Impurity‐Induced First‐Order Phase Transitions in Highly Crystalline V2O3 Nanocrystals

A first‐order phase transition in a bulk material is generally considered to arise at extended defects such as grain boundaries or dislocations, where the energetic barrier between the two phases is reduced. Downsizing a crystal to the nanoscale can exclude the number of defects, leading to enhanced kinetic stabilization of the metastable phase. Here, the disappearance of the first‐order metal–insulator transition in defect‐free V₂O₃ nanocrystals and the revival of the transition by introducing a certain Cr or Ti impurity content are investigated. The hysteresis width of the transition corresponding to the barrier height decreases with the impurity content. It is proposed that homogeneous impurity doping is a universal method that can control the occurrence of a first‐order phase transition in nanoscale materials.     

Shape correction of optical surfaces using plasma chemical vaporization machining with a hemispherical tip electrode

We propose a plasma chemical vaporization machining device with a hemispherical tip electrode for optical fabrication. Radio-frequency plasma is generated close to the electrode under atmospheric conditions, and a workpiece is scanned relative to the stationary electrode under three-axis motion control to remove target areas on a workpiece surface. Experimental results demonstrate that surface removal progresses although process gas is not forcibly supplied to the plasma. The correction of shape errors on conventionally polished spheres is performed. As a result, highly accurate smooth surfaces with the desired rms shape accuracy of 3 nm are successfully obtained, which confirms that the device is effective for the fabrication of optics.     

Research on traversability of tracked vehicle on slope with unfixed obstacles: derivation of climbing-over,tipping-over,and sliding-down conditions

When a tracked robot explores a volcanic environment, it faces difficulty in climbing over unfixed obstacles such as loose rocks on the ground. Such unfixed obstacles sometimes cause the sliding-down or tipping-over of the robot. Although such phenomena should be avoided for the success of the mission, they have not been sufficiently studied yet. Therefore, this research aims at understanding the phenomena for a tracked vehicle climbing an unfixed obstacle on a slope, and considers the conditions of climbing-over, tipping-over, and sliding-down. To simplify the problem, a model of a single track and circular cross-section obstacle is used in this research. The climbing-over and tipping-over conditions are derived from the geometric relationship, and the sliding-down condition is derived from statics. Moreover, some experiments using an actual robot are conducted to verify the validity of the conditions. The results show that the derived conditions are reasonable. Furthermore, it is revealed that unfixed obstacles typically tend to slide down more than fixed obstacles because of the number of contact points that can support a robot.     

Motion support during the swing phase using cooperative walking support system

Walking support systems have been developed for supporting the motion of the elderly and physically disabled. In this research, we propose a walking support system based on the cooperation between wearable-type and cane-type walking support systems for supporting hemiplegic patients with disabilities. The system is controlled based on the intended motion of the user, their state and environmental information. In this system, we aim to realize several functions for supporting the daily life of the user by cooperatively controlling each walking support systems including walking support, sit-to-stand assistance, navigation, fall prevention and so on. As the first step to build this system, we focus on the walking support in this paper. For realizing the walking support, we propose a wearable-type walking support system that assists leg motion during the swing phase based on the motion of a cane-type walking support system moved by the user.     

Double‐faced TFT‐LCD having one LC panel and one lighting system

Abstract— We have developed a novel liquid‐crystal‐display (LCD) system referred to as a “Double‐Faced LCD.” It has only one LC panel and one lighting system, but it works not only as a transmissive‐type LCD from one side but also as a reflective‐type LCD from the other side. Therefore, the thickness and the weight of the Double‐Faced LCD can be reduced compared to those of conventional LC modules that have two LC panels and two lighting systems.     

Optoelectronic oscillator employing reciprocating optical modulator for millimetre-wave generation

An optoelectronic oscillator that employs a reciprocating optical modulator is demonstrated. By giving positive optoelectronic feedback to the modulator, the reciprocating modulation in the modulator effectively multiplies the fundamental oscillation frequency by several times. A 52.8 GHz millimetre-wave signal is generated by self-oscillation.     

Differential scanning calorimetry of polysulfone at high pressures of CO2 and N2O

Summary Polysulfone is less plasticized by compressed CO₂ than are amorphous vinyl polymers such as atactic polystyrene or poly(methyl methacrylate). N₂O, which is more polar than CO₂, is slightly more effective for plasticizing polysulfone than CO₂. Under the atmosphere of each gas, the depression in T _g is found to be linear with pressure. The dependence of T _g on pressure of CO₂ is −0.52 K·bar⁻¹, while that for N₂O is −0.60 K·bar⁻¹. Chow's thermodynamic model in combination with readily available gas solubility data does not describe well the pressure dependence of T _g in the polysulfone/CO₂ system. Received: 7 June 1999/Revised version: 19 August 1999/Accepted: 23 August 1999     

Long-life planar oxygen sensor

A planar amperometric oxygen sensor has been developed using a printing method for an Ag anode and a four-layered structure for an electrolyte solution. The sensor consists of four glass substrates stuck together by epoxy resin. A Pt cathode and an Ag anode are deposited on one of these glass substrates by r.f. sputtering and by printing, respectively. An internal electrolyte solution is enclosed in the structure and sealed off by an oxygen-permeable membrane. A linear relationship is obtained between the reduction current and the partial pressure of oxygen in the range 0–600 mmHg. The current at an oxygen pressure of 100 mmHg is stable for more than 2000 h. The amount of Ag anode patterned by the printing method is found to be sufficient for continuous long-term use. Based on methods and structures similar to those described in this paper, it should be possible to fabricate miniaturized oxygen sensors and biosensors.     

High efficiency ester condensation using hydrophobic zeolite membranes

We successfully developed zeolite membranes with hydrophilic character, by choosing appropriate zeolites in terms of hydrophilicity and high acid tolerance. We evaluated thus developed membranes by their pervaporation (PV) performance, dehydration from acidic organic solvent. The zeolite membranes we developed, based on merlinoite (MER), chabazite (CHA) or phillipsite (PHI), are shown to exhibit stable dehydration performance, respectively. We successfully applied the membranes to the selective removal of water in an ester condensation reaction starting from a stoichiometric mixture of a carboxylic acid and an alcohol. The availability of pervaporation-assisted ester condensation reaction was validated by various kinds of combinations of carboxylic acid and alcohols, which implies the general availability of pervaporation-assisted process intensification by zeolite membranes. This paper was presented at the 11th Korea-Japan Symposium on Catatysis held at Seoul, Korea, May 21–24, 2007.     

A novel hermetic‐sealing material for FEDs

Abstract— An hermetic‐sealing material for FEDs composed of thermosetting polyimide and glass fiber, has been developed. The main backbone and end‐capping material of polyimide were investigated to satisfy both high Tg and high flowability. A thermosetting function, 4‐phenylethynylphthalic anhydride (PEPA), was used as the end‐capping material. The fracture of a rigid and softening structure was optimized in the main polymer structure. The obtained polyimide demonstrated both a high Tg (265°C) and low viscosity (98 Pa‐sec at a sealing temperature of 350°C). In order to improve the gas permeability and the mechanical and thermal characteristics of the sealing material, a mixture of various types of ceramic fillers and polyimide has been investigated, and glass fiber was adopted. When 30 wt.% of glass fiber was combined when the developed polyimide, the Ar permeability and coefficient of thermal expansion of the sealing material decreased to below one‐half of the base polyimide. This material enables us to seal at a temperature of about 350°C in nitrogen atmosphere and shows superior performance suitable for glass‐to‐glass sealing.