In this work, we choose Nb3Al/Nb3Sn as a new test case for flat/steep band model of superconductivity. Based on the density functional theory in the generalized gradient approximation, the electronic structure of Nb3A...In this work, we choose Nb3Al/Nb3Sn as a new test case for flat/steep band model of superconductivity. Based on the density functional theory in the generalized gradient approximation, the electronic structure of Nb3Al/ Nb3Sn has been studied. The obtained results agree well with those of the earlier studies and show clearly fiat bands around the Fermi level. The steep bands as characterized in this work locate around the M point in the first Brillouin zone. The obtained results reveal that Nb3Al/Nb3Sn fits more to the ＂Flat/steep＂ band model than to the van-Hove singularity scenario. The fiat/steep band condition for superconductivity implies a different thermodynamic behavior of superconductors other than that predicted from the conventional BCS theory. This observation sets up an indicator for selecting a suitable superconductor when its large-scale industrial use is needed, for example, in superconducting maglev system or ITER project.展开更多
现有大跨径桥梁有限元模型修正(finite element model updating,FEMU)方法一般未考虑运营荷载对结构动力特性的影响,导致修正后模型的参数变异性大。鉴于此,提出了一种考虑运营荷载的层次贝叶斯有限元模型修正方法,该方法包含考虑温度...现有大跨径桥梁有限元模型修正(finite element model updating,FEMU)方法一般未考虑运营荷载对结构动力特性的影响,导致修正后模型的参数变异性大。鉴于此,提出了一种考虑运营荷载的层次贝叶斯有限元模型修正方法,该方法包含考虑温度和交通荷载的概率参数修正、概率响应预测和结构状态评估。首先,根据监测数据的相关性分析结果确定了计算理论频率时需要考虑的荷载。随后,建立了温度-弹性模量线性关系,并基于动态称重(weigh-in-motion,WIM)数据,提出一种车辆荷载估计方法,以在有限元模型中定量考虑运营荷载对结构频率的影响。同时,引入两阶段马尔科夫链蒙特卡洛(Markov chain Monte Carlo,MCMC)采样方法和响应面代理模型,以提高概率模型修正的计算速率。该方法在一座采集了两年监测数据的大跨径拱桥上得到了验证。结果表明,在考虑运营荷载、参数不确定性和建模误差后,实测频率基本处于预测频率的95%置信区间内。最后,基于实测响应和预测响应置信区间提出了一个结构状态指标,并利用该指标检测出该桥的路面铺装更换过程。展开更多
圆筒型浮式生产储卸油装置(Floating Production Storage and Offloading,FPSO)通常在主甲板与工艺甲板间采用挡浪墙结构,但在高海况下容易遭受强浪砰击。为了设计兼顾强度要求与重量控制的挡浪墙,以流花11-1油田二次开发项目采用的圆筒...圆筒型浮式生产储卸油装置(Floating Production Storage and Offloading,FPSO)通常在主甲板与工艺甲板间采用挡浪墙结构,但在高海况下容易遭受强浪砰击。为了设计兼顾强度要求与重量控制的挡浪墙,以流花11-1油田二次开发项目采用的圆筒型FPSO为例,运用理论计算与有限元分析相互结合的方法,将局部计算模型体量设定为优化目标,把采用各异边界条件当作优化途径,提出一种可兼顾设计效率与计算精准性的外飘挡浪墙结构分析方法。明确以6 m×6 m的最小区域作为挡浪墙局部校核时砰击载荷的加载范围,并外延至相邻1档强肋位区间,以此作为模型的选定范围。该方案在现有工程实践中得到成功应用,亦可为类似结构设计工作提供有益借鉴。展开更多
基金financially supported by the Science Foundation for International Cooperation of Sichuan Province (2014HH0016)the Fundamental Research Funds for the Central Universities (SWJTU2014: A0920502051113-10000)National Magnetic Confinement Fusion Science Program (2011GB112001)
文摘In this work, we choose Nb3Al/Nb3Sn as a new test case for flat/steep band model of superconductivity. Based on the density functional theory in the generalized gradient approximation, the electronic structure of Nb3Al/ Nb3Sn has been studied. The obtained results agree well with those of the earlier studies and show clearly fiat bands around the Fermi level. The steep bands as characterized in this work locate around the M point in the first Brillouin zone. The obtained results reveal that Nb3Al/Nb3Sn fits more to the ＂Flat/steep＂ band model than to the van-Hove singularity scenario. The fiat/steep band condition for superconductivity implies a different thermodynamic behavior of superconductors other than that predicted from the conventional BCS theory. This observation sets up an indicator for selecting a suitable superconductor when its large-scale industrial use is needed, for example, in superconducting maglev system or ITER project.
文摘现有大跨径桥梁有限元模型修正(finite element model updating,FEMU)方法一般未考虑运营荷载对结构动力特性的影响,导致修正后模型的参数变异性大。鉴于此,提出了一种考虑运营荷载的层次贝叶斯有限元模型修正方法,该方法包含考虑温度和交通荷载的概率参数修正、概率响应预测和结构状态评估。首先,根据监测数据的相关性分析结果确定了计算理论频率时需要考虑的荷载。随后,建立了温度-弹性模量线性关系,并基于动态称重(weigh-in-motion,WIM)数据,提出一种车辆荷载估计方法,以在有限元模型中定量考虑运营荷载对结构频率的影响。同时,引入两阶段马尔科夫链蒙特卡洛(Markov chain Monte Carlo,MCMC)采样方法和响应面代理模型,以提高概率模型修正的计算速率。该方法在一座采集了两年监测数据的大跨径拱桥上得到了验证。结果表明,在考虑运营荷载、参数不确定性和建模误差后,实测频率基本处于预测频率的95%置信区间内。最后,基于实测响应和预测响应置信区间提出了一个结构状态指标,并利用该指标检测出该桥的路面铺装更换过程。
文摘圆筒型浮式生产储卸油装置(Floating Production Storage and Offloading,FPSO)通常在主甲板与工艺甲板间采用挡浪墙结构,但在高海况下容易遭受强浪砰击。为了设计兼顾强度要求与重量控制的挡浪墙,以流花11-1油田二次开发项目采用的圆筒型FPSO为例,运用理论计算与有限元分析相互结合的方法,将局部计算模型体量设定为优化目标,把采用各异边界条件当作优化途径,提出一种可兼顾设计效率与计算精准性的外飘挡浪墙结构分析方法。明确以6 m×6 m的最小区域作为挡浪墙局部校核时砰击载荷的加载范围,并外延至相邻1档强肋位区间,以此作为模型的选定范围。该方案在现有工程实践中得到成功应用,亦可为类似结构设计工作提供有益借鉴。
