The calcium-containing rare earth solution is generated during the recovery processes of NdFeB waste,which is treated as wastewater by enterprises.In this paper,the carbon dioxide carbonization method was applied to t...The calcium-containing rare earth solution is generated during the recovery processes of NdFeB waste,which is treated as wastewater by enterprises.In this paper,the carbon dioxide carbonization method was applied to the separation of rare earths and calcium in the solution,as well as the preparation of rare earth oxides with a large specific surface.It is shown that the process of CO_(2)carbonization of solution includes reactions such as the dissolution,diffusion and ionization of CO_(2),the carbonate precipitation of rare earth ions,and the neutralization of hydrogen ions.At a pH of 4.5,the carbonization precipitation rate is effectively controlled,enabling homogeneous precipitation and ensuring both high precipitation yield and rare earth oxides purity.In this way,the crystallization of carbonization products is a process dominated by the oriented attachment theory and coexisting with the Ostwald ripening theory,resulting in abundant pores formed by multiple layers of stacking in the products.With the optimal carbonization conditions,the rare earth precipitation yield solution reaches 99.32%.The obtained carbonization products are crystalline(LaCe)(CO_(3))_(3)·8H_(2)O,and the purity of the rare earth oxides is as high as 99.22 wt%.The specific surface area of the rare earth oxides reaches 94.7 m^(2)/g,and its adsorption efficiency for tetracycline hydrochloride in solution can reach 92.6%in a short time.The rare earth oxides are expected to be used as an adsorption material for wastewater treatment and other adsorption environments.展开更多
Developing efficient oxygen evolution reaction(OER) electrocatalysts such as transition metal sulfides(TMSs) is of great importance to advance renewable hydrogen fuel toward further practical applications.Herein,NiCoS...Developing efficient oxygen evolution reaction(OER) electrocatalysts such as transition metal sulfides(TMSs) is of great importance to advance renewable hydrogen fuel toward further practical applications.Herein,NiCoS_(2) nanoparticles well decorated on double-sided N-doped reduced graphene oxide sheets(NiCoS_(2)/rGO) are prepared from an Al-containing ternary NiCoAl-layered double hydroxide precursor(NiCoAl-LDH) grown on GO support as an OER electrocatalyst.The Al-confinementassisted sulfurization,followed by selective acid treatment,endows the resulting NiCoS_(2)/rGO composite with the advantages:well-dispersed NiCoS_(2) nanoparticles,dualsided rGO support,as well as a large specific surface area of 119.4 m^(2)·g^(-1) and meso-/macroporous size distribution.The NiCoS_(2)/rGO electrocatalyst exhibits an overpotential of 273 mV at 10 mA·cm^(-2) and a good stability of 24 h,which outperform those of the counterparts of NiS_(2)/rGO and CoS_(2)/rGO.The results of electrochemical active surface area and electrochemical impedance spectra experimentally provide convincing rationales of the information of active sites and good conductivity,both underpin the enhanced electrocatalytic performances.展开更多
Moving particle semi-implicit （MPS） method is a fully Lagrangian particle method which can easily solve problems with violent free surface. Although it has demonstrated its advantage in ocean engineering application...Moving particle semi-implicit （MPS） method is a fully Lagrangian particle method which can easily solve problems with violent free surface. Although it has demonstrated its advantage in ocean engineering applications, it still has some defects to be improved. In this paper, MPS method is extended to the large eddy simulation （LES） by coupling with a sub-particle-scale （SPS） turbulence model. The SPS turbulence model turns into the Reynolds stress terms in the filtered momentum equation, and the Smagorinsky model is introduced to describe the Reynolds stress terms. Although MPS method has the advantage in the simulation of the free surface flow, a lot of non-free surface particles are treated as free surface particles in the original MPS model. In this paper, we use a new free surface tracing method and the key point is ＂neighbor particle＂. In this new method, the zone around each particle is