Structure Calculations Research Articles

Ab initio calculations of electronic band structure of CdMnS semimagnetic semiconductors

This work is devoted to theoretical investigations of Cd1-xMnxS semimagnetic semiconductors (SMSC). The purpose of this work was to calculate the electronic band structure of ideal and defective Cd1- xMnxS SMSC in both antiferromagnetic (AFM) and ferromagnetic (FM) phases. Ab initio, calculations are performed in the Atomistix Toolkit (ATK) program within the Density Functional Theory (DFT) and Local Spin Density Approximation (LSDA) on Double Zeta Double Polarized (DZDP) basis. We have used Hubbard U potential UMn = 3.59 eV for 3d states for Mn atoms. Supercells of 8 and 64 atoms were constructed. After the construction of Cd1-xMnxS (x = 6.25 %; 25 %) supercells and atom relaxation and optimization of the crystal structure were carried out. Electronic band structure and density of states were calculated, the total energy has been defined in antiferromagnetic (AFM) and ferromagnetic (FM) phases. Our calculations show that the band gap increases with the increase in Mn ion concentration. It has been established that Cd or S vacancy in the crystal structure leads to the change of band gap, Fermi level shifts towards the valence or conduction band.

ПОСТРОЕНИЕ ДИАГРАММЫ СЖАТИЯ ДЛЯ БЕТОНА С КОСВЕННЫМ АРМИРОВАНИЕМ В РАМКАХ ТЕОРИИ ПРЕДЕЛЬНЫХ СОСТОЯНИЙ

When constructing a stress-strain compression diagram for concrete with indirect reinforcement within the framework of the theory of limit state design, it is necessary to assign the strength values of materials with the required security. To do this, a transition is made from average strength value obtained from the results of experiments to reduced characteristic compressive strength and the design value of strength. In view of this, a contradiction arises due to the fact that initially the formulas for determining the deformations corresponding to the top of the compression diagram were obtained for experimental value of strength, and in the calculations of structures it is proposed to use reduced characteristic compressive strength and the design value of strength, which can lead to incorrect results. The article compares the calculated values of strains with experimental data and notes a significant overestimation when calculating by the characteristic compressive strength and the design value of strength.

Information technologies of teaching in a secondary school

The conference participants are offered components of the educational and methodological complex in physics, which are obtained not by advanced pedagogical experience, ie by trial and error, but by detailed and complete analysis and calculation of structures and algorithms of the educational process in secondary school and its individual components. It is a guide for students, systematization of educational information, algorithm for solving physical problems, solving standard physical problems on a computer, diagnosing student performance and rating assessment of knowledge.

Weakly-bound clusters of atmospheric molecules: infrared spectra and structural calculations of (CO2)n-(CO)m-(N2)p, (n,m,p) = (2,1,0), (2,0,1), (1,2,0), (1,0,2), (1,1,1), (1,3,0), (1,0,3), (1,2,1), (1,1,2).

Structural calculations and high-resolution infrared spectra are reported for trimers and tetramers containing CO2 together with CO and/or N2. Among the 9 clusters studied here, only (CO2)2-CO was previously observed by high-resolution spectroscopy. The spectra, which occur in the region of the ν3 fundamental of CO2 (≈2350 cm-1), were recorded using a tunable optical parametric oscillator source to probe a pulsed supersonic slit jet expansion. The trimers (CO2)2-CO and (CO2)2-N2 have structures in which the CO or N2 is aligned along the symmetry axis of a staggered side-by-side CO2 dimer unit. The observation of two fundamental bands for (CO2)2-CO and (CO2)2-N2 shows that this CO2 dimer unit is non-planar, unlike (CO2)2 itself. For the trimers CO2-(CO)2 and CO2-(N2)2, the CO or N2 monomers occupy equivalent positions in the 'equatorial plane' of the CO2, pointing toward its C atom. To form the tetramers CO2-(CO)3 and CO2-(N2)3, a third CO or N2 monomer is then added off to the 'side' of the first two. In the mixed tetramers CO2-(CO)2-N2 and CO2-CO-(N2)2, this 'side' position is taken by N2 and not CO. In addition to the fundamental bands, combination bands are also observed for (CO2)2-CO, CO2-(CO)2, and CO2-(N2)2, yielding some information about their low-frequency intermolecular vibrations.

