Loading Rate Research Articles

Studying Impact of Moisture, Node Position and Loading Rate of Paddy Straw on its Mechanical Properties

In this study, mechanical properties of paddy straw such as bending strength, shear strength and Young's modulus were determined through force-deformation curve using textural analyzer with 50 kg load cell. The mechanical properties were determined at three moisture contents, i.e., 18.4% (M1), 13.5% (M2) and 10.8% (M3), at three node positions, i.e., N1, N2 and N3 and three loading rates, i.e., 25, 30 and 35 mm min-1, respectively. The results revealed that moisture content and loading rate at different node positions significantly (p<0.01) affected the bending strength, shear strength, and Young's modulus of straw, whose values varied from 5.35 to 17.34 MPa, 4.99 to 7.35 MPa, 0.43 to 1.39 GPa, respectively, through N1 to N3 with decrease in moisture content; likewise, other findings also indicated increase in output values on increasing loads through N1 to N3. Cutting force was also significantly affected (p<0.01) by shear angle and moisture content, which varied from 6.39 to 22.9 N, and cutting energy ranged from 142 to 511 J by Straw Management System serrated blade and was found to be minimum at 20° shear angle. The mechanical property of the straw for residue management in the context of cutting force for node position N3 at the initial moisture content was found optimum.

Impact of elevated loading rates on the shape of the Master Curve (ASTM E1921) for a German RPV steel

The Master Curve Methodology (ASTM E1921) experimentally assesses a materials temperature-dependent fracture toughness, predominantly for quasi-static testing conditions. The treatment of elevated loading rates is described by the annex A1 of ASTM E1921 and A14 of ASTM E1820. This paper presents results of the evaluation of a large and standard-conforming database in order to verify the procedures recommended by the standard for elevated loading rates. Testing involved C(T)- and SEN(B)-specimens of the RPV-steel 22NiMoCr3-7 (A508 Grade 2) for loading rates of 100 MPa√m/s ≤ K̇ ≤ 104 MPa√m/s in the ductile to brittle transition region. While valid T0-values were found, single-temperature T0-values were observed to differ more than expected from multi-temperature T0-values, which cannot be explained by the Master Curve uncertainty. The shape and underlying distribution of the Master Curve show deviations with increased loading rate. The shape factor p is optimized with respect to the individual data, and it increases with K̇, but deviations are not completely overcome. This can be linked to a change in distribution, which was demonstrated by an optimization of minimum fracture toughness Kmin, which increases with temperature. It is argued that the cause for the observations is linked to both heating processes and local crack arrest that severely influence macroscopic fracture behavior. Also, an individual adjustment of p or Kmin is not helpful due to the material-dependency in practice. It is recommended that fracture mechanics testing at elevated loading rates is performed close to or below T0 in order to minimize the influence of dynamic loading conditions on the assessment.

Effects of increasing walking cadence on gait biomechanics in adults with knee osteoarthritis

Gait retraining is a strategy to manage altered loading patterns and pain characteristic of knee osteoarthritis. Lower walking cadence is associated with higher knee joint loading, vertical ground reaction forces, and risk for cartilage worsening. Therefore, we determined the acute effects of increasing walking cadence on measures of lower extremity loading and knee pain in knee osteoarthritis. Twenty-five participants with knee osteoarthritis (age = 62.5 ± 7.2; 76.0 % female) walked at fixed speed on an instrumented treadmill from which baseline cadence was measured. Five, randomized experimental cadence conditions (2 %, 4 %, 6 %, 8 %, or 10 % over baseline cadence) were completed. Real-time auditory and visual feedback on cadence was provided while kinematics and ground reaction forces were sampled. Linear mixed effects models evaluated the effect of cadence on knee adduction and flexion moment peaks and impulses, impact loading metrics (vertical ground reaction force impact peak, vertical average and instantaneous loading rates), and knee pain. Increasing cadence by 2–10 % did not significantly change knee adduction moment peaks or impulse. Peak knee flexion moment increased by 3–32 % and knee flexion moment impulse reduced by 2–9 % with increases in cadence, but these results were not significant (peak knee flexion moment, p = 0.070; knee flexion moment impulse, p = 0.085). Increasing cadence significantly increased the vertical impact peak (p < 0.001), and the vertical average (p = 0.010), and instantaneous (p = 0.007) loading rates. Small increases in cadence at a fixed gait speed does not significantly change surrogate measures of knee joint loading or pain, but does increase measures of impact loading.

