810 research outputs found
Oxidation and agglomeration resistance of thin gage dispersion strengthened alloys Final report
Measuring oxidation resistance of thin dispersion strengthened nickel-chromium alloys for aircraft application
Specific volumes of the Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 alloy in the liquid, glass, and crystalline states
The specific volumes of the Zr41.2Ti13.8CU12.5Ni10.0Be2.25 alloy as a function of temperature, T, are determined by employing an image digitizing technique and numerical calculation methods applied to the electrostatically levitated spherical alloy. The linear fitting of the volumes of the alloy in the liquid, V-l, glass, V-g, and crystalline V-c, states in the temperature ranges shown in parentheses are V-l(T) = 0.1583 + 8.877 x 10(-6)T(cm^(3)/g) (700-1300 K); V-g(T) = 0.1603 + 5.528 x 10^(-6)T (400-550 K); V-c(T) = 0.1583 + 6.211 x 10(-6)T(400-850 K). The average volume thermal expansion coefficients within the temperature ranges are determined to be 5.32, 3.39, and 3.83 x 10^(-5) (1/K) for the liquid, glass, and crystalline states, respectively
Rheological study of structural transitions in triblock copolymers in a liquid crystal solvent
Rheological properties of triblock copolymers dissolved in a nematic liquid crystal (LC) solvent demonstrate that their microphase separated structure is heavily influenced by changes in LC order. Nematic gels were created by swelling a well-defined, high molecular weight ABA block copolymer with the small-molecule nematic LC solvent 4-pentyl-4-cyanobiphenyl (5CB). The B midblock is a side-group liquid crystal polymer (SGLCP) designed to be soluble in 5CB and the A endblocks are polystyrene, which is LC-phobic and microphase separates to produce a physically cross-linked, thermoreversible, macroscopic polymer network. At sufficiently low polymer concentration a plateau modulus in the nematic phase, characteristic of a gel, abruptly transitions to terminal behavior when the gel is heated into its isotropic phase. In more concentrated gels, endblock aggregates persist into the isotopic phase. Dramatic changes in network structure are observed over small temperature windows (as little as 1 °C) due to tccche rapidly changing LC order near the isotropization point. The discontinuous change in solvent quality produces an abrupt change in viscoelastic properties for three polymers having different pendant mesogenic groups and matched block lengths
Nonlinear stochastic controllers for semiactive and regenerative structural systems, with guaranteed quadratic performance margins
In many applications of vibration control, the circumstances of the application impose constraints on the energy available for the actuation of control forces. Semiactive dampers (i.e., viscous dampers with controllable coefficients) constitute the simplest example of such actuation in structural control applications. Regenerative Force Actuation (RFA) networks are an extension of semiactive devices, in which mechanical energy is first converted to electrical energy, which is then dissipated in a controllable resistive network. A fairly general class of semiactive and regenerative systems can be characterized by a differential equation which is bilinear (i.e., linear in state, linear in control input, but nonlinear in both). This paper presents a general approach to bilinear feedback control system design for semiactive and regenerative systems, which is analytically guaranteed to out-perform optimal linear viscous damping in stationary stochastic response, under the familiar Quadratic Gaussian performance measure. The design for full-state feedback and for the more practical case of noise-corrupted and incomplete measurements (i.e., output feedback) are separately discussed. Variants of the theory are shown to exist for other quadratic performance measures, including risk-sensitive and multi-objective frameworks. An illustrative application to civil engineering is presented
Support for Redistribution in Western Europe: Assessing the role of religion
Previous sociological studies have paid little attention to religion as a central determinant of individual preferences for redistribution. In this article we argue that religious individuals, living in increasingly secular societies, differ in political preferences from their secular counterparts. Based on the theory of religious cleavages, we expect that religious individuals will oppose income redistribution by the state. Furthermore, in contexts where the polarization between religious and secular individuals is large, preferences for redistribution will be lower. In the empirical analysis we test our predictions in a multilevel framework, using data from the European Social Survey 2002–2006 for 16 Western European countries. After controlling for a wide range of individual socio-economic factors and for welfare-state policies, religion plays and important explanatory role. We find that both Catholics and Protestants strongly oppose income redistribution by the state. The cleavage between religious and secular individuals is far more important than the difference between denominations. Using a refined measure of religious polarization, we also find that in more polarized context the overall level of support for redistribution is lower
State Capacity and the Environmental Investment Gap in Authoritarian States
We construct an n-period, constrained optimization model where the authoritarian ruler maximizes expected rents subject to budget constraint of available surplus. We show that the larger state capacity is in the previous period, the worse environmental quality will be in the next period: while infrastructural investment and environmental protection increase with state capacity, the former increases at a faster rate which enlarges the gap between the two?the environmental investment gap. Given infrastructural public goods typically damage the environment, the larger this gap is the worse the environmental quality would be. This follows from rulers? optimizing logic of equating marginal returns once we assume the declining marginal productivity of factors of production of surplus. We model three types of air and water pollutants in autocracies as a function of state capacity and other relevant variables. State capacity is associated with higher levels of all three types of pollutants
OPEN XAL Status Report 2015
MOPW1050International audienceOpen XAL is an accelerator physics software platformdeveloped in collaboration among several facilitiesaround the world. The Open XAL collaboration wasformed in 2010 to port, improve and extend the successfulXAL platform used at the Spallation Neutron Source foruse in the broader accelerator community and to establishit as the standard platform for accelerator physicssoftware. The site-independent core is complete, activeapplications have been ported, and now we are in theprocess of verification and transitioning to using OpenXAL in production. This paper will present the currentstatus and a roadmap for this project
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Sozialstaatliche Kürzungspolitik in Deutschland: Nur eine Mär? Eine quantitative Gesetzgebungsanalyse 1974–2014
Quantitative analyses on welfare state dynamics have to cope with the “dependent variable problem”, as studies on social spending reach different conclusions than analyses of replacement rate data. This article suggests a way around this problem by presenting results from a fine-grained analysis of welfare state legislation in Germany between 1974 and 2014.
