Formation Of Paths Research Articles

Meter-scale MICP improvement of medium graded very gravelly sands: Lab measurement, transport modelling, mechanical and microstructural analysis

Microbially induced carbonate precipitation (MICP) is a promising biogrouting method for ground improvement. Most studies to date have focused on MICP treatment of uniform clean sands, with few studies having been conducted at large-scale on well-graded soils more representative of in situ deposits. This study presents a laboratory meter-scale MICP test on medium-graded very gravelly sands. The MICP treatment was conducted in a radial flow cell (diameter: ∼1 m; thickness: ∼0.15 m) with an injection well located at the centre and a constant hydraulic head at the outer boundary to replicate field conditions. Aqueous chemistry of the effluent samples inside the flow cell was continuously monitored. Transport modelling and effluent sampling monitoring of the electrical conductivity and pH show that, in general, there was good delivery and reaction of the bacteria and chemicals in the radial flow cell, with some preferential flow paths being present. The MICP-treated soil was subjected to a series of hydraulic and mechanical tests and microstructural analysis. Interestingly, the biocemented medium-graded very gravelly sands had higher strengths (UCS values of 2.6–7.4 MPa) for a given calcite content (9.2–15.1%) than those in comparable studies where uniform soils have been treated. This can be attributed to the higher initial density of grain-to-grain contact points in the medium-graded soil, and a high grain angularity which resulted in particle interlocking and longer grain-to-grain contact surfaces, as can be seen from Scanning Electron Microscopy images. Consolidated-drained triaxial tests on two cores showed peak deviatoric strengths of 5.9 MPa and 3.7 MPa under an effective confining stress of 100 kPa, with the clear formation of shear bands during shearing, compared to a peak deviatoric strength of 0.5 MPa determined for the untreated soil. MICP treatment clearly enhanced the shear strength and stiffness of the material. The study shows that formation of preferential flow paths may be a challenge for producing uniform biocementation in field applications of MICP. We propose that successful MICP treatment in heterogeneous soils will require a well-designed and well-executed site investigation programme that can identify, a priori, the geometry of any significant high or low permeability features within the soil body to inform the final MICP treatment strategy.

Impact of Continuous Cable-Strut Joints on the Anti-Progressive-Collapse Performance of Suspended-Dome Structures

In suspended-dome structures, cable-strut joints can be categorized into discontinuous joints and continuous joints. In calculations, the discontinuous joints can be treated as hinge joints. However, in the event of a cable breakage, the continuous joints might experience slip and detachment phenomena. Simplifying continuous cable-strut joints as hinge joints for calculation purposes can result in a significant discrepancy from the actual load-bearing state of the continuous joints. In fact, under the scenario of cable rupture, the continuous cable-strut joints might undergo slip and detachment. This could influence the formation of new tension paths within the cable support system, thereby affecting the anti-collapse performance of the suspended-dome structure. Therefore, this paper investigates the influence of the slippage and detachment of continuous cable-strut joints on the anti-progressive collapse performance of suspended-dome structures through joint tests, numerical simulations, and theoretical analyses. Firstly, two cable-strut joint test models were constructed. Apart from the difference that one uses a discontinuous cable-strut joint and the other a continuous cable-strut joint, all other conditions were kept identical. Research was conducted on the hoop cable failure test. The results indicate that the slippage and detachment of continuous joints hinder the formation of new tension paths in the lower cable-strut system. Structures using continuous cable-strut joints have lower anti-collapse capabilities compared to those using discontinuous cable-strut joints. Secondly, a simplified numerical simulation algorithm for cable-strut joints’ slippage and detachment is proposed. This algorithm only considers the support of struts to the upper structure and uses an Abaqus subroutine to achieve an equivalent simulation of the slippage and detachment phenomena of continuous joints during the finite element computation process. Then, using this algorithm, a progressive collapse analysis of suspended domes using continuous cable-strut joints was carried out. It was found that for suspended domes with continuous cable-strut joints, the slippage and detachment of the cable-strut joints are extremely detrimental to forming new tension paths, making the structure more susceptible to a progressive collapse. Lastly, using the resistance index, a quantitative analysis was conducted on the anti-collapse carrying capacity of suspended domes using both continuous and discontinuous cable-strut joints.

