Asymmetric Pulse Research Articles

Optimization of the structure of the vibratory feeders with electromagnetic vibrating drive and a combined oscillating system

Vibration loading devices are widely used in various branches of mechanical engineering to load piece blanks of automatic machines and automatic lines as well as robotic systems, automated systems and flexible automated production. Vibration devices for transportation and loading of miniature, small and medium-sized products are the most widely used. In the study of vibration transport, one of the most important issues is the study of the dependence of the average transport speed on the parameters of the oscillation of the carrier tray. It is most convenient to conduct a study in dimensionless quantities when expressing the speed of transportation through the speed coefficient, which shows how much the real speed of the part is close to the maximum speed of the transporting surface. For vibration conveyors and vibratory feeders with non-separable transportation parts using modes that are implemented mainly elliptical or asymmetric longitudinal vibrations of the bearing plane. Asymmetric laws of motion of vibration conveyors provide the highest performance in a non-invasive mode of movement of billets, but such conveyors have found a very limited distribution due to the complexity of the implementation of asymmetric vibrations by simple means. To implement the asymmetric laws of oscillation of the working body and thereby increase the speed coefficient used as power sources generators asymmetric types of oscillations, which have a very high cost. Modern production involves the creation of new models of machines with high technical and economic indicators, therefore, improving the efficiency of existing equipment and the development of new schemes of machines is an important task for designers and manufacturers of technological equipment, as the minimum improvement of its technological and operational performance can lead to a tangible economic effect. To solve this problem, the authors developed a new design of vibration hopper feeder, which carries out the transportation of products in the mode without throwing with an asymmetric law of oscillation of the carrier tray when connected directly to the AC network without using an asymmetric pulse generator and conducted an experimental study of its design to determine the speed coefficient during vibration transportation.

High‐voltage pulse generator using sequentially charged full‐bridge modular multilevel converter Sub‐modules, for water treatment applications

This paper proposes a new high-voltage pulse generator (PG) fed from a low-voltage DC supply Vs , which charges one arm of N series-connected full-bridge (FB) modular multilevel converter (MMC) sub-module (SM) capacitors sequentially, through a resistive-inductive branch. By utilising FB-SMs, the proposed PG is able to generate bipolar rectangular pulses of peak NVs and unipolar rectangular pulses of either polarity, at high repetition rates. Asymmetrical pulses are also possible. The proposed topology is assessed via simulation and scaled-down experimentation, which establish the viability of the topology for water treatment applications.

Increasing the application fields of magnesium by ultraceramic®: Corrosion and wear protection by plasma electrolytical oxidation (PEO) of Mg alloys

Due to its low density and high strength, magnesium has increasing potential in the lightweight area, especially as a material for structural components. To address the corrosion problem, which is the main issue with using Mg alloys in the automotive industry, as well as to address wear problems, a new technique that uses an asymmetric potential pulse waveform to form nanocrystalline PEO (plasma electrolytical oxidation) coatings on Mg substrates, especially on sheet Mg plates, is developed in this study.The results of the analysis of PEO coatings on different sheet Mg alloy plates, which are characterized by electrochemical analysis methods including electrochemical impedance spectroscopy and potentiodynamic polarization are presented in this study. Furthermore, the coatings are characterized regarding their morphology and wear resistance, while varying the coating thickness by different processing times. A further improvement of the applied waveform by an on-top modification of the pulse signal leads to higher corrosion resistance as well as to a better performance in the tribological testing.

A Complete Analytical Solution for the On and Off Dynamic Equations of a TaO Memristor

In this brief we provide a complete analytical model for the time evolution of the state of a real-world memristor under any dc stimulus and for all initial conditions. The analytical dc model is derived through the application of mathematical techniques to Strachan’s accurate mathematical description of a tantalum oxide nano-device from Hewlett Packard Labs. Under positive dc inputs the state equation of the Strachan model can be solved analytically, providing a closed-form expression for the device memory state response. However, to the best of our knowledge, the analytical integration of the state equation of the Strachan model under dc inputs of negative polarity is an unsolved mathematical problem. In order to bypass this issue, the state evolution function is first expanded in a series of Lagrange polynomials, which reproduces accurately the original model predictions on the device off-switching kinetics. The solution to the resulting state equation approximation may then be computed analytically by applying methods from the field of mathematics. Our full analytical model matches both qualitatively and quantitatively the tantalum oxide memristor response captured by the original differential algebraic equation set to typical stimuli of interest such as symmetric and asymmetric pulse excitations. It is further insensitive to the convergence issues that typically arise in the numerical integration of the original model, and may be easily integrated into software programs for circuit synthesis, providing designers with a reliable tool for exploratory studies on the capability of a certain circuit topology to satisfy given design specifications.

