Propagation Path Research Articles

Serratia marcescens outbreak in a neonatal intensive care unit associated with contaminated handwashing sinks

PurposeThis article describes the origin of a S. marcescens outbreak in a neonatal intensive care unit (NICU). Materials and methodsA retrospective case-control study including 12 S. marcescens-positive and 22 S. marcescens-negative neonates in the NICU was performed to identify the source of the outbreak. S. marcescens isolates were collected during the outbreak and analyzed using whole-genome sequencing (WGS). IQ-Tree software, BEAST2 software package and SCOTTI software were used to construct a phylogenetic tree and a propagation path map. ResultsThe index case occurred on February 21st and outbreak ended on March 9th, 2021, affecting a total of 12 neonates (2 with S. marcescens infection and 10 with S. marcescens colonization). Multivariate logistic regression identified that the distance of <0.8 m between the bed unit and the sink (odds ratio [OR], 20.50; 95 % confidence interval [CI], 1.09–384.86), a large number of rotating nurses within a week (OR 2.58, 95 % CI, 1.09–6.11) and use of humidification water in the incubator (OR 189.70, 95 % CI, 2.76–13027.31) were significant increased risk factors for S. marcescens infection or colonization in the outbreak. WGS sifted out a predominant clone between contaminated handwashing sinks and patients, suggesting that cross-transmission was involved in the dissemination of S. marcescens. ConclusionContaminated handwashing sinks can be a communication intermediary of S. marcescens infection or colonization of neonates in the NICU. A distance of <0.8 m between the bed unit and the sink, and a large number of rotating nurses might play important roles in this outbreak. Attention should be paid to sinks contamination and contact transmission to prevent outbreaks.

Employing stable isotopes to reveal temporal trajectories of water travelling through the soil–plant-atmosphere continuum

The spatiotemporal patterns of water travelling through the soil–plant-atmosphere continuum (SPAC) have received much attention due to the frequency of extreme weather and water scarcity. However, the interconnections and transboundary transport of specific compartments within the hydrologic cycle are poorly understood. We portrayed the propagation paths of water isotope signals by analyzing isotopes of precipitation, soil water, and xylem water. The isotope sine curves analysis method was improved to quantify water transfer efficiency, mean transmission time from precipitation to soil (MTT1), mean transmission time from soil to trees (MTT2), mean residence time within soil (MRTSW), and mean residence time within tree xylems (MRTXY). The temporal trajectory of water traveling through SPAC was depicted, and its influencing factors and intrinsic mechanisms were explored. Our results showed that (1) water isotopes were blocked when crossing water pools (precipitation, soil water, and xylem water) and the transfer efficiency was progressively weaker (85.5 %→13.5 %). (2) The MTT1 was significantly and positively correlated with soil porosity (Spearman correlation coefficient, 0.551). Its spatiotemporal pattern (0.8–15.9d) indicated that the transport and mixing of soil water involved two modes: displacement flow and bypass flow. The MTT2 (−13.2d–4.3d) of Platycadus orientalis was in general smaller than that of Quercus variabilis (−4.7d–11.5d). (3) The MRT (35.2d–343.8d) was influenced by a combination of soil physicochemical properties, root distribution, and tree morphological traits. Our study shows that connectivity between pools is better reflected with transfer efficiency. Comparing MTT and MRT of P. orientalis and Q. variabilis, tree hydrodynamic processes were quantified, and P. orientalis was more sensitive to seasonal moisture variability. Additionally, our study improved the understanding of the “black box” within the hydrological interface of plant-soil interactions.

Influence of Spatially Varied Soil Property on Train-Induced Soil-to-Column Vibration Transmission

The proximity of residential areas to traffic corridors has raised concerns among researchers regarding train-induced vibrations. Experimental studies have consistently shown variations in train-induced vibrations, which can be attributed to uncertainties and randomness in both the vibration source and propagation path. This study aims to investigate the influence factors and quantify their contributions to train-induced vibration variations through a comprehensive field measurement campaign and numerical simulations using random finite element models. During the field measurements, vibrations were recorded at the ground surface and the column base for a total of 53 passbys of the same type of metro train on parallel rail lines. Variations in train-induced vibrations caused by the source-to-receiver distance and spatially varied soil properties were analyzed and compared. Specifically, the investigation focused on the spatial variation of soil properties including elastic modulus, density and damping ratio in the topsoil and the second layer of clay, while simultaneously considering the influence of spatial variations of all three soil properties on the transmission of train-induced vibrations from the surface soil to the structural columns. Understanding these variations is crucial for the probabilistic assessment of building serviceability during train passbys. The findings of this research provide valuable insights for probabilistic prediction and evaluation of building vibration comfort.