Younger students’ creative abilities activation considering the individual approach in art classes in the additional education system

The article is devoted to the issue of activating creative abilities of younger schoolchildren in fine art classes in the system of additional education through the use of dialogue discussion, the manifestation of impressions and life experience of the child, activation of the child’s ideas about the world, the choice of artistic material. Since fine art classes are a special kind of activity, it is necessary to apply new pedagogical technologies, search for new methods and means of individual teaching approaches that will help to activate the creative abilities of students. The system of additional education has all the conditions for the introduction of individual educational trajectories, for the formation of learning paths, both taking into account individual personality characteristics, interests, level of knowledge, and taking into account the specific capabilities and needs of each child. The role of the teacher of additional education, who will help to notice the creative potential of the child in time and create conditions for its development, is particularly highlighted, and attention is also focused on the use of pedagogical technologies in visual activities.

Revealing the effect of Co/Cu (d7/d9) cationic doping on an electronic acceptor ZnO nanocage surface for the adsorption of citric acid, vinyl alcohol, and sulfamethoxazole ligands: DFT-D3, QTAIM, IGM-NCI, and MD analysis

The electron-spin duality and propagation of the active sites of free electrons are of interest for adsorbing the guests and fixing them with strong hydrogen bonds (HB). The coherence of the systems with the guests is one of the main parameters that favor the experimentation of new systems on primary column adsorption phenomena. The stability and the adaptable symmetries in all directions justify the use of a “nanocage” (ZnO) for studying adsorption phenomena. The formation of stable electronic charge transfer paths between sites occupied by very stable atomic orbitals ensures the success of the adsorption of the ligands. Electronic characterization (MES, FMO, DOS, and cationic doping) is used to describe the movement of the intra-Cu-Co/Zn19O20 electrons. The phenomena of charge transfer, stability, types of orbital occupations, adsorption sites, electron migration direction, conductivity, and reactivity of such systems are thoroughly explored. Based on these findings, the efficiency of a Cu–Co/Zn19O20 nanocage to adsorb three different ligands (medical ligands, prostate biomarkers, and antibiotics) is studied. From the reactivity parameter discussions, it is found that the copper or cobalt-doped nanocage-Citric Acid has a strongly electronegative index (4.40 eV and 4.91 eV) and hardness (1.99 eV and 1.82 eV) properties. The Fourier transform infrared analyses and orbital localizations (α and β) clearly demonstrate that the charge transfer occurs inter-surface, from nanocages to adsorbed ligands. Bader's theory analysis for the adsorption ligands VA (Vinyl Alcohol), CA (Citric Acid), and SMX (Sulfamethoxazole) by the doped copper and cobalt nanocages demonstrates that these systems are much more adequate for adsorbing the ligand antibiotics than the other hosts. The highly adsorbent energy of sulfamethoxazole by Cu–Zn19O20 is equal to −582.86 kJ.mol-1. The IGM-NCI/ELF analyses support these findings, revealing that the Cu/Co–Zn19O20 nanocages adsorb SMX via hydrogen bonding and van der Waals interactions, as they also did in DFT-D3 and FT-IR analyses. LOL analyses support this claim by visualizing single-pair spins in excess surrounding acceptor atoms (O) in the two systems. Molecular dynamics simulations show that SMX is quickly adsorbed by nanocages of Zn19O20 doped with copper (d9) or cobalt (d7).

A Printing Strategy for Embedding Conductor Paths into FFF Printed Parts.

A novel approach to manufacture components with integrated conductor paths involves embedding and sintering an isotropic conductive adhesive (ICA) during fused filament fabrication (FFF). However, the molten plastic is deposited directly onto the adhesive path which causes an inhomogeneous displacement of the uncured ICA. This paper presents a 3D printing strategy to achieve a homogeneous cross-section of the conductor path. The approach involves embedding the ICA into a printed groove and sealing it with a wide extruded plastic strand. Three parameter studies are conducted to obtain a consistent cavity for uniform formation of the ICA path. Specimens made of polylactic acid (PLA) with embedded ICA paths are printed and evaluated. The optimal parameters include a groove printed with a layer height of 0.1 mm, depth of 0.4 mm, and sealed with a PLA strand of 700 µm diameter. This resulted in a conductor path with a homogeneous cross-section, measuring 660 µm ± 22 µm in width (relative standard deviation: 3.3%) and a cross-sectional area of 0.108 mm2 ± 0.008 mm2 (relative standard deviation 7.2%). This is the first study to demonstrate the successful implementation of a printing strategy for embedding conductive traces with a homogeneous cross-sectional area in FFF 3D printing.

