Добірка наукової літератури з теми "Oscilatory modes"

Introduction/purpose: Detailed theoretical and experimental studies have been carried out in order to investigate the problem of a phase stability in electrodynamically uncoupled Gunn oscillators. Methods: The influence of modulating pulse instabilities has been investigated by means of computer simulation in the framework of a nonlinear one-dimensional theoretical model of the GaAs Gunn diode semiconductor active region. Experimental observations were also conducted including microwave measurements and antenna far-field estimation. They confirm the main theoretical results and extend the key work conclusions. Results: It was shown that the initial phase of the microwave oscillation out of the Gunn oscillator is independent of internal noises of the semiconductor structure and can be fixed only by the modulating voltage pulse. Conclusion: Gunn-diodes based microwave oscillators were stabilized using the leading edge of the voltage pulse from the modulating power supply. These results open up serious prospects for designing antenna phased arrays based on Gunn oscillators without mutual feedback (electrodynamically independent).

In recent years the term ergodicity has come into scientific vogue in various physical problems. In particular when a system exibits chaotic behavior, it is often said to be ergodic. Is it a correct usage of the term ergodicity? Does it not mean that the time and ensemble averages of a variable are equal? Are they really related one to one? We examine this issue via simple models of harmonic oscilators by means of the theorems of Birkhoff and Khinchin and also by our own physical theory of ergometry. This study also considers the chaotic behavior in the logistic map.

En este trabajo se describe, por la primera vez, la posibilidad de la detección electroanalítica del fármaco aripiprazol, asistida por el oxihidróxido de cobalto trivalente. En el medio alcalino, el aripiprazol se hidroliza formando un compuesto hidroquinónico, que se suele oxidar hacia la respectiva quinona y polimerizarse. El análisis del modelo correspondiente confirma que el proceso electroanalítico se mantiene eficiente, aunque sea “ramificado” el mecanismo de oxidación del fármaco. Cuanto a la inestabilidad oscilatoria, esta se realiza por causa de la influencia de la etapa electroquímica a la doble capa eléctrica. In this work we describe, for the first time, the possibility of electroanalytical detection of the drug aripiprazole, assisted by trivalent cobalt oxyhydroxide. In the alkaline medium, aripiprazole is hydrolyzed to form a hydroquinone compound, which is usually oxidized to the respective quinone and polymerized. The analysis of the corresponding model confirms that the electroanalytical process remains efficient, although the oxidation mechanism of the drug is "branched". As for the oscillatory instability, it is due to the influence of the electrochemical step on the electrical double layer.

Convective heat transfer coefficients were evaluated during end-over-end rotation processing of cans filled with liquid and particle mixtures in a pilot-scale, overpressure water-immersion, rotary retort. Two modes of end-over-end agitation were employed, one involving a continuous and the other involving an oscillatory rotation of the cage containing cans. Nylon spheres of diameter 0.025 m were used as test particles and a high temperature bath oil was used as the test liquid. A lumped capacity approach was employed to determine the overall heat transfer coefficient, U, and an inverse heat transfer approach was used to determined the fluid to particle heat transfer coefficient, hfp. Effects of the two modes of rotation (continuous and oscillation) on the associated heat transfer coefficients were evaluated at three speeds (8, 16 and 24 rpm) and three radii of rotation (0,13 and 26 cm). An analysis of variance showed that the effects of rotation speed and mode of rotation on both U and htp were significant ( p < 0.05). However, the effect of radius of rotation was significant only with U. These factors also affected the calculated process times for achieving an accumulated lethality ( Fo) of 10 min at the particle center and in the can liquid in a similar fashion. In general, U and hfp values associated with continuous rotation were 10-40% higher than those associated with oscillatory rotation.

Abstract This animal study was conducted in order to verify the effects of combining highfrequency oscillatory ventilation and prone positioning and the order of application of both methods on blood gas exchange in an experimental model of acute respiratory distress syndrome. Forty domestic pigs were used for the study. Saline solution washout was produced by bilateral lung lavage. The lavage process was repeated until adequate impairment of gas exchange (defined as PaO2 < 100 mmHg) 60 min following the last lavage was achieved. Subsequently, lung injury was established and each model was randomized to one of five groups, with differences in the type of mechanical ventilation used (conventional mechanical ventilation in accordance with the principles of protective lung ventilation or high-frequency oscillatory ventilation) and also in the positioning of the experimental model (supine position or mode changing prone and supine positions in a ratio 18:6 hours). The best oxygenation was achieved in the group prone position + high-frequency oscillatory ventilation. The most favorable combination in terms of carbon dioxide elimination is the high-frequency oscillatory ventilation + prone position. The best results in terms of oxygenation index value were obtained in the combination of a prone position with the high-frequency oscillatory ventilation and in the prone position. In conclusion, by using combinations of prone positioning and high-frequency oscillatory ventilation, one can achieve better blood gas parameters during acute respiratory distress syndrome.

