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Search Results: 1 - 10 of 78475 matches for " Xiaomei Chen "
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Testing the Equality Hypothesis on a Cross-Covariance Matrix  [PDF]
Xiaomei Chen, Shibin Zhang
Open Access Library Journal (OALib Journal) , 2019, DOI: 10.4236/oalib.1105584
This paper is concerned about testing whether a cross-covariance matrix deviates from a pre-assigned one or not. For this purpose, a new test statistic is constructed based on the Frobenius norm of the difference between the sample cross-covariance matrix and the pre-assigned matrix. The test is implemented by applying the parametric bootstrap scheme. We conduct a simulation study to examine the performance of the test and compare it with other competitive tests. As multiple simulation examples show, our empirical powers are clearly superior to others in detecting any deviation of the cross-covariance from the pre-assigned matrix. In addition, the proposed test is insensitive to non-cross-covariance elements in the covariance matrix. As an illustration, we also investigate its performance in testing pairwise time-reversibility.
Analysis of Nonlinear Characteristics of Turbine Governor and Its Impact on Power System Oscillation  [PDF]
Ge Jin, Hanting Yan, Shaoxiang Deng, Xiaomei Chen, Zexiang Cai
Energy and Power Engineering (EPE) , 2013, DOI: 10.4236/epe.2013.54B144

In this paper, the model of turbine governor based on the physical principles is constituted to improve the accuracy of power system dynamic simulation, making the results of simulation consistent with the actual situation. The unit and grid coupling model which reflects the interaction between thermal system of power plant and power system is built using EMTDC/PSCAD. The influence of nonlinear characteristics on the valve opening and the steam turbine mechanical power is also analyzed in this paper. The results of simulation show that the improper setting of parameters reflecting nonlinear characteristics of turbine governor can lead to the cyclical oscillations of the valve opening and the steam turbine mechanical power, and even can lead to the power oscillation persistently. The research achievements in this paper have a certain reference value on exploring the causes of power oscillation from the prime mover.

Isoniazid-Induced Facial Tics in a Patient on Hemodialysis  [PDF]
Yuanwei Wang, Xiaodong Chen, Xiaomei Li, Baolin Zhu, Daoming Tong
Neuroscience & Medicine (NM) , 2017, DOI: 10.4236/nm.2017.83003
Abstract: We report isoniazid (INH) induced tics in one male patient on hemodialysis at end-stage renal failure. He had pulmonary tuberculosis, accepted isoniazid, rifampin, ethambutol, pyrazinamide and rifampicin. He developed tics on both sides of the face. Surprisingly, he was also found the bilateral symmetrical frontal lobe and dentate nucleus hyperintensities on T2-weighted and T2 FLAIR MR imaging. After excluding other causes, INH induced neurological side effect was suspected so the drug was stopped, pyridoxine was added and hemoperfusion was applicated. Tics disappeared after 1 week.
Complexity Analysis of Mixed Constraint Satisfaction Problems  [PDF]
Xiaomei Shi
Open Journal of Applied Sciences (OJAppS) , 2017, DOI: 10.4236/ojapps.2017.74011
Abstract: This paper analyzes the resolution complexity of a random CSP model named model RBmix, the instance of which is composed by constraints with different length. For model RBmix, the existence of phase transitions has been established and the threshold points have been located exactly. By encoding the random instances into CNF formulas, it is proved that almost all instances of model RBmix have no tree-like resolution proofs of less than exponential size. Thus the model RBmix can generate abundant hard instances in the threshold. This result is of great significance for algorithm testing and complexity analysis in NP-complete problems.
Research on the Influence Factors and Coordinated Control Strategies between Unit and Grid for Isolated Power System  [PDF]
Ge Jin, Xiaomei Chen, Yongxin Feng, Shaoxiang Deng, Hanting Yan, Zexiang Cai
Energy and Power Engineering (EPE) , 2013, DOI: 10.4236/epe.2013.54B086

As the existing coordinated control strategies between grid and unit have limitations in isolated power system, this paper introduces new coordinated control strategies which can improve the stability of isolated system operation. This paper analyzes the power grid side and unit side influence factors on the isolated power system. The dynamic models which are suitable for islanding operation are applied to simulate and analyze the stability and dynamic characteristics of the isolated power system under the conditions of different load disturbances and governor parameters. With considering the differences of frequency characteristics between the interconnected and isolated power system, the adjusting and optimization methods of under frequency load shedding are proposed to meet the frequency stability requirements simultaneously in the two cases. Not only proper control strategies of the power plant but the settings of their parameters are suggested to improve the operation stability of the isolated power system. To confirm the correctness and effectiveness of the method mentioned above, the isolated system operation test was conducted under the real power system condition, and the results show that the proposed coordinated control strategies can greatly improve stability of the isolated power system.


