Decrease In Ambient Pressure Research Articles

Experimental study on the flame trajectory evolution of horizontal jet fires under reduced pressures

Jet fire including process pipeline/tank leakage, oil exploitation industry of tail gas treatment flare or other industrial combustors as a common phenomenon can be found at high altitude areas. This work characterizes the flame trajectory evolution of horizontal jet fires under reduced pressures, which is rarely studied. The experimental results show that the horizontal flame projection distance increases monotonously, but the vertical flame length first increases and afterward decreases with the increase of heat release rate and the decrease of ambient pressure. Meanwhile, flame trajectory length increases significantly and then slowly with increasing heat release rate, but first increases to a maximum value and afterward declines with decreasing ambient pressure. Meanwhile, the turning point of vertical flame length appears earlier than that of flame trajectory length with increasing heat release rate (or jet velocity at source) and decreasing ambient pressure. Then, a mathematical model based on the flame arc hypothesis and a dimensionless model were proposed to describe the flame trajectory length, the momentum-buoyancy length scale Lm=(M0/g′)1/3 was used to normalize the flame trajectory length. The measured flame trajectory length in terms of the nozzle diameter, heat release rate, and ambient pressure was satisfactorily correlated by the proposed models.

Experimental Investigation on Thermal Runaway of Lithium-Ion Batteries under Low Pressure and Low Temperature

Understanding the thermal runaway mechanism of lithium-ion batteries under low pressure and low temperature is paramount for their application and transportation in the aviation industry. This work investigated the coupling effects of ambient pressure (100 kPa, 70 kPa, 40 kPa) and ambient temperature (−15 °C, 0 °C, 25 °C) on thermal behaviors in an altitude temperature chamber. The experimental results indicate that lowering ambient pressure and temperature could attenuate the thermal runaway intensity, which is mainly attributable to the reduction in oxygen concentration and the increase in heat loss. Such a dual effect leads to the maximum temperature decreasing from 811.9 °C to 667.5 °C, and the maximum temperature rate declines up to 2.6 times. Correspondingly, the whole thermal runaway process is deferred, the total time increases from 370 s to 503 s, and the time interval, Δt, from safety venting gains by 32.3% as the ambient pressure and temperature decrease. This work delivers an in-depth understanding of the thermal characteristics under low pressure and low temperature and provides meritorious guidance for the safety of cell transportation in aviation.

Wasted efforts of elite Marathon runners under a warming climate primarily due to atmospheric oxygen reduction

Meteorological conditions exert influences on sport performances via complex processes. Previous studies conventionally investigate the effects of weather conditions on marathon performance by following events held at the same places, which brings large uncertainties due to the changed participants. Via following each athlete to eliminate these uncertainties, we show that elite athletes’ marathon-running performance tends to monotonically worsen as ambient temperature rises except when it is extremely cold based on the best 16 athletes from each of the sex continents. It worsens by 0.56 (0.39 for men and 0.71 for women) min/°C when it rises beyond 15 °C. Theoretical analysis based on global marathon performance and weather observation datasets shows that more than half of this effect is mediated by reduced oxygen partial density as warmer temperature expands air and increases vapor pressure for both the men and women athletes, which is confirmed by the methods of Baron–Kenny. This atmospheric thermodynamic mechanism has not been emphasized previously. We also show that world-top athletes’ marathon performance approximately linearly worsens as ambient pressure decreases and slightly worsens as relative humidity rises if not extremely wet. These results substantially differ from the previous ones following the events instead of each athlete. Multi-variable changes in climate system are projected to slow Olympic marathon athletes by 2.51 and 1.06 min by the end of the 21st century in relative to 2020 under the high and intermediate emission scenario, respectively. Therefore, future progression of marathon performance is likely to be substantially slowed or even halted by climate changes without efficient greenhouse gas mitigation.

Influence of reduced pressure on arc and weld pool properties in TIG welding

In this article, transient transport phenomena in the arc and weld pool for different ambient pressures during tungsten inert gas welding were reported. Arc plasma and weld pool behaviour vary with ambient pressure because of changes in arc thermophysical properties. The maximum arc temperature decreases with decreasing ambient pressure because of reduced plasma electrical conductivity. Decreased arc mass density results in a lower maximum weld pool surface temperature and a decrease in maximum metal vapour content as ambient pressure decreases. Arc pressure decreases with decrease in ambient pressure, resulting in shallower penetration. Calculated arc temperature distribution and weld cross-section are compared with experiments to validate the modeling method for simulating heat and mass transfer phenomena in low ambient pressure welding.

