最小二乘法的改进算法辨识棱镜摄谱仪定标多项式

提出了采用最小二乘法的改进算法拟和一元非线性函数,并用该算法辨识棱镜摄谱仪的定标多项式,数值计算结果表明:采用改进的算法,非常显著地降低了求解定标多项式系数方程组的系数矩阵的条件数,定标多项式能更精确地反映谱平面坐标和谱线波长的定量关系。     

Nonlinear Dynamic Response of HDRB and Hybrid HDRB-Friction Sliders Base Isolation Systems

The isolation systems are usually made of rubber bearings that are sometimes coupled in hybrid combination with frictional devices; this is the case of an in-site experimental campaign, performed on a base isolated apartment building in Rapolla (south of Italy). Several dropout tests at initial displacements up to 17cm allowed to obtain in-site information on the true dynamic response of the isolation system (building and isolators). The tests carried out allow a comparison between the free vibration responses of a building, isolated by using a 28 HDRB isolation system only, or an HDRB-Friction Sliders Hybrid one. The paper highlights the main differences of the response in the superstructure (the structure over the isolation system) obtained by using only HDRB isolation system, or the Hybrid one (HDRB and Friction Sliders in parallel system). Analysis and comparisons of experimental data, show the influence of nonlinearities on structural higher modes amplification, especially observed by using the higher nonlinear Hybrid isolation system. Tests results confirm that, in the case of a regular superstructure, like the Rapolla building, the isolation system nonlinearities influence the structural response.     

CO2 Flux Estimation by Different Regression Methods from an Alpine Meadow on the Qinghai-Tibetan Plateau

CO2 efflux was estimated using different regression methods in static chamber observation from an alpine meadow on the Qinghai-Tibetan Plateau. The CO2 efflux showed a seasonal pattern, with the maximun flux occurring in the middle of July. The temperature sensitivity of CO2 efflux (Q10> was 3.9, which was at the high end of the range of global values. CO2 emissions calculated by linear and nonlinear regression were significantly different (p<0.05). Compared with the linear regression, CO2 emissions calculated by exponential regression and quadratic regression were 12.7% and 11.2% larger, respectively. However, there were no significant differences in temperature sensitivity values estimated by the three methods. In the entire growing season, the CO2 efflux estimated by linear regression may be underestimated by up to 25% compared to the real CO2 efflux. Consequently, great caution should be taken when using published flux data obtained by linear regression of static chamber observations to estimate the regional CO2 flux in alpine meadows on the Qinghai-Tibetan Plateau.     

Sensitivity of Nonlinearity on the ENSO Cycle in a Simple Air-sea Coupled Model

In this paper,the influence of the El NioSouthern Oscillation (ENSO) cycle on the sensitivity of nonlinear factors in the numerical simulation is investigated by conducting numerical experiments in a simple air-sea coupled model for ENSO prediction.Two sets of experiments are conducted in which zonal nonlinear factors,meridional nonlinear factors,or both are incorporated into the governing equations for the atmosphere or ocean.The results suggest that the ENSO cycle is very sensitive to the nonlinear factor of the governing equation for the atmosphere or ocean.Thus,incorporating nonlinearity into air-sea coupled models is of exclusive importance for improving ENSO simulation.     

Factors affecting site response to multi-directional earthquake loading

This paper presents an investigation into various factors that may affect the ground response to multi-directional earthquake loading, focusing mainly on the behavior of vertical ground motion and its relation with the horizontal counterpart. The factors investigated herein include the intensity of input motion and the associated soil nonlinearity, the location of input motion (rock outcrop versus bedrock), the variation of water table, and the damping property of soil. Influence of these factors is studied on the characteristics of site amplification in both vertical and horizontal directions, the response spectra of vertical and horizontal ground surface motions, the spectral ratio between the two components (V/H) at the ground surface, and the distributions of stresses and strains in the ground. One of the main results is that varying water table can bring about a significant impact on vertical motion and the relationship between vertical and horizontal motions. The surface response spectral ratio (V/H) can largely exceed the rule-of-thumb value of 2/3 at low periods with lowering the water table, but does not appear to be substantially affected at long periods.     

