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1
Godun, D. V., S. V. Bordusau e G. P. Budzko. "Output Current Control System of a High Voltage Electric Pulse Generator for Plasma Excitation". PLASMA PHYSICS AND TECHNOLOGY 6, n. 1 (2019): 7–9. http://dx.doi.org/10.14311/ppt.2019.1.7.
Testo completoAbstract (sommario):
A control and pulse discharge current limiting system integrated into an AC/DC converter and pulse modulator of a high voltage pulse generator have been developed. The peculiarity of such system\textquotesingle s operation is the stabilization of the power supplied to the discharge and the correction of the width of output electric pulses towards decrease upon reaching the specified pulsed current amplitude value. The system enables the pulse generator to work in the modes close to the ``short circuited load'' mode. In this case the driving module of a composite IGBT key performs the correction of the working pulse width and blocks the pulse generator operation if needed. The suggested circuit design solutions allow using the generator in a wide range of electric plasma-forming parameters' modes and working with various types of vacuum gas discharge systems.
2
Deke Yan, Deke Yan, Yongsheng Gou Yongsheng Gou, Zhiyuan Song Zhiyuan Song, Chuandong Sun Chuandong Sun e Shaolan Zhu Shaolan Zhu. "Study on the circuit producing high-speed pulse with high peak current". Chinese Optics Letters 9, s1 (2011): s10307–310310. http://dx.doi.org/10.3788/col201109.s10307.
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Fan, Xian Guang, Zhen Bang Hu, Ying Jie Xu, Xiu Fen Wang, Xin Wang e Yong Zuo. "Pulsed Driver Control System for High-Power LED". Applied Mechanics and Materials 536-537 (aprile 2014): 1178–82. http://dx.doi.org/10.4028/www.scientific.net/amm.536-537.1178.
Testo completoAbstract (sommario):
Pulsed current source is used to drive high-power LED in thermal analysis and testing. A new scheme to design the high-power LED pulsed current source, which integrates FPGA device, with highly quality single-chip microcomputer C8051F as the control center, is introduced. In order to obtain the LED automatic current control, the negative feedback is used in the LED pulsed driver. The pulsed current source consists of constant-current source and couple output interface controlled by square pulse signal, which ensures the stability of pulsed current, rise time and fall time. It is convenient to adjust the pulse current amplitude, pulse width, pulse cycle and sampling gate independently. Results show that the current stability of the driver control system can obtain 0.01%.
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Hu, L., B. Gao, J. K. Lv, S. C. Sun, Y. Hao e G. F. Tu. "Halo Evolution of Hypereutectic Al-17.5Si Alloy Treated with High-Current Pulsed Electron Beam". Journal of Nanomaterials 2015 (2015): 1–6. http://dx.doi.org/10.1155/2015/806151.
Testo completoAbstract (sommario):
Halo evolution of an Al-17.5Si alloy surface after treatment with increasing pulse numbers of a high-current pulsed electron beam (HCPEB) was investigated. A halo is a ring microstructure resembling a bull’s eye. SEM results indicate that the nanocrystallization of halo induced by HCPEB treatment leads to gradual diffusion of the Si phase. Multiple pulses numbers cause the Si phase to be significantly refined and uniformly distributed. In addition, nanosilicon particles with a grain size of 30~100 nm were formed after HCPEB treatment, as shown by TEM observation. XRD results indicate that Si diffraction peaks broadened after HCPEB treatment. The microhardness tests demonstrate that the microhardness at the midpoint from the halo edge to center decreased sharply from 9770.7 MPa at 5 pulses to 2664.14 MPa at 25 pulses. The relative wear resistance of a 15-pulse sample is effectively improved by a factor of 6.5, exhibiting optimal wear resistance.
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Sun, Yue, Kui Li, Bo Gao, Pengyue Sun, Haiyang Fu, Zhuang Liu e Juntai Yin. "Study on microstructure and wear resistance of Zr-17Nb alloy irradiated by high current pulsed electron beam". REVIEWS ON ADVANCED MATERIALS SCIENCE 59, n. 1 (6 novembre 2020): 514–22. http://dx.doi.org/10.1515/rams-2020-0047.
Testo completoAbstract (sommario):
AbstractIn this paper, the microstructure and wear resistance of Zr-17Nb alloy treated by high current pulsed electron beam were studied in detail. A phase change occurs after pulse treatments using X-Ray Diffraction (XRD) analysis, showing β (Nb) phase and α (Zr) phase transformed by a part of β (Zr, Nb) phase. Also, narrowing and shifting of β (Zr, Nb) diffraction peaks were found. Scanning Electron Microscope (SEM) and metallographic analysis results reveal that the microstructure of alloy surface before high current pulsed electron beam (HCPEB) treatment is composed of equiaxed crystals. But, after 15 and 30 pulse treatments, crater structures are significantly reduced. Besides, it was also found that the alloy surface has undergone eutectoid transformation after 30 pulse treatments, and the reaction of β (Zr, Nb) → αZr + βNb had occurred. Microhardness test results show that microhardness value presents a downward trend as the number of pulses increases, which is mainly due to the coarsening of the grains and the formation of a softer β (Nb) phase after phase transformation. The wear resistance test results show that the friction coefficient increases first, then decreases and then increases with the increase of pulse number.
6
Kuznetsov, V. A., G. D. Polkovnikov, V. E. Gromov, V. A. Kuznetsova e O. A. Peregudov. "High power current pulse generator based on reversible thyristor converter". Izvestiya. Ferrous Metallurgy 62, n. 12 (15 gennaio 2020): 964–71. http://dx.doi.org/10.17073/0368-0797-2019-12-964-971.
Testo completoAbstract (sommario):
In metal forming using high power current pulses, it becomes necessary to control both reproduction frequency and pulse amplitude. Description of a generator of high power current pulses with controlled thyristor converter is provided as a power source of charging device (charger) for regulating voltage (pulse amplitude) of capacitor charge. Faults of the generators associated with inrush current in capacitor charge modes are revealed, which reduces quality of supply network. To reduce time of transient processes while lowering voltage across capacitors, application of reverse thyristor converter is applied as a power source. Structural diagram of generator is considered, which includes reversible thyristor converter with separate control, power unit, capacitor recharge device, charger parameters automatic control system and capacitor charge process control system. Calculation of parameters of automatic control system regulators is presented. To obtain optimal transients, standard methodology for setting regulators to a modular optimum was used. In order to reduce overshoot at time of disturbances appearance, which can reach 100 % and higher, socalled logical device was introduced into the automatic control system. It blocks control pulses on thyristors of converter and simultaneously reduces signal at the output of current regulator to zero. Simulation model of high power current pulse generator in MatLab – Simulink environment was synthesized. Analysis of the model was carried out, and graphs are given that explain principle of device operation and transition processes under various operating modes. Generator application will allow user to adjust amplitude of current pulses with high speed and to obtain sufficiently high-quality transient processes of capacitors charge (discharge), which will have beneficial effect on supply network. Application of better converters will significantly increase frequency of reproduction of current pulses.
7
Park, Hyeong-Gyu, Beom-Soo Kang e Jeong Kim. "Numerical Modeling and Experimental Verification for High-Speed Forming of Al5052 with Single Current Pulse". Metals 9, n. 12 (5 dicembre 2019): 1311. http://dx.doi.org/10.3390/met9121311.
