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51.
Mechanical joints can have significant effects on the dynamics of assembled structures. However, the lack of efficacious predictive
dynamic models for joints hinders accurate prediction of their dynamic behavior. The goal of our work is to develop physics-based,
reduced-order, finite element models that are capable of replicating the effects of joints on vibrating structures. The authors
recently developed the so-called two-dimensional adjusted Iwan beam element (2-D AIBE) to simulate the hysteretic behavior
of bolted joints in 2-D beam structures. In this paper, 2-D AIBE is extended to three-dimensional cases by formulating a three-dimensional
adjusted Iwan beam element (3-D AIBE). Impulsive loading experiments are applied to a jointed frame structure and a beam structure
containing the same joint. The frame is subjected to excitation out of plane so that the joint is under rotation and single
axis bending. By assuming that the rotation in the joint is linear elastic, the parameters of the joint associated with bending
in the frame are identified from acceleration responses of the jointed beam structure, using a multi-layer feed-forward neural
network (MLFF). Numerical simulation is then performed on the frame structure using the identified parameters. The good agreement
between the simulated and experimental impulsive acceleration responses of the frame structure validates the efficacy of the
presented 3-D AIBE, and indicates that the model can potentially be applied to more complex structural systems with joint
parameters identified from a relatively simple structure. 相似文献
52.
The Monsoon Trough Boundary Layer Experiment held in 1990 was a multi-institutional effort to probe the atmospheric boundary
layer over the monsoon trough over northern India. For this experiment, four micrometeorological towers were set up at four
different locations along the normal position of the trough. One such tower of 30m height was located at Jodhpur (26‡18′N,
73‡04′E), Rajasthan. The fast and slow response data available during the experiment have been used in the present study to
determine a suitable layer-structure of the surface layer for evaluation of sensible heat flux using the multilayer hypothesis
of Kramm (1989). 相似文献
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54.
随着计算机技术特别是网络、图形和数据库技术的快速发展，基于数据库的信息管理系统已经在很多领域中取得了广泛的应用。由于传统的油气藏描述系统结构和功能单一，不能实现系统的完整管理，从而不能满足用户多方面的需要。考虑以上缺陷，这里提出了一种新的基于多层次结构，面向对象的油气藏描述系统模型，并结合Delphi和Oracle，建立了一个以数据库服务器为支撑的可视化应用系统体系，为油层描述系统和其它信息管理系统提供了一种规范的开发模式。该系统还具有很好的应用逻辑封装性，增强了软件结构的透明性、独立性、重用性和可维护性。它不仅提供给用户一套完整的数据解决方案，而且是一种能支持具有大量多元参数的数据动态分析及其可视化技术。同时，该系统还可以支持更多更复杂的数据类型，具有很强的扩展功能。 相似文献
55.
The theoretical model and non-homogeneous differential equation of equal thickness multi-layer folds sandwiched in different thickness and same character media are established by elas-tic and plastic mechanics.The special answer of the non-homogeneous differential equation and the common answer of the homogeneous differential equation are deduced by applying logistic equation and special function,and the dominant wavelength theory of equal thickness multi-layer folds sand-wiched in different thickness and same character media.In addition,the experimental folding in both elastic and sticky materials proves the dominant wavelength theory. 相似文献
56.
This study tested the use of machine learning techniques for the estimation of above-ground biomass (AGB) of Sonneratia caseolaris in a coastal area of Hai Phong city, Vietnam. We employed a GIS database and multi-layer perceptron neural networks (MLPNN) to build and verify an AGB model, drawing upon data from a survey of 1508 mangrove trees in 18 sampling plots and ALOS-2 PALSAR imagery. We assessed the model’s performance using root-mean-square error, mean absolute error, coefficient of determination (R2), and leave-one-out cross-validation. We also compared the model’s usability with four machine learning techniques: support vector regression, radial basis function neural networks, Gaussian process, and random forest. The MLPNN model performed well and outperformed the machine learning techniques. The MLPNN model-estimated AGB ranged between 2.78 and 298.95 Mg ha?1 (average = 55.8 Mg ha?1); below-ground biomass ranged between 4.06 and 436.47 Mg ha?1 (average = 81.47 Mg ha?1), and total carbon stock ranged between 3.22 and 345.65 Mg C ha?1 (average = 64.52 Mg C ha?1). We conclude that ALOS-2 PALSAR data can be accurately used with MLPNN models for estimating mangrove forest biomass in tropical areas. 相似文献
57.
Global multi-layer network of human mobility 总被引：2，自引：0，他引：2
Alexander Belyi Iva Bojic Izabela Sitko Bartosz Hawelka Lada Rudikova 《International journal of geographical information science》2017,31(7):1381-1402
Recent availability of geo-localized data capturing individual human activity together with the statistical data on international migration opened up unprecedented opportunities for a study on global mobility. In this paper, we consider it from the perspective of a multi-layer complex network, built using a combination of three datasets: Twitter, Flickr and official migration data. Those datasets provide different, but equally important insights on the global mobility – while the first two highlight short-term visits of people from one country to another, the last one – migration – shows the long-term mobility perspective, when people relocate for good. The main purpose of the paper is to emphasize importance of this multi-layer approach capturing both aspects of human mobility at the same time. On the one hand, we show that although the general properties of different layers of the global mobility network are similar, there are important quantitative differences among them. On the other hand, we demonstrate that consideration of mobility from a multi-layer perspective can reveal important global spatial patterns in a way more consistent with those observed in other available relevant sources of international connections, in comparison to the spatial structure inferred from each network layer taken separately. 相似文献
58.
将非线性神经元及多层感知机分类行为分析建筑在模糊集理论基础上，提出模糊线性判别函数、模糊判别面、模糊模式分类等概念，并引导出将多层感知机的隐层权重值均匀地分布在权重空间超球面上的网络初始化方法。以一系列实验验证此方法能明显提高多层感知机收敛性能，且与所用的学习算法、神经元的激励函数形式无关。 相似文献
59.
Zhou Mingyu Chen Jingnan Li Shiming Zheng Yueming Su Lirong L&#;Naiping 《Acta Meteorologica Sinica》1991,5(3):331-341
A Doppler sodar system controlled by microcomputer is described in this paper. The sodar was usedto detect the vertical distribution of wind and temperature stratification in the atmospheric boundary layer.The detecting results show that at night the vertical distribution of wind is very complicated, which can appearas a structure of two or three layers. In nocturnal atmospheric boundary layer sometimes there exists verythin layer in multi-layer inversion and it can be retained for a long time. 相似文献
60.
非对称多层薄板折算力学模量的讨论 总被引：4，自引：0，他引：4
为使有限单元法中的板壳单元更适合于分析地学问题,本文放弃前人对多层薄板的几何和弹性对称性限制,根据等效原则,重新推导了非对称多层薄板的中性面位置,进而给出了用各分层弹性模量和厚度表示的折合抗弯刚度及弹性模量。并结合两个三层地壳模型例题讨论了地壳各分层弯曲和薄膜应力与等效应力的差异. 相似文献