Search Results (420)

In this study, we report the results of the structural characterization and electrochemical evaluation of novel cobalt-free layered Ruddlesden–Popper (RP) oxides, La₂SrFe₂O_7−δ and La₂SrFe_1.8Ga_0.2O_7−δ, as electrode materials for intermediate-temperature solid oxide cells. X-ray diffraction confirmed the formation of RP phases and phase stability after reducing treatment. The materials showed compatible thermal expansion behavior, with slightly lower thermal expansion coefficients for the Ga-doped composition. Oxygen pressure relaxation measurements demonstrated that the oxygen surface exchange coefficient increases with temperature and pO₂, while Ga substitution slightly reduces the O₂/oxide exchange rate, which may be associated with a lower concentration of oxygen vacancies. The electrical conductivity in air was higher for La₂SrFe₂O_7−δ than for the Ga-doped sample, while both compositions showed much lower conductivity under reducing conditions. Symmetrical cell impedance spectroscopy showed high polarization resistance for the electrodes, which was substantially reduced by applying a Ag current collector (0.43 Ω cm² for La₂SrFe₂O_7−δ and 0.73 Ω cm² for La₂SrFe_1.8Ga_0.2O_7−δ at 800 °C), consistent with the limited electronic conductivity of the oxide layers. Overall, both oxides exhibit structural stability, acceptable thermomechanical compatibility, and measurable oxygen exchange activity, making them promising candidates for further development as cobalt-free electrodes in solid oxide cells. Full article

Superparamagnetic materials have attracted increasing attention for high-frequency microwave absorption because superparamagnetic relaxation can partially overcome the high-frequency limitations of conventional magnetic absorbers. Herein, Fe₃O₄/rGO composite powders were prepared by electrostatic self-assembly and subsequently incorporated into an epoxy matrix, and magnetic-field-induced alignment was introduced during curing. Owing to the synergistic effects of interfacial polarization, magnetic dissipation, and improved impedance matching, the optimized composites exhibited markedly enhanced microwave absorption performance. In particular, when the rGO content was 10 wt% and an external magnetic field was applied, the composite achieved effective absorption across the entire X-band (8–12 GHz) within a thickness range of 1–3 mm, together with a minimum reflection loss of −40.3 dB. The enhanced performance is attributed to the combined contributions of abundant heterogeneous interfaces, superparamagnetic relaxation, and field-induced orientation of Fe₃O₄-decorated rGO sheets. This work provides a simple physical strategy for the microstructural regulation of magnetic–dielectric composites toward high-performance microwave absorption. Full article

Resveratrol (RSV) is a poorly water-soluble polyphenolic compound with various potential health benefits, but its pharmaceutical application is limited by low aqueous solubility and poor oral bioavailability. Additive manufacturing (AM), particularly fused deposition modeling (FDM) 3D printing, offers a flexible approach for fabricating oral dosage forms with customized geometry and internal architecture. In this study, hot-melt extrusion (HME) combined with fused deposition modeling (FDM) 3D printing was used to prepare RSV-loaded tablets with different infill patterns. Hydroxypropyl methylcellulose acetate succinate and hydroxypropyl cellulose were selected as polymeric carriers to prepare RSV-loaded filaments suitable for FDM printing. The effects of infill pattern on the solid-state characteristics, dimensional accuracy, mechanical properties, floating behavior, and in vitro drug release of the printed tablets were systematically investigated. Differential scanning calorimetry, powder X-ray diffraction, and polarized light microscopy indicated that RSV was mainly converted into an amorphous or molecularly dispersed state after HME and FDM processing. All designed tablets were successfully printed and showed acceptable shape fidelity, while different infill patterns resulted in variations in tablet weight, mechanical strength, floating duration, and release behavior. In vitro dissolution studies showed that the RSV release profiles were dependent on the internal infill architecture. Tablets with more complex infill patterns generally exhibited slower drug release, which may be related to differences in internal pore structure, medium penetration pathways, matrix hydration, and diffusion distance. Release kinetic analysis further suggested that RSV release from the printed tablets involved a combination of diffusion and polymer relaxation processes. These results demonstrate that infill pattern is an important structural parameter for modulating the mechanical performance and drug release behavior of FDM 3D-printed RSV tablets. This study provides useful guidance for the design of 3D-printed oral dosage forms with tunable release characteristics. Full article

