Search Results (6,330)

The performance of soil nailed walls is evaluated based on lateral displacements, especially in high walls. In this study, the displacement behavior of nailed walls, which are frequently preferred in retaining wall systems in hard clayey soils, was examined by taking into account the corner effect. The nailed wall model was created using Plaxis 2D v.23, and the performance of the model was verified with the results of inclinometer measurements taken on-site. To assess the influence of excavation pit dimensions on the corner effect, 25 three-dimensional and 25 plane–strain slice models were created using Plaxis 3D v.23, and the effect of excavation pit dimensions on the plane–strain ratio (PSR) was determined. Then, analysis studies were carried out by creating 336 3D and 336 plane–strain slice models with variable parameters, such as slope angle (β), wall angle (α), nail length (L/H), excavation depth (H), and distance from the corner (xH). Its effects on PSR were determined. The interactions of the parameters with each other and PSR estimation were evaluated using machine learning (ML) methods: artificial neural networks (ANN), classifical and regression tree (CART), support vector regression (SVR), extreme gradient boosting (XGBoost). The proposed ML prediction methods and PSR results were compared with performance metrics and reliable results were obtained. Full article

Lithium-ion batteries are superior energy storage devices that are widely utilized in various fields, from electric cars to small portable electric devices. However, their susceptibility to thermal runaway necessitates improvements in battery case materials to improve their safety. This study used electrochemical analyses, including open-circuit potential (OCP), potentiodynamic polarization, and critical pitting temperature (CPT) analyses, to investigate the corrosion resistance of super duplex stainless steel (SAF 2507) applied to battery cases in relation to post-weld heat treatment (PWHT) time. The microstructure during the manufacture, laser welding, and PWHT was analyzed using field-emission scanning electron microscopy, X-ray diffraction, and electron backscatter diffraction, and the chemical composition was analyzed using dispersive X-ray spectroscopy and electron probe micro-analysis. The PWHT increased the volume fraction of austenite from 5% to 50% over 3 min at 1200 °C; this increased the OCP from −0.21 V to +0.03 V, and increased the CPT from 56 °C to 73 °C. The PWHT effectively improved the corrosion resistance, laying the groundwork for utilizing SAF 2507 in battery case materials. But the alloy segregation and heterogeneous grain morphology after PWHT needs improvement. Full article

Spinel-type InGaMgO₄ with a = 8.56615(3) Å was prepared by treating layered YbFe₂O₄-type InGaMgO₄ at 6 GPa and 1473 K. DFT calculation and Rietveld analysis of synchrotron X-ray powder diffraction data revealed the inverse spinel structure with In³⁺:Ga³⁺/Mg²⁺ = 0.726:0.274 in the tetrahedral site and 0.137:0.863 in the octahedral site. InGaMgO₄ spinel is an insulator with an experimental band gap of 2.80 eV, and the attempt at hole doping by post-annealing in a reducing atmosphere to introduce an oxygen defect was unsuccessful. This is the first report of the bulk synthesis of AB₂O₄ compounds with both YbFe₂O₄ and spinel polymorphs. Full article

Two-dimensional (2D) ferromagnetic semiconductors (FM SCs) provide an ideal platform for the development of quantum information technology in nanoscale devices. However, many developed 2D FM materials present a very low Curie temperature (T_C), greatly limiting their application in spintronic devices. In this work, we predict two stable 2D transition metal chalcogenides, V₃Se₃X₂ (X = S, Te) monolayers, by using first-principles calculations. Our results show that the V₃Se₃Te₂ monolayer is a robust bipolar magnetic SC with a moderate bandgap of 0.53 eV, while V₃Se₃S₂ is a direct band-gap FM SC with a bandgap of 0.59 eV. Interestingly, the ferromagnetisms of both monolayers are robust due to the V–S/Se/Te–V superexchange interaction, and T_Cs are about 406 K and 301 K, respectively. Applying biaxial strains, the FM SC to antiferromagnetic (AFM) SC transition is revealed at 5% and 3% of biaxial tensile strain. In addition, their high mechanical, dynamical, and thermal stabilities are further verified by phonon dispersion calculations and ab initio molecular dynamics (AIMD) calculations. Their outstanding attributes render the V₃Se₃Y₂ (Y = S, Te) monolayers promising candidates as 2D FM SCs for a wide range of applications. Full article

