Anisotropic Way Research Articles

Photochemically Patterning Graphene in a Highly Efficient, Anisotropic, and Clean Way

Photochemically Patterning Graphene in a Highly Efficient, Anisotropic, and Clean Way

Nodal Sets of Eigenfunctions of Sub-Laplacians

Abstract Nodal sets of eigenfunctions of elliptic operators on compact manifolds have been studied extensively over the past decades. In this note, we initiate the study of nodal sets of eigenfunctions of hypoelliptic operators on compact manifolds, focusing on sub-Laplacians. A standard example is the sum of squares of bracket-generating vector fields on compact quotients of the Heisenberg group. Our results show that nodal sets behave in an anisotropic way, which can be analyzed with standard tools from sub-Riemannian geometry such as sub-Riemannian dilations, nilpotent approximation, and desingularization at singular points. Furthermore, we provide a simple example demonstrating that for sub-Laplacians, the Hausdorff measure of nodal sets of eigenfunctions cannot be bounded above by $\sqrt \lambda $, which is the bound conjectured by Yau for Laplace–Beltrami operators on smooth manifolds.

Three-dimensional nanoscale reduced-angle ptycho-tomographic imaging with deep learning (RAPID)

X-ray ptychographic tomography is a nondestructive method for three dimensional (3D) imaging with nanometer-sized resolvable features. The size of the volume that can be imaged is almost arbitrary, limited only by the penetration depth and the available scanning time. Here we present a method that rapidly accelerates the imaging operation over a given volume through acquiring a limited set of data via large angular reduction and compensating for the resulting ill-posedness through deeply learned priors. The proposed 3D reconstruction method “RAPID” relies initially on a subset of the object measured with the nominal number of required illumination angles and treats the reconstructions from the conventional two-step approach as ground truth. It is then trained to reproduce equal fidelity from much fewer angles. After training, it performs with similar fidelity on the hitherto unexamined portions of the object, previously not shown during training, with a limited set of acquisitions. In our experimental demonstration, the nominal number of angles was 349 and the reduced number of angles was 21, resulting in a times 140 aggregate speedup over a volume of 4.48times 93.18times 3.92, upmu text {m}^3 and with (14,text {nm})^3 feature size, i.e. sim 10^8 voxels. RAPID’s key distinguishing feature over earlier attempts is the incorporation of atrous spatial pyramid pooling modules into the deep neural network framework in an anisotropic way. We found that adjusting the atrous rate improves reconstruction fidelity because it expands the convolutional kernels’ range to match the physics of multi-slice ptychography without significantly increasing the number of parameters.

Numerical simulation of mechanical tests on a living skin using anisotropic hyperelastic law

The skin is a living tissue that behaves in a hyperelastic and anisotropic way. A constitutive law called HGO-Yeoh is proposed to model the skin by improving the classical HGO constitutive law. This model is implemented in a finite element code FER “Finite Element Research” to benefit from its tools, including the bipotential contact method, a very efficient function coupling contact and friction. Identifying the skin-related material parameters is done through an optimisation procedure using analytic and experimental data. A tensile test is simulated using the codes FER and ANSYS. Then, the results are compared with the experimental data. Finally, a simulation of an indentation test using a bipotential contact law is done.

Phonon thermal Hall effect in a metallic spin ice

It has become common knowledge that phonons can generate thermal Hall effect in a wide variety of materials, although the underlying mechanism is still controversial. We study longitudinal κxx and transverse κxy thermal conductivity in Pr2Ir2O7, which is a metallic analog of spin ice. Despite the presence of mobile charge carriers, we find that both κxx and κxy are dominated by phonons. A T/H scaling of κxx unambiguously reveals that longitudinal heat current is substantially impeded by resonant scattering of phonons on paramagnetic spins. Upon cooling, the resonant scattering is strongly affected by a development of spin ice correlation and κxx deviates from the scaling in an anisotropic way with respect to field directions. Strikingly, a set of the κxx and κxy data clearly shows that κxy correlates with κxx in its response to magnetic field including a success of the T/H scaling and its failure at low temperature. This remarkable correlation provides solid evidence that an indispensable role is played by spin-phonon scattering not only for hindering the longitudinal heat conduction, but also for generating the transverse response.

