed ‘DVM-scar’, and tissue immediately surrounding (up to 0.5mV) was termed "DVM-Borderzone (BZ)". Results Twenty-five patients (mean age 64.4±11.0 years, 88% male, LV ejection fraction 31.8±6.9%, 16.4±8.5 years since infarct) were studied (n=15 Carto; n=10 EnSite). Across all cases, the mean shell area with voltage <0.50 mV was 36.8±20.3 cm2. The mean DVM scar threshold was 0.24±0.07 mV (Carto: 0.22±0.07 mV [range 0.12–0.35 mV]; EnSite: 0.26±0.08 [range 0.18–0.50 mV]). The mean DVM-scar area was 18.4±14.3 cm2, significantly smaller than the traditional 0.50mV value (p=0.0002). In the 8 patients where stable VT was mapped, the VT isthmus sites co-located within the DVM-BZ in all cases, exemplified in the figures. Pace-mapping at the DVM-BZ matched the remaining unmappable VT morphologies. Ablation lesions were retrospectively superimposed onto the DVM map and generally co-located within the DVM-BZ. No ablation was delivered in tissues >0.5mV. At median follow-up of 8.8 months, VT burden significantly reduced (median 3 episodes in 3-months pre vs. 0 post; p<0.001), with 76% of patients VT-free. Conclusion DVM appears to improve the delineation of the post-infarct VT substrate, and is feasible using two commercially-available mapping systems. The mean voltage threshold that differentiated DVM-Scar from BZ tissue was significantly lower than the traditional 0.50 mV scar definition, at 0.24mV, though ranged widely, suggesting that scar thresholds require individualised substrate definition. Targeted ablation of DVM-BZ may be effective at reducing future VT, though requires prospective validation.Figure 1Figure 2

A new high-frequency multilevel inverter effecting cables weight and energy efficiency of aircraft

Purpose Static inverters are very important for the emergency energy distribution system of aircraft and similar machines. At the same time, the electrical energy produced at high frequency for electrical devices is used to reduce the weight of the cables in the aircraft and spacecraft because of the skin effect. In the high-frequency system, a thinner cable cross-section is used, and a great weight reduction occurs in the aircraft. So, fuel economy, less and late wear of the materials (landing gear, etc.) can be obtained with decreasing weight. This paper aims to present the development of a functional multilevel inverter (FMLI) with fractional sinus pulse width modulation (FSPWM) and a reduced number of switches to provide high-frequency and quality electrical energy conversion. Design/methodology/approach After the production of FSPWM for FMLI with a reduced component, which, to the best of the authors’ knowledge, is presented for the first time in this study, is explained step by step, and eight operating states are given according to different FSPWMs operating the circuit. The designed inverter and modulation technique are compared by testing the conventional modular multilevel inverter on different loads. Findings According to application results, it is seen that there is a 50% reduction in cross-section from 100 Hz to 400 Hz with the skin effect. At 1000 Hz, there is a 90% cross-section reduction. The decrease can be in cable weights that may occur in aircraft from 10 kg to 100 kg according to different frequencies. It causes less harmonic distortion than conventional converters. This supports the safer operation of the system. Compared to the traditional system, the proposed system provides more amplitude in converting the source to alternating voltage and increases the efficiency. Practical implications FSPWM is developed for multilevel inverters with reduced components at the high frequency and cascaded switching studies in the power electronics of aircraft. Social implications Although the proposed system has less current and power loss as mentioned in the previous sections, it contains fewer power elements than conventional inverters that are equivalent for different hardware levels. This not only reduces the cost of the system but also provides ease of maintenance. To reduce the cable load in aircraft and create more efficient working conditions, 400 Hz alternative voltage is used. The proposed system causes less losses and lower harmonic distortions than traditional systems. This will reduce possible malfunctions and contribute to aircraft reliability for passengers and cargo. As technology develops, it is revealed that the proposed inverter system will be more efficient than traditional inverters when devices operating at frequencies higher than 400 Hz are used. With the proposed inverter, safer operation will be ensured, while there will be less energy loss, less fuel consumption and less carbon emissions to the environment. Originality/value The proposed inverter structure shows that it can provide energy transmission for electrical devices in space and aircraft by using the skin effect. It also contains less power elements than the traditional inverters, which are equivalent for different levels of hardware.

