Indian Journal of Physics最新文献

The present study focuses on the investigation of bioconvection applications, shedding light on the significant implications for environmentally friendly and sustainable ‘green’ fuel cell technologies. In this context, the study paves the way for further exploration of the Oldroyd-B fluid model in the presence of gyrotactic microorganisms. The analysis delves into the mixed convection of the Oldroyd-B fluid with gyrotactic microorganisms, exploring the effects of an elastic surface and magnetic field interactions. Notably, the study considers the influence of chemical reaction processes, convective heating, and thermal radiation, enhancing our understanding of these complex phenomena. The governing two-dimensional equations for motion, momentum, mass, and energy were normalized using nonlinear system-wide ordinary differential equations through appropriate transformation methods. The resulting solution for this intricate physical problem was obtained using the bvp4c method, and its validity was confirmed by comparing it with previously reported findings in the literature. The study indicates that higher porosity and magnetic parameters significantly influence velocity profiles. Meanwhile, the temperature profile improves, and the thermal field is enhanced by Brownian diffusion and radiation variables. Additionally, the Peclet number affects the density of microorganisms. Furthermore, an increase in thermophoresis significantly reduces the wall heat transfer rate for both radiation and non-radiation cases.

Here, we have proposed new transformation relations between two inertial frames with relative velocity greater than speed of light and discussed the required conditions to detect superluminal particles in the physical realm. A novel theoretical formulation is conceptualized to uniquely depict the frame of reference, valid for all ranges of velocities, in a complex plane. In the tachyonic regime, the super-relativistic gamma factor is obtained by parameterizing the generalised gamma factor using the complementary frames of reference of superluminal and subluminal spaces. The formulations of transformation relations have been analysed in four different classes, i.e., two inter and two intra classes of frames, for subluminal and superluminal particles. The intra classes of frames encompass real gamma factors, whilst, inter classes of frames involve imaginary gamma factors. These transformation relations in all four different classes are expressed in 4-vector form with their respective transformation matrices ((Lambda )) and are found to be invariant under the transformations. This invariancy has led to the establishment of relationships among the transformation factors in stationary and moving frames. The velocity 4-vector relations for subluminal and superluminal particles, both in moving and stationary frames, have been evaluated. The 4-velocity transformation relations between particle velocity in stationary and moving frames are also introduced by using the transformation matrices. Based on these 4-velocity transformations, relative velocity addition relations have been deduced and discussed corresponding to each of the transformation relations. The generalised gamma factor has been concluded and validated for both frames of reference.

The present communication explores the optical, structural, compositional, and electrical properties of Copper Zinc Tin Sulfide (CZTS) and Nickel (Ni)-CZTS solar cells. A microwave-based synthesis method has been employed to synthesize CZTS and Ni-doped CZTS powders. X-ray diffraction and Raman scattering spectroscopy have confirmed the monophase kesterite crystal structure of CZTS and Ni-CZTS. Optical absorption spectroscopy of films in the UV–Visible range displays a strong absorption coefficient of more than (10^{4} {text{cm}}^{ - 1}). In response to Ni doping, the optical band gap energy of CZTS decreased to 1.41 eV from 1.5 eV. In both samples, positive Hall coefficients were detected, confirming the presence of p-type conductivity. This study aims to determine the effects of Ni-CZTS incorporation on the performance of FTO/CZTS/CdS/ZnO/Ag solar cells. The introduction of Ni-CZTS between CZTS and CdS resulted in optimum alignment and higher efficiency. 5% Ni doping concentration is found to be the optimum doping concentration, resulting in (J_{sc} = 32.5;{text{mA}}/{text{cm}}^{2}), (V_{{{text{oc}}}} = 0.541;{text{V}}), ({text{FF}} = 31%) and the efficiency is 5.4%.

A quick, efficient, and environment-friendly solution combustion approach was used to develop intense red light emitting Eu³⁺ activated Ca₉La(VO₄)₇ nanophosphor. Rietveld’s refinement of patterns obtained from XRD validated the trigonal structure & (R3c 161 space group) of the crystallized nanophosphors. Elemental analysis and surface morphology of the red phosphors were investigated by EDAX and SEM techniques. Tauc’s theory was used to determine the band gap of the host & optimized nanosample. The excitation spectra at 331 nm indicate energy transfer between VO₄³⁻ → Eu³⁺ ions, which is confirmed by photoluminescence lifetime measurements. The designated nanophosphors emit bright red light due to the ⁵D₀ → ⁷F₂ radiative transition. Dexter’s hypothesis and I–H model were used to demonstrate that dipole–dipole interactions are a true phenomenon for concentration quenching. Furthermore, the optical properties of Ca₉La_0.6Eu_0.4(VO₄)₇ nanophosphor exhibit quantum efficacy (58.67%), CIE co-ordinates (0.5192, 0.3313), and color-temperature (1717 K), making it suitable for use in wLEDs, photonic devices and based on the previously mentioned results, the optimum (i.e. Ca₉La_(1-x)Eu_x(VO₄)₇ (x = 0.4 mol%)) nanophosphor was shown to be useful for LFP (latent fingerprinting).

