It is important to understand the mechanism and implications of different modifiers on analytical and preparative processes under chromatography with supercritical fluids (SFs) and under extraction with SFs. Supercrit...It is important to understand the mechanism and implications of different modifiers on analytical and preparative processes under chromatography with supercritical fluids (SFs) and under extraction with SFs. Supercritical fluid chromatography (SFC) and supercritical fluid extraction are generally carried out with neat supercritical carbon dioxide (SCCO2) or with SCCO2 containing modifiers (or cosolvents), especially for strongly polar compounds. For example, methanol is added as a cosolvent/modifier to SCCO2 for the extraction/separation of polar compounds. This paper discusses the influence of the modifier on the colligative properties of the principal mobile phase, which may define the situation in the total mobile phase in a chromatography column or in parts of a column under SFC. No colligative behavior of solutions reflects individual properties of the solutes. Their cross-interactions with solvents are discussed.展开更多
The monomer fraction density based analysis of precise thermophysical data for pure fluids is developed to study the molecular structures in supercritical fluids in general and in CO2 in particular. The series expansi...The monomer fraction density based analysis of precise thermophysical data for pure fluids is developed to study the molecular structures in supercritical fluids in general and in CO2 in particular. The series expansion by powers of the monomer fraction density of the potential energy density is used to discover the cluster structure in supercritical fluids and the clusters’ bond energies in CO2. The method of clusters separation between classes of loose and dense clusters in the CO2 supercritical fluid is developed. The method of the energetically averaged number of dense clusters is developed to study the mechanism of the soft structural transition between the gas-like and liquid-like fluids in the supercritical CO2.展开更多
The thermal analysis of precise thermophysical data for pure fluids from electronic databases is developed to investigate the molecular interaction mechanisms and parameters and the structural features of heterogeneit...The thermal analysis of precise thermophysical data for pure fluids from electronic databases is developed to investigate the molecular interaction mechanisms and parameters and the structural features of heterogeneities in fluids. The method is based on the series expansion of thermophysical values by powers of the monomer fraction density. Unlike the virial expansion by powers of the total density, the series expansion terms in this method directly reflect properties of the corresponding cluster fractions. The internal energy had been selected among thermophysical properties as the most informative for this method. The thermal analysis of its series expansion coefficients permits to estimate the temperature dependence of the pair bond parameters, the clusters’ bond energies and equilibrium constants, the structural transitions between dominating isomers of clusters. The application of method to different pure fluids, including noble and molecular gases with van der Waals and polar molecular interactions, brings unknown clusters’ characteristics for the fluids under investigation. The thermal analysis of the ordinary and heavy Water vapors points on no trivial isotopic effects. The unpredictable growth of the pair bond energy with temperature in Alkanes points on existence in hydrocarbons of some unknown molecular interaction forces in addition to dispersion forces.展开更多
To discover particular features of pure supercritical fluids, important for the supercritical fluid extraction and cleaning technologies, the preprocessed and generalized experimental data from the US National Institu...To discover particular features of pure supercritical fluids, important for the supercritical fluid extraction and cleaning technologies, the preprocessed and generalized experimental data from the US National Institute of Standards and Technology (NIST) online database have been analyzed. The soft transition between gas-like and liquid-like structures in pure supercritical fluids has been considered in comparison with the abrupt vapor-liquid phase transition. A rough, diffused and boiling boundary between these structures in conditions of extra high gravity is opposed to a flat vapor-liquid boundary at a moderate gravity. The model for molecular diffusivity in carbon dioxide at temperatures near the critical temperature discovers its proportionality to the monomer fraction density. The cluster fraction based model for small molecular weight solids’ solubility in supercritical fluids has been suggested and successfully compared with the well-known experimental results for the solubility of silica in water.The model shows that at growing pressure the dissolution process has already startedin a real gas and discovers the cluster fractions’ role in the solubility process.展开更多
The aim of this research is to apply the author’s original computer aided analysis of thermophysical data for pure fluids to noble gases to investigate the unknown aspects in their equilibrium thermal physics. The me...The aim of this research is to apply the author’s original computer aided analysis of thermophysical data for pure fluids to noble gases to investigate the unknown aspects in their equilibrium thermal physics. The methodology of the analysis is based on the potential energy density series expansion by the monomer fraction density. To discover the important details and particular features of pair atomic interactions in noble gases, the preprocessed and generalized experimental data have been taken from the US National Institute of Standards and Technology (NIST) online database. In this work the temperature range for analysis of the dimers’ bonding parameters is extended as compared to previous author’s works due to accounting for the specific temperature dependence of the repulsions’ contribution to the potential energy. The found temperature dependences of the pair interaction bond energies signal about the hindered rotation of atoms in dimers near the triple point due to the lack of rotational symmetry of their electronic outer shells. The discovered mutually correlated anomalous temperature dependences of the pair bond energy and the constant volume heat capacity in gaseous Helium require a special investigation of this remarkable phenomenon.展开更多
Federated Learning(FL)has recently attracted a lot of attention due to its ability to train a machine learning model using data from multiple clients without divulging their privacy.However,the training data across cl...Federated Learning(FL)has recently attracted a lot of attention due to its ability to train a machine learning model using data from multiple clients without divulging their privacy.However,the training data across clients can be very heterogeneous in terms of quality,amount,occurrences of specific features,etc.In this paper,we demonstrate how the server can observe data heterogeneity by mining gradient trajectories that the clients compute from a two-dimensional mapping of high-dimensional gradients computed by each client from its bottom layer.Based on these ideas,we propose a new clustered federated learning with gradient trajectory method,called CFLGT,which dynamically clusters clients together based on the gradient trajectories.We analyze CFLGT both theoretically and experimentally to show that it overcomes several drawbacks of mainstream Clustered Federated Learning(CFL)methods and outperforms other baselines.展开更多
文摘It is important to understand the mechanism and implications of different modifiers on analytical and preparative processes under chromatography with supercritical fluids (SFs) and under extraction with SFs. Supercritical fluid chromatography (SFC) and supercritical fluid extraction are generally carried out with neat supercritical carbon dioxide (SCCO2) or with SCCO2 containing modifiers (or cosolvents), especially for strongly polar compounds. For example, methanol is added as a cosolvent/modifier to SCCO2 for the extraction/separation of polar compounds. This paper discusses the influence of the modifier on the colligative properties of the principal mobile phase, which may define the situation in the total mobile phase in a chromatography column or in parts of a column under SFC. No colligative behavior of solutions reflects individual properties of the solutes. Their cross-interactions with solvents are discussed.
