弹道计算中正常重力的计算方法分析

针对弹道计算中正常重力的计算问题,分析了两种正常重力计算方法的特点,认为拉普拉斯方法的缺点是大地水准面形状确定困难而斯托克斯方法缺少地球表面外空间的正常重力算法.根据斯托克斯方法所定义的正常重力模型,将索米里安公式推广到地球表面的外空间,从而得到了一种正常重力的精确算法.通过计算对比这两种重力计算方法的差异,得出在使用拉普拉斯方法计算正常重力并取合适的球谐级数项时,可直接采用正常地球椭球面作为大地水准面,不会对弹道计算造成大的计算误差.     

Effects of Ca2+, Mg2+, Na+, and K+ substitutions on the microstructure and electrical properties of GdCoO3 ceramics

Journal of Electroceramics - GdCoO3-δ, Gd0.975Na0.025CoO3-δ, Gd0.98K0.02CoO3-δ, Gd0.98Ca0.02CoO3-δ, and GdCo0.99Mg0.01O3-δ ceramics were prepared via a solid-state reaction...     

Feature analysis of women's wedding dresses in new,style weddings in the Wu culture region in modern times北大核心CSCD

To further clarify the features of wedding dresses in new, style weddings in cities and towns of the Wu culture region, the author sorted out and made a statistical analysis of modern journals and periodicals as well as conducted a comparison in combination with diaries of celebrities and novels in modern times to collect 368 wedding photos in total in the Wu culture region. The analysis results indicate that wedding dresses in the Wu culture region were mainly of modified styles from 1859 to 1949, the development of wedding dresses went through the stages of unitary styles, mixed styles and diversified styles, in each of which there were also representative regular ways of matching. In general, wedding dresses were in simple, elegant and delicate styles, and the silhouettes kept up with popular western styles, showing a high level of acceptance of foreign cultures. The colors of wedding dresses tended to combinations of light colors, while traditional colors were gradually reduced. Besides, patterns of flowers and plants with thin stems and leaves were mainly used to decorate wedding dresses, showing the distribution features of scattering and covering. © 2018 China Silk Association. All rights reserved.     

振动沉管灌注桩的沉管贯入阻力及沉桩可能性分析

简述了影响振动沉管灌注桩施工过程中沉管的主要因素,根据振动沉管灌注桩的沉管贯入机理,提出了沉管过程中贯入阻力的估算公式,并通过具体实例进行了分析,以合理选择施工桩机与施工顺序,从而达到设计要求。     

Seismic response analysis of self-anchored suspension bridge with multi-tower

Seismic performance of a self-anchored suspension bridge with three-tower were investigated. A three-dimensional nonlinear finite element model of the bridge was developed using Sap2000. Nonlinear time history analysis was conducted using Fast Nonlinear Analysis Method (FNA), while beam-column effect and nonlinear behavior of bearing and damper were taken into consideration. The analyze results showed that the middle tower was more vulnerable compared with the two side towers; there existed risk of buckling of composite beam, and the most vulnerable part lied near steel-concrete composite segment. Viscous dampers were effective to reduce seismic response of towers as well as girders.

     

Time-dependent reliability of ageing structures: an approximate approach

Concrete structures may deteriorate over time due to aggressive service environments, leading to a reduction in their strengths, stiffnesses and reliabilities. In general, the assessment of time-dependent reliability of ageing structures must consider uncertainties in structural deterioration as well as non-stationarities in the structural load processes. This paper develops an approximate method for assessing the impact of structural deterioration and non-stationary live loads on structures, which requires only low-dimensional integration and reduces the cost of assessing time-dependent reliability over a service life extending to 50 years significantly. This approximate method is demonstrated through several examples. The importance of non-stationarities in the resistance and load processes on time-dependent reliability is illustrated and the accuracy of the method is confirmed in several cases utilising Monte Carlo simulation.     

Ultrafast terahertz responses in monolayer graphene

ABSTRACT

We theoretically investigate the ultrafast terahertz (THz) properties of monolayer graphene. The analytical formulations of the photon carrier, electric polarization and optical current are obtained by solving the Bloch-equations in present of the ultrafast THz Gaussian pulse. Graphene shows a large nonlinear and ultrafast optical response at THz frequencies due to the gapless and relativistic Dirac particles with nearly linear energy dispersion. It is found that the photon carrier density, electric polarization and optical current density increase with increasing the frequency of the THz pulse. These theoretical results are in agreement with recent experimental findings. This study confirms further that graphene exhibits important features and is relevant to the applications in the ultrafast THz fields.     

唐口煤业9301工作面“绿色”充填开采技术

本文叙述了唐口煤业公司首个充填开采工作面-9301工作面的充填原理及相关的充填技术要求,并且论述了沿空留巷技术方案以及为满足9301充填工作面通风要求而进行的工作面推进3.5m时的切眼留巷技术方案。预计9301工作面通过的充填开采,下沉较小,地表建(构)筑物采动损害等级均在轻微的Ⅰ级采动损害范围内。     

“建筑”作为公共话语的出现:一个词语的断代史

回顾从19世纪末到20世纪初在中国近代社会观念和文教制度剧变的特定背景下,“建筑”这个词语在现代汉语以及社会大众观念话语中的历史性出现的过程,并试图多角度全方位地阐明这一历史性的事件是“如何可能”的.以词语或概念为建筑史研究的对象,是希望以词为镜,折射出宏观的社会观念史在特定历史时刻的变迁.     

基于现场试验的水文地质参数计算可视化程序设计与应用

水文地质参数的计算工作一直是工程地质和水文地质界工程师们所关注的重点问题之一,传统的计算方法比较繁琐、费时,国内外目前也没有比较全面的水文地质求参软件,因此,本文利用Visual Basic语言研究开发了一款基于现场试验的水文地质参数计算的新型软件SHP,通过数据库调用Excel文件录入数据,利用最小二乘法原理拟合直线。实现了手动配线和自动配线两种方法求参。通过南京市玄武湖隧道工程实例的校验,结果表明,该软件实用性强、计算精度较高、人机交互简单,满足工程需要。