In this paper, a three-dimensional numerical simulation of the merged droplet formation (MDF) in the double T-junction microchannel was performed to investigate the effects of the flow rate of the continuous phase, continuous viscosity and the interfacial tension on the pressure by the level-set method. We divide the droplet formation process into three stages, namely filling, blocking and breakup. We define the time to generate a droplet as the droplet generation period. The characteristic length L/W (L is the length of the droplet, and W is the width of the main channel) decreases as the capillary number increases. The pressure (P-A) at a special position at the junction of the two phases occurs periodically during the droplet formation process, which directly and precisely reflects the mechanism of the MDF in the microchannel. Therefore, we define the time during the pressure fluctuates periodically as the pressure fluctuation period. New insights into the pressure during the MDF in the squeezing time are reported. The results show that the pressure fluctuation period and pressure drop period are the same as the droplet generation period. When the continuous flow rate and viscosity increase, the peak and valley values of P-A and the pressure drop increase, and the time of the pressure cycle decreases. However, when the interfacial tension increases, the peak and theperiod increase and the valley decreases. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
This paper investigates whether household beliefs on the determinants of success affect their stock market participation decisions. Using national survey data from China, I show that Chinese households believe that personal effort is the most influential factor in people’s success, followed by family social connections, aptitude, and luck. Moreover, households that believe more in effort are less likely to participate in the stock market, while those who place more emphasis on family social connections are more likely to participate. The negative (positive) effects of effort (family social connections) are more profound for agricultural (workplace-affiliated) households. Further, I offer belief mechanisms to explain the heterogeneity of stock market participation for different occupations.
Since the concentration of target molecules contained in most reagents in analytical chemistry experiments is lower than the minimum concentration required for subsequent detection, it is necessary for sample enrichment. Electrokinetic trapping that utilizes the principle of ion concentration polarization to achieve biomacromolecular enrichment is the most efficient. In this paper, based on the Poisson-Nernst-Plank equation, a novel design of nanochannel structure in a micro-nanofluidic preconcentrator for electrokinetic ion enrichment is carried out by numerical simulation. The results show that the enrichment process can be divided into three stages: enrichment generation, enrichment promotion and enrichment breakdown when the applied voltage is increased. Importantly, by comparing the six different structure nanochannels (straight line type, square wave type, rectangular type, circle type, zigzag type and multi-wave type), we found that the enrichment ratio produced by the rectangular nanochannel is the highest of the six nanochannels, which is 20.7 times. Rectangular nanochannel requires the lowest applied voltage to achieve the highest enrichment ratio. This work provides a novel design method and theoretical basis for the design of detection equipment in ultra-low concentration molecular detection tasks.
D-amino acid (DAA) an environmentally friendly biofilm inhibitor, has low efficiency for membrane biofouling control due to its instability. To address this challenge, a novel nanocomposite was prepared with DAA adhering to polydopamine (PDA)-coated halloysite nanotube (HNTs) through the interactions of H-bonding and π-π stacking between PDA and DAA. Membrane modified with such nanocomposite was fabricated via blending phase inversion, and the nanocomposite was uniformly distributed in the modified membrane matrix. In comparison with the pristine membrane, the addition of nanocomposites resulted in robust mechanical property for modified membrane with the ultimate stress and strain increased by 23.97% and 35.62%, respectively. Moreover, an excellent tradeoff between water flux (2.5 folds of pristine membrane) and selectivity was achieved, probably due to the improved membrane hydrophilicity. Meanwhile, bovine serum protein (BSA) static adsorption as well as dynamic filtration experiments exhibited excellent antifouling ability of the modified membrane. Most importantly, a superior anti-biofouling stability over a 10-day period was obtained for the membrane modified with nanocomposite, indicating that the activity of DAA to mitigate biofouling was effectively maintained. This study developed a novel and promising strategy for membrane biofouling mitigation.
Unbounded potentials are always utilized to strictly confine quantum dynamics and generate bound or stationary states due to the existence of quantum tunneling. However, the existed accurate Wigner solvers are often designed for either localized potentials or those of the polynomial type. This paper attempts to solve the time-dependent Wigner equation in the presence of a general class of unbounded potentials by exploiting two equivalent forms of the pseudo-differential operator: integral form and series form (i.e., the Moyal expansion). The unbounded parts at infinities are approximated or modeled by polynomials and then a remaining localized potential dominates the central area. The fact that the Moyal expansion reduces to a finite series for polynomial potentials is fully utilized. In order to accurately resolve both the pseudo-differential operator and the linear differential operator, a spectral collocation scheme for the phase space and an explicit fourth-order Runge-Kutta time discretization are adopted. We are able to prove that the resulting full discrete spectral scheme conserves both mass and energy. Several typical quantum systems are simulated with a high accuracy and reliable estimation of macroscopically measurable quantities is thus obtained.
The coastal area of the East China Sea has experienced rapid urbanization and industrialization in China since 1980s, resulting in severe pollution of its environments. Antibiotic resistance genes (ARGs) are regarded as a kind of emerging pollutant with potential high risk. The sediment samples were collected from Hangzhou Bay (HB), Xiangshan Bay (XB), and Taizhou Bay (TB) to investigate the spatial occurrence and distribution of 27 ARGs and class I integron–integrase gene (intI1) in the coastal area of the East China Sea. The PCR results showed the frequent presence of 11 ARGs and intI1 in the sediments of the three bays. The qPCR results further showed that sulfonamide resistance was the most prevalent ARG type and antibiotic target replacement and protection were the most important resistance mechanisms in the sediments. Regarding the subtype of ARGs, sulI, tetW, and dfrA13 were the most abundant ARGs, in which sulI was higher in TB (based on both the absolute and relative abundances) and dfrA13 was higher in HB (based on the relative abundances). The network analysis revealed that intI1 had significant correlations with tetC, sulI, sulII, and blaPSE-1. Oil was the key connected factor, which had positive connections with sulI, sulII, and blaPSE-1. In addition, the joint effect of heavy metals and nutrients & organic pollutants might be crucial for the fate of ARGs in the coastal sediments.
Sr-bearing marine barite [(Bax, Sr1−x)SO4] cycling has been widely used to reconstruct geochemical evolutions of paleoenvironments. However, an understanding of barite precipitation in the ocean, which is globally undersaturated with respect to barite, is missing. Moreover, the reason for the occurrence of higher Sr content in marine barites than expected for classical crystal growth processes remains unknown. Field data analyses suggested that organic molecules may regulate the formation and composition of marine barites; however, the specific organic–mineral interactions are unclear. Using in situ grazing incidence small-angle X-ray scattering (GISAXS), size and total volume evolutions of barite precipitates on organic films were characterized. The results show that barite forms on organic films from undersaturated solutions. Moreover, from a single supersaturated solution with respect to barite, Sr-rich barite nanoparticles formed on organics, while micrometer-size Sr-poor barites formed in bulk solutions. Ion adsorption experiments showed that organic films can enrich cation concentrations in the adjacent solution, thus increasing the local supersaturation and promoting barite nucleation on organic films, even when the bulk solution was undersaturated. The Sr enrichment in barites formed on organic films was found to be controlled by solid-solution nucleation rates; instead, the Sr-poor barite formation in bulk solution was found to be controlled by solid-solution growth rates. This study provides a mechanistic explanation for Sr-rich marine barite formation and offers insights for understanding and controlling the compositions of solid solutions by separately tuning their nucleation and growth rates via the unique chemistry of solution–organic interfaces.