间歇性降雨对土壤团聚体粒级及磷、铜、锌富集的影响

探讨间歇降雨条件下土壤干湿交替对团聚体粒级动态变化的影响,对加深径流泥沙运移和分选机制的理解、揭示土壤微量元素随地表径流迁移的规律具有重要意义。通过37 d内的5场间歇性人工降雨实验,观测了降雨激发的团聚体破碎过程和降雨间歇段干缩过程导致的团聚体粒径分布的动态变化,并通过分析不同团聚体粒级总磷、铜、锌含量的动态变化,评估了间歇降雨对土壤污染物富集特征的影响。结果表明,间歇性降雨导致的土壤干湿交替引发了剧烈的团聚体粒级周转,团聚体稳定性随实验推移呈总体退化状态,具体体现在>250μm微团聚体的比例随实验推移显著下降,而<250μm微粒的比例显著上升(P<0.05)。团聚体粒径分布的变化引起了不同粒径磷、铜、锌含量的同步变化,三种元素从>250μm向<63μm粒级逐渐转移,造成<63μm粒级内各元素浓度在实验末期达到最高,这意味着间歇性降雨引起的团聚体结构退化和<250μm微粒的增加及微量元素富集会加大水土流失及伴随污染物排放的风险。本研究揭示了间歇性降雨引起的土壤团聚体结构变化及对泥沙分选和元素迁移过程的影响,为土壤侵蚀引起的横向物质运移机制提供了一定的理论参考。

分子筛表面接枝TDI的研究

结合 FTIR,TG等分析手段对 TDI改性的不同孔径、不同表面性质的沸石分子筛进行研究 ,证实了

免耕制度下耕作土壤结构演化的数字图像分析

利用数字图像方法 ,研究了室内模拟和自然田间免耕下的土壤结构演化状况。图像定性表明随免耕时间的推移土壤中团聚体由小变大 ,土体逐渐趋于紧实。图像定量分析结果表明随着免耕时间的推移 ,小团聚体和小孔隙减少而大团聚体和大孔隙增加。田间土样的结果表明了自然的阶段性降雨对土壤结构可能具有一定的调节作用 ,但从图像与团聚体粒径分布和孔隙孔径分布的变化来看 。

北方土石山区土地利用方式对褐土团聚体稳定性的影响

土地利用方式是影响土壤团聚体稳定性的重要因素,但关于北方土石山区土地利用方式对土壤团聚体稳定性的影响仍不清晰。选取北方土石山区耕地、荒地、休闲地和金银花地的褐土为研究对象,基于Le Bissonnais法,分析了快速湿润(FW)、机械振荡(WS)和慢速湿润(SW)处理下团聚体粒径分布特征、稳定性和可蚀性。结果表明:(1)FW处理后,耕地、荒地和休闲地团聚体集中分布于<0.5 mm,而金银花地则为>0.2 mm;WS和SW处理后,均以>0.2 mm团聚体为主。3种处理下,土地利用方式间2~5 mm团聚体差异最大。(2)土壤团聚体平均重量直径(MWD)表现为:SW>WS>FW,而土壤可蚀性K值则为FW>WS>SW,且相对消散指数显著大于相对机械破碎指数。说明褐土团聚体主要破碎机制是消散作用,其次为机械破坏作用。(3)3种处理下,土壤团聚体MWD均表现为金银花地>休闲地>荒地>耕地。(4)相对消散指数和K值表现为:耕地>荒地>休闲地>金银花地。说明金银花地利用方式可有效提高土壤稳定性,增强土壤抗侵蚀能力。

Use of Solid SMEDDS in Delivery of Carvedilol

Aim A new solid SMEDDS (self-microemulsifying drug delivery system) capsule has been developed to increase the solubility and dissolution rate. Methods The solubilities of carvedilol in various bases were investigated. Ternary phase diagrams were used to evaluate the self-emulsification and self-microemulsfication domains. The particle size distribution and ζ-potential were determined. The mean diameter of the three formulae decreased with an increase of Lutrol F68. Results The in vitro dissolution rate of ...

