Search Results (2,834)

This study investigates the residual web crippling behavior of pultruded glass fiber-reinforced polymer (P-GFRP) hollow sections after exposure to elevated temperatures. The primary objective is to evaluate the combined influence of temperature and loading configuration on web crippling capacity, failure mechanisms, and structural performance, and to develop practical prediction models for engineering applications. A total of twenty pultruded GFRP hollow section specimens were exposed to temperatures of 24 °C, 200 °C, 250 °C, 300 °C, and 350 °C and tested under four loading configurations: End Ground (EG), Interior Ground (IG), End Two Flange (ETF), and Interior Two Flange (ITF). In addition to web crippling tests, tensile, SEM-EDS, TGA-DSC, DMA, and FT-IR analyses were conducted to investigate the mechanical, thermal, and microstructural degradation mechanisms. The results showed that elevated temperatures significantly reduced the web crippling capacity, with strength losses reaching up to 80% at 350 °C due to matrix degradation, fiber–matrix debonding, and loss of structural integrity. Among the investigated loading configurations, IG exhibited the highest load-carrying performance, whereas ETF experienced the greatest capacity reduction. A temperature-dependent reduction factor and unified empirical prediction equations were developed and demonstrated good agreement with the experimental results, with experimental-to-predicted ratios ranging from 0.97 to 1.15. The findings provide valuable insight into the post-fire behavior of pultruded GFRP hollow sections and offer practical guidance for the design, assessment, and fire safety evaluation of GFRP structural members exposed to elevated-temperature environments. Full article

In this study, twin screw extruded Polyetherimide (PEI)/Poly(ethylene terephthalate) (PET) polymer blends (90/10, 70/30, 50/50 w/w%) were investigated to elucidate the composition–property relationship governed by morphological, structural, rheological, thermomechanical, mechanical, and electromagnetic shielding (EMI) performance behavior. Among other polymer blends, the 70/30 blend exhibits superior thermomechanical stability with a significant glass transition temperature of 132.7 °C, where a robust confinement effect effectively restricts the mobility of PET chains. This morphology, characterized by a domain size of 562 nm, provides proof of concept for interface-driven attenuation, reaching a maximum EMI shielding effectiveness of 2.54 dB within the investigated blends. This performance is primarily governed by Maxwell–Wagner–Sillars polarization at the immiscible boundaries, alongside an optimized dielectric loss of tan δ ≈ 0.065. The design of these high-temperature PEI blends provides a proof of concept for interface-driven attenuation and demonstrates their potential for developing advanced EMI shielding matrices. Full article

The decades-long development of curvilinear steel bar forms has relied on both physical and analytical modelling. This study integrates these complementary approaches to optimise the geometry and topology of a paraboloid-like steel bar structure, with the aim of enhancing structural performance and material efficiency. The developed method introduces a novel Discrete Catenary Model (DCM), generated through dynamic relaxation, to define the geometry of a steel bar roof suitable for flat quadrilateral (PQ) parallelogram panels. The DCMs were arranged in parallel at equal spacing, forming a bar grid supported by four corner columns. Static analyses were performed for various cladding materials—glass, polycarbonate, and metal sheets—to compare structural material demands, with serviceability limit states for nodal displacements and member deformations serving as key criteria. The proportions of structural material consumption for structures with glass, polycarbonate, and metal panels were 1.00:0.68:0.61. For the glass-clad variant, a physical prototype of a recreational shelter was developed and subjected to laboratory testing under near-real conditions. The test results confirmed the analytical predictions regarding the structural response under loading; the differences in nodal displacements were in the order of tenths of a millimetre. The findings indicate that the application of a parametric DCM makes it possible to obtain the intended and efficient geometry already at the preliminary design stage. Therefore, the generation of a DCM can serve as a practical tool for shaping efficient curvilinear steel bar structures with PQ panels. The proposed original method can be further developed through alternative DCM forms to design efficient steel bar roof systems. Full article

