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A CFD-DEM-FEM coupling method for the ice-induced fatigue damage assessment of ships in brash ice channels

Polar transport ships frequently traverse in the brash ice channel opened by icebreakers. Although the substantial ice resistance caused by direct collisions with the level ice is avoided, the hull still encounters collisions with the brash ice, leading to periodic damage and exacerbating the fatigue issues of the hull structure. To address the fatigue challenges faced by ships sailing in the brash ice channels, this paper proposes an ice-induced fatigue damage assessment method based on the CFD-DEM-FEM. Referring to the brash ice model test conducted at the Hamburg Ship Model Basin (HSVA), a discrete element ice model and a numerical brash ice tank are established using the CFD-DEM coupling method. The simulated ship-ice interaction is compared with HSVA’s experimental results to validate the reliability of the numerical brash ice tank and ice load. The ice load time history resulting from the ship-brash ice collision is applied to the hull, and the hot spot stress time history under each fatigue sub-condition is calculated using the FEM. The improved rain-flow counting method is employed to determine the stress level of the hot spot stress time history, and the S-N curve method based on the linear cumulative damage criterion is used to calculate the total fatigue damage of hot spots. Finally, the results of the proposed method are compared with those of the LR method. This study can serve as a valuable reference for the ice-induced fatigue assessment of ships navigating in brash ice channels.

Using Extracted Sugars from Spoiled Date Fruits as a Sustainable Feedstock for Ethanol Production by New Yeast Isolates.

This study focuses on investigating sugar recovery from spoiled date fruits (SDF) for sustainable ethanol production using newly isolated yeasts. Upon their isolation from different food products, yeast strains were identified through PCR amplification of the D1/D2 region and subsequent comparison with the GenBank database, confirming isolates KKU30, KKU32, and KKU33 as Saccharomyces cerevisiae; KKU21 as Zygosaccharomyces rouxii; and KKU35m as Meyerozyma guilliermondii. Optimization of sugar extraction from SDF pulp employed response surface methodology (RSM), varying solid loading (20-40%), temperature (20-40 °C), and extraction time (10-30 min). Linear models for sugar concentration (R1) and extraction efficiency (R2) showed relatively high R2 values, indicating a good model fit. Statistical analysis revealed significant effects of temperature and extraction time on extraction efficiency. The results of batch ethanol production from SDF extracts using mono-cultures indicated varying consumption rates of sugars, biomass production, and ethanol yields among strains. Notably, S. cerevisiae strains exhibited rapid sugar consumption and high ethanol productivity, outperforming Z. rouxii and M. guilliermondii, and they were selected for scaling up the process at fed-batch mode in a co-culture. Co-cultivation resulted in complete sugar consumption and higher ethanol yields compared to mono-cultures, whereas the ethanol titer reached 46.8 ± 0.2 g/L.

A Performance Analysis of Hybrid and Columnar Cloud Databases for Efficient Schema Design in Distributed Data Warehouse as a Service

A Data Warehouse (DW) is a centralized database that stores large volumes of historical data for analysis and reporting. In a world where enterprise data grows exponentially, new architectures are being investigated to overcome the deficiencies of traditional Database Management Systems (DBMSs), driving a shift towards more modern, cloud-based solutions that provide resources such as distributed processing, columnar storage, and horizontal scalability without the overhead of physical hardware management, i.e., a Database as a Service (DBaaS). Choosing the appropriate class of DBMS is a critical decision for organizations, and there are important differences that impact data volume and query performance (e.g., architecture, data models, and storage) to support analytics in a distributed cloud environment efficiently. In this sense, we carry out an experimental evaluation to analyze the performance of several DBaaS and the impact of data modeling, specifically the usage of a partially normalized Star Schema and a fully denormalized Flat Table Schema, to further comprehend their behavior in different configurations and designs in terms of data schema, storage form, memory availability, and cluster size. The analysis is done in two volumes of data generated by a well-established benchmark, comparing the performance of the DW in terms of average execution time, memory usage, data volume, and loading time. Our results provide guidelines for efficient DW design, showing, for example, that the denormalization of the schema does not guarantee improved performance, as solutions performed differently depending on its architecture. We also show that a Hybrid Processing (HTAP) NewSQL solution can outperform solutions that support only Online Analytical Processing (OLAP) in terms of overall execution time, but that the performance of each query is deeply influenced by its selectivity and by the number of join functions.

