Simultaneous Effects Of Pressure Research Articles

Simultaneous effects of pressure, temperature, and external magnetic field on absorption threshold frequency of tuned quantum dot/ring systems: an analytical study

Simultaneous effects of pressure, temperature, and external magnetic field on absorption threshold frequency of tuned quantum dot/ring systems: an analytical study

Swelling and rheological behavior of preformed particle gel nanocomposite: simultaneous effect of pressure, temperature, and salinity

Swelling and rheological behavior of preformed particle gel nanocomposite: simultaneous effect of pressure, temperature, and salinity

Exciton radiative recombination time in a group III-V/II-VI core/shell quantum dot: Simultaneous effects of pressure and temperature

Excitonic properties of a compound semiconductor from group III-V and group II-VI materials are studied applying external perturbations. The simultaneous effects of pressure and temperature on exciton energies in an InP/ZnS quantum dot (core/shell) are found taking into account the ratio of radius of core/shell dot. The results bring out that the radiative lifetime enhances monotonically when the ratio of radius of core to shell quantum dot increases and it reaches a saturation value when Rc/Rs → 1 and the radiative recombination lifetime enhances upto 9 ns. The results can be applied for tailoring the excitonic optical transitions in nano-optical devices.

Simulation and multi-objective optimization of a radial flow gas-cooled membrane reactor, considering reduction of CO2 emissions in methanol synthesis

This paper deals with a steady-state simulation of a Radial Flow Gas-Cooled Reactor (RF-GCR) and a Radial Flow Gas-Cooled Membrane Reactor (RF-GCMR) for enhancing CO2 removal in the methanol synthesis process. Reactors consist of annular packed-beds (subsections) and annular cooling-chambers. This configuration creates radial flows for reacting and synthesis gases and results in a negligible pressure drop along the beds. Each subsection is in contact with two cooling-chambers from top and bottom that offers an excellent heat transfer area and contributes to a noteworthy reduction in reaction phase temperature. Besides, hydrogen permeation through Pd–Ag membrane layer in upper and lower walls of RF-GCMR cooling-chambers shifts the reaction toward more products. Simultaneous effects of pressure, temperature, and H2 permeation increases CO2 removal and methanol production rates by 592% and 6.84%, respectively in RF-GCMR compared to Conventional Gas-Cooled Reactor (CGCR). Afterward, a two-objective optimization of RF-GCMR is implemented using Non-dominated Sorting Genetic Algorithm-II (NSGA-II) to maximize methanol production rate and selectivity. Final Pareto-optimal solution is found by TOPSIS, LINMAP, and Shannon’s Entropy decision-making methods. Shannon’s Entropy, with the lowest deviation index, improves CO2 removal and methanol production rates 78.3% and 10.77%, respectively in Optimized RF-GCMR (ORF-GCMR) compared to non-optimized RF-GCMR.

Magnetic Susceptibility of Cylindrical Quantum Dot with Aharonov-Bohm Flux: Simultaneous Effects of Pressure, Temperature, and Magnetic Field

Using canonical ensemble, we have studied the magnetic properties of a cylindrical GaAs quantum dot in this paper. The system is under the direct influence of external static electric and magnetic fields and an Aharonov-Bohm magnetic flux. Considering the temperature- and pressure-dependent effective parameters, the magnetic susceptibility is calculated and plotted in different regimes. Results clearly show the magnetic susceptibility, magnetic transition, and critical points strongly depend on temperature, pressure, and magnetic field. Moreover, Aharonov-Bohm magnetic flux has considerable effects on the magnetic susceptibility of the system.

Combined effect of pressure and temperature for yogurt production.

