Solid Model Research Articles

Evaluating the accuracy between hollow and solid dental aligner models: a comparative study of printing technologies

Abstract Objective To evaluate the accuracy between hollow and solid dental models produced using a StereoLithography Apparatus (SLA), Digital Light Processing (DLP), and PolyJet 3D printing technologies. Materials and methods Hollow (of 1 mm, 2 mm, 3 mm shell thicknesses) and solid maxillary models were produced using SLA, DLP, and PolyJet printers. To determine the accuracy of the tested models and deviations from the reference models, 3D digital superimposition was performed. For a detailed analysis, the dental arch was subdivided into five regions which yielded root mean square (RMS) values post-registration. Six different RMS values were generated, one for the total dental arch and one for each of the five individual regions. One-Way ANOVA analysis was applied for intergroup comparisons, and post hoc comparisons were conducted using the Tukey test. The significance of the deviation of RMS values from zero was evaluated through the one-sample t test. Results The PolyJet printer produced models with the least deviation for the total arch, while the SLA printer showed the greatest deviation. The DLP printer produced models with the least deviation for the hollow designs in the anterior region, while the SLA printer produced models with the least deviation of the solid design. The PolyJet printer showed the least deviation for both hollow and solid designs of 2 mm and 3 mm shell thicknesses in the molar regions. Except for the 1 mm shell thickness hollow design on the right side, the PolyJet printer showed the highest accuracy in the premolar-canine regions. Conclusion Accuracy varies in the posterior and anterior regions of the dental arch as a result of different shell thicknesses produced by 3D printing technologies. The clinician should select a design that is appropriate for the intended 3D printing technology based on use and required accuracy.

Investigation on gas–liquid–solid three-phase flow model and flow characteristics in mining riser for deep-sea gas hydrate exploitation

In response to the problem of gas–liquid–solid three-phase flow in deep-sea hydrate extraction pipelines, a gas–liquid–solid three-phase flow model considering the dynamic decomposition of hydrates is established using continuity equations, momentum equations, and energy equations. The numerical solution of the theoretical model is achieved using the finite difference method. Comparing the theoretical model with the experimental results, the results showed that the average error of gas holdup, liquid holdup, solid phase content, gas phase velocity, liquid phase velocity, and solid phase velocity obtained from the theory and experiment are 8.24%, 0.41%, 1.88%, 5.80%, 2.81%, and 2.22%, respectively, which verified the correctness of the theoretical model. On this basis, the influences of hydrate abundance, liquid phase displacement, and wellhead backpressure on the gas–liquid–solid three-phase flow characteristics in the pipeline were investigated, and it was found that the gas holdup rate will increase with the increase in hydrate abundance, liquid phase displacement, and wellhead backpressure, with the influence of hydrate abundance being more sensitive. The liquid holdup rate increases with the increase in hydrate abundance and liquid phase displacement, but decreases first and then increases toward the wellhead position with the increase in wellhead backpressure. The solid phase content decreases with the increase in hydrate abundance, and first increases and then decreases toward the wellhead position as the liquid phase displacement and wellhead backpressure increase. The influence of gas phase velocity on the abundance of hydrates is relatively small, but it increases with the increase in liquid phase displacement. When the wellhead backpressure increases, the instantaneous increase then tends to flatten out. The influence of hydrate abundance on the liquid phase velocity is also relatively small, but it increases with the increase in liquid phase displacement and decreases with the increase in wellhead backpressure. The solid phase velocity will increase with the increase in hydrate abundance and liquid phase displacement, but it will not show significant changes with the change of wellhead backpressure. The research results can provide a theoretical basis for the safety of hydrate mining.

Low-dose gamma radiation controls let -7a and miR-21 in a solid tumor model.

Low-dose gamma radiation controls let -7a and miR-21 in a solid tumor model.

