Linear Pulse Research Articles

Anisotropic polyethersulfone foam for bicycle helmet liners to reduce rotational acceleration during oblique impact.

Although current standard bicycle helmets protect cyclists against linear acceleration, they still lack sufficient protection against rotational acceleration during oblique impact events. Rotational acceleration is correlated with serious traumatic brain injuries such as acute subdural haematoma and thus should be minimized. This study proposes using highly anisotropic polyethersulfone foam for bicycle helmet liners in order to limit the rotational acceleration. Helmet prototypes, made of polyethersulfone foam with cell anisotropy direction perpendicular to the head, have been produced and compared to a standard commercial helmet. Standard helmets consist of expanded polystyrene foam. Oblique impact tests were performed to measure both linear and rotational accelerations and impact pulse duration. Results demonstrate that the peak rotational acceleration of the polyethersulfone prototype helmet showed a decrease of around 40% compared to the reference expanded polystyrene helmet. Moreover, the peak linear acceleration showed an average decrease of about 37%. Upon impact, the polyethersulfone helmet showed improved head injury protection when analysed based on global biomechanical head injury criteria such as HIC15 and HICrot as well as generalized acceleration model for brain injury threshold, brain injury criterion and head impact power, with a predicted sixfold decrease in likelihood of concussion.

A TECHNIQUE OF EXPERIMENTAL INVESTIGATIONS OF LINEAR IMPULSE ELECTROMECHANICAL CONVERTERS

Purpose. Development of a technique of experimental studies linear pulse electromechanical converters parameters, which are used as shock-power devices and electromechanical accelerators, and comparing the experimental results with the calculated indices obtained using the mathematical model. Methodology. Method of experimental investigations of linear electromechanical converter is that the electrical parameters are recorded simultaneously (inductor winding current) and mechanical parameters characterizing the power and speed indicators of the joke with actuator. Power indicators are primarily important for shock-power devices, and high velocity - for electromechanical accelerators. Power indices were investigated using piezoelectric sensors, a system of strain sensors, pressure pulsation sensor and high-speed videorecording. Velocity indicators were investigated using a resistive movement sensor which allows to record character of the armature movement with actuating element in each moment. Results. The technique of experimental research, which is the simultaneous recording of electrical and mechanical power and velocity parameters of the linear electromechanical converter pulse, is developed. In the converter as a shock-power device power indicators are recorded using a piezoelectric transducer, strain sensors system, pressure pulsation sensor and high-speed video. The parameters of the inductor winding current pulse, the time lag of mechanical processes in relation to the time of occurrence of the inductor winding current, the average speed of the joke, the magnitude and momentum of electrodynamics forces acting on the plate strikes are experimentally determined. In the converter as an electromechanical accelerator velocity performance recorded using resistive displacement sensors. It is shown that electromechanical converter processes have complex spatial-temporal character. The experimental results are in good agreement with the calculated figures obtained by means of a mathematical model that describes the ultrafast electromagnetic, thermal and mechanical processes that occur when the yoke moves relative to the inductor. Originality. For the first time offered during experimental studies of impulse linear electromechanical converter to both to measure the electrical parameters, namely the inductor winding current, and mechanical parameters characterizing the power and velocity performance with yoke actuator. Practical value. The technique of experimental investigations the parameters of the linear pulse electromechanical converter that can be used to investigate the shock-power devices and electromechanical accelerators is proposed.

Linear transformer and primary low-inductance switch and capacitor modules for fast charging of PFL

A step-up linear pulse transformer and a modular primary powering system were developed for fast (≈350 ns) charging of a pulse forming line (PFL) of a high-current electron accelerator. The linear transformer is assembled of a set of 20 inductors with circular ferromagnetic cores and one–turn primary windings. The secondary turn is formed by housing tube walls and a voltage adder with a film-glycerol insulation installed inside of the inductors. The primary powering system assembles 10 modules, each of them is a low-inductance site of two capacitors of 0,35 µF and one gas switch mounted at the same enclosure. The total stored energy is 5.5 kJ at the charging voltage of 40 kV. According to test results, the equivalent parameters at the output of the transformer are the next: a capacity – 17.5 nF, an inductance – 2 µH, a resistance – 3.2 Ohms.

