464 research outputs found

    Kinetostatics of Wheel Vehicle in the Category of Spiral-Screw Routes

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    International audienceDeterministic mathematical model of kinetostatics of wheel vehicle in terms of different modes of spatial motion in the context of curved route is proposed. Earth-based coordinate system is introduced which pole and axial orientation are determined by the convenience of route description as well as vehicle-related coordinates which pole axial orientation are determined within inertial space with the help of natural trihedral. Turn of the natural trihedral within inertial coordinates is described by means of quaternion matrices in the context of Rodrigues-Hamilton parameters. Rodrigues-Hamilton parameters are in matrix form in direct accordance with specified hodograph. Kinetostatics of wheel vehicle is considered in terms of spatial motion with an allowance for three-dimensional aerodynamic forces, gravity, and tangential and centrifugal inertial forces. In the context of spiral-screw lines deterministic mathematical model of wheel vehicle kinetostatics is proposed in the form of hodograph in terms of uniform motion, accelerated motion, and decelerated motion within following route sections: straight and horizontal; in terms of vertical grade; in terms of horizontal plane. Analytical approach to determine animated contact drive-control forces of wheel vehicle for structural diagrams having one and two support points involving of a driving-driven wheel characteristic is proposed based on kinetostatics equations. Mathematical model of wheel vehicle kinetostatics in terms of spatial motion is constructed on the basis of nonlinear differential Euler-Lagrange equations; it is proposed to consider physically implemented motion trajectories of wheel vehicles in the context of spiral-screw lines; hodograph determines spatial displacement; Rodrigues-Hamilton parameters determines spatial turn; Varignon theorem is applied to identify components of drive (control) force. The obtained results make it possible to solve a wide range of problems connected with dynamic design of wheel vehicles involving controllability, and estimation of dynamic load of both system and support surface

    Wind generators

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    Temperature-controlled interlayer exchange coupling in strong/weak ferromagnetic multilayers: a thermo-magnetic Curie-switch

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    We investigate a novel type of interlayer exchange coupling based on driving a strong/weak/strong ferromagnetic tri-layer through the Curie point of the weakly ferromagnetic spacer, with the exchange coupling between the strongly ferromagnetic outer layers that can be switched, on and off, or varied continuously in magnitude by controlling the temperature of the material. We use Ni-Cu alloy of varied composition as the spacer material and model the effects of proximity-induced magnetism and the interlayer exchange coupling through the spacer from first principles, taking into account not only thermal spin-disorder but also the dependence of the atomic moment of Ni on the nearest-neighbor concentration of the non-magnetic Cu. We propose and demonstrate a gradient-composition spacer, with a lower Ni-concentration at the interfaces, for greatly improved effective-exchange uniformity and significantly improved thermo-magnetic switching in the structure. The reported magnetic multilayer materials can form the base for a variety of novel magnetic devices, such as sensors, oscillators, and memory elements based on thermo-magnetic Curie-switching in the device.Comment: 15 pages, 5 figure

    Singular-phase nanooptics: towards label-free single molecule detection

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    Non-trivial topology of phase is crucial for many important physics phenomena such as, for example, the Aharonov-Bohm effect 1 and the Berry phase 2. Light phase allows one to create "twisted" photons 3, 4 , vortex knots 5, dislocations 6 which has led to an emerging field of singular optics relying on abrupt phase changes 7. Here we demonstrate the feasibility of singular visible-light nanooptics which exploits the benefits of both plasmonic field enhancement and non-trivial topology of light phase. We show that properly designed plasmonic nanomaterials exhibit topologically protected singular phase behaviour which can be employed to radically improve sensitivity of detectors based on plasmon resonances. By using reversible hydrogenation of graphene 8 and a streptavidin-biotin test 9, we demonstrate areal mass sensitivity at a level of femto-grams per mm2 and detection of individual biomolecules, respectively. Our proof-of-concept results offer a way towards simple and scalable single-molecular label-free biosensing technologies.Comment: 19 pages, 4 figure

    Tracking Rates of Forest Disturbance and Associated Carbon Loss in Areas of Illegal Amber Mining in Ukraine Using Landsat Time Series

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    Mapping forest disturbance is crucial for many applications related to decision-making for sustainable forest management. This study identified the effect of illegal amber mining on forest change and accumulated carbon stock across a study area of 8125.5 ha in northern Ukraine. Our method relies on the Google Earth Engine (GEE) implementation of the Landsat-based Detection of Trends in Disturbance and Recovery (LandTrendr) temporal segmentation algorithm of Landsat time-series (LTS) to derive yearly maps of forest disturbance and recovery in areas affected by amber extraction operations. We used virtual reality (VR) 360 interactive panoramic images taken from the sites to attribute four levels of forest disturbance associated with the delta normalized burn ratio (dNBR) and then calculated the carbon loss. We revealed that illegal amber extraction in Ukraine has been occurring since the middle of the 1990s, yielding 3260 ha of total disturbed area up to 2019. This study indicated that the area of forest disturbance increased dramatically during 2013–2014, and illegal amber operations persist. As a result, regrowth processes were mapped on only 375 ha of total disturbed area. The results were integrated into the Forest Stewardship Council® (FSC®) quality management system in the region to categorize Forest Management Units (FMUs) conforming to different disturbance rates and taking actions related to their certification status. Moreover, carbon loss evaluation allows the responsible forest management systems to be streamlined and to endorse ecosystem service assessment

