Minor Influence Research Articles

Multiphysics monitoring of cementation operation: implications for wellbore integrity and hydrogeological characterization

The application of optical fibers for assessing cemented wellbore’s integrity attracted considerable attention recently, because of low cost, decent temporal/spatial resolution and absence of downhole electronics. This study presents an integrated approach to compare measurements from distributed temperature sensing (DTS), distributed strain sensing (DSS) and fiber Bragg grating (FBG), at different stages of the wellbore cementation at Bedretto Underground Laboratory for Geosciences and Geoenergies. Before the cementation, the measurements from DTS provided information about the hydrogeological settings of the wellbore, including the major flow zones, and presence of a highly conductive hydraulic shortcut to a nearby wellbore. During the cement injection, the temperature sensors (DTS and temperature FBG) clearly detected the evolution of the top of the cement. While the mechanical deformation sensors (DSS and strain FBG) did not provide significant insights during this stage, their role became more pronounced in subsequent phases. Results show that the irregularities on the wall have minor influence on the thermo-mechanical response of the wellbore, both during and after cementation. After cementation, the temperature sensors (DTS and temperature FBG) traced different phases of cement-hardening process, while DSS measurements identified areas of major deformation, primarily in fracture/fault zones. It was also observed that localized elevation of temperature and extensional deformation along the wellbore during the cement-hardening are correlated with the presence of permeable structures, most likely due to continuous supply of water. Results of this study show that monitoring of the cemented wellbores using optical fibers, in particular during cement hardening, not only can be used to efficiently assess the wellbore integrity but also can provide us additional important information about the hydrogeological settings of the target reservoir volume.

A Mechanistic Model and Experiments on Bedrock Incision and Channelization by Rockfall

AbstractRockfall and rock avalanches are common in steep terrain on Earth and potentially on other planetary bodies such as the Moon and Mars. Since impacting rocks can damage exposed bedrock as they roll and bounce downhill, rockfall might be an important erosive agent in steep landscapes, even in the absence of water. We developed a new theory for rockfall‐driven bedrock abrasion using the ballistic trajectories of rocks transported under gravity. We calibrated this theory using laboratory experiments of rockfall over an inclined bedrock simulant. Both the experiments and the model demonstrate that bedrock hillslopes can be abraded by dry rockfall, even at gradients below the angle of repose, depending on the bedrock roughness. Feedback between abrasion and topographic steering of rockfall can produce channel‐like forms, such as bedrock chutes, in the absence of water. Particle size has a dominant influence on abrasion rates and runout distances, while the hillslope angle has a comparatively minor influence. Rockfall transport is sensitive to bedrock roughness; terrain with high friction angles can trap rocks creating patches of rock cover that affect subsequent rockfall pathways. Our results suggest that dry rockfall can play an important role in eroding and channelizing steep, rocky terrain on Earth and other planets, such as crater degradation on the Moon and Mars.

Quantification of Pluronic F127 used on PLGA nanoparticle preparation and comparing purification techniques by centrifugation, tangential flow filtration, and ultrafiltration

Emerging research in polymeric nanoparticles (PNP) in the field of drug delivery systems focuses on the preferable use of biocompatible materials like poly(lactic-co-glycolic) acid (PLGA). However, the substantial use of surfactant in achieving colloidal stability requires its subsequent elimination to avoid side effects. This study aimed to establish suitable conditions for detecting and quantifying Pluronic® F127 (F127), a non-ionic surfactant widely used for this specific purpose, through a precise Size Exclusion Chromatography (SEC) method. Then, comparing the F127 removal efficacy via three purification techniques: Centrifugation (Cf), Ultrafiltration (UF), and tangential flow filtration (TFF), determining the minor influence of surfactant removal on the colloidal and morphological properties of surfactant-free PLGA suspensions. Thus, to determine the most suitable strategy for purifying PNP. The initial results of the SEC method revealed two distinct molar mass distributions of F127, associated with a blend of triblock alongside a minor fraction of homopolymer or diblock. The method exhibited a high linear correlation (R2 0.99991) for surfactant concentrations ranging from 0.3 to 14.7 mg/mL. While assessing the three purification techniques, UF demonstrated proficiency in concentrating nanoparticle suspensions, albeit tending to retain a significant portion of the surfactant. In contrast, Cf displayed a remarkable capability in removing more than 90 % of the incorporated F127. However, Cf recovered only 60 % of the initial nanoparticles, predominantly eliminating smaller diameter particles. Conversely, TFF demonstrated high efficacy in surfactant removal, requiring an extended washing process and leading to minimal nanoparticle loss while leaving the colloidal variables unaffected.