Effective section on grapevine plants (Vitis vinifera L.) attacked by Xylotrechus arvicola Olivier (Coleoptera: Cerambycidae) grubs: Influence and effects on its resistance

Xylotrechus arvicola Olivier 1795 (Coleoptera: Cerambycidae) is an insect pest that affects Vitis vinifera L. 1753 (Vitales: Vitaceae) plants in the main wine-producing regions of Spain. X. arvicola larvae bore into grapevine wood, causing both direct damage (ingestion of vascular tissues) and indirect damages (introduction of wood fungi) to the plant. The aim of research was to evaluate the effective section of wood damaged by larvae and assess its resistance capacity through compression tests and loading and breaking times. Compressive tests (on trunks) and flexural tests (on branches) were performed to evaluate the effective section. Trunk samples exhibited a higher effective section than branches samples, with effective section percentages ranging from 91.49 % to 93.53 % in trunks and decreasing from 84.91 % to 86.95 % in branches. Both loading times (Time 1) and breakage times (Time 2) increased with the effective section of the wood, although these times were lower in damaged wood samples of both trunks and branches. Additionally, significant differences were observed in the interactions between loading time x effective section and breakage time x effective section in dry trunks. This indicates a stronger relationship between the effective section and increased resistance in trunks. The results suggest that, in ‘Tempranillo’ variety, branches with a lower effective section are more prone to breakage when affected by X. arvicola larvae, whereas trunks, with a greater effective section, maintain better stability. This research should be continued with the evaluation of other vine varieties and different years of X. arvicola attacks, as the current findings are based on a single variety (‘Tempranillo’) over a period of ten years.

Assessment of blood viral load in asymptomatic and symptomatic cases of congenital cytomegalovirus infection.

This study aimed to retrospectively evaluate the baseline and follow-up viral loads and viral clearance times in cases followed for asymptomatic and symptomatic congenital cytomegalovirus (cCMV) infection between August 2010 and August 2022. Among 93 cases, they had asymptomatic (n: 55) and symptomatic (n: 38). The median baseline blood viral load detected in the symptomatic cCMV (ScCMV) infection (13 054 IU/mL) was significantly higher than that of asymptomatic cCMV (AcCMV) infection (4636 IU/mL) (p < 0.013). There was no difference in median viral clearance times (75 and 90 days, respectively) in baseline viremic cases in the ScCMV and AcCMV infection groups. There were no differences in median baseline blood viral load (6930 IU/mL and 14 268 IU/mL, respectively) and median viral clearance times (75 and 85 days, respectively) between the 6-week and 6-month antiviral treatment group. No correlation was found between baseline blood viral load, clinical severity, and the number of systems involved. However, in initial viremic cases, the viral load threshold for a symptomatic case was 8856 IU/mL, with 85.7% sensitivity and 54.5% specificity.

STRATEGIES FOR OPTIMIZING THE PERFORMANCE OF MOBILE APPLICATIONS

The performance of mobile applications has a critical impact on the user experience and, as a result, on the rating of the application in online stores, which directly correlates with its commercial success. According to Google, 53 % of users delete an app if it takes more than 3 seconds to download. The primary task of optimizing the performance of mobile applications is to minimize the loading time. The article provides a comprehensive analysis of existing methods and technologies for optimizing the performance of mobile applications based on multidimensional analysis. The experiments suggest the following solution: the integration of asynchronous algorithms and multithreading in order to increase the level of performance by at least an order of magnitude 30 %. The evaluation of algorithms for accelerating the loading and initialization of resources in mobile applications was carried out using the decomposition method, which allows us to identify a correlation between the initialization time and the overall performance of the application. According to the experiments conducted, the integration of asynchronous algorithms and multithreading can increase performance by an order of 30-40 %. The article provides not only a quantitative, but also a qualitative assessment of how effective certain strategies are that can optimize applications, influence their architectural solution and the specifics of the user experience. Empirical data and analytical models are supported by the results, which indicate that the most optimal strategy in this case is an integrated approach, which will optimize from the technical and economic side.

