Ratio Of Energy Density Research Articles

Investigation on the Linear Energy Storage and Dissipation Laws of Rock Materials Under Uniaxial Compression

To investigate the energy evolution characteristics of rock materials under uniaxial compression, the single-cyclic loading–unloading uniaxial compression tests of four rock materials (Qingshan granite, Yellow sandstone, Longdong limestone and Black sandstone) were conducted under five unloading stress levels. The stress–strain curves and failure characteristics of rock specimens under the single-cyclic loading–unloading uniaxial compression tests basically corresponded with those of under uniaxial compression, which indicates that single-cyclic loading–unloading has minimal effects on the variations in the loading–deformation response of rocks. The input energy density, elastic energy density and dissipated energy density of four rocks under five unloading stress levels were calculated using the graphical integration method, and variation characteristics of those three energy density parameters with different unloading stress levels were explored. The results show that all three energy density parameters above increased nonlinearly with increasing unloading stress level as quadratic polynomial functions. Meanwhile, both the elastic and dissipated energy density increased linearly when the input energy density increased, and the linear energy storage and dissipation laws for rock materials were observed. Furthermore, a linear relationship between the dissipated and elastic energy density was also proposed. Using the linear energy storage or dissipation law, the elastic and dissipated energy density at any stress levels can be calculated, and the internal elastic (or dissipated) energy density at peak compressive strength (the peak elastic and dissipated energy density for short) can be obtained. The ratio of the elastic energy density to dissipated energy density with increasing input energy density was investigated using a new method, and the results show that this ratio tends to be constant at the peak compressive strength of rock specimens.

Effect of process parameters on formability and surface quality of selective laser melted Al-Zn-Sc-Zr alloy from single track to block specimen

The effects of the laser power and the scanning speed on molten pool shape, liquid metal spreading characteristics, and surface quality of the Al-Zn-Sc-Zr alloy fabricated by selective laser melting (SLM) were studied. The results showed that at the highest laser power of 360 W and the lowest scanning speed of 400 mm/s, the width and penetration of single track reached the maximum values of 244 μm and 241 μm. The powders were fully melted, and the liquid metal had more time to spread out when the line energy input is 800 J/m. The hole and balling defects disappeared, and the surface quality of the block specimen was significantly improved. With a decrease in the line energy density, the width, penetration, and overlap ratio of the single track gradually decreased. The surface morphology became rough with less melting and spreading time of the liquid metals. When the line energy density decreased from 800 J/m to 160 J/m, the roughness of the top surface increased from 9.4 to 16.1, and the densities of the block specimen increased from 98.1% to 99.5%.

A peak-strength strain energy storage index for rock burst proneness of rock materials

Judgement of rock burst proneness of rock materials is one of the basic problems in the field of rock burst research. In this study, a peak-strength strain energy storage index is proposed for estimating and classifying the rock burst proneness of rock materials. The method for determining this index is also introduced in this paper. The peak-strength strain energy storage index is defined as the ratio of the elastic strain energy density to the dissipated strain energy density corresponding to the peak compressive strength of rock specimen. In order to obtain the elastic strain energy density and the dissipated strain energy density at the peak strength, a series of single cyclic loading-unloading uniaxial compression tests on nine rock materials were conducted. The relationships between the total input energy density and the elastic strain energy density at different unloading stress levels were investigated. The results show that, for every rock material, the elastic strain energy density increases linearly with the increase of the total input energy density. Based on this linear storage energy law, the elastic & dissipated strain energy density at the peak strength can be calculated for each specimen, and the peak-strength strain energy storage index can be obtained accordingly. A new criterion for rock burst proneness of rock materials is proposed. The rock burst proneness of nine rock materials estimated with the proposed criterion agreed well with the laboratory test results.

