Hydrothermal Synthesis of Manganese Zinc Ferrite Powders from Oxides

Manganese zinc (MnZn) ferrite powders were prepared via the hydrothermal treatment of a homogeneous mixture of the raw oxides (i.e., Fe₂O₃, ZnO, and Mn₃O₄ or MnO) at temperatures of 220°-320°C in air or an inert atmosphere. The final results of the hydrothermal reactions between the raw oxides were fine powders with a heterogeneous phase composition. In addition to lower concentrations of the residual reactants (Fe₂O₃, Mn₃O₄), two types of spinel-structure-based reaction products-ferrite ((Mn²⁺,Zn)Fe₂O₄) and manganate ((Zn,Mn²⁺)Mn₂³⁺O₄)-were detected after the synthesis. The composition of the ferrite products, as well as the ratio of ferrite products to manganate products, were mainly functions of the oxidation state of the manganese that was present during treatment. The oxidation state of manganese during reaction was dependent on the valence of the manganese in the starting manganese oxide and on the atmosphere in the autoclave during reaction. When the hydrothermal reaction was conducted in air, almost-pure zinc ferrite was identified, whereas during reaction in an inert atmosphere, MnZn ferrite was formed. The kinetics of the hydrothermal reactions also were dependent on the oxidation state of manganese, as well as the temperature and specific surface area of the starting Fe₂O₃.     

Hydrothermal Synthesis of Ba-Hexaferrite Nanoparticles

Barium hexaferrite BaFe₁₂O₁₉ nanoparticles with a single-domain size were synthesized using a controlled hydrothermal process involving the LaMer–Dinger principle and the Ostwald ripening mechanism. Nanocrystalline particles of BaFe₁₂O₁₉ were obtained when the molar ratio of the precursor composition Ba(OH)₂·8H₂O/γ-Fe₂O₃ was 0.3 and the concentration of the suspension was about 1 wt%. The as-synthesized crystalline BaFe₁₂O₁₉ platelets approximately 50 nm in length and 5 nm in thickness exhibited a saturation magnetization of 40 Am²/kg.     

Processing and properties of 0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 thick films

We have investigated the processing of 0.65Pb(Mg_1/3Nb_2/3)O₃–0.35PbTiO₃ (PMN–PT) thick films on platinised alumina substrates. Nanosized PMN–PT powder with 2 mol% of excess PbO was prepared by high-energy milling and deposited on the substrate using screen-printing technology. The films were then sintered at 950 °C in a PbO-rich atmosphere. The influence of the sintering time and the amount of PbO-containing packing powder was studied and related to the structural, microstructural, dielectric and piezoelectric properties of the film. In order to obtain a homogeneous and dense thick film without any secondary phase, the PMN–PT films had to be sintered in the presence of a PbO-based liquid phase that had to be completely removed from the thick film during the final stage of the sintering. Under optimal sintering conditions we obtained a room temperature relative dielectric permittivity of 3600, dielectric losses of 0.036, a T_m of 174 °C, a permittivity at the T_m of 21,000 and a d₃₃ of 140 pC/N.     

Intelligent Programming of CNC Turning Operations using Genetic Algorithm

CAD/CAM systems are nowadays tightly connected to ensure that CAD data can be used for optimal tool path determination and generation of CNC programs for machine tools. The aim of our research is the design of a computer-aided, intelligent and genetic algorithm(GA) based programming system for CNC cutting tools selection, tool sequences planning and optimisation of cutting conditions. The first step is geometrical feature recognition and classification. On the basis of recognised features the module for GA-based determination of technological data determine cutting tools, cutting parameters (according to work piece material and cutting tool material) and detailed tool sequence planning. Material, which will be removed, is split into several cuts, each consisting of a number of basic tool movements. In the next step, GA operations such as reproduction, crossover and mutation are applied. The process of GA-based optimisation runs in cycles in which new generations of individuals are created with increased average fitness of a population. During the evaluation of calculated results (generated NC programmes) several rules and constraints like rapid and cutting tool movement, collision, clamping and minimum machining time, which represent the fitness function, were taken into account. A case study was made for the turning operation of a rotational part. The results show that the GA-based programming has a higher efficiency. The total machining time was reduced by 16%. The demand for a high skilled worker on CAD/CAM systems and CNC machine tools was also reduced. Received: September 2004 / Accepted: September 2005     