The use of the empirical crack orientation tensor to characterize the damage anisotropy

In practice, a dominant failure mode of brittle materials, such as fiber-reinforced thermosets is the initiation and propagation of cracks under cyclic loading. In general, the damage in composites with irregular microstructure do not occur in regular patterns. There are several state-of-the-art continuum mechanical models which take the anisotropic damage for predicting the material behavior into account. Since damage generally occurs in an anisotropic way, methods that experimentally characterize the damage anisotropy are needed.Micro-Computed Tomography systems (μCT) acquire volumetric images in a non-destructive way. By combining μCT scanning and mechanical in-situ testing, detailed microstructure data of specimens under load are generated. Based on image processing methods, the damage propagation from crack initiation to fracture is analyzed. In practice, cyclic load is a common load case for many components. Consequently, fatigue and cycle load tests are essential for a comprehensive material characterization.In this contribution interrupted in-situ μCT tests with cyclic tensile load are performed on Sheet Molding Compounds (SMC), a discontinuous glass fiber-reinforced thermset composite. Image processing methods are introduced for the experimental determination of the anisotropic damage characteristic based on volumetric images. The methods enable analyzing the spatial crack orientation distribution. In order to quantify the damage anisotropy, empirical formulations of the crack density distribution and second-order crack orientation tensor are applied. The presented work in this contribution extends the results of preliminary experimental damage investigations. In addition to previous studies, the damage anisotropy is quantified and analyzed.

Anisotropic tensor renormalization group

We propose a new tensor renormalization group algorithm, Anisotropic Tensor Renormalization Group (ATRG), for lattice models in arbitrary dimensions. The proposed method shares the same versatility with the Higher-Order Tensor Renormalization Group (HOTRG) algorithm, i.e., it preserves the lattice topology after the renormalization. In comparison with HOTRG, both of the computation cost and the memory footprint of our method are drastically reduced, especially in higher dimensions, by renormalizing tensors in an anisotropic way after the singular value decomposition. We demonstrate the ability of ATRG for the square lattice and the simple cubic lattice Ising models. Although the accuracy of the present method degrades when compared with HOTRG of the same bond dimension, the accuracy with fixed computation time is improved greatly due to the drastic reduction of the computation cost.

Adaptive anisotropic response surface method based on univariate dimension-reduction model and its high-order revision

PurposeBased on univariate dimension-reduction model, this study aims to propose an adaptive anisotropic response surface method (ARSM) and its high-order revision (HARSM) to balance the accuracy and efficiency for response surface method (RSM).Design/methodology/approachFirst, judgment criteria for the constitution of a univariate function are derived mathematically, together with the practical implementation. Second, by combining separate polynomial approximation of each component function of univariate dimension-reduction model with its constitution analysis, the anisotropic ARSM is proposed. Third, the high-order revision for component functions is introduced to improve the accuracy of ARSM, namely, HARSM, in which the revision is also anisotropic. Finally, several examples are investigated to verify the accuracy, efficiency and convergence of the proposed methods, and the influence of parameters on the proposed methods is also performed.FindingsThe criteria for constitution analysis are appropriate and practical. Obtaining the undetermined coefficients for every component functions is easier than the existing RSMs. The existence of special component functions is useful to improve the efficiency of the ARSM. HARSM is helpful for improving accuracy significantly and it is more robust than ARSM and the existing quadratic polynomial RSMs and linear RSM. ARSM and HARSM can achieve appropriate balance between precision and efficiency.Originality/valueThe constitution of univariate function can be determined adaptively and the nonlinearity of different variables in the response surface can be treated in an anisotropic way.

