Subjects: Information Science and Systems Science >> Basic Disciplines of Information Science and Systems Science Subjects: Physics >> Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics Subjects: Astronomy >> Astrophysical processes submitted time 2024-05-22
Abstract: The electromagnetic fields of point sources with time varying charges moving in the vacuum are derived using the Liénard-Wiechert potentials. The properties of the propagation velocities and the Doppler effect are discussed based on their far fields. The results show that the velocity of the electromagnetic waves and the velocity of the sources cannot be added like vectors; the velocity of electromagnetic waves of moving sources are anisotropic in the vacuum; the transverse Doppler shift is intrinsically included in the fields of the moving sources and is not a pure relativity effect caused by time dilation. Since the fields are rigorous solutions of the Maxwell’s equations, the findings can help us to abort the long-standing misinterpretations concerning about the classic mechanics and the classic electromagnetic theory. Although it may violate the theory of the special relativity, we show mathematically that, when the sources move faster than the light in the vacuum, the electromagnetic barriers and the electromagnetic shock waves can be clearly predicted using the exact solutions. Since they cannot be detected by observers in the region outside their shock wave zones, an intuitive and reasonable hypothesis can be made that the superluminal sources may be considered as a kind of electromagnetic blackholes.
Peer Review Status:Awaiting Review
Subjects: Nuclear Science and Technology >> Radiation Physics and Technology submitted time 2024-05-08
Abstract: Accurate and efficient online parameter identification and state estimation are crucial for leveraging Digital Twin simulations to optimize the operation of near-carbon-free nuclear energy systems. In previous studies, we developed a reactor operation digital twin (RODT). However, non-differentiabilities and discontinuities arise when employing machine-learning-based surrogate forward models, challenging traditional gradient-based in verse methods and their variants. This study investigated deterministic and metaheuristic algorithms and developed hybrid algorithms to address these issues. An efficient modular RODT software framework that incorpo rates these methods into its post-evaluation module is presented for comprehensive comparison. The methods were rigorously assessed based on convergence profiles, stability with respect to noise, and computational performance. The numerical results show that the hybrid KNNLHS algorithm excels in real-time online applications, balancing accuracy and efficiency with a prediction error rate of only 1% and processing times of less than 0.1 s. Contrastingly, algorithms such as FSA, DE, and ADE, although slightly slower (approximately 1s), demonstrated higher accuracy with a 0.3% relative L2 error, which advances RODT methodologies to harness machine learning and system modeling for improved reactor monitoring, systematic diagnosis of off-normal events, and lifetime management strategies. The developed modular software and novel optimization methods presented offer pathways to realize the full potential of RODT for transforming energy engineering practices.
Subjects: Information Science and Systems Science >> Basic Disciplines of Information Science and Systems Science Subjects: Physics >> Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics Subjects: Electronics and Communication Technology >> Optoelectronics and Laser Subjects: Physics >> Geophysics, Astronomy, and Astrophysics Subjects: Physics >> The Physics of Elementary Particles and Fields submitted time 2024-04-08
Abstract: The Einstein’s theory of special relativity is based on his two postulates. The first is that the laws of physics are the same in all inertial reference frames. The second is that the velocity of light in the vacuum is the same in all inertial frames. The theory of special relativity is considered to be supported by a large number of experiments. This paper revisits the two postulates according to the new interpretations to the exact solutions of moving sources in the laboratory frame. The exact solutions are obtained using the classic Maxwell’s theory, which clearly show that the propagation velocity of the electromagnetic waves of moving sources in the vacuum is not isotropic; the propagation velocity of the electromagnetic waves and the moving velocity of the sources cannot be added like vectors; the transverse Doppler effect is intrinsically included in the fields of the moving sources. The electromagnetic sources are subject to the Newtonian mechanics, while the electromagnetic fields are subject to the Maxwell’s theory. We argue that since their behaviors are quite different, it is not a best choice to try to bind them together and force them to undergo the same coordinate transformations as a whole, like that in the Lorentz transformations. Furthermore, the Maxwell’s theory does not impose any limitations on the velocity of the electromagnetic waves. To assume that all objects cannot move faster than the light in the vacuum need more examinations. We have carefully checked the main experiment results that were considered as supporting the special relativity. Unfortunately, we found that the experimental results may have been misinterpreted. We here propose a Galilean-Newtonian-Maxwellian relativity, which can give the same or even better explanations to those experimental results.
