Kolm Setu nalja-juttu : Armsalõ maa- ja liina rahwallõ opusõst ja meeleparandusõst kirjä panto

http://tartu.ester.ee/record=b1769304~S1*es

Alatarõ Hippo Peterbuura reis ja imelik unõnägo inne toda : Üli naljakas jutt Setu keelemurrakus

http://tartu.ester.ee/record=b1538880~S1*es

Tölpsaarõ Andre ja Lükowa Iwwani kokkosaamine Jurjowah üle hulga ajo : (Naljakas Setude kaksikkõne)

http://tartu.ester.ee/record=b1539423~S1*es

Töganitsa Höödo naise wõtmise ja tarõ palamise lugu : Üts wäega armas ja hallõ laul, miä Höödo esi umah suurõh süäme waluh ja kurbtusõh om wällä märknö

http://tartu.ester.ee/record=b1539418~S1*es

Investigation of Unwanted Oscillations of Electrically Modulated Magnetoelectric Cantilever Sensors

Magnetoelectric thin-film cantilevers consisting of strain-coupled magnetostrictive and piezoelectric layers are promising candidates for magnetic field measurements in biomedical applications. In this study, we investigate magnetoelectric cantilevers that are electrically excited and operated in a special mechanical mode with resonance frequencies above 500 kHz. In this particular mode, the cantilever bends in the short axis, forming a distinctive U-shape and exhibiting high-quality factors and a promising limit of detection of 70pT/Hz1/2 at 10 Hz. Despite this U mode, the sensors show a superimposed mechanical oscillation along the long axis. The induced local mechanical strain in the magnetostrictive layer results in magnetic domain activity. Due to this, the mechanical oscillation may cause additional magnetic noise, deteriorating the limit of detection of such sensors. We compare finite element method simulations with measurements of magnetoelectric cantilevers in order to understand the presence of oscillations. From this, we identify strategies for eliminating the external effects that affect sensor operation. Furthermore, we investigate the influence of different design parameters, in particular the cantilever length, material parameters and the type of clamping, on the amplitude of the undesired superimposed oscillations. We propose design guidelines to minimize the unwanted oscillations

Signal-to-noise ratio enhanced electrode configurations for magnetoelectric cantilever sensors

Magnetoelectric cantilevers consisting of strain-coupled magnetostrictive and piezoelectric (PE) layers are applicable to magnetic-fi eld sens- ing. For the fi rst bending mode, the magnetic fi eld-induced stress distribution is of equal sign along the cantilever length. Thus, a plate- capacitor electrode configuration encompassing the complete PE layer may be used for collecting the strain-induced charge. For higher order modes, stress regions of the opposite sign occur in the cantilever length direction. To prevent charge cancellation and to harvest the piezo- electric induced charge effi ciently, segmented electrodes are employed. This study investigates the effect of the electrode confi gurationon the signal-to-noise ratio (SNR) for higher order bending modes. The charges collected by the electrodes are calculated using a fi nite element method simulation considering the mechanical, electrical, and magnetic properties of the cantilever. By combination with an analytic noise model, taking into account the sensor and amplifi er noise sources, the SNR is obtained. We analyze a 3 mm long, 1 mm wide, and 50 μm thick silicon cantilever with layers of 2 μm magnetostrictive soft amorphous metal (FeCoSiB) and 2 μm piezoelectric aluminum nitride. We demonstrate that an SNR-optimized electrode design yields an SNR improvement by 2.3 dB and 2.4 dB for the second and third bending modes compared to a signal optimized design

