Variation Of Vapor Pressure Research Articles

Simulation study on the cavitation flow characteristics of liquid ammonia in the nozzle under high-pressure injection conditions

In this study, a non-isothermal compressible cavitating flow simulation model for liquid ammonia in high-pressure injector, accounting for the phase change properties, was established. The model was validated using experimental data from existing literature. The cavitation phase change process of liquid ammonia within the injector nozzle was investigated, and the differences in cavitation distribution between ammonia and diesel were explored. The results indicate that with increasing injection pressure, the vapor volume fraction of ammonia increases linearly, while that of diesel fuel shows a rapid initial rise followed by a decelerating trend. In terms of flow coefficient, ammonia is lower than diesel, though the two values converge at higher injection pressures. Under low injection pressure, the heat absorbed by the cavitation phase change of ammonia exceeded the heat generated by the high-speed friction of ammonia flow against the nozzle wall, leading to a temperature drop at the nozzle inlet. Conversely, at high injection pressure, the temperature of ammonia on the nozzle wall increases by more than 20 K, resulting in a rapid rise in saturated vapor pressure and significantly intensifying the cavitation effect. Compared to ammonia, diesel experienced a higher temperature rise within the nozzle but exhibited smaller variations in saturated vapor pressure, making the temperature effect on cavitation less pronounced. Diesel’s higher density and viscosity resulted in lower flow velocities compared to ammonia, leading to more developed cavitation in the lower wall region of the nozzle and creating a higher pressure region on the upper wall of the nozzle, which was more distant from the nozzle inlet and inhibited cavitation development there. The research results provide theoretical support for the design of liquid ammonia injectors.

Densely stocked neighborhood reduces the risk of tree mortality in drylands: Evidence from Populus euphratica forests along the Tarim River corridor

To mitigate forest loss under current environmental challenges, it is increasingly urgent to model how tree mortality is mediated by both biotic and abiotic agents. However, the role of neighborhood interactions in mediating tree survival in dryland forests has been poorly understood, as it is often presupposed to be irrelevant in low-density stands coupled with overriding drought stress. Here, we conducted a failure time analysis of Populus euphratica forests (known as Tugay forests) in the Tarim River corridor (NW China) to examine the presupposition. We collected a spatial-explicit population inventory dataset with >7000 trees on ca. 14-ha land area with varying vapor pressure deficit (VPD), groundwater table depth (GWD), and stand density. Hegyi's competition index (CI) and stand density index (SDI, the number of large trees with an equivalent diameter of 25.4 cm) were employed to characterize neighborhood structures of each individual tree. Aridity stresses (higher VPD and GWD) tended to elevate tree mortality risk, and showed weaker effects than neighborhood structures did. Tree mortality risk increased drastically with higher CI, suggesting a strong role of competition for critical water resource. However, tree mortality risk reduced with higher SDI, likely due to ameliorated stresses of excessive light and/or temperature under less open canopies. This study highlights the importance of localized inter-tree interactions in regulating tree populations under prevalent drought stress and reiterates classic cautions against inferences about competition/facilitation in absence of spatial-explicit contexts. We recommend the priority of preserving large trees aggregated as closed stands in dryland forest conservation.

Decoding stomatal characteristics regulating water use efficiency at leaf and plant scales in rice genotypes.

Stomatal traits in rice genotypes affect water use efficiency. Low-frequency small-size stomata correlate with whole plant efficiency, while low-frequency large-size stomata show intrinsic efficiency and responsiveness to vapour pressure deficit. Leaf surface and the patterning of the epidermal layer play a vital role in determining plant growth. While the surface helps in determining radiation interception, epidermal pattern of stomatal factors strongly regulate gas exchange and water use efficiency (WUE). This study focuses on identifying distinct stomatal traits among rice genotypes to comprehend their influence on WUE. Stomatal frequency ranged from 353 to 687 per mm2 and the size varied between 128.31 and 339.01 μm2 among 150 rice germplasm with significant variability in abaxial and adaxial surfaces. The cumulative water transpired and WUE determined at the outdoor phenomics platform, over the entire crop growth period as well as during specific hours of a 24h-day did not correlate with stomatal frequency nor size. However, genotypes with low-frequency and large-size stomata recorded higher intrinsic water use efficiency (67.04μmol CO2 mol-1 H2O) and showed a quicker response to varying vapour pressure deficit that diurnally ranged between 0.03 and 2.17kPa. The study demonstrated the role of stomatal factors in determining physiological subcomponents of WUE both at single leaf and whole plant levels. Differential expression patterns of stomatal regulatory genes among the contrasting groups explained variations in the epidermal patterning. Increased expression of ERECTA, TMM and YODA genes appear to contribute to decreased stomatal frequency in low stomatal frequency genotypes. These findings underscore the significance of stomatal traits in breeding programs and strongly support the importance of these genes that govern variability in stomatal architecture in future crop improvement programs.

