Formation Of Paths Research Articles

Model of Adaptive System for Mathematical Training of Students within eLearning Environment

The article discusses issues related to the design, development and implementation of the model of adaptive system for mathematical training of students within eLearning environment. It proposes a systematic set of scientific, theoretical and methodological provisions and approaches that determine the design of the model. The research objective of the paper is designing, developing and implementing a model of the adaptive e-learning system for students to improve their mathematical skills. The article gives the definition of the adaptive system for mathematical training of students. It describes the algorithm of adaptive learning of students within the system in the form of a sequence of operations and actions focused on achieving the learning outcomes, including diagnostics and detailing of personal student’s characteristics; designing a student model based on personal student’s characteristics and preferences; differentiation and selection of educational technologies, resources and teaching methods depending on personal student’s characteristics and preferences; formation and provision of an individual learning path to a student; assessment and analysis of student’ performance. In the work the authors used theoretical, empirical and mathematical research methods. The article gives the results of a pedagogical experiment on the use of the adaptive system for mathematical training of students within eLearning environment in the educational process of the higher educational institution, which proves a positive dynamics in the level of mathematical preparedness of students studying within the proposed adaptive system.

Magnetic‐Oriented Nickel Particles and Nickel‐Coated Carbon Nanotubes: An Efficient Tool for Enhancing Thermal Conductivity of PDMS Composites

AbstractIn this study, PDMS composites are thermally cured with nickel particles and nickel‐coated carbon nanotubes as fillers. Both fillers are oriented with the aim to increase the thermal conductivity of the silicone polymer network, due to the formation of a continuous thermal path. Scanning electron microscopy (SEM) gives a picture of the polymer network's morphology, proving the effective alignment of the nickel particles. Rheology and attenuated total reflectance Fourier transform infrared spectroscopy (ATR‐FTIR) studies confirm the full curing of the silicon network and no influence in the curing kinetics of the type and content of fillers and their orientation. Dynamic mechanical thermal analysis (DMTA) and tensile analysis show instead different thermo‐mechanical behavior of the polymer network due to the presence of different fillers, different fillers percentage, and orientation. Finally, the thermal transmittance coefficient (k) is studied by means of hot disk analysis, revealing the increment of almost 200% due to magnetic filler orientation.

The influence of alloying on slip intermittency and the implications for dwell fatigue in titanium

Dwell fatigue, the reduction in fatigue life experienced by titanium alloys due to holds at stresses as low as 60% of yield, has been implicated in several uncontained jet engine failures. Dislocation slip has long been observed to be an intermittent, scale-bridging phenomenon, similar to that seen in earthquakes but at the nanoscale, leading to the speculation that large stress bursts might promote the initial opening of a crack. Here we observe such stress bursts at the scale of individual grains in situ, using high energy X-ray diffraction microscopy in Ti–7Al–O alloys. This shows that the detrimental effect of precipitation of ordered Ti3Al is to increase the magnitude of rare pri〈a〉 and bas〈a〉 slip bursts associated with slip localisation. By contrast, the addition of trace O interstitials is beneficial, reducing the magnitude of slip bursts and promoting a higher frequency of smaller events. This is further evidence that the formation of long paths for easy basal plane slip localisation should be avoided when engineering titanium alloys against dwell fatigue.

Atomic-layer-deposited TiO2 and SnO2 coupled with CdS as double buffer layers for HTL-free Sb2S3 thin-film solar cells

