Biaxial compression tests on plain concrete suffered high temperature ranging from 200 ℃ to 600 ℃ were carried out using the large-scale dynamic-static tri-axial concrete test system at the State Key Laboratory of C...Biaxial compression tests on plain concrete suffered high temperature ranging from 200 ℃ to 600 ℃ were carried out using the large-scale dynamic-static tri-axial concrete test system at the State Key Laboratory of Coastal and Offshore Engineering with designated stress ratios of 0, 0.25, 0.5, 0.75 and 1, respectively. The measured strength and strain were reported and the changes in both biaxial compressive failure envelopes and strains at peak stresses were analyzed. The regressive equation of initial elastic modulus in the biggest principal compressive stress direction was derived from test results. With the published results from previous biaxial tension-compression experiments, a three-parameter failure criterion has been proposed. A biaxial nonlinear elastic incremental constitutive model was developed for the compressive stress directions by using the equivalent uniaxial strain values deduced from test results. Analytical results obtained from the proposed biaxial constitutive model achieve good agreement with the experimental results.展开更多
Fixed-point attractors with global stability manifest themselves in a number of gene regulatory networks. This property indicates the stability of regulatory networks against small state perturbations and is closely r...Fixed-point attractors with global stability manifest themselves in a number of gene regulatory networks. This property indicates the stability of regulatory networks against small state perturbations and is closely related to other complex dynamics. In this paper, we aim to reveal the core modules in regulatory networks that determine their global attractors and the relationship between these core modules and other motifs. This work has been done via three steps. Firstly, inspired by the signal transmission in the regulation process, we extract the model of chain-like network from regulation networks. We propose a module of "ideal transmission chain(ITC)", which is proved sufficient and necessary(under certain condition) to form a global fixed-point in the context of chain-like network. Secondly, by examining two well-studied regulatory networks(i.e., the cell-cycle regulatory networks of Budding yeast and Fission yeast), we identify the ideal modules in true regulation networks and demonstrate that the modules have a superior contribution to network stability(quantified by the relative size of the biggest attraction basin). Thirdly, in these two regulation networks, we find that the double negative feedback loops, which are the key motifs of forming bistability in regulation, are connected to these core modules with high network stability. These results have shed new light on the connection between the topological feature and the dynamic property of regulatory networks.展开更多
A virus that can cause a global pandemic must be highly adaptive to human conditions.Such adaptation is not likely to have emerged suddenly but,instead,may have evolved step by step with each step favored by natural s...A virus that can cause a global pandemic must be highly adaptive to human conditions.Such adaptation is not likely to have emerged suddenly but,instead,may have evolved step by step with each step favored by natural selection.It is thus necessary to develop a theory about the origin in order to guide the search.Here,we propose such a model whereby evolution occurs in both the virus and the hosts(where the evolution is somatic;i.e.,in the immune system).The hosts comprise three groups–the wild animal hosts,the nearby human population,and farther-away human populations.The theory suggests that the conditions under which the pandemic has initially evolved are:(i)an abundance of wild animals in the place of origin(PL_(0));(ii)a nearby human population of low density;(iii)frequent and long-term animal-human contacts to permit step-by-step evolution;and(iv)a level of herd immunity in the animal and human hosts.In this model,the evolving virus may have regularly spread out of PL_(0) although such invasions often fail,leaving sporadic cases of early infections.The place of the first epidemic(PL_(1)),where humans are immunologically naïve to the virus,is likely a distance away from PL_(0).Finally,this current model is only a first attempt and more theoretical models can be expected to guide the search for the origin of SARS-CoV-2.展开更多
基金Sponsored by the Science Foundation of Educational Department of Liaoning Province(Grant No.2023901023)
文摘Biaxial compression tests on plain concrete suffered high temperature ranging from 200 ℃ to 600 ℃ were carried out using the large-scale dynamic-static tri-axial concrete test system at the State Key Laboratory of Coastal and Offshore Engineering with designated stress ratios of 0, 0.25, 0.5, 0.75 and 1, respectively. The measured strength and strain were reported and the changes in both biaxial compressive failure envelopes and strains at peak stresses were analyzed. The regressive equation of initial elastic modulus in the biggest principal compressive stress direction was derived from test results. With the published results from previous biaxial tension-compression experiments, a three-parameter failure criterion has been proposed. A biaxial nonlinear elastic incremental constitutive model was developed for the compressive stress directions by using the equivalent uniaxial strain values deduced from test results. Analytical results obtained from the proposed biaxial constitutive model achieve good agreement with the experimental results.
基金supported by the National Natural Science Foundation of China(Grant No.11331011)Support from the Center for Statistical Science of Peking University was also gratefully acknowledged
文摘Fixed-point attractors with global stability manifest themselves in a number of gene regulatory networks. This property indicates the stability of regulatory networks against small state perturbations and is closely related to other complex dynamics. In this paper, we aim to reveal the core modules in regulatory networks that determine their global attractors and the relationship between these core modules and other motifs. This work has been done via three steps. Firstly, inspired by the signal transmission in the regulation process, we extract the model of chain-like network from regulation networks. We propose a module of "ideal transmission chain(ITC)", which is proved sufficient and necessary(under certain condition) to form a global fixed-point in the context of chain-like network. Secondly, by examining two well-studied regulatory networks(i.e., the cell-cycle regulatory networks of Budding yeast and Fission yeast), we identify the ideal modules in true regulation networks and demonstrate that the modules have a superior contribution to network stability(quantified by the relative size of the biggest attraction basin). Thirdly, in these two regulation networks, we find that the double negative feedback loops, which are the key motifs of forming bistability in regulation, are connected to these core modules with high network stability. These results have shed new light on the connection between the topological feature and the dynamic property of regulatory networks.
基金supported by the National Natural Science Foundation of China (31730046, 91731000, 31900417, and 81972691)Guangdong Basic and Applied Basic Research Foundation (2020B1515020030, 2019A1515010708)the National Key Research and Development Project of China (2020YFC0847000)
文摘A virus that can cause a global pandemic must be highly adaptive to human conditions.Such adaptation is not likely to have emerged suddenly but,instead,may have evolved step by step with each step favored by natural selection.It is thus necessary to develop a theory about the origin in order to guide the search.Here,we propose such a model whereby evolution occurs in both the virus and the hosts(where the evolution is somatic;i.e.,in the immune system).The hosts comprise three groups–the wild animal hosts,the nearby human population,and farther-away human populations.The theory suggests that the conditions under which the pandemic has initially evolved are:(i)an abundance of wild animals in the place of origin(PL_(0));(ii)a nearby human population of low density;(iii)frequent and long-term animal-human contacts to permit step-by-step evolution;and(iv)a level of herd immunity in the animal and human hosts.In this model,the evolving virus may have regularly spread out of PL_(0) although such invasions often fail,leaving sporadic cases of early infections.The place of the first epidemic(PL_(1)),where humans are immunologically naïve to the virus,is likely a distance away from PL_(0).Finally,this current model is only a first attempt and more theoretical models can be expected to guide the search for the origin of SARS-CoV-2.
