With the prevalence of COVID-19,the phenomenon of viruses spreading through aerosols has become a focus of attention.Diners in university dining halls have a high risk of exposure to respiratory droplets from others w...With the prevalence of COVID-19,the phenomenon of viruses spreading through aerosols has become a focus of attention.Diners in university dining halls have a high risk of exposure to respiratory droplets from others without the protection of face masks,which greatly increases the risk of COVID-19 transmission.Therefore,the transmission mechanism of respiratory droplets in extremely crowded dining environments should be investigated.In this study,a numerical simulation of coughing at dining tables under two conditions was performed,namely the presence and absence of protective partitions,and the evaporation and condensation of aerosol droplets in the air were examined.By using the numerical method,we analyzed and verified the isolation effect of dining table partitions in the propagation of aerosol droplets.The effect of changes in room temperature on the diffusion of coughed aerosols when partitions were present was analyzed.We demonstrated how respiratory droplets spread through coughing and how these droplets affect others.Finally,we proposed a design for a dining table partition that minimizes the transmission of COVID-19.展开更多
According to two properties of the life cycle and to fluctuation with parities, four mathemati- cal models, the Poisson cycle model, the cubic polyno- mial model, the modified quadratic polynomial model- I artd the mo...According to two properties of the life cycle and to fluctuation with parities, four mathemati- cal models, the Poisson cycle model, the cubic polyno- mial model, the modified quadratic polynomial model- I artd the modified quadratic polynomial model-H, were used to fit the records of litter size in Jiangquhai sows. From the viewpoint of statistics and biological significance, the modified quadratic polynomial mod- el-I was found to be the optimum model. A single traitanimal model and DFREML procedures were further used to estimate the heritability values of optimum model parameters. The results show that the heritabili- ty values for the coefficients A and B and the herita- bility value for the acme of the model pure quadric curve are larger than the heritability value for the litter size. This suggests that selection for model parameters may be more effective than direct selection for litter size.展开更多
Silica(SiO_(2))coating is finding increasing use as a means of improving the properties of ZnO nanomaterials.However,the current literature contains seemingly contradictory reports of the effect of such coatings on th...Silica(SiO_(2))coating is finding increasing use as a means of improving the properties of ZnO nanomaterials.However,the current literature contains seemingly contradictory reports of the effect of such coatings on their photoluminescence(PL)properties.Two types of ZnO nanorod(henceforth termed Types A and B)were synthesized using the same hydrothermal method(differing only in the chosen precursor concentrations),then subjected to the exact same SiO_(2)-coating procedure.SiO_(2)coating is seen to have a strikingly different effect on the Type A and B nanorod morphologies and their PL.In the case of Type A nanorods,(i.e.nanorods grown using high precursor concentrations),SiO_(2)coating has no discernible morphological effect but causes an obvious increase in the intensity of the visible component within the PL emission.Type B nanorods(grown from 20-times less concentrated reactive solution),in contrast,show a very different response to SiO_(2)coating:morphologically,they appear as many ZnO nanodots in the silica shell that surrounds the etched ZnO core,and their ultraviolet PL is boosted.Systematic investigation of the effects of various other post-treatments on the PL from Type A and B nanorods leads to the conclusion that the different responses to SiO_(2)coating can be traced to the different nanorod growth chemistries–i.e.by precipitation from Zn(OH)_(2)intermediates(Type A nanorods)or by direct reaction of Zn^(2+)and OH^(−)ions(Type B material).The present study advances our understanding both of the controlled synthesis and of routes to optimising the properties of bare and silica-coated ZnO nanomaterials for nanodevice applications.展开更多
The Proton Improvement Plan(PIP)-II project is part of Fermilab’s upgrade of its proton accelerator complex,to provide a powerful,high-intensity proton beam to the laboratory’s upcoming research program.The project ...The Proton Improvement Plan(PIP)-II project is part of Fermilab’s upgrade of its proton accelerator complex,to provide a powerful,high-intensity proton beam to the laboratory’s upcoming research program.The project includes an 800 MeV superconducting(SC)linear accelerator(linac),with five flavours of cavities and cryomodules.The medium energy section of the linac contains two types of superconducting Single Spoke Resonator(SSR)RF cavities(SSR1 and SSR2),which are interleaved with strong solenoid focusing lenses.A unified design of the solenoid has been developed,with one solenoid design satisfying both SSR1 and SSR2 requirements.The integral focusing strength requirement of 4.5 T^(2)m with a full width half maximum(FWHM)of 180 mm indicates the peak field strength∼6.8 T in the magnet aperture,necessitating a superconducting design within the limits of NbTi as magnet wire strand.These are complex combined units that include one focusing solenoid with bucking coils to minimize fringe fields and four corrector coils each,with independent current leads to produce dipole and quadrupole fields.To simplify the current lead design and reduce complexity,the project opted conduction cooling for these magnets,thus requiring a redesign compared to previous prototype bath cooled units.Existing designs for high energy accelerators adopt bath cooled design of the solenoid focusing lenses for medium energy cryomodules.The present design explores a unique and technically superior solution for the cryomodule operation by decoupling the magnet and cavity cooling to certain extent.Reliability in cryomodule operations shall be studied after integration of magnets in the Linac beamline.Here we discuss the design requirements,challenges,electromagnetic design,superconducting wire selection and the results from magnetic measurements of the first pre-series units.展开更多
基金the National Natural Science Foundation of China(11872353,91852102)the Natural Science Foundation of Zhejiang Province(LZ22A020004)。
文摘With the prevalence of COVID-19,the phenomenon of viruses spreading through aerosols has become a focus of attention.Diners in university dining halls have a high risk of exposure to respiratory droplets from others without the protection of face masks,which greatly increases the risk of COVID-19 transmission.Therefore,the transmission mechanism of respiratory droplets in extremely crowded dining environments should be investigated.In this study,a numerical simulation of coughing at dining tables under two conditions was performed,namely the presence and absence of protective partitions,and the evaporation and condensation of aerosol droplets in the air were examined.By using the numerical method,we analyzed and verified the isolation effect of dining table partitions in the propagation of aerosol droplets.The effect of changes in room temperature on the diffusion of coughed aerosols when partitions were present was analyzed.We demonstrated how respiratory droplets spread through coughing and how these droplets affect others.Finally,we proposed a design for a dining table partition that minimizes the transmission of COVID-19.
