The existence of rare earth elements(REEs) in coal sources at elevated concentrations has been the focus of several studies over the past decade. However, limited research has been conducted on methods to recover and ...The existence of rare earth elements(REEs) in coal sources at elevated concentrations has been the focus of several studies over the past decade. However, limited research has been conducted on methods to recover and refine the REEs. This paper reports the results of a detailed study into the potential of selectively recovering REEs in an Illinois basin coal source by leaching. Leaching characteristics are obtained for several segments obtained from a core sample as well as three different reject materials collected at a coal processing plant. Using a 1.2 mol/L sulfuric acid solution at 75 ℃,over 60% REE recovery is achieved from the direct floor and an inner parting material as well as the coal-rich core segments that are pretreated by low-temperature plasma oxidation to obtain access to the microdispersed mineral matter. In the leachable parting material, fluorapatite is detected by XRD analysis,which is one of the more soluble phosphate minerals with a documented association with REEs. For the three plant reject samples, the leaching recovery values obtained for the heavy REEs are higher than those obtained for the light REEs under the standard leaching conditions and when 0.1 mol/L(NH_4)_2SO_4 was used to extract REEs by an ion exchange mechanism. Thermal activation by roasting or chemical activation by pretreatment using 8 mol/L NaOH solution increases the total REE recovery with significantly higher gains obtained for the light REEs. Leaching kinetics are relatively fast within the first 2 h and then slow to provide relatively low overall recovery values under the standard test conditions for the coarse and fine reject samples. However, significantly higher recovery values are realized when treating mixed-phase(middling) particles existing within the coarse reject material.展开更多
A model of coupling macro finite volume method(FVM) and cellular automata(CA) is proposed in this paper to explore the columnar-to-equiaxed transition(CET) during selective laser melting(SLM) of rare earth magnesium a...A model of coupling macro finite volume method(FVM) and cellular automata(CA) is proposed in this paper to explore the columnar-to-equiaxed transition(CET) during selective laser melting(SLM) of rare earth magnesium alloy.Taking into account the impact of recoil pressure and Marangoni convection on the molten pool temperature field,the grain structure is simulated.As suggested by the simulation results,with the undissolved Zr serving as heterogeneous nucleation sites,the liquid undercooled layer under the combined action of forced cooling,the temperature gradient and the liquid solute concentration gradient leads to CET.While considering the dissolution of Zr in magnesium matrix,the results demonstrate that the dissolution of element Zr is effective in significantly inhibiting the growth of columnar crystals and ensuring the sufficient constitutional supercooling(CS) required for nucleation.In addition,to raise the preheating temperature contributes to enhancing the outcome of nucleation and incresing the grain size.Invoking the interdependence model(IM),with the cooling rate gradually increasing in the SLM process of magnesium alloy,the nucleation-free zone(NFZ) reduces by decreasing the solute diffusion layer in the front of the solid/liquid(SL) interface and the temperature gradient.The reduction in temperature gradient can promote undercooling for nucleation and facilitate the development of equiaxed crystals.The simulation results are qualitatively verified as highly consistent through experimentation.展开更多
The deformation and failure of soft rock affected by hydro-mechanical（HM） effect are one of the most concerns in geotechnical engineering, which are basically attributed to the grain sliding of soft rock. This study...The deformation and failure of soft rock affected by hydro-mechanical（HM） effect are one of the most concerns in geotechnical engineering, which are basically attributed to the grain sliding of soft rock. This study tried to develop a dissolution-diffusion sliding model for the typical red bed soft rock in South China. Based on hydration film, mineral dissolution and diffusion theory, and geochemical thermodynamics, a dissolution-diffusion sliding model with the HM effect was established to account for the sliding rate. Combined with the digital image processing technology, the relationship between the grain size of soft rock and the amplitude of sliding surface was presented. An equation for the strain rate of soft rocks under steady state was also derived. The reliability of the dissolution-diffusion sliding model was verified by triaxial creep tests on the soft rock with the HM coupling effect and by the relationship between the inversion average disjoining pressure and the average thickness of the hydration film. The results showed that the sliding rate of the soft rock grains was affected significantly by the waviness of sliding surface, the shear stress, and the average thickness of hydration film. The average grain size is essential for controlling the steady-state creep rate of soft rock. This study provides a new idea for investigating the deformation and failure of soft rock with the HM effect.展开更多
