Accelerated Iterative Calculation of Transonic Nacelle Flowfields

AIAA Journal ◽  
1977 ◽  
Vol 15 (10) ◽  
pp. 1474-1480 ◽  
Author(s):  
D.A. Caughey ◽  
Antony Jameson
Keyword(s):  
Iterative Calculation

scholarly journals Estimation for Two-Dimensional Nonsymmetric Coherently Distributed Source in L-Shaped Arrays

2018 ◽  
Vol 2018 ◽  
pp. 1-16
Author(s):  
Tao Wu ◽  
Zhenghong Deng ◽  
Qingyue Gu ◽  
Jiwei Xu
Keyword(s):  
Expectation Maximization ◽  
Two Dimensional ◽  
Signal Distribution ◽  
Distributed Source ◽  
One Dimensional ◽  
Least Squares Estimators ◽  
Iterative Calculation ◽  
Symmetric Source ◽  
Relationship Of ◽  
The Relationship

We explore the estimation of a two-dimensional (2D) nonsymmetric coherently distributed (CD) source using L-shaped arrays. Compared with a symmetric source, the modeling and estimation of a nonsymmetric source are more practical. A nonsymmetric CD source is established through modeling the deterministic angular signal distribution function as a summation of Gaussian probability density functions. Parameter estimation of the nonsymmetric distributed source is proposed under an expectation maximization (EM) framework. The proposed EM iterative calculation contains three steps in each cycle. Firstly, the nominal azimuth angles and nominal elevation angles of Gaussian components in the nonsymmetric source are obtained from the relationship of rotational invariance matrices. Then, angular spreads can be solved through one-dimensional (1D) searching based on nominal angles. Finally, the powers of Gaussian components are obtained by solving least-squares estimators. Simulations are conducted to verify the effectiveness of the nonsymmetric CD model and estimation technique.

Differential Equation Based Adaptive Distance Relaying Setting Method for Series Compensated Line

2014 ◽  
Vol 1044-1045 ◽  
pp. 482-485
Author(s):  
Jin Hu Zhang ◽  
Zhen Yu Xu ◽  
Zhi Peng Su
Keyword(s):  
Differential Equation ◽  
Transmission Lines ◽  
Distance Relay ◽  
Iterative Calculation ◽  
Simple Simulation ◽  
Simulation Results ◽  
Distance Relays ◽  
Distance Relaying

The distance relays of transmission lines find limitations in the presence of series compensated capacitor. One of them is the distance relay setting issue, in which either over-reach problem or under-reach problem may occur. To deal with this issue, a differential equation based adaptive distance relaying setting method for series compensated line is proposed. As for it do not need to identify whether SC/MOV is in fault loop, not need to know the parameters and the operating states of SC/MOV/GAP, and furthermore, it can be realized without the iterative calculation, it is very suitable to be used for the distance relaying adaptive setting of series compensated line. Simple simulation results certificate the proposed adaptive setting method.

scholarly journals Obstacle Avoidance Control for Multisteering Mode of Multiaxle Wheeled Robot Based on Trajectory Prediction Strategy

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Yongqiang Zhu ◽  
Junru Zhu ◽  
Pingxia Zhang
Keyword(s):  
Obstacle Avoidance ◽  
Control Strategy ◽  
Trajectory Prediction ◽  
Coverage Area ◽  
Iterative Calculation ◽  
Wheeled Robot ◽  
Avoidance Control ◽  
Narrow Space ◽  
The Relationship ◽  
Prediction Strategy

A multiaxle wheeled robot is difficult to be controlled due to its long body and a large number of axles, especially for obstacle avoidance and steering in narrow space. To solve this problem, a multisteering mode control strategy based on front and rear virtual wheels is proposed, and the driving trajectory prediction of the multiaxle wheeled robot is analyzed. On this basis, an obstacle avoidance control strategy based on trajectory prediction is proposed. By calculating the relationship between the lidar points of the obstacle and the trajectory coverage area, the iterative calculation of the obstacle avoidance scheme for the proposed steering is carried out, and the feasible obstacle avoidance scheme is obtained. The mechanical structure, hardware, and software control system of a five-axle wheeled robot are designed. Finally, to verify the effectiveness of the obstacle avoidance strategy, a Z-shaped obstacle avoidance experiment was carried out. The results confirm the effectiveness of the proposed control strategy.

Rainwater Ponding on Roof Structures with Interaction between Main Girders and Purlins

2019 ◽  
Author(s):  
H. H. (Bert) Snijder ◽  
S. N. M. (Simon) Wijte
Keyword(s):  
Design Method ◽  
Rain Intensity ◽  
Roof Structure ◽  
Iterative Calculation ◽  
Linear Behavior ◽  
Flat Steel ◽  
Design Calculations ◽  
Flat Roof ◽  
Near Future ◽  
Flat Roofs

<p>Rainwater causes flat roofs to deflect resulting in ponding. Due to the deflection, extra rainwater flows to the lower area of the roof, resulting in a larger loading with a larger deflection, resulting in more rainwater flowing towards this area, etc. Failure of flat roof structures due to ponding under heavy rainfall frequently happens in The Netherlands with an average of 15 incidents each year in the last decades. An increase in rain intensity due to climate change is expected to increase these numbers in the near future. Nevertheless, ponding on light roof structures is still underestimated as a significant load case in design. Moreover, the design calculations necessary are complex due to geometrical non-linear behavior. A number of software programs are available, but to keep insight in the process of rainwater ponding, a simple analytical design method for ponding of flat (steel) roof structures was developed including the interaction between main girders and purlins. The paper presents this method which avoids an iterative calculation procedure. Subsequently, this method is used to analyze a roof structure concluding that the interaction between main girders and purlins cannot be neglected.</p>

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