A dynamic food chain model and program, DYFOM 95, for predicting the radiological consequences of nuclear accident has been developed, which is not only suitable to the West food chain but also to Chinese food chain. ...A dynamic food chain model and program, DYFOM 95, for predicting the radiological consequences of nuclear accident has been developed, which is not only suitable to the West food chain but also to Chinese food chain. The following processes, caused by accident release which will make an impact on radionuclide concentration in the edible parts of vegetable were considered: dry and wet deposition interception and initial retention, translocation, percolation, root uptake and tillage. Activity intake rate of animals, effects of processing and activity intake of human through ingestion pathway ware also considered in calculations. The effects of leaf area index LAI of vegetable were considered in dry deposition model. A method for calculating the contribution of rain with different period and different intensity to total wet deposition was established. The program contains 1 main code and 5 sub codes to calculate dry and wet deposition on surface of vegetable and soil, translocation of nuclides in vegetable, nuclide concentration in the edible parts of vegetable and in animal products and activity intake of human and so on.展开更多
After building a dynamic evolutionary game model, the essay studies the stability of the equilibrium in the game between the commercial banks and the closed-loop supply chain(CLSC) enterprises. By design of systematic...After building a dynamic evolutionary game model, the essay studies the stability of the equilibrium in the game between the commercial banks and the closed-loop supply chain(CLSC) enterprises. By design of systematic mechanism based on system dynamics theory, capital chains of independent small and medium-sized enterprises(SMEs) on CLSC are organically linked together. Moreover, a comparative simulation is studied for the previous independent and post-design dependent systems. The study shows that with business expanding and market risk growing, the independent finance chains of SMEs on CLSC often take on a certain vulnerability, while the SMEs closed-loop supply chain finance system itself is with a strong rigidity and concerto.展开更多
Brownian dynamics simulations are employed to explore the effects of chain stiffness and trivalent salt concentration on the conformational behavior of spherical polyelectrolyte brush. The rigid brush adopts bundle-li...Brownian dynamics simulations are employed to explore the effects of chain stiffness and trivalent salt concentration on the conformational behavior of spherical polyelectrolyte brush. The rigid brush adopts bundle-like morphology at a wide range of trivalent salt concentration. The number variation of bundles pinned on the colloid surface shows a non-monotonic profile as a function of the chain stiffness. The radial distributions of monomers and ions and the charge ratio between condensed ions and monomers are calculated. The charge inversion is observed for the high salt concentration regardless of chain rigidity. Furthermore, the pair correlation functions of monomer-monomer and monomer-salt cation are used to elucidate the aggregated mechanism of the bundle-like structure.展开更多
The chain dynamics of a pair of diblock poly(styrene-b-butadiene) (PS210-b-PB960) and triblock poly(styrene-b-butadiene-b-styrene) (PS200-b-PB1815-b-PS200) copolymers in both dilute and semidilute toluene solutions ha...The chain dynamics of a pair of diblock poly(styrene-b-butadiene) (PS210-b-PB960) and triblock poly(styrene-b-butadiene-b-styrene) (PS200-b-PB1815-b-PS200) copolymers in both dilute and semidilute toluene solutions has been comparatively studied by dynamic laser light scattering. As expected, the mutual diffusion of individual chain changes into a fast cooperative diffusion of the chain segments ('blobs') between two neighboring entanglement points for both the copolymers as the solution changes from dilute to semidilute. Further increases of the concentration lead to a second slow relaxation mode. For the triblock chains, there exists an additional middle relaxation between the fast and the slow modes. The concentration (c) dependent study of the average characteristic decay time of the fast mode ((tau(f))) reveals that 1/(tau(f)) - c(-a) with 0.33 < alpha < 0.44, much smaller than 0.75 predicted or 0.72 observed for linear homopolymer chains in good solvent. It implies that the solvent quality of toluene for PB might not be as good as that for PS. Due to such a difference in solubility, it is reasonable to speculate that the PB and PS blocks are transiently segregated in semidilute solution. The relaxation of these transient PB and PS richer domains leads to the observed slow relaxation. Such a speculation is supported by the appearance of an additional slow relaxation mode in the study of polyisoprene-b-polystyrene-b-polyisoprene in semidilute solution in cyclohexane, a non-selective solvent, in which we alternated the solubility difference by a variation of the solution temperature.展开更多