Control of subthreshold swing using an in situ PEALD nano-laminated IGZO/Al2O3 multi-channel structured TFT

This study presents the development of multi-channel thin-film transistors (TFTs) using plasma-enhanced atomic layer deposition (PEALD) to stack layers of IGZO/Al2O3, with the number of stacking layers ranging from 1 to 10 (1S, 3S, 5S and 10S). To optimize the performance of the AM-LED display, the subthreshold swing (S·S) and mobility of each type of transistor, such as switching and driving transistors, were customized to meet specific requirements. The results show that as the number of stacking layers increased, the field-effect mobility (µ FE) improved by 323% from 1.34 to 4.33 cm2/Vs, while S·S improved by 0.14 V/dec from 0.31 to 0.45 V/dec, with no variation in threshold voltage (V th) and reliability. The study attributes the improvement in µ FE and S·S to the formation of multiple electron transport paths as confirmed by a TCAD simulation showing an increase in current density. Overall, this study demonstrates the potential of PEALD in creating multi-channel TFTs with improved performance by customizing oxide semiconductor properties. This research may have important implications in the development of advanced electronic devices that rely on thin-film transistors, as it provides a new approach in enhancing the performance of these devices.

Formation of TiO2 nanowires and BNNPs using in situ hydrothermal reaction to improve thermal conductivity of cellulose

Constructing an efficient heat pathway is of utmost importance for improving the thermal conductivity of polymer-based composites. Three-dimensional (3D) filler structures can be excellently utilized to prepare thermally conductive pathways in polymer composites. A composite consisting of titanium dioxide nanowires (TiO2 NWs), boron nitride nanoparticles (BNNPs), and cellulose nanofibers (CNFs) was fabricated using a hydrothermal process, focusing on the formation of TiO2 NWs and BNNPs. After the formation of the heat transfer path, the fabricated composite with a 50 wt% filler content exhibited a 450% increase in thermal conductivity compared to raw CNF, surpassing the composites prepared via random dispersion methods. Therefore, this paper presents a promising strategy for significantly enhancing the thermal properties of the composites.

Microscopic gas displacement efficiency of enhanced gas recovery in carbonate gas reservoirs with edge and bottom water

Carbonate gas reservoirs with edge and bottom water contain abundant reserves, making them key production targets in the Tarim Basin, Sichuan Basin, Ordos Basin, and other petroleum provinces. Water invasion may occur in the middle and late development stages of such reservoirs, leading to reduction of gas displacement efficiency and gas recovery. In this paper, a pore-scale water-gas immiscible flow model is established by coupling the fluid flow equation and the gas-water contact (GWC) tracking equation. The process of gas displacement with water is simulated in the heterogeneous porous media generated by the quartet structure generation set (QSGS). Finally, the mechanisms of remaining gas distribution and formation are analyzed, and the variation mechanism of microscopic gas displacement efficiency is discussed. The results are obtained in three aspects. First, the remaining gas is distributed at the blind end, in the pore-throat and as clusters, with their proportions and scales jointly controlled by microscopic pore structures, wettability and capillary number. The remaining gas can be further produced by changing the production pressure differential to disturb the original pressure system and gas expansion, so as to improve the microscopic gas displacement efficiency. Second, the microscopic gas displacement efficiency is closely related to the gas flow process. Formation or expansion of each water flow path may cause rapid increase of water cut and slows down the increase of gas displacement efficiency. Third, the microscopic pore structure and wettability are the inherent features of the gas reservoir, so the capillary number can be optimized to change the mode of GWC advancement, and then to effectively improve the microscopic gas displacement efficiency. It is concluded that for real gas wells, the evolution of mechanical mechanisms of GWC advancement should be revealed depending upon the microscopic pore structure and wettability of the reservoir, and then the optimal capillary number can be determined. Furthermore, clarifying the pore-scale water-gas flow characteristics and physical mechanism of microscopic gas displacement provides guidance for the planning of enhanced gas recovery.

