We present an inverse analysis of the conductive and radiative heat transfer problem in fibrous porous materials.The porosity and total heat transmission are simultaneously recovered in the finite-volume method and ge...We present an inverse analysis of the conductive and radiative heat transfer problem in fibrous porous materials.The porosity and total heat transmission are simultaneously recovered in the finite-volume method and genetic algorithm scheme for both uniform and nonuniform porosity distributions.We solve the heat transfer equations directly to obtain the total heat transmission that defines the objective function to be minimized in the inverse analysis.The results show that the combined scheme is an effective tool for the inverse analysis of fibrous porous materials.展开更多
The aim of this work is to find an alternative lubricating grease formulation that can be produced from renewable and biodegradable sources with minimal risks to human health and the environment.We used a castor oil a...The aim of this work is to find an alternative lubricating grease formulation that can be produced from renewable and biodegradable sources with minimal risks to human health and the environment.We used a castor oil and electrospun cellulose acetate propionate(CAp)as raw materials.We hypothesized that the acetyl and propionyl groups could provide an adequate chemical compatibility with the castor oil and that the electrospun nanostructures could enable improved physical stability by creating a variety of morphologies allowing the tailoring of the rheological and tribological properties of the resulting greases.The experimental results show that the use of electrospun CAp nanostructures can indeed yield physically stable formulations,even when used at low concentrations(3 wt%).The resulting dispersions went through structural transitions due to changes in the thickener morphologies and/or concentration,as shown by oscillatory rheology,oil holding capacity,tackiness,and lubrication performance in metal–metal contact.We found that the formulations,containing smooth or porous CAp nanofibers,at 5 wt%as a thickener,possess suitable rheological and tribological properties with a performance comparable to that of traditional lithium lubricating greases.展开更多
Piezoelectric materials are highly desirable for wearable electronics and energy harvesting.Piezoelectric PVDF/ZnO com-posite nanofibers are particularly desirable for their nontoxicity,breathability,and flexibility.H...Piezoelectric materials are highly desirable for wearable electronics and energy harvesting.Piezoelectric PVDF/ZnO com-posite nanofibers are particularly desirable for their nontoxicity,breathability,and flexibility.Here,we investigated three methods of fabricating PVDF and ZnO composite nanofibers aimed at optimum piezoelectric responses.It was found,(1)adding ZnO nanorod as fillers within the PVDF nanofiber did not improve piezoelectric response due to the fact that the process made the material more dielectric;(2)ZnO nanorods on the PVDF surface increased the power output due to the combined effects of piezoelectricity of ZnO nanorods as well as the triboelectric response of the increased surface roughness;(3)electrospraying pre-synthesized ZnO nanorods on PVDF nanofibers resulted in the highest piezoelectric response due to the combined effect of the greater piezoelectricity of aligned ZnO nanorods and PVDF nanofibers,and larger triboelectric response from increased surface roughness.展开更多
The finite volume method （FVM） and the lattice Boltzmann method （LBM） are coupled with each other to construct a new cross-scaling method to deal with the porous flow problem. To check the effectiveness of our dev...The finite volume method （FVM） and the lattice Boltzmann method （LBM） are coupled with each other to construct a new cross-scaling method to deal with the porous flow problem. To check the effectiveness of our developed cross-scaling LBM-FVM, the above mentioned problem is also solved by the well known LBM-LBM. Based on the data checking of the published data and the results of LBM-FVM and LBM-LBM, good agreement is observed.展开更多
Solar-driven evaporation has been considered as one of the potentialmethods for desalination and sewage treatment.However,optical concentrators andcomplex multi-component systems are essential in advanced technologies...Solar-driven evaporation has been considered as one of the potentialmethods for desalination and sewage treatment.However,optical concentrators andcomplex multi-component systems are essential in advanced technologies,resulting inlow efficiency and high cost.Here,we synthesize a reduced graphene oxide-basedporous calcium alginate(CA-rGO)hydrogel which exhibits good performance in lightabsorption.More than 90%of the light in the whole spectrum can be absorbed.Meanwhile,the water vapor escapes from the CA-rGO film extremely fast.The waterevaporation rate is 1.47 kg·m^(-2)·h^(-1),corresponding to the efficiency 77%under only 1 kW'm 2 irradiation.The high evaporation efficiency is attributed to the distinctive structureof the film,which contains inherent porous structure of hydrogel enabling rapid watertransport throughout the film,and the concave water surfaces formed in the hydrophilicpores provide a large surface area for evaporation.Hydrophobic rGO divides theevaporation surface and provides a longer three-phase evaporation line.The test onmultiple cyclic radiation shows that the material has good stability.The CA-rGO hydrogelmay have promising application as a membrane for solar steam generation indesalination and sewage treatment.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 10932010,51176172,11072220 and U1262109。
文摘We present an inverse analysis of the conductive and radiative heat transfer problem in fibrous porous materials.The porosity and total heat transmission are simultaneously recovered in the finite-volume method and genetic algorithm scheme for both uniform and nonuniform porosity distributions.We solve the heat transfer equations directly to obtain the total heat transmission that defines the objective function to be minimized in the inverse analysis.The results show that the combined scheme is an effective tool for the inverse analysis of fibrous porous materials.
