Computer Simulation Method Research Articles

Phase Stability and Mechanical Properties Analysis of AlCoxCrFeNi HEAs Based on First Principles

With the in-depth research on high-entropy alloys (HEAs), most of the current research uses experimental methods to verify the effects of the main elements of HEAs on the mechanical properties of the alloys. However, this is limited by the long experimental period and the influence of many external factors. The computer simulation method can not only effectively save costs and shorten the test cycle, but also help to discover new materials and broaden the field of materials. Therefore, in this paper, the physical properties (such as lattice constant, density and elastic constant) of AlCoxCrFeNi (x = 0, 0.25, 0.5, 0.75, 1) HEAs were calculated based on the first-principles calculation method and virtual crystal approximate modeling method. It is found that AlCoxCrFeNi HEAs have the best hardness and toughness properties, with a Co content of 0.5~0.7. The research results can provide theoretical guidance for the preparation of HEAs with optimal mechanical properties.

Construction of a mathematical model and numerical study of interaction between moisture-, heat-, and mass transfer processes of salt solutions in an unsaturated soil layer

Methods of mathematical modeling and computer simulation were used to investigate the influence of interrelated processes of transfer of saline solutions in the unsaturated soil layer. To this end, a mathematical model has been built for modeling the corresponding processes of the moisture-, heat-, and mass transfer of saline solutions in an unsaturated soil layer. An effective computational algorithm was developed to solve the corresponding nonlinear boundary problem numerically by the method of finite differences; it was implemented in the Asp.net programming environment in the C++ language. Based on the numerical experiments carried out, the distribution of moisture, concentration, and temperature fields in the aeration zone (incomplete saturation) was obtained. To study the influence of mass transfer of salts on moisture transfer, a numerical solution was found to the problem of moisture transfer, the problem of moisture transfer taking into consideration mass transfer and moisture transfer, taking into consideration mass transfer in the presence of osmosis. Analysis of the results showed that the distribution of the concentration of saline solutions over time is slower and more predictable. It was established that the distribution of moisture heads increases with depth and time when saline solutions fall on the surface of the soil massif. With the influence of salt concentration, the distribution of moisture increases with depth and time throughout the entire area of moisture transfer by 1–3 %. The distribution of moisture heads taking into consideration the concentration of salts and osmosis is reduced by 3–5 % compared to the results of the problem without taking into consideration the phenomenon of osmosis. The distribution of the concentration of saline solutions during moisture transfer and osmosis acquires higher values compared to the results without taking osmosis into consideration. The established features can be successfully applied to clean the fertile soil layer and resume agricultural activities

Formation of defects on the surface of LiF crystals under irradiation with different ions mass

In this work, we consider the experimental and theoretical results of studies of the formation of defects on the surface of LiF crystals under irradiation with ions using total current spectroscopy and the SRIM software package. A comparative study was carried out with ions of different masses, and inconsistencies of the occurring physical phenomena between our early concepts were found. It is shown that in the case of heavy ions irradiation, they are implanted and appear substitutional atoms into the bulk of the crystal. For ions with the smallest ion mass, the distribution of interstitial defects is greater on the surface than in the bulk of the crystal. An attempt is made to explain the formation of some defects on the surface (formed peaks in the total current spectra) by the method of computer simulation. Highlights Formation of defects on the surface of LiF films at ions irradiation. Influence of irradiation ions mass on the formation of surface defects. The different distribution of substitutional atoms on the surface. Formation of vacancies and interstitial defects on the surface of LiF films at ions irradiation.

Synthesis of a Control System for Planning a Rocket Projectile on a Passive Flight Section along a Program-Defined Trajectory

The article solves a problem aimed at creating a control system for the planning of a rocket projectile. The existing method of calculating the missile range does not provide the necessary accuracy. The use of computer simulation methods is the most promising approach for the development of a rocket planning control system based on laws. The proposed control system is based on the use of a reference trajectory of the rocket flight calculated for the predicted average values of the velocity of the longitudinal component of the wind. An algorithm for controlling the planning of a rocket by changing the angle of rotation of a horizontal support is proposed, based on the dependence of vertical and horizontal coordinates and on the pitch angle. The computer system of visual programming Simulink was used as a platform for the development of the algorithm. As a result, a block diagram of the rocket planning control was obtained, including a model of the rocket flight path as a control object and an on-board control system organized on the basis of a dual-core ESP-32 microcontroller. The technique of wireless recording of the control program into the memory of the microcontroller in the field is proposed. Based on the Simulink Desktop software package, a half-scale rocket flight model was developed in real time, including an ESP-32 microcontroller, a PCI-1710HG board and a Simulink rocket flight trajectory model with a variable mass in the vertical plane. A series of experiments were conducted that showed a high degree of accuracy of the missile hitting the target because of the projectile planning control system.

