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Enhancement of thermal rectification by asymmetry engineering of thermal conductivity and geometric structure for multi-segment thermal rectifier 被引量:1
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作者 杜甫烨 张望 +1 位作者 王惠琼 郑金成 《Chinese Physics B》 SCIE EI CAS CSCD 2023年第6期34-43,共10页
Thermal rectification is an exotic thermal transport phenomenon,an analog to electrical rectification,in which heat flux along one direction is larger than that in the other direction and is of significant interest in... Thermal rectification is an exotic thermal transport phenomenon,an analog to electrical rectification,in which heat flux along one direction is larger than that in the other direction and is of significant interest in electronic device applications.However,achieving high thermal rectification efficiency or rectification ratio is still a scientific challenge.In this work,we performed a systematic simulation of thermal rectification by considering both efforts of thermal conductivity asymmetry and geometrical asymmetry in a multi-segment thermal rectifier.It is found that the high asymmetry of thermal conductivity and the asymmetry of the geometric structure of multi-segment thermal rectifiers can significantly enhance the thermal rectification,and the combination of both thermal conductivity asymmetry and geometrical asymmetry can further improve thermal rectification efficiency.This work suggests a possible way for improving thermal rectification devices by asymmetry engineering. 展开更多
关键词 thermal conductivity SIMULATION thermal rectification multi-segment thermal rectifier
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A two-parameter multiple shooting method and its application to the natural vibrations of non-prismatic multi-segment beams
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作者 R.HOŁUBOWSKI K.JARCZEWSKA 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI CSCD 2023年第12期2243-2252,共10页
This paper presents an enhanced version of the standard shooting method that enables problems with two unknown parameters to be solved.A novel approach is applied to the analysis of the natural vibrations of Euler-Ber... This paper presents an enhanced version of the standard shooting method that enables problems with two unknown parameters to be solved.A novel approach is applied to the analysis of the natural vibrations of Euler-Bernoulli beams.The proposed algorithm,named as two-parameter multiple shooting method,is a new powerful numerical tool for calculating the natural frequencies and modes of multi-segment prismatic and non-prismatic beams with different boundary conditions.The impact of the axial force and additional point masses is also taken into account.Due to the fact that the method is based directly on the fourth-order ordinary differential equation,the structures do not have to be divided into many small elements to obtain an accurate enough solution,even though the geometry is very complex.To verify the proposed method,three different examples are considered,i.e.,a three-segment non-prismatic beam,a prismatic column subject to non-uniformly distributed compressive loads,and a two-segment beam with an additional point mass.Numerical analyses are carried out with the software MATHEMATICA.The results are compared with the solutions computed by the commercial finite element program SOFiSTiK.Good agreement is achieved,which confirms the correctness and high effectiveness of the formulated algorithm. 展开更多
关键词 two-parameter multiple shooting method two-point boundary value problem natural vibration non-prismatic beam multi-segment beam
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Multi-segmented nanowires for vortex magnetic domain wall racetrack memory
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作者 M Al Bahri M Al Hinaai T Al Harthy 《Chinese Physics B》 SCIE EI CAS CSCD 2023年第12期582-588,共7页
A vortex domain wall's(VW) magnetic racetrack memory's high performance depends on VW structural stability,high speed, low power consumption and high storage density. In this study, these critical parameters w... A vortex domain wall's(VW) magnetic racetrack memory's high performance depends on VW structural stability,high speed, low power consumption and high storage density. In this study, these critical parameters were investigated in magnetic multi-segmented nanowires using micromagnetic simulation. Thus, an offset magnetic nanowire with a junction at the center was proposed for this purpose. This junction was implemented by shifting one portion of the magnetic nanowire horizontally in the x-direction(l) and vertically(d) in the y-direction. The VW structure became stable by manipulating magnetic properties, such as magnetic saturation(M_(4)) and magnetic anisotropy energy(K_(u)). In