Main Variables Research Articles

Investigating the nuclear properties of highly accreting active galactic nuclei with XMM-Newton

Highly accreting active galactic nuclei (AGNs) have unique features that make them ideal laboratories for studying black hole accretion physics under extreme conditions. However, our understanding of the nuclear properties of these sources is hampered by the lack of a complete systematic investigation of this AGN class in terms of their main spectral and variability properties, and by the relative paucity of them in the local Universe, especially those powered by supermassive black holes with MBH > 108 M⊙. To overcome this limitation, we present here the X-ray spectral analysis of a new, large sample of 61 highly accreting AGNs named as the XMM-Newton High-Eddington Serendipitous AGN Sample, or X-HESS, obtained by cross-correlating the 11th release of the XMM-Newton serendipitous catalogue and the catalogue of spectral properties of quasars from the SDSS DR14. The X-HESS AGNs are spread across wide intervals with a redshift of 0.06 < z < 3.3, a black hole mass of 6.8 < log(MBH/M⊙) < 9.8, a bolometric luminosity of 44.7 < log(Lbol/erg s−1) < 48.3, and an Eddington ratio of −0.2 < log λEdd < 0.5, and more than one third of these AGNs can rely on multiple observations at different epochs, allowing us to complement their X-ray spectroscopic study with a variability analysis. We find a large scatter in the Γ − λEdd distribution of the highly accreting X-HESS AGNs, in agreement with previous findings. A significant correlation is only found by considering a sample of lower-λEdd AGNs with λEdd ≲ 0.3. We get hints that the Γ − λEdd relation appears to be more statistically sound for AGNs with lower MBH and/or Lbol. We investigate the possibility of transforming the Γ − λEdd plane into a fully epoch-dependent frame by calculating the Eddington ratio from the simultaneous optical/UV data from the optical monitor, λEdd, O/UV. Interestingly, we recover a significant correlation with Γ and a spread roughly comparable to that obtained when Lbol is estimated from SDSS spectra. Finally, we also get a mild indication of a possible anti-correlation between Γ and the strength of the soft excess, providing hints that reflection from an ionised disc may be effective in at least a fraction of the X-HESS AGNs, though Comptonisation from hot and warm coronae cannot be ruled out as well.

Features of subseasonal concurrent variations between subtropical and polar front jets and their association with temperature anomalies in China

Subseasonal variability of atmospheric circulation in mid-high latitudes is highly correlated to the upper-level jet streams, acting as a major contributor to the global or regional persistent climate anomalies. In this study, the features of subseasonal concurrent variations (SCVs) between East Asian Polar Front Jet (EAPJ) and Subtropical Jet (EASJ), and corresponding atmospheric circulation and temperature anomalies in China are investigated by using the observational data and NCEP/NCAR reanalysis datasets. Results show that the main variability modes of the winter upper-level wind fields on subseasonal time scales are characterized by the meridional shift in opposite directions and out-of-phase variations in the intensity of the EASJ and EAPJ. These concurrent variations between the two jets have a significant oscillation cycle with a period of 10–25 days. Accompanied by the location (intensity) SCV of the two jets, the mid-latitude circulation systems show significant zonal shifts (local intensity changes), resulting in alternations of the atmospheric circulation between zonal and meridional types. The typical meridional circulation is characterized by a strong East Asian trough and its upstream strong high-pressure ridges. Meanwhile, gradient force between Siberian high and the Aleutian low is anomalously strong. As a result, the SCVs between two jets can cause widespread and persistent low temperature anomalies over China, usually lasting more than three days. In the case of the location SCV of the two jets, the low temperature anomalies concentrate in northern China, particularly in north of 40°N. In the case of the intensity SCV of the two jets, the low temperature anomalies occur in most parts of China, notably in south of 40°N. These results are helpful to improve the prediction of atmospheric circulation and temperature anomalies in East Asia during winter.