Solid Oxide Cell Reactor Model for Transient and Stationary Electrochemical H2O and CO2 Conversion Process Studies

The ability of high-temperature solid oxide cell (SOC) electrochemical reactors to efficiently convert atmospheric carbon to high value chemicals for industrial and energy storage applications via CO2 and co-electrolysis makes them a key technology for active carbon utilisation. However, due to additional operational risks from thermochemical reactions on thermal management, limited experimental capacity, and relative novelty, CO2 and co-electrolysis lag behind steam electrolysis in large-scale adoption. Here, a 1D+1D SOC model based on fundamental first principles considering three-dimensional heat transfer was improved via a unique method for representing co-electrolysis electrochemistry, solving with low computational effort. Validation against experimental data for two compositions and pressures, showed high levels of accuracy with respect to characteristic cell voltages, temperatures, and outlet compositions. The model also showed CO2 reduction during co-electrolysis mainly occurred via reverse water gas shift, while CO2 electrolysis still accounted for up to 35% of the total share. Pressurised co-electrolysis operation promotes exothermic methanation, causing pronounced heating of the reactor, consequently reducing the isothermal current density. Therefore, low to moderate pressurisation is likely most suited for coupling with downstream synthesis processes to avoid the installation of unnecessarily large systems and associated high costs.

Simulation and analysis of movement trajectories of fresh tea leaf particles based on CFD‐EDEM coupling

AbstractTo study the air‐suction separation mechanism of fresh tea leaves, this article adopts the coupling simulation method of discrete elements and computational fluid dynamics to conduct numerical simulation and experimental research on the movement of fresh tea leaves adsorbed by negative pressure air flow. In the gas–solid coupling model, three‐dimensional scanning technology is applied to establish a three‐dimensional model of fresh tea leaves with one bud and two leaves. Through the Fluent module in CFD, the negative pressure adsorption gas phase of the simulation process was established, bench tests were established, and parameters of the coupling model were optimized. Finally, the minimum error between the simulated value and the test value was 2.85% and the maximum error was 7.43%, indicating that the coupling model established had certain accuracy and could be theoretically analyzed according to the coupling model established. It is found that when the static pressure values of the adsorption surface are −120 Pa, −340 Pa, and −500 Pa respectively, the initial distance from the adsorption surface is 250–550 mm. It is found that fresh tea leaves with one bud and two leaves all fall to the pipe before adsorption, and then move to the adsorption surface. Under the same static pressure value of the adsorption surface, the initial falling distance of tea particles from the adsorption surface (250–550 mm) has a linear function relationship with the distance between the turning point and the adsorption surface. When the initial distance between falling tea particles and the adsorption surface is the same, the distance between the turning point and the adsorption surface is an exponential function when the initial position is 250–350 mm from the adsorption surface, and the distance between the turning point and the adsorption surface is a linear function when the initial position is 400–550 mm from the adsorption surface.

Loss of pre-stress in impregnated superconducting magnets, experimental results and numerical analysis

The SMC (Short Model Coil) R&D program was started at CERN around 2007 to develop the Nb3Sn technology. The small magnet structure allowed relatively cheap and fast testing of various superconducting coils. One of the key questions to be answered, was related to the relation between the pre-stress and the magnet’s performance. To measure this dozens of strain gauges were installed on the coils, the axial tie-rods and the external shell. The experimental results of the strain measurements during all stages of the load: room temperature (RT) pre-stress, cool-down, powering, warm-up were analyzed in an extensive report [56]. A repeatable pattern of a decreasing strain after the warm-up, compared to the value before the cool-down, was observed on the external cylinder for all the tested coils. Values from 2 % to 50 % were reported.In this work a viscoelastic model was used to explain this effect. The Nb3Sn coil was treated as a composite material with decreasing stiffness due to mechanical damage. The Generalized Maxwell Solid model (Prony series model) was employed, including one spring and one damper, leading to a relatively simple model characterized by only two parameters. The two constants of the viscoelastic model were found: 1st – the relative relaxation moduli α based on a calibration curve derived from the experimental results of the SMC program and the 2nd one – relaxation time τ – based on minimizing the computational cost, by finding the asymptotic solution in one integration step. The model showed the capability of explaining the strain drop (loss of pre-stress) of more than 80 %. In addition to the viscoelastic effects, the role of friction coefficient was studied revealing the possibility of explaining up to 14 % of the strain drop. Yet, to fit with the experimentally measures strains on the SMC cylinder, especially during the RT pre-load, the most-probable value of the friction coefficient should be μ<0.4. The strong impact of the stiffness of the G-10/G-11 laminate used to spread the load on the coil was found, indicating the need of knowing the elastic properties of this material very precisely. In addition, the experimentally measured strain values showed strong asymmetric, both in plane and along the magnet’s axis, revealing the potential sensitivity to the geometric imperfections and the need for 360° magnet models.