Effect of reagent films on coupling relationship between glass surface and particles

The experiments were conducted to investigate the behavior of airborne particles adhering to the glass slides which were coated by several reagent films. The results showed that the adhesion level could be significantly changed by the reagent films. There were no evident rules between the average size of particles and sampling time interval, the placing angle and reagent concentration. The average particle size on the surface coated by composite reagent （2-3 μm） was smaller than that on the single reagent coated surface, while the largest particle size （4-5 μm） was observed on the surface coated with the Tween 60. The experiment also demonstrated that the best adhesive performance was obtained on the surface which was coated with 0.5% SDBS and 0.5% fluorocarbon composite reagents. The experiment results indicated that each reagent had a certain optimum adhesive range to the particle. The composite reagents with different proportion of single reagents exhibited some particular physical and chemical properties, which could effectively change the adhesive performance between the solid surface and the particles.

多粒径高炉渣在移动床内余热回收的数值模拟

本文采用CFD-DEM耦合法(Computational Fluid Dynamics and Discrete Element Method)对三维移动床中多粒径高炉渣颗粒的余热回收过程进行了数值模拟与分析。研究了三种不同粒径分布系统:均一粒径系统,二元混合粒径系统和正态分布粒径系统的气-固换热特性。通过应用程序编程接口Api控制高炉渣颗粒的质量流率,使得移动床内颗粒流动达到动态平衡。进一步分析了颗粒相和流体相的温度场、对流和辐射换热率、颗粒和气体的出口温度以及移动床的余热回收率,获得了不同粒径分布颗粒系统的气固换热规律。研究发现:在相同工况下,二元混合粒径系统的颗粒出口温度最低,气体出口温度最高,换热效果最好,余热回收率相较于其余两种粒径系统也最高。

Influence of abrasive hardness on erosion wear of abrasive air jets

To make clear the influence of abrasive hardness on the erosion effect,the erosion experiments of abrasive air jet with the same impact energy were carried out.The influence of abrasive hardness on the erosion effect is clarified by comparing the different erosion depths.The main conclusions are as follows.Under the same mass flow rate and mesh number,the abrasive with a higher density needs greater pressure irrespective of hardness.After erosion damage,the abrasive size exhibits a Weibull distribution.The shape parameterβand Weibull distribution function of four types of abrasives are derived by the least squares method;moreover,βis found to have a quadratic relation with abrasive hardness.The results of the erosion experiments show that abrasive hardness and erosion depth are quadratically related.By calculating the increase in surface energy after abrasive erosion crushing,it is found that abrasive hardness has a quadratic relation with surface energy and that the increases in erosion depth and surface energy consumption are basically identical.In conclusion,the effect is a soft abrasive impact when the ratio of abrasive hardness(Ha)to the material hardness(Hm)is<2.6,and it is a hard abrasive impact when Ha/Hm>3.

A Theoretical Model for the Size Prediction of Single Bubbles Formed under Liquid Cross-flow

The size of initial bubbles is an important factor to the developed bubble size distribution in a gas-liquid contactor. A liquid cross-flow over a sparger can produce smaller bubbles, and hereby enhance the performance of contactor. A one stage model by balancing the forces acting on a growing bubble was developed to describe the formation of the bubble from an orifice exposed to liquid cross-flow. The prediction with this model agrees with the experimental data available in the literatures, and show that orifice size strongly affects the bubble size. It is showed that the shear-lift force, inertia force, surface tension force and buoyancy force are major forces, and a simplified mathematical model was developed, and the detachment bubble diameter can be predicted with accuracy of <±21%.

MEASUREMENTS OF PARTICLE NUMBER SIZE DISTRIBUTIONS AND NEW PARTICLE FORMATION EVENTS DURING WINTER IN THE PEARL RIVER DELTA REGION,CHINA

Particle number size distribution(PNSD) between 10 nm and 20 μm were measured in the Pearl River Delta(PRD) region in winter 2011.The average particle number concentration of the nucleation mode(10-20 nm),Aitken mode(20-100 nm),accumulation mode(100 nm-1μm) and coarse mode(1-20 μm) particles were 1 552,7 470,4 012,and 19 cm-3,respectively.The volume concentration of accumulation mode particles with peak at 300 nm accounted for over 70% of the total volume concentration.Diurnal variations and dependencies on meteorological parameters of PNSD were investigated.The diurnal variation of nucleation mode particles was mainly influenced by new particle formation events,while the diurnal variation of Aitken mode particles correlated to the traffic emission and the growth process of nucleation mode particles.When the PRD region was controlled by a cold high pressure,conditions of low relative humidity,high wind speed and strong radiation are favorable for the occurrence of new particle formation(NPF) events.The frequency of occurrence of NPF events was 21.3% during the whole measurement period.Parameters describing NPF events,including growth rate(GR) and source rate of condensable vapor(Q),were slightly larger than those in previous literature.This suggests that intense photochemical and biological activities may be the source of condensable vapor for particle growth,even during winter in the PRD.

