DEM Analysis Research Articles

DEM analysis of wetting deformation characteristics of rockfill material considering the influence of different compaction levels

DEM analysis of wetting deformation characteristics of rockfill material considering the influence of different compaction levels

Experimental and DEM analyses of type I fracture characteristics of waste rock aggregate reinforced cemented tailing backfill

Experimental and DEM analyses of type I fracture characteristics of waste rock aggregate reinforced cemented tailing backfill

Digital Feminism, Public Theology, and the Reshaping of Female Subjectivity in Ghana

Abstract Taking the online feminist group Pepper Dem Ministries as a case study, this article assesses how a public theological approach to gender activism underlies public gender discourses by allowing online feminism to attain global-local and post-colonial dimensions. This is explored through a rhetorical analysis of Pepper Dem Ministries’ online and offline discourses, and the response of young Christian women to their activism. These responses are obtained from semi-structured interviews conducted via zoom calls. The discourse of identity fragmentation in modernity frames the analysis of this data, revealing the coherence of Pepper Dem Ministries’ rhetoric with fragmentary or unsystematic theology as a mode of public theological engagement. The article concludes that the social shaping of female subjectivity in Ghana transpires as a public theological discourse influenced by and coherent with global discursive patterns in online feminism, Christian and secular feminist discourse, and public theology.

Interaction properties of wine grapes: DEM analysis and experimental investigation

The processing of wine grapes is both labor-intensive and time-consuming, necessitating equipment improvements to enhance productivity. Virtualizing machining processes is crucial for designing and researching equipment aimed at improving food quality and safety standards. Accurate modeling requires detailed knowledge of material and interaction properties. Therefore, the contact properties of wine grapes were obtained using the progressive optimization method. Experimental and simulated results of particle collision and rolling during processing were compared to select accurate input parameters. The experiment concluded that the coefficient of restitution (CoRg-g), coefficient of rolling friction (CoRg-g), and static friction coefficient (CoSg-g) between grape particles were 0.178, 0.400, and 0.459, respectively. Similarly, the corresponding values for interactions between grapes and stainless steel were 0.411, 0.027, and 0.643, respectively. Notably, these values have been independently verified through simulations.

Optimizing Hydrological Research: Comparative Analysis of DEMs for Enhanced Catchment Area Delineation

Optimizing Hydrological Research: Comparative Analysis of DEMs for Enhanced Catchment Area Delineation

DEM Analysis of Masonry Open Vaults with Square Bays

ABSTRACT Masonry vaults are usually considered as shell structures, whose geometry strongly determines the mechanical behaviour. In this article, the discrete element method is applied as a tool to perform virtual experiments to study three different types of open vaults (sail vault, fan vault, and cross vault). The three vaults have the same ground plan, but the sail vault is an elliptical shell, the fan vault is hyperbolic, and the cross vault is parabolic. All vaults are first gradually equilibrated under their self-weight, and then submitted to gradually increasing downwards forces at different positions, or to quasi-statically increasing outwards support displacements. The ultimate loads and the failure mechanisms of the vaults are compared. The orientation of the reactions is measured. The main results of the investigations are that (1) under concentrated loads, while the elliptic shell (the sail vault) fails locally, the hyperbolic vault (i.e. the fan vault) show either global failure or local failure but global cracking, depending on the position of the load; (2) under gradually increasing outwards support displacements, the orientation of the reactions is most favourable for the fan vault and worst is for the cross vault.

DEM analysis of the load transfer mechanism of sand-rubber mixtures subjected to constrained compression

Despite the significant progresses in the multi-scale studies of sand-rubber mixtures, the load-transfer mechanism within the soft-rigid granulate networks is highly unexplored. In this study, roles of sand and rubber particles in different contact networks subjected to constrained compression were investigated using DEM. The simulations were respectively calibrated using experimental data at element and grain scales, providing an opportunity to look at the role of rubber within whole granulate networks. When the behavior of mixtures is dominated by sand (rubber content <30%), the constitutive responses at sand - sand, sand - rubber and rubber - rubber contacts can be described by the Hertz contact model; within this range, the rubber majorly formulates the weak and intermediate contacts, but sliding fraction in the strong network increases with rubber content. A more homogeneous fabric and a lower deviatoric stress at the strong network were observed after rubber inclusion.

