Pulse Packet Research Articles

Generation of pulse bursts with controllable number of pulses and of spectral broadening directly at the laser output from a km-long Yb-doped all-fiber laser

In this work, we study the pulse burst regime of a fiber laser, which allows generating packets of multiple pulses whose number can be precisely controlled by modifying the polarization state by means of two retarder plates (QWR, HWR). The proposed experimental scheme is a highly energetic Yb-doped all-fiber ring pulsed laser operating in the 1064 nm wavelength region and using a nonlinear polarization rotation (NPR)-based passive mode locking technique. Raman scattering effects can be found by increasing pump power to achieve the formation of up to four Stokes, resulting in a spectral broadening over more than 200 nm.

Laser processing of silicon with GHz burst pumped third harmonics for precise microfabrication.

Femtosecond laser processing has proved to be a valuable tool for various microfabrication applications. In order to further increase the quality and efficiency of femtosecond laser processing, processing with GHz burst mode lasers has gained attention in recent years, where packets of high-repetition rate pulses are used instead of single pulses at the fundamental repetition rate. However, the use of burst-pulses has mainly been limited to the fundamental wavelength of powerful regenerative amplifier systems, often near 1 micrometer wavelength. In this study, we explore the characteristics and potential benefits of further wavelength conversion of burst-pulses emitted at the near-infrared to the ultraviolet region via direct third-harmonic generation. We construct an in-line process evaluation setup with a chromatic confocal sensor, and evaluate the ablation characteristics of the burst-pumped and non-burst processing of silicon. We observe that burst-mode processing has significantly reduced surface roughness and debris, resulting in high-quality laser processing. To demonstrate the utility of such burst-pumped UV processing, we show the successful milling of a spherical structure enabled by in-line surface profile feedback, while similar processing with non-burst conditions did not work. We believe such results show the strong potential of burst laser sources for use in accurate microfabrication of structures with micrometer-scale resolution.

Selected aspects of measurement data processing in electronic warfare devices

Electronic warfare (Polish acronym WRE ‒ walka radioelektroniczna) is a set of militaryactions based on the use of the electromagnetic spectrum and it includes:— reception and identification of electromagnetic emissions,— reducing the effectiveness of the enemy’s electronic devices,— enabling effective use of the spectrum by own forces.The task of the WRE in peacetime is to obtain information about radio-electronic devices, especiallyradars. These tasks are performed by ELINT (Electronic Intelligence) and/or ESM (Electronic WarfareSupport Measures) devices. They operate passively in the 0.5÷18 GHz band, their detection is difficultand the information they provide allows to detect a threat to own forces and to take appropriatecountermeasures. Radar recognition is a complex process that involves the following stages. The firststage: gathering measurements and their grouping into the so-called packets and graphical display ofthe received pulse trains. The measurements are represented by the so-called measurement vectors(descriptors) containing signal parameters, including the TOA (Time of Arrival) pulse with nanosecondaccuracy. The second stage: associating pulse packets with logical sources in order to obtainrepresentative data strings. This stage is signal sorting and deinterleaving. The third stage: estimationof the WS signal vector based on the associated pulse packets. The final stage of data processing is thecomparison of the obtained signal descriptor parameters WS with Database (BD) radar patterns. Thereconnaissance result allows for the assessment of the threat resulting from the operation of this radar.Radar recognition requires precise determination of many parameters of its signal. For pulsed radars,important parameters are the Pulse Repetition Interval (PRI) and the type of PRI modulation. Radarsare characterised by a high complexity of PRI changes. This provides great utility and makes it possibleto distinguish even radar units and changes in their locations. This allows for the detection and fullidentification of objects that use radars (e.g. ships) with the given object completely out of sight; it alsoallows to predict intentions of the target. The basic inter-pulse PRI modulations include: stagger, dwelland switch, jitter or sliding. PRI changes in radar signals may be periodic with long cycles, difficultto identify in cluttered conditions. Unfortunately, the received pulse trains are usually distorted. Thismakes the WS estimation process difficult ‒ especially in automatic mode. PRI analysis has receivedmuch attention in the literature. The methods are computationally complex and have numerouslimitations. This article presents ASWC algorithm (Sequential Cycle Detection Algorithm) of PRIproprietary, with relatively low computational complexity. Examples of test results confirming its higheffectiveness in automatic PRI analysis performed under interference conditions were also presented.Keywords: radars, electronic warfare, radar recognition, ELINT, ESM, pulse descriptor, PRI

