Mode-matching analysis of a shielded rectangular dielectric-rod waveguide

Rectangular cross-section dielectric waveguides are widely used at millimeter wavelengths. In addition, shielded dielectric resonators having a square cross-section are often used as filter elements, however there is almost no information available on the effect of the shield. Rectangular or square dielectric waveguide is notoriously difficult to analyze, because of the singular behaviour of the fields at the corners. Most published analyses are for materials with a low dielectric constant, and do not include the effects of a shield. This paper describes a numerically efficient mode matching method for the analysis of shielded dielectric rod waveguide, which is applicable to both low and high dielectric constant materials. The effect of the shield on the propagation behaviour is studied. The shield dimensions may be selected such that the shield has a negligible effect, so that results can be compared with free space data. The results are verified by comparison with several sets of published data, and have been confirmed by measurement for a nominal 'e' r of 37.4

Adapting a Standard Thin-Layer Chromatography Apparatus for Laboratory Use

Author Institution: Cranbrook Institute of Science, Bloomfield Hills, Michigan 48013The Eastman Chromagram apparatus was employed in thin-layer chromatographic studies involving United States species of Polymnia (Compositae). Certain technical modifications of this apparatus were made in an attempt to more efficiently saturate the chamber with vapors of the eluents. Results indicated that a critical level of reproducibility could be achieved only with modified apparatus, which included the insertion of saturated "fT'-shaped filter paper, with a glass rod across the base of the "| j " , all held securely between the two glass plates by additional clips

PeV-Scale Supersymmetry

Although supersymmetry has not been seen directly by experiment, there are powerful physics reasons to suspect that it should be an ingredient of nature and that superpartner masses should be somewhat near the weak scale. I present an argument that if we dismiss our ordinary intuition of finetuning, and focus entirely on more concrete physics issues, the PeV scale might be the best place for supersymmetry. PeV-scale supersymmetry admits gauge coupling unification, predicts a Higgs mass between 125 GeV and 155 GeV, and generally disallows flavor changing neutral currents and CP violating effects in conflict with current experiment. The PeV scale is motivated independently by dark matter and neutrino mass considerations.Comment: 5 RevTex page

Survey of vector-like fermion extensions of the Standard Model and their phenomenological implications

With the renewed interest in vector-like fermion extensions of the Standard Model, we present here a study of multiple vector-like theories and their phenomenological implications. Our focus is mostly on minimal flavor conserving theories that couple the vector-like fermions to the SM gauge fields and mix only weakly with SM fermions so as to avoid flavor problems. We present calculations for precision electroweak and vector-like state decays, which are needed to investigate compatibility with currently known data. We investigate the impact of vector-like fermions on Higgs boson production and decay, including loop contributions, in a wide variety of vector-like extensions and their parameter spaces.Comment: 43 pages, 17 figures; v2: text modified to improve readability, references added, journal versio

Virtual effects of light gauginos and higgsinos: a precision electroweak analysis of split supersymmetry

We compute corrections to precision electroweak observables in supersymmetry in the limit that scalar superpartners are very massive and decoupled. This leaves charginos and neutralinos and a Standard Model-like Higgs boson as the only states with unknown mass substantially affecting the analysis. We give complete formulas for the chargino and neutralino contributions, derive simple analytic results for the pure gaugino and higgsino cases, and study the general case. We find that in all circumstances, the precision electroweak fit improves when the charginos and neutralinos are near the current direct limits. Larger higgsino and gaugino masses worsen the fit as the theory predictions asymptotically approach those of the Standard Model. Since the Standard Model is considered by most to be an adequate fit to the precision electroweak data, an important corollary to our analysis is that all regions of parameter space allowed by direct collider constraints are also allowed by precision electroweak constraints in split supersymmetry.Comment: 22 pages, 5 figures, v2: typos fixed and note adde

Curling Burley Tobacco from an Automated Harvesting System

If burley tobacco can be successfully cured at high density under waterproof covers in the field, a producer can expand production without the necessity of building new curing barns and can thereby more easily justify investment in the automated burley tobacco harvesting system (Wells et al., 1990a, b). Curing under waterproof covers in the field and curing on frames in the barn were evaluated over three curing seasons using two varieties (KY 14 and TN 86), two plant densities (32 and 43 plants/m2, 3 and 4 plants/ft2), position of tobacco on the frame (four levels ranging from edge to center) and stalk position (bottom, middle and top). Conventionally cured tobacco was used as the standard of comparison and grade index was used as the assessment of quality. Averaged over a three-year period, burley tobacco cured in the field over sod and under waterproof covers and conventionally cured tobacco were of equal quality (56.0 and 55.8 grade index, respectively) and were both superior to tobacco cured on frames in the barn (52.0). During the dry curing season, burley tobacco cured under the covers had a higher grade index (54.9) than that cured conventionally (43.5) or on frames in the barn (43.7) but during the moderately wet and wet curing seasons, conventionally cured burley tobacco had a higher grade index (62.3 and 61.5, respectively) than that cured under covers (58.9 and 54.2, respectively) or on frame in the barn (59.0 and 53.4, respectively). During the wet curing season, leaf tips near the sod in the field and near the concrete in the barn cured dark red resulting in a lowered grade index. Burley tobacco from the automated harvesting system is better cured outside under waterproof covers than cured in a barn

Wind Drag on Burley Tobacco Plants

Drag coefficient and center of resistance to wind forces were determined for four varieties of burley tobacco at three stages of growth and using wind velocities ranging from about 3 to 17 m/s. Drag coefficients determined ranged from about 0.024 at the highest velocity to about 0.081 at the lowest velocity. Stage of growth and wind velocity had significant effects on drag coefficient. Variety did not have a significant effect on drag coefficient. Mean center of resistance varied from 42.3 percent of the distance from bottom leaf to top leaf at the early stage of growth to 71.2 percent at harvest stage. Center of resistance was significantly affected by variety, stage of growth, and wind velocity