Effects of graphene nano-platelets (GNPs) on the microstructural characteristics and textural development of an Al-Mg alloy during friction-stir processing

The final publication is available at Elsevier via http:/dx.doi.org/10.1016/j.surfcoat.2017.12.045 © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/The aim of this research is to characterize the unique microstructural features of Al-matrix nanocomposites reinforced by graphene nano-platelets (GNPs), fabricated by multi-pass friction-stir processing (FSP). During this process, secondary phase GNPs were dispersed within the stir zone (SZ) of an AA5052 alloy matrix, with a homogenous distribution achieved after five cumulative passes. The microstructural characteristics and crystallographic textures of different regions in the FSPed nanocomposite, i.e., base metal (BM), heat affected zone (HAZ), thermo-mechanical affected zone (TMAZ), and SZ, were evaluated using electron back scattering diffraction (EBSD) and transmission electron microscopy (TEM) analyses. The annealed BM consisted of a nearly random crystal orientation distribution with an average grain size of 10.7μm. The SZ exhibited equiaxed recrystallized grains with a mean size of 2μm and a high fraction of high-angle grain boundaries (HAGBs) caused by a discontinuous dynamic recrystallization (DDRX) enhanced by pinning of grain boundaries by GNPs. The sub-grains and grain structure modification within the HAZ and TMAZ regions are governed by dislocation annihilation and reorganization in the grain interiors/within grains which convert low-angle to high-angle grain boundaries via dynamic recovery (DRV). The FSP process and incorporation of GNPs produced a pre-dominantly {100} cube texture component in the SZ induced by the stirring action of the rotating tool and hindering effect of nano-platelets. Although, a very strong {112} simple shear texture was found in the HAZ and TMAZ regions governed by additional heating and deformation imposed by the tool shoulder. These grain structure and texture features lead to a hardness and tensile strength increases of about 55% and 220%, respectively.Slovak Foundation VEGA [grant 2_0158_16, and by grant APVV-14-0936

Математична модель утворення зубців циліндричної прямозубої передачі гіперболічним вихідним контуром

The aim of this work is to create a fundamentals of mathematical model which consists in definition of geometry of a generating surface and machining gearing for novel cylindrical spur transmission. The generating surface is considered as rack-cutter with teeth, which profiled by hyperbola – a curve which is smooth at whole addendum and dedendum parts of reference profile. The equations of teeth surfaces which help the basic performances of this generating surface surveyed, namely quadratic forms and normal curvatures in the given directions are presented. The equations of machining gearing which help to obtain the equations of surfaces of teeth which can be applied both for working surfaces and for their fillets are obtained. For these surfaces quadratic forms also defined. Boundaries of a contact zone are defined. The results obtained in a paper can be used for definition of quality indicators of serviceability of novel transmissions which will allow carrying out a comparative estimation of novel transmission with conventional one and with other types of transmissions.Представлено теоретичне дослідження внутрішньої геометрії виробної поверхні та верстатного зачеплення для утворення зубців циліндричних прямозубих передач нового типу. Виробна поверхня розглядається як інструментальна рейка з вихідним контуром, що спрофільовано гіперболою. Наведено рівняння поверхонь зубців інструментальної рейки, розглянуто основні характеристики цієї виробної поверхні, а саме квадратичні форми і нормальні кривизни в заданих напрямках. Представлено рівняння верстатного зачеплення, за допомогою якого одержано рівняння поверхонь зубців, як робочих так і перехідних. Для цих поверхонь також визначено коефіцієнти квадратичних форм та кривизни. Визначено межі поля зачеплення. Результати, одержані в статті, в подальшому можна використовувати для визначення якісних показників працездатності нового типу передач, що дозволить проводити їх порівняльну оцінку із традиційними та іншими видами передач

Depth-sensing thermal stability of accumulative fold-forged nanostructured materials

Accumulative fold-forging (AFF) as a newly developed severe plastic deformation (SPD) process based on the repetitive fold-forging steps is implemented for the production of the layered UFG (~200 nm) AA8006 alloy and AA8006-B4C nanocomposite (~35 nm, 10 vol%) materials from the initial AA8006 alloy foil. The remarkably refined grains and nanoparticles can control metallic materials' mechanical properties, including the strength, strain rate dependency, and thermal stability behavior. In this context, nano-grains' local mechanical response during nanoindentation can vary considerably depending on the testing temperature, and this has yet to be discussed. In this research, after materials characterization of produced nanostructured materials according to the AFF route, the relating depth-sensing thermal stability of them assessed by conducting the nanoindentation testing at different temperatures in the range of 300–523 K. Depth sensing softening behavior is elaborated to identify the low-temperature thermal stability of processed materials. The results enunciated the occurrence of thermal softening by refining the grain structure. However, introducing the reinforcing nanoparticles lead to a pinning action that stabilized the grain boundaries.The authors would like to acknowledge the Natural Sciences and Engineering Research Council of Canada (NSERC). FIB-TEM microscopy was performed at the Canadian Centre for Electron Microscopy at McMaster University, supported by NSERC and the Canadian Foundation for Innovation. The first author wants to thank Slovak Academy Information Agency (SAIA) for supporting the scholarship. This work was supported by the Slovak Research and Development Agency by grant APVV-18-0508 is gratefully acknowledged

