High temperature field effect hydrogen and hydrocarbon gas sensors based on SiC MOS devices

The growing need for reliable, efficient, high temperature hydrogen and hydrocarbon monitoring has fueled research into novel structures for gas sensing. Metal oxide semiconductor (MOS) devices employing a catalytic metal layer have emerged as one of the leading sensing platforms for such applications, owing to their high sensitivity and inherent capability for signal amplification. The limited operating temperature of such devices employing silicon as the semiconductor has led research efforts to focus on replacing them with devices based on silicon carbide (SiC). More recently, MOS devices having different oxide layers exhibiting improved sensing performance have emerged. Considering the amount of research that has been carried out in this area in recent times, it is important to elucidate the new findings and the gas interaction mechanisms that have been ascribed to such devices, and bring together several theories proposed by different research groups. In this paper we first highlight the needs which have driven research into SiC based field effect hydrogen and hydrocarbon sensors, illustrate the various structures being investigated, and describe the device evolution and current status. We provide several sensing examples of devices that make use of different oxide layers and demonstrate how their electrical properties change in the presence of the gases, as well as presenting the hydrogen gas interaction mechanisms of these sensors.     

Evolution of optical properties with deposition time of silicon nitride and diamond-like carbon films deposited by radio-frequency plasma-enhanced chemical vapor deposition method

The paper presents investigations of the optical properties of thin high-refractive-index silicon nitride (SiN_x) and diamond-like carbon (DLC) films deposited by the radio-frequency plasma-enhanced chemical vapor deposition method for applications in tuning the functional properties of optical devices working in the infrared spectral range, e.g., optical sensors, filters or resonators. The deposition technique offers the ability to control the film's optical properties and thickness on the nanometer scale. We obtained thin, high-refractive-index films of both types at deposition temperatures below 350 °C, which is acceptable under the thermal budget of most optical devices. In the case of SiN_x films, it was found that for short deposition processes (up to 5 min long) the refractive index of the film increases in parallel with its thickness (up to 50 nm), while for longer processes the refractive index becomes almost constant. For DLC films, the effect of refractive index increase was observed up to 220 nm in film thickness.     

Parallel implementation of synthetic aperture radar algorithms

Two sequences of operations necessary for implementation of high resolution image formation in strip and spotlight modes of the synthetic aperture radar (SAR) are presented. The sequences are mapped onto a mesh-connected SIMD architecture. The mapping includes not only parallel implementation of all the basic computation steps, but also all the necessary data transformation and communication operations. Detailed estimates of the processing times are provided for Hughes Research Laboratories Systolic/Cellular architecture.This work was partially supported by NSF grant No MIP-8714689     

Parallel programming on a high‐performance application‐runtime

High‐performance application development remains challenging, particularly for scientists making the transition to a heterogeneous grid environment. In general areas of computing, virtual environments such as Java and .Net have proved to be successful in fostering application development, allowing users to target and compile to a single environment, rather than a range of platforms, instruction sets and libraries. However, existing runtime environments are focused on business and desktop computing and they do not support the necessary high‐performance computing (HPC) abstractions required by e‐Scientists. Our work is focused on developing an application‐runtime that can support these services natively. The result is a new approach to the development of an application‐runtime for HPC: the Motor system has been developed by integrating a high‐performance communication library directly within a virtual machine. The Motor message passing library is integrated alongside and in cooperation with other runtime libraries and services while retaining a strong message passing performance. As a result, the application developer is provided with a common environment for HPC application development. This environment supports both procedural languages, such as C, and modern object‐oriented languages, such as C#. This paper describes the unique Motor architecture, presents its implementation and demonstrates its performance and use. Copyright © 2008 John Wiley & Sons, Ltd.     

WebFlow – a visual programming paradigm for Web/Java based coarse grain distributed computing

We present here recent work at NPAC aimed at developing WebFlow – a general purpose Web-based visual interactive programming environment for coarse grain distributed computing. We follow the 3-tier architecture with the central control and integration WebVM layer in tier-2, interacting with the visual graph editor applets in tier-1 (front-end) and the legacy systems in tier-3. WebVM is given by a mesh of Java Web servers such as Jeeves from JavaSoft or Jigsaw from MIT/W3C. All system control structures are implemented as URL-addressable servlets which enable Web browser-based authoring, monitoring, publication, documentation and software distribution tools for distributed computing. We view WebFlow/WEbVM as a promising programming paradigm and co-ordination model for the exploding volume of Web/Java software, and we illustrate it in a set of ongoing application development activities. © 1997 John Wiley & Sons, Ltd.     