3D Modelling and Simulation Based on Kinematic Analysis for Hippotherapy

The engineering perspective on the physiology and anatomy of living things has led to the emergence of the science of biomechanics. Developing computer technologies have made it possible to examine the behaviour of living things in more detail and to develop technologies that enable kinetic and kinematic analysis of movements to imitate real limbs. In this study, the natural gaits of horses (Walk, Canter and Trot) were analysed with image processing techniques, kinematic analyses were made and three-dimensional solid models were created. Giving movement ability to the extracted solid models was carried out with the simulation software prepared on the Matlab-SimMechanic platform. By comparing the findings obtained as a result of image processing and simulation, the success of transferring the movements to a developed system was evaluated. After mathematical equations were created in the MATLAB environment, the equations were tested on the developed system and their performance rates were determined. With the developed system, joint angles, ability to reach the correct position and movement ability were analysed and it was shown how the mathematical equations required to perform the movements could be derived. As a result, a design process model for movement analysis, simulation and control of different living groups is presented with the equations obtained by formulating the information obtained from the developed system.

Design and Research of Intelligent Fixture for Drawing Machine

Tensile machine is a very sophisticated test equipment, which can test the mechanical properties of some materials. In the drawing machine, the clamping device is to prevent the relative displacement and vibration phenomenon in the process of tensile test. The clamping device is the most important part of the structure of the test machine, and the main task of the clamping device is to control the degree of freedom of the specimen needs to be clamped, so as to further add loads to the various specimens to be held, and finally complete the mechanical property test of the material. But at present, the existing fixture mechanism is mainly hydraulic, pneumatic, mechanical fixture. At present, the existing mechanical fixture still has bending stress during the clamping process, which will affect the accuracy of the experiment. Therefore, a clamping mechanism with adjustable clamping force and flat pushing is designed. An electric control type fixture mechanism is very rare, so in this paper, an electrically controlled fixture is designed on this basis. The main contents are as follows: (1) On the basis of the existing fixture types, the working mode of the fixture is studied, and the working principle related to the fixture is mastered. (2) The main components of the fixture mechanism are analysed, the design scheme is determined, and the selection of the components of the drive part and the selection of the related components within the fixture mechanism is completed. ( 3) The force analysis of the main body of the fixture is carried out by using theoretical mechanics knowledge, and the relevant calculations are completed. The solid modeling of the whole mechanism is completed by using SolidWorks. The force analysis of key parts is carried out by using ANSYS software, and the correctness and safety of material selection and design are verified. The main parts of the fixture mechanism to complete the corresponding force analysis, and the theoretical calculation results are compared and verified, and finally realize the electric control of the fixture mechanism and complete the design of the fixture mechanism.

In vivo AAV-SB-CRISPR screens of tumor-infiltrating primary NK cells identify genetic checkpoints of CAR-NK therapy.

Natural killer (NK) cells have clinical potential against cancer; however, multiple limitations hinder the success of NK cell therapy. Here, we performed unbiased functional mapping of tumor-infiltrating NK (TINK) cells using in vivo adeno-associated virus (AAV)-SB (Sleeping Beauty)-CRISPR (clustered regularly interspaced short palindromic repeats) screens in four solid tumor mouse models. In parallel, we characterized single-cell transcriptomic landscapes of TINK cells, which identified previously unexplored subpopulations of NK cells and differentially expressed TINK genes. As a convergent hit, CALHM2-knockout (KO) NK cells showed enhanced cytotoxicity and tumor infiltration in mouse primary NK cells and human chimeric antigen receptor (CAR)-NK cells. CALHM2 mRNA reversed the CALHM2-KO phenotype. CALHM2 KO in human primary NK cells enhanced their cytotoxicity, degranulation and cytokine production. Transcriptomics profiling revealed CALHM2-KO-altered genes and pathways in both baseline and stimulated conditions. In a solid tumor model resistant to unmodified CAR-NK cells, CALHM2-KO CAR-NK cells showed potent in vivo antitumor efficacy. These data identify endogenous genetic checkpoints that naturally limit NK cell function and demonstrate the use of CALHM2 KO for engineering enhanced NK cell-based immunotherapies.