The Transformation of LIGHT into MATTER

Within the scope of this article, LIGHT has been considered as any arbitrary Electromagnetic Radiation within a very wide frequency range, because during the transformation from Visible Light into the Gravitational Electromagnetic Confinement, the frequency changes in a very wide range. This frequency transformation is possible because of the combined Lorentz / Doppler-Effect transformation during the collapse (contraction) of the radiation when the Gravitational Electromagnetic Confinement has been formed (Implosion of Visible Light). Within the scope of this article MATTER is considered to be any kind of 3-dimensional confined (Electromagnetic) energy. The inner structure of a photon is based on a 3-dimensional anisotropic equilibrium within the electromagnetic pulses in which an equilibrium does exist for the Electric and the Magnetic Fields separately generated by the pulses. A photon cannot be considered as a particle. Because particles are 3-dimensional confinements. Photons are anisotropic (in 1st and 2nd dimension a particle and in the 3rd dimension a wave) confinements of electromagnetic pulses, generated during the energy transitions within the atoms. Photons are 2-dimensional confinements of electromagnetic energy and demonstrate the property of inertia (electromagnetic mass) in the 2 directions of confinement. In the 3rd direction, the direction of propagation, photons can only be considered as an electromagnetic wave and for that reason do not demonstrate the property of inertia. Electromagnetic waves cannot be accelerated or decelerated because the speed of light is a universal constant. For that reason, photons interact with a gravitational field in an anisotropic way. Due to a gravitational field, photons can be accelerated or decelerated in the directions perpendicular to the direction of propagation and follow a curved path. But a gravitational field in the direction of propagation will have no impact on the speed of the photons, which will remain the unchanged universal constant, the speed of light. Photonics is the physical science of light based on the concept of “photons” introduced by Albert Einstein in the early 20th century. Einstein introduced this concept in the “particle-wave duality” discussion with Niels Bohr to demonstrate that even light has particle properties (mass and momentum) and wave properties (frequency). That concept became a metaphor and from that time on a beam of light has been generally considered as a beam of particles (photons). Which is a wrong understanding. Light particles do not exist. Photons are nothing else but electromagnetic complex wave configurations and light particles are not like “particles” but separated electromagnetic wave packages, 2-dimensionally confined in the directions perpendicular to the direction of propagation and in a perfect equilibrium with the radiation pressure and the inertia of electromagnetic energy in the forward direction, controlling the speed of light. This new theory will explain how electromagnetic wave packages demonstrate inertia, mass and momentum and which forces keep the wave packages together in a way that they can be measured like particles with their own specific mass and momentum. All we know about light, and in generally about any electromagnetic field configuration, has been based only on two fundamental theories. James Clerk Maxwell introduced in 1865 the “Theory of Electrodynamics” with the publication: “A Dynamical Theory of the Electromagnetic Field” and Albert Einstein introduced in 1905 the “Theory of Special Relativity” with the publication: “On the Electrodynamics of Moving Bodies” and in 1913 the “Theory of General Relativity” with the publication ”Outline of a Generalized Theory of Relativity and of a Theory of Gravitation”. However, both theories are not capable to explain the property of electromagnetic mass and in specific the anisotropy of the phenomenon of electromagnetic mass presented e.g. in a LASER beam. To understand what electromagnetic inertia and the corresponding electromagnetic mass is and how the anisotropy of electromagnetic mass can be explained and how it has to be defined, a New Theory about Light has to be developed. A part of this “New Theory about Light”, based on Newton’s well- known Equation in 3 dimensions will be published in this article in an extension into 4 dimensions. Newton’s 4-dimensional law in the 3 spatial dimensions results in an improved version of the classical Maxwell equations and Newton’s law in the 4th dimension (time) results in the quantum mechanical Schrödinger wave equation (at non-relativistic velocities) and the relativistic Dirac equation.