Deep Dive into the factors influencing acoustic velocity in the Dalan-Kangan formations, the central Persian Gulf

The propagation of acoustic waves in rocks is directly influenced by the rocks’ elastic properties. To evaluate petrophysical properties from acoustic data, it is essential to understand the factors that influence the variations in acoustic velocity of sedimentary rocks. Carbonate reservoirs are heterogeneous, and their evaluation is complicated. A closer look at the factors affecting the elastic properties of these rocks is essential because they reveal important information about the reservoir properties and their formation evaluation. Rock physics modeling relies on laboratory-measured acoustic data. This study, however, employs acoustic logs to elucidate the key factors influencing sonic velocity, offering a more comprehensive and field-applicable perspective. Samples were prepared from the Permian–Triassic Upper Dalan and Kangan formations. Porosity, permeability, sedimentary textures, mineralogy, and pore types were investigated. Furthermore, compressional, shear, and Stoneley well-logs data were recorded and converted to acoustic velocity in the sampled interval. Porosity-velocity modeling based on the differential effective medium (DEM) theory was performed for different values of equivalent pore aspect ratio (EPAR). The results show that there is a strong inverse relationship between acoustic velocities and porosity. Acoustic velocities also exhibit an inverse correlation with permeability, but the strength of these relationships is relatively weak. Acoustic velocities are not affected by carbonate textures. A specific texture may exhibit different velocities due to the influence of diagenetic processes. Mineralogy has only a minor influence on acoustic velocities. Dolostones have a slightly higher velocity than limestones, but the difference is insignificant. Stoneley log values are slightly different in limestone and dolostone, because this wave propagates along the mud-borehole interface. The velocities were affected by the variations in pore types within the studied formations. Therefore, in carbonate rocks, porosity, and the pore types play a significant role in controlling acoustic velocities. The value of EPAR = 0.15 can be considered as the boundary between stiff pores (moldic and vuggy) and soft pores (interparticle, intercrystalline, micro-intercrystalline, and microporosity). The lower EPAR value of interparticle pores in limestones compared to dolostones can be attributed to diagenetic processes such as dolomitization and compaction. The findings of this study can help to better understand what factors affect acoustic velocity in carbonate rocks. This study also shows that acoustic logs data can be effectively used in rock physics modeling and pore type identification. By identifying the pore types, it is possible to recognize diagenetic processes and determine the rock types to control the heterogeneity and estimate reservoir quality.

Investigation of the renewed methane growth post-2007 with high-resolution 3-D variational inverse modeling and isotopic constraints