Effect of electrode configuration on minichannel heat sink with EHD vortex generators

A numerical study has been performed to understand the effects of electrode spacing on thermo-hydraulic performance in a minichannel assisted with electrohydrodynamics (EHD) based active vortex generation. A minichannel design with alternate high voltage and grounded electrodes flushed to the walls of the channel is considered. Multiple cases with different combinations of electrode length and spacing (pitch) at Reynolds number varying from 200 to 1000 are investigated. The numerical framework consisting of the two-way coupled governing equations for flow, thermal, charge, and electric potential fields is developed in the open-source finite-volume framework of OpenFOAM®. Applying an electric field induces the Onsager–Wien effect, producing flow vortices from electrode pairs. The EHD vortices disrupt the inherent laminar flow structure in the minichannel. The flow morphology is characterized by alternate vortex and shear dominant zones near the top and bottom walls. The EHD vortex dominant zones near the channel wall disrupt the laminar boundary layers. Thus, fluid mixing and heat transfer in the minichannel are enhanced. Electrode size and spacing influence the electric field distribution in the flow domain. As a result, electrode length and the inter-electrode spacing notably influenced the flow structure and the resulting heat transfer in the minichannel. The electrode spacing or the pitch decides the number of electrode pairs in the minichannel. An increase in pitch leads to fewer electrode pairs; thus, the electric field intensity is weak. Hence, EHD vortices in configurations with wider electrode spacing are weaker in strength. Longer electrodes produced stronger electric fields due to increased charge accumulation. Therefore, EHD vortices generated by longer electrodes are prominent and influential. The influence of EHD vortices on flow disruption and heat transfer is significant at lower Reynolds numbers. Cases with smaller electrodes perform well at higher Reynolds numbers, whereas usage of bigger electrodes exhibits higher performance at lower Reynolds numbers. Within the parameter space of this study, a minimum of 38.1% and a maximum of 60.6% enhancement in heat transfer is observed. A maximum performance factor of 1.46 is obtained in the present study using an electric current of 30μA with an electric power consumption of 30.1mW, which are notably low. Thus, the results of the present study exhibit that EHD vortex generation using the Onsager–Wien effect is a viable and economical option for thermo-hydraulic performance enhancement in a minichannel. Insights provided in the present study will be helpful to engineers and researchers in designing minichannel heat sinks with EHD-based performance improvement.

Optimizing contact angle changes for droplet actuation by optoelectrowetting (OEW): A numerical multi-parameter analysis

With the transition of fluid-capillary-based “Lab on a chip 1.0″ concepts in analytical chemistry to “Lab on a chip 2.0″ approaches relying on distinct fluid droplets (“digital microfluidics”, DMF), the need for reliable methods for droplet actuation has increasingly come into focus. One possible approach is based on “electrowetting on dielectric” (EWOD). This technique has the disadvantage that any possible desired later positions of the droplets on the chip have to be defined prior to chip realization because one of the EWOD electrode layers has to be structured accordingly. “Optoelectrowetting” (OEW) goes a step further in the sense that the later droplet positions do not have to be known before, and none of the electrode layers has to be structured. Instead, the electrical parameters of the layer sequence can be altered locally by an impinging (and movable) light spot. Although some research groups have succeeded in demonstrating OEW actuation of droplets, the optimization of the relevant parameters of the layer sequence and the droplet – at least half a dozen parameters altogether – is tedious and not straight-forward. In this contribution, for optimization purposes, the equations governing OEW are revisited and altered again, e.g., by numerical implementation of the experimentally well-known saturation of the contact angle change. Additionally, a Nelder-Mead algorithm is applied to find the parameters, on which the optimization has to focus to maximize contact angle changes and, thus, mechanical forces on the droplets. The numerical investigation yields diverse results, e.g., the finding that the droplet’s contact area on the dielectric layer has a strong influence on the contact angle change and the question whether the droplet is pulled or pushed. Moreover, the interplay between frequency and amplitude of the applied rectangular alternate voltage is important for optimization.

