Influence of hot deformation on the transformation behaviour and structure of pearlitic steels

A study was made of the influence of hot deformation on the transformation behaviour, the structure and the mechanical properties of a pearlitic steel containing 0.65% C. The production parameters of a modern hot strip mill were taken as a basis for the deformation schedule and cooling performed with the aid of a hot deformation simulator (Wumsi). Parameters to be pointed out as significantly influencing the transformation behaviour are, in particular, the finishing temperature and the cooling rate after hot deformation. By exploiting the possibility of raising the cooling rate after deformation in the same measure as is attainable on a hot strip mill, a yield strength increase of at least 150 MPa is achievable.     

New binary thermoresponsive polymeric system for local chemoradiotherapy

Radiolabeled thermoresponsive polymers (TRPs) with cloud‐point temperatures between room temperature and body temperature may have an advantage for local radiotherapeutical applications because TRPs may be isotopically labeled in solution at room temperature and injected as a solution, and at the site of application, the polymers form a depo because of phase separation at body temperature. A new polymeric drug‐delivery system designed for combined local chemoradiotherapy with an injectable TRP bearing a radionuclide and the hydrophobic moiety doxorubicin (DOX) was synthesized and characterized. In the system, DOX served as an antiproliferative agent with known synergic effects with ionizing radiation and the hydrophobic moiety controlling bioerosion and elimination of the system at the same time. DOX was bound to the polymer carrier by a hydrolytically labile N‐glycosylamine bond. Hydrolysis of the N‐glycosylamine bond thus controlled the DOX release and dissolution of the system in the model aqueous milieu. DOX was slowly released during incubation in aqueous milieu at 37°C, which caused complete dissolution of the bioerodable polymer within about 2 weeks. The model radionuclide iodine 125, bound to a small amount of poly(N‐isopropylacrylamide‐co‐N‐methacryloyl tyrosinamide), was retained in the separated phase and also slowly dissolved during the incubation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Sequencing and analysis of 51 kb on the right arm of chromosome XV from Saccharomyces cerevisiae reveals 30 open reading frames

We have sequenced a region of 51 kb of the right arm from chromosome XV of Saccharomyces cerevisiae. The sequence contains 30 open reading frames (ORFs) of more than 100 amino acid residues. Thirteen new genes have been identified. Thirteen ORFs correspond to known yeast genes. One delta element and one tRNA gene were identified. Upstream of the RPO31 gene, encoding the largest subunit of RNA polymerase III, lies a Abf1p binding site. The nucleotide sequence data reported in this paper are available in the EMBL, GenBank and DDBJ nucleotide sequence databases under the Accession Number X90518.     

Possibilities of influencing the γ-α-transformation products of hot-rolled pearlitic steels

Controlled alloying, optimum configuration of the rolling schedules, and a suitable cooling strategy make it possible to broadly influence the microstructure and mechanical properties of higher-carbon steels. Increasing the manganese content and microalloying with vanadium delay the diffusion-controlled γ-α-transformation, and the increase in the amount of pearlite improves strength properties. Lowering of the finishing temperature refines the austenite microstructure, and increases the level of residual strengthening that remains in the austenite. This changes the amount of ferrite and improves the resistance to brittle fracture. Applying a cooling interruption step in the ferrite formation temperature range also permits an additional variation of the amount of ferrite. The extent to which recalescence develops during the formation of pearlite can bring about significant changes in the pearlite morphology and hence influence strength and toughness properties. Accelerated cooling to a low coiling temperature, as a further process-related modification, promotes the formation of bainite, obtaining high strength properties without any mentionable loss of toughness.     

Hot deformation-enhanced globularization of pearlite

A plain high-carbon steel (0.74% C) was used to study the globularization (spheroidization and coalescence) of pearlite. In order to induce and/or enhance this process, specimens were deformed in the temperature range of austenite-to-pearlite transformation. It was found that only hot deformation applied after the completion of pearlite transformation leads to spheroidization of pearlite. The rate of this process is accelerated by a factor of 10⁴ compared with annealing without deformation. The kinetics of pearlite spheroidization are dependent on the pearlite lamellae thickness as well as pearlite orientation with respect to the direction of deformation. The final microstructure is, compared with that after a conventional soft annealing, considerably finer, the strength properties thus being largely retained.     

Mechanical Behavior of Ensete ventricosum Fiber Under Tension Loading

The mechanical behavior of Ensete ventricosum fibers, expressed as the dependency of tension force in relation to the elongation, was determined for fibers with gauge length 50 mm and transformed into general linear mathematical model describing dependency of tension stress and strain. The average rupture force (10.88 ± 1.11) N, rupture stress (390.33 ± 21.96) MPa, rupture strain (0.021 ± 2 · 10^–5), and volume energy (3.39 ± 0.22) J m^?3 were also determined at this conducted study. Using image analyses, it was determined that the cross section of Ensete ventricosum fiber has circle shape and its dimension was specified. From the study, it implies that Ensete ventricosum fiber, with respect to its mechanical behavior under tension loading having regard to its density and to the fact that it is environmentally friendly, biodegradable and recyclable, could be used as a perspective construction material of the future. Determined model of mechanical behavior could be applied as background for further research focused on the Ensete fiber application.     

Artificial intelligence based optimization for vibration energy harvesting applications

This paper deals with optimization studies based on artificial intelligence methods. These modern optimization methods can be very useful for design improving of an electromagnetic vibration energy harvester. The vibration energy harvester is a complex mechatronic device which harvests electrical energy from ambient mechanical vibrations. The harvester design consists of a precise mechanical resonator, electromagnetic converter and electronics. The optimization study of such complex mechatronic device is complicated however artificial intelligence methods can be used for set up of optimal harvester parameters. Used optimization strategies are applied to optimize the design of the electro-magnetic vibration energy harvester according to multi-objective fitness functions. Optimization results of the harvester are summarized in this paper. Presented optimization algorithms can be used for a design of new energy harvesting systems or for improving on existing energy harvesting systems.     

Power sensitivity of vibration energy harvester

This paper deals with a power sensitivity improvement of an electromagnetic vibration energy harvester which generates electrical energy from ambient vibrations. The harvester provides an autonomous source of energy for wireless applications, with an expected power consumption of several mW, placed in environment excited by ambient mechanical vibrations. An appropriately tuned up design of the harvester with adequate sensitivity provides sufficient generating of electrical energy for some wireless applications and maximal harvested power depends on a harvester mass, frequency and level of the vibration and sensitivity of the energy harvester. The design of our harvester is based on electromagnetic converter and it contains a unique spring-less resonance mechanism where stiffness is provided by repelled magnetic forces. The greater sensitivity of the harvester provides more generated power or decrease of the harvester size and weight.     

Microstructures of FeSi2 based thermoelectric materials prepared by rapid solidification and hot pressing

FeSi2 based thermoelectric materials have been prepared by melt spinning and vacuum hot pressing. Most of the rapidly solidified (melt spinning) powders are thin flakes with a thickness less than 0.1 mm. Scanning electron microscope (SEM) surface profiles show there are further finer grain structures with the characteristic size of about 100 nm in a flake. The samples obtained by hot uniaxial pressing (HUP) in vacuum have densities higher than 90% the theoretical density of the materials. It was found by SEM observations that the microstructures are very different for vertical and parallel sections of the HUP samples. X-ray diffraction (XRD)analyses show there are some texture features in the samples. It is considered that the textures of the samples are originated from the orientation of the flakes that tended to align perpendicular to the hot press axis. WSi2 was introduced into the powders unexpectedly during melting process before the rapid solidification, but it makes the microstrucmres more easily to be explained.