Debris Concentration Research Articles

A post-hurricane building debris estimation workflow enabled by uncertainty-aware AI and crowdsourcing

Climate disasters often result in large amounts of debris that need to be cleaned up in the event's aftermath. Effective post-disaster debris management poses unique challenges due to limited resources, high expenses, and the nonhomogeneous and hazardous debris content. Current practices of debris cleanup rely on time-consuming and error-prone field-based estimation, which impedes immediate response and accurate analysis. While new approaches such as artificial intelligence (AI) and crowdsourcing have shown promise in various domains, their potential for debris estimation remains underexplored. This study leverages a human-AI teaming workflow that estimates post-disaster debris volume and composition. The workflow begins with the utilization of drones to capture aerial views for efficient disaster infrastructure reconnaissance. Subsequently, an AI model and a crowdsourcing module are calibrated and work together to rapidly and reliably detect damaged buildings and classify the levels of damage based on aerial imagery. By establishing a connection between building damage states and the resulting generated debris, these damage level predictions serve as a foundation for the efficient and accurate estimation of debris. Overall, the proposed approach uses drones for rapid data collection and AI to automate damage detection and classification, which reduces the time required for debris estimation from days to a few hours as well as minimizes predictive uncertainty with crowdsourcing by up to 40%. A case study on Hurricane Laura in 2020 was conducted to validate the proposed approach. Findings of this study lead to predicting debris volume and composition with minimal errors, particularly for partially damaged buildings.

Wear characteristics evolution of helical gear with initial defects of bearing inner ring

This study investigated the wear characteristics and operational condition of gears with initial defects of the bearing inner ring. The working states of gears were evaluated through a combination of vibration signal analysis, wear debris concentration analysis, qualitative analysis of the wear debris, and tooth surface analysis. Based on the Hertz contact theory, a dynamic model for the gear drive system was constructed, enabling the simulation and comparison of vibration acceleration signals under normal and fault conditions. The research results revealed that bearing defects induced irregularities in vibration frequency and amplitude, adversely affecting the performance and stability of the gear system. Furthermore, these defects trigger the creation of substantial wear debris, which exacerbates gear wear and reduces the gear lifespan by about 15%. Additionally, bearing defects induced intermittent load spikes and uneven stress distribution across tooth contacts, resulting in localized high shear stresses, material flaking, and surface spalling. Consequently, initial defects of the bearing will accelerate gear wear progression and lead to abnormal wear patterns, potentially resulting in the premature failure of the gear train system. The study investigates the underlying mechanisms of gear wear evolution influenced by these defects and offers practical guidelines for the engineering, manufacturing, and maintenance of gear systems.

Geological genesis and identification of high-porosity and low-permeability sandstones in the Cretaceous Bashkirchik Formation, northern Tarim Basin

Abstract The genesis and prediction of high-porosity and low-permeability sandstone reservoirs are hot spots in oil and gas geology research worldwide. High-porosity and low-permeability sandstone reservoirs are developed in the Cretaceous Bashkirchik Formation of the Luntai Uplift in the northern Tarim Basin, China. In this article, we conducted a systematic study on the geological origin and logging identification of high-porosity and low-permeability tight sandstone based on core observation, thin section, logging index response, and mathematical discrimination methods. The results show that the K1bs sandstone segment in the study area generally contains calcium carbonate, which mainly comes from carbonate rock debris and calcite cement. Calcite cement mainly fills the pores between primary particles, and it is the main factor leading to the densification of the reservoir. The geological origin of the formation of low-permeability layer is mainly due to the early cementation of carbonate, and the development mode of the low-permeability layer is “high content of calcium debris → severe calcium cementation → poor petrophysical properties → formation of low-permeability layer.” The low-permeability layer has the characteristics of high gamma and high resistivity, and the multi-parameter discriminant method established based on the Fisher criterion has a good identification effect for the low-permeability layer. The low-permeability layer has a small thickness, poor stability and continuity, and strong longitudinal heterogeneity, thus it can form a low-permeability baffle inside the reservoir, which greatly reduces the oil and gas migration capacity.

