The authors proposed a flexible microresonator based on nanowires composed of Ⅱ–Ⅵ compounds to detect the small strain caused by external motion. The nanowire ring resonator is embedded in polydimethylsiloxane (PDMS) flexibility to improve the coupling efficiency. In this work, CdS nanowire is fabricated onto a PDMS flexible substrate. With the help of a fibre tip, the single nanowire is manipulated under a microscope, allowing the curved line to be a ring and making the litter overlapping. This overlap increases coupling efficiency and sensor performance. The ring cavity has the parameters of diameter 1 µm, length 75 µm and radius ∼10 µm. Experiments demonstrated the process of fabricating a strain sensor and detected peak shifts. This resonant wavelength appeared red-shift and linear tuned when stretching the flexible substrate. The quality factor was about 2000 and the gauge factor was about 80 nm per stretching unit. Being a small structure and high sensitivity, the sensor can be integrated into the chip. This promotes the development of miniaturisation to some extent. As a result, this work is beneficial to optical manipulation, further being extended to the tunable light source.

The study reported here shows that PDMS polymer resonators can be tuned using an external electric field. The studies also show the potential for high-resolution electric field sensors and non-contact displacement sensors. The sensitivity of the microsphere to an applied external electric field can be improved if the microsphere is poled in an external electric field. In addition, if the polymer microsphere is doped with magnetic polarizable particle, it can be tuned using an external magnetic field, and could potentially be used as a magnetic field sensor. The data reported here show a sensor resolution of the order of mT using a microresonator with optical quality factor of 107. This resolution could be improved using softer polymers and magnetic polarizable particles with larger magnetic permeability.

Thrust testing units with a piezoelectric dynamometer have unique traits such as excessive stiffness, tremendous measurement accuracy, dynamic performance and no hysteresis. These are widely used in the applications requiring force/thrust measurements in the aerospace industry and high-end tool condition monitoring. The performance of these units is necessary to be evaluated. In this study, an improved layout of six-degree of freedom force/thrust measurement stand is proposed and analysed theoretically and experimentally. The measurement stand is a structural component to measure six components of force, such as axial force/thrust (F_X , F_Y , and F_Z ) and other components (M_X , M_Y , and M_Z ). Test stand consists of seven piezoelectric sensors in two sections. The front part consists of four piezoelectric force sensors, while the rear part consists of three sensors. The rear section is hexagonal, with three sensors mounted at 120°. The measurement stand can measure the principal force/thrust up to 50,000 N. A mathematical model is derived for every sensor against forces in all directions. To calibrate the stand, a calibration platform is designed and fabricated. The calibration platform can generate a range of forces/moments. Calibration experiments verifies that the measurement stand is fairly functional to measure variety of forces/moments with high repeatability.

This Letter proposes the application of RF technology for the non-destructive detection of spoiled coconut at the pre-processing stage. Since the dielectric property of coconut water changes at different stages of coconut, the sensor measures the content of water inside a coconut sample non-destructively at 2.45 GHz. The sensor has been trained to determine the threshold water level between healthy and spoiled coconut which in turn can be used to sort the coconuts. The measurement results have been presented for different processing stages of coconut for different samples. Detecting coconut quality through dielectric sensing reveals some very impressive results and opens the doors for better consumption.

Mechanical–structural vibration and/or rotational parts of the targets will induce micro-Doppler frequency in addition to the main Doppler components. In the today's military era, detections, measurements and decision making have to be made after the thorough analysis of main and micro-Doppler signatures of the targets to get their full profile particularly for defence applications. In addition, few of the low radar cross-section targets can be detected only by extracting and processing the micro-Doppler signatures corresponding to the rotations of their propellant rotor blades. Therefore, experimental studies to measure the micro-to-macro rotation/motion generated Doppler frequency and performing its associated measurements become significant. The authors built a C-band (5.3 GHz) continuous wave radar and used it to measure the Doppler frequency generated by micro-to-macro rotations/motions. The detection and measurement accuracy of the developed radar is assessed by series of different open-environment experimental case studies: revolution per minute measurement of rotating blades, separation of multiple rotating blades, oscillation per minute measurement of a swinging pendulum, detection of approaching/receding motion and the Doppler signature extraction of walking/jogging/cycling person. All these measurement values are validated against the standard master instrument readings and theoretical calculations. Finally, the limitations of this system and required near-future research works to enhance its performance are listed.