Hydrogen sensing using gold nanoclusters supported on tungsten trioxide thin films

Controlled amounts of chemically synthesised gold (Au) nanoclusters were deposited onto tungsten trioxide (WO₃) nanostructured thin films as sensors for hydrogen. The Au/WO₃ thin films were characterised by XPS, XRD, SEM and TEM. Performance of Au/WO₃ films was tested at operating temperatures varying from room temperature to 450 °C. It was demonstrated that Au metal loading plays an important role in defining enhancement of the sensor response towards hydrogen. “Less is more” principle applies to the reported here sensors as materials made using lower concentration of Au nanoclusters demonstrated significantly better response. HRTEM images of the Au/WO₃ thin films provide evidence that the more active sensors are enriched with smaller Au nanoparticles (≤5 nm). Fast response towards H₂ within a wide range of industrially relevant concentrations, excellent baseline stability and signal reproducibility at optimized operating temperature demonstrate feasibility of this novel approach toward fabrication of sensors.     

Parallel implementation of neural networks

This paper presents systematic methods, based on graph theoretic approach, for mapping of neural networks onto mesh connected SIMD arrays. The methods are applicable to a large class of multilayer network models, which can be represented in terms of sparse matrix vector operations. The class of computers, that the mappings are suitable for, encompasses most of the experimental and commercial mesh-connected SIMD arrays of processors. There are three methods described in the paper, one for the case of a processor array, which is larger or equal to the network size and two for the partitioned case, i.e. array smaller than the input data size. The methods are illustrated on an example of a multilayer perceptron with back-propagation learning, which consists ofn nuerons ande synaptic connections. For the first method, the processor array is assumed to be of sizeN×N, whereN ² n+e, and the required local memory of processors is limited to only a few registers. The implementation of a single iteration of a recall phase according to the method requires 24(N-1) shifts. For this method we have developed a software tool, which generates a sequence of pseudo instructions, such as elemental data shift and arithmetic operations, that implement a given neural network on a given size processor array. For the two partitioned methods, the processor array is of sizeP×P, whereP ²n+e, and the local memory in the processors is of sizeO(K). The faster of the two methods requiresO(N ³/P ³ K) time for an iteration of the recall or learning phase.This research was supported in part by the National Science Foundation under grant MIP-8714689 and IRI-9145810.Preliminary versions of the results contained in this paper appear in the International Conference on Applications-Specific Array Processors 1990 and the IEEE Workshop on VLSI Signal Processing 1990.     

Rapid polymer fiber airbrushing: Impact of a device design on the fiber fabrication and matrix quality

Polymer fiber matrixes can be used in a variety of applications, including electronics, tissue engineering, or coatings. Polymer airbrushing (air‐blast spinning) has the potential to overcome some of the limitations of electrospinning and has the advantage of depositing nanofibers directly on various materials. The airbrushing technique has yet to be better evaluated and optimized to achieve a higher fiber reproducibility and bulk material quality. In this study, a gravity‐fed brush (commercial airbrush) and syringe‐pump‐operated brush [custom‐built airbrush (CBA)] were compared to determine the effect of the coaxial brush design on the efficacy of fiber fabrication. At comparable fiber deposition rates, gas pressures, and polymer concentrations, the CBA produced smaller and more uniform fibers with a lower average size of polymer beads. The obtained data suggest that capillary pinching was the dominant mechanism responsible for fiber formation when we used the CBA. The estimated pinching energy was lower for the CBA at the compared polymer concentrations and at a high gas pressure. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42813.     

Living Environment, Social Participation and Wellbeing in Older Age: The Relevance of Housing and Local Area Disadvantage

This paper explores the links between the quality of the living environment, social participation and wellbeing in older age using data from the Household, Income and Labour Dynamics in Australia (HILDA) survey. Using nine waves of the data, random-effects models are estimated to isolate the ‘net effect’ of the living environment on social participation and well being, while controlling for a number of background factors. The findings reveal a considerable penalty associated with living in disadvantaged housing and disadvantaged areas on some of the critical aspects of social participation, such as the frequency of contacts with other people, and access to social support, as well as on overall wellbeing of older persons. The contribution of this paper lies in demonstrating that the quality of one’s living environment plays a significant role in shaping social participation and wellbeing in older age based on robust methodology and reliable longitudinal data.