Loading Rate Research Articles

Dynamic failure assessment analysis of 15MnTi steel supporting structure with a circumferential surface crack under impact loads

Supporting structures, whose strength have great influence on the safe operation of the whole equipment, are widely used in various ship equipment. In this paper, dynamic failure assessment analysis is carried out to discuss the structural integrity of the cracked supporting structure under impact loads. Considering the dynamic response characteristics of structures, the dynamic fracture toughness determined by the loading rate of dynamic J-integrals is used to calculate the failure assessment point (FAP). Due to the widespread uncertainties in practical engineering, such as crack size and mechanical properties of materials, the failure assessment results will also have uncertainty. To analyze the structural integrity affected by uncertain variables, the polygonal convex set (PCS) model is introduced to the failure assessment diagram (FAD) to propose a non-probabilistic failure assessment method. The FAP is extended to a failure assessment region, and structural integrity can be analyzed by the non-probabilistic reliability degree. Compared with the traditional interval model, the non-probabilistic reliability degree calculated by PCS model is closer to the probabilistic reliability degree, which avoids premature judgement of structural failure. For the 15MnTi supporting structure with a circumferential semi-elliptical surface crack under impact loads, the critical depth obtained by non-probabilistic methods decrease by 10% compared with deterministic results, and the failure mechanism is summarized as plastic collapse resulting from the excessive net section stress. In the absence of statistical data on crack size or mechanical properties, the non-probabilistic failure assessment method can be used as an effective alternative to the probabilistic method.

Minimization of metabolic cost of transport predicts changes in gait mechanics over a range of ankle-foot orthosis stiffnesses in individuals with bilateral plantar flexor weakness

Neuromuscular disorders often lead to ankle plantar flexor muscle weakness, which impairs ankle push-off power and forward propulsion during gait. To improve walking speed and reduce metabolic cost of transport (mCoT), patients with plantar flexor weakness are provided dorsal-leaf spring ankle-foot orthoses (AFOs). It is widely believed that mCoT during gait depends on the AFO stiffness and an optimal AFO stiffness that minimizes mCoT exists. The biomechanics behind why and how an optimal stiffness exists and benefits individuals with plantar flexor weakness are not well understood. We hypothesized that the AFO would reduce the required support moment and, hence, metabolic cost contributions of the ankle plantar flexor and knee extensor muscles during stance, and reduce hip flexor metabolic cost to initiate swing. To test these hypotheses, we generated neuromusculoskeletal simulations to represent gait of an individual with bilateral plantar flexor weakness wearing an AFO with varying stiffness. Predictions were based on the objective of minimizing mCoT, loading rates at impact and head accelerations at each stiffness level, and the motor patterns were determined via dynamic optimization. The predictive gait simulation results were compared to experimental data from subjects with bilateral plantar flexor weakness walking with varying AFO stiffness. Our simulations demonstrated that reductions in mCoT with increasing stiffness were attributed to reductions in quadriceps metabolic cost during midstance. Increases in mCoT above optimum stiffness were attributed to the increasing metabolic cost of both hip flexor and hamstrings muscles. The insights gained from our predictive gait simulations could inform clinicians on the prescription of personalized AFOs. With further model individualization, simulations based on mCoT minimization may sufficiently predict adaptations to an AFO in individuals with plantar flexor weakness.

Incremental Load Respiratory Muscle Training Improves Respiratory Muscle Strength and Pulmonary Function in Children with Bronchiectasis.

Participants underwent respiratory muscle training for 24 weeks. The main results were changes in respiratory muscle strength and pulmonary function indices (forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), FEV1/FVC, peak expiratory flow rate (PEF), forced expiratory flow 25-75% (FEF25-75%), and maximal midexpiratory flow 75/25 (MMEF75/25)) before, 12 weeks after, and 24 weeks after the intervention. The secondary outcomes were changes in the exercise load and work rate, exercise work, Leicester Cough Questionnaire (LCQ) scale, and Fatigue Severity Scale (FSS). Compared with before the intervention, after 24 weeks of respiratory muscle training, the maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) were significantly enhanced (P < 0.05), while FVC, FEV1, and PEF were significantly increased (P < 0.01). FEF25-75 and MMEF75/25 values showed significant improvement compared to those before training (P < 0.05). The exercise loading, work, and exercise work rate of expiratory muscle training were significantly improved compared to those before intervention (P < 0.05). The LCQ score increased significantly (P < 0.001), and the FSS score decreased significantly (P < 0.001). Incremental load respiratory muscle training effectively improved children's lung function over the long term, improved the strength of their inspiratory and expiratory muscles, and improved their quality of life.