Testo completoAbstract (sommario):
Application of electric current pulses during plastic deformation changes the mechanical behavior owing to the electro-plastic effect. The effect of electric current pulses on the Al5052 alloy is investigated in this study. In order to demonstrate the advantages of passing electric current pulses through a metal sheet during the forming process, a uniaxial tensile test with an electric current pulse was carried out using a self-designed device; this device can apply a 2-kA electric current pulse to the specimen for a short period (>100ms). The electric current increases the temperature of the specimen due to Joule heating. It is, therefore, necessary to decouple the thermal effect from the overall behavior to understand only the contribution of electric current in the mechanical behavior. Firstly, an electro-thermo-mechanical finite element study of an electrically assisted uniaxial tensile test of Al5052 alloy is performed to isolate the thermal effect. The simulated results yielded the thermal effect due to the electric current. By comparing the experimental and simulated results, the contribution of electric current is decoupled from that of thermal effect. The electric current-dependent material model is implemented into the commercial FEM code LS-DYNA using user-defined material(UMAT) subroutine. The electric current-dependent material model was used to simulate the electro-mechanical finite element analysis of the high-speed forming of an aluminum sheet with electric current pulse. Simulation results were compared with experimental results at several applied electric currents to evaluate the accuracy of the UMAT. The present work can be utilized to develop simpler constitutive models for the mechanical behavior of metals subjected to a pulsed electric current.
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Wei, Xianqi, Xiaoli Wang, Xin Li e Weihua Liu. "Electronic Pulses from Pulsed Field Emission of CNT Cathodes". Journal of Nanomaterials 2018 (2018): 1–6. http://dx.doi.org/10.1155/2018/4396430.
Testo completoAbstract (sommario):
We presented a demonstration of infrared laser irradiated field emission electronic pulse based on carbon nanotube (CNT) cathodes. Electronic pulses greatly depended on pulsed infrared laser and were almost synchronous with laser pulses. We have designed a pulsed field emission cathode based on CNTs and investigated correlation between electronic pulse and laser pulse, acquiring the shortest width of electronic pulses about 50 ms and turn-on field less than 0.14 V/μm. Besides, we have studied the thermal effect on the pulsed field emission of CNT cathodes caused by laser heating. Interestingly, the thermal effect has caused an enhancement of emission current but resulted in a waveform distortion on short electronic pulses. The application of laser pulses on CNT cathodes would extend conventional electron sources to a pulsed electron source and offered a possibility of pulsed field emission. These results were encouraging us to prepare further studies of ultrafast electronic pulses for high-frequency electron sources.
9
Kandratsyeu, Aleh, Uladzimir Sabaleuski, Luis Redondo e 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, n. 24 (11 dicembre 2021): 11782. http://dx.doi.org/10.3390/app112411782.
Testo completoAbstract (sommario):
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.
10
Fathimulla, A., H. Hier e J. Abrahams. "High-current pulse-doped GaInAs MESFET". Electronics Letters 24, n. 8 (1988): 498. http://dx.doi.org/10.1049/el:19880338.
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Dutta, P., S. C. Panja e G. R. K. Sastry. "An Investigation of Machining Time and Surface Roughness in Wire-EDM for Inconel 800". Applied Mechanics and Materials 789-790 (settembre 2015): 20–24. http://dx.doi.org/10.4028/www.scientific.net/amm.789-790.20.
Testo completoAbstract (sommario):
This paper presents an experimental investigation on the influences of EDM parameters on machining time and surface roughness for machining Inconel 800.Inconel800is widely used in construction of equipment that must have high strength and resist carburization, oxidation and other harmful effects of high temperature exposure. The selected WEDM parameters are pulsed current (210,220 and 230A), pulse-on time (2,3.25, 4.5, 5.75, 7 and 8.25μs) and pulse-off time (19 and 46μs). It has been observed that surface roughness increases with the increase of pulse-on time and pulse current. Similarly machining time decreases with the increase of pulse current and pulse-on time. Conversely, a decreased value of pulsed current and pulse-on time results in a better surface finish and increased machining time.
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Aladov, A. V., A. E. Chernyakov, A. E. Ivanov e A. L. Zakgeim. "Study of power limitation of AlGaInN LEDs in pulse regime at high current". Journal of Physics: Conference Series 2103, n. 1 (1 novembre 2021): 012186. http://dx.doi.org/10.1088/1742-6596/2103/1/012186.
Testo completoAbstract (sommario):
Abstract LEDs operating under high pulsed current are of a great interest for different applications, in particular, for VLC (LiFi) systems and laser pumping. Current dependences of the efficiency and emission spectra as well as the rise and fall times of high-power blue LEDs were investigated under extremely high pulse current density up to 7 kA/cm2 and pulse duration from 100 ns to 3 μs. Analysis of the pulse behaviour of the LEDs reveals that the main droop in the efficiency and change in spectra occur up to the current densities ~ 1 kA/cm2 and seems to be non-thermal.
13
Ge, Feiyu, Ziteng Xia, Haoming Yuan, Siyang Guo, Zhijun Hu, Jintong Guan, Jie Cai, Qingfeng Guan e Peng Lyu. "Microstructure and Properties of TiN/TiCN/Al2O3/TiN Coating Enhanced by High-Current Pulsed Electron Beam". Coatings 14, n. 4 (23 marzo 2024): 378. http://dx.doi.org/10.3390/coatings14040378.
Testo completoAbstract (sommario):
In this work, a TiN/TiCN/Al2O3/TiN coating deposited onto cemented carbide matrix by chemical vapor deposition was irradiated by high-current pulsed electron beam (HCPEB). The influence of pulse times on the phase composition, microstructure, and mechanical properties of the coating investigated. The results showed that no new phase was produced, the grain size of the coating surface was refined, the surface became flat, and the surface roughness decreased after HCPEB treatment. The TiN/TiCN/Al2O3/TiN coating presented a smooth surface with good mechanical performance after HCPEB. A maximum hardness was obtained after 15 pulses, and the 15-pulse irradiated coating showed better wear resistance. The improvement in the coating’s performance after irradiation was mainly attributed to the formation of grain refinement and crystal defects, as well as the change of stress field inside the coating. The objective of this study was to evaluate the potential of HCPEB modification in the preparation of high-performance coating by analyzing the microstructure and property of coating under different pulses.
14
Levinshtein, Michael E., Tigran T. Mnatsakanov, Pavel A. Ivanov, John W. Palmour, Mrinal K. Das e Brett A. Hull. "Self-Heating of 4H-SiC PiN Diodes at High Current Densities". Materials Science Forum 600-603 (settembre 2008): 1007–10. http://dx.doi.org/10.4028/www.scientific.net/msf.600-603.1007.
Testo completoAbstract (sommario):
Self-heating in high-voltage 4H-SiC PiN diodes has been studied experimentally and theoretically in dc and 8-ms single pulse modes. To simulate the self-heating, an electro-thermal model was used to calculate non-isothermal current-voltage characteristics at dc and current-time dependences at pulsed measurements. The dynamic instability of N-type was observed: the current decreases in spite of increasing of bias applied to the structure. At dc, irreversible diode degradation was found to occur at a current density of about 1700 A/cm2. Under a single current surge 8-ms pulse, the loss of thermal stability has been found at a current density of approximately 9000 A/cm2. Comparison of experimental data and simulations showed that the local temperature in the diode base at the end of the 8-ms, 9000-A/cm2 pulse reaches 2000 – 2300 K.
15
Nowak, Mikołaj, Kazimierz Jakubiuk, Daniel Kowalak, Marek Pikoń, Józef Czucha e Jacek Starzyński. "Current divider-based nanosecond high current pulse measuring systems". Measurement 181 (agosto 2021): 109600. http://dx.doi.org/10.1016/j.measurement.2021.109600.
