Computational Modeling Methods Research Articles

ЦИФРОВОЙ ПОДХОД К ФОРМИРОВАНИЮ СПОСОБОВ ДЕЙСТВИЙ ПО МАТЕМАТИЧЕСКОМУ МОДЕЛИРОВАНИЮ В ИНЖЕНЕРНОМ ОБРАЗОВАНИИ

One of the ways to increase the efficiency of higher engineering education is its digitalization, aimed at integrating mathematical and computer modeling. In this regard, there is a problem of creating a training system for future engineers at a technical university aimed at forming methods of mathematical and computer modeling based on the integration of mathematical and applied science in combination with digital technologies. This approach involves the use of modern information and communication technologies (ICT), simulation tools, application software packages at all stages of students' study of basic and variable disciplines. The authors refer to such disciplines: higher mathematics as a means of fundamentalizing the basic training of a future engineer; applied mathematics as a means of implementing higher mathematics in building models of technical processes and systems; operations research, optimization methods, multidimensional statistical and factor analysis as varieties of professional disciplines reflecting the practical orientation of engineering training. The article presents a system of teaching mathematical modeling to students of technical training areas in the context of higher engineering education. The main idea is the introduction of mixed and hybrid technologies for teaching students, providing the process of setting and solving mathematical modeling tasks based on modern ICT tools, including the author's software product "Automated workplace "Teacher – student", which provide an opportunity for future engineers to form both mathematical and digital competencies necessary they are interested in their future professional activities.

Finite element simulation for microclimate normalization at the crane operator workplace

The object of the study is the cabins of technological machines, where an unfavorable microclimate is observed. The method of mathematical and computer modeling used in the study is relevant and allows significantly speed up the design process due to the transition from a large number of field tests to virtual numerical experiments. The adaptation of the known mathematical models of thermal radiation and a model of a continuous medium based on the Navier-Stokes and heat transfer equations to the solution of the problem of determining the thermodynamic parameters in the cabins of technological machines has been carried out. The methodology for calculating and selecting the main equipment of the climatic system of the crane cabins has been clarified based on the developed finite element 3D models of the cabins. In addition, thermal protection equipment was used to reduce the load on the climate system. The using of modeling permit significantly speeds up the design process.

The current state of district heating processes in China and directions for the development of the methodological and instrumental base to support them

The article assesses the current state of district heating systems covering more than 100 cities in northern China. The main features of such systems, as well as the problems that arise during their design and operation, are disclosed. The relevance of the development and application of independent methods of mathematical and computer modeling to solve these problems is disclosed. As a methodological basis, it is proposed to use the modern achievements of the theory of hydraulic circuits developed at the Energy System Institute of the Siberian Branch of the Russian Academy of Sciences. The characteristics of the possibilities of the software tools available here are given. The main directions and prospects for the development of these scientific, methodological and software developments are disclosed.

Изменение температуры плавления металлов с ростом давления

A new analytical (i.e., without computer modeling) method for calculating the dependence of the melting temperature (Tm) of a single-component crystal on pressure (P) is proposed. The method is based on the delocalization melting criterion and does not contain fitting constants. The baric dependences of the melting temperature Tm(P) and its pressure derivative Tm(P) for gold, platinum and niobium in the pressure range: P = 0 – 1000 GPa were calculated by this method. It was shown that the dependences calculated by this method for gold and platinum agree better with the experimental data than the dependences obtained by computer simulation methods. For niobium, the calculated dependence Tm(P) turned out to be steeper, i.e., the value Tm(P) turned out to be larger than in the experiment. It was indicated that this discrepancy might be due both to a decrease in the Lindemann parameter with increasing pressure and to a redistribution of electrons on the s-d-orbitals during compression of transition metals with a BCC structure.

