Damp Conditions Research Articles

Modal analysis of concrete gravity dam incorporating pre-stress condition along with soil–structure interaction

Purpose The fundamental period of the structure plays an important role in the seismic analysis. This study aims to analyze the modal response of dam, the two-dimensional (2D) FEM model is developed by using ANSYS 2022 R1 software. Design/methodology/approach To examine the optimized mesh size to achieve grid independence, the variable element size has been considered, and its optimal value is calculated using the technique of response surface optimization. Further, the effect of damping ratios of 5%, 8% and 10% is also considered for the free vibration analysis of the dam structure. Findings The results show that the natural frequencies of the dam decrease with a reduction in stiffness of the whole structure. Further, the effect of pre-stress conditions is analyzed and the study has proved that the natural frequency increases after considering the pre-stress as initial condition during modal analysis. Further, it is found that the damping has a substantial effect on frequency for higher modes of vibrations. Research limitations/implications The study only focused on modal analysis of the gravity dam, and this study’s results can be used further to evaluate the dynamic behavior of the dam including hydrodynamic conditions. Originality/value The finite element tool is used to evaluate the modal response of gravity dam incorporating pre-stress and damping ratio along with soil–structure interaction. Moreover, to the best of the authors’ knowledge, no earlier study has been conducted to evaluate the effect of damping and pre-stress conditions on the stability and natural frequency of the system.

Moving beyond species: fungal function in house dust provides novel targets for potential indicators of mold growth in homes

BackgroundIncreased risk of asthma and other respiratory diseases is associated with exposures to microbial communities growing in damp and moldy indoor environments. The exact causal mechanisms remain unknown, and occupant health effects have not been consistently associated with any species-based mold measurement methods. We need new quantitative methods to identify homes with potentially harmful fungal growth that are not dependent upon species. The goal of this study was to identify genes consistently associated with fungal growth and associated function under damp conditions for use as potential indicators of mold in homes regardless of fungal species present. A de novo metatranscriptomic analysis was performed using house dust from across the US, incubated at 50%, 85%, or 100% equilibrium relative humidity (ERH) for 1 week.ResultsGene expression was a function of moisture (adonis2 p < 0.001), with fungal metabolic activity increasing with an increase in moisture condition (Kruskal–Wallis p = 0.003). Genes associated with fungal growth such as sporulation (n = 264), hyphal growth (n = 62), and secondary metabolism (n = 124) were significantly upregulated at elevated ERH conditions when compared to the low 50% ERH (FDR-adjusted p ≤ 0.001, log2FC ≥ 2), indicating that fungal function is influenced by damp conditions. A total of 67 genes were identified as consistently associated with the elevated 85% or 100% ERH conditions and included fungal developmental regulators and secondary metabolite genes such as brlA (log2FC = 7.39, upregulated at 100% compared to 85%) and stcC (log2FC = 8.78, upregulated at 85% compared to 50%).ConclusionsOur results demonstrate that moisture conditions more strongly influence gene expression of indoor fungal communities compared to species presence. Identifying genes indicative of microbial growth under damp conditions will help develop robust monitoring techniques for indoor microbial exposures and improve understanding of how dampness and mold are linked to disease.-X5AkW-U2mftBzktcaxDSrVideo

PACC: A platoon-based adaptive cruise control strategy based on leader-following information topology to mitigate traffic oscillations under CAV environment

