Search

Usually an induction machine with closed slots on the rotor has lower harmonics in stator line currents than that with open slots. However, some induction machines with closed-rotor slots may suffer from local saturation in the rotor slot bridges, and thus, exhibit significant low-order time harmonics in the stator currents. Such phenomenon is revealed with theoretical analysis, and validated with both finite element analysis and experiments. This study is of reference value for the induction machine design so as to avoid the low-order current harmonics. [ABSTRACT FROM AUTHOR]

Serious current harmonics and reactive power pollution are caused in power grid by the wide use of nonlinear loads A single-phase pulse width modulation( PWM) rectifier with little pollution to the power grid was designed A control strategy with voltage and current dual-closed-loop was given by establishing the topology and mathematical model of the single-phase PWM rectifier In the inner current loop control a method of constructing a virtual current was utilized to achieve decoupling control, and in the outer voltage loop control instantaneous active and reactive power theory was utilized to achieve the linearization control of voltage.Then, simulation was made using the software of Matlab /Simulink, while hardware system was designed and prototyped.Simulation and experimental results verify the feasibility of the voltage and current dual-closed-loop control method. And, the results also demonstrate that the singlephase PWM rectifier has advantages of unit power factor operation and sinusoidal current in the AC side small ripple in the DC output voltageetc Thus current harmonics and reactive power pollution to the power grid caused by single-phase rectifier are all very small. [ABSTRACT FROM AUTHOR]

Based on a model deformation video-measuring system, a method was presented to investigate static aeroelastic effects on aerodynamic forces based on a model deformation video-measuring system and computational fluid dynamic. Static aeroelastic deformation of wing tunnel model under aerodynamic loads was measured by the system and was used to drive the original model surface mesh to move to get deformed surface mesh for CFD. Then CFD results of aerodynamic forces on original shape and deformed shape were acquired to investigate the static aeroelastic effects. Analysis on deformation measurements and computation- al results of a high aspect ratio joined wing shows that the maximum lift coefficient variation occurs near the maximum attack angle in linear region of lift force while the maximum drag coefficient variation occurs ne the stall angle. The variation of aerodynamic forces caused by static aeroelastic deformation is far beyond the precision target set for wind tunnel aerodynamic forces tests. So, it is quite necessary to investigate and mod ify static aeroelastic effects of wind tunnel model on aerodynamic forces. [ABSTRACT FROM AUTHOR]

A two-season soil culture experiment was continually conducted to study the effects of three organic materials,namely Danty, Peat and Biochar,respectively,on combined forms and bio-availability of cadmium (Cd) and lead (Pb) under Cd and Pb in single and combined pollution during 2014-2015. This study aimed to provide a theoretical basis for remediating greenhouse soil contaminated with heavy metals Cd and Pb using organic materials. The main results were as follows: the content of DTPA-Cd decreased significantly by 11.9%( P <0.05) in the soil of Cd and Pb combined pollution with the application of danty, the total of exchangeable Cd, carbonate-bound Cd and iron-manganese oxide bound Cd was reduced by 26.4% and 34.4% in the soil, and the accumulation of Cd in shoots was significantly cut down by 32.0% and 28.0% ( P <0.05) respectively in Cd single and Cd and Pb combined pollution after applying danty; the content of DTPA-Pb was significantly depleted by 83.5% and 83.8%( P <0.05), the total of exchangeable Pb, carbonate-bound Pb and iron-manganese oxide bound Pb was decreased by 34.5% and 13.9% in the soil and the accumulation of Pb in shoots was significantly reduced by 32.0% and 30.0% ( P <0.05) in Pb single and Cd and Pb combined pollution respectively as the use of danty. The content of DTPA-Cd was significantly decreased by 18.9% ( P <0.05) in the soil of Cd and Pb combined pollution with the use of peat, the accumulation of Cd in shoots was reduced by 38.0% and 23.4%( P <0.05) in Cd single and Cd-Pb combined pollution respectively after the application of peat; The content of DTPA-Pb was significantly decreased by 2.7% and 7.2%( P <0.05), the total of exchangeable Pb, carbonate-bound Pb and iron-manganese oxide bound Pb was decreased by 15.8% and 14.6% in the soil and the accumulation of Pb in shoots was significantly reduced by 12.7% and 23.4% ( P <0.05) respectively in Pb single and Cd and Pb combined pollution due to the application of peat. The pH value of the soil was increased by the use of biochar, the content of DTPA-Cd was reduced by 4.7% and 15.0% respectively in the soil of Cd single and Cd and Pb combined pollution, and the accumulation of Cd in shoots was significantly minified by 38.0% and 23.4% respectively in Cd single and Cd and Pb combined pollution as the application of biochar. The content of DTPA-Pb was decreased by 6.8% and 1.0% and the total of exchangeable Pb, carbonate-bound Pb and iron-manganese oxide bound Pb was cut down by 11.9% and 30.0% in the soil of Pb single and Cd and Pb combined pollution respectively by the application of biochar. The content of Cd in plant was most significantly positively correlated with the content of exchangeable Cd in soil ( P <0.01). The content of Pb in plant was most significantly positively correlated with the total of exchangeable Pb, carbonate-bound Pb and iron-manganese oxide bound Pb ( P <0.01). In summary, after the application of danty, peat and biochar, the proportion of highly active content of Cd and Pb was minified through adjusting soil pH and immobilizing Cd and Pb by means of adsorption and complexation in greenhouse soil. With the analysis of input-output, the application of danty, peat and biochar costs 4050 yuan·hm -2 , 11250 yuan·hm -2 and 22500 yuan·hm -2 , respectively. Thus danty, peat and biochar could be used as effective organic agents in the remediation of Cd and Pb contaminated greenhouse soil.