Bioregionalization of the subarctic Pacific based on phytoplankton phenology and composition

The subarctic Pacific is generally perceived as relatively homogeneous since the North Pacific Subpolar Gyre dominates the water circulation in the area. However, previous research showed significant spatial differences in phytoplankton abundance and community structure. This study aimed to identify regions associated with distinct phytoplankton phenology and composition to comprehensively describe the main phytoplankton variability patterns across the subarctic Pacific. To this end, satellite GlobColour time series observations and an extensive in situ phytoplankton pigment dataset were used in the analysis. Five bioregions were identified, based on the Self-Organized Mapping technique, using a greater than 20-year satellite data series. The bioregions in the open Pacific waters were dominated by green algae, haptophytes, and pelagophytes and were divided into the areas affected by the North Pacific Transition Zone and beyond. The other bioregions were defined around the Pacific basin margins where the diatom contribution was generally higher, with a particular distinction of waters surrounding the Kuril and the Aleutian Islands. Our bioregion designations allow for future evaluation of the processes controlling the physical and biological dynamics within each bioregion, which has direct implications for foraging conditions available to higher trophic levels, including potential food resource competition.

Hydroclimate variability in the Tropical Andes recorded by δ18O isotopes from a new network of Polylepis tarapacana tree-rings

Stable oxygen isotopes records (δ18O) in tree-rings are commonly used to assess the response of trees to environmental variability being a valuable tool for studying past climate at different temporal and spatial scales. This is particularly relevant in semi-arid regions like the southern Tropical Andes, where ongoing environmental changes coincide with a rapidly increasing demand for hydrological resources, presenting a challenge for ecosystem dynamics and water resource management. In this study, we aim to determine the main spatio-temporal variability of a new network of δ18O Polylepis tarapacana chronologies during the last century, and their relationships with hydroclimate and tropical circulation at local to subcontinental scales throughout the Tropical Andes. For this purpose, we develop six δ18O P. tarapacana tree-ring chronologies across a 450 km latitudinal moisture gradient in the southern Tropical Andes adjacent to the Atacama Desert, covering the period 1900–2007. Results show a clear latitudinal gradient in the δ18O values across the network and significant relationships are observed with other δ18O tree-ring chronologies in Tropical South America, demonstrating clear regional climate influences at a subcontinental scale. A principal component analysis of the δ18O tree-ring chronologies demonstrate a strong regional environmental signal contained in the network, exhibiting a main temporal pattern (PC1 δ18O) that explains 63% of the total variance during the period 1900–2007. Comparisons between PC1 δ18O and environmental variables showed significant negative relationships with precipitation and soil moisture, and positive relationships with temperature and vapor pressure deficit (VPD) during summer when the South American monsoon occurs. The main δ18O tree-ring network signal clearly records tropical atmospheric and circulation patterns across South America. The easterly wind flux conditions from the Amazon basin favor lower δ18O values, and the PC1 δ18O exhibit significant positive correlations with VPD across the entire Tropical Andes and the northern portion of the Amazon basin, and as well as outgoing longwave radiation across the southern Tropical Andes and part of the Amazon basin. The close relationships between the regional signals from our δ18O tree-ring network with the previously mentioned parameters, highlight the potential to develop future hydroclimatic-related reconstructions with these δ18O records to assess climate variability and change across the Tropical Andes.

Comprehensive assessment of global spinal sagittal alignment and related normal spinal loads in a healthy population

Abnormal postoperative global sagittal alignment (GSA) is associated with an increased risk of mechanical complications after spinal surgery. Typical assessment of sagittal alignment relies on a few selected measures, disregarding global complexity and variability of the sagittal curvature. The normative range of spinal loads associated with GSA has not yet been considered in clinical evaluation. The study objectives were to develop a new GSA assessment method that holistically describes the inherent relationships within GSA and to estimate the related spinal loads.Vertebral endplates were annotated on radiographs of 85 non-pathological subjects. A Principal Component Analysis (PCA) was performed to derive a Statistical Shape Model (SSM). Associations between identified GSA variability modes and conventional alignment measures were assessed. Simulations of respective Shape Modes (SMs) were performed using an established musculoskeletal AnyBody model to estimate normal variation in cervico-thoraco-lumbar loads.The first six principal components explained 97.96% of GSA variance. The SSM provides the normative range of GSA and a visual representation of the main variability modes. Normal variation relative to the population mean in identified alignment features was found to influence spinal loads, e.g. the lower bound of the second shape mode (SM2-2σ) corresponds to an increase in L4L5-compression by 378.64 N (67.86%).Six unique alignment features were sufficient to describe GSA almost entirely, demonstrating the value of the proposed method for an objective and comprehensive analysis of GSA. The influence of these features on spinal loads provides a normative biomechanical reference, eventually guiding surgical planning of deformity correction in the future.

