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Air pollution models plays a critical role in atmospheric environment research. Chemical kinetic equations is an important component of air pollution models. The chemical equations is numerically sticky because of its stiffness, nonlinearity, coupling and nonnegativity of the exact solutions. Over the past decades, numerous papers about chemical equation solvers have been published. However, these solvers cannot preserve the nonnegativity of the exact solutions. Therefore, in the calculation, the negative numerical concentration values are usually set to zero artificially, which may cause simulation errors. To obtain real nonnegative numerical concentration values, very small step-size has to be adopted. Then enormous amount of CPU time is consumed to solve the chemical equations. In this paper, we revisit this topic and derive a new algorithm. Our algorithm Modified-Backward-Euler (MBE) Method can unconditionally preserve the nonnegativity of the exact solutions. MBE is a simple, robust and efficient solver. It is much faster and more precise than the traditional solvers such as LSODE and QSSA. The numerical results and parameter suggestions are shown at the end of the paper. MBE is based on the P-L structure of the chemical equations and a deeper view into the nature of Euler Methods. It cannot only be used to solve chemical equations, but can also be applied to conquer ordinary differential equations (ODEs) with similar P-L structure.

Joint study of multicomponent chemical zonality of rock-forming minerals with actual metamorphic reactions in metapelite of Yenisey Range had been completed. Calculations of chemical equations, analysis of substance balance and peculiarities of changing of mineral composition during collision metamorphism of pelite attest to isochemical character of the processes in most of the system components.

Open coordination sites (OCSs) in metal-organic frameworks (MOFs) often function as key factors in the potential applications of MOFs, such as gas separation, gas sorption, and catalysis. For these applications, the activation process to remove the solvent molecules coordinated at the OCSs is an essential step that must be performed prior to use of the MOFs. To date, the thermal method performed by applying heat and vacuum has been the only method for such activation. In this report, we demonstrate that methylene chloride (MC) itself can perform the activation role: this process can serve as an alternative "chemical route" for the activation that does not require applying heat. To the best of our knowledge, no previous study has demonstrated this function of MC, although MC has been popularly used in the pretreatment step prior to the thermal activation process. On the basis of a Raman study, we propose a plausible mechanism for the chemical activation, in which the function of MC is possibly due to its coordination with the Cu(2+) center and subsequent spontaneous decoordination. Using HKUST-1 film, we further demonstrate that this chemical activation route is highly suitable for activating large-area MOF films.

This paper deals with the long time behavior in terms of complete spreading for a population model described by a reaction-diffusion equation with delay, of which the corresponding reaction equation is bistable. When a complete spreading occurs in the corresponding undelayed equation with initial value admitting compact support, it is proved that the invasion can also be successful in the delayed equation if the time delay is small. To spur on a complete spreading, the choice of the initial value would be very technical due to the combination of delay and Allee effects. In addition, we show the possible failure of complete spreading in a quasimonotone delayed equation to illustrate the complexity of the problem.

In this report we analyze a subset of chemical equations that have equal numbers of elements and unknown coefficients; linear algebraically, these relate to n X n matrix systems. Here we associate inhomogeneous eigenvector occurrences to structural properties of chemical equations.

The transformation of three types of polyoxovanadates, {(n-C4H9)4N}3[H3V10O28], {(n-C4H9)4N}4[V12O32] and {(n-C4H9)4N}3[V13O34] have been investigated according to the rational chemical equations, and the best transformation conditions were reported. By the reaction of [H3V10O28]3− with 0.33 equivalents of {(n-C4H9)4N}OH in acetonitrile at 80 °C, [V12O32]4− was formed with 92% yield. The reaction in nitroethane with 0.69 equivalents of p-toluenesulfonic acid gave [V13O34]3− with 91% yield. The 51V NMR observation of each reaction suggests the complete transformations of [H3V10O28]3− to [V12O32]4− and to [V13O34]3− proceeded without the formation of any byproducts and it provides the reliable synthetic route. Decavanadates were produced by the hydrolysis of [V12O32]4− or [V13O34]3−. While the direct transformation of [V13O34]3− to [V12O32]4− partly proceeded, the reverse one could not be observed. For the thioanisole oxidation, [V13O34]3− showed the highest activity of the three.

