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This study reveals that the persistence of North Atlantic Oscillation (NAO) during boreal winter is closely linked to the phase of the Quasi‐Biennial Oscillation (QBO) at 30 hPa for the period 1958–2020. Our results show that the early winter (i.e., November–December) NAO signal tends to persist into the subsequent January in the easterly phase of the QBO (EQBO). However, in the westerly phase of the QBO (WQBO) there is hardly connection between the early winter and the subsequent January NAO signals. Further analysis suggests that there is stronger stratosphere–troposphere connection and stronger amplitude of the NAO during the early winters of the EQBO compared to those of the WQBO. A stronger NAO in the EQBO tends to induce enhanced positive feedback of air–sea interaction, which may contribute to a prolonged signal of the NAO. Specifically, significant surface heat flux anomalies over the high‐latitude and subtropical regions of North Atlantic induced by a stronger early winter NAO may trigger a tripolar pattern of anomalous sea surface temperature in the North Atlantic in the subsequent January. And this anomalous SST pattern may have a feedback on the atmosphere to strength the anomalous NAO by changing the atmospheric baroclinicity and synoptic eddy activities. In contrast, the NAO in the early winters of the WQBO tends to have a weaker amplitude and be confined to the troposphere. This weaker NAO is shown to induce a weaker air–sea interaction in the North Atlantic, and tends not to favour a prolonged NAO. [ABSTRACT FROM AUTHOR]

The heteroatom-doped graphene has attracted a lot of research due to its excellent physical, chemical and electrochemical properties considered to be the most promising electrocatalytic material for oxygen reduction reaction (ORR). Multi-doping can exert the synergistic effect between different doped heteroatoms and effectively improve the catalytic activity of doped graphene catalysts. N, P, S tri-doped graphene catalysts were prepared by simple and convenient hydrothermal and high-temperature treatment. The experimental results show that different phosphorus sources have a significant impact on the structure and performance of the prepared catalyst materials. The NSP-Gr-1 catalyst shows the high onset potential (1.035 V), half-wave potential (0.79 V) and limiting current density (−5.33 mA cm−2) for ORR. The power density of the zinc-air battery assembled with the NSP-Gr-1 catalyst achieves 163.1 mW cm−2 at 186.7 mA cm−2, which is much higher than the maximum power density of 140.0 mW cm−2 at 190 mA cm−2 for commercial Pt/C. The discharge stability under different current densities is outstanding. [ABSTRACT FROM AUTHOR]

Recently, Ye et al. (Int. J. Theor. Phys. 56, 1517–1529, 2017) proposed a quantum private comparison (QPC) protocol based on five-qubit entanglement state. Two parties can verify that their secret information is equal or not with the help of the semi-honest third party (TP). However, in this paper we will point out the Ye et al.'s initial protocol is not safe under a special participant attack. That is a malicious participant can get the other party's secret input information illegally under the forgery attack. Furthermore, we give two possible improvement protocols, which can perform this protocol secure against this kind of attack. [ABSTRACT FROM AUTHOR]

Recently, He proposed a novel quantum private comparison protocol without a third party (G. P. He, Int. J. Quantum Inf. 15(2) (2016) 1750014). This paper points out that two security loopholes in He's protocol are existent. And a new QPC protocol which can avoid these loopholes is proposed without the help of a third party in this paper. [ABSTRACT FROM AUTHOR]

Quantum public key encryption system provides information confidentiality using quantum mechanics. This paper presents a quantum public key cryptosystem (QPKC) based on the Bell states. By Holevo’s theorem, the presented scheme provides the security of the secret key using one-wayness during the QPKC. While the QPKC scheme is information theoretic security under chosen plaintext attack (CPA). Finally some important features of presented QPKC scheme can be compared with other QPKC scheme. [ABSTRACT FROM AUTHOR]

