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This paper presents the design method of an adaptive fuzzy controller (AFC) for a magnetorheological elastomer (MRE) vibration isolation system with time-varying sinusoidal excitations. In the first place, Kelvin model of MRE isolator without application of driving current is obtained by acceleration sweep experiments on a shake table, which establishes a foundation for the design of adaptive law. Secondly, a semi-active AFC with factor adjustment mechanism is designed based on the transmissibility curves under zero magnetic application and semi-active fuzzy control theory, which is independent of the isolation system model and adaptive to time-varying excitations in amplitudes and frequencies without adopting complicated fast Fourier transformation (FFT) analyzer. Finally, acceleration responses of the system with AFC to time-varying sinusoidal excitations are evaluated by numerical simulation and physical experiments, which indicate that the AFC could maintain satisfying control effect in the presence of time-varying sinusoidal excitations in amplitudes and frequencies, and is also more optimal than conventional fuzzy controller (FC).

The present paper analytically investigates the contact problem of a half-infinite one-dimensional hexagonal quasi-crystal medium punched by a rigid flat-ended cylindrical indenter with uniform heat flux or temperature. The contact between the two objects is assumed to be frictionless. Based on the general solution, the three-dimensional thermo-elastic coupling field variables in the half-space are explicitly obtained by the generalized potential theory method. For the case of heat flux load, the thermo-elastic field variables are expressed in terms of elementary functions and in closed-forms. In contrast, for the case of uniform temperature load, the corresponding variables are in terms of linear integrals, all the integrands are elementary functions. Furthermore, the maximum shear stress and the von Mises stress in the half-space are also obtained. Some significant physical quantities on the contact plane, such as vertical and radial displacements, normal stresses, temperature and heat flux, are presented as well. An illustrative numerical calculation is performed to show the distributions of the thermo-elastic fields in the vicinity of the contact area. The present solution could be served as the theoretical basis for scanning probe microscopy technology to explore the material properties of one-dimensional hexagonal quasi-crystals.

Current theoretical and experimental methods cannot fully reveal the mechanisms of the rapid and complex thermal shock-induced crack initiation and propagation processes in ceramic materials. Herein, a three-dimensional (3D) coupled thermo-mechanical phase-field model (PFM) is developed for thermal shock-induced fracture with the consideration of the temperature dependence of material properties. Compared with other PFMs, the present model can eliminate the unexpected damage evolution at the initially intact area of materials by introducing a temperature-dependent fracture energy threshold. Both the two-dimensional (2D) and 3D phase-field modeling results of thermal shock-induced fracture show strong agreement with the experimental results. The net-like topologies of thermal shock-induced cracks on the specimen surfaces are captured. Specifically, the crack topologies on the bottom surface (i.e., the first part submerged in water) are significantly different from those on the top surface in 3D cases. These essential findings reveal the mechanism that the tensile part of the strain energy mainly dominates the thermal shock-induced cracking in ceramics. This work was supported by the National Natural Science Foundation of China [grant numbers 11972100, 11602043, and 11727802]; the National Science Foundation Project of Chongqing [grant number cstc2019jcyj-msxm1870].

Furan-based derivatives are promising biomass fuels that may be used directly in internal combustion engines as alternative fuels or as additives to fossil fuels. In this work, the experimental studies of 2-acetylfuran (AF2) pyrolysis were carried out in a jet-stirred reactor in the temperature range of 770 – 1130 K and at the pressure of 760 Torr, using synchrotron vacuum ultraviolet photo-ionization mass spectrometry, coupled with gas chromatography. Key pyrolysis intermediates such as methane, ethylene, acetylene, ketene, vinylacetylene, cyclopentadiene, ethynylketene, 2-methylfuran, furfural, carbon monoxide and isomers such as allene/propyne, furan/vinylketene, benzene/fulvene, etc., were identified and quantified. The potential energy surfaces of AF2 unimolecular decomposition reactions were calculated at CBS-QB3 level. The temperature- and pressure-dependent rate constants of the relevant reactions were calculated by solving the master equation based on Rice-Ramsperger-Kassel-Marcus theory. A detailed pyrolysis kinetics of AF2 was developed based on the previous combustion models of 2-methylfuran and was validated against the current experimental results. Rate of production and sensitivity analysis showed that the main consumption pathways of AF2 pyrolysis under atmospheric pressure are unimolecular decomposition reactions, leading to 2-furyl + acetyl and furoyl + methyl, and hydrogen atom-addition reaction to C(5), leading to 2,3-dihydro-5-acetyl-3-furyl, accounting at 1070 K for 25.1%, 13.2% and 20.7% of AF2 consumption, respectively (the remaining 41.0% are due to minor reaction channels contributing

