CFD modeling of reaction and mass transfer through a single pellet: Catalytic oxidative coupling of methane

In this study a mathematical model of a small scale single pellet for the oxidative coupling of methane(OCM)over titanite pervoskite is developed.The method is based on a computational fluid dynamics(CFD)code which known as Fluent may be adopted to model the reactions that take place inside the porous catalyst pellet.The steady state single pellet model is coupled with a kinetic model and the intra-pellet concentration profiles of species are provided.Subsequent to achieving this goal,a nonlinear reaction network consisting of nine catalytic reactions and one gas phase reaction as an external program is successfully implemented to CFD-code as a reaction term in solving the equations.This study is based on the experimental design which is conducted in a differential reactor with a Sn/BaTiO3 catalyst(7-8 mesh) at atmospheric pressure,GHSV of 12000 h-1,ratio of methane to oxygen of 2,and three different temperatures of 1023,1048 and 1073 K.The modeling results such as selectivity and conversion at the pellet exit are in good agreement with the experimental data.Therefore,it is suggested that to achieve high yield in OCM process the modeling of the single pellet should be considered as the heart of catalytic fixed bed reactor.     

Theoretical Studies on Critical Properties of Binary System with Supercritical Carbon Dioxide

A new expression of mixing rule is suggested according to the Mayson‘s mixing rule in this paper,which adopts the Redlich-Kwong cubic equation of state and the modifed Chueh-Prausnitz method to calculate the experiment critical points of six binary mixtures CO2 toluene,CO2 cyclohexane,CO2 n-butanal,CO2 i-butanal,CO2 methanol,CO2 ethanol.The coefficients of interaction parameter in the expression of mixing rule were optimized from experimental data.The calculated results of critical temperature and critical pressure meet the experiment data well.The maximum relative errore of temperature and pressure between the calculation results and experiment data are 1.493% and 5.2236% respectively,indicating that the proposed expression of mixing rule is reasonable.This may provide a fundamental method for studying and predicting the properties of supercritical fluids.     

A NEW METHOD FOR ESTIMATION OF WEIGHT-AVERAGE MOLECULAR WEIGHT OF POLYMER FROM THE INTRINSIC VISCOSITY AND CHROMATOGRAM

A new method is proposed for estimation of weight-average molecular weight from the intrinsicviscosity and GPC chromatogram of a polymer sample for which Mark-Houwink coefficients are notknown. The method bases on an approximate relationship between GPC data and the intrinsicviscosity of the sample. Reliability of this method was tested by comparing with the universalcalibration method which requires known Mark-Houwink coefficients for seven samples havingdifferent molecular weight distributions. Results obtained by the new method are in excellent agree-ment with those by the universal calibration method.     

STUDY ON POLYMERIC CATALYST-PALLADIUM COMPLEX WITH RADIATION GRAFTING ACRYLONITRILE ON INORGANIC COMPOUND

Polymer bound palladium (Pd)complex catalysts with grafting acrylonitrile on inorganic compound(MgO,Y-molecular sieve and SiOz) by pre-radiation method were studied. The palladium - grafting polymers have been investigated by X-ray photoelectron spectrscopy(XPS). It is indicated that peak width of C1s and O1s spectra of MgO-g-PAN - Pd (radiation - induced graft) is wider than that of MgO -PAN - Pd(chemical method) and peak numbers of former are one more than later.According to the report in reference, this peak is attributed togroup. Thus, the graft acrylonitrile on MgO may complete through oxygen atoms in MgO and β-carbon atoms in acrylonitrile. The polymer catalyst obtained by radiation grafting is a higher active hydrogenation catalyst for olefines and better antitoxic than that of one obtained by chemical method, and it has selectivity for hydrogenation catalyst.     

A procedure of determining potential energy surfaces of triatomic molecules from inversion of spectroscopic data

In this paper,we have suggested an iterative procedure of optimization of the linearparameters in an analytic potential energy function for a triatomic molecule,by combining both variational and second order perturbation methods.The most important feature of this procedure is that the objective function is an analytical expression which can be optimized easily.The application to the water molecule is presented.     

