Improving the accuracy of autotransformer and transformer alternating-current bridges

Variable-ratio and computational methods are described for improving the accuracy of autotransformer and transformer ac bridges that take into account and eliminate the additive and multiplicative components of the systematic error due to connecting leads and jumpers of the measuring circuit. Translated from Izmeritel'naya Tekhnika, No. 6, pp. 61–63, June, 1996.     

Effects of benzoyl peroxide on some properties of composites based on hemp and natural rubber

The obtaining and characterization of polymer composites based on natural rubber and hemp, in which the elastomer crosslinking has been achieved with benzoyl peroxide, are presented. The mechanical characteristics, gel fraction, crosslink density, water uptake swelling parameters and FTIR of the composites based on natural rubber and hemp fiber vulcanized by dibenzoyl peroxide have been investigated as a function of the hemp content. The hardness, modulus at 100 % elongation, tearing strength, tensile strength and elongation at break have been improving with the increasing of fiber content in composites materials due to the better interaction of fiber in natural rubber composites. These results indicate that hemp has a reinforcing effect on natural rubber. Gel fraction value is over 95 % for all blends and varies irregularly depending on the amount of hemp in the composites. The crosslinking density (ν) of samples increases as the amount of hemp in blends increases, because hemp act as a filler in natural rubber blends and leads to reinforcement of the blends. The water uptake and swelling parameters also increases with the increasing of the amount of fiber content, because of the hemp hydrophilic characteristics.     

The improvement of the resistance to Candida Albicans and Trichophyton interdigitale of some cotton textile materials by treating with oxygen plasma and chitosan

This paper presents the improvement of the resistance to fungi of some cotton textile materials by treating in the manufacturing process with oxygen plasma and chitosan. Thus, after the weaving and preliminary finishing, the fabrics were cleaned in oxygen plasma atmosphere and after dyeing, have been treated with chitosan solution with concentrations of 1 or 5 g/l, in order to confer them antimicrobial properties. The antimicrobial tests were performed with two fungi: Candida albicans and Tricophyton interdigitale. The obtained antimicrobial effect was considerably higher compared to that of the raw fabrics. The colour resistance of dyed fabrics was not significantly influenced by applying the treatment-based chitosan.     

An automatic bridge for the comparison of the impedance standards

The paper describes an automatic autotransformer bridge for comparison of the impedances (capacitance, resistance, inductance, etc.) over a wide range of values. The proposed bridge structure, algorithm and processing of two unbalance signals eliminates the influence of the cable impedance on the measurement results. The autotransformer bridge uses only one inductive divider for a wide range of measurement. Automation of the measurement is based on a variational method of the precise bridge unbalance determination. This simplifies the bridge inductive divider and twice reduces the number of its digits without decreasing of the automatic bridge accuracy. The bridge measurement uncertainty on main ranges is better than 1 ppm; the sensitivity is better than 0.01 ppm.     

BiFeO3-synthesis,characterization and its photocatalytic activity towards doxorubicin degradation from water

Pure bismuth ferrite was successfully obtained through the thermolysis of new bismuth ferrioxalate coordination compound, namely BiFe(C₂O₄)₃·3H₂O. The synthesized precursor was characterized by chemical analysis, infrared spectroscopy and thermal analysis. The bismuth ferrite obtained after a heating treatment of the precursor for at 450–800?°C/1?h was investigated by X-ray diffraction, FE-SEM, TEM and HRTEM. The obtained pure bismuth ferrite nanoparticles (480?°C) was tested as photocatalyst towards the degradation of doxorubicin (DOX), a well-known anti-cancer drug commonly used for the treatment of various cancer types, which has been detected in hospital effluent water. The comparative results of DOX degradation through photolysis and photocatalysis under UV irradiation showed a great photocatalytic activity of bismuth ferrite towards DOX degradation and mineralization from water. The kinetics aspects were discussed based on the first-order kinetics model that fitted the best the experimental photocatalysis results.     

Electric and magnetic properties of ferromagnetic/piezoelectric bilayered composite

One of the most promising ways for the realization of multi-functional materials is the integration of oxides with different properties in artificial heterostructures. In this paper, a novel piezoelectric–ferromagnetic heterostructure consisting of 0.92Na_0.5Bi_0.5TiO₃–0.08BaTiO₃ (abbreviated as BNT–BT_0.08) and CoFe₂O₄ layers is fabricated on Si–Pt substrate, by sol–gel method coupled with spin-coating technique. The composite thin film shows only perovskite Bi_0.5Na_0.5TiO₃-like rhombohedral phase and CoFe₂O₄ cubic phase. The thickness of CoFe₂O₄ and BNT–BT_0.08 layers is ~?280 and?~?400 nm, respectively. BNT–BT_0.08/CoFe₂O₄ heterostructure thin film shows a saturation magnetization of 0.11 emu/g at 5 K and 0.07 emu/g at 295 K, dielectric constant of 235 at 1 kHz and tunability of 70% at 1 kHz and an electric field E?=?110 kV/cm. The results reveal that the investigated hybrid piezoelectric/ferromagnetic structure shows piezoelectric behavior, good ferroelectric and ferromagnetic properties. This bilayer composite can be used in miniature low-frequency magnetic sensor and piezoelectric sensor for biomedical domain.     

A variation of the operating mode of a standard measure to extend the range in apparatus for measuring the resistance of platinum resistance thermometers

The theoretical principles of a method of varying the operating mode of a standard measure when constructing apparatus for measuring the resistance of platinum resistance thermometers are described. Examples are given of the measuring circuits. A method of extending the measurement ranges is described, which enables the number of necessary standard measures to be halved. The method is based on splitting the whole measurement range of the instrument into pairs of adjacent ranges and measuring reciprocal quantities (for example, resistance and conductance) in each such pair of ranges.