文摘The monomer fraction density based analysis of precise thermophysical data for pure fluids is developed to study the molecular structures in supercritical fluids in general and in CO2 in particular. The series expansion by powers of the monomer fraction density of the potential energy density is used to discover the cluster structure in supercritical fluids and the clusters’ bond energies in CO2. The method of clusters separation between classes of loose and dense clusters in the CO2 supercritical fluid is developed. The method of the energetically averaged number of dense clusters is developed to study the mechanism of the soft structural transition between the gas-like and liquid-like fluids in the supercritical CO2.
文摘The thermal analysis of precise thermophysical data for pure fluids from electronic databases is developed to investigate the molecular interaction mechanisms and parameters and the structural features of heterogeneities in fluids. The method is based on the series expansion of thermophysical values by powers of the monomer fraction density. Unlike the virial expansion by powers of the total density, the series expansion terms in this method directly reflect properties of the corresponding cluster fractions. The internal energy had been selected among thermophysical properties as the most informative for this method. The thermal analysis of its series expansion coefficients permits to estimate the temperature dependence of the pair bond parameters, the clusters’ bond energies and equilibrium constants, the structural transitions between dominating isomers of clusters. The application of method to different pure fluids, including noble and molecular gases with van der Waals and polar molecular interactions, brings unknown clusters’ characteristics for the fluids under investigation. The thermal analysis of the ordinary and heavy Water vapors points on no trivial isotopic effects. The unpredictable growth of the pair bond energy with temperature in Alkanes points on existence in hydrocarbons of some unknown molecular interaction forces in addition to dispersion forces.
文摘To discover particular features of pure supercritical fluids, important for the supercritical fluid extraction and cleaning technologies, the preprocessed and generalized experimental data from the US National Institute of Standards and Technology (NIST) online database have been analyzed. The soft transition between gas-like and liquid-like structures in pure supercritical fluids has been considered in comparison with the abrupt vapor-liquid phase transition. A rough, diffused and boiling boundary between these structures in conditions of extra high gravity is opposed to a flat vapor-liquid boundary at a moderate gravity. The model for molecular diffusivity in carbon dioxide at temperatures near the critical temperature discovers its proportionality to the monomer fraction density. The cluster fraction based model for small molecular weight solids’ solubility in supercritical fluids has been suggested and successfully compared with the well-known experimental results for the solubility of silica in water.The model shows that at growing pressure the dissolution process has already startedin a real gas and discovers the cluster fractions’ role in the solubility process.
文摘The aim of this research is to apply the author’s original computer aided analysis of thermophysical data for pure fluids to noble gases to investigate the unknown aspects in their equilibrium thermal physics. The methodology of the analysis is based on the potential energy density series expansion by the monomer fraction density. To discover the important details and particular features of pair atomic interactions in noble gases, the preprocessed and generalized experimental data have been taken from the US National Institute of Standards and Technology (NIST) online database. In this work the temperature range for analysis of the dimers’ bonding parameters is extended as compared to previous author’s works due to accounting for the specific temperature dependence of the repulsions’ contribution to the potential energy. The found temperature dependences of the pair interaction bond energies signal about the hindered rotation of atoms in dimers near the triple point due to the lack of rotational symmetry of their electronic outer shells. The discovered mutually correlated anomalous temperature dependences of the pair bond energy and the constant volume heat capacity in gaseous Helium require a special investigation of this remarkable phenomenon.
基金supported by the National Natural Science Foundation of China(No.62072485)the Guangdong Basic and Applied Basic Research Foundation(No.2022A1515011294).
文摘Federated Learning(FL)has recently attracted a lot of attention due to its ability to train a machine learning model using data from multiple clients without divulging their privacy.However,the training data across clients can be very heterogeneous in terms of quality,amount,occurrences of specific features,etc.In this paper,we demonstrate how the server can observe data heterogeneity by mining gradient trajectories that the clients compute from a two-dimensional mapping of high-dimensional gradients computed by each client from its bottom layer.Based on these ideas,we propose a new clustered federated learning with gradient trajectory method,called CFLGT,which dynamically clusters clients together based on the gradient trajectories.We analyze CFLGT both theoretically and experimentally to show that it overcomes several drawbacks of mainstream Clustered Federated Learning(CFL)methods and outperforms other baselines.
