In the scenario of a steam generator tube rupture accident in a lead-cooled fast reactor,secondary circuit subcooled water under high pressure is injected into an ordinary-pressure primary vessel,where a molten lead-b...In the scenario of a steam generator tube rupture accident in a lead-cooled fast reactor,secondary circuit subcooled water under high pressure is injected into an ordinary-pressure primary vessel,where a molten lead-based alloy(typically pure lead or lead-bismuth eutectic(LBE))is used as the coolant.To clarify the pressure build-up characteristics under water-jet injection,this study conducted several experiments by injecting pressurized water into a molten LBE pool at Sun Yat-sen University.To obtain a further understanding,several new experimental parameters were adopted,including the melt temperature,water subcooling,injection pressure,injection duration,and nozzle diameter.Through detailed analyses,it was found that the pressure and temperature during the water-melt interaction exhibited a consistent variation trend with our previous water-droplet injection mode LBE experiment.Similarly,the existence of a steam explosion was confirmed,which typically results in a much stronger pressure build-up.For the non-explosion cases,increasing the injection pressure,melt-pool temperature,nozzle diameter,and water subcooling promoted pressure build-up in the melt pool.However,a limited enhancement effect was observed when increasing the injection duration,which may be owing to the continually rising pressure in the interaction vessel or the isolation effect of the generated steam cavity.Regardless of whether a steam explosion occurred,the calculated mechanical and kinetic energy conversion efficiencies of the melt were relatively small(not exceeding 4.1%and 0.7%,respectively).Moreover,the range of the conversion efficiency was similar to that of previous water-droplet experiments,although the upper limit of the jet mode was slightly lower.展开更多
This article discusses the outcomes of a research project on nutrients build-up on urban road surfaces. Nutrient build-up was investigated on road sites belonging to residential, industrial and commercial land use. Co...This article discusses the outcomes of a research project on nutrients build-up on urban road surfaces. Nutrient build-up was investigated on road sites belonging to residential, industrial and commercial land use. Collected build-up samples were separated into five particle size ranges and were tested for total nitrogen （TN）, total phosphorus （TP） and sub species of nutrients, namely, NO2^-, NO3^-, TKN and PO4^3-. Multivariate analytical techniques were used to analyse the data and to develop detailed understanding on build- up. Data analysis revealed that the solids loads on urban road surfaces are highly influenced by factors such as land use, antecedent dry period and traffic volume. However, the nutrient build-up process was found to be independent of the type of land use. It was solely dependent on the particle size of solids build-up. Most of the nutrients were associated with the particle size range 〈150 μm. Therefore, the removal of particles below 150 μm from road surfaces is of importance for the removal of nitrogen and phosphorus from road surface solids build-up. It is also important to consider the difference in the composition of nitrogen and phosphorus build-up in the context of designing effective stormwater quality mitigation strategies.展开更多
Metal pollution of stormwater runoff can cause potential toxic impacts on the receiving water environment and human health. Effective pollution mitigation requires accurate stormwater quality modeling. Even though a s...Metal pollution of stormwater runoff can cause potential toxic impacts on the receiving water environment and human health. Effective pollution mitigation requires accurate stormwater quality modeling. Even though a significant knowledge base exists on the factors influencing metal build-up on urban roads, very limited studies have investigated how metal–particulate interaction influences metal build-up. This study quantitatively assessed the influence of particulate characteristics, together with vehicular traffic and land use, on the build-up of Zn, Cu, Pb, Cr, Ni and Cd on urban roads. The study outcomes revealed that the variability in metal build-up is highly influenced by the variability associated with metal adsorption to particulates. The percentage contribution from particulate properties influencing metal adsorption in the case of < 150 μm size road dust particles was found to be higher(Zn 44%, Cu 52%, Cr 16%, Ni 27% and Cd 45%) when compared to traffic and land use characteristics(Zn 21%, Cu 13%, Cr and Ni <10% and Cd 34%). Similar adsorption behavior was noted for metals associated with > 150 μm size road dust particles. Among different particulate properties influencing metal adsorption, effective cation exchange capacity showed a strong positive relationship with the build-up of Cd compared to other metals,highlighting the potential role of Cd in stormwater quality as a readily available metal. The build-up of metals such as Cr and Ni are highly influenced by metal oxides of Al, Fe and Mn and clay forming minerals, indicating that Cr and Ni are relatively stable in nature.展开更多
