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There are a growing number of reports suggesting that the specific surface area in graphitic materials is not a critical parameter to determine the CO2 capture capacity, but rather the pore size and its geometry are more relevant, yet a detailed theoretical and quantitative understanding that could facilitate further developments for the pore size effects is presently lacking. Using the thermodynamic continuum model combined with electronic structure calculations, we identify the critical size of pores in graphitic materials for enhanced carbon dioxide (CO2) uptake as well as its selectivity relative to N2. We find that there exists a value of pore size which is most optimal in the CO2 capture capacity as well as CO2/N2 selectivity at a given pressure and temperature, supporting the previous experimental observations regarding critical parameters determining the CO2 adsorption capacity of porous carbon materials. The calculated results emphasize the importance of graphitic pore size from 8 to10 A in CO2 c...

In this study, the effect of environmental conditions on plant operation was investigated for hydrogen refuelling stations with an external storage facility. Hydrogen storage pressure with respect to tank surface temperatures have been measured and used to create empirical equations for each tank showing the effect of surface temperature on the tank pressure. A physical model of the hydrogen storage tanks has been created in DesignBuilder (EnergyPlus) to simulate the surface temperature of tanks throughout the course of a year with respect to location, site orientation, tank size and surface colour, shading and operating pressure. Finally, the effect that environmental conditions may have on a plant operation is assessed through the prediction of pressure dependent events, namely the frequency of alarms and pressure relief occurrences and hours of plant downtime over the course of a year. The modelling results indicate that location, tank size, surface colour and sunshade can have substantial impacts on the plant operation, whereas the influence of site orientation is less significant. Frequency of pressure dependant events increase as the tank size decreases due to more significant heat gain observed with higher surface-to-volume ratios. Simulation results also prove that the provision of a sunshade or white paint colour could avoid/minimise the interference of ambient conditions in plant operation in cold and mild climates. However, they are not sufficient enough to mitigate against solar gain effect in warmer climates. Although reducing the maximum operating pressure would also help reduce the number of solar gain pressure events, it would also result in increased cushion level and hence reduced plant performance. The optimum design and operating strategy should be chosen for each individual station considering the daily and annual temperature profiles of the location.

In this work, the volume and pressure effects on thermodynamic quantities including Gruneisen parameter and melting temperature of sodium have been studied of to 65 GPa. The volume dependence of Gruneisen parameter of sodium has been firstly analyzed. Based on this result and the Lindemann criterion of melting we derived the analytical expression of volume-dependent melting temperature. Combining with Vinet equation-of-state, the melting curve of sodium at high pressure has been proposed. Numerical calculations were performed for solid sodium up to pressure 65 GPa. Theoretical calculations are compared with available experimental data showing the good and reasonable agreements in the pressure range 0–30 GPa. This research proposes the good volume- and pressure-dependent Gruneisen parameter as well as the potential of Lindemann criterion approach on predicting high-pressure melting of materials.

A theoretical study of the thermal decomposition of β-propiolactone is carried out using ab initio molecular orbital (MO) methods at the MP2/6-311+G ∗∗ level and Rice–Ramsperger–Kassel–Marcus (RRKM) theory. The reported experimental results showed that decomposition of β-propiolactone occurred by three competing homogeneous and first order reactions. For the three reactions, the calculation was also performed at the MP2/6-311+G ∗∗ level of theory, as well as by single-point calculations at the B3LYP/6-311+G ∗∗ //MP2/6-311+G ∗∗ , and MP4/6-311+G ∗∗ //MP2/6-311+G ∗∗ levels of theory. The fall-off pressures for the decomposition in these reactions are found to be 2.415, 9.423 × 10 −2 and 3.676 × 10 −3 mmHg, respectively.

Secondary cone-type crushing machines are an important part of the aggregate production process. These devices process roughly crushed material into aggregate of greater consistency and homogeneity. We apply a continuum model for granular materials (`A Constitutive Law For Dense Granular Flows', Nature 441, p727-730, 2006) to flows of granular material in representative two-dimensional channels, applying a cyclic applied crushing stress in lieu of a moving boundary. Using finite element methods we solve a sequence of quasi-steady fluid problems within the framework of a pressure dependent particle size problem in time. Upon approximating output quantity and particle size we adjust the frequency and strength of the crushing stroke to assess their impact on the output.

The coefficient of earth pressure at rest (K0) for normally consolidated clays increases nonlinearly with increasing consolidation pressure toward a steady value under high pressure rather ...