this case, increasing the values of M_(4) ≥ 800 kA/m keeps the VW structure stable during its dynamics and pinning and depinning in offset nanowires,which contributes to maintenance of the storage memory's lifetime for a longer period. It was also found that the VW moved with a speed of 500 m/s, which is desirable for VW racetrack memory devices. Moreover, it was revealed that the VW velocity could be controlled by adjusting the offset area dimensions(l and d), which helps to drive the VW by using low current densities and reducing the thermal-magnetic spin fluctuations. Further, the depinning current density of the VW(J_(d)) over the offset area increases as d increases and l decreases. In addition, magnetic properties, such as the M_(4) and K_(u),can affect the depinning process of the VW through the offset area. For high storage density, magnetic nanowires(multisegmented) with four junctions were designed. In total, six states were found with high VW stability, which means three bits per cell. Herein, we observed that the depinning current density(J_(d)) for moving the VW from one state to another was highly influenced by the offset area geometry(l and d) and the material's magnetic properties, such as the M_(4) and K_(u). 展开更多
关键词 micromagnetic simulation vortex domain wall racetrack memory multi-segmented magnetic nanowire spin transfer torque
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DDoS Defense Algorithm Based on Multi-Segment Timeout Technology 被引量:1
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作者 DU Ruizhong YANG Xiaohui MA Xiaoxue HE Xinfeng 《Wuhan University Journal of Natural Sciences》 CAS 2006年第6期1823-1826,共4页
Through the analysis to the DDoS(distributed denial of service) attack, it will conclude that at different time segments, the arrive rate of normal SYN (Synchronization) package are similar, while the abnormal pac... Through the analysis to the DDoS(distributed denial of service) attack, it will conclude that at different time segments, the arrive rate of normal SYN (Synchronization) package are similar, while the abnormal packages are different with the normal ones. Toward this situation a DDoS defense algorithm based on multi-segment timeout technology is presented, more than one timeout segment are set to control the net flow. Experiment results show that in the case of little flow, multi-segment timeout has the ability dynamic defense, so the system performance is improved and the system has high response rate. 展开更多
关键词 DDoS(distributed denial of service) multi-segments timeout dynamic defense net flow analysis
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Multi-segment and Multi-ply Overlapping Process of Multi Coupled Activities Based on Valid Information Evolution 被引量:1
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作者 WANG Zhiliang WANG Yunxia QIU Shenghai 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2013年第1期176-188,共13页
Complex product development will inevitably face the design planning of the multi-coupled activities, and overlapping these activities could potentially reduce product development time, but there is a risk of the addi... Complex product development will inevitably face the design planning of the multi-coupled activities, and overlapping these activities could potentially reduce product development time, but there is a risk of the additional cost. Although the downstream task information dependence to the upstream task is already considered in the current researches, but the design process overall iteration caused by the information interdependence between activities is hardly discussed; especially the impact on the design process' overall iteration from the valid information accumulation process. Secondly, most studies only focus on the single overlapping process of two activities, rarely take multi-segment and multi-ply overlapping process of multi coupled activities into account; especially the inherent link between product development time and cost which originates from the overlapping process of multi coupled activities. For the purpose of solving the above problems, as to the insufficiency of the accumulated valid information in overlapping process, the function of the valid information evolution (VIE) degree is constructed. Stochastic process theory is used to describe the design information exchange and the valid information accumulation in the overlapping segment, and then the planning models of the single overlapping segment are built. On these bases, by analyzing overlapping processes and overlapping features of multi-coupling activities, multi-segment and multi-ply overlapping planning models are built; by sorting overlapping processes and analyzing the construction of these planning models, two conclusions are obtained: (1) As to multi-segment