16 results
Search Results
2. Numerical research on the lateral global buckling characteristics of a high temperature and pressure pipeline with two initial imperfections.
- Author
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Liu, Wenbin and Liu, Aimin
- Subjects
MECHANICAL buckling ,WATER pipelines ,IMPERFECTION ,COMPUTER simulation ,WAVELENGTHS - Abstract
With the exploitation of offshore oil and gas gradually moving to deep water, higher temperature differences and pressure differences are applied to the pipeline system, making the global buckling of the pipeline more serious. For unburied deep-water pipelines, the lateral buckling is the major buckling form. The initial imperfections widely exist in the pipeline system due to manufacture defects or the influence of uneven seabed, and the distribution and geometry features of initial imperfections are random. They can be divided into two kinds based on shape: single-arch imperfections and double-arch imperfections. This paper analyzed the global buckling process of a pipeline with 2 initial imperfections by using a numerical simulation method and revealed how the ratio of the initial imperfection’s space length to the imperfection’s wavelength and the combination of imperfections affects the buckling process. The results show that a pipeline with 2 initial imperfections may suffer the superposition of global buckling. The growth ratios of buckling displacement, axial force and bending moment in the superposition zone are several times larger than no buckling superposition pipeline. The ratio of the initial imperfection’s space length to the imperfection’s wavelength decides whether a pipeline suffers buckling superposition. The potential failure point of pipeline exhibiting buckling superposition is as same as the no buckling superposition pipeline, but the failure risk of pipeline exhibiting buckling superposition is much higher. The shape and direction of two nearby imperfections also affects the failure risk of pipeline exhibiting global buckling superposition. The failure risk of pipeline with two double-arch imperfections is higher than pipeline with two single-arch imperfections. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
3. Correction of failure in linear antenna arrays with greedy sparseness constrained optimization technique.
- Author
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Khan, Shafqat Ullah, Rahim, M. K. A., Aminu-Baba, Murtala, and Murad, N. A.
- Subjects
LINEAR antenna arrays ,CORRECTION factors ,CONSTRAINED optimization ,ORTHOGONAL matching pursuit ,COMPUTER simulation - Abstract
This paper proposes the correction of faulty sensors using a synthesis of the greedy sparse constrained optimization GSCO) technique. The failure of sensors can damage the radiation power pattern in terms of sidelobes and nulls. The synthesis problem can recover the wanted power pattern with reduced number of sensors into the background of greedy algorithm and solved with orthogonal matching pursuit (OMP) technique. Numerical simulation examples of linear arrays are offered to demonstrate the effectiveness of getting the wanted power pattern with a reduced number of antenna sensors which is compared with the available techniques in terms of sidelobes level and number of nulls. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
4. A novel Gravity-FREAK feature extraction and Gravity-KLT tracking registration algorithm based on iPhone MEMS mobile sensor in mobile environment.
- Author
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Hong, Zhiling, Lin, Fan, and Xiao, Bin
- Subjects
FEATURE extraction ,IPHONE (Smartphone) ,COMPUTER algorithms ,ELECTRONIC information resources ,MICROELECTROMECHANICAL systems ,COMPUTER simulation - Abstract
Based on the traditional Fast Retina Keypoint (FREAK) feature description algorithm, this paper proposed a Gravity-FREAK feature description algorithm based on Micro-electromechanical Systems (MEMS) sensor to overcome the limited computing performance and memory resources of mobile devices and further improve the reality interaction experience of clients through digital information added to the real world by augmented reality technology. The algorithm takes the gravity projection vector corresponding to the feature point as its feature orientation, which saved the time of calculating the neighborhood gray gradient of each feature point, reduced the cost of calculation and improved the accuracy of feature extraction. In the case of registration method of matching and tracking natural features, the adaptive and generic corner detection based on the Gravity-FREAK matching purification algorithm was used to eliminate abnormal matches, and Gravity Kaneda-Lucas Tracking (KLT) algorithm based on MEMS sensor can be used for the tracking registration of the targets and robustness improvement of tracking registration algorithm under mobile environment. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
5. A multi-domain trust management model for supporting RFID applications of IoT.
- Author
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Wu, Xu and Li, Feng
- Subjects
RADIO frequency identification systems ,INTERNET of things ,COMPUTER simulation ,MATHEMATICAL models ,HIERARCHICAL clustering (Cluster analysis) - Abstract
The use of RFID technology in complex and distributed environments often leads to a multi-domain RFID system, in which trust establishment among entities from heterogeneous domains without past interaction or prior agreed policy, is a challenge. The current trust management mechanisms in the literature do not meet the specific requirements in multi-domain RFID systems. Therefore, this paper analyzes the special challenges on trust management in multi-domain RFID systems, and identifies the implications and the requirements of the challenges on the solutions to the trust management of multi-domain RFID systems. A multi-domain trust management model is proposed, which provides a hierarchical trust management framework include a diversity of trust evaluation and establishment approaches. The simulation results and analysis show that the proposed method has excellent ability to deal with the trust relationships, better security, and higher accuracy rate. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
6. Implementation of real-time energy management strategy based on reinforcement learning for hybrid electric vehicles and simulation validation.