Author(s): Jeanne, P; Guglielmi, Y; Rutqvist, J; Nussbaum, C; Birkholzer, J | Abstract: We studied the relation between rupture and changes in permeability within a fault zone intersecting the Opalinus Clay formation at 300nm depth in the Mont Terri Underground Research Laboratory (Switzerland). A series of water injection experiments were performed in a borehole straddle interval set within the damage zone of the main fault. A three-component displacement sensor allowed an estimation of the displacement of a minor fault plane reactivated during a succession of step rate pressure tests. The experiment reveals that the fault hydromechanical (HM) behavior is different from one test to the other with varying pressure levels needed to trigger rupture and different slip behavior under similar pressure conditions. Numerical simulations were performed to better understand the reason for such different behavior and to investigate the relation between rupture nucleation, permeability change, pressure diffusion, and rupture propagation. Our main findings are as follows: (i) a rate frictional law and a rate-and-state permeability law can reproduce the first test, but it appears that the rate constitutive parameters must be pressure dependent to reproduce the complex HM behavior observed during the successive injection tests; (ii) almost similar ruptures can create or destroy the fluid diffusion pathways; (iii) a too high or too low diffusivity created by the main rupture prevents secondary rupture events from occurring whereas “intermediate” diffusivity favors the nucleation of a secondary rupture associated with the fluid diffusion. However, because rupture may in certain cases destroy permeability, this succession of ruptures may not necessarily create a continuous hydraulic pathway.

In this work we develop the a priori and a posteriori error analyses of a mixed finite element method for Darcy’s equations with porosity depending exponentially on the pressure. A simple change of variable for this unknown allows to transform the original nonlinear problem into a linear one whose dual-mixed variational formulation falls into the frameworks of the generalized linear saddle point problems and the fixed point equations satisfied by an affine mapping. According to the latter, we are able to show the well-posedness of both the continuous and discrete schemes, as well as the associated Cea estimate, by simply applying a suitable combination of the classical Babuska-Brezzi theory and the Banach fixed point Theorem. In particular, given any integer k ≥ 0, the stability of the Galerkin scheme is guaranteed by employing Raviart-Thomas elements of order k for the velocity, piecewise polynomials of degree k for the pressure, and continuous piecewise polynomials of degree k+1 for an additional Lagrange multiplier given by the trace of the pressure on the Neumann boundary. Note that the two ways of writing the continuous formulation suggest accordingly two different methods for solving the discrete schemes. Next, we derive a reliable and efficient residualbased a posteriori error estimator for this problem. The global inf-sup condition satisfied by the continuous formulation, Helmholtz decompositions, and the local approximation properties of the Raviart-Thomas and Cl´ement interpolation operators are the main tools for proving the reliability. In turn, inverse and discrete inequalities, and the localization technique based on triangle-bubble and edge-bubble functions are utilized to show the efficiency. Finally, several numerical results illustrating the good performance of both methods, confirming the aforementioned properties of the estimator, and showing the behaviour of the associated adaptive algorithm, are reported. Centro de Investigación en Ingeniería Matemática (CI2MA), Universidad de Concepción University of Lausanne Ministry of Education, Youth and Sports of the Czech Republic

Steel has been used in vehicles from the automotive industry’s inception. Different steel grades are continually being developed in order to satisfy new fuel economy requirements. For example, advanced high strength steel grades (AHSS) are widely used due to their good strength/weight ratio. Because each steel grade has a different microstructure composition and hardness, they show different behaviors when they are subjected to different strain paths. Similarly, the friction behavior when using different contact pressures is considerably altered. In the present paper, four different steel grades, ZSt380, DP600, DP780 and Fortiform 1050 materials are deeply characterized using uniaxial and cyclic tension-compression tests. Coefficient of friction (COF) is also obtained using strip drawing tests. These results have been used to calibrate mixed kinematic-hardening material models as well as pressure dependent friction models. Finally, the geometrical accuracy of the different material and friction models has been evaluated by comparing the numerical predictions with experimental demonstrators obtained using a U-Drawing tester.

We consider the incompressible fluid with a pressure-dependent viscosity flowing through a multiple pipe system. The viscosity-pressure relation is given by the Barus law commonly used in the engineering applications. Assuming that the ratio between pipes thickness and its length is small, we propose a rigorous asymptotic approach based on the concept of the transformed pressure. As a result, we obtain new macroscopic model describing the effective behavior of the fluid in the system. In particular, the generalized version of the Kirchhoff's law is derived giving the explicit formula for the junction pressure. The error estimate for the asymptotic approximation is also provided. Mathematical analysis presented here can be applied to a general viscosity- pressure relation satisfied by other empiric laws.

