Consequences of advances in agricultural technologies for the distribution of segetal plant communities and species in the Republic of Bashkortostan
G. R. Khasanovaa, *, M. V. Lebedevab, **, B. M. Mirkinc, and L. G. Naumovad, *** aBashkir State Agrarian University, Ufa, 450001 Russia bBotanical Garden-Institute, Ufa Scientific Center, Russian Academy of Sciences, Ufa, 450080 Russia cUfa Institute of Biology, Russian Academy of Sciences, 450054 Russia dBashkir State Pedagogical University, Ufa, 450000 Russia *e-mail: gulnazrim@yandex.ru **e-mail: lebedevamv@mail.ru ***е-mail: leniza.gumerovna@yandex.ru Received May 12, 2016
Segetal vegetation of Central Yakutia
Seven associations of segetal vegetation are distinguished for the vast arable lands of Central Yakutia. Low species richness and the prevalence of annual weeds are the main features of these communities. Only two dominant speciesSphallerocarpus gracilis andSaussurea amara represent Asian types of areals. Other dominantsFallopia convolvulus, Elytrigia repens, Chenopodium album, Brassica campestris, Lappula squarrosa, Scutellaria galericulata, Thlaspi arvense, Avena fatua andCrepis tectorum are typically cosmopolitan. The phytosociological system of the segetal communities is described.
Joint strength of aluminum ultrasonic soldered under liquidus temperature of Sn–Zn hypereutectic solder
Abstract In order to obtain high-strength aluminum joints, ultrasonic soldering of 1070 aluminum was conducted under liquidus temperature of Sn–Zn hypereutectic solder. A device for ultrasonic soldering was assembled, which propagated ultrasonic vibrations in a direction perpendicular to joining surfaces. This device joined 1070-Al using quasi-melting Sn–Zn hypereutectic solder without using any artificial spacers. The strength of the solder joints was evaluated by tensile tests. The optimum joining conditions were determined, and the effects of solder compositions and soldering temperature on the joint strength and the solder layer thickness were examined. In this ultrasonic soldering process, the highest tensile strength was obtained for the solder joints fabricated at 220 °C for the Sn–23Zn and Sn–40Zn solder compositions. The joint strength was equivalent to that of 1070-Al heat treated at 220 °C. The sound joints were obtained at 300 °C using Sn–82Zn solder, the liquid phase volume fraction of which was theoretically only 0.24. The present work also revealed that the thickness of retained solder layer in the joint after ultrasonic soldering could be estimated. Accordingly, ultrasonic soldering under the liquidus temperature of Sn–Zn hypereutectic solder could be a spacer-free soldering method to obtain high-strength aluminum joints.