Provocation of verbal interaction of dolphins via a hydro-acoustic channel on the basis of cognitive empathy

The provocation of the hydroacoustic communication interaction of Tursiops truncatus dolphins based on cognitive empathy showed that they use packets of ultrashort pulses (USPs) in the process of “dialogue”. The duration of bursts varies from 40 ms to 3000 ms with modulation of the interval between USPs from ~1 to ~120 ms and pauses between bursts. The interval modulation pattern is structured using various modulation laws. The communication signals were obtained in an experiment with theparticipation of three animals, who knew the main task of sequential acoustic differentiation of two objective stimuli. The impetus for hydroacoustic interaction is the resolution of uncertainty when teaching the respondent the inverse differentiation problem. This generates emotional empathy in observers and provokes vocalization between individuals. The advantages and disadvantages of methodological methods of provoking hydroacoustic interaction are considered in detail, starting the process of cognitive empathy. In the method under consideration, echolocation and communication signals are spaced apart in time and space, which allows them to be uniquely identified.

Estimation of requirements for signal parameters at V-shaped frequency distribution in the mathematical model of a planar phased array antenna

A brief review provides methods of focusing electromagnetic radiation of a flat phased array antenna based on mutually consistent spatial-amplitude-phase-frequency control of the radiated signals and limitations of their potential capabilities arising from various random fluctuations of signal and antenna parameters. The performed statistical study revealed the influence of various random and deterministic changes in the electrical and structural parameters of antennas, control systems for radiated signals with a V-shaped frequency distribution over the aperture of a flat phased array on the peak power level, duration, and repetition period of focused pulses. The parameters of the law of spatial-amplitude-phase-frequency control should be stable for a time equal to the average pulse duration at the output of the emitters when forming a single spatiotemporal pulse, and when forming a sequence of spatiotemporal pulses within duration of this packet of spatiotemporal pulses. The requirements for the accuracy and stability of parameters of the space-phase-frequency signal control law are considered. The analyses of influence of various deviations from the set values of the parameters of the law of spatial-phase-frequency control of emitted signals in the channels of a multi-position system of emitters in the formation of sequences of spatiotemporal pulses is analyzed. It is shown that the influence of errors in the location of the phase centers of the emitters in the direction of radiation does not depend on the distance to the focusing point, but is significant and requires special measures to reduce them. The influence of initial phase setting errors on the characteristics of the generated sequence of spatiotemporal pulses also does not depend on the radiation time. The range of permissible values of the maximum initial phase setting errors behind the aperture of a flat phased antenna array, in which the decrease in the power flux density value does not exceed 10%, should not exceed p/3. The discreteness and random errors in establishing the initial phases of individual radiation sources of a flat phased array equal to p/3 practically do not affect the duration and repetition period of the sequence of spatiotemporal pulses.

Next generation CANCAN focusing for remote stimulation by nanosecond electric pulses

Focusing electric pulse effects away from electrodes is a challenge because the electric field weakens with distance. Previously we introduced a remote focusing method based on bipolar cancellation, a phenomenon of low efficiency of bipolar nanosecond electric pulses (nsEP). Superpositioning two bipolar nsEP into a unipolar pulse canceled bipolar cancellation (“CANCAN” effect), enhancing bioeffects at a distance despite the electric field weakening. Here, we introduce the next generation (NG) CANCAN focusing with unipolar nsEP packets designed to produce bipolar waveforms near electrodes (suppressing electroporation) but not at the remote target. NG-CANCAN was tested in CHO cell monolayers using a quadrupole electrode array and labeling electroporated cells with YO-PRO-1 dye. We routinely achieved 1.5–2 times stronger electroporation in the center of the quadrupole than near electrodes, despite a 3–4-fold field attenuation. With the array lifted 1–2 mm above the monolayer (imitating a 3D treatment), the remote effect was enhanced up to 6-fold. We analyzed the role of nsEP number, amplitude, rotation, and inter-pulse delay, and showed how remote focusing is enhanced when re-created bipolar waveforms exhibit stronger cancellation. Advantages of NG-CANCAN include the exceptional versatility of designing pulse packets and easy remote focusing using an off-the-shelf 4-channel nsEP generator.

