The magnetic hysteresis loop was measured to know the magnetic property of molybdenite concentrate.In order to evaluate its microwave absorption capacity, the dielectric properties of molybdenite concentrate was inves...The magnetic hysteresis loop was measured to know the magnetic property of molybdenite concentrate.In order to evaluate its microwave absorption capacity, the dielectric properties of molybdenite concentrate was investigated using cavity perturbation method at 915 MHz dependent on densities and temperatures.The parameter data were fitted using regression fit and a model related to the same density and temperature ranges was developed.A nonlinear surface fitting was used to present visually the effect of dielectric parameters on the microwave penetrate depth of molybdnite concentrate.The crystal products of MoO 3 obtained from microwave roasting at different temperatures were examined by scanning electron microscopy (SEM) and X-ray diffraction (XRD).The results show both the dielectric constants and loss factors increase in the increase of apparent densities and temperatures with different growth rates in the experimental range.Due to the distinguished trend of dielectric performance dependent on temperatures, two parts in the heating scenario for the molybdenite concentrate samples were divided.The microwave penetration depth is inversely proportional to both apparent densities and temperatures.The nonlinear fitting surfaces indicate the increase of dielectric loss provides an enough decrease in microwave penetration depth.In contrast, the dielectric constant has a positive effect for it.Pure MoO 3 was produced at 800 ℃ by using microwave energy.This work can be helpful to design and simulate microwave system for efficient beneficiation of molybdenite concentrate and to prepare molybdenum products from this concentrate.展开更多
The present work explores the application of microwave heating for the melting of powdered tin. The mor- phology and particle size of powdered tin prepared by the centrifugal atomization method were charac- terized. T...The present work explores the application of microwave heating for the melting of powdered tin. The mor- phology and particle size of powdered tin prepared by the centrifugal atomization method were charac- terized. The tin particles were uniform and spherical in shape, with 90% of the particles in the size range of 38-75μm. The microwave absorption characteristic of the tin powder was assessed by an estimation of the dielectric properties. Microwave penetration was found to have good volumetric heating on powdered tin. Conduction losses were the main loss mechanisms for powdered tin by microwave heating at temperatures above 150 ℃. A 20 kW commercial-scale microwave tin-melting unit was designed, developed, and utilized for production. This unit achieved a heating rate that was at least 10 times higher than those of conventional methods, as well as a far shorter melting duration. The results suggest that microwave heating accelerates the heating rate and shortens the melting time. Tin recovery rate was 97.79%, with a slag ratio of only 1.65% and other losses accounting for less than 0.56%. The unit energy consumption was only 0.17 （kW·h）·kg-1- far lower than the energy required by conventional melting methods. Thus, the microwave melting process improved heating efficiency and reduced energy consumption.展开更多
With the rapid development of terahertz technology,terahertz detectors are expected to play a key role in diverse areas such as homeland security and imaging,materials diagnostics,biology,medical sciences,and communic...With the rapid development of terahertz technology,terahertz detectors are expected to play a key role in diverse areas such as homeland security and imaging,materials diagnostics,biology,medical sciences,and communication.Whereas self-powered,rapid response,and room temperature terahertz photodetectors are confronted with huge challenges.Here,we report a novel rapid response and self-powered terahertz photothermoelectronic(PTE)photodetector based on a lowdimensional material:palladium selenide(Pd Se_(2)).An order of magnitude performance enhancement was observed in photodetection based on PdSe_(2)/graphene heterojunction that resulted from the integration of graphene and enhanced the Seebeck effect.Under 0.1-THz and 0.3-THz irradiations,the device displays a stable and repeatable photoresponse at room temperature without bias.Furthermore,rapid rise(5.0μs)and decay(5.4μs)times are recorded under 0.1-THz irradiation.Our results demonstrate the promising prospect of the detector based on Pd Se2 in terms of air-stable,suitable sensitivity and speed,which may have great application in terahertz detection.展开更多
The present work focuses on a numerical investigation of the solids residence time distribution(RTD) and the fluidized structure of a multi-compartment fluidized bed, in which the flow pattern is proved to be close to...The present work focuses on a numerical investigation of the solids residence time distribution(RTD) and the fluidized structure of a multi-compartment fluidized bed, in which the flow pattern is proved to be close to plug flow by using computational fluid dynamics(CFD) simulations. With the fluidizing gas velocity or the bed outlet height rising, the solids flow out of bed more quickly with a wider spread of residence time and a larger RTD variance(σ2). It is just the heterogeneous fluidized structure that being more prominent with the bed height increasing induces the widely non-uniform RTD. The division of the individual internal circulation into double ones improves the flow pattern to be close to plug flow.展开更多
In this study, the flow stability of the flat-bottomed hopper was investigated via GPU-based discrete element method(DEM) simulation. With the material height inside the hopper reducing, the fluctuation of the flow ra...In this study, the flow stability of the flat-bottomed hopper was investigated via GPU-based discrete element method(DEM) simulation. With the material height inside the hopper reducing, the fluctuation of the flow rate indicates an unstable discharge. The flow regions of the unstable discharge were compared with that of the stable discharge, a key transformation zone, where the voidage showed the largest difference between unstable and stable discharge, was revealed. To identify the relevance of the key transformation zone and the hopper flow stability, the voidage variation of the key transformation zone with material height reducing was studied.A sharp increase in the voidage in the key transformation zone was considered to be the standard for judging the unstable hopper flow, and the ‘Top–Bottom effect' of the hopper was defined, which indicated the hopper flow was unstable when the hopper only had the top area and the bottom area, because the voidage of particles in the top area and the bottom area were both variables.展开更多
