Narrow Results

A solid–solid contact model of a rough surface with a single peak was established to explore the thermal effect of interfacial friction. From the perspective of friction force, temperature and energy, the law of the thermal effect was revealed. The results showed that the temperature of the asperities gradually increased during the shearing process, and a stress concentration formed in the shearing zone. After contact, the asperities had undergone unrecoverable plastic deformation. At each indentation depth, as the rotation angle of the crystal increased, the friction force, average temperature, and the sum of the changes in thermal kinetic and thermal potential energy first increased and then decreased; the trends of the three parameters changing with the rotation angle of the crystal were consistent. The average decreases in the friction force, average temperature, and the sum of the changes in thermal kinetic and thermal potential energy were 52.47%, 30.91% and 56.75%, respectively, for a crystal structure with a rotation angle of 45^∘ compared to a crystal structure with a rotation angle of 0^∘. The methods used in this study provide a reference for the design of frictional pairs and the reduction of the thermal effect of interfacial friction.

The mesoscopic single RLC (resistance-inductance-capacitance) circuit and the RLC circuit including complicated coupling are quantized by employing Dirac's standard canonical quantization method. The thermal effects for the systems are investigated by virtue of GHFT (the generalized Hellmann–Feynman theorem). The results distinctly show the effect of temperature on the quantum fluctuation.

This paper designed a perfect optical absorber based on three-tier gate nanostructure, which shows a wide-band perfect absorption in the wavelength range of 200–560 nm as a transverse wave incidents to the nanostructure with the incident angle 35°< θ< 65°. When θ = 45°, a wide absorption band with the absorption rate more than 94% is observed, with the maximum of absorption rate reaching 99.3% at the wavelength of 430 nm. We also analyze the thermal characteristics of the perfect absorber. The band ranging from 560 nm to 1200 nm presents an increasing absorption rate with the increase of temperature. The calculation results of multi-physics analysis indicate that different cooling method causes different temperature distribution for the perfect absorber. This three-tier gate perfect absorber may find applications on broadband visible detectors, microbolometer and thermal imaging.

Passively Q-switching performance of the composite Nd:YVO₄ laser was experimentally investigated by using V:YAG as saturable absorber. The comparisons between the temperature distributions and thermal focal lengths in Nd:YVO₄ crystals were numerically analyzed by using a finite element method. The maximum CW output power of 1.65 W with an optical slope efficiency of 25.6% was obtained by YVO₄/Nd:YVO₄ composite crystal under an incident pump power of 7.1 W. For Q-switching regime, the highest output power was 664 mW with a pulse repetition rate of 30 kHz and pulse duration of 35 ns.

Based on nonlocal strain gradient theory, wave propagation in fluid-conveying viscoelastic single-walled carbon nanotubes (SWCNTs) is studied in this paper. With consideration of thermal effect and surface effect, wave equation is derived for fluid-conveying viscoelastic SWCNTs under longitudinal magnetic field utilizing Euler–Bernoulli beam theory. The closed-form expressions are derived for the frequency and phase velocity of the wave motion. The influences of fluid flow velocity, structural damping coefficient, temperature change, magnetic flux and surface effect are discussed in detail. SWCNTs’ viscoelasticity reduces the wave frequency of the system and the influence gets remarkable with the increase of wave number. The fluid in SWCNTs decreases the frequency of wave propagation to a certain extent. The frequency (phase velocity) gets larger due to the existence of surface effect, especially when the diameters of SWCNTs and the wave number decrease. The wave frequency increases with the increase of the longitudinal magnetic field, while decreases with the increase of the temperature change. The results may be helpful for better understanding the potential applications of SWCNTs in nanotechnology.

High-temperature superconducting (HTS) film-substrate structures have great potential applications in magnets and superconducting cables that have great potential for high temperature superconducting wires in space solar power stations. The most important issue in the successful application of those structures is the delamination of interfaces. Therefore, in this paper, the delamination induced by electromagnetic force and temperature change in the superconducting film-substrate structure is studied. Energy release rates of delamination are given. It is found that thermal effect on the energy release rate is more significant when the electromagnetic force increases. If without electromagnetic force, as the crack length reaches at its critical value, the film will be buckling and the crack becomes a mixed crack. The closed-form solution of the energy release rate of the mixed crack is provided. On the other hand, when the crack length is smaller than its critical buckling length and the crack is the mode II crack. The influence of the stress intensity factor of the mode II crack is more significant for a thicker film. This suggests that the film should be designed to be thinner. This study is useful for engineers to design HTS film-substrate structures.

