Symmetric Energy Research Articles

Some remarks on relativistic fluids of divergence type

Relativistic fluids of divergence type constitute a special class of fluids whose states are determined from the knowledge of a scalar generating function χ and a dissipation tensor i.e. a second rank, symmetric and traceless tensor. Both depend upon fourteen variables, known in the literature as Lagrange multipliers, and these multipliers satisfy a symmetric, quasilinear, first order system determined by . For particular choices of the generating function χ, this system can be symmetric-hyperbolic and causal. We show in this work that this characteristic property of fluids of divergence type originates in the overdetermined nature of their dynamical equations. Combining their overdetermined nature with the work of Friedrichs on overdetermined system of conservation laws with more recent work by Boillat, Ruggeri and coworkers, we prove that fluids of divergence type are locally determined by a vector potential depending upon the Lagrange multipliers. For the case where the dynamical variables describing fluid states contain a symmetric energy momentum tensor, this vector potential is the gradient of a scalar field and this field is precisely the generating function χ introduced by Pennisi and independently by Geroch and Lindblom. Examples of scalar generating functions χ are discussed where this system is a symmetric hyperbolic and causal system in an open vicinity of equilibrium states.

Dark Energy Star: Physical Constraints on the Bounds

AbstractIn the present article, we explore a new solution to the Einstein‐Maxwell field equations to describe spherically symmetric, charged and anisotropic dark energy stars. The interior of such stars containing two non‐interacting fluids like dark and normal matter with a relation that the dark energy density is proportional to the energy density of a isotropic matter. We have used modified chaplygin gas equation to define the dark energy part. Also we have defined the interior space‐time through Krori‐Barua (KB) space‐time and matched it with the exterior Reissner‐Nordström space‐time. The well‐behaveness of the physical attributes have been discussed by plotting graphs for three specific compact objects with respect to our solutions. We conclude that all the physical attributes satisfy the required conditions for viability as well as stability and hence our model can be used to characterize dark energy stars for a set of parametric values belong to the present study.

Experimental Research of Symmetrical Airfoil Piezoelectric Energy Harvester Excited by Vortex-Induced Flutter Coupling

In order to solve the problem of self-energy supply of vehicle-mounted micro-sensors, bridge detection and some other low-power electronic devices in their working state, a vortex-induced flutter composite nonlinear piezoelectric energy harvester (VFPEH) with symmetrical airfoils on both sides of a cylindrical bluff body is designed. The VFPEH consists of a cantilever beam, a cylindrical bluff body connected to the free end of the cantilever beam, and two airfoil components symmetrically fixed at both ends of the shaft, which enables coupling between vortex-induced vibration and flutter. The airfoil symmetrically arranged on both sides of the cylindrical bluff body induces the cantilever beam to produce bending and torsional composite vibrations at high wind velocities, realizing energy harvest in the two degrees of freedom motion direction, which can effectively improve the output power of the energy harvester. Based on a wind tunnel experimental platform, the effect of key parameters matching impedance and the diameter of the cylindrical bluff body on the output performance of the VFPEH is investigated, together with the output performance of the classical vortex-induced energy harvester (VEH), the flutter energy harvester (FEH) and the VFPEH. The experimental results show that for the VFPEH under a combination of vortex-induced vibrations and flutter vibrations has a better output performance than the VEH and the FEH when using the same size. The coupling of vortex-induced vibration and flutter can reduce the start-up wind velocity of the VFPEH and expand the wind velocity range of the high output power of the VFPEH. The VFPEH has a better output performance at the cylindrical bluff body diameter of 30 mm and a load resistance of 140 kΩ. When the wind velocity range is 2 m/s–15 m/s, the maximum output power of the VFPEH is 6.47 mW, which is 129.4 times and 24.9 times of the maximum output power of the VEH (0.05 mW) and FEH (0.26 mW), respectively.

