Search Results (77)

To investigate the dynamic behavior of smart composite structures with embedded heat sources over a wide temperature range, this study employed thermoplastic polypropylene as the matrix, combined with glass/carbon fiber prepregs and Ni80Cr20 alloy heating wires, and fabricated functional laminated specimens with integrated heating elements via a prepreg molding process. Using a self-developed variable-temperature cantilever beam vibration testing system, the evolution of natural frequencies and damping ratios from room temperature to 140 °C was systematically examined. Results indicate that temperature-induced thermal softening of the polypropylene matrix reduces the effective bending stiffness of the composites, leading to a decline in natural frequencies across all modes. For example, the first-order natural frequency of the sample decreased from approximately 30.8 Hz at room temperature to about 28.3 Hz at 140 °C, representing a reduction of approximately 8.12%. The second-order reduction reached about 8.99%, and the third-order reduction was approximately 9.65%. Carbon fiber-reinforced specimens exhibited relatively smaller frequency reductions due to the high modulus of the fibers. Concurrently, elevated temperatures enhance molecular chain mobility and interfacial viscoelastic dissipation at the fiber–matrix interface, causing a sharp increase in damping ratios at high temperatures (>100 °C). For instance, the damping ratio of the first-order mode increased significantly from approximately 1.02% at room temperature to about 2.9% at 140 °C. By comparatively analyzing carbon fiber and glass fiber systems, the study elucidated the distinct mechanisms underlying the “fiber-dominated” stiffness retention effect and the “resin/interface-dominated” damping dissipation effect under thermal influence. These findings provide critical experimental data and theoretical references for the active thermal regulation of structural performance in thermoplastic composite structures with integrated heat sources, thereby mitigating damage caused by external disturbances. Full article

This study investigates additive-free cold calendering of ELT-derived rubber powders across three particle size fractions (<0.5 mm, 0.5–0.71 mm, and 0.71–0.90 mm) using a two-roll mill without external heating or virgin polymers, aiming to obtain a cohesive material. Results demonstrate particle size effects on material properties. The finest fraction exhibited the highest crosslink density (5.30 × 10⁻⁴ mol·cm⁻³), approximately 18% greater than coarser fractions, correlating with superior hardness (≈65 ShA) and elastic modulus (≈7.5 MPa). Tensile properties ranged from 1.6–1.8 MPa stress and 60–75% elongation at break, positioning calendered sheets between low-temperature compression-molded GTR and high-pressure sintered materials reported in the literature. The cold calendering process achieves competitive mechanical performance with reduced energy consumption, simplified processing, and complete retention of recycled content. These findings support the development of regulation-compliant ELT recycling technologies, with potential applications in nonstructural construction panels, vibration-damping components, and protective barriers, advancing circular economy objectives while addressing emerging microplastic concerns. Full article

Shape-memory polymers (SMPs) are a unique class of smart materials capable of recovering their original shape upon external stimuli, with thermoresponsive polyurethane (PU) being one of the most widely studied systems. However, the relatively low mechanical strength, thermal stability, and durability of PU limit its broader functional applications. PU/ND composites containing 0.1–0.5 wt.% ND were fabricated via melt blending and injection molding method. The objective was to evaluate the effect of ND reinforcement on the mechanical, scratch, thermal, rheological, and shape-memory properties. Results show that tensile strength increased up to 114% and Young’s modulus by 11% at 0.5 wt.% ND, while elongation at break decreased due to restricted chain mobility. Hardness improved by 21%, and scratch resistance was significantly enhanced, with the coefficient of friction reduced by 56% at low loads. Thermal stability was improved, with the maximum degradation temperature shifting from 350 °C (pure PU) to 362 °C (0.5 wt.% PU/ND) and char yield increasing by 34%. DSC revealed an increase in glass transition temperature from 65 °C to 68.6 °C. Rheological analysis showed an 89% reduction in damping factor (tan δ), indicating enhanced elasticity. Shape-memory tests confirmed notable improvements in both shape fixity and recovery ratios across successive cycles compared to neat PU, with the highest enhancements observed for the 0.5 wt.% PU/ND nanocomposite—showing up to 7.6% higher fixity and 32% higher recovery than pure PU. These results demonstrate that ND reinforcement effectively strengthens PU while preserving and improving its shape-memory behavior, making the composites promising candidates for high-performance smart materials in sensors, actuators, and aerospace applications. Full article