This paper presents a method for estimating moisture content (%MC) in power transformers. It primarily relies on the analysis of the statistical properties of relaxation times characterizing the dielectric frequency response (DFR), which is fitted as a sum of rational functions using the Vector Fitting (VF) tool. The DFR is modeled as a sum of Debye terms (accounting for materials exhibiting different relaxation times due to multiple polarization processes) characterized by poles and residues provided by VF. These parameters are then used to derive statistical factors that correlate with the shape of the dielectric response curve in the context of the Havriliak–Negami (HN) model, which is known for its effectiveness in characterizing materials with multiple relaxation times. By correlating the statistical factors with the HN model parameters, substantial insights into the insulation condition can be achieved. A moisture index (MI) is proposed from these parameters, which, when combined with conductivity, allows for accurate %MC estimation in the solid insulation system (cellulose). The combined MI and conductivity capture combined effects on moisture behavior, addressing both conductivity and polarization losses at different frequencies. The proposed method provides an efficient and straightforward non-invasive approach to insulation assessment without complex optimization algorithms. Experimental work on transformers at varying moisture levels provides validation of the proposed approach and demonstrates strong correlation with industry standards. The results confirm its reliability for moisture evaluation in transformer monitoring. Full article

High-temperature vulcanized (HTV) silicone rubber serves as the core material for composite insulators, and its high-frequency dielectric properties directly dictate its macroscopic insulation performance. However, traditional electrical detection methods encounter a “high-frequency blind zone” above the gigahertz (GHz) range due to limited precision and ambiguous physical mechanisms. In this study, terahertz time-domain spectroscopy (THz-TDS) was employed to characterize the complex permittivity spectra of silicone rubber specimens, incorporated with varying ratios of alumina trihydrate (ATH) and silica (SiO₂) fillers, across the 0.1–3.0 THz frequency range. Experimental results reveal that the terahertz dielectric characteristics of silicone rubber exhibit a pronounced filler dependency: as the ATH content increases from 95 phr to 185 phr, the real part of the permittivity at 1 THz increases by 32%. Notably, all specimens manifest a sharp dielectric transition near 1.2 THz, characterized by distinct dual absorption peaks in the imaginary permittivity spectra. To characterize this non-linear transition, a hybrid Debye–Lorentz model is innovatively introduced. This approach overcomes the inherent limitations of traditional double Debye models, which are restricted to relaxation processes and fail to account for high-frequency resonance. Fitting results and physical analysis demonstrate that the response at 1.2 THz is primarily attributed to the bending vibrations of Si-O-Si bonds in the polymer backbone, alongside the collective vibration modes of Al-O bonds and the hydrogen-bonded network within the fillers. The hybrid model successfully decouples three distinct polarization mechanisms: conduction loss (<0.5 THz), dipole relaxation (0.5–1.0 THz), and lattice resonance (>1.0 THz). This work provides a robust characterization framework for the quantitative evaluation of the high-frequency dielectric response and microstructural integrity of composite insulators. Full article

Biomass-derived carbon-based electromagnetic wave (EMW) absorbers have attracted significant attention for their abundant availability and environmentally friendly characteristics. A novel strategy combining biomass templates with a ZIF-67-assisted approach was developed to fabricate Co₃O₄@C composites via pyrolysis. This work demonstrates that the intrinsic structure of biomass templates can be effectively leveraged to regulate both the microstructure and the electromagnetic properties of the resulting composites, enabling tunable microwave absorption performance. Among the prepared samples, M3 exhibits the lowest reflection loss (RL) of −54.79 dB at a thickness of 4.61 mm, and achieves an effective absorption bandwidth (EAB) of 3.43 GHz at 2.82 mm. This superior performance originates from the synergistic optimization of impedance matching and the coupling of dielectric and magnetic loss mechanisms. The porous biomass-derived carbon framework not only enhances multiple scattering and impedance matching but also provides abundant interfaces to induce strong interfacial and dipole polarization. Meanwhile, the uniform in situ growth of ZIF-67-derived Co₃O₄ nanoparticles introduces enhanced magnetic loss through exchange resonance, while structural defects further promote multiple dielectric relaxation processes. This study presents a novel waste-to-value strategy for the rational design of hierarchical composite absorbers, offering high-performance EMW absorption while demonstrating a low-cost, environmentally friendly, and scalable route for converting natural wood waste into functional materials. This work not only provides new insights into constructing high-performance, lightweight, and cost-effective EMW-absorbing materials but also aligns with the principles of sustainable development, resource efficiency, and green chemistry. Full article