- Author
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Kong, Zehui, Zou, Yuan, and Liu, Teng
- Subjects
HYBRID electric vehicles ,COMPUTER simulation ,AUTOMOTIVE fuel consumption standards ,ENERGY management ,REINFORCEMENT learning ,ENERGY consumption - Abstract
To further improve the fuel economy of series hybrid electric tracked vehicles, a reinforcement learning (RL)-based real-time energy management strategy is developed in this paper. In order to utilize the statistical characteristics of online driving schedule effectively, a recursive algorithm for the transition probability matrix (TPM) of power-request is derived. The reinforcement learning (RL) is applied to calculate and update the control policy at regular time, adapting to the varying driving conditions. A facing-forward powertrain model is built in detail, including the engine-generator model, battery model and vehicle dynamical model. The robustness and adaptability of real-time energy management strategy are validated through the comparison with the stationary control strategy based on initial transition probability matrix (TPM) generated from a long naturalistic driving cycle in the simulation. Results indicate that proposed method has better fuel economy than stationary one and is more effective in real-time control. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
7. Comparison of two SVD-based color image compression schemes.
- Author
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Li, Ying, Wei, Musheng, Zhang, Fengxia, and Zhao, Jianli
- Subjects
COLOR image processing ,IMAGE compression ,COMPARATIVE studies ,QUATERNIONS ,IMAGE quality analysis ,COMPUTER simulation - Abstract
Color image compression is a commonly used process to represent image data as few bits as possible, which removes redundancy in the data while maintaining an appropriate level of quality for the user. Color image compression algorithms based on quaternion are very common in recent years. In this paper, we propose a color image compression scheme, based on the real SVD, named real compression scheme. First, we form a new real rectangular matrix C according to the red, green and blue components of the original color image and perform the real SVD for C. Then we select several largest singular values and the corresponding vectors in the left and right unitary matrices to compress the color image. We compare the real compression scheme with quaternion compression scheme by performing quaternion SVD using the real structure-preserving algorithm. We compare the two schemes in terms of operation amount, assignment number, operation speed, PSNR and CR. The experimental results show that with the same numbers of selected singular values, the real compression scheme offers higher CR, much less operation time, but a little bit smaller PSNR than the quaternion compression scheme. When these two schemes have the same CR, the real compression scheme shows more prominent advantages both on the operation time and PSNR. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
8. Evolutionary Algorithm for RNA Secondary Structure Prediction Based on Simulated SHAPE Data.
- Author
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Montaseri, Soheila, Ganjtabesh, Mohammad, and Zare-Mirakabad, Fatemeh
- Subjects
MOLECULAR structure of RNA ,BIOLOGICAL evolution ,GENETICS ,NON-coding RNA ,GENETIC algorithms ,THERMODYNAMICS ,COMPUTER simulation - Abstract
Background: Non-coding RNAs perform a wide range of functions inside the living cells that are related to their structures. Several algorithms have been proposed to predict RNA secondary structure based on minimum free energy. Low prediction accuracy of these algorithms indicates that free energy alone is not sufficient to predict the functional secondary structure. Recently, the obtained information from the SHAPE experiment greatly improves the accuracy of RNA secondary structure prediction by adding this information to the thermodynamic free energy as pseudo-free energy. Method: In this paper, a new method is proposed to predict RNA secondary structure based on both free energy and SHAPE pseudo-free energy. For each RNA sequence, a population of secondary structures is constructed and their SHAPE data are simulated. Then, an evolutionary algorithm is used to improve each structure based on both free and pseudo-free energies. Finally, a structure with minimum summation of free and pseudo-free energies is considered as the predicted RNA secondary structure. Results and Conclusions: Computationally simulating the SHAPE data for a given RNA sequence requires its secondary structure. Here, we overcome this limitation by employing a population of secondary structures. This helps us to simulate the SHAPE data for any RNA sequence and consequently improves the accuracy of RNA secondary structure prediction as it is confirmed by our experiments. The source code and web server of our proposed method are freely available at . [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
