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1
Zhang, Yangkai, and Qian Li. "Influence of Hydraulic Parameters on Multi-Stage Pulse Characteristics of Pressurized Pulsed Water Jet." Processes 11, no. 8 (August 20, 2023): 2502. http://dx.doi.org/10.3390/pr11082502.
Повний текст джерелаАнотація:
The multi-stage pulse competition of pressurized pulsed water jet becomes the initial pulse at the head tip, and hydraulic parameters are the key parameters that affect the characteristics of multiple pulses. Based on the ultra-high-speed imaging system, a pressurized pulsed water jet flow field capture system was constructed, and the effects of initial pressure and driving pressure of the pressurized chamber on the characteristics of multi-stage pulses were studied. The experimental results show that as the initial pressure of the booster chamber increases, the jet changes from a discontinuous state to a continuous state, and the multi-level pulse simultaneously changes from dominant multi-pulse to implicit multi-pulse; as the driving pressure increases, the initial spacing between the first pulse and the second pulse increases, and the peak velocity of the initial pulse gradually increases. At the same time, the location of the peak velocity also shifts away from the nozzle as the driving pressure increases. In addition, the peak velocity of the initial pulse is relatively close to the theoretical velocity of the continuous jet under driving pressure conditions.
2
Su, Zhi, Haohua Zong, Hua Liang, Jun Li, and Xiancong Chen. "Characteristics of a dielectric barrier discharge plasma actuator driven by pulsed-DC high voltage." Journal of Physics D: Applied Physics 55, no. 7 (November 12, 2021): 075203. http://dx.doi.org/10.1088/1361-6463/ac30bc.
Повний текст джерелаАнотація:
Abstract Dielectric barrier discharge using pulsed-DC high voltage (pulsed-DC DBD) have been proven to be capable of effectively reducing skin friction drag in turbulent boundary layers with limited power consumption, thus producing significant net power savings. In this work, the characteristics of pulsed-DC DBD, including power consumption, induced flow structure, thermal effect, and body force, are investigated sequentially. Both the power consumption and pressure waves produced by pulsed-DC DBD are similar to that of DBD using nanosecond pulses (ns-DBD), whereas the wall-bounded jet structure resembles that of DBD using sinusoidal high voltage (ac-DBD). A curved wall jet is induced at a small pulse width, which turns into a straight one due to the combined effect of momentum and thermal addition when the pulse width increases. With increasing pulse width, the induced body force goes up while the thermal effect weakens. Although pulse frequency has no impact on the wall-bounded jet topology, the body force increases with pulse frequency because of the enhanced energy entrainment. With these results, four parameters that affect the performance of pulsed-DC DBD are extracted, including the pulse leading edge, pulse width, frequency, and amplitude, which lays the foundation for the optimization of pulsed-DC DBD.
3
Seol, Youbin, Minsu Choi, Hongyoung Chang, and Shinjae You. "Study on OH Radical Production Depending on the Pulse Characteristics in an Atmospheric-Pressure Nanosecond-Pulsed Plasma Jet." Materials 16, no. 10 (May 19, 2023): 3846. http://dx.doi.org/10.3390/ma16103846.
Повний текст джерелаАнотація:
Hydroxyl radicals (OH) play a crucial role in plasma-bio applications. As pulsed plasma operation is preferred, and even expanded to the nanosecond range, it is essential to study the relationship between OH radical production and pulse characteristics. In this study, we use optical emission spectroscopy to investigate OH radical production with nanosecond pulse characteristics. The experimental results reveal that longer pulses generate more OH radicals. To confirm the effect of pulse properties on OH radical generation, we conduct computational chemical simulations, focusing on two types of pulse properties: pulse instant power and pulse width. The simulation results show that, similar to the experimental results, longer pulses generate more OH radicals. In the nanosecond range, reaction time is critical for OH radical generation. In terms of chemical aspects, N2 metastable species mainly contribute to OH radical generation. It is a unique behavior observed in nanosecond range pulsed operation. Furthermore, humidity can turn over the tendency of OH radical production in nanosecond pulses. In a humid condition, shorter pulses are advantageous for generating OH radicals. Electrons play key roles in this condition and high instant power contributes to them.
4
King, Emma, Deirdre Cobbin, and Damien Ryan. "The Reliable Measurement of Radial Pulse: Gender Differences in Pulse Profiles." Acupuncture in Medicine 20, no. 4 (December 2002): 160–67. http://dx.doi.org/10.1136/aim.20.4.160.
Повний текст джерелаАнотація:
This study was undertaken to determine whether healthy adults exhibited characteristic pulse profiles. Pulse characteristics measured for 83 women and 65 men included presence at the Traditional Chinese Medicine (TCM) locations ( Cun, Guan, Chi); and depth (superficial, middle, deep), overall pulse force, relative pulse force, pulse width and pulse rhythm. Most subjects had similar values for many of the characteristics investigated including relative pulse force at the three traditional palpation locations ( Cun, Guan and Chi), pulse width and pulse rhythm. There were some significant gender differences. The pulse was present beyond Chi in 90% of males compared with 56% of females. Female pulses tended to be less forceful compared with males. However, with the exception of overall force, there was little support for TCM assumptions of gender differences in pulse such as in left/right balance. There was some support for the use of the TCM palpation locations Cun, Guan and Chi to discriminate between pulses since there was significant differences in manifestations of some pulse characteristics among these locations.
5
YATSUI, KIYOSHI, KOUICHI SHIMIYA, KATSUMI MASUGATA, MASAO SHIGETA, and KAZUHIKO SHIBATA. "Characteristics of pulsed power generator by versatile inductive voltage adder." Laser and Particle Beams 23, no. 4 (October 2005): 573–81. http://dx.doi.org/10.1017/s0263034605050779.
Повний текст джерелаАнотація:
A pulsed power generator by inductive voltage adder, versatile inductive voltage adder (VIVA-I), which features a high average potential gradient (2.5 MV/m), was designed and is currently in operation,. It was designed to produce an output pulse of 4 MV/60 ns by adding 2 MV pulses in two-stages of induction cells, where amorphous cores are installed. As a pulse forming line, we used a Blumlein line with the switching reversed, where cores are automatically biased due to the presence of prepulse. Good reproducibility was obtained even in the absence of the reset pulse. Within ∼40% of full charge voltage, pulsed power characteristics of Marx generator, pulse forming line (PFL), transmission line (TL), and induction cells were tested for three types of loads; open-circuit, dummy load of liquid (CuSO4) resistor, and electron beam diode. In the open-circuit test, ∼2.0 MV of output voltage was obtained with good reproducibility. Dependences of output voltage on diode impedances were evaluated by using various dummy loads, and the results were found as expected. An electron-beam diode was operated successfully, and ∼18 kA of beam current was obtained at the diode voltage of ∼1 MV.
6
Shaburova, Nataliya, Valeriy Krymsky, and Ahmad Ostovari Moghaddam. "Theory and Practice of Using Pulsed Electromagnetic Processing of Metal Melts." Materials 15, no. 3 (February 7, 2022): 1235. http://dx.doi.org/10.3390/ma15031235.
Повний текст джерелаАнотація:
In industrial practice, various methods of external influences on metal melts are used. For example, vibration processing, exposure to ultrasound, and other physical fields. The main purpose of such influences is purposeful grinding of the metal structure, which contributes to the improvement of mechanical characteristics. The article presents an overview of research on pulse processing of ferrous and non-ferrous melts: processing with pulsed current, electromagnetic pulses and pulsed magnetic fields. The results of the analysis showed that, despite the different methods and devices used for these treatments, their effect on the structure and properties of the cast metal is generally the same. The main effect is observed in the refinement of the macro and microstructure and a simultaneous increase in the strength properties and plasticity. The intensity of the observed effects depends on the characteristics of the equipment used to create the pulses. The main characteristics are: pulse duration, pulse frequency, current amplitude, and power.
