胶济客运专线精控网的分析处理

通过胶济客运专线精密工程控制测量网的对比研究,参考国内郑西、武广客运专线精密工程测量方法和成果,提出时速200～250 km客运专线精密工程测量值得借鉴的成功经验和设计内业调整的分析处理方法,以减少设计和施工中不必要的失误,加快工程进度。

基于高精度测量网的既有线平纵断面设计研究

通过胶济客运专线既有工程测量网和精密工程控制测量网的对比研究,提出基于高精度测量网兼容低精度网的设计、施工分析处理方法,并在胶济客运专线施工图阶段平纵断面设计以及如何与现场施工相结合进行技术处理等方面进行了实际应用,减少设计返工与避免施工中的废弃工程。通过3年多的运营证明,胶济客运专线高精度测量网兼容低精度网的测设方法和成果、线路平纵断面设计处理方法,满足了建设、运营、维护的要求。

Ultra-precision positioning control technique based on neural network

Due to the non-linearity behavior of the precision positioning system, an accurate mathematical control model is difficult to set up, a novel control method for ultra-precision alignment is presented. This method relies on neural network and alignment marks that are in the form of 100μm pitch gratings. The 0-th order Moire signals＇ intensity and its intensity rate are chosen as input variables of the neural network. The characteristics of the neural network make it possible to perform self-training and self-adjusting so as to achieve automatic precision alignment. A neural network model for precision positioning is set up. The model is composed of three neural layers, i.e. input layer, hidden layer and output layer. Driving signal is obtained by mapping Moire signals＇ intensity and its intensity rate. The experimental results show that neural network control for precision positioning can effectively improve positioning speed with high accuracy. It has the advantages of fast, stable response and good robustness. The device based on neural network can achieve the positioning accuracy of ± 0. 5μm.

CONTROL WORK IN CLOSE RANGE PHOTOGRAMMETRY

The purpose, classification, required accuracy and surveying methods of control work for close range photogrammetry have been briefly stated. The different methods for definition of space, object coordinate system are also reviewed. It is suggested that the habitu-ally-practised rotation angle system for aerophotogrammetry in China should be used for the future teaching and resaarching work in the close range photogrammetry, and that the rotation angle system for terrestrial deformation photogrammetry should be left out in order to avoid the confuse and reduce the amount of expanse for making softwares. It has been emphasized that there are three improtant aspects in the close range control work with high accurary using the conventional method of engineering surveying: the use of standard scale for measurement of distance between two general stations, the accurate determination of start direction line between two general stations and the handling method of influence of 2C change. A method for setting up industrial surveying control net with extra-high accuracy ±(0.05–0.20) mm is presented by the author. This kind of industrial control net is necessary for batch process of large industrial components with purposes of measurement, inspect and lofting. There are some special methods of control work in the close range photogrammetry, including two methods presented by the author.

On Exact Controllability of Networks of Nonlinear Elastic Strings in 3-Dimensional Space

This paper concerns a system of nonlinear wave equations describing the vibra- tions of a 3-dimensional network of elastic strings. The authors derive the equations and appropriate nodal conditions, determine equilibrium solutions, and, by using the methods of quasilinear hyperbolic systems, prove that for tree networks the natural initial, boundary value problem has classical solutions existing in neighborhoods of the ＂stretched＂ equilibrium solutions. Then the local controllability of such networks near such equilib- rium configurations in a certain specified time interval is proved. Finally, it is proved that, given two different equilibrium states satisfying certain conditions, it is possible to control the network from states in a small enough neighborhood of one equilibrium to any state in a suitable neighborhood of the second equilibrium over a sufficiently large time interval.

A high-resolution gas-kinetic scheme with minimized dispersion and controllable dissipation reconstruction

In order to simulate multiscale problems such as turbulent flows effectively, the high-order accurate reconstruction based on minimized dispersion and controllable dissipation(MDCD) is implemented in the second-order accurate gas-kinetic scheme(GKS) to improve the accuracy and resolution. MDCD is firstly extended to non-uniform grids through the modification of dissipation and dispersion coefficients for uniform grids based on the local stretch ratio. Remarkable improvements in accuracy and resolution are achieved on general grids. Then a new scheme, MDCD-GKS is constructed, with the help of MDCD reconstruction, not only for conservative variables, but also for their gradients. MDCD-GKS shows good accuracy and efficiency in typical numerical tests.MDCD-GKS is also coupled with the improved delayed detached-eddy simulation(IDDES) hybrid model and applied in the fine simulation of turbulent flow around a cylinder, and the prediction is in good agreement with experiments when using the relatively coarse grid. The high accuracy and resolution of the developed GKS guarantee its high efficiency in practical applications.