Review of the New World genera of the Leafhopper Tribe Erythroneurini (Hemiptera: Cicadellidae: Typhlocycbinae)

The genus-level classification of New World Erythroneurini is revised based on results of a phylogenetic analysis of 100 morphological characters. The 704 known species are placed into 18 genera. Erasmoneura Young and Eratoneura Young, previously treated as subgenera of Erythroneura Fitch, and Erythridula Young, most recently treated as a subgenus of Arboridia Zachvatkin, are elevated to generic status. Three species previously included in Erasmoneura are placed in a new genus, Rossmoneura (type species, Erythroneura tecta McAtee). The concept of Erythroneura is thereby narrowed to include only those species previously included in the nominotypical subgenus. New World species previously included in Zygina Fieber are not closely related to the European type species of that genus and are therefore placed in new genera. Neozygina, n. gen., based on type species Erythroneura ceonothana Beamer, includes all species previously included in the ???ceonothana group???, and Zyginama, n. gen., based on type species Erythroneura ritana Beamer, includes most species previously included in the ???ritana group??? of New World Zygina. Five additional new genera are described to include other previously described North American Erythroneurini: Hepzygina, n. gen., based on type species Erythroneura milleri Beamer and also including E. aprica McAtee; Mexigina, n. gen., based on type species Erythroneura oculata McAtee; Nelionidia, n. gen., based on type species N. pueblensis, n. sp., three additional new species, and Erythroneura amicis Ross; Neoimbecilla, n. gen., based on type species Erythroneura kiperi Beamer and one new species; and Illinigina, n. gen., based on type species Erythroneura illinoiensis Gillette. Five new genera, based on previously undescribed species, are also recognized: Aztegina, n. gen, based on A. punctinota, n. sp., from Mexico; Amazygina, n. gen., based on type species A. decaspina, n. sp., and three additional new species from Ecuador; Hamagina, n. gen., based on type species H. spinigera, n. sp., and two additional new species from Peru and Ecuador; Napogina, n. gen., based on type species N. recta, n. sp., and one additional new species from Ecuador; Perugina, n. gen., based on type species P. denticula, n. sp., from Peru; and Spinigina, n. gen., based on type species S. hirsuta, n. sp., and an additional new species from Peru. Phylogenetic analysis suggests that the New World Erythroneurini consist of three lineages resulting from separate invasions from the Old World.published or submitted for publicationis peer reviewe

Translationally invariant nonlinear Schrodinger lattices

Persistence of stationary and traveling single-humped localized solutions in the spatial discretizations of the nonlinear Schrodinger (NLS) equation is addressed. The discrete NLS equation with the most general cubic polynomial function is considered. Constraints on the nonlinear function are found from the condition that the second-order difference equation for stationary solutions can be reduced to the first-order difference map. The discrete NLS equation with such an exceptional nonlinear function is shown to have a conserved momentum but admits no standard Hamiltonian structure. It is proved that the reduction to the first-order difference map gives a sufficient condition for existence of translationally invariant single-humped stationary solutions and a necessary condition for existence of single-humped traveling solutions. Other constraints on the nonlinear function are found from the condition that the differential advance-delay equation for traveling solutions admits a reduction to an integrable normal form given by a third-order differential equation. This reduction also gives a necessary condition for existence of single-humped traveling solutions. The nonlinear function which admits both reductions defines a two-parameter family of discrete NLS equations which generalizes the integrable Ablowitz--Ladik lattice.Comment: 24 pages, 4 figure

Elastic properties of fullerites and diamond-like phases

Diamond‐like structures, that include sp2 and sp3 hybridized carbon atoms, are of considerable interest nowadays. In the present work, various carbon auxetic structures are studied by the combination of molecular dynamics (MD) and analytical approach. Two fullerites based on the fullerene C60 and fullerene‐like molecule C48 are investigated as well as diamond‐like structures based on other fullerene‐like molecules (called fulleranes), carbon nanotubes (called tubulanes) and graphene sheets. MD is used to find the equilibrium states of the structures and calculate compliance and stiffness coefficients for stable configurations. Analytical methods are used to calculate the engineering elastic coefficients (Young's modulus, Poisson's ratio, shear modulus and bulk modulus), and to study their transformation under rotation of the coordinate system. All the considered structures are partial auxetics with the negative value of Poisson's ratio for properly chosen tensile directions. It is shown that some of these structures, in a particular tension direction, have a very high Young's modulus, that is, 1852 GPa for tubulane TA6

ABOUT METHODS OF SEISMIC ANALYSIS OF UNDERGROUND STRUCTURES

As is known, underground facilities are an integral part of the infrastructure of modern society. These objects have some specific characteristics such as complex construction, high cost, long life cycle, etc. Once it is destroyed, the direct and indirect losses are more seriousness than the general structure in the ground. Under-ground facilities built in areas subject to earthquake activity must withstand both seismic and static loading. Therefore, it is very important to carry on the seismic design of the underground structure in a safe and economi-cal way. The distinctive paper presents a summary of the current state of seismic analysis for underground struc-tures. Classification and brief overview of methods of seismic analysis of underground structures (force-based methods, displacement-based methods, numerical methods of seismic analysis of coupled system “soil – under-ground structure”) are presented, problems of soil-structure interaction are under consideration as well. So-called static finite element method with substructure technique for seismic analysis of underground structures is de-scribed

