A Block-Adaptive Blind Separation Algorithm for Post-Nonlinear Mixture of Sub- and Super-Gaussian Signals

The problem of blind separation of signals in post nonlinear mixture is addressed in this paper. The post nonlinear mixture is formed by a component wise nonlinear distortion after the linear mixture. Hence a nonlinear adjusting part placed in front of the linear separation structure is needed to compensate for the distortion in separating such signals. The learning rules for the post nonlinear separation structure are derived by a maximum likelihood approach. An algorithm for blind separation of post nonlinearly mixed sub and super Gaussian signals is proposed based on some previous work. Multilayer perceptrons are used in this algorithm to model the nonlinear part of the separation structure. The algorithm switches between sub and super Gaussian probability models during learning according to a stability condition and operates in a block adaptive manner. The effectiveness of the algorithm is verified by experiments on simulated and real world signals.

Separation of CO_2/CH_4 and CH_4/N_2 mixtures using MOF-5 and Cu_3(BTC)_2

In this paper we used MOF-5 and Cu3（BTC）2 to separate CO2/CH4 and CI-I4/N2 mixtures under dynamic conditions. Both materials were synthesized and pelletized, thus allowing for a meaningful characterization in view of process scale-up. The materials were characterized by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. By performing breakthrough experiments, we found that Cu3（BTC）2 separated CO2/CH4 slightly better than MOF-5. Because the crystal structure of Cu3 （BTC）2 includes unsaturated accessible metal sites formed via dehydration, it predominantly interacted with CO2 molecules and more easily captured them. Conversely, MOF-5 with a suitable pore size separated CH4/N2 more efficiently in our breakthrough test.

Membrane materials in the pervaporation separation of aromatic/aliphatic hydrocarbon mixtures—A review

The separation of aromatic/aliphatic hydrocarbon mixtures is a significant process in chemical industry, but challenged in some cases. Compared with conventional separation technologies, pervaporation is quite promising in terms of its economical, energy-saving, and eco-friendly advantages. However, this technique has not been used in industry for separating aromatic/aliphatic mixtures yet. One of the main reasons is that the separation performance of existed pervaporation membranes is unsatisfactory. Membrane material is an important factor that affects the separation performance. This review provides an overview on the advances in studying membrane materials for the pervaporation separation of aromatic/aliphatic mixtures over the past decade. Explored pristine polymers and their hybrid materials(as hybrid membranes) are summarized to highlight their nature and separation performance. We anticipate that this review could provide some guidance in the development of new materials for the aromatic/aliphatic pervaporation separation.

Optimal activated carbon for separation of CO_2 from(H_2 + CO_2) gas mixture

Seven types of activated carbon were used to investigate the effect of their structure on separation of CO2 from（H2 ＋ CO2） gas mixture by the adsorption method at ambient temperature and higher pressures. The results showed that the limiting factors for separation of CO2 from 53.6 mol% H2 ＋ 46.4 mol% CO2 mixture and from 85.1 mol% H2 ＋ 14.9 mol% CO2 mixture were different at 20 °C and about 2 MPa. The best separation result could be achieved when the pore diameter of the activated carbon ranged from 0.77 to 1.20 nm, and the median particle size was about2.07 lm for 53.6 mol% H2 ＋ 46.4 mol% CO2 mixture and 1.41 lm for 85.1 mol% H2 ＋ 14.9 mol% CO2 mixture. The effect of specific area and pore diameter of activated carbon on separation CO2 from 53.6 mol% H2 ＋ 46.4 mol% CO2 mixture was more significant than that from 85.1 mol% H2 ＋ 14.9 mol% CO2 mixture. CO2 in the gas phase can be decreased from 46.4 mol% to 2.3 mol%–4.3 mol% with a two-stage separation process.

