Seismic effectiveness evaluation and optimized design of tie up method for securing museum collections

To quantify the seismic effectiveness of the most commonly used fishing line tie up method for securing museum collections and optimize fixed strategies for exhibitions,shaking table tests of the seismic systems used for typical museum collection replicas have been carried out.The influence of body shape and fixed measure parameters on the seismic responses of replicas and the interaction behavior between replicas and fixed measures have been explored.Based on the results,seismic effectiveness evaluation indexes of the tie up method are proposed.Reasonable suggestions for fixed strategies are given,which provide a basis for the exhibition of delicate museum collections considering the principle of minimizing seismic responses and intervention.The analysis results show that a larger ratio of height of mass center to bottom diameter led to more intense rocking responses.Increasing the initial pretension of fishing lines was conducive to reducing the seismic responses and stress variation of the lines.Through comprehensive consideration of the interaction forces and effective securement,it is recommended to apply 20%of breaking stress as the initial pretension.For specific museum collections that cannot be effectively protected by the independent tie up method,an optimized strategy of a combination of fishing lines and fasteners is recommended.

Research of NO_(2) vertical profiles with look-up table method based on MAX-DOAS

Obtaining the vertical distribution profile of trace gas is of great significance for studying the diffusion procedure of air pollution.In this article,a look-up table method based on multi-axis differential optical absorption spectroscopy(MAX-DOAS)technology is established for retrieving the tropospheric NO_(2) vertical distribution profiles.This method retrieves the aerosol extinction profiles with minimum cost function.Then,the aerosol extinction profiles and the atmospheric radiation transfer model(RTM)are employed to establish the look-up table for retrieving the NO_(2) vertical column densities(VCDs)and profiles.The measured NO_(2) differential slant column densities(DSCDs)are compared with the NO_(2) DSCDs simulated by the atmospheric RTM,and the NO_(2) VCDs,the weight factor of NO_(2) in the boundary layer,and the boundary layer height are obtained by the minimization process.The look-up table is established to retrieve NO_(2) VCDs based on MAX-DOAS measurements in Huaibei area,and the results are compared with the data from Copernicus Atmospheric Monitoring Service(CAMS)model.It is found that there are nearly consistent and the correlation coefficient R2 is more than 0.86.The results show that this technology provides a more convenient and accurate retrieval method for the stereoscopic monitoring of atmospheric environment.

Study on the methods to calculate the numbers of elements in every period in the periodic table

The previous methods of figuring the numbers of chemical elements is summed up in this paper. Based on that, another two creative calculative methods are introduced as well.

Mapping of the Water Table Levels of Unconfined Aquifers Using Two Interpolation Methods

The spatial prediction of the water table can be used for many applications related to civil works (foundations, excavations) and other urban and environmental management activities. Deterministic and geostatistical interpolation methods were used to predict the spatial distribution of water table levels (unconfined aquifers) of important geological formations of the Joao Pessoa City (capital of Paraiba State, Brazil) with dense urban occupation and high demand for new civil works. The deterministic (topo to raster) and geostatistical (ordinary kriging) interpolation methods were evaluated using a Geographic Information System (GIS)-based investigation. The water table levels were obtained from 276 boring logs of Standard Penetration Test (SPT) in situ investigation distributed over the geological formations studied (an area of 59.8 km2, covering 40 districts of the Joao Pessoa City). The Nspt values and textural characterization data are stored for levels of 1 m depth. Some boreholes located in the area investigated were not included in the interpolation processes in order to be compared with estimated values (validation of the results). Maps of the water table depths were also produced to further analyze the quality of the water table surfaces interpolated by both methods. The phreatic surface interpolations provided satisfactory results for both methods (RMSE = 1.8 m). The topo to raster method showed a slight general tendency to be less affected by local values in relation to the kriging method and also has the advantage of integrating the drainage flow system, which is a relevant aspect for spatial models of the water table levels of unconfined aquifers. The ordinary kriging (geostatistical method) provides a prediction surface and some measure of the certainty or accuracy of the predictions.

