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Oztekin A.,Hi Tec Systems Inc | Oztekin A.,Aviation Research Division
15th AIAA Aviation Technology, Integration, and Operations Conference | Year: 2015

This paper introduces a Facility Risk Assessment Tool (FRAT) to perform data-driven, risk-based assessment of Air Traffic Control (ATC) facilities. FRAT facilitates comparative analysis of facilities within a control group, trending facility performance over time, and drill-down analysis of facility data underlying emerging safety trends to proactively manage risk by assigning oversight resources towards facilities with the highest priority. FRAT calculates quantitative ratings for an ATC facility modeled as an influence network using a set of risk factors. A novel hybrid approach employing network-based fuzzy inference systems is introduced to propagate the model. Statistical analysis of system-wide data for each risk factor is performed to identify outliers and understand underlying distributions. They are then used to define fuzzy membership functions for model variables. Analytical Hierarch Process (AHP) is used to determine rules required by the model’s inference engine. Finally, the paper presents a prototype application of FRAT based on a subset of available domain data. © 2015 American Institute of Aeronautics and Astronautics Inc, AIAA. All right reserved. Source

Huang C.,University of Central Florida | Huang C.,Aviation Research Division | Bunmi Odetola C.,University of Central Florida | Bunmi Odetola C.,University of Ontario Institute of Technology | And 2 more authors.
Applied Catalysis A: General | Year: 2015

Pulse electroplating technology has been applied in the preparation of Pt/C electrocatalysts for hydrogen fuel cell electrodes for decades. The major challenge remaining unsolved is the aggregation of Pt nanoparticles on the carbon support. This research reports a nanoparticle seeded pulse electroplating method for preparing Pt/C electrocatalysts used for oxygen reduction reaction (ORR). Pt or Pt alloy nanoparticles were pre-deposited onto a carbon support as nuclei, followed by Pt pulse electrodeposition. This new approach is able to overcome Pt particle aggregation issues and improve catalyst performance. The technology can also be used for the preparation of core/shell Pt/C electrodes when non-Pt or Pt alloy nanoparticles are used as seeding materials. Experimental results show that a Pt/C electrode with less than 0.1 mg/cm2 Pt loading density, synthesized based on 3.0 nm Pt nanoparticle seeds, can achieve a higher ORR activity than a commercial electrode with 0.5 mg/cm2 Pt loading. When Pt-Pd-Ru alloy nanoparticles of 2.0 nm average diameter were used as seeding nuclei the prepared Pt/C electrode showed higher ORR performance than the commercial electrode, further reduced Pt loading density. Atomic level STEM analyses showed that numerous free Pt atoms were surrounding Pt nanoparticles, serving as nuclei. The seeding atoms, along with nanoparticles, promote the even growth of Pt particles on carbon support during electroplating. This result is verified by SEM images which indicate that electroplated Pt particles on the carbon surface are uniformly distributed and each particle is loosely packed with Pt nanosized flakes. The flower-like structure, with higher surface areas, enhances mass transfer rates and leads to higher ORR efficiencies. Although a commercial Pt/C electrode was used as a baseline catalyst for comparing prepared electrodes, this exploratory research was based on a rotational disk electrode. Fuel cell testing is needed to confirm the finding. Source

Lyon R.E.,Aviation Research Division | Walters R.N.,Aviation Research Division
Journal of Hazardous Materials | Year: 2016

The energy released by failure of rechargeable 18-mm diameter by 65-mm long cylindrical (18650) lithium ion cells/batteries was measured in a bomb calorimeter for 4 different commercial cathode chemistries over the full range of charge using a method developed for this purpose. Thermal runaway was induced by electrical resistance (Joule) heating of the cell in the nitrogen-filled pressure vessel (bomb) to preclude combustion. The total energy released by cell failure, ΔHf, was assumed to be comprised of the stored electrical energy E (cell potential × charge) and the chemical energy of mixing, reaction and thermal decomposition of the cell components, ΔUrxn. The contribution of E and ΔUrxn to ΔHf was determined and the mass of volatile, combustible thermal decomposition products was measured in an effort to characterize the fire safety hazard of rechargeable lithium ion cells. © 2016 Source

Luo M.,Shanghai University of Electric Power | Yao W.,Shanghai University of Electric Power | Huang C.,Aviation Research Division | Wu Q.,Shanghai University of Electric Power | Xu Q.,Shanghai University of Electric Power
RSC Advances | Year: 2015

Pd nanocubes and nanooctahedrons were synthesized via shape-controlled technology and loaded onto a commercial CdS semiconductor photocatalyst for visible light photocatalytic hydrogen production via photooxidation of an aqueous ammonium sulfite solution. High resolution TEM analysis indicates that Pd nanooctahedrons (Pd NOTs) are enclosed by eight {111} facets, while synthesized Pd nanocubes (Pd NCs) are enclosed by six {100} crystal planes. The hydrogen evolution rate of Pd NC loaded CdS photocatalyst (Pd-NCs/CdS) is 1.38 times higher than that of Pd NOT loaded Pd-NOTs/CdS photocatalyst. The electrochemical characterization reveals that the higher photocatalytic activity of Pd-NCs/CdS is attributed to the higher electrochemical active surface area (ECSA) and the electrochemical activities of the Pd {100} crystal planes of Pd NCs. © The Royal Society of Chemistry 2015. Source

Luo M.,Shanghai University of Electric Power | Yao W.,Shanghai University of Electric Power | Huang C.,Aviation Research Division | Wu Q.,Shanghai University of Electric Power | Xu Q.,Shanghai University of Electric Power
Journal of Materials Chemistry A | Year: 2015

The shape effects of Pt cocatalysts on the photocatalytic activity of Pt/CdS for hydrogen production were investigated for the first time. Nano-cubic and nano-spherical Pt particles were prepared via a shape-and-size-controlled technology and loaded onto a CdS semiconductor photocatalyst for visible light photocatalytic hydrogen production from an aqueous ammonium sulfite solution. Unlike conventional photodeposition and impregnation methods, shape-controlled synthesis is able to produce cubic Pt cocatalysts with tunable sizes. Pt nanocube loaded Pt/CdS photocatalysts show strong shape enhanced photocatalytic activity compared to those of Pt nanospherical particle loaded Pt/CdS photocatalysts. With the same Pt loading and Pt particle size the efficiencies of Pt nanocube loaded Pt/CdS catalysts are 52% and 31% higher than those of Pt nanosphere loaded Pt/CdS photocatalysts at 5.7 nm and 4.0 nm, respectively. In comparison with Pt/CdS photocatalysts prepared via photodeposition, more than 25% efficiency improvement has been achieved with the Pt nanocube loaded Pt/CdS photocatalysts. The electrochemical characterization of Pt nanoparticles revealed that photocatalytic activities of Pt/CdS photocatalysts rely on both the shape and size of the Pt particles. The higher the electrocatalytic activity of the Pt nanoparticles, the higher the efficiency of photocatalytic hydrogen evolution. This journal is © The Royal Society of Chemistry. Source

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