Results in Physics最新文献

Significance

The thermal analysis of nanofluid in a vertical cylinder (artery) in a magnetized environment holds significant implications in physiological and thermal regulation networks. This research is significant in biomedical engineering with applications like medical diagnostics and treatment strategies.

Motive

This study investigates the thermal behavior of a magnetized blood-based ternary Carreau nanofluid flowing through a vertically bounded artery with quadratic convection. Velocity and heat transfer analysis is conducted within the artery, utilizing thermal radiation and quadratic convection in a magnetized setting. The base fluid consists of blood, augmented with three nanoparticles: CuO, Al₂O₃, and TiO₂. The investigation centers on examining the properties of blood nanofluid, arterial geometry, and thermal dynamics.

Methodology

The physical model generates a set of partial differential equations (PDEs) and similarities mechanism is utilized to fetch its non dimensional form in terms of ordinary differential equations (ODEs). Furthermore, numerical outcomes are obtained with Matlab function bvp4c and obtained data set is trained through robust scheme Levenberg-Marquardt neural network (LMNN) procedure to predict the solution.

Findings

Velocity of blood is reduced with increased values of wiessenberg number, magnetic parameter and mixed convection parameter and velocity increases for Second-order convection parameter. Temperature profile decreases with curvature parameter, mixed convection parameter and permeability parameter.

Geometries, stabilities, bonding nature, and vibrational properties of bimetallic KMg_n^0/– (n = 2–12) clusters have been comprehensively studied by CALYPSO code within DFT calculations. The results reveal the structural transition from 2D to 3D at n = 3. From n ≥ 8, the geometry of KMg_n^0/– transfers a hollow framework with a six-atom triangular prism unit. By comparing the geometry of neutral and anionic KMg_n^0/– clusters, most of them are structurally different. In all doped clusters, the K atoms tend to localize on the convex positions of the skeleton and play the role of electron donors. Two highly stable clusters KMg₉ and KMg₉^– have been found, and studies showed that the prominent stability benefits from their compact magnesium structural motifs and quasi-full/full shell electronic configurations. Additionally, bonding nature analysis reflects there is much weak K-Mg interaction than Mg-Mg interaction in the KMg₉^0/– clusters. The spectroscopic properties based on the PES, IR and Raman spectra have also been discussed.

Herein, the modification of indium oxide thermoelectric materials was carried out to investigate the effect of Si doping on the thermoelectric properties of In₂O₃. By precisely controlling the doping concentration of Si, a series of Si-doped In₂O₃ have been successfully prepared, and the thermoelectric properties have been systematically studied. The experimental results indicate that appropriate Si doping content can optimize the band structure and carrier concentration, significantly increase the electrical conductivity and power factor of In₂O₃, and effectively reduce the thermal conductivity, increase the thermoelectric value (ZT value) of the material with the highest value of ∼0.316 (973 K). In addition, Si doping could enhance the Vickers hardness of the material and improve the mechanical properties of the material. This study not only provides a new idea for optimizing the performances of indium oxide thermoelectric materials, but also provides a valuable reference for the development and application of thermoelectric materials.

In this work, an in situ characterization of the high-pressure and high-temperature phase diagram of ruthenium was carried out. This experiment was performed using a combination of laser-heated diamond anvil cell (LH-DAC) and X-ray diffraction (XRD) techniques at the beamline ID27 of the European Synchrotron Radiation Facility (ESRF). XRD patterns were collected in the range of 15 GPa to 110 GPa and from ambient temperature up to 6600 K. While the hcp-fcc transition, predicted to occur at elevated temperatures was not observed, this study has produced the first experimental observation of a solid–liquid phase transition of Ru at HP conditions. A P-V-T equation of state valid up to 100 GPa and 3000 K is reported.