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Grishin, A. V., S. L. Glushkov, B. P. Mironychev, D. A. Kalashnikov, A. V. Kozachek, V. M. Martynov, V. V. Turutin et al. "Design of a synchronization system for the “Gamma-4” electrophysical facility". International Journal of Modern Physics: Conference Series 32 (gennaio 2014): 1460333. http://dx.doi.org/10.1142/s2010194514603330.
Testo completoAbstract (sommario):
At RFNC-VNIIEF on the basis of a “Gamma-1” high-current pulsed accelerator there is being developed a four-module “Gamma-4” electrophysical facility. A synchronization system of the "Gamma-4" facility is meant for a simultaneous (with precision not worse than ±3 ns) triggering of high-volt gas-filled trigatron type switches of modules' pulse forming systems (144 items, operating voltage ≤ 1 MV), modules' pre-pulse switches (24 items, ≤ 3 MV) and 8 Marx generators (40 items, ≤ 100 kV). The synchronization system comprises 54 pulse generators, involving 25 generators on the basis of water insulated forming lines with distributed parameters and multi-channel gas-filled switches. On matched cable loads with resistances 0.45 Ohm these generators form voltage pulses with amplitudes 100 kV with durations 25 ns. A jitter of switches of these generators does not exceed ± 2 ns. To raise the amplitude of pulse drivers of pulse forming system switches and pre-pulse switches of modules in the facility synchronization system there are used step-up transformers based on pulsed high-voltage cables.
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Remnev, G. E., Mikhail V. Zhuravlev, M. V. Belyakov, I. A. Koryashov, I. N. Pyatkov, M. I. Kaikanov e A. V. Tikhonov. "HIGH-POWER DOUBLE-PULSE GENERATOR FOR POWER SUPPLY TO PULSED HIGH-CURRENT ACCELERATOR". High Temperature Material Processes An International Quarterly of High-Technology Plasma Processes 21, n. 4 (2017): 309–15. http://dx.doi.org/10.1615/hightempmatproc.2018025165.
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Flaxer, E. "High-voltage pulse modulated radio frequency generator for dielectric barrier discharge combined with ultra-fast high power pulse generator". Journal of Instrumentation 16, n. 10 (1 ottobre 2021): P10003. http://dx.doi.org/10.1088/1748-0221/16/10/p10003.
Testo completoAbstract (sommario):
Abstract Dielectric barrier discharge is the electrical discharge between two electrodes separated by an insulating dielectric barrier. The discharge process typically uses a high-voltage alternating current in the range of several kilohertz to several gigahertz. A high-frequency and high-power pulse generator is required to drive the discharge process through the capacitance load. There are two main techniques to implement this type of generator: the forced and resonant modes. This work demonstrates the implementation of a programmable digital circuit based on a digital signal controller and a full H-bridge that combines the two topologies and can be used as a controller for dielectric barrier discharge with varying capacitance and structure. We integrated an ultra-fast, high-resolution, and high-power pulse generator into a radio frequency generator to drive high-pressure, supersonic, pulsed valves. The excitation based on our DBD and the combined generator produces cold plasma beams. The controller generates discharge voltages of up to 5 kV, in pulses of 10 to 50 μs wide, at rates of up to 1 kHz, while the discharge frequency ranges are from 1 to 3 MHz under a capacitive load of 100 pF. The power generator applies a current pulse of up to 20 A and voltage of up to 150 V.
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Kiziridi P. P. e Ozur G.E. "Pulse energy of a non-relativistic, high-current electron beam". Technical Physics 92, n. 6 (2022): 740. http://dx.doi.org/10.21883/tp.2022.06.54421.316-21.
Testo completoAbstract (sommario):
Energetic characteristics of a high-current electron gun with a cathode assembly based on multi-gap initiation of explosive emission by dielectric surface flashover in the mode of vacuum and gas-filled diode were investigated. It has been shown that it is better to measure high-current electron beam pulse energy using a calorimetric (thermal imaging) method than to calculate it from the waveforms of accelerating voltage and beam current onto collector (target) since the beam current values may be essentially overstated because of decay current of a dense plasma emergent under the bombardment of a collector by the beam electrons. The best efficiency of the energy transfer from the capacitive storage of the high-voltage pulsed generator supplying an electron gun was observed in the case of gas-filled diode at a moderate pressure of the working gas (argon, 0.093 Pa). Keywords: high-current electron beams, explosive emission, multi-gap initiation, dielectric surface flashover, beam pulse energy, plasma decay current, thermal imaging.
20
Hao, Sheng Zhi, Yang Xu, Min Cai Li e Chuang Dong. "Surface Treatment of 316L Stainless Steel by High Current Pulsed Electron Beam". Materials Science Forum 654-656 (giugno 2010): 1803–6. http://dx.doi.org/10.4028/www.scientific.net/msf.654-656.1803.
Testo completoAbstract (sommario):
High current pulsed electron beam has been developing as a useful tool for surface modification of materials. This paper presents our research on the surface treatment of 316L stainless steel with an equipment of working parameters as electron energy 20-30keV, pulse duration 1.5µs and energy density ~6J/cm2. The surface microstructure was characterized with metallography, X-ray diffractometry and electron backscatter diffraction (EBSD) techniques. It was found that the modified samples showed significant improvement on corrosion resistance when using increased pulse number and higher energy density. This result is discussed in relation to the coupled temperature-stress fields formed after the absorption of electron beam energy.
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Hu, Ye Lin, Zhi Wen Du e Zhao Quan Chen. "Development of a Pulsed DC Power Supply for Generating Cold Plasma Jet". Advanced Materials Research 791-793 (settembre 2013): 1841–44. http://dx.doi.org/10.4028/www.scientific.net/amr.791-793.1841.
Testo completoAbstract (sommario):
This paper discusses a lithium battery-driven cold plasma jet at atmospheric pressure with a pulsed power supply of design and its simulation. H.V. DC(High voltage directed current) and pulsed discharge circuit comprise of the entire pulse power system. H.V. DC circuit using TIs TMS320F28335 chips as the core of the circuit control module, the chip improves the stability of the H.V.DC circuits. Pulsed discharge circuit design plays a crucial impact on the formation of the narrowed pulses. A new double pulsed discharge circuit is designed by the proposed program. As discharge experiment shown finally, the steep narrowed pulse of pulsed power supply can be used to stabilize the output of the pulsed front.
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Tang, Xiongmin, Tianhong Jiang e Wenrui Fang. "A unipolar compact nanosecond pulsed power supply with high power factor for dielectric barrier discharge applications". Review of Scientific Instruments 93, n. 8 (1 agosto 2022): 084707. http://dx.doi.org/10.1063/5.0089020.
Testo completoAbstract (sommario):
A high voltage with a very short duration and fast rising time is beneficial to generate uniform and diffuse plasma in dielectric barrier discharge (DBD) loads, and a power supply with a high power factor (PF) can reduce the impact on the power grid. According to two requirements, a unipolar high voltage pulsed power supply with power factor correction (PFC) is proposed in this paper. The power supply consists of a unipolar pulse high voltage generating unit, a PFC unit, and a driving circuit. By introducing a feedback clamping diode and a reverse current blocking diode in a flyback converter, repetitive nanosecond pulses are generated in the unipolar pulse high voltage generating unit. Because a discontinuous current mode strategy is adopted in the PFC unit and the driving signal is shared by the two units, a compact structure of the power supply is achieved, and a high PF is obtained. To validate the proposed pulsed power supply, an experimental setup is built for a DBD excimer lamp. The results show that the proposed power supply has the capability of not only providing a unipolar nanosecond pulse high voltage for the DBD excimer lamp but also achieving PF close to 1 and total harmonic distortion of less than 24%.