This paper is dedicated to investigating the problem of an infinite one-dimensional hexagonal quasi-crystal medium weakened by a penny-shaped crack and subjected to a pair of anti-symmetric and identical uniform heat fluxes. In view of the anti-symmetry with respect to the crack plane, this problem is formulated by a mixed boundary value problem of the half-space. Based on the general thermo-elastic solution, the mixed boundary value problem is solved by means of the generalized potential theory method. The thermo-elastic field variables in the entire three-dimensional space are explicitly expressed in terms of elementary functions. Some important physical quantities on the crack plane, e.g., temperature, crack slip displacement, shear stress and stress intensity factor, are also presented in closed-forms. Numerical calculations are carried out to validate the present analytical solution and to graphically show the distribution of the thermo-elastic coupling field around the crack. The present solution may be served as a benchmark for the experimental investigations by infrared-thermography technique.

This paper investigates the problem of an infinite multiferroic composite medium weakened by a penny-shaped crack, which is symmetrically subjected to four pairs of generalized loads on the upper and lower surfaces. These loads could be mechanical pressures, electric displacements, magnetic inductions and temperature increments. In view of the magneto-electric properties of the crack surfaces, four mixed boundary problems are formulated. Based on the general solution, the three-dimensional thermo-magneto-electro-elastic coupling field variables in the three-dimensional full space for various boundary cases are explicitly obtained by means of the generalized potential theory method. Some important physical quantities in fracture mechanics, such as the generalized stress intensity factors and the generalized crack surface displacements, are presented as well. Numerical calculations are performed to validate the present solutions and to show the distributions of the 3D coupled fields. The influences of the magneto-electric properties of the crack surfaces on the generalized stresses and stress intensity factors are revealed.

In the present paper, the electric polarization saturation at the front of a thermally loaded penny-shaped crack in an infinite thermo-piezo-elastic medium is studied in both analytical and numerical manners. This crack is assumed to be electrically semi-permeable, and the electric field in the crack cavity is taken into account. An approximate analytical solution to the present non-linear crack problem is derived on the basis of the electric polarization saturation model together with the fundamental solutions for two concentrated loading crack problems. Further, the refined crack surface displacement, crack surface electric potential and electric displacement outside the crack are also presented in closed-forms. The validity of the analytical solution is checked via the numerical discrete method together with an iterative approach. A good agreement is observed. The influences of some material constants on the electric yielding zone are numerically revealed. An empirical formula is developed for the extent of electric yielding zone at the crack tip. In view of the wide applications of piezoelectric ceramics in various thermal environments, the present analysis could serve as a reference for the design of various smart structures of piezoelectric media.

In the present work, a penny-shaped/half-infinite plane crack problem is investigated in the framework of thermo-elasticity of two-dimensional quasi-crystals. In view of the symmetry with respect to the crack plane, the original problem is formulated by a mixed boundary-value problem defined in a half-space. The boundary integral equations are derived by virtue of the general solution and the method of generalized potential theory. For the crack subjected to a pair of point temperature loadings, the corresponding fundamental thermo-elastic field variables are exactly and explicitly obtained in terms of elementary functions. Furthermore, the physical quantities on the crack plane, which are important in fracture mechanics, are given. Numerical calculations are carried out to discuss the validity of the present solutions and to characterize the thermo-phonon-phason coupling effect. The present analytical solutions may serve as benchmarks for future computational fracture mechanics of QCs and as a guide for the infrared thermography techniques in non-destructive detection.