Effects of notch width and loading rate on the dynamic mode II fracture toughness of Ti-6Al-4V

Existing work on size effects in the measurement of dynamic fracture toughness (DFT) has focused mainly on the overall geometric dimensions of the test specimens, while the effects of notch width and loading rate were not explored. In this paper, DFT experiments were conducted using Ti-6Al-4V alloy to study the effects of notch width effect and loading rate effect on its dynamic mode II fracture toughness. An extrapolation method is proposed to estimate the DFT of an ideal sharp crack, and the relationship between DFT, loading rate, and notch width is captured with a 3D spatial plane. Results revealed that the DFT decreases with a reduction of the notch width and increases with loading rate. The effects of notch width on DFT will be shown to be more sensitive compared to loading rate. The failure mode transitional behavior from ductile fracture to adiabatic shearing will be revealed through fractographic analysis of the microstructural evolution, which will elucidate the effects of loading rate on the failure mechanism of the material.

Neural network-driven interpretability analysis for evaluating compressive stress in polymer foams

This research presents a method to analyze how neural network models, applied to Expanded Polypropylene and Expanded Polystyrene foams, predict their compressive stress responses. By using SHAP values and Partial Dependence Plots, the study elucidates the models’ decision-making processes. It focuses on three main features for both materials: density, loading rate, and strain, with an additional feature concerning loading and unloading for Expanded Polystyrene foam. The findings highlight that increased density and loading rate are closely correlated with higher compressive responses, and strain emerges as the most influential factor for the response of both materials. Partial Dependence Plots reveal a linear relationship with density, whereas other variables demonstrate non-linear relationships. These results validate the use of neural networks in analyzing material behavior, showing that the models’ outputs are in line with empirical observations. In conclusion, as presented, the integration of interpretability tools with neural network models offers a robust method for material response analysis, contributing to a deeper understanding of material science.

Measurement of the interfacial energy release rate (ERR) and cohesive law parameters of polyvinyl butyral laminated glass using a novel beam-type test specimen

The polyvinyl butyral (PVB) laminated glass (LG) structures are widely used in architectural and automotive sectors. Determination of the interfacial fracture energy (i.e. G) between the PVB layer and glass is one of the most vital procedures for ensuring the structural safety and fracture resistance of these kinds of components. The present study investigates the adhesion characteristics between glass and PVB interface in a LG composite structure. A new simple test fixture is introduced to measure the mixed-mode fracture energy from pure mode I (i.e. GI) to pure mode II (i.e. GII). By making use of the concept of Equivalent material Concept (EMC), linear elastic fracture mechanics (LEFM) formulations together with finite element (FE) analysis can be used to compute the compliance parameter of the system and pure modes I/II fracture energies. Besides, the interaction of cohesive forces between the PVB layer and glass are simulated by using a FE method based on a bi-linear cohesive zone model (CZM) technique. In this regard, the cohesive law parameters are computed for mode I and mode II in an iterative process. Then, the obtained pure mode cohesive law parameters are utilized to predict the mixed-mode load–displacement diagrams. The obtained results demonstrate the satisfactory accuracy of the cohesive law parameters and fracture energies in predicting the mixed-mode loading results across four different loading rates (i.e. LR = 2, 5, 10, and 15 mm/min).