This chapter introduces stoichiometry beginning with the mole concept and using Avogadro’s number as a conversion factor between the number of moles and the number of fundamental units in a substance. Case studies are used to present the determination of the empirical and molecular formulas from experimental data. Methods for balancing chemical equations and determining the limiting reactant are covered. The difference between percent yield and atom economy in chemical reactions is discussed in terms of determining the most economical and greener processes, using the steel industry as a Case Study. The process controlling the aqueous solubility of ionic compounds and their influences on precipitation reactions is discussed. The determination of the concentration of aqueous solutions in molarity is also covered.

It has been mentioned earlier that a reaction seldom occurs as simply as represented by chemical equation. For example, consider the reactions.

We consider similarity solutions of the generalized convection-diffusion-reaction equation with both space- and time-dependent convection, diffusion and reaction terms. By introducing the similarity variable, the reaction-diffusion equation is reduced to an ordinary differential equation. Matching the resulting ordinary differential equation with known exactly solvable equations, one can obtain corresponding exactly solvable convection-diffusion-reaction systems. Some representative examples of exactly solvable systems are presented. We also describe how an equivalent convection-diffusion-reaction system can be constructed which admits the same similarity solution of another convection-diffusion-reaction system., Comment: 9 pages, 6 figures. arXiv admin note: text overlap with arXiv:1508.00167

Education research results point to frequent misconceptions of basic chemical concepts among students at all levels of education. One reason for this is the abstract nature of the subject, which requires higher cognitive abilities of students in the learning process. Considering these insights, research was conducted with the aim to identify and analyze students’ misconceptions associated with the concept of chemical equation. The results served to design and implement a quasi-experiment aiming to enhance teaching of the mentioned concept, which is presently under way. The research, conducted in December 2013, included 357 eighth grade students from several primary schools. Multiple-choice questions were used in assessing the ability of associating two different ways of presenting a chemical reaction, namely chemical equation and particulate drawing. Analysis of the collected data revealed different misconceptions associated with insufficient understanding of the concepts of atom and molecule, stoichiometric number and index, reaction system and elementary reaction, and difficulties in applying the law of conservation of mass. The research results emphasize the value of particulate drawing as a teaching tool whose application in assessing knowledge enables an analysis of the conceptual understanding of the chemical equation., Rezultati edukacijskih istraživanja ukazuju na učestalost pogrešnih shvaćanja temeljnih kemijskih pojmova kod učenika svih obrazovnih razina. Uzrok tome je i apstraktna priroda nastavnog predmeta koja od učenika zahtijeva više kognitivne sposobnosti pri usvajanju sadržaja. Uzimajući u obzir te spoznaje, provedeno je istraživanje čiji je cilj bio prepoznati i analizirati pogrešna shvaćanja učenika povezana s konceptom jednadžbe kemijske reakcije. Rezultati ovog istraživanja poslužili su za osmišljavanje i provedbu kvazieksperimenta s ciljem unaprjeđenja poučavanja navedenog koncepta, koje je u tijeku. U istraživanju koje je provedeno u prosincu 2013. godine sudjelovalo je 357 učenika osmih razreda osnovnih škola. Zadatcima višestrukog izbora provjeravana je sposobnost povezivanja dvaju načina prikaza kemijske promjene, jednadžbom kemijske reakcije i čestičnim crtežom. Analizom prikupljenih podataka uočena su različita pogrešna shvaćanja povezana s nerazumijevanjem pojmova: atom i molekula, stehiometrijski broj i indeks, reakcijski sustav i elementarna pretvorba, kao i poteškoće primjene zakona o očuvanju mase. Rezultati ovog istraživanja ističu vrijednost čestičnog crteža kao nastavnog alata čija uporaba pri provjeri znanja omogućava analizu konceptualnog razumijevanja jednadžbe kemijske reakcije.

