Resistance Of Discharge Research Articles

Designing the Spigot Structure of Hydrocyclones to Reduce Fine Particle Misplacement in Underflow

Hydrocyclones can be used to concentrate the entrained sands in sewage and alleviate the clogging and erosion of the drainage network, but in practical application, there are problems such as low concentrations of underflow and a high content of fine particles, which cause a significant load on the subsequent sand dewatering and recycling. This paper designs five spigot structures of hydrocyclones and investigates the separation performance by numerical simulation, aiming to improve the applicability of hydrocyclones in the sewage treatment process by optimizing the spigot structure. The research results show that a large cone spigot delays the external downward swirling flow and reduces fine particle content in the underflow, but its effective separation space is reduced, and the turbulence in the cone section area is more intensive, which influences the separation accuracy. An elongated spigot has a reduced underflow water distribution; fine particles are more enriched in the internal swirling flow, and the underflow recoveries of 1 μm and 5 μm particles drop by 2.34% and 2.31%. The spigot structure affects the downward fluid and air intake states; complicated spigot structures contribute to increasing the resistance of particle discharge through underflow, alleviating fine particle misplacement.

Extended state-based finite-time fuzzy optimal recoil control for nonlinear drilling riser systems after emergency disconnection

To guarantee the safety and reliability of drilling riser after emergency disconnection, it is significant to investigate and refrain recoil response of the riser. This paper deals with the problem of Takagi–Sugeno (T-S) fuzzy recoil dynamic modeling and optimal recoil control of nonlinear deepwater drilling riser systems subject to friction resistance of fluid discharge and platform heave motion. First, a nonlinear recoil control model of coupled riser-tensioner is proposed by taking the nonlinear top tension of tensioner into account. Then, a T-S fuzzy dynamic model of the riser-tensioner system is established to approximate the original nonlinear one by using fuzzy modeling scheme. Third, an augmented T-S fuzzy model of riser system is proposed, where the linear exosystem model of friction resistance and platform heave motion is utilized. Fourth, a finite-time fuzzy optimal recoil controller is designed to suppress the recoil response of the riser, the existence and design algorithm of the fuzzy optimal recoil controller are derived. Simulation results demonstrate that the nonlinear recoil model is more accurate than the existing linear one to describe the recoil characteristics of the riser, and the fuzzy optimal recoil controllers are effective to reduce recoil responses and guarantee the safety of the riser significantly.

Discrete recoil control system modelling and optimal recoil damping of deepwater drilling riser systems

This study addresses discrete dynamic modelling and the optimal recoil control problem of deepwater drilling riser systems subject to the friction resistance of fluid discharge and platform heave motion. First, a discrete-time exosystem model for friction resistance of drilling fluid discharge is developed; then, a discrete-time dynamic model of platform heave motion is established. Third, a finite-time discrete optimal recoil controller with feedforward compensation mechanisms was designed. The optimal recoil controller gains can be obtained by iteratively solving discrete equations. The simulation results show that under the discrete feedforward and feedback optimal recoil controller and pure feedback optimal recoil controller, the recoil movements of the riser system are significantly restrained. Moreover, the former is more effective than the latter at resisting the riser recoil response.

Direct current arc quenching performance of a model electric fuse equipped with SiO2 sand and additive silicone resin as an arc quenching medium: the effect of a vaporized silicone decomposition mixture on transient arc resistance

Most high-power electric fuses installed in DC distributions of automobiles employ silica sand (chemical formula SiO2) as arc quenching material to implement the limitation and subsequent interruption of high direct currents. This paper on arc quenching material describes the effects of the addition of silicone resin (chemical formula C2H6SiO) on SiO2 sand, based on the resistance of an arc discharge in SiO2 vapor mixed with silicone resin vapor. The measurement results obtained for the fuse operation of a model electric fuse show that the addition of silicone resin, e.g. an even coating of silicone resin on the surface of a Cu fuse element, attains a shorter arc quenching time. This phenomenon is subsequently explained based on the rise effect of an arc column resistance achieved by mixing with silicone vapor decomposition. The chemical compositions of high-temperature SiO2 vapor mixed with C2H6SiO vapor decomposition are evaluated to show the predominant chemical species at 30 000 K–5000 K for several C2H6SiO vapor concentrations, . The results obtained for of 10%–50% reveal that a H atom originating from C2H6SiO is present at high molar fractions above 0.1 over a wide temperature range of 12 000 K–5000 K. Further evaluations of the electrical resistivity for the high-temperature vapor show that mixing with C2H6SiO vapor contributes to a rise in at temperatures of 10 000 K–6000 K. A contribution analysis of the reveals that the rise effect of the is accomplished chiefly by the presence of a H atom that has dissociated from C2H6SiO.

