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An exact solution of coarse-grained polymer models with fluctuating internal friction and hydrodynamic interactions has not been proposed so far due to a one-to-all coupling between the connector vector velocities that precludes the formulation of the governing stochastic differential equations. A methodology for the removal of this coupling is presented, and the governing stochastic differential equations, obtained by attaching a kinetic interpretation to the Fokker-Planck equation for the system, are integrated numerically using Brownian dynamics simulations. The proposed computational route eliminates the calculation of the divergence of the diffusion tensor which appears in models with internal friction, and is about an order of magnitude faster than the recursion-based algorithm for the decoupling of connector-vector velocities previously developed [J. Rheol., 65, 903 (2021)] for the solution of freely draining models with internal friction. The effects of the interplay of various combinations of finite extensibility, internal friction and hydrodynamic interactions on the steady-shear-viscosity is examined. While finite extensibility leads solely to shear-thinning, both internal friction and hydrodynamic interactions result in shear-thinning followed by shear-thickening. The shear-thickening induced by internal friction effects are more pronounced than that due to hydrodynamic interactions., Comment: Comments: To appear in the Journal of Rheology, 20 pages, 9 figures, includes Supplemental Material

The distribution of lubricating oil in the bearing cavity is of great significance to bearing lubrication and cooling. A new idea is provided to further study the ball bearings lubrication, to achieve effective lubrication of bearings. The flow field of oil injection lubrication ball bearings is studied by the moving particle semi-implicit (MPS) method. The accuracy of the numerical calculation method is verified by experiments. The oil distribution of the bearing lubrication flow field and churning torque of the ball and cage at different speeds are analyzed. The research results show the maximum oil content in the bearing cavity is distributed in the range of about 90° to 120°. As the increase of rotating speed, the number of particles in the bearing cavity decreases. The churning torque decreases with the increase of rotating speed and increases with the increase of the oil viscosity. This study provides a new numerical calculation method for the lubrication flow field of ball bearings.

A necklace can be considered as a cyclic list of n red and n blue beads in an arbitrary order. In the necklace folding problem the goal is to find a large crossing-free matching of pairs of beads of different colors in such a way that there exists a “folding” of the necklace, that is a partition into two contiguous arcs, which splits the beads of any matching edge into different arcs. We give counterexamples for some conjectures about the necklace folding problem, also known as the separated matching problem. The main conjecture (given independently by three sets of authors) states that [Formula presented], where μ is the ratio of the maximum number of matched beads to the total number of beads. We refute this conjecture by giving a construction which proves that μ≤2−2

One of the grand challenges of utilizing machine learning for the discovery of innovative new polymers lies in the difficulty of accurately representing the complex structures of polymeric materials. Although a wide array of hand-designed polymer representations have been explored, there has yet to be an ideal solution for how to capture the periodicity of polymer structures, and how to develop polymer descriptors without the need for human feature design. In this work, we tackle these problems through the development of our periodic polymer graph representation. Our pipeline for polymer property predictions is comprised of our polymer graph representation that naturally accounts for the periodicity of polymers, followed by a message-passing neural network (MPNN) that leverages the power of graph deep learning to automatically learn chemically-relevant polymer descriptors. Across a diverse dataset of 10 polymer properties, we find that this polymer graph representation consistently outperforms hand-designed representations with a 20% average reduction in prediction error. Our results illustrate how the incorporation of chemical intuition through directly encoding periodicity into our polymer graph representation leads to a considerable improvement in the accuracy and reliability of polymer property predictions. We also demonstrate how combining polymer graph representations with message-passing neural network architectures can automatically extract meaningful polymer features that are consistent with human intuition, while outperforming human-derived features. This work highlights the advancement in predictive capability that is possible if using chemical descriptors that are specifically optimized for capturing the unique chemical structure of polymers.

The gas–liquid–solid mini fluidized bed (GLSMFB) combines the advantages of fluidized bed and micro-reactor, and meets the requirements for safety and efficiency of green development of process industry. However, there are few studies on its flow performance and no studies on its mass and heat transfer performance. In this paper, the characteristics of gas–liquid mass transfer in a GLSMFB were studied in order to provide basic guidance for the study of GLSMFB reaction performance and application. Using CO2 absorption by NaOH as the model process, the gas–liquid mass transfer performance of GLSMFB was investigated. The results show that the liquid volumetric mass transfer coefficient and the gas–liquid interfacial area both increase with the increase of the superficial gas velocity within the experimental parameter range under the same given superficial liquid velocity. At the same ratio of superficial gas to liquid velocity, the liquid volumetric mass transfer coefficient increases with the increase of the superficial liquid velocity. Fluidized solid particles strengthen the liquid mass transfer process, and the liquid volumetric mass transfer coefficient is about 13% higher than that of gas–liquid mini bubble column.

Monodisperse suspensions of Brownian colloidal spheres crystallize at high densities, and ordering under shear has been observed at densities below the crystallization threshold. We perform large-scale simulations of a model suspension containing over [Formula: see text] particles to quantitatively study the ordering under shear and to investigate its link to the rheological properties of the suspension. We find that at high rates, for [Formula: see text], the shear flow induces an ordering transition that significantly decreases the measured viscosity. This ordering is analyzed in terms of the development of layering and planar order, and we determine that particles are packed into hexagonal crystal layers (with numerous defects) that slide past each other. By computing local [Formula: see text] and [Formula: see text] order parameters, we determine that the defects correspond to chains of particles in a squarelike lattice. We compute the individual particle contributions to the stress tensor and discover that the largest contributors to the shear stress are primarily located in these lower density, defect regions. The defect structure enables the formation of compressed chains of particles to resist the shear, but these chains are transient and short-lived. The inclusion of a contact friction force allows the stress-bearing structures to grow into a system-spanning network, thereby disrupting the order and drastically increasing the suspension viscosity.