Virtual resection evaluation based on sEEG propagation network for drug-resistant epilepsy

Drug-resistant epilepsy with frequent seizures are considered to undergo surgery to become seizure-free, but seizure-free rates have not dramatically improved, partly due to imprecise intervention locations. To address this clinical need, we construct effective connectivity to reveal epilepsy brain dynamics. Based on the propagation path captured by the high order effective connectivity, calculate the control centrality evaluation scheme of the excised area. We used three datasets: simulation dataset, clinical dataset, and public dataset. The epileptogenic propagation network was quantified by calculating high-order effective connection to obtain accurate propagation path, based on this, combined with the outdegree index for virtual resection. By removing electrodes and recalculating control centrality, we quantify each electrode or region’s control centrality to evaluate the virtual resection scheme. Three datasets obtained consistent results. We track the accurate propagation path and find the obvious inflection points occurring during the excision process. The minimum intervention targets were obtained by comparing different schemes without recurrence. The clinical data with multiple seizures found that after resection, the brain reaches a stable state and is less likely to continue spreading. By quantitative analysis of control centrality to evaluate the possible excision scheme, finally we obtain the best intervention area for epilepsy, which assist in developing surgical plans.

Ultra-thin low-frequency broadband absorber based on layered coiled channel structure

To improve and broaden the performance in absorbing sound waves of metamaterials at the lower and mid-frequency ranges, a layered coiled channel composite structure (LCCS) with deep subwavelengths is proposed in this paper, which extends the acoustic wave propagation paths longitudinally by connecting the Helmholtz resonator channels in each layer and achieves the multistep resonance of the coupling cavities, which results in the cancellation of acoustic energies, reduces the acoustic reflections and scattering, and enhances the absorption performance. A model to simulate theoretical sound absorption and finite elements simulation of the metamaterial were evolved to reveal its potential mechanismfor absorbing sound. Using the single-variable method to study the impact of altering structural parameters on the effectiveness of sound absorption, it shows good tunability in the target frequency range and obtains four fundamental unit LCCSs having distinct frequency absorption peaks, and designs a multi-unit coupling construction having low frequencies wideband sound absorption performance by connecting them in parallel to realize a large-broadband continuous and high-efficiency sound absorption within the scope of 370–1400 Hz, using a mean peak sound absorption value higher than 0.7. The structure was put together by 3D printing, and the impedance tube method test verified the precision of the simulation’s findings. This study offers a practical means to create lightweight, low-frequency broadband acoustic absorbing metamaterials.

Fatigue Fracture Mechanism and Life Prediction of TA1 Titanium Alloy Clinched Joints

ABSTRACTThis study investigated the fatigue fracture mechanisms and life prediction of clinched joints made from titanium alloy TA1. The fatigue tests revealed that TA1 titanium alloy clinched joints exhibited failure characterized by fracture of the lower plate at three distinct fatigue load levels. Additionally, finite element analysis indicated that cold work hardening enhanced the fatigue performance of these joints. Observations of fracture surfaces using scanning electron microscopy identified the crack source and its propagation path, which correlated with the location of maximum principal stress from the finite element simulations. Fretting wear was also observed in this critical region. Furthermore, fatigue life predictions for TA1 titanium alloy clinched joints were made using Paris' law and the local strain approach. Both methods closely matched experimental results across different fatigue life intervals. Overall, the local strain approach exhibited superior predictive capability compared to Paris' law, taking into account various influencing factors.

