In recent years,there has been a significant acceleration in the thinning,calving and retreat of the Pine Island Ice Shelf(PIIS).The basal channels,results of enhanced basal melting,have the potential to significantly...In recent years,there has been a significant acceleration in the thinning,calving and retreat of the Pine Island Ice Shelf(PIIS).The basal channels,results of enhanced basal melting,have the potential to significantly impact the stability of the PIIS.In this study,we used a variety of remote sensing data,including Landsat,REMA DEM,ICESat-1 and ICESat-2 satellite altimetry observations,and Ice Bridge airborne measurements,to study the spatiotemporal changes in the basal channels from 2003 to 2020 and basal melt rate from 2010 to 2017 of the PIIS under the Eulerian framework.We found that the basal channels are highly developed in the PIIS,with a total length exceeding 450 km.Most of the basal channels are ocean-sourced or groundingline-sourced basal channels,caused by the rapid melting under the ice shelf or near the groundingline.A raised seabed prevented warm water intrusion into the eastern branch of the PIIS,resulting in a lower basal melt rate in that area.In contrast,a deepsea trough facilitates warm seawater into the mainstream and the western branch of the PIIS,resulting in a higher basal melt rate in the main-stream,and the surface elevation changes above the basal channels of the mainstream and western branch are more significant.The El Ni?o event in 2015–2016 possibly slowed down the basal melting of the PIIS by modulating wind field,surface sea temperature and depth seawater temperature.Ocean and atmospheric changes were driven by El Ni?o,which can further explain and confirm the changes in the basal melting of the PIIS.展开更多
Based on the coexistence theory of slag melt structure and Butler’s equation,a new calculation model has been proposed for the calculation of surface tension of slag melt.This model establishes a specific correlation...Based on the coexistence theory of slag melt structure and Butler’s equation,a new calculation model has been proposed for the calculation of surface tension of slag melt.This model establishes a specific correlation between surface tension and mass action concentrations(activities) in the melt and on its surface on the basis of inner and surficial structures of slag melt.Calculated surface tensions of CaO-SiOand MnO-SiOslag melts are consistent with those measured.Furthermore,iso-surface tension lines of CaO-MnO-SiOslag melt have also been calculated.展开更多
Zircon stability in silicate melts-which can be quantitatively constrained by laboratory measurements of zircon saturation-is important for understanding the evolution of magma.Although the original zircon saturation ...Zircon stability in silicate melts-which can be quantitatively constrained by laboratory measurements of zircon saturation-is important for understanding the evolution of magma.Although the original zircon saturation model proposed by Watson and Harrison(Earth Planet Sci Lett 64(2):295-304,1983) is widely cited and has been updated recently,the three main models currently in use may generate large uncertainties due to extrapolation beyond their respective calibrated ranges.This paper reviews and updates zircon saturation models developed with temperature and compositional parameters.All available data on zircon saturation ranging in composition from mafic to silicic(and/or peralkaline to peraluminous)at temperatures from 750 to 1400℃ were collected to develop two refined models(1 and 2) that may be applied to the wider range of compositions.Model 1 is given by lnCZr(melt)=(14.297±0.308)+(0.964 ± 0.066).M-(11113±374)/r,and model 2 given by lnCZr(melt)=(18.99±0.423)-(1.069±0.102)·lnG-(12288±593)/T,where CZr(melt) is the Zr concentration of the melt in ppm and parameters M [=(Na+K+2 Ca)/(Al·Si)](cation ratios) and G [=(3·Al2 O3+SiO2)/(Na2-O+K2 O+CaO+MgO+FeO)](molar proportions)represent the melt composition.The errors are at one sigma,and T is the temperature in Kelvin.Before applying these models to natural rocks,it is necessary to ensure that the zircon used to date is crystallized from the host magmatic rock.Assessment of the application of both new and old models to natural rocks suggests that model 1 may be the best for magmatic temperature estimates of metaluminous to peraluminous rocks and that model 2 may be the best for estimating magmatic temperatures of alkaline to peralkaline rocks.展开更多
Conceptually, an imagined conformation ellipsoid is supposed to represent the shape of a polymer chain for polymer melts in flow fields and to be equivalent to the volume element in a mathematical sense in continuum m...Conceptually, an imagined conformation ellipsoid is supposed to represent the shape of a polymer chain for polymer melts in flow fields and to be equivalent to the volume element in a mathematical sense in continuum mechanics. A power law dependence of shear modulus of polymer melts on detC, referred to as envelope volume, is proposed. Based on those assumptions and the non-linear relation of shear modulus, a phenomenological viscoelastic model is derived. The model is tested in simple shear flow, simple elongational flow, oscillatory shear flow, and relaxation process after flow suddenly stopped. The results show that the model works well to predict the change of internal structure and viscoelastic performance of polymer melts in flow fields.展开更多
A constitutive model of quasi-Newtonian fluid based on the type of flow is used in abrupt planar contraction now.The numerical results from finite element analysis are consistent with experimental data for stress patt...A constitutive model of quasi-Newtonian fluid based on the type of flow is used in abrupt planar contraction now.The numerical results from finite element analysis are consistent with experimental data for stress patterns and velocityprofiles in the flow field. The chain conformations of polymer melts are then investigated in such a planar contraction byusing the phenomenological model with internal parameters proposed by the author. That is, the shape and orientation ofpolymer chain coils are predicted and discussed in different flow regions of the contraction flow field that possess simpleshear flow, extensional flow, vortical flow, and mixed flow respectively.展开更多