Dynamic behaviors of special noise-like pulses and rogue waves in an L-band ultrafast fiber laser

We demonstrate a composite regime of the special noise-like pulses (NLPs) and rogue waves (RWs) in an L-band dispersion-managed fiber laser. Apart from stable ultrashort pulses, the fiber laser can easily generate unique NLPs with clear peak on broad spectrum at high pump power and proper polarization state. In this regime, these tiny pulses with irregular intervals experience random fluctuations, making the dynamic evolutions of these pulse envelopes look like the endless undulating mountains along the hundreds of intra-cavity roundtrips. In addition, the real-time observation based on the time-stretch technique shows that there are the unique lacking pieces and changeable pulse durations in this NLPs regime. Besides, the chaotic pulse packets with intensity fluctuations are observed at the proper condition, showing the typical statistical distribution with L shape, which can be called as the typical RWs. It is believed that these results will facilitate the further understanding of the nonlinear characteristics of the NLPs and RWs in ultrafast fiber lasers.

Observation of Ultrabroadband Striped Space-Time Surface Plasmon Polaritons

Because surface plasmon polaritons (SPPs) are surface waves characterized by one free transverse dimension, the only monochromatic diffraction-free spatial profiles for SPPs are cosine and Airy waves. Pulsed SPP wave packets have been recently formulated that are propagation-invariant and localized in the in-plane dimensions by virtue of a tight spectral association between their spatial and temporal frequencies, which have thus been dubbed “space-time” (ST) SPPs. Because of the spatiotemporal spectral structure unique to ST-SPPs, the optimal launching strategy of such novel plasmonic field configurations remains an open question. We present here a critical step toward realizing ST-SPPs by reporting observations of ultrabroadband striped ST-SPPs. These are SPPs in which each wavelength travels at a prescribed angle with respect to the propagation axis to produce a periodic (striped) transverse spatial profile that is diffraction-free. We start with a free-space ST wave packet that is coupled to a ST-SPP at a gold-dielectric interface, and unambiguously identify the ST-SPP via an axial beating detected in two-photon fluorescence produced by the superposition of incident ST wave packet and the excited surface-bound ST-SPP. These results highlight a viable approach for efficient and reliable coupling to ST-SPPs and, thus, represent the first crucial step toward realization of the full potential of ST-SPPs for plasmonic sensing and imaging.

Inhibition allocates spikes during hippocampal ripples

Sets of spikes emitted sequentially across neurons constitute fundamental pulse packets in neural information processing, including offline memory replay during hippocampal sharp-wave ripples (SWRs). The relative timing of neuronal spikes is fine-tuned in each spike sequence but can vary between different sequences. However, the microcircuitry mechanism that enables such flexible spike sequencing remains unexplored. We recorded the membrane potentials of multiple hippocampal CA1 pyramidal cells in mice and found that the neurons were transiently hyperpolarized prior to SWRs. The pre-SWR hyperpolarizations were spatiotemporally heterogeneous, and larger hyperpolarizations were associated with later spikes during SWRs. Intracellular blockade of Cl−-mediated inhibition reduced pre-SWR hyperpolarizations and advanced spike times. Single-unit recordings also revealed that the pre-SWR firing rates of inhibitory interneurons predicted the SWR-relevant spike times of pyramidal cells. Thus, pre-SWR inhibitory activity determines the sequential spike times of pyramidal cells and diversifies the repertoire of sequence patterns.