Biomimetic supported polyoxometalate structures designed and its applications for the ultra-deep oxidative desulfurization of fuels

Inspired by the fact that human nose cilia can effectively contact with particles to prevent their entry into our body, this kind novel biomimetic structures are designed and synthesized to enable the loading efficiency between the polyoxometalate catalytic species (POMs) and the carrier, thereby improving their loading rate and promoting their catalytic performance. The mullite whiskers-uniformed cordierite (CMW) is used as a carrier to support POMs, in which mullite whiskers regarding as the cilia in our nose, this kind catalyst could not only overcome the shortcomings of simple POMs with low specific surface and easy to self-agglomerate, but also could greatly increase their contact probability with the carrier. At the same time, the advantage of the cordierite block structure also greatly conducive to their actual application value on the reusing operation. A series of Keggin-type POM-loaded bulk materials, POM@CMW, [VimAm]Br@POM@CMW, [DVim]Br@POM@CMW, have been developed with various ionic liquid-based POMs (ionic liquid = ILs, chosen these two kinds of [VimAm]Br and [DVim]Br) to a comparative study. The oxidative desulfurization reaction (ODS) for fuels was performed using the obtained materials as catalysts and H2O2 as oxidant, without the additional extractants for the existing of ILs in catalyst. Through experimental evaluations, [DVim]Br@POM@CMW was found the excellent efficiency on the Sulfur removal, with an DBT removal of 96.34 % at 70 °C for 120 min. According to the FT-IR and SEM results after the reaction, the catalyst could retain their original structure and the dibenzothiophene (DBT) removal could still be maintained above 95 % after 7 reuses. Furthermore, the oxidation reactivity of different substrates was in the following order: DBT > 4,6-dimethyldibenzothiophene (4,6-DMDBT) > thiophene (BT) and the high activity in actual diesel oil could be also exhibited. The enhanced reaction activity, excellent structural stability, and recyclability can be attributed to the abundance of active sites and outstanding mechanical properties provided by cordierite/mullite whiskers as a carrier, indicating their potential in the novel biomimetic-structured POMs-loaded catalysts.

Evaluation of compression behaviour of 316L SS Gyroid and Diamond structures using SLM process – Experimental programme under static and dynamic compression loadings

The relative comparison in terms of energy absorption efficiency for a set of 4 structures made of various Triply Periodic Minimal Surfaces (TPMS) topologies is experimentally investigated. These TPMS structures are printed by Selective Laser Melting AM process using 316L SS. The study is carried out in consideration of the effect of parameters such as relative density, compressive loading directions and loading rates, number of unit cells for Diamond and Gyroids TPMS both declined for Sheet and Skeletal topologies. The objective is to quantify their structural responses in terms of apparent stress and strain, dynamic enhancement and Specific Energy Absorbed (SEA) and to evaluate their structural integrity in terms of collapse stability. The results reveal that the Sheet pattern of TPMS structures with its constant wall thickness and uniform geometry exhibits better energy absorption capabilities than the Skeletal pattern. The Diamond family shows greater interest rather than the Gyroid family only in the case of the Sheet pattern. The increase in relative density from 20 to 30% is characterized by improved manufacturing quality, an increase in energy absorption capacity and more homogeneous progressive deformations during compression. On the whole, the set of TPMS geometries exhibits energy absorption capacities prior to those of other conventional cellular materials currently used for impact engineering applications. Finally, in a first approach, an original design methodology using charts can be developed to establish a link between the energy absorption capabilities and the design geometric parameters of TPMS structures.

