Whilst methods exist to indirectly measure the effects of increased flow or gastro-oesophageal refluxing, they cannot quantitatively measure the amount of acid travelling back up into the oesophagus during reflux, nor...Whilst methods exist to indirectly measure the effects of increased flow or gastro-oesophageal refluxing, they cannot quantitatively measure the amount of acid travelling back up into the oesophagus during reflux, nor can they indicate the flow rate through the oesophagogastric junction (OGJ). Since OGJ dysfunction affects flow it seems most appropriate to describe the geometry of the OGJ and its effect on the flow. A device known as the functional lumen imaging probe (FLIP) has been shown to reliably measure the geometry of and pressure changes in the OGJ. FLIP cannot directly measure flow but the data gathered from the probe can be used to model flow through the junction by using computational flow dynamics (CFD). CFD uses a set of equations known as the Navier-Stokes equations to predict flow patterns and is a technique widely used in engineering. These equations are complex and require appropriate assumptions to provide simplifications before useful data can be obtained. With the assumption that the cross-sectional areas obtained via FLIP are circular, the radii of these circles can be obtained. A cubic interpolation scheme can then be applied to give a high-resolution geometry for the OGJ. In the case of modelling a reflux scenario, it can be seen that at the narrowest section a jet of fluid squirts into the oesophagus at a higher velocity than the fluid surrounding it. This jet has a maximum velocity of almost 2 ms-1 that occurs where the OGJ is at its narrowest. This simple prediction of acid ‘squirting’ into the oesophagusillustrates how the use of numerical methods can be used to develop a better understanding of the OGJ. This initial work using CFD shows some considerable promise for the future.展开更多
Based on the steady-state strain measured by single-pass hot compression tests,the method by a double-pass hot compression testing was developed to measure the metadynamic-recrystallization kinetics.The metadynamic re...Based on the steady-state strain measured by single-pass hot compression tests,the method by a double-pass hot compression testing was developed to measure the metadynamic-recrystallization kinetics.The metadynamic recrystallization behavior of low-alloy steel Q345B during hot compression deformation was investigated in the temperature range of 1 000-1 100℃,the strain rate range of 0.01-0.10 s -1 and the interpass time range of 0.5-50 s on a Gleeble-3500 thermo-simulation machine.The results show that metadynamic recrystallization during the interpass time can be observed.As the deformation temperature and strain rate increase,softening caused by metadynamic recrystallization is obvious.According to the data of thermo-simulation,the metadynamic recrystallization activation energy is obtained to be Qmd=100.674 kJ/mol and metadynamic recrystallization kinetics model is set up.Finally,the error analysis of metadynamic recrystallization kinetics model proves that the model has high accuracy(correlation coefficient R=0.988 6).展开更多
After analyzing the working condition of the conventional diesel forklift,an energy recovery system in hybrid forklift is considered and its simulation model is built.Then,the control strategy for the proposed energy ...After analyzing the working condition of the conventional diesel forklift,an energy recovery system in hybrid forklift is considered and its simulation model is built.Then,the control strategy for the proposed energy recovery system is discussed,which is validated and evaluated by simulation.The simulation results show that the proposed control strategy can achieve balance of the power and keep the state of charge(SOC) of ultra capacitor in a reasonable range,and the fuel consumption can be reduced by about 20.8% compared with the conventional diesel forklift.Finally,the feasibility of the simulation results is experimentally verified based on the lifting energy recovery system.展开更多
Atomic force micriscope (AFM)-based dip-pen nanolithography (DPN) is an emerging approach for con-structing nanostructures on material surfaces such as gold, silicon and silicon oxide. Although DPN is a powerful tech-...Atomic force micriscope (AFM)-based dip-pen nanolithography (DPN) is an emerging approach for con-structing nanostructures on material surfaces such as gold, silicon and silicon oxide. Although DPN is a powerful tech-nique, it has not shown its ability of direct-writing and pat-terning of nanostructures on surfaces of soft materials, for example biomacromolecules. Direct depositing on soft sur-faces becomes possible with the introduction of a com-bined-dynamic mode DPN rather than mostly used contact mode DPN or tapping mode DPN. In this report, the com-bined dynamic mode DPN is used for direct depositing pro-tein ink on DNA molecules at the nanometer scale.展开更多
In modeling fluidized bed gasification experiments,equilibrium and CFD models are valuable options.The existence of multi-dimensional effects inside the reactor vessel due to the kinetics of the process and the fluid ...In modeling fluidized bed gasification experiments,equilibrium and CFD models are valuable options.The existence of multi-dimensional effects inside the reactor vessel due to the kinetics of the process and the fluid dynamics phenomena could result in deviation from the zero-dimensional assumption.Complex models integrating kinetics and hydrodynamics are being developed by using a computer fluid dynamics(CFD)approach.The objective of this investigation is to assess and compare the adequacy of zero-dimensional and CFD approaches in modeling fluidized bed gasification regarding a semi-industrial scale(numerical results are validated under experimental runs).Results show that the zero-dimensional model based on the approach of dual stage equilibrium performs reasonably well in adequately predicting the product gas composition at different operating conditions and for different feedstocks,although with quantitative discrepancy.Furthermore,the discrepancy depends on the oxygen content of the oxidation agent and on the steam-to biomass ratio decreasing when these parameters increased.CFD models provide deeper information being able to estimate the syngas composition or other operating parameter at any point of space and time.Despite of some quantitative discrepancy,the zero-dimensional modeling approach is deemed satisfactory from the viewpoint of the determining design conditions simulation.展开更多