Mechanism of domain walls drift in pulsed magnetic fields in iron garnet crystals

Conditions for the drift of domain walls in pulsed magnetic fields of various organization (bipolar and unipolar pulsed magnetic fields, pulse packets) are established. Dependences of domain walls drift velocity on the parameters of pulsed magnetic fields (frequency, amplitude, pulse duration) are obtained. As a result of numerical simulation of domain walls drift in a uniaxial sample, an experimentally confirmed mechanism of domain walls drift in pulsed magnetic fields is proposed. Keywords: pulsed magnetic fields, iron garnets, domain walls, dynamic domain structures, drift of domain walls.

Space-Quasiperiodic and Time-Chaotic Parametric Patterns in a Magnonic Quasicrystal Active Ring Resonator

We demonstrate the dissipative spatiotemporal patterns that are generated by an active ring resonator based on a magnonic quasicrystal (MQC) with Fibonacci-type structure. The dissipative patterns are formed through the magnetostatic surface spin-wave (MSSW) parametric decay into exchange spin waves (SWs), temporal dispersion of the ring resonator and amplification. In the spatial domain, the MSSW and SW parametric patterns measured with the help of Brillouin light spectroscopy have the quasiperiodic spatial localization in crests and grooves of the MQC, respectively. In contrast to the optical quasiperiodic parametric spatial conservative solitons, the amplitude profiles of the magnonic quasiperiodic parametric spatial dissipative patterns correspond to the profiles of the crests and grooves of the MQC. In the time domain, the packets of the chaotic parametric pulses, which are analogs of temporal solitons, are generated at each point of the spatial patterns. The chaotic nature of such pulses is confirmed by an estimate of a highest Lyapunov exponent from the experimental time series. The pulse packets are formed through the time-filtering technique using the external microwave (MW) pulses to control a ring gain. It is shown that at a certain duty factor of the external MW pulses, the parametric MSSW pulses have the amplitude and phase profiles corresponding to the profiles of a conservative bright envelope soliton.

MP07-17 STONE ABLATION EFFICACY OF A NEW PROTOTYPE HOLMIUM:YAG PULSE-MODULATED LASER AT WORKING DISTANCES OF UP TO 3 mm

You have accessJournal of UrologyStone Disease: Basic Research & Pathophysiology (MP07)1 Sep 2021MP07-17 STONE ABLATION EFFICACY OF A NEW PROTOTYPE HOLMIUM:YAG PULSE-MODULATED LASER AT WORKING DISTANCES OF UP TO 3 mm Bingyuan Yang, Isha Parab, Jasmine Cancino, Sanwei Liu, Aditi Ray, Thomas Hasenberg, Tim Harrah, and Ben Turney Bingyuan YangBingyuan Yang More articles by this author , Isha ParabIsha Parab More articles by this author , Jasmine CancinoJasmine Cancino More articles by this author , Sanwei LiuSanwei Liu More articles by this author , Aditi RayAditi Ray More articles by this author , Thomas HasenbergThomas Hasenberg More articles by this author , Tim HarrahTim Harrah More articles by this author , and Ben TurneyBen Turney More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000001980.17AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Holmium:YAG laser has been the lithotrite of choice for around 30 years in kidney stone surgery. The relatively high absorption in water is clinically useful but also limits the effective range of these lasers. Laser technology has taken advantage of the “Moses effect” to improve energy delivery to the target while reducing heating of the irrigation fluid. We report on a new prototype Holmium laser that fires multiple micro-pulses in pulse packets and present stone phantom ablation rate results at fiber-to-stone working distances of up to 3mm utilizing a bench model. METHODS: Uniform, homogeneous BegoStones (15:3 BegoStone:water) were used. A 242mm core fiber was attached to the prototype laser and the fiber was moved over the surface of the stone in a predetermined pattern using an automated system. A range of pulse packet energy/frequency settings from 20 W to 45 W were investigated. Stone ablation efficiency was measured by dry-weight difference before and after treatment. A range of working distances (WDs) from 0.5 mm to 3 mm were used to investigate the effect of increased distance to the stone. RESULTS: Measurable ablation rates were observed with the prototype pulse-modulated laser up to a working distance of 3 mm, across a range of powers (figure 1). The ablation rate at 3 mm WD was 27.6% of that at 0.5 mm WD (range 12.9-44.4%). Results from a reference holmium laser using the same methodology are also included. CONCLUSIONS: The prototype laser demonstrated an impressive working range in our bench testing across a range of power settings, with measurable ablation even at a WD of 3 mm. This suggests that these micro-pulses produce a significant Moses effect. We feel that pulse-modulation with packets of micro-pulses can synergise well with the Moses effect to increase the effective range and needs to be further tested in a clinical setting. (Disclaimer: Concept device or technology. Not available for sale). Source of Funding: Boston Scientific Corp © 2021 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 206Issue Supplement 3September 2021Page: e146-e146 Advertisement Copyright & Permissions© 2021 by American Urological Association Education and Research, Inc.MetricsAuthor Information Bingyuan Yang More articles by this author Isha Parab More articles by this author Jasmine Cancino More articles by this author Sanwei Liu More articles by this author Aditi Ray More articles by this author Thomas Hasenberg More articles by this author Tim Harrah More articles by this author Ben Turney More articles by this author Expand All Advertisement Loading ...

