Advanced Calculation Methods Research Articles

Recent Advances in Carbon Nitride Supported Single‐Atom Catalysts: Synthesis, Characterization, and Applications for CO2 Photoreduction

AbstractPhotoreduction of CO2 into value‐added chemicals and fuels is a promising green technology for solar‐to‐chemical conversion. Owing to the atomic utilization, unique metal‐support interaction, and unsaturated coordination active sites, single‐atom catalysts (SACs) have been attracting great attention in achieving high activity and selectivity of CO2 photoreduction reactions. On the other hand, carbon nitride (C3N4) with abundant periodically unsaturated coordination of nitrogen atoms can serve as an excellent support for anchoring metal single atoms. In this context, extensive research efforts have been paid in C3N4‐based SACs for CO2 photoreduction in recent years. In this review, we report the recent advances in C3N4 supported SACs for CO2 photoreduction. We start from the introduction of synthetic strategies of various C3N4 supported metal SACs. Secondly, the main advanced characterization techniques and calculation methods for identifying the single‐atoms and their coordination environments of C3N4‐based SACs are summarized. Thirdly, some state‐of‐the‐art works on the rational design of C3N4‐based SACs and their applications in CO2 photoreduction are introduced. Lastly, we briefly summarize the main challenges and propose important perspectives of C3N4‐based SACs in CO2 photoreduction. This review is expected to provide some useful guidelines for the development of efficient and stable C3N4‐based SACs for CO2 photoreduction.

Intelligent Inversion of Coastal Earth Resistivity

Coastal grounding electrodes are currently an important means to alleviate land grounding electrode land constraints. In order to better invert the terrestrial geodesic resistivity in the coastal region, this paper proposes a complete set of inversion technology schemes. First, this paper proposes a layered land model for the coastal region, and a composite geodetic model is modeled by the fold junction of the land model and the ocean. Based on this, an adaptive subdivision boundary element method is proposed for solving the composite soil grounding calculation problem, and the accuracy and advantages of the method are demonstrated by examples. Finally, the paper uses the differential evolutionary algorithm to invert the exploration data of the four-point method in the coastal area, and obtains the parameters of the terrestrial layered geodetic model that meet the engineering requirements. The comparison with the grounding software CDEGS illustrates the effectiveness of the method. This paper carries out the research on the modeling and inversion methods of composite layered soil model, combining advanced numerical calculation methods and artificial intelligence algorithms to provide the support of computational tools for coastal resistivity inversion.

Advanced Optimisation and Forecasting Methods in Power Engineering—Introduction to the Special Issue

Modern power engineering is struggling with various problems that have not been observed before or have occurred very rarely. The main cause of these problems results from the increasing number of connected distributed electricity sources, mainly renewable energy sources (RESs). Therefore, energy generation is becoming more and more diverse, both in terms of technology and location. Grids that have so far worked as receiving networks change their original function and become generation networks. The directions of power flow have changed. In the case of distribution networks, this is manifested by power flows towards transformer stations and further to the network with a higher voltage level. As a result of a large number of RESs, their total share in the total generation increases. This has a significant impact on various aspects of the operation of the power system. Voltage profiles, branch loads, power flows and directions of power flows between areas change. As a result of the random nature of RES generation, there are problems with the quality of electricity, source stability issues, branch overloading, voltage exceedances and power balance. The occurrence of various types of problems requires the use of more and more advanced methods to solve them. This review paper, which is an introduction to the Special Issue Advanced Optimisation and Forecasting Methods in Power Engineering, describes and justifies the need to reach for effective and available mathematical and IT methods that are necessary to deal with the existing threats appearing in the operation of modern power systems. It indicates exemplary, current problems and advanced methods to solve them. This article is an introduction and justification for the use of advanced calculation methods and algorithms. Engineering intuition and experience are often not enough due to the size and complexity of power grid operation. Therefore, it becomes necessary to use methods based on artificial intelligence and other advanced solutions that will facilitate and support decision making in practice.

