Different Values Of Density Research Articles

Dynamic properties of polyurethane from resonant column tests for numerical GSI study

The paper focuses on the detailed analysis of the dynamic characterisation of polyurethane to evaluate the effects of polyurethane injections into soil with the aim of geotechnical seismic isolation. To determine the dynamic properties, resonant column (RC) tests were performed at the University Kore of Enna (Italy) on specimens of pure polyurethane with different values of density and subjected to different mean confining pressures. The results obtained by means of RC tests, in terms of shear modulus G and the damping ratio D as a function of shear strain γc, allowed to develop an analytical formulation for G-γc and D-γc curves, taking into account the linear relationship with density, of both the maximum value of shear modulus Gmax and the minimum value of damping ratio Dmin. The analytical formulation derived from the experimental results is applied for ground response seismic analyses of cohesive soils injected with polyurethane, using a finite element code. The numerical results show that the polyurethane injections reduce the value of maximum acceleration on the ground surface and the reduction varies with the thickness of the soil modified by polyurethane injections.

Effects of nonthermal electrons and ion beams on ion-acoustic double layers in warm ion plasma

The effects of nonthermal electrons and ion beams on the ion acoustic double layers in warm ion plasma have been studied using the pseudopotential technique. Sagdeev potential of ion-acoustic wave in the plasma has been derived and the solution of ion acoustic double layers has been obtained. The critical value of nonthermal parameter of electrons for existence of double layers is obtained and discussed. The profiles of double layers in the plasma are drawn taking different values of density and temperature of ion beams, and the nonthermal parameter of electrons obeying the critical condition. It has been shown that both compressive and rarefactive double layers are excited in the plasma depending on the values of nonthermal electrons and ion beam parameters. The width of double layers is also graphically discussed. The results are new and may be useful in understanding the acceleration processes of charged particles in space plasma.

Влияние плотности цементно-песчаной матрицы и вида стальной фибры на плотность и модуль упругости сталефибробетонов при нагреве в процессе пожара

The paper considers the results of the impact of high temperatures during the fire on changes in the density and elasticity modulus of steel fiber reinforced concrete (SFRC) at different values of density of the cement-sand matrix corresponding to its flexural strength of 5.0 and 8.5 MPa. It is shown that in the temperature range from 20 to 1100 °C, the diagrams «Density of steel fiber reinforced concrete - heating temperature» are linear and their shape does not depend on the type of fiber and its content in steel fiber reinforced concrete. The results of the performed studies allow determining the change in the elastic modulus of the SFRC after heating.

Relationship Between Depth of Seismicity and Heat Flow: The Case of the Gargano Area (Italy)

We consider a thermo-rheological model made of a viscoelastic half-space with Maxwell rheology and temperature-dependent viscosity. The half-space is made of layers with different values of density, thermal conductivity, activation energy and heat productivity. The model relates the surface heat flow to the depth of the brittle-ductile transition and the thickness of the seismogenic layer. The model is applied to the Gargano area (Italy) which is subject to a frequent low-magnitude seismic activity, although it lies out of the Apennine axis, which is the main Italian seismogenic area. The seismic activity in the Gargano area and surroundings occurs at depths that are systematically different in the north-eastern zone with respect to the south-western zone. In correspondence with the change in depth of earthquake foci, we observe a change in the value of surface heat flow. Starting from these observations and from the knowledge of the lithospheric structure, we propose two different geotherms for the two zones. Assuming a constant strain rate, the shear stress is computed as a function of depth and the thickness of the seismogenic layer in the two zones is inferred. The comparison of the results of the thermo-rheological model with the seismological observation is good.

The Effect of Density and Concentration of Trapping Centers on Charge Carrier Mobility in Polymer Dielectrics

The spectra of the currents of thermostimulated depolarization and the time dependences of the electret potential difference were measured in polymers irradiated with soft X-rays of electric gas discharge. The results of measurements are used to determining the mobility of electrons and holes in polymer cable and capacitor dielectrics having different values of density and concentration of electrically active trapping centers.

