L. Mehnen

Method for continuous nondisturbing monitoring of blood pressure by magnetoelastic skin curvature sensor and ECG

This paper concerns continuous nondisturbing estimation of blood pressure using mechanical plethysmography in connection with standard electrocardiography (ECG). The plethysmography is given by a novel magnetoelastic skin curvature sensor (SC-sensor) applied on the neck over the carotid artery. The sensor consists of a magnetoelastic bilayer partly enclosed by a coil. Bending the bilayer causes large changes of magnetic permeability which can be measured by the coil. The SC-sensor signal and the ECG signal are adaptively processed in order to estimate blood pressure according to a specifically established theoretical model. The model uses estimated vessel radius changes and pulse transit time as parameters. The results show cross correlation coefficients in the range 0.8 up to 0.9 between reference and estimated values of systolic blood pressure, diastolic blood pressure, and systolic/diastolic blood pressure change, whereas the estimation error was below 4 +/- 7 mmHg at rest and increased with the stress level. Limitations of the model applicability are given by a hysteretic behavior of both model parameters due to inert changes in artery stiffness. The SC-sensor and the ECG electrodes cause minimal inconvenience to the patient and offer an approach for a continuous nondisturbing monitoring of blood pressure changes, as being relevant for sleep monitoring or biomechanic feedback

Magnetostrictive amorphous bimetal sensors

The paper describes the application of a magnetostrictive amorphous ribbon (AR) for the detection of bending. In order to increase sensitivity, a bimetal structure is used which consists of AR and a nonmagnetic carrier ribbon. Several methods for the preparation of the bimetal are discussed. Results of the bending sensitivities are given for various combinations of the material types indicating crucial problems of bimetal preparation.

A magnetostrictive acceleration sensor for registration of chest wall displacements

Abstract The present study concerns a novel acceleration sensor built up using a bimetallic strip with one freely oscillating end. The strip consists of a magnetostrictive amorphous ribbon glued on a nonmagnetic metal ribbon. The sensor’s effectiveness is demonstrated for the case of chest wall displacements as resulting from cardiorespiratory activity. The cheap and easy-to-handle novel sensor offers multiple information on the so-called sleep apnea syndrome.

Magnetostrictive amorphous bilayers and trilayers for thermal sensors

Abstract The study concerns agglutinated bilayers as thermal sensors. Different thermal expansion coefficients of the bilayer—a magnetostrictive amorphous ribbon and a non-magnetic metal counter ribbon—yield mechanical stress of the first by temperature change and thus a change of permeability. The sensitivity is of the order 1% permeability change per Kelvin which can be increased by preventing bilayer bending.

Magnetoelastic skin curvature sensor for biomedical applications

The present paper concerns the versatile applicability of a novel skin curvature sensor family for multiparametric monitoring of physiological parameters. The basic element of the sensor is a magnetoelastic bilayer which shows a magnetoelastic amorphous layer and a nonmagnetic layer. Bending the bilayer causes the magnetoelastic layer to experience either tensile or compressive stress, depending on the direction of bending. The resulting large changes of magnetic permeability can be measured using a coil. The extreme thinness of the sensor favors its application on the skin in various medical diagnostic areas. On the neck and on the chest wall, the sensor registers cardiorespiratory activity and interrupted breathing, both being relevant for the so-called sleep apnea syndrome. Registration of leg movements is demonstrated on the calf for the diagnosis of the restless leg syndrome. Assessment of eye movements is shown using a miniature sensor version.

Displacement sensor based on an amorphous bilayer including a magnetostrictive component

The present study concerns a novel type of bilayer material for displacement sensors based on the detection of curvature changes through the magnetoelastic effect. For increased bilayer stability, attempts were made to use a double-nozzle melt spinning technique (DNT) for direct flow-cast of bilayers. Compared to an agglutination technique, DNT yielded much lower sensitivity but improved long-term stability.

Design of a small satellite for performing measurements in a ground station network

Small satellites gain more and more interests from both educational and academic institutions, but also from the industry. They constitute a cheap alternative to large, more expensive and more complex satellites. A consequence of their small form factor is the lack of space for secondary payload, like advanced communication facilities. These deficiencies make it difficult to apply quality assurances concerning satellite communication links on the ground segment. Previous approaches have been primarily passive and focused only on the bit error rate of receiving links at ground stations. The results therefor covered only one direction of a bidirectional link and even if they were quite accurate in common, they were nevertheless only approximations. In this paper a novel design solution based on a small satellite cluster is going to be proposed to offer quality assurance for the ground segment in both sending and receiving directions in multiple amateur frequency bands based on highaccurate error rate information.

A global satellite link sensor network

With the raising number of space missions performed with nano-and pico-sized satellites, significant increase of mission data return becomes more and more important. As a consequence of the low earth orbit the satellites are deployed in, the communication timeframe between spacecrafts and ground stations is limited to half an hour a day. Nowadays non-commercial ground stations join forces by establishing ground station networks to optimize resource utilization and data return. Although the primary goal of such networks is to increase the amount of data transferred between spacecrafts and ground controls, link quality measurements performed by the ground stations during each satellite pass provide impressive remote sensing potential. In this paper the interpretation of more than two thousand satellite pass recordings performed during the last year at the University of Aalborg in Denmark are presented. Furthermore the potential of remote sensing utilizing ground station networks is demonstrated by means of possible scenarios described in detail.

Applying Methods of Soft Computing to Space Link Quality Prediction

The development of nano- and picosatellites for educational and scientific purposes becomes more and more popular. As these satellites are very small, high-integrated devices and are therefore not equippedwith high-gain antennas, data transmission between ground and satellite is vulnerable to several ascendancies in both directions. Another handicap is the lower earth orbit wherein the satellites are usually located as it keeps the communication time frame very short. To counter these disadvantages, ground station networks have been established. One input size for optimal scheduling of timeframes for the communication between a ground station and a satellite is the predicted quality of the satellite links. This paper introduces a satellite link quality prediction approach based on machine learning.

Cardiovascular Oscillations of the Carotid Artery Assessed by Magnetoelastic Skin Curvature Sensor

The present study concerns the nondisturbing assessment of cardiovascular oscillations of the carotid artery using a novel skin curvature sensor on the neck. The mechanical oscillations of the skin reflect changes of the artery radius and thus relevant physiological data such as cardiac and respiratory activities, their mutual dependencies, and even changes of blood pressure. The skin curvature sensor is easy to handle and it minimally disturbs the patient, which is relevant for many medical areas such as sleep monitoring.