Assessment of fire exposure on the load bearing capacity of basement storey walls

This paper presents the numerical modelling of the fire exposure on structural element and its static analysis taking account of the material properties reduction due to elevated temperature.
 The reinforced concrete wall of basement storey was subjected to one side fire exposure.
 Advanced calculation methods were used to assess the fire exposure on the structural element as most reliable and approximate to fire test results. Thermal analysis was performed with LIRA-CAD software by the simulating of three main heat-transfer ways: thermal conductivity, convection and radiation. As a result of the thermal analysis, temperature distribution in the concrete and reinforcement parts of the structural element cross-section was obtained. The thermal analysis of the wall structural element was performed for 120 minutes in standard fire exposure. Reduction factors for the strength of concrete and reinforcement steel were determined based on the temperature distribution in the wall structural element cross-section. The cross-section is divided into a number of parallel zones of equal thickness where the mean temperature and the corresponding mean compressive strength is assessed according to the Zone method procedure. The fire damaged zone of thickness az at the fire exposed sides and reduced cross-section were obtained.
 Static analysis of the wall load-bearing capa-city was performed using the procedure applicable for normal temperature design. The Deformation method for normal temperature design taking to account concrete deformation was used. The Deformation method for normal design taken to account concrete deformation at every step of iteration was used. The reduced load-bearing capacity of the fire damaged wall taking into account residual concrete strength was calculated and relevant load-bearing capacity diagrams were determined.

Advances in theoretical calculations of MXenes as hydrogen and oxygen evolution reaction (water splitting) electrocatalysts

Two-dimensional transition metal carbides/nitrides/carbon nitrides (MXenes) have great potential to be excellent H and O evolution reaction (HER and OER) electrocatalysts due to their special properties, such as large specific surface area, good electrical conductivity, and abundant active sites. Researchers have carried out many types of investigations on MXenes as HER and OER electrocatalysts. So far, great progress has been made in screening MXenes as HER and OER electrocatalysts, in which the theoretical calculation method plays an important role. In the present study, we briefly summarize the progress regarding theoretical calculations of MXenes as HER and OER electrocatalysts. First, we introduce the standard computational methods and basic mechanisms of HER and OER. We then present some recent studies of theoretical calculations and experiments combined with theoretical calculations. Finally, some specific perspectives are provided for the future development of MXenes as excellent HER and OER electrocatalysts. We believe theoretical computational studies of MXenes as HER and OER electrocatalysts may flourish by considering the natural reaction environment and electrochemical kinetic processes, the proposal of more activity descriptors, close integration of theory and experiments, and the development of advanced calculation methods.

A Comprehensive Evaluation of the Attenuation Characteristics of Some Sliding Bearing Alloys under 0.015-15 MeV Gamma-Ray Exposure.

In this study, three different sliding bearing alloy samples were investigated in terms of their performance on attenuation characteristics and behavioral attitudes under 0.015–15 MeV gamma-ray exposure. Accordingly, different types of advanced calculation methods were utilized to calculate the radiation shielding parameters. Next, several gamma-ray shielding parameters and exposure rates in addition to fast neutron removal cross-section were determined. Furthermore, exposure and energy absorption buildup factors were determined by using G-P fitting method. Mass attenuation coefficients (MAC) values were recorded as 2.5246, 2.5703, and 2.5827 (cm2/g) for Alloy1, Alloy2, and Alloy3 samples at 15 MeV photon energy, respectively. At 40 mfp, the highest EBF values were reported as 1,376,274, 1,003,593, and 969,373 for Alloy1, Alloy2, and Alloy3 samples. The results of this extended investigation showed that the Alloy3 sample with the highest Pb reinforcement amount has superior shielding capability among the investigated samples. It can be concluded from the results that substitution of Pb with Bi in the recent alloy structure has a monotonic effect on different types of shielding parameters. Therefore, it can also be concluded that Pb is a remarkable tool for the improvement of the shielding properties of studied alloy structures.