Seismic response of underground utility tunnels: shaking table testing and FEM analysis

Underground utility tunnels are widely used in urban areas throughout the world for lifeline networks due to their easy maintenance and environmental protection capabilities. However, knowledge about their seismic performance is still quite limited and seismic design procedures are not included in current design codes. This paper describes a series of shaking table tests the authors performed on a scaled utility tunnel model to explore its performance under earthquake excitation. Details of the experimental setup are first presented focusing on aspects such as the design of the soil container, scaled structural model, sensor array arrangement and test procedure. The main observations from the test program, including structural response, soil response, soil-structure interaction and earth pressure, are summarized and discussed. Further, a finite element model （FEM） of the test utility tunnel is established where the nonlinear soil properties are modeled by the Drucker- Prager constitutive model; the master-slave surface mechanism is employed to simulate the soil-structure dynamic interaction; and the confining effect of the laminar shear box to soil is considered by proper boundary modeling. The results from the numerical model are compared with experiment measurements in terms of displacement, acceleration and amplification factor of the structural model and the soil. The comparison shows that the numerical results match the experimental measurements quite well. The validated numerical model can be adopted for further analysis.

A general purpose exact Rayleigh scattering look-up table for ocean color remote sensing

The current exact Rayleigh scattering calculation of ocean color remote sensing uses the look-up table （LUT）, which is usually created for a special remote sensor and cannot be applied to other sensors. For practical application, a general purpose Rayleigh scattering LUT which can be applied to all ocean color remote sensors is generated. An adding-doubling method to solve the vector radiative transfer equation in the plane-parallel atmosphere is deduced in detail. Compared with the exact Rayleigh scattering radiance derived from the MODIS exact Rayleigh scattering LUT, it is proved that the relative error of Rayleigh scattering calculation with the adding-doubling method is less than 0.25%, which meets the required accuracy of the atmospheric correction of ocean color remote sensing. Therefore, the adding-doubling method can be used to generate the exact Rayleigh scattering LUT for the ocean color remote sensors. Finally, the general purpose exact Rayleigh scattering LUT is generated using the adding-doubling method. On the basis of the general purpose LUT, the calculated Rayleigh scattering radiance is tested by comparing with the LUTs ofMODIS, SeaWiFS and the other ocean color sensors, showing that the relative errors are all less than 0.5%, and this general purpose LUT can be applied to all ocean color remote sensors.

Numerical simulations of shake-table experiment for dynamic soil-pile-structure interaction in liquefi able soils

A shake-table experiment on pile foundations in liquefi able soils composed of liquefi able sand and overlying soft clay is studied. A three-dimensional(3D) effective stress fi nite element(FE) analysis is employed to simulate the experiment. A recently developed multi-surface elasto-plastic constitutive model and a fully coupled dynamic inelastic FE formulation(u-p) are used to model the liquefaction behavior of the sand. The soil domains are discretized using a solid-fl uid fully coupled(u-p) 20-8 noded brick element. The pile is simulated using beam-column elements. Upon careful calibration, very good agreement is obtained between the computed and the measured dynamic behavior of the ground and the pile. A parametric analysis is also conducted on the model to investigate the effect of pile-pinning, pile diameter, pile stiffness, ground inclination angle, superstructure mass and pile head restraints on the ground improvement. It is found that the pile foundation has a noticeable pinning effect that reduces the lateral soil displacement. It is observed that a larger pile diameter and fi xed pile head restraints contribute to decreasing the lateral pile deformation; however, a higher ground inclination angle tends to increase the lateral pile head displacements and pile stiffness, and superstructure mass seems to effectively infl uence the lateral pile displacements.