divided into eight parts, and the particle will be treated as a free surface particle as long as there are no ＂neighbor particles＂ in any two parts of the zone. As the number density parameter judging method has a high efficiency for the free surface particles tracing, we combine it with the neighbor detected method. First, we select out the particles which may be mistreated with high probabilities by using the number density parameter judging method. And then we deal with these particles with the neighbor detected method. By doing this, the new mixed free surface tracing method can reduce the mistreatment problem efficiently. The serious pressure fluctuation is an obvious defect in MPS method, and therefore an area-time average technique is used in this paper to remove the pressure fluctuation with a quite good result. With these improvements, the modified MPS-LES method is applied to simulate liquid sloshing problems with large deforming free surface. Results show that the modified MPS-LES method can simulate the large deforming free surface easily. It can not only capture the large impact pressure accurately on rolling tank wall but also can generate all physical phenomena successfully. The good agreement between numerical and experimental results proves that the modified MPS-LES method is a good CFD methodology in free surface flow simulations.展开更多
Large intelligent surface(LIS)is considered as a new solution to enhance the performance of wireless networks[1].LIS comprises low-cost passive elements which can be well controlled.In this paper,a LIS is invoked in t...Large intelligent surface(LIS)is considered as a new solution to enhance the performance of wireless networks[1].LIS comprises low-cost passive elements which can be well controlled.In this paper,a LIS is invoked in the vehicular networks.We analyze the system performance under Weibull fading.We derive a novel exact analytical expression for outage probability in closed form.Based on the analytical result,we discuss three special scenarios including high SNR case,low SNR case,as well as weak interference case.The corresponding approximations for three cases are provided,respectively.In order to gain more insights,we obtain the diversity order of outage probability and it is proved that the outage probability at high SNR depends on the interference,threshold and fading parameters which leads to 0 diversity order.Furthermore,we investigate the ergodic achievable rate of LIS-assisted vehicular networks and present the closed-form tight bounds.Similar to the outage performance,three special cases are studied and the asymptotic expressions are provided in simple forms.A rate ceiling is shown for high SNRs due to the existence of interference which results 0 high SNR slope.Finally,we give the energy efficiency of LIS-assisted vehicular network.Numerical results are presented to verify the accuracy of our analysis.It is evident that the performance of LIS-assisted vehicular networks with optimal phase shift scheme exceeds that of traditional vehicular networks and random phase Received:Aug.6,2020 Revised:Nov.17,2020 Editor:Caijun Zhong shift scheme significantly.展开更多
The measurement principle of large curved surface through theodolite industry survey system is introduced. Two methods are suggested with respect to the distribution range of curved surface error. The experiments show...The measurement principle of large curved surface through theodolite industry survey system is introduced. Two methods are suggested with respect to the distribution range of curved surface error. The experiments show that the measurement precision can be up to 0.15 mm with relative precision of 3×10 -5 . Finally, something needed paying attention to and the application aspects on theodolite industry survey system are given.展开更多
In view of the fact that cages and bait are not allowed in large water surface aquiculture,1-2 kinds of new green feeds"plankton+microecologics"were developed to solve the problems of yield reduction,slow gr...In view of the fact that cages and bait are not allowed in large water surface aquiculture,1-2 kinds of new green feeds"plankton+microecologics"were developed to solve the problems of yield reduction,slow growth and difficulty in fishing of aquatic organisms caused by extensive mode.The new green feed is ecological,environmentally friendly and residue-free,which not only supplements nutrition but also meets the requirements of environmental protection.展开更多
