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This paper investigates the thermoelastic behavior of porous materials under magnetic fields using a dual-phase lag (DPL) model, with a specific focus on an unbounded porous body containing a cylindrical cavity. By applying the Laplace transform to address the time-dependent aspects of the governing equations, we investigate the effects of harmonically varying heat loads on the material's porous–thermoelastic response. Numerical simulations provide insights into the distribution of excess pore water pressure, temperature, displacement, thermal stresses, and the magnetic field within the material. Results are presented through graphical analyses, facilitating a detailed comparison of porous–thermoelastic behaviors under different conditions. This approach not only validates the model's accuracy but also enhances our understanding of porous materials' responses to thermal and magnetic stimuli, offering valuable implications for their design and safety in engineering applications. [ABSTRACT FROM AUTHOR]

This paper presents an analytical solution for combined vertical and torsional shear loading of a cylindrical cavity in undrained modified Cam‐Clay. The governing partial differential equations for the cylindrical cavity are established in the polar coordinate. The problem is formulated as a set of first‐order differential equations by using the axisymmetric condition, equilibrium equations, and elastic‐plastic constitutive relationship. The influence of the second shear loading on the initial shear strain is considered in the plastic state. Then the stress‐strain distributions can be calculated by integrating within the elastic and plastic zones around the cavity. A finite element method simulation of the cavity under combined shear loading is established to verify the proposed approach, and the results are in good agreement with the proposed analytical solution. Parametric analyses are carried out on the effects of clay overconsolidation ratios and in situ stress coefficients under different loading paths and loading ratios. The results show that the combined shear loading on the cavity wall has a significant effect on the stress distribution of the surrounding soil, and the influence of the loading path cannot be neglected. [ABSTRACT FROM AUTHOR]

This study investigates the dynamic response of an infinite structure comprising two coaxial cylinders employing the one-relaxation-time generalized thermoelastic diffusion model. The inner cylinder, serving as a cavity, possessing a radius a, while the outer cylinder has radius b. The inner cylinder is insulated and experiencing a localized thermal load with thickness 2 h. The outer cylinder, with radius b, is also experiencing to a localized thermal load with width 2 h, and its surface exhibits no traction. Additionally, the structure experiences the influence of a solenoidal body force. The analysis of this problem employs a combination of Laplace transform, inverse Laplace transform, and exponential Fourier transform techniques. Numerical analysis of the resulting solutions reveals the variations in temperature, displacement, radial stress, concentration, and potential fields as a function of the radial coordinate. Results indicate a minimal impact of the time interval on the temperature distribution, while displacement and radial stress exhibit significant time-dependent behavior. These findings highlight the significance of incorporating thermoelastic diffusion theory in the analysis of real-world engineering problems. [ABSTRACT FROM AUTHOR]

This paper studies the photo-thermoelasticity interactions in an infinite semiconductor medium with cavities. A new hyperbolic two-temperature photo-thermoelasticity theory with one thermal delay time is used to investigate this problem. The eigenvalue approach under the Laplace transform method is used to get the analytical solutions of physical field variations. Also, the thermoelasticity properties are considered without neglecting the coupling between the thermo-elastic and the plasma wave. Finally, the numerical results are graphically presented to display the difference between the generalized hyperbolic two-temperature theory and the generalized classical two-temperature theory. [ABSTRACT FROM AUTHOR]

Flexoelectricity, a remarkable size-dependent effect, means that strain gradients can give rise to electric polarization. This effect is particularly pronounced near defects within flexoelectric solids, where large strain gradients exist. A thorough understanding of the internal defects of flexoelectric devices and their surrounding multiphysics fields is crucial to comprehend their damage and failure mechanisms. Motivated by this, strain gradient elasticity theory is utilized to investigate the mechanical and electrical behaviors of flexoelectric solids with cylindrical cavities under biaxial tension. Closed-form solutions are obtained under the assumptions of plane strain and electrically impermeable defects. In particular, this study extends the Kirsch problem of classical elasticity theory to the theoretical framework of higher-order electroelasticity for the first time. Our research reveals that different length scale parameters of the strain gradient and bidirectional loading ratios significantly affect the hoop stress field, radial electric polarization field, and electric potential field near the inner cylindrical cavity of the flexoelectric solid. Furthermore, we validate our analytical solution by numerical verification using mixed finite elements. The congruence between the two methods confirms our analytical solution's accuracy. The findings presented in this paper provide deeper insights into the internal defects of flexoelectric materials and can serve as a foundation for studying more complex defects in flexoelectric solids. [ABSTRACT FROM AUTHOR]

