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Vibrations of Discretely Layered Structures Using a Continuous Variation Model
No full textRecently, there has been a large body of work directed towards the use of non-homogeneous materials in controlling waves and vibrations in elastic media. Two broad categories have been studied, namely, media with continuous variation of properties and those with discrete layers (cells). Structures with both a finite and infinite number of cells (periodic layout) have been examined. For the former, direct numerical simulation or transfer matrix methods have been used. The current work focuses on one-dimensional cases, in particular a two-layer cell. Transfer matrix methods require writing solutions for each layer of the basic cell and then matching them across the interface, a process that can be quite lengthy. Here an alternate strategy is explored in which the discrete cell properties are modeled by continuously varying functions (here logistic functions), which has the advantage of working with a single differential equation. Natural frequencies have been obtained using a forced motion method and are in excellent agreement with those found using a transfer matrix approach. Mode shapes for the continuous variation model have been obtained using a finite difference scheme and compare well with those obtained via the transfer matrix approach
Cutaneous Electrode Positioning
Get PDFA device and method for positioning a cutaneous electrode for delivery of electrical stimulation to a subject\u27s head. A harness is worn on a subject\u27s head with a first band of the harness worn in a closed loop around the subject\u27s head and around a desired contact location on the subject\u27s head. A tensioning strap of the harness is worn across the desired contact location and connected at spaced-apart attachment locations of the strap to spaced-apart attachment locations of the harness such that an electrode disposed over the desired contact location on the subject\u27s head is held in place by the tensioning strap
Production of Biodiesel from Michigan Soybean Oil Using Supercritical Methanol with Acetic Acid
No full textBiodiesel is an affordable and renewable transportation fuel. Within the United States it is commonly produced from soybean oil. In conventional production of biodiesel, the transesterfication reaction is typically catalyzed in batch reactors with reaction times greater than 1 hour. Supercritical methanol is an alternative to catalyzed biodiesel production resulting in significantly reduced reaction times at temperatures greater than 350 °C. The addition of acetic acid enables the transesterfication reaction to proceed in supercritical methanol at lower temperatures, nearing methanol’s critical temperature of 240 °C. Lower temperatures could result in a decrease in the energy costs of supercritical methanol biodiesel production. The effects of temperature, concentration of acetic acid, methanol concentration, and reaction time on the production of biodiesel from Michigan soybean oil were evaluated in an agitated 500 mL Hastelloy C276 batch reactor. In addition, the effect of adding biodiesel as a recycle into the reactor to facilitate mixing was also evaluated. The product composition was characterized using ASTM D6584. The viscosity, acidity, and density of the biodiesel product were also evaluated
Wear Resistant and Biocompatible Coatings for Medical Devices and Method of Fabrication
Get PDFAbstract: A method of forming a biocompatible or biologically inert article for use in an application in which the article will make contact with at least one tissue, organ, or fluid within a human or animal body is provided. The method generally comprises providing an article having an external sur face; selecting chemical precursors; using a means to direct one or more chemical precursors towards or to apply such chemical precursors to the ex ternal surface; activating the chemical precursors by exposing said precursors to atmospheric pressure plasma; and grafting and/or cross-linking the chem ical precursors to form a solid coating adjacent to the external surface of the article
Long-Term SOFCs Button Cell Testing
No full textThis paper reports a new study where relatively long-term tests of about a 1000 h are performed on several planar anode-supported solid oxide fuel cells. The cell electrochemical behaviors are studied by using voltage-current density measurement, electrochemical impedance spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The cell total polarization obtained from electrochemical impedance spectroscopy results is shown to be consistent with the area-specific resistance calculated from the voltage-current density curve over the course of the test. In addition, a four-constant phase element model is used to analyze the cell components resistances at different intervals over the lifetime of the test. Scanning electron microscopy and energy-dispersive X-ray spectroscopy are used postmortem to determine if any damages occurred to the cells and to determine if any change in composition occurred to the lanthanum strontium cobalt ferrite cathode. This study shows that the tested cells remain stable with a relatively small increase in the cell total polarization but with no increase in ohmic resistance
Analysis of siloxanes in hydrocarbon mixtures using comprehensive two-dimensional gas chromatography
No full textA comprehensive two-dimensional gas chromatography (GC × GC) method for separating siloxanes from hydrocarbons has been developed using a systematic process. First, the retention indices of a set of siloxanes and a set of hydrocarbons were determined on 6 different stationary phases. The retention indices were then used to model GC × GC separation on 15 different stationary phase pairs. The SPB-Octyl × DB-1 pair was predicted to provide the best separation of the siloxanes from the hydrocarbons. The efficacy of this stationary phase pair was experimentally tested by performing a GC × GC analysis of gasoline spiked with siloxanes and by analyzing biogas obtained from a local wastewater treatment facility. The model predictions agreed well with the experimental results. The SPB-Octyl × DB-1 stationary phase pair constrained the hydrocarbons to a narrow range of secondary retention times and fully isolated the siloxanes from the hydrocarbon band. The resulting GC × GC method allows siloxanes to be resolved from complex mixtures of hydrocarbons without requiring the use of a selective detector