Assessing the Impact of Organic Loading Rate on Hydrogen Consumption Rates during In Situ Biomethanation

Biogas upgrading via biomethanation has been extensively studied recently, but the influence of organic loading rate on process performance remains to be fully understood. This is particularly significant because both organic loading rate and hydrogen injection can lead to volatile fatty acid accumulation during anaerobic digestion. This study investigated the impact of a wide range of organic loading rates (from 1.25 to 3.25 g VS/L/d) on hydrogen consumption rates, organic acid accumulation, and microbial communities during in situ biomethanation. It also provided kinetics data and metabolite production data for different control reactors, including anaerobic digestion, ex situ biomethanation, and endogenous control reactors. Hydrogen was injected into parallel batch reactors using digestate from a semi-continuous lab-scale reactor subjected to increasing organic loading rates (1.25–3.25 g VS/L/d) as an inoculum. The inoculum was well adapted to each tested organic loading rate. The batch experiments were replicated following a 12 h hydrogen starvation period to assess the stability of hydrogen consumption rates. High organic loading rate values resulted in increased hydrogen consumption rates, peaking at 68 mg COD/L/h at an organic loading rate of 3.25 g VS/L/d (maximum value tested), with no significant organic acid accumulation despite the high hydrogen partial pressures. The hydrogen consumption rates were maintained after the starvation period. Furthermore, the addition of an organic substrate did not impact the hydrogen consumption rate (i.e., the in situ and ex situ rates were similar). A higher organic loading rate resulted in higher relative abundances of hydrogenotrophic methanogens (i.e., Methanospirillum sp.). This study highlights that increasing the organic loading rate can accelerate the rate of hydrogen consumption during in situ biomethanation, consequently reducing both capital and operational costs.

Design of non-linear, viscoelastic architected foams

Flexible viscoelastic foams with relative density in the range of 5-50% are widely used to control interaction forces, notably in cushions for impact protection, shoes, mechanical grippers, etc. The design of new foams to improve performance is challenging, due to the lack of efficient models to connect cellular architecture, viscoelasticity of the base resin, and non-linear responses that stem from large deformation of open pores. This paper presents highly efficient solutions for the response of linearly viscoelastic, kinematically non-linear and shear-deformable struts that are loaded at an oblique angle to their axis. The models can be used to predict structure-property relationships for strut-based metamaterials, including non-linear stress-strain response and accompanying hysteresis. To illustrate this, the entire design space of a simple unit cell is mapped in terms of a broad range of strut angles and thicknesses; the unit cell is inspired by features in stochastic foams that dominate their response. An enormous range of stress-strain responses can be obtained from this single foam-like cell, including purely softening, purely stiffening, and non-monotonic stiffness with adjustable tangent moduli. The model is also used to illustrate connections between viscoelastic material parameters, loading rate, and hysteresis for two distinct classifications of non-linear stress-strain response.

Comparative Study of the Mechanical Properties of a Novel Epoxy Composite Material Reinforced by Bidirectional Woven Carbon Fabric and Hybrid Kevlar/E-Glass

The objective of this work is to carry out a comparison of different materials in the form of a bidirectional carbon fabric and hybrid Kevlar and glass as reinforcements in an epoxy matrix with a loading rate of 30wt%. Two experimental tests have been carried out in order to determine the mechanical properties, such as tensile and Brinell hardness tests. In the case of tensile and Brinell hardness tests, the characterization was performed on two types of composite plates reinforced with Woven Carbon Fiber and Hybrid Woven Kevlar and E-Glass with Epoxy (WCF-HWKG/EPOXY) and Hybrid Woven Kevlar and E-Glass with Epoxy (HWKG/EPOXY). Consequently, it has been observed that the tensile and hardness properties of the hybrid composite material (HWKG/EPOXY) are respectively 36% and 46.43% lower compared to (WCF-HWKG/EPOXY). Based on these findings, the studied materials demonstrate potential applications across various fields, including aeronautics, aerospace, and high-performance automotive sectors.