Fermentation under non-conventional conditions has gained prominence in the last years, due to the possible process improvements. Fermentation under sub-lethal pressures is one of such cases, and may bring novel characteristics and features to fermentative processes and products. In this work, the effect of both pressure (10-100 MPa) and temperature (25-50 °C) on yogurt production fermentation kinetics was studied, as a case-study. Product formation and substrate consumption were evaluated over fermentation time and the profiles were highly dependent on the fermentation conditions used. For instance, the increase of pressure slowed down yogurt fermentation, but fermentative profiles similar to atmospheric pressure (0.1 MPa) were obtained at 10 MPa at almost all temperatures tested. Regarding temperature, higher fermentative rates were achieved at 43 °C for all pressures tested. Moreover, the inhibitory effect of pressure increased when temperature decreased, with complete inhibition of fermentation occurring at 50 MPa for 25-35 °C, contrasting to 43 °C where inhibition occurred only at 100 MPa. Therefore, an antagonistic effect seems to occur, since yogurt fermentation was slowed down by pressure increasing, on one hand, and by temperature decreasing, on the other hand. Additionally, some kinetic parameters were calculated and fermentation at 43 °C presented the best results for yogurt production, with lower fermentation times and higher lactic acid productivities. Interestingly, fermentation at 10 MPa/43 °C presented the optimal conditions, with improved yield and lactic acid production efficiency, when compared to fermentation at 0.1 MPa (efficiency of 75% at 10 MPa, against 40% at 0.1 MPa). As the authors are aware, this work gives the first insights about the simultaneous effect of pressure and temperature variation on a microbial fermentation process, which can be combined to modulate the metabolic activity of microorganisms during fermentation in order to improve the fermentative yields and productivities of the desired product.

Low-temperature anatase-to-rutile phase transformation and unusual grain coarsening in titanium oxide nanopowders by high-pressure torsion straining

Simultaneous effect of pressure, temperature and plastic strain on structural evolution of titania ceramic nanopowder was investigated using the high-pressure torsion (HPT) method. Unlike static annealing, in which the anatase-to-rutile phase transformation occurred at 1173 K, the transformation was observed at low temperatures as 473–573 K by HPT processing. The formation of rutile phase accompanied with dynamic recrystallization and an unusual grain growth, indicating that severe plastic deformation at low homologous temperatures does not necessarily result in grain refinement of metastable nanoceramics. Besides the coarsened grains of rutile phase, a high-pressure TiO2-II columbite phase was also detected in small nanograins.

Simultaneous effects of pressure and temperature on the optical transition energies in a Ga0.7In0.3N/GaN quantum ring

Simultaneous effects of pressure and temperature on electronic and optical properties are studied in a Ga0.7In0.3N/GaN quantum ring using variational formulism. The changes in exciton binding energy due to the applications of hydrostatic pressure and temperature are obtained taking into account the geometrical confinement. The transition energies of interband and intersubband as a function of hydrostatic pressure, at a constant temperature, are obtained. The oscillator strength due to interband and intersubband optical transitions with the combined effects of hydrostatic pressure and temperature is found. The pressure and temperature induced absorption coefficients as a function of photon energy are investigated in a Ga0.7In0.3N/GaN quantum ring. The results show that the application of pressure leads to blue shift of the resonant peaks of the optical transition whereas the effect of temperature suffers red shift of the resonant peaks.

Simultaneous effects of pressure and temperature on excitons in Pöschl–Teller quantum well

Binding energies of the heavy hole and light hole exciton in a quantum well with Pöschl–Teller (PT) potential composed of GaAs have been studied variationally within effective mass approximation. The effects of pressure and temperature on exciton binding energy are analyzed individually and also simultaneously for symmetric and asymmetric configuration of the well. The results show that exciton binding energy (i) decreases as the well width increases, (ii) increases with pressure and (iii) decreases with temperature. Simultaneous effects of these perturbations lead to more binding of the exciton. The results are compared with the existing literature.