STUDY ON POLYMERIC CATALYST—PALLADIUM COMPLEX WITH RADIATION GRAFTING ACRYLONITRILE ON INORGANIC COMPOUND

Polymer bound palladium (Pd) complex catalysts with grafting acrylonitrile on inorganic compound(MgO,Y-molecular sieve and SiO2) by pre-radiation method were studies.The palladium-grafting polymers have been investigated by X-ray photoelectron spectrscopy(XPS).It is indicated that peak width of C1s and O1s spectra of MgO-g-PAN-Pd(radiation-induced graft) is wider than that of MgO-PAN-Pd(chemical method) and Peak numbers of former are one more than later.According to the report in reference,this peak is attributed to -O-C group.Thus,the graft acrylonitrile on MgO may complete through oxygen atoms im MgO and β-carbon atoms in acrylonitrile.The polymer catalyst obtained by radiation grafting is a higher active hydrogenation catalyst for olefines and better antioxic than that of one obtained by chemical method,and it has selectivity for hydrogenation catalyst.     

Prominently Promoting the Formation of Poly(butylene adipate) α-Form Crystals by Coalescing from Inclusion Complex

We successfully use a co-precipitation method to prepare inclusion complex between poly(butylene adipate)(PBA) chains(guest component) and urea molecules(host component). The PBA/urea inclusion complex is confirmed to adopt a hexagonal crystal modification with lattice parameters of a = 8.14 ? and c = 10.92 ?, and the interaction between PBA chains and urea is van der Waals force. The singly isolated PBA chains are suggested to take some gauche conformation, which is different from the all-trans conformation in β-form PBA. Furthermore, we employ the isolated PBA chains which are uniformly pre-established in a specific conformation in urea channels to regulate the crystal form of PBA for the first time. After removing the host urea molecules, the coalesced PBA chains are found to solely crystallize into α-form crystals at different coalescing temperatures. By comparing the FTIR spectra, it is found that PBA chains in inclusion complex plausibly contain some similar conformers as those in α-form crystal, which is suggested to be the intrinsic reason for the sole formation of α-form crystals. This research proves that inclusion complex can be used as a very effective method to regulate polymorphism of semi-crystalline polymers.     

Application of 2D fluorescence correlation method to investigate the dilution-induced heterogeneous distribution of the bound FMN in azoreductase

AzoR is a homodimeric,flavin mononucleotide(FMN)-containing,NADH-dependent azoreductase from Escherichia coli.In this paper,we investigated the effect of the concentration of both AzoR and R59 G on the spectral behavior of the bound FMN using two-dimensional fluorescence correlation spectra.Two cross peaks(530,490) and(580,530) were observed from the dilution-induced 2D asynchronous correlation map of wt AzoR,while only one cross peak appeared at(600,530) for R59 C mutant.This result indicated that the mutation at site 59 influenced the formation of dilution-induced intermediates.The specific activity of both AzoR and R59 G mutant was unaffected by dilution when the enzyme concentration is below 1 μmol/L,which suggested that no significant dissociation of FMN occurred at low concentrations.Additionally,in order to explore the origin of these intermediates,we carried out a2 D correlation analysis using excitation wavelength-dependent fluorescence emission spectroscopy.The results showed that there coexisted two types of FMN that emitted fluorescence at 530 nm and 500 nm,respectively.Taken together,these results suggested that the 2D method is a very powerful method to identify the heterogeneous distribution of the bound FMN in solution.     

RELATION BETWEEN THE OPTICAL ANISO-TROPY INDEX AND THE POLARIZABILITY ELLIPSOID OF ATOM GROUPS

The optical anisotropy index is a new conception which has been proposed by the author of this paper on the basis of the Gladstone refractivity (i.e. specific energy by Larsen). The conception is very useful for studying the structural-optical mineralogy. The polarizability ellipsoid of atom groups in minerals may be obtained from the optical anisotropy index; conversely, when the crystal structure, orientation, and the polarizability ellipsoid of atom groups are known, the optical anisotropy index of the minerals may be calculated, and then three principal refractive indices, and the optical axis angles may be calculated, too. The calculated values of optical properties are in very good agreement with the experimental values. This calculation method is much simpler thanBragg's for the carbonates, and the precision of calculated values is much higher than that of Bragg's. The principle of calculation method is suitable for all the minerals containing some strong anisotropic atom groups, besides carbonat     