文摘According to two properties of the life cycle and to fluctuation with parities, four mathemati- cal models, the Poisson cycle model, the cubic polyno- mial model, the modified quadratic polynomial model- I artd the modified quadratic polynomial model-H, were used to fit the records of litter size in Jiangquhai sows. From the viewpoint of statistics and biological significance, the modified quadratic polynomial mod- el-I was found to be the optimum model. A single traitanimal model and DFREML procedures were further used to estimate the heritability values of optimum model parameters. The results show that the heritabili- ty values for the coefficients A and B and the herita- bility value for the acme of the model pure quadric curve are larger than the heritability value for the litter size. This suggests that selection for model parameters may be more effective than direct selection for litter size.
基金Financial support for this work was provided by the National Natural Science Foundation of China(grant no.11104046)the National Basic Research Program of China(973 Program)(grant no.2013CB632900)the Fundamental Research Funds for the Central University(grant no.HIT.BRETIII.201216,HIT.BRETIII.201225 and HIT.BRETIV.201313)。
文摘Silica(SiO_(2))coating is finding increasing use as a means of improving the properties of ZnO nanomaterials.However,the current literature contains seemingly contradictory reports of the effect of such coatings on their photoluminescence(PL)properties.Two types of ZnO nanorod(henceforth termed Types A and B)were synthesized using the same hydrothermal method(differing only in the chosen precursor concentrations),then subjected to the exact same SiO_(2)-coating procedure.SiO_(2)coating is seen to have a strikingly different effect on the Type A and B nanorod morphologies and their PL.In the case of Type A nanorods,(i.e.nanorods grown using high precursor concentrations),SiO_(2)coating has no discernible morphological effect but causes an obvious increase in the intensity of the visible component within the PL emission.Type B nanorods(grown from 20-times less concentrated reactive solution),in contrast,show a very different response to SiO_(2)coating:morphologically,they appear as many ZnO nanodots in the silica shell that surrounds the etched ZnO core,and their ultraviolet PL is boosted.Systematic investigation of the effects of various other post-treatments on the PL from Type A and B nanorods leads to the conclusion that the different responses to SiO_(2)coating can be traced to the different nanorod growth chemistries–i.e.by precipitation from Zn(OH)_(2)intermediates(Type A nanorods)or by direct reaction of Zn^(2+)and OH^(−)ions(Type B material).The present study advances our understanding both of the controlled synthesis and of routes to optimising the properties of bare and silica-coated ZnO nanomaterials for nanodevice applications.
文摘The Proton Improvement Plan(PIP)-II project is part of Fermilab’s upgrade of its proton accelerator complex,to provide a powerful,high-intensity proton beam to the laboratory’s upcoming research program.The project includes an 800 MeV superconducting(SC)linear accelerator(linac),with five flavours of cavities and cryomodules.The medium energy section of the linac contains two types of superconducting Single Spoke Resonator(SSR)RF cavities(SSR1 and SSR2),which are interleaved with strong solenoid focusing lenses.A unified design of the solenoid has been developed,with one solenoid design satisfying both SSR1 and SSR2 requirements.The integral focusing strength requirement of 4.5 T^(2)m with a full width half maximum(FWHM)of 180 mm indicates the peak field strength∼6.8 T in the magnet aperture,necessitating a superconducting design within the limits of NbTi as magnet wire strand.These are complex combined units that include one focusing solenoid with bucking coils to minimize fringe fields and four corrector coils each,with independent current leads to produce dipole and quadrupole fields.To simplify the current lead design and reduce complexity,the project opted conduction cooling for these magnets,thus requiring a redesign compared to previous prototype bath cooled units.Existing designs for high energy accelerators adopt bath cooled design of the solenoid focusing lenses for medium energy cryomodules.The present design explores a unique and technically superior solution for the cryomodule operation by decoupling the magnet and cavity cooling to certain extent.Reliability in cryomodule operations shall be studied after integration of magnets in the Linac beamline.Here we discuss the design requirements,challenges,electromagnetic design,superconducting wire selection and the results from magnetic measurements of the first pre-series units.