Change in the melting temperature of metals with an increase in pressure

A new analytical (i.e., without computer modeling) method for calculating the dependence of the melting temperature Tm of a single-component crystal on pressure P is proposed. The method is based on the delocalization melting criterion and does not contain fitting constants. The baric dependences of the melting temperature Tm(P) and its pressure derivative T'm(P) for gold, platinum and niobium in the pressure range: P=0-1000 GPa were calculated by this method. It was shown that the dependences calculated by this method for gold and platinum agree better with the experimental data than the dependences obtained by computer simulation methods. For niobium, the calculated dependence Tm(P) turned out to be steeper, i.e., the value T'm(P) turned out to be larger than in the experiment. It was indicated that this discrepancy might be due both to a decrease in the Lindemann parameter with increasing pressure and to a redistribution of electrons on the s-d-orbitals during compression of transition metals with a BCC structure. Keywords: melting point, pressure, interatomic interaction, gold, platinum, niobium.

Computer modeling of robotic systems made of composite materials, analysis of the stress-strain state under dynamic influences

In the present study, a robotic system is considered: a multi-stage semi-natural simulation stand. The stand is designed to simulate the flight characteristics of aircraft instruments in laboratory conditions. The use of such stands can significantly reduce the cost of developing and testing aircraft instruments and contains all the attributes of robotic systems, which allows the developed method of computer modeling and analysis of stands to be applied in the field of robotic systems. The problem is solved by the finite element method. As a result of the study, a technique has been developed for approximating parts that carry out movements: gear rims, bearings, gearboxes, motors in the finite element method. Comparison with the available experimental studies showed the effectiveness of the developed methodology. As the stand material, a composite material is used, which has a high specific strength, which makes it possible to change the physical and mechanical characteristics depending on the location of the composite base in the layers of the multilayer composite structure. A technique has been developed for arranging the base layers in a multilayer composite to obtain maximum strength and rigidity of the stand, which is one of the main factors in the efficiency of the stand. The analysis of the behavior and stress-strain state of the bench under dynamic impact has been carried out.

К ВОПРОСУ ГЕОМЕХАНИЧЕСКОГО ОБОСНОВАНИЯ РАЗРАБОТКИ ГОРЕВСКОГО МЕСТОРОЖДЕНИЯ СВИНЦОВО-ЦИНКОВЫХ РУД

The Gorevskoye lead-zinc ore deposit is unique in terms of metal reserves and ore quality, as well as in terms of geomechanical and hydrogeological development conditions. The deposit is located on the banks of the Angara River, part of the ore bodies goes under the channel. Ore mining is carried out by an open method, in the future it is planned to deepen the quarry to a depth of -435 m and switch to a combined method of mining the deposit. It is noted in this work that increasing the depth of the quarry can change the deformed state of the rock column and cause the development of dangerous deformation processes in it, which in turn can cause the penetration of natural water into mine workings. Some developments of the IPCON RAS on the solution of the issues under consideration are outlined. It is proposed to use a comprehensive, interdisciplinary approach that combines engineering methods of forecasting based on production experience, methods of computer modeling of diverse problems (rock displacement, formation of zones of induced permeability of the massif, filtration, explosive impact) and geomechanical monitoring.

Создание базы данных техногенно-нарушенных территорий Новосибирской области

Today, the problem of assessing the impact of technologically disturbed territories on the environment and analyzing decisions on their further use, taking into account environmental measures, is becoming more and more acute. The article discusses the sources of obtaining initial data for the assessment of technologically disturbed territories and their features when integrated into a single dynamically updated database. The structural elements of such a database and the stored characteristics are described both from the point of view of spatial data and from the ecological state of objects. The article proposes the concept of a multilevel system of various methods of computer modeling of complex, spatially distributed nonlinear systems "natural environment – technological space – man-made disturbed territory". It also describes the general scheme of the repository that solves the task and a set of software solutions that allow automating the processes of collecting and integrating data from open sources to the territory of interest.