Flexural waves usually propagate in one-and two-dimensional structures.To further our understanding on their transmission properties from the viewpoint of discrete lattice dynamics,we systematically established analyt...Flexural waves usually propagate in one-and two-dimensional structures.To further our understanding on their transmission properties from the viewpoint of discrete lattice dynamics,we systematically established analytical atom chain models with mass defects and side branches.Both mechanisms of the Bragg scattering and the local resonance corresponding to mass defects and side branches,respectively,are elucidated by means of the present models.The results from the models show that increasing the number of mass defects or side branches decreases the transmission magnitude gradually,and the finite-width phononic bandgap may form due to the periodical arrangement of defects.The interplay between the local resonance and the Bragg scattering gives rise to the narrow phononic bandgap for lattice chains only with periodical side branches.The width of the bandgap strongly depends on the stiffness of side branches.The transmission is insensitive to the tensile strain considered for both kinds of defects,but significantly decreases with an increase in damping or wave frequency.The present work helps further our understanding on the dynamics of flexural waves.展开更多
The carbon-13 spin-spin relaxation times of fluorine-containing ionomers are measured and motional correlation times τ;and τ;are calculated by using VJGM model . The results show that the motions of polymer main cha...The carbon-13 spin-spin relaxation times of fluorine-containing ionomers are measured and motional correlation times τ;and τ;are calculated by using VJGM model . The results show that the motions of polymer main chain in ionomers become more difficult with increasing of ionization degree and contents of functional group, and depend on the fine structures and stability of ionic microdomains.展开更多
In this paper a dynamic food chain model for Hong Kong which simulates the transfer of radioactive substances from a fallout deposition via the food chain into the human bodies is built. The model is based on the RADF...In this paper a dynamic food chain model for Hong Kong which simulates the transfer of radioactive substances from a fallout deposition via the food chain into the human bodies is built. The model is based on the RADFOOD model and the BirchallJames algorithm. The radionuclides 13if and 90Sr representing the short-term and long-term risk situations have been studied as sample cases. Various types of crops,and the dietary pattern of the public have been collsidered. The resulting internal radiation doses have been calculated. The results are obtained for food consumption starting at various time after the fallout deposition and for different consumption durations.展开更多
Measurement error of unbalance's vibration response plays a crucial role in calibration and on-line updating of influence coefficient(IC).Focusing on the two problems that the moment estimator of data used in cali...Measurement error of unbalance's vibration response plays a crucial role in calibration and on-line updating of influence coefficient(IC).Focusing on the two problems that the moment estimator of data used in calibration process cannot fulfill the accuracy requirement under small sample and the disturbance of measurement error cannot be effectively suppressed in updating process,an IC calibration and on-line updating method based on hierarchical Bayesian method for automatic dynamic balancing machine was proposed.During calibration process,for the repeatedly-measured data obtained from experiments with different trial weights,according to the fact that measurement error of each sensor had the same statistical characteristics,the joint posterior distribution model for the true values of the vibration response under all trial weights and measurement error was established.During the updating process,information obtained from calibration was regarded as prior information,which was utilized to update the posterior distribution of IC combined with the real-time reference information to implement online updating.Moreover,Gibbs sampling method of Markov Chain Monte Carlo(MCMC)was adopted to obtain the maximum posterior estimation of parameters to be estimated.On the independent developed dynamic balancing testbed,prediction was carried out for multiple groups of data through the proposed method and the traditional method respectively,the result indicated that estimator of influence coefficient obtained through the proposed method had higher accuracy;the proposed updating method more effectively guaranteed the measurement accuracy during the whole producing process,and meantime more reasonably compromised between the sensitivity of IC change and suppression of randomness of vibration response.展开更多