Dynamics of interaction of components during mixing

The effect of mechanical action on the mixing and whipping of the mixture of components contributes to the formation of a three-dimensional spongy-reticulate continuous structure of the gluten frame, because it determines the elastic and elastic properties of the medium and is relevant in dispersing gas in a liquid. That is why, the objective of the research was to establish the relationship between the gas-holding capacity of the medium and the energy spent on the hydration of the components. The research solved the problem of determining the gas-holding capacity of the medium with variable parameters of the height of the liquid phase depending on the intensity of mixing, time of the transient processes of formation of the full volume of the gas-liquid medium, time of the transient process of the output of the dispersed gas phase. The difference in levels before the formation of the gas phase and in the mode of mixing (aeration) determines the value of the gas-holding capacity. In this regard, we came to the conclusion about the expediency of the complete destabilization of the established regimes due to the change in the modes of action of the working body in the flow system. At the same time, one more feature should be mentioned. Part of the gas phase that existed and continues to exist in a new regime after mixing enters the regime of the transition process. Therefore, the most effective mixing occurs in case of compliance with the shifted mode of dosing of components in a suspended state and the mechanical influence of the working body. Considering the problems and conditions for mixing the scam, the requirements for the design of the mixer are determined, and also it is established that feeding of components should last at least 45 seconds. During this period, hydration occurs and energy consumption is reduced. This approach of the formation of pulsed flows of surface contours during the interaction in a suspended state of the dosing components, under the rotating action of the disc-shaped working body and the forces of gravity, creates the conditions for intensification of transferring the mass and biochemical processes under conditions of thermodynamic equilibrium with the corresponding desorption bonds of the dissolved part of the gaseous phase and liquid, which reveals a new method of mixing and allows further use of cylindrical working chambers in structural calculations.

Dynamic balance design and simulation verification of reed system of loom beating up mechanism

In order to reduce the vibration caused by the eccentricity of the reed system in the beating up mechanism of the loom, the centrifugal force generated by the eccentric reed system is decomposed into two parallel base planes, and a dynamic balance design scheme based on the principle of counterweight is established. Based on structural analysis and theoretical calculation, the reasonable balance weight mass, structure and assembly position are determined, and the reed system simulation model based on Adams/view platform is constructed. The correctness of the dynamic balance design scheme is verified by rigid body dynamics simulation and error analysis. The analysis results show that the centrifugal force simulation value F=347.008N, the design value F1=347.222N, and the error is 0.06%, which meets the requirements of mechanical accuracy design. It provides an important technical reference for dynamic balance design, vibration reduction and noise reduction of fixed axis rotation system.

Graphoanalytic Method of the Complex Systems Structural Reliability Approximate Calculations

Graphoanalytic Method of the Complex Systems Structural Reliability Approximate Calculations

BIM Structural Project Applied in A Case Study: Interoperability Analyses, Reinforcement Detailing Drawings and Quantity Take-off

Background: The Building Information Modelling (BIM) methodology has been acquiring, worldwide, a growing acceptance in all sectors of the Construction industry, and the study intends to contribute to its implementation within the structural design. The fundamental concept of BIM is based on the generation of a centralized virtual model with all information concerning different specialties. This is supported in efficient interoperability, but within the structural design, this aspect is difficult to achieve completely, as currently, the interoperability of this system is still inefficient. Introduction: This study intends to analyze the degree of interoperability verified in the development of all the processes (modelling, transposition, structural analyses and reinforcement detailing) involved in a structural design using BIM tools. Methods: A structural project concerning a study case was performed in order to identify benefits and limitations, based on the consistency analysis of the transposed data between systems, Revit and Robot, in all steps required in a BIM process. This text describes the stages of modelling, checking the suitability of the analytical model, its transference to the analysis tool in order to proceed with the structural calculations and detailing drawings and, finally, the transfer of drawings to the main BIM model. Results: The limitations verified in the last stage were partially surpassed with complementary work enabling the automatic transfer of drawings and quantities of materials. In addition, the study explores new capacities of BIM, namely, the extraction of information allowing the presentation of specific drawings and maps of the geometry of the reinforcement rods. Conclusion: This study identifies a working strategy that leads to an appropriate use of BIM software contributing to the optimization of labor in a structural office.