Evaluation of Water-Alternating-Gas Efficiency when Using Wide Range of Gas Composition

There are two methods aimed at uniform displacement of oil without any gas breakthroughs. One of such methods is the replacement of gas with a mixture of gas and water, alternating the injection of water and gas rims and another one is the decrease in gas mobility, using foam. The article is devoted to the study of the first method. The object of the study was an area of Ach reservoir of the Vyintoiskoe oil field. To assess the influence of gas composition on the displacement process, modeling of the injection of a mixture of water with both dry and wet gases was carried out. The difference in the component composition of dry and wet gases was set by assigning different values of density and viscosity. With the help of the ECLIPSE 300 the gas density determines its interaction with the oil phase by simulating multicomponent gas. For both a single-layer and a two-layer model of an oil field the exploitation indices were obtained (for gas contents in the injected water-gas mixture of 0; 10; 25; 40; 50; 60; 90; 100 %). The use of wet gas in a mixture with water makes it possible to increase the final oil recovery factor (ORF) up to 68%, which is 4% higher compared to the value of this indicator when using water (64%). These results remain valid with the gas content up to 60%. The use of mixtures enriched with gas is impractical due to the early breakthrough of gas to the production well. In comparison with the water displacement, an earlier breakthrough of gas is observed when the gas content exceeds 10%. On the contrary, when the gas content is 10%, a later breakthrough is observed. For this type of collector it is recommended to apply the mixture with gas content of 10% to achieve the optimum effect.

In vitro and in vivo comparison between methods based on quantitative ultrasound and on resonance frequency analysis to assess dental implant stability

Resonance frequency analyses (RFA) and quantitative ultrasound (QUS) methods have been suggested to dental assess implant stability. The aim of this study was to compare the results obtained using these two techniques in vitro and in vivo. Implants were inserted in bone phantoms with different values of density and cortical thickness to assess the effect of bone quality on the ultrasonic indicator (UI) and on the ISQ values. 81 identical implants were inserted in the iliac crests of 11 sheep. The QUS and RFA measurements were realized after different healing times. ISQ values increase and UI values decrease when i) the bone density and ii) cortical thickness increase. The error realized on the estimation of the trabecular density (respectively cortical thickness) with the QUS device is around 4 (respectively, 8) times lower compared to that made with the RFA technique. The error made on the estimation of the healing time using the QUS technique was 10 times lower than using the RFA technique. The results show that ultrasound technique provides a better estimation of different parameters related to the implant stability compared to the RFA technique, paving the way towards the development of a decision support system to dental surgeons.

A multimass correction for multicomponent fluid flow simulation using smoothed particle hydrodynamics

SummaryIn multicomponent fluid flow simulations using smoothed particle hydrodynamics, the Lagrangian particles used are mostly of equal mass. This is preferred over multimass particle setup (particles with different values of mass), as it resolves the fluid interfaces comparatively better. But the flip side of using uniform mass particle setup is that it may not be computationally economical in situations with large‐density ratios. Hence, using multimass particle setup is both economical and perhaps inevitable. An attractive feature of multimass particle setup is that it allows uniform resolution in regions with different values of density. To take advantage of the multimass setup, it is therefore imperative to reduce the error associated with its usage. In this work, we present suitable multimass correction terms and assess its effectiveness using the ∇h–smooth particle hydrodynamics scheme. Standard benchmark problems, viz, shock tube test, triple‐point shock test, Rayleigh‐Taylor instability, and Kelvin‐Helmholtz instability were solved with multimass particle setup, where significant improvements could be achieved in resolving the associated contact discontinuities.

The equation of state of n-pentane in the atomistic model TraPPE–EH

In this work, we study the vapor–liquid equilibrium in n-pentane. We use the TraPPE–EH (transferable potentials for phase equilibria–explicit hydrogen) forcefield, where each hydrogen and carbon atom is considered as independent center of force. The fluid behavior was investigated with different values of density and temperature by molecular dynamics method. The n-pentane evaporation curve was calculated in the temperature range of 290 to 390 K. The densities of the coexisting phases are also calculated. The compression curve at 370 K was calculated and isothermal bulk modulus was found. The simulated properties of n-pentane are in good agreement with data from a database of the National Institute of Standards and Technology, so the TraPPE–EH model can be recommended for simulations of hydrocarbons.

Experimental investigation and numerical evaluation of adoption of multi- layered wall with vacuum insulation panel for typical Mediterranean climate

This study is focused on the evaluation of the effectiveness of vacuum insulation panel (VIP) for typical Mediterranean climate. The interest for this material is due to indisputable advantages in term of insulation performance both for new and refurbished buildings; mainly in retrofit design, adoption of lower thickness assure same results with less invasive interventions. The problem is the behavior during the summer period, not investigated in the available scientific literature.Numerical and experimental approaches are used in this paper to compare the performance of several wall packages integrating VIP with constructive technologies that result in different stationary and dynamic parameters. More in detail the results of a yearly measurement campaign in three real building of south Italy are presented; recorded data of the surface and the mean air temperatures as well as of the heat flux are commented. Data for one typical week of each season are evaluated to compare the wall made of concrete block and vacuum insulation material with a massive structure and also with a concrete wall with expanded polystyrene as insulation material. Furthermore, simulation results (by means of EnergyPlus) are presented to study, mainly during the summer, the effect of integration of vacuum insulation panel in multi-layered wall made of concrete blocks with different values of density and thermal conductivity; moreover these configurations are compared with a wall made of innovative insulated interlocking brick and with the wall types considered in the experimental phase. Using a typical office building as case study, energy consumptions and environmental and economic indexes are valuated.Experimental and numerical results show the effectiveness of solution with VIPs also for Mediterranean climate.