Pasteuria penetrans will build-up faster where there is a high initial nematode density and can suppress root-knot nematode populations in the roots of tomato plants. The effect of different initial densities of nemat...Pasteuria penetrans will build-up faster where there is a high initial nematode density and can suppress root-knot nematode populations in the roots of tomato plants. The effect of different initial densities of nematode (Meloidogyne javanica)(150, 750, 1500, 3000) and P. penetrans infected females (F1, F3) densities (F0=control and AC=absolute control without nematode or P. penetrans inoculum) on the build-up of Pasteuria population was investigated over four crop cycles. Two major points of interest were highlighted. First, that within a confined soil volume, densities of P. penetrans can increase >100 times within 2 or 3 crop cycles. Second, from a relatively small amount of spore inoculum, infection of the host is very high. There were more infected females in the higher P. penetrans doses. The root growth data confirms the greater number of females in the controls particularly at the higher inoculum densities in the third and fourth crops. P. penetrans generally caused the fresh root weights to be higher than those in the control. P. penetrans has shown greater reduction of egg masses per plant at most densities.The effects of different initial densities of M. javanica and P. penetrans on the development of the pest and parasite populations were monitored. And no attempt was made to return the P. penetrans spores to the pots after each crop so the build-up in actual numbers of infected females and spores under natural conditions may be underestimated.展开更多
In this work, we report on a closed-form formulation for the build-up factor and absorbed energy, in one and two di- mensional Cartesian geometry for photons and electrons, in the Compton energy range. For the one-dim...In this work, we report on a closed-form formulation for the build-up factor and absorbed energy, in one and two di- mensional Cartesian geometry for photons and electrons, in the Compton energy range. For the one-dimensional case we use the LTSN method, assuming the Klein-Nishina scattering kernel for the determination of the angular radiation intensity for photons. We apply the two-dimensional LTSN nodal solution for the averaged angular radiation evaluation for the two-dimensional case, using the Klein-Nishina kernel for photons and the Compton kernel for electrons. From the angular radiation intensity we construct a closed-form solution for the build-up factor and evaluate the absorbed energy. We present numerical simulations and comparisons against results from the literature.展开更多
We consider the time dependent neutron diffusion equation for one energy group in cylinder coordinates, assuming translational symmetry along the cylinder axis. This problem for a specific energy group is solved analy...We consider the time dependent neutron diffusion equation for one energy group in cylinder coordinates, assuming translational symmetry along the cylinder axis. This problem for a specific energy group is solved analytically applying the Hankel transform in the radial coordinate r. Our special interest rests in the build-up factor for a time dependent linear neutron source aligned with the cylinder axis, which in the limit of zero decay constant reproduces also the static case. The new approach to solve the diffusion equation by integral transform technique is presented and results for several parameter sets and truncation in the solution for the flux and build-up factor are shown and found to be compatible to those of literature [1,2].展开更多
After 45 years’ of unremitting efforts since the founding of the CAS,contingents of carders, S&T researchers and auxiliary workers in the Academy, which have developed not only in quantity but also in quality,hav...After 45 years’ of unremitting efforts since the founding of the CAS,contingents of carders, S&T researchers and auxiliary workers in the Academy, which have developed not only in quantity but also in quality,have made important contributions both to the country’s S&T development and to national economic construction. Since the beginning of the reform and opening, the Academy has adopted, through continued exploration and reform,a set of measures to build up the three contingents in the light of new state of S&T reform in the country.展开更多