This article considers the problem of nonlinear oscillations of the motion of liquids completely filling an axisymmetric cylindrical vessel moving around the horizontal axis. The motion of each fluid is assumed to be potential and formulated in a cylindrical coordinate system. The influence of nonlinear coefficients on the characteristics of dynamic processes during the finite rotational motions of the vessel is estimated and the case of the forced angular oscillations of a vessel with liquids relative to a fixed axis is considered. The main nonlinear effects associated with the rotation of the diameter of the interface of liquids are also revealed. An approximate solution of the obtained nonlinear equations, found by the Bubnov–Galerkin method, is used in the article. As a result of the transformation, the amplitude-frequency characteristics (AFC) and stability regions of a two-layer liquid are constructed under the forced angular oscillations of a round cylindrical vessel. [ABSTRACT FROM AUTHOR]

The article describes the numerical studies on propagation of hydraulic fracture in the nonuniform-stress elastic environment around a cylindrical cavity. The modeling used the extended method of finite elements. The scope of the modeling embraced different variants of the principal stress orientation relative to the cavity and a disk-shaped initiation fracture. The influence of the stress ratio and stress level on the fracture path is described. The main types of the created fractures are shown. The conditions when the created fracture reaches the cavity surface or propagates along it are analyzed. The features of the fracture propagation and opening pressure are described for the fractures of various shapes depending on the volume of the injection fluid. [ABSTRACT FROM AUTHOR]

In order to understand the influences of Rayleigh number, geometric dimensions of closed cylindrical cavity and cylindrical heat source, the coupled natural convection inside and outside a closed cylindrical cavity with a uniform temperature heat source in the center of the cavity is simulated. The results indicate that the secondary vortex will appear in the closed cavity with the increasing dimensionless height of the internal heat source and the aspect ratio of the closed cavity. The heat transfer ability of the coupled natural convection reduces with the increasing dimensionless height and the radius of the heat source, and the decreasing the aspect ratio of the closed cavity. Compared with the results in an isothermal closed cavity, the heat transfer ability exhibits a different variation. Eventually, a heat transfer correlation on the heat exchange between the internal heat source and the external environment is obtained, which can be used as a reference for the heat dissipation calculation of electronic devices.

Copyright of Chinese Journal of Liquid Crystal & Displays is the property of Chinese Journal of Liquid Crystal & Displays and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper, an anisotropic critical state model for saturated soils was extended to unsaturated conditions by introducing suction into its yield function. Combining this model with soil-water characteristic curves related to porosity ratio was employed to characterize the coupled hydromechanical behavior of unsaturated anisotropic soil. Based on the plane stress condition, the problem of the cylindrical cavity expansion in unsaturated anisotropic soils was transformed into first-order differential equations using the Lagrangian description. The equations were solved as an initial value problem using the Runge-Kutta algorithm, which can reflect the soil-water retention behavior during cavity expansion. Parametric analyses were conducted to investigate the influences of overconsolidation ratio (OCR), suction, and degree of saturation on the expansion responses of a cylindrical cavity in unsaturated anisotropic soil under plane stress condition. The results show that the above factors have obvious influences on the cavity responses, and the plane strain solution tends to overestimate expansion pressure and degree of saturation but underestimates suction around the cavity compared to the proposed plane stress solution. The theoretical model proposed in this paper provides a reasonable and effective method for simulating pile installation and soil pressure gauge tests near the ground surface of the unsaturated soils.

The current work is devoted to introduce a novel thermoelastic heat conduction model where the Moore-Gibson-Thompson (MGT) equation describes the heat equation. The constructed model is characterized by allowing limited velocities of heat wave propagation within the material, consistent with physical phenomena. The Green–Naghdi Type III model is improved by introducing the delay factor into the modified Fourier law. Also, from the presented model, some other models of thermoelasticity can be derived at specific states. Based on the suggested model, an infinite orthotropic material with a cylindrical hole exposed to time-dependent temperature variation was studied. It has also been considered that the coefficient of thermal conductivity varies with temperature, unlike in many other cases where this value is considered constant. The viscoelastic material of the investigated medium was assumed to be of the Kelvin–Voigt type. The Laplace transform method provides general solutions to the studied field variables equations. The effects of viscosity and thermal variability parameters on these fields are discussed and graphically presented. In addition, the numerical results were presented in tables, and a comparison with previous models was made to ensure the accuracy of the results of the proposed model.