Fire resistance assessment of RC columns with advanced calculation methods

This paper contains the results of fire resistance calculation of reinforced concrete columns with advanced calculation methods.
 For columns that are tested unloaded, determine the cross-sectional temperature distribution and values of temperature in reinforcement. The fire resistance of columns that have been tested without load is determined according to temperature measurements, with calculation methods according to the requirements of DBN B.1.1-7 andDBN B.1.2-7.
 According to the tabulated method, the fire resistance of reinforced concrete columns is determined by geometric parameters such as cross-section width, axis distance of the reinforcement, amount of reinforcement, length or height of the element, load level during the fire exposure, heating conditions during the fire exposure (number of fire exposed sides).
 Accidental combination of actions during the fire situation consists of characteristic values of permanent and variable long-term actions taking into account the safety factor for the consequence class of the object (CC2) and the type of design situation (accidental).
 Thermal analysis of the column was performed under conditions of the standard fire exposure. In such conditions it was assumed that the column is exposed to fire with four sides for 120 minutes that corresponds to the required fire resistance class R120.
 The thermal state of the column was determined using transient thermal models that take into account radiation-convective heat transfer in the ambient from the heat source to the structural surface, convective heat transfer in the structure, radiation-convective heat exchange from the structure to the ambient environment.
 The residual load-bearing capacity of the reinforced concrete column after the fire exposure was calculated with the reduced cross-section determined using zone method in accordance with the requirements of DSTU-N B B.2.6-197 and DSTU-N B EN 1992-1-2.
 The fire resistance period of columns for the load-bearing criterion was determined on the basis of the results of of thermal and static analysis.

Prediction of Protein-Protein Interaction Sites Based on Stratified Attentional Mechanisms.

Proteins are the basic substances that undertake human life activities, and they often perform their biological functions through interactions with other biological macromolecules, such as cell transmission and signal transduction. Predicting the interaction sites between proteins can deepen the understanding of the principle of protein interactions, but traditional experimental methods are time-consuming and labor-intensive. In this study, a new hierarchical attention network structure, named HANPPIS, by adding six effective features of protein sequence, position-specific scoring matrix (PSSM), secondary structure, pre-training vector, hydrophilic, and amino acid position, is proposed to predict protein–protein interaction (PPI) sites. The experiment proved that our model has obtained very effective results, which was better than the existing advanced calculation methods. More importantly, we used the double-layer attention mechanism to improve the interpretability of the model and to a certain extent solved the problem of the “black box” of deep neural networks, which can be used as a reference for location positioning on the biological level.

Development of test methodologies for experimental lifetime investigations of tidal turbines

As a regenerative energy source, tidal energy can significantly contribute to greenhouse gas reduction, even though the potentially achievable energy output is lower than that of wind or solar energy. The decisive advantage of tidal turbines lies in the simply and reliably predictable energy output. However, their commercial use has so far been impeded by the fact that on the one hand complex mechanical systems are required to convert energy of tidal currents and on the other hand multi-axial loading conditions caused by turbulent ocean currents act on the turbine. For this reason, field tests on prototypes are an essential part of the development strategy to ensure operational reliability. However, in-field tests do not allow for accelerated lifetime testing, so that test bench experiments are becoming an increasingly important alternative. Today, established procedures for testing the turbines main bearings and gearing system are already available, both for setting up the required test configuration and for determining the corresponding test loads. However, the use of advanced calculation methods, such as the finite element method for stress calculation, requires a deep understanding of the examined components and hinders the transfer of the approaches to other components.To simplify the process of test loads determination, a general methodology is presented, which relies exclusively on standardized empirical calculation rules. Doing this, fatigue equivalent loads can be determined for any component in a simple process. It was shown that the achieved reduction in complexity opens further potential for test acceleration, since several components can be tested simultaneously.

Prevention of Freshwater Breakthrough into Potassium Mines

The exploitation ofpotash salt deposits is associated with a need to protect mines from freshwater breakthroughs. Advanced monitoring tools and calculation methods make it possible to identify areas that can be dangerous due to discontinuities in the waterblocking stratum, separating the water-bearing horizon from the mined-out area. This is the first time that a method for preventing freshwater breakthrough into mine workings has been proposed and it is currently at the design stage. A hazardous area is isolated by constructing bulkheads and the mined-out space is then filled with relatively saturated brines. Since the freshwater density is lower than the density of the brines, even if the continuity of the waterblocking stratum is disrupted, then the freshwater will not flow into the mined-out space and so it will not lead to massive dissolution of the salt rock. At the same time, the brines pumped into the goaf are not completely saturated with NaCl and KCl. They will be saturated already during mine flooding. We estimated the negative consequences associated with the elimination of a dangerous area using integrated filtration-migration and geomechanical numerical modelling. According to the computed results, we localised the zones within which the elimination of a potentially hazardous area causes an increase in the human-induced impact on the waterblocking stratum and imposes the threat of destruction. To minimise the risk of discontinuity of the waterblocking stratum in the submerged western part of the potentially hazardous area, it is recommended that saturated brines are used to fill it. The implementation of these measures will make it possible to reduce the degree of dissolution of the salt rocks in this area and reduce the human-induced impact on the layers of the waterblocking stratum.

