On the existence of traveling waves in the 3D Boussinesq system

We extend earlier work on traveling waves in premixed flames in a gravitationally stratified medium, subject to the Boussinesq approximation. For three-dimensional channels not aligned with the gravity direction and under the Dirichlet boundary conditions in the fluid velocity, it is shown that a non-planar traveling wave, corresponding to a non-zero reaction, exists, under an explicit condition relating the geometry of the crossection of the channel to the magnitude of the Prandtl and Rayleigh numbers, or when the advection term in the flow equations is neglected.Comment: 15 pages, to appear in Communications in Mathematical Physic

Smart operational load monitoring using decision trees and artificial neural networks: a comparative study

Operational Load Monitoring is an industrial process that allows to predict the remaining in-service life of a mechanical structure under variable loads. Data from sensors embedded or mounted on the structure is acquired and allows to estimate the number and amplitude of load cycles that the structure has withstood so far in its working environment. This process is especially important in the aerospace industry where mechanical structures of an aircraft are monitored in order to maximize their operating lifetime. Smart Operational Load Monitoring means implementation of artificial intelligence techniques to the process in order to make predictions based on measurements from reduced number of sensors. In this paper a composite lightweight structure of typical geometry used in aircraft structures is taken as an example for Smart Operational Load Monitoring. The predictions are made from measurements from six strain gauges mounted to the structure, using carefully prepared artificial intelligence-based models. Efficiency of the models is compared, in terms of their prediction accuracies and computational complexities.National Agency for Academic Exchange of PolandSilesian University of Technology. Faculty of Mechanical Engineerin

Role of social environment and social clustering in spread of opinions in co-evolving networks

Taking a pragmatic approach to the processes involved in the phenomena of collective opinion formation, we investigate two specific modifications to the co-evolving network voter model of opinion formation, studied by Holme and Newman [1]. First, we replace the rewiring probability parameter by a distribution of probability of accepting or rejecting opinions between individuals, accounting for the asymmetric influences in relationships among individuals in a social group. Second, we modify the rewiring step by a path-length-based preference for rewiring that reinforces local clustering. We have investigated the influences of these modifications on the outcomes of the simulations of this model. We found that varying the shape of the distribution of probability of accepting or rejecting opinions can lead to the emergence of two qualitatively distinct final states, one having several isolated connected components each in internal consensus leading to the existence of diverse set of opinions and the other having one single dominant connected component with each node within it having the same opinion. Furthermore, and more importantly, we found that the initial clustering in network can also induce similar transitions. Our investigation also brings forward that these transitions are governed by a weak and complex dependence on system size. We found that the networks in the final states of the model have rich structural properties including the small world property for some parameter regimes. [1] P. Holme and M. Newman, Phys. Rev. E 74, 056108 (2006)

New operational load monitoring approach using digital image correlation and image classification networks

The following paper presents a novel approach that can be applied to Operational Load Monitoring and Structural Health Monitoring processes. The approach is based on artificial intelligence (AI) and digital image correlation (DIC) techniques. DIC is an optical method that allows measuring full-field structural displacements and strains. In the presented approach only a relatively small fragment of the material's surface is monitored by DIC. The obtained partial image of strains or displacements is then processed by a carefully trained AI model, an image classification network, able to predict the state of whole structure (e.g. materials stresses, potential loss of material continuity). The assumption is that all possible load cases and states of the monitored structure can be identified and simulated, so the data obtained from simulations can then be used to train the image classification network. A numerical example is presented as proof of the presented concept. A modern lightweight aerostructure in the form of a hat-stiffened composite panel was used as monitored structure in the presented example and its Operational Load Monitoring was performed based on a relatively small fragment of normal strains map. The reference maps to train the network were simulated numerically. The prediction model estimates the Tsai-Wu failure criterion value for the whole composite material. The obtained accuracy of predictions proved the effectiveness and efficiency of the proposed approach.- (undefined

Mechanical Behavior and Failure of Riveting Joints in Tensile and Shear Tests

Основным критерием прочности заклепочных соединений при их разработке является сопротивление материала заклепок сдвиговому нагружению. При испытании на сдвиг обычных заклепочных соединений определяющими являются механические характеристики материала заклепки. Поэтому необходимо описание механизма разрушения различных соединений при испытаниях на растяжение. Оценивается прочность разных листовых материалов (сталь DC01, алюминиевый сплав AW-5754 и их комбинация) в заклепочном соединении. Анализируется механизм разрушения заклепочных соединений при одноосном растяжении Т-образных образцов из различных листовых материалов. Выполнено сравнение экспериментальных результатов, полученных при растяжении и сдвиге заклепочных соединений внахлестку для одного и того же типа.Основним критерієм міцності заклепочних з’єднань при їх розробці є опір матеріалу заклепок зсувному навантаженню. При випробуваннях на зсув звичайних заклепочних з’єднань визначальними є механічні характеристики матеріалу заклепки. У зв’язку з цим необхідно описання механізму руйнування різних з’єднань при випробуваннях на розтяг. Оцінюється міцність різних листових матеріалів (сталь DC01, алюмінієвий сплав AW-5754 та їх комбінація) у заклепочних з’єднаннях. Аналізується механізм руйнування заклепочних з’єднань при одновісному розтязі Т-подібних зразків із різних листових матеріалів. Виконано порівняння експериментальних результатів, отриманих при розтязі і стиску заклепочних з’єднать внапуск для одного і того ж типу

FEM Analysis of Stress Distribution in the Hermetic Harmonic Drive Flexspline

The paper deals with the numerical stress calculation in the flexspline tooth rim of the harmonic drive. Due to the complex geometry of the toothed ring in the flexspline, the teeth were modeled as a ring, which height corresponded to the particular stress concentration in the teeth. To study the effect of type of wave generator on the stress distribution in the flexspline, the following models were elaborated: two-roller, four-roller, cam, and disk. The stress calculations were performed for the two cases: a zero torque load and the torque load value, corresponding to the true operation conditions of the hermetic harmonic drivВиконано чисельний розрахунок напружень у гнучкому сплайні зубчатої передачі гармонічного (хвильового) редуктора. Зубчате кільце у гнучкому сплайні через складну геометрію моделювалось у вигляді кільця. Висоту кільця приймали з урахуванням напруженості в зубцях. Для вивчення впливу різних типів хвильових генераторів на розподіл напружень у гнучкому сплайні розглядали моделі з двома та чотирма роликами, ексцентриком або диском. Розрахунок напружень виконували для двох варіантів: без обертального моменту та з обертальним моментом, що відповідає реальним умовам роботи герметичного гармонічного редуктора.Проведен численный расчет напряжений в гибком сплайне зубчатой передачи гармонического (волнового) редуктора. Зубчатое кольцо в гибком сплайне из-за сложной геометрии моделировалось в виде кольца. Высоту кольца принимали с учетом напряженности в зубьях. Для изучения влияния различных типов волновых генераторов на распределение напряжений в гибком сплайне рассматривали модели с двумя и четырьмя роликами, эксцентриком и диском. Расчет напряжений выполняли для двух вариантов: без вращающего момента и с вращающим моментом, соответствующим реальным условиям работы герметического гармонического редуктора