An equation of the dynamics of formation and radiation of a quasi-empty oscillating cylindrical cavity in a fluid is derived for the first time with due allowance for the changes in the sound speed and the volume fraction of cavitation nuclei. A dimensionless formulation of the problem is proposed and analyzed under the condition of identical pressures in the cavitation zone and inside the cylindrical cavity at its boundary. As a result, a dynamic relationship between the volume fraction (sound speed) in the cavitation zone and the radius of the cylindrical cavity is found. [ABSTRACT FROM AUTHOR]

An interesting feature that appears in the thermoelastic interaction in an orthotropic material containing cylindrical cavities is addressed in this study. For this purpose, the Finite Element Method is applied to analyze a generalized thermoelasticity theory with a relaxation time. For the development of the model, a thermal conductivity that is dependent on the temperature of the orthotropic medium was considered. The boundary condition for the internal surface of a cylindrical hollow is defined by the thermal shocks and the traction on the free surface. The nonlinear formulations of thermoelastic based on thermal relaxation time in orthotropic mediums are abbreviated using the Finite Element Method. The nonlinear equations without Kirchhoff's transformations are presented. The results are graphically represented to demonstrate how changing thermal conductivity affects all physical values. [ABSTRACT FROM AUTHOR]

This study presents a large‐strain analysis for cylindrical cavity unloading–contraction problem in strain‐softening geomaterials. Based on the unified strength theory (UST) and non‐associated flow rule, the process of cavity contraction in cohesive‐frictional geomaterials is regarded as a large‐strain problem by introducing the UST parameters and the volumetric force of seepage into the conventional cylindrical cavity contraction analysis, the effects of strain‐softening characteristic, intermediate principal stress, large‐strain, and seepage are considered. Finally, according to the comparison of the results of the radius ratio with those in the published literature, the correctness and reliability of the theoretical method are proved. The results show that it is necessary to consider the effect of volume force of seepage in the stability of excavation problem in geomaterial, the larger the volume force of seepage, the smaller the plastic radius. The traditional two‐dimensional cavity contraction solution overestimates the plastic radius. The results provide a theoretical basis for the elasto‐plastic analysis of excavation in rich water geomaterial and have a certain reference value for engineering design. [ABSTRACT FROM AUTHOR]

The problem of a piezoelectric body with a cylindrical cavity is studied within the framework of the 3D exact equations of electro-elasticity theory using Hamilton's principle. It is supposed that the plate has simply-supported, mechanical and short-circuit conditions with respect to the electric potential along all its lateral edge surfaces. The solution to the corresponding free vibration problems is determined numerically by 3D FEM with the help of programs and algorithms composed by the authors. This paper successfully identifies the hole (cavity) size, volume fraction and location in finite piezoelectric plates as well as the coupling effect between the mechanical and electrical fields on the natural frequencies. The numerical results that confirm the effectiveness of the proposed method for cavity identification in piezoelectric plates are presented in detail. [ABSTRACT FROM AUTHOR]

The current paper is concerned with a new size-dependent thermoelastic model where the constitutive and the motion equations are modified. The governing equations of the introduced model are derived based on the generalized dual-phase-lag thermoelastic model and non-local elasticity theory. Additionally, the present work is an attempt to investigate a thermoelastic interaction in an infinite medium with a cylindrical cavity based on the proposed model. The cavity surface is traction free and exposed to a time-dependent moving heat source. The analytical formulas for the field quantities are obtained first in the Laplace transform domain. To find the inverse Laplace transform into the physical quantities, a numerical technique is performed. The numerical results are discussed in different cases to highlight the effect of the size -scale parameter and the speed of the heat source on the studied thermo-physical fields. [ABSTRACT FROM AUTHOR]

Due to the inhomogeneity of shear modulus, the constitutive form of the medium becomes more complicated, which increases the difficulty of solving the analytical solution. In this paper, a new form of shear modulus is derived. Meanwhile, the wave number in the medium is also variable. By using the method of complex function and conformal transformation, the problem of dynamic stress concentration around a cylindrical cavity in an infinite inhomogeneous medium is solved. Combined with an auxiliary displacement function and a pair of new mapping functions, in the solving process, the analytical expressions of displacement field and stress field are given. The validity of this method is verified by comparing with the published results. Through numerical results, the distribution of dynamic stress concentration factor around a cylindrical cavity is analyzed under different inhomogeneous parameters and reference wave numbers. [ABSTRACT FROM AUTHOR]

