High Loading Rates Research Articles

Factors Associated With High-Risk and Low-Risk Bone Stress Injury in Female Runners: Implications for Risk Factor Stratification and Management.

Bone stress injury (BSI) is a common overuse injury in active women. BSIs can be classified as high-risk (pelvis, sacrum, and femoral neck) or low-risk (tibia, fibula, and metatarsals). Risk factors for BSI include low energy availability, menstrual dysfunction, and poor bone health. Higher vertical load rates during running have been observed in women with a history of BSI. The purpose of this study was to characterize factors associated with BSI in a population of premenopausal women, comparing those with a history of high-risk or low-risk BSI with those with no history of BSI. It was hypothesized that women with a history of high-risk BSI would be more likely to exhibit lower bone mineral density (BMD) and related factors and less favorable bone microarchitecture compared with women with a history of low-risk BSI. In contrast, women with a history of low-risk BSI would have higher load rates. Cross-sectional study; Level of evidence, 3. Enrolled were 15 women with a history of high-risk BSI, 15 with a history of low-risk BSI, and 15 with no history of BSI. BMD for the whole body, hip, and spine was standardized using z scores on dual-energy x-ray absorptiometry. High-resolution peripheral quantitative computed tomography was used to quantify bone microarchitecture at the radius and distal tibia. Participants completed surveys characterizing factors that influence bone health-including sleep, menstrual history, and eating behaviors-utilizing the Eating Disorder Examination Questionnaire (EDE-Q). Each participant completed a biomechanical assessment using an instrumented treadmill to measure load rates before and after a run to exertion. Women with a history of high-risk BSI had lower spine z scores than those with low-risk BSI (-1.04 ± 0.76 vs -0.01 ± 1.15; P < .05). Women with a history of high-risk BSI, compared with low-risk BSI and no BSI, had the highest EDE-Q subscores for Shape Concern (1.46 ± 1.28 vs 0.76 ± 0.78 and 0.43 ± 0.43) and Eating Concern (0.55 ± 0.75 vs 0.16 ± 0.38 and 0.11 ± 0.21), as well as the greatest difference between minimum and maximum weight at current height (11.3 ± 5.4 vs 7.7 ± 2.9 and 7.6 ± 3.3 kg) (P < .05 for all). Women with a history of high-risk BSI were more likely than those with no history of BSI to sleep <7 hours on average per night during the week (80% vs 33.3%; P < .05). The mean and instantaneous vertical load rates were not different between groups. Women with a history of high-risk BSI were more likely to exhibit risk factors for poor bone health, including lower BMD, while load rates did not distinguish women with a history of BSI.

Dynamic shear behaviours of granite under coupled static and high-rate loadings

Understanding dynamic shear behaviours of rock under quasi-static confinement and dynamic loads is not only of great importance in underground engineering structures, but also beneficial to reveal earthquake mechanics regarding pre-stressed rocks fracturing from initial intact to rapid shear sliding. Here we propose a dynamic shear test setup and present full-field observations of stressed rock failure at high shear rate (up to γ˙ = 220 s−1) and sliding at high slip velocity over 10 m/s in the order of coseismic slip, with the integration of a novel triaxial Hopkinson bar (Tri-HB) and high-speed three-dimensional Digital Image Correlation (3D-DIC) techniques. Dynamic shear strength and friction coefficient are determined during the dynamic shear test under confinement, with different shear strain rates and pre-stresses. The dynamic shearing process can be divided into three stages, i.e. shear deformation, fracture degradation and dynamic frictional sliding. The high energy density of shear fracture band is observed, the rate and stress state dependences of rock shear strength and dynamic frictional coefficient are revealed. The dynamic shear strength of granite follows the Mohr-Coulomb criteria under varying pre-stresses and strain rates. The gouge materials with size of 1∼10 μm are generated within the high-rate shearing zone, and this appears to control the frictional resistance. The results could help determination of rock shear strength and post-shear failure, as well as explain the shear rupture and the resistance to slip mechanism of rock faults and strong near-surface earthquake events.