Mercury-containing catalysts are widely used for acetylene hydrochlorination in China. Surface chemical characteristics of the fresh low-level mercury catalysts and spent low-level mercury catalysts were compared usin...Mercury-containing catalysts are widely used for acetylene hydrochlorination in China. Surface chemical characteristics of the fresh low-level mercury catalysts and spent low-level mercury catalysts were compared using multiple characterization methods. Pore blockage and active site coverage caused by chlorine-containing organics are responsible for catalyst deactivation. The reactions of chloroethylene and acetylene with chlorine free radical can generate chlorine-containing organic species. SiO_2 and functional groups on activated carbon contribute to the generation of carbon deposition. No significant reduction in the total content of mercury was observed after catalyst deactivation, while there was mercury loss locally. The irreversible loss of HgCl_2 caused by volatilization, reduction and poisoning of elements S and P also can lead to catalyst deactivation. Si, Al, Ca and Fe oxides are scattered on the activated carbon. Active components are still uniformly absorbed on activated carbon after catalyst deactivation.展开更多
Dielectric properties were measured using cavity perturbation method. The temperature rising behaviors of molybdenite concentrate were investigated in the field of microwave. This process was conducted to show the mic...Dielectric properties were measured using cavity perturbation method. The temperature rising behaviors of molybdenite concentrate were investigated in the field of microwave. This process was conducted to show the microwave absorption properties of molybdenite concentrate and the feasibility of microwave roasting molybdenite concentrate to prepare high purity MOO3. The dielectric constant,dielectric loss,and loss tangent increase from 3. 51 to 5. 04,0. 22 to 0. 51 and 0. 065 to 0. 102 respectively. They are proportional to the apparent density of molybdenite concentrate in the range of 0. 9-1. 4 g/cm3. The results show that the molybdenite concentrate has good microwave absorption capacity in the conventional density range. The temperature rising curves show that the apparent heating rate of the molybdenite concentrate increases with the increase in microwave power and decreases with the increase in the sample mass and thickness. The temperature of concentrate sample of 100 g reaches approximately 800 ℃ after 5 min of microwave treatment at 0. 5 kW of power. Our findings show that it is feasible to prepare high-purity MOO3from molybdenite concentrate by microwave roasting.展开更多
Oxidation of petroleum-based byproduct dicyclopentadiene derived diformyltricyclodecanes(DFTD) to dicarboxyltriclodecanesacids(DCTDA) was conducted under catalyst-free and ultra-low temperature conditions with O2 as o...Oxidation of petroleum-based byproduct dicyclopentadiene derived diformyltricyclodecanes(DFTD) to dicarboxyltriclodecanesacids(DCTDA) was conducted under catalyst-free and ultra-low temperature conditions with O2 as oxidant. In the perspective of industry process, oxygen pressure and contents, solvent and raw material initial concentrations were screened to evaluate their influence on DCTDA generation. Results indicate that DFTD oxidation can occur rather easily under no-catalyst and ultra-low temperature conditions with O2 as oxidant. Oxygen content and pressure had positive effect on DCTDA production, γ-valerolactone(GVL) behaved best on DFTD generation in dynamics, while methanol could be used as a protective solvent to preserve DFTD.Besides, the existence of water in solvent was not beneficial to DCTDA production because of poor DFTD compatibility with water. The mechanisms of O2 and solvent influence on DCTDA generation were discussed. Meanwhile,the oxidation route of DFTD–Intermediate–DCTDA was proposed. The present work exhibits the valued potential of DFTD, which will have a positive effect on high added value of petroleum based by-products.展开更多
Arsenic is one of the main harmful elements in industrial wastewater.How to remove arsenic has always been one of the research hotspots in academic circles.In the process of arsenic removal by traditional sulfuration,...Arsenic is one of the main harmful elements in industrial wastewater.How to remove arsenic has always been one of the research hotspots in academic circles.In the process of arsenic removal by traditional sulfuration,the use of traditional sulfurizing agent will introduce new metal cations,which will affect the recycling of acid.In this study,phosphorus pentasulfide (P_(2)S_(5)) was used as sulfurizing agent,which hydrolyzed to produce H_(3)PO_(4) and H_(2)S without introducing new metal cations.The effect of ultrasound on arsenic removal by P_(2)S_(5) was studied.Under the action of ultrasound,the utilization of P_(2)S_(5) was improved and the reaction time was shortened.The effects of S/As molar ratio and reaction time on arsenic removal rate were investigated under ultrasonic conditions.Ultrasonic enhanced heat and mass transfer so that the arsenic removal rate of 94.5%could be achieved under the conditions of S/As molar ratio of 2.1:1 and reaction time of 20 min.In the first 60 min,under the same S/As molar ratio and reaction time,the ultrasonic hydrolysis efficiency of P_(2)S_(5) was higher.This is because P_(2)S_(5) forms ([(P_(2)S_(4))])^(2+)under the ultrasonic action,and the structure is damaged,which is easier to be hydrolyzed.In addition,the precipitation after arsenic removal was characterized and analyzed by X-ray diffraction,scanning electron microscope-energy dispersive spectrometer,X-ray fluorescence spectrometer and X-ray photoelectron spectroscopy.Our research avoids the introduction of metal cations in the arsenic removal process,and shortens the reaction time.展开更多