A rapid review was undertaken to consider the evidence for human exposure to harmful microorganisms from indoor air and surfaces. Published information about these contaminants, as well as measures to control them, including building design and energy conservation, were included in this review. Information on domestic dwellings, office environments, and other non-industrial settings was assessed to determine the reported prevalence, persistence, and transmission of microorganisms in these settings. Environmental factors that influence indoor microbiological colonization were also included. The evidence strongly indicates that ventilation is the primary factor for controlling indoor dampness, helping to mitigate indoor mold colonization and the accumulation of other indoor contaminants, including infectious microorganisms. Although modern building airtightness, including retrofits of older builds, contributes to thermal comfort and building energy efficiency, this may also limit a building’s ventilation capacity. This in turn can potentially allow biological pollutants to accumulate, increasing the likelihood of harmful exposures and ill-health effects for building occupants. Effective building design and maintenance, which promote appropriate levels of air exchange for indoor spaces, are therefore important for the control of indoor moisture and microbiological contamination. Full article

Flooding from hurricanes creates damp indoor environments that support mold growth and microbial contamination, posing long-term health risks for occupants. This pilot study evaluated TMVOCs, microbial activity, and environmental conditions in 13 Hurricane Ian-affected residences across multiple flood-affected neighborhoods. Air samples were collected using sorbent tubes and analyzed by gas chromatography–mass spectrometry, while microbial activity on surfaces was assessed via ATP bioluminescence. Visible mold and dampness were documented with the CDC/NIOSH Dampness and Mold Assessment Tool, and environmental measurements included temperature, relative humidity, and surface as well as hidden moisture. Median (IQR) TMVOC concentrations were 12 (8) µg/m³, with 61% of homes exceeding the 10 µg/m³ benchmark set by previous researchers despite minimal visible contamination. Spearman’s correlation revealed significant negative relationships between odor and surface microbial activity (ρ = −0.569, p < 0.05), indicating that organic debris may play a more crucial role in microbial activity within the tested homes, and that odors might originate from hidden microbes instead of surface microbial growth. Our study emphasizes the necessity of utilizing both chemical (TMVOC) and biological (ATP) indicators to evaluate poor air quality caused by molds in flood-affected homes, serving as a supplement to routine visible mold assessments. Full article

A damping spacer rod is a key protective device in ultrahigh voltage transmission lines, which not only keeps the distance of split wires and limits the whipping and collision caused by the relative motion between sub-wires, but also inhibits the vibration of wires. This study aims to solve the problem of typical faults, such as loose wire clamps, that are prone to occur in damping isolation rods during long-term operation in ultra-high voltage transmission lines. Taking the spacer rod FGZ-450/34B as the object, a new high-pressure casting process for spacer rod frames is explored. The spacer rods were simulated by using the ABAQUS finite element software to predict the stress distribution and identify the dangerous sections. Based on this, the mold process was optimized to avoid die-casting defects. Meanwhile, mechanical property tests were carried out on the products produced by the two types of molds. The research finds that by optimizing the mold process, the die-casting quality of the dangerous section of the spacer rod can be effectively improved, and the best high-pressure die-casting scheme has been obtained through comparison. This research achievement provides technical support for enhancing the anti-vibration performance, anti-loosening reliability, short-circuit current thermal shock resistance, and anti-ultraviolet aging performance of damping isolation rods. It is of great significance for ensuring the stable operation of ultra-high voltage transmission lines and improving the production process level of damping isolation rods. Full article

Hybrid materials have multifunctional capabilities that are particularly attractive for space applications in order to overcome issues related to the harshness of the environment, especially during long-duration missions. Hybridization is traditionally carried out by mixing reinforcements of different natures, such as carbon with glass/kevlar fibers, or by integrating nanomaterials into the composite structure. Promising results in terms of improved toughness, ductility, and damping ability have been recorded by placing a thermoplastic interlayer between adjacent thermosetting plies reinforced with carbon fibers. These hybrid materials have additional functionalities such as thermoformability and repairability, which make them suitable for several industrial applications. In this work, a literature review on hybrid composites is presented and experimental results on the manufacturing of hybrid carbon fiber epoxy/PEEK laminates are reported. Thermoplastic films of 25 μm and 200 μm thickness have been used as well as two manufacturing procedures. The high-thickness interlayer laminate, that was compression-molded at 250 °C, showed the highest mechanical properties with a bending strength of 340 MPa and an elastic moules of 50 GPa. The other composite, that was molded at 350 °C, exhibited reduced mechanical properties. Full article