SPECIES CONCEPT AND TAXONOMIC PRINCIPLES

Based on the species concept of changing versus unchanging, the present work deals with the following two problems: First, why would the taxonomic system reflect evolutionary history? Second, how is this effeeted?Species are changing in the sense that each species has its own characteristics and there is no complete identity between any two species. On the other hand, species are unchanging and each one conserves a set of ancestral characters which allocates its taxonomic position, and this is the reason why the taxonomic system reflects evolutionary history.The taxonomic system is constructed to reflect evolutionary history mainly through the process of character analysis. Combining the viewpoints of cladistics and evolutionary systematics, the writer proposes six rules for character analysis which will provide the basis for analyzing evolutionary history.     

Temperature Controlled Lateral Pattern Formation in Confined Polymer Thin Films

The thermal induced topography change in a model system consisting of a polymer film on a Si substrate capped by a thin metal layer has been studied by using AFM. Regular lateral patterns over large areas were observed on the surface when the system was heated to a sufficiently high temperature. 2D-FFT analysis to the AFM images indicates that the patterns are isotropic and have well defined periodicities. The periodicities of the characteristic patterns are found to depend strongly on the annealing temperature. The study of the ki-netics of the formation reveals that such a topography forms almost instantaneously once the critical tempera-ture is reached. It is suggested that this wave-like surface morphology is driven by the thermal expansion co-efficient mismatch of the different layers. This method for generating regular wave-like patterns could be used as a general method for patterning various organic materials into micro/nanostructures.     

A preliminary study on sea wave packet equations on slowly varying topography

There is a common hypothesis for the presently popular mild-slope equations that wave particle motion is irrotational. In this paper, an attempt is made to abandon the irrotational assumption and to set up new sea wave packet equations on slowly varying topography by use of the WKBJ method. To simplify the deduction, the two-dimensional shallow water equations are used to describe the sea wave particle motion in the very shallow nearshore area. The established equations can give some characteristics of wave propagation near shore.     

Lithium manganese spinel materials for high-rate electrochemical applications

In order to successively compete with supercapacitors, an ability of fast discharge is a must for lithium-ion batteries. From this point of view, stoichiometric and substituted lithium manganese spinels as cathode materials are one of the most prospective candidates, especially in their nanosized form. In this article, an overview of the most recent data regarding physico-chemical and electrochemical properties of lithium manganese spinels, especially, LiMn2O4 and LiNi0.5Mn1.5O4, synthesized by means of various methods is presented, with special emphasis of their use in high-rate electrochemical applications. In particular, specific capacities and rate capabilities of spinel materials are analyzed. It is suggested that reduced specific capacity is determined primarily by the aggregation of material particles, whereas good high-rate capability is governed not only by the size of crystallites but also by the perfectness of crystals. The most technologically advantageous solutions are described, existing gaps in the knowledge of spinel materials are outlined, and the ways of their filling are suggested, in a hope to be helpful in keeping lithium batteries afloat in the struggle for a worthy place among electrochemical energy systems of the 21st century.     

THE PARAMETER KERNELS FOR THE LINEAR INVERSION OF THE FREE OSCILLATION OF THE EARTH (Ⅱ)

This is the second instalment of the paper, in which the method of derivation of the for-mulas of parameter kernels for the spheroidal oscillations are considered. The principle ofRayleigh is used to derive the formulas of the kernels of the two elastic parameters, i.e. μand λ. But for that of ρ, it is found very difficult to get satisfactory results. A new butsimpler approach is followed and very satisfactory results are obtained.     

