1,815 research outputs found
Status of wind-energy conversion
The utilization of wind energy is technically feasible as evidenced by the many past demonstrations of wind generators. The cost of energy from the wind has been high compared to fossil fuel systems; a sustained development effort is needed to obtain economical systems. The variability of the wind makes it an unreliable source on a short term basis. However, the effects of this variability can be reduced by storage systems or connecting wind generators to: (1) fossil fuel systems; (2) hydroelectric systems; or (3) dispersing them throughout a large grid network. Wind energy appears to have the potential to meet a significant amount of our energy needs
Recommended from our members
Bilateral abducens nerve palsy due to septic thrombophlebitis.
PurposeTo report a case of septic thrombophlebitis producing bilateral abducens nerve palsy.ObservationA 65 year-old woman with recent sinus surgery experienced the onset of horizontal diplopia during treatment for bacteremia. Computer tomography of head and a neck ultrasonography showed right internal jugular vein occlusion. Ophthalmology examination was consistent with bilateral abducens nerve palsy. She was treated with systemic antibiotics and antiplatelet therapy with resolution of the internal jugular vein occlusion. The diplopia improved over a six-months.Conclusion and importanceOur patient had Lemierre syndrome with an unusual presentation. The patient was treated for septic thrombophlebitis with a resolution of her ocular symptoms
An experimental 100 kilowatt wind turbine generator
Experimental generator consists of two blades mounted on 100 foot tower, driving transmission train and electric generator mounted on top of tower. Machine generates 100 kW of electricity at wind speeds from 18 to 60 miles per hour. Yaw control mechanism automatically orients machine into wind
Pol\uedticas infraestructurales y consumo de suelo en V\ue9neto: una uni\uf3n desafortunada
La \u2018ciudad difusa\u2019 \u2013 una compleja organizaci\uf3n de asentamientos investigada y descrita por numerosos acad\ue9micos desde finales de la d\ue9cada de 1980 ubicada en la regi\uf3n central del V\ue9neto \u2013 es din\ue1mica y est\ue1 en constante evoluci\uf3n, presenta elevados consumos de suelo y una creciente congesti\uf3n en la movilidad. Los informes indican que uno de los factores con m\ue1s influencia en este \ufaltimo aspecto es el desarrollo del sistema de infraestructuras, especialmente en los \ufaltimos 20-25 a\uf1os, que ha soportado una movilidad muy alta: una movilidad err\ue1tica parcialmente basada en el commuting regular pero tambi\ue9n en los desplazamientos para satisfacer necesidades b\ue1sicas. La respuesta institucional a esta creciente demanda de movilidad ha sido incremental e inadecuada, proporcionando diversas grandes infraestructuras sin inversiones significativas para mejorar el transporte ferroviario o el transporte intermodal p\ufablico o p\ufablico-privado. En vez de contrarrestar el consumo de suelo como se indica en los Planes Regionales, esta intervenci\uf3n p\ufablica, incentiva una nueva forma de sprawl, impulsando la construcci\uf3n de nuevas centralidades, intensificando la presi\uf3n antr\uf3pica en una regi\uf3n de por s\ued afectada por problemas de despilfarro de recursos ambientales. La construcci\uf3n de nuevas infraestructuras viarias est\ue1 alterando las caracter\uedsticas originales de la regi\uf3n, reforzando el sprawl e impulsando la conversi\uf3n de \ue1reas rurales en predios construidos
Dietary modifications for infantile colic
Infantile colic can be defined as periods of inconsolable, unexplained, and incessant crying in a seemingly healthy infant that, quite understandably, leads to exhausted, frustrated, and concerned parents seeking to comfort their child (Landgren 2010).