Traffic oscillations, often induced by repetitive acceleration and deceleration maneuvers in vehicles’ car-following behaviors, can cause many negative impacts on the traffic flow. With the development of connected and automated vehicle (CAV) technologies recently, scholars have made numerous effects on mitigating the propagation of traffic oscillations through a variety of advanced CAV control strategies, especially those related to the CAV platoon control. Different from the previous works, this paper proposed a platoon-based adaptive cruise control (PACC) strategy for CAV platoon to mitigate the traffic oscillations. The strategy is designed based on the novel and unique leader-following (LF) information topology. Built on the classical proportional-derivative (PD) controller that is implemented in the adaptive cruise control (ACC) strategy of autonomous vehicles (AVs), the PACC strategy is exquisitely designed to ensure the string stability of entire CAV platoon and the critically damped condition of each following CAV in the platoon. Credit to the rapid response of following CAV to the vibration of leading CAV’s dynamic status under LF information topology and the thorough consideration of string stability and damping characteristics in the PD controller design, the PACC strategy enables the CAV platoon to mitigate the traffic oscillations more efficiently than the existing cooperative adaptive cruise control (CACC) and ACC strategies. The numerical experiment for the mixed traffic flow on a single-lane ring road indicates that, when the CAV platoon adopts the PACC strategy, the performance of traffic flow in terms of operational efficiency, driving safety, passenger’s comfort, and fuel economy is substantially enhanced, compared with CACC and ACC strategies. In addition, the performance of PACC strategy gradually improves with the increase of market penetration rate (MPR) of CAVs and length of CAV platoon. Overall, the proposed PACC strategy is a promising solution to the mitigation of traffic oscillation under the CAV environment.

“Freedom to move through the house”: How a healthy housing initiative improves quality of life in Aotearoa New Zealand

ObjectiveThis study explores experiences of the Healthy Housing Initiative (HHI). Aimed at children at risk of housing-related illness, the HHI package includes the provision of items such as curtains, heaters, bedding, and insulation, advocacy to encourage landlords to install improvements, and education and advice to help people optimise their home environment. MethodsWe conducted semi-structured, in-depth interviews with 20 people living in rental housing who received the HHI intervention. ResultsParticipants felt heard and supported by HHI assessors. They reported that the intervention increased the warmth and dryness of the home, improved their respiratory and mental health, reduced their bills, and enabled the use of more parts of their home. However, some continued to live in cold and damp conditions due to structural inadequacies and energy poverty. ConclusionsThe qualitative evidence presented in this study shows how health-focussed interventions also benefit quality of life. Implications for public healthThis research emphasises that healthy housing interventions can yield extensive benefits by adopting a holistic and home-based approach. Such interventions have the potential to create improvements in individuals' lives far beyond health.

Subharmonic response suppression of a quasi-zero stiffness system

Quasi-zero stiffness (QZS) isolators can effectively suppress low-frequency vibration due to high-static-low-dynamic stiffness (HSLDS) characteristics. The existence of nonlinearity induces intricate nonlinear phenomena in QZS isolators, particularly under conditions of small damping and large excitation. These nonlinear characteristics can seriously affect the vibration isolation performance, which has rarely been focused on in existing studies. This study examines a typical QZS isolator with nonlinear damping. The modified incremental harmonic balance (IHB) method is applied to directly analyze its dynamic characteristics and investigate the suppression of the subharmonic response. The dynamic analysis results indicate multiple subharmonic vibration intervals, including the 1/2, the 1/3, and the 1/9 subharmonic vibration. The basin of attraction at different excitation frequencies shows that subharmonic vibration is highly likely to occur. The effect of different damping on the transmissibility proves to be different. Simultaneously, rational parameter matching can guarantee the absence of subharmonic vibration while maintaining the primary resonance frequency and amplitude unchanged. The research results of this study provide theoretical support for the parameter selection of QZS isolators. In addition, the higher-order approximations of most isolators have the same form, so these results can guide other QZS isolators in suppressing subharmonic vibrations and improving their operating range.

Analyzing the effect of hydrodynamic damping on the wake behavior in circular blade cascades: numerical study on a global mode

Abstract In this study, a numerical investigation has been performed to extract and compare the hydrodynamic damping of a non-rotating system of eight planar hydrofoils, arranged in a radial configuration, with the related wake behaviour downstream the structure. A modal acoustic analysis has been performed on the structure in order to extract the global modes corresponding to Nodal Diameter 0. Using the deformation related to the global mode, the hydrodynamic damping has been extracted for different velocities, ranging from 2 to 14 m/s, by analyzing the work done on the structure from the fluid, following the so-called “flutter” method developed by ANSYS®. The related wake behaviour has been analyzed for each specific velocity and hydrodynamic damping conditions. This numerical study has been performed in ANSYS Mechanical® and CFX®. The results for the present geometry suggest that the primary factor governing vortex shedding frequency is the motion of the body itself, in the present case locked to the excitation frequency of the global structural mode (ND0). The study identifies a lock-in region around 10 m/s, consistent with empirical formulas. After the region of lock-in, the fluctuations of velocity and pressure values tend to converge, indicating a stabilization of the wake dynamics. The observed hydrodynamic damping trend exhibits a linear pattern preceding the lock-in region, succeeded by a steep rise thereafter. This pattern aligns with established literature, affirming its consistency with prior research findings. Overall, this numerical approach offers valuable insights into wake behavior and hydrodynamic damping value serving as a promising tool for preliminary estimation and analysis of oscillating systems in water flowing environments. Its low computational complexity and rapid completion time make it a viable alternative to more complex FSI simulations, facilitating comprehensive exploration of multiple flow scenarios within a reasonable time frame of weeks.