The effects of polaronic mass and conduction band non-parabolicity on a donor binding energy under the simultaneous effect of pressure and temperature basing on the numerical FEM in a spherical quantum dot

Basing on the numerical Finite Element Method (FEM), we have investigated the influences of polaronic mass and conduction band non-parabolicity on the binding energy of the ground state of an on-center hydrogenic donor impurity in a spherical GaAs/Ga1−xAlxAs quantum dot structure. The calculations have been made with a realistic potential barrier height in the framework of the effective mass approximation including the combined effect of hydrostatic pressure and temperature. The donor binding energy is computed as a function of dot size, Al concentration x, hydrostatic pressure and temperature both in the absence and presence of polaronic mass and conduction band non-parabolicity effects. We have taken into account the electronic effective mass, dielectric constant, and conduction band offset between the dot and barriers varying with pressure and temperature. It has been found that the binding energy is strongly affected by the effect of polaronic mass and conduction band non-parabolicity for narrow quantum dot and large Al concentration x. The results show again that the donor binding energy increases linearly with the pressure in direct gap regime and its variation is larger for narrower dots only and drops slightly with the temperature. A good agreement is obtained with the existing literature values.

The Effectiveness Factor Determination for a Three-hole Cylindrical Catalyst Pellet in a Steam Methane Reforming Reaction

Pressure and temperature effects on steam methane reforming catalysts were investigated. The investigation was carried out by developing an effectiveness factor relation for a three-hole (trefoil) common shape catalyst pellet in industrial units to check the simultaneous effects of pressure and temperature on the extent of the reaction. Two methods for estimation of the effectiveness factor were applied: A—simplified method and B—a new method based on more realistic conditions of the reaction. The results obtained based on this study would be useful for optimizing pressure and temperature of SMR catalysts.

Effectiveness Factor Determination for a Four-hole Catalyst Pellet in a Steam Methane Reforming Reaction

Pressure and temperature effects on steam methane reforming (SMR) catalysts were investigated. The investigation was carried out by developing of an effectiveness factor relation for four-hole common shape catalyst pellet in industrial units, to check the simultaneous effects of pressure and temperature on the extent of the reaction. Two methods for estimation of the effectiveness factor were applied: a simplified method and a new method based on more realistic conditions of the reaction. The results obtained based on this study would be useful for optimizing of pressure and temperature of SMR catalysts.

Multilateral Analysis of Pressure and Temperature Effects on Steam Methane Reforming Reaction

Pressure and temperature effects on steam methane reforming (SMR) process in porous media and at equilibrium conditions of the reaction were investigated. The investigation was carried out by developing of a computer program to check the simultaneous effects of pressure and temperature on the extent of the reaction. Two methods for estimation of the effective diffusivity coefficients through porous catalysts were applied: (a) simplified method and (b) a new method based on more realistic conditions of the reaction. The results obtained based on this study would be useful for optimizing of pressure and temperature of SMR reaction.

Simultaneous effects of pressure and temperature on the binding energy and diamagnetic susceptibility of a laser dressed donor in a spherical quantum dot

Binding energies and diamagnetic susceptibility of an impurity in a spherical GaAs quantum dot under the simultaneous influence of static pressure, temperature and laser radiation are investigated. Pressure- and temperature-dependent dressed potential which is produced by the combined effects of laser radiation and impurity considerably change the energy spectrum and diamagnetic susceptibility of the system. It is shown that binding energies and diamagnetic susceptibility increase with increasing pressure. Moreover, laser radiation effects on the diamagnetic susceptibility are not significant in comparison with its effects on the binding energy.