The application of double buffer layers has been proven to be a beneficial approach for the enhancement of the power conversion efficiency (PCE) of antimony sulfide (Sb2S3) thin-film solar cells (TFSCs). Recently, solution-processed SnO2/CdS, TiO2/CdS, ZnMgO/CdS, and ZnSnO/CdS electron transport layers (ETLs) have been investigated as double buffer layers for Sb2S3 TFSCs. Herein, atomic-layer-deposited (ALD) SnO2 and TiO2 ETLs were applied as a double buffer layer with CdS for Sb2S3 TFSCs. The Sb2S3 absorber was deposited using a facile hydrothermal method. The TFSC devices were fabricated based on FTO/SnO2/CdS/Sb2S3/Au or FTO/TiO2/CdS/Sb2S3/Au structure without hole transport layers (HTLs). Experimental analysis revealed the reduction of the surface roughness of ETLs and decreased unfavorable (hk0) orientation of the Sb2S3 absorber after utilizing double buffer layers. Initially, incomplete nucleation of Sb2S3 was observed on SnO2 and TiO2 ETLs, which resulted in the formation of a shunting path. Conversely, complete nucleation of Sb2S3 was observed on CdS and double buffer layers. The highest PCEs of 3.98% and 4.23% were obtained for SnO2/CdS and TiO2/CdS double-buffer-layer-based cells with improvements exceeding 1% compared with the reference CdS buffer layer. Additionally, improvements in open-circuit voltage (VOC) of the order of ∼25 mV and ∼45 mV were respectively observed for SnO2/CdS (VOC = 0.676 V) and TiO2/CdS (VOC = 0.696 V) double-buffer-layer-based devices compared with the reference CdS buffer layer (VOC = 0.648 V). The enhanced device properties are mainly attributed to the improved charge carrier collection and formation of suitable band offset at the absorber and ETLs interfaces.

Spatial-Temporal Differentiation and Dynamic Evolution of Digital Finance Inclusive Development in the Yangtze River Delta Economic Cluster of China

Clarifying the sources of the digital finance inclusive development gap helps profoundly understand the regional characteristics of inclusive digital finance and benefits and formulate and implement specific policies scientifically and reasonably. Based on the 2011–2020 “Peking University Digital Finance Inclusive Index,” this study explores the regional disparity in digital finance inclusive development and its sources in the Yangtze River Delta economic cluster using the methods of the center of gravity shift, standard deviation ellipse, nested Theil index difference decomposition, and Kernel density. We found that inclusive digital finance shows a rising trend year by year, with evident heterogeneity and spatial agglomeration characteristics; interprovincial differences are the primary sources of the overall differences in inclusive digital finance in the Yangtze River Delta. The spatial effect of digital inclusion finance between the Yangtze River Delta regions has continuity. Because of the significant positive spatial correlation of digital inclusion finance between regions, digital inclusion finance in this region is vulnerable to potential shocks from neighboring regions. Moreover, with or without the spatial lag term, the level of inclusive digital finance in all regions of the Yangtze River Delta shows a leap forward. This paper looks at the regional gap of inclusive digital finance and its structural decomposition in the Yangtze River Delta city cluster from three perspectives: time trend, spatial structure, and dynamic evolution. This gives an empirical basis for the different kinds of digital finance inclusive development policies and a guide for making decisions to speed up the formation of a regional digital finance inclusive synergistic development path.

Highly water-dispersed composite of cellulose nanofibers and boron nitride nanosheets

In this work, a composite of cellulose nanofibers (CNFs) and boron nitride nanosheets (BNNSs) with high dispersity in water is prepared via the combination of ball-milling and high-pressure homogenization, which is then transformed into paper-like film by vacuum assisted filtering and drying. The obtained CNF/BNNS dispersions can stably exist over 30 days without the observation of sediments. CNFs as a medium of ball-milling can protect the exfoliated BNNSs from being reaggregation and severely destroyed in violent collisions, and the BNNSs and CNFs can promote their exfoliation with each other. The hydrophilicity and electrostatic repulsion of CNFs, as well as the strong interfacial interactions and stereo-hindrance effects between one-dimensional (1D) CNFs and two-dimensional (2D) BNNSs are the reasons for the high dispersity of the composite in water, which in turn results in the favorable mechanical properties of the formed films. Although the introduction of BNNSs lowers the stress, strain, and toughness of the neat CNF films, but increases their modulus due to the stiffness of BNNSs. However, the thermal conductivities of the homogenized samples are inferior to the unhomogenized ones, as the decreased lateral sizes and excellent dispersibility of BNNSs are unfavorable to the formation of connective path of thermal conduction.Graphical abstract

Vertically oriented 2D layered perovskite-based resistive random access memory (ReRAM) crossbar arrays

