Fracture Process of Silicon Carbide Fiber-Reinforced Glasses

This paper evaluates the fracture process for fiber-reinforced glasses under tensile loading. Two types of unidirectionally aligned Nicalon SiC-fiber-reinforced glass with different fiber coatings were examined. One channel acoustic emission (AE) measurement was employed during the tensile tests. Probabilistic fracture analysis as well as the replication technique were used to investigate the relation between the AE signals and fracture processes. The AE technique proved to be an effective method for observing fracture processes of the material systems studied. The fracture process could be distinguished in terms of the AE amplitude. AE signals with high amplitudes corresponded to fiber breaking; AE signals with low amplitudes corresponded to matrix cracking, interfacial debonding, and fiber pullout. In the well-toughened material studied the reinforcing fibers would break extensively over 75% load of the ultimate strength.     

Electrode heat balances of electrochemical cells: application to NaCl electrolysis

This paper deals with a method of estimating single electrode heat balances during the electrolysis of molten NaCl-ZnCl₂ in a cell using a-alumina diaphragm. By measuring the thermoelectric power of the thermogalvanic cells: (T) Na/-alumina/NaCl-ZnCl₂/-alumina/Na(T+dT) and (T) C,Cl₂/NaCl-ZnCl₂/Cl₂,C(T+dT) the single electrode Peltier heat for sodium deposition and for chlorine evolution at 370° C were estimated to be –0.026±0.001 JC^–1 and+0.614±0.096 J C^–1, respectively.     

Production of clean fuels by solvent skimming of coal at around 350 °C

The authors have recently presented a new coal extraction method by which various kinds of coals ranging from brown coals to bituminous coals could be extracted up to 80% of the parent coals in a flowing stream of tetralin or a coal derived oil, carbol oil, under 10 MPa at 350 °C. The extract obtained by this method was almost free from inorganic materials. In this study the effect of solvent recycling on the extraction behavior was examined to make the method practically applicable. The solvent recycling was found to be effective in enhancing the extraction yield and in decreasing further the inorganic fraction in the extract. The extract and residue obtained were characterized through various analyses. To examine how inorganic materials are removed by the extraction, the contents of inorganic elements, including harmful trace elements, in the extract were investigated. It was clarified that the presented method was effective in the removal of most of the inorganic elements including even harmful trace elements from coals, although the degree of removal was dependent on the kind of element.     

Solvothermal syntheses of semiconductor photocatalysts of ultra-high activities

Thermal treatment of titanium(IV) butoxide dissolved in 2-butanol at 573 K under autogenous pressure (alcohothermal treatment) yielded microcrystalline anatase-type titanium(IV) oxide (TiO₂). Thermal treatment of oxobis(2,4-pentanedionato-O,O′)titanium (TiO(acac)₂) in ethylene glycol (EG) in the presence of sodium acetate and a small amount of water at 573 K yielded microcrystalline brookite-type TiO₂. Tungsten(VI) oxide (WO₃) powders of monoclinic crystal structure with high crystallinity were synthesized by hydrothermal treatment (HTT), at 523 or 573 K, of aqueous tungstic acid (H₂WO₄) solutions prepared from sodium tungstate by ion-exchange (IE) with a proton-type resin. Anatase and brookite TiO₂ products were calcined at various temperatures and then used for photocatalytic mineralization of acetic acid in aqueous solutions under aerated conditions and dehydrogenation of 2-propanol under deaerated conditions. Almost all the anatase-type TiO₂ samples showed the activities more than twice higher than those of representative active photocatalysts, Degussa P-25 and Ishihara ST-01 in both reactions. A brookite sample with improved crystallinity and sufficient surface area obtained by calcination at 973 K exhibited the hydrogen evolution rate almost equal to P-25. HTT WO₃ powders with various physical properties were used as photocatalyst for evolution of oxygen (O₂) from an aqueous silver sulfate solution. WO₃ powder of high crystallinity, e.g., IE-HTT-WO₃ synthesized at 573 K, gave much higher O₂ yield than commercially available WO₃ samples.     

