Electromyogram-Based Classification of Hand and Finger Gestures Using Artificial Neural Networks

Electromyogram (EMG) signals have been increasingly used for hand and finger gesture recognition. However, most studies have focused on the wrist and whole-hand gestures and not on individual finger (IF) gestures, which are considered more challenging. In this study, we develop EMG-based hand/finger gesture classifiers based on fixed electrode placement using machine learning methods. Ten healthy subjects performed ten hand/finger gestures, including seven IF gestures. EMG signals were measured from three channels, and six time-domain (TD) features were extracted from each channel. A total of 18 features was used to build personalized classifiers for ten gestures with an artificial neural network (ANN), a support vector machine (SVM), a random forest (RF), and a logistic regression (LR). The ANN, SVM, RF, and LR achieved mean accuracies of 0.940, 0.876, 0.831, and 0.539, respectively. One-way analyses of variance and F-tests showed that the ANN achieved the highest mean accuracy and the lowest inter-subject variance in the accuracy, respectively, suggesting that it was the least affected by individual variability in EMG signals. Using only TD features, we achieved a higher ratio of gestures to channels than other similar studies, suggesting that the proposed method can improve the system usability and reduce the computational burden.

Nonlinear dynamics of mode-localized MEMS accelerometer with two electrostatically coupled microbeam sensing elements

In the presented work, a model of a microelectromechanical accelerometer with two movable beam elements located between two fixed electrodes is proposed. The action of the transfer forces of inertia in the longitudinal direction leads to a change in the spectral properties of the system, which is a useful output signal of the sensor. The dynamics of the system in the presence of a weak electrostatic coupling between the sensitive elements is characterized by the phenomenon of modal localization - a significant change in the amplitude ratios for the forms of inphase and antiphase oscillations with small changes in the measured component of the acceleration vector of the moving object. Diagrams of equilibrium positions are plotted for varying the potential difference between a fixed electrode and a movable element and between two movable elements. The dependences of the frequencies and the ratio of the components of the eigenvectors on the magnitude of the inertial action are investigated. It is shown that the sensitivity of a sensor based on modal localization can be orders of magnitude higher than the sensitivity of known systems based on measuring the shift of natural frequencies. A nonlinear dynamic model of an accelerometer with external harmonic electrostatic excitation of oscillations is constructed. Resonance characteristics are obtained, a comparison is made between the model describing the modal characteristics of the system and the model describing the real dynamic mode of operation taking into account nonlinear factors.

Poly-3-thienylboronic acid: a chemosensitive derivative of polythiophene

Poly-3-thiopheneboronic acid was synthesized by electrochemical polymerization from 3-thienylboronic acid dissolved in the mixture of boron trifluoride diethyl etherate and acetonitrile. Cyclic voltammetry during electropolymerization shows oxidative and reductive peaks growing in each next cycle. An investigation by scanning electron microscopy displayed the polymer layer like a highly flexible film of 110 nm thick with grains of 60–120 nm in size. Strong negative solvatochromic effect was observed. Optical spectra of poly-3-thienylboronic acid at different potentials and pH were studied. Potential cycling leads to a well reversible electrochromic effect. At pH 7.4, the increase of potential leads to the decrease in the absorption band at 480 nm and to the rise in the absorption band at 810 nm with an isosbestic point at 585 nm. Spectroelectrochemical behavior of poly-3-thienylboronic acid and polythiophene was compared. Binding of sorbitol at fixed electrode potential leads to an increase in the absorbance in the shortwave band and to the decrease in the longwave band; the effect depends on the electrode potential and pH. Perspectives of application of poly-3-thienylboronic acid as new chemosensitive material are discussed.

Application of Biosurfactants and Pulsating Electrode Configurations as Potential Enhancers for Electrokinetic Remediation of Petrochemical Contaminated Soil

The remediation of soil contaminated with petrochemicals using conventional methods is very difficult because of the complex emulsions formed by solids, oil, and water. Electrokinetic remediation has of recent shown promising potential in the removal of organics from contaminated media as calls for further improvement of the technology are still made. This work investigated the performance of electrokinetic remediation of soil contaminated with petrochemicals by applying fixed electrode configurations and continuous approaching electrode configurations. This was done in combination with bioremediation by inoculating hydrocarbon degrading bacteria and biosurfactants with the aim of obtaining an improved method of remediation. The results obtained show that the biosurfactant produced by the hydrocarbon degrading bacteria Pseudomonas aeruginosa was able to enhance oil extraction to 74.72 ± 2.87%, 57.375 ± 3.75%, and 46.2 ± 4.39% for 185 mm fixed electrodes, 335-260-185 mm continuous approaching electrodes, and 335 mm fixed electrode configurations, respectively. By maintaining high current flow, the 335-260-185 mm continuous approaching electrodes configuration enhanced electroosmotic flow (EOF) on every event of electrodes movement. The fixed electrode configuration of 185 mm provided amiable pH conditions for bacterial growth by allowing quick neutrality of the pH due to high EOF as compared to the 335 mm fixed electrodes configuration. After 240 h, the carbon content in the soil was reduced from 0.428 ± 0.11 mg of carbon/mg of the soil to 0.103 ± 0.005, 0.11355 ± 0.0006, and 0.1309 ± 0.004 for 185 mm, 335-260-185 mm, and 335 mm, respectively. The application of biosurfactants and continuous approaching electrodes reduced the energy expenditure of electrokinetic remediation by enhancing the decontamination process with respect to time.

