Symmetric Sheet Research Articles

Phyllotaxis: Leaf arrangement on a horizontal branch and crystallographic borders

Phyllotaxis is an orderly arrangement of leaves on plant stems and branches. The natural reason of this arrangement is that each species based on the habitat conditions in the course of evolution in one way or another solved the problem of optimising the light flux reaching each leaf and providing photosynthesis. The found optimum was fixed in the genotype and became a species phenotypic trait. In a scientific study, it should be recorded with a reliability that allows for small fluctuations inherent in plant forms under the influence of the environment. Crystallography methods are used to describe the arrangement of leaves. In the course of the study, it has been proposed to describe the arrangement of leaves on a horizontal branch and a vertical stem using the theory of crystallographic borders in the first case, and helical axes – in the second. When describing the arrangement of leaves on a horizontal branch, seven types of crystallographic borders turned out to be theoretically consistent. The nomenclature of types according to the generating operations of symmetry is considered unambiguously fixing the orthogonal increment of a symmetrical sheet (PT, ST, RPT, PT*) and oblique – symmetrical and asymmetrical (T, T*, RT); their botanical prototypes have been established. The arrangement of leaves in many plants is not described by the proposed apparatus (they optimize the light flux differently), which guides scientists to search for deeper patterns and methods of mathematical description.

Effect of Rolling Process on the Microstructure and Mechanical Properties of TC4/6061/AZ31B/6061/TC4 Symmetrical Clad Sheets

Effect of Rolling Process on the Microstructure and Mechanical Properties of TC4/6061/AZ31B/6061/TC4 Symmetrical Clad Sheets

Measurement of alternating and rotational magnetostrictions of Non-oriented silicon steel sheets

Extensive numerical analyses and experimental tests have shown that while major regions of magnetic cores in electromagnetic devices, such as transformers and rotating electric machines, are dominated by the alternating magnetic fields, the rotating magnetic fields exist in the corner joints of multi-phase transformers and the yoke area behind the teeth of rotating electric machines. These magnetic fields cause core losses due to hysteresis and eddy currents, mechanical vibration and acoustic noises due to magnetostriction. Many studies have been reported in the literature on alternating and rotational core losses and alternating magnetostriction, but not so much on rotational magnetostriction, especially in non-oriented (NO) silicon steel sheets. The vibration and noise caused by rotational magnetostriction are much higher than those caused by alternating magnetostriction. This paper reports the development of a magnetostriction measurement system consisting of a 2D symmetrical single sheet tester (SST) and resistance strain gauges. The selection considerations of resistance strain gauges are summarized. The alternating and rotational magnetostriction characteristics of a NO silicon steel, B35A300 (0.35 mm), are measured. Because the rotating magnetic field in the stator is not always ideally circular but more often elliptical, the magnetostriction under elliptical magnetizations with different axis ratios is also measured. The magnetostriction anisotropy of the NO steel sheet is observed and analyzed. The elongation and contraction under alternating, circular and elliptical rotating magnetizations with different axis ratios are discussed. The results can provide data support for calculating and designing multi-phase transformers and rotating electric machines under different types of magnetizations. The research can provide theoretical and practical guidance for mitigating mechanical vibration and acoustic noise caused by magnetostriction.

Quadratic regression analysis for nonlinear heat source/sink and mathematical Fourier heat law influences on Reiner-Philippoff hybrid nanofluid flow applying Galerkin finite element method

