Development and calibration of discrete element method inputs to mechanical responses of granular materials

Simulation of soil excavation is difficult. Tools which manipulate soil are difficult to evaluate in a virtual environment prior to prototype or manufacture. Soil behaves as a discontinuous material in normal excavation activities. Therefore, numerical methods which naturally model discontinuous media, such as the Discrete Element Method (DEM), can be used to perform simulations of soil excavation. However, DEM input parameters must be calibrated to accurately model the mechanical behavior of soil. The goal of this research was to develop intelligent methodologies to calibrate DEM input parameters to reproduce the mechanical responses of soil and other granular materials subject to traditional laboratory tests, such as triaxial and direct shear tests. A mechanistic understanding of the interaction between sliding and rolling friction was developed and correlated with the critical state strength of drained granular media. In addition, the fundamental soil mechanics concept of relative density was successfully applied to the DEM calibration methodology to predict peak granular strength and dilatancy. Sensitivity analyses of DEM input parameters were used to enhance the characterization of mechanical behavior of DEM specimens. A calibration algorithm was developed to quickly and mechanistically relate DEM input parameters to laboratory measured mechanical behavior of soils. The algorithm eliminates unnecessary iterations during the DEM parameter calibration by enforcing a sophisticated understanding of the mechanisms of granular shear strength. The outcomes of this research greatly simplify the calibration of DEM parameters of soil for use in industrial excavation problems

Stress analysis of welded gusseted frames

Welded gusseted frame design for fatigue loading is largely not addressed in modern machine design texts. This research intends to uncover stress solutions for critical locations on welded gusseted frames so that such a common engineering structure can have design basis. The problem was approached using static equilibrium relations to populate coefficients of deliberately chosen line stress functions. The results from that analysis were used in a subsequent fracture mechanics analysis to develop the singular stress field at a weld toe. The current research resulted in solutions for the two most critical stress states on welded gusseted frame structures

Effects of microscale rolling friction on dense virtual particle assemblies

Discrete element method (DEM) is helpful in determining how microscale particle roughness and shape affect the mechanical behavior of dense particle assemblies. Researchers have found analogs between microscale rolling friction and the effects of surface roughness and particle shape. Although rolling friction effects have been studied thoroughly in loose granular flows, there is a need to understand the global effects of microscale rolling friction on dense particle assemblies. This article investigates the effects of rolling friction on various mechanical responses of virtual particle assemblies in simulated triaxial and oedometer tests. Several tests were simulated while broadly varying rolling friction. Global-scale stress‑strain and volume change responses are captured and analyzed. Results can be used to simplify and speed DEM models by exchanging computationally heavy particle shapes for more efficient rolling friction formulations

Discrete Element Modeling (DEM) of Cone Penetration Testing on Soil With Varying Relative Soil Density

Modeling soil-tool interaction is essential for equipment design and performance evaluation on soil behavior responses under loading. Computational tools based on particle-based mechanics such as Discrete Element Modeling (DEM) and Smoothed Particle Hydrodynamics (SPH) have potential in modeling large strain soil dynamic behaviors from soil-tool interaction. The objective of this study is to validate the accuracy and robustness of DEM calibration methodology as it relates to soil deformation during cone penetration on varying initial soil relative density. The influence of factors such as DEM material properties and cone to particle size ratio on DEM cone penetration simulation will be investigated. The paper presents a comparison of DEM predicted cone penetration resistance and laboratory measured penetration data on Norfolk sandy loam. Soil mechanical behavior was modeled with Hertz-Mindlin (HM) contact stiffness model and a new coupled frictional law for static and rolling resistance coefficients. The DEM material properties were calibrated using residual strength from direct shear test. DEM simulations were performed using LIGGGHTS, open source DEM code. Cone penetrometer experiments using anÂASABE standard cone with 12.53 mm cone base diameter and 30-degree cone tip were used to validate the calibrated DEM model. DEM prediction of cone penetration resistance trend and steady state values were in close agreement with the laboratory measured data for relative density range from 5 to 30%. At higher dense states (relative density of 90%), DEM calibration requires further improvement