Methods for fungiform papillae assessment: A collaborative study among European research units

Fungiform papillae (FP) are the anatomical structures dedicated to gustatory and somatosensory signal triggering. Whether the density of FP (FPD = FP/cm2) is associated with oral responsiveness is controversial, and the disparity in previous findings may be partially due to the diversity in methods used to quantify FP. The present study aims at mapping methods used to estimate FPD and at tentatively assessing the impact of the main procedure variables in FPD estimation. An on-line survey was specifically developed and launched among the European Sensory Science Society members to collect information on methods and procedure variables and to share datasets on FP counting. Seven European research centres responded to the survey. Manual counting was the most popular methodology, and a merged dataset of 1006 observations was obtained. The type of device used for tongue picture acquisition (low-resolution - LR vs high-resolution - HR) was the main procedure variable. FPD mean values were lower when assessed by LR (35.8) than with HR devices (41.5). Distribution of FPD for LR and HR datasets were similar thus comparisons among studies in which different resolution devices have been used are reliable. Picture modifications and data validation did not significantly affect FPD estimation obtained from HR devices, while both these variables significantly affected FPD values collected with LR devices. Both HR and LR procedures were able to capture the differences in FPD due to age and gender. Overall, measures from HR devices appear the best option to depict the inter-individual variability in FPD. Automated procedures appear underutilised.

A cross-sectional analysis of the association between sleep disorders and cancer using data from the National Health and Nutrition Examination Survey (NHANES) 2005-2014.

Cancer is one of the main causes of death in the world, and sleep disorders are a serious public health problem, especially in large cities; of these, insomnia and obstructive sleep apnea (OSA) are the most common. In the last decade, studies have pointed to a possible association between sleep disorders and cancer. The aim of this study is to evaluate whether there is any association between sleep disorders and cancer. Five National Health and Nutrition Examination Surveys (NHANES) (2005-2014) from the United States were combined in order to obtain the sample. Two main sleep variables were assessed: having trouble sleeping and/or ever telling a doctor one had a sleep problem. The odds ratio of ever having a cancer diagnosis was the main outcome. Data were analyzed by binary logistic regression models in Jamovi. The final sample comprised 26,821 participants. Individuals who reported having trouble sleeping had an odds ratio of 1.48 (95% confidence interval = [1.336-1.646]; P < .001) of having been diagnosed with cancer, and those who had already been diagnosed with a sleep disorder had an odds ratio of 1.21 (95% confidence interval = [1.046-1.415]; P = .011), showing an increased chance of having been diagnosed with cancer. In men, these values were even greater, with an odds ratio of 1.56 (95% confidence interval = [1.321-1.843]; P < .001) and an odds ratio of 1.26 (95% confidence interval = [1.013-1.582]; P = .037), respectively, for having trouble sleeping and for having been diagnosed with a sleep disorder, in relation to having been diagnosed with cancer. Individuals who had trouble sleeping or who had been diagnosed with a sleep disorder at any time in their life were more likely to have been diagnosed with cancer. Porcacchia AS, Pires GN, Andersen ML, Tufik S. A cross-sectional analysis of the association between sleep disorders and cancer using data from the National Health and Nutrition Examination Survey (NHANES) 2005-2014. J Clin Sleep Med. 2024;20(4):515-520.