BackgroundScientists across the world have tried to explore the effect of non-Newtonian fluids moving over a symmetric stretchable sheet with the presence of diverse influences revealed in this study due to its tremendous applications in various engineering and industrialized sectors like aerodynamics extrusion of plastic surfaces, condensation procedure of metal symmetric plate in a refrigeration immersion, and extrusion of a polymeric surface from a dye.Proposed modelReiner-Philippoff fluids flowing related to a symmetric stretch surface with the inclusion of effects like Forchheimer velocity, thermal radiative, and Cattaneo Christov heat fluxing are considered in the momentum and temperature equation. Novel tetra hybrid nanoparticles are considered to check the thermo physical behaviour of the proposed model. MethodologyThe showed PDEs are transformed into ODEs with the utilization of symmetric and self-similarity variables and further attempted numerically with the assistance of the Galerkin finite element methodology (G-FEM). The obtained findings are scrutinized in the form of figures and tables.FindingsFrom obtained outcomes, it is perceived that the heat transfer Nusselt magnifies extra in the instance of tetra hybrid nanofluids (THNFs) in disparity to tri and di hybrid nanoparticles. Darcy Forcheeimer effect Fr diminishes the fluid velocity and the temperature outline amplifies owed to amplification in thermal radiative variable Rd. The insertion of nanoparticles supports in the stabilizating of a nanofluid's flowand provides the symmetric of thestructure. Error in heat transfer Nusselt number diminishes by the virtue of magnification in Rd and the heat deliverance phenomenon magnifies as a consequence of enlargement in the thermal relaxation constraint.Practical application of the proposed modelDue to its particle use in manufacturing and engineering for shells that expand and contract, like stretchable (shrinkable) packaging, bundle wrapping, hot roll, sheet material extrusion, wire roll, glass fiber manufacturing, metallic packags, and aluminum bottles manufacturing, parabolic tough surface collectors, cooling of thermal reactors, polymer production, etc., the examination of two-dimensional flowing over an extending shallow has attracted attention. The proposed model outcomes are utilized in order the enhance heat transfer of the various liquids by utilizing tetra hybrid nanoparticles and effects like nonlinear based thermal radiation, Cattaneo-Christov heat flux and heat source/sink phenomenon.NoveltyThe effort is novel in its sagacity that no nanofluid model has been developed yet to examine the effect of tetra hybrid nanoparticles on liquid moving over any sort of surface.

Graphene-integrated hybridized metamaterials for wide-angle tunable THz absorbers

Metamaterial absorbers with excellent absorption properties and real-time tunability are desirable for practical applications. In this paper, we design and numerically investigate a polarization insensitive wide-angle metamaterial absorber with tunable absorption strength formed by finite-length symmetric metallic plates and graphene sheet. This structure achieves a near perfect absorption, and remains highly absorptive with wide incident-angle, higher than 80% at 60o for TE mode and around 90% at 70o for TM mode. Absorption strength can be varied between 97% and 52% by controlling the Fermi energy of graphene while the operating frequency remains relatively stable. Also without the presence of a ground plane as in other conventional absorbers, waves outside of the absorption band are allowed to travel through. The absorbing principle and absorption tunability mechanism are elucidated using effective medium analysis and finite integration simulations.

Optimization and Characterization of Polyurethane Electro-Spun Nano-Membranes Used for the Surfaces of Sound Absorbent Multi-Layer Sheets

With more and more attention paid to the quality of life, noise pollution has been ranked the third in environmental pollution. In this study a symmetrical multi-layer sheet was designed for a sound absorbent material. Needleless electro-spinning nano-membranes of polyurethane (PU) were used as the surfaces of the sound absorbent multi-layer sheets. The effects of the PU concentration, solvent ratio, membrane thickness and solvent additives on the surface morphology of the nano-membranes and the sound absorption coefficient of the sound absorbent sheets were carefully investigated by scanning electron microscopy and sound absorption measurements. The results showed that the optimal spinning solution was 10 wt.% PU and the solvents ratio of N,N-dimethylformamide (DMF) and tetrahydrofuran (THF) at 1:1. Under this condition, the average sound absorption coefficient of the multi-layer sheets increased from 0.29 for the 0 mm nano-membranes to 0.57 for the 1.2 mm nano-membranes (spinning time 240 minutes). For the nano-membranes in the range of 0.2–1.2 mm, it was noted that the average sound absorption factor of the multi-layer sheets increased with the increasing of the nano-membranes’ thickness and the absorption frequency for which the highest sound absorption coefficient occurred moved to lower frequencies with the increasing of the membranes’ thickness. By adding sodium dodecyl sulfonate (0.5 wt.%) and sodium chloride (1.0 wt.%) into the optimal solution, a nano-membrane with a nano-cobweb structure of 100% coverage rate was formed. Under the spinning condition of 10 wt.% PU, 1.0 wt.% NaCl, 0.5 wt.% SDS, 1:1 DMF/THF and 240 minutes, a nano-cobweb multi-layer material with an average sound absorption factor of 0.63 was obtained. Although not a large increase from the sound absorption coefficient for the nano-membrane multi-layer sheet material of 0.57, the results showed that the multi-layer sheet with nano-cobweb layer had a great improvement of sound absorption in the range of 500–2000 Hz relative to the nano-membranes. Therefore, a good sound absorption sheet with multi-layer structures was obtained successfully.

