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Piezoelectric materials are an attractive option for electromechanical transduction on the mesoscale due to their intrinsic high force production, large bandwidth, and favorable scaling characteristics. However, the small displacements they inherently produce are typically too small to be directly used in robotic systems, and thus displacement amplification is needed. Here we present a piezoelectric...
GaAs phototransducers with 5 to 12 p/n junctions are shown to demonstrate breakthrough performance in optical conversion efficiency ranging from 65% to just under 70%. In particular, for a current-matched 12 junction device we have recorded an efficiency of 66.5% at Voc = 14.46V (open circuit voltage) with an approximately 650 suns / 841 nm monochromatic source. Our simulations reproduce the PV characteristics...
This paper describes the fabrication, measurement, and modelling of radio-frequency (RF), tunable interdigital capacitors (IDC). The devices utilize electric-field tunable BaxSr(1−x)TiO3 (BST) thin films grown by hybrid molecular beam epitaxy (MBE) on LaAlO3 (LAO) substrates, a first growth of its kind. A high-quality interface was achieved by hot-sputtering epitaxial platinum. S/L-band IDCs demonstrate...
We study the constraints on the electrical and thermal efficiency of an integrated photovoltaic and solar heating system over a large range of possible design parameters. These include the geometry of the set-up, solar concentration ratios, the properties of the materials used (emissivities, thermal conductivities, etc.) and flow rates. Our model quantifies the relative influence exhibited by each...
The needle-sized surgical tools used in arthroscopy, otolaryngology, and other surgical fields could become even more valuable to surgeons if endowed with the ability to navigate around sharp corners to manipulate or visualize tissue. We present a needle-sized wrist design that grants this ability. It can be easily interfaced with manual tools or concentric tube robots and is straightforward and inexpensive...
From the initial availability of spontaneously arising obesity models, newer molecular and genetic technologies have enabled the development of a vast number of new models through regulating specific gene expression in the whole animal, an individual tissue or a specific cell type. These have encompassed the whole animal kingdom from simple species up to primates. These models have facilitated research...
Reconstructed images produced using Electrical Impedance Tomography (EIT) are notorious for their poor spatial resolution. This is largely due to the ill-posed nature of the EIT problem. Much effort has been made in order to improve on spatial resolution of reconstructed images. One of the more direct approaches is by improving the amount of information obtainable. With the development and transition...
We have developed and tested two prototype linear transformer drivers (LTDs): LTD III [1], which is a single LTD cavity that generates a peak electrical power of 79 GW, and Mykonos II [2,3], which is a two-cavity 142 GW LTD module. LTD III is driven by 20 bricks, each of which includes an 85-nH gas switch and two 60-nF capacitors. LTD III has been successfully tested on 3,500 shots at a charge voltage...
A voltage activated barium strontium titanate solidly mounted resonator was fabricated and measured. The barium strontium titanate was deposited on a chemical mechanical polished acoustic Bragg reflector with a surface roughness of 0.504nm RMS. Data was collected on the device at a dc bias voltage range of 0V to 25V in 5V increments. The barium strontium titanate solidly mounted resonator showed an...
A high-efficiency class F MMIC power amplifier designed at 4 GHz using AlGaN/GaN HEMT technology is presented. At VDS = 20 V the circuit produced 69 % PAE, 30.4 dBm of output power and gain of 11.4 dB. When the drain bias was increased to 35 V, the circuit produced 60% PAE, 34.3 dBm of output power and gain of 12.3 dBm, corresponding to a power density of 5.36 W/mm. The results show significant improvement...
The paper reports on the potential of using a type of artificial neural network, the self-organising map, for processing tomographic data from pipe separators to estimate interface levels. This is motivated by a desire to estimate process parameters without recourse to image reconstruction. Results show direct quantitative estimation of volume fraction of two-component flow mixtures containing oil...
Temperature dependent scattering parameter data was collected on a 30 × 30 µm2 voltage activated barium strontium titanate solidly mounted resonator. The frequency variation over the temperature range of −40°C to 120°C normalized to room temperature was as low as 0.41% and as high as 0.84%. The resonant frequency measurements also show a step at −10°C which is believed to be a structural phase transition...
A MMIC frequency doubler using the AlGaN/GaN HEMT technology is presented in this letter. At the design frequency of f0 = 4 GHz and VDS = 35 V the circuit produced maximum output power of 30 dBm with a conversion gain of 5.5 dB, and maximum conversion gain of 13.8 dB with output power of 23 dBm and output fundamental suppression of more than 11 dBc. The best output fundamental suppression was achieved...
This paper reports on the demonstration of a voltage switchable barium strontium titanate solidly mounted resonator filter at 6 GHz. The filter insertion loss was measured to be −4.26 dB and the return loss to be −13.5 dB. The 3 dB bandwidth was measured to be 72 MHz and the quality factor was calculated to be 83. The data was collected at a dc bias voltage of 10 V.
A DC voltage switchable Barium Strontium Titanate (BST) solidly mounted Bulk Acoustic Wave (BAW) capacitively coupled resonator filter with −3.66 dB insertion loss and −13.74 dB return loss has been demonstrated for the first time. The filter consists of two switchable BAW solidly mounted resonators coupled with a high-Q BST capacitor. The electromechanical coupling coefficient of the resonator is...
A dc voltage switchable barium strontium titanate solidly mounted bulk acoustic wave capacitively coupled resonators filter has been demonstrated for the first time. The filter consists of two switchable bulk acoustic wave solidly mounted resonators coupled with a high-Q barium strontium titanate capacitor. The resonators have a measured loaded series and parallel quality factors of 135 and 87 in...
This paper describes research into determining the 3D position of a flow follower in a confined space. The flow follower is able to transmit ultrasonic signals to receivers that are fixed to the wall of the vessel. A key challenge is to accurately determine the location of the flow follower. Transducers must be small, low power and low cost. The present work explores modifications to the Time Difference...
Two high-efficiency Class E MMIC power amplifiers designed at 4 GHz using AlGaN/GaN HEMT technology are presented. The first circuit was designed using a 0.5 mm (4 × 125 um) HEMT and when biased at 25 V drain bias it produced 61 % PAE, 33.8 dBm of output power and maximum gain of 14.8 dB. The second circuit used a 1 mm (8 × 125 um) HEMT and at 30 V drain bias it produced 57% PAE, 36 dBm of output...
Two high-efficiency Class E MMIC power amplifiers designed at 4 GHz using AlGaN/GaN HEMT technology are presented. The first circuit was designed using a 0.5 mm (4 × 125 μm) HEMT and when biased at 25 V drain bias it produced 61 % PAE, 33.8 dBm of output power and maximum gain of 14.8 dB. The second circuit used a 1 mm (8 × 125 μm) HEMT and at 30 V drain bias it produced 57% PAE, 36 dBm of output...
We demonstrate a wire-obstructed cluster flow technique for making periodically modulated plasma waveguides in hydrogen, nitrogen, and argon with sharp, stable voids as short as 50 mum with a period as small as 200 mum.
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