This paper presents a fast and reliable method to evaluate risk of single or multiple commutation failures for multi-infeed HVDC systems following faults occurring at the receiving-end ac system. ...First, a fast calculation method of multi-infeed interaction factor, describing the interactivity and mutual impact between two inverter AC buses on is proposed. It is then refined to being the AC-DC system voltage interaction factor (ADVIF) to represent the relationship in bus voltages between inverter and AC buses at the receiving-end systems. Then, a critical AC-DC system voltage interaction factor (CADVIF) based on the minimum extinction angle criteria is proposed. By calculating and comparing ADVIFs and CADVIFs, which can be obtained quickly, it is possible to identify AC buses that, if a fault occurs, would cause commutation failures at one or more HVDC systems. The validity and accuracy of the proposed approach are demonstrated by comparing with simulations results using a two-infeed HVDC test system and an actual large power grid.
It is generally expected that adding light sterile species would increase the effective number of neutrinos, Neff. In this paper we discuss a scenario that Neff can actually decrease due to the ...neutrino oscillation effect if sterile neutrinos have self-interactions. We specifically focus on the eV mass range, as suggested by the neutrino anomalies. With large self-interactions, sterile neutrinos are not fully thermalized in the early Universe because of the suppressed effective mixing angle or matter effect. As the Universe cools down, flavor equilibrium between active and sterile species can be reached after big bang nucleosynthesis (BBN) epoch, but leading to a decrease of Neff. In such a scenario, we also show that the conflict with cosmological mass bounds on the additional sterile neutrinos can be relaxed further when more light species are introduced. To be consistent with the latest Planck results, at least 3 sterile species are needed.
This manuscript delves into a comprehensive investigation of significant exact solutions pertaining to the extended modified Vakhnenko–Parkes equation (emVPE), with a focus on novel solutions. By ...taking into account various kinds of auxiliary functions, we are able to generate a number of high order solitons, bifurcations, and breathers solutions for the given model. The study of multiple solitons, multiple bifurcation solitons, high order breathers, and hybrid breathers are all part of our current research. Our proposed results are validated through graphical visualizations.
Optical solitons are solitary waves that propagate without changing shape due to a balance between dispersion and nonlinearity in the medium. Therefore, solitary optical waves are important solutions ...to nonlinear partial differential equations for modeling pulse propagation in optics. Our work derives new solitary wave solutions to the Kundu–Mukherjee–Naskar (KMN) equation, which governs complex nonlinear optical wave phenomena. Using innovative logarithmic transformation-based analytical techniques, various solution forms are obtained and expressed in closed form via elementary functions. The solutions are validated through direct substitution into the original KMN equation. Our new solutions provide fresh perspectives into the intricate soliton landscape described by this model. Since the KMN equation finds use in fiber optic communications, fluid dynamics, and other domains, these findings have broad implications. The methods showcase promising new pathways for unraveling soliton behaviors by fractional- and integer-order nonlinear models alike. Researchers can build upon these techniques to further advance understanding of the profound mathematical structures underlying real-world physical systems.
•Derives new closed-form solitary wave solutions to the KMN equation using logarithmic transformations.•Validates solutions and provides fresh perspectives on solitons described by KMN model.•Showcases promising analytical techniques for nonlinear fractional- and integer-order models.•Advances understanding of mathematical structures in real-world physical systems.•Broad implications for fiber optics, fluid dynamics, and other KMN applications.
•A review of the applications and developments of UTHPs for electronic cooling is reported.•The UTHPs are particularly suitable for the heat dissipation of ultra-slim portable electronic devices.•The ...sintered mesh/fibres are the most commonly used wick structures for UTHPs in actual production.•The flattened thickness exerts significant influence on the thermal performance of UTHPs.
The development of miniaturization and high-density packaging of electronic components demands heat dissipation components that are compact and exhibit high performance. An ultra-thin micro heat pipe (UTHP), as a novel heat pipe with a flat shape that is highly suitable for application with high power and limited heat dissipation space, has been extensively investigated and widely used in mobile electronics. Understanding the influence of the manufacturing processes, capillary wick structures and flattened thickness on the thermal performance of UTHPs has been the aim of numerous studies. This paper presents a comprehensive review of the recent developments and applications of UTHPs for thermal management of electronics. The different types and applications of UTHPs are introduced, and the packaging technologies of UTHPs are summarized and compared. Furthermore, the fabrication methodology and heat transfer characteristics of various wick structures used for UTHPs are reviewed and analysed in detail. Finally, the challenges affecting the development and application of UTHPs are outlined, and recommendations for future research are presented.
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We consider the simplest possibility for a model of particle dark matter in which dark matter has only gravitational interaction with the standard model sector. Even in such a case, it is ...known that the gravitational particle production in an expanding universe may lead to a correct relic abundance depending on the ination scale and the mass of dark matter particle. We provide a comprehensive and systematic analysis of the gravitational particle production of fermionic and vectorial dark matter, and emphasize that particles which are much heavier than the Hubble parameter but lighter than inaton can also be produced abundantly.
We investigate possible cosmological effects of interacting scalar radiation and dark matter. After its decoupling, scalar radiation can stream freely as neutrinos or self-interact strongly as ...perfect fluid, highly depending on the magnitude of its self-couplings. We obtain the general and novel structure for self-scattering rate and compare it with the expansion rate of our Universe. If its trilinear/cubic coupling is non-zero, scalar radiation can be eventually treated as perfect fluid. Possible effects on CMB are also discussed. When this scalar also mediates interaction among dark matter particles, the linear matter power spectrum for large scale structure can be modified differently from other models. We propose to use Debye shielding to avoid the singularity appearing in the scattering between scalar radiation and dark matter.
We propose a novel particle physics model in which vector dark matter (VDM) and dark radiation (DR) originate from the same non-Abelian dark sector. We show an illustrating example where dark SU(3) ...is spontaneously broken into SU(2) subgroup by the nonzero vacuum expectation value (VEV) of a complex scalar in fundamental representation of SU(3). The massless gauge bosons associated with the residual unbroken SU(2) constitute DR and help to relieve the tension in Hubble constant measurements between Planck and Hubble Space Telescope. In the meantime, massive dark gauge bosons associated with the broken generators are VDM candidates. Intrinsically, this non-Abelian VDM can interact with non-Abelian DR in the cosmic background, which results in a suppressed matter power spectrum and leads to a smaller σ8 for structure formation.
Recently, the XENON1T experiment has reported an excess in the electronic recoil events. The excess is consistent with the interpretation of absorption of 3 keV bosonic dark matter, for example, ...hidden photon dark matter with kinetic mixing of the order of 10−15. We point out that the minimally gravitational production provides a viable mechanism for obtaining a correct relic hidden photon abundance. We present parameter dependence of the hidden photon dark matter abundance on the inflationary scale Hinf and also the reheating temperature TR. We show that the inflationary Hubble scale and reheating temperature are both bounded from below, Hinf≳7×1011 GeV,TR≳102 GeV. In particular, the high-scale inflation is consistent with 3 keV hidden photon dark matter.
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