Abstract. We investigate the causes of the renewed growth of atmospheric methane (CH4) amount fractions after 2007 by using variational inverse modeling with a three-dimensional chemistry-transport model. Together with CH4 amount fraction data, we use the additional information provided by observations of CH4 isotopic compositions (13C : 12C and D : H) to better differentiate between the emission categories compared to the differentiation achieved by assimilating CH4 amount fractions alone. Our system allows us to optimize either the CH4 emissions only or both the emissions and the source isotopic signatures (δsource(13C,CH4) and δsource(D,CH4)) of five emission categories. Consequently, we also assess, for the first time, the influence of applying random errors to both emissions and source signatures in an inversion framework. As the computational cost of a single inversion is high at present, the methodology applied to prescribe source signature uncertainties is simple, so it can serve as a basis for future work. Here, we investigate the post-2007 increase in atmospheric CH4 using the differences between 2002–2007 and 2007–2014. When random uncertainties in source isotopic signatures are accounted for, our results suggest that the post-2007 increase (here defined using the two periods 2002–2007 and 2007–2014) in atmospheric CH4 was caused by increases in emissions from (1) fossil sources (51 % of the net increase in emissions) and (2) agriculture and waste sources (49 %), which were slightly compensated for by a small decrease in biofuel- and biomass-burning emissions. The conclusions are very similar when assimilating CH4 amount fractions alone, suggesting either that random uncertainties in source signatures are too large at present to impose any additional constraint on the inversion problem or that we overestimate these uncertainties in our setups. On the other hand, if the source isotopic signatures are considered to be perfectly known (i.e., ignoring their uncertainties), the relative contributions of the different emission categories are significantly changed. Compared to the inversion where random uncertainties are accounted for, fossil emissions and biofuel- and biomass-burning emissions are increased by 24 % and 41 %, respectively, on average over 2002–2014. Wetland emissions and agricultural and waste emissions are decreased by 14 % and 7 %, respectively. Also, in this case, our results suggest that the increase in CH4 amount fractions after 2007 (despite a large decrease in biofuel- and biomass-burning emissions) was caused by increases in emissions from (1) fossil fuels (46 %), (2) agriculture and waste (37 %), and (3) wetlands (17 %). Additionally, some other sensitivity tests have been performed. While the prescribed interannual variability in OH can have a large impact on the results, assimilating δ(D,CH4) observations in addition to the other constraints has only a minor influence. Using all the information derived from these tests, the net increase in emissions is still primarily attributed to fossil sources (50 ± 3 %) and agriculture and waste sources (47 ± 5 %). Although our methods have room for improvement, these results illustrate the full capacity of our inversion framework, which can be used to consistently account for random uncertainties in both emissions and source signatures.

Influence of Cementation Mode and Ferrule Design on the Fatigue Resistance of Monolithic Zirconia Endocrowns.

Background: Classic endocrowns made of dental ceramics are considered a promising alternative to traditional post-endodontic restorations. The use of circular ferrules in endocrowns is a topic of controversial discussion. Therefore, the present study aims to evaluate the effect of ferrule design and cementation mode on the fatigue resistance of zirconia endocrowns. Methods: Eighty human molars were divided into four groups (n = 20): NFC (no-ferrule, conventional cementation), NFA (no-ferrule, adhesive luting), FC (ferrule, conventional cementation) and FA (ferrule, adhesive luting). Both the classic and the modified endocrown preparation with a two-millimeter ferrule design were carried out. Endocrowns were fabricated from zirconia using the CEREC system. After thermocycling, specimens were loaded according to the step-stress test up to 1500 N. Results: Failure rate was low; 88.8% of total specimens passed the step-stress test. Fractures were distributed between all groups; no significant differences in fatigue resistance were detected for preparation design and cementation mode. Conclusions: Endocrowns appear to be a promising concept for endodontically treated molars. Ferrule and also cementation mode have only a minor influence on fatigue resistance of zirconia endocrowns. However, at very high forces, the marginal area of the ferrule represents a weak point.

Shrinkage Reduction in Nanopore-Rich Cement Paste Based on Facile Organic Modification of Montmorillonite.

The organic modification of montmorillonite was successfully achieved using cetyltrimethyl ammonium bromide under facile conditions. The modified montmorillonite was subsequently used for the fabrication of montmorillonite-induced nanopore-rich cement paste (MNCP), and the shrinkage behavior and fundamental performance of MNCP were also investigated. The results indicate that alkali cations on a montmorillonite layer surface were exchanged by using CTAB under 80 °C, successfully achieving the organic modification of montmorillonite. As a pore-forming agent, the modified montmorillonite caused a reduction in shrinkage: the 28-day autogenous shrinkage at a design density of 400 kg/m3 and 800 kg/m3 was reduced to 2.05 mm/m and 0.24 mm/m, and the highest reduction percentages during the 28-day drying shrinkage were 68.1% and 62.2%, respectively. The enlarged interlamellar pores and hydrophobic effects caused by the organic modification of montmorillonite aided this process. Organic-modified montmorillonite had a minor influence on dry density and thermal conductivity and could contribute to an enhancement of strength in MNCP.