Multi-Mode Love-Wave SAW Magnetic-Field Sensors

A surface-acoustic-wave (SAW) magnetic-field sensor utilizing fundamental, first- and second-order Love-wave modes is investigated. A 4.5   μ m SiO2 guiding layer on an ST-cut quartz substrate is coated with a 200 n m (Fe90Co10)78Si12B10 magnetostrictive layer in a delay-line configuration. Love-waves are excited and detected by two interdigital transducers (IDT). The delta-E effect in the magnetostrictive layer causes a phase change with applied magnetic field. A sensitivity of 1250 ° / m T is measured for the fundamental Love mode at 263 M Hz . For the first-order Love mode a value of 45 ° / m T is obtained at 352 M Hz . This result is compared to finite-element-method (FEM) simulations using one-dimensional (1D) and two-and-a-half-dimensional (2.5 D) models. The FEM simulations confirm the large drop in sensitivity as the first-order mode is close to cut-off. For multi-mode operation, we identify as a suitable geometry a guiding layer to wavelength ratio of h GL / λ ≈ 1.5 for an IDT pitch of p = 12   μ m . For this layer configuration, the first three modes are sufficiently far away from cut-off and show good sensitivity

Ultrasensitive Magnetoelectric Sensing System for pico-Tesla MagnetoMyoGraphy

MagnetoMyoGraphy (MMG) with superconducting quantum interference devices (SQUIDs) enabled the measurement of very weak magnetic fields (femto to pico Tesla) generated from the human skeletal muscles during contraction. However, SQUIDs are bulky, costly and require working in a temperature-controlled environment, limiting wide-spread clinical use. We introduce a low-profile magnetoelectric (ME) sensor with analog frontend circuitry that has sensitivity to measure pico-Tesla MMG signals at room temperature. It comprises magnetostrictive and piezoelectric materials, FeCoSiB/AlN. Accurate device modelling and simulation are presented to predict device fabrication process comprehensively using the finite element method (FEM) in COMSOL Multiphysics®. The fabricated ME chip with its readout circuit was characterized under a dynamic geomagnetic field cancellation technique. The ME sensor experiment validate a very linear response with high sensitivities of up to 378 V/T driven at a resonance frequency of fres = 7.76 kHz. Measurements show the sensor limit of detections of down to 175 pT/Hz at resonance, which is in the range of MMG signals. Such a small-scale sensor has the potential to monitor chronic movement disorders and improve the end-user acceptance of human-machine interfaces

Analysis of magnetoelectric sensors for use at higher modes applying the finite element method

