Geometrical aspects of optimum truss like structures for three-force problem

In this paper, similarities between three-force and three-point non-smooth optimization problems are highlighted. Starting from geometrical rules controlling discrete optimum solutions for three-point problems a reasonable hypothesis is created for similar geometrical rules to control discrete optimum structures for three-force problems. The hypothesis is confirmed through a numerical approach. A step-by-step method to graphically obtain a discrete optimum structure for any set of three balanced forces is provided. It is shown that discrete optimum structures with large number of elements converge to the known continuum optimum solutions in the literature.     

Robust nonlinear position-flux zero-bias control for uncertain AMB system

This paper presents a robust nonlinear control law that combines a parametric uncertainty of the single one-degree-of-freedom active magnetic bearing (AMB) system with disturbance. The robust nonlinear feedback tool such as control Lyapunov function (CLF) and robust stability techniques are developed. The control objective is to globally stabilise the mass position of an AMB with flux feedback. The flux-based control model for an AMB system is derived due to voltage switching strategy with voltage saturation. This strategy enables the flux control under a zero-bias or low-bias flux operation. In the zero-bias control, only one electromagnet in each axis of the AMB is active at any given time, depending on the rotor displacement. The proposed robust nonlinear CLF with a zero-bias for an uncertain AMB system can achieve a dynamic performance superior to that of a linear controller with the zero-bias or with the classical bias operations.     

Purification of Commercially Available β-Sitosterol via Chemical Synthesis

β-Sitosterol, a plant sterol, is found to be useful in the nutraceutical and pharmaceutical industries, but is also frequently employed in biological research. In addition to stigmasterol, phytosterols are available as mixtures, and it is challenging to obtain highly pure β-sitosterol in larger quantities. Two methods for the purification of β-sitosterol from commercially available phytosterols are presented. Both methods are based on increasing the polarity by either epoxidation or dihydroxylation reactions with the Δ^5–6 double bond of the sterol. The synthesis methods and purification are chosen to be simple with inexpensive and easily obtained reagents and equipment in the laboratory. The purifications described afford β-sitosterol in gram quantities with high purity (>95%) at 37–39% and 32% yields for epoxidation and dihydroxylation reactions, respectively. The highly pure β-sitosterol is only available in small quantities, which makes it expensive. The presented methods can be used for obtaining the pure β-sitosterol in large scale using relatively simple organic chemistry and preparative chromatography. The use of the method may significantly increase the quantity available, which causes a reduction in price and, consequently, increases the number of research and applications available with the use of β-sitosterol.     

Thermo-mechanical and mechanical behavior of hybrid isotactic polypropylene glass fiber reinforced composites (GFRC) modified with calcium carbonate (CaCO3)

The study investigates the thermo-mechanical properties of isotactic polypropylene (iPP) hybrid composites in reference to various amounts of particle- and fiber-shaped inorganic fillers. Three grades of hybrid composites were prepared as a function of filler amount: 5, 10, and 20 wt% and different ratios of glass fiber (GF) and calcium carbonate (CaCO₃). The main objective is to describe the relationship between the hybridization efficiency and mechanical performance of polypropylene-based composites. The analysis of the thermo-mechanical properties of the composites shows that both the total amount of the filler and the ratio of GF and CaCO₃ clearly influence the properties of the composites. Hybrid composites with the highest amount of the GF display improved thermo-mechanical stability. The presence of well-dispersed CaCO₃ in the composites was found to improve elongation at break and Vicat softening temperature values. Even though it is glass fiber, which shows higher filler effectiveness and visibly reinforces the composite samples, causing an increase in tensile strength or reinforcing efficiency, replacing up to 50% of this filler with calcium carbonate does not result in a considerable deterioration of the properties of the material.     

