Indian Journal of Pure & Applied Physics (IJPAP)

Hybrid Nanofluid Flow for Mixed Convection along a Vertical Sheet in Presence of Porous Media with Heat Source, Variable Temperature, and Thermal Radiation

2025-05-01T10:08:59+0530

The study of a hybrid nanofluid flowing in a mixed convection along a vertical sheet in the presence of porous media with heat source, variable temperature, and thermal radiation is examined. By the similarity transformation, the governing equations are transformed into non-dimensional differential equations and solved with the help of the shooting technique using the Runge-Kutta method. The physical significance of the contributive parameters through graphs and tables are presented by the bvp4c solver in Matlab software and found that an increase in the heat source, thermal radiation, and mixed convection increases the fluid velocity of the hybrid nanofluid. The inclusion of variable temperature boundary conditions leads to a decrease in fluid velocity and temperature with the involvement of the particle concentration.

Reliable EAR Method to Increase the Performance of a Solar PV Array connected in TCT fashion even in Partial Shading Condition

2025-04-28T11:06:38+0530

In partial shading condition (PSC), the solar photo-voltaic (PV) array’s efficiency is significantly reduced. Although using a bypass diode increases the efficiency of a PV array that is connected in series, it also causes problems with multiple peaks (local and global peaks). Total-Cross-Tied (TCT) connections are suggested in the literature as a solution to these problems. Despite having superior performance when compared to other configurations like SP, bridge links, honeycomb, etc., the TCT-connected PV array does not provide satisfactory results for all types of shading patterns. This work proposes a robust algorithm to address these problems, allowing PV installers to achieve high efficiency under any type of shading pattern. The electrical array reconfiguration (EAR) technique is used in the proposed algorithm. The results of laboratoryscale experiments and MATLAB simulations used to verify the proposed model demonstrate extremely close coordination.

Possible Solution for the Gauge Hierarchy Problem and Vacuum Catastrophe

2025-04-28T11:46:09+0530

The two important problems, namely the 'gauge hierarchy problem' or 'fine-tuning problem,' and the problem of the 'vacuum catastrophe' or the 'cosmological constant problem,' pose significant challenges to our deeper understanding of both micro and macro-level energy systems. The methods of renormalization and supersymmetry (SUSY) are applied in both cases, either to fine-tune or to theoretically cancel out the energy. In this paper, we propose that, in reality, no energy gets cancelled out, contrary to SUSY, but instead remains unchanged. We demonstrate mathematically that the energy of a quantum state remains in a particular state to maintain its full potential, thus remaining undetected. Following a dynamics of the fundamental quantum energy state, referred to as the "Like Potential Energy" (LPE) dynamics, we explain the nature of this undetectable quantum state. We have discovered that by keeping the area of the quantum phase space constant while increasing the energy of the Quantum Harmonic Oscillator (QHO), we may reach a situation where the vibration becomes extremely high, resulting in a high energy level in the QHO. However, the Quantum
Oscillatory Energy (QOE) remains unmanifested, having no discernible impact on its surroundings.
As a result, we have developed a new wave equation and a tensor using the LPE dynamics.

Contribution of Tensor Forces and Exchange Term for (3He, t) Charge Exchange Reactions on Different Mass Targets

2025-05-05T11:27:22+0530

The angular distribution and unit cross-section for (3He, t) charge exchange reactions at 140 MeV/nucleon on ¹³C, ²⁶Mg, ⁵⁸Ni, and ¹²⁰Sn targets have been computed by employing the distorted wave impulse approximation. Particularly, the contribution of tensor forces and knock-on exchange term have been estimated and the substantial quantitative variations in the cross-section have been found which in turn brings the predications closure to the experimental results.

Miniaturized Metamaterial Loaded Multiband Antenna for Sub-6 GHz Applications

2025-04-23T15:47:35+0530

A multiband metamaterial loaded antenna of dimensions 37.5 × 45 mm² is designed to resonate at four frequencies 1.74, 2.48, 3, and 3.5 GHz respectively suitable for sub-6 GHz applications. The initial structure incorporates slots to facilitate multiband capabilities. The slot dimensions in the radiating patch are determined through parametric analysis. Further, Genetic Algorithm (GA) and Quasi Newton (QN) optimization are utilized to validate the results of parametric analysis. For miniaturization, the Split Ring Resonator (SRR) and Complementary Split Ring Resonator (CSRR) are incorporated and analyzed. The inclusion of a metamaterial unit cell resulted in a size reduction of 53% from the conventional structure. Along with size reduction, there is a substantial improvement in gain for CSRR incorporated structure. The proposed CSRR implemented structure has been fabricated and the validation of the results is carried out.

Sequential Phase Feed Based Circularly Polarized RFID Reader Antenna for 2.45 GHz Applications

2025-04-30T12:13:43+0530

A wideband, circularly polarized (CP) reader antenna is presented for 2.45 GHz RFID systems. To achieve circular
polarization, the antenna features a circular radiating patch on the top layer, fed by a sequential phase feed network located
on the bottom layer. An air gap is introduced between the two layers to minimize dielectric loss, thereby enhancing
directivity and radiation efficiency, which in turn increases overall gain. Cylindrical copper wires passing through the air
gap connect the bottom feed network to the top patch layer. By implementing incremental phase variations across the four
outputs of the feed network, the antenna achieves a −10 dB impedance bandwidth of 650 MHz (2.02–2.67 GHz) and a
circular polarization axial ratio (CP AR) bandwidth of 150 MHz (2.366–2.527 GHz). The antenna exhibits a peak gain of
8.4 dBiC and maintains a symmetric radiation pattern at 2.45 GHz. The physical dimensions of the antenna are 70 × 70 ×
13.2 mm³. The design provides a 3 dB axial ratio beamwidth of 91° and a half-power beamwidth of 63.9° in the X–Z plane
and 64° in the Y–Z plane. An equivalent circuit analysis is performed to better estimate the antenna's performance. The
design is experimentally verified and compared with simulation results. The proposed antenna is particularly suitable for
mobile RFID applications operating at 2.45 GHz, such as inventory management, asset tracking, access control, electronic
toll collection, and medication distribution.