9. Enhancing the Flexibility of TCP in Heterogeneous Network.
- Author
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Hui, Wang, Peiyu, Li, Zhihui, Fan, Zheqing, Li, and Xuhui, Wei
- Subjects
TCP/IP ,CHAOS theory ,INITIAL value problems ,CONVERGENCE (Telecommunication) ,COMPUTER simulation - Abstract
Due to a set of constant initial values, the performance of conventional TCP drops significantly encountering heterogeneous network, showing low throughput and unfairness. This paper firstly demonstrates the chaotic character of TCP congestion control in heterogeneous network, especially the sensitivity to initial value. Inspired by merit of nature-inspired algorithm, a novel structure of TCP congestion control (IPPM, Internet Prey-Predator Model) is proposed. Parameters such as available link capacity(C), congestion window (W) and queue length (Q) are collected by IPPM, which calculates the max value of C according to the interacting relationship existing in C, W and Q, and IPPM initiates the TCP ssthresh with the calculated value. Plenty of simulation results show that the modified TCP can effectively avoid network congestion and packet loss. Besides, it holds high resource utilization, convergence speeds, fairness and stability. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
10. Spectral X-Ray CT Image Reconstruction with a Combination of Energy-Integrating and Photon-Counting Detectors.
- Author
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Yang, Qingsong, Cong, Wenxiang, Xi, Yan, and Wang, Ge
- Subjects
COMPUTED tomography ,IMAGE reconstruction ,PHOTON counting ,COMPUTER simulation ,ALGORITHMS ,FEATURE extraction - Abstract
The purpose of this paper is to develop an algorithm for hybrid spectral computed tomography (CT) which combines energy-integrating and photon-counting detectors. While the energy-integrating scan is global, the photon-counting scan can have a local field of view (FOV). The algorithm synthesizes both spectral data and energy-integrating data. Low rank and sparsity prior is used for spectral CT reconstruction. An initial estimation is obtained from the projection data based on physical principles of x-ray interaction with the matter, which provides a more accurate Taylor expansion than previous work and can guarantee the convergence of the algorithm. Numerical simulation with clinical CT images are performed. The proposed algorithm produces very good spectral features outside the FOV when no K-edge material exists. Exterior reconstruction of K-edge material can be partially achieved. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
11. Structural Controllability of Complex Networks Based on Preferential Matching.
- Author
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Zhang, Xizhe, Lv, Tianyang, Yang, XueYing, and Zhang, Bin
- Subjects
CONTROLLABILITY in systems engineering ,STRUCTURAL engineering ,COMPUTER simulation ,APPLICATION software ,COMPUTER networks - Abstract
Minimum driver node sets (MDSs) play an important role in studying the structural controllability of complex networks. Recent research has shown that MDSs tend to avoid high-degree nodes. However, this observation is based on the analysis of a small number of MDSs, because enumerating all of the MDSs of a network is a #P problem. Therefore, past research has not been sufficient to arrive at a convincing conclusion. In this paper, first, we propose a preferential matching algorithm to find MDSs that have a specific degree property. Then, we show that the MDSs obtained by preferential matching can be composed of high- and medium-degree nodes. Moreover, the experimental results also show that the average degree of the MDSs of some networks tends to be greater than that of the overall network, even when the MDSs are obtained using previous research method. Further analysis shows that whether the driver nodes tend to be high-degree nodes or not is closely related to the edge direction of the network. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
12. Unscented Kalman Filter-Trained Neural Networks for Slip Model Prediction.
- Author
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Li, Zhencai, Wang, Yang, and Liu, Zhen
- Subjects
KALMAN filtering ,ARTIFICIAL neural networks ,DEVIATION (Statistics) ,COMPUTER simulation ,CONTROL theory (Engineering) - Abstract
The purpose of this work is to investigate the accurate trajectory tracking control of a wheeled mobile robot (WMR) based on the slip model prediction. Generally, a nonholonomic WMR may increase the slippage risk, when traveling on outdoor unstructured terrain (such as longitudinal and lateral slippage of wheels). In order to control a WMR stably and accurately under the effect of slippage, an unscented Kalman filter and neural networks (NNs) are applied to estimate the slip model in real time. This method exploits the model approximating capabilities of nonlinear state–space NN, and the unscented Kalman filter is used to train NN’s weights online. The slip parameters can be estimated and used to predict the time series of deviation velocity, which can be used to compensate control inputs of a WMR. The results of numerical simulation show that the desired trajectory tracking control can be performed by predicting the nonlinear slip model. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
13. Implicit finite-difference schemes, based on the Rosenbrock method, for nonlinear Schrödinger equation with artificial boundary conditions.
- Author
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Trofimov, Vyacheslav A. and Trykin, Evgeny M.
