Piezoelectric Sensors Operating at Very High Temperatures and in Extreme Environments Made of Flexible Ultrawide-Bandgap Single-Crystalline AlN Thin Films

Extreme environments are often faced in energy, transportation, aerospace, and defense applications and pose a technical challenge in sensing. Piezoelectric sensor based on single-crystalline AlN transducers is developed to address this challenge. The pressure sensor shows high sensitivities of 0.4–0.5 mV per psi up to 900 °C and output voltages from 73.3 to 143.2 mV for input gas pressure range of 50 to 200 psi at 800 °C. The sensitivity and output voltage also exhibit the dependence on temperature due to two origins. A decrease in elastic modulus (Young's modulus) of the diaphragm slightly enhances the sensitivity and the generation of free carriers degrades the voltage output beyond 800 °C, which also matches with theoretical estimation. The performance characteristics of the sensor are also compared with polycrystalline AlN and single-crystalline GaN thin films to investigate the importance of single crystallinity on the piezoelectric effect and bandgap energy-related free carrier generation in piezoelectric devices for high-temperature operation. The operation of the sensor at 900 °C is amongst the highest for pressure sensors and the inherent properties of AlN including chemical and thermal stability and radiation resistance indicate this approach offers a new solution for sensing in extreme environments.     

A comparison of different geometrical elements to model fluid wicking in paper-based microfluidic devices

Recently, microfluidic paper-based analytical devices (μPADs) have outstripped polymeric microfluidic devices in the ease of fabrication and simplicity. Surface tension-based fluid motion in the paper's porous structure has made the paper a suitable substrate for multiple biological assays by directing fluid into multiple assay zones. The widespread assumption in most works for modeling wicking in a paper is that the paper is a combination of capillaries with the same diameter equal to the effective pore diameter. Although assuming paper as a bundle of capillaries gives a good insight into pressure force that drives the fluid inside the paper, there are some difficulties using the effective pore radius. The effective pore radius is totally different from the average geometrical pore radius which makes it impossible to predict wicking in μPADs based on geometrical parameters. In this article, we introduce different analytical and numerical models to investigate the possibility of determining the permeability of the paper, based on geometrical parameters rather than effective parameters. The lattice Boltzmann method is used for numerical simulations. The permeability of each of the proposed models was compared with the experimental permeability. Results indicated that assuming paper as a combination of capillaries and annuluses leads to accurate results that totally depend on average geometrical values rather than effective values. This paves the way for prediction of the fluid wicking only by considering average geometrical pore and fiber diameters.     

Stability and stabilization of linear sampled-data systems with multi-rate samplers and time driven zero order holds

In multi-rate sampled-data systems, a continuous-time plant is controlled by a discrete-time controller which is located in the feedback loop between sensors with different sampling rates and actuators with different refresh rates. The main contribution of this paper is to propose sufficient Krasovskii-based stability and stabilization criteria for linear sampled-data systems, with multi-rate samplers and time driven zero order holds. For stability analysis, it is assumed that an exponentially stabilizing controller is already designed in continuous-time and is implemented as a discrete-time controller. For each sensor (or actuator), the problem of finding an upper bound on the lowest sampling frequency (or refresh rate) that guarantees exponential stability is cast as an optimization problem in terms of linear matrix inequalities (LMIs). Furthermore, sufficient conditions for controller synthesis are formulated as LMIs. It is shown through examples that choosing the right sensors (or actuators) with adequate sampling frequencies (or refresh rates) has a considerable impact on stability of the closed-loop system.     

Recent Progress in Photonic Processing of Metal‐Oxide Transistors

Over the past few decades, significant progress has been made in the field of photonic processing of electronic materials using a variety of light sources. Several of these technologies have now been exploited in conjunction with emerging electronic materials as alternatives to conventional high‐temperature thermal annealing, offering rapid manufacturing times and compatibility with temperature‐sensitive substrate materials among other potential advantages. Herein, recent advances in photonic processing paradigms of metal‐oxide thin‐film transistors (TFTs) are presented with particular emphasis on the use of various light source technologies for the photochemical and thermochemical conversion of precursor materials or postdeposition treatment of metal oxides and their application in thin‐film electronics. The pros and cons of the different technologies are discussed in light of recent developments and prospective research in the field of modern large‐area electronics is highlighted.     

