Linear Function Of Pressure Research Articles

NaxSb Alloy-Based Low-Frequency Mechanical Energy Harvesters for Virtual Taste Sensations.

Batteries can be activated by external mechanical force and generate current, enabling a smart class of electrochemical-mechanical strain energy harvesters therefrom. Here, we have developed a NaxSb alloy-based harvester that is able to electrochemically convert low-frequency bending or pressing mechanical energy into electrical energy. The device is designed as a flexible symmetric cell incorporating two sodiated antimony nanoflake electrodes, whose peak power and energy output are more than twice those of other sodium-alloyed electrochemical-mechanical strain energy harvesters reported. We demonstrate that the open-circuit voltage of the device is an asymptotic function of the curvature radius in the bending mode and a linear function of pressure in the pressing mode. Taking advantage of the tunability of voltage, we present a new technology that simulates various tastes by releasing low-voltage electrical signals from the harvester. This technology can not only help people with impaired taste but also be integrated into a virtual reality system to create immersive taste experiences.

Determination of Viscosity, Density and Interfacial Tension of the Carbon Dioxide–Isopropanol, Argon–Isopropanol, Sulphur Hexafluoride–Isopropanol Binary Systems at 313.15 K and 333.15 K and at Elevated Pressures

Viscosity, density, and interfacial tension of three binary systems (carbon dioxide–isopropanol, argon–isopropanol, and sulphur hexafluoride–isopropanol) were measured at temperatures of 313.15 K and 333.15 K and at pressures up to 100 bar for carbon dioxide, and for argon and sulphur hexafluoride up to 500 bar. A vibrating tube densimeter method has been used for density measurements and a variable-volume high-pressure optical view cell with some modifications for the other measurements. The results showed that pressure does not have a high impact on viscosity. Density is found to be a linear function of pressure and temperature and the densities of the investigated binary systems increase with pressure and decrease with temperature. Interfacial tension decreased with the elevated pressure at a constant temperature for all the investigated systems. Accurate prediction of thermodynamic and mass transfer data is fundamental in various engineering and industrial operations to design processes with a higher yield of targeted compounds.

Drivers of PM2.5 in the urban agglomeration on the northern slope of the Tianshan Mountains, China

Fine particulate matter (PM2.5) is a major source of air pollution in China. Although there have been many studies of the drivers of PM2.5 pollution in the megacities clustered in eastern China, the behavior of PM2.5 in the northwestern urban agglomeration is not well understood. This study used near-surface observation data for 2015–2019 obtained from the national air environmental monitoring network to examine variation in PM2.5 in the urban agglomeration on the northern slopes of the Tianshan Mountains (UANSTM). Two-factor interaction provided new insights into the dominant factors of PM2.5 in the study region. The annual average PM2.5 concentrations over the study period was 54.3 μg/m3, with an exceedance rate of 23.3%. Wavelet analysis showed two dominant cycles of 320–370 d and 150–200 d with high pollution events occurring in winter. The generalized additive model (GAM) contained linear functions of pressure, non-linear functions of SO2, NO2, relative humidity, sunshine duration and temperature. The two most primary variables, NO2 and SO2, represent 20.65% and 19.54% of the total deviance explained, respectively, while the meteorological factors account for 36.1% of the total deviance explained. In addition, the interaction between NO2 and other factors had the strongest effect on PM2.5. The deviance explained in the two factor interaction model (88.5%) was higher than that in the single factor model (78.4%). Our study emphasized that interaction between meteorological factors and pollutant emissions enhanced the impact on PM2.5 compared with individual factors, which can provide a scientific basis for developing effective emission reduction strategies in UANSTM.

Pressure effects on the EXAFS Debye-Waller factor of iron.