Flowsheet development for and commissioning of the Kamoa-Kakula project

The Kamoa-Kakula copper resource, located west of Kolwezi in the Democratic Republic of the Congo, was discovered and explored by Ivanhoe from 2008/9 on. As a greenfield project with prospects of high grade ore and a long life-of-mine, the need for best practice flowsheet development was recognised, so as to ensure sustainability of metallurgical performance at the at the maximum economic level from the orebody during metallurgical operations. Process Mineralogy, a hybrid discipline, has been developed in the mining industry over the last forty years, and its proper use has seen very successful outcomes in flowsheet development (Bradshaw, 2014; Lotter, 2011; Lotter et al., 2003; McKay et al., 2007; Pease et al., 2005). Drill core was sampled at site across six phases of flowsheet development that worked with the developing mine plan. The two main geomet units were hypogene and supergene, with the hypogene being unusually rich in bornite. The main variability is between supergene and hypogene, and between Kamoa and Kakula, but with less spatial variability within them. The first viable flowsheet was developed and demonstrated in nine months of test work, followed by various revisions and iterations as required by the discovery of variable mineralogy. The first flowsheet, called “Milestone”, was then challenged with an opportunity for a simpler but better-performing flowsheet, which became known as IFS4A. The simultaneous discovery of the Kakula resource refocussed the project due to its shallower depth and higher grade. Laboratory scale flotation testing using IFS4A in Phase 6 of Kamoa and two drill-holes of Kakula quickly confirmed that the Kakula ore outperformed the Kamoa supergene ore using this flowsheet. A mini-pilot plant campaign was run in 2019 with this flowsheet plus modifications, using 985 kg of metallurgical drill cores material to demonstrate the full flowsheet mass and value balance on a continuous operating campaign. This mass and value balance produced an estimated 85.6 % Cu recovery with a saleable concentrate grading 57.3 % Cu. Whereas this paper concentrates on the mineralogy and its contribution to process implications such as grinding requirements and flotation strategy, it is recognized that first-class design, engineering and construction contributed in no small measure to the successful start-up. This mass and value balance was used in the design of the grinding and flotation circuits, and contributed to the successful commissioning of the new concentrator in 2021, which averaged a recovery of 84.7 % at a grade of 50.5 % Cu, in good agreement with the testwork. A McNulty model for the commissioning data shows a better than Type 1A start-up. The flowsheet development part of the project is discussed in this paper as a case study.

Biosecurity practices in the dairy farms of southern Brazil.

Biosecurity refers to a set of practices that prevents and/or controls the introduction, spread, and elimination of harmful biological agents in a production system. In this study, we aimed to survey the biosecurity practices and determine their correlation with the size of production systems. A biosecurity assessment form was provided to 69 farms in the Campos Gerais region of Paraná, Brazil. The questionnaire was divided into two sections: general and bovine viral diarrhea virus- and bovine herpesvirus type-1-specific sections. The general section covered topics on traffic control, quarantine and animal isolation, hygiene practices, carcass disposal, and disease monitoring/control. The specific section consisted of questions on the reproductive and respiratory factors, use of antimicrobials, and vaccination schedule. The 69 farms were also classified into small (≤ 61), medium (62-201), and large (≥ 202) size farms based on the number of lactating cows. Moreover, multiple correspondence analysis (MCA) was performed between the biosecurity measures and farm size. The main risk factors and variability were related to the traffic control of people, animals, and vehicles/equipment, animal quarantine/isolation, and hygiene practices. MCA revealed that the small farms exhibited a lack of biosecurity measures, including those related to traffic control, animal quarantine, and hygiene. In medium-size farms, contact between bovine animals of different ages and difficulty in animal isolation in the quarantine system were among the main risk factors. In contrast, isolation of sick animals was easy, but the need to frequently purchase cattle was an important risk factor in large farms. These results highlight the relationship between biosecurity measures and farm size, providing valuable insights for the development of better biosecurity plans for production systems.

