Laboratory Simulation Research Articles

Analysis of strength size effect and failure mechanism of asphalt mixtures based on discrete element method

The purpose of this study is to further investigate the strength size effect and failure mechanism of asphalt mixtures and clarify the strength parameter conversion relationship between standard and non-standard size samples. The article established an improved microscopic model for uniaxial compression and indirect tensile testing of asphalt mixtures based on laboratory and discrete element simulation tests. The effects of thickness and gradation on the uniaxial compressive strength (UCS) and indirect tensile strength (ITS) of asphalt mixtures were studied. The loading rates of the UCS and ITS tests were set at 2 mm/min and 50 mm/min, respectively. Additionally, the tensile-compressive stress distribution, crack propagation, and strength contribution rates of different contact types within the sample were investigated during the virtual model loading process. The reliability of the model was validated through laboratory test results. Finally, the strength parameter conversion relationship between standard and non-standard size samples was investigated. The study found that the UCS of asphalt mixtures decreases with increasing thickness, while the ITS increases with increasing thickness, with average reduction and increase rates of 70.69 % and 24.18 %, respectively. The contact fracture ratio and the strength contribution rate of the aggregate-asphalt mortar contacts both exceed 50 %, indicating that the fracture of these contacts is the primary cause of asphalt mixture failure. The use of small-sized samples instead of standard samples in practical applications is promising. These research work outcomes can serve as a theoretical basis for designing asphalt pavement materials and acquiring existing asphalt pavement material parameters.

Procedures Group Chat: A Resident-Driven Approach to Increase Procedural Competency

Introduction: In 2007, the American Board of Internal Medicine (ABIM) shifted away from requiring completion of procedures during residency training and towards emphasizing common procedural indications, contraindications, and complications. As a result, many procedures are now referred to consulting services such as critical care and interventional radiology (IR). Our aim was to address this training gap through a resident-driven initiative that provided daily opportunities to collaborate on procedures in a supervised clinical setting. Methodology: In January 2023, we created a secure group chat and invited Internal Medicine (IM) residents to voluntarily join if they were interested in learning or teaching bedside procedures such as thoracenteses, paracenteses, lumbar punctures, and line placement. Residents who identified a need for a non-emergent bedside procedure would reach out in the group chat to see if a resident certified to perform and supervise that procedure would be available and could subsequently coordinate availability. A two-question survey was sent to the entire residency program asking residents whether they were a part of the group chat and whether they found the chat helpful in advancing their medical knowledge. The impact of the initiative was measured through procedures logged in to New Innovations, a website used by graduate medical education to log completed procedures. We chose five procedures (paracenteses, thoracenteses, central lines, arterial lines, and lumbar punctures) to compare changes in procedure volume performed by IM residents one year before and after the group chat was set up. Results: 64 out of 108 residents responded to the survey (59% response rate). 90% of respondents stated that they were part of the group chat and 76.6% responded they “agree/strongly agree” that the procedures group chat has been helpful. Objective measures of the group chat’s impact revealed a 93% increase in the number of procedures performed by residents. IM Residents logged 122 procedures in 2022, the year prior to the initiation of the group chat, compared to 235 procedures logged in 2023, the year after. There was a 96% increase in paracentesis and 387% change in thoracenteses completed after the group chat was established. Conclusions: The procedures group chat nearly doubled the number of procedures completed and logged by residents. This group chat has fostered enthusiasm for patient care by helping us overcome some of the barriers and delays in health care due to factors out of our control, such as limited resources or staffing. Due to the inexpensive nature of this initiative, it can be easily replicated at other IM programs across the country, especially those without resources such as simulation centers. Future goals include creating formal teaching sessions including cadaver lab simulations and a proceduralist elective for procedures to be taught and supervised by certified residents, attendings, and subspeciality services for a multidisciplinary education.

Rapid Production Nasal Osteotomy Simulators With Multi-Modality Manufacturing: 3D Printing, Casting, and Molding.