7
Wang, Fuyong, Zhipeng Qin, Jing Luo, Xiudong Zhou, and Bo Li. "Duration-controllable mid-infrared pulse from bias-pumped Er:ZBLAN fiber laser." Laser Physics 32, no. 1 (December 6, 2021): 015102. http://dx.doi.org/10.1088/1555-6611/ac3d0f.
Повний текст джерелаАнотація:
Abstract We experimentally demonstrate the generation of duration-controllable pulses at 2.8 µm based on bias-pump technique for the first time. Bias-pumped by a 976 nm continuous-wave (CW)-pulsed combined laser, duration-controllable pulses are produced from an Er:ZBLAN fiber laser and the duration is entirely determined by the duration of pump pulse. Numerical simulations agree with experimental results well, and further predict that the temporal profile of output pulse from bias-pumped Er:ZBLAN fiber laser can also be identical with that of pump pulse under certain conditions. The pump-controlled mid-infrared pulse may have more applications in various areas due to its manageable temporal characteristics.
8
Kandratsyeu, Aleh, Uladzimir Sabaleuski, Luis Redondo, and Andrei G. Pakhomov. "Four Channel 6.5 kV, 65 A, 100 ns–100 µs Generator with Advanced Control of Pulse and Burst Protocols for Biomedical and Biotechnological Applications." Applied Sciences 11, no. 24 (December 11, 2021): 11782. http://dx.doi.org/10.3390/app112411782.
Повний текст джерелаАнотація:
Pulsed electric fields in the sub-microsecond range are being increasingly used in biomedical and biotechnology applications, where the demand for high-voltage and high-frequency pulse generators with enhanced performance and pulse flexibility is pushing the limits of pulse power solid state technology. In the scope of this article, a new pulsed generator, which includes four independent MOSFET based Marx modulators, operating individually or combined, controlled from a computer user interface, is described. The generator is capable of applying different pulse shapes, from unipolar to bipolar pulses into biological loads, in symmetric and asymmetric modes, with voltages up to 6.5 kV and currents up to 65 A, in pulse widths from 100 ns to 100 µs, including short-circuit protection, current and voltage monitoring. This new scientific tool can open new research possibility due to the flexibility it provides in pulse generation, particularly in adjusting pulse width, polarity, and amplitude from pulse-to-pulse. It also permits operating in burst mode up to 5 MHz in four independent channels, for example in the application of synchronized asymmetric bipolar pulses, which is shown together with other characteristics of the generator.
9
Wang, Wen Bin, Dao Yuan Liu, and Yu Qin Yao. "Study of Transmission Characteristics of Optical Pulse in the Dispersive Fiber." Applied Mechanics and Materials 513-517 (February 2014): 2775–77. http://dx.doi.org/10.4028/www.scientific.net/amm.513-517.2775.
Повний текст джерелаАнотація:
Chromatic dispersion and nonlinearity effect are the two important factors affecting the optical pulse which propagates in the optical fiber. The former makes the pulse broaden, the latter mainly broaden pulse spectrum. Therefore, the linear and nonlinear dispersive propagation and control of optical pulses in the fiber has always been an important research topic of concern. In this paper, Starting from the nonlinear Schrodinger equation of the optical pulse and neglecting the chromatic dispersion, under the situation of chirp and chirp-free Gaussian pulse, we analytical analyzed, calculated and simulated the frequency chirp, pulse broadening factor and waveform of the Gaussian optical pulses in dispersion fiber. And numerical studied the waveform evolution of chirp-free super-Gaussian optical pulse with distance, analyzed the influence of optical pulse propagation by dispersion in different shapes and different initial chirp.
10
Fujii, T., R. Gobbo, and M. Rea. "Pulse corona characteristics." IEEE Transactions on Industry Applications 29, no. 1 (1993): 98–102. http://dx.doi.org/10.1109/28.195894.
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11
Adhikari, Pitri Bhakta, and Aashutosh Adhikari. "Comparing the Wave Characteristics of Breakdown Pulses of the Lightning Waveforms in the Himalayan Region." Scientific World Journal 2021 (February 19, 2021): 1–9. http://dx.doi.org/10.1155/2021/6381439.
Повний текст джерелаАнотація:
We have analyzed the breakdown pulse train with or without the main event in this paper. Among the selected 81 flashes, 36 flashes are starting positively, and 45 are starting negatively. Also, 58 flashes contain positive pulses, and 67 flashes contain negative pulses, whereas 44 flashes contain both positive and negative pulses. Among these 81 flashes, 22 flashes follow the main events, and the rest are isolated events. In this study, we got the main duration of PB pulses as 1.94 ms and the time interval between the breakdown pulse and return stroke as 61.49 ms. On taking each pulse train, we found the rise time to be 2.6 μs, zero-crossing time 14.95 μs, and the time interval between pulses 199.3 μs. The largest pulse amplitude ratio in the preliminary breakdown pulse to the main event return stroke was 0.43.
12
Zhang, Chunlong, Chunying Li, Dongbo Lv, Hao Zhu, and Hongyan Xing. "An Experimental Study on the Effect of Multiple Lightning Waveform Parameters on the Aging Characteristics of ZnO Varistors." Electronics 9, no. 6 (June 3, 2020): 930. http://dx.doi.org/10.3390/electronics9060930.
Повний текст джерелаАнотація:
In this study, in order to study the effect of multi-pulse waveform parameters on the aging characteristics of ZnO varistor, the aging rate and surface temperature rise of ZnO varistor under the impact of multi-pulse current were analyzed. The number of pulses and the pulse interval under multiple pulses play a decisive role in the aging rate of ZnO varistor. The greater the number of pulses and the smaller the pulse interval, the higher the temperature rise of the ZnO varistor and the faster the aging rate, the more likely to be failure and damage. The surface temperature distribution of the ZnO varistor under multi-pulse is not uniform, and the more pulses, the more uneven the temperature distribution, but the surface temperature rise has a nonlinear relationship with the number of pulses. The relationship between pulse interval, impact times and average surface temperature rise is established. The aging mechanism of the ZnO varistor under a multi-pulse lightning stroke was revealed from the perspective of energy absorption and heat transfer modelling. The energy sustained by the ZnO varistor under multiple pulses have a nonlinear multiple relationship with the energy of the single pulse current wave at the same amplitude. The superimposed cumulative energy of the impact under multiple pulses accelerates the aging process of the ZnO varistor, and eventually produces an irreversible structural destruction.
13
Gapeev, M. I., Yu I. Senkevich, and O. O. Lukovenkova. "Estimation of Probability Distributions of Geoacoustic Signal Characteristics." Journal of Physics: Conference Series 2096, no. 1 (November 1, 2021): 012018. http://dx.doi.org/10.1088/1742-6596/2096/1/012018.
Повний текст джерелаАнотація:
Abstract The paper presents an estimation of probability distributions of geoacoustic signal characteristics. The studied signals have a pulsed nature. The ones have been recording at the geodynamic test site of the IKIR FEB RAS (Kamchatka Peninsula) for more than 20 years. To estimate the distribution of characteristics, such time intervals were determined in which histograms of the distribution did not change. The following characteristics were chosen for the estimation: maximum amplitude, the position of pulse envelope maximum, duration, filling frequency, and pulse-to-pulse interval. The obtained estimates made it possible to develop an empirical model of the geoacoustic emission signal. The model can help to test new and existing algorithms for the processing and analysis of geoacoustic signals. The paper also shows that the formalization of the selected characteristics makes it possible to search for anomalies, including those associated with seismic events, by the characteristic variations.
14
Romantsov, V. N., S. V. Romantsov, and N. V. Romantsova. "Frequency Response Extension of a Pulsed Magnetic Field Meter Based on an RL Integrator." Journal of the Russian Universities. Radioelectronics 26, no. 1 (March 7, 2023): 99–112. http://dx.doi.org/10.32603/1993-8985-2023-26-1-99-112.