P450 fatty acid decarboxylase Ole T from Staphylococcus aureus(Ole TSA)is a novel cytochrome P450 enzyme that catalyzes the oxidative decarboxylation of fatty acids to yield primarily terminal alkenes and CO_(2) or mi...P450 fatty acid decarboxylase Ole T from Staphylococcus aureus(Ole TSA)is a novel cytochrome P450 enzyme that catalyzes the oxidative decarboxylation of fatty acids to yield primarily terminal alkenes and CO_(2) or minor a-andβ-hydroxylated fatty acids as side-products.In this work,the interactions between a series of cycloalkyl phosphorus heterocycles(CPHs)and Ole TSAwere investigated in detail by fluorescence titration experiment,ultraviolet-visible(UV-vis)and31 P NMR spectroscopies.Fluorescence titration experiment results clearly showed that a dynamic quenching occurred when CPH-6,a representative CPHs,interacted with Ole TSAwith a binding constant value of 15.2×104 M-1 at 293 K.The thermodynamic parameters(ΔH,ΔS andΔG)showed that the hydrogen bond and van der Waals force played major roles in the interaction between Ole TSAand CPHs.The UV-vis and31 P NMR studies indicated the penetration of CPH-6 into the interior environment of Ole TSA,which greatly affects the enzymatic activity of Ole TSA.Therefore,our study revealed an effective way to use phosphorus heterocyclic compounds to modulate the activity of cytochrome P450 enzymes.展开更多
Mn_(3)Sn_(2)has been proposed as an ideal material for magnetic refrigeration.It undergoes two successive ferromagnetic transitions(T_(C1)=262 K and T_(C2)=227 K)and one antiferromagnetic transition(TN=192 K).Herein w...Mn_(3)Sn_(2)has been proposed as an ideal material for magnetic refrigeration.It undergoes two successive ferromagnetic transitions(T_(C1)=262 K and T_(C2)=227 K)and one antiferromagnetic transition(TN=192 K).Herein we report,for the first time,the preparation of single crystals of Mn_(3)Sn_(2)from Bi flux.The resultant anisotropic magnetic properties and magnetocaloric effect are investigated along the three principal crystallographic directions of the crystal.Significant anisotropy of magnetic susceptibility and multiple field-induced metamagnetic transitions were found at low fields,whereas the magnetocaloric effect was found to be almost isotropic and larger than that of the polycrystalline one.The maximum magnetic entropy change amounts to-ΔSM=4.01 J·kg^(-1)·K^(-1)near T_(C1)under a magnetic field change of μ_(0)ΔH=5 T along the c-axis,with the corresponding refrigerant capacity of 1750 mJ·cm^(-3).Combined with a much wider cooling temperature span(~80 K),our results demonstrate Mn_(3)Sn_(2)single crystal to be an attractive candidate working material for active magnetic refrigeration at low temperatures.展开更多
We present an experiment of observing the geometric phase in a superconducting circuit where the resonator and the qutrit energy levels are dispersively coupled. The drive applied to the resonator displaces its state ...We present an experiment of observing the geometric phase in a superconducting circuit where the resonator and the qutrit energy levels are dispersively coupled. The drive applied to the resonator displaces its state components associated with the qutrit＇s ground state and first-excited state along different circular trajectories in phase space. We identify the resonator＇s phase-space trajectories by Wigner tomography using an ancilla qubit, following which we observe the difference between the geometric phases associated with these trajectories using Ramsey interferometry. This geometric phase is further used to construct the single-qubit It-phase gate with a process fidelity of 0.851± 0.001.展开更多
Taking GCr15 bearing steel as experiment material, the effects of suspension casting process and low superheat casting process on the solidification of ingot were studied comparehvely. The results show that both suspe...Taking GCr15 bearing steel as experiment material, the effects of suspension casting process and low superheat casting process on the solidification of ingot were studied comparehvely. The results show that both suspension casting process and low superheat casting process can improve the censeal segregation and crystal structure of ingot. As the acting mechanism is different between the two kinds of processes, it is found that suspension casting process is more effective than low superheat casting process in improving the quality of ingot.展开更多
This study was conducted to provide reference for rational fertilization and agrochemical application in cucumber plantation,and relieve the problem of environmental pollution and vegetable agrochemical residues. The ...This study was conducted to provide reference for rational fertilization and agrochemical application in cucumber plantation,and relieve the problem of environmental pollution and vegetable agrochemical residues. The effects of different combinations of fertilization and agrochemical application on cucumber yield and cost input were investigated. Four treatments were conducted,including T1（ conventional fertilization ＋ conventional agrochemical application,CK）,T2（ conventional fertilization ＋ recommended agrochemical application）,T3（ recommended fertilization ＋ conventional agrochemical application） and T4（ recommended fertilization ＋ recommended agrochemical application）. The results showed that T4 had fewer kinds of fertilizers and agrochemicals than that of T1,and had a yield increasing effect on cucumber,and the yield increase was 7 003. 5 kg/hm^2,with an increasing rate of 19. 25%; and it also had obvious cost-saving and benefit-increasing effects,specifically,the cost was saved by 10 941 yuan/hm^2 and the benefit was increased by 31 951. 5 yuan/hm^2. The results of this experiment were satisfactory,and higher benefit was obtained with lower input. This study will provide reference for cucumber planter to choose fertilizers and agrochemicals,and lays a foundation for alleviating the ecological soil problems.展开更多
Pyran-and furanocoumarins are key representatives of tetrahydropyrans and tetrahydrofurans,respectively,exhibiting diverse physiological and medical bioactivities.However,the biosynthetic mechanisms for their core str...Pyran-and furanocoumarins are key representatives of tetrahydropyrans and tetrahydrofurans,respectively,exhibiting diverse physiological and medical bioactivities.However,the biosynthetic mechanisms for their core structures remain poorly understood.Here we combined multiomics analyses of biosynthetic enzymes in Peucedanum praeruptorum and in vitro functional verification and identified two types of key enzymes critical for pyran and furan ring biosynthesis in plants.These included three distinct P.praeruptorum prenyltransferases(PpPT1e3)responsible for the prenylation of the simple coumarin skeleton 7 into linear or angular precursors,and two novel CYP450 cyclases(PpDC and PpOC)crucial for the cyclization of the linear/angular precursors into either tetrahydropyran or tetrahydrofuran scaffolds.Biochemical analyses of cyclases indicated that acid/base-assisted epoxide ring opening contributed to the enzyme-catalyzed tetrahydropyran and tetrahydrofuran ring refactoring.The possible acid/base-assisted catalytic mechanisms of the identified cyclases were theoretically investigated and assessed using site-specific mutagenesis.We identified two possible acidic amino acids Glu303 in PpDC and Asp301 in PpOC as vital in the catalytic process.This study provides new enzymatic tools in the epoxide formation/epoxide-opening mediated cascade reaction and exemplifies how plants become chemically diverse in terms of enzyme function and catalytic process.展开更多
