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Abstract We successfully excite the multi-mode rain-wind induced vibrations (RWIVs) of a flexible stay cable in a wind tunnel by guiding water rivulets along the cable surface. The first, second and third mode RWIVs are excited respectively by increasing the incoming wind speed. The movement of upper rivulet during the first, second and third mode RWIVs are recorded with a high-speed camera. By employing a computer vision based recognition technique, the upper-rivulet dynamics of different modes of RWIVs are recognized and analyzed. The wake flow structures around the dry cable and the cable suffering from RWIVs are measured by using a particle image velocimetry (PIV) system. Experiment results show that the oscillation frequency of the upper rivulet is synchronized with the cable vibration frequency for the first, second and third mode RWIVs. Based on experiment results, bubble burst is proposed as a possible mechanism for the excitation of RWIVs. [ABSTRACT FROM AUTHOR]

Heavy metal contamination of soils has been a global environmental issue over the past decades, threatening food security and human health. Understanding the migration and transformation of heavy metals in soils is critical for restoring an impaired environment and developing sustainable agriculture, particularly in the face of global warming. However, little effort has been devoted to investigating the impact of elevated temperatures on the migration and distribution of exogenous heavy metals in soils. This study experimented with a 180-day incubation at 15 °C, 30 °C, and 45 °C with an arable soil (Alfisol) of Huang-Huai-Hai River Basin, China, which was initially spiked with copper (Cu). A comparison of the results revealed that the percentage of soil water-soluble Cu doubled at 45 °C compared with 15 °C. The percentage of protein-like substances in dissolved organic matter (DOM) was the highest at 45 °C, suggesting that proteinaceous components play a more significant role in controlling the dissolution of Cu into DOM. Moreover, by sequential extraction and micro-X-ray fluorescence (μ-XRF), Cu was facilitatively transformed from exchangeable, and specifically adsorbed fractions, to iron (Fe)/manganese (Mn) oxides bound species by 7.75% 23.63% with the elevation of temperature from 15 °C to 45 °C. The conversion of Cu speciation is attributed to the significant release of organic carbon from Fe/Mn oxides, especially the Mn oxide components, which are available for Cu binding. The findings of this work will provide an in-depth understanding of the fate of Cu in soils, which is fundamental for the risk assessment and remediation of Cu-polluted soils in the Huang-Huai-Hai River Basin under the context of global warming. [Display omitted] • Warming enhanced Cu transformation to soil solution and solid phases. • The proteinaceous components control the binding of Cu with soil DOM. • The release of OC from Fe/Mn oxides offered the binding sites for Cu. • The μ-XRF provided direct evidence for the formation of stable Cu in soil. [ABSTRACT FROM AUTHOR]

In the present study, a coupled wake oscillator dynamic equation was established to predict the vortex-induced vibration (VIV) response of a circular cylinder immersed in a fluid. A classical structural dynamic equation was applied to describe the one-degree-of-freedom vibration of a circular cylinder. The revised van der Pol equation was used to model the wake flow dynamics and the fluctuating aerodynamic force derived from periodic alternating vortex shedding. The coupled structural dynamic equation and revised van der Pol equation were utilized to describe the features of VIV, such as the frequency component of aerodynamic forces, vibration amplitude, and lock-in domains. The results show that the proposed model can more precisely predict the VIV response and frequency features. An experiment was performed to study the passive jet flow control for VIV of a circular cylinder. The surface pressure distribution was measured to obtain the sectional aerodynamic forces acting on the model containing passive jet rings with different distances. The influencing range of the aerodynamic force caused by the passive jet rings was obtained and incorporated into the coupled model. The revised coupled model was found to predict well the VIV response of a circular cylinder equipped with adjacent passive jet rings having different distances. • The improved model is successfully to model the completely dominant frequency component for the lift force acting on circular cylinder. • The coupled model can predict the oscillation amplitude and lock-in of vortex induced vibration (VIV) of circular cylinder. • Revised coupled model commendably predict the control effectiveness for VIV of circular cylinder equipped with passive jet ring. [ABSTRACT FROM AUTHOR]