Analysis of the Influence of the GPS Errors Occurred While Collecting Electrode Coordinates on the Electrical Resistivity of Tumuli

In archaeological applications the accurate reconstruction of buried structures is mandatory. Electrical resistivity tomography is widely used for this purpose. Nevertheless, resistivity errors could be generated by wrong placement of electrodes. Papers in the literature do not discuss the influence of errors connected with the electrode position location (GPS-error). In this paper the first results of a Monte Carlo simulation analysis of data acquired on a tumulus are presented. The main research questions were: (i) if it is correct to ignore the GPS-error collect, and (ii) if a minimum threshold, that significantly affect the inversion, exists. Results, obtained considering planimetric GPS-errors of about one third of the fixed electrode distances, show that the GPS-errors affect resistivity, but the generated errors/anomalies: (a) are lower than that obtained without considering the topography, and (b) are significant from a numerical point of view, but do not affect the interpretation, being compatible with the soil resistivity ranges.

The Analysis of the Influence of Threshold on the Dynamic Contact Process of a Fabricated Vertically Driven MEMS Inertial Switch

In this work, to evaluate the influence of the threshold on the dynamic contact process, five models (number 1, 2, 3, 4, 5) with different thresholds were proposed and fabricated with surface micromachining technology. The contact time and response time were used to characterize the dynamic contact performance. The dynamic contact processes of the inertial switches with gradually increasing thresholds were researched using analytical, simulation, and experimental methods. The basic working principle analysis of the inertial switch shows that the contact time of the inertial switch with a low-g value can be extended by using a simply supported beam as the fixed electrode, but the high-G inertial needs more elasticity for fixed electrode. The simulation results indicate that the response time and contact time decrease with the increment in the designed threshold. Prototypes were tested using a dropping hammer system, and the test result indicates that the contact time of the inertial switch with a fixed electrode of the simply supported beam is about 15 and 5 μs when the threshold is about 280 and 580 g, respectively. Meanwhile, the contact time can be extended to 100 μs for the inertial switch using a spring as the fixed electrode when the threshold is about 280 and 580 g. These test results not only prove that the spring fixed electrode can effectively extend the contact time, but also prove that the style of the fixed electrode is the deciding factor affecting the contact time of the high-G inertial switch.

Nonlinear Analysis and Performance of Electret-Based Microcantilever Energy Harvesters

An energy harvester composed of a microcantilever beam with a tip mass and a fixed electrode covered with an electret layer is investigated when subject to an external harmonic base excitation. The tip mass and fixed electrode form a variable capacitor connected to a load resistance. A single-degree-of-freedom model, derived based on Newton’s and Kirshoff’s laws, shows that the tip mass displacement and charge in the variable capacitor are nonlinearly coupled. Analysis of the eigenvalue problem indicates the influence of the electret surface voltage and electrical load resistance on the harvester linear characteristics, namely the harvester coupled frequency and electromechanical damping. Then, the frequency–response curves are obtained numerically for a range of load resistance, electret voltage and base excitation amplitudes. A softening nonlinear effect is observed as a result of decreasing the load resistance and increasing the electret voltage. It is found that there is an optimal electret voltage with the highest harvested electrical power. Below this optimal value, the bandwidth is very small, whereas the bandwidth is large when the electret voltage is above this optimal value. In addition, it is noted that for a certain excitation frequency, the harvested power decreases or increases as a function of electrical load resistance when the coupled frequency is closer to short- or open-circuit frequency, respectively. However, when the coupled frequency is between the short-circuit and open-circuit frequencies, the harvested power has an optimal resistance with the highest power. Increasing the excitation amplitude to raise the harvested power could be accompanied with dynamic pull-in instability and/or softening behavior depending on the electrical load resistance and electret voltage. However, large softening behavior would prevent the pull-in instability, increase the level of the harvested power, and broaden the bandwidth. These observations give a deeper insight into the behavior of such energy harvesters and are of great importance to the designers of electrostatic energy harvesters.

Unified Rate Theory of Electrochemistry and Electrocatalysis: Fixed Potential Formulation for General, Electron Transfer, and Proton-Coupled Electron Transfer Reactions

<div>Atomistic modeling of electrocatalytic reactions is most naturally conducted within the grand canonical ensemble (GCE) which enables fixed chemical potential calculations. While GCE has been widely adopted for modeling electrochemical and electrocatalytic thermodynamics, the electrochemical reaction rate theory within GCE is lacking. Molecular and condensed phase rate theories are formulated within microcanonical and canonical ensembles, respectively, but electrocatalytic systems described within the GCE require extension of the conventionally used rate theories for computation reaction rates at fixed electrode potentials. In this work, rate theories from (micro)canonical ensemble are generalized to the GCE providing the theoretical basis for the computation reaction rates in electrochemical and electrocatalytic systems. It is shown that all canonical rate theories can be extended to the GCE. From the generalized grand canonical rate theory developed herein, fixed electrode potential rate equations are derived for i) general reactions within the GCE transition state theory (GCE-TST), ii) adiabatic curve-crossing rate theory within the empirical valence bond theory (GCE-EVB), and iii) (non-)adiabatic electron and proton-coupled electron transfer reactions. The rate expressions can be readily combined with ab initio methods to study reaction kinetics reactions at complex electrochemical interfaces as a function of the electrode potential. The theoretical work herein provides a single, unified approach for electrochemical and electrocatalytic kinetics and the inclusion of non-adiabatic and tunneling effects in electrochemical environments widening the scope of reactions amenable to computational studies.</div>