Correlations and impact of anaerobic digestion operating parameters on the start-up duration: Database construction for robust start-up guidelines

Anaerobic digestion (AD) has become a popular technique for organic waste management while offering economic and environmental advantages. As AD becomes increasingly prevalent worldwide, research efforts are primarily focused on optimizing its processes. During the operation of AD systems, the occurrence of unstable events is inevitable. So far, numerous conclusions have been drawn from full and lab-scale studies regarding the driving factors of start-up perturbations. However, the lack of standardized practices reported in start-up studies raises concerns about the comparability and reliability of obtained data. This study aims to develop a knowledge database and investigate the possibility of applying machine learning techniques on experimentation-extracted data to assist start-up planning and monitoring. Thus, a standardized database referencing 75 cases of start-up of one-stage wet continuously-stirred tank reactors (CSTR) processing agricultural, industrial, or municipal organic effluent in mono-digestion from 31 studies was constructed. 10 % of the total observations included in this database concern failed start-up experiments. Then, correlations between the parameters and their impacts on the start-up duration were studied using multivariate analysis and a model-based ranking methodology. Insights into trends of choices were highlighted through the correlation analysis of the database. As such, scenarios favoring short start-up duration were found to involve relatively low retention times (average initial and final hydraulic retention times, (HRTi) and (HRTf) of 26.25 and 20.6 days, respectively), high mean organic loading rates (average OLRmean of 5.24 g VS·d−1·L −1) and the processing of highly fermentable substrates (average feed volatile solids (VSfeed) of 81.35 g L−1). The model-based ranking of AD parameters demonstrated that the HRTf, the VSfeed, and the target temperature (Tf) have the strongest impact on the start-up duration, receiving the highest relative scores among the evaluated AD parameters. The database could serve as a reference for comparison purposes of future start-up studies allowing the identification of factors that should be closely controlled.

A prediction and load shed-based approach of controlling a medium voltage AC/DC testbed

Shipboard power systems have previously relied on oversized generators with minimal monitoring of the output, preventing the implementation of many real-time controls. Redundant generation is implemented instead of controls, resulting in uncontrolled load sheds when capacity is exceeded, or generators fail. The naval power system community is extensively studying the advantages of distributed zonal power system architectures that allow for the buffering of multiple generation sources and loads using energy storage and regulating power electronics. Extensive sensing and controls are necessary for successful operation of a distributed power system, and they must be evaluated adjoint to representative hardware topologies. The University of Texas at Arlington (UTA) is utilising a medium voltage (MV) AC/DC testbed to examine predictive high ramp rate (PHRR) and advanced load shed (ALS) control algorithms developed and modelled by Clarkson University (CU). A single zone of a zonal power system is being emulated using UTA’s testbed. Experimental results collected after integrating the CU control strategies into the UTA testbed will be discussed here.

Assessing measurement uncertainties on high-speed DCB testing of composites

This study investigates dynamic behavior in Double Cantilever Beam (DCB) tests across loading rates from 6 mm/min to 3 m/s. Comprehensive instrumentation has been used to investigate the sources of measurement errors (load, opening and crack length) or biases (asymmetry) and to quantify their effects on the fracture toughness determination using three variations of the Corrected Beam Theory. In particular, challenges in establishing zero load and displacement references were revealed through monitoring initial test phases. The resulting uncertainties in the fracture toughness have been estimated to be between 7 and 15%. Arms asymmetry during higher loading rates (1 m/s and 3 m/s) has been recorded using Digital Images Correlation. Using this data and a simple beam model, mode mixity (GII/GI from Williams approach) computed is in the order of 10%–20%.

Genome and secretome insights: unravelling the lignocellulolytic potential of Myceliophthora verrucosa for enhanced hydrolysis of lignocellulosic biomass.

Lignocellulolytic enzymes from a novel Myceliophthora verrucosa (5DR) strain was found to potentiate the efficacy of benchmark cellulase during saccharification of acid/alkali treated bagasse by ~ 2.24 fold, indicating it to be an important source of auxiliary enzymes. The De-novo sequencing and analysis of M. verrucosa genome (31.7Mb) revealed to encode for 7989 putative genes, representing a wide array of CAZymes (366) with a high proportions of auxiliary activity (AA) genes (76). The LC/MS QTOF based secretome analysis of M. verrucosa showed high abundance of glycosyl hydrolases and AA proteins with cellobiose dehydrogenase (CDH) (AA8), being the most prominent auxiliary protein. A gene coding for lytic polysaccharide monooxygenase (LPMO) was expressed in Pichia pastoris and CDH produced by M. verrucosa culture on rice straw based solidified medium were purified and characterized. The mass spectrometry of LPMO catalyzed hydrolytic products of avicel showed the release of both C1/C4 oxidized products, indicating it to be type-3. The lignocellulolytic cocktail comprising of in-house cellulase produced by Aspergillus allahabadii strain spiked with LPMO & CDH exhibited enhanced and better hydrolysis of mild alkali deacetylated (MAD) and unwashed acid pretreated rice straw slurry (UWAP), when compared to Cellic CTec3 at high substrate loading rate.

