Loading Rate Research Articles

Enhanced degradation and methane production of food waste anaerobic digestate using an integrated system of anaerobic digestion and microbial electrolysis cells for long-term operation.

The integrated system of anaerobic digestion and microbial electrolysis cells (AD-MEC) was a novel approach to enhance the degradation of food waste anaerobic digestate and recover methane. Through long-term operation, the start-up method, organic loading, and methane production mechanism of the digestate have been investigated. At an organic loading rate of 4000mg/L, AD-MEC increased methane production by 3-4 times and soluble chemical oxygen demand (SCOD) removal by 20.3% compared with anaerobic digestion (AD). The abundance of bacteria Fastidiosipila and Geobacter, which participated in the acid degradation and direct electron transfer in the AD-MEC, increased dramatically compared to that in the AD. The dominant methanogenic archaea in the AD-MEC and AD were Methanobacterium (44.4-56.3%) and Methanocalculus (70.05%), respectively. Geobacter and Methanobacterium were dominant in the AD-MEC by direct electron transfer of organic matter into synthetic methane intermediates. AD-MEC showed a perfect SCOD removal efficiency of the digestate, while methane as clean energy was obtained. Therefore, AD-MEC was a promising technology for deep energy transformation from digestate.

Dynamic rock tensile failure under hydrostatic pressure analyzed with wavelet transform of acoustic emission signals

We develop a novel experimental apparatus, integrated into a dynamic testing system, for the real-time monitoring of the failure process of deep rocks. Four groups of Brazilian disc (BD) granite specimens subjected to various hydrostatic confinements (0, 10, 20, 30 MPa) are tested under different loading rates. A strain gauge and an acoustic emission (AE) transducer are attached to each specimen to obtain the real-time failure signals during the impact. The continuous wavelet transform is utilized to analyze the recorded AE signals. It is observed that tensile crack initiation and propagation effectively absorb AE signals produced by stress waves above 50 kHz, which indicates that post-failure AE signals are predominantly generated by the cracks themselves. It is also found that the proportion of AE signals within the 100–150 kHz range increases with the loading rate, suggesting that higher loading rates encourage the emergence of smaller cracks. Moreover, higher hydrostatic stress enhances the dynamic tensile strength of the rock, thereby restraining crack initiation. When the confining stress is applied, the AE signals exceeding 100 kHz are delayed in their occurrence as compare with the failure, contrasting with those within the 50–100 kHz range that appear simultaneously with the failure. This pattern indicates that cracks generate AE signals within the 50–100 kHz range during the tensile failure, while those with frequencies above 100 kHz are produced by tensile crack propagation following the failure.

Crack propagation characteristics of coal body around the borehole under different loading rates

The loading rate is a crucial factor influencing the deformation and fracture of the coal body around a borehole. The uniaxial compression tests and digital image correlation methods were adopted to scrutinize the mechanical parameters, failure modes, and lateral strains of specimens. A comprehensive analysis of crack propagation characteristics under different loading rates was conducted. Based on the cohesion model, the intrinsic interplay between crack propagation characteristics and loading rates was elucidated. Combined with the actual situation on site, the treatment method of gas anomaly in high recovery rate working face is given. With an increase in loading rate, the peak strength, peak strain, and the initial stress level of cracks gradually increased and tended to stabilize. The elastic modulus exhibited an initial increase followed by a decrease. The failure mode transitioned from shear to tensile, and the fracture process became more intense. Tensile crack propagation was divided into four stages, with the first three stages characterized by “closed-open-closed” patterns. In the fourth stage, lateral strains fluctuated between positive and negative values at high loading rates, exhibiting high-strength nonlinearity, the accumulation of deformation energy density is “rupture → rupture again”. Due to the influence of cohesion, tensile crack propagation at low loading rates was hindered, resulting in K1 = 0 at the tensile crack tip. Under high loading rates, K1 > 0, leading to extensive tensile failure in the internal load-bearing structure. At the same time, combined with the abnormal situation of gas in the working face with high mining rate, specific solutions are put forward.