This paper deals with the problem of an infinite isotropic solid weakened by a penny-shaped crack, which is subjected to a pair of uniform heat flux loadings symmetrically exerted on the upper and lower crack surfaces. Three-dimensional thermo-elastic field variables are obtained by means of potential theory method in company with the newly developed general solution. Some physical quantities on the cracked plane, such as temperature, radial displacement, crack surface displacement, normal stress at the crack front and stress intensity factor, which are important parameters in fracture mechanics, are presented in closed-forms. In the framework of ideal thermo-elasto-plasticity, the extent of the plastic zone at the crack front is determined by the Dugdale crack model, which linearizes the original non-linear problem. The refined crack surface displacement and normal stress outside the crack are also obtained via the principle of superposition. Numerical calculations are carried out to validate the present solutions and to show the distributions of the axisymmetric thermo-mechanical fields. The present solution could be served as a reference for the infrared-thermography technique.

With the application of innovative anchor concepts and advanced technologies in deepwater moorings, anchor behaviors in the seabed are becoming more complicated and significantly affected by the anchor line. Based on the coupled Eulerian–Lagrangian (CEL) method, a numerical approach incorporating anchor line effects is developed to investigate comprehensive anchor behaviors in the soil, including penetration of drag anchors, keying of suction embedded plate anchors and diving of gravity installed anchors. Compared to the method directly incorporating the anchor line into the CEL analysis, the proposed method is computationally efficient. To examine the robustness and accuracy of the proposed method, numerical probe tests and then comparative studies are carried out. It is found that the penetration (or diving) and keying behaviors of anchors can be well simulated. A parametric study is also undertaken to quantify the effects of various factors on the behavior of OMNI-Max anchors, whose mechanisms are not yet fully understood. The maximum embedment loss of OMNI-Max anchors during keying is not influenced by the initial anchor embedment depth, whereas significantly increases with increasing drag angle at the embedment point. With decreasing initial anchor embedment depth or increasing soil strength gradient, drag angle at the embedment point and diameter of the anchor line, the behavior of OMNI-Max anchors could change from diving to pullout, which is undesirable in offshore engineering practice. If the drag angle increases over a certain limit, the anchor will fail similar to a suction anchor.

The rapid increase in the demand for propylene and its derivatives requires urgently developing propylene-producing technology. To better understand the complicated reactions on W-based metathesis catalyst for propylene production and further to clarify the involved reaction mechanism, thermodynamic calculation was first performed to analyze the gas mixture under different conditions theoretically. The analyzed reaction system is close to the ideal gas under typical reaction conditions. The detailed investigation of reactions under different conditions was then carried out using WO 3 /SiO 2 and MgO catalysts in a fixed-bed tubular micro reactor. Experimental results together with calculation demonstrate that temperature plays the most important role in regulating metathesis reaction compared with other factors such as pressure, ethylene content and weight hourly space velocity (WHSV). Also, ethylene content in the feedstock affects a lot on metathesis process. With an optimized ratio of ethylene/ n -butene, cross-metathesis of 2-butene and ethylene is more likely to take place than that of 1-butene and 2-butene, and trans -2-butene has a generally better activity to react with ethylene than cis -2-butene due to the steric effect. On the other hand, isomerization is more independent on temperature compared with metathesis reaction. The consumption of 2-butene in metathesis will promote isomerization of 1-butene to 2-butene. Some extreme conditions such as higher pressures, larger ethylene contents and lower temperatures will provide opportunities for polymerization of ethylene. Based on the reaction analysis under different conditions, the reaction routes are summarized and a supposing mechanism for the formation of metallacyclobutane intermediate from trans / cis -2-butene is proposed.