Physical chemistry, chemical physics 20(36), 23281 - 23293 (2018). doi:10.1039/C8CP01898G, Acid–base equilibria of carboxylic acids and alkyl amines in the aqueous surface region were studied using surface-sensitive X-ray photoelectron spectroscopy and molecular dynamics simulations. Solutions of these organic compounds were examined as a function of pH, concentration and chain length to investigate the distribution of acid and base form in the surface region as compared to the aqueous bulk. Results from these experiments show that the neutral forms of the studied acid–base pairs are strongly enriched in the aqueous surface region. Moreover, we show that for species with at least four carbon atoms in their alkyl-chain, their charged forms are also found to be abundant in the surface region. Using a combination of XPS and MD results, a model is proposed that effectively describes the surface composition. Resulting absolute surface concentration estimations show clearly that the total organic mole fractions in the surface region change drastically as a function of solution pH. The origin of the observed surface phenomena, hydronium/hydroxide concentrations in the aqueous surface region and why standard chemical equations, used to describe equilibria in dilute bulk solution are not valid in the aqueous surface region, are discussed in detail. The reported results are of considerable importance especially for the detailed understanding of properties of small aqueous droplets that can be found in the atmosphere., Published by RSC Publ., Cambridge

Graphene-sheet-supported uniform ultrasmall (≈3 nm) silicon quantum dots are successfully synthesized using a simple and effective self-assembly strategy. They exhibit unprecedented fast, surface-controlled lithium-storage behavior and outstanding lithium-storage properties including extraordinary rate capability and remarkable cycling stability, attributable to the intrinsic role of approaching the downsizing limit of silicon. (Chemical Equation Presented).

Ethanol is a important fuel that can be produced with renewable energy resources. Based on a mechanism with 377 reactions and 56 species, we combine two methods for mechanism reduction, Directed Relation Graph (DRG) and Sensitivity Analysis, to develop a 34 reactions and 23 species reduced mechanism. DRG is a method that shows the coupling of species through a coefficient based on the reaction rate, while sensitivity analysis uses the eigenvalues and eigenvectors of the sensitivity matrix to provide an absolute measure of significance for some species of the mechanism. The main advantage of the mechanism reduction is the decrease of computational cost needed to solve the chemical equations, of one order of magnitude for ethanol.

In this paper, the Backlund transformation of fractional Riccati equation is presented to establish traveling wave solutions for two nonlinear space–time fractional differential equations in the sense of modified Riemann–Liouville derivatives, namely, the space–time fractional generalized reaction duffing equation and the space–time fractional diffusion reaction equation with cubic nonlinearity. The proposed method is effective and convenient for solving nonlinear evolution equations with fractional order. Copyright © 2014 John Wiley & Sons, Ltd.

Through this letter to the editor (Rebuttal), we had given our explanation for the queries raised by Professor Juan J. Melendez commenting on the high substitution energies, the small simulation supercells, and the inconsistence of experimental data and simulation results. We agree with the comment that applying a “chemical potential diagram” is a general way to study defect system. However, there are some experimental concerns on “what the initial materials should be used”, whereas many degrees of freedom become feasible. Therefore, the formation energy equation (with foreign atoms substitution) cannot be trivially answered by the formation energy within a chemical potential diagram framework, unlike substitution energy calculated directly from our suggested chemical equation. We explain in the details on our approach and confirm the validity of our main equation; FeO+Ba 8 Ti 8 O 23 →Ba 8 Ti 7 FeO 23 +TiO 2 for the substitution energy with 2×2×2 supercell size which the results still show some suggestive trends.

