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Researchers at Rice University in Texas have developed a sustainable method for 3D printing using ink made from recycled wood. By breaking down leftover wood into lignin and cellulose, the team created nanofibers and nanocrystals that could be combined with water to form an ink-like substance. The ink was then used to 3D print objects, which were strengthened by freeze-drying and heating. The researchers hope that this method could eventually be used to build larger structures, such as houses, without the need for cutting down trees. [Extracted from the article]

The 2D-GDQM (Two-Dimensional Generalized Differential Quadrature Method) and adaptively tuned deep neural network are two computational methods that have been proposed for the frequency analysis of sandwich disks with honeycomb cores. Sandwich disks are commonly used in aerospace and automotive industries due to their lightweight and high strength properties. However, accurately predicting their natural frequencies is crucial for ensuring their structural integrity. The 2D-GDQM is a numerical method that discretizes the equations of motion of the sandwich disk using a grid-based approach. The method has been used to obtain accurate and efficient frequency solutions for various types of sandwich structures. In this study, the 2D-GDQM was applied to analyze the frequency response of the sandwich disk with honeycomb core with first and higher-order deformation theories to model displacement field. Additionally, an adaptively tuned deep neural network was used to predict the natural frequencies of the sandwich disk. This method involves training a deep neural network with a dataset of frequency solutions obtained from the 2D-GDQM simulations. The neural network is then optimized to provide accurate predictions for new cases. The results of this study showed that both the 2D-GDQM and the adaptively tuned deep neural network can provide accurate predictions of the natural frequencies of the sandwich disk with honeycomb core. The 2D-GDQM was found to be more computationally efficient, while the neural network approach can be more flexible and adaptable to new geometries or material properties. [ABSTRACT FROM AUTHOR]

In an unconstrained elastic body, emergence of zero natural frequencies is an expectable outcome on account of the body's ability to purely translate or rotate with no structural deformation. Recent advances in literature have pushed such conventional definition and demonstrated properties transcending typical zero-frequency modes, such as localization of deformation at a structural edge or corner. In this paper, a spring–mass honeycomb lattice with an elastic foundation, referred to here as mechanical graphene, is designed to exhibit zero-frequency corner modes. A central element in the proposed design is the elastic foundation, and the zero-frequency corner modes are enabled by intricate modulation of the elastic-foundation's stiffness. These modes are proven to have their origins from the dynamics of a diatomic chain, made from a single strip of the mechanical graphene with free boundaries. Different shapes of finite mechanical graphene with free boundaries are considered and conditions leading to the manifestation of corner modes are correlated with the angle of corners and stiffness of springs supporting them. Finally, the effect of defects on zero-frequency corner modes is briefly discussed, demonstrating robustness against structural defects that are distant from corners. • The concept of zero-frequency corner modes in a mechanical graphene is introduced. • Elastic foundation of positive-negative springs enables zero-frequency corner modes. • Corner modes origin is connected to edge modes in a comparable diatomic lattice. • Corner modes only occur in mechanical graphene having 60°-angle corners. • Theory is verified numerically using different shapes of mechanical graphene. [Display omitted] [ABSTRACT FROM AUTHOR]

Extensive studies on hexagonal honeycombs under in-plane compression have demonstrated that the structure's symmetry plays a decisive part in the emergence of deformation patterns in post-bifurcated configurations. In this work, the aim is to take advantage of this property by presenting a new group-theoretic approach to list the various attainable post-bifurcated patterns of periodic architectured materials. As of today, some group-theoretic approaches have been elaborated for determining the post-bifurcated paths and thus patterns of a symmetric system submitted to specific loading conditions. However, the application of these approaches requires knowledge of the system's governing equations. By making use of another group-theoretic tool, this work predicts the various possible post-bifurcated configurations of a periodic architectured material a priori of any non-linear computation by simply assessing the symmetry group of its undeformed configuration. This approach is applied, as an example, to the buckling of regular hexagonal honeycombs but can be easily transferred to any periodic architectured material. This work is a first step towards the elaboration of a more general process for the design of architectured materials when harnessing post-bifurcated behaviour is essential. [ABSTRACT FROM AUTHOR]