Transformation of LIGHT into MATTER

Within the scope of this article, LIGHT has been considered as any arbitrary Electromagnetic Radiation within a very wide frequency range, because during the transformation from Visible Light into the Gravitational Electromagnetic Confinement, the frequency changes in a very wide range. This frequency transformation is possible because of the combined Lorentz / Doppler-Effect transformation during the collapse (contraction) of the radiation when the Gravitational Electromagnetic Confinement has been formed (Implosion of Visible Light). Within the scope of this article MATTER is considered to be any kind of 3-dimensional confined (Electromagnetic) energy. The inner structure of a photon is based on a 3-dimensional anisotropic equilibrium within the electromagnetic pulses in which an equilibrium does exist for the Electric and the Magnetic Fields separately generated by the pulses. A photon cannot be considered as a particle. Because particles are 3-dimensional confinements. Photons are anisotropic (in 1st and 2nd dimension a particle and in the 3rd dimension a wave) confinements of electromagnetic pulses, generated during the energy transitions within the atoms. Photons are 2-dimensional confinements of electromagnetic energy and demonstrate the property of inertia (electromagnetic mass) in the 2 directions of confinement. In the 3rd direction, the direction of propagation, photons can only be considered as an electromagnetic wave and for that reason do not demonstrate the property of inertia. Electromagnetic waves cannot be accelerated or decelerated because the speed of light is a universal constant. For that reason, photons interact with a gravitational field in an anisotropic way. Due to a gravitational field, photons can be accelerated or decelerated in the directions perpendicular to the direction of propagation and follow a curved path. But a gravitational field in the direction of propagation will have no impact on the speed of the photons, which will remain the unchanged universal constant, the speed of light. Photonics is the physical science of light based on the concept of “photons” introduced by Albert Einstein in the early 20th century. Einstein introduced this concept in the “particle-wave duality” discussion with Niels Bohr to demonstrate that even light has particle properties (mass and momentum) and wave properties (frequency). That concept became a metaphor and from that time on a beam of light has been generally considered as a beam of particles (photons). Which is a wrong understanding. Light particles do not exist. Photons are nothing else but electromagnetic complex wave configurations and light particles are not like “particles” but separated electromagnetic wave packages, 2-dimensionally confined in the directions perpendicular to the direction of propagation and in a perfect equilibrium with the radiation pressure and the inertia of electromagnetic energy in the forward direction, controlling the speed of light. This new theory will explain how electromagnetic wave packages demonstrate inertia, mass and momentum and which forces keep the wave packages together in a way that they can be measured like particles with their own specific mass and momentum. All we know about light, and in generally about any electromagnetic field configuration, has been based only on two fundamental theories. James Clerk Maxwell introduced in 1865 the “Theory of Electrodynamics” with the publication: “A Dynamical Theory of the Electromagnetic Field” and Albert Einstein introduced in 1905 the “Theory of Special Relativity” with the publication: “On the Electrodynamics of Moving Bodies” and in 1913 the “Theory of General Relativity” with the publication ”Outline of a Generalized Theory of Relativity and of a Theory of Gravitation”. However, both theories are not capable to explain the property of electromagnetic mass and in specific the anisotropy of the phenomenon of electromagnetic mass presented e.g. in a LASER beam. To understand what electromagnetic inertia and the corresponding electromagnetic mass is and how the anisotropy of electromagnetic mass can be explained and how it has to be defined, a New Theory about Light has to be developed. A part of this “New Theory about Light”, based on Newton’s well- known Equation in 3 dimensions will be published in this article in an extension into 4 dimensions. Newton’s 4-dimensional law in the 3 spatial dimensions results in an improved version of the classical Maxwell equations and Newton’s law in the 4th dimension (time) results in the quantum mechanical Schrödinger wave equation (at non-relativistic velocities) and the relativistic Dirac equation.