Use of Continuous Stirred Tank Reactors for Anaerobic Co-Digestion of Dairy and Meat Industry By-Products for Biogas Production

The dairy and meat industries generate thousands of tons of organic waste and by-products each year, making them two of the least environmentally sustainable sectors. Typical waste includes not only processing by-products such as curds but also commercial products that are defective or unsaleable due to expiration or damaged packaging. This study aimed to evaluate the methanogenic potential of a mixture of 80% inedible curds and 20% expired sausages, as a substrate, using two continuously stirred tank reactors (CSTR). The reactors were fed daily with increasing doses of the 80–20% mixture and an organic loading rate ranging from 0.31 gVS/litre/day at the beginning of the trials to 7.20 gVS/litre/day toward the end. The produced biogas was continuously analysed from both quantitative and qualitative point of view. Also, the process was continuously monitored by withdrawing samples from each reactor during the whole process, to analyse their physical–chemical parameters, including pH, total solids (TS), total volatile solids (TVS), chemical oxygen demand (COD), ammonium nitrogen (NH4+-N), total Kjeldahl nitrogen (TKN) and total volatile fatty acids (VFA). The results of this study show a promising increase in biogas production with the increase in feed. In terms of biogas production, organic waste from the dairy and meat industry shows the potential to be exploited as a substrate to produce biomethane. Indeed, in this study, biomethane cumulative production reached 410.86 NLCH4∙gTVS−1 using an 8 L capacity reactor filled up to 6 L. This makes the tested by-products usable as a renewable energy source in the future, particularly within a circular economy approach, helping to mitigate the effects of global warming and addressing sustainable development goals.

Application of Mechano-Luminescence-Optoelectronic Composites for Delamination Detection in Fiber Reinforced Polymer Composites

Abstract Fiber reinforced polymer (FRP) composites have attracted significant attention from the aerospace industry in recent years. FRP composites have the advantage of being light weight, high strength and resistant to corrosion making them an attractive option for various applications in the aerospace industry. However, FRP composites are prone to delamination which can eventually compromise structural integrity leading to sudden failure. An effective damage detection methodology is therefore necessary to monitor delamination in structures. In this study, mechano-luminescence-optoelectronic (MLO) composites were integrated with FRP composites to create MLO-FRP test coupons for delamination detection. The MLO composites were prepared by coupling a Poly(3-hexylthiophene) (P3HT)-based sensor with a copper dopped zinc sulfide (ZnS:Cu) composite. MLO composites were attached to the surface of FRP composites to create MLO-FRP test coupons. The MLO-FRP test coupon was mounted on a 3-point bending load frame and subjected to cyclic loading and unloadings at various displacements with the first displacement starting from zero to 5 mm. The second displacement starting from zero to 6 mm and so on. A direct current (DC) voltage was recorded from the MLO composites at a constant loading rate to validate its DC-based strain sensing capability. Other parameters such as applied load, strain energy release rate and strain were also obtained with the aim of tracking delamination propagation in FRP composites. Results showed MLO composites were sensitive to delamination propagation highlighting their potential to be used in structures for health monitoring.

Nitrification–Autotrophic Denitrification Using Elemental Sulfur as an Electron Donor in a Sequencing Batch Reactor (SBR): Performance and Kinetic Analysis

Simultaneous nitrification and autotrophic denitrification (SNAD) has received attention as an efficient biological nitrogen removal alternative. However, SNAD using elemental sulfur (S0) has scarcely been studied. Thus, the main objective of this research was to study the behavior of a simultaneous nitrification–autotrophic denitrification operation in a sequential batch reactor (SNAD-SBR) at a lab scale using S0 as an electron donor, including its kinetics. Two-scale reactors were operated at lab scales in cycles for 155 days with an increasing nitrogen loading rate (NLR: 0.0296 to 0.0511 kg N-NH4+/m3/d) at 31 °C. As a result, simultaneous nitrification–autotrophic denitrification using S0 as an electron donor was performed successfully, with nitrification efficiency of 98.63% and denitrification efficiency of 44.9%, with autotrophic denitrification as the limiting phase. The kinetic model adjusted for ammonium-oxidizing bacteria (AOB) was the Monod-type kinetic model (µmax = 0.791 d−1), while, for nitrite-oxidizing bacteria (NOB), the Haldane-type model was employed (µmax = 0.822 d−1). For denitrifying microorganisms, the kinetic model was adjusted by a half order (k1/2v = 0.2054 mg1/2/L1/2/h). Thus, we concluded that SNAD could be feasible using S0 as an electron donor, with kinetic behavior similar to that of other processes.