Stormier Southern Hemisphere induced by topography and ocean circulation

A defining feature of Earth's present-day climate is that the Southern Hemisphere is stormier than the Northern Hemisphere. Consistently, the Southern Hemisphere has a stronger jet stream and more extreme weather events than the Northern Hemisphere. Understanding the relative importance of land-ocean contrast, including topography, radiative processes, and ocean circulation for determining this storminess asymmetry is important and may be helpful for interpreting projections of future storminess. Here, we show that the stormier Southern Hemisphere is induced by nearly equal contributions from topography and the ocean circulation, which moves energy from the Southern to Northern Hemisphere. These findings are based on 1) diagnostic energetic analyses applied to observations and climate model simulations and 2) modifying surface (land and ocean) boundary conditions in climate model simulations. Flattening topography and prescribing hemispherically symmetric surface energy fluxes (the manifestation of ocean energy transport on the atmosphere) in a climate model reduce the storminess asymmetry from 23 to 12% and 11%, respectively. Finally, we use the energetic perspective to interpret storminess trends since the beginning of the satellite era. We show that the Southern Hemisphere has become stormier, consistent with implied ocean energy transport changes in the Southern Ocean. In the Northern Hemisphere, storminess has not changed significantly consistent with oceanic and radiative (increased absorption of sunlight due to the loss of sea ice and snow) changes opposing one another. The trends are qualitatively consistent with climate model projections.

Design of novel cobalt-based perovskite derivatives using sulfurization as active material of energy storage devices

Metal organic framework (MOF) derivatives have attracted much attention as efficient active material of energy storage device, due to large surface area, excellent pore structure and abundant redox states. Previously ammonia fluoride is used to control morphology of zeolitic imidazolate framework 67 (ZIF-67) and supply NH4+ and F− to enhance charge transfer. More treatments are worthy to apply for improving energy storage ability of this ZIF-67 derivative. In this study, sulfurized ammonium-decorated cobalt fluoride (S-NH4-CoF) is firstly synthesized using ZIF-67 derivative and sulfur powder in the one-step annealing process at different temperatures as active material. The optimized S-NH4-CoF electrode prepared at 400 °C shows specific capacitance (CF) of 462.1 F g−1 at 20 mV s−1, due to round particle-assembled sphere morphology with high surface area and large pore volume, and suitable ratio of cobalt fluoride and cobalt sulfide. The symmetric energy storage device composed of optimized S-NH4-CoF electrodes shows maximum energy density of 30.47 Wh kg−1 at 800 W kg−1. The CF retention of 85% and Coulombic efficiency higher than 97% are obtained after 20,000 charge/discharge times. This study supplies important information about sulfurization on MOF derivatives. Other parameters like sulfurization precursor and duration are worthy to discuss for enhancing energy storage ability of S-NH4-CoF.

Vector Bessel beams: General classification and scattering simulations

Apart from a lot of fundamental interest, vector Bessel beams are widely used in optical manipulation, material processing, and imaging. However, the existing description of such beams remains fragmentary, especially when their scattering by small particles is considered. We propose a new general classification of all existing vortex Bessel beam types in an isotropic medium based on the superposition of transverse Hertz vector potentials. This theoretical framework contains duality and coordinate rotations as elementary matrix operations and naturally describes all relations between various beam types. This leads to various bases for Bessel beams and uncovers the novel beam type with circularly symmetric energy density. We also discuss quadratic functionals of the fields (such as the energy density and Poynting vector) and derive orthogonality relations between various beam types. Altogether, it provides a comprehensive reference of all properties of Bessel beams that may be relevant for applications. Next we generalize the formalism of the Mueller scattering matrices to arbitrary Bessel beams accounting for their vorticity. Finally, we implement these beams in the ADDA code - an open-source parallel implementation of the discrete dipole approximation. This enables easy and efficient simulation of Bessel-beams scattering by particles with arbitrary shape and internal structure.

