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Zhang W.,Wuhan Naval University of Engineering | Wu X.,Wuhan Naval University of Engineering | Cao W.,Wuhan Environmental Protection science Research Institute
Applied Mechanics and Materials | Year: 2011

Piezoelectric system shunted with proper negative capacitance in series has low dynamic stiffness. According to frequency characteristic equations of the piezoelectric system, optimal parameters and characteristics of both shunted series structures were deduced and compared theoretically. One is negative-capacitance and resistance in series, and the other is negative-capacitance, resistance and inductance in seires. It presented that high damping characteristic can be obtained at low frequencies when shunted with series negative-capacitance. If proper inductance is included in shunt circuit, effective bandwidth could be extended and the peak of amplitude of response is decreased, what' more, the stability of this structure is enhanced. This technology can be used in vibration isolators or sensors and the shunt structure including inductance is recommended. © (2011) Trans Tech Publications. Source


Pei F.,Wuhan University | Pei F.,Tanggu Environmental Protection Industry Service Center | Pei F.,Tianjin Tian Ren He Environmental Science and Technology Development Center | Luo Z.-J.,Wuhan University | And 2 more authors.
Huanjing Kexue/Environmental Science | Year: 2012

To study the distribution of phenol compounds in a retired refinery site, 21 soil sampling sites and 8 shallow groundwater wells were investigated. The results showed, shallow unconfined groundwater of the site was in a serious pollution situation and the phenols concentration was much higher than quality standard for ground water. Confined water sample was slightly contaminated by phenols and the total quality was good. Approximately half of the area was heavily polluted by phenol compounds. According to the retired refinery layout, the phenols pollution distribution in shallow groundwater and soil exhibited the regional similarity. The highly contaminated area was production workshop, oil tank and plant storage. Horizontal diffusion of pollutants was not serious. Vertical diffusion of pollutants was different, and a site with pollutant diffusion was deeper than ten meters. The 2-chlorophenol, 2-nitrophenol, 2, 4-xylenol, 2, 4-dichlorophenol and 2, 4, 6-trichlorophenol, 2, 4-dinitrophenol and 2-methyl-4, 6-dinitrophenol in typical soils were analyzed by GC/MS. It showed that concentrations of seven phenol compounds were 0.01-232.96 mg·kg-1, and the concentrations of 2, 4-dinitrophenol and 2-methyl-4, 6-dinitrophenol were high. Source


Liu C.,Wuhan Environmental Protection science Research Institute
Advanced Materials Research | Year: 2012

This paper presents a study of effects of low power ultrasonication on anaerobic digestion of sludge. Based on the optimizing tests, large lab scale experiments were implemented to investigate impact of different dosage of ultrasonication on a sludge anaerobic process. Hydrolysis capacity of sludge for protein, cellulose and fat, pH, content of coenzyme F420 and daily yield of biogas were detected to observe changes of the main biochemical steps. The underlying mechanisms for the enhancement of sludge digestion efficiency by low power ultrasonication are also discussed. © (2012) Trans Tech Publications, Switzerland. Source


Zhang W.,NUE | Wu X.,NUE | Cao W.,Wuhan Environmental Protection science Research Institute
Advanced Materials Research | Year: 2011

Piezoelectric acoustic sensor with negative impedance matching circuit is put forward to enhance its sensitivity at low frequencies. The multi-physics problem coupled with sound wave equations, structure stress-strain equations, piezoelectric constitutive equations and electric ordinary equations is analyzed with FEM in detail. Frequency response characteristics are simulated when shunted with negative-capacitance, resistance in series. Sensitivity is obtained from 1kHz to 5kHz. When used proper electrical elements, the sensitivity of the piezoelectric sensor can even exceed that of no matching circuit over 2 factors in broad band. © (2011) Trans Tech Publications, Switzerland. Source


Zhang W.,NUE | Wu X.,NUE | Cao W.,Wuhan Environmental Protection science Research Institute
Applied Mechanics and Materials | Year: 2012

Piezoelectric transducer with negative impedance matching circuit is put forward to enhance its performance in broadband frequencies. The typical multi-physics problem is coupled with sound wave equations, structure stress-strain equations, piezoelectric constitutive equations and electric ordinary equations, and it is analyzed with FEM in detail. Frequency response characteristics are simulated when shunted with negative-impedance in series. When proper negative synthesized elements are connected, the performance of low frequencies and bandwidth are enhanced obviously. © (2012) Trans Tech Publications, Switzerland. Source

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