It is widely known that watershed hydrology is dependent on many factors, including land use, climate, and soil conditions. But the relative impacts of different types of land use on the surface water are yet to be ascertained and quantified. This research attempted to use a comprehensive approach to examine the hydrologic effects of land use at both a regional and a local scale. Statistical and spatial analyses were employed to examine the statistical and spatial relationships of land use and the flow and water quality in receiving waters on a regional scale in the State of Ohio. Besides, a widely accepted watershed-based water quality assessment tool, the Better Assessment Science Integrating Point and Nonpoint Sources (BASINS), was adopted to model the plausible effects of land use on water quality in a local watershed in the East Fork Little Miami River Basin. The results from the statistical analyses revealed that there was a significant relationship between land use and in-stream water quality, especially for nitrogen, phosphorus and Fecal coliform. The geographic information systems (GIS) spatial analyses identified the watersheds that have high levels of contaminants and percentages of agricultural and urban lands. Furthermore, the hydrologic and water quality modeling showed that agricultural and impervious urban lands produced a much higher level of nitrogen and phosphorus than other land surfaces. From this research, it seems that the approach adopted in this study is comprehensive, covering both the regional and local scales. It also reveals that BASINS is a very useful and reliable tool, capable of characterizing the flow and water quality conditions for the study area under different watershed scales. With little modification, these models should be able to adapt to other watersheds or to simulate other contaminants. They also can be used to study the plausible impacts of global environmental change. In addition, the information on the hydrologic effects of land use is very useful. It can provide guidelines not only for resource managers in restoring our aquatic ecosystems, but also for local planners in devising viable and ecologically-sound watershed development plans, as well as for policy makers in evaluating alternate land management decisions. [Copyright &y& Elsevier]

An experimental investigation was carried out on the effects of attachments on the aerodynamic characteristics and vortex-induced vibration (VIV) of a twin-box girder. In the study, the flow pattern, pressure distribution, vortex shedding frequency, and VIV of five models, namely Model A (twin-box girder without attachments), Model B (twin-box girder with handrails and crash barriers), Model C (twin-box girder with handrails, crash barriers, and wind barriers), Model D (twin-box girder with maintenance rails), and Model E (twin-box girder with full ancillaries), are compared with a bare deck in detail. The results demonstrate that, owing to the large leading flow separation induced by the attachments, the flow characteristics and VIVs of the twin-box girder with attachments differ considerably from the bare twin-box girder. Because of the large porous ratio, the handrails and crash barriers exert relatively weak influences on the surface pressure distribution. However, the leading wind barrier and maintenance rail generate large flow separation at the leading edges, resulting in larger pressure fluctuations, a wider wake, and larger scale vortex with lower shedding frequency than that of the bare deck. Furthermore, owing to the large leading flow separation, the vertical VIV induced by the motion-induced vortex in the gap is suppressed. However, a torsional VIV is generated by the large-scale alternately shedding vortex in the wake of the downstream box girder. [ABSTRACT FROM AUTHOR]

Experiments are performed on three spring-supported separated-box girder section models in a closed wind tunnel to investigate the vortex-induced vibration (VIV) characteristics. A particle image velocimetry (PIV) instrument is employed to obtain the flow field around the models. Four VIV-sensitive velocity intervals are observed for the test model, in which vertical and torsional oscillations are repeatedly induced. Comparisons with the control groups show that vortex shedding in the gap is the crucial factor that induces VIVs. Wake-induced vibration (WIV) is observed to occur with VIV in the gap, accompanied by a dramatic magnification in vibrational amplitude. The WIV becomes weaker and disappears as the wind velocity increases, and the wake vortex-shedding mode changes from the classic 2 S mode to a 2(2 S ) mode. The vortex-shedding frequency shows that it is a special lock-in mode of 1:2 phase-locking, which is found by taking the vibrating model and vortex-shedding as two coupled oscillators. [ABSTRACT FROM AUTHOR]

Traditional manual visual inspections have demonstrated certain shortcomings in post-earthquake assessment of urban buildings, such as being time-consuming and laborious. In contrast, computer vision (CV) and unmanned aerial vehicle (UAV) approaches have revealed competitive potentials in the fields of automatic data acquisition, data processing, and autonomous decision-making. In UAV images, structural components of post-earthquake buildings often present different scales, which are affected by different local damage. Therefore, acquiring the feature information of structural components has precisely been significant for refined damage assessment of post-earthquake buildings. This study proposes a geometry-informed deep learning-based structural component segmentation of post-earthquake buildings. An Enhanced UNet model is established with a new synthetical loss function containing the geometric consistency (GC) term. Given an edge closure of a connected domain for homogeneous structural components, the GC term comprises split line loss and area loss to adapt to the circumference and area constraints of each component region. The Enhanced UNet network is designed to improve the extraction capability of high-level features, and it includes six encoder stages (superior to five in the original version), of which the bottom four stages have many convolution layers, and five corresponding decoders. The investigated synthetic QuakeCity dataset includes 4,809 images with a resolution of 1,920 × 1,080 pixels. Training and test results reveal that compared to the original UNet, the proposed method achieves a more stable training process and higher test accuracy for structural component segmentation. The proposed method can achieve a mIoU of 97.97 %, which is 1.29 % higher than that of the original UNet. In addition, misrecognition of inner voids inside structural components is addressed, which further validates the optimization efficiency of the proposed geometric constraints. Ablation experiments are conducted to confirm the effectiveness of the proposed GC loss and Enhanced UNet network. The proposed method shows good generalization ability in robustness tests in complex real-world scenarios under various disturbances, including abnormal exposure and rain lines in various intensities. [ABSTRACT FROM AUTHOR]