This study assessed the performances of the traditional temperature-index snowmelt runoff model(SRM) and an SRM model with a finer zonation based on aspect and slope(SRM + AS model) in a data-scarce mountain watershed...This study assessed the performances of the traditional temperature-index snowmelt runoff model(SRM) and an SRM model with a finer zonation based on aspect and slope(SRM + AS model) in a data-scarce mountain watershed in the Urumqi River Basin,in Northwest China.The proposed SRM + AS model was used to estimate the melt rate with the degree-day factor(DDF) through the division of watershed elevation zones based on aspect and slope.The simulation results of the SRM + AS model were compared with those of the traditional SRM model to identify the improvements of the SRM + AS model's performance with consideration of topographic features of the watershed.The results show that the performance of the SRM + AS model has improved slightly compared to that of the SRM model.The coefficients of determination increased from 0.73,0.69,and 0.79 with the SRM model to 0.76,0.76,and 0.81 with the SRM + AS model during the simulation and validation periods in 2005,2006,and 2007,respectively.The proposed SRM + AS model that considers aspect and slope can improve the accuracy of snowmelt runoff simulation compared to the traditional SRM model in mountain watersheds in arid regions by proper parameterization,careful input data selection,and data preparation.展开更多
Melt ponds significantly affect Arctic sea ice thermodynamic processes.The melt pond parameterization scheme in the Los Alamos sea ice model(CICE6.0) can predict the volume,area fraction(the ratio between melt pond ar...Melt ponds significantly affect Arctic sea ice thermodynamic processes.The melt pond parameterization scheme in the Los Alamos sea ice model(CICE6.0) can predict the volume,area fraction(the ratio between melt pond area to sea ice area in a model grid),and depth of melt ponds.However,this scheme has some uncertain parameters that affect melt pond simulations.These parameters could be determined through a conventional parameter estimation method,which requires a large number of sensitivity simulations.The adjoint model can calculate the parameter sensitivity efficiently.In the present research,an adjoint model was developed for the CESM(Community Earth System Model) melt pond scheme.A melt pond parameter estimation algorithm was then developed based on the CICE6.0 sea ice model,melt pond adjoint model,and L-BFGS(Limited-memory Broyden-Fletcher-Goldfard-Shanno) minimization algorithm.The parameter estimation algorithm was verified under idealized conditions.By using MODIS(Moderate Resolution Imaging Spectroradiometer)melt pond fraction observation as a constraint and the developed parameter estimation algorithm,the melt pond aspect ratio parameter in CESM scheme,which is defined as the ratio between pond depth and pond area fraction,was estimated every eight days during summertime for two different regions in the Arctic.One region was covered by multi-year ice(MYI) and the other by first-year ice(FYI).The estimated parameter was then used in simulations and the results show that:(1) the estimated parameter varies over time and is quite different for MYI and FYI;(2) the estimated parameter improved the simulation of the melt pond fraction.展开更多
An approach of stochastically statistical mechanics and a unified molecular theory of nonlinear viscoelasticity with constraints of Nagai chain entanglement for polymer melts have been proposed. A multimode model stru...An approach of stochastically statistical mechanics and a unified molecular theory of nonlinear viscoelasticity with constraints of Nagai chain entanglement for polymer melts have been proposed. A multimode model structure for a single polymer chain with n tail segments and N reversible entanglement sites on the test polymer chain is developed. Based on the above model structure and the mechanism of molecular flow by the dynamical reorganization of entanglement sites, the probability distribution function of the end-to-end vectr for a single polymer chain at entangled state and the viscoelastic free energy of deformation for polymer melts are calculated by using the method of the stochastically statistical mechanics. The four types of stress-strain relation and the memory function are derived from this thery. The above theoretical relations are verified by the experimentaf data for various polymer melts. These relations are found to be in good agreement with the experimental results展开更多
The anharmonic vibrator, whose expression of potential energy contains second and third powers of coordinates, is treated on the basis of dynamical procedure, which presents the state of motion by means of mean positi...The anharmonic vibrator, whose expression of potential energy contains second and third powers of coordinates, is treated on the basis of dynamical procedure, which presents the state of motion by means of mean position and mean amplitude of vibration. The divergent statistical integral comes here not into consideration. The free energy is represented through mean atomic displacement and developed in power series, retaining fourth degree. The graphs show that at certain temperature, the minimum in free energy disappears, and the atom escapes from the potential pit. A simple atomic model that represents this phenomenon is proposed and the influence of model dimension and pressure on melting temperature will be presented.展开更多
