Influence of Material Removal Strategy on Machining Deformation of Aluminum Plates with Asymmetric Residual Stresses.

In this paper, the effects of material removal strategies and initial stress states on the machining deformation of aluminum alloy plates were investigated through a combination of finite element simulation and experiments. We developed different machining strategies described by Tm+Bn, which removal m mm materials form top and n mm materials from the bottom of the plate. The results demonstrate that the maximum deformation of structural components with the T10+B0 machining strategy could reach 1.94 mm, whereas with the T3+B7 machining strategy was only 0.065 mm, decreasing by more than 95%. The asymmetric initial stress state had a significant impact on the machining deformation of the thick plate. The machined deformation of thick plates increased with the increase in the initial stress state. The concavity of the thick plates changed with the T3+B7 machining strategy due to the asymmetry of the stress level. The deformation of frame parts was smaller when the frame opening was facing the high-stress level surface during machining than when it was facing the low-stress level. Moreover, the modeling results for the stress state and machining deformation were accurate and in good accordance with the experimental findings.

[Isolation and identification of a PAHs-degrading strain Gordonia sp. He4 and its dynamics during bioremediation of phenanthrene polluted soil].

A bacterial strain, He4, capable of degrading n-hexadecane and other polycyclic aromatic compounds was isolated from petroleum polluted soil. This strain was identified as Gordonia sp. He4 according to its morphology, physiological, biochemical properties and the analysis of its 16S rRNA gene sequence. Based on its 16S rRNA gene sequence, specific primers were designed and a competitor template was amplified by PCR. The dynamics of strain He4 in phenanthrene polluted soil was analyzed by colony forming unit (CFU) method and QC-PCR method. The results showed that partial of He4 become non-culturable and un-detectable by CFU method. But by using QC-PCR, the population density of strain He4 could be measured accurately.

[Function analysis of the effective strain Rhodococcus ruber Em1 in wastewater treatment system by quantitative competitive PCR].

A quantitative competitive PCR (QC-PCR) system was developed to quantify the number and analyze the function of the Rhodococcus ruber Em1 strain in a wastewater treatment system in Nanchong oil refinery plant. Strain Em1 was able to degrade various kinds of hydrocarbons and aromatic compounds with high efficiency and produce bioemulsifier, so it was introduced into the waste liquid petroleum-disposing system. The sediment samples were collected from the disposing system in the range of 5 months, and then the numbers of strain Eml and degrading efficiencies were studied. The results showed that the primers based on 16S rRNA gene sequence of strain Em1 were specific at species level. The PCR products amplified from sediment total DNA with the specific primers were cloned and sequenced, in which 62.2% were the fragments of 16S rRNA gene of strain Em1. Furthermore, the number of Em1 strain ranging from 3.4 x 10(5) - 4.3 x 10(8) CFU/g in the sediment samples were detected, which indicated that the strain Eml added into purposely did exist stably and reproduced well in the waste-deposing system during a long period. The high relativity, with relative coefficient R2 of 0.89, between Eml cell number and the amount of COD (Chemical Oxygen Demand) removal proved that the strain Em1 played an important role in this bio-augmentation treatment system.

Arbuscular mycorrhizal status of plants and the spore density of arbuscular mycorrhizal fungi in the tropical rain forest of Xishuangbanna, southwest China.

The arbuscular mycorrhizal status of 112 plant species and the spore density of arbuscular mycorrhizal fungi (AMF) in the rhizosphere soil of these plants in the tropical rain forest of Xishuangbanna, southwest China, were surveyed. It was found that 56% of the surveyed species were arbuscular mycorrhizal, 31% were possibly arbuscular mycorrhizal and 13% were non-mycorrhizal. The spore density of AMF ranged from 55 to 1,908 per 100 g soil, with an average of 476. The rhizosphere soil from the arbuscular mycorrhizal plants did not always have a higher AMF spore density than that from the possibly mycorrhizal and non-mycorrhizal plants. The clumped distribution of AMF spores and the complex structure of the underground component of the tropical rain forest may be two important factors that affected the spore density of AMF. Fungi belonging to the genera Acaulospora and Glomus are the dominant AMF in the soil of the tropical rain forest of Xishuangbanna.