Use of recycled construction and demolition waste as substrate in constructed wetlands for the wastewater treatment of cheese production

Recycled building debris has recently emerged as a suitable wetland infill substrate due to its low density, exceptional water absorption capabilities, and high porosity. This study investigated, for the first time, the use of construction demolition wastes (CDW), and rock processing residues (RPR) as substrate materials in vertical-horizontal flow hybrid constructed wetlands for the treatment of cheese production wastewater. Results showed that the use of both CDW as well as RPR, as substrate material, provided an equal or even better quality of treated wastewater compared to the conventional use of gravel as a substrate. High removal efficiencies were recorded for turbidity (CDW: 91–92%, RPR: 97%), solids (CDW: 85–88%, RPR: 96–97%), organic matter (CDW: 79–84%, RPR: 96–98%), and total phosphorus (CDW: 72–76%, RPR: 87%) for both examined recycled materials. During the experiment, different loadings rates (HLR) were tested: 25 mm d−1 and 37.5 mm d−1. Radiological measurements indicate that, their use did not cause toxic effects on the environment, as the amounts of radioactivity found in the effluent of the systems are not significant. Increasing the hydraulic loading rate appeared to have no negative effect on pollutant removal, as the systems and plants were fully acclimated and mature. This approach offers several advantages, including the use of readily available and abundant waste material, potential cost savings, and the environmental benefits of recycling CDW and RPR instead of disposing of them in landfills.

Monitoring bridge bearings based on rubber-based composite materials

To improve the real-time monitoring capability of bridge structure safety, intelligent bridge bearings were prepared based on rubber based composite materials. The study selected T4/3-5 intelligent rubber bearings and conducted a systematic experimental analysis on their response characteristics under different loading speeds and holding states. By measuring the displacement and resistance changes of the intelligent bearings under various load conditions, their sensitivity and stability were evaluated. These experiments confirmed that the T4/3-5 intelligent rubber bearings exhibited a total creep deformation of approximately 1 mm and 1.5 mm under loads of 60 kN and 45 kN, respectively. This suggests that the molecular chains reach a relatively stable configuration under high loads and are not prone to further changes. Moreover, the resistance reduction ratio under a load of 60 kN is approximately 0.57, while under a load of 45 kN it is approximately 0.62, indicating that nickel powder particles in the composite material form a more stable conductive network after molecular rearrangement. At different loading rates, the displacement-load and load-resistance curves of the bearings show consistent trends, and the creep and resistance relaxation behaviors exhibit certain regularity with the concentration of load size. Through the analysis of these data, the study elucidated the resistance change mechanism in the bearings and validated the feasibility of intelligent bearings as a real-time load monitoring tool.

Research on the expansion of energy-saving boundary for CCHP system under all operating conditions based on collaborative integration

In this study, the impact of load demands on the energy-saving characteristics of the systems was analyzed, and the mathematical model was derived for the relationship between the load supply and demands under different capacity design modes and operation strategies, and the influence of the key parameters (load demands, load rate, matching degree) on system integration and operation characteristics in different energy use scenarios was quantitative analyzed to elucidate the inherent mechanism of energy saving characteristics. Furthermore, the impact of energy-matching degree and system efficiency on the energy saving rate (ESR) was discussed, and based on the load demands, an universal system boundary of the ESR was constructed. Based on this, the coupling mechanism between the system and users from a global perspective was reconstructed, and an collaborative integrated method based on centralized energy supply systems, CCHP systems, and load demands was proposed to expand the energy-saving boundary under all operating conditions. Finally, a case analysis and method verification were conducted using typical summer days at Beijing hotel as an example. The results show that this method universally characterizes the coupling matching relationship and energy-saving characteristics. Through collaborative integration, the ESR increase of 5% can be achieved.