Temporal evolution of fracture transport properties of fractured shales during long-term stress compaction

Understanding the temporal evolution of fracture transport properties in shales is of increasing importance for the long-term safe operation of many underground engineering projects. Here, a series of long-term (60 days each) water seepage and gas breakthrough experiments utilizing three shale samples, each with a single artificial fracture, was conducted to evaluate the time-dependent evolution of permeability and gas breakthrough pressure (GBP) under constant confining stress. Our results show continuous decreases in permeability and increases in GBP with time, and the rate of change in both is initially rapid but then slows. As the loading time increases, the permeabilities and GBPs become relatively constant. The inferred mechanisms are aperture reductions caused by mechanical creep and clay swelling of fractures. Pretest and posttest scans of fracture surfaces reveal some changes in asperity height, which demonstrates the occurrence of mechanical damage to the fracture during the experiments. Long-term stress compaction causes flow channels to narrow or even partially close over time. The fluid flow in confined fracture is controlled by some narrow apertures in the flow channels, which act as bottleneck points. The apertures at these points decrease to the micro-nano level under stress, significantly reducing fracture transport properties. While the fracture transport properties of fractured shale obviously decrease during long-term stress compaction, residual fracture voids still dominate the fluid flow over a longer period, and are especially prone to gas escape.

Fracture energy of concrete after sustained loading

The fracture energy of concrete after sustained loading is a necessary parameter to calculate the residual carrying capacity of concrete structures in service. This study investigated the fracture energy of concrete after sustained loading by combining experimental observations and theoretical analyses. Firstly, a series of creep fracture tests were conducted on 100 three-point bending beams under various sustained loads, i.e., 75 %, 80 %, 85 %, and 90 % of peak loads. After different loading time, i.e., 10 %, 30 %, 50 %, 70 %, and 90 % of creep fracture lifetimes, the static fracture tests were performed until failure. Then, based on the relationship between the work done by external forces and the energy consumed by the crack propagation of specimens, an analytical model for the fracture energy of concrete after sustained loading was developed, describing the quantitative relationship between the fracture energy of concrete and the crack opening displacement, and the loading time. Finally, the impact of the loading time and sustained load levels on the fracture energy was investigated. The results indicated that the fracture energy of concrete after sustained loading decayed rapidly, with the decay rate gradually decreasing until stability over the loading time. Additionally, specimens subjected to lower sustained load levels experienced a longer loading time for the same crack opening displacement, indicating a greater decay degree of the fracture energy. The analytical model proposed in this study can be employed for predicting and evaluating the crack propagation process and residual carrying capacity of concrete structures during their service life.

Low cycle fracture resistance of the superalloy at single- and two-frequency modes of loading

Fatigue and long static damages to the majority of high-loaded units develop under repeated stresses and strains of large amplitudes in elastic and elastoplastic regions at a low number of the main cycles and superimposition of dynamic stresses of significantly smaller value with higher frequencies which results in the so-called two-frequency modes of loading. It is shown that in the region of elevated and high temperatures, which determine the manifestation of temperature and time effects in the material, parameters of the rate and duration of deformation which enter the basic equation for determination of the fatigue life through the frequency and time of loading become the most significant parameters determining the fracture process. The results of theoretical and experimental study carried out on nickel superalloy specimens under a hard mode of loading and high temperatures have shown that estimation of the strength and fatigue life in this case for the single-frequency and two-frequency modes of loading can be performed on the basis of the analysis of strain parameters and diagrams of cyclic elastoplastic deformation using the deformation-kinetic criterion of summation of damages accumulated in the material. A decrease in the fatigue life under two-frequency mode of loading and the possibility of estimating it using the specified criterion and corresponding dependences with the introduction of the parameters of frequency/amplitude ratios of the strains (both full and that imposed on the main process) is experimentally proved. The calculated dependences include the parameters of temperature conditions, frequency and duration of loading which allows (when assessing damage from low-frequency and high-frequency components of cyclic strains) taking into account the effects of cyclicity and time of loading, as well as the existence of a variable coefficient of the asymmetry of high-frequency cycles of the two-frequency mode during high-temperature cyclic elastoplastic deformation.

Stress transfer law in laboratory hydraulic fracturing experiments

During the true triaxial hydraulic fracturing experiments, the compression stress applied to the specimen surface cannot be transferred to the interior immediately, resulting in inconsistency with in-situ stress conditions. To quantitatively analyze the stress transfer process from the surface to the interior of the specimen, an experimental method for monitoring the inside stress was proposed based on Fiber Bragg Grating (FBG) sensing technique, based on which the true triaxial stress loading experiments were conducted on a concrete-like specimen of 30 cm × 30 cm × 30 cm. The results show that the stresses inside the specimen require a certain loading time to reach the uniform state. The loading time required for stress transfer from the surface to the interior of the specimen decreases with the increase of compression stresses. The stress transfer process in rock materials is determined by creep. The closure of microcracks results in stress redistribution inside the specimen during creep. Moreover, a 3-D Burgers model is modified to describe the stress transfer process. Finally, the stress transfer phenomenon during hydraulic fracturing was verified by coal fracturing experiments. This study can help to understand the stress transfer mechanism, providing guidance for standardizing the laboratory simulation of in-situ stress.