The prevalence of excessive crying varies according to the definition used although, most often, it peaks during the second month of life,with a prevalence of 1.5%to 11.9%(Reijneveld 2001).Traditionally, the definition of the condition was based on the rule of
three (Wessel 1954): that is, unexplained episodes of paroxysmal crying for more than three hours per day, for three days per week, for at least three weeks. More recently a new definition has been proposed. It refers to a clinical condition of fussing and crying for at least one week in an otherwise healthy infant (Hyman 2006). Colic can be graded as mild, moderate, or severe, though there is no consensus for this classification. Colic can affect up to 10% to 30% of infants worldwide (Clifford 2002; Rosen 2007)
Large fluctuations of the nonlinearities in isotropic turbulence. Anisotropic filtering analysis
Using a Navier–Stokes isotropic turbulent field numerically simulated in a box with a discretization of
10243 (Biferale et al., 2005), we show that the probability of having a stretching–tilting larger than a
few times the local enstrophy is low. By using an anisotropic kind of filter in the Fourier space, where
wavenumbers that have at least one component below a threshold or inside a range are removed, we
analyze these survival statistics when the large, the small inertial or the small inertial and dissipation
scales are filtered out. By considering a flow obtained by randomizing the phases of the Fourier modes,
and applying our filtering techniques, we identified clearly the properties attributable to turbulence.
It can be observed that, in the unfiltered isotropic Navier–Stokes field, the probability of the ratio
(|ω·∇U|/|ω|2) being higher than a given threshold is higher than in the fields where the large scales were
filtered out. At the same time, it is lower than in the fields where the small inertial and dissipation range
of scales is filtered out. This is basically due to the suppression of compact structures in the ranges that
have been filtered in different ways. The partial removal of the background of filaments and sheets does
not have a first order effect on these statistics. These results are discussed in the light of a hypothesized
relation between vortical filaments, sheets and blobs in physical space and in Fourier space. The study
in fact can be viewed as a kind of test for this idea and tries to highlight its limits. We conclude that a
qualitative relation in physical space and in Fourier space can be supposed to exist for blobs only. That is
for the near isotropic structures which are sufficiently described by a single spatial scale and do not suffer
from the disambiguation problem as filaments and sheets do.
Information is also given on the filtering effect on statistics concerning the inclination of the strain rate
tensor eigenvectors with respect to vorticity. In all filtered ranges, eigenvector 2 reduces its alignment,
while eigenvector 3 reduces its misalignment. All filters increase the gap between the most extensional
eigenvalue ⟨λ1⟩ and the intermediate one ⟨λ2⟩ and the gap between this last ⟨λ2⟩ and the contractile
eigenvalue ⟨λ3⟩. When the large scales are missing, the modulus of the eigenvalue 1 becomes nearly
equal to that of the eigenvalue 3, similarly to the modulus of the associated components of the enstrophy
production
Wind tunnel measurements of the tower shadow on models of the ERDA/NASA 100 KW wind turbine tower
Detailed wind speed profile measurements were made in the wake of 1/25 scale and 1/48 scale tower models to determine the magnitude of the speed reduction (the tower shadow). The 1/25 scale tower modeled closely the actual wind turbine including the service stairway and the equipment elevator rails on one face. The 1/48 scale model was made of all tubular members. Measurements were made on the 1/25 scale model with and without the stairway and elevator rails, and on the 1/48 all tube model without stairs and rails. The test results show that the stairs and rails were a major source of wind flow blockage. The all tubular 1/48 scale tower was found to offer less resistance to the wind than the 1/25 scale model that contained a large number of square sections. Shadow photos are included to show the extent of the blockage offered to the wind from various directions
Semi-basements used as dwellings: hygienic considerations and analysis of the regulations.
Current housing shortage in Italy is forcing a growing number of individuals to use as living environment spaces that were originally devoted to other purposes. Among such spaces, semi-basements hold a particular relevance because of their specific characteristics and their effects on human health. The authors analyse the relatively scarce legislation about this topic at both national and regional level. The local Building Codes of the ten most populous cities of Italy are reviewed, assessing whether the use of semi-basements as living spaces is allowed and, if so, which restrictions and requirements are imposed. The authors conclude that, on one hand, further research is strongly needed to estimate the amount of exposed population and their health risk, on the other the existing legislation on the topic is often discretionary and deeply unhomogeneous across the country
- …