Fracture toughness of short carbon fibre reinforced thermoplastic polyimide

The fracture toughness testing of short fibre reinforced thermoplastic materials were performed. Materials tested were the polyimide resin and also that reinforced with 20 wt% or 30 wt% short carbon fibre. For introducing the initial crack, the tapping method, the sliding method and the bridge indentation method were examined. Among them, the sliding method was found to be effective for every case. The fracture tests were conducted by the three-point bending test with several loading rates. Stable crack growth was observed for the neat material while unstable fracture occurred for the reinforced materials. The critical values of the stress intensity factor at crack initiation were greater for the reinforced materials than for the neat resin. The fracture toughness of the 30 wt% reinforced material was independent of loading rate while that of 20 wt% reinforced material increased with loading rate. In order to investigate the fracture mechanisms, fractographic observations were also performed.     

Anomalies of the tracheobronchial tree in patients with esophageal atresia

Bone marrow examination revealed a lipid-laden histiocytosis in seven patients undergoing long-term total parenteral nutrition necessitated by extensive short-bowel surgical resection. Clinical abnormalities occurred during this treatment which required bone marrow examination. These included hepatosplenomegaly and peripheral blood cytopenia; the median time to the detection of these abnormalities was 64 months. The most striking change within the bone marrow was the presence of many pigment-laden histiocytes which had the typical morphology of sea-blue histiocytes seen in the so-called idiopathic sea-blue histiocyte syndrome. The occurrence of sea-blue histiocytosis in the bone marrow in association with long-term parenteral nutrition for short-bowel syndrome has not, to our knowledge, been reported previously and should now be considered in the differential diagnosis of bone marrow sea-blue histiocytosis.     

Augmentation of boiling heat transfer from horizontal cylinder to liquid by movable particles

This paper presents a series of experimental results on a passive augmentation technique of boiling heat transfer by supplying solid particles in liquid. A cylindrical heater 0.88 mm in diameter is placed in saturated water, in which a lot of mobile particles exist, and the nucleate and film boiling heat transfer characteristics are measured. Particle materials used were alumina, glass, and porous alumina, and the diameter ranged from 0.3 mm to 2.5 mm. Particles are fluidized by the occurrence of boiling without any additive power, and the heat transfer is augmented. The maximum augmentation ratio obtained in this experiment reaches about ten times the heat transfer coefficient obtained in liquid alone. The augmentation ratio is mainly affected by the particle material, diameter, and the height of the particle bed set at no boiling condition. The augmentation mechanism is discussed on the basis of the experimental results. © 2001 Scripta Technica, Heat Trans Asian Res, 31(1): 28–41, 2002     

Novel anion exchange membranes having fluorocarbon backbone: Preparation and stability

Anion exchange membranes with excellent durability were prepared by chemical modification of Nafion. The modification was achieved by transformation of the sulfonic acid group into quaternary ammonium group. Namely, Nafion membrane was first converted into an amide-type membrane. Reduction of the carbonxyl group to methylene followed by quaternarization with alkyl iodide resulted in the formation of an anion exchange membrane. The electric resistance of the resulting membranes depends on the equivalent weight of the starting membranes (4.4–6.0 Ω cm² in 0.5N NaCl). The characteristics of the membranes are the excellent stability toward chemical substances such as organic solvents, oxidizing agents, acids, etc. For example, the membranes are stable in aqueous saturated chlorine solution at 60°C for 1000 hr.     

66/77-kV C-GIS using composite insulation in SF6 gas

A second-generation model of cubicletype gas-insulated switchgear (C-GIS) with composite insulation incorporating SF₆ gas has been developed. The design does not require a gas process in field assembly; it has high reliability and its installation is more rapid; and a further reduction in size is achieved. The design principles are described in detail.     

