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Research Article
Impact of Varying Thermal Conductivity and Viscosity on Natural Convection Flow Along a Vertical Flat Plate with Heat Conduction and Viscous Dissipation
Md. Al-Amin,
Md. Mahmud Alam,
Sree Pradip Kumer Sarker*
Issue:
Volume 13, Issue 6, December 2025
Pages:
148-161
Received:
19 April 2025
Accepted:
26 May 2025
Published:
9 December 2025
Abstract: This study examines how natural convection flow down a vertical flat plate is affected by varying viscosity and thermal conductivity, taking into account the effects of heat conduction and viscous dissipation. The fluid flow and heat transfer are described mathematically, accounting for temperature-dependent changes in thermal conductivity and viscosity. Using suitable boundary conditions, the governing equations—such as the momentum, energy, and continuity equations—are numerically solved. The impact of these changes on temperature distributions, velocity profiles, Nusselt number, and total heat transfer efficiency is the main focus of the analysis. The findings show that changes in thermal conductivity and viscosity have a major effect on the establishment of thermal boundary layers, heat transfer efficiency, and flow characteristics. The research was conducted to improve the comprehension and prediction of heat transfer processes in a variety of engineering applications by examining the effect of varying thermal conductivity and viscosity on natural convection flow along a vertical flat plate with heat conduction and viscous dissipation. Natural convection is essential in situations where heat transmission occurs without external mechanical aid, including cooling systems, electronic gadgets, and building ventilation. Researchers seek to create more precise models for predicting fluid flow and heat transfer behaviour under varying settings by examining these changes.
Abstract: This study examines how natural convection flow down a vertical flat plate is affected by varying viscosity and thermal conductivity, taking into account the effects of heat conduction and viscous dissipation. The fluid flow and heat transfer are described mathematically, accounting for temperature-dependent changes in thermal conductivity and visc...
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Research Article
Evaluation of Patient Dose from Chest Ct Examinations in Selected Diagnostics Centres in Abuja, Nigeria
Issue:
Volume 13, Issue 6, December 2025
Pages:
162-168
Received:
14 October 2025
Accepted:
27 October 2025
Published:
9 December 2025
Abstract: This study assessed patient radiation exposure from chest computed tomography (CT) examinations across three diagnostic centers (A, B, and C) in Abuja, Nigeria. A total of chest 60 CT scan records were retrospectively analyzed, and radiation dose parameters including weighted CT dose index (CTDIw), dose length product (DLP), and effective dose were evaluated. Technical factors such as tube current (mAs), tube voltage (kVp), pitch, and patient body weight were also collected to determine their influence on dose variations. The mean CTDIw values were 5.49, 5.88, and 7.42 mGy.cm for Centers A, B, and C, respectively, while the corresponding DLP values were 271.48 ± 183.2, 253.32 ± 120.4, and 437.16 ± 433.5 mGy·cm. Effective doses to the chest were 4.62, 4.31, and 7.43 mSv. Centers A and B demonstrated relatively optimized protocols, whereas Center C consistently reported higher radiation metrics. Technical and demographic data revealed higher mAs (220 ± 35), tube voltage (120 kVp), lower pitch (0.9), and higher mean body weight (78 ± 12 kg) in Center C compared with Centers A and B, accounting for its higher dose indices. Compared with international benchmarks, results from Centers A and B were consistent with European and Turkish diagnostic reference levels (DRLs), while Center C exceeded some international thresholds but remained within Nigerian DRL frameworks. These findings highlight the influence of patient and technical factors on dose variation and emphasize the need for protocol harmonization to optimize patient safety without compromising diagnostic quality.
Abstract: This study assessed patient radiation exposure from chest computed tomography (CT) examinations across three diagnostic centers (A, B, and C) in Abuja, Nigeria. A total of chest 60 CT scan records were retrospectively analyzed, and radiation dose parameters including weighted CT dose index (CTDIw), dose length product (DLP), and effective dose were...