Catalytic reactions always accompany steric and electronic effects. Due to the modulated structure and functionality, the surface charge of porous coordination cage can be tuned under the same topology. This provides a straightforward way to investigate the steric and electronic effects by using cage catalysts. Herein, we prepared two cages with 24- negative surface charge and zero surface charge and applied them in guest encapsulation and Knoevenagel condensation. The high anionic cage shows considerably higher adsorption kinetic for positive guests and much-improved reactivity in the catalytic reaction when comparing to the neutral counterpart. The negative charge was proved to be the dominant factor for the much-improved catalytic reactivity, rather than the cage structure. This finding provides new thoughts for design a suitable platform to investigate the individual impact factors for the catalytic reactions.

A thermodynamically consistent model for soft deformable viscoelastic magnets is formulated in actual space (Eulerian) coordinates. The possibility of a ferro-paramagnetic-type (or ferri-antiferromagnetic) transition exploiting Landau phase transition theory as well as mechanical melting or solidification is considered, being motivated and applicable to paleomagnetism (involving both thermo- and isothermal and viscous remanent magnetization) in rocks in Earth's crust and to rock-magma transition. The temperature-dependent Jeffreys rheology in the deviatoric part combined with the Kelvin-Voigt rheology in the spherical (volumetric) part is used. The energy balance and the entropy imbalance behind the model are demonstrated, and its analysis is performed by time discretization, proving existence of weak solutions., arXiv admin note: text overlap with arXiv:2012.15248, with some math mistakes and typos in corrected

We investigate the swelling of polymer model networks prepared at different polymer volume fractions and in solvents of different quality. We extend the existing theory to describe residual bond orientations (the vector and the tensor order parameters) for theta, good, and athermal solvents and put these relations in context with modulus at preparation conditions and the equilibrium degree of swelling. We find a good agreement with the assumption of affine swelling for the weakly entangled networks of our study. The same scaling relations (up to numerical coefficients) are obtained for the vector order parameter, m, and the tensor order parameter, S, as a function of the prepration conditions, network structure, the equilibrium degree of swelling, Q, and the modulus at swelling equilibrium, G. We obtain m\propto Q^{-2} and G\propto m^{3/2} for swelling in theta solvents and m\propto Q^{-1.08} with G\propto m^{2.14} in the good-solvent regime, in both cases independent of preparation conditions. Modulus and residual bond orientation are related by G\propto\phi_{0}m and G\propto\phi_{0}^{1.23}m as a function of the preparation polymer volume fraction \phi_{0} for theta solvents and good solvents, respectively. Computer simulations and experimental data for the good-solvent regime show good agreement with the predictions.

Water-based fire extinguishing agent is the main means to deal with smoldering fires. However, due to the hydrophobic properties of the particle surface, the porous medium channel provide resistance and slow down the extinguishing agent flow during the downward permeation process. To promote the liquid permeation process in such porous media, this work studied liquid imbibition process and analyzed the oscillating and attenuating process of liquid level in capillary channel by theoretical, experimental, and numerical methods. An empirical mathematical equation was proposed to describe the oscillating process, and the effects of the capillary diameter and contact angle parameters on the transportation process were analyzed. Based on this, the “relay-mode” was proposed to promote the liquid transportation forward. Finally, the transient simulation results of liquid permeation in coal stacks showed when the liquid flowed through the channel with changed diameter from large to small ones, the transportation distance was several times longer than that through the unidiameter ones. The trend of liquid “relay-mode” in capillaries can be used to promote the permeation in granular materials porous media stacks. The relevant results also provide new thoughts to develop the water-based fire extinguishing agents and then improve the firefighting efficiency of deep-seated fire in porous media stacks.

Due to their unique topology of having no chain ends, dilute solutions of ring polymers exhibit behaviour distinct from their linear chain counterparts. The universality of their static and dynamic properties, as a function of solvent quality $z$ in the thermal crossover regime between $\theta$ and athermal solvents, is studied here using Brownian dynamics simulations. The universal ratio $U_{\text{RD}}$ of the radius of gyration $R_g$ to the hydrodynamic radius $R_H$ is determined, and a comparative study of the swelling ratio $\alpha_g$ of the radius of gyration, the swelling ratio $\alpha_H$ of the hydrodynamic radius, and the swelling ratio $\alpha_X$ of the mean polymer stretch $X$ along the $x$-axis, for linear and ring polymers, is carried out. The ratio $U_{\text{RD}}$ for dilute ring polymer solutions is found to converge asymptotically to a constant value as $z \to \infty$, which is a major difference from the behaviour of solutions of linear chains, where no such asymptotic limit exists. Additionally, the ratio of the mean stretch along the $x$-axis to the hydrodynamic radius, $(X/R_H)$, is found to be independent of $z$ for polymeric rings, unlike in the case for linear polymers. These results indicate a fundamental difference in the scaling of static and dynamic properties of rings and linear chains in the thermal crossover regime., Comment: 20 pages, 14 figures. To appear in the Special Issue of the Journal of Rheology on Ring Polymers

