Simulating the aerodynamic performance and wake dynamics of a vertical-axis wind turbine

The accurate prediction of the aerodynamics and performance of vertical-axis wind turbines is essential if their design is to be improved but poses a signifi cant challenge to numerical simulation tools. The cyclic motion of the blades induces large variations in the angle of attack of the blades that can manifest as dynamic stall. In addition, predicting the interaction between the blades and the wake developed by the rotor requires a high-fi delity representation of the vortical structures within the fl ow fi eld in which the turbine operates. The aerodynamic performance and wake dynamics of a Darrieus-type vertical-axis wind turbine consisting of two straight blades is simulated using Brown’s Vorticity Transport Model. The predicted variation with azimuth of the normal and tangential force on the turbine blades compares well with experimental measurements. The interaction between the blades and the vortices that are shed and trailed in previous revolutions of the turbine is shown to have a signifi cant effect on the distribution of aerodynamic loading on the blades. Furthermore, it is suggested that the disagreement between experimental and numerical data that has been presented in previous studies arises because the blade–vortex interactions on the rotor were not modelled with sufficient fidelity

Regulation of Water Use and Takings—The Government Lawyer’s Perspective

11 pages. Contains 3 pages of references

Inverse Condemnation Litigation in the 1990s—The Uncertain Legacy of the Supreme Court\u27s Lucas and Yee Decisions

This Article focuses on what the Yee and Lucas decisions hold, what Takings Clause issues they leave unresolved and, perhaps most importantly, what key inverse condemnation questions are likely to be the focus of future takings litigation in the muddled wake of Yee and Lucas

Regulation of Water Use and Takings—The Government Lawyer’s Perspective

11 pages. Contains 3 pages of references

Early Retirement and Public Disability Insurance Applications: Exploring the Impact of Depression

This paper investigates the impact of depression on labor force participation among older workers. Empirically, we use two analytic strategies and rely on a sample drawn from the Health and Retirement Survey. Depression directly and indirectly increases individuals%u2019 probability of retiring early and applying for DI benefits, after accounting for other predictors of labor force exit. Accounting for the independent effects of depression, disability associated with physical illness may be smaller than the official statistics suggest. There may be great economic gains in increasing depression treatment awareness and access to treatment for individuals, employers and society.

Clarifying eudaimonia and psychological functioning to complement evaluative and experiential well-being : Why basic psychological needs should be measured in national accounts of well-being

Measuring subjective well-being as a key indicator of national wellness has increasingly become part of the international agenda. Current recommendations for measuring well-being at a national level propose three separate dimensions: evaluative well-being, experiential well-being, and eudaimonia. Whereas the measurement of the first two dimensions is relatively standardized, the third category has remained undertheorized, lacking consensus on how to define and operationalize it. To remedy the situation, we propose that the third dimension should focus on psychological functioning and the identification of key psychological factors humans generally need to live well. A key part of psychological functioning is the satisfaction of basic psychological needs—specific types of satisfying experiences that are essential for psychological health and well-being. Psychological needs as a category provides a parsimonious set of elements with clear inclusion criteria that are strongly anchored in theory and our current understanding of human nature—and could thus form a core part of the third, “eudaimonic” dimension of well-being. The needs for autonomy, competence, and relatedness have especially received broad empirical support. Accordingly, national accounts of well-being should include measures for key psychological needs to gain an enriched and practically useful understanding of the well-being of the citizens

Determination of biomembrane bending moduli in fully atomistic simulations.

The bilayer bending modulus (Kc) is one of the most important physical constants characterizing lipid membranes, but precisely measuring it is a challenge, both experimentally and computationally. Experimental measurements on chemically identical bilayers often differ depending upon the techniques employed, and robust simulation results have previously been limited to coarse-grained models (at varying levels of resolution). This Communication demonstrates the extraction of Kc from fully atomistic molecular dynamics simulations for three different single-component lipid bilayers (DPPC, DOPC, and DOPE). The results agree quantitatively with experiments that measure thermal shape fluctuations in giant unilamellar vesicles. Lipid tilt, twist, and compression moduli are also reported

Dual Band Electrodes in Generator-Collector Mode: Simultaneous Measurement of Two Species

A computational model for the simulation of a double band collector-generator experiment is applied to the situation where two electrochemical reactions occur concurrently. It is shown that chronoamperometric measurements can be used to take advantage of differences in diffusion coefficients to measure the concentrations of both electroactive species simultaneously, by measuring the time at which the collection efficiency reaches a specific value. The separation of the electrodes is shown to not affect the sensitivity of the method (in terms of percentage changes in the measured time to reach the specified collection efficiency), but wider gaps can provide a greater range of (larger) absolute values of this characteristic time. It is also shown that measuring the time taken to reach smaller collection efficiencies can allow for the detection of smaller amounts of whichever species diffuses faster. The case of a system containing both ascorbic acid and opamine in water is used to exemplify the method, and it is shown that mole fractions of ascorbic acid between 0.055 and 0.96 can, in principle, be accurately measured.Comment: 34 pages, 8 figure