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Zhang, Xi, K. N. Tu, Zhong Chen, Y. K. Tan, C. C. Wong, S. G. Mhaisalkar, X. M. Li, C. H. Tung e C. K. Cheng. "Pulse Electroplating of Copper Film: A Study of Process and Microstructure". Journal of Nanoscience and Nanotechnology 8, n. 5 (1 maggio 2008): 2568–74. http://dx.doi.org/10.1166/jnn.2008.18288.
Testo completoAbstract (sommario):
Copper films with high density of twin boundaries are known for high mechanical strength with little tradeoff in electrical conductivity. To achieve such a high density, twin lamellae and spacing will be on the nanoscale. In the current study, 10 μm copper films were prepared by pulse electrodeposition with different applied pulse peak current densities and pulse on-times. It was found that the deposits microstructure was dependent on the parameters of pulse plating. Higher energy pulses caused stronger self-annealing effect on grain recrystallization and growth, thus leading to enhanced fiber textures, while lower energy pulses gave rise to more random microstructure in the deposits and rougher surface topography. However in the extremes of pulse currents we applied, the twin densities were not as high as those resulted from the medium or relatively high pulse currents. The highest amount of nanoscale twinning was found to form from a proper degree of self-annealing induced grain structure evolution. The driving force behind the self-annealing is discussed.
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Hao, Sheng Zhi, B. Gao, Ai Min Wu, Jian Xin Zou, Ying Qin, Chuang Dong e Q. F. Guan. "Surface Treatment of Materials with High Current Pulsed Electron Beam". Materials Science Forum 475-479 (gennaio 2005): 3959–62. http://dx.doi.org/10.4028/www.scientific.net/msf.475-479.3959.
Testo completoAbstract (sommario):
High current pulsed electron beam (HCPEB) is now becoming a promising energetic source for the surface treatment of materials. When the concentrated electron flux transferring its energy into a very thin surface layer within a short pulse time, superfast processes such as heating, melting, evaporation and consequent solidification, as well as dynamic stress field induced by an abrupt thermal distribution in the interactive zone impart surface layer with improved physicochemical and mechanical properties. The present paper reports mainly our experimental research work on this new-style technique. Investigations performed with a variety of constructional materials (aluminum, carbon and mold steel, magnesium alloys) have shown that the most pronounced changes of composition, microstructure and properties occur in the near-surface layers, while the thickness of the modified layer with improved mechanical properties (several hundreds of micrometers) is significantly greater than that of the heat-affected zone due to the propagation of stress wave. The surfaces treated with either simply several pulses of bombardment or complex techniques, such as rapid alloying by HCPEB can exhibit improved mechanical and physicochemical properties to some extent.
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Li, Zerui. "Analysis of the Principles and Applications of Ultra-intensity and Ultrashort Laser". Highlights in Science, Engineering and Technology 76 (31 dicembre 2023): 441–49. http://dx.doi.org/10.54097/9s9fm882.
Testo completoAbstract (sommario):
With the development of laser technology, how to improve the output performance and peak power of lasers has become one of the hot directions of current research. This study analyzes the principles and applications of ultra-intensity and ultrashort pulse laser. It firstly outlines the development history of laser technology and the basic definition of ultra-intensity and ultrashort pulse laser. It also mentions the realization methods for generating ultra-intensity and ultrashort pulse lasers, such as mode-locked femtosecond oscillators and CPA-based femtosecond amplifiers. The paper describes the principles of CPA technique and emphasizes its importance in realizing high power ultrashort pulses. The paper discusses various applications of ultra-intensity and ultrashort pulsed laser and summarizes and discusses the major bottlenecks facing current and future ultra-intensity and ultrashort pulsed lasers and their possible solutions. The technical review in this paper aims to enhance the understanding of ultra-intensity and ultrashort pulsed laser and provide insights into the next phase of research exploration in ultra-intensity and ultrashort pulsed lasers.
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Korolkov, O. E., M. A. Pakhomov e V. V. Stolyarov. "The electroplastic effect in titanium alloys under tension". Industrial laboratory. Diagnostics of materials 88, n. 10 (25 ottobre 2022): 73–82. http://dx.doi.org/10.26896/1028-6861-2022-88-10-73-82.
Testo completoAbstract (sommario):
The electroplastic effect (EPE) is a phenomenon which consists in a decrease in the strain resistance and enhancing of the plasticity of metals under the effect of the electric current of a sufficiently high density [1]. The goal of the study is to compare the deformation behavior of single-phase commercially pure titanium Grade 4 and two-phase VT6 alloy under tension and external heating with introduction of a pulsed current. Current of various pulse ratio and density was supplied to the grips of the tensile testing machine from a pulse generator. To estimate the relative contribution of the electroplastic effect during passage of current to the reduction of flow stresses, the materials were also exposed to external heating. The microstructure of the samples in the sample head and in the vicinity of the fracture region in the longitudinal section was studied using optical microscopy. The electroplastic effect in the studied materials is manifested on the tensile curve through individual jumps in the downward flow stress at a high pulse ratio, whereas at a low current pulse ratio a decrease in the flow stress and strain hardening and increase in the plasticity are observed. It is shown that tension of the sample under the effect of current results in a greater decrease in the flow stresses than that observed under external heating at the same temperature for both materials. This confirms the athermal nature of the pulsed current effect. The critical density of the high pulse ratio current (q - 5000) capable of providing manifestation of the electroplastic effect is two times lower for a VT6 alloy than for pure titanium Grade 4. Under the same pulsed current modes, the flow stresses for VT6 decrease more than for Grade 4. Pulsed current of high pulse ratio caused an anomalous hardening effect in a VT6 alloy, but the physical nature of this effect requires an additional study. The pulsed current modes used in the study did not lead to any structural changes noticeable under optical magnification in the samples under tension, except for the disappearance of twins and separation of the impurity particles in Grade 4 and spheroidization of grains in VT6.
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Shim, Chi Hyun, Ki Moon Nam, Yong Woon Parc e Dong Eon Kim. "Isolated terawatt sub-attosecond high-energy x-ray pulse generated by an x-ray free-electron laser". APL Photonics 7, n. 5 (1 maggio 2022): 056105. http://dx.doi.org/10.1063/5.0067074.
Testo completoAbstract (sommario):
The endless quest for dynamics in natural phenomena has resulted in the generation and application of attosecond pulses to trace electron dynamics in atomic and molecular systems. The next challenge is to generate powerful pulses on the zeptosecond time scale, which is currently inaccessible. Through a simulation study, a new type of x-ray source that can generate an isolated terawatt sub-attosecond pulse at high-energy x rays by combining attosecond pulse technology with free-electron laser technology is proposed. The successful generation of a sub-attosecond pulse necessitates the consideration of nanometer-wide current-spikes, the sub-attosecond pulse amplification, and pulse duration and background noise control. The underlying interaction mechanism between a sub-attosecond pulse and a current-spike is closely investigated using the simulation results. The proposed method is expected to produce an isolated ∼700 zs pulse with a peak output of 2.9 TW at a photon energy of 247.5 keV.
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Obukhov, V. A., A. V. Ovchnnikov, A. F. Piskunkov e N. P. Shishaev. "High-Speed Macroparticle Destruction in a High-Current Pulse Discharge". IEEE Transactions on Magnetics 45, n. 1 (gennaio 2009): 626–30. http://dx.doi.org/10.1109/tmag.2008.2008615.
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Tantavichet, Nisit, e Mark D. Pritzker. "Low- and High-Frequency Pulse Current and Pulse Reverse Plating of Copper". Journal of The Electrochemical Society 150, n. 10 (2003): C665. http://dx.doi.org/10.1149/1.1602457.
