Vapour liquid equilibrium with association in both phases: A model with the concentration-dependent liquid phase association constant applied to acetic acid—benzene, -toluene, -p- and -o-xylene

A model employing the correction factors of Marek and Standart, but using a concentration-dependent liquid phase association factor of Jenkins—Robinson, has been used to model vapour—liquid equilibrium data for mixtures of acetic acid with benzene, toluene, o-xylene and p-xylene. With the aim to use systems of acetic acid—benzene and acetic acid—toluene as the test mixtures for distillation columns, the examination of the systems of acetic acid—aromatic hydrocarbons was undertaken. The model promises to be useful in modelling isobaric and isothermal data of acetic acid—benzine, acetic acid—toluene, acetic acid-p-xylene and acetic acid-o-xylene systems. Deviation plots show that the isothermal and isobaric data are represented well.     

SDR receiver computational model for application in power control

Software-defined radio (SDR) permits dynamic switches of the employed radio access technology (RAT), over-the-air (OTA) software updates, software and hardware reuse. This extended flexibility comes at the price of a higher computing complexity and, in particular, the energy consumption at the receiver. The analysis of the computational profile of signal processing algorithms is of great importance in SDR for understanding the implication on the energy consumption. Several signal processing algorithms show a different profile as a function of the signal quality perceived at the receiver antenna. Therefore, power control policies have an implication on the computational performance of SDR receivers. Understanding the behaviour of these algorithms allows trading transmitted power against receiver energy consumption. This paper presents a model for characterizing the computational profile of Turbo and LDPC decoders and demonstrates is applicability in existing power control strategies.     

An initial study on feasible treatment of Serbian lignite through utilization of low-rank coal upgrading technologies

Despite benefiting from vast fuel reserves, combustion of low-rank coals is commonly characterized by low thermal efficiency and high pollutant emissions, partly due to high moisture content of the coals in question. Thus, removal of moisture from low-rank coals is deemed an important quality upgrading method. The paper provides an overview of the current status of low-rank coal upgrading technologies, particularly with respect to utilization of drying and dewatering procedures. In order to examine the influence of relevant parameters on the moisture removal process, a model of convective coal drying in a packed, as well as in a fluid bed combustion arrangement, is developed and presented. Product-specific data (intraparticle mass transfer, gas–solid moisture equilibrium) related to the coal variety addressed herein (lignite) are obtained through preliminary investigations. Effective thermal conductivity of the packed bed as defined by Zehner/Bauer/Schlünder is used to define heat transfer mechanisms occurring in the packed bed. Similar two-phase fluidization model has been validated for different types of biomaterials.     

Structural and spectroelectrochemical (UV–vis and IR) studies of nanocrystalline sol–gel derived TiO2 films

Nanocrystalline TiO₂ films with a high surface roughness were prepared by the sol–gel route from titanium (IV) iso-propoxide and brij 56 surfactant. XRD and TEM showed that the films consisted predominantly of anatase nanoparticles embedded in an amorphous phase. Addition of the surfactant significantly increased the intensity of the surface hydroxyl modes between 3600 and 3750 cm⁻¹ in IR spectra. Spectroelectrochemical measurements of the films in 0.1 M LiOH electrolyte revealed optical modulation beyond 70%T. Slow-scan cyclovoltammetry showed that bleaching occurred in two steps, suggested to correspond to anatase and amorphous phase. The changes that occur during intercalation and deintercalation were followed by ex-situ IR transmission measurements in the regions of Ti–O, carbonate and surface hydroxyl bands.     

Effect of the organic–inorganic template ICS-PPG on sol–gel deposited V2O5 electrochromic thin film

We produced V₂O₅ thin films with sol–gel technique, using in the synthesis as a template agent, the so-called ICS-PPG. We studied the electrochromic behaviour of thin films with electrochemical techniques as slow scan cyclic voltammetry and cyclic voltammetry (SSCV, CV), impedance spectroscopy (EIS) and potentiostatic intermittent titration (PITT). Moreover, we measured transmittance spectra, optical bandgap of the material and, with the help of transmission electron microscopy (TEM), we found out informations about films structure. The addition of ICS-PPG produces more transparent samples in comparison with samples prepared without template agent. The ion storage capacity is only slightly increased and, with ageing, some deposits appear on the surface limiting the electrochemical performances.     

Solar absorber coatings based on CoCuMnOx spinels prepared via the sol–gel process: structural and optical properties

Titanium-doped and undoped CuCoMnO_x spinel films were deposited on Al substrates from sols which were made from the following: Co-acetate, Cu-chloride and Mn-acetate (Ti:CoCuMnO_x-I); and Co-acetate, Cu-nitrate and Mn-acetate (CoCuMnO_x-II). The precursors’ ratio Co:Cu:Mn was equal to 1:3:3. The solar absorptance (α_s) and the thermal emittance (_T) of the films, which were annealed at 450°C for 15 or 30 min, were determined from the corresponding diffuse reflectance spectra in the 0.32–20 μm range. The results show that the CoCuMnO_x-II films with SiO_x protective over-coatings exhibited values of α_s=0.85–0.91 and _T below 0.036 after just a single dipping/annealing cycle.The structure of the films was studied with X-ray diffraction (XRD), infrared (IR) absorbance and near-grazing incidence angle (NGIA) reflection-absorption spectroscopy. Our results suggested that the films have a spinel structure with the composition CoCuMnO_x. The stability of the films was tested by soaking them in boiling water for 2 h. NGIA IR spectra of the treated films confirmed the formation of the hydrated mixed oxide (Mn-, Co-, Cu-) phases. To improve the stability of the films two kinds of protective over-coatings were tested: one over-coating was based on polysiloxane resin and the other on high-density silica (T-resin). Films that were resistant to boiling water were obtained by applying the high-density silica protective over-coating, which was cured at 140°C for 30 min.     

