Adsorption isotherms and kinetics of methylene blue on a low-cost adsorbent recovered from a spent catalyst of vinyl acetate synthesis

A regenerated activated carbon used as catalyst support in the synthesis of vinyl acetate has been tested as a low-cost adsorbent for the removal of dyes. After a thorough textural characterization of the regenerated activated carbon, its adsorption isotherms and kinetics were determined using methylene blue as model compound at different initial concentrations. Both Langmuir and Freundlich isotherm models were developed and then compared. It was found that the equilibrium data were best represented by the Langmuir isotherm model. The kinetic data were fitted to pseudo-first-order, pseudo-second-order and intraparticle diffusion models, and it was found that the best fitting corresponded to the pseudo-second-order kinetic model. The results showed that this novel adsorbent had a high adsorption capacity, making it suitable for use in the treatment of methylene blue enriched wastewater.     

Enhanced dielectric properties of lead barium zirconate thin films by manganese doping

(Pb_0.5Ba_0.5)ZrO₃ (PBZ) and 1 mol% Mn-doped (Pb_0.5Ba_0.5)ZrO₃ (Mn-PBZ) sol were successfully fabricated, and corresponding thin films were deposited on Pt(1 1 1)/TiO₂/SiO₂/Si(1 0 0) substrates by spin-coating method. Effects of Mn doping on the microstructure and electrical properties of PBZ thin films were investigated systemically. X-ray diffraction patterns showed that both films had a polycrystalline perovskite structure, and that the degree of (1 1 1) orientation were increased by Mn doping. Dielectric measurements illustrated that Mn-doped PBZ thin films not only had a larger dielectric constant, but also possessed a smaller dielectric loss. Accordingly, the tunability and the figure of merit of PBZ films were improved by Mn doping.     

Exponential synchronization of complex networks with nonidentical time-delayed dynamical nodes

In this Letter, exponential synchronization of a complex network with nonidentical time-delayed dynamical nodes is considered. Two effective control schemes are proposed to drive the network to synchronize globally exponentially onto any smooth goal dynamics. By applying open-loop control to all nodes and adding some intermittent controllers to partial nodes, some simple criteria for exponential synchronization of such network are established. Meanwhile, a pinning scheme deciding which nodes need to be pinned and a simply approximate formula for estimating the least number of pinned nodes are also provided. By introducing impulsive effects to the open-loop controlled network, another synchronization scheme is developed for the network with nonidentical time-delayed dynamical nodes, and an estimate of the upper bound of impulsive intervals ensuring global exponential stability of the synchronization process is also given. Numerical simulations are presented finally to demonstrate the effectiveness of the theoretical results.     

A three-dimensional steady-state tumor system

The growth of tumors can be modeled as a free boundary problem involving partial differential equations. We consider one such model and compute steady-state solutions for this model. These solutions include radially symmetric solutions where the free boundary is a sphere and nonradially symmetric solutions. Linear and nonlinear stability for these solutions are determined numerically.     

All-silicon chiral metasurfaces and wavefront shaping assisted by interference

The usage of full-color imaging in digital pathology produces significant results. Compared with a grayscale image or a pseudocolor image containing contrast information, a full-color image can identify and detect the target object better with color texture information. Fourier ptychographic microscopy(FPM) is a high-throughput computational imaging technique that breaks the tradeoff between high resolution(HR) and a large field of view. It also eliminates the artifacts of scanning and stitching in digital pathology and improves its imaging efficiency. However, the conventional full-color digital pathology based on FPM is still time-consuming because of the repeated experiments with tri-wavelengths. A color transfer FPM approach termed "CFPM" was reported. The color texture information of a low-resolution full-color pathologic image is directly transferred to the HR grayscale FPM image captured by only a single wavelength. Both of the color space of FPM based on the standard CIE-XYZ color model and the display based on the standard RGB color space were established. Different FPM colorization schemes were analyzed and compared with 30 biological samples. Three types of evaluation approaches were provided, including the root-mean-square error(RMSE), the difference maps, and the image histogram cosine similarity. The average RMSE values of the conventional method and CFPM compared with the ground truth were 5.3% and 5.7%, respectively. Therefore, the reconstruction time is significantly reduced by 2/3 with the sacrifice of precision of only 0.4%. The CFPM method is also compatible with advanced fast FPM approaches to further reduce computation time.     

Asymptotic behavior for a nematic liquid crystal model with different kinematic transport properties

We study the asymptotic behavior of global classical solutions to hydrodynamical systems modeling the nematic liquid crystal flows under kinematic transports for molecules of different shapes. The coupling system consists of Navier–Stokes equations and kinematic transport equations for the molecular orientations. We prove the convergence of global solutions to single steady states as time tends to infinity as well as estimates on the convergence rate both in 2D for arbitrary regular initial data and in 3D for certain particular cases.     

Dissipative particle dynamics simulation for the effect of interaction on the self-assembly behaviours of heterogemini surfactant in aqueous solution

Self-assembly behaviours of heterogemini surfactant in aqueous solution have been explored by means of dissipative particle dynamics simulation. Five kinds of heterogemini molecules are involved and a variety of novel morphologies have been obtained. Results based on detailed analyses show that head–tail and tail–water interactions play different roles in the formation of six kinds of self-assembly morphologies. The key factors are tail–water and head–tail repulsions separately for morphology with small (sphere) and relatively large scales (rod, planar grid, lamella and tunnels). Besides, the appearance of network in only one system can be regarded as a particular type of intermediate state. Coexistence of several sphere micelles in an amplified dissipative particle dynamics system gives us a better understanding of interactions inside the soft matter. Our simulation results can provide a theoretical guide to further research towards self-assembly behaviours of heterogemini surfactants and practical applications of these matters.     

Level surfaces of non-degenerate functions inR n+1

We study level surfaces of non-degenerate functions inR ⁿ⁺¹. Such level surfaces are non-degenerate in the sense of affine differential geometry. In affine differential geometry, the affine normal plays an important role for the study of a non-degenerate hypersurface. In this note, being motivated by Koszul's work we take a canonical vector field for level surfaces of a non-degenerate function and give certain characterizations of when is transversal, by the shape operatorS, the transversal connection , and consider the difference between and the affine normal.     

The application of lightning forecasting based on surface electrostatic field observations and radar data

This paper presents an analysis of lightning forecasting based on atmospheric electrostatic field (EF), radar and lightning location data in Nanjing of China. The warning behavior with EF data in summer of 2009 was analyzed and the suitable EF warning indexes were determined. To improve EF warnings effect, a method of cloud-ground (CG) lightning nowcasting based on EF observations, radar data, etc. was proposed and the best radar forecasting index was selected in the paper. The experimental (2009) and independent test (2010) results show that POD is 82.7%, FAR is 14.6%, CSI is 72.4% and average lead time is 20.8 min.     

On Cycles in 3-Connected Graphs

 Let G be a 3-connected graph of order n and S a subset of vertices. Denote by δ(S) the minimum degree (in G) of vertices of S. Then we prove that the circumference of G is at least min{|S|, 2δ(S)} if the degree sum of any four independent vertices of S is at least n+6. A cycle C is called S-maximum if there is no cycle C ^′ with |C ^′∩S|>|C∩S|. We also show that if ∑⁴ _i=1 d(a _i)≥n+3+|⋂⁴ _i=1 N(a _i)| for any four independent vertices a ₁, a ₂, a ₃, a ₄ in S, then G has an S-weak-dominating S-maximum cycle C, i.e. an S-maximum cycle such that every component in G−C contains at most one vertex in S. Received: March 9, 1998 Revised: January 7, 1999