Plastic forming processes of transverse non-homogeneous composite metallic sheets

Abstract In this work an analysis of the radial stress and velocity fields is performed according to the J 2 flow theory for a rigid/perfectly plastic material. The flow field is used to simulate the forming processes of sheets. The significant achievement of this paper is the generalization of the work by Nadai & Hill for homogenous material in the sense of its yield stress, to a material with general transverse non-homogeneity. In Addition, a special un-coupled form of the system of equations is obtained where the task of solving it reduces to the solution of a single non-linear algebraic differential equation for the shear stress. A semi-analytical solution is attained solving numerically this equation and the rest of the stresses term together with the velocity field is calculated analytically. As a case study a tri-layered symmetrical sheet is chosen for two configurations: soft inner core and hard coating, hard inner core and soft coating. The main practical outcome of this work is the derivation of the validity limit for radial solution by mapping the “state space” that encompasses all possible configurations of the forming process. This configuration mapping defines the “safe” range of configurations parameters in which flawless processes can be achieved. Several aspects are researched: the ratio of material's properties of two adjacent layers, the location of layers interface and friction coefficient with the walls of the dies.

Simulation of interaction behavior between dislocation and graphene during nanoindentation of graphene/aluminum matrix nanocomposites

Graphene has been thought to be an ideal reinforcement material for metal matrix composite due to its superior mechanical properties and unique two-dimensional geometry. However, the deformation mechanism of graphene/aluminum matrix composite is still unclear. In this paper, molecular dynamics simulation is used to elucidate the evolution details of the dislocation microstructure and the underlying interaction behavior between dislocation and graphene during nanoindentation of the graphene/aluminum matrix composite with various graphene orientations. To this end, four different cases, i.e. the pure aluminum and the graphene/aluminum matrix composite with the graphene orientation of 90°, 45° and 0° are examined, respectively. Based on the force-indentation depth curve, the interaction behavior between dislocation and graphene and its effect on the plastic zone are analyzed. The results indicate that the graphene can act as an effective dislocation motion barrier, and the elastic deformation of graphene can occur locally along the direction of dislocation slip. Using the visualization technique of dislocation extraction algorithm, the nucleation and propagation of dislocation are investigated. The results show that the differences in interaction behavior between dislocation and graphene with various orientations affect the spreading trend of the plastic zone and the blocking strength of graphene to dislocation. For the composite with the graphene orientations of 45° and 0°, the interaction between graphene and dislocation causes the number of dislocations to increase. Additionally, the plastic zone of the composite with the graphene orientation of 45° is tangent to two symmetrical graphene sheets. For the composite with the graphene orientation of 90°, the interaction between graphene and dislocation shortens the total length of the dislocation line, and the volume shrinkage of plastic zone is most significant after indenter retraction. Here, the hardness is also calculated to quantitatively evaluate the influence of graphene orientation on the mechanical properties of graphene/aluminum matrix composite. The hardness of the composite with the graphene orientation of 45° is highest, which is due to the decrease of the volume of the plastic zone and the increase of dislocation number. The decrease of the hardness of the composite with the graphene orientation of 90° is attributed to the reduction of dislocation number in the plastic zone. However, for the composite with the graphene orientation of 0°, the interaction between graphene and dislocation results in the softening effect, because of a wide range of elastic deformation in the graphene plane. The study can provide a certain theoretical guidance for designing and preparing the high-performance graphene/metal matrix composites.

