Cheap and Tight Bounds on the Solution Set of Perturbed Systems of Nonlinear Equations

This paper presents an iterative method for computing an outer interval bound on the solution set of parameters-dependent systems of non-linear equations for the case where the parameters take on their values within present intervals. The method is based on a recently suggested alternative linear interval enclosure of factorable non-linear functions in a given box. It comprises two stages: during the first stage, a relatively narrow starting box is determined using an appropriate inflation technique while the second stage aims at reducing the width of the starting box. Two algorithms implementing the method have been programmed in a C++ environment. Numerical examples seem to indicate that the second algorithm is rather efficient computation-wise. The method is self-validating: the fulfillment of a simple inclusion rule checked during its second stage ensures that the interval bound thus found is an outer approximation to the solution set of the perturbed system investigated. This revised version was published online in August 2006 with corrections to the Cover Date.     

Assessment of the antioxidant potential of selected plant extracts – In vitro and in vivo experiments on pork

The antioxidant potential of selected plant extracts was assessed in vitro and in vivo experiments on pork. In the in vitro experiment, the anti-oxidative capacity of ethanol–water extract of Melissa officinalis (MW), ethanol–propylene–glycol extracts of M. officinalis (MP), Origanum vulgaris (O) and Salvia officinalis (S) at different dilutions was analysed. Furthermore a 2% essential oil concentrate was added to Origanum (OSi) and Salvia (SSi). In the two in vivo experiments in total 104 Slovak White Meaty pigs were fed with plant extracts (MW and O) at different doses with/without additional vitamin E.     

Evaluation of different clay minerals as additives for soil water repellency alleviation

The objective of this study was to evaluate the effectiveness of kaolinite, illite, Na- and Ca-montmorillonite in alleviating water repellency for a simple model soil material of known composition before and after wetting and drying phases. Sand was rendered water repellent by adding 10 and 30 g kg^− 1 stearic acid followed by adding different amounts (1, 2 and 3 mass %) of respective clays. Treated and untreated control sand were wetted and exposed to prolonged drying phase at 50 °C to simulate the effects of wetting followed by drying under a hot spell. The persistence of water repellency was measured with the water drop penetration time (WDPT) test. During the wetting/drying cycle, the control samples (stearic acid treated sand) and clay treated sands behaved in a fashion typically observed in water repellent soils: they were wettable above and water repellent below a critical water content, with repellency persistence (WDPT) increasing with decreasing water content. Kaolinite and Na-montmorillonite were found to be the only clay minerals able to lower the persistence of repellency of the stearic acid sand. The difference between Ca- and Na-montmorillonite ability to alleviate water repellency is explained by the differences in inter-particle forces in the clay–exchangeable cation–water system. During the prolonged drying phase at 50 °C, the persistence of water repellency increased with the duration of heating at 50 °C, with the increase being greatest during the first 48 h in the majority of the samples. While kaolinite and Na-montmorillonite addition resulted in a reduction in the persistence of water repellency of the stearic acid sand, Ca-montmorillonite and illite addition increased the persistence of water repellency of the stearic acid sand. The net effect of clay mineral addition is dependent on the amount of Ca²⁺ ions occurring at the surface of clay minerals. Pools of available (exchangeable) calcium decrease in the order as follows: Ca-montmorillonite >> illite >> Na-montmorillonite ≈ kaolinite.     

Comprehensive Performance Analysis of Lightweight Mesh and Its Comparison with ZigBee Pro Technology

As there is a rising demand on energy efficiency the proper network stack is an essential for every wireless sensor network application. This paper gives a comprehensive view on performance comparison of \(\hbox {Atmel}^{\circledR }\) Lightweight Mesh (LWM) and ZigBee Pro technology based on extensive real measurements. We focused mainly on application layer throughput, routing latency and self-healing capability. Although the LWM clearly outperforms ZigBee Pro in most aspects, the LWM has particular drawbacks. Particularly, the LWM provides smaller footprint and faster stack processing along with higher application throughput. The most notable throughput difference where the LWM outperforms the BitCloud was by as much as thirteen times.     