Formation of polymerizable layer on a photo-alignment layer of liquid crystal cell and its image sticking characteristics

The effect for polymerizable layer on a vertical-type photo-alignment layer was investigated from the point of image sticking characteristics. Fabrication process of the polymerizable layer is followings; photo-alignment treatment is firstly carried out by exposing polarized ultraviolet (UV) from the oblique direction. After construction of the liquid crystal (LC) cell, the LC material including monomers is injected, and unpolarized UV is exposed for formation of the polymerizable layer. For avoiding pretilt angle shift during the exposure, fast rate constant of polymerization is necessary, and mixed monomers 4,4’-dimethacryloyl-oxy-biphenyl (4,4’-DMABiph) and 4,4’-dimethacryloyl-oxy-benzilketal (4,4’-DMABzk) are appropriate for obtaining small level of image sticking parameters. As the image sticking parameters, residual direct current voltage (V rDC) and difference in pretilt angle (Δtilt) before and after application of alternate current voltage were evaluated, and the results of V rDC and Δtilt indicated that 6% 4,4’-DMABzk in the mixed monomers 4,4’-DMABiph and 4,4’-DMABzk would be useful for obtaining the small level of image sticking.

Coronary artery lipid accumulation prevention through vibrating piezo electric nano plates embedded in smart stent.

Considering the lipid concentration and side effects regarding the stents used by surgeons, a new heart stent model is proposed. In the new stent, a few piezo plates are designed and attached to the stents by which release of the lipids can take place due to the applied alternative voltages. Due to the vibrations of small-scale piezoelectric plates, the deposition of low-density-lipoproteins (LDL) floating in the blood flow in the coronary arteries is prevented. Small-scale effects are considered using nonlocal elasticity theory, and the interaction between fluid and solid is modeled using the Navier-Stokes equation. The effect of fluid parameters as well as applied voltage and geometry structure is reported. Developing of smart stents maybe the key for prevention of short time conventional stents failure.

Hybrid Multi-Vector Modulated Model Predictive Control Strategy for Voltage Source Inverters Based on a New Visualization Analysis Method

Conventional model predictive control (MPC) strategy for voltage source inverters has large current ripple since only one voltage vector is applied in each control cycle. Although the multi-vector modulated MPC strategy can reduce the current ripple, its lack of theoretical basis makes its optimality questionable. To solve this problem, a new visualization analysis method is proposed in this article to evaluate the effectiveness of the conventional multi-vector modulated MPC strategy, based on which a new hybrid multi-vector modulated MPC strategy is further presented to improve the current control performance. First, the principle of the proposed visualization analysis method is introduced, based on which it is verified that the conventional multi-vector modulated MPC has better control performance than the single-vector MPC. Second, based on the proposed visualization analysis method, it is also found that both the conventional double-vector and triple-vector modulated MPC strategies cannot achieve optimal control. Thus, a new hybrid multi-vector modulated MPC strategy is further proposed. By selecting an optimal voltage vector from 18 alternative voltage vector combinations, the current control performance is improved. Detailed comparative experimental results based on experimental platform and StarSim hardware-in-the-loop platform validate the effectiveness of the proposed hybrid multi-vector modulated MPC strategy.

Stability Impacts of an Alternate Voltage Controller (AVC) on Wind Turbines with Different Grid Strengths

This paper studies the stability impact of the alternate voltage controller’s (AVC) low-pass filter (LPF) in a wind turbine’s grid-connected voltage source converter (VSC). A small-signal model of the grid-connected converter is designed with a grid-following synchronization control. More specifically, the non-linear state-space model of the grid-connected converter was developed, including the dynamics of both the inner and outer control loops of the converter, the dynamics of the elements of the electrical system, as well as the digital time delay. An eigenvalue-based stability analysis gives insight into the stability impacts of the outer-loop controllers. It is proven that the cutoff frequency of the AVC’s LPF affects the phase-locked loop (PLL) and AVC bandwidths of instability, as well as the corresponding critical oscillation frequencies. This phenomenon is observed in both weak and strong grids. Consequently, the small-signal stability regions of the PLL and AVC bandwidth can be identified for the range of the AVC’s LPF cutoff frequency under study. The stability regions of the PLL and AVC, which are obtained from the small-signal model, as well as the determined critical oscillation frequencies, are validated through time domain simulations and fast-Fourier transformation (FFT) analysis.

