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Search Results: 1 - 10 of 19377 matches for " Lixin Gao "
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Distributed H_{infinity} Coordination of Multi-agent Systems with Directed Switching Topology and Time-delay
Lixin Gao,Yanping Luo
Journal of Computers , 2012, DOI: 10.4304/jcp.7.5.1261-1269
Abstract: In this paper, we consider multi-agent H_{infinity} consensus control problems with external disturbance under directed switching topologies. Both switching networks with and without time-delay are taken into consideration. By the model transformation, the multi-agent H_{infinity} control problem is converted into the switching linear system H_{infinity} control problem with special structure. Based on graph theory and common Lyapunov function method, we establish LMI sufficient conditions under which all agents can reach consensus with the desired H_{infinity} performance in two cases of zero and nonzero communication delays respectively. Specially, we obtain an explicit estimation expression of H_{infinity} performance index in undirected non-time-delay switching topology case. Finally, two numerical examples are provided to illustrate the effectiveness of the obtained results.
Second-Order Consensus for Multiagent Systems under Directed and Switching Topologies
Lixin Gao,Jingjing Zhang,Wenhai Chen
Mathematical Problems in Engineering , 2012, DOI: 10.1155/2012/273140
Abstract: We consider multiagent consensus problems in a decentralized fashion. The interconnection topology among the agents is switching and directed. The agent dynamics is expressed in the form of a double-integrator model. Two different cases are considered: one is the leader-following case and the other is the leaderless case. Based on graph theory and the common Lyapunov function method, some sufficient conditions are established for the consensus stability of the considered systems with the neighbor-based feedback laws in both leader-following case and leaderless case, respectively. As special cases, the consensus conditions for balanced and undirected interconnection topology cases can be established directly. Finally, two numerical examples are given to illustrate the obtained results.
The L2-LInfinite Control for Leader-following Coordination with Switching Topology and Time-delay
Yanping Luo,Lixin Gao,Fang Wang
Journal of Networks , 2010, DOI: 10.4304/jnw.5.12.1513-1520
Abstract: In this paper, we investigate the L_2 - L_infinity leader-following coordination problems with undirected switching topologies and external disturbance in two cases of the time delay and non-delayed networks. The agent dynamics is expressed in the form of a second-order model and the control laws are neighbor-based feedback laws. We first establish LMI sufficient conditions to guarantee that all following agents can track the leader agent with zero and nonzero communication delays respectively. Furthermore, we get a explicit estimation expression of L_2 - L_infinity disturbance attenuation by constructing a parameter-dependent common Lyapunov function in case that there is no delay time. Finally, numerical examples are provided to illustrate the effectiveness of our results.
The Theory of Vector-Valued Function in Locally Convex Space  [PDF]
Lixin Ma
Applied Mathematics (AM) , 2012, DOI: 10.4236/am.2012.38133
Abstract: In this paper, the vector-valued regular functions are extended to the locally convex space. The residues theory of the functions in the locally convex space is achieved. Thereby the Cauchy theory and Cauchy integral formula are extended to the locally convex space.
Intelligent Gearbox Diagnosis Methods Based on SVM, Wavelet Lifting and RBR
Lixin Gao,Zhiqiang Ren,Wenliang Tang,Huaqing Wang,Peng Chen
Sensors , 2010, DOI: 10.3390/s100504602
Abstract: Given the problems in intelligent gearbox diagnosis methods, it is difficult to obtain the desired information and a large enough sample size to study; therefore, we propose the application of various methods for gearbox fault diagnosis, including wavelet lifting, a support vector machine (SVM) and rule-based reasoning (RBR). In a complex field environment, it is less likely for machines to have the same fault; moreover, the fault features can also vary. Therefore, a SVM could be used for the initial diagnosis. First, gearbox vibration signals were processed with wavelet packet decomposition, and the signal energy coefficients of each frequency band were extracted and used as input feature vectors in SVM for normal and faulty pattern recognition. Second, precision analysis using wavelet lifting could successfully filter out the noisy signals while maintaining the impulse characteristics of the fault; thus effectively extracting the fault frequency of the machine. Lastly, the knowledge base was built based on the field rules summarized by experts to identify the detailed fault type. Results have shown that SVM is a powerful tool to accomplish gearbox fault pattern recognition when the sample size is small, whereas the wavelet lifting scheme can effectively extract fault features, and rule-based reasoning can be used to identify the detailed fault type. Therefore, a method that combines SVM, wavelet lifting and rule-based reasoning ensures effective gearbox fault diagnosis.
Roller Bearing Fault Diagnosis Based on Nonlinear Redundant Lifting Wavelet Packet Analysis
Lixin Gao,Zijing Yang,Ligang Cai,Huaqing Wang,Peng Chen
Sensors , 2011, DOI: 10.3390/s110100260
Abstract: A nonlinear redundant lifting wavelet packet algorithm was put forward in this study. For the node signals to be decomposed in different layers, predicting operators and updating operators with different orders of vanishing moments were chosen to take norm ?of the scale coefficient and wavelet coefficient acquired from decomposition, the predicting operator and updating operator corresponding to the minimal norm value were used as the optimal operators to match the information characteristics of a node. With the problems of frequency alias and band interlacing in the analysis of redundant lifting wavelet packet being investigated, an improved algorithm for decomposition and node single-branch reconstruction was put forward. The normalized energy of the bottommost decomposition node coefficient was calculated, and the node signals with the maximal energy were extracted for demodulation. The roller bearing faults were detected successfully with the improved analysis on nonlinear redundant lifting wavelet packet being applied to the fault diagnosis of the roller bearings of the finishing mills in a plant. This application proved the validity and practicality of this method.