Design logical linguistic models to calculate necessity in trucks during agricultural cargoes logistics using fuzzy logic

The study is aimed to develop the logic-linguistic models to design a number of rules for the correct calculation of the vehicles needed, taking into account the technical, technological, and weather and climate conditions of the harvesting and transport complex. The article has shown that the construction of the design of logic-linguistic models was not performed earlier to solve the problem of the agro-industrial production transportation support, considering the opportunity of forecasting size of influences of the weather and climatic factors on improving the productivity of the harvesting and transport complex elements. It is determined that the experience of applying the fuzzy logic theory in many practice situations confirms the universality of the mathematical apparatus. This toolkit provides better results than classical approaches (set theory, probability theory). This aspect indicates the expediency of the chosen mathematical apparatus for solving the tasks. The article using fuzzy logic explores the relationship and interdependence of technical, technological factors and weather and climate conditions for modeling transport support in harvesting and transport complex. Fuzzification of the parameters is carried out, based on the compiled equations using trapezoidal and triangular membership functions. The set of rules necessary for the creation of logical-linguistic models (LLM) for each factor has been arranged. LLMs were developed for dependent parameters, which will allow further modeling of the transport support of the harvesting and transport complex in the Fuzzy Logic Toolbox application of the MATLAB package

Адекватный менеджмент пациентов с дистрофинопатиями (мышечная дистрофия Дюшенна/Беккера): применение объективизирующих шкал и дополнительных методов исследования

There are still no guidlines on managment of Duchenne/Becker myodystrophy in domestic medical practice. It leads to decrease of quality of life and, what is more important, lifespan of patients. In this article we have described our Western coleagues lаst decade experience, including consensus guidelines published in 2010 on mаnаgment of Duchenne myodystrophy, supplemented with our practicle experience. We have described standardized motor development scale and muscle tone score for patients with MDD/MDB, and algorithm of multidiscipline care with focus on prevention, diagnosis and treatment of main disease and steroid therapy complications: cardiovascular, orthopedics, respirator etc. These recommendations not only improve quality of live and extend lifespan of MDD/MDB patients, but allow to take part in multicentre trials on searching of pathognomonic and symptomatic treatment.В отечественной медицинской практике отсутствует четкая стандартизация подходов к курации больных миодистрофией Дюшенна/Беккера (МДД/МДБ). Это зачастую приводит к снижению качества жизни пациентов и, что наиболее важно, уменьшению ее продолжительности. В статье отражен накопленный за последнее десятилетие опыт западных коллег, в том числе объединенный в соглашении консенсуса 2010 г. по курации пациентов с МДД, дополненный наблюдениями из собственной клинической практики. Описаны стандартные шкалы оценки степени ограничения моторных навыков и мышечной слабости у пациентов с МДД/МДБ, а также представлен алгоритм мультидисциплинарного подхода с фокусом внимания на профилактике, своевременной диагностике и лечении основных осложнений заболевания и терапии кортикостероидами: кардиоваскулярных, ортопедических, респираторных и т.д. Применение представленных рекомендаций позволяет не только значительно улучшить качество и продолжительность жизни пациентов с МДД/МДБ, но и участвовать в мультицентровых исследованиях с целью поиска патогномоничного и симптоматического лечения

Global urban environmental change drives adaptation in white clover.

Urbanization transforms environments in ways that alter biological evolution. We examined whether urban environmental change drives parallel evolution by sampling 110,019 white clover plants from 6169 populations in 160 cities globally. Plants were assayed for a Mendelian antiherbivore defense that also affects tolerance to abiotic stressors. Urban-rural gradients were associated with the evolution of clines in defense in 47% of cities throughout the world. Variation in the strength of clines was explained by environmental changes in drought stress and vegetation cover that varied among cities. Sequencing 2074 genomes from 26 cities revealed that the evolution of urban-rural clines was best explained by adaptive evolution, but the degree of parallel adaptation varied among cities. Our results demonstrate that urbanization leads to adaptation at a global scale