The rice-crayfish co-culture (RC) is a putative sustainable agricultural system. However, studies on the ecological effects of long-term RC systems were still lacking. Here, we compare enzymatic stoichiometry, microbial necromass, and microbial community between the RC and rice monoculture systems (RM). Soil enzymatic stoichiometry analysis showed that after transformation from RM to RC for about three years, ammonium nitrogen (NH 4 +-N) availability increased to depress relative N-acquiring enzyme production, especially for leucine aminopeptidase. The contents of microbial necromass increased approximately onefold in the RC system, making microbial necromass' contribution to the soil nitrogen (N) reach up to 46.72%. Elevation in NH 4 + decreased N-acquiring enzyme, and a relatively more effective C acquisition likely benefited microbial necromass retention and production in the RC system. This study highlights that the rice-crayfish co-culture could modify the N pool of the surface paddy soil. • 1: Microbial necromass N increased under rice-crayfish co-culture (RC). • 2: Rice-crayfish co-culture increased N availability to reduce LAP activity. • 3: Higher EEA C:N benefited microbial necromass retention. [ABSTRACT FROM AUTHOR]

Abstract: Stationary and dynamic wind tunnel tests of twin box girders with a space ratio of L/D=1.70 have been performed in this study. The vortex-shedding phenomenon under stationary and dynamic conditions and vortex-induced vibration are observed and analyzed. The results indicate that regular vortex shedding occurs only at the trailing edge of the downstream box girder under stationary conditions. Although the strength of the vortex is very weak under stationary conditions, it gives rise to vortex-induced vibrations with a lock-in range of 0.570≤U r ≤0.668 in dynamic testing. The higher harmonics of wind speed around the body is observed and is attributed to nonlinear effects from aerodynamic forces. To further study the flow characteristics around the twin box girder when undergoing vortex-induced vibration, a hybrid method combining experiments with numerical simulations is employed. The pressure distributions, energy transfer between the flow and motion of the body, and evolution of flow patterns over vortex-induced vibration process are analyzed based on the computational results. The results indicate that with an increase in oscillation amplitude, strong vortices form in the gap between the two box girders. These vortices impinge on the windward wall of the downstream box girder and cause the flow to separate and re-attach periodically around the windward corners of the downstream box girder. Based on the analysis of the vortices in the gap, five control measures are used in the wind tunnel test to suppress the vortex-induced vibration of the twin box girders, and the most effective control scheme is obtained. [Copyright &y& Elsevier]

Deciphering the pivotal components of nutrient metabolism in compost is of paramount importance. To this end, ecoenzymatic stoichiometry, enzyme vector modeling, and statistical analysis were employed to explore the impact of exogenous ore improver on nutrient changes throughout the livestock composting process. The total phosphorus increased from 12.86 to 18.72 g kg−1, accompanied by a marked neutralized pH with ore improver, resulting in the Carbon-, nitrogen-, and phosphorus-related enzyme activities decreases. However, the potential C:P and N:P acquisition activities represented by ln(βG + CB): ln(ALP) and ln(NAG): ln(ALP), were increased with ore improver addition. Based on the ecoenzymatic stoiometry theory, these changes reflect a decreasing trend in the relative P/N limitation, with pH and total phosphorus as the decisive factors. Our study showed that the practical employment of eco stoichiometry could benefit the manure composting process. Moreover, we should also consider the ecological effects from pH for the waste material utilization in sustainable agriculture. [Display omitted] • Ore improver significantly enhanced total phosphorus from 12.86 to 18.72 g kg−1. • Ore improver notably affected compost pH. • Ore improver decreases microbial enzyme activity and alleviate nutrient limitation. • Ore improver significantly increased the potential C:P and N:P acquisition ratios. • pH and P fractions dominate the metabolic limitation of compost microbes. [ABSTRACT FROM AUTHOR]