Improved delay-dependent stability analysis for uncertain stochastic neural networks with time-varying delay

This paper focuses on the problem of delay-dependent robust stability analysis for a class of uncertain stochastic neural networks with time-varying delay by employing improved free-weighting matrix method. Taking the relationship among the time-varying delay, its upper bound and their difference into account and using It[^(o)]'s\hbox{It}\hat{o}\hbox{'s} differential formula, some improved LMI-based delay-dependent stability criteria for stochastic neural networks are obtained without ignoring any terms, which guarantee systems globally robustly stochastically stable in the mean square. Finally, three numerical examples are given to demonstrate the effectiveness and the benefits of the proposed method.     

Three DOF parallel link mechanism utilizing smooth impact drive mechanism

For a wide range of purposes, a compact and smart positioning stage is in strong demand. Our final goal is to fabricate a positioning mechanism that possesses multi-degrees of freedom, a wide movable area, dexterity, rigidity, and high speed. To meet most of requirements, i.e., except that of a wide movable area, a parallel mechanism is superior to a serial link mechanism. However, a lack of smart actuators has previously resulted in a large and complicated construction of a parallel mechanism.A purpose of this paper is to propose a new parallel link that utilizes a smart actuator called smooth impact drive mechanism (SIDM), and to verify its advantage for a smart and compact positioning stage. The SIDM actuator is an interesting mechanism that achieves a long stroke with fine positioning resolution. This paper treats a three DOF stage containing three SIDM actuators and a two-dimensional positioning sensor. The first operation test was carried out, and it was confirmed that a position control was successful. The average deviation was 18.6 μm and the standard deviation was 9.31 μm. As another trial, a circle 3.0 mm in diameter was successfully drawn. These values were insufficient for the SIDM actuator that has potentially nanometer-level resolution. The rough positioning resolution seems to be due to inferior driving method and mechanical ricketiness of the joints. In the near future, high speed and accurate positioning control could be realized with overcoming these problems.     

Indoor air quality for chemical and ultrafine particle contaminants from printers

There are various emission sources of chemical contaminants, such as volatile organic compounds (VOCs) and ozone and particulate matter. This report is a study into the indoor air of a room containing either a laser printer/ink-jet printer, and the air contaminations were monitored for VOCs, ozone and ultrafine particle. The result confirmed an increase in the concentration of ozone and ultrafine particle numbers in the printing processes of the printer. The emission of VOCs and ozone were measured by the use of a test chamber. The chamber concentrations of styrene, xylenes and ozone were increased in printing process of the laser printer, and pentanol was detected from the ink-jet printer. The results suggest that an office or residential printer may be a source of indoor air contamination. It is necessary for emission from printers to monitor not only VOCs and particle but also ultrafine particles and other contaminants in indoor air.     

Development of the residual sodium quantification method for a fuel pin bundle of SFRs before and after dry cleaning

ABSTRACT

In a fuel handling system of sodium-cooled fast reactors (SFRs), it is necessary to remove the sodium remaining on spent fuel assemblies (FAs) before storing them in a spent fuel water pool (SFP). A next-generation SFR in Japan has adopted an advanced dry-cleaning system that consists of argon gas blowing to remove the metallic residual sodium on the FA, which increases economic competitiveness and reduces waste products thanks to a waterless process. In this R&D work, the performance of the dry cleaning process has been investigated.

This paper describes experimental and analytical studies focusing on the amount of residual sodium remaining on a fuel pin bundle before and after the argon gas blowing process. The experiments were conducted using a sodium test loop and a short (approximately 1 m) specimen consisting of a 7-pin bundle. The effects of the blowing gas velocity and the blowing time were quantitatively analyzed in the experiments. The blowing gas velocity was varied from 3.9 to 31.3 m/s, and 113 data-points of the residual sodium were collected during the experiment. On the basis of these experimental results, the residual sodium quantification method for the fuel pin bundle was constructed.     

Influences of repetition rate of laser pulses on growth of crystalline AlN films on sapphire(0001) substrates by pulsed laser deposition

We investigated influences of a repetition frequency of laser pulses on growth of AlN crystalline films by pulsed laser deposition. The structural and morphological properties of the films were studied by X-ray diffraction and scanning electron microscopy. Employment of high frequency laser pulses not only enhanced the growth of AlN crystallites, but also afforded the crystal growth at higher nitrogen pressures. Growth of α-AlN was dramatically enhanced with an increase in the laser pulse frequency, while β-AlN was grown at the high frequency of laser pulses and high nitrogen pressures.