Influences of across-strike heterogeneous viscosity on the earthquake cycle in a three-dimensional strike-slip fault model

Geodetic observations have shown that there exist large differences in the viscosity of the deep lithosphere across many large strike-slip faults.Heterogeneity in lithospheric viscosity structure can influence the efficiency of stress transfer and thus may have a significant effect on the earthquake cycle.Until now,how the lateral viscosity variation across strike-slip faults affects the earthquake cycles is still not well understood.Here,we investigate the effects of across-strike viscosity variation on long-term earthquake behaviors with a three-dimensional strike-slip fault model.Our model is a quasi-static model which is controlled by the slip-weakening friction law and powerlaw rheology.By comparing with the reference case,we find that low viscosity on one side of the fault results in a smaller rupture area but with a higher Coulomb stress drop on the ruptured fault region.In addition,low viscosity also leads to a small Coulomb stress accumulation rate.These combined effects increase the earthquake recurrence interval by approximately 10%and the earthquake moments by about 30%when the low viscosity is related to a geothermal gradient of 30 K/km.In addition,across-strike viscosity variation causes asymmetric interseismic ground surface deformation rate.As the viscosity contrast increases,the difference in the interseismic ground surface deformation rate between the two sides of the fault gradually increases,although the asymmetric feature is not pronounced.This asymmetry of interseismic ground deformation rate across a strike-slip fault is supposed to result in asymmetric coseismic deformation if the long-term plate motion velocity is invariant.As a result,this kind of asymmetry of interseismic deformation may influence the evaluation of potential earthquake hazards along large strike-slip faults with lateral viscosity contrast.

Influences of the heterogeneity of viscoelastic medium on postseismic deformation of the 2008 M_(W) 7.9 Wenchuan earthquake

The study of postseismic deformation is important for constraining the viscoelastic properties of the Earth and inverting the post-earthquake process.The levelling survey revealed that the area near Bei-chuan elevated 5.3 cm about two years after the M_(W) 7.9 Wenchuan earthquake(05/12/2008),during which the area underwent significant downward movement.The GPS horizontal displacements showed a non-monotonic variation after the Wenchuan earthquake.In this study,a 3-D viscoelastic finite element model is employed to simulate the coseismic and postseismic deformation of the Wenchuan earthquake.The numerical simulations show that the lateral heterogeneity across the Longmenshan fault plays an important role in the postseismic displacements.The results reveal that the coseismic defor-mation is not sensitive to the horizontal heterogeneity,but the postseismic deformation is sensitive to it.The postseismic deformation of the horizontally heterogeneous model is generally consistent with the observations of all geodetic surveys,such as GPS,InSAR and levelling,but not for the horizontally homogenous model.We also find that the non-monotonous variation of the postseismic deformation of the Wenchuan earthquake could be explained by a viscoelastic relaxation model with lateral heterogeneous medium across the Longmenshan fault.

Modulation of antiviral cytokine production and lung protection against influenza virus by the glycosides from Ligustrum purpurascens

Ligustrum purpurascens has been used as a traditional herb for over 2,000 years in China.This study was design to investigate the modulation of antiviral cytokines and reduction in lung inflammation of virus-infected mice by the glycosides isolated from Ligustrum purpurascens.Methods:Ligustrum purpurascens glycosides(LPG)were isolated from the leaves of Ligustrum purpurascens.Proliferation of spleen lymphocytes were investigated after LPG treatment.The in vitro and in vivo cytokine modulation of LPG was studied.Furthermore,the anti-inflammatory and antiviral activities of LPG,with the potential to reduce inflammatory lung disorders,were investigated by influenza A virus infected mice.Results:LPG could significantly promote the proliferation,and also could stimulate the production of IFN-γby spleen lymphocytes in a dose-dependent manner.IFN-γexpression level was increased significantly compared to the control and presented a dose-dependent manner in vitro.Furthermore,LPG inhibit the expression of TNF-αand IL-10,which return to normal level in the cyclophosphamide-induced mice model in vivo.Besides,the histopathological analysis indicated LPG reduced acute lung injury in mice infected with influenza virus.Conclusion:This study suggested that LPG could increase the exression of IFN-γ,immunoregulation and decrease lung inflammation of virus-infected mice.