Temperature-independent elastic modulus is termed as Elinvar effect,which is available by tuning the continuous spin transition of ferromagnetic alloys via composition optimization and the first-order martensitic tran...Temperature-independent elastic modulus is termed as Elinvar effect,which is available by tuning the continuous spin transition of ferromagnetic alloys via composition optimization and the first-order martensitic transformation of shape memory alloys via plastic deformation.However,these reversible mechanisms are restricted generally in a narrow temperature range of less than 300 K.Here reports,by tuning a spinodal decomposition in a Ti-Nb-based titanium alloy via aging treatment,both the Elinvar effect in a wide temperature range of about 500 K and a high strength-to-modulus ratio of about 1.5%can be obtained by a continuous and reversible crystal ordering mechanism.The results demonstrate that the alloy aged at 723 K for 4 h has a nanoscale plate-like modulatedβ+α"two-phase microstructure and its elastic modulus keeps almost constant from 100 to 600 K.Synchrotron and in-situ X-ray diffraction measurements reveal that the crystal ordering parameter of theα"phase increases linearly with temper-ature from 0.88 at 133 K to 0.97 at 523 K but its volume fraction keeps a constant of about 33.8%.This suggests that the continuous ordering of theα"phase toward the high modulusαphase induces a posi-tive modulus-temperature relation to balance the negative relation of the elastically stableβphase.The aged alloy exhibits a high yield strength of 1200 MPa,good ductility of 16%and a high elastic admissible strain of 1.5%.Our results provide a novel strategy to extend the Elinvar temperature range and enhance the strength by tuning the crystal ordering of decomposition alloys.展开更多
The Lobster Eye Imager for Astronomy(LEIA),a pathfinder of the Wide-field X-ray Telescope of the Einstein Probe mission,was successfully launched onboard the SATech-01 satellite of the Chinese Academy of Sciences on20...The Lobster Eye Imager for Astronomy(LEIA),a pathfinder of the Wide-field X-ray Telescope of the Einstein Probe mission,was successfully launched onboard the SATech-01 satellite of the Chinese Academy of Sciences on2022 July 27.In this paper,we introduce the design and on-ground test results of the LEIA instrument.Using stateof-the-art Micro-Pore Optics(MPO),a wide field of view of 346 square degrees(18.6°×18.6°)of the X-ray imager is realized.An optical assembly composed of 36 MPO chips is used to focus incident X-ray photons,and four large-format complementary metal-oxide semiconductor(CMOS)sensors,each of size 6 cm×6 cm,are used as the focal plane detectors.The instrument has an angular resolution of 4’-8’(in terms of FWHM)for the central focal spot of the point-spread function,and an effective area of 2-3 cm^(2) at 1 keV in essentially all the directions within the field of view.The detection passband is 0.5-4 keV in soft X-rays and the sensitivity is2-3×10^(-11) erg s^(-1) cm^(-2)(about 1 milliCrab)with a 1000 s observation.The total weight of LEIA is 56 kg and the power is 85 W.The satellite,with a design lifetime of 2 yr,operates in a Sun-synchronous orbit of 500 km with an orbital period of 95 minutes.LEIA is paving the way for future missions by verifying in flight the technologies of both novel focusing imaging optics and CMOS sensors for X-ray observation,and by optimizing the working setups of the instrumental parameters.In addition,LEIA is able to carry out scientific observations to find new transients and to monitor known sources in the soft X-ray band,albeit with limited useful observing time available.展开更多
1 Results Nanocomposite has attracted more and more interest all over the world.Polystyrene (PS) is a commercialized and mass-productive polymer,continuous research efforts have been devoted to the development of poly...1 Results Nanocomposite has attracted more and more interest all over the world.Polystyrene (PS) is a commercialized and mass-productive polymer,continuous research efforts have been devoted to the development of polystyrene/montmorillonite (PS/MMT) nanocomposites[1-2].But the polarity of styrene (St) is too small to intercalate the space between the clay layers.The polarity of hydrophilic monomer is so strong that it can intercalate the MMT easily,the intercalated smectic clays maybe exfoliated by usin...展开更多
This paper presents a bilinear log model,for predicting temperature-dependent ultimate strength of high-entropy alloys(HEAs)based on 21 HEA compositions.We consider the break temperature,Tbreak,introduced in the model...This paper presents a bilinear log model,for predicting temperature-dependent ultimate strength of high-entropy alloys(HEAs)based on 21 HEA compositions.We consider the break temperature,Tbreak,introduced in the model,an important parameter for design of materials with attractive high-temperature properties,one warranting inclusion in alloy specifications.For reliable operation,the operating temperature of alloys may need to stay below Tbreak.We introduce a technique of global optimization,one enabling concurrent optimization of model parameters over low-temperature and high-temperature regimes.Furthermore,we suggest a general framework for joint optimization of alloy properties,capable of accounting for physics-based dependencies,and show how a special case can be formulated to address the identification of HEAs offering attractive ultimate strength.We advocate for the selection of an optimization technique suitable for the problem at hand and the data available,and for properly accounting for the underlying sources of variations.展开更多
