Mitigating Blind Ranges via Staggered PRI and Pulse Width Optimization

This paper proposes an efficient algorithm for automatic and optimal tuning of pulse amplitude and width for sequential parameter estimation (SPE) of the neural membrane time constant and input-output (IO) curve parameters in closed-loop electromyography-guided (EMG-guided) controllable transcranial magnetic stimulation (cTMS). The proposed SPE is performed by administering a train of optimally tuned TMS pulses and updating the estimations until a stopping rule is satisfied or the maximum number of pulses is reached. The pulse amplitude is computed by the Fisher information maximization. The pulse width is chosen by maximizing a normalized depolarization factor, which is defined to separate the optimization and tuning of the pulse amplitude and width. The normalized depolarization factor maximization identifies the critical pulse width, which is an important parameter in the identifiability analysis, without any prior neurophysiological or anatomical knowledge of the neural membrane. The effectiveness of the proposed algorithm is evaluated through simulation. The results confirm satisfactory estimation of the membrane time constant and IO curve parameters for the simulation case. By defining the stopping rule based on the satisfaction of the convergence criterion with tolerance of 0.01 for 5 consecutive times for all parameters, the IO curve parameters are estimated with 52 TMS pulses, with absolute relative estimation errors (AREs) of less than 7%. The membrane time constant is estimated with 0.67% ARE, and the pulse width value tends to the critical pulse width with 0.16% ARE with 52 TMS pulses. The results confirm that the pulse width and amplitude can be tuned optimally and automatically to estimate the membrane time constant and IO curve parameters in real-time with closed-loop EMG-guided cTMS.

The impact induced by cavitation bubble collapse can be utilized for mechanical surface treatment to improve fatigue properties of metals including additive manufactured metallic materials. A peening method using cavitation impact induced by a pulsed laser is called “laser cavitation peening (LCP)”. Normally, a Q-switched Nd:YAG laser, whose pulse width is a few nanoseconds, is used for LCP, which improves the fatigue strength. The problem with LCP is that the processing time is too slow. If a laser pulse whose pulse width is a few hundred microseconds can be utilized for LCP, the repetition frequency can be increased drastically using other types of laser systems such as a fiber laser. In the present paper, in order to reveal the possibility of LCP using a pulsed laser width of a few hundred microseconds, the use of LCP with a normal-oscillation Nd:YAG laser (pulse width ≈ 200 μs) was investigated. It is demonstrated that LCP with the normal-oscillation Nd:YAG laser produced curvature in an aluminum alloy plate. The shock pressure wave and impulsive vibration of the target surface at the first collapse of laser cavitation (LC), which was induced by the normal-oscillation Nd:YAG laser, was 3–4 times larger than those of laser ablation (LA).

Transcutaneous electrical nerve stimulation (TENS) has been a commonly used modality to relieve aches and pain for over 40 years. Commercially available devices provide multiple therapy modes involving a different combination of frequency and pulse width with intensity. While frequency sets sensation, intensity helps determine tolerability, longer pulse width is reported to induce a feeling of deeper stimulation. In fact, longer pulse width has been empirically shown to deliver current into deeper tissues, but in context of other electrical stimulation modalities. The goal of this study was to unpack the relationship between pulse width and activation depth in TENS. A highly realistic, anatomically-based, 3D finite element model of the forearm was used to simulate the electric field (E-field) distribution, as the pulse width is varied. A typical titration-guided mechanism was used to obtain the strength-duration (S-D) curves of a sensory McIntyre-Richardson-Grill (MRG) axonal model simulating the pain-transmitting A-delta fibers. The pulse widths tested ranged from 30 μs to 495 μs. As expected, shorter pulse widths required more current to achieve activation, resulting in a larger E-field. The S-D curve of the target median nerve indicates a rheobase of 1.75 mA and a chronaxie of 232 µs. When the applied currents are the same, shorter pulse widths result in a smaller volume of tissue activated (VTA) compared to the longer pulse widths. A 21 fold difference in VTA was found between the longest and shortest pulse widths considered. For the conditions tested in the study, an increase in pulse width resulted in an increase in activation depth, exhibiting a linear relationship. Our findings highlight the impact of pulse width on activation depth. While choice of a given therapy mode is usually based on an ad-hoc desirable sensation basis, medical professionals may consider advocating a certain therapy mode based on the depth of the intended target nerve.