In this paper, a theoretical study of the combined effects of surface roughness and the variation of viscosity with pressure on the squeeze film lubrication between sphere and a flat plate is presented. Based on the Christensen’s stochastic theory for the hydrodynamic lubrication of rough surfaces, two types of one-dimensional surface roughness (radial and azimutal) patterns are considered. The generalized averaged Reynold’s equation for Stokes couple stress fluids accounting for the pressure dependent viscosity is mathematically derived for the problem under consideration. The standard perturbation technique is used to solve the averaged nonlinear Reynold’s equation and an approximate analytical solution for the fluid film mean pressure is obtained for the two types of one-dimensional roughness patterns. It is found that, the effects of couple stresses and pressure dependent viscosity variation are to improve the squeeze film characteristics.

The objective of this paper is the investigation of the implemented pressure dependent friction model in the FE simulation program AutoForm. Since the values for the required parameters of this approach are not defined in the actual FE simulation program, this paper contributes to a first definition of these parameters. Therefore, experimental investigations with the cup drawing tests are carried out. With the support of the experimental results regarding the maximum stamping force, the model is calibrated and subsequently validated by the comparison of the sheet thicknesses of the experimental and numerical investigations. The results of this validation reveal a good accordance of simulation and reality in nearly all areas. However there are also areas in which the prediction accuracy decreases in comparison to the basic simulation. Therefore, additional investigations have to be carried out which concentrate on the modification of this pressure dependent approach towards a better universal prediction accuracy of the simulation.

This paper reports the couple stresses squeeze film lubrication of circular stepped plates with pressure-dependent viscosity (PDV). The modified Reynolds equation accounting for the viscosity variation of couplestress fluid is mathematically derived. From the results, it has been found that the non-dimensional pressure, non-dimensional load-carrying capacity, and the non-dimensional squeeze film time increases as compared with iso-viscous lubricant case. Further, the present results are in good agreement with the earlier works in the limiting conditions of iso-viscous lubricant case.

In this paper, a theoretical study of the effect of pressure dependent viscosity on couple stress squeeze film lubrication between rough parallel plates is analyzed on the basis of Barus experimental results. Stokes micro continuum theory of couple stress fluids and Christensen’s stochastic theory for the lubrication of rough surfaces have been used for the derivation of generalized stochastic Reynold’s type equation with pressure dependent viscosity. In the context of Christensen’s theory, the two types of one dimensional roughness (Longitudinal and transverse) patterns are considered. Expressions for the squeeze film pressure, the load carrying capacity and time-height relations are obtained. It is found that, the effect of roughness parameter is to increase (decrease) the load carrying capacity and the response time for transverse (longitudinal) roughness patterns as compared to the smooth case. Further the effect of pressure dependent viscosity variation is to reduce the load carrying capacity and squeeze film time as compared to the constant viscosity case.

The selection of optimal positive end expiratory pressure (PEEP) levels during ventilation therapy of patients with ARDS (acute respiratory distress syndrome) remains a problem for clinicians. One particular mooted strategy states that minimizing the energy transferred to the lung by mechanical ventilation could potentially be used to determine the optimal PEEP level. This minimization could potentially be undertaken by finding the minimum range of dynamic elastance. In this study, we compare an adapted Gauss-Newton method with the typical gauss newton method in terms of the level of agreement obtained in elastance-pressure curves across different PEEP levels in 10 patients. The Gauss-Newton adaptation effectively ignored characteristics in the data that are un-modelled. The adapted method successfully determined regions of the data that were un-modelled, as expected. In ignoring this un-modelled behavior, the adapted method captured the desired elastance-pressure curves with more consistency than the typical least-squares Gauss Newton method.

Accurate models are critical for the effective management of leaks in our water distribution systems. The increased use of plastic pipes has emphasised the need to assess the ability of current leakage assessment tools in quantifying the real losses from complex time and pressure dependent leaks. The numerical study presented in this paper shows that traditional Minimum Night Flow (MNF) analyses provide good approximations of the leak response, when the loading history and discrete pressure regimes are accounted for, of leaks in viscoelastic pipe. The time and dependent nature of such leaks are of greater significance when the response to short time period pressure transients are quantified, important for active leakage control methodologies in particular.

