A Method Used for Mechanism’s Motion Accuracy Reliability Analysis

2014 ◽  
Vol 945-949 ◽  
pp. 1069-1072
Author(s):  
Chang Li ◽  
Bing Chen Wang ◽  
Xing Han ◽  
Shuang Yi Zhang
Keyword(s):  
Reliability Analysis ◽  
Parametric Modeling ◽  
Dynamic Responses ◽  
Test Model ◽  
Large Sample ◽  
Virtual Test ◽  
Stochastic Error ◽  
Sample Data ◽  
Multi Body ◽  
Develop Program

Dynamic responses of a certain system could vary with the place, environment and time of use even if the system itself did not change. Traditionally, kinematical reliability analysis of a multi-body mechanism was a hard point in the reliability field. In order to obtain a large sample data of mechanism’s transient kinetic characteristics, it needed to take lots of time, labor and finance input to acquire. It reported an effective method used for mechanism kinetic reliability analysis, with the combination of VC++ and CAE software’s second develop program, it built a parametric virtual test model for complex mechanism system. Where, it used multiplicative congruent method to program a pseudo-random number function that conformed to normal distribution to simulate the stochastic error distribution of the mechanism, which was convenient for the Monte Carlo parametric modeling to obtain large sample data and calculate the system kinetic reliability.

Model Test and Numerical Analysis of an Offshore Bottom Fixed Pentapod Wind Turbine Under Seismic Loads

2016 ◽  
Author(s):  
Wenhua Wang ◽  
Zhen Gao ◽  
Xin Li ◽  
Torgeir Moan ◽  
Bin Wang
Keyword(s):  
Wind Turbine ◽  
Wind Wave ◽  
Seismic Analysis ◽  
Wind Farms ◽  
Dynamic Responses ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Test Model ◽  
Structural Dynamic ◽  
Load Conditions

In the last decade the wind energy industry has developed rapidly in China, especially offshore. For a water depth less than 20m, monopile and multi-pile substructures (tripod, pentapod) are applied widely in offshore wind farms. Some wind farms in China are located in high seismicity regions, thus, the earthquake load may become the dominant load for offshore wind turbines. This paper deals with the seismic behavior of an offshore wind turbine (OWT) consisting of the NREL 5MW baseline wind turbine, a pentapod substructure and a pile foundation of a real offshore wind turbine in China. A test model of the OWT is designed based on the hydro-elastic similarity. Test cases of different load combinations are performed with the environmental conditions generated by the Joint Earthquake, Wave and Current Simulation System and the Simple Wind Field Generation System at Dalian University of Technology, China, in order to investigate the structural dynamic responses under different load conditions. In the tests, a circular disk is used to model the rotor-nacelle system, and a force gauge is fixed at the center of the disk to measure the wind forces during the tests. A series of accelerometers are arranged along the model tower and the pentapod piles, and strain gauges glued on the substructure members are intended to measure the structural dynamic responses. A finite element model of the complete wind turbine is also established in order to compare the theoretical results with the test data. The hydro-elastic similarity is validated based on the comparison of the measured dynamic characteristics and the results of the prototype modal analysis. The numerical results agree well with the experimental data. Based on the comparisons of the results, the effect of the wind and sea loads on the structural responses subjected to seismic is demonstrated, especially the influence on the global response of the structure. It is seen that the effect of the combined seismic, wind, wave and current load conditions can not be simply superimposed. Hence the interaction effect in the seismic analysis should be considered when the wind, wave and current loads have a non-negligible effect.

Reliability Analysis for Link Mechanism under Influence of Multiple Factors Based on Support Vector Machine

2013 ◽  
Vol 753-755 ◽  
pp. 2904-2907 ◽  
Author(s):  
Xue Wei Ke ◽  
Jian Hou ◽  
Ting Feng Chen
Keyword(s):  
Support Vector Machine ◽  
Reliability Analysis ◽  
Support Vector ◽  
Computational Costs ◽  
Link Mechanism ◽  
Normal Probability ◽  
Normal Probability Distribution ◽  
Dimensional Errors ◽  
Multi Body ◽  
External Loads

Considering the influence of dimensional errors,clearances,friction coefficients,external loads and flex of part comprehensively,a multi-body dynamic model of link mechanism is established by using commercial software.Assuming that the above factors follow normal probability distribution are independent with each other,a mechanism reliability analysis method by combining simulation technology and support vector machine (SVM) are proposed to reduce the computational costs. The obtained results show that the computational costs of the proposed methods are much less than the computational costs of Monte Carlo Simulation (MCS).Therefore, the proposed methods might be efficient and valuable for the reliability analysis of complex mechanism.

