Power Envelope Expansion using a Solidity Matching Scheme for a Circulation Controlled Vertical Axis Wind Turbine

Constant rotational speed vertical axis wind turbines (VAWTs) with fixed blades can have a limited performance envelope as the wind speed changes. Unlike horizontal axis wind turbines that can change the blade pitch to compensate for wind speed changes, vertical axis wind turbines are currently unable to achieve a blade pitch change reliably. A different method of changing the blade\u27s lift characteristics is needed by vertical axis wind turbines to increase its power envelope.;Circulation control (CC) can change the characteristics of an aerofoil by expelling air, moving at multiple times the free stream velocity, out of a thin slot along a rounded trailing edge. This jet of air bends around the rounded edge and entrains the free stream air, which ultimately increases lift. The use of an upper slot increases lift for positive angles of attack, while another slot on the lower surface can be used for negative angles of attack. The opposite may also be applied for a resultant decrease in lift. These slots are controllable by a valve inside the blade and can be turned on and off many times during rotation. The amount of lift increase due to circulation control is roughly proportional to the mass flow and velocity of the jet, within blade stall.;The ability to control lift, depending upon the amount of blowing, was applied to the blade of a vertical axis wind turbine to control lift generation and thus affect the power envelope. The solidity, or the ratio of the number of blades times the chord divided by the radius, greatly affects the performance of a turbine. A low solidity out-performs a high solidity rotor at low tip speed ratios and the opposite for mid-to-high tip speed ratios. Analyzing simulations of a VAWT with the same radius but different solidities, it was found that the solidity and tip speed ratio are the determining factors in performance. Circulation control can, for a VAWT, change the virtual chord and in effect both increase and decrease the virtual solidity. To mimic the solidity from a given initial solidity, circulation control was used to match the performance during rotation. The result is a VAWT that can change its apparent solidity depending upon the tip speed ratio.;An analytical model of a vertical axis wind turbine with valved circulation controlled dual slots was created and used to develop a control scheme to increase a VAWT\u27s performance envelope. A control scheme was then developed and simulated which changed the apparent solidity of the CC-VAWT depending upon the wind speed which resulted in an increase of about 22% in overall power capture

Aircraft intercom system design for project oculus

Project Oculus is an ongoing development project at WVU that aims to create a quick and easy sensor platform for deployment on the C-130 aircraft. Because this platform will be operated inside the noisy cargo bay of the C-130, an intercom system needed to be designed in the operator station of Project Oculus that would allow for different types of headsets and future expandability.;An intercom system was designed, constructed, and tested that uses military and civilian headsets to communicate both internally for Project Oculus and externally to the C-130 crew and provides support for a headset to be connected externally of the operator station

Einsatz von Nebenprodukten in der biologischen Milchviehfütterung zur Verbesserung der Lebensmittelkonversionseffizienz

Dairy cows are very efficient in converting fibrous forages into nutritious foods for humans. However, when fed potentially human-edible feeds, such as grains and pulses, dairy cows show very low efficiency in terms of net food production. In this debate, by-products are often mentioned as high quality feeds with reduced human-edible fractions for dairy cows. The aim of this feeding trial was therefore to evaluate the effect of a full substitution of a common concentrate mixture (COM) with a mixture including solely industrial by-products (BP) on milk production, feed intake, and the edible feed conversion ratio (eFCR) in organic dairy production. Cows receiving the BP mixture showed higher intakes of fibre fractions and ether extract, while starch intake was reduced as compared to cows receiving the COM mixture. The substitution did not impair feed intake or affect cows´ live weight changes. Milk yield and milk solids were not affected by treatment. However, the eFCR, defined as human-edible output per human-edible input, in the BP-group were about 4 and 2.7 times higher for energy and protein, respectively. In conclusion, this study showed that by-products were adequate substitutes for common concentrates and could greatly improve eFCR

Environmental public health tracking of childhood asthma using California health interview survey, traffic, and outdoor air pollution data.

BackgroundDespite extensive evidence that air pollution affects childhood asthma, state-level and national-level tracking of asthma outcomes in relation to air pollution is limited.ObjectivesOur goals were to evaluate the feasibility of linking the 2001 California Health Interview Survey (CHIS), air monitoring, and traffic data; estimate associations between traffic density (TD) or outdoor air pollutant concentrations and childhood asthma morbidity; and evaluate the usefulness of such databases, linkages, and analyses to Environmental Public Health Tracking (EPHT).MethodsWe estimated TD within 500 feet of residential cross-streets of respondents and annual average pollutant concentrations based on monitoring station measurements. We used logistic regression to examine associations with reported asthma symptoms and emergency department (ED) visits/hospitalizations.ResultsAssignment of TD and air pollution exposures for cross-streets was successful for 82% of children with asthma in Los Angeles and San Diego, California, Counties. Children with asthma living in high ozone areas and areas with high concentrations of particulate matter < 10 microm in aerodynamic diameter experienced symptoms more frequently, and those living close to heavy traffic reported more ED visits/hospitalizations. The advantages of the CHIS for asthma EPHT include a large and representative sample, biennial data collection, and ascertainment of important socio-demographic and residential address information. Disadvantages are its cross-sectional design, reliance on parental reports of diagnoses and symptoms, and lack of information on some potential confounders.ConclusionsDespite limitations, the CHIS provides a useful framework for examining air pollution and childhood asthma morbidity in support of EPHT, especially because later surveys address some noted gaps. We plan to employ CHIS 2003 and 2005 data and novel exposure assessment methods to re-examine the questions raised here

An interpolating particle method for the Vlasov-Poisson equation

In this paper we present a novel particle method for the Vlasov--Poisson equation. Unlike in conventional particle methods, the particles are not interpreted as point charges, but as point values of the distribution function. In between the particles, the distribution function is reconstructed using mesh-free interpolation. Our numerical experiments confirm that this approach results in significantly increased accuracy and noise reduction. At the same time, many benefits of the conventional schemes are preserved

First passage times in integrate-and-fire neurons with stochastic thresholds

We consider a leaky integrate--and--fire neuron with deterministic subthreshold dynamics and a firing threshold that evolves as an Ornstein-Uhlenbeck process. The formulation of this minimal model is motivated by the experimentally observed widespread variation of neural firing thresholds. We show numerically that the mean first passage time can depend non-monotonically on the noise amplitude. For sufficiently large values of the correlation time of the stochastic threshold the mean first passage time is maximal for non-vanishing noise. We provide an explanation for this effect by analytically transforming the original model into a first passage time problem for Brownian motion. This transformation also allows for a perturbative calculation of the first passage time histograms. In turn this provides quantitative insights into the mechanisms that lead to the non-monotonic behaviour of the mean first passage time. The perturbation expansion is in excellent agreement with direct numerical simulations. The approach developed here can be applied to any deterministic subthreshold dynamics and any Gauss-Markov processes for the firing threshold. This opens up the possibility to incorporate biophysically detailed components into the subthreshold dynamics, rendering our approach a powerful framework that sits between traditional integrate-and-fire models and complex mechanistic descriptions of neural dynamics