Dissipative properties of composite structures. 1. Statement of problem

Object and purpose of research. The object under study is a sandwich plate with two rigid anisotropic layers and a filler of soft isotropic viscoelastic polymer. Each rigid layer is an anisotropic structure formed by a finite number of orthotropic viscoelastic composite plies of arbitrary orientation. The purpose is to develop a mathematical model of sandwich plate. Materials and methods. The mathematical model of sandwich plate decaying oscillations is based on Hamilton variational principle, Bolotin’s theory of multilayer structures, improved theory of the first order plates (Reissner-Mindlin theory), complex modulus model and principle of elastic-viscoelastic correspondence in the linear theory of viscoelasticity. In description of physical relations for rigid layers the effects of oscillation frequencies and ambient temperature are considered as negligible, while for the soft viscoelastic polymer layer the temperaturefrequency relation of elastic-dissipative characteristics are taken into account based on experimentally obtained generalized curves. Main results. Minimization of the Hamilton functional makes it possible to reduce the problem of decaying oscillations of anisotropic sandwich plate to the algebraic problem of complex eigenvalues. As a specific case of the general problem, the equations of decaying longitudinal and transversal oscillations are obtained for the globally orthotropic sandwich rod by neglecting deformations of middle surfaces of rigid layers in one of the sandwich plate rigid layer axes directions. Conclusions. The paper will be followed by description of a numerical method used to solve the problem of decaying oscillations of anisotropic sandwich plate, estimations of its convergence and reliability are given, as well as the results of numerical experiments are presented.

Generalized chest CT and lab curves throughout the course of COVID-19

A better understanding of temporal relationships between chest CT and labs may provide a reference for disease severity over the disease course. Generalized curves of lung opacity volume and density over time can be used as standardized references from well before symptoms develop to over a month after recovery, when residual lung opacities remain. 739 patients with COVID-19 underwent CT and RT-PCR in an outbreak setting between January 21st and April 12th, 2020. 29 of 739 patients had serial exams (121 CTs and 279 laboratory measurements) over 50 ± 16 days, with an average of 4.2 sequential CTs each. Sequential volumes of total lung, overall opacity and opacity subtypes (ground glass opacity [GGO] and consolidation) were extracted using deep learning and manual segmentation. Generalized temporal curves of CT and laboratory measurements were correlated. Lung opacities appeared 3.4 ± 2.2 days prior to symptom onset. Opacity peaked 1 day after symptom onset. GGO onset was earlier and resolved later than consolidation. Lactate dehydrogenase, and C-reactive protein peaked earlier than procalcitonin and leukopenia. The temporal relationships of quantitative CT features and clinical labs have distinctive patterns and peaks in relation to symptom onset, which may inform early clinical course in patients with mild COVID-19 pneumonia, or may shed light upon chronic lung effects or mechanisms of medical countermeasures in clinical trials.

TRENDS OF THE INTERANNUAL FLUCTUATIONS IN THE WORLD OCEAN LEVEL DURING THE LAST CENTURY

The changes of the sea level in the Atlantic, Pacific, Indian Oceans and the whole World Ocean for the period from 1880 till 2010 years were examined. The estimates of the values of the sea level increasing for that time period in each of the oceans and on the west and east coasts of the Atlantic and Pacific oceans were made. For this purpose, the annual sea level data were averaged over years for 68 stations in the Atlantic Ocean, 71 stations – in the Pacific and 33 stations – the Indian. Analysis of the temporary distributions of the sea level shows that increasing of the Atlantic sea level during that period (131 years) is 24,2 cm. Sea levels of Pacific and Indian Oceans during the same period increased on smaller value, 14,5 and 12,4 cm respectively. The reason for difference between the Atlantic and the Pacific Ocean in values of sea level rising, as it seems, is significant rising of the land (raising of the East coast of the Asian continent), which was occurred in about half of the stations on the west coast of the Pacific. In the Indian Ocean the zero level of water posts was not correct for many stations, and in some cases there were low quality data. The highest maxima in the sea level in the generalized curves of the temporary distributions appear with about 10-year cycles on the sea level of all oceans that is in good correlation with El Niño years.

Integral Pumping Devices for Dual Mechanical Seals: Hydraulic Performance Generalization Using Dimensional Analysis

An experimental study is carried out investigating hydraulic performance for various designs of dual-mechanical-seal cartridges with integral pumping-rings. The tested devices are classified into two main families: radial-flow and axial-flow. The radial-flow family utilizes the modified-paddle-wheel (MPW) pumping ring with either a radial or a tangential oriented cartridge outlet port, while the axial-flow family utilizes the pumping scroll (PS) pumping ring in the following cartridge-geometries: single-pumping-scroll (SS) and double-pumping-scroll (DS); as both types can be of either a radial or a tangential outlet port; and of an internal clearance value complying with American Petroleum Institute (API) 682 standard or smaller clearance. An experimental setup is constructed, and appropriate instrumentation is employed to measure inlet pressure, outlet pressure, rotational speed, and barrier fluid flow rate acquiring flow-head characteristic curves. Moreover, empirical generalized characteristic curves are deduced from experimental observations obtained from the present study and previous companion work. The generalized curves can be employed in estimating pumping ring performance for a different size or other operation conditions such as varying rotational speed or fluid type. They can be also utilized to validate numerical simulations for geometrically similar designs.

Influence of discharge on fish habitat suitability curves in mountain watercourses in IFIM methodology

In this study, the quality of the aquatic habitats of mountain and piedmont streams was evaluated using the ‘Instream Flow Incremental Methodology (IFIM)’ decision-making tool. The quality of habitats was interpreted from the behaviour of bioindicators in the form of habitat suitability curves (HSCs). From 1995 until the present, 59 different reaches of 43 mountain streams in Slovakia and 3 validation reaches were evaluated, and the results analysed. The aim of this study was to generalize the parameters of the HSCs for the brown trout. The generalized curves will be useful for water management planning. It is difficult and time-consuming to take hydrometrical and ichthyological measurements at different water levels. Therefore, we developed a methodology for modifying suitability curves based on an ichthyological survey during a low flow and a flow at which fish lose the ability to resist the flow velocity. The study provides the information how such curves can be modified for a wider flow range. In summary, this study shows that generalized HSCs provide representative data that can be used to support both the design of river restoration and the assessment of the impacts of the water use or of climate change on stream habitat quality.

GEODYNAMICS

A method and results of determination of geoelectric parameters of mantle of Earth is expounded on territory between 520 and 47.50с.ш., 210 and 310в.д. on the basis of unidimensional inversion of the generalized crooked soundings. The generalized curves are built by the coarticulation of the crooked deep magnitotteluric soundings in the items of area with by the curves of the магнитовариационного sounding, got with the use of quiet daily sun-allowance variations and Dst- of variations on the geomagnetical observatories of Kiev and Lviv

GINZBURG–LANDAU VORTEX LINES AND THE ELASTICA FUNCTIONAL

We examine the asymptotic behavior of a family of second-order functionals arising in the theory of Ginzburg–Landau vortices. The results point towards Γ-convergence with the elastica functional for generalized curves as the limit.

Fouling and Air Bleed Extracted Flow Influence on Compressor Performance

Compressor performance deterioration with operating time has been analyzed and a method for the description of actual scaled map curves is discussed. These curves are obtained from actual operating point data from the monitoring system. Suitable scaling functions have been introduced. An inverse stage stacking technique solution has been adopted to obtain reference quantities to be used with generalized curves. In order to account for machine peculiar real phenomena, shape factors have been introduced for best fitting of given data. An example is presented to discuss the deteriorated compressor map and the influence of mass flows extracted from bleeds.