This paper aims to analytically study the three-dimensional steady-state thermo-elastic field in an infinite space containing a penny-shaped crack subjected to a set of temperature loadings. The material is assumed to be isotropic and the loadings are symmetrically applied on the crack surfaces. In view of the symmetry with respect to the cracked plane, the present crack problem is formulated as a mixed boundary-value problem. The corresponding boundary integral and integro-differential equations are solved by virtue of the potential theory method in conjunction with the newly developed general solution. For the crack subjected to point or uniform temperature loadings, the thermo-elastic field variables are explicitly and exactly obtained in terms of elementary functions, in a complete manner. In both non-axisymmetric and axisymmetric cases, some important parameters in fracture mechanics, e.g., the crack surface displacement, the normal stress in the intact subregion of the crack plane and the stress intensity factor are explicitly derived as well. The validity of the present solutions is discussed analytically and by virtue of finite element simulation. The obtained analytical results can be combined with experimental investigations by the infrared-thermography technique.

This paper develops a closed-form analytical solution for the problem of an infinite transversely isotropic thermoporoelastic rock weakened by an elliptic crack lying in the transverse plane. The crack is symmetrically subjected to three pairs of uniform generalized loads, i.e., mechanical pressure, pore pressure and temperature increment, on the upper and lower crack surfaces. Based on the general solution, the three-dimensional (3D) steady-state thermoporoelastic field in the rock are explicitly derived in terms of elemental functions and elliptic integrals by the generalized potential theory method. The crack surface displacements, crack stiffness, normal stress in the cracked plane, and stress intensity factor at the crack tip are obtained as well. In the numerical calculation, the obtained analytical solution is first degenerated into the one for a circular crack for the purpose of verification, and then used to demonstrate the thermoporoelastic field around an elliptic crack and its geometric effect on the stress intensity factor at its tips. The present solution can serve as a convenient benchmark to various numerical codes for simulations of rock fracture.

The tensile behavior of single crystal superalloys CMSX-4 was investigated under different strain rates at room temperature. The objective of this study is to identify the strain rate sensitivity and understand the damage failure mechanism by checking stress-strain curves and microstructure of the deformed sample. Experimental results show that the stress-strain curves including strain hardening behavior at both strain rates are different. The size of cleavage facets and dimples in the tensile fracture surface is related to the strain rates. The shearing lines cross through the γ matrix and γ' precipitates, which is related to the movement of dislocations. Then, Schmid factor and the damage failure mechanism during tensile tests are estimated and discussed.

The present paper is devoted to determining the crack tip plasticity of a half-infinite Dugdale crack embedded in an infinite space of one-dimensional hexagonal quasicrystal. A pair of equal but opposite line loadings is assumed to be exerted on the upper and lower crack lips. By applying the Dugdale hypothesis together with the elastic results for a half-infinite crack, the extent of the plastic zone in the crack front is estimated. The normal stress outside the enlarged crack and crack surface displacements are explicitly presented, via the principle of superposition. The validity of the present solutions is discussed analytically by examining the overall equilibrium of the half-space.

A well-defined heterogeneous palladium catalyst, graphene oxide grafted with PdCl 2 , was prepared and found to be an effective catalyst for the C–C, C–N coupling of hetero aryl sulfonates with aryl boronic acids, terminal alkynes, amines, respectively, leading to the desired coupling products in moderate to excellent yields. The catalyst was characterized by XRD, IR, SEM, TEM, XPS and ICP. It is worthy noting that this catalyst offers a number of advantages such as high stability and negligible metal leaching. It also retains good activity for at least five successive runs without any additional activation treatment, showing a better performance than the well-known commercial Pd/C catalysts. This approach would be very useful from a practical viewpoint.