The onset of instability in a parametric resonance energy harvester under panchromatic excitations

This paper further explores the potential of parametric resonance to enhance wave energy conversion in a pendulum-based pitching floating energy harvester, considering power extraction and panchromatic excitation. Unlike traditional parametric systems that focus on inertial mechanical instability induced by floater motion, this concept, firstly proposed in a previous recent publication, leverages the parametric resonance induced by nonlinear hydrodynamic coupling between heave and pitch. By deliberately integrating parametric instability into the floater design with a 2:1 ratio of natural periods in two hydrodynamic degrees of freedom, the frequency bandwidth of the mechanical system is expanded, leading to two distinct regions of significant power production. The research advances current understanding in three key areas: (i) the use of Bezier curves to advance a computationally efficient nonlinear hydrodynamic model based on nonlinear Froude–Krylov force calculations tailored for prismatic floaters, (ii) investigation of the impact of power extraction on the severity of nonlinear parametric resonance, and (iii) consideration of more realistic panchromatic waves to quantify the onset of instability and the decrease in the severity of parametric resonance response, also addressing practical implications for numerical simulations and signal processing. Findings indicate that beneficial parametric resonance persists across various damping and wave conditions, although the relative importance of the contribution of the 2:1 parametric resonance region to power extraction decreases by 75%, on average.

Epoxy resin multimode optical waveguide fabricated by non-contact photolithography

Multimode polymer waveguides were created using epoxy resin materials. The fabrication process used non-contact photolithography, which is a simple and cost-effective method. During the experiments, a reliable and efficient developer was obtained. The samples were analyzed using scanning electron microscopy and the results showed that the ridge waveguides had a smooth surface and vertical sidewalls. The cross-section size was approximately 50 × 55 μm2. The waveguides had a transmission loss was about 0.08 dB/cm at a wavelength of 850 nm, which was measured using the cut-back method. Additionally, the waveguides were found to be stable in thermal and damp heat conditions.

Stability for coupled thermoelastic systems with nonlinear localized damping and Wentzell boundary conditions

Stability for coupled thermoelastic systems with nonlinear localized damping and Wentzell boundary conditions

Slow energy relaxation in anharmonic chains with and without on-site potentials: Roles of distinct types of discrete breathers

Slow energy relaxation has been observed in one-dimensional lattices with and without a nonlinear on-site potential; however, a comprehensive understanding of the detailed relaxation process remains elusive. Here we revisit this issue by introducing damping conditions at the free-end boundary of a thermalized lattice. We reveal that, in the long-cooling-time regime considered, for systems with a nonlinear on-site potential, energy relaxation exhibits a strong temperature-dependent behavior and with the increase of temperature, there is a crossover between decaying and non-decaying behaviors, around a crossover temperature point of Tc≃4.2. This non-decaying behavior at higher temperature is attributed to the presence of standing multi Sievers–Takeno discrete breather (DB) states. Conversely, for systems without on-site potentials, relaxation is nearly independent of temperature but dependent on interparticle potential. Notably, we observe that the cubic anharmonicity can generate moving single Page DB states that contribute to the unusual slow energy relaxation within a specific time regime. Our results provide enhanced insights into the mechanisms governing slow energy relaxation during lattice cooling.

Enhanced Intrinsic Self-Healing Performance of Mussel Inspired Coating via In-Situ Cation Capture.