Effect of computational grid cell size and heterogeneity of computing area for estimated fire detection time

Introduction . In Russia, based on the provisions of the current regulatory documents, the time for the start of evacuation for a room in which a fire broke out is determined depending on the area of the room. According to some authors, the time of the start of the evacuation of people is a combination of “technical”, which includes the time of detection of a fire, and “psychophysical”, determined by the behavioral and organizational characteristics of the people who make it up. The fire detection time is currently not taken into account. Purpose . Evaluation of the influence of the size of the cells of the computational grid and the inhomogeneity of the computational domain on the estimated time of fire detection. Aims. 1. Establish the qualitative nature of the influence of the size of the cells of the computational grid and the inhomogeneity of the computational domain on the estimated time of fire detection. 2. Offer recommendations for determining the estimated time of fire detection. Methods . For research, computer simulation methods were used using the Fire Dynamics Simulator software package. Results and discussion . The use of grids with different cell sizes can significantly reduce the number of cells in the computational domain and, as a result, the computation time. However, this leads to rather contradictory results. The minimum time values are reduced by almost 3–4 times compared to a homogeneous computational grid, and the maximum time increases by 2 times. Conclusions . 1. The size of the cells of the computational grid and the inhomogeneity of the computational domain have a significant impact on the time of fire detection. 2. A sufficiently large spread in the values of the estimated fire detection time may indicate an unreliable estimate of the total time for the start of evacuation and incorrect conclusions about the safe evacuation of people and/or the probability of evacuation of people. 3. For a correct estimate of the evacuation start time, taken into account the estimated fire detection time, it is recommended to use homogeneous computational grids with cell sizes not exceeding 0.25 m.

DETERMINATION OF THE FEATURES OF THE SHAPE AND VIBRATION FREQUENCY OF TURBINE BLADES ON DIGITAL MODELS

A digital solid model of a turbine blade with a mounting shelf has been developed in SolidWorks. The description of complex surfaces is made using spline functions. The method of computer simulation using SolidWorks Simulation was used to study the distribution of natural oscillations of the blade depending on the method of its fixing during machining. The spectra of natural oscillations of the blade in the sound range have been obtained and analyzed. The form of natural vibrations of complex surfaces is also analyzed. For the correct choice of processing parameters during machining, it is necessary to take into account both the conditions for fixing the part in the fixture and the natural frequency of the part. It is noted that an equally important parameter is the form of oscillations of a thin surface at the studied frequencies. It is noted that in the future it is possible to solve these problems through computer simulation.

A Study on College Students’ Cognitive Intention and Path Choice of Entrepreneurship from the Perspective of Individual and Group Cooperation

In order to study the overall low entrepreneurial enthusiasm of college students, a method was proposed based on the cognitive intention and path choice of college students’ entrepreneurship from the perspective of individual and group cooperation. The method briefly introduces the achievement motivation theory, entrepreneurial intention theory, entrepreneurial cognition theory, classical game theory, computer simulation, and experimental methods. Then, the research hypothesis and model construction method are elaborated, and a questionnaire is designed to study the cognitive intention and path of entrepreneurship of college students. Finally, data analysis and hypothesis testing are described to provide a guarantee for college students’ entrepreneurship. The results show that the fundamental driving force for the great progress of entrepreneurship education in colleges and universities is to meet the needs of both the collective and the individual in the top-level design and to realize the mechanism through which entrepreneurship education can achieve common development.