A search for the rare decays W^(+)→D_(s)^(+)γ and Z→D0γis performed using proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of 13TeV,corresponding to an integrated luminosity...A search for the rare decays W^(+)→D_(s)^(+)γ and Z→D0γis performed using proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of 13TeV,corresponding to an integrated luminosity of 2.0fb−1.No significant signal is observed for either decay mode and upper limits on their branching fractions are set using W^(+)→D_(s)^(+)γ and Z→μ+μ−decays as normalization channels.The upper limits are 6.5×10^(−4) and 2.1×10^(−3) at 95% confidence level for the W^(+)→D_(s)^(+)γ and Z→D^(0)γ decay modes,respectively.This is the first reported search for the Z→D^(0)γ decay,while the upper limit on the W+→D+sγbranching fraction improves upon the previous best limit.展开更多
We report on an ultrafast nonequilibrium phase transition with a strikingly long-lived martensitic anomaly driven by above-threshold single-cycle terahertz pulses with a peak field of more than 1 MV/cm.A nonthermal,te...We report on an ultrafast nonequilibrium phase transition with a strikingly long-lived martensitic anomaly driven by above-threshold single-cycle terahertz pulses with a peak field of more than 1 MV/cm.A nonthermal,terahertz-induced depletion of low-frequency conductivity in Nb_(3)Sn indicates increased gap splitting of high-energy Г_(12) bands by removal of their degeneracies,which induces the martensitic phase above their equilibrium transition temperature.In contrast,optical pumping leads to a Г_(12) gap thermal melting.Such light-induced nonequilibrium martensitic phase exhibits a substantially enhanced critical temperature up to~100 K,i.e.,more than twice the equilibrium temperature,and can be stabilized beyond technologically relevant,nanosecond time scales.Together with first-principle simulations,we identify a compelling terahertz tuning mechanism of structural order via Г_(12) phonons to achieve the ultrafast phase transition to a metastable electronic state out of equilibrium at high temperatures far exceeding those for equilibrium states.展开更多
According to the features of high-resolution panchromatic imagery of Beijing-1 small satellite,an approach to extracting information of residential areas is proposed in this paper based on Gabor texture segmentation.T...According to the features of high-resolution panchromatic imagery of Beijing-1 small satellite,an approach to extracting information of residential areas is proposed in this paper based on Gabor texture segmentation.The algorithm extracts the features in different directions and different scales by building the Gabor filter,uses cluster analysis of multiple features to segment the image,and performs the fusion processing based on morphological scale space.It solves the problems in image processing resulting from low contrast between remote sensing objects and background,the blurring of image edges and high noise.It has the benefits of direction selection and frequency selection with strong self-adaptive ability.Our experiments prove the effectiveness of the approach for extracting information of residential areas from Beijing-1 high-resolution imagery.展开更多
基金Project supported by the Department of Energy of United States(DE-FE0027035)
文摘The existence of rare earth elements(REEs) in coal sources at elevated concentrations has been the focus of several studies over the past decade. However, limited research has been conducted on methods to recover and refine the REEs. This paper reports the results of a detailed study into the potential of selectively recovering REEs in an Illinois basin coal source by leaching. Leaching characteristics are obtained for several segments obtained from a core sample as well as three different reject materials collected at a coal processing plant. Using a 1.2 mol/L sulfuric acid solution at 75 ℃,over 60% REE recovery is achieved from the direct floor and an inner parting material as well as the coal-rich core segments that are pretreated by low-temperature plasma oxidation to obtain access to the microdispersed mineral matter. In the leachable parting material, fluorapatite is detected by XRD analysis,which is one of the more soluble phosphate minerals with a documented association with REEs. For the three plant reject samples, the leaching recovery values obtained for the heavy REEs are higher than those obtained for the light REEs under the standard leaching conditions and when 0.1 mol/L(NH_4)_2SO_4 was used to extract REEs by an ion exchange mechanism. Thermal activation by roasting or chemical activation by pretreatment using 8 mol/L NaOH solution increases the total REE recovery with significantly higher gains obtained for the light REEs. Leaching kinetics are relatively fast within the first 2 h and then slow to provide relatively low overall recovery values under the standard test conditions for the coarse and fine reject samples. However, significantly higher recovery values are realized when treating mixed-phase(middling) particles existing within the coarse reject material.