Multi‐scale mechanics of polydisperse granular materials: From micro‐scale and wave propagation experiments to DEM analysis

AbstractThis paper presents a multiscale experimental study integrated with numerical simulations examining the mechanics of polydisperse granular mixtures composed of coarse‐grained particles mixed with varying percentages of fines. The study includes macroscale wave propagation tests using bender elements on isotopically compressed granular samples to investigate the stiffness variation with changes in size ratio (SR) and fines content (FC). Empirical equations were developed to predict stiffness based on the experimental data, using the concept of equivalent void ratio to represent the influence of void ratio on stiffness. A newly introduced parameter called size disparity indicator was used to consider the coupled effects of size disparity and fines content on stiffness. Microscale assessment of the individual contacting grains revealed that stiffness (at grain scale) is affected by changes in grain size, even when the SR is less than 6, however, the experimental observations of the shear modulus behavior from the macroscale test results reveal minimal effect of FC. Furthermore, numerical simulations using the discrete element method were conducted on the polydisperse granular mixtures to demonstrate the coupled effect of SR and FC on the structural matrix formation, thereby influencing the force transfer among contacts resulting in varying stiffness behavior. Our findings provide valuable insights into the behavior of polydisperse granular mixtures in engineering applications.

Experimental and DEM analysis for the shear characteristics of interface between sand and irregular concrete under dynamic normal loading

To explore the dynamic shear property of sand–irregular concrete interface, a series of direct shear tests were conducted under dynamic normal loading. These tests were designed with various joint roughness coefficients (JRC), amplitudes and frequencies of dynamic normal loading. DEM models were established to analyze the microscopic mechanical behavior. The research results indicate that a larger amplitude and frequency of the dynamic normal loading would lead to a decrease in the interface shear stress and dilation. As the JRC increased, the interface shear strength first increased and then decreased, and the dilation increased. A rougher surface would reduce the phase shift between peak shear and normal stress. The phase shift between normal stress and friction coefficient was always half a normal loading cycle. A greater JRC would activate a more violent particle motion and a thicker shear band. The increase in effective roughness would lead to an increase in the deviation angle of the anisotropic direction. The evolution of force chains was observed in three-dimensional space. Weak force chains were screened out during the shearing process. As the shearing developed, the number of force chains decreased, the average length and strength of force chains continued to increase.

Internal Instability of Granular Soils at Particle Scale: A DEM Analysis

Internal Instability of Granular Soils at Particle Scale: A DEM Analysis

Preliminary study of waste storage ponds delineation area in the Ungaran Geothermal Mining working area, Semarang, Indonesia

The Gedongsongo and Nglimut areas have the potential for Indonesian geothermal exploration projects. One of the problems of the PLTP sector is producing geothermal waste in the form of brine, and geothermal mud can endanger human health and ecosystems. This study aimed to determine the best zone for waste storage ponds in this prospect area. The method integrates DEM and Landsat data analysis, producing Maps of Slopes and Lineaments to delineate the best area for making ponds. There are several parameters for determining the pond-making zone: area with a slope of less than 15%, distance from the fault is more than 200 m, and distance from areas of geothermal manifestations such as hot springs and fumaroles is more significant than 200 m. This analysis results in four delineation zones suitable for creating waste storage ponds. In the Nglimut area, there are N1 and N2; in the Gedongsongo area, there are G1 and G2 as potential zones. The best zones were N2 and G1. Locations N1 and G2 are fair zones because the eastern area of G2 is 200 m from the fault, and the northern region of N1 is close to the hot spring.

DEM Analysis of the P-Wave Anisotropy Response to the Microstructure of Sedimentary Rock Under Biaxial Compression

DEM Analysis of the P-Wave Anisotropy Response to the Microstructure of Sedimentary Rock Under Biaxial Compression

Soil Application of Bacillus subtilis Regulates Flavonoid and Alkaloids Biosynthesis in Mulberry Leaves.