By the so-called wormlike chain （WLC） model in polymer physics envision- ing an isotropic rod that is continuously flexible, the force-extension relations of semi- flexible polymer chains strongly constrained by var...By the so-called wormlike chain （WLC） model in polymer physics envision- ing an isotropic rod that is continuously flexible, the force-extension relations of semi- flexible polymer chains strongly constrained by various confinements are theoretically investigated, including a slab-like confinement where the polymer chains are sandwiched between two parallel impenetrable walls, and a capped nanochannel confinement with a circular or rectangular cross-section where the chains are bounded in three directions. The Brownian dynamics （BD） simulations based on the generalized bead-rod （GBR） model are performed to verify the theoretical predictions.展开更多
When dynamic load is applied on a granular assembly,the time-dependent dynamic load and initial static load(such as gravity stress)act together on individual particles.In order to better understand how dynamic load tr...When dynamic load is applied on a granular assembly,the time-dependent dynamic load and initial static load(such as gravity stress)act together on individual particles.In order to better understand how dynamic load triggers the micro-structure's evolution and furtherly the ensemble behavior of a granular assembly,we propose a criterion to recognize the major propagation path of dynamic load in 2D granular materials,called the“dynamic force chain”.Two steps are involved in recognizing dynamic force chains:(1)pick out particles with dynamic load larger than the threshold stress,where the attenuation of dynamic stress with distance is considered;(2)among which quasi-linear arrangement of three or more particles are identified as a force chain.The spatial distribution of dynamic force chains in indentation of granular materials provides a direct measure of dynamic load diffusion.The statistical evolution of dynamic force chains shows strong correlation with the indentation behaviors.展开更多
Dynamic fund protection provides a guarantee that the account value of the investor never drops below a barrier over the investment period.In order to reduce the downside risk taken by vendors,Han,et al.(2016)proposed...Dynamic fund protection provides a guarantee that the account value of the investor never drops below a barrier over the investment period.In order to reduce the downside risk taken by vendors,Han,et al.(2016)proposed a chained dynamic fund protection(CDFP),whose protection is activated only if the value of basic fund reaches a predefined upper protection line.Motivated by them,we consider a new CDFP plan under a stochastic interest rate environment.The explicit pricing formula for a CDFP is obtained when the protection lines are proportional to a zero-coupon bond.Furthermore,the authors present some numerical results for the value of CDFP at time 0 to show how the model parameters impact the value of CDFP.展开更多
The capture of circulating tumor cells(CTCs)is of great significance in reducing cancer mortality and complications.However,the nonspecific binding of proteins and white blood cells(WBCs)weakens the targeting capabili...The capture of circulating tumor cells(CTCs)is of great significance in reducing cancer mortality and complications.However,the nonspecific binding of proteins and white blood cells(WBCs)weakens the targeting capabilities of the capture surfaces,which critically hampers the efficiency and purity of the captured CTCs.Herein,we propose a liquid-like interface design strategy that consists of liquid-like polymer chains and anti-EpCAM modification processes for high-purity and high-efficiency capture of CTCs.The dynamic flexible feature of the liquid-like chains endows the modified surfaces with excellent antiadhesion property for proteins and blood cells.The liquid-like surfaces can capture the target CTCs and show high cell viability due to the environmentfriendly surface modification processes.When liquid-like surface designs were introduced in the deterministic lateral displacement(DLD)-patterned microfluidic chip,the nonspecific adhesion rate of WBCs was reduced by more than fivefold compared to that in the DLD chip without liquid-like interface design,while maintaining comparable capture efficiency.Overall,this strategy provides a novel perspective on surface design for achieving high purity and efficient capture of CTCs.展开更多