Construction of Riboswitches for Screening Antibacterial Agents from Forest Plants

Forest plants contain abundant natural products, providing a valuable resource for obtaining compounds with various functional activities, such as antimicrobial, lipid-lowering, and immunoregulatory activities. The development of efficient tools for rapidly screening functional natural products from forest plants is essential for human health. In this study, we constructed some transgenic strains (Escherichia coli) containing Ahy1-1 riboswitches that respond to cyclic di-guanylate (c-di-GMP), serving as a novel bacteriostatic target. The Ahy1-1 riboswitches contained the LacZ gene (encoding β-galactosidase) and c-di-GMP aptamer in order to monitor β-galactosidase activity due to changes in c-di-GMP. After co-incubating with extracts from fresh orange peel, fresh tea leaves, and Fuzhuan brick tea, the orange peel exhibited a significant inhibition of c-di-GMP generation. The extract of tea leaves had a minor influence on the synthesis of c-di-GMP, whereas Fuzhuan brick tea, which is fermented by various microorganisms, inhibited the production of c-di-GMP. Our constructed transgenic strains could be used to screen for antibacterial agents from forest plants. Beyond antibacterial agents, other functional compounds from forest plants could be selected by designing diverse riboswitches.

Comparison of Measured and Calculated Porosity Parameters of Woven Fabrics to Results Obtained with Image Analysis.

Porosity, the measure of the open spaces within a fabric structure, is a decisive factor in the performance of textiles. It influences breathability, permeability to liquids or gases, and suitability for various industries such as apparel, medical, and technical textiles. This study compares classical porosity calculation methods with non-destructive image analysis for 24 woven fabric samples that differ in density and weave pattern. Factors such as fabric density, weave pattern, illumination conditions, magnification, and the influence of the Otsu and Yen threshold algorithms were considered. The multifactor ANOVA statistical analysis shows that fabric density and weave pattern significantly influence porosity, with illumination playing an important role, while the threshold algorithm has a minor influence. A strong correlation is found between the actual fabric porosity and the results of the image analysis, except for double-sided illumination (reflective and transmissive), where the correlation is weakest. This comprehensive investigation provides valuable insights into the reliability of different porosity assessment approaches, which is essential for applications in various textile industries.

Impact of heavy alcohol consumption on cortical bone mechanical properties in male rhesus macaques

Chronic heavy alcohol consumption may influence the skeleton by suppressing intracortical bone remodeling which may impact the quality of bone and its mechanical properties. However, this aspect has not been thoroughly assessed in either humans or animal models whose cortical bone microstructure resembles the microstructure of human cortical bone. The current study is the first to investigate the effects of chronic heavy alcohol consumption on various mechanical properties of bone in a non-human primate model with intracortical remodeling. Male rhesus macaques (5.3 years old at the initiation of treatment) were induced to drink alcohol and then given the choice to voluntarily self-administer water or ethanol (4 % w/v) for approximately 14 months, followed by three abstinence phases (lasting 34, 41, and 39–46 days) with approximately 3 months of ethanol access in between. During the initial 14 months of open-access, monkeys in the alcohol group consumed an average of 2.9 ± 0.8 g/kg/d ethanol (mean ± SD) resulting in a blood ethanol concentration of 89 ± 47 mg/dl in longitudinal samples taken at 7 h after the daily sessions began. To understand the impact of alcohol consumption on material properties, various mechanical tests were conducted on the distal tibia diaphysis of 2–5 monkeys per test group, including dynamic mechanical analysis (DMA) testing, nano-indentation, microhardness testing, compression testing, and fracture resistance curve (R-curve) testing. Additionally, compositional analyses were performed using Fourier-transform infrared (FTIR) spectroscopy. Significant differences in microhardness, compressive stress-strain response, and composition were not observed with alcohol consumption, and only minor differences were detected in hardness and elastic modulus of the matrix and osteons from nanoindentation. Furthermore, the R-curves of both groups overlapped, with similar crack initiation toughness, despite a significant decrease in crack growth toughness (p = 0.032) with alcohol consumption. However, storage modulus (p = 0.029) and loss factor (p = 0.015) from DMA testing were significantly increased in the alcohol group compared to the control group, while loss modulus remained unchanged. These results indicate that heavy alcohol consumption may have only a minor influence on the material properties and the composition of cortical bone in young adult male rhesus macaques.

