scholarly journals Effect of Pulsed Ultrasound on Plasma Morphology and Its Changing Mechanism

2021 ◽  
Author(s):  
Huijing Zhang ◽  
Fan Qing-Kai ◽  
Chenglei Fan ◽  
Chen Chao
Keyword(s):  
Acoustic Streaming ◽  
Pulse Frequency ◽  
Arc Plasma ◽  
Pulsed Ultrasound ◽  
Control Effect ◽  
High Pulse Frequency ◽  
Ultrasound Field ◽  
Contraction Ratio ◽  
Arc Shape ◽  
Ultrasonic Influence

Abstract Arc plasma shape under pulsed and continuous ultrasound field were studied in this research using self-developed welding device which combines arc and ultrasound field coaxially. The results show that, compared with the arc of conventional tungsten inert gas welding, the shape of arc under pulsed ultrasound field relate to the pulse frequency. From 1 Hz to 20 Hz, the arc plasma expands and contracts periodically in one pulse. When more than 20 Hz, the arc plasma contracts as the pulse frequency increases. During high pulse frequency, the arc shape become steady and similar to those in continuous ultrasound field. When in 500 Hz, the contraction ratio of arc projected area under pulsed ultrasound field reaches 38 %, comparing with 30 % of the same power continuous ultrasound field, i.e., in high frequency, low power pulsed ultrasound can obtain arc control effect similar to high power continuous ultrasound, raising ultrasound energy efficiency. The mechanism of ultrasonic influence on arc is analyzed based on sound pressure and acoustic streaming.

scholarly journals Femtosecond-Laser Assisted Surgery of the Eye: Overview and Impact of the Low-Energy Concept

Micromachines ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 122
Author(s):  
Catharina Latz ◽  
Thomas Asshauer ◽  
Christian Rathjen ◽  
Alireza Mirshahi
Keyword(s):  
Surgical Techniques ◽  
Numerical Aperture ◽  
Optical Breakdown ◽  
Pulse Frequency ◽  
Low Energy ◽  
Human Cornea ◽  
Energy Concept ◽  
High Pulse Frequency ◽  
Fs Laser ◽  
High Pulse

This article provides an overview of both established and innovative applications of femtosecond (fs)-laser-assisted surgical techniques in ophthalmology. Fs-laser technology is unique because it allows cutting tissue at very high precision inside the eye. Fs lasers are mainly used for surgery of the human cornea and lens. New areas of application in ophthalmology are on the horizon. The latest improvement is the high pulse frequency, low-energy concept; by enlarging the numerical aperture of the focusing optics, the pulse energy threshold for optical breakdown decreases, and cutting with practically no side effects is enabled.

scholarly journals Characteristics of Gliding Arc Plasma and Its Application in Swirl Flame Static Instability Control

Processes ◽  
2020 ◽  
Vol 8 (6) ◽  
pp. 684 ◽  
Author(s):  
Weiqi Chen ◽  
Di Jin ◽  
Wei Cui ◽  
Shengfang Huang
Keyword(s):  
Flow Rate ◽  
Experimental System ◽  
Low Flow ◽  
Flow Mode ◽  
Arc Plasma ◽  
Control Effect ◽  
Gliding Arc ◽  
Gliding Arc Plasma ◽  
Static Instability ◽  
Swirl Flame

Based on an experimental system involving a pulsating airflow burner and gliding arc generator, the characteristics of gliding arc plasma at different flow rates and its control effect on the static instability of the swirl flame have been studied. The current, voltage, and power wave forms, as well as the simultaneous evolution of plasma topology, were measured to reveal the discharge characteristics of the gliding arc. A bandpass filter was used to capture the chemiluminescence of CH in the flame, and pressure at the burner outlet was acquired to investigate the static instability. Experimental results showed that there were two different discharge types in gliding arc plasma. With the low flow rate, the glow type discharge was sustained and the current was nearly a sine wave with hundreds of milliamperes of amplitude. With the high flow rate, the spark type discharge appeared and spikes which approached almost 1 ampere in 1 μs were found in the current waveform. The lean blowout limits increased when the flame mode changed from stable to pulsating, and decreased significantly after applying the gliding arc plasma. In pulsating flow mode, the measured pressure indicated that static instability was generated at the frequency of 10 Hz, and the images of flame with plasma showed that the plasma may have acted as the ignition source which injected the heat into the flame.

