Semi-empirical approach to modeling of soil flushing: model development, application to soil polluted by zinc and copper

This paper describes a semi-empirical approach to modeling the soil flushing technology. A new mathematical model aimed at predicting the course of the continuous soil flushing process by use of the input data obtained from simple batch laboratory experiments is described in the theoretical part. An objective of the study is to apply this new model to soil polluted by zinc and copper (11949 mg kg(-1) and 1895 mg kg(-1), respectively) by flushing the soil with an ammonia nitrogen solution. A set of batch experiments provided both equilibrium and kinetic data characterizing the leaching ability of both metals. By use of the model, the optimal ammonia concentration in the flushing solution was estimated (0.6 mol L(-1)). For this concentration, validity of the model results was verified by a column experiment. The removal efficiency obtained was 44% (zinc) and 54% (copper). The model correctly predicted the period of time needed for the removal of weakly bound metal fractions as well as the estimate of the overall removal efficiency of metals from the soil during the flushing process. It has also proven that it is possible to use the column experiment for model calibration through the modification of the input data. Agreement of the model and experimental results can be further improved this way.     

Tax optimization in an agent-based model of real-time spectrum secondary market

The wireless communication industry is an essential sector boosting economic progress worldwide. The structure of the legacy wireless communication market, characterised by static licensing schemes, is moving towards real-time secondary spectrum markets. While the technological body of spectrum trading has been discussed in detail, from an economic perspectives there are still a lot of gaps in understanding how these transactions affect the economy of future communication standards. A challenging aspect of the real-time spectrum market deployment is the implementation of the appropriate tax system that impacts the market structure. With regards to this, we aim to build an agent-based model of the real-time secondary spectrum market in which various taxes including value-added tax, corporate tax, consumption tax and fixed tax, are employed. The relations between selected tax type rates and the hypothetical revenue of the national regulator is established using Laffer curves. The results of the analysis confirm the existence of a tax distortion, i.e. a system deviation from the efficient system functioning affected by the tax introduction. To measure the complexity of the tax strategies and the emergent tax distortion, an original approach based on Euclidean metrics defined over a vector space of the system performance indicators was proposed. This approach was later applied in parallel with the traditional Harberger’s triangle methodology. We found that the constrained optimisation with the tax distortion restrictions provide satisfactory results regarding the stability of the tax distortion measure. Therefore, we propose the application of the most effective corporate tax optimisation complemented by selected additional tax types.     

SU(1,1) Squeezing of SU(1,1) Generalized Coherent States

Abstract

In this paper we have introduced a new class of the SU(1,1) coherent states which are the eigenstates of the generalized annihilation operator K_. We have also studied the SU(1,1) squeezing of the SU(1,1) generalized coherent states interacting with a nonlinear medium modelled as an anharmonic oscillator.     

Intensification of 1‐phenylethanol production by periodical membrane extraction of the product from fermentation broth

BACKGROUND: Enantioselective bioreduction of acetophenone to S‐(?)‐1‐phenylethanol by Saccharomyces cerevisiae under non‐growth conditions is inhibited by the product created. This study investigated the possibility of intensification and mathematical simulation of 1‐phenylethanol production using periodic product removal carried out by membrane extraction in a hollow fiber membrane module. RESULTS: The highest reaction rate was observed at the beginning of the biotransformation. With increased product concentration in the reaction medium, the reaction rate gradually decreased by about 50% after 20 h of biotransformation. The low concentration of product maintained in the reaction medium using membrane extraction had positive influence on the 1‐phenylethanol production with a high yield (96%) and mean reaction rate of 0.226 mg h^?1g^?1, 35% higher than biotransformation without product removal. The equilibrium change and membrane fouling caused by biomass were not significant. It was possible to mathematically simulate the whole course of the extractive biotransformation with good agreement with experimental data. CONCLUSION: Bioreductive production of 1‐phenylethanol is more effective when using periodic membrane extraction of the product from the fermentation broth, which gives higher reaction rate, higher yield and simpler downstream process than biotransformation without product removal. Copyright © 2012 Society of Chemical Industry     

Corrosion behaviour of Ni-based superalloys in molten FLiNaK salts

High-temperature corrosion tests of alloys, Nimonic 80A, Inconel 718 and Inconel C-276, were investigated at 680°C in molten alkali fluoride salt (LiF–NaF–KF: 46.5–11.5–42%) environment. In this work, techniques included were weight loss measurements and potentiodynamic polarisation curves measurements. Inconel C-276 and Inconel 718 showed better corrosion resistance, while Nimonic 80A exhibited comparatively lower corrosion resistance. The high-temperature corrosion behaviour was observed using measurements of the oxide morphology and thickness. The corrosion rates were determined by recording the weight changes of the sample alloys at different time intervals. Microstructural examination showed the depletion of Cr near the surface of the alloys and hence the significant weight loss in the early stages of corrosion tests. The corrosion mechanism of the alloys is discussed in detail.     

