Presence Of Thermal Effects Research Articles

Exploring the impact of weak measurements on exciton–exciton interactions

In our study of super quantum discord between two excitonic qubits inside a coupled semiconductor quantum dots system, our primary focus is to uncover the impact of weak measurement on its quantum characteristics. To achieve this, we analyze how varying the measurement strength x, affects this super quantum correlation in the presence of thermal effects. Additionally, we assess the effect of this variation on the system’s evolution against its associated quantum parameters; external electric fields, exciton–exciton dipole interaction energy and Förster interaction. Our findings indicate that adjusting x to smaller values effectively enhances the super quantum correlation, making weak measurements act as a catalyst. This adjustment ensures its robustness against thermal effects while preserving the non-classical attributes of the system. Furthermore, our study unveils that the effect of weak measurements on this latter surpasses the quantum effects associated with the system. Indeed, manipulating the parameter x allows the weak measurement to function as a versatile tool for modulating quantum characteristics and controlling exciton–exciton interactions within the coupled semiconductor quantum dots system.

Study of thermal effects induced by the high-frequency probing laser in nonlinear opto-acoustic frequency-mixing technique

Photo-thermal modulation-based nonlinear opto-acoustic frequency-mixing technique is an effective method for detecting micro-cracks. When using this technique for micro-crack detection, the selection of laser source parameters is particularly crucial. Compared to traditional piezo-transducer-based mixing techniques, the characteristic of using a laser as the detection source is the presence of thermal effects. The thermal effect caused by laser irradiation on the sample surface can not only generate acoustic waves but also affect the crack state, thus influencing nonlinear signals. In this paper, an experimental setup using photo-thermal modulation-based nonlinear opto-acoustic frequency-mixing technique has been set up to investigate the thermal effects of the probe laser source. In addition, a corresponding physical model has been established to discuss the physical mechanisms revealed by the experimental results. This study provides a basis for selecting appropriate probe source parameters and scanning positions of laser sources when detecting micro-cracks using the photo-thermal modulation-based nonlinear opto-acoustic frequency-mixing technique.

Linearized Kinetic Theory of Plasma Waves

A striking illustration of the shortcomings of the simple fluid description appeared in the dispersion relation obtained in the presence of thermal effects. In this work, it is shown that the substitution of the fluid description with the tools of the kinetic theory leads to solving these limitations. The distribution function f_α is linearized and the Vlasov–Poisson kinetic system is described. The three terms that control the evolution of the perturbed distribution function and their physical effects are discussed.

High-power continuous-wave mid-infrared difference-frequency generation in the presence of thermal effects

We report performance studies of high-power, continuous-wave (cw), mid-infrared (mid-IR) difference-frequency generation (DFG) in MgO:PPLN at 2262 nm based on a narrowband Yb-fiber laser as pump and a Tm-fiber laser as signal source. Using a 50-mm-long crystal, we generate as much as 3.84 W of DFG output power at a single-pass conversion efficiency up to 0.57%/W, with a passive power stability better than 0.53% rms and passive spectral stability better than 0.01% over 1 h. The DFG beam also exhibits excellent spatial beam quality in T E M 00 mode profile with M 2 < 1.2 , and a beam pointing stability better than 16 µrad over > --> 1 h . Simulations based on focused Gaussian beam theory provide an accurate estimate of the generated DFG output power and confirm thermal effects. Detailed thermal analysis indicates the role of linear absorption at the interacting wavelengths in local heating within the focal volume of the MgO:PPLN crystal. To the best of our knowledge, this is the highest cw DFG output power and conversion efficiency achieved in bulk MgO:PPLN in the mid-IR.