We find the Lie point symmetries of a class of second-order nonlinear diffusion–convection–reaction equations containing an unspecified coefficient function of the independent variable t and determine the subclasses of these equations which are nonlinearly self-adjoint. By using a general theorem on conservation laws proved recently by N.H. Ibragimov we establish conservation laws corresponding to the aforementioned Lie point symmetries, one by one, for the simultaneous system of the original equation together with its adjoint equation through a formal Lagrangian. Particularly, for the nonlinearly self-adjoint subclasses, we construct conservation laws for the corresponding equations themselves.

The molten corium-concrete interaction (MCCI) phenomenon was analyzed based on the Moving Particle Semi-implicit (MPS) method. The developed code was applied to one-dimensional SURC-2 and SURC-4 experiments, in which a mixture composed of UO2–ZrO2–Zr and Steel-Zr was used as the melt materials. The phase transition of the melt and the concrete was modeled based on a phase transition model for mixture. The effect of Zr oxidation on the concrete ablation was taken into consideration by introducing the reaction heat of Zr/SiO2 obtained from the condensed phase chemical equations into the melt pool. The calculated concrete ablation rate was compared with the experimental measurements and the simulation results of the CORCON code. The simulation results by MPS agreed well with the experimental measurements. The experimental and MPS results both indicated that for both experiments Zr oxidation could significantly increase the ablation rate. On the other hand, crust formation and remelting was observed to occur on the interface between the melt and the concrete in the MPS simulation. During the period before crust remelted, the concrete ablation rate calculated by MPS decreased significantly. It was indicated by the MPS results that the crust formation could play an important part in MCCI since it could slow down the concrete ablation rate by preventing the melt from interacting with the concrete. Although the experiments did not clarify this observation, the proof for this phenomenon could be deduced from the decreased concrete ablation rate during the same period of interaction presented by the experimental results.

The simple linear linking ligand diazabicyclo[2.2.2]octane (dabco) combines with silver(I) to form three-dimensional (3D) coordination polymers which have either a zeolitic mtn topology structure or a (10,3)-b ths network according to the counteranion used. The tetrahedral anions BF4- or ReO4- promote formation of [Ag(dabco)2]·X, which has a 3D four-connected mtn framework of fused 512 and 64512 cages, and the material shows modest absorption of iodine. The bulky anion [Co(C2B9H11)2]- and an excess of dabco promote formation of complex [Ag2(dabco)3(CH3CN)2]·2[Co(C2B9H11)2] with a three-connected (10,3)-b network, while use of 1 equiv of dabco gives a previously reported [Ag(dabco)]·[Co(C2B9H11)2], which has a one-dimensional coordination chain structure. (Chemical Equation Presented).

This paper presents the variational multiscale element free Galerkin method to solve convection-diffusion-reaction equation. The equation under consideration involves a small diffusivity and a large reaction coefficient, which leads to reaction-convection dominated problem. The variational multiscale element free Galerkin method is derived based on Hughes׳s variational multiscale formulation and element free Galerkin method, thus it inherits the advantages of variational multiscale and meshless methods, meanwhile, the formulation is free of any user-defined parameters owing to the stabilization parameter arises naturally. In order to investigate the presented method, both steady and unsteady 2D convection-diffusion-reaction problems are considered, and the numerical results illustrate the proposed method has the high accuracy and stability for solving convection-diffusion-reaction equation.

A laboratory method for teaching inorganic qualitative analysis and chemical equations is described. The experiment has been designed to focus attention on cations and anions that react to form products. This leads to a logical approach to understand and write chemical equations. The procedure uses 3 mL plastic micropipettes to store and deliver the samples. All tests are performed on a plastic sheet that covers a template using one drop each of the sample and the reagent. The entire experiment consists of four parts: (i) Acid–Base Properties of Twelve Solutions, (ii) Survey of Chemical Reactions and Writing of Equations, (iii) Identification of Eight Unknown Samples, and (iv) Matching of a Set of Five Samples with their Respective Formulas. Schemes of analyses utilize the acid–base properties, the chemical reactions of cations and anions, and the solubility of compounds formed to make the identification easy. During the binary mixing of a diverse set of 12 colorless compounds, it was observed that each s...