The propagation of surface waves in a double layered medium over an anisotropic liquid saturated porous half space

A model of surface wave propagation in a transversely isotropic elastic solid layer lying between a homogeneous liquid layer and liquid saturated porous anisotropic half space has been considered. This appears to be a realistic model of interest as the bottom of ocean is likely to be anisotropic homogeneous to some kilometers. The frequency equation has been obtained in the form of ninth order determinant and gives complex velocities representing the attenuated waves when the liquidsaturated porous solid is dissipative. Some special cases have been discussed and numerical computations have been done by Symbolab Solutions with mathematical approximation method. The dimensionless phase velocity ratios have been plotted against the dimensionless wave number for different values of density and different values of ratio of anisotropy parameters C/F with the help of MATLAB graphical routines. Finally, conclusions have been drawn on the basis of analysis of results and graphs.

Remarks on a Strongly Nonlinear Model for Two‐Layer Flows with a Top Free Surface

We revisit in this paper the strongly nonlinear long wave model for large amplitude internal waves in two‐layer flows with a free surface proposed by Choi and Camassa [1] and Barros et al. [2]. Its solitary‐wave solutions were the object of the work by Barros and Gavrilyuk [3], who proved that such solutions are governed by a Hamiltonian system with two degrees of freedom. A detailed analysis of the critical points of the system is presented here, leading to some new results. It is shown that conjugate states for the long wave model are the same as those predicted by the fully nonlinear Euler equations. Some emphasis will be given to the baroclinic mode, where interfacial waves are known to change polarity according to different values of density and depth ratios. A critical depth ratio separates these two regimes and its analytical expression is derived directly from the model. In addition, we prove that such waves cannot exist throughout the whole range of speeds.

FFLO order in ultra-cold atoms in three-dimensional optical lattices

We investigate different ground-state phases of attractive spin-imbalanced populations of fermions in three-dimensional optical lattices. Detailed numerical calculations are performed using Hartree–Fock–Bogoliubov theory to determine the ground-state properties systematically for different values of density, spin polarization and interaction strength. We first consider the high density and low polarization regime, in which the effect of the optical lattice is most evident. We then proceed to the low density and high polarization regime where the effects of the underlying lattice are less significant and the system begins to resemble a continuum Fermi gas. We explore the effects of density, polarization and interaction on the character of the phases in each regime and highlight the qualitative differences between the two regimes. In the high-density regime, the order is found to be of Larkin–Ovchinnikov type, linearly oriented with one characteristic wave vector but varying in its direction with the parameters. At lower densities the order parameter develops more structures involving multiple wave vectors.

Ion acoustic solitary waves in an electron–ion–positron plasma

Large amplitude ion-acoustic solitary waves have been theoretically studied in a non-collisional plasma consisting of warm positive ions, positrons and isothermal electrons using pseudo-potential (effective potential) method. The expressions of phase velocities of slow- and fast- modes of the wave have been derived and graphically analyzed. The critical values of densities of the positrons and the ions, Mach number and positron temperature for the excitation of ion-acoustic solitary wave have also been obtained. The solutions of the first-order and next higher order solitary waves have been obtained and the profiles of the solitary waves have been drawn taking different values of the plasma parameters. It has been observed that both compressive and rarefactive solitary waves are being excited in presence of positrons in the plasma. The variation of amplitudes of the solitary waves has been shown graphically for different values of density and temperature of positrons, drift velocity and temperature of the ions.

Effects of Surfactant-Emulsified Oil-Based Mud on Borehole Resistivity Measurements