The sequestration of^(99)Tc represents one of the most challenging tasks in nuclear waste decontamination In the event of a radioactive waste leak,^(99)TcO_(4)^(-)(a main form of^(99)Tc)would spread into the groundwa ...The sequestration of^(99)Tc represents one of the most challenging tasks in nuclear waste decontamination In the event of a radioactive waste leak,^(99)TcO_(4)^(-)(a main form of^(99)Tc)would spread into the groundwa ter,a scenario difficult to address with conventional anion exchange materials like resin and inorganic cationic sorbents.Herein,we present a nickel(II)metal-organic framework(MOF),TNU-143,featuring3D four-fold interpenetrated networks.TNU-143 exhibits efficient ReO_(4)^(-)(a nonradioactive analogue o^(99)TcO_(4)^(–))removal with fast anion exchange kinetics(<1 min),high sorption capacity(844 mg/g for ReO_(4)^(-))and outstanding selectivity over common anions.More importantly,TNU-143 shows superior stability in alkaline solution and can remove 91.6%ReO_(4)^(-)from simulated alkaline high-level waste(HLW)stream with solid-liquid ratio of 40 g/L.The uptake mechanism is elucidated by the single-crystal structure o TNU-143(Re),showing that ReO_(4)^(-)anions are firmly coordinated to nickel cation to result in a 2D lay ered structures.Density functional theory(DFT)calculations confirm the transformation from TNU-143 to TNU-143(Re)is a thermodynamically favorable process.This work presents a new approach to the removal of Re O_(4)^(-)/^(99)TcO_(4)^(-)from alkaline nulcear fuel using MOF sorbents.展开更多
Bipolar blocking and commutation failure in the renewable energy transmission system through ultra-high voltage direct current will produce significant temporary overvoltage.This paper analyzes the physical process of...Bipolar blocking and commutation failure in the renewable energy transmission system through ultra-high voltage direct current will produce significant temporary overvoltage.This paper analyzes the physical process of sending end grid overvoltage caused by two types of DC faults and establishes a DC overvoltage model considering renewable energy sources.According to characteristics of the sending end grid,the influence of the system equivalent impedance,the proportion of renewable energy output,the active and reactive power coefficients of the renewable energy sources during the low voltage ride through process on the overvoltage is analyzed respectively,and the relationship between the proportion of renewable energy output and the short-circuit ratio under the overvoltage constraint is constructed.The validity and practicality of the model and analysis method proposed in this paper are verified by combining the typical transmission system at the sending end of the actual power grid and regional power grid systems.展开更多
While the common practice of decomposing general quantum algorithms into a collection of single-and two-qubit gates is conceptually simple,in many cases it is possible to have more efficient solutions where quantum ga...While the common practice of decomposing general quantum algorithms into a collection of single-and two-qubit gates is conceptually simple,in many cases it is possible to have more efficient solutions where quantum gates engaging multiple qubits are used.In the noisy intermediate-scale quantum(NISQ)era where a universal error correction is still unavailable,this strategy is particularly appealing since it can significantly reduce the computational resources required for executing quantum algorithms.In this work,we experimentally investigate a three-qubit ControlledCPHASE-SWAP(CCZS)gate on superconducting quantum circuits.By exploiting the higher energy levels of superconducting qubits,we are able to realize a Fredkin-like CCZS gate with a duration of 40 ns,which is comparable to typical single-and two-qubit gates realized on the same platform.By performing quantum process tomography for the two target qubits,we obtain a process fidelity of86.0%and 81.1%for the control qubit being prepared in|0>and|1>,respectively.We also show that our scheme can be readily extended to realize a general CCZS gate with an arbitrary swap angle.The results reported here provide valuable additions to the toolbox for achieving large-scale hardware-efficient quantum circuits.展开更多
基金Sponsored by the National Natural Science Foundation-Yunnan Joint Fund Project of China(Grant No.U1402274)the National Natural Science Foundation of China(Grant No.51564033)+1 种基金the Yunnan Applied Basic Research Project(Grant No.2016FA023)the State Key Laboratory of Complex Nonferrous M etal Resources Clean Utilization,Kunming University of Science and Technology(Grant No.CNM RCUXT1403)
文摘The magnetic hysteresis loop was measured to know the magnetic property of molybdenite concentrate.In order to evaluate its microwave absorption capacity, the dielectric properties of molybdenite concentrate was investigated using cavity perturbation method at 915 MHz dependent on densities and temperatures.The parameter data were fitted using regression fit and a model related to the same density and temperature ranges was developed.A nonlinear surface fitting was used to present visually the effect of dielectric parameters on the microwave penetrate depth of molybdnite concentrate.The crystal products of MoO 3 obtained from microwave roasting at different temperatures were examined by scanning electron microscopy (SEM) and X-ray diffraction (XRD).The results show both the dielectric constants and loss factors increase in the increase of apparent densities and temperatures with different growth rates in the experimental range.Due to the distinguished trend of dielectric performance dependent on temperatures, two parts in the heating scenario for the molybdenite concentrate samples were divided.The microwave penetration depth is inversely proportional to both apparent densities and temperatures.The nonlinear fitting surfaces indicate the increase of dielectric loss provides an enough decrease in microwave penetration depth.In contrast, the dielectric constant has a positive effect for it.Pure MoO 3 was produced at 800 ℃ by using microwave energy.This work can be helpful to design and simulate microwave system for efficient beneficiation of molybdenite concentrate and to prepare molybdenum products from this concentrate.