Photothermal spectroscopy is a method of measuring the optical absorption and thermal properties of semiconductor materials using high-sensitivity spectroscopic techniques. Heating occurs due to light, which is absorbed but not dissipated by emission. In this paper, a new model is provided that can be used to understand the process of optical thermal transfer and the interaction between elastic plasma waves and heat. The proposed photothermal model is described by the Moore–Gibson–Thompson heat equation. Using the proposed model, the thermal and photoacoustic effects in an infinite isotropic and homogeneous body with a cylindrical cavity of semiconductor material crossed into a fixed magnetic field and subjected to high-intensity laser heat flux were investigated. The inner surface of the cavity is considered to be traction-free, and the carrier density is photogenerated by a laser pulse heat flux that decays exponentially. The numerical calculations for the components of thermal stresses, displacement, temperature field, and carrier density are obtained using the Laplace transform approach. The propagation of heat, elastic, and plasma waves, as well as the distributions of each investigated field, were examined and explained. The comparison is also used to see how different thermal response features, such as thermal relaxation, laser pulse duration, and lifetime, affect the thermoelastic response. [ABSTRACT FROM AUTHOR]

The behavior of the gas inside a vibrating cylindrical cavity at near-resonance vibration frequencies is studied numerically. A constant temperature is set on the walls of the cavity. Several vibration amplitudes are considered. The features of the bulk temperature, the period average temperature, as well as the local heat flux through the lateral surface [ABSTRACT FROM AUTHOR]

This study investigates the photo-thermo-elastic interaction in an infinite semi-conductor material with cylindrical cavities. The effect of variable thermal conductivity through the photo-thermo-elastic transport process is studied using the coupled models of thermo-elasticity and plasma waves. The internal surface of the cylindrical cavity is loaded by a thermal shock varying heat. The eigenvalue method, under Laplace transform scheme, is used to get the analytical solution of the studied field distribution as parts of this phenomenon. A detailed analysis of the impacts of the variable thermal conductivity on the physical fields is debated. The numerical outcomes of the studied fields are displayed graphically. According to them, the variable thermal conductivity offers finite speed of the mechanical wave and the thermal wave propagations.

We study numerically the equilibrium configurations of nematic liquid crystals confined in cylindrical cavities with strong and weak homeotropic anchoring conditions, respectively, on the basis of the elastic continuum theory and the difference iterative method. The lyotropic chromonic liquid crystal disodium cromoglycate exhibits a completely different spontaneous chiral configuration from 5CB due to the large ratio of the saddle-splay elastic constant to the twist elastic constant. We show that how the elastic constants affect the director alignment in chiral structure with strong homeotropic anchoring conditions. For the weak homeotropic anchoring conditions, the theoretically predicted transition from a twisted and escaped radial to an escaped twisted configuration of DSCG and the transition from an escaped radial to a UA configuration of 5CB, on reduction of the anchoring coefficient below a certain threshold, are confirmed to occur at A∼10−8J/m2. Remarkably, it provides a more accurate theoretical analysis for the prediction of director configurations in cylindrical cavities under different conditions in experiments. [ABSTRACT FROM AUTHOR]

The scattering of elastic waves by underground cavities is an active research topic for its broad applications in various fields, such as earthquake engineering, the blast resistance of underground structures, geophysical exploration, etc. In most previous studies, the sounding medium was treated as an ideal elastic medium or a saturated poroelastic medium. The understanding of the scattering of elastic waves by cavities in unsaturated porous media is limited. In this study, the scattering of plane P1 waves and SV waves by a cavity with a permeable surface in an infinite unsaturated porous medium is solved by the wave function expansion method. The dynamic stress concentration at the cavity surface is investigated by taking P1 wave incidence, for example. Numerical results illustrate that the scattering of plane waves around the cavity strongly depends on the frequency of the incident waves, and the saturation, Poisson’s ratio, and porosity of the surrounding medium.