PD06-07 EFFECT OF PULSE WIDTH VARIATIONS ON SACRAL NEUROMODULATION FOR OVERACTIVE BLADDER SYMPTOMS: A PROSPECTIVE RANDOMIZED CROSSOVER PILOT STUDY

Aims To examine the association between pulse width and HRQoL measured within one week after electroconvulsive therapy (ECT) and at six-month follow-up in patients with unipolar or bipolar depression. Methods This was an observational register study using data from the Swedish National Quality Registry for ECT (2011–2019). Inclusion criteria were: age ≥18 years; index treatment for unipolar/bipolar depression; unilateral electrode placement; information on pulse width; EQ-5D measurements before and after ECT. Multiple linear regressions were performed to investigate the association between pulse width (<0.5 ms; 0.5 ms; >0.5 ms) and HRQoL (EQ-5D-3L index; EQ VAS) one week after ECT (primary outcome) and six months after ECT (secondary outcome). Results The sample included 5,046 patients with unipolar (82%) or bipolar (18%) depression. At first ECT session, 741 patients (14.7%) had pulse width <0.5 ms, 3,639 (72.1%) had 0.5 ms, and 666 (13.2%) had >0.5 ms. There were no statistically significant associations between pulse width and HRQoL one week after ECT. In the subsample of patients with an EQ-5D index recorded six months after ECT (n = 730), patients receiving 0.5 ms had significantly lower HRQoL (−0.089) compared to <0.5 ms, after adjusting for demographic and clinical characteristics (p = .011). The corresponding analysis for EQ VAS did not show any statistically significant associations. Conclusion No robust associations were observed between pulse width and HRQoL after ECT. On average, significant improvements in HRQoL were observed one week and six months after ECT for patients with unipolar or bipolar disease, independent of the pulse width received.

Environmentally-safe high-power impulse magnetron sputtering (HiPIMS) technology was utilized to deposit chromium films. This research focused on the influences of the HiPIMS pulse widths on the microstructure of films deposited at different deposition pressures and substrate bias voltages. Under the conditions of the same average HiPIMS power and duty cycle, the deposition rate of the Cr thin film at working pressure 0.8 Pa is slightly higher than at 1.2 Pa. Also, the difference between deposition rates under two pressures decreases with the discharge pulse width. The deposition rate of the short pulse width 60 μs is lowest, but those of 200 and 360 μs are approximately the same. With no or small direct current substrate biasing, the microstructure of films coated at short pulse width is similar to the typical magnetron sputtering deposited films. Elongating the pulse width enhances the ion flux toward the substrate and changes the film structure from individual prism-like columns into tangled 3-point/4-point star columns. Substantial synchronized substrate biasing and longer pulse width changes the preferred orientation of Cr films from Cr (110) to Cr (200) and Cr (211). The films deposited at longer pulse width exhibit a higher hardness due to the reducing of intercolumn voids.

Objective. There is a high variability in the physiological effects of transcranial magnetic brain stimulation, resulting in limited generalizability of measurements. The cause of the variability is assumed to be primarily based on differences in brain function and structure of the stimulated individuals, while the variability of the physical properties of the magnetic stimulus has so far been largely neglected. Thus, this study is dedicated to the systematic investigation of variability in the pulse width of different TMS pulse sources at different stimulation intensities. Approach. The pulse widths of seven MagVenture® pulse sources were measured at the output of 10%–100% stimulation intensity in 10% increments via Near Field Probe and oscilloscope. The same C-B60 coil was used to deliver biphasic pulses. Pulse widths were compared between pulse sources and stimulation intensities. Main results. The mean sample pulse width was 288.11 ± 0.37 µs, which deviates from the value of 280 µs specified by the manufacturer. The pulse sources and stimulation intensities differ in their average pulse width (p’s < .001). However, the coefficient of variation within the groups (pulse source; stimulation intensity) were moderately low (CV = 0.13%–0.67%). Significance. The technical parameter of pulse width shows deviations from the proposed manufacturer value. According to our data, within a pulse source of the same manufacturer, the pulse width variability is minimal, but varies between pulse sources of the same and other pulse source models. Whether the observed variability in pulse width has potential physiological relevance was tested in a pilot experiment on a single healthy subject, showing no significant difference in motor evoked potential amplitude and significant difference in latencies. Future research should systematically investigate the physiological effects of different pulse lengths. Furthermore, potential hardware ageing effects and pulse amplitude should be investigated.

Site-specific sodiation of peptides studied by pulsed nanoelectrospray ionization

Pulse duration modulation (PDM), often referred to as pulse width modulation (PWM), is a simple and effective means of remotely controlling linear autonomous dynamical systems. [1]-[6] However, state-dependent noise can cause a PDM control policy to become unstable. Sufficient conditions which guarantee asymptotic PDM controller stability, in the large, with probability one, are presented.

