Easily Separated and Recyclable Amino-functionalized Porous SiO2 Beads with 3D Continuous Meso/Macropore Channels

Amino-fimctionalized porous SiO2 beads with a diameter of 200--800 μm（PSB-NH2） have been success- fully synthesized by grafting 3-ammopropyl-triethoxysilane onto meso/macroporous silica beads（PSB）, in which the PSB was prepared by hydrothermal synthetic method with a porous hard template anion-exchange resin. The as-prepared materials were characterized by means of nitrogen sorption and transmission electron micrographs（TEM）, showing the presence of 3D interconnected and continuous large mesopores and macropores inside. The beads were used to catalyze Knoevenagel condensation and proved to be highly active and selective due to the high accessibility of the reactants to the amino groups via the continuous 3D meso/macopores. Notably, such material in bead format facilitates the extremely straightforward separation from reaction solution without any centrifugation or filtration. Moreover, PSB-NH2 proved to be a stable catalyst via leaching experiment test, and can be easily recovered and reused without significant loss of activity in successive catalytic cycles.

Infiltration,runoff,and slope stability behaviors of infinite slope with macropores based on an improved Green–Ampt model

Infiltration–runoff–slope instability mechanism of macropore slope under heavy rainfall is unclear.This paper studied its instability mechanism with an improved Green–Ampt(GA)model considering the dual-porosity(i.e.,matrix and macropore)and ponding condition,and proposed the infiltration equations,infiltration–runoff coupled model,and safety factor calculation method.Results show that the infiltration processes of macropore slope can be divided into three stages,and the proposed model is rational by a comparative analysis.The wetting front depth of the traditional unsaturated slope is 17.2%larger than that of the macropore slope in the early rainfall stage and 27%smaller than that of the macropore slope in the late rainfall stage.Then,macropores benefit the slope stability in the early rainfall but not in the latter.Macropore flow does not occur initially but becomes pronounced with increasing rainfall duration.The equal depth of the wetting front in the two domains is regarded as the onset criteria of macropore flow.Parameter analysis shows that macropore flow is delayed by increasing proportion of macropore domain(ω_(f)),whereas promoted by increasing ratio of saturated permeability coefficients between the two domains(μ).The increasing trend of ponding depth is sharp at first and then grows slowly.Finally,when rainfall duration is less than 3 h,ωf andμhave no significant effect on the safety factor,whereas it decreases with increasingωf and increases with increasingμunder longer duration(≥3 h).With the increase ofω_(f),the slope maximum instability time advances by 10.5 h,and with the increase ofμ,the slope maximum instability time delays by 3.1 h.

往返平飘式探空在CMA-MESO三维变分中的同化及对模式预报的影响

往返平飘式探空通过一次探空气球施放实现“上升段-平飘段-下降段”三段观测,其下降段能实现在06时(世界时,下同)和18时自动垂直加密观测大气,具备提升区域高分辨率快速同化循环预报系统在06时和18时的预报技巧潜力。为了实现往返平飘式探空在区域高分辨率模式中的同化,分析其对预报的影响,初步提出了“选取模式层最接近观测”的垂直稀疏化方法来预处理资料,深入分析了稀疏化对同化效果的影响,论证了资料垂直稀疏化对于同化应用的必要性;在此基础上,开展了为期1个月的批量同化影响试验,着重分析了往返平飘式探空在长江中下游区域的组网观测对CMA-MESO模式预报技巧的影响。稀疏化敏感性试验结果表明,同化不稀疏化的往返平飘式探空相比同化传统业务探空,分析和预报误差显著增加,降水预报评分也显著降低,相反,“选取最接近模式层”数据的垂直稀疏化方案能提高模式的分析和预报技巧,表明往返平飘式探空同化前必须进行垂直稀疏化。批量同化试验结果表明,在冷启动时刻(00时和12时,为常规探空释放时刻),同化往返平飘式探空(上升段)相对同化传统业务探空,分析误差和预报误差变化较小。但在暖启动时刻(03、06、09、15、18、21时,无常规探空释放时刻),增加往返平飘式探空下降段数据,相比控制试验,分析场精度提高了约0.4%。此外,0~12 h累计降水预报的ETS评分变化较小,但12~24 h累计降水预报在0.1、1.0、5.0、10.0、25.0 mm量级降水ETS评分提高了约0.5%,在50.0 mm量级的降水ETS评分提高了约2.3%。总体而言,同化往返平飘式探空对于区域高分辨率快速同化循环预报系统在暖启动时刻的降水预报技巧有正贡献。

