基于EC细网格产品在乌鲁木齐机场低能见度预测中的释用

利用2015—2018年乌鲁木齐机场航空例行天气报告(METAR报)、ECMWF(European Centre for Medium-Range Weather Forecasting)细网格数值预报产品对影响能见度的主要因子进行分析,提取与低能见度相关性高的物理量作为预报因子,采用SVM方法,分别基于Poly、RBF核函数建立乌鲁木齐机场未来21 h能见度预报模型。结果表明:(1)基于预报因子区间分类的SVM模型物理意义明确,试验结果较好;以RBF为函数建立的SVM模型(SVM-RBF)预报能力更好,其训练样本预测的TS评分0.84,准确率89.20%。(2)SVM-RBF模型的检验样本中,预报准确样本的预报误差整体偏小;在漏报样本中则有能见度越低、预报误差越大的特点,模型的振荡性明显。(3)结合NCEP/NCAR再分析资料研究SVM-RBF模型对天气过程的预报表现,发现模型对于特定天气形势下引发的低能见度天气,预报误差较小且预报提前量较大。     

利用DPGrid系统制作1∶500正射影像图

利用了DPGrid系统,实现了新疆奎屯市城区1∶500数字正射影像图生产,试验表明其可以实现城市大比例尺数字正射影像图的高效率生产。     

空间地理信息组织表达方法探讨

随着空间地理信息以及各种新型地图产品在各个领域的广泛应用,人们发现不同时期,应用需求对空间地理信息组织表达的要求是不同的,不同领域和部门对地理信息的组织表达方式也是不同的。但是,目前空间地理信息的共享和互操作、空间地理信息的多尺度分析与表达等,都要求空间地理信息的组织与表达要科学、合理和规范,否则难以满足测绘信息服务化及信息化测绘体系的建设。本文以交通类信息组织表达为例,详尽阐述当前空间地理信息组织表达的现状,分析其原因,并提出了解决这一问题的思路和方法,为今后信息化测绘体系建设、数据库数据组织和地理信息表达,提供理论和方法借鉴。     

异构环境下地理空间信息网格计算模式及体系结构研究

与机群系统相比,地理空间信息网格计算模式的优势在于可以更好地解决资源的异构性问题,支持资源的柔性伸缩及多种并行编程环境,支持科学计算库与工具软件,支持可视化动态人机交互。地理空间信息网格计算模式的体系结构是具有一定智能的分层结构。本文参考五层沙漏结构思想和前人的研究成果,研究设计了具有资源底层、安全调度层、抽象接口层、中间件层、应用接口层和应用层等六个层面的地理空间信息网格计算系统多层体系结构。     

数字近景摄影测量建筑容积率调查技术研究

城市建筑容积率是城市土地利用集约化程度的一个重要标志。基于遥感影像进行容积率调查的方法应用范围广,但误差较大。本文将数字近景摄影测量技术应用于精准容积率调查,研究了基于数字地图的单张像片参数以及顾及空间固定条件的立体像对前方交会方法,实现高精度的三维坐标获取。本文将普通数码相机和PDA相结合,辅助以GPS和全站仪等,实现了价格低廉、应用灵活快速的容积率调查集成系统,能够现场完成数据采集、存储。     

配BFG蒸压加气混凝土砌块砌体基本力学性能数值模拟

将蒸压加气混凝土(AAC)砌体填充墙采用薄灰缝专用砂浆砌筑,并在灰缝中配置玄武岩纤维格栅(BFG),可以提高墙体的抗压强度和延性。为了研究配BFG的AAC砌块砌体的基本力学性能,设计了9组27个试件进行抗压和抗剪试验。在试验的基础上,首先分析了砌体的抗压和抗剪性能,给出抗压上升段本构方程和抗压、抗剪强度建议公式;其次运用ABAQUS对砌体的抗压和抗剪性能进行模拟,通过比较模拟结果与试验结果,验证了有限元模型的合理性;最后分析了模型受压时的应力-应变关系,给出抗压下降段本构方程。研究表明:荷载施加处,接触面上剪应力集中是砌体通缝抗剪破坏的主要原因;本构方程可为配BFG蒸压加气混凝土砌体填充墙抗震性能的研究提供参考。     

Benchmark computations for flows around a stationary cylinder with high Reynolds numbers by RANS-overset grid approach