The effect of nonlinear acoustic oscillations on the current-voltage characteristics of a glow discharge

In this work the effect of nonlinear acoustic oscillations on the current-voltage characteristics of a glow discharge are investigated experimentally. At fixed current values, an increase in the electrical resistance of the glow discharge and the energy input is observed. In the experiment, nonlinear medium oscillations are observed.

An empirical resistance equation for the modelling of corona discharge in saline water

We present a study that was undertaken to calculate the resistance of low current corona discharge in saline water. A novel empirical model was obtained, based on several assumptions, which allowed us to determine the corona resistance using the measured current. This resistance could be then exploited to compute the power deposited to the corona as a function of time. The wall motion of a bubble freely oscillating in saline water was calculated using hydrodynamic equations and the calculated power function. A comparison of numerical simulations with experimental results showed that good agreement was achieved.

Influence of the damping matrix and mud discharge on the recoil response of deepwater drilling riser after emergency disconnection

In this paper, the influence of the damping matrix and mud discharge on the recoil response of deepwater drilling riser after emergency disconnection is studied based on our published study. Mathematically, the deepwater drilling riser is discretized into a mass-spring-damping system with three degrees of freedom (DOF). The governing equation is solved by the principal coordinates analysis method (Method A) and the complex modal analysis method (Method B), respectively. Firstly, the mathematical expression of the frictional resistance acting on the riser during mud discharge is obtained by curve fitting. Then, the detailed solving process and the difference of the results calculated by the two solving methods are shown. The influence of the non-diagonal elements in the damping matrix on the recoil response is studied. In addition, the effect of the frictional resistance of mud discharge on the recoil characteristics is assessed. Finally, conclusions are drawn based on the analysis.

Study on threshold capabilities of a copper bromide vapor laser

This paper presents theoretical and simulation results for the operating parameters of a copper bromide (CBr) laser. The CuBr active medium finds applications as both as a laser source and a vapor amplifier. A methodology is developed to serve as the basis for the solution of a two-dimensional quasi-stationary heat conductivity equation on the cross-section of the gas tube for modeling the temperature of the neutral gas and the electron temperature of the discharge. This methodology makes it possible to determine the maximum electrical power supplied and the maximum electron temperature in terms of thermal ionization and electric ionization resistance of the gas discharge. Analytical results are applied in computer simulations and for the assessment of parameters of an actual CuBr laser.

Computer study of the gas temperature profile in copper and copper vapor halide lasers

Due to their unique radiation properties, metal vapor lasers find a variety of applications, including being used as a high- brightness amplifier in new active optical systems. This type of systems has been actively developed in recent years and is applied for visual control of fast processes in screening the background illuminations. A computer model is built and applied to an existing laser source allowing to determine the radial distribution of gas temperature in the cross section of the laser tube. Computations are performed using a preset qualitative type radial distribution of the electric power supplied to the gas discharge. The influence of the electric power supplied to the gas discharge and the wall temperature on the thermal resistance of the gas discharge was evaluated by means of computer simulations. The proposed methodology allows the planning of experiments and developing new laser sources with improved output characteristics.

Analysis on the influencing factors of imbibition and the effect evaluation of imbibition in tight reservoirs

Abstract To exert the imbibition between cracks and matrix effectively and enhance the development effect of tight oil reservoirs, a physical simulation method for imbibition in different scales of cores is developed by combining a high-pressure large-model physical simulation system and nuclear magnetic resonance technology (NMR) to investigate the influencing factors of imbibition process in tight reservoirs, and construct a quantitative evaluation method for the imbibition in water flooding. The results show that in the process of counter-current imbibition, the lower the permeability, the later the oil droplet precipitation, the longer the imbibition equilibrium time, and the lower the recovery degree. Fractures can effectively expand the area of imbibition and the front edge of imbibition in the contact between the dense matrix and water, reduce the resistance of oil discharge, and improve the imbibition speed and the degree of recovery. The more hydrophilic the rock, the higher the imbibition rate and imbibition recovery of tight rocks. In the process of co-current imbibition, the lower the permeability, the more obvious the imbibition, and the displacement recovery is positively correlated with permeability, while the imbibition recovery is negatively correlated with the permeability. It also shows that the imbibition distance of the cyclic water injection is greater than that of the counter-current imbibition, and the higher the permeability and the injection multiple, the longer the imbibition distance. The combination of large-scale volume fracturing with changing reservoir wettability and cyclic water injection is conducive to improving the imbibition ability of tight reservoirs.

