The liquid slug length distribution is crucial for designing the downstream processing system with mul-tiphase pipeline. Experiments were conducted in a 133m long horizontal test loop. The measurements were per-formed...The liquid slug length distribution is crucial for designing the downstream processing system with mul-tiphase pipeline. Experiments were conducted in a 133m long horizontal test loop. The measurements were per-formed by conductivity probes to determine the liquid slug length distribution. The data covered both the slug and plug flow regimes. From experimental results, the mean liquid slug lengths were relatively insensitive to gas and liquid flow rates in the higher mixture velocity range. But in the lower mixture velocity range, the mean liquid slug length decreased and then increased with mixture velocity. It shows that the development length of slug flow was longer than x/D=1157. A slug tracking model was adapted to study the evolution of liquid slug length distribution in a horizontal pipeline. In the present model, the wake effect of elongated bubble and the pressure drop due to accel-eration are taken into account and random slug lengths are introduced at the entrance. The results of the model are compared with the measured slug length distributions of slug flow regime. It shows that the predicted mean and maximum slug lengths are in agreement with the experimental data at x/D=1157 and the form of the slug length distributions is also predicted well by the model.展开更多
Failure of rock under impact loadings involves complex micro-fracturing and progressive damage. Strength increase and splitting failure have been observed during dynamic tests of rock materials. However, the failure m...Failure of rock under impact loadings involves complex micro-fracturing and progressive damage. Strength increase and splitting failure have been observed during dynamic tests of rock materials. However, the failure mechanism still remains unclear. In this work, based on laboratory tests, numerical simulations with the particle flow code(PFC) were carried out to reproduce the micro-fracturing process of granite specimens. Shear and tensile cracks were both recorded to investigate the failure mode of rocks under different loading conditions. At the same time, a dynamic damage model based on the Weibull distribution was established to predict the deformation and degradation behavior of specimens. It is found that micro-cracks play important roles in controlling the dynamic deformation and failure process of rock under impact loadings. The sharp increase in the number of cracks may be the reason for the strength increase of rock under high strain rates. Tensile cracks tend to be the key reason for splitting failure of specimens. Numerical simulation of crack propagation by PFC can give vivid description of the failure process. However, it is not enough for evaluation of material degradation. The dynamic damage model is able to predict the stress-strain relationship of specimens reasonably well, and can be used to explain the degradation of specimens under impact loadings at macro-scale. Crack and damage can describe material degradation at different scales and can be used together to reveal the failure mechanism of rocks.展开更多
This paper describes the use of a numerical and physical modelling study in the design of large breakwaters for a new port and dry dock complex on the southern coast of Oman. The numerical modelling was carried out to...This paper describes the use of a numerical and physical modelling study in the design of large breakwaters for a new port and dry dock complex on the southern coast of Oman. The numerical modelling was carried out to optimise the entrance channel layout with respect to wave penetration into the port and to refine design conditions for the sizing of the primary armour on the breakwaters. Wave conditions inside and outside of the port have been assessed using the 2-dimensional numerical wave penetration model MIKE21 EMS (Elliptic Mild-Slope). As part of the design process, 3D physical modelling studies were also undertaken at Delft Hydraulics in the Netherlands to confirm the stability of the armour on the trunk and roundhead of the breakwaters and to verify the influence of the deep approach channel on stability. The opportunity was taken to extend the physical model tests to assess the influence of the deep channel on wave penetration through the port entrance. The paper focuses on the influence of the deep channel on wave conditions in the entrance to the port and compares the results from the numerical and physical modelling.展开更多
The combination of photovoltaic system with a thermal to form the hybrid PVT (photovoltaic thermal), which together will generate electricity and heat. This energy depends on the input that is to say the energy of s...The combination of photovoltaic system with a thermal to form the hybrid PVT (photovoltaic thermal), which together will generate electricity and heat. This energy depends on the input that is to say the energy of solar radiation, temperature and speed wind and output which is the operating temperature of the system. This production also depends on the mode of heat removal. The authors present in this article; a study by a numerical simulation of the thermal behavior of a prototype hybrid sensor through the development of an energy balance that involves heat exchange between the different components of the hybrid sensor, and it will allow us to study the influence of internal and external parameters on the temperature variation in the different layers of the prototype PV/T studied.展开更多
