Effects of Initial Surface Evaporation on the Performance of Fly Ash-Based Geopolymer Paste at Elevated Temperatures

Geopolymer concrete is a valuable and alternative type of concrete that is free of traditional cement. Generally, geopolymer concretes require a source material, which is rich in silicon and aluminum. Furthermore, fly ash-based geopolymer concretes have been proven to have superior fire resistance, primarily due to their ceramic properties, and are inherently environmentally-friendly given their zero-cement content. This paper presents the effects on initial evaporation on the performance of fly ash-based geopolymer pastes after exposure to elevated temperatures of 400 °C and 800 °C. The fly ash (FA) samples used in the present study included: Gladstone and Gladstone/Callide. The results for sealed samples placed in the oven during curing were much more consistent than the samples that were not kept covered. In addition, Gladstone fly ash-based geopolymer samples that were sealed recorded an initial maximum compressive strength reading of ca. 75 MPa, while sealed Gladstone/Callide fly ash-based geopolymer samples, of the same mix design, only recorded an initial maximum compressive strength reading of ca. 50 MPa (both subjected to oven curing at 60 °C for 24 h). However, Gladstone/Callide fly ash-based geopolymer samples exhibited a significant strength gain, ca. 90 MPa, even after being subjected to 400 °C.

Optimization of Subsurface Smart Irrigation System for Sandy Soils of Arid Climate

The Arabian Peninsula is an arid zone with a hot desert climate and severe water scarcity. The low humidity, elevated ambient temperatures, and high evaporation rates in the region deemed conventional surface irrigation unsustainable. The IoT-based subsurface smart irrigation systems can be essentially developed for these regions to avoid surface evaporation losses. In this research, the sandy soil conditions of western Saudi Arabia have been considered in numerical simulations to evaluate the performance of a subsurface smart irrigation system. The influence zone of saturation generated by subsurface diffusers in the target root region has been analysed for two different types of sandy soils. The simulation results generated by the COMSOL Multiphysics program reveal that the subsurface smart irrigation system can be effectively applied to simultaneously manage the target root zone at the ideal saturated conditions and prevent surface evaporation losses.

Coal Moisture Variations in Response to Rainfall Events in Mine and Coal-Fired Power Plant Stockpiles—Part 2: Evaporation

Additional moisture added in coal stockpiles due to rain and other climatic processes causes a significant problem worldwide, which leads to not only decrease in the heating value of the coal but also creates an extra efficiency penalty. Therefore, it is important to make some predictions for control of coal moisture within stockpiles after the rainfall. When the rain falls on the stockpile, it either runs off the surface or infiltrates the stockpile. The infiltrated water may evaporate from the surface, drain or stay within the stockpile. The aims of this study (parts 1 and 2) are to describe and compare the changes in coal moisture content following rainfall events. The mechanisms of runoff, infiltration and drainage after rainfall were described in the first paper of this series. In part 2 the influence of coal particle size and ambient conditions on the rate and depth of moisture evaporation within the stockpile is investigated. The laboratory experiments showed cyclic events of adsorbing moisture overnight and desorbing this moisture during the day as part of the coal surface evaporation process. The rate of evaporation from the surface of the fine coal stockpile was faster than the coarse stockpile; however, the coarse stockpile experienced a more efficient evaporation process because of its porous structure. Fine coal beds experienced evaporation only near the surface, while the maximum influencing layer of evaporation is a depth of 0.4 cm below the surface in coarse coal beds.

The Connection between Carnot and CAPE Formulations of TC Potential Intensity

Tropical cyclone (TC) potential intensity (PI) theory has a well known form, consistent with a Carnot cycle interpretation of TC energetics, which relates PI to mean environmental conditions: the difference between surface and TC outflow temperatures and the air–sea enthalpy disequilibrium. PI has also been defined as a difference in convective available potential energy (CAPE) between two parcels, and quantitative assessments of future changes make use of a numerical algorithm based on this definition. Here, an analysis shows the conditions under which these Carnot and CAPE-based PI definitions are equivalent. There are multiple conditions, not previously enumerated, which in particular reveal a role for irreversible entropy production from surface evaporation. This mathematical analysis is verified by numerical calculations of PI’s sensitivity to large changes in surface-air relative humidity. To gain physical insight into the connection between the CAPE and Carnot formulations of PI, we use a recently developed analytic theory for CAPE to derive, starting from the CAPE-based definition, a new approximate formula for PI which nearly recovers the previous Carnot PI formula. The derivation shows that the difference in undilute buoyancies of saturated and environmental parcels which determines CAPE PI can in fact be expressed as a difference in the parcels’ surface moist static energy, providing a physical link between the Carnot and CAPE formulations of PI. This combination of analysis and physical interpretation builds confidence in previous numerical CAPE-based PI calculations that use climate model projections of the future tropical environment.