To expand and improve upon previously described nasal osteotomy models with the goals of decreasing cost and production time while ensuring model fidelity. To assess change in participant confidence in their understanding of and ability to perform nasal osteotomies following completion of the simulation course. Prospective study. Simulation training course for otolaryngology residents at West Virginia University. A combined methodology of 3D printing, silicone molding, and resin casting was used to design a nasal osteotomy model to address material issues such as print delamination. Multiple models were then used in a simulation lab on performing nasal osteotomies. Model utility and impact on participant confidence was assessed at baseline, postlecture, and postsimulation lab. Using a combined manufacturing methodology, we achieved a production time reduction of 97.71% and a cost reduction of 82.02% for this polyurethane resin nasal osteotomy model relative to a previously described osteotomy model. Participants in the simulation course were noted to have a significant improvement in confidence in their understanding of and ability to perform nasal osteotomies from baseline and postlecture and also from postlecture and postsimulation lab (P < .05 for all). By incorporating multiple manufacturing modalities (molding and casting) in addition to 3D printing, this study achieved a large reduction in both production time and cost in fabrication of a nasal osteotomy simulator and addressed material limitations imposed by fused deposition modelingprinters. This design methodology serves as an example on how these barriers may be addressed in unrelated simulation projects. Model fidelity was improved with addition of a silicone soft tissue midface. Improvement in participant confidence was noted following completion of the simulation lab.

Determination of Activation Energy For Static Re-Crystallization in Nb- Ti Low Carbon Micro Alloyed Steel

Data required for calculation the static re-crystallization kinetics have been evaluated from laboratory simulations. Series of two hit isothermal tests were conducted on high temperature torsion machine. These tests were conducted on four different temperatures and using inter-pass times between 0.5 and 5s with aim to investigate the influence of thermal activation on static re-crystallization. All tests were conducted on temperatures over TNR temperature, i.e. in temperature range in which all niobium is present only in solid solution. Method of evaluation of re-crystallization fraction was mechanical metallography, i.e. evaluation based on shape of each stress- strain curve. The fraction softening was calculated for all temperatures, together with avrami exponent, nA, and activation energy for re-crystallization, QSRX. Activation energy for static re-crystallization QSRX  281 KJ/mol and avrami exponent nA  1 determined in this work are in excellent agreement with previously reported data.

Analisis Pengaruh Suhu Terhadap Nilai Konduktivitas Pada Perpindahan Panas Secara Konduksi Menggunakan Virtual Lab Amrita

This study aims to determine the effect of temperature value on conductivity value (conduction heat rate) in conduction heat transfer. The method used in this research is an experimental method with variable temperature and variable conductivity values of materials using amrita virtual lab simulation software. The variable variation used in this study is the difference in materials using cardboard and glass with variations in voltage, current, diameter and thickness of the same material. The results of this study indicate the effect of temperature on the conductivity value, if the conductivity value of a material is small then the temperature will be large because this experiment was conducted on insulating materials on both objects. Temperature will inhibit heat transfer by conduction, it can be concluded that both materials are good heat insulators. Keywords: Conduction heat transfer, Temperature, vlab Amrita.

Analisis Pengaruh Ketinggian Lintasan Terhadap Gaya Gesek dan Kecepatan Benda Pada Bidang Miring Menggunakan PhET Simulation

Physics is an empirical science, meaning that physics is based on observation and experimentation. One of the fundamental concepts in physics that is the foundation for many calculations is the law of mechanical energy conservation, especially on inclined planes. This study aims to analyze the effect of track height on the friction force and velocity of objects when crossing an inclined plane. This research uses a virtual PhET Simulation laboratory with a virtual experimental research design. This research uses a quantitative approach, the data analysis technique uses statistical methods to determine the effect of track height on the friction and speed of objects. The result of this study is that the height of the track affects the value of the friction force, with increasing track height, the value of the friction force will decrease, this is due to the normal force acting on the inclined plane. In addition, with increasing track height on an inclined plane, the value of mechanical energy will increase. This is because the higher the trajectory, the greater the gravitational potential energy possessed by the object. Keywords: Altitude, Inclined plane, Mechanics, Speed.

Effect of Nitrogen on the Structure and Composition of Primordial Organic Matter Analogs.

