Numerical Prediction on the Flow Field of Molten Steel and the Trajectory of Inclusion in Continuous Casting Mold Effected by Electromagnetic Field

Through coupling electromagnetic field equations with turbulent flow equations,the numerical prediction has been conducted on the flow field of molten steel and the trajectory of inclusion particle in the continuous casting mold effected by electromagnetic field.The difference between the maximum and the minimum of the shear stress on mold wall is used to scale the impingement strength of molten steel discharged from immersed nozzle to the solidifying shell on the narrow wall of mold.The flow field of molten steel in the mold is changed greatly and the impingement strength of the jet is reduced while electromagnetic field is applied.It is found that the successful control of flow field depends on the current and location of coil.At the same time,the new floating paths of inclusion particles are formed and the upward particles that are far away from the solidifying zone on the narrow wall of mold change their moving directions with the change of flow field,so that the particles can avoid being entrapped by the solidifying shell.

Mechanism of Electromagnetic Flow Control Enhanced by Electro-Discharge in Water

Pulsed discharge utilized to achieve large current density in the electromagnetic flow control is numerically studied. A mathematic discharge model is established to calculate the plasma channel, and an actuator is designed to generate the Lorentz force in the micro plasma channel. During the discharge process, the resistance in the channel decreases rapidly and a large current density appears between the discharge electrodes. After the actuator is applied in the leading edge of a flat plate, the separation region and downstream turbulent boundary layer on the plate disappear. Meanwhile, a skin-friction drag force reduction is achieved.

Controlling of the Polarization States of Electromagnetic Waves Using Epsilon-near-Zero Metamaterials

We demonstrate theoretically that the epsilon-near-zero materials can be utilized to control effectively the polarization conversion of an electromagnetic wave through reflection. The significant feature differing from all other means based on whatever natural materials or metamaterials is that for TM incident wave, the reflected phase is a constant, while for TE wave, the reflected phase is a linear function of the incident angle. The phase difference between them covers the range from -180°to 0°, and the polarization conversions from linear states to elliptical or circular states can be obtained by only adjusting the incident angle. Because no complex structures are employed, our proposal promises a simple approach for manipulating polarization conversion at both terahertz and optical frequencies.

Thermal-force control ability under variation of electromagnetic stick structure parameters in RPECT

Thermal-force driving of roll profile electromagnetic control technology(RPECT),which can be used to adjust the roll profile,can be affected by the sequential temperature rise between the electromagnetic stick(ES)and electromagnetic control roll.Due to the limited space of ES and induction coil,the cross-sectional area of induction coil can be inevitably affected by changing the size of the ES induction zone,which can further change the energy input under the same electromagnetic parameters,the temperature rising effect and the bulging ability.To investigate this phenomenon,the effects of the radius of the induction zone on the thermal-force contribution ratio,the heating ability of ES and the temperature distribution were analyzed through an electromagnetic-thermal-structural finite element model.To ensure that the results are applicable to RPECT,the thermal energy conversion ability and thermal-force roll crown control ability under different lengths of the induction zone were analyzed.It was found that whether the current density regulation mode or the current frequency regulation mode is adopted,the cases with 20 or 25 mm radius of the induction zone have the great thermal energy conversion ability and the good thermal-force roll crown control ability.The reasonable adjustment of the length of the induction zone can reduce the radius required for the maximum energy efficiency regulation.Combined with the results of the simulation analysis,the optimization of ES based on the control ability maximization requirement is achieved,which provides the base for the design and configuration of ES in RPECT.

Theoretical and numerical research on effect of tension mechanisms in strip flatness electromagnetic control rolling mills

To achieve stable rolling,the influence of a tension mechanism of a large diameter ratio roll system on the rolling process of a strip flatness electromagnetic control rolling mill is studied.Through the analysis of the rolling deformation zone,the deformation zone composition form of a large diameter ratio roll system and a calculation formula of neutral angle under tension are proposed.To analyze the effect of front and post tensions on the rolling characteristic and the strip flatness control characteristic,a three-dimensional rolling finite element(FE)model of a large diameter ratio roll system with the function of roll profile electromagnetic control is established by FE software and verified by a strip flatness electromagnetic control rolling mill.Based on the model,the strip thickness characteristic,metal transverse flow,strip flatness state,and adjustment range of the loaded roll gap are analyzed for different front and post tensions setting values.The results show that changing the front or post tension setting values can improve the single-pass reduction rate of a large diameter ratio roll system and have little effect on the flatness control ability of the strip flatness electromagnetic control rolling mill.