Transition metal oxides (TMOs) are important anode materials in sodium-ion batteries (SIBs) due to their high theoretical capacities, abundant resources, and cost-effectiveness. However, issues such as the low conductivity and large volume variation of TMO bulk materials during the cycling process result in poor electrochemical performance. Nanosizing and compositing with carbon materials are two effective strategies to overcome these issues. In this study, spherical MnFe₂O₄@xC nanocomposites composed of MnFe₂O₄ inner cores and tunable carbon shell thicknesses were successfully prepared and utilized as anode materials for SIBs. It was found that the property of the carbon shell plays a crucial role in tuning the electrochemical performance of MnFe₂O₄@xC nanocomposites and an appropriate carbon shell thickness (content) leads to the optimal battery performance. Thus, compared to MnFe₂O₄@1C and MnFe₂O₄@8C, MnFe₂O₄@4C nanocomposite exhibits optimal electrochemical performance by releasing a reversible specific capacity of around 308 mAh·g⁻¹ at 0.1 A·g⁻¹ with 93% capacity retention after 100 cycles, 250 mAh·g⁻¹ at 1.0 A g⁻¹ with 73% capacity retention after 300 cycles in a half cell, and around 111 mAh·g⁻¹ at 1.0 C when coupled with a Na₃V₂(PO₄)₃ (NVP) cathode in a full SIB cell. Full article

Hexavalent chromium (Cr(VI)), a pervasive industrial contaminant, is highly toxic to both humans and animals. However, its effects on turtles are largely unexplored. Our study aimed to investigate the toxic effects of Cr(VI) on the Reeves’ turtles (Mauremys reevesii) primary hepatocytes. We exposed hepatocytes to two concentrations (25 μM and 50 μM) of Cr(VI) for 24 h. The results showed that compared to controls, Cr(VI)-treated cells showed elevated antioxidant enzyme activity (catalase (CAT) and superoxide dismutase (SOD)) and increased reactive oxygen species (ROS) levels. Adenosine triphosphatae (ATP) levels decreased, indicating mitochondrial dysfunction. Additionally, we found significant changes in mitochondrial dynamics related genes, with downregulation of mitofusin 2 (Mfn2) and silent information regulator 1 (SIRT1) and a decrease in sirtuin 3 (SIRT3) and tumor protein 53 (p53) mRNA levels. Annexin V-FITC fluorescence staining-positive cells increased with higher Cr(VI) concentrations, marked by elevated bcl-2-associated X protein (Bax) and cysteinyl aspartate specific proteinase (Caspase3) mRNA levels and reduced B-cell lymphoma-2 (Bcl2) expression. Autophagy-related genes were also affected, with increased microtubule-associated protein 1 light chain 3 (LC3-I), microtubule-associated protein light chain 3II (LC3-II), unc-51-like autophagy-activating kinase 1 (ULK1), and sequestosome 1 (p62/SQSTM1) mRNA levels and decreased mammalian target of rapamycin (mTOR) and Beclin1 expression. Taken together, Cr(VI) promotes cell apoptosis and autophagy in turtle hepatocytes by inducing oxidative stress and disrupting mitochondrial function. These findings highlight the serious health risks posed by Cr(VI) pollution and emphasize the need for protecting wild turtle populations. Full article

Although many people have been vaccinated against COVID-19, infections with SARS-CoV-2 seem hard to avoid. There is a need to develop more effective vaccines and immunization strategies against emerging variants of infectious diseases. To understand whether different immunization strategies using variants sequence-based virus-like particles (VLPs) vaccines could offer superior immunity against future SARS-CoV-2 variants, our team constructed VLPs for the original Wuhan-Hu-1 strain (prototype), Delta (δ) variant, and Omicron (ο) variant of SARS-CoV-2, using baculovirus-insect expression system. Then we used these VLPs to assess the immune responses induced by homologous prime-boost, heterologous prime-boost, and sequential immunizations strategies in a mouse model. Our results showed that the pro+δ+ο sequential strategies elicited better neutralizing antibody responses. These sequential strategies also take advantage of inducing CD4⁺ T and CD8⁺ T lymphocytes proliferation and tendency to cytokine of Th1. Currently, our data suggest that sequential immunization with VLPs of encoding spike protein derived from SARS-CoV-2 variants of concern may be a potential vaccine strategy against emerging diseases, such as “Disease X”. Full article