The Predictors of Spontaneous Coronary Reperfusion in Patients with ST-Segment Elevation Myocardial Infarction at the West Nusa Tenggara General Hospital

Background: In ST-segment elevation myocardial infarction (STEMI) management, some patients undergo spontaneous coronary reperfusion (SCR) with a better prognosis than those without SCR, but predictors for SCR remain unclear. Objective: To investigate several potential predictors of SCR, including smoking status, BMI, DAPT loading time, hemoglobin levels, platelet count, random blood sugar levels, uric acid levels, creatinine clearance, and the Syntax score. Material and Methods: This case-control study was conducted at the West Nusa Tenggara General Hospital in Indonesia from December 2022 to September 2023. Data collection encompassed various patient demographics and clinical parameters, including name, medical record number, age, gender, smoking status, BMI, DAPT loading time, hemoglobin levels, platelet count, random blood sugar, uric acid, creatinine clearance, the Syntax score, and the occurrence of SCR. Statistical analysis for this study involved multivariate logistic regression analysis. Result: A total of thirty-two patients were included, evenly divided into 16 subjects allocated to the SCR group and 16 to the non-SCR group. The analysis indicated that only BMI demonstrated a statistically significant association with SCR occurrence. However, the study did not yield conclusive evidence regarding the influence of smoking status, DAPT loading time, hemoglobin levels, platelet count, random blood sugar levels, uric acid levels, creatinine clearance, and the Syntax score on the likelihood of SCR. Conclusion: A normal BMI is identified as a robust predictor for the incidence of SCR in patients diagnosed with STEMI. Keyword: Predictors, Spontaneous Coronary Reperfusion, ST-Segment Elevation Myocardial Infarction.

CHITOSAN / HEXAMOLYBDATE NANOSTRUCTURES FOR ORAL DRUG DELIVERY

Background: In recent decades, substantial progress has been achieved in the field of drug delivery through the creation of controlled-release formulations, leading to significant medical advancements. The primary objective of these controlled release systems is to sustain the desired drug concentration in the bloodstream or specific tissues for an extended duration. One class of nanostructures is polyoxometalates (POMs), which are negatively charged anionic nanoclusters consisting of metal and oxygen atoms. POMs are notable for their ability to be precisely controlled in size and shape. These characteristics, combined with their inherent negative charge, contribute to their stability and make them highly versatile structures. Aim: This study aimed to examine the self-assembly of organic-inorganic hybrids using polyoxometalate (POM) Lindqvist-type hexamolybdate and chitosan to synthesize novel 3D nanostructures. These nanostructures were then investigated for their suitability as nanocarriers for the chemotherapy drug )Temozolomide TMZ(. The release of TMZ from the nanocarrier was studied under various pH conditions. Methods: This study comprises two practical components. The first part focuses on synthesizing hierarchical nanostructures designed to load TMZ drugs. The amount of drug loaded onto the as-prepared nanostructure of POM-Chitosan was determined using High-Performance Liquid Chromatography (HPLC) at various loading times. The second part of the study investigates the release process of the TMZ drug from the hierarchical nanostructures. This release process is examined in two buffer solutions with distinct pH values. Results: The surface characteristics, size, chemical composition, and identity of the nanostructures were confirmed using techniques such as HPLC, FTIR, XRD, SEM, and XPS. The results confirm the successful complexation of chitosan with POM Lindqvist-type hexamolybdate. Discussion: The nanocarriers demonstrated an intriguing pH-dependent release behavior, suggesting their potential application in drug delivery systems. Conclusions: In this study, new nanocarriers of chitosan and POM were successfully prepared and loaded with TMZ (21% loading) via self-assembly for oral drug delivery. The as-prepared nanocarrier form of TMZ was fully characterized via XRD, FTIR, XPS, and SEM. The as-prepared oral form of TMZ showed an excellent pH-dependent release of TMZ, where the release rate at pH 7.4 was considerably faster than at pH 2.8.

