Influence of silicon oxide(SiO_2) and aluminum oxide(Al_2O_3) nanoparticles on the stability of nanoparticles and sodium dodecyl sulfate(SDS) mixed solution foams was studied at bulk and bubble-scale. Foam apparent vi...Influence of silicon oxide(SiO_2) and aluminum oxide(Al_2O_3) nanoparticles on the stability of nanoparticles and sodium dodecyl sulfate(SDS) mixed solution foams was studied at bulk and bubble-scale. Foam apparent viscosity was also determined in Hele-Shaw cell In order to investigate the foam performance at static and dynamic conditions. Results show that the maximum adsorption of surfactant on the nanoparticles occurs at 3 wt% surfactant concentration. Foam stability increases while the foamability decreases with the increasing nanoparticle concentration. However, optimum nanoparticle concentration corresponding to maximum foam stability was obtained at 1.0 wt% nanoparticle concentration for the hydrophilic SiO_2/SDS and Al_2O_3/SDS foams. Foam performance was enhanced with increasing nanoparticles hydrophobicity. Air-foams were generally more stable than CO_2 foams.Foam apparent viscosity increased in the presence of nanoparticles from 20.34 mPa·s to 84.84 mPa·s while the film thickness increased from 27.5 μm to 136 μm. This study suggests that the static and dynamic stability of conventional foams could be improved with addition of appropriate concentration of nanoparticles into the surfactant solution. The nanoparticles improve foam stability by their adsorption and aggregation at the foam lamellae to increase film thickness and dilational viscoelasticity. This prevents liquid drainage and film thinning and improves foam stability both at the bulk and bubble scale.展开更多
The problem of stabilizing a class of large-scale non-linear multiple delay systems is considered.The complicated system is decomposed into several subsystems; each function of them is expressed by a set of components...The problem of stabilizing a class of large-scale non-linear multiple delay systems is considered.The complicated system is decomposed into several subsystems; each function of them is expressed by a set of components of the overall state vector,with interconnections between them, and the subsystems are coupled by the delayed state. In this paper, a method is devised to be a suitable choice of state feedback controls of every subsystems, moreover, it is proved that the large-scale system is exponential stable.展开更多
Understanding how population sizes vary over time is a key aspect of ecological research. Unfortunately, our under- standing of population dynamics has historically been based on an assumption that individuals are ide...Understanding how population sizes vary over time is a key aspect of ecological research. Unfortunately, our under- standing of population dynamics has historically been based on an assumption that individuals are identical with homogenous life-history properties. This assumption is certainly false for most natural systems, raising the question of what role individual variation plays in the dynamics of populations. While there has been an increase of interest regarding the effects of within popula- tion variation on the dynamics of single populations, there has been little study of the effects of differences in within population variation on patterns observed across populations. We found that life-history differences （clutch size） among individuals ex- plained the majority of the variation observed in the degree to which population sizes of eastern fence lizards Sceloporus undula- tus fluctuated. This finding suggests that differences across populations cannot be understood without an examination of differences at the level of a system rather than at the level of the individual展开更多
基金the Ministry of Higher Education(Vot no.Q.J130000.2542.08H61)Universiti Teknologi(UTM)Malaysia,for supporting this research through research management grant
文摘Influence of silicon oxide(SiO_2) and aluminum oxide(Al_2O_3) nanoparticles on the stability of nanoparticles and sodium dodecyl sulfate(SDS) mixed solution foams was studied at bulk and bubble-scale. Foam apparent viscosity was also determined in Hele-Shaw cell In order to investigate the foam performance at static and dynamic conditions. Results show that the maximum adsorption of surfactant on the nanoparticles occurs at 3 wt% surfactant concentration. Foam stability increases while the foamability decreases with the increasing nanoparticle concentration. However, optimum nanoparticle concentration corresponding to maximum foam stability was obtained at 1.0 wt% nanoparticle concentration for the hydrophilic SiO_2/SDS and Al_2O_3/SDS foams. Foam performance was enhanced with increasing nanoparticles hydrophobicity. Air-foams were generally more stable than CO_2 foams.Foam apparent viscosity increased in the presence of nanoparticles from 20.34 mPa·s to 84.84 mPa·s while the film thickness increased from 27.5 μm to 136 μm. This study suggests that the static and dynamic stability of conventional foams could be improved with addition of appropriate concentration of nanoparticles into the surfactant solution. The nanoparticles improve foam stability by their adsorption and aggregation at the foam lamellae to increase film thickness and dilational viscoelasticity. This prevents liquid drainage and film thinning and improves foam stability both at the bulk and bubble scale.
文摘The problem of stabilizing a class of large-scale non-linear multiple delay systems is considered.The complicated system is decomposed into several subsystems; each function of them is expressed by a set of components of the overall state vector,with interconnections between them, and the subsystems are coupled by the delayed state. In this paper, a method is devised to be a suitable choice of state feedback controls of every subsystems, moreover, it is proved that the large-scale system is exponential stable.
文摘Understanding how population sizes vary over time is a key aspect of ecological research. Unfortunately, our under- standing of population dynamics has historically been based on an assumption that individuals are identical with homogenous life-history properties. This assumption is certainly false for most natural systems, raising the question of what role individual variation plays in the dynamics of populations. While there has been an increase of interest regarding the effects of within popula- tion variation on the dynamics of single populations, there has been little study of the effects of differences in within population variation on patterns observed across populations. We found that life-history differences （clutch size） among individuals ex- plained the majority of the variation observed in the degree to which population sizes of eastern fence lizards Sceloporus undula- tus fluctuated. This finding suggests that differences across populations cannot be understood without an examination of differences at the level of a system rather than at the level of the individual