Flexural and shear load rate evaluation on Pre-stressed concrete Box Girder Superstructure under the effect of IRC Loading

Flexural and shear load rate evaluation on Pre-stressed concrete Box Girder Superstructure under the effect of IRC Loading

Management strategy of granular sludge settleability in saline denitrification: Insights from machine learning

The settleability of granular sludge is a crucial factor in maintaining an adequate amount of granules in the wastewater treatment process (WWTP). However, Accurate measurement of settleability is challenging due to the complex interactions in WWTP. To address this issue, an intelligent strategy for controlling the settleability of granular sludge is required. This study developed a machine learning (ML)-based model to predict the sludge volume index (SVI30). Three ML models, namely artificial neural networks (ANNs), random forest (RF), and support vector machine (SVM) models, were employed with an ANNs-based mixed liquor suspended solids (MLSS) soft sensor, which served as input data for predicting SVI30 using ML. The combination of the soft sensor’s output and ANNs yielded the highest performance with R2 and mean absolute error (MAE) of 0.8946 and 5.5 mL/g, respectively. The Shapely Additive Explanations (SHAP) analysis revealed that MLSS, salinity, glucose loading rate, and pH were significant factors influencing SVI30. The surrogate model-based optimization strategy of SVI30 was conducted using core control parameters (CCPs), namely glucose loading rate, effluent pH, and salinity. It was suggested that a glucose loading rate over 3.0 kg-N/m3-d and an effluent pH exceeding 9.0 can deteriorate the SVI30. To the best of our knowledge, this is the first study on the surrogate model-based suggestion of the management strategy in the granular sludge process under saline denitrification conditions.

Alien species water hyacinth realizes waste into treasure: The preparation of biomass sorbent to determine benzoylurea insecticides in tea products.

A fast and effective analytical method with biomass solid-phase microextraction sorbent combined with a high-performance liquid chromatography-ultraviolet detector was proposed for the determination of benzoylurea (BU) insecticides in tea products. The novel sorbent was prepared by activating and then carbonizing water hyacinth with a fast growth rate and low application value as raw material and showed a high specific surface area and multiple interactions with analytes, such as electrostatic action, hydrogen bonding, and π-π conjugation. After optimizing the three most important extraction parameters (pH [X1], sample loading rate [X2], and solution volume [X3]) by Box-Behnken design, the as-established analytical method showed good extraction performance: excellent recovery (80.13%-106.66%) and wide linear range (1-400µg/L) with a determination coefficient of 0.9992-0.9999, a low limit of detection of 0.02-0.1µg/L and the satisfactory practical application results in tea products. All these indicate that the water hyacinth-derived material has the potential as a solid-phase extraction sorbent for the detection and removal of BU insecticides from tea products, and at the same time, it can also achieve the effect of rational use of biological resources, maintaining ecological balance, turning waste into treasure, and achieving industrial production.

Multiscale finite element modeling of origami-inspired dual matrix deployable composite with visco-hyperelastic hinge

Dual matrix deployable composites with viscoelastic materials are prone to experiencing relaxation in their stored strain energy, leading to potential degradation in their deployment performance. This study presents a multiscale FE modeling approach to investigate the folding and deployment behavior of origami inspired dual-matrix deployable composite with visco-hyperelastic hinge. A typical dual-matrix origami composite fold was manufactured using a hot compression molding technique and hand layup method and folding tests were carried out. The visco-hyperelastic behavior of elastomer used in the folding region was characterized. Experiments were carried out on elastomer under rate dependent loading, single-step, multi-step, and cyclic tests and material parameters for constitutive model were identified. The homogenized properties of hybrid laminate and elastomer laminate were obtained from XCT-driven FE based homogenization of real RVE. First, the multiscale FE model was validated with the experimentally-measured moment-curvature diagram. Next, the proposed multiscale FE model was employed to simulate the influence of modulus relaxation of pure elastomer on the deployment behavior of a simple rectangular fold and an origami-inspired waterbomb base structure. The variation of moment-curvature, and relaxation in strain energies during stowage under controlled and free deployment are reported. The effect of incomplete folding and stowage durations on strain energy and deployment time was investigated. In the end, the influence of the loading rate effect on the bending stiffness relaxation of pure elastomer and elastomer laminate fold was investigated.