Organic molecules are ubiquitous in primitive solar system bodies such as comets and asteroids. These primordial organic compounds may have formed in the interstellar medium and in protoplanetary disks (PPDs) before being accreted and further transformed in the parent bodies of meteorites, icy moons, and dwarf planets. The present study describes the composition of primordial organics analogs produced in a laboratory simulator of the PPD (the Nebulotron experiment at the CRPG laboratory) with nitrogen contents varying from N/C < 0.01 to N/C = 0.63. We present the first Fourier transform ion cyclotron resonance mass spectrometry analysis of these analogs. Several thousands of molecules with masses between m/z 100 and 500 are characterized. The mass spectra show a Gaussian shape with maxima around m/z 250. Highly condensed polyaromatic hydrocarbons (PAH) are the most common compounds identified in the samples with lower nitrogen contents. As the amount of nitrogen increases, a dramatic increase of the chemical diversity is observed. Nitrogen-bearing compounds are also dominated by polyaromatic hydrocarbons (PANH) made of 5- and 6-membered rings containing up to four nitrogen atoms, including triazine and pyrazole rings. Such N-rich aromatic species are expected to decompose easily in the presence of water at higher temperatures. Pure carbon molecules are also observed for samples with relatively small fractions of nitrogen. MS peaks compatible with the presence of amino acids and nucleobases, or their isomers, are detected. When comparing these Nebulotron samples with the insoluble fraction of the Paris meteorite organic matter, we observe that the samples with intermediate N/C ratios bracketing that of the Paris insoluble organic matter (IOM) display relative proportions of the CH, CHO, CHN, and CHNO chemical families also bracketing those of the Paris IOM. Our results support that Nebulotron samples are relevant laboratory analogs of primitive chondritic organic matter.

The Application of Virtual Simulation Laboratory in University Physics Teaching

The Application of Virtual Simulation Laboratory in University Physics Teaching

Impact of gas arising from gas hydrate decomposition on the effective permeability of bottom sediments of the Arctic shelf: a laboratory simulation

Relevance. The necessity to investigate the mechanism of gas (methane) flow occurring during decomposition of gas hydrate formations within the layers of bottom sediments. This process is evident through substantial releases of methane bubbles in extensive shallow regions of the Russian Arctic shelf and has the potential to alter the equilibrium of atmospheric methane, a critical greenhouse gas. Aim. To quantitatively investigate, within the context of gas transport in bottom sediments, the impact of free and bound gas within the pores on the nonlinearity of filtration flows. Methods. The model samples with filtration properties similar to those of the bottom rocks of the East Siberian Arctic shelf. During the experiments, a specific amount of gas was injected into the saturated model sample, followed by the measurement of its effective permeability during a slow decrease in pore pressure gradient. The obtained curve was interpreted within the framework of the threshold gradient model. Results. The experiments yielded curves showing the dependency of the threshold gradient magnitude on gas saturation for several samples. It was found that the threshold gradient linearly increases with the growth in gas fraction within the pore space. Already at a gas fraction of approximately 0.02, this value in the experiments reached 0.01 MPa/m, corresponding to the hydrostatic pressure gradient in water. This suggests that even areas with relatively low gas saturation may be impermeable to convective fluid flow. This possibility should be considered when creating models for bubble gas transporting through the rock layers of bottom sediments. Furthermore, the existence of gas-saturated zones with threshold gradients can significantly impact the vertical profile of pore pressure and lead to a reassessment of the depth of gas hydrate stability zones.

Field Compaction Characteristics of Ultra-Thin Porous Friction Course Based on Laboratory Simulation

As a preventive maintenance treatment, the ultra-thin porous friction course (UPFC) has been widely recognized and used in road maintenance because of its excellent performance and cost effectiveness. The Marshall compaction method (MCM) has been adopted to design UPFC mixtures worldwide, particularly in China. However, there are few studies concerning the field compaction properties of MCM-designed UPFCs. The laboratory test results of this study from simulating on-site compaction showed that all UPFC specimens with thicknesses of less than 20 mm barely achieved the target compaction thickness, and all UPFC specimens with different thicknesses failed to meet the air void (AV) requirements of UPFC mixes designed using the MCM. According to the results of a virtual compaction test, and using the discrete element method, the strong force chains were strengthened as the UPFC thickness decreased inside the specimen, making it difficult to evenly diffuse and transfer inside the specimen and resulting in insufficient compaction of the UPFC. Furthermore, it was demonstrated that the MCM-designed UPFC specimens showed significant differences in the AV distributions along the vertical and lateral directions from those of the UPFC specimens that simulated field compaction. The UPFCs designed using the MCM had a poor correlation with field compaction.