Повний текст джерелаАнотація:
Introduction. Measurements of the amplitude-time characteristics of pulsed magnetic fields are required in various research and technology areas. Such measurements are carried out during pulsed magnetic field immunity testing, with the magnetic field pulse rise time being hundreds of ns, and the pulse duration to its half initial value (halfdroop) being hundreds of µs.Aim. To develop a meter of magnetic field strength with a linear conversion characteristic for measuring the pulse rise time, the pulse duration to its half-droop, and the peak value of the pulsed magnetic field strength.Materials and methods. Among several available methods for measuring pulsed magnetic field parameters, the induction method was selected. To obtain a signal proportional to the pulsed magnetic field strength, a signal from the induction transducer is integrated using a self-integrating induction transducer (RL integration) or by using an external RC integrator. The former method shows good results when measuring signals with a duration of hundreds of ns; however, this method is inefficient when measuring the parameters of longer-duration pulses. The latter method is used to determine the parameters of signals with a duration of hundreds of µs and ms; however, this method gives a large error when measuring the parameters of signals with a duration of hundreds of ns and less. The consecutive use of the two integration methods leads to an additional error in the measurement of the pulse duration to its half-drop.Results. A setup for determining the required magnetic field pulse parameters using a pulse magnetic field meter based on an RL integrator was developed. The relative measurement errors comprised 10, 10, and 9 %, respectively. The developed setup eliminates the error caused by losses in the active resistance of an induction transducer, thus enabling the pulse duration to its half-droop to be measured without additional errors under the pulse rise time of hundreds of ns and the pulse droop time of hundreds of µs.Conclusion. The development of a functional converter made it possible to extend the frequency response of a pulsed magnetic field meter based on an RL integrator to the low-frequency region.
15
Luo, Han, Sijie Shen, Zhenzhen Wang, Junjie Yan, and Yoshihiro Deguchi. "Copper signal characteristics using collinear LS-DP-LIBS for underwater measurement." Journal of Laser Applications 35, no. 2 (May 2023): 022017. http://dx.doi.org/10.2351/7.0000940.
Повний текст джерелаАнотація:
The collinear long-short double-pulse laser-induced breakdown spectroscopy (LS-DP-LIBS) was employed in the detection of underwater copper samples. Discrete emission lines were obtained using LS-DP-LIBS with an appropriate delay between two pulses, while characteristic emission lines were covered by continuous background and noise using LIBS with a single pulse. In the condition of LS-DP-LIBS, signal characteristics of the measured spectra at different experimental parameters including long-pulse width, lens-to-sample distance (LTSD), and long-pulse energy have been investigated to determine the optimal condition. The results indicated that the long-pulse width and the long-pulse energy were closely related to the formation of a cavitation bubble, thus affecting the plasma state and signal characteristics for underwater measurement. The parameter of the LTSD imposed an effect on the spectral signal through changing the ablation mass of the sample and the plasma temperature. The experimental results demonstrated the feasibility of the underwater measurement of metal samples using the collinear LS-DP-LIBS and showed a significant signal improvement through this method. With further development, it is of great potential to apply this new method based on LIBS to ocean exploration.
16
Zhang, Qian, Zhiheng Liu, Deling Lin, Yuzhe Hu, Borui Zheng, and Taifei Zhao. "Analysis of discharge characteristics of pulsed plasma power source in the microsecond scale." Journal of Physics: Conference Series 2313, no. 1 (July 1, 2022): 012023. http://dx.doi.org/10.1088/1742-6596/2313/1/012023.
Повний текст джерелаАнотація:
Abstract The characteristics test of plasma discharge is an essential physical basis for studying plasma flow control. The power consumption of pulsed plasma aerodynamic actuation is 30% lower than when the actuation voltage is a continuous sine wave. This paper uses a self-developed pulsed plasma power source to superimpose DC. The power source conducts the discharge measurement on the sliding discharge plasma. The experimental results show that the power source effectively outputs 0-20 kV pulsed high voltage. The superimposed DC power source generates a negative DC high voltage, accelerating the drift speed of positive ions in the plasma and forming a stable and uniform surface discharge. But the essence of pulse discharge is still filamentary discharge. In a cycle, the plasma discharge is mainly concentrated on the rising edge of the pulse. In contrast, the pulse current is bipolar, and the negative pulse current has a more obvious growth trend, which is more effective for improving the flow control ability.
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Zhang, Zhenqing, Fusheng Deng, Feng Wu, and Chengjie Zhu. "Dynamical characteristics of ultrashort terahertz pulse in metamaterials." Laser Physics Letters 19, no. 5 (March 16, 2022): 056001. http://dx.doi.org/10.1088/1612-202x/ac59bc.
Повний текст джерелаАнотація:
Abstract We develop a time-dependent theoretical approach to study the interaction between the ultrashort terahertz pulse and the metamaterials beyond the steady-state approximation. By using photoconductive silicon, we show that the system dispersion is changed from abnormal to normal via the classical interference effect. As a result, the terahertz pulse propagates through the material with subluminal/superluminal group velocity. We show that it is not accurate to predict the propagation characteristics of the terahertz pulses by using the steady-state solution of coupled wave equations, and the high-order dispersion terms take a significant role which attributes to the pulse shape deformation and the position-dependent group velocity modification. The theoretical approach presented here is essential of describing the propagation properties of the terahertz pulse in metamaterials and is helpful to understand the nature of quantum interference in electromagnetically induced transparency metamaterial.
18
Wang, De Qiang, Shi Liang Dong, and Yuan Jun Zhou. "Analysis of the 18-Pulse ATRU Filtering Characteristics Applied to the Pulse Load." Applied Mechanics and Materials 373-375 (August 2013): 1573–77. http://dx.doi.org/10.4028/www.scientific.net/amm.373-375.1573.
Повний текст джерелаАнотація:
A popular harmonic current reduction method specifically is to increase the number of rectification pulses such as 18-pulse ATRU. This paper presents a 2-order Butterworth LC filter designed to suppress the DC output voltage ripple of the ATRU. And an EMI filter is designed to overcome the electromagnetic interference caused by the high frequency pulse load. Because of the same position and configuration, the same filter is verified in theory to achieve both purposes. Finally, a simulation model of 18-pulse ATRU is built and the two filter's characteristics in the time domain are tested and analyzed.
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Endo, Fumihiko, Kaoru Atsumi, Katsuya Okamura, Yukio Watanabe, Eiji Kaneko, and Iwao Ohshima. "Pulse Switching Characteristics of MAGTs for Pulsed Power Applications." IEEJ Transactions on Industry Applications 113, no. 4 (1993): 445–52. http://dx.doi.org/10.1541/ieejias.113.445.
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Endo, Fumihiko, Kaoru Atsumi, Katsuya Okamura, Yukio Watanabe, Eiji Kaneko, and Iwao Ohshima. "Pulse switching characteristics of MAGTs for pulsed power applications." Electrical Engineering in Japan 114, no. 5 (1994): 108–18. http://dx.doi.org/10.1002/eej.4391140513.
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Mir, Hanan, Fabian Meyer, Andreas A. Brand, Katrin Erath-Dulitz, and Jan Frederik Nekarda. "Study of GHz-Burst Femtosecond Laser Micro-Punching of 4H-SiC Wafers." Solid State Phenomena 344 (June 6, 2023): 29–33. http://dx.doi.org/10.4028/p-q6725d.
Повний текст джерелаАнотація:
The micromaching of silicon carbide using femtosecond laser pulses is becoming an important field of research. High-repetition-rate sub-pulse trains, so-called pulse bursts, are a particularly promising route towards completely new process regimes. We report on the results of micro-punching n-type 4H-silicon carbide wafers using GHz pulse burst in order to systematically investigate the influence of the temporal energy distribution on laser processing. Pulse-burst experiments are performed at a laser wavelength of λ= 1030 nm using a single GHz burst containing a varying number of pulses and then compared with standard single femtosecond pulse exposures. The pulse energy is swept across the ablation threshold. For each set of parameters, the micromachining efficiency is evaluated in terms of ablation efficiency and burr characteristics. Scanning electron micrographs provide qualitative information about the machining quality. The characteristics of the laser modification are discussed in relation to an increase in the number of pulses in a burst envelope and to an increase in pulse energy. We observe that, compared to a single pulse, a GHz burst comprised of 10 lower-energy pulses leads to an increase in the ablation rate by a factor of ≤ 10.
