Transform methods for precision continuum and control models of flexible space structures

An open loop optimal control algorithm is developed for general flexible structures, based on Laplace transform methods. A distributed parameter model of the structure is first presented, followed by a derivation of the optimal control algorithm. The control inputs are expressed in terms of their Fourier series expansions, so that a numerical solution can be easily obtained. The algorithm deals directly with the transcendental transfer functions from control inputs to outputs of interest, and structural deformation penalties, as well as penalties on control effort, are included in the formulation. The algorithm is applied to several structures of increasing complexity to show its generality

Stabilization of solitons of the multidimensional nonlinear Schrodinger equation: Matter-wave breathers

We demonstrate that stabilization of solitons of the multidimensional Schrodinger equation with a cubic nonlinearity may be achieved by a suitable periodic control of the nonlinear term. The effect of this control is to stabilize the unstable solitary waves which belong to the frontier between expanding and collapsing solutions and to provide an oscillating solitonic structure, some sort of breather-type solution. We obtain precise conditions on the control parameters to achieve the stabilization and compare our results with accurate numerical simulations of the nonlinear Schrodinger equation. Because of the application of these ideas to matter waves these solutions are some sort of matter breathers

Does Immigration Affect the Long-Term Educational Outcomes of Natives? Quasi-Experimental Evidence

This paper uses the mass migration wave to Israel in the 1990s to examine the impact of immigrant concentration in elementary school on the long-term academic outcomes of native students in high school. To identify the causal effect of immigrant children on their peers, we exploit random variation in the number of immigrants across grades within the same school. The results suggest that the overall presence of immigrants had essentially no effect on the quality of the high school attended by native Israelis and on dropout rates, and at most a mild negative effect on high school matriculation rates. However, when we break up the sample by parents' education and by ethnic origin, we find that disadvantaged children were more likely to have been adversely affected by a higher immigrant concentration in elementary school. Focusing on the impact of Ethiopian immigrants who are from a much lower socio-economic background, we find stronger evidence of adverse effects, especially for disadvantaged students and in classes where immigrant concentration was particularly high.

A Game Theoretic Approach to Analyse Cooperation between Rural Households in Northern Nigeria

To improve the livelihood of the poor in Sub-Saharan Africa (SSA) much attention has been paid to the development of new agricultural technologies. We hypothesize that farmers can also improve their livelihood through cooperation. Partial cooperation, in which knowledge is shared or bargaining power improved, is relatively common in SSA, while cooperation where all resources are fully shared, which we address, has rarely been investigated. An important pre-requisite to establish such cooperation, is the need for a fair division rule for the gains of the cooperation. This paper combines linear programming and cooperative game theory to model the effects of cooperation of (individual) households on income and farm plans. Linear programming establishes insight in the optimal farm plans in cooperation, and cooperative game theory is used to generate fair division rules. The model is applied to a village in Northern Nigeria. Households are clustered based on socio-economic parameters, and we explore cooperation between clusters. Cooperation leads to increased income and results in changes in farm plans, because more efficient use of resources leads to more intensified agriculture (labour intensive – high value crops).Cooperations, Linear Programming, Nigeria, Livelihood, Agricultural and Food Policy, Community/Rural/Urban Development, Consumer/Household Economics, Environmental Economics and Policy, Food Consumption/Nutrition/Food Safety, Food Security and Poverty, International Relations/Trade, Marketing, Productivity Analysis, Research and Development/Tech Change/Emerging Technologies,

Episodic Learning with Control Lyapunov Functions for Uncertain Robotic Systems

Many modern nonlinear control methods aim to endow systems with guaranteed properties, such as stability or safety, and have been successfully applied to the domain of robotics. However, model uncertainty remains a persistent challenge, weakening theoretical guarantees and causing implementation failures on physical systems. This paper develops a machine learning framework centered around Control Lyapunov Functions (CLFs) to adapt to parametric uncertainty and unmodeled dynamics in general robotic systems. Our proposed method proceeds by iteratively updating estimates of Lyapunov function derivatives and improving controllers, ultimately yielding a stabilizing quadratic program model-based controller. We validate our approach on a planar Segway simulation, demonstrating substantial performance improvements by iteratively refining on a base model-free controller

Spreading Academic Pay over Nine or Twelve Months: Economists Are Supposed to Know Better, but Do They Act Better?

Our paper empirically considers two general hypotheses related to the literature of behavioral economics. First, we test the null hypothesis that individuals behave, on average, in a manner more consistent with the rational expectations hypothesis than with the idea of self-control in the face of hyperbolic discounting in their saving decisions. Second, along a variety of dimensions, we examine whether individuals exhibit Herbert Simon’s notion that the goal formation of individuals will differ depending upon their relative levels of experience and knowledge. Perhaps there are significant differences among groups in their saving decisions that depend upon their apparent levels of intelligence, education, and knowledge. Finally, using a variety of individual-specific control variables, we test for robustness of the results.Consumer Economics, Empirical Analysis, Life Cycle Models and Saving