On-field Management of Shoulder and Elbow Injuries in Baseball Athletes.

The goal of this review article is to help medical personnel of all levels and backgrounds identify and appropriately manage on-field acute shoulder and elbow injuries in the baseball athlete. This article discusses the most common acute shoulder and elbow injuries in baseball players along with recommendations for appropriate on-field management. Shoulder and elbow injuries are very common in baseball players and can be problematic because of the unique demands placed on the shoulder and elbow during the throwing and swinging motions. While many shoulder and elbow injuries in baseball players are chronic, some acute injuries, including dislocations and fractures, require urgent on-field management. Evaluation should begin with a broad assessment to rule out life-threatening emergencies prior to performing a neurovascular evaluation of the affected extremity. Red-flag signs during examination, such as difficulty breathing, asymmetric pulses, weakness, and limb discoloration, require emergent treatment. In the absence of an emergency, the evaluating medical team should complete a basic neurovascular exam before performing any further on-field care. Contusions, dislocations, and fractures are the most commonly seen acute shoulder and elbow injuries in baseball athletes. Athletic trainers and physicians caring for these athletes should be familiar with these injuries and their appropriate on-field management.

Asymmetrical seismic pulses before a large earthquake

This study is concerned with the behavior of seismic noise in the period range of a few minutes based on records made by broadband IRIS stations before the catastrophic earthquake of March 11, 2011 in Japan. A formalized technique was used to identify discrete asymmetrical pulses whose amplitudes were an order of magnitude higher than the noise level and that were spaced at intervals longer than 30 minutes. The frequency of pulses at the MAJO station on Honshu 400 km of the earthquake epicenter increased on January 30, 2011 and remained high until March 2, 2011. No such phenomena have been observed at MAJO in the same periods during the preceding 15 years, when the station was in regular operation. The records of other similar stations farther than 1700 km from the epicenter were not found to contain increases in the rate of pulses. We believe that these asymmetrical pulses were due to dilatancy in shallow crustal layers beneath the MAJO station.

Stimulation strategies for selective activation of retinal ganglion cell soma and threshold reduction

Objective. Retinal prosthetic implants restore partial vision to patients blinded due to outer retinal degeneration, using a camera-guided multielectrode array (MEA) that electrically stimulates surviving retinal neurons. Commercial epi-retinal prostheses use millisecond-scale charge-balanced, symmetric, cathodic-first biphasic pulses to depolarize retinal ganglion cells (RGCs) and bipolar cells (BCs), frequently creating oblong perceptions of light related to axonal activation of RGCs. Stimulation strategies that avoid axonal stimulation and decrease the threshold of targeted neurons may significantly improve prosthetic vision in terms of spatial resolution and power efficiency. Approach. We developed a virus-transduced genetically encoded calcium indicator (GECI) GCaMP6f and microscopy platform for calcium imaging to record the neural activity from RGCs at single-cell resolution in wholemount retinas. Multiple stimulation paradigms were applied through a microelectrode array (MEA) with transparent indium tin oxide electrodes. The evoked neuronal activities were converted to corresponding 2D calcium imaging transient pattern and spatial threshold map to identify the ideal focal response which corresponds to optimal percept in patient. Main results. The proposed optical system with GCaMP6f is capable of recording from population of mouse RGCs in real time during electrical stimulation with precise location information relative to the stimulation sites. Optimal duration and phase order of pulse were identified to avoid axonal stimulation and selectively activate targeted RGC somas, without requiring a significant increase in stimulation charge. Additionally, we show that reduced stimulus threshold can be achieved with the special design of asymmetric anodic-first pulse. Significance. Our findings support the possibility of manipulating the responses of RGCs through varying the stimulation waveform. Focal response can be achieved with relative short duration (⩽120 μs) pulses, and can be improved by reversing the standard phase order. The RGCs threshold can be significantly reduced by 33.3%–50% in terms of charge through applying hyperpolarizing pre-pulses with a 20:1 ratio (pre-pulse:stimulus pulse). The results support the future retinal prosthesis design that potentially forms more ideal shape perception with higher spatial resolution and power efficiency.