L'objectif principal qui guide les développements en traitement du signal de cette thèse est la mise au point d'un outil qui s'inscrit dans une démarche de physiologie intégrative où, à chaque échelle, le modèle des signaux peut être différent On cherche ici à restreindre le jeu d'hypothèses a priori à un ensemble de règles physiologiques qui régissent les interactions entre functions physiologiques en l'absence d'hypothèses fonnelles et: mathématiques sur les signaux. Nous avons appliqué cette démarche au problème de la détection des ondes cardiaques et: de l' estimation cycle à cycle du volume d'éjection dans le signal RIP (Respiratoty Inductive Plethysmography). L'approche par décomposition empirique se prête particulièrement à notre logique. Nous proposons ici la première version d'un algorithme basé sur une double décomposition empirique du signal RIP. La méthode choisie et: les outils correspondants ont été testés sur deux types de données, d'une part des signaux simulés, d'autre part des signaux enregistrés sur volontaires sains. Notre objectif est donc aussi de mettre au point un modèle cardiorespiratoire pouvant servir d'outil de simulation des signaux ventilatoires, cardiaques et: de RIP avec la simulation de l'effet de chaque système sur l'autre. Les résultats montrent que la méthode proposée est adaptée à l'analyse du signal RIP et: à l' estimation du volume d'éjection
The main objective that guides the signal processing approaches ofthis thesis is the development of a tool that oould be part of an integrative physiology approach where, at each scale, the model of signais may be different We seek here the restriction of asstnnptions a priori to a set: of rules goveming the physiological interactions between physiological functions in the absence of fannal and mathematical assumptions. We applied this approach to the problem of cardiac waves detection and estimation of cycle-to-cycle stroke volume in the RIP signal (Respiratory Inductive Plethysmography). The empirical decomposition approach seems to be particularly adapted to our logic. We propose here the first version of an algorithm based on RIP double decomposition. The method and its COITeSpül1ding tools have been tested on two types of data, simulated signais and real signais recorded at healthy volunteers. Our aim is also therefore to develop a cardio-respiratory model that can serve as a tool for ventilatory, cardiac and RIP signals simulation along with the simulation of the effect of each system on the other. The results show that the proposed method is suitable for RIP signal analysis and for stroke volume estimation

碩士
國立臺灣大學
物理研究所
102
It is shown that harmonic cyclotron interaction can alleviate the magnetic-field requirement by a factor of s . However, the harmonic coupling coefficient decreases with s and increases with rL, which suggests that greater beam power and higher electron energy are required to generate the required field strength for efficient harmonic interaction. This trend may be exploited for the generation of high peak power beyond that obtainable in the fundamental harmonic interaction. In this study, we try to find the optimum working condition for a gyrotron oscillator at second harmonic mode. We also investigate the advantage of taper magnetic field in the enhancement of efficiency.

AbstractStarting sometime in 2008/2009 one expects to be able to take a glimpse at physics at the TeV scale. This will be done through the Large Hadronic Collider (LHC) at CERN, Geneva. It will be a result of an unprecedented coordinated international scientific effort. This chapter is written in 2007. It is essentially inviting disaster to spell out in full detail what the current various theoretical speculations on the physics are, as well motivated as they may seem at this time. What I find of more value is to elaborate on some of the ideas and the motivations behind them. Some may stay with us, some may evolve and some may be discarded as the results of the experiments unfold. When the proton antiproton collider was turned on in the early eighties of the last century at Cern the theoretical ideas were ready to face the experimental results in confidence, a confidence which actually had prevailed. The emphasis was on the tremendous experimental challenges that needed to be overcome in both the production and the detection of the new particles. As far as theory was concerned this was about the physics of the standard model and not about the physics beyond it. The latter part was left safely unchallenged. That situation started changing when the large electron positron (LEP) collider experiments also at Cern were turned on as well the experiments at the Tevatron at Fermilab. Today it is with rather little, scientifically based, theoretical confidence that one is anticipating the outcome of the experiments. It is less the method and foundations that are tested and more the prejudices. It is these which are at the center of this chapter. Some claim to detect over the years an oscilatory behavior in the amount of conservatism expressed by leaders in physics. The generation in whose life time relativity and quantum mechanics were discovered remained non-conservative throughout their life. Some of the latter developed eventually such adventurous ideas as to form as a reaction a much more conservative following generation. The conservative generation perfected the inherited tools and has uncovered and constructed the Standard Model. They themselves were followed by a less conservative generation. The new generation was presented with a seemingly complete description of the known forces. In order to go outside the severe constraints of the Standard Model the new generation has drawn upon some of the more adventurous ideas of the older generation as well as created it own ideas. In a way almost all accepted notions were challenged. In the past such an attitude has led to major discoveries such as relativity and quantum mechanics. In some cases it was carried too far, the discovery of the neutrino was initially missed as energy conservation was temporarily given up.