Low-PAPR Hybrid Filter for SC-FDMA

We propose a hybrid filter to reduce the peak-to-average power ratio (PAPR) on the transmitter side in a long-term evolution uplink scheme. The design of the proposed filter is based on two key components: a finite impulse response filter and a Nyquist-I pulse. We consider an envelope-constrained filter design to optimize the impulse response of the proposed filter in terms of PAPR reduction. Moreover, we propose a new family of Nyquist-I pulses, the exponential linear pulse, which has a new design parameter that helps reduce PAPR for a given roll-off factor and transmission scheme. Theoretical and numerical results show that the proposed filter outperforms existing filters in terms of PAPR and symbol error rate, and it has a less computationally complex impulse response expression than existing filters for the interleaved subcarrier mode of single-carrier frequency-division multiple access.

Pulse Propagation Models with Bands of Forbidden Frequencies or Forbidden Wavenumbers: A Consequence of Abandoning the Slowly Varying Envelope Approximation and Taking into Account Higher-Order Dispersion

We study linear and nonlinear pulse propagation models whose linear dispersion relations present bands of forbidden frequencies or forbidden wavenumbers. These bands are due to the interplay between higher-order dispersion and one of the terms (a second-order derivative with respect to the propagation direction) which appears when we abandon the slowly varying envelope approximation. We show that as a consequence of these forbidden bands, narrow pulses radiate in a novel and peculiar way. We also show that the nonlinear equations studied in this paper have exact soliton-like solutions of different forms, some of them being embedded solitons. The solutions obtained (of the linear as well as the nonlinear equations) are interesting since several arguments suggest that the Cauchy problems for these equations are ill-posed, and therefore the specification of the initial conditions is a delicate issue. It is also shown that some of these equations are related to elliptic curves, thus suggesting that these equations might be related to other fields where these curves appear, such as the theory of modular forms and Weierstrass ℘ functions, or the design of cryptographic protocols.

리니어 펄스모터의 고정자 상권선 적층에 따른 추력 리플 저감 기법 연구

The stator phase winding of a linear pulse motor, which is a new type of linear motor, is comprised of two phases and is structurally characterized by a stacking method in which the winding of one phase is laid on top of the winding of another phase. Such a structural characteristic induces a difference in the flux linkage resulting from the flux of each stator phase winding in the same condition. The difference in the induced flux linkage acts as a kind of thrust ripple component in terms of the generated thrust. Thus, in order to maintain consistent thrust force, a method is required to solve the problem caused by the structural singularity. Hence, in this study, we present a technique for reducing the thrust force ripple generated by the stacking of the stator phase windings of a linear pulse motor through the generation of a compensating current reference value of the current controller in order to keep the torque constant. The proposed compensating algorithm is validated by simulations and experimental results.

On Time Compression Overlap-Add Technique in Linear Frequency Modulation Pulse Compression Radar Systems: Design and Performance Evaluation

This paper introduces a novel approach to incorporate the time compression overlap-add (TC-OLA) technique used in communication systems into linear frequency modulation pulse compression (LFM-PC) radar systems. This technique significantly boosts the signal-to-noise ratio (SNR) and provides a robust processing gain compared with the traditional radar LFM-PC systems. In addition, TC-OLA provides a better immunity against powerful jamming techniques. At the transmitter side, we divide a digitized LFM chirp signal into a controlled number of overlapping segments. We then speed up each segment by increasing the sampling rate to account for the segment overlap. At the receiver side, we apply OLA to reconstruct the signal with a much higher gain. To simulate and evaluate the performance of the new system, we extend the conventional LFM-PC radar model, which includes matched filter (MF) processor, moving target detector (MTD), and two common constant false alarm rate (CFAR) algorithms, by suitably adding TC and OLA blocks at the transmitter and receiver, respectively. Using the TC-OLA-based LFM radar system, we have control over the SNR level and the spectrum spread while preserving the same Doppler shift and target time delay as the conventional LFM radar system. Furthermore, we transform LFM chirp signal into a novel TC signal that inherits LFM properties while possessing better immunity to jamming. Moreover, the proposed radar model relies on high sample rates only when needed and, therefore, does not require changing MF, MTD, and CFAR as is the case for a wideband LFM radar with the same processing gain. Detailed comparisons between the conventional LFM and the wideband LFM radars against the proposed model are also presented.

