Application of the Elastoplastic-Viscoplastic Bounding Surface Model to Cyclic Loading

The predictive capabilities of the elastoplastic-viscoplastic bonding surface mode, with emphasis response of cohesive soils subjected to cyclic loading, are discussed herein. This model, which represents a generalized three-dimensional constitutive formulation for isotropic cohesive soils, is developed within the framework coupled elastoplasticity-viscoplasticity and critical state soil mechanics

Improved shape hardening function for bounding surface model for cohesive soils

AbstractA shape hardening function is developed that improves the predictive capabilities of the generalized bounding surface model for cohesive soils, especially when applied to overconsolidated specimens. This improvement is realized without any changes to the simple elliptical shape of the bounding surface, and actually reduces the number of parameters associated with the model by one

The Exciton Spectra Simulator of Photosynthetic Protein-pigment Complex

The solar energy is one of the most successful alternative energy sources because of its unlimited availability and environmental friendliness. However, the energy transfer rate in artificial solar devices is significantly lower than the energy transfer rate in plants and bacteria. The key factor that governs efficient energy transfer is the electronic couplings between photosynthetic pigments within living organisms. We are applying quantum mechanical / molecular mechanical (QM/MM), quantum mechanical / effective fragment potential (QM/EFP) and fragment molecular orbital (fmo) methods to elucidate the energy transfer pathway in Fenna-Matthews-Olson (FMO) complex through computing the site energies of bacteriochlorophylls and the electronic couplings between them. Based on the values of site energies and couplings computed with QM/MM, QM/EFP and fmo methods we generate the multiple electronic Hamiltonians describinga the energy transfer within the FMO complex. In this research, I am focusing on the improving the algorithm and developing the GUI for computing emission and absorption spectra for molecular systems with multiple chromophores. After taking the Hamiltonians matrixes as inputs, the researchers were able to predict the theoretical absorption and circular dichroism spectra. By comparing these spectra to experimental data, we managed to compare the efficiency and accuracy of the chosen methods and demonstrate the importance of accurate description of protein environment when studying the energy transfer within the pigment-protein complexes

Conical Indentation of a Viscoelastic Sphere

Instrumented indentation is commonly used for determining mechanical properties of a range of materials, including viscoelastic materials. However, most—if not all—studies are limited to a flat substrate being indented by various shaped indenters (e.g., conical or spherical). This work investigates the possibility of extending instrumented indentation to nonflat viscoelastic substrates. In particular, conical indentation of a sphere is investigated where a semi-analytical approach based on “the method of functional equations” has been developed to obtain the force–displacement relationship. To verify the accuracy of the proposed methodology selected numerical experiments have been performed and good agreement was obtained. Since it takes significantly less time to obtain force–displacement relationships using the proposed method compared to conducting full finite element simulations, the proposed method is an efficient substitute of the finite element method in determining material properties of viscoelatic spherical particles using indentation testing

Column Supported Embankments with Geosynthetic Encased Columns: Validity of the Unit Cell Concept

Abstract: Column supported embankments (CSEs) are used to overcome common problems associated with the construction of embankments over soft compressible soils. The use of granular columns as deep foundation elements for CSEs can be problematic in soft soils due to the lack of adequate lateral confining pressure, particularly in the upper portion of the column. Using a high-strength geosynthetic for granular column confinement forms geosynthetic encased columns (GECs); the confinement imposed by the geosynthetic increases the strength of the column, and also prevents its lateral displacement into the soft surrounding soil. This paper presents the results of finite element analyses of a hypothetical geosynthetic reinforced column supported embankment (GRCSE) (i.e., a CSE underlain by geosynthetic reinforcement) that is constructed with GECs as the deep foundation elements. Full three-dimensional (3-d), 3-d unit cell, and axisymmetric unit cell analyses of the GRCSE were carried out to investigate the validity of the unit cell concept. The effect of the degree of nodal constraint along the bottom boundary when numerically modeling GRCSEs was also studied in this paper. Numerical results show that a full 3-d idealization is required to more precisely determine the tension forces that are produced in the geosynthetic reinforcement that underlies the GRCSE. A number of design parameters such as the average vertical stresses carried by the GECs, lateral displacement of the GECs, and the maximum settlement of the soft foundation soil, however, can be successfully calculated using unit cell analyses

3D zero-thickness coupled interface finite element:Formulation and application

In many fields of geotechnical engineering, the modelling of interfaces requires special numerical tools. This paper presents the formulation of a 3D fully coupled hydro-mechanical finite element of interface. The element belongs to the zero-thickness family and the contact constraint is enforced by the penalty method. Fluid flow is discretised through a three-node scheme, discretising the inner flow by additional nodes. The element is able to reproduce the contact/loss of contact between two solids as well as shearing/sliding of the interface. Fluid flow through and across the interface can be modelled. Opening of a gap within the interface influences the longitudinal transmissivity as well as the storage of water inside the interface. Moreover the computation of an effective pressure within the interface, according to the Terzaghi’s principle creates an additional hydro-mechanical coupling. The uplifting simulation of a suction caisson embedded in a soil layer illustrates the main features of the element. Friction is progressively mobilised along the shaft of the caisson and sliding finally takes place. A gap is created below the top of the caisson and filled with water. It illustrates the storage capacity within the interface and the transversal flow. Longitudinal fluid flow is highlighted between the shaft of the caisson and the soil. The fluid flow depends on the opening of the gap and is related to the cubic law

The OpenMolcas Web: A Community-Driven Approach to Advancing Computational Chemistry