Push-the-bit rotary steering system can greatly improve the rate of penetration(ROP),hole conditions and hole extension length and represents the development direction of modern steering drilling technology.In order t...Push-the-bit rotary steering system can greatly improve the rate of penetration(ROP),hole conditions and hole extension length and represents the development direction of modern steering drilling technology.In order to accurately predict and evaluate the build-up rate of pushthe-bit rotary steering system(RSS),this paper establishes the drilling trajectory prediction model and the calculation methods of‘limit build-up rate’and‘corrected build-up rate’for push-the-bit rotary steering system by comprehensively considering the interaction between thruster and sidewall and between bit and formation,the structure of RSS and other influential factors based on the mechanical model of the conventional RSS.Then,the influence mechanisms on the build-up rate are revealed from the aspects of‘leverage effect’,‘pendulum effect’and‘thrust effect’.Finally,the influence laws of thrust force,weight on bit(WOB),borehole inclination angle,bit and formation anisotropy on the build-up rate are analyzed.And the following research results are obtained.First,the build-up rate of RSS is the comprehensive result of various effects,among which‘thrust effect’plays a dominant role and‘leverage effect’and‘pendulum effect’play secondary roles.Second,as for the push-thebit rotary steering system,the proportion of‘leverage effect’increases,the proportion of‘thrust effect’decreases and the build-up rate declines with the increase of WOB.Third,the build-up rate is in a close relationship with structural parameters,thrust force,bit properties and drilling parameters of RSS.In conclusion,the research results can provide an important theoretical basis for the prediction of build-up rate of push-thebit rotary steering system and the optimization of RSS structure.展开更多
The thixotropic structural build-up is crucial in extrusion-based three-dimensional(3D)concrete printing.This paper uses a theoretical model to predict the evolution of static and dynamic yield stress for printed conc...The thixotropic structural build-up is crucial in extrusion-based three-dimensional(3D)concrete printing.This paper uses a theoretical model to predict the evolution of static and dynamic yield stress for printed concrete.The model employs a structural kinetics framework to create a time-independent constitutive link between shear stress and shear rate.The model considers flocculation,deflocculation,and chemical hydration to anticipate structural buildability.The reversible and irreversible contributions that occur throughout the build-up,breakdown,and hydration are defined based on the proposed structural parameters.Additionally,detailed parametric studies are conducted to evaluate the impact of model parameters.It is revealed that the proposed model is in good agreement with the experimental results,and it effectively characterizes the structural build-up of 3D printable concrete.展开更多
基金supported by Basic and Applied Basic research foundation of Guangdong province(Nos.2021A1515010343 and 2022A1515011582)the Science and Technology Program of Guangdong Province(Nos.2021A0505030026 and 2022A0505050029).
文摘In the scenario of a steam generator tube rupture accident in a lead-cooled fast reactor,secondary circuit subcooled water under high pressure is injected into an ordinary-pressure primary vessel,where a molten lead-based alloy(typically pure lead or lead-bismuth eutectic(LBE))is used as the coolant.To clarify the pressure build-up characteristics under water-jet injection,this study conducted several experiments by injecting pressurized water into a molten LBE pool at Sun Yat-sen University.To obtain a further understanding,several new experimental parameters were adopted,including the melt temperature,water subcooling,injection pressure,injection duration,and nozzle diameter.Through detailed analyses,it was found that the pressure and temperature during the water-melt interaction exhibited a consistent variation trend with our previous water-droplet injection mode LBE experiment.Similarly,the existence of a steam explosion was confirmed,which typically results in a much stronger pressure build-up.For the non-explosion cases,increasing the injection pressure,melt-pool temperature,nozzle diameter,and water subcooling promoted pressure build-up in the melt pool.However,a limited enhancement effect was observed when increasing the injection duration,which may be owing to the continually rising pressure in the interaction vessel or the isolation effect of the generated steam cavity.Regardless of whether a steam explosion occurred,the calculated mechanical and kinetic energy conversion efficiencies of the melt were relatively small(not exceeding 4.1%and 0.7%,respectively).Moreover,the range of the conversion efficiency was similar to that of previous water-droplet experiments,although the upper limit of the jet mode was slightly lower.
