Method for grinding and delaminating muscovite

A method of dry grinding muscovite based on the use of knife-mills is reported. It was possible to produce mica with a particle size below 100 and 45 μm. After grinding, the samples were submitted to sonication treatment, which promoted delamination of the material. The particle size distribution shows that sonicated mica has more particles in the size range 10-50 μm than does non-sonicated mica have.This also indicates a decrease in the average particle size. Characterization of the treated muscovite by scanning electron microscopy revealed a highly delaminated material with a plate-like structure. The products were characterized by chemical analysis and X-ray diffraction, too. This mica has already been used for the synthesis of pearlescent pigments.     

Dependence of tunneling current through a single molecule of phenylene oligomers on the molecular length

The electrical properties of single phenylene oligomers were studied in terms of the dependence of the tunneling current on the length of the oligomers using self-assembling techniques and scanning tunneling microscopy (STM). It is important to isolate single molecules in an insulating matrix for the measurement of the conductivity of the single molecule. We demonstrate here a novel self-assembled monolayer (SAM) matrix appropriate for isolation of the single molecules. A bicyclo[2.2.2]octane derivative was used for a SAM matrix, in which the single molecules were inserted at molecular lattice defects. The isolated single molecules of phenylene oligomers inserted in the SAM matrix were observed as protrusions in STM topography using a constant current mode. We measured the topographic heights of the molecular protrusions using STM and estimated the decay constant, beta, of the tunneling current through the single phenylene oligomers using a bilayer tunnel junction model.     

Human-sized anthropomorphic robot hand with detachable mechanism at the wrist

In this paper, we proposed a human-sized multi-fingered robot hand with detachable mechanism at the wrist. The fingers are tendon-driven by wires and the actuators are embedded in the arm part. The driving forces from the arm part are transmitted to the hand part by a gear mechanism at the wrist. The gear mechanism makes the hand part and the arm part splittable. The detachable mechanism enables separate maintenance of the hand and arm parts. To avoid undesired joint mutual interferences due to the tendon-driven mechanism, a joint motion correction control is implemented in that counteracting motions are ordered to actuators. The correction coefficient can be calculated based on the mechanical configuration. The developed robot hand has the size of 200[mm](length) × 78[mm](width) × 24.6[mm](thickness) and can exert 10[N] at the fingertip. The performance of the developed robot hand was shown by a motion control experiment.     

Tunnelling through an embankment using all ground fasten method

The Tohoku Shinkansen Railway between Morioka and Hachinoe was opened on December 1, 2002. In this section, there are 20 tunnels. Second Itsukaichi tunnel is one of them, and it is a relatively short tunnel of 1175 m. At the Morioka portal, this tunnel crosses under National Highway No. 4 with a small depth of overburden 2–5 m where approximately 15,000 vehicles pass a day. The tunnel was excavated by NATM method. All Ground Fasten method was used as an auxiliary method. As a result, the face was prevented from collapsing and the tunnel was excavated while keeping the ground surface settlement to a minimum without interfering with road traffic.     

The effects of surfactant on the multiscale structure of bubbly flows

It is well known that a bubble in contaminated water rises much slower than one in purified water, and the rising velocity in a contaminated system can be less than half that in a purified system. This phenomenon is explained by the so-called Marangoni effect caused by surfactant adsorption on the bubble surface. In other words, while a bubble is rising, there exists a surface concentration distribution of surfactant along the bubble surface because the adsorbed surfactant is swept off from the front part and accumulates in the rear part by advection. Owing to this surfactant accumulation in the rear part, a variation of surface tension appears along the surface and this causes a tangential shear stress on the bubble surface. This shear stress results in the decrease in the rising velocity of the bubble in contaminated liquid. More interestingly, this Marangoni effect influences not only the bubble's rising velocity but also its lateral migration in the presence of mean shear. Together, these influences cause a drastic change of the whole bubbly flow structures. In this paper, we discuss some experimental results related to this drastic change in bubbly flow structure. We show that bubble clustering phenomena are observed in an upward bubbly channel flow under certain conditions of surfactant concentrations. This cluster disappears with an increase in the concentration. We explain this phenomenon by reference to the lift force acting on a bubble in aqueous surfactant solutions. It is shown that the shear-induced lift force acting on a contaminated bubble of 1mm size can be much smaller than that on a clean bubble.     

