Wu Z.,Peking University |
Chen G.Q.,Peking University |
Zeng L.,China Ship Development And Design Center
Ecological Modelling | Year: 2011
As an extension of the modelling on environmental dispersion in a single zone wetland [Zeng, L., Chen, G.Q., 2009. Ecological degradation and hydraulic dispersion of contaminant in wetland. Ecol. Model., 222, 293-300], the typical case of a pulsed contaminant emission into a steady flow through a distinctively vegetated two-zone shallow wetland channel is analytically explored in this paper in terms of the longitudinal evolution of the lateral mean concentration under environmental dispersion. The velocity profile of a fully developed flow through the wetland is derived, with that for a single zone wetland flow included as a special case. Taylor's classical analysis and Aris's method of concentration moments for solute dispersion in a single phase fluid flow are rigorously generalized for the two-zone case of a wetland flow to develop the dispersion model and to determine the dispersivity, which is illustrated with an asymptotic time variation characterized by stem dominated, transitional, and width-stem dominated stages. For typical contaminant constituents of chemical oxygen demand, biochemical oxygen demand, total phosphorus, total nitrogen and heavy metal, the evolution of contaminant cloud is illustrated with the critical length and duration of the contaminant cloud with constituent concentration beyond some given environmental standard level. © 2010 Elsevier B.V.
Niu M.,China Ship Development And Design Center |
Zang S.,Shanghai JiaoTong University
Experimental Thermal and Fluid Science | Year: 2011
This investigation presents detailed experimental measurements of an active tip-clearance control method based on tip injection in a high-turning axial turbine cascade. Besides that, numerical investigations are also conducted to study phenomena which are not easily measured in the experiments. It aims to study the influence of tip injection on tip clearance flow, with emphasis on the effects of injection locations. Detailed flow field measurements were made downstream of the cascade using a three-hole probe. Static pressure distributions were also measured on the blade surface at 50% and 97.5% span, respectively. The results suggest that tip injection can weaken tip clearance flow, reducing the tip clearance mass flow and its associated losses. Meanwhile, the heat transfer condition on the blade tip surface can be also improved significantly. It also can be found that injection chordwise location plays an important role in the redistribution of secondary flow within the cascade passage. When the same number of injection holes and injection mass flow are applied, holes located in the aft part of blade can perform much better than that in the front part. © 2011 Elsevier Inc.
Peng W.-C.,China Ship Development And Design Center
2016 IEEE International Conference on Mechatronics and Automation, IEEE ICMA 2016 | Year: 2016
For the prediction of ship structural vibration and noise, it is important to measure exciting forces transferred to ship hull from machinery. For resiliently-mounted machine, indirect estimation based on impedances of the isolator and direct measurement based on transducer for force were discussed. Test validated the proposed method by small diesel engine, and direct force measured by PCB transducer. Experiments eliminate the noise effect of force transducer, improving the test precision. Experiments show that the error of indirect estimation is less than 3dB, and satisfying practical engineering applications. © 2016 IEEE.
Wang Z.,China Ship Development And Design Center
2016 IEEE International Conference on Mechatronics and Automation, IEEE ICMA 2016 | Year: 2016
A 4-node quadrilateral piezoelectric element with thin piezoelectric layers embedded on top and bottom surfaces is derived based on the first-order shear deformation theory, and the dynamic equation of a composite beam with distributed sensors and actuators is established by Hamilton's principle. Considering the influence of plant noise and measurement noise, linear quadratic Gauss (LQG) control algorithm is obtained by using Kalman filter for state estimation. The active vibration control of a piezoelectric composite beam subjected to the pulse, harmonic and random excitation is achieved by LQR and LQG control algorithm, respectively. The results indicate that, if the effect of the noise is taken into consideration and the entire states cannot be fully observed, the LQG algorithm demands a lower actuation voltage than LQR does. © 2016 IEEE.