Sensitivity of Marine Controllable Source Electromagnetic Soundings for Identifying Plume Migration in Offshore CO_(2) Storage

Offshore carbon dioxide(CO_(2)) storage is an effective method for reducing greenhouse gas emissions. However, when using traditional seismic wave methods to monitor the migration of sequestration CO_(2) plumes, the characteristics of wave velocity changes tend to become insignificant beyond a certain limit. In contrast, the controllable source electromagnetic method(CSEM) remains highly sensitive to resistivity changes. By simulating different CO_(2) plume migration conditions, we established the relevant models and calculated the corresponding electric field response characteristic curves, allowing us to analyze the CSEM's ability to monitor CO_(2) plumes. We considered potential scenarios for the migration and diffusion of offshore CO_(2) storage, including various burial depths, vertical extension diffusion, lateral extension diffusion,multiple combinations of lateral intervals, and electric field components. We also obtained differences in resistivity inversion imaging obtained by CSEM to evaluate its feasibility in monitoring and to analyze all the electric field(Ex, Ey, and Ez) response characteristics. CSEM has great potential in monitoring CO_(2) plume migration in offshore saltwater reservoirs due to its high sensitivity and accuracy. Furthermore, changes in electromagnetic field response reflect the transport status of CO_(2) plumes, providing an important basis for monitoring and evaluating CO_(2)transport behavior during storage processes.

Ultralow-noise single-photon detection based on precise temperature controlled photomultiplier with enhanced electromagnetic shielding

We demonstrate an ultralow-noise single-photon detection system based on a sensitive photomultiplier tube（PMT） with precise temperature control, which can capture fast single photons with intervals around 10 ns.By improvement of the electromagnetic shielding and introduction of the self-differencing method, the dark counts（DCs） are cut down to ~1%. We further develop an ultra-stable PMT cooling subsystem and observe that the DC goes down by a factor of 3.9 each time the temperature drops 10°C. At -20°C it is reduced 400 times with respect to the room temperature（25°C）, that is, it becomes only 2 counts per second, which is on par with the superconducting nanowire detectors. Meanwhile, despite a 50% loss, the detection efficiency is still 13%. Our detector is available for ultra-precise single-photon detection in environments with strong electromagnetic disturbances.

New Intellectual Economized Technique on Electricity Based on DSP

In order to resolve the problean of the unbalanced threephase and unstable voltage, intellectual economized technique on elec- tricity based on electromagnetic regulation and control is proposed in this paper. We choose the TMS320LF2407A as the control chip and stepper motor as the executing agency. The equipment controls the movable contact reaching to the assigned position on the magnetic coil quickly and accurately, and outputs the sine-wave voltage steadily along with the network voltage variation though the fuzzy Porportional Integral Derivative（PID） control algorithm of integral separation and incremental mode with setting dead area. The principle of work and the key technique on the electromagnetic regulation and control are introduced in detail in this paper. The experiment result gives a proof for all the algorithm mentioned in this paper.

The influences of wall Lorentz force and field Lorentz force on the cylinder drag reduction

In this paper,the effects of Lorentz force on drag reduction for a circular cylinder have been studied experimentally and numerically.Based on its effects on drag reduction,the Lorentz force is found to be classified into two parts：one acts directly on the cylinder,named as the wall Lorentz force,and the other called the field Lorentz force acts on the fluid inside the boundary layer.The wall Lorentz force leads to the generation of a thrust,whereas the field Lorentz force results in drag increase.Since the former dominates the drag variation,the drag would reduce accordingly and even turn into negative （thrust） with the application of Lorentz force.

Electromagnetic Control of the Weld Pool Dynamics in Partial Penetration Laser Beam Welding of Aluminium Alloys

The main characteristic feature of deep penetration laser beam welding is a large temperature difference between the plasma cavity(keyhole)in the weld pool centre and the melting/solidification front.Large temperature gradients in the weld pool result in very intensive thermocapillary(Marangoni)convection.The weld pool surface width becomes very large and unstable.However,an externally applied oscillating magnetic field can stabilize the surface of the melt.In the present work this technology was used to stabilize the weld pool surface in partial penetration 4.4 kW Nd:YAG laser beam welding of AW-5754 aluminium alloy in PA position.An AC magnet was mounted on the laser welding head.The oscillating magnetic field was oriented perpendicular to the welding direction.It was found that the AC magnetic field can drastically reduce the surface roughness of welds.X-ray image analysis shows a drastic reduction of welds porosity.This effect can be explained as a result of electromagnetic rectification of the melt.

Roll profile electromagnetic control characteristics under roll heterogeneity

The electromagnetic control roll(ECR)and electromagnetic stick(ES)are the core elements and the main driving parts of roll profile electromagnetic control technology(RPECT).To prolong the service life,it is necessary to treat ECR and ES surfaces.According to the heterogeneous characteristics of surface treatments,the roll profile electromagnetic control characteristics were analyzed for different parameters.An electromagnetic-thermal-force coupled axisymmetric finite element model was built to explore the differences in performance as a result of several treatment strategies,and the model was verified by experimental results measured with a roll profile electromagnetic control experimental platform.This model was used to analyze the influence of the heterogeneity of ECR inner hole and ES on the roll crown,the roll profile,the average contact pressure,and the stress state during RPECT process.The results indicate that the heterogeneous layer at ECR inner hole has a restrictive effect on RPECT and that the heterogeneous layer of ES can enhance the profile control ability of RPECT.A reasonable configuration scheme between the heterogeneity of ECR inner hole and the ES can increase the life of ECR and maintain the control ability of RPECT.