- Subjects
FINITE difference method ,NONLINEAR Schrodinger equation ,BOUNDARY value problems ,COMPUTER simulation ,INFORMATION science - Abstract
We investigate the effectiveness of using the Rosenbrock method for numerical solution of 1D nonlinear Schrödinger equation (or the set of equations) with artificial boundary conditions (ABCs). We compare the computer simulation results obtained during long time interval at using the finite-difference scheme based on the Rosenbrock method and at using the conservative finite-difference scheme. We show, that the finite-difference scheme based on the Rosenbrock method is conditionally conservative one. To combine the advantages of both numerical methods, we propose new implicit and conditionally conservative combined method based on using both the conservative finite-difference scheme and conditionally conservative Rosenbrock method and investigate its effectiveness. The combined method allows decreasing the computer simulation time in comparison with the corresponding computer simulation time at using the Rosenbrock method. In practice, the combined method is effective at computation during short time interval, which does not require an asymptotic stability property for the finite-difference scheme. We generalize also the combined method with ABCs for 2D case. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
14. Multiqubit and multilevel quantum reinforcement learning with quantum technologies.
- Author
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Cárdenas-López, F. A., Lamata, L., Retamal, J. C., and Solano, E.
- Subjects
REINFORCEMENT learning ,SUPERCONDUCTING circuits ,ELECTROMAGNETIC radiation ,COMPUTER simulation ,MACHINE learning ,QUANTUM theory - Abstract
We propose a protocol to perform quantum reinforcement learning with quantum technologies. At variance with recent results on quantum reinforcement learning with superconducting circuits, in our current protocol coherent feedback during the learning process is not required, enabling its implementation in a wide variety of quantum systems. We consider diverse possible scenarios for an agent, an environment, and a register that connects them, involving multiqubit and multilevel systems, as well as open-system dynamics. We finally propose possible implementations of this protocol in trapped ions and superconducting circuits. The field of quantum reinforcement learning with quantum technologies will enable enhanced quantum control, as well as more efficient machine learning calculations. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
15. Moth-inspired navigation algorithm in a turbulent odor plume from a pulsating source.
- Author
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Liberzon, Alexander, Harrington, Kyra, Daniel, Nimrod, Gurka, Roi, Harari, Ally, and Zilman, Gregory
- Subjects
PHEROMONES ,COMPUTER simulation ,UNSTEADY flow ,ALGORITHMS ,TURBULENT flow - Abstract
Some female moths attract male moths by emitting series of pulses of pheromone filaments propagating downwind. The turbulent nature of the wind creates a complex flow environment, and causes the filaments to propagate in the form of patches with varying concentration distributions. Inspired by moth navigation capabilities, we propose a navigation strategy that enables a flier to locate an upwind pulsating odor source in a windy environment using a single threshold-based detection sensor. This optomotor anemotaxis strategy is constructed based on the physical properties of the turbulent flow carrying discrete puffs of odor and does not involve learning, memory, complex decision making or statistical methods. We suggest that in turbulent plumes from a pulsating point source, an instantaneously measurable quantity referred as a “puff crossing time”, improves the success rate as compared to the navigation strategies based on temporally regular zigzags due to intermittent contact, or an “internal counter”, that do not use this information. Using computer simulations of fliers navigating in turbulent plumes of the pulsating point source for varying flow parameters such as turbulent intensities, plume meandering and wind gusts, we obtained statistics of navigation paths towards the pheromone sources. We quantified the probability of a successful navigation as well as the flight parameters such as the time spent searching and the total flight time, with respect to different turbulent intensities, meandering or gusts. The concepts learned using this model may help to design odor-based navigation of miniature airborne autonomous vehicles. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
16. A new data assimilation method for high-dimensional models.
- Author
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Wang, Guangjie, Cao, Xiaoqun, Cai, Xun, Sun, Jingzhe, Li, Xiaoyong, and Wang, Heng
- Subjects
AUTOMATIC differentiation ,NONLINEAR dynamical systems ,DEGENERATE parabolic equations ,COMPUTER simulation ,SIMULATION methods & models - Abstract
In the variational data assimilation (VarDA), the typical way for gradient computation is using the adjoint method. However, the adjoint method has many problems, such as low accuracy, difficult implementation and considerable complexity, for high-dimensional models. To overcome these shortcomings, a new data assimilation method based on dual number automatic differentiation (AD) is proposed. The important advantages of the method lies in that the coding of the tangent-linear/adjoint model is no longer necessary and that the value of the cost function and its corresponding gradient vector can be obtained simultaneously through only one forward computation in dual number space. The numerical simulations for data assimilation are implemented for a typical nonlinear advection equation and a parabolic equation. The results demonstrate that the new method can reconstruct the initial conditions of the high-dimensional nonlinear dynamical system conveniently and accurately. Additionally, the estimated initial values can converge to the true values quickly, even if noise is present in the observations. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
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