Insights into effect of lignocellulosic biomass framework types on bio-based shape stable composite phase change materials

The utilization of biomass waste as framework materials to inhibit the leakage of phase change material (PCMs) has gained widespread attention. In this work, three new kinds of shape stable composite phase change materials (sscPCMs) were prepared which combined with stearic acid (SA) and peanut shell powders (PSP), poplar wood powders (PWP), and corn straw powders (CSP), respectively. The influence of lignocellulosic biomass types on the thermal energy storage performance of sscPCMs was studied by comparing three types of sscPCMs. The research results indicated that SA/CSP exhibited superior properties in terms of load capacity and thermal energy storage performance. According to leakage experiments the load capacity of SA/PSP, SA/PWP and SA/CSP was 31.67 %, 44.69 %, and 50.09 %, respectively. The phase change latent heat of SA/PSP, SA/PWP, and SA/CSP was 55.78, 84.27 and 98.47 J/g, respectively. In addition, the relationship between biomass component content and load rates was studied. The results showed that there was a positive correlation between the loading rates of SA and the ratio of holocellulose (cellulose + hemicellulose) to lignin. The results provided a promising approach for the selection of lignocellulosic biomass framework materials.

External characteristics of cardio-strength load based on local exercises and heart rate response during its performance

In modern health-enhancing physical culture the use of complex training sessions with successive tasks solving is mainly provided and almost no attention to complex training sessions with parallel task solving. In this regard, it is important to find out the possibility of building training sessions that would allow influencing the cardio respiratory system through the use of strength exercises. The purpose of the study is to explore the characteristics of the load and heart rate changing in complex cardio-strength training sessions with parallel task solving. Experimental total training sessions included a warm-up (10-12 min) and 6 local strength exercises divided into three pairs (biceps - triceps, deltoid - latissimus dorsi, rhomboid - pectoral muscles) performed as circuit training. The duration of cardio- strength sessions – 30 min., intensity – 12 RM, repetition – 4, rest – changing exercises. A 62 years old man with high physical fitness for this age took place in a research. The heart rate study was carried out by the POLAR cardio-tracker. The sound recording of the exercise commentary was simultaneously activated with the heart rate sensor. This made it possible to study the duration of exercises, rests and heart rate during each exercise. Research has shown it is possible to ensure a cardiovascular reaction appropriate for cardio training by using strength exercises. But it requires certain resistance, repetition and rest between exercises at the training session. It is advisable to call such loads as cardio-strength loads. A person is able to provide the necessary duration of exercises and rests in such training sessions without a clock or sound leader. The current heart rate during certain cardio-strength exercise is determined by the complex, ambiguous interaction of several factors. For loads of 1/3 of 12 RM (4 repetitions per set) the most impotent is the initial position. In the initial position the most influential is the body position while performing exercises (lying, sitting, bending over and standing); the activity of the synergist muscles is also important here. In addition, the heart rate reaction depends on a resistance, the preliminary exercise and the activity during the changing exercises.

Cyclic loading and unloading strain equations and damage evolution of gypsum specimens considering damping effects