Stable Routh-Padé-type approximation in model reduction of interval systems

An interval Pade-type approximation is introduced and then Routh-Pade-type method （IRPTM） is presented to model reduction in interval systems. The denominator in reduced model is obtained from the stable Routh table, and its numerator is constructed by the interval Pade-type definition. Compared to the existing Routh-Pade method, IRPTM does not need to solve linear interval equations theoretical analysis shows that IRPTM has example is given to illustrate our method. Hence, we do not have to compute smaller computational cost than that interval division in the process. Moreover, of Routh-Pade method. A typical numerical

基于幂指数法的地震模拟振动台频域前馈补偿方法

针对地震模拟振动台受到系统和试件非线性等因素影响,导致波形再现精度不高的问题,提出基于幂指数法的地震模拟振动台频域前馈补偿方法以提高振动台的控制效果,通过数值仿真和实际振动台试验对该方法的控制性能进行研究。研究结果表明:基于幂指数法的地震模拟振动台频域前馈补偿方法能够快速收敛,迭代次数较少,可以大幅提高振动台的波形复现精度,能够提高振动台的控制性能。

砖石古塔模型振动台试验的离散元模拟分析

砖石古塔块体间黏结强度较低,受地震作用易产生裂缝后发生破坏,为研究砖石古塔在地震作用下开裂及裂缝发展机制,以玄奘塔1/8缩尺模型结构为对象,建立离散元模型,计算了地震波激励下结构的加速度及位移反应,与振动台试验结果进行对比,分析了塔体开裂破坏全过程。结果表明,数值计算所得结构的加速度及位移反应与振动台试验结果一致,当地震烈度较低时,两者顶层位移变化曲线基本一致;烈度提高后,塔体开裂导致结构动力响应的计算值与试验结果出现差异,但两者的变化规律相同。在地震波激励下,塔体首层先开裂,随地震烈度的提高延伸至中部塔层,块体第2层出现阶梯状错动,模型损伤过程与试验裂缝发展状况基本吻合。研究结果为砖石古塔地震损伤及破坏过程分析提供了参考。

颗粒阻尼器对输电塔线系统减震性能研究

对输电塔线系统进行缩尺模型振动台实验,从时域和频域的角度,对比了调谐质量阻尼器和颗粒阻尼器对输电塔的减震效果。利用ABAQUS建立了颗粒阻尼器控制输电塔线系统的离散元-有限元高精度耦合数值模型,对比了实验和模拟结果,并对塔线系统的耗能情况及颗粒阻尼器内部颗粒运动碰撞情况进行分析。研究结果表明:在地震激励下,颗粒阻尼器的减震效果较调谐质量阻尼器有更好的鲁棒性;该文所建立的颗粒阻尼器控制输电塔线系统模型能够良好地反映试件的动力特性和地震响应;在颗粒阻尼器的控制下,塔线系统总能量降低24.12%。当颗粒之间的碰撞次数和颗粒与容器的碰撞次数满足一定比例关系时,颗粒阻尼器能实现更优的控制效果。

地下管廊抗震研究现状综述

针对地下管廊工程建设高速发展、抗震减灾需求愈发凸显的现状,综述地下管廊抗震研究现状.首先,通过国内外以往的震害实例,对地下管廊的震害形式、震害影响因素及震害机理进行了系统性总结.其次,从拟静力试验和振动台试验两个方面总结了地下管廊抗震性能的试验研究现状.再次,总结了地下管廊抗震分析的简化分析方法、动力时程方法、地震易损性评估及减隔震技术的研究现状.最后,基于文献综述提出了目前地下管廊抗震研究亟待解决的问题并做出展望,以期促进地下管廊抗震研究的发展.研究表明:地下管廊在地震作用下的破坏形式主要有混凝土剥落、裂缝贯通、接缝错位或张开、管廊受剪断裂等;地震作用下地下管廊穿越非均匀场地时动力响应的放大效应显著,地下管廊穿越软硬交互等非均匀场地时的抗震性能研究值得重视;交叉节点是地下管廊的薄弱环节,交叉管廊的抗震设计方法研究值得关注;预制管廊接头易受到地震破坏,不同类型预制管廊接头的抗震性能研究需深入探索;城市大型地下管廊系统抗震性能受到不同交叉节点和不同管廊之间的交互影响,高效的地下管廊系统建模方法和高效的简化分析方法亟待研究;城市大型地下管廊系统地震易损性分析是重要的发展方向;地下管廊的减隔震技术值得发展.