AlGaAs/GaAs Quantum Well Infrared Photodetectors

In this article, we present an overview of a focal plane array (FPA) with 640 × 512 pixels based on the AlGaAs quantum well infrared photodetector (QWIP). The physical principles of the QWIP operation and their parameters for the spectral range of 8–10 μm have been discussed. The technology of the manufacturing FPA based on the QWIP structures with the pixels 384 × 288 and 640 × 512 has been demonstrated. The parameters of the manufactured 640 × 512 FPA with a step of 20 μm have been given. At the operating temperature of 72 K, the temperature resolution of QWIP focal plane arrays is less than 35 mK. The number of defective elements in the matrix does not exceed 0.5%. The stability and uniformity of the FPA have been demonstrated

High-pressure phase and transition phenomena in ammonia borane NH3BH3 from X-ray diffraction, Landau theory, and ab initio calculations

Structural evolution of a prospective hydrogen storage material, ammonia borane NH3BH3, has been studied at high pressures up to 12 GPa and at low temperatures by synchrotron powder diffraction. At 293 K and above 1.1 GPa a disordered I4mm structure reversibly transforms into a new ordered phase. Its Cmc21 structure was solved from the diffraction data, the positions of N and B atoms and the orientation of NH3 and BH3 groups were finally assigned with the help of density functional theory calculations. Group-theoretical analysis identifies a single two-component order parameter, combining ordering and atomic displacement mechanisms, which link an orientationally disordered parent phase I4mm with ordered distorted Cmc21, Pmn21 and P21 structures. We propose a generic phase diagram for NH3BH3, mapping three experimentally found and one predicted (P21) phases as a function of temperature and pressure, along with the evolution of the corresponding structural distortions. Ammonia borane belongs to the class of improper ferroelastics and we show that both temperature- and pressure-induced phase transitions can be driven to be of the second order. The role of N-H...H-B dihydrogen bonds and other intermolecular interactions in the stability of NH3BH3 polymorphs is examined.Comment: 23 pages, 7 figure

Numerical study and experimental validation of deformation of <111> FCC CuAl single crystal obtained by additive manufacturing

The importance of taking into account directional solidification of grains formed during 3D printing is determined by a substantial influence of their crystallographic orientation on the mechanical properties of a loaded material. This issue is studied in the present study using molecular dynamics simulations. The compression of an FCC single crystal of aluminum bronze was performed along the axis. A Ni single crystal, which is characterized by higher stacking fault energy (SFE) than aluminum bronze, was also considered. It was found that the first dislocations started to move earlier in the material with lower SFE, in which the slip of two Shockley partials was observed. In the case of the material with higher SFE, the slip of a full dislocation occurred via successive splitting of its segments into partial dislocations. Regardless of the SFE value, the deformation was primarily occurred by means of the formation of dislocation complexes involved stair-rod dislocations and partial dislocations on adjacent slip planes. Hardening and softening segments of the calculated stress–strain curve were shown to correspond to the periods of hindering of dislocations at dislocation pileups and dislocation movement between them. The simulation results well agree with the experimental findings

Reduction of a fan vibration activity in a life support system of oil and gas stations

Relevance. Electromechanical fans are widely used in life support systems of oil and gas stations, operate in conditions of vibration, high rotational speeds and loads. Design, technological and operational reasons influence vibration activity of an electromechanical device. The greatest "contribution" to the existing vibrations, according to the frequency spectrum, is made by the imperfection of the design elements of the ball bearing. They are: separator movement, variable stiffness under the action of radial load, interaction of micro-dimensions of working surfaces, facet and waviness of working surfaces of rings and balls. In addition, the resulting vibrations negatively affect both the reliability and durability of the fan. Since it is technically impossible to completely eliminate the vibration activity of an electromechanical device, it is advisable to reduce it with the help of a technical solution by introducing a damping element into a kinematic circuit of the vibration source. In this regard, the development of a damping device is an integral technical task that helps to reduce the vibration activity of technical life support systems of oil and gas stations, as well as to improve the quality of environmental conditions of human life. To reduce vibration activity, a damper design is proposed that takes into account various types of energy dissipation. However, given the dense spectrum of vibration frequencies from ball bearings, a viscous friction element is introduced into the damper design. To determine the effectiveness of reducing vibration activity, a model of the damper in question was made based on the developed 3D model. For tests in determining the effectiveness of applying a viscous friction element, two variants of the damper design were used. In the first version of the damper design, there was no viscous friction element, and in the second version there was one. According to the test results of the damper layouts, it can be seen that the developed technical solution to reduce the vibration activity of the electromechanical device has practical confirmation. The studies underlying the developed design of the damper with a viscous friction element allows for reduction in the vibration amplitude. Object. Electromechanical device in operating mode. Aim. To describe the vibration activity in the operating mode of an electromechanical device in the entire spectrum of disturbing effects acting along the axes, taking into account the imperfect geometry of ball bearing parts; to develop a damper for reducing the vibration activity level in the electromechanical device. Methods. Vibration diagnostics, computational mathematics, measuring instruments, software "Vibration recorder-F", "Vibration Recorder-M2", "Logger"-recorder and "Bearing". Results. The paper demonstrated the effectiveness of the proposed technical solution to reduce the vibration amplitude in the operating frequency range of the electromechanical device rotor up to 4 times compared with the corresponding maximum amplitude value without its use