Presence Of Thermal Effects Research Articles

Stabilization of von K�rm�n plate in the presence of thermal effects in a subsonic potential flow of gas

We discuss the problem of nonlinear oscillations of a clamped plate in the presence of thermal effects in a subsonic gas flow. The dynamics of the plate is described by von Kármán system in the presence of thermal effects, in which rotational inertia is accounted for. To describe influence of the gas flow we apply the linearized theory of potential flows. Our main result states that each weak solution of the problem considered tends to the set of the stationary points of the problem.

Thermal effects and cavity solitons in passive semiconductor microresonators

We formulate a model including the thermal dynamics in the time evolution of a passive semiconductor microresonator, containing a bulk medium, driven by a coherent holding beam. Thermal effects are taken into account via a dynamical equation for the lattice temperature, describing heat dissipation toward the environment, heating due to carrier generation, and thermal diffusion. The temperature dynamics is coupled to the carrier and field dynamics via the material susceptibility, a red-shift of the band-gap energy of the semiconductor upon an increase of temperature and a linear shift of the cavity resonance. The presence of thermal effects introduces a Hopf instability which, in certain regions of the parameter space, dominates the dynamics of the system. In this case our numerical simulations show that the output intensity may oscillate for constant holding beam intensity (regenerative oscillations), and if the input intensity grows slowly enough the hysteresis cycle may be inverted (switching point inversion). Oscillatory instabilities can also develop a modulational character, meaning that travelling patterns can be found. These phenomena develop over the slow timescale (microseconds) characterizing thermal effects in these devices. In other parameter regimes, the well-known Turing instability giving rise to stationary modulated patterns prevails, and the system displays the usual scenario of stable patterns and cavity solitons. Thermal effects seem not to play any relevant role in these regimes.

Stabilization of von Kármán plate in the presence of thermal effects in a subsonic potential flow of gas

We discuss the problem of nonlinear oscillations of a clamped plate in the presence of thermal effects in a subsonic gas flow. The dynamics of the plate is described by von Kármán system in the presence of thermal effects, in which rotational inertia is accounted for. To describe influence of the gas flow we apply the linearized theory of potential flows. Our main result states that each weak solution of the problem considered tends to the set of the stationary points of the problem.

On exponential stability for von Kármán equations in the presence of thermal effects

We consider a dynamical von Kármán system in the presence of thermal effects. Our model includes the possibility of a rotational inertia term in the system. We show that the total energy of the solution of such system decays exponentially as t→+∞. The decay rates we obtain are uniform on bounded sets of the energy space. The main ingredients of our method of proof are suitable properties of a decoupled system, the energy method and the compactness of the nonlinear map associated to the von Kármán system. © 1998 B. G. Teubner Stuttgart–John Wiley & Sons Ltd.

On exponential stability for von Kármán equations in the presence of thermal effects

We consider a dynamical von Kármán system in the presence of thermal effects. Our model includes the possibility of a rotational inertia term in the system. We show that the total energy of the solution of such system decays exponentially as t→+∞. The decay rates we obtain are uniform on bounded sets of the energy space. The main ingredients of our method of proof are suitable properties of a decoupled system, the energy method and the compactness of the nonlinear map associated to the von Kármán system. © 1998 B. G. Teubner Stuttgart–John Wiley & Sons Ltd.

PDT時における腫瘍内温度と温熱効果についての検討

Photodynamic therapy (PDT) for malignant tumors is performed increasingly throughout the world. However, detailed information concerning the optimum power density, light dose and thermal effects are unknown. Therefore the authors investigated tumor response and tumor temperature during PDT using transplanted B-16 melanoma in mice. A thermister probe was fixed at a depth of 2mm from the tumor surface. At the site, the tumor temperature rose 8°C at 150mW/cm2, 13°C at 300mW/cm2, 21°C at 450mW/cm22, 28°C at 600mW/cm2 above the base line value. A tumor response study showed increased effects with increased power density. Mice receiving a high power density (450mW/cm2, 600mW/cm2) without photosensitizer indicated same result. The presence of thermal effects was suggested in the high power density group of PDT. The increased light dose showed improvement of results over the low power density group (150mW/cm2, 300mW/cm2).

Spectroscopic studies of benzene hydrogenation on platinum-loaded zeolites. Part 2.—Hydrogenation of adsorbed species

The hydrogenation of benzene adsorbed on Y zeolites containing various low platinum contents has been followed by u.v. and i.r. spectroscopies. Hydrogenation involves benzene which is irreversibly adsorbed at room temperature on PtNaY, PtHY or PtCaY samples. The reaction was performed in a static system with a constant and known hydrogen pressure. The concentration of benzene adsorbed on the zeolite decreases linearly as a function of the time of contact under hydrogen. Experiments using CO as a test molecule suggest that the platinum particles are covered by C6H6 during the hydrogenation process. By varying the hydrogen pressure, the rate of the reaction was found to be proportional to H2 pressure. It was concluded that the hydrogenation reaction takes place on the metal: hydrogen is dissociated on the platinum particles and C6H6 weakly adsorbed on the support can migrate towards the metallic phase to be hydrogenated. Determination of turnover number, N, shows an increase of N with platinum content suggesting either the presence of thermal effects or changes of catalytic activity with the metal particle size.

A refined model for the thermal elastohydrodynamic in let zone

The formation of lubricant films in the elastohydrodynamic inlet zone in the presence of thermal effects is considered according to the analysis of Grubin. The analyses indicate that surface contacts with unequal temperatures as well as viscous heating play an important role in determing the inlet film thickness. A simple equation is presented to calculate the lubricant film thickness in the inlet of elastohydrodynamically lubricated contacts. Effects of viscous heating and surface temperature difference are included.