Adaptive differential steering strategy for distributed driving unmanned ground vehicle with variable configurations based on modified localized modelling sliding mode control

When performing complex tasks such as position transfer and material transportation, the distributed driving unmanned platform with variable configurations needs to address the challenge of multi-wheel cooperative torque distribution control to achieve high-performance differential steering and enhance vehicle dynamics. The configuration change will impact the dynamic performance of the unmanned platform, posing a challenge to the performance of the existing control strategy based on mathematical model development. In order to address the aforementioned issues, this paper analyzes the impact of changes in vehicle configuration on steering gain and proposes a hierarchical adaptive differential steering strategy based on variable vehicle configurations. Firstly, the response characteristics of the yaw angle relative to the active yaw moment under the influence of changes in wheelbase and tread are analyzed. Based on this analysis, two structural modes, maneuverable and balanced, are selected. Secondly, a localized-modelling sliding mode control method with an extended state observer is proposed to estimate the desired yaw moment in the upper controller, considering the motor's execution delay. Then, the lower controller optimizes the torque of each wheel in real-time using the whale optimization algorithm. It aims to optimize tire energy dissipation and tire load rate while ensuring driving stability and achieving differential steering. Finally, through co-simulation and experiments on a scaled prototype, the reliability of the dynamics theory and the superiority of the control algorithm are validated. This optimization has led to significant improvements in the tire dissipation energy index and tire load rate index.

Enhanced brain-targeting and efficacy of cannabidiol via RVG-Exo/CBD nanodelivery system

This study introduces an innovative brain-targeted drug delivery system, RVG-Exo/CBD, utilizing rabies virus glycoprotein (RVG)-engineered exosomes for encapsulating cannabidiol (CBD). The novel delivery system was meticulously characterized, confirming the maintenance of exosomal integrity, size, and successful drug encapsulation with a high drug loading rate of 83.0 %. Evaluation of the RVG-Exo/CBD's brain-targeting capability demonstrated superior distribution and retention in brain tissue compared to unmodified exosomes, primarily validated through in vivo fluorescence imaging. The efficacy of this delivery system was assessed using a behavioral sensitization model in mice, where RVG-Exo/CBD notably suppressed methamphetamine-induced hyperactivity more effectively than CBD alone, indicating a reduction in effective dose and enhanced bioavailability. Overall, the RVG-Exo/CBD system emerges as a promising strategy for enhancing the therapeutic efficacy and safety of CBD, particularly for neurological applications, highlighting its potential for addressing the limitations associated with traditional CBD administration in clinical settings.

Aerobic granular sludge sequencing batch reactor for high strength domestic wastewater treatment: Assessing kinetic models and microbial community dynamics

The study aims to treat high strength domestic wastewater (HSDW) and cultivate microbial granular sludge in a sequencing batch reactor (SBR). A bench-scale bioreactor was used for startup. Response surface methodology (RSM) was used to determine the ideal parameters for removing organic materials from HSDW. Organic loading rate (OLR) and cycle time were the independent variables taken into consideration, while the response variable was COD removal. Results from RSM revealed that the optimal conditions for achieving > 98 % COD and TP (>80) removal were a cycle length of 6 h and an OLR of 1.5 kgCOD/m3d. The Modified-Kincannon and the Grau second-order kinetic models were compared to the COD removal rate for the SBR system. The saturation rate constant (Ni) and maximal substrate removal rate (Vc) were proposed to be 6.8 g L−1 d−1 and 0.83 g L−1 d−1, respectively, based on the modified Stover-Kincannon model. The modified Stover-Kincannon (R2 = 0.93673) and Grau second order (R2 = 0.99219) models high correlation coefficient values show that the experimental results and the prediction for the microbial aerobic granular based SBR system accord well. It was discovered that the modified Stover-Kincannon model was less suitable than the Grau second order model. The system microbial community changed because of the granulation process, as the reactor design operation had a big impact on the community structure. Decreased filamentous bacteria favoured several taxa that have been found to exist in granular biomass that is appropriate for treating wastewater. This study sheds important light on the complex interactions that occur between microbial populations and operational variables all through the granulation process in SBR.