Carbon fiber composite continuous sucker rod string is more and more widely used in deep and ultradeep wells because of its light weight, high strength, and corrosion resistance. In order to analyze the dynamic problems of carbon fiber sucker rod string in actual oil wells, a transverse vibration simulation model of carbon fiber and steel (carbon-steel) hybrid rod string excited by buckling deformation in vertical wells is established with the compression buckling deformation of weighting rod. Considering the influence of wellbore trajectory and the constraint of tubing, the transverse vibration simulation model of carbon-steel hybrid rod string in directional wells under borehole trajectory excitation is also established in this paper. The finite difference method is used to discretize the well depth node, the numerical integration method (Newmark-β) is used to discretize the reciprocating periodic time node, and simulation methods for the contact and collision dynamics of rod-tubing in vertical wells and directional wells are formed. Through programming calculation, the distribution laws of transverse displacement, contact force, collision force, and bending stress of carbon-steel hybrid sucker rod string in vertical wells and directional wells along well depth are obtained. The simulation results in vertical wells show that the strong collision between the rod and tubing occurs near the bottom steel rod, while the upper load is small and the rod-tubing collision load of the upper rod of the carbon-steel hybrid rod string is much lower than that of the traditional steel rod string at the same position. Furthermore, the bending stress of the upper carbon fiber is also much less than that of the bottom steel rod. The simulation results in directional wells show that the collision phenomenon of the deflecting section and the bottom weighting rod compression section are the strongest and the rod-tubing contact pressure is also the largest. Second, the impact force of the upper carbon fiber rod is also much lower than that of the steel rod. Again, the maximum bending stress of the whole well occurs near the deviation section where the deviation angle changes suddenly. The transverse vibration mechanical model in directional wells in this paper lays a theoretical foundation and provides theoretical support for the optimal design of fracture and splitting prevention measures of carbon fiber sucker rod.

A water-in-water (W/W) emulsion consists of droplets formed by the spontaneous liquid–liquid separation of two immiscible aqueous phases. The inherent properties of the W/W interfaces, low or ultra...

Knowledge graphs have received intensive research interests. When the labels of most nodes or datapoints are missing, anchor graph and hierarchical anchor graph models can be employed. With an anchor graph or hierarchical anchor graph, we only need to optimize the labels of the coarsest anchors, and the labels of datapoints can be inferred from these anchors in a coarse-to-fine manner. The complexity of optimization is therefore reduced to a cubic cost with respect to the number of the coarsest anchors. However, to obtain a high accuracy when a data distribution is complex, the scale of this anchor set still needs to be large, which thus inevitably incurs an expensive computational burden. As such, a challenge in scaling up these models is how to efficiently estimate the labels of these anchors while keeping classification performance. To address this problem, we propose a novel approach that adds an anchor label predictor in the conventional anchor graph and hierarchical anchor graph models. In the proposed approach, the labels of the coarsest anchors are not directly optimized, and instead, we learn a label predictor which estimates the labels of these anchors with their spectral representations. The predictor is optimized with a regularization on all datapoints based on a hierarchical anchor graph, and we show that its solution only involves the inversion of a small-size matrix. Built upon the anchor hierarchy, we design a sparse intra-layer adjacency matrix over these anchors, which can simultaneously accelerate spectral embedding and enhance effectiveness. Our approach is named Faster Learning6 on Anchor Graph (FLAG) as it improves conventional anchor-graph-based methods in terms of efficiency. Experiments on a variety of publicly available datasets with sizes varying fromthousands to millions of Q1 samples demonstrate the effectiveness of our approach.

A modified wake model was proposed for the newly developed bubble-induced three-phase inverse fluidized bed (BIFB), by combining the generalized wake model and the gas-perturbed liquid model. On the basis of the modified wake model, the solids and liquid holdups and the complete fluidization gas velocity in BIFB system have been successfully predicted with two established correlations. The predictions achieved very good agreements with the experimental data.

Understanding seismic wave propagation in granular porous media is important for subsurface characterization. The presence of fluids, their distribution, and the prevailing wettability condition result in additional complexities. Although it is known that wave propagation in dry granular porous media is dominated by the presence of force chains, their influence in (partially) saturated granular porous media with different wettability conditions remains largely unexplored. To make progress in this direction, we have designed laboratory experiments by combining core flooding and ultrasonic measurements in glass bead packings that are chemically treated to alternate the wettability. The P- and S-wave velocity-saturation relation and attenuation-saturation relation are retrieved from the waveforms for water- and gas-wetting samples. The results demonstrate that there is a transition from an attenuating but stable P-wave pulse at low and moderate saturation to a set of incoherently scattered waves at high saturation. The incoherent scattering in the gas-wetting case is negligibly small, whereas it is more pronounced in the water-wetting case. We interpret these observations in terms of the wettability-dependent ability for water to penetrate into grain contacts. In the water-wetting case, liquid bridges are thought to locally reinforce the force chains and to increase their characteristic length scale. This leads to an increase in P-wave velocity and promotes incoherent scattering because the ratio of dominant wavelength to characteristic length scale decreases. In the gas-wetting case, however, the presence of gas prevents the water from direct contact with the glass beads and therefore stops the formation and growth of the liquid bridges within the force-chain network.

The relative geometry of the anchors and the emitter plays important role in the estimation accuracy of the emitter location. In this paper, it is assumed that there are a number of anchors with known location in a 2D wireless network. Each anchor either measures the distance between itself and the emitter or it measures the look angle to the emitter. Knowing the location of the anchors, the emitter location can be estimated using these noisy measurements. It is assumed that one wants to add a number of new anchors to this network to improve the accuracy of estimating the emitter location. In this paper, we have used the frame theory to obtain an algorithm which proposes the optimum location of the new anchors in the network. The optimization criterion for anchors placement is maximizing the Fisher information matrix (FIM) determinant, which is equivalent to minimizing the trace of the Cramer Rao Lower Bound (CRLB) in our assumed problem. Numerical simulations confirm the ability of the proposed algorithm to find the optimal location for new anchors.