This study aims to establish a strain instanton equation and damage factor evolution law for gypsum specimens by considering damping. First, damping energy is calculated based on the single-degree-of-freedom vibration model, and the instantaneous strain equation is obtained based on the stress balance equation. Second, the dissipation energy is divided into damping and damage energies, and a damage-factor correction algorithm is obtained. Third, cyclic loading and unloading tests were performed at different loading rates and stress amplitudes to verify the accuracy of the strain equation. Finally, the specimens’ magnitude curves and crack characteristics were monitored using moment–tensor acoustic emission simulations. The factors influencing the damping energy and strain equations, energy and damage evolution laws of the specimens, and damage patterns of the specimens at different loading rates were analysed. The results show that the instantaneous strain equation and the modified damage factor considering the damping effect can effectively reflect the deformation law and damage state of the specimens. In contrast, the damage to the specimens in the lower limit of the variable stress experiment was lower than that in the lower limit of the constant stress experiment. As the loading rate increases, the damage energy density of the specimen decreases, and the damage factor within a single cycle gradually decreases. As the loading rate increases, the number of crack events in the model increases significantly, size becomes more uniform, and sequentially exhibits dense and sparse distribution patterns, percentage of shear cracks decreases significantly, number of mixed cracks increases significantly, brittle behaviour of the specimen becomes obvious, and a complete damage state is attained known as the ‘crushed’ state. This study provides a theoretical reference for damage assessments of viscoelastic–plastic materials subjected to perturbing loads.

Biomechanical Effects of the Badminton Split-Step on Forecourt Lunging Footwork.

This research investigates the biomechanical impact of the split-step technique on forehand and backhand lunges in badminton, aiming to enhance players' on-court movement efficiency. Despite the importance of agile positioning in badminton, the specific contributions of the split-step to the biomechanical impact of lunging footwork still need to be determined. This study examined the lower limb kinematics and ground reaction forces of 18 male badminton players performing forehand and backhand lunges. Data were collected using the VICON motion capture system and Kistler force platforms. Variability in biomechanical characteristics was assessed using paired-sample t-tests and Statistical Parametric Mapping 1D (SPM1D). The study demonstrates that the split-step technique in badminton lunges significantly affects lower limb biomechanics. During forehand lunges, the split-step increases hip abduction and rotation while decreasing knee flexion at foot contact. In backhand lunges, it increases knee rotation and decreases ankle rotation. Additionally, the split-step enhances the loading rate of the initial ground reaction force peak and narrows the time gap between the first two peaks. These findings underscore the split-step's potential in optimizing lunging techniques, improving performance and reducing injury risks in badminton athletes.

Healthy and diseased tensile mechanics of mouse lung parenchyma

The mechanics of the lung, consisting of high deformation, non-linear, rapid and cyclic loading, remain a critical unknown, hindering advancements in the field despite the pressing urgency of incurable and often fatal pulmonary diseases; such multi-scale ailments impair organ mechanical function by inducing tissue-level alterations. Here, the tensile mechanics of healthy and diseased murine lung parenchyma with induced variable fibrosis and emphysema are compared—exploring multi-rate and directional tissue elasticity and energetics. Remarkably, parenchymal tissue is found to be notably elastic and non-hysteresis prone. Additionally, chronic fibrosis-induced tissues reveal significantly reduced compliance compared to age-matched controls, indicating characteristic stiffening; moreover, maximum stress tends to be greater in exposed than controls. Emphysematous tissues tend to show lower maximum stress than controls, reflective of hallmark tissue destruction and softening. Furthermore, faster loading rate is found to generally yield elevated stiffness and maximum stress, significantly for fibrosis group exposed tissue—this interdependence between loading rate and tissue disease is notable considering the dynamics of breathing. Generally, control tissues are found to be isotropic, as are emphysematous tissues, but fibrosis may lead to increased anisotropy. Additionally, fibrotic and mature-healthy lungs are found to show age effect trends, such as increased strain energy. Along with these findings, this study additionally facilitates future analyses of other diseases by establishing lung biaxial testing protocols for small-scale murine specimens, which can serve as practical and ethical models for exploring human diseases. Overall, this study offers fundamental material characterizations which will enable future formulations of experimentally informed computational models.