Electron and Proton Heating in Transrelativistic Guide Field Reconnection

Abstract The plasma in low-luminosity accretion flows, such as the one around the black hole at the center of M87 or Sgr A* at our Galactic Center, is expected to be collisioness and of two temperatures, with protons hotter than electrons. Here, particle heating is expected to be controlled by magnetic reconnection in the transrelativistic regime , where the magnetization is the ratio of magnetic energy density to plasma enthalpy density. Using large-scale 2D particle-in-cell simulations, we explore for a fiducial how the dissipated magnetic energy is partitioned between electrons and protons as a function of (the ratio of proton thermal pressure to magnetic pressure) and of the strength of a guide field perpendicular to the reversing field B 0. At low , we find that the fraction of initial magnetic energy per particle converted into electron irreversible heat is nearly independent of , whereas protons are heated much less with increasing . As a result, for large , electrons receive the overwhelming majority of irreversible particle heating (∼93% for ). This is significantly different than the antiparallel case , in which irreversible electron heating accounts for only ∼18% of the total particle heating (Rowan et al. 2017). At , when both species start already relativistically hot (for our fiducial ), electrons and protons each receive ∼50% of the irreversible particle heating, regardless of the guide field strength. Our results provide important insights into the plasma physics of electron and proton heating in hot accretion flows around supermassive black holes.

A study of novel high performance and energy dense zeolite composite materials for domestic interseasonal thermochemical energy storage

Thermochemical Energy Storage (TCES) materials can be used to store and release thermal energy during times of high demand for applications such as Domestic Space Heating (DSH) or Domestic Hot Water (DHW). Novel composite materials have been created by 2 methods, i) impregnating zeolites with MgSO4 using a modified wetness impregnation method and ii) forming zeolites impregnated with MgSO4 into 4mm pellets using a pellet preparation method and a binder, these composite pellets have been named ZMK. Differential Scanning Calorimetry (DSC) measurements were used to assess the composite materials energy density and performance ratio. The ZMK pellets were also tested on a larger (200g) scale using an in-situ open fixed bed reactor. It was found that ZMK dehydrates at a temperature of 150˚C with a dehydration enthalpy of 715 J/g, with an overall performance ratio of 85% at a 10mg scale. ZMK was found to have a volumetric energy density of 415MJ/m3 and a specific energy density of 702J/g at a 200g scale when hydrated (discharged) with 68% RH air at 20˚C, making it a suitable candidate for interseasonal TCES.

Application of SN-EMD in Mode Feature Extraction of Ship Radiated Noise

Due to the randomness of added noise, noise-assisted versions based on EMD (empirical mode decomposition) usually cause new “mode mixing” problem. In addition, these algorithms also have problems such as high time-consuming and large recovering error. For the reasons, a new method SN-EMD (Selective Noise-assisted EMD) is put forward in this paper. It determines whether to add noise as assistance by judging whether there is high frequency intermittent component contained in the signal or not. The new method was proved to have the optimal performance by comparing the performance parameters for evaluating the decomposition. In this paper, SN-EMD was used to decompose ship radiated noise. On account of the differences in the original information contained in each mode of radiated noise signals from different ship, we selected the first three modes for processing. Average instantaneous frequency, center frequency, energy density, and energy distribution ratio were extracted as mode feature of ship targets for classification and recognition. Spatial distribution of the feature quantities in three-dimensional space verified similarity of the same target and separability of different targets.

Manipulating Thermal Conductance of Supported Graphene via Surface Hydroxylation of Substrates

Surface functionalization of substrates is a promising strategy to tune thermal transport in supported graphene. In this work, we have conducted molecular dynamics simulations to investigate how the surface hydroxylation of amorphous SiO2 substrate affects heat conduction in supported graphene. The results show that the thermal conductivity of supported graphene is decreased by introducing hydroxyl groups on the substrate surface. The underlying physics of thermal conductivity suppression is explained by analyzing the phonon spectral energy density, lifetime, and participation ratio. We have observed that the surface hydroxylation decreases the phonon lifetime and causes remarkable damping of out-of-plane flexural phonons. Moreover, the hydroxyl groups induce modifications of the graphene configuration, which result in the phonon localization and, correspondingly, the low thermal conductivity. Our findings highlight the importance of the substrate surface on thermal conductivity of supported graphene and provide guidance on the design of substrates to control heat transport in graphene.