Substantiation and development of innovative container technology for rock mass lifting from deep open pits

Purpose. The research purpose is to substantiate the rational parameters of innovative container technology for transporting mine rocks in open pits with account of technological advantages. Methods. The winding machine normal operation was determined by calculation performed. The container metal structure was designed in the environment of the Compass-3D software complex. The structural elements were tested for normal operation using computer modeling methods in the APM WinMachine 9.7 program, which gives the possibility to obtain the strength calculation values. Findings. The results of modeling the stresses on the wall of the container and the frame, as well as the yield strength are presented. The test calculation confirms the technical feasibility for operating the dragline-based mine winding machines. The influence of the container capacity on the performance of the winding machine has been determined and the dependence of the economic efficiency of the container technology introduction at the open pit depth has been revealed. Originality. For the first time, on the basis of computer modeling, the parameters of stress distribution on the container wall have been substantiated when performing a strength calculation. It has been determined that the maximum stress in the container wall is 117.52 N/mm2; the principal stress value is 83.85 N/mm2. The safety factor for yield strength is 1.8. The maximum load acting on the structure is 957.5 kgf, which does not exceed the calculated value. Practical implications. The practical importance is to improve mining efficiency, reduce the cost of transporting rocks and ensure automatic container unloading. The use of replaceable containers in open pits can significantly change the formation principles of shovels and transport complexes, increase their performance and the efficiency of shovels in the main processes.

STUDY OF ABNORMAL INDICATORS OF COAL COKING PROCESS ON THE BASIS OF MACHINE LEARNING

On the basis of computer modeling and machine learning methods, an algorithm for preparing and training data taken from technological databases and journals for the preparation of raw materials for coke production was compiled. After statistical analysis, conclusions were drawn, which were accepted in production for implementation. In a continuous production process, the ability to timely detect defects in equipment and logistics directly affects the economic effect. Any field in the modern world tends to develop artificial intelligence and machine learning technologies. Novokuznetsk enterprises, including metallurgical ones, are also actively developing robots - prompters and systems for predicting product quality. Artificial intelligence is concerned with the task of using computers to understand human intelligence. This is an important direction in the construction of human-like systems. At this stage in the development of machine learning, a number of algorithms and software systems began to be attributed to it, the distinguishing feature of which is that they can solve some problems in the same way as a person thinking about their solution would do. But with respect to actively developing information technologysystems, metallurgical processes live much longer, so finding solutions to combine the knowledge and experience of technologists and artificial intelligence is a difficult but interesting task for finding possible problems in production. Identification of abnormal deviations helps to avoid unplanned downtime, and, accordingly, avoid economic losses. This article is a demonstration of the path that has been taken to combine information technologies in the field of artificial intelligence and metallurgy, namely the production of coking coal, based on the technological indicators of coke production.

Development of recommendations for optimizing the geometry of tower cranes

Problem. Special attention is paid to maintaining tower cranes in good working order and serviceable condition through their proper operation. Unfortunately, violation of the operating rules can lead to an emergency situation. In this case, both the crane operator and other workers on the construction site may be injured. And in some cases even to death. Therefore, the development of measures for safe operation is very important. It is also important to ensure sufficient strength of the load-bearing steel structures, which make up the bulk of the tower cranes, the breakdown of which leads to significant costs to restore the working condition of the tower. Goal. The goal of the work is to develop a method of interactive graphical modeling of three-dimensional models of metal structures with the use of a forced variation of their dimensions in the environment of computer-aided design – Autodesk Inventor package. Methodology. The solution of the set tasks implied the use of computer modeling methods with the use of modern 3-D modeling programs. Experimental studies were also carried out to determine loading modes. Results. A comprehensive methodology has been developed that uses the method of interactive graphical modeling of three-dimensional models of metal structures with a forced variation of their dimensions in the computer-aided design environment - Autodesk Inventor. It allows you to obtain rational parameters of the main elements of the tower crane – tower, boom, and others. This technique significantly increases the productivity and quality of the designer's work and reduces the time for research (tower cranes) and design documentation. Originality. The method of interactive graphic modeling of three-dimensional models of metal structures on the example of the tower crane with the use of a forced variation of their dimensions in the computer-aided design environment – Autodesk Inventor package is offered. Practical value. The use of the proposed methodology will significantly improve the efficiency of the design and operation of tower cranes.