基金the Key Research and Development Plan of Shaanxi Province (No. 2020GY-255)Scientific Research Plan Projects of Shaanxi Education Department (No. 20JC020)Scientific Research Plan Projects of Xi’an Technology Department (No. 2020KJRC0052)。
文摘A model of coupling macro finite volume method(FVM) and cellular automata(CA) is proposed in this paper to explore the columnar-to-equiaxed transition(CET) during selective laser melting(SLM) of rare earth magnesium alloy.Taking into account the impact of recoil pressure and Marangoni convection on the molten pool temperature field,the grain structure is simulated.As suggested by the simulation results,with the undissolved Zr serving as heterogeneous nucleation sites,the liquid undercooled layer under the combined action of forced cooling,the temperature gradient and the liquid solute concentration gradient leads to CET.While considering the dissolution of Zr in magnesium matrix,the results demonstrate that the dissolution of element Zr is effective in significantly inhibiting the growth of columnar crystals and ensuring the sufficient constitutional supercooling(CS) required for nucleation.In addition,to raise the preheating temperature contributes to enhancing the outcome of nucleation and incresing the grain size.Invoking the interdependence model(IM),with the cooling rate gradually increasing in the SLM process of magnesium alloy,the nucleation-free zone(NFZ) reduces by decreasing the solute diffusion layer in the front of the solid/liquid(SL) interface and the temperature gradient.The reduction in temperature gradient can promote undercooling for nucleation and facilitate the development of equiaxed crystals.The simulation results are qualitatively verified as highly consistent through experimentation.
基金supported by the National Key Research and Development Project (Grant No. SQ2017YFSF060085)the National Natural Science Foundation of China (NSFC)(Grant Nos. 41472257, 41530638, and 41372302)+1 种基金the Special Fund Key Project of Applied Science and Technology Research and Development in Guangdong (Grant No. 2016B010124007)the Special Support Program for High Level Talents in Guangdong (Grant No. 2015TQ01Z344)
文摘The deformation and failure of soft rock affected by hydro-mechanical（HM） effect are one of the most concerns in geotechnical engineering, which are basically attributed to the grain sliding of soft rock. This study tried to develop a dissolution-diffusion sliding model for the typical red bed soft rock in South China. Based on hydration film, mineral dissolution and diffusion theory, and geochemical thermodynamics, a dissolution-diffusion sliding model with the HM effect was established to account for the sliding rate. Combined with the digital image processing technology, the relationship between the grain size of soft rock and the amplitude of sliding surface was presented. An equation for the strain rate of soft rocks under steady state was also derived. The reliability of the dissolution-diffusion sliding model was verified by triaxial creep tests on the soft rock with the HM coupling effect and by the relationship between the inversion average disjoining pressure and the average thickness of the hydration film. The results showed that the sliding rate of the soft rock grains was affected significantly by the waviness of sliding surface, the shear stress, and the average thickness of hydration film. The average grain size is essential for controlling the steady-state creep rate of soft rock. This study provides a new idea for investigating the deformation and failure of soft rock with the HM effect.
基金supported by the National Natural Science Foundation of China (Nos.51771209 and 51901042)the Foun-dation 91960202 and CAS (No.QYZDJ-SSW-JSC031).
