Linear Pulse Research Articles

AN OPTIMIZATION APPROACH TO THE CHOICE OF PARAMETERS OF LINEAR PULSE INDUCTION ELECTROMECHANICAL CONVERTER

Purpose. The purpose of the paper is to select the main parameters of the linear pulse induction electromechanical converters (LPIEC) for high-speed and power use with the use of the optimization approach, which provides an increase in speed and power indicators with limited electric, thermal and mass-dimensions. Methodology. A technique for finding the maximum of the integral efficiency criterion of LPIEC in the search space using a global optimization method that randomly searches for parameters, preventing entry into a local maximum, and a local method ensuring the contraction of the range of parameters with a global maximum to minimum dimensions is developed. As a global optimization method, genetic algorithms are used, and the Nelder-Mead method is used as the local method. Results. The LPIEC inductor should have a maximum external and minimum internal diameter, and its height should be less than that of the LPIEC of the basic design. The armature should have a maximum outer diameter, and the thickness of its wire should be minimal. The armature should be made with a significantly higher height, a greater number of turns and a wider wire. The height of the LPIEC inductor for power purposes should be almost the same as that of the LPIEC of the basic design. In this case, the number of turns of the inductor and the cross section of its wire should be approximately the same. The armature should be made with a slightly larger inner diameter and a significantly higher height. This armature should have a larger number of turns of wire, which must be stacked in 4 layers, and a large width of the wire. The average energy value and voltage of the capacitive energy storage for the LPIEC for high-speed and power applications should be higher than for the LPIEC of the basic design. Originality. An optimization approach to the choice of LPIEC parameters with a multi-turn squirrel arm is developed, which consists in finding the maximum of an integral efficiency criterion that takes into account the maximum speed and efficiency in a high-speed converter, the amplitude and magnitude of the electrodynamic force pulse in a power converter, with minimum temperature excesses, the mass of active elements and current of the inductor. The optimization uses a chain mathematical model that takes into account the interconnected electrical, magnetic, thermal and mechanical processes of the LPIEC. Practical value. The electric parameters of the capacitive energy storage device and the geometric parameters of the LPIEC are determined, which ensure the largest values of the integral efficiency criterion depending on the adopted version of the efficiency evaluation strategy. In optimized speed and power transfer converters, the integral efficiency criteria are 2.2 times higher on average than in the basic performance of the LPIEC.

Cobalt oxide nanoparticles anchored polyaniline-appended cobalt tetracarboxy phthalocyanine, modified glassy carbon electrode for facile electrocatalysis of amitrole

Cobalt oxide nanoparticles were anchored on polyaniline-appended cobalt phthalocyanine and used to modify glassy carbon electrodes for enhanced electrocatalytic oxidation of amitrole. The modified electrodes were characterised by cyclic voltammetry, electrochemical impedance spectroscopy and scanning electron microscopy. Cyclic voltammetry, linear sweep voltammetry, chronoamperometry and differential pulse voltammetry were used to evaluate the electrocatalytic behaviour of the designed sensors. Catalytic rate constant of 6.26 × 105 M−1 s−1 and apparent electron transfer rate constant of 8.84 × 10−3 cm s−1 were observed on CoTCPc-PANI-Co3O4NP-GCE. The adsorption equilibrium constant and Gibbs energy were 4.8 × 101 M−1 and − 12.1 kJ mol−1, respectively, confirming substrate adsorption during a spontaneous reaction on the surface of the modified electrode. The limit of detection and limit of quantification were 6.61 × 10−8 M and 2 × 10−7 M, respectively, for the electrocatalytic detection of amitrole and only suffered 4% signal loss after repetitive ten runs in 1 mM amitrole.

Improvement of the memory quality of optical pulse pairs in atomic systems via four-wave mixing

We present a scheme to improve the memory quality of linear and nonlinear optical pulse pairs via four-wave mixing (FWM) in an atomic gas. We show that in a linear regime the efficiency and fidelity of the memory of the probe and Stokes pulses can be largely improved through an elimination of the fast-light mode (and hence the suppression of the optical gain induced by the FWM process). We also show that in a nonlinear regime the system may support stable optical soliton pairs with ultraslow propagation velocity and ultralow generation power, which can also be stored and retrieved with a better quality. The improved optical pulse pair memory suggested here may have promising applications in optical information processing and transformation.

