Sensitivity studies on the air flow characteristics In Kharagpur using a meso-scale model

A three-dimensional hydrostatic model has been employed for the study of sea breeze circulations over south West Bengal with special reference to an inland station Kharagpur (22°.21' N, 87° 19'E). A series of sensitivity experiments have been performed to stress the Importance of differential heating on circulation over south West Bengal during pre-monsoon period. It is found that due to differential heating rate between land and sea surfaces, sea breezes can penetrate to the inland station Kharagpur and beyond even in case of moderate gradient wind. Surface observations at Kharagpur and pilot balloon observation at nearby station Kalaikunda are used to compare the model results. The onset of sea breezes, variation of the air temperature and humidity are In fairly good agreement whereas It over estimates the depth of the circulation and cannot predict the variation of the late morning hours surface wind.

Self-healing of asphalt mixture: the impact of the minerals forming the aggregates in the efficiency of the heating by microwaves.

The current concern for the environment and the need to reduce greenhouse gas emissions have led to new technologies related to microwave energy. One of these technologies is the self-healing of asphalt mixtures, which consists of repairing pavements through microwave application on the surface, avoiding premature road failure. Asphalt mixtures for roads are made up of more than 90% by weight of aggregates of different compositions and origins, in addition to a bituminous binder and sometimes additives. From other studies, it is known that the physical behaviour of aggregates is a function of their composition, that is, of their minerals and their proportions. Microwave heating of aggregates has proven to be an effective technique, but there are gaps in understanding how microwaves interact with aggregates and the reasons for their differential heating. This research has studied 18 minerals that are commonly part of the rocks used as road aggregates. The objective is to identify the minerals that present the best heating rates to relate them to the differential heating of aggregates for roads. The results obtained are promising, facilitating the understanding of microwave heating of minerals. Regarding chemical composition, elements such as MgO, MnO, TiO, Al2O3, Fe2O3, and CaO (in silicate minerals) favour the heating of minerals and other elements such as SiO2 and K2O Na2O, and CaO (in carbonate minerals) retard the heating. Regarding the physical properties, density and habit of the minerals do not influence the heating, but other properties, such as the diaphaneity and the size of the crystals, influence the heating with microwaves.

Differential heating of metal nanostructures by radio frequencies: a theoretical study

Nanoparticles with strong absorption of incident radio frequency (RF) or microwave irradiation are desirable for remote hyperthermia treatments. While controversy has surrounded the absorption properties of spherical metallic nanoparticles, other geometries such as prolate and oblate spheroids have not received sufficient attention for application in hyperthermia therapies. Here, we use the electrostatic approximation to calculate the relative absorption ratio of metallic nanoparticles in various biological tissues. We consider a broad parameter space, sweeping across frequencies from 1 MHz to 10 GHz, while also tuning the nanoparticle dimensions from spheres to high-aspect-ratio spheroids approximating nanowires and nanodiscs. We find that while spherical metallic nanoparticles do not offer differential heating in tissue, large absorption cross sections can be obtained from long prolate spheroids, while thin oblate spheroids offer minor potential for absorption. Our results suggest that metallic nanowires should be considered for RF- and microwave-based wireless hyperthermia treatments in many tissues going forward.

Water Exchanges and Phosphorus Flux between a Reservoir and Eutrophic Littoral Zone

HighlightsConvective currents led to hydraulic flux and transport of P between bottom and surface waters of the littoral zone.Hydraulic flux was primarily into the bottom of the cove and out of the cove along the surface.Eutrophic littoral areas are a significant source of P to the photic zone of reservoirs, supporting algal growth.Abstract. Eutrophication of surface waters is defined by excessive algal growth, with consequences for drinking water treatment. The sources of phosphorus (P) in southern U.S. reservoirs that fuel peak algal productivity in late summer are still not fully understood. One potential source is reservoir littoral zones, which have been described as the most productive zone of a waterbody. A shallow cove named Granny Hollow in Beaver Lake, northwest Arkansas, was selected as an isolated and semi-controlled location to measure and model sources of P and its transport in a littoral area for the month of July 2018. Hydraulic and P fluxes between the reservoir and littoral area were quantified through field measurements and a 3D lake model. In quantifying hydraulic flux for the month of July, the model indicated that water tended to move into the cove along the bottom and out along the top, with a net hydraulic flux out of the cove of -723,000 m3. Peak surface velocity in the cove averaged 2.09 cm s-1 for the month of July, while peak bottom velocity was 1.29 cm s-1. Diurnally, water movement switched directions, moving out of the cove along the surface during differential heating and into the cove along the surface during differential cooling due to thermoconvective flow. During differential heating, the water velocity and hydraulic flux to the main reservoir channel along the surface of the cove were greater than the velocity and flux in the opposite direction during differential cooling. The sources of P within the cove during July included P released from bottom sediments within the cove and littoral zone and transport of P from the reservoir channel to the cove. Transport of P from the main reservoir into the cove was a result of thermoconvective flow. During differential heating, bottom waters from the main reservoir channel were transported to the surface within the littoral zone by thermoconvective currents flowing upslope from deeper to shallower waters. This resulted in P exchange between the reservoir and littoral area and is significant because it represents movement of P from the bottom of the reservoir upward into the photic zone, where it can be used for algal productivity. During July 2018, it was estimated that 13.3 kg of P were transported from the bottom of the cove to the surface by convective currents and subsequently out of the cove. This study shows that eutrophic coves represent a significant source of P to the reservoir and more importantly to the photic zone, supporting algal growth. Keywords: 3D reservoir model, Eutrophication, Internal loading, Thermoconvective flow.

Radiative heating of ice-covered waterbodies of varying morphologies

<p>Millions of small, high-altitude lakes freeze their surface waters each winter season. Observations, however, reveal that their water temperature is increasing and the ice-on period is declining. Altering the thermal regime of ice-covered lakes have multiple impacts, including the loss of ecosystem services to increments in greenhouse gas emissions. These pervasive changes are affected by the heating rate of under-ice waters, which in turn regulates the water-to-ice heat flux, and therefore the rate of ice melting. In such aquatic systems, solar radiation warms the water beneath a diffusive boundary layer, thereby increasing its density and providing energy for convection in a diurnally-active mixing layer. Shallow regions are differentially heated to warmer temperatures, driving downslope buoyancy-driven currents that transport warm water to the interior basin. We characterize the energetics of these processes, focusing on the rate at which solar radiation supplies energy that is available to drive fluid motion. Using numerical simulations, we show that advective fluxes due to differential heating contribute to the evolution of the mixed-layer in waterbodies with significant shallow areas. We use a heat balance to assess the relative importance of differential heating to the one-dimensional effects of radiative heating and diffusive cooling at the ice-water interface in waterbodies of varying morphologies.</p>