Control of vortex-induced vibrations of the cylinder by using split-ter plates immersed in the cylinder wake at low Reynolds number

The vortex-induced vibrations of a cylinder with two plates symmetrically distributed along the centerline of the wake are studied by using the fluid-structure interaction simulations on the Arbitrary Lagrangian-Eulerian method. In this study, the different geo-metrical distribution parameters of the splitter plates and inflow velocities are taken into account. The physical mechanisms of vortex-induced vibration of the cylinder with symmetrical plates are revealed from the cylinder amplitude, hydrodynamic force characteristics, vortex shedding frequency, and flow pattern modification. The results show that the dynamic interaction between the vortex shed from the oscillation cylinder and plates is responsible for the wake stabilization mechanism, and the stable wake and the dynamic response reduction of the main cylinder can be achieved at a wide range of reduced velocities by placing sym-metrical sheets at suitable locations.

Planar Airy beam light-sheet for two-photon microscopy.

We demonstrate the first planar Airy light-sheet microscope. Fluorescence light-sheet microscopy has become the method of choice to study large biological samples with cellular or sub-cellular resolution. The propagation-invariant Airy beam enables a ten-fold increase in field-of-view with single-photon excitation; however, the characteristic asymmetry of the light-sheet limits its potential for multi-photon excitation. Here we show how a planar light-sheet can be formed from the curved propagation-invariant Airy beam. The resulting symmetric light sheet excites two-photon fluorescence uniformly across an extended field-of-view without the need for deconvolution. We demonstrate the method for rapid two-photon imaging of large volumes of neuronal tissue.

Mechanical properties, radiation mitigation and fire resistance of OPC-recycled glass powder composites containing nanoparticles

The main target of this research is the utilization of low- cost nanoparticles as substantive additions for bolstering the physicomechanical, mitigation of gamma radiation, thermal stability and morphological characteristics of OPC-recycled glass powder hardened composites. Nano MgO and MgFe2O4 spinel NPs were synthesized via the sol–gel route. Characterization of MgO (NM) and MgFe2O4 (NMF) spinel NPs was done using XRD, SEM, TEM, and EDX techniques. Compressive strength, water absorption, bulk density, and total porosity results revealed that partial replacement of OPC by different ratios of waste glass powder waste (WGP) affect negatively on the physicomechanical properties of hardened composites. Inclusion of NPs (NM or NMF) 0.5 and 1 mass % boosts the physicomechanical features of different OPC-WGP hardened composites at most curing ages. The activity of synthesized MgO and MgFe2O4 NPs was affirmed via TGA/DTG and XRD techniques which indicated the formation of diverse hydration yields like CSHs, AFt, AFm, CASHs, MH, CAHs, MSH, CFSH, and CFH that enhances the physicomechanical characteristics as well as the γ- rays shielding % of different OPC-WGP hardened nanocomposites. The thermal stability test was performed at elevated temperatures (300, 500 and 700 °C) for 180 min for all hardened prepared composites after curing for 28 days under normal conditions. The results indicated that the composite containing OPC-10WGP-0.5NMF showed the highest thermal stability. These results were confirmed via SEM/EDX images which displayed a compact and closely packed microstructure of rods-like crystals of CSHs, stacked plates of CASHs, ettringite fibers and symmetrical hexagonal sheets of CH.

Electron microscopic study of Golgi-impregnated and gold-toned neurons and fibers in the claustrum of the cat.

The claustrum is a subcortical nucleus found in the telencephalon of all placental mammals. It is a symmetrical, thin and irregular sheet of grey matter which lies between the inner surface of the insular cortex and the outer surface of the putamen. The claustrum has extensive connections with the visual, auditory, somatosensory and motor regions of the cortex, as well as with subcortical and allocortical regions. The aim of this study was to provide a detailed description of the morphology of different types of Golgi-impregnated and gold-toned neurons and fibers in the dorsal claustrum of the cat employing the combined Golgi-electron microscope Fairén method. We were able to distinguish two major types of neurons: those with dendritic spines (spiny) and those without dendritic spines (aspiny). In both groups we observed large (21-40µm in diameter), medium-sized (16-21µm in diameter) and small cells (10-16µm in diameter), describing their ultrastructural organization and characteristic features, including the presence of terminal boutons. These ultrastructural findings allow us to conclude that large and medium-sized spiny claustral neurons are indeed efferent neurons, projecting to the cortex, while the small spiny and the different types of aspiny neurons are most likely inhibitory local circuit interneurons. The findings in the present study will hopefully contribute to a better understanding of the role of the claustrum.