Frequency response analysis is widely used as a method for the offline diagnosis of winding deformations in power transformers. To apply it to a working transformer, people need to determine how to inject the excitation signal and measure the response signal for windings that bear a rated voltage and current. In this study, a method to obtain the frequency response curve online is proposed. It uses the principle of magnetic field coupling to inject a frequency sweep signal into the windings through a Rogowski coil. Another Rogowski coil sensor placed at the root of a high-voltage bushing is used to measure the response current signal. Experiments on a 72.5 kV bushing show that metal accessories of the bushing have no influence on the injection or the measurement. The feasibility of this method was verified by experiments on charged 110/35/10 kV transformers at a factory and a working 35 kV transformer in a power station. The results show that it is safe to install the Rogowski coil at the root of the high-voltage bushing. The excitation signal can be injected into live windings and the response signal is measurable. Strong electromagnetic power frequency noise can be reduced and the frequency response curve can be measured online.

This chapter discusses new approaches to sense and acquire vibration data and to pre-process these data on aeroelastic certification test flights. These new approaches aim to reduce the time to identify the aeroelastic phenomenon and to reduce the size of hardware that must be boarded in the aircraft, thus minimising the risks and costs of the vibration tests. The presented experiments construct a way to develop a non -contact measurement system for flight vibration tests in the aircraft certification process. These experiments have shown that the techniques used today for in-flight trials will be obsolete in the near future, as the aeronautical structures are becoming lighter every day, thus not admitting any additional mass for instrumentation in-flight trials.

Electric and magnetic fields are too important and too common to be neglected by nature in its grand design. Many animals and organisms have found ways to take advantage of these fundamental forces for sensing and actuation. The electric field in particular is used for both sensing and actuation. Almost all rays and sharks can sense electric fields produced by prey, as can some catfish, eels, and the platypus. Electric fields are sensed through use of special gelatinous pores that form electroreceptors called ampullae of Lorenzini. Sensing can be passive or active. Sharks and rays use passive sensing; prey is located by sensing weak electric fields produced by the muscles and nerves in the prey. Some animals, such as the electric fish, can generate electric fields for the purpose of active electrolocation of prey. The same basic sensory system is used by young sharks for protection by freezing in place when electrolocation fields are detected. But perhaps, the best known example of electrolocation is the platypus, which uses electroreceptors in its bill to hunt by night. Actuation is just as common and is used primarily to stun prey, and also for protection. The torpedo or electric ray (genus Torpedinidae) is one of some 70 species of rays that can produce electric charge and apply it in a manner similar to a battery. The charge is produced in a pair of electric organs made of plates connected to a nervous system that controls them. In rays, these biological batteries are connected in parallel to produce low -voltage, high -current sources. The range is between 8V and more than 200 V, with currents that can reach a few amperes. Another example is the electric eel (Electrophorus electricus). Since it lives in freshwater, which is less conductive than seawater, it has its plates in series to produce higher voltages (up to 600 V at perhaps 1 A, in short pulses).

With the development of large-aperture and high-frequency radio telescopes, a surface adjustment procedure for the compensation of surface deformations has become of great importance. In this study, an innovative surface adjustment strategy is proposed to achieve an automated adjustment for the large radio telescope with adjustable dual reflectors. In the proposed strategy, a high-precision and long-distance measurement instrument is adopted and installed on the back of the sub-reflector to measure the distances and elevation angles of the target points on the main reflector. Here, two surface adjustment purposes are discussed. The first purpose is to ensure that the main reflector and sub-reflector are always positioned at their ideal locations during operation. The second purpose is to adjust the main reflector to the location of the best fitting reflector, and the sub-reflector to the focus of the best fitting reflector. Next, the calculation procedures for the adjustments of the main reflector and the sub-reflector are discussed in detail, and corresponding simulations are carried out to verify the proposed method. The results show that the proposed strategy is effective. This study can provide helpful guidance for the design of automated surface adjustments for large telescopes.

The surface stress-based biosensor has been applied in fast and sensitive identification of Escherichia coli (E. coli)with significance for public health, food, and water safety. However, the stable sensitive element of flexible biosensor based on surface stress is still crucial and challengeable. Here, the authors reported surface stress-induced biosensors based on double-layer stable gold nanostructures (D-AuNS-SSMB) for E. coli O157:H7 detection. Bacterial detection demonstrates the high stability of the biosensor. The resistance change of biosensor is linear to the logarithmic value of the E. coli O157:H7 concentrations ranging from 10³ to 10⁷ CFU/mL with a limit of detection (LOD) of 43 CFU/mL. The captured signals of D-AuNS-SSMB comes from surface stress generated by antigen–antibody binding. In addition, the biosensor exhibits good stability, reproducibility and specificity in detection of E. coli O157:H7 as well. This study provides a new preparation method of stable sensitive element for the E. coli detection.