AIM: To investigate the use of the Gaumard's Noelle S550.100 Maternal and Neonatal Simulators for teaching forceps delivery.METHODS: Twenty two(n = 22) resident physicians were enrolled in a simulation course on o...AIM: To investigate the use of the Gaumard's Noelle S550.100 Maternal and Neonatal Simulators for teaching forceps delivery.METHODS: Twenty two(n = 22) resident physicians were enrolled in a simulation course on operative forceps deliveries. The physicians enrolled in the course were all part of an accredited Obstetrics and Gynecology residency program and ranged in their training from post graduate year(PGY) 1-4. Each participant received simulation based teaching on the indications, contraindications, proper application, delivery and removal of forceps by a single teacher. The Gaumard's simulator and Simpson forceps were used for this course. Statistical analysis using SPSS statistical software was performed after the completion of the simulation training program. A paired student t-test was performed to compare the cohort's mean pretest and post simulation training scores. Follow up skills assessment scores at one month, 3 mo and 6 mo were compared to thebaseline pretest score using a paired student t-test. RESULTS: There was statistically significant improvement in the post simulation training performance evaluations compared to the pretest, 13.7(SD = 3.14) vs 7.9(SD = 4.92), P < 0.05. Scores at 1 mo, 3 mo, and 6 mo were compared to the pretest score and showed retention of skills: 4.6(SD = 5.5, 95%CI: 2.21-7.07), 4.4(SD = 5.2, 95%CI: 2.13-6.70), and 5.6(SD = 4.8, 95%CI: 3.53-7.75) points, respectively. There were statistically significant differences between residents by post graduate training year on pretest scores, however these differences were not present after simulation training. Pretest scores for PGY 1, 2, 3, 4 were 3.5(SD = 2.27, 95%CI: 2.13-5.00), 7.25(SD = 6.70, 95%CI: 1.50-13.00), 10.75(SD = 1.5, 95%CI: 9.50-12.00), 12.17(SD = 2.57, 95%CI: 10.33-14.00). After simulation training PGY 1 residents did as well as well as the upper level residents. Posttest mean test scores for PGY 1, 2, 3, 4 were 13.75(SD = 1.49, 95%CI: 12.75-14.63), 10.25(SD = 0.24, 95%CI: 4.25-14.00), 15.00(SD = 1.16, 95%CI: 14.00-16.00), 15.17(SD = 0.75, 95%CI: 14.67-15.67). CONCLUSION: Our simulation based training program not only produced short term gains, but participants were able to retain the skills learned and demonstrate their knowledge months later.展开更多
To investigate the differences and the development trends of the 400 kA aluminum reduction cell, four representative cells were deeply analyzed. By using numerical simulation methods in ANSYS software, the structure p...To investigate the differences and the development trends of the 400 kA aluminum reduction cell, four representative cells were deeply analyzed. By using numerical simulation methods in ANSYS software, the structure parameters were firstly compared, and then three-dimensional models of electric-magnetic-flow field were built and solved with finite element method(FEM). The comparison of the structures reveals that the cell bodies are similar while the current flow path and distribution ratio of bus bars are different. It appears that most of the current(70%-80%) in side A are used as the magnetic field compensation current and flow through two ends. The numerical simulation results indicate that the distributions of magnetic fields are different but all satisfy with the magnetohydrodynamics(MHD) stabilization, and the flow patterns are all two or multi vortexes with appropriate velocities. The comparison shows that all studied cells can satisfy with the physical field requirement, and the commercial applications also verify that the 400 kA cells have become the product of the mature and world's leading technology.展开更多
Modelling of carob batch fermentation is established basing on mass transfer balances. The modelling treats the reaction kinetics of substrate (S), the micro-organisms (X) and the ethanol (E). Nine models are ta...Modelling of carob batch fermentation is established basing on mass transfer balances. The modelling treats the reaction kinetics of substrate (S), the micro-organisms (X) and the ethanol (E). Nine models are taken from the literature to describe specific organism growth rate and specific ethanol development rate. These models treat all types of fermentation. The Phisalapbong et al. model and the Ghose and Tyagi model show the best fit of the experimental data. This affirms that the batch fermentation of carob is conducted with substrate and/or ethanol inhibition. Some simulations and relationships (X = f(S), E = f(S)) are obtained from the Phisalaphong et al. model. Those simulations show a lot of important and useful results of carob batch fermentation process.展开更多
基金Supported by the National Natural Science Foundation of China (No.50536020 and 50323001).