Machine learning-based intelligent localization technique for channel classification in massive MIMO

Multiple-input multiple-output (MIMO) technology has been widely adopted in wireless communications, which enables the simultaneous transmission of multiple data streams via multiple transmitting and receiving antennas. In a MIMO system with non-line-of-sight (NLOS), transmitted signals are reflected by various obstacles along the path, reaching the antenna at different angles and times. In 5G networks, the NLOS problem is a major challenge for massive MIMO localization, significantly reducing positioning accuracy. In this work, an intelligent localization technique based on NLOS identification and mitigation is proposed to address this problem. In this solution, a Convolutional Neural Network (CNN) based hybrid Archimedes-based Salp Swarm Algorithm (HASSA) technique is proposed to detect NLOS or the line of sight (LOS) and estimate the location. The accuracy can be analyzed by considering the angle of arrival of signals, threshold-based time of arrival, and time difference of arrival from different antennas. A novel reinforcement learning-based optimization approach is used for the mitigation of NLOS in the radio wave propagation path, which in turn reduces the computational complexity. We use the Ensemble Deep Deterministic Policy Gradient-Based Approach (EDDPG)-based Honey Badger algorithm (HBA) for the aforementioned process. The simulation of this approach assesses diverse scenarios and considers different parameters, and the approach is compared with various state-of-the-art works. From the simulation results, our proposed approach can be used for the identification and detection of LOS and NLOS components and can precisely enhance the localization compared with other approaches.

Measurement of surface rectangular defect depth based on laser-excited transmitted surface waves

ABSTRACT In order to study the effect of laser-excited surface waves on the transmission of surface rectangular defects, the transmission information of surface waves is used to achieve the quantitative calculation of defect depth. In this paper, the finite element method is employed to analyse the transmission process of laser-excited surface waves on rectangular defects. Subsequently, the influence of the front and back edges of rectangular defects on the transmission of surface waves is examined, and the formation mechanisms of feature points in the time-domain signals at detection points are elucidated. Ultimately, the calculation formula for defect depth is derived on the basis of the propagation path of each component after transmission. The experimental results are consistent with the simulation results, and the relative error of the surface rectangular defect depth calculation is within 9%. The validation of the proposed method on homogeneous isotropic metallic materials demonstrates the effectiveness and applicability of the proposed method. These results will provide a reliable method for characterising the depth of rectangular defects on surfaces by laser ultrasonic technology.

Role of trophic interactions in transfer and cascading impacts of plant protection products on biodiversity: a literature review.

Plant protection products (PPPs) have historically been one of the classes of chemical compounds at the frontline of raising scientific and public awareness of the global nature of environmental pollution and the role of trophic interactions in shaping the impacts of chemicals on ecosystems. Despite increasingly strong regulatory measures since the 1970s designed to avoid unintentional effects of PPPs, their use is now recognised as a driver of biodiversity erosion. The French Ministries for the Environment, Agriculture and Research commissioned a collective scientific assessment to synthesise the current science and knowledge on the impacts of PPPs on biodiversity and ecosystem services. Here we report a literature review of the state of knowledge on the propagation of PPP residues and the effects of PPPs in food webs, including biopesticides, with a focus on current-use PPPs. Currently used PPPs may be stronger drivers of the current biodiversity loss than the banned compounds no longer in use, and there have been far fewer reviews on current-use PPPs than legacy PPPs. We first provide a detailed overview of the transfer and propagation of effects of PPPs through trophic interactions in both terrestrial and aquatic ecosystems. We then review cross-ecosystem trophic paths of PPP propagation, and provide insight on the role of trophic interactions in the impacts of PPPs on ecological functions. We conclude with a summary of the available knowledge and the perspectives for tackling the main gaps, and address areas that warrant further research and pathways to advancing environmental risk assessment.