Radial Non-uniformity Index Research on High-density,High-flux CFB Riser with Stratified Injection

A high-density, high-flux circulating fluidized bed （CFB） riser （100 mm in ID and 10.614 m in height） was ap- plied in a wide range of operating conditions （with solid fluxes up to 400 kg/m2s and superficial gas velocities up to 12 m/s） to examine its radial non-uniformity dynamics. The solids holdup was determined through the use of a fiber-optic probe at 11 axial levels. The results indicated that under all operating conditions, the high superficial gas velocity and low solid flux- es maintained a low radial non-uniformity index （RNI）. The high-density/flux CFB riser had several unique characteristics, so that the peak of the radial solids holdup profile occurred at a position with r/R=0.8. The RNI and solids holdup at the cross-sectional position had a good logarithmic relationship at the low-density condition （with a mean solids holdup of 〈0.2）, and the RNI decreased when the mean solids holdup exceeded 0.2. Investigation of the dynamics of stratified injec- tion revealed that the feed ratio had an important effect on G, and on solids holdup distribution. A novel ＂〈＂ shaped axial solids holdup profile was found. Gs decreased sharply when the up-flow feed ratio exceeded 0.5, and RNI was lowest when the up-flow feed ratio was 1.

Size Distributions and Source Function of Sea Spray Aerosol over the South China Sea

The number concentrations in the radius range of 0.06 – 5 μm of aerosol particles and meteorological parameters were measured on board during a cruise in the South China Sea from August 25 to October 12, 2012. Effective fluxes in the reference height of 10 m were estimated by steady state dry deposition method based on the observed data, and the influences of different air masses on flux were discussed in this paper. The number size distribution was characterized by a bimodal mode, with the average total number concentration of（1.50 ± 0.76）×10~3 cm^（-3）. The two mode radii were 0.099 μm and 0.886 μm, both of which were within the scope of accumulation mode. A typical daily average size distribution was compared with that measured in the Bay of Bengal. In the whole radius range, the number concentrations were in agreement with each other; the modes were more distinct in this study than that abtained in the Bay of Bengal. The size distribution of the fluxes was fitted with the sum of log-normal and power-law distribution. The impact of different air masses was mainly on flux magnitude, rather than the shape of spectral distribution. A semiempirical source function that is applicable in the radius range of 0.06 μm

Solution Properties of Soy Protein in DMSO/Urea Solvent System

Solution properties of 7S globulins (7S), 11S globulins (11S) and soy protein isolates (SPI) in dimethylsulfoxide (DMSO)/urea solvent system were studied by intrinsic viscosity and particle size distributions. The results showed that the existence of urea was the main reason for the denaturation and solubility of soy protein in the system, and the effects were more obvious with increasing of urea concentration in solutions. Suitably dissolution temperature and time contributed to the solubility of soy proteins.

Spatial Density Distributions and Correlations in a Quasi-one-Dimensional Polydisperse Granular Gas

By Monte Carlo simulations, the effect of the dispersion of particle size distribution on the spatial density distributions and correlations of a quasi one-dimensional polydisperse granular gas with fractal size distribution is investigated in the same inelasticity. The dispersive degree of the particle size distribution can be measured by a fractal dimension dr, and the smooth particles are constrained to move along a circle of length L, colliding inelastically with each other and thermalized by a viscosity heat bath. When the typical relaxation time τ of the driving Brownian process is longer than the mean collision time To, the system can reach a nonequilibrium steady state. The average energy of the system decays exponentially with time towards a stable asymptotic value, and the energy relaxation time τB to the steady state becomes shorter with increasing values of df. In the steady state, the spatial density distribution becomes more clusterized as df increases, which can be quantitatively characterized by statistical entropy of the system. Furthermore, the spatial correlation functions of density and velocities are found to be a power-law form for small separation distance of particles, and both of the correlations become stronger with the increase of df. Also, tile density clusterization is explained from the correlations.

Polarimetric Study of the Fine Aerosol Fraction in Beijing

Measurements of aerosol optical characteris- tics were carried out with a Photoelectric Aerosol Nephelometer （PhAN） in Beijing and at Xinglong Obser- vatory, which is located 150 km northeast of Beijing. Aerosol size distributions were retrieved by means of the inverse problem solution. Mean volume size distributions of the fine aerosol fraction were unimodal with the maximum radius in the range 0.11-0.15 pm. Accumula- tion of aerosol matter in the air basin of Beijing takes place mainly due to the growth of particle size, but not their number. A simple optical method to detect aerosol nonsphericity is proposed.

