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We consider a nonlocal hyperbolic problem. It arises in the field of MEMS control. First, we review the stationary problem and state that there exists a unique and no solution for small and large parameter, respectively. Next, we introduce the results of global existence and dynamical properties of solution for the hyperbolic equation. Finally, we derive the result of the quenching behaviour. As proven in similar problems, we show that the quenching occurs for large parameter. This criterion is also expressed by means of the first eigenvalue of Laplace operator. [ABSTRACT FROM AUTHOR]

The influence of processing procedures and microstructural features on the functional properties of relaxor ferroelectric ceramics are of fundamental interest and directly relevant to their applications in dielectric capacitors and electromechanical sensors/actuators. In the present work, solid solutions of 0.65(K0.5Bi0.5)TiO3-0.35(Ba0.94Ca0.06)(Ti0.93Zr0.07)O3 (0.65KBT-0.35BCZT) were processed by solid-state reaction using two different procedures, distinguished in terms of mixed or separate calcination of the KBT and BCZT components and leading to homogeneous or core-shell-type relaxor ferroelectric ceramics, respectively. Systematic research was conducted on the impact of the processing techniques and air-quenching procedures on the structure and ferroelectric and electromechanical properties. Higher remanent polarization of the separately calcined materials was ascribed to the ferroelectric nature of the core regions, along with the non-ergodic relaxor ferroelectric response in the shell, which was enhanced by the quenching process. It was also demonstrated that the thermal depolarization temperature increased significantly after quenching, from ~100 to ~160 °C for the separately calcined ceramic, and from ~50 to ~130 °C for the mixed material; moreover, these effects are linked to notable improvements in the ferroelectric tetragonal phase content by air-quenching. [ABSTRACT FROM AUTHOR]

Understanding the volume fractions of microstructure constituents such as ferrite, pearlite, bainite, and martensite in low-alloy steels is critical for tailoring mechanical properties to specific engineering applications. To address the complexity of these relationships, this study explores the use of artificial neural networks (ANNs) as a robust tool for predicting these microstructure constituents based on alloy composition, specific Jominy distance, and heat treatment parameters. Unlike previous ANN-based predictions that rely on the hardness after quenching as an input parameter, this study excludes hardness. The developed model relies on readily available input parameters, enabling accurate estimation of microstructure composition prior to heat treatment, which significantly improves its practicality for process planning, optimization, and reducing trial-and-error on industrial applications. Three different input configurations were tested to evaluate the predictive capabilities of ANNs, with results showing that the use of specific Jominy distance as an input variable enhances model performance. Furthermore, the findings suggest that specific Jominy distance could serve as a practical alternative to detailed chemical composition data in industrial applications. The predictions for ferrite, pearlite, and martensite were more accurate than those for bainite, which can be attributed to the complex nature of bainite formation. [ABSTRACT FROM AUTHOR]

As reported during the last five years, SnSe is one of the leading thermoelectric (TE) materials with a very low lattice thermal conductivity. However, its elements are not as heavy as those of classical thermoelectric materials like PbTe or Bi2Te3. Its outstanding TE properties were revealed after repeated purification steps to minimize the amount of oxygen contamination, followed by spark plasma sintering. Recently, we showed that hot-pressing—once optimized—can yield comparable or even better TE performance using the examples of Na- and Cu- as well as Na- and Ag-co-doped SnSe. However, long-term stability remains a challenge during cycling between low and high temperatures. Here, we investigated whether the cooling procedure has a significant impact on the thermoelectric properties of SnSe. We compared cooling of the melt with a 1:1 ratio of Sn:Se from 1273 K down to room temperature in air with quenching in water. As typical for undoped SnSe, both materials were extrinsic p-type semiconductors due to Sn defects. The air-quenched sample exhibited higher thermal conductivity, lower electrical conductivity, and higher Seebeck coefficient, all consistent with a smaller number of defects and thus a smaller number of charge carriers due to the slower cooling procedure. This resulted in a comparatively low peak figure-of-merit value zT of 0.61 at 823 K for the air-quenched sample, compared to the substantially higher peak zT of 1.58 at 813 K for the water-quenched sample. [ABSTRACT FROM AUTHOR]