Increasing urine nitrification performance with sequential membrane aerated biofilm reactors

Increasing urine nitrification performance with sequential membrane aerated biofilm reactors

Production of ammonium nitrate for nitrogen recovery in a single bioreactor operating at pH 3

Ammonium nitrate (AN), i.e. NH4NO3, is extensively utilized in agricultural, mining, and civil construction sectors, with an annual production of approximately 16 million tons. Although the biological nitrification processes has been proven to be an important alternative to overcome the intensive energy consumption of the conventional chemical process for AN production, it necessitates ample chemical input for stable performance. This study marks the first demonstration of stable AN production from ammonium-rich wastewater employing a purely microbial-derived one-stage process, without the need for external chemical addition. This process functioned through an acidophilic ammonia-oxidizing bacteria (AOB), i.e., Candidatus (Ca.) Nitrosoglobus, which oxidized the ammonium in the feed to nitrite while simultaneously reducing the reactor pH to 3.2−3.4. Under these pH conditions, nitrite was chemically oxidized to nitrate with the provision of oxygen. Long-term bioreactor operation (>230 days) revealed consistent AN production from high ammonium wastewater at a nitrogen loading rate of 0.15 kg N/m3/d. Batch tests revealed that microbial ammonium oxidation was the rate-determining step in the overall AN production process. Further microbial enrichment and process optimization can enhance the microbial ammonium oxidation rate. In summary, the proposed acidic one-stage bioprocess presents a promising avenue for AN production from ammonium-rich wastewater.

Regulatory mechanisms of biochar alleviating ammonia inhibition to methanogenesis during long-term operation of anaerobic membrane bioreactor treating swine wastewater

Anaerobic Membrane Bioreactor (AnMBR) is regarded as an advanced technology for the anaerobic digestion (AD) of swine wastewater. However, the high ammonia level in swine wastewater is a crucial issue to inhibit methane production. This study aimed to establish a biochar-assisted AnMBR (BC) to mitigate ammonia inhibition during AD of swine wastewater. As the gradual ammonia loading rate (ALR) increased from 3.0 g/L to 6.0 g/L, BC maintained methane yields ranging from 74.9 % to 48.1 %, which were 9.1 % to 33.3 % higher than those of a regular AnMBR (CT). Moreover, the COD removal efficiency steadily surpassed 80 %. Although the increase in ALR had negative effects on both BC and CT, the presence of biochar enhanced the methanogenic activity of bulk sludge, specifically accelerating processes involved in syntrophic acetate oxidation and CO2-reducing methanogenesis under high ALR conditions. Integrated characterizations using PARAFAC-based EPS analysis, INT-ETS, and WO3 probe-based extracellular electron transfer (EET) activities indicated that biochar stimulated the secretion of humic-like and aromatic protein-like compounds in the TB-EPS, which likely established a redox-active matrix with biochar between VFA oxidation bacteria and CO2-reducing methanogens to facilitate EET. This potentially made the syntrophic VFA oxidation with favorably thermodynamic kinetics under high ammonia stress. Furthermore, the analysis of microbial community coupling prediction of functional genes associated with methanogenic pathways revealed that as ALR increased, the presence of biochar re-shaped the microbial communities by enriching electro-active Syntrophomonas and Methanosarcina/Methanospirillum, which mainly triggering EET-based syntrophic methanogenesis by accelerating the intracellular enzymatic transformation from Formylmethanofuran to 5,10-Methylenetetrahydromethanopterin process. We expect the major findings of this study provide new insights to understand the mechanisms of biochar alleviating ammonia inhibition during long-term operation of AnMBR.