Polyhydroxyalkanoates (PHAs) are bio-based, biodegradable polyesters increasingly explored as sustainable biomaterials for regenerative medicine. This review summarizes recent advances in PHA-based bone substitute materials, highlighting their properties, fabrication methods, and biological performance. PHAs combine biocompatibility, tunable mechanical behavior, and degradation into non-toxic metabolites, while copolymerization and monomer selection modulate the stiffness, crystallinity, and resorption rate. Processing techniques such as solvent casting, electrospinning, and additive manufacturing allow the production of porous architectures that mimic bone extracellular matrix. Electrospinning is particularly suitable for nanoscale fibrous matrices, whereas 3D printing enables patient-specific scaffolds with controlled geometry and interconnected porosity. Scaffold performance can be further improved through the incorporation of osteoconductive fillers, including hydroxyapatite, β-tricalcium phosphate, bioactive glasses, graphene oxide, and carbon nanotubes, as well as through drug-delivery and pro-angiogenic functionalization. In vitro and in vivo studies consistently report favorable cytocompatibility, enhanced osteogenic differentiation, vascularization, and effective repair of bone defects in animal models. However, clinical translation remains limited by production costs, variability in polymer quality, thermal processing constraints, and regulatory challenges. Future progress will rely on more efficient biosynthesis, medical-grade purification, multifunctional scaffold design, and stronger collaboration between academia, industry, and clinicians to unlock the full potential of PHAs in regenerative bone therapies. Full article

The copolymerization of biologically active N-(carboxyphenyl)maleimides with styrene was systematically investigated to elucidate the effect of positional isomerism (ortho-, meta-, and para-) on monomer reactivity and copolymer properties. Reactivity ratios (r₁, r₂) were determined using the Fineman–Ross method, and Q–e parameters were evaluated within the Alfrey–Price framework, revealing distinct electronic effects governing copolymerization behavior. Increasing the maleimide fraction in the feed resulted in decreased copolymer yield, intrinsic viscosity, molecular weight, and glass transition temperature, while all copolymers remained styrene-rich, indicating preferential styrene propagation. Comprehensive structural characterization (NMR, FTIR, and UV–Vis) confirmed successful incorporation of both monomer units. Rheological analysis demonstrated a clear viscosity trend (ortho > meta > para), highlighting the influence of substituent position on chain interactions and macromolecular architecture. Thermal analysis (TGA/DTA) showed good thermal stability up to 250–300 °C. Notably, the copolymers exhibited significant antibacterial and antifungal activity, with maximum inhibition observed against Candida albicans. This study establishes a direct correlation between substituent position and structure–property relationships, providing new insights for the rational design of functional styrenic copolymers with potential applications in antimicrobial and biomedical materials. Full article

Thermally conductive epoxy potting compounds require high filler loadings for effective heat dissipation. However, high filler loadings can increase viscosity and brittleness, thereby impairing processability and service reliability. In this study, a mesogen-containing reactive liquid–crystalline epoxy monomer (LCE) was designed, synthesized, and incorporated into a commercial thermally conductive epoxy potting compound to investigate its effects on thermal behavior, rheological and mechanical properties, thermal conductivity, and fracture-surface morphology. The chemical structure and thermotropic liquid–crystalline behavior of LCE were characterized via Fourier-transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, differential scanning calorimetry, and polarized optical microscopy. Increasing LCE loading elevated the DSC-derived glass transition temperature (T_g) from 59 °C to 96 °C and markedly increased the room-temperature complex viscosity. Single-point measurements at 25 °C showed a monotonic decrease in thermal conductivity from 0.95 to 0.52 W/(m·K) with increasing LCE content. Mechanical testing revealed that the nominal 10% LCE formulation provided the best balance between load-bearing capacity and ductility among the tested formulations, whereas higher LCE loadings were associated with greater local microstructural variation and reduced mechanical properties. This study clarifies the modulation effect of LCE on the performance balance of highly filled epoxy potting compounds, providing valuable insights for future formulation optimization. Full article