Investigation of the geometrical nonlinear action of doubly curved shell panels (DCSPs) in micro scale is the main target of this paper. The proposed microshell panels (MSPs) are assumed to be made of an auxetic honeycomb core (AHOC), leading to negative magnitudes of Poisson's ratio, covered by two nanocomposite enriched coating layers (NCECLs). To conduct the size-dependent nonlinear analysis and achieve the corresponding nonlinear equilibrium path (EQP) of the proposed MSPs, the nonlocal strain gradient theory (NLSGT) is utilized. The governing equations containing the equilibrium and compatibility nonlinear partial differential equations in terms of the deformation components are analytically solved based on the Galerkin technique for different types of simply-supported panels. The achieved results of the present solution exhibit the fact that nonlocal and material length scale parameters significantly affect the EQP of the proposed MSPs especially at their post-buckling stage during their snap-through instability. By solving several numerical examples, the effects of various parameters on the size-dependent EQP of the proposed MSPs are investigated. The results indicate that the influences of size-dependency are significantly affected by the curvature and also boundary conditions of the microshells. [ABSTRACT FROM AUTHOR]

Next, the researchers applied different magnetic fields to the graphene to measure how its magnetoresistance changed. This is partly down to graphene's electrons and holes being highly mobile and therefore sensitive to tiny changes in an external magnetic field, the researchers write in their paper. Its unparalleled ability to increase or decrease its electrical resistance in response to a magnetic field could one day have applications for how we store data. [Extracted from the article]

The article discusses the construction of the Giant Magellan Telescope, which will be Earth's most powerful optical instrument. The telescope will consist of seven primary mirrors, each 8.5 meters wide, arranged in a flower-like formation. It will be located in Chile's Atacama Desert and will capture optical and near-infrared light, potentially allowing for the discovery of habitable planets and signs of alien life. The mirrors are made by melting borosilicate glass and shaping it into a honeycomb structure, which is then polished and coated with aluminum. [Extracted from the article]

Two patients, a 12-year-old boy and a 75-year-old woman, developed honeycomb hypertrophy while being treated with netarsudil for ocular conditions. The boy had a history of corticosteroid-induced ocular hypertension and the woman had neovascular glaucoma. Both patients experienced resolution of their symptoms after discontinuing netarsudil treatment. The article provides a concise description of the cases without making any judgments or assumptions. [Extracted from the article]

The importance of cellular materials continues to increase in lightweight structural applications as more industries realize these materials are becoming more reliable, repeatable and allowing for lower production costs. Among all the common structural applications of cellular architected materials, cores for sandwich panels may perhaps be the most important one, and therefore, were the focus of this work. On the other hand, the fast-paced growth of computational power, in combination with the development of software and numerical methods such as Meshless Methods provide the necessary conditions to study intricate topologies which may offer improved mechanical properties for each different application. In this work, two periodic cellular topologies which are typically used in the cores of sandwich structures were designed, namely conventional honeycombs and re-entrant honeycombs, for 7 different values of relative density, and tested in two different in-plane directions in the linear-elastic domain. The Radial Point Interpolation Method (RPIM) is used in this study, for the first time in the literature, to simulate the elasto-static behaviour of honeycomb structures and provides advantages over the Finite Element Method (FEM) in this field. [ABSTRACT FROM AUTHOR]

Purpose: Paper aims to present problem of aerodynamic heating of a metallic heat shield. The key elements of this construction are metallic layers of superalloy honeycomb, which significantly increase the structure's resistance to impact. Paper describes the problem of influence of damage size on increase of thermal load. Design/methodology/approach: Numerical analysis was performed in a non-commercial environment FreeFem++ using finite element method, and its results were compared with the results given in the literature. Findings: In thermal protection system, a modification was used to delay increase in temperature on the underlying structure as well as to reduce its maximum value. Originality/value: In the further part of the paper, selected insulation material was modified by adding additional conductive material. [ABSTRACT FROM AUTHOR]

The article discusses a study on synthesizing 2D silicon carbide conducted by researchers at the University of New Mexico and Lund University, Chalmers University of Technology, and Linköping University, published in the journal "Nanomaterials" and "Physical Review Letters," respectively. Two different approaches, top-down and bottom-up synthesis methods, were employed to achieve monolayer silicon carbide, showcasing it applications in luminescent devices and micro/nano electronic circuits.

In this research, a computational technique is developed for determining effective in-plane properties of hexagonal core honeycombs utilizing homogenization multi-scale technique based on averaging theorems. Purposely associated with engineering constants, specialized unit cells under appropriate boundary conditions are elaborated for two well-known configurations of uniform cell wall thickness and doubled thickness vertical cell walls hexagonal honeycombs. Constant boundary element method (CBEM) are employed for discretizing the boundary integral form of equivalent stress and strain equations and avoiding dependency to the mesh density and elements type selection challenges at cell walls intersection. Comparing with available experimental data for uniform cell wall thickness hexagonal honeycombs, the proposed method validated for a wide range of relative densities. Then comparing with well-defined existing analytical methods which have been previously validated experimentally, the verification of proposed method is done for uniform cell wall thickness and double thickness vertical cell walls. The results show that the proposed methods can present a well approximation of in-plane engineering constants for relative densities lower than 0.3 and also can be applied to higher relative densities by defining proper unit cells where available analytical methods encounter with significant inability. [ABSTRACT FROM AUTHOR]

The article discusses various research related to graphene, which are sheets of carbon that are one atom thick. Graphene have two-dimensional honeycomb lattice of carbon atoms that possess fantastic electrical conductivity and a strength that is 10 times of a steel. Research on graphene explored various issues including the fabrication of graphene photodetector, the role of nanoparticles in generating nanoribbons from graphene sheets and the relevance of graphene to the oil industry.