Analysis of long-endurance station-keeping flight scenarios for stratospheric airships in the presence of thermal effects

The ability to achieve long-endurance station-keeping flights makes stratospheric airships desirable platforms for the provision of communication and surveillance services. To maintain long-endurance flights, it is necessary to consider the problem of energy consumption. In this paper, we discuss long-endurance flight scenarios of stratospheric airships in the presence of thermal effects. The balance between buoyancy and gravity is influenced by thermal effects during the diurnal cycle. We perform a theoretical analysis based on the helium’s mass, pressure differential, and altitude as the main factors. To verify the effectiveness of the control over the pressure differential and the altitude, three long-endurance flight scenarios are proposed and compared. Then, the corresponding optimization problems are constructed to determine the energy-minimum flight. Finally, further efforts are made to reduce energy consumption. The realization and limitations of two strategies for improvement are analyzed. A comparison with other scenarios shows the effectiveness of energy conservation. The study in this paper thus provides a reference for station-keeping applications of stratospheric airships.

The thermogravimetric study of the ointment with the water-soluble proteinpolysaccharide complex of Pleurotus ostreatus

The manufacturing process for soft dosage forms is always accompanied by the action of a certain temperature, which violation can lead not only to the deterioration of technological indicators, but also significantly affect the pharmacological activity of the finished drug.Aim. To study the water-soluble protein-polysaccharide complex (WSPPC) of Pleurotus ostreatus (oyster mushroom) and the ointment composition developed on its basis using thermogravimetry.Materials and methods. The thermogravimetric analysis, which allowed determining the change of the mass of the test sample under the conditions of the controlled temperature rise, was chosen as the research method. Determination of thermogravimetric characteristics was performed using a Q-1500 D derivatograph of the “F. Paulik, J. Paulik, L. Erdey” system with a platinum-platinum-rhodium thermocouple when heating samples 30 to 250 °C.Results and discussion. In the course of the thermogravimetric study it has been determined that WSPPC and the ointment composition developed on its basis have physical transformations at certain temperatures. The presence of thermal effects on the thermogram of the ointment developed coincides with the thermal effects of WSPPC; and it subjectively indicates the absence of the chemical interaction between the active pharmaceutical ingredient and the excipients of the carrier base.Conclusions. Based on the results obtained the optimal conditions of the temperature regime for the manufacturing process have been determined. They will provide the stability of the physicochemical properties and the pharmacological effect of the finished ointment.

Stability analysis of non-isothermal fibre spinning of polymeric solutions

The stability of fibre spinning flow of a polymeric fluid is analysed in the presence of thermal effects. The spinline is modelled as a one-dimensional slender-body filament of the entangled polymer solution. The previous study (Gupta & Chokshi,J. Fluid Mech., vol. 776, 2015, pp. 268–289) analysed linear and nonlinear stability behaviour of an isothermal extensional flow in the air gap during the fibre spinning process. The present study extends the analysis to take in to account the non-isothermal spinning flow in which the spinline loses heat by convection to the surrounding air as well as by solvent evaporation. The nonlinear rheology of the polymer solution is described using the eXtended Pom-Pom (XPP) model. The non-isothermal effects influence the rheology of the fluid through viscosity, which is taken to be temperature and concentration dependent. The linear stability analysis is carried out to obtain the draw ratio for the onset of instability, known as the draw resonance, and a stability diagram is constructed in the$DR_{c}{-}De$plane.$DR_{c}$is the critical draw ratio, and$De$is the flow Deborah number. The enhancement in viscosity driven by spinline cooling leads to postponement in the onset of draw resonance, indicating the stabilising role of non-isothermal effects. Weakly nonlinear stability analysis is also performed to reveal the role of nonlinearities in the finite amplitude manifold in the vicinity of the flow transition point. For low to moderate Deborah numbers, the bifurcation is supercritical, and the flow attains an oscillatory state with an equilibrium amplitude post-transition when$DR>DR_{c}$. The equilibrium amplitude of the resonating state is found to be smaller when non-isothermal effects are incorporated in comparison to the isothermal spinning flow. For very fast flows in the regime of high Deborah numbers, the finite amplitude manifold crosses over to a subcritical state. In this limit, the nonlinearities render the flow unstable even in the linearly stable regime of$DR<DR_{c}$.

