In this paper, the three-level inverter of micro-gird is used to improve output current wave-form, power factor and power energy transmission. Due to the Randomness and fluctuation of Circuit parameters and the signal, a closed-loop control strategy of fuzzy hysteresis current controller and the direct current side voltage fuzzy Proportional-Integral controller is introduced. The obtained results showed the reliability and feasibility of the above mentioned control strategy in MATLAB Simulation.
The effects of sodium lauryl sulfate(SLS) and 1.4-butynediol(BOZ) on Ni-W electro-deposition,electrodepositing layer quality,targeted inhibition,hardness and corrosion were investigated by complex theory,grain characterization,surface morphology,microstructure and ΦPYMKNH equation.The inhibition mechanism and the cause of hardness decreasing were explored in the present paper.The results show that,when SLS is 0.2 g/L and BOZ is 0.4 g/L,surfactant reaches the critical micelle concentration(CMC),inhibition becomes obvious and the depositing velocity drops quickly.Meanwhile,the Ni-W electrodepositing layers show refine grain and its surface becomes smoother.In addition,corrosion resistance is improved significantly with year corrosion rate(Ke) of 0.0025 mm/y and corrosion resistance of class 2.During the electrodepositing,SLS shows a significant inhibition to tungsten,meaning that tungsten content in the electrodepositing layer and the hardness of the electrodepositing layer decrease with increasing SLS concentration.Small amount of SLS can prevent pinholes and bubbles,while the electroplated layers are dislocated obviously and its surface becomes rough when SLS is 0.4 g/L.However,the dislocated layers and cracks can be removed by adding BOZ.Extraordinary smooth coating is obtained with SLS of 0.2 g/L and BOZ of 0.4 g/L.
In order to obtain more bioelectrical impedance information at different frequencies simultaneously, a multi-frequency excitation source and a multi-frequency demodulation module are developed using FPGA. The source can provide both sweep frequency and multi-frequency excitation signal. The range of frequency is 0∼16.67 MHz, phase and amplitude of the generator can be changed conveniently. Result shows that the source has many advantages, such as high precision, good stability and convenient adjustment. Multi-frequency digital quadrature demodulation is also accomplished by FPGA, since the excitation signal and the reference signal are generated at the same time, error caused by the difference of frequency between the two signals is avoided effectively. It can meet the need for data acquisition system in multi-frequency electrical impedance tomography very wel1.
Abstract As an important energy generation device of the compressed air energy storage (CAES) system, the radial-inflow turbine with shrouded impeller is employed to avoid the leakage flow in the rotor, especially in the high-pressure stages. However, a lack of clarity in the leakage characteristics and their drivers still prevents a systematic approach to the efficient performance and proper design of the shrouded radial turbine. In the present work, the shroud cavity leakage of the shrouded radial turbine has been studied numerically. The physical quantity synergy is innovatively employed to research the internal flow field of the shroud cavity. It is found that the influence of high rotating speed on the seal leakage cannot be neglected, and the average reduced rate of seal leakage is found to be about 9.9% for the designed clearance. The leakage mass flow rate could be reduced by increasing the rotating speed or decreasing the seal clearance. The synergy angle is able to predict the flow resistance in shroud cavity very well. According to the volume-averaged synergy angle in the seal, the dimensionless seal clearance smaller than 1.5% in the shrouded radial turbine is recommended. Compared with the seal clearance in other high-pressure shrouded turbomachines, the current recommended clearance should be within a reasonable field.
Recent microwave nondestructive measurement in biomedical engineering are reviewed. A novel method for non-contact monitoring of stress-induced autonomic activation through the back of a chair is developed, using a compact 24 GHz microwave radar (8 × 5 × 3 cm), without large scale equipment and placing a heavy burden on the monitored individual. This method appears to be promising for future monitoring of stress induced autonomic activation of operators and may reduce stress induced accidents. A novel in vitro test of blood analysis based on the measurement of the dielectric properties at microwave frequencies is reported. The measurements were made using rectangular cavity perturbation technique at the S-band of microwave frequency with the different samples of blood obtained from healthy donors as well as from patients. The measurements are in good agreement with clinical analysis. Novel planar type probes were developed to demonstrate the possibility of replacing the existing high cost open-ended coaxial probes. Three probes are developed. The measurement results of each probe showed excellent compatibility with those of the open-ended coaxial probe up to almost 40 GHz. The proposed planar type probes have great potentials for practical medical applications in view of low cost, disposability, and monolithic integration capability with the driving circuits. Finally the technical challenges of microwave nondestructive measurement in biomedical engineering are discussed.
This paper presents a three-layer Artificial Neural Network as the short-term load forecasting model adopting the fastest back-propagation algorithm with robustness, i.e., Levenberg-Marquardt optimization, and moreover, the momentum factor is considered during the learning process. Based on predicted data by aforementioned model, size determination of energy storage system in terms of power rating and capacity is undertaken according to the desired level of shaving peak demand. The illustrative example in reference to the weather and power load data of office building from July to August in 2011 gets the results that the average relative error -0.7% and the root-mean-square error 2.79% which show aforementioned forecasting model can work effectively with the attractive percentage, i.e. 87.5%, of error within the acceptable one 2.79%; Furthermore, size determination of energy storage system adopting battery energy storage technology, i.e. 7.03kW/36.42kWh, is carried out to meet the desired peak shaving demand.
Four kinds of nanocrystalline Ni-W-Cr-Nd alloy coatings with different tungsten contents,as substitutes for chromium coating,were successfully obtained by pulse electrodeposition.The surface morphology,composition and phase structure of as-deposited alloy coatings were analyzed by means of scanning electron microscopy,energy dispersive spectrometry and X-ray diffraction.The corrosion resistance of the alloy coatings was evaluated using potentiodynamic scan technique and electrochemical impedance spectroscopy.It was found that as-deposited Ni-W-Cr-Nd alloy coatings were dense and uniform,and had no cracks.Grain sizes of the alloy coatings with 22%,26%,31%,36% W were 14,17,21,26 nm respectively.Particularly,the alloy coating with 22% W possessed better high-temperature oxidation resistance and corrosion resistance than Cr coating,and the alloy coating heat-treated at 400 ℃ had a high hardness of 1 132 HV and good wear resistance,showing a small wear rate of 0.018 3 mg/(cm2·h).
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