High Strain Rate Superplasticity in Microcrystalline and Nanocrystalline Materials

Superplasticity has evolved to become a significant industrial forming process. The phenomenon of superplasticity is explored at high strain rates where it is economically more attractive. True tensile superplasticity has been demonstrated in nanocrystalline materials. The difference in the details of superplasticity between the nanocrystalline and microcrystalline state is emphasised

Virtual Reality and Implications for Destination Marketing

Virtual Reality and Implications for Destination Marketing Abstract This study considers the impact of Virtual Reality (VR) in affecting destination image. Three groups viewed related promotional content on South Africa as either a website, a 2D Video, or an immersive VR video using a head mounted display. Participants were asked questions relating to destination image and advertisement effectiveness. Results show that VR positively impacted affective destination image, as well as most items within conative destination image and advertisement effectiveness. Practitioners should consider using VR to visually promote their destinations and experiences, as participants did generally feel more positive emotions towards the destination, and were more likely to share their experiences about the destination and the advertisement itself with friends and relatives

Features of Duplex Microstructural Evolution and Mechanical Behavior in the Titanium Alloy Processed by Equal‐Channel Angular Pressing.

This report describes a study of the regularities in the kinetics of microstructure evolution and recrystallization processes in the Ti–5.7Al–3.8Mo–1.2Zr–1.3Sn alloy (Russian analogue VT8M‐1) during processing by equal‐channel angular pressing (ECAP). To produce a duplex (globular‐lamellar) structure, the billets are subjected to preliminary heat treatment, including water‐quenching from a temperature below the β‐transus followed by annealing at 700 °С. For the ECAP temperature selection, the deformation behavior of the alloy with a duplex structure is investigated under upsetting in the temperature range of 650–800 °С. The evolution of the globular and lamellar fractions is examined during ECAP processing, and an emphasis is placed on the role of phase transformations, dynamic recrystallization, and spheroidization of the α‐phase which is realized with increasing accumulated strain when processing by ECAP. It is demonstrated that after 6 ECAP passes an equiaxed ultrafine‐grained structure is formed with a mean α‐phase grain/subgrain size of ≈0.6 μm. The investigation includes an examination of the effect of microstructure on the mechanical properties of the alloy

Grain refinement and superplastic flow in a fully lamellar Ti-6Al-4V alloy processed by high-pressure torsion

A cold-rolled Ti-6Al-4V alloy was subjected to consecutive heat treatments at 1283 K for 1 h and at 823 K for 3 h in order to produce a fully lamellar microstructure. Thereafter, the material was processed by high-pressure torsion (HPT) through various numbers of turns up to a maximum of 30. It is shown that the HPT processing leads to exceptional grain refinement with average grain sizes of ~ 70 and ~ 50 nm after 20 and 30 turns, respectively. Tensile testing was conducted at 873 and 923 K with different initial strain rates using the material processed through 20 turns of HPT and this gave a maximum superplastic elongation of 820% at the relatively low temperature of 923 K when testing with an initial strain rate of 5.0 × 10−4s−1. The associated strain rate sensitivity for this low temperature superplasticity was estimated as m ≈ 0.5 which is consistent with flow by grain boundary sliding

High potency silencing by single-stranded boranophosphate siRNA

In RNA interference (RNAi), double-stranded short interfering RNA (ds-siRNA) inhibits expression from complementary mRNAs. Recently, it was demonstrated that short, single-stranded antisense RNA (ss-siRNA) can also induce RNAi. While ss-siRNA may offer several advantages in both clinical and research applications, its overall poor activity compared with ds-siRNA has prevented its widespread use. In contrast to the poor gene silencing activity of native ss-siRNA, we found that the silencing activity of boranophosphate-modified ss-siRNA is comparable with that of unmodified ds-siRNA. Boranophosphate ss-siRNA has excellent maximum silencing activity and is highly effective at low concentrations. The silencing activity of boranophosphate ss-siRNA is also durable, with significant silencing up to 1 week after transfection. Thus, we have demonstrated that boranophosphate-modified ss-siRNA can silence gene expression as well as native ds-siRNA, suggesting that boranophosphate-modified ss-siRNAs should be investigated as a potential new class of therapeutic agents

Estimation of the elastic modulus and the work of adhesion of soft materials using the extended Borodich–Galanov (BG) method and depth sensing indentation

© 2018 Elsevier Ltd The depth-sensing indentation (DSI) is currently one of the main experimental techniques for studying elastic properties of materials of small volumes. Usually DSI tests are performed using sharp pyramidal indenters and the load-displacement curves obtained are used for estimations of elastic moduli of materials, while the curve analysis for these estimations is based on the assumptions of the Hertz contact theory of non-adhesive contact. The Borodich–Galanov (BG) method provides an alternative methodology for estimations of the elastic moduli along with estimations of the work of adhesion of the contacting pair in a single experiment using the experimental DSI data for spherical indenters. The method assumes fitting the experimental points of the load-displacement curves using a dimensionless expression of an appropriate theory of adhesive contact. Earlier numerical simulations showed that the BG method was robust. Here first the original BG method is modified and then its accuracy in the estimation of the reduced elastic modulus is directly tested by comparison with the results of conventional tensile tests. The method modification is twofold: (i) a two-stage fitting of the theoretical DSI dependency to the experimental data is used and (ii) a new objective functional is introduced which minimizes the squared norm of difference between the theoretical curve and the one used in preliminary data fitting. The direct experimental validation of accuracy and robustness of the BG method has two independent steps. First the material properties of polyvinyl siloxane (PVS) are determined from a DSI data by means of the modified BG method; and then the obtained results for the reduced elastic modulus are compared with the results of tensile tests on dumbbell specimens made of the same charge of PVS. Comparison of the results of the two experiments showed that the absolute minimum in relative difference between individual identified values of the reduced elastic modulus in the two experiments was 3.80%; the absolute maximum of the same quantity was 27.38%; the relative difference in averaged values of the reduced elastic modulus varied in the range 16.20.. 17.09% depending on particular settings used during preliminary fitting. Hence, the comparison of the results shows that the experimental values of the elastic modulus obtained by the tensile tests are in good agreement with the results of the extended BG method. Our analysis shows that unaccounted factors and phenomena tend to decrease the difference in the results of the two experiments. Thus, the robustness and accuracy of the proposed extension of the BG method has been directly validated