Laminated carbon fiber clothes were infiltrated to prepare carbon fiber reinforced pyrolytic carbon （C/C） using isothermal chemical vapor infiltration （CVI）. The bending fatigue behavior of the infiltrated C/C com...Laminated carbon fiber clothes were infiltrated to prepare carbon fiber reinforced pyrolytic carbon （C/C） using isothermal chemical vapor infiltration （CVI）. The bending fatigue behavior of the infiltrated C/C composites was tested under two different stress levels. The residual strength and modulus of all fatigued samples were tested to investigate the effect of maximum stress level on fatigue behavior of C/C composites. The microstructure and damage mechanism were also investigated. The results showed that the residual strength and modulus of fatigued samples were improved. High stress level is more effective to increase the modulus. And for the increase of flexural strength, high stress level is more effective only in low cycles. The fatigue loading weakens the bonding between the matrix and fiber, and then affects the damage propagation pathway, and increases the energy consumption. So the properties of C/C composites are improved.展开更多
Activated carbon(AC) was prepared from surplus sludge using chemical activation method with the assistance of ZnCl2. The influences of process parameters on the AC's specific surface area and adsorption capacity f...Activated carbon(AC) was prepared from surplus sludge using chemical activation method with the assistance of ZnCl2. The influences of process parameters on the AC's specific surface area and adsorption capacity for Pb2+ were examined to optimize these parameters. The optimal conditions for the preparation of AC were determined to be activation temperature of 500 °C, activation time of 1 h, impregnation ratio of 1:1(solid-to-liquid volume) with the 30% ZnCl2 solution(mass fraction), giving the BET surface area of 393.85 m2/g and yield of 30.14% with 33.45% ash. Also, the pyrolysis temperature was found to be the most important parameter in chemical activation. FTIR spectra provided the evidence of some surface structures such as C=C and C—O—C. In the adsorption studies, a rise in solution pH led to a significant increase in adsorption capacity when the pH value varied from 3.0 to 7.0, and the optimal pH for removal of Pb2+ was 7.0. It was observed that the pseudo-second-order equation provided better correlation for the adsorption rate than the pseudo-first-order and the Langmuir model fitted better than the Freundlich model for adsorption isotherm. The adsorption capacity of AC to Pb2+ was 11.75 mg/L at solution pH 7.0, the equilibrium time 480 min and 25 °C. Moreover, the adsorption process is endothermic according to the value of enthalpy change.展开更多
In order to enhance the efficiency of aerobic digestion, the excess sludge was irradiated by low intensity ultrasound at a frequency of 28 kHz and acoustic intensity of 0.53 W/cm^2. The results show that the sludge st...In order to enhance the efficiency of aerobic digestion, the excess sludge was irradiated by low intensity ultrasound at a frequency of 28 kHz and acoustic intensity of 0.53 W/cm^2. The results show that the sludge stabilization without ultrasonic treatment can be achieved after 17 d of digestion, whereas the digestion time of ultrasonic groups can be cut by 3-7 d. During the same digestion elapsing, in ultrasonic groups the total volatile suspended solid removal rate is higher than that in the control group. The kinetics of aerobic digestion of excess sludge with ultrasound can also be described with first-order reaction.展开更多
The Longyangxia Gorge Key Water Control System is the first of the stairstep power sations along the Longyangxi-a-Qingtongxia river section. It has been playing an very important role in providing power, protecting fl...The Longyangxia Gorge Key Water Control System is the first of the stairstep power sations along the Longyangxi-a-Qingtongxia river section. It has been playing an very important role in providing power, protecting flood and ice run supplying and irrigation etc. in the northwestern China. Therefore, the study on trend prediction, variation on the flow into the Longyangxia Reservoir are of the great social and economic benefits. In the medium-and-long-range runoff forecast, all kinds of regression equation are often used for predicting future hydrologic regime. However, these regression models aren’t appropriate to super long -range runoff forecast because of the restricting on weather data and so on. So a new super long-range runoff forecast model don’t depend on Reai-time weather data and called “Period correcting for residual error series GM (1, 1) model” is presented based on analyzing for the relational hydrologic data and the variation on the flow into the Longyangxia Reservoir, and the forecast model was applied successfully to predict the recent and super long -term trends of the flow into the Longyangxia Reservoir. The results indicate that the annual flow into the Longyangxia Reservoir is in the ending minimum period of the runoff history. The runoff increasing is expected in for the coming years.展开更多
基金Projects(50832004,51105132)supported by the National Natural Science Foundation of ChinaProject(B08040)supported by Program of Introducing Talents of Discipline to Universities,China
文摘Laminated carbon fiber clothes were infiltrated to prepare carbon fiber reinforced pyrolytic carbon （C/C） using isothermal chemical vapor infiltration （CVI）. The bending fatigue behavior of the infiltrated C/C composites was tested under two different stress levels. The residual strength and modulus of all fatigued samples were tested to investigate the effect of maximum stress level on fatigue behavior of C/C composites. The microstructure and damage mechanism were also investigated. The results showed that the residual strength and modulus of fatigued samples were improved. High stress level is more effective to increase the modulus. And for the increase of flexural strength, high stress level is more effective only in low cycles. The fatigue loading weakens the bonding between the matrix and fiber, and then affects the damage propagation pathway, and increases the energy consumption. So the properties of C/C composites are improved.