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Baranov, M. I., S. G. Buriakovskyi e V. V. Kniaziev. "Destruction of polymer insulation and threshold amplitudes of current pulses of different temporal shapes for electric wires and cables in the low- and high-current circuits of pulse power engineering, electrical engineering and electronic devices". Electrical Engineering & Electromechanics, n. 6 (3 dicembre 2021): 31–38. http://dx.doi.org/10.20998/2074-272x.2021.6.05.
Testo completoAbstract (sommario):
Goal. Development of engineering method for settlement of threshold amplitudes Impk of single-pulse current ip(t) of different temporal shapes for electric wires and cables with polyethylene (PET), polyvinylchloride (PVC) and rubber (R) half-length insulation, used in modern pulsed power engineering, electrical engineering and electronics in their low- and high-current circuits. Methodology. Basis of the theoretical and applied electrical engineering, electrical power engineering, electrophysics bases of technique of high-voltage and large pulsed currents, bases of low- and high-current electronics, measuring technique, electromagnetic compatibility and standardization. Results. Development of engineering method is executed on close calculation determination of threshold amplitudes Impk of single-pulse axial-flow current ip(t) of different temporal shapes for electric wires and cables with copper (aluminum) current-carrying parts and PET, PVC and R half-length insulation, used in the ow- and high-current circuits of pulsed electrical power engineering, electrical engineering and electronics. Electrothermal resistibility of half-length insulation of the examined cable and wire products (CWP), proper maximum to the possible temperatures of heating of current-carrying and insulating parts of the probed wires and cables and shutting out the offensive of the phenomenon destruction in the indicated insulation of CWP, was fixed based on this method. Calculation analytical correlations are obtained for finding in probed CWP of threshold numeral values of Impk amplitudes of pulses of current ip(t), time-varying both on aperiodic dependence of type τf/τp with duration of their front τf and duration of their pulses τp and by law of exponential attenuation sinewave. It is shown that at Imp>Impk destruction of their half-length insulation, resulting in the decline of service life of CWP, will come from the thermal overheat of current-carrying parts of the examined electric wires and cables. The examples of practical application of the offered method are resulted upon settlement for a radiofrequency coaxial cable RC 50-4-11 with middle sizes is easily soiled with continuous PET insulation of threshold amplitudes of Impk of standard aperiodic pulses of current ip(t) from nano-, micro- and millisecond temporal ranges of shape of τf/τp=5 ns/200 ns, τf/τp=10 μs/350 μs and τf/τp=7 ms/160 ms. It is shown that with the proper growth of parameter τp>>τf for flow on a continuous copper tendon and split copper shell of radiofrequency coaxial cable RC 50-4-11 with middle sizes is easily soiled indicated homopolar pulses of current ip(t) substantial diminishing of their threshold amplitudes of Impk (with 531,2 кА for the nanosecond pulse of current of type 5 ns/200 ns to 1.84 кА for the millisecond impulse of current of type of 7 ms/160 ms takes place). Originality. An engineering method is first developed for close settlement of threshold numeral values of Impk amplitudes of single-pulse axial-flow current ip(t) of arbitrary peak-temporal parameters for electric wires and cables with copper (aluminum) current-carrying parts and PET, PVC and R half-length insulation. Practical value. Application in electrical engineering practice of the offered engineering method for determination of threshold amplitudes Impk of the indicated pulses of axial-flow current ip(t) for the probed electric wires and cables will allow considerably to increase service life of examined CWP.
31
Song, Falun, Fei Li, Beizhen Zhang, Mingdong Zhu, Chunxia Li, Ganping Wang, Haitao Gong, Yanqing Gan e Xiao Jin. "Recent advances in compact repetitive high-power Marx generators". Laser and Particle Beams 37, n. 01 (marzo 2019): 110–21. http://dx.doi.org/10.1017/s0263034619000272.
Testo completoAbstract (sommario):
AbstractThis paper introduces recent activities on Marx-based compact repetitive pulsed power generators at the Institute of Applied Electronics (IAE), China Academy of Engineering Physics (CAEP), over the period 2010–2018. A characteristic feature of the generators described is the use of a simplified bipolar charged Marx circuit, in which the normal isolation resistors or inductors to ground are removed to make the circuit simpler. Several pulse-forming modules developed to generate a 100 ns square wave output are introduced, including thin-film dielectric lines of different structures, a pulse-forming line based on a Printed Circuit Board, and non-uniform pulse-forming networks. A compact repetitive three-electrode spark gap switch with low-jitter, high-voltage, and high-current was developed and is used in the generators. A positive and negative series resonant constant current power supply with high precision and high power is introduced. As an important part of the repetitive pulse power generator, a lower jitter pulse trigger source is introduced. Several typical high-power repetitive pulsed power generators developed at IAE are introduced including a 30 GW low-impedance Marx generator, a compact square-wave pulse generator based on Kapton-film dielectric Blumlein line, a 20 GW high pulse-energy repetitive PFN-Marx generator, and a coaxial Marx generator based on ceramic capacitors. The research of key technologies and their development status are discussed, which can provide a reference for the future development and application of miniaturization of compact and repetitive Marx generators.
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Bujnowicz, Łukasz, e Marcin Sarewicz. "Multichannel pulse high-current driver of magnetic actuator". HardwareX 11 (aprile 2022): e00286. http://dx.doi.org/10.1016/j.ohx.2022.e00286.
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LI, Xiaohai. "ELECTROLYTIC MICROMACHINING WITH HIGH FREQUENCY SHORT PULSE CURRENT". Chinese Journal of Mechanical Engineering 42, n. 01 (2006): 162. http://dx.doi.org/10.3901/jme.2006.01.162.
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Pirc, Eva, Damijan Miklavčič, Katja Uršič, Gregor Serša e Matej Reberšek. "High-Frequency and High-Voltage Asymmetric Bipolar Pulse Generator for Electroporation Based Technologies and Therapies". Electronics 10, n. 10 (18 maggio 2021): 1203. http://dx.doi.org/10.3390/electronics10101203.
Testo completoAbstract (sommario):
Currently, in high-frequency electroporation, much progress has been made but limited to research groups with custom-made laboratory prototype electroporators. According to the review of electroporators and economic evaluations, there is still an area of pulse parameters that needs to be investigated. The development of an asymmetric bipolar pulse generator with a maximum voltage of 4 kV and minimum duration time of a few hundred nanoseconds, would enable in vivo evaluation of biological effects of high-frequency electroporation pulses. Herein, from a series of most commonly used drivers and optical isolations in high-voltage pulse generators the one with optimal characteristics was used. In addition, the circuit topology of the developed device is described in detail. The developed device is able to generate 4 kV pulses, with theoretical 131 A maximal current and 200 ns minimal pulse duration, the maximal pulse repetition rate is 2 MHz and the burst maximal repetition rate is 1 MHz. The device was tested in vivo. The effectiveness of electrochemotherapy of high-frequency electroporation pulses is compared to “classical” electrochemotherapy pulses. In vivo electrochemotherapy with high-frequency electroporation pulses was at least as effective as with “classical” well-established electric pulses, resulting in 86% and 50% complete responses, respectively. In contrast to previous reports, however, muscle contractions were comparable between the two protocols.
35
Qin, Feng, Wei Chen, Xutong Wang, Tao Huang, Zhitong Cui e Xin Nie. "Transient Response Characteristics of Metal Oxide Arrester under High-Altitude Electromagnetic Pulse". Energies 15, n. 9 (30 aprile 2022): 3303. http://dx.doi.org/10.3390/en15093303.