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Research Article
Dynamic Evolution of Quantum Correlations with PSO Algorithm in the Three-qubit Heisenberg XYZ Model Considering DM and KSEA Interactions
Issue:
Volume 13, Issue 6, December 2025
Pages:
169-180
Received:
23 September 2025
Accepted:
10 October 2025
Published:
19 December 2025
Abstract: In this paper, we consider the three-qubit Heisenberg XYZ model considering DM interaction and KSEA interaction. We use the concurrence, geometric quantum discord, and local quantum uncertainty between the first and third spin as quantum correlation measures. In the absence of a magnetic field and in the presence of a constant magnetic field, quantum correlations appear sudden death and birth, and exhibit a random behavior. In summary, the Heisenberg XYZ model, no adjustment of the exchange interaction strength, DM interaction strength, KSEA interaction strength, and external magnetic field can eliminate the sudden death and births in the evolution of quantum correlations. Thus, we use the particle swarm optimization algorithm (PSO) to determine the magnetic field strength at each time step to increase the quantum correlation. The numerical simulation results show that the quantum correlation increases and reaches a maximum value by our method, and the quantum correlation remains constant at a maximum even after the external magnetic field is cancelled. This result shows that, for any exchange interaction strength, DM interaction strength, and KSEA interaction strength, the quantum correlations reach a certain value and remain at their maximum after the magnetic field is quenched, once the time-varying magnetic field is properly designed. This result provides sufficient possibilities for the use of Heisenberg spin chains as quantum channel.
Abstract: In this paper, we consider the three-qubit Heisenberg XYZ model considering DM interaction and KSEA interaction. We use the concurrence, geometric quantum discord, and local quantum uncertainty between the first and third spin as quantum correlation measures. In the absence of a magnetic field and in the presence of a constant magnetic field, quant...
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Research Article
The Dead Universe Theory (DUT) Simulator 1.0: Exploring the Final Cosmos Through Non-Singular Quantum Gravitational Computation
Joel Almeida*
Issue:
Volume 13, Issue 6, December 2025
Pages:
181-194
Received:
20 June 2025
Accepted:
5 July 2025
Published:
26 December 2025
DOI:
10.11648/j.ajpa.20251306.14
Downloads:
Views:
Abstract: The Dead Universe Theory (DUT) introduces a novel cosmological framework in which the universe evolves toward a final state of thermodynamic and quantum equilibrium, challenging the conventional Big Bang paradigm. This study presents a computational analysis based on the DUT Simulator 1.0, which models gravitational collapse, entropy gradients, and vacuum structure without singularities. The simulator applies regularized gravitational potentials and quantum thermodynamic parameters to describe the internal dynamics of a closed cosmic system. Simulations accurately reproduce the observed properties of high-redshift massive galaxies detected by the James Webb Space Telescope, including CEERS-1019 (z = 8.67, M⋆ ≈ 1.1 × 1010 M☉) and GLASS-z13 (z = 13.1, M⋆ ≈ 1.5 × 1010 M☉), with an average deviation below 5% in stellar mass estimation. Additionally, the model explains the emergence of structural stability in extreme gravitational regimes, offering falsifiable predictions about the long-term decay of entropy and the cessation of cosmic expansion. This article also proposes experimental pathways for DUT validation through observational astrophysics and controlled laboratory analogues. By integrating quantum information dynamics with gravitational thermodynamics, DUT offers a consistent alternative to ΛCDM, particularly in addressing the cosmological constant problem and the entropy flow in late-universe scenarios.
Abstract: The Dead Universe Theory (DUT) introduces a novel cosmological framework in which the universe evolves toward a final state of thermodynamic and quantum equilibrium, challenging the conventional Big Bang paradigm. This study presents a computational analysis based on the DUT Simulator 1.0, which models gravitational collapse, entropy gradients, and...
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