Effects of forward velocity on noise for a J85 turbojet engine with multitube suppressor from wind tunnel and flight tests

Flight and wind tunnel noise tests were conducted using a J85 turbojet engine as a part of comprehensive programs to obtain an understanding of forward velocity effects on jet exhaust noise. Nozzle configurations of primary interest were a 104-tube suppressor with and without an acoustically-treated shroud. The installed configuration of the engine was as similar as possible in the flight and wind tunnel tests. Exact simultaneous matching of engine speed, exhaust velocity, and exhaust temperature was not possible, and the wind tunnel maximum Mach number was approximately 0.27, while the flight Mach number was approximately 0.37. The nominal jet velocity range was 450 to 640 m/sec. For both experiments, background noise limited the jet velocity range for which significant data could be obtained. In the present tests the observed directivity and forward velocity effects for the suppressor are more similar to predicted trends for internally-generated noise than unsuppressed jet noise

Soil Quality Under Permanent and Annual Pastures: Its Implications for Soil Microbial Activity and Nutrient Turnover

Dairy farming in humid, subtropical parts of South Africa is based on permanent kikuyu grass (Pennisetum clandestinum) swards. However, there is a shortage of feed during the winter because low temperatures limit kikuyu growth. As a result, annual pastures incorporating temperate grasses, are grown for winter feed production. The grasses used are typically annual ryegrass (Lolium multiflorum) and sometimes perennial ryegrass (Lolium perenne). Kikuyu is so invasive in the locality that it becomes dominant within a few years, even if the field is sown to perennial ryegrass. For that reason, the swards are usually incorporated using a rotary cultivator, each summer and resown. Concern has arisen in recent years about soil degradation that is possibly occurring under annually-tilled pastures. Observations have suggested that with time, production has progressively declined and this is suspected to be related to soil degradation, particularly a decrease in organic matter content and a loss of related soil microbial and physical properties. The purpose of this study was to compare the effects of permanent pasture and annually-tilled ryegrass pasture on soil organic matter content, size and activity of the microbial biomass and aggregate stability

Type II superlattices for infrared detectors and devices

Superlattices consisting of combinations of III-V semiconductors with type II band alignments are of interest for infrared applications because their energy gaps can be made smaller than those of any 'natural' III-V compounds. Specifically, it has been demonstrated that both InSb/InAsxSb1-x superlattices and Ga1-xInxSb/InAs superlattices can possess energy gaps in the 8-14 mu m range. The efforts have focused on the Ga1-xInxSb/InAs system because of its extreme broken gap band alignment, which results in narrow energy gaps for very short superlattice periods. The authors report the use of in situ chemical doping of Ga1-xInxSb/InAs superlattices to fabricate p-n photodiodes. These diodes display a clear photovoltaic response with a threshold near 12 mu m. They have also attained outstanding structural quality in Ga1-xInxSb/InAs superlattices grown on radiatively heated GaSb substrates. Cross-sectional transmission electron microscope images of these superlattices display no dislocations, while high resolution X-ray diffraction scans reveal sharp high-order superlattice satellites and strong Pendellosung fringes

Plasma deposition of constrained layer damping coatings

Plasma techniques are used to generate constrained layer damping (CLD) coatings on metallic substrates. The process involves the deposition of relatively thick, hard ceramic layers on to soft polymeric damping materials while maintaining the integrity of both layers. Reactive plasma sputter-deposition from an aluminium alloy target is used to deposit alumina layers, with Young's modulus in the range 77-220GPa and thickness up to 335 μ, on top of a silicone film. This methodology is also used to deposit a 40 μ alumina layer on a conventional viscoelastic damping film to produce an integral damping coating. Plasma CLD systems are shown to give at least 50 per cent more damping than equivalent metal-foil-based treatments. Numerical methods for rapid prediction of the performance of such coatings are discussed and validated by comparison with experimental results

The psychological impact of a colorectal cancer diagnosis following a negative fecal occult blood test result.

- Background: Screening using fecal occult blood testing (FOBt) reduces colorectal cancer (CRC) mortality, but the test has low sensitivity. A 'missed' cancer may cause psychological harms in the screened population that partially counteract the benefits of early detection. - Methods: 311 people diagnosed with CRC: i) after a negative FOBt result (interval cancer), ii) a positive result (screen-detected cancer), or iii) in regions where screening was not offered, completed questions on quality of life (FACT-C), depression (CES-D), perceived diagnostic delay, and trust in the results of FOBt screening. 15 withheld consent to data matching with medical records, leaving a sample size of 296. - Results: Controlling for demographic and clinical variables, patients with an interval cancer reported poorer quality of life (difference in means = 6.16, p = 0.03) and more diagnostic delay (OR: 0.37, p = 0.02) than patients with screen-detected disease, with no differences in depression. No differences were observed between the interval cancer group and the group not offered screening on these measures. Patients with an interval cancer reported the lowest levels of trust in FOB testing. Conclusions: An interval cancer has adverse effects on trust in FOBt but does not result in worse psychological outcomes compared with people diagnosed in areas with no screening programme. People with an interval cancer report poorer quality of life than people with screen-detected disease. - Impact: Improvements in test sensitivity could improve quality of life among people who complete an FOB test over and above any benefits already conferred by earlier detection

Asymptotic statistics of the n-sided planar Poisson-Voronoi cell. I. Exact results

We achieve a detailed understanding of the $n$-sided planar Poisson-Voronoi cell in the limit of large $n$. Let ${p}\_n$ be the probability for a cell to have $n$ sides. We construct the asymptotic expansion of $\log {p}\_n$ up to terms that vanish as $n\to\infty$. We obtain the statistics of the lengths of the perimeter segments and of the angles between adjoining segments: to leading order as $n\to\infty$, and after appropriate scaling, these become independent random variables whose laws we determine; and to next order in $1/n$ they have nontrivial long range correlations whose expressions we provide. The $n$-sided cell tends towards a circle of radius (n/4\pi\lambda)^{\half}, where $\lambda$ is the cell density; hence Lewis' law for the average area $A\_n$ of the $n$-sided cell behaves as $A\_n \simeq cn/\lambda$ with $c=1/4$. For $n\to\infty$ the cell perimeter, expressed as a function $R(\phi)$ of the polar angle $\phi$, satisfies $d^2 R/d\phi^2 = F(\phi)$, where $F$ is known Gaussian noise; we deduce from it the probability law for the perimeter's long wavelength deviations from circularity. Many other quantities related to the asymptotic cell shape become accessible to calculation.Comment: 54 pages, 3 figure

Pathways through organizational socialization: a longitudinal qualitative study based on the psychological contract

In this study, we explore different pathways during organizational socialization through the lens of the psychological contract using in-depth longitudinal qualitative methods. Analysis of 112 critical incident interviews with 27 newcomers across their first year of work reveals five distinct psychological contract pathways through socialization, within which fulfilment and breach influence adjustment by facilitating or restricting opportunities to learn and integrate, as well as influencing attitudes and behavior. The analysis reveals that whilst perceived psychological contract fulfilment facilitates newcomer adjustment, perceived breach can disrupt the process. We provide a detailed account of the way socialization and the psychological contract unfold for newcomers over time, and show that psychological contract events can significantly alter the course of adjustment