Influence of the sport specific training background on the symmetry of the single legged vertical counter movement jump among female ballet dancers and volleyball players

IntroductionVertical jumps are the key components of performance in the classical ballet and volleyball. Asymmetry of performance between the lower extremities is a potential risk factor for injury. PurposeThe purpose of this study was to analyse the symmetry of the unilateral vertical countermovement jump (CMJ) in a group of female ballet dancers and in a group of female college volleyball players. MethodsWe tested the CMJ with the dominant and nondominant leg and the bilateral CMJ among 15 female ballet dancers and 15 female volleyball players aged 18–24 years. Ground reaction forces were recorded with the force plate and five variables were analysed - jump height, power, energy, and time to flight and time to maximum force during landing. Results2 × 2 repeated measures of ANOVA indicates that type of sport is influencing some of the single leg CMJ variables (energy used and time to maximal force in landing), there was a significant asymmetry between dominant and non-dominant leg in some of the vertical CMJ variables (CMJ height, energy used and the average power was marginally significant). The interaction between the type of sport and leg dominance however was not significant for all of the analysed CMJ variables indicating no difference in asymmetry between the dominant and non-dominant leg in the two investigated sports. The results expressed in the percentage differences between both legs that is widely used in the scientific literature showed that ballet dancers exhibited more symmetrical CMJ height, power, and energy compared to volleyball players. The average percent difference in CMJ height between the dominant and non-dominant leg was 4.26 (10.60) % and 13.36 (14.72) %, respectively. On average, volleyball players jumped slightly higher at the bilateral CMJ (p < 0.001). ConclusionSport-specific training background could explain the observed contralateral deficit differences between two sport groups. The elements of ballet training could be introduced into the volleyball training to overcome observed this contralateral deficit.

Phase Space Transport in a Symmetric Caldera Potential with Three Index-1 Saddles and No Minima

We apply the method of Lagrangian Descriptors (LDs) to a symmetric Caldera-type potential energy surface which has three index-1 saddles surrounding a relatively flat region that contains no minimum. Using this method we show the phase space transport mechanism that is responsible for the existence and nonexistence of the phenomenon of dynamical matching for this form of Caldera potential energy surface.

Fabrication of Nanocluster-Aggregated Dense Ce2(MoO4)3 Microspherical Architectures for High-Voltage Energy Storage and High Catalytic Energy Conversion Applications

Recent progress has been made toward high-performance electrochemical energy storage and energy conversion devices to overcome the energy crisis. This article highlights the performance enhancement parameter of energy storage devices such as a symmetric supercapacitor and energy conversion such as methanol oxidation and water splitting studies for the generation of efficient oxygen and hydrogen. We have prepared a dense cerium molybdate microspherical architecture by the hydrothermal route, and further physical characterization has been performed to evaluate the structural parameters. Charge storage contributions, external surface charge, and internal surface-accumulated charge are calculated by Dunn’s and Trassati’s approaches. A solid-state symmetric supercapacitor device has been assembled, which exhibits outstanding electrochemical performance with a device capacity of 198 C g–1 at 1 A g–1, a large electrochemical potential window of 2.2 V, an enormous cyclic retention of 89.5% after 10,000 cycles, a maximum specific energy of 60.5 W h kg–1, and a maximum specific power of 10.6 kW kg–1. Furthermore, the prepared microspherical architectures were evaluated for oxygen/hydrogen evolution reactions and methanol oxidation. The prepared electrode exhibits excellent oxygen evolution performance, while keeping the lowest overpotential as 316 mV, and for hydrogen evolution reaction, the overpotential was obtained as 178 mV. The microspherical architecture electrode also exhibits attractive catalytic performance for methanol oxidation and exhibits a maximum current density of 157 mA cm–2, while having an onset potential of 1.314 V (versus RHE). Thus, the prepared nanocluster-aggregated microspherical architecture of Ce2(MoO4)3 can efficiently serve as the next-generation multifunction materials for energy storage and energy conversion applications.