The rise in electromagnetic radiation has created a dire need for the development of sheer absorbing composites with tunable dielectric and magnetic responses. With interfacial engineering in carbonaceous systems, high absorption efficiency and sheerness can be obtained in the X-band region. In this work, acid-functionalized carbon nanotube/ZnO (f-MWNT/ZnO) composites have been developed and investigated to understand the effect of functionalization on electromagnetic response. Permittivity data revealed a stronger frequency-dependent response in f-MWNT/ZnO, ascribed to polarization losses induced by oxygen-containing functional groups. Furthermore, dielectric loss and Cole–Cole plots indicated numerous Debye relaxation processes in combination with Maxwell–Wagner–Sillars polarizations. Permeability measurements signify distinct peaks for f-MWNT/ZnO attributed to exchange and natural resonance; however, the pristine carbon nanotube-derived (MWNT/ZnO) composite exhibits a weaker response. Stemming from the synergy of dielectric–magnetic interactions and improved impedance matching, the f-MWNT/ZnO composite with a thickness of 1.9 mm achieved an RL of −12.7 dB, corresponding to a ~94% absorption efficiency at 12.3 GHz. Additionally, the composite exhibited autonomous self-healing, enabling the reintegration of two separated segments at 70 °C for 40 min. The findings highlight the critical role of functionalization in tailoring interfacial characteristics and enhancing absorption performance. Full article

To address the durability limitations of conventional crack sealants under coupled extreme temperatures and traffic loads in long-life pavements, a bio-oil composite-modified patching material was developed using 90# base asphalt as the matrix, synergistically modified with crumb rubber (CR) and epoxidized soybean oil (ESO). To resolve the contradictory requirements for high elasticity and thermal expansion/contraction coordination in sealants, ESO was introduced; its polar epoxy groups optimize phase compatibility and promote low-temperature stress relaxation without restricting thermal deformability. Rheological evaluations revealed that the optimal system (OPT) successfully extended the service temperature window from PG 76–−24 °C (baseline) to PG 82–−24 °C, significantly enhancing its adaptability to extreme climatic fluctuations. At −24 °C, OPT exhibited a reduced creep stiffness (S) of 164 MPa and an increased creep rate (m) of 0.312, with a cracking resistance ratio (k) as low as 525.6; the quantitative significance of these metrics lies in granting the sealant superior stress relaxation capacity, enabling it to accommodate dynamic crack widening without interfacial debonding or brittle fracture. Fatigue testing via time sweeps demonstrated that N_f50 reached 2890 cycles, highlighting robust long-term resistance against high-frequency shear strains induced by tire edges. Micro-mechanistic analyses (FTIR, TG/DTG, and DSC) confirmed that the modification is primarily driven by physical blending. The elevation of the thermal decomposition threshold (T5%) to 302.4 °C and the residue at 600 °C to 44.8% provide a critical safety margin for high-temperature construction heating, preventing thermal degradation. Furthermore, the glass transition temperature (T_g) decreased to approximately −35.2 °C. These findings establish a rigorous quantitative and mechanistic framework for designing sustainable, high-performance patching materials for resilient pavement maintenance. Full article

Fast and scalable lithium-ion cell diagnostics require measurements that are shorter and simpler than full impedance analysis, yet richer and more interpretable than single scalar resistance indicators or raw waveform classification alone. This paper introduces a practical recovery stamp screening method in which short post-load voltage recovery intervals after pulse and pulse–multisine excitation are treated as compact diagnostic events, rather than as single resistance-like indices or parameter identification segments. For this purpose, a constrained two-timescale relaxation model is introduced to retain fast and slower recovery contributions in a low-dimensional form. Using laboratory measurements on two lithium-ion pouch cell families based on nickel manganese cobalt oxide (NMC)/graphite and LiFePO₄/graphite chemistry, each retained load removal event is converted into a signed, current-normalized recovery curve and parameterized by the proposed model. The fitted parameters provide a compact, physics-informed recovery state, while the resampled local waveform preserves transition morphology and short-time relaxation structure that are not fully retained by compact variables alone. These two inputs are evaluated separately and jointly in ordered event sequences under a reference-centered binary screening formulation. The curated dataset comprises 48 original recovery events. Local label-preserving augmentation is applied as training-side regularization, yielding 490 event instances and 230 event sequences. A scalar recovery-amplitude baseline has reached balanced accuracies of 0.833 without and 0.929 with operating context, whereas the best deep learning result is obtained only when fitted variables and waveform are combined. In that setting, TimesNet has reached a median validation balanced accuracy of 0.938. These findings show that post-load polarization recovery contains diagnostically useful information beyond scalar amplitude measures and can support rapid, interpretable reference-deviation screening. Full article

