A highly miniaturized electron and ion energy spectrometer prototype for the rapid analysis of space plasmas.

MEMS (Micro Electro-Mechanical Systems) plasma analyzers are a promising possibility for future space missions but conventional instrument designs are not necessarily well suited to micro-fabrication. Here, a candidate design for a MEMS-based instrument has been prototyped using electron-discharge machining. The device features 10 electrostatic analyzers that, with a single voltage applied to it, allow five different energies of electron and five different energies of positive ion to be simultaneously sampled. It has been simulated using SIMION and the electron response characteristics tested in an instrument calibration chamber. Small deviations found in the electrode spacing of the as-built prototype were found to have some effect on the electron response characteristics but do not significantly impede its performance

Stochastic stability for a model representing the intake manifold pressure of an automotive engine

The paper presents conditions to assure stochastic stability for a nonlinear model. The proposed model is used to represent the input-output dynamics of the angle of aperture of the throttle valve (input) and the manifold absolute pressure (output) in an automotive spark-ignition engine. The automotive model is second moment stable, as stated by the theoretical result—data collected from real-time experiments supports this finding.Peer ReviewedPostprint (author's final draft

Self-consistent theory of large amplitude collective motion: Applications to approximate quantization of non-separable systems and to nuclear physics

The goal of the present account is to review our efforts to obtain and apply a ``collective'' Hamiltonian for a few, approximately decoupled, adiabatic degrees of freedom, starting from a Hamiltonian system with more or many more degrees of freedom. The approach is based on an analysis of the classical limit of quantum-mechanical problems. Initially, we study the classical problem within the framework of Hamiltonian dynamics and derive a fully self-consistent theory of large amplitude collective motion with small velocities. We derive a measure for the quality of decoupling of the collective degree of freedom. We show for several simple examples, where the classical limit is obvious, that when decoupling is good, a quantization of the collective Hamiltonian leads to accurate descriptions of the low energy properties of the systems studied. In nuclear physics problems we construct the classical Hamiltonian by means of time-dependent mean-field theory, and we transcribe our formalism to this case. We report studies of a model for monopole vibrations, of $^{28}$Si with a realistic interaction, several qualitative models of heavier nuclei, and preliminary results for a more realistic approach to heavy nuclei. Other topics included are a nuclear Born-Oppenheimer approximation for an {\em ab initio} quantum theory and a theory of the transfer of energy between collective and non-collective degrees of freedom when the decoupling is not exact. The explicit account is based on the work of the authors, but a thorough survey of other work is included.Comment: 203 pages, many figure

A Centered Index of Spatial Concentration : Axiomatic Approach with an Application to Population and Capital Cities

We construct an axiomatic index of spatial concentration around a center or capital point of interest, a concept with wide applicability from urban economics, economic geography and trade, to political economy and industrial organization. We propose basic axioms (decomposability and monotonicity) and renement axioms (order preservation, convexity, and local monotonicity) for how the index should respond to changes in the underlying distribution. We obtain a unique class of functions satisfying all these properties, defined over any n-dimensional Euclidian space : the sum of a decreasing, isoelastic function of individual distances to the capital point of interest, with specifc boundaries for the elasticity coecient that depend on n. We apply our index to measure the concentration of population around capital cities across countries and US states, and also in US metropolitan areas. We show its advantages over alternative measures, and explore its correlations with many economic and political variables of interest.Spatial Concentration, Population Concentration, Capital Cities, Gravity, CRRA, Harmonic Functions, Axiomatics

A Centered Index of Spatial Concentration: Axiomatic Approach with an Application to Population and Capital Cities

We construct an axiomatic index of spatial concentration around a center or capital point of interest, a concept with wide applicability from urban economics, economic geography and trade, to political economy and industrial organization. We propose basic axioms (decomposability and monotonicity) and refinement axioms (order preservation, convexity, and local monotonicity) for how the index should respond to changes in the underlying distribution. We obtain a unique class of functions satisfying all these properties, defined over any n-dimensional Euclidian space: the sum of a decreasing, isoelastic function of individual distances to the capital point of interest, with specific boundaries for the elasticity coefficient that depend on n. We apply our index to measure the concentration of population around capital cities across countries and US states, and also in US metropolitan areas. We show its advantages over alternative measures, and explore its correlations with many economic and political variables of interest.

A Centered Index of Spatial Concentration: Axiomatic Approach with an Application to Population and Capital Cities

We construct an axiomatic index of spatial concentration around a center or capital point of interest, a concept with wide applicability from urban economics, economic geography and trade, to political economy and industrial organization. We propose basic axioms (decomposability and monotonicity) and refinement axioms (order preservation, convexity, and local monotonicity) for how the index should respond to changes in the underlying distribution. We obtain a unique class of functions satisfying all these properties, defined over any n-dimensional Euclidian space: the sum of a decreasing, isoelastic function of individual distances to the capital point of interest, with specific boundaries for the elasticity coefficient that depend on n. We apply our index to measure the concentration of population around capital cities across countries and US states, and also in US metropolitan areas. We show its advantages over alternative measures, and explore its correlations with many economic and political variables of interest.Spatial Concentration, Population Concentration, Capital Cities, Gravity, CRRA, Harmonic Functions, Axiomatics.

Keeping Dictators Honest: the Role of Population Concentration

In order to explain the apparently paradoxical presence of acceptable governance in many non-democratic regimes, economists and political scientists have focused mostly on institutions acting as de facto checks and balances. In this paper, we propose that population plays a similar role in guaranteeing the quality of governance and redistribution. around the policy making center serves as an insurgency threat to a dictatorship, inducing it to yield to more redistribution and better governance. We bring this centered concept of population concentration to the data through the Centered Index of Spatial Concentration developed by Do & Campante (2008). The evidence supports our predictions: only in the sample of autocracies, population concentration around the capital city is positively associated with better governance and more redistribution (proxied by post-tax inequality), in OLS and IV regressions. Finally, we provide arguments to dismiss possible reverse causation as well as alternative, non-political economy explanations of such regularity, discuss the general applicability of our index and conclude with policy implications.Capital Cities, Gravity, Governance, Inequality, Redistribution, Population Concentration, Revolutions, Harmonic Functions, Axiomatics

Power-law statistics and stellar rotational velocities in the Pleiades

In this paper we will show that, the non-gaussian statistics framework based on the Kaniadakis statistics is more appropriate to fit the observed distributions of projected rotational velocity measurements of stars in the Pleiades open cluster. To this end, we compare the results from the $\kappa$ and $q$-distributions with the Maxwellian.Comment: 13 pages, 3 figure