Theoretical Computer Modeling Research Articles

МОДЕЛЮВАННЯ ТА АНАЛІЗ РОЗГОРТАННЯ КОСМЕТИЧНОЇ СІТЧАСТОЇ АНТЕНИ

The aim of work is to create a dynamic model of a space antenna with the pantograph structure and study the processes of its deployment using open-source software. The methods of theoretical mechanics, multi-body dynamics, computational mechanics, and computer modeling were used for this research. The object for modeling is a novel mesh antenna, which is designed for mini-satellites. The most significant difference between this antenna and others is the design of the support ring in the form of a pantograph. Using the built model, antenna deployment is simulated for different cases. Values of deployment time and cable tension during the antenna deployment are analyzed.

Mesoporous collapsing encapsulated carbon dots: Direct evidence for the effect of multiple-confined interactions of silica on efficient long-lived phosphorescence

Coupling with a matrix is the common strategy to improve the phosphorescence performance of carbon dots (CDs). However, there is a lack of clear and direct evidence about the formation mechanism of the inner relationship between CDs and matrix, and the specific effect of matrix on the phosphorescence performance. Mesoporous silica nanospheres (MSNs) were used as the research model to provide the direct evidence of the dense structure formation process and to construct a quantum chemical theoretical computational model of the effect of dense matrix on phosphorescence performance. Due to the multiple domain-limiting effects of rigid Si-C covalent bonds and SiO2 dense structure, the calcined-carbonized polymer dots-mesoporous silica nanospheres (C-CPDs-MSNs) can exhibit thermally activated delayed fluorescence (TADF) by tuning the HOMO-LUMO gap and enriching the electrons in the surface region. With a long lifetime of 3.07 s, the composite can also maintain stable phosphorescence performance under harsh conditions and has been successfully applied in multilevel information encryption, fingerprint identification, and cellular imaging. This work provides the direct evidence for the process of dense SiO2 structure enhancing the phosphorescence performance of CDs and offers a general strategy and method for the design and preparation of efficient and practical CDs-based phosphorescent materials.

Towards Sustainable Energy Solutions: A Comprehensive Analysis of Piezoelectric Sensors for Power Generation

This research review paper comprehensively analyzes electric power generation using piezoelectric sensors. Piezoelectric materials, with their ability to convert mechanical energy into electrical energy, have emerged as promising candidates for energy harvesting applications. Through an extensive literature review, this paper examines various studies exploring the principles, advancements, challenges, and applications of piezoelectric-based energy generation. The review encompasses theoretical frameworks, experimental methodologies, and computational models employed in the field. Key findings from the literature are synthesized to identify trends, gaps, and opportunities for further research. The abstract highlights the significance of piezoelectric energy harvesting in the context of sustainable energy solutions and outlines potential directions for future investigation

Performance analysis and reliability optimization of internal feedback hydrostatic rotary table support

Abstract The internal feedback hydrostatic rotary table is a precision supporting device, the performance of which largely depends on the oil pad, a core component. However, uncertainties in the manufacturing process are often overlooked during the stiffness optimization, affecting the reliability of the optimized results. Accordingly, this paper aims to analyze the influence of structural parameters on the stiffness performance of the internal feedback hydrostatic rotary table and to perform reliability optimization considering the uncertainties. Initially, a theoretical computational model of internal feedback hydrostatic rotary table, accounting for the oil leakage effect, is proposed. The model's accuracy is validated through comparative simulation calculations, and based on this model, the load-bearing performance of the table is further analyzed. Subsequently, focusing on the structural characteristics of the oil pad, a reliability optimization model that considers manufacturing uncertainties is proposed. To improve the optimization efficiency, a Levenberg-Marquardt Backpropagation (LM-BP) neural network is introduced as a surrogate model for theoretical calculations. The oil pad is optimized through a particle swarm optimization algorithm. Ultimately, the optimal structural size parameters of the oil pad are obtained, achieving maximal stiffness under a high level of reliability. Both the stiffness performance and the reliability level of the rotary table are substantially enhanced. The results indicate that the proposed method significantly improves performance and reliability in practical applications.

A comparative analysis of compression bearing capacity in recycled concrete brick walls and composite walls incorporating coal-ash blocks.