True slime molds (Eumycetozoa) remain under-explored globally, particularly in water-logged forest habitats. Despite evidence suggesting a high biodiversity potential in the Knyszyn Forest of north-eastern Poland, no systematic effort had previously been undertaken there. In the present survey, plant substrates from eight swampy sub-compartments were incubated for over four months, resulting in the detection of fifteen slime mold species. Four of these taxa are newly reported for northern and north-eastern Poland, while several have been recorded only a handful of times in the global literature. These findings underscore how damp, nutrient-rich conditions foster Eumycetozoa and demonstrate the effectiveness of moist-chamber culturing in revealing rare or overlooked taxa. Current evidence shows that, although slime molds may occasionally colonize living plant or fungal tissues, their influence on crop productivity and tree vitality is negligible; they are therefore better regarded as biodiversity indicators than as pathogens or pests. By establishing a replicable framework for studying water-logged environments worldwide, this work highlights the ecological importance of swamp forests in sustaining microbial and slime mold diversity. Full article

Preserving historical porous materials requires careful monitoring of surface humidity to mitigate deterioration processes like salt crystallization, mold growth, and material decay. While microclimate monitoring is a recognized preventive conservation tool, its role in detecting surface-specific moisture risks remains underexplored. This study evaluates the relationship between indoor microclimate fluctuations and surface moisture dynamics across 13 historical sites in Northern Italy (Lake Como, Valtellina, Valposchiavo), encompassing diverse masonry typologies and environmental conditions. High-resolution sensors recorded temperature and relative humidity for a minimum of 13 months, and eight indicators—including dew point depression, critical temperature–humidity zones, and damp effect indices—were analyzed to assess the moisture risks. The results demonstrate that multivariate microclimate data could effectively predict humidity accumulation. The key findings reveal the impact of seasonal ventilation, thermal inertia, and localized air stagnation on moisture distribution, with unheated alpine sites showing the highest condensation risk. The study highlights the need for integrated monitoring approaches, combining dew point analysis, mixing ratio stability, and buffering performance, to enable early risk detection and targeted conservation strategies. These insights bridge the gap between environmental monitoring and surface moisture diagnostics in porous heritage materials. Full article

Traditional magnetorheological elastomers (MREs) often suffer from limited modulus tunability and insufficient energy dissipation, which restrict their applications. This study prepared a novel composite material by an MR gel (MRG) embedded within the MRE, called the MRE encapsulating MRG, to synergistically enhance these properties. Annular and radial MRE encapsulating MRG configurations were fabricated using 3D-printed molds, and their dynamic mechanical performance was characterized under varying magnetic fields (0–1 T) via a rheometer. The results revealed that the composite materials demonstrated significantly improved magnetic-induced modulus and magnetorheological (MR) effects compared to conventional MREs. Specifically, the annular MRE encapsulating MRG exhibited a 238.47% increase in the MR effect and a 51.35% enhancement in the magnetic-induced modulus compared to traditional MREs. Correspondingly, the radial configuration showed respective improvements of 168.19% and 27.03%. Furthermore, both the annular and radial composites displayed superior energy dissipation capabilities, with loss factors 2.68 and 2.03 times greater than those of pure MREs, respectively. Dynamic response tests indicated that composite materials, particularly the annular MRE encapsulating MRG, achieve faster response times. These advancements highlight the composite’s potential for high-precision damping systems, vibration isolation, and adaptive control applications. Full article

Herein, we address the peculiar lack of scientific reporting on odor potent chloroanisoles (CAs) in the built environment. We have searched and critically examined sources beyond peer-reviewed scientific journals, namely research conferences, parliamentary records, newspaper articles, and cartoons. We provide evidence that CAs evolved on a large scale in Swedish buildings in the early 1970s and evoked a typical sticky malodor that was attributed to mold and gave rise to the term “mold houses”. The term first appeared in Swedish newspapers in 1978, and the media attention increased rapidly. The malodorous “mold houses” reached the Swedish parliament and led to economic compensation for afflicted homeowners. The “mold houses” became “sick houses” as researchers, predominantly from Sweden, introduced and became world leaders on the “sick buildings syndrome” (SBS). Researchers became aware of the CAs but did not mention them in peer-reviewed articles, just as they did not mention a well-known source of the sticky malodor, namely, legacy preserved wood where CAs were formed through microbial methylation of toxic chlorophenols (CPs). Thus, the mold story from the early 1970s was maintained and prevented the malodorous CAs from becoming recognized as indicators of the presence of hazardous CPs. Our study is the first to report the impact of an indoor malodor, not only on a few people, but on society. Full article