基金supported by the Faculty of Built Environment and Engineering,Queensland University of Technology (QUT),Brisbane,Australia
文摘This article discusses the outcomes of a research project on nutrients build-up on urban road surfaces. Nutrient build-up was investigated on road sites belonging to residential, industrial and commercial land use. Collected build-up samples were separated into five particle size ranges and were tested for total nitrogen （TN）, total phosphorus （TP） and sub species of nutrients, namely, NO2^-, NO3^-, TKN and PO4^3-. Multivariate analytical techniques were used to analyse the data and to develop detailed understanding on build- up. Data analysis revealed that the solids loads on urban road surfaces are highly influenced by factors such as land use, antecedent dry period and traffic volume. However, the nutrient build-up process was found to be independent of the type of land use. It was solely dependent on the particle size of solids build-up. Most of the nutrients were associated with the particle size range 〈150 μm. Therefore, the removal of particles below 150 μm from road surfaces is of importance for the removal of nitrogen and phosphorus from road surface solids build-up. It is also important to consider the difference in the composition of nitrogen and phosphorus build-up in the context of designing effective stormwater quality mitigation strategies.
文摘Metal pollution of stormwater runoff can cause potential toxic impacts on the receiving water environment and human health. Effective pollution mitigation requires accurate stormwater quality modeling. Even though a significant knowledge base exists on the factors influencing metal build-up on urban roads, very limited studies have investigated how metal–particulate interaction influences metal build-up. This study quantitatively assessed the influence of particulate characteristics, together with vehicular traffic and land use, on the build-up of Zn, Cu, Pb, Cr, Ni and Cd on urban roads. The study outcomes revealed that the variability in metal build-up is highly influenced by the variability associated with metal adsorption to particulates. The percentage contribution from particulate properties influencing metal adsorption in the case of < 150 μm size road dust particles was found to be higher(Zn 44%, Cu 52%, Cr 16%, Ni 27% and Cd 45%) when compared to traffic and land use characteristics(Zn 21%, Cu 13%, Cr and Ni <10% and Cd 34%). Similar adsorption behavior was noted for metals associated with > 150 μm size road dust particles. Among different particulate properties influencing metal adsorption, effective cation exchange capacity showed a strong positive relationship with the build-up of Cd compared to other metals,highlighting the potential role of Cd in stormwater quality as a readily available metal. The build-up of metals such as Cr and Ni are highly influenced by metal oxides of Al, Fe and Mn and clay forming minerals, indicating that Cr and Ni are relatively stable in nature.
文摘Pasteuria penetrans will build-up faster where there is a high initial nematode density and can suppress root-knot nematode populations in the roots of tomato plants. The effect of different initial densities of nematode (Meloidogyne javanica)(150, 750, 1500, 3000) and P. penetrans infected females (F1, F3) densities (F0=control and AC=absolute control without nematode or P. penetrans inoculum) on the build-up of Pasteuria population was investigated over four crop cycles. Two major points of interest were highlighted. First, that within a confined soil volume, densities of P. penetrans can increase >100 times within 2 or 3 crop cycles. Second, from a relatively small amount of spore inoculum, infection of the host is very high. There were more infected females in the higher P. penetrans doses. The root growth data confirms the greater number of females in the controls particularly at the higher inoculum densities in the third and fourth crops. P. penetrans generally caused the fresh root weights to be higher than those in the control. P. penetrans has shown greater reduction of egg masses per plant at most densities.The effects of different initial densities of M. javanica and P. penetrans on the development of the pest and parasite populations were monitored. And no attempt was made to return the P. penetrans spores to the pots after each crop so the build-up in actual numbers of infected females and spores under natural conditions may be underestimated.
文摘In this work, we report on a closed-form formulation for the build-up factor and absorbed energy, in one and two di- mensional Cartesian geometry for photons and electrons, in the Compton energy range. For the one-dimensional case we use the LTSN method, assuming the Klein-Nishina scattering kernel for the determination of the angular radiation intensity for photons. We apply the two-dimensional LTSN nodal solution for the averaged angular radiation evaluation for the two-dimensional case, using the Klein-Nishina kernel for photons and the Compton kernel for electrons. From the angular radiation intensity we construct a closed-form solution for the build-up factor and evaluate the absorbed energy. We present numerical simulations and comparisons against results from the literature.