The kinematics of pace bowling associated with lumbar bone stress injuries: Disparities observed in elite male and female cricketers

Elite cricket pace bowlers commonly sustain debilitating bone stress injuries. Lumbar bone stress injuries are more prominent in males, while lower limb bone stress injuries are more common in females. Bone stress injuries are partly attributable to bowling technique; however, scant research exists comparing bowling techniques of males and females as to better understand why males are more susceptible to lumbar bone stress injury. Three-dimensional pace bowling kinematics previously linked with lumbar bone stress injury were compared between 59 male and 19 female elite pace bowlers. Participants bowled 18 match-intensity deliveries indoors from a full run-up, whereby the mean of six deliveries was analyzed. Compared to females, males exhibited: a more extended thoraco-pelvic segment at back foot contact ( p = 0.039, g = 0.46), larger shoulder counter-rotation from back foot contact to front foot flat ( p = 0.021, g = 0.64), greater thoraco-pelvic lateral flexion at front foot flat ( p = 0.001, g = 0.95), larger front knee flexion at ball release ( p = 0.046, g = 0.57), and greater maximum front knee flexion from front foot flat to ball release ( p = 0.009, g = 0.57). Australian elite male pace bowlers performed techniques linked to lumbar bone stress injury to a much greater extent than their female counterparts. A straighter front leg technique observed in elite Australian females may be why they more commonly experience lower limb bone stress injuries via possibly higher vertical loading rates. This information may assist in developing sex-specific bone stress injury risk mitigation approaches.

MgBu2 nanosheets encapsulated in ZIF-8 for producing carbon scaffold in situ nanoconfined Mg hydrogen storage materials: Record-high loading and decreased dehydrogenation enthalpy

Nanoconfinement is an effective strategy to improve the kinetic and thermodynamic properties of the Mg/MgH2 system. However, current nanoconfinement approaches including porous scaffolds impregnation and surface anchoring can hardly obtain high loading, agglomeration resistant, and air-stable Mg nanoparticles. Herein, we report a novel strategy for preparing carbon scaffold in situ nanoconfined Mg hydrogen storage materials. The 12.2 nm MgBu2 nanosheets precipitated by solvent displacement are encapsulated in ZIF-8 to prepare MgBu2@ZIF-8, which are then pyrolyzed at 800°C to obtain Mg@C nanocomposites with 8.7 nm Mg embedded in a carbon scaffold. First principles calculations have demonstrated that the addition of MgBu2 promotes the nucleation and growth of ZIF-8 to form MgBu2@ZIF-8. It is worth noting that the loading rate of Mg@C-3 sample reaches a record high of 76.3% and exhibits outstanding hydrogen storage performances. Surprisingly, the enthalpy of hydrogen absorption/desorption sharply decreases to −62.0/63.1 kJ mol−1 H2. Mg@C-3 can absorb 4.4 wt% H2 at 200°C and desorb 4.0 wt% H2 at 250°C, and the activation energy for hydrogen absorption/desorption is reduced to a staggering 53.1/74.2 kJ mol−1 H2. Moreover, Mg@C-3 shows high cycling stability and antioxidant performance. This work opens a novel approach for the development of nanoconfined Mg nanocomposites with excellent performances.

Biogas Production Potential of Mixed Banana and Pineapple Waste as Assessed by Long-Term Laboratory-Scale Anaerobic Digestion

Biogas is a renewable energy source generated through the anaerobic digestion (AD) of organic feedstocks. This study aims to quantify the biogas production potential (BPP) of fruit wastes via semi-continuous lab-scale mesophilic AD over a total of 100 days. The feed was composed of 80% banana peelings and 20% pineapple residues, mimicking the waste composition of a Costa Rican fruit processing facility used as a test case. The average loading rate of volatile suspended solids (VSS) corresponded to 3.6 kg VSS·m−3·d−1. Biogas yield and composition were monitored, along with the concentration of ammonium, volatile fatty acids, and pH. Discounting the start-up phase, the BPP averaged to 526 LN (kg VSS)−1 with a methane concentration of around 54%, suggesting suitability of the substrate for AD. We calculated that if upscaled to the Costa Rican test case facility, these values translate into a gross average heat and electricity production via AD of around 5100 MWhel·a−1 and 5100 MWhth·a−1, respectively. Deducting self-consumption of the AD treatment, this is equivalent to 73% of the facility’s electricity demand, and could save about 450,000 L of heavy oil per year for heat generation. To circumvent nitrogen shortage, the addition of a co-substrate such as dry manure seems advisable.