Abstract This paper presents a study of the mechanical response of hexachiral honeycombs with transversally curved ligaments under planar uniaxial tensile, compressive and shear loads. The impact of the chiral cell design parameters on the resulting macroscopic behaviour is assessed utilising finite elements calculations. It is shown that the presence of ligament curvature permits to attain mechanical responses which are not achievable through conventional chiral honeycomb designs. In addition, the resulting responses exhibit, for all considered load cases, significant tunability through the investigated geometrical design parameters. Two chiral lattices with identical geometries, only differing in their ligament curvature, were manufactured and experimentally tested to validate the finite elements predictions. A connection and assembly strategy is presented and utilised, offering a fast and robust approach to build larger finite lattice structures through 3D printed single basic cells. The hexachiral lattices were tested in tension, compression and in-plane shear, showing good agreement with the numerical predictions. [ABSTRACT FROM AUTHOR]

The advent of additive manufacturing has enabled the precise manufacturing of lattice materials at different length scales. While honeycombs are usually constructed from a tessellated array of identical unit cells, most structures in nature tend towards stochastic or disordered tessellation. In this work, we explore the effect of disorder properties of honeycombs, in particular, stiffness, strength, fracture toughness, and crack propagation paths using finite element models. The honeycombs are created using Voronoi tessellations with different levels of disorder measured by a regularity parameter δ , where δ = 1 corresponds to a regular hexagonal honeycomb and decreasing values of δ correspond to increasing levels of disorder. We consider three constituent materials: very brittle, quasi-brittle, and very ductile (0.0007–0.25 in failure strain). The results show that pseudo-order realizations with 0.5 ≤ δ ≤ 0.8 show the best strength-toughness trade-off. With increased plasticity, the improvement in fracture toughness compared to regular honeycombs can be as high as 50% at the expense of a 20% decrease in strength. This increase in fracture toughness is achieved both at crack initiation with crack blunting intrinsically and extrinsically during crack growth by a combination of crack deflection and crack bridging. Also, a single mathematical variable δ usually referred to as a "regularity parameter" to control cell stochasticity cannot account for the variability in tensile strength and fracture toughness parameters for brittle or quasi-brittle constituent materials and significantly more for a ductile constituent material. Thus, a local parameter for disorder is required to explain the large statistical variance seen in the mechanical properties of disordered honeycomb structures across the same irregularity value. [ABSTRACT FROM AUTHOR]

The article focuses on interpreting composite drawings, particularly those used in aerospace structures in aircraft designing. Topics include understanding fiber orientation symbols, ply definition diagrams, and reading ply tables and notes to interpret the laminate construction and materials used in the composite part.

The article offers information on rehabilitating channels using a novel stabilization approach. Topics include information on urgent remediation response; how watercourses had to be reshaped since the gulley sides; and plans for establishing new vegetation to prevent the disturbed soil from washing away in the following rainy season.

The article offers information on several sound equipment including CS10 two-way full-range loudspeaker from Adamson Systems Engineering; SR-A12S two-way line array speaker from TOA Electronics; and VXL Series from Yamaha.

Topological edge states form at the edges of periodic materials with specific degeneracies in their modal spectra, such as Dirac points, under the action of effects breaking certain symmetries of the system. In particular, in Floquet topological insulators unidirectional edge states appear upon breakup of the effective time-reversal symmetry due to dynamical modulations of the underlying lattice potential. However, such states are usually reported for certain simple lattice terminations, for example, at zigzag or bearded edges in honeycomb lattices. Here we show that unconventional topological edge states may exist in Floquet insulators based on arrays of helical waveguides with hybrid edges involving alternating zigzag and armchair segments, even if the latter are long. Such edge states appear in the largest part of the first Brillouin zone and show topological protection upon passage through the defects. Topological states at hybrid edges persist in the presence of focusing nonlinearity of the material. Our results can be extended to other lattice types and physical systems, they lift some of the constraints connected with lattice terminations that may not support edge states in the absence of effects breaking time-reversal symmetry of the system and expand the variety of geometrical shapes in which topological insulators can be constructed. • Topological edge states may exist in Floquet insulators with hybrid zigzag–armchair edges. • Such edge states appear in the largest part of the first Brillouin zone and show topological protection. • Topological states at hybrid edges persist in the presence of focusing nonlinearity of the material. [ABSTRACT FROM AUTHOR]