Phase separation and super diffusion of binary mixtures of active and passive particles

Computer simulations were performed to study the dense mixtures of passive particles and active particles in two dimensions.Two systems with different kinds of passive particles(e.g.,spherical particles and rod-like particles)were considered.At small active forces,the high-density and low-density regions emerge in both systems,indicating a phase separation.At higher active forces,the systems return to a homogeneous state with large fluctuation of particle area in contrast with the thermo-equilibrium state.Structurally,the rod-like particles accumulate loosely due to the shape anisotropy compared with the spherical particles at the high-density region.Moreover,there exists a positive correlation between Voronoi area and velocity of the particles.Additionally,a small number of active particles capably give rise to super-diffusion of passive particles in both systems when the self-propelled force is turned on.

SEPARATION OF FORMIC ACID-WATER AZEOTROPIC MIXTURES BY MEMBRANE DISTILLATION

The azeotrope disappeared when the formic acid-water mixtures were treated by membrane distillation. Membrane distillation were used for separation of formic acid-water azeotropic mixtures for the first time.

A WEIGHTED GENERAL DISCRETE FOURIER TRANSFORM FOR THE FREQUENCY-DOMAIN BLIND SOURCE SEPARATION OF CONVOLUTIVE MIXTURES

This letter deals with the frequency domain Blind Source Separation of Convolutive Mixtures (CMBSS). From the frequency representation of the "overlap and save", a Weighted General Discrete Fourier Transform (WGDFT) is derived to replace the traditional Discrete Fourier Transform (DFT). The mixing matrix on each frequency bin could be estimated more precisely from WGDFT coefficients than from DFT coefficients, which improves separation performance. Simulation results verify the validity of WGDFT for frequency domain blind source separation of convolutive mixtures.

Distinguished discriminatory separation of CO2 from its methane-containing gas mixture via PEBAX mixed matrix membrane

Highly selective separation of CO_2 from its methane-containing binary gas mixture can be achieved by using Poly(ether-block-amide)(PEBAX)mixed matrix membranes(MMMs).According to FESEM and AFM analyses,silica-based nanoparticles were homogenously integrated within the polymer matrix,facilitating penetration of CO_2 through the membrane while acting as barrier for methane gas.The membrane containing 4.6 wt% fumed silica(FS)(PEBAX/4.6 wt%FS)exhibits astonishing selectivity results where binary gas mixture of CO_2/CH_4 was used as feed gas.As detected by gas chromatography,in the permeate side,data showed a significant increase of CO_2 permeance,while CH_4 transport through the mixed matrix membrane was not detectable.Moreover,PEBAX/4.6 wt%FS greatly exceeds the Robeson limit.According to data reported on CO_2/CH_4 gas pair separation in the literature,the results achieved in this work are beyond those data reported in the literature,particularly when PEBAX/4.6 wt%FS membrane was utilized.

SELECTIVE SEPARATION OF WATER-ETHANOL MIXTURES THROUGH COPOLYMERIC MEMBRANES: Ⅰ. ACRYLIC ACID AND ACRYLONITRILE COPOLYMER AND ITS IONIZED MEMBRANES

The copolymer of acrylic acid and acrylonitrile has been synthesized and pervaporation properties of the copolymeric membranes have been investigated. In order to elucidate the influence of membrane-permeate interaction on the pervaporation of water-ethanol mixtures and to prepare much improved membranes, the membranes have been treated with alkali metal, alkali earth metal and transition metal salt aqueous solutions. The treated membranes (ionized membranes) exhibited higher separation factors than the untreated membranes. The separation factors of various alkali metal cation membranes decreased in the following order : Li^+>Na^+>K^+, and the permeation rates showed an opposite tendency. The dependence of pervaporation behavior on the copolymer composition ,feed concentration and operating temperature have been studied with both ionized and non-ionized membranes. The apparent activation energies of water and ethanol permeation were calculated.