Effect of kHz electrical stimulation on hippocampal brain slice excitability and network dynamics

Understanding the cellular mechanisms of kHz electrical stimulation is of broad interest in neuromodulation including forms of transcranial electrical stimulation (tES), interferential stimulation, and high-rate spinal cord stimulation (SCS). Yet, the well-established low-pass filtering by neuronal membrane suggests minimal neuronal polarization in response to charge-balanced kHz stimulation. The hippocampal brain slice model is among the most characterized systems in neuroscience and exhaustively studied in screening the effects of electrical stimulation. Testing for changes in neuronal excitability by kHZ electrical stimulation in brain slices is a litmus test for feasibility and mechanism. High-frequency electric field of varied amplitudes (1-120 V/m), waveforms (sinusoidal, symmetrical pule, asymmetrical pulse) and frequencies (1 or 10 kHz) were tested. Single and paired-pulse field excitatory post-synaptic potentials (fEPSP) in CA1 were measured before, during, and after stimulation in radial and tangential direction and for different application time (30 s acute,30 min). Small polarization of individual neurons leads to changes in network dynamic through nonlinear amplification mechanisms at the cellular and/or network level resulting a more sensitive system to an exogenous electric field. Effect of kHZ stimulation on ongoing endogenous network activity was evaluated in carbachol-induced gamma oscillation of CA3a region of rat hippocampal slices. Extracellular local field potential oscillations were recorded and analyzed before, during and after 2s of kHZ stimulation. In order to fully investigate the opportunities in kHZ stimulation, ongoing work on kHz stimulation should consider different mechanisms of action absent in this tested system and different cortical and spinal neurons.

Off-State Operation of a Three Terminal Ionic FET for Logic-in-Memory

We demonstrate a novel concept for low power compute-in-memory applications in a room temperature fabricated ZnO/Ta <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> thin film transistor. By writing during the off-state, the device power consumption is reduced to nW despite a large L/W ratio. A thinner gate insulator thickness gives higher on/off ratio, nevertheless this reduces the retention time. The on/off ratio in the thicker oxide can be improved by asymmetric voltage pulses of higher magnitude in the off state without affecting power consumption. Benchmarked against other ReRAM devices, the device shows a competitive 8 nJ per transition, which allows a reduction in power consumption compared to a filamentary device. Such non-filamentary devices have closer similarity to biological synapses on account of slow operating speed.

Colour tuning and enhancement of gel-based electrochemiluminescence devices utilising Ru(ii) and Ir(iii) complexes.

Combining luminophores in ratios that compensate for energy transfer provides a readily selectable range of new emission colours for gel-based electrochemiluminescence devices (ECLDs). A novel blue ECLD luminophore is also introduced and shown to enhance the intensity of the conventional green emitter through a mixed annihilation ECL mechanism. Peak-to-peak voltages were minimised using asymmetric potential pulse sequences, which increased the longevity of the ECLD emission.

Numerical Investigation on the Transient Evolution Mechanisms of Nonlinear Phenomena in a Helium Dielectric Barrier Discharge at Atmospheric Pressure