Each helmet is custom-3D-printed--the $320 price tag includes a "fit kit" and a virtual fit session--with a carbon-fiber composite, a low-profile "antimushroom" silhouette, and an impact-efficient honeycomb structure inspired by aerospace engineering. This sleek helmet makes an argument that safety and custom-fit comfort can go hand in hand. In April, the Silicon Valley--based brand KAV Sports launched its Portola helmet, boasting that it exceeds U.S. helmet protection standards by 25%. [Extracted from the article]

Finite strain numerical solutions are derived for the in-plane, elastic-plastic response of a filled hexagonal honeycomb in uniaxial compression and in uniaxial tension. The cell walls and core are treated as elastic, ideally plastic von Mises solids, but the uniaxial strength of the core material is much less than that of the cell walls. The honeycomb has sides of equal length, and its inclined (but non-vertical) cell walls subtend an angle with respect to the transverse direction that can deviate from the usual value of +/- 30 ° which is characteristic of a regular honeycomb. Two responses of the core are assumed: the fully bonded, 'non-cavitating core' (in the presence of a sufficiently high macroscopic pressure) and a 'cavitating core' that can cavitate or debond freely from the cell walls. When the honeycomb has cell walls that are inclined at 30 ° or less, the unit-cell response in uniaxial compression is stable and displays macroscopic hardening, regardless of whether the core can cavitate or not. In contrast, when the inclination of the cell walls exceeds 30 ° , the honeycomb with a cavitating core displays mild softening in uniaxial compression while the honeycomb with a non-cavitating core has a high initial yield strength, followed immediately by a strongly softening response. The strongly softening, isochoric mode occurs in an inclined shear band by the rotation of inextensional plastic hinges in the cell walls over a wavelength of two cells. A Maxwell construction is adequate for prediction of the propagation stress of the shear band in a finite specimen from a starter defect. Additional insight into the collapse mechanisms of the filled honeycomb (with a cavitating or non-cavitating core) is obtained via analytical solutions for a rigid, ideally plastic honeycomb, whereby the cell walls are treated as slender beams and the core has vanishing deviatoric strength. The full numerical solutions reveal that the filled honeycomb exhibits strong tension-compression asymmetry for both a cavitating core and a non-cavitating core. [ABSTRACT FROM AUTHOR]

The article offers discusses about the factors impacting the porosity, voids and bridging in prepreg autoclave and vacuum bag-only laminates which arise due to material selection, layup and/or bagging procedures, tooling and design. The article further discusses about the impact on various forms of fabric, Honeycomb sandwich panels and molding.

The theoretical basis leading to the creation of a light field with a hexagonal honeycomb structure resembling graphene is considered along with its experimental realization and its interaction with atoms. It is argued that associated with such a light field is an optical dipole potential which leads to the diffraction of the atoms, but the details depend on whether the transverse spread of the atomic wave packet is larger than the transverse dimensions of the optical lattice (resonant Kapitza-Dirac effect) or smaller (optical Stern-Gerlach effect). Another effect in this context involves the creation of gauge fields due to the Berry phase acquired by the atom moving in the light field. The experimental realization of the light field with a honeycomb hexagonal structure is described using holographic methods and we proceed to explore the atom diffraction in the Kapitza-Dirac regime as well as the optical Stern-Gerlach regime, leading to momentum distributions with characteristic but different hexagonal structures. The artificial gauge fields too are shown to have the same hexagonal spatial structure and their magnitude can be significantly large. The effects are discussed with reference to typical parameters for the atoms and the fields. [ABSTRACT FROM AUTHOR]

We systematically study the localization effect in discrete-time quantum walks on a honeycomb network and establish the mathematical framework. We focus on the Grover walk first and rigorously derive the limit form of the walker's state, showing it has a certain probability to be localized at the starting position. The relationship between localization and the initial coin state is concisely represented by a linear map. We also define and calculate the average probability of localization by generating random initial states. Further, coin operators varying with positions are considered and the sufficient condition for localization is discussed. We also similarly analyze another four-state Grover walk. Theoretical predictions are all in accord with numerical simulation results. Finally, our results are compared with previous works to demonstrate the unusual trapping effect of quantum walks on a honeycomb network, as well as the advantages of our method. [ABSTRACT FROM AUTHOR]

