Oscillations and Dynamical Systems: Normalization Procedures and Averaging

The present lecture deals with the development of new normalization procedures and averaging algorithms in problems of nonlinear vibrations. Namely, the development of asymptotic methods of perturbation theory is considered, making wide use of group theoretical techniques. Various assumptions about specific group properties are investigated, and are shown to lead to modifications of existing methods, such as the Bogoliubov averaging method and the Poincar'e-Birkhoff normal form, as well as to the formulation of new ones. The development of normalization techniques on Lie groups is also treated

Blockchain Infrastructure and Growth of Global Power Consumption

The paper proposes the link between cryptocurrency implementation in the financial sector and energy consumption worldwide. The underlying mechanism of this blockchain infrastructure is described, practical cases of its adoption in various segments of the financial sector are provided. This paper tries to explain the power consumption of the cryptocurrency mining at the case of Bitcoin, Ethereum, Monero, Litecoin. Since mining is not regulated by the state, and even banned in some countries, it is difficult to find accurate data on how much electricity is spent on it. Method of Herfindahl–Hirschman is used for efficiency estimate of crypto market. Keywords: energy consumption, mining pools, bitcoin, blockchain, cryptocurrency, cloud mining. JEL Classifications: G32, G34, O33. DOI: https://doi.org/10.32479/ijeep.768

Probing low-energy hyperbolic polaritons in van der Waals crystals with an electron microscope

Van der Waals materials exhibit intriguing structural, electronic, and photonic properties. Electron energy loss spectroscopy within scanning transmission electron microscopy allows for nanoscale mapping of such properties. However, its detection is typically limited to energy losses in the eV range-too large for probing low-energy excitations such as phonons or mid-infrared plasmons. Here, we adapt a conventional instrument to probe energy loss down to 100 meV, and map phononic states in hexagonal boron nitride, a representative van der Waals material. The boron nitride spectra depend on the flake thickness and on the distance of the electron beam to the flake edges. To explain these observations, we developed a classical response theory that describes the interaction of fast electrons with (anisotropic) van der Waals slabs, revealing that the electron energy loss is dominated by excitation of hyperbolic phonon polaritons, and not of bulk phonons as often reported. Thus, our work is of fundamental importance for interpreting future low-energy loss spectra of van der Waals materials.We acknowledge financial support from the European Commission under the Graphene Flagship (GrapheneCore1, grant no. 696656), the ERC starting grant SPINTROS (grant no. 257654), and the Spanish Ministry of Economy and Competitiveness (National plans MAT2014-53432-C5-4-R, MAT2015-65159-R, MAT2015-65525-R, and FIS2016-80174-P). A.K. also thanks for the Czechoslovak Microscopic Society/FEI scholarship.Peer Reviewe

Probing low-energy hyperbolic polaritons in van der Waals crystals with an electron microscope

Resumen del trabajo presentado a la International Conference on Nanoscience + Technology (ICN+T), celebrada en Brno (Czech Republic) del 22 al 27 de julio de 2018.Only recently, specially designed instrumentation for spatially-resolved electron energy-loss spectroscopy (EELS) has been developed to substantially improve spectral resolution and operating spectral range. This progress has dramatically broadened application potential of EELS in probing low-loss vibrational excitations. Pioneering experiments demonstrated capability of probing vibrational signal in organic samples, ionic crystals, and also van der Waals materials. In our work, we theoretically and experimentally studied the very low-loss EELS of multilayer hexagonal boron nitride (h-BN), a representative van der Waals structure. The weak coupling between individual atomic layer results in extreme optical anisotropy, which gives rise to hyperbolic phonon polaritons (h-PhPs): coupled excitations of optical phonons and light with hyperbolic dispersion in the range of 90 – 200 meV. H-PhPs might be a key to many emerging photonic technologies relying on nanoscale light confinement and manipulation. Thus, efficient design and utilization of h-BN structures require spectroscopic studies with adequate spatial resolution, which can be provided by EELS utilizing electrons as localized electromagnetic probes. To that end, we performed spatially-resolved EELS on a simple h-BN flake structure with an optimized STEM-EELS tool, which revealed the peak energy dependence on the h-BN thickness and on the proximity of the electron beam to the h-BN edge. Such behavior is a consequence of the polaritonic nature of the induced excitations. Indeed, with help of the classical dielectric response theory for EELS, applied to anisotropic slabs and edges, we demonstrate that the electron energy loss in h-BN is dominated by h-PhP excitation and not directly by bulk phonons as in preliminary interpretations. This finding describes and quantitatively matches experimental observations. We thus suggest that EELS can be a technique complementary to scanning near-field optical microscopy for characterization of low-energy phonon polaritons.Peer reviewe