Effects of low ambient pressure on the flame characteristics of ethanol−gasoline blended pool fire

The flame characteristics of Ethanol−Gasoline pool fire with different blend ratios were experimentally studied in a large−scale pressure−controlled compartment with ambient pressure of 40 kPa, 61 kPa, 80 kPa, and 101 kPa. The flame height, centerline temperature, and radiant heat flux were measured. The flame height increases notably with decreasing ambient pressure, but the flame temperature (intermittent and plume regions) slightly increases. With increasing ethanol ratio, the flame height and temperature decrease monotonously under large ambient pressure, but show a non−monotonic variation with a peak value at low ambient pressure and ethanol ratio of 10 %∼20 %. Heskestad’s flame height and temperature correlations were not suitable for blends pool fire under low ambient pressure. The new modified model for flame height correlation with ambient pressure and combustion heat of blends, and flame temperature correlation with flame height, fuel property parameter, and ambient pressure were developed with a better prediction. The addition of ethanol and decrease of ambient pressure led to the reduction of radiation loss from flame, and the non−monotonic variation with a peak value also occurs with increasing ethanol ratio at relatively large ambient pressure and ethanol ratio of 20 %. A new modified model based on the classical solid flame model was also developed to predict the radiative fraction, considering the ambient pressure, stoichiometric ratio, and the ratio of the combustion heat to the vaporization heat.

Blast wave propagation characteristics of moving charge at diminished pressure

The effects of different diminished pressures on moving charge blast wave parameters were investigated by employing the AUTODYN software. Meanwhile, a theoretical calculation model was established to predict the peak overpressure of the moving charge under diminished pressure conditions and was verified by experimental data and numerical simulations. Results indicate that the model can evaluate the blast wave peak overpressure of moving charge at diminished pressure effectively. As the velocity of the moving charge increases, the peak overpressure of the blast wave from the moving charge increases when the azimuth angle is less than 90°, but it decreases when the azimuth angle is greater than 90°. The blast wave peak overpressure of moving charge decreases but the blast wave action range increases as the ambient pressure decreases.

Multicentric case series of scuba diving fatalities: The role of intracardiac gaseous carbon dioxide in the forensic diagnosis

Scuba diving fatalities post-mortem diagnosis presents a higher level of forensic complexity because of their occurrence in a non-natural human life environment. Scuba divers are equipped with diving gas to breathe underwater. It is essential for them to be fully trained in order to be able to manage their dive safely despite the varying increase of ambient pressure and temperature decrease. Throughout the dive, the inhaled diving gas is dissolved in the diver’s tissues during the descent and if the decompression steps are not respected during the ascent, the balance between the dissolved gas and the tissues (including blood) is disrupted, leading to a gaseous release in the organism. Depending on the magnitude of this gaseous release, free gas can occur in blood and tissue. Venous or arterial gas embolism can also occur as a consequence of decompression sickness or barotraumatism. It can also induce drowsiness that consequently leads to drowning. As a result, the occurrence of gas in dead scuba divers is very complex to interpret, as is the difficulty to distinguish it from resuscitation maneuver artifacts or body decomposition. Although the literature is scarce in this domain, significant work has been done to provide a precise intracadaveric gas sampling method to enlighten the cause and circumstances of death during the dive. The aim of this study is to obtain higher statistical significance by collecting a number of cases to confirm the gas sampling protocol and analysis and gain more information about the cause of death and the events surrounding the fatality through the establishment of clear management guidelines.

