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‘Sonication - cryptic growth’ technology can reduce 30-80% excess sludge in wastewater treatment systems. Various mechanisms contribute to the sludge reduction but the role of each one is unclear. This paper quantitatively studied the potential mechanisms in ‘sonication - cryptic growth’. The operation condition was: every day 20% sludge was sonicated under 1.2 Wml-1 for 15 min and then returned to the wastewater treatment reactor for cryptic growth. The results showed that under such conditions, ‘sonication - cryptic growth’ reduced the excess sludge by 57.3% and the effluent met the national discharge standard. Multiple mechanisms were involved in the process. Detailed analysis showed that the ‘lysis-cryptic growth’ mechanism was the most important one and accounted for 49.1% of sludge reduction. Biodegradation of residual sludge was the second important one and contributed 19.5%. Other potential mechanisms included the altered microbial community, longer sludge retention time, and accumulation of persistent materials. But organic load increase had virtually no impact.

A kind of classical product codes based on repeated-root cyclic codes are considered in this paper, and the classical product codes are applied to construct the asymmetric quantum product codes. The novel asymmetric quantum product codes have great asymmetry for correcting Z errors and X errors, and the parameters of asymmetric quantum product codes can be precisely determined by the properties of the repeated-root cyclic codes and their dual codes. The examples show that these asymmetric quantum product codes based repeated-root cyclic codes are more efficient than some existent asymmetric quantum product codes.

Ni-P ultra-black films were prepared by ultrasonic chemical etching of electroless plated Ni-P films using 8 mol/L nitric acid at 40 °C for 20 s with different ultrasonic power ranging from 0 to 195 W. Scanning electron microscopy (SEM) was used to study topographic characteristics of the films. The results show that ultrasonic oscillation plays an important role during ultrasonic chemical etching of electroless plated Ni-P films. The enhanced pore features with higher porosity through coalescence of adjacent isolated pores have been observed at 0-105 W. The increase in pore size of Ni-P etched films with the ultrasonic power (from 105 to 195 W) has been confirmed by SEM characterization. Generally, the dependences of relative etching rate on ultrasonic power are closely associated with pore size, pore shape and the distribution of etching pores.