Classical public key cryptosystems ( P K C), such as R S A, E I G a m a l, E C C, are no longer secure in quantum algorithms, and quantum cryptography has become a novel research topic. In this paper we present a quantum asymmetrical cryptosystem i.e. quantum public key cryptosystem ( Q P K C) based on the Bell states. In particular, in the proposed QPKC the public key are given by the first n particles of Bell states and generalized Pauli operations. The corresponding secret key are the last n particles of Bell states and the inverse of generalized Pauli operations. The proposed QPKC encrypts the message using a public key and decrypts the ciphertext using a private key. By H o l e v o s theorem, we proved the security of the secret key and messages during the QPKC. [ABSTRACT FROM AUTHOR]

Since the discovery of Hawking radiation, its consistency with quantum theory has been widely questioned. In the widely described picture, irrespective of what initial state a black hole starts with before collapsing, it eventually evolves into a thermal state of Hawking radiations after the black hole is exhausted. This scenario violates the principle of unitarity as required for quantum mechanics and leads to the acclaimed 'information loss paradox'. This paradox has become an obstacle or a reversed touchstone for any possible theory to unify the gravity and quantum mechanics. Based on the results from Hawking radiation as tunneling, we recently show that Hawking radiations can carry off all information about the collapsed matter in a black hole. After discovering the existence of information-carrying correlation, we show in great detail that entropy is conserved for Hawking radiation based on standard probability theory and statistics. We claim that information previously considered lost remains hidden inside Hawking radiation. More specifically, it is encoded into correlations between Hawking radiations. Our study thus establishes harmony between Hawking radiation and the unitarity of quantum mechanics, which establishes the basis for a significant milestone toward resolving the long-standing information loss paradox. The paper provides a brief review of the exciting development on Hawking radiation. In addition to summarize our own work on this subject, we compare and address other related studies. [ABSTRACT FROM AUTHOR]

Si3N4 powder was activated under several shock-wave pressures by using an explosion driven flyer impact technique. The powders had been sintered to ceramics under hot-pressing conditions during the subsequent processing. Features of the ceramics sintered from the both activated powders and original powders had been observed by SEM, TEM and XRD. Comparison of structures and mechanical properties of the ceramics showed that, the best comprehensive mechanical properties had been obtained for ceramics sintered at 1800 °C from around 40 GPa shock-wave activated powders. Bending strength and shock toughness of the ceramics were about 40–50% higher than that in the normal case. It means that the shock activation can enhance the ceramics properties with convenience and lower cost. [Copyright &y& Elsevier]

In this paper, we present a derivation of the black hole area entropy with the relationship between entropy and information. The curved space of a black hole allows objects to be imaged in the same way as camera lenses. The maximal information that a black hole can gain is limited by both the Compton wavelength of the object and the diameter of the black hole. When an object falls into a black hole, its information disappears due to the no-hair theorem, and the entropy of the black hole increases correspondingly. The area entropy of a black hole can thus be obtained, which indicates that the Bekenstein–Hawking entropy is information entropy rather than thermodynamic entropy. The quantum corrections of black hole entropy are also obtained according to the limit of Compton wavelength of the captured particles, which makes the mass of a black hole naturally quantized. Our work provides an information-theoretic perspective for understanding the nature of black hole entropy. [ABSTRACT FROM AUTHOR]

The present study proposed a noninvasive, automated, in vivo assessment method based on optical coherence tomography (OCT) and deep learning techniques to qualitatively and quantitatively analyze the biological effects of 2-µm laser-induced skin damage at different irradiation doses. Different doses of 2-µm laser irradiation established a mouse skin damage model, after which the skin-damaged tissues were imaged non-invasively in vivo using OCT. The acquired images were preprocessed to construct the dataset required for deep learning. The deep learning models used were U-Net, DeepLabV3+, PSP-Net, and HR-Net, and the trained models were used to segment the damage images and further quantify the damage volume of mouse skin under different irradiation doses. The comparison of the qualitative and quantitative results of the four network models showed that HR-Net had the best performance, the highest agreement between the segmentation results and real values, and the smallest error in the quantitative assessment of the damage volume. Based on HR-Net to segment the damage image and quantify the damage volume, the irradiation doses 5.41, 9.55, 13.05, 20.85, 32.71, 52.92, 76.71, and 97.24 J/cm² corresponded to a damage volume of 4.58, 12.56, 16.74, 20.88, 24.52, 30.75, 34.13, and 37.32 mm³. The damage volume increased in a radiation dose-dependent manner. [ABSTRACT FROM AUTHOR]