文摘The present work explores the application of microwave heating for the melting of powdered tin. The mor- phology and particle size of powdered tin prepared by the centrifugal atomization method were charac- terized. The tin particles were uniform and spherical in shape, with 90% of the particles in the size range of 38-75μm. The microwave absorption characteristic of the tin powder was assessed by an estimation of the dielectric properties. Microwave penetration was found to have good volumetric heating on powdered tin. Conduction losses were the main loss mechanisms for powdered tin by microwave heating at temperatures above 150 ℃. A 20 kW commercial-scale microwave tin-melting unit was designed, developed, and utilized for production. This unit achieved a heating rate that was at least 10 times higher than those of conventional methods, as well as a far shorter melting duration. The results suggest that microwave heating accelerates the heating rate and shortens the melting time. Tin recovery rate was 97.79%, with a slag ratio of only 1.65% and other losses accounting for less than 0.56%. The unit energy consumption was only 0.17 （kW·h）·kg-1- far lower than the energy required by conventional melting methods. Thus, the microwave melting process improved heating efficiency and reduced energy consumption.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61521005,61875217,91850208,61474130,and 62075230)the Natural Science Foundation of Shanghai,China(Grant Nos.19ZR1465400,21ZR1473800+1 种基金20142200600)the Fund from Zhejiang Laboratory(Grant No.2021MB0AB01)。
文摘With the rapid development of terahertz technology,terahertz detectors are expected to play a key role in diverse areas such as homeland security and imaging,materials diagnostics,biology,medical sciences,and communication.Whereas self-powered,rapid response,and room temperature terahertz photodetectors are confronted with huge challenges.Here,we report a novel rapid response and self-powered terahertz photothermoelectronic(PTE)photodetector based on a lowdimensional material:palladium selenide(Pd Se_(2)).An order of magnitude performance enhancement was observed in photodetection based on PdSe_(2)/graphene heterojunction that resulted from the integration of graphene and enhanced the Seebeck effect.Under 0.1-THz and 0.3-THz irradiations,the device displays a stable and repeatable photoresponse at room temperature without bias.Furthermore,rapid rise(5.0μs)and decay(5.4μs)times are recorded under 0.1-THz irradiation.Our results demonstrate the promising prospect of the detector based on Pd Se2 in terms of air-stable,suitable sensitivity and speed,which may have great application in terahertz detection.
基金Supported by the National Natural Science Foundation of China(21406237 and 21325628)the State Key Development Program for Basic Research of China(2015CB251402)
文摘The present work focuses on a numerical investigation of the solids residence time distribution(RTD) and the fluidized structure of a multi-compartment fluidized bed, in which the flow pattern is proved to be close to plug flow by using computational fluid dynamics(CFD) simulations. With the fluidizing gas velocity or the bed outlet height rising, the solids flow out of bed more quickly with a wider spread of residence time and a larger RTD variance(σ2). It is just the heterogeneous fluidized structure that being more prominent with the bed height increasing induces the widely non-uniform RTD. The division of the individual internal circulation into double ones improves the flow pattern to be close to plug flow.
基金Supported by the State Key Development Program for Basic Research of China(2015CB251402)the National Natural Science Foundation of China(21325628,91334108)the Mole-8.5 Supercomputing System developed by Institute of Process Engineering,Chinese Academy of Sciences
文摘In this study, the flow stability of the flat-bottomed hopper was investigated via GPU-based discrete element method(DEM) simulation. With the material height inside the hopper reducing, the fluctuation of the flow rate indicates an unstable discharge. The flow regions of the unstable discharge were compared with that of the stable discharge, a key transformation zone, where the voidage showed the largest difference between unstable and stable discharge, was revealed. To identify the relevance of the key transformation zone and the hopper flow stability, the voidage variation of the key transformation zone with material height reducing was studied.A sharp increase in the voidage in the key transformation zone was considered to be the standard for judging the unstable hopper flow, and the ‘Top–Bottom effect' of the hopper was defined, which indicated the hopper flow was unstable when the hopper only had the top area and the bottom area, because the voidage of particles in the top area and the bottom area were both variables.
