800 publications from this institution
Multi-spectral image contains abundant spectral information, which is widely used in all fields like resource exploration, meteorological observation and modern military. Image preprocessing, such as image feature extraction and matching, is indispensable while dealing with multi-spectral remote sensing image. Although the feature matching algorithm based on linear scale such as SIFT and SURF performs strong on robustness, the local accuracy cannot be guaranteed. Therefore, this paper proposes an improved KAZE algorithm, which is based on nonlinear scale, to raise the number of feature and to enhance the matching rate by using the adjusted-cosine vector. The experiment result shows that the number of feature and the matching rate of the improved KAZE are remarkably than the original KAZE algorithm.
The influence of transmission loss on the economic and social benefits of DC transmission project can not be ignored.It also plays a key role in voltage and conductor cross-section selection for the DC transmission project.On the basis of research on the relationship between line energy loss ratio and line power loss ratio,DC energy loss estimation method based on practical data is proposed.Through case study,the effect of conductor size selection on transmission loss is explained.And it also indicates that the loss reduction to DC transmission project with long distance and high availability hour is more prominent by using large sized conductor.
Modeling of structural nonlinear dynamic behavior is a central challenge in civil and mechanical engineering communities. The phase space embedding of response time series has been demonstrated to be an efficient coordinate basis for data-driven approximation of the modern Koopman operator, which can fully capture the global evolution of nonlinear dynamics by a linear representation. This study demonstrates that linear and nonlinear structural dynamic vibrations can be represented by a universal forced linear model in a finite dimension space projected by time-delay coordinates. Compared with the existing methods, the proposed approach improves the performance of finite linear representation of nonlinear structural dynamics on two essential issues including the robustness to measurement noise and applicability to multidegree-of-freedom (MDOF) systems. For linear structures, the dynamic mode shapes and the corresponding natural frequencies can be accurately identified by using the time-delay dynamic mode decomposition (DMD) algorithm with acceleration response data experimentally measured from an 8-story shear-type linear steel frame. Modal parameters extracted from the time-delay DMD matched well with those identified from traditional modal identification methods, such as frequency domain decomposition (FDD) and complex mode indicator function (CMIF). In addition, numerical and experimental studies on nonlinear structures are conducted to demonstrate that the finite-dimensional DMD based on the discrete Hankel singular value decomposition (SVD) coordinate is highly symmetrically structured, and is able to accurately obtain a linear representation of structural nonlinear vibration. The resulting linearized data-driven equation-free model can be used to accurately predict the responses of nonlinear systems with limited training data sets.
The performance of surface permanent magnet bearingless snchronous motor(sPMBLM) system is usually affected by its parameter unknown or change with temperature and saturation.An online identification method for sPMBLM was presented based on current pridiction using the grey prediction method.The position and speed sensorless control system of sPMBLM based on system identification was proposed.The simulating and experimental results show that this method has such advantages as simple model,rapid convergence and small error.The system can achieve the stable suspension under the larger interference.
A new multi-criteria decision-making method for interval-valued intuitionistic fuzzy number is proposed by the advantage of intuitionistic fuzzy set and ELECTRE method. Firstly, the possibility-degree and deviation-degree of interval number are used to establish the preference relation of interval-valued intuitionistic fuzzy number. Then, we exposit the decision theory and the steps of this method. Finally, a numerical example is given to illustrate the application of the method. The numerical results show that it is feasible and effective.
주행중인 차량의 동적 거동에 대한 응답을 해석하기 위하여 시간영역에서 뿐만 아니라 주파수 영역에서의 해석이 필요하다. 주파수 영역에서의 해석을 위하여 시간영역에서의 값을 FFT를 이용하여 주파수 영역으로 변화하는 방법이 일반적으로 사용되어 왔다. 본 연구에서는 최대 엔트로피 방법을 이용하여 기존의 FFT 방법보다 차량의 과도응답특성을 시간영역 및 주파수 영역에서 편리하게 해석할 수 있는 방법을 제시하고 있다. In this paper the nonstationary response of accelerating vehicle is firstly obtained by using nonstationary road roughness model in time domain. To get the result of nonstationary response in frequency domain, the maximum entropy method is used for Processing nonstationary response of vehicle in frequency domain. The three-dimensional transient maximum entropy spectrum (MES) of response is given.
A novel structure is adopted in anchorage zone of cable tower on Chongqing Dongshuimen Yangtze River Bridge,the end plates in anchorage zone of common external steel anchor box cable tower are cancelled,and the steel anchor boxes are connected with concrete tower limbs by means of shear studs,in the mean time the prestress among tower limbs is arranged,enabling close connection between the steel anchor boxes and concrete,and the shear studs,side pulling plates and friction force are used to bear the force of stayed cables.Aiming at this novel structure,this paper establishes a nonlinear contact model for anchorage zone of cable tower via large-scale finite element software Midas FEA,the stress distribution in the steel anchor boxes,side pulling plates,shear studs and concrete on tower walls are acquired as well as transfer and distribution of cable force based on exquisite simulation calculation for the model.
Segmented wavemakers which consist of numerous individually programmed paddles have become important in the study of wave and its interaction with ocean engineering structures in ocean basin. There are some key problems greatly affecting the simulation quality of segmented wavemakers, including the limitation of direction angle of oblique wave simulation induced by paddle width and wave period, the generation of spurious waves and the effective test area of 3D shortcrested wave. The following results are obtained through the analysis of the performance of two-sided segmented wavemakers:(1)The relationship between oblique wave angle and wave period; (2)Wave direction limitation to prevent spurious waves; (3)Effective test area of simulated 3D short-crested wave. The results are significant to high quality wave simulation and providing better wave environment conditions for model tests of various ocean engineering structures in deep ocean basin.
Acoustic impedance (AI) estimated from seismic data has been a powerful tool for reservoir characterization for nearly three decades. However, because of the difficulty of building an accurate initial model and the restrictions of model updating, inverted AI often leads to false interpretation, especially for reservoirs with rapid lateral changes. To avoid that difficulty, we use an approach that starts with 3D seismic data and integrates AI inversion, spectral decomposition, and elastic impedance inversion for Poisson's ratio to simultaneously predict thickness and hydrocarbon‐bearing quality of the reservoir. We then apply this method to an area in the northern part of the Chezhen Sag, Shengli Oilfield, eastern China. The results of this study were used to locate and design three appraisal wells that were drilled and had hydrocarbon shows.
In order to meet the requirements of next generation chip manufacturing equipments, a high acceleration and high precision air bearing stage is designed and manufactured in this paper. In the stage, friction is very low, which eliminates the effects of nonlinear friction on the stage's positioning and acceleration performance. At the same time, a controller consisting of current loop, velocity loop and position loop is designed to improve the damping characteristics of the system to avoid the system to be extreme oscillating. By using suitable controlling parameters in the velocity loop, the acceleration of the stage excesses 7G and the positioning accuracy is within ±1.5μm. Moreover, the experiments show that the stage has excellent repeatable accuracy.