A set of universal equations on the reduced stress relaxation modulus with K-W-W stretched exponential function has been derived from the dynamics of α and β structural relaxation processes. In the present work, the...A set of universal equations on the reduced stress relaxation modulus with K-W-W stretched exponential function has been derived from the dynamics of α and β structural relaxation processes. In the present work, the K-W-W decay function is used to define the three types of relaxations (single α, single β relaxation and α-β co-relaxation), then their average times of relaxation are theoretically calculated from the reduced shear stress relaxation modulus and the relaxation time spectrum function H(τ). When the average time of co-relaxation, the reference temperatures (ficitive Tf and glass transition Tg) and the isostructural parameter achieved from the conditions of isostructural glass state are introduced into the reduced shear stress relaxation modulus (GT) under the equilibrium state, a set of correlations between isochoric fragility index (mvα, mvβ and mvαβ) and the coupling strength (α and β) under the reference temperatures are derived from the exact definition of isochoric fragility. So the theory of dynamic fragility for glass substances at isochoric state is developed. The theory can predict the following main features of structural relaxations and behavior of isochoric fragility: the temperature dependence of peak relaxation frequency exhibits a bifurcation with a pair of single α and single β relaxations; the temperature dependence of Stickel equation on 1/T exhibits two crossovers with VFTH(1) and VFTH(2) at the temperatures of Tf and Tg regime; there are two linear correlations between isochoric fragility index (mvα and mvβ) and the coupling strength. Fine agreements between the theoretical calculation and experimental results are obtained.展开更多
We first recall some basic facts from the theory of discrete-time Markov chains arising from two types neutral and non-neutral evolution models of population genetics with constant size. We then define and analyze a v...We first recall some basic facts from the theory of discrete-time Markov chains arising from two types neutral and non-neutral evolution models of population genetics with constant size. We then define and analyze a version of such models whose fluctuating total population size is conserved on average only. In our model, the population of interest is seen as being embedded in a frame process which is a critical Galton Watson process. In this context, we address problems such as extinction, fixation, size of the population at fixation and survival probability to a bottleneck effect of the environment.展开更多
文摘A dynamic food chain model and program, DYFOM 95, for predicting the radiological consequences of nuclear accident has been developed, which is not only suitable to the West food chain but also to Chinese food chain. The following processes, caused by accident release which will make an impact on radionuclide concentration in the edible parts of vegetable were considered: dry and wet deposition interception and initial retention, translocation, percolation, root uptake and tillage. Activity intake rate of animals, effects of processing and activity intake of human through ingestion pathway ware also considered in calculations. The effects of leaf area index LAI of vegetable were considered in dry deposition model. A method for calculating the contribution of rain with different period and different intensity to total wet deposition was established. The program contains 1 main code and 5 sub codes to calculate dry and wet deposition on surface of vegetable and soil, translocation of nuclides in vegetable, nuclide concentration in the edible parts of vegetable and in animal products and activity intake of human and so on.
基金the Natural Science Research Fund of Hubei Province(No.2014BDH121)
文摘After building a dynamic evolutionary game model, the essay studies the stability of the equilibrium in the game between the commercial banks and the closed-loop supply chain(CLSC) enterprises. By design of systematic mechanism based on system dynamics theory, capital chains of independent small and medium-sized enterprises(SMEs) on CLSC are organically linked together. Moreover, a comparative simulation is studied for the previous independent and post-design dependent systems. The study shows that with business expanding and market risk growing, the independent finance chains of SMEs on CLSC often take on a certain vulnerability, while the SMEs closed-loop supply chain finance system itself is with a strong rigidity and concerto.