The initial–boundary value problem for a nonlinear two-dimensional convection–diffusion–reaction equation (1) ∂ u ∂ t + ∑ α = 1 2 a α ∂ u ∂ x α = ∑ α = 1 2 ∂ ∂ x α ( k α ( u ) ∂ u ∂ x α ) + λ u , ( x , t ) ∈ Ω × ( 0 , T ] , (2) u ( x , 0 ) = u 0 ( x ) , x ∈ Ω ¯ , u | x ∈ ∂ Ω = g ( x , t ) , ( x , t ) ∈ ∂ Ω × ( 0 , T ] , is considered. The traveling-wave solutions of the problem are under special consideration. The problem is approximated by the difference scheme, which is exact for this type of solutions. Presented numerical experiments illustrate the theoretical results investigated in the paper.

Many degenerate diffusion–reaction equations permit sharp travelling wave solutions that describe the propagation of an interface with finite speed. If the equation is at least double degenerate, the derivative of the travelling wave solution can blow up at the interface, which poses considerable challenges for the computation of the travelling wave speed. We propose a numerical method for this problem that is based on the idea to approximate the multiple degenerate problem by a family of simple degenerate problems. For the latter we propose an interval-bracketing algorithm based on the theory of Sanchez-Garduno and Maini. The travelling wave speed of the original problem is obtained as the limit of the travelling wave speeds of the auxiliary problems. The performance of the method is investigated in a numerical simulation experiment for a problem that arises in the mathematical modelling of biofilm processes.

For centuries, chemists have written equations representing chemical reactions by using symbols for atoms and molecules; for example, 2H2O + 2Na → 2NaOH + H2. This short notation shows only four reacting particles, but even in a classroom demonstration where a small piece of sodium is dropped in water, the total number of reactants will be on the order of Avogadro's number (∼6 × 1023). On page 900 of this issue, Liu et al. ( 1 ) instead study a chemical reaction taking place between a minimal number of participants. In their experiment, exactly two atoms collide, absorb a photon, and form a molecule in the excited state. And this time, the reaction equation, Na + Cs → NaCs* (where the asterisk denotes an excited molecule), describes exactly the process that takes place in the laboratory.

Major efforts in the search for techniques for the development of reduced kinetic mechanisms for biodiesel have been observed, since these mechanisms may have thousands of species. This paper proposes a reduction strategy and presents the development of a reduced kinetic mechanism for piloted jet diffusion flame of methyl decanoate (MD). The strategy consists of applying the DRG, Directed Relation Graph, technique for initial reduction, and the use of Layerless Neural Network (LNN) to define the main chain and obtain a skeletal mechanism. Hence the hypotheses of steady-state and partial equilibrium are applied, and the assumptions are justified by an asymptotic analysis. The main advantage of the strategy is to reduce the work required to solve the system of chemical equations by at least two orders of magnitude for MD, since the number of species is decreased in the same order.

We setup boundary value problems (BVPs) for exponentially graded media. The BVPs are governed by a diffusion convection-reaction (DCR) equation of spatially varying coefficients (with an anisotropic diffusion coefficient). A boundary element method (BEM) is utilized to find numerical solutions to BVPs. The numerical solutions obtained verify the validity of the analysis used to derive the BEM with accurate and consistent solutions. The computation shows that the BEM procedure elapses very efficient time in producing the solutions. In addition, the results show the effect of anisotropy and inhomogeneity of the media on the solutions. To illustrate the application, an example of a layered material is presented.

A boundary element method (BEM) is utilized to find numerical solutions to boundary value problems of quadratically graded media governed by a spatially varying coefficients anisotropic-diffusion convection-reaction (DCR) equation. The variable coefficients equation is firstly transformed into a constant coefficients equation for which a boundary integral equation can be formulated. A BEM is then derived from the boundary integral equation. Some problems are considered. A FORTRAN script is developed for the computation of the solutions. The numerical solutions verify the validity of the analysis used to derive the boundary element method with accurate and consistent solutions. The computation shows that the BEM procedure elapses very efficient time in producing the solutions. In addition, results obtained for the considered examples show the effect of anisotropy and inhomogeneity of the media on the solutions. An example of a layered material is presented as an illustration of the application.