CMA-MESO千米尺度变分同化系统中极小化控制变量的重构

重构GRAPES(Global/Regional Assimilation and Prediction System)全球、区域一体化变分同化系统中的极小化控制变量,提升中、小尺度同化分析能力,为中国气象局业务区域数值预报系统CMA-MESO提供千米尺度适用的同化方案。新方案用纬向风速(u)和经向风速(v)替代原有流函数和势函数作为新的风场控制变量,采用温度和地面气压(T,ps)替代原有非平衡无量纲气压作为新的质量场控制变量,同时不再考虑准地转平衡约束,而是采用连续方程弱约束保证分析平衡。背景误差参数统计和数值试验结果表明,采用重构后的极小化控制变量,观测信息传播更加局地,分析结构更加合理,避免了原方案在中、小尺度应用时存在的虚假相关问题。连续方程弱约束的引入,限制了同化分析中辐合、辐散的不合理增长,帮助新方案在分析更加局地的同时保证分析平衡。为期1个月的连续同化循环和预报试验结果表明,新方案可以减小风场和质量场分析误差,CMAMESO系统地面降水和10 m风场的预报评分显著提升。

地形影响的水平相关模型在CMA-MESO中的应用

在背景误差水平相关模型中引入地形作用,研究复杂地形下近地面观测资料同化对分析和预报的影响。CMAMESO三维变分系统中背景误差水平相关关系采用高斯相关模型描述,观测信息在高度追随坐标的模式面上各向同性传播。然而在地形复杂的近地面层,观测信息传播受到山脉阻挡,因而其背景误差协方差非均匀且各向异性,观测信息传播应随地形高度变化。为此,采用美国国家气象中心NMC方法统计复杂地形下背景误差水平相关结构,构建包含地形高度和地形梯度影响的高斯相关模型,并将改进的水平相关模型应用于CMA-MESO三维变分分析。理想试验表明:考虑地形项的水平相关模型方案使观测信息以随地形高度变化的各向异性形式传播,越过大地形观测信息影响明显减弱,分析增量更加合理。我国北方一次强降水过程分析预报试验表明:随地形高度变化的水平相关模型方案使地面观测信息各向异性传播,削弱了大地形处近地面的分析增量,对降水预报略有正贡献。针对华东地区降水过程进行5 d逐小时快速更新分析预报循环试验结果表明,随地形变化的水平相关模型方案对10 m风场和24 h时效内降水预报有正贡献。

葵花-8卫星AOD资料在CMA-MESO/CUACE CW 3DVar同化系统中的个例应用研究

CMA-MESO/CUACE CW化学天气耦合模式是自主研发的大气化学耦合模式,目前CMA-MESO/CUACE CW3DVar同化系统实现了地面气溶胶观测可吸入颗粒物PM_(2.5)和PM10的同化,为增强耦合同化系统非常规观测的同化能力,文中在CMA-MESO大气化学天气耦合三维变分同化框架基础上,利用查表法获得气溶胶消光系数,然后建立气溶胶光学厚度(AerosolOpticalDepth,AOD)和气溶胶组分之间关系的观测算子、切线性观测算子和伴随观测算子,实现AOD观测资料的同化应用。针对2016年12月18-20日华北、黄淮地区一次污染天气过程进行同化预报试验,试验结果表明同化葵花-8卫星(Hi‐mawari-8)气溶胶光学厚度观测后,PM_(2.5)分析的重污染区范围有所扩大,山西东南部分析与实况分布更为接近,但是山东大部地区PM_(2.5)分析偏强,与观测相比PM_(2.5)质量浓度存在高估。同时同化Himawari-8 AOD观测和地面气溶胶站点观测的PM_(2.5)分析最优,分析与观测距平相关系数最高,平均偏差、均方根误差及标准差最小。重污染区的PM_(2.5)预报检验结果表明,同化Himawari-8AOD观测对大于350µg·m^(-3)量级PM_(2.5)预报正贡献可以持续到48 h,但整体来说,同时同化Himawari-8AOD观测和地面气溶胶站点观测对各个量级的PM_(2.5)质量浓度预报质量最优。