A modified mixed-mode Timoshenko-based peridynamics model considering shear deformation

The original two-dimensional bond-based peridynamic (BBPD) framework, which only considers the pairwise forces (compression and tension) between two material points, is extended by incorporating the effect of shear deformation in the calculations and its influence on the failure of the bonds. To this end, each bond is considered as a short Timoshenko beam, and by doing so, the traditional BBPD is enhanced into a more comprehensive model known as multi-polar peridynamic (MPPD). The proposed novel approach explicitly considers the shear influence factor used in Timoshenko beams and introduces a strain-based shear deformation failure criterion. The model is then validated against two benchmark experimental tests (i.e., a standard pure mode I edge crack, and a Kalthoff-Winkler configuration) reported in the literature under in-plane dynamic loading and plane stress conditions. In most cases, the developed model is shown to be more accurate in predicting the crack paths obtained from the experimental results when compared to other theoretical methods delineated in the literature. Furthermore, a noticeable change in crack branching and crack path is observed in a study on the effects of Poisson's ratio and the loading rate. This investigation also demonstrated that the proposed MPPD model can accommodate materials with Poisson's ratios up to 1/3, expanding the range beyond the traditional BBPD limitations.

Dynamic tensile intralaminar fracture and continuum damage evolution of 2D woven composite laminates at high loading rate

The intralaminar tensile failure of 2D woven composites under dynamic tensile load was investigated in this paper. Compact tension samples were tested at high loading rate with an electromagnetic Hopkinson bar system. The strain field was obtained with high-speed imaging and digital image correlation, and the J-integral method was employed to obtain the fracture toughness and corresponding R-curve. The continuum damage evolution of intralaminar failure was then analyzed by tracking the opening near the initial crack tip. It is found that the dynamic intralaminar fracture toughness is decreased by 51% compared to the quasi-static condition, the continuum damage evolution and its dependence on loading rate have been reported as well. The failure mechanisms were studied with thermal imaging and scanned electron microscopy, shorter fibre pull-out length and thinner failure process zone may be responsible for the reduced toughness at high loading rate.

UV Filter NanoCapsule with Broad‐Spectrum UV Protection

AbstractIn this study, nanocapsules encapsulating avobenzone (AVB) compounded with isooctyl p‐dimethylaminobenzoate (OD‐PABA) were prepared via miniemulsion polymerization using methyl methacrylate (MMA) as the monomer, ethylene glycol dimethacrylate (EGDMA) as the cross‐linker, and poly(styrene‐co‐methacrylic acid) (P(St‐co‐MAA)) as the polymeric emulsifier. When a solid ultraviolet radiation A (UVA) filter, AVB, was encapsulated in nanocapsules (A‐UVNCs), the encapsulation and loading rates were 67.6% and 9.7%, respectively. When a liquid ultraviolet radiation B (UVB) filter, OD‐PABA, was combined with AVB, the encapsulation and loading rates of the nanocapsules (A/O‐UVNCs) of AVB and OD‐PABA increased to 90.0% and 15.6%, respectively, and 71.5% and 14.0%, respectively. The A/O‐UVNCs realized broad‐spectrum ultraviolet (UV) protection with an SPF value of 46.3. The A/O‐UVNCs have raspberry‐like nanostructures. These submicron particles can scatter and reflect a portion of the UV radiation and synergistically enhance UV protection. After exposure to simulated sunlight for four hours, the UVAPF of a sunscreen containing A‐UVNCs or A/O‐UVNCs decreased to a smaller extent than that of the sunscreen containing free AVB. Cell toxicity experiments showed that the cell viability of A‐UVNCs and A/O‐UVNCs was 85.9% and 83.0%, respectively. Therefore, UVNCs not only enhance UV protection but also improve photostability and safety.

Two-stage robust optimization for optimal operation of hybrid hydrogen–electricity storage system considering ladder-type carbon trading

The prominent problems of renewable energy curtailment and its uncertainty have become a hot topic. To the end, with consideration of environmental friendliness, energy utilization efficiency and operation cost, this paper proposes a hybrid hydrogen–electricity storage system (HHES) operation framework comprising assorted types of coupling devices and carbon capture system (CCS) under ladder-type carbon trading (LCT) mechanism. By considering energy balance constraints, equipments’ operation constraints and erratic rates of RESs and multiple loads, a scheduling model with source-load uncertainties is developed with the goal of minimizing the system’s operation cost and carbon emission. Then, a two-stage tri-level robust model is built to find the optimal scheduling plan under multiple uncertainties given the various sources and loads. The first level is to make an optimal dispatch plan and the second level is to find the worst scenario under the given uncertainty set. The third level aims at enhancing renewable energy accommodation rate and reducing load shedding rate in the worst case. Since the model is formed as a tri-level mixed integer optimization problem, the Column and Constraint Generation (CCG) method is adopted to achieve the optimal result. Finally, numerical analyses are performed. The results show that the proposed approach realizes a flexible dispatch of multiple energy and a high utilization level of multiple storages. Furthermore, this paper studies the influence of uncertainty and uncertainty budget parameters with the comparison of the deterministic model and robust models with different uncertainties. The results show that the proposed HHES has strong robustness and can provide a good reference for energy dispatch.