An interesting feature that appears in the thermoelastic interaction in an orthotropic material containing cylindrical cavities is addressed in this study. For this purpose, the Finite Element Method is applied to analyze a generalized thermoelasticity theory with a relaxation time. For the development of the model, a thermal conductivity that is dependent on the temperature of the orthotropic medium was considered. The boundary condition for the internal surface of a cylindrical hollow is defined by the thermal shocks and the traction on the free surface. The nonlinear formulations of thermoelastic based on thermal relaxation time in orthotropic mediums are abbreviated using the Finite Element Method. The nonlinear equations without Kirchhoff’s transformations are presented. The results are graphically represented to demonstrate how changing thermal conductivity affects all physical values.

We consider a 2D problem for an infinite body with a cylindrical cavity formed of a thermoelastic substance. The body is under the action of a nonsolenoidal body force. The theory used is that of Generalized Thermoelasticity. The surface is assumed to be traction free and subjected to an asymmetrical thermal shock. Laplace transform is used. The inversion process is carried out numerically. All the relevant functions are represented graphically. [ABSTRACT FROM AUTHOR]

Medium power electron accelerators have many applications in industrial irradiations. In order to meet the industry needs of Iran, several investigations for design and construction of the medium power linear electron accelerator in the VHF band frequency with the energy range of 1 MeV - 5 MeV have been started. The acceleration cavity is one of the important components of this design. In this article the design and construction of the cavity are reported and the results of the simulations and measurements are compered. Mean while the essential parameters, including resonance frequency, quality factor, shunt impedance, figure of merit and transit time factor are evaluated for several configuration of cylindrical cavity using (CST), (HFSS) and (SUPERFISH) codes in order to design an efficient cavity for electron beam with the maximum energy up to 5 MeV and 50 kW power with the lowest power loss. After repeating the simulations and reliability of the results, the designed cavity was constructed and its parameters were measured. The results showed that the measured parameters are in good agreement with simulation results.

A simplified finite element method (FEM) simulation method has been established and validated for analyzing the sound absorption mechanism of structures with periodic axisymmetric cavities. Combined with genetic algorithm, the simplified FEM method is used to optimize the sound absorption coefficient of the structure containing periodic cylindrical cavities and variable cross section cavities. The result of variable section cavities is much better than the case of cylindrical cavities. The effect of cavity shape on sound absorption mechanism is discussed through energy dissipation, structure deformation and modal analysis of the absorption structures. It is found that the cavity structure resonances include bending vibration of the surface layer and radial motion of particles near the cavities. The radial motion also changes along the axial direction. Adding geometric design parameters of the cavity cross section are conducive to moving the radial mode to low frequency. The radial vibration has a great influence on absorption performance, which is more conducive to promoting the conversion of longitudinal waves into transverse waves with more energy dissipation. Finally, a better sound absorption performance is obtained by introducing the material parameter of Young's modulus into the optimization model, indicating that comprehensive consideration of geometry and material parameters for optimization is expected to obtain the desired sound absorption structure in engineering practice. [ABSTRACT FROM AUTHOR]

Photo-thermal-elastic interactions in an unbounded semiconductor media containing a cylindrical hole under a hyperbolic two-temperature are investigated using the coupled theory of thermo-elasticity and plasma waves. A new hyperbolic two-temperature model is used to study this problem. The internal surface of the cylindrical cavity is loaded by exponentially decaying pulse boundary heat flux and traction free. The Laplace transform technique are presented to obtain the exact solutions of this problem in the transformed domains by the eigenvalue approach. The inverse of Laplace transforms was numerically carried. The results show that the analytical solutions can overcome the mathematical problems to analyzes this problem. According to the numerical outcomes, the hyperbolic two-temperature thermoelastic theory offers finite velocity of the mechanical waves and thermal waves propagations. [ABSTRACT FROM AUTHOR]

This article presents a new design of a differentially fed substrate integrated planar antenna array with dual-polarization. Compared with the traditional dual-polarized antenna arrays, the proposed array antenna has the advantages of simple configuration, high cross-polarization discrimination (XPD), and high gain. The 2 × 2-element subarray design with a via-loaded crossover structure is used, which reduces the complexity of the array antenna. The operation bandwidth is improved by generating three resonances in the subarray. An 8 × 8 antenna array is designed, prototyped, and tested to exemplify its potential applications in large dual-polarized antenna arrays. A planar orthomode transducer is used to achieve differential excitation for the antenna array. The measured results show that the proposed antenna array has an impedance bandwidth of 19.2–20.7 GHz for |S11|< −10 dB and port isolation higher than 20 dB. The array antenna exhibits a high XPD of 43 dB and a flat gain of about 22.2 dBi within the bandwidth. [ABSTRACT FROM AUTHOR]

