Investigation of the dynamic behavior of soybean plants during cutting

Shatter losses of soybeans are still a substantial percentage of potential profits despite extensive research of the problem. Previous efforts have tended to be concerned with the design and operating aspects of harvesting machinery rather than the dynamic characteristics of the plant. In contrast, this study focused on the dynamic behavior of soybean plants during cutting. Mathematical models were developed for the dynamics of the components of the soybean plant: the stalk and pod. The Euler-Bernoulli beam appeared to be a satisfactory model for the stalk, predicting modes of vibration with corresponding natural frequencies. The simple pendulum with a torsional spring was adequate for modeling some aspects of pod motion. The coupled stalk-single pod model showed the effect of the pod on the motion of the stalk to be due to: the added mass of the pod, the motion of the pod, and collisions between the pod and stalk. The model also predicted that the pod and stalk tended to move out of phase for vibration at most frequencies, and that the response of the pod to stalk vibration was frequency dependent, the most significant pod response occurring at lower frequencies. The notion of a cutting function was introduced to represent the aspects of cutting that cause motion of the plant. For the type of cutting device used in this study, a multi-tooth circular saw blade, a sequence of pulses appeared to be an adequate mathematical model cutting function. Experimental determination of cutting functions using stalks with pods attached was hindered by the nonlinearities caused by friction between pods and collisions between pods and the stalk. Data collection was accomplished with accelerometers and an analog-to-digital data acquisition system. The presence of the accelerometers and cables affected the response of the plant and the instrumentation would very likely be damaged by severe plant motion; therefore, another method of sensing plant response would be more appropriate. Digital signal analysis using Fast Fourier Transform methods proved to be an effective method of data analysis. The application of this technology to the study of crop dynamics appears as promising as it has been for other areas of vibration research

Stress-induced Phase Change Sintering: A Novel Approach to the Fabrication of Barium Chloride Transparent Ceramic Scintillators

For the precise in-field identification of dangerous radioisotopes, the desire for higher resolution, cheaper, and more rugged gamma-ray scintillator detectors has pushed the materials science community to investigate new compounds and processing techniques. One particular solution is Eu:BaCl2 transparent ceramics processed by the novel phase-change sintering technique. Typically, optical transparency in BaCl2 would be limited by birefringence scattering at grain boundaries due to mismatch in refractive index. Traditional ceramic processing routes would also predispose this volatile and hygroscopic material to the formation of defects, which interrupt the energy transfer in the scintillation process. Literature shows that these challenges have prevented halide gamma-ray scintillator ceramics, including Ce:LaBr3, Eu:SrI2, and Ce:Cs2LiYCl6, from reaching the performance of their single-crystalline counterparts. The sintering method explored in this thesis utilizes a polymorphic orthorhombic to cubic phase transition followed by plastic deformation. The experimental implementation of this method necessitated the design of a unique airtight hot-pressing device, capable of developing conditions for this phase conversion, and the synthesis of high purity powders. Systematic experiments on powder synthesis and on densification were carried out to demonstrate the feasibility of this approach and understand the conditions for phase-change sintering. These experiments, supported by characterizations including x-ray diffraction, electron microscopy, and thermal analysis, lead to the production of optically isotropic cubic barium chloride ceramic samples. Finally, the optical and scintillation properties of Eu:BaCl2 ceramic samples were investigated, revealing an energy resolution of 6% at 662 keV, an unprecedented value for a halide ceramic scintillator

Postcard from H. C. Shoulders to B. R. Colson

Postcard from H. C. Shoulders to B. R. Colson. The handwritten note is dated 23 February 1910. There is a transcript of the correspondence in the item PDF

Letter from H. C. Shoulders to B. R. Colson

Letter from H. C. Shoulders to B. R. Colson. The three-page handwritten note is dated 19 February 1910. There is a transcript of the correspondence in the item PDF

Aeration, Phosphorous, and Lime Affect Nitrogen Mineralization in Imperfectly Drained Forest Soils

Unamended, limed, and phosphorus-enriched Caddo, Beauregard, and Wrightsville silt loams (A1 horizon) were incubated for six months at room temperature under two moisture regimes. At field capacity, unamended soils lost 0.7% of organic matter and converted 166 ppm of organic nitrogen to inorganic forms. Ninety-five percent of the converted nitrogen was present as N₄-H or NO₃-N. Limed and phosphorus-treated soils at field capacity lost about 1.0% of organic matter and accumulated 191 to 201 ppm of inorganic nitrogen. Submerged soils lost very little organic matter and accumulated only 24 to 28 ppm of inorganic nitrogen. There was a loss of 35 to 78 ppm of nitrogen from the submerged soils, presumably through denitrification

Encouraging teacher change within the realities of school-based agricultural education: lessons from teachers’ initial use of socioscientific issues-based instruction

Calls for increased interdisciplinary education have led to the development of numerous teaching techniques designed to help teachers provide meaningful experiences for their students. However, methods of guiding teachers in the successful adoption of innovative teaching approaches are not firmly set. This qualitative study sought to better understand how school-based agricultural education teachers decide to adopt or discontinue a teaching innovation when introduced through ready-made lesson plans, which is currently a common practice of teaching method integration in school-based agricultural education (SBAE). Constant comparative analysis unveiled themes within the reactions to the teaching method’s use, as well as how teacher actions to those reactions led to their ultimate adoption or discontinuance of the teaching method

Effect of Cultural Treatment and Wood-type On Some Physical Properties of Longleaf and Slash Pine Wood

Wood was studied from relatively mature longleaf and slash pine trees that had been growing under experimental treatments including cultivation, two levels of thinning, and four levels of fertilization in various combinations. From discs taken at five heights and separated into three wood-types, green moisture content, radial shrinkage, tangential shrinkage, volumetric shrinkage, latewood percentage, number of rings per inch, and specific gravity were determined. In longleaf pine, there were indications of treatment effect on latewood percentage and the number of rings per inch, with the more intensive treatments generally leading to fewer rings and higher amounts of latewood. In slash pine, a similar trend was found with these two variables. The species exhibited an almost identical trend in the interrelationships among properties. Green moisture content was negatively correlated with specific gravity and moisture content of the innerwood and middlewood increased with height. Shrinkage was found to be negatively correlated with height and positively correlated with specific gravity, except in the innerwood. Latewood percentage accounted for much of the variation in specific gravity in all wood-types. In the outerwood only, there was a positive but weak correlation of number of rings with specific gravity