基金Supported by the National Science Fund for Excellent Young Scholars of China(No.51522405)
文摘Mercury-containing catalysts are widely used for acetylene hydrochlorination in China. Surface chemical characteristics of the fresh low-level mercury catalysts and spent low-level mercury catalysts were compared using multiple characterization methods. Pore blockage and active site coverage caused by chlorine-containing organics are responsible for catalyst deactivation. The reactions of chloroethylene and acetylene with chlorine free radical can generate chlorine-containing organic species. SiO_2 and functional groups on activated carbon contribute to the generation of carbon deposition. No significant reduction in the total content of mercury was observed after catalyst deactivation, while there was mercury loss locally. The irreversible loss of HgCl_2 caused by volatilization, reduction and poisoning of elements S and P also can lead to catalyst deactivation. Si, Al, Ca and Fe oxides are scattered on the activated carbon. Active components are still uniformly absorbed on activated carbon after catalyst deactivation.
基金Supported by the National Natural Science Foundation-Yunnan Joint Fund Project of China(U1402274)the National Natural Science Foundation of China(51564033)Yunnan Applied Basic Research Project(2016FA023)
文摘Dielectric properties were measured using cavity perturbation method. The temperature rising behaviors of molybdenite concentrate were investigated in the field of microwave. This process was conducted to show the microwave absorption properties of molybdenite concentrate and the feasibility of microwave roasting molybdenite concentrate to prepare high purity MOO3. The dielectric constant,dielectric loss,and loss tangent increase from 3. 51 to 5. 04,0. 22 to 0. 51 and 0. 065 to 0. 102 respectively. They are proportional to the apparent density of molybdenite concentrate in the range of 0. 9-1. 4 g/cm3. The results show that the molybdenite concentrate has good microwave absorption capacity in the conventional density range. The temperature rising curves show that the apparent heating rate of the molybdenite concentrate increases with the increase in microwave power and decreases with the increase in the sample mass and thickness. The temperature of concentrate sample of 100 g reaches approximately 800 ℃ after 5 min of microwave treatment at 0. 5 kW of power. Our findings show that it is feasible to prepare high-purity MOO3from molybdenite concentrate by microwave roasting.
基金Supported by the Research Foundation of China University of Petroleum,-Beijing at Karamay(YJ2018B02006)the Chinese Government “Thousand Talent” Program(Y42H291501).
文摘Oxidation of petroleum-based byproduct dicyclopentadiene derived diformyltricyclodecanes(DFTD) to dicarboxyltriclodecanesacids(DCTDA) was conducted under catalyst-free and ultra-low temperature conditions with O2 as oxidant. In the perspective of industry process, oxygen pressure and contents, solvent and raw material initial concentrations were screened to evaluate their influence on DCTDA generation. Results indicate that DFTD oxidation can occur rather easily under no-catalyst and ultra-low temperature conditions with O2 as oxidant. Oxygen content and pressure had positive effect on DCTDA production, γ-valerolactone(GVL) behaved best on DFTD generation in dynamics, while methanol could be used as a protective solvent to preserve DFTD.Besides, the existence of water in solvent was not beneficial to DCTDA production because of poor DFTD compatibility with water. The mechanisms of O2 and solvent influence on DCTDA generation were discussed. Meanwhile,the oxidation route of DFTD–Intermediate–DCTDA was proposed. The present work exhibits the valued potential of DFTD, which will have a positive effect on high added value of petroleum based by-products.
基金support of the Basic Research Project of Science and Technology Planning Project of Yunnan Provincial Department of Science and Technology (202201AS070031)Yunnan Pronince Top young talents of The Ten Thousand Project+4 种基金the central government guides local science and technology development projects (CB22005R006A)the National Key Research and Development Program of China (2019YFC1904204)Kunming Key Laboratory of Special MetallurgyKunming Academician Workstation of Advanced Preparation for Super hard Materials FieldKunming Academician Workstation of Metallurgical Process Intensification。
文摘Arsenic is one of the main harmful elements in industrial wastewater.How to remove arsenic has always been one of the research hotspots in academic circles.In the process of arsenic removal by traditional sulfuration,the use of traditional sulfurizing agent will introduce new metal cations,which will affect the recycling of acid.In this study,phosphorus pentasulfide (P_(2)S_(5)) was used as sulfurizing agent,which hydrolyzed to produce H_(3)PO_(4) and H_(2)S without introducing new metal cations.The effect of ultrasound on arsenic removal by P_(2)S_(5) was studied.Under the action of ultrasound,the utilization of P_(2)S_(5) was improved and the reaction time was shortened.The effects of S/As molar ratio and reaction time on arsenic removal rate were investigated under ultrasonic conditions.Ultrasonic enhanced heat and mass transfer so that the arsenic removal rate of 94.5%could be achieved under the conditions of S/As molar ratio of 2.1:1 and reaction time of 20 min.In the first 60 min,under the same S/As molar ratio and reaction time,the ultrasonic hydrolysis efficiency of P_(2)S_(5) was higher.This is because P_(2)S_(5) forms ([(P_(2)S_(4))])^(2+)under the ultrasonic action,and the structure is damaged,which is easier to be hydrolyzed.In addition,the precipitation after arsenic removal was characterized and analyzed by X-ray diffraction,scanning electron microscope-energy dispersive spectrometer,X-ray fluorescence spectrometer and X-ray photoelectron spectroscopy.Our research avoids the introduction of metal cations in the arsenic removal process,and shortens the reaction time.