In this paper, the thermal effect on wave dispersion characteristic induced by the spinning and longitudinal motions in the viscoelastic carbon nanotubes (CNTs) conveying fluid is presented. Hamilton’s principle is utilized to derive the governing equation of this nanotube based on the non-local strain gradient and Euler–Bernoulli beam theories. Then, the dispersion solution is found by using the Naiver method. Based on this, the influences of the spinning and longitudinal motion velocities, structural damping, temperature and flow velocity on dispersion relation of the nanotubes are discussed according to numerical simulation. In view of the results of numerical examples, some interesting conclusions can be drawn. The existence of spinning motion leads to the coupling between the vibration in the $y$ and $z$ directions, which induces that the first-order transverse wave frequency increases/decreases for small/large wave number and the second-order one increases. The important solutions presented in the work will provide the useful information for the designation of the nanotubes conveying fluid with the spinning and longitudinal motion.

The crystal structure and thermal properties of the ${\mathrm{\text{Ca}}}_{0.5}{\mathrm{\text{In}}}_{1.5}{\mathrm{\text{Se}}}_3$ compound have been investigated. Structural studies were performed by X-ray diffraction at room temperature. The crystal structure of this compound was found to correspond to the hexagonal symmetry of the space group P6₁. Thermal properties were studied using a differential scanning calorimetry (DSC). It was found in the temperature range $25^{\circ }\mathrm{\text{C}}\le T\le 950^{\circ }\mathrm{\text{C}}$ that thermal effects occur at temperatures $T_1=102^{\circ }\mathrm{\text{C}}$ and $T_2=848^{\circ }\mathrm{\text{C}}$. The thermodynamic parameters of these effects are calculated.

Supernova matter consisting of protons, neutrons and electrons with proton fraction y_p = 0.3 are studied within finite temperature Brueckner–Goldstone approach with effective two-body Sussex interaction for various values of densities and at temperatures T = 5, 7 and 10 MeV. It is found that at a given density, temperature and proton fraction, the entropy production, internal energy per nucleon, free energy per nucleon and pressure generated by protons and electrons are not equal. Entropy produced in the supernova matter is larger than that of corresponding asymmetric nuclear matter. The rise in temperature with densities in this matter under adiabatic condition is relatively suppressed with respect to corresponding asymmetric nuclear matter. Contribution to internal energy and free energy due to electron components is more pronounced than those of nuclear components. But the contribution to entropy and pressure due to nuclear components is larger than those of electron components. It is observed that for the matter with proton fraction y_p = 0.1, the internal energy, free energy and pressure generated due to protons are density-independent whereas, for supernova matter, these quantities are density-dependent. Distribution function, fraction of particles and mean field are the key factors to explain the characteristic properties of the constituent particles of supernova matter.

Presented herein is a new computational strategy to eliminate the thermal effect in measured responses. The internal forces of a structure and its thermal load components are estimated alternately at each time step based on a recursive least-squares algorithm. The noise effect in the measured data and the estimated force in previous steps are removed with the Kalman filter. This approach directly models the thermal effects on the dynamic responses without the temperature information. This approach adopts force identification technique which has been researched extensively in the last two decades. The effectiveness of the proposed approach is validated via numerical studies with a bridge structure with or without noise in the measured data. The thermal load in the structural components can be estimated accurately with the proposed strategy with less than 8% error when there is 10% noise in the measured responses of the structure.

This work investigates the longitudinal vibration characteristics of the pipe pile in the liquid-saturated ground due to Rayleigh waves propagation with considering the influence of the nonisothermal condition on the wave motion. Firstly, the Rayleigh wavefield in the liquid-saturated thermoelastic ground is deduced theoretically with taking advantage of the Biot theory and the non-Fourier law of heat conduction. Secondly, the longitudinal frequency domain solution of the pipe pile under Rayleigh waves is derived analytically. Finally, the dependence of the pipe pile response on the physical parameter is illustrated by utilizing several numerical examples. The result reveals that increase in the thermal expansion coefficient of saturated soil significantly augments the longitudinal displacement and side friction of pile body. Increase in the permeability of saturated soil will reduce the pile head displacement. When the pile length is less than its effective length, the rise of the pile length will reduce the pile head displacement. Augment of both the outer radius and wall thickness of the pipe pile will help to reduce the pile head displacement. However, the lateral inertia effect of the pipe pile has slight influence on its longitudinal behavior under Rayleigh waves.

