A Semi-Parametric Factor Model for Interest Rates.

Understanding the dynamics of interest rates and the term structure has important implications for issues as diverse as real economic activity, monetary policy, pricing of interest rate derivative securities and public debt financing. Our paper follows a longstanding tradition of using factor models of interest rates but proposes a semi-parametric procedure to model interest rates.

Parametric and Nonparametric Approaches to Price and Tax Reform.

In the analysis of tax reform, when equity is traded off against efficiency, the measurement of the latter requires us to know how tax-induced price changes affect quantities supplied and demanded. in this paper, we present various econometric procedures for estimating how taxes affect demand.

Effets de la vibration des muscles sur les mécanismes neuronaux et la fonction du membre supérieur et inférieur des personnes ayant une hémiparésie chronique

Cette thèse vise à répondre à trois questions fondamentales: 1) La diminution de l’excitabilité corticospinale et le manque d’inhibition intracorticale observés suite à la stimulation magnétique transcrânienne (SMT) du cortex moteur de la main atteinte de sujets hémiparétiques sont-ils aussi présents suite à la SMT du cortex moteur de la jambe atteinte? 2) Est-ce que les altérations dans l’excitabilité corticomotrice sont corrélées aux déficits et incapacités motrices des personnes ayant subi un accident vasculaire cérébral depuis plus de 6 mois? 3) La vibration musculaire, étant la source d’une forte afférence sensorielle, peut-elle moduler l’excitabilité corticomotrice et améliorer la performance motrice de ces personnes? Premièrement, afin d’appuyer notre choix d’intervention et d’évaluer le potentiel de la vibration mécanique locale pour favoriser la réadaptation des personnes ayant une atteinte neurologique, nous avons réalisé une révision en profondeur de ses applications et intérêts cliniques à partir d’informations trouvées dans la littérature scientifique (article 1). La quantité importante d’information sur les effets physiologiques de la vibration contraste avec la pauvreté des études qui ont évalué son effet thérapeutique. Nous avons trouvé que, malgré le manque d’études, les résultats sur son utilisation sont encourageants et positifs et aucun effet adverse n’a été rapporté. Dans les trois autres articles qui composent cette thèse, l’excitabilité des circuits corticospinaux et intracorticaux a été étudiée chez 27 sujets hémiparétiques et 20 sujets sains sans atteintes neurologiques. Les fonctions sensorimotrices ont aussi été évaluées par des tests cliniques valides et fidèles. Tel qu’observé à la main chez les sujets hémiparétiques, nous avons trouvé, par rapport aux sujets sains, une diminution de l’excitabilité corticospinale ainsi qu’un manque d’inhibition intracorticale suite à la SMT du cortex moteur de la jambe atteinte (article 2). Les sujets hémiparétiques ont également montré un manque de focus de la commande motrice lors de l’activation volontaire des fléchisseurs plantaires. Ceci était caractérisé par une augmentation de l’excitabilité nerveuse des muscles agonistes, mais aussi généralisée aux synergistes et même aux antagonistes. De plus, ces altérations ont été corrélées aux déficits moteurs au membre parétique. Le but principal de cette thèse était de tester les effets potentiels de la vibration des muscles de la main (article 3) et de la cuisse (article 4) sur les mécanismes neuronaux qui contrôlent ces muscles. Nous avons trouvé que la vibration augmente l’amplitude de la réponse motrice des muscles vibrés, même chez des personnes n’ayant pas de réponse motrice au repos ou lors d’une contraction volontaire. La vibration a également diminué l’inhibition intracorticale enregistrée au quadriceps parétique (muscle vibré). La diminution n’a cependant pas été significative au niveau de la main. Finalement, lors d’un devis d’investigation croisé, la vibration de la main ou de la jambe parétique a résulté en une amélioration spécifique de la dextérité manuelle ou de la coordination de la jambe, respectivement. Au membre inférieur, la vibration du quadriceps a également diminuée la spasticité des patients. Les résultats obtenus dans cette thèse sont très prometteurs pour la rééducation de la personne hémiparétique car avec une seule séance de vibration, nous avons obtenu des améliorations neurophysiologiques et cliniques.

Thermal lens spectrum of organic dyes using optical parametric oscillator

The wavelength dependence of thermal lens signal from organic dyes are studied using dual beam thermal lens technique. It is found that the profile of thermal lens spectrum widely differ from the conventional absorption spectrum in the case of rhodamine B unlike in the case of crystal violet. This is explained on the basis of varying contribution of nonradiative relaxations from the excited vibronic levels.