This paper is concerned with finding numerical solutions to boundary value problems (BVPs) governed by a diffusion convection-reaction (DCR) equation of in-spatial-trigonometrically varying coefficients with an anisotropic diffusion coefficient. The variable coefficients equation is firstly transformed into a constant coefficients equation. A boundary integral equation is the derived from the constant coefficients equation. Consequently, a boundary element method (BEM) is developed and utilized to find numerical solutions to the boundary value problems. For the computation of the solutions for some examples of problems, a FORTRAN script is constructed. The numerical solutions obtained verify the validity of the analysis used to derive the BEM. The results also show that the BEM procedure elapses very efficient time in producing very accurate and consistent solutions. Moreover, the results indicate the effect of anisotropy and inhomogeneity of the media on the solutions.

A novel method of order reduction is proposed to the high-dimensional convection-diffusion-reaction equation with Robin boundary condition based on the multiquadric radial basis function-generated finite difference method (MQ RBF-FD). The main motivation is to get not only a second-order accurate solution but also a second-order accurate gradient. Key to the proposed method is introducing the intermediate variables representing the first-order derivatives to reduce the original second-order problem into an equivalent system of first-order partial differential equations. Then a discrete scheme for the latter is constructed, in which MQ RBF-FD method is applied to approximate the first-order derivatives of the original variable at the center point with decoupled method. Moreover, we can obtain an equivalent discrete scheme about the original variable and intermediate variables which can be proven all second-order convergent, that is, the convergence rate of the gradient of solution is also second-order. Finally numerical examples are presented to show the efficiency and accuracy of the proposed method.

An applied electric field can enhance the photocatalytic performance of TiO2. However, there has not been a quantitative analysis of the effects of a strong electric field on various intermediates and the degradation of organic matter in the photocatalytic process under certain illumination conditions. The current work uses simulation calculations to explore the effects of an applied electric field on TiO2 photocatalysis. The multi-particle Schrödinger equation is solved by a first-principles approach, and the concentration changes of various substances on the surface of the wire under different electric fields are obtained using a step-by-step reaction equation and Fick’s law. The changes in organic matter concentration during the photocatalytic process caused by the applied electric field were analyzed. Curves of the concentrations of holes, hydroxyl radicals, and organic matter on the surface of the wire under different electric fields were obtained under various temperature and illumination conditions. At the same time, the distribution of organic matter and holes on the surface of the power wires at different times also had been obtained.

This interdisciplinary study sketches the ways in which proportional reasoning is involved in the solution of chemistry problems, more specifically, problems involving quantities in chemical reactions (commonly referred to as stoichiometry problems). By building on the expertise of both mathematics and chemistry education research, the present paper shows how the theoretical constructs in proportional reasoning in mathematics education offer rich explanatory accounts of the complexities involved in solving stoichiometry problems. Using Vergnaud's concept of measure spaces, the theoretical analysis shows that proportionality situations are relatively more intricate, involving various layers of complexity in chemistry as compared to those in the mathematics curriculum. Knowledge of proportionality and chemistry are simultaneously required to provide solutions to chemical reactions. Our analysis of a range of stoichiometry situations led us to propose a problem analysis framework involving five levels of difficulty. Further, the specificity of proportionality in stoichiometry is that it can only be established when quantities are interpreted in the unit “mole,” a unit which does not have any physical embodiment in terms of a measure of quantity unlike mass and volume. Our analysis of student-teachers' solution to the stoichiometry problems, shows that they tend to incorrectly (probably intuitively) set proportional relationships when two quantities in a reaction are expressed in non-molar quantities such as mass. The data also bring to the fore the primarily formulaic approach that student-teachers use in setting inherent proportionality relationships. An important finding is the interpretation of a chemical equation as a mathematical equation, rather than a statement of proportionality.

