Arsenic removal from acidic industrial wastewater by ultrasonic activated phosphorus pentasulfide

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.

Highly Anisotropic Magnetism and Nearly Isotropic Magnetocaloric Effect in Mn_(3)Sn_(2)Single Crystals

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.

超越激进与保守:话语分析与历史展望

在五四新文化运动百周年之际,在新时代中国特色社会主义扬帆远航之时,重温上世纪90年代的激进与保守之争,追溯百年来的激进主义与保守主义,可以看出,激进和保守的思潮应该在现代化的背景下来理解,传统也不应被视作现代化的对立面,启蒙、救亡和革命相辅相成,共同构成了20世纪的中国历史主题。对这一主题的重述,需要梳理进化论的流变,把握变迁的节奏,捕捉并非整齐划一的片段。超越激进与保守之争,走向文化自觉和文化自信,是中国特色社会主义文化的必由之路。

Dielectric Characterization and Microwave Roasting of Molybdenite Concentrates at 915 MHz Frequency

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.

GPU-based discrete element simulation on flow stability of flat-bottomed hopper

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.

Surface chemical characterization of deactivated low-level mercury catalysts for acetylene hydrochlorination

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.

CFD simulation of solids residence time distribution in a multi-compartment fluidized bed

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.

A self-powered and sensitive terahertz photodetection based on PdSe_(2)

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.

Dielectric Properties and Microwave Heating of Molybdenite Concentrate at 2.45 GHz Frequency

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.

Oxidation of petroleum-based byproducts diformyltricyclodecanes(DFTD)with O2 under catalyst-free and ultra-low temperature

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.

Spectroscopic studies of the interaction between phosphorus heterocycles and cytochrome P450

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.

Observation of geometric phase in a dispersively coupled resonator-qutrit system

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.

A Comparison Study between Suspension Casting Process and Low Superheat Casting Process

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.

Effects of Different Combinations of Fertilization and Agrochemical Application on Yield and Cost-effectiveness of Cucumber

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.

Two types of coumarins-specific enzymes complete the last missing steps in pyran- and furanocoumarins biosynthesis

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.

Wafer-scale patterned growth of type-II Dirac semimetal platinum ditelluride for sensitive room-temperature terahertz photodetection

As the lastly unexplored electromagnetic wave,terahertz(THz)radiation has been exploited in a plenty of contexts such as fundamental research,military and civil fields.Most recently,representative two-dimensional(2D)topological semimetal,platinum ditelluride(PtTe_(2))has attracted considerable research interest in THz detection due to its unique physical properties.However,to achieve practical applications,the low-cost,large-scale,controllable synthesis and efficient patterning of 2D materials are key requirements,which remain a challenge for PtTe_(2)and its photodetectors(PDs).Herein,a facile approach is developed to obtain waferscale(2-inches)patterned PtTe_(2)arrays using one-step tellurium-vapor transformation method and micro-Nano technology.PtTe_(2)PD arrays are fabricated with the as-grown PtTe_(2)arrays evenly distributed on a 2-inch wafer,exhibiting high conductivity(~2.7×105 S m^(-1))and good electrical consistency.Driven by the Dirac fermions,PtTe_(2)PDs achieve a broadband(0.02-0.3 THz)response with a fast response speed(~4.7μs),a high sensitivity(~47 pW Hz^(-1/2))and high-resolution transmission THz-imaging capability,which displays the potential of large-area THz array imaging.These results are one step towards the practical applications of integrated PD arrays based on 2D materials.

Visual object tracking:Progress,challenge,and future

Visual object tracking aims to continuously localize the target object of interest in a video sequence.As one of the most fundamental problems in computer vision,visual object tracking has a long list of critical applications including video surveillance,autonomous driving,human-machine interaction,augmented reality,robotics,etc.,in which the tracking system provides the capacity to report target positions in real time for subsequent visual analysis.In the past decades,visual object tracking has been extensively explored and has witnessed considerable progress,especially in deep-learning-based tracking.

江苏盐城滨海地区风机对鸟类的影响

近年来我国风力发电发展迅速,已有研究发现风电工程会对鸟类多样性产生不同程度的影响。然而,过去的研究多以区域内鸟类常规调查为主,未直接对风机致死鸟类进行长期系统的调查监测,也未进一步探究风机致死可能的方式和原因,从而难以根据风机致死鸟类的实际情况提出有针对性的防范措施和应对方法。本文以江苏盐城滨海地区风电场为例,基于2020年10月至2021年9月共22次连续的调查监测,应用尸体搜索法调查了研究区域内风机致死鸟类的情况。结果表明:(1)风机下发现的死亡鸟类有8目10科12种,死亡鸟类主要为留鸟或已在研究区域内繁殖的种类,占死亡鸟类种类的66.7%;(2)风机下共发现死亡鸟类41只,环颈雉(Phasianuscolchicus)死亡数量最多,有19只,大部分位于农田及农田防护林中;夜鹭(Nycticoraxnycticorax)和白鹭(Egrettagarzetta)死亡数量也较多,共11只,主要位于鱼塘中;(3)通过对风机下死亡鸟类的情况分析发现,在风机基座比风机扇叶造成的碰撞致死情况多。最后,本文提出了减缓风机对鸟类影响的措施和建议,包括持续开展鸟类监测,及时开展风机下生境的治理,加强鸟类相关驱避技术装备研发等,为我国风电与生态环境保护之间的协调发展提供参考。

Demand Response Based and Wind Farm Integrated Economic Dispatch

Increased penetration of intermittent renewable energy resources is pushing the grid to prepare more reserves to meet the supply and demand balance.Demand response(DR)is an efficient strategy to reduce the overall load at peak times.In order to fully utilize the application of DR and make DR capable of actively supporting grid operations at all times,this paper builds a DR and wind farm integrated economic dispatch model.The objective is to minimize the total operation costs,such as fuel cost,startup cost,greenhouse gas(GHG)emission costs,and DR cost.DR maximum participating time and DR ramp rate constraints are considered.A system with 10 traditional units,one large-scale wind farm,three types of DR,including interruptible load,direct load control,and load as capacity resource are selected to verify the proposed model.Four DR penetration rates are analyzed:0%,10%,20%and 30%.The results indicate that DR penetration can decrease total operation costs.The lower price DR resource gets the priority to be committed.The DR and wind farm integration is indispensable in the future economic dispatch.