Global Responses and Loads Analysis of a 750-kW Semi-Submersible Floating Offshore Wind Turbine Under Extreme Environmental Conditions

2019 ◽  
Author(s):  
Thanh Dam Pham ◽  
Junbae Kim ◽  
Byoungcheon Seo ◽  
Rupesh Kumar ◽  
Youngjae Yu ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Environmental Conditions ◽  
Dynamic Responses ◽  
Offshore Wind ◽  
East Sea ◽  
Offshore Wind Turbine ◽  
Test Model ◽  
Scaled Model ◽  
Floating Offshore Wind Turbine ◽  
Extreme Loads

Abstract A pilot floating offshore wind turbine project of Korea was proposed for installing in the East Sea of Korea. The prototype is a semisubmersible platform supporting a 750-kW wind turbine. A scaled model was tested in the basin tank of the University of Ulsan at scale ratio 1:40. The 750-kW floating offshore wind turbine was modeled by using the NREL-FAST code. Numerical results were validated by comparing with those of the test model. This paper analyzes dynamic responses and loads of the wind turbine system under extreme environmental conditions. Extreme environmental conditions based on metocean data of East Sea Korea. Extreme responses and extreme loads are important data for designing the structure of the 750 kW semi-submersible floating offshore wind turbine.

Continuity and Change in the Contemporary Canadian Feminist Movement

2017 ◽  
Vol 50 (2) ◽  
pp. 443-459 ◽  
Author(s):  
Brenda O'Neill
Keyword(s):  
Social Movement ◽  
Collective Identity ◽  
Feminist Movement ◽  
Changing Environment ◽  
Data Set ◽  
Large Sample ◽  
Continuity And Change ◽  
Political Generations ◽  
Sample Data ◽  
Formative Experiences

AbstractThis article examines how the changing environment faced by and context within the Canadian feminist movement is reflected in the beliefs and strategies of recruits to the movement at a given point in time. The framework for the investigation is Whittier's generational approach (1997) that posits that different political generations—defined as cohorts of recruits who join a social movement during distinctive periods of protest—introduce change to its collective identity given the formative experiences faced by each generation. Using an original large sample data set, I provide evidence that the changes experienced by the Canadian feminist movement from the 1980s onwards are reflected in noticeable shifts in the collective identity and activist strategies of subsequent waves of feminist recruits. The findings suggest that further research into cohort recruitment and replacement is essential for understanding the forces at play in shaping the contemporary Canadian feminist movement.

scholarly journals Fuzzy reliability analysis based on support vector machine

2021 ◽  
Author(s):  
xiao bo Nie ◽  
Haibin Li ◽  
Hongxia Chen ◽  
Ruying Pang ◽  
Honghua Sun
Keyword(s):  
Support Vector Machine ◽  
Probability Distribution ◽  
Reliability Analysis ◽  
Small Sample ◽  
Learning Ability ◽  
Support Vector ◽  
Fuzzy Reliability ◽  
Performance Function ◽  
Sample Data ◽  
Distribution Parameters

Abstract For a structure with implicit performance function structure and less sample data, it is difficult to obtain accurate probability distribution parameters by traditional statistical analysis methods. To address the issue, the probability distribution parameters of samples are often regarded as fuzzy numbers. In this paper, a novel fuzzy reliability analysis method based on support vector machine is proposed. Firstly, the fuzzy variable is converted into an equivalent random variable, and the equivalent mean and equivalent standard deviation are calculated. Secondly, the support vector regression machine with excellent small sample learning ability is used to train the sample data. Subsequently, and the performance function is approximated. Finally, the Monte Carlo method is used to obtain fuzzy reliability. Numerical examples are investigated to demonstrate the effectiveness of the proposed method, which provides a feasible way for fuzzy reliability analysis problems of small sample data.