Testo completoAbstract (sommario):
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.
36
Cernák, M., e T. Hosokawa. "Negative Corona Current Pulses and Cathode Sheath Instabilities in a Short Point-Plane Gap in CO2". Australian Journal of Physics 45, n. 2 (1992): 193. http://dx.doi.org/10.1071/ph920193.
Testo completoAbstract (sommario):
Waveforms ofthe first negative corona current pulses have been measured in C02 and C02+SF6 mixtures as a function of applied voltage and gas pressure in the range 6�67-66�7 kPa. A complex form of the pulses with a step on the pulse leading edge and a current hump on the pulse trailing part has been found at gas pressures below 40 kPa. Changing the cathode surface material from copper to copper iodide, which has an exceptionally high photoelectric yield, resulted in at least a twofold increase in height of the step on the pulse leading edge, but had little effect on the main current rise to the pulse peak. The use of unconditioned cathodes resulted in the appearance of peculiar current spikes on the pulse tail, which are tentatively attributed to positive-streamer-like instabilities of the cathode sheath. The implications of these results for theories of Trichel pulse formation are discussed, and a physical picture of the phenomenon based on the presumed existence of a cathode-directed streamer associated with the steep pulse rise is outlined.
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Bedrin, Alexander G., Alexander N. Zhylin e Igor L. Lovchy. "Using a fiber optic sensor for registration of pulsed plasma discharge current". Izmeritel`naya Tekhnika, n. 9 (2021): 28–34. http://dx.doi.org/10.32446/0368-1025it.2021-9-28-34.
Testo completoAbstract (sommario):
The problem of increasing the accuracy of recording the pulse shape of a rapidly changing current of a powerful plasma emitter under conditions of powerful electromagnetic interference is considered. To register high-current pulsed discharges, it is proposed to use a polarimetric fiber-optic current sensor based on a Spun-type fiber. Using the indicated current sensor, a technique for recording high-current pulsed discharges of a plasma emitter in the mode of time profiling of the current pulse of two high-voltage capacitive storage devices with a total energy of up to 1800 kJ is realized. The discharge chamber, power supply circuits, and the formation of a plasma discharge are described. The design and principle of operation of a prototype of a two-pass polarimetric fiberoptic sensor with a Spun-type fiber and a Faraday compensator of mutual optical anisotropy are presented. The general scheme of current measurements, the sensor calibration scheme is presented, and the experience of using a prototype sensor for measuring high-power pulse currents is described. The features of the preliminary calibration of the sensor are discussed. The results of measuring the current by optical and traditional recording methods based on the Rogowski coil and Hall sensors are compared with each other, and a noticeable increase in the accuracy of reproducing the current pulse shape by the optical recording method is noted. Possible options for upgrading a fiber-optic sensor to expand the range of current recording are considered.
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Eshpulatov, Nodir, Tolib Khalmuradov, Rakhmаnberdi Khalilov, Abdulkhay Obidov, Sobir Nurmanov e Dilmurat Omonov. "Theoretical substantiation of the influence of electric pulse processing on the process of obtaining juice from grapes and fruits". E3S Web of Conferences 264 (2021): 04086. http://dx.doi.org/10.1051/e3sconf/202126404086.
Testo completoAbstract (sommario):
The article presents the theoretical basis of the effect of electrical pulse processing on the process of obtaining juice from grapes and fruits. High-voltage pulsed electrical processing technology for biological products has a higher damaging effect on living cells than other electrical effects, and this can be achieved due to the passage of large discharges of current through tissues and cells in a short period of time. It has been found that high efficiency in killing living cells by secretion can be achieved as a result of a pulsed energy effect. In order to develop energy-efficient electrical technology for extracting juice from fruits and grapes, it has been found that high-voltage electric pulse discharge treatment of grapes and apples before extracting juice has a good effect. Analytical expressions between electrical impulse processing parameters (pulse energy and capacitor capacity) and juice output were determined. The degree of damage to fruit and grape cells depends on the capacitance of the capacitor, the discharge voltage, and the number of pulses.
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Zou, Hui, H. R. Jing, Sheng Zhi Hao e Chuang Dong. "Nanostructure of 45# Carbon Steel by High Current Pulsed Electron Beam". Advanced Materials Research 79-82 (agosto 2009): 317–20. http://dx.doi.org/10.4028/www.scientific.net/amr.79-82.317.
Testo completoAbstract (sommario):
When high current pulsed electron beam (HCPEB) transferring its energy into a very thin surface layer within a short pulse time, super fast processes such as heating, melting, evaporation and consequent solidification, as well as dynamic stress induced may impart the surface layer with improved properties. In this paper, HCPEB modification of 45# carbon steel with working parameters of electron energy 25 kV, pulse duration 3.5µs, and energy density 4 J/cm2 was investigated. The microstructures of modified surface were analyzed by scanning electron microscope (SEM) of type JSM 5310 and transmission electron microscope (TEM) of type H-800. It is found that the modified surface layer can be divided into three zones: the white layer or melted layer of depth 3 to10µm, the heat and stress effecting zone 10 µm below and about 250 µm, then matrix, where a nanostructure and/or amorphous layer formed in the near-surface region. It is proved that the whole treatment process is not complex and cost-effective, and has a substantial potential to be applied in industries.
40
Rai, Krishna Kumar, A. V. Giridhar, D. R. Jahagirdhar, Ashish Rai e Akash Kumar Paul. "Investigation on the Effect of Cable Length on Pulse Shape of High Voltage High Pulse Power Supply". Defence Science Journal 72, n. 2 (11 maggio 2022): 243–49. http://dx.doi.org/10.14429/dsj.72.17548.
Testo completoAbstract (sommario):
In the present scenario of pulse power applications, transmission of high voltage pulses varies as per load condition. In the early days of its application, High Voltage High Pulse Power Supply (HVHPPS) design saw short distance between load and source, where the effect of cable length was not taken into account for design. This paper presents the effect of cable length on pulse shape of High Voltage High Pulse Power Supply. The load under observation is Klystron based high energy particle accelerator system. The performance of pulse power systems were observed continuously on a daily basis throughout the year and detailed analysis was carried out. This paper generates the model of pulse forming system and provides details of pattern distortion of the pulse shape due to various dynamic parameter changes i.e. impedance, Load Voltage, Load Current, Cavity Dimensional Changes (Microwave components) due to temperature variations and performance of the power supply. The results were analysed and validated with hardware results across a range of actual industrial loads.
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Rogov, Aleksey B. "Smart Arbitrary Waveform Generator with Digital Feedback Control for High-Voltage Electrochemistry". Instruments 3, n. 1 (7 febbraio 2019): 13. http://dx.doi.org/10.3390/instruments3010013.
Testo completoAbstract (sommario):
This paper describes a design approach to a control system of power supply for high-voltage electrochemical processes such as plasma electrolytic oxidation (PEO) or high-voltage anodising (HVA), which require alternating polarisation pulses up to 750 V and a typical current density of 50–500 mA/cm2. Complex characteristics of the electrochemical system response on applied polarisations (positive or negative) cause necessity of precise control of polarising pulse shapes for better process operation and its understanding. A device performs cycle-by-cycle pulse-width modulation (PWM) control, including feedback based on digital analysis of the instantaneous current and/or voltage output, and the desired pulse waveform stored in memory for each output polarity. The output stage has four states corresponding to positive or negative pulses, as well as open- or short-circuit conditions, with respect to an electrochemical cell. A fully programmable controller allows one to generate arbitrary waveforms, as well as their sequences, by means of “regime designer” software. Moreover, a smart feedback system can provide adaptation of the next pulse parameter from analysis of the process prehistory. For instance, this approach allows one to separate main electrochemical process (coating formation) and diagnosis of the phenomenon through introduction of high-voltage triangular voltage sweep pulse within a pause of the main process, which is normally carried out under a current control.