Functional principal component analysis for incomplete space–time data

Environmental signals, acquired, e.g., by remote sensing, often present large gaps of missing observations in space and time. In this work, we present an innovative approach to identify the main variability patterns, in space–time data, when data may be affected by complex missing data structures. We formalize the problem in the framework of functional data analysis, proposing an innovative method of functional principal component analysis (fPCA) for incomplete space–time data. The functional nature of the proposed method permits to borrow information from measurements observed at nearby spatio-temporal locations. The resulting functional principal components are smooth fields over the considered spatio-temporal domain, and can lead to interesting insights in the spatio-temporal dynamic of the phenomenon under study. Moreover, they can be used to provide a reconstruction of the missing entries, also under severe missing data patterns. The proposed model combines a weighted rank-one approximation of the data matrix with a roughness penalty. We show that the estimation problem can be solved using a majorize–minimization approach, and provide a numerically efficient algorithm for its solution. Thanks to a discretization based on finite elements in space and B-splines in time, the proposed method can handle multidimensional spatial domains with complex shapes, such as water bodies with complicated shorelines, or curved spatial regions with complex orography. As shown by simulation studies, the proposed space–time fPCA is superior to alternative techniques for Principal Component Analysis with missing data. We further highlight the potentiality of the proposed method for environmental problems, by applying space–time fPCA to the study of the lake water surface temperature (LWST) of Lake Victoria, in Central Africa, starting from satellite measurements with large gaps. LWST is considered one of the fundamental indicators of how climate change is affecting the environment, and is recognized as an essential climate variable.

A Grave Concern: Water-Intensive Crops and Subsidized Electricity Amplifying Groundwater Depletion in India

This study investigates the consequences of agricultural activities on groundwater depletion, with a specific focus on the overproduction of water-intensive crops. Addressing this existing research gap, this study challenges the prevailing notion that groundwater depletion reduces agricultural activity. Instead, our study reveals a significant relationship between intensified cropping practices, particularly the production of water-intensive crops (Paddy, Sugarcane and Wheat) and the depletion of groundwater. Further, we identify how subsidized electricity helps to accelerate groundwater depletion. Therefore, we use variables related to groundwater and agricultural practices for the period 2004–2020. In doing so, we find that the Northern states of India are most vulnerable in terms of groundwater depletion (PNB: 59.92, SGD: 106.3), followed by southern, central, western, eastern and northeastern states. Additionally, the regression results suggest that our main variables, magnitude of electricity consumption in agriculture and irrigation intensity of water-intensive crops, have a positive and significant impact on groundwater depletion. In fact, our study found that other variables such as cropping intensity (CI), state population (SP), agriculture credit (AC) and total electric pumps (TP) are also significant and positively associated with groundwater depletion while the magnitude of annual rainfall (AR) shows a negative impact on groundwater depletion. Based on the findings, this study presents an alternative perspective that underscores the contribution of ineffective government policies in regulating subsidize electricity and the cultivation of water-intensive crops, leading to the exploitation of groundwater resources in Indian states with regional variations. These findings emphasize the critical and immediate need for effective regulations on the production of water-intensive crops to address this pressing issue.

Performance Evaluation of Architectural Modular Member with Ultra-High-Performance Fiber-Reinforced Concrete for Application

As the modular industry expands, the most widely used building materials are primarily concrete, steel, and wood. However, the use of wood and steel is severely limited compared to concrete for reasons such as durability and economy. To overcome these shortcomings, we aimed to apply ultra-high-performance fiber-reinforced concrete (UHPFRC), which has excellent compressive strength and tensile strength, high durability, and minimal reinforcement with steel fibers. In this study, research was conducted on the development of unit box-type architectural modules using UHPFRC with a compressive strength of 120 MPa and a tensile strength of greater than 7 MPa. Various amounts of steel fibers (Vf = 1.0, 1.5, and 2.0%) were evaluated to determine the optimal mixing ratio of UHPFRC, in which both the durability and mechanical performance were assessed. The compressive strength and tensile strength of UHPFRC were found to be 132 MPa and 10.1 MPa, respectively, while its resistance to chloride penetration averaged 14.47 coulombs, indicating superior durability compared to conventional concrete. To reduce the weight of the unit components of the architectural modular system, both normal concrete (NC) components and UHPFRC were applied. The main variables in the flexural tests were the cross-sectional thickness, steel fiber content, and presence of an insulation material, comprising a total of three variables for evaluating the flexural performance. The application of UHPFRC with a compressive strength of 120 MPa, a cross-sectional thickness of 120 mm, and a 10 mm diameter reinforcement provided a similar performance to that of NC components while reducing concrete usage by 60% compared to NC components. Additionally, structural analysis was performed to prototype the unit box-type modular structure using UHPFRC. The modular structural system developed in this study was found to reduce construction costs by 18.7% compared to traditional steel structural systems. Further research is necessary to address issues such as floor slab vibration and noise, connections, and expansion to multistory buildings for commercialization of modular structures using UHPFRC.