Optimal Battery Energy Storage System Scheduling Based on Mutation-Improved Grey Wolf Optimizer Using GPU-Accelerated Load Flow in Active Distribution Networks

In this paper, a novel Mutation-Improved Grey Wolf Optimizer (MIGWO) model is introduced in order to solve the optimal scheduling problem for battery energy storage systems (BESS), considering the mass integration of renewable energy sources (RES), such as solar and wind generation, in active distribution networks. In this regard, four improvements are applied to the conventional GWO algorithm to modify the exploration–exploitation balance for an enhanced convergence rate. The validity and performance of the proposed model are tested on 23 classical benchmark functions and compared to the original algorithm. The new technologies present in active distribution networks lead to increased complexity in the efficient coordination of existing resources, making it necessary to resort to advanced optimization and calculation methods. As operational planning and control functions in power systems are computationally demanding and require multiple power flow calculations, the necessity of simultaneous (parallel) computing techniques emerged. In order to reduce the computing time, an accelerated GPU parallel computing technique is also applied in the proposed model. The MIGWO algorithm is further applied on the modified IEEE-33 bus system aiming to minimize the total power losses, based on the optimal coordination of BESS operation scheduling and RES generation for multiple load demand and local generation scenarios, as well as for various initial state-of-charge values of BESS.

Quantum Information and Algorithms for Correlated Quantum Matter.

Discoveries in quantum materials, which are characterized by the strongly quantum-mechanical nature of electrons and atoms, have revealed exotic properties that arise from correlations. It is the promise of quantum materials for quantum information science superimposed with the potential of new computational quantum algorithms to discover new quantum materials that inspires this Review. We anticipate that quantum materials to be discovered and developed in the next years will transform the areas of quantum information processing including communication, storage, and computing. Simultaneously, efforts toward developing new quantum algorithmic approaches for quantum simulation and advanced calculation methods for many-body quantum systems enable major advances toward functional quantum materials and their deployment. The advent of quantum computing brings new possibilities for eliminating the exponential complexity that has stymied simulation of correlated quantum systems on high-performance classical computers. Here, we review new algorithms and computational approaches to predict and understand the behavior of correlated quantum matter. The strongly interdisciplinary nature of the topics covered necessitates a common language to integrate ideas from these fields. We aim to provide this common language while weaving together fields across electronic structure theory, quantum electrodynamics, algorithm design, and open quantum systems. Our Review is timely in presenting the state-of-the-art in the field toward algorithms with nonexponential complexity for correlated quantum matter with applications in grand-challenge problems. Looking to the future, at the intersection of quantum information science and algorithms for correlated quantum matter, we envision seminal advances in predicting many-body quantum states and describing excitonic quantum matter and large-scale entangled states, a better understanding of high-temperature superconductivity, and quantifying open quantum system dynamics.

Experimental and numerical analyses of rounded dovetail timber connections (RDC) under fire conditions

The use of rounded dovetail connections has gained popularity in timber floor and ceiling structures due to the advance in computerized numeric control machinery. However, European building regulations for fire safety in timber structures from Eurocode 5 standard does not provide a specific method to calculate the fire performance of this kind of connections. In this work, two experimental fire tests were made to evaluate the fire performance and load-bearing capacity of this timber connection. A numerical coupled thermo-mechanical simulation of the tests was developed using the general advanced calculation methods proposed in annex B of Eurocode 5. The experimental tests showed that this connection is not able to accomplish with a R30 fire resistance class, which is the minimum requirement for lightweight timber frame assemblies. A loss of material caused by charring under the tenon of the connection leads to the failure. The general methods proposed in annex B of Eurocode 5 does not take into account the heating inside the connection. However, the simulation results showed an underestimation of the charring rate in the connection. A new simulation considering the thermal flux inside the connection was developed and it shown good agreement with the experimental tests.