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Mamedov, N. V., A. S. Rohmanenkov, and A. A. Solodovnikov. "Magnetic field influence on the Penning discharge characteristics." Journal of Physics: Conference Series 2064, no. 1 (November 1, 2021): 012039. http://dx.doi.org/10.1088/1742-6596/2064/1/012039.
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Abstract In this work characteristics of pulsed penning ion source for miniature linear accelerators was investigated by experimental measurements and PIC (Particle-In-Cell) simulations. The paper presents dependences of the discharge current and extracted current on intensities of the uniform magnetic field for different pressure. Also, typical examples of the current pulse waveforms obtained by PIC simulation and experiment for different magnetic field are presented. The simulated electron and ion distributions inside discharge gap give qualitative explanation of the experimentally observed fluctuations in current pulses. These current fluctuations arise as a result of the violation of the electric field axial symmetry due to the electron spoke movement of the towards the anode.
23
WANG, P. X., Y. K. HO, Q. KONG, X. Q. YUAN, N. CAO, and L. FENG. "CHARACTERISTICS OF GeV ELECTRON BUNCHES ACCELERATED BY INTENSE LASERS IN VACUUM." Modern Physics Letters B 14, no. 19 (August 20, 2000): 693–99. http://dx.doi.org/10.1142/s0217984900000902.
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This paper studies the characteristics of GeV electron bunches driven by ultra-intense lasers in vacuum based on the mechanism of capture and violent acceleration scenario [CAS, see, e.g. J. X. Wang et al., Phys. Rev.E58, 6575 (1998)], which shows an interesting prospect of becoming a new principle of laser-driven accelerators. It has been found that the accelerated GeV electron bunch is a macro-pulse composed of a lot of micro-pulses, which is analogous to the structure of the bunches produced by conventional linacs. The macro-pulse corresponds to the duration of the laser pulse while the micro-pulse corresponds to the periodicity of the laser wave. Therefore, provided that the incoming electron bunch with comparable sizes as that of the laser pulse synchronously impinges on the laser pulse, the total fraction of electrons captured and accelerated to GeV energy can reach more than 20%. These results demonstrate that the mechanisms of CAS is a relatively effective accelerator mechanism.
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Stühmeier-Niehe, Corinna, Luca Lass, Miriam Brocksieper, Panagiotis Chanos, and Christian Hertel. "Pre-Treatment of Starter Cultures with Mild Pulsed Electric Fields Influences the Characteristics of Set Yogurt." Foods 12, no. 3 (January 17, 2023): 442. http://dx.doi.org/10.3390/foods12030442.
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The aim of this study was to investigate the effect of pulsed electric field (PEF) pre-treatment of a dairy starter culture of Lactobacillus delbrueckii subsp. bulgaricus LB186 and Streptococcus thermophilus ST504 on the fermentation and final product characteristics of set-style yogurt. The effects of PEF treatment parameters, voltage (4–20 kV), pulse number (20–80 pulses), frequency (1–21 Hz), and pulse (5–8 µs) width on pH development, cell counts, and proteolytic activity, as well as on texture and degree of syneresis in yogurt were investigated by use of a two-level full factorial design. Pulse frequency and pulse width had a significant effect on the yogurt stiffness (p < 0.05) and the interaction of voltage and frequency had a significant effect on both stiffness and proteolytic activity (p < 0.05). Further experiments confirmed that pre-treatment of the dairy culture with specific PEF parameters immediately before addition to milk could accelerate fermentation of, increase stiffness of, and reduce syneresis in the final yogurt. This effect of the PEF-pre-treated culture was partially retained even after flash-freezing and 14 days of storage of the culture at −20 °C. The effects were attributed to responses to oxidative stress induced by the PEF pre-treatment.
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Antonov, Alexander, Irina Matveeva, Igor Shubin, and Ilya Tsukernikov. "CALCULATION OF IMPULSE NOISE WITH MIRROR-DIFUSE REFLECTION OF SOUND FROM FENCES." Akustika 34 (November 1, 2019): 88–94. http://dx.doi.org/10.36336/akustika20193488.
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The choice and acoustic efficiency of construction and acoustic means of noise control is determined on the basis of calculations of changes in the spatio-temporal characteristics of the pulses of sound energy emitted by the sound source. The paper proposes a combined computational model for estimating the energy characteristics of pulse noise and their spatiotemporal changes. The model describes the formation and distribution of the reflected sound energy of pulses in the mirror-scattered reflection of sound from the fences. The principles of construction of the computational model and the computer program implementing it are stated. Evaluation of the computational model is performed by comparative analysis of experimental and computational data obtained by the action of a pulsed noise source in complex geometrically shaped rooms. It is found that the calculated graphs of the decay of the reflected pulse energy in time coincide with the experimentally determined declines.
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Sang, Pil, Junseok Heo, Hui Park, and Hyoung Baac. "Photoacoustic Energy Sensor for Nanosecond Optical Pulse Measurement." Sensors 18, no. 11 (November 11, 2018): 3879. http://dx.doi.org/10.3390/s18113879.
Повний текст джерелаАнотація:
We demonstrate a photoacoustic sensor capable of measuring high-energy nanosecond optical pulses in terms of temporal width and energy fluence per pulse. This was achieved by using a hybrid combination of a carbon nanotube-polydimethylsiloxane (CNT-PDMS)-based photoacoustic transmitter (i.e., light-to-sound converter) and a piezoelectric receiver (i.e., sound detector). In this photoacoustic energy sensor (PES), input pulsed optical energy is heavily absorbed by the CNT-PDMS composite film and then efficiently converted into an ultrasonic output. The output ultrasonic pulse is then measured and analyzed to retrieve the input optical characteristics. We quantitatively compared the PES performance with that of a commercial thermal energy meter. Due to the efficient energy transduction and sensing mechanism of the hybrid structure, the minimum-measurable pulsed optical energy was significantly lowered, ~157 nJ/cm2, corresponding to 1/760 of the reference pyroelectric detector. Moreover, despite the limited acoustic frequency bandwidth of the piezoelectric receiver, laser pulse widths over a range of 6–130 ns could be measured with a linear relationship to the ultrasound pulse width of 22–153 ns. As CNT has a wide electromagnetic absorption spectrum, the proposed pulsed sensor system can be extensively applied to high-energy pulse measurement over visible through terahertz spectral ranges.
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Asayonak, M. A., A. O. Zenevich, Ya V. Novikau, and S. A. Saroca. "Influence of optical radiation parameters on the amplitude characteristics of silicon photoelectron multipliers." Proceedings of the National Academy of Sciences of Belarus, Physical-Technical Series 65, no. 1 (April 6, 2020): 104–9. http://dx.doi.org/10.29235/1561-8358-2020-65-1-104-109.
Повний текст джерелаАнотація:
At present, silicon photoelectronic multipliers with a low voltage, high sensitivity in the visible and near infrared spectral regions, and large amplification factors are often used to record optical radiation in a wide range of intensities of the visible and near infrared spectral regions. The purpose of this article is to determine the dependence of the type of amplitude distribution of pulses, created by silicon photoelectronic multipliers, on the intensity of the recorded optical radiation. As research objects, commercially available Ketek PM 3325 and ON Semi FC 30035 silicon photomultiplier tubes have been used, as well as multipliers from a pilot batch manufactured by OJSC “INTEGRAL” (Republic of Belarus). The paper studies the amplitude distribution of voltage pulses, formed on the load resistor of silicon photoelectronic multipliers by the photocurrent for various values of the energy exposure of optical pulses. The range of values of the energy exposure of optical pulses was determined at which the amplitude distributions of these pulses have pronounced peaks. It was found out that with increasing energy exposure of the optical pulse, part of the peaks disappears. It was established that all the dependencies of the average amplitude of such pulses on the magnitude of the energy exposure of the optical pulse for silicon photomultiplier tubes have a linear section. The performed experimental studies showed that an increase in the energy exposure of optical pulses results in an increase in the dispersion of the amplitude distribution of pulses. It was found that for a linear dependence of the energy exposure of the optical pulse on the optical pulse duration in the range from 50 ns to 1 μs, the studied silicon photoelectronic multipliers formed voltage pulses of 1 μs duration with the same rising and falling edges. In this case, the average amplitude of these pulses had a linear dependence on the duration of the optical pulse. The results can be used in design of photodetector devices for monitoring the level of ionization radiation for nuclear power plants, for quantum information systems and in optical communications for transmitting information with monitoring the presence of information leakage channels.