Balanced corpus of contemporary written Japanese

The balanced corpus of contemporary written Japanese (BCCWJ) is Japan’s first 100 million words balanced corpus. It consists of three subcorpora (publication subcorpus, library subcorpus, and special-purpose subcorpus) and covers a wide range of text registers including books in general, magazines, newspapers, governmental white papers, best-selling books, an internet bulletin-board, a blog, school textbooks, minutes of the national diet, publicity newsletters of local governments, laws, and poetry verses. A random sampling technique is utilized whenever possible in order to maximize the representativeness of the corpus. The corpus is annotated in terms of dual POS analysis, document structure, and bibliographical information. The BCCWJ is currently accessible in three different ways including Chunagon a web-based interface to the dual POS analysis data. Lastly, results of some pilot evaluation of the corpus with respect to the textual diversity are reported. The analyses include POS distribution, word-class distribution, entropy of orthography, sentence length, and variation of the adjective predicate. High textual diversity is observed in all these analyses.     

Stability of fine water droplet clouds

The rate of evaporation of monodisperse water droplets was first evaluated by solving numerically the modified Maxwell equation, assuming the cellular model for a droplet clouds. The results are discussed in comparison with those for a single isolated droplet, which can be obtained analytically. The critical conditions for the droplet cloud to be stable are then evaluated as a function of droplet number concentration, droplet size and initial conditions of the surrounding air. Secondly, the equilibrated system, where a water droplet cloud is steadily mixed with unsaturated air, was analysed on the basis of enthalpy and material balance of the system to evaluate the total volume change of the droplets. Some of these analyses were verified by experiment, using an ultramicroscopic technique which is useful for droplet size analysis.     

Heterogeneous nucleation of organic vapours on a cold substrate

The heterogeneous phase transition of the organic vapours, cyclohexane and p-xylene, on a cold substrate was observed by cooling the substrate at a slow rate under reduced pressure conditions. Either organic vapour at a vapour pressure lower than 130 Pa formed directly solid crystals but p-xylene vapour at a higher vapour pressure formed liquid condensates with subsequent formation of solid crystals. The dependence of the critical supersaturation ratios on the critical temperatures and the physical properties of the organic vapours has been clarified by the equation derived on the basis of classical nucleation theory.     

Influences of perforation ratio in characteristics of capacitive micromachined ultrasonic transducers in air

Capacitive micromachined ultrasonic transducers (CMUTs) with a perforated membrane have been fabricated and characterized in air. Two types of CMUT device have been fabricated having perforation ratio (area ratio of holes = AR) of 10% and 20%, and analyzed about electrical and mechanical characteristics. The perforation ratio (AR) of membrane substantially influences on the electrostatic force and mechanical restoring force of the device since it leads to the area variation of electrode and membrane, it subsequently influences on the sensitivity and frequency response of the CMUT device. The electrostatic force and mechanical restoring force were improved by decreasing the AR and increasing the DC bias voltage. The open-circuit sensitivity of a CMUT having AR 10% membrane, 8.45 μV/Pa, is larger than that of AR 20%, 4.07 μV/Pa at DC 15 V. Furthermore, the resonance behaviors were observed in the range of 60-80 kHz, and the resonance frequency could be changed by varying the applied DC voltage and AR.     

Preparation of ferroelectric Ba(Ti/sub 0.85/Sn/sub 0.15/)O/sub 3/ thin films by metal-organic decomposition

Ferroelectric Ba(Ti/sub 0.85/Sn/sub 0.15/)O/sub 3/ (BTS/sub 15/) thin film is newly prepared on the Pt/Ti/SiO/sub 2//Si substrate by metal-organic decomposition. The firing condition is determined by thermogravimetric and differential thermal analysis. The BTS/sub 15/ thin film with a flat surface and uniform thickness is obtained by spin coating in N/sub 2/ atmosphere that avoids moisture. The BTS/sub 15/ film has a perovskite phase and a preferential [110] texture. It is also found that the crystalline structure is cubic at 24/spl deg/C with a lattice constant of 4.01 /spl Aring/, and a grain size of about 30 nm was estimated by Scherrer equation and SEM image. From P-E hysteresis loop at 20/spl deg/C, the polarization at E=0 and the electric field at P=0 are found to be 1.07 /spl mu/C/cm/sup 2/ and 24.0 kV/cm, respectively. It is observed that the dielectric constant decreases monotonously from about 830 to 630 with increasing temperature ranging from 20/spl deg/C to 50/spl deg/C. Finally, it is found that the BTS/sub 15/ thin film shows a sufficient ferroelectricity and is an attractive material for functional ferroelectric devices, such as thermal-type infrared sensors.