It is shown theoretically that the viscoelasticity of polymer melts is determined by three combining factorst they are the primary molecular weight and its distribution, the number of entanglement sites on polymer cha...It is shown theoretically that the viscoelasticity of polymer melts is determined by three combining factorst they are the primary molecular weight and its distribution, the number of entanglement sites on polymer chain and the sequence distribution of constituent chains in entanglement spacings. A unified quantity for the three combing factors is the average constrained dimensional number of constituent chains in the long entanglement spacings (v). A new relation of v to the primary molecular weight and the number of testing polymers were derived from the multiple entanglement and reptation model, and a new method for determining v was proposed. The dependences of linear viscoelastic functions on the primary molecular weight and its distribution were derived by the statistical method. When Mn=6Me to 18 Me, the values of (v) can range from 3.33 to 3.70. Their values are in a good agreement with the experiment data, and it can slightjy vary with the different species of polymers and the different ranges of molecular weight of polymers展开更多
Maize (Zea mays L.) is one of the three major food crops and an important source of carbohydrates for maintaining food security around the world.Plant height (H),stem diameter (SD),leaf area index (LAI) and dry matter...Maize (Zea mays L.) is one of the three major food crops and an important source of carbohydrates for maintaining food security around the world.Plant height (H),stem diameter (SD),leaf area index (LAI) and dry matter (DM) are important growth parameters that influence maize production.However,the combined effect of temperature and light on maize growth is rarely considered in crop growth models.Ten maize growth models based on the modified logistic growth equation (Mlog) and the Mitscherlich growth equation (Mit) were proposed to simulate the H,SD,LAI and DM of maize under different mulching practices based on experimental data from 2015–2018.Either the accumulative growing degree-days (AGDD),helio thermal units (HTU),photothermal units (PTU) or photoperiod thermal units (PPTU,first proposed here) was used as a single driving factor in the models;or AGDD was combined with either accumulative actual solar hours (ASS),accumulative photoperiod response (APR,first proposed here) or accumulative maximum possible sunshine hours (ADL) as the dual driving factors in the models.The model performances were evaluated using seven statistical indicators and a global performance index.The results showed that the three mulching practices significantly increased the maize growth rates and the maximum values of the growth curves compared with non-mulching.Among the four single factor-driven models,the overall performance of the Mlog_(PTU)Model was the best,followed by the Mlog_(AGDD)Model.The Mlog_(PPTU)Model was better than the Mlog_(AGDD)Model in simulating SD and LAI.Among the 10 models,the overall performance of the Mlog_(AGDD–APR)Model was the best,followed by the Mlog_(AGDD–ASS)Model.Specifically,the Mlog_(AGDD–APR)Model performed the best in simulating H and LAI,while the Mlog_(AGDD–ADL)and Mlog_(AGDD–ASS)models performed the best in simulating SD and DM,respectively.In conclusion,the modified logistic growth equations with AGDD and either APR,ASS or ADL as the dual driving factors outperformed the commonly used modified logistic growth model with AGDD as a single driving factor in simulating maize growth.展开更多
Glacier mass balance, the difference between accumulation and ablation at the glacier surface, is the direct reflection of the local climate regime. Under global warming, the simulation of glacier mass balance at the ...Glacier mass balance, the difference between accumulation and ablation at the glacier surface, is the direct reflection of the local climate regime. Under global warming, the simulation of glacier mass balance at the regional scale has attracted increasing interests. This study selects Urumqi Glacier No. 1 as the testbed for examining the transferability in space and time of two commonly used glacier mass balance simulation models: i.e., the Degree-Day Model(DDM) and the simplified Energy Balance Model(s EBM). Four experiments were carried out for assessing both models’ temporal and spatial transferability. The results show that the spatial transferability of both the DDM and s EBM is strong, whereas the temporal transferability of the DDM is relatively weak. For all four experiments, the overall simulation effect of the s EBM is better than that of the DDM. At the zone around Equilibrium Line Altitude(ELA), the DDM performed better than the s EBM.Also, the accuracy of parameters, including the lapse rate of air temperature and vertical gradient of precipitation at the glacier surface, is of great significance for improving the spatial transferability of both models.展开更多
We present a thermodynamically consistent model for diblock copolymer melts coupled with an electric field derived using the Onsager linear response theory.We compare the model with the thermodynamically inconsistent ...We present a thermodynamically consistent model for diblock copolymer melts coupled with an electric field derived using the Onsager linear response theory.We compare the model with the thermodynamically inconsistent one previously used for the coupled system to highlight their differences in describing transient dynamics.展开更多
Recent reports on the selective laser melting(SLM)process under a vacuum or low ambient pressure have shown fewer defects and better surface quality of the as-printed products.Although the physical process of SLM in a...Recent reports on the selective laser melting(SLM)process under a vacuum or low ambient pressure have shown fewer defects and better surface quality of the as-printed products.Although the physical process of SLM in a vacuum has been investigated by high-speed imaging,the underlying mechanisms governing the heat transfer and molten flow are still not well understood.Herein,we first developed a mesoscopic model of SLM under variable ambient pressure based on our recent laser-welding studies.We simulated the transport phenomena of SLM 316L stainless steel powders under atmospheric and 100 Pa ambient pressure.For typical process parameters(laser power:200W;scanning speed:2m∙s^(-1);powder diameter:27 lm),the average surface temperature of the cavity approached 2800 K under atmospheric pressure,while it came close to 2300 K under 100 Pa pressure.More vigorous fluid flow(average speed:4m∙s^(-1))was observed under 100 Pa ambient pressure,because the pressure difference between the