文摘The liquid slug length distribution is crucial for designing the downstream processing system with mul-tiphase pipeline. Experiments were conducted in a 133m long horizontal test loop. The measurements were per-formed by conductivity probes to determine the liquid slug length distribution. The data covered both the slug and plug flow regimes. From experimental results, the mean liquid slug lengths were relatively insensitive to gas and liquid flow rates in the higher mixture velocity range. But in the lower mixture velocity range, the mean liquid slug length decreased and then increased with mixture velocity. It shows that the development length of slug flow was longer than x/D=1157. A slug tracking model was adapted to study the evolution of liquid slug length distribution in a horizontal pipeline. In the present model, the wake effect of elongated bubble and the pressure drop due to accel-eration are taken into account and random slug lengths are introduced at the entrance. The results of the model are compared with the measured slug length distributions of slug flow regime. It shows that the predicted mean and maximum slug lengths are in agreement with the experimental data at x/D=1157 and the form of the slug length distributions is also predicted well by the model.
基金Projects(51274254,51322403)supported by the National Natural Science Foundation of ChinaProject(NCET-11-0528)supported by theProgram for New Century Excellent Talents in University,ChinaProject(2013SK2011)supported by Hunan Province Science andTechnology Plan,China
文摘Failure of rock under impact loadings involves complex micro-fracturing and progressive damage. Strength increase and splitting failure have been observed during dynamic tests of rock materials. However, the failure mechanism still remains unclear. In this work, based on laboratory tests, numerical simulations with the particle flow code(PFC) were carried out to reproduce the micro-fracturing process of granite specimens. Shear and tensile cracks were both recorded to investigate the failure mode of rocks under different loading conditions. At the same time, a dynamic damage model based on the Weibull distribution was established to predict the deformation and degradation behavior of specimens. It is found that micro-cracks play important roles in controlling the dynamic deformation and failure process of rock under impact loadings. The sharp increase in the number of cracks may be the reason for the strength increase of rock under high strain rates. Tensile cracks tend to be the key reason for splitting failure of specimens. Numerical simulation of crack propagation by PFC can give vivid description of the failure process. However, it is not enough for evaluation of material degradation. The dynamic damage model is able to predict the stress-strain relationship of specimens reasonably well, and can be used to explain the degradation of specimens under impact loadings at macro-scale. Crack and damage can describe material degradation at different scales and can be used together to reveal the failure mechanism of rocks.
文摘This paper describes the use of a numerical and physical modelling study in the design of large breakwaters for a new port and dry dock complex on the southern coast of Oman. The numerical modelling was carried out to optimise the entrance channel layout with respect to wave penetration into the port and to refine design conditions for the sizing of the primary armour on the breakwaters. Wave conditions inside and outside of the port have been assessed using the 2-dimensional numerical wave penetration model MIKE21 EMS (Elliptic Mild-Slope). As part of the design process, 3D physical modelling studies were also undertaken at Delft Hydraulics in the Netherlands to confirm the stability of the armour on the trunk and roundhead of the breakwaters and to verify the influence of the deep approach channel on stability. The opportunity was taken to extend the physical model tests to assess the influence of the deep channel on wave penetration through the port entrance. The paper focuses on the influence of the deep channel on wave conditions in the entrance to the port and compares the results from the numerical and physical modelling.
文摘The combination of photovoltaic system with a thermal to form the hybrid PVT (photovoltaic thermal), which together will generate electricity and heat. This energy depends on the input that is to say the energy of solar radiation, temperature and speed wind and output which is the operating temperature of the system. This production also depends on the mode of heat removal. The authors present in this article; a study by a numerical simulation of the thermal behavior of a prototype hybrid sensor through the development of an energy balance that involves heat exchange between the different components of the hybrid sensor, and it will allow us to study the influence of internal and external parameters on the temperature variation in the different layers of the prototype PV/T studied.