In the face of the problem of waste disposal in the demolition of concrete structures, a composite wall composed of recycled concrete bricks and fly ash blocks was proposed, and based on the previous thermal performance research, its axial compression performance were further studied. Four types of walls were designed and constructed: (1) clay brick masonry (CBM), (2) recycled concrete brick masonry (RBM), (3) bilateral clay bricks masonry with coal-ash blocks sandwich insulation wall (CFCM), and (4) bilateral recycled concrete bricks masonry with coal-ash blocks sandwich insulation wall (RFRM). The test results showed that recycled concrete brick masonry exhibited a higher bearing capacity than clay brick masonry. The ultimate load of RBM was 15% higher than that of CBM. Moreover, the ultimate load of CFCM was 21% higher than that of CBM. Following the addition of sandwich coal-ash blocks in RBM, its ultimate load increased by over 42% than that of CBM. Following the addition of coal-ash blocks sandwich in both clay and recycled concrete bricks masonry, both the bearing capacity and strain exhibited improvement, the yielding load and compressive strength of them increased. Thus, it could be concluded that coal-ash blocks improved its bearing capacity. Based on the analysis of the axial compression tests, a theoretical computational model was developed and a computational expression to explain the compressive bearing capacity of a two-sided brick with coal-ash blocks sandwich insulation wall. Comparisons between the test ultimate loads (FT) and the estimated ultimate loads (FE) confirmed the accuracy of the theoretical calculation model for the compressive bearing capacity. Thus, theoretical computational models are highly recommended for the design of two-sided bricks with insulating walls constructed from coal-ash blocks being sandwiched together. This study provides a theoretical basis for the engineering application of recycled concrete brick wall and fly ash block composite wall.

Special Issue on Rotor Dynamics: Theoretical Analysis, Computer and Experimental Modelling, Measurements

Rotors and shafts are essential, often used, and highly loaded components of rotating machines and machine devices [...]

The gap between theoretical computational theories and application models

This paper examined two key generalization assumptions in the theoretical and computational fields and discussed three dominant pre-training models from multiple computer science concentrations. Then, this paper illustrated the increasingly severe gap between theoretical research and model applications for current machine learning studies. This paper discussed four advanced concepts in academia regarding possible solutions for the gap. The researchers developed these concepts to redirect future machine learning work by helping the academia re-understand the concept of “learning” and its appropriate implementation in the machine learning field. Finally, one possible reason for such a gap to exist is explained, and based on the interpretation of advanced concepts, possible solutions the academia can try to implement are also discussed.

Slug flow in tubular membrane in which air and activated sludge flow: A CFD study

Air bubbles have been widely applied to alleviate membrane fouling of tubular membranes in membrane bioreactors. However, the impact of the air bubbles on the flow at the membrane surface as well as the removal of membrane foulant are not well understood. Therefore, a theoretical computational fluid dynamics model was established to address this. In the model, air and activated sludge flowed at the superficial velocities of 0.7 m/s and 0.3 m/s, respectively. Furthermore, sludge concentrations were 5 g/L and 10 g/L, respectively. The model showed that the activated sludge did not flow downwards in the film zone and eddies were not observed in the zone below the tail of a bubble. The viscosity of sludge varied significantly in the film zone. Mass transfer capacities at membrane surface gradually decreased from the nose to the end of a bubble. Moreover, a lower sludge concentration resulted in a higher mass transfer capacity. The highest shear stress at membrane surface was 14 and 11 Pa, which were significantly higher than the shear stress achieved in submerged membranes being aerated. Microparticles (3–10 µm) at membrane surface could be shifted towards the filtrated bulk solution and sucked at the membrane surface alternatively when a gas slug flowed nearby. Furthermore, the bubbles are not effective in shifting microparticles (<3 µm) toward a bulk solution.

