53,909 research outputs found
Binscatter Regressions
We introduce the \texttt{Stata} (and \texttt{R}) package \textsf{Binsreg},
which implements the binscatter methods developed in
\citet*{Cattaneo-Crump-Farrell-Feng_2019_Binscatter}. The package includes the
commands \texttt{binsreg}, \texttt{binsregtest}, and \texttt{binsregselect}.
The first command (\texttt{binsreg}) implements binscatter for the regression
function and its derivatives, offering several point estimation, confidence
intervals and confidence bands procedures, with particular focus on
constructing binned scatter plots. The second command (\texttt{binsregtest})
implements hypothesis testing procedures for parametric specification and for
nonparametric shape restrictions of the unknown regression function. Finally,
the third command (\texttt{binsregselect}) implements data-driven number of
bins selectors for binscatter implementation using either quantile-spaced or
evenly-spaced binning/partitioning. All the commands allow for covariate
adjustment, smoothness restrictions, weighting and clustering, among other
features. A companion \texttt{R} package with the same capabilities is also
available
Model correlation and damage location for large space truss structures: Secant method development and evaluation
On-orbit testing of a large space structure will be required to complete the certification of any mathematical model for the structure dynamic response. The process of establishing a mathematical model that matches measured structure response is referred to as model correlation. Most model correlation approaches have an identification technique to determine structural characteristics from the measurements of the structure response. This problem is approached with one particular class of identification techniques - matrix adjustment methods - which use measured data to produce an optimal update of the structure property matrix, often the stiffness matrix. New methods were developed for identification to handle problems of the size and complexity expected for large space structures. Further development and refinement of these secant-method identification algorithms were undertaken. Also, evaluation of these techniques is an approach for model correlation and damage location was initiated
Splitting methods for constrained diffusion-reaction systems
We consider Lie and Strang splitting for the time integration of constrained
partial differential equations with a nonlinear reaction term. Since such
systems are known to be sensitive with respect to perturbations, the splitting
procedure seems promising as we can treat the nonlinearity separately. This has
some computational advantages, since we only have to solve a linear constrained
system and a nonlinear ODE. However, Strang splitting suffers from order
reduction which limits its efficiency. This is caused by the fact that the
nonlinear subsystem produces inconsistent initial values for the constrained
subsystem. The incorporation of an additional correction term resolves this
problem without increasing the computational cost. Numerical examples including
a coupled mechanical system illustrate the proven convergence results
Optimal dynamic taxation, saving and investment
Fiscal Policy;Optimization;public economics
Revisiting topology optimization with buckling constraints
We review some features of topology optimization with a lower bound on the
critical load factor, as computed by linearized buckling analysis. The change
of the optimized design, the competition between stiffness and stability
requirements and the activation of several buckling modes, depending on the
value of such lower bound, are studied. We also discuss some specific issues
which are of particular interest for this problem, as the use of non-conforming
finite elements for the analysis, the use of inconsistent sensitivities in the
optimization and the replacement of the single eigenvalue constraints with an
aggregated measure. We discuss the influence of these practices on the
optimization result, giving some recommendations.Comment: 15 pages, 12 figures, 2 table
A Behavioral and Neural Evaluation of Prospective Decision-Making under Risk
Making the best choice when faced with a chain of decisions requires a person to judge both anticipated outcomes and future actions. Although economic decision-making models account for both risk and reward in single-choice contexts, there is a dearth of similar knowledge about sequential choice. Classical utility-based models assume that decision-makers select and follow an optimal predetermined strategy, regardless of the particular order in which options are presented. An alternative model involves continuously reevaluating decision utilities, without prescribing a specific future set of choices. Here, using behavioral and functional magnetic resonance imaging (fMRI) data, we studied human subjects in a sequential choice task and use these data to compare alternative decision models of valuation and strategy selection. We provide evidence that subjects adopt a model of reevaluating decision utilities, in which available strategies are continuously updated and combined in assessing action values. We validate this model by using simultaneously acquired fMRI data to show that sequential choice evokes a pattern of neural response consistent with a tracking of anticipated distribution of future reward, as expected in such a model. Thus, brain activity evoked at each decision point reflects the expected mean, variance, and skewness of possible payoffs, consistent with the idea that sequential choice evokes a prospective evaluation of both available strategies and possible outcomes
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