文摘Temperature-independent elastic modulus is termed as Elinvar effect,which is available by tuning the continuous spin transition of ferromagnetic alloys via composition optimization and the first-order martensitic transformation of shape memory alloys via plastic deformation.However,these reversible mechanisms are restricted generally in a narrow temperature range of less than 300 K.Here reports,by tuning a spinodal decomposition in a Ti-Nb-based titanium alloy via aging treatment,both the Elinvar effect in a wide temperature range of about 500 K and a high strength-to-modulus ratio of about 1.5%can be obtained by a continuous and reversible crystal ordering mechanism.The results demonstrate that the alloy aged at 723 K for 4 h has a nanoscale plate-like modulatedβ+α"two-phase microstructure and its elastic modulus keeps almost constant from 100 to 600 K.Synchrotron and in-situ X-ray diffraction measurements reveal that the crystal ordering parameter of theα"phase increases linearly with temper-ature from 0.88 at 133 K to 0.97 at 523 K but its volume fraction keeps a constant of about 33.8%.This suggests that the continuous ordering of theα"phase toward the high modulusαphase induces a posi-tive modulus-temperature relation to balance the negative relation of the elastically stableβphase.The aged alloy exhibits a high yield strength of 1200 MPa,good ductility of 16%and a high elastic admissible strain of 1.5%.Our results provide a novel strategy to extend the Elinvar temperature range and enhance the strength by tuning the crystal ordering of decomposition alloys.
基金supported by the Einstein Probe project,a mission in the Strategic Priority Program on Space Science of CAS(grant Nos.XDA15310000,XDA15052100)in part been supported by the European Union’s Horizon 2020 Program under the AHEAD2020 project(grant No.871158).
文摘The Lobster Eye Imager for Astronomy(LEIA),a pathfinder of the Wide-field X-ray Telescope of the Einstein Probe mission,was successfully launched onboard the SATech-01 satellite of the Chinese Academy of Sciences on2022 July 27.In this paper,we introduce the design and on-ground test results of the LEIA instrument.Using stateof-the-art Micro-Pore Optics(MPO),a wide field of view of 346 square degrees(18.6°×18.6°)of the X-ray imager is realized.An optical assembly composed of 36 MPO chips is used to focus incident X-ray photons,and four large-format complementary metal-oxide semiconductor(CMOS)sensors,each of size 6 cm×6 cm,are used as the focal plane detectors.The instrument has an angular resolution of 4’-8’(in terms of FWHM)for the central focal spot of the point-spread function,and an effective area of 2-3 cm^(2) at 1 keV in essentially all the directions within the field of view.The detection passband is 0.5-4 keV in soft X-rays and the sensitivity is2-3×10^(-11) erg s^(-1) cm^(-2)(about 1 milliCrab)with a 1000 s observation.The total weight of LEIA is 56 kg and the power is 85 W.The satellite,with a design lifetime of 2 yr,operates in a Sun-synchronous orbit of 500 km with an orbital period of 95 minutes.LEIA is paving the way for future missions by verifying in flight the technologies of both novel focusing imaging optics and CMOS sensors for X-ray observation,and by optimizing the working setups of the instrumental parameters.In addition,LEIA is able to carry out scientific observations to find new transients and to monitor known sources in the soft X-ray band,albeit with limited useful observing time available.
文摘1 Results Nanocomposite has attracted more and more interest all over the world.Polystyrene (PS) is a commercialized and mass-productive polymer,continuous research efforts have been devoted to the development of polystyrene/montmorillonite (PS/MMT) nanocomposites[1-2].But the polarity of styrene (St) is too small to intercalate the space between the clay layers.The polarity of hydrophilic monomer is so strong that it can intercalate the MMT easily,the intercalated smectic clays maybe exfoliated by usin...