INVESTIGATION OF LINEAR PULSE ELECTROMECHANICAL CONVERTER OF INDUCTION TYPE WITH DOUBLE ARMATURE INTENDED FOR DESTROYING INFORMATION ON SSD STORAGE DEVICE

Purpose. The goal of the paper is to determine the influence of the linear pulse electromechanical converter (LPEC) parameters with a double armature on its electrical, power and temperature indices and experimental verification of the proposed design for an information destruction device in a flat SSD storage device. Methodology. Using the mathematical model that takes into account interrelated electrical, magnetic, thermal and mechanical processes, the influence of geometric parameters on the electrodynamic characteristics and the indices of the induction type LPEC with a double armature spanning the inductor from opposite sides is investigated. Results. It is shown that the currents in the inductor and armature change in accordance with the oscillation-damping law practically in antiphase. The maximum value of the current density in the inductor is 215.8 A/mm2, and in each of the identical parts of the double armature it is 299.7 A/mm2. The maximum value of electrodynamic forces (EDF) acting in opposite directions on the front and rear of the double armature is 11.99 kN, and the value of the EDF pulse is 4.59 N∙s. Originality. It is established that with axial removal of the rear part of the armature from the inductor, the maximum current densities in the inductor decrease, in the front part of the armature increase, and in the rear part of the armature decrease. The maximum value and the pulse of the EDF between the armature parts decrease. With an increase in the number of turns in the inductor and a decrease in the thickness of the copper bus, all the basic indicators of the LPEC increase. With an increase in the number of turns of the inductor from 26 to 56, the maximum EDF value acting between the parts of the armature increases almost 3 times, and the magnitude of the EDF pulse is 3.3 times. With an increase in the width of the copper bus and the width of the inductor, the main indicators of the LPEC decrease. With an increase in the width of the inductor from 10 mm to 20 mm, the maximum EDF between the armature parts decreases by 1.3 times, and the value of the EDF pulse decreases by 1.2 times. Practical value. Based on the conducted studies, an induction-type LPEC model with a double armature was designed and tested experimentally, designed to destroy information located on a solid-state digital SSD storage device.

Specimen-Bar Impedance Mismatch Effects on Equilibrium and Rate Constancy for Kolsky Bar Experiments

During a Kolsky bar, also known as a split Hopkinson pressure bar (SHPB), experiment, stress equilibrium and strain rate constancy conditions directly contribute to the measurement quality for rate-sensitive materials. A Kolsky bar specimen is initially at rest, and then gradually accelerated to a desired rate. Stress equilibrium is incrementally achieved by multiple stress pulse reflections inside the specimen to reach the desired mean stress. The critical time to achieve constant strain rate and equilibrium stress depends on the impedance mismatch between the bars and the specimen. This paper examined this critical time based on using linear elastic specimens under uniaxial compression. In the first part, the critical time is experimentally measured for PMMA specimens loaded by aluminum, titanium, and steel bars using linear ramp incident pulses. The results show that increasing impedance mismatch increases the time to reach a constant rate, while the time to satisfy equilibrium remains nearly the same. In the second part, optimal bilinear-shaped incident loadings were evaluated and shown to achieve both conditions faster than linear loadings. The time to satisfy both conditions was mapped via simulation using various bilinear pulses over a wide range of impedance mismatches. The analysis shows bilinear loadings with initial rise time between 1.75 and 2.15 transits in the sample require minimum time to equilibrium. There exists an optimum region of bilinear loadings that can reduce the time to reach constant rate. Within such region, the bilinear slope ratio can be approximated to be a reciprocal function of initial rise time.

Bond selective dissociation of the BrHBr transition state complex using linear chirp laser pulses

Bond selective dissociation of the BrHBr transition state complex using linear chirp laser pulses

Investigation of different configurations and operation regimes of fiber pulse generators based on nonlinear spectral re-shaping.

In this work, we investigate the operation of linear fiber pulse generator circuits, based on self-phase modulation-induced spectral broadening and offset-alternating spectral filtering. The influence of fiber chromatic dispersion and other parameters of the circuit for stable pulse generation and the characteristics of generated pulses are described by numerical calculations and confirmed by experiments. Self-starting pulse generation is demonstrated experimentally, and conditions allowing the achievement of self-starting are discussed.

Development of an ultra-fast photomultiplier tube for gamma-ray Cherenkov detectors at the National Ignition Facility (PD-PMT).