Automated visual inspection of imprint quality of pharmaceutical tablets

Visual appearance is an important quality factor of pharmaceutical tablets. Moreover, it plays a key role in identification of tablets, which is needed to prevent mix-ups among various types of tablets. Since identification of tablets is most frequently done by imprints, good imprint quality, a property that makes the imprint readable, is of utmost importance in preventing mix-ups among the tablets. In this paper, we propose a novel method for automated visual inspection of tablets. Besides defect detection, imprint quality inspection is also considered. Performance of the method was evaluated on three different real tablet image databases of imprinted tablets. A “gold standard” was established by manually classifying tablets into a good and a defective class. The receiver operating characteristics (ROC) analysis indicated that the proposed method yields better sensitivity and specificity than the previous defect detection method.     

The influence of the coordinate reduction on the identification of the joint dynamic properties

A problem of establishing a theoretical model of a joint from the measured frequency-response function (FRF) data is discussed in this paper. The model of the joint is considered as a coupled dynamic stiffness matrix, which generally includes six degrees of freedom (DoFs). For two types of least-squares solution the terms of use are clarified. The effect of coordinate reduction on the identification results is demonstrated numerically. Also the effect of added noise is studied. Using a substructure synthesis method and the identified joint dynamic properties the assembly response is reconstructed.     

Sorption properties of wood impregnated with aqueous solution of boric acid and montan wax emulsion

Nonbiocidal techniques for wood protection have become more and more important in the last few years. One of the possible treatments to enhance wood durability is use of water repellents. In this research, the influence of one of the possible water repellents, the montan wax emulsion, on the moisturizing and the sorption characteristics of impregnated wood was investigated. To achieve a better protection against wood decay fungi, wood was impregnated with montan wax emulsion enriched with boric acid. The equilibrium moisture content (MC) was monitored during the adsorption and the desorption processes at five levels of relative air humidity (RH₁ = 20%, RH₂ = 33%, RH₃ = 65%, RH₄ = 88%, and RH₅ = 98%). Water repellence efficiency was monitored in the chamber with high RH (87%) and during dipping in the water. Impregnated samples were also exposed outdoors in a covered position for 5 months to determine MC changes according to changes in outdoor humidity and temperature. The results showed that the sorption properties of the impregnated wood are strongly related to retention of preservative solutions after impregnation and its composition. Montan wax reduced equilibrium MC of the impregnated wood up to 25% (relatively), whereas specimens impregnated with combination of montan wax and boric acid resulted in decreased MC in some cases and in increased MC in some cases. The Guggenheim–Andersen–deBoer model of sorption isotherms was fitted to experimental data to explain the sorption mechanisms. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and characterization of maghemite nanosheets

Magnetic maghemite nanoparticles in the form of nanosheets were prepared by a topotactic transformation during the dehydroxylation of a γ-FeO(OH) precursor. The precursor was synthesized from tetrapyridin Fe(II) chloride (Fe(py)₄Cl₂). The nanosheets are several hundreds of nanometers wide, and less than 5 nm thick; they frequently bend and curl at the edges; they are nanocrystalline; and they are composed of smaller maghemite nanostructured domains, from a few nanometers up to several tens of nanometers wide.     

Autonomous evolutionary algorithm in medical data analysis

An autonomous evolutionary algorithm for constructing decision trees is presented. The algorithm requires no or minimal human interaction and shows some interesting properties when used on different medical datasets. The algorithm uses a non-standard implicit fitness evaluation in the selection phase of a co-evolving environment. Together with self-adaptation of evolution parameters and with some other improvements it can monitor and adjust its own behavior. The algorithm's capability to self-adapt to a given problem is used as a measure to predict if some dataset is just difficult or impossible to analyze. The autonomous algorithm on average produces very general solutions or gives no solution if the dataset is prone to the overfitting problem.     

Performance of wood impregnated with N-methylol and copper based aqueous solutions

The combination of copper and N-methylol compounds considerably improves the performance against copper sensitive fungi (G. trabeum and T. versicolor), while the fungicidal effect against copper tolerant strain (A. vaillantii) remained insufficient. Addition of N-methylol compounds to copper solution significantly reduces leaching from wood blocks impregnated with the solution of the lowest copper concentration (c_Cu =0.1%), and less notably reduces leaching from wood blocks impregnated with solutions of higher copper contents (c_Cu=0.5%).