Nocturnal Water Use Partitioning and Its Environmental and Stomatal Control Mechanism in Caragana korshinskii Kom in a Semi-Arid Region of Northern China

As an important aspect of plant water consumption, nocturnal water use (En) behavior provides reliable information on the effect of plantation carbon and water budgets at stand and regional scales. Therefore, quantifying En and its environmental and stomatal controlling mechanisms is urgent to establish adaptation strategies for plantation management in semiarid regions. With the help of the sap flow technique, our study investigated the seasonal variations in canopy transpiration and canopy conductance in a Caragana korshinskii Kom plantation. Environmental variables were measured concurrently during the growing seasons of 2020 and 2021. The results indicated that the average En values were 0.10 mm d−1 and 0.09 mm d−1, which accounted for 14% and 13% of daily water use, respectively, over two years. The proportions of nocturnal transpiration (Tn) to En were approximately 49.76% and 54.44%, while stem refilling (Re) accounted for 50.24% and 45.56% of En in 2020 and 2021, respectively, indicating that C. korshinskii was able to draw on stored stem water to support transpiration. En was predominantly affected by nocturnal canopy conductance (Gc–n), air temperature (Ta–n) and wind speed (u2-n). In contrast, Gc–n and Ta–n explained the highest variation in Tn and nocturnal vapor pressure (VPDn), and u2-n explained the highest variation in Re. Total effects of the five environmental and stomatal variables explained 50%, 36% and 32% of En, Tn and Re variation, respectively. These findings could enable a better understanding of nocturnal water use dynamics and their allocation patterns in C. korshinskii plantations on the Bashang Plateau. Moreover, our results reveal the water use strategies of artificial shrubs and highlight the importance of incorporating nocturnal water use processes into large-scale ecohydrological models in semiarid regions.

Experimental study on separation of isopropanol-water azeotrope by packed capillary distillation and the prediction model of artificial neural network

ABSTRACT Capillary distillation is an azeotropic distillation technology, which combines the mechanism of surface adsorption, capillary action, as well as the distillation process. Different variations of activity coefficient and saturated vapor pressure of azeotropic components occur in the capillary pore structure, which leads to the separation. In this paper, 5A, 4A, and 3A molecular sieve capillary porous media were selected as capillary packing to study the separation effect on azeotropic mixture of isopropanol-water solution experimentally. It was found that 4A molecular sieve worked better, the best reflux ratio is 6, and the best packing height is 0.4 m. Based on the abovementioned experimental results, a back propagation (BP) neural network is developed and utilized in the separation process. The effects of parameters such as the composition of feedstock solution, reflux ratio, and packing height on the concentration of isopropyl alcohol at the top of packed capillary distillation column were predicted, and the accuracy reached 96.7%. The proposed prediction method is helpful for developing the technology of separating azeotropic solution by capillary distillation with packing suitable for industrial application.

Thermodynamic assessment of binary chloride salt material for heat transfer and storage applications in CSP system

Molten chloride salt is recognized as a promising heat transfer fluid and thermal energy storage material (TES) in concentrating solar power (CSP) in recent years, and its phase diagram as key data for material design still need further research. In this work, the phase equilibrium characteristics of solid-liquid equilibrium and vapor-liquid equilibrium for binary chloride salt system (Na/K–Ca/Mg) are investigated respectively. Based on Wilson model, the activity coefficient and non-ideal behavior of liquid salts are predicted effectively, and then the solid-liquid phase diagrams of binary salts are calculated, and the predicted eutectic temperature and component agree well with experimental data. Vapor-liquid phase diagrams of binary salts are also calculated, and azeotropic temperature can only be found in the MgCl2 based mixed salts. As the system pressure rises, the azeotropic temperature increases, while azeotropic component slightly changes. According to the variation of vapor pressure for eutectic salts, the correlations for vapor pressure with temperature and composition are developed. Thermal stability of eutectic salts is experimentally studied by Thermo-gravimetric analyzer (TGA) and operating temperature ranges of these mixed salts are revealed. It can be found that the mass loss rate at different temperature is directly proportional to the vapor pressure. In general, present binary chloride salts show wide operating temperature range and high heat storage density, and eutectic NaCl–MgCl2 with advantage of heat storage density and azeotropic point existence is recommended as TES in the CSP plant.