High-performance multifunctional(Hf^(0.2)Nb_(0.2)Ta_(0.2)Ti_(0.2)Zr_(0.2))C high-entropy ceramic reinforced with low-loading 3D hybrid graphene–carbon nanotube

There has been growing interest in the high-entropy ceramic(HEC)recently owing to its tailorable compositions and microstructures,versatile properties,together with promising structural and functional applications.However,inferior fracture toughness(KIC)and damage tolerance restricted many practical applications of the HEC.Herein,we addressed this challenge by incorporating a threedimensional graphene–carbon nanotube(3D G–CNT)as toughening agent in(Hf_(0.2)Nb_(0.2)Ta_(0.2)Ti_(0.2)Zr_(0.2))C.The resulting enhanced 3D G–CNT/(Hf_(0.2)Nb_(0.2)Ta_(0.2)Ti_(0.2)Zr_(0.2))C featured an outstanding toughness of 8.23 MPa·m^(1/2),while remaining superior strength(763 MPa)and hardness(24.7 GPa).An ultralow friction coefficient(0.15)coupled with an ultralow wear rate(w,2.6×10^(−7) mm^(3)/(N·m))in the 3D G–CNT/(Hf_(0.2)Nb_(0.2)Ta_(0.2)Ti_(0.2)Zr_(0.2))C was obtained primarily as a function of lubricating scrolls,in which two-dimensional(2D)graphene acted as a tribolayer,and one-dimensional(1D)carbon nanotubes acted as nano ball bearings embedded inside.Strikingly,the 3D G–CNT/(Hf_(0.2)Nb_(0.2)Ta_(0.2)Ti_(0.2)Zr_(0.2))C exhibited rather low thermal conductivity(κ)yet excellent electrical conductivity(σ,1.3×10^(6) S/m)in comparison with the pure(Hf_(0.2)Nb_(0.2)Ta_(0.2)Ti_(0.2)Zr_(0.2))C.This study provided great potential for maximizing the physical and functional properties of the HEC for various applications.

机器直觉

当前以深度学习代表的人工智能技术所能解决的问题往往需要具有大量可以借鉴学习的训练集,同时要求所获取的信息是完备的.但在复杂时变的真实应用环境中,采集到的数据往往包含大量噪声与不确定性,且仅包含环境的局部信息,导致了基于深度学习的人工智能应用的局限性.而在同样环境下,人类却往往可以依靠直觉做出较为迅速且适宜的判断,这为我们发展新的人工智能理论解决上述问题提供了灵感.本文系统地对人类直觉的概念、机理、类别等内容进行论述,分析了不同学科已有相关研究进展及存在的不足.在此基础上,提出了机器直觉这一新的交叉学科研究方向,并给出了实现机器直觉的基本准则,以及通过让机器实现类似甚至超过人类的直觉能力、赋予机器洞察力与创造性的研究目标.本文尝试设计了机器直觉的通用整体架构,确定了全息感知、直觉认知、直觉决策和博弈行动几个主要功能模块的基本原理和内涵.最后,从脑科学、认知科学、人工智能等多学科交叉研究角度,对机器直觉的应用与未来研究方向进行了展望,为后续展开机器直觉的研究提供方向性指引.

An underwater acoustic direct sequence spread spectrum communication system using dual spread spectrum code

With the goal of achieving high stability and reliability to support underwater point-to-point communications and code division multiple access(CDMA) based underwater networks, a direct sequence spread spectrum based underwater acoustic communication system using dual spread spectrum code is proposed. To solve the contradictions between the information data rate and the accuracy of Doppler estimation, channel estimation, and frame synchronization, a data frame structure based on dual spread spectrum code is designed. A long spread spectrum code is used as the training sequence, which can be used for data frame detection and synchronization, Doppler estimation, and channel estimation. A short spread spectrum code is used to modulate the effective information data. A delay cross-correlation algorithm is used for Doppler estimation, and a correlation algorithm is used for channel estimation. For underwater networking, each user is assigned a different pair of spread spectrum codes. Simulation results show that the system has a good anti-multipath, anti-interference, and anti-Doppler performance, the bit error rate can be smaller than 10^(-6) when the signal-to-noise ratio is larger than-10 dB, the data rate can be as high as 355 bits/s, and the system can be used in the downlink of CDMA based networks.

Novel crosslinked alginate/hyaluronic acid hydrogels for nerve tissue engineering

CT： Artificial tissue engineering scaffods can potentially provide supportand guidance for the regrowth of severed axons following nerve injury. In this study a hybrid biomaterial composed of alginate and hyaluronic acid （HA） was synthesized characterized in terms of its suitability for covalent modification, biocompatibility fir living Schwann cells and feasibility to construct three dimensional （3D） Carbodiimide mediated amide formation for the purpose of covalent crosslinking of the HA was carried out in the presence of calcium ions that ionically crosslink alginate.Amide formation was found to be dependent on the concentrations of cabodiimide and calclum chloride. The double-crosslinked composite hydrogels display blocompatibllity that is comparable to simple HA hydrogels, allowing for Schwann cell survival and significant difference was found between composite hydrogels made from different of alginate and HA. A 3D BioPIotterTM rapid prototyping system was used to fabricats 3D scaffolds. The result indicated that combining HA with alginate facilitated the fabrication process and that 3D scaffolds with porous inner structure can be fabricated ;from the composite hydrogels, but not from HA alone. This information provides a basis for continuing in vitro and in vivo tests of the suitability of alginate/HA hydrogel as a biomaterial to create living cell scaffolds to support nerve regeneration.