Biblio

Solidly mounted resonators (SMRs) built on dielectric acoustic reflectors can save several fabrication steps as well as avoid undesired parasitic effects when exciting extended electrodes via capacitive coupling. In this work we manufacture and measure the frequency response of AlN-based SMRs built on 7-layer ZnO/SiO2 acoustic reflectors with SiO2 working as low impedance material and ZnO as high impedance material. After applying a 700°C treatment, their frequency response is measured again and compared with the pre-treatment measurements.

We present results from a vibrating mesh nebulizer for which the mesh is a micro-machined silicon membrane perforated with up to a thousand micron-sized, pyramidal holes. Finite element modelling is used to better understand the measured results of the nebulizer when tested in the dry state as well as when loaded with a liquid. In particular, we found that the frequency response of the system is well represented by the superposition of the frequency response of its two main subcomponents: the piezo driving unit and the silicon membrane. As such, the system is found to have resonance peaks for which the complete assembly flexes in addition to peaks that correspond to the flexural resonance modes of the silicon membrane on its own. Similarly, finite element modelling was used to understand differences observed between the frequency response measured on the nebulizer in the dry condition compared to its wet or liquid loaded operation. It was found that coupling between the structural and the acoustic domains shifts the resonance peaks significantly to the left of the frequency plot. In fact, it was found that at the operating frequency of the nebulizer, the system resonates in a (0,3) when the membrane is loaded with a liquid compared with a (0,2) resonance mode when it is operating in the dry state.

Since 2016, the northwest power grid has organized new energy sources to participate in the rapid frequency regulation research and carried out pilot test work at the sending end large power grid. The experimental results show that new energy generator has the ability to participate in the grid's rapid frequency regulation, and its performance is better than that of conventional power supply units. This paper analyses the requirements for fast frequency control of the sending end large power grid in northwest China, and proposes the segmented participation indexes of photovoltaic and wind power in the frequency regulation of power grids. In accordance with the idea of "clear responsibilities, various types of unit coordination", the parameter setting of new energy sources rapid frequency regulation is completed based on the coordinated control based on multi-frequency regulation resources in northwest power grid. The new energy fast frequency regulation model was established, through the PSASP power grid stability simulation program and the large-scale power grid stability simulation analysis was completed. The simulation results show that the wind power and photovoltaic adopting differential rapid frequency regulation parameters can better utilize the rapid frequency regulation capability of various types of power sources, realize the coordinated rapid frequency regulation of all types of units, and effectively improve the frequency security prevention and control level of the sending end large power grid.

One of the primary motivations for using ultrasound reflectometry for fingerprint imaging is the promise of increased spoof resistance over conventional optical or capacitive sensing approaches due to the ability for ultrasound to determine the elastic impedance of the imaged material. A fake 3D printed plastic finger can therefore be easily distinguished from a real finger. However, ultrasonic sensors are still vulnerable to materials that are similar in impedance to tissue, such as water or rubber. Previously we demonstrated an ultrasonic fingerprint reader operating with 1.3GHz ultrasound based on pulse echo impedance imaging on the backside silicon interface. In this work, we utilize the large bandwidth of these sensors to differentiate between a finger and materials with similar impedances using the frequency response of elastic impedance obtained by transducer excitation with a wideband RF chirp signal. The reflected signal is a strong function of impedance mismatch and absorption [Hoople 2015].

Multiple Inductive Loop Detectors are advanced Inductive Loop Sensors that can measure traffic flow parameters in even conditions where the traffic is heterogeneous and does not conform to lanes. This sensor consists of many inductive loops in series, with each loop having a parallel capacitor across it. These inductive and capacitive elements of the sensor may undergo open or short circuit faults during operation. Such faults lead to erroneous interpretation of data acquired from the loops. Conventional methods used for fault diagnosis in inductive loop detectors consume time and effort as they require experienced technicians and involve extraction of loops from the saw-cut slots on the road. This also means that the traffic flow parameters cannot be measured until the sensor system becomes functional again. The repair activities would also disturb traffic flow. This paper presents a method for automating fault diagnosis for series-connected Multiple Inductive Loop Detectors, based on an impulse test. The system helps in the diagnosis of open/short faults associated with the inductive and capacitive elements of the sensor structure by displaying the fault status conveniently. Since the fault location as well as the fault type can be precisely identified using this method, the repair actions are also localised. The proposed system thereby results in significant savings in both repair time and repair costs. An embedded system was developed to realize this scheme and the same was tested on a loop prototype.