Numerical investigation of bond-slip behaviour between CFRP strips and concrete in shear tests under static and blast loads

The paper is structured into two main sections. In the first part, the focus is on the finite element (FE) analysis of bond slip in a single bond shear test between concrete and carbon fiber reinforced polymer (CFRP) strips under static loads. To model the test set-up, a plastic damage material model and an elastic material model are used for the concrete prism and the unidirectional CFRP strip respectively. Three approaches, including a perfect bond model, a cohesive bond model, and contact algorithms based on recent bond slip models, are employed to simulate the bond interface. The numerical model's validity is confirmed through comparison with experimental results from the literature. The paper predicts the debonding failure mode, the strain evolution along the bond length, and the delamination loads of the CFRP strip. The cohesive bond model exhibits good agreement between numerical and experimental data. In the second part of the paper, the developed FE model is tested under blast loading and compared to the experimental results of the blast tests conducted by the authors. The experimental and numerical findings highlight a significant dynamic enhancement effect on bond-slip properties due to the propagation of the blast wave within the concrete and the high loading rate.

An amino acid ionic liquid-based biphasic solvent with low viscosity, small rich-phase volume, and high CO2 loading rate for efficient CO2 capture

In order to achieve efficient CO2 capture, a novel biphasic solvent based on diethylenetriamine serine ionic liquid/polyethylene glycol dimethyl ether/water ([DETA][SER]/NHD/H2O) was developed. This study achieved low viscosity by weakening the hydrogen bonding and van der Waals interactions within the pure ionic liquid (IL) by adding NHD and H2O to [DETA][SER]. Additionally, due to the low polarity and fewer hydrogen bonds formed by NHD, it is separated. The formation of a tight hydrogen bond network in the rich-phase after the reaction enables the enrichment of the product. Based on this, the optimal mass ratio of [DETA][SER]/NHD/H2O is determined to be 20 wt%/40 wt%/40 wt%. The viscosity of this solvent is 7.82 mPa·s, with a total absorption load of 1.26 mol·mol−1 IL, where the rich-phase load accounts for 99 % of the total load and occupies only 37 % of the volume. The mechanism of CO2 capture was investigated using 13C NMR, revealing the formation of zwitterions from the reaction of the primary amines on [DETA]+ and [SER]− with CO2. Subsequently, proton transfer and hydrolysis of the carbamate esters were observed. Notably, NHD was found to promote phase separation without participating in chemical reactions. These findings demonstrate the potential of this biphasic solvent system as a high-capacity solution for CO2 capture.

Ag-MWCNT Composites for Improving the Electrical and Thermal Properties of Electronic Paste.

With the development of microelectronics products with high density and high power, it is urgent to improve the electrical and thermal conductivity of electronic paste to achieve the new requirements of packaging materials. In this work, a new synthesis method of Ag-MWCNTs was designed: Firstly, carboxylated MWCNTs and stannous chloride were used as raw materials to prepare high-loading-rate Sn-MWCNT composite material to ensure the high loading rate of metal on the MWCNT surface. Then, Ag-MWCNT composite material was prepared by the chemical displacement method to solve the problem of the low loading rate of silver nanoparticles on the MWCNT surface. On the basis of this innovation, we analyzed and compared the electrical, thermal, and mechanical properties of Ag-MWCNT composite electronic paste. Compared with the electronic paste without adding Ag-MWCNTs, the resistivity was reduced by 77%, the thermal conductivity was increased by 66%, and the shear strength was increased by 15%. Therefore, the addition of Ag-MWCNTs effectively improves the electrical, thermal, and mechanical properties of the paste, making it a promising and competitive choice for new packaging materials in the future.