The piezoelectric injection-system provides a reliable approach for precise small-quantity fuel injection due to its fast, dynamic response. Considering the nonlinearity of a piezoelectric actuator, the complete electro-mechanical-hydraulic model of the piezoelectric injector was established and verified experimentally, which showed that it could accurately predict the fuel injection quantity. The small-quantity fuel injection with different driving voltages, pulse widths, and rail pressures was analyzed. The effects of key structural parameters of the injector on the delivery, control-chamber pressure fluctuation, and small-quantity injection characteristics were studied. The results show that the linearity of the curve of the injection volume with the pulse width was relatively poor, and there was a significant inflection point when the piezoelectric injector worked in the small pulse width region (PW < 0.6 ms). The bypass valve significantly accelerated the establishment of the control-chamber pressure, reduced the pressure fluctuation in the chamber, shortened the closing delay and duration of the needle valve, and reduced the rate of the fuel-quantity change so that it provided a greater control margin for the pulse width over the same fuel volume change interval. Under the condition of a small-quantity fuel injection of 20 mm3, decreasing the inlet orifice diameter and increasing the outlet orifice diameter shortened the minimum control pulse width and fuel injection duration required for the injector injection, which is beneficial for multiple and small-quantity fuel injection. However, these behaviors reduce the control margin for the pulse width, especially in small pulse width regions.

Hydroxyl radical plays an important role in many biomedical applications (e.g. wound disinfection and cancer treatment) due to its strong oxidation potential. This study investigated the effects of pulse width ranging from 200 ns to 4 μs on generation and evolution of OH radicals in a pulsed helium plasma jet interacting with a water-covered ground electrode under 6 kV pulses at 1 kHz via emission spectroscopy and electrical measurements. Integrated optical emission spectroscopy revealed that total OH yield along the discharge gap increased with pulse width up to 800 ns and decreased with pulse width increasing from 800 ns to 4 μs. Terephthalic acid (TA) was used to trap OH radicals forming 2-hydroxyterephthalic acid (HTA) from which the fluorescence can be measured for determining OH aq concentration in liquid. It is found that the highest OH yield in liquid phase was at a pulse width of 200 ns. These results suggest that higher production efficiency for OH radicals in both gas- and liquid- phase can be obtained with pulse widths in the nanosecond-range under studied experimental conditions. In addition, temporally and spatially resolved gas-phase OH is discussed. Correlations between the OH emission intensity and its correspondent electrical parameters under various pulse widths are discussed.

Microchip lasers are the most compact (~1mm3) and the simplest diode pumped solid state lasers The mirrors of the optical cavity are directly deposited on the polished faces of a thin (-1mm) laser material. They are fabricated using collective fabrication processes allowing a low cost mass production. A microchip laser has a typical size of 1×1×0.5 mm3. It is very reliable and simple to use. The microchip laser is a kind of optical transformer which transforms a poor quality laser diode beam to a diffraction limited TEM00 and single frequency laser beam Moreover, by active or passive Q-switching , very short pulses (-0.4 to 2 ns) with very high peak power (0.5 to 50 kW) can be obtained. Standard wavelengths are: 1μm or 1.3μm with Nd doped materials such as YAG, YVO4, LMA, etc.; 1.5μm with Er and Yb co-doped phosphate glass; 2μm with Tm doped materials. The laser threshold is generally low, i.e as low as 9mW for 1.5μm microchip laser with a slope efficiency of 38%. Passively Q-switched Nd:YAG microchip laser can be fabricated using a novel process. A thin film (~30-50μm) of Cr4+:YAG, which is a saturable absorber at 1064nm, is epitaxially grown on 25mm diameter and 0.5 to 1mm thick Nd:YAG subtrates. The absorption coefficient of the epitaxial thin film saturable absorber is ~20-25 cm-1, about five times higher than the bulk Cr4+:YAG. The saturable absorption is adjusted by polishing the thin film. This process has the advantage to keep the monolithic structure of the microchip laser without any optical interface between the active and passive materials, and allows a great flexibility for the design of Q-switched lasers. Typical pulse energies are between 0.5 to 5μJ using low power diode pumps, and the pulse width is 0.4 to 2ns. Repetition rates as high 100kHz have been obtained. The pulse energy, width and peak power are independant of the pump power, which acts only on the pulse repetition rate which increases linearly with the diode pump power. The plane-parallel Fabry-Perot cavity of the microchip laser is optically stabilized by thermal effects due to the heating by the pump power. The laser mode is also defined by thermal effects. In order to avoid this problem, stable plano-concave optical cavities are fabricated using photolithography and ion beam etching technologies such as used currently in microelectronics. Small microlenses with 100-200μm in diameter and 1μm thick are directly fabricated with a collective process on laser materials such as Nd:YAG or Er,Yb:glass. The microlense acts as a concave micromirror for the microchip laser cavity, with a radius of curvature of few mm, so that the cavity is optically stable and the laser mode is well defined. The laser threshold is drastically reduced, i.e. less than 2mW incident pump power in CW mode Moreover, this technology allows also the fabrication of micro-optical components, such as microlenses on silica substrates, which can be used for the fabrication of optical microsystems including microchip lasers. For exemple such microlenses are used for the fiber coupling of a stable cavity microchip laser. The low cost, the re lability, the excellent beam quality and the high peak power of the microchip lasers are very useful for several industrial applications such as: time of flight range finding; micro-marking of materials; compact green laser for alignment; injection locking; etc.