Experimental and computational study of morphological and electrical properties of tin/plasma polymer nanocomposites

Composite tin/n-hexane plasma polymer films were prepared by means of RF magnetron sputtering of tin target in Ar:n-hexane mixture and characterised by various analytical techniques. Their chemical composition was examined by XPS, current-voltage characteristics were measured, and their structure was investigated by conventional TEM and electron tomography. The acquired three-dimensional reconstructions were morphologically analysed by a self-made computer analytical tool, which estimated the mean form factor and the average effective radius of the reconstructed metal inclusions.     

Nanohydroxyapatite prepared from non-toxic organic Ca2+ compounds by precipitation in aqueous solution

Nanocrystalline hydroxyapatites were prepared by the precipitation method using a water soluble Ca²⁺ organic compounds and (NH₄)₂HPO₄. The fine nanohydroxyapatites had spherical, needle-like or mixed morphology and specific areas around 150 m²/g. The nanocrystalline powders differed by thermal stability and they were transformed to bi- or three-phasic systems with hydroxyapatite, βTCP and αTCP phases after annealing at 1000 °C.     

A numerical method for calculation of transients in electric circuits

 The present paper describes a numerical method for calculation of transients in electric circuits,using a step by step approach.For a small interval of time △t=const,for each branch j of circuit one calculates α_j=R_j+L_j/△t+△t/C_j,β_j=R_j+△t/C_j and θ=△t/C_j.After that,for each interval △t the current increments △i_(jk),the currents i_(jk)=i_(jk-1)+△i_(jk)and the capacitor\'s voltage u_(cjk)=u_(cjk-1)+Au_(cjk)are calculated. The values of △i_(jk)are the roots of a system of simultaneous linear equations.The results of numerical calculation of transients by the proposed method do not differ from those obtained by analytical ones.The proposed method can be applied to a large number of problems in electrical engineering.A similar approach can be used for the calculation of transients in non-linear electric circuits and in other engineering disciplines(mechanics,thermodynamics,hydraulics etc.).Several numerical examples show how the pro- posed method can be applied.     

Acid dissolution of mineral matrix in Green River oil shale

The mineral matrix in Green River oil shale was partially removed by treatment with dilute HCl. The major ionic species in the solution from acid treatment (AT) were identified as Na⁺, Al³⁺, Fe²⁺, Mg²⁺, and Ca²⁺. The ion yields expected from reaction stochiometry, gravimetric analyses and comparison of calculated CO₂ yields with measured levels were consistent with the fact that Na⁺ and Al³⁺ originated primarily from analcite: Fe²⁺ and Mg²⁺ from dolomitic ankerite and Ca²⁺ from both dolomitic ankerite and calcite. Temperature and shale particle size were important parameters in the efficacy of AT. An increase in temperature and a decrease in particle size increased the rate of mineral dissolution. Fe²⁺ showed an anomalous trend in that the rate initially declined with increasing temperature after which it showed the usual increase with temperature. The kinetics of ion build-up in the solution from AT were analysed in detail for the case of Al³⁺. The Arrhenius expression was found to be valid only for finer particle sizes (e.g., ?35, +45 US mesh shale). A simple model is finally presented to account for the combined effect of temperature and shale particle size on mineral dissolution rates.     

Acoustic wave propagation in oil shale: 2. Modelling

Experimental data on acoustic wave propagation through oil shale, summarized in a previous paper¹, were used to develop a semi-empirical model. This model predicts the variation of pressure, effective compressional wave velocity, effective density and acoustic impedance with depth for a modified in-situ oil shale retort. Results from computer simulation of a variety of retort conditions establish the possibility of employing seismic propagation and reflection techniques for mapping of pyrolysis fronts in in-situ oil shale process beds. Such techniques are potentially free from uncertainties associated with proximate sensing of temperature profiles in these beds.