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Shtreker, Denis, Mikhail Polishchuck, and Arkadii Popov. "Influence of the shaper parameters on the characteristics of acceleration pulses reproduced by mechatronic shock machines." E3S Web of Conferences 326 (2021): 00004. http://dx.doi.org/10.1051/e3sconf/202132600004.
Повний текст джерелаАнотація:
In this paper the influence of the shaper parameters on the characteristics of acceleration pulses (peak value and duration) reproduced on mechatronic shock machines is analyzed. A comparison of the acceleration pulses obtained experimentally and by computational methods is presented. Recommendations for clarifying the requirements for methodological calculations of pulse parameters are given. The dependence of the elastic force of the shock pulse shaper on its deformation is presented. The influence of this characteristic on the peak value and duration of the acceleration pulse is estimated. The influence of the height of the shaper on the parameters of the acceleration pulses is analyzed. The concept of a device that allows you to automatically change the height of the shaper to obtain a wider range of acceleration pulses is presented. The interaction of the shock table with the shaper by means of computer modeling is modelled. Conclusions about the dependences of the duration and peak value of the acceleration pulses on the parameters of the shaper (stiffness and height) are drawn. Recommendations for selecting the parameters of the shaper to obtain acceleration pulses with the desired parameters are given.
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Wei, Chao, Yuping Ma, Yuan Han, Yao Zhang, Liu Yang, and Xuehui Chen. "Study on Femtosecond Laser Processing Characteristics of Nano-Crystalline CVD Diamond Coating." Applied Sciences 9, no. 20 (October 12, 2019): 4273. http://dx.doi.org/10.3390/app9204273.
Повний текст джерелаАнотація:
Ultra-short pulse laser interaction with diamond materials has attracted extensive interest in micro- and nano-machining, especially for the fabrication of micro tools, because of the straightforward method and high precision. Thanks to the development of chemical vapor deposition (CVD) technology, high-quality CVD diamonds are employed in more varieties of tools as performance-enhancing coatings. The purpose of the experiments reported here was to explore the machinability of CVD diamond coating under the irradiation of femtosecond (fs) pulsed laser. The factor-control approach was adopted to investigate the influence of scanning speed, single pulse energy and repetition rate on the surface quality and carbon phase transition of CVD diamond coating. The material removal rate and surface roughness were evaluated. The interaction mechanism of scanning speed, single pulse energy, and repetition rate were discussed, and the fs laser ablation threshold of CVD diamond coating was calculated. It was demonstrated that two ablation mechanisms (weak and intensive) were in existence as evidenced by the distinct surface morphologies induced under different processing conditions. A strong dependence on the variation of scanning speed and pulse energy is identified in the examination of surface roughness and removal rate. Lorentzian–Gaussian deconvolution of Raman spectra illustrates that fs laser irradiation yields a strong modification effect on the coating and release the compressive stress in it. Furthermore, a newly defined parameter referring to the fs laser energies applied to unit volume was introduced to depict the degree of ablation and the Taguchi method was used to figure out the significance of different parameters. The ablation threshold of CVD diamond coating at the effective pulses of 90 is calculated to be 0.138 J/cm2.
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Chen, Zhiwen, Yingying Yan, Jun Shu, Kefu Liu, and Jian Qiu. "Modulated High Power and Narrow Pulse Width Laser Drive Circuit for Lidar System." Electronics 10, no. 7 (March 30, 2021): 823. http://dx.doi.org/10.3390/electronics10070823.
Повний текст джерелаАнотація:
This manuscript introduces a laser drive circuit for a light detection and ranging (Lidar) system. A Lidar system usually requires its drive circuit to provide laser pulses with nanosecond pulse width, >100 W peak power and high repetition frequency. However, the existing research results show difficulties in meeting these requirements. In order to reduce the pulse width and increase the peak power of laser pulses, special circuit design and component selection are used to optimize the parasitic parameters of the drive circuit, and GaN devices are used to increase the switching speed. The characteristics of laser pulses are tested under different input voltage, pulse per second and switch conducting time. Meanwhile, the reasons for the changes in these characteristics are analyzed and explained. In order to meet the requirements of the Lidar system to detect targets at different distances, a modulation method to change the peak power of the laser pulse is proposed. In our experiment, ideally, the peak power of the laser pulse reaches 135 W, and the pulse width is less than 2 ns at a pulse per second rate of 400 kHz.
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Wang, Anran, Lin Yang, Chengyu Liu, Jingxuan Cui, Yao Li, Xingxing Yang, Song Zhang, and Dingchang Zheng. "Athletic Differences in the Characteristics of the Photoplethysmographic Pulse Shape: Effect of Maximal Oxygen Uptake and Maximal Muscular Voluntary Contraction." BioMed Research International 2015 (2015): 1–8. http://dx.doi.org/10.1155/2015/752570.
Повний текст джерелаАнотація:
This study aimed to investigate the athletic differences in the characteristics of the photoplethysmographic (PPG) pulse shape. 304 athletes were enrolled and divided into three subgroups according to a typical sport classification in terms of the maximal oxygen uptake (MaxO2_low, MaxO2_middle and MaxO2_high groups) or the maximal muscular voluntary contraction (MMVC_low, MMVC_middle, and MMVC_high groups). Finger PPG pulses were digitally recorded and then normalized to derive the pulse area, pulse peak timeTp, dicrotic notch timeTn, and pulse reflection index (RI). The four parameters were finally compared between the three subgroups categorized by MaxO2or by MMVC. In conclusion, it has been demonstrated by quantifying the characteristics of the PPG pulses in different athletes that MaxO2, but not MMVC, had significant effect on the arterial properties.
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Du, Gai Hong, and Yang Meng Tian. "The Coupling Effect of Electromagnetic Pulse and Computer." Applied Mechanics and Materials 541-542 (March 2014): 452–57. http://dx.doi.org/10.4028/www.scientific.net/amm.541-542.452.
Повний текст джерелаАнотація:
Coupling characteristic of EM pulse into the computer enclose with aperture and the coupling effect of electromagnetic pulse and computer box are studied. The impact of coupling characteristic of EM pulse into the computer enclose with aperture includes the three aspects (1) the effect of hole shape on the coupling characteristics (2) the effects of the apertures area on the coupling property characteristics (3) the effects of the polarization direction of the electromagnetic pulse on the coupling characteristics; The brief overview of electromagnetic pulse coupling phenomena on the computer includes the following three aspects (1) the physical model of the computer chassis (2) the coupling coefficient of electric field in the computer box and the computer center (3) the change characteristics of the electromagnetic pulse in the computer box; Finally we discussing the preventive approach of computers electromagnetic coupling is.
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Razhev A M, Kargapol`tsev E. S., and Trunov I. A. "Pulsed RF excitation inductive discharge CO-=SUB=-2-=/SUB=- laser with the radiation energy of 1 J and high efficiency." Optics and Spectroscopy 132, no. 3 (2022): 368. http://dx.doi.org/10.21883/eos.2022.03.53559.2836-21.