In Türkiye, working life operates within a hybrid structure in which modern production relations and traditional gender roles intertwine. The automotive sector, in particular, where hegemonic masculinity and conservative values are reproduced, creates a breeding ground for discriminatory practices and safety issues affecting LGB employees. This study aims to analyze the psychosocial and organizational mechanisms underlying LGB individuals’ decisions to disclose or conceal their identities in the context of neoconservative social pressure and industrial masculine culture in Türkiye. Using a qualitative research design grounded in the social constructivist paradigm, semi-structured interviews were conducted with 15 LGB individuals working at different levels of the sector. Data were analyzed using reflective thematic analysis. The findings revealed themes of controlled openness, emotional labor, defense mechanisms, organizational silence, micro-solidarity, and ordinary visibility. It was determined that identity management is experienced as “strategic risk management” rather than an act of liberation, that hierarchical advancement increases the “glass closet” effect, and that employees constantly exhaust their cognitive capacity in a state of “hyper-vigilance”. In conclusion, the study examines the divergence between multinational corporations’ global inclusion policies and local practices and explores the structural factors that sustain organizational silence. Full article

In recent years, the touch panel industry has experienced rapid growth. With technological maturation and progressive cost reduction, touch technology has been widely adopted in human–machine interfaces. Currently, touch panels are predominantly employed in smartphones and tablet devices, and the industry is increasingly pursuing thinner, lighter designs, driving the development of diverse touch technologies, including one-glass solution (OGS), on-cell, and in-cell architectures. To enhance competitive advantage within the touch panel industry, it is essential to improve production efficiency and elevate product quality; consequently, yield has become a critical metric for evaluating industrial competitiveness. This study adopts the electrical test yield of Touch-on-Lens (TOL) touch-sensing glass as the primary performance indicator. A Six Sigma DMAIC (Define, Measure, Analyze, Improve, Control) framework is applied to systematically address impedance-related quality defects occurring during manufacturing. First, key quality characteristics (KQCs) of the TOL touch-sensing glass process are rigorously defined. Subsequently, measurement system analysis (MSA) and process capability assessment are conducted. Next, the Taguchi method is employed to identify the most influential process factors affecting electrical test yield. Finally, response surface methodology (RSM) is utilized to determine the optimal combination of process parameter settings that maximize electrical test yield. Results from the empirical case study demonstrate that the electrical test yield improved significantly—from 90.2% to 93.6%. This outcome validates that the integrated application of the Six Sigma DMAIC methodology, combined with the Taguchi method and RSM, effectively enhances the electrical test yield of TOL sensing glass. The proposed approach offers a robust, data-driven improvement framework applicable to touch panel manufacturers seeking to optimize sensing-glass fabrication processes—thereby supporting broader industry efforts to improve product quality and reduce manufacturing costs. Full article

Fiber contamination originating from disposable dental microapplicators has received limited attention despite its potential influence on adhesive procedures. The aim of this pilot in vitro study was to evaluate fiber-like structure release associated with different microapplicator types during the application of universal adhesive systems. Three universal adhesives (Clearfil Universal Bond Quick, Gluma Universal, and G-Premio BOND) and five microapplicator types (X-Slim, Clinique, Prima, Single TIM, and ZerofloX silicone-bristle microapplicators) were evaluated. A total of 75 adhesive applications were performed on standardized sandblasted glass substrates under controlled laboratory conditions. Adhesives were actively applied for 10 s, and fiber-like structures were quantified microscopically using ImageJ software. Statistical analysis included descriptive statistics, two-way ANOVA, and Tukey post hoc testing (α = 0.05). Significant differences were observed among microapplicator types. X-Slim applicators produced the highest fiber counts, whereas Single TIM applicators demonstrated substantially lower values. No detectable fiber-like structures were observed in specimens treated with the ZerofloX silicone-bristle microapplicator. Adhesive system type showed a comparatively smaller influence on fiber counts than microapplicator design. Within the limitations of this pilot in vitro study, microapplicator type appeared to be the primary factor influencing visible fiber contamination during adhesive application. Further studies are required to determine whether the contamination patterns observed influence adhesive performance under clinically relevant conditions. Full article