Mitigation mechanism of porous media hood for the sonic boom emitted from maglev tunnel portals

The micro-pressure waves (MPW) released from maglev tunnel portals can generate audible sonic booms and cause structural resonance in surrounding buildings, posing challenges to developing high-speed maglev trains. This paper proposes a novel porous media hood (PMH) and investigates its mechanism for mitigating the sonic booms emitted from tunnels. The numerical model employs the improved delayed detached eddy simulation turbulence model and overset grid technology, validated against data from moving-model experiments. The influences of the PMH's inherent properties and geometric parameters on MPW, flow field evolution, and aerodynamic loads on the train body were comprehensively discussed. The research demonstrates that PMH effectively dampens the initial wavefront gradient at the entrance and reduces the MPW amplitude by intensifying radiation within its exit vicinity. The porosity of 0.2 facilitates a seamless transition for the streamlined head from the ventilated PMH to the airtight tunnel. Lengthening the PMH enhances its MPW mitigation effect, whereas the impact of PMH thickness is minor. The PMH effectively diminishes the reflection intensity of compression and expansion waves at the tunnel ends, leading to a reduction in the magnitude and changing rate of train aerodynamic loads. This underscores the PMH's potential to enhance passengers' auditory comfort and alleviate issues related to train sway.

Estimation of the Durbin Spatial Semi-Parametric Regression Model using the Sub-Segment Regression Method

This study dealt with the penalty segment (PS) regression method to estimate the smoothing functions m(x) and m(x*), the Durbin semi-parametric spatial regression model, using the modified spatial adjacency matrix, under the standard adjoining rock, this method is one of the important non-parametric methods, were used to estimate non-parametric regression functions, it was applied using real-world data for a sample size of 75 observations, to find out the effect of average value, and it was analysed The research covered a period of five consecutive years (2018-2022), during which time it encompassed all 15 governorates of Iraq (with the exception of the three governorates that make up the Kurdistan Region). In consideration of the geographical impacts that exist across the governorates, the findings demonstrated that there was a discernible relationship between the rate of electrical loads and the temperature as well as the population density.

Should individuals with unilateral transtibial amputation carry a load on their intact or prosthetic side?

Carrying side loads often occurs during activities of daily living. As walking is most unstable mediolaterally, side load carriage may further compromise gait biomechanics, especially for transtibial amputees (TTAs). This study investigated the effects of side load carriage on gait kinetics during steady-state walking to determine which side, intact or prosthetic, TTAs should carry a load. Twelve unilateral TTAs wore a passive-elastic foot and carried a side load of 13.6 kg while walking at their self-selected speed. Kinetic metrics, including ground reaction force peaks and impulses, loading and unloading rates, and joint moments and powers, were analyzed. TTAs had smaller propulsive forces on their intact limb during the prosthetic side load condition. During the intact side load condition, they exhibited smaller hip flexor moment in late stance and smaller knee flexor moment at the end of swing on their intact limb. They had higher hip and knee abductor moments on their intact limb and prosthetic limb in early and late stance during the contralateral side load condition. TTAs generated higher hip extensor power at weight acceptance during the ipsilateral side load. Significant interactions were observed in hip extensor power and abductor moment, suggesting strong associations between hip extensor power generation and the ipsilateral side load and between hip abductor moment and the contralateral side load. These mixed results demonstrate some kinetic changes due to side load carriage and suggest that the side TTAs should carry a load depends on the desired effects, primarily on their intact limb.