Investigation of the accuracy and convergence of the results of thin shells analysis using the PRINS program

The theoretical foundations of compatible finite elements construction for static and dynamic analysis of single-layer and multilayer shells are discussed. These finite elements are implemented in the PRINS computer program. The paper presents verification tests to investigate the accuracy and convergence of the results of calculating various shells using these finite elements. Shell structures are widely used in various fields of technology - construction, mechanical engineering, aircraft construction, shipbuilding, etc. Specialists on the design and calculation of such structures need a reliable and accessible tool for the practical problems solving. Computer program PRINS can be one of such tools. It can be effectively used by engineers of design and scientific organizations to solve a wide class of engineering problems related to the calculations of shell structures. The paper describes the finite elements of the shells, implemented in the PRINS program. The results of verification calculations are presented, which confirm the high accuracy of this program.

The economic feasibility of taking into account the joint work of load-bearing and enclosing elements in large-span wooden spatial structures

Large-span wooden spatial structures in the form of domes, developed in JSC Research Center of Construction under the leadership of A.A. Pogoreltsev, are built in large numbers for roofing various buildings. Such designs have high performance indicators and continue to improve. In 2020 the Manual on accounting for the joint work of the frame and fencing in wooden spatial structures of buildings and structures was developed as an addition to SP 64.13330.2017, containing examples of strength calculation and optimization of rib cross-section dimensions, as well as an example of determining the long-term strength of the shell cladding. These structures, in fact unique, are designed so far in the margin of safety without taking into account the participation of the enclosing part (panels, decking, etc.) in the bearing loads. Taking into account the work of the decking, especially when exposed to asymmetric loads, can lead to material savings. In addition to the above theory of nonlinear shell calculation, the authors have also developed a calculation of composite anisotropic panels operating under complex stress conditions, i.e. under biaxial compression (tension) and shear. The calculation of such structures under both short-term and long-term loads presents certain difficulties and requires the introduction of strength theories and criteria for their description that are unusual for specialists of design organizations.

Study on Structural Performance of Horizontal Axis Wind Turbine with Air Duct for Coal Mine

Considering the characteristics of narrow underground space and energy distribution, based on blade element momentum theory, Wilson optimization model and MATLAB programming calculation results, the torsion angle and chord length of wind turbine blade under the optimized conditions were obtained. Through coordinate transformation, the data were transformed into three-dimensional form. The three-dimensional model of the blade was constructed, and the horizontal axis wind turbine blade under the underground low wind speed environment was designed. The static structural analysis and modal analysis were carried out. Structural design, optimization calculation and aerodynamic analysis were carried out for three kinds of air ducts: external convex, internal concave and linear. The results show that the velocity distribution in the throat of linear air duct is relatively uniform and the growth rate is large, so it should be preferred. When the tunnel wind speed is 4.3 m/s and the rated speed is 224 rad/s, the maximum displacement of the blade is in the blade tip area and the maximum stress is at the blade root, which is not easy to resonate. The change rate of displacement, stress and strain of blade is positively correlated with speed. The energy of blade vibration is mainly concentrated in the swing vibration of the first and second modes. With the increase in vibration mode order, the amplitude and shape of the blade gradually transition to the coupling vibration of swing, swing and torsion. The stress and strain of the blade are lower than the allowable stress and strain of glass fiber reinforced plastics (FRP), and resonance is not easy to occur in the first two steps. The blade is generally safe and meets the design requirements.

Calculation of Building Heat Losses through Slab-on-Ground Structures Based on Soil Temperature Measured In Situ

The article aims to assess the effects of soil temperature measured in situ on the heat loss analyses of a building. Numerical analyses and in situ measurements of soil temperature profiles for real conditions under a residential building (profile I) in Poland and under the area outside the building (profile II) were performed. Based on the measurement results, a proprietary geometric model of the partition was proposed. The heat flux and heat flow results obtained for reliable models are 4.9% and 6.9% higher compared to a model based on a typical meteorological year for the wall–foundation system and 10.0% and 10.1% higher for the slab-on-ground structure for profile I. The adoption of temperatures from the area outside the building as the boundary condition (profile II) results in greater differences between the obtained results. The difference in heat flow obtained in the numerical analyses for profiles I and II is about 2 W/m2, both for the wall–foundation system and for the slab-on-ground structure calculations. The adoption of temperatures for the ground outside the building led to overestimation in the heat flux calculations, this being due to lower temperatures in these particular layers of the ground.