Current sheet bending as destabilizing factor in magnetotail dynamics

The problem of the magnetohydrodynamical stability of bent magnetotail current sheets is considered by means of 2.5-dimensional numerical simulations. This study is focused on the cross-tail transversal mode, modeling the magnetotail flapping motions, at the background of the Kan-like magnetoplasma equilibrium. It is found that in symmetrical current sheets, both stable and unstable branches of the solution may coexist; the growth rate of the unstable mode is rather small, so that the sheet may be considered as stable at the substorm timescale. With the increasing dipole tilt angle, the sheet bends and the growth rate rises. For sufficiently large tilt angles, the stable branch of the solution disappears. Thereby, the sheet destabilization timescale shortens for an order of magnitude, down to several minutes. The analysis of the background parameters has shown that stability loss is not related to buoyancy; it is controlled by the cross-sheet distribution of the total pressure.

DFT Optimization of Isolated Molecular Chain Sheet Models Constituting Native Cellulose Crystal Structures.

Because of high crystallinity and natural abundance, the crystal structures of the native cellulose allomorphs have been theoretically investigated to elucidate the cellulose chain packing schemes. Here, we report systematic structure optimization of cellulose chain sheet models isolated from the cellulose Iα and Iβ crystals by density functional theory (DFT). For each allomorph, the three-dimensional chain packing structure was partitioned along each of the three main crystal planes to construct either a flat chain sheet model or two stacked chain sheet models, each consisting of four cello-octamers. Various combinations of the basis set and DFT functional were investigated. The flat chain sheet models constituting the cellulose Iα (110) and Iβ (100) planes, where the cellulose chains are mainly linked by intermolecular hydrogen bonds, exhibit a right-handed twist. More uniform and symmetrical sheet twists are observed when the flat chain sheet models are optimized using a basis set with diffuse functions (6-31+G(d,p)). The intermolecular interactions are more stable when the chain sheet models are optimized with the two hybrid functionals CAM-B3LYP and M06-2X. Optimization of the two stacked chain sheet models, where van der Waals interactions predominated between adjacent chains, gave differing results; those retaining the initial structures and those losing the sheet appearance, corresponding to the cellulose Iα/Iβ (010)/(11̅0) and (100)/(110) chain sheet models, respectively. The cellulose Iβ (11̅0) chain sheet model is more stable using the M06-2X functional than using the CAM-B3LYP functional.

Modelling, Simulation and Control of Incremental Sheet Metal Forming Process using CNC Machine Tool

Incremental sheet forming (ISF) is an advanced metal forming technology. Local progressive deformation of the metal sheet is achieved to get desired shape through ISF. It is gaining popularity in customized production. However, ISF has lower geometric accuracy compared to the conventional sheet metal forming methods such as bending, deep drawing and stamping. The geometric accuracy can be improved by adopting suitable control system strategy in machine tool. Hence this paper deals with the modelling and simulation of ISF CNC machine tool to address this issue. The CNC milling machine model was developed using CAD and kinematics. A mechanistic model was developed by integrating separately developed models of all mechanical and electrical components of CNC machine tool. Cascade control strategies were applied and compared to find the most accurate one. The best control strategy was also validated for ISF using two different symmetric sheet metal CAD models.

Drop deformation by laser-pulse impact

A free falling, absorbing liquid drop hit by a nanosecond laser pulse experiences a strong recoil pressure kick. As a consequence, the drop propels forward and deforms into a thin sheet which eventually fragments. We study how the drop deformation depends on the pulse shape and drop properties. We first derive the velocity field inside the drop on the time scale of the pressure pulse, when the drop is still spherical. This yields the kinetic energy partition inside the drop, which precisely measures the deformation rate with respect to the propulsion rate, before surface tension comes into play. On the time scale where surface tension is important, the drop has evolved into a thin sheet. Its expansion dynamics is described with a slender-slope model, which uses the impulsive energy partition as an initial condition. Completed with boundary integral simulations, this two-stage model explains the entire drop dynamics and its dependence on the pulse shape: for a given propulsion, a tightly focused pulse results in a thin curved sheet which maximizes the lateral expansion, while a uniform illumination yields a smaller expansion but a flat symmetric sheet, in good agreement with experimental observations.

