Tungsten copper and molybdenum copper composites, with weight percent copper in the range of 20% - 40%, have been produced using the spark plasma sintering (SPS) technique. Other specimens having similar compositions ...Tungsten copper and molybdenum copper composites, with weight percent copper in the range of 20% - 40%, have been produced using the spark plasma sintering (SPS) technique. Other specimens having similar compositions were also developed using the conventional techniques of Liquid Phase Sintering (LPS) and Infiltration. Electrical conductivity measurements showed that the specimens produced by the SPS process had substantially higher levels of electrical conductivity than those produced by the other methods. Relative density measurements showed that the SPS specimens achieved very high densification, with relative densities in the range of 99.1% - 100%. On the other hand, the specimens produced by LPS and infiltration had relative densities in the range of 88% - 92% and 96% - 98% respectively. The superior conductivity of the SPS specimens has been attributed to the virtually full densification achieved by the process. The effect of porosity on electrical conductivity has been discussed and three standard models were assessed using results from porous sintered skeletons of pure tungsten and pure molybdenum.展开更多
The degradation rate of Volatile Fatty Acids (VFAs) produced predominantly in the acidogenesis stage is a key process parameter to be optimised to ensure a successful Anaerobic digestion (AD). Thermodynamically, the o...The degradation rate of Volatile Fatty Acids (VFAs) produced predominantly in the acidogenesis stage is a key process parameter to be optimised to ensure a successful Anaerobic digestion (AD). Thermodynamically, the oxidation of the VFAs are energetically unfavourable, and as such external energy source apart from the energy derived from the hydrolysis of Adenosine Triphosphate (ATP) is needed for the initial activation of the VFAs, initial growth of the methanogens in AD process and improved degradation rate of the VFAs. Thus, this research investigated the influence of polyphosphate hydrolysis on the degradation rate of the VFAs at high concentration. Sodium-propionate, Sodium-butyrate and Sodium-acetate salts were added at the start of experiments in order to increase the concentration of the VFAs. The polyphosphate salts used were;Na-hexametaphosphate, Na-tripolyphosphate and potassium pyrophosphate. The control experiment was polyphosphate free and three process parameters (degradation rate, cumulative biogas production and specific methane content) of anaerobic digestion were investigated. The experiments were carried out at a mesophilic temperature of 37.5°C for 41 days. The results of the investigation showed that the treated reactors with the polyphosphate salt solution in low concentration performed better than the reactors with high concentration of the polyphosphate salts solution. All the treated reactors with poly-P salts performed better than reactor Nr-9 (control experiment), but reactor Nr-1 was outstanding with an improved degradation rate of 47%, cumulative biogas production of 21% and specific methane content of 23%.展开更多
The optimization and kinetics of glucose production via enzymatic hydrolysis of mixed peels were carried out.The substrate was characterized using proximate analysis and hydrolysis.The process was optimized using resp...The optimization and kinetics of glucose production via enzymatic hydrolysis of mixed peels were carried out.The substrate was characterized using proximate analysis and hydrolysis.The process was optimized using response surface methodology while the kinetics of the hydrolysis was studied using Michealis-menten model.The results obtained showed that the mixed peels have high hemicellulose content,hydrolysable carbohydrate and cellulose.The optimum conditions for glucose yield of 79%by enzymatic hydrolysis are temperature of 36℃,time of five days,pH of 4.55 and enzyme dosage of 0.428 g/50 mL.Enzymatic hydrolysis obeyed Michealis-Menten kinetic model with spontaneous and feasible reactions.Therefore,the results have proved that mixed peels(cassava and potato peels)is a good substrate for glucose production and study of other waste peels as feed-stock is recommended.展开更多
In this study,response surface methodology(RSM)and artificial neural network(ANN)were used to optimize Terminalia catappa L.kernel oil(TCKO)yield.Solvent extraction method was used for the oil extraction,with n-hexane...In this study,response surface methodology(RSM)and artificial neural network(ANN)were used to optimize Terminalia catappa L.kernel oil(TCKO)yield.Solvent extraction method was used for the oil extraction,with n-hexane as the extracting solvent.The highest oil yield was obtained at 55℃,150 min,and 0.5 mm.The physicochemical properties of the TCKO were determined using standard methods.Gas chromatographic(GC)analysis and Fourier Transform Infrared(FTIR)were respectively,used to determine the fatty acid composition and prevalent functional groups in TCKO.At optimum conditions of temperature,particle size and extraction time,the RSM predicted oil yield was 62.92%,which was validated as 60.34%,whereas ANN predicted yield was 60.39%,which was validated as 60.40%.The results of the physicochemical characterization of TCKO showed that the dielectric strength(DS),viscosity,flash and pour points values were 30.61 KV,20.29 mm^2 s^−1,260°C,and 3℃,respectively.Physicochemical characterization and FTIR results of TCKOindicated its potential industrial application,especially as transformer fluid.Fatty acids compositions result indicated that the oil was highly unsaturated;while XRD results of Terminalia catappa L.kernel(TCK)samples obtained,both before and after extraction,showed difference in their peaks and corresponding intensities,due to the damage effect of solvent.Finally,the obtained optimization results indicated that ANN was a better and more effective tool than RSM,due to its higher R^2 and lower RMS values.展开更多
文摘Tungsten copper and molybdenum copper composites, with weight percent copper in the range of 20% - 40%, have been produced using the spark plasma sintering (SPS) technique. Other specimens having similar compositions were also developed using the conventional techniques of Liquid Phase Sintering (LPS) and Infiltration. Electrical conductivity measurements showed that the specimens produced by the SPS process had substantially higher levels of electrical conductivity than those produced by the other methods. Relative density measurements showed that the SPS specimens achieved very high densification, with relative densities in the range of 99.1% - 100%. On the other hand, the specimens produced by LPS and infiltration had relative densities in the range of 88% - 92% and 96% - 98% respectively. The superior conductivity of the SPS specimens has been attributed to the virtually full densification achieved by the process. The effect of porosity on electrical conductivity has been discussed and three standard models were assessed using results from porous sintered skeletons of pure tungsten and pure molybdenum.