Повний текст джерелаАнотація:
An efficient pulsed gas-discharge inductive CO2-laser with a radiation energy of 1.05 J has been developed for the first time. In this case, the pulse duration of the laser radiation was about 10 msec. The maximum efficiency of 21.1% was obtained at a radiation energy of 340 mJ. RF current pulses propagated along the inductor conductor and, thus, an inductive discharge was formed to create an inverse population at the infrared (IR) transitions of CO2* molecules. The temporal and energy characteristics of the radiation of the inductive CO2-laser depending on the duration of the pump pulse are investigated. The spatial characteristics and spectrum of the radiation of the developed laser are estimated. The divergence of the laser radiation was 0.52 mrad. The cross-sectional dimension of the laser output beam was about 35 mm in diameter. Keywords: inductive discharge in a mixture of gases, high-frequency modulation of the pump voltage, population inversion, output characteristics of laser radiation.
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Lin, Munan, Jianbin Zhu, Wenqing Zhang, Yu Bao, Haibo Li, and Xin Qi. "A low characteristic impedance quasi-rectangular pulser based on solid-state inductive adder for High rEpetition rate Muon Source at CSNS." Journal of Instrumentation 18, no. 07 (July 1, 2023): T07005. http://dx.doi.org/10.1088/1748-0221/18/07/t07005.
Повний текст джерелаАнотація:
Abstract A solid-state inductive adder-based quasi-rectangular pulser featuring a low characteristic impedance has been developed in the laboratory to demonstrate the technical viability of using such a pulser for the HEMS muon source. The pulser consists of five layers connected in series, with each layer comprising 24 parallel branches. The paper mainly presents the design of the low characteristic impedance quasi-rectangular pulser from three aspects: primary driver circuit, coaxial central structure and transformer magnetic core. The experimental results show that through the careful design of the above three items, a quasi-rectangular pulse with fast rise and fall time can be achieved. The typical parameters of pulse voltage, pulse current, pulse flattop, repetitive rate, rise time and fall time at a charging voltage of 700 V are 3.5 kV, 560 A, 315 ns, 1 kHz, 47 ns, and 66 ns, respectively, on a 6.25 Ω matching resistor. In addition, the output characteristics of the pulser are investigated by varying critical parameters such as the charging voltages, the load resistances, and the number of parallel branches. The findings and results outlined in this paper offer valuable insights for the initial phase of developing an inductive adder pulser. They can aid in assessing the feasibility of the project, selecting critical parameters for essential components, and enhancing the output pulse's performance. A full-scale pulser with a peak pulse current of 3 kA and rise and fall time of ≤ 75 ns for HEMS muon source will be developed in the near future.
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Xia, Xinfan, Lihua Liu, Shengbo Ye, Hongfei Guan, and Guangyou Fang. "A Novel Subnanosecond Monocycle Pulse Generator for UWB Radar Applications." Journal of Sensors 2014 (2014): 1–4. http://dx.doi.org/10.1155/2014/150549.
Повний текст джерелаАнотація:
A novel ultra-wideband (UWB) monocycle pulse generator with good performance is designed and demonstrated in this paper. It contains a power supply circuit, a pulse drive circuit, a unique pulse forming circuit, and a novel monopolar-to-monocycle pulse transition circuit. The drive circuit employs wideband bipolar junction transistors (BJTs) and linear power amplifier transistor to produce a high amplitude drive pulse, and the pulse forming circuit uses the transition characteristics of step recovery diode (SRD) effectively to produce a negative narrow pulse. At last, the monocycle pulse forming circuit utilizes a novel inductanceLshort-circuited stub to generate the monocycle pulse directly. Measurement results show that the waveform of the generated monocycle pulses is over 76 V in peak-to-peak amplitude and 3.2 ns in pulse full-width. These characteristics of the monocycle pulse are advantageous for obtaining long detection range and high resolution, when it is applied to ultra-wideband radar applications.
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Chen, Ping, Jin Miao, Yin Gu, Fen Huang, Xinyang Zhou, Zhaoyun Leng, Jiefeng Wan, and Chen Li. "Comparative Study on Characteristics of Partial Discharge Optical Pulse and UHF Pulse in Switch Equipment." Journal of Physics: Conference Series 2136, no. 1 (December 1, 2021): 012024. http://dx.doi.org/10.1088/1742-6596/2136/1/012024.
Повний текст джерелаАнотація:
Abstract The article explores the performance of the new silicon photoelectric sensor in partial discharge detection, and compares the measured optical pulse with the traditional UHF pulse. Through optical and electrical synchronous partial discharge experiments, the article analyzes and discusses the detection performance, working characteristics and statistical characteristics of various sensors, and explores the advantages and feasibility of silicon photoelectric partial discharge sensors in actual discharge monitoring; In addition, the statistical performance of the two physical phenomena of partial light radiation and electromagnetic radiation was obtained through the analysis of optical and electrical synchronous monitoring data. Compared with UHF sensor, silicon photoelectric sensor under the optimal working voltage has a higher signal-to-noise ratio (SNR); Under the electromagnetic interference of the high-frequency motor, silicon photoelectric sensor exhibits better anti-electromagnetic interference ability; Discharge phase interval and characteristics reflected by the PRPD obtained by two detection methods maintain good consistency; Pulse repetition rate has the same trend with applied voltage, but statistical frequency of optical pulses obtained is higher than that of electromagnetic pulses because silicon photoelectric sensor has a higher SNR and single-photon sensitivity.
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Chen, Gao. "Isolated attosecond pulse generation from helium atom irradiated by a three-color laser pulse." Acta Physica Sinica 71, no. 5 (2022): 054204. http://dx.doi.org/10.7498/aps.71.20211502.
Повний текст джерелаАнотація:
Isolated attosecond pulses enables the studying and controlling of ultrafast electron processes in atoms and molecules. High-order harmonic generation (HHG) is the most promising way to generate such pulses, benefiting from the broad plateau structure of the typical HHG spectrum. We theoretically investigate high-order harmonic and attosecond pulse generation from helium atom in a three-color laser field, which is synthesized by 16 fs/1600 nm, 15 fs/1100 nm and 5 fs/800 nm pulse laser. Compared with harmonic spectrum generated by a two-color laser field synthesized by 16 fs/1600 nm and 15 fs/1100 nm, the harmonic spectrum generated from the synthesized three-color field exhibits high conversion efficiency and broadband supercontinuum characteristics. The continuous spectrum range covers from 230th to 690th harmonics, and the generation of 128 attosecond isolated short pulses with higher intensity is realized after Fourier transform. This result is attributable to the fact that the synthesized three-color electric field exhibits high-intensity and few-cycle mid-infrared femtosecond pulse laser characteristics, which can effectively control atomic ionization and recombination occurring within an effective optical period of the mid-infrared femtosecond pulse. This scheme solves the problems faced by the current femtosecond pulse laser technology, i.e. the few-cycle mid-infrared femtosecond pulse laser cannot have both carrier envelope phase stability and high power output.
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Geyer, M., M. Serylak, F. Abbate, M. Bailes, S. Buchner, J. Chilufya, S. Johnston, et al. "The Thousand-Pulsar-Array programme on MeerKAT – III. Giant pulse characteristics of PSR J0540−6919." Monthly Notices of the Royal Astronomical Society 505, no. 3 (May 29, 2021): 4468–82. http://dx.doi.org/10.1093/mnras/stab1501.