Linearization of the Dynamic Properties of a Reversible Single Bivalve-Type Converter. P. 2. A Linearized Valve-Type Converter in a Fast Operation Constraint Current Control System

The results of the dynamic properties linearization of the reversible valve inverter operated on bilateral switches (bivalves) with the use of the modified phase control method are considered. The determining influence on the linearized pulse amplitude modulation (PAM) converter dynamics is shown, which allows solving the synthesis problems solving by means of the linear pulse systems methods. The converter pulse model on the basis of PAM-1 is described. The model usage sample for obtaining the finite duration transient processes in the power reversible current control system was also presented.

A Sensitive Electrochemical DNA Biosensor for Anticancer Drug Topotecan Based on Graphene Carbon Paste Electrode

Linear sweep voltammetry (LSV) and differential pulse voltammetry (DPV) at graphene paste electrode (GPE) were applied to study the interaction of the anticancer drug topotecan with ds-DNA. A linear dependence was observed for the topotecan concentration level from 0.7 to 90.0 μM and the limit of detection of the topotecan was achieved 0.37 μM under the optimal conditions. Moreover, the application of analysis was studied for real samples and the outcomes showed the good ability of the proposed DNA biosensor for sensitive, quick, easy, and cost effective measurement of topotecan in specimens of human blood serum and urine samples.

ERICA: an energy resolving photon counting readout ASIC for X-ray in-line cameras

We present ERICA (Energy Resolving Inline X-ray Camera) a photon-counting readout ASIC, with 6 energy bins. The ASIC is composed of a matrix of 8 × 20 pixels controlled by a global digital controller and biased with 7 independent digital to analog converters (DACs) and a band-gap current reference. The pixel analog front-end includes a charge sensitive amplifier with 16 mV/ke− gain and dynamic range of 45 ke−. ERICA has programmable pulse width, an adjustable constant current feedback resistor, a linear test pulse generator, and six discriminators with 6-bit local threshold adjustment. The pixel digital back-end includes the digital controller, 8 counters of 8-bit depth, half-full buffer flag for any of the 8 counters, a 74-bit shadow/shift register, a 74-bit configuration latch, and charge sharing compensation processing to perform the energy classification and counting operations of every detected photon in 1 μ s. The pixel size is 330 μm × 330 μm and its average consumption is 150 μW. Implemented in TSMC 0.25 μm CMOS process, the ASIC pixel's equivalent noise charge (ENC) is 90 e− RMS connected to a 1 mm thickness matching CdTe detector biased at −300 V with a total leakage current of 20 nA.

Submicrosecond linear pulse transformer for 800 kV voltage with modular low-inductance primary power supply

A pulsed power source with voltage amplitude up to 800 kV for fast charging (350–400 ns) of the forming line of a high-current nanosecond accelerator is developed. The source includes capacitive energy storage and a linear pulse transformer. The linear transformer consists of a set of 20 inductors with circular ferromagnetic cores surrounded by primary windings inside of which a common stock adder of voltage with film-glycerol insulation is placed. The primary energy storage consists of ten modules, each of which is a low-inductance assembly of two capacitors with a capacitance of 0.35 μF and one gas switch mounted in the same frame. The total energy stored in capacitors is 5.5 kJ at the operating voltage of 40 kV. According to test results, the parameters of the equivalent circuit of the source are the following: shock capacitance = 17.5 nF, inductance = 2 μH, resistance = 3.2 Ω.

Monitoring coherent electron wave packet excitation dynamics by two-color attosecond laser pulses.

We propose a method to monitor coherent electron wave packet (CEWP) excitation dynamics with two-color attosecond laser pulses. Simulations are performed on aligned H2+ by numerically solving the three-dimensional time-dependent Schrödinger equation with combinations of a resonant linearly polarized λl= 100/70 nm pump pulse and a circularly polarized λc=5 nm attosecond probe pulse. It is found that time dependent diffraction patterns in molecular frame photoelectron angular distributions (MFPADs) produced by the circular probe pulse exhibit sensitivity to the molecular alignments and time-dependent geometry of the CEWPs during and after the coherent excitation between the ground and excited states induced by the linear pump pulse. The time dependent MFPADs are described by an ultrafast diffraction model for the ionization of the bound CEWPs.

