Freeze-in Dark Matter via Lepton Portal: Hubble Tension and Stellar Cooling

We propose a new freeze-in dark matter candidate which feebly couples to the standard model charged leptons. The feeble interactions allow it (i) to freeze-in from the Standard Model thermal bath with its relic density being either a fraction or the entirety of the observed dark matter density and (ii) to radiatively decay to two photons in the dark matter mass ranges of order keV scale with lifetime larger than the age of Universe. These features make this model a realistic realization of dark matter with late-time decay to reduce Hubble tension. We show the best-fit value of H_{0}=68.31(69.34) km s^{-1}Mpc^{-1} in light of Planck 2018+BAO(+LSS)+Pantheon data sets. We then use stellar cooling data to place constraints on the parameter space favored by the Hubble tension. While the universal coupling scenario is excluded, the hierarchical coupling scenario can be tested by future observations of white dwarfs after a careful look into photon inverse decay, Primakoff and Bremsstrahlung emission of the dark matter in various stellar systems. The viable parameter space may be linked to anomalies in future X-ray telescopes.Comment: 21 pages, 8 figure

Analysis of Shelley’s Poetry from the perspective of foregrounding

This paper explores Shelly’s poetry Ode to the West Wind from the perspective of foregrounding. Through the framework of the new model, it fi nds out that the poetry involves various kinds of foregrounding. For this, the poetry can be more understandable. From the analysis of deviation and overregularity, the deviation involves many kinds and the overregularity involves many kinds, either. Through these foregrounding, we analyze them with the social context. Therefore we can relatively be objective about the poem through the study of analysis.Key words: The model; Ode to the West Wind; Analysis of the poetryRésumé Cet article explore la poésie Ode Shelly au vent d’ouest dans la perspective de mise en avant. Grâce au cadre du nouveau modèle, il découvre que la poésie implique différents types de mise en avant. Pour cela, la poésie peut être plus compréhensible. De l’analyse de l’écart et overregularity, l’écart implique de nombreux types et le overregularity implique de nombreux types, que ce soit. Grâce à ces mise en avant, nous les analysons avec le contexte social. Par conséquent, nous pouvons relativement être objectif à propos du poème à travers l’étude de l’analyse.Mots clés: Le modèle; D’Ode pour; L'analyse de la poésie du vent d’oues

A Concept Knowledge Graph for User Next Intent Prediction at Alipay

This paper illustrates the technologies of user next intent prediction with a concept knowledge graph. The system has been deployed on the Web at Alipay, serving more than 100 million daily active users. To explicitly characterize user intent, we propose AlipayKG, which is an offline concept knowledge graph in the Life-Service domain modeling the historical behaviors of users, the rich content interacted by users and the relations between them. We further introduce a Transformer-based model which integrates expert rules from the knowledge graph to infer the online user's next intent. Experimental results demonstrate that the proposed system can effectively enhance the performance of the downstream tasks while retaining explainability.Comment: Accepted by WWW 2023 poste

Doping inorganic ions to regulate bioactivity of Ca–P coating on bioabsorbable high purity magnesium

AbstractPerformance of biomaterials was strongly affected by their surface properties and could be designed artificially to meet specific biomedical requirements. In this study, F−(F), SiO42−(Si), or HCO3−(C)-doped Ca–P coatings were fabricated by biomimetic deposition on the surface of biodegradable high-purity magnesium (HP Mg). The crystalline phases, morphologies and compositions of Ca–P coatings had been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The biomineralization and corrosion resistance of doped Ca–P coatings had also been investigated. The results showed that the Ca–P coating with or without doped elements mainly contained the plate-like dicalcium phosphate dehydrate (DCPD) phase. The doped F, Si, or C changed the surface morphology of Ca–P coatings after mineralization. Doped F enhanced the mineralization of Ca–P coating, and doped Si retarded the mineralization of Ca–P coating. However, H2 evolution of HP Mg discs with different Ca–P coatings was close to 0.4–0.7ml/cm2 after two-week immersion. That meant that the corrosion resistance of the Ca–P coatings with different or without doped elements did not change significantly

Direct imaging of short-range order and its impact on deformation in Ti-6Al.

