Microstructure and mechanical behavior of TiC-reinforced Ti-Mo-Al alloys

Ti-based alloys have gained extensive attractions in high-temperature engineering applications over the past several decades because of their low density, impressive strength and wear resistance. The continuing demands for advanced structural materials in aerospace and automobile sectors encourage further exploits of Ti-based alloys. Solid-solution hardening has been confirmed as an effective way to improve the mechanical performance of Ti-based alloys. Recent studies suggest that the incorporation of fibrous or particulate reinforcements, such as SiC, TiB and TiC, is necessary to maintain their high specific strength at elevated temperatures. In this study, Ti-Mo-Al (Ti50Mo35Al15, at.%) alloys with various TiC additions (1, 5, 10 at.%) were prepared by arc melting technique. We examined the microstructure of these as-cast alloys by X-ray diffractometry (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution TEM (HRTEM). Their mechanical properties were systematically evaluated via compression experiments at various temperatures (T=298, 1073 and 1273 K), Vickers hardness as well as four-point bending tests. According to the experimental observations, all the alloys prepared in this work were composed of two phases, Ti-Mo-Al solid solution ( phase) matrix and TiC particles. Most of the TiC particles precipitated along grain boundaries, following the N-W crystallographic relationship with the matrix. Moreover, the effect of TiC addition on the microstructure of Ti-Mo-Al alloys was mainly manifested in the reduction of average grain size, which is ~80 m in the alloy without TiC but ~30 m in the 10 at.% TiC-added one. The addition of TiC leads to an obvious enhancement of strength at both room and high temperatures, without impairing the ductility. It is worth noting that the maximum flow stress achieved in the TiC-reinforced Ti-Mo-Al alloys at 1273 K is ~400 MPa. Therefore, the reinforcement by TiC is an effective way in improving the mechanical performance of Ti-Mo-Al alloys

Optimal Simple Regret in Bayesian Best Arm Identification

We consider Bayesian best arm identification in the multi-armed bandit problem. Assuming certain continuity conditions of the prior, we characterize the rate of the Bayesian simple regret. Differing from Bayesian regret minimization (Lai, 1987), the leading factor in Bayesian simple regret derives from the region where the gap between optimal and sub-optimal arms is smaller than $\sqrt{\frac{\log T}{T}}$. We propose a simple and easy-to-compute algorithm with its leading factor matches with the lower bound up to a constant factor; simulation results support our theoretical findings

The biosynthetic pathway of potato solanidanes diverged from that of spirosolanes due to evolution of a dioxygenase

ジャガイモの毒α-ソラニンはトマトの苦味成分から分岐進化したことを解明. 京都大学プレスリリース. 2021-03-03.Potato (Solanum tuberosum), a worldwide major food crop, produces the toxic, bitter tasting solanidane glycoalkaloids α-solanine and α-chaconine. Controlling levels of glycoalkaloids is an important focus on potato breeding. Tomato (Solanum lycopersicum) contains a bitter spirosolane glycoalkaloid, α-tomatine. These glycoalkaloids are biosynthesized from cholesterol via a partly common pathway, although the mechanisms giving rise to the structural differences between solanidane and spirosolane remained elusive. Here we identify a 2-oxoglutarate dependent dioxygenase, designated as DPS (Dioxygenase for Potato Solanidane synthesis), that is a key enzyme for solanidane glycoalkaloid biosynthesis in potato. DPS catalyzes the ring-rearrangement from spirosolane to solanidane via C-16 hydroxylation. Evolutionary divergence of spirosolane-metabolizing dioxygenases contributes to the emergence of toxic solanidane glycoalkaloids in potato and the chemical diversity in Solanaceae

Unruptured Arteriovenous Malformations of Brain: An overview

Arteriovenous malformations are congenital lesions that occur most commonly in the supratentorial region. These space-occupying vascular lesions consist of multiple arteries and veins, connecting as a fistula without an intervening normal capillary bed. Typically, AVM’s are single lesions, except when associated with hereditary hemorrhagic telangiectasia. The histology includes clusters of normal or dilated arteries and abnormal veins with calcification and occasionally some prior haemorrhage

Multiple early gastric cancer with duodenal invasion

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Differences in gait kinetics and kinematics between patients with rotating hinge knee and cruciate-retaining prostheses : A cross-sectional study

東京都立大学Tokyo Metropolitan University博士（理学療法学）doctoral thesi

Movement patterns of the functional reach test do not reflect physical function in healthy young and older participants

東京都立大学Tokyo Metropolitan University博士（理学療法学）doctoral thesi