First-principles investigation of the structural and dynamical stability, electronic and thermal properties of two-dimensional Yn+1Cn (n = 1, 2, and 3) MXenes

This paper studies the structural and dynamical stability, electronic and thermal properties of two-dimensional Yn+1Cn (n = 1, 2, and 3) MXenes in the hexagonal structure. The calculations are carried out using the computational software package QUANTUM-ESPRESSO/PWSCF based on density functional theory (DFT) and the pseudopotential method. The calculated lattice parameters a and c are in good agreement with the previous theoretical and experimental studies. Structural calculations described that Y4C3 is more stable than Y3C2 and Y2C. Analyzing cohesive energy indicates that the structural stability of these compounds increases with increasing n-index due to the increase in the number of stronger bonds between Y and C atoms in the thicker MXene monolayers. The phonon dispersion calculations show that the Yn+1Cn MXenes are dynamically stable at ambient pressure, and it is possible to be experimentally synthesized.Based on the electronic results, it can be argued that the Yn+1Cn has a metallic behavior in the hexagonal structure. Also, the electron charge density distribution confirms the metallic behavior of Yn+1Cn structures. The thermodynamic calculations indicate that enthalpy increases continuously and steadily by increasing pressure and n-index in the Yn+1Cn structures. Generally, for Yn+1Cn (n = 1, 2, and 3) MXenes with the increasing n-index, Debye temperature and stiffness decrease, followed by heat capacity increases.

Determining the dynamic characteristics of elastic shell structures

Building structures are very often operated under the action of dynamic loads, both natural and man-made. The calculation of structures under the influence of static loads has been quite widely studied in detail. When structures are exposed to dynamic loads, additional tests are carried out, where measuring instruments are installed on the structures to register stresses and deformations that occur during dynamic influences. Elastic elements are the responsible functional unit of many measuring instruments. Therefore, the quality of elastic elements ensures the operational stability of the entire structure. This determines the increased attention that is paid to technology and construction to elastic elements. Previously, the work of elastic elements made of homogeneous mono materials with the same physical and geometric properties in all directions and over the entire surface of the element was studied. The elastic element was considered as a shell of rotation with a complex shape of the meridian and various physical and mechanical properties at various points caused by uneven reinforcement. Two types of reinforcement were implied ‒ radial and circular. Elastic shell elements (ESE) operate under conditions of dynamic loading. The equation was derived for determining the dynamic characteristics of inhomogeneous elastic elements. The dependences of the first three natural frequencies of oscillations on the thickness of the shell and the depth of the corrugation and the first two natural frequencies of oscillations on the thickness of the shell have been analyzed. The amplitude-frequency characteristics (AFC) and the phase-frequency characteristics (PFC) of the shell depending on the geometric parameters have been calculated. All these results could significantly improve the quality of the readings of the instruments, which depend on the sensitivity of the shell elastic elements. And it, in turn, depends on the geometric and physical properties of the shell elastic elements.

Acoustic Tunneling Study for Hexachiral Phononic Crystals Based on Dirac-Cone Dispersion Properties

Acoustic tunneling is an essential property for phononic crystals in a Dirac-cone state. By analyzing the linear dispersion relations for the accidental degeneracy of Bloch eigenstates, the influence of geometric parameters on opening the Dirac-cone state and the directional band gaps’ widths are investigated. For two-dimensional hexachiral phononic crystals, for example, the four-fold accidental degenerate Dirac point emerges at the center of the irreducible Brillouin zone (IBZ). The Dirac cone properties and the band structure inversion problem are discussed. Finally, to verify acoustic transmission properties near the double-Dirac-cone frequency region, the numerical calculation of the finite-width phononic crystal structure is carried out, and the acoustic transmission tunneling effect is proved. The results enrich and expand the manipulating method in the topological insulator problem for hexachiral phononic crystals.

Electronic structure and Thermoelectric Properties of Hybrid Organic-Inorganic Perovskites [NH3-(CH2)3-COOH]2CdCl4

In this work, we conducted the first principle calculation of electronic structure and transport properties of [NH3-(CH2)3-COOH]2CdCl4 (Acid-Cd). The generalized gradient approximation is used in structural optimization and electronic structure. The theoretical band gap value found is in good agreement with experimental. Electronic thermal conductivity, electrical conductivity, Seebeck coefficient (S) and figure of merit (ZT) have been calculated using semi-local Boltzmann theory to predict the thermoelectric characteristic of the studied materials.