Tailoring Elastic, Mechanical, Thermophysical and Ultrasonic Properties of TMCs (TM= V, Nb, Ta)

2025-04-23T16:01:41+0530

The elastic, mechanical, and thermoacoustic properties of transition metal carbides (VC, NbC, and TaC) were systematically
analyzed with respect to orientation and temperature. The second-third-and fourth-order elastic constants were determined using
the Coulomb and Born-Mayer potential model in the temperature regime 0–500 K. The analysis confirmed the elastic stability
of VC, NbC and TaC. Mechanical properties derived from the second-order elastic constants, reveals that VC, NbC, and TaC
exhibit brittle characteristics at room temperature. The thermal parameters, including Debye temperature, thermal conductivity
and thermal relaxation time were evaluated along the <100>, <110>, <111> orientations. The Debye velocity and Debye temperature were observed to reach maximum values along the <100> direction. The relaxation time due to thermal phonon process is of the order of intermetallics. Ultrasonic attenuation was predominantly governed by the Akhiezer mechanism rather than thermal relaxation effects. The calculated values were compared with other B1-structured materials, and the performance of VC, NbC, and TaC was assessed based on the obtained parameters.

Design Voltage-Controlled Oscillator using I-MOS Varactor for Selective Tuning for UHF Band Applications

2025-05-02T16:43:56+0530

To optimize frequency tuning, noise performance, and power efficiency under various process, voltage, and temperature
(PVT) conditions, the study investigates the design, implementation, and evaluation of two novel voltage-controlled oscillators
(VCOs) for Ultra High Frequency (UHF) applications. The first design is a 180-nm CMOS, five-stage Current-Starved Voltage
Controlled Oscillator (CSVCO) with improved tuning via an Inversion mode MOS (I-MOS) varactor. Fine-grained frequency
modulation is made possible by an exact bias current control method. Monte Carlo simulations and extensive PVT analysis
verify the circuit's robustness. Power-sensitive applications benefit greatly from the CSVCO's broad tuning range (0.119–2.91
GHz), low power consumption (1.16 mW), and phase noise of -91.80 dBc/Hz at a 1 MHz offset.
In order to improve tuning and spectrum purity, the second design is an LC-VCO with a current-controlled tail biasing
structure. The LC tank balances low noise, efficiency, and stability for UHF wireless systems by improving phase noise,
attaining -128.37 dBc/Hz at 1 MHz offset throughout a tuning range of 2.418–2.439 GHz with a 5.66 mW power consumption.
These ideas improve the efficiency and dependability of contemporary UHF circuits by introducing innovative tuning
methods and optimizations.

Thermal Impact of Chronic Exposure to High-Frequency Non-ionizing EM Radiation on Avian Skin: A Theoretical Approach

2025-04-23T16:09:21+0530

The manuscript reveals that the high-frequency electromagnetic radiations emitted from transmission towers affect birds' health. As the number of mobile phones is increasing rapidly, this radiation is present almost everywhere in the environment. This study uses a theoretical model based on Maxwell's equations to evaluate the thermal effects of electromagnetic radiation (EMR) of 3.5 GHz to 5.5 GHz frequency on avian skin. When birds fly from 1 to 10 m around a mobile phone tower, the electric field intensity is decreased by 90%. The results of the Specific Absorption Rate (SAR) inside the skin of avian show that its value is directly proportional to the frequency of the incident electromagnetic wave. The change in temperature in the skin tissue is calculated for the electromagnetic wave exposure duration of 1 to 15 min. At a frequency of 5.5 GHz and 1 m from a transmission source, the SAR reached 27.65 W/kg, and the skin temperature increased by up to 7.11°C after 15 min of exposure, indicating significant bioeffects. This study aids in the protection of birds by evaluating the thermal effects of electromagnetic radiation exposure and contributes to establishing safer exposure limits.

Structural Modification of Sol-Gel derived Nickel Ferrite and its derivatives via Rare Earth Doping and Its Impact on Electrical Properties

2025-04-28T16:08:12+0530

Nickel ferrite (NiFe₂O₄), known for its exceptional magnetic behaviour and high electrical resistance, is commonly used in magnetic sensors, transformers, and high-frequency electronics. However, its inherent electrical qualities frequently require improvement for application in more demanding technological situations. This paper examines the structural and electrical evolution of nickel ferrite generated in sol-gel using rare earth (RE) ions such Gd³⁺, La³⁺, Nd³⁺, Sm³⁺, and Ho³⁺. Because of their greater ionic sizes and different electronic structures, these dopants cause significant lattice distortions, change cation site distributions, and, at higher concentrations, generate secondary non-spinel phases. These alterations greatly impact electron transport by affecting the Fe²⁺/Fe³⁺ hopping process. This allows for manipulation of resistivity and dielectric characteristics. The article also examines how critical synthesis parameters, such as solution pH and combustion agent selection, affect phase formation and microstructural uniformity. RE replacement improves the dielectric constant, loss characteristics, and electrical conductivity of these modified ferrites, highlighting their potential in applications such as electromagnetic interference (EMI) shielding, energy storage systems, and downsized electronic components. The research continues by discussing optimization tactics for dopant inclusion and synthesis conditions in order to modify functional features of Nickel ferrite family for future device integration.