The electric breakdown characteristics in microcavity structure under repeated frequency pulse (RFP) were studied, and the physical mechanism was investigated quantitatively based on the full statistical distribution of breakdown time delay obtained in step rectangular pulse (SRP). Experimentally, microcavity heights of 300, 800, and 2000 μm were used. In RFP, the occurrence of breakdown becomes probabilistic when the time delay t d and pulse width t PW satisfy the condition t s-min < t PW < t s-max. The breakdown probability increases with pulse width, and the probability distributions are roughly exponential and Gaussian at pulse frequencies of 3 and 1000 Hz, respectively. We found the results are attributed to the similar distributions of time delay in RFP and SRP with similar afterglow time and pulse voltage, and the equal distributions of breakdown probability (with pulse width) and cumulative probability of t d in RFP. The microcavity effect will decrease the breakdown probability under given pulse width and voltage. Additionally, it is found that in RFP the increase of pulse width from 1 to 1000 μ s will decrease the threshold voltages at 0% and 100% breakdown probabilities, and the threshold voltage difference will decrease simultaneously to around 0, which results in the transition of breakdown feature from probability to certainty. This phenomenon is due to that the reduction of pulse voltage will increase the time delay significantly and meanwhile the variation rate of time delay with pulse voltage Δt d/ΔU w decreases sharply. The microcavity effect will cause the increase of threshold breakdown voltages at a given pulse width and frequency. Finally, it is found that in RFP the breakdown voltage will decrease with the rise of pulse frequency from 10° to 104 Hz, which is consistent with the variation of time delay with afterglow time (from 10−1 to 103 ms) in the memory curve measured in SRP under similar afterglow time. Overall, the microcavity effect will enhance the adsorption of charged and excited species by dielectric walls during afterglow period and enlarge the time delay in the following pulse breakdown, and then influence the RFP breakdown characteristics.

This paper analyzes the effects of scaling and measurement conditions on the performance of hybrid organic inorganic perovskite (HOIP) devices having bipolar resistive switching characteristics. Electroforming voltage, SET current, and ON/OFF ratios are found to be area dependent. Linear voltage sweep and pulse voltage characterization showed that parameters such as compliance current, voltage scan rate, pulse width, amplitude, and frequency significantly alter the device switching parameters. The CH3NH3PbI3 memristors fabricated has FORMING, SET, and RESET voltages of 1.18, 0.17, and −0.13 V, respectively, along with an ON/OFF ratio of 1.3 × 103. It has been found that, both the RESET voltage and current significantly increase with scan rate, whereas the ON/OFF ratio increases significantly with compliance current. In case of voltage pulse characterization, the ON/OFF ratio can be enhanced by increasing the pulse amplitude and width. Additionally, the experimental data fitting to a SPICE based analytical model establishes that the HOIP memristor current conduction is dominated by tunneling process in the OFF state and is ohmic in the ON state. Based on the results, the authors arrive at a general protocol that can be used to characterize memristors made of HOIPs and other related materials such that they can operate optimally.

Effects of different pulse widths on morphologies and corrosion resistance of diamond-like carbon (DLC) coatings prepared on the surface of high nitrogen nickel-free stainless steel (HNSS) were investigated. It was found that different pulse widths of 10, 15 and 20[Formula: see text][Formula: see text]s mainly affect the porosity and internal stress within the coatings. The energies of the implantation ions were decreased as the pulse width increase. The growth mechanism of the coating with the pulse width of 20[Formula: see text][Formula: see text]s was mainly surface diffusion, in which the coating was porous and prone to corrosion. With the decrease of pulse width, the growth mechanism was mainly sub-plantation. The DLC coating became dense and the corrosion resistance was improved significantly. However, with further decrease of pulse width, internal stress within the coating was also increased. The effect of stress corrosion cracking may decrease the corrosion resistance of the DLC coating with the pulse width of 10[Formula: see text][Formula: see text]s. The influencing mechanisms of the pulse width on corrosion resistance and growth mechanism of DLC coating on the surface of HNSS are also discussed.