Collision dynamics analysis of lifting the pantograph

2020 ◽  
pp. 095440972094339
Author(s):  
Yongming Yao ◽  
Ning Zhou ◽  
Dong Zou ◽  
Guiming Mei ◽  
Weihua Zhang
Keyword(s):  
Contact Force ◽  
Element Model ◽  
Vertical Displacement ◽  
Dynamic Responses ◽  
Hertzian Contact ◽  
Collision Dynamics ◽  
Collision Model ◽  
Collision Force ◽  
Multi Body ◽  
Hertzian Contact Theory

An extended pantograph-catenary (PAC) contact collision model is presented in this paper. The catenary is described by a finite element model while the pantograph is described by a multi-body model. The normal collision model is established by using the Hertzian contact theory. A 1:1 PAC collision contact test rig is built to validate the pantograph-lifting model. The dynamic responses of the PAC system during lifting the pantograph with different velocities and positions are studied. The research results show that the velocity and position of lifting the pantograph will affect the pantograph-lifting time, acceleration of collector piece, vertical displacement and contact force in the process of lifting pantograph. When the velocity of lifting the pantograph exceeds 0.5 m/s, the contact force between the pantograph and the contact wire will exceed 250 N, which is the allowed value set in the provisions of EN50367. It is essential to control the velocity of lifting the pantograph below 0.4 m/s to prevent the catenary or contact piece from being damaged due to the excessive impact force. The distribution of the droppers also affects the collision force between the PAC system.

Reliability Analysis of Medical Imaging Systems Based on Observer Studies

1983 ◽  
Vol 22 (01) ◽  
pp. 37-44
Author(s):  
J. E. Goin ◽  
L. T. Cook ◽  
S. L. Fritz
Keyword(s):  
Differential Diagnosis ◽  
Medical Imaging ◽  
Diagnostic Imaging ◽  
Reliability Analysis ◽  
Imaging Systems ◽  
Sample Variance ◽  
Statistical Methodology ◽  
Large Sample ◽  
Reliability Criterion ◽  
Observer Studies

Statistical methodology is presented which can be used in analyzing the reliability of diagnostic imaging systems in differential diagnosis situations. A reliability criterion is developed along with formulas for estimating its large sample variance. Several hypothetical examples are given to illustrate the methodology.

Hydrodynamic Analysis of Multi-Body Floating Piers

2008 ◽  
Author(s):  
Zahra Tajali ◽  
Mehdi Shafieefar ◽  
Mahmood Akhyani
Keyword(s):  
Transfer Functions ◽  
Three Dimensional ◽  
Diffraction Method ◽  
Dynamic Responses ◽  
Floating Structure ◽  
Hydrodynamic Analysis ◽  
Wide Range ◽  
The Individual ◽  
Multi Body ◽  
Wave Induced

Hydrodynamic analysis of a floating multi-body pier interacting with incident waves is carried out in the present research and results of wave-induced motions and structural responses are described. The objective is to develop a procedure which can be used to analyze the motions of such a floating structure consisting of a number of rigid pontoons linked together. Also, optimization of pontoons geometry for a desired length of the pier is examined. In this regard, different alternative arrangements of pontoons with different numbers and dimensions are studied and dynamic responses of these alternatives are investigated. Analysis of the multi-body floating structure is carried out in the frequency domain. The wave-induced forces and the responses are computed by three-dimensional diffraction method. To examine the effect of using different pontoons on pier hydrodynamic response, motion-amplitude transfer functions (RAO) and connector forces for a wide range of wave frequency and heading angle are computed. Results include the absolute and relative responses of the individual pontoons and prediction of pier motions for a wide variety of pontoon geometries in different wave frequencies and heading angles. Also results include effects of pontoons dimension on the response of structure and present heave, roll and pitch motions for floating pier structural system.

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