Multidimensional optimization algorithms numerical results

This paper presents some multidimensional optimization algorithms. By using the "penalty function" method, these algorithms are used to solving an entire class of economic optimization problems. Comparative numerical results of certain new multidimensional optimization algorithms for solving some test problems known on literature are shown.optimization algorithm, multidimensional optimization, penalty function

Degradation modeling applied to residual lifetime prediction using functional data analysis

Sensor-based degradation signals measure the accumulation of damage of an engineering system using sensor technology. Degradation signals can be used to estimate, for example, the distribution of the remaining life of partially degraded systems and/or their components. In this paper we present a nonparametric degradation modeling framework for making inference on the evolution of degradation signals that are observed sparsely or over short intervals of times. Furthermore, an empirical Bayes approach is used to update the stochastic parameters of the degradation model in real-time using training degradation signals for online monitoring of components operating in the field. The primary application of this Bayesian framework is updating the residual lifetime up to a degradation threshold of partially degraded components. We validate our degradation modeling approach using a real-world crack growth data set as well as a case study of simulated degradation signals.Comment: Published in at http://dx.doi.org/10.1214/10-AOAS448 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

Domain wall in a chiral p-wave superconductor: a pathway for electrical current

Superconductors with p+ip pairing symmetry are characterized by chiral edge states, but these are difficult to detect in equilibrium since the resulting magnetic field is screened by the Meissner effect. Nonequilibrium detection is hindered by the fact that the edge excitations are unpaired Majorana fermions, which cannot transport charge near the Fermi level. Here we show that the boundary between p_x+ip_y and p_x-ip_y domains forms a one-way channel for electrical charge. We derive a product rule for the domain wall conductance, which allows to cancel the effect of a tunnel barrier between metal electrodes and superconductor and provides a unique signature of topological superconductors in the chiral p-wave symmetry class.Comment: 6 pages, 3 figure

The Muddle of the 'Westminster Model': A Concept Stretched Beyond Repair

The term ‘Westminster model’, widely used in both the academic and practitioner literatures, is a familiar one. But detailed examination finds significant confusion about its meaning. This article follows Giovanni Sartori's advice for ‘reconstructing’ a social science term whose meaning may be unclear through review of its use in the recent literature. It finds that many authors in comparative politics use the term ‘Westminster model’ without definition, while those providing definitions associate it with a large (and sometimes conflicting) set of attributes, and a set of countries often not demonstrating those attributes. Some have sought to respect this diversity by proposing variants like ‘Washminster’ or ‘Eastminster’, while others suggest that the term should be seen as a loose ‘family resemblance’ concept. But on examination it no longer meets even the – relatively weak – requirements for family resemblance. To end the muddle, and the risk of flawed inferences and false generalization, comparative scholars should drop this term, and select cases based on more precise attributes instead

Why it Is Indeed Time for the Westminster Model to Be Retired from Comparative Politics

The term ‘Westminster model’ is frequently used by political scientists and practitioners. But our recent examination (Russell and Serban 2021), published in this journal, uncovered wide variation in how it is defined – demonstrating that it is more ‘muddle’ than ‘model’. This sparked a response article from Flinders et al. (2021), which we in turn respond to in this piece. We briefly revisit our initial research questions, methodology and findings, before reflecting on their analysis. We emphasize that, notwithstanding the critics’ negative tone, we and they agree on certain fundamentals. In particular on our original central point, that the ‘Westminster model’ is an ill-defined term with a long history, which mostly makes it unsuited to positivist comparative political science research. While the ‘Westminster model’ may have some valid vestigial uses, within the UK political system, or as an object of study for interpretivist political science, it does not provide a rigorous basis for case selection and comparative political science analysis

Thermophoresis effect on the free convective flow in a differentially heated square cavity

A numerical analysis is made for thermophoretic transport of small particles through the convective flow in a differentially heated square cavity. The governing gas-particle partial differential equations are solved numerically for some values of the considered parameters to investigate their influence on the flow, heat, and mass transfer patterns. It is found that the effect of thermophoresis can be quite significant in appropriate situations

Evolution récente du régime hydrologique de quelquesrivières de Roumanie Centrale. (Courte note)

L'étude de la stationnarité de séries de débits annuels et saisonniers de 15 rivières roumaines et du Danube à Orsova met en évidence l'existence d'une "phase hydrologique" sèche importante depuis 1983. L'écoulement hivernal a diminué de 50% depuis cette date et semble principalement responsable de cette sécheresse hydrologique. L'extension géographique de cette sécheresse est précisée en Roumanie Centrale. L'analyse des débits du Danube montre qu'une partie importante de son bassin versant est touché par le phénomène.A statistical study of annual and seasonal discharges series for 15 Romanian rivers and the Danube River at Orsova exhibits a very important dry hydrological period which began around 1983. The winter discharge decreased 50% during this period and seems to be the main cause of this hydrological drought. The spatial distribution of this drought is defined in Central Romania. The analysis of the Danube discharge series demonstrates that an important part of its watershed is in the same situation

Optimal control for halo orbit missions

This paper addresses the computation of the required trajectory correction maneuvers (TCM) for a halo orbit space mission to compensate for the launch velocity errors introduced by inaccuracies of the launch vehicle. By combiningdynamical systems theory with optimal control techniques, we produce a portrait of the complex landscape of the trajectory design space. This approach enables parametric studies not available to mission designers a few years ago, such as how the magnitude of the errors and the timingof the first TCM affect the correction ΔV. The impetus for combiningdynamical systems theory and optimal control in this problem arises from design issues for the Genesis Discovery mission being developed for NASA by the Jet Propulsion Laboratory

Strong coupling from the Hubbard model

It was recently observed that the one dimensional half-filled Hubbard model reproduces the known part of the perturbative spectrum of planar N=4 super Yang-Mills in the SU(2) sector. Assuming that this identification is valid beyond perturbation theory, we investigate the behavior of this spectrum as the 't Hooft parameter \lambda becomes large. We show that the full dimension \Delta of the Konishi superpartner is the solution of a sixth order polynomial while \Delta for a bare dimension 5 operator is the solution of a cubic. In both cases the equations can be solved easily as a series expansion for both small and large \lambda and the equations can be inverted to express \lambda as an explicit function of \Delta. We then consider more general operators and show how \Delta depends on \lambda in the strong coupling limit. We are also able to distinguish those states in the Hubbard model which correspond to the gauge invariant operators for all values of \lambda. Finally, we compare our results with known results for strings on AdS_5\times S^5, where we find agreement for a range of R-charges.Comment: 14 pages; v2: 17 pages, 2 figures, appendix and references added; typos fixed, minor changes; v3 fixed figures; v4 more references added, minor correctio