文摘The degradation rate of Volatile Fatty Acids (VFAs) produced predominantly in the acidogenesis stage is a key process parameter to be optimised to ensure a successful Anaerobic digestion (AD). Thermodynamically, the oxidation of the VFAs are energetically unfavourable, and as such external energy source apart from the energy derived from the hydrolysis of Adenosine Triphosphate (ATP) is needed for the initial activation of the VFAs, initial growth of the methanogens in AD process and improved degradation rate of the VFAs. Thus, this research investigated the influence of polyphosphate hydrolysis on the degradation rate of the VFAs at high concentration. Sodium-propionate, Sodium-butyrate and Sodium-acetate salts were added at the start of experiments in order to increase the concentration of the VFAs. The polyphosphate salts used were;Na-hexametaphosphate, Na-tripolyphosphate and potassium pyrophosphate. The control experiment was polyphosphate free and three process parameters (degradation rate, cumulative biogas production and specific methane content) of anaerobic digestion were investigated. The experiments were carried out at a mesophilic temperature of 37.5°C for 41 days. The results of the investigation showed that the treated reactors with the polyphosphate salt solution in low concentration performed better than the reactors with high concentration of the polyphosphate salts solution. All the treated reactors with poly-P salts performed better than reactor Nr-9 (control experiment), but reactor Nr-1 was outstanding with an improved degradation rate of 47%, cumulative biogas production of 21% and specific methane content of 23%.
文摘The optimization and kinetics of glucose production via enzymatic hydrolysis of mixed peels were carried out.The substrate was characterized using proximate analysis and hydrolysis.The process was optimized using response surface methodology while the kinetics of the hydrolysis was studied using Michealis-menten model.The results obtained showed that the mixed peels have high hemicellulose content,hydrolysable carbohydrate and cellulose.The optimum conditions for glucose yield of 79%by enzymatic hydrolysis are temperature of 36℃,time of five days,pH of 4.55 and enzyme dosage of 0.428 g/50 mL.Enzymatic hydrolysis obeyed Michealis-Menten kinetic model with spontaneous and feasible reactions.Therefore,the results have proved that mixed peels(cassava and potato peels)is a good substrate for glucose production and study of other waste peels as feed-stock is recommended.
文摘In this study,response surface methodology(RSM)and artificial neural network(ANN)were used to optimize Terminalia catappa L.kernel oil(TCKO)yield.Solvent extraction method was used for the oil extraction,with n-hexane as the extracting solvent.The highest oil yield was obtained at 55℃,150 min,and 0.5 mm.The physicochemical properties of the TCKO were determined using standard methods.Gas chromatographic(GC)analysis and Fourier Transform Infrared(FTIR)were respectively,used to determine the fatty acid composition and prevalent functional groups in TCKO.At optimum conditions of temperature,particle size and extraction time,the RSM predicted oil yield was 62.92%,which was validated as 60.34%,whereas ANN predicted yield was 60.39%,which was validated as 60.40%.The results of the physicochemical characterization of TCKO showed that the dielectric strength(DS),viscosity,flash and pour points values were 30.61 KV,20.29 mm^2 s^−1,260°C,and 3℃,respectively.Physicochemical characterization and FTIR results of TCKOindicated its potential industrial application,especially as transformer fluid.Fatty acids compositions result indicated that the oil was highly unsaturated;while XRD results of Terminalia catappa L.kernel(TCK)samples obtained,both before and after extraction,showed difference in their peaks and corresponding intensities,due to the damage effect of solvent.Finally,the obtained optimization results indicated that ANN was a better and more effective tool than RSM,due to its higher R^2 and lower RMS values.