Functionalization of polylactic acid through direct melt polycondensation in the presence of tricarboxylic acid

The goal of the article was to describe the preparation of carboxyl‐functionalized polylactic acid (PLA) through the method of direct melt copolycondensation of lactic and citric acid (CA). In addition, detailed study of copolycondensation process, its limitations and investigation of the reaction products properties are another issue this article deals with. The effect of tricarboxylic CA on the resulting properties of the functionalized lactic acid (LA) polycondesates was studied in a wide range of LA/CA molar ratios. The influence of CA on molecular weight, thermal and physicochemical properties, and chemical structure of the products was investigated, using viscometric measurements of the polymer solutions, gel permeation chromatography, ¹H nuclear magnetic resonance spectroscopy, differential scanning calorimetry, acidity number determination, and Fourier‐transform infrared and ultraviolet spectroscopy. The results show the significant effect of CA on the structure and physicochemical properties as well as high efficiency of functionalization. Furthermore, a branched structure was detected at low CA concentrations, while higher CA content leads to termination of the polycondensates chains by citryl units and a reduction in the molecular weight. Here, insights on the characterization methods of PLA‐based materials are given by various experimental techniques. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

The Influence of Vanadium Microalloying on Voids Occurence in Low-Alloyed Cr-Mo Steels After Continuous Casting

We discuss the correlation between segregation of carbide forming elements (vanadium) and void initiation and propagation in low-alloyed Cr-Mo steels. The internal defects are created during blooms straightening in radial type of casting machine due to strain deformation field in the temperature range characteristic for vanadium nitride, carbide or carbonitride precipitation. Based on the statistical analysis (1097 continuously cast blooms) of three low-alloyed Cr-Mo steel variants with different vanadium content, we conclude that the void occurence is strongly associated with the level of vanadium content. The experiments performed by means of microstructural, fractographic investigations and microchemical point analysis proved that preffered areas for void initiation are interdendritic segregations in the core of bloom. We observed vanadium carbide precipitates that are situated close to the cracks, whereas the content of vanadium was 7,5 times more then in an average smelt composition. The further development of defects is connected with fast heating up to the austenization temperature in soaking pit. Our results confirm that marked decrease of defects can be achieved by optimization of production process, i. e. optimized casting speed, steel overheat above the liquidus temperature and/or application of M-EMS.     

Replacement of traditional emulsifying salts by selected hydrocolloids in processed cheese production

Different hydrocolloids were examined as possible replacements for traditional phosphate- and citrate-based emulsifying salts in processed cheese production. The following hydrocolloids (at concentrations in the final product of ≤1.0%, w/w) were chosen: modified starch (with bound sodium octenyl succinate), low methoxyl pectin (alone or combined with lecithin), locust bean gum, κ-carrageenan and ι-carrageenan. The products were assessed by sensory analysis, microscopic image analysis and dynamic oscillatory rheometry. Modified starch, locust bean gum and low methoxyl pectin could not be recommended as replacements for traditional emulsifying salts. Model processed cheeses without traditional emulsifying salts of 40% (w/w) dry matter and 55% (w/w) fat-in-dry matter containing 1.0% (w/w) κ-carrageenan or ι-carrageenan were found to be homogeneous, however the products were hard with fracturable texture.     

N-level Atom Interacting with Single-mode Radiation Field: An Exactly Solvable Model with Multiphoton Transitions and Intensity-dependent Coupling

Abstract

We study the dynamics of an N-level atom coupled in a lossless cavity to a single-mode near-resonant quantized field. The atomic levels are coupled by the multiphoton transitions and the coupling constants between the field and the atomic levels are supposed to be intensity dependent. We find the exact solution for the state vector describing the dynamics of the atom-plus-field system. As an illustration we use the model for studying (i) the time evolution of the atomic occupation probability with the initially coherent field and (ii) the light squeezing, when the cavity field is initially in the vacuum state and the atom is prepared in the atomic ‘coherent state’ (a superposition of atomic states).     

Thermal Noise and Hydrodynamic Memory Effects on Force Measurements at Microscales

The paper is devoted to the problem of the determination of regular forces acting on microscopic and smaller objects in fluids when the presence of thermal noise affects the results of measurements. One of the methods on how these forces are determined is the measurement of the drift velocity of Brownian particles. Traditionally such experiments are interpreted on the basis of the overdamped Langevin equation. An exact expression has been obtained for this velocity within the linear hydrodynamic theory of the Brownian motion in incompressible fluids, when the external force is constant and when the particle is in a harmonic potential well. It is shown that for sufficiently short experimental times the influence of the hydrodynamic memory effects in the drift velocity determination is significant. The obtained solutions contain algebraic long-time tails due to which the results expected from the standard theory are approached very slowly with the increase of time.