Stability and Electronic Properties of Rocksalt (CdO)n, (SrO)n, and (BaO)n Nanoparticles

The low-lying isomeric structures in the shapes of hexagonal prisms and cuboids for (MO)n, M = Cd, Sr, and Ba for n ≤ 45 were explored using density functional theory. The rocksalt cuboid structures are found to be the lowest energy isomers for (MO)n for almost all sizes. Among the cuboid isomers, the particles in approximate aspect ratio of 1:1:1 are found to be most energetically favorable for particles of the same size. Density functional theory exchange-correlation functionals for predicting the stability of the (MO)n particles at the cluster and bulk limits were benchmarked against correlated molecular orbital theory. A fragment-based structure–energy relationship model was used to predict the particle position-related surface energy density and size-related particle aspect ratio transitions for rocksalt (MO)n nanoclusters. The critical sizes at which transitions of the particle aspect ratio may occur for the rocksalt particles were predicted. Linear correlations were found between the ionization pot...

Assessment of sliding block methods performance considering energy-representative parameters

In this research, permanent deformation of ten real earth dams were estimated using all the sliding block models and then, the errors between calculated deformations by each model and observed deformations of earth dams were presented and discussed in detail. The applied motion for estimating displacement of each dam was the recorded acceleration in the dam site. It was indicated that, conservative and non-conservative estimations of each model can be separated by Specific Energy Density and Response Ratio parameters in the time and frequency domains, respectively. It was also shown that, there is a logical relationship between the occurred earthquake-induced displacements and the specific energy density.

Electron and Proton Acceleration in Trans-relativistic Magnetic Reconnection: Dependence on Plasma Beta and Magnetization

Abstract Nonthermal electron acceleration via magnetic reconnection is thought to play an important role in powering the variable X-ray emission from radiatively inefficient accretion flows around black holes. The trans-relativistic regime of magnetic reconnection—where the magnetization σ, defined as the ratio of magnetic energy density to enthalpy density, is ∼1—is frequently encountered in such flows. By means of a large suite of two-dimensional particle-in-cell simulations, we investigate electron and proton acceleration in the trans-relativistic regime. We focus on the dependence of the electron energy spectrum on σ and the proton β (the ratio of proton thermal pressure to magnetic pressure). We find that the electron spectrum in the reconnection region is nonthermal and can be modeled as a power law. At low β, the slope, p, is independent of β and hardens with increasing σ as p ≃ 1.8 + 0.7 / σ . Electrons are primarily accelerated by the nonideal electric field at X-points, either in the initial current layer or in current sheets generated between merging magnetic islands. At higher values of β, the electron power law steepens, and the electron spectrum eventually approaches a Maxwellian distribution for all values of σ. At values of β near β max ≈ 1/4σ, when both electrons and protons are relativistically hot prior to reconnection, the spectra of both species display an additional component at high energies, containing a few percent of particles. These particles are accelerated via a Fermi-like process by bouncing between the reconnection outflow and a stationary magnetic island

Surface effect in axisymmetric Hertzian contact problems

Surface effect in three different axisymmetric Hertzian contact models is investigated in this paper with a recently developed elastic theory for nanostructured materials, including a Boussinesq problem, contact problem between a rigid flat-ended cylindrical indenter and an elastic half space as well as contact problem between a rigid spherical indenter and an elastic half space. With the help of the Love's strain function method and Hankel integral transformation, closed-form solutions of the stress and displacement fields at the surface of an elastic half space subjected to a concentrated force are achieved, based on which the interface tractions and displacements in the three different axisymmetric contact problems can be further obtained. It is found that surface effect in these contact problems can be characterized only by an intrinsic length, i.e., the ratio of the bulk surface energy density to the bulk shear modulus of the indented material. When the contact radius is comparable with the intrinsic length, surface effect is much obvious, leading to a serious deviation between the two solutions predicted respectively by the theoretical model developed for nanomaterials and the classical contact model. A more interesting phenomenon is about surface effect on the indentation hardness, which is found to increase with the reduction of the indenter radius when the external load is fixed, or to increase with the decrease of the external load when the indenter radius keeps unchanged. All the results in this paper should be helpful not only for deep understanding of the surface effect on nano-contact behaviors but also for further revealing the nature of surface effect of nano-indentation hardness.