Fatigue-Healing Performance Analysis of Warm-Mix Rubber Asphalt Mastic Using the Simplified Viscoelastic Continuum Damage Theory

As a green and low-carbon road material, warm-mix rubber asphalt (WMRA) has received extensive attention from scholars for its road performance. In the in-depth study of its properties, the fatigue characteristics of WMRA are particularly critical. However, in current studies on asphalt fatigue performance, its self-healing ability is often underestimated or neglected. Furthermore, the simplified viscoelastic continuum damage theory (S-VECD), with its accuracy, speed, and convenience, provides a powerful tool for analyzing asphalt fatigue performance. Therefore, to analyze the fatigue and self-healing performances of WMRA in practical applications, four sample materials were selected in this study: virgin asphalt mastic (VAM), rubber asphalt mastic (RAM), Sasobit rubber asphalt mastic (SRAM), and Evotherm rubber asphalt mastic (ERAM). Subsequently, the samples were subjected to a comprehensive experimental design with frequency sweep tests, linear amplitude sweep tests, and multiple intermittent loading time sweep tests under different aging conditions. The fatigue and self-healing performances of different aging degrees and different types of WMRA were evaluated based on the S-VECD theory. The results show that aging reduces the fatigue and self-healing performances of asphalt mastic to a certain extent, and at a 7% strain, the fatigue life of SRAM after long-term aging is only 30.7% of the life of the unaged sample. The greater the aging degree, the more pronounced the effect. Under different aging levels, the warm-mix agent can significantly improve the fatigue and self-healing performances of rubber asphalt mastic. After undergoing ten fatigue intermittent loading tests, the recovery rate of the complex shear modulus for the long-term aged VAM was 0.65, which is lower than that of SRAM under the same conditions, and the warm mix can further extend the fatigue life of rubber asphalt by improving the self-healing properties of the asphalt. The role of Sasobit in enhancing the fatigue and self-healing performances of rubber asphalt mastic is more significant. This study can provide a theoretical basis for the promotion and application of WMRA pavements and contribute to the sustainable development of road construction.

Effects of blood flow restriction training on physical fitness among athletes: a systematic review and meta-analysis

Blood flow restriction training (BFRT) is an effective, scientific and safe training method, but its effect on the overall quality of athletes remains unclear. The aim of this systematic review with meta-analysis was to clarify the effects of BFRT on the physical fitness among athletes. Based on the PRISMA guidelines, searches were performed in PubMed, Web of Science, SPORTDiscus, and SCOUPS, the Cochrane bias risk assessment tool was used to assess methodological quality, and RevMan 5.4 and STATA 15.0 software were used to analyze the data. A meta-analysis of 28 studies with a total sample size of 542 athletes aged 14–26 years and assessed as low risk for quality was performed. Our results revealed that the BFRT intervention had small to large improvements in the athletes' strength (ES = 0.74–1.03), power (ES = 0.46), speed (ES = 0.54), endurance (ES = 1.39–1.40), body composition (ES = 0.28–1.23), while there was no significant effect on body mass (p > 0.05). Subgroup analyses revealed that moderator variables (training duration, frequency, load, cuff pressure, and pressurization time) also had varying degrees of effect on athletes' physical fitness parameters. In conclusion, BFRT had a positive effect on the physical fitness parameters of the athletes, with significantly improved strength, power, speed, endurance and body composition, but not body mass parameters. When the training frequency ≥ 3 times/week, cuff pressure ≥ 160 mmHg, and pressurization time ≥ 10 min, the BFRT group was more favorable for the improvement of physical fitness parameters.

P2Y12 adenosine receptor inhibitors preloading among patients with non-ST-elevation acute coronary syndromes; insights from a nationwide multicenter registry.