Hydrogeological functions of obskoye and baksinskoye swamps in the southeast of West Siberian Plain

Based on hydrological data from 1966 to 2019, quantitative estimates of the water balance of the Baksinskoye and Obskoye fens. The decrease in surface evaporation of the swamp and the increase in water runoff occurred in the main distribution of the swamp. This will exacerbate the degree of swamping in the area. The impact of marsh water on groundwater is most likely to occur during the dry season in summer and autumn. During this period: 1) possible overflow of bog waters into underground horizons in areas of 800–900 m; 2) increased permeability. When the water mass is discharged from the fens plain into the river, the impact of the fens water reaches its maximum during the subside of the flood.

Experimental Investigation to Determine the Concentration of Radon in Cosmetics Using a Nuclear Track Detector (CR-39)

The nuclear track detector CR-39 is used in the detection of radon gas concentration in selected samples of cosmetics in the local market. Products of wide use are selected and employed in the current study. Six types of cosmetic products of different origins are tested by taking equivalent quantities of these products and putting them in plastic boxes. The detector is left with the samples for a period of 50 days. In addition to measuring the rate of surface evaporation of radon gas, measurements of the annual equivalent dose of radon gas are also carried out. The results show that the highest concentration of radon gas is in Charcoal Facial SCRuB (American origin) and it is equal to 0.0795 Bq/m3, whereas the lowest one in "bb" cream basis (5 in 1) is equal to 0.0355 Bq/m3. Based on specific international organizations and agencies, the concentration of radon in the samples under consideration is within the acceptable limits.

A Stable Isotope Approach for Estimating the Contribution of Recycled Moisture to Precipitation in Lanzhou City, China

The proportional contribution of recycled moisture to local precipitation is a geographically dependent parameter that cannot be ignored in water budgets. Stable hydrogen and oxygen isotopes are sensitive to environmental changes and can be applied to investigate the modern water cycle. In this study, a three-component mixing model is used to calculate the contribution of different water vapors (advection, evaporation and transpiration) to summer precipitation in Lanzhou city, Northwest China. The results show that for all sampling sites in Lanzhou, the contribution of advection vapor to precipitation is the largest, followed by the plant transpiration vapor, and the contribution of surface evaporation water vapor is usually the least, with the average values of 87.96%, 9.1% and 2.9%, respectively. The spatial differences of plant transpiration vapor are generally larger than those of advection vapor and surface evaporation vapor, and the high values appear in Yongdeng, Daheng and Gaolan.

A model study of the role of Convection in Westerly Wind Burst Dynamics

Westerly wind bursts (WWBs) are anomalous surface wind gusts that play an important role in ENSO dynamics. Previous studies have identified several mechanisms that may be involved in the dynamics of WWBs. In particular, many have examined the importance of atmospheric deep convection to WWBs, including convection due to tropical cyclones, equatorial waves, and the Madden Julian Oscillation. Still, the WWB mechanism is not yet fully understood. In this study, we investigate the location of atmospheric convection which leads to WWBs and the role of positive feedbacks involving surface evaporation. We find that disabling surface flux feedbacks a few days before a WWB peaks does not weaken the event, arguing against local surface flux feedbacks serving as a WWB growth mechanism on individual events. On the other hand, directly suppressing convection by inhibiting latent heat release or eliminating surface evaporation rapidly weakens a WWB. By selectively suppressing convection near or further away from the equator, we find that convection related to off-equatorial cyclonic vortices is most important to equatorial WWB winds, while on-equator convection is unimportant. Despite strong resemblance of WWB wind patterns to the Gill response to equatorial heating, our findings indicate that equatorial convection is not necessary for WWBs to develop. Our conclusions are consistent with the idea that tropical cyclones, generally occurring more than 5° away from the equator, may be responsible for the majority of WWBs.