Flavonoids and alkaloids are the major active ingredients in mulberry leaves that have outstanding medicinal value. Bacillus subtilis can effectively activate the plants defense response and regulate the plant secondary metabolism. In this study, we explored the effects of soil application of B. subtilis on the content of flavonoids and the most important alkaloids (1-deoxynojirimycin, DNJ) in mulberry leaves. Significant decreases in flavonoid content were observed in tender leaves and mature leaves after treatment with B. subtilis; at the same time, significant increases in DNJ content were observed in tender leaves. Based on widely targeted LC-MS/MS and high-throughput approaches, we screened out 904 differentially synthesized metabolites (DSMs) and 9715 differentially expressed genes (DEGs). KEGG analyses showed that these DSMs and DEGs were both significantly enriched in the biosynthesis of secondary metabolites, flavonoid synthesis and plant hormone signal transduction. Further correlation analysis of DEMs and DEGs showed that 40 key genes were involved in flavonoid biosynthesis, with 6 key genes involved in DNJ biosynthesis. The expression of CHS, CHI, F3H, F3'H, FLS, UGT and AOC significantly responded to B. subtilis soil application. This study broadens our understanding of the molecular mechanisms underlying the accumulation of flavonoids and alkaloids in mulberry leaves.

DEM analysis of flow dynamics of cohesive particles in a rotating drum

Cohesive particles, prevalent in chemical and metallurgical industries, necessitate a comprehensive investigation of their behavior. This study employs the discrete element method to predict the motion of two distinct types of cohesive particles within a three-dimensional rotating drum, with the evaluation of the influence of rotational speed on particle-level parameters, encompassing velocities, angular velocities, dispersion coefficients, and contact forces. The findings reveal that wet particles treated with a honey-additive exhibit heightened inter-particle bonding, resulting in flatter surfaces on inclined planes. Cohesive particles within the active region attain greater translational velocities than their counterparts within the passive region. The x-direction dispersion intensity of water-additive particles in both the active and passive regions increases from 2.41 × 10−4 m2/s and 9.99 × 10−5 m2/s to 5.75 × 10−4 m2/s and 3.34 × 10−4 m2/s, respectively, with the increase in rotational speed from 5.6 RPM to 11.6 RPM. Particles with a honey-additive demonstrate larger dispersion coefficients along the x- and y-axes, as well as higher velocities and contact forces, albeit lower angular velocities in contrast to particles treated with a water-additive. Furthermore, an escalation in rotational speed amplifies the dispersion coefficients and contact forces of the cohesive particles. The rotating kinetic energy of the particles with water-additive and honey-additive increases from 0.005 J and 0.01 J to 0.01 J and 0.045 J, respectively.

Prediction of debris flow initiation points using high resolution DEM and GIS analysis in South Korea

This study presents a GIS analysis model that utilizes high-resolution Digital Elevation Map data to predict the initiation points of debris flow through the overlap of slope stability analysis techniques and rainfall flow analysis. The debris flow that occurred on Mount Woomyun in Seoul, South Korea in 2011 was selected as the case study for comparing and analyzing the prediction model against the actual case. In South Korea, occurrences of debris flow mostly happen during the summer monsoon season. When a substantial amount of rainfall accumulates and heavy rainfall events occur, the pore water pressure within slopes reaches saturation. Consequently, flow is initiated along “temporary streams.” In this study, areas with a combination of low slope stability and abrupt changes in velocity vectors were assumed to have the highest probability of debris flow occurrence due to the overlapping of these factors. The research model was conducted under this assumption. To evaluate the performance of the model, 3D coordinates of the model’s result point, and actual occurrence points were obtained, and a Pearson correlation analysis was conducted to compare them. With these results, R2 values of X = 0.9147, Y = 0.8625, and H = 0.8942 were obtained. These high R2 indicate a strong correlation between the model’s predictions and actual occurrences.

A GPU-accelerated simulator for the DEM analysis of granular systems composed of clump-shaped elements

A GPU-accelerated simulator for the DEM analysis of granular systems composed of clump-shaped elements

Transcriptomics integrated with metabolomics reveals the effect of cold stress on rice microspores