Nickel oxide(NiO)microsphere with a large surface area was novelly synthesized through nickel bicarbonate(Ni(HCO3)2)precursor.The obtained nickel oxide(NiO)microsphere was characterized by X-ray pattern diffraction,sc...Nickel oxide(NiO)microsphere with a large surface area was novelly synthesized through nickel bicarbonate(Ni(HCO3)2)precursor.The obtained nickel oxide(NiO)microsphere was characterized by X-ray pattern diffraction,scanning electron microscopy,CO2 temperature-programmed desorption,H2 temperature-programmed reduction,N2 adsorption/desorption and laser scattering particle size distribution analyzer.It was found that nickel oxide(NiO)synthesized by the thermal decomposition of Ni(HCO3)2through area hydrolysis,presented very nice microsphere with high surface area.The catalytic properties of obtained nickel oxide(NiO)microsphere were studied in the reaction of carbon dioxide reforming of methane where 91.3% conversion of CH4 with 93% conversion of CO2 was observed.Besides,the catalyst maintained high stability over 200 h on the stream.展开更多
This study is directed towards a comprehensive exploration on the deformation mechanism of the thin membrane transducer（TMT） caused by surface stress variation.We stress that the biomolecular interaction has changed...This study is directed towards a comprehensive exploration on the deformation mechanism of the thin membrane transducer（TMT） caused by surface stress variation.We stress that the biomolecular interaction has changed the magnitude of the surface stress;and when the surface stress exceeds a critical value the TMT will buckle and deform.Based upon Gurtin＇s theory of surface elasticity and principle of finite deformation,we abstract the TMT as a nanobeam with two clamped ends,and the close-formed governing equation set is derived accordingly.A computer code via the shooting method is developed to solve the presented two-point boundary value problem.In succession,the nanobeam deflection and critical parameters for buckling are quantitatively discussed.This investigation lays the theoretical foundation of TMTs;and it is also beneficial to gain deep insight into characterizing mechanical properties of nanomaterials and engineering nano-devices.展开更多
We report a non-destructive characterization of planar two-dimensional （2D） photonic crystals （PhCs） made in silicon on insulator （SOI） wafers using ellipsometric or Fourier transformed infrared （FTIR） spectro...We report a non-destructive characterization of planar two-dimensional （2D） photonic crystals （PhCs） made in silicon on insulator （SOI） wafers using ellipsometric or Fourier transformed infrared （FTIR） spectroscope. At large wavelengths, devices behave as homogeneous isotropic materials defined by an effective filling factor. The experimental results related to the PhC limited dimensions confirm this characterization.展开更多
Water electrolysis is severely impeded by the kinetically sluggish oxygen evolution reaction(OER)due to its inherent multistep four-electron transfer mechanism.However,designing advanced OER electrocatalysts with abun...Water electrolysis is severely impeded by the kinetically sluggish oxygen evolution reaction(OER)due to its inherent multistep four-electron transfer mechanism.However,designing advanced OER electrocatalysts with abundant active sites,robust stability,and low cost remains a huge challenge.Herein,a facile and versatile multiscale manipulating strategy was proposed to construct a novel V-NiFe_(2)O_(4)@Ni_(2)P heterostructure self-supported on Ni foam(V-NiFe_(2)O_(4)@Ni_(2)P/NF).In such unique architecture,the intrinsic OER catalytic activity was greatly boosted by the in-situ generated heterogeneous Ni_(2)P phase induced by precisely selective phosphorylation of the NiFe-precursor,while the synchronous metal V doping stimulated the activity via modulating the electronic configuration,thus synergistically promoting its OER kinetics.In addition,the binder-free catalyst built from three-dimensional(3D)nanosheet arrays(NSs)can offer a large active surface for efficient charge/mass transfer and a robust scaffold for the integrated structure.The as-prepared flexible electrode exhibited superior OER activity with an ultra-low overpotential of 230 mV at 50 mA·cm^(−2)and outstanding long-term stability for 40 h.This discovery is expected to provide an opportunity to explore efficient and stable commercial materials for scalable,efficient,and robust electrochemical hydrogen(H_(2))production.展开更多