Microstructures fabricated by use of focused ion beam (FIB) direct scanning is useful for microsystems. However, a new phenomenon was found recently by our experimental results. After the FIB bombardment in the defined area, the microstructures were formed under the competence between the ion sputtering induced surface roughening and surface diffusion induced surface smoothing. The process was called self-organized formation. The generated microstructures were characterized by atomic force microscope (AFM). The measured results show that the dimensions of the microstructures were changed with time. In other word, the measured results were different between the samples just processed and that one finished over one week, and the former with smaller dimensions than the latter. The reason maybe due to the thermal effect induced by the FIB bombardment. We called it a natural annealing. The fabricated microstructures were not in stable state due to the internal stress caused by ion sputtering and thermal diffusion. At initial state, it is in dynamic balance. After the natural annealing with several days, the dynamic balance is changed by the thermal diffusion which caused the dimensions of the microstructures varied continuously. In addition, the surface oxidation is also another factor.

This paper provides a study of the bending behavior of a circularly curved functionally graded piezoelectric cantilever actuator under an applied electric load and heat conduction. As a special case, the curved piezoelectric actuator is assumed to have graded property for the piezoelectric parameter g₃₁ only in the thickness direction, which is expanded by Taylor series. Based on the theory of linear piezoelectricity, the analytical formulations are developed by introducing the Airy stress function. Numerical simulations are made to show the effects of material gradient and heat conduction on the bending behavior of the actuators. It is found that the electroelastic field of the curved actuator is significantly influenced by the thermal load. The results will be very helpful for the design and optimization of curved functionally graded piezoelectric actuators when these devices experience heat transfer.

This paper deals with the nonlinear large deflection torsional buckling of functionally graded carbon nanotube (CNT) orthogonally reinforced composite cylindrical shells surrounded by Pasternak’s elastic foundations with the thermal effect. The shell is made by two layers where the polymeric matrix is reinforced by the CNTs in longitudinal and circumferential directions for outer and inner layers, respectively. The stability equation system is obtained by combining the Donnell’s shell theory, von Kármán nonlinearity terms, the circumferential condition in average sense and three-state solution form of deflection. The critical torsional buckling load, postbuckling load-deflection and the load-end shortening expressions are obtained by applying the Galerkin procedure. The effects of temperature change, foundation parameters, geometrical properties and CNT distribution law on the nonlinear behavior of cylindrical shell are numerically predicted. Especially, the effect of orthogonal reinforcement in comparison with longitudinal and circumferential reinforcement on the torsional buckling behavior of shells is observed.

In this paper, we consider a one-dimensional Lord–Shulman thermoelastic system [C. Cattaneo, On a form of heat equation which eliminates the paradox of instantaneous propagation, C. R. Acad. Sci. Paris 247 (1958) 431–433] with porous damping and distributed delay term acting on the porous equation. Under suitable assumptions on the weight of distributed delay, we establish the well posedness of the system by using semigroup theory and we show that the dissipations due to thermal effects with porous damping are strong enough to stabilise the system exponentially, independently of the wave speeds of the system.

In response to the occurrence of wellhead growth in some deep wells in west China during production, particular attention is first given to the casing program and well construction. Then, a multistring system and a calculation method for wellhead movement are provided. Using a case study of a deep well in west China, a comparative analysis was conducted to investigate the variations of wellhead movement and casing axial forces. The calculated results are in good agreement with the field observations of wellhead growth. Increased temperature is the root cause of wellhead growth, while free length of surface casing is a sensitive factor. Wellhead upward displacement can be effectively relieved by the use of setting load. As the setting load increases, wellhead growth decreases. On the other hand, when the free length of surface casing decreases, wellhead displacement decreases. Setting loads and good surface casing cementing quality are advised to prevent wellhead growth in the process of well construction.