基金sponsored by MCIN/AEI/10.13039/501100011033“ERDF A way of making Europe”(grant PID2021-125637OB-I00)FEDER/Junta de Andalucía Programmes(grants PY20_00751 and UHU202029).
文摘The aim of this work is to find an alternative lubricating grease formulation that can be produced from renewable and biodegradable sources with minimal risks to human health and the environment.We used a castor oil and electrospun cellulose acetate propionate(CAp)as raw materials.We hypothesized that the acetyl and propionyl groups could provide an adequate chemical compatibility with the castor oil and that the electrospun nanostructures could enable improved physical stability by creating a variety of morphologies allowing the tailoring of the rheological and tribological properties of the resulting greases.The experimental results show that the use of electrospun CAp nanostructures can indeed yield physically stable formulations,even when used at low concentrations(3 wt%).The resulting dispersions went through structural transitions due to changes in the thickener morphologies and/or concentration,as shown by oscillatory rheology,oil holding capacity,tackiness,and lubrication performance in metal–metal contact.We found that the formulations,containing smooth or porous CAp nanofibers,at 5 wt%as a thickener,possess suitable rheological and tribological properties with a performance comparable to that of traditional lithium lubricating greases.
基金the Cornell Center for Materials Research Shared Facilities which are supported through the NSF MRSEC program(DMR-1719875).
文摘Piezoelectric materials are highly desirable for wearable electronics and energy harvesting.Piezoelectric PVDF/ZnO com-posite nanofibers are particularly desirable for their nontoxicity,breathability,and flexibility.Here,we investigated three methods of fabricating PVDF and ZnO composite nanofibers aimed at optimum piezoelectric responses.It was found,(1)adding ZnO nanorod as fillers within the PVDF nanofiber did not improve piezoelectric response due to the fact that the process made the material more dielectric;(2)ZnO nanorods on the PVDF surface increased the power output due to the combined effects of piezoelectricity of ZnO nanorods as well as the triboelectric response of the increased surface roughness;(3)electrospraying pre-synthesized ZnO nanorods on PVDF nanofibers resulted in the highest piezoelectric response due to the combined effect of the greater piezoelectricity of aligned ZnO nanorods and PVDF nanofibers,and larger triboelectric response from increased surface roughness.
基金supported by the National Nature Science Foundation of China (10932010,51176172,11072220)the Research Grants Council of the Government of the HKSAR (PolyU5172/02E,PolyU5221/05E)
文摘The finite volume method （FVM） and the lattice Boltzmann method （LBM） are coupled with each other to construct a new cross-scaling method to deal with the porous flow problem. To check the effectiveness of our developed cross-scaling LBM-FVM, the above mentioned problem is also solved by the well known LBM-LBM. Based on the data checking of the published data and the results of LBM-FVM and LBM-LBM, good agreement is observed.
基金supported partly by the Zhejiang Provincial Natural Science Foundation of China(No.R21A020001)the National Natural Science Foundation of China(Grant No.11774313)+1 种基金the College Fund of Physics and Electronic Information Engineering of ZJNU(No.YS128X2001)supported by the Start-up Fund ofZhejiang Normal University.
文摘Solar-driven evaporation has been considered as one of the potentialmethods for desalination and sewage treatment.However,optical concentrators andcomplex multi-component systems are essential in advanced technologies,resulting inlow efficiency and high cost.Here,we synthesize a reduced graphene oxide-basedporous calcium alginate(CA-rGO)hydrogel which exhibits good performance in lightabsorption.More than 90%of the light in the whole spectrum can be absorbed.Meanwhile,the water vapor escapes from the CA-rGO film extremely fast.The waterevaporation rate is 1.47 kg·m^(-2)·h^(-1),corresponding to the efficiency 77%under only 1 kW'm 2 irradiation.The high evaporation efficiency is attributed to the distinctive structureof the film,which contains inherent porous structure of hydrogel enabling rapid watertransport throughout the film,and the concave water surfaces formed in the hydrophilicpores provide a large surface area for evaporation.Hydrophobic rGO divides theevaporation surface and provides a longer three-phase evaporation line.The test onmultiple cyclic radiation shows that the material has good stability.The CA-rGO hydrogelmay have promising application as a membrane for solar steam generation indesalination and sewage treatment.