Biofilm-forming Ability of Bacillus thuringiensis Strains from Biopesticides on Polystyrene and their Attachment on Spinach

Bacillus thuringiensis-based commercial products as a biopesticide have been used for more than 60 years in agriculture. However, as one of the species in B. cereus group, B. thuringiensis has been considered as an emerging hazard with the potential to cause food toxico-infections. The present study aimed to evaluate the biofilm-forming ability of B. thuringiensis biopesticide strains and their attachment on spinach, compared to foodborne B. cereus strains. Biofilm formations of tested strains were found to be strain-specific and affected by the nutrient conditions more than the incubation time. Nutrient starvation conditions generally reduced the biofilm formation of tested B. thuringiensis and B. cereus strains, particularly B. thuringiensis ABTS-1857 strain was found as the nonbiofilm former in starvation conditions. It is worth mentioning that B. thuringiensis SA-11 strain showed stronger biofilm-forming ability with more air–liquid interface biofilm than the other two B. thuringiensis biopesticide strains, but no such higher attachment of B. thuringiensis SA-11 to spinach was observed. These results indicate that B. thuringiensis SA-11 strain can enter the food processing lines by the attachment on spinach leaves, and it has the potential to form biofilms throughout the processing lines or the production environment when sufficient nutrients are available. However, more biofilm tests of B. thuringiensis biopesticide strains in the vegetable production chain should be performed. The dry formulation of commercial B. thuringiensis biopesticides enhanced their adhesion on spinach leaves, whereas the strength of adhesion was not improved by the formulation. In addition, 1–2 log reductions of spores after the intensive washing of spinach leaves in the lab were detected. However, the log reduction due to the actual washing done by the food processing companies in large-volume washing baths or by consumers at home would be limited and less than this lab simulation.

Novel design of multi-point injection system for laboratory simulation of Martian low-pressure dust devils

The Martian surface is frequently traversed by dust devils, presenting formidable challenges to exploration missions and posing significant safety risks. Establishing a ground-based simulation device for low-pressure Martian dust devils is essential for conducting reliability testing and research on extreme environments relevant to Mars rovers. This study introduces a Martian dust devil simulator comprising a simulation cabin and multi-point injectors. This apparatus facilitates the investigation of velocity and pressure distribution patterns within the flow field under varying operational conditions by adjusting injector positions, inlet pressure, and internal pressure. The simulator's design allows it to replicate Martian dust devil velocity fluctuations from 0 to 50 m/s and pressure variations spanning 100–1500 Pa, thereby meeting crucial criteria for simulating Martian atmospheric conditions. Through computational fluid dynamics (CFD) simulation, we analyzed the characteristics of dust devils generated by the simulation device and scrutinized the flow field properties following the coupling of sand-dust particles with airflow. The observed dust devil flow field closely resembles the Vastitas Borealis vortex. Additionally, experimental research was conducted. Comparing experimental, simulated, and theoretical models revealed a high degree of consistency in the internal flow field characteristics of the simulated dust devils. The apparatus's versatility extends to simulating various dust devil morphologies, offering significant potential for conducting model experiments pertinent to Martian probes and facilitating future crewed Mars exploration endeavors.

Curriculum teaching of mechatronics in the information age

Abstract: In the wave of digital education, the teaching design and practice of mechatronics integration courses in the information age become the key to innovative education. The course combines online teaching, virtual experiments and remote control techniques to break the limitations of a traditional classroom. Through multimedia courseware, real-time interactive platform and virtual simulation laboratory, students can not only master theoretical knowledge flexibly, but also conduct practical training online. Remote control technology enables students to operate practical equipment in real time and enhance their practical skills. The preliminary practice shows that this mixed teaching mode effectively improves students' interest in learning and practical ability, and provides a new direction and opportunity for mechatronics education.

Photosynthetic response to a winter heatwave in leading and trailing edge populations of the intertidal red alga Corallina officinalis (Rhodophyta)

Marine heatwaves (MHWs) caused by anthropogenic climate change are becoming a key driver of change at the ecosystem level. Thermal conditions experienced by marine organisms across their distribution, particularly towards the equator, are likely to approach their physiological limits, resulting in extensive mortality and subsequent changes at the population level. Populations at the margins of their species’ distribution are thought to be more sensitive to climate-induced environmental pressures than central populations, but our understanding of variability in fitness-related physiological traits in trailing versus leading-edge populations is limited. In a laboratory simulation study, we tested whether two leading (Iceland) and two trailing (Spain) peripheral populations of the intertidal macroalga Corallina officinalis display different levels of maximum potential quantum efficiency (Fv/Fm) resilience to current and future winter MHWs scenarios. Our study revealed that ongoing and future local winter MHWs will not negatively affect leading-edge populations of C. officinalis, which exhibited stable photosynthetic efficiency throughout the study. Trailing edge populations showed a positive though non-significant trend in photosynthetic efficiency throughout winter MHWs exposure. Poleward and equatorward populations did not produce significantly different results, with winter MHWs having no negative affect on Fv/Fm of either population. Additionally, we found no long-term regional or population-level influence of a winter MHWs on this species’ photosynthetic efficiency. Thus, we found no statistically significant difference in thermal stress responses between leading and trailing populations. Nonetheless, C. officinalis showed a trend towards higher stress responses in southern than northern populations. Because responses rest on a variety of local population traits, they are difficult to predict based solely on thermal pressures.