Recent advances in realizing artificial gauge fields on optical lattices promise experimental detection of topologically nontrivial energy spectra. Self-similar fractal energy structures generally known as Hofstadter butterflies depend sensitively on the geometry of the underlying lattice, as well as the applied magnetic field. The recent demonstration of an adjustable lattice geometry [L. Tarruell, D. Greif, T. Uehlinger, G. Jotzu, and T. Esslinger, Nature (London) 483,302 (2012)] presents a unique opportunity to study this dependence. In this paper, we calculate the Hofstadter butterflies that can be obtained in such an adjustable lattice and find three qualitatively different regimes. We show that the existence of Dirac points at zero magnetic field does not imply the topological equivalence of spectra at finite field. As the real-space structure evolves from the checkerboard lattice to the honeycomb lattice, two square-lattice Hofstadter butterflies merge to form a honeycomb lattice butterfly. This merging is topologically nontrivial, as it is accomplished by sequential closings of gaps. Ensuing Chern number transfer between the bands can be probed with the adjustable lattice experiments. We also calculate the Chern numbers of the gaps for qualitatively different spectra and discuss the evolution of topological properties with underlying lattice geometry. [ABSTRACT FROM AUTHOR]

Electromagnetic driving in a honeycomb lattice can induce gaps and topological edge states with a structure of increasing complexity as the frequency of the driving lowers. While the high-frequency case is the most simple to analyze we focus on the multiple photon processes allowed in the low-frequency regime to unveil the hierarchy of Floquet edge states. In the case of low intensities an analytical approach allows us to derive effective Hamiltonians and address the topological character of each gap in a constructive manner. At high intensities we obtain the net number of edge states, given by the winding number, with a numerical calculation of the Chern numbers of each Floquet band. Using these methods, we find a hierarchy that resembles that of a Russian nesting doll. This hierarchy classifies the gaps and the associated edge states in different orders according to the electron-photon coupling strength. For large driving intensities, we rely on the numerical calculation of the winding number, illustrated in a map of topological phase transitions. The hierarchy unveiled with the low-energy effective Hamiltonians, along with the map of topological phase transitions, discloses the complexity of the Floquet band structure in the low-frequency regime. The proposed method for obtaining the effective Hamiltonian can be easily adapted to other Dirac Hamiltonians of two-dimensional materials and even the surface of a three-dimensional topological insulator. [ABSTRACT FROM AUTHOR]

We propose a detailed experimental procedure for preparing relativistic vortices, governed by the nonlinear Dirac equation, in a two-dimensional Bose-Einstein condensate (BEC) in a honeycomb optical lattice. Our setup contains Dirac points, in direct analogy to graphene. We determine a range of practical values for all relevant physical parameters needed to realize relativistic vortices in a BEC of 87Rb atoms. Seven distinct vortex types, including Anderson-Toulouse and Mermin-Ho skyrmion textures and half-quantum vortices, are obtained, and their discrete spectra and stability properties are calculated in a weak harmonic trap. We predict that most vortices are stable, with a lifetime between 1 and 10 s. [ABSTRACT FROM AUTHOR]

We investigate Zitterbewegung (ZB) of the ultracold atoms in a tunable honeycomb optical lattice. By tuning the parameters of the lattice one can realize the merging of two Dirac points. The process of two Dirac points merging into a hybrid point implies a topological phase transition from a semimetallic to a band insulator phase. After merging, it presents a linear-quadratic dispersion relation which is linear in one direction and quadric in the other orthogonal direction. We show that ZB occurs isotropically before merging but occurs only in the direction of the linear dispersion after merging. Furthermore, we obtain that ZB is exponentially damping for a negative energy gap but is a stable oscillation for a positive energy gap. The frequency and amplitude of ZB can be controlled in a detectable range, so the phenomena can be observable in the ultracold atomic experiments. [ABSTRACT FROM AUTHOR]

We study the dynamics of extended collective excitations in the pristine honeycomb lattice in the presence of the cubic nonlinearity. We show that not only band-gap excitations but also, stable and quasistable, extended excitations between the two lowest bands of the honeycomb system and labeled as in band exist. We also show that some solutions bifurcate from the saddle points of the Floquet band structure. Among other results, we report the existence of nontrivial stationary solutions even for the Floquet eigenvalue where the Dirac points occur. Numerical findings, in fair agreement with our theoretical predictions, are also reported. [ABSTRACT FROM AUTHOR]

Traveling unidirectional localized edge states in optical honeycomb lattices are analytically constructed. They are found in honeycomb arrays of helical waveguides designed to induce a periodic pseudomagnetic field varying in the direction of propagation. Conditions on whether a given pseudofield supports a traveling edge mode are discussed; a special case of the pseudofields studied agrees with recent experiments. Interesting classes of dispersion relations are obtained. Envelopes of nonlinear edge modes are described by the classical one-dimensional nonlinear Schrödinger equation along the edge. Nonlinear states termed edge solitons are predicted analytically and are found numerically. [ABSTRACT FROM AUTHOR]

The article focuses on ThermHex Waben's thermoplastic polypropylene honeycomb panels, which offer high mechanical performance and surface quality, making them suitable for lightweight applications in various industries, such as automotive, transport, wind and solar, logistics, B&C, and furniture.

