Numerical modelling of heat treatment of concrete of monolithic structures of buildings in winter conditions of construction

The paper presents the results of numerical modeling of heat treatment of concrete of a monolithic floor using a heating wire in winter conditions, depending on factors such as ambient temperature, wind speed, isothermal curing temperature, and others. The following parameters were taken as the main parameters for calculating the heat treatment of concrete: the geometric dimensions of the concreting area, the type and dimensions of the thermal insulation layer to ensure thermal protection of the monolithic structure during the heat treatment of concrete, the type and characteristics of transformers that provide the necessary power for preheating and heating concrete of monolithic floors, as well as the class of concrete, cement consumption and type of heating wire. As a result of calculations, the values of the required power for heating concrete of monolithic structures, the number of transformers, the voltage on the transformer for heating the concrete, as well as the duration of the periods of heating, isothermal curing and cooling during the heat treatment of concrete were obtained. As a result of the performed numerical experiments, the modes of heat treatment of a monolithic floor were deter-mined, which ensure the achievement of the required strength of concrete of monolithic structures. This type of heat treatment of concrete during winter periods has established itself as energy efficient and versatile, since heating wires can be used in structures of any type, configuration and reinforcement. With the correct use of heating wires, it is possible to obtain high-quality reinforced concrete structures erected at negative ambient temperatures.

Effect of phase transitions on operation of air-to-air heat exchangers with drop irrigation

The article presents the results of experimental studies of the thermal and humidity parameters of air flows of a regenerative air-to-air heat exchanger with drop irrigation and an intermediate heat carrier when operating in winter conditions with negative outside temperatures. The dependences of temperature and humidity efficiency of the heat exchanger on saline solution flow rate were determined, while the maximum temperature efficiency in the heating column was more than 70%. It is shown that under all investigated regimes in the heating column, moisture evaporated from the saline solution, and the air entering the room became more humid, which is a positive factor that increases the comfort of premises at negative outside temperatures.

Paved Paradise: Belowground Parking Structures Sustain Urban Mosquito Populations in Washington, DC

ABSTRACT After notification of mosquitoes within federal buildings in Washington, DC, we surveyed belowground levels of nearby parking structures for mosquitoes and standing water in the summer months of 2018 and 2019. Aedes aegypti, Ae. albopictus, and members of the Culex pipiens Assemblage were found. Genotyping revealed pipiens, molestus, and quinquefasciatus ancestry among Cx. pipiens Assemblage mosquitoes, and allele frequency comparisons indicated a stable, resident population. Winter and spring aboveground temperatures ranged from −11°C to 35°C, while belowground temperatures never dropped below 5°C or exceeded 30°C, and winter temperatures were significantly higher belowground compared with aboveground. Moderated winter conditions suggest that belowground urban structures could act as refugia for warmer-climate species, like Ae. aegypti and Cx. quinquefasciatus, allowing them to overcome assumed thermal barriers. Surveys of parking structures should be incorporated into integrated vector management programs in urban areas.

A microclimate regulation study of Ficus altissima under winter conditions in lower subtropical China

As a widespread practice in urban landscape design, tree planting plays a vital role in improving the ecological environment and microclimate. This study obtained the physical, physiological, and meteorological data of Ficus altissima, a typical tree species in lower subtropical China, through field measurement, and analyzed its functional performance in microclimate regulation. Its results indicated that: (1) the leaf area index (LAI), sky visible factor (SVF), ground cover (GC), and other indicators of Ficus altissima had essential relationships with radiation attenuation, temperature, and humidity regulation under winter conditions in lower subtropical China; (2) there were significant differences in leaf surface temperature and transpiration between east, west, north, and south during daytime; and, (3) thermal comfort represented by physiological equivalent temperature(PET)in the shade could be expressed as functions of solar radiation (SR), mean radiation temperature (MRT), air temperature (Ta), air humidity (RH), globe temperature (Tg), and wind speed (V). Based on these results, the following were the suggestions: firstly, Ficus altissima with higher LAI values should be selected for planting; secondly, trees must be planted on the east side of the site should solitary planting be undertaken to obtain maximum thermal comfort; and finally, activities under the canopy of Ficus altissima should be prioritized at 11:00–16:00 during winter.

Shoot Growth and Flower Bud Production of Peony Plants under Subtropical Conditions

Peony plants require temperate winter temperatures to break underground bud dormancy and allow shoot emergence and flowering in spring. This study assessed whether artificial chilling at 4 °C for 2–6 weeks could induce shoot emergence and flowering under subtropical conditions. It also assessed whether pre-treatment at cool temperatures prior to chilling, or gibberellin application after chilling, promoted shoot emergence and flowering. Artificial chilling at 4 °C for 4 or 6 weeks promoted the greatest shoot emergence. Pre-treatment at cool temperatures did not affect shoot growth or flower bud production but it improved shoot emergence from plants also treated with gibberellin. Gibberellin more than doubled the number of shoots per plant without affecting shoot length. The optimal treatment combination for shoot emergence, growth and flower bud production was pre-treatment from 20 °C to 8 °C over an 8-day period in autumn, chilling at 4 °C for 6 weeks in early winter, and treatment with 250 mL of 100 mg/L GA3, before returning plants to subtropical winter conditions. This treatment combination provided medians of 3 (0–7) and 8 (0–31) flower buds per plant in the second and third years of production, respectively. Peony flowers can be produced in subtropical climates using artificial chilling and gibberellin, allowing out-of-season market supply.

Changing winter diet of thick-billed murres Uria lomvia in Southwest Greenland, 1990s versus 2010s

Southwest Greenland constitutes an internationally important wintering area for seabirds, including thick-billed murres (Uria lomvia Linnaeus, 1758), but their prey may be affected by the general warming of this sub-Arctic region. We compare murre diet collected in winter in the 1990s and 2010s around Nuuk. Fish made up 36% of the diet (wet mass) and crustaceans 63% in the 1990s, changing to 22% and 78% in the 2010s, respectively. Capelin (Mallotus villosus Müller, 1776) was the dominant fish species, and the smaller contribution in the 2010s coincided with declining densities of capelin around Nuuk. The crustaceans were dominated by two krill species, Meganyctiphanes norvegica M. Sars, 1857, and Thysanoessa inermis Krøyer, 1846. However, M. norvegica was only important in the 2010s (51% wet mass), while T. inermis was dominating the 1990s with 62% wet mass and only 23% in 2010s. The dominance of M. norvegica in the 2010s confirmed our expectations of a gradual “borealization” of this region due to the generally warming sub-Arctic. The smaller contribution of fish in the diet may also support the hypothesis of deteriorating winter conditions for murres. Apart from the diet, plastic was found in 15% of the birds and 53% had parasitic nematods.