Universal scaling of quench-induced correlations in a one-dimensional channel at finite temperature

It has been shown that a quantum quench of interactions in a one-dimensional fermion system at zero temperature induces a universal power law $\propto t^{-2}$ in its long-time dynamics. In this paper we demonstrate that this behaviour is robust even in the presence of thermal effects. The system is initially prepared in a thermal state, then at a given time the bath is disconnected and the interaction strength is suddenly quenched. The corresponding effects on the long times dynamics of the non-equilibrium fermionic spectral function are considered. We show that the non-universal power laws, present at zero temperature, acquire an exponential decay due to thermal effects and are washed out at long times, while the universal behaviour $\propto t^{-2}$ is always present. To verify our findings, we argue that these features are also visible in transport properties at finite temperature. The long-time dynamics of the current injected from a biased probe exhibits the same universal power law relaxation, in sharp contrast with the non-quenched case which features a fast exponential decay of the current towards its steady value, and thus represents a fingerprint of quench-induced dynamics. Finally, we show that a proper tuning of the probe temperature, compared to that of the one-dimensional channel, can enhance the visibility of the universal power-law behaviour.

Inner cladding influence on mode interaction in symmetry-free photonic crystal fibers under heat load

A further output power scaling of Yb-doped double-cladding photonic crystal fiber lasers, required for practical applications in many industrial fields, is currently prevented by thermal effects, which significantly worsen the beam quality. In this work the mode interaction and, consequently, the single-mode regime of Yb-doped air-silica symmetry-free photonic crystal fibers have been numerically investigated in different heat load conditions using simulation tools based on the finite element method. The effect of the main inner cladding geometric parameters, in particular of the inner cladding dimension, on the guided-mode delocalization has been analyzed, with the aim to identify a design of the large mode area active fiber providing single-mode operation despite the presence of thermal effects. Simulation results have demonstrated that the inner cladding enlargement causes a stronger coupling between core-guided and cladding modes, as well as an increase of the differential overlap between fundamental and first higher-order mode for moderate heat load values. However, the inner cladding influence becomes less important under severe heat load, being the fiber behaviour mainly affected by the thermally-induced refractive index change in the doped core.

Global Existence and Uniqueness of Weak and Regular Solutions of Shallow Shells with Thermal Effects

We study a dynamical thin shallow shell whose elastic deformations are described by a nonlinear system of Marguerre---Vlasov's type under the presence of thermal effects. Our main result is the proof of a global existence and uniqueness of a weak solution in the case of clamped boundary conditions. Standard techniques for uniqueness do not work directly in this case. We overcame this difficulty using recent work due to Lasiecka (Appl Anal 4:1376---1422, 1998).

Focusing Optimization for High-Power Continuous-Wave Second-Harmonic Generation in the Presence of Thermal Effects

We study thermal effects in high-power single-pass second-harmonic generation (SP-SHG) of continuous-wave (cw) green radiation in MgO:sPPLT and describe optimization of critical factors including the fundamental beam waist, position, and focusing parameter, for attainment of maximum SP-SHG efficiency. By developing a numerical model combining split-step Fourier and finite-element methods, we compute the relevant parameters for optimization of SP-SHG of a cw Yb-fiber laser at 1064 nm in a 30-mm-long crystal. Real experimental parameters and boundary conditions are used to simulate nonuniform heat distribution in the crystal under high-power operation and study its effects on SP-SHG optimization. The results indicate that for input powers exceeding a certain limit, the Boyd and Kleinman (BK) criteria for optimum focusing are no longer valid. By increasing the fundamental power to 50 W, we find that the optimum focusing parameter decreases by a factor of 4, from ξ =2.8 to 0.7. We also find that the maximum SP-SHG output power is always obtained for fundamental waist at the center of the crystal, and we present a general strategy for the choice of ξ at different fundamental powers. Using a top-sinked oven design, the BK focusing condition can be established even at high fundamental powers.

