Benefits of protected areas for nonbreeding waterbirds adjusting their distributions under climate warming

Climate warming is driving changes in species distributions and community composition. Many species have a so-called climatic debt, that is, shifts in range lag behind shifts in temperature isoclines. Inside protected areas (PAs), community changes in response to climate warming can be facilitated by greater colonization rates by warm-dwelling species, but also mitigated by lowering extirpation rates of cold-dwelling species. An evaluation of the relative importance of colonization-extirpation processes is important to inform conservation strategies that aim for both climate debt reduction and species conservation. We assessed the colonization-extirpation dynamics involved in community changes in response to climate inside and outside PAs. To do so, we used 25 years of occurrence data of nonbreeding waterbirds in the western Palearctic (97 species, 7071 sites, 39 countries, 1993-2017). We used a community temperature index (CTI) framework based on species thermal affinities to investigate species turnover induced by temperature increase. We determined whether thermal community adjustment was associated with colonization by warm-dwelling species or extirpation of cold-dwelling species by modeling change in standard deviation of the CTI (CTISD). Using linear mixed-effects models, we investigated whether communities in PAs had lower climatic debt and different patterns of community change than communities outside PAs. For CTI and CTISD combined, communities inside PAs had more species, higher colonization, lower extirpation, and lower climatic debt (16%) than communities outside PAs. Thus, our results suggest that PAs facilitate 2 independent processes that shape community dynamics and maintain biodiversity. The community adjustment was, however, not sufficiently fast to keep pace with the large temperature increases in the central and northeastern western Palearctic. Our results underline the potential of combining CTI and CTISD metrics to improve understanding of the colonization-extirpation patterns driven by climate warming

Numerical investigation of the interaction of twin supersonic jet with a flat obstacle

This paper presents the results of mathematical modeling of the interaction of supersonic twin jet flow with a flat obstacle. The influence of the distance between the nozzles on the shock-wave structure of the gas flow for the Mach numbers 4.7 on the nozzle exit are studied. In the studies, the distance from the nozzle exit to obstacle was 0.5 meters, the distance between the nozzles varied from 0.1 to 4.0 nozzle exit diameters. It was found that in the range of distances between nozzles 0.1-1 nozzle exit diameters, the shock-wave structure of the flow and pressure distribution along the obstacle are similar. With an increase in the distance between the nozzles of more than 1.0 nozzle exit diameters the maximum pressure on the obstacle is two times less. For distance 4.0 of nozzle exit dimeter in the region of the triple configuration of shock waves oscillations are observed

The development of a cloud system for investigation of UAVs aerodynamic characteristics

The paper presents the results of the development of a cloud system for multi-parameter aerodynamic calculations of unmanned aerial vehicles (UAVs). The developed cloud system consists of the following functional parts: web client – provides an access to the computing cloud, allows interactively preparing a task, sending prepared data to a computing cluster, getting and visualizing calculation results; and computing cloud – provides communication with the web client using an open API and manages the computing process. The computing process of the cloud is based on using open technologies of the OpenFOAM software adapted for solving aerodynamics problems. The authors carried out parametric studies of the external flow of UAV at free-stream velocities of 20, 25, 30 m/s with angles of attack from –4 to 12 degrees. It was found that the smallest drag force is observed for 0-3 degrees of the angle of attack of the flying wing, and the best lift to drag ratio is detected for 5 degrees attack angle. For 5 degrees attack angle the lift force is 47 N for an air free-stream velocity 20 m/s, 74 N – 25 m/s, 106 N – 30 m/s