Neuropathic pain (NP) is a frequent finding in patients diagnosed with spinal cord injuries (SCIs). To improve our understanding of the maladaptive changes taking place in the lumbar spinal cord that can lead to the development of NP and to find alternative options to treat this condition, we aimed to investigate the effects of voluntary exercise on NP after SCI and to elucidate its potential mechanisms. A rat model of post-SCI NP induced by compression of the posterior or lateral cervical spinal cord was used to evaluate the effects of voluntary exercise by measuring the bilateral withdrawal of the hind paws using the Von Frey filament and Hargreaves tests. The place escape/avoid paradigm was used to evaluate supraspinal pain processing and somatosensory evoked potentials (SEPs) were used to examine disturbances in proprioception. Locomotor function was evaluated using Basso, Beattie, and Bresnahan (BBB) scoring. Pathologic findings in hematoxylin and eosin-stained tissue and magnetic resonance imaging were used to evaluate the morphological changes after SCI. The lesion size within the cervical spinal cord was evaluated by staining with Eriochrome cyanine R. Quantitative polymerase chain reaction and immunohistochemistry were used to assess the expression of calcitonin gene-related peptide (CGRP) and ionized calcium-binding adapter molecule 1 (Iba-1) in the lumbar dorsal horns. All injured rats developed mechanical hypersensitivity, hyposensitivity, and thermal hyperalgesia in the contralateral hind paws at 1 week post-injury. Rats that underwent lateral compression injury developed NP in the ipsilateral hind paws 1 week later than rats with a posterior compression injury. Our findings revealed that voluntary exercise ameliorated mechanical allodynia and thermal hyperalgesia, and significantly improved proprioception as measured by SEP, but had no impact on mechanical hypoalgesia or motor recovery and provided no significant neuroprotection after recovery from an acute SCI. SCI-induced NP was accompanied by increased expression of CGRP and Iba-1 in the lumbar dorsal horn. These responses were reduced in rats that underwent voluntary exercise. Voluntary exercise ameliorates NP that develops in rats after compression injury. Increased expression of CGRP and Iba-1 in the lumbar dorsal horns of rats exhibiting symptoms of NP suggests that microglial activation might play a crucial role in its development. Collectively, voluntary exercise may be a promising therapeutic modality to treat NP that develops clinically in response to SCI. • Voluntary exercise ameliorates NP that develops in rats after compression cervical SCI; • SCI-induced NP was accompanied by increased expression of CGRP and Iba-1 in the lumbar dorsal horn; • Increased expression of CGRP and Iba-1 were reduced in rats that underwent voluntary exercise; • Voluntary exercise may be a promising therapeutic modality to treat NP that develops clinically in response to SCI. [ABSTRACT FROM AUTHOR]

As the portal of plants, rhizosphere microorganisms play an essential role in controlling the species, transformation, and bioavailability of heavy metals, yet the potential passivation mechanism is still unclear. In this study, two heavy metal resistant and growth-promoting rhizosphere bacteria were screened, and their mechanisms in dealing with external stress and immobilizing heavy metal were explored. The results showed that heavy metals inhibited the ability of Pseudomonas sp. H13 and Brevundomonas sp. H16 to promote plant growth, but stimulated the production of extracellular polysaccharides and inorganic labile sulfide, and enhanced biofilm formation, thereby significantly improved the removal efficiency of Cu2+, Zn2+, Cd2+, and Pb2+. Compared with H16, the biofilm of H13 disintegrated rapidly in the later stage, so more metal ions were adsorbed on the planktonic cells. The C–OH and P O groups related to polysaccharides play a crucial role in heavy metal adsorption, and the immobilization mechanism of the planktonic cell is mainly ion exchange and group complex, but for H16, intracellular enrichment cannot be ignored. Functional group complexes played a dominant role in biofilm, and the immobilized heavy metals were more difficult to release into the environment. This study highlighted the potential application prospects of biofilm bacteria in heavy metal remediation and explained the reactive barrier of rhizosphere bacteria to heavy metals. [Display omitted] • H13 and H16 produced more inorganic sulfide and exopolysaccharide under heavy metal. • The formation of biofilm improves the removal of heavy metals. • Physisorption and ion exchange dominated the adsorption of planktonic cells. • Biofilm has a more robust immobilization capacity for heavy metal ions. • Reactive barrier is an ideal way of bioremediation. [ABSTRACT FROM AUTHOR]

Two vortex-induced vibration (VIV) events of the main girder of long-span bridges successively happened on the Yingwuzhou suspension bridge and Humen suspension bridge in China, 2020, and drew public attention. Especially for the Humen suspension bridge, the amplitude of VIV was so notable that the traffic was closed for 10 days. Generally, VIV is sensitive to the structural and ambient issues and large-amplitude VIV is unacceptable for engineering structures as it could result in potential fatigue failure of some key joint components. Therefore, it is of great significance to explore the excitation mechanism of VIV and develop effective methods to mitigate excessive vibration of main-girders. From the perspective of vortex dynamics, we present a selective review of recent progress on the mechanism of VIV occurred in long-span bridges and aerodynamic countermeasures to attenuate the VIV amplitude. Notwithstanding the VIV mechanism of girders has not been thoroughly clarified, it is generally accepted that VIV rises from the unsteady vortex shedding from the main girder. Besides, the flow control methods, which are proposed to manipulate the surrounding flow patterns around the girder, are also focused in this review. Some perspectives are finally presented for future studies in fluid–structure interaction and aerodynamic vibration mitigation of long-span bridges. [ABSTRACT FROM AUTHOR]