High-throughput computing has been widely used in the field of material design because of its feasibility, efficiency, accuracy and predictability. Fourteen new high-temperature SiC polymorphs were theoretically established via high-throughput screening, and density functional theory (DFT) was employed to investigate their physical properties. The new SiC polymorphs have mechanical and thermodynamic stability, and 10 of them can even maintain thermal stability at high temperatures up to 2000 K. The electronic band structure obtained by the Heyd–Scuseria–Ernzerhof (HSE06) hybrid functional shows that 13 of the new SiC polymorphs have a wide bandgap, 6 of which have a direct or quasi-direct bandgap. Notably, compared with those of 3C-SiC, the holes of I4₁/a-II SiC, I4₁/a-IV SiC, and P4/ncc-I SiC have lower effective masses in the [1 0 0] direction; in particular, the hole effective mass of P4/ncc-I SiC is only approximately 4.6 % of that of 3C-SiC. Owing to their direct wide bandgap, excellent thermal stability and low effective mass, the newly proposed SiC polymorphs have great application potential in the field of microelectronics.

We propose an on-chip photoelectric hybrid convolution accelerator based on Bragg grating array. The weight of the convolution kernel can be adjusted by controlling the central wavelengths of the Bragg grating array. We conducted simulation verification of the functionality and scalability of this on-chip photoelectric hybrid convolution accelerator. Subsequently, we constructed a neural network model to conduct handwritten digit classification simulations using this accelerator, achieving a simulation accuracy of 93.99%. Finally, the concept of the proposed on-chip photoelectric hybrid convolution accelerator is successfully verified. Due to the merits of Bragg grating, the proposed scheme paves the way for realizing high-performance on-chip optical neural networks.

In this paper, we present a graphene-based metamaterial ultrawideband absorber operating in the terahertz regime. The absorber is composed of two patterned and continuous graphene layers, a bottom gold layer, and a SiO₂ substrate that separates the continuous graphene layer from the gold layer. The absorption spectrum is enhanced by integrating a graphene resonator with water, which has frequency-dependent permittivity. The water is encapsulated in polytetrafluoroethylene (PTFE) in the form of a circular ring sandwiched between the two graphene layers. Simulation results show that the absorber attains a 90 % absorption bandwidth of about 14.55 THz. The proposed absorber is polarization-insensitive under normal incidence. For TE polarization, the absorption level remains stable for incident angles θ from 0° to 55° across the entire frequency band (14.55 THz), except for the 5–8 THz range. For TM polarization, the absorption level remains stable for θ ranging from 0° to 60° over the entire bandwidth. Additionally, the absorption level is consistent for both TM and TE polarizations across the entire bandwidth for incident angles φ from 0° to 90°.

Carbyne nanocrystal (CN), as a kind of one-dimensional (1D) sp-hybridized carbon allotrope, has attracted much attention due to its excellent optical and transport properties. However, the lattice properties of 1D CNs under high temperature remain unclear. In our work, we investigate the stability and lattice properties of 1DCNs based on the atomic-bond-relaxation (ABR) approach and first-principles calculations. We find the change of transverse vibration frequencies and bond kinks induced by the thermal effect plays a significant role in the mechanical properties of 1D CNs. We establish a relationship between kink angle and phonon vibration modes, giving a deep inside into high frequency and low-frequency vibration behavior of 1D CNs. Our results indicate the phonon vibration modes modulated by kinks under applied temperatures can lead to a negative thermal expansion behavior in the axial direction of 1D CNs, suggesting an effective way to control the thermal properties of 1D CNs for practical applications.

Broadband metamaterial absorbers hold promise for solar energy harvesting, but their complex designs and use of expensive noble metals hinder scalability and thermal stability. Additionally, traditional design methods are time-consuming. We propose a novel approach that combines a genetic algorithm with the transfer matrix method to optimize both material composition and layer structure for large-scale, cost-effective, and thermally stable solar absorbers. This method enables the design of near-perfect absorbers with an average absorptance exceeding 90 % and over 80 % across a broad wavelength range (0.3–2.5 μm) within the key solar spectrum. By optimizing the arrangement of metal and insulator layers using nitride materials (e.g., vanadium nitride), we achieve superior performance compared to traditional metal–insulator and insulator–metal structures. This optimization utilizes resonant absorption and the inherent absorption of metal layers. Our work paves the way for efficient and scalable solar energy harvesting devices.