A comparative study of the effects of thrombin and electrodesiccation used for haemostasis on inflammation and adhesion formation

Electrodesiccation or chemical agents, such as thrombin and fibrin sealant, may be used to control oozing in the peritoneal cavity. Electrodesiccation is time consuming and associated with adjacent thermal damage. Adhesion formation remains a concern with the use of thrombin and fibrin sealant. In this study, adhesion formation and various histological parameters of inflammation were evaluated following haemostasis with electromicrodesiccation or thrombin in the rabbit model (n = 36). Following laparotomy, the right uterine horn was subjected to a measured injury producing sufficient oozing. After the injury was effected, the animals were randomized to haemostasis with electromicrodesiccation (n = 18) or thrombin (n = 18). In the first phase of the study, the histological parameters of acute injury and haemostasis with either modality were evaluated in two animals in each group. In the second phase, one, two and 10 animals, in each group, were submitted to second-look laparotomy on post-operative days 2, 7, and 15, respectively and the type and extent of adhesions were quantified. Histological parameters of inflammation as well as the type and extent of adhesions were comparable between the two groups. We conclude that local application of thrombin is not associated with a statistically greater degree of post-operative adhesions when compared to electromicrodesiccation.     

Multidisciplinary design of a guided flying vehicle using simplex nondominated sorting genetic algorithm II

This paper presents design of a typical Guided Flying Vehicle (GFV) using the multidisciplinary design optimization (MDO). The main objectives of this multi-disciplinary design are maximizing the payload’s weight as well as minimizing the miss distance. The main disciplines considered for this design include aerodynamics, dynamic, guidance, control, structure, weight and balance. This design of GFV is applied to three and six Degree of Freedom (DOF) to show comparison of simulation results. The hybrid scheme of optimization algorithm is based on Nelder-Mead Simplex optimization algorithm and Nondominated Sorting Genetic Algorithm II (NSGA II), called Simplex-NSGA II. This scheme is implemented for finding an optimal solution through the MDO. The Simplex-NSGA II method is a heuristic optimization algorithm that applies to multi-objective functions and the results are then compared with the most famous algorithms, like Nondominated Sorting Genetic Algorithm II (NSGA II) and Multi-Objective Particle Swarm Optimization (MOPSO). Simulation results demonstrate the superior performance of the Simplex-NSGA II over NSGA II and MOPSO. Also, it is used in this study in order to achieve an optimal solution using MDO in both 3DOF and 6DOF simulations of GFV to reach desirable performance index.     

Colour Doppler hysterosalpingosonography: a simple and potentially useful method to evaluate fallopian tubal patency

The functional state of the amacrine cells which contain enkephalin-, neurotensin- and somatostatin-like immunoreactivity of the chicken retina was monitored by measuring the rate of change in the levels of [Leu]enkephalin-like immunoreactivity in the retina. Dark-adapted birds were exposed to lights of different intensities for 12 h. At light levels of < or = 0.03 microW/cm2, the ENSLI amacrine cells were highly active but, by 0.08 microW/cm2, they reached a state of maximum inactivation. Thus, the ENSLI amacrine cells act as flip-flop devices, inactivated by critical levels of light, which correspond to those which inactivate pineal melatonin synthesis. They may, therefore, be involved in retinal pathways which signal the difference between day and night.     

Operation principle and applications of multiterminalsuperconductive magnetic energy storage systems

The basic operation principle of a multiterminal superconductive magnetic energy storage (MSMES) system is introduced. The motivation for developing the MSMES systems is to combine and maximize the flexibility benefits provided by energy storage and the controllability benefits provided by power electronic systems. A MSMES system can be used simultaneously as an energy storage device and a power flow control device. This attribute enables MSMES systems to perform some unique functions in electric power systems. Potential applications of MSMES systems and their impact on solving the problems faced by power systems today are discussed     

Numerical modeling of two-phase supersonic ejectors for work-recovery applications

An ejector is a fluid pumping device that uses the energy of a high pressure motive fluid to raise the pressure of a secondary lower-pressure fluid. Motive pressure is converted into momentum through a choked nozzle creating a high velocity jet which entrains the surrounding low-momentum suction flow. The two streams mix and finally pressure is recovered through a diffuser. There has been little progress on high fidelity modeling of the expanding supersonic two-phase flow in refrigerant expansion work recovery ejectors due to rather complex physics involving nonequilibrium thermodynamics, shear mixing, and void fraction-dependent speed of sound. However, this technology can be applied to significantly increase the efficiency of space cooling and refrigeration devices. The approach developed in this study integrates models for real-fluid properties, local mass and energy transfer between the phases, and two-phase sonic velocity in the presence of phase change into a commercial CFD code. The intent is to create a practical design tool with better fidelity than HEM CFD models yet with tractability lacking in current boundary tracking phase change CFD models. The developed model has been validated through comparison of key performance metrics against test data under certain operating conditions.