The pressure effects on atomic mean-square relative displacement characterizing the extended X-ray absorption fine structure (EXAFS) Debye-Waller factor of iron metal have been investigated based on the Debye model. The analytical expressions of the Debye frequency and EXAFS Debye-Waller factor have been derived as functions of crystal volume compressibility. Based on the well established equation-of-state including the contributions of the anharmonic and electronic thermal pressures, numerical calculations have been performed for iron up to a pressure of 220 GPa and compared with experimental data when possible. These results show that the Debye frequency increases rapidly with compression, and beyond 150 GPa it behaves as a linear function of pressure. Meanwhile the mean-square relative displacement curve drops robustly with pressure, especially at pressures smaller than 100 GPa. This phenomenon causes the enhancement of EXAFS signals at high pressure. Reversely, the increasing of temperature will reduce the amplitude of EXAFS spectra.

Laminar burning velocities of LCV syngas-air mixtures at high temperature and pressure conditions

Laminar burning velocities of low-calorific value syngas-air mixtures are measured at elevated temperature and pressure conditions using externally heated diverging channel method. The technique facilitates direct measurement of laminar burning velocities simultaneously at elevated pressures and temperatures. The mixture burning velocities are observed to increase with mixture enthalpy at elevated temperatures and decrease with an increase in the mixture pressure. The measurements are carried out for a mixture temperature range of 300–650 K and up to 5 bar pressure. Based on these measurements a new relation for the variation of laminar burning velocity with pressure and temperature is proposed. The power-exponents of temperature and pressure were expressed as linear functions of pressure and temperature ratios, respectively. The comparison of the measured burning velocities with the best performing kinetic schemes (FFCM-1 and Aramco 3) revealed that a significant deviation in the predictions is observed, when a simultaneous increase in pressure and temperature are considered.

Investigation of melting point, Debye frequency and temperature of iron at high pressure

The Debye model has been developed to investigate the pressure effects on melting point, Debye frequency and Debye temperature of iron metal. The analytical expressions of these thermodynamic quantities have been derived as functions of crystal volume compressibility. The pressure dependence of them is studied based on the well-established equation-of-state which includes the contributions of the anharmonic and electronic thermal pressures. We performed numerical calculations for iron up to pressure 350 GPa and compared with experimental data when possible. Our results show that the Debye frequency and Debye temperature increase rapidly with compression, and beyond 150 GPa they behave like linear functions of pressure. From the pressure-dependent melting point of iron, we deduce the temperatures of the Earth’s inner-outer core boundary (ICB) and core-mantle boundary (CMB). The temperatures of the Earth’s ICB and CMB are predicted lower than 5540(±170) K and about 4060 K, respectively.

High-Pressure Effects on the Intermetallic Superconductor Ti0.85Pd0.15

This work reports superconductivity studies in the intermetallic Ti$_{0.85}$Pd$_{0.15}$ performed in normal conditions and under hydrostatic pressure. The crystal structure of the compound has a body centered cubic at room temperature and atmospheric pressure as unstable $\beta$-Ti phase. X-Ray diffraction pattern shows space group $Im\bar{3}m$ with parameter $a=3.2226(4)$ \AA and density around 5.6242 g/cm$^{3}$. The superconducting transition temperature, T$_{C}=3.7$ K was determined from resistance, magnetization, and specific heat measurements. The two critical magnetic fields, the coherence length, Ginzburg-Landau parameter, London penetration depth, the superconducting energy gap, the Debye temperature, the electron-phonon coupling constant and density of states at the Fermi level were calculated. These parameters were obtained at ambient pressure. Under hydrostatic pressure, the magnetic susceptibility measurements show a small increment on T$_{C}$, the maximum T$_{C}=3.83$ K was obtained at the maximum applied pressure of 1.03 GPa. The slope calculated for T$_{C}$ as a linear function of pressure was about 0.14 K/GPa, possibly associated with an increase in the electronic density of states.