A data-driven prediction for concrete crack propagation path based on deep learning method

Accurate and efficient prediction of concrete crack propagation path facilitates timely maintenance. To avoid errors arising from assumptions in physical models and parameter measurements, a data-driven prediction method for concrete crack propagation path is proposed. The spatio-temporal prediction approach is presented by unifying the conditional Generative Adversarial Network and Long Short-Term Memory Network (UcGLS-Net). The UcGLS-Net has the advantage of enabling temporal (by Long Short-Term Memory Network, LSTM) and spatial information (by the conditional Generative Adversarial Network, cGAN) in the concrete crack propagation process to be treated simultaneously and distinctly thus improving prediction accuracy. Notably, results demonstrate that UcGLS-Net still works in crack propagation path prediction even with unknown aggregate distribution. Moreover, the effects of historical input quantity and prediction intervals on prediction accuracy of the UcGLS-Net are studied and the network framework is optimized. Due to high efficiency, this study provides a new adaptable and real-time prediction method for concrete crack propagation path, offering support for the design, damage prediction, assessment, and maintenance of concrete structures.

Inline UV pulse synthesizer

We demonstrated an inline synthesizer for generating ultrashort pulses in the ultraviolet (UV) range. The inline UV pulse synthesizer comprised three nonlinear crystals located in the propagation path of the fundamental driving laser pulse. Second-harmonic signals with central wavelengths of 420, 375, and 345 nm were generated in turn in the three BBO crystals, resulting in a synthesized UV pulse subsequent to the final nonlinear crystal. Its temporal amplitude and phase could be manipulated easily by changing the relative positions of the crystals, allowing for flexibility of the waveform. The minimum pulse duration of the synthesized UV pulse was 4.7 fs, which was close to the Fourier-transform-limited pulse duration. This ultrashort UV pulse with 19 μ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\upmu$$\\end{document}J energy can be utilized in various applications such as high harmonic generation and frustrated tunneling ionization.

Long-term corrosion protection of reinforcing bars via a self-responsive coating incorporating ZrP functional fillers

The conventional coating of reinforcing bars exhibits inadequate anti-corrosion efficacy stemming from a non-specific, blind protection mechanism, poses a threat to the durability of concrete. We devised a novel self-responsive functional filler, L-arginine (LA) intercalated zirconium phosphate (LCZrP), synthesized via an intercalation reaction. This innovative filler was seamlessly integrated into an epoxy (EP) resin matrix, yielding a smart anticorrosive coating that harmoniously combines active and passive corrosion protection strategies. The integration of LCZrP within the coating matrix serves a trifecta of purposes: it extends the corrosion propagation path, effectively disperses nanofiller agglomeration, and enhances interfacial adhesion with the epoxy coating. Critically, the controlled release of corrosion inhibitors from the interlayer further fortifies the coating's resistance to corrosion, imparting a multi-layered protective shield. After enduring a 60-day immersion in a simulated concrete pore solution, the LCZrP/EP coating demonstrated exceptional durability, maintaining a low-frequency impedance modulus value consistently within the range of 4.27×1010 to 5.12×1010 Ω·cm2, marking a remarkable 34-fold enhancement over the performance of the epoxy coating alone. This breakthrough underscores the LCZrP/EP coating's potential as a groundbreaking solution for reinforcing bar protection in concrete, harnessing the complementary strengths of epoxy resin's physical barrier, the impermeability of two-dimensional lamellar structures, and the proactive release of corrosion inhibitors to forge a robust, multi-faceted passivation layer.

Electrical damage mechanism analysis of traction motor bearings on high-speed trains considering overvoltage impulse

ABSTRACT As the critical rotating knuckle, traction motor bearings play a vital role in transmitting torque from motors to wheels for high-speed trains, while some electrochemical corrosion signs appear in traction motor bearings. To maintain the safety of the traction system, it is essential to explore the electrical damage mechanism of traction motor bearings considering the impact brought from current or overvoltage impulses. Herein, via analysing the electrochemical corrosion evolutionary process of bearings, main influencing factors are determined that both transient overvoltage impulse and long-term grounding current bring dramatic impact on bearings. To assess overvoltage distribution on different carriages, a ‘catenary-train-substation’ traction power supply model is launched based on practically collected impedances. A ‘carriage-bogie-motor’ circuit model is built to evaluate the overvoltage propagation path, meanwhile, the 3D finite element geometry of the bogie with bearings is launched to observe the overvoltage distribution in the bearings for evaluating breakdown risk.