The safety and efficacy of treatment with P2Y12 adenosine-diphosphate receptor inhibitors (P2Y12-RI) before coronary angiography among patients with non-ST-segment elevation acute coronary syndromes (NSTEACS) are questionable. To assess the pretreatment rate with P2Y12-RI and its association with ischemic and bleeding risks among patients with NSTEACS. The study comprised patients with NSTEACS referred for coronary angiography and included in the Acute Coronary Syndrome Israeli Surveys between 2013 and 2021. Patients were divided into two groups according to the timing of P2Y12-RI loading concerning coronary angiography: pretreatment and posttreatment. The primary endpoints were 30-day major adverse cardiovascular events (MACE; composite of cardiovascular mortality, myocardial infarction, stroke, stent thrombosis, and urgent revascularization) and 1-year all-cause mortality. Of 3076 patients, 2423 (78.8%) received pretreatment with a P2Y12-RI, and 653 (21.2%) received P2Y12-RI posttreatment. Prasugrel and ticagrelor were used more in the posttreatment group compared to the pretreatment group (16% vs. 6% and 38% vs. 25%, respectively, p < 0.001 for both). No difference was observed in the rate of 30-day MACE comparing pretreatment and posttreatment (5.3% vs. 2.2%, respectively, p = 0.62). A sensitivity analysis of 30-day MACE among patients from the 2021 survey demonstrated similar results (2.5% in the posttreatment group vs. 8.0% in the pretreatment group, p = 0.13). There were no differences in 1-year all-cause mortality rates between the pretreatment and posttreatment groups (4.8% vs. 3.8%, p = 0.31). Among patients with NSTEACS referred for an invasive strategy, the P2Y12-RI posttreatment strategy was associated with similar 30-day and 1-year MACE as the pretreatment strategy. These large-scale, multicenter, real-world data provide reassurance on the safety and efficacy of delaying P2Y12-IR until after coronary stratification to improve clinical decision-making.

Hydrochar from Pine Needles as a Green Alternative for Catalytic Electrodes in Energy Applications.

Hydrothermal carbonization (HTC) serves as a sustainable method to transform pine needle waste into nitrogen-doped (N-doped) hydrochars. The primary focus is on evaluating these hydrochars as catalytic electrodes for the oxygen reduction reaction (ORR) and carbon dioxide reduction reaction (CO2RR), which are pivotal processes with significant environmental implications. Hydrochars were synthesized by varying the parameters such as nitrogen loading, temperature, and residence time. These materials were then thoroughly characterized using diverse analytical techniques, including elemental analysis, density measurements, BET surface area analysis, and spectroscopies like Raman, FTIR, and XPS, along with optical and scanning electron microscopies. The subsequent electrochemical assessment involved preparing electrocatalytic inks by combining hydrochars with an anion exchange ionomer (AEI) to leverage their synergistic effects. To the best of our knowledge, there are no previous reports on catalytic electrodes that simultaneously incorporate both a hydrochar and AEI. Evaluation metrics such as current densities, onset and half-wave potentials, and Koutecky-Levich and Tafel plots provided insights into their electrocatalytic performances. Notably, hydrochars synthesized at 230 °C exhibited an onset potential of 0.92 V vs. RHE, marking the highest reported value for a hydrochar. They also facilitated the exchange of four electrons at 0.26 V vs. RHE in the ORR. Additionally, the CO2RR yielded valuable C2 products like acetaldehyde and acetate. These findings highlight the remarkable electrocatalytic activity of the optimized hydrochars, which could be attributed, at least in part, to their optimal porosity.

Rapid Start-up of Continuous Autotrophic Nitrogen Removal Reactor by Hybrid-inoculating PN and PN/A Granular Sludges

The rapid cultivation of partial nitritation/ANAMMOX （PN/A） granular sludge in a continuous-flow mode is one of the key technologies for efficient biological nitrogen removal in domestic wastewater treatment. Compared with that in PN/A granular sludge, PN granular sludge demonstrates a shorter incubation period and suitability for batch culture. It is also a good carrier for enriching ANAMMOX （AMX） bacteria. In this study, we established a continuous-flow autotrophic nitrogen removal process in three continuously stirred tank reactors （CSTR） （R1-R3） by hybrid-inoculating PN/A and PN granular sludge at the mass ratios of 3∶1, 1∶1, and 1∶3, respectively. By implementing high ammonium nitrogen loading and short hydraulic retention time, continuous autotrophic nitrogen removal processes were successfully started up in the three CSTRs. The results showed that compared with that of R1 and R2, R3 had a longer start-up time but a similar steady-state nitrogen removal performance. The total nitrogen removal load of R3 could be more than 2.6 kg·（m3·d）-1. Intriguingly, the inoculated PN granular sludge served as a precursor for PN/A granular sludge cultivation. This approach facilitated the enrichment of anaerobic ammonia-oxidizing bacteria （AMX） by introducing abundant ammonium-oxidizing bacteria （AOB） and nitrite nitrogen substrates into the CSTR. According to the results of high-throughput sequencing, the microbial abundance and diversity of the mature granules in R1-R3 were significantly higher than those of the inoculation sludge. AOB （genus Nitrosomonas）, AMX （genera Candidatus Kuenenia and Candidatus Brocadia）, and symbiotic heterotrophs, such as Chloroflexi, Bacteroidetes, and Chlorobi, drove the autotrophic nitrogen removal process and maintained the stability of the granular structure. In summary, a novel start-up strategy of hybrid-inoculating granular sludge was provided for a continuous-flow autotrophic nitrogen removal in engineering application.