Under damp or aquatic conditions, the corrosion products deposited on micro-cracks/pore sites bring about the failure of intrinsically healable organic coatings. Inspired by mussels, a composite coating of poly (methyl methacrylate-co-butyl acylate-co-dopamine acrylamide)/phenylalanine-functionalized boron nitride (PMBD/BN-Phe) is successfully prepared on the reinforcing steel, which exhibits excellent anti-corrosion and underwater self-healing capabilities. The self-healing property of PMBD is derived from the synergistic effect of hydrogen bonding and metal-ligand coordination bonding, and thereby the continuous generation of corrosion products can be significantly suppressed through in situ capture of cations by the catechol group. Furthermore, the corrosion protection ability can be remarkably improved by the labyrinth effect of BN and the inhibition role of Phe, and the desired interfacial compatibility can be formed by the hydrogen bonds between BN-Phe and PMBD matrix. The corrosion current density (icorr) of PMBD/BN-Phe coating is determined as 7.95×10-11Acm-2. The low-frequency impedance modulus (|Z|f = 0.0 1 Hz is remained at 3.47×109Ωcm2, indicating an ultra-high self-healing efficiency (≈89.5%). It is anticipated to provide a unique strategy for development of an underwater self-healing coating and robust durability for application in anti-corrosion engineering of marine buildings.

Design of dynamic test specimens and fixtures for large structural components of civil aircraft

In the course of designing and certifying civil aircraft, a significant number of dynamic tests are necessary. If the test specimen is too large in volume or weight, it will place higher demands on the loading capacity of the test equipment. The main focus in the design process of dynamic test specimens is to ensure consistency in the dynamic characteristics compared to the original structure, specifically with regard to natural frequency and mode shapes. Factors such as stiffness, damping, and boundary conditions are taken into consideration. In order to facilitate test implementation and reduce manufacturing costs, a combined approach involving finite element analysis and experimental verification is employed to provide guidance for the design of dynamic test specimens and fixtures for civil aircraft.

Surface Energy-Assisted Patterning of Vapor Deposited All-Inorganic Perovskite Arrays for Wearable Optoelectronics.

Solution-based methods for fabricating all-inorganic perovskite film arrays often suffer from limited control over nucleation and crystallization, resulting in poor homogeneity and coverage. To improve film quality, advanced vapor deposition techniques are employed for continuous film. Here, the vapor deposition strategy to the all-inorganic perovskite films array, enabling area-selective deposition of perovskite through substrate modulation is expanded. It can yield a high-quality perovskite film array with different pixel shapes, various perovskite compositions, and a high resolution of 423dpi. The resulting photodetector arrays exhibit remarkable optoelectronic performance with an on/off ratio of 13 887 and responsivity of 47.5AW-1. The device also displays long-term stability in a damp condition for up to 12h. Moreover, a pulse monitoring sensor based on the perovskite films array demonstrates stable monitoring for pulse signals after being worn for 12h and with a low illumination of 0.055mWcm-2, highlighting the potential application in wearable optoelectronic devices.

Two decades of dune slack restoration in North Wales: diversity, community and habitat specialists

Humid dunes slacks are a highly threatened habitat, listed as vulnerable in the EU habitat red list. Accelerated successional processes in dune systems have resulted in the loss and degradation of ideal conditions for specialist dune slack species, hence the need for conservation management. We investigated the restoration of a dune slack in North Wales, UK, where vegetation and soil removal to 10 cm depth was undertaken to reinstate nutrient‐poor, open and damp conditions. We assessed the outcomes of the management for dune slack communities over the 18 years since restoration. We also assessed the differences between restored and unrestored areas of dune slacks. The dunes were restored in the winter of 2004/2005, after which we conducted vegetation surveys in fixed quadrats for most years in the restored and adjacent, un‐restored dune slacks. Species diversity and plant community composition changes over time were assessed using Shannon's index, multivariate analysis and indicator species analysis. Comparisons between the restored and unrestored areas of the dune slacks were also made. Ellenberg indicator values (EIVs) were examined to identify potential environmental drivers of post management successional changes. After 18 years the restored dune slacks developed a species‐rich and diverse community. compared to the unrestored slacks. The establishment of species occurred rapidly in the first three years, followed by continued but slower increases in species richness and diversity. This is due to the addition of new species without losses of established species. EIVs show no significant difference over time suggesting the restored areas are still at an early stage of succession. Distinct stages of community change since restoration are characterised by different indicator species. Plants are likely to be largely recruited from an existing seed bank. Restoration by turf removal may be suitable for other low nutrient, species rich habitats dependent upon fluctuating groundwater levels.

