6,538 research outputs found
Cream-Skimming, Parking and Other Intended and Unintended Effects of Performance-Based Contracting in Social Welfare Services
In a growing number of countries, the delivery of social welfare services is contracted out to private providers, and increasingly, using performance-based contracts. Critics of performance-based incentive contracts stress their potential unintended effects, including cream-skimming and other gaming activities intended to raise measured performance outcomes. We analyze the incentive effects of performance-based contracts, as well as their impacts on provider job placement rates, using unique data on Dutch cohorts of unemployed and disabled workers that were assigned to private social welfare providers in 2002-2005. We take advantage of variation in contract design over this period, where procured contracts gradually moved from partial performance-contingent pay to contracts with 100%-performance contingent reward schemes, and analyze the impact of these changes using panel data that allow us to control for cohort types and to develop explicit measures of selection into the programs. We find evidence of cream-skimming and other gaming activities on the part of providers but little impact of these activities on job placement rates. Overall, moving to a system with contract payments fully contingent on performance appears to increase job placements for more readily employable workers, although it does not affect the duration of their jobs.social welfare, performance contracting
Relativistic Mean Field in 80 nuclei and low energy proton reactions
Relativistic Mean Field calculations have been performed for a number of
nuclei in mass 80 region. Ground state binding energy, charge radius
and charge density values have been compared with experiment. Optical potential
have been generated folding the nuclear density with the microscopic nuclear
interaction DDM3Y. S-factors for low energy () and () reactions
have been calculated and compared with experiment.Comment: To appear in Physical Review
Spin-mediated dissipation and frequency shifts of a cantilever at milliKelvin temperatures
We measure the dissipation and frequency shift of a magnetically coupled
cantilever in the vicinity of a silicon chip, down to mK. The dissipation
and frequency shift originates from the interaction with the unpaired
electrons, associated with the dangling bonds in the native oxide layer of the
silicon, which form a two dimensional system of electron spins. We approach the
sample with a m-diameter magnetic particle attached to an ultrasoft
cantilever, and measure the frequency shift and quality factor as a function of
temperature and the distance. Using a recent theoretical analysis [J. M. de
Voogd et al., arXiv:1508.07972 (2015)] of the dynamics of a system consisting
of a spin and a magnetic resonator, we are able to fit the data and extract the
relaxation time ms and spin density
spins per nm. Our analysis shows that at temperatures mK magnetic
dissipation is an important source of non-contact friction.Comment: 5 pages, 3 figure
Optimization of Low Reynolds Number Airfoils for Martian Rotor Applications Using an Evolutionary Algorithm
The Mars Helicopter (MH) will be flying on the NASA Mars 2020 rover mission scheduled to launch in July of 2020. Research is being performed at the Jet Propulsion Laboratory (JPL) and NASA Ames Research Center to extend the current capabilities and develop the Mars Science Helicopter (MSH) as the next possible step for Martian rotorcraft. The low atmospheric density and the relatively small-scale rotors result in very low chord-based Reynolds number flows over the rotor airfoils. The low Reynolds number regime results in rapid performance degradation for conventional airfoils due to laminar separation without reattachment. Unconventional airfoil shapes with sharp leading edges are explored and optimized for aerodynamic performance at representative Reynolds-Mach combinations for a concept rotor. Sharp leading edges initiate immediate flow separation, and the occurrence of large-scale vortex shedding is found to contribute to the relative performance increase of the optimized airfoils, compared to conventional airfoil shapes. The oscillations are shown to occur independent from laminar-turbulent transition and therefore result in sustainable performance at lower Reynolds numbers. Comparisons are presented to conventional airfoil shapes and peak lift-to-drag ratio increases between 17% and 41% are observed for similar section lift
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