Low-temperature chemical synthesis of intermetallic TiFe nanoparticles for hydrogen absorption

Nanosizing of TiFe hydrogen storage alloy is conducted to facilitate its activation. Here, pure intermetallic TiFe nanoparticles (45 nm) were prepared using chemical reduction of oxide precursors at 600 °C, which is the lowest temperature ever used in chemical synthesis. This was achieved using a strong reducing agent (CaH₂) in a molten LiCl. When used for hydrogen absorption, the obtained nanoparticles surprisingly exhibited almost no hydrogen absorption. The results demonstrated that TiFe nanoparticles are more difficult to activate than the bulk powder because the oxidized surface layers of the nanoparticles become stabilized, which prevents the morphological change necessary for their activation.     

Mechanical properties and microstructures of β Ti–25Nb–11Sn ternary alloy for biomedical applications

The mechanical properties and microstructures of β Ti–25%Nb–11%Sn ternary alloy rods were investigated for biomedical applications as a function of heat treatment temperature after swaging by an 86% reduction in cross-section area. An as-swaged rod consisting of a β (bcc) single phase shows a low Young's modulus of 53 GPa, which is interpreted in terms of both the metastable composition of the β alloy undergoing neither an athermal ω transformation nor a deformation-induced ω transformation and < 110>texture development during swaging. Heat treatment at 673 K (400 °C) for 2 h leads to a high strength of approximately 1330 MPa and a high spring-back ratio of yield stress to Young's modulus over 15 × 10^? 3, with acceptable elongation. This high strength is attributable to needle-like α precipitates, which are identified by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and high-resolution electron microscopy (HREM).     

A screening gate to prevent entry of mobile telephone handsets inthe speaking/standby mode into prohibited and restricted areas

Electromagnetic interference to electronic equipment by mobile telephone handsets is well known. We present an automatic screening gate that detects concealed mobile telephone handsets and classifies them by type. The screening method used in the gate does not require any additions to or reconstruction of mobile telephone systems     

Gestural cue analysis in automated semantic miscommunication annotation

The automated annotation of conversational video by semantic miscommunication labels is a challenging topic. Although miscommunications are often obvious to the speakers as well as the observers, it is difficult for machines to detect them from the low-level features. We investigate the utility of gestural cues in this paper among various non-verbal features. Compared with gesture recognition tasks in human-computer interaction, this process is difficult due to the lack of understanding on which cues contribute to miscommunications and the implicitness of gestures. Nine simple gestural features are taken from gesture data, and both simple and complex classifiers are constructed using machine learning. The experimental results suggest that there is no single gestural feature that can predict or explain the occurrence of semantic miscommunication in our setting.     

Macro—and microstructural changes in hydrogenated TiMn2 and Ta

Binary TiMn2 alloys with various compositions were arc melted in an Ar atmosphere.These alloys consist of TiMn2 and a small amount of TiMn depending on alloy composition.Annealed Ti-59.4%Mn exhibits the greatest capacity for hydrogen absorption and the smallest degradation of capacity during repeated hydrogen absorption and desorption.No apparent macro-and microstructural chanes are observed in Ti-59.4%Mn by repeated hydrogenation of 30cycles.At Mn content higher than 59.4%Mn,the formation of nano-sized Ti-hydride and the lattice expansion due to retained interstitial hydrogen were confirmed in repeatedly hydrogenated alloys.Pulverized powders were refined in all the alloys with increasing the number of repeated hydrogenation cycles.Many onion-like cracks are introduced in annealed pure Ta with 100℃m equi-axed grains by holding at 1473K followed by furnace cooling to room temperature in a hydrogen atmosphere,but no crack is observed after holding at 1473K in a hydrogen atmosphere followed by furnace cooling in an Ar atmosphere.It is concluded that the surface activation is attained in a hydrogen atmosphere at 1473K and multiple cracking occurs by absorbing a large amount of hydrogen at lower temperature.Volume expansion and dislocations generated by hydrogenation and hydride formation are responsible for multiple cracking.Hydrogen-induced multiple cracking in Ta occurs in the following sequence:hydrogen absorption,lattice expansion,hydride formation,and crack nucleation and propagation.Powder fabrication of Ta by hydrogenation is discussed in comparison with the hydrogen pulverization of intermetallic alloys.     

Analysis of the self-excited three-phase synchronous generator utilizing the second space harmonic for excitation

In a previous paper, we proposed a new self-excited three-phase synchronous generator in which the second space harmonic component of the armature reaction field is used for exciting the field system, and clarified its operating principles and basic characteristics by experiment. The new generator has a series excitation characteristic, and responds quickly to a sudden change of load, because an excitation power can be directly obtained from the armature reaction field. This paper introduces a method for analyzing the steady-state performance of our new generator. In the analysis, an equivalent circuit of the generator is derived from a duality between interlinked electric and magnetic circuits. A simple determination method of parameters in the equivalent circuit is also shown. Calculated results are compared with the experimentally obtained values on a laboratory machine, and good agreement between both values has been observed. The proposed analysis is useful for simulating the steady-state performance of the generator by taking into account the nonlinear effect of the iron core due to magnetic saturation. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 121(1): 70–81, 1997     

Growth of Polarity-Controlled ZnO Films on (0001) Al<Subscript>2</Subscript>O<Subscript>3</Subscript>

The polarity control of ZnO films grown on (0001) Al₂O₃ substrates by plasma-assisted molecular-beam epitaxy (P-MBE) was achieved by using a novel CrN buffer layer. Zn-polar ZnO films were obtained by using a Zn-terminated CrN buffer layer, while O-polar ZnO films were achieved by using a Cr₂O₃ layer formed by O-plasma exposure of a CrN layer. The mechanism of polarity control was proposed. Optical and structural quality of ZnO films was characterized by high-resolution X-ray diffraction and photoluminescence (PL) spectroscopy. Low-temperature PL spectra of Zn-polar and O-polar samples show dominant bound exciton (I₈) and strong free exciton emissions. Finally, one-dimensional periodic structures consisting of Zn-polar and O-polar ZnO films were simultaneously grown on the same substrate. The periodic inversion of polarity was confirmed in terms of growth rate, surface morphology, and piezo response microscopy (PRM) measurement.     

Successful treatment of dark-colored epidermal nevus with ruby laser

The pulsed ruby laser has a selective thermolytic effect. Recently, it has been available for the treatment of superficial pigmented disorders. We studied 5 cases of epidermal nevus treated with the pulsed ruby laser. In comparison with the usual methods including electrocautery, cryotherapy and skin abrasion, ruby laser therapy is an excellent tool due to technological ease and rapid improvement. Depigmentation after treatment in 2 cases was the only side effect of this therapy. Bose cases had a dark pigmentation of the skin. Despite of the risk of discoloration, the ruby laser is one of the most effective tools for therapy of pigmented epidermal nevus.