基金Supported by a Science Foundation Ireland through the ETS Walton Visiting Professor Programme a grant from the Higher Education Authority in Ireland
文摘Whilst methods exist to indirectly measure the effects of increased flow or gastro-oesophageal refluxing, they cannot quantitatively measure the amount of acid travelling back up into the oesophagus during reflux, nor can they indicate the flow rate through the oesophagogastric junction (OGJ). Since OGJ dysfunction affects flow it seems most appropriate to describe the geometry of the OGJ and its effect on the flow. A device known as the functional lumen imaging probe (FLIP) has been shown to reliably measure the geometry of and pressure changes in the OGJ. FLIP cannot directly measure flow but the data gathered from the probe can be used to model flow through the junction by using computational flow dynamics (CFD). CFD uses a set of equations known as the Navier-Stokes equations to predict flow patterns and is a technique widely used in engineering. These equations are complex and require appropriate assumptions to provide simplifications before useful data can be obtained. With the assumption that the cross-sectional areas obtained via FLIP are circular, the radii of these circles can be obtained. A cubic interpolation scheme can then be applied to give a high-resolution geometry for the OGJ. In the case of modelling a reflux scenario, it can be seen that at the narrowest section a jet of fluid squirts into the oesophagus at a higher velocity than the fluid surrounding it. This jet has a maximum velocity of almost 2 ms-1 that occurs where the OGJ is at its narrowest. This simple prediction of acid ‘squirting’ into the oesophagusillustrates how the use of numerical methods can be used to develop a better understanding of the OGJ. This initial work using CFD shows some considerable promise for the future.
基金Project(101048) supported by Fok Ying Tung Education FoundationProject(E2008000835) supported by the Natural Science Foundation of Hebei Province,China
文摘Based on the steady-state strain measured by single-pass hot compression tests,the method by a double-pass hot compression testing was developed to measure the metadynamic-recrystallization kinetics.The metadynamic recrystallization behavior of low-alloy steel Q345B during hot compression deformation was investigated in the temperature range of 1 000-1 100℃,the strain rate range of 0.01-0.10 s -1 and the interpass time range of 0.5-50 s on a Gleeble-3500 thermo-simulation machine.The results show that metadynamic recrystallization during the interpass time can be observed.As the deformation temperature and strain rate increase,softening caused by metadynamic recrystallization is obvious.According to the data of thermo-simulation,the metadynamic recrystallization activation energy is obtained to be Qmd=100.674 kJ/mol and metadynamic recrystallization kinetics model is set up.Finally,the error analysis of metadynamic recrystallization kinetics model proves that the model has high accuracy(correlation coefficient R=0.988 6).
基金Project(2013BAF07B02)supported by National Science and Technology Support Program of China
文摘After analyzing the working condition of the conventional diesel forklift,an energy recovery system in hybrid forklift is considered and its simulation model is built.Then,the control strategy for the proposed energy recovery system is discussed,which is validated and evaluated by simulation.The simulation results show that the proposed control strategy can achieve balance of the power and keep the state of charge(SOC) of ultra capacitor in a reasonable range,and the fuel consumption can be reduced by about 20.8% compared with the conventional diesel forklift.Finally,the feasibility of the simulation results is experimentally verified based on the lifting energy recovery system.
文摘Atomic force micriscope (AFM)-based dip-pen nanolithography (DPN) is an emerging approach for con-structing nanostructures on material surfaces such as gold, silicon and silicon oxide. Although DPN is a powerful tech-nique, it has not shown its ability of direct-writing and pat-terning of nanostructures on surfaces of soft materials, for example biomacromolecules. Direct depositing on soft sur-faces becomes possible with the introduction of a com-bined-dynamic mode DPN rather than mostly used contact mode DPN or tapping mode DPN. In this report, the com-bined dynamic mode DPN is used for direct depositing pro-tein ink on DNA molecules at the nanometer scale.
基金support given to grant SFRH/BD/86068/2012project PTDC/AAC-AMB/103119/2008ALTERCEXAPOCTEC Program
文摘In modeling fluidized bed gasification experiments,equilibrium and CFD models are valuable options.The existence of multi-dimensional effects inside the reactor vessel due to the kinetics of the process and the fluid dynamics phenomena could result in deviation from the zero-dimensional assumption.Complex models integrating kinetics and hydrodynamics are being developed by using a computer fluid dynamics(CFD)approach.The objective of this investigation is to assess and compare the adequacy of zero-dimensional and CFD approaches in modeling fluidized bed gasification regarding a semi-industrial scale(numerical results are validated under experimental runs).Results show that the zero-dimensional model based on the approach of dual stage equilibrium performs reasonably well in adequately predicting the product gas composition at different operating conditions and for different feedstocks,although with quantitative discrepancy.Furthermore,the discrepancy depends on the oxygen content of the oxidation agent and on the steam-to biomass ratio decreasing when these parameters increased.CFD models provide deeper information being able to estimate the syngas composition or other operating parameter at any point of space and time.Despite of some quantitative discrepancy,the zero-dimensional modeling approach is deemed satisfactory from the viewpoint of the determining design conditions simulation.