In this paper, the evolution and transition mechanisms of typical nonlinear phenomena in an atmospheric pressure helium dielectric barrier discharge (DBD) are investigated from the perspective of transient evolution properties through fluid modeling. By gradually up-regulating the interelectrode gap width, the discharge (steady state) evolves from symmetric single-period (SP1), through asymmetric single-period (AP1), into Period-2 (P2) state. Similar evolution trace can also be obtained when increasing the driving frequency. Right after the initial breakdown, the discharge goes through several transient periods featuring unstable asymmetric current pulses before the establishment of steady-state discharge. As the bifurcation parameter increases in excess of the critical value, the discrepancy between the seed electron level of positive and negative discharges accumulates over the transient periods, switching the discharge into AP1 state. After then, a further elevation in the gas gap width (or driving frequency) leads to the generation of a “moderate intensity” positive pulse. With the “moderate intensity” positive pulse and a stronger positive pulse emerging alternatively in the temporal waveform sequence, the discharge evolves into P2 state. Finally, based on the transient evolution mechanisms, a preliminary state-controlling method regarding the use of a first-peak-leveled applied voltage is proposed, which may shed light on the modification of nonlinear states in some practical DBD application scenarios.

Asymmetrical Seismic Pulses before a Large Earthquake

Asymmetrical Seismic Pulses before a Large Earthquake

Asymmetric Pulse Frequency Modulation With Constant On-Time for Series Resonant Converter in High-Voltage High-Power Applications

The series resonant converter (SRC), controlled by the traditional pulse frequency modulation (PFM) with constant on-time, can operate in discontinuous conduction mode (DCM) and is applicable for high-voltage high-power applications with the requirement of a wide output voltage range. However, in the traditional PFM with constant on-time, the resonant capacitor voltage will be higher than the input voltage during the zero current stage, leading to a higher maximum magnetic flux density (MMFD) case. To avoid this, a novel asymmetric pulse frequency modulation (APFM) with constant on-time is proposed for SRC operating in DCM, where the MMFD of transformer core varies linearly with the operating frequency and output voltage among the whole output voltage range. The high-power transformer can be designed according to highest operating frequency and the transformer turns ratio can be designed to be small. Furthermore, the proposed APFM leads to smaller peak current for all switches and fully zero-current-switching can be achieved. The output power and voltage can be still regulated, meeting the high-voltage high-power applications. For the proposed APFM, there are four different driver combinations with exact the same effects and advantages. The theoretical analysis has been validated by the established simulation model and experimental platform.

Control of soliton self-frequency shift dynamics via Airy soliton interaction.

We investigate Airy-soliton interaction in a nonlinear fiber with Raman effect. We find that Airy solitons may fuse upon interaction at a position that can be controlled by a proper engineering of the Airy tail direction. This control allows us to generate Airy solitons with varying deceleration. At variance with the case of two solitons interaction, Raman-induced soliton self-frequency shift (SSFS) is strongly enhanced when the leading soliton is replaced with the accelerating Airy pulse and slightly suppressed for the decelerating one. These notable features are ascribed to the unique properties of asymmetrical Airy pulses with a switchable direction of the oscillatory tails. We show the way these processes are uncovered unambiguously by cross-correlation frequency resolved optical gating. We also investigate the impact of chirp imposed on the input pulse on the SSFS dynamics. Our results not only provide a new way to manipulate the SSFS, but may help to improve the control of soliton fusion events during supercontinuum generation, optical rogue waves and giant dispersive waves formation.

Resonant Hybrid Flyback, a New Topology for High Density Power Adaptors

In this article, an innovative power adaptor based on the asymmetrical pulse width modulation (PWM) flyback topology will be presented. Its benefits compared to other state-of-the-art topologies, such as the active clamp flyback, are analyzed in detail. It will also describe the control methods to achieve high efficiency and power density using zero-voltage switching (ZVS) and zero-current switching (ZCS) techniques over the full range of the input voltage and the output load, providing comprehensive guidelines for the practical design. Finally, we demonstrate the convenience of the proposed design methods with a 65 W adaptor prototype achieving a peak efficiency of close to 95% and a minimum efficiency of 93.4% at full load over the range of the input voltage, as well as a world-class power density of 22 W/inch3 cased.