Wang J.-G.,China Ship Development And Design Center
Chinese Control Conference, CCC | Year: 2012
A new dynamic neural network was constructed by borrowing ideas from Jordan and Elman neural networks. To accelerate the rate of convergence and avoid getting into local extremum, a hybrid learning algorithm by Genetic algorithm (GA) and error back propagation algorithm (BP) was used to tune the weight values of the network. Finally, the improved neural network was utilized to identify the AUV hydrodynamic model. The simulation results show that the new network can remember the history state of hidden layer and tune the effect of the past signal to the current value real-timely. And in the presented network, the feedback of output layer nodes is increased to enhance the ability of handling signals. The neural network by hybrid learning algorithm improves the learning rapidity of convergence and identification precision. © 2012 Chinese Assoc of Automati.
Zhu Z.,China Ship Development And Design Center
Journal of Medical Systems | Year: 2012
To ensure patients' privacy, such as telephone number, medical record number, health information, etc.; authentication schemes for telecare medicine information systems (TMIS) have been studied widely. Recently, Wei et al. proposed an efficient authentication scheme for TMIS. They claimed their scheme could resist various attacks. However, in this paper, we will show their scheme is vulnerable to an off-line password guessing attack when user's smart card is lost. To improve the security, we propose a new authentication scheme for TMIS. The analysis shows our scheme could overcome the weaknesses in Wei et al.'s scheme and has better performance than their scheme. © 2012 Springer Science+Business Media, LLC.
Yue L.,China Ship Development And Design Center
Proceedings - 2015 8th International Symposium on Computational Intelligence and Design, ISCID 2015 | Year: 2016
For the design of ship information system is still based on the functional integration and difficult to promote overall ship's information exchange and disposal efficiency, a mission-oriented simulating and optimizing method for ship system information flow is proposed. Based on resolving total ship's mission and relating fight node, the information flow model of ship system is established through adopting the technology of DoDAF architecture view. The simulation results have shown that this method could be not only applicable to check the veracity and rationality of information flow, but also to evaluate the key node and perform efficiency of information exchange model, so it is an availability technology method of quantitative analysis to validate and optimize the scheme of ship informatization. © 2015 IEEE.
Sun F.,Harbin Engineering University |
Tang L.-J.,China Ship Development And Design Center
Kongzhi yu Juece/Control and Decision | Year: 2013
In order to select the appropriate filtering method from the UKF and CKF for the different dimensions nonlinear systems estimation, the two filters are analyzed and compared through the Taylor expansion of function and the numerical stability. Due to the different dimension, the captured high-order item degree of function Taylor expansion and the numerical stability are different to appear different filter precisions, so that the filter choice ways of different dimension are acquired. Simulation results show the correctness of with the theoretical analysis.
Xiang J.,Zhejiang University |
Zhong C.,China Ship Development And Design Center |
Wei W.,Zhejiang University
IEEE Transactions on Robotics | Year: 2012
A varied weights (VW) method is proposed in this paper for the kinematic control of redundant manipulators with multiple constraints. A weight factor rule to reflect the transition of the state of constraint subtask between activeness and inactiveness is presented. Each constraint has a VW factor in such a way that every time only the main task and the active constraint subtasks are considered. A new concept of effective singular value is presented for the design of damping factors to avoid the pseudosingularity arising from the transition of weight factors. The experiments on the seven-degree-of-freedom (7-DOF) Ping-Pong manipulator illustrate the efficacy of the proposed VW method. © 2012 IEEE.
Li N.,Shanghai Second Polytechnic University |
Zhou R.,China Ship Development And Design Center |
Hu Q.,Harbin Institute of Technology |
Liu X.,Shanghai Second Polytechnic University
Mechanical Systems and Signal Processing | Year: 2012
This paper investigates the application of the redundant second generation wavelet package transform (RSGWPT), neighborhood rough set (NRS) and support vector machine (SVM) on faulty detection, attribute reduction and pattern classification. On this basis, a novel method for mechanical faulty diagnosis based on RSGWPT, NRS and SVM is presented, which utilizes the RSGWPT to extract faulty feature parameters from the statistical characteristics of wavelet package coefficients to constitute feature vectors, and then makes the attribute reduction by NRS method to obtain the key features, lastly these key features are input into SVM to accomplish faulty pattern classification. The experimental results of the proposed method to fault diagnosis of the gearbox and gasoline engine valve trains show that this method can extract the faulty features, which have better classification ability and at the same time reduce a lot of redundant features in case of assuring the classification accuracy, accordingly improve the classifier efficiency and achieve a better classification performance. © 2011 Elsevier Ltd. All rights reserved.