and multi-ply overlapping of multi coupled activities, the total decrement of the task set development time is the sum of the time decrement caused by basic overlapping segments, and minus the sum of the time increment caused by multiple overlapping segments; (2) the total increment of development cost is the sum of the cost increment caused by all overlapping process. And then, based on overlapping degree analysis of these planning models, by the V1E degree function, the four lemmas theory proofs are represented, and two propositions are finally proved: (1) The multi-ply overlapping of the multi coupled activities will weaken the basic overlapping effect on the development cycle time reduction (2) Overlapping the multi coupled activities will decrease product development cycle, but increase product development cost. And there is trade-off between development time and cost. And so, two methods are given to slacken and eliminate multi-ply overlapping effects. At last, an example about a vehicle upper subsystem design illustrates the application of the proposed models; compared with a sequential execution pattern, the decreasing of development cycle (22%) and the increasing of development cost (3%) show the validity of the method in the example The proposed research not only lays a theoretical foundation for correctly planning complex product development process, but also provides specific and effective operation methods for overlapping multi coupled activities. 展开更多
关键词 multi coupled activities valid information evolution multi-segment multi-ply overlapping development time and cost trade-ofl iteration
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High-power and high optical conversion efficiency diode-end-pumped laser with multi-segmented Nd:YAG/Nd:YVO-4
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作者 Meng-Yao Wu Peng-Fei Qu +3 位作者 Shi-Yu Wang SEl Zhen Guo De-Fang Cai Bing-Bin Li 《Chinese Physics B》 SCIE EI CAS CSCD 2018年第9期306-310,共5页
A novel flat-flat resonator consisting of two crystals(Nd:YAG + Nd:YVO4) is established for power scaling in a diode-end-pumped solid-state laser. We systematically compare laser characteristics between multi-seg... A novel flat-flat resonator consisting of two crystals(Nd:YAG + Nd:YVO4) is established for power scaling in a diode-end-pumped solid-state laser. We systematically compare laser characteristics between multi-segmented(Nd:YAG + Nd:YVO4) and conventional composite(Nd:YAG + Nd:YAG) crystals to demonstrate the feasibility of spectral line matching for output power scale-up in end-pumped lasers. A maximum continuous-wave output power of 79.2 W is reported at 1064 nm, with Mx2= 4.82, My2= 5.48, and a pumping power of 136 W in the multi-segmented crystals(Nd:YAG + Nd:YVO4). Compared to conventional composite crystals(Nd:YAG + Nd:YAG), the optical-optical conversion efficiency of multi-segmented crystals(Nd:YAG + Nd:YVO4) from 808 nm to 1064 nm is enhanced from 30% to 58.8%,while the laser output sensitivity as affected by the diode-laser temperature is reduced from 55% to 9%. 展开更多
关键词 diode-pumped solid-state laser multi-segmented crystals(Nd:YAG Nd:YVO4) spectral line matching diode-laser temperature
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High-resolution flood modeling of urban areas using MSN_Flood 被引量:3
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作者 Michael Hartnett Stephen Nash 《Water Science and Engineering》 EI CAS CSCD 2017年第3期175-183,共9页
Although existing hydraulic models have been used to simulate and predict urban flooding, most of these models are inadequate due to the high spatial resolution required to simulate flows in urban floodplains. Nesting... Although existing hydraulic models have been used to simulate and predict urban flooding, most of these models are inadequate due to the high spatial resolution required to simulate flows in urban floodplains. Nesting high-resolution subdomains within coarser-resolution models is an efficient solution for enabling simultaneous calculation of flooding due to tides, surges, and high river flows. MSN_Flood has been developed to incorporate moving boundaries around nested domains, permitting alternate flooding and drying along the boundary and in the interior of the domain. Ghost cells adjacent to open boundary cells convert open boundaries, in effect, into internal boundaries. The moving boundary may be multi-segmented and non-continuous, with recirculating flow across the boundary. When combined with a bespoke adaptive interpolation scheme, this approach facilitates a dynamic internal boundary. Based on an alternating-direction semi-implicit finite difference scheme,MSN_Flood was used to hindcast a major flood event in Cork City resulting from the combined pressures of fluvial, tidal, and storm surge processes. The results show that the model is computationally efficient, as the 2-m high-resolution nest is used only in the urban flooded region.Elsewhere, lower-resolution nests are used. The results also show that the model is highly accurate when compared with measured data. The model is capable of incorporating nested sub-domains when the nested boundary is multi-segmented and highly complex with lateral gradients of elevation and velocities. This is a major benefit when modelling urban floodplains at very high resolution. 展开更多