A new ultra-fast photomultiplier tube and associated drivers have been developed for use in the next generation of gamma-ray high pressure gas Cherenkov detectors for inertial confinement fusion experiments at the National Ignition Facility. Pulse-dilation technology has been applied to a standard micro-channel-plate-based photomultiplier tube to improve the temporal response by about 10×. The tube has been packaged suitably for deployment on the National Ignition Facility, and remote electronics have been designed to deliver the required non-linear waveforms to the pulse dilation electrode. This is achieved with an avalanche pulse generator system capable of generating fast arbitrary waveforms over the useful parameter space. The pulse is delivered via fast impedance-matching transformers and isolators, allowing the cathode to be ramped on a sub-nanosecond time scale between two high voltages in a controlled non-linear manner. This results in near linear pulse dilation over several ns. The device has a built-in fiducial system that allows easy calibration and testing with fiber optic laser sources. Results are presented demonstrating the greatly improved response time and other parameters of the device.

Digital Adaptive Hysteresis Current Control for Multi-Functional Inverters

This paper proposes a digital adaptive hysteresis current control method for multi-functional inverters in a power-flow control device called digital grid router. Each inverter can be controlled in master, grid-connected, or stand-alone modes, which can be specified by the controller. While the popular linear sine-triangle pulse width modulation (SPWM) control technique requires complicated proportional-integral (PI) regulators with an unavoidable time delay, hysteresis current control has a simple structure, fast responses, and robustness due to its independent system of parameters. Since the hysteresis current control method controls the output current stay around the reference current directly, in the multi-functional inverter, the reference output is not given by a current directly. Thus, the reference current used to implement the hysteresis current control in this study is calculated from the given reference voltage or power in each control mode. The controller uses high-speed sampled data at MHz level and is implemented by using a field-programmable gate array (FPGA). Experimental results show good performances of the proposed controller in controlling power exchanges in the digital grid router.

Linearly chirped mid-infrared supercontinuum in all-normal-dispersion chalcogenide photonic crystal fibers.

We demonstrate all-normal dispersion supercontinuum generation in chalcogenide photonic crystal fibers pumped at 2070-2080 nm with a femtosecond fiber laser. At 2.9 kW peak power, the generated supercontinuum has a 3 dB bandwidth of 27.6 THz and -20 dB bandwidth of 75.5 THz. We experimentally investigated the supercontinuum evolution inside our sample fiber at various peak powers and fiber lengths and study the impact of fiber water absorption on the generated supercontinuum spectrum. Multiple tests with fiber length- ranging from 0.34 to 10 cm-provide insight on pulse evolution along fiber length. Our simulations, which utilizes the generalized nonlinear Schrodinger equation model, match perfectly the experiments for all tested pump powers and fiber lengths, and confirm that the output pulse has a linear chirp, allowing linear pulse compression.

Subnanosecond magnetization reversal of a magnetic nanoparticle driven by a chirp microwave field pulse

We investigate the magnetization reversal of single-domain magnetic nanoparticle driven by linear down-chirp microwave magnetic field pulse. Numerical simulations based on the Landau-Lifshitz-Gilbert equation reveal that solely down-chirp pulse is capable of inducing subnanosecond magnetization reversal. With a certain range of initial frequency and chirp rate, the required field amplitude is much smaller than that of constant-frequency microwave field. The fast reversal is because the down-chirp microwave field acts as an energy source and sink for the magnetic particle before and after crossing over the energy barrier, respectively. Applying a spin-polarized current additively to the system further reduces the microwave field amplitude. Our findings provide a new way to realize low-cost and fast magnetization reversal.

Improved Active Echo Cancellation Against Synthetic Aperture Radar Based on Nonperiodic Interrupted Sampling Modulation

Echo cancellation is an ingenious method that protects the target of interest (TOI) by cancelling target echo at radar receiver with an active source. Recently the cancellation method using frequency and time-delay modulation has been proposed, considering the unavoidable processing time for the canceler when synthetic aperture radar (SAR) transmits large time bandwidth product signals such as linear frequency modulation pulses. Then the cancellation signal can cancel out the target echo even when it lags behind. However, echo cancellation also requires precise amplitude match of cancellation signal and target echo at SAR receiver. Amplitude match relies on accurate transmitting power calculation, which is difficult to guarantee considering prior information errors. In the presence of amplitude mismatch, the target echo cannot be completely cancelled thus remains visible in the SAR image. In this paper, we proposed an improved echo cancellation method based on nonperiodic interrupted sampling modulation, which produces high-level side lobes performing as a continuous jamming strip along range direction after matched filtering processing. By applying the proposed method, the residual of TOI in SAR image is covered by the jamming strip, thus a more robust echo cancellation is obtained in the presence of amplitude mismatch. Measured SAR data simulations demonstrate the effectiveness of the proposed method.