Electrical Conductivity of Subsurface Ocean Analogue Solutions from Molecular Dynamics Simulations.

Investigating the habitability of ocean worlds is a priority of current and future NASA missions. The Europa Clipper mission will conduct approximately 50 flybys of Jupiter's moon Europa, returning a detailed portrait of its interior from the synthesis of data from its instrument suite. The magnetometer on board has the capability of decoupling Europa's induced magnetic field to high precision, and when these data are inverted, the electrical conductivity profile from the electrically conducting subsurface salty ocean may be constrained. To optimize the interpretation of magnetic induction data near ocean worlds and constrain salinity from electrical conductivity, accurate laboratory electrical conductivity data are needed under the conditions expected in their subsurface oceans. At the high-pressure, low-temperature (HPLT) conditions of icy worlds, comprehensive conductivity data sets are sparse or absent from either laboratory data or simulations. We conducted molecular dynamics simulations of candidate ocean compositions of aqueous NaCl under HPLT conditions at multiple concentrations. Our results predict electrical conductivity as a function of temperature, pressure, and composition, showing a decrease in conductivity as the pressure increases deeper into the interior of an icy moon. These data can guide laboratory experiments at conditions relevant to icy moons and can be used in tandem to forward-model the magnetic induction signals at ocean worlds and compare with future spacecraft data. We discuss implications for the Europa Clipper mission.

Electrode structural effects on the mechanism of high-voltage pulse rock breaking

In the oil drilling process, drilling costs account for more than 50% of total E&P costs. High-voltage electric pulse rock breaking is an economical and effective rock-breaking method that has received widespread attention. At present, there is not much research on the influence of the shape of the electrode tip on high-voltage pulse rock breaking. This paper establishes a system of equations that control the electric breakdown field based on the changes in the electric field inside the rock. Then, using this model, we conducted simulation and laboratory experiments to understand how rocks break under different conditions, such as load voltages, electrode spacing, and electrode tip shapes. The results show that the volume of broken rock is directly related to the loading voltage. The best loading voltage range is between 200 and 220 kV. Increasing the spacing between electrodes helps break more rock, but if the electrode spacing is too large, it's hard to make a hole in the rock, and the rock won't break. An electrode spacing of around 35 mm is the best. The shape of different electrode tips directly affects the high-voltage pulse breaking effect. Hemispherical electrode tips are less favorable for rock breaking, while oval electrode tips are the best. The laboratory experiments and simulations give the same conclusions and verify the applicability and correctness of our model. This study aims to help design high-voltage electric pulse devices.

A laboratory infrared model of astrophysical pyrimidines

ABSTRACT Nucleobases are essential molecules for life, forming integral parts of deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) in all terrestrial life forms. Despite evidence of their abiotic synthesis in meteorites and laboratory simulations of interstellar medium (ISM) conditions, nucleobases have not been detected in the ISM. This study investigates the infrared spectra of uracil, cytosine, and thymine – pyrimidine nucleobases – embedded in an ice mixture simulating common volatiles found in protostellar discs. Our objective was to explore the feasibility of identifying unique infrared bands of pyrimidines in the ISM, despite significant overlapping absorption features from simpler, more abundant interstellar species such as H2O, CO, CH3OH, and NH3. Laboratory results revealed that although two common bands (1240 and 760 cm−1 in uracil; 1236 and 763 cm−1 in cytosine; and 1249 and 760 cm−1 in thymine) were identified, the detection of these bands in space is challenged by overlapping absorption features. Recent observations with the JWST have shown that interstellar organic species exhibit infrared signals within similar ranges, making it impossible to distinguish pyrimidine bands from these organics. Thus, detecting pyrimidines with current telescopes is infeasible, not due to sensitivity limitations or the need for more powerful instrumentation, but because of the intrinsic overlap in spectral features. This study complements previous research on purines by examining pyrimidines and including the impact of common ISM volatiles in the ice composition. The results highlight the significant challenges in detecting complex molecules in the ISM, underscoring the importance of understanding the spectral complexities and interactions to interpret astronomical observations accurately.

