Abstract
This study utilized 3D Large-eddy simulation to investigate the crosswind drag force on a square cylinder subjected to transverse wind fluctuation. Two distinct methods were employed to ...generate the fluctuation: a prescribed sine function at the inlet boundary and an upwind barrier. The frequency was normalized in the same Strouhal number form. The transverse wind fluctuation with a normalized frequency above 0.05 tends to excite the square cylinder transversely with the same frequency band. The frequency effect also exists on the square cylinder located downwind an obstacle half the square cylinder’s size. However, an obstacle 2.5 times the size of the square cylinder generates a cross-wind fluctuation with the normalized frequency of 0.04, which cannot excite the square cylinder transversely. The frequency effect from the upwind barrier significantly dampens with the distance and disappears at 8–10 times the square cylinder size.
An online analyzer for Monitoring for AeRosols and Gases (MARGA) was employed to measure major water-soluble (WS) inorganic ions in PM10 at 1-h time resolution in Shanghai from May 27 to June 16, ...2009. During the field campaign, hazy days were encountered over which atmospheric visibility was commonly less than 10 km, and hourly average PM10 reached peaks of exceeding 150 μg m
−3. Based on WS ions and pollution gases, the haze events were classified as biomass burning induced, complicated and secondary aerosol pollutions depending on their distinct formation schemes. During the biomass burning induced pollution, which was aroused from biomass burning plume, the concentration of K
+ was increasing up to maximum about 19 times higher than the average of clear days, and K
+ behaved a strong positive linear correlation with Cl
−. Because of sulfate and nitrate significantly enhanced by secondary production, in which precursor gases of SO
2 and NO
2 were converted into SO
4
2− and NO
3
− on the surface of pre-existing KCl particles, the complicated pollution was responsible for a combining contribution of aerosols directly transported from biomass burning sources and known secondary aerosols linked to local emission. Under high atmospheric oxidation ability and steady atmosphere condition, the secondary pollution resulted from a significant increase of sulfate and nitrate aerosols which were oxidized from large amounts of anthropogenic gases of SO
2 and NO
2 in the urban atmosphere.
► The data at 1-h resolution is help to characterizing haze pollution more details. ► The haze events were classified as biomass burning, complicated and secondary pollutions. ► Biomass burning plumes could cause complicated pollution over downwind regions.
The gate-type carbon nanotubes cathodes exhibit advantages in long-term stable emission owing to the uniformity of electrical field on the carbon nanotubes, but the gate inevitably reduces the ...transmittance of electron beam, posing challenges for system stabilities. In this work, we introduce electron beam focusing technique using the self-charging SiN
/Au/Si gate. The potential of SiN
is measured to be approximately -60 V quickly after the cathode turning on, the negative potential can be maintained as the emission goes on. The charged surface generates rebounding electrostatic forces on the following electrons, significantly focusing the electron beam on the center of gate hole and allowing them to pass through gate with minimal interceptions. An average transmittance of 96.17% is observed during 550 hours prototype test, the transmittance above 95% is recorded for the cathode current from 2.14 μA to 3.25 mA with the current density up to 17.54 mA cm
.
Tb
3+
and/or Eu
3+
doped Mg
3
Y
2
Ge
3
O
12
phosphors were synthesized successfully through solid-state reaction. The X-ray diffraction (XRD) patterns, photoluminescence (PL), fluorescence decay ...curve and energy transfer behavior of the samples were studied in detail. XRD patterns show all samples are attributed to inverse garnet structure. Under UV excitation, the singly doped phosphors with Tb
3+
and Eu
3+
ions showed green and red characteristic emission. The emission color of Mg
3
Y
2
Ge
3
O
12
:Tb
3+
, Eu
3+
can be adjusted by the corresponding Tb
3+
–Eu
3+
energy transfer, which also demonstrated excellent thermal stability at 448 K (78.09%). These results indicate that the Mg
3
Y
2
Ge
3
O
12
:Tb
3+
, Eu
3+
phosphors will have potential use in n-UV pumped LED devices.
