Applied Mechanics and Materials Vols. 71-78

Abstract: Monitoring and analysis of the content of five heavy metals (i.e., Cd, Hg, As, Pb and Cr) in soybean plantation soils in central Sanjiang plain were conducted using the geographic information system (GIS). Statistical analysis indicated, strong intensities of spatial correlation among As, Cr, and Pb, whereas moderate intensities of spatial correlation were observed between Cd and Hg. Therefore, the content and the spatial distribution of the heavy metals are primarily affected by the parent material, topography, soil properties, and other internal factors. However, the effect of external factors, such as industrial pollution, farming methods, as well as the application of pesticide and fertilizer, should also be investigated.

Abstract: In order to obtain a better insight of the possible threat of environmental factor to wildlife, especially to amphibians, we studied influences of dicofol on heart rate in R. nigromaculata by applying biological signal recording and monitoring system. R. nigromaculata was injected in ventral lymph follicle in different doses of dicofol solution, and then observed the changes of heart rate after 7 days. The results showed that with the concentration of dicofol solution increasing, the heart rate, systolic tension and diastolic tension changed. The aim of this research is to discuss the cause of dicofol on the physiology in frogs. It can be concluded that dicofol affects the electronic activity of the frog’s heart.

Abstract: This paper study on surplus sludge of high pressure combined with thermal hydrolysis; investigate the start-up of ethanol-type fermentation. The results show that under the condition of HRT 3.6 d, the organic loading rate for 4.40kgVS/m³•d, the pH of acidogenic phase should be controlled in the scale of 4.0～4.5, the acidogenic phase could stable at the ethanol-type fermentation stage after the experiment lasting for 22d, the contractions of outlet sludge in VFA reached 3820～3980mg/L, in which the sum of ethanol and acetic could reach more than 72% VFA, the specific hydrogen production of acidogenic phase in this condition achieved 0.018 L•H²/g•VS.

Abstract: Using coagulation sedimentation process in the advanced treatment of urban secondary effluent which can be recycled to circulating cooling water system in power plant is only perform well on turbidity removal. But the concentrations of organic matter and NH₃ in effluent can not meet the requirements of circulating cooling water. Therefore, the feasibility of biological aerated filter (BAF) as a pretreatment enhancing coagulation sedimentation process was studied. The results show that the BAF pretreatment removes NH₃ effectively, and the turbidity and COD_Cr of effluent of BAF-coagulation sedimentation process is much lower than individual coagulation sedimentation process. The final effluent qualities meet the requirements of circulating cooling water system in power plant.

Abstract: Workmen for the wastewater treatment advocated wastewater reusing in the conference which the technically development and strategic research of China are main topic.Biofilter is useful as tertiary biofilm reacter.However, it often accrues clogging during cold period and needs frequent backwashing. Backblowing and partial backwashing can slow it. The average flux rised from 2.65 m³/m².h to 2.84 m³/m².h. The removal of NH₃-N of cocurrent-flow and counter-flow biofilter can be improved. The parameter of partial backwashing depended on the rate of expanding.of counter-flow biofilter.The effect of different backblowing parameters on flux of cocurrent-flow biofilter would be described in this paper. From the parameters studied the bioifiltration time is the most important factor affecting the flux. The results show that the best flux is obtained when backblowing was made for 60s every 12h during 72h where the air pressure was 63 m³/m².h and water pressure was 25.2 m³/m².h.

Abstract: Stratified rock mass is widely existing in tunnel engineering. The most relevant feature of stratified rocks is the occurrence of very persistent bedding, which makes the rock-mass highly non-isotropic. A number of techniques for designing underground excavations in stratified media have been described in the literature, like theoretical method and laboratory test, which can only be applied in analyzing the problem with simple geometry and costs much expense. Recently, with rapid development of computer technique, numerical simulation methods have been widely applied in engineerin. Among all the numerical simulation methods, fast lagrangian explicit finite difference code of continua (FLAC3D) is widely used to solve practical problems, especially in field of elasto-plastic characteristic, large deformation analysis and construction procedure. So in the present paper, numerical simulation for the failure mode of stratified rock mass after tunnel excavation is done by FLAC3D, which can give further guidance to understand the anisotropic characteristic of stratified rock mass.

Abstract: Methylmercury (MeHg) production from inorganic mercury in natural environment leads to bioaccumulation in fish, putting human being under the risk of exposure. This study investigated the transformation of enriched stable isotope tracer, ¹⁹⁹Hg²⁺, in sediment slurry of the Florida Everglades. Incubation experiments were conducted under four different laboratory conditions. The results suggest that methylation of mercury mainly happened under anaerobic condition, with microbial activity playing the major role. The relative methylation rate was determined to be 1% per day at the first few days, and then this transformation process slowed down. At the end of incubation experiment, totally around 20% of the isotope tracer ¹⁹⁹Hg²⁺ was transformed to its methylated form, Me¹⁹⁹Hg. This high potential of mercury methylation partially accounts for the contamination and bioaccumulation of MeHg in the relatively pristine Florida Everglades ecosystem.

Abstract: Hwang et al. showed that the Chien et al.'s partially blind signature scheme based on RSA public cryptosystem could not meet the untraceability property of a blind signature. Wen et al. and Wu et al. claimed that Hwang et al.'s attack is incorrect. Later, Fang et al. gave an improvement to against Hwang et al.'s method. In this paper, we pointed out some typographical errors in Wen et al. and Wu et al.'s article; and certained their claims are correction. Thus, the Fang et al. improved scheme may not becomes to be necessary. Chien et al.'s partially blind signature scheme is still satisfy the untraceability property.

Abstract: This paper takes the urban sewage as treatment target, analyses chemical phosphorous removal effect of PFS, PAC, PAFSI, PAFC and the PAFC which is used by Wu Family Village sewage treatment plant. Taking into consideration of the economic factors in actual operation, the author proposed that the PAFC used by Wu Family Village sewage treatment plant should be served as a chemical auxiliary medicament, under β ≤ 4.33 conditions, β values and effluent TP concentration showed a good correlation. In this paper, the mixing intensity, mixing time, dosage and pH are treated as mainly investigate factors, the four factors and three levels orthogonal test is established. The flocculation conditions of best treatment effect on the effluent TP are as follows: mixing intensity is 200 r/min, stirring time is 90s , dosage is 220 mg / L and pH is 6.CLC number: X703.5

Abstract: This paper studied Beijing sanitary wastewater and investigated phosphorus removal effect and related factors under PFS and polyacrylamide (PAM) synergistic effect. The results show that the effect of phosphorus removal would be improved to a certain extent when the PFS combined with the PAM. The optimum dosage of PAM, the best mixing intensity and time, and the best pH are all defined and the order of coagulation influencing factors is: stirring intensity> pH> stirring time> dosage.