Effectiveness of hydrogen enrichment strategy for Wankel engines in unmanned aerial vehicle applications at various altitudes

This study investigates the effectiveness of the hydrogen-enrichment strategy on a Wankel engine for unmanned aerial vehicles (UAVs). The primary motivation behind this study is to contribute to the Wankel-type rotary engine designs by revealing the influences of the hydrogen enrichment method on the Wankel engine performance at various altitudes. To achieve these objectives, CFD simulations were conducted by applying a hydrogen enrichment method to a neat gasoline Wankel engine model at sea level, 5000 ft and 15,000 ft altitudes. The hydrogen energy fraction at the intake was gradually increased from 0% to 10%. The decrease in ambient air temperature, pressure, density, and insufficient fresh charge with the increase in altitude leads to the reduced reference chamber temperature and pressure of the Wankel engine. Thus, the combustion worsens, the heat release rate (HRR) and performance decrease, also emissions deteriorate in these colder operating conditions. On the other hand, the unique physicochemical properties of hydrogen such as wide flammability limits, high homogeneity, relatively small quenching distance and high flame speed allow hydrogen-enriched mixture flames to propagate toward the narrower gaps in the combustion chamber and make up for some drawbacks of Wankel engines. As a result, flame propagation is accelerated and fuel burning rate, peak pressure and temperature values in the reference chamber are increased by hydrogen addition. For the cases at sea level with 5% and 10% hydrogen energy fraction, IMEP is increased by 6.59%, 8.50%, and the indicated power is increased by 35.51% and 52.47%. In the cases with the same energy fraction at 15,000 ft, IMEP is increased by 26.61% and 48.75%, and the indicated power is reduced by 26.61% and 48.75%, respectively. It has been proven that a small amount of hydrogen by energy fraction improves combustion efficiency and performance. The findings show that hydrogen has excellent compatibility with Wankel engines and hydrogen enrichment is a very practical concept for the improvement of the performance of these engines for UAVs. Thus, Wankel engines, which are already a very favorable power source for UAVs, become even more favorable by the hydrogen-blending strategy.

Droplet characteristics of multi-plume flash boiling spray evaluation using SLIPI-LIEF/Mie planar imaging technique

Flash boiling atomization is a promising approach whose primary breakup heavily relies on the phase change inside the nozzle. Droplet size measurement is crucial for fundamental studies of flash boiling sprays. However, the interference of the vapor phase and multiple scatterings in droplet-dense regions notably impact the accuracy of spray droplet size measurement. In this work, we utilized a three-phase structured laser illumination planar imaging, laser-induced exciplex fluorescence/Mie scattering (3p-SLIPI-LIEF/Mie) method in evaluating the droplet size distribution for a two-hole fuel injector and an ECN Spray G injector. The SMD characteristics of the fuel spray under various temperature and pressure boundary conditions were examined, and flash boiling spray collapse conditions were emphasized. The results show that the proposed SLIPI-LIEF/Mie method is superior to PDI techniques in providing more comprehensive results while maintaining satisfactory accuracy. The SLIPI-LIEF/Mie results show that the near-field plume expansion and SMD distribution strongly correlate with the flash boiling phase transition process. The droplet in the collapsed region was larger than that in the primary plume regions. However, whether or not the spray collapses, the SMD of the spray reduces as the fuel temperature increases, ambient pressure decreases, and injection pressure increases.

Vapor-induced flow and its impact on powder entrainment in laser powder bed fusion

A 2D axisymmetric transient Thermal-Fluid-Evaporation model coupled with melt pool dynamics and gas kinetics is developed to study the formation mechanisms of vapor-induced flow and the resulting powder entrainment in powder bed fusion using laser beam (PBF-LB) for 316 L powders. The interactions between keyhole formation inside the melt pool, vapor plume flow, and vapor-induced shielding gas flow are investigated. Vapor plume flow results in powder spattering with much higher speed, while vapor-induced gas flow significantly contributes to powder denudation with lower speed. It is also reported that powder spattering is stronger in 1 atm argon than that in 1 atm helium because the drag force for spattering is 2.72 times larger in 1 atm argon, but powder denudation becomes greater in 1 atm helium as the ratio of drag force for denudation in 1 atm argon to that in 1 atm helium is only 0.582. Furthermore, the vapor plume results in more spatters with the decrease of ambient pressure from 1 atm to 0.05 atm in argon because the plume is diluted faster with a twofold wider plume head and the two times higher peak velocity as a result of the pressure drop-induced significant reduction of viscosity restriction. A larger divergency angle in 0.05 atm argon is also recorded at the same time for the weaker restriction and faster dilution. In combination with in-situ observations, the proposed model provides insights into the vapor-induced flow, and its impact on powder entrainment under different gas types and ambient pressures.