Oxidative Desulfurization of Fuel Oil at Room Temperature Catalyzed by Ordered Meso-macroporous HPW/SiO2

A serial of ordered meso-macroporous phosphotungstic acid(HPW) supported on SiO2 nanocomposites were successfully prepared by a homogeneous precipitation method, using monodispersed polystyrene(PS) microspheres and cationic surfactant as structure directing agent. These nanocomposites were used as catalysts for oxidative desulfurization(ODS) of model fuel. The materials were characterized by scanning electron microscopy(SEM), transmission electron microscopy(TEM), N2 adsorption-desorption isothrem, X-ray diffraction(XRD), and Fourier transform infrared spectra(FTIR). The characterization results suggested that the as-prepared material possessed ordered meso-macroporous architectures with Keggin type phosphotungstic acid dispersed homogeneously in SiO2 matrix. Under the selected reaction conditions, dibenzothiophene(DBT) in model fuel can be removed within 2 h at room temperature(30 ℃). In addition, only 1.2% of efficiency lose than the fresh catalyst even after 5 cycles.

Soil Macropore Structure Characterized by X-Ray Computed Tomography

Undisturbed soil core with many macropores and disturbed soil core with onlyone macropore (diameter is 10 mm) were probed by X-ray computed tomography (CT). The size, number,shape and continuity of macropores in the transverse and vertical sectionsof soil were characterizedusing CT scanning images. The probability densities of macropores in the transverse section of soilcore exhibited a logarithmic P distribution. Results indicated that CT scanning was a promisingnondestructive method for characterizing macropores in soils.

Dye tracer infiltration technique to investigate macropore flow paths in Maka Mountain, Yunnan Province, China

In order to investigate the differences of macropores vertical distribution under different surface plants, and to assess the influences of root systems, organic matter and texture on macropore flow paths, two dye tracer infiltration experiments were performed in slopes under two different plants(Campylotropis polyantha(Franch.) Schindl vs. Cynodon dactylon(Linn.) Pers). Dye tracer infiltration experiments with field observations and measurements of soil properties were combined. Results show that the discrepancy in macropores distribution between two slopes under different plants is significant. Root systems have significant effects on macropore flow paths distribution and the effect become more pronounced as the diameter of roots become larger. Organic matter and stone are important factors to affect macropores distribution. Root-soil interface, inter-aggregate macropore and stone-soil interface are important macropore flow paths in well vegetated slopes.

Meso-macroporous Fe-doped Cu O: Synthesis, characterization, and structurally enhanced adsorption and visible-light photocatalytic activity

The meso-macroporous Fe-doped Cu O was prepared by a simple hydrothermal method combined with post-annealing. The samples were characterized by X-ray powder diffraction(XRD), scanning electron microscopy(SEM), Brunauer-Emmett-Teller N2 adsorption-desorption analyses and UV-vis diffuses reflectance spectroscopy. The Fe-doped Cu O sample shows higher adsorption capacity and photocatalytic activity for xanthate degradation than pure Cu O under visible light irradiation. In addition, the adsorption process is found to fit Langmuir isotherms and pseudo-second-order kinetics. The the first order kinetic Langmuir Hinshelwood model was used to study the reaction kinetics of photocatalytic degradation, and the apparent rate constant( k) was calculated. The value of k for Fe-doped Cu O is 1.5 times that of pure Cu O. The higher photocatalytic activity of Fe-doped Cu O is attributed to higher specific surface area together with stronger visible light absorption.