关键词 Multi-scale NESTING Surge-fluvial FLOODING Urban FLOODING multi-segmented BOUNDARY Moving BOUNDARY
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Buckling of Multiple Intersecting Spherical Shells
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作者 Jian Zhang Shengqiu Li +3 位作者 Weicheng Cui Kai Xiang Fang Wang Wenxian Tang 《Journal of Marine Science and Application》 CSCD 2020年第4期634-641,共8页
This study explored the buckling of multiple intersecting spherical shells.A three-segment spherical shell was designed using the theory of deformation coordination;the design was compared with that of a volume-equiva... This study explored the buckling of multiple intersecting spherical shells.A three-segment spherical shell was designed using the theory of deformation coordination;the design was compared with that of a volume-equivalent cylindrical shell and ring-ribbed cylindrical shell.The numerical results indicated that the buckling capacity of the three-segment spherical shell was superior to those of the other two cylindrical shells.To validate our numerical approach,three laboratory-scale shell models were fabricated.Each model was accurately measured and slowly tested in a pressure chamber;thus,the tested shells were studied numerically.The experimental collapse modes agreed well with numerical results,and the collapse load of the three-segment pressure shell was considerably higher than that of the two cylindrical shells. 展开更多
关键词 multi-segment spherical shell Cylindrical shell External pressure BUCKLING
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Characteristics of seismic performance of building structures located in mountainous areas
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作者 Yuping Sun Takashi Takeuchi Yingmin Li 《西部人居环境学刊》 2015年第A01期17-23,共7页
关键词 multi-segment beam element Seismic performance Construction topography Mountainous areas
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Study on clinical effects of pedicle screw combined with immobilized implantation bone by wirerope and hallow compression screw immobilization in treating spondylolysis of lumbar vertebra of multiple segments of adults
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作者 Dongdong Zhao Feng Li +1 位作者 Yao Wu Xiaoyan Zhang 《Discussion of Clinical Cases》 2019年第3期19-23,共5页
Objective:To observe clinical effects of pedicle screw fixation combined with cable wires and bone graft and cannulated compression screws on adult multi-segment lumbar spondylolysis.Methods:70 cases of patients with ... Objective:To observe clinical effects of pedicle screw fixation combined with cable wires and bone graft and cannulated compression screws on adult multi-segment lumbar spondylolysis.Methods:70 cases of patients with multi-segment lumbar spondylolysis were selected in our hospital.According to different surgical schemes,these patients were divided into the observation group(35 cases)and the control group(35 cases).The observation group received pedicle screw fixation combined with cable wires and bone graft and the control group received cannulated compression screw fixation.Macnab criteria were adopted to implement a therapeutic evaluation of two groups of patients to make an observation and comparison of the excellent and good rate of surgery and a series of indicators including perioperative clinical effects,intraoperative blood loss,duration of surgery,hospital length of stay(HLOS),visual analogue scale(VAS),Oswestry disability index and Japanese Orthopaedic Association(JOA)score.Results:The excellent and good rate of the observation group was 97.14%,and that of the control group was 82.86%,the difference between two groups was statistically significant(χ^(2)=6.248,p=0.012).The differences in intraoperative blood loss,duration of surgery and HLOS between two groups were statistically significant(t=-4.55,t=-4.55,t=-4.55;p<0.05).Oswestry index,VAS score and JOA score of the observation group were(2.4±0.9),(28.5±6.4)and(27.1±3.1)respectively,and these of the control group were(3.5±1.2),(37.1±7.8)and(21.3±2.7)respectively,the differences between two groups were statistically significant(t=4.338,t=5.043,t=8.347,p<0.05).Conclusions:Pedicle screw combined with immobilized implantation bone by wirerope has an excellent clinical effect on the treatment of adult multi-segment lumbar spondylolysis,and it has a series of advantages such as fast postoperative recovery,small surgical trauma and so on.In addition,this technique can also restore the stability of spinal segments and relieve pains to a greater degree. 展开更多