The developments of the open-source OpenMolcas chemistry software environment since spring 2020 are described, with a focus on novel functionalities accessible in the stable branch of the package or via interfaces with other packages. These developments span a wide range of topics in computational chemistry and are presented in thematic sections: electronic structure theory, electronic spectroscopy simulations, analytic gradients and molecular structure optimizations, ab initio molecular dynamics, and other new features. This report offers an overview of the chemical phenomena and processes OpenMolcas can address, while showing that OpenMolcas is an attractive platform for state-of-the-art atomistic computer simulations

Исследование влияния мощных электромагнитных излучений на приемные антенные системы со сверхпроводящими защитными устройствами

Yeromina, N. S. Investigation of Powerful Electromagnetic Radiation Influence on Receiving Antenna Systems with Superconducting Protective Devices / Yeromina N. S., Kravchenko I. I., Kurylov M. N. and ot. // Problemele Energeticii Regionale. - 2022. - № 3 (55). - P. 140-155. -DOI: https://doi.org/10.52254/1857-0070.2022.3-55.11.Досліджено вплив потужного електромагнітного випромінювання ультракороткої тривалості на надпровідний пристрій захисту, як навантаження антенно-фідерного тракту радіоелектронних систем, що використовуються в системах моніторингу земної поверхні на користь сільського господарства, геодезії, картографуванні, моніторингу поверхні землі та океану, а також шарів атмосфери, у системах дистанційного керування в машинобудуванні та суміжних галузях промисловості. Найбільш суттєвим результатом є запропонований підхід до визначення зв'язку реакції довільної антени на вплив випромінювання з її характеристиками як випромінювання. Показано, що при визначенні шуканого зв'язку такими характеристиками антенних систем є вхідний імпеданс антени та комплексна діаграма нормованої спрямованості в режимі випромінювання на довільній частоті. Значимість отриманих результатів полягає в отриманні аналітичних співвідношень для оцінки впливу випромінювання, що розглядається, на захисний пристрій, що знаходиться в надпровідному, змішаному і нормальному фазових станах. Особливість отриманих результатів полягає у можливості врахування ступеня узгодження антеної системи з пристроєм захисту на основі надпровідної тонкої плівки, а також перетворення енергії випромінювання в енергію наведених струмів, що є основою для вибору та конструктивного розрахунку пристроїв захисту радіоелектронних засобів від впливу потужного електромагнітного випромінювання на основі мікросмужкових ліній передачі. Новизна роботи полягає в тому, що набула подальшого розвитку теорія захисту радіоелектронних засобів, що використовуються в різних галузях народного господарства та оснащені антенними системами з надпровідними захисними пристроями в умовах впливу потужного електромагнітного випромінювання, практичне застосування якої забезпечить надійність функціонування цих систем.This work is devoted to the problem of the effect of a powerful ultra-short duration electromagnetic radiation on the superconducting protection device as a load of antenna-feeder circuit of radioelectronic systems. The above device is used in the monitoring systems of the land surface to the benefit of agriculture, geodesy, mapping, monitoring of land and ocean surfaces, and, also, the atmospheric layers, remote control systems in engineering and industry related branches. This goal was achieved by substantiation of the approach to the description of the arbitrary antenna response to the electromagnetic radiation, using the antenna system frequency response. The most significant result is the offered approach to the relationship determination between the response of the arbitrary antenna to the radiation influence and its characteristics in a radiation mode. The sought relationship determination showed that, such characteristics of the antenna systems are the antenna input impedance and the complex normalized radiation pattern in the radiation mode at an arbitrary frequency. The significance of the results is in obtainment of the analytical relations to estimate the effect of the radiation under consideration on the device that is in superconducting, mixed and normal phase states. The peculiarity of the obtained results makes it possible to consider the antenna system coordination degree of the protection device based on superconducting thin film. Conversion of the radiation energy into the induced currents’ energy that is the basis for selection and structural calculation of protection devices of the radio electronic facilities against powerful electromagnetic radiation build upon microstrip transmission lines.Исследовано влияния мощного электромагнитного излучения ультракороткой длительности на сверхпроводящее устройство защиты, как нагрузку антенно-фидерного тракта радиоэлектронных систем, используемых в системах мониторинга земной поверхности в интересах сельского хозяйства, геодезии, картографировании, мониторинге поверхности земли и океана, а также слоев атмосферы, системах дистанционного управления в машиностроении и смежных отраслях промышленности. Наиболее существенным результатом является предложенный подход к определению связи реакции произвольной антенны на воздействие излучения с ее характеристиками в режиме излучения. Показано, что при определении искомой связи такими характеристиками антенных систем являются входной импеданс антенны и комплексная нормированная диаграмма направленности в режиме излучения на произвольной частоте. Значимость полученных результатов состоит в получении аналитических соотношений для оценки влияния рассматриваемого излучения на защитное устройство, находящееся в сверхпроводящем, смешанном и нормальном фазовых состояниях. Особенность полученных результатов заключается в возможности учёта степени согласования антенной системы с устройством защиты на основе сверхпроводящей тонкой пленки, а также преобразование энергии излучения в энергию наведенных токов, что является основой для выбора и конструктивного расчета устройств защиты радиоэлектронных средств от воздействия мощного электромагнитного излучения на основе микрополосковых линий передачи. Новизна работы заключается в том, что получила дальнейшее развитие теория защиты радиоэлектронных средств, используемых в разных отраслях народного хозяйства и оснащенных антенными системами со сверхпроводящими защитными устройствами в условиях воздействия мощного электромагнитного излучения, практическое применение которой обеспечит надежности функционирования этих систем