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Roguing and replanting are the most common strategies to control plant diseases and pests. How to build the mathematical models of plant virus transmission and consider the impact of roguing and replanting strategies on plant virus eradication is of great practical significance. In the present paper, we propose the mathematical models for plant virus transmission with continuous and impulsive roguing control. For the model with continuous control strategies, the threshold values for the existences and stabilities of multiple equilibria have been given, and the effect of roguing strategies on the threshold values is also addressed. Furthermore, the model with impulsive roguing control tactics is proposed, and the existence and stability of the plant-only and disease-free periodic solutions of the model are investigated by calculating several threshold values. Moreover, when selecting the design control strategy to minimize the threshold, we systematically analyze the existence of the optimal times of roguing infected plants within a replanting cycle, which is of great significance to the design and optimization of the prevention and control strategy of plant virus transmission. Finally, numerical investigations are given to reveal the main conclusions, and the biological implications of the main results are briefly discussed in the last section. [ABSTRACT FROM AUTHOR]

P(Sts-HEMA) magnetic microspheres were synthesized by dispersion polymerization and then reacted with ethylene diamine to yield amino-functionalized [P(St-HEMA)-EDA] magnetic microspheres. The prepared [P(S-sHEMA)sEDA] magnetic microspheres were characterized by scanning electron microscope (SEM), Fourier transform infrared spectrometer (FTIIR) and vibrating stamp! Magnetometer (VSM). Magnetic microspheres were used to adsorb Pb2+ from simulated wastewater. The effects of Pb2+ adsorptions were investigated in different pH, adsorbent dosage and adsorption time by batch experiments. The results showed that the synthesized [P(StsHEMA)EDA] magnetic microspheres had a strong potential for Pb2+ removal. The adsorption reached equilibrium within 90 min. The process followed pseudo-second-order kinetic and the adsorption of Pb2+ in aqueous solution belonged to a chemisorption process. Under 298 K, the saturated adsorption was aprons mainly 87.566 mg/g. The process about magnetic microspheres adsorbing Pb2+ conformed to Langmuir model. [ABSTRACT FROM AUTHOR]

The fly ash zeolite (FAZ) was prepared by hydrothermal method using fly ash (FA) as raw material. The fly ash zeolite loaded silica (FAZS) modified by Na2SiO3 was used as an adsorbent for Cu2+ wastewater treatment. FAZS was characterized by means of X-ray diffraction(XRD), scanning electron microscopy (SEM) and pore size distribution measurement by nitrogen adsorption(BET). The effects of Cu2+ adsorptions were investigated in different pH, FAZS dosage, adsorption time on the adsorption process when copper ions were used as adsorptive ions. The results showed that the synthesized FAZS had a strong potential for Cu2+ removal. Under 298 K, the adsorption on the FAZS reached equilibrium within 80 min, and the process followed pseudo-second-order kinetic. The adsorption of heavy metal ions in aqueous solution belonged to a chemisorption process. The highest adsorption capacity was approximately 127.4 mg/g at 298 K. The adsorption process conformed to Langmuir model. The thermodynamic data showed that the adsorption process was endothermic and spontaneous. [ABSTRACT FROM AUTHOR]

This study built the test system of membrane surface flow field. The system was built under the condition of photo-metric optical fiber instead of hollow fiber membrane filaments. The paper analyzed the affection regularity of aeration intensity to fluid mechanics characteristics of hollow fiber membrane surface under the condition of clear water and three different aeration pore sizes of 1, 1.5, 2.5 mm based on the particle image velocimetry (PIV) technology. Further experiments were carried out on the variation of turbulence intensity values of hollow fiber membrane surface and liquid velocity values under the condition of different aeration intensities for three different aeration pore sizes. The movement of continuous phase (liquid) in PIV technology was marked by fluorescent particles to identify the velocity field of liquid. Under the conditions of this experiment, the trajectory of the bubble itself could reflect its velocity vector substantially, and the velocity field of each phase can be obtained after the phases were separated when we used the image processing techniques of each single phase. The results indicated that the increasing range of the average liquid velocity on the surface of the membrane appeared to be the highest when the aeration intensity was 140 L/h; and when over 140 L/h, it decreased to be much lower, so under the condition of this experiment, the optimum aeration intensity is 140 L/h, and more optimal turbulence intensity values are corresponding to this aeration intensity. In the project, according to optimized parameters, we can not only save the cost of system operating, but also eliminate the cake layer on the membrane surface and reduce the concentration polarization on both sides of the membrane surface. Under the condition of three different aeration pore sizes, the average speed of the liquid near the membrane surface is basically consistent with the aeration intensity; when the aeration is at 1 mm aperture, the velocity vectors of liquid near the surface of the membrane increase with the increase of aeration intensity, when the aeration intensity is over 140 L/h, the liquid velocity vectors near the membrane surface are basically the same; at lower aeration intensity, the liquid velocity of the membrane surface near the aeration pore is significantly higher than the ones which locate other places, and the liquid appears the phenomenon of rocking after affected by the bubble rising trajectory; at higher aeration intensity, liquid velocity value increases significantly in the horizontal direction; with the increase of the liquid velocity, the ranges of membrane filaments influenced correspondingly increase; and when the aeration intensity reaches 140 L/h, 6 membrane filaments are influenced at different degrees, and the shaking of the bubbles causes the rocking of the membrane filaments, which can play an active role in controlling the pollution of the membrane. This research provides a theoretic foundation for the optimization of flow field in membrane bioreactor so as to improve the membrane fouling problem. [ABSTRACT FROM AUTHOR]