Повний текст джерелаАнотація:
ABSTRACT PSR J0540−6919 is the second-most energetic radio pulsar known and resides in the Large Magellanic Cloud. Like the Crab pulsar, it is observed to emit giant radio pulses (GPs). We used the newly commissioned PTUSE instrument on the MeerKAT radio telescope to search for GPs across three observations. In a total integration time of 5.7 h, we detected 865 pulses above our 7σ threshold. With full polarization information for a subset of the data, we estimated the Faraday rotation measure, $\rm {RM}=-245.8 \pm 1.0$ rad m−2 towards the pulsar. The brightest of these pulses is ∼60 per cent linearly polarized but the pulse-to-pulse variability in the polarization fraction is significant. We find that the cumulative GP flux distribution follows a power-law distribution with index −2.75 ± 0.02. Although the detected GPs make up only ∼10 per cent of the mean flux, their average pulse shape is indistinguishable from the integrated pulse profile, and we postulate that, unlike in the Crab pulsar, there are no additional regular emission components. The pulses are scattered at L-band frequencies with the brightest pulse exhibiting a scattering time-scale of τ = 0.92 ± 0.02 ms at 1.2 GHz. We find several of the giants display very narrow-band flux knots similar to those seen in many Fast Radio Bursts, which we assert cannot be due to scintillation or plasma lensing. The GP time-of-arrival distribution is found to be Poissonian on all but the shortest time-scales where we find four GPs in six rotations, which if GPs are statistically independent is expected to occur in only 1 of 7000 observations equivalent to our data.
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Ambigaipalan, P., R. Hoover, E. Donner, and Q. Liu. "Retrogradation characteristics of pulse starches." Food Research International 54, no. 1 (November 2013): 203–12. http://dx.doi.org/10.1016/j.foodres.2013.06.012.
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Qin, Feng, Wei Chen, Xutong Wang, Tao Huang, Zhitong Cui, and Xin Nie. "Transient Response Characteristics of Metal Oxide Arrester under High-Altitude Electromagnetic Pulse." Energies 15, no. 9 (April 30, 2022): 3303. http://dx.doi.org/10.3390/en15093303.
Повний текст джерелаАнотація:
In order to study the strong electromagnetic pulse effect of critically vulnerable equipment in power systems and evaluate the survivability under high-altitude electromagnetic pulses, it is necessary to study the characteristics of the transient response of metal oxide arresters to the high-altitude electromagnetic pulse by experiment. In this paper, an experimental platform for high-altitude electromagnetic pulse conduction current injection for a typical 10 kV metal oxide arrester was set up, and the key parameters such as peak value of overshoot voltage, peak value of residual voltage, action voltage and response time were obtained by the experiment. The results show that: the action voltage of this type of metal oxide arrester is 3.53 times higher than that of its rated voltage; the peak value of overshoot voltage is 2.19 times that of the peak value of residual voltage under lightning impulse current; the peak value of residual voltage is 1.57 times that under lightning impulse; and the response time varies little with the electromagnetic pulse conduction current amplitude, averaging 46.86 nanoseconds under a high-altitude electromagnetic pulse conduction environment.
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Ражев, А. М., Е. С. Каргапольцев та И. А. Трунов. "Импульсный индукционный CO-=SUB=-2-=/SUB=--лазер с энергией излучения 1 J и высоким КПД с ВЧ возбуждением". Оптика и спектроскопия 130, № 3 (2022): 400. http://dx.doi.org/10.21883/os.2022.03.52169.2836-21.
Повний текст джерелаАнотація:
An efficient pulsed gas-discharge inductive CO2-laser with a radiation energy of 1.05 J has been developed for the first time. In this case, the pulse duration of the laser radiation was about 10 msec. The maximum efficiency of 21.1% was obtained at a radiation energy of 340 mJ. RF current pulses propagated along the inductor conductor and, thus, an inductive discharge was formed to create an inverse population at the infrared (IR) transitions of CO2* molecules. The temporal and energy characteristics of the radiation of the inductive CO2-laser depending on the duration of the pump pulse are investigated. The spatial characteristics and spectrum of the radiation of the developed laser are estimated. The divergence of the laser radiation was 0.52 mrad. The cross-sectional dimension of the laser output beam was about 35 mm in diameter.
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Lebedev, V., G. Zuck G., and M. Brykov. "PERFORMANCE CHARACTERISTICS OF NICKEL-CONTAINING STEEL STRUCTURES DURING MECHANIZED WELDING-SURFACING WITH MODIFIED (DOSED) ELECTRODE WIRE FEEDING." Innovative Materials and Technologies in Metallurgy and Mechanical Engineering, no. 1 (June 28, 2022): 36–48. http://dx.doi.org/10.15588/1607-6885-2022-1-5.
Повний текст джерелаАнотація:
Purpose. To study and analyze in a comparative order the influence of factors of the controlled pulse process of electrode wire supply on some basic mechanical characteristics of seams and welded rollers in the processes of welding and surfacing of nickel-containing steels.
Methods of research. The study the mechanical characteristics of seams and welded rollers was carried out using modern laboratory equipment and appropriate techniques. This made it possible to determine how the pulse feed parameters affect the strength characteristics of the weld and near the weld zone over the entire cross-sectional area of the weld or weld layer. Detailed characteristics of feed pulses were determined using a welding process analyzer to obtain oscillograms of power parameters of arc combustion with their analysis, including determining the stability of the arc process for different types of pulses. Important for the improvement of welding results is the controlled nature of the electrode metal transfer synchronous with the pulsed movement of the electrode. It is noted that the energy consumption of the arc process during the pulse supply of the electrode wire with an indication of its reduction compared to traditional welding.
Experimental work was performed using a special electrode wire, which is usually used for welding and surfacing of nickel-containing steels. These processes were carried out in a protective environment of CO2 in automatic mode.
Results. Due to the fact that the strength characteristics of the weld are among the most important, attention is paid to their definition and analysis. The strength characteristics depend on many parameters, in particular the thermal characteristics of the process, the structure of the weld metal, the presence of non-metallic inclusions and so on. All these factors were studied with the help of appropriate instruments, and on the basis of numerous comparative photos of microstructures on sections of the cross section. The analysis of the sections revealed the types of microstructures obtained, the presence of inclusions and more. It is determined, in particular, that the structure of weld metal in pulsed electrode wire welding differs significantly from the structure of traditional welding in reducing inclusions, finer grains, etc., which improves the mechanical properties of the weld and seam area.
Scientific novelty. Based on a series of experimental studies, the use of pulse algorithms for the movement of the electrode wire with certain parameters in automatic mode for welding and surfacing of nickel-containing steels to improve the mechanical properties of seams and welded rollers.
Practical value. It is determined that the method of pulse welding of electrode wire to the controlled variant, including nickel-containing steels is effective and can be widely used in industry using specially designed equipment that provides a suitable process with stronger characteristics.
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Shemyakin, A. N., M. Yu Rachkov, N. G. Solov’ev та M. Yu Yakimov. "Radiation Power Control of the Industrial CO2 Laser Excited by а Nonself-Sustained Glow Discharge by Changing the Frequency of Ionization Pulses". Mekhatronika, Avtomatizatsiya, Upravlenie 21, № 4 (11 квітня 2020): 224–31. http://dx.doi.org/10.17587/mau.21.224-231.
Повний текст джерелаАнотація:
The article describes radiation power control of industrial CO2 lasers of Lantan series excited by а nonself-sustained glow discharge in the automatic mode. These lasers are closed-cycle fast gas-transport lasers excited by a nonself-sustained glow discharge with ionization by periodic-pulsed capacitively coupled auxiliary discharge. In this case, ionization and conductivity are provided by periodic-pulsed capacitively coupled discharge. The energy contribution to molecular oscillations is provided by the passage of the main discharge current through the plasma with electron density given by ionization. This permits easy laser power control, provides excellent optical homogeneity and stability of an active volume together with high laser efficiency. A system of a nonself-sustained glow discharge with ionization by periodic-pulsed capacitively coupled auxiliary discharge, the stages of creation and brief characteristics of the Lantan series lasers is presented. The method of controlling the power of laser radiation by changing the frequency of the ionization pulses is determined. This control method allows operating of the laser in continuous and in pulse-periodic modes with adjustable pulse ratio and pulse duration, and also provides switching from one mode to another. In the continuous mode, the radiation power is controlled by changing the frequency of ionization pulses, which are high voltage pulses with duration of 100 ns, given with the frequency of 1-5 kHz. Pulse-periodic radiation control is performed by modulating ionization pulses that consists of pulses being delivered in batches. The frequency of the pulses in a batch determines the radiation power in a pulse. The frequency of the batches following is the frequency of the pulse mode, and the length of the batch determines the pulses duration. Based on the experimental data, the dependence of the radiation power on the ionization pulses frequency was determined. An experimental system is presented and the measuring accuracy of the laser radiation power and the frequency of ionization pulses is determined. Data acquiring and processing of experimental results were performed using the NI 6008 USB data acquisition device in the LabVIEW programs of National Instruments. To study the dependence of the laser power on Мехатроника, автоматизация, управление, Том 21, № 4, 2020 231 the frequency of the ionization pulses, a regression analysis method was applied. Studies have shown that the dependence of the laser power on the ionization pulses frequency is linear in a wide range of parameters. The equation of the direct regression is calculated. The confidence estimates of the coefficients of the direct regression and the confidence estimates of the deviation of the theoretical direct regression from the empirical one are calculated with a confidence level of 95%.
