Effect Of Water Vapor Pressure Research Articles

Spatio-temporal variation of water requirement and meteorological impact factors of maize Shaanxi, China

To quantitatively reveal the characteristics of the spatial and temporal distribution and the influencing factors of the maize water requirement in Shaanxi Province, the Penman-Monteith model and path analysis were used to systematically analyze the interannual variation and spatial distribution of the maize water requirement at different growth stages in three climatic zones in Shaanxi Province. And the relationship between the water requirement and meteorological factors based on daily meteorological data in Shaanxi Province for the past 60 years. The results showed that the maize water requirement during the whole growth period decreased from 1960 to 1989, with a rate of change of −2.08 mm/a, increased from 1989 to 2019, with a rate of change of 0.38 mm/a, and decreased from 1960 to 2019, with a rate of change of −0.46 mm/a. The water requirement of maize decreases from north to south during the whole reproductive period. That of seedling and male stage are more in the Guanzhong, followed by the north and the least in the south. The water requirement of maize at jointing stage increased from north to south. And the water requirement distribution is more in the north, followed by the south and the least in the Guanzhong area during the maturity period. The average temperature and the duration of the sunshine are the key factors that affect maize water requirement in Shaanxi Province, and have an increasing effect on water requirement, wind speed has an increasing effect on water requirement but is not obvious, water vapor pressure and relative humidity have an inhibiting effect on water requirement. For spring maize, the promoting effect of the duration of the sunshine on maize water requirement was gradually strengthened from north to south. The promoting effect of mean temperature and wind speed decreased gradually. The inhibitory effect of water vapor pressure and relative humidity decreases continuously. This study can provide a scientific basis for the management of irrigation quota in maize growing areas under similar cropping conditions.

Study on regulation mechanism of morphology and particle size of molybdenum powder in hydrogen reduction process

This study applied a novel process for manufacturing molybdenum powder to regulate the morphology and particle size. The effects of water vapor pressure, temperature, and holding time on the morphology and particle size of molybdenum powder were studied, in which bottom-blowing hydrogen was configured with a consistent flow direction of water vapor generated by hydrogen reduction. The results showed that polyhedral molybdenum powders with uniform sizes were prepared at different positions in the crucible via a single nucleation mechanism, and the water vapor pressure was identified as a key factor for controlling the particle size. By adjusting the water vapor pressure, reaction time, and temperature, the molybdenum powders with a particle size between 1 μm and 10 μm was obtained. When the hydrogen reduction temperature increased from 950 °C to 1150 °C, the average particle size increased from 1.8 μm to 3.4 μm, and particle aggregation was exacerbated. Upon extending the holding time from 60 min to 180 min, the average particle size increased marginally from 3.4 μm to 4 μm. This study provides a new method and important theoretical guidance for manufacturing molybdenum powders with a uniform morphology and particle size.

Effect of water vapor pressure on positive and negative tone electron-beam patterning of poly(methyl methacrylate)

Variable-pressure electron-beam lithography (VP-EBL) employs an ambient gas at subatmospheric pressures to reduce charging during electron-beam lithography. VP-EBL has been previously shown to eliminate pattern distortion and provide improved resolution when patterning poly(methyl methacrylate) (PMMA) on insulating substrates. However, it remains unknown how water vapor affects the contrast and clearing dose nor has the effect of water vapor on the negative-tone behavior of PMMA been studied. In addition, water vapor has recently been shown to alter the radiation chemistry of the VP-EBL process for Teflon AF. Such changes in radiation chemistry have not been explored for PMMA. In this work, VP-EBL was conducted on conductive substrates to study the effect of water vapor on PMMA patterning separately from the effects of charge dissipation. In addition, both positive and negative-tone processes were studied to determine the effect of water vapor on both chain scission and cross-linking. The contrast of PMMA was found to improve significantly with increasing water vapor pressure for both positive and negative-tone patterning. The clearing dose for positive-tone patterning increases moderately with vapor pressure as would be expected for electron scattering in a gas. However, the onset set dose for negative-tone patterning increased dramatically with pressure revealing a more significant change in the exposure mechanism. X-ray photoelectron spectra and infrared transmission spectra indicate that water vapor only slightly alters the composition of exposed PMMA. Also, electron scattering in water vapor yielded a much larger clear region around negative-tone patterns. This effect could be useful for increasing the range of the developed region around cross-linked PMMA beyond the backscattered electron range. Thus, VP-EBL for PMMA introduces a new means of tuning clearing/onset dose and contrast, while allowing additional control over the size of the cleared region around negative-tone patterns.

