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Search Results: 1 - 10 of 47805 matches for " Xia Zhao "
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Hierarchical Coordinated Control for Power System Voltage Using Linear Temporal Logic  [PDF]
Hongshan ZHAO, Hongliang GAO, Yang XIA
Engineering (ENG) , 2009, DOI: 10.4236/eng.2009.12014
Abstract: The paper proposed an approach to study the power system voltage coordinated control using Linear Temporal Logic (LTL). First, the hybrid Automata model for power system voltage control was given, and a hierarchical coordinated voltage control framework was described in detail. In the hierarchical control structure, the high layer is the coordinated layer for global voltage control, and the low layer is the power system controlled. Then, the paper introduced the LTL language, its specification formula and basic method for control. In the high layer, global voltage coordinated control specification was defined by LTL specification formula. In order to implement system voltage coordinated control, the LTL specification formula was transformed into hybrid Automata model by the proposed algorithms. The hybrid Automata in high layer could coordinate the different distributed voltage controller, and have constituted a closed loop global voltage control system satisfied the LTL specification formula. Finally, a simple example of power system voltage control include the OLTC controller, the switched capacitor controller and the under-voltage shedding load controller was given for simulating analysis and verification by the proposed approach for power system coordinated voltage control. The results of simulation showed that the proposed method in the paper is feasible.
Flexible Time-Triggered Sampling in Smart Sensor-Based Wireless Control Systems
Feng Xia,Wenhong Zhao
Sensors , 2007, DOI: 10.3390/s7112548
Abstract: Wireless control systems (WCSs) often have to operate in dynamic environmentswhere the network traffic load may vary unpredictably over time. The sampling in sensors isconventionally time triggered with fixed periods. In this context, only worse-than-possiblequality of control (QoC) can be achieved when the network is underloaded, whileoverloaded conditions may significantly degrade the QoC, even causing system instability.This is particularly true when the bandwidth of the wireless network is limited and sharedby multiple control loops. To address these problems, a flexible time-triggered samplingscheme is presented in this work. Smart sensors are used to facilitate dynamic adjustment ofsampling periods, which enhances the flexibility and resource efficiency of the system basedon time-triggered sampling. Feedback control technology is exploited for adapting samplingperiods in a periodic manner. The deadline miss ratio in each control loop is maintainedat/around a desired level, regardless of workload variations. Simulation results show that theproposed sampling scheme is able to deal with dynamic and unpredictable variations innetwork traffic load. Compared to conventional time-triggered sampling, it leads to muchbetter QoC in WCSs operating in dynamic environments.
Witten multiple zeta values attached to sl(4)
Jianqiang Zhao,Xia Zhou
Mathematics , 2009,
Abstract: In this paper we shall prove that every Witten multiple zeta value of weight w>3 attached to sl(4) at nonnegative integer arguments is a finite rational linear combinations of MZVs of the weight w and the depths three or less, except for the nine irregular cases where the Riemann zeta value zeta(w-2) and the double zeta values of weight w-1 and depth <3 are also needed.
Reducibility of Signed Cyclic Sums of Mordell-Tornheim Zeta and L-Values
Jianqiang Zhao,Xia Zhou
Mathematics , 2009,
Abstract: In this paper, we shall show that certain signed cyclic sums of Mordell-Tornheim L-values are rational linear combinations of products of multiple L-values of lower depths (i.e., reducible). This simultaneously generalizes some results of Subbarao and Sitaramachandrarao, and Matsumoto et al. As a direct corollary, we can prove that for any integer k>2 and positive integer n, the Mordell-Tornheim sums zeta_\MT(\{n\}_k) is reducible.
Flexible Time-Triggered Sampling in Smart Sensor-Based Wireless Control Systems
Feng Xia,Wenhong Zhao
Computer Science , 2008,
Abstract: Wireless control systems (WCSs) often have to operate in dynamic environments where the network traffic load may vary unpredictably over time. The sampling in sensors is conventionally time triggered with fixed periods. In this context, only worse-than-possible quality of control (QoC) can be achieved when the network is underloaded, while overloaded conditions may significantly degrade the QoC, even causing system instability. This is particularly true when the bandwidth of the wireless network is limited and shared by multiple control loops. To address these problems, a flexible time-triggered sampling scheme is presented in this work. Smart sensors are used to facilitate dynamic adjustment of sampling periods, which enhances the flexibility and resource efficiency of the system based on time-triggered sampling. Feedback control technology is exploited for adapting sampling periods in a periodic manner. The deadline miss ratio in each control loop is maintained at/around a desired level, regardless of workload variations. Simulation results show that the proposed sampling scheme is able to deal with dynamic and unpredictable variations in network traffic load. Compared to conventional time-triggered sampling, it leads to much better QoC in WCSs operating in dynamic environments.
Block Compressed Sensing Image Reconstruction Based on SL0 Algorithm
Block Compressed Sensing Image Reconstruction Based on SL0 Algorithm