Optimized removal of natural organic matter by ultrasound-assisted coagulation of recycling drinking water treatment sludge

In previous work we have shown that recycling pre-sonicated drinking water treatment sludge (DWTS) could improve coagulated water quality. Here, the removal of naturally occurring organic matter of source water was further optimized using response surface methodology (RSM) with Box-Behnken Design (BBD). The four variables, i.e., volumetric recycling ratio of DWTS, energy density, ultra-sonication time and duty cycle in an experimental jar test of ultrasound assisted flocculation-coagulation were optimized. All the variables showed a significant effect on dissolved organic carbon (DOC) removal of source water (p < .05), of which the duty cycle had a stronger effect on the removal performance compared to the other independent variables. The predicted optimal DOC removal rate was 36.94%, and this matched well the observed performance of 36.54 ± 0.56%, obtained by ultra-sonicating the sludge prior to recycling using a power input of 1.015 W/mL, an ultra-sonication time of 9 min 50 s, and a duty cycle of 80%, while the volumetric recycling ratio of DWTS was 5.8%. The natural organic matter fractions in the coagulated water samples indicated that recycling sonicated DWTS that had been washed prior to recycling in order to remove solubilized extracellular polymers could enhance removal of hydrophobic acids and 3–30 kDa fractions, but this treatment increased the presence of substances with molecular weight <3 kDa. Humic-like substances were effectively removed while tyrosine-like substances could be enriched. Sludge samples (raw DWTS, sonicated DWTS, sludge formed by recycling raw DWTS, and sludge formed by recycling sonicated DWTS without solubilized extracellular organics) were characterized by XRF, X-ray diffraction patterns and FE-SEM-EDS to reveal possible physical characteristics that could be related to the DOC removal performance.

Augmented longitudinal acoustic trap for scalable microparticle enrichment.

We introduce an acoustic microfluidic device architecture that locally augments the pressure field for separation and enrichment of targeted microparticles in a longitudinal acoustic trap. Pairs of pillar arrays comprise "pseudo walls" that are oriented perpendicular to the inflow direction. Though sample flow is unimpeded, pillar arrays support half-wave resonances that correspond to the array gap width. Positive acoustic contrast particles of supracritical diameter focus to nodal locations of the acoustic field and are held against drag from the bulk fluid motion. Thus, the longitudinal standing bulk acoustic wave (LSBAW) device achieves size-selective and material-specific separation and enrichment of microparticles from a continuous sample flow. A finite element analysis model is used to predict eigenfrequencies of LSBAW architectures with two pillar geometries, slanted and lamellar. Corresponding pressure fields are used to identify longitudinal resonances that are suitable for microparticle enrichment. Optimal operating conditions exhibit maxima in the ratio of acoustic energy density in the LSBAW trap to that in inlet and outlet regions of the microchannel. Model results guide fabrication and experimental evaluation of realized LSBAW assemblies regarding enrichment capability. We demonstrate separation and isolation of 20 μm polystyrene and ∼10 μm antibody-decorated glass beads within both pillar geometries. The results also establish several practical attributes of our approach. The LSBAW device is inherently scalable and enables continuous enrichment at a prescribed location. These features benefit separations applications while also allowing concurrent observation and analysis of trap contents.