Stability and Interaction Processes within Separate Magnetic and Electric Fields and Equilibrium within Electromagnetic Confinements

The inner structure of a photon is based on a 3-dimensional anisotropic equilibrium within the electromagnetic pulses in which an equilibrium does exist for the Electric and the Magnetic Fields separately generated by the pulses. A photon cannot be considered as a particle. Because particles are 3-dimensional confinements. Photons are anisotropic (in 1st and 2nd dimension a particle and in the 3rd dimension a wave) confinements of electromagnetic pulses, generated during the energy transitions within the atoms. Photons are 2-dimensional confinements of electromagnetic energy and demonstrate the property of inertia (electromagnetic mass) in the 2 directions of confinement. In the 3rd direction, the direction of propagation, photons can only be considered as an electromagnetic wave and for that reason do not demonstrate the property of inertia. Electromagnetic waves cannot be accelerated or decelerated because the speed of light is a universal constant. For that reason, photons interact with a gravitational field in an anisotropic way. Due to a gravitational field, photons can be accelerated or decelerated in the directions perpendicular to the direction of propagation and follow a curved path. But a gravitational field in the direction of propagation will have no impact on the speed of the photons, which will remain the unchanged universal constant, the speed of light. Photonics is the physical science of light based on the concept of “photons” introduced by Albert Einstein in the early 20th century. Einstein introduced this concept in the “particle-wave duality” discussion with Niels Bohr to demonstrate that even light has particle properties (mass and momentum) and wave properties (frequency). That concept became a metaphor and from that time on a beam of light has been generally considered as a beam of particles (photons). Which is a wrong understanding. Light particles do not exist. Photons are nothing else but electromagnetic complex wave configurations and light particles are not like “particles” but separated electromagnetic wave packages, 2-dimensionally confined in the directions perpendicular to the direction of propagation and in a perfect equilibrium with the radiation pressure and the inertia of electromagnetic energy in the forward direction, controlling the speed of light. This new theory will explain how electromagnetic wave packages demonstrate inertia, mass and momentum and which forces keep the wave packages together in a way that they can be measured like particles with their own specific mass and momentum. All we know about light, and in generally about any electromagnetic field configuration, has been based only on two fundamental theories. James Clerk Maxwell introduced in 1865 the “Theory of Electrodynamics” with the publication: “A Dynamical Theory of the Electromagnetic Field” and Albert Einstein introduced in 1905 the “Theory of Special Relativity” with the publication: “On the Electrodynamics of Moving Bodies” and in 1913 the “Theory of General Relativity” with the publication ”Outline of a Generalized Theory of Relativity and of a Theory of Gravitation”. However, both theories are not capable to explain the property of electromagnetic mass and in specific the anisotropy of the phenomenon of electromagnetic mass presented e.g. in a LASER beam. To understand what electromagnetic inertia and the corresponding electromagnetic mass is and how the anisotropy of electromagnetic mass can be explained and how it has to be defined, a New Theory about Light has to be developed. A part of this “New Theory about Light”, based on Newton’s well- known Equation in 3 dimensions will be published in this article in an extension into 4 dimensions. Newton’s 4-dimensional law in the 3 spatial dimensions results in an improved version of the classical Maxwell equations and Newton’s law in the 4th dimension (time) results in the quantum mechanical Schrödinger wave equation (at non-relativistic velocities) and the relativistic Dirac equation.

Stability and Interaction Processes within Separate Magnetic and Electric Fields and Equilibrium within Electromagnetic Confinements