Chemical Evolution of Pore Solution in Metakaolin Concrete During Water Evaporation

Metakaolin concrete is a kind of porous material, which contains a variety of chemical ions in the pores. Solutions in these pores are exposed to the atmosphere and exist evaporation and condensation processes, therefore, the pore solution volume of concrete changes all the time. When the ion concentration in the pore solution changes, it has an important impact on the strength development and durability of concrete. However, the real-time monitoring of the concentration of pore solution was difficult. To study the chemical evolution of pore solution in concrete, the variation of saturated vapor pressure on the surface of metakaolin concrete was studied based on the Cisternas-Lam rule. The evaporation rate of solvent in the pore solution of concrete under the corresponding saturated vapor pressure in this paper was studied by the Stefan diffusion method. The dynamic equilibrium process equation of ions in pore solution was then established based on the thermodynamic equilibrium equation. Based on the above model, the change process of the pore solution of metakaolin concrete was studied, and it was verified by the results of the literature.

Effects of physical parameters on the temperature and vapor-pressure behavior of bamboo scrimber during hot-pressing

ABSTRACT Bamboo scrimber was made by “hot in-cold out” hot-pressing with hot parameters of 5 MPa, 150°C and 40–180 min. The variation of temperature and vapor pressure were investigated during hot-pressing of bamboo slabs with various initial moisture content (IMC; 5, 10, 15, and 20%), slab target density (TD; 0.9, 1.0, 1.1, and 1.2 g/cm3), slab target thickness (TT; 15, 30, 45, and 60 mm) using thermocouple sensors and a self-made press-monitoring system. The results showed obvious stages in the temperature and vapor pressure behavior of bamboo slabs during hot-pressing. IMC showed a limited effect on temperature but an obvious increase in vapor pressure. TD and target TT exhibited good linear relationships with the time to reach 120°C in the core layer, suggesting this can be used as an indicator of hot-pressing time. However, both TD and TT correlate less well with the vapor pressure, which might reflect differences in the size or fluffing degree of bamboo bundles.

A nanoparticle formation model considering layered motion based on an electrical explosion experiment with Al wires

To study the evolution of nanoparticles during Al wire electrical explosion, a nanoparticle formation model that considered layered motion was developed, and an experimental system was set up to carry out electrical explosion experiments using 0.1 mm and 0.2 mm Al wires. The characteristic parameters and evolution process during the formation of nanoparticles were calculated and analyzed. The results show that the maximum velocities of the innermost and outermost layers are about 1200 m·s−1 and 1600 m·s−1, and the velocity of the middle layer is about 1400 m·s−1, respectively. Most of the nanoparticles are formed in the temperature range of 2600 K‒2500 K. The characteristic temperature for the formation of Al nanoparticles is ∼2520 K, which is also the characteristic temperature of other parameters. The size distribution range of the formed nanoparticles is 18 to 110 nm, and most of them are around 22 nm. The variation of saturated vapor pressure determines the temperature distribution range of particle nucleation. There is a minimum critical diameter of particles (∼25 nm); particles smaller than the critical diameter can grow into larger particles during surface growth. Particle motion has an effect on the surface growth and aggregation process of particles, and also on the distribution area of larger-diameter particles. The simulation results are in good agreement with the experiments. We provide a method to estimate the size and distribution of nanoparticles, which is of great significance to understand the formation process of particles during the evolution of wire electrical explosion.