Progress towards a gas-flow standard using microwave and acoustic resonances

We describe our progress in developing a novel gas flow standard that utilizes 1) microwave resonances to measure the volume, and 2) acoustic resonances to measure the average gas density of a collection tank/pressure vessel. The collection tank is a 1.85 m3, nearly-spherical, steel vessel used at pressures up to 7 MPa. Previously, using the cavity's microwave resonance frequencies, we determined the cavity's pressure- and temperature-dependent volume VBBB with the expanded uncertainty of 0.022% (coverage factor k = 2, corresponding to 95% confidence level). This was the first step in developing a pressure, volume, speed of sound, and time (PVwt) primary standard. In the present work, when the shell was filled with argon, measurements of pressure and acoustic resonance frequencies determined the “acoustic mass” Macst that agreed with gravimetric measurements within 0.04%, even when temperature gradients were present. Most of these differences were a linear function of pressure; therefore, they can be reduced by further research. We designed and implemented a novel positive feedback system to measure the acoustic resonance frequencies. Using the measurements of VBBB, pressure, and acoustic resonance frequencies of the enclosed gas (nitrogen or argon), we calibrated 3 critical flow venturis that NIST has used as working standards for over 10 years. The two independent flow calibrations agreed within the long-term reproducibility of each CFV, which is less than 0.053%. Furthermore, the feasibility of a dynamic tracking technique using this feedback loop was tested by comparing ΔMacst computed under no-flow conditions and ΔMacst computed by the rate of fall or rise during a flow. This was done for flows ranging from 0.11 g/s to 3.9 g/s.

Regularities of liquid potassium at different temperatures

Several new regularities in liquid potassium have been found from the existing experimental data and calculated thermodynamic properties along the isothermal lines with the equation of state (EoS) of a power law form. The quantity (Z − 1)V2 is linearly proportional to V2 with a common intersection point for all isotherms at high temperature and PintV versus V−2 is nearly linear, where Z, V and Pint are compressibility factor, molar volume and internal pressure. Both the isothermal bulk modulus and internal pressure are nearly a linear function of pressure at constant temperature. There is a linear relationship existing between the calculated reduced isothermal bulk modulus and V−2. Based on the linear isotherm regularity EoS, analytical expression of thermodynamic properties of liquid potassium can be obtained. Furthermore, we found crossing points existing in the isobaric thermal expansion coefficient and Anderson-Grüneisen parameter.

Incorporating the Modified Orifice Equation into Pipe Network Solvers for More Realistic Leakage Modeling

AbstractIt has been well established in several experimental and modeling studies that leak areas are often not fixed, but vary as linear functions of pressure. Replacing this linear equation into ...

Predicting the Head-area Slopes of Circular Holes in Water Pipes

Leak openings in water distribution system pipes are not static, but vary with pressure. These changes in area affect the way that leaks respond to changes in pressure, and are thus important for municipal engineers to understand. In this study, the behavior of round holes in pressurized pipes was investigated using finite element analysis (FEA), under the assumption of linear elastic behavior. It was found that the areas of the round holes vary as linear functions of pressure in the pipe. A sensitivity analysis was then carried out to investigate parameters that influence the head-area slope. The elastic modulus, internal pipe diameter and pipe wall thickness were found to be the most important parameters. Solid mechanics theory was used to develop an equation to predict the head-area slope m of round holes in pipes. Finally, the results were compared to the findings of an experimental study. The comparison showed that the head-area slopes for both the equation and the FEA were within or close to the 95% confidence intervals of the experimental study.

Metal matrix syntactic foams produced by pressure infiltration—The effect of infiltration parameters

Metal matrix syntactic foams (MMSFs) were produced by pressure infiltration. Two parameters of the infiltration process (pressure and time) were varied and the infiltrated length was measured as the function of infiltration parameters in order to get data for the implementation of pressure infiltration as mass-production of MMSFs similar to injection mould casting, especially in the short infiltration time range (<10s). The infiltrated length was found to be linear function of pressure and square-root function of time. The effect of the infiltration parameters on the microstructure and mechanical properties of MMSFs were investigated by optical microscopy and standardised compression tests. The microscopic images were used to qualify the pressure infiltration and showed that more than one combination of infiltration parameters can be found for successful production of a part with given required dimensions. Considering the compression tests, the main characterising properties were mapped as function of infiltration parameters. The registered values showed dependency on the infiltration parameters and indicated that a given infiltration length produced by higher pressure and shorter time has better mechanical properties. The infiltrated specimens were isotropic, anisotropy was not observed in the reference measurements.