Small molecule crystals with 1D water wires modulate electronic properties of surface water networks

This study evaluates the effect of water vapor pressure on the surface conductivity of a hydrated small molecule crystal under dry and wet conditions. The crystal contains a discrete metal complex with waters of hydration in structural positions and in 1D water wires. Under dry conditions, the surface of the hydrated crystal behaves as a near ideal capacitor. Under wet conditions, the waters of hydration serve as a template to assemble surface water networks by organization of water from the environment. The surface water provides pathways for charge transfer attributed to proton mobility that increases conductivity by > 3 orders in magnitude. Modulation between wet and dry conditions tunes the conductivity of the crystal surface via a two-step process, which has been evaluated kinetically as a function of the water vapor pressure.

Revealing the effect of water vapor pressure on the kinetics of thermal decomposition of magnesium hydroxide.

This study aims to establish an advanced kinetic theory for reactions in solid state and solid-gas systems, achieving a universal kinetic description over a range of temperature and partial pressure of reactant or product gases. The thermal decomposition of Mg(OH)2 to MgO was selected as a model reaction system, and the effect of water vapor pressure p(H2O) on the kinetics was investigated via humidity controlled thermogravimetry. The reaction rate of the thermal decomposition process at a constant temperature was systematically decreased by increasing the p(H2O) value, accompanied by an increase in the sigmoidal feature of mass-loss curves. Under nonisothermal conditions at a given heating rate, mass-loss curves shifted systematically to higher temperatures depending on the p(H2O) value. The kinetic behavior under different temperature and p(H2O) conditions was universally analyzed by introducing an accommodation function (AF) of the form (P°/p(H2O))a[1 - (p(H2O)/Peq(T))b], where P° and Peq(T) are the standard and equilibrium pressures, respectively, into the fundamental kinetic equation. Two kinetic approaches were examined based on the isoconversional kinetic relationship and a physico-geometrical consecutive reaction model. In both the kinetic approaches, universal kinetic descriptions are achieved using the modified kinetic equation with the AF. The kinetic features of thermal decomposition are revealed by correlating the results from the two universal kinetic approaches. Furthermore, advanced features for the kinetic understanding of thermal decomposition of solids revealed by the universal kinetic descriptions are discussed by comparing the present kinetic results with those reported previously for the thermal decomposition of Ca(OH)2 and Cu(OH)2.

The effect of water vapor pressure on muscle collagen solubility and selected characteristics of the longissimus lumborum muscle in crossbred cattle

Abstract Most scientific studies are dedicated to the possibility of preparing beef for consumption under industrial conditions. Few publications are devoted to the issue of collagen thermohydrolysis in conditions available to the consumer. This study has analyzed the effect of small values of water vapor pressure on major culinary indices and chemical components of the longissimus lumborum muscle obtained from bulls with different growth rates. The experiment involved 48 animals. On the basis of the gain during the fattening time, the animals were divided into a low growth intensity group, with a daily body weight gain of ≤900 g, and a high growth intensity group with a daily gain of >900 g/day. A part of the samples of the longissimus lumborum muscle (control) was thermally treated in a water bath at 75°C. Another part was heat treated in a pressure-pot at 150°C, at a pressure of 0.1 MPa. The next part of samples was subjected to the same temperature, but the pressure was 0.2 MPa. The obtained results indicate that the values of the studied indices were largely affected by thermal processing parameters rather than the animals’ growth rate. The highest contents of total protein and water-soluble collagen were obtained in the case of a temperature of 150°C and the highest pressure (0.2 MPa). Water vapor with increased temperature and pressure also created favorable conditions for obtaining better meat tenderness and more favorable values of the water holding capacity. The latter characteristic appeared to be strongly connected with an increasing amount of water-soluble collagen, which was confirmed by relatively high values of the correlation coefficient between these characteristics. A strong positive correlation was also shown between thermal drip and the total collagen content in meat.