Third-Harmonic-Type Modulation Minimizing the DC-Link Energy Storage Requirement of Isolated Phase-Modular Three-Phase PFC Rectifier Systems

A three-phase ac/dc converter with high-frequency isolation can be realized as a monolithic three-phase or as a phase-modular system by combining three single-phase Power Factor Correction (PFC) rectifier modules with individual isolated dc-dc converters. Advantageously, for a phase-modular system the module configuration can be changed depending on the instantaneous input-output voltage ratio (i.e., a star-(Y)- or a delta-(Δ)-arrangement such that wide voltage ranges can be covered without a massive over-dimensioning of the main power components. However, the main disadvantage of a phase-modular converter realization is the fact that the input power of each PFC rectifier module pulsates at twice the mains frequency (which is inherent to single-phase power conversion) such that large dc-link capacitors are required. Recent literature predicts a substantial power pulsation reduction enabled by means of third-(3 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rd</sup> )-harmonic injection modulation which is applicable for the Y-connection (where a common-mode (CM) / zero-sequence (ZS) voltage is injected), and for the Δ-connection of the three single-phase PFC rectifier modules (where a CM / ZS current is injected). This changes the distribution of the power flow in the three-phase system and the power pulsation is shifted to higher frequencies. This paper experimentally verifies and extends the dc-link energy storage requirement reduction of the 3 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rd</sup> -harmonic injection modulation concept: In a first step, the derivation of the harmonic injection concept is recapitulated and suitable control methods are discussed for both CM voltage (Y-arrangement) and CM current (Δ-arrangement) injection. Further, an alternative CM voltage injection strategy with simplified reference generation based only on the instantaneous grid voltage measurements is presented and compared to the pure 3 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rd</sup> -harmonic injection modulation. Measurement results obtained from a 6 kW prototype reveal a dc-link voltage variation and/or energy buffering reduction by up to 38.6 % enabled by the harmonic injection modulation compared to conventional operation without 3 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rd</sup> -harmonic injection modulation.

A prototype for water content measurement in partially saturated soils

The paper presents the technological set-up and calibration of a system based on impedance spectroscopy for measuring water content in partially saturated soils. The technique adopted is relatively recent in geotechnical practice; it is used herein to characterize the electrical response of a soil specimen among two conducting electrodes upon application of an alternate voltage and the measurement of the current intensity resulting across the specimen, for frequency values in the range [500 Hz – 50 kHz]. The complex impedance of the soil specimen is due to both resistance, i.e. opposition to current, and reactance, i.e. tendency of the system to yield and retrieve energy, and it depends on the specimen water content. An on-purpose experimental plan has been conceived and is presented herein, aimed at building a calibration function for deriving the water content in pyroclastic soils from the impedance measurements. Preliminary results reveal an adequate level of repeatability of the measurements and suggest the existence of a monotonic correlation between the impedance modulus and the gravimetric water content.

Robust Allocation of FACTS Devices in Coordinated Transmission and Generation Expansion Planning considering Renewable Resources and Demand Response Programs

Nowadays, the use of demand response programs (DRPs) in a variety of long-term and short-term planning problems has been explored. In this paper, a generation and transmission expansion planning (GTEP) model along with FACTS device allocation is presented. Furthermore, demand response programs are taken into account for more load flexibility. The proposed model is presented as a multi-objective minimizing problem considering emission, cost, and voltage security index. Furthermore, the conventional Pareto optimization is adopted using fuzzy weighted sum method (FWSM) to achieve a single-objective model. The final problem is constrained by equations of alternative current power flow, operation and voltage security limits, planning model of shunt FACTS devices, and operation of the DRP. Adaptive robust optimization (ARO) is used to reach suitable models for the active power of renewable resources and power consumption. As a main search algorithm, a hybrid combination of water cycle algorithm (WCA) and ant lion optimization (ALO) is proposed to find the optimum solution with a small standard deviation. The problem is tested on different standard IEEE systems, and the results validate the operation and network security improvement due to optimal location of FACTS devices. According to the results, the economic and environmental status of the network has also improved.

Corrosion resistance of NiCr(Ti) coatings for metallic bipolar plates

In the present work, the electrochemical behavior of various NiCr(Ti) protective coatings manufactured using laser cladding were studied. The coatings were obtained by adding Ti in different wt% to the NiCr-based feedstock material. Thus, the coatings are investigated as new materials with potential applications for metallic bipolar plates used in polymer electrolyte membrane fuel cell (PEMFC) applications. The electrochemical tests were carried out at room temperature in a solution of H2SO4 0.5 M (pH = 0.3) + 2 ppm F- used as electrolyte. Chronoamperometry measurements were first employed in simulated anodic and cathodic conditions for 6 h. Afterward, electrochemical impedance spectroscopy (EIS) studies were performed in the frequency range of 100 mHz − 100 kHz with an alternative voltage amplitude of 10 mV. The recorded EIS data were fitted with an equivalent electrical circuit (EEC). Furthermore, the potentiodynamic polarization curves were recorded at a scan rate of 1 mV/s in the potential range of −250 mV to + 250 mV versus to the OCP values. Finally, the obtained data were analysed and compared. The studies showed that the corrosion behavior of the studied materials increase with the content of Ti addition.