Sulfurization of nickel–cobalt fluoride decorating ammonia ions as efficient active material of supercapacitor

Nickel cobalt fluoride decorating ammonia ions (NCNF) with excellent energy storage ability is proposed by incorporating ammonia fluoride during synthesizing ZIF-67 in our previous work. It is necessary to modify NCNF for achieving better energy storage ability and widen its application. In this study, sulfurization and copper decoration are firstly adopted to enhance energy storage ability of NCNF. Without Cu decoration, aggregations completely convert to separated nanoparticles at sulfurization temperature of 160°C, which also shows partial conversion of NCNF to cobalt sulfide. The highest specific capacitance (CF) of 1666.1 ​F/g (277.7 mAh/g) is achieved for optimized NCNF-derived sulfide, and untreated NCNF electrode only shows a CF value of 519.8 ​F/g (277.7 mAh/g), due to partial sulfurization of the former case with high electrocapacitive property of NCNF and high electrical conductivity of sulfide. Copper is then incorporated using one-step and two-step hydrothermal processes. However, the best performed copper-decorated NCNF-derived sulfide electrode only shows a CF value of 508.5 ​F/g (84.8 mAh/g), due to the dominated formation of copper sulfide and limited appearances of cobalt sulfide and NCNF. A symmetric energy storage device comprising optimized NCNF-derived sulfide electrodes presents a maximum energy density of 8.64 ​Wh/kg at 2.16 ​kW/kg and high capacitance retention of 125% after 13,000 cycles.

Climate Change and Its Impact Worldwide Particularly On Pakistan and Measures to Control Its Effects

Quantitative and qualitative data analysis shows that revolutionary climate changes have been observed in recent decades in world history. The earth’s temperature is rising to the ever-alarming limits the world is facing the noticeable and direct impacts of climate change in the form of extreme weather events, irregular precipitation, reduction in water resources, formless average temperature trends, other damages to natural ecosystems and human health due to green-house gases and anthropogenic emissions. Pakistan is one of the most affected countries globally. Previous studies confirmed the direct relationship of climate changes with drought, migration, flooding, diseases, poverty, un-equality, agriculture, Land and soil devastation, diseases, gender, and the impeding effect on the economy of Pakistan. Comparative excerpts are highlighted and solutions proffered; highlighting climate change policy objectives (CCPOs) based on symmetric principles, i.e., energy, transport, urban and town planning, industry, and agriculture as criteria, with 17 sub-criteria in total and strategies included.

Proton gravitational form factors and mechanical properties in a light-front quark-diquark model

We present our recent calculation of the gravitational form factors (GFFs) of proton using the light-front quark-diquark model constructed by the soft-wall AdS/QCD. We extract the four quark GFFs by calculating the matrix elements of the symmetric energy momentum tensor. Using the D-term we calculate the pressure and shear distributions of quarks inside the proton in the impact parameter space. The GFFs, A(Q2) and B(Q2) are found to be consistent with the lattice QCD, while the qualitative behavior of the D-term form factor is in agreement with the extracted data from the deeply virtual Compton scattering (DVCS) experiments at JLab, the lattice QCD, and the predictions of different phenomenological models.

A Splitting Scheme for Flip-Free Distortion Energies

We introduce a robust optimization method for flip-free distortion energies used, for example, in parametrization, deformation, and volume correspondence. This method can minimize a variety of distortion energies, such as the symmetric Dirichlet energy and our new symmetric gradient energy. We identify and exploit the special structure of distortion energies to employ an operator splitting technique, leading us to propose a novel Alternating Direction Method of Multipliers (ADMM) algorithm to deal with the non-convex, non-smooth nature of distortion energies. The scheme results in an efficient method where the global step involves a single matrix multiplication and the local steps are closed-form per-triangle/per-tetrahedron expressions that are highly parallelizable. The resulting general-purpose optimization algorithm exhibits robustness to flipped triangles and tetrahedra in initial data as well as during the optimization. We establish the convergence of our proposed algorithm under certain conditions and demonstrate applications to parametrization, deformation, and volume correspondence.