Variation in mid-south soybean genotypes for recovery of transpiration rate and leaf maintenance following severe water-deficit stress

Ninety-four percent of U.S. soybeans are produced under rainfed conditions with potential for intermittent late season droughts during reproductive stages. Therefore, the ability of a crop to recover effectively from drought is important for yield stability. In 2019 and 2020, two controlled environment and two field studies were conducted to screen nine soybean genotypes for transpiration rate (TR) recovery following water-deficit stress. In experiment 1, under a controlled environment, soybeans were grown in pots sealed to prevent evaporation. Soybeans gradually transpired until the endpoint of transpirable soil water before being re-watered. In experiment 2, soybeans were exposed to varying vapor pressure deficit (VPD) levels. In both experiments, TR was measured gravimetrically. In field studies, portable rainout shelters were used to exclude precipitation. In experiment 1 and the field studies, recovery irrigation was applied after a period of extreme water-deficit. Then, leaf wilting score (WS) was rated visually on a scale of zero to five. Stomatal conductance (g s ), pre- and post-recovery canopy temperature (CT), and stomatal density (SD) were measured under field conditions. Genotypic differences in soybean contributed to differentiated recovery from water-deficit in experiment 1 and field studies. In experiment 1, genotypes TN09–029, TN16–520R1, and Ellis had superior recovery from water-deficit based on WS while USG Allen and TN09–008 had the most rapid TR recovery; RIL #1360 and USG 7496XTS showed the least recovery. In experiment 2, seven genotypes expressed a limited-TR trait under high VPD. In the field studies, Ellis, USG Allen, and TN09–029 exhibited a more robust recovery based on WS and Ellis exhibited the highest post-recovery g s . TN09–029 and Ellis had the largest reduction in CT after recovery. The top five yielding genotypes all expressed desirable responses in several of the individual drought recovery traits, confirming the utility of these phenotypes. Ellis produced the highest yield at 3517 kg ha −1 , consistently expressed the early decrease in TR with delayed wilting when soil water-deficit developed, and had the highest g s post-recovery. Response and recovery to drought and high yield relative to other genotypes under the water-deficit conditions make Ellis and related lines good candidates in future efforts to breed for drought tolerance traits. • The ability of a crop to recover effectively from drought is important for yield stability. • Identifying variation in mid-south genotypes transpiration and leaf maintenance recovery from severe water-deficit stress. • Field studies confirmed the results found and reported in the controlled environment experiments. • The top yielding genotypes had early stomatal closure, lower stomatal density, and lower thermal rate following recovery.

Optimization of hollow fiber membrane module for vacuum membrane distillation (VMD) via experimental study

Membrane distillation (MD) is an attractive desalination technology for treating high salt concentration water/wastewater. Nonetheless, developing membrane modules with high flux and fouling resistance but low energy consumption for industrial application remains a critical challenge. In this work, a novel vacuum membrane distillation (VMD) module with a central perforated tube was developed. The variation of vapor pressure on the shell side was monitored to analyze the relationship between the mass transfer driving force and the permeate flux. The energy consumption of each piece of equipment in the VMD device was evaluated. The heater, chiller, and vacuum pump consumed about 1/3 of the total energy for the VMD system. The central perforated tube suction decreased the mean vapor pressure better than the shell suction. Double suction enabled more uniform pressure distribution on the shell side. The permeate flux under double suction was 50–70 % higher than that under single suction. Consequently, the optimal length, packing fraction, and suction mode were proposed based on energy saving. Our results that include the first report on the generation of superheated vapor in VMD can guide engineers in designing the relevant modules and system scale-up and process optimization for industrial applications.

The Consistent Variations of Precipitable Water and Surface Water Vapor Pressure at Interannual and Long-Term Scales: An Examination Using Reanalysis

Water vapor (WV) is a vital basis of water and energy cycles and varies with space and time. When researching the variations of moisture in the atmosphere, it is intuitive to think about the total WV of the atmosphere column, precipitable water (PW). It is an element that needs high-altitude observations. A surface quantity, surface WV pressure (SVP), has a close relationship to PW because of the internal physical linkage between them. The stability of their linkage at climatic scales is verified using monthly mean data from 1979 to 2021, while studies before mainly focused on daily and annual cycles in local areas. The consistency of their variations is checked with three reanalysis datasets from three angles, the interannual variations, the long-term trends, and the empirical orthogonal function (EOF) modes. Results show that the interannual correlation of SVP and PW can reach a level that is quite high and are significant in most areas, and the weak correlation mainly exists over low-latitude oceans. The long-term trends, as well as the first EOF modes of these two quantities, also show that their variations are consistent, with spatial correlation coefficients between the long-term trends of two variables that are generally over 0.6, but specific differences appearing in some regions including the Tropical Indian Ocean and Middle Africa. With the correspondence of PW and SVP, the variations of total column WV can be indicated by surface elements. The correspondence is also meaningful for the analysis of the co-variation in total column vapor and temperature. For example, we could research the relations between SVP and air temperature, and they can reflect the co-variance of total column vapor and near-surface air temperature, which can avoid analyzing the relation between column-integrated moisture content and surface air temperature directly.