Tropical atmospheric convection generated by the El Niño–Southern Oscillation (ENSO) plays a crucial role in affecting the western Pacific pattern (WP) in the boreal winter by triggering an atmospheric teleconnection. Here we show from analysis of observations and model simulations that the Atlantic Multidecadal Oscillation (AMO) asymmetrically modulates the relationship between ENSO and WP. We find a significant modulatory effect of AMO on the relationship between wintertime El Niño and WP. A robust El Niño−WP relation can be attributed to the negative AMO phase (−AMO), yet a weak relationship during the positive AMO phase (+AMO). In contrast, the relationship between La Niña and WP is independent of AMO modulation. Furthermore, during the −AMO period, stronger El Niño amplitudes lead to stronger atmospheric convection anomalies over the tropical western North Pacific, which excites stronger atmospheric teleconnection and thus has a more significant effect on WP than during the +AMO period. Plain Language Summary: The western Pacific pattern (WP) is one of the most crucial teleconnection patterns in boreal winter over the Northern Hemisphere, which exerts substantial impacts on weather and climate in Eurasia and North America. El Niño–Southern Oscillation (ENSO) is the most prominent air‐sea coupling system in the tropics, considered to exert great impacts on the WP via triggering atmospheric teleconnection. In this study, we revealed that the Atlantic Multidecadal Oscillation (AMO) has a significant asymmetrical modulation on the relation between the ENSO and WP. In particular, a significant El Niño‒WP connection only occurs in the negative AMO phase (‒AMO). Physical mechanisms of the modulation effects of AMO on the ENSO–WP relationship are further analyzed. The results suggest that stronger El Niño amplitude during the −AMO phase leads to larger atmospheric convection anomalies in the equatorial central Pacific and tropical western North Pacific compared to those during the +AMO phase. As such, stronger atmospheric convection anomalies during El Niño events have a greater impact on WP events during the −AMO phase; however, for La Niña events, there is no significant impact on WP events during the −AMO phase. Results obtained in this study may help to improve our understanding of the WP variability. Key Points: The connection between El Niño–Southern Oscillation (ENSO) and the western Pacific pattern (WP) varies markedly in different Atlantic Multidecadal Oscillation (AMO) phasesA robust connection between ENSO and the WP in the boreal winter can only be observed during the negative AMO phaseThe AMO influences the ENSO‐WP relationship via modulating the ENSO amplitude and the associated change in atmospheric convection [ABSTRACT FROM AUTHOR]

Southern China spring rainfall (SCSR) is significant for agricultural sowing and soil moisture accumulation before the rainy summer. A better prediction of the rainfall improves our ability to risk response to natural disasters. It is found that the SCSR can be promoted by multi‐year El Niño events through the high‐latitude pathway (HP) and low‐latitude pathway (LP). The long‐lasting El Niño warming heats the tropical troposphere persistently until the decaying spring, which strengthens the Arctic polar vortex and the mid‐latitude blockings. This HP is in favor of more southward transport of Rossby wave energy and cold air, resulting in strong ascending motions over southern China (SC) in spring. The multi‐year El Niño also induces an enhanced western North Pacific anticyclone and a secondary circulation transporting moisture to SC through the LP. The HP is more important in the early spring, while the LP dominates the heavy SCSR in the late spring. Plain Language Summary: Southern China (SC) experiences a period of rainy time in spring, with the rainband located from South China to the Yangtze River. The southern China spring rainfall (SCSR) is influential for agriculture and soil moisture accumulation before the flood season in summer. A better prediction of the SCSR improves our ability to risk response to natural disasters. El Niño‐Southern Oscillation (ENSO) is the dominant climate signal that exerts significant remote impacts, especially in East Asia. However, whether it can help to predict the SCSR is still unclear. In this study, we show that a particular type of ENSO event, the multi‐year El Niño, initiates remarkable impacts on the SCSR. The long‐lasting Pacific warming favors a HP that transports more cold air and wave energy southward to SC during the decaying spring. Moreover, it also strengthens the western North Pacific anticyclone and generates a meridional secondary circulation with low‐level moisture transport toward SC. The low‐latitude and HPs collaborate to generate strong ascending motions and water vapor convergence in SC, being responsible for the large SCSR. Thus, the remote climate impact of multi‐year ENSO events is distinctive from the other ENSO events. Key Points: Multi‐year El Niño enhances southern China (SC) spring rainfall through both the low‐latitude pathway (LP) and the high‐latitude pathway (HP)Long‐lasting tropical warming supports the HP which transports wave energy and cold air to SC and exerts ascending motionsThese ascending motions and moisture transportation by El Niño‐induced western Pacific anticyclone can be further intensified by the LP [ABSTRACT FROM AUTHOR]

