In this paper we investigate the multiwavelengths properties of the magnetic early B-type star HR7355. We present its radio light curves at several frequencies, taken with the Jansky Very Large Array, and X-ray spectra, taken with the XMM X-ray telescope. Modeling of the radio light curves for the Stokes I and V provides a quantitative analysis of the HR7355 magnetosphere. A comparison between HR7355 and a similar analysis for the Ap star CUVir, allows us to study how the different physical parameters of the two stars affect the structure of the respective magnetospheres where the non-thermal electrons originate. Our model includes a cold thermal plasma component that accumulates at high magnetic latitudes that influences the radio regime, but does not give rise to X-ray emission. Instead, the thermal X-ray emission arises from shocks generated by wind stream collisions close to the magnetic equatorial plane. The analysis of the X-ray spectrum of HR7355 also suggests the presence of a non-thermal radiation. Comparison between the spectral index of the power-law X-ray energy distribution with the non-thermal electron energy distribution indicates that the non-thermal X-ray component could be the auroral signature of the non-thermal electrons that impact the stellar surface, the same non-thermal electrons that are responsible for the observed radio emission. On the basis of our analysis, we suggest a novel model that simultaneously explains the X-ray and the radio features of HR7355 and is likely relevant for magnetospheres of other magnetic early type stars.

We report the detection of the auroral radio emission from the early-type magnetic star HD 142301. New VLA observations of HD 142301 detected highly polarized amplified emission occurring at fixed stellar orientations. The coherent emission mechanism responsible for the stellar auroral radio emission amplifies the radiation within a narrow beam, making the star where this phenomenon occurs similar to a radio lighthouse. The elementary emission process responsible for the auroral radiation mainly amplifies one of the two magneto-ionic modes of the electromagnetic wave. This explains why the auroral pulses are highly circularly polarized. The auroral radio emission of HD 142301 is characterized by a reversal of the sense of polarization as the star rotates. The effective magnetic field curve of HD 142301 is also available making it possible to correlate the transition from the left to the right-hand circular polarization sense (and vice versa) of the auroral pulses with the known orientation of the stellar magnetic field. The results presented in this letter have implications for the estimation of the dominant magneto-ionic mode amplified within the HD 142301 magnetosphere.

<p><p>To improve the speed measurement of construction equipment, different sensor technologies have been investigated. Many of these sensor technologies are very interesting but to keep the extent of the thesis only two was chosen for testing, magnetic absolute angle sensors using Hall and GMR technology, to investigate if those are a valid replacement for the current measurement system that is using a passive sensor. Tests show that these sensors are capable of speed measurement, but because of noisy angle estimates they need filtering for good speed computation. This filtering introduces a large time delay that is of significance for the quality of the estimate. A Kalman filter has been implemented in an attempt to lower the time delays but since only a very simple model has been used it does not give any improvements over ordinary low pass filtering. For these sensors the mounting tolerance is of great interest. For best performance the offset between the sensor and magnet centres need to be kept small for both sensors. This is due to a non-linearity effect this causes. The distance between the sensors and the magnet is not critical for linearity issues, but only for the quality of the signal, where it might drop out when the distance is too large. This is where the sensor using GMR technology stands out. Compared to the Hall technology sensor, the GMR sensor can handle distances that are more than 10 times larger. The conclusion is that these sensors can be a valid replacement of the current measurement system. They will introduce more functionality with the capability of detecting rotational direction and zero velocity. In an application with more than one sensor they can also be used for more purposes, like detecting slip in clutches etc. Depending on the application, the time delays may not be critical, else more work need to be done to improve the estimate, e.g. with a more advanced model for the Kalman filter.</p></p><p> </p>

Melt flow plays an important role in directional solidification of multicrystalline silicon influencing the temperature field and the crystallization interface as well as the transport of impurities. This work investigates the potential of a traveling magnetic field (TMF) for an active control of the melt flow. A system of 3D numerical models was developed and adapted based on open-source software for calculations of Lorentz force, melt flow, and related phenomena. Isothermal and non-isothermal model experiments with a square GaInSn melt were used to validate the numerical models by direct velocity measurements. Several new 3D flow structures of turbulent TMF flows were observed for different melt heights. Further numerical parameter studies carried out for silicon melts showed that already a weak TMF-induced Lorentz force can stir impurities near to the complete mixing limit. Simultaneously, the deformed temperature field leads to an increase of the deflection of crystallization interface, which may exhibit a distinct asymmetry. The numerical results of this work were implemented in a research-scale silicon crystallization furnace. Scaling laws for various phenomena were derived allowing a limited transfer of the results to the industrial scale.

To improve the speed measurement of construction equipment, different sensor technologies have been investigated. Many of these sensor technologies are very interesting but to keep the extent of the thesis only two was chosen for testing, magnetic absolute angle sensors using Hall and GMR technology, to investigate if those are a valid replacement for the current measurement system that is using a passive sensor. Tests show that these sensors are capable of speed measurement, but because of noisy angle estimates they need filtering for good speed computation. This filtering introduces a large time delay that is of significance for the quality of the estimate. A Kalman filter has been implemented in an attempt to lower the time delays but since only a very simple model has been used it does not give any improvements over ordinary low pass filtering. For these sensors the mounting tolerance is of great interest. For best performance the offset between the sensor and magnet centres need to be kept small for both sensors. This is due to a non-linearity effect this causes. The distance between the sensors and the magnet is not critical for linearity issues, but only for the quality of the signal, where it might drop out when the distance is too large. This is where the sensor using GMR technology stands out. Compared to the Hall technology sensor, the GMR sensor can handle distances that are more than 10 times larger. The conclusion is that these sensors can be a valid replacement of the current measurement system. They will introduce more functionality with the capability of detecting rotational direction and zero velocity. In an application with more than one sensor they can also be used for more purposes, like detecting slip in clutches etc. Depending on the application, the time delays may not be critical, else more work need to be done to improve the estimate, e.g. with a more advanced model for the Kalman filter.

