Magnetography with superconducting quantum interference device (SQUID) sensor arrays is a well-established technique for measuring subtle magnetic fields generated by physiological phenomena in the human body. Unfortunately, the SQUID-based systems have some limitations related to the need to cool them down with liquid helium. The room-temperature alternatives for SQUIDs are optically pumped magnetometers (OPM) operating in spin exchange relaxation-free (SERF) regime, which require a very low ambient magnetic field. The most common two-layer magnetically shielded rooms (MSR) with residual magnetic field of 50 nT may not be sufficiently magnetically attenuated and additional compensation of external magnetic field is required. A cost-efficient compensation system based on square Helmholtz coils was designed and successfully used for preliminary measurements with commercially available zero-field OPM. The presented setup can reduce the static ambient magnetic field inside a magnetically shielded room, which improves the usability of OPMs by providing a proper environment for them to operate, independent of initial conditions in MSR.
The aim of the study was to verify the possibility of application of multifilament carbon fibre electrodes for electrical discharge machining process. In the article, the novel type of tool electrode in form of a rod that is composed of carbon fibres was proposed. The performed analysis taking into account the influence of input parameter from RC generator like voltage, capacitance and resistance along with evaluation of the process with this novel type of electrodes was considered. The manufacturing technique was assessed by analysing the geometry parameters of machined holes like diameters and maximum depth. The detailed analysis and quantitative values of the impact of each of the input factors were presented and response surfaces according to the experimental methodology were obtained. The key efficiency parameter which was expressed by material removal rate (MRR) was also calculated and compared with data for other materials used as tool electrodes that were presented previously in literature. The comparison study proved that with multifilament carbon fibre electrodes the comparable range of MRR parameter in similar electro-erosive conditions can be obtained. Thus, they can be considered as complementary material for tool electrode purposes.
Mechanomyography (MMG) is a technique of recording muscles activity that may be considered a suitable choice for human–machine interfaces (HMI). The design of sensors used for MMG and their spatial distribution are among the deciding factors behind their successful implementation to HMI. We present a new design of a MMG sensor, which consists of two coupled piezoelectric discs in a single housing. The sensor’s functionality was verified in two experimental setups related to typical MMG applications: an estimation of the force/MMG relationship under static conditions and a neural network-based gesture classification. The results showed exponential relationships between acquired MMG and exerted force (for up to 60% of the maximal voluntary contraction) alongside good classification accuracy (94.3%) of eight hand motions based on MMG from a single-site acquisition at the forearm. The simplification of the MMG-based HMI interface in terms of spatial arrangement is rendered possible with the designed sensor.
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