Computational modelling and simulation to mitigate the risk of daylight exposure in tropical museum buildings

In museum design and operation, daylight is typically discouraged due to high risk of damaging the display objects. However, past studies in high-latitude regions have shown the possibility to apply daylight in museums, so long as it is carefully planned, and the display objects are not from the category of high responsive materials. In the tropical region, the influence of daylighting on light exposure on museum objects is still unknown. This study therefore aims to assess and mitigate the impact of annual daylight exposure on objects with low responsive materials in a tropical daylit museum building. Annual daylight modelling and simulation are performed to achieve the objective, followed with Morris sensitivity analysis and Mahalanobis distance classifier to optimise the outcome. It is found that either WWR or glazing transmissivity gives the greatest influence on the performance indicators. Based on the proposed optimisation algorithm, it is possible to determine the optimum solutions satisfying the performance indicators target, for a certain opening type. Overall, the contribution of this study is the proposed computational modelling and simulation methods to mitigate the exposure risk while optimising daylight as a renewable energy source.

Identification and analysis of B cell epitopes of hemagglutinin of H1N1 influenza virus.

The frequent variation of influenza virus hemagglutinin (HA) antigen is the main cause of influenza pandemic. Therefore, the study of B cell epitopes of HA is of great significance in the prevention and control of influenza virus. In this study, the split vaccine of 2009 H1N1 influenza virus was used as immunogen, and the monoclonal antibodies (mAbs) were prepared by conventional hybridoma fusion and screening techniques. The characteristics of mAbs were identified by ELISA method, Western-blot test and hemagglutination inhibition test (HI). Using the obtained mAbs as a tool, the B cell epitopes of HA were predicted by ELISA blocking test, sandwich ELISA method and computer simulation method. Finally, four mAbs against HA antigen of H1N1 influenza virus were obtained. The results of ELISA and computer prediction showed that there were at least two types of epitopes on HA of influenza virus. The results of this study complemented the existing methods for predicting HA epitopes, and also provided a new method for predicting other pathogenic microorganisms.

The chemical Langevin equation for biochemical systems in dynamic environments.

Modeling and simulation of complex biochemical reaction networks form cornerstones of modern biophysics. Many of the approaches developed so far capture temporal fluctuations due to the inherent stochasticity of the biophysical processes, referred to as intrinsic noise. Stochastic fluctuations, however, predominantly stem from the interplay of the network with many other-and mostly unknown-fluctuating processes, as well as with various random signals arising from the extracellular world; these sources contribute extrinsic noise. Here, we provide a computational simulation method to probe the stochastic dynamics of biochemical systems subject to both intrinsic and extrinsic noise. We develop an extrinsic chemical Langevin equation (CLE)-a physically motivated extension of the CLE-to model intrinsically noisy reaction networks embedded in a stochastically fluctuating environment. The extrinsic CLE is a continuous approximation to the chemical master equation (CME) with time-varying propensities. In our approach, noise is incorporated at the level of the CME, and it can account for the full dynamics of the exogenous noise process, irrespective of timescales and their mismatches. We show that our method accurately captures the first two moments of the stationary probability density when compared with exact stochastic simulation methods while reducing the computational runtime by several orders of magnitude. Our approach provides a method that is practical, computationally efficient, and physically accurate to study systems that are simultaneously subject to a variety of noise sources.

Fish habitat restoration on the basis of water morphology simulation.

The hydrodynamic conditions of rivers affect fish habitats by influencing parameters such as river bottom topography. Ecological restoration projects change the water morphological characteristics of rivers. Here, water flow characteristics of the upper Yangtze River before and after the construction of a restoration project were analyzed using the computational fluid dynamics simulation method. The longitudinal diversion dam could divide the river into two flow velocity zones, and the outer flow is similar to the original river with a flow velocity of 0.75 m/s. However, flow velocity on the inner side of the river was about 0.25 m/s, forming a larger buffer area. The eddy became more diversified and stable, with a high eddy viscosity coefficient and less fluctuations, at 9 Pa·s; this was conducive to fish aggregation and spawning. At different depths, large gradient differences were observed between the inner and outer sides of the longitudinal diversion dam, and the turbulent current and upward flow of the inner side were obvious; this was more favorable to the aggregation of different fish species. The longitudinal dam body was under a pressure of about 200.2 Pa at the same flow rate; this was significantly lower than the pressure on the transverse dam body. The field flow test and fish survey data showed that the error rate of the simulation using the RNG turbulent model was less than 10% compared with actual mapping. After the restoration of fish habitats by the longitudinal diversion dam, the number of fish species in the area increased from 40 to 49; The density of fish in the water increased from 71.40 fish per 1,000 m2 before the project to 315.70 fish per 1,000 m2 after the project. These results can provide a reference for the rapid assessment of water morphology and fish habitat restoration in the future.