Variation of Relative Humidity as Seen through Linking Water Vapor to Air Temperature: An Assessment of Interannual Variations in the Near-Surface Atmosphere

It has generally been regarded that, in the warming climate, atmospheric water vapor may increase due to the enhancement in surface evaporation, which is expected from the Clausius–Clapeyron (C–C) equation, along with the assumption that relative humidity experiences small changes. If the variation in relative humidity is small, the response of water vapor to temperature will be closely in line with the C–C equation. However, whether relative humidity experiences large or small changes needs be assessed, and the change of relative humidity should be compared with the change in surface–air temperature. In this study, we link surface vapor pressure, which characterizes atmospheric water vapor, to surface-air temperature, and treat both the temperature and relative humidity as influencing factors. A method based on linear regression is applied to compare the interannual variabilities of relative humidity and temperature in the interannual variation in surface vapor pressure. Whether the year-to-year perturbation of relative humidity is important, compared with the perturbation in surface-air temperature, is explored Results show that, at high latitudes of both hemispheres, the variation in vapor pressure is dominated by air temperature, and relative humidity has small positive contributions. Thus, the variation in relative humidity over these regions is comparably small, and the response of water vapor to temperature can well follow the C–C equation. Differently, at mid-low latitudes, especially on land, air temperature plays a negative role in the variation in vapor pressure. Relative humidity offsets the negative contribution and dominates the variation in vapor pressure, suggesting that the variation in the relative humidity over these regions is comparably large. Hence, the response of water vapor to temperature deviate from the C–C equation. Analysis indicates that the different results of the dominance from the two influencing factors are affected by the dual effects of precipitation or wet-air transport over land. Both precipitation and the transport of cold wet air could break the C–C relation between water vapor pressure and temperature.

Optimization of PTFE Content in Catalyst Layer of Gas Diffusion Electrode for Alkaline Fuel Cell

Alkaline fuel cell (AFC) is historically 1st successfully applied fuel cell type. The main benefit of AFC is still possibility to use non platinum based catalysts at ambient conditions. With increase of demand for platinum metals for PEM water electrolysis and fuel cell this benefit would become more significant. Therefore it has sense to focus on AFC development.Gas diffusion electrodes (GDE) are crucial part in numerous technologies. Its main function is to enable contact of gaseous reactant with electron conductor and ionic conductor. Enlargement of contact area of mentioned three phase boundary lead to increase of electrode performance. In the case of liquid electrolyte like potassium hydroxide in AFC it is crucial to balance penetration of liquid into pores of electrode and to keep part of electrode unflooded. It must be realized in catalytic layer of GDE. Variation of temperature change electrolyte viscosity and vapor pressure both influences flooding of electrode.Beside suitable structure GDE for AFC must be stable in strong alkaline solutions. Standard GDE construction is based on combination of hydrophilic a hydrophobic materials to reach desired wettability. Also, the preparation method influences the porosity of the catalytic layer. GDE consist of three layers: catalytic, diffusion and supporting. The gas/liquid interface must be realized in catalytic layer. It is usually composed of catalyst and binder. Catalyst is chosen with respect to electrochemical reaction running on electrode thus binder must deliver desired hydrophobicity. Most typical binders are perfluorinated polymers like PTFE polytetrafluoroethylene (PTFE) with excellent chemical resistivity. Nickel, manganese, platinum, silver etc. are widely used in alkaline systems like catalysts. The most important property of the catalytic layer is the ratio of catalyst to PTFE which provides suitable hydrophobicity. The diffusion layer (GDL) is usually made of a mixture of carbon blacks/graphite and PTFE. The support layer is typically made of nickel foam or carbon paper.This work aims to optimize the ratio of PTFE to platinum catalyst in the catalytic layer. The commercial catalyst HiSPEC 40 wt. % Pt/C was used and Pt load was set to 0.5 mg/cm2. Electrodes were prepared by ink spraying technique on commercial GDL Sigracet® BC28. The ink with different ratios of PTFE to catalyst was applied to prepare GDE with PTFE content from 5 wt. % to 40 wt. %. Electrode baking under inert atmosphere was the last preparation step to increase mechanical stability.As the first characteristic the contact angle was measured. The droplet of water was placed on catalyst layer surface. The contact angle of droplet to GDE surface represents the level of hydrophobicity. A high level of hydrophobicity brings about low inundation GDE and bad contact between liquid, gas and catalyst. On the other hand, if GDE has low hydrophobicity, liquid can inundate the catalytic layer easily. As it was found already 5% of PTFE makes GDE surface hydrophobic. Higher loading of PTFE lead only to small angle increase. But significant decrease was found after GDE operation and PTFE loading over 15% is necessary to prevent further hydrophobicity decrease.In the second step prepared GDE were tested in the laboratory AFC. Pure hydrogen and pure oxygen were dosed to GDE chambers. 25% KOH solution was used as electrolyte. The I-V curve at the beginning of cell assembly, performance in time and I-V curve at the end of experiment was measure. The power of AFC with prepared electrodes improves if the hydrophobicity of GDE decreases. However, the penetration of liquid through the GDE was observed in low hydrophobic GDE in a long time testing alkaline fuel cell. Also the gradual decrease of cell performance was observed due to the flooding of the catalytic layer. After stop of operation and repeated start the performance of the cell again improved but no to the origin level. Only if the PTFE content was over 40% the performance was identical for several repeated experiments.The importance of PTFE loading in catalyst layer composition was demonstrated and its influence on AFC performance. The low loading of PTFE in GDE shows the highest performance but with fast drop. For longtime operation it is necessary to use PTFE leading at least 40%. Acknowledgment Financial support of this research by the Technological Agency of the Czech Republic under the project No TK02030001 “Research and development of advanced flow energy storage technologies” is gratefully acknowledged.