Juan Zhao,Xia Bai
- , 2017, DOI: 10.15918/j.jbit1004-0579.201726.0311
Abstract: By applying smoothed l0 norm (SL0) algorithm, a block compressive sensing (BCS) algorithm called BCS-SL0 is proposed, which deploys SL0 and smoothing filter for image reconstruction. Furthermore, BCS-ReSL0 algorithm is developed to use regularized SL0 (ReSL0) in a reconstruction process to deal with noisy situations. The study shows that the proposed BCS-SL0 takes less execution time than the classical BCS with smoothed projected Landweber (BCS-SPL) algorithm in low measurement ratio, while achieving comparable reconstruction quality, and improving the blocking artifacts especially. The experiment results also verify that the reconstruction performance of BCS-ReSL0 is better than that of the BCS-SPL in terms of noise tolerance at low measurement ratio.
By applying smoothed l0 norm (SL0) algorithm, a block compressive sensing (BCS) algorithm called BCS-SL0 is proposed, which deploys SL0 and smoothing filter for image reconstruction. Furthermore, BCS-ReSL0 algorithm is developed to use regularized SL0 (ReSL0) in a reconstruction process to deal with noisy situations. The study shows that the proposed BCS-SL0 takes less execution time than the classical BCS with smoothed projected Landweber (BCS-SPL) algorithm in low measurement ratio, while achieving comparable reconstruction quality, and improving the blocking artifacts especially. The experiment results also verify that the reconstruction performance of BCS-ReSL0 is better than that of the BCS-SPL in terms of noise tolerance at low measurement ratio.
The Benefits of Exogenous NO: Enhancing Arabidopsis to Resist Botrytis cinerea  [PDF]
Hongyu Yang, Xiaodan Zhao, Jia Wu, Min Hu, Shaolei Xia
American Journal of Plant Sciences (AJPS) , 2011, DOI: 10.4236/ajps.2011.23060
Abstract: Botrytis cinerea is a necrotrophic fungal pathogen that impacts a wide range of hosts, including Arabidopsis. Pretreatment with nitric oxide (NO) donor sodium nitroprusside (SNP) on Arabidopsis leaves suppressed Botrytis cinerea infection development. Additionally, in this study the dosage levels of SNP applied to the leaves had no direct, toxic impact on the development of the pathogen. The relationship between NO and reactive oxidant species (ROS) was studied by using both spectrophotometrical methods and staining leaf material with fluorescent dyes, nitro blue tetrazolium (NBT), and with 3,3-diaminobenzidine (DAB). The results showed that exogenous NO restrained the generation of ROS, especially H2O2, as the pathogen interacted with the Arabidopsis plant. And this inhibition of reactive oxidant burst coincided with delay infection development in NO-supplied leaves. The influence of elevated level of NO on antioxidant enzymes was investigated in this study. The activities of catalase (CAT) and guaiacol peroxidase (POD) were increased to different degrees in both: 1) SNP treated only leaves, and 2) SNP pretreated leaves that were subsequently inoculateted with pathogens. However, the activity of superoxide dismutase (SOD) was unchanged in the leaves studied. The decrease in H2O2 content probably resulted from the increase in activities of POD and CAT. Our study suggests that NO might trigger some metabolic reactions, i.e. enhanced enzyme activity that restrains H2O2 which ultimately results in resistance to B. cinerea infection.
Research on Co-phase Power Supply Test System  [PDF]
Yuanzhe Zhao, Qunzhan Li, Yankun Xia, Zeliang Shu
Energy and Power Engineering (EPE) , 2013, DOI: 10.4236/epe.2013.54B100
Abstract:

Co-phase power supply system can solve the problems of power quality of heavy unbalanced three phase, large harmonics and reactive power and cancel neutral section in electric railway power supply system. In order to do further research, a co-phase power supply test system is proposed. By mean of analyzing on structures and principles of YNvd transformer, integrated power flow controller (IPFC) and simulation load, establishing control strategy on IPFC and simulation load, the system is simulated dynamically. The results illustrate that the scheme can well simulate co-phase system, and the negative sequence is eliminated, harmonic and reactive power are real-timely compensated in system.

Semi-Global Inference in Phenotype-Protein Network  [PDF]
Siliang Xia, Guangri Quan, Yongbo Zhao, Xuhui Jia
Engineering (ENG) , 2013, DOI: 10.4236/eng.2013.510B039
Abstract:

Discovering genetic basis of diseases is an important goal and a challenging problem in bioinformatics research. Inspired by network-based global inference approach, Semi-global inference method is proposed to capture the complex associations between phenotypes and genes. The proposed method integrates phenotype similarities and protein-protein interactions, and it establishes the profile vectors of phenotypes and proteins. Then the relevance between each candidate gene and the target phenotype is evaluated. Candidate genes are then ranked according to relevance mark and genes that are potentially associated with target disease are identified based on this ranking. The model selects nodes in integrated phenotype-protein network for inference, by exploiting Phenotype Similarity Threshold (PST), which throws lights on selection of similar phenotypes for gene prediction problem. Different vector relevance metrics for computing the relevance marks of candidate genes are discussed. The performance of the model is evaluated on Online Mendelian Inheritance in Man (OMIM) data sets and experimental evaluation shows high performance of proposed Semi-global method outperforms existing global inference methods.

Analysis of Commutation Failure in Multi-Infeed HVDC System under Different Load Models  [PDF]
Chengjun Xia, Zhongchao Yang, Kun Men, Yong Zhao
Journal of Power and Energy Engineering (JPEE) , 2014, DOI: 10.4236/jpee.2014.29022
Abstract:

HVDC technology has been widely used in modern power system. On one hand, HVDC has the advantages of economy, high efficiency and strong controllability. While on the other hand, it makes the dynamic characteristics of the power system becoming more and more complex. That puts forward a new challenge to system stability and raises new questions for power system simulation. This paper focuses on the interaction between AC and DC systems, especially the problem of commutation failure caused by AC system fault. Based on the data of China Southern Power Grid, this paper calculates the fault regions that may cause commutation failure and calculates the system critical clearance time under different load models, analyzes the impacts of different load models on commutation failure and the stability of AC/DC hybrid system.

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