Experimental and numerical study on the dynamic mode III fracture behaviors of rock using an axially notched flattened Brazilian disc in SHPB tests

The dynamic mode I and mode II fracture of rock have been widely investigated over the past decades. However, the lack of dynamic mode III fracture testing method and the rare understanding of mode III fracture mechanism of rock remain a significant knowledge gap in the realm of rock mechanics. In this work, an innovative axially notched flattened Brazilian disc (ANFBD) sample is proposed for the mode III fracture tests of rocks using the split Hopkinson pressure bar (SHPB). Firstly, the optimal geometrical dimension of the ANFBD sample for achieving true mode III fracture of rocks is comprehensively discussed using finite element method (FEM) analysis. Then, the reliability of ANFBD-SHPB method is experimentally verified through dynamic mode III fracture experiments on the Fangshan marble (FM). Laboratory experimental results show that the mode III fracture toughness (KIIId) values of FM are approximately 2.8 times of the mode I fracture toughness (KId) values at similar dynamic loading rates. Post-mortem examinations on the fracture surfaces show that the famous facet coarsening mechanism in mode III fracture is suppressed under high loading rates. Furthermore, insightful assessments regarding the inner progressive fracturing behaviors of the ANFBD sample are given by virtue of three-dimensional discrete element method (DEM) simulation. Moment tensor (MT) analysis indicates that the shear fracture mechanism mainly dominates the whole failure process of the ANFBD sample, while the tensile fracture mechanism slightly increases during the facet coarsening process. These results are of significant importance for revealing the failure mechanism of rock under dynamic mode III loading and give some beneficial implications for natural strike-slip fault structures.

Progress in Multi-Soil-Layering Systems for Wastewater Treatment

The use of decentralized wastewater treatment technologies is a reasonable solution for rural areas. As a decentralized treatment technology, the multi-soil-layering (MSL) system has recently drawn an increasing amount of attention owing to its merits, such as a high hydraulic load rate, small land area occupation, low probability of clogging, low investment, and low operation cost. This review summarizes the progress in MSL systems in the past decade, focusing on the directions of efforts for system optimization, the latest applications of MSL systems to various wastewater treatments, and the integration of MSL with other technologies. The great application potential of MSL systems is illustrated, and future research directions regarding better application of MSL systems are provided.

Application of AIE luminogen-loaded core–shell fibers in self-warning and self-healing polymer coatings with enhanced corrosion resistance

Aggregation-induced emission (AIE) materials have been used for non-destructive visual detection of cracks and damages to prevent the final structural failure and increase the service life of coatings. In this study, a self-warning and self-healing core–shell fiber is synthesized for developing AIE composite coatings. In these core–shell fibers, a mixture of hmethylene diisocyanate (HDI) and tetraphenylethylene (TPE) is used as core constituent, and polyacrylonitrile (PAN) is used for preparing the shell, which are continuously wrapped with a high loading rate through coaxial electrospinning technology. The parameters of electrospinning process are optimized to achieve core–shell fibers with smooth surface and average diameter of 100 ± 50 nm. The composite coating reveals effective fluorescence in case of cracks in a corrosive environment. The maximum self-healing efficiency of the fiber coating is 94.8 % after soaking for 120 h. The introduced composite coating paves the way for improving the safety and reliability of critical engineering components.

Incorporation of Disposed Face Mask to Cement Mortar Material: An Insight into the Dynamic Mechanical Properties

Incorporating masks into building materials offers a potential solution to the environmental threat of disposable masks with promising material performance. However, research on their dynamic properties is lacking to further determine the application range of the new composite. This study addresses this gap by shredding face masks into strips and incorporating them into mortars at varying volume ratios. The integrity and compactness of the mortar was measured and characterized by P-wave velocity, while dynamic compression properties were explored using a split Hopkinson pressure bar (SHPB) system. Subsequently, sieve analysis was conducted on the fractured specimens. The results indicate that incorporating masks generally improves the mortar integrity and the fragmentation after impacting. The dynamic uniaxial compression strength (DUCS) decreased for all mixing designs compared to plain ones under a constant loading rate. Meanwhile, the dissipated energy density showed a similar trend to the P-wave velocity, exhibiting less pronounced enhancement at higher loading rates. According to the dynamic characteristics, a dynamic constitutive model based on the Lemaitre principle and Weibull distribution of damage is developed and validated. The test results are further understood through the perspective of the mechanism of mask inclusion.