Influence of machining processes on rim zone properties and high temperature oxidation behavior of 42CrMo4

AbstractThe influence of different machining processes, grinding, electrochemical machining, and electro discharge machining on the surface integrity, described by residual stresses, roughness, and chemical composition, is investigated to explain their effect on the high temperature oxidation behavior of martensitic 42CrMo4 steel in an oxygen atmosphere. The results obtained by thermogravimetric in situ experiments reveal that compressive residual stresses and a smaller reactive surface adjusted by grinding lead to an improved oxidation resistance compared with electrochemical machined surfaces. Surface modification by electro discharge machining appears to be most suitable to achieve oxidation resistance due to decelerated initiation of the oxide layer growth compared with the ground surface. The improved oxidation resistance of electro discharge machined and ground surfaces is linked to the modified chemical composition of the rim zone and the rim zone residual stresses, respectively.

Full-Wave Simulation of System-Level Disruption During Secondary ESD Events in a Smartphone

To demonstrate the electromagnetic full-wave simulation of a secondary electrostatic discharge (ESD), an ESD generator is modeled in three dimensions (3D) and in contact mode discharging to a non-grounded, metallic ear-mesh of a smartphone. The nonlinear Rompe–Weizel SPICE model computes the arc resistance of the secondary discharge between ungrounded metal and a grounded enclosure. The SPICE model is solved using a circuit simulator, and the 3-D model is solved using the transmission-line matrix time-domain numerical method. Transient cosimulation is a new technique that is used to solve both circuit and 3-D models at the same time. The simulation predicts the coupling from ESD to a victim trace in the smartphone. Measurements performed at several stages validate the simulation results. Using this novel methodology, the user can simulate the secondary discharge in products to predict ESD damage and disruption on a system level.

Methodic of the computer calculation of the plasma impedance of the glow discharge lasers

In this work an expression for the dynamic resistance of a glow discharge in long tubes was obtained and analyzed. The expression describes the physical processes taking place in the positive column of a glow discharge. The analysis of the frequency dependences of the active and reactive constituents, as well as the dynamic resistance module for discharge conditions corresponding to glow discharge lasers, was performed. On the basis of the expressions obtained a computer program for modeling the dynamic resistance of discharge was developed. The program allows you to calculate and display the plots of the frequency dependences of the active and reactive constituents, as well as the module of the dynamic resistance of the discharge gaps of lasers. Also, the program provides a function for constructing hodographs of dynamic resistance.

Determination of the plasma impedance of a glow discharge in carbon dioxide

In this work an expression for the dynamic resistance of a glow discharge flowing in long tubes is obtained and analyzed. The expression describes the physical processes occurring in the positive column of a glow discharge. The frequency dependences of the active and reactive components as well as the dynamic resistance module for the discharge conditions corresponding to CO2–lasers have been calculated. Based on the simulation results developed a computer program in the C# programming language for modeling the dynamic resistance discharge of glow discharge lasers.

Wear analysis and cyclic fatigue resistance of electro discharge machined NiTi rotary instruments

AimTo evaluate the wear of new rotary instruments produced via electro discharge machining and to test their fatigue resistance. MethodologyTwenty-one HyFlex EDM (Coltène/Whaledent, Switzerland) files were used for laboratory instrumentation of curved root canals of extracted teeth. Superficial characteristics were analyzed pre- and postoperatively by scanning electron microscopy (SEM) (JSM-5200, JEOL, Tokyo, Japan) at same points and with same angulations to identify the wear features. Number of fractures, microcracks blunt/disruption of cutting edge and tip deformations were reported.Twenty HyFlex EDM and 20 HyFlex CM (Coltène/Whaledent, Switzerland) were subjected to cyclic fatigue test in a 70° artificial metal canal. Results were statistically analyzed using Mann–Whitney tests. ResultsNo fractures were registered during laboratory canal instrumentation. No wear and no degradation of the 25.12 and 25.08 files were reported. Slight plastic deformations were only observed in three 10.05 files. The cyclic fatigue test revealed a significant increase of fatigue resistance of EDM files compared to CM (p=0.0001). ConclusionsThe typical irregular surface of HyFlex EDM remained unaffected after multiple uses, confirming a high wear resistance. The new manufacturing process of electrical discharge machining had a substantial impact on fatigue lifetime of EDM files when compared with HyFlex CM. Within limitations of the present in vitro results, EDM files appeared suitable in shaping severely curved canals.

HyFlex EDM: superficial features, metallurgical analysis and fatigue resistance of innovative electro discharge machined NiTi rotary instruments.