evaporation-induced surface pressure and the ambient pressure was relatively larger and drives the flow under lower pressure.It was also shown that there are periodical ripple flows(period:14ls)affecting the surface roughness of the as-printed track.Moreover,the molten flow was shown to be laminar because the Reynolds number is less than 400 and is far below the critical value of turbulence;thus,the viscous dissipation is significant.It was demonstrated that under a vacuum or lower ambient pressure,the ripple flow can be dissipated more easily by the viscous effect because the trajectory length of the ripple is longer;thus,the surface quality of the tracks is improved.To summarize,our model elucidates the physical mechanisms of the interesting transport phenomena that have been observed in independent experimental studies of the SLM process under variable ambient pressure,which could be a powerful tool for optimizing the SLM process in the future.展开更多
Experiments of alloy melting were carried out in water/HCl H 2O eutectic model system. The eutectic has a solid liquid equilibrium temperature of -74 ℃. 5 cm diameter spheres of the eutectic in which three thermoc...Experiments of alloy melting were carried out in water/HCl H 2O eutectic model system. The eutectic has a solid liquid equilibrium temperature of -74 ℃. 5 cm diameter spheres of the eutectic in which three thermocouples in the core, on the edge and in the middle between them had been positioned were cooled to -196 ℃ in liquid nitrogen. After cooling the spheres were immersed into water of 10 ℃, and the changes of temperatures with time in the three thermocouples were measured. In some experiments the temperature on the outer side of the spheres where an ice shell grew up was also measured. In these experiments, the growing rate of the shell was additionally determined. The results for the first minute of the melting process, where the system can be considered as one dimensional, were described by an exact solution of Fouriers equation. The density of liquid ferromanganese at 1 500 ℃ was measured.展开更多
A system-level evaluation was used to analyze the induction furnace operation and process system in this study. This paper presents an investigation into the relationship between the instantaneous chemical composition...A system-level evaluation was used to analyze the induction furnace operation and process system in this study. This paper presents an investigation into the relationship between the instantaneous chemical composition of a molten bath and its energy consumption in steelmaking. This was evaluated using numerical modelling to solve for the estimated melting time prediction for the induction furnace operation. This work provides an insight into the lowering of energy consumption and estimated production time in steelmaking using material charge balancing approach. Enthalpy computation was implemented to develop an energy consumption model for the molten metal using a specific charge composition approach. Computational simulation program engine (CastMELT) was also developed in Java programming language with a MySQL database server for seamless specific charge composition analysis and testing. The model performance was established using real-time production data from a cast iron-based foundry with a 1 and 2-ton induction furnace capacity and a medium carbon-based foundry with a 10- and 15-ton induction furnace capacity. Using parameter fitting techniques on the measured operational data of the induction furnaces at different periods of melting, the results from the model predictions and real-time melting showed good correlation between 81% - 95%. A further analysis that compared the relationship between the mass composition of a current molten bath and melting, time showed that energy consumption can be reduced with effective material balancing and controlled charge. Melting time was obtained as a function of the elemental charge composition of the molten bath in relation to the overall scrap material charge. This validates the approach taken by this research using material charge and thermodynamic of melting to optimize and better control melting operation in foundry and reduce traditional waste during iron and steel making.展开更多
The present study investigated the vaporization kinetics of MgCl_2,CaCl_2 and their binary melts in a fluidized bed at1073-1273 K,and developed a vaporization model for the binary melts to explore the possibility of a...The present study investigated the vaporization kinetics of MgCl_2,CaCl_2 and their binary melts in a fluidized bed at1073-1273 K,and developed a vaporization model for the binary melts to explore the possibility of achieving enhanced vaporization rate for the feedstock containing CaO greater than 0.2 wt%.The vaporization rate constant of MgCl_2 is more than seven times than that of CaCl_2 at 1273 K.The vaporization rate of the binary melt was significantly affected by the composition,a small quantity of CaCl_2 can remarkably deteriorate the overall vaporization rate.Experimental results coincide well with the numerical simulation by the vaporization model which regards the evolution of vaporization rate with melts composition.A correlation between the necessary operation temperature and the CaO/(CaO + MgO) of the feedstock was proposed.Predictions reveal that a similar vaporization rate for 0.2 wt%-0.4 wt%CaO content feedstock with 0.2 wt%could be achieved at lower than 1365 K.展开更多
A novel Ti-5.55Al-6.70Zr-1.50V-0.70Mo-3.41Nb-0.21Si alloy was designed using the cluster formula approach(cluster-plus-glue-atom model)and prepared by laser melting deposition(LMD).Its composition formula 12[Al-Ti_(12...A novel Ti-5.55Al-6.70Zr-1.50V-0.70Mo-3.41Nb-0.21Si alloy was designed using the cluster formula approach(cluster-plus-glue-atom model)and prepared by laser melting deposition(LMD).Its composition formula 12[Al-Ti_(12)](AlTi_(2))+5[Al_(0.8)Si_(0.2)-Ti_(12)Zr_(2)](V_(0.8)Mo_(0.2)Nb_(1)Ti)features an enhancedβ-Ti via co-alloying of Zr,V,Mo,Nb and Si.The experimental results show that the cluster formula ofαandβphases in the novel alloy are respectivelyα-[Al-Ti_(11.5)Zr_(0.5)](Al_(1)Ti_(2))andβ-[Al_(0.8)Si_(0.2)-Ti_(13.2)Zr_(0.8)](V_(1)Mo_(0.4)Nb_(1.6)),both containing Zr elements.The fitted composition via the α andβphase cluster formulas has little difference with the actual alloy composition,suggesting that the validity of cluster-plus-glue-atom model in the alloy composition design.After hot isostatic pressing(HIP),both the Ti-6Al-4V and the novel alloy by LMD are characterized by prior-βcolumnar grains,while the typical<100>texture disappears.Compared with Ti-6Al-4V,Ti-5.55Al-6.70Zr-1.50V-0.70Mo-3.41Nb-0.21Si alloy exhibits a combination of higher strength(1,056 MPa)and higher ductility(14%)at room temperature and higher strength(580 MPa)at 550℃ after HIP,and can potentially serves as LMD materials.展开更多