Tunable microwave generation based on frequency quadrupling

To generate linearly chirped microwave signals with large frequency tunable range, a photonic approach is proposed. A dual-output dual-parallel Mach–Zehnder modulator followed by a polarisation beam combiner and an optical filter are utilised to generate orthogonally polarised ± second-order optical sidebands. A polarisation modulator is employed to achieve phase modulation of the two wavelengths. The balanced detection is applied to suppress the distortion and background noise. The central frequency of the generated signal is four times that of the local oscillator frequency. Simulation results show that a linear pulse is produced with time-bandwidth as well as a compression ratio for the pulse of 11 and 9.3 respectively. Moreover, a peak-to-sidelobe ratio of 7.4 dB is generated. The system has both good reconfigurability and tunability, and its frequency can be continuously adjusted from about 10 GHz to as much as 50 GHz in principle.

Comparative Analysis on Traumatic Brain Injury Risk Due to Primary and Secondary Impacts in a Pedestrian Sideswipe Accident

A series of pedestrian sideswipe impacts were computationally reconstructed; a fast-walking pedestrian was collided laterally with the side of a moving vehicle at 25 km/h or 40 km/h, which resulted in rotating the pedestrian's body axially. Potential severity of traumatic brain injury (TBI) was assessed using linear and rotational acceleration pulses applied to the head and by measuring intracranial brain tissue deformation. We found that TBI risk due to secondary head strike with the ground can be much greater than that due to primary head strike with the vehicle. Further, an “effective” head mass, meff, was computed based upon the impulse and vertical velocity change involved in the secondary head strike, which mostly exceeded the mass of the adult head-form impactor (4.5 kg) commonly used for a current regulatory impact test for pedestrian safety assessment. Our results demonstrated that a sport utility vehicle (SUV) is more aggressive than a sedan due to the differences in frontal shape. Additionally, it was highlighted that a striking vehicle velocity should be lower than 25 km/h at the moment of impact to exclude the potential risk of sustaining TBI, which would be mitigated by actively controlling meff, because meff is closely associated with a rotational acceleration pulse applied to the head involved in the final event of ground contact.

Liquid‐to‐solid ratio control as an advanced process control solution for continuous twin‐screw wet granulation

Assuring compliance of intermediate and final quality attributes in a continuous pharmaceutical manufacturing campaign is of utmost importance. Application of corrective actions might be required in real‐time. This work exemplifies the steps needed to identify a linear pulse transfer function for the dynamic behavior of the granule liquid‐to‐solid ratio (%w/w) at the end of the granulation unit of a commercial ConsiGmaTM‐25 production line. Near‐infrared spectroscopy was used to monitor the granule composition in‐line. The outcome for both the tracking and regulator problem using either conventional or model predictive control was implemented and evaluated. Dynamic setpoints were correctly followed and an RMSE of 0.25%w/w with respect to the setpoint was obtained when inducing artificial disturbances. Important practical challenges were also tackled. Examples are fouling, computational limitations, and the limited flexibility of the automation software. Applying the proposed advanced process control solution offers an answer to upstream material flow rate deviations. © 2018 American Institute of Chemical EngineersAIChE J, 64: 2500–2514, 2018

Formation of nanograting in fused silica by temporally delayed femtosecond double-pulse irradiation

A 1 kHz femtosecond double-pulse sequence irradiation is used to study the temporal evolution of nanograting in fused silica by controlling the delay times and polarization combinations of two independent beams from a Mach–Zehnder interferometer. A lateral laser-scan experiment with speed at 5 µm s−1 and each pulse energy of 1 µJ is firstly performed with the delay time from sub-picosecond to 10 ps, and then the written nanostructures are systematically studied under a cross-polarized microscope because the intensity of birefringence signal nearly corresponds to optical retardance and development level of the induced nanograting. The trend shows that the induced nanogratings can continue developing with a decrease of delay time in the case of the linear polarization pulse arriving before. In another vertical laser-scan experiment at the same speed and pulse energy, the morphologies of nanogratings embedded in the lines are characterized by scanning electron microscope after mechanical polishing and chemical etching. The self-organized patterns have a commonly spatial period of 200–300 nm and the orientation is always perpendicular to the polarization of the first laser pulse, and the second pulse in each sequence seems to promote the as-formed nanograting developing further even if the polarized direction is different from the previous pulse. These new findings verify again that a localized memory effect can make positive feedback to reinforce the patterned nanostripes. In that process, the impact ionization from the seed electrons left by the first pulse excitation and the photoionization of self-trapped excitons with lower ionization threshold results in an increase of the re-excited carriers during the second pulse irradiation and the subsequent development of the as-formed nanograting. Our result provides further proofs for understanding the physical mechanism of nanograting strongly connection with the interplay on multiple ionization channels.

