Abstract
Einstein–Podolsky–Rosen (EPR) steering is a quantum effect based on quantum entanglement and it is the key resource for building quantum networks because of its useful properties. Based on ...the criterion for genuine multipartite EPR steering, the genuine quadripartite EPR steering is confirmed and it can be generated by a spontaneous parametric down-conversion cascaded process with two sum-frequency generations in an optical superlattice. This occurs either below the oscillation threshold and without oscillation threshold. The influence of the parameters of cascaded nonlinear process on the quadripartite EPR steering among signal, idler, and two sum-frequency beams are also discussed. Choosing appropriate nonlinear parameters can achieve good quadripartite quantum steering. This scheme of the generation of genuine quadripartite EPR steering has potential applications in quantum communication and computing.
The extension of the cosmic-ray spectrum beyond 1 petaelectronvolt (PeV; 10
electronvolts) indicates the existence of the so-called PeVatrons-cosmic-ray factories that accelerate particles to PeV ...energies. We need to locate and identify such objects to find the origin of Galactic cosmic rays
. The principal signature of both electron and proton PeVatrons is ultrahigh-energy (exceeding 100 TeV) γ radiation. Evidence of the presence of a proton PeVatron has been found in the Galactic Centre, according to the detection of a hard-spectrum radiation extending to 0.04 PeV (ref.
). Although γ-rays with energies slightly higher than 0.1 PeV have been reported from a few objects in the Galactic plane
, unbiased identification and in-depth exploration of PeVatrons requires detection of γ-rays with energies well above 0.1 PeV. Here we report the detection of more than 530 photons at energies above 100 teraelectronvolts and up to 1.4 PeV from 12 ultrahigh-energy γ-ray sources with a statistical significance greater than seven standard deviations. Despite having several potential counterparts in their proximity, including pulsar wind nebulae, supernova remnants and star-forming regions, the PeVatrons responsible for the ultrahigh-energy γ-rays have not yet been firmly localized and identified (except for the Crab Nebula), leaving open the origin of these extreme accelerators.
Abstract
Einstein–Podolsky–Rosen (EPR) steering is different from quantum entanglement because of its unique asymmetry. Multipartite asymmetric EPR steering can break through one-to-one monogamy ...steering and achieve one to many one-way steering. That is to say, the state of one part can steer the other rest parts simultaneously, while the other parts cannot steer this part. Here, a scheme is proposed to generate one to many one-way steering by optical parametric amplification cascaded with a sum-frequency generation process. One to many non-monogamy EPR steering, such as one to two and one to three one-way steering are demonstrated based on the criterion for asymmetric EPR steering. It is also find that different kinds of asymmetric EPR steering can be obtained by choosing different nonlinear parameters. This non-monogamous one to many quantum control has potential application in constructing quantum networks and realizing one-way quantum computing.
Coronavirus disease 2019 (COVID-19) has brought great uncertainty to our society and it may have disrupted people's ontological security. Consequently, this hospital-based study concerns the impact ...of ontological insecurity on vaccination behavior against COVID-19.
This cross-sectional study was conducted among hospital inpatients.
A questionnaire survey addressing inpatient ontological insecurity and vaccination behavior against COVID-19 was administered in Taizhou, China. A total of 1223 questionnaires were collected; specifically, 1185 of them were credible, for a validity rate of 96.9%.
The score of ontological insecurity was 13.27 ± 7.84, which was higher in participants who did not recommend vaccination for others than those who did (12.95 ± 8.25 vs 14.00 ± 6.78, P = 0.022). There was no difference between the vaccinated and unvaccinated groups (13.22 ± 7.96 vs 13.35 ± 7.67, P = 0.779). Lower ontological insecurity (odds ratio OR = 1.40, 95% confidence interval CI: 1.08–1.81) and being inoculated with COVID-19 vaccines (OR = 2.17, 95% CI: 1.67–2.82) were significantly associated with recommendation of COVID-19 vaccines to others after adjusting for sex, age, education, and occupation. Associations between low ontological insecurity and recommendations for COVID-19 vaccines were observed in men, adults aged 18–59 years, non-farmers, and vaccine recipients.
This study suggests that the ontological insecurity of participants affects their behavior of recommending the COVID-19 vaccination to others rather than getting vaccinated themselves. This promotion of vaccination can be considered from the perspective of improving ontological security in China.
Some gamma-ray bursts (GRBs) have a tera-electron volt (TeV) afterglow, but the early onset of this has not been observed. We report observations with the Large High Altitude Air Shower Observatory ...(LHAASO) of the bright GRB 221009A, which serendipitously occurred within the instrument's field of view. More than 64,000 photons >0.2 TeV were detected within the first 3000 seconds. The TeV flux began several minutes after the GRB trigger and then rose to a peak ~10 seconds later. This was followed by a decay phase, which became more rapid ~650 seconds after the peak. We interpret the emission using a model of a relativistic jet with half-opening angle of ~0.8°. This is consistent with the core of a structured jet and could explain the high isotropic energy of this GRB.
Pulsed plasma arc additive manufacturing (PPAM) is a novel additive manufacturing (AM) technology due to its big potential in efficiency, convenience and cost-savings comparing with other AM process. ...In this research, several Ti-6Al-4V thin walls were deposited by an optimized weld wire-feed PPAM process, in which the heat input was gradually decreased layer by layer. The deposited thin wall consisted of various morphologies with different microstructure, such as epitaxial growth of prior β-grains, martensite and horizontal layer bands of Widmanstätten, which depend on the heat input, multiple thermal cycles and gradual cooling rate in the deposition process. Reducing heat input of each bead and using pulsed current in the PPAM process, the microstructure of thin wall was refined. Meanwhile, the thin wall was strengthening and toughening. The average yield strength (YS) and ultimate tensile strength (UTS) reach 909MPa and 988MPa, respectively, and elongation reaches about 7.5%. The thin wall exhibited excellent performance in the aeronautical applications owing to the high values of mechanical properties in the room temperature.