PERVAPORATION SEPARATION OF WATER-ACETIC ACID MIXTURES THROUGH AN-co-AA MEMBRANES TREATED WITH RARE EARTH METAL IONS

Pervaporation separation of water-acetic acid mixtures through Poly(AN-co-AA) membranes and rare earth metal ions treated Poly(AN-co-AA)membranes was investigated for the first time. The results showed that the treatment with rare earth metal ions could greatly improve the characteristics of the separation of water-acetic acid mixtures.

A Proton Nuclear Magnetic Resonance (¹H NMR) Investigation of NaCl-Induced Phase Separation of Acetonitrile-Water Mixtures

The microscopic properties of NaCl-induced phase separation of acetonitrile (ACN)-water mixtures have been studied by proton nuclear magnetic resonance (1H NMR). Acetonitrile-rich phase increases with increasing NaCl concentration (cNaCl) at xACN ≈ 0.25. 1H chemical shift of water for acetonitrile-rich phase rapidly decreases with decreasing NaCl mole concentration and that for water-rich phase quickly increases with increasing cNaCl. However, 1H chemical shift of acetonitrile has nothing to do with the molar concentration of NaCl, and it keeps relatively stable for all solutions (±0.002). These results reveal that Na+ and Cl- are rapidly hydrated by water, not by acetonitrile. The change of 1H chemical shift of water has shown that the number of hydrogen bond increases or hydrogen bond strengths with increasing NaCl molarity in mixtures. But hydrogen bond is broken or weaken with the temperature rising. 1H chemical shifts of pure water and the water in acetonitrile-rich phase have been investigated at 293 K, 298 K and 303 K. The hydration number of Na+ (6.05) in water-rich phase is determined by an empirical equation involving 1H chemical shift, temperature and NaCl molarity, which is in good agreement with the literatures.

Environmental,economic and exergy analysis of separation of ternary azeotrope by variable pressure extractive distillation based on multi-objective optimization

In this work,the ternary azeotrope of tert-butyl alcohol/ethyl acetate/water is separated by extractive distillation(ED)to recover the available constituents and protect the environment.Based on the conductor like shielding model and relative volatility method,ethylene glycol was selected as the extractant in the separation process.In addition,in view of the characteristic that the relative volatility between components changes with pressure,the multi-objective optimization method based on nondominated sorting genetic algorithm II optimizes the pressure and the amount of solvent cooperatively to avoid falling into the optimal local solution.Based on the optimal process parameters,the proposed heat-integrated process can reduce the gas emissions by 29.30%.The heat-integrated ED,further coupled with the pervaporation process,can reduce gas emission by 42.36%and has the highest exergy efficiency of 47.56%.In addition,based on the heat-integrated process,the proposed two heat pump assisted heat-integrated ED processes show good economic and environmental performance.The double heat pump assisted heat-integrated ED can reduce the total annual cost by 28.78%and the gas emissions by 55.83%compared with the basis process,which has a good application prospect.This work provides a feasible approach for the separation of ternary azeotropes.

Boosting kinetic separation of ethylene and ethane on microporous materials via crystal size control

The adsorptive separation of C_(2)H_(4)and C_(2)H_(6),as an alternative to distillation units consuming high energy,is a promising yet challenging research.The great similarity in the molecular size of C_(2)H_(4)and C_(2)H_(6)brings challenges to the regulation of adsorbents to realize efficient dynamic separation.Herein,we reported the enhancement of the kinetic separation of C_(2)H_(4)/C_(2)H_(6)by controlling the crystal size of ZnAtzPO_(4)(Atz=3-amino-1,2,4-triazole)to amplify the diffusion difference of C_(2)H_(4)and C_(2)H_(6).Through adjusting the synthesis temperature,reactant concentration,and ligands/metal ions molar ratio,ZnAtzPO4 crystals with different sizes were obtained.Both single-component kinetic adsorption tests and binary-component dynamic breakthrough experiments confirmed the enhancement of the dynamic separation of C_(2)H_(4)/C_(2)H_(6)with the increase in the crystal size of ZnAtzPO_(4).The separation selectivity of C_(2)H_(4)/C_(2)H_(6)increased from 1.3 to 98.5 with the increase in the crystal size of ZnAtzPO_(4).This work demonstrated the role of morphology and size control of adsorbent crystals in the improvement of the C_(2)H_(4)/C_(2)H_(6)kinetic separation performance.