The ion cyclotron parametric instabilities and the anomalous heating of ions in the scrape-off layer of tokamak plasma in the high harmonic fast wave heating regime

The electrostatic parametric instabilities of a plasma, driven by the high harmonic fast wave (HHFW) with frequency at ion cyclotron (IC) harmonics of order 30–50 are investigated numerically. The derived numerical results are consistent with parametric decay of HHFW into the high harmonic IC (Bernstein) wave and an unobserved IC quasimode under conditions of the negligible small electron Landau damping. The detected instability develops in the finite interval of the HHFW wavelength along the toroidal magnetic field. The development of this ion kinetic quasimode decay instability is accompanied by the anomalous anisotropic heating of ions, resulted from the interaction of ions with IC parametric turbulence. It was found that the anomalous heating rate of ions across the magnetic field is much larger than the heating rate of ions along the magnetic field. The anisotropic heating of the scrape-off layer ions was observed on the National Spherical Torus Experiment experiments with HHFW heating and current drive at IC harmonics of order 10 [G. Taylor et al. Phys. Plasmas 17, 056114 (2010), and J. Hosea et al. Phys. Plasmas 15, 056104 (2008)]. The derived results predict that these experimental results will be reproduced qualitatively in the experiments with HHFW heating and current drive using HHFW at IC harmonics of order 30–50.

Measuring the internal damping of thin metal beams in flexure

Since the internal damping of most metals is a relatively small quantity, precise measurement requires that both acoustic radiation damping and boundary condition damping be either eliminated or highly minimized. In this talk, an experiment setup will be described which can measure the internal damping of metal beams in flexure. To perform a measurement, a beam specimen is placed on wire supports within a vacuum chamber and excited by an autonomous force hammer located within the chamber. The wire supports are located exactly at the nodal lines of the beam mode of interest, so that the frictional losses created by the wire supports are minimized. Once excited, the beam deflection is measured with a single point laser vibrometer. The signal decay measured by the vibrometer is used to estimate damping of the mode of interest using either the Hilbert transform or the half- power method. The wire supports are then moved, and the procedure is repeated for the next mode of interest. Results for several metal specimens will be presented and compared to Zener’s thermoelastic model, which describes the losses created by thermal currents for a beam in flexure, to demonstrate the accuracy of the measurement method.

First Report of Apiospora arundinis Causing Wet Root Rot of Pseudostellaria heterophylla in China.