In this paper, fractional derivatives in the sense of modified Riemann-Liouville derivative and first integral method are applied for constructing exact solutions of nonlinear fractional generalized reaction duffing model and nonlinear fractional diffusion reaction equation with quadratic and cubic nonlinearity. Our approach provides first integrals in polynomial form with a high accuracy for two-dimensional plane autonomous systems. Exact soliton solutions are constructed through established first integrals.

In this paper we report on a novel method for solving systems of nonlinear differential equations which is an extension of the spectral homotopy analysis method (SHAM). The proposed method extends the application of the SHAM to initial value problems that model the Michaelis-Menten enzymatic reaction equation. Results from the proposed method are compared with Runge-Kutta routines as a measure of accuracy and efficiency.

The entropy of chemical language was estimated basing on Shannon’s theory of information. The alphabet of the language was defined. It contains 110 symbols of chemical elements, indices, coefficients, brackets, condition signs, and some other (a total of 166 symbols). The probabilities of the symbols were calculated using a higher school chemistry textbook. The upper bound of entropy of chemical language was estimated at 4.55 bits per symbol. The table of frequencies and self-information for the language was given, and the way to calculate the amount of information was shown.

Parabolic equations with advection, diffusion and reaction terms are used to model many physical and biological systems. In many applications the unknowns represent quantities that cannot be negative such as concentrations of chemical compounds or population sizes. Widely used schemes such as finite differences may produce negative solutions because of truncation errors and may then become unstable. We propose a new scheme that guarantees the positivity of the solutions for arbitrary step sizes. It works for reaction terms that consist of the sum of a positive function and a negative function. We develop it for one advection–diffusion reaction equation in one spatial dimension with constant velocity and diffusion and state how to generalize it. The method is applicable to both advection and diffusion dominated problems. We give some examples from different applications.

In this work is induced a new topology of solutions of chemical equations by virtue of point-set topology in an abstract stoichiometrical space. Subgenerators of this topology are the coefficients of chemical reaction. Complex chemical reactions, as those of direct reduction of hematite with a carbon, often exhibit distinct properties which can be interpreted as higher level mathematical structures. Here we used a mathematical model that exploits the stoichiometric structure, which can be seen as a topology too, to derive an algebraic picture of chemical equations. This abstract expression suggests exploring the chemical meaning of topological concept. Topological models at different levels of realism can be used to generate a large number of reaction modifications, with a particular aim to determine their general properties. The more abstract the theory is, the stronger the cognitive power is.

We examine the solution of the two-dimensional Cahn-Hilliard-reaction (CHR) equation in the xy plane as a model of Li+ intercalation into LiFePO4 material. We validate our numerical solution against the solution of the depth-averaged equation, which has been used to model intercalation in the limit of highly orthotropic diffusivity and gradient penalty tensors. We then examine the phase-change behaviour in the full CHR system as these parameters become more isotropic, and find that as the Li+ diffusivity is increased in the x direction, phase separation persists at high currents, even in small crystals with averaged coherency strain included. The resulting voltage curves decrease monotonically, which has previously been considered a hallmark of crystals that fill homogeneously.

Bioethanol is a fuel additive or a fuel substitute that has the benefit of being cleaner and price competitive with gasoline. Therefore, we develop a reduced kinetic mechanism capable of modeling the ethanol combustion and the generation of the combustion products $$\text{H}_{2}\text{O},~\text{CO}_{2},~\text{CO},~ \text{H}_{2},~ \text{C}_{2}\text{H}_{4}$$ and OH. Based on a mechanism composed by 372 reversible elementary reactions among 56 reactive species, we propose a reduction strategy to obtain an eight-step mechanism for the ethanol. The reduction strategy consists in estimating the order of magnitude of the reaction rate coefficients, defining the main chain, applying the steady-state and partial equilibrium hypotheses, and justifying the assumptions through an asymptotic analysis. The main advantage of the obtained reduced mechanism is the decrease of the work needed to solve the system of chemical equations proportionally to the number of elementary reactions present in the complete mechanism. Numerical tests are carried out for a jet diffusion flame of ethanol and the results compare well with available data in the literature.