Molecular evidence for increased hematopoietic proliferation in the spleen of the b/b laboratory rat

The splenomegaly and the appearance of a significant number of CFU-E (erythroid colony-forming units) and BFU-E1 (erythroid burst-forming units) in the Belgrade laboratory rat (b/b) spleen prompted us to analyse further the molecular evidence for increased hematopoietic proliferation in the b/b spleen. Messenger RNAs (mRNAs) specific for globins, proteins for iron transport and deposition and the band 3 protein were used in rat erythropoietic tissues as markers for proliferation and erythroid differentiation. In the b/b spleen, all mRNAs analysed display an erythroid-specific pattern of expression. This analysis also revealed an enhanced level of mRNA for ferritin in the +/b spleen, whereas erythrocyte-specific mRNA production was normal.     

Characterization of interaction effects between ductile tearing and intense fatigue cycling

The objective of this work was to develop an initial understanding of interaction effects which occur during complex loading in the elastic-plastic regime. A simple superposition model is presented for the accumulation of crack extension from ductile tearing and intense elastic-plastic cycling. Baseline cyclic data and baseline J based resistance curve data was developed for an HSLA steel using compact specimen geometries. Then a series of specimens were tested with alternate ductile tear and intense cyclic loadings.Conclusions from the analysis of these specimens were that the cyclic crack growth rate resulting from the intense cyclic intervals is only slightly elevated by the presence of ductile tearing load steps and is very constant over cyclic growth periods of 1 mm extent showing little acceleration or decceleration due to the ductile tearing step. Also demonstrated was that the ductile tearing resistance as measured by the J integral is almost unaffected by periods of intense cyclic loading if the R ratio is small and is inceased as the R ratio approaches 0.5. Both measured effects would lead to conservative results if the simple superposition model was used to predict the plastic cycling punctuated by occasional ductile tearing steps.

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Résumé Le but du travail était de développer une compréhension de base des effets d'interaction qui se produisent au cours d'une sollicitation complexe dans le régime élasto-plastique. On présente un modèle de superposition simple représentant l'accumulation de l'extension de la fissure à partir d'un arrachement ductile et d'alternances élasto-plastiques sévères. On développe les données cycliques minimales et les données minimales de la courbe de résistance basée sur J, dans le cas d'un acier à haute résistance faiblement allié, à l'aide d'éprouvettes de traction compactes. Une série d'éprouvettes est ensuite soumise à arrachement ductile alterné et à des sollicitations cycliques intenses.De l'analyse des éprouvettes, on conclut que la croissance cyclique de la fissure, résultant des intervales d'alternances sévères n'est que peu éprouvée par la présence de ressauts de la charge d'arrachement ductile, et est très uniforme sur des périodes de croissance cyclique de l'ordre de 1 mm d'étendue, ne faisant état que de peu d'accélération ou de décélération lors d'un ressaut d'arrachement ductile. On démontre également que la résistance à l'arrachement ductile mesurée par l'intégrale J n'est pas du tout affectée par des périodes de cyclage intense, si le rapport R est faible, et qu'elle croît lorsque R se rapproche de 0,5. Ces deux effects mesurés conduiraient à des résultats conservatifs si le modèle de superposition simple était utilisé pour prédire la croissance d'une fissure correspondant à une histoire de la mise en charge qui serait constituée par un cyclage élasto-plastique intense accompagné par des ressauts d'arrachement ductile occasionnels.

     

An X-ray photoelectron study of the (Ca2.5Th0.5)Zr2Fe3O12, (Ca1.5GdTh0.5)(ZrFe)Fe3O12, and (Ca2.5Ce0.5)Zr2Fe3O12 ceramics with a garnet structure

X-ray photoelectron spectroscopy (XPS) was for the first time applied to examination of the (Ca_2.5Th_0.5)Zr₂Fe₃O₁₂ (I), (Ca_1.5GdTh_0.5)(ZrFe)Fe₃O₁₂ (II), and (Ca_2.5Ce_0.5)Zr₂Fe₃O₁₂ (III) ceramics with a garnet structure. The component ratio in the initial charge was set so as to obtain phases with a garnet structure, promising as matrices for immobilization of long-lived actinides. Gadolinium was introduced as a neutron absorber and a simulator of trivalent actinides, Am and Cm. Ceramics I and III are comprised primarily of a phase with a garnet structure and contain a small amount of oxides with the perovskite and fluorite structures; ceramics II consists entirely of a phase with a garnet structure. The oxidation states of the metal ions in the ceramics, as well as the Me-O interatomic distances in the phase structure, were determined by XPS. To this end, both traditional characteristics (line intensities and energy positions) of the X-ray photoelectron spectra of inner electrons and the fine-structure characteristics of the spectra of the valence and inner electrons were used. A change of the composition of the surface of ceramics II and III upon treatment with 0.01 HCl solution at 150°C and the saturated vapor pressure for 30 days was examined.     

Development of Al-base lubricating grease thickeners

In this paper are presented the results of work on the development of poly-oxo–aluminium acylates that are dissolved in synthetic lubricants, polyalphaolefins (PAOs) andpolyisobutenes (PIBs), and one pharmaceutical mineral oil in order to produce a range of greases that can be food-grade, and have chemical stability. The method of synthesis is described, together with the results using different base oils (two different PAOs, four different polybutenes, and a pharmaceutical grade IS0 VG 46 white mineral oil. These greases are characterised here in terms of their mechanical stability and physical properties. As well as being of food grade, these greases are also shown to be chemically stable.