Advanced Materials Research Vols. 347-353

Abstract: Given the ambiguity of the type and classification in groundwater quality standards, this paper based on fuzzy mathematics theory, take TDS, fluoride and other components as the nine evaluation factors, determine its weight according to the pollution of different factors on water quality; using fuzzy membership to describe the classification boundaries of the evaluation in water quality. Established a number of pollution assessment factors of fuzzy sets such as evaluation set, membership function and weight set;after the compound operation of fuzzy matrixes, using the maximum membership degree law, to evaluate the groundwater quality of a monitoring well in study area ,the conclusions are objective.

Abstract: The relationship between phytoplankton abundance, Chl a concentration and environmental factors was analyzed on the investigation data in the Southern Ocean during 1989-2009. In the sea area near Prydz Bay, the water abundance of phytoplankton cells was 3.9×104 ～2.83×105 cells/dm3, and the average water abundance of phytoplankton cells was 7.38×104cells/dm3. In the net samples, the dominant species were Fragilariopsis kerguelensis, Fragilariopsis curta, Pseudo-nitzschia lineola, Eucampia antarctica, Thalassiosira antarctica, Corethron criophilum, etc. In the water samples, the dominant species were Fragilariopsis curta, Pseudo-nitzschia lineola, etc. The regression statistical analysis showed the phytoplankton cell abundance was in significant positive correlation with water temperature, DO, and Chl a, and significant negative correlation with PO43- and NO3-.

Abstract: A field experiment was conducted to study the characteristics of non-point source nitrogen (N) in the surface runoff from sloping croplands and the influences of rainfall and cropland slope gradient. The results showed that dissolved total N (DTN) was the major form of N in the runoff, and the proportion occupied by dissolved inorganic nitrogen (DIN) ranged from 45% to 85%. The level of NH₄⁺-N was generally higher than the level of NO₃^--N, and averaged at 2.50 mg·L^-1 and 1.07 mg·L^-1 respectively. DIN was positively correlated with DTN (R²=0.962). Dissolved organic N (DON) presented a moderate seasonal change and averaged at 1.40 mg·L^-1. Rainfall amount and rainfall intensity significantly affected the components of DTN in the runoff. With the increase of rainfall amount and rainfall intensity, the concentrations of DTN, NH₄⁺-N and NO₃^--N presented a decreased trend, while the concentration of DON showed an increased trend. N loss went up with an increase in the gradient of sloping cropland, and was less when the duration was longer from the time of N fertilization.fertilization.

Abstract: Sixteen tree-rings of Polar (P. Euramericana) were collected in the different function districts of Kaifeng City, China. Concentrations of Cu and Zn in the xylem of tree-rings from 1990 to 2009 were measured using F-AAS, and that of Co using ICP-MS. The results show that concentrations of Cu and Zn in tree-rings in the control area do not vary significantly in the period from 1990 to 2009 and much lower than that in urban areas. The accumulation sequences of Zn in tree-rings in different urban districts appear increasing trends in the period, and that of Cu present waved rising trends. The sequences of Co in tree-rings both in urban and control area had no significant change in the period. Copper and Zinc are the typical anthropogenic metals, and Co is a natural source metal. We can understand the heavy metal pollution changes in urban area from their accumulation sequences in tree-rings.

Abstract: Ti/Sn1–xIrxO2 electrodes were prepared on titanium substrates by thermal decomposition method. The structure and the surface morphologies of the electrodes were characterized by XRD, SEM, and the electrochemical properties were investigated by linear scan voltammetry. The results showed that in NaCl solution and Na2SO4 solution, with increasing the Ir content, the potential gap of electrochemical oxidation（△E）between chlorine evolution and oxygen evolution decreased. The electrode containing 30% Ir (by mol%) had the highest chlorine evolution efficiency. Using Ti/Sn0.7Ir0.3O2 electrode as anode, a simulated wastewater with p-chlorophenol as pollutant was degraded by constant current electrolysis. The degradation rate of p-chlorophenol in presence of NaCl was faster than in presence of Na2SO4.