New Enzymatic Targets for Organophosphorus Compounds

It is known that several decarboxylases (aromatic amino acid decarboxylase (AAD), histidine decarboxylase (HD) and glutamate decarboxylase (GD) with different molecular weights catalyze the most important reactions of neurotransmitter and neuromodulator biosynthesis. Pyridoxal phosphate, which serves as a cofactor for these enzymes, is one of organophosphorus compounds (OPC) having a structure similar to highly toxic substances such as warfare agents (WA) sarin, soman, Vx, a substance of type Vx, tabun and the so-called «Novichoks» (A230, A232, A234), as well as pesticides, widely used in agriculture (chlorpyrifos, malathion, glyphosate, mipafox, diazinon, paraoxon), based on their inhibitory effect on cholinesterases (ChE). The purpose of this work was to use computer modeling methods to evaluate the possible binding of various OPC to the catalytic centers of these enzymes instead of a cofactor, as well as similar interactions of decarboxylases (DC) with OPC when the active centers of DC already contain a built-in cofactor. Molecular docking has shown that a number of these OPC can compete with the cofactor for binding to the active centers of DC, and absolutely all the studied OPC (pesticides and WA) create obstacles to embedding the cofactor in the active center of AAD and HD. Such interactions will lead to a decrease in the level of formation of products of the corresponding catalytic reactions (dopamine, serotonin, phenylethylamine, serotonin, γ-aminobutyric acid) and the manifestation of their physiological functions. It was found that in the presence of a cofactor in the active center of the studied DC, the interaction of a number of OPC with the surface of these enzymes near the active center increases and exceeds the strength of the interaction of same enzymes with their typical substrates. At the same time, the maximum interaction that can lead to a significant inactivation of all the studied DC was revealed for the pesticides, while the effect of their presence was lower for WA. One of the highest levels of possible influence on the activity of DC was revealed for chlorpyrifos and diazinon. In total, for DC, the more dangerous substances with high potential neurotoxicity turned out to be not WA at all, including «Novichoks», namely pesticides, which, according to their known effect on ChE, are considered as low-toxic OPC. The conducted new theoretical studies indicate that, firstly, direct experimental studies are required that will confirm the bioinformatics calculations made; secondly, a revision of long-standing approaches to assessing the neurotoxicity of various OPC, based mainly on the use of ChE for these purposes, is necessary; thirdly, it may be necessary to formulate tasks for the development and the use of new systems for the determination of potentially neurotoxic substances, the effect of which will be based on the use of different DC; fourth, to study the possible using DC as a basis for the development of new catalytic enzymatic detoxifiers (antidotes) and CNS regenerators.

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.

Computational modelling of potential Zn-sensitive non-β-lactam inhibitors of imipenemase-1 (IMP-1)