The inner structure of a photon is based on a 3-dimensional anisotropic equilibrium within the electromagnetic pulses in which an equilibrium does exist for the Electric and the Magnetic Fields separately generated by the pulses. A photon cannot be considered as a particle. Because particles are 3-dimensional confinements. Photons are anisotropic (in 1st and 2nd dimension a particle and in the 3rd dimension a wave) confinements of electromagnetic pulses, generated during the energy transitions within the atoms. Photons are 2-dimensional confinements of electromagnetic energy and demonstrate the property of inertia (electromagnetic mass) in the 2 directions of confinement. In the 3rd direction, the direction of propagation, photons can only be considered as an electromagnetic wave and for that reason do not demonstrate the property of inertia. Electromagnetic waves cannot be accelerated or decelerated because the speed of light is a universal constant. For that reason, photons interact with a gravitational field in an anisotropic way. Due to a gravitational field, photons can be accelerated or decelerated in the directions perpendicular to the direction of propagation and follow a curved path. But a gravitational field in the direction of propagation will have no impact on the speed of the photons, which will remain the unchanged universal constant, the speed of light. Photonics is the physical science of light based on the concept of “photons” introduced by Albert Einstein in the early 20th century. Einstein introduced this concept in the “particle-wave duality” discussion with Niels Bohr to demonstrate that even light has particle properties (mass and momentum) and wave properties (frequency). That concept became a metaphor and from that time on a beam of light has been generally considered as a beam of particles (photons). Which is a wrong understanding. Light particles do not exist. Photons are nothing else but electromagnetic complex wave configurations and light particles are not like “particles” but separated electromagnetic wave packages, 2-dimensionally confined in the directions perpendicular to the direction of propagation and in a perfect equilibrium with the radiation pressure and the inertia of electromagnetic energy in the forward direction, controlling the speed of light. This new theory will explain how electromagnetic wave packages demonstrate inertia, mass and momentum and which forces keep the wave packages together in a way that they can be measured like particles with their own specific mass and momentum. All we know about light, and in generally about any electromagnetic field configuration, has been based only on two fundamental theories. James Clerk Maxwell introduced in 1865 the “Theory of Electrodynamics” with the publication: “A Dynamical Theory of the Electromagnetic Field” and Albert Einstein introduced in 1905 the “Theory of Special Relativity” with the publication: “On the Electrodynamics of Moving Bodies” and in 1913 the “Theory of General Relativity” with the publication ”Outline of a Generalized Theory of Relativity and of a Theory of Gravitation”. However, both theories are not capable to explain the property of electromagnetic mass and in specific the anisotropy of the phenomenon of electromagnetic mass presented e.g. in a LASER beam. To understand what electromagnetic inertia and the corresponding electromagnetic mass is and how the anisotropy of electromagnetic mass can be explained and how it has to be defined, a New Theory about Light has to be developed. A part of this “New Theory about Light”, based on Newton’s well- known Equation in 3 dimensions will be published in this article in an extension into 4 dimensions. Newton’s 4-dimensional law in the 3 spatial dimensions results in an improved version of the classical Maxwell equations and Newton’s law in the 4th dimension (time) results in the quantum mechanical Schrödinger wave equation (at non-relativistic velocities) and the relativistic Dirac equation.

Deformation and flow of amorphous solids: Insights from elastoplastic models

The deformation and flow of disordered solids, such as metallic glasses and concentrated emulsions, involves swift localized rearrangements of particles that induce a long-range deformation field. To describe these heterogeneous processes, elastoplastic models handle the material as a collection of 'mesoscopic' blocks alternating between an elastic behavior and plastic relaxation, when they are too loaded. Plastic relaxation events redistribute stresses in the system in a very anisotropic way. We review not only the physical insight provided by these models into practical issues such as strain localization, creep and steady-state rheology, but also the fundamental questions that they address with respect to criticality at the yielding point and the statistics of avalanches of plastic events. Furthermore, we discuss connections with concurrent mean-field approaches and with related problems such as the plasticity of crystals and the depinning of an elastic line.

Mesh Optimization for Discontinuous Galerkin Methods Using a Continuous Mesh Model

A method for anisotropic mesh adaptation and optimization for high-order discontinuous Galerkin schemes is presented. Given the total number of degrees of freedom, a metric-based method is proposed, which aims to globally optimize the mesh with respect to the norm of the error. This is done by minimizing a suitable error model associated with the approximation space. Advantages of using a metric-based method in this context are several. First, it facilitates changing and manipulating the mesh in a general anisotropic way. Second, defining a suitable continuous interpolation operator allows the use of an analytic optimization framework that operates on the metric field, rather than the discrete mesh. The formulation of the method is presented as well as numerical experiments in the context of convection–diffusion systems.