P-T phase diagram of iron arsenide superconductor NdFeAsO0.88F0.12

NdFeAsO0.88F0.12 belongs to the recently discovered family of high-TC iron-based superconductors. We have studied the influence of high pressure on transport properties of this material at low temperatures using the four-probe electrical conductivity technique in a diamond cell. Contrary to La-based compounds, we did not observe a maximum in TC under pressure. Under compression, TC drops rapidly as a linear function of pressure with the slope k = −2.8 ± 0.1 K/GPa. Under decompression, the behavior is completely reversible. The extrapolated value of TC at zero pressure is about TC (0) = 51.7 ± 0.4 K. At pressures higher than ∼18.4 GPa, the superconducting state disappears at all measured temperatures, although electrical resistance changes slope dramatically and shows a concave behavior. These observations may be related to the Kondo effect or to a weak localization of two-dimensional carriers at high pressures and low temperatures below ∼45 K, indicating a competition mechanism with the superconducting phase. On the bases of our experimental data, we propose a tentative P-T phase diagram of NdFeAsO0.88F0.12.

Sulfur mass-independent fractionation patterns in the broadband UV photolysis of sulfur dioxide: Pressure and third body effects

The production of mass-independent fractionation (MIF) in the products of the middle/far UV photolysis of SO 2 isotopologues has been linked to large S-MIF signatures observed in the pre-2.45 Ga rock record, and provides a valuable proxy for the evolution of atmospheric O 2. The origin of such large MIF signatures in photolytic products has recently been ascribed to the optical self-shielding of SO 2 isotopologues in photon-limited regions of the lower atmosphere. To better characterize the origin of such a signal we have performed pressure-variant broadband UV photolysis experiments of SO 2 and SO 2–He mixtures. Low pressure (~ 20 Torr) photolysis of SO 2 produces extractable sulfur with large δ 34S ≈ 120–180‰, Δ 33S ~ 20‰, and Δ 36S/Δ 33S ≈ − 2.5, while near atmospheric pressures produce sulfur with Δ 33S ~ 2‰, and Δ 36S/Δ 33S ≈ − 12. Similar experiments conducted with variable pressures of helium bath gas produce a similar diminution in Δ 33S, and in both cases a Δ 36S/Δ 33S ratio that is a linear function of pressure over several orders of magnitude. We postulate a photochemical and kinetic origin for the large S-MIF observed in these static cell experiments, produced from the excited state predissociative dynamics of SO 2, but cannot expressly rule out self-shielding as a contributor to fractionations observed here.

Measurement and Correlation of Solubility of Carbon Monoxide in Phenol+Ethanol Solvents

The solubility of carbon monoxide in phenol+ethanol mixed solvents at elevated pressures is reported in this article. The experimental results revealed the influence of pressure on the solubility of CO in phenol+ethanol mixtures. These mixtures are a poorer solvent for carbon monoxide. The solubility of CO is a linear function of pressure, and the extended Henry's constants were presented at different concentrations of phenol. The cubic Soave-Redlich-Kwong equation of state was used to correlate the experimental gas liquid equilibrium data and to predict the solubility of CO. At the same time, the binary interaction parameters, k ij , for CO-phenol, CO-ethanol and phenol-ethanol systems were estimated by fitting experimental GLE data at 303.15 K and at 2.0–9.0 MPa. Hence, a model was suggested for the solubility of CO in phenol+ethanol mixed solvents. The agreement between experimental and calculated solubilities with the proposed model was rather satisfactory.

Studies of the collision frequency of ideal gas particles with the surfaces of the objects created using the ballistic deposition technique

This paper is a continuation of our studies of the collision frequency of ideal gas particles with the rough/fractal surfaces. Here, we applied a more realistic surface growth model, i.e. ballistic deposition for creation of fractal objects. We found that the collision frequency with irregular surfaces is the linear function of pressure and this frequency per unit pressure is quite a complicated function of the surface fractal dimension as well as the diameter of colliding particle. The collision frequency with rough surfaces cannot be exactly described by the analytical formula called the Langmuir–Hertz equation. However, we have stated that the deviations of the true collision frequency from the Langmuir–Hertz prediction are not huge and in typical catalytic studies the error introduced by replacing the true frequency by the Langmuir–Hertz prediction can be safely neglected. We have also studied the probability of finding on the surface an atom which has been hit a certain number of times by a gas particle. This probability reveals an interesting behaviour for small gas particles, i.e. it perfectly correlates with the number of directions from which the surface atom is accessible from the gas phase. We have also estimated the evolution of the adsorption energy distribution with the increasing fractal dimension of the surface in the ballistic deposition.