Passivation of perovskite layer surface states with pyridine in flexible and printed perovskite solar cells

Perovskite solar cells (PSCs), prepared by using solution-processed printing techniques, gained much attention over the past few years and a considerable progress has been achieved in improving the power conversion efficiencies of these devices. Nevertheless, there are still some advancements that can be implemented, especially in terms of passivation of surface defects in the perovskite photoactive layer. Passivation can afford considerable reduction in surface recombination of charge carriers in the photoactive layer and help to obtain devices with better performance. In this work, poly(3-hexylthiophene-2,5-diyl)-based inks with small amount of pyridine as an additive are used to deposit the hole transport layer and simultaneously passivate the surface defects of the perovskite layer in flexible and printed PSCs. The devices are fabricated on flexible conductive plastic substrates using a slot-die coating method. It is found that 2.5 wt.% pyridine-containing inks for preparing hole transport layer have a positive effect on the performance of resulting PSCs. On average, around 13% improvement in the power conversion efficiency is observed for the devices with passivation as opposed to the reference devices without passivation. The effect of pyridine passivation on the structural and electronic properties of the perovskite layer on a flexible substrate is studied using experimental and analytical techniques, whereas the computer simulation methods are employed to rule out the possible mechanisms for the performance improvements in the devices with passivation. The approach presented here can be useful for developing simplified protocols for printing of flexible PSCs with the passivated perovskite layer and improved device efficiency.

Thermodynamic Swings: How Ideal Complex of Cas9-RNA/DNA Forms.

Most processes of the recognition and formation of specific complexes in living systems begin with collisions in solutions or quasi-solutions. Then, the thermodynamic regulation of complex formation and fine tuning of complexes come into play. Precise regulation is very important in all cellular processes, including genome editing using the CRISPR–Cas9 tool. The Cas9 endonuclease is an essential component of the CRISPR–Cas-based genome editing systems. The attainment of high-specificity and -efficiency Cas9 during targeted DNA cleavage is the main problem that limits the practical application of the CRISPR–Cas9 system. In this study, we analyzed the thermodynamics of interaction of a complex’s components of Cas9–RNA/DNA through experimental and computer simulation methods. We found that there is a small energetic preference during Cas9–RNA/DNA formation from the Cas9–RNA and DNA/DNA duplex. The small difference in binding energy is relevant for biological interactions and could be part of the sequence-specific recognition of double-stranded DNA by the CRISPR–Cas9 system.

The design and evaluation of bionic porous bone scaffolds in fluid flow characteristics and mechanical properties

Background and objectiveAt present, there is a lack of efficient modeling methods for bionic artificial bone scaffolds, and the tissue fluid/nutrient mass transport characteristics of bone scaffolds has not been evaluated sufficiently. This study aims to explore an effective and efficient modeling method for biomimetic porous bone scaffolds for biological three-dimensional printing based on the imitation of the histomorphological characteristics of human vertebral cancellous bone. The fluid mass transport and mechanical characteristics of the porous scaffolds were evaluated and compared with those of a human cancellous bone,and the relationship between the geometric parameters (e.g., the size, number, shape of pores and porosity) and the performence of biomimetic porous bone scaffolds are revealed. MethodsThe bionic modeling design method proposed in this study considers the biological characteristics of vertebral cancellous tissue and performs imitation and design of vertebrae-like two-dimensional slices images.It then reconstructs the slices layer-by-layer to form porous scaffolds with a three-dimensional reconstruction method, similar to computed tomography image reconstruction. By controlling the design parameters, this method can easily realize the formation of plate-like (femoral cancellous bone-like) or rod-like (vertebral cancellous bone-like) porous scaffolds. The flow characterization of porous structures was performed using the computational fluid simulation method. ResultsThe flow characterization results showed that the permeability of the porous scaffolds and human bone was 10−8∼10−9m2,and when the porosity of the porous scaffolds was higher than 70%, the permeability was higher than that of human vertebrae with a porosity of 82%. The maximum shear stress of the designed porous scaffolds and human vertebra were less than 0.8Mpa, which was conducive to cell adhesion, cell migration, and cell differentiation. The results of 3D printing and mechanical testing showed good printability and reflected the relationship between the mechanical properties and design parameters. ConclusionsThe design method proposed in this study has many controllable parameters, which can be adjusted to generate diversified functional porous structures to meet specific needs, increase the potential of bone scaffold design, and leave room for meeting the new requirements for bone scaffold characteristics in the future.

