Wind turbine acoustics

Available information on the physical characteristics of the noise generated by wind turbines is summarized, with example sound pressure time histories, narrow- and broadband frequency spectra, and noise radiation patterns. Reviewed are noise measurement standards, analysis technology, and a method of characterizing wind turbine noise. Prediction methods are given for both low-frequency rotational harmonics and broadband noise components. Also included are atmospheric propagation data showing the effects of distance and refraction by wind shear. Human perception thresholds, based on laboratory and field tests, are given. Building vibration analysis methods are summarized. The bibliography of this report lists technical publications on all aspects of wind turbine acoustics

Adolescent sexual competence and sexual risk-taking : an ecological model of risk and protection

Using Bronfenbrenner\u27s ecological paradigm of human development as a framework, this study investigated the risk and protective factors associated with adolescent sexual behaviors and introduced the concept of sexual competence. Using data from the National Longitudinal Study of Adolescent Health, longitudinal and cross-sectional models were tested. Key findings include: (a) individual-level variables as well as family, peer, and school variables contribute to the total variance explained and have a direct effect on adolescents\u27 sexual competence; (b) the early influence of peers on sexual competence is later replaced by parental influences; (c) parent\u27s membership in a parent-teacher organization is associated with increased sexual competence; (d) the associations between the predictor variables and sexual competence are fairly consistent across gender and ethnicity; (e) overall, risk factors seem to be stronger predictors of adolescent sexual competence than protective factors; and (f) engaging in other health-risk behaviors and perceiving that there are obstacles to contraceptive use are strong indicators of sexual competence. These findings support the proposition that within an adolescent\u27s sphere of influence there are specific factors that promote the development of sexual competence as well as factors that inhibit the development of sexual competence. In addition, these findings indicate that the affect of these factors is consistent across gender and ethnicity

Confirmatory factor analysis and invariance testing between Blacks and Whites of the Multidimensional Health Locus of Control scale.

The factor structure of the Multidimensional Health Locus of Control scale remains in question. Additionally, research on health belief differences between Black and White respondents suggests that the Multidimensional Health Locus of Control scale may not be invariant. We reviewed the literature regarding the latent variable structure of the Multidimensional Health Locus of Control scale, used confirmatory factor analysis to confirm the three-factor structure of the Multidimensional Health Locus of Control, and analyzed between-group differences in the Multidimensional Health Locus of Control structure and means across Black and White respondents. Our results indicate differences in means and structure, indicating more research is needed to inform decisions regarding whether and how to deploy the Multidimensional Health Locus of Control appropriately

Wind Turbine Acoustics

Wind turbine generators, ranging in size from a few kilowatts to several megawatts, are producing electricity both singly and in wind power stations that encompass hundreds of machines. Many installations are in uninhabited areas far from established residences, and therefore there are no apparent environmental impacts in terms of noise. There is, however, the potential for situations in which the radiated noise can be heard by residents of adjacent neighborhoods, particularly those neighborhoods with low ambient noise levels. A widely publicized incident of this nature occurred with the operation of the experimental Mod-1 2-MW wind turbine, which is described in detail elsewhere. Pioneering studies which were conducted at the Mod-1 site on the causes and remedies of noise from wind turbines form the foundation of much of the technology described in this chapter

A common garden design reveals population-specific variability in potential impacts of hybridisation between populations of farmed and wild Atlantic salmon, Salmo salar L

Released individuals can have negative impacts on native populations through various mechanisms; including competition, disease transfer and introduction of maladapted gene-complexes. Previous studies indicate that the level of farmed Atlantic salmon introgression in native populations is population-specific. However few studies have explored the potential role of population diversity or river characteristics, such as temperature, on the consequences of hybridisation. We compared freshwater growth of multiple families derived from two farmed, five wild, and two F1 hybrid salmon populations at three contrasting temperatures (7°C, 12°C, and 16°C) in a common garden experiment. As expected, farmed salmon outgrew wild salmon at all temperatures, with hybrids displaying intermediate growth. However, differences in growth were population-specific and some wild populations performed better than others relative to the hybrid and farmed populations at certain temperatures. Therefore, the competitive balance between farmed and wild salmon may depend both on the thermal profile of the river and the genetic characteristics of the respective farmed and wild strains. While limited to F1 hybridisation, the present study shows the merits in adopting a more complex spatially resolved approach to risk management of local populations

Two Stacked PXIeTM Cards in 1U

PXITM/PXIeTM is an open-standards based platform that is popular for high-end test and measurement. One issue is combining enterprise-class computing with PXIe test and measurement cards in a compact 1U enclosure. This article discloses a means to install four single-width, 3U PXIe cards in a 1U, rack-mountable enclosure