We report the role of pressure dependent growth of micro and nanorod arrays of zinc oxide by an aqueous solution route. Initially, both micro- and nano-ZnO surfaces show hydrophobicity with water contact angles of 140° ± 3° and 130° ± 3°, respectively. We find that the temporal decay in water contact angle is faster in the case of the nanorod surface compared to that of the microrod surface. While for the microrod surface, the small change in contact angle happens due to water droplet evaporation, the significant change in the particular case of the nanorod surface is attributed to the capillary action.

Layered BN is a graphite analogue with exceptionally strong covalent bonding, while dense phases, particularly cubic and wurtzite BN are important hard materials for machine tools and other applications. BN is invariably formed in the layered form and must be converted to the dense phase under pressure. We report the pressure dependent structure of BN and energy barriers for the transformations as a function of initial structure based on first-principles methods including dispersion interactions, which we find to be important. The cohesive energies of the layered structures are similar to that of wurtzite BN. The energy barriers for transformation from rhombohedral layered BN to dense cubic BN and that from hexagonal layered BN to dense wurtzite BN are found to be similar at low pressure. Increasing pressure results in a rapid decrease of these energy barriers. The phase transition from ordered layered structures to the dense phase should be completed at approximately 25 GPa. We find a large energy barrier for layer glides under pressure, which provides an explanation for the difficulty in ambient temperature, high pressure formation of cubic dense BN from layered starting materials that contains stacking faults.

The effects of pressure on the magnetization and isothermal entropy change, AC susceptibility, and resistivity for Nd7Pd3 have been studied. Nd7Pd3 shows three magnetic transitions Tt (=15 K), TC (=34 K), and TN (=38 K) at a pressure of zero bar. TC and TN are very sensitive to the pressure and rates of change of TC and TN with respect to pressure, i.e., dTC/dp and dTN/dp are −1.906 K kbar−1 and −0.313 K kbar−1 respectively, whereas Tt is insensitive to pressure change. It has also been observed that the isothermal entropy change is also sensitive to pressure. Below 15 K, an indication of spin glass nature in the AC susceptibility data is seen. The time dependent magnetization at low temperatures also supports the spin glass nature, but at high temperatures it indicates a complex nature. The electrical resistivity data has been fitted to the relation ρ = ρ0 + AT2 in the temperature range 12–30 K and ρ = ρ0 + BT − CT3 in the temperature range 40–220 K. The M–H isotherm confirms the AFM nature of Nd7Pd3, which is confirmed further by the Arrott’s plot.

In the present work experimental data from seven perforated (7PF) JA2 propellant combustion in a micro closed bomb is presented and the linear burning rate of the JA2 propellant is determined. The burn rate measurement is based on a sophisticated lumped parameter model which accounts among other things for arbitrary cross sectional propellant geometries with the help of the ICT-Cellular-Combustion-Algorithm (ICCA), pressure dependent thermophysical parameters and heat loss. The model is used to construct a vivacity based objective function which depends on the parameters of the empirical law for the linear burning velocity. With the Nelder-Mead downhill simplex optimization algorithm the objective function is minimized and the burn rate parameters determined. The comparison of the results to published data show that with the new burn rate measurement method the linear burning rate can be determined with great accuracy even when only a few propellant grains with a total propellant mass of less than 8 g per shot are used.

CETIAT’s calibration laboratory, accredited by COFRAC, is a secondary thermometry laboratory. It uses overflow and stirred calibration baths $$(\hbox {from} -\,80\,{^{\circ }}\hbox {C} \hbox { up } \hbox { to } +\,215\,{^{\circ }}\hbox {C})$$ , dry blocks and furnaces $$(\hbox {from } +\,100\,{^{\circ }}\hbox {C} \hbox { up } \hbox { to } +\,1050\,{^{\circ }}\hbox {C})$$ and thermostatic chambers $$(\hbox {from } -\,30\,{^{\circ }}\hbox {C} \hbox { up } \hbox { to } +\,160\,{^{\circ }}\hbox {C})$$ . Typical calibration uncertainties that can be reached for platinum resistance thermometers in a thermostatic bath are between $$0.03\,{^{\circ }}\hbox {C}$$ and $$0.06\,{^{\circ }}\hbox {C}$$ . In order to improve its calibration capabilities, CETIAT is working on the implementation of a gas-controlled heat pipe (GCHP) temperature generator, used for industrial sensor calibrations. This article presents the results obtained during the characterization of water GCHP for industrial applications. This is a new approach to the use of a heat pipe as a temperature generator for industrial sensor calibrations. The objective of this work is to improve measurement uncertainties and daily productivity. Indeed, as has been shown in many studies (Dunn and Reay in Heat Pipes, Pergamon Press, Oxford, 1976; Merlone et al. 2012), the temperature of the system is pressure dependent and the response time, in temperature, follows the pressure accordingly. Thanks to this generator, it is possible to perform faster calibrations with smaller uncertainties. In collaboration with INRiM, the GCHP developed at CETIAT works with water and covers a temperature range from $$+\,30\,{^{\circ }}\hbox {C}$$ up to $$+\,150\,{^{\circ }}\hbox {C}$$ . This device includes some improvements such as a removable cover, which allows us to have different sets of thermometric wells adjustable according to the probe to be calibrated, and a pressure controller based on a temperature sensor. This article presents the metrological characterization in terms of homogeneity and stability in temperature. A rough investigation of the response time of the system is also presented in order to evaluate the time for reaching thermal equilibrium. The results obtained in this study concern stability and thermal homogeneity. The homogeneity on 200 mm is better than 5 mK and with a calibration uncertainty reduced by a factor of three.