Numerical Investigation of Blade-to-Blade Surface Layout in the Ram-rotor

A numerical investigation has been conducted on the ram-rotor with various blade-to-blade profiles to achieve potential benefits in enhancing their performance. The blade-to-blade profile is changed by adjusting the strake camber line to enable the formation of expansive and contractive flow paths. Results indicate that the expansive flow path can significantly improve the total pressure ratio of the ram-rotor by altering the position of shock trains. Subsonic airflow after the shock train is decelerated and pressurized, which further contributes to the pressure rising capacity. The leakage flow is suppressed as the flow path is contractive in the blade-to-blade view. This, in turn, leads to a significant reduction of both tip leakage loss and the interference effect between the leakage and the shocks.

The prototype of the system for the formation of an individual learning path

Objective. The purpose of the study is to identify the dependence of the quality of education in a general educational organization on the educational environment.Method. To determine the influence of various factors on the quality of education, an artificial neural network was trained, for which statistical data were previously collected on the participants in the educational process in the ANEO “Knowledge House”.Result. An artificial neural network has been implemented, which makes it possible to identify the dependence of individual elements of the educational environment on the quality of education in a general educational organization. The training of the artificial neural network showed an insignificant error in the assessment on a ten-point scale, which, when converted to a five-point system, was about 0.5 points.Conclusion. The proposed method makes it possible to qualitatively and quantitatively assess the progress of students using an artificial neural network according to data that correlates with the progress of a student in an educational organization.

Large-Scale Nonequilibrium Molecular Studies of Thermal Hydrate Dissociation.

The energy content of methane hydrate reservoirs (MHRs) is at least twice that of conventional fossil fuels. So, there is considerable interest in their commercial development by heating, among other dissociation mechanisms. However, a few researchers have highlighted the potentially uncontrollable release of methane from MHRs, which could occur because of global warming. Therefore, it is crucial to understand the kinetics of thermal hydrate dissociation to safely develop these resources and prevent the release of this greenhouse gas into the environment. Although there have been several molecular studies of thermal dissociation, most of these use small simulation domains that cannot capture the transient nature of the process. To address this limitation, we performed coarse-grained molecular dynamics (CGMD) simulations on a significantly larger domain with a hundred times more hydrate unit cells than those used in previous studies. We monitored the kinetics of dissociation using an image-processing algorithm and observed the dynamics of the process while maintaining a thermal gradient at the dissociation front. For the first time, we report the formation of an unstable secondary dissociation path that triggers gas bubbles within the solid hydrate. The kinetics of thermal dissociation appears to occur in three stages. In the first stage, the energy of the system increases until it exceeds the activation energy, and dissociation is initiated. Consistent dissociation occurs in the second stage, whereas the third stage involves the dissociation of the remaining hydrates across a nonplanar and heterogeneous interface.

Influence of Cu and Cr contents on the solidification path and microstructure formation of hypoeutectic as-cast Al–Cu–Cr alloys

Influence of Cu and Cr contents on the solidification path and microstructure formation of hypoeutectic as-cast Al–Cu–Cr alloys

Laboratory hydraulic shearing of granitic fractures with surface roughness under stress states of EGS: Permeability changes and energy balance