Gujarat’s plastic plight: unveiling characterization, abundance, and pollution index of beachside plastic pollution

Plastic pollution poses a pervasive threat to ecosystems worldwide, jeopardizing marine life, contaminating water sources, and perpetuating a global environmental crisis. Spatial and temporal distribution of beach debris was quantitatively assessed on three recreational beaches in Gujarat State, India. A total of six debris categories were recorded with a mean of 0.9 items/m2 in number and 3.62 g/m2 in weight. A total of Mean debris concentrations and weight per debris item did not vary significantly between study sites. Highest debris concentrations were observed in October 2021 at all sites. Around 90% was macro-debris (2.5–100 cm), with white and transparent colours most frequently encountered. Based on Clean Coast Index findings, all sites were categorized as "dirty". Plastic Abundance Index revealed that all sites had a very high abundance of plastics compared to other beach debris. Recreational activities on beaches, tourism, and extensive fishing can be the possible source of marine debris on Gujarat State. The findings of the current investigation is vital to understanding its pervasive environmental impact, encompassing threats to biodiversity, water quality, and ecosystems, while guiding effective policies to mitigate these repercussions on a global scale. It can be helpful to establish mitigation strategies urgently required to reduce marine debris pollution along the Gujarat Coast. It is recomanded to implement urgently needed mitigation strategies to diminish marine debris pollution along the Gujarat Coast.

Content and Composition of Rock Debris at Lomonosov Ridge (83° N): Indication of Palaeoenvironmental Changes

Content and Composition of Rock Debris at Lomonosov Ridge (83° N): Indication of Palaeoenvironmental Changes

Asymmetry of hemispheric climate during MIS 16 versus MIS 12

Marine isotope stage (MIS) 16 (676-621 ka) and MIS 12 (478-424 ka) stand out as two significant glacial periods during the late Quaternary, demonstrating consistent continental ice volume or sea level, as discerned from benthic δ18O records. Intriguingly, the average sea surface temperature (SST) during MIS 16 surpasses that of MIS 12 by approximately 0.54–0.79 °C, while the atmospheric CO2 concentration during MIS 16 is approximately 16 ppmv lower than that of MIS 12. The underlying mechanism driving these discrepancies remains enigmatic. In this study, we present new high-resolution X-ray fluorescence (XRF) and grain size records covering the interval from 700 to 400 ka from Ocean Drilling Program (ODP) Site 1090 in the South Atlantic Ocean. We also integrated benthic δ13C, ice-rafted debris (IRD) and carbonate ion concentration ([CO32−]) records globally, to elucidate the distinct climate evolution during the MIS 16 versus MIS 12. Our findings suggest that MIS 12 is distinguished by a more substantial Antarctic ice-sheet, coupled with a weakened and/or equatorward displacement of southern westerly winds, and expansion of southern source water (SSW) alongside contractive northern source water (NSW). Conversely, the opposite climate state can be observed in MIS 16. The elevated atmospheric CO2 in MIS 12 and diminished atmospheric CO2 in MIS 16 may be attributed to reconfigurations in the ocean carbon reservoir regulated by the reorganization of deep-water masses and meridional ocean circulation, as a result of the divergent evolution of bipolar ice-sheets. Our study underscores the critical role of the interplay between the two polar regions in modulating deep-sea carbon storage on the orbital timescale and atmospheric CO2. This interplay is essential for a comprehensive understanding of past and future carbon cycle adjustments in response to climate change.

Evaluation of Sedimentary Characteristics of the Chang 9 Oil Layer Formation in the Yanchang Formation, Ordos Basin