Computer Flow Simulation and Verification for Turbine Blade Channel Formed by the C-90-22 A Profile

Currently, software products for numerical simulation of fluid dynamics processes (Ansys, Star CCM+, Comsol) are widely used in the power engineering industry when designing new equipment. However, computer simulation methods embedded in proprietary software products make specialists choose grid settings, boundary conditions, and a solver providing the minimal deviation from experimental data with the maximal calculation speed. This paper analyzes the influence of the main grid settings and boundary conditions in the Ansys software package on the error in the computer simulation of flows in standard elements of power equipment and gives recommendations for their optimal choice. As standard elements were considered blade turbine channels formed by C-90-22 A profiles.

Micellization, aggregation, and molecular interactions involved in CTAB‐Alizarin Red S complexation

AbstractSurfactant–dye complexation between anionic dye: Alizarin Red S (ARS) and cationic surfactant:cetyltrimethylammonium bromide (CTAB) was investigated in an aqueous medium at 303.15 K employing various physicochemical characterization to offer an understanding of the micellization conduct. Here, micellization and thermodynamic parameters have been calculated using the tensiometry and conductivity approach. The critical micelle concentration (CMC) of CTAB is observed to decrease in presence of ARS. The Gibbs energy of micellization () remains be negative on increasing the ARS content which indicated the spontaneity of the overall micellization process. Cyclic voltammetry (CV) reflected the impact of interactions between CTAB and ARS. ARS solubilization in CTAB micelles caused a red (bathochromic) shift in the ultraviolet–visible spectrum below the CMC thereby inferring that ARS undergoes J‐type aggregation in the pre‐micellar region. The intercept drawn following the Job's (corrected absorbance vs. CTAB volume ratio plot) method depicted the volume fractions of (equimolar) ARS (VARS) and CTAB (VCTAB) expressed in v/v occurring at VARS/VCTAB = 0.52/0.48, suggesting their stoichiometric ratio of 1:1 amid each molecule of ARS and CTAB leading to CTAB‐ARS ion‐pair complexation. A computational simulation method using molecular orbital energy calculations was used to evaluate the successive correlation between CTAB and ARS to comprehend the binding mechanism. The lower energy gap (ΔE) value of CTAB‐ARS indicated the favorable interaction of ARS with CTAB. Thus, the present work will reflect the significance of surfactant–dye systems in analytical and biochemistry research; and may open novel possibilities in dye absorption and their applications in the removal of dyes using surfactants.

Helium in uranium dioxide: Computer simulation (Review Article)

Recent results of experimental studies, as well as computer modeling of the helium behavior in uranium-based nuclear fuels, are reviewed. Potential models of interaction of helium atoms, uranium and oxygen ions, results of application and perspectives of computer simulation methods in prediction of the most important properties of solid solutions of helium, such as its solubility and diffusion coefficients in stoichiometric and nonstoichiometric uranium dioxide, are discussed.

Elucidation on inhibition and binding mechanism of bovine liver catalase by nifedipine: multispectroscopic analysis and computer simulation methods.