The aim of this work was to investigate the effects that a magnetic field can induce during the electrodeposition of Ni and Ni-Fe alloys. Special regard was given to mass transport controlled effects. Magnetic field effects on the nucleation and growth of ferromagnetic layers and on the properties of electrodeposited layers (like grain size, texture, morphology or roughness) were investigated. The influence of a magnetic field on the magnetic properties of Ni layers and on the composition of Ni-Fe alloys was also studied. Nucleation and growth of thin Ni layers on gold electrodes under a superimposed magnetic field were analysed in-situ with the Electrochemical Quartz Crystal Microbalance technique. Three theoretical models were chosen for characterizing the Ni nucleation: Scharifker-Hills (SH), Scharifker-Mostany (SM) and Heerman-Tarallo (HT). The AFM images proved that more nuclei appear in a magnetic field in the case that the Lorentz force and the natural convection act in the same direction. From all the models, the HT model gave the best agreement with the AFM results. When the Lorentz force and the natural convection act in the same direction, an increase of the Ni partial current with the magnetic field was obtained. When they act in opposite directions, the Ni current was influenced just at the beginning of deposition (first 10 seconds). At longer times, the magnetic field has no effect on the Ni current. However, the total current (jNi+jHER) decreases with the magnetic field. In the absence of a macroscopic MHD convection, the Ni current decreases with the magnetic field the first 10-15 seconds of deposition. On longer time scales no influence of the magnetic field could be noticed for this configuration. When the magnetic field was applied perpendicular to the electric current, an increase of the hydrogen evolution reaction (HER) with the magnetic flux density was noticed. Hydrogen reduction is mass transport controlled. Therefore, the magnetic field will increase the limiting current of the HER. Optical microscopy images showed that the hydrogen bubbles were circular in the absence of the MHD convection and that they presented a tail when a Lorentz force was present. The direction of the tail depends on the net force induced by the natural and MHD convections. The interplay between the natural and MHD convections proved to be important during Ni-Fe alloy deposition, too. When the Lorentz force and the natural convection act in the same direction, an increase of the Fe content of the alloys with the magnetic field was observed. When the Lorentz force was perpendicular to the natural convection, no significant changes were observed in the composition of the layers. The alloy composition did not change with the magnetic field when the electric current was parallel to the magnetic field lines. Two surfactants were used in the case that Ni was electrodeposited from a sulfamate bath: SDS and sulfirol 8. The Ni layers obtained from a sulfamate bath with sulfirol 8 presented larger grains compared to the layers deposited from a bath free of surfactants. This increase of the grain size was attributed to the incorporation of the surfactant in the deposit. Coarser layers were obtained in a magnetic field (applied perpendicular to the electric current) when the electrodeposition was done from an electrolyte with surfactants. The number of grains increased with the magnetic field for the Ni layers electrodeposited from a bath free of surfactants and for a bath with SDS. As a consequence, the grain size decreased. In the case of the electrolyte with sulfirol 8, the number of grains decreased with the magnetic field, and their size increased. For the Ni-Fe alloys, which contained less than 10 at% Fe, the preferred crystalline orientation changes from (220), in the absence of a magnetic field, to (111), (when the magnetic field was applied perpendicular to the electric current). When the magnetic field lines were parallel to the electric current, both the (111) and (220) textures were preferred in almost the same proportion. As a general conclusion of this work it can be said that by choosing the right experimental condition, one can improve the morphology and the properties of the deposited layers by applying a magnetic field. At the same time, the mass transport processes can be influenced by a magnetic field.

We have used a series of observations of HD119419, performed in 2012 and 2013at the European Southern Observatory 3.6-m telescope in La Silla, Chile. These are high resolutionspectropolarimetric observations with coverage in all four Stokes parameters. We performed a chemical abundance analysis of HD119419, in the absence of any being published previously for this star. We used a LLmodels stellar atmosphere code with effective temperature11500 K and surface gravity log g = 4.0, together with the spectrum synthesis code synmast. Abundances were adjusted until the synthetic spectra matched the mean observed spectra as well as possible, and these abundances were assumed to be representative of the photosphere of HD119419. We found good estimates for some Fe-peak elements and rare-earth elements. The abundance estimates were used to compute least-squares deconvolution Stokes spectra, from which we calculated how the longitudinal magnetic field and net linear polarization varies with rotational phase for HD119419. We calculated an improved rotational period for HD119419 using our longitudinal magnetic field measurements together with previous measurements from the literature, determining it to be 2.60059(1) days. We found that the Stokes QUV are unusually strong for the rare-earth elements in HD119419, considering their weaker Stokes I profiles compared to the Fe-peak elements in particular.

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