Curing of epoxy resin by ultrafine silica modified by grafting of hyperbranched polyamidoamine using dendrimer synthesis methodology

Hyperbranched polyamidoamine–grafted silica was prepared according to dendrimer synthesis methodology. The modified silica was dispersed uniformly in epoxy resin, and the curing of epoxy resin proceeded successfully by heating in the presence of the modified silica; the gel fraction of the epoxy resin cured by the hyperbranched polyamidoamine–grafted silica (grafting = 80.2%) reached 77% at 170°C after 48 h. The gel fraction increased with increasing terminal amino group content of the hyperbranched polyamidoamine–grafted silica. In addition, the curing ability of the silica increased by complexation of the terminal amino groups of the grafted polyamidoamine with boron trifluoride. The modulus of elasticity of the curing materials obtained using the modified silica as a curing agent was lower than that using conventional a curing agent such as ethylenediamine in the presence of untreated silica. On the other hand, the heat resistance of the curing product using the modified silica was superior to that using ethylenediamine, but no difference in glass‐transition temperature was observed. It is expected that hyperbranched polyamidoamine grafted‐silica is incorporated uniformly with chemical bonds in the matrix of the epoxy resin. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 573–579, 2001     

A three‐phase hybrid stepping motor drive system combined with position‐sensorless closed‐loop control

This paper proposes a drive system for a three‐phase hybrid stepping motor, combining sensorless closed‐loop control with conventional open‐loop control. It is characterized by sophisticated control providing both prevention of pulling out from synchronism and suppression of natural rotor oscillation, without any position sensor attached to the motor shaft. A switching technique in chopper control which can enlarge the speed range controllable in the sensorless closed‐loop control is described. Starting and stopping sequences are developed to reduce mechanical natural oscillation produced in the transient state. Finally, the proposed drive system is compared experimentally with a conventional constant‐current open‐loop drive system. It is shown that the proposed drive system can perform the switchover from starting to sensorless closed‐loop operation within 20 ms, and can reduce the natural oscillation caused just after positioning. © 2000 Scripta Technica, Electr Eng Jpn, 131(3): 80–90, 2000     

Control and performance of a zero‐current‐switched,three‐phase PWM inverter equipped with resonant circuits on the ac side

This paper presents a zero‐current‐switched voltage‐fed inverter equipped with resonant circuits on the ac side. The current flowing through a switching device, that is, IGBT, is the sum of the load current and the resonant current. When the amplitude of the resonant current is larger than that of the load current, the current in the switching device becomes zero at an instant in each resonant cycle. This allows the switching device to be turned on or off at the zero current. The zero‐current switching makes a significant contribution to reduction of switching losses and electromagnetic noises. In this paper, the principle of zero‐current‐switching operation, along with a novel control scheme, is described from a theoretical and practical point of view. Experimental results obtained from a laboratory system of 5 kVA verify the practicability. Moreover, the switching and conduction losses of the proposed soft‐switched inverter are compared with those of a conventional hard‐switched inverter. © 2000 Scripta Technica, Electr Eng Jpn, 131(4): 85–95, 2000     

Accumulation of Misfolded Protein Aggregates Leads to the Formation of Russell Body-like Dilated Endoplasmic Reticulum in Yeast

RNAP-I, an aspartic proteinase from a filamentous fungus Rhizopus niveus, is secreted very efficiently in Saccharomyces cerevisiae. It is synthesized first as a precursor form with signal sequence and prosequence in its amino-terminus. Our previous study indicated that the prosequence of RNAP-I had important roles in its correct folding and secretion in yeast, and that a prosequence-deleted derivative of RNAP-I, Δpro, was not secreted but was retained and degraded in the yeast endoplasmic reticulum (ER). In the present study, we show that the accumulation of Δpro in the yeast ER caused elevated synthesis of ER resident chaperones, indicating that Δpro is recognized as an unfolded protein species in the ER. Our biochemical data demonstrated that Δpro formed aggregates which contained BiP, but not protein disulfide isomerase (PDI), in the ER. Immunoelectron microscopical analysis revealed that the Δpro aggregates were indeed visible as electron-dense regions in the ER and nuclear envelope. Such ‘chaperone-associated misfolded protein bodies’ were observed for the first time in yeast. Morphologies of the ER and nucleus were drastically altered by the accumulation of the Δpro aggregates. The ER lost its flat cisternal shape; the ER lumen extended aberrantly and the ER membrane irregularly proliferated. The misfolded Δpro proteins are probably sorted from the ordinary ER lumen to form the aggregates so that the ER function would not be grossly impaired, and the dilated ER may represent an ER subcompartment where the Δpro aggregates are degraded. © 1997 by John Wiley & Sons, Ltd.