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Experimental investigation of long-term characteristics of greenschist
Zhang, Qing-Zhao,Shen, Ming-Rong,Ding, Wen-Qi,Jang, Hyun-Sic,Jang, Bo-An Techno-Press 2016 Geomechanics & engineering Vol.11 No.4
The greenschist in the Jinping II Hydropower Station in southwest China exhibits continuous creep behaviour because of the geological conditions in the region. This phenomenon illustrates the time-dependent deformation and progressive damage that occurs after excavation. In this study, the responses of greenschist to stress over time were determined in a series of laboratory tests on samples collected from the access tunnel walls at the construction site. The results showed that the greenschist presented time-dependent behaviour under long-term loading. The samples generally experienced two stages: transient creep and steady creep, but no accelerating creep. The periods of transient creep and steady creep increased with increasing stress levels. The long-term strength of the greenschist was identified based on the variation of creep strain and creep rate. The ratio of long-term strength to conventional strength was around 80% and did not vary much with confining pressures. A quantitative method for predicting the failure period of greenschist, based on analysis of the stress-strain curve, is presented and implemented. At a confining pressure of 40 MPa, greenschist was predicted to fail in 5000 days under a stress of 290 MPa and to fail in 85 days under the stress of 320 MPa, indicating that the long-term strength identified by the creep rate and creep strain is a reliable estimate.
( Yun Cheng Wu ),( Jun Yuan ),( Waseem Raza ),( Qi Rong Shen ),( Qi Wei Huang ) 한국미생물 · 생명공학회 2014 Journal of microbiology and biotechnology Vol.24 No.10
Bacillus amyloliquefaciens strain NJZJSB3 has shown antagonism of several phytopathogens in vitro, especially Sclerotinia sclerotiorum. Both the broth culture and cell suspension of strain NJZJSB3 could completely protect the detached leaves of canola (Brassica napus) from S. sclerotiorum infection. In pot experiments, the application of strain NJZJSB3 cell suspension (108 CFU/ml) decreased the disease incidence by 83.3%, a result similar to commercially available fungicide (Dimetachlone). In order to investigate the potential biocontrol mechanisms of strain NJZJSB3, the nonvolatile antifungal compounds it produces were identified as iturin homologs using HPLC-ESI-MS. Antifungal volatile organic compounds were identified by gas chromatography-mass spectrometry. The detected volatiles toluene, phenol, and benzothiazole showed antifungal effects against S. sclerotiorum in chemical control experiments. Strain NJZJSB3 also produced biofilm, siderophores and cell-wall-degrading enzymes (protease and β-1,3-glucanase). These results suggest that strain NJZJSB3 can be a tremendous potential agent for the biological control of sclerotinia stem rot.
( Luo Yi ),( Guo Yi Zhang ),( Zhen Zhu ),( Xiao Hui Wang ),( Wei Ran ),( Qi Rong Shen ) 한국미생물생명공학회(구 한국산업미생물학회) 2013 한국미생물·생명공학회지 Vol.41 No.1
The nutritional requirements for the maximum production of lipopeptides by Bacillus subtilis N7 (B. subtilis N7) were investigated and optimized using response surface methodology (RSM) under shake flask fermentation. A one-factor-at-a time experimental setup was used to screen carbon and nitrogen sources. A Plackett?Burman design (PBD) was employed to screen the most critical variables for lipopeptides production amongst ten nutritional elements. The central composite experimental design (CCD) was finally adopted to elucidate the composition of the fermentation medium. Statistical analyses (analysis of variance, ANOVA) of the results showed that KCl, MnSO4 and FeSO4·6H2O were important components and that their interactions were strong. Lipopeptide production was predicted to reach 709.87 mg/L after a 60 h incubation using an optimum fermentation medium composed of glucose 7.5 g/L, peanut oil 1.25 g/L, MgSO4 0.37 g/L, KH2PO4 0.75 g/L, monosodium glutamate 6.75 g/L, yeast extract and NH4Cl (5:3 w/w) 10 g/L, KCl 0.16 g/L, FeSO4·6H2O 0.24 mg/L, MnSO4 0.76 mg/L, and an initial pH of 7.0. Lipopeptide production (706.57 ± 3.70 mg/L) in the optimized medium confirmed the validity of the predicted model.