Lubricant flow in pressure pipes during wire drawing in a hydrodynamic friction mode

The process of wire drawing under hydrodynamic friction is simulated by a liquid flow whose viscosity is a linear function of pressure. Accurate analytical solutions for the velocity and pressure distribution over the clearance between the moving wire and the pressure pipe lengthwise and through depth are obtained. The pressure distribution is shown to be asymmetrical through depth and nonlinear along the channel length, the velocity profile being other than parabolic.

Transient Burning Characteristics of JA2 Propellant Using Experimentally Determined Zel'dovich Map

Combustion characteristics of JA2 propellant were studied both experimentally and theoretically. Its steady-state burning behavior was investigated using an optical strand burner. The parameters measured were the regression rate, subsurface temperature profile, and burning surface temperature at different initial temperatures (-40<T i <80°C) and pressures (0.1<P<68 MPa). The measured burning rates r b were correlated as a function of T i and pressure up to 300 MPa. Predicted r b from the correlation are in close agreement with experimental data. The temperature sensitivity σ p was found to decrease as pressure increases, reaching an asymptotic value of 0.0024 K -1 at high pressures. Surface-temperature data were correlated as a linear function of pressure with temperature-dependent coefficients. The Zel'dovich map was constructed from the experimental data. This map was then used in a computer simulation to investigate the transient burning characteristics of JA2 under different pressurization rates. From the simulation results, it was found that JA2 propellant only exhibits a mild transient burning effect. This finding is further confirmed with the observations obtained from a parallel experimental study using an interrupted burner coupled with a real-time X-ray radiography. The reason for this finding is the low value of σ p and its rapid decay as the pressure increases for P < 20 MPa.

Study on diffusion and flow of benzene, n-hexane and CCl 4 in activated carbon by a differential permeation method

In this paper the diffusion and flow of carbon tetrachloride, benzene and n-hexane through a commercial activated carbon is studied by a differential permeation method. The range of pressure is covered from very low pressure to a pressure range where significant capillary condensation occurs. Helium as a non-adsorbing gas is used to determine the characteristics of the porous medium. For adsorbing gases and vapors, the motion of adsorbed molecules in small pores gives rise to a sharp increase in permeability at very low pressures. The interplay between a decreasing behavior in permeability due to the saturation of small pores with adsorbed molecules and an increasing behavior due to viscous flow in larger pores with pressure could lead to a minimum in the plot of total permeability versus pressure. This phenomenon is observed for n-hexane at 30°C. At relative pressure of 0.1–0.8 where the gaseous viscous flow dominates, the permeability is a linear function of pressure. Since activated carbon has a wide pore size distribution, the mobility mechanism of these adsorbed molecules is different from pore to pore. In very small pores where adsorbate molecules fill the pore the permeability decreases with an increase in pressure, while in intermediate pores the permeability of such transport increases with pressure due to the increasing build-up of layers of adsorbed molecules. For even larger pores, the transport is mostly due to diffusion and flow of free molecules, which gives rise to linear permeability with respect to pressure.

Drying with superheated steam: maximum drying rate as a linear function of pressure

Drying with superheated steam (SS) as heating agent is controlled through three operative variables, the steam temperature, the recycle velocity, and the system pressure. Once the other conditions are fixed, there is an optimum pressure at which drying rate reaches its maximum value. The exact optimum conditions can be found through a differential mass and energy balance over the heat exchange area, resulting in two equations. The first one to calculate the drying rate as function of the operating conditions and the second one to find the values of those conditions which make the operation optimum. Then, using these equations, this paper shows that the relationship between maximum drying rate and pressure can be rewritten in a unique linear equation. Experiments were performed in a model system to obtain a family of drying rates versus pressure curves, and in accordance with the predicted behaviour, it was observed that all maximum drying rates lay on a straight line.