Shallow-water deltas are a subject of sedimentary research and represent a significant target for oil and gas exploration. The Yanchang Formation of the Triassic in the Ordos Basin comprises numerous shallow-water delta blocks. This paper addresses the core issues pertaining to the sedimentary facies, sedimentary characteristics and sand body distribution of the Chang 9 oil layer formation of the Upper Triassic in the Ordos Basin. Guided by the relevant theories and methods of contemporary sedimentology and sedimentary geology, the reservoir characteristics are described and studied in detail through ordinary thin sections, cast thin sections, graphical representations of particle size and scanning electron microscopy experiments. The experimental results indicate that the porosity in the study area ranges from 3% to 12% and that the permeability is between 0 and 1.5 × 10−3 μm2, which is consistent with classification as an ultra-low-porosity and ultra-low-permeability reservoir. The Chang 9 sandstone is composed of feldspar sandstone and lithic feldspar sandstone. The average content of quartz is low, at less than 31%, while the average content of feldspar is high, at more than 34%. The average content of rock debris is between 10% and 20%. Therefore, the compositional maturity of the Chang 9 sand body is generally low. The particle size distribution exhibits a positive deviation, indicating that the sediments in the sand body are primarily coarse-grained components. The kurtosis of the particle size–frequency curve is observed to vary from flat to very sharp. The Chang 91 lake is classified as a shore shallow lake with basin subsidence and lake transgression. The Chang 9 period saw the development of the Chang 91 sedimentary facies into a semi-deep lake–deep lake environment. The vertical structural style of the Chang 9 oil layer formation in the basin can be roughly summarized into three basic structural types: the sedimentary structures observed in the area include box-shaped upward thinning, bell-shaped upward thinning and funnel-shaped upward thickening. The delta front area in Chang 9 is notable for its size and the prevalence of underwater distributary channel microfacies. The sand body distribution is stable, with sand layer thicknesses ranging from 15 to 30 m. The evaluation and summary of the sedimentary characteristics of the Chang 9 oil layer formation provide a geological basis for future exploration and development in the study area.

Experimental study on Local Scour around Bridge Pier Models generated by Flash Floods carrying Debris

The analysis of local scouring around bridge piers currently is based on typical river flood discharges. However, extreme events like flash floods with high velocity and discharge, carry wooden debris that accumulates upstream of the bridge pier. This results in additional forces due to flow diversion and reduction in flow area, so impacting hydraulic structures and exacerbating the scouring process. The study objective was to examine the impact of debris transported by flash floods on the depth and distribution patterns of scouring around bridge piers. This research was conducted in a 15.5-m-length, 0.5-m-width, and 1.0-m-height glass flume, layered by 25 cm thick of sand which is d50=0.52 mm and σg=2.327. Flash flood simulations were conducted by flowing the water mixed with debris content of 0, 5, 10, and 15% to hit a sharp nose pier model which is installed in the channel. Scour depth was measured using point gauges at 50 points around the pier. The findings indicated that an irregular distribution pattern of scour is formed around the pier, and scour depth decrease when increasing debris content. It is necessary to corrected in the range of 0.65-1.43 for 0-15% debris content carried by the flash flood compared to normal flood.

Deformation, Strength and Tectonic Evolution of Basal Ice in Taylor Glacier, Antarctica

AbstractObservation and measurements of ice structure and deformation made in tunnels excavated into the margin of Taylor Glacier, a polythermal glacier in the McMurdo Dry Valleys of Antarctica, reveal a complex, rapidly deforming basal ice sequence. Displacement measurements in the basal ice, which is at a temperature of −18°C, together with the occurrence of cavities and slickenslides, suggest that sliding or rapid deformation in thin zones of high shear occurs at structural discontinuities within the basal zone. Strain measurements show that the highest strain rates occur in ice with average debris concentrations of 26% followed by ice with debris concentrations of around 12%. The lowest strain rates occur in clean bubbly ice that has very low debris concentrations (<0.02%). Deformation within the basal ice sequence is dominated by simple shear but disrupted by folding which results in shortening of the debris‐bearing ice followed by attenuation of the folds due to progressive simple shear which generates predominantly laminar basal ice structures. About 60% of glacier surface velocity can be attributed to deformation within the 4.5 m thick sequence of basal ice that was monitored for this study, and 15% of motion can be attributed to sliding or very localized shear. The combination of high debris concentrations and high strain rates in the debris‐bearing ice results in high rates of abrasion and the production of striated and facetted clasts typical of temperate glaciers, even though the basal ice is at a temperature of −18°C.