Experimental Study on GFRP Surface Cracks Detection Using Truncated-Correlation Photothermal Coherence Tomography

In this paper, truncated-correlation photothermal coherence tomography (TC-PCT) was used as a nondestructive inspection technique to evaluate glass-fiber reinforced polymer (GFRP) composite surface cracks. Chirped-pulsed signal that combines linear frequency modulation and pulse excitation was proposed as an excitation signal to detect GFRP composite surface cracks. The basic principle of TC-PCT and extraction algorithm of the thermal wave signal feature was described. The comparison experiments between lock-in thermography, thermal wave radar imaging and chirped-pulsed photothermal radar for detecting GFRP artificial surface cracks were carried out. Experimental results illustrated that chirped-pulsed photothermal radar has the merits of high signal-to-noise ratio in detecting GFRP composite surface cracks. TC-PCT as a depth-resolved photothermal imaging modality was employed to enable three-dimensional visualization of GFRP composite surface cracks. The results showed that TC-PCT can effectively evaluate the cracks depth of GFRP composite.

Modified Chirp Waveforms-Based OCC-UWB System With Multiple Interferences Suppression

To improve the performance of the ultra-wideband (UWB) system against multiple interferences existed in wireless personal area network (WPAN), such as narrowband interference (NBI), multiple-access interference (MAI), and multipath interference (MI), we present an orthogonal complementary code (OCC)-based UWB system with modified chirp waveforms. Considering the time–frequency characteristics of the chirp functions and the principle of NBI suppression, we first propose the modified linear and nonlinear chirp function-based flexible UWB pulses to suppress the multiple NBIs. Furthermore, with the implementation of OCC spread modulation, the modified chirp waveform-based UWB system is presented to effectively alleviate the influence of the MAI and MI. Simulation results and analysis validate the efficiency of the modified chirp pulse-based OCC-UWB system in the suppression of NBIs, MAI, and MI.

Determination of vanillin by using gold nanoparticle-modified screen-printed carbon electrode modified with graphene quantum dots and Nafion.

A voltammetric analytical assay for the selective quantification of vanillin is described. It is based on the use of a gold nanoparticle-modified screen-printed carbon electrode (SPCE) modified with graphene quantum dots (GQD) in a Nafion matrix. The GQD were synthesized by an acidic thermal method and characterized by UV-Vis, photoluminescence, and FTIR spectroscopy. The modified SPCE displays a strongly enhanced response to vanillin. Linear sweep voltammetry (LSV) and differential pulse voltammetry (DPV) were applied to optimize the methods. The analytical assay has linear responses in the 13 to 660μM and 0.66 to 33μM vanillin concentration ranges. The detection limits are 3.9μM and 0.32μM when using LSV and DPV, respectively. The analytical assay is selective and stable. It was applied to the determination of vanillin in several food samples with satisfactory results. Recoveries from spiked samples ranged between 92.1 and 113.0%. Graphical abstract The selective and sensitive quantification of vanillin is carried out by the use of a gold nanoparticle-modified screen-printed carbon electrode modified with graphene quantum dots in a Nafion matrix.

Photonics-based coherent wideband linear frequency modulation pulsed signal generation.

A photonics-based scheme is proposed to generate wideband linear frequency modulation pulses with broadly tunable carrier frequencies for coherent radars. The approach integrates the concept of the microwave-photonic multiplication and coherent beating to enable reconfiguration of the bandwidth and carrier frequency of the generated pulses. The phase fluctuation between two beating arms is suppressed by a stabilization technique based on an optical phase-locked loop to maintain the pulse-to-pulse phase coherence. Further, we also demonstrate a coherent radar system, including the generation, wireless transmission and detection of the radar echo signal in the Ka-band. The coherent integration of several echo signals is achieved. About 8dB of signal-to-noise ratio improvement is obtained with every ten-fold of integration times. The range resolution of the radar system is ∼3.75 cm, which is close to the theoretical prediction.