The Application of the “3 + 1” Mode in the COVID-19 Epidemic Prevention and Control at the Infection Ward of a Designated Comprehensive Hospital for COVID-19 Treatment

Objective: We assess the application effect of the “3 + 1” mode in the COVID-19 epidemic prevention and control at the infection ward of a designated comprehensive hospital for COVID-19 treatment. Method: Based on the features of the inpatients of the infection ward and their relatives, a “3 + 1” mode for the COVID-19 prevention and control is developed to conform to the demands for epidemic prevention and control and the overall prevention and control scheme of the whole hospital. Here, “3” stands for the epidemic prevention and control system, personnel management, and prevention and control measures;“1” stands for COVID-19 testing. Result: From March 1, 2020 to March 31, 2021, a total of 3056 patients were hospitalized in the three infection wards. Among them, 265 patients had a fever, and 113 patients had respiratory symptoms. None of them were infected with COVID-19. The participation rate of the test about the knowledge related to COVID-19 and the knowledge mastery rate were both 100% among the medical staff. None of the inpatients and their companions or the medical staff was diagnosed with COVID-19. Conclusion: Thus the “3 + 1” mode proves successful for avoiding nosocomial infection and the spread of the epidemic.

Dynamic Elastic Modulus and Damping Ratio of Lignin-Modified Loess

To effectively improve the poor engineering properties of loess and enhance its seismic performance,the industrial by-product lignin is used as a modified material.Based on lots of dynamic triaxial tests,the dynamic elastic modulus and damping ratio of lignin-modified loess were tested.The effects of lignin content on the dynamic elastic modulus and damping ratio of lignin-modified loess were analyzed.Combined with scanning electron microscopy(SEM)and X-ray diffraction(XRD),the microscopic mechanism of lignin to improve the dynamic properties of loess was studied.The results show that lignin can effectively modify the dynamic deformation of loess under dynamic load.Under the same dynamic stress condition,the dynamic strain of lignin-modified loess is smaller than compacted loess.The dynamic elastic modulus of modified loess with different lignin content are quite different,but both decrease with the increase of dynamic strain.And the dynamic elastic modulus of modified loess is greater than compacted loess.The maximum dynamic elastic modulus of modified loess with a lignin content of 1%are significantly greater than others.Under the same dynamic strain condition,the damping ratio of lignin-modified loess is smaller than compacted loess.Lignin can effectively fill loess pores and cement loess particles.Compared with compacted loess,no new mineral components are generated in the lignin-modified loess.The optimum lignin content of dynamics characteristic of modified loess is present,and the optimum lignin content is 1%.

Evaluation and Analysis of the Effect of Lignin Amelioration on Loess Collapsibility

The road subgrade and road surface in collapsible loess area are prone to many engineering diseases such as uneven subgrade settlement,insufficient bearing capacity of soaked foundation,collapse and instability of sub-grade side slope due to the special properties of loess.As an environment-friendly,low-cost soil modifier with good adhesion and chelation properties,lignin has been considered to be used in highway subgrade construction.In order to explore the effect of lignin on loess,the compressive and collapsible properties of modified loess with different lignin contents were analyzed based on consolidation compression test.The improvement mechanism of lignin on loess collapsibility was studied by means of infiltration test and SEM test.The results show that lignin fibers can promote the agglomeration of loose particles and form a network structure in the soil particle pores,enhance the cementation strength between particles and soil skeleton,and reduce the permeability of loess.With the increase of lignin fiber content,the improvement degree of loess collaps ility shows a trend of first increasing and then decreasing.When the lignin fiber content is 2%,the effect is the best,and the improved loess ollapsi-bility is eliminated.

The Influence of Freeze-Thaw Cycles on Unconfined Compressive Strength of Lignin Fiber-Reinforced Loess

In the seasonal permafrost region with loess distribution,the influence of freeze-thaw cycles on the engineering performance of reinforced loess must be paid attention to.Many studies have shown that the use of fiber materials can improve the engineering performance of soil and its ability to resist freeze-thaw cycles.At the same time,as eco-environmental protection has become the focus,which has been paid more and more attention to,it has become a trend to find new environmentally friendly improved materials that can replace traditional chemical additives.The purpose of this paper uses new environmental-friendly improved materials to reinforce the engineering performance of loess,improve the ability of loess to resist freeze-thaw cycles,and reduce the negative impact on the ecological environment.To reinforce the engineering performance of loess and improve its ability to resist freeze-thaw cycles,lignin fiber is used as a reinforcing material.Through a series of laboratory tests,the unconfined compressive strength(UCS)of lignin fiber-reinforced loess under different freeze-thaw cycles was studied.The effects of lignin fiber content and freeze-thaw cycles on the strength and deformation modulus of loess were analyzed.Combined with the microstructure features,the change mechanism of lignin fiber-reinforced loess strength under freeze-thaw cycles was discussed.The results show that lignin fiber can improve the UCS of loess under freeze-thaw cycles,but the strengthening effect no longer increases with the increase of fiber content.When the fiber content is less than 1%,the UCS growth rate of loess is the fastest under freeze-thaw cycles.And the UCS of loess with 1%fiber content is the most stable under freeze-thaw cycles.The freeze-thaw cycles increase the deformation modulus of loess with 1%fiber content,and its ability to resist deformation is obviously better than loess with 1.5%,2%and 3%fiber content.The fiber content over 1%will weaken the strengthening effect of lignin fiber-reinforced loess,and the optimum fiber content of lignin fiber-reinforced loess under freeze-thaw cycles is 1%.