Quantifying potential marine debris sources and potential threats to penguins on the West Antarctic Peninsula

Marine pollution is becoming ubiquitous in the environment. Observations of pollution on beaches, in the coastal ocean, and in organisms in the Antarctic are becoming distressingly common. Increasing human activity, growing tourism, and an expanding krill fishing industry along the West Antarctic Peninsula all represent potential sources of plastic pollution and other debris (collectively referred to as debris) to the region. However, the sources of these pollutants from point (pollutants released from discrete sources) versus non-point (pollutants from a large area rather than a specific source) sources are poorly understood. We used buoyant simulated particles released in a high-resolution physical ocean model to quantify pollutant loads throughout the region. We considered non-point sources of debris from the Antarctic Circumpolar Current, Bellingshausen Sea, Weddell Sea, and point source pollution from human activities including tourism, research, and fishing. We also determined possible origins for observed debris based on data from the Southern Ocean Observing System and Palmer Long-Term Ecological Research program. Our results indicate that point source pollution released in the coastal Antarctic is more likely to serve as a source for observed debris than non-point sources, and that the dominant source of pollution is region-specific. Penguin colonies in the South Shetland and Elephant Islands had the greatest debris load from point sources whereas loads from non-point sources were greatest around the southernmost colonies. Penguin colonies at Cornwallis Island and Fort Point were exposed to the highest theoretical debris loads. While these results do not include physical processes such as windage and Stokes Drift that are known to impact debris distributions and transport in the coastal ocean, these results provide critical insights to building an effective stratified sampling and monitoring effort to better understand debris distributions, concentrations, and origins throughout the West Antarctic Peninsula.

Ecological ramifications of marine debris in mangrove ecosystems: Estimation of substrate coverage and physical effects of marine debris on mangrove ecosystem in Negombo Lagoon, Sri Lanka

The adverse environmental impacts on mangrove ecosystems due to anthropogenic marine debris contamination have attracted public attention not only in Sri Lanka but worldwide. Therefore, quantification of marine debris in sensitive ecosystems like mangroves is critical to assess the impacts on ecosystem vitality and services. We conducted this study to assess the abundance and density of marine debris in Negombo lagoon, Western Province, Sri Lanka. We selected two sites (n = 2) using the purposive sampling technique. Marine debris cover and concentration were calculated to explore the extent of pollution from marine debris. The findings revealed that 9.83 ± 1.05 % of the substrate of the mangrove ecosystem is covered by debris. Nine types of marine debris were recorded, and a higher abundance belonged to single-use plastic items. A significantly higher debris cover was found in Kadolkele (18.80 ± 1.74 %, n = 120) than in Molekadolwetiya (0.85 ± 0.03 %, n = 120) (One-way ANOVA, p < 0.05). The study indicated that the mangroves in lagoon are highly polluted with marine debris and act as “litter catchers.” Correlation coefficient analysis was used to find the impact of debris cover on physical damage to roots, seedlings, and undergrowth vegetation. Correlation analysis revealed that physical damage to seedlings and branches/barks have a positive correlation with debris cover. To conserve these valuable coastal habitats in Negombo lagoon, it is recommended to take remedial measures to reduce arriving debris loads and to remove the debris present in mangroves.

Hotspots of Floating Plastic Particles across the North Pacific Ocean.

The pollution of the marine environment with plastic debris is expected to increase, where ocean currents and winds cause their accumulation in convergence zones like the North Pacific Subtropical Gyre (NPSG). Surface-floating plastic (>330 μm) was collected in the North Pacific Ocean between Vancouver (Canada) and Singapore using a neuston catamaran and identified by Fourier-transform infrared spectroscopy (FT-IR). Baseline concentrations of 41,600-102,700 items km-2 were found, dominated by polyethylene and polypropylene. Higher concentrations (factors 4-10) of plastic items occurred not only in the NPSG (452,800 items km-2) but also in a second area, the Papaha̅naumokua̅kea Marine National Monument (PMNM, 285,200 items km-2). This second maximum was neither reported previously nor predicted by the applied ocean current model. Visual observations of floating debris (>5 cm; 8-2565 items km-2 and 34-4941 items km-2 including smaller "white bits") yielded similar patterns of baseline pollution (34-3265 items km-2) and elevated concentrations of plastic debris in the NPSG (67-4941 items km-2) and the PMNM (295-3748 items km-2). These findings suggest that ocean currents are not the only factor provoking plastic debris accumulation in the ocean. Visual observations may be useful to increase our knowledge of large-scale (micro)plastic pollution in the global oceans.