Perseveration and Shifting in Obsessive-Compulsive Disorder as a Function of Uncertainty, Punishment, and Serotonergic Medication

BackgroundThe nature of cognitive flexibility deficits in obsessive-compulsive disorder (OCD), which historically have been tested with probabilistic reversal learning tasks, remains elusive. Here, a novel deterministic reversal task and inclusion of unmedicated patients in the study sample illuminated the role of fixed versus uncertain rules/contingencies and of serotonergic medication. Additionally, our understanding of probabilistic reversal was enhanced through theoretical computational modeling of cognitive flexibility in OCD. MethodsWe recruited 49 patients with OCD, 21 of whom were unmedicated, and 43 healthy control participants matched for age, IQ, and gender. Participants were tested on 2 tasks: a novel visuomotor deterministic reversal learning task with 3 reversals (feedback rewarding/punishing/neutral) measuring accuracy/perseveration and a 2-choice visual probabilistic reversal learning task with uncertain feedback and a single reversal measuring win-stay and lose-shift. Bayesian computational modeling provided measures of learning rate, reinforcement sensitivity, and stimulus stickiness. ResultsUnmedicated patients with OCD were impaired on the deterministic reversal task under punishment only at the first and third reversals compared with both control participants and medicated patients with OCD, who had no deficit. Perseverative errors were correlated with OCD severity. On the probabilistic reversal task, unmedicated patients were only impaired at reversal, whereas medicated patients were impaired at both the learning and reversal stages. Computational modeling showed that the overall change was reduced feedback sensitivity in both OCD groups. ConclusionsBoth perseveration and increased shifting can be observed in OCD, depending on test conditions including the predictability of reinforcement. Perseveration was related to clinical severity and remediated by serotonergic medication.

Unveiling the Excited State Dynamics of Indole in Solution.

In this paper, we reconstruct in detail the dynamics of the emitting electronic excited state of aqueous indole, investigating its relaxation mechanism and kinetics to be related to the time-dependent fluorescence signal. Taking advantage of the results shown in a very recent paper, we were able to model the relaxation process in solution in terms of the transitions between two gas-phase singlet electronic states (1La and 1Lb), subsequently irreversibly relaxing to the gas-phase singlet dark state (1πσ*). A comparison of the results with the available experimental data shows that the relaxation mechanism we obtain by our theoretical-computational model is reliable, reproducing rather accurately all the experimental observables.

Dependence of cardiomyocyte force, velocity, and power generation on ATP concentration

Theoretical analysis and computer modeling of myocardial energy metabolism under physiological and heart failure conditions predicts that cytoplasmic ATP and ADP levels both fall roughly in proportion to reductions in total adenine nucleotide pool observed in heart failure. Assessing sub-maximal force and velocity in loaded myocardial muscle at MgATP levels in the range of 2 to 8 mM, Beard et al. ( Biophys. J. 2022. 121: 3213–3223) observed effects of MgATP on myocardial power generation that suggest that although maximal force and velocity are not substantially sensitive to differences in [MgATP] that occur in the normal versus failing myocardium, maximal power generation, which occurs at submaximal force and velocity, is sensitive to [MgATP]. Previously developed computational models are not able to reproduce the observed dependence on MgATP. The goals of the present study are to construct and analyze a computational model of muscle dynamics to analyze data on the dependence of maximal force, velocity, and power generation on [MgATP] in order to determine a potential mechanism to explain the MgATP-dependent phenomena. Model development and identification was guided by dynamic measurements on permeabilized mouse trabecular fibers. The data include force-velocity relation and time constant of tension development. The mathematical model used to simulate cardiomyocyte crossbridge mechanics was based on the previous crossbridge and calcium models from Tewari et al. (J Mol Cell Cardiol, 2016. 96: 11-25) and Campbell et al. (Biophys J, 2018. 115: 543-553). The developed model includes strain- and metabolite-dependent transition between attachment states, and ATP-dependent destabilization of the super-relaxed (SRX) myosin state. Model-based analysis of force and velocity dyanmics is consistent with the hypothesis that ATP assocition with the myosin protein influence the kinetics and thermodynamics of transitions between the SRX and disorded (DRX) states. Funding: Department of Veterans Affairs Merit Review Award I01BX000740 (A.J.B.) and National Heart, Lung, and Blood Institute grant R01 HL154624 (A.J.B., D.A.B.) This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Theoretical-Computational Modeling of CD Spectra of Aqueous Monosaccharides by Means of Molecular Dynamics Simulations and Perturbed Matrix Method.