Polarized vector oscillons

Oscillons are spatially localized, time-periodic, and long-lived configurations that were primarily proposed in scalar field theories with attractive self-interactions. In this paper, we demonstrate that oscillons also exist in the low-energy effective theory of an interacting massive (real) vector field. We provide two types of vector oscillons with vanishing orbital angular momentum, and approximately spherically symmetric energy density, but not field configurations. These are: (1) ``directional'' oscillons (linearly polarized), with vanishing total intrinsic spin, and (2) ``spinning'' oscillons (circularly polarized) with a macroscopic intrinsic spin equal to $\ensuremath{\hbar}\ifmmode\times\else\texttimes\fi{}$ number of particles in the oscillon. In contrast to the case with only gravitational interactions, the two oscillons have different energy at a fixed particle number even in the nonrelativistic limit. By carrying out relativistic $3+1\mathrm{d}$ simulations, we show that these oscillons can be long-lived (compared to the oscillation time for the fields), and can arise from a range of Gaussian initial spatial profiles. These considerations make vector oscillons potentially relevant during the early universe and in dark photon dark matter, with novel phenomenology related to their polarization.

Particle–hole asymmetry and quantum confinement effects on the magneto-optical response of topological insulator thin-films

Intrinsically broken symmetries in the bulk of topological insulators (TIs) are manifested in their surface states. Despite particle–hole asymmetry in TIs, it has often been assumed that their surface states are characterized by a particle–hole symmetric Dirac energy dispersion. In this work, we demonstrate that the effect of particle–hole asymmetry is essential to correctly describe the energy spectrum and the magneto-optical response in TIs thin-films. In thin-films of TIs with a substantial degree of particle–hole symmetry breaking, such as Sb2Te3, the longitudinal optical conductivity displays absorption peaks arising from optical transitions between bulk and surface Landau levels for low photon energies. The transition energies between the bulk and surface Landau levels exhibit clearly discernable signatures from those between surface Landau levels due to their distinct magnetic field dependence. Bulk contributions to the magneto-optical conductivity in a TI thin-film are enhanced via one type of doping while being suppressed by the other. This asymmetric dependence on the type of doping aids in revealing the particle–hole asymmetry in TI thin-films.

Study of axially symmetric viscous Ricci dark energy model in Brans–Dicke theory

In this paper, we have investigated axially symmetric and anisotropic space–time filled with viscous Ricci dark energy and pressure-less dark matter in the frame-work of Brans–Dicke(BD) theory of gravitation. To solve the field equations, we use the following conditions: (i) the relationship between metric potentials which is obtained from the condition that shear scalar of the model is directly proportional to the expansion scalar, (ii) the average scale factor varies with time as a(t)=[sinh(αt)]1k, and (iii) the bulk viscous coefficient (ξ) as ξ=ξ0+ξ1h+ξ2h′′, where ξ0, ξ1 and ξ2 are constants and h=HH0. We have studied the cosmological parameters, like bulk viscosity coefficient (ξ), effective equation of state (ωeft), deceleration (q), Om diagnostic and cosmological planes like state-finder diagnostics {r,s} and {r,q} planes. And also, we have analyzed the physical behavior of these parameters through pictorial representation. The deceleration and effective equation of state parameters are very close to recent observational data in our model.