To evaluate the surface and microstructural alterations of new and used HyFlex EDM prototypes and to test their fatigue resistance. Fifteen HyFlex EDM prototypes were used for in vitro instrumentation of severely curved root canals. Surface and microstructural characteristics of new and used files were compared by ESEM analysis equipped with energy dispersive X-ray spectrophotometry (EDS) and optical metallographic imaging. Usage-induced degradation was assessed. Thirty additional HyFlex EDM prototypes and 20 standard manufactured HyFlex CM files were subjected to cyclic fatigue tests. Time to fracture was recorded, and results were validated using the Kruskal-Wallis test (α-level 0.05). Fatigued files were analysed by ESEM for fractographic evaluation. Surface and microstructural characterization of EDM prototypes revealed the typical spark-machined surface of a NiTi EDM alloy. No fractures were registered during root canal instrumentation. No evident surface alterations and minor degradation were observed between new and used instruments. The metallographic analysis of new and used files disclosed a homogeneous structure, mostly composed of lenticular martensite grains, and some residual austenite. The cyclic fatigue test showed an increase of fatigue resistance up to 700% on the EDM compared to CM files. Spark-machined peculiar surface is the main feature of HyFlex EDM. Low degradation was observed after multiple canal instrumentations. Prototypes exhibited surprising high values of cyclic fatigue resistance and a safe in vitro use in severely curved canals.

Measurement of the electron density in Transient Spark discharge

This paper presents our measurements of the electron density in a streamer-to-spark transition discharge, which is named transient spark (TS), in atmospheric pressure air. Despite the dc applied voltage, TS has a pulsed character with short (∼10–100 ns) high current (>1 A) pulses, with a repetition frequency on the order of kHz. The electron density ne ∼ 1017 cm−3 at maximum is reached in TS with repetition frequencies below ∼3 kHz, using relatively low power delivered to the plasma (0.2–3 W).The temporal evolution of ne was estimated from the resistance of the plasma discharge, which was obtained by a detailed analysis of the electric circuit representing the TS and the discharge diameter measurements using a fast intensified charge-coupled device (iCCD) camera. This estimate was compared with ne calculated from the measured Stark broadening of several atomic lines: Hα, N at 746 nm, and O triplet at 777 nm. Good agreement was obtained, although the method based on the plasma resistance is sensitive to an accurate determination of the discharge diameter. We have found that this method is also limited for strongly ionized plasmas. On the other hand, a lower ne detection limit can be obtained by this method than from the Stark broadening of atomic lines.

Resistance Models Applied to the Return Stroke Phase of Negative Pulsed Surface Discharges in Air

The energy deposition during the return stroke phase of a pulsed surface discharge is driven by the electrical circuit and the electrical properties of the discharge. To control these factors, a parametric study is performed with varying the circuit parameters, for different discharge lengths and voltages between -19 to -26 kV. The electrical characteristics of the discharge are then simulated using different plasma resistance models, which assume a time-varying resistance: the Toepler model, the Rompe-Weizel model, and the Vlastós model. The model parameters are optimized to fit the experimental results. The analysis shows that for long pulses obtained with large inductance, the three models fare equally well, since the discharge resistance is mainly constant during the pulse. In low-inductance cases, the Toepler model leads to larger errors during the initial current pulse, whereas the Rompe-Weizel and Vlastós models describe with a good agreement the experiments. The discharge resistance evolves during the first 300 ns, then remains mostly constant until the end of the pulse. The constant part of the resistance gives the surface-averaged conductivity of the discharge, which increases linearly with the linear energy dissipated in the discharge. Finally, theoretical estimates of the varying resistance parameters are in fair agreement with the parameters obtained while fitting the experiments, in particular in the Rompe-Weizel case. These findings can be used to estimate the channel resistance of a pulsed surface discharge, and to help optimizing the high-voltage circuit.

Shrink Resistance of Pulse Corona Discharge / Keratinase Treated Wool Fabrics : Relation between Shrink Resistance and Strength

Shrink Resistance of Pulse Corona Discharge / Keratinase Treated Wool Fabrics : Relation between Shrink Resistance and Strength

Experimental study of patterns of energy input into hybrid low pressure discharge for varying RF generator power and argon pressure

Patterns of energy release in the plasma of a new modification of RF discharge, viz., hybrid RF discharge, which are maintained by vortex and potential RF electric fields, are experimentally studied. RF power input unit in the form of inductor and capacitor plates connected in parallel are used for initiating this discharge. This paper presents data obtained during the investigation of the influence of power supplied to the plasma and argon pressure on the equivalent resistance of the hybrid discharge, which is the measure of plasma capability of absorbing RF power. The role of the capacitive channel in the balance of RF power supplied to the discharge is considered.