基金X.F.and P.K.L.very much appreciate the support of the U.S.Army Research Office Project(W911NF-13-1-0438 and W911NF-19-2-0049)with the program managersDrs M.P.Bakas,S.N.Mathaudhu,and D.M.Stepp,as well as the support from the Bunch Fellowship.XF and PKL also would like to acknowledge funding from the State of Tennessee and Tennessee Higher Education Commission(THEC)through their support of the Center for Materials Processing(CMP).P.K.L.,furthermore,thanks the support from the National Science Foundation(DMR-1611180 and 1809640)with the program directors+1 种基金Drs J.Yang,G.Shiflet,and D.Farkas.B.S.very much appreciates the support from the National Science Foundation(IIP-1447395 and IIP-1632408)with the program directorsDr G.Larsen and R.Mehta,from the U.S.Air Force(FA864921P0754),with J.Evans as the program manager,and from the U.S.Navy(N6833521C0420),with Drs D.Shifler and J.Wolk as the program managers.M.C.G.acknowledges the support of the US Department of Energy’s Fossil Energy Crosscutting Technology Research Program.The authors also want to thank Dr.G.Tewksbury for bringing to their attention suspicious recordings of the US from the literature,which have prompted the data curation effort.
文摘This paper presents a bilinear log model,for predicting temperature-dependent ultimate strength of high-entropy alloys(HEAs)based on 21 HEA compositions.We consider the break temperature,Tbreak,introduced in the model,an important parameter for design of materials with attractive high-temperature properties,one warranting inclusion in alloy specifications.For reliable operation,the operating temperature of alloys may need to stay below Tbreak.We introduce a technique of global optimization,one enabling concurrent optimization of model parameters over low-temperature and high-temperature regimes.Furthermore,we suggest a general framework for joint optimization of alloy properties,capable of accounting for physics-based dependencies,and show how a special case can be formulated to address the identification of HEAs offering attractive ultimate strength.We advocate for the selection of an optimization technique suitable for the problem at hand and the data available,and for properly accounting for the underlying sources of variations.
文摘A search for the rare decays W^(+)→D_(s)^(+)γ and Z→D0γis performed using proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of 13TeV,corresponding to an integrated luminosity of 2.0fb−1.No significant signal is observed for either decay mode and upper limits on their branching fractions are set using W^(+)→D_(s)^(+)γ and Z→μ+μ−decays as normalization channels.The upper limits are 6.5×10^(−4) and 2.1×10^(−3) at 95% confidence level for the W^(+)→D_(s)^(+)γ and Z→D^(0)γ decay modes,respectively.This is the first reported search for the Z→D^(0)γ decay,while the upper limit on the W+→D+sγbranching fraction improves upon the previous best limit.
基金supported by the U.S.Department of Energy,Office of Science,Basic Energy Sciences,Materials Science and Engineering Division under contract no.DEAC02-07CH11358(scientific drive,THz spectroscopy characterization of Martensitic phase,and theoretical prediction and analysis).
文摘We report on an ultrafast nonequilibrium phase transition with a strikingly long-lived martensitic anomaly driven by above-threshold single-cycle terahertz pulses with a peak field of more than 1 MV/cm.A nonthermal,terahertz-induced depletion of low-frequency conductivity in Nb_(3)Sn indicates increased gap splitting of high-energy Г_(12) bands by removal of their degeneracies,which induces the martensitic phase above their equilibrium transition temperature.In contrast,optical pumping leads to a Г_(12) gap thermal melting.Such light-induced nonequilibrium martensitic phase exhibits a substantially enhanced critical temperature up to~100 K,i.e.,more than twice the equilibrium temperature,and can be stabilized beyond technologically relevant,nanosecond time scales.Together with first-principle simulations,we identify a compelling terahertz tuning mechanism of structural order via Г_(12) phonons to achieve the ultrafast phase transition to a metastable electronic state out of equilibrium at high temperatures far exceeding those for equilibrium states.
基金supported by a grant from the National High Technology Research and Development Program of China(863 Program)(No.2005AA133013,No.2006CB701305)the Major State Basic Research Development Program of China(973 Program)(No.2006CB701305).
文摘According to the features of high-resolution panchromatic imagery of Beijing-1 small satellite,an approach to extracting information of residential areas is proposed in this paper based on Gabor texture segmentation.The algorithm extracts the features in different directions and different scales by building the Gabor filter,uses cluster analysis of multiple features to segment the image,and performs the fusion processing based on morphological scale space.It solves the problems in image processing resulting from low contrast between remote sensing objects and background,the blurring of image edges and high noise.It has the benefits of direction selection and frequency selection with strong self-adaptive ability.Our experiments prove the effectiveness of the approach for extracting information of residential areas from Beijing-1 high-resolution imagery.
