It has been found that air entrainment occurs when the average jet velocity at the plunging point reaches a certain value. This velocity is called the critical velocity of air entrainment. The analysis of studies in this field shows that the process of jet interaction with the liquid surface is complex, while the theoretical approaches to its description are insufficient. The conditions at which air entrainment begins are related to the behavior and shape of the meniscus. The mechanism of meniscus formation is based on the complicated kinematic structure of motion in the vicinity of the point of interaction between the jet and the liquid in the quiescent state. Experiments and observations show that the meniscus behavior is closely related to the initial conditions of air entrainment. Calculating the critical velocity of air entrainment Ue, analysis of the meniscus shape, and use of the limit equilibrium condition were used to derive a new criterion relationship for the air entrainment conditions of turbulent jets flowing from long smooth nozzles. The results of calculations are compared with experimental data.

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Резюме. Обсуждается влияние весенних низовых растительных пожаров на фауну пчел на равнинных участках в Хинганском заповеднике. Предложены мероприятия по снижению частоты и силы пожаров в весенний период, основанные на наблюдениях за процессом снеготаяния. Приведены сведения об устойчивости некоторых видов пчел по отношению к низовым растительным пожарам, а также заселении представителями семейств Colletidae и Megachilidae послепожарных участков.Summary. The impact of spring low vegetation fires on bee fauna at the plain areas of Khinganskii Nature Reserve is discussed. Some ways of decreasing the frequency and destructive force of spring fires, which are based on the observation of snow melting are proposed. Data on the resistance of some bee species to the low vegetation fires are reviewed and information about the after-fire colonization of the area by the bees from the families Colletidae and Megachilidae are given.

Резюме. Приведены оригинальные сведения о посещении пчёлами 84 видов цветковых растений, произрастающих на территории Хинганского (крайний юго-восток Амурской области) и Зейского (центральная часть Амурской области, хр. Тукурингра) заповедников. Summary. Original data on the trophic connections between bees and 84 species of flowering plants found in the Khinganskii (extreme south-east of Amurskaya oblast) and Zeiskii (central part of Amurskaya oblast, Tukuringra Ridge) Nature Reserves are presented.

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