The electronic circular dichroism (ECD) spectra of aqueous d-glucose and d-galactose were modeled using a theoretical-computational approach combining molecular dynamics (MD) simulations and perturbed matrix method (PMM) calculations, hereafter termed MD-PMM. The experimental spectra were reproduced with a satisfactory accuracy, confirming the good performances of MD-PMM in modeling different spectral features in complex atomic-molecular systems, as already reported in previous studies. The underlying strategy of the method was to perform a preliminary long timescale MD simulation of the chromophore followed by the extraction of the relevant conformations through essential dynamics analysis. On this (limited) number of relevant conformations, the ECD spectrum was calculated via the PMM approach. This study showed that MD-PMM was able to reproduce the essential features of the ECD spectrum (i.e., the position, the intensity, and the shape of the bands) of d-glucose and d-galactose while avoiding the rather computationally expensive aspects, which were demonstrated to be important for the final outcome, such as (i) the use of a large number of chromophore conformations; (ii) the inclusion of quantum vibronic coupling; and (iii) the inclusion of explicit solvent molecules interacting with the chromophore atoms within the chromophore itself (e.g., via hydrogen bonds).

Networks of splicing processors: simulations between topologies

Networks of splicing processors are one of the theoretical computational models that take inspiration from nature to efficiently solve problems that our current computational knowledge is not able to. One of the issues restricting/hindering is practical implementation is the arbitrariness of the underlying graph, since our computational systems usually conform to a predefined topology. We propose simulations of networks of splicing processors having arbitrary underlying graphs by networks whose underlying graphs are of a predefined topology: complete, star, and grid graphs. We show that all of these simulations are time efficient in the meaning that they preserve the time complexity of the original network: each computational step in that network is simulated by a fixed number of computational steps in the new topologic networks. Moreover, these simulations do not modify the order of magnitude of the network size.

Recent Progress in Theoretical Studies and Computer Modeling of Non-Covalent Interactions

It is not at all surprising that the topic of non-covalent interactions, a key pillar of supramolecular chemistry, has seen interest grow enormously within the last decade [...]

Lorentz quantum computer

A theoretical model of computation is proposed based on Lorentz quantum mechanics. Besides the standard qubits, this model has an additional bit, which we call hyperbolic bit (or hybit in short). A set of basic logical gates are constructed and their universality is proved. As an application, a search algorithm is designed for this computer model and is found to be exponentially faster than Grover’s search algorithm.

Modelling of space antenna deployment using open source software

The goal of this article is to develop a dynamic model of a space antenna with the pantograph structure and to study the processes of its deployment using open-source software. Methods of theoretical mechanics, multibody dynamics, computational mechanics, and computer modeling were used in the research. A mesh antenna of the novel design, which is recommended for mini-satellites, is considered as the object for modeling. The most significant difference between this antenna and others is the design of the support ring in the form of a pantograph. To develop a model of the space antenna dynamics and implement it using open-source software, some simplifications were made due to the complexity of the structure. The antenna model is represented as a system of rigid and flexible bodies connected by hinges. Carbon fiber rods are modeled with the help of a flexible finite element using the method of absolute nodal coordinates, which allows one to model large deformations of the structure. Aluminum hinge assemblies are modeled as several rotation joints connected by conventional rigid elements. The main modeled properties of these hinge assemblies are the stiffness, location, and direction of the axes of rotation of the hinges. The tension forces created by the stretched mesh are modeled using springs. The cable drive of the antenna deployment mechanism is modeled as a load acting on the corresponding elements in defined local positions. An algorithm for building a model of the space antenna to simulate the reflector deployment process in the HotInt open-source software is presented. Using the built model, antenna deployment simulations are carried out for different cases, which differ in the forces used for the deployment. Values of deployment time, variations of angles between the V-folded bars, and tensions in the diagonal rods of the antenna sections during the antenna deployment are obtained. The approach proposed in the article can be implemented using free software, ensures flexibility of modeling, and reduces the model development time.