Microorganisms are one of the most critical factors involved in the degradation of buildings. Fungi that develop in historic spaces not only cause the degradation of monuments (immovable and movable) but can also negatively affect those who visit or use such spaces. This article is a case study of the 16th-century St. Catherine Church in Cięcina (Poland), whose walls became severely damp as a result of changes made to the church’s surroundings (relocation of the riverbed of the Cięcinka River, raising the level of St. Catherine Street and building a wooden fence on a concrete foundation around the church). The effect of the severe dampness of the building was the intensive development of Serpula lacrymans fungus and mold. This article highlights the importance of a multidisciplinary approach to hazard diagnosis in historic buildings. Full article

Multi-head 3D printers afford the ability to create composite structures with significant differences in properties compared to those created through traditional molding techniques. In addition to the usage of different viscoelastic polymeric materials, the selective spatial placement of the build materials enables the creation of layered and graded geometries to achieve specific mechanical and/or vibrational characteristics. This paper describes how the mechanical properties of the individual materials can be used to predict the damping and natural frequencies of a 3D-printed graded structure. Such structures can find usage in rotating machinery, beams, etc., where vibrational characteristics must be controlled. The simulation and experimental results are presented and two forms of the storage and loss modulus are considered: fixed and variable. For the latter condition, E′ and E″ are established as functions of temperature and frequency. Modal vibration testing of the graded samples shows a good match between the simulation and experimental trials, thereby supporting the proposed model as a useful tool for prescribing the structure of a printed part with tailored dynamic properties. Full article

Okra (Abelmoschus esculentus) is an important agricultural crop of the Malvaceae family, cultivated across tropical, subtropical, and warm temperate regions. However, okra production faces numerous challenges from diverse pest species, including insects, nematodes, arachnids, and mites, that significantly reduce its yield. Major economic pests include the cotton aphid, cotton spotted bollworm, Egyptian bollworm, cotton mealybug, whitefly, cotton leafhopper, cotton bollworm, two-spotted spider mite, root-knot nematode, reniform nematode, cotton leaf roller, and flea beetle. Additionally, less prevalent pests such as the blister beetle, okra stem fly, red cotton bug, cotton seed bug, cotton looper, onion thrips, green plant bug, and lesion nematode are also described. This review also addresses fungal and oomycete diseases that present high risks to okra production, including damping-off, powdery mildew, Cercospora leaf spot, gray mold, Alternaria leaf spot and pod rot, Phyllosticta leaf spot, Fusarium wilt, Verticillium wilt, collar rot, stem canker, anthracnose, and fruit rot. In addition to these fungal diseases, okra is also severely affected by several viral diseases, with the most important being okra yellow vein mosaic disease, okra enation leaf curl disease, and okra mosaic disease, which can cause significant yield losses. Moreover, okra may also suffer from bacterial diseases, with bacterial leaf spot and blight, caused primarily by Pseudomonas syringae, being the most significant. This manuscript synthesizes the current knowledge on these pests. It outlines various management techniques and strategies to expand the knowledge base of farmers and researchers, highlighting the key role of integrated pest management (IPM). Full article

This paper introduces a new methodology for a routine metal analysis of plastic waste (PW) and PW blended with petroleum feedstock such as vacuum gas oil and VGO (PW/VGO). For such purposes, recycled polyethylene and polypropylene plastic were selected to mimic the potential feeds to be integrated at the Fluid Catalytic Cracking unit (FCC) to produce valuable products. Elements such as P, Ca, Al, Mg, Na, Zn, B, Fe, Ti, and Si were included in the method development. Different sample preparation methods were evaluated, such as microwave-assisted acid digestion (MWAD) and dry/wet ashing, followed by a fusion of the ash with lithium borate flux. Some PW homogenization pretreatments, such as cryogenic grinding and hot press molding, were also covered. The finding of this work suggests that MWAD with HNO₃ and H₂O₂ is adequate for both types of samples and is the quickest sample preparation; however, the sample needed to be homogenized, and recoveries for Si and Ti may be biased for PW due to the limited solubilities of these elements in the nitric acid media. Carbon removal is required before fusion sample preparation and analysis due to the amount of carbon in PW samples. The sample needed to be homogenized for wet ash fusion but not for the pre-ash (dry) method. A benefit to the damp ash pretreatment is that the ash for the sample was created in the same crucible used for fusion digestion, avoiding material loss during sample management. Fusion from wet ash or carbon removal allowed for better acid solubility for Si and Ti in PW. The results of the PW samples evaluated matched well with those of both sample preparation methodologies. For most elements, precision was <10% regardless of the sample preparation; however, Fe and P had some variation using wet ash fusion, possibly due to contamination in an open digestion system or variation due to being close to the method limit of quantification (LOQ). The methodology reported here is robust enough to be implemented as routine analysis in any laboratory facility. Full article