    Luminescence Properties and Decay Kinetics of Mn 2+ and Eu 3+ Co-Dopant Ions in MgGa 2 O 4 Ceramics

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    A. Luchechko gratefully acknowledges a grant from the Institute of Physics PAS for a research visit to the institute, while A.I. Popov has been supported by project LZP-2018/1-0214 from the Latvian Council of Science.The MgGa 2 O 4 ceramics co-doped with Mn 2+ and Eu 3+ ions were synthesized via a higherature solid-state reaction technique. The samples with various Eu 3+ concentrations were characterised using high-resolution photoluminescence (PL) spectroscopy. The PL spectra show weak matrix emission in a blue spectral region with dominant excitation band around 380 nm. Manganese ions are highly excited deeply in UV region and exhibit emission band peaked at 502 nm. The Eu 3+ ions show characteristic f-f excitation and emission lines. The energy transfer between host defects and activator ions was observed. Luminescence decay curves of Mn 2+ and Eu 3+ emission showed complex kinetics with both Eu 3+ -ion concentration and excitation wavelength changes.Latvian Council of Science LZP-2018/1-0214; Latvian–Ukrainian Joint Research Project LV-UA/2016/1,M/.8-2018; project DB/RIDER0117U004443; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART

    ЗАСТОСУВАННЯ ВІДКРИТОГО ПРОГРАМНОГО КОМПЛЕКСУ ДЛЯ ОБРОБКИ МЕДИЧНИХ ЗОБРАЖЕНЬ MEVISLAB ПРИ ВИВЧЕННІ КУРCУ «МЕДИЧНА ІНФОРМАТИКА»

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    The main capabilities of the MeVisLab image analysis suite to the medical images processing are shown. The application software package structure and the user interface are described. The methodology of the MeVisLab software package usageto the studying of the corresponded topics of the Medical Informatics course is presented. An approach of the implementation of the image elements recognition algorithm is demonstrated.Показаны основные возможности программного комплекса MeVisLab в области обработки медицинских изображений. Описана его структура и интерфейс пользователя. Приведена методика применения программного комплексаMeVisLab при изучении отдельных разделов курса «Медицинская информатика». Продемонстрировано подходы к реализации алгоритмов распознавания отдельных элементов изображения.Показано основні можливості програмного комплексу MeVisLab у галузі обробки медичних зображень. Описано його структуру та інтерфейс користувача. Наведено методику застосування програмного комплексу MeVisLab при вивченні окремих розділів курсу «Медична інформатика». Продемонстровано підходи до реалізації алгоритмів розпізнавання окремих елементів зображення

    Impermeable Barrier Films and Protective Coatings Based on Reduced Graphene Oxide

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    Barrier films preventing permeation of gases and moistures are important for many industries ranging from food to medical and from chemical to electronic. From this perspective, graphene has recently attracted particular interest because its defect free monolayers are impermeable to all gases and liquids. However, it has proved challenging to develop large-area defectless graphene films suitable for industrial use. Here we report barrier properties of multilayer graphitic films made by chemical reduction of easily and cheaply produced graphene oxide laminates. They are found to provide a practically perfect barrier that blocks all gases, liquids and aggressive chemicals including, for example, hydrofluoric acid. In particular, if graphene oxide laminates are reduced in hydroiodic acid, no permeation of hydrogen and water could be detected for films as thin as 30 nm, which remain optically transparent. The films thicker than 100 nm become completely impermeable. The exceptional barrier properties are attributed to a high degree of graphitization of the laminates and little structural damage during reduction. This work indicates a close prospect of thin protective coatings with stability and inertness similar to that of graphene and bulk graphite, which can be interesting for numerous applications

    ЗАСТОСУВАННЯ РЕСУРСУ WOLFRAMALPHA ДЛЯ МАТЕМАТИЧНОГО МОДЕЛЮВАННЯ ФАРМАКОКІНЕТИЧНИХ ПРОЦЕСІВ

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    Using information technologies in the process of teaching higher mathematics, information technologies in pharmacy helps to develop students creativethinking and better skills of work in a computer environment. It also provides the higher level of getting knowledge, helps to create and study mathematical models of different phenomena; shows how to use and research mathematical methods. The article deals with advantages and disadvantages of using WolframAlpha while  forming mathematical competence of future pharmacists.Использование современных новейших технологий в процессе преподавания курсов высшей математики, компьютерных технологий в фармации способствует формированию умений и навыков работы в условиях компьютерной среды, созданию и изучению математических моделей разнообразных явлений и процессов, демонстрации применения математических методов и их исследования. В статье рассмотрены преимущества и недостатки применения Wolframalpha в формировании предметной математической компетентности будущих фармацевтов.Використання сучасних новітніх технологій в процесі викладання вищої математики, комп'ютерних технологій уфармації сприяє формуванню вмінь та навичок роботи в умовах комп'ютерного середовища, створенню та вивченню математичних моделей різноманітних явищ та процесів, демонстрації застосування математичних методів та їх дослідження. У статті розглянуто переваги та недоліки застосування WolframAlpha у формуванні предметноїматематичної компетентності майбутніх фармацевтів
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