The aim of this paper is to evaluate the accuracy, stability and efficiency of the overset grid approach coupled with the RANS (Reynolds Averaged Navier-Stokes) model via the benchmark computations of flows around a stationary smooth circular cylinder. Two dimensional numerical results are presented within a wide range of Reynolds numbers (6.31 × 10⁴ ∼ 7.57 × 10⁵) including the critical flow regime. All the simulations are carried out using the RANS solver pimpleFoam provided by OpenFOAM, an open source CFD (Computational Fluid Dynamics) toolkit. Firstly, a grid convergence study is performed. The results of the time-averaged drag and lift force coefficients, root-mean square value of lift force coefficient and Strouhal number (St number) are then compared with the experimental data. The velocity, vorticity fields and pressure distribution are also given. One main conclusion is that the numerical solutions in regard to a fixed cylinderare not deteriorated due to the implementation of the overset grid. Furthermore, it can be an appealing approach to facilitate simulations of Vortex Induced Vibrations (VIV), which involves grid deformation. The present study is a good start to implement the overset grid to solve VIV problems in the future.     

利用三维高斯射线束成像进行地震定位

常规的地震定位方法通常需要拾取地震记录的初至,当初至不明显或被较高水平的噪声淹没时精度较低.本文采用基于三维高斯射线束的偏移成像方法对震源进行定位,较好地解决了该问题.通过三维高斯射线束对台站记录进行偏移归位,并将各台站成像结果的交点作为地震能量释放的中心位置;当各台站成像结果不能交于一点时,采用三维空间高斯滤波方法可实现震源位置的自动获取.提出的变网格计算方案极大地减少了计算量,显著地提高了成像精度和计算效率.利用首都圈地震台网数据,对涿鹿、滦县以及房山三个地震事件进行试算,结果表明:基于变网格三维高斯束偏移成像的地震定位方法自动化程度很高,而且具有较好的抗噪能力,特别适合处理低信噪比资料的地震定位问题.     

Optimum design and application of non‐traditional tuned mass damper toward seismic response control with experimental test verification

A variant type of tuned mass damper (TMD) termed as ‘non‐traditional TMD (NTTMD)’ is recently proposed. Mainly focusing on the employment of TMD for seismic response control, especially for base‐isolated or high‐rise structures, this paper aims to derive design formulae of NTTMDs based on two methodologies with different targets. One is the fixed points theory with the performance index set as the maximum magnitude of the frequency response function of the relative displacement of the primary structure with respect to the ground acceleration, and the other is the stability maximization criterion (SMC) to make the free vibration of the primary structure decay in the minimum duration. Such optimally designed NTTMDs are compared with traditional TMDs by conducting both numerical simulations and experiments. The optimum‐designed NTTMDs are demonstrated to be more effective than the optimum‐designed traditional TMDs, with smaller stroke length required. In particular, the effectiveness of the TMDs combined with a base‐isolated structure is investigated by small‐scale model experimental tests subjected to a time scaled long period impulsive excitation, and it is demonstrated that the SMC‐based NTTMD can suppress structural free vibration responses in the minimum duration and requires much smaller accommodation space. Additionally, a small‐scale shaking table experiment on a high‐rise bending model attached with a SMC‐based NTTMD is conducted. This study indicates that NTTMD has a high potential to apply to seismic response control or retrofit of structures such as base‐isolated or central column‐integrated high‐rise structures even if only a limited space is available for accommodating TMDs. Copyright © 2015 John Wiley & Sons, Ltd.     

一种基于全局优化的交错网格有限差分法

在地震波场数值模拟中, 交错网格有限差分技术得到了广泛的应用, 但是在弹性模量变化较大时, 通常会因插值而导致模拟误差增大. 旋转交错网格可以很好地克服这个缺点, 因而适合于各向异性介质正演模拟. 但是对于同样大小的网格单元, 旋转交错网格需要的步长比常规交错网格要大, 这会使梯度和散度算子的误差增大因而更易产生空间数值频散. 针对这些问题, 本文提出了旋转交错网格与紧致有限差分相结合的方法, 并基于模拟退火算法进行全局优化, 压制数值频散, 拓宽波数范围. 数值模拟结果表明, 此方法可以有效地压制数值频散, 且具有较高的模拟精度.