填埋场振动台试验及渐进式损伤能量识别

为了探讨地震作用下含导排衬垫层填埋场的损伤变形特性,开展了含导排衬垫层的填埋场边坡的大型振动台试验,并根据填埋场各处动态响应规律,提出了一种基于希尔伯特-黄(HHT)和边际谱的能量识别方法。该方法能够用于识别填埋场整体损伤和局部损伤,并根据实测位移值对该方法的有效性进行了讨论。试验结果表明,在输入波峰值加速度为0.3g时,坡脚正位移峰值及坡中负位移峰值突变;希尔波特谱峰值(PSHEA)随着高度的增加而增加,填埋场固废层希尔伯特能量大于衬垫及导排系统;输入波峰值加速度为0.3g及0.4g时,导排衬垫界处抗剪强度低面及中老固废交界震陷,边际谱峰值(PMSA)发生突变,能量传递异常。填埋场在地震作用下的损伤主要分为3个阶段:0.1g~0.2g未发生破坏阶段,0.3g~0.4g局部损伤阶段,破坏由导排及衬垫系统开始,0.5g整体破坏阶段填埋场边坡进入塑性变化;输入波幅值达到0.3g时衬垫导排层先产生滑移,峰值时刻固废交界处发生破坏。研究成果可为填埋场在地震作用下的损伤预测及填埋场抗震减灾技术设计提供参考依据。

基于目标机动噪声的末制导弹命中概率模型

末制导火箭弹对机动目标打击过程中,火控系统对机动目标的解算及命中概率是值得关注的问题。用射表拟合函数与目标运动方程联立建立解命中模型,并采用弦截法迭代求解。用离散的短时状态转移方程推导出长时期状态转移方程,从中分离出各短时间段内的高斯白噪声的累积和作为长期预测的概率模型。针对不同机动模型,用历史采样数据估计概率模型中白噪声的方差,从而可确定模型整体方差,并根据火箭弹飞行时间及末制导弹制导范围可计算命中概率。对CV模型、CT模型、CA模型和singer模型进行了解命中和概率计算,通过仿真验证了概率模型的准确性。

中国数字经济核心产业规模再测算研究

针对现有文献在数字经济规模的测算方法方面存在的分歧,首先基于国家统计局发布的《数字经济及其核心产业统计分类(2021)》,明确了投入产出表中的部门分类与数字经济核心产业各细分行业的对应关系;然后基于官方发布的投入产出表及投入产出延长表、学者编制的时间序列投入产出表,结合历次经济普查数据,采取将数字经济核心产业各细分行业的增加值按比例从国民经济各行业增加值中剥离出来的做法,测算了中国1981—2020年数字经济核心产业的规模及其各细分行业的占比;并与代表性文献在同口径下进行了比较,验证了测算结果的稳健性。在此基础上,预测了“十四五”时期各年中国数字经济核心产业可能达到的规模及其各细分行业的占比,并对未来数字经济核心产业的发展趋势以及数字经济统计制度建设进行了展望。