基金financially supported by the National Natural Science Foundation of China (No. 21474005)the Fundamental Research Funds for the Central Universities (No. 3122016L011)
文摘Brownian dynamics simulations are employed to explore the effects of chain stiffness and trivalent salt concentration on the conformational behavior of spherical polyelectrolyte brush. The rigid brush adopts bundle-like morphology at a wide range of trivalent salt concentration. The number variation of bundles pinned on the colloid surface shows a non-monotonic profile as a function of the chain stiffness. The radial distributions of monomers and ions and the charge ratio between condensed ions and monomers are calculated. The charge inversion is observed for the high salt concentration regardless of chain rigidity. Furthermore, the pair correlation functions of monomer-monomer and monomer-salt cation are used to elucidate the aggregated mechanism of the bundle-like structure.
基金The financial support of the Hong Kong Special Administration Region Earmarked Grants (CUHK4257/01P, 2160174), theSpecial Funds for Major State Basic Research Projects (G1999064800), the CAS Bai Ren Project and the National ScienceFoundation of China (NSFC) are gratefully acknowledged.
文摘The chain dynamics of a pair of diblock poly(styrene-b-butadiene) (PS210-b-PB960) and triblock poly(styrene-b-butadiene-b-styrene) (PS200-b-PB1815-b-PS200) copolymers in both dilute and semidilute toluene solutions has been comparatively studied by dynamic laser light scattering. As expected, the mutual diffusion of individual chain changes into a fast cooperative diffusion of the chain segments ('blobs') between two neighboring entanglement points for both the copolymers as the solution changes from dilute to semidilute. Further increases of the concentration lead to a second slow relaxation mode. For the triblock chains, there exists an additional middle relaxation between the fast and the slow modes. The concentration (c) dependent study of the average characteristic decay time of the fast mode ((tau(f))) reveals that 1/(tau(f)) - c(-a) with 0.33 < alpha < 0.44, much smaller than 0.75 predicted or 0.72 observed for linear homopolymer chains in good solvent. It implies that the solvent quality of toluene for PB might not be as good as that for PS. Due to such a difference in solubility, it is reasonable to speculate that the PB and PS blocks are transiently segregated in semidilute solution. The relaxation of these transient PB and PS richer domains leads to the observed slow relaxation. Such a speculation is supported by the appearance of an additional slow relaxation mode in the study of polyisoprene-b-polystyrene-b-polyisoprene in semidilute solution in cyclohexane, a non-selective solvent, in which we alternated the solubility difference by a variation of the solution temperature.
基金support from the NationalNatural Science Foundation of China under Grant No.12172150the Guang Dong Basic and Applied Basic Research Foundation under Grant No.2022A1515010287.
文摘Flexural waves usually propagate in one-and two-dimensional structures.To further our understanding on their transmission properties from the viewpoint of discrete lattice dynamics,we systematically established analytical atom chain models with mass defects and side branches.Both mechanisms of the Bragg scattering and the local resonance corresponding to mass defects and side branches,respectively,are elucidated by means of the present models.The results from the models show that increasing the number of mass defects or side branches decreases the transmission magnitude gradually,and the finite-width phononic bandgap may form due to the periodical arrangement of defects.The interplay between the local resonance and the Bragg scattering gives rise to the narrow phononic bandgap for lattice chains only with periodical side branches.The width of the bandgap strongly depends on the stiffness of side branches.The transmission is insensitive to the tensile strain considered for both kinds of defects,but significantly decreases with an increase in damping or wave frequency.The present work helps further our understanding on the dynamics of flexural waves.
基金The work was supported by National Natural Science Foundation of China
文摘The carbon-13 spin-spin relaxation times of fluorine-containing ionomers are measured and motional correlation times τ;and τ;are calculated by using VJGM model . The results show that the motions of polymer main chain in ionomers become more difficult with increasing of ionization degree and contents of functional group, and depend on the fine structures and stability of ionic microdomains.
文摘In this paper a dynamic food chain model for Hong Kong which simulates the transfer of radioactive substances from a fallout deposition via the food chain into the human bodies is built. The model is based on the RADFOOD model and the BirchallJames algorithm. The radionuclides 13if and 90Sr representing the short-term and long-term risk situations have been studied as sample cases. Various types of crops,and the dietary pattern of the public have been collsidered. The resulting internal radiation doses have been calculated. The results are obtained for food consumption starting at various time after the fallout deposition and for different consumption durations.