基金supported by the China Scholarship Council and Fujian University-Industry Research Cooperation Project(Project No.:2018N5013)。
文摘P450 fatty acid decarboxylase Ole T from Staphylococcus aureus(Ole TSA)is a novel cytochrome P450 enzyme that catalyzes the oxidative decarboxylation of fatty acids to yield primarily terminal alkenes and CO_(2) or minor a-andβ-hydroxylated fatty acids as side-products.In this work,the interactions between a series of cycloalkyl phosphorus heterocycles(CPHs)and Ole TSAwere investigated in detail by fluorescence titration experiment,ultraviolet-visible(UV-vis)and31 P NMR spectroscopies.Fluorescence titration experiment results clearly showed that a dynamic quenching occurred when CPH-6,a representative CPHs,interacted with Ole TSAwith a binding constant value of 15.2×104 M-1 at 293 K.The thermodynamic parameters(ΔH,ΔS andΔG)showed that the hydrogen bond and van der Waals force played major roles in the interaction between Ole TSAand CPHs.The UV-vis and31 P NMR studies indicated the penetration of CPH-6 into the interior environment of Ole TSA,which greatly affects the enzymatic activity of Ole TSA.Therefore,our study revealed an effective way to use phosphorus heterocyclic compounds to modulate the activity of cytochrome P450 enzymes.
基金supported by the National Natural Science Foundation of China(Grant No.12274440)the Strategic Priority Research Program(B)of Chinese Academy of Sciences(Grant No.XDB33010100)National Key R&D Program of China(Grant No.2022YFA1403903)。
文摘Mn_(3)Sn_(2)has been proposed as an ideal material for magnetic refrigeration.It undergoes two successive ferromagnetic transitions(T_(C1)=262 K and T_(C2)=227 K)and one antiferromagnetic transition(TN=192 K).Herein we report,for the first time,the preparation of single crystals of Mn_(3)Sn_(2)from Bi flux.The resultant anisotropic magnetic properties and magnetocaloric effect are investigated along the three principal crystallographic directions of the crystal.Significant anisotropy of magnetic susceptibility and multiple field-induced metamagnetic transitions were found at low fields,whereas the magnetocaloric effect was found to be almost isotropic and larger than that of the polycrystalline one.The maximum magnetic entropy change amounts to-ΔSM=4.01 J·kg^(-1)·K^(-1)near T_(C1)under a magnetic field change of μ_(0)ΔH=5 T along the c-axis,with the corresponding refrigerant capacity of 1750 mJ·cm^(-3).Combined with a much wider cooling temperature span(~80 K),our results demonstrate Mn_(3)Sn_(2)single crystal to be an attractive candidate working material for active magnetic refrigeration at low temperatures.
基金Project supported by the National Basic Research Program of China(Grant No.2014CB921201)the National Natural Science Foundation of China(Grant Nos.11434008 and 11574380)
文摘We present an experiment of observing the geometric phase in a superconducting circuit where the resonator and the qutrit energy levels are dispersively coupled. The drive applied to the resonator displaces its state components associated with the qutrit＇s ground state and first-excited state along different circular trajectories in phase space. We identify the resonator＇s phase-space trajectories by Wigner tomography using an ancilla qubit, following which we observe the difference between the geometric phases associated with these trajectories using Ramsey interferometry. This geometric phase is further used to construct the single-qubit It-phase gate with a process fidelity of 0.851± 0.001.
文摘Taking GCr15 bearing steel as experiment material, the effects of suspension casting process and low superheat casting process on the solidification of ingot were studied comparehvely. The results show that both suspension casting process and low superheat casting process can improve the censeal segregation and crystal structure of ingot. As the acting mechanism is different between the two kinds of processes, it is found that suspension casting process is more effective than low superheat casting process in improving the quality of ingot.
基金Supported by Special Fund of Agro-scientific Research in Public Interest(201303129)Analysis of Sulforaphane Content in Brassica juncea Coss.var.foliosa Bailey and Related SSR Markers(2017FD200)National Staple Vegetable Industrial Technology System(CARS-23-G37)
文摘This study was conducted to provide reference for rational fertilization and agrochemical application in cucumber plantation,and relieve the problem of environmental pollution and vegetable agrochemical residues. The effects of different combinations of fertilization and agrochemical application on cucumber yield and cost input were investigated. Four treatments were conducted,including T1（ conventional fertilization ＋ conventional agrochemical application,CK）,T2（ conventional fertilization ＋ recommended agrochemical application）,T3（ recommended fertilization ＋ conventional agrochemical application） and T4（ recommended fertilization ＋ recommended agrochemical application）. The results showed that T4 had fewer kinds of fertilizers and agrochemicals than that of T1,and had a yield increasing effect on cucumber,and the yield increase was 7 003. 5 kg/hm^2,with an increasing rate of 19. 25%; and it also had obvious cost-saving and benefit-increasing effects,specifically,the cost was saved by 10 941 yuan/hm^2 and the benefit was increased by 31 951. 5 yuan/hm^2. The results of this experiment were satisfactory,and higher benefit was obtained with lower input. This study will provide reference for cucumber planter to choose fertilizers and agrochemicals,and lays a foundation for alleviating the ecological soil problems.