基金Project supported by the Open Fund of State Key Laboratory of Photocatalysis,China
文摘Activated carbon(AC) was prepared from surplus sludge using chemical activation method with the assistance of ZnCl2. The influences of process parameters on the AC's specific surface area and adsorption capacity for Pb2+ were examined to optimize these parameters. The optimal conditions for the preparation of AC were determined to be activation temperature of 500 °C, activation time of 1 h, impregnation ratio of 1:1(solid-to-liquid volume) with the 30% ZnCl2 solution(mass fraction), giving the BET surface area of 393.85 m2/g and yield of 30.14% with 33.45% ash. Also, the pyrolysis temperature was found to be the most important parameter in chemical activation. FTIR spectra provided the evidence of some surface structures such as C=C and C—O—C. In the adsorption studies, a rise in solution pH led to a significant increase in adsorption capacity when the pH value varied from 3.0 to 7.0, and the optimal pH for removal of Pb2+ was 7.0. It was observed that the pseudo-second-order equation provided better correlation for the adsorption rate than the pseudo-first-order and the Langmuir model fitted better than the Freundlich model for adsorption isotherm. The adsorption capacity of AC to Pb2+ was 11.75 mg/L at solution pH 7.0, the equilibrium time 480 min and 25 °C. Moreover, the adsorption process is endothermic according to the value of enthalpy change.
文摘In order to enhance the efficiency of aerobic digestion, the excess sludge was irradiated by low intensity ultrasound at a frequency of 28 kHz and acoustic intensity of 0.53 W/cm^2. The results show that the sludge stabilization without ultrasonic treatment can be achieved after 17 d of digestion, whereas the digestion time of ultrasonic groups can be cut by 3-7 d. During the same digestion elapsing, in ultrasonic groups the total volatile suspended solid removal rate is higher than that in the control group. The kinetics of aerobic digestion of excess sludge with ultrasound can also be described with first-order reaction.
基金Ninth-Five-Year"Key Project of the State Science and Technology Commission (96-912-01-02-05 ) and National NaturalScience Fou
文摘The Longyangxia Gorge Key Water Control System is the first of the stairstep power sations along the Longyangxi-a-Qingtongxia river section. It has been playing an very important role in providing power, protecting flood and ice run supplying and irrigation etc. in the northwestern China. Therefore, the study on trend prediction, variation on the flow into the Longyangxia Reservoir are of the great social and economic benefits. In the medium-and-long-range runoff forecast, all kinds of regression equation are often used for predicting future hydrologic regime. However, these regression models aren’t appropriate to super long -range runoff forecast because of the restricting on weather data and so on. So a new super long-range runoff forecast model don’t depend on Reai-time weather data and called “Period correcting for residual error series GM (1, 1) model” is presented based on analyzing for the relational hydrologic data and the variation on the flow into the Longyangxia Reservoir, and the forecast model was applied successfully to predict the recent and super long -term trends of the flow into the Longyangxia Reservoir. The results indicate that the annual flow into the Longyangxia Reservoir is in the ending minimum period of the runoff history. The runoff increasing is expected in for the coming years.