Fluorescent lifetimes of dissolved organic matter (DOM) and associated physicochemical parameters were measured over 14 months in an estuary in Southern California, USA. Measurements were made on 77 samples from sites near the inlet, mid-estuary, and outlet to maximize the range of physicochemical variables. Time-resolved fluorescence data were well fit to a triexponential model with an intermediate lifetime component (τ1: 1 to 5 ns), a long lifetime component (τ2: 2 to 15 ns), and a short lifetime component (τ3: < 1 ns). The amplitude of the short-lived component dominated all measurements (60–70%). However, fractional contributions to steady-state fluorescence were dominated by the intermediate and long-lived components at most wavelengths. Lifetimes varied as a function of both excitation and emission wavelength suggesting structural differences in DOM fluorophores. Lifetimes decreased from the estuary inlet to the outlet and were positively correlated with absorbance and DOC concentrations and negatively correlated with salinity and spectral slope. Quenching experiments with halide ions demonstrated that fluorophores are quenched by heavy ions and that different fluorophores are quenched at different rates. However, concentrations of ions in seawater are not high enough for quenching to completely account for observed lifetime changes across the estuary. The observed variation in lifetimes between sites is instead primarily attributed to structural changes associated with DOM processing. Higher lifetimes are associated with less processed material at the inlet site. [ABSTRACT FROM AUTHOR]

The effects of erbium (III) oxide (Er2O3) on the structural, photoluminescence, mechanical, and dielectric characteristics of glass (70 − x)B2O3 + 10BaTiO3 + 20Li2O + xEr2O3 where (x = 0, 0.25, 0.50, 0.75, and 1 mol%) have been explored. The melt quenching technique was used for manufacturing borate glasses with various Er2O3 concentrations. The FTIR spectra exhibit many absorption bands at various wavenumbers, which are associated with the vibrational modes of the borate network and the Ba2+, Li2+, and OH groups. The photoluminescence was examined through the excitation of the prepared glass samples by a helium–cadmium laser with a wavelength of 325 nm; the peak of the emission transition, which ranges from 4S3/2 to 4I15/2 at 543 nm, is most intense, and its intensity increases as the amount of Er3+ ions increases. The mechanical investigations demonstrated that adding rare earth ions changed the network structure of these glasses, causing the longitudinal velocity (VL) to decline from 6415.4 to 5950 m/s and the shear velocity (VS) to decrease from 3528.9 to 3281.5 m/s. The dielectric studies showed that the dielectric constant and the electrical conductivity increase with increasing Er2O3 up to 0.5 mol%; after that, they reduce, while the dielectric loss decreases noticeably at low frequencies as the concentration of Er3+ ions increases. [ABSTRACT FROM AUTHOR]

Detecting antibiotic residues is crucial for monitoring their excessive use in healthcare and agricultural practices. Herein, a new 3D metal–organic framework (MOF) containing {[Cd (bpyp)(sdba)]·DMF·2H2O}n (1) (bpyp = 2,5‐bis (pyrid‐4‐yl)pyridine and H2sdba = 4,4′‐sulfonyldibenzoic acid) has been designed and synthesized. MOF 1 displays sensitive detection tetracycline (TCY) with a limit of detection below 7.67 × 10−6 M in an aqueous solution. The detection mechanism involves competitive absorption between MOF 1 and antibiotics, supported by UV–vis spectroscopy and fluorescence lifetime measurements. MOF 1 exhibits a visible fluorescence response to TCY under a 254 nm UV lamp. MOF 1 is applied in the quantitative detection of TCY in lake water with the recovery based on the sensing platform was 92.26–107.54% with RSD (%) less than 4.38%, indicating outstanding reliability. [ABSTRACT FROM AUTHOR]

