The Influence of the Thermomechanical Processing Regime on the Structural Evolution of Mo-Nb-Ti-V Microalloyed Steel Subjected to High-Pressure Torsion

Metallurgical and Materials Transactions A - In the present study the effect of the thermal-mechanical processing regime—cold high-pressure torsion (HPT) at room temperature, cold HPT...     

Rotary jet head – a device for accelerating the fermentation process in brewing

The world beer market is dominated by lagers, with production estimated at hundreds of millions of hectolitres per year. The vast majority of the beer is produced using CCT (cylindro‐conical tank) technology. Fermentation and maturation are time‐consuming processes and the bottlenecks of beer production. A rotary jet head (RJH) – a device originally used as a cleaning device – is proposed for use as a tool to provide homogeneity in the tank and to increase the activity of the yeast cells by keeping them in suspension during the fermentation process. The main objective of the study was to analyse the impact of mixing the content of the fermentation tank (by the means of an RJH) on the time of fermentation, maturation and cooling. The experiments were carried out under full industrial operational conditions. It was concluded that mechanical mixing, in a CCT of 3800 hL, shortened the time of lager beer production process by ca. 15%, the time of fermentation by ca. 24 h and the cooling time by ca. 35 h. Copyright © 2016 The Institute of Brewing & Distilling     

Kinetics of particle nucleation and growth in the emulsion polymerization of acrylic monomers

The rates of particle formation and growth during the earliest stages of the emulsion polymerization of several acrylic monomers have been studied as a function of surfactant concentration by means of the time-dependence of light scattering from the reaction mixtures. Investigated were methyl methacrylate, and methyl, ethyl and butyl acrylates at concentrations of SDS surfactant from 0 to several times the CMC. Under continuous photoinitiation the Rayleigh scattering intensities rose rapidly with slopes that increased with decreasing SDS concentration. The more water-soluble the monomer, the more slowly was the rate of increase in scattering intensity. Computer modeling, using HUFT theory, could be used to obtain values for the various parameters involved for MMA. The Fuchs stability factor, W, was found to be 1 for [SDS] = 0 and infinity for [SDS] = CMC or grester. The partition coefficient for J-mer oligomers between the aqueous and organic phases must rise exponentially with J. Electrostatic effects on radical capture by particles are considered to be negligible, but very important as they affect coagulation kinetics.     

Protolytic and complexing properties of microcrystalline chitosan with Co(II), Zn(II), and Cu(II) ions

It has been evidenced that microcrystalline chitosan (MCCh) with a determined (by the potentiometric method in nonaqueous medium) degree of deacetylation of 0.87 acts as a polymeric chelating agent with cobalt(II) and zinc(II). The predomination of hydrolytic reactions, in the case of copper(II) ions, has been attributed to a change in crystalline character of the ligand. The protolytic reactions have been studied using the Katchalsky–Spitnik equation. The pH profiles have been shown for Co(II)–MCCh and Zn(II)–MCCh systems and the corresponding equilibrium constants have been determined as well. Both the amino and hydroxyl groups are involved in Co²⁺ complexation, whereas for Zn²⁺, the complexes are formed only via amino nitrogen. © 1995 John Wiley & Sons, Inc.     

High efficiency laser photothermal excitation of microcantilever vibrations in air and liquids

Photothermal excitation is a promising means of actuating microscale structures. It is gaining increased interest for its capability to excite atomic force microscopy (AFM) microcantilevers with wide frequency bandwidth in liquid environments yielding clean resonance peaks without spurious resonances. These capabilities are particularly relevant for high speed and high resolution, quantitative AFM. However, photothermal efficiency is low, which means a large amount of laser power is required for a given mechanical response. The high laser power may cause local heating effects, or spill over the cantilever and damage sensitive samples. In this work, it is shown that by simply changing from a probe with a rectangular cross-section to one with a trapezoidal cross-section, the photothermal efficiency of an uncoated silicon cantilever can be increased by more than a order of magnitude, and the efficiency of a coated cantilever can be increased by a factor of 2. This effect is demonstrated experimentally and explained theoretically using thermomechanical analysis. Results are shown for both air and water, and for normal bending and torsional oscillations.     

Exploiting cantilever curvature for noise reduction in atomic force microscopy

Optical beam deflection is a widely used method for detecting the deflection of atomic force microscope (AFM) cantilevers. This paper presents a first order derivation for the angular detection noise density which determines the lower limit for deflection sensing. Surprisingly, the cantilever radius of curvature, commonly not considered, plays a crucial role and can be exploited to decrease angular detection noise. We demonstrate a reduction in angular detection shot noise of more than an order of magnitude on a home-built AFM with a commercial 450 μm long cantilever by exploiting the optical properties of the cantilever curvature caused by the reflective gold coating. Lastly, we demonstrate how cantilever curvature can be responsible for up to 45% of the variability in the measured sensitivity of cantilevers on commercially available AFMs.     

Microstructural Development in SnO2-Doped ZnO–Bi2O3 Ceramics

The effects of adding small quantities of SnO₂ to the basic ZnO–Bi₂O₃ varistor composition were studied in terms of phase reactions, microstructural development, and the formation of inversion boundaries. Scanning and transmission electron microscopy studies showed that the inversion boundaries, triggered by the addition of SnO₂, cause anisotropic grain growth in the early stages of sintering. ZnO grains that include inversion boundaries grow exaggeratedly, at the expense of normal grains, until they dominate the microstructure. Higher additions of SnO₂ lead to an increase in number of grains with inversion boundaries and to a more fine-grained microstructure. The increasing amount of secondary phases is also related to a higher level of SnO₂ addition; however, the influence of these phases on ZnO grain growth is subordinate to the role of inversion boundaries.     

Chlorinated polyurethanes based on 2,4-toluenediisocyanate: Thermal analysis and flammability evaluation

A series of polyurethanes based on 2,4-toluenediisocyanate (TDI), with different amounts of 3-chloro-1,2-propanediol (CPDO), have been prepared. The process of thermal degradation was monitored by thermogravimetric analysis (TGA) alone or coupled with infrared spectroscopy (TGA/FTIR) and differential scanning calorimetry (DSC). Flammability of the polymers was determined using the oxygen index (OI) method. The influence of CPDO on the thermal decomposition parameters [e.g., initial decomposition temperature (IDT), char residue at 500°C, and DTG-max-temperature] and on the OI values have been discussed. Some correlations between thermogravimetric data and OI values were found, thus making it possible to apply the TGA method for certain flammability predictions of modified polyurethanes. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1465–1471, 1998     

Reducing the negative effects of stress in teams through cross-training: A job demands-resources model.

The purpose of this study was to utilize the job demands-resources model to examine the direct and interactive effects of job demands and cross-training on cognitive, behavioral, and affective outcomes in teams. Results from 54 teams indicated that an increase in job demands reduced mental model accuracy and information allocation and increased tension among team members. Cross-training, on the other hand, increased mental model accuracy and decreased tension among team members. More importantly, the direct effects of cross-training were qualified by the interaction. When job demands were high, cross-trained teams evidenced higher mental model accuracy, more information allocation, and less tension than teams that were not cross-trained. Cross-training was less influential when job demands were low, indicating that cross-training acted as a resource to buffer the negative impact of job demands in teams. (PsycINFO Database Record (c) 2011 APA, all rights reserved)