PromptIR: Prompting for All-in-One Blind Image Restoration

Image restoration involves recovering a high-quality clean image from its degraded version. Deep learning-based methods have significantly improved image restoration performance, however, they have limited generalization ability to different degradation types and levels. This restricts their real-world application since it requires training individual models for each specific degradation and knowing the input degradation type to apply the relevant model. We present a prompt-based learning approach, PromptIR, for All-In-One image restoration that can effectively restore images from various types and levels of degradation. In particular, our method uses prompts to encode degradation-specific information, which is then used to dynamically guide the restoration network. This allows our method to generalize to different degradation types and levels, while still achieving state-of-the-art results on image denoising, deraining, and dehazing. Overall, PromptIR offers a generic and efficient plugin module with few lightweight prompts that can be used to restore images of various types and levels of degradation with no prior information on the corruptions present in the image. Our code and pretrained models are available here: https://github.com/va1shn9v/PromptI

Wheelchair lifter

Basically, a wheelchair stair lift is a motorized, meaning by carrying a person seated in a wheelchair up and down stairs. A wheelchair lift, also known as a platform lift, or vertical platform lift is a fully powered device designed to raise a wheelchair and its occupant in order to overcome a step or similar vertical barrier (Figure 8.1). Wheelchair lifts can be installed in homes or businesses and are often added to both private and public vehicles in order to meet accessibility requirements laid out by the Americans with Disabilities Act of 1990 (ADA). These mobility devices are often installed in homes as an alternative to a stair lift, which only transport a passenger and not his/her wheelchair or mobility scooter. It is installed over the stairs in such a way that the stairs can still be used in the usual fashion. There is no need of breaking down or reconstructing the existing building

Antioxidant activity influenced by in vivo and in vitro mutagenesis in sugarcane (Saccharum officinarum L.)

The antioxidant potential (1,1-diphenyl-2-picrylhydrazyl (DPPHº)-scavenging activity) of in vitro regenerated and induced mutant sugarcane (Saccharum officinarum L.) was investigated. Efficient callus induction and shoot regeneration were induced in bud explants when incubated on Murashige and Skoog (MS) medium supplemented with different plant growth regulators (PGRs). Best callogenesis was observed on MS-medium supplemented with 3 mg L-1 2,4 dichlorophenoxyacetic acid (2,4 D) and on ½ MS medium with 2 mg L-1 2,4 D after 30-days of culture. Almost 85% shoot organogenesis was observed on MS-medium supplemented with 2 mg L-1 6-benzyladenine (BA) and 0.5 mg L-1 gibberellic acid (GA3) within 30 days. Optimum percentage rooting (89%), were obtained for 2 mg L-1 of BA alone. Mother plant setts were irradiated with 60Co mutagen source. Assay of antioxidant activity of in vitro and in vivo grown tissues was evaluated as gross parameter of medicinal efficacy. Significantly higher antioxidant activity (60%) in in vitro regenerated sugarcane was observed as compared to induced mutant (57%) and mother plant (53%).Key words: Saccharum officinarum, in vitro regeneration, induced mutation, antioxidant

Burstormer: Burst Image Restoration and Enhancement Transformer

On a shutter press, modern handheld cameras capture multiple images in rapid succession and merge them to generate a single image. However, individual frames in a burst are misaligned due to inevitable motions and contain multiple degradations. The challenge is to properly align the successive image shots and merge their complimentary information to achieve high-quality outputs. Towards this direction, we propose Burstormer: a novel transformer-based architecture for burst image restoration and enhancement. In comparison to existing works, our approach exploits multi-scale local and non-local features to achieve improved alignment and feature fusion. Our key idea is to enable inter-frame communication in the burst neighborhoods for information aggregation and progressive fusion while modeling the burst-wide context. However, the input burst frames need to be properly aligned before fusing their information. Therefore, we propose an enhanced deformable alignment module for aligning burst features with regards to the reference frame. Unlike existing methods, the proposed alignment module not only aligns burst features but also exchanges feature information and maintains focused communication with the reference frame through the proposed reference-based feature enrichment mechanism, which facilitates handling complex motions. After multi-level alignment and enrichment, we re-emphasize on inter-frame communication within burst using a cyclic burst sampling module. Finally, the inter-frame information is aggregated using the proposed burst feature fusion module followed by progressive upsampling. Our Burstormer outperforms state-of-the-art methods on burst super-resolution, burst denoising and burst low-light enhancement. Our codes and pretrained models are available at https:// github.com/akshaydudhane16/BurstormerComment: Accepted at CVPR 202