To offer key parameters and constitutive laws required for field-scale multiphysics simulations that can accurately predict created fracture network structures in enhanced geothermal systems (EGS) and resulting energy extraction, we explore the full spectral of hydraulic shear process of granite fracture and revisits the linkage between hydraulic and mechanical properties during shear slips. Key results from our novel lab-experiments include the followings: (1) fracture permeability of granite increases due to the hydraulic shear slip even at an effective normal stress of over 50 MPa, (2) shear slip and stress drop are in proportion and increment of the fracture permeability increases with increasing total shear slip displacement, and (3) although hydraulic shear slip tends to make fracture surfaces slightly smoother, the factual characteristics of surface are maintained after slip. By combining our experimental results with the seismological analysis, we first explore energy balance during hydraulic shearing of the preexisting rock fracture and point out the crucial role of the elastic potential energy stored in the surrounding bulk rock masses. Subsequently, we derive a constitutive model related to permeability change of granite fracture during hydraulic shearing under the typical crustal stress of EGS and presume that the maximum change in fracture permeability due to shear dilation is ∼20-fold, although scale effect is not considered. Finally, via the high resolution 2-D mapping of the surface damages, we illuminate the formation of preferential flow paths within rock fracture during hydraulic shearing and its possible role on the improvement of fracture permeability. Thus, we successfully demonstrate both new and sophisticated insights in hydro-mechanical coupled processes during hydraulic shearing to improve the accuracy of fracture network designs in EGS technology.

In situ growth of Bi/Ag double quantum dots on hollow Bi2MoO6 microspheres: Enhancement of the surface plasmon resonance effect on PMS activation

In this work, the effect of Bi/Ag double quantum dots on plasmon resonance and PMS activation was investigated. Bi/Ag double quantum dots were generated in situ on hollow Bi2MoO6 microspheres by stepwise irradiation using a high-energy β electron beam. The formation of Bi/Ag DQDs greatly optimized the drawbacks of Bi2MoO6 in terms of light absorption. Synergistic introduction of DQDs greatly reduced the band gap from 2.72 eV to 2.12 eV. The Bi−Ag@Bi2MoO6 − 400/PMS system degraded ciprofloxacin with kinetic constants 10 and 12 times higher than those of the Bi@Bi2MoO6/PMS and Bi2MoO6/PMS systems. The formation of an electron transfer path from Ag QDs to Bi QDs enhanced the SPR effect of Bi QDs.·O2− and 1O2 played a major role in the CIP degradation process. This study will provide a new strategy for enhancing the Bi plasmon resonance effect and provide a technical method to the efficient degradation of antibiotics in water.

Potential Induced Degradation in Photovoltaic Modules: A Review of the Latest Research and Developments

Photovoltaic (PV) technology plays a crucial role in the transition towards a low-carbon energy system, but the potential-induced degradation (PID) phenomenon can significantly impact the performance and lifespan of PV modules. PID occurs when a high voltage potential difference exists between the module and ground, leading to ion migration and the formation of conductive paths. This results in reduced power output and poses a challenge for PV systems. Research and development efforts have focused on the use of new materials, designs, and mitigation strategies to prevent or mitigate PID. Materials such as conductive polymers, anti-reflective coatings, and specialized coatings have been developed, along with mitigation strategies such as bypass diodes and DC-DC converters. Understanding the various factors that contribute to PID, such as temperature and humidity, is critical for the development of effective approaches to prevent and mitigate this issue. This review aims to provide an overview of the latest research and developments in the field of PID in PV modules, highlighting the materials, designs, and strategies that have been developed to address this issue. We emphasize the importance of PID research and development in the context of the global effort to combat climate change. By improving the performance and reliability of PV systems, we can increase their contribution to the transition towards a low-carbon energy system.

Recyclable, Self-Healing, and Highly Thermal Conductive Natural Rubber Nanocomposites Enabled by a Dynamic Covalent Network with Carboxylated Boron Nitride Nanosheets

It is of great significance for saving resources and protecting the environment to endow rubber with excellent recycling ability. Recyclable and self-healing ENR/BN-COOH/GO nanocomposites were prepared through dynamic covalent crosslinking between epoxidized natural rubber (ENR) and carboxylated boron nitride (BN-COOH), and graphene oxide (GO) was used as a reinforcing filler. The constructed dynamic β-hydroxyl ester bond between ENR and BN-COOH resulted in the remarkable enhancement of interfacial interaction and effective energy dissipation, which contributed to good mechanical properties of the nanocomposites, increasing by 116 and 79% in comparison with ENR and ENR/GO, respectively. An exchangeable β-hydroxyl ester bond could regulate a network topology structure via a transesterification reaction at the interface, endowing ENR with desirable recycling and self-healing ability. Moreover, the significant improvement of thermal conductivity for ENR/BN-COOH/GO nanocomposites was achieved, reaching 2.853 W/(m·K) at only 6 wt % BN-COOH content, indicating the formation of effective thermal conductive paths via the β-hydroxyl ester bond and hybrid thermal conductive network of BN-COOH/GO. Meanwhile, the thermal conductivity of recycled samples still maintained a high level due to the construction of the stable thermal conductive network. Such a facile strategy exhibits a promising perspective in preparing recyclable and highly thermal conductive rubber nanocomposites for applications in efficient thermal management fields.

