Investigation of variables in turbine erosion, influence of aerodynamic and geometric parameters

Influence of aerodynamic and geometric parameters in turbine erosio

Geospatial Analysis of Rurality and Food Banks in Appalachian Ohio

Introduction: Food insecurity is a problem for individuals across Ohio, including those living in Appalachia. Adequate access to resources that help combat food insecurity is important for these populations. Purpose: To examine how rurality relates to food insecurity and need for food resources, as well as availability of those resources including food pantries and soup kitchens, in 15 northern Ohio Appalachian counties. Methods: A cross-sectional study with a geographical analysis was conducted using data from the American Community Survey census data, County Health Rankings data, and regional foodbank websites. Results: Rural counties had a higher ratio of potential clients per service for food insecurity than did non-rural counties. They also had slightly more children eligible for free or reduced-price lunches than non-rural counties. However, the non-rural counties had slightly higher percentages of residents classified as food insecure and with limited access to healthy food. Implications: There are more potential clients per service for food insecurity in rural counties compared to non-rural counties. To promote greater access, additional food pantries should be opened in rural counties

Carbon nanotube four-terminal devices for pressure sensing applications

Carbon nanotubes (CNTs) are of high interest for sensing applications,owing to their superior mechanical strength, high Young’s modulus and low density. In this work, we report on a facile approach for the fabrication of carbon nanotube devices using a four terminal configuration. Oriented carbon nanotube films were pulled out from a CNT forest wafer and then twisted into a yarn. Both the CNT film and yarn were arranged on elastomer membranes/diaphragms which were arranged on a laser cut acrylic frame to form pressure sensors. The sensors were calibrated using a precisely controlled pressure system, showing a large change of the output voltage of approximately 50 mV at a constant supply current of 100 μA and under a low applied pressure of 15 mbar. The results indicate the high potential of using CNT films and yarns for pressure sensing applications

CHEMICAL SLUDGE HEEL REMOVAL AT THE SAVANNAH RIVER SITE F TANK FARM CLOSURE PROJECT 8183

Chemical Sludge Removal (CSR) is the final waste removal activity planned for some of the oldest nuclear waste tanks located at the Savannah River Site (SRS) in Aiken, SC. In 2008, CSR will be used to empty two of these waste tanks in preparation for final closure. The two waste tanks chosen to undergo this process have previously leaked small amounts of nuclear waste from the primary tank into an underground secondary containment pan. CSR involves adding aqueous oxalic acid to the waste tank in order to dissolve the remaining sludge heel. The resultant acidic waste solution is then pumped to another waste tank where it will be neutralized and then stored awaiting further processing. The waste tanks to be cleaned have a storage capacity of 2.84E+06 liters (750,000 gallons) and a target sludge heel volume of 1.89E+04 liters (5,000 gallons) or less for the initiation of CSR. The purpose of this paper is to describe the CSR process and to discuss the most significant technical issues associated with the development of CSR

Mechanical Metamaterials with Negative Compressibility Transitions

When tensioned, ordinary materials expand along the direction of the applied force. Here, we explore network concepts to design metamaterials exhibiting negative compressibility transitions, during which a material undergoes contraction when tensioned (or expansion when pressured). Continuous contraction of a material in the same direction of an applied tension, and in response to this tension, is inherently unstable. The conceptually similar effect we demonstrate can be achieved, however, through destabilisations of (meta)stable equilibria of the constituents. These destabilisations give rise to a stress-induced solid-solid phase transition associated with a twisted hysteresis curve for the stress-strain relationship. The strain-driven counterpart of negative compressibility transitions is a force amplification phenomenon, where an increase in deformation induces a discontinuous increase in response force. We suggest that the proposed materials could be useful for the design of actuators, force amplifiers, micro-mechanical controls, and protective devices.Comment: Supplementary information available at http://www.nature.com/nmat/journal/v11/n7/abs/nmat3331.htm

Diffusion and Transport Coefficients in Synthetic Opals

Opals are structures composed of the closed packing of spheres in the size range of nano-to-micro meter. They are sintered to create small necks at the points of contact. We have solved the diffusion problem in such structures. The relation between the diffusion coefficient and the termal and electrical conductivity makes possible to estimate the transport coefficients of opal structures. We estimate this changes as function of the neck size and the mean-free path of the carriers. The theory presented is also applicable to the diffusion problem in other periodic structures.Comment: Submitted to PR

Carbon Nanotubes as Nanoelectromechanical Systems

We theoretically study the interplay between electrical and mechanical properties of suspended, doubly clamped carbon nanotubes in which charging effects dominate. In this geometry, the capacitance between the nanotube and the gate(s) depends on the distance between them. This dependence modifies the usual Coulomb models and we show that it needs to be incorporated to capture the physics of the problem correctly. We find that the tube position changes in discrete steps every time an electron tunnels onto it. Edges of Coulomb diamonds acquire a (small) curvature. We also show that bistability in the tube position occurs and that tunneling of an electron onto the tube drastically modifies the quantized eigenmodes of the tube. Experimental verification of these predictions is possible in suspended tubes of sub-micron length.Comment: 8 pages, 5 eps figures included. Major changes; new material adde