Character of jet flows in mass-spectrometric interfaces at various pressures and chamber lengths

Samples-in particular, of bioorganic matter—are usually introduced into a mass spectrometer from atmosphere to high vacuum via a gasdynamic interface that represents a chamber with intermediate pressure or a system of chambers with gradually decreasing pressure. Transformation of the character of an expanding jet flow in a single-chamber interface has been studied as dependent on the chamber length and pressure. Knowledge of this character allows the system parameters to be most effectively used so as to ensure high ion transmission and decrease mass discriminatio

Electromechanical Imaging of Biological Systems with Sub-10 nm Resolution

Electromechanical imaging of tooth dentin and enamel has been performed with sub-10 nm resolution using piezoresponse force microscopy. Characteristic piezoelectric domain size and local protein fiber ordering in dentin have been determined. The shape of a single collagen fibril in enamel is visualized in real space and local hysteresis loops are measured. Because of the ubiquitous presence of piezoelectricity in biological systems, this approach is expected to find broad application in high-resolution studies of a wide range of biomaterials.Comment: 12 pages, 4 figures, submitted for publication in Appl. Phys. Let

Peculiarities of strained state of the buggy undercarriage under torsional loading

This paper deals with the traits of strained state of buggy undercarriage torsional loading. The buggy undercarriage represents a tubular space frame consisting of round cross-section elements. The strained state of the buggy space frame can be characterized by a number of specific features such as: a centerline distortion and front sub-frame cross-sections twisting about their own pivot points. The possible reasons for it are considered as well as their negative effects. Practical recommendations to minimize the negative effects are proposed. All the represented results are obtained with the help of a computer simulation technique based on the finite element method. © 2019 Published under licence by IOP Publishing Ltd

Using the simulation modeling with stochastic estimation of trafficability of forest transport systems

Forecasting trafficability of logging and forest transport systems on the ground, which have a multi-sectional layout solution is considered in the paper. Trafficability problems are evaluated from the point of view of the stochastic character of indicators of traction properties - the forces of resistance to movement and the adhesion force of the driving wheels with the supporting surface. With the stochastic estimation of trafficability the law of Gaussian distribution for random values of the rolling resistance coefficient and the two-parameter Weibull distribution law with a negative asymmetry coefficient or values of the shape parameter greater than 4 for the cohesion coefficient was adopted. A stochastic approach to the evaluation of trafficability allows to ensure a rational distribution of the power flows between propulsors of the transport-technological system, which is shown in this paper. © 2019 Published under licence by IOP Publishing Ltd

Discontinuous Bifurcations under 2-DOF Vibroimpact System Moving

Dynamic behaviour of strongly nonlinear non-smooth discontinuous vibroimpact system isstudied. Under variation of system parameters we find the disconti nuousbi furcati onsthat are the dangerousones. It is phenomenon unique to non-smooth systems with discontinuous right-hand side. We investigate the 2-DOF vibroimpact system by numerical parameter continuation method in conjunction with shooting and Newton-Raphson methods, Wife simulate the impact by nonlinear contact interactive force according to Hertz's contact law. We find the discontinuous bifurcations by Floquet multipliers values. At such points set-valued Floquet multipliers cross the unit circle by jump that istheir moduli becoming more than unit by jump. Wealso learn the bifurcation picture change when the impact between system bodi es became the soft one due the change of system parameters, This paper is the continuation of the previous works

Optical vortex generation from molecular chromophore arrays

The generation of light endowed with orbital angular momentum, frequently termed optical vortex light, is commonly achieved by passing a conventional beam through suitably constructed optical elements. This Letter shows that the necessary phase structure for vortex propagation can be directly produced through the creation of twisted light from the vacuum. The mechanism is based on optical emission from a family of chromophore nanoarrays that satisfy specific geometric and symmetry constraints. Each such array can support pairs of electronically delocalized doubly degenerate excitons whose azimuthal phase progression is responsible for the helical wave front of the emitted radiation. The exciton symmetry dictates the maximum magnitude of topological charge; detailed analysis secures the conditions necessary to deliver optical vortices of arbitrary order

Using the simulation modeling with stochastic estimation of trafficability of forest transport systems

Forecasting trafficability of logging and forest transport systems on the ground, which have a multi-sectional layout solution is considered in the paper. Trafficability problems are evaluated from the point of view of the stochastic character of indicators of traction properties - the forces of resistance to movement and the adhesion force of the driving wheels with the supporting surface. With the stochastic estimation of trafficability the law of Gaussian distribution for random values of the rolling resistance coefficient and the two-parameter Weibull distribution law with a negative asymmetry coefficient or values of the shape parameter greater than 4 for the cohesion coefficient was adopted. A stochastic approach to the evaluation of trafficability allows to ensure a rational distribution of the power flows between propulsors of the transport-technological system, which is shown in this paper. © 2019 Published under licence by IOP Publishing Ltd

Modelling of continual fracture of spatial bodies under long-term static and cyclic loading

Представлено методику моделювання процесів континуального руйнування кругових та призматичних тіл складної форми в умовах тривалого статичного і багатоциклового навантаження: скінчено-елементна база для визначення напружено-деформованого стану просторових тіл на основі напіваналітичного методу скінчених елементів (НМСЕ), алгоритми визначення феноменологічного параметра пошкодженості та моделювання еволюційних процесів розповсюдження зон континуального руйнування. Наведено результати розв’язання практичних задач із визначення розрахункового і додаткового ресурсу відповідальних просторових об’єктів.Techniques of continual fracture process modelling of complex shape circular and prismatic bodies under elastic high-cycle deformation and in condition of creep under prolonged static load is presented in this paper. The semianalytic finite element method (SFEM) to determine the stress-strain state is used. SFEM involves the application of finite element mesh in the cross section of the body, and using one finite element in the direction of straight or curved creating, which provides significantly lower computational cost for three- dimensional problems solving. The Kachanov-Rabotnov’s scalar damage parameter to describe the continual fracture of the material and the degree dependence of the damage parameter accumulation rate of on the stress state parameters are used. Stepping algorithms for the stress-strain state and damage parameter determining for considered deformation process have been developed. The algorithm of simulation of evolutionary processes of macroscopic defects (continual fracture zone) growth after local loss of material bearing capacity because of damage parameter’s critical value has been obtained. A solution of practical problems of determining of the calculated lifetime (to local loss of material bearing capacity) and the additional lifetime (time of continual fracture zone growth) for high pressure connecting pipe and the gas turbine blade has been presented. It is shown, that for the connecting pipe which represents thick-wall rotation body, lifetime is not limited to local loss of material bearing capacity and can be significantly extended by additional lifetime. At the same time for the blade under creep condition lifetime is completely determined by the local loss of material bearing capacity, because the value of additional lifetime is related to the continual fracture zone growth of only about 5% of the calculated lifetime

Mechanism of fragmentation and atomization of molecular ions in gasdynamic transport cell

The fragmentation of molecular ions formed upon the electrospraying of a sample and transported through the gasdynamic system of a mass spectrometer equipped with an IESAP (Ion Extraction from Solution at Atmospheric Pressure) source has been experimentally studied. It is established that ion fragmentation in a Kantorowicz-Gray type cell takes place in the immediate vicinity of a skimmer port, apparently, as a result of collisions between ions (accelerated in an electric field) and stagnant gas. Molecular mechanisms of fragmentation are considered and it is concluded that this process can take place in a single ion-molecule collision even