Determination of thermal conductivity of composites with dispersed spherical inclusions

The existing shortcomings of the models for determining the thermal conductivity of composite materials with dispersed spherical inclusions raise the issue of creating more advanced calculation methods. This paper proposes a model for determining the thermal conductivity of composite materials, taking into account influence of thermal resistance at the material-inclusion boundary. The analysis of numerical and theoretical calculations showed that the analytical dependence is consistent with the results of numerical modelling for relatively small values of thermal conductivity of the filler and inclusion diameter. This paper considers several models that have been recently developed and that allow calculating thermal conductivity of such materials. They are compared with the model that takes into account influence of thermal resistance of the phase boundary. Applicability intervals of the considered model for various ratios of the thermal conductivity of inclusion material and matrix material are given.

Approach for modelling thermal properties of intumescent coating applied on steel members

Thin intumescent coating (IC) are nowadays the dominant passive system used to protect structural steel in case of fire. This paper proposes a general procedure for modelling intumescent coating in both simplified and advanced calculation methods, starting from lab-scale test results. The small-scale tests were useful for identifying the parameters that mostly can affect the behaviour of the IC under fire and the salient temperatures, which characterize the IC thermal conductivity. Starting from these results, a standard multivariate linear regression analysis is applied, in order to obtain a general expression for calculating the thermal conductivity of IC, useful for performing analytical and numerical modelling of the IC. Indeed, the proposed formula was validated against both small-scale and real-scale experimental tests, obtaining a very good agreement between experimental and simulated data. The procedure proposed in the paper can be used both in the simplified calculations, according with the prescriptive based approach, and in advanced analyses, using the performance based criteria for structural fire safety.

Investigation of the thermal conductivity of composite materials with a spherical filler

In the light of the disadvantages of existing methods for determining the thermal conductivity of composite materials, the major practical issue is the need for creating more advanced calculation methods that take into account the geometry of the dispersed inclusions and their properties, i.e., those capable of evaluating the heat-conducting parameters of the composite with consideration of the properties of its components and their relative positions. In this paper, the analytical formulas, containing the ratio of the thermal conductivity coefficients of the base material and the filler, are derived for calculating the thermal conductivity of composite. The proposed model uses averaging of parameters at the "matrix-dispersed inclusion" phase boundary. We consider several well-known models developed by domestic and foreign researchers in recent years, which allows us to calculate the coefficient of thermal conductivity of such composites. The results of comparison of these models with the analytical dependence obtained in this paper are presented, and its applicability intervals are specified for different ratios of the inclusion thermal conductivity coefficient and the matrix material. The main goal is to fill the lack of information on thermal conductivity of spherical filler composites. The model considered in this paper is based on a change in the thermal resistance at the phase boundary. Since most materials used in industry contain inclusions with different geometric characteristics, then it is necessary to use the equivalent volume method - the reduction of various geometric inclusions to a given spherical one - which makes it possible to determine a change in the thermal conductivity coefficient for different physical and geometric values of the matrix material and filler. Various dependences of the change in the thermal conductivity coefficient of composite materials on the volume content of the spherical inclusion are compared with the numerical and experimental results. The analytical dependence given in this paper is consistent with the experimental and numerical results for relatively small values of the thermal conductivity coefficient and the inclusion diameter.

Development of Nationwide Surface Spectral Acceleration Maps for Earthquake Resistant Design of Bridges Based on National Hazard Maps of Indonesia 2017

Spectral acceleration at the ground surface, including peak ground acceleration, provides essential information for earthquake resistant design and must be provided to bridge engineers in easily accessible media. Spectra acceleration maps are one way to deliver such information, but unfortunately the most recent Indonesian earthquake resistant design standard for bridges, SNI 2833-2016, only provides maps of earthquake hazard at bedrock. The development of earthquake acceleration maps at the ground surface for Indonesia in this study was based on earthquake hazard maps at bedrock with probability of exceedance (PE) 7% in 75 years, i.e. equal to an earthquake with a return period of 1034 years. Site conditions were adopted from the nationwide Vs30 map of Indonesia proposed by Irsyam (2017), which is a modified version of the Vs30 map proposed by Imamura & Furuta (2015). Site conditions combined with hazard value were used to determine the amplification factors according to the criteria in SNI 2833-2016 and then multiplied with hazard at bedrock to obtain surface spectra acceleration maps. The resulting maps are very useful for determining earthquake loads for bridge design at the preliminary design stage. Improvements to incorporate more advanced calculation methods and updated data in a future research are recommended and very feasible.

