Synthetic Aperture Anomaly Imaging

Previous research has shown that in the presence of foliage occlusion, anomaly detection performs significantly better in integral images resulting from synthetic aperture imaging compared to applying it to conventional aerial images. In this article, we hypothesize and demonstrate that integrating detected anomalies is even more effective than detecting anomalies in integrals. This results in enhanced occlusion removal, outlier suppression, and higher chances of visually as well as computationally detecting targets that are otherwise occluded. Our hypothesis was validated through both: simulations and field experiments. We also present a real-time application that makes our findings practically available for blue-light organizations and others using commercial drone platforms. It is designed to address use-cases that suffer from strong occlusion caused by vegetation, such as search and rescue, wildlife observation, early wildfire detection, and sur-veillance

ZnO nanowire array growth on precisely controlled patterns of inkjet-printed zinc acetate at low-temperatures.

ZnO nanowires have been fabricated through the hydrothermal method on inkjet-printed patterns of zinc acetate dihydrate. The silicon substrate used was heated accordingly during the printing period in order to maintain good spatial uniformity of the zinc acetate nanoparticles, responsible for the pattern morphology. Printing more than one pass of precursor ink leads to an increase in seed layer thickness that subsequently alters the density and dimensions of nanowires. It has been demonstrated that with the right inkjet-printing parameters and substrate temperature, ZnO nanowires can be effortlessly fabricated in accordance with the desired pattern variations under low temperature and mild conditions that ensures promising applications in optoelectronic devices.Engineering and Physical Sciences Research CouncilThis is the author accepted manuscript. The final version is available from the Royal Society of Chemistry via http://dx.doi.org/10.1039/C6NR02962

Oxygen Defect-Induced Metastability in Oxide Semiconductors Probed by Gate Pulse Spectroscopy.

We investigate instability mechanisms in amorphous In-Ga-Zn-O transistors based on bias and illumination stress-recovery experiments coupled with analysis using stretched exponentials and inverse Laplace transform to retrieve the distribution of activation energies associated with metastable oxygen defects. Results show that the recovery process after illumination stress is persistently slow by virtue of defect states with a broad range, 0.85 eV to 1.38 eV, suggesting the presence of ionized oxygen vacancies and interstitials. We also rule out charge trapping/detrapping events since this requires a much smaller activation energy ~0.53 eV, and which tends to be much quicker. These arguments are supported by measurements using a novel gate-pulse spectroscopy probing technique that reveals the post-stress ionized oxygen defect profile, including anti-bonding states within the conduction band.Authors thank to the EU-FP7 under Project ORAMA CP-IP 246334-2. Also, they would like to thank Dr. J. W. Jin, University of Cambridge, UK for technical discussions.This is the final version of the article. It first appeared from Nature Publishing Group via http://dx.doi.org/10.1038/srep1490

Localized Tail States and Electron Mobility in Amorphous ZnON Thin Film Transistors.

The density of localized tail states in amorphous ZnON (a-ZnON) thin film transistors (TFTs) is deduced from the measured current-voltage characteristics. The extracted values of tail state density at the conduction band minima (N(tc)) and its characteristic energy (kT(t)) are about 2 × 10(20) cm(-3)eV(-1) and 29 meV, respectively, suggesting trap-limited conduction prevails at room temperature. Based on trap-limited conduction theory where these tail state parameters are considered, electron mobility is accurately retrieved using a self-consistent extraction method along with the scaling factor '1/(α + 1)' associated with trapping events at the localized tail states. Additionally, it is found that defects, e.g. oxygen and/or nitrogen vacancies, can be ionized under illumination with hv ≫ E(g), leading to very mild persistent photoconductivity (PPC) in a-ZnON TFTs.This is the final published version. It has been published by NPG in Scientific Reports here: http://www.nature.com/articles/srep13467#abstract