Deposited Ti-6Al-4V wall by pulsed plasma arc additive manufacturing (PPAM) consisted various morphologies with different microstructure. The evolution of horizontal layer bands and varying prior β grains are related to pulsed frequency and gradually decrease heat input of layer by layer. The phase transformation of β-α follows the Burgers orientation relationship, and three orientations out of the twelve possibilities occupy dominating orientations, which finally form triangular stars or rhombic patterns. Display omitted
•The pulsed plasma arc additive manufacturing(PPAM)process deposited Ti-6Al-4V thin-wall by an optimized weld wire-feed PPAM process, in which the heat input was gradually decreased layer by layer.•The results show the mechanical properties of the deposited wall at room temperature exceed the standard of casting wall, and the strength is even higher than that of forged wall.•It is Indicate that both of the morphology of horizontal Layer Bands(LBs) and prior β grains are affected by the gradually reduced heat input of the pulsed plasma arc.•The transformation of β-α occurs follows the Burgers orientation relationship, and three orientations out of twelve possibilities occupy dominate orientation formed triangular stars or into rhombic patterns
Storm surges are responsible for much of the damage and loss of life associated with landfalling tropical cyclones (TCs). Thus, understanding the characteristics of risk associated with TC storm ...surges for the coastal regions of China is of great interest. Based on a comprehensive assessment of hazard indices for TC storm surges and vulnerability indices for coastal counties, we obtained a risk assessment for coastal regions of China as a county‐level unit. The hazard index was calculated using a model based on the parameters of a TC landfall frequency index (f) and maximum storm surge elevation (MSSE). The MSSE was calculated from the TC maximum sustained wind and tide gauge records using a regression function. Vulnerability indices were obtained from indices on socioeconomics, land use, the ecological environment, and resilience. From this study, it can be concluded that the hazard level of TC storm surges increases from north to south along the Chinese coast, the vulnerabilities have significant spatial heterogeneity, and coastal regions of China can be divided into four zones of risk level. The results of this study can provide scientific support for marine disaster mitigation and decision making. Additionally, the risk assessment methodology used here for storm surges could be extended and applied to other coastal areas.
Key Points
Developed a parametric representation of hazard on tropical storm surge
Estimated the vulnerabilities for coastal regions of China
Divided the coastal region of China into four risk level zones
A large Mg-4.50Zn-1.13Ca (wt%) alloy ingot 350mm in diameter and 1730mm long was successfully fabricated by semi-continuous casting. The microstructures and mechanical properties of the as-cast and ...as-extruded alloys were investigated. The as-cast alloy exhibits uniform chemical composition and microstructure from the centre to the surface of the ingot and mainly consists of α-Mg and Ca2Mg6Zn3. The coarse grains and network-like second phases that are distributed at the grain boundaries result in poor mechanical properties for the as-cast alloy. The mechanical properties of the as-extruded alloys are significantly enhanced. The high yield strengths of the as-extruded alloys mainly result from the fine DRXed grain and the stronger basal texture.
Display omitted
► At the beginning of hot extrusion the twins such as
{
1
0
1
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2
}
twins are formed. ► The main DmRX mechanism is the continuous DRX near the original grain boundaries. ► ...DRX seldom occurs in the twins and massive substructures formed in original grains. ► Quasicrystalline phase can accelerate DRX by obstructing the slip of dislocations. ► The extruded alloy shows yield strength: 317
MPa, UTS: 363
MPa and elongation: 12%.
In this study, firstly, dynamic microstructural changes of an as-cast Mg–5.0 Zn–0.9 Y–0.16 Zr (wt.%) alloy (designated ZWK510) during hot extrusion at 350
°C and a ram speed of 3.33
mm
s
−1 was systematically investigated by electron backscattering diffraction (EBSD) analysis. The dynamic recrystallization (DRX) mechanism during hot extrusion was discussed. Then, the effect of microstructure and texture on the mechanical properties of the as-extruded alloy specimens at room temperature was discussed. The as-cast ZWK510 alloy consists of
a-Mg and quasicrystalline I-phase. During hot extrusion at 350
°C, the main DRX mechanism is the continuous DRX near the original grain boundaries. The I-phase can accelerate the DRX behavior near these areas by obstructing the slip of dislocations. The deformation twins and massive blocky substructures formed in original grains can coordinate the DRX process near the original grain boundaries, however the DRX seldom occurs inside of these area. After further deformation, these deformation twins and massive blocky substructures are elongated along the material flow and become so-called unDRXed area, then a bimodal “necklace structure” composed of fine DRXed grains of about 2.1
μm and unrecrystallized coarse area is formed. The extruded ZWK510 alloy shows a DRX ratio of about 58% and a typical basal fiber texture of
(
0
0
0
1
)
1
0
1
¯
0
matrix
/
/
extrusion direction (ED). In the DRXed area around the crushed eutectic I-phase a large number of fine I-phase precipitates are observed pinning at the newly formed DRXed grain boundaries. The 0.2% proof strength and the ultimate tensile strength of the extruded ZWK510 alloy specimen are 317 and 363
MPa, respectively, with an elongation to failure of 12%, which have been attributed to strong basal fiber texture, refined grain size as well as the existence of fine precipitates formed during the hot extrusion.
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