基金supported by National Hi-tech Research and Development Program of China(863 Program,Grant No.2008 AA04Z114)
文摘Measurement error of unbalance's vibration response plays a crucial role in calibration and on-line updating of influence coefficient(IC).Focusing on the two problems that the moment estimator of data used in calibration process cannot fulfill the accuracy requirement under small sample and the disturbance of measurement error cannot be effectively suppressed in updating process,an IC calibration and on-line updating method based on hierarchical Bayesian method for automatic dynamic balancing machine was proposed.During calibration process,for the repeatedly-measured data obtained from experiments with different trial weights,according to the fact that measurement error of each sensor had the same statistical characteristics,the joint posterior distribution model for the true values of the vibration response under all trial weights and measurement error was established.During the updating process,information obtained from calibration was regarded as prior information,which was utilized to update the posterior distribution of IC combined with the real-time reference information to implement online updating.Moreover,Gibbs sampling method of Markov Chain Monte Carlo(MCMC)was adopted to obtain the maximum posterior estimation of parameters to be estimated.On the independent developed dynamic balancing testbed,prediction was carried out for multiple groups of data through the proposed method and the traditional method respectively,the result indicated that estimator of influence coefficient obtained through the proposed method had higher accuracy;the proposed updating method more effectively guaranteed the measurement accuracy during the whole producing process,and meantime more reasonably compromised between the sensitivity of IC change and suppression of randomness of vibration response.
基金supported the National Natural Science Foundation of China(Nos.11032006,11072094,and11121202)the Ph.D.Program Foundation of Ministry of Education of China(No.20100211110022)+1 种基金the National Key Project of Magneto-Constrained Fusion Energy Development Program of China(No.2013GB110002)the Fundamental Research Funds for the Central Universities(No.lzujbky2013-1)
文摘By the so-called wormlike chain （WLC） model in polymer physics envision- ing an isotropic rod that is continuously flexible, the force-extension relations of semi- flexible polymer chains strongly constrained by various confinements are theoretically investigated, including a slab-like confinement where the polymer chains are sandwiched between two parallel impenetrable walls, and a capped nanochannel confinement with a circular or rectangular cross-section where the chains are bounded in three directions. The Brownian dynamics （BD） simulations based on the generalized bead-rod （GBR） model are performed to verify the theoretical predictions.
基金The authors are grateful to the Natural Science Foundation of Shanghai(grant No.21ZR1465400)for providing financial support for this research。
文摘When dynamic load is applied on a granular assembly,the time-dependent dynamic load and initial static load(such as gravity stress)act together on individual particles.In order to better understand how dynamic load triggers the micro-structure's evolution and furtherly the ensemble behavior of a granular assembly,we propose a criterion to recognize the major propagation path of dynamic load in 2D granular materials,called the“dynamic force chain”.Two steps are involved in recognizing dynamic force chains:(1)pick out particles with dynamic load larger than the threshold stress,where the attenuation of dynamic stress with distance is considered;(2)among which quasi-linear arrangement of three or more particles are identified as a force chain.The spatial distribution of dynamic force chains in indentation of granular materials provides a direct measure of dynamic load diffusion.The statistical evolution of dynamic force chains shows strong correlation with the indentation behaviors.
基金supported by the NSF of Jiangsu Province under Grant No.BK20170064the NNSF of China under Grant No.11771320+2 种基金Qing Lan Project of Jiangsu Provincethe scholarship of Jiangsu Overseas Visiting Scholar Programthe Graduate Innovation Program of USTS(SKCX18-Y06)
文摘Dynamic fund protection provides a guarantee that the account value of the investor never drops below a barrier over the investment period.In order to reduce the downside risk taken by vendors,Han,et al.(2016)proposed a chained dynamic fund protection(CDFP),whose protection is activated only if the value of basic fund reaches a predefined upper protection line.Motivated by them,we consider a new CDFP plan under a stochastic interest rate environment.The explicit pricing formula for a CDFP is obtained when the protection lines are proportional to a zero-coupon bond.Furthermore,the authors present some numerical results for the value of CDFP at time 0 to show how the model parameters impact the value of CDFP.