Some properties of shallow shells with thermal effects

We consider a dynamical nonlinear model for shallow shells of the Marguerre--Vlasov's type in the presence of thermal effects. Results on existence and uniqueness of global weak solutions are already available. We consider the above model depending on a parameter $\varepsilon>0$ and study its weak limit as $\varepsilon\rightarrow 0^+$. The limit model turns out to be a nonlinear Timoshenko's equation with thermal effects on the manifold (the shell). We also analyze the asymptotic behavior of the total energy of the nonlinear model of Marguerre--Vlasov's type with thermal effects.

Experimental Characterization of Electro–Thermo–Mechanical Coupling in Gold RF Microswitches

This paper analyses the multiple coupling occurring in some metallic microstructures electrostatically actuated in presence of thermal effect. Some relevant issues of basic procedures implemented to identify the relevant design parameters and the material properties of micro-electro-mechanical systems (MEMS) are preliminarily discussed. Temperature effects on the MEMS strain distribution in operating conditions are then investigated. Thermo-mechanical coupling is studied through some experiments performed on microbridge prototypes electrostatically actuated by comparing their behavior in case of superposed electro-thermal actuation and of thermal loading without electrostatic coupling. A detailed analysis is here performed to evaluate the role of the thermal stress upon the buckling of the microstructure and its effect on the deformed shape of the microbeam. Electro-thermo-mechanical coupling is therefore modeled and experimentally analyzed. Pull-in tests are used to detect some effects of mutual interaction between temperature and electrical actuation. The methodologies, here proposed, apply to several materials used in microfabrication, although experimental evidence described herein concerns some gold microbridges to be included in RF devices.

Thermal effects on postbuckling of nonlinear microbeams based on the modified strain gradient theory

In this paper, thermal effects on postbuckling of nonlinear microbeams are investigated. A nonlinear model based on the modified strain gradient theory that considers small scale effects is presented. Poisson’s effect is included in order to maintain the consistency of equations. Two general cases of microbeams with immovable (axial) and movable ends are studied and for different transverse boundary conditions, analytical solutions for their postbuckling behavior in the presence of thermal effects are constructed. Results are verified with relevant previous works and excellent consistency is shown.

Thermal adaptive implicit method: Time step selection

Abstract We present new linear-stability criteria for the Thermal Adaptive Implicit Method (TAIM). The analysis is applied to the mass and energy conservation equations that describe the flow and transport of an arbitrary number of components, which can partition across multiple fluid phases, in the presence of thermal effects. The existing TAIM criteria ( Moncorge and Tchelepi, 2009 ) do not guarantee oscillation-free numerical solutions for thermal compositional displacement processes that involve very steep temperature fronts. We derive a new stability limit on temperature that overcomes these numerical problems. The methodology is based on linear-stability analysis of the standard low-order space and time discretization schemes of the conservation laws used in general-purpose thermal-compositional reservoir simulators. Specifically, for spatial discretization, phase-based, upstream weighting is used for first derivatives and central differencing is used for second derivatives. In terms of the robustness and accuracy of the TAIM stability limits, our analysis and computational results indicate that honoring the divergence of the total-velocity in the linearized system of coupled mass and energy conservation equations is more important than accounting for the rock and fluids compressibility effects. Moreover, we demonstrate through scaling analysis and numerical examples that for most problems of practical interest, a simple stability criterion obtained by assuming incompressible multiphase flow is quite robust. The relationship between the full and simplified stability criteria is analyzed in detail. The methodology is demonstrated using several thermal–compositional examples, including Steam Assisted Gravity Drainage (SAGD). Finally, the criterion for the numerical stability of the temperature is divided into convection and conduction parts. Detailed testing using several simulation models shows clearly that the conduction part of the criterion is quite important across the parameter space of practical interest. Thus, in order to simulate the flow dynamics of large, thermal–compositional reservoir models, the conduction term should always be discretized implicitly, and the TAIM stability criteria should be applied to the mass conservation equations and the convection terms in the energy balance. This means that temperature, like pressure, is an unknown variable in every gridlock.