Pseudostellaria heterophylla is one of the traditional medicines in China. From 2020 to 2022, postharvest wet root rot disease was observed with an incidence of 2~5% on the tuberous roots of the harvested P. heterophylla in Zherong county, Fujian province, China, which usually occurs under damp and unventilated conditions. The symptoms of the disease were as follows: white mycelia grew on the surface of tuberous root initially and gradually wrapped around the roots, the internal root tissue turned yellow and became wet decay finally. To identify the causal agent, a total of 20 samples with symptomatic tuberous roots were collected. Small pieces (3 mm2) were treated by surface disinfection with 75% ethanol and 1% NaOCl, then rinsed 3 times with sterile water. These treated pieces were transferred onto potato dextrose agar (PDA) and incubated at 25°C in the dark for 7 d. Ten pure cultures were obtained using single-spore isolation method. The fungus colonies initially produced white aerial mycelium, subsequently exhibited yellow pigmentation. Mycelia were consisted of smooth, hyaline, branched, and septate hyphae. The conidia were solitary or clustered, brown or dark brown, smooth, ellipsoidal to spherical, 6.66 (5.50-7.81)×5.65 (4.17-7.22) µm (n=50) in size. The conidiophores were hyaline or pale brown and produced conidiogenous cells, which were pale brown, smooth, ampulliform, and 10.14 (8.82-15.30) um long (n=50). Based on these morphological characteristics, the fungus was identified as the genus Apiospora (Arthrinium). The rDNA-ITS region and partial β-tubulin gene (BenA) were amplified using the primers ITS1/ITS4 (White et al. 1990) and Bt2a/Bt2b (Glass and Donaldson 1995), respectively. The sequences of isolates FJAT-32563 and FJAT-32564 were deposited in GenBank (ITS, OM920984 and OM920985; BenA, OM953823 and OM953824). All sequences had more than 99% similarity with those of A. arundinis strain CBS:106.12 (ITS, KF144883; BenA, KF144973). In the multilocus phylogenetic analysis (ITS + BenA), the two isolates clustered together with other strains of A. arundinis with 100% bootstrap support. The isolates were therefore identified as A. arundinis based on both morphological and molecular characteristics. To confirm the pathogenicity, fresh tuberous roots were selected and surface disinfected, then the roots were immersed with a quarter length in the conidial suspension (106/mL) for 30 min, whereas the control roots were immersed with sterile water (n=30). They were placed in petri dish with wet filter paper at 25±2℃, maintaining 80% relative humidity in the dark. The white aerial mycelium appeared at 5 days after inoculation, and wet root rot decaying occurred after inoculation for 21 days. The symptoms were similar to those described above, whereas the control roots were asymptomatic. The same fungus was re-isolated from the infected roots, showing similar morphological characteristics and molecular traits. Koch's postulates were completed and the pathogenicity test for the isolates has been repeated thrice. Previously, A. arundinis was reported to infect peach and sugarcane (Ji et al. 2020; Liao et al. 2022). To our knowledge, this is the first report of A. arundinis causing wet root rot of P. heterophylla in China. The disease would be a potentially new threat to this medicinal plant.

Single-shot all-optical switching of magnetization in TbFe

Thermally induced magnetization switching (TIMS) relying solely on a single laser without any applied magnetic field is a key research direction of current spintronics. Most studies on TbFe so far have focused on helicity-dependent all-optical switching (HD-AOS). In this work, we observe the TIMS on TbFe alloys excited by atomic spin dynamics simulations combined with a two-temperature model. The results show that the magnetization switching of TbFe can be found under certain damping conditions. In addition, we further investigated the reasons why energy density leads to the opposite switching time behavior of Tb and Fe, and our research results also found that changes in damping can affect the concentration and energy density range of the switching, as well as the maximum pulse duration. The dynamic behavior indicates that TbFe switching in 2 ps or less. Our findings widen the basis for fast optical switching of magnetization and break new ground for engineered materials that can be used for nonvolatile ultrafast switching using ultrashort pulses of light.

Diagnostics of Piezoelectric Bending Actuators Subjected to Varying Operating Conditions

In applications of piezoelectric actuators and sensors, the dependability and particularly the reliability throughout their lifetime are vital to manufacturers and end-users and are enabled through condition-monitoring approaches. Existing approaches often utilize impedance measurements over a range of frequencies or velocity measurements and require additional equipment or sensors, such as a laser Doppler vibrometer. Furthermore, the non-negligible effects of varying operating conditions are often unconsidered. To minimize the need for additional sensors while maintaining the dependability of piezoelectric bending actuators irrespective of varying operating conditions, an online diagnostics approach is proposed. To this end, time- and frequency-domain features are extracted from monitored current signals to reflect hairline crack development in bending actuators. For validation of applicability, the presented analysis method was evaluated on piezoelectric bending actuators subjected to accelerated lifetime tests at varying voltage amplitudes and under external damping conditions. In the presence of a crack and due to a diminished stiffness, the resonance frequency decreases and the root-mean-square amplitude of the current signal simultaneously abruptly drops during the lifetime tests. Furthermore, the piezoelectric crack surfaces clapping is reflected in higher harmonics of the current signal. Thus, time-domain features and harmonics of the current signals are sufficient to diagnose hairline cracks in the actuators.

Stability for variable-coefficient wave equation with local frictional damping and memory type dynamic boundary conditions

Stability for variable-coefficient wave equation with local frictional damping and memory type dynamic boundary conditions