Copyright of Eastern-European Journal of Enterprise Technologies is the property of PC TECHNOLOGY CENTER and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Lyotropic chromonic liquid crystals (LCLCs) confined in cylindrical cavity can form an escaped-twisted (ET) configuration, resulting from the saddle-splay elastic constant is great much than twist elastic constant. The thermotropic liquid crystal 5CB does not meet the conditions for the formation of ET configuration, but it can be achieved under the appropriate planar anchoring and the action of chiral dopant. The equilibrium configuration of nematic liquid crystals confined in cylindrical cavities with azimuthal and axial surface anchoring conditions respectively is studied by the elastic continuum theory and the difference iterative method. We obtain the analytical solution of the distribution of the director without chiral dopant and the numerical solution of the chiral dopant. We find that the planar anchoring, the saddle-splay elastic constant and the chirality determine whether an ET configuration is formed. Furthermore, the cavity radius and the bend elastic constant can affect the value of twist angle. It provides a good theoretical basis for the determination of anchoring energy and saddle-splay elastic constant. [ABSTRACT FROM AUTHOR]

The knowledge of the dielectric properties of oils is of great importance for several industrial applications, such as microwave-assisted oil frying for foods and high voltage electric power transmission. In this paper, we present the complex permittivity of vegetable oils (canola, olive, soybean, coconut) at 2.50 GHz using the cavity perturbation technique from 28 to 200 °C (temperature close to the smoking point of oils). The measurements were taken with a cylindrical cavity operating at the TE111 mode with an unloaded Q of 4950. In addition, free fatty acids, peroxide index and color were measured before and after heating. [ABSTRACT FROM AUTHOR]

A Langevin dynamics computer simulation is carried out to study the translocation of a single homogeneous star polymer out of a cylindrical cavity connected to a membrane wall with a circular nanopore along the tube axis. The ejection process is driven through an external pulling force applied on the free end monomer of the chain leading arm. The results show that, for a given chain mass and for relatively narrow pores, the mean translocation time 〈τ〉 exhibits a non‐monotonic dependence on the chain functionality f with the existence of a minimum at a critical functionality that defines a boundary between two distinct translocation regimes. Moreover, for a given functionality, the variations of the mean translocation time with respect to the chain mass and the magnitude of the pulling force respectively, are both found to follow a power law relationship. Finally, it has been demonstrated that the translocation dynamics can be significantly altered by changing the confining tube dimensions, with the existence of an optimal tube aspect ratio that minimizes the chain mean translocation time 〈τ〉. [ABSTRACT FROM AUTHOR]

In a cylindrical cavity with a degenerate planar anchoring, the lyotropic chromonic nematic liquid crystals without intrinsic chirality tend to exhibit an escaped twisted configuration for the large saddle-splay-to-twist elastic modulus ratio, which is not found in most thermotropic liquid crystals. In this work, we consider thermotropic nematic liquid crystal 5CB with a chiral dopant confined in a cylindrical cavity with a degenerate planar anchoring. Based on the elastic theory of liquid crystal and the variation method, Euler equation and boundary conditions are obtained. The numerical results show that the director of 5CB forms an escaped twisted configuration, and the twist angle is influenced by the chiral parameter and the saddle-splay elastic constant. Under an axial electric field, the dielectric effect and the flexoelectric effect affect the LC director distribution. The single flexoelectric coefficient e1 has a large radial orientation effect on the director. The results provide a clearer understanding of the director configuration in the cylindrical cavity under the electric field and a theoretical basis for the measurement of the flexoelectric coefficients. [ABSTRACT FROM AUTHOR]

Under the back-side windy condition, the convection and radiation heat transfer characteristics in an iso-flux upward-facing cylindrical cavity were studied by three-dimensional numerical simulation. The impacts of cavity tilt angle, wind incident angle and wind speed on convection and radiation heat transfer Nusselt number Nuc and Nur were analyzed, and the possible explanations for their impacts were presented. Results show that due to the disturbance of wind, the influence of cavity tilt angle becomes more complicated and is related to wind incident angle and wind speed. The variation of Nuc or Nur with wind incident angle is different for different cavity tilt angles. Despite of the changes of cavity tilt angle or wind incident angle, the Nuc increases with the wind speed while the Nur presents a declination with the increasing of wind speed. Hence, compared with cavity tilt angle and wind incident angle, wind speed may be the dominant factor affecting or controlling the convective and radiation heat transfer of cavity. [ABSTRACT FROM AUTHOR]