Thermal lens spectrum of organic dyes using optical parametric oscillator

The wavelength dependence of thermal lens signal from organic dyes are studied using dual beam thermal lens technique. It is found that the profile of thermal lens spectrum widely differ from the conventional absorption spectrum in the case of rhodamine B unlike in the case of crystal violet. This is explained on the basis of varying contribution of nonradiative relaxations from the excited vibronic levels.

Dynamics of the logistic map under discrete parametric perturbation

By introducing a periodic perturbation in the control parameter of the logistic map we have investigated the period locking properties of the map. The map then gets locked onto the periodicity of the perturbation for a wide range of values of the parameter and hence can lead to a control of the chaotic regime. This parametrically perturbed map exhibits many other interesting features like the presence of bubble structures, repeated reappearance of periodic cycles beyond the chaotic regime, dependence of the escape parameter on the seed value and also on the initial phase of the perturbation etc.

Fabrication And Parametric Measurements Of N2 Laser Pumped Dye Laser And Its Application To Energy Transfer Studies In Mixed Dyes

Eventhough a large number of schemes have been proposed and develoned for N9 laser ouined dye lasers the relatively low efficiency compelled the scientists to device new methods to improve the system efficiencs. Energy transfer mechanism has been shown to he a convenien tool for the enhancement of efficiency of dye lasers. Th p resent work covers a detailed study of the performance characteristics of a N2 laser pumped dye laser in the con— ventional mode and also, when pumped by the energy transfer mechanism. For .th.e present investigations a dye laser pumped by a'N2 laser (A4200 kw peak power) was fabricated. The grating at grazing incidence was used as the beam expanding device; A t its best performance the system was giving an output peak power of l5 kW for a 5 X lC"3H/l Rh—€ solution in methanol. T he conversion efficiency was 7.5; The output beam was having 3 divergence of 2 mrad and bandwidth o.9 A. Suitable modifications were suggested for obtaining better conversion efficiency and bandwidth.

Development and parametric studies of pulsed nitrogen and d-switched nd:glass lasers and some of their applications

Laser engineering is an area in which developments in the existing design concepts and technology appear at an alarming rate. Now—a-days, emphasis has shifted from innovation to cost reduction and system improvement. To a major extent, these studies are aimed at attaining larger power densities, higher system efficiency and identification of new lasing media and new lasing wavelengths. Todate researchers have put to use all the ditferent Forms of matter as lasing material. Laser action was observed For the first time in a gaseous system - the He-Ne system. This was Followed by a variety of solidstate and gas laser systems. Uarious organic dyes dissolved in suitable solvents were found to lase when pumped optically. Broad band emission characteristics of these dye molecules made wavelength tuning possible using optical devices. Laser action was also observed in certain p-n junctions of semiconductor materials and some of these systems are also tunable. The recent addition to this list was the observation of laser action from certain laser produced plasmas. The purpose of this investigation was to examine the design and Fabrication techniques of pulsed Nitrogen lasers and high power Nd: Glass laserso Attempt was also made to put the systems developed into certain related experiments

Semiactive backstepping control for vibration attenuation in structures equipped with magnetorheological actuatorscat

This paper deals with the problem of semiactive vibration control of civil engineering structures subject to unknown external disturbances (for example, earthquakes, winds, etc.). Two kinds of semiactive controllers are proposed based on the backstepping control technique. The experimental setup used is a 6-story test structure equipped with shear-mode semiactive magnetorheological dampers being installed in the Washington University Structural Control and Earthquake Engineering Laboratory (WUSCEEL). The experimental results obtained have verified the effectiveness of the proposed control algorithms

A mixed H2/H∞-based semiactive control for vibration mitigation in flexible structures

In this paper, we address this problem through the design of a semiactive controller based on the mixed H2/H∞ control theory. The vibrations caused by the seismic motions are mitigated by a semiactive damper installed in the bottom of the structure. It is meant by semiactive damper, a device that absorbs but cannot inject energy into the system. Sufficient conditions for the design of a desired control are given in terms of linear matrix inequalities (LMIs). A controller that guarantees asymptotic stability and a mixed H2/H∞ performance is then developed. An algorithm is proposed to handle the semiactive nature of the actuator. The performance of the controller is experimentally evaluated in a real-time hybrid testing facility that consists of a physical specimen (a small-scale magnetorheological damper) and a numerical model (a large-scale three-story building)