Chemical Composition and Oxidative Stability of Selected Plant Oils

Scientific data on the oxidative stability of borage oil, Camelina sativa oil, linseed oil, evening primrose oil and pumpkin seed oil are scarce. Chemiluminescence (CL) methods most commonly used to determine the oxidative stability of oils include measurement of hydroperoxide, intensity of light emitted during the accelerated oxidation process performed at high (>100 °C) temperatures or assisted by forced flow of air/oxygen through the sample. The aim of this study was to investigate the chemical composition and oxidative stability of selected vegetable oils available on the Polish market. Oxidative stability was determined using a fast, novel chemiluminescence-based method, in which light emitted during oxidation process conducted at 70 °C in the presence of some catalyzing Fe²⁺ ions is measured. A reaction of the applied type has not been reported so far. High contents of tocopherols and phytosterols were found in the analyzed oil samples. Oxidative stability of the samples was in most cases higher than the stability of refined rapeseed oil, a relatively stable substance from the oxidation point of view.     

Chemical Stability of the Lipid Phase in Concentrated Beverage Emulsions Colored with Natural β-Carotene

The aim of this study was to examine the oxidation of selected plant oils in concentrated beverage emulsions colored with natural β-carotene. Carotenoid preparations obtained from carrots were dissolved in cold-pressed linseed oil, refined canola oil, and refined palm olein. Oxidative stability of the lipids was examined with and without addition of the pigment to the oil/water (O/W) emulsion. Carotenoid/lipid hydro peroxide (LOOH) concentration was evaluated using two different methods: LOOH + Fe²⁺ reaction connected with a colored complex of ammonium thiocyanate determined with the help of a spectrophotometer, and LOOH determined with the help of a chemiluminometer. It was shown that oxidation rate of lipids in the O/W emulsions strongly depended on chemical composition of the lipid fraction (type of oil used). Presence of the carotenoid pigment increased the rate. Therefore, if a carotenoid-containing emulsion is to be stable, it should be based on oils of a high oxidative stability.     

Oxidative Stability of Lipids by Means of EPR Spectroscopy and Chemiluminescence

The aim of this study was to investigate the oxidation of selected vegetable oils (CLSO, CCSO, CBO) at accelerated oxidation rates. Several seldom used analytical methods were applied including electron paramagnetic resonance (EPR), spin trapping with α-(4-pyridyl-1-oxide)-N-tert-butylnitrone (POBN) and 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), Fe²⁺-induced chemiluminescence, Rancimat tests, and the determination of conjugated diens at λ = 233 nm. The antioxidative properties of POBN and DMPO were also investigated. The time required for each method was determined. EPR spectrometry of trapped radicals generated during oxidation turned out to be the fastest method to determine oxidative stability. Chemiluminometric determination of oxidation kinetics showed that POBN has a very strong anti-oxidative potential: it significantly (by 160–277%) lengthened the time to the chemiluminescence peak, as well as the induction time in the Rancimat test (by 110–140%). Photo-oxidation studies showed that superoxide anion radicals are the main factor responsible for the oxidation of lipids in the investigated oils.     

Properties and potential applications of zeolitic materials produced from fly ash using simple method of synthesis

Very low energy-consuming procedure is proposed for synthesis of zeolitic materials from fly ash. Three different zeolite materials (X, P and S), rich in zeolite phases, Na-X (FAU), NaP1 (GIS) and sodalite (SOD) were produced from F-class fly ash, using NaOH and NaCl solutions under atmospheric pressure at temperature below 110 °C.Obtained zeolitic products were analysed for their composition and physicochemical properties then compared to the raw fly ash and commercial adsorbents. The zeolitization results in a significant increase of CEC (from 5.5 up to 239 meq 100 g^− 1), and the high ability to adsorb heavy metal ions (over 40 mg g^− 1) and retain complex and organic molecules (EGME), mostly evident for material X. Adsorptive purification of waste and working lubricating oils using zeolitic products allow to provide their commercial applications in petroleum industry. Leachability of toxic elements after standard post-reaction washing is environmentally safe.