Role of behavioral biases in the investment decisions of Pakistan Stock Exchange investors: Moderating role of investment experience

Despite many revolutionary asset pricing models developed over the past decades, traditional finance does not explain investor behavior very well. The purpose of this study is to examine the influence of behavioral biases on the investment decisions of investors of Pakistan Stock Exchange. In addition, the moderating influence of investment experience investigated in this study. The findings were reported using a sample of 230 individual investors, who make their own investments, typically through a mutual fund, bank, or internet broker. They make investments to achieve their unique investment objectives, such as saving for retirement, a child’s education, or increasing their overall wealth. The influence of behavioral biases on investment decisions was calculated using regression analysis. Regression results show that beta and t-values are significant and have a significant impact on investment decisions. Regression findings show that Confirmation Bias, Gamblers Fallacy Bias, Negativity Bias, Bandwagon Effect Bias, Loss Aversion Bias, and Overconfidence Bias all have a substantial impact on Investment Decisions. Status quo prejudice and endowment bias have a favorable but minor influence on Investment Decisions. Investment Experience is regarded as an essential component that contributes to successful decision making under risk and uncertainty, however the results of this study show that moderating variables have a minor influence. According to the findings, the moderating variable had no effect on the connection between behavioral biases and investment decisions. And the reason for this is that behavioral biases persist regardless of investing experience.

Comparative analysis of internal flow characteristics and particle trajectories of centrifugal pumps with different impeller structures under solid-liquid two-phase flow conditions

The disc pump is a non-conventional centrifugal pump that utilizes centrifugal force and boundary layer effects to transport fluids. This pump is widely used in industries such as petrochemicals. However, due to the presence of particles in the solid-liquid two-phase flow, it causes wear and performance degradation of the pump’s flow components. However, due to the presence of particles in the solid-liquid two-phase flow, it can cause wear and performance degradation of the pump components. To study the internal flow characteristics of solid-liquid flow and the particle trajectory in a bladed disc pump, numerical simulation method was adopted to perform steady-state numerical simulation of spherical particles with different diameters (0.1 mm, 0.25 mm, 0.4 mm) in the bladed disc pump. The results indicate that compared to conventional centrifugal pumps, the performance of the bladed disc pump is lower. The variation in particle diameter has a minor influence on the intensity of the internal flow field in the bladed disc pump. The particle trajectories inside the impeller of the bladed disc pump are more chaotic, with larger diameter particles exhibiting a wider range of trajectory variations, while smaller diameter particles maintain relatively stable motion trajectories.

Robust Grasping of a Variable Stiffness Soft Gripper in High-Speed Motion Based on Reinforcement Learning.

Industrial robots are widely deployed to perform pick-and-place tasks at high speeds to minimize manufacturing time and boost productivity. When dealing with delicate or fragile goods, soft robotic grippers are better end effectors than rigid grippers due to their softness and safe interaction. However, high-speed motion causes the soft robotic gripper to vibrate, leading to damage of the objects or failed grasping. Soft grippers with variable stiffness are considered to be effective in suppressing vibrations by adding damping devices, but it is quite challenging to compromise between stiffness and compliance. In this article, a controller based on deep reinforcement learning is proposed to control the stiffness of the soft robotic gripper, which can accurately suppress the vibration with only a minor influence on its compliance and softness. The proposed controller is a real-time vibration control strategy, which estimates the output of the controller based on the current operating environment. To demonstrate the effectiveness of the proposed controller, experiments were done with a UR5 robotic arm. For different situations, experimental results show that the proposed controller responds quickly and reduces the amplitude of the oscillation substantially.