A moving-point approach to model shallow ice sheets: a study case with radially symmetrical ice sheets

Abstract. Predicting the evolution of ice sheets requires numerical models able to accurately track the migration of ice sheet continental margins or grounding lines. We introduce a physically based moving-point approach for the flow of ice sheets based on the conservation of local masses. This allows the ice sheet margins to be tracked explicitly. Our approach is also well suited to capture waiting-time behaviour efficiently. A finite-difference moving-point scheme is derived and applied in a simplified context (continental radially symmetrical shallow ice approximation). The scheme, which is inexpensive, is verified by comparing the results with steady states obtained from an analytic solution and with exact moving-margin transient solutions. In both cases the scheme is able to track the position of the ice sheet margin with high accuracy.

Improved CO2 separation performance of Matrimid®5218 membrane by addition of low molecular weight polyethylene glycol

AbstractPolyethylene glycols have received worldwide attention as a highly permeable CO2‐philic polymer in carbon dioxide separation applications. In this study, we investigated the influence of a low molecular weight polyethylene glycol (PEG 200) on physicochemical, morphological, and gas separation properties of Matrimid®5218 as a novel polymer blend. Both symmetric and asymmetric Matrimid flat sheet membranes with 0–20 wt.% PEG were prepared via a dense film‐casting method. The miscibility of blends at low PEG concentrations (3–5 wt.%) was confirmed by differential scanning calorimetry (DSC) and polarized light microscopy (PLM). Moreover, the blends were partially miscible at higher PEG concentrations (10–20 wt.%). Matrimid/PEG molecular interactions were further studied by FTIR and XRD analysis. SEM images indicated an impressive influence of PEG on the symmetric structure of Matrimid membrane. An asymmetric structure with a dense thin skin layer and a highly porous sub‐layer was observed for the blends containing 10–20 wt.% PEG. The CO2 permeability and CO2/CH4 selectivity of the best‐yield CO2‐selective blend membrane (Matrimid/PEG (95:5)) incvreased about 25% (from 7.68 to 9.62 Barrer) and 15% (from 35 to 40) compared to pure Matrimid, respectively. Furthermore studying the plasticization pressures of the membranes revealed that the more PEG content in blend the less the plasticization pressure obtained. © 2015 Society of Chemical Industry and John Wiley & Sons, Ltd

On filtration of a liquid from a foundation pit fenced with sheet piles

Liquid flow from a foundation pit fenced with symmetric Zhukovskii sheet piles in the presence of a well-permeable head water-bearing horizon and infiltration onto the free surface is considered within the framework of plane steadystate filtration. For studying this flow, a mixed multiparametric boundary-value problem of the theory of analytical functions is formulated and solved with the Polubarinova-Kochina method. An algorithm of calculation of the characteristic dimensions of the flow diagram is developed based on this model. Results of numerical calculations and an analysis of the influence of all physical parameters of the model are given. Limiting cases of motion are noted which are related to the absence of upthrust in the well-permeable underlying bed and to the transformation of the foundation pit into a submergence band semiinfinite on the left.

Effect of Process Parameters on Quality of Cold Spinned Tube Head

Metal spinning can be used to produce hollow, axially symmetric sheet metal parts with low tooling and production costs, high flexibility, and low waste. Spinning parameters determine the quality of the spinned parts and are of interest for enabling the spinning of thick sheet metals. In this study, conventional metal spinning was conducted on a 6 mm thick low carbon steel with process below its recrystallization temperature to fabricate tube head, requiring maximum deflection of about 90º at its edge. Spinning parameters varied were temperature (at room temperature and 300°C), feed (2 mm and 5 mm), and spinning speed (200 rpm and 250 rpm). Evaluation was made on the resulted surface morphology, thickness variation, and further analysis on hardness and microstructure of the spinned tube head. The resulted tube heads were of acceptable quality in terms of surface morphology and thickness variation, while hardness and microstructure analysis showed that inner parts of the workpiece were not affected by the spinning process.