Influences of Pulse Frequency on Structure and Mechanical Properties of DLC Films Synthesized by Pulsed Cathodic Arc Evaporation

2014 ◽  
Vol 670-671 ◽  
pp. 560-564 ◽  
Author(s):  
Bing Ye ◽  
Xiao Hong Jiang ◽  
Bing Zhou ◽  
D.G. Piliptsou ◽  
A.V. Rogachev
Keyword(s):  
Crystal Surface ◽  
Pulse Frequency ◽  
Arc Plasma ◽  
Double Crystal ◽  
Force Microscopy ◽  
Atomic Force ◽  
Microstructure Morphology ◽  
Cathodic Arc Evaporation ◽  
Arc Evaporation ◽  
Cathodic Arc

Diamond-like carbon (DLC) films were prepared on the Si (100) substrates by pulsed cathodic arc plasma. The influences of given pulse frequency on the microstructure, morphology, mechanical and optical properties of DLC films were investigated by Raman spectroscopy, atomic force microscopy, Knoop sclerometer, X-ray double-crystal surface profilometer. The results showed that the variation of pulse frequency could significantly change the microstructure of DLC films, including the size and ordering of sp2carbon clusters and movement or diffusion of carbon atoms. The increasing of pulse frequency led to the variation of the relative fraction of Csp3/Csp2. The hardness and internal stress of the DLC films were affected accordingly. The results might contribute to the synthesis of DLC films with excellent structure and properties by cathodic arc evaporation.

Pulse Frequency-dependent Regulation of Lysozyme Reactivity under Pulsed Ultrasound Irradiation

2009 ◽  
Vol 38 (6) ◽  
pp. 536-537 ◽  
Author(s):  
Takayoshi Kawasaki ◽  
Momoko Toyoda ◽  
Yoshio Okahata
Keyword(s):  
Ultrasound Irradiation ◽  
Pulse Frequency ◽  
Pulsed Ultrasound ◽  
Frequency Dependent

Numerical Analysis of Arc Plasma with Metal Transfer in GMAW

2008 ◽  
Vol 580-582 ◽  
pp. 359-362
Author(s):  
Yoshinori Hirata ◽  
K. Ohnishi
Keyword(s):  
Metal Transfer ◽  
Time Dependent ◽  
Arc Plasma ◽  
Metal Drop ◽  
Spray Transfer ◽  
Drop Detachment ◽  
Globular Transfer ◽  
Arc Shape ◽  
The Moment ◽  
Kinetics Of

A numerical model of time-dependent gas shielded metal arc is described, which was developed in order to make clear the kinetics of arc plasma together with metal transfer. It is possible to calculate and visualize time-dependent temperature and fluid flow field of argon shielded metal arc plasma with the grow-up and the subsequent detachment of the liquid metal drop at the wire tip. Numerical calculation shows that the arc shape in globular transfer abruptly changes at the moment of metal drop detachment. Whereas, the spray transfer arc seems to be stable and almost does not fluctuate with metal transfer.

Effects of acoustic streaming from moderate-intensity pulsed ultrasound for enhancing biofilm mitigation effectiveness of drug-loaded liposomes

2015 ◽  
Vol 138 (2) ◽  
pp. 1043-1051 ◽  
Author(s):  
Dong Ma ◽  
Adam M. Green ◽  
Graham G. Willsey ◽  
Jeffrey S. Marshall ◽  
Matthew J. Wargo ◽  
...  
Keyword(s):  
Acoustic Streaming ◽  
Moderate Intensity ◽  
Pulsed Ultrasound