The role of high-pressure in the reactivity of simple molecules: implications in prebiotic chemistry

Simple molecules are abundant in several space environments and the knowledge of their physical properties and chemical reactivity is central in many disciplines. Pressure plays a key role in this scenario causing intriguing and unexpected aggregation forms and chemical transformations also for the simplest molecules like water, nitrogen and carbon dioxide. Particularly interesting is the simultaneous effect of pressure and absorption of radiation, a common scenario in spatial environments, because of the electronic changes produced in the molecular systems which result able to trigger chemical processes by exploiting the high-density conditions. Here we will provide some examples of the high-pressure reactivity of few simple model molecules and of their mixtures. These molecules have been selected on the basis of their abundance and relevance in a prebiotic chemical framework. In most of the examples, attention is posed on the comparison between purely pressure-induced and laser-assisted high-pressure reactions in order to account and discriminate the effects of the two variables on the reactivity. The technical approaches employed to reproduce in laboratory, the pressure and temperature conditions of interest for simulating the conditions encountered in different spatial environments will also be briefly reviewed.

Simultaneous effects of pressure and temperature on donor binding energy in Pöschl–Teller quantum well

Abstract In the frame of the variational method and the effective-mass approximation, the effects of hydrostatic pressure and temperature on the binding energy for donor impurities in the Poschl–Teller quantum well are studied. The binding energy dependencies on the width of the quantum well, the hydrostatic pressure, the impurity position, the temperature, and the parameters of the confining potential are reported. The results show that the binding energy increases (decreases) with the increasing of the hydrostatic pressure (temperature). It is also found that, associated with the symmetry breaking in the Poschl–Teller quantum well, and depending on the impurity position, the binding energy can increase or decrease.

Simultaneous effects of pressure and magnetic field on intersubband optical transitions in Pöschl–Teller quantum well

The simultaneous effects of hydrostatic pressure and magnetic field applied along the quantization direction on intersubband optical transitions in Pöschl–Teller quantum well are investigated. The expression of the absorption coefficient and some selection rules are obtained. The dependences of the absorption coefficient on magnetic field induction and incident photon energy for different values of pressure and parameters of quantum well are obtained as well.

Simultaneous effects of pressure and laser field on donors in GaAs/Ga 1−xAl xAs quantum wells

Within the framework of effective-mass approximation, using a variational method, the combined effect of the hydrostatic pressure and high-frequency laser field on the binding energy of a hydrogenic impurity in square and parabolic GaAs/Ga 1− x Al x As quantum wells is investigated. Our numerical results show that the effects of the laser field on the electronic properties are more pronounced than those of the pressure ones, and the changes in the binding energy are dependent on the shape of the confinement potential. The variations of the impurity binding energy in intense laser fields can be tuned by the hydrostatic pressure.

Simultaneous effects of pressure and magnetic field on donors in a parabolic quantum dot

The binding energy of shallow hydrogenic impurities in parabolic quantum dots is calculated using a variational approach within the effective mass approximation. The binding energies are worked out for GaAs/Ga 1− x Al x As structures as a function of dot size when the static pressure and the magnetic field are applied simultaneously. The results show that the impurity binding energy (i) increases with the reduction in dot sizes for a given pressure and magnetic field; (ii) decreases for a given dot in the presence of pressure; (iii) increases for a given dot by the influence of magnetic field and (iv) increases for a given dot in the presence of pressure and magnetic field applied simultaneously. The result shows that the ionization energy is purely pressure dependent for dots of size less than an effective Bohr radius. The results are compared with available data in the literature.

Simultaneous effects of pressure and temperature on donors in a GaAlAs/GaAs quantum well

The ground state and a few excited state energies of a hydrogenic donor in a quantum well are computed in the presence of pressure and temperature. The binding energies are worked out for GaAs/ Ga1−xAlxAs structures as a function of well size when the pressure and temperature are applied simultaneously. A variational approach within the effective mass approximation is considered. The results show that for a constant applied pressure, an increase in temperature results in a decrease in donor impurity binding energy while an increase in the pressure for the same temperature enhances the binding energy. When the pressure and temperature are applied simultaneously the binding energy decreases as the well width increases. In all the cases, it is observed that there is an increase in the binding energy due to the decrease in the quantum well size and in the dielectric constant whereas the effects of temperature on the effective mass are minimal.