Overall time spent by clients from entry to exit and associated factors in out-patient departments in public hospitals of Jimma Zone southwest, Ethiopia.

The overall time refers to the amount of time a patient spends in a health care facility, from the time he or she enters to the time he or she leaves. As a result of the imbalance between supply and demand, waiting times occur. Ethiopian hospitals are being reformed to improve the quality of care they provide. The time a patient spends in the hospital is one of the most important indicators of quality of care, as it provides insight into customer satisfaction and provider success. However, the overall time patients spend in hospitals was not studied. The study aimed to assess the overall time spent by clients from entry to exit and associated factors in the outpatient departments of Jimma zone hospitals. An institution-based cross-sectional study was conducted. Patients from outpatient units at Jimma zone public hospitals participated in the study from March 15 to May 17, 2018. Data were collected using a time and motion tool coupled with an interviewer-administered structured questionnaire on 249 samples. Participants in the study were selected using the consecutive sampling method. Overall time, in terms of waiting and service times at each section unit, and the relationship of socio-demographic and clinical factors with overall time was the main outcome variables. Data were analyzed using descriptive and linear regression analysis. Simple linear regression analysis was used to determine the relationship between the dependent and explanatory variables. Variables were considered significantly associated with the overall time if they had a p-value of less than 0.05 at the 95% confidence interval (CI). The overall response rate was 94.8%. Overall, patients spent a median time of 342.5 minutes. Patients spent 12.7% of the total time as service time and 86% of the time waiting for care. The longest overall times were spent in the laboratory (170 minutes), imaging (95 minutes), other diagnostic units (84 minutes) and examination (83 minutes). The average overall time was increased by 52.03 minutes (95%CI 21.65, 82.412), 4.65 minutes (95%CI 3.983, 5.324), and 96.43 minutes (95%CI 52.076, 140.787) when the patient was referred, the number of patients at the queue was increased by one unit, and patients who had other diagnostic tests performed respectively with P <0.005 &adjusted R2 = 0.522. The majority of patients stayed for a longer period. Most time was spent waiting for services, particularly in the examination, laboratory, and imaging units. This is strongly related to high patient load, an absence of some services, being referred patients, and patients who had other diagnostic tests. To reduce the number of patients in the queues, hospitals should work hand in hand with the Ministry of Health to enforce policies that are understood and adopted by all workers in the lower healthcare facilities. And hospital administrators are working to strengthen the triaging system to screen patients with minor illnesses. This is because most patients with minor illnesses queue with those with more complicated illnesses. Finally, we recommend that researchers conduct further research on service quality.

Process intensification of metal solvent extraction studies using a miniaturized solvent extraction plant

This study examines the potential of a miniaturized solvent extraction plant (MSXP) to improve the efficiency and reproducibility of laboratory and pilot-scale metallurgical studies that typically require extended testing periods. The MSXP has been designed to replace conventional solvent extraction (SX) apparatus and aims to reduce start-up time, time to reach equilibrium, and overall test time. Two copper solvent extraction (Cu-SX) research campaigns were conducted to test the functionality, ease of operation, modularity, and reproducibility of the MSXP. The first campaign quantified the extraction efficiency and net copper transfer, while the second campaign operated the MSXP in a semicontinuous countercurrent flow configuration with three extraction and two stripping stages. The main variables studied in the first campaign are the number of stages (1-3), volumetric flow rates (O/A, 1-3), and organic phase residence time in the micro-contactor (0.7-2.4 min). The results demonstrate that the MSXP can work with very low stage efficiencies (48%), while achieving high copper recoveries (> 90%). At the stripping circuit level, we show that the MSXP can operate at superior stage efficiencies (> 100%), with low copper recoveries (30%–55%). The reproducibility evaluation also demonstrates high statistical confidence (< 6% CV) in the obtained process values. The MSXP offers great flexibility in net copper transfer and can be used to benchmark and emulate a wide range of Cu-SX systems. Experimental Cu-SX campaigns can be run in about 60 min while investing roughly US$1.4/h on reagents, which is significantly lower compared to typical campaigns that can last from days to weeks to reach reliable research outcomes and require about US$62/h for reagents. The potential of MSXP extends to more elaborate solvent extraction systems, specifically those designed to purify energy-critical elements like lithium, nickel, cobalt, or rare-earth elements. This study demonstrates the promise of process intensification approaches for improving the efficiency of laboratory and pilot-scale SX studies, which can help in reducing time, reagents, and energy consumption while improving the reproducibility of results.

