Larry F. Stikeleather

Axial Vibration of Threaded External Fixation Pins: Detection of Pin Loosening

The hypothesis of this study was that a nondestructive vibrational method could detect bone lysis at the external fixation pin–bone interface prior to current clinical and radiographic methods. In vitro models were used to simulate changes observed during pin loosening in vivo. Fixation pin axial natural frequency decreased with decreasing tensile modulus of the material into which it was implanted. In a live animal study the right tibia of 12 dogs was fractured and stabilized with a four-pin unilateral external fixation frame. The axial natural frequency of each pin was measured and radiographs were taken at 0, 2, 4, 6, 8, and 10 weeks after surgery. The natural frequency did not change when the first radiographic changes around the interface were observed. Pins were palpably stable at this point. As loosening progressed, the natural frequency did decrease. Frequency and quasistatic tests of dissected pin–bone structures revealed a good correlation between natural frequency and pin–bone interface stiffness. In addition, the measurement of natural frequency was more sensitive to bone structure changes at the pin–bone interface than low-load quasi-static stiffness. Therefore, a nondestructive vibration technique could be used instead of low-load quasistatic tests for assessing the pin–bone interface ex vivo.

Design and Operation of a Biofilter for Treatment of Swine House Pit Ventilation Exhaust.

A down-flow biofilter was designed to treat exhaust air from a swine barn pit ventilation fan in Raleigh, NC. Computational Fluid Dynamics was used to model airflow to ensure spatial uniformity of treatment. The biofilter medium consisted of ~70% compost and 30% woodchips by volume. The biofilter was evaluated during August 2010 through April 2011 under different summer, fall, and winter conditions. The medium depth was 0.3 m, empty bed residence time (EBRT) was 7.6 s, residence time was 2.7 s, and the biofilter had a unit airflow rate (U) of 0.04 m3/m2-s. A photoacoustic multi-gas field monitor (Innova) was used to measure concentrations of ammonia, carbon dioxide, methane, and nitrous oxide. The Innova was evaluated with regard to its response time for ammonia, nitrous oxide, and methane. Boric acid scrubbers were also used to measure time averaged ammonia concentrations. Air samples were collected and analyzed in a gas chromatograph (GC) for methane and VOCs. Operating conditions such as temperature, medium moisture content, and system pressure drop were measured during biofilter operation. Pressure drop across the fan averaged 125 Pa. The biofilter’s removal efficiencies (RE) for ammonia ranged from 89 to 92%. Greenhouse gases methane and nitrous oxide REs ranged from 13 to 50% and 14 to 17% respectively, while carbon dioxide REs ranged from -6 to 37%. Results show that the biofilter can be effective at removing gases such as ammonia, but also, methane and nitrous oxide. The cost of the system was

Hydrocarbon Fuels From Gas Phase Decarboxylation of Hydrolyzed Free Fatty Acid

1,225 per 0.50 m3/s.

Design and Evaluation of a Porous Windbreak Wall for Treating Swine House Emissions

This material is based upon work supported in part by the National Science Foundation EFRI program under Grant EFRI-093772 and by Department of Energy Applied Research Project Agency-Energy under Grant No. 25A5144.

Process for conversion of biomass to fuel

Emissions from animal houses include gases that may harm the environment and emanate unfavorable odors. A potential solution to this problem is the implementation of a porous windbreak wall. This device incorporates a windbreak wall, which is used for dilution and a biofilter for treatment of emissions. The design process involved research in the identification of a suitable biomass and computational fluid dynamics (CFD). Based on these results, woodchips were chosen as a fitting media and a distance of six feet was deemed as an appropriate length between the fan and the media. The overall design of the device consisted of three main pieces that include the frame containing the woodchips, an upper wall consisting of tarp and two wooden columns that hold the structure together. The testing performed involved the measurement of gas concentrations, volumetric flow rate, pressure drop and odor. Results from these tests show that ammonia had a well defined correlation reduction with an average value of 1.8%. Test results from nitrous oxide, carbon dioxide and methane show no treatment correlation and had intangible treatment results. These results suggest that treatment effectiveness needs to be increased for the technology to be viable, whether through a more effective design or through better media management