冻土弹塑性本构模型研究现状

土体的本构模型是分析计算土工结构变形规律的关键。自剑桥模型提出以来,对于土体本构模型的研究,各国学者在不同环境条件下发展研究了适用于相应试验条件下的各类模型。随着寒区经济的发展,关于冻土力学性质的研究日益增多,许多学者借鉴常规融土的研究方法建立了不同条件下的冻土弹塑性本构模型。为了进一步理清冻土变形行为的特征,完善适用于冻土弹塑性行为的本构模拟理论和方法,作者总结和分析了各类冻土弹塑性本构模型的理论基础、建模方法、参数确定方法等内容,对进一步发展可准确描述冻土复杂力学行为的本构模型具有指导意义。     

非线性视角下的上海旅游地复杂系统演化过程及动力学特征

随着旅游地发展复杂性的增加,非线性研究方法成为旅游地演化研究的有效选择。以上海为案例地,运用水平可视图算法,将旅游需求作为旅游地复杂系统动态行为表征,探讨旅游地复杂系统演化过程及动力学特征。研究发现：旅游地复杂系统演化具有小世界和近似无标度网络特性,混沌动态行为特征,表现为混沌确定非线性动力系统;上海旅游地复杂系统演化处于“无序中的有序”混沌或混沌边缘,原有秩序已瓦解,系统新的属性和结构逐渐涌现,有待新的高级有序态生成;旅游地复杂系统遵循“有序—混沌（边缘）—涌现—新有序”,从低级有序向高级有序演化跃升的过程;外部环境和主体系统主导下的重要事件是旅游地复杂系统由低级有序向高级有序演化的“关键要素”,政府学习创新能力的提升对系统阶段性演进起到“推进器”作用,旅游企业开始显现主导地位,成为未来推动上海旅游地复杂系统演替发展的主导力量。上海国际入境旅游客源国（日、韩、新、德、英、法、加、澳）和国内旅游外地游客市场处于不稳定的混沌区域,是影响上海旅游地复杂系统混沌行为的重要因素,应进行混沌控制,加强管理和引导,促进上海旅游地复杂系统新演化阶段有序态的生成。     

西安地区高层建筑桩土共同作用非线性研究

对西安地区桩土共同作用的研究现状进行分析,并对目前共同作用的计算理论研究进行总结．探讨了共同作用地基非线性,对西安地区高层建筑桩土共同作用数值模拟及动力反应研究成果和有待于进一步研究的问题作了介绍。     

边坡加固的抗震性能参数分析

传统基于瑞典法的边坡加固抗震性能参数分析,通过建立强度参数与临界滑动面对应关系完成推导,由于因荷载过大,边坡建筑物抗震性能降低,准确率不高等问题,提出新的边坡加固抗震性能参数分析方法,对边坡加固的抗震性能参数进行分析,更好地通过加固提高其抗震性能。运用新型边坡加固抗震性能参数分析方法,采用基于极向条分的极限分析上限法和非线性Mohr-Coulomb破坏准则,分析边坡加固措施对边坡抗震性能的影响,通过对比有、无加固措施状态下不同能量功率的运算确定边坡抗震性能,利用MATLAB软件获取边坡加固抗震性能参数的最优解。经实验证明,边坡潜在破坏范围受边坡坡顶受荷和边坡加固情况的作用较大,地震荷载系数及非线性系数越大,土体强度非线性越小,边坡抗震性能受地震荷载的作用也越大。边坡抗滑桩最优抗震支护方位位于X_F/L_x=0.7处,在地震荷载从0上升至0.2的情况下,非线性系数为1.2、1.4、1.6以及2.0时的边坡抗震性能分别下降了40.1%、46.8%、57.5%以及61.5%。新型的抗震性能参数分析方法有效地提高了结果准确率,对边坡加固的抗震性能能达到准确分析。     

Experimental and theoretical methods on determination of stress-dependent natural frequency of marine sedimentary clay

Excited by the vibration sources in dynamic engineering, the natural frequency and damping factor of the saturated marine sedimentary clay are key dynamic parameters that influence the responses under cyclic loads. Experimental and theoretical methods are proposed in this paper to analyze the natural frequency and the stress-dependent nonlinearity. The experimental method shows that the natural frequency of soils with specific stress state subjected to large cyclic shear strain can be estimated from the data of dynamic triaxial tests based on the amplitude–frequency response curve. Trial and error by the criterion from the half-power bandwidth method is used to determine the optimal fitting. The results of a theoretical study on the free vibration of soil layers are then presented to derive the analytic solution of natural frequency. In addition to the two frequency-independent elements (a lumped mass matrix and a stiffness matrix), the system’s equivalent damping coefficient matrix is iteratively determined based upon the forced vibration experimentally. Finally, the impacts of the resonance phenomenon on the dynamic shear modulus and hysteretic loop are discussed.