BackgroundMicrospore culture is one of the important biotechnological tools in plant breeding. The induction of microspore embryogenesis is a critical factor that affects the yield of microspore-derived embryo productions. Cold treatment has been reported to reprogram the gametophytic pathway in various plant species. However, the exact mechanism(s) underlying the effect of cold pre-treatment of floral buds on the efficiency of ME is still not clear.ResultsIn this study, the effects of cold stress on the microspore totipotency of rice cultivar Zhonghua 11 were investigated. Our results revealed that a 10-day cold treatment is necessary for microspore embryogenesis initiation. During this period, the survival rate of microspores increased and reached a peak at 7 days post treatment (dpt), before decreasing at 10 dpt. RNA-seq analysis showed that the number of DEGs increased from 3 dpt to 10 dpt, with more downregulated DEGs than upregulated ones at the same time point. GO enrichment analysis showed a shift from ‘Response to abiotic stimulus’ at 3 dpt to ‘Metabolic process’ at 7 and 10 dpt, with the most significant category in the cellular component being ‘cell wall’. KEGG analysis of the pathways revealed changes during cold treatment. Mass spectrometry was used to evaluate the variations in metabolites at 10 dpt compared to 0 dpt, with more downregulated DEMs being determined in both GC-MS and LC-MS modes. These DEMs were classified into 11 categories, Most of the DEMs belonged to ‘lipids and lipid-like molecules’. KEGG analysis of DEMs indicates pathways related to amino acid and nucleotide metabolism being upregulated and those related to carbohydrate metabolism being downregulated. An integration analysis of transcriptomics and metabolomics showed that most pathways belonged to ‘Amino acid metabolism’ and ‘Carbohydrate metabolism’. Four DEMs were identified in the interaction network, with stearidonic acid involving in the most correlations, suggesting the potential role in microspore totipotency.ConclusionsOur findings exhibited the molecular events occurring during stress-induced rice microspore. Pathways related to ‘Amino acid metabolism’ and ‘Carbohydrate metabolism’ may play important roles in rice microspore totipotency. Stearidonic acid was identified, which may participate in the initiation of microspore embryogenesis.

Experimental and DEM analysis of granite multi-angle centrally single-cracked Brazilian disks (CSCBD) fracture behaviors

Experimental and DEM analysis of granite multi-angle centrally single-cracked Brazilian disks (CSCBD) fracture behaviors

DEM analyses of mesoscopic failure mechanism and stress bearing mechanism of compacted snow subjected to unconfined compressive loading

In order to explore the mesoscopic failure mechanism and bearing mechanism of compacted snow under loading. First, the skeleton of dendritic snow crystal was constructed by 13 ice rigid sphere particles which are bonded together using a completed bond contact model. Second, a "falling snow method" was proposed and used to simulate the whole process of natural snowfall, i.e. snow generation, snow falling, snow deposition, and snow compaction. Third, the compacted snow sample was sintered at different temperatures with different times; in sintering process, the snow particles were bonded together by the completed bond contact model. Finally, after contact model parameter calibration by reported snow test results, the unconfined compression tests on the finished sintering snow were carried out and the mesoscopic failure mechanism and stress bearing mechanism were analyzed. Take the sintering temperature of −10 °C and finished sintering samples for example, the results show that the number of compacted snow bond breaks was mainly contributed by tension bond breaks. Meanwhile, with the increase of density, the ratio of bond breaks in tension and compression was higher. When the density was below 475 kg·m−3, the bond breakage was dominated by bending. While the density was above 475 kg·m−3, the bond breakage was mainly shearing. The contribution of the normal contact force to the total axial stress accounted for about 65% which was greater than that of the tangential contact force (ρ = 400 kg m−3). This study can provide support for the mesomechanical failure theory of compacted snow engineering, such as snow roads, compacted snow runways, and snow foundations.

Estimating Typhoon-Induced Maximum Flood for Spillway Safety Assessment—Case Studies in Taiwan

Dam safety assessment is usually conducted regularly to investigate the risks associated with the dam and propose remedies to ensure effective reservoir operations. One crucial aspect of the evaluation involves performing hydrological analyses to determine if the existing spillway can successfully deliver the probable maximum flood (PMF) downstream. This study applied storm transposition and typhoon rainstorm methods for PMP estimations. The resulting PMP values were then used as input for runoff models to generate flood hydrographs for PMF determination. A modification for the storm transposition method was proposed to determine the barrier height considering the moisture inflow direction. In estimating the orographic rainfall in the typhoon rainstorm model, an effective terrain slope was suggested according to different windward directions based on DEM analysis. Shihmen Reservoir and Feitsui Reservoir, located in northern Taiwan, were used as examples to conduct the PMP and PMF analysis. The obtained PMPs were further compared with the results generated by Hershfield’s method to assess the reasonability of the estimation. The results show that the maximum deviation of the 24-h PMP values estimated by the three methods is within 30% in the Shihmen watershed and 16% in the Feitsui watershed. The PMF estimations in the two reservoir watersheds are larger than the design discharges of the existing spillways. Hence, extending the capacity of the existing spillways or constructing upstream bypasses to avoid catastrophic flooding downstream is required.