Simulation of Heat and Mass Transfer in a Grain Pile on the Basis of a 2D Irregular Pore Network

The so-called pore network model has great advantages in describing the process of heat and mass transfer in porous media.In order to construct a random two-dimensional(2D)irregular pore network model for an unconsolidated material,image processing technology was used to extract the required topological and geometric information from a 2D sample of soybean particles,and a dedicated algorithm was elaborated to merge some adjacent small pores.Based on the extracted information,a 2D pore network model including particle information was reconstructed and verified to reflect the pore structure of discrete particles.This method was used to reconstruct a random 2D irregular pore network model of wheat.Accordingly,a multi-scale heat and mass transfer model was implemented to simulate the drying of wheat.The simulation results were consistent with the experimental results,which indicates that the reconstructed irregular pore network model can effectively simulate the real pore structure inside unconsolidated porous media.The present approach may be regarded as the foundation for establishing in the future a three-dimensional pore network model and studying the heat and mass transfer process in a grain pile.

On cross-correlation indicators of an S-box

Substitution boxes （S-boxes） are often used as the most important nonlinear components in many symmetric encryption algorithms. The cryptographic properties of an S-box directly affect the security of the whole cipher system. Recently, generalized global avalanche characteristics （GGAC） were introduced to measure the correlation between two arbitrary Boolean functions. In this paper, to better evaluate the security of an S-box, we present two cross-correlation indicators for it. In addition, by studying the related properties of the cross-correlation between two balanced Boolean func- tions, we propose the lower bounds on the sum-of-squares indicator related to GGAC for two balanced functions and also for an S-box.

Sequential separation of Cu(Ⅱ)/Ni(Ⅱ)/Fe(Ⅱ)from strong-acidic pickling wastewater with a two-stage process based on a bi-pyridine chelating resin

A self-synthesized bi-pyridine chelating resin(PAPY)could separate Cu(Ⅱ)/Ni(Ⅱ)/Fe(Ⅱ)sequentially from strong-acidic pickling wastewater by a two-stage p H-adjusted process,in which Cu(Ⅱ),Ni(Ⅱ),and Fe(Ⅱ)were successively preferred by PAPY.In the first stage(p H 1.0),the separation factor of Cu(Ⅱ)over Ni(Ⅱ)reached 61.43 in Cu(Ⅱ)-Ni(Ⅱ)-Fe(Ⅱ)systems.In the second stage(p H 2.0),the separation factor of Ni(Ⅱ)over Fe(Ⅱ)reached 92.82 in Ni(Ⅱ)-Fe(Ⅱ)systems.Emphasis was placed on the selective separation of Cu(Ⅱ)and Ni(Ⅱ)in the first-stage.The adsorption amounts of Cu(Ⅱ)onto PAPY were 1.2 mmol/g in the first stage,while those of Ni(Ⅱ)and Fe(Ⅱ)were lower than 0.3 mmol/g.Cu(Ⅱ)adsorption was hardly affected by Ni(Ⅱ)with the presence of dense Fe(Ⅱ),but Cu(Ⅱ)inhibited Ni(Ⅱ)adsorption strongly.Part of preloaded Ni(Ⅱ)could be replaced by Cu(Ⅱ)based on the replacement effect.Compared with the absence of Fe(Ⅱ),dense Fe(Ⅱ)could obviously enhance the separation of Cu(Ⅱ)-Ni(Ⅱ).More than 95.0%of Cu(Ⅱ)could be removed in the former 240 BV(BV for bed volume of the adsorbent)in the fixed-bed adsorption column process with the flow rate of 2.5 BV/h.As proved by X-ray photoelectron spectrometry(XPS)and density functional theory(DFT)analyses,Cu(Ⅱ)exerted a much stronger deprotonation and chelation ability toward PAPY than Ni(Ⅱ)and Fe(Ⅱ).Thus,the work shows a great potential in the separation and purification of heavy metal resources from strong-acidic pickling wastewaters.