Nifedipine (NDP), a dihydropyridine calcium antagonist, is widely used for the treatment of hypertension and angina pectoris. Catalase is a key antioxidant enzyme that is closely relevant to the level of reactive oxygen specie in vivo. Here, the research explored the effects of NDP on the conformation and catalytic function of bovine liver catalase (BLC) through enzymatic reaction kinetic techniques, multispectroscopic analysis, and computer simulation methods. Kinetic studies clarified that the NDP reduced the activity of BLC using a noncompetitive inhibition mechanism. Based on trial data, a static quenching mechanism functioned in quenching the intrinsic fluorescence of BLC. The binding constant value was (4.486 ± 0.008) × 104 M-1 (298 K) and BLC had one binding site for NDP. Tyr was prone to be exposed more to a hydrophilic environment in wake of a shift in fluorescence value. The binding reaction of BLC to NDP caused a conformational change in BLC, which in turn led to increase in the α-helix content and a decline in the β-sheet content. Furthermore, several amino acids residues interacted with NDP by means of van der Waals forces, whereas Gln397, Asn368, Gln371, Asn384, and Pro377 formed several hydrogen bonds with NDP.

Modeling the Temperature Field in Frozen Soil under Buildings in the City of Salekhard Taking into Account Temperature Monitoring

Most residential buildings and capital structures in the permafrost zone are constructed on the principle of maintaining the frozen state of the foundation soils. The changing climate and the increasing anthropogenic impact on the environment lead to changes in the boundaries of permafrost. These changes are especially relevant in the areas of piling foundations of residential buildings and other engineering structures located in the northern regions since they can lead to serious accidents caused by the degradation of permafrost and decrease the bearing capacity of the soil in such areas. Therefore, organization of temperature monitoring and forecasting of temperature changes in the soil under the buildings is an actual problem. To solve this problem, we use computer simulation methods of three-dimensional nonstationary thermal fields in the soil in combination with real-time monitoring of the temperature of the soil in thermometric wells. The developed approach is verified by using the temperature monitoring data for a specific residential building in the city of Salekhard. Comparison of the results of numerical calculations with experimental data showed good agreement. Using the developed computer software, nonstationary temperature fields under this building are obtained and, on this basis, the bearing capacities of all piles are calculated and a forecast of their changes in the future is given. To avoid decreasing the bearing capacity of piles it is necessary to prevent the degradation of permafrost and to supply the thermal stabilization of the soil. The proposed approach, based on a combination of the soil temperature monitoring and computer modeling methods, can be used to improve geotechnical monitoring methods.

Supporting electrolyte interaction with the AACVD synthesized Rh thin film influences the OER activity

Electrocatalytic oxygen evolution reaction (OER) is one of the most promising candidates for the sustainable energy. This has led researchers to focus towards developing highly active electrocatalysts. Our work takes a wholistic approach to understanding the key factors that influence the OER process. We focused on preparing a metallic electrocatalyst and tested out its OER performance using two different supporting electrolytes. We also studied the effect of crystal planes of the electrocatalyst on the OER process using computational simulation (CS) methods. For this, rhodium (Rh) thin film (RhTF) electrocatalysts on indium tin oxide (RhTF_ITO) were fabricated for OER through aerosol assisted chemical vapor deposition (AACVD). The prepared electrodes showed excellent electrocatalytic activity for OER (for 10 mA/cm2 η = 273 mV in 1.0 M KOH). The effect of the supporting electrolytes and the crystal planes of RhTF electrodes were analyzed using electroanalytical techniques and CS methods. Tafel slope (TS) analysis revealed that electron transfer kinetics was slower for the NaOH compared to the KOH. The scan rate (ν) analysis indicated that there is weak electrostatic interaction between the hydrated outer Helmholtz plane (OHP) of Na+ and K+ ions with the adsorbed OH(ad) that impacts the OER process. With increasing ν the restructuring of the electrochemical double layer (EDL) increases resulting in similar OER performance for both the supporting electrolytes. The micro-kinetic analysis showed that the rate determining step (RDS) for NaOH and KOH required around 1.67 eV and 1.07 eV. The density functional theory (DFT) analysis revealed that these energy values are closest to the Rh (111) plane reaction pathway. Adsorption locator (AL) analysis further revealed that the hydrated cations could directly get adsorbed on the Rh crystal planes hindering the electron transfer (ET) in the OER process. The DFT analysis further revealed that the lowest energy pathway for the OER process is followed on the Rh (220) plane. These analyses demonstrated that it is possible to fine tune the OER using supporting electrolyte and electrocatalysts that can work synergistically for getting the optimal OER performance.