Generalized anxiety disorder (GAD) is characterized by persistent, excessive, and difficult-to-control worry. The Contrast Avoidance Model (CAM) proposes that individuals with GAD use worry to sustain negative emotional arousal, thereby avoiding sharp negative emotional contrasts that would otherwise follow unexpected adverse events. A virtual reality (VR) protocol was developed to simulate such contrasts by alternating guided relaxation with brief anxiety-inducing scenarios (skyline plank, crowded elevator, and loose dog encounter). This study evaluated the usability and feasibility of this protocol in 20 subclinical adults aged 18–45 who met a screening threshold of GAD-7 ≥ 5, using a Meta Quest 3 headset and Polar H10 heart rate sensor. Exposure segments produced a significant decrease in RMSSD (β = −0.185, p < 0.001), consistent with reduced parasympathetic activity during exposure, whereas heart rate did not differ significantly between conditions. Subjectively, exposure increased SUDS (β = 2.23, p < 0.001) and SAM arousal (β = 1.95, p < 0.001), and decreased SAM valence (β = −2.68, p < 0.001) and dominance (β = −1.70, p = 0.005). Presence scores, cybersickness ratings, and qualitative feedback supported the usability of the protocol and identified concrete design refinements. These results support the feasibility of the protocol and provide a foundation for future controlled clinical evaluation. Full article

Negative capacitance (NC) has been reported across a wide range of physical systems, yet its interpretation has remained fragmented due to the lack of a unified conceptual framework. Existing explanations—spanning ferroelectric free-energy curvature, tunneling transport, plasmonic resonances, and electronic compressibility—have often been treated as unrelated or even contradictory. This review resolves these inconsistencies by showing that all manifestations of NC arise from non-synchronization between external excitation and internal response. We classify NC into three fundamental categories: temporal mismatch, originating from delays or inertia in charge or polarization dynamics; spatial mismatch, caused by nonuniform field or mode distributions; and quantitative mismatch, resulting from intrinsic parameter reversal such as negative curvature or negative compressibility. Despite their diverse physical origins, these mechanisms share the same mathematical signature (${\mathrm{C}}_{eff}=\partial \mathrm{Q}/\partial \mathrm{V}<0$). Organizing NC within this unified framework clarifies long-standing ambiguities, connects previously isolated research fields, and establishes a systematic foundation for engineering NC in electronic, photonic, and quantum devices. The framework further highlights tunnel-current-induced NC as a representative single-particle mechanism within the temporal mismatch category, expanding the scope of NC beyond ferroelectricity and collective modes. Overall, this work positions NC not as a singular anomaly but as a universal response class emerging from the interplay between excitation and internal dynamics. Full article

Nanocomposites consisting of titanium carbonitride nanoparticles (TiCN) and epoxy resin were fabricated and studied as the filler content was varied. Nanocomposites’ structural investigation was conducted via X-ray Diffraction technique (XRD), while their morphology was examined by employing Scanning Electron Microscopy (SEM). Viscoelastic mechanical properties were assessed by Dynamic Mechanical Thermal Analysis (DMTA). Results revealed the reinforcing ability of TiCN nanoparticles. The dielectric characterization of the nanocomposites was carried out using Broadband Dielectric Spectroscopy (BDS) over a wide frequency and temperature range. Dielectric spectroscopy revealed two relaxation processes related to the polymer matrix: the α-relaxation, associated with the glass-to-rubber transition, and the β-relaxation, associated with the rearrangement of side polar groups. In addition, in the low-frequency–high-temperature region, interfacial polarization (IP) was observed. IP is related to the presence of nanoparticles and to the accumulation of unbound charges at the system’s interface and includes contributions from a dipolar process and charge migration (conductivity). Alternating current conductivity generally increases with filler content, though it is also affected by frequency and temperature. Conductivity could influence Electrode Polarization (EP), which often masks the dipolar process of IP. A simple method for removing the EP effect is formulated and tested. Full article