Sound field reproduction of the aircraft and submarine within a cabin mock-up using a loudspeaker array is of great importance to the active noise control technology.The conventional method is to calculate the driving functions of the secondary sources by solving an acoustic inverse problem in a least square sense, which requires a large number of microphones and only the sound field near the microphone array can be reproduced accurately.In order to overcome these drawbacks, higher order ambisonics (HOA) method which is widely used in spatial sound field synthesis for a large room is introduced to reproduce a low frequency sound field within a cylindrical cavity.Due to the different sound propagation characteristics within the cavity compared with a free field and a diffuse field, the Green function spectrum in spherical harmonics domain which is modeled as a superposition of the acoustic modes and the reproduction formulas are deduced.Reproduction characteristics are investigated by numerical simulations.Results show that for a small, the Green function spectrum in spherical harmonics domain is mainly concentrated on low orders and contributed by the low order acoustic modes, with the increase of, high order components of the Green function arise and the contributions of high order acoustic modes increase.In the reproduction process, the high order components of the pressure spectrum over the sphere in harmonics domain will be greatly amplified by the reproduction filter.Finally, HOA method is compared with the acoustic inversion method in terms of the microphone array system, the impact factors on the reproductions and the reproduction accuracy, and validated through experiments.Results show that HOA can better reproduce the entire sound field within the cylindrical cavity and the reproduction accuracy is improved.

The influence of the thermophysical variable properties on the buoyancy-driven flows of liquid sodium and gallium established in a cylindrical cavity is numerically investigated, for the entire range of Rayleigh number corresponding to practical applications. Axisymmetric turbulent simulations (initially steady) are obtained, considering appropriate boundary and reference conditions for simulating the emergency cooling of a nuclear reactor. The results obtained for different heating intensities are analyzed and compared. In the case of sodium, the expected decay in the heat transfer coefficients is less relevant than that previously obtained for airflows. In turn, strong differences in the gallium thermal behavior are encountered. In fact, a trend opposite to that of sodium is detected for wide ranges of Rayleigh number and heating parameter. Additional transient simulations are carried out to complete a comparative assessment of the performance of both liquid sodium and gallium as cooling agents. [ABSTRACT FROM AUTHOR]

Our present work is concerned with the study of a semi-infinitely long, conducting solid with a cavity in cylindrical form in the context of magneto-thermo-elastic diffusion with two-temperature and three-phase-lag effect. The medium we have considered here is supposed to be initially quiescent. The material is assumed to be made of an isotropic homogeneous thermo-elastic material and put in a magnetic field which is uniform and acted in the direction of the axis of the cylindrical cavity. The solution to the problem is done in Laplace transform domain. Inversion process is applied to obtain the solution in space time domain and finally illustrated graphically. [ABSTRACT FROM AUTHOR]

This paper combines numerical and experimental to study the heat transfer by free convection for nanofluids of molten salt within a cavity with cylindrical shape which is heated at the bottom and releases heat at the top. The aim is to acquire the free convection laws for nanofluids of molten salt in a cylindrical cavity. It is found that after adding nanoparticles, the molten salts have lower viscosity, higher flow velocity and higher heat transfer rate, and therefore, the free convection heat transfer is enhanced. Meanwhile, nanofluids Nusselt number is larger than that of the molten salts at the same Rayleigh number. In addition, as the classical Garon's equation cannot provide good predictions of free convection heat transfer for the nanofluids of molten salt, this paper establishes a free convection equation for the nanofluids of molten salt in a cylindrical cavity. This equation is able to predict with an error less than 20% the experimental results. Therefore, the findings can provide a basis for engineering applications of nanofluids and for designing optimal systems of heat stockpile with a single tank. [ABSTRACT FROM AUTHOR]

Generalized thermoelastic interactions due to three-phase-lag time-nonlocal heat transfer in a Kelvin-Voigt type infinitely extended visco-thermoelastic continuum with cylindrical cavity has been investigated. The two-temperature generalized thermoelasticity theory has also been taken into account. The problem has been solved in the domain of Laplace on the assumption that the surface of the cavity is free from traction and is subjected to a smooth and time-dependent-heating effect. Laplace inversion of the transformed solutions has been carried out numerically. The obtained numerical data for different considerations are plotted in graphs to study the effects of time-nonlocal parameter, two-temperature parameter and visco-thermoelastic relaxation parameter on different thermoelastic quantities of physical interest. [ABSTRACT FROM AUTHOR]

