Vibration and noise analysis of a gear transmission system

This paper presents a comprehensive procedure to predict both the vibration and noise generated by a gear transmission system under normal operating conditions. The gearbox vibrations were obtained from both numerical simulation and experimental studies using a gear noise test rig. In addition, the noise generated by the gearbox vibrations was recorded during the experimental testing. A numerical method was used to develop linear relationships between the gearbox vibration and the generated noise. The hypercoherence function is introduced to correlate the nonlinear relationship between the fundamental noise frequency and its harmonics. A numerical procedure was developed using both the linear and nonlinear relationships generated from the experimental data to predict noise resulting from the gearbox vibrations. The application of this methodology is demonstrated by comparing the numerical and experimental results from the gear noise test rig

Relationship between hippocampal structure and memory function in elderly humans

With progressing age, the ability to recollect personal events declines, whereas familiarity-based memory remains relatively intact. It has been hypothesized that age-related hippocampal atrophy may contribute to this pattern because of its critical role for recollection in younger humans and after acute injury. Here, we show that hippocampal volume loss in healthy older persons correlates with gray matter loss (estimated with voxel-based morphometry) of the entire limbic system and shows no correlation with an electrophysiological (event-related potential [ERP]) index of recollection. Instead, it covaries with more substantial and less specific electrophysiological changes of stimulus processing. Age-related changes in another complementary structural measure, hippocampal diffusion, on the other hand, seemed to be more regionally selective and showed the expected correlation with the ERP index of recollection. Thus, hippocampal atrophy in older persons accompanies limbic atrophy, and its functional impact on memory is more fundamental than merely affecting recollection

An improved technique for microbiological sampling of surfaces - Agar spray Research report, period ending 30 Sep. 1968

Improved agar spray technique for sampling surface microorganis

A Comparison of Tree Growth in Loblolly Pine (Pinus taeda) Plantations and Silvopasture Settings in East Texas

A desire by landowners to diversify potential income sources has resulted in an increased interest in silvopasture. This intensive land management option allows for the production of timber, livestock and/or forage on the same land base. With traditional plantation systems featuring loblolly pine (Pinus taeda) common in the western gulf coast region of the southeastern United States, comparisons of tree growth are needed to justify the use of silvopasture. This study evaluated the height, diameter and volume growth 13 years post-establishment of loblolly pine in both silvopasture and plantation spacings on a single site in east Texas. Individual trees in silvopasture plots had greater diameter and volume than those in plantation plots; however, plantation plots yielded greater volume per hectare. The greater volume per hectare was driven by the greater number of trees planted (1282 trees ha-1) in plantation plots than those planted (598 trees ha-1) in silvopasture. In silvopasture, site resources are concentrated on producing larger-diameter, sawtimber size, and theoretically, higher-value trees

Formation of disclination lines near a free nematic interface

We have studied the nucleation and the physical properties of a -1/2 wedge disclination line near the free surface of a confined nematic liquid crystal. The position of the disclination line has been related to the material parameters (elastic constants, anchoring energy and favored anchoring angle of the molecules at the free surface). The use of a planar model for the structure of the director field (whose predictions have been contrasted to those of a fully three-dimensional model) has allowed us to relate the experimentally observed position of the disclination line to the relevant properties of the liquid crystals. In particular, we have been able to observe the collapse of the disclination line due to a temperature-induced anchoring angle transition, which has allowed us to rule out the presence of a real disclination line near the nematic/isotropic front in directional growth experiments. 61.30.Jf,61.30.G

Calculating Milnor Numbers and Versal Component Dimensions from P-Resolution Fans

We use Altmann's toric fan description of P-resolutions to formulate a new description of deformation theory invariants for two-dimensional cyclic quotient singularities. In particular, we show how to calculate the dimensions of the (reduced) versal base space components as well as Milnor numbers of smoothings over them.Comment: 8 pages; 2 figures; v2 added section on Milnor numbers, reworked proof of dimension formula, new example, and new titl

Physiological and Growth Responses of Midrotation Loblolly Pine to Treatments of Fire, Herbicide, and Fertilizer

The objectives of this study were to examine the effects of fertilizer and understory vegetation control (herbicide and prescribed fire) on mature tree physiology and to link observed physiological responses with tree growth. Photosynthetic rate (photosynthesis), transpiration, stomatal conductance, stem diameter, and crown area were measured in two midrotation loblolly pine plantations in East Texas. Rates of photosynthesis, E and gs for the midsummer measurements were significantly reduced by fertilizer treatments on both sites. Drought in east Texas during the last 3 years may have influenced this result. Trees receiving fire at the site with a comparatively more dense live pre-treatment understory exhibited higher rates of photosynthesis; however, prescribed fire had no positive effect on growth. Herbicide treatment significantly increased the change in diameter growth of unfertilized trees at both sites between 1999-2001 by an average of 5 percent, but had no effect on growth of fertilized trees. Increase in diameter growth per unit crown area was significantly greater in unfertilized trees receiving herbicide than in controls

Effects of Midrotation Intensive Silviculture on Forest Soils in East Texas: First-Year Results

Intensive forest management is becoming increasingly common in east Texas. Included in intensive management are such practices as mid-rotation fertilization, prescribed fire, and herbicide application. There is insufficient information about the effects of these treatments on soil physical, chemical, and biological properties when applied at mid-rotation. The objectives of this research are to evaluate the effects of these treatments on soil physical properties including organic matter content and bulk density; chemical properties including soil nitrogen and phosphorus; and on populations of resident earthworms. Five replications were installed in each of two loblolly pine (Pinus taeda L.) plantations aged 15 and 17. Both were thinned in 1998. Accord SP and Chopper emulsion were ground applied in the fall of 1999. The prescribed burn treatment occurred the following spring. Fertilizer was applied one to two weeks after completion of the burn to supply 224 kilograms per hectare of N and 28 kilograms per hectare of P. First-year results are presented