The PM2.5 (fine particulate matter with diameter ≤2.5 μm) concentration anomalies over the North China Plain (NCP) in early and late winter sometimes show a subseasonal reversal, which brings a great challenge for precise control of air pollution, and mechanisms are not well understood. This paper reveals the key role of the Barents Sea sea‐ice in this reversal. In early winter, a negative Scandinavian‐like pattern causes an anticyclonic anomaly over Northeast Asia and thus leads to the positive PM2.5 concentration anomaly over the NCP. In addition, anomalous warm advection associated with the positive North Atlantic Oscillation‐like pattern accelerates winter sea‐ice loss in the Barents Sea, especially in late winter, which increases the surface turbulent heating flux. These heating causes a negative Polar/Eurasian‐like pattern that induces a cyclonic anomaly over Northeast Asia and eventually leads to a negative PM2.5 concentration anomaly over the NCP in late winter. Vice versa. Plain Language Summary: In this study, we find that there is a significant seesaw pattern of PM2.5 concentration anomalies over the North China Plain (NCP) in early and late winter. Further results reveal that variations in Barents Sea sea‐ice play a crucial role. More specifically, a negative (positive) Scandinavian‐like pattern in early winter tends to induce an anticyclonic (a cyclonic) anomaly over Northeast Asia. This anticyclonic (cyclonic) anomaly leads to a higher (lower) PM2.5 concentration anomaly over the NCP in early winter. In addition, a North Atlantic Oscillation‐related warm (cold) temperature advection promotes (inhibits) the sea‐ice loss in the Barents Sea, especially in late winter. The Barents Sea‐ice loss (increment) in late winter tends to heat (cool) the lower‐level atmosphere and thus triggers an anticyclonic (a cyclonic) response in the upper troposphere there. The anticyclonic (cyclonic) response in the Barents Sea region as a part of the negative (positive) Polar/Eurasian‐like pattern induces a cyclonic (an anticyclonic) anomaly over Northeast Asia, which leads to a lower (higher) PM2.5 concentration anomaly over the NCP in late winter. These findings could be of great value for the subseasonal predictions of PM2.5 concentrations over the NCP in winter. Key Points: PM2.5 concentration anomaly over the North China Plain shows an visibly subseasonal reversal in early and late winter on interannual scaleThe Scandinavia‐like pattern and Polar/Eurasian‐like pattern are responsible for the seesaw pattern of PM2.5 concentration anomaliesThe sea‐ice variations in the Barents Sea play a key role in modulating such atmospheric circulations [ABSTRACT FROM AUTHOR]

At present, PPF-based point cloud recognition algorithms can perform better matching than competitors and be verified in the case of severe occlusion and stacking. However, including certain superfluous feature point pairs in the global model description would significantly lower the algorithm's efficiency. As a result, this paper delves into the Point Pair Feature (PPF) algorithm and proposes a 6D pose estimation method based on Keypoint Pair Feature (K-PPF) voting. The K-PPF algorithm is based on the PPF algorithm and proposes an improved algorithm for the sampling point part. The sample points are retrieved using a combination of curvature-adaptive and grid ISS, and the angle-adaptive judgment is performed on the sampling points to extract the keypoints, therefore improving the point pair feature difference and matching accuracy. To verify the effectiveness of the method, we analyze the experimental results in scenes with different occlusion and complexity levels under the evaluation metrics of ADD-S, Recall, Precision, and Overlap rate. The results show that the algorithm in this paper reduces redundant point pairs and improves recognition efficiency and robustness compared with PPF. Compared with FPFH, CSHOT, SHOT and SI algorithms, this paper improves the recall rate by more than 12.5%. [ABSTRACT FROM AUTHOR]