Effect of water vapor pressure on the phase composition of lithium monoaluminates formed in the interaction of aluminum hydroxide and lithium carbonate

It is shown that the partial water vapor pressure affects the phase composition of lithium monoaluminates formed when aluminum hydroxide (gibbsite) and lithium carbonate are heated in air, in the atmosphere of helium, and in a dynamic vacuum. When the mixture is heated to 800°C in an air atmosphere with partial water pressure of 1300 Pa, a nearly single-phase lithium monoaluminate α-LiAlO2 is formed. In the reaction in the atmosphere of helium, in which the partial water vapor pressure does not exceed 4 Pa, γ-LiAlO2 is formed together with α-LiAlO2, with the content of the former exceeding that produced in the reaction in air. When the mixture is heated under dynamic vacuum conditions with partial water vapor pressure lower than 0.1 Pa, mostly γ-LiAlO2 is formed.

被覆肥料の溶出に及ぼす水蒸気圧の影響 : 樹脂系被覆肥料の溶出機構と反応速度論的解析による溶出評価(第1報)

被覆肥料の溶出に及ぼす水蒸気圧の影響 : 樹脂系被覆肥料の溶出機構と反応速度論的解析による溶出評価(第1報)

Effect of water vapor pressure on fatigue crack growth in Al–Zn–Cu–Mg over wide-range stress intensity factor loading

Investigation of the deleterious effect of high purity water vapor on fatigue crack growth rate (da/dN) in 7075-T651 shows that growth rate declines with decreasing water vapor pressure (PH2O) over a wide range of stress intensity range (ΔK). Decreasing ΔK experiments exhibit a novel minimum in da/dN for intermediate PH2O and low ΔK. This minimum and testing protocol dependent environmental-fatigue behavior are explained by crack wake fracture morphology and R-dependent crack opening displacement effects on molecular flow to the crack tip. This environmentally-based mechanism leads to the onset and reversal of a non-conservative and false high threshold stress intensity range.

Nanofibrous membrane-based absorption refrigeration system

This paper presents a study on the efficacy of highly porous nanofibrous membranes for application in membrane-based absorbers and desorbers. Permeability studies showed that membranes with a pore size greater than about one micron have a sufficient permeability for application in the absorber heat exchanger. Membranes with smaller pores were found to be adequate for the desorber heat exchanger. The membranes were implemented in experimental membrane-based absorber and desorber modules and successfully tested. Parametric studies were conducted on both absorber and desorber processes. Studies on the absorption process were focused on the effects of water vapor pressure, cooling water temperature, and the solution velocity on the absorption rate. Desorption studies were conducted on the effects of wall temperature, vapor and solution pressures, and the solution velocity on the desorption rate. Significantly higher absorption and desorption rates than in the falling film absorbers and desorbers were achieved.

Absorption characteristics of lithium bromide (LiBr) solution constrained by superhydrophobic nanofibrous structures

An experimental study on absorption characteristics of water vapor into a thin lithium bromide (LiBr) solution flow is presented. The LiBr solution flow is constrained between a superhydrophobic vapor permeable wall and a solid surface that removes the heat of absorption. As opposed to conventional falling film absorbers, in this configuration, the solution film thickness and velocity can be controlled independently to enhance the absorption rate. The effects of water vapor pressure, cooling surface temperature, solution film thickness, and solution flow velocity on the absorption rate are studied. An absorption rate of approximately 0.006kg/m2s was measured at a LiBr solution channel thickness and flow velocity of 100μm and 5mm/s, respectively. The absorption rate increased linearly with the water vapor driving potential at the test conditions of this study. It was demonstrated that decreasing the solution film thickness and increasing the solution velocity enhance the absorption rate. The high absorption rate and the inherently compact form of the proposed absorber facilitate development of compact small-scale waste heat or solar-thermal driven cooling systems.

Unusual Effect of Water Vapor Pressure on Dehydration of Dibasic Calcium Phosphate Dihydrate

Dibasic calcium phosphate occurs as an anhydrate (DCPA; CaHPO₄) and as a dihydrate (DCPD; CaHPO₄•2H₂O). Our objective was to investigate the unusual behavior of these phases. Dibasic calcium phosphate dihydrate was dehydrated in a (i) differential scanning calorimeter (DSC) in different pan configurations; (ii) variable-temperature X-ray diffractometer (XRD) at atmospheric and under reduced pressure, and in sealed capillaries; and (iii) water vapor sorption analyzer at varying temperature and humidity conditions. Dehydration was complete by 210°C in an open DSC pan and under atmospheric pressure in the XRD. Unlike "conventional" hydrates, the dehydration of DCPD was facilitated in the presence of water vapor. Variable-temperature XRD in a sealed capillary and DSC in a hermetic pan with pinhole caused complete dehydration by 100°C and 140°C, respectively. Under reduced pressure, conversion to the anhydrate was incomplete even at 300°C. The increase in dehydration rate with increase in water vapor pressure has been explained by the Smith-Topley effect. Under "dry" conditions, a coating of poorly crystalline product is believed to form on the surface of particles and act as a barrier to further dehydration. However, in the presence of water vapor, recrystallization occurs, creating cracks and channels and facilitating continued dehydration.