Energy source and circuit cost are two critical challenges for the future development of the Internet of Things(IoT).Backscatter communications offer a potential solution to conveniently obtain power and reduce cost f...Energy source and circuit cost are two critical challenges for the future development of the Internet of Things(IoT).Backscatter communications offer a potential solution to conveniently obtain power and reduce cost for sensors in IoT,and researchers are paying close attention to the technology.Backscatter technology originated from the Second World War and has been widely applied in the logistics domain.Recently,both the academic and industrial worlds are proposing a series of new types of backscatter technologies for communications and IoT.In this paper,we review the history of both IoT and backscatter,describe the new types of backscatter,demonstrate their applications,and discuss the open challenges.展开更多
基金Project supported by the National Key Research and Development Project of China(2022YFC2905202)Natural Science Foundation of Jiangxi Province(20232ACB204014)Youth Jinggang Scholars Program in Jiangxi Province(QNJG2019056)。
文摘The calcium-containing rare earth solution is generated during the recovery processes of NdFeB waste,which is treated as wastewater by enterprises.In this paper,the carbon dioxide carbonization method was applied to the separation of rare earths and calcium in the solution,as well as the preparation of rare earth oxides with a large specific surface.It is shown that the process of CO_(2)carbonization of solution includes reactions such as the dissolution,diffusion and ionization of CO_(2),the carbonate precipitation of rare earth ions,and the neutralization of hydrogen ions.At a pH of 4.5,the carbonization precipitation rate is effectively controlled,enabling homogeneous precipitation and ensuring both high precipitation yield and rare earth oxides purity.In this way,the crystallization of carbonization products is a process dominated by the oriented attachment theory and coexisting with the Ostwald ripening theory,resulting in abundant pores formed by multiple layers of stacking in the products.With the optimal carbonization conditions,the rare earth precipitation yield solution reaches 99.32%.The obtained carbonization products are crystalline(LaCe)(CO_(3))_(3)·8H_(2)O,and the purity of the rare earth oxides is as high as 99.22 wt%.The specific surface area of the rare earth oxides reaches 94.7 m^(2)/g,and its adsorption efficiency for tetracycline hydrochloride in solution can reach 92.6%in a short time.The rare earth oxides are expected to be used as an adsorption material for wastewater treatment and other adsorption environments.
基金financially supported by the National Natural Science Foundation of China(No.U1607128)。
文摘Developing efficient oxygen evolution reaction(OER) electrocatalysts such as transition metal sulfides(TMSs) is of great importance to advance renewable hydrogen fuel toward further practical applications.Herein,NiCoS_(2) nanoparticles well decorated on double-sided N-doped reduced graphene oxide sheets(NiCoS_(2)/rGO) are prepared from an Al-containing ternary NiCoAl-layered double hydroxide precursor(NiCoAl-LDH) grown on GO support as an OER electrocatalyst.The Al-confinementassisted sulfurization,followed by selective acid treatment,endows the resulting NiCoS_(2)/rGO composite with the advantages:well-dispersed NiCoS_(2) nanoparticles,dualsided rGO support,as well as a large specific surface area of 119.4 m^(2)·g^(-1) and meso-/macroporous size distribution.The NiCoS_(2)/rGO electrocatalyst exhibits an overpotential of 273 mV at 10 mA·cm^(-2) and a good stability of 24 h,which outperform those of the counterparts of NiS_(2)/rGO and CoS_(2)/rGO.The results of electrochemical active surface area and electrochemical impedance spectra experimentally provide convincing rationales of the information of active sites and good conductivity,both underpin the enhanced electrocatalytic performances.
