LTCC compatible PLZT thick-films for piezoelectric devices

The production of PLZT thick-films for piezoelectric devices prepared from perovskite-type (Pb, La)(Zr, Ti)O₃ powders is described. The powder manufacture, paste preparation and thick-film production compatible with the low temperature co-fired ceramics (LTCC) process are detailed. The maximum firing temperature of applied technology is 850 °C. Measurements of the dielectric and piezoelectric properties of the produced films are carried out. The low dielectric loss (0.022) and high d₃₃ and d₃₁ piezoelectric coefficients (85.7×10⁻¹² and −34.6×10⁻¹² m/V, respectively) of the material, together with a relatively low sintering temperature, make it suitable for various applications, e.g. ultrasonics.     

Periodic solutions in a porous catalyst pellet—homoclinic orbits

The analysis performed as well as extensive numerical simulations have revealed the possibility of the generation of homoclinic orbits as a result of homoclinic bifurcation in the model which describes transport phenomena and chemical reaction in a porous catalyst pellet. A method has been proposed for the development of a special type of diagrams—the so-called bifurcation diagrams. These diagrams comprise the locus of homoclinic orbits together with the lines of limit points bounding the region of multiple steady states as well as the locus of the points of Hopf bifurcation. Thus, they define a set of parameters for which homoclinic bifurcation can take place. They also make it possible to determine conditions under which homoclinic orbits are generated.Two kinds of homoclinic orbits have been observed, namely semistable and unstable orbits. It is found that the character of the homoclinic orbit depends on the stability features of the limit cycle which is linked with the saddle point.Very interesting dynamic phenomena are associated with the two kinds of homoclinic orbits; these phenomena have been illustrated in the solution diagrams and phase diagrams.     

Energy and exergy system analysis of thermal improvements of blast‐furnace plants

The blast‐furnace process dominating in the production of steel all over the world is still continuously improved due to its effectiveness (exergy efficiency is about 70%). The thermal improvement consist in an increase of the temperature of the blast and its oxygen enrichment, as well as the injection of cheaper auxiliary fuels. The main aim is to save coke because its consumption is the predominating item of the input energy both in the blast‐furnace plant and in ironworks. Besides coke also other energy carriers undergo changes, like the consumption of blast, production of the chemical energy of blast‐furnace gas, its consumption in Cowper‐stoves and by other consumers, as well as the production of electricity in the recovery turbine. These changes affect the whole energy management of ironworks due to the close connections between energy and technological processes. That means the production of steam, electricity, compressed air, tonnage oxygen, industrial water, feed water undergo changes as well. In order to determine the system changes inside the ironworks a mathematical model of the energy management of the industrial plant was applied. The results of calculations of the supply of energy carriers to ironworks can then be used to determine the cumulative energy and exergy consumption basing on average values of cumulative energy and exergy indices concerning the whole country. Such a model was also used in the system analysis of exergy losses. Copyright © 2005 John Wiley & Sons, Ltd.     

Medical data on demand with WebMIA.

This article focuses on the creation of a system for managing and archiving large-scale medical data. Specifically, this case study demonstrates the new paradigm through the prototype system WebMIA. The system enables storage, maintenance, sharing, updating, and retrieval of medical files based on the existing Internet facilities and the state-of-the-art literature in medical image indexing and multimedia information presentation. It also incorporates our current research in image retrieval and multimodal medical image fusion. It surpasses the existing systems in the commercial and research sectors as it provides convenient, efficient, effective, and flexible online processing, annotation, and multimodal querying capabilities in one forum. The patient confidentiality issue is well addressed when the sharing of the medical information is provided. This technology will assist medical practitioners/researchers by enabling efficient management and sharing of medical files within or across a community, without being subject to geographical restrictions an d without creating the problems of inconsistent and fragmented medical data.     

Crystalline structure and mechanical properties of wet‐spun dibutyrylchitin fibers and products of their alkaline treatment

Dibutyrylchitin was obtained during krill chitin esterification with butyric anhydride in the presence of perchloric acid. The wet spinning of a 14.5% solution in dimethylformamide created dibutyrylchitin filaments, which were treated with an alkali solution for chitin regeneration. Fiber samples with different degrees of chitin restoration were obtained, and their fine structure and mechanical properties were investigated. The restoration of the chitin structure resulted in a gradual increase in the degree of crystallinity, the density of the structured area, the tensile strength, and the average elongation at rupture and in a decrease in the diameter of the fibers. The crystallinity degree of fully regenerated chitin, the final product of alkaline hydrolysis, reached a value close to that of native chitin. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1861–1868, 2004     

Synthesis and structural characterization of the Re3 triangular 4,4′-bipyridinium aqua-tris(μ-triiodo)-octachlorotrirhenium dihydrate complex

The Re₃ cluster compound (4,4′-bipyH₂) Re₃Cl₈I₃H₂O · 2H₂O was obtained by thermal reaction of (NH₄)₄[Re₂OCl₁₀] with 4,4′-bipirydine triiodide. The structure of this compound has been established by X-ray measurement. This is the three-centre rhenium cluster with Re centres bonded by iodide bridges. The cations and anions positions are stabilized by hydrogen bonding network.     

Simulation of the coupling of the external electromagnetic field to PCB traces in the SPICE simulator

In this article, a simple method of modeling and simulating electromagnetic field coupling to PCB in the SPICE simulator is presented. The method exploits two assumptions: quasi-TEM wave propagation along PCB traces and representation of an external electromagnetic noise by a plane wave. Under these assumptions, a model of electromagnetic field coupling to the PCB traces is created in the form of an active n-wire transmission line placed in an inhomogeneous (that is, three layers) medium. Next, using the method of successive approximations, an equivalent active n-port (described by means of scattering parameters) is found. This work results in formulas that express the external electromagnetic field in the form of current sources and the way they are simulated in SPICE. The method is illustrated with two examples. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14, 190–200, 2004.     

Nickel hydroxide electrocatalysts for alcohol oxidation reactions: An evaluation by infrared spectroscopy and electrochemical methods

We have investigated the electrochemical oxidation of four alcohols (methanol, 1-, 2- and tertiary butanol) at Ni hydroxide electrodes in alkaline electrolytes. In situ FTIR spectroscopy and electrochemical methods have been used to examine these oxidation reactions. Oxidation of the primary and secondary alcohols commences in the potential region where it is proposed that multi-layers of NiOOH are formed on the electrode surface; while no reaction occurs with tertiary butanol. Methanol oxidation occurs in two stages, with predominantly formate being formed in the potential window 0.36-0.44 V (vs. SCE), followed by further oxidation to carbonate at potentials above approx. 0.45 V. Butanoate is the only detected reaction product for 1-butanol electrooxidation in the potential range 0.36-0.5 V. The oxidation of 2-butanol is more complex. In the lower potential range (0.36-0.44 V) the major reaction product is butanone, which is further oxidised at higher potentials to either acetate or a mixture of propanoate and formate (or carbonate). In addition, rate constants have been determined for the first stage of the electrochemical oxidation of all the alcohols investigated.