Computer-driven formulation development of Ginsenoside Rh2 ternary solid dispersion.

(20S)-Ginsenoside Rh2 is a natural saponin derived from Panax ginseng Meyer (P. ginseng), which showed significantly potent anticancer properties. However, its low water solubility and bioavailability strongly restrict its pharmaceutical applications. The aim of current research is to develop a modified (20S)-Ginsenoside Rh2 formulation with high solubility, dissolution rate and bioavailability by combined computational and experimental methodology. The "PharmSD" model was employed to predict the optimal polymer for (20S)-Ginsenoside Rh2 solid dispersion formulations. The solubility of (20S)-Ginsenoside Rh2 in various polymers was assessed, and the optimal ternary solid dispersion was evaluated across different dissolution mediums. Characterization techniques included the Powder X-ray diffraction (PXRD) and Fourier transform infrared spectroscopy (FTIR). Molecular dynamics simulations were employed to elucidate the formation mechanism of the solid dispersion and the interactions among active pharmaceutical ingredient (API) and excipient molecules. Cell and animal experiments were conducted to evaluate the in vivo performance of the modified formulation. The "PharmSD" solid dispersion model identified Gelucire 44/14 as the most effective polymer for enhancing the dissolution rate of Rh2. Subsequent experiment also confirmed that Gelucire 44/14 outperformed the other selected polymers. Moreover, the addition of the third component, sodium dodecyl sulfate (SDS), in the ternary solid dispersion formulation significantly amplified dissolution rates than the binary systems. Characterization experiments revealed that the API existed in an amorphous state and interacted via hydrogen bonding with SDS and Gelucire. Moreover, molecular modeling results provided additional evidence of hydrogen bonding interactions between the API and excipient molecules within the optimal ternary solid dispersion. Cell experiments demonstrated efflux ratio (EfR) of Rh2 ternary solid dispersion was lower than that of pure Rh2. In vivo experiments revealed that the modified formulation substantially improved the absorption of Rh2 in rats. Our research successfully developed an optimal ternary solid dispersion for Rh2 with high solubility, dissolution rate and bioavailability by integrated computational and experimental tools. The combination of Artificial Intelligence (AI) technology and molecular dynamics simulation is a wise way to support the future formulation development.

Solutions of crack constraint parameter in 3D models − I: Through curve shape similarity

Two-parameter approaches of elastic plastic fracture mechanics, e.g., J-A(A2), J-Q, can be used to obtain more accurate fracture analysis results, especially under low crack constraint condition which commonly observed in practical engineering structures. While, theoretical solutions of the constraint parameters in the two-parameter approaches are not available, and substantial consumption of resources and time makes it inappropriate to numerically determine constraint parameters (e.g., A(A2), Q), especially in 3D solid models. In this work, based on the curve shape similarity, the estimation theory and formulae for constraint parameter A in 3D solid models are developed through theoretical and numerical analyses to obtain parameter A solutions quickly and efficiently, so as to enable the application of two-parameter approaches in practical engineering structures. The proposed estimation formulae here are used to predict the constraint parameter A in two actual engineering structures.

JAK inhibition enhances checkpoint blockade immunotherapy in patients with Hodgkin lymphoma.

Unleashing antitumor T cell activity by checkpoint inhibitor immunotherapy is effective in cancer patients, but clinical responses are limited. Cytokine signaling through the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway correlates with checkpoint immunotherapy resistance. We report a phase I clinical trial of the JAK inhibitor ruxolitinib with anti-PD-1 antibody nivolumab in Hodgkin lymphoma patients relapsed or refractory following checkpoint inhibitor immunotherapy. The combination yielded a best overall response rate of 53% (10/19). Ruxolitinib significantly reduced neutrophil-to-lymphocyte ratios and percentages of myeloid suppressor cells but increased numbers of cytokine-producing T cells. Ruxolitinib rescued the function of exhausted T cells and enhanced the efficacy of immune checkpoint blockade in preclinical solid tumor and lymphoma models. This synergy was characterized by a switch from suppressive to immunostimulatory myeloid cells, which enhanced T cell division.