Optimization of local modified metakaolin-based geopolymer concrete by Taguchi method

Abstract Geopolymer in recent concrete (GP) has gained significant attention due to its sustainability and environmental friendliness. Local metakaolin-based geopolymer is weaker than geopolymers made from other materials due to its low Si/Al ratio. A consistent mixture design is also lacking because geopolymers are affected by many variables. This study presents a method to find the optimal geopolymer mixture based on locally modified metakaolin as a source of aluminates and silicates using the Taguchi method. Metakaolin was modified using different contents of materials rich in silica, such as silica fume (SF), or materials rich in calcium, such as calcium oxide (CaO) of 5, 10, and 15%. The inclusion of 5% SF, 10% CaO, and a combination of 5% SF and 5% CaO as substitutes for metakaolin increases the compressive strength by 16.8, 6.9, and 22.8%, respectively, compared to the reference mixture without any modifications. In other words, adding 5% SF and CaO increased the molar ratio of SiO2/Al2O3 (R) from 1.782 to 1.914, resulting in the highest compressive strength of 53.3 MPa after 7 days of sun curing. To obtain the optimal mixture that achieves the highest compressive strength, the impact of three main variables, including the concentration of sodium hydroxide (SH), alkali solution-to-binder (Al/B) ratio, and sodium silicate-to-sodium hydroxide (SS/SH) ratio, must be considered using Taguchi method. A total of nine mixtures were investigated. It was found that 13 M of SH, 0.65 Al/B, and 2.5 SS/SH give a high compressive strength of 58.6 MPa at 7 days. Also, it was found that the concentration of SH plays a more important role in increasing the compressive strength than the alkali-to-binder ratio and SS/SH ratio. The scanning electron microscopy images show that the 5% weight replacement of metakaolin by silica and CaO could source fewer and smaller pores and reduce the microcracks’ width.

Dynamic modeling and force-vibration mapping mechanism construction of rolling bearings considering cage flexibility and local faults

Rolling bearings are one of important components of rotating machinery transmissions and thus its health condition is important for the safety of machinery. Thus, rolling bearing vibration analysis is critical for bearing health condition monitoring. Current bearing vibration analysis ignores multiple compound influencing factors for dynamic modeling. Hence, a more accurate bearing dynamic model, considering multiple factors including cage flexibility, time-varying displacement excitations caused by local defects and elastohydrodynamic (EHD) lubrication, is proposed to accurately reflect force states among bearing elements and vibration responses of bearings. Furthermore, the force states and vibration responses of bearings with localized defects in the proposed model are analyzed in details: (1) the main excitation source of the dynamic model under faulty conditions is identified as the contact force between the rolling element and the raceway by analyzing the vibration signals and main physical variables (the contact forces and the friction forces) in numerical values and change trends; (2) the mapping mechanism between the main excitation source and the vibration response is constructed. The force states among bearing elements are detailedly analyzed in the proposed model and the relationship between the forces and bearing vibration responses is revealed, facilitating the bearing health condition monitoring and vibration control of machinery.

Root colonisation effects on the key hydrogeological properties of a reclamation cover with an elevated water table