文摘We consider the time dependent neutron diffusion equation for one energy group in cylinder coordinates, assuming translational symmetry along the cylinder axis. This problem for a specific energy group is solved analytically applying the Hankel transform in the radial coordinate r. Our special interest rests in the build-up factor for a time dependent linear neutron source aligned with the cylinder axis, which in the limit of zero decay constant reproduces also the static case. The new approach to solve the diffusion equation by integral transform technique is presented and results for several parameter sets and truncation in the solution for the flux and build-up factor are shown and found to be compatible to those of literature [1,2].
文摘After 45 years’ of unremitting efforts since the founding of the CAS,contingents of carders, S&T researchers and auxiliary workers in the Academy, which have developed not only in quantity but also in quality,have made important contributions both to the country’s S&T development and to national economic construction. Since the beginning of the reform and opening, the Academy has adopted, through continued exploration and reform,a set of measures to build up the three contingents in the light of new state of S&T reform in the country.
基金Project supported by the National Natural Science Foundation of China“Research on Critical Dynamic Buckling Conditions of Rotary Drill Strings and Post-buckling Snaking Swing and Helical Whirling Behaviors”(No.51904317)National Natural Science Foundation of China“Basic Research on Drilling and Completion in Complex Oil and Gas Well”(No.51821092)+2 种基金National Natural Science Foundation of China“Basic Research on Well Construction in Efficient Development of Shale and Tight Oil and Gas Fields”(No.U1762214)Special Topic on CNPC's Strategic Cooperation Science and Technology Project“Research on ROP Acceleration Technology in Deep Drilling in Terrestrial Shale Oil”(No.ZLZX2020-01-07-01)Science Foundation of China University of Petroleum(Beijing)(No.ZX20180414).
文摘Push-the-bit rotary steering system can greatly improve the rate of penetration(ROP),hole conditions and hole extension length and represents the development direction of modern steering drilling technology.In order to accurately predict and evaluate the build-up rate of pushthe-bit rotary steering system(RSS),this paper establishes the drilling trajectory prediction model and the calculation methods of‘limit build-up rate’and‘corrected build-up rate’for push-the-bit rotary steering system by comprehensively considering the interaction between thruster and sidewall and between bit and formation,the structure of RSS and other influential factors based on the mechanical model of the conventional RSS.Then,the influence mechanisms on the build-up rate are revealed from the aspects of‘leverage effect’,‘pendulum effect’and‘thrust effect’.Finally,the influence laws of thrust force,weight on bit(WOB),borehole inclination angle,bit and formation anisotropy on the build-up rate are analyzed.And the following research results are obtained.First,the build-up rate of RSS is the comprehensive result of various effects,among which‘thrust effect’plays a dominant role and‘leverage effect’and‘pendulum effect’play secondary roles.Second,as for the push-thebit rotary steering system,the proportion of‘leverage effect’increases,the proportion of‘thrust effect’decreases and the build-up rate declines with the increase of WOB.Third,the build-up rate is in a close relationship with structural parameters,thrust force,bit properties and drilling parameters of RSS.In conclusion,the research results can provide an important theoretical basis for the prediction of build-up rate of push-thebit rotary steering system and the optimization of RSS structure.
基金A grant from CSIR,New Delhi,generously funds this studypartially supported by the City University of Hong Kong,China(No.9610661).
文摘The thixotropic structural build-up is crucial in extrusion-based three-dimensional(3D)concrete printing.This paper uses a theoretical model to predict the evolution of static and dynamic yield stress for printed concrete.The model employs a structural kinetics framework to create a time-independent constitutive link between shear stress and shear rate.The model considers flocculation,deflocculation,and chemical hydration to anticipate structural buildability.The reversible and irreversible contributions that occur throughout the build-up,breakdown,and hydration are defined based on the proposed structural parameters.Additionally,detailed parametric studies are conducted to evaluate the impact of model parameters.It is revealed that the proposed model is in good agreement with the experimental results,and it effectively characterizes the structural build-up of 3D printable concrete.