How electron beam melting tailors the Al-sensitive microstructure and mechanical response of a novel process-adapted [formula omitted]-TiAl based alloy

Additive manufacturing of lightweight intermetallic γ-TiAl based alloys combines process-related freedom of design with material-specific excellent high-temperature properties. Nevertheless, where locally melting the powder by an electron beam, there is a risk that Al evaporates due to its high vapor pressure, causing compositional and microstructural variations. This work investigates the impact of different process parameters on the total and local Al-content as well as the resulting as-built and heat-treated microstructure in a complex multiphase Ti-44.8Al-4.1Nb-0.7W-1.1Zr-0.4Si-0.5C-0.1B (at.%) alloy. The examinations applied are complementary, employing electron microscopy, X-ray spectroscopy and diffraction experiments with synchrotron X-ray radiation, supported by numerical simulations. The mechanical anisotropy of the heat-treated microstructure was analyzed by micro-hardness measurements. The results demonstrate that the amount of γ-TiAl phase decreases with increasing energy input of the electron beam in the as-built and heat-treated microstructure owing to the total and local loss of Al. Besides, the investigations of the crystal orientations within the multiphase alloy reveal a preferred orientation of the γ phase at high energy inputs. This follows from the fact that the preferred γ orientation is inherited through directional solidification of the β phase. The obtained process-microstructure-property relationships show that tailor-made material properties of additively manufactured γ-TiAl components are achievable.

Assessing the Impact of Ambient Fabrication Temperature on the Performance of Planar CH3NH3PbI3 Perovskite Solar Cells

AbstractThe ambient fabrication temperature inside the glove box is found to play an important role in determining the overall power conversion efficiency in solar cells based on CH3NH3PbI3 (MAPI) hybrid organic‐inorganic perovskites. We find that a variation of the ambient temperature of only 10 °C during the fabrication process has a crucial impact on both the reproducibility and the efficiency of the devices. Atomic Force Microscopy, XRD, UV‐Vis absorption spectroscopy, and electroluminescence studies have been carried out to investigate the origin of this behavior. We conclude that the partial vapor pressure variation of the solvent impacts the crystallization process, inducing an increased density of traps within the bandgap of the perovskite.

VARIABILITY OF THE MAIN CLIMATIC INDICATORS IN THE TERRITORY OF THE VOLGA FEDERAL DISTRICT IN THE PERIOD 1966-2018

The spatio-temporal variability of air temperature and humidity, atmospheric precipitation in the Volga Federal District in 1966-2018 is considered. As a result of statistical processing of data from 20 weather stations, a clear warming trend in recent decades and a weak increase in annual precipitation are revealed, except for the south-east of the region. The annual variation of water vapor pressure and relative humidity is considered, statistics of the distribution of "dry" and "wet" days by stations in different months are carried out. Correlations between individual circulation modes (AO, NAO, SCAND, EAWR) and air temperature are revealed. It is shown that positive relationships are closer in winter with the AO and NAO indices than in summer. A sufficiently high negative correlation is established with the SCAND index in winter (r = -0,7), and with the EAWR index in summer (the correlation coefficient reaches a value of -0,6).