Negative Load Rates In Ground Reaction Forces During Running By Footstrike Type And Injury Status

Negative Load Rates In Ground Reaction Forces During Running By Footstrike Type And Injury Status

A foundational framework for the mesoscale modeling of dynamic elastomers and gels

Discrete mesoscale network models, in which explicitly modeled polymer chains are replaced by implicit pairwise potentials, are capable of predicting the macroscale mechanical response of polymeric materials such as elastomers and gels, while offering greater insight into microstructural phenomena than constitutive theory or macroscale experiments alone. However, whether such mesoscale models accurately represent the molecular structures of polymer networks requires investigation during their development, particularly in the case of dynamic polymers that restructure in time. We here introduce and compare the topological and mechanical predictions of an idealized, reduced-order mesoscale approach in which only tethered dynamic bonding sites and crosslinks in a polymer’s backbone are explicitly modeled, to those of molecular theory and a Kremer-Grest, coarse-grained molecular dynamics approach. We find that for short chain networks (∼12 Kuhn lengths per chain segment) at intermediate polymer packing fractions, undergoing relatively slow loading rates (compared to the monomer diffusion rate), the mesoscale approach reasonably reproduces the chain conformations, bond kinetic rates, and ensemble stress responses predicted by molecular theory and the bead–spring model. Further, it does so with a 90% reduction in computational cost. These savings grant the mesoscale model access to larger spatiotemporal domains than conventional molecular dynamics, enabling simulation of large deformations as well as durations approaching experimental timescales (e.g., those utilized in dynamic mechanical analysis). While the model investigated is for monodisperse polymer networks in theta-solvent, without entanglement, charge interactions, long-range dynamic bond interactions, or other confounding physical effects, this work highlights the utility of these models and lays a foundational groundwork for the incorporation of such phenomena moving forward.

HKUST-1 in-situ loaded ultrastable covalently crosslinked agarose aerogel with solvothermal for highly efficient removal of methylene blue.

A new HKUST-1@covalently crosslinked agarose aerogel (HKUST-1@CCAGA) was synthesized for the highly effective elimination of Methylene Blue (MB). Firstly, the covalently crosslinked agarose aerogel (CCAGA) was obtained by hydrothermal crosslinking reaction with epichlorohydrin (ECH) as crosslinker, which remained stabilized under hydrothermal and solvothermal conditions. Then, HKUST-1 was made to bind to CCAGA by in situ solvothermal assays, and the HKUST-1 loading rate reached 47.4 % based on thermogravimetric data and calculated using the cross over method. Meanwhile, the SEM exhibited the complete 3D honeycomb structure of CCAGA, and HKUST-1 particles uniformly distributed on its layers. Additionally, the specific surface area of HKUST-1@CCAGA can reached 648.59 m2·g-1. The HKUST-1@CCAGA composite was utilized for MB removal, achieving a high adsorption capacity of 424.30 mg·g-1 at pH 8. The adsorption of MB was also maintained at 80 % after 5 cycles of the experiment. The composite aerogel exhibits good recyclability and has excellent adsorption capacity.

Analysis of movements involved in raising lower garments during toileting in patients with stroke and hemiplegia: An analysis focused on manipulation on the paretic side

BackgroundMovements to raise lower garments in patients with stroke and hemiplegia consist of downward reach, non-paretic-side manipulation, and paretic-side manipulation. In this study, we focused on paretic-side manipulation, which is particularly difficult, and investigated the factors that make it challenging. MethodsForty-eight patients with stroke and hemiplegia (23 and 25 patients in independent and dependent groups, respectively) participated in this study. First, we investigated the difficulty of each manipulation using a visual analog scale to confirm the usefulness of focusing on paretic-side manipulation. Characteristics of the paretic side manipulation were compared between the dependent and independent groups using a three-dimensional motion analysis system. FindingsThe dependent group showed greater difficulty in manipulation on the paretic side compared to manipulation on the non-paretic side. The dependent group had a lower paretic limb loading ratio (p < 0.01), greater pelvic rotation angle (p < 0.01), and longer paretic side manipulation time (p < 0.01) than those in the independent group. InterpretationThe factors that contributed to greater difficulty in manipulating the paretic side were a lower limb loading rate and larger pelvic rotation angle toward the paretic side. These factors make it difficult to reach the lower garment and result in inefficient manipulation of the paretic side.