A laboratory experiment was devised and performed to investigate the pressure dependence of Sea-Bird Electronics SBE35 and SBE3 deep-ocean thermometers. The thermometers were mounted in a massive brass comparator together with a calibrated standard platinum resistance thermometer. The measurements were performed in a pressure chamber in the pressure range 0.1 MPa to 60 MPa. The results showed that both the investigated SBE35 and SBE3 thermometers are pressure dependent, with a pressure sensitivity of +41 $$\upmu $$ K $$\cdot $$ MPa $$^{-1}$$ and $$-77$$ $$\upmu $$ K $$\cdot $$ MPa $$^{-1}$$ , respectively. Nevertheless, the results obtained in only one individual device per model (one SBE35 and one SBE3) cannot be generalized and further investigations of a larger number of devices per model are needed.

The paper deals with the electrical properties of Montmorillonite (MMT)/Polyaniline (PANI) composites. These materials show specific electrical properties as relatively high anisotropic electrical conductivity, pressure dependent electrical resistance with relatively high hysteresis. Metallographic analyse as well as the Vickers micro-hardness dsof sample surfaces is presented. All these properties predetermine this material as an interesting piezoresistor.

In the current study, a multiaxial plastic-damage constitutive model for concrete at different temperatures is developed. The model is implemented in three-dimensional finite element analys...

An implantable pressure monitoring system is a compelling approach to home monitoring of intracranial pressure in the long term. In our approach, an on-body unit powers a cranially concealed system where a piezoresistive element senses the pressure. A data transmission unit built in the same platform emits a signal at a pressure dependent frequency through a miniature far field antenna. In this work, we focus on assessing the impact of variable temperature on the pressure readout at an off-body unit through in-vitro experiments. submittedVersion

Experimental evidence investigating the high-pressure response (0--9 GPa) of aligned single-walled carbon nanotube (SWNT) arrays in the extreme low Raman shift region (10--100 ${\mathrm{cm}}^{\ensuremath{-}1}$, squash mode region) is provided to verify a predictive model for deformation-related phase transitions. In addition to the well-known radial breathing mode (RBM) and despite the technical challenges associated with the detection of Raman signals very close to the exciting laser frequency, clear SWNT squash mode peaks were identified and used to refine the predictive model. Furthermore, this paper investigates and proposes explanations for the detailed behavior of the pressure dependent cross-sectional transition. The results demonstrate experimentally, and confirm earlier theoretical models, that the critical pressure scales $\ensuremath{\propto}1/\mathcal{O}({d}_{t}^{3})$ against the chirality dependent nanotube diameter ${d}_{t}$. Finally, the pressure and chirality dependent Raman upshifts of the squash mode, characterizing the phase transition, are found to be larger than those of the RBM, respectively, confirming the general theoretical prediction of greater environmental sensitivity of squash modes.