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Egoryan, A. J., A. N. Kraiko, K. S. P’yankov, and A. P. Tishin. "Characteristics of pulse detonation engine versus ramjet characteristics." Thermophysics and Aeromechanics 23, no. 2 (March 2016): 297–300. http://dx.doi.org/10.1134/s0869864316020177.
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Kun Cheng, Kun Cheng, Sujuan Zhang Sujuan Zhang, Wei Li Wei Li, Wanjun Dai Wanjun Dai, Dongxia Hu Dongxia Hu, and Feng Jing Feng Jing. "Temporal self-modifying characteristics of pulse propagation in multiphoton absorbers." Chinese Optics Letters 13, no. 7 (2015): 070009–70012. http://dx.doi.org/10.3788/col201513.070009.
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Ditchek, Sarah D., Kristen L. Corbosiero, Robert G. Fovell, and John Molinari. "Electrically Active Diurnal Pulses in Hurricane Harvey (2017)." Monthly Weather Review 148, no. 6 (May 7, 2020): 2283–305. http://dx.doi.org/10.1175/mwr-d-20-0022.1.
Повний текст джерелаАнотація:
Abstract Recent research has found that diurnal pulses are ubiquitous features of tropical cyclones. To gain further insight into the characteristics of these pulses, a case study of an electrically active (ACT) cooling pulse and an off-the-clock ACT cooling pulse that occurred in Hurricane Harvey (2017) was conducted. Using GridSat-B1 IR brightness temperatures, World Wide Lightning Location Network (WWLLN) lightning data, the 85–91-GHz channels on microwave satellite imagers, and Level-II Doppler radar reflectivity data from WSR-88D stations (i.e., NEXRAD), these pulses were found to share many similar characteristics: both propagated outward on the right-of-shear side of Harvey and were associated with elevated cloud ice content and high reflectivity. Additionally, using HRRR model output, both pulses were found to be associated with 1) column-deep total condensate, 2) a surface cold pool, 3) an overturning circulation, and 4) an enhanced low-level jet. These characteristics are similar to those found in tropical squall lines, supporting the tropical squall-line interpretation of diurnal pulses put forth in recent studies. A hypothesis for ACT pulse initiation was then introduced, tested, and confirmed: inner rainbands that propagated outward into a more favorable environment for deep convection reinvigorated into ACT pulses that had tropical squall-line characteristics.
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Morozov, Yu V., M. A. Rajfeld, and A. A. Spektor. "NOISE AND TARGET SIGNALS SIMULATION IN PASSIVE SEISMIC LOCATION SYSTEMS." Issues of radio electronics, no. 4 (April 20, 2018): 73–78. http://dx.doi.org/10.21778/2218-5453-2018-4-73-78.
Повний текст джерелаАнотація:
The paper proposes the model of a person seismic signal with noise for the investigation of passive seismic location system characteristics. The known models based on Gabor and Berlage pulses have been analyzed. These models are not able wholly to consider statistical properties of seismic signals. The proposed model is based on almost cyclic character of seismic signals, Gauss character of fluctuations inside a pulse, random amplitude change from pulse to pulse and relatively small fluctuation of separate pulses positions. The simulation procedure consists of passing the white noise through a linear generating filter with characteristics formed by real steps of a person, and the primary pulse sequence modulation by Gauss functions. The model permits to control the signal-to-noise ratio after its reduction to unity and to vary pulse shifts with respect to person steps irregularity. It has been shown that the model of a person seismic signal with noise agrees with experimental data.
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Wiatrowski, A., and W. M. Posadowski. "The impact of medium frequency pulsed magnetron discharge power on the single probe Langmuir measurements and resulted plasma parameters." Materials Science-Poland 34, no. 2 (June 1, 2016): 374–85. http://dx.doi.org/10.1515/msp-2016-0012.
Повний текст джерелаАнотація:
AbstractThe resonant type power supplies of medium frequency designed for magnetron sputtering processes often use pulse density modulation to regulate the average discharge power level. While the output power level changes then number of pulses in a group changes, but the discharge current pulses are the same from pulse to pulse: their parameters (duration time, amplitude) do not change with the discharge power. The goal of this paper is to present the influence of medium frequency discharge power level on the direct current I-V characteristics of a single Langmuir probe and resulting plasma parameters caused by the pulse density modulation. The sputtering processes of titanium and copper were diagnosed at two spatial positions. The measured Langmuir probe I-V characteristics showed strong dependence on the discharge power. As the discharge powering pulses stay the same with the discharge power level change, such influence was unlikely to occur. Using time-resolved analysis of probe current waveforms the origin of this influence was indicated. The influence of discharge power level on the single probe Langmuir I-V characteristics and resulting plasma parameters was eliminated using a simple method of scaling the results. Finally, the reliable plasma parameters were calculated.
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Scharnholz, Sigo, Ralf Hassdorf, Gontran Pâques, Bertrand Vergne, and Dominique Planson. "Pulse Current Characterization of SiC GTO Thyristors with Etched JTE." Materials Science Forum 740-742 (January 2013): 986–89. http://dx.doi.org/10.4028/www.scientific.net/msf.740-742.986.
Повний текст джерелаАнотація:
In this paper we highlight our latest results on high voltage SiC thyristors comprising an etched JTE. Compared to our previous design concepts, the thyristors described here are larger in size and have been investigated regarding pulsed power applications. Quasi-static on-state characteristics show that the devices withstand a repetitive current load of up to 16 A corresponding to a current density of 825 A/cm2. Their switching behavior was evaluated up to 1000 V demonstrating characteristic waveforms at turn-on and gate turn-off. Moreover, pulsed current characteristics show that the typical device under test sustained a current pulse of 20 μs with a peak value of 200 A and 10 kA/cm2, respectively.
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King, Emma, Deirdre M. Cobbin, Sean Walsh, and Damien Ryan. "The Reliable Measurement of Radial Pulse Characteristics." Acupuncture in Medicine 20, no. 4 (December 2002): 150–59. http://dx.doi.org/10.1136/aim.20.4.150.
Повний текст джерелаАнотація:
The use of the radial pulse as a diagnostic tool is an integral part of the Traditional Chinese Medicine (TCM) patient evaluation. In spite of its long history of use, there is little systematic information available to support the many claims about the relationship between pulse qualities and physiological condition contained in the ancient Chinese texts and echoed in modern pulse terminology. This study reports the development of a reliable means of measuring and recording pulse characteristics. This was achieved by reporting on the physical sensations that are detected under the fingertips when the radial pulse is palpated, rather than attempting to translate these into the complex and typically ambiguously defined TCM pulse qualities. The study involved development of a standardised pulse taking procedure and development of concrete operational definitions for each of the characteristics of the pulse being measured. The inter-rater reliability of the pulse taking procedure and operational definitions was assessed by determining agreement levels between two independent pulse assessors for each characteristic. Inter-rater agreement averaged 80% between the two assessors in both the initial data collection (66 subjects) and in a replication collection (30 subjects) completed two months later. Demonstrating reliability of the procedure represents an essential first step for examining the validity of TCM pulse diagnosis assumptions.