Collisionless coupling of a high-β expansion to an ambient, magnetized plasma. I. Rayleigh model and scaling

The dynamics of a magnetized, expanding plasma with a high ratio of kinetic energy density to ambient magnetic field energy density, or β, are examined by adapting a model of gaseous bubbles expanding in liquids as developed by Lord Rayleigh. New features include scale magnitudes and evolution of the electric fields in the system. The collisionless coupling between the expanding and ambient plasma due to these fields is described as well as the relevant scaling relations. Several different responses of the ambient plasma to the expansion are identified in this model, and for most laboratory experiments, ambient ions should be pulled inward, against the expansion due to the dominance of the electrostatic field.

Peridynamic Modeling for Crack Propagation Analysis of Materials

In this paper, the computer simulations are carried out by using the peridynamic theory model with various conditions including quasi-static loads, dynamic loads and crack propagation, branching crack pattern and isotropic materials, orthotropic materials. Three examples, a plate with a hole under quasi-static loading, a plate with a pre-existing crack under dynamic loading and a lamina with a pre-existing crack under quasi-static loading are analyzed by computational simulations. In order to simulate the quasi-static load, an adaptive dynamic relaxation technique is used. In the orthotropic material analysis, a homogenization method is used considering the strain energy density ratio between the classical continuum mechanics and the peridynamic. As a result, crack propagation and branching cracks are observed successfully and the direction and initiation of the crack are also captured within the peridynamic modeling. In case of applying peridynamic used homogenization method to a relatively complicated orthotropic material, it is also verified by comparing with experimental results

Laser-Assisted Removal of Graffiti from Granite: Advantages of the Simultaneous Use of Two Wavelengths

Currently, removal of graffiti from stone monuments is a particularly challenging task. Lasers, being highly controllable and precise tools with minimal chemical waste, offer a key solution in this respect and a significant amount of research has been dedicated to this subject. Studies related to the laser cleaning of carbonate stones (such as limestone and marble) reported the extraction of the graffiti layer, although minimal damage to the substrate can be also detected. Recently, research efforts have been focused on the cleaning of granite, which is a complex stone due to its grained and polymineralic texture. Tests involving different wavelengths indicated that the effectiveness of the cleaning procedure is highly dependent on two components: The composition of the binding medium of the graffiti and the fissure system of the granite. In that direction, the aim of this paper is to investigate and to compare the cleaning effectiveness of two wavelengths emitted from a nanosecond (ns) Q-Switched Nd:YAG laser system (IR at 1064 nm and UV at 355 nm), as well as their simultaneous application at different energy density ratios FIR/FUV. The effectiveness of this combined methodology has been shown in several other cases; i.e., for the removal of pollution crusts from carbonate stones (marble). For this study, three different in composition graffiti paints (blue, black, and silver) were applied on a fine-grained granite originating from the NW Iberian Peninsula. Prior to the irradiation tests, the damage thresholds of the granite, as well as the extraction thresholds of the graffiti, were determined. Then, several tests involving a variety of parameters (fluence value, number of pulses, etc.) were performed and the most satisfactory irradiation conditions from each individual wavelength as well as their combination were compared, based on graffiti extraction level and any damage induced on the granite forming minerals. The analytical techniques used for the evaluation were stereomicroscopy, color measurements in CIELAB and CIELCH color spaces, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) and confocal microscopy. The experiments indicated the superiority of the combined laser cleaning regarding blue and black graffiti extraction.