The functionality of the NiTi shape memory alloy was improved through engineering Ag-SiO₂-TiO₂ nanocomposite coatings. For this purpose, an anaphoretic deposition process, conducted at a constant voltage of 40 V and deposition times ranging from 1 to 10 min, was used. Scanning electron microscopy (SEM) analysis demonstrated that the deposition parameters significantly impacted the morphology of the coatings. Complementary Raman Spectroscopy and X-ray diffraction (XRD) analyses confirmed the successful formation of distinct nanocomposite layers, and revealed the details of their crystalline structure and chemical composition. After that, the adhesion between the NiTi substrate and the electrophoretically deposited ceramic coatings was improved through a post-deposition heat treatment. To prevent excessive shrinkage and cracking of the coating, tests were carried out to characterize the behavior of the coating material at elevated temperatures. The nanocomposite coatings were exposed to a temperature of 800 °C for 2 h. The annealing induced significant structural and morphological transformations, resulting in layers that were distinctly different from both the original materials and those produced solely through electrophoretic deposition. The thermal treatment resulted in the formation of a new kind of nanocomposite structure with enhanced reactivity. Full article

This study explores the utilization of cathodic vacuum arc (CVA) technology to address the limitations of magnetron sputtering technology in preparing amorphous carbon (a-C) coatings, such as having a low ionization rate, low deposition rate, and insufficiently dense structure. Specifically, a-C coatings were prepared by the cathodic vacuum arc (CVA)and the filtered cathodic vacuum arc (FCVA) technology,, one with embedded carbon particles and one without, both having closely related carbon structures. Research is currently underway on bipolar plate coatings for fuel cells. The corrosion behavior of the prepared a-C coatings was examined through Tafel polarization analysis under simulated fuel cell operating conditions as well as potentiostatic analysis at 0.6 V under normal conditions and 1.6 V under start–stop conditions for 7200 s. The coatings before and after corrosion are characterized using scanning electron microscopy, energy-dispersive X-ray spectroscopy, Raman spectroscopy, and infrared spectroscopy. The results reveal that the incorporation of conductive graphite-like particles in the coatings reduces their contact resistance. However, the gaps between these particles and the coatings act as pathways for corrosive solution, exacerbating the corrosion of the coatings. After corrosion at 0.6 V, both sets of coatings with sp²-hybridized carbon structures are contaminated by elements such as hydrogen and oxygen, leading to an increase in their contact resistance. Under high potential conditions (1.6 V), large corrosion pits and defects appear at the locations of graphite-like carbon particles. Furthermore, both sets of samples exhibit more severe oxygen contamination and a transformation of broken carbon bonds from sp³- to sp²-hybridized forms, irrespective of whether embedded graphite particles are present. Full article

Energy storage efficiency (η) and large recoverable energy density (W_re) are necessary for antiferroelectric materials in order to develop antiferroelectric-based dielectric capacitors with exceptional energy storage capacity. In the present paper, the effect of doping La³⁺ on the energy storage capacity of Pb_1−xLa_x(Hf_0.45Sn_0.55)_0.995O₃ antiferroelectric ceramics was studied. Adjusting the content of La and changing the phase structure of PLHS from antiferroelectric to relaxor ferroelectric gradually, which narrowed its hysteresis loop, yielded a high energy storage efficiency of 81.9% and the maximum breakdown field strength of 200 kV/cm when x = 2 mol%. In addition, the recoverable energy density and energy storage efficiency both showed excellent temperature stability and frequency stability in the temperature range of 10–110 °C and the frequency range of 10–100 Hz, suggesting that Pb_0.98La_0.02(Hf_0.45Sn_0.55)_0.995O₃ are favorable materials candidates for the preparation of pulsed-power capacitors that can be used in a wide range of conditions. Full article

Recently, the application of two–dimensional (2D) piezoelectric materials has been seriously hindered because most of them possess only in–plane piezoelectricity but lack out–of–plane piezoelectricity. In this work, using first–principles calculation, by atomic substitution of penta–graphene (PG) with tiny out–of–plane piezoelectricity, we design and predict stable 2D X–PG (X = Si or Ge) semiconductors with excellent in–plane and out–of–plane piezoelectricity and extremely high in–plane hole mobility. Among them, Ge–PG exhibits better performance in all aspects with an in–plane strain piezoelectric coefficient d₁₁ = 8.43 pm/V, an out–of–plane strain piezoelectric coefficient d₃₃ = −3.63 pm/V, and in–plane hole mobility μ_h = 57.33 × 10³ cm² V⁻¹ s⁻¹. By doping Si and Ge atoms, the negative Poisson’s ratio of PG approaches zero and reaches a positive value, which is due to the gradual weakening of the structure’s mechanical strength. The bandgaps of Si–PG (0.78 eV) and Ge–PG (0.89 eV) are much smaller than that of PG (2.20 eV), by 2.82 and 2.47 times, respectively. This indicates that the substitution of X atoms can regulate the bandgap of PG. Importantly, the physical mechanism of the out–of–plane piezoelectricity of these monolayers is revealed. The super–dipole–moment effect proposed in the previous work is proved to exist in PG and X–PG, i.e., it is proved that their out–of–plane piezoelectric stress coefficient e₃₃ increases with the super–dipole–moment. The e₃₃–induced polarization direction is also consistent with the super–dipole–moment direction. X–PG is predicted to have prominent potential for nanodevices applied as electromechanical coupling systems: wearable, ultra–thin devices; high–speed electronic transmission devices; and so on. Full article