Resistive random-access memory (ReRAM) based on 2D layered perovskites have recently emerged as a new class of data storage devices, and the switching materials used in these devices have attracted extensive attention in recent years. There is a certain amount of variability in ReRAM owing to the stochastic nature of the formation and rupture of the conductive path, causing failure of the switching operation in the memory array. In this work, we fabricated both randomly and vertically oriented PEA2MA4Pb5I16-based ReRAM devices and conducted comparative studies of their switching variability. We demonstrated the formation of vertical alignment in PEA2MA4Pb5I16 films using methylammonium chloride (MACl) additives. Thereafter, the fabrication of 8×8 ReRAM crossbar arrays by patterning perovskites (∼600μm) and electrodes (line width ∼ 5 μm) using photolithography and e-beam lithography is demonstrated, and the resistive switching characteristics of both samples are discussed. Both cycle-to-cycle and device-to-device switching uniformity were improved in the vertically oriented film-based ReRAM devices, which can be explained by the narrow distribution of the energy barriers for VI migration owing to the vertically aligned charge transport path. These results suggest that vertically oriented 2D layered perovskites have great potential in ReRAM devices with improved switching uniformity.

Effects of Bi substitution on electroresistance behaviours in La0.8-xBixNa0.2MnO3 manganites

The observation of the electroresistance (ER) effect related to the reduction of resistivity under increased applied current indicates the potential of manganite material for next-generation spintronic-based devices. The observed behaviour was attributed to the presence of magnetic inhomogeneity. However, such relation is still not well understood, hence the current-induced effect on the resistivity in monovalent-doped La0.8-xBixNa0.2MnO3 (x = 0–0.20) manganite prepared via solid-state method is reported. All samples exhibited low resistivity in the temperature ranges of 30 K–300 K under a higher applied current of 5 mA compared with 1 mA, leading to the observation of the ER effect. The reduction of resistivity in the metallic region was due to the enhancement of DE itinerant hopping and the decrease in the scattering effect of conduction electrons, whereas in the insulating region, resistivity reduction is suggested to be related to the weakening of the electron–lattice attraction, as indicated by the reduction in activation energy (Ea) of charge carriers. Both x = 0.15 and x = 0.20 samples respectively exhibited large ER effects of 158% and 171% at 300 K amongst the studied samples. The enhancement of ER with Bi substitution is suggested due to the presence of magnetic inhomogeneities induced by MnO6 distortion which favours the formation of filamentary conduction paths under the presence of high applied current. The findings indicate that Bi substitution in La0.8-xBixNa0.2MnO3 (x = 0–0.20) manganites enhanced the sensitivity to the changes in electric field which shows that the investigated samples could be potentially used for non-volatile memory devices.

Preparation of VCo-MOF@MXene composite catalyst and study on its removal of ciprofloxacin by catalytically activating peroxymonosulfate: Construction of ternary system and superoxide radical pathway

The synergistic effect between transition metal active centers and the generation of multiple removal pathways has a significant impact on the catalytic activation efficiency of peroxymonosulfate. In this work, a kind of composite catalyst was prepared by growing VCo-metal–organic frameworks (VCo-MOF) in-situ on the surface of Ti3C2Tx by a solvothermal method. The morphology and structure are characterized by Transmission Electron Microscope (TEM), Energy Dispersion Spectrum (EDS), Atomic Force Microscope (AFM), etc. Response surface methodology was used to optimize the experimental conditions. Only 5 mg catalyst can be used to effectively activate PMS and remove 96.14 % ciprofloxacin (CIP, 20 mg/L) within 30 min. The removal effect of catalyst on CIP in different actual water environment was explored. In addition, the fluorescence spectrum test also verified the effective removal of ciprofloxacin. V-Co-Ti ternary system provides a wealth of active sites for CIP removal. Cyclic voltammetry (CV) and lear sweep voltammetry (LSV) tests showed the existence of the electron transfer pathway. The results of density functional theory (DFT) calculation show that VCo-MOF@Ti3C2Tx has excellent adsorption and activation ability for PMS. At the same time, the hydrophilicity of the catalyst makes PMS more inclined to react with water molecules, which promotes the formation of a unique superoxide radical path.