Nano Si preparation by constant cell voltage electrolysis of FFC-Cambridge Process in molten CaCl₂

Using FFC-Cambridge Process to prepare Si from SiO2 is a promising method to prepare nanostructured and highly pure silicon for solar cells.However,the method still has many problems unsolved and the controlling effect of the cell voltage on silicon product is not clear.Here we report in this article that nano cluster-like silicon product with purity of 99.95%has been prepared by complete conversion of raw material SiO2,quartz glass plate,using constant cell voltage electrolysis FFC-Cambridge Process.By analysis of XRD,EDS,TEM,HRTEM and ICP-AES as well as the discussion from the thermodynamics calculation,the morphology and components of the product based on the change of cell voltage are clarified.It is clear that pure silicon could be prepared at the cell voltage of 1.7 2.1 V in this reaction system.The silicon material have cluster-like structure which are made of silicon nanoparticles in 20 100 nm size.Interestingly,the cluster-like nano structure of the silicon can be tuned by the used cell voltage.The purity,yield and the energy cost of silicon product prepared at the optimized cell voltage are discussed.The purity of the silicon product could be further improved,hence this method is promising for the preparation of solar grade silicon in future.     

A NEW METHOD FOR CALCULATING THE ABSORPTION AMOUNT OF DRUG

In this paper, a new method is suggested for calculating the absorption amount of drug. The method is based on the general linear compartment model for pharmacokinetics, hence applicable to any proper linear compartment model for pharmacokinetics. For the linear one compartment model, it is in agreement with the Wagner-Nelson method which is often used nowadays. For the linear two compartment model, it has advantages over the Loo-Riegelman method, which is also in common use in, for example, simplicity in mathematical derivation, less computation, etc. And it can be easily extended to some particular nonlinear compartment model.     

Electrochemical Study on the Interaction of Protein with Bromothymol Blue and Its Analytical Application

The interaction of bromothymol blue（BB） with human serum albumin（HSA） was studied by electrochemical techniques and a sensitive method for proteins assay was developed. When BB interacted with HSA, the voltammetric peak current value of BB decreased linearly with the concentration of HSA in a range of 1.0--40.0 mg/L, and the peak potential shifted negatively. Based on the results, a sensitive assay method for proteins, such as HSA, bovine serum albumin（BSA）, and egg albumin etc. was established. This method was further applied to determining the HSA in healthy human blood samples, and the results are not significantly different from those obtained by the classic Coomassie Brilliant Blue G-250 spectrophotometic method. The detecting conditions of this method were optimized and the interaction mechanism was discussed. The results show that the electrochemical parameters（formal potential E^0, standard rate constant of the electrode reaction ks, parameter of kinetic nα） of BB have no obvious changes before and after the interaction, which indicate that BB can interact with HSA, forming an electrochemical non-active complex. The equilibrium constant（βs） and the binding ratio（m） for this complex were calculated. The m is 4 and βs is 1.41 × 10^19. This method is fast, simple, highly sensitive, and has good selectivity, which can be used in clinical measurements.     

丌-丌电荷转移复合物的光谱及其图解方法的探讨

In this report, a method for deconvoluting the multi-band spectra of charge-transfer complex is presented and a relation between double-bands is proposed. 49 such spectra in which double-bands appear are calculated. It has been found that the deviation between the calculated and the measured values is less than 3%. The scheme can be extended to deconvolute the CT peaks are used to evaluate the electron affinities of these acceptors. But, the scheme can be used to the π-π charge-transfer complexes.     

First-order Derivative Spectrophotometry for the Determination of Vitamin C in Medicament

A novel method for the determination of vitamin C（Vc） is proposed in this article. After the reaction with Folin-Ciocalteau reagent at ambient temperature, Vc solution was scanned at 750--1100 nm, and its first-order derivative spectrum were obtained from the original spectrum. The values of derivative selected at 995 nm were used for determination. It was proved that Vc could quickly react with Folin-Ciocalteau reagent within 5 min and the product was quite stable for a long time. The conditions required for this method is not very complicated, its precision and accuracy are similar to those of the iodometric titration described in Chinese Pharmacopoeia, and the limit of detection is 0.312 μg/mL. The determination of the results of vitamin C tablet, pill, and injection demonstrates that this method has wide pharmaceutical applications.