水平地震作用下双级加筋土挡墙损伤识别研究

因对台阶式加筋土挡墙损伤识别的研究不足,开展了双级加筋土挡墙的大型振动台试验。采用时域识别方法分析了水平地震作用下模型的动力响应特征,阐述了上、下级挡墙自振频率、阻尼比的分布规律,探究了结构损伤程度与自振频率、阻尼比间的对应关系。研究结果表明:加载前上、下级挡墙的自振频率基本一致,阻尼比随墙高的增加而减小;随着加载工况的累积,自振频率逐渐减小,阻尼比逐渐增大。采用数学方法对自振频率和阻尼比分布曲线进行多项式拟合,对比分析可得:当自振频率减小0~15.41%、阻尼比增大0~299.35%时,结构处于基本完好阶段;当自振频率减小15.41%~18.92%、阻尼比增大299.35%~360.07%时,结构处于轻微破坏阶段;当自振频率减小18.92%~21.29%、阻尼比增大360.07%~398.21%时,结构处于中等破坏阶段;当自振频率减小21.29%~29.60%、阻尼比增大398.21%~532.99%时,结构处于毁坏状态。

基于时程分析方法的黏滞阻尼减震结构附加阻尼比计算研究

附设黏滞阻尼器后结构的附加阻尼比是进行减震结构设计的关键。基于目前计算附加阻尼比时应用得十分广泛的时程分析方法进行研究,首先从基本理论出发,分析基于特征向量法的快速非线性分析(FNA)方法、Ritz向量法的FNA方法、直接积分方法以及与3种计算方法对应的能量比法在附加阻尼比计算时所面临的主要问题及重要参数设置;然后通过一单自由度体系的振动台试验测试结果与各种计算方法的数值模拟结果进行对比分析,得到较为适合的附加阻尼比计算方法;最后将研究成果应用于实际工程结构,进一步验证所推荐方法和参数设置的正确合理性。研究旨在为今后广大一线减震设计工程师计算较为真实的附加阻尼比提供重要参考。

备战巴黎奥运会周期我国男乒主要竞争对手技战术能力监控与分析

采用文献资料法、录像观察法、四段指标评估法、经典技术效益值评估法、数理统计法,对我国男乒队5位主要竞争对手共20场比赛的技战术能力进行监控与分析,旨在为中国男乒队备战巴黎奥运会提供参考。研究结论:张本智和的发球结合快攻打法特点鲜明,发球轮能力优于接发球轮;林昀儒的接发球技战术体系较为全面,在接抢段的得分效果最佳,接发球轮能力优于发球轮;雨果变化多端的发球旋转特点鲜明,中远台的强强对抗能力较为突出,接发球轮发挥极不稳定,发球轮能力优于接发球轮;奥恰洛夫的发球轮和接发球轮发挥均不突出,尤其在相持阶段的技战术体系运用不合理,战术灵活性较差;张禹珍的抢攻意识较强,发球抢攻为主要得分手段与技战术实施,多数在前4板内便分出胜负,相持阶段的能力为弱势阶段,发球轮能力优于接发球轮。

茛苕装饰纹样在家具中的应用

为了给茛苕装饰纹样的现代化创新应用提供新思路,对茛苕装饰纹样的演变历程和造型结构特点进行探究。茛苕装饰纹样是欧洲传统的装饰艺术纹样,有丰富的文化内涵和美学思想,对家具的发展和创新有很大的借鉴作用。以茛苕装饰纹样为研究对象,采用文献分析法以时代脉络为线索分析茛苕装饰纹样的演变与发展,并探讨不同时期、不同背景、不同地域对茛苕装饰纹样造型变化的影响,得出茛苕装饰纹样的造型结构特点;采用变形重组法对提取的茛苕装饰纹样元素S形茛苕叶进行设计转变,得到茛苕装饰纹样在家具上的现代化创新应用思路,通过CAD与3ds MAX软件设计出具有茛苕装饰纹样的茶几家具设计作品。

基于物理沙盘模型的“种群密度的调查方法”教学设计

在“种群密度的调查方法”教学中,以“在潮来潮往之间:台州湾潮间带生物多样性科学考察”为情境,基于项目化的学习方式,利用丰富的课程资源激发学生的学习兴趣,通过真实场景下的驱动问题引导学生持续、深入地参与探究活动,在构建重要概念的过程中发展核心素养。