Investigations of Spray Painting Processes Using an Airless Spray Gun

This paper presents experimental and numerical studies on spray painting processes by using airless spray guns for ship painting. A computational fluid dynamics code was applied to calculate the flow field and the droplet trajectories. Droplet size distributions and droplet velocities as necessary inlet characteristics for the simulations were experimentally obtained using a Spraytec Fraunhofer type particle sizer and laser-Doppler anemometry. Effects of shoreline winds and painting distance on the transfer efficiency and on the paint film thickness distributions on the target were numerically studied.

Coarse aerosol particle size and shape characteristics near ground level of Shijiazhuang city, China

This research sampled subaerial ambient coarse aerosol particles （〉2μm of equivalent area diameter） in the typical air polluted city of Shijiazhuang to measure the particle size distribution and shape characteristics by the analyzer of CIS-50 and the scan electronic microscope of S-570 in the non-heating period and heating period respectively. The results show that the coarse aerosol particle size distribution mode is 2-4μm in the non-heating period and 3-5μm in the heating period, with the size range of 0.8-120μm, mostly under 10μm; and the square or square like particle shape is dominant, the sphere like lesser, the acute-angle and lathy shape sparse. There exist particle size distribution and shape characteristics differences in the non-heating period and heating period influenced greatly by the ground coal combustion emission and windblown dust. In the heating period, particle size average increases by 53.2%, principally in the size range of 5-10μm, and 20-50μm secondly. Meanwhile, the particle number of quasi-round and round shape group and those with convex-concave fractal edge increase obviously. These quasi-round particles are agglomerate derived from combustion in the SEM images. The relationship between particle size and shape is demonstrated by that the percentage of PM5 and the particle number of the quasi-square and square shape group are positively correlative with r of 0.9458; quasi-round and round shape group negatively correlative with r of-0.9726 respectively.

Modeling flame propagation speed and quenching distance of aluminum dust flame with spatially random distribution of particles

In this research combustion of aluminum dust particles in a quiescent medium with spatially discrete sources distributed in a random way was studied by a numerical approach.A new thermal model was generated to estimate flame propagation speed in a lean/rich reaction medium.Flame speed for different particle diameters and the effects of various oxidizers such as carbon dioxide and oxygen on flame speed were studied.Nitrogen was considered the inert gas.In addition,the quenching distance and the minimum ignition energy(MIE) were studied as a function of dust concentration.Different burning time models for aluminum were employed and their results were compared with each other.The model was based on conduction heat transfer mechanism using the heat point source method.The combustion of single-particle was first studied and the solution was presented.Then the dust combustion was investigated using the superposition principle to include the effects of surrounding particles.It is found that larger particles have higher values of quenching distance in comparison with smaller particles in an assumed dust concentration.With the increase of dust concentration the value of MIE would be decreased for an assumed particle diameter.Considering random discrete heat sources method,the obtained results of random distribution of fuel particles in space provide closer and realistic predictions of the combustion physics of aluminum dust flame as compared with the experimental findings.

Preparation of Ultrafine SiO2 Powder from Rice Husk and Properties of Its Infrared Spectrum

This paper discussed impact of temperature on the size distribution in preparing ultrafine silica from rice husk.The samples prepared were analyzed with infrared spectrum,and the relation between the particle size and intensity of characteristic absorption peak of IR at center around 1 100 cm-1 was disscussed with the baseline method.Results show that when the temperature is 650 ℃ and roasting time is 11 h,at optimal reaction conditions,the size distribution of the ultrafine silica powder prepared is relatively concentrated,and the average particle size is 199.5 nm.Moreover,the characteristic absorption band of IR is broadening gradually along with particle size decreasing.

Method for grinding and delaminating muscovite

A method of dry grinding muscovite based on the use of knife-mills is reported.It was possible to produce mica with a particle size below 100 and 45μm.After grinding,the samples were submitted to sonication treatment,which promoted delamination of the material.The particle size distribution shows that sonicated mica has more particles in the size range 10-50μm than does non-sonicated mica have. This also indicates a decrease in the average particle size.Characterization of the treated muscovite by scanning electron microscopy revealed a highly delaminated material with a plate-like structure.The products were characterized by chemical analysis and X-ray diffraction,too.This mica has already been used for the synthesis of pearlescent pigments.