Whole-slice mapping of GABA and GABA+ at 7T via adiabatic MEGA-editing, real-time instability correction, and concentric circle readout

An adiabatic MEscher-GArwood (MEGA)-editing scheme, using asymmetric hyperbolic secant editing pulses, was developed and implemented in a B1+-insensitive, 1D-semiLASER (Localization by Adiabatic SElective Refocusing) MR spectroscopic imaging (MRSI) sequence for the non-invasive mapping of γ-aminobutyric acid (GABA) over a whole brain slice. Our approach exploits the advantages of edited-MRSI at 7T while tackling challenges that arise with ultra-high-field-scans. Spatial-spectral encoding, using density-weighted, concentric circle echo planar trajectory readout, enabled substantial MRSI acceleration and an improved point-spread-function, thereby reducing extracranial lipid signals. Subject motion and scanner instabilities were corrected in real-time using volumetric navigators optimized for 7T, in combination with selective reacquisition of corrupted data to ensure robust subtraction-based MEGA-editing.Simulations and phantom measurements of the adiabatic MEGA-editing scheme demonstrated stable editing efficiency even in the presence of ±0.15 ppm editing frequency offsets and B1+ variations of up to ±30% (as typically encountered in vivo at 7T), in contrast to conventional Gaussian editing pulses. Volunteer measurements were performed with and without global inversion recovery (IR) to study regional GABA levels and their underlying, co-edited, macromolecular (MM) signals at 2.99 ppm. High-quality in vivo spectra allowed mapping of pure GABA and MM-contaminated GABA+ (GABA + MM) along with Glx (Glu + Gln), with high-resolution (eff. voxel size: 1.4 cm3) and whole-slice coverage in 24 min scan time. Metabolic ratio maps of GABA/tNAA, GABA+/tNAA, and Glx/tNAA were correlated linearly with the gray matter fraction of each voxel. A 2.15-fold increase in gray matter to white matter contrast was observed for GABA when enabling IR, which we attribute to the higher abundance of macromolecules at 2.99 ppm in the white matter than in the gray matter.In conclusion, adiabatic MEGA-editing with 1D-semiLASER selection is as a promising approach for edited-MRSI at 7T. Our sequence capitalizes on the benefits of ultra-high-field MRSI while successfully mitigating the challenges related to B0/B1+ inhomogeneities, prolonged scan times, and motion/scanner instability artifacts. Robust and accurate 2D mapping has been shown for the neurotransmitters GABA and Glx.

Accuracy of Distance Determination by Range–Intensity Correlation Methods for Nonrectangular Illuminating Pulse Shape

We have analyzed the accuracy of distance determination by range–intensity correlation methods in the case of an arbitrary pulse shape. We show that the absolute error is proportional to the pulse duration τL. For a trapezoidal pulse shape, which is a reasonable approximation of the real pulse shape, we obtain an analytical estimate of the extremal error and the distance at which is it realized. The maximum error in the distance obtained in calculations with trapezoidal pulses corresponds to an extremely asymmetric pulse and is a little over 10% of the spatial pulse length τLc, where c is the speed of light. Symmetric pulses give an error due to nonrectangularity of the pulse that is smaller by a factor of ~2. Since a trapezoidal shape can qualitatively reproduce the shape of practically any real pulse, probably the trapezoidal pulse model gives an estimate of the highest possible error.

Invited Article: Spectral focusing with asymmetric pulses for high-contrast pump–probe stimulated Raman scattering microscopy

Purely label-free imaging to directly monitor small molecules in a biological organism is still challenging despite recent technical advancements. Time-resolved pump–probe coherent Raman scattering microscopy is a promising label-free approach to increase chemical specificity. However, conventional time-resolved methods involve a compromise between three conflicting requirements: high spectral resolution, low background levels, and high sensitivity. Here, we present an advanced spectral-focusing technique using asymmetric pulses produced by nonlinear chirping and demonstrate its performance in pump–probe phase-modulated stimulated Raman scattering microscopy. In addition, we report for the first time a novel frequency-scanning spectral-focusing system using tunable bandpass filters. Our concept uses the filters not only as a frequency allocation tool for the probe pulses but also as a pulse-shaping tool that provides a strong nonlinear chirp. The spectral resolution and signal-to-noise ratio are greatly improved by highly efficient time-resolved detection using asymmetric spectrally focused probe pulses. We achieve a spectral resolution of ∼25 cm−1, a reduced nonresonant background level on the order of 10−8, and a detectable concentration limit of 0.01% dimethyl sulfoxide/water solution (1.5 mM). Using this method, we demonstrate high-contrast imaging of a small-molecule drug in a tissue. These advancements will allow time-resolved coherent Raman microscopy to be used as a practical drug-imaging tool for biomedical sciences.