Real-Time High Frame Rate Color Flow Mapping System.

Plane wave (PW) transmission (TX) can be profitably used to improve the performance of color flow mapping (CFM) systems by increasing the autocorrelation ensemble length (EL) and/or the frame rate (FR). Although high-end scanners tend to include imaging schemes using PW TX and parallel receive beams, high frame rate (HFR) CFM has been so far experimentally implemented mostly through research platforms that transmit PWs and beamform/process the received channel data off-line. In this article, full real-time implementation of PW CFM with continuous-time clutter filtering and extended FR/EL is reported. The field-programmable gate arrays (FPGAs) and digital signal processors (DSPs) onboard the ULA-OP 256 research scanner were programmed to perform high-speed parallel beamforming and autocorrelation-based CFM processing, respectively. Different strategies were tested, in which the TX of PWs for CFM is either continuous or interleaved with the TX of packets of B-mode pulses. A fourth-order Chebyshev continuous-time high-pass filter with programmable cutoff frequency was implemented and its clutter rejection performance was positively compared with that obtained when operating on packet data. CFM FRs up to 575 were obtained. The possibility of programming the autocorrelation EL up to 64 permitted to detect flow with high sensitivity and accuracy (average relative errors down to 0.4% ± 8.4%). In vivo HFR movies are presented, showing the dynamics of flow in the common carotid artery, which highlight the presence of secondary flow components.

Development of an optimization method for measuring the Doppler frequency of a packet taking into account the fluctuations of the initial phases of its radio pulses

The necessity of estimating the decrease in the accuracy of measuring the informative parameters of a radar signal in real conditions of its propagation and reflection has been substantiated. The results of the estimation determine the requirements for optimizing this measurement to achieve the required efficiency. A numerical analysis of the decrease in the accuracy of measuring the Doppler frequency of a coherent packet is presented, depending on the statistical characteristics of fluctuations of the initial phases of its radio pulses. Expressions are given for calculating the fluctuation component of the measurement error of radio pulse packet frequency for various coefficients of interpulse correlation of phase fluctuations. An assessment is made of the possibility of increasing the accuracy of Doppler frequency measurement, which can be ensured by statistical optimization of the algorithm for time-frequency processing of a given radar signal by taking into account its phase fluctuations. The conditions for the multiplicative influence of phase fluctuations of radio pulses of the received packet are substantiated, which determine the efficiency of optimization of Doppler frequency measurement. Based on the results of the study, an optimization method for measuring the Doppler frequency of the packet taking into account fluctuations in the initial phases of its radio pulses is proposed. The accuracy of Doppler frequency measurement under the influence of both the internal noise of the radar receiver and the correlated phase fluctuations of its radio pulses is estimated. The efficiency of optimization of measuring the Doppler frequency of the packet is estimated taking into account fluctuations of the initial phases of its radio pulses by means of computer simulation. It is proved that, under the influence of phase fluctuations, the accuracy of Doppler frequency measurement can be increased due to the performed optimization from 1.86 to 6.29 times. This opens the way to improving the existing algorithms for measuring the higher time range derivatives to improve the quality of tracking complex maneuvering aerodynamic objects. This explains the importance and usefulness of the work for the radar theory.