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Naganawa Toshio, Pavleino M. A., Pavleino O. M. e Safonov M. S. "Method for estimating the initial welding current of closed high-current contacts under pulsed heating". Technical Physics 92, n. 10 (2022): 1380. http://dx.doi.org/10.21883/tp.2022.10.54366.155-22.
Testo completoAbstract (sommario):
A study of the softening process of contact spots of closed high-current copper contacts caused by recrystallization of the material during short-circuit shock currents has been carried out. An original method has been developed for calculating the magnitude of the pulse current, which initiates the welding of contacts, which does not require preliminary experimental measurements. Keywords: Electrical contact, pulse heating, numerical calculation, welding.
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Bozorov, Elmurod, e Husniddin Abdullayev. "Study on the effect of electric pulse treatment for disinfestation of vegetables". E3S Web of Conferences 434 (2023): 01024. http://dx.doi.org/10.1051/e3sconf/202343401024.
Testo completoAbstract (sommario):
This paper describes a method of using pulsed discharge to control nematode diseases on tomato and cucumber rhizomes and crops grown in dacha plots. When pulsed discharges are applied to living tissue, certain chemical, physical, and biological processes occur, depending on the pulse energy, pulse discharge current, pulse discharge voltage, pulse discharge exposure time, pulse discharge impact current, and other similar factors. Electric pulses were applied to grafts of nematode-infested vegetables, tomatoes and cucumbers, to measure grafting ability. Crop yields were estimated by the total amount of produce grown on arable land, and the level of yield enhancement was determined by land sedimentation and proper placement of varieties and plant species. Proper selection of modern high-yielding varieties imported from Uzbekistan provides resistance to external adverse effects of nature and diseases. The creation of high-yielding varieties requires the discovery and cultivation of resistant hybrid varieties and the development and introduction of new progressive technological methods of plant cultivation. The objective of this study was to identify the main factors affecting the electric pulse discharge treatment of tomato and cucumber root crops infected with nematodes and their larvae. Various diseases occur in cotton, cereals, melons, vegetable crops, and indoors(greenhouses) on newly established farms in the Republic. Yields are particularly high in vegetable, melon, and greenhouse fields. In recent years, the impact of nematodes on plants has caused severe damage to crop yields. Treating crops with this formulation prevents nematode infestation of leaf veins. The economic damage caused by nematodes to agriculture is enormous. For example, in greenhouse vegetables (cucumbers and tomatoes) this indicator reaches 60% and in potatoes 80%. Therefore, the proposed method is realized in combination with an agrotechnical treatment process that is energy-saving, environmentally safe, and productive.
44
BADZIAK, J., S. GŁOWACZ, S. JABŁOŃSKI, P. PARYS, J. WOŁOWSKI e H. HORA. "Laser-driven generation of high-current ion beams using skin-layer ponderomotive acceleration". Laser and Particle Beams 23, n. 4 (ottobre 2005): 401–9. http://dx.doi.org/10.1017/s0263034605050573.
Testo completoAbstract (sommario):
Basic properties of generation of high-current ion beams using the skin-layer ponderomotive acceleration (S-LPA) mechanism, induced by a short laser pulse interacting with a solid target are studied. Simplified scaling laws for the ion energies, the ion current densities, the ion beam intensities, and the efficiency of ions' production are derived for the cases of subrelativistic and relativistic laser-plasma interactions. The results of the time-of-flight measurements performed for both backward-accelerated ion beams from a massive target and forward-accelerated beams from a thin foil target irradiated by 1-ps laser pulse of intensity up to ∼ 1017 W/cm2 are presented. The ion current densities and the ion beam intensities at the source obtained from these measurements are compared to the ones achieved in recent short-pulse experiments using the target normal sheath acceleration (TNSA) mechanism at relativistic (>1019 W/cm2) laser intensities. The possibility of application of high-current ion beams produced by S-LPA at relativistic intensities for fast ignition of fusion target is considered. Using the derived scaling laws for the ion beam parameters, the achievement conditions for ignition of compressed DT fuel with ion beams driven by ps laser pulses of total energy ≤ 100 kJ is shown.
45
Powers, R. K., e M. D. Binder. "Experimental evaluation of input-output models of motoneuron discharge". Journal of Neurophysiology 75, n. 1 (1 gennaio 1996): 367–79. http://dx.doi.org/10.1152/jn.1996.75.1.367.
Testo completoAbstract (sommario):
1. We measured the modulation of the background firing rate of cat spinal motoneurons produced by simulated, repetitive excitatory postsynaptic potentials (EPSPs) to test the accuracy of several proposed motoneuron input-output functions. Rhythmic discharge was elicited in the motoneurons by injecting suprathreshold current steps 1-1.5 s in duration. On alternate trials, trains of short (0.5-5 ms) current pulses were superimposed on the current steps to stimulate the effects of trains of individual EPSPs. The increase in firing rate (delta F) due to the addition of the pulses was calculated as the difference in motoneuron discharge rate between trials with and without the superimposed pulse trains. 2. In the same motoneurons, we were able to study the effects of changes in pulse frequency, duration, and amplitude, as well as changes in the background discharge rate. A sublinear relationship between pulse rate and delta F was observed, with delta F rising relatively steeply with increasing pulse frequency at low pulse rates and saturating at high pulse rates. A similarly shaped relation was observed between delta F and pulse duration. In contrast, delta F generally increased in a greater than linear fashion with increasing pulse amplitude. 3. In previous studies we demonstrated that when a relatively constant synaptic input is produced by high-frequency synaptic activity, delta F is approximately equal to the product of the net synaptic current reaching the soma and the slope of the motoneuron's steady-state frequency-current (f-I) relation. In the present study, this input-output function consistently underestimated the observed delta F, particularly for low input rates, indicating that the transient current pulses are more effective in modulating motoneuron discharge than an equivalent amount of constant current. 4. Other investigators have proposed input-output functions derived from the relation between synaptic potential amplitude and the magnitude of the peak of a cross correlogram compiled from the discharge of the pre- and postsynaptic neurons. These functions consistently overestimated the observed delta F, particularly for high pulse rates. This overestimation may result in part from the fact that the effects of a synaptic potential (or current pulse) on postsynaptic discharge probability also include a period of decreased firing probability. Moreover, the cross correlation function may depend on the arrival rate of synaptic potentials (or current pulses). 5. Another proposed input-output function based on a simple threshold-crossing model of the motoneuron with a fixed spike threshold predicts firing rates that were often close to the observed delta F. However, the model did not reproduce the observed relations between delta F and input pulse rate or pulse duration. 6. The deficiencies of the basic threshold-crossing model may arise from the fact that it does not incorporate variations in membrane conductance and firing threshold that occur in real motoneurons. A more complete motoneuron model that incorporates both of these features was able to replicate the observed delta Fs associated with changes in input pulse frequency and duration.
46
Lü, Ze-Qi, Yan-Zhao Xie, Ming-Yue Gou, Xiao-Yu Chen, Jin-Shan Zhou, Mei Li e Yi Zhou. "Development of 200 kV multi-function pulsed radiation system". Acta Physica Sinica 70, n. 20 (2021): 205206. http://dx.doi.org/10.7498/aps.70.20210583.