基金The National Natural Science Foundation of China under contract Nos 41941010 and 42006184the Fundamental Research Funds for the Central Universities under contract No.2042022kf1068。
文摘In recent years,there has been a significant acceleration in the thinning,calving and retreat of the Pine Island Ice Shelf(PIIS).The basal channels,results of enhanced basal melting,have the potential to significantly impact the stability of the PIIS.In this study,we used a variety of remote sensing data,including Landsat,REMA DEM,ICESat-1 and ICESat-2 satellite altimetry observations,and Ice Bridge airborne measurements,to study the spatiotemporal changes in the basal channels from 2003 to 2020 and basal melt rate from 2010 to 2017 of the PIIS under the Eulerian framework.We found that the basal channels are highly developed in the PIIS,with a total length exceeding 450 km.Most of the basal channels are ocean-sourced or groundingline-sourced basal channels,caused by the rapid melting under the ice shelf or near the groundingline.A raised seabed prevented warm water intrusion into the eastern branch of the PIIS,resulting in a lower basal melt rate in that area.In contrast,a deepsea trough facilitates warm seawater into the mainstream and the western branch of the PIIS,resulting in a higher basal melt rate in the main-stream,and the surface elevation changes above the basal channels of the mainstream and western branch are more significant.The El Ni?o event in 2015–2016 possibly slowed down the basal melting of the PIIS by modulating wind field,surface sea temperature and depth seawater temperature.Ocean and atmospheric changes were driven by El Ni?o,which can further explain and confirm the changes in the basal melting of the PIIS.
基金supported by the Chinese-Norwegian Collaboration Projects within Climate Systems jointly funded by the National Key Research and Development Program of China[grant number 2022YFE0106800]the National Natural Science Foundation of China[grant number 42088101]+1 种基金a Research Council of Norway funded project(MAPARC)[grant number 328943]the Innovation Group Project of the Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)[grant number 311020001].
文摘Based on the coexistence theory of slag melt structure and Butler’s equation,a new calculation model has been proposed for the calculation of surface tension of slag melt.This model establishes a specific correlation between surface tension and mass action concentrations(activities) in the melt and on its surface on the basis of inner and surficial structures of slag melt.Calculated surface tensions of CaO-SiOand MnO-SiOslag melts are consistent with those measured.Furthermore,iso-surface tension lines of CaO-MnO-SiOslag melt have also been calculated.
基金financially supported by the Strategic Priority Research Program (B) of the Chinese Academy of Sciences (Grant No. XDB18010402)the National Natural Science Foundation of China (Grant No. 41702224)the Pearl River Talent Plan of Guangdong Province
文摘Zircon stability in silicate melts-which can be quantitatively constrained by laboratory measurements of zircon saturation-is important for understanding the evolution of magma.Although the original zircon saturation model proposed by Watson and Harrison(Earth Planet Sci Lett 64(2):295-304,1983) is widely cited and has been updated recently,the three main models currently in use may generate large uncertainties due to extrapolation beyond their respective calibrated ranges.This paper reviews and updates zircon saturation models developed with temperature and compositional parameters.All available data on zircon saturation ranging in composition from mafic to silicic(and/or peralkaline to peraluminous)at temperatures from 750 to 1400℃ were collected to develop two refined models(1 and 2) that may be applied to the wider range of compositions.Model 1 is given by lnCZr(melt)=(14.297±0.308)+(0.964 ± 0.066).M-(11113±374)/r,and model 2 given by lnCZr(melt)=(18.99±0.423)-(1.069±0.102)·lnG-(12288±593)/T,where CZr(melt) is the Zr concentration of the melt in ppm and parameters M [=(Na+K+2 Ca)/(Al·Si)](cation ratios) and G [=(3·Al2 O3+SiO2)/(Na2-O+K2 O+CaO+MgO+FeO)](molar proportions)represent the melt composition.The errors are at one sigma,and T is the temperature in Kelvin.Before applying these models to natural rocks,it is necessary to ensure that the zircon used to date is crystallized from the host magmatic rock.Assessment of the application of both new and old models to natural rocks suggests that model 1 may be the best for magmatic temperature estimates of metaluminous to peraluminous rocks and that model 2 may be the best for estimating magmatic temperatures of alkaline to peralkaline rocks.
基金This project is supported by the National Natural Science Foundation of China
文摘Conceptually, an imagined conformation ellipsoid is supposed to represent the shape of a polymer chain for polymer melts in flow fields and to be equivalent to the volume element in a mathematical sense in continuum mechanics. A power law dependence of shear modulus of polymer melts on detC, referred to as envelope volume, is proposed. Based on those assumptions and the non-linear relation of shear modulus, a phenomenological viscoelastic model is derived. The model is tested in simple shear flow, simple elongational flow, oscillatory shear flow, and relaxation process after flow suddenly stopped. The results show that the model works well to predict the change of internal structure and viscoelastic performance of polymer melts in flow fields.