Particle-in-cell simulation of Buneman instability beyond quasilinear saturation

Spatio-temporal evolution of Buneman instability has been followed numerically till its quasilinear quenching and beyond, using an in-house developed electrostatic 1D particle-in-cell (PIC) simulation code. For different initial drift velocities and for a wide range of electron to ion mass ratios, the growth rate obtained from simulation agrees well with the numerical solution of the fourth order dispersion relation. Quasi-linear saturation of Buneman instability occurs when the ratio of electrostatic field energy density to initial electron drift kinetic energy density reaches up to a constant value, which, as predicted by Hirose [Plasma Phys. 20, 481 (1978)], is independent of initial electron drift velocity but varies with the electron to ion mass ratio (m/M) as ≈(m/M)1/3. This result stands verified in our simulations. The growth of the instability beyond the first saturation (quasilinear saturation) till its final saturation [Ishihara et al., PRL 44, 1404 (1980)] follows an algebraic scaling with time. In contrast to the quasilinear saturation, the ratio of final saturated electrostatic field energy density to initial kinetic energy density is relatively independent of the electron to ion mass ratio and is found from simulation to depend only on the initial drift velocity. Beyond the final saturation, electron phase space holes coupled to large amplitude ion solitary waves, a state known as coupled hole-soliton, have been identified in our simulations. The propagation characteristics (amplitude–speed relation) of these coherent modes, as measured from present simulation, are found to be consistent with the theory of Saeki et al. [PRL 80, 1224 (1998)]. Our studies thus represent the first extensive quantitative comparison between PIC simulation and the fluid/kinetic model of Buneman instability.

Electron and Proton Heating in Transrelativistic Magnetic Reconnection

Abstract Hot collisionless accretion flows, such as the one in Sgr A* at our Galactic center, provide a unique setting for the investigation of magnetic reconnection. Here protons are nonrelativistic, while electrons can be ultrarelativistic. By means of 2D particle-in-cell simulations, we investigate electron and proton heating in the outflows of transrelativistic reconnection (i.e., σ w ∼ 0.1 – 1 , where the magnetization σ w is the ratio of magnetic energy density to enthalpy density). For both electrons and protons, we find that heating at high β i (here β i is the ratio of proton thermal pressure to magnetic pressure) is dominated by adiabatic compression (“adiabatic heating”), while at low β i it is accompanied by a genuine increase in entropy (“irreversible heating”). For our fiducial σ w = 0.1 , the irreversible heating efficiency at β i ≲ 1 is nearly independent of the electron-to-proton temperature ratio T e / T i (which we vary from 0.1 up to 1), and it asymptotes to ∼ 2 % of the inflowing magnetic energy in the low- β i limit. Protons are heated more efficiently than electrons at low and moderate β i (by a factor of ∼7), whereas the electron and proton heating efficiencies become comparable at β i ∼ 2 if T e / T i = 1 , when both species start already relativistically hot. We find comparable heating efficiencies between the two species also in the limit of relativistic reconnection ( σ w ≳ 1 ). Our results have important implications for the two-temperature nature of collisionless accretion flows and may provide the subgrid physics needed in general relativistic MHD simulations.

Constraining the equation of state with identified particle spectra

We show that in a central nucleus-nucleus collision, the variation of the mean transverse mass with the multiplicity is determined, up to a rescaling, by the variation of the energy over entropy ratio as a function of the entropy density, thus providing a direct link between experimental data and the equation of state. Each colliding energy thus probes the equation of state at an effective entropy density, whose approximate value is $19$ fm$^{-3}$ for Au+Au collisions at 200 GeV and $41$ fm$^{-3}$ for Pb+Pb collisions at 2.76 TeV, corresponding to temperatures of $227$ MeV and $279$ MeV if the equation of state is taken from lattice calculations. The relative change of the mean transverse mass as a function of the colliding energy gives a direct measure of the pressure over energy density ratio $P/\epsilon$, at the corresponding effective density. Using RHIC and LHC data, we obtain $P/\epsilon=0.21\pm 0.10$, in agreement with the lattice value $P/\epsilon=0.23$ in the corresponding temperature range. Measurements over a wide range of colliding energies using a single detector with good particle identification would help reducing the error.

Dynamics of coupled phantom and tachyon fields

In this paper, we apply the dynamical analysis to a coupled phantom field with scaling potential taking particular forms of the coupling (linear and combination of linear), and present phase space analysis. We investigate if there exists a late time accelerated scaling attractor that has the ratio of dark energy and dark matter densities of the order one. We observe that the scrutinized couplings cannot alleviate the coincidence problem, however, they acquire stable late time accelerated solutions. We also discuss a coupled tachyon field with inverse square potential assuming linear coupling.