Detection and Estimation of Diffuse Signal Components Using the Periodogram

One basic limitation of using the periodogram as a frequency estimator is that any of its significant peaks may result from a diffuse (or spread) frequency component rather than a pure one. Diffuse components are common in applications such as channel estimation, in which a given periodogram peak reveals the presence of a complex multipath distribution (unresolvable propagation paths or diffuse scattering, for example). We present a method to detect the presence of a diffuse component in a given peak based on analyzing the projection of the data vector onto the span of the signature’s derivatives up to a given order. Fundamentally, a diffuse component is detected if the energy in the derivatives’ subspace is too high at the peak’s frequency, and its spread is estimated as the ratio between this last energy and the peak’s energy. The method is based on exploiting the signature’s Vandermonde structure through the properties of discrete Chebyshev polynomials. We also present an efficient numerical procedure for computing the data component in the derivatives’ span based on barycentric interpolation. The paper contains a numerical assessment of the proposed estimator and detector.

Combining Effective Plastic Strain and Surface Roughness for Predicting Future Propagation Path of Microstructure‐ Sensitive Crack (MSC) in Polycrystalline Nickel

ABSTRACTThis work introduces a damage index (DI) that combines the effective plastic strain and surface roughness changes to predict the future propagation path of a microstructure‐sensitive crack (MSC) in a polycrystalline nickel fatigue sample. The surface topography of a fatigue sample was measured at short fatigue intervals, from which both the effective plastic strain and surface roughness changes were calculated using digital image correlation (DIC). Three DIs based on the effective plastic strain, surface roughness changes, and their combinations were studied using two criteria, that is, the highest intensity and the confidence threshold. Comparing the crack path predicted by these DIs with the actual crack path acquired at later fatigue cycles, we demonstrated that the combined DI is more accurate and has less uncertainty in predicting the future crack path.

Numerical Simulation of Rubber Concrete Considering Fatigue Damage Accumulation of Cohesive Zone Model.

Rubber concrete (RC) has been used in fatigue-resistant components due to its durability, yet the numerical simulation of its fatigue properties remains in its early stages. This study proposes a cohesive zone model (CZM) that accounts for the accumulation of fatigue damage at the mesoscale to investigate the fatigue performance of RC. The model integrates static and fatigue damage in the CZM, effectively capturing damage caused by fatigue loading. Validation was conducted using experimental data from the existing literature. Based on this validation, four concrete beams with varying rubber replacement rates (0%, 5%, 10%, and 15%) were tested. The CZM was employed to describe the mechanical behavior of the interface transition zones (ITZs) and the mortar interior, which were simulated and analyzed under different stress levels. The results demonstrate that the model accurately simulates crack propagation paths, interface damage evolution, and the fatigue life of RC beams under fatigue loading. A functional relationship between fatigue life and stress level was established for various rubber replacement rates. This study provides a reference model for numerical simulations of RC under fatigue loading conditions and introduces new approaches for analyzing the fatigue performance of other materials.

Numerical Simulation of Hydraulic Fracture Propagation in Unconsolidated Sandstone Reservoirs

In order to comprehensively understand the complex fracture mechanisms in thick and loose sandstone formations, we have carefully developed a coupled finite element numerical model that captures the complex interactions between fluid flow and solid deformation. This model is the cornerstone of our future exploration. Based on this model, the crack propagation problem of hydraulic fracturing under different engineering and geological conditions was studied. In addition, we conducted in-depth research on the key factors that shape the geometry of hydraulic fractures, revealing their subtle differences and complexities. It is worth noting that the sharp contrast between the stress profile and mechanical properties between the production layer and the boundary layer often leads to fascinating phenomena, such as the vertical merging of hydraulic fracture propagation. The convergence of cracks originating from adjacent layers is a recurring theme in these strata. Sensitivity analysis clarified our understanding, revealing that increased elastic modulus promotes longer crack propagation paths. As the elastic modulus increases from 12 GPa to 18 GPa, overall, the maximum crack width slightly decreases, with a less than 10% reduction rate. The increased fluid leakage rate will significantly shorten the length and width of hydraulic fractures (with a maximum decrease of over 70% in fracture width). The increase in viscosity of fracturing fluid causes a change in fracture morphology, with a reduction in length of about 32% and an increase in fracture width of about 25%. It is worth noting that as the leakage rate of fracturing fluid increases, the importance of the viscosity of fracturing fluid decreases relatively. Strategies such as increasing fluid viscosity or adding anti-filtration agents can alleviate these challenges and improve the efficiency of fracturing fluids. In summary, our research findings provide valuable insights that can provide information and optimization for hydraulic fracturing filling and fracturing strategies in loose sandstone formations, promoting more efficient and influential oil and gas extraction work.