Semiconductor device optimization in the presence of thermal effects

AbstractOptimal design problems for semiconductor devices with relevant thermal effects can be formulated by help of the energy transport model. In this paper we perform a sensitivity analysis to derive the first‐order necessary condition for the optimization. Exploiting the special structure of the KKT system we use a special variant of the classical Gummel iteration to provide a very fast optimization algorithm. Numerical results for a ballistic diode underline the feasibility of our approach.

On the exponential stabilization of a thermo piezoelectric/piezomagnetic system

This paper is motivated by a piezoelectric/piezomagnetic phenomenon in the presence of thermal effects. The evolution system we consider is linear and coupled between one hyperbolic , two elliptic and one parabolic equation. We show the equivalence between ``the exponential decay of the total energy of our system' and an ``observability inequality for an anisotropic elastic wave system' assuming that a geometric condition is satisfied. This geometric condition ensures that the elliptic operator associated with the mechanical part of our system has no eigenfunctions $ \Psi $ such that the divergence div (Λ $ \Psi $ ) = 0 in $\Omega$ where $ Λ $ denotes the thermal expansion tensor.

Analysis of Thermal Effects in a Cavitating Orifice Using Rayleigh Equation and Experiments

The cavitation phenomenon interests a wide range of machines, from internal combustion engines to turbines and pumps of all sizes. It affects negatively the hydraulic machines’ performance and may cause materials’ erosion. The cavitation, in most cases, is a phenomenon that develops at a constant temperature, and only a relatively small amount of heat is required for the formation of a significant volume of vapor, and the flow is assumed isothermal. However, in some cases, such as thermosensible fluids and cryogenic liquid, the heat transfer needed for the vaporization is such that phase change occurs at a temperature lower than the ambient liquid temperature. The focus of this research is the experimental and analytical studies of the cavitation phenomena in internal flows in the presence of thermal effects. Experiments have been done on water and nitrogen cavitating flows in orifices at different operating conditions. Transient growth process of the cloud cavitation induced by flow through the throat is observed using high-speed video images and analyzed by pressure signals. The experiments show different cavitating behaviors at different temperatures and different fluids; this is related to the bubble dynamics inside the flow. So to investigate possible explanations for the influence of fluid temperature and of heat transfer during the phase change, initially, a steady, quasi-one-dimensional model has been implemented to study an internal cavitating flow. The nonlinear dynamics of the bubbles has been modeled by Rayleigh–Plesset equation. In the case of nitrogen, thermal effects in the Rayleigh equation are taken into account by considering the vapor pressure at the actual bubble temperature, which is different from the liquid temperature far from the bubble. A convective approach has been used to estimate the bubble temperature. The quasisteady one-dimensional model can be extensively used to conduct parametric studies useful for fast estimation of the overall performance of any geometric design. For complex geometry, three-dimensional computational fluid dynamic (CFD) codes are necessary. In the present work good agreements have been found between numerical predictions by the CFD FLUENT code, in which a simplified form of the Rayleigh equation taking into account thermal effects has been implemented by external user routines and some experimental observations.

Light Self-Action in NLCs with Orientational and Thermal Nonlinearities

The properties of a light beam passed through an NLC layer with positive orientational nonlinearity and then reflected from the NLC–substrate interface have been experimentally studied. The divergence and the intensity profile of this beam were found to be quite different from those of the beam transmitted through the NLC cell. It is shown that the aberrational pattern in the cross-section of the reflected beam and the dynamics of its formation can be used to study the orientational nonlinearity even in the presence of thermal effects.

Dynamics of a thermoelastic von Kármán plate in a subsonic gas flow

We discuss the problem of non-linear oscillations of a clamped thermoelastic plate in a subsonic gas flow. The dynamics of the plate is described by von Karman system in the presence of thermal effects. No mechanical damping is assumed. To describe the 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.