An Optimized Grid‐Forming Control Strategy for the Flexible Interconnection System in Distribution Transformer Areas

The flexible interconnection system (FIS) in distribution transformer areas can improve the local consumption capacity of high penetration rate distributed photovoltaics and solve the problem of the high loading rate of distribution transformers. This paper presents an optimized grid‐forming control strategy for the FIS in distribution transformer areas. First, the DC side impedance small signal model of the FIS is built, and the reason for the stability difference of the FIS is analyzed when the active power flows in different directions. An optimized control structure is then presented based on the conventional grid‐forming control strategy. The theoretical analysis shows that the optimized grid‐forming control strategy can improve the stability of the FIS. Finally, the controller hardware‐in‐the‐loop experiments based on RT‐LAB confirm the effectiveness of the presented optimized control strategy. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

Constitutive and Dynamic Behavior of Nylon 66 Polymer Under Quasi and High Rate of Loading

Constitutive and Dynamic Behavior of Nylon 66 Polymer Under Quasi and High Rate of Loading

Response to internal pressure shock and hoop strength of SiCf/SiC cladding

This study investigated the mechanical behavior of silicon carbide fiber-reinforced silicon carbide matrix (SiCf/SiC) cladding using expanding plug tests at 0.5 and 2 mm/min. A three-stage mechanical response for SiCf/SiC was observed, with significant differences in Stage 3 between specimens tested at different rates. Specimens tested at the slower rate (0.5 mm/min) exhibited a characteristic hoop strength of 112.4 MPa and homogeneous destruction behavior, indicative of uniform stress distribution. In contrast, the hoop stress in SiCf/SiC became unsteady at the faster rate (2 mm/min), leading to cracking at a lower nominal proportional limit stress (PLS), structural instability, non-uniform fiber pull-out, and a lower characteristic hoop strength of 92.4 MPa. This suggests that similar phenomena might occur at higher loading rates during internal pressure shock. Therefore, considering the application of SiCf/SiC, to conduct hoop strength testing at faster rates was recommend, such as 2 mm/min.

Simulation models of microbial community, pH, and volatile fatty acids of anaerobic digestion developed by machine learning

Anaerobic digestion (AD) is a promising method for treating high-content organic waste via the microbiome in an anaerobic environment. However, because AD is a complex process involving microbial community (MC), it is essential to determine the relationship between the MC, pH, and volatile fatty acids (VFAs). This study employed five machine learning models: artificial neural network, convolutional neural network, extra trees, extreme gradient boost, and support vector machine to estimate the relationship between MC, pH, and VFAs. Methanoregulaceae, Methanomicrobiaceae, Spirochaetes, pH, acetic acid, isobutyric acid, and isovaleric acid were estimated with high accuracy, with R2 >0.800. The variable importance of the models with the highest accuracy was calculated based on the shapley additive explanations analysis. As a result, the MC estimation models suggested syntrophic acetate oxidation by Spirochaetes, and VFAs-pH estimation models suggested that the high organic loading rate during the start-up phase can lead to isovaleric acid accumulation. In an in-silico test using the machine learning simulator, the change of MC resulted in the critical effects on the acetate accumulation from 500 to 1500 mg/L. The optimal relative abundance of Mehtanoregulaceae and Methanomicrobiaceae for the stable operation was suggested as 15–37 % and 3–15 %, respectively, resulting in the acetic acid concentration below 1000 mg/L.

Experimental assessment on the dynamic mechanical characteristics and cracking mechanism of hybrid basalt-sisal fiber reinforced concrete