The article focuses on a collaboration between EconCore, Airbus, the Technical University of Denmark, and Fraunhofer to develop a potentially recyclable rudder made from thermoplastic honeycomb sandwich composites for an Airbus A320 aircraft, aiming to replace the current rudder structure.

We introduce an explicit scheme to realize Chern insulating phases employing cold atoms trapped in a state-dependent optical lattice and laser-induced tunneling processes. The scheme uses two internal states, a ground state and a long-lived excited state, respectively trapped in separate triangular and honeycomb optical lattices. A resonant laser coherently coupling the two internal states enables hopping between the two sublattices with a Peierls-like phase factor. Although laser-induced hopping by itself does not lead to topological bands with nonzero Chern numbers, we find that such bands emerge when adding an auxiliary lattice that perturbs the lattice structure, effectively turning it at low energies into a realization of the Haldane model: a two-dimensional honeycomb lattice breaking time-reversal symmetry. We investigate the parameters of the resulting tight-binding model using first-principles band-structure calculations to estimate the relevant regime for experimental implementation. [ABSTRACT FROM AUTHOR]

Universal quantum computation can be achieved by simply performing single-spin measurements on a highly entangled resource state, such as cluster states. The family of Affleck-Kennedy-Lieb-Tasaki (AKLT) states has recently been explored; for example, the spin-1 AKLT chain can be used to simulate single-qubit gate operations on a single qubit, and the spin-3/2 two-dimensional AKLT state on the honeycomb lattice can be used as a universal resource. However, it is unclear whether such universality is a coincidence for the specific state or a shared feature in all two-dimensional AKLT states. Here we consider the family of spin-3/2 AKLT states on various trivalent Archimedean lattices and show that in addition to the honeycomb lattice, the spin-3/2 AKLT states on the square octagon (4,82) and the "cross" (4,6,12) lattices are also universal resource, whereas the AKLT state on the "star" (3,122) lattice is likely not due to geometric frustration [ABSTRACT FROM AUTHOR]

Abstract: Meshes are widely used topologies for Networks on Chip (NoC). Honeycomb meshes have better topological properties than Meshes. In order to communicate efficiently in a linear or cyclic manner, it is benefited that there is a Hamiltonian path or Hamiltonian cycle in NoC. In this paper, we give a necessary and sufficient condition for the existence of Hamiltonian path between any pair of vertices in a honeycomb mesh and for the existence of Hamiltonian path in a honeycomb mesh with one faulty vertex. Besides, we give a systematic method to construct a Hamiltonian path in Honeycomb meshes. [Copyright &y& Elsevier]

4 lbs, 24.5-31.5 Atomic Hawx Ultra 130 S GW $850 Designers updated this 130-flex boot by beefing up the polyurethane shell, adding an extra band of plastic around the ankle to reinforce the cuff and improve lateral stiffness and all-around power. Yet the additional plastic plumped this boot's weight by only 3.8 ounces, so testers never felt taxed during boot-packs to far-flung powder stashes. Ski and Snowboard Rossignol Alltrack 130 GW $700 With a 102-millimeter last and 50 degrees of cuff range in walk mode, the Alltrack 130 GW accommodates wide-footed shralpers and gives average feet some wiggle room. [Extracted from the article]

We derive ab initio local Hubbard models for several optical-lattice potentials of current interest, including the honeycomb and kagome lattices, verifying their accuracy on each occasion by comparing the interpolated band structures against the originals. To achieve this, we calculate the maximally localized generalized Wannier basis by implementing the steepest-descent algorithm of Marzari and Vanderbilt [Phys. Rev. B 56,12847 (1997)] directly in one and two dimensions. To avoid local minima we develop an initialization procedure that is both robust and requires no prior knowledge of the optimal Wannier basis. [ABSTRACT FROM AUTHOR]