Reversible electrical percolation in a stretchable and self-healable silver-gradient nanocomposite bilayer

The reversibly stable formation and rupture processes of electrical percolative pathways in organic and inorganic insulating materials are essential prerequisites for operating non-volatile resistive memory devices. However, such resistive switching has not yet been reported for dynamically cross-linked polymers capable of intrinsic stretchability and self-healing. This is attributable to the uncontrollable interplay between the conducting filler and the polymer. Herein, we present the development of the self-healing, stretchable, and reconfigurable resistive random-access memory. The device was fabricated via the self-assembly of a silver-gradient nanocomposite bilayer which is capable of easily forming the metal-insulator-metal structure. To realize stable resistive switching in dynamic molecular networks, our device features the following properties: i) self-reconstruction of nanoscale conducting fillers in dynamic hydrogen bonding for self-healing and reconfiguration and ii) stronger interaction among the conducting fillers than with polymers for the formation of robust percolation paths. Based on these unique features, we successfully demonstrated stable data storage of cardiac signals, damage-reliable memory triggering system using a triboelectric energy-harvesting device, and touch sensing via pressure-induced resistive switching.

Significantly improving thermal conductivity of carbon fiber polymer composite by weaving highly conductive films

This paper significantly improved the transverse thermal conductivity (TC) of unidirectional carbon fiber reinforced polymer (CFRP) laminates by a simple and effective method of weaving highly conductive films (HCFs), including Copper (Cu) film and highly oriented graphite film (HOGF). The TC and interlaminar shear strength (ILSS) of HCF enhanced CFRP (HCF-CFRP) composite laminates were measured. The results show that the HCF-CFRP composite with a larger geometric undulation of HCF has a higher through-thickness TC. And the through-thickness and in-plane transverse TCs can be regulated by the undulation of HCF. The maximum through-thickness TCs of HCF-CFRPs are up to 49.19 W m−1 K−1 for HOGF-CFRP with 1.97 vol% HOGF, and up to 21.45 W m−1 K−1 for Cu-CFRP with 1.74 vol% Cu film, which are 11029% and 4753% higher than that of CFRP, respectively. Numerical simulation and infrared thermography demonstrate that the geometric undulation and ultrahigh in-plane TC of HOGF lead to the formation of a rapid through-thickness heat transfer path. In addition, the ILSSs of HOGF-CFRP and Cu-CFRP are 44.01 and 40.91 MPa, respectively, which are 13.76% and 19.77% lower than that of CFRP.

Effect of geometric disorder on chaotic viscoelastic porous media flows

Many practical applications, such as enhanced oil recovery or groundwater remediation, encounter the flow of viscoelastic fluids in porous media. Once the flow rate exceeds a critical value in such flows, an elastic instability with a fluctuating flow field is observed, which ultimately transits to a more chaotic and turbulence-like flow structure as the flow rate further increases. In this study, we present an extensive numerical investigation of the viscoelastic fluid flows in a model porous media consisting of a microchannel with many micropillars placed in it by considering both their initial staggered and aligned configurations. Within the present range of conditions encompassed in this study, we find that the geometric disorder always increases the chaotic fluctuations irrespective of the initial arrangement of micropillars. We propose that it is due to the formation of preferential paths or lanes and the formation of highly curved streamlines, which results in the local stretching of polymer molecules and, hence, significant origin in the local elastic stresses. We further show that this chaotic flow behavior strongly depends on the competitive influence between the strain-hardening and shear-thinning behaviors of a viscoelastic fluid, which again strongly depends on the polymer extensibility parameter, polymer viscosity ratio, and geometric disorder parameter. In particular, we show that the strain-hardening behavior of a viscoelastic fluid promotes these chaotic fluctuations, whereas the shear-thinning behavior tends to suppress these. Therefore, it is not a general phenomenon that can always be seen in the flows of a viscoelastic fluid in porous media.

Renewable energy transition in Senegal? Exploring the dynamics of emerging paths to a sustainable energy system

Research into the transition of energy systems has attracted considerable attention in recent years from a wide range of disciplines and perspectives. From evolutionary economic geography (EEG), scholars have emphasized the processes underlying the formation of new energy paths in energy system transitions. These processes have been well studied in Global North countries, but insights into the processes shaping the energy transition in sub-Saharan Africa are still limited. This study provides a contribution to fill that gap by exploring the emerging energy paths in Senegal through the lens of EEG, using the framework of regional path creation processes to analyze qualitative interview data from 17 experts in the Senegalese energy sector. Senegal is an instructive country to study, as its energy sector is undergoing substantial reform that has accelerated the deployment of large-scale renewable energy projects in recent years. The study uncovers three parallel evolving energy paths stemming from path transplantation, indigenous path creation, and path upgrading. Each path differs greatly in its legitimation and in the role of institutions as enablers. These results not only contribute to the ongoing scientific debate; but also provide insights for development agencies, national and regional institutions, NGOs and private actors involved in the Senegalese energy system.