The negative internal energetic contribution to the elastic modulus (negative energetic elasticity) has been recently observed in polymer gels. This finding challenges the conventional notion that the elastic moduli of rubberlike materials are determined mainly by entropic elasticity. However, the microscopic origin of negative energetic elasticity has not yet been clarified. Here, we consider the $n$-step interacting self-avoiding walk on a cubic lattice as a model of a single polymer chain (a subchain of a network in a polymer gel) in a solvent. We theoretically demonstrate the emergence of negative energetic elasticity based on an exact enumeration up to $n=20$ and analytic expressions for arbitrary $n$ in special cases. Furthermore, we demonstrate that the negative energetic elasticity of this model originates from the attractive polymer--solvent interaction, which locally stiffens the chain and conversely softens the stiffness of the entire chain. This model qualitatively reproduces the temperature dependence of negative energetic elasticity observed in the polymer-gel experiments, indicating that the analysis of a single chain can explain the properties of negative energetic elasticity in polymer gels., Comment: 6 pages, 5 figures (main text); 21 pages, 4 figures (Supplemental Material)

Continuum models of active nematic gels have proved successful to describe a number of biological systems consisting of a population of rod-like motile subunits in a fluid environment. However, to get a thorough understanding of the collective processes underlying the behaviour of active biosystems, the theoretical underpinnings of these models still need to be critically examined. To this end, we derive a minimal model based on a nematic elastomer energy, where the key parameters have a simple physical interpretation and the irreversible nature of activity emerges clearly. The interplay between viscoelastic material response and active dynamics of the microscopic constituents is accounted for by material remodelling. Partial degree of order and defect dynamics is included as a result of the kinematic coupling between the nematic elastomer shape-tensor and the orientational ordering tensor Q . In a simple one-dimensional channel geometry, we use linear stability analysis to show that even in the isotropic phase, the interaction between flow-induced local nematic order and activity results in a spontaneous flow of particles.

An alternative to the well-known complete form of the Mie-Gr\"uneisen equation of state (EOS) for water is suggested. A closed analytical description of the self-consistent EOS for an arbitrary medium based only on the first law of thermodynamics and on a new form of virial theorem is obtained. This form of the virial theorem (allowing a variable power-law exponent of the particles interaction potential) is a result of the generalization of the known method of similarity (Feynman et al., 1949). In the new EOS, the description of the internal potential energy as a solution of a nonlinear Riemann-Hopf type equation is proposed., Comment: 37 pages, 5 figures

Below the onset temperature $T_\text{o}$, the equilibrium relaxation time of most glass-forming liquids exhibits glassy dynamics characterized by super-Arrhenius temperature dependence. In this supercooled regime, the relaxation dynamics also proceeds through localized elastic excitations corresponding to hopping events between inherent states, i.e., potential-energy minimizing configurations of the liquid. Despite its importance in distinguishing the supercooled regime from the high-temperature regime, the microscopic origin of $T_\text{o}$ is not yet known. Here, we construct a theory for the onset temperature in two dimensions and find that inherent-state melting transition, described by the binding-unbinding transition of dipolar elastic excitations, delineates the supercooled regime from the high-temperature regime. The corresponding melting transition temperature is in good agreement with the onset temperature found in various two-dimensional atomistic models of glass formers. We discuss the predictions of our theory on the displacement and density correlations of two-dimensional supercooled liquids, which are consistent with observations of the Mermin-Wagner fluctuations in recent experiments and molecular simulations., Comment: 8 pages, 4 figures, 1 table

Koszul type Coxeter simplex tilings exist in hyperbolic $n$-space $\mathbb{H}^n$ up to $ n = 9$, and their horoball packings achieve the highest known regular ball packing densities for $n = 3, 4, 5$. In this paper we determine the optimal horoball packing densities of Koszul simplex tilings in dimensions $6 \leq n \leq 9$, which give new lower bounds for optimal packing density in each dimension. The symmetries of the packings are given by Coxeter simplex groups, and a parameter related to the Busemann function gives an isometry invariant description of different optimal horoball packing configurations., Comment: 16 Pages, 6 Tables, 1 Figure. arXiv admin note: substantial text overlap with arXiv:1809.05411, arXiv:1401.6084

This study looks into the steady heat transfer issue of a flow of an incompressible Carreau fluid. Carreau fluid exhibits the shear thinning and thickening characteristics at low, moderate, and high shear rates. At the tubule wall, the fluid absorption is used as a function of pressure gradient and wall permeability through the tubule wall. Supposing the tubule radius considerably small in comparison to its length, the governing equations are considerably simplified. Significant quantities of interest are computed analytically by using perturbation, and the influence of emergent parameters is discussed through graphical results. The comparisons of results with existing data are set up to be good agreement.

Stabilised dense emulsions display a rich phenomenology connecting microstructure and rheology. In this work, we study how an emulsion with a finite yield stress can be built via large-scale stirring. By gradually increasing the volume fraction of the dispersed minority phase, under the constant action of a stirring force, we are able to achieve a volume fraction close to 80%. Despite the fact that our system is highly concentrated and not yet turbulent we observe a droplet size distribution consistent with the −10/3 scaling, often associated with inertial range droplets breakup. We report that the polydispersity of droplet sizes correlates with the dynamics of the emulsion formation process. Additionally, we quantify the visco-elastic properties of the dense emulsion finally obtained and we demonstrate the presence of a finite yield stress. The approach reported can pave the way to a quantitative understanding of the complex interplay between the dynamics of mesoscale constituents and the large-scale flow properties of yield stress fluids.