关键词 Pedicle screw Cable wires and bone graft Cannulated compression screw fixation Adult multi-segment lumbar spondylolysis
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Three-dimensional numerical analysis on combustion performance and flow of hybrid rocket motor with multi-segmented grain 被引量:6
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作者 Hui TIAN Yu DUAN Hao ZHU 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2020年第4期1181-1191,共11页
This paper presents the combustion characteristics in hybrid rocket motors with multisegmented grain through three-dimensional numerical simulations.Multi-segmented grain is composed of several thin grains with two or... This paper presents the combustion characteristics in hybrid rocket motors with multisegmented grain through three-dimensional numerical simulations.Multi-segmented grain is composed of several thin grains with two or more ports.The numerical model consists of Navier-Stokes equations with turbulence,solid fuel pyrolysis,chemical reactions,a fluid–solid coupling model and a regression rate model.The simulations adopt 90%Hydrogen Peroxide(HP)and PolyEthylene(PE)as the propellant combination.The effects of the rotation,port number,fuel grain segment number and mid-chamber length on the flow field and combustion performances are analyzed.The results indicate that the multi-segmented grain configuration can strengthen the flow field,and the regression rate and combustion efficiency are enhanced.Take the cases with two grain segments and three ports for example,the regression rate is increased by 32.4%-45.1%and the combustion efficiency increases by 6%-8.6%in different rotation angles. 展开更多
关键词 Combustion efficiency Hybrid rocket motor multi-segmented grain Regression rate Rotation angle
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Optimizing the cleanliness in multi-segment disk amplifiers based on vector flow schemes 被引量:1
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作者 Zhiyuan Ren Jianqiang Zhu +1 位作者 Zhigang Liu Xiaowei Yang 《High Power Laser Science and Engineering》 SCIE CAS CSCD 2018年第1期1-6,共6页
The objective of maintaining the cleanliness of the multi-segment disk amplifier in Shenguang-II(SG-II) is to reduce laser-induced damage for optics. The flow field of clean gas, which is used for the transportation o... The objective of maintaining the cleanliness of the multi-segment disk amplifier in Shenguang-II(SG-II) is to reduce laser-induced damage for optics. The flow field of clean gas, which is used for the transportation of contaminant particles,is a key factor affecting the cleanliness level in the multi-segment disk amplifier. We developed a gas–solid coupling and three-dimensional flow numerical simulation model. The three-dimensional and two-phase flow model is verified by the flow-field smog experiment and the particle concentration measurement experiment with the 130-disk amplifier in SG-II. By optimizing the boundary conditions with the same flow rate, the multi-inlet vector flow scheme can not only effectively reduce the purging time, but also prevent the reverse diffusion of contaminant particles in the multi-segment disk amplifier and the deposition of contaminant particles on the surface of the Nd:glass. 展开更多
关键词 CLEANLINESS computational fluid dynamics flow field multi-segment disk amplifier vector flow
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Multi-segment linear gradient optimization strategy based on resolution map in HPLC
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作者 Andreas Seidel-Morgenstern 《Science China Chemistry》 SCIE EI CAS 2006年第4期315-325,共11页
Based on the mechanism of chromatographic retention (the relationship between the retention of solute and the mobile phase conditions) and method of resolution map, several methods of optimizing multi-segment linear g... Based on the mechanism of chromatographic retention (the relationship between the retention of solute and the mobile phase conditions) and method of resolution map, several methods of optimizing multi-segment linear gradient elution conditions were proposed according to the different separation requirements of various samples. These methods were verified using literature data. Moreover, the advantages and disadvantages of these methods were compared. It was proved that the third method is a fast optimization method which is capable of separating all the components with relatively high resolution. 展开更多
关键词 optimization multi-segment LINEAR gradient RESOLUTION map LIQUID chromatography.