Flight control and collision avoidance of three UAVs following each other

An unmanned aerial vehicle is a hardware and software complex with multi-purpose control. Unlike manned aviation, an unmanned aerial vehicle requires additional modules in its control system. These include the drone itself, the operator's workplace, software, data transmission lines and blocks necessary to fulfil the set flight objectives. The range of applications of unmanned aerial vehicles in the civil sector is not limited, but with the current state of the legal framework for the use of airspace, flight operations are somewhat difficult. The article formulates the main scientific position on the methodology of solving auxiliary tasks set in the work. The methodology specifies the main research stages, and it is a generalized methodological algorithm for the implementation of scientific research, which provides theoretical developments, field observations and simulation computer modelling. As a result of the study, it was found that the motion control systems of unmanned aerial vehicles are used for the process of their differentiation by the principle of complete external control, the advantages of which are considered in the work. For external control of divergence process of unmanned aerial vehicles, a method is considered for assessing the situation of convergence of unmanned aerial vehicles and choosing the manoeuvre of their difference using the area of dangerous courses, unmanned aerial vehicles approach, and it is possible to take into account the inertia of unmanned aerial vehicles when turning and the presence of navigational hazards that are in the manoeuvring area.

Theoretical-Computational Modeling of Gas-State Thermodynamics in Flexible Molecular Systems: Ionic Liquids in the Gas Phase as a Case Study.

A theoretical-computational procedure based on the quasi-Gaussian entropy (QGE) theory and molecular dynamics (MD) simulations is proposed for the calculation of thermodynamic properties for molecular and supra-molecular species in the gas phase. The peculiarity of the methodology reported in this study is its ability to construct an analytical model of all the most relevant thermodynamic properties, even within a wide temperature range, based on a practically automatic sampling of the entire conformational repertoire of highly flexible systems, thereby bypassing the need for an explicit search for all possible conformers/rotamers deemed relevant. In this respect, the reliability of the presented method mainly depends on the quality of the force field used in the MD simulations and on the ability to discriminate in a physically coherent way between semi-classical and quantum degrees of freedom. The method was tested on six model systems (n-butane, n-butane, n-octanol, octadecane, 1-butyl-3-methylimidazolium hexafluorophosphate and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic pairs), which, being experimentally characterized and already addressed by other theoretical-computational methods, were considered as particularly suitable to allow us to evaluate the method's accuracy and efficiency, bringing out advantages and possible drawbacks. The results demonstrate that such a physically coherent yet relatively simple method can represent a further valid computational tool that is alternative and complementary to other extremely efficient computational methods, as it is particularly suited for addressing the thermodynamics of gaseous systems with a high conformational complexity over a large range of temperature.

Modeling Charge Transfer Reactions by Hopping between Electronic Ground State Minima: Application to Hole Transfer between DNA Bases.

In this paper, we extend the previously described general model for charge transfer reactions, introducing specific changes to treat the hopping between energy minima of the electronic ground state (i.e., transitions between the corresponding vibrational ground states). We applied the theoretical-computational model to the charge transfer reactions in DNA molecules which still represent a challenge for a rational full understanding of their mechanism. Results show that the presented model can provide a valid, relatively simple, approach to quantitatively study such reactions shedding light on several important aspects of the reaction mechanism.

Development and validation of theoretical-computational model for nuclear powered hydrogen production: A case study for Saudi Arabia

Recently, the Kingdom of Saudi Arabia announced plans to build a green hydrogen power plant that will run on 4 GW of renewable energy, the largest hydrogen production project in the world to date. This is a defining moment for the Kingdom's development and a key element of Saudi Vision 2030, which contributes to the strategy for clean energy and a circular economy, and nuclear cogeneration for hydrogen production can support such a pragmatic move. Therefore, the current study focuses on the production of hydrogen gas in a high-temperature gas-cooled reactor (HTGR) using the thermochemical energy of sodium iodine (SI) for water decomposition. The study investigates the performance of the HTGR cogeneration system for both electricity and hydrogen gas production under different operating scenarios. Based on the developed deterministic mathematical model, which includes 1800 operating scenarios, an energy-related cost analysis is provided. The techno-economic analysis showed that the maximization of hydrogen production for the HTGR process results in a maximum thermal exergy with an energetic efficiency of 70 % and a production rate of 105,615 m3/h at the lowest production cost of 7.7 cents/m3. The cost of electricity production from cogeneration was calculated as 3.23 cents/kWh, compared to other renewable energy sources (5 cents/kWh). This optimal operating scenario was selected to provide information needed to attract investment in Saudi Arabia for the deployment of this promising cogeneration technology based on deterministic exergy cost analysis approach.