ABSTRACT The performance of reclamation cover systems could be affected by the colonization of plant roots, which may modify the hydrogeological properties of the construction materials. A four-year field investigation was conducted using six experimental cells with various soil layering designs over AMD-generating tailings reclaimed with an oxygen-barrier cover combined with an elevated water table. Both herbaceous and woody vegetation were installed on top of the cells to compare the influence on the properties of the cover material. Consecutive and undisturbed cores were collected from the cover’s functional layer in 2020 and 2021, respectively. Root parameters, such as root length density, and hydrogeological properties were measured on the core samples to assess the possible relationships between the two categories of variables. Root observation trenches were also cut in each cell to better analyze the root density and occurrence profiles. Results showed that, within the four-year monitoring period of the study, both herbaceous and woody vegetation roots mostly colonized the top overburden layer of the cell (>86% visible roots) and barely occupied the functional layer of the reclamation cover (<10% visible roots). The observed maximum desorption rates for the functional layer were lower than the predicted values, which could be a short-term effect of the fine roots. No significant impact of roots on the main hydrogeological variables controlling the oxygen barrier efficiency were noted. At the end of the four-year study period, the hydrogeological behavior of the functional layer in all cells with/without vegetation/additional soil layers was found to be similar.

Experimental and numerical study on flow characteristics of dual‐cavity die based on multi‐objective optimization

AbstractSlot die coating is a common method of manufacturing electrodes for lithium‐ion batteries. In this paper, a multi‐objective optimization research on the geometry of dual‐cavity die is investigated based on the numerical simulation of lithium battery anode slurry flow combined with the surface response optimization method. First, we use the Plackett–Burman test method to screen the geometric parameters significantly affecting the optimization objective. Then, based on the Box–Behnken response surface analysis method, we determine the optimal combination of parameters. The results show that the inner cavity radius and slot gap are the main structural variables affecting exit‐velocity uniformity and die deformation. The slot gap and slot length mainly affect the inlet pressure. The coefficient of deviation of exit velocity uniformity and average inlet pressure of the optimized die structure decreased by 51.3% and 7.6%, respectively. This research provides theoretical guidance for the design of slot coating dies.Highlights Screening significant geometric parameters using Plackett–Burman test methodology. Box–Behnken response surface analysis to determine optimal parameters. Velocity uniformity and inlet pressure increased by 51.3% and 7.6%, respectively.

Relationship between Parenting Style and High School Students’ Anxious Thoughts: A Case Study in Iran

Parenting styles are variables that affect their children&amp;rsquo;s anxious thoughts. The present study aimed to examine the relationship between parenting styles with anxious thoughts of the students in selected high schools of Mashhad, Iran. A quantitative methodology in form of a correlational design was employed in this research, which comprised two main variables including parenting styles and Iranian teenagers&amp;rsquo; anxious thoughts. To address the research objective, 180 teenagers who were students at some schools in Mashhad, Iran, and their parents, completed the study questionnaires which included Baumarind parenting styles Scale (1971) and the Anxious Thoughts Inventory (AnTI) designed by Wells (1994). The analysis of the data obtained from implementing the questionnaires was performed through SPSS25 software in two sections: descriptive and inferential (Pearson Correlation Coefficient and regression analysis, i.e. ANOVA). The results showed that there was a significant relationship between anxious thoughts and the three parenting styles. Also, the relationship between the authoritarian parenting style and the symptoms of anxious thoughts (r = -0.731) is significant in a negative way. On the other hand, it is observed that there is a positive correlation between authoritarian parenting style and anxious thoughts (r = 0.511). Finally, it is seen that there is a positive correlation between permissive parenting style and anxious thoughts (0.461), (p&amp;lt;/01). It can be concluded that parenting styles can strongly predict anxious thoughts and determine 0.544 of variances of the anxious thoughts.

The Structural Performance Of Short Circular Concrete Columns Made With Reactive Powder Concrete And Externally Reinforced With Textile Fabric

In the current laboratory investigation, the behavior of hollow circular concrete columns exposed to vertical compressive force is examined. The columns are externally strengthened with Glass Fibre Reinforced Polymer bars and textile fabric (one layer and two layers). The longitudinal reinforcement cast using concrete Reactive Powder Concrete has an outer diameter of (250 mm), a bore diameter of (100 mm), and a length of (1000 mm). The number of textile layers (one or two layers) is one of the main variables used in this experiment study. According to the experimental findings, the hollow circular concrete columns raised the tested concrete columns' bearing capacities by roughly (9.93%) and (17.8%), respectively, after the specimens were allowed to cure for 28 days. This improvement was made for strengthening columns that were subjected to compressive loads and had one or two layers of textile fabric.