The impact of team competence on short- and long-term team performance

PurposeDue to the current shortage of skilled employees, there is a growing need to cope with given team settings and to offer appropriate team training. For team training, it is important to know how different competences influence team performance. Therefore, this study aims to examine the influence of social and cognitive competences on team performance and the relationship of the different competence dimensions to each other.Design/methodology/approachData of 53 student and work teams was collected through a digital simulation laboratory, designed as an escape game. Competences of 228 team members were assessed through questionnaires prior to the simulation. Team performance was measured through short-term performance indicators. Additionally, a postsimulation survey regarding a long-term performance indicator was carried out. Three multiple regression analyses and mediation analyses were conducted.FindingsA tradeoff between cognitive and social competences regarding their impact on short- and long-term team performance is observed. Facets of cognitive competences enhanced short-term performance, whereas facets of social competences reduced short-term performance while enhancing long-term performance. Although cognitive competences show a positive direct effect on short term performance, a negative indirect effect, mediated by social competences, became apparent.Originality/valueThis paper contributes to harmonizing contradictory findings on the impact of high achievers in teams. Although they can have an impact on rapid problem solving, long-term performance depends more on facets of social competences than cognitive competences. Furthermore, social and cognitive competences are positively correlated, showing that teams with higher cognitive competences tend to become stronger in terms of their social competences over time.

Integrating Transcriptomics and Proteomics to Characterize the Intestinal Responses to Cadmium Exposure Using a Piglet Model.

Cadmium (Cd) is a heavy metal element with a wide range of hazards and severe biotoxicity. Since Cd can be easily accumulated in the edible parts of plants, the exposure of humans to Cd is mainly through the intake of Cd-contaminated food. However, the intestinal responses to Cd exposure are not completely characterized. Herein, we simulated laboratory and environmental Cd exposure by feeding the piglets with CdCl2-added rice and Cd-contaminated rice (Cdcr) contained diet, as piglets show anatomical and physiological similarities to humans. Subsequent analysis of the metal element concentrations showed that exposure to the two types of Cd significantly increased Cd levels in piglets. After verifying the expression of major Cd transporters by Western blots, multi-omics further expanded the possible transporters of Cd and found Cd exposure causes wide alterations in the metabolism of piglets. Of significance, CdCl2 and Cdcr exhibited different body distribution and metabolic rewiring, and Cdcr had stronger carcinogenic and diabetes-inducing potential. Together, our results indicate that CdCl2 had a significant difference compared with Cdcr, which has important implications for a more intense study of Cd toxicity.

Bacterial surface properties and transport behavior actively respond to an extracellular polymeric substance gradient in saturated porous media

The transport and retention of bacteria in porous media, such as aquifer, are governed by the solid-liquid interface characteristics and bacterial mobility. The secretion of extracellular polymeric substance (EPS) by bacteria modifies their surface property, and thereby has effects on their adhesion to surface. The role of EPS in bacterial mobility within saturated quartz sand media is uncertain, as both promoting and inhibitory effects have been reported, and underlying mechanisms remain unclear. In this study, the effects of EPS on bacterial transport behavior and possible underlying mechanism were investigated at 4 concentrations (0 mg L−1, 50 mg L−1, 200 mg L−1 and 1000 mg L−1) using laboratory simulation experiments in conjunction with Extend Derjaguin-Landau-Verweu-Overbeek (XDLVO) modeling. The results showed that EPS facilitated bacterial mobility at all tested concentrations. It could be partially explained by the increased energy barrier between bacterial cells and quartz sand surface in the presence of EPS. The XDLVO sphere-plate model predicted that EPS induced a higher electrostatic double layer (EDL) repulsive force, Lewis acid-base (AB) and steric stabilization (ST), as well as a lower Lifshitz-van der Waals (LW) attractive force. However, at the highest EPS concentration (1000 mg L−1), the promotion of EPS on bacterial mobility weakened as a result of lower repulsive interactions between cells, which was supported by observed enhanced bacterial aggregation. Consequently, the increased aggregation led to greater bio-colloidal straining and ripening in the sand column, weakening the positive impact of EPS on bacterial transport. These findings suggested that EPS exhibited concentration-dependent effects on bacterial surface properties and transport behavior and revealed non-intuitive dual effects of EPS on those processes.