Hybrid basalt-sisal fiber reinforced concrete (BSFRC) has good application prospects in construction engineering, while the research on its mechanical properties and impact resistance is rather limited. In this study, to systematically investigate the dynamic compressive behavior and cracking characteristics of BSFRC, 9 kinds of concrete specimens containing different fibers and contents were prepared and a series of dynamic compression tests under strain rates of 45–150 s−1 were conducted via the split Hopkinson pressure bar (SHPB) apparatus. For the 9 typical types of concrete prepared in this study, the B1SP2 (i.e., concrete containing 0.1 vol% basalt fibers, 0.1 vol% sisal fibers and 0.1 vol% polypropylene fibers) shows the highest dynamic compressive strength, and the B2S2 (i.e., concrete containing 0.2 vol% basalt fibers and 0.2 vol% sisal fibers) exhibits the highest energy dissipation density. By means of high-speed photography, digital image correlation (DIC) and scanning electron microscope (SEM) techniques, the progressive failure process and microscopic fracture mechanism of BSFRC were further revealed. Fibers in BSFRC effectively inhibit the expansion and penetration of microcracks, and thus delay the initiation and coalescence of macrocracks. Similar to basalt fibers, sisal fibers control cracking behavior of concrete mainly by cutting crack propagation path and exerting bridging effect, and its fiber action is more remarkable for larger cracks. Furthermore, the coupling effect of strain rate and fiber action on the dynamic mechanical behavior of BSFRC were discussed. High loading rate activates more fibers to exert the strength-enhancement and crack-inhibition effect, and the fiber action makes the strain rate dependance of compressive strength more pronounced in BSFRC than that in plain concrete.

Poly(malic acid)-budesonide nanoconjugates embedded in microparticles for lung administration.

To improve the therapeutic activity of inhaled glucocorticoids and reduce potential side effects, we designed a formulation combining the advantages of nanoparticles, which have an enhanced uptake by alveolar cells, allow targeted delivery and sustained drug release, as well as limited drug systemic passage, with those of microparticles, which display good alveolar deposition. Herein, a polymer-drug conjugate, poly(malic acid)-budesonide (PMAB), was first synthesized with either 11, 20, 33, or 43mol% budesonide (drug:polymer from 1:8 to 3:4), the drug creating hydrophobic domains. The obtained conjugates self-assemble into nanoconjugates in water, yielding excellent drug loading of up to 73 wt%, with 80-100nm diameters. In vitro assays showed that budesonide could be steadily released from the nanoconjugates, and the anti-inflammatory activity was preserved, as evidenced by reduced cytokine production in LPS-activated RAW 264.7 macrophages. Nanoconjugates were then embedded into microparticles through spray-drying with L-leucine, forming nano-embedded microparticles (NEMs). NEMs were produced with an aerodynamic diameter close to 1µm and a density below 0.1 g.cm-3, indicative of a high alveolar deposition. NEMs spray-dried with the less hydrophobic nanoconjugates, PMAB 1:4, were readily dissolved in simulated lung fluid and were chosen for in vivo experiments to study pharmacokinetics in healthy rats. As it was released in vivo from NEMs, sustained distribution of budesonide was obtained for 48 h in lung tissue, cells, and lining fluid. With high loading rates, modulable release kinetics, and low cytotoxicity, these nanoconjugates delivered by NEMs are promising for the more efficient treatment of pulmonary inflammatory diseases.

Anammox process in anaerobic baffled biofilm reactors with columnar packings: Characteristics of flow field and microbial community

The enrichment of anammox bacteria is a key issue in the application of anammox processes. A new type of reactor － anaerobic baffle biofilm reactor (ABBR) developed from anaerobic baffle reactor (ABR) was filled with columnar packings and established for effective enrichment of anammox bacteria. The flow field analysis showed that, compared with ABR, ABBR narrowed the dead zone so as to improve the substrate transferring performances. Two ABBRs with different types of columnar packings (Packings 1 and Packings 2) were constructed to culture anammox biofilms. Packings 1 consisted of the single-form honeycomb carriers while Packings 2 was modular composite packings consisting of non-woven fabric and honeycomb carriers. The effects of different types of columnar packings on microbial community and nitrogen removal were studied. The ABBR filled with Packings 2 had a higher retention rate of biomass than the ABBR filled with Packings 1, making the anammox start-up period be shortened by 21.28%. The enrichment of anammox bacteria were achieved and the dominant anammox bacteria were Candidatus Brocadia in both R1 and R2. However, there were four genera of anammox bacteria in R2 and one genus of anammox bacteria in R1, and the cell density of anammox bacteria in R2 was 95% higher than that in R1. R2 has the advantage of maintaining excellent and stable nitrogen removal performance at high nitrogen loading rate. The results revealed that the packings composed of two types of carriers may have a better enrichment effect on anammox bacteria. This study is of great significance for the rapid enrichment of anammox bacteria and the technical promotion of anammox process.