Genetic mechanisms of high-quality tight siliciclastic reservoirs: A case study from the Upper Triassic Xujiahe Formation in the Yuanba area, Sichuan Basin, China

This study analyzed the petrological characteristics, diagenesis, pore types, and physical properties of the tight coarse-grained siliciclastic sequences in the third member of the Upper Triassic Xujiahe Formation (also referred to as the Xu-3 Member) in the western Yuanba area in the northeastern Sichuan Basin, China, based on the results of 242.61-m-long core description, 292 thin-section observations, scanning electron microscopy (SEM), and 292 physical property tests. The types and genetic mechanisms of high-quality tight coarse-grained siliciclastic reservoirs in this member was determined thereafter. The research objective is to guide the exploration and development of the tight coarse-grained siliciclastic sequences in the Xu-3 Member. The results of this study are as follows. Two types of high-quality reservoirs are developed in the coarse-grained siliciclastic sequences of the Xu-3 Member, namely the fractured fine-grained sandy conglomerate type and porous medium-grained calcarenaceous sandstone type. Hydrodynamic energy in the sedimentary environment is the key factor controlling the formation of high-quality reservoirs. These high-quality reservoirs are developed mainly in the transitional zone with moderately high hydrodynamic energy between delta-plain braided channels and delta-front subaqueous distributary channels. The dolomitic debris (gravel) content is the main factor affecting the reservoirs’ physical properties. The micritic algal debris and sandy debris in the dolomitic debris (or gravels) tend to recrystallize during burial, forming intercrystalline pores within. In the medium-grained calcarenaceous sandstones, intercrystalline pores in the dolomitic debris are formed at the early diagenetic stage, and a pore system consisting of structural fractures connecting intergranular pores, intergranular dissolution pores, and kaolinite intergranular micropores is developed at the late stage of diagenesis. The formation of intercrystalline pores in dolomite gravels and gravel-edge fractures, a pore system connected by gravel-edge and tectonic fractures, is closely related to the dolomite gravels in the sandy fine-grained conglomerates.

Impact of spheroidal graphite morphology on the functionalization of graphene oxide surface

This study conducted a comparative analysis of graphene oxide (GO) surfaces generated using the modified Hummers method at low temperature, employing spheroidal, flake, and micronized graphite with d50 values of approximately 49 µm, 330 µm and 7 µm, respectively. The characterization of the resulting GOs involved TGA, HRTEM, AFM, as well as UV–vis, FTIR, XPS and Raman spectroscopy. Spheroidal graphite produced GO sheets with a thickness of only 1 nm, displaying a zeta potential of −41 mV after 3 h of intercalation and oxidation reaction. In contrast, flake and micronized graphite also yielded 1-nm-thick GO sheets but exhibited a wider size distribution, with zeta potential values of −32 mV and −35 mV, respectively. Moreover, the GO surface derived from spheroidal graphite showed an increased presence of epoxy groups and a reduced concentration of oxidative debris compared to GOs from other graphite types. The curvature of graphite crystals within spheroidal graphite had a more pronounced impact on graphite oxidation than on graphene layer exfoliation. This research highlights the significance of considering graphite sheet curvature as a crucial variable in GO production, providing insights into the novel and noteworthy role that graphite sheet curvature can play in GO materials.

Investigation of Abundance and Spatial Distribution of Marine Debris on Ghanaian Urban Coastal Beaches

Marine debris has been identified as a form of pollution for more than half a century, and it is a major concern for the general public due to its detrimental effects on the environment and human health. The accumulation of marine debris not only affects the aesthetic appeal of our oceans but also poses a significant threat to safety. The impact of marine debris on the tourism industry, especially the eco-tourism sector, is a growing concern both locally and globally. The objective of this study was to conduct a comprehensive assessment of marine debris on three beaches of Ghana along the Gulf of Guinea. It sought to survey the spatiotemporal changes in the concentration of marine debris, quantify the perceptions of locals and beach users of marine debris, examine the citizen science perspectives on marine debris and finally analyse the effects of marine debris on coastal resources. The study employed a shoreline debris survey and citizen science approach to achieve this objective. Content analysis in NVivo was deployed to analyze transcriptions from the interviews. A standing stock beach survey was used to survey debris in 100 m2 quadrants for 30 occasions each for the three studied beaches at 12-day intervals, which spanned one year. Debris was classified and quantified according to the NOAA classification scheme for marine debris. The quantitative data generated were analyzed in SPSS 23.0 to establish debris abundance and spatiotemporal differences. Results revealed that plastics are the dominant debris type, accounting for 52% of the total debris surveyed, which was confirmed by the citizen science approach. Biriwa Beach had a minor debris abundance, statistically different from Abandze and Anomabo. The paper found significant seasonal differences in the concentration and spatial distribution of all debris types except for plastics and processed lumber. Respondents acknowledged the effects of marine debris on humans and the environment. The study recommends making adequate waste management infrastructure available in the area. NGOs and the Municipal Assembly should educate residents on effective mass participation in waste management practices to curb debris accumulation.