Современные математические методы прогноза условий поддержания и крепления горных выработок

The research focuses on mathematical methods of mining pressure forecast to develop rational support patterns for mining tunnels and to ensure safety of mining operations. The purpose of research is to develop the methodology of applying advanced calculation methods and software solutions based on neural networks to reduce dispersion of factors influencing stability of mining tunnels, as well as to define rational parameters of mining tunnel support. The authors review the algorithm of geomechanical process examination, which is divided into several stages. First of all, it is proposed to use cluster analysis to examine location conditions of man-made outcrops, which allows to divide all the diversity of existing conditions for mining tunnel construction. Cluster analysis first allows to reduce the dispersion of factors that influence the stability of mining tunnels in various clusters, and then to determine rational parameters of tunnel support in each cluster. After the problem of cluster analysis is solved, it is proposed to use software programs that allow to study geomechanical processes in each cluster. At this stage, both standard methods (normative techniques, numerical modelling, analogies use, etc.) and the most advanced methods – neural networks – can be applied. Described algorithm of solving geomechanical problems, which utilizes advanced numerical methods and a software package based on neural networks, ensures an individual approach to estimation of mining pressure under varying conditions of man-made outcrop location in the rock mass.

Factors Determining the Pipelines Installation Features during the Liquid Rocket Engine Assembly

A liquid rocket engine contains a vast number of pipelines. The present article describes some of the features with respect to the pipelines fabrication, introduces the main factors influencing the mismatches during the engine assembly, proposes an approach to the pipelines fabrication based on the application of the advanced design, calculation, fabrication and inspection methods based on the 3D geometrical model of an object. The existing technology of the assembly provides for the manufacture of the engine layout, the reference design of the templates. Manufactured pipeline in accordance with the standard for each specific instance of the engine requires adjustment. The exclusion of modifications and adjustments during assembly requires the use of modern methods of design, production and control based on the use of the model-oriented approach. Including calculation mathematical modeling of all processes occurring during the manufacture and assembly of pipelines.

The impact of airway geometry on the distribution of methane concen-trations at the outlet from a longwall

In underground hard coal mining, there are various types of natural hazards, which is related to human interference with the natural environment and the consequent disturbance of its equilibrium. The mining industry is an important component of the Polish economy, because coal is the basic raw material for power generation in the country. Therefore, there are numerous tests and studies to make the mining activities safe and effective. As a result, a crucial role is played by research and scientific work that result in the improvement of safety in this branch of industry. One of the areas undertaken by such research is dedicated to limiting the methane hazard in mines. The underlying cause of this problem is methane release from the body of coal and excavated coal, because this gas is flammable and explosive. These properties place the methane hazard amongst one of the most dangerous mining phenomena. The paper concentrates on the determination of methane concentrations in the area of ongoing exploitation, depending on airway geometry. The analysis is based on the model-based tests using computational fluid dynamics (CFD). The related calculations were performed by means of ANSYS Fluent based on the finite volume method (FVM). The analysis was conducted on a numerical model, reflecting the real-world region of the exploitation. The input data for the calculations were obtained from the results of measurements carried out in real-world conditions. The model developed takes into account a series of solutions that are the original scientific achievement of the Authors. This particularly refers to the modelling of goaves with caving as a porous medium. The calculations made it possible to determine the physical and chemical parameters of an air-methane mixture in each point of the region analysed. This is particularly true of the most dangerous area, namely the outlet from a longwall. In the case at hand, the calculations were carried out for several variants of airway geometry. The methodology of model-based testing presented in the paper, taking into consideration the real-world measurements and the results obtained, is an example of how advanced calculation methods can be used for solving practical problems.DOI: http://dx.doi.org/10.5755/j01.mech.24.5.21194