Evaluating Queries and Updates on Big XML Documents

In this paper we present Andromeda, a system for processing queries and updates on large XML documents. The system is based on the idea of statically and dynamically partitioning the input document, so as to distribute the computing load among the machines of a MapReduce cluster.     

Engaging residents in affordable housing—resident engagement pilot at Denver Housing Authority Westridge apartments

Denver Housing Authority (DHA) has invested considerably into designing, building, and maintaining a resource efficient portfolio and this effort is becoming increasingly comprehensive as they continuously refine and build upon their approach. One of the more recent strategies was to incorporate resident engagement efforts focused on energy and water efficiency into their programming as a way not only to maximize realized energy savings from these investments but to also to engage with building occupants around sustainability initiatives and develop a holistic approach to reducing their resource consumption. In 2014, DHA hired Energy Outreach Colorado and Group14 Engineering (the Team) to develop and implement a voluntary program designed to encourage positive environmental and social actions around energy and water use. The Team developed a comprehensive resident engagement and outreach program involving on-site staff, resident leaders, and residents. The program plan identified both low/no-cost solutions and more extensive outreach efforts targeted at the DHA Westridge community. Upon completion of the pilot, the program achieved 24,864 kWh (4.5%) savings in electricity consumption. Valued at the 2014 effective blended rate for Westridge, this equals $3493 dollars in annual savings and a program payback of 11 years. The project’s participation goal was exceeded, with 60% of the neighborhood households participating in the program. The team concluded that achieving savings through resident engagement is possible but also the level of effort put forth in the project is important to consider.     

Chaos in a novel Wien bridge-based RC chaotic oscillator: dynamic analysis with application to image encryption

Analog Integrated Circuits and Signal Processing -     

Weather extremes and household welfare in rural Kenya

Households in rural Kenya are sensitive to weather shocks through their reliance on rain-fed agriculture and livestock. Yet the extent of vulnerability is poorly understood, particularly in reference to extreme weather. This paper uses temporally and spatially disaggregated weather data and three waves of household panel survey data to understand the impact of weather extremes –including periods of high and low rainfall, heat, and wind– on household welfare. Particular attention is paid to heterogeneous effects across agro-ecological regions. We find that all types of extreme weather affect household well-being, although effects sometimes differ for income and calorie estimates. Periods of drought are the most consistently negative weather shock across various regions. An examination of the channels through which weather affects welfare reveals that drought conditions reduce income from both on- and off-farm sources, though households compensate for diminished on-farm production with food purchases. The paper further explores the household and community characteristics that mitigate the adverse effects of drought. In particular, access to credit and a more diverse income base seem to render a household more resilient.     

A micro-solid oxide fuel cell system as battery replacement

The concept and the design of a micro-solid oxide fuel cell system is described and discussed. The system in this study is called the ONEBAT system and consists of the fuel cell PEN (positive electrode – electrolyte – negative electrode) element, a gas processing unit, and a thermal system. PEN elements of free-standing multi-layer membranes are fabricated on Foturan^® and on Si substrates using thin film deposition and microfabrication techniques. Open circuit voltages of up to 1.06 V and power of 150 mW cm⁻² are achieved at 550 °C. The membranes are stable up to 600 °C. The gas processing unit allows butane conversion of 95% and hydrogen selectivity of 83% at 550 °C in the reformer and efficient after-burning of hydrogen, carbon monoxide, and lower hydrocarbons in the post-combustor. Thermal system simulations prove that a large thermal gradient of more than 500 °C between the hot module and its exterior are feasible. The correlation between electrical power output – system size and thermal conductivity – heat-transfer coefficient of the thermal insulation material are shown. The system design studies show that the single sub-systems can be integrated into a complete system and that the requirements for portable electronic devices can be achieved with a base unit of 2.5 W and a modular approach.     

Three-dimensional SU-8 sub-micrometer structuring by electron beam lithography

We demonstrate electron beam lithography on the negative tone electron resist SU-8 to fabricate self-supporting three-dimensional structures in sub-micrometer range. Applying SU-8 thin films spin cast on glass substrates and forming layers of 1 μm thickness, the structuring is performed in a two step process. First, the SU-8 film is exposed for supporting structures down to the substrate, a second exposure step with accordingly modified parameters leads to elevated structures. Applications as microscale shadow masks for evaporation based deposition processes and microfluidics are discussed.     

Interface properties and deep levels in InGaAsN/GaAs and GaAsN/GaAs heterojunctions

Interface properties of dilute slightly lattice mismatched GaAsN/GaAs (0.35 at.% N) and closely lattice matched InGaAsN (1 at.% In, 0.35 at.% N) heterojunctions (HJs) were studied by means of capacitance–voltage profiling, deep levels transient spectroscopy (DLTS) and current–voltage measurements. It is found that the lattice matched HJs show no electrical breakdown when the space charge region crosses the interface. The carrier concentration profiles in such HJ show, as expected, the accumulation region on the low-bandgap side and the depletion region on the high-bandgap side of the HJ. This is not the case for the GaAsN/GaAs (GaAsN layer on top) and the GaAs/GaAsN (GaAs layer on top) HJ. The density of deep traps in GaAsN, InGaAsN films and in GaAs films grown on GaAsN underlayers was very much higher than in epitaxial GaAs films. The dominant deep centers were the EL6 and the EL3 electron traps. The interface regions of the GaAs/GaAsN and the InGaAsN/GaAs HJs were shown to be enriched by EL3 traps, while for the GaAsN/GaAs HJ those regions were enriched by EL6 traps which was associated with the former films being Ga-rich and thus facilitating incorporation of oxygen on As sites.     

Studies of deep centers in dilute GaAsN and InGaAsN films grown by molecular beam epitaxy

Deep levels spectra DLTS, 77 K photoluminescence (PL) spectra and photosensitivity were measured for GaAsN and InGaAsN films with low N and In concentration grown by molecular beam epitaxy and in GaAs films grown on GaAsN buffer. It is shown that the bandedge luminescence intensity is greatly decreased in GaAsN, GaAs/GaAsN and particularly in InGaAsN structures compared to the homoepitaxial GaAs. Comparison of the DLTS and PL spectra strongly suggests that the main recombination center in such films is the EL3-like electron trap whose concentration greatly increases upon In and N incorporation into the solid solution. Based on published results the trap is associated with substitutional oxygen on As site and the results are discussed in view of such possible assignment.