Sedimentary stratigraphy and provenance off Dronning Maud Land (East Antarctica) during the mid-Pleistocene transition: Implications for paleoclimate and ice dynamics

Glacial-marine sediments from the Antarctic continental margin provide a record of depositional environment, oceanographic variability and ice dynamics that is tapped with scientific ocean drilling. This study focuses on Ocean Drilling Program Core 693A-2R, a 9.7 m sediment core retrieved from near the continental margin of the Archean Grunehogna Craton in Dronning Maud Land (DML), East Antarctica. The results contribute to a better understanding of ice-shelf behavior in DML during the mid-Pleistocene transition (MPT), a well-known transition from 40-kyr to 100-kyr cycle periods. The age model, constructed based on Sr isotope stratigraphy and geomagnetic reversals, indicates that the core spans 1.20 to 0.65 Ma. The dynamic behavior of DML ice shelves with periodic iceberg calving is revealed by the glacial–interglacial variation in sedimentation patterns, with interglacials characterized by higher concentrations of ice-rafted debris (IRD) associated with enhanced paleoproductivity than glacial intervals. The responses of DML ice shelves to warm climates are represented by a prolonged interglacial period at 1.0–1.1 Ma (MIS 31–27) and significant interglacial expressions during MIS 19 and 17. The 40Ar/39Ar ages of individual ice-rafted hornblende grains are compared with the on-land geology of DML and neighboring regions to determine the provenances of IRD. Specifically, 40Ar/39Ar results record primarily late Neoproterozoic to Cambrian ages (600–400 Ma) with a predominant peak of 520–480 Ma. This Pan-African/Ross orogeny signature is very common in East Antarctica but is not found in the most proximal margin of the Grunehogna Craton, and is instead associated with the region of DML several hundred kilometers east of the deposition site. This indicates that significant discharges of icebergs occurred in the remote DML, which were then transported by the westward-flowing Antarctic Coastal Current to deposit IRD at the studied site during the MPT. This study establishes a confirmed MPT sedimentary sequence off DML, against which future MPT proxy records from the Weddell Sea embayment and other sectors in Antarctica can be compared and correlated, and provides a basis for more detailed analyses of the response of DML ice sheet to Pleistocene climate variations.

Microbes and microplastics: Community shifts along an urban coastal contaminant gradient.

Plastic substrates introduced to the environment during the Anthropocene have introduced new pathways for microbial selection and dispersal. Some plastic-colonising microorganisms have adapted phenotypes for plastic degradation (selection), while the spatial transport (dispersal) potential of plastic colonisers remains controlled by polymer-specific density, hydrography and currents. Plastic-degrading enzyme abundances have recently been correlated with concentrations of plastic debris in open ocean environments, making it critical to better understand colonisation of hydrocarbon degraders with plastic degradation potential in urbanised watersheds where plastic pollution often originates. We found that microbial colonisation by reputed hydrocarbon degraders on microplastics (MPs) correlated with a spatial contaminant gradient (New York City/Long Island waterways), polymer types, temporal scales, microbial domains and putative cell activity (DNA vs. RNA). Hydrocarbon-degrading taxa enriched on polyethylene and polyvinyl chloride substrates relative to other polymers and were more commonly recovered in samples proximal to New York City. These differences in MP colonisation could indicate phenotypic adaptation processes resulting from increased exposure to urban plastic runoff as well as differences in carbon bioavailability across polymer types. Shifts in MP community potential across urban coastal contaminant gradients and polymer types improve our understanding of environmental plastic discharge impacts toward biogeochemical cycling across the global ocean.