Adaptive Redundant Lifting Wavelet Transform Based on Fitting for Fault Feature Extraction of Roller Bearings
Zijing Yang,Ligang Cai,Lixin Gao,Huaqing Wang
Sensors , 2012, DOI: 10.3390/s120404381
Abstract: A least square method based on data fitting is proposed to construct a new lifting wavelet, together with the nonlinear idea and redundant algorithm, the adaptive redundant lifting transform based on fitting is firstly stated in this paper. By variable combination selections of basis function, sample number and dimension of basis function, a total of nine wavelets with different characteristics are constructed, which are respectively adopted to perform redundant lifting wavelet transforms on low-frequency approximate signals at each layer. Then the normalized lP norms of the new node-signal obtained through decomposition are calculated to adaptively determine the optimal wavelet for the decomposed approximate signal. Next, the original signal is taken for subsection power spectrum analysis to choose the node-signal for single branch reconstruction and demodulation. Experiment signals and engineering signals are respectively used to verify the above method and the results show that bearing faults can be diagnosed more effectively by the method presented here than by both spectrum analysis and demodulation analysis. Meanwhile, compared with the symmetrical wavelets constructed with Lagrange interpolation algorithm, the asymmetrical wavelets constructed based on data fitting are more suitable in feature extraction of fault signal of roller bearings.
Pleural aspergillosis complicated by recurrent pneumothorax: a case report
Weihua Zhang, Ye Hu, Liang'an Chen, Jie Gao, Lixin Xie
Journal of Medical Case Reports , 2010, DOI: 10.1186/1752-1947-4-180
Abstract: A 31-year-old asthmatic Chinese man presented with recurrent spontaneous pneumothorax and underwent lobectomy due to persistent air leakage. Aspergillus was detected histopathologically in the visceral pleural cavity. He was treated with itraconazole at 200 mg a day, and nine months later he had no recurrent pneumothorax or aspergillus infection.Recurrent pneumothorax may be a rare manifestation of aspergillus infection. Aspergillus species infection should be considered in the differential diagnosis of recurrent pneumothorax patients, particularly those with chronic lung disease.Aspergillus spp. are ubiquitous fungi that are acquired by inhalation of airborne spores and may cause a variety of clinical lung syndromes. The severity of lung aspergillosis depends upon immune status and the presence of underlying lung disease. The manifestations range from invasive pulmonary aspergillosis in severely immunocompromised patients to chronic necrotizing aspergillosis in patients with chronic lung disease and/or mildly compromised immune systems. Aspergilloma is primarily seen in patients with cavitary lung disease, while acute bronchopulmonary aspergillosis (ABPA) is a hypersensitivity disease of the lungs that almost always affects patients with asthma or cystic fibrosis. In this paper, we report a rare case of a patient who had multiple blebs, recurrent pneumothorax and pleura that was infected by aspergillus, with clinical features that were different from those described in the literature [1].A 31-year-old Chinese man was referred for recurrent pneumothorax and right lower lobe atelectasis with two occurrences of spontaneous pneumothorax during the previous four months. He had a 20-year history of asthmatic disease and no smoking history. He had irregularly taken 5 to 10 mg of oral prednisone per day for half a year. On admission, chest computed tomography (CT) showed multiple lung blebs in the upper lobes, a large bleb in the right middle lobe, and right lower lobe col

ZHANG Daquan,Gao Lixin,

腐蚀科学与防护技术 , 2001,
Abstract: The efficiency of imidazole(IM) and benzotriazole(BTA) as corrosion inhibitors for copper in 3%NaCl solution was investigated by weight-loss method. The inhibition efficiency of 100ppm IM for copper was only 47.7%, while the inhibition efficiency of 100ppm BTA for copper was 73 2%. When 70ppm IM and 30ppm BTA were used as complex corrosion inhibitor, inhibition for copper was increased and reached at value of 94.3%. This was beneficial to reduce the deficiency of BTA for its toxicity. Electrochemical polarization curve shows that IM suppressed the cathodic reaction of copper, BTA had inhibition effect for the anodic reaction and the complex inhibitor of IM and BTA suppressed both cathodic and anodic reactions. The molecular structure parameters of IM and BTA were obtained via MM2 forcefield program and PPP-SCF quantum chemical calculation. The electron transfer between IM and BTA was aid to their adsorption and passivity on copper electrode surface. This resulted in the synergistic effects between IM and BTA, improving their protective ability for copper in 3% NaCl solution.
Consensus of Multi-agent Systems with Time Delays and Measurement Noises
Xiaole Xu,Wei Huang,Shengyong Chen,Lixin Gao
TELKOMNIKA : Indonesian Journal of Electrical Engineering , 2012, DOI: 10.11591/telkomnika.v10i6.1429
Abstract: In this paper, the leader-following consensus problem of high order multi-agent systems with time-varying communication delays and noises is considered. The interconnection topology among the agents is assumed to be switching and undirected. The dynamics of each agent and the leader is a linear system. To track the active leader, a neighbor-based control of each following agent is designed in using local information. The control design technique is based on algebraic graph theory, Riccati inequality and Lyapunov inequality. By using Lyapunov-Razumikhim and stochastic analysis methods, we prove that the closed loop tracking control system is stochastically stable in mean square and the estimation errors converge to zero in mean square as well. Finally, a numerical example is given to illustrate the obtained result.
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