Formation of polymer-sustained-alignment layer of a liquid crystal cell exposed by light-emitting-diode visible light

A new fabrication technique and mixed monomers for a polymer-sustained-alignment liquid-crystal (PSA-LC) cell were proposed in this study. The proposed process for formation of the PSA layer is exposing visible light for polymerization instead of exposing ultraviolet (UV) light. The backlight consisted of light emitting diode (LED) for the LC display (LCD) was used as the source of the visible light, and the mixed monomers were 2,7-dimethacryloyl-oxy-phenanthrene (2,7-DMAPhen) and 4,4’-dimethacryloyl-oxy-benzil (4,4’-DMABzl). Since the monomer 4,4’-DMABzl could generate radicals by a hydrogen abstraction reaction under exposure of the visible light, the PSA layer was formed under the LED-backlight exposure through an intermediary of a polarizer. The fabricated PSA-LC cell showed equal level of voltage holding ratio, residual direct current voltage, and difference in pretilt angle before and after application of an alternate current voltage to the PSA-LC cell fabricated by the UV light exposure. Therefore, we expect that future PSA-LCD would be fabricated without exposure of the UV light.

Image sticking and long-term stability of polymer-sustained-alignment liquid crystal cell produced from the mixed monomers containing phenanthrene- and benzophenon-moieties

As a model of polymer-sustained-alignment liquid crystal display (PSA-LCD), the LC cells having the PSA layers (PSA-LC cells) formed by mixed monomers of 2,7-dimethacryloyl-oxy-phenanthrene (2,7-DMAPhen) and 4,4’-dimethacryloyl-oxy-benzophenon (4,4’-DMABenz) were fabricated, and image sticking parameters and long-term stability under LED-backlight exposure were investigated. Residual direct current voltage (V rDC) and difference in pretilt angle (Δtilt) before and after application of alternate current voltage were evaluated as the image sticking parameters. The V rDC was improved with the addition of a small amount of 4,4’-DMABenz because the concentrations of radical and/or ion in the LC layer had decreased significantly. It was shown that with the addition of 3.8 wt% of 4,4’-DMABenz in the mixed monomers, V rDC can be kept low without increasing Δtilt. Voltage holding ratio was maintained high under the LED-backlight exposure for 1,000 h, indicating that the PSA-LC cell shows high long-term stability. Hence we expect that the proposed PSA-LC cell would be useful for high luminance LCDs.

A Non-Isolated DC-DC Modular Multilevel Converter with Proposed Middle Cells

Unlike the modular multilevel converter (MMC) topology operated under the rectifier or inverter modes, control of the balanced state for the submodule (SM) capacitor voltage has emerged as the key issue for DC-DC MMCs. This is mainly caused by no balanced alternative powers being used for balancing SM capacitor voltages, which can be absorbed from the input or output DC sides of the converter. Typically, the alternative voltages and currents should be injected to achieve SM capacitor voltage balance in the DC-DC MMC. However, this solution is based on the cost of adopting the bulky LC filter components. For interconnecting different DC voltages in medium-voltage applications, this paper presents a non-isolated DC-DC MMC equipped with the proposed middle cells. It is intended to achieve DC voltage conversion without adopting bulky passive LC filters. On the one hand, the alternative currents, used for balancing the SM capacitor voltages, are arranged for flowing only within the phase legs of the proposed DC-DC MMC without disturbing the input current. On the other hand, through appropriate control of the middle cells, compensated components can be developed to eliminate the undesirable voltages on the output DC side. The middle cells of the proposed DC-DC MMC are supplied with the function of the active filter, which enables the DC-DC MMC system to escape the bulky LC components. Through theoretical analysis and a control strategy, the proposed DC-DC MMC has been analyzed comprehensively. Finally, the simulation and experimental results are verified to evaluate the effectiveness of the proposed DC-DC MMC.