Protic guanidine isothiocyanate plus acetamide deep eutectic solvents with low viscosity for efficient NH3 capture and NH3/CO2 separation

Deep eutectic solvents (DES) are regarded as the second generation ionic liquids with potential application in gas capture and separation field due to negligible vapor pressure and abundant formation variation. In present work, protic guanidine isothiocyanate was selected as hydrogen bond acceptor and paired with acetamide as hydrgen bond donor to construct low viscosity DES. The DESs were characterized with phycsichemical properties and utilized in NH3 capture and NH3/CO2 separation systematically. The gas solubility enhcanced with the increasing molar ratio of GI to AT, increasing pressure, and falling temperature. The solubilities of NH3 and CO2 were correlated by Henry's law. The thermodynamic parameters were further calculated according to the temperature dependence of Henry's constants. The NH3 saturated DES could be easily recycled five times with persistent absorption performance. The ideal NH3/CO2 selectivity at 303.15 K was 151 and higher than most solvents reported in the literatures. The absorption mechanism was further deduced by NMR and F-IR spectroscopy. These DESs presented efficient NH3 absorption and selective separation performance due to good absorption performance, reversibility, and high NH3/CO2 selectivity.

Morphology Evolution of a High-Efficiency PSC by Modulating the Vapor Process.

The morphological quality of the photoactive layer is the key component affecting the performance metrics of a photovoltaic device. Therefore, fine adjustment of the crystallization dynamics is urgently required. By manipulating the amount of dimethyl sulfoxide (DMSO) remaining in the spin-coated perovskite films during the annealing treatment, an obvious morphological evolution arises. The crystallization kinetics is significantly altered due to the formation of intermediate phases and the variation of DMSO vapor pressure via producing the semienclosed space with a covering. On the one hand, the obviously formed intermediate phase MA2 Pb3 I8 (DMSO)2 retards the crystallization process. On the other hand, the DMSO vapor in the semienclosed space intrigues the recrystallization process and results in Ostwald ripening to produce large-aspect-ratio grains with fewer defect states, decreased carrier doping, and longer carrier lifetimes. Thus, nonradiative processes are greatly suppressed. Besides, combined with X-ray photoelectron spectroscopy measurement and the surface energy of MAI- and PbI-terminated surface model calculated by density functional theory, the defect states are identified and the causes of Pb0 defect states are explained. Using this strategy, a high power conversion efficiency of 20.09% is achieved based on MAPbI3 photovoltaic solar cell, and the long-term ambient shelf and thermal stability are obviously improved.

Climate sensitivity to decadal land cover and land use change across the conterminous United States

Abstract Transitions to terrestrial ecosystems attributable to land cover and land use change (LCLUC) and climate change can affect the climate at local to regional scales. However, conclusions from most previous studies do not provide information about local climate effects, and little research has directly quantified how LCLUC intensity within different ecoregions relates to climate variation. In this study, we present an observation-based analysis of climate sensitivity to LCLUC based on decadal LCLUC and climate data in different ecoregions. Our results revealed that variations in land surface temperature and vapor pressure were most sensitive to LCLUC across the conterminous United States, while precipitation was less sensitive. Persistent warming effects were produced from LCLUC in Appalachian and some of the central U.S., High Plains, and northwest ecoregions, but cooling effects were evident in the many southeast, northeast and some Great Lakes and Intermountain West ecoregions. Most of the warming and a few cooling ecoregions were sensitive to LCLUC. Ecoregions with increasing vapor pressure were found across the Great Plains, Intermountain West, and West Coast ecoregions and several of these regions in the Great Plains and West Coast were sensitive to LCLUC. A combination of changes in temperature, precipitation, and vapor pressure was used to characterize climate sensitivity associated with LCLUC forcing, and five major persistent patterns were found in some ecoregions. These findings suggest that climate conditions, especially temperature and vapor pressure, in some ecoregions are sensitive to LCLUC and such change should be better incorporated into regional climate assessments.