SummaryWe quantify the influence of oil-based mud (OBM)-filtrate invasion and formation-fluid properties on the spatial distribution of fluid saturation and electrical resistivity in the near-wellbore region. The objective is to appraise the sensitivity of borehole resistivity measurements to the spatial distribution of fluid saturation resulting from the compositional mixing of OBM and in-situ hydrocarbons.First, we consider a simple two-component formulation for the oil phase (OBM and reservoir oil) wherein the components are first-contact miscible. A second approach consists of adding water and surfactant to a multicomponent OBM invading a formation saturated with multiple hydrocarbon components. Simulations also include presence of irreducible, capillary-bound, and movable water. The dynamic process of OBM invasion causes component concentrations to vary with space and time. In addition, the relative mobility of the oil phase varies during the process of invasion because oil viscosity and oil density are both dependent on component concentrations.Presence of surfactants in the OBM is simulated with a commercial adaptive implicit compositional formulation that models the flow of three-phase multicomponent fluids in porous media. Simulations of the process of OBM invasion yield 2D spatial distributions of water and oil saturation that are transformed into spatial distributions of electrical resistivity. Subsequently, we simulate the corresponding array-induction measurements assuming axial-symmetric variations of electrical resistivity.We perform sensitivity analyses on field measurements acquired in a well that penetrates a clastic formation and that includes different values of density and viscosity for mud filtrate and formation hydrocarbon. These analyses provide evidence of the presence of a high-resistivity region near the borehole wall followed by a low-resistivity annulus close to the noninvaded resistivity region. Such an abnormal resistivity annulus is predominantly caused by high viscosity contrasts between mud filtrate and formation oil. The combined simulation of invasion and array-induction logs in the presence of OBM invasion provides a more reliable estimate of water saturation, which improves the assessment of in-place hydrocarbon reserves.

Mass dependence of sputtering characteristics for a number of metals with different properties

Molecular dynamic simulation has been used to study how the sputtering characteristics of metal polycrystals are dependent on the mass m 1 of bombarding ions of low-energy E 0. The influence of target parameters on mass dependence of sputtering has been calculated for Al, Ba, Ce and Au, which were not previously studied. These metals have very different values of density ρ, the lattice constant d, and the surface binding energy E b (the parameters that define the sputtering process). The features of sputtering characteristics for the metals studied are discussed.

On features of metal and binary compound sputtering by low-energy ions

Molecular dynamic simulation has been used to study how the characteristics of metal and binary compound sputtering change under the bombardment by different low-energy ions. The influence of the target parameters on the anomalous mass dependence of sputtering yield has been investigated, both for targets with similar and very different values of density, the lattice constant and the surface binding energy. Together with the ratio of the target atoms’ mass to the mass of the ions, the density of the target and the binding energy turn out to be the important parameters that determine the unusual shape of the mass dependence of sputtering by low-energy ions.

Diffusion dynamics of laser-ablated noble-metal nanoparticles in liquids

The diffusion dynamics in water of Brownian particles constituted by noble-metal nanoclusters has been treated by a transport model across a limiting surface that separates two layers of the same fluid, having different values of density and temperature. This model, developed by Parrondo and adapted by Streater, has recently been shown to be useful in several situations like ours by the work of Grillo et al. By this approach, which introduces a one-dimensional vertical adiabatic potential produced by density gradients governing the net current of particles across the limiting surface, we are able to explain the mass and thermal energy transport, which rapidly restores the equilibrium conditions when they are perturbed by laser ablation of a noble-metal target vertically submerged in water. Experimentally, the laser ablation of noble-metal targets has been performed by irradiating pure metal sheets submerged in water with a pulsed Nd:YAG laser at 500 mJ cm−2 fluency for 5 min and pulses of duration on the nanosecond timescale.

An experimental investigation of the critical state of aqueous solutions of aliphatic alcohols

The ballast-free constant-volume piezometer technique is used for measuring the p, ρ, T dependences of aqueous solutions of aliphatic alcohols (methanol, ethanol, and 1-propanol) with 0.2, 0.5, and 0.8 mole fraction of alcohol in the temperature range from 373.15 to 623.15 K and at pressures up to 50 MPa for different values of density. The data of p, ρ, T measurements in the near-critical region are used to determine the parameters of critical state of solutions as a function of composition. Diagrams are constructed of projections of lines of critical points of thermodynamic surface in different planes.

Molecular Dynamic Simulation of Side‐Chain Liquid Crystalline Elastomer

AbstractSummary: Molecular dynamic simulation of side chain liquid crystalline elastomer has been carried out. As an initial state a flexible polymer network in a low molecular liquid‐crystal (LC) solvent was used. The LC solvent comprises of anisotropic rod‐like semiflexible linear molecules (mesogens) composed of particles bonded into the chain by FENE potential. Rigidity of LC molecules was induced by a bending potential. All interactions between nonbonded particles are described by a repulsive Lennard‐Jones potential. For the systems with different values of density and order parameter obtained after sufficiently long trajectory the attachment of ends of mesogens to the polymer network was simulated. The kinetic of the process of mesogens attachment to network was studied as well as morphology of attachment. The structural and dynamical behaviour of side chain LC elastomer was studied and compared with systems of polymer network in low molecular LC solvent.