A command layer for anisotropic plasmonic photo-thermal effects in liquid crystal

ABSTRACTPhoto-anisotropic properties of a particular command layer for Liquid Crystals (LCs), based on azo-benzene material, are exploited to control the photo-thermal response of a single layer of homogeneously and uniformly distributed Au nanoparticles, immobilised on a glass substrate. Experiments demonstrate that the intrinsic anisotropy of materials can influence the photo-thermal response of plasmonic systems. Indeed, the resonant absorption of radiation by plasmonic subunits is followed by a noticeable increase of their temperature. However, the thermal response observed in presence of a homogeneous and random array of AuNPs directly exposed to air or embedded in ice is typically isotropic; on the contrary, a homogenous, yet thin, coating made of a particular command layer for LCs, deposited on a large-area carpet of AuNPs, influences their thermal response in an anisotropic way. In particular, the temperature increase, induced by pumping with a laser source of resonant wavelength with the plasmonic AuNPs, strongly depends on the alignment direction of the command layer. This effect makes the command layer of particular interest for its capability to drive intriguing optically induced ‘thermal-reorientational’ effects in a liquid crystal film.

Superposition rheology and anisotropy in rheological properties of sheared colloidal gels

Gelling colloidal suspensions represent an important class of soft materials. Their mechanical response is characterized by a solid-to-liquid transition at a given shear stress level. Moreover, they often exhibit a complex time-dependent rheological behavior known as thixotropy. The viscosity changes find their origin in the microstructure, which depends on flow history. Yet, the structural response of colloidal gels to flow differs fundamentally from most complex fluids, where flow induces orientation. Upon yielding, low to intermediate volume fraction gels break down in a spatially anisotropic way. Bonds in the velocity-velocity gradient plane are broken, whereas microstructural features in other planes are less affected. The subsequent flow-induced microstructural anisotropy is characterized by typical butterfly scattering patterns. However, as yet there was no evidence for the pertinence of this anisotropy for the rheological properties of these systems. In the present work, orthogonal superposition rheometry was first used to evaluate how the flow-induced microstructure affects the viscoelastic properties. It was shown to retain significant elasticity in the velocity-vorticity plane, even when the structure liquefied. Further, the shear-induced mechanical anisotropy was measured using two-dimensional small amplitude oscillatory shear, exploiting the fact that for suitable thixotropic samples the recovery after arresting the flow is relatively slow. It was hence possible to measure the anisotropy of the moduli upon cessation of flow. The mechanical anisotropy was shown to be spectacular, with the storage moduli in perpendicular directions differing by as much as 2 orders of magnitude.

A method to improve the use of 6-dof robots as machine tools

Since the introduction of robots in the automotive industry for pick and place tasks, new technologies have been developed in order to adapt robots to different manufacturing processes. Among them, the use of robots as machine tools is a technological trend that demands further investigation. Industrial robots with 6 DOF (degrees of freedom) in a serial kinematic chain have larger workspace and more flexibility, when compared with CNC machines. However, robots’ stiffness is lower than that of CNC machines. Consequently, vibration problems are expected, which can have a direct impact on the quality of the machined workpieces. This work proposes a method to evaluate and customize the use of a COTS (commercial off-the-shelf) robot equipped with a spindle for machining processes. It aims at improving the machining processes based on the measurement of the workpiece waviness and explores the fact that the accuracy and rigidity of industrial robots with serial kinematic chains behave in an anisotropic way, according to the robot pose and the cutting force direction. The method is composed of a set of five experiments and is applied to the evaluation of a robot machining aluminium workpieces. The results allow the identification of the relevant factors that affect the surface quality of the workpiece and recommend the best robot configuration for meeting the waviness requirements of the workpiece. Even though the application case describes the machining of aluminium workpiece, the proposed method is generic enough to be applied to different workpiece geometries and materials.