The effect of fine grits and fine debris concentrations on the MLVSS/MLSS ratio of an activated sludge system

This study embarks on an explorative investigation into the effects of typical concentrations and varying particle sizes of fine grits (FG, the involatile portion of suspended solids) and fine debris (FD, the volatile yet unbiodegradable fraction of suspended solids) within the influent on the mixed liquor volatile suspended solids (MLVSS)/mixed liquor suspended solids (MLSS) ratio of an activated sludge system. Through meticulous experimentation, it was discerned that the addition of FG or FD, the particle size of FG, and the concentration of FD bore no substantial impact on the pollutant removal efficiency (denoted by the removal rate of COD and ammonia nitrogen) under constant operational conditions. However, a notable decrease in the MLVSS/MLSS ratio was observed with a typical FG concentration of 20 mg/L, with smaller FG particle sizes exacerbating this reduction. Additionally, variations in FD concentrations influenced both MLSS and MLVSS/MLSS ratios; a higher FD concentration led to an increased MLSS and a reduced MLVSS/MLSS ratio, indicating FD accumulation in the system. A predictive model for MLVSS/MLSS was constructed based on quality balance calculations, offering a tool for foreseeing the MLVSS/MLSS ratio under stable long-term influent conditions of FG and FD. This model, validated using data from the BXH wastewater treatment plant (WWTP), showcased remarkable accuracy.

Investigation on wear behavior for SUS420 steel gear based on discrete laser surface melting

Gears are critical components that ensure the stable operation of a gearbox. In the era of mechanical equipment advancing towards higher speeds and heavier loads, more stringent requirements have been set for the wear performance of existing gears. Drawing inspiration from observations of natural organisms, particularly scallops, which have developed unique microstructure and excellent wear properties through long-term evolution, this paper focuses on the application of discrete laser surface melting (DLSM for short) technology to prepare units on the surface of SUS420 steel gears, simulating the radial rib structures found on scallop surfaces. The laser processing was carried out with varying defocusing amount and distribution types of discrete laser surface melted (DLSMed for short) units. The study encompassed microstructure observations, microhardness and residual stress testing, and bench wear experiments on DLSMed gears. The experimental findings reveal that a crack-free and porous-free hardened layer has formed on the tooth surface. The hardened layer consisted of the melting zone, heat-affected zone, and substrate, resulting in a surface structure characterized by alternating soft and hard phases. Comparing the wear behavior of as-received gear to DLSMed gears, it is evident that the wear damage on DLSMed gears is less pronounced. The DLSM treatment had altered the wear mechanism of the gears. During the wear test, the quantity of wear debris and iron (Fe) concentration in DLSMed gears consistently remained lower than that of as-received gears, indicating superior wear resistance in DLSMed gears. Furthermore, an increase in the defocus amount led to a deterioration in the wear performance of DLSMed gears. Notably, transverse units exhibited better efficacy in enhancing the wear resistance of gears compared to longitudinal units. There exists a positive correlation between the percentage of DLSMed unit area on the gear surface and the wear behavior of the gear.

In Situ Observation of Bubbles and the Effect of Ultrasonic Vibration on Bubble Behavior in EDM.

Accumulation and concentration of debris in deep hole electrical discharge machining (EDM) significantly hinder its machining efficiency and accuracy. It is believed that the movement of bubbles associated with the discharge gap flow field play a pivotal role in debris removal and influence the discharge conditions. Ultrasonic vibration (USV) of the electrode is thought to be an effective method for improving EDM-generated bubbles and debris exclusion. In this study, we first elucidated the behavior of bubbles during EDM of holes with varying aspect ratios. Subsequently, USV was introduced to EDM. The behavior of dielectric fluid flow under the influence of ultrasonic vibration was analyzed using computational fluid dynamics (CFD), which revealed time-varying changes in discharge gap flow pressure and velocity. The velocity of the dielectric flow field near the electrode's side face was found to reach a maximum of approximately 15.2 m/s, greatly facilitating debris removal. High-speed camera observations revealed that bubbles were dispersed within the side gap, with most of them adhering to the electrode's wall. Furthermore, the bubbles exhibited a tendency to continuously break up and coalesce near the hole's outlet before escaping in the USV-assisted EDM. These observed characteristics of bubble behavior under the influence of USV are expected to significantly enhance debris removal and promote efficient dielectric exchange.