Addressing vibrational excitations in Van der Waals materials and molecular layers within electron energy loss spectroscopy

Trabajo presentado al Microscopy & Microanalysis Meeting, celebrado en Baltimore (USA) del 5 al 9 de agosto de 2018.AK acknowledges Thermo Fisher Scientific and the Czechoslovak Microscopic Society scholarship for young researchers.Peer reviewe

1874-draft(2)_31_12_23-Excel.xlsx

This paper is the first to propose an aggregate S-trend factor production function to estimate total factor productivity (TFP) and investment efficiency in an economy. This function implements Charles R. Hulten's organizing principle: to what extent the growth of the economy is due to an increase in "productivity" (progress in technology and organization of production) and to what extent to "capital formation" (increased investment in human capital, knowledge and fixed capital). Estimation of future members of the series is usually done by a forecast model. It is a model that approximates a trend. The Verhulst's S-curve is used as the approximation function. By aggregate S-trend production function we mean a two factor production function It represents the growth of the economy, which is by raw data and takes into account all influencing factors, and is certainly broader than the concept of " capital formation ",is a total factor productivity TFP. The error of approximation is quantitatively measured by the MAPE criterion.</p

Mammal remains from the Lower Cretaceous Bol'shoi Terekhtyul' locality in West Siberia, Russia

Four mammalian taxa have been identified based on upper molariform tooth and edentulous dentary fragments from the Bol'shoi Terekhtyul' locality of the Lower Cretaceous Ilek Formation (Krasnoyarsk Territory, Russia): Docodonta indet., Amphidontidae indet., Zhangheotheria indet. sp. A and sp. B. The docodontan from Bol'shoi Terekhtyul is smaller than Sibirotherium rossicum from the Ilek Formation at Shestakovo 1 locality (Kemerovo Province, Russia) and may belong to a distinct taxon. It is one of the younger docodontans in the fossil record. The mammal assemblage from the Bol'shoi Terekhtyul' locality is drastically different from the mammal assemblage of nearby localities of the Ilek Formation along Bol'shoi Kemchug River, which consists of Gobiconodontidae and Amphilestidae. The reason for this faunal discrepancy is unclear for the moment

Mammal remains from the Lower Cretaceous Bol'shoi Terekhtyul' locality in West Siberia, Russia

Four mammalian taxa have been identified based on upper molariform tooth and edentulous dentary fragments from the Bol'shoi Terekhtyul' locality of the Lower Cretaceous Ilek Formation (Krasnoyarsk Territory, Russia): Docodonta indet., Amphidontidae indet., Zhangheotheria indet. sp. A and sp. B. The docodontan from Bol'shoi Terekhtyul is smaller than Sibirotherium rossicum from the Ilek Formation at Shestakovo 1 locality (Kemerovo Province, Russia) and may belong to a distinct taxon. It is one of the younger docodontans in the fossil record. The mammal assemblage from the Bol'shoi Terekhtyul' locality is drastically different from the mammal assemblage of nearby localities of the Ilek Formation along Bol'shoi Kemchug River, which consists of Gobiconodontidae and Amphilestidae. The reason for this faunal discrepancy is unclear for the moment