Cooling an Optically Trapped Ultracold Fermi Gas by Periodical Driving.

We present a cooling method for a cold Fermi gas by parametrically driving atomic motions in a crossed-beam optical dipole trap (ODT). Our method employs the anharmonicity of the ODT, in which the hotter atoms at the edge of the trap feel the anharmonic components of the trapping potential, while the colder atoms in the center of the trap feel the harmonic one. By modulating the trap depth with frequencies that are resonant with the anharmonic components, we selectively excite the hotter atoms out of the trap while keeping the colder atoms in the trap, generating parametric cooling. This experimental protocol starts with a magneto-optical trap (MOT) that is loaded by a Zeeman slower. The precooled atoms in the MOT are then transferred to an ODT, and a bias magnetic field is applied to create an interacting Fermi gas. We then lower the trapping potential to prepare a cold Fermi gas near the degenerate temperature. After that, we sweep the magnetic field to the noninteracting regime of the Fermi gas, in which the parametric cooling can be manifested by modulating the intensity of the optical trapping beams. We find that the parametric cooling effect strongly depends on the modulation frequencies and amplitudes. With the optimized frequency and amplitude, we measure the dependence of the cloud energy on the modulation time. We observe that the cloud energy is changed in an anisotropic way, where the energy of the axial direction is significantly reduced by parametric driving. The cooling effect is limited to the axial direction because the dominant anharmonicity of the crossed-beam ODT is along the axial direction. Finally, we propose to extend this protocol for the trapping potentials of large anharmonicity in all directions, which provides a promising scheme for cooling quantum gases using external driving.

Durability of the Li1+xTi2–xAlx(PO4)3 Solid Electrolyte in Lithium–Sulfur Batteries

Adoption of cells with a solid-state electrolyte is a promising solution for eliminating the polysulfide shuttle problem in Li–S batteries. Among the various known lithium-ion conducting solid electrolytes, the sodium superionic conductor (NASICON)-type Li1+xTi2–xAlx(PO4)3 offers the advantage of good stability under ambient conditions and in contact with air. Accordingly, we present here a comprehensive assessment of the durability of Li1+xTi2–xAlx(PO4)3 in contact with polysulfide solution and in Li–S cells. Because of its high reduction potential (2.5 V vs Li/Li+), Li1+xTi2–xAlx(PO4)3 gets lithiated in contact with lithium polysulfide solution and Li2CO3 is formed on the particle surface, blocking the interfacial lithium-ion transport between the liquid and solid-state electrolytes. After the lithium insertion into the NASICON framework, the crystal expands in an anisotropic way, weakening the crystal bonds, causing fissures and resultant cracks in the ceramic, corroding the grain boundaries by polysul...

Integration of excess material into a semi-finished product to form complex composite parts

With a view to minimizing production costs of carbon fiber-reinforced plastics (CFRP), a contoured, variable-axial reinforcing fabric, so-called “CoCo – contoured composites,” has been developed for complex, primary structural components,. Thereby, scrap in the production of lightweight high-performance components out of CFRP is reduced. Furthermore, components can be designed in an anisotropic way, thus lighter and adapted to the fiber properties. Moreover, production speed will be by far higher than that of conventional variable-axial textiles, like tailored fiber placement and fiber patch preforming. Furthermore, these textiles will show higher drapability than conventional production techniques, like tape-laying or standard textiles. The main focus of this paper is the investigation of draping mechanisms of variable-axial, tailored textiles and their feasibility. To reach high drapability of these semi-finished products, a new draping strategy has been developed. Reinforcing rovings are laid in meander way onto a carrier material holding excess material available for draping. For the textile “CoCo” new draping characteristics have been investigated, showing a kind of stretch forming of the carrier material and a straightening of the reinforcing fibers previously laid in meander. Due to this draping mechanism the material has the ability to form over very complex shapes without showing draping defects, like loops, gaps, or waviness. The calculation of the excess material and the draping mechanism are investigated on a complex form and proven by draping trials.