This study examines the relationship between the Quasi‐Biennial Oscillation (QBO) and the variability of the East Asian winter monsoon (EAWM) in the Northern Hemisphere (NH) winter. Here, we consider the effects of QBO winds in the lower stratosphere at 70 hPa. It is found that during the period of 1958–2019, the EAWM in the early winter months (November–December) is weaker in the easterly phase of the QBO (EQBO) than in the westerly phase of the QBO (WQBO). During EQBO, the northerly monsoon flow is weakened, and anomalous warm temperatures occur over East Asia. Moreover, components of the EAWM circulation system, including the Siberian High, Aleutian Low, East Asian trough, and East Asian jet stream, are all weakened. Our further analysis suggests that the QBO may influence the EAWM directly via a subtropical pathway. The EQBO tends to weaken the East Asian jet stream and shift it poleward, and the changes in the East Asian jet stream lead to a weakened EAWM. The activities of planetary waves are also changed in association with the QBO. Examinations of individual zonal wavenumbers (WNs) of planetary waves in the SLP field reveal that WN 1 is strengthened while WNs 2 and 3 are weakened during EQBO. Specifically, the anomalous WN 2 leads to weakening of the Siberian High, Aleutian Low, and East Asian trough, and the anomalous WN 3 reduces the pressure gradient between the East Asia landmass and the western Pacific. The changes in WNs 2 and 3 associated with the QBO play a dominant role in anomalous EAWM. [ABSTRACT FROM AUTHOR]

Generally, the relative parameters of continuous multi-impacts are ambiguous in the practical engineering. In this paper, continuous twice-impacts of Ultra-High Molecule Weight Polyethylene (UHMWPE) laminate which is fixed by four bolted joints are designed and conducted by experiment and simulation. The experimental results of first impact are used to verify the numerical model, in which a solid blunt projectile penetrates the laminate with the velocity of 216 m/s. The obtained results of experiment and simulation indicate that strong lateral effects can be observed for the twice-impacts of UHMWPE target fixed with bolted joints, then the deformation responses of bolt holes are studied to discuss parameters identification of secondary non-penetration impact, i.e., the velocity and impact position of secondary penetrator are identified based on inverse problem model. Finally, the numerical results calculated with the identification parameters are in good agreement with the twice-impacts test. The research scheme of this paper is significant to recognize the process of multi-impacts. [ABSTRACT FROM AUTHOR]

Experimental study on the ballistic behavior of mosaic Silicon Carbide (SiC) ceramics bonding with Ultra-High Molecular Weight Polyethylene (UHMWPE) plate is presented against 7.62 mm×51 mm Armor Piercing (AP) projectile. The effect of SiC ceramics on the ballistic performance of mosaic SiC/UHMWPE composite armors is systematically investigated, and the bulletproof process of the composite armor combining the hard/brittle SiC and soft/flexible UHMWPE is clarified in detail. The test results show that the ballistic performance of composite armors is significant influenced by the geometry of mosaic SiC ceramics and the impact zone of front layer, different impact zones are defined for the cylindrical mosaic SiC/UHMWPE composite armor. The residual velocities of AP projectile are varied from 648 m/s to 0 m/s for the cylindrical, hexagonal and square mosaic SiC ceramics, when the launch speeds of bullets are 780 m/s with a standard deviation of 10 m/s. The bulge lengths of UHMWPE plate are also changed from 16.5 mm to 43.2 mm for different structures of mosaic SiC ceramic front layer. The bulletproof property can be significantly enhanced by prolonging the interaction time between bullet and target. The conclusions of this paper are practically useful for designing the hard/flexible composite armor systems. [ABSTRACT FROM AUTHOR]