Due to harsh operating environments in underground coal seams, the key components (e.g., gear pairs and bearings) in the power transmission systems of coal cutters suffer from extreme wear and functional damages. To guarantee the safe and reliable operation of the coal cutters, it is important to monitor the condition of their transmission systems and detect possible faults in a timely manner. A challenging task here is to diagnose multiple concurrent faults. A literature review indicates that the current interests lie on the decoupling of multiple co-existing faults and that the very limited work has been done to deal with the dependence/correlation between the fault signals. To address this issue, this work extends our previous work on gear crack detection using the bounded component analysis (BCA) and proposes an improved BCA-based approach for decoupling hybrid faults with high dependence/correlation in coal cutter transmission systems. The proposed approach incorporates the Vold–Kalman order tracking and spectral kurtosis into an improved BCA framework (OTBCA-SK). Owing to the uniform sampling of order tracking, the influence of background noise and rotational speed variation on vibration signals can be effectively reduced. Since BCA is capable of handling vibration sources that are statistically dependent, OTBCA-SK can decouple both independent and dependent source signals. As a result, the vibration sources excited by hybrid faults, although maybe dependent/correlated, can be fully decoupled into single-fault vibration source signals. Three specially designed case studies were used to evaluate the effectiveness of the proposed OTBCA-SK approach in decoupling hybrid gear faults. The analysis results demonstrate better performance of hybrid fault decoupling using OTBCA-SK than that of three representative techniques, i.e., Erdogan's BCA (E-BCA), joint approximate diagonalization of eigen matrices (JADE) and fast independent component analysis (FastICA). These case studies also suggest that the proposed OTBCA-SK approach can retain the physical meaning of the original vibration and is hence suitable for hybrid fault diagnosis in practical applications.

In this work, two model identification methods are used to estimate the nonlinear large deformation behavior of a nonlinear resonator in the time and frequency domains. A doubly clamped beam with a slender geometry carrying a central intraspan mass when subject to a transverse excitation is used as the highly nonlinear resonator. A nonlinear Duffing equation has been used to represent the system for which the main source of nonlinearity arises from large midplane stretching. The first model identification technique uses the free vibration of the system and the Hilbert transform (HT) to identify a nonlinear force–displacement relationship in the large deformation region. The second method uses the frequency response of the system at various base accelerations to relate the maximum resonance frequency to the nonlinear parameter arising from the centerline extensibility. Experiments were conducted using the doubly clamped slender beam and an electrodynamic shaker to identify the model parameters of the system using both of the identification techniques. It was found that both methods produced near identical model parameters; an excellent agreement between theory and experiments was obtained using either of the identification techniques. This follows that two different model identification techniques in the time and frequency domains can be employed to accurately predict the nonlinear response of a highly nonlinear resonator.

Plasma is a host of numerous analytes such as proteins, metabolites, circulating nucleic acids (CNAs), and pathogens, and it contains massive information about the functioning of the whole body, which is of great importance for the clinical diagnosis. Plasma needs to be completely cell-free for effective detection of these analytes. The key process of plasma extraction is to eliminate the contamination from blood cells. Centrifugation, a golden standard method for blood separation, is generally lab-intensive, time consuming, and even dangerous to some extent, and needs to be operated by well-trained staffs. Membrane filtration can filter cells very effectively according to its pore size, but it is prone to clogging by dense particle concentration and suffers from limited capacity of filtration. Frequent rinse is lab-intensive and undesirable. In this work, we proposed and fabricated an integrated microfluidic device that combined particle inertial focusing and membrane filter for high efficient blood plasma separation. The integrated microfluidic device was evaluated by the diluted (×1/10, ×1/20) whole blood, and the quality of the extracted blood plasma was measured and compared with that from the standard centrifugation. We found that the quality of the extracted blood plasma from the proposed device can be equivalent to that from the standard centrifugation. This study demonstrates a significant progress toward the practical application of inertial microfluidics with membrane filter for high-throughput and highly efficient blood plasma extraction.

A nonlinearly broadband tuneable energy harvesting device has been designed, fabricated, and tested based on the nonlinear dynamical response of a parametrically excited clamped–clamped beam carrying a central point mass as the core element; a tuning mechanism in the form of an initial axial displacement applied to one of the clamped–clamped beam ends has been introduced to the system which enables tuning of device's natural frequency. Magnets have been used as the central point mass which generates a backward electromotive force (EMF) as they move through a coil when parametrically excited. The tuning parameter was set to a value for which the primary and principal nonlinear resonant regions become close to each other; hence, the frequency bandwidth is broadened substantially, leading to a larger amount of electrical power harvested; moreover, the nonlinear behavior, due to flexural/restoring-electromagnetic couplings, increased the operating bandwidth considerably. The system was parametrically excited using an electrodynamic shaker, and the corresponding motions of the magnets were measured. By increasing the tuning parameter, the fundamental natural frequency reduces and the system nonlinearity significantly increases; it has been discovered that when the initial axial displacement is approximately the thickness of the beam the fundamental and principal parametric resonance branches combine thus, the frequency bandwidth (and hence the range of the energy harvested) is significantly increased due to the parametric excitation, nonlinear behavior, and initial axial displacement.

In this work, for the first time, an energy harvester based on the nonlinear dynamical response of a parametrically excited cantilever beam in contact with mechanical stoppers has been fabricated and tested; a 145% increase in the bandwidth at which energy can be effectively harvested has been observed. Experimental and theoretical investigations have been performed in order to assess the increased operating bandwidth of the energy harvester fabricated; for the experimental investigations, an electrodynamic shaker connected to a shaking table has been used to parametrically stimulate the energy harvesting device. Results showed that the parametric energy harvester without stoppers displayed a weak softening-type nonlinear response; however, with the addition of mechanical stoppers the energy harvester displayed a strong hardening-type nonlinear response which is ideal for capturing kinetic energy over larger bandwidths. The addition of mechanical stoppers on a parametrically excited cantilever beam has significant qualitative and quantitative effects on the nonlinear parametric energy harvesting; the energy harvesting bandwidth was increased in the range of 35–145% by adjusting the stoppers.

There is an increasing need to incorporate an actively controlled drug delivery system (DDS) into the next generation of capsule endoscopy in order to treat diseases in the gastrointestinal tract in a noninvasive way. Despite a number of attempts to magnetically actuate drug delivery mechanisms embedded in endoscopic capsules, longer operating distances and further miniaturization of on-board components are still drawbacks of such systems. In this paper, we propose an innovative magnetic system that consists of an array of magnets, which activates a DDS, based on an overly miniaturized slider–crank mechanism. We use analytical models to compare the magnetic fields generated by cylindrical and arc-shaped magnets. Our experimental results, which are in agreement with the analytical results, show that an optimally configured array of the magnets enhances the magnetic field and also the driving magnetic torque and subsequently, it imposes a high enough force on the piston of the DDS to expel a required dose of a drug out of a reservoir. We conclude that the proposed magnetic field optimization method is effective in establishing an active DDS that is designed to deliver drug profiles with accurate control of the release rate, release amount, and number of doses.