Antibiotic resistance (AR) remains one of the leading global health challenges, mostly implicated in disease-related deaths. The Enterobacteriaceae-producing metallo-β-lactamases (MBLs) are critically involved in AR pathogenesis through Zn-dependent catalytic destruction of β-lactam antibiotics, yet with limited successful clinical inhibitors. The efficacy of relevant broad-spectrum β-lactams including imipenem and meropenem are seriously challenged by their susceptibility to the Zn-dependent carbapenemase hydrolysis, as such, searching for alternatives remains imperative. In this study, computational molecular modelling and virtual screening methods were extensively applied to identify new putative Zn-sensitive broad-spectrum inhibitors of MBLs, specifically imipenemase-1 (IMP-1) from the IBScreen database. Three ligands, STOCK3S-30154, STOCK3S-30418 and STOCK3S-30514 selectively displayed stronger binding interactions with the enzymes compared to reference inhibitors, imipenem and meropenem. For instance, the ligands showed molecular docking scores of −9.450, −8.005 and −10.159 kcal/mol, and MM-GBSA values of −40.404, −31.902 and −33.680 kcal/mol respectively against the IMP-1. Whereas, imipenem and meropenem showed docking scores of −9.038 and −10.875 kcal/mol, and MM-GBSA of −31.184 and −32.330 kcal/mol respectively against the enzyme. The ligands demonstrated good thermodynamic stability and compactness in complexes with IMP-1 throughout the 100 ns molecular dynamics (MD) trajectories. Interestingly, their binding affinities and stabilities were significantly affected in contacts with the remodelled Zn-deficient IMP-1, indicating sensitivity to the carbapenemase active Zn site, however, with non-β-lactam scaffolds, tenable to resist catalytic hydrolysis. They displayed ideal drug-like ADMET properties, thus, representing putative Zn-sensitive non-β-lactam inhibitors of IMP-1 amenable for further experimental studies.

In silico prediction of persistent, mobile, and toxic pharmaceuticals (PMT): A case study in São Paulo Metropolitan Region, Brazil

Computational modelling (in silico) methods based on quantitative structure-activity relationship ((Q)SAR) models, are powerful tools for the assessment of the potential “persistency, mobility, and toxicity” (PMT) of pharmaceuticals compounds. Moreover, the use of (Q)SAR models, is recommended by European Union’s REACH Regulation. In this context, the aims of this research were estimating, for the first time and based by REACH guidelines, the PMT potentials of 115 most sold pharmaceuticals in São Paulo Metropolitan Region (a megacity with 21 million of Brazilian), through five (Q)SAR updated models, namely: the OPERA QSAR; the VEGA QSAR (Version 1.1.5); the EPI Suite (Version 4.11); the ECOSAR (Version, 2.0); and the QSAR Toolbox (Version 4.5). This study prioritized the in-silico predictions from the OPERA and the VEGA, because both QSARs can generate reliable predictions, i.e., they have detailed information about the applicability domains. In silico predictions were performed considering ten endpoints: (i) Molecular weight (MW); (ii) “STP total removal”: Sewage Treatment Plant; (iii) Octanol-water partition coefficient (KOW); (iv) Predicted ready biodegradability; (v) Soil organic adsorption coefficient (KOC); (vi) “Short-term and long-term ecological assessments”; (vii) “Carcinogenicity”; (viii) “Mutagenicity”; (ix) “Estrogen receptor binding”; (x) “Cramer decision tree”. The main results showed that: (a) These 115 pharmaceuticals cover a wide range of so-called small molecules (range from 100 to 600 MW); (b) In STP, a predicted removal lower than 10 % was found for 76 pharmaceuticals; (c) Additionally, 101 chemicals has low (Log KOW <2.5), or medium sorption potential (2.5< log KOW <4.0); (d) Ultimately, 36 PPCPs were considered “persistent” after a weight-of-evidence assessment. In addiction, 17 among these 36 persistent chemicals, were classified as “very mobile” in water (log KOC <3). Finally, only three among 17 PPCPs, namely ciprofibrate, fluconazole and metoclopramide, exhibited one or more toxic characteristics (described in items vi – x). These results it will be possible to alert about the potential risks arising from the indiscriminate disposal of these PPCPs along the water sources of this Brazilian mega metropolis.

Reconstruction of Cooperite (PtS) Surfaces: A DFT-D+U Study.