Giant room-temperature electrical switching effects in water-in-oil emulsions

Thermally-triggered electrical switching materials are of urgent demand for developing novel temperature sensors, overheat protection circuits, thermal controllers, battery management systems against overheating, etc. Here, we report a water-in-oil emulsion system with giant electrical switching ratios at room temperature prepared by a simple and efficient method. The temperature-sensitive phase transition process of alkanes as the oil phase causes the formation and collapse of conductive paths in the emulsion, resulting in electrical switching ratios of up to 6 orders of magnitude. The emulsions have good thermal cycle stability, and the switching ratio remains essentially unchanged after 100 cycles. The switching temperature can be easily adjusted by using alkanes of various chain lengths. In addition, the similar electrical switching effect is observed in four emulsions containing different neutral salts, ensuring the tunability and versatility of the system. The electrical switching emulsions offer a promising avenue to developing future high-performance, energy-saving, and low-cost electrical switching systems.

An analytical local tool path smoothing method with curvature control

In traditional multi-axis machining, the linear tool path generated by computer-aided manufacturing systems is still in a broad tool path format, resulting in discontinuities at the corners, which slow down tool motion, and also trigger tool vibration, reducing machining accuracy and surface quality. In order to ensure the C3 continuity of the tool during the multi-axis machining process, this paper proposes an analytical B-spline local smoothing method with curvature control. The tool position trajectory and tool orientation are both smoothed by a 5th spline curve with 9 control points. Optimal control points are determined for position and orientation splines to achieve C3 continuity at the junctions between the spline and linear segment while preserving the predefined geometric tolerance limits and minimizing the maximum curvature of the inserted B-spline curve. The smoothed tool path is expected to have less curvature fluctuation, which can significantly improve both the kinematic performance of the machine tool and the machining efficiency. Both computer simulations and physical printing experiments are carried out to demonstrate the improvements of our proposed method in motion smoothness and tracking accuracy in multi-axis machining tasks.

TiO2 nanowire formation and GO reduction through a hydrothermal reaction to improve the thermal conductivity of epoxy composites

AbstractThe thermal path must be properly configured to improve the thermal properties of polymer composites. Three‐dimensional (3D) thermally conductive networks can be used as an excellent means for building high‐speed conductive pathways in polymer composites. Titanium dioxide (TiO2) nanowire (NW)/reduced graphene oxide (rGO)/epoxy (EP) composite material has a 3D foam structure and focuses on TiO2 NW formation and rGO gelation through a hydrothermal process. The thermal conductivity of the synthetic composite material through filler loading at 50 wt.% and heat transfer path formation was 805% higher than that of pure EP, and the thermal conductivity was superior to that of the composite material with randomly dispersed fillers. Therefore, this work describes an advanced process to improve the thermal conductivity of polymer composites significantly.

Agroecology and Agrarian Transitions: Current Debate in India

The article critically evaluates the attempt by the Modi government to promote the model of zero-budget natural farming (ZBNF) as an alternate path to agrarian development in India. It is well apparent from the analysis of the National Mission on Natural Farming (NMNF) guidelines that the advocates of natural farming have chosen to turn a blind eye to the constraints of Indian agrarian structures in the shift away from selective delinking for food security to global integration, with landlord capitalists and corporate capital in control of the path formation. The cheap nature and cheap labor outlook is built in the input correction emphasis of natural farming and in the assumption of “zero budgets” for the farmer and the government. The ZBNF model will prevent the NMNF from tackling the landscape, structural, and system-level challenges of agrarian transformation. Significant barriers to the adoption of agroecological approaches can be expected to arise due to the lack of commitment to help the peasants and landless proletariat with the protection of the commons and the public investment needed for the promotion of agroecological approaches.