基金National Key Research and Development Program of China (2018YFA0902000)the key project at central government level:the ability establishment of sustainable use for valuable Chinese medicine resources(2060302,China)+3 种基金the open foundation of Shaanxi University of Chinese Medicine state key laboratory of R&D of Characteristic Qin Medicine Resources (SUCM-QM202202,China)the fund of Traditional Chinese Medicine Institute of Anhui Dabie Mountain (TCMADM-2023-18,China)National Natural Science Foundation of China (32070364)Hainan Provincial Natural Science Foundation of China(2019RC309)
文摘Pyran-and furanocoumarins are key representatives of tetrahydropyrans and tetrahydrofurans,respectively,exhibiting diverse physiological and medical bioactivities.However,the biosynthetic mechanisms for their core structures remain poorly understood.Here we combined multiomics analyses of biosynthetic enzymes in Peucedanum praeruptorum and in vitro functional verification and identified two types of key enzymes critical for pyran and furan ring biosynthesis in plants.These included three distinct P.praeruptorum prenyltransferases(PpPT1e3)responsible for the prenylation of the simple coumarin skeleton 7 into linear or angular precursors,and two novel CYP450 cyclases(PpDC and PpOC)crucial for the cyclization of the linear/angular precursors into either tetrahydropyran or tetrahydrofuran scaffolds.Biochemical analyses of cyclases indicated that acid/base-assisted epoxide ring opening contributed to the enzyme-catalyzed tetrahydropyran and tetrahydrofuran ring refactoring.The possible acid/base-assisted catalytic mechanisms of the identified cyclases were theoretically investigated and assessed using site-specific mutagenesis.We identified two possible acidic amino acids Glu303 in PpDC and Asp301 in PpOC as vital in the catalytic process.This study provides new enzymatic tools in the epoxide formation/epoxide-opening mediated cascade reaction and exemplifies how plants become chemically diverse in terms of enzyme function and catalytic process.
基金supported by National Natural Science Foundation of China(No.22171210)Research Project of Tianjin Education Commission(No.2023KJ182)Tianjin Research Innovation Project for Postgraduate Students(No.2022BKY200)。
文摘The sequestration of^(99)Tc represents one of the most challenging tasks in nuclear waste decontamination In the event of a radioactive waste leak,^(99)TcO_(4)^(-)(a main form of^(99)Tc)would spread into the groundwa ter,a scenario difficult to address with conventional anion exchange materials like resin and inorganic cationic sorbents.Herein,we present a nickel(II)metal-organic framework(MOF),TNU-143,featuring3D four-fold interpenetrated networks.TNU-143 exhibits efficient ReO_(4)^(-)(a nonradioactive analogue o^(99)TcO_(4)^(–))removal with fast anion exchange kinetics(<1 min),high sorption capacity(844 mg/g for ReO_(4)^(-))and outstanding selectivity over common anions.More importantly,TNU-143 shows superior stability in alkaline solution and can remove 91.6%ReO_(4)^(-)from simulated alkaline high-level waste(HLW)stream with solid-liquid ratio of 40 g/L.The uptake mechanism is elucidated by the single-crystal structure o TNU-143(Re),showing that ReO_(4)^(-)anions are firmly coordinated to nickel cation to result in a 2D lay ered structures.Density functional theory(DFT)calculations confirm the transformation from TNU-143 to TNU-143(Re)is a thermodynamically favorable process.This work presents a new approach to the removal of Re O_(4)^(-)/^(99)TcO_(4)^(-)from alkaline nulcear fuel using MOF sorbents.
基金supported by the National Key R&D Program of China(2022YFB2403100).
文摘Bipolar blocking and commutation failure in the renewable energy transmission system through ultra-high voltage direct current will produce significant temporary overvoltage.This paper analyzes the physical process of sending end grid overvoltage caused by two types of DC faults and establishes a DC overvoltage model considering renewable energy sources.According to characteristics of the sending end grid,the influence of the system equivalent impedance,the proportion of renewable energy output,the active and reactive power coefficients of the renewable energy sources during the low voltage ride through process on the overvoltage is analyzed respectively,and the relationship between the proportion of renewable energy output and the short-circuit ratio under the overvoltage constraint is constructed.The validity and practicality of the model and analysis method proposed in this paper are verified by combining the typical transmission system at the sending end of the actual power grid and regional power grid systems.
基金supported by the Key-Area Research and Development Program of Guangdong Province(No.2018B030326001)the National Natural Science Foundation of China(Nos.12074166 and 12004162)the Guangdong Provincial Key Laboratory(No.2019B121203002).
文摘While the common practice of decomposing general quantum algorithms into a collection of single-and two-qubit gates is conceptually simple,in many cases it is possible to have more efficient solutions where quantum gates engaging multiple qubits are used.In the noisy intermediate-scale quantum(NISQ)era where a universal error correction is still unavailable,this strategy is particularly appealing since it can significantly reduce the computational resources required for executing quantum algorithms.In this work,we experimentally investigate a three-qubit ControlledCPHASE-SWAP(CCZS)gate on superconducting quantum circuits.By exploiting the higher energy levels of superconducting qubits,we are able to realize a Fredkin-like CCZS gate with a duration of 40 ns,which is comparable to typical single-and two-qubit gates realized on the same platform.By performing quantum process tomography for the two target qubits,we obtain a process fidelity of86.0%and 81.1%for the control qubit being prepared in|0>and|1>,respectively.We also show that our scheme can be readily extended to realize a general CCZS gate with an arbitrary swap angle.The results reported here provide valuable additions to the toolbox for achieving large-scale hardware-efficient quantum circuits.