Integrated 16-ps Pulse Generator Based on a Reflective SOA-EAM for UWB Schemes

A flexible pulse shaping photonic structure that is capable of generating train pulses that hold pulsewidths of approximately 16 ps and a Gaussian profile at a repetition rate of 20 GHz is proposed and experimentally demonstrated. The key component is a monolithically integrated reflective semiconductor optical amplifier (SOA)-electroabsorption modulator device that operates within the 1.55-μm frequency band. The generated pulses have low chirp, which is experimentally measured using a novel linear pulse characterization technique. The pulses have the potential to be used as seed pulses for optical ultra-wide band photonic communications systems.

Oxidation and reduction of omeprazole on boron-doped diamond electrode: Mechanistic, kinetic and sensing performance studies

Voltammetric behavior of omeprazole on chemically unmodified boron-doped diamond electrode was investigated. Omeprazole is possible to oxidize and reduce in various supporting electrolytes. Both processes are strongly dependent on pH value of the solution. Well defined oxidation and reduction signal of omeprazole was observed at high and low pH values of supporting electrolyte. Kinetics of charge transfer in the pH range from 3 to 10 in various supporting electrolytes was studied and characterized by the estimation of formal potentials (+1.07 to +0.89V for oxidation and −0.95 to −1.18V for omeprazole reduction), charge transfer coefficients (0.52–0.33 for oxidation and 0.19–0.17 for reduction) together with standard heterogeneous rate constants. The analytical performance was studied with linear sweep voltammetry, square-wave voltammetry and differential pulse voltammetry. The lowest detection limit of 9.1×10−8molL−1 for oxidation of omeprazole was achieved by SWV technique. The proposed simple, sensitive and cheap method was validated and applied for pharmaceutical formulations and human urine as real samples.

Fabrication of a highly sensitive and selective electrochemical sensor based on chitosan-coated Fe3O4magnetic nanoparticle for determination of antibiotic ciprofloxacin and its application in biological samples

A simple and sensitive sensor has been developed for the electrochemical determination of ciprofloxacin (CF). The proposed sensor was designed by chitosan-coated Fe3O4magnetic nanoparticle incorporated in the carbon paste electrode (CPE), which provides remarkably improved sensitivity for the electrochemical determination of CF. The proposed sensor was characterized with scanning electron microscopy and electrochemical impedance spectroscopy. Under optimum conditions, the sensor provides two linear differential pulse voltammetry responses in the range of 0.05–6 μmol/L and 6–75 μmol/L for CF with a detection limit of 0.01 μmol/L. The proposed sensor exhibited high sensitivity and good selectivity and was successfully applied for CF determination in serum and urine samples.

Investigation of radiation detection properties of CRY-018 and CRY-019 scintillators for medical imaging

During the last years the research for new scintillation crystals has been crucial for the improvement of imaging performance in nuclear medicine applications. Crytur company has recently released two new scintillators named CRY-018 and CRY-019 which are non hygroscopic, have short decay time and low refraction index. They represent the ideal candidates to substitute NaI:Tl and BGO crystals in future PET ad SPECT applications. The purpose of this work is to characterize this unknown crystals, look for possible applications in imaging for nuclear medicine. The results of this work were compared with the results obtained with a LaBr3:ce scintillation crystal. This particular crystal is used as a comparison benchmark because of its strong linear pulse height uniformity response and high energy resolution. Measurements have been performed with a high count rate which is typical for medical applications. Irradiation of the crystals have been performed in three different geometries and in a photon energy range suitable with SPECT and PET applications. The experimental results identify the CRY-018 as an Yttrium and Silicon mixture and the CRY-019 with as Lutetium and Silicon one. Moreover a light yield of about 45% of LaBr3 one, was obtained for both the CRY-018 and CRY-019. This is one of the higher light yield between most of the scintillation crystals usually used in nuclear medicine. Both crystals are characterized by a non-proportionality in the pulse height linearity response. Energy resolutions of 7.4% for CRY-018 and 8.4% for CRY-019 at 661 keV, have been measured. The intrinsic component of the energy resolution has been esteemed for all three scintillators. An intrinsic detection efficiency of about 45% at 122 keV for CRY-018 and 14% at 661 keV for CRY-019 has been measured. Compared with LaBr3:Ce efficiency, which is highly deteriorated by the coating required by the hygroscopicity, CRY-018 and CRY-019 are really interesting considering that these two samples are only 6 mm thick. Crytur's crystals seem to be suitable for nuclear medicine applications.