The interphase interval within a bipolar nanosecond electric pulse modulates bipolar cancellation.

Nanosecond electric pulse (nsEP) exposure generates an array of physiological effects. The extent of these effects is impacted by whether the nsEP is a unipolar (UP) or bipolar (BP) exposure. A 600 ns pulse can generate 71% more YO-PRO-1 uptake compared to a 600 ns + 600 ns pulse exposure. This observation is termed "bipolar cancellation" (BPC) because despite the BP nsEP consisting of an additional 600 ns pulse, it generates reduced membrane perturbation. BPC is achieved by varying pulse amplitudes, and symmetrical and asymmetric pulse widths. The effect appears to reverse by increasing the interphase interval between symmetric BP pulses, suggesting membrane recovery is a BPC factor. To date, the impact of the interphase interval between asymmetrical BP and other BPC-inducing symmetrical BP nsEPs has not been fully explored. Additionally, interpulse intervals beyond 50 μs have not been explored to understand the impact of time between the BP nsEP phases. Here, we surveyed different interphase intervals among symmetrical and asymmetrical BP nsEPs to monitor their impact on BPC of YO-PRO-1 uptake. We identified that a 10 microsecond (ms) interphase interval within a symmetrical 600 ns + 600 ns, and 900 ns + 900 ns pulse can resolve BPC. Furthermore, the interphase interval to resolve asymmetric BPC from a 300 ns + 900 ns pulse versus 600 ns pulse exposure is greater (<10 ms) compared to symmetrical BP nsEPs. From these findings, we extended on our conceptual model that BPC is balanced by localized charging and discharging events across the membrane. Bioelectromagnetics. 39:441-450, 2018. Published 2018. This article is a U.S. Government work and is in the public domain in the USA.

Mechanisms of electrical vasoconstriction

BackgroundElectrical vasoconstriction is a promising approach to control blood pressure or restrict bleeding in non-compressible wounds. We explore the neural and non-neural pathways of electrical vasoconstriction in-vivo.MethodsCharge-balanced, asymmetric pulses were delivered through a pair of metal disc electrodes. Vasoconstriction was assessed by measuring the diameter of rat saphenous vessels stimulated with low-voltage (20 V, 1 ms) and high-voltage (150 V, 10 μs) stimuli at 10 Hz for 5 min. Activation pathways were explored by topical application of a specific neural agonist (phenylephrine, alpha-1 receptor), a non-specific agonist (KCl) and neural inhibitors (phenoxybenzamine, 25 mg/ml; guanethidine, 1 mg/ml). Acute tissue damage was assessed with a membrane permeability (live-dead) fluorescent assay. The Joule heating in tissue was estimated using COMSOL Multiphysics modeling.ResultsDuring stimulation, arteries constricted to 41 ± 8% and 37 ± 6% of their pre-stimulus diameter with low- and high-voltage stimuli, while veins constricted to 80 ± 18% and 40 ± 11%, respectively. In arteries, despite similar extent of constriction, the recovery time was very different: about 30 s for low-voltage and 10 min for high-voltage stimuli. Neural inhibitors significantly reduced low-voltage arterial constriction, but did not affect high-voltage arterial or venous constriction, indicating that high-voltage stimuli activate non-neural vasoconstriction pathways. Adrenergic pathways predominantly controlled low-voltage arterial but not venous constriction, which may involve a purinergic pathway. Viability staining confirmed that stimuli were below the electroporation threshold. Modeling indicates that heating of the blood vessels during stimulation (< 0.2 °C) is too low to cause vasoconstriction.ConclusionsWe demonstrate that low-voltage stimuli induce reversible vasoconstriction through neural pathways, while high-voltage stimuli activate non-neural pathways, likely in addition to neural stimulation. Different stimuli providing precise control over the extent of arterial and venous constriction as well as relaxation rate could be used to control bleeding, perfusion or blood pressure.