Structure and Dynamics of the Isozymes II and IX of Human Carbonic Anhydrase.

Human carbonic anhydrases (HCAs) are responsible for the pH control and sensing in our body and constitute key components in the central pH paradigm connected to cancer therapeutics. However, little or no molecular level studies are available on the pH-dependent stability and functional dynamics of the known isozymes of HCA. The main objective of this Article is to report the first bench-marking study on the structure and dynamics of the two most efficient isozymes, HCA II and IX, at neutral pH using classical molecular dynamics (MD) and constant pH MD (CpHMD) simulations combined with umbrella sampling, transition path sampling, and Markov state models. Starting from the known crystal structures of HCA II and the monomeric catalytic domain of HCA IX (labeled as HCA IX-c), we have generated classical MD and CpHMD trajectories (of length 1 μs each). In all cases, the overall stability, RMSD, and secondary structure segments of the two isozymes are found to be quite similar. Functionally important dynamics of these two enzymes have been probed in terms of active site hydration, coordination of the Zn(II) ion to a transient excess water, and the formation of putative proton transfer paths. The most important difference between the two isozymes is observed for the side-chain fluctuations of His-64 that is expected to shuttle an excess proton out of the active site as a part of the rate-determining intramolecular proton transfer reaction. The relative stability of the stable inward and outward conformations of the His-64 side-chain and the underlying free energy surfaces are found to depend strongly on the isozyme. In each case, a lower free energy barrier is detected between predominantly inward conformations from predominantly outward ones when simulated under constant pH conditions. The kinetic rate constants of interconversion between different free energy basins are found to span 107–108 s–1 with faster conformational transitions predicted at constant pH condition. The estimated rate constants and free energies are expected to validate if the fluctuation of the His-64 side-chain in HCA IX may have a significance similar to that known in the multistep catalytic cycle of HCA II.

The task system for the first All-Russian Olympiad in artificial intelligence for schoolchildren

The article discusses the main approaches to the development and use of the task system for the first All-Russian Olympiad in artificial intelligence for schoolchildren. The first Olympiad in artificial intelligence for schoolchildren, held by the Ministry of Education of the Russian Federation, had distinctive features in the procedure of the competition and in competition tasks. These features can be used for comparative analysis and expert evaluation of intellectual competitions for schoolchildren held in Russia. The subjects of the Olympiad tasks are Natural Language Processing, Computer Vision, and Data Science.The Python programming language was used. The tasks were focused on the formation of an individual path for the student to prepare for the final stage of the Olympiad in artificial intelligence, i. e. thematic continuity was observed at all stages and the practical orientation of tasks using data sets was observed in the second and third rounds. For the assessment, a rating assessment was used (as in the professional community Kaggle.com) of the individual abilities of schoolchildren in the complex application of mathematical and digital skills in solving artificial intelligence tasks.The article may be useful for informatics teachers who include the topic in an advanced informatics course and teachers of additional education who prepare schoolchildren for Olympiads in programming.

Mechanistic Insight into Ultrafast Kinetics of Sodium Cointercalation in Few-Layer Graphitic Carbon.

Fast-charging sodium ion batteries remain deeply challenged by the lack of suitable carbonaceous anodes that exhibit intercalation plateau with fast kinetics. Here we develop a few-layer graphitic carbon with nanoscale architecture, which enables shortened Na+ ion diffusion path and fast formation of fully intercalated phase at the same time. Combined in situ Raman and electrochemical test reveal that this graphitic carbon with highly crystalline few layers follows surface-controlled intercalation rather than typical diffusion-controlled kinetics observed in natural graphite. As a result, a few-layer graphitic carbon anode maintains the reversible capacity of 106 mAh g-1 at 10 A g-1 and achieves 87% capacity retention even after 10 000 cycles at 1 A g-1. This work provides new insight on the Na storage mechanism in fast-charging graphitic carbon as well as the design of carbon anodes for high-rate sodium ion batteries.