Background: The clinical significance of pressure-dependent intra-beat changes in local pulse-wave velocity (C) has recently come to light [1]. While reported methods require arterial pressure and diameter measurements from a single site to assess intra-beat changes in C, we present an image-free fast ultrasound device that performs this by capturing diameter waveforms from two proximal locations on an artery.. Methods: The functionality was assessed on eight normotensive participants (26 ± 4 years). By perturbing blood pressure through a short duration moderate lower body negative pressure intervention [2], CD and CF pulse wave velocities corresponding to diastolic and 80% of peak pressure were measured from the carotid artery. Human NIBP system (ADInstruments, India) was used for monitoring continuous pressure. Results: The device captured dual-diameter waveforms and evaluated CD and CF, with a beat-to-beat variation 0.6, p < 0.001) of CD and CF with the diastolic and systolic pressures for each individual was preserved even after adjusting for heart-rate. Conclusions: The device demonstrated its functionality and reliably measured the incremental nature of C. Its pressure-dependent intra-beat variations and inter-beat dynamics during the intervention concurred with literature. Further studies are underway to demonstrate the potential use of the device in vascular research and clinical applications.

The granular soils are pressure dependent materials and substantial volume change occurs during loading. Some granular soils contract (volume decrease) when sheared and some dilate (volume increase), depending on their initial state. Owing to the plastic volume change that accompanied plastic deformation, the lack of normality rule arises and the granular soil exhibits a non-associated flow rule. As known the non normality has destabilizing effect on the soil behavior in the hardening regime (loss of positive definiteness of the second order work). The unstable behavior usually develops in association with dilation. A contracting soil displaying hardening and stable material behavior under drained conditions, may succumb to unstable flow type when its behavior becomes dilating. This paper deals with the extension of the static shakedown theorem to dilative granular soils in drained conditions, exhibiting pre-failure instability in the hardening regime, in the framework of non associated plasticity.

A review of available correlations for graphite oxidation by steam, relevant in case of water ingress accidents in HTR, was performed. Accuracy of the available correlation for the primary reaction was investigated by performing comparison with available data. A new correlation was proposed. The new correlation is an extension of the existing correlation of Kubaschewski–Heinrich, obtained by introducing a pressure dependent and burn-off dependent multiplier for best estimate as well as conservative calculations. The best estimate correlation shows significant improvement of accuracy when compared with the same data. The maximum error and applicability range of the best estimate correlation are provided. The maximum deviation of the new correlation results and experimental data is –27% and +15%, compared to the maximum deviations of –72% and +76%, found for the original correlation. The range of application of the correlation is: 1000 K÷1300 K, 10 5 Pa÷55 × 10 5 Pa total pressure and 14÷10 5 Pa steam partial pressure. The work presented in this paper was done within the ARCHER project.

The pressure dependence of Raman spectra for whitlockite β-Ca3(PO4)2 was investigated up to 18.0 GPa using a diamond-anvil cell at room temperature. The Raman frequencies of all observed bands for β-Ca3(PO4)2 continuously increase with increasing pressure. The quantitative analysis of pressure dependence of Raman bands for the sample shows that the ν 3 asymmetric and ν 1 symmetric stretching vibrations are with the larger pressure coefficients (from 3.44 to 4.59 cm−1 GPa−1) and that the ν 4 bending and ν 2 deforming vibrations are with the smaller pressure coefficients (from 1.46 to 3.12 cm−1 GPa−1). Combined with previous result, the isothermal mode Gruneisen parameters of β-Ca3(PO4)2 were calculated. The splitting of the PO4 symmetric stretching ν 1 vibrations changes during compression and disappears around 15.4 GPa, which may be attributed to the evolution of PO4 tetrahedra under high pressure.

In the classical theory of rigid perfectly/plastic solids, the calculation of plane strain characteristic fields is reduced to solving the telegraph equation and subsequent evaluation of ordinary integrals. The telegraph equation can be integrated by the method of Riemann. In the present brief note this approach is extended to pressure-dependent plasticity based on the Coulomb-Mohr yield function. Body forces are neglected and kinematic theories are not considered.

A universal empirical relation is derived to predict the reaction delay times of aluminum particles as a function of particle diameter and gas temperature in explosives. The predicted delay times are shown to be in reasonable agreement with experimental data obtained in both low temperature and high temperature explosives. A convective heat transfer model is used to estimate the surface temperature of the solid aluminum particles. The reaction delay time of aluminum is shown to be close to the time when the particle surface reaches the pressure dependent melting point of aluminum.

In this paper we investigate some one-dimensional flows of a Bingham fluid with pressure dependent rheological parameters. We determine explicit solutions and show conditions for existence or non-existence of a rigid plug. In particular we show how the classical profiles are modified assuming that the dependence on pressure of both viscosity and yield stress is linear.