Cr:YAG passively Q-switched single-frequency Nd:YVO_4 ring cavity laser

We design and demonstrate a thermally stable four-mirror discrete-component planar ring cavity for Q-switched laser output. An 880 nm fiber-coupled laser diode is used to pump a-cut Nd:YVO4 directly. A magnetic rotation glass (MR3-2) inserted into a permanent cylinder magnet, in combination with a half-wave plate and the polarized emission properties of Nd:YVO4, is used to obtain unidirectional laser operation. With this setup, for a pump power of 5 W, 2.75 W of continuous 1064 nm single-frequency laser output is obtained. Next, a Cr:YAG with small signal transmittance of 75% is inserted in between the two concave mirrors where the beam waist is located. Consequently, a passive Q-switching single-frequency linear polarization pulse with an average power of 1.02 W, pulse width of 60 ns, frequency of 21 kHz, peak power of 810 W, and single-pulse energy of 48 μJ is obtained. Further, we also propose a new method of using a Fabry–Perot (FP) scanning interferometer to observe high-repetition rate Q-switched pulse output longitudinal-mode signals.

Voltammetric Response and Determination of an Anti‐Inflammatory Drug at a Cationic Surfactant‐Modified Glassy Carbon Electrode

AbstractElectrochemical oxidation of thiosalicylic acid in the presence of cationic surfactant, cetyl trimethylammonium bromide (CTAB), at a glassy carbon electrode was investigated. The electrochemical response of a modified sensor towards thiosalicylic acid determination was studied by the means of cyclic voltammetry, linear sweep voltammetry and differential pulse voltammetry (DPV). The liquid phase oxidation of thiosalicylic acid in the presence of CTAB leads to a notable enhancement in the peak current and a lowering of the peak potential. The electrochemical process was observed to be adsorption‐controlled, irreversible and involves oxidation of one electron. Effects of anodic peak potential (Ep), anodic peak current (Ipa) and heterogeneous rate constant (k0) were calculated. The linear response was obtained in the range of 1.0 µM–1.0 mM with a detection limit of 113 nM.

A digital matched filter for reverse time chaos.

The use of reverse time chaos allows the realization of hardware chaotic systems that can operate at speeds equivalent to existing state of the art while requiring significantly less complex circuitry. Matched filter decoding is possible for the reverse time system since it exhibits a closed form solution formed partially by a linear basis pulse. Coefficients have been calculated and are used to realize the matched filter digitally as a finite impulse response filter. Numerical simulations confirm that this correctly implements a matched filter that can be used for detection of the chaotic signal. In addition, the direct form of the filter has been implemented in hardware description language and demonstrates performance in agreement with numerical results.

Two-photon microscopy using fiber-based nanosecond excitation.

Two-photon excitation fluorescence (TPEF) microscopy is a powerful technique for sensitive tissue imaging at depths of up to 1000 micrometers. However, due to the shallow penetration, for in vivo imaging of internal organs in patients beam delivery by an endoscope is crucial. Until today, this is hindered by linear and non-linear pulse broadening of the femtosecond pulses in the optical fibers of the endoscopes. Here we present an endoscope-ready, fiber-based TPEF microscope, using nanosecond pulses at low repetition rates instead of femtosecond pulses. These nanosecond pulses lack most of the problems connected with femtosecond pulses but are equally suited for TPEF imaging. We derive and demonstrate that at given cw-power the TPEF signal only depends on the duty cycle of the laser source. Due to the higher pulse energy at the same peak power we can also demonstrate single shot two-photon fluorescence lifetime measurements.