Performance of Inner-core Supersonic Gas Separation Device with Droplet Enlargement Method

To improve the separation performance of a supersonic gas separation device for the treatment of gas mixture with a single heavy component, a novel structure with shorter settlement distance was constructed and a method of droplet enlargement was applied. A series of experiments were carried out in the improved separation device under various conditions, using air-ethanol vapor as the medium and micro water droplets as nucleation cen- ters. The effects of the inlet pressure, temperature and relative humidity, the swirling intensity, and mass flow rate of water on the separation performance were investigated. The separation was improved by increasing the inlet pressure and relative humidity. With the decrease of swirling intensity and mass flow rate of water, the separation efficiency increased first and then decreased. The inlet temperature had a slight effect on the separation. The results showed that the separation performance was effectively improved using the proposed structure and method, and the best separation in this study was obtained with the ethanol removal rate about 55% and dew point depression 27 K. The addition of water had little pollution to the air-ethanol vapor system since the water carry-over rate was within the range of -2 %-0 in most cases.

The infinite separation principle

In this paper,we propose“The Infinite Separation Principle”.This principle contains two implications:firstly,even exhausting all separation approaches,including chemical techniques,it is impossible to achieve 100%purity for separating a mixture;secondly,separation can continue infinitely without an endpoint.

Research on Blind Source Separation for Machine Vibrations

Blind source separation is a signal processing method based on independent component analysis, its aim is to separate the source signals from a set of observations (output of sensors) by assuming the source signals independently. This paper reviews the general concept of BSS firstly;especially the theory for convolutive mixtures, the model of convolutive mixture and two deconvolution structures, then adopts a BSS algorithm for convolutive mixtures based on residual cross-talking error threshold control criteria, the simulation testing points out good performance for simulated mixtures.

Maximum Likelihood Blind Separation of Convolutively Mixed Discrete Sources

In this paper,a Maximum Likelihood(ML) approach,implemented by Expectation-Maximization(EM) algorithm,is proposed to blind separation of convolutively mixed discrete sources.In order to carry out the expectation procedure of the EM algorithm with a less computational load,the algorithm named Iterative Maximum Likelihood algorithm(IML) is proposed to calculate the likelihood and recover the source signals.An important feature of the ML approach is that it has robust performance in noise environments by treating the covariance matrix of the additive Gaussian noise as a parameter.Another striking feature of the ML approach is that it is possible to separate more sources than sensors by exploiting the finite alphabet property of the sources.Simulation results show that the proposed ML approach works well either in determined mixtures or underdetermined mixtures.Furthermore,the performance of the proposed ML algorithm is close to the performance with perfect knowledge of the channel filters.

Determined Reverberant Blind Source Separation of Audio Mixing Signals

Audio signal separation is an open and challenging issue in the classical“Cocktail Party Problem”.Especially in a reverberation environment,the separation of mixed signals is more difficult separated due to the influence of reverberation and echo.To solve the problem,we propose a determined reverberant blind source separation algorithm.The main innovation of the algorithm focuses on the estimation of the mixing matrix.A new cost function is built to obtain the accurate demixing matrix,which shows the gap between the prediction and the actual data.Then,the update rule of the demixing matrix is derived using Newton gradient descent method.The identity matrix is employed as the initial demixing matrix for avoiding local optima problem.Through the real-time iterative update of the demixing matrix,frequency-domain sources are obtained.Then,time-domain sources can be obtained using an inverse short-time Fourier transform.Experi-mental results based on a series of source separation of speech and music mixing signals demonstrate that the proposed algorithm achieves better separation performance than the state-of-the-art methods.In particular,it has much better superiority in the highly reverberant environment.