The effects of benzene (C6H6) on the radial distribution function, coordination number, spatial distribution function, physical and chemical properties such as density, viscosity, conductivity and ...transport properties of triethylamine hydrochloride /chloroaluminate (Et3NH Cl/AlCl3) ionic liquid were studied by first principle and molecular dynamics simulation. The stable geometry and electronic properties of benzene and ionic liquids, as well as their optimized adsorption on Cu (111) surface were obtained. The density, viscosity and conductivity obtained agreed well with the experimental values. It is found that the adsorption of cations, anions and benzene on Cu (111) surface is physical adsorption, and the adsorption capacity is Et3NH > C6H6 > Al2Cl7−. With the increase of benzene concentration, the density of the system decreases gradually, the interaction between cations and anions gradually weakens, resulting in the decrease of viscosity, the enhancement of diffusion and the increase of conductivity. Since the diffusion and adsorption capacity of benzene are greater than that of electroactive ion of Al2Cl7−, benzene would be easier to adsorb on the protruding part of the electrode surface, so as to reduce the effective surface area of the cathode, slow down the reduction speed of Al2Cl7− on the cathode surface and increase the over-potential, so the grain refined deposition layers can be obtained in electrodeposition.
The reactivity and adsorption behavior of three pyridine amide additives (Nicotinamide, Pyridine-2-formamide and Pyridine-4-formamide) on the Pt (111) surface was studied by First principle methods. ...The quantum chemical calculations of molecular reactivity show that the frontier orbitals of the three additives are distributed around the pyridine ring, oxygen atom of carbonyl and nitrogen atom of amino, and the nucleophilic and electrophilic active centers are located on the nitrogen atoms of pyridine ring, oxygen atom of carbonyl and nitrogen atom of amino. All three molecules were adsorbed with the chemical adsorption on the Pt (111) surface, and the order of adsorption was Nicotinamide > Pyridine-2-formamide > Pyridine-4-formamide. The C and N atoms of three derivatives forms C-Pt and N-Pt bonds with the Pt atoms of the Pt (111) surface, which makes derivatives stably adsorb on the Pt surface and form a protective film. The protective film inhibits the diffusion of atoms to the surface of the growth center, so as to inhibit the formation of dendrite and obtain a smooth aluminum deposition layer.
•The low molecular weight PAHs predominated at the Humen river mouth.•Concentrations of PAHs during the ebb tide were higher than during the flood tide.•Different composition patterns of PAHs ...occurred during the flood and ebb tides.•The source and estuarine hydrodynamics influenced the distribution of PAHs.•The PAHs were derived from primarily petroleum and coal combustion sources.
Five different water samples were collected from the surface to the bottom layers at the Humen river mouth in the Pearl River delta during the flood and ebb tides in August 2011, respectively. Changes in the distribution and characteristics of polycyclic aromatic hydrocarbons (PAHs) were examined to explore their transportation process. More than 62 types of PAHs were detected in the water columns. The mean concentration of the total PAHs ranged from 849.33 to 1370.53ng/l and from 629.21 to 2019.91ng/l during the flood and ebb tides, respectively. Furthermore, 2-ring PAHs were the most abundant species, followed by 3-ring PAHs. There were different composition patterns of the PAHs during the flood and ebb tides. And the transportation process of PAHs was influenced by their sources and different estuarine hydrodynamics. Analysis of the sources of the PAHs indicated that the PAHs were derived from primarily petroleum and coal combustion sources.
Hourly measurements of water‐soluble inorganic ionic species in ambient atmospheric particles were conducted at Shanghai, Hangzhou, and Guangzhou sampling sites in China during the period of ...2009–2011. The relation between sulfate and nitrate in particulate matter (PM10 and PM2.5) was examined based on these measurements. Results showed that the mass fraction of sulfate was strongly negatively correlated with that of nitrate in atmospheric particles on most of the sampling days, especially when sulfate and nitrate made up the vast majority of the total soluble anions and cations (Na+, K+, Ca2+, and Mg2+) made a small contribution to the total water‐soluble ions, revealing that the formation mechanisms of sulfate and nitrate in the atmosphere are highly correlated, and there exists a significant negative correlation trend between sulfate and nitrate mass fractions in the atmospheric particles. We found that local meteorological conditions presented opposite influences on the mass fractions of sulfate and nitrate. Further analysis indicated that the two mass fractions were modulated by the neutralizing level of atmospheric aerosols, and the negative correlation could be found in acidic atmospheric particles. Strong negative correlation was usually observed on clear days, hazy days, foggy days, and respirable particulate air pollution days, whereas poor negative correlation was often observed during cloud, rain, snow, dust storm, and suspended dust events. The results can help to better understand the formation mechanisms of atmospheric sulfate and nitrate during air pollution episodes and to better explain field results of atmospheric chemistry concerning sulfate and nitrate.