文摘AIM: To investigate the use of the Gaumard's Noelle S550.100 Maternal and Neonatal Simulators for teaching forceps delivery.METHODS: Twenty two(n = 22) resident physicians were enrolled in a simulation course on operative forceps deliveries. The physicians enrolled in the course were all part of an accredited Obstetrics and Gynecology residency program and ranged in their training from post graduate year(PGY) 1-4. Each participant received simulation based teaching on the indications, contraindications, proper application, delivery and removal of forceps by a single teacher. The Gaumard's simulator and Simpson forceps were used for this course. Statistical analysis using SPSS statistical software was performed after the completion of the simulation training program. A paired student t-test was performed to compare the cohort's mean pretest and post simulation training scores. Follow up skills assessment scores at one month, 3 mo and 6 mo were compared to thebaseline pretest score using a paired student t-test. RESULTS: There was statistically significant improvement in the post simulation training performance evaluations compared to the pretest, 13.7(SD = 3.14) vs 7.9(SD = 4.92), P < 0.05. Scores at 1 mo, 3 mo, and 6 mo were compared to the pretest score and showed retention of skills: 4.6(SD = 5.5, 95%CI: 2.21-7.07), 4.4(SD = 5.2, 95%CI: 2.13-6.70), and 5.6(SD = 4.8, 95%CI: 3.53-7.75) points, respectively. There were statistically significant differences between residents by post graduate training year on pretest scores, however these differences were not present after simulation training. Pretest scores for PGY 1, 2, 3, 4 were 3.5(SD = 2.27, 95%CI: 2.13-5.00), 7.25(SD = 6.70, 95%CI: 1.50-13.00), 10.75(SD = 1.5, 95%CI: 9.50-12.00), 12.17(SD = 2.57, 95%CI: 10.33-14.00). After simulation training PGY 1 residents did as well as well as the upper level residents. Posttest mean test scores for PGY 1, 2, 3, 4 were 13.75(SD = 1.49, 95%CI: 12.75-14.63), 10.25(SD = 0.24, 95%CI: 4.25-14.00), 15.00(SD = 1.16, 95%CI: 14.00-16.00), 15.17(SD = 0.75, 95%CI: 14.67-15.67). CONCLUSION: Our simulation based training program not only produced short term gains, but participants were able to retain the skills learned and demonstrate their knowledge months later.
基金Projects(51104187,51274241,61321003) supported by the National Natural Science Foundation of ChinaProject(20100162120008) supported by Doctoral Fund of Ministry of Education of China
文摘To investigate the differences and the development trends of the 400 kA aluminum reduction cell, four representative cells were deeply analyzed. By using numerical simulation methods in ANSYS software, the structure parameters were firstly compared, and then three-dimensional models of electric-magnetic-flow field were built and solved with finite element method(FEM). The comparison of the structures reveals that the cell bodies are similar while the current flow path and distribution ratio of bus bars are different. It appears that most of the current(70%-80%) in side A are used as the magnetic field compensation current and flow through two ends. The numerical simulation results indicate that the distributions of magnetic fields are different but all satisfy with the magnetohydrodynamics(MHD) stabilization, and the flow patterns are all two or multi vortexes with appropriate velocities. The comparison shows that all studied cells can satisfy with the physical field requirement, and the commercial applications also verify that the 400 kA cells have become the product of the mature and world's leading technology.
文摘Modelling of carob batch fermentation is established basing on mass transfer balances. The modelling treats the reaction kinetics of substrate (S), the micro-organisms (X) and the ethanol (E). Nine models are taken from the literature to describe specific organism growth rate and specific ethanol development rate. These models treat all types of fermentation. The Phisalapbong et al. model and the Ghose and Tyagi model show the best fit of the experimental data. This affirms that the batch fermentation of carob is conducted with substrate and/or ethanol inhibition. Some simulations and relationships (X = f(S), E = f(S)) are obtained from the Phisalaphong et al. model. Those simulations show a lot of important and useful results of carob batch fermentation process.