It is of significance to investigate deeply the hydrodynamic features of the bubble contaminated by impurities in view of the fact that the industrial liquid is difficult to keep absolutely pure. On the basis of the finite volume method, the bubble interface contaminated by the surfactant (1-pentanol) is achieved through solving the concentration transport equations in liquid and along the bubble interface, and solving the absorption and desorption equation at the bubble interface. And the three-dimensional momentum equation is solved at the same time. It is investigated in detail on the influence of interfacial contamination degrees (described with the cap angle θ) on hydrodynamic characteristics of the spherical bubble when the bubble Reynolds number (Re) is larger than 200. The θ is realized by changing the surfactant concentration (C0) in liquid. The present results show that the hydrodynamic characteristics, such as interfacial concentration, interfacial shear stress, interfacial velocity and wake flow, are related to both Re and C0 for the contaminated bubble. When C0 is relatively low in liquid (i.e., the contamination degree of the bubble interface is relatively slight), the hydrodynamic characteristics of the bubble can still keep the 2D features even if Re>200. The decrease of θ or the increase of Re can promote the appearance of the unsteady wake flow. For the present investigation, when Re>200 and θ≤60°, the hydrodynamic characteristics of the bubble show the 3D phenomena, which indicates that axisymmetric model is no longer valid.

The topology of polymers plays an essential role in their chemical, physical and biological properties. However, their effects on chirality-related functions remain unclear. Here, we reported the topology-controlled chirality expression in the chiral supramolecular system for the first time. Two topological supramolecular polymers, hyperbranched (HP) and linear (LP) supramolecular polymers produced by the host–guest interactions of branched and linear monomers, respectively, exhibited completely different chirality expressions despite the same molecular chirality of their monomers. Significantly, due to the branch points and strong steric hindrance existing in HP, cis-HP showed an enhanced and sign-inverted Cotton effect in the n–π* bands compared with cis-LP, as a result that the distinctive chirality induction and transfer were controlled by the topological skeletons. This topology-controlled chirality induction and transfer in the photoswitchable supramolecular polymers not only enables us to elucidate the in-depth effects of topology on the chiral expression in biopolymers but also inspires the design of chiroptical and bioinspired materials.

Viscoelastic (Maxwellian) slow, immiscible liquid-liquid displacement in a permeable medium is considered. The necessary and sufficient criteria for stability are that the displacing fluid is denser and less mobile than the displaced fluid. The instability criteria and critical wave length are found to be the same as those for ordinary viscous liquid-liquid displacements in permeable media.

Like-charge attraction, driven by ionic correlations, challenges our understanding of electrostatics both in soft and hard matter. For two charged planar surfaces confining counterions and water, we prove that, even at relatively low correlation strength, the relevant physics is the ground-state one, oblivious of fluctuations. Based on this, we derive a simple and accurate interaction pressure that fulfills known exact requirements and can be used as an effective potential. We test this equation against implicit-solvent Monte Carlo simulations and against explicit-solvent simulations of cement and several types of clays. We argue that water destructuring under nanometric confinement drastically reduces dielectric screening, enhancing ionic correlations. Our equation of state at reduced permittivity therefore explains the exotic attractive regime reported for these materials, even in the absence of multivalent counterions.

Due to the brittle nature of the glass, to study the response of glass elements subjected to dynamics loadings is of great interest, mainly when human injury resulting from glass breakage may occur. Laminated glass consists of two or more layers of monolithic glass and one or more viscoelastic interlayers. In this paper, a technique to predict the dynamic response (deflections and stresses) of laminated glass elements using a linear elastic monolithic model is proposed and validated. In a first step, the modal parameters and the dynamic response of a monolithic model are calculated using the modal superposition technique. Then, the modal parameters and the modal coordinates of the laminated glass element are estimated using the equations derived in this paper. Finally, the stresses in time and frequency domain are estimated using an effective stress Young’s modulus.

We present a generalization of the Maier-Saupe (MS) theory that incorporates the description of the ferroelectric nematic phase (NF) within its scope of application. The extension of the theory is carried out in a natural way, by adding to the nematic potential of MS a term proportional to cos{\theta} and to the polar order parameter , where {\theta} is the angle between the long molecular axis and the spontaneous polarization. The NF phase can be reached by cooling from the isotropic phase with or without the formation of an intermediate normal nematic phase, depending on the relative intensity of the polar and nonpolar terms of the nematic potential. For both phase sequences all the transitions are first order. The temperature dependence of the polar and nonpolar order parameters is calculated, and some results derived from the theory are compared with the experimental observations. It is argued that the theory is a valuable first approximation to describe some of the properties of ferroelectric nematics., Comment: 13 pages, 4 figures

RNA oligomers exhibit lyotropic chiral nematic and columnar liquid crystal phases. The lyotropic chiral nematic and columnar phases with special emphasize on the isotropic to columnar phase transition in RNA solutions are described based on Landau theory. A free energy is constructed based on the order parameters to describe the chiral nematic and columnar liquid crystal phases and isotropic to columnar phase transition. The lyotropic isotropic to columnar phase transition is found to be always first order. The birefringence has been calculated in the isotropic phase of isotropic to columnar phase transition. Theoretical observation of the existence of the lyotropic isotropic to columnar phase transition in RNA solutions is confirmed with experimental results.