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A 14-bit wide temperature range differential SAR ADC with an on-chip multi-segment BGR
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作者 乔宁 高见头 +3 位作者 赵凯 杨波 刘忠立 于芳 《Journal of Semiconductors》 EI CAS CSCD 北大核心 2011年第8期80-86,共7页
A 14-bit low power self-timed differential successive approximation(SAR) ADC with an on-chip multisegment bandgap reference(BGR) is described.An on-chip multi-segment BGR,which has a temperature coefficient of 1.3... A 14-bit low power self-timed differential successive approximation(SAR) ADC with an on-chip multisegment bandgap reference(BGR) is described.An on-chip multi-segment BGR,which has a temperature coefficient of 1.3 ppm/℃and a thermal drift of about 100μV over the temperature range of -40 to 120℃is implemented to provide a high precision reference voltage for the SAR ADC.The Gray code form is utilized instead of binary form mode control to reduce substrate noise and enhance the linearity of the whole system.Self-timed bit-cycling is adopted to enhance the time efficiency.The 14-bit ADC was fabricated in a TSMC 0.13μm CMOS process. With the on-chip BGR,the SAR ADC achieves an SNDR of 81.2 dB(13.2 ENOB) and an SFDR of 85.2 dB with a conversion rate of 2 MS/s at room temperature and can keep an ENOB of more than 12 bits at a conversion rate of 2 MS/s over the temperature range from -40 to 120℃. 展开更多
关键词 differential successive approximation ADC self-timed bit-cycling gray code on-chip multi-segment BGR
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From active fault segmentation to risks of earthquake hazards and property and life losses—A case study from the Xianshuihe-Xiaojiang fault zone 被引量:2
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作者 Jia CHENG Chong XU +2 位作者 Jian MA Xiwei XU Pengyu ZHU 《Science China Earth Sciences》 SCIE EI CAS CSCD 2023年第6期1345-1364,共20页
Strong earthquakes generally rupture along active faults,and associated ground motion can cause earthquake disasters,property losses,and casualties from kilometers to tens of kilometers away.Therefore,one of the most ... Strong earthquakes generally rupture along active faults,and associated ground motion can cause earthquake disasters,property losses,and casualties from kilometers to tens of kilometers away.Therefore,one of the most effective ways to find earthquake’s dangerous parts of faults is to study the seismic hazards on fault segments.After that,we can also evaluate the probabilities of landslides hazard,property losses,and casualties.In this study,using fault slip rates and magnitude-frequency relationship as constraints,we calculated the earthquake occurrence rates for the segments along the Xianshuihe-Xiaojiang fault zone.We obtained 11 sites of single-segment or multi-segment rupturing risk.We also provided these potential events conditional probabilities in the next 30 years.For the 11 potential earthquakes,we calculated the property loss of residential buildings in the ground motion field.The most significant property loss is CNY 7.65 billion caused by the single-segment rupturing of the F19 segment on the Anninghe fault.We applied the deep learning neural network method in predicting the number of casualties for the potential earthquakes,showing that the most significant event is the multi-segment rupturing of the F29 and F30 segments on the Anninghe fault with the predicted death number of 279-317.We also evaluated the probabilities of earthquake landslides after the potential earthquakes.The results show that areas with intense compressional tectonic stress are highly unstable and prone to earthquake induced landslides,including the southern section of the Yuke fault,the southern section of the Xianshuihe fault,and the conjugated area between the southern section of the Daliangshan fault and the Lianfeng fault.These areas have a considerable number of earthquake landslides with probabilities>10%.The methodology and results will give us a new effective way of applying active fault data in earthquake hazard and risk analysis and provide a scientific path for earthquake prevention,disaster reduction,and emergency rescue preparation. 展开更多
关键词 Xianshuihe-Xiaojiang fault Fault segmentation multi-segment rupture Probabilities of landslide Property losses
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