Abundant plastic waste degradation to microplastics may cause pollution hazards for the environment. The circulation of microplastic pollution supports the initiation of research related to detecting microplastics in the environment. One method for detecting microplastics is the utilization of the fluorescence properties of carbon quantum dots (CQDs). In this study, CQDs will be produced through the hydrothermal method using oil palm fronds as a carbon source because of their lignin levels of up to 26%. To obtain this carbon, oil palm fronds are crushed and then converted into biochar through a pyrolysis process. Biochar is used as a precursor for the manufacture of CQDs produced through the hydrothermal method at temperature variations of 180°C, 190°C, and 200°C. In this study, CQDs were produced with a peak of 291 nm in the UV wavelength range, which indicates the presence of a π-π* absorption band in the carbon structure of CQDs. The emergence of dominant C=C, O-H and C=O groups in the FTIR test also proves the success of CQDs production through this hydrothermal method. The CQDs produced at the three temperature variations are less than 10 nm in size and have the highest fluorescence intensity at 200°C when excited at 405 nm. Moreover, CQDs exhibit a promising ability for detecting microplastics, as indicated by their decreasing fluorescence intensity trend in response to polyethylene (PE) and polyethylene terephthalate (PET) added solution. [ABSTRACT FROM AUTHOR]

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The rapid development of nanotechnology has significantly revolutionized wearable electronics and expanded their functionality. Through introducing innovative solutions for energy harvesting and autonomous sensing, this research presents a cost‐effective strategy to enhance the performance of triboelectric nanogenerators (TENGs). The TENG was fabricated from polyvinylidene fluoride (PVDF) and N, N′‐poly(methyl methacrylate) (PMMA) blend with a porous structure via a novel optimized quenching method. The developed approach results in a high β‐phase content (85.7%) PVDF/3wt.%PMMA porous blend, known for its superior piezoelectric properties. PVDF/3wt.%PMMA modified porous TENG demonstrates remarkable electrical output, with a dielectric constant of 40 and an open‐circuit voltage of approximately 600 V. The porous matrix notably increases durability, enduring over 36 000 operational cycles without performance degradation. Moreover, practical applications were explored in this research, including powering LEDs and pacemakers with a maximum power output of 750 mW m−2. Also, TENG served as a self‐powered tactile sensor for robotic applications in various temperature conditions. The work highlights the potential of the PVDF/PMMA porous blend to utilize the next‐generation self‐powered sensors and power small electronic devices. [ABSTRACT FROM AUTHOR]

Undoped and Mn-doped TiO2 nanoparticles (NPs) are synthesized by a sol–gel method and calcined at 500 °C for 2 h. The shift in XPS analyses confirmed the incorporation of Mn in the TiO2 lattice, which induces surface-related oxygen vacancies accompanied by the formation of Ti3+ and Mn4+ oxidation states. The XRD analysis reveals that a pure anatase phase is observed for undoped and 0.05 mol% Mn-doped, whereas anatase–rutile mixed phase with a dominant anatase phase is formed at 0.1–0.2 mol% Mn doping. The crystallite size calculated using the Scherrer model decreases from 25 to 17 nm, while the specific surface area increases from 65.6 to 77.7 m2/g with increasing Mn content (0–0.2 mol%). The HRTEM image reveals that the lattice fringe spacing is 0.35 nm, which is in line with the (101) plane of the TiO2 anatase phase. The SAED pattern further supports the polycrystalline nature of the observed structure. The optical band gap for undoped TiO2 NPs was found to be 3.2 eV, and this value is increased to 3.3 eV for 0.2 mol% Mn-doped TiO2 NPs. The highest PL emission intensity was obtained for 0.2 mol% Mn, and this intensity was significantly reduced at a higher Mn doping level. The oxygen defects and Mn related impurities act as luminescence centers and increase the PL emission intensity. The composition-optimized 0.2 mol% Mn-doped TiO2 exhibited strong PL emission, a high value of quantum efficiency, and a prolonged lifetime. The results of this work suggest that Mn-doped TiO2 nanoparticles may be a good option for making light-emitting devices. [ABSTRACT FROM AUTHOR]