On the Dynamic Stability of Gold Electrodes Exposed to Alternative Voltages in Microfluidic Systems

While gold is a stable metal in water, it is not uncommon for microfluidic experimenters using biologically-relevant fluids such as phosphate-buffered saline (PBS) to witness their precious gold electrodes quickly vanish from the microchannel once the voltage exceeds a few volts. This stability issue concerns multiple fields where high voltage provides superior actuator or sensor performance, such as resistive pulse sensing (RPS), electroosmosis, electrowetting and so on. One solution to protect metallic electrodes is using alternative voltages (AV) as opposed to continuous voltages. After recalling that gold dissolution is enabled by the chloride ions present in most biologically-relevant solutions, we explore the stability conditions of the electrodes for voltages from 1 to 20 V pp (Peak to Peak voltage amplitude), actuation frequencies between 0 and 5 kHz, and for various pH and electrolytes (NaCl, Na2SO4, HCl). We find that the dissolution threshold voltage depends on the ratio of reaction to diffusion rate given by the Damkhöler number Da. In mass-transfer limited regime, the dissolution threshold is independent of the frequency, whereas the dissolution voltage is observed to grow as Da−1/2 in the reaction limited regime. These findings provide guidelines to design more reliable electrowetting, electroosmosis, dielectrophoresis and resistive pulse sensing devices.

Reconfigurable Battery for Charging 48 V EVs in High-Voltage Infrastructure

48 V is emerging as a safe-to-touch alternative voltage level for electric vehicles (EVs). Using a low- instead of a high-voltage drive train reduces isolation efforts, eliminates the risk of electric shock, and thus increases the system safety. In contrast, fast charging of a 48 V battery would require very high currents and is incompatible with the widely established high-voltage electric vehicle charging infrastructure. Instead of employing additional on board power converters for fast charging, the concept of a reconfigurable battery is presented. A small-scale prototype system is designed consisting of eight 48 V lithium iron phosphate battery modules. In series configuration, they can be charged at 460 V with up to 25 A. In 48 V parallel configuration, the peak discharge current is up to 800 A. The MOSFET-based reconfiguration system also operates as a module charge balancer during high-voltage charging. The cost overhead for the reconfiguration system is estimated to 3% for a scaled-up full size EV. Due to the additional reconfiguration switch resistances, the simulation of a 48 V 75 kW electric vehicle in the World harmonized Light-duty vehicles Test Procedure showed a performance reduction of 0.24%.

KHz Plasma Pencil

Recently several investigators reported on various devices of generating cold plasma jets at atmospheric pressure. A pulsed plasma source developed and reported, the plasma pencil, is one of them. This device is capable of generating a cold plasma plume several centimeters in length using a DC pulsed high voltage source. In this study, kHz alternative current voltage (18 kV-15 kHz) was applied to the electrodes similar to the electrode system of the plasma pencil instead of direct current pulse voltage and a 2-3 cm long plasma jet was produced in an air using the helium gas. This new plasma jet device named as the kHz plasma pencil. The jets produced by the kHz plasma pencil are as cold as room temperature. The optical emission spectrum of the jet of the kHz plasma pencil and the change of the jet length with the gas flow rate have been investigated. Unlike the plasma pencil, the kHz plasma pencil produces jet in two different regimes as filamentary and diffusive and it emits more radiation in the UV range. Preliminary results show that the dynamics of the kHz plasma pencil are also different from the plasma pencil. Keywords: atmospheric pressure cold plasma jet, kHz, plasma pencil, Emission spectrum.

Килогерцевый плазменный карандаш

Recently several investigators reported on various devices of generating cold plasma jets at atmospheric pressure. A pulsed plasma source developed and reported, “the plasma pencil”, is one of them. This device is capable of generating a cold plasma plume several centimeters in length using a DC pulsed high voltage source. In this study, kHz alternative current voltage (18 kV-15 kHz) was applied to the electrodes similar to the electrode system of the plasma pencil instead of direct current pulse voltage and a 2-3 cm long plasma jet was produced in an air using the helium gas. This new plasma jet device named as the “kHz plasma pencil”. The jets produced by the kHz plasma pencil are as cold as room temperature. The optical emission spectrum of the jet of the kHz plasma pencil and the change of the jet length with the gas flow rate have been investigated. Unlike the plasma pencil, the kHz plasma pencil produces jet in two different regimes as filamentary and diffusive and it emits more radiation in the UV range. Preliminary results show that the dynamics of the kHz plasma pencil are also different from the plasma pencil.