Key Points
Field experiment provides direct evidence for correlation of sulfate and nitrate
Linear dependence between sulfate and nitrate in atmospheric particles
New insights into potential link between atmospheric sulfate to nitrate
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•Interfacial properties between ionic liquids with different alkyl chain lengths and Pt(1 1 1) surface are revealed.•The electrostatic interaction between ILs and Pt(111) increases ...via the electro-donating effect of alkyl chain.•The increase of dipole interaction and adsorption between ILs and Pt(111) can refine the grain of aluminum deposits.
The structure, active sites, and adsorption mechanism of imidazole-based ionic liquids (CnMIMAl2Cl7) (n = 1, 2, 4, or 6) on the Pt(111) surface and their effects on aluminum electrodeposition were evaluated by first-principles approaches. The active sites of imidazolium ILs were on the cationic imidazole ring. The adsorption order was HMIMAl2Cl7 >BMIMAl2Cl7 >EMIMAl2Cl7 > C1MIMAl2Cl7. The electrostatic interaction, electrostatic induction, and the interfacial dipole effect made the ionic liquids with longer alkyl chain increase the coverage of cations on the Pt(111) surface as well as the number of charge transfers from ionic liquids to the Pt(111) surface, and decrease the distance between chlorine atoms and the Pt(111) surface. This is beneficial to suppress the dendrite formation during the electrochemical process and deposit aluminum in smaller sizes. These results will provide a basis for the selection of efficient ionic liquids of aluminum electrodeposition.
The electrolyte/electrode interface is vital for aluminum electrodeposition, and is directly linked by the slight change of an imidazolium cation. The effect of functional groups substitution on the ...reactivity and adsorption behavior of methyl-imidazole heptachloride aluminum ILs such as 1-hydrogen-3-methylimidazole heptachloride aluminum (H1MIMAl2Cl7), 1-allyl-3-methylimidazole heptachloride aluminum (AMIMAl2Cl7), 1-Propyl-3-methylimidazole heptachloride aluminum (C3MIMAl2Cl7) and 1-methoxyethyl-3-methylimidazole heptachloride aluminum (MoeMIMAl2Cl7) on the Pt(111) surface were revealed by first-principles methods. The active centers of H1MIMAl2Cl7 and C3MIMAl2Cl7are distributed on the imidazole ring and the Cl atoms of the anion, while the active centers of AMIMAl2Cl7 andMoeMIMAl2Cl7 are distributed on the imidazole ring, the C or O atoms in the alkyl chain, and the Cl atoms of the anion. Moreover, the imidazole ring of AMIMAl2Cl7 has the minimum surface maximum value of electrostatic potential. It suggested that the imidazolium rings of these four ionic liquids (ILs) tend to adsorb on the Pt(111) surface in a flat-lying orientation, and that AMIMAl2Cl7more easily adsorbs on the surface. The distances between the Cl atoms of Al2Cl7- and the Pt(111) surface decrease, indicating that the Al2Cl7- of AMIMAl2Cl7 can easily penetrate the electric double layer and move to the cathode surface to be discharged, which speeds up the nucleation rate. Additionally, C3MIM+,AMIM+, and MoeMIM+have stronger interaction with the surfaces and larger volumes than H1MIM+, causing them to flatten the electrode surface and refine the grains during aluminum deposition. The results of adsorption calculations are found to be consistent with both the previous predictions and the experimental deposition effect of AMIMAl2Cl7and H1MIMAl2Cl7 on the Pt electrode.
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•The structure and adsorption properties of four imidazolium chloroaluminate on the Pt(111) surface are revealed.•The introduction of alkenyl, propyl and ether to imidazole ring enhances the interaction and adsorption between ILs with Pt (111).•The increase of cation volume and adsorption of ILs with Pt(111) can refine the grain of aluminum deposits.
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