Peer Review Status:Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2023-10-06
Abstract: Micro mobile heat pipe-cooled nuclear power plants are promising candidates for distributed energy resource power generators and can be flexibly deployed in remote places to meet increasing electric power demands. However, previous steady-state simulations and experiments have deviated significantly from actual micronuclear system operations. Hence, a transient analysis is required for performance optimization and safety assessment. In this study, a hardware-in-the-loop (HIL) approach was used to investigate the dynamic behavior of scaled-down heat pipe-cooled systems. The real-time features of the HIL architecture were interpreted and validated, and an optimal time step of 500 ms was selected for the thermal transient. The power transient was modeled using point kinetic equations, and a scaled-down thermHeal prototype was set up to avoid modeling unpredictable heat transfer behaviors and feeding temperature samples into the main program running on a desktop PC. A series of dynamic test results showed significant power and temperature oscillations during the transient process, owing to the inconsistency of the rapid nuclear reaction rate and large thermal inertia. The proposed HIL approach is stable and effective for further studying of the dynamic characteristics and control optimization of solid-state small nuclear-powered systems at an early prototyping stage.
Subjects: Nuclear Science and Technology >> Engineering Technology of Fission Reactor submitted time 2023-06-06
Abstract: The lightweight shielding design of small reactors is a research hotspot. Based on a small helium-xenon-cooled solid reactor, the effects of thickness and number of shielding layers on the radiation dose are first studied. It is found that when photons are shielded first and the number of shielding layers is odd, the radiation dose can be significantly reduced. To reduce the weight of the shielding body, the relative thickness of the shielding layers is optimized by the genetic algorithm. The optimized scheme can reduce the radiation dose by up to 57% and helps reduce the weight by 11.84%. To determine the total thickness of shielding layers and avoid the local optimal solution, a formula that gives the relationship between the total thickness and the radiation dose is established through large-scale calculations, which has an error of 0.8%~7.45% compared with the Monte Carlo method. A semi-empirical and semi-quantitative lightweight shielding design algorithm is proposed to integrate the above works, and a code SDIC1.0 is developed to achieve the optimized lightweight shielding design for small reactors. It has been verified that the error between SDIC1.0 and Monte Carlo code RMC is about 10%, and the time has increased by 6.3 times.
Peer Review Status:Awaiting Review
Subjects: Nuclear Science and Technology >> Engineering Technology of Fission Reactor submitted time 2023-05-31
Abstract: Transplutonium isotopes are scarce and need to be produced by irradiation in high flux reactors, but their production is inefficient and optimization studies are needed. This paper analyzes the physics nature of transplutonium isotopes production by taking Cf-252, Cm-244, Cm-242 and Pu-238 as examples. Traditional methods based on the Monte Carlo burnup calculation are faced with the shortcomings of large amounts of calculation and are unable to analyze the individual energy intervals in more detail, thus cannot support the refined evaluation, screening and optimization of the irradiation schemes. After grasping the physics nature and simplifying the complexity of the production process, we proposed a rapid diagnosis method for evaluating the radiation schemes based on the concept of “Single Energy Interval Value (SEIV)” and “Energy Spectrum Total Value (ESTV)”. The rapid diagnosis method can not only avoid the tedious burnup calculation but also help to provide direction for optimization. The optimal irradiation schemes for producing Cf-252, Cm-244, Cm-242 and Pu-238 are determined based on the rapid diagnosis method. The optimal irradiation schemes can greatly improve production efficiency. Compared with the initial scheme, the optimal scheme improves the production efficiency of Pu-238 by 7.41 times, 11.98 times for Cm-242, 65.20 times for Cm-244 and 15.08 times for Cf-252, respectively. The work in this paper realizes the refined analysis of transplutonium isotopes production and provides a theoretical basis for improving production efficiency.
Peer Review Status:Awaiting Review
Subjects: Nuclear Science and Technology >> Engineering Technology of Fission Reactor Subjects: Nuclear Science and Technology >> Engineering of Nuclear Power submitted time 2023-05-30
Abstract:
Subjects: Traffic and Transportation Engineering >> Ship Engineering submitted time 2018-03-30
Abstract: The hydroelastic behavior of very large floating structures (VLFSs) is investigated based on the proposed multi-modules beam theory (MBT). To carry out the analysis, the VLFS is first divided into multiple sub-modules that are connected through their gravity center by a spatial beam with specific stiffness. The external force exerted on the sub-modules includes the wave hydrodynamic force as well as the beam bending force due to the relative displacements of different sub-modules. The wave hydrodynamic force is computed based on three-dimensional incompressible velocity potential theory, and the boundary element method with the free surface Green function as the integral kernel is adopted to numerically find the solution. The beam bending force is expressed in the form of a stiffness matrix. The coupled motion equation is established according to the continuous conditions of the displacement and force. The motion response defined at the gravity center of the sub-modules is solved by the multi-body hydrodynamic control equations, then both the displacement and the structure bending moment of the VLFS are determined from the stiffness matrix equations. To account for the moving point mass effects, the proposed method is extended to the time domain based on impulse response function (IRF) theory. The accuracy of the proposed method is verified by comparison with existing results. Detailed results through the displacement and bending moment of the VLFS are provided to show the influence of the number of the sub-modules, and the influence of the moving point mass.
Peer Review Status:Awaiting Review