Thrust characteristics of a truncated Laval nozzle with a bell-shaped tip

This paper presents the results of a thrust performance study of an unconventionally shaped supersonic nozzle in the form of a truncated Laval nozzle with a bell-shaped tip. This nozzle shape may be used in the development of compact layouts of multistage rockets. The study was carried out using the ANSYS software package in a 3D formulation. The methodological approaches to the numerical calculation of a complex separated gas flow used in this study were verified in a previous study of the flow pattern in similar nozzle. Some results of exact calculations were compared with the results of experimental studies carried out at the Institute of Technical mechanics of the National Academy of Sciences of Ukraine and the State Space Agency of Ukraine for a model of a similar truncated nozzle with a bell-shaped tip blown with a cold air. This study detailed the features of the separated gas flow in a spherical tip connected (at the corner point) to a truncated supersonic Laval nozzle of conical shape. It was found that the pattern of the separated flow in the tip depends on the nozzle flow expansion degree (nozzle inlet pressure). At a relatively low nozzle inlet pressure, a developed separation zone is observed in the nozzle tip (between the jet boundary and the nozzle wall) with a subsonic flow from the external environment, which forms an almost constant static pressure from the tip inlet cross-section to the tip exit. At a nozzle inlet pressure at which the free boundary of the jet flowing from the truncated nozzle adjoins the nozzle wall, the static pressure in the tip varies almost linearly along the tip length from the corner point with the minimum pressure to the tip exit. The dependence of the thrust of a tipped nozzle on the nozzle inlet pressure is nonlinear. As the pressure upstream of the nozzle increases (or the ambient pressure decreases), the effect of the external environment on the tipped-nozzle thrust diminishes. It is shown that under "terrestrial conditions" the thrust of a truncated nozzle with a tip exceeds the thrust of a profiled nozzle with the same geometric expansion degree (due to the atmosphere “entering” the tip). Under "vacuum” conditions, the former is 8% less than the latter.

Layer-to-layer thermal runaway propagation of open-circuit cylindrical li-ion batteries: Effect of ambient pressure

Preventing thermal runaway propagation is crucial to ensure the safety of lithium-ion battery system, especially in low-pressure air-transport and the near-vacuum space environment. This work investigates the linear thermal-runaway propagation in LiNi0.5Co0.2Mn0.3O2 18,650 cylindrical battery layers under ambient pressure from 0 atm to 1 atm. Results indicate that the 1-D layer-to-layer thermal runaway propagation rate decreases with decreasing SOC and ambient pressure. As the SOC decreases from 100 % to 30 %, the thermal runaway propagation rate decreases from 1.73 [layer/min] to 0.30 [layer/min] at 1 atm. For 30 % SOC cells, the thermal runaway propagation rate decreases by about 23 % as the ambient pressure decreases from 1 atm to 0.2 atm and eventually drops to zero at 0 atm. The X-ray computed tomography imaging reveals that low pressure can weaken both external flaming combustion and internal thermal runaway reactions during the venting stage. As the ambient pressure decreases, such dual effect increases the thermal runaway temperature from 200 to 310°C, reduces the maximum surface temperature from 800 °C to 400 °C, and lowers the burning mass loss fraction from 32 % to 10 %. Finally, a simplified heat transfer model is proposed to explain the effects of SOC and ambient pressure on thermal runaway propagation. These findings provide a new way to mitigate the thermal runaway propagation and help to assess the safety of battery piles in storage and transport.

Investigating the material properties of HfO2/SiO2-based anti-reflection coatings during 1064 nm laser-induced breakdown in air and vacuum conditions

It is important to understand the damage process of optical coatings subjected to nanosecond laser ablation. However, investigating the high power laser interaction with optical coatings in a short time and space resolution is challenging. The dynamic evolution of materials ejection and layer peeling-off processes during damage of HfO2/SiO2-based anti-reflection coatings induced by 1064 nm pulsed laser were systematically examined by employing the time-resolved shadowgraph technique. Therefore, materials response imaging was performed by shadowgraphy to better understand the interaction between coatings and laser beam in air and vacuum conditions. The coatings damage in vacuum was not influenced by the plasma plume, which showed markedly different responses to the laser-coatings interaction. By comparing the form of damage crater and layer peeling-off through SEM analysis and step profiler, it was found that more laser energy dissipated into the target with the decrease in ambient air pressure. For the reverse damage process in air and vacuum, materials ejection by the continuous impact of the laser energy was observed and the forms of materials ejection and damaged craters were the same. Investigating the materials response under different air pressure conditions provided valuable insights into the damage mechanisms during the nanosecond laser-induced damage of optical coatings.