Cooperite (PtS) is one of the main sources of platinum in the world and has not been given much attention, in particular from the computational aspect. Besides, the surface stability of cooperite is not fully understood, in particular the preferred surface cleavage. In the current study, we employed computer modeling methods within the plane-wave framework of density functional theory with dispersion correction and the U parameter to correctly predict the bulk and surface properties. We reconstructed and calculated the geometries and surface energies of (001), (100), (101), (112), (110), (111), and (211) cooperite surfaces of stoichiometric planes. The Pt d-orbitals with U = 4.5 eV and S p-orbitals with U = 5.5 eV were found optimum to correctly predict a band gap of 1.408 eV for the bulk cooperite model, which agreed with an experimental value of 1.41 eV. The PtS-, Pt-, and S-terminated surfaces were investigated. The structural and electronic properties of the reconstructed surfaces were discussed in detail. We observed one major mechanism of relaxation of cooperite surface reconstructions that emerged from this study, which was the formation of Pt-Pt bonds. It emanated that the (110) and (111) cooperite surfaces underwent significant reconstruction in which the Pt2+ cation relaxed into the surface, forming new Pt-Pt (Pt2 2+) bonds. Similar behavior was perceived for (101) and (211) surfaces, where the Pt2+ cation relaxed inward and sideways on the surface, forming new Pt-Pt (Pt2 2+) bonds. The surface stability decreased in the order (101) > (100) ≈ (112) > (211) > (111) > (110) > (001), indicating that the (101) surface was the most stable, leading to an octahedron cooperite crystal morphology with truncated corners under equilibrium conditions. However, the electronic structures indicated that the chemical reactivity stability of the surfaces would be determined by band gaps. It was found that the (112) surface had a larger band gap than the other surfaces and thus was a chemical stability competitor to the (101) surface. In addition, it was established that the surfaces had different reactivities, which largely depended on the atomic coordination and charge state based on population atomic charges. This study has shown that cooperite has many planes/surface cleavages as determined by the computed crystal morphology, which is in agreement with experimental X-ray diffraction (XRD) pattern findings and the formation of irregular morphology shapes.

Nanoporous Alumina Support Covered by Imidazole Moiety-Based Ionic Liquids: Optical Characterization and Application.

This work analyzes chemical surface and optical characteristics of a commercial nanoporous alumina structure (NPAS) as a result of surface coverage by different imidazolium-based ionic liquids (1-butyl-3-metylimidazolium hexafluorophosphate, 3-methyl-1-octylimidazolium hexafluorophosphate, or 1-ethyl-3-methylimidazolium tetrafluoroborate). Optical characteristics of the IL/NPAS samples were determined by photoluminescence (at different excitation wavelengths (from 300 nm to 400 nm), ellipsometry spectroscopy, and light transmittance/reflectance measurements for a range of wavelengths that provide information on modifications related to both visible and near-infrared regions. Chemical surface characterization of the three IL/NPAS samples was performed by X-ray photoelectron spectroscopy (XPS), which indicates almost total support coverage by the ILs. The IL/NPAS analyzed samples exhibit different photoluminescence behavior, high transparency (<85%), and a reflection maximum at wavelength ~380 nm, with slight differences depending on the IL, while the refractive index values are rather similar to those shown by the ILs. Moreover, the illuminated I−V curves (under standard conditions) of the IL/NPAS samples were also measured for determining the efficiency energy conversion to estimate their possible application as solar cells. On the other hand, a computational quantum mechanical modeling method (DFT) was used to establish the most stable bond between the ILs and the NPAS support.

Synthesis, testing, and computational modeling of pleuromutilin 1,2,3-triazole derivatives in the ribosome

Pleuromutilin antimicrobials have given rise to the most recently FDA approved class of antibiotics for systemic human use. In this work, we describe a synthesis, assay, modeling approach to pleuromutilin development for the highly complex bacterial ribosome. Libraries of substituted 1,2,3-triazole derivatives were synthesized at the pleuromutilin C20 position by applying a recent anti-Markovnikov hydroazidation protocol to directly install an azido group, and at the C22 position through established methods. To learn about the interactions of these libraries with the ribosome and assess the potential for subsequent derivatization, an unbiased computational modeling method was used to biochemically rationalize binding modes of the C20 and C22 pleuromutilin derivatives. A pattern emerged where the triazole and its pendant chain, be it off the C20 or C22 position, moved to occupy the space vacated by the C22 sulfide group of clinical pleuromutilin compounds. Subsequent activity testing and comparative ranking of the computationally docked derivatives to the in vitro activity results showed a high predictability rating for the C22 substituted compounds. These combined investigations reveal potential restrictions and sites for expansion, paving the way for the development of future pleuromutilin derivates and other ribosome targeting antibiotics.