Deformation and size effects on electronic properties of toroidal quantum dot in the presence of an off-center donor atom

This work focused on studying the energy changes due to a cylindrical quantum dot (CQD) deformation compared to a toroidal quantum dot (TQD). The energies and the electronic states are studied as a function of the TQD geometrical parameters(RC, Rg, φ0, θ0). The transition energy between the ground and first excited states is also studied. In the framework of the effective mass approximation, we obtained the eigenenergies and eigenfunctions of the nanostructure from the Schrödinger equation solution using the 3D finite difference and finite element methods. Our numerical results show that the donor position significantly affects the electron impurity binding energy; we detected a symmetrical binding energy behavior when the donor atom moves from the center of the first transversal section to the second TQD transversal section. On the other hand, the increases of the TQD volume leads to a strong Coulombic interaction when the impurity is fixed at the center of the effective cross-section, leading to a very important binding energy. Indeed, the main idea of this paper is to compare the electronic properties of a TQD with those in the CQD and to show how the curvature effect reacts on the electron-impurity binding energy.

Solid metal-hydrogen solutions with a symmetric miscibility gap

It is shown that the T-x projection of the miscibility gap in solid interstitial MeH x solutions will be symmetric and the pressure vs . temperature dependence of the corresponding isomorphic phase transformation will be determined by the reaction Me + ( z /2)H 2 = MeH z with a fixed z value attained at T → 0 K, if the mixing Gibbs energy of the solutions is a symmetric two-well function of the H content with a maximum at z /2. Based on these findings and using the literature data for the pure metal Me and the hydride MeH z , it is explained why the experimental dependences of the standard Gibbs energy for the isomorphic transformation between two solid phases of variable composition in the Pd–H and Pd-D systems ( z = 0.63) and in the Ni–H and Ni-D systems ( z = 1) are close to linear in the entire investigated temperature range. • Model of solid solutions Pd–H with a symmetric two-well mixing energy is considered. • The model explains the linear dependence ln P (1/ T ) for formation of palladium hydride. • The formation pressure is determined by the reaction Pd + ( z /2)H 2 = PdH z at z = 0.63 • Deviation of ln P (1/ T ) from linearity in this approximation is 1% at 194.5 ≤ T ≤ 565 K. • Similar results are obtained for the systems Pd-D, Ni–H, and Ni-D.

Domains of the adsorbed benzene monolayer on graphene

We consider the adsorbed benzene monolayer on graphene and show that the monolayer’s structure can be very complicated even for benzene, the simplest representative of the cyclic hydrocarbons. We base this on previous the first principal investigations, which found different energy states of the adsorbed benzene molecule. We find the existence of the six domains (star domains) for the stable molecular monolayer. The representatives of these domains (grains) at the graphene hexagonal layer are star vectors that describe transitions from symmetric high energy state into the stable low symmetric position. In the hexagon lattice of any benzene close pack domain, we introduce the primitive unit vectors, which are twice longer than the graphene primitive unit ones. The symmetry elements of the adsorbed benzene monolayer on graphene are found, left and right domains are introduced. Besides, half-translation of the benzene domains on the graphene primitive unit vectors leads to a further increase in the variety of the domain types. We introduce the selection procedure to decrease the number of the possible domains, find zero-block cells, and the complete number of the benzene domains — eight. We find all types of the structural domains and show their relation with the graphene unit cell construction.

Volumetric Parameterization of the Placenta to a Flattened Template.

We present a volumetric mesh-based algorithm for parameterizing the placenta to a flattened template to enable effective visualization of local anatomy and function. MRI shows potential as a research tool as it provides signals directly related to placental function. However, due to the curved and highly variable in vivo shape of the placenta, interpreting and visualizing these images is difficult. We address interpretation challenges by mapping the placenta so that it resembles the familiar ex vivo shape. We formulate the parameterization as an optimization problem for mapping the placental shape represented by a volumetric mesh to a flattened template. We employ the symmetric Dirichlet energy to control local distortion throughout the volume. Local injectivity in the mapping is enforced by a constrained line search during the gradient descent optimization. We validate our method using a research study of 111 placental shapes extracted from BOLD MRI images. Our mapping achieves sub-voxel accuracy in matching the template while maintaining low distortion throughout the volume. We demonstrate how the resulting flattening of the placenta improves visualization of anatomy and function. Our code is freely available at https://github.com/mabulnaga/placenta-flattening.