3D macropore carbon-vacancy g-C_(3)N_(4) constructed using polymethylmethacrylate spheres for enhanced photocatalytic H_(2) evolution and CO_(2) reduction

Metal-free g-C_3N_4 is widely used in photocatalytic reactions owing to its suitable band structure.However, it has low specific surface area and insufficient absorbance for visible light, and its photoexcited carriers have high recombination rates. In this study, the 3 D macropore C-vacancy g-C_3N_4 was prepared through a facile one-step route. Polymethylmethacrylate is used as a template to increase the surface reaction sites of g-C_3N_4 and extend its visible-light range. Compared to unmodified g-C_3N_4, the H2 production and CO_2 reduction rates of the fabricated g-C_3N_4 significantly improved. The special pore structure significantly improved the light utilization efficiency of g-C_3N_4 and increased the number of surface-active sites. The introduction of C-vacancy extended the absorption band of visible-light and suppressed the carrier recombination. The newly developed synthesis strategy can improve solar energy conversion efficiency and potentially modifies g-C_3N_4.

Characteristics of rock fragments in different forest stony soil and its relationship with macropore characteristics in mountain area, northern China

Rock fragments have major effect on soil macropores and water movement. However, the characteristics of rock fragments and their relationship with macropore characteristics remain elusive in forest stony soils in northern mountainous area of China. The objectives of this study are to(1) use Industrial Computed Tomography(CT) scanning to quantitatively analyze rock fragment characteristics in intact soil columns in different forest lands and(2) identify the relationship between characteristics of rock fragments and that of the macropores. Intact soil columns that were 100 mm in diameter and 300 mm long were randomly taken from six local forest stony soils in Wuzuolou Forest Station in Miyun, Beijing. Industrial CT was used to scan all soil column samples, and then the scanned images were utilized to obtain the three-dimensional(3 D) images of rock fragments and macropore structures. Next, theparameters of the rock fragments and macropore structure were measured, including the volume, diameter, surface area, and number of rock fragments, as well as the volume, diameter, surface area, length, angle, tortuosity and number of macropores. The results showed that no significant difference was found in soil rock fragments content in the 10-30 cm layer between mixed forest and pure forest, but in the 0-10 cm soil layer, the rock fragments in mixed forest were significantly less than in pure forest. The number density of macropores has significant negative correlation with the number of rock fragments in the 0-10 cm soil layer, whereas this correlation is not significant in 10-20 cm and 20-30 cm soil layers. The volume density of macropore was not correlated with the volume density of rock fragments, and there is no correlation between the density of macropore surface area and the density of rock fragment surface area. Industrial CT scanning combined with image processing technology canprovide a better way to explore 3 D distribution of rock fragments in soil. The content of rock fragments in soil is mainly determined by parent rocks. The surface soil(0-10 cm) of forest contains fewer rock fragments and more macropores, which may be caused by bioturbation, root systems, gravitational settling and faunal undermining.

Meso-macroporous Al_2O_3 supported Ru catalysts for CO preferential oxidation in hydrogen-rich gases

Series of meso-macroporous Al2O3 supported Ru catalysts with different loadings were prepared by incipient wetness method and applied to preferential oxidation of CO in hydrogen-rich gases. N2 adsorption-desorption, SEM, XRD, TEM, CO chemisorption and H2-TPR techniques were employed to characterize the catalysts. The results indicate that Ru/Al2O3 catalysts have meso-macroporous structure, high surface area and high metal dispersion. The characterization results of XRD and CO chemisorption indicate the entry of Ru ions into Al2O3 lattice. The results of catalytic performance tests indicate that the meso-macroporous Al2O3 supported Ru catalysts for CO preferential oxidation showed good activity under high space velocity. It is proposed that the macropores in the Ru/Al2O3 catalyst favor mass transfer and mesopores help to improve the dispersion of metal, resulting in the excellent catalytic performance.