Motivated by recent experiments on atomic Dirac fermions in a tunable honeycomb optical lattice, we study the attractive Hubbard model of superfluidity in the anisotropic honeycomb lattice. At weak coupling, we find that the maximum mean-field pairing transition temperature, as a function of density and interaction strength, occurs for the case with isotropic hopping amplitudes. In this isotropic case, we go beyond mean-field theory and study collective fluctuations, treating both pairing and density fluctuations for interaction strengths ranging from weak to strong coupling. We find evidence for a sharp sound mode, together with a well-defined Leggett mode over a wide region of the phase diagram. We also calculate the superfluid order parameter and collective modes in the presence of nonzero superfluid flow. The flow-induced softening of these collective modes leads to dynamical instabilities involving stripelike density modulations as well as a Leggett-mode instability associated with the natural sublattice symmetry-breaking charge-ordered state on the honeycomb lattice. The latter provides a nontrivial test for the experimental realization of the one-band Hubbard model. We delineate regimes of the phase diagram where the critical current is limited by depairing or by such collective instabilities, and discuss experimental implications of our results [ABSTRACT FROM AUTHOR]

Abstract: In this study we investigate the effect of imperfect (not perfectly bonded) interfaces on the stiffness and strength of hierarchical polycrystalline materials. As a case study we consider a honeycomb cellular polycrystal used for drilling and cutting tools. The conclusions of the analysis are, however, general and applicable to any material with structural hierarchy. Regarding the stiffness, generalized expressions for the Voigt and Reuss estimates of the bounds to the effective elastic modulus of heterogeneous materials are derived. The generalizations regard two aspects that are not included in the standard Reuss and Voigt estimates. The first novelty consists in considering finite thickness interfaces between the constituents undergoing damage up to final debonding. The second generalization consists of interfaces not perpendicular or parallel to the loading direction, i.e., when isostress or isostrain conditions are not satisfied. In this case, approximate expressions for the effective elastic modulus are obtained by performing a computational homogenization approach. In the second part of the paper, the homogenized response of a representative volume element (RVE) of the honeycomb cellular polycrystalline material with one or two levels of hierarchy is numerically investigated. This is put forward by using the cohesive zone model (CZM) for finite thickness interfaces recently proposed by the authors and implemented in the finite element program FEAP. From tensile tests we find that the interface nonlinearity significantly contributes to the deformability of the material. Increasing the number of hierarchical levels, the deformability increases. The RVE is tested in two different directions and, due to different orientations of the interfaces and Mixed Mode deformation, anisotropy in stiffness and strength is observed. Stiffness anisotropy is amplified by increasing the number of hierarchical levels. Finally, the interaction between interfaces at different hierarchical levels is numerically characterized. A condition for scale separation, which corresponds to the independence of the material tensile strength from the properties of the interfaces in the second level, is established. When this condition is fulfilled, the material microstructure at the second level can be efficiently replaced by an effective homogeneous continuum with a homogenized stress–strain response. From the engineering point of view, the proposed criterion of scale separation suggests how to design the optimal microstructure of a hierarchical level to maximize the material tensile strength. An interpretation of this phenomenon according to the concept of flaw tolerance is finally presented. [Copyright &y& Elsevier]

Inspired by the recent creation of a honeycomb optical lattice and the realization of a Mott-insulating state in a square lattice by shaking, we study here the shaken honeycomb optical lattice. For a periodic shaking of the lattice. Floquet theory may be applied to derive a time-independent Hamiltonian. In this effective description, the hopping parameters are renormalized by a Bessel function, which depends on the shaking direction, amplitude, and frequency. Consequently, the hopping parameters can vanish and even change sign, in an anisotropic manner, thus yielding different band structures. Here, we study the merging and the alignment of Dirac points and dimensional crossovers from the two-dimensional system to one-dimensional chains and zero-dimensional dimers. We also consider next-nearest-neighbor hopping, which breaks the particle-hole symmetry and leads to a metallic phase when it becomes dominant over the nearest-neighbor hopping. Furthermore, we include weak repulsive on-site interactions and find the density profiles for different values of the hopping parameters and interactions, both in a homogeneous system and in the presence of a trapping potential. Our results may be experimentally observed by use of momentum-resolved Raman spectroscopy. [ABSTRACT FROM AUTHOR]

We theoretically investigate the flow of electromagnetic waves in complex honeycomb photonic lattices with local PT symmetries. Such PT structure is introduced via a judicious arrangement of gain and loss across the honeycomb lattice, characterized by a gain and loss parameter y. We found a class of conical diffraction phenomena where the formed cone is brighter and travels along the lattice with a transverse speed proportional to J√&ggr;. [ABSTRACT FROM AUTHOR]

The article describes the design and fabrication of a full-scale prototype fiber-reinforced polymer honeycomb (FRPH) bridge panel installed in Huron County, Ohio as well as the results of the laboratory testing and low-speed truck tests conducted from October 2008 to 2010. The project was funded by a Federal Highway Administration innovative Bridge Program Grant. Results show that the bridge provided a satisfactory lightweight solution for replacement of a steel stringer and wooden deck bridge.