An unified approach is presented for the analysis of the expansion of both cylindrical and spherical cavities in an infinite elastic–perfectly plastic "Hoek–Brown" (H–B) material. The H–B failure criterion expressed in scaled form is adopted with a plastic flow rule characterized by a constant dilatancy angle ψ . Closed form expressions are given for the extent of the plastic region and the related stress. Solutions of the displacement field in the plastic region are provided based on both small-strain and large-strain theories. An original relationship between the cavity pressure and its expansion is derived. The developed closed-form solutions are validated employing the finite element method. For comparison purposes, an approximate solution is presented by neglecting the elastic strains in the plastic region which reveals that the assumption of no elastic strains does not influence the results for strong rocks in contrast with weak rocks. For practical purposes, design charts are provided allowing easy and accurate estimates of the limit pressure for cavity expansion in rock masses. The cavity expansion solution is finally validated against results obtained using the Finite Element modelling. [ABSTRACT FROM AUTHOR]

This study investigates the photo-thermo-elastic interaction in an infinite semi-conductor material with cylindrical cavities. The effect of variable thermal conductivity through the photo-thermo-elastic transport process is studied using the coupled models of thermo-elasticity and plasma waves. The internal surface of the cylindrical cavity is loaded by a thermal shock varying heat. The eigenvalue method, under Laplace transform scheme, is used to get the analytical solution of the studied field distribution as parts of this phenomenon. A detailed analysis of the impacts of the variable thermal conductivity on the physical fields is debated. The numerical outcomes of the studied fields are displayed graphically. According to them, the variable thermal conductivity offers finite speed of the mechanical wave and the thermal wave propagations. [ABSTRACT FROM AUTHOR]

Resonant structure is one of the proposed methods in combining power in RF systems of RF accelerators. In this structure, fabrication of RF power divider or combiner using coaxial and cylindrical cavity is important. In this study, two combiners, in the same frequency band, are designed and fabricated; and their results are compared. The experimental results confirmed the simulation results and showed that compared with cyclical cavity, the power combiner with coaxial cavity is smaller, more easily adjustable, and is more suitable for use in RF systems of RF accelerators

Acoustic streaming in a vibrating air-filled cylindrical cavity is numerically investigated. Adiabatic and isothermal boundary conditions are considered, as well as the case in which adiabatic and isothermal boundary conditions are set respectively at the ends of the cavity and on its lateral surface. The value of the cavity radius at which the axial component of acoustic streaming velocity attains its maximum is found. The influence of the radius of the cavity and boundary conditions at its ends on the free oscillations, at the initial stage of the process, on the period average temperature, and on the acoustic streaming pattern is described. [ABSTRACT FROM AUTHOR]

To explore the approach for generating high-power frequency-tunable subterahertz (sub-THz) to THz radiation, a 220-GHz high-order axial modes (HOAMs) gyrotron is developed, and the proof-of-principle experiment is presented in this paper. Experimental results demonstrate that driven by an electron beam of high voltage and high current, HOAMs are successfully excited in a long cylindrical cavity. By tuning the operating magnetic field, a mode transition between the first four axial modes was experimentally observed with a stepwise frequency tuning range of 0.79 GHz around 219 GHz, while a 0.58-GHz frequency tuning range via beam voltage tuning by operating in the first three axial modes. During the process of frequency tuning, the output power was kept not less than 0.45 kW, while the maximum output power was 3.80 kW with an output efficiency of 6%. These experimental results of mode transition and mode competition between axial modes in high-power millimeter-wave gyrotron could be beneficial for the development of frequency-tunable gyrotron toward some up-and-coming novel THz applications. [ABSTRACT FROM AUTHOR]

Equations for thermal vibrational convection in a nonuniformly heated liquid with thermal density inversion subjected to high-frequency small-amplitude vibrations are obtained by averaging method. The problem of thermal vibrational convection in a horizontal cylinder filled with a liquid with quadratic temperature dependence of density is studied analytically on the basis of these equations for arbitrary orientations of temperature gradient, gravity and vibration axis. The heating is carried out in such a way that the point of temperature inversion of density is located at the cylinder axis. It is shown that by changing the direction of vibrations and their intensity, it is possible to control the structure and intensity of average flow. [ABSTRACT FROM AUTHOR]