Influence of Water Vapor Pressure on Superconducting Properties of YBCO Film by TFA-MOD

We fabricated YBa2Cu3O7−x (YBCO) films on LaAlO3 (LAO) substrates using metal organic deposition of precursor solutions containing metal trifluoroacetates (TFA-MOD). The effect of water vapor pressure on the microstructure, degree of texture, and critical current of prepared YBCO films was evaluated. The firing process was performed in the water vapor pressure range from 7 to 31 kPa. According to the results of the XRD, SEM and X-ray ω scan analyses, the causes of critical properties’ change with the different water pressure were explained. The YBCO film prepared at the lower water pressure showed the low critical current because of the a–b axis grain. The films fired at 20 kPa showed the highest critical current of 3.8 MA/cm2.

Simulation of surface structural relaxation kinetics in silica glass accelerated by water vapor

It is known that surface structural relaxation of silica glass takes place more rapidly than bulk structural relaxation, especially in the presence of water vapor. The effect of water vapor pressure, heat-treatment temperature and initial fictive temperature on the surface structural relaxation kinetics in silica glasses was investigated by measuring the change of the surface fictive temperature determined from the IR reflection peak shift of silica structural bands. The superimposed component of bulk structural relaxation was subtracted from the measured surface structural relaxation data to isolate the true surface structural relaxation kinetics. The obtained surface structural relaxation data as a function of fictive temperature, heating temperature and water vapor pressure were simulated with a model based on the diffusion equation with time-dependent surface concentration. The simulation model was used to predict the surface structural relaxation kinetics of the optical fiber having a high fictive temperature of ∼ 1650°C at 950°C under 355torr of water vapor, and it was confirmed that the present model can simulate surface structural relaxation of the fiber reasonably well.

Water Vapor Absorption on Nanostructured Carbide Derived Carbon (CDC)

In this work, carbide derived carbon (CDC) layers were synthesized on SiC and kept isolated from the environment until exposed to controlled water vapor atmospheres, so that the effects of water vapor pressure on the absorption could be quantified. The effects of high temperature hydrogen treatment are also described. CDC samples after chlorination are very hygroscopic, absorbing up to 35% of their weight in water in low humidity environments.

Effect of water vapour pressure on monoterpene measurements using proton transfer reaction-mass spectrometry (PTR-MS)

The effects of water vapour pressure (WVP) on the fragmentation of seven monoterpene and related C 10 volatile organic compounds (VOCs) in the drift tube of a proton transfer reaction-mass spectrometer (PTR-MS) were investigated. In addition, the combined effects of varying WVP and the ratios of electric field strength to number density of the buffer gas ( E/ N) were investigated in detail for three of these compounds, the monoterpenes α-pinene and sabinene plus the related C 10 VOC p-cymene. Under normal operating conditions ( E/ N = 124 Td), WVP affected the fragment patterns of all compounds with the exception of β-pinene and the three oxygenated C 10 VOCs. WVP had a significant effect on the fragment patterns of α-pinene and sabinene at the lower E/ N ratios (around 80 Td) but had little effect on fragmentation towards the higher E/ N ratios used here (∼142 Td). On the other hand, p-cymene fragmentation was most affected by WVP under normal operating conditions. PTR-MS sensitivity towards the three compounds was also considered under three conditions where reaction was assumed with (1) H 3O + only; (2) H 3O + and H 3O +H 2O; and (3) H 3O +, H 3O +H 2O and H 3O +(H 2O) 2. Our results indicate that α-pinene and sabinene react not only with H 3O + and H 3O +H 2O via direct proton transfer but also with H 3O +(H 2O) 2 via ligand switching. p-Cymene seems to react only with H 3O + via direct proton transfer and with H 3O +H 2O via ligand switching. It is speculated that the WVP effect on fragmentation results from the differing abundances of hydrated reagent ions which causes different frequencies of individual reactions to occur, thus, determining how ‘soft’ the overall reaction is. These results also indicate that under normal conditions, a correction should be made for WVP if the concentration of p-cymene in air samples is to be determined from the single ion signal of either protonated molecular ions or the most dominant fragment ions.

