Uniaxial and biaxial soft deformations of nematic elastomers

We give a geometric interpretation of the soft elastic deformation modes of nematic elastomers, with explicit examples, for both uniaxial and biaxial nematic order. We show the importance of body rotations in this non-classical elasticity and how the invariance under rotations of the reference and target states gives soft elasticity (the Golubovic and Lubensky theorem). The role of rotations makes the Polar Decomposition Theorem vital for decomposing general deformations into body rotations and symmetric strains. The role of the square roots of tensors is discussed in this context and that of finding explicit forms for soft deformations (the approach of Olmsted).Comment: 10 pages, 10 figures, RevTex, AmsTe

An Adaptive Computational Model for Predicting the Density Distribution of the Proximal Femur

A custom algorithm was developed to simulate adaptive boneremodeling. The process of adaptive bone remodeling can besimulated with a self-optimizing finite element method (FEM). Thebasic remodeling rule attempts to obtain a constant value for thestrain energy per unit bone mass, by adapting density. The precisesolution is dependent on the loads, initial conditions and theparameters in the remodeling rule. The aim of this study was toidentify how the bone density distribution of the proximal femurwas affected by parameters which govern the remodeling process.The forces at different phases of the gait cycle were applied asboundary conditions. The bone density distributions from theseforces were averaged to estimate the density distribution in theproximal femur. The effect of varying the spatial influencefunction, and the influence range on the converged solution wereinvestigated. It was shown that varying these parameters withinreasonable upper and lower bounds had very little impact on thequalitative form of the converged solution. In all cases, thesolutions obtained are comparable with the actual density in theproximal femur, as measured by DEXA scans

It Depends on What You Share: The Elusive Cost Savings from Service Sharing

Intermunicipal cooperation is the most prevalent alternative service delivery method for US local governments. While aspirations for budgetary savings are one motivating factor, increased service quality and regional coordination are also important goals. We use an original 2013 survey of local governments in New York State to assess the level of service sharing and outcomes. We match our survey with 20 years (1996–2016) of service-level costs data to explore the relationships between sharing and costs across 12 common local government services. We contribute to the literature by providing the first multivariate assessment of the effect of cooperation on costs in the United States, and we contribute theoretical insights on the objectives and type of cooperation to explain differences in the effects of cooperation on costs across a variety of services. Our multivariate time series regressions find that service sharing leads to cost reductions in solid waste management, roads and highways, police, library, and sewer services; no difference in costs for economic development, ambulance/EMS, fire, water, and youth recreation; and higher costs in elder services, and planning and zoning. These differences are explained by whether services have characteristics such as asset specificity and the ability to achieve economies of scale on the one hand, or if sharing leads to greater administrative intensity or promotes other objectives such as quality and regional coordination outcomes on the other hand. We also analyze the effect of sharing on service costs over time, and find solid waste, roads and highways, police, and library are the only services where costs show a continued downward trend. These results show the limited role for economies of scale, even in asset specific services. Because cost savings are elusive, public sector reformers should be careful not to assume cost savings from sharing. The theoretical foundations for service sharing extend beyond economies of scale and transaction costs. Scholars should give more attention to organizational form and the broader goals of sharing

High Speed Photometry of SDSS J013701.06-091234.9

We present high speed photometry of the Sloan Digital Sky Survey cataclysmic variable SDSS J013701.06-091234.9 in quiescence and during its 2003 December superoutburst. The orbital modulation at 79.71\pm0.01 min is double humped; the superhump period is 81.702\pm0.007 min. Towards the end of the outburst late superhumps with a period of 81.29\pm0.01 min were observed. We argue that this is a system of very low mass transfer rate, and that it probably has a long outburst interval.Comment: 5 pages, 8 figures. Accepted for publication in MNRA

Iron-Line Emission as a Probe of Bardeen-Petterson Accretion Disks

In this work we show that Bardeen-Petterson accretion disks can exhibit unique, detectable features in relativistically broadened emission line profiles. Some of the unique characteristics include inverted line profiles with sharper red horns and softer blue horns and even profiles with more than 2 horns from a single rest-frame line. We demonstrate these points by constructing a series of synthetic line profiles using simple two-component disk models. We find that the resultant profiles are very sensitive to the two key parameters one would like to constrain, namely the Bardeen-Petterson transition radius r_{BP} and the relative tilt \beta between the two disk components over a range of likely values [10 < r_{BP}/(GM/c^2) < 40 ; 15deg < \beta < 45deg]. We use our findings to show that some of the ``extra'' line features observed in the spectrum of the Seyfert-I galaxy MCG--6-30-15 may be attributable to a Bardeen-Petterson disk structure. Similarly, we apply our findings to two likely Bardeen-Petterson candidate Galactic black holes - GRO J1655-40 and XTE J1550-564. We provide synthetic line profiles of these systems using observationally constrained sets of parameters. Although we do not formally fit the data for any of these systems, we confirm that our synthetic spectra are consistent with current observations.Comment: 13 pages, 11 figures, submitted to Ap

Fuel conservative guidance concept for shipboard landing of powered-life aircraft

A simulation study was undertaken to investigate the application of energy conservative guidance (ECG) software, developed at NASA Ames Research Center, to improve the time and fuel efficiency of powered lift airplanes operating from aircraft carriers at sea. When a flightpath is indicated by a set of initial conditions for the aircraft and a set of positional waypoints with associated airspeeds, the ECG software synthesizes the necessary guidance commands to optimize fuel and time along the specified path. A major feature of the ECG system is the ability to synthesize a trajectory that will allow the aircraft to capture the specified path at any waypoint with the desired heading and airspeed from an arbitrary set of initial conditions. Five paths were identified and studied. These paths demonstrate the ECG system's ability to save flight time and fuel by more efficiently managing the aircraft's capabilities. Results of this simulation study show that when restrictions on the approach flightpath imposed for manual operation are removed completely, fuel consumption during the approach was reduced by as much as 49% (610 lb fuel) and the time required to fly the flightpath was reduced by as much as 41% (5 min). Savings due to ECG were produced by: (1) shortening the total flight time; (2) keeping the airspeed high as long as possible to minimize time spent flying in a regime in which more engine thrust is required for lift to aid the aerodynamic lift; (3) minimizing time spent flying at constant altitude at slow airspeeds; and (4) synthesizing a path from any location for a direct approach to landing without entering a holding pattern or other fixed approach path

Photonic gaps in cholesteric elastomers under deformation

Cholesteric liquid crystal elastomers have interesting and potentially very useful photonic properties. In an ideal monodomain configuration of these materials, one finds a Bragg-reflection of light in a narrow wavelength range and a particular circular polarization. This is due to the periodic structure of the material along one dimension. In many practical cases, the cholesteric rubber possesses a sufficient degree of quenched disorder, which makes the selective reflection broadband. We investigate experimentally the problem of how the transmittance of light is affected by mechanical deformation of the elastomer, and the relation to changes in liquid crystalline structure. We explore a series of samples which have been synthesized with photonic stop-gaps across the visible range. This allows us to compare results with detailed theoretical predictions regarding the evolution of stop-gaps in cholesteric elastomers

Individual Time Perspective And Alliance Formation Behavior

The impact of time orientation on leaders&rsquo; behavior has been largely unexplored in research.&nbsp; This study examined the role of time perspective in alliance formation.&nbsp; Using a game, participants formed alliances using information about past behavior.&nbsp; Findings suggest that participants with future time perspective were more likely to initiate alliances and those with a past-negative perspective were more likely to cooperate.&nbsp; This finding supports the Theory of Leadership and Time Orientation.&nbsp