Contactless Inductive Flow Tomography for Real-Time Control of Electromagnetic Actuators in Metal Casting.

Flow control of liquid metals based on the actual flow condition is important in many metallurgical applications. For instance, the liquid steel flow in the mould of a continuous caster strongly influences the product quality. The flow can be modified by an electromagnetic brake (EMBr). However, due to the lack of appropriate flow measurement techniques, the control of those actuators is usually not based on the actual flow condition. This article describes the recent developments of the Contactless Inductive Flow Tomography (CIFT) towards a real-time monitoring system, which can be used as an input to the control loop for an EMBr. CIFT relies on measuring the flow-induced perturbation of an applied magnetic field and the solution of an underlying linear inverse problem. In order to implement the CIFT reconstructions in combination with EMBr, two issues have to be solved: (i) compensation of the effects of the change in EMBr strength on the CIFT measurement system and (ii) a real-time solution of the inverse problem. We present solutions of both problems for a model of a continuous caster with a ruler-type EMBr. The EMBr introduces offsets of the measured magnetic field that are several orders of magnitude larger than the very flow-induced perturbations. The offset stems from the ferromagnetic hysteresis exhibited by the ferrous parts of the EMBr in the proximity of the measurement coils. Compensation of the offset was successfully achieved by implementing a numerical model of hysteresis to predict the offset. Real-time reconstruction was achieved by precalculating the computationally heavy matrix inverses for a predefined set of regularization parameters and choosing the optimal one in every measurement frame. Finally, we show that this approach does not hinder the reconstruction quality.

Phased Array Ultrasound System for Planar Flow Mapping in Liquid Metals.

Controllable magnetic fields can be used to optimize flows in technical and industrial processes involving liquid metals in order to improve quality and yield. However, experimental studies in magnetohydrodynamics often involve complex, turbulent flows and require planar, two-component (2c) velocity measurements through only one acoustical access. We present the phased array ultrasound Doppler velocimeter as a modular research platform for flow mapping in liquid metals. It combines the pulse wave Doppler method with the phased array technique to adaptively focus the ultrasound beam. This makes it possible to resolve smaller flow structures in planar measurements compared with fixed-beam sensors and enables 2c flow mapping with only one acoustical access via the cross beam technique. From simultaneously measured 2-D velocity fields, quantities for turbulence characterization can be derived. The capabilities of this measurement system are demonstrated through measurements in the alloy gallium-indium-tin at room temperature. The 2-D, 2c velocity measurements of a flow in a cubic vessel driven by a rotating magnetic field (RMF) with a spatial resolution of up to 2.2 mm are presented. The measurement results are in good agreement with a semianalytical simulation. As a highlight, two-point correlation functions of the velocity field for different magnitudes of the RMF are presented.

Contactless Inductive Bubble Detection in a Liquid Metal Flow.

The detection of bubbles in liquid metals is important for many technical applications. The opaqueness and the high temperature of liquid metals set high demands on the measurement system. The high electrical conductivity of the liquid metal can be exploited for contactless methods based on electromagnetic induction. We will present a measurement system which consists of one excitation coil and a pickup coil system on the opposite sides of the pipe. With this sensor we were able to detect bubbles in a sodium flow inside a stainless steel pipe and bubbles in a column filled with a liquid Gallium alloy.

Experimental evidence for nonaxisymmetric magnetorotational instability in a rotating liquid metal exposed to an azimuthal magnetic field.

The azimuthal version of the magnetorotational instability (MRI) is a nonaxisymmetric instability of a hydrodynamically stable differentially rotating flow under the influence of a purely or predominantly azimuthal magnetic field. It may be of considerable importance for destabilizing accretion disks, and plays a central role in the concept of the MRI dynamo. We report the results of a liquid metal Taylor-Couette experiment that shows the occurrence of an azimuthal MRI in the expected range of Hartmann numbers.

Comparación del grado de sedación, profundidad anestésica y efectos colaterales de cinco protocolos anestésicos en perros sanos / Comparison of the degree of sedation, anaesthetic depth and collateral effects of five anaesthetic protocols in healthy dogs

El objetivo de este estudio fue comparar el grado de sedación, profundidad anestésica y efectos colaterales de cinco protocolos anestésicos utilizados de rutina en caninos sanos en la Universidad Nacional de Colombia. Se anestesiaron quince caninos adultos (1-5 años de edad), de raza criolla (cinco machos, diez hembras), 15-20 kg de peso, usando los siguientes protocolos: 1. Atropina + xilazine seguidos por tiopental sódico; 2. Atropina + xilazine seguidos por ketamina + diazepam; 3. Acepromazina, seguida por atropina + hidromorfona y luego por tiopental sódico; 4. Atropina + hidromorfona, seguidas por diazepam y luego tiopental sódico y; 5. Atropina + hidromorfona, seguidas por diazepam y luego propofol. Los animales se encontraban sanos y en cada uno se usaron los cinco protocolos anestésicos, con un intervalo mínimo de una semana. No se llevó a cabo ningún procedimiento quirúrgico. Se encontraron diferencias significativas entre protocolos, en cuanto a la necesidad de restricción (p=0,0043), profundidad anestésica (p=0,0183) y analgesia a los 0 y 5 minutos postinducción (p=0,0045 y 0,0233, respectivamente). Con respecto a los efectos colaterales, hubo diferencias significativas en parámetros, como la pérdida de temperatura (p=0,0137) y saturación parcial de oxígeno (p=0,0001). No hubo diferencias significativas en parámetros importantes, tales como la frecuencia de presentación de arritmias (p=0,7404), pero estas fueron más severas al usar el protocolo 1. Los tiempos anestésicos más largos fueron observados con el protocolo 3. Se concluye que el protocolo 5 es superior a los demás, ya que provee adecuada profundidad anestésica, con efectos colaterales menos severos.

The purpose of this study was to compare the degree of sedation, anesthetic depth and collateraleffects of five anesthetic protocols routinely used in healthy canine patients at the National University of Colombia. Fifteen adult (1-5 years old), mixed-breed dogs (5 males, 10 females), weighting 15-20 kg, were anaesthetized using the following protocols: 1. Atropine +Xylazine followed by Thiopental; 2. Atropine + Xylazine followed by Ketamine + Diazepam; 3. Acepromazine, followed by Atropine + Hydromorphone and then Thiopental; 4. Atropine + Hydromorphone followed by Diazepam and then Thiopental and; 5. Atropine + Hydromorphone followed by Diazepam and then Propofol. The animals were healthy and each onewas anaesthetized with the five anesthetic protocols, with an interval of at least one week. No surgical procedures were performed. Significant differences were found in the degreeof sedation between protocols, specifically regarding the need for restriction (p=0.0043), anesthetic depth (p=0.0183) and analgesia at 0 and 5 minutes post induction (p=0.0045 and 0.0233, respectively). As far as collateral effects are concerned, there were significant differences in parameters such as temperature loss (p=0.0137) and partial oxygen saturation (p=0.0001). There were no significant differences between protocols regarding important parameters, such as the frequency of arrhythmias (p=0.7404), but they were more severe when using protocol 1. The longest anesthetic times were observed during protocol 3. It is concluded that protocol 5 is superior to the others, since it provided an adequate anestheticdepth, with less severe collateral effects.