基金This work was supported by the research grants from the National Nature Science Foundation of China (No. 20174024) and the Special Founds for Major State Basic Research Projects (G199906408)
文摘A constitutive model of quasi-Newtonian fluid based on the type of flow is used in abrupt planar contraction now.The numerical results from finite element analysis are consistent with experimental data for stress patterns and velocityprofiles in the flow field. The chain conformations of polymer melts are then investigated in such a planar contraction byusing the phenomenological model with internal parameters proposed by the author. That is, the shape and orientation ofpolymer chain coils are predicted and discussed in different flow regions of the contraction flow field that possess simpleshear flow, extensional flow, vortical flow, and mixed flow respectively.
基金supported by the National Natural Science Foundation of China(Grant No.51069017)the International Collaborative Research Program of Xinjiang Science and Technology Commission(Grant No.20126013)
文摘This study assessed the performances of the traditional temperature-index snowmelt runoff model(SRM) and an SRM model with a finer zonation based on aspect and slope(SRM + AS model) in a data-scarce mountain watershed in the Urumqi River Basin,in Northwest China.The proposed SRM + AS model was used to estimate the melt rate with the degree-day factor(DDF) through the division of watershed elevation zones based on aspect and slope.The simulation results of the SRM + AS model were compared with those of the traditional SRM model to identify the improvements of the SRM + AS model's performance with consideration of topographic features of the watershed.The results show that the performance of the SRM + AS model has improved slightly compared to that of the SRM model.The coefficients of determination increased from 0.73,0.69,and 0.79 with the SRM model to 0.76,0.76,and 0.81 with the SRM + AS model during the simulation and validation periods in 2005,2006,and 2007,respectively.The proposed SRM + AS model that considers aspect and slope can improve the accuracy of snowmelt runoff simulation compared to the traditional SRM model in mountain watersheds in arid regions by proper parameterization,careful input data selection,and data preparation.
基金funded by the National Key R&D Program of China (Grant No.2018YFA0605904)。
文摘Melt ponds significantly affect Arctic sea ice thermodynamic processes.The melt pond parameterization scheme in the Los Alamos sea ice model(CICE6.0) can predict the volume,area fraction(the ratio between melt pond area to sea ice area in a model grid),and depth of melt ponds.However,this scheme has some uncertain parameters that affect melt pond simulations.These parameters could be determined through a conventional parameter estimation method,which requires a large number of sensitivity simulations.The adjoint model can calculate the parameter sensitivity efficiently.In the present research,an adjoint model was developed for the CESM(Community Earth System Model) melt pond scheme.A melt pond parameter estimation algorithm was then developed based on the CICE6.0 sea ice model,melt pond adjoint model,and L-BFGS(Limited-memory Broyden-Fletcher-Goldfard-Shanno) minimization algorithm.The parameter estimation algorithm was verified under idealized conditions.By using MODIS(Moderate Resolution Imaging Spectroradiometer)melt pond fraction observation as a constraint and the developed parameter estimation algorithm,the melt pond aspect ratio parameter in CESM scheme,which is defined as the ratio between pond depth and pond area fraction,was estimated every eight days during summertime for two different regions in the Arctic.One region was covered by multi-year ice(MYI) and the other by first-year ice(FYI).The estimated parameter was then used in simulations and the results show that:(1) the estimated parameter varies over time and is quite different for MYI and FYI;(2) the estimated parameter improved the simulation of the melt pond fraction.
文摘An approach of stochastically statistical mechanics and a unified molecular theory of nonlinear viscoelasticity with constraints of Nagai chain entanglement for polymer melts have been proposed. A multimode model structure for a single polymer chain with n tail segments and N reversible entanglement sites on the test polymer chain is developed. Based on the above model structure and the mechanism of molecular flow by the dynamical reorganization of entanglement sites, the probability distribution function of the end-to-end vectr for a single polymer chain at entangled state and the viscoelastic free energy of deformation for polymer melts are calculated by using the method of the stochastically statistical mechanics. The four types of stress-strain relation and the memory function are derived from this thery. The above theoretical relations are verified by the experimentaf data for various polymer melts. These relations are found to be in good agreement with the experimental results
文摘The anharmonic vibrator, whose expression of potential energy contains second and third powers of coordinates, is treated on the basis of dynamical procedure, which presents the state of motion by means of mean position and mean amplitude of vibration. The divergent statistical integral comes here not into consideration. The free energy is represented through mean atomic displacement and developed in power series, retaining fourth degree. The graphs show that at certain temperature, the minimum in free energy disappears, and the atom escapes from the potential pit. A simple atomic model that represents this phenomenon is proposed and the influence of model dimension and pressure on melting temperature will be presented.