This study focuses on the prediction of the porosity of nonuniform sediment mixtures, considering the effects of particle packing. A random particle packing model has been developed for the porosity of bimodal mixtures by extending the existing random particle filling theory. Coefficients in the developed model are calibrated by fitting the model to measured data for a variety of bimodal mixtures, including spherical glass particles, rounded quarry grains, and natural sediments. The model coefficients are found to be functions of the diameter ratio of coarse and fine particles, separately for spherical glass particles and natural sediments due to differences in particle shapes. The bimodal mixture model is then extended to trimodal particle mixtures in three approaches: two based on serial packing and one based on random packing. These models are tested against experimental data of six trimodal mixtures with spherical glass beads. The results show that the random packing model and the fine–medium–coarse particle serial packing model predict well the observed trimodal mixture porosities.

We show that a viscous liquid confined between two low thermal conductive surfaces (Al2O3) emit a thermal response upon applying a low frequency (Hz) shear excitation. Hot and cold thermal waves are observed in situ at atmospheric pressure and room temperature, in polypropylene glycol layers of various thicknesses ranging from 100 microns up to 340 microns, upon applying a mechanical oscillatory shear strain. The observed thermal effects, synchronous with the mechanical excitation, are inconsistent with a homogeneous viscous flow. It indicates that mesoscopic liquids are able to (partly) convert mechanical shear energy in non-equilibrium thermodynamic states. This effect called thermoelasticity is well known in solid materials. The observation of a thermal coupling to the mechanical shear deformation reinforces the assumption of elastically correlated liquid molecules. The amplitude of the thermoelastic waves increases linearly by increasing the shear strain amplitude up to a transition to a non-linear thermal behavior, similar in strain behavior to an elastic to plastic regime. The thermo-elastic effects are not detectable via stress measurements and thus appear as a complementary liquid dynamic characterization., Comment: 10_pages

Dissipative particle dynamics (DPD) simulations are performed on coarse-grained replicas of linear, monodisperse entangled polyethylene melts C1000H2002 and C3000H6002 undergoing both steady-state and transient planar elongational flow (PEF). The fidelity of the DPD simulations is verified by direct comparison of flow topological and rheological properties of a 334-particle chain liquid against the united-atom C1000H2002 liquid, simulated using nonequilibrium molecular dynamics (NEMD). These DPD simulations demonstrate that a flow-induced coil-stretch transition (CST) and its associated hysteresis caused by configurational microphase separation, as observed in previous NEMD simulations of PEF, can be replicated using a more computationally efficient coarse-grained system. Results indicate that the breadth of the CST hysteresis loop is enlarged for the longer molecule liquid relative to the shorter one. Furthermore, relaxation simulations reveal that reducing the applied flow Deborah number (De) from a high value corresponding to a homogeneous phase of highly stretched molecules to a De within the biphasic region results in a two-stage relaxation process. There is a fast initial stratification of the kinetically trapped highly stretched chains into regions of highly extended and less extended chains, which displays similar behavior to a system undergoing a spinodal decomposition caused by spatial configurational free energy fluctuations. After a short induction period of apparently random duration, the less extended chain regions experience a stochastic nucleation event that induces configurational relaxation to domains composed of coiled molecules over a much longer time scale, leaving the more highly extended chains in surrounding sheetlike domains. The time scales of these two relaxation processes are of the same order of magnitude as the Rouse and disengagement times of the equilibrium liquids.

The first-order phase transition of an MBBA nematic liquid crystal with benzene impurity has been studied by the critical opalescence method at a large cell thickness. Opalescence has been observed at two critical transition points. The spatial transverse parameters of the domains are determined from the Fraunhofer diffraction. The hypothesis about the longitudinal correlation parameter of domains is equal to the cell length has been proposed.

Using spin-coating method, the poly (methyl methacrylate) (PMMA)/multi-walled carbon nanotubes (MWCNTs) thin films are prepared. The optical features from the band gap, refractive index and optical connectivity are studied. The gap was calculated from the UV-Vis spectra. The superficial structure is examined through the use of the atomic force microscope (AFM) to investigate the dispersion of MWCNT within the polymer matrix.

Under the condition of constant external stress, the displacement and stress of the joint will be adjusted continuously with time, resulting in the creep phenomenon, that is, the continuous increase of the strain with time, which further causes the damage of the jointed rock mass. In order to study the size effect of joint shear rheological mechanical properties, this paper conducted shear rheological numerical simulations on nonpenetrating and penetrating joint models established in Particle Flow Code (PFC) and analyzed the effect of specimen size on the rheological and shear mechanical behavior of the model. The results show the following: (1) For the rheological direct shear test, the instantaneous shear displacement of the joint increases continuously as the size increases, showing a significant positive size effect. (2) For through-type joints, only the cohesion shows a certain size effect, and the shear strength and friction angle have a nonobvious relation with specimen size. (3) For anchored through-type joints, the increase of the model size leads to a decrease in shear strength, while the friction angle-size effect of joints is not remarkable.

Glass formation is encountered in diverse materials. Experiments have revealed that dynamic relaxation spectra of supercooled liquids generically become asymmetric near the glass transition temperature, $T_g$, where an extended power law emerges at high frequencies. The microscopic origin of this "wing" remains unknown, and was so far inaccessible to simulations. Here, we develop a novel computational approach and study the equilibrium dynamics of model supercooled liquids near $T_g$. We demonstrate the emergence of a power law wing in numerical spectra, which originates from relaxation at rare, localised regions over broadly-distributed timescales. We rationalise the asymmetric shape of relaxation spectra by constructing an empirical model associating heterogeneous activated dynamics with dynamic facilitation, which are the two minimal physical ingredients revealed by our simulations. Our work offers a glimpse of the molecular motion responsible for glass formation at relevant experimental conditions., Comment: 5 pages, 4 figures, supplementary materials

This article analyzes modulated phases in liquid crystals, from the long-established cholesteric and blue phases to the recently discovered twist-bend, splay-bend, and splay nematic phases, as well as the twist-grain-boundary (TGB) and helical nanofilament variations on smectic phases. The analysis uses the concept of four fundamental modes of director deformation: twist, bend, splay, and a fourth mode related to saddle-splay. Each mode is coupled to a specific type of molecular order: chirality, polarization perpendicular and parallel to the director, and octupolar order. When the liquid crystal develops one type of spontaneous order, the ideal local structure becomes nonuniform, with the corresponding director deformation. In general, the ideal local structure is frustrated; it cannot fill space. As a result, the liquid crystal must form a complex global phase, which may have a combination of deformation modes, and may have a periodic array of defects. Thus, the concept of an ideal local structure under geometric frustration provides a unified framework to understand the wide variety of modulated phases.