Third-order nonlinear intra-conduction band optical properties of (In,Ga)N–GaN spherical quantum dot are investigated. Linear, third-order nonlinear and total absorption coefficients (ACs) of 1p–1d and 1d–1f transitions are computed using a combination of Quantum Genetic Algorithm (QGA) and Hartree–Fock–Roothaan (HFR) method. Hydrostatic pressure effect is examined within the single band effective-mass and the one parabolic band approximations under finite potential barrier. The results show that the hydrostatic pressure has a great impact on the optical properties of QDs. A blue shift of the resonant peak is observed while the maximum of the amplitude of optical absorption coefficients decreases nonlinearly under hydrostatic pressure effect. Two competing parameters are suggested to explain our results. Compared with the finding results, a good agreement is shown.

Background The pressure dependent recruitment model (PRM) is a comprehensive mathematical description of pulmonary mechanics in acute respiratory distress syndrome (ARDS). However, previous investigations of the PRM implied that the number of model parameters may cause inaccurate parameter estimation. Methods PRM models were evaluated for 12 ARDS patients that underwent a low-flow recruitment manoeuvre. The identified parameter set formed the basis of a parameter reduction investigation of the PRM. The parameter reduction investigation measured the mean cohort residual error (ψ) yielded by each possible combination of identified parameter set with the non-identified parameter values set to a priori population constants. Results Reducing the five variable PRM to a particular three variable model configuration produced a limited increase in model fit to data residuals (ψ5 = 22.68, ψ3 = 29.21 mbar). The reduced model evaluates airway-resistance, compliance and distension as model variables and uses population values for alveoli opening pressure and the ratio of open alveoli at end expiratory. Conclusions The reduced PRM model captures all major pressure–volume response features in the ARDS patients. Reduced parameterisation allows more robust parameter identification and thus more reliable parameter estimates that may prove more useful in a clinical setting.

We present an ab-initio study of the elastic and magnetic properties of Cr-based full-Heusler alloys within the first-principles density functional theory. The lattice constant, magnetic moment, bulk modulus and density of states are calculated using the full-potential nonorthogonal local-orbital minimum basis (FPLO) code in the Generalized Gradient Approximation (GGA) scheme. Only the two alloys Co 2 CrSi and Fe 2 CrSi are half-metallic with energy gaps of 0.88 and 0.55 eV in the spin-down channel respectively. We have predicted the metallicity state for Fe 2 CrSb, Ni 2 CrIn, Cu 2 CrIn, and Cu 2 CrSi alloys. Fe 2 CrSb shows a strong pressure dependent, e.g. exhibits metallicity at zero pressure and turns into a half-metal at P ≥10 GPa. The total and partial magnetic moments of these alloys were studied under higher pressure, e.g. in Co 2 CrIn, the total magnetic moment is almost unchanged under higher pressure up to 500 GPa.

Water quality models are increasingly being routinely used to help ascertain the quality of water in drinking water distribution systems for design and operational management purposes. Conventional water quality models are demand driven and consequently do not incorporate the effects of any deficiency in pressure on the water quality throughout the distribution network. This paper assesses a new integrated pressure-dependent hydraulic and water quality model. The model is an extension of the well-known Epanet 2 model that has an embedded logistic pressure-dependent nodal flow function. Hydraulic and water quality analyses based on two water supply zones in the UK were conducted for a range of simulated operating conditions including normal and subnormal pressure and pipe closures. It is shown that operating conditions with subnormal pressures, if severe and protracted, can lead to spatial and temporal distributions of the water age and concentrations of chlorine and disinfection by-products that are significantly different from operating conditions in which the pressure is satisfactory. The results presented may be indicative of modelling errors that may not have been recognised explicitly hitherto.

Using a variant of a spectral collocation method we numerically solve the problem of the motion of a highly viscous fluid with pressure dependent viscosity under a surface load, which is a problem relevant in many applications, in particular in geophysics and polymer melts processing. We compare the results with the results obtained by the classical Navier–Stokes fluid (constant viscosity). It turns out that for a realistic parameter values the two models give substantially different predictions concerning the motion of the free surface and the velocity and the pressure fields beneath the free surface. As a byproduct of the effort to test the numerical scheme we obtain an analytical solution—for the classical Navier–Stokes fluid—of the surface load problem in a layer of finite depth.