Quantification of 3D macropore networks in forest soils in Touzhai valley(Yunnan,China)using X-ray computed tomography and image analysis

The three dimensional （3D） geometry of soil macropores largely controls preferential flow, which is a significant infiltrating mechanism for rainfall in forest soils and affects slope stability. However, detailed studies on the 3D geometry of macropore networks in forest soils are rare. The intense rainfall-triggered potentially unstable slopes were threatening the villages at the downstream of Touzhai valley （Yunnan, China）. We visualized and quantified the 3D macropore networks in undisturbed soil columns （Histosols） taken from a forest hillslope in Touzhai valley, and compared them with those in agricultural soils （corn and soybean in USA; barley, fodder beet and red fescue in Denmark） and grassland soils in USA. We took two large undisturbed soil columns （250 mm^25o mmxsoo mm）, and scanned the soil columns at in-situ soil water content conditions using X-ray computed tomography at a voxel resolution of 0.945 × 0.945 × 1.500o mm^3. After reconstruction and visualization, we quantified the characteristics of macropore networks. In the studied forest soils, the main types of maeropores were root channels, inter-aggregate voids, maeropores without knowing origin, root-soil interfaee and stone-soil interface. While maeropore networks tend to be more eomplex, larger, deeper and longer. The forest soils have high maeroporosity, total maeropore wall area density, node density, and large maeropore volume, hydraulie radius, mean maeropore length, angle, and low tortuosity. The findings suggest that maeropore networks in the forest soils have high inter- connectivity, vertical continuity, linearity and less vertically oriented.

Mechanical characteristics of soil-rock mixtures containing macropore structure based on 3D modeling technology

Soil-rock mixtures containing macropore(SRMCM)is a kind of geological material with special mechanical properties.Located in the project area of Lenggu hydropower station on the Yalong River,Sichuan Province,China,there is an extremely unstable Mahe talus slide with a total volume of nearly160 million cubic meters,which is mainly composed of SRMCM.The study on the mechanical properties of SRMCM is of great significance for the engineering construction and safe operation.In this paper,laboratory tests and discrete element numerical tests based on three-dimensional scanning technology were conducted to study the influence of stone content,stone size,and the angle of the macropore structure on shear characteristics of SRMCM.The failure mechanism of SRMCM was discussed from a microscopic perspective.This work explains the internal mechanism of the influence of stone content,stone size,and the angle of the macropore structure on the strength of SRMCM through the microscopic level of stone rotation,force chain distribution,and crack propagation.As the macropore structure that intersects with the preset shear plane at a large angle could act as a skeleton-like support to resist the shear force,the fracture of the weak cemented surface of soil and stone in the macropore structure is an important cause of SRMCM destruction.

Micro–meso-macroporous FeCo-N-C derived from hierarchical bimetallic FeCo-ZIFs as cathode catalysts for enhanced Li-O2 batteries performance

Developing bifunctional catalysts that increase both the OER and ORR kinetics and transport reactants with high efficiency is desirable. Herein, micro–meso-macroporous FeCo-N-C-X(denoted as "MFeCo-N-C-X", X represents Fe/Co molar ratio in bimetallic zeolite imidazole frameworks FeCo-ZIFs) catalysts derived from hierarchical M-FeCo-ZIFs-X was prepared. The micropores in M-FeCo-N-C-X have strong capability in O2 capture as well as dictate the nucleation and early-stage deposition of Li2O2,the mesopores provided a channel for the electrolyte wetting, and the macroporous structure promoted more available active sites when used as cathode for Li-O2 batteries. More importantly, M-Fe CoN-C-0.2 based cathode showed a high initial capacity(18,750 mAh g-1@0.1 A g-1), good rate capability(7900 m Ah g-1@0.5 A g-1), and cycle stability up to 192 cycles. Interestingly, the FeCo-N-C-0.2 without macropores suffered relatively poorer stability with only 75 cycles, although its discharge capacity was still as high as 17,200 mA h g-1(@0.1 A g-1). The excellent performance attributed to the synergistic contribution of homogeneous Fe, Co nanoparticles and N co-doping carbon frameworks with special micro–meso-macroporous structure. The results showed that hierarchical FeCo-N-C architectures are promising cathode catalysts for Li-O2 batteries.