The objective of this paper is to present an approach for the detection of change in rolling element bearings (REB) operating conditions that can lead to premature failure. The developed technique is based on the measurement of the kinematics of the bearing cage. The rotational motion of the cage is driven by the traction forces produced in the contacts of the rolling elements with the races. It is known that the cage angular frequency relative to shaft angular frequency is dependent of the bearing load, the bearing speed and the lubrication condition, as these factors are determinant for the lubricant film thickness and the associated traction forces. As an important part of REB failures are caused by misalignment or lubrication problems, any evidence of these conditions should be interpreted as an incipient fault. In this paper a novel method for the determination of the instantaneous angular speed (IAS) of the cage is developed. The method is evaluated in a deep grove ball bearing test rig equipped with the cage IAS sensor, as well as custom acoustic emission (AE) transducer and a piezoelectric accelerometer. The cage IAS is analyzed under different bearing loads and shaft speed, showing the dependence of the cage angular speed with the calculated lubricant film thickness. Typical bearing faulty operating conditions (mixed lubrication regime, lubricant depletion and misalignment) are recreated and it is shown that the cage IAS is dependent on the lubrication regime and is sensitive to misalignment. The AE signal is used as a lubrication regime evaluator as well. Experimental results show that the proposed technique can be used as a condition monitoring tool to detect abnormal REB conditions that can lead to premature failure.

The excitation of space-wave, leaky-wave and creeping-waves in a cylindrical rod with uniaxial anisotropic permittivity and permeability is thoroughly characterized. Closed-form expressions of the space, leaky and creeping-waves in the uniaxial rod are derived for all source polarizations through the rigorous formulation, taking into account all higher-order azimuthal harmonics and TE-TM mode coupling for the space-wave and creeping-waves. Conditions for obtaining a high space-wave and leaky-wave directivity are thoroughly examined for all source polarizations with variation in the vertical and horizontal permittivity / permeability and the rod-radius. The leaky-wave phase and attenuation constants with variation in the rod parameters are investigated to identify the leaky-wave propagation regions of the uniaxial rod. Beam-scanning characteristics for the space- and leaky-waves are examined with variation in the uniaxial rod-parameters. The complex pole-loci for the azimuthally propagating creeping-waves around the uniaxial rod is also investigated to identify the leaky, creeping and the trapped-mode regions.

An interaction function was constructed based on the axial compression/tension and shear loads of orthotropic plates. The coefficients of the polynomial function were determined by uniaxial test results. Buckling interaction and failure interaction formulae under combined axial tension/compression and shear loads were established. Based on the uniaxial load test results of orthotropic plates, the buckling load and bearing capacity under any proportion of the combined loads could be predicted by using the proposed interaction formulae. The buckling interaction curves and failure envelopes predicted by the proposed interaction formulae were in excellent agreement with the test results.

Theoretical expressions for the intrinsic viscosity, the Huggins coefficient, zero-shear viscosity, and storage and loss moduli for stiff-chain polymer solutions are reviewed. Especially, the mean-field Green function method is explained in detail to consider the intermolecular collision effect on the rheological properties of concentrated stiff-chain polymer solutions, by applying the method to monodisperse and polydisperse straight cylinders and monodisperse fuzzy cylinder models. The theoretical expressions reviewed are compared with experimental results for aqueous solutions of two rigid helical polysaccharides, schizophyllan and xanthan.

Soft glasses of colloidal rods ( fd-virus particles) with orientational domains were recently shown to exhibit inhomogeneous flow profiles [Dhont et al., Phys. Rev. Fluids 2, 043301 (2017)]: fracture and accompanied plug flow at small shear rates, which transits to gradient shear-banding on increasing the shear rate, while a uniform flow profile develops at sufficiently high shear rates. These flow profiles coexist with Taylor-vorticity bands. The texture of such glasses under flow conditions consists of domains with varying orientations. The observed gradient shear-banding was solely attributed to the strong shear thinning behavior of the material inside the domains (henceforth abbreviated as domain-interior), without considering the texture stress that is due to interactions between the glassy domains. Here, we present new experiments on the shear-banding transition to assess the role played by the texture stress in comparison to the domain-interior stress. For a large concentration, well into the glassy state, it is found that both texture stress and domain-interior stress contribute significantly to the gradient shear-banding transition in the shear-rate region where it occurs. On the other hand, for a small concentration close to the glass-transition concentration, the domains are shown to coalesce within the shear-rate range where gradient shear-banding is observed. As a result, the texture stress diminishes and the domain-interior stress increases upon coalescence, leading to a stress plateau. Thus, a subtle interplay exists between the stresses arising from the structural order on two widely separated length scales from interactions between domains and from the rod-rod interactions within the domain-interior for both concentrations.