基金supported by the National Natural Science Foundation of China(grant nos.52025132,21975209,22275156,21621091,22021001,22005255,and T2241022)the National Science Foundation of Fujian Province of China(grant no.2022J02059)+4 种基金the Fundamental Research Funds for the Central Universities of China(grant nos.20720220019 and 20720220085)the 111 Project(grant nos.B17027 and B16029)the Science and Technology Projects of Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province(grant no.RD2022070601)the State Key Laboratory of Bio-Fibers and Eco-Textiles(Qingdao University)(grant no.KFKT202221)the Tencent Foundation(The XPLORER PRIZE).
文摘The capture of circulating tumor cells(CTCs)is of great significance in reducing cancer mortality and complications.However,the nonspecific binding of proteins and white blood cells(WBCs)weakens the targeting capabilities of the capture surfaces,which critically hampers the efficiency and purity of the captured CTCs.Herein,we propose a liquid-like interface design strategy that consists of liquid-like polymer chains and anti-EpCAM modification processes for high-purity and high-efficiency capture of CTCs.The dynamic flexible feature of the liquid-like chains endows the modified surfaces with excellent antiadhesion property for proteins and blood cells.The liquid-like surfaces can capture the target CTCs and show high cell viability due to the environmentfriendly surface modification processes.When liquid-like surface designs were introduced in the deterministic lateral displacement(DLD)-patterned microfluidic chip,the nonspecific adhesion rate of WBCs was reduced by more than fivefold compared to that in the DLD chip without liquid-like interface design,while maintaining comparable capture efficiency.Overall,this strategy provides a novel perspective on surface design for achieving high purity and efficient capture of CTCs.
基金supported by the National Natural Science Foundation of China (Grant No. 50973007)
文摘A set of universal equations on the reduced stress relaxation modulus with K-W-W stretched exponential function has been derived from the dynamics of α and β structural relaxation processes. In the present work, the K-W-W decay function is used to define the three types of relaxations (single α, single β relaxation and α-β co-relaxation), then their average times of relaxation are theoretically calculated from the reduced shear stress relaxation modulus and the relaxation time spectrum function H(τ). When the average time of co-relaxation, the reference temperatures (ficitive Tf and glass transition Tg) and the isostructural parameter achieved from the conditions of isostructural glass state are introduced into the reduced shear stress relaxation modulus (GT) under the equilibrium state, a set of correlations between isochoric fragility index (mvα, mvβ and mvαβ) and the coupling strength (α and β) under the reference temperatures are derived from the exact definition of isochoric fragility. So the theory of dynamic fragility for glass substances at isochoric state is developed. The theory can predict the following main features of structural relaxations and behavior of isochoric fragility: the temperature dependence of peak relaxation frequency exhibits a bifurcation with a pair of single α and single β relaxations; the temperature dependence of Stickel equation on 1/T exhibits two crossovers with VFTH(1) and VFTH(2) at the temperatures of Tf and Tg regime; there are two linear correlations between isochoric fragility index (mvα and mvβ) and the coupling strength. Fine agreements between the theoretical calculation and experimental results are obtained.
文摘We first recall some basic facts from the theory of discrete-time Markov chains arising from two types neutral and non-neutral evolution models of population genetics with constant size. We then define and analyze a version of such models whose fluctuating total population size is conserved on average only. In our model, the population of interest is seen as being embedded in a frame process which is a critical Galton Watson process. In this context, we address problems such as extinction, fixation, size of the population at fixation and survival probability to a bottleneck effect of the environment.
