Adsorption equilibrium for Z-ligustilide on C18-bonded silica from supercritical carbon dioxide

Adsorption equilibrium is of great importance for the preparative supercritical fluid chromatography(pre-SFC) in defining supercritical adsorption behavior and the industrial amplification.This paper presents adsorption isotherms of Z-ligustilide from supercritical carbon dioxide(SC-CO_2) on C18-bonded silica.Adsorption behavior was studied at 305.15 K,313.15 K and 323.15 K with SC-CO_2 density varying from 0.687 g·cm^(-3) to0.863 g·cm^(-3) with the elution by characteristic points(ECP) method.The adsorption amount of Z-ligustilide from SC-CO_2 on C18-bonded silica decreased with the increasing density of the mobile phase as well as the increasing temperature.Adsorption equilibrium data were fitted by Langmuir and Freundlich isotherm models,and the Langmuir isotherm model performed better for describing the whole adsorption process on the column.The monolayer saturation adsorption capacity of Z-ligustilide is in the range of 3.0 × 10^(-4) mg·cm^(-3) to5.5 × 10^(-4) mg·cm^(-3) with an average value of 4.0 × 10^(-4) mg·cm^(-3).

Planning and analysis of the demonstration project of the MVDC distribution network in Zhuhai

The DC distribution system is an important development direction of the distribution system,which can improve the reliability and the quality of the power supply,and support the new energy,the energy storage,the electric vehicles,and the flexible access of AC and DC loads to grid.To realize the demonstration application of the DC distribution technology,China's first demonstration project of the medium voltage DC distribution network will be built in Zhuhai,Guangdong Province to support the construction of the city energy internet.First,this paper analyzes the demand of the DC distribution network project,and puts forward the construction content and construction target.Then,it designs and analyzes the electrical connection mode,system operation mode,and startup and shutdown mode of the DC distribution network,and proposes the overall project construction plan.Finally,it conducts the specific project design and analysis,which mainly in elude the selection of equipment such as inverters,DC transformers and DC circuit breakers,the design and analysis of the DC control and protection system,the design and analysis of the overvoltage protection and the configuration scheme of the lightning arrester,and analysis of the system transient characteristics.The design and analysis of the engineering program is a combination of China's distribution network engineering practice and technical characteristics,which lays a solid foundation for the advancement of the DC power distribution technology in China,and has reference value and demonstration effect for the design and construction of other projects.

A novel aluminum-carbon nanotubes nanocomposite with doubled strength and preserved electrical conductivity

Enhancing the mechanical strength of highly conductive pure metals usually causes significant reduction in their electrical conductivity.For example,introducing phase/matrix interfaces or more grain boundaries,are common and effective methods to strengthen metals.But it simultaneously increases the electron scattering at the interface,thus reducing the electrical conductivity.In this study,we demonstrate that pure aluminum(Al)/carbon nanotubes(CNTs)nanocomposites prepared by friction stir processing have successfully broken through these limitations.The yield strength and tensile strength of Al/CNTs nanocomposites have improved by 104.7%and 51.8%compared to pure Al,while the electrical conductivity remained comparable to that of pure Al.To explore the potential mechanisms,the interface between CNTs and Al was examined and characterized by transmission electron microscopy(TEM)and Raman spectroscopy.Little interfacial reaction compounds were present and no visible physical gaps were observed at CNTs and Al interfaces.We defined it as a clean and tightly bonded interface.Although the quantity of phase interface has increased,the electrical conductivity of the nanocomposite remains approximately unchanged.We attribute the preserved electrical conductivity to the clean and tightly bonded CNTs/Al interface in the nanocomposite.