Abstract: In order to better research wind power generation technology in the laboratory, this paper analyzes the characteristics of the wind turbine. Then on the basis of the analysis results, a wind turbine simulation model is built in MATLAB/SIMULINK and a simple torque imitation scheme is proposed. The program imitates the output torque characteristics of wind turbine, by controlling the induction motor torque current to control its output torque. The simulation results verify the feasibility of the wind turbine imitation program. It lays the foundation for the wind energy study.

Abstract: An increasing number of large wind turbines with a variable-speed variable pitch control mechanism are developed to improve the response speed of wind turbines and get maximum active power .Designing a reasonable pitch control system requires both a good control scheme and a more accurate wind turbine model. Base on the analysis of wind turbines’ principle, a local linearization model of wind turbine is built by using linearization method of small deviation in this paper. The model’s inputs are the data of wind speed and pitch angle, and the output is the active power. The accuracy of the model is verified by studying the active power output of wind turbine under different circumstances in which the pitch angle changes with a constant wind speed and the wind speed changes with a constant pitch angle. At the same time, this paper provides pitch control program based on internal model control after analyzing the disadvantages of PID pitch controller. When the wind speed is beyond the rating, the active power can be limited reasonably around the power rating of wind turbines by adjusting the pitch angle.

Abstract: Fluctuating wind speed spectrum, which is closer to the actual working conditions, was simulated by davenport wind speed model, and displacement and stress distribution of blade under fluctuating wind speed were calculated by finite element analysis software. The numerical results indicate that the growth trend of vibration amplitude for whole blade at flapping direction is nonlinear along the wingspan. The max von-mises stress appears when the vibration amplitude of tip reaches the maximum, and it is mainly concentrated in the central part of the blade. The stress at trailing edge and tip is smaller than the central part. Above results provide a reference for the strength safety design of wind turbine blade.,Fluctuating wind speed spectrum, which is closer to the actual working conditions, was simulated by davenport wind speed model, and displacement and stress distribution of blade under fluctuating wind speed were calculated by finite element analysis software. The numerical results indicate that the growth trend of vibration amplitude for whole blade at flapping direction is nonlinear along the wingspan. The max von-mises stress appears when the vibration amplitude of tip reaches the maximum, and it is mainly concentrated in the central part of the blade. The stress at trailing edge and tip is smaller than the central part. Above results provide a reference for the strength safety design of wind turbine blade.

Abstract: Based on the single kernel function relevance vector machine(RVM) models，a multiple load-forecasting model has been established and simulated with several compound kernel functions, including Gauss kernel, Laplace, linear compounded by Gauss and Laplace, Gauss and polynomial kernel. Each model gained comparatively reasonable results in simulation .Moreover, multi linear-compound kernel RVMs performed better than single kernel RVMs in terms of most evaluating indicators, which prove that RVM is an appropriate machine learning method in monitoring status of components of wind turbines.

Abstract: With increasing installation capacity and wind farms penetration, wind power plays more important role in power systems, and the modeling of wind farms has become an interesting research topic. In this paper, a coherency-based equivalent model has been discussed for the doubly fed induction generator (DFIG). Firstly, the dynamic models of wind turbines, DFIG and the mechanisms are briefly introduced. Some existing dynamic equivalent methods such as equivalent wind model, variable speed wind turbine model, parameter identification method and modal equivalent method to be used in wind farm aggregation are discussed. Then, considering wind power fluctuations, a new equivalent model of a wind farm equipped with doubly-fed induction generators is proposed to represent the interactions of the wind farm and grid. The method proposed is based on aggregating the coherent group wind turbines into an equivalent one. Finally, the effectiveness of the equivalent model is demonstrated by comparison with the wind farm response obtained from the detailed model. The dynamic simulations show that the present model can greatly reduce the computation time and model complexity.