Interplay of fluid rheology and micro-patterning toward modulating draining characteristics on an inclined substrate

We investigate a gravity-driven thin film flow of a non-Newtonian liquid over an inclined micro-patterned surface. We demonstrate the effect of micro-patterning on the film draining rate and the velocity profile by varying the relative slit width (Tr) and the length of the periodic irregularities (L). We unveil the interplay of the substrate structure and the fluid rheology by modeling the non-Newtonian thin film using the Carreau model, and the rheology of the film is varied for different values of power index n. Through numerical simulations, we delineate the effects of inertia, viscous, and capillary forces on the physics of thin film flow. We report a significant augmentation of flow velocity for both shear-thinning and shear-thickening fluids as a result of substrate micro-patterning, with the relative slit width playing a dominant role while the length of the periodic irregularities has only a minor influence on drainage characteristics. However, when the sole effect of fluid rheology is considered, flow velocity enhances for pseudoplastic fluid and decreases for dilatant fluid in comparison to Newtonian fluid. We examine the combined effect of rheology and substrate topography, revealing the dominating influence of micro-patterning at high slit-widths, while the fluid rheology has a greater role to play at lower slit-widths. We also demonstrate that the susceptibility of flow physics on varying rheology or topography is greatest for low viscosity liquids. Finally, we mark different regimes where the augmentation of average velocity and surface velocity are individually achieved. Hence, we propose a suitable combination of substrate structure and fluid rheology to engineer a flow characteristic. Based on the suitability for various applications, we provide the key to simultaneously optimizing the fluid rheology and substrate micro-patterning for precise engineering and controlling the draining characteristics of a thin film.

Hybrid Material Extrusion Process Optimization for Printability and Adhesion in 3D‐Printed Electronics

3D printing exhibits strong potential in electronics manufacturing for its capability of manufacturing complex structures with a wide range of materials. However, thermoplastic polyurethane (TPU) has rarely been fabricated by 3D printing for electronics due to the limited understanding of its printability and the adhesion of the conductors on it. Herein, we invetigate the printability of TPU using varying layer height and printing temperature in the Materials Extrusion (MEX) process, their impacts on the printability, and the adhesion of conductive trace on TPU. The printability is characterized by the surface roughness, stability of dimension and mass, and the adhesion is evaluated by a standard cross‐cutting method. In this research, 0.20 mm layer height and 220 °C printing temperature have consistently proven to be optimal configuration parameters for MEX printing of TPU. Larger layer height in TPU printing causes poorer printing quality (lower dimensional accuracy, more porous structure, rougher surface), lower ink–TPU adhesion, and transforms the adhesive failure of ink against peeling to cohesive failure. Higher printing temperature causes less homogeneous structure and rougher surface with minor influence on the width and conductivity of ink on TPU, and no influence on the mechanism of ink failure against peeling.

Simplified solution for calculating active thrusts on retaining walls with a broken backslope

This paper reviewed Satyanarayana’s solution for calculating the active thrust on a retaining wall with a broken backslope. To improve Satyanarayana’s solution, a limit broken backslope height was proposed. A parametric study was conducted to investigate the influences of several key factors on the calculated active thrusts and their application point heights using the Satyanarayana solution. To simplify the calculation method, this paper proposes an equivalent infinite backslope angle based on the force equivalency between Satyanarayana’s and Coulomb’s solutions. This paper also proposes an empirical formula to estimate the equivalent infinite backslope angle and a simplified solution for calculating the active thrust. A numerical method was used to examine design examples of retaining walls with a broken backslope as compared with the Satyanarayana, Coulomb, and simplified solutions. The parametric study showed that the broken backslope height, the soil internal friction angle, the wall inclination angle, and the broken backslope angle had significant effects on active thrusts, while the wall-soil interface angle had a minor influence on the active thrust. The calculated equivalent infinite backslope angle using the proposed empirical formula well matched that calculated based on the force equilibrium. The design examples demonstrated that the simplified solution was easy and accurate for the design of retaining walls with a broken backslope.