基金supported by the National Natural Science Foundation of China(Grant No.50979059)
文摘Moving particle semi-implicit （MPS） method is a fully Lagrangian particle method which can easily solve problems with violent free surface. Although it has demonstrated its advantage in ocean engineering applications, it still has some defects to be improved. In this paper, MPS method is extended to the large eddy simulation （LES） by coupling with a sub-particle-scale （SPS） turbulence model. The SPS turbulence model turns into the Reynolds stress terms in the filtered momentum equation, and the Smagorinsky model is introduced to describe the Reynolds stress terms. Although MPS method has the advantage in the simulation of the free surface flow, a lot of non-free surface particles are treated as free surface particles in the original MPS model. In this paper, we use a new free surface tracing method and the key point is ＂neighbor particle＂. In this new method, the zone around each particle is divided into eight parts, and the particle will be treated as a free surface particle as long as there are no ＂neighbor particles＂ in any two parts of the zone. As the number density parameter judging method has a high efficiency for the free surface particles tracing, we combine it with the neighbor detected method. First, we select out the particles which may be mistreated with high probabilities by using the number density parameter judging method. And then we deal with these particles with the neighbor detected method. By doing this, the new mixed free surface tracing method can reduce the mistreatment problem efficiently. The serious pressure fluctuation is an obvious defect in MPS method, and therefore an area-time average technique is used in this paper to remove the pressure fluctuation with a quite good result. With these improvements, the modified MPS-LES method is applied to simulate liquid sloshing problems with large deforming free surface. Results show that the modified MPS-LES method can simulate the large deforming free surface easily. It can not only capture the large impact pressure accurately on rolling tank wall but also can generate all physical phenomena successfully. The good agreement between numerical and experimental results proves that the modified MPS-LES method is a good CFD methodology in free surface flow simulations.
基金supported by the National Natural Science Foundation of China(No.61701201,61771252,61801244,61801238)the National Key Research and Development Program(No.2020YFB1806608,2019YFB2103004)+1 种基金Six Talent Peaks Project in Jiangsu ProvinceProject of Key Laboratory of Wireless Communications of Jiangsu Province.
文摘Large intelligent surface(LIS)is considered as a new solution to enhance the performance of wireless networks[1].LIS comprises low-cost passive elements which can be well controlled.In this paper,a LIS is invoked in the vehicular networks.We analyze the system performance under Weibull fading.We derive a novel exact analytical expression for outage probability in closed form.Based on the analytical result,we discuss three special scenarios including high SNR case,low SNR case,as well as weak interference case.The corresponding approximations for three cases are provided,respectively.In order to gain more insights,we obtain the diversity order of outage probability and it is proved that the outage probability at high SNR depends on the interference,threshold and fading parameters which leads to 0 diversity order.Furthermore,we investigate the ergodic achievable rate of LIS-assisted vehicular networks and present the closed-form tight bounds.Similar to the outage performance,three special cases are studied and the asymptotic expressions are provided in simple forms.A rate ceiling is shown for high SNRs due to the existence of interference which results 0 high SNR slope.Finally,we give the energy efficiency of LIS-assisted vehicular network.Numerical results are presented to verify the accuracy of our analysis.It is evident that the performance of LIS-assisted vehicular networks with optimal phase shift scheme exceeds that of traditional vehicular networks and random phase Received:Aug.6,2020 Revised:Nov.17,2020 Editor:Caijun Zhong shift scheme significantly.
文摘The measurement principle of large curved surface through theodolite industry survey system is introduced. Two methods are suggested with respect to the distribution range of curved surface error. The experiments show that the measurement precision can be up to 0.15 mm with relative precision of 3×10 -5 . Finally, something needed paying attention to and the application aspects on theodolite industry survey system are given.
文摘In view of the fact that cages and bait are not allowed in large water surface aquiculture,1-2 kinds of new green feeds"plankton+microecologics"were developed to solve the problems of yield reduction,slow growth and difficulty in fishing of aquatic organisms caused by extensive mode.The new green feed is ecological,environmentally friendly and residue-free,which not only supplements nutrition but also meets the requirements of environmental protection.
基金Project(50872086)supported by the National Natural Science Foundation of ChinaProject(2012021006-3)supported by the Natural Science Foundation of Shanxi Province,China+1 种基金Project(2012L022)supported by the Special/Youth Foundation of Taiyuan University of Technology,ChinaProject(120238)supported by the Science and Technology Department of Taiyuan,China
文摘Nickel oxide(NiO)microsphere with a large surface area was novelly synthesized through nickel bicarbonate(Ni(HCO3)2)precursor.The obtained nickel oxide(NiO)microsphere was characterized by X-ray pattern diffraction,scanning electron microscopy,CO2 temperature-programmed desorption,H2 temperature-programmed reduction,N2 adsorption/desorption and laser scattering particle size distribution analyzer.It was found that nickel oxide(NiO)synthesized by the thermal decomposition of Ni(HCO3)2through area hydrolysis,presented very nice microsphere with high surface area.The catalytic properties of obtained nickel oxide(NiO)microsphere were studied in the reaction of carbon dioxide reforming of methane where 91.3% conversion of CH4 with 93% conversion of CO2 was observed.Besides,the catalyst maintained high stability over 200 h on the stream.