We investigate discrete nondiffracting beams (DNBs) being the foundation of periodic and qt, asiperiodic intensity distributions. Besides the number of interfering plane waves, the phase relation among these waves is decisive to form a particular intensity lattice. In this manner, we systematize different classes of DNBs and present similarities as well as differences. As one prominent instance, we introduce the class of sixfold nondiffracting beams, offering four entirely different transverse intensity distributions: in detail, the hexagonal, kagome, and honeycomb pattern, as well as a hexagonal vortex beam. We further extend our considerations to quasiperiodic structures and show the changeover to Bessel beams. In addition, we introduce a highly flexible implementation of the experimental analog of DNBs, namely discrete pseudo-nondiffracting beams, and present locally resolved intensity and phase measurements, which underline the nondiffracting character of the generated wave fields. [ABSTRACT FROM AUTHOR]

Abstract: Electronic, magnetic, and structural properties of graphene flakes depend sensitively upon the type of edge atoms. We present a simple software tool for determining the type of edge atoms in a honeycomb lattice. The algorithm is based on nearest neighbor counting. Whether an edge atom is of armchair or zigzag type is decided by the unique pattern of its nearest neighbors. Particular attention is paid to the practical aspects of using the tool, as additional features such as extracting out the edges from the lattice could help in analyzing images from transmission microscopy or other experimental probes. Ultimately, the tool in combination with density-functional theory or tight-binding method can also be helpful in correlating the properties of graphene flakes with the different armchair-to-zigzag ratios. Program summary: Program title: edgecount Catalogue identifier: AEIA_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEIA_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 66 685 No. of bytes in distributed program, including test data, etc.: 485 381 Distribution format: tar.gz Programming language: Fortran 90/95 Computer: Most UNIX-based platforms Operating system: Linux, Mac OS Classification: 16.1, 7.8 Nature of problem: Detection and classification of edge atoms in a finite patch of honeycomb lattice. Solution method: Build nearest neighbor (NN) list; assign types to edge atoms on the basis of their NN pattern. Running time: Typically ∼second(s) for all examples. [ABSTRACT FROM AUTHOR]

Abstract: Micro-pillars of anodic aluminium oxide with nano-sized honeycomb channels along the pillar axis exhibit compressive stress–strain response with large excursions corresponding to discrete, inhomogeneous deformation events. Each excursion is found to associate with the severe distortion of a material layer at the pillar’s head, whereas the remaining of the pillar remains intact. The stresses at which these excursions occur do not exhibit any significant dependence on the pillar size. A simple model is proposed to describe the response of pillars under compression, which energetically, as well as kinetically, explains as to why the localized deformation always takes place at the pillar head. Predictions on the occurrence of instability events from this model also quantitatively agree with the experimental observations. [ABSTRACT FROM AUTHOR]

Abstract: The macroscopic mechanical behavior of elliptical cell honeycombs are characterized using couple-stress elasticity theory. General expressions for the couple-stress elastic constants are obtained through a combination of non-dimensional analysis and numerical analysis. The expressions for the six in-plane orthotropic couple-stress compliances are derived in terms of the honeycomb cell size, cell wall thickness, cell ellipticity and the linear elastic properties of the cell wall material. The derived expressions are validated through numerical analyses. [ABSTRACT FROM AUTHOR]

Abstract: Examples of chiral materials include some auxetic materials, bones, some honeycomb structures, as well as composites with inclusions. The chiral effects cannot be described within classical elasticity. In the context of the linear theory of Cosserat elastic solids, we investigate the deformation of a chiral rod subjected to tractions on the lateral surface, to body loads, and to resultant forces and moments on the ends. The work is motivated by the recent interest in the using of the Cosserat elastic solid as model for auxetic composites, carbon nanotubes and bones. The three-dimensional problem is reduced to the study of some generalized plane strain problems. New chiral effects are presented. In the case of cylinders of arbitrary cross-section, the flexure produced by a transversal force, in contrast with the case of achiral materials, is accompanied by extension and bending by terminal couples. The body loads and the tractions on the lateral surface produce extension, flexure, torsion, bending by terminal couples and a plane strain. It is shown that a uniform pressure acting on the lateral surface of a chiral circular cylinder does not produce bending effects. [ABSTRACT FROM AUTHOR]