Evaluation on the progressive collapse resistance of infilled reinforced concrete frames based on numerical and semi-analytical methods

The effect of infill walls on the progressive collapse behaviour of reinforced concrete (RC) frames should be fully considered due to the formation of alternative load paths. To explore the configuration that could affect the progressive collapse resistance of infilled RC frames, parametric analyses are performed based on the validated simulation method. In the study, the impact introduced by the extra tie and integrity rebars in walls is emphasised. It is indicated that the variation in the reinforcement ratio of tie rebars leads to a limited change in structural progressive collapse resistance. In contrast, with the arrangement of the integrity reinforcement, the progressive collapse resistance of the infilled frames is enhanced and the propagation of the diagonal cracks in partial infill walls is suppressed. The notable re-ascending trend in the resistance curve for models with integrity rebars reveals the significant development of the catenary action in the integrity reinforcement. Then, with the help of linear regression and gene expression programming (GEP) techniques, a semi-analytical model is proposed for the prediction of the load-bearing capacity of infilled frames after column loss. In the prediction model, the linear effect of geometrical parameters and the non-linear effect of openings on the progressive collapse resistance are included by introducing three modification coefficients. Based on the statistical assessment, the capability of this explainable model is verified, and the appropriate amount of integrity reinforcement to mitigate the progressive collapse is discussed.

Experimental and computational understanding of pulsatile release mechanism from biodegradable core-shell microparticles.

Next-generation therapeutics require advanced drug delivery platforms with precise control over morphology and release kinetics. A recently developed microfabrication technique enables fabrication of a new class of injectable microparticles with a hollow core-shell structure that displays pulsatile release kinetics, providing such capabilities. Here, we study this technology and the resulting core-shell microstructures. We demonstrated that pulsatile release is governed by a sudden increase in porosity of the polymeric matrix, leading to the formation of a porous path connecting the core to the environment. Moreover, the release kinetics within the range studied remained primarily independent of the particle geometry but highly dependent on its composition. A qualitative technique was developed to study the pattern of pH evolution in the particles. A computational model successfully modeled deformations, indicating sudden expansion of the particle before onset of release. Results of this study contribute to the understanding and design of advanced drug delivery systems.

Impacts of intensive seepage flow on suffusion development in cohesionless soil: Insight from a theoretical model

Intensive seepage widely occurs due to seepage area constriction and local soil grading coarsening, which will mutually accelerate the suffusion process with greater particle loss and rapid soil structure changes. However, less research has focused on the quantitative impacts of the various intensive seepage degrees and locations on suffusion. This paper uses a verified one-dimensional model to theoretically simulate these impacts by considering two mechanisms: seepage area constriction and local soil grading coarsening. These two mechanisms are realized with gradual constricted seepage areas formed by external boundaries and coarsened soil grading of a specific layer with higher permeability. The results indicate that the two mechanisms can significantly accelerate the particle loss rate in suffusion. The acceleration is nonlinear, with the increasing proportion of the particle loss being much larger than the constriction rate. The outlet constriction causes a more extensive increase in particle movement than the midlayer constriction in the whole soil column, with the particle loss increasing by many times in most layers under the 50% constriction. Local soil grading coarsening promotes particle loss in the upstream layers. The midlayer coarsening causes a greater violence of suffusion than the outlet coarsening by serving as another outlet for particle loss. Midlayer coarsening may lead to stronger particle movement and a severalfold soil permeability increase. Intensive seepage can further promote heterogeneous development and the upward erosion of the suffusion process and then contribute to the formation of preferential paths.

Cationic Interstitials: An Overlooked Ionic Defect in Memristors.

Metal oxide-based memristors are promising candidates for breaking through the limitations in data storage density and transmission efficiency in traditional von Neumann systems, owing to their great potential in multi-state data storage and achievement of the in-memory neuromorphic computing paradigm. Currently, the resistive switching behavior of those is mainly ascribed to the formation and rupture of conductive filaments or paths formed by the migration of cations from electrodes or oxygen vacancies in oxides. However, due to the relatively low stability and endurance of the cations from electrodes, and the high mobility and weak immunity of oxygen vacancies, intermediate resistance states can be hardly retained for multilevel or synaptic resistive switching. Herein, we reviewed the memristors based on cationic interstitials which have been overlooked in achieving digital or analog resistive switching processes. Both theoretical calculations and experimental works have been surveyed, which may provide reference and inspiration for the rational design of multifunctional memristors, and will promote the increments in the memristor fabrications.