基金Project supported by National Natural Science Foundation of China(Nos.11272357 and 11320003)the Natural Science Fund for Distinguished Young Scholar of Shandong Province(No.JQ201302)
文摘This study is directed towards a comprehensive exploration on the deformation mechanism of the thin membrane transducer（TMT） caused by surface stress variation.We stress that the biomolecular interaction has changed the magnitude of the surface stress;and when the surface stress exceeds a critical value the TMT will buckle and deform.Based upon Gurtin＇s theory of surface elasticity and principle of finite deformation,we abstract the TMT as a nanobeam with two clamped ends,and the close-formed governing equation set is derived accordingly.A computer code via the shooting method is developed to solve the presented two-point boundary value problem.In succession,the nanobeam deflection and critical parameters for buckling are quantitatively discussed.This investigation lays the theoretical foundation of TMTs;and it is also beneficial to gain deep insight into characterizing mechanical properties of nanomaterials and engineering nano-devices.
文摘We report a non-destructive characterization of planar two-dimensional （2D） photonic crystals （PhCs） made in silicon on insulator （SOI） wafers using ellipsometric or Fourier transformed infrared （FTIR） spectroscope. At large wavelengths, devices behave as homogeneous isotropic materials defined by an effective filling factor. The experimental results related to the PhC limited dimensions confirm this characterization.
基金supported by the Natural Science Foundation of Hubei Province,China(Nos.2019CFB569 and 2020CFB430)the Science and Technology Foundation for Creative Research Group of Hubei Normal University,China(No.2019CZ08).
文摘Water electrolysis is severely impeded by the kinetically sluggish oxygen evolution reaction(OER)due to its inherent multistep four-electron transfer mechanism.However,designing advanced OER electrocatalysts with abundant active sites,robust stability,and low cost remains a huge challenge.Herein,a facile and versatile multiscale manipulating strategy was proposed to construct a novel V-NiFe_(2)O_(4)@Ni_(2)P heterostructure self-supported on Ni foam(V-NiFe_(2)O_(4)@Ni_(2)P/NF).In such unique architecture,the intrinsic OER catalytic activity was greatly boosted by the in-situ generated heterogeneous Ni_(2)P phase induced by precisely selective phosphorylation of the NiFe-precursor,while the synchronous metal V doping stimulated the activity via modulating the electronic configuration,thus synergistically promoting its OER kinetics.In addition,the binder-free catalyst built from three-dimensional(3D)nanosheet arrays(NSs)can offer a large active surface for efficient charge/mass transfer and a robust scaffold for the integrated structure.The as-prepared flexible electrode exhibited superior OER activity with an ultra-low overpotential of 230 mV at 50 mA·cm^(−2)and outstanding long-term stability for 40 h.This discovery is expected to provide an opportunity to explore efficient and stable commercial materials for scalable,efficient,and robust electrochemical hydrogen(H_(2))production.
基金This study was supported in part by the Fundamental Research Funds for the Central Universities(No.2020YJS044)in part by the National Natural Science Foundation of China(Nos.61871026 and U1834210).
文摘Energy source and circuit cost are two critical challenges for the future development of the Internet of Things(IoT).Backscatter communications offer a potential solution to conveniently obtain power and reduce cost for sensors in IoT,and researchers are paying close attention to the technology.Backscatter technology originated from the Second World War and has been widely applied in the logistics domain.Recently,both the academic and industrial worlds are proposing a series of new types of backscatter technologies for communications and IoT.In this paper,we review the history of both IoT and backscatter,describe the new types of backscatter,demonstrate their applications,and discuss the open challenges.