Intelligent Generation Method of Innovative Structures Based on Topology Optimization and Deep Learning.

Computer-aided design has been widely used in structural calculation and analysis, but there are still challenges in generating innovative structures intelligently. Aiming at this issue, a new method was proposed to realize the intelligent generation of innovative structures based on topology optimization and deep learning. Firstly, a large number of structural models obtained from topology optimization under different optimization parameters were extracted to produce the training set images, and the training set labels were defined as the corresponding load cases. Then, the boundary equilibrium generative adversarial networks (BEGAN) deep learning algorithm was applied to generate numerous innovative structures. Finally, the generated structures were evaluated by a series of evaluation indexes, including innovation, aesthetics, machinability, and mechanical performance. Combined with two engineering cases, the application process of the above method is described here in detail. Furthermore, the 3D reconstruction and additive manufacturing techniques were applied to manufacture the structural models. The research results showed that the proposed approach of structural generation based on topology optimization and deep learning is feasible, and can not only generate innovative structures but also optimize the material consumption and mechanical performance further.

ERRATA: CORRIGENDA TO VIRTUAL HULL MONITORING: CONTINUOUS FATIGUE ASSESSMENT WITHOUT ADDITIONAL INSTRUMENTATION

Following publication of this study, work continued to enable more efficient structural response calculations. As part of that effort, two errors were identified and fixed.

Synthesis of tetragonally stabilized lanthanum doped bismuth vanadium oxide nanoparticles and its enhanced visible light induced photocatalytic performance

ABSTRACT In order to enhance the performance of bismuth vanadium oxide (Bi4V2O11) we synthesized La doped Bi4V2O11 in different concentrations (La = 5%, 10%, 15%) by using sol-gel method. The nanoparticles are stabilized in tetragonal phase in the range of 50 nm particle size. With the help of XPS it was confirmed that in La/Bi4V2O11 lattice La is in 3+ oxidation state and replaces Bi3+ in the lattice. SEM and EDX show the amorphous nature and chemical compositions of the nanoparticles. The structural analysis and energy calculations revealed that La3+ ion replaces Bi3+ in Bi4V2O11 lattice without disturbing its host structure. The PL results revealed that photogenerated charges recombination was significantly reduced. The photocatalytic degradation of MB under visible light illumination is performed and the best photocatalytic activity among various compositions of La/Bi4V2O11 is shown by 15% La/Bi4V2O11 nanoparticles. 15% La/Bi4V2O11 photocatalyst show 98% of degradation of MB in 120 mins.

Features of derivation of formulas for calculation of nodal reactions and coefficients of matrix of rigidity of a finite element with averaged mechanical and geometrical parameters

Currently, the most widely used finite element method for the calculation of spatial structures, significant progress in the development of which is associated with the work of domestic and foreign scientists. In Ukrainian publications the problems of theoretical substantiation of the finite element method and its connection with other methods are considered, concrete types of finite elements and their application to various problems of mechanics of a continuous environment are studied. Much attention is paid to the choice of the appropriate shape of the finite element, the type and degree of approximating functions, as well as the development of methods for deriving stiffness matrices.
 The study of prismatic bodies with constants along one of the coordinates of mechanical and geometric parameters is most appropriate to carry out on the basis of the semi-analytical method of finite elements. Its essence is a combination of finite element sampling and decomposition of displacements in the characteristic direction by a system of trigonometric coordinate functions.
 The analysis of the literature shows that the issues related to the application of the semi-analytical finite element method to the calculation of thin-walled prismatic bodies in elastic-plastic, and massive even in elastic formulations, have not been properly reflected. In addition, there are no publications in this area devoted to the development of universal prismatic finite elements that allow you to explore massive, thin-walled and combined structures.
 The direction of this study is to create on the basis of the semi-analytical method of finite elements of an effective apparatus for numerical analysis of the stress-strain state of massive and thin-walled arbitrarily loaded properties of the material and solve a number of new practically important problems. Therefore, in this work, based on the moment diagram of finite elements, formulas for calculating nodal reactions and stiffness matrix coefficients of a finite element with averaged mechanical and geometric parameters for the study of massive, thin-walled and combined structures are derived.