文摘It is shown theoretically that the viscoelasticity of polymer melts is determined by three combining factorst they are the primary molecular weight and its distribution, the number of entanglement sites on polymer chain and the sequence distribution of constituent chains in entanglement spacings. A unified quantity for the three combing factors is the average constrained dimensional number of constituent chains in the long entanglement spacings (v). A new relation of v to the primary molecular weight and the number of testing polymers were derived from the multiple entanglement and reptation model, and a new method for determining v was proposed. The dependences of linear viscoelastic functions on the primary molecular weight and its distribution were derived by the statistical method. When Mn=6Me to 18 Me, the values of (v) can range from 3.33 to 3.70. Their values are in a good agreement with the experiment data, and it can slightjy vary with the different species of polymers and the different ranges of molecular weight of polymers
基金funded by the National Natural Science Foundation of China (51879226)the Chinese Universities Scientific Fund (2452020018)。
文摘Maize (Zea mays L.) is one of the three major food crops and an important source of carbohydrates for maintaining food security around the world.Plant height (H),stem diameter (SD),leaf area index (LAI) and dry matter (DM) are important growth parameters that influence maize production.However,the combined effect of temperature and light on maize growth is rarely considered in crop growth models.Ten maize growth models based on the modified logistic growth equation (Mlog) and the Mitscherlich growth equation (Mit) were proposed to simulate the H,SD,LAI and DM of maize under different mulching practices based on experimental data from 2015–2018.Either the accumulative growing degree-days (AGDD),helio thermal units (HTU),photothermal units (PTU) or photoperiod thermal units (PPTU,first proposed here) was used as a single driving factor in the models;or AGDD was combined with either accumulative actual solar hours (ASS),accumulative photoperiod response (APR,first proposed here) or accumulative maximum possible sunshine hours (ADL) as the dual driving factors in the models.The model performances were evaluated using seven statistical indicators and a global performance index.The results showed that the three mulching practices significantly increased the maize growth rates and the maximum values of the growth curves compared with non-mulching.Among the four single factor-driven models,the overall performance of the Mlog_(PTU)Model was the best,followed by the Mlog_(AGDD)Model.The Mlog_(PPTU)Model was better than the Mlog_(AGDD)Model in simulating SD and LAI.Among the 10 models,the overall performance of the Mlog_(AGDD–APR)Model was the best,followed by the Mlog_(AGDD–ASS)Model.Specifically,the Mlog_(AGDD–APR)Model performed the best in simulating H and LAI,while the Mlog_(AGDD–ADL)and Mlog_(AGDD–ASS)models performed the best in simulating SD and DM,respectively.In conclusion,the modified logistic growth equations with AGDD and either APR,ASS or ADL as the dual driving factors outperformed the commonly used modified logistic growth model with AGDD as a single driving factor in simulating maize growth.
基金supported by the Key Research Program of Frontier Sciences of Chinese Academy of Sciences(Grant No.QYZDB-SSW-SYS024)National Natural Science Foundation of China(Grant Nos.41771081 and 41761134093).
文摘Glacier mass balance, the difference between accumulation and ablation at the glacier surface, is the direct reflection of the local climate regime. Under global warming, the simulation of glacier mass balance at the regional scale has attracted increasing interests. This study selects Urumqi Glacier No. 1 as the testbed for examining the transferability in space and time of two commonly used glacier mass balance simulation models: i.e., the Degree-Day Model(DDM) and the simplified Energy Balance Model(s EBM). Four experiments were carried out for assessing both models’ temporal and spatial transferability. The results show that the spatial transferability of both the DDM and s EBM is strong, whereas the temporal transferability of the DDM is relatively weak. For all four experiments, the overall simulation effect of the s EBM is better than that of the DDM. At the zone around Equilibrium Line Altitude(ELA), the DDM performed better than the s EBM.Also, the accuracy of parameters, including the lapse rate of air temperature and vertical gradient of precipitation at the glacier surface, is of great significance for improving the spatial transferability of both models.
基金partially supported by the National Natural Science Foundation of China(Grant Nos.11971051 and U1930402)partially supported by National Science Foundation grants(award DMS-1815921,1954532 and OIA-1655740)a GEAR award from SC EPSCoR/IDeA Program。
文摘We present a thermodynamically consistent model for diblock copolymer melts coupled with an electric field derived using the Onsager linear response theory.We compare the model with the thermodynamically inconsistent one previously used for the coupled system to highlight their differences in describing transient dynamics.
基金This research was supported by the National Science Fund for Excellent Young Scholars(52022033)the National Key Research and Development Program of China(2017YFE0100100 and 2018YFB1105300)+1 种基金was partially supported by the Government of Perm Krai(S-26/794)the Russian Foundation for Basic Research(16-48-590208).
文摘Recent reports on the selective laser melting(SLM)process under a vacuum or low ambient pressure have shown fewer defects and better surface quality of the as-printed products.Although the physical process of SLM in a vacuum has been investigated by high-speed imaging,the underlying mechanisms governing the heat transfer and molten flow are still not well understood.Herein,we first developed a mesoscopic model of SLM under variable ambient pressure based on our recent laser-welding studies.We simulated the transport phenomena of SLM 316L stainless steel powders under atmospheric and 100 Pa ambient pressure.For typical process parameters(laser power:200W;scanning speed:2m∙s^(-1);powder diameter:27 lm),the average surface temperature of the cavity approached 2800 K under atmospheric pressure,while it came close to 2300 K under 100 Pa pressure.More vigorous fluid flow(average speed:4m∙s^(-1))was observed under 100 Pa ambient pressure,because the pressure difference between the evaporation-induced surface pressure and the ambient pressure was relatively larger and drives the flow under lower pressure.It was also shown that there are periodical ripple flows(period:14ls)affecting the surface roughness of the as-printed track.Moreover,the molten flow was shown to be laminar because the Reynolds number is less than 400 and is far below the critical value of turbulence;thus,the viscous dissipation is significant.It was demonstrated that under a vacuum or lower ambient pressure,the ripple flow can be dissipated more easily by the viscous effect because the trajectory length of the ripple is longer;thus,the surface quality of the tracks is improved.To summarize,our model elucidates the physical mechanisms of the interesting transport phenomena that have been observed in independent experimental studies of the SLM process under variable ambient pressure,which could be a powerful tool for optimizing the SLM process in the future.