Different aspects of biochar addition on semi-dry anaerobic digestion of organic fraction of municipal solid waste in continuous mode

This study investigated the use of biochar, derived from a wood gasifier, in semi-dry anaerobic digestion of organic fraction of municipal solid waste (OFMSW). The experiment was conducted in three phases, without biochar and changing the hydraulic retention time (HRT) from 50 to 15 days until first acidification condition (on pH = 6.5), with biochar at an optimal concentration of 30 g/L in HRT= 20–10 day. Also, countermeasures for the acidified reactor with biochar during the dormancy period were investigated. The results demonstrated that adding biochar led to a rapid recovery of the acidified reactor, improved stability parameters, and removed foaming as a disturbance. Biochar addition (30 g/L) enhanced the organic loading rate (OLR) up to 11 kgVS/m3.day with an HRT of 20 days leading to specific methane production of 383 L/kgVS and a volumetric production increase of biomethane by 85 %. However, at higher OLRs with HRT of 10 days, acidification condition resurfaced leading to homogeneous foaming. Excess adding of biochar did not have significant treatment effects but necessitated a no-feeding period (about 45 days) and gentle stirring with long intervals for stable conditions. Overall, the use of biochar along with the OFMSW biogas plant was demonstrated to enhance production efficiency.

Cues To Land Softly And Quietly Result In Acute Load Rate Reductions In Runners

Cues To Land Softly And Quietly Result In Acute Load Rate Reductions In Runners

Anaerobic biodegradation of real pharmaceutical-grade lactose manufacturing wastewater in a modified Internal Circulation Reactor

Pharmaceutical-grade lactose (PL) manufacturing generates wastewater containing high concentrations of biodegradable organic matter. In the absence of a suitable alternative, industries handle such concentrated streams by completely evaporating the entire stream and disposing of water-soluble solid residue in a landfill. Such a process is energy-intensive, and nothing useful is recovered from the stream. This study demonstrates the efficient and sustainable anaerobic biodegradation of real PL wastewater using a lab-scale internal circulation reactor (ICR) combined with an external recirculation system. The effects of feed Chemical Oxygen Demand (COD) concentration, organic loading rate (OLR), and hydraulic retention time (HRT) on COD removal efficiency, methane production, and the volatile fatty acids/alkalinity (VFA/ALK) ratio were evaluated. Under the highest feed COD concentration of 60,000mg/L, OLR of 4.5kg/m³∙d, and HRT of 13.33 days, the system achieved an average COD removal efficiency of 93.8% with methane production of 25.2L/d (specific methane generation of 0.32L/g CODremoved). By increasing the up-flow velocity from 0.044m/h (without external recirculation) to 1.5m/h (with external recirculation), COD removal improved from 63.6% to 93.4%, and methane production increased from 7.5L/d to 14L/d. The kinetics of COD removal fitted well in the modified Stover-Kincannon model (R2 = 0.99). A unique finding of this study is that the loose anaerobic sludge became granulated after 120 days, with 50% of the granules having diameters ≥ 2.0mm. The results of this study establish anaerobic biodegradation as a suitable treatment option for PL wastewater, thereby achieving UNSDG 6 (Clean Water and Sanitation) and 7 (Affordable and Clean Energy).

First full-scale application of barium carbonate as an effective dispersed alkaline substrate for sulfate removal from acid mine drainage

A full-scale passive treatment plant using barium carbonate (BaCO3), the mineral witherite, as a Dispersed Alkaline Substrate (DAS) for strongly contaminated acid mine drainage was implemented for the first time globally at Mina Concepción, located in the Iberian Pyrite Belt (SW Spain). The plant was monitored over a 105-day period, covering the wettest months of the hydrological year and with a mean flow around 4 L s−1. The AMD treated in the plant exhibits a high strength, with an average sulfate concentration around 1500 mg L−1 and net acidity close to 1000 mg L−1 as CaCO₃ equivalent. According to the above, the loading rate for SO4 and Fe was around 400 and 80 kg day−1, respectively. The treatment process produced an alkaline effluent with low metal content. Nearly complete removal of most metal(loid)s was achieved, with significant sulfate decrease to below 500 mg L−1 in the alkaline outflow of the barium carbonate tank. Barium carbonate demonstrated superior performance compared to magnesia, particularly in enhancing alkalinity and lowering net acidity and concentrations of sulfate and manganese. The high efficiency attained by the plant after the barium carbonate treatment is evidenced by compliance with environmental water quality standards for most contaminants.