Physics-based digital twin updating and twin-based explainable crack identification of mechanical lap joint

The mechanical joints, including the lap joint, weld, bolt, and pin, are vulnerable to fatigue failure because of stress concentration and internal flaws. Digital twin (DTw) strategies were proposed to prevent catastrophic system failure by fatigue damage in mechanical joints. In previous studies, the data-driven approach, such as deep learning and machine learning were utilized to estimate severity of the damage. However, it needs to improve its prediction accuracy because of insufficient data and physical interpretability. In this study, the physics-based digital twin model updating and twin-based crack identification of fatigue damage in riveted lap joints were proposed using lamb waves with consideration of uncertain crack growth path. The proposed approach is based on three techniques; (i) Data pre-processing, including filtering and optimization-based signal synchronization, (ii) Lamb-wave propagation analysis with sensor dynamics model and uncertain crack path, and (iii) Optimization based physics-based model updating and inference. In data pre-processing, the excitation frequency magnitude and truncation time are estimated using the observed actuator signal in the Lamb-wave test. The sensor dynamic model and model parameters are updated using the Bayesian optimization method to minimize both the errors in the predicted (y^t) and observed (yt) wave signal and the errors in the inferred (l*) and observed (l) crack length. The crack growth path is sampled based on angular and spline schemes to consider uncertain crack propagation paths. The validity of the proposed method is demonstrated using an open data set (2019 PHM society data challenge). The results conclude that the proposed digital twin approach can improve estimation accuracy considering both the crack growth path and sensor dynamics model.

Hydrogen Embrittlement Behavior of API X70 Linepipe Steel under Ex Situ and In Situ Hydrogen Charging.

This study investigates the hydrogen embrittlement behavior of API X70 linepipe steel. The microstructure was primarily composed of a dislocation-rich bainitic microstructure and polygonal ferrite. Slow strain-rate tests (SSRTs) were performed under both ex situ and in situ electrochemical hydrogen charging conditions to examine the difference between hydrogen diffusion and trapping behaviors. The ex situ SSRTs showed almost the same tensile properties as air and a limited brittle fracture confined to near the surface. In contrast, the in situ SSRTs showed an abrupt failure after the maximum tensile load, leading to a brittle fracture across the entire fracture surface with stress-oriented hydrogen-induced cracking (SOHIC). The crack trace analysis results indicated that SOHIC propagation paths were influenced by localized hydrogen accumulation due to high-stress fields. As a result, the dominant hydrogen embrittlement mechanisms, such as hydrogen-enhanced localized plasticity (HELP) and hydrogen-enhanced decohesion (HEDE), changed. These findings provide critical insights into the microstructural factors affecting hydrogen embrittlement, which are essential for the design of hydrogen-resistant steels in hydrogen infrastructure applications.

Mid-frequency propagation path analysis on vehicle body using structural intensity

With the penetration of electric vehicles, reduction of structure-borne road noise gets important issue to realize comfortable vehicles for customers.Sound generation mechanism of structure-borne road noise on vehicle body is analyzed basically by modal analysis in low-frequency range. On the other hand, as frequency increases, modal analysis cannot clarify vibration mechanism because vibration wavelength gets shorter, mode density gets high and mode shape gets complicated. Therefore, it is difficult to identify efficient countermeasure parts and inefficient damping materials are added to response panels in mid-frequency range. So alternative analytical methods in mid-frequency range are under research to understand vibration mechanism. In this paper, Structural intensity (SI) analysis is introduced to clarify sound propagation mechanism. This analysis method makes it possible to clarify the main energy propagation path from input point to vibrating panels on vehicle body. The results show that SI analysis unveils the main energy propagation path and gives the opportunity to reduce the panel vibration efficiently by controlling the energy propagation path in body frame structure without damping materials.