Enhanced Toughening of the Lamellar Structure in a Black Coral by Interlocking Spines.

The black corals possess a branched, tree-like skeleton that is composed of chitin fibrils embedded within a protein matrix. This skeleton exhibits growth rings interlocked by spines. The lamellae are tightly wrapped around the spines, creating a structure akin to an onion. The indentation hardness and Young's modulus of the spines are comparable to those of the chitin rings. The compressive stress and the fracture toughness are increased by approximately 14.6% and 32.2% at higher loading rate in the dry state, but remain comparable at different loading rates in the wet state. The lamellar interfaces have a tendency to resist sliding in the dry state. As a result, the lamellae that curve around the spines are prone to fracturing one by one, just like an onion being peeled. This allows the material to absorb more fracture energy, ensuring that the spines can effectively resist the lamellar delamination.

Effect of Shear Loading Conditions on the Measured Strength of Ice Adhesion to Superhydrophobic Surfaces

Despite the significant interest of researchers, icing of aircraft, vehicles, ships, and equipment of offshore oil structures remains to be an urgent problem. This paper considers the factors that promote a decrease in the strength of the contact between ice and surfaces under an applied shear load. The main attention is focused on studying the influence of the rate of shear loading on the fracture of the interfacial contact between ice and superhydrophobic coatings. The strength of the adhesive contact under the conditions of controlled variations in the applied load is measured using a technique based on the detachment of ice from a surface under the influence of centrifugal force. The study is carried out for large ensembles of samples in the temperature range from −5 to −20°C, thereby making it possible to evaluate the influence of the quasi-liquid layer and the Rehbinder effect on a decrease in the shear adhesive strength. The results obtained indicate that the contact between ice and a superhydrophobic coating is fractured through a mixed viscous–brittle mechanism. In this case, a decrease in temperature or an increase in the loading rate causes a transition from the viscous to the brittle fracture. These results indicate a potential acceleration of ice shedding with an increase in the growth rate of the shear stress.

Analysis of the Effect of Loading Rate on Mechanical Properties of Fissured Rock Materials and Acoustic Emission Characteristic Parameters

Analysis of the Effect of Loading Rate on Mechanical Properties of Fissured Rock Materials and Acoustic Emission Characteristic Parameters

Coordinated torque control for enhanced steering and stability of independently driven mobile robots

Purpose Mobile robots with independent wheel control face challenges in steering precision, motion stability and robustness across various wheel and steering system types. This paper aims to propose a coordinated torque distribution control approach that compensates for tracking deviations using the longitudinal moment generated by active steering. Design/methodology/approach Building upon a two-degree-of-freedom robot model, an adaptive robust controller is used to compute the total longitudinal moment, while the robot actuator is regulated based on the difference between autonomous steering and the longitudinal moment. An adaptive robust control scheme is developed to achieve accurate and stable generation of the desired total moment value. Furthermore, quadratic programming is used for torque allocation, optimizing maneuverability and tracking precision by considering the robot’s dynamic model, tire load rate and maximum motor torque output. Findings Comparative evaluations with autonomous steering Ackermann speed control and the average torque method validate the superior performance of the proposed control strategy, demonstrating improved tracking accuracy and robot stability under diverse driving conditions. Research limitations/implications When designing adaptive algorithms, using models with higher degrees of freedom can enhance accuracy. Furthermore, incorporating additional objective functions in moment distribution can be explored to enhance adaptability, particularly in extreme environments. Originality/value By combining this method with the path-tracking algorithm, the robot’s structural path-tracking capabilities and ability to navigate a variety of difficult terrains can be optimized and improved.