Automated tuning of an electronic circuit board using the artificial neural network approach

Manufacturing of electronic circuits for microwave communication boards often requires tuning of different circuit characteristics by manual adjustment of several trimmer components, including the trimmer's resistance and capacitance. This manual tuning process was automated by applying the artificial neural network modeling approach. In the considered tuning process, which required manual adjustment of a set of trimmers, multiple specification criteria had to be satisfied by several trimmer rotations. The tuning process was described in terms of three independent steps: the circuit output measurement, trimmer selection, and trimmer rotation. The trimmer selection was performed by a semi-supervised neural network, which learned the patterns of circuit characteristics and the deviations between the ideal and practical outputs. Another network was developed for determination of trimmer rotation rate. The results, based on computer simulation of the tuning process, showed that the developed system improved performance of the tuning process, allowing for automation of the microwave circuit board tuning task in a real manufacturing environment.     

Determination ofp-cymene-2,3-diol, thymol, and carvacrol in different foodstuffs

p-Cymene-2,3-diol, carvacrol and thymol are components of thyme that exhibit antioxidant activities. The concentration of each substance was determined in different foodstuffs containing thyme extract. The stabilities ofp-cymene-2,3-diol, carvacrol and thymol were examined by heating lard containing thyme extract at temperatures from 80 °C to 160 °C.     

Ceranapril and cerebral blood flow autoregulation

In order to investigate the levels of the polycyclic aromatic hydrocarbons, mainly benzo[a]pyrene because of its carcinogenicity, 55 samples of smoke flavour and smoked foods were analysed. The samples tested included 11 samples of liquid smoke flavour and 44 samples of smoked foods like bacon, loin, turkey, sausage, ox rib, etc. from different brands. A liquid chromatographic method was developed using a fluorescence detector. Benzo[a]pyrene was found in 73% of the liquid smoke flavour samples analysed. The levels varied from 0.1 to 336.6 micrograms/kg. Three liquid smoke flavour samples showed levels of benzo[a]pyrene above the maximum level recommended by FAO/WHO (10 micrograms/kg). From the total of 44 smoked food samples analysed, benzo(a)pyrene was detected in 23 samples (52%). The levels varied from 0.1 to 5.9 micrograms/kg. Anthracene and fluoranthene, non-carcinogenic polycyclic aromatic hydrocarbons, were found in almost all the samples analysed. Benzo[ghi]perylene, 3,4-benzofluoranthene and 1,2,3,4-dibenzopyrene were not found in any of the 55 samples analysed.     

Thin layer activity depth distribution for wear measurements of cast iron

Theoretical activity distribution was determined for ⁵⁶Co obtained from the ⁵⁶Fe (p, n) reaction. The reaction was induced by an 8.3 MeV proton beam in a thin surface layer of cast-iron. The distribution was then verified experimentally. The standard deviation of the measured points from the theoretical curve was 3.3 μm. For the thickness range between 5 and 35 μm, frequently used in wear studies, a linear approximation was suggested by the experimental results. Standard error of estimate was 0.69 μm for this range. The S.D. of the experimental points from the theoretical curve 3 as 1.14 μm for the same range.The studies were made with a view to their prospective application in the measurements of wear of car engine components.     

Multiangular elements in plate bending

The problem of bending a thin plate is solved by the finite element method. Using a differential equation of the plate element equilibrium determines the potential energy by contour values of displacements and their first derivatives. In the equilibrium state they have to be such that the potential energy reaches its minimum. The suggested calculation algorithm enables the use of multiangular elements of arbitrary shape instead of integration in the area of this element in which curvilinear integrals appear along the element contour. Elaborated also is the program for calculation by computer and verified usability of the method for various elements based on the example of the square plate.     

Evaluation of oxygen content on silicon nitride powder surface from the measurement of the isoelectric point

The oxygen content associated to the surface of silicon nitride powder particles was characterized using a method which is based on the measurement of the specific surface area and the isoelectric point in aqueous solution. From the dissociation model of hydrolyzed surface groups a linear dependence between the fraction of silanol groups (SiOH) and the pH of the isoelectric point is predicted, which was confirmed by electrophoretic measurements of various commercial silicon nitride powders. The proposed method provides rapid information on the particle surface composition, which is of particular relevance for colloidal processing of silicon nitride powders.     

Detonation and Blast Wave Characteristics of Nitromethane Mixed with Particles of an Aluminium–Magnesium Alloy

Investigation of detonation parameters, blast wave characteristics and quasi‐static pressures (QSPs) for the mixtures of nitromethane and particles of an aluminium and magnesium (Al₃Mg₄) alloy was carried out. The mixtures of gelled nitromethane containing 15–60 wt.‐% Al Mg alloy were tested. Detonation velocity and Gurney energy were determined. Parameters of blast waves produced by charges of the investigated explosives were measured. QSP measurements were conducted in a steel chamber of 0.15 m³ volume filled with air. Thermochemical and gasdynamical calculations were also performed. The degree of combustion of the metallic addition with the gaseous products during detonation and expansion is discussed.     

Analysis of glycerophosphonolipids in egg yolk

Glycerophosphonolipids are a relatively unknown class of polar lipids. Little information is available on any special biological function of these substances or specific technological use for them. Since glycerophosphonolipids have been reported to occur in egg yolk, further studies are needed in order to determine their relevancy. However, analysis of these lipids is rather difficult, due both to their chemical similarity to phospholipids and the lack of commercially available reference substances. Therefore, a reference substance for phosphono analogues of phosphatidylethanolamine (PnE)—1,2-dioctadecanoyl-glycero-3-aminoethylphosphonate—has been synthesized and an HPLC/ELSD method to separate PnE from its phosphonoanalog was developed. Although the present results showed no evidence of glycerophosphonolipids in egg yolk (limit of detection <0.02% for PnE), the spectroscopic data gathered here do point to an approach for further analysis of glycerophosphonolipids. Furthermore, a characteristic ESI–MS² fragmentation pattern for PnE was established, which can be used as a “fingerprint” for the identification of this substance in other biological systems. It was found to be characteristic for a fatty acid fragment to be split off as an internal anhydride (ketene) [M–H–RCH=C=O]⁻ along with the whole fatty acid fragment [M–H–RCH₂COOH]⁻ in the negative ion mode. In the positive mode, there was a selective loss of only the head group of the phosphonolipid [PO₃H₂–C₂H₄–NH₃]⁺, resulting in the so-called “diacylglycerol-like fragment ion” [DAG]⁺.