Orthogonal time frequency space (OTFS) modulation has recently found its place in the literature as a much more effective waveform in time-varying channels. It is anticipated that OTFS will be widely used in the communications of smart vehicles, especially those considered within the scope of Internet of Things (IoT). There are efforts to obtain customized traditional point-to-point single-input single-output (SISO)-OTFS studies in the literature, but their BER performance seems a bit low. It is possible to use cooperative communications in order improve BER performance, but it is noticeable that there are very few OTFS studies in the area of cooperative communications. In this study, to the best of the authors’ knowledge, it is addressed for the first time in the literature that better performance is achieved for the OTFS waveform transmission in a selective decode-and-forward (SDF) cooperative communication scenario. In this context, by establishing a cooperative communication model consisting of a base station/source, a traffic sign/relay and a smart vehicle/destination moving at a constant speed, an end-to-end BER expression is derived. SNR-BER analysis is performed with this SDF-OTFS scheme and it is shown that a superior BER performance is achieved compared to the traditional point-to-point single-input single-output (SISO)-OTFS structure. Full article

Assessing physical activity is important in the treatment of chronic conditions, including chronic low back pain (cLBP). ActiGraph™, a widely used physical activity monitor, collects raw acceleration data, and processes these data through proprietary algorithms to produce physical activity measures. The purpose of this study was to replicate ActiGraph™ algorithms in MATLAB and test the validity of this method with both healthy controls and participants with cLBP. MATLAB code was developed to replicate ActiGraph™’s activity counts and step counts algorithms, to sum the activity counts into counts per minute (CPM), and categorize each minute into activity intensity cut points. A free-living validation was performed where 24 individuals, 12 cLBP and 12 healthy, wore an ActiGraph™ GT9X on their non-dominant hip for up to seven days. The raw acceleration data were processed in both ActiLife™ (v6), ActiGraph™’s data analysis software platform, and through MATLAB (2022a). Percent errors between methods for all 24 participants, as well as separated by cLBP and healthy, were all less than 2%. ActiGraph™ algorithms were replicated and validated for both populations, based on minimal error differences between ActiLife™ and MATLAB, allowing researchers to analyze data from any accelerometer in a manner comparable to ActiLife™. Full article

We report the effect of high-temperature treatment on the structure and photoluminescence of zinc selenite nanocrystals (ZnSeO₃) deposited into SiO₂/Si track templates. The templates were formed via irradiation with Xe ions (200 MeV, 10⁸ ions/cm²) followed by etching in HF solution. ZnSeO₃ nanocrystals were obtained via chemical deposition from the aqueous solution of ZnCl₂ and SeO₂ as Zn-, Se- and O-precursors. To estimate the thermal stability of the deposited precipitates, heat treatment was carried out at 800 and 1000 °C for 60 min in a vacuum environment. Scanning electron microscopy (SEM), X-ray diffractometry (XRD), photoluminescence (PL) spectroscopy, and electrical measurements were used for the characterization of ZnSeO₃/SiO_2nanoporous/Si nanocomposites. Thermal treatment of the synthesized nanocomposites resulted in structural transformations with the formation of ZnSe and ZnO phases while the content of the ZnSeO₃ phase decreased. For the as-deposited and annealed precipitates, an emission in the range of (400 to 600) nm was observed. PL spectra were approximated by four Gaussian curves with maxima at ~550 nm (2.2 eV), 488 nm (2.54 eV), ~440 nm (2.82 eV), and 410 nm (3.03 eV). Annealing resulted in a decrease in PL intensity that was possibly due to the weight loss of the deposited substance during high-temperature treatment. The redistribution of maxima intensities after annealing was also observed with an increase in blue and violet emissions. The origin of the observed PL is discussed. The I–V curve analysis revealed an electronic type of conductivity for the ZnSeO₃(NCs)/SiO_2nanoporous/Si structure. The values of the specific conductivity were calculated within the percolation model. The sample annealed at 800 °C showed the highest specific conductivity of 8.5 × 10⁻⁶ Ohm⁻¹·cm⁻¹. Full article