Information propagation in recurrent neuronal populations with mixed excitatory–inhibitory synaptic connections

Information propagation in the cortical neural network has attracted a large amount of attention. In this paper, a feedforward network is constructed with each subnetwork being a recurrent neuronal population, consisting of neurons coupled by excitatory and inhibitory synapses, in which neurons have both types of outgoing synapses. Namely, neurons in the constructed feedforward neuronal networks have mixed excitatory–inhibitory synapses. Here, propagation of population firing rate and pulse packets are investigated. For the propagation of population firing rate, it is found that proper feedforward connection probability and strength could promote the propagation of population firing rate. Properly larger feedforward synaptic time constant could considerably enhance the fidelity of the propagating population firing rate. For the propagation of pulse packet, we find suitably adjusting the relative strength, recurrent probability, and feedforward synaptic connection can promote propagation of pulse packet. Notably, different from each other, larger feedforward synaptic time constant can considerably promote the propagation of population firing rate while hindering the propagation of pulse packets.

Myocardial Strain Measured by Epicardial Transducers—Comparison Between Velocity Estimators

This study describes results from an experimental ultrasound system with miniature transducers sutured directly onto the epicardial surface and used to measure heart contractions continuously. This system was used to find velocity distributions through the myocardium. The resulting velocities were used to track the motion of four layers at different depths through the myocardium and to find the regional strain in each of the four layers. Velocities inside the myocardium vary from the epicardial to the endocardial borders. Conventional velocity estimators based on Doppler and on time delay estimation were modified to better handle these variations. Results from four different velocity estimators were tested against a simulation model for ultrasound echoes from moving tissue and on ultrasound recordings from five animals. We observed that the tested velocity estimators were able to reproduce the myocardial velocity distributions, track the myocardial layer motion and estimate strain at different positions inside the myocardium for both simulated and real ultrasound recordings. The most accurate results were obtained when the digitized ultrasound scanlines were upsampled by a factor of 10 before applying cross-correlation to estimate time delays. A modified Doppler algorithm allowing the velocity to vary linearly with time throughout the duration of the pulse packet (constant acceleration Doppler) was found to be better at capturing rapidly changing velocities compared with conventional Doppler processing. The best results were obtained using upsamling and time delay estimation, but the long computation time required by this method may make it best suited in a laboratory setting. In a real-time system, the computationally quicker constant acceleration Doppler may be preferred.

Physical and rheological properties of liquid whole egg after treatment of concentrated microwave field (CMF)

The influence of selected physical and rheological properties of the egg mass after the treatment of concentrated microwave field (CMF) was analysed in the study. CMF treatment can be generated in the continuous or pulsed way where microwave field is concentrated by a special waveguide. The raw material for the research was fresh hen eggs obtained from Leghorn Brown laying hens at the age of 30-50 weeks. The study investigated the effect of CMF pulses on the raw material, where the variable parameters were intervals between single pulses of 0.5 s, 1.0 s or 1.5 s, as well as 3 different numbers of CMF pulse packets for each of these intervals (5, 7 or 9). In this way, 9 research variants were obtained, not counting the control sample. After completion of the CMF treatment, the temperature of the samples was measured, and then they were cooled down to the temperature of 20 °C, where the analysis of active acidity (pH), color measurements expressed as L*a*b* and viscosity was performed. The results were statistically processed using the analysis of variations, Duncan’s test and the so-called “Response Surface Methodology” with corresponding Pareto charts showing the significance of the analyzed variables and their interactions. It was found that both the amount of energy supplied to the system and the intervals between the CMF pulses for most of the analyzed parameters had a statistically significant effect. The “response surface” models may have practical application, eg in industrial conditions, in determining the impact of individual technological parameters on the final quality of food products, including physical and rheological characteristics.