Objectives To evaluate the expression of TAZ and its role in tumor invasion and metastasis in human glioma. Methods The expression of TAZ protein was measured in 48 samples of surgically resected human glioma and 13 samples of normal brain tissues using immunohistochemistry. TAZ was knocked down by a retrovirus-mediated TAZ shRNA in a glioma cell line, SNB19. Transwell cell migration and invasion assays were used to determine migration and invasion of SNB19 cells. Results The positive expression rate of TAZ protein in glioma tissues was significantly higher than that in normal brain tissues (79.2% vs. 15.4%, P 0.001). Furthermore, clinical analysis suggested that the positive expression rate of TAZ protein in poorly differentiated tumor tissues was significantly higher as compared with that in well differentiated tissues (96.0% vs. 60.9%, P 0.01). TAZ was significantly knocked down by TAZ shRNA ( P 0.001), and TAZ knockdown significantly reduced cell migration and invasion ( P 0.01, respectively) in SNB19 cells. Conclusions TAZ protein overexpression is observed in human glioma and its elevated expression is significantly correlated with poor differentiation. TAZ knockdown prominently reduces cell migration and invasion in SNB19 cells, suggesting that TAZ may play a key role in the initiation and progression of human glioma.

Ordered Ni/Fe shell/core structured nanocable arrays were successfully fabricated by a two-step electrodeposition process. Firstly, nickel (Ni) nanotubes were prepared by electrodeposition in nanoporous of anodic aluminum oxide (AAO) template. Then the AAO/Ni nanotube composite membrane was used as a secondary template to deposit Ferrum (Fe) nanowires into Ni nanotubes. The morphology and microstructure of the nanocables was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The chemical composition of the nanocables was confirmed by X-ray diffraction (XRD). Magnetization measurements revealed that Ni/Fe nanocable arrays have a lower remanence ratio than Ni nanotube and Fe nanowire arrays respectively.

In this paper, a set of 3D general solutions to static problems of 1D hexagonal piezoelectric quasicrystals is obtained by introducing two displacement functions and utilizing the rigorous operator theory. All the physical quantities are expressed by five quasi-harmonic functions. Based on the general solutions and with the help of the superposition principle, fundamental solutions for infinite/half-infinite spaces are presented by trial-and-error technique. The general solutions can be conveniently used to solve the boundary value problems regarding dislocations, cracks and inhomogeneities. The fundamental solutions are of primary significance to development of numerical codes such as boundary element method.

This Letter is concerned with thermo-elastic fundamental solutions of an infinite space, which is composed of two half-infinite bodies of different one-dimensional hexagonal quasi-crystals. A point thermal source is embedded in a half-space. The interface can be either perfectly bonded or smoothly contacted. On the basis of the newly developed general solution, the temperature-induced elastic field in full space is explicitly presented in terms of elementary functions. The interactions among the temperature, phonon and phason fields are revealed. The present work can play an important role in constructing farther analytical solutions for crack, inclusion and dislocation problems.

This Letter presents three-dimensional general solutions for static problems in thermo-elasticity of one-dimensional hexagonal quasi-crystals. Two displacement potentials are introduced to simplify the equilibrium equations in terms of displacement and temperature. Rigorous operator theory and generalized Almansiʼs theorem are applied to derive the general solutions in terms of five quasi-harmonic functions. To show the significance of the general solutions, a semi-infinite space and an infinite space, both of which are subjected to a heat source, are considered. In these two cases, closed form fundamental phonon–phason-elastic fields are expressed by elementary functions, which play an important role in numerical simulations.

Highly ordered circular patterns of copper nanowire arrays were successfully deposited into designed anodic aluminum oxide templates. High-resolution transmission electron microscopy was used to study the microstructure of these Cu nanostructures. The results showed that the growth orientation of the copper nanowires was along [220] direction, and the broken orientation were along [202] and [022] directions, respectively. Regular cones were formed at the broken end of nanowires. Bent nanowires were also observed, this means that the copper nanowires have good mechanical properties when applied external force. Chemical analysis has been performed on Cu nanowires using electron energy-loss spectroscopy.

An effective mean-field theory based on cumulant expansion (EMFC) is applied to the spin-S Ising model on general d-dimensional hypercubic lattice. It gives straightforwardly the analytical expressions Tc(ν)(S,d) that approach the Curie temperature order by order. For general d, the results up to fifth order are given. Numerical results up to seventh order for d=2,3,4 are presented.