The paper explores the gravity-driven flow of the thin film of a viscoelastic-fluid-based nanofluids(VFBN)along an inclined plane under non-isothermal conditions and subjected to convective cooling at the free-surface...The paper explores the gravity-driven flow of the thin film of a viscoelastic-fluid-based nanofluids(VFBN)along an inclined plane under non-isothermal conditions and subjected to convective cooling at the free-surface.The Newton’s law of cooling is used to model the convective heat-exchange with the ambient at the free-surface.The Giesekus viscoelastic constitutive model,with appropriate modifications to account for non-isothermal effects,is employed to describe the polymeric effects.The unsteady and coupled non-linear partial differential equations(PDEs)describing the model problem are obtained and solved via efficient semi-implicit numerical schemes based on finite difference methods(FDM)implemented in Matlab.The response of the VFBN velocity,temperature,thermal-conductivity and polymeric-stresses to variations in the volume-fraction of embedded nanoparticles is investigated.It is shown that these quantities all increase as the nanoparticle volume-fraction becomes higher.展开更多
The use of coconut shell particulates to enhance the insulating refractory properties of Ukpor, Osiele and Kankara fireclays in Nigeria was studied in this paper. The chemical analysis of the raw materials was conduct...The use of coconut shell particulates to enhance the insulating refractory properties of Ukpor, Osiele and Kankara fireclays in Nigeria was studied in this paper. The chemical analysis of the raw materials was conducted using Atomic Absorption spectrometer. The samples used for different tests were prepared by mixing the clay, bentonite and coconut shell, of grain sizes of 212 - 600 μm. The prepared samples were air and oven dried for 24 hours at room temperature and at 110°C respectively. The samples were then fired at different temperatures in the range of 950°C to 1200°C at 50°C interval and at 2.5°C/min. The fired samples were investigated for their physical, insulating (thermal) and mechanical properties. Micro-structural examination was also carried out. The results indicate that clays with 25 wt% - 30 wt% coconut shell and grain sizes of 212 - 300 μm fired at 1150°C - 1200°C possess enhanced mechanical, physical and insulating (thermal) properties. The SEM micrograph revealed the formation of mullite phase in the bricks fired at 1150°C. Thus, high quality refractory bricks with enhanced insulating properties could be produced from Ukpor, Osiele and Kankara fire-clays blended with coconut shell particulates.展开更多
Porous titanium is produced by thepowder metallurgy method. Dependence of the electrical conductivity on the porosity and pore size is investigated and the experimental results are compared with a number of models. It...Porous titanium is produced by thepowder metallurgy method. Dependence of the electrical conductivity on the porosity and pore size is investigated and the experimental results are compared with a number of models. It is found that the minimum solid area model could be successfully applied to describe the relationship between the electrical conductivity and the porosity of porous titanium. This kind of conductivity increases with increasing pore sizes.展开更多
The process of heat conduction in one-dimensional dimerized systems is studied by means of numerical simulation. Taking into account the difference between the strong bond and the weak one of the systems, our calculat...The process of heat conduction in one-dimensional dimerized systems is studied by means of numerical simulation. Taking into account the difference between the strong bond and the weak one of the systems, our calculation indicates that heat conduction in the lattice is anomalous. For the typical parameter related to a real physical system, the divergent exponent is shown to be in agreement with that predicted by the mode-coupling theory. Moreover, our study shows that the homogeneous chain is the best thermal conductor.展开更多
Influences of the carrier concentration and mobility of heavily doped n-type Si80 Ge20 alloys on the thermoelectrical power factor are investigated. The experimental results indicate that thermoeleetrieal power factor...Influences of the carrier concentration and mobility of heavily doped n-type Si80 Ge20 alloys on the thermoelectrical power factor are investigated. The experimental results indicate that thermoeleetrieal power factors of 32- 36μWem-1K^-2 eouM be consistently achieved with carrier concentrations of 2.1-2.9 × 10^20cm^-3 and carrier mobilities of 36-40 cm^2 V^-1s^-1. However, many samples with suitable carrier concentrations do not always have high mobilities and high power factors. Some possible explanations for this behaviour are discussed.展开更多
文摘The paper explores the gravity-driven flow of the thin film of a viscoelastic-fluid-based nanofluids(VFBN)along an inclined plane under non-isothermal conditions and subjected to convective cooling at the free-surface.The Newton’s law of cooling is used to model the convective heat-exchange with the ambient at the free-surface.The Giesekus viscoelastic constitutive model,with appropriate modifications to account for non-isothermal effects,is employed to describe the polymeric effects.The unsteady and coupled non-linear partial differential equations(PDEs)describing the model problem are obtained and solved via efficient semi-implicit numerical schemes based on finite difference methods(FDM)implemented in Matlab.The response of the VFBN velocity,temperature,thermal-conductivity and polymeric-stresses to variations in the volume-fraction of embedded nanoparticles is investigated.It is shown that these quantities all increase as the nanoparticle volume-fraction becomes higher.
文摘The use of coconut shell particulates to enhance the insulating refractory properties of Ukpor, Osiele and Kankara fireclays in Nigeria was studied in this paper. The chemical analysis of the raw materials was conducted using Atomic Absorption spectrometer. The samples used for different tests were prepared by mixing the clay, bentonite and coconut shell, of grain sizes of 212 - 600 μm. The prepared samples were air and oven dried for 24 hours at room temperature and at 110°C respectively. The samples were then fired at different temperatures in the range of 950°C to 1200°C at 50°C interval and at 2.5°C/min. The fired samples were investigated for their physical, insulating (thermal) and mechanical properties. Micro-structural examination was also carried out. The results indicate that clays with 25 wt% - 30 wt% coconut shell and grain sizes of 212 - 300 μm fired at 1150°C - 1200°C possess enhanced mechanical, physical and insulating (thermal) properties. The SEM micrograph revealed the formation of mullite phase in the bricks fired at 1150°C. Thus, high quality refractory bricks with enhanced insulating properties could be produced from Ukpor, Osiele and Kankara fire-clays blended with coconut shell particulates.
基金Supported by the National Natural Science Foundation of China under Grant No 10374089, and the Knowledge Innovation Program of Chinese Academy of Sciences under Grant No KJCX2-SW-W17.
文摘Porous titanium is produced by thepowder metallurgy method. Dependence of the electrical conductivity on the porosity and pore size is investigated and the experimental results are compared with a number of models. It is found that the minimum solid area model could be successfully applied to describe the relationship between the electrical conductivity and the porosity of porous titanium. This kind of conductivity increases with increasing pore sizes.
文摘The process of heat conduction in one-dimensional dimerized systems is studied by means of numerical simulation. Taking into account the difference between the strong bond and the weak one of the systems, our calculation indicates that heat conduction in the lattice is anomalous. For the typical parameter related to a real physical system, the divergent exponent is shown to be in agreement with that predicted by the mode-coupling theory. Moreover, our study shows that the homogeneous chain is the best thermal conductor.
基金Supported by the National Natural Science Foundation of China under Grant No 60176004, and the Hi-Tech Research and Development Programme of China under Grant No 2002AA302406.
文摘Influences of the carrier concentration and mobility of heavily doped n-type Si80 Ge20 alloys on the thermoelectrical power factor are investigated. The experimental results indicate that thermoeleetrieal power factors of 32- 36μWem-1K^-2 eouM be consistently achieved with carrier concentrations of 2.1-2.9 × 10^20cm^-3 and carrier mobilities of 36-40 cm^2 V^-1s^-1. However, many samples with suitable carrier concentrations do not always have high mobilities and high power factors. Some possible explanations for this behaviour are discussed.