Interactive Intelligent Systems and Haptic Interfaces

No abstract available

Stereoscopic Depth Perception Through Foliage

Both humans and computational methods struggle to discriminate the depths of objects hidden beneath foliage. However, such discrimination becomes feasible when we combine computational optical synthetic aperture sensing with the human ability to fuse stereoscopic images. For object identification tasks, as required in search and rescue, wildlife observation, surveillance, and early wildfire detection, depth assists in differentiating true from false findings, such as people, animals, or vehicles vs. sun-heated patches at the ground level or in the tree crowns, or ground fires vs. tree trunks. We used video captured by a drone above dense woodland to test users' ability to discriminate depth. We found that this is impossible when viewing monoscopic video and relying on motion parallax. The same was true with stereoscopic video because of the occlusions caused by foliage. However, when synthetic aperture sensing was used to reduce occlusions and disparity-scaled stereoscopic video was presented, whereas computational (stereoscopic matching) methods were unsuccessful, human observers successfully discriminated depth. This shows the potential of systems which exploit the synergy between computational methods and human vision to perform tasks that neither can perform alone

Threshold Voltage Compensation Error in Voltage Programmed AMOLED Displays

A new accurate voltage-programmed pixel circuit for active matrix organic light-emitting diode (AMOLED) displays is presented. Composed of three TFTs and one storage capacitor, the proposed pixel circuit is implemented both in a-Si and a-IGZO TFT technologies for the same pixel size for fair comparison. The simulation result for the a-Si-based design shows that, during a programming time of 90 μs, the pixel circuit was able to compensate for a 3V threshold voltage (Vth) shift of the drive TFT with almost no error. In contrast, the a-IGZO-based pixel circuit, has a larger current error (of around 8%), despite its proven three-fold higher speed.Authors thank to the EPSRC under Project EP/M013650/1

Invited - Droplets driving and sensing pixel circuits for thin film transistor-based digital microfluidics

Thin film transistor-based active-matrix digital microfluidics (AM-DMF) is an emerging and promising technology for large-scale parallel biological sample handling. With electrowetting-on-dielectric (EWOD) method, DMF chip can realize accurately controlling discrete droplets, thus it has great application prospects in biology, chemistry, and drug discovery. With the rapid development of micro-analysis and detection requirements, the precise control of droplets in DMF chips is increasingly required, so it is necessary to conduct the real-time sensing of droplet position. Figure 1 shows the designed droplet position detection unit circuit. The circuit consists of six thin film transistors, T1-T6. The input signals mainly include the enable signal Ven, the reverse enable signal Venb, the discharge signal Vdischarge, the detection signal Vdetect, and the ground signal Vgnd. The signal Vdrive is the driving voltage applied for driving electrode. Cpixel is the equivalent capacitance between the two plates of a pixel electrode in a microfluidic chip. Vout is the output voltage signal. Please click Download on the upper right corner to see the full abstract

Printed subthreshold organic transistors operating at high gain and ultralow power.

Overcoming the trade-offs among power consumption, fabrication cost, and signal amplification has been a long-standing issue for wearable electronics. We report a high-gain, fully inkjet-printed Schottky barrier organic thin-film transistor amplifier circuit. The transistor signal amplification efficiency is 38.2 siemens per ampere, which is near the theoretical thermionic limit, with an ultralow power consumption of 60 decibels and noise voltage of <0.3 microvolt per hertz1/2 at 100 hertz.EPSRC, EC, China Scholarship Council, IEEE Electron Device Societ

Inkjet-printed Ag electrodes on paper for high sensitivity impedance measurements

Low-cost electrodes were fabricated by a standard office inkjet printer with commercial silver ink on glossy paper. Compared to conventional thin-film metal thermal evaporated gold electrodes, the paper-based ones show a two-order enhanced sensitivity for impedance measurement over a low frequency range. The high surface roughness of paper electrodes increases the effective area of the electrolyte–electrode double layer capacitance, and therefore reduces the measured impedance at low frequency range. A passivation layer on the top of the paper electrodes is used to mimic the behaviour of the double layer capacitance. The surface roughness was characterized by optical microscopy and atomic force microscopy. Finite element analysis and impedance equivalent model analysis were also performed for different thin-film electrode devices.This is the author accepted manuscript. The final version is available from The Royal Society of Chemistry via http://dx.doi.org/10.1039/c6ra18645