In der medizinischen Diagnostik besteht das Interesse die sehr schwachen Magnetfelder von biologischen Funktionen, wie beispielsweise von Herz- oder Gehirnaktivitäten, zu messen. Hierfür eignen sich insbesondere magnetoelektrische (ME) Sensoren aufgrund ihrer sehr niedrigen Nachweisgrenze, des möglichen Betriebs bei Raumtemperatur sowie ihres kostengünstigen Herstellungsverfahrens. Innerhalb dieser Arbeit wurden vorrangig zwei unterschiedliche Konzepte von ME-Sensoren mittels numerischer Simulationen unter Verwendung der Finite-Elemente-Methode (FEM) systematisch analysiert und auf mögliche Optimierungspotentiale hin untersucht: magnetoelektrische Biegebalken und magnetoelastische akustische Oberflächenwellensensoren. Besonderes Augenmerk wurde hierbei auf den Multi-Moden-Betrieb der Sensoren gelegt, bei dem sowohl die Grundmode als auch deren höhere Harmonische für die Magnetfelddetektion genutzt werden können. Bei den magnetoelektrischen Biegebalken konnte durch FEM-Simulationen gezeigt werden, dass das Elektrodendesign für den Betrieb bei den höheren Moden einen signifikanten Einfluss auf das Signal-Rausch-Verhältnis (SNR) hat. So kann beispielsweise ein SNR-Gewinn von bis zu 2,4 dB erzielt werden, wenn die Elektroden nicht wie bisher üblich an den Dehnungsknoten unterbrochen werden, sondern deren Länge weiter reduziert wird. Diese Verkürzung steht im Gegensatz zu dem üblichen Bestreben, das Signal zu maximieren. Da jedoch das Rauschen an den Rändern einer maximal langen Elektrode stärker zunimmt als das Signal, führt eine Verkürzung der Elektroden zu einem höheren SNR. Für magnetoelastische akustische Oberflächenwellensensoren (SAW) wurde der Einfluss verschiedener Designparameter auf die Sensitivität untersucht. Es konnte gezeigt werden, dass die Schichtdicke der Führungsschicht einen erheblichen Einfluss auf die Sensitivität besitzt und diese für 8 μmmaximal wird. Ein Erhöhen der Resonanzfrequenz führt zu einer stärkeren Konzentration derWelle an der Oberfläche und damit ebenfalls zu einer höheren Sensitivität. Dies konnte dadurch bestätigt werden, dass durch eine Erhöhung der Resonanzfrequenz von 148MHz auf 263MHz die Sensitivität der Grundmode von 504 °/mT auf etwa 1250 °/mT gesteigert werden konnte. Weiter konnte gezeigt werden, dass die Sensitivität der höheren Moden grundsätzlich kleiner ist als die der Grundmode. Es konnte dennoch ein Arbeitspunkt identifiziert werden, an dem die ersten drei Moden eine ausreichend hohe Sensitivität für einen Multi-Moden-Betrieb besitzen. Die Sensitivitäten aller Moden dieses Sensors mit 12 μm Wellenlänge waren höher als die eines Sensors mit 28 μm Wellenlänge. Die entwickelten Modelle und die hiermit erzielten Ergebnisse bezüglich der potentiellenVerbesserung der Biegebalken- und SAW-Sensoren können dazu beitragen, die Messung von biomagnetischen Signalen zukünftig zu optimieren und damit den Einsatz zur Messung sehr niedriger biomagnetischer Felder zu ermöglichen.In medical diagnostics, there is a need for measuring extremely weak magnetic fields of biologic functions, e.g. heart or brain, to extrapolate their activities. Magnetoelectric (ME) sensors are particularly well suited for this purpose due to their very low detection limit, potential to be operated at room temperature, and cost-effective manufacturing process. In this work, two different concepts of ME sensors were systematically analyzed using numerical simulations with the finite element method (FEM) to determine potential optimization strategies: magnetoelectric cantilevers and magnetoelastic acoustic surface wave sensors. Special focus lays on multi-mode-operation of these sensors using both the basic mode and higher modes for magnetic field detection. For magnetoelectric cantilevers, FEM simulations showed, that the electrode design had a significant influence on their signal-to-noise-ratio (SNR) in higher mode operation. Segmentation of the electrodes is usually performed at the strain-node positions. Nevertheless, further shortening of their lengths led to an improvement of the SNR of up to 2.4 dB; shortening the electrodes is contrary to the usual approach to maximize the signal. However, as the noise increases to a higher extent than the signal on the last percentage of the maximal electrode length, shortening of the electrodes leads to a higher SNR. For magnetoelastic surface acoustic wave (SAW) sensors, the influence of different design parameters on the sensitivity has been analyzed. It was observed that the layer thickness of the guiding layer had substantial influence on the sensitivity and that a layer thickness of 8 μm showed a maximum. Increasing the resonance frequency resulted in a higher concentration of the wave at the surface and therefore led to higher sensitivities. This was confirmed by the fact that increasing the resonance frequency from 148 MHz to 263 MHz increased the sensitivity of the fundamental mode from 504 °/mT to 1250 °/mT. The higher order modes’ sensitivities were found to be generally lower compared to the fundamental mode’s. Nevertheless an operating point with sufficiently high sensitivity was determined, enabling multi-mode operation. The sensitivities of all three modes of this sensor with 12 μm wavelength were higher compared to the sensor with 28 μm wavelength. The developed models and obtained results on the possibilities of cantilever and SAW sensor improvement may contribute to the optimization of biomagnetic Field measurements and thereby enable future measurements of substantially lower biomagnetic signals

Kae määrne hüä õnn : Üts wahtnõ Seto-lugu, miä igäl inemisel, kiä uma süämele rahu ja hingelõndsust taht saia, läbi tulõ lukõ

http://tartu.ester.ee/record=b1539420~S1*es