Design on Arc Plasma Temperature Online Detecting System

2013 ◽  
Vol 325-326 ◽  
pp. 1427-1430
Author(s):  
Chun Guang Hou ◽  
Shi Yu Zhang ◽  
Yun Dong Cao ◽  
Shu Xin Liu
Keyword(s):  
Optical Fibers ◽  
High Speed ◽  
Shape Change ◽  
Sampling Rate ◽  
Circuit Breaker ◽  
Plasma Temperature ◽  
Electric Arc ◽  
Space Distribution ◽  
Arc Plasma ◽  
Arc Shape

Aiming at the arc plasma characteristics of high voltage circuit breaker, a set of multichannel, high speed, the synchronous detecting system is designed. The space distribution and time variation law of electric arc plasma, specially electric arc shape change law, are well reflected. Based on the ARM + CPLD + SDRAM detecting schemes, the system realized the functions of 64 groups optical fibers sampling, 4M/s sampling rate of every sampling channel, and the synchronous sampling. Through the detailed research and design to EMC, system error analysis, visual interface and database as well as the related interface program of ARM, CPLD, SDRAM and so on, has completed the multichannel, high speed and the real-time synchronized sampling, and mass data memory, computation, analysis, curve and animation demonstration and so on functions. The stability, feasibility and accuracy of the detecting system are proved by the practical application.

Application of Inverse Methods for Spatial Deconvolution of Pulsed Ultrasound Fields Radiated in Solids

2010 ◽  
Vol 636-637 ◽  
pp. 1541-1547 ◽  
Author(s):  
Wahiba Djerir ◽  
Tarek Boutkedjirt ◽  
Ali Badidi Bouda ◽  
A. Satour
Keyword(s):  
Signal To Noise Ratio ◽  
Finite Size ◽  
Maximum A Posteriori ◽  
A Posteriori ◽  
Pulsed Ultrasound ◽  
Spatial Properties ◽  
Spatial Frequencies ◽  
Power Spectral ◽  
Ultrasound Field

When measuring the ultrasound field, the signal provided by the receiving transducer is affected by its spatial properties. Particularly, the displacement normal to its surface is spatially averaged because of the receiver finite size. In this study, we show using a numerical simulation, the effectiveness of the spatial deconvolution of these effects for a rectangular transducer. For that, three methods allowing the inversion of the aperture effect are tested 1) Wiener’s method; 2) the power spectral equalization (PSE) method, and 3) the maximum a posteriori (MAP) method. The obtained results show that the three methods are able to reconstruct the ultrasound field from the spatially averaged values and the quality of the reconstruction depends strongly upon the signal to noise ratio (SNR) and the spatial frequencies of the ultrasound field investigated

scholarly journals A New Filter Concept for High Pulse-Frequency 3-Phase AFE Motor Drives

Energies ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2814
Author(s):  
Stefan Hoffmann ◽  
Matthias Bock ◽  
Eckart Hoene
Keyword(s):  
Pulse Frequency ◽  
Motor Drives ◽  
Common Mode ◽  
The Public ◽  
Electrical Potentials ◽  
Common Mode Voltage ◽  
High Pulse Frequency ◽  
Power Modules ◽  
High Pulse ◽  
The Difference

The size of back-to-back converters with active front end is significantly determined by the size of the passive filter components. This paper presents a new complete EMC filter concept for this type of converter system that is effective on the input and the output. This involves filtering the main common mode interferences from the grid and motor sides with a single CM choke. Since only the difference of the generated common mode voltage-time areas of both converters is absorbed by this component, the size of the required filter can be greatly reduced compared to conventional filter concepts. The concept is validated on a grid feeding inverter that can be connected to the public distribution network with an output power of 63 kW. The size reduction is demonstrated by means of a design example on a system with the same power and electrical requirements. It is elaborated why, applying the new filter concept, the impedance of the DC link potentials to ground and other electrical potentials should be as high as possible and therefore associated parasitic capacitances should be minimized. From this requirement, rules for the design of the power modules of PFC and motor converters for the application of this filter concept are derived.

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