Evolution of microstructure and crystallographic texture during dissimilar friction stir welding of duplex stainless steel to low carbon-manganese structural steel

Electron backscattered diffraction (EBSD) was used to analyze the evolution of microstructure and crystallographic texture during friction stir welding of dissimilar type 2205 duplex stainless steel (DSS) to type S275 low carbon-manganese structural steel. The results of microstructural analyses show that the temperature in the center of stirred zone reached temperatures between Ac 1 and Ac 3 during welding, resulting in a minor ferrite-to-austenite phase transformation in the S275 steel, and no changes in the fractions of ferrite and austenite in the DSS. Temperatures in the thermomechanically affected and shoulder-affected zones of both materials, in particular toward the root of the weld, did not exceed the Ac 1 of S275 steel. The shear generated by the friction between the material and the rotating probe occurred in austenitic/ferritic phase field of the S275 and DSS. In the former, the transformed austenite regions of the microstructure were transformed to acicular ferrite, on cooling, while the dual-phase austenitic/ferritic structure of the latter was retained. Studying the development of crystallographic textures with regard to shear flow lines generated by the probe tool showed the dominance of simple shear components across the whole weld in both materials. The ferrite texture in S275 steel was dominated by D 1, D 2, E, E¯ , and F, where the fraction of acicular ferrite formed on cooling showed a negligible deviation from the texture for the ideal shear texture components of bcc metals. The ferrite texture in DSS was dominated by D 1, D 2, I, I¯ , and F, and that of austenite was dominated by the A, A¯ , B, and B¯ of the ideal shear texture components for bcc and fcc metals, respectively. While D 1, D 2, and F components of the ideal shear texture are common between the ferrite in S275 steel and that of dual-phase DSS, the preferential partitioning of strain into the ferrite phase of DSS led to the development of I and I¯ components in DSS, as opposed to E and E¯ in the S275 steel. The formations of fine and ultrafine equiaxed grains were observed in different regions of both materials that are believed to be due to strain-induced continuous dynamic recrystallization (CDRX) in ferrite of both DSS and S275 steel, and discontinuous dynamic recrystallization (DDRX) in austenite phase of DSS

Controls on microbial activity and tidal flat evolution in Shark Bay, Western Australia

Microbial deposits at Shark Bay constitute a diverse living microbial carbonate system, developed in a semi-arid, highly evaporative marine setting. Three tidal flats located in different embayments within the World Heritage area were investigated in order to compare microbial deposits and their Holocene evolution. The stressing conditions in the intertidal–subtidal environment have produced a microbial ecosystem that is trapping, binding and biologically inducing CaCO3 precipitation, producing laminated stromatolites (tufted, smooth and colloform), non-laminated thrombolitic forms (pustular) and cryptomicrobial non-laminated forms (microbial pavement). A general shallowing-upwards sedimentary cycle was recognized and correlated with Holocene sea-level variations, where microbial deposits constitute the younger (2360 years BP) and shallower sedimentary veneer. In addition, sediments have been documented with evidence of exposure during the Holocene, from 1040 to 940 14C years BP, when sea-level was apparently lower than present.Filamentous bacteria constitute the dominant group in the blister, tufted and smooth mat types, and coccus bacteria dominate the pustular, colloform and microbial pavement deposit types. In the subtidal environment within colloform and pavement structures, microbial communities coexist with organisms such as bivalves, serpulids, diatoms, green algae (Acetabularia), crustaceans, foraminifera and micro-gastropods, which are responsible for exoskeleton supply and extensive bioturbation. The internal fabric of the microbial deposits is laminated, sub-laminar, scalloped, irregular or clotted, depending on the amount of fine-grained carbonate and the natural ability of microbial communities to trap and bind particles or induce carbonate precipitation. Nilemah tidal flat contains the thickest (1.3 m) and best-developed microbial sedimentary system; its deposition pre-dated the Rocky Point and Garden Point tidal flats, with the most positive isotope values for δ13C and δ18O, reflecting strong microbial activity in a highly evaporative environment. There is an evolutionary series preserved within the tidal flats reflecting relative ages and degree of salinity elevation

Direct controller design and iterative tuning applied to the coupled drives apparatus

V příspěvku je použita přímá metoda návrhu regulátorů VRFT ( Virtual Reference Feedback Tuning) pro iterační způsob návrhu a doladění regulátoru. V práci je využito série experimentů bez omezení na způsob jejich generování pro návrh optimálního regulátoru zvolené struktury bez nutnosti identifikovat řízený proces. Přístup je úspěšně aplikován při návrhu a dolaďování regulátoru pro elektrické zařízení - systém spřažených servomotorů, a to přizpůsobováním požadované doby ustálení řízené veličiny.The paper utilizes the direct method Virtual Reference Feedback Tuning (VRFT) for the iterative way of controller design and fine-tuning. In the work, a series of experiments with no restriction on data generation is used to design an optimal controller of desired structure without the intermediate plant identification step. The approach is shown to be successful for the design and fine-tuning of a controller for the electric device - coupled drives apparatus by means of adjusting a desired settling-time of controlled output

Evaluation of different models to describe egg and pupal development of Xyleborus fornicatus Eichh. (Coleoptera: Scolytidae), the shot-hole borer of tea in Sri Lanka

Abstract Development data of eggs and pupae of Xyleborus fornicatus Eichh. (Coleoptera: Scolytidae), the shot-hole borer of tea in Sri Lanka, at constant temperatures were used to evaluate a linear and seven nonlinear models for insect development. Model evaluation was based on fit to data (residual sum of squares and coefficient of determination or coefficient of nonlinear regression), number of measurable parameters, the biological value of the fitted coefficients and accuracy in the estimation of thresholds. Of the nonlinear models, the Lactin model fitted experimental data well and along with the linear model, can be used to describe the temperature-dependent development of this species