Thermal runaway propagation in linear battery module under low atmospheric pressure

Understanding the mechanism of battery thermal runaway propagation under low atmospheric pressure is critical for the safe operation of battery energy storage systems. This work explores the thermal runaway propagation over a linear arrayed 18650-type lithium-ion battery module in a low-pressure chamber. The effects of ambient pressure (0.1 kPa to 100 kPa), temperature, and electrical connection mode are comprehensively investigated. Results indicate that the propensity of thermal runaway propagation for the open-circuit battery array is much lower, and it only occurs at high ambient temperature and ambient pressure. For parallel-connected battery modules, as ambient pressure decreases, the rate of thermal-runaway propagation first increases due to the reduced environmental cooling (i.e., thermal controlled). It then falls due to lower remaining electrolytes after venting (i.e., venting controlled). The pressure of maximum thermal runaway propagation speed is 60 kPa. The maximum time interval for the thermal runaway of the next cell is about 7 min. A simplified heat transfer analysis was proposed to explain the trend and limits of thermal runaway propagation and reveal the dual effect of pressure. This work provides new insights into thermal runaway propagation, which can deepen the understanding of battery fire safety under low pressure and inspire the thermal-safety design of the lithium-ion battery modules.

Effect of ambient pressure on bead shape, microstructure and corrosion behavior of 4043 Al alloy fabricated by laser coaxial wire feeding additive manufacturing in vacuum environment

4043 Al alloy was fabricated by laser coaxial wire feeding additive manufacturing (LWAM) technique in vacuum environment. The effect of ambient pressure (1 Pa, 10 Pa, 50 Pa, 120 Pa) on the bead shape, microstructure and corrosion behavior was investigated. Compared the specimen fabricated at 1 Pa and 120 Pa, results showed that with the decrease of ambient pressure, the wettability became better. It was suggested that for obtaining good forming, the LWAM processing was conducted at lower ambient pressure. The microstructure was cellular consisting of primary Al-rich phase surrounded by Si phase at the cellular boundaries. With the increase of ambient pressure, the morphology of Si network became partially broken and less connected. In addition, it was found that with the decrease of ambient pressure (compared 1 Pa and 120 Pa), the corrosion resistance was improved both in H2SO4 and NaCl electrolyte. This was mainly attributed to the partially broken and less connected Si network and more porosities at 120 Pa.

Effect of lithium salts LiPF6 and LiBF4 on combustion properties of electrolyte with EC/PC/EMC under different pressures

In this paper, the combustion properties of ethylene carbonate/propylene carbonate/ethyl methyl carbonate (EC/PC/EMC) with LiPF6 or LiPF4 were studied by cone calorimeter under various environmental pressures in Hefei (100.09 kPa), Lijiang (76.11 kPa) and Lhasa (65.23 kPa), respectively. The impact of lithium salts and pressure on the significant fire parameters of electrolyte such as flame temperature, mass loss rate (MLR) and heat release rate (HRR) were analyzed to evaluate the degree of thermal hazard. The experimental results showed that with the decrease of ambient pressure, the peak HRR (pHRR) and total heat release (THR) declined, and the combustion duration increased significantly. In the steady combustion stage of electrolyte pool fire, the mean value of MLR had an exponential relationship with the external pressure. The error of HRR obtained by oxygen consumption (OC) calorimetry and stoichiometric thermochemistry (TC) theory was about 15%.

Influence of ambient pressure on thermal response of polymer matrix composites

AbstractAmbient pressure is crucial to the thermal performance of polymer matrix composites, which are usually used as the thermal protection system (TPS) materials of hypersonic vehicles. Aiming at studying the influence of ambient pressure on thermal response of polymer matrix composites, a novel pyrolysis layer model with pressure is presented, and its mathematical model is deduced and programmed in MATLAB. Comparison between numerical results and experimental results of theoretical ablative composite for open testing is given to verify the accuracy of the presented model. After that, thermal responses of phenolic impregnated carbon ablator under ambient pressures range from 1 to 500 kPa are simulated. It is found that accumulation and backstreaming of generated pyrolysis gasses begin to appear with the increase of ambient pressure. And there is an obvious linear correlation between the reciprocal of the material internal pressure and the ambient pressure. In addition, bondline temperature of polymer matrix composites declines as the ambient pressure decreases. Effect of ambient pressure on thermal response of polymer matrix composites cannot be neglected, which should be taken into account in the TPS design. This study contributes to the accurate prediction of thermal response of polymer matrix composites.