CMA-MESO模式对“21·7”河南特大暴雨的预报评估与误差分析

为分析CMA-MESO模式对2021年7月19—21日河南特大暴雨的预报性能,除了常规观测资料,还利用雷达和卫星非常规观测资料,对模拟回波和云产品开展传统和新型空间检验,以揭示对流风暴和中尺度对流系统(MCS,基于卫星红外通道)的模式预报偏差细节,并从降水形成的水汽、动力、触发和维持机制等角度分析模式误差产生的原因。结果表明:模式能较好预报雨带形态、弱回波持续时间以及主要降水发生前期和后期MCS的面积和强度演变趋势;模式偏差主要体现在低估了降水强度且未报出郑州站极端小时降水,错报主雨带小时降水演变,严重低估了对流风暴和强对流风暴的持续时间,未能报出午后MCS面积陡增的变化趋势且MCS位置预报偏西、偏北;模式降水偏差的原因主要在于水汽的模拟,模式水汽垂直分布不合理,对台风烟花和查帕卡的水汽输送均偏弱,而水汽输送不足的根源是低空急流偏弱和超低空急流脉动不足。另外,模式未能在郑州站附近预报出稳定少动的地面中尺度辐合线,加之大气层结不稳定度不足和对流不稳定能量偏低,使得对流发展不够旺盛,最终导致降水预报不足。

Effect of seepage-induced erosion on soil macropore structure

Internal erosion is one of the important factors causing geological disasters.The microstructure of soil can change with seepage erosion,resulting in changes in the hydraulic and mechanical properties of the soil.The evolution of seepage erosion is investigated with X-ray computed tomography(CT)in this study.The change in macropore structure characteristics during the seepage erosion test is quantified and the influence of seepage erosion on soil deformation is analyzed.Moreover,a pore network model(PNM)is established for the specimens and the evolution of the connected pore size characteristics is assessed.The results show that the macropore structure is significantly affected by seepage erosion,especially in terms of the porosity and pore geometry characteristics.The changes in macropore structure characteristics are most obvious in the lower part of the specimen.The influence of seepage erosion on the pore size distribution(PSD)and soil deformation is heterogeneous and closely dependent on the spatial location of the soil.Moreover,seepage erosion enhances macropore connectivity and has a directional impact on macropore orientation.These findings can provide a reference for the theoretical modeling and numerical simulation of the seepage erosion and improve the understanding of the seepage erosion evolution in engineering practice.

CMA-MESO模式对2020年夏季四川盆地及周边降水预报性能的评估

利用2020年夏季(6~8月)CMA-MESO模式逐日08:00(北京时,下同)起报的12~36 h逐时降水预报数据和地面—卫星—雷达三源融合逐时降水产品,着眼于小时尺度降水特征,细致评估了CMA-MESO对四川盆地及周边地区的降水预报性能。结果表明,CMA-MESO较好把握了夏季降水的空间分布特征,即小时平均降水量和降水频率的大值区位于四川盆地西部、北部和东部的高海拔山区,而降水强度大值区主要位于山脉迎风坡一侧,但CMA-MESO预报的降水量和频率大值区位置较观测偏南。CMA-MESO合理描述了研究区域内降水量和频率峰值时间位相自西向东逐步滞后的特征,能够把握区域平均的降水量和频率清晨主峰、傍晚次峰的双峰形态以及降水强度的单峰特征,但预报的降水日变化位相超前于观测。CMA-MESO预报的逐时降水量均大于观测,明显的降水量预报正偏差发生于夜间(21:00至次日03:00)和午后至傍晚(14:00~20:00),分别由一般性降水(0.1~10 mm h-1)预报偏差和强降水(≥10 mm h-1)预报偏差主导,其偏差大值区分别位于青藏高原东南缘至四川盆地西部和四川盆地以东、以南地区,模式对热力和动力场的预报偏差结合地形的影响是降水量预报偏差的成因。

Structural Features of Nuclei in Leaf Mesophyll Cells of Salt-Tolerant Artemisia marschalliana

All nuclei in mesophyll cells of Artemisia marschalliana are located in vacuoles and occupy up to 90% of their volume. The ultrastructural organization of chromatin in nuclei shows different degrees of its decondensation, up to complete separation of DNA from histones. It is possible that the separation of DNA from histones enables Artemisia to grow in soils with high salinity.