Testo completoAbstract (sommario):
<sec>A multi-functional pulsed radiation system with a peak voltage of 200 kV, an impedance of 2 Ω, and a full width at half maximum (FWHM) of 30 ns is developed. The system can be switched flexibly in two states of generating pulsed electron beam and pulsed X-ray by changing the cathode and anode. It consists of a pulse power driving source, a vacuum diode, and an experimental cavity. A Marx generator, a high energy storage water transmission line, and two pulse compression switches are utilized to generate a high voltage on diode. An effector can be placed in the experimental cavity which has the same vacuum as diode. An insulation structure of transmission line and a diode are optimized to guide in system design. The system can provide a multi-functional experimental platform for investigating pulse power technology, system-generated electromagnetic pulse, biological radiation effect, etc.</sec><sec> The Marx generator generates a high-voltage pulse with hundreds of nanoseconds in FWHM and hundreds of kilovolts in peak value. The pulse is compressed by the main switch and pulse forming switch and then loaded to the diode. Electrons are emitted from diode cathode under the high-voltage pulse and accelerated in the gap. The electrons are extracted directly or converted into X-ray through the anode. Aluminized polyethylene is used as an anode when pulsed electron beam is generated, and tantalum film is used when pulsed X-ray is generated. Working state can be switched by changing the cathode and anode of diode.</sec><sec> The result shows that a current of 83 kA pulsed electron beam and an average energy of 67 keV X-ray are generated. Pulsed X-ray has good uniformity and low electron proportion (0.02%). In order to monitor the operation state and output parameter of the system comprehensively, a complete measurement system is established. Three capacitive voltage dividers are set at the beginning of transmission line, the end of pulse forming line, and the end of output line, while a B - dot current monitor is set at the diode. A Faraday cup is developed to measure the current intensity and the total energy of pulsed electron beam. For energy spectrum, dose and electron proportion, the measurement system composed of pulsed X-ray including spectrometric system, dose system and Rogowski Coil is build.</sec>
47
Lü, Ze-Qi, Yan-Zhao Xie, Ming-Yue Gou, Xiao-Yu Chen, Jin-Shan Zhou, Mei Li e Yi Zhou. "Development of 200 kV multi-function pulsed radiation system". Acta Physica Sinica 70, n. 20 (2021): 205206. http://dx.doi.org/10.7498/aps.70.20210583.
Testo completoAbstract (sommario):
<sec>A multi-functional pulsed radiation system with a peak voltage of 200 kV, an impedance of 2 Ω, and a full width at half maximum (FWHM) of 30 ns is developed. The system can be switched flexibly in two states of generating pulsed electron beam and pulsed X-ray by changing the cathode and anode. It consists of a pulse power driving source, a vacuum diode, and an experimental cavity. A Marx generator, a high energy storage water transmission line, and two pulse compression switches are utilized to generate a high voltage on diode. An effector can be placed in the experimental cavity which has the same vacuum as diode. An insulation structure of transmission line and a diode are optimized to guide in system design. The system can provide a multi-functional experimental platform for investigating pulse power technology, system-generated electromagnetic pulse, biological radiation effect, etc.</sec><sec> The Marx generator generates a high-voltage pulse with hundreds of nanoseconds in FWHM and hundreds of kilovolts in peak value. The pulse is compressed by the main switch and pulse forming switch and then loaded to the diode. Electrons are emitted from diode cathode under the high-voltage pulse and accelerated in the gap. The electrons are extracted directly or converted into X-ray through the anode. Aluminized polyethylene is used as an anode when pulsed electron beam is generated, and tantalum film is used when pulsed X-ray is generated. Working state can be switched by changing the cathode and anode of diode.</sec><sec> The result shows that a current of 83 kA pulsed electron beam and an average energy of 67 keV X-ray are generated. Pulsed X-ray has good uniformity and low electron proportion (0.02%). In order to monitor the operation state and output parameter of the system comprehensively, a complete measurement system is established. Three capacitive voltage dividers are set at the beginning of transmission line, the end of pulse forming line, and the end of output line, while a B - dot current monitor is set at the diode. A Faraday cup is developed to measure the current intensity and the total energy of pulsed electron beam. For energy spectrum, dose and electron proportion, the measurement system composed of pulsed X-ray including spectrometric system, dose system and Rogowski Coil is build.</sec>
48
Wang, Min, Jie Chen, Niu Liu e Ya Wang. "Inter-Pulse Spectroscopy Based on Room-Temperature Pulsed Quantum-Cascade Laser for N2O Detection". Applied Mechanics and Materials 128-129 (ottobre 2011): 607–10. http://dx.doi.org/10.4028/www.scientific.net/amm.128-129.607.
Testo completoAbstract (sommario):
Mid-infrared lasers are very suitable for high-sensitive trace-gases detection for their wavelengths cover the fundamental absorption lines of most gases. Quantum-cascade (QC) lasers have been demonstrated to be ideal light sources with its special power, tuning and capability of operating in room-temperature. All these merits make it appropriate for the high resolution spectrum analysis. The absorption spectrum monitoring technology based on the QC laser pulsed operating in the room temperature, combining with the strong absorption of the gas molecule in the basic frequency, has become an effective way to monitor the trace gas with the characteristic of high sensitivity, good selectivity and fast response. In this paper, the inter-pulse spectroscopy based on a room-temperature distributed-feedback pulsed QC laser was introduced. Our approach to trace gas monitoring with QC lasers relies on short current pulses which are designed to produce even shorter light pulses. Each pulse corresponds to a single point in a spectrum. The N2O absorption spectrum centered at 2178.2cm-1was also obtained.
49
Morris, Steven A., Ruichen Zhao e Zinovy Krugliak. "Experimental results of testing high-temperature-high-current pulsed operation of SiC MOSETs and SiC diodes". Additional Conferences (Device Packaging, HiTEC, HiTEN, and CICMT) 2014, HITEC (1 gennaio 2014): 000066–71. http://dx.doi.org/10.4071/hitec-tp13.
Testo completoAbstract (sommario):
Using hot plate experiments testing to a maximum temperature of 200 °C, we performed tests to determine the maximum single pulse current allowable for Cree CMF20120D SiC MOSFETs and Cree C4D40120D Schottky diodes. Using single pulse switching of a resonant circuit, a half-sine shaped current pulse of 5∼10 μsec duration was used to test the devices. A criterion for maximum allowable peak current was determined from the point of dramatic increase in conduction loss as a function of peak current. At 200 °C, maximum single pulse current was found to be 200 amp for the SiC MOSFET and about 500 amp for the SiC Schottky diode (both legs in parallel). We also report measurements of leakage current on the devices as a function of temperature, and will present measurements on an IGBT device of comparable current rating for comparison. Simple measurements of this type are a useful way of determining operational limits of SiC devices at temperatures that are not reported in the device data sheet.
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V. Akimov, Aleksandr, Petr A. Bak, Andrey A. Korepanov, Pavel V. Logachev, Viktor D. Bochkov, Dmitriy V. Bochkov, Vladimir M. Dyagilev e Vladimir G. Ushich. "Application of Unheated Cathode Thyratrons for High-Voltage High Current Pulse Series Formation". Siberian Journal of Physics 3, n. 4 (1 dicembre 2008): 68–73. http://dx.doi.org/10.54362/1818-7919-2008-3-4-68-73.
Testo completoAbstract (sommario):
The circuit of modulator, serving to supply inductive-resistive load in double-pulse mode with currents up to 10 kA and pulse duration of 300 ns, is described. As switching components unheated cathode thyratrons (pseudospark switches) TPI1-10k/50 and TPI5-10k/50 with anode voltage up to 50 kV have been used. The results of tests, confirming possibility of the thyratron reverse dielectric strength recovery within some microseconds after switching of 10 kA forward anode current, are presented.