文摘Experiments of alloy melting were carried out in water/HCl H 2O eutectic model system. The eutectic has a solid liquid equilibrium temperature of -74 ℃. 5 cm diameter spheres of the eutectic in which three thermocouples in the core, on the edge and in the middle between them had been positioned were cooled to -196 ℃ in liquid nitrogen. After cooling the spheres were immersed into water of 10 ℃, and the changes of temperatures with time in the three thermocouples were measured. In some experiments the temperature on the outer side of the spheres where an ice shell grew up was also measured. In these experiments, the growing rate of the shell was additionally determined. The results for the first minute of the melting process, where the system can be considered as one dimensional, were described by an exact solution of Fouriers equation. The density of liquid ferromanganese at 1 500 ℃ was measured.
文摘A system-level evaluation was used to analyze the induction furnace operation and process system in this study. This paper presents an investigation into the relationship between the instantaneous chemical composition of a molten bath and its energy consumption in steelmaking. This was evaluated using numerical modelling to solve for the estimated melting time prediction for the induction furnace operation. This work provides an insight into the lowering of energy consumption and estimated production time in steelmaking using material charge balancing approach. Enthalpy computation was implemented to develop an energy consumption model for the molten metal using a specific charge composition approach. Computational simulation program engine (CastMELT) was also developed in Java programming language with a MySQL database server for seamless specific charge composition analysis and testing. The model performance was established using real-time production data from a cast iron-based foundry with a 1 and 2-ton induction furnace capacity and a medium carbon-based foundry with a 10- and 15-ton induction furnace capacity. Using parameter fitting techniques on the measured operational data of the induction furnaces at different periods of melting, the results from the model predictions and real-time melting showed good correlation between 81% - 95%. A further analysis that compared the relationship between the mass composition of a current molten bath and melting, time showed that energy consumption can be reduced with effective material balancing and controlled charge. Melting time was obtained as a function of the elemental charge composition of the molten bath in relation to the overall scrap material charge. This validates the approach taken by this research using material charge and thermodynamic of melting to optimize and better control melting operation in foundry and reduce traditional waste during iron and steel making.
基金Supported by the National Natural Science Foundation of China(NSFC)Distinguished Young Scholar project(No.21325628)
文摘The present study investigated the vaporization kinetics of MgCl_2,CaCl_2 and their binary melts in a fluidized bed at1073-1273 K,and developed a vaporization model for the binary melts to explore the possibility of achieving enhanced vaporization rate for the feedstock containing CaO greater than 0.2 wt%.The vaporization rate constant of MgCl_2 is more than seven times than that of CaCl_2 at 1273 K.The vaporization rate of the binary melt was significantly affected by the composition,a small quantity of CaCl_2 can remarkably deteriorate the overall vaporization rate.Experimental results coincide well with the numerical simulation by the vaporization model which regards the evolution of vaporization rate with melts composition.A correlation between the necessary operation temperature and the CaO/(CaO + MgO) of the feedstock was proposed.Predictions reveal that a similar vaporization rate for 0.2 wt%-0.4 wt%CaO content feedstock with 0.2 wt%could be achieved at lower than 1365 K.
基金supported by the Natural Science Foundation of Shenyang,China(Grant No.22315605).
文摘A novel Ti-5.55Al-6.70Zr-1.50V-0.70Mo-3.41Nb-0.21Si alloy was designed using the cluster formula approach(cluster-plus-glue-atom model)and prepared by laser melting deposition(LMD).Its composition formula 12[Al-Ti_(12)](AlTi_(2))+5[Al_(0.8)Si_(0.2)-Ti_(12)Zr_(2)](V_(0.8)Mo_(0.2)Nb_(1)Ti)features an enhancedβ-Ti via co-alloying of Zr,V,Mo,Nb and Si.The experimental results show that the cluster formula ofαandβphases in the novel alloy are respectivelyα-[Al-Ti_(11.5)Zr_(0.5)](Al_(1)Ti_(2))andβ-[Al_(0.8)Si_(0.2)-Ti_(13.2)Zr_(0.8)](V_(1)Mo_(0.4)Nb_(1.6)),both containing Zr elements.The fitted composition via the α andβphase cluster formulas has little difference with the actual alloy composition,suggesting that the validity of cluster-plus-glue-atom model in the alloy composition design.After hot isostatic pressing(HIP),both the Ti-6Al-4V and the novel alloy by LMD are characterized by prior-βcolumnar grains,while the typical<100>texture disappears.Compared with Ti-6Al-4V,Ti-5.55Al-6.70Zr-1.50V-0.70Mo-3.41Nb-0.21Si alloy exhibits a combination of higher strength(1,056 MPa)and higher ductility(14%)at room temperature and higher strength(580 MPa)at 550℃ after HIP,and can potentially serves as LMD materials.