Effect of Low Ambient Pressure on Spray Cone Angle of Pressure Swirl Atomizer

Pressure swirl atomizers are widely used in gas turbine combustor; this paper is aimed at researching the effect of low ambient pressure (0.1 MPa to 0.01 MPa, lower than an atmosphere) on the spray cone angle of pressure swirl atomizer. The spray angle is captured by high-speed photography; then, an image post program is used to process the spray angle magnitude. A mathematical model of a single droplet’s movement and trajectory based on force analysis is proposed to validate the spray angle variation. The maximum variation of the spray cone angle, which is observed when fuel supply pressure drop through the atomizer is 1 MPa as the ambient pressure decreases from 0.1 MPa to 0.01 MPa, is found to be 23.9%. The experimental results show that the spray cone angle is expected to increase with the ambient pressure decrease; meanwhile, mathematical results agree well with this trend.

Supersonic Several Bells Design of Minimum Length Nozzle Contours for More Altitudes Level Adaptations

This wok focuses to develop a numerical computation program allowing to design new contours of a supersonic nozzle having several bells, adapted to several levels of different altitudes, going from sea level and progressively with the altitude up to space, giving a supersonic uniform and parallel flow to the exit section and a maximum possible thrust without loss, aiming to reduce considerably the side loads caused in the conventional and the dual bell nozzles when the ambient pressure decrease with the altitude. The first bell has a sonic, uniform and parallel inlet to the throat, and a sea level adaptation with a reduced supersonic Mach number, while the other bell have a supersonic, parallel and uniform inlet and an adaptation to a given altitude with a progressed increase of supersonic Mach number. The transition from one level of adaptation to another adjacent is done without mechanical activation. The purpose of this type of nozzle is to have the possibility of flying in several supersonic regimes adapted to several different altitudes with a reduced side loads. This type of nozzle is named by Several Bell Nozzle and has inflection points between bell and adjacent other. The design is done in the context of a calorically and thermally perfect gas. The problem is to design a typical bell having a uniform and parallel supersonic inlet and exit with two given Mach numbers. The design is made by the use of the Method of Characteristics. The resolution of the equations is done numerically by the finite difference corrector predictor algorithm. The validation of the results is controlled by the convergence of the ratio of the critical sections, calculated numerically, to that given by the theory. In this case, all the design parameters converge automatically to the desired solution. The application is made for axisymmetric MLN having 3, 4, 5 and 10 bells.

Frequency Response of Pressure-Sensitive Paints under Low-Pressure Conditions.

The characteristics of fast-response pressure-sensitive paints (PSPs) in low-pressure conditions were evaluated. Three representative porous binders were investigated: polymer-ceramic PSP (PC-PSP), anodized-aluminum PSP (AA-PSP), and thin-layer chromatography PSP (TLC-PSP). For each PSP, two types of luminophores, Pt(II) meso-tetra (pentafluorophenyl) porphine (PtTFPP) and tris(bathophenanthroline) ruthenium dichloride (Ru(dpp)), were used as sensor molecules. Pressure sensitivities, temperature sensitivities, and photodegradation rates were measured and evaluated using a pressure chamber. The effect of ambient pressure on the frequency response was investigated using an acoustic resonance tube. The diffusivity coefficients of PSPs were estimated from the measured frequency response and luminescent lifetime, and the governing factor of the frequency response under low-pressure conditions was identified. The results of static calibration show that PC-PSP/PtTFPP, AA-PSP/Ru(dpp), and TLC-PSP/PtTFPP have high pressure sensitivities that exceed 4%/kPa under low-pressure conditions and that temperature sensitivity and photodegradation rates become lower as the ambient pressure decreases. Dynamic calibration results show that the dynamic characteristics of PSPs with PtTFPP are dependent on the ambient pressure, whereas those of PSPs with Ru(dpp) are not influenced by the ambient pressure. This observation indicates that the governing factor in the frequency response under low-pressure conditions is the lifetime for PC-PSP and TLC-PSP, whereas the governing factor for AA-PSP is diffusion.