Harnessing adrenergic blockade in stress-promoted TNBC in vitro and solid tumor in vivo: disrupting HIF-1α and GSK-3β/β-catenin driven resistance to doxorubicin.

Sympathetic activation triggered by chronic stress afflicting cancer survivors is an emerging modulator of tumorigenesis. Adrenergic blockade was previously associated with improving response to doxorubicin (DOX) in triple-negative breast cancer (TNBC), yet the precise underlying mechanisms remain obscure. The resilience of cancer stem cells (CSCs) during chemotherapy fosters resistance and relapse. Hypoxia-inducible factor-1α (HIF-1α) and β-catenin are intertwined transcriptional factors that enrich CSCs and evidence suggests that their expression could be modulated by systemic adrenergic signals. Herein, we aimed to explore the impact of adrenoreceptor blockade using carvedilol (CAR) on DOX and its potential to modulate CSCs overcoming chemoresistance. To achieve this aim, in vitro studies were conducted using adrenaline-preincubated MDA-MB-231 cells and in vivo studies using a chronic restraint stress-promoted solid tumor mouse model. Results revealed that adrenaline increased TNBC proliferation and induced a phenotypic switch reminiscent of CSCs, as evidenced by enhanced mammosphere formation. These results paralleled an increase in aldehyde dehydrogenase-1 (ALDH-1) and Nanog expression levels as well as HIF-1α and β-catenin upsurge. In vivo, larger tumor volumes were observed in mice under chronic stress compared to their unstressed counterparts. Adrenergic blockade using CAR, however, enhanced the impact DOX had on halting TNBC cell proliferation and tumor growth via enhanced apoptosis. CAR also curbed HIF-1α and β-catenin tumor levels subsequently suppressing ALDH-1 and SOX2. Our study unveils a central role for HIF-1α linking stress-induced sympathetic activation fueling CSC enrichment via the β-catenin pathway. It also highlights novel insights into CAR's capacity in reversing DOX chemoresistance in TNBC.

METB-03. SOLID PEDIATRIC TUMORS IN MICE REVEAL MODEL-SPECIFIC GLOBAL DNA METHYLATION AND CNV PROFILES CORRESPONDING TO HUMAN COUNTERPARTS

Abstract BACKGROUND The analysis and comparison of global DNA methylation patterns has become a gold standard in modern neuropathology. For human central nervous system (CNS) tumors and other cancers, the research community has collected thousands of methylation profiles, leading to the discovery and definition of numerous molecularly distinct tumor types and subtypes. Although reliable preclinical mouse models are essential for the understanding of tumor development and the validation of therapeutic approaches, such DNA methylation analyses have so far not been systematically performed for murine tumors owing to technical limitations. METHODS We employed the Illumina Bead Chip 285k mouse methylation array to profile ~500 samples covering 90 different mouse models representing 33 pediatric solid tumor types, including CNS tumors and sarcomas from 18 laboratories. We compared DNA methylation profiles of these models between each other and to human CNS tumors, performed immune cell deconvolution and conducted an in-depth analysis of copy number variants (CNVs) during tumor evolution. RESULTS Unsupervised clustering showed that mouse models form groups of their presumed tumor types. Using a tailor-made cross-species analysis based on syntenic CpG sites, we found that most tumors also group with their corresponding human counterparts. Immune cell deconvolution revealed distinct tumor microenvironments that showed clear similarities to human tumors. We further identified recurrent, model-specific CNVs that are syntenic to genomic aberrations in respective human tumors, suggesting an essential role of CNVs during tumor initiation or maintenance. CONCLUSION We provide a global resource of well characterized pediatric solid cancer models representing numerous different tumor types. Our comparative analyses reveal novel molecular model characteristics and validate their reliability as human disease models. Our data provide new biological insights into immune composition, tumor cell identities and tumor development by identifying model-specific CNV profiles.