The speed of sound is a critical parameter in the test of mechanical and thermal properties. In this work, we proposed a testing method to obtain the elastic modulus of silica aerogel from the sound speed formulas. The solid thermal conductivity of the silica aerogel is experimentally measured for predicting the sound speeds, and then the elastic modulus is calculated based on the elasticity sound speed model. The experimental data of the solid thermal conductivity of silica aerogels with different densities are employed and the obtained elastic modulus is fitted as a power-law exponential function of the density. Two existing sound speed models and three groups of available experimental data are also employed to validate the present fitting relation, and good agreement is obtained for the silica aerogel in the density range of 150–350 kg/m3. The fitting formula can also be extended to estimate the elastic modulus of the glass fiber-reinforced silica aerogel composite. The results show that the elastic modulus of the aerogel composite is sensitive to the glass fiber volume fraction, while the thermal conductivity is weakly dependent on the glass fiber volume fraction at room temperature in the studied range of fiber volume fraction.

In view of the classical Lucas-Washburn equation, which can only describe the spontaneous imbibition of single wetted capillary, a tilted composite capillary model with circular cross section, composed of different wettability capillary wall was established. The model can describe the spontaneous oil-water imbibition of water-wet capillary, oil-wet capillary and mixed wetting capillary. Through numerical solution of the model equation, it is found that the component content of the capillary walls, the capillary radius and the oil-water viscosity ratio have great effects on the spontaneous oil-water imbibition. Effects of capillary inclination angle and inertia force on spontaneous oil-water imbibition are related to the capillary scale. Effects of capillary inclination angle and inertia force can be ignored in small radius capillary, while effects of inclination angle and inertia force can not be ignored in large radius capillary.

A molecular-kinetic model of the processes of highly elastic deformation of amorphous polymers is proposed and, on its basis, nonlinear rheological equations are obtained; these latter make it possible to describe these processes under changes of deformation conditions in a wide range: temperature, deforming stress, and strain rate. A connection of the nonlinear micromechanical model of a polymer with the classical macromechanical model of a standard linear body is established. The transitions between the structural-deformation states of a warm and frozen elastomer, as well as the effects of low-temperature deformation melting and quantum elasticity of an amorphous polymer, are discussed.

In this study, a modified three rail shear test (or double shear test) procedure is described for the determination of the shear moduli and the shear strength values of rigid foamed materials and test results are presented for light extruded polystyrene, which is a typical core material used in sandwich construction. The main idea is to obtain a nearly uniform shear stress distribution in the shear test specimens by strengthening them against bending. First, using a finite element model, it is numerically shown that a nearly pure shear stress state may be obtained in the strengthened three rail shear test specimens. Then, it is shown that the finite element numerical results obtained for the strengthened specimens are in excellent agreement with the analytical results. Next, three rail shear tests are performed on bare and strengthened specimens and the experimental results obtained are presented in comparison with the analytical results. Also, clamped beam vibration and three-point bending tests are conducted to validate the shear modulus values obtained. The results obtained show that, the strengthened three rail shear test specimens yield more accurate results for both shear modulus, and strength comparing with the bare specimens.

Cellulose nanocrystals (CNCs) self-assemble in water suspensions into liquid crystalline assemblies. Here, we elucidate the microstructural changes associated with nonlinear deformations in (2–9 wt%) CNC suspensions through nonlinear rheological analysis, that was performed in parallel with coupled rheology—polarized light imaging. We show that nonlinear material parameters from Fourier-transform rheology and stress decomposition are sensitive to all CNC phases investigated, i.e. isotropic, biphasic and liquid crystalline. This is in contrast to steady shear and linear viscoelastic dynamic moduli where the three-region behavior and weak strain overshoot cannot distinguish between biphasic and liquid crystalline phases. Thus, the inter-cycle and intra-cycle nonlinear parameters investigated are a more sensitive approach to relate rheological measurements to CNC phase behavior.

The swelling of polyelectrolyte hydrogels has been often explained using simple models derived from the Flory-Rehner model. While these models qualitatively predict the experimentally observed trends, they also introduce strong approximations and neglect some important contributions. Consequently, they sometimes incorrectly ascribe the observed trends to contributions which are of minor importance under the given conditions. In this work, we investigate the swelling properties of weak (pH-responsive) polyelectrolyte gels at various pH and salt concentrations, using a hierarchy of models, gradually introducing various approximations. For the first time, we introduce a three-dimensional particle-based model which accounts for the topology of the hydrogel network, for electrostatic interactions between gel segments and small ions and for acid-base equilibrium coupled to the Donnan partitioning of small ions. This model is the most accurate one, therefore, we use it as a reference when assessing the effect of various approximations. As the first approximation, we introduce the affine deformation, which allows us to replace the network of many chains by a single chain, while retaining the particle-based representation. In the next step, we use the mean-field approximation to replace particles by density fields, combining the Poisson-Boltzmann equation with elastic stretching of the chain. Finally, we introduce an ideal gel model by neglecting the electrostatics while retaining all other features of the previous model. Comparing predictions from all four models allows us to understand which contributions dominate at high or low pH or salt concentrations. We observe that the field-based models overestimate the ionization degree of the gel because they underestimate the electrostatic interactions. Nevertheless, a cancellation of effects on the electrostatic interactions and Donnan partitioning causes that both particle-based and field-based models consistently predict the swelling of the gels as a function of pH and salt concentration. Thus, we can conclude that any of the employed models can rationalize the known experimental trends in gel swelling, however, only the particle-based models fully account for the true effects causing these trends. The full understanding of differences between various models is important when interpreting experimental results in the framework of existing theories and for ascribing the observed trends to particular contributions, such as the Donnan partitioning of ions, osmotic pressure or electrostatic interactions.