In this study, Fe₇₀Ni₃₀ metal was deposited onto continuous glass fiber composites via magnetron sputtering, followed by surface coating with SiO₂. The effects of key process parameters-including Fe₇₀Ni₃₀ sputtering duration (2, 5, 10, 20, and 30 min) and SiO₂ surface coating-on the electromagnetic properties and microwave absorption performance of the materials were systematically investigated. Scanning electron microscopy (SEM) characterization revealed that as sputtering time increased, the metal coating evolved from discrete small particles into a continuous film. Cross-sectional SEM analysis further demonstrated the formation of a bilayer structure after SiO₂ introduction. X-ray diffraction (XRD) patterns confirmed the presence of diffraction peaks corresponding to the Fe₇₀Ni₃₀ alloy solid solution. Electromagnetic parameter measurements indicated that the influence of sputtering time on electromagnetic properties was primarily pronounced during the metal layer growth stage; once a continuous film was formed, the variation in electromagnetic parameters diminished. Concurrently, the SiO₂ coating exhibited a significant regulatory effect on dielectric parameters. Reflection coefficient calculations showed that the optimal absorption thickness for the single-layer material ranged from 2.5 to 3.0 mm, with the absorption peak shifting toward lower frequencies as thickness increased. However, the effective absorption bandwidth (EAB) was only 3–5 GHz, failing to meet wideband requirements. In contrast, the three-layer composite structure (total thickness: 3.8 mm) optimized via genetic algorithm achieved impedance gradient and loss synergy, expanding the EBW (R < −10 dB) from 4.8 GHz (single layer) to 10 GHz (8–18.0 GHz)-a substantial improvement over the single-layer configuration. This work provides experimental evidence and technical support for the structural design and process optimization of lightweight, high-efficiency, wideband microwave-absorbing materials. Full article

This paper investigates the viability of utilizing Fused Deposition Modeling (FDM) for the fabrication and follow-up testing of a hemispherical resonator (HR). This form of resonator has several significant applications, including the design of vibratory gyroscopes. While traditional high-precision resonators for this application rely on expensive fused-silica fabrication, this study proposes a macro-scale approach using Polylactic Acid (PLA) to enable accessible lab-scale experimentation. The specimens, featuring a unique central-hole mounting configuration, were designed in SolidWorks and analyzed via finite element methods to establish the modal hierarchy. Experimental Modal Analysis (EMA) was conducted using a Laser Doppler Vibrometer (LDV) to acquire vibration signals, which were then analyzed in NVGate, MATLAB, and MEscope to extract natural frequencies and quality factor. Results for a lab-scale HR specimen identified the n = 2 wine-glass mode with a deviation from theoretical natural frequency predictions largely attributed to inherent defects in the fabrication process. Furthermore, a frequency split of 2.15 Hz was observed due to the inherent asymmetries and mass imbalances of the fabrication method. The quality factor was evaluated via the ring-down method and validated using the half-power bandwidth (HPBW) technique. This work demonstrates that 3D-printed resonators serve as an effective, low-cost platform for isolating modal behaviors and optimizing geometric parameters before advancing to micro-scale fabrication. Full article

Large-format photovoltaic modules are increasingly adopted to improve power output and reduce system cost, but their larger exposed area may also increase wind-induced structural demand and reduce structural safety under strong wind loading. This study investigated whether large-size photovoltaic modules and their support system could remain within an acceptable safety range under representative wind loading conditions in boundary free one-directional solar arrays in Ontario. Finite element models were developed in SAP2000 to assess the effects of module size, wind speed, and tilt angle on internal force, displacement, stress, and safety factor under static wind loading. For the array comparison, literature-derived pressure coefficients were used to represent the difference between the isolated single-row case and the front row of the 8-row array. The results showed that the large-size module consistently developed higher bending moments and larger displacements than the normal-size module under the same loading condition, indicating a clear size effect. The isolated single-row case produced a larger immediate structural response than the front row of the 8-row array under the selected loading input. Under a fixed 0° tilt angle and increasing wind speed, the glass panel remained the governing safety component. Under the fixed 27 m/s wind condition and increasing tilt angle, the governing component shifted to the purlin in the large-size module, especially under high-tilt cases. These findings provide a design-oriented basis for assessing the structural safety of large-size photovoltaic systems under wind loading. Full article