In this paper, we have studied the motion around the non-collinear equilibrium points in the perturbed circular restricted three-body problem. The bigger primary is considered a point mass, and the smaller primary is an unstable elongated primary. The unstable elongated primary refers to the elongated primary rotates about its centre point, i.e. at an instant, the line joining the two ends of the elongated primary and the x-axis makes an angle, (theta in [0,360^circ )). Computations of the non-collinear equilibrium points (L_{4,5}), and their linear stability, are investigated, and the results are applied to the Jupiter-Amalthea, Saturn-Prometheus and Pluto-Hydra systems. It is found that the positions of the non-collinear equilibrium points (L_{4,5}) remain unchanged with variation in the angle, (theta ), but small variation in the critical mass parameter, (mu _c) is observed. Variations of the critical mass, (mu _c), with different segment-length and its rotation are studied. Stable solutions around (L_4) are obtained in the systems of Jupiter-Amalthea, Saturn-Prometheus, and Pluto-Hydra using the established results.

The present study aims to examine the concentration effect of Eu³⁺ ions in Boro Tellurite glass and how it affects its physicochemical and photo luminescent characteristics. Using the melt quenching method, a series of Boro-Telluride glasses with the composition (30-x) TeO₂–30B₂O₃–10ZnO–30BaO–xEu₂O₃ (where x = 0.00, 0.05, 0.10, 0.50, 1.00, 1.50, 2.00, and 2.50 mol%) were synthesized. The results of the XRD analysis revealed that the prepared samples are amorphous. As the concentration of the Eu₂O₃ increases, the density and refractive index rise, but the molar volume decreases, indicating that the glass matrix has become more compact. Similarly, the absorption spectra and oscillator strength calculated with JO theory demonstrate the transition from 7F₀ to ⁵L₆ (in the UV–Vis region) and ⁷F₀ to ⁵L₆ (in the NIR region) is more intense. For TBZB–Eu7 glass, the phonon sideband energy is estimated to be 717 cm⁻¹ and compared with the BGO scintillator, the integrated scintillation efficiency is estimated to be 16.14%. These findings demonstrate that the current glasses doped with 2 mol% Eu³⁺ exhibit strong luminescence qualities and can be used for portal imaging systems (MeV energies) non-destructive analysis such as industrial and medical X-ray imaging systems, and also have potential for laser application.

The study investigates the transport properties of a ferromagnetic–non-magnetic–ferromagnetic metallic trilayer system at room temperature, focusing on electronic current flow within the plane of the film. The analysis is conducted by solving the Boltzmann kinetic equation to explore the impact of geometric random roughness on the magnetoresistance effect and the resistivity behaviour in two magnetic configurations: parallel and antiparallel. The research also examines the effects of altering the chemical composition of the interfaces. Two scattering scenarios at the outer surfaces are considered: fully specular and fully diffuse. The findings indicate that the quality of the surfaces significantly affects electron transport in these ultra-thin magnetic layers. Notably, the highest magnetoresistance is observed in trilayers with smooth interfaces and completely diffusive surfaces.

In the present study, newly synthesized nitrobenzene derivatives (PBT and PBF) doped poly(methyl methacrylate) films were prepared using spin coating techniques, and their optical properties were analyzed. The absorption spectra of various weight percentages (0.02%, 0.1%, 0.2%, and 0.3%) of nitrobenzene derivative-doped polymer films were recorded using a UV–visible spectrometer. From the absorption spectra, optical properties such as refractive index, band gap energy, extinction coefficient, and dielectric constant were calculated. The effect of doping on the optical properties of PMMA was investigated, with results revealing normal dispersive behavior from the refractive index and extinction coefficient. Atomic force microscopy and scanning electron microscopy images indicated that the synthesized films have a low degree of roughness and a smooth surface. Additionally, the nonlinear optical properties of the PBF-doped polymer film were investigated, and the β value was determined to be 7.403 cm/W. Overall, the findings suggest that PBF-doped polymer films are promising candidates for photonic applications.

This paper investigates the enhancement of absorption in thin-film silicon solar cells using rectangular prism nanoparticles, analyzed through the finite-difference time-domain method. The study incorporates perfectly matched layer boundaries and periodic boundary conditions to accurately model light interaction. Monitors placed 5 nm within the silicon layer are used to assess input and output light intensities and minimize undesired reflections. The primary focus is on studying the impact of nanoparticle positioning within the silicon layer (referred to as buried nanoparticles) on absorption enhancement. Results indicate that absorption enhancement increases as nanoparticles are buried deeper into the silicon absorber layer, up to a depth of 60 nm. However, beyond this depth (up to 80 nm), the enhancement diminishes, achieving only 40% of the maximum enhancement observed. When nanoparticles are buried 100 nm into the silicon absorber layer, the absorption enhancement reaches 84%, representing the highest reported enhancement in this study.

A tunable multi-channel band-pass plasmonic filter in the near-infrared range is investigated using the finite element numerical method (FEM). The structure of the proposed waveguide filter consists of several dielectric slots sandwiched between two metal layers. The slots are filled with air and silica. Numerical analysis and simulation demonstrate that the number of bandpass channels, amplitude, intensity, and bandwidth can be adjusted by changing the geometrical parameters such as material, length of each slot, width, and number of intermediate slots in the filter. The proposed filter was studied in the wavelength range of 1–4 μm, exhibiting 2 to 5 transmission peaks with varying transmission powers. Given that the incident wavelength in this article is larger than the dimensions of the waveguide and slot, this structure can focus the light within a sub-wavelength scale. The proposed structure is expected to be used as an essential component of photonics devices due to its ability to confine light in the sub-wavelength region, simple fabrication, and multi-channel operation.