The frictional behaviors between metal forming tool and three different metallic materials were evaluated using the microforming T-shape test. A mathematical function is proposed to describe the calibration curves for different friction coefficients. Round bars of copper, aluminum and silver of diameter 1 mm and length 5 mm were used as the workpieces to study the material influence on friction factor, m, during unlubricated microforming process through comparison between simulation and experimental results. Furthermore, various lubricants were used with the aluminum and copper to examine their performance in microforming. The results have shown that the workpiece materials not only determine the friction factor, m, during unlubricated microforming, but also influence the performance of lubricants. Lubricant can be completely ineffective and may not produce discernible friction reduction in microforming, unlike in conventional metal forming. By considering the influence of contact pressure on lubricant effectiveness, a novel pressure dependent frictional model and a lubricant evaluation method are proposed. © 2013 Elsevier B.V. All rights reserved. ispartof: Journal of Materials Processing Technology vol:214 issue:4 pages:998-1007 status: published

Mechanical ventilation (MV) is a lifesaving therapy for patients with the acute respiratory distress syndrome. However, selecting the optimal MV settings is a difficult process as setting a high positive end-expiratory pressure (PEEP) value will improve oxygenation, but can produce ventilator induced lung injuries (VILI). To find a suitable value is patient specific and depends on different things like the underlying illness and the current state. In this study, a respiratory model that defined constant bronchial resistance and pressure-dependent variable elastance was fitted to pressure volume (PV) responses for 12 datasets of 10 acute respiratory distress syndrome (ARDS) patients which underwent a recruitment maneuver (RM) to open previous collapsed alveoli. We believe that the range of minimal elastance represents that range in which oxygenation can be improved by recruitment with reducing the risk of VILI. The first order model with a variable elastance ( E drs ) described by Chiew et al. (2011) was modified with a factor α to express added end-expiratory volume due to an increased PEEP. Model parameters were identified using a nonlinear least square method that optimized E drs agreement across PEEP-levels. The model yielded an increase in overlapping quality of pressure dependent E drs -curves. A best pressure range for PEEP could be identified in 9 of 12 datasets. The model could potentially provide a simple method of decision support at the bedside for clinicians and could prospectively an automated extend in mechanical ventilation devices.

This paper presents the approach followed by WaterNetGen – an EPANET extension – to simulate water distribution systems considering both normal pressure and pressure-deficient scenarios. WaterNetGen models pressure-deficient scenarios by incorporating a pressure-demand relationship, which computes the available demand as a function of the current pressure, and considering leakage at pipe level (background and bursts). This new capability is fully integrated into the original EPANET interface, so the same network model can be used to perform demand-driven and pressure-driven analysis, leading to a faster a more accurate modelling of water distribution systems.

This paper presents a three-dimensional implementation of the so-called µ ( I ) rheology to accurately and efficiently compute steady-state dense granular flows. The tricky pressure dependent visco-plastic behaviour within an incompressible flow solver has been overcome using a regularisation technique along with a complete derivation of the incremental formulation associated with the Newton-Raphson algorithm. The computational accuracy and efficiency of the proposed numerical model have been assessed on two representative problems that have an analytical solution. Then, two application examples dealing with actual lab experiments have also been considered: the first one concerns a granular flow on a heap and the second one deals with the granular flow around a cylinder. In both configurations the obtained computational results are in good agreement with available experimental data.

The pressure dependent magnetic behavior of β -[Mn III TClPP] + [TCNE] − {MnTClPP = (4-tetrakis(4-chlorophenyl)porphyrinato)manganese(III); TCNE = tetracyanoethylene} and [Mn III TClPP] + [TCNE] − ·2PhMe up to 7.51 and 10.66 kbar, respectively, was determined. The T c ( P ) for non-solvated β -[MnTClPP][TCNE] reversibly increases with applied pressure by 50% from 5.4 K at ambient pressure to 8.1 K at 7.51 kbar at an average rate of 0.36 K/kbar. This is attributed to reduction of the intrachain Mn⋯Mn separation, the Mn–N–C angle, and the dihedral angle between the MnN 4 and [TCNE] − mean planes increasing the intra- and interchain interactions. Solvated [Mn III TClPP] + [TCNE] − ·2PhMe, likewise, has an initial increase in T c with applied pressure, but irreversible behavior is evident and this is attributed to the irreversible loss of solvent from the lattice. The increasing T c ( P ) with applied pressure differs from previous results reported for related substituted tetraphenylporphyrin manganese(III) TCNE compounds.

We investigate the pressure dependent fluidic damping in mechanical resonators from room pressure down to 3 Pa for a broad variety of designs. Air gaps underneath the suspended parts ranging from micro to nano-scale lead to a wide operating regime from the continuum regime down to the free molecular flow regime. Two pposed simulation approaches for modelling the airflow inside the gap are presented and both approaches are compared to measurements of mechanical resonators.