This study analyzes tourist loyalty in the Monarch Butterfly Biosphere Reserve by integrating affinity-based segmentation and the Forgotten Effects Theory within a fuzzy logic framework. The objective was to identify how visitor affinities condition the indirect construction of loyalty in contexts of high environmental complexity. Data were collected through a structured questionnaire administered to 316 tourists using a non-probabilistic sampling approach. Using the Pichat Algorithm and the Forgotten Effects Theory, the research captured gradual membership patterns and mediated relationships that conventional models often overlook. Results indicate that, while age, particularly Generation X, acts as a connecting axis, postgraduate education levels generate a polarization of visitor perceptions across segments. Significant forgotten effects (up to 0.30) were identified, suggesting that variables such as satisfaction, entertainment, and relaxation act as mediating mechanisms between learning, perceived value, and the intention to revisit. This study suggests that loyalty is not constructed directly but is indirectly shaped by affinity-based visitor structures. It recommends that management strategies evolve toward environmental edutainment models and that marketing efforts be diversified according to differentiated visitor profiles. These findings demonstrate the utility of fuzzy logic for the strategic management of high-value ecological destinations. Full article

An aluminum-doped NaTaO₃ perovskite sample was prepared by the ultrasonic method, employing an immersed sonotrode, followed by thermal treatment at 600 °C for 6 h in air. X-ray diffraction analysis reveals a biphasic system with relatively low crystallinity, consisting of a dominant NaTaO₃ perovskite phase and a secondary Na₂Ta₄O₁₁ phase. Optical investigations indicate a reduced band gap energy of 3.77 eV compared to undoped NaTaO₃ (4 eV), suggesting enhanced absorption toward the infrared region and improved photocatalytic potential. Fourier Transform Infrared FTIR Spectroscopy highlights the emergence of a distinct absorption band at 670 cm⁻¹, attributed to Ta–O and Al–O stretching vibrations, evidencing successful incorporation of Al dopants. Complex impedance analysis over the frequency and temperature ranges of (20 Hz–2 MHz) and (29–100) °C identifies, for the first time, the semiconductor–conductor transition temperature at 58 °C. Nyquist analysis further supports the coexistence of grain and grain boundary contributions, modeled via equivalent R and CPE parallel circuits. Conductivity studies confirm obedience to Jonscher’s universal law, with a change in σ_DC slope near 54 °C, corroborating semiconductor–conductor transition behavior. Dielectric measurements similarly indicate a relaxation process linked to interfacial polarization, with a transition temperature of (~54 °C). Overall, the ultrasonic synthesis route uniquely enables a biphasic structure that facilitates the observation of a low-temperature semiconductor-to-conductor transition, absent in analogous single-phase materials obtained via sol–gel methods. Full article

Tensile fracture in asphalt involves complex mechanical responses and component migration. This study employs molecular dynamics (MD) simulations with the COPMASS II force field to investigate water intrusion at the asphalt–aggregate interface and subsequent tensile cracking at the nanoscale. To evaluate moisture damage, a ternary interface model was constructed using a specific distribution of water molecules at a target density. Results indicate that thickness significantly enhances moisture resistance; specifically, the asphalt film in the thinnest model (AS1) was penetrated by water molecules, leading to localized interfacial failure. Further uniaxial tensile simulations at a loading rate of 0.01 Å/psreveal that as film thickness increases (AS1 to AS4), the peak stress rises from 103.2 to 113.8 MPa, and the fracture energy increases from 136 to 747 kcal/mol. Based on the density redistribution of SARA fractions, component migration is divided into three stages: structural relaxation, resin-driven de-peptization, and polar component re-aggregation. Finally, the Asphaltene Index (I_A) is proposed as a predictive indicator, showing that cracks consistently initiate in regions with minimum I_A values. These findings provide quantitative insights into the molecular mechanisms underlying asphalt durability. Full article