Effect of surface hydrophilicity and water vapor pressure on the interfacial shear strength of adsorbed water layer

We investigated the effect of water vapor pressure and surface hydrophilicity on the tribological behavior in wearless sliding condition. Friction and interfacial shear strength of silicon surfaces with different water affinity (contact angles of <5°, 30°, and 85°) against a glass sphere (contact angle 40°) were examined under various water vapor pressure conditions. The friction of hydrophilic surface decreased as vapor pressure increased and the least hydrophilic surface showed stable and low friction force regardless of relative vapor pressure. However, it showed that the hydrophilic surface with high relative vapor pressure exhibited lower shear strength than a less hydrophilic surface independent of capillary effect. It was explained in terms of capillary wetting and the role of adsorbed water in contact area.

Controlled Rate Thermal Analysis of kaolinite dehydroxylation: effect of water vapour pressure on the mechanism

The present kinetic study is focused on one aspect of kaolinite dehydroxylation, namely the influence of water vapour pressure in the 10 −3 to 5 hPa range and in the presence of crystalline defects. The experimental problem of keeping, throughout the dehydroxylation, the pressure gradients negligible around and within the sample is solved by means of Controlled Rate Evolved Gas Detection (CR-EGD). The dehydroxylation rate selected is as low as 0.014 h −1 (which corresponds to a duration of 70 h for the whole experiment). Moreover, more than 20 independent measurements of the apparent Arrhenius energy of activation are carried out all along the dehydroxylation, with help of the rate–jump method, and therefore, without any assumption about the rate law of the determining step. In these conditions, the apparent Arrhenius energy of activation measured during the dehydroxylation of a poorly crystallised kaolinite is shown to be constant in the range 0.02< α<0.84 (under 10 −3 hPa) and in the range 0.18< α<0.80 (under 5 hPa), indicating that the rate law obeys the Arrhenius law in this range of extent of reaction. The corresponding activation energies obtained are (233±15) kJ/mol under 10 −3 hPa and only (188±10) kJ/mol under 5 hPa. Although this decrease is in contradiction with previously published results, it can be interpreted by considering that, under 10 −3 hPa, diffusion is the limiting step whereas, under 5 hPa, the part of water desorption probably becomes predominant.

Defect chemistry modeling of high-temperature proton-conducting cerates

The appropriate equations governing proton incorporation into perovskite oxides with an emphasis on high-temperature proton conductors (HTPCs) are reviewed. The prototypical compound SrCe 0.95Y 0.05O 3− δ is considered in detail. The mathematical approach of Poulsen is applied and the defect concentrations are modeled with a C language routine. A cluster-defect model is not considered here. Defect concentrations are calculated as a function of water vapor pressure and oxygen partial pressure. The solutions are presented in the form of two- and three-dimensional graphs of defect concentrations versus water vapor and oxygen partial pressures. Their physical meanings are explained by pertinent proton incorporation equations. Effects of water vapor pressure and A/B ratio on the n– p transition point are simulated.

Improvements on the back-calculation technique for estimating anthropogenic CO 2

The back-calculation technique for evaluating the anthropogenic CO 2 ( C ANT) input corrects total inorganic carbon for the remineralisation of organic matter and the dissolution of calcium carbonate, along with subtracting the pre-industrial equilibrium total inorganic carbon. This technique is mainly dependent on the estimation of the preformed values of total alkalinity, oxygen and partial pressure of CO 2 ( pCO 2). A new approach for estimating the preformed alkalinity (TA 0) in the North Atlantic Ocean is suggested. TA 0 is parameterised as a function of the inorganic to organic carbon decomposition ratio in the water column in agreement with sediment trap data and a recent review by Milliman et al. (Deep-Sea Res. I 46 (1999) 1653), which gives evidence for a considerable calcium carbonate dissolution in the upper 500–1000 m of the ocean, above the lysocline. We recalculated the C ANT content in a section along the Eastern North Atlantic (OacesNAtlIIB-93) using this new TA 0, the Mehrbach et al. (Limnol. Oceanogr. 8 (1973) 897) CO 2 dissociation constants, and including the effect of water vapour pressure on estimation of the pre-industrial pCO 2. Our findings lead us to conclude that the CO 2 disequilibrium when water masses are formed is small and not significant. Direct and indirect evidence based on available high-quality CO 2 data taken in formation areas in late winter conditions support this argument.