We show that the German welfare state has seen both cuts and expansions occur in all decades. Moreover, we show by means of a regression analysis that partisan politics play a role. Supporting the “Nixon-in-China”-thesis, social democratic governments are associated with a higher probability of cutbacks – especially in times of budgetary pressure – whereas expansions are more likely under Christian democratic governments
Psychological determinants of whole-body endurance performance
Background: No literature reviews have systematically identified and evaluated research on the psychological determinants of endurance performance, and sport psychology performance-enhancement guidelines for endurance sports are not founded on a systematic appraisal of endurance-specific research.
Objective: A systematic literature review was conducted to identify practical psychological interventions that improve endurance performance and to identify additional psychological factors that affect endurance performance. Additional objectives were to evaluate the research practices of included studies, to suggest theoretical and applied implications, and to guide future research.
Methods: Electronic databases, forward-citation searches, and manual searches of reference lists were used to locate relevant studies. Peer-reviewed studies were included when they chose an experimental or quasi-experimental research design, a psychological manipulation, endurance performance as the dependent variable, and athletes or physically-active, healthy adults as participants.
Results: Consistent support was found for using imagery, self-talk, and goal setting to improve endurance performance, but it is unclear whether learning multiple psychological skills is more beneficial than learning one psychological skill. The results also demonstrated that mental fatigue undermines endurance performance, and verbal encouragement and head-to-head competition can have a beneficial effect. Interventions that influenced perception of effort consistently affected endurance performance.
Conclusions: Psychological skills training could benefit an endurance athlete. Researchers are encouraged to compare different practical psychological interventions, to examine the effects of these interventions for athletes in competition, and to include a placebo control condition or an alternative control treatment. Researchers are also encouraged to explore additional psychological factors that could have a negative effect on endurance performance. Future research should include psychological mediating variables and moderating variables. Implications for theoretical explanations of endurance performance and evidence-based practice are described
A calibration protocol for population-specific accelerometer cut-points in children
PurposeTo test a field-based protocol using intermittent activities representative of children\u27s physical activity behaviours, to generate behaviourally valid, population-specific accelerometer cut-points for sedentary behaviour, moderate, and vigorous physical activity.MethodsTwenty-eight children (46% boys) aged 10–11 years wore a hip-mounted uniaxial GT1M ActiGraph and engaged in 6 activities representative of children\u27s play. A validated direct observation protocol was used as the criterion measure of physical activity. Receiver Operating Characteristics (ROC) curve analyses were conducted with four semi-structured activities to determine the accelerometer cut-points. To examine classification differences, cut-points were cross-validated with free-play and DVD viewing activities.ResultsCut-points of ≤372, >2160 and >4806 counts•min−1 representing sedentary, moderate and vigorous intensity thresholds, respectively, provided the optimal balance between the related needs for sensitivity (accurately detecting activity) and specificity (limiting misclassification of the activity). Cross-validation data demonstrated that these values yielded the best overall kappa scores (0.97; 0.71; 0.62), and a high classification agreement (98.6%; 89.0%; 87.2%), respectively. Specificity values of 96–97% showed that the developed cut-points accurately detected physical activity, and sensitivity values (89–99%) indicated that minutes of activity were seldom incorrectly classified as inactivity.ConclusionThe development of an inexpensive and replicable field-based protocol to generate behaviourally valid and population-specific accelerometer cut-points may improve the classification of physical activity levels in children, which could enhance subsequent intervention and observational studies.<br /
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