This paper will discuss and analyze the effect of chemical reactions number on the design and performance of the industrial secondary reformer reactor. The secondary reformer reactor is a large-scale unit in the Ammonia production plants. The secondary reformer reactor operation is adjusted to achieve the required stoichiometric ratio of Nitrogen and Hydrogen necessary for ammonia production. The Carbon Dioxide Reforming reaction equation in the catalyst bed of secondary reformer reactor has been investigated for two models A and B. The comparative study between the two models is carried out relative to the same operation conditions. The two models have been checked successfully against data available in the industrial secondary reformer reactor in the State Company of Fertilizers South Region in the Basra/Iraq. The theoretical results of model A are closer to the industrial plant data than model B.

A coding scheme is presented and used to evaluate solutions of seventeen students working on twenty five stoichiometry problems in a think-aloud protocol. The stoichiometry problems are evaluated as a series of sub-problems (e.g., empirical formulas, mass percent, or balancing chemical equations), and the coding scheme was used to categorize each sub-problem solution as successful, neutral, or unsuccessful, with more detailed codes comprising the neutral and unsuccessful categories, for a total of eight codes. A relatively high frequency of neutral results was found in which students simply did not realize when or how to approach a sub-problem. A lack of conceptual understanding of the mole concept appears to be closely related to students skipping crucial steps in stoichiometry problems, especially the sub-problems stoichiometric ratio and mole concept. Students' failures were also observed to be due to a lack of basic knowledge, such as the names of chemical compounds. The application of the new code system was shown to reveal difficulties that might have otherwise been missed by an analysis that focused on end results only.

In-situ fabrication of TiB ceramic coating by laser cladding technology (LC) was investigated. Pulsed YAG laser with the power of 500 W was used. The mixture of Titanium powder (with the size of 20 m) and B powder (with the size of 140 m) were utilized as the precursor. The reactive transformation mechanism and phase constituents of the in-situ fabricating coating during the laser cladding process were studied by thermodynamics analysis, as well as XRD methods. Gibbs free energy theory was used to calculate the increment of Gibbs free energy at different temperature. The results show that the increment of the Gibbs free energy for the reaction equation to the in-situ fabricate TiB2 keep to be negative within the temperature of 3000K, this indicate that TiB2 can be obtained by laser cladding the mixture powder of Ti and B. XRD results show that the main phases of the coating are TiB2, TiO2 and B2O3 with relative percentage of 67.6%, 18.0% and 14.4%, respectively.

PDF format of scanned document images is not searchable. OCR tries to remedy this adversity by converting document images into editable and searchable data, but it has its own limitations in presence of equations - both mathematical and chemical. OCR system for mathematical equation is already a major research area and has provided successful result. However, chemical equation segmentation has been a less ventured road. In this paper, we present a novel method for automated generation of searchable PDF format of segmented chemical equations from scanned document images by performing chemical symbol recognition and auto-correction of OCR output. We use existing OCR system, pattern recognition technique, contextual data analysis and a standard LaTeX package to generate the chemical equation in searchable PDF format. The effectiveness of the proposed method is verified through exhaustive testing on 234 document images.

Multi-threading in Java enhances computational performance and facilitates the development of parallel software. To obtain high performance on multi-core systems, this study develops a multi-threaded simulation code using Java for the chemical reacting flow of ethanol. Three ethanol reaction models were implemented in this code to investigate the effects of multi-threaded processing on three multi-core CPUs. The computational load for the chemical reaction significantly increases with the number of chemical equations and high temperature portion of the domain. To enhance parallel performance, the domain in which the chemical reaction occurs is appropriately decomposed at each time step, resulting in improved parallel performance.