LES of a swirl-stabilized 40 kWth biomass flame and comparison to a coal flame

Recent advancements have introduced high-fidelity simulations in pulverized coal combustion, yet the shift toward renewable fuels like biomass raises questions about suitable modeling approaches to understand the influence of the new fuel. The current study aims to examine the variations between biomass and pulverized coal flames by employing extended high-fidelity modeling approaches integrated into a Large Eddy Simulation (LES) framework. A fully coupled solid fuel-gas phase model is developed to investigate pulverized biomass and coal flames. Models for particles that are treated in a Lagrangian manner include state-of-the-art devolatilization and char models calibrated with advanced conversion models for the conditions under investigation. Using five-dimensional tabulated flamelet manifolds, gas phase reactions are modeled by two chemical mechanisms tailored to the respective fuel properties. Radiation is considered by solving the radiative transfer equation employing the weighted sum of gray gas model. This high-fidelity simulation framework is applied to a self-sustained, swirl-stabilized 40 kWth burner that is fired with walnut shells and Rhenish lignite, respectively. Both fuels are studied under the same flow conditions and thermal output to enable a thorough analysis of the fuel effects. The results are validated with experimental particle velocities. Using advanced post-processing for particle grouping, a close link between flame shape and differences in particle trajectories is established, indicating the high significance of particle size when transitioning between fuels.

Intermittent MEK Inhibition with GITR Costimulation Rescues T-cell Function for Increased Efficacy with CTLA-4 Blockade in Solid Tumor Models.

MEK inhibitors (MEKi) have shown limited success as a treatment for MAPK/ERK pathway-dependent cancers due to various resistance mechanisms tumor cells can employ. CH5126766 (CKI27) is an inhibitor that binds to MEK and prevents release of RAF, reducing the relief of negative feedback commonly observed with other MEKis. We observed that CKI27 increased MHC expression in tumor cells and improved T cell-mediated killing. Yet, CKI27 also decreased T-cell proliferation, activation, and cytolytic activity by inhibiting the MAPK/ERK pathway that is activated downstream of T-cell receptor signaling. Therefore, we aimed to balance the positive and negative immunomodulatory effects of MEKis for optimal combination with immunotherapy. Intermittent administration of CKI27 allowed T cells to partially recover and costimulation via GITR and OX-40 agonist antibodies completely alleviated inhibition of function. In Kras mutant lung and colon tumor mouse models, intermittent CKI27 and anti-GITR significantly decreased tumor growth and prolonged survival when further combined with CTLA-4 immune checkpoint blockade. Moreover, this triple combination increased CD8+ and CD4+ T-cell proliferation, activation, and effector/memory subsets in the tumor-draining lymph nodes and tumors and led to intratumoral regulatory T-cell destabilization. These data, collectively, will allow for more informed decisions when optimizing combination regimens by overcoming resistance, reducing toxicity, and generating long-term immune responses.

Numerical Simulation and Experimental Study of Gas–Solid Two-Phase Spraying of Dry Powder Fire-Extinguishing System Based on Fire-Extinguishing Inspection Robot

In order to solve the problem where the traditional intelligent inspection robot only has a single inspection function, we studied the use of a dry powder (including an ultra-fine dry powder) as a fire-extinguishing medium for the first time. In fire-extinguishing robots, the spray pressure is difficult to control, and there are several other issues. For integrated inspection, an intelligent, nitrogen-driven fire-extinguishing robot using a dry powder in a pressure-controlled spray was developed. On this basis, in order to investigate nitrogen-driven dry powder particle spraying as a gas–solid two-phase mechanism, as well as the flow characteristics and the influence of relevant parameters on the spraying effect, a nitrogen-driven dry powder particle spraying system was established as part of a gas–solid two-phase computational fluid dynamics model. The flow field of the spraying system and the particle motion characteristics were analyzed to explore the micro-mechanisms of the influence of different driving pressures, pipe diameters, and nozzle configurations on the spraying of the dry powder. In order to investigate the macroscopic effect of dry powder spraying where the gas–solid two-phase micro-mechanisms could not be revealed, an experimental platform was set up, and the experiments verified the accuracy of the numerical simulation results. We also investigated the dry powder spraying effect under different driving pressures, pipe diameters, nozzle configurations, and loading ratios. Finally, an orthogonal test was designed based on the results of the single-factor experiments to find the best combination of parameters required to achieve the optimal spraying effect. The research results can provide a theoretical and technical reference for the design and development of nitrogen-driven dry powder spraying systems.