High-energy noise-like pulses and cylindrical vector beam generation in an Er,Yb-codoped mode-locked fiber laser

As required by nonlinear polarization rotation (NPR) mode-locked Er,Yb co-doped fiber laser, high energy noise-like pulses (NLPs) with cylindrical symmetry, namely cylindrical vector beam (CVB), are obtained. The noise-like pulsed CVBs are produced by passing a q-plate with a topological charge of 1/2 positioned at the output port of the laser cavity. In the fiber laser, a stable mode-locking regime is initiated at the threshold input pump power of 1.44 W. As the input pump power is raised to 11.67 W, the duration of the mode-locking pulse packet is prolonged from 458.6 ps to 2.758 ns, and the corresponding average output power is linearly raised from 35 to 253.3 mW with a maximal pulse packet energy of 260 nJ and the pulse repetition rate of 973.5 kHz. We obtain the mode-locked pulses based on the NLP of measuring autocorrelation curves with coherent peaks on a wide base. The produced ultrafast high-energy CVBs (radially polarized and azimuthally polarized) can be potentially used for applications like particle acceleration and light trapping.

Freezing and freeze-drying of strawberries with an additional effect of micro-vibrations.

Our research focuses on the formation of ice crystals and evaluating the structure of preserved frozen and freeze-dried strawberries. Strawberries were frozen in two ways. One-half of strawberries were frozen at -30°C under conditions of convective heat exchange. The other half of strawberries were frozen under the same conditions with an additional effect on the strawberries of micro-vibrations created in the air of the freezer according to a specific program. A digital frequency synthesizer that generates 250W/m3 electromagnetic field rectangular pulse packets in the frequency bands of 2500-5000kHz creates micro-vibrations. The microstructure of strawberries, the number of cells that have retained their structure and firmness were determined in frozen strawberries. The strawberries retained 25-30% of the cell structure of their total number during traditional freezing, and 65-70% of the cell structure when frozen under micro-vibration. The data of the penetration and shear stress showed that the strawberries frozen under micro-vibration conditions were 10-15% stronger. Then researched strawberries were vacuum freeze-dried. The primary drying temperature was 30 + 1°C below zero and at the secondary drying the temperature was 38-40°C. The microstructure and firmness of strawberries were researched in dried samples also. Freeze-dried strawberries frozen under micro-vibration had small and evenly distributed capillaries and their firmness was 8-10% higher than freeze-dried strawberries frozen by the traditional method. Thus, freezing strawberries with the additional effect of micro-vibration have a positive effect on the firmness of both frozen strawberries and freeze-dried strawberries.

Reduction of auto seismic oscillations of the ballistic laser gravimeter on account of the excitation of the induction-dynamic catapult by a pulse packet

In order to reduce auto seismic oscillations in the ballistic laser gravimeters (BLG) with a symmetric method of measuring the gravitational acceleration (GA), an induction-dynamic catapult (IDC) is used, which is excited by a pulse packet from a capacitive energy storage unit (CES). With such excitation, a decrease in the amplitude of auto seismic oscillations is achieved by reducing the amplitude and increasing the duration of action of the electrodynamic force that occurs in the IDC when pushing the test body (TB).A mathematical model of the IDC of the ballistic laser gravimeter with a symmetric method of measuring the GA is developed and the modeling of its electromechanical characteristics is carried out. Various methods of generating a packet of excitation pulses of the IDC inductor are considered and the characteristics of electrodynamic force pulses that accelerate the armature of the catapult with TB are investigated for them. The effect of IDC excitation by a pulse packet on the auto seismic component of the GA measurement is investigated. It is shown that on account of the excitation of the IDC by a ten-pulse packet, the auto seismic component of the uncertainty of the GA measurement by ballistic gravimeters can be reduced several (3–5) times in comparison with the excitation of the catapult by a single pulse.