A novel AC chopper integrated with active measurement of wideband impedance for wind power system

Large-scale wind farms are susceptible to oscillations like any other power systems with high penetration of power electronics, whose characteristics of wideband impedance hold the key to resolving this issue. However, due to the high cost of impedance measurements for power systems, computational modelling methods are usually used, accuracy of which is difficult to be verified. This paper proposes a novel AC chopper integrated with active measurement of wideband impedance (AIM-ACC), which can be slightly modified from the existing energy consuming devices in wind power systems. With the help of the proposed Reversed-phase Chirp Pulse Width Modulation (RC-PWM) signal, the AIM-ACC generates chopper current within a desired wide frequency band, avoiding the spectral shifting effects of sinusoidal voltages. Thus, the impedance characteristics of wind system are obtained by measuring the injected current and its corresponding voltage, with fast excitation time, good controllability and high accuracy. Finally, the verification of an experiment with single-phase branch and a simulation with the proposed AC chopper in wind power system was carried out for the effectiveness of the proposed method.

The Effects of Tinnitus in Probabilistic Learning Tasks: Protocol for an Ecological Momentary Assessment Study.

Chronic tinnitus is an increasing worldwide health concern, causing a significant burden to the health care system each year. The COVID-19 pandemic has seen a further increase in reported cases. For people with tinnitus, symptoms are exacerbated because of social isolation and the elevated levels of anxiety and depression caused by quarantines and lockdowns. Although it has been reported that patients with tinnitus can experience changes in cognitive capabilities, changes in adaptive learning via decision-making tasks for people with tinnitus have not yet been investigated. In this study, we aim to assess state- and trait-related impairments in adaptive learning ability on probabilistic learning tasks among people with tinnitus. Given that performance in such tasks can be quantified through computational modeling methods using a small set of neural-informed model parameters, such approaches are promising in terms of the assessment of tinnitus severity. We will first examine baseline differences in the characterization of decision-making under uncertainty between healthy individuals and people with tinnitus in terms of differences in the parameters of computational models in a cross-sectional experiment. We will also investigate whether these computational markers, which capture characteristics of decision-making, can be used to understand the cognitive impact of tinnitus symptom fluctuations through a longitudinal experimental design. We have developed a mobile app, AthenaCX, to deliver e-consent and baseline tinnitus and psychological assessments as well as regular ecological momentary assessments (EMAs) of perceived tinnitus loudness and a web-based aversive version of a probabilistic decision-making task, which can be triggered based on the participants' responses to the EMA surveys. Computational models will be developed to fit participants' choice data in the task, and cognitive parameters will be estimated to characterize participants' current ability to adapt learning to the change of the simulated environment at each session when the task is triggered. Linear regression analysis will be conducted to evaluate the impacts of baseline tinnitus severity on adapting decision-making performance. Repeated measures linear regression analysis will be used to examine model-derived parameters of decision-making in measuring real-time perceived tinnitus loudness fluctuations. Ethics approval was received in December 2020 from Dublin City University (DCUREC/2021/070). The implementation of the experiments, including both the surveys and the web-based decision-making task, has been prepared. Recruitment flyers have been shared with audiologists, and a video instruction has been created to illustrate to the participants how to participate in the experiment. We expect to finish data collection over 12 months and complete data analysis 6 months after this. The results are expected to be published in December 2023. We believe that EMA with context-aware triggering can facilitate a deeper understanding of the effects of tinnitus symptom severity upon decision-making processes as measured outside of the laboratory. PRR1-10.2196/36583.