Behavior of Zn5Al hot-dip galvanized steel members under fire exposure

PurposeBased on the known positive effects of conventional hot-dip galvanizing under fire exposure and indicative results on zinc–aluminum coatings from smallscale tests, a series of tests were conducted on zinc-5% aluminum galvanized test specimens under fire loads to verify the previous positive findings under largescale boundary conditions.Design/methodology/approachThe emissivity of zinc-5% aluminum galvanized surfaces applied to steel specimens was determined experimentally under real fire loads and laboratory thermal loads in accordance with the normative specifications of the standard fire curve. Both large and smallscale specimens were used in this study. The steel grade and surface conditions of the specimens were varied for both test scenarios.FindingsLargescale tests on specimens with typical steel construction dimensions under fire loads showed that the surface emissivity of zinc-5% aluminum galvanized steel was significantly lower than that of the conventionally galvanized steel. Only minor influences from the weathering of the specimens and steel chemistry were observed. These results agree well with those obtained from smallscale tests. The design values of zinc-5% aluminum melt (Zn5Al) required for the structural fire design were proposed based on the obtained results.Originality/valueThe novel tests presented in this study are the first ones to study the behavior of zinc-5% aluminum galvanized largescale steel construction components under the influence of real fire exposure and their positive effect on the emissivity of steel components galvanized by this method. The results provide valuable insights and information on the behavior in the case of fire and the associated savings potential for steel construction.

First principle investigation of structural, electronic, optical and thermoelectric properties of Chalcogenide Sr2GeX4(X=S, Se)

The electronic and optical properties of ternary-type chalcogenides are of great interest for solar energy conversion applications. In this study, we investigated the optical, electronic, and transport properties of Sr2GeX4 (X = S and Se) materials using first-principles calculations based on density functional theory. We found that these materials have a robust covalent bond nature and substantial band gaps. The density of states calculations revealed that the Sr-s and Ge-s states play a predominant role, while the S-s and S-p states have a minor influence. The optical properties of the materials are anisotropic, and they have significant UV absorption. The positive Seebeck coefficient values suggest that holes are the primary charge carriers in both materials. The study also discussed various other crucial thermoelectric parameters, which collectively suggest the suitability of these materials for thermoelectric applications. Overall, this study provides valuable insights into the optoelectronic and thermoelectric properties of Sr2GeX4 materials, which could significantly contribute to the development of efficient optoelectronic devices.

SEISMIC MITIGATION EFFECT FOR LARGE-SPACE UNDERGROUND STRUCTURES CONSIDERING SPATIALLY VARYING SOIL PROPERTIES

The seismic response of the large-space underground structure (LSUS) is significantly influenced by the physical properties of the surrounding soil media, while the soil owns a strong spatial variability. This study proposes a seismic response analysis process of the soil-LSUS interaction system is proposed, which can consider the characteristic of the spatially distributed soil properties. The proposed process begins with establishing the spatially random field model of the soil properties using the improved latent space method. Then, the model is calibrated based on the real data and Bayesian approach, and the realization of the random field is accomplished. Further, the soil-LSUS interaction finite element (FE) model is established, which incorporating the soil physical properties generated from the random field. Finally, the nonlinear time-history analysis of the soil-LSUS interaction FE model is conducted. As an illustration of the proposed process, a typical LSUS located in Guangzhou is selected as an example, and the seismic mitigation measure which the lead-filled steel tube damper (LFSTD) is installed between the intermediate column and the top beam is adopted for the LSUS. The influence of the spatial variability of soil properties on the seismic mitigation effect of the LSUS is investigated. Results indicate that the spatial variability of the soil properties can cause a minor influence on the force and deformation of the intermediate column and the energy dissipation ratio between the LFSTD and structure, while it can bring a significant influence on the maximum deformation and force and the shape of the hysteresis loop of the LFSTD.

Modeling of heat transfer and fluid flow in the metal being welded during DC and HFPC TIG spot welding

A mathematical model of non-stationary electromagnetic, heat and mass transfer processes in the metal during high frequency pulsed current (HFPC) TIG spot welding has been proposed. A computational algorithm for the the numerical solution of the corresponding mathematical problems has been developed and implemented in Wolfram Language. A comparative analysis of the hydrodynamic and heat transfer processes in the specimen of steel S-235JR during HFPC TIG welding with 10 kHz square wave pulse current modulation and direct current (DC) TIG welding with current equal to the mean current of HFPC mode has been carried out. As simulations showed, the HFPC modulation results to appreciable weld penetration with minor influence on the radius of the fusion zone compared to the DC process.