A Multiple-Dimensional Tree Routing Protocol for Multisink Wireless Sensor Networks Based on Ant Colony Optimization
Hui Zhou,Dongliang Qing,Xiaomei Zhang,Honglin Yuan,Chen Xu
International Journal of Distributed Sensor Networks , 2012, DOI: 10.1155/2012/397961
Abstract: Routing protocol is an important topic in the wireless sensor networks. For MultiSink wireless sensor networks, the routing protocol designs and implementations are more difficult due to the structure complexity. The paper deals with the problem of a multiple-dimensional tree routing protocol for multisink wireless sensor networks based on ant colony optimization. The proposed protocol is as follows: (1) listening mechanism is used to establish and maintain multidimensional tree routing topology; (2) taking into consideration hops, packet losses, retransmission, and delay account, a distributed ant colony algorithm is proposed. When nodes select routes in the data transmission, the algorithm is utilized to realize the real-time optimization by coordination between nodes. The simulation results show that the proposed protocol can realize the QoS optimization for multisink wireless sensor networks, and its performance is better than the routing protocol of minimum hop numbers. 1. Introduction Multisink wireless sensor architecture networks have received more and more attention due to their advantages such as improving network throughput, balancing energy consumption, and prolonging network lifetime. Moreover, the reliability and robustness of networks are improved because multisink nodes increase the transmission routines of the sensor node information [1, 2]. Due to multiple sink nodes in multisink wireless sensor networks (multisink WSNs), the network topology is complex, which brings many difficulties to design and implement the network protocols. Currently, research on multisink WSNs is still insufficient, especially for the cooperation and quality of service (QoS) of multisink WSNs. In this paper, the problem of a multiple dimensional tree routing protocol for multisink WSNs will be investigated based on listening and ant colony optimization (ACO), where multiple dimensional tree routing is defined in Section 3. Listening mechanism is first used to establish and maintain multidimensional tree routing topology in the proposed protocol. Then, a distributed ant colony algorithm is presented with the consideration of hops, packet losses, retransmission and delay. The rest of this paper is organized as follows. (i) Section 2 states the related works about the multisink WSNs routing researches and the applications of the ant colony optimization in WSNs. (ii) Section 3 describes the multisink WSNs model. (iii) Section 4 introduces the routing establishment of the listening-based routes for the multisink WSNs and the routing selection based on the
IVTA as Adjunctive Treatment to PRP and MPC for PDR and Macular Edema: A Meta-Analysis
Lei Liu, Xiaomei Wu, Jin Geng, Zhe Yuan, Lei Chen
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0044683
Abstract: Background To quantify the effect of a combination treatment of intravitreal triamcinolone acetonide (IVTA) injection, panretinal photocoagulation (PRP), and macular photocoagulation (MPC) in patients with proliferative diabetic retinopathy (PDR) and diabetic macular edema (DME). Methodology/Principal Findings We conducted a meta-analysis and searched for reports concerning IVTA injection combined with PRP for the treatment of PDR and DME using Medline, EMbase, Web of Science, the Cochrane Library, and Google according to Cochrane evaluation guidelines. The quality of the reports was evaluated using the Jadad score. Only four studies were ultimately included in this meta-analysis and the fixed-effects model was used. Treatment with IVTA injection combined with PRP and MPC significantly improved BCVA (p<0.001) from one to six months, compared with PRP and MPC alone. There was a statistically significant mean difference in central macular thickness (CMT), at the one-month follow-up (p<0.001). No evidence of publication bias was present. There was a low level of heterogeneity in this group of studies. Conclusions/Significance This meta-analysis indicates that IVTA injection combined with PRP and MPC results in an improvement of BCVA, and CMT reduction in patients with PDR and DME.
The Influence of Skin Microcirculation Blood Perfusion at Zusanli Acupoint by Stimulating with Lift-Thrust Reinforcing and Reducing Acupuncture Manipulation Methods on Healthy Adults
Xiaomei Li,Yanqi Li,Jingzi Chen,Dan Zhou
Evidence-Based Complementary and Alternative Medicine , 2013, DOI: 10.1155/2013/452697
A Comparison of the Performance of the I-gel? vs. the LMA-S?during Anesthesia: A Meta-Analysis of Randomized Controlled Trials
Xiaoguang Chen, Jinghua Jiao, Xuefeng Cong, Lei Liu, Xiaomei Wu
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0071910
Abstract: Background and Objective Conflicting results were found between the I-gel? and the LMA-Supreme? during anesthesia, so we conducted a meta-analysis of randomized controlled trials (RCTs) to compare the effectiveness and safety of the I-gel? vs. the LMA-Supreme?during anesthesia. Methods A comprehensive search was conducted using Pubmed, EMbase, ISI Web of Knowledge, the Cochrane Library, China Journal Full-text Database, Chinese Biomedical Database, Chinese Scientific Journals Full-text Database, CMA Digital Periodicals, and Google scholar to find RCTs that compare the LMA-S? with the i-gel?during anesthesia. Two reviewers independently selected trials, extracted data, and assessed the methodological qualities and evidence levels. Data were analyzed by RevMan 5.0 and comprehensive meta-analysis software. Results Ten RCTs were included. There were no significant differences in oropharyngeal leak pressures (mean difference [MD] 0.72, 95% confidence interval [CI] –1.10 2.53), device placement time (MD –1.3, 95%CI –4.07 1.44), first attempt insertion success (risk ratio [RR] 1.01, 95% CI 0.9 1.14), grade 3 and 4 fiberoptic view (RR 0.89, 95%CI 0.65 1.21), and blood on removal (RR 0.62, 95%CI 0.32 1.22) between the i-gel? and the LMA-Supreme?, respectively. However, the LMA-Supreme?was associated with easier gastric tube insertion (RR 1.17, 95%CI 1.07 1.29), and more sore throat (RR 2.56, 95%CI 1.60 4.12) than the i-gel? group. Conclusions The LMA-Supreme? and i-gel? were similarly successful and rapidly inserted. However, the LMA-Supreme? was shown to be easier for gastric tube insertion and associated with more sore throat compared with the i-gel?.
A Literature Review on the Definition and Process of Project-Based Learning and Other Relative Studies  [PDF]
Xiaomei Du, Jie Han
Creative Education (CE) , 2016, DOI: 10.4236/ce.2016.77112
Abstract: Project-Based Learning (PBL) is a student-centered model that organizes learning and studying around projects. It has gained some popularity in second language education and exercised positive influence on educational practices. This paper gives a selective review of the researches on Project-Based Learning from different aspects, including the definition of PBL, the process of PBL and other relative studies, in the hope that this may, to some extent, render help to teachers who employ PBL in varying degrees.
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