Additively manufactured cellular architectures frequently exhibit brittle failure under impact due to layer-induced stress concentrations. Through the programming of architectural and material design, specifically combining Fused Deposition Modeling (FDM) lattice topology with hyperelastic polyurea infiltration, this study achieves active control over the macroscopic transition from catastrophic structural fragmentation to stable progressive collapse. To evaluate this, auxetic and honeycomb specimens printed with ABS and glass-fiber-reinforced polyamide (PA-GF) were evaluated in unreinforced and polyurea-infiltrated states under quasi-static compression, three-point bending, and Charpy impact loading. Results show that the compressive response depends primarily on cellular topology; the pure auxetic (A-A) configuration provided the highest stiffness and energy absorption. Polyurea infiltration did not significantly alter elastic stiffness but increased post-yield stability, leading to a 96.6% elastic recovery in PA-GF A-A structures. In flexure, the base polymer governed stiffness, with ABS structures measuring 68% stiffer than PA-GF. Unreinforced ABS achieved 34% higher specific energy absorption (SEA) than PA-GF under compression, with the A-H topology maximizing SEA. Under dynamic impact, PA-GF absorbed an average of 70% more energy than ABS, and the H-A configuration recorded the highest impact resistance. The addition of polyurea shifted the failure mode from brittle fragmentation to stable elastomeric deformation, increasing absorbed impact energy by 52% for ABS and over 30% for PA-GF, preventing catastrophic structural failure. Integrating topological sequencing with elastomeric confinement provides a direct method to control energy dissipation and damage tolerance in 3D-printed cellular composites. Full article

Insects secrete volatile organic compounds (VOCs) for various reasons, such as intra- or inter-species communication, attracting mates, or repelling predators. The volatiles from indoor insect pests, e.g., phenolic secretions, can impact inhabitants in various ways, causing allergies, skin and eye irritations, etc. The Mupli beetle (Luprops tristis Fabricius, 1801) is one such nuisance pest that aggregates in great numbers in indoor spaces, especially near rubber plantations in tropical African and Asian countries. This study aimed to understand the whole-body volatilome of L. tristis, comprising the first detailed study of volatiles in this insect, particularly under aggregation and laboratory conditions. Whole-body VOCs were collected from sets of 500 and 1000 beetles at different time intervals and analysed by solvent-assisted desorption followed by gas chromatography–mass spectrometry (GC-MS). Compounds released by the Mupli beetle, such as 1-Octadecanesulphonyl chloride, Decane-1,1′-oxybis-, n-Nonadecanol-1 and n-Heptadecanol-1, are reported in the literature to be allergens that cause allergic reactions such as skin and eye irritations in humans. This understanding may indicate the possible reasons for the allergic reactions in people living in these insect-inhabited indoor spaces. We also report and describe the design and development of an economically feasible glass chamber for the dynamic headspace collection of volatiles released by these beetles. Full article

Mono- and bis-guanyl hydrazone-functionalized tricyclic compounds were here designed and investigated as putative G-quadruplex ligands in the context of anticancer drug development. The G-quadruplex on Controlled Pore Glass (G4-CPG) assay, a fast and easy screening method based on affinity chromatography for identifying potential G-quadruplex binders, together with biophysical techniques such as circular dichroism and fluorescence spectroscopy, demonstrated a higher selectivity of mono- with respect to disubstituted derivatives in recognizing G-quadruplexes from telomeric and oncogenic DNA regions vs. duplexes. Among the mono-substituted compounds, higher G-quadruplex selectivity was found for those containing the pyrido [3,4-b]indole and dibenzofuran scaffolds compared to the 9H-fluorene, 9H-carbazole, and dibenzothiophene ones. Molecular docking studies suggested that the investigated ligands bound the hybrid telomeric G-quadruplex model by adopting a coplanar arrangement of the core and guanyl hydrazone moieties, both stacked on the 5′-G-quartet, while in the interaction with the parallel oncogenic G-quadruplex model the guanyl hydrazone moieties pointed towards the grooves/loops. Finally, biological assays highlighted the higher potential of mono-guanyl hydrazone-derivatized tricyclic compounds as selective anticancer agents, showing higher anticancer activity and selectivity of action than the bis-guanyl hydrazone derivatives. Full article