Numerical research on disastrous mechanism of seepage instability of karst collapse column considering variable mass effect

In order to reveal the disastrous mechanism of seepage instability of karst collapse column considering variable mass effect, a variable mass fluid–solid coupling mechanical model of water inrush is established, by considering the random distribution characteristics of a collapse column. Taking Qianjin coal mine as the research background, based on the Weibull distribution theory, the heterogeneous distribution characteristics of rock mass is described, and COMSOL Multiphysics numerical simulation software is employed to simulate the seepage characteristics and inrush water changes in collapse columns under different conditions of homogeneity, water pressure, and initial porosity. The research results show that the greater the homogeneity is, the more water conduction channels are formed, and the porosity increases accordingly, when considering the influence of different homogeneity on the seepage characteristics of broken rock mass, which eventually leads to water inrush accidents and a sharp increase in water inflow. Besides, when studying the seepage evolution law of different water pressures on a broken rock mass, an elevation of water pressure dramatically increases the porosity and seepage rate of the water. Over time, the broken rock particles gradually migrate and the fine particles are transported and eroded by the water flow, resulting in changes in the seepage characteristics and the formation of potential water diversion channels. Finally, when taking into account the effect of different initial porosity on the fractured rock mass seepage characteristics, the greater the original porosity is, the higher the seepage velocity is, and the particle migration increases the permeability. This leads to a more pronounced conductive water passage formation, which reveals the disastrous mechanism of seepage instability of karst collapse column considering variable mass effect.

CFD MODELLING OF THE DUST AND AIR VELOCITY BEHAVIOUR AT AN UNDERGROUND COAL MINE ROADWAY

Dust pollution for ventilation systems is a big problem for mine workers in underground coal mines. The respirable dust concentration is important to the physical and spiritual health of miners. It is hazardous up to 2 mg/m3in the air in underground coal galleries. In the present work, the airflow velocity and dust concentration values were measured at Çay 1-Kartiye roadway in Kozlu, Zonguldak. The goal of this research is modelling to the dust concentration and airflow velocity values by the computational fluid dynamics (CFD) method. An airflow and dust fluid and solid model was done using the Eularian-Granular multiphase method with the k-epsilon two-equation model. The results showed that dust concentration values were too low and fixed. The error percentage of airflow velocity values changed between 5% and 17%. Thus, this roadway is safe for coal dust explorations.

Simplified Modeling Method for Prefabricated Shear Walls Considering Sleeve Grouting Defects

The sleeve grouting connection is the most common form of vertical connection for prefabricated shear walls. However, during construction, this type of connection is prone to defects such as insufficient anchorage length of reinforcement, deviation of reinforcement, and insufficient amount of sleeve grouting, which significantly impact the integrity and seismic performance of the prefabricated shear wall structure. The finite element analysis of the prefabricated shear wall with sleeve grouting connection is still based on solid element modeling. This method has the disadvantages of complex models and low computational efficiency. In this paper, a simplified modeling method for prefabricated shear walls considering sleeve grouting defects was proposed to address this issue. Firstly, the equivalent constitutive relationship of the sleeve grouting defect connector was constructed based on the uniaxial tensile test of the existing sleeve grouting defect connector, and the T3D2 element was used to simulate the sleeve grouting connector. Then, the mechanical behavior of the horizontal joint between the shear wall and the foundation beam was simulated by the cohesive force model, and the prefabricated shear wall models with sleeve grouting defects were established. The accuracy of the simplified modeling method was verified by comparing the experimental results and numerical simulation results of the seismic performance of the prefabricated shear wall with sleeve grouting defects. The results showed that the hysteresis curve, skeleton curve, and failure mode of the numerical simulation were in good agreement with the test results. However, the stiffness of the concrete degenerated rapidly due to the apparent development of plastic-damaged concrete, which made the falling section of the hysteresis curve of the numerical simulation different from that of the test. The proposed simplified modeling method can be further applied to the performance study of prefabricated shear walls with sleeve grouting defects and can provide a reference for structural performance evaluation, design optimization, and construction quality control to a certain extent.