Chemical short-range order (SRO) within a nominally single-phase solid solution is known to affect the mechanical properties of alloys. While SRO has been indirectly related to deformation, direct observation of the SRO domain structure, and its effects on deformation mechanisms at the nanoscale, has remained elusive. Here, we report the direct observation of SRO in relation to deformation using energy-filtered imaging in a transmission electron microscope (TEM). The diffraction contrast is enhanced by reducing the inelastically scattered electrons, revealing subnanometer SRO-enhanced domains. The destruction of these domains by dislocation planar slip is observed after ex situ and in situ TEM mechanical testing. These results confirm the impact of SRO in Ti-Al alloys on the scale of angstroms. The direct confirmation of SRO in relationship to dislocation plasticity in metals can provide insight into how the mechanical behavior of concentrated solid solutions by the material's thermal history

Dielectric Screening in Perovskite Photovoltaics

The performance of perovskite photovoltaics is fundamentally impeded by the presence of undesirable defects that contribute to non-radiative losses within the devices. Although mitigating these losses has been extensively reported by numerous passivation strategies, a detailed understanding of loss origins within the devices remains elusive. Here, we demonstrate that the defect capturing probability estimated by the capture cross-section is decreased by varying the dielectric response, producing the dielectric screening effect in the perovskite. The resulting perovskites also show reduced surface recombination and a weaker electron-phonon coupling. All of these boost the power conversion efficiency to 22.3% for an inverted perovskite photovoltaic device with a high open-circuit voltage of 1.25 V and a low voltage deficit of 0.37 V (a bandgap similar to 1.62 eV). Our results provide not only an in-depth understanding of the carrier capture processes in perovskites, but also a promising pathway for realizing highly efficient devices via dielectric regulation

SWIPT in MISO full-duplex systems

This paper investigates a multiuser multiple-input singleoutput (MISO) full-duplex (FD) system for simultaneous wireless information and power transfer (SWIPT), in which a multiantenna base station (BS) simultaneously sends wirelessly information and power to a set of single-antenna mobile stations (MSs) using power splitters (PSs) in the downlink and receives information in the uplink in FD mode. In particular, we address the joint design of the receive PS ratio and the transmit power at the MSs, and the beamforming matrix at the BS under signal-to-interferenceplus- noise ratio (SINR) and the harvested power constraints. Using semidefinite relaxation (SDR), we obtain the solution to the problem with imperfect channel state information (CSI) of the selfinterfering channels. Furthermore, we propose another suboptimal zero-forcing (ZF) based solution by separating the optimization of the transmit beamforming vector and the PS ratio. Simulation results are provided to evaluate the performance of the proposed beamforming designs

Exceptional fracture toughness of CrCoNi-based medium- and high-entropy alloys close to liquid helium temperatures

Medium- and high-entropy alloys based on the CrCoNi-system have been shown to display outstanding strength, tensile ductility and fracture toughness (damage-tolerance properties), especially at cryogenic temperatures. Here we examine the JIc and (back-calculated) KJIc fracture toughness values of the face-centered cubic, equiatomic CrCoNi and CrMnFeCoNi alloys at 20 K. At flow stress values of ~1.5 GPa, crack-initiation KJIc toughnesses were found to be exceptionally high, respectively 235 and 415 MPa(square-root)m for CrMnFeCoNi and CrCoNi, with the latter displaying a crack-growth toughness Kss exceeding 540 MPa(square-root)m after 2.25 mm of stable cracking, which to our knowledge is the highest such value ever reported. Characterization of the crack-tip regions in CrCoNi by scanning electron and transmission electron microscopy reveal deformation structures at 20 K that are quite distinct from those at higher temperatures and involve heterogeneous nucleation, but restricted growth, of stacking faults and fine nano-twins, together with transformation to the hexagonal closed-packed phase. The coherent interfaces of these features can promote both the arrest and transmission of dislocations to generate respectively strength and ductility which strongly contributes to sustained strain hardening. Indeed, we believe that these nominally single-phase, concentrated solid-solution alloys develop their fracture resistance through a progressive synergy of deformation mechanisms, including dislocation glide, stacking-fault formation, nano-twinning and eventually in situ phase transformation, all of which serve to extend continuous strain hardening which simultaneously elevates strength and ductility (by delaying plastic instability), leading to truly exceptional resistance to fracture.Comment: 31 pages, 10 figures, including Supplementary Informatio