Assessment of spatiotemporal risks for nationwide groundwater nitrate contamination

National assessments of groundwater contamination risks are crucial for sustaining high-quality groundwater supplies. However, traditional methods often treat groundwater contamination risk as a steady-state indicator without considering spatiotemporal variation in risk, both geographically and over time, caused by anthropogenic and climatic factors. In this work, XGBoost, a tree-based algorithm, was applied to comprehensively analyze the drivers of groundwater contamination from nitrate, using data on 13 physical features (as used by the index-based ranking method DRASTIC) and 30 anthropogenic features from 1985 to 2010 in the contiguous United States (CONUS). The results indicate that physical features controlling the transport processes, particularly those affecting contaminant travel time from land surface to groundwater (depth to water table and transmissivity), were the dominant factors for nitrate contamination in groundwater. This was followed by features representing the potential nitrogen loading. Positive correlations between most features and the nitrogen loading time (year) were found, suggesting their growing influence on contamination risk. Based on the drivers identified for nitrate concentrations exceeding 10 mg/L in groundwater and their varying temporal contributions, this study proposes a reformulated index-based method for contamination risk assessment. With this method, an overall accuracy of around 70 % was achieved based on the validation data set. The predicted high-risk areas are mainly intensive irrigation regions, such as the High Plains, northern Midwest, and Central Valley. This new approach contributes to a more accurate and effective assessment of the contamination risks of groundwater on a regional and national scale under temporally varying environmental conditions.

Control strategies for mode switching of a large marine two-stroke engine equipped with exhaust gas recirculation and turbocharger cut-off systems

To meet the stringent nitrogen oxides emissions regulations, the recent marine two-stroke engines are equipped with exhaust gas recirculation (EGR) systems. Crossing the boundaries of exhaust control areas requires switching between the engine operating modes associated with the activation or deactivation the EGR system, which imposes challenges to the engine operation. This study aims to develop and numerically test effective control strategies for improving the mode switching of marine two-stroke engines with EGR systems. The investigated engine dynamic model is developed by integrating a zero-dimensional thermodynamic model developed in GT-POWER and the control model developed in MATLAB/Simulink. This model is first validated against the experimentally measured engine performance parameters, and subsequently employed to simulate the engine dynamic operation with mode switching. The simulation results are assessed to quantify the impact of several control strategies on the engine performance. The derived perrformannce parameters time variations demonstrate that the deactivation of the EGR branch and the small engine–turbocharger result in exceeding the manufacturer limits at high loads and increasing the fuel consumption. The proposed load-based control strategies, which employ load thresholds and time delays for the control of the EGR and turbocharging systems activation/deactivation, are proved effective, as the engine performance parameters are retained within their limits and fuel consumption penalties are minimised. This study provides insights for developing the control of the marine engines after-treatment systems, hence contributing towards enhancing shipping sustainability.

Prediction of Helicopter Rotor Loads and Fatigue Damage Evaluation with Neural Networks

AbstractIn recent years, machine learning algorithms have experienced rapid advancement, driven by the exponential growth of data availability and computational capabilities. Among these algorithms, artificial neural networks stand out as one of the most renowned and effective classes, possessing the ability to discern relationships within data. In this study, we harness neural networks to deduce the relationship between flight mechanics parameters and resulting loads in an articulated rotor configuration. The accuracy of these algorithms hinges closely on the quality of the dataset used for training. Given that rotor loads manifest as time-periodic signals with precise harmonic content, we train dedicated neural networks to predict each harmonic individually. Subsequently, the load time history is reconstructed post hoc by amalgamating predictions from each individual network. Various network architectures are explored, and a sensitivity analysis is conducted on hyper-parameters to determine the optimal configuration for this specific application. Moreover, these predictions serve as input for a fatigue damage calculation algorithm.