A master-slave control system for a semi-autonomous underwater vehicle-manipulator system

Underwater vehicle-manipulator systems (UVMS) are expected to play an important role in ocean exploration. It is considered that UVMS will be operated by both automatic and manual control. We have proposed an automatic control method. In this article, we propose a master-slave system for a UVMS. The effectiveness of the proposed master-slave control system is demonstrated by using a floating underwater robot with a 2-link manipulator.     

Strain-rate dependence of low cycle fatigue behavior in a simulated BWR environment

The strain-rate dependence of low cycle fatigue behavior of ASTM A533B low-alloy steel was investigated in a simulated BWR environment. Fatigue resistance of the steel was found to be closely dependent on cyclic strain rate in high-temperature water. A tortuous cracking morphology was dominant at high strain rate and typical fan-like or quasi-cleavage cracking patterns were frequently observed on the corresponding fracture surface. An entirely straight cracking morphology, however, became dominant at low strain rate. Evidence of crack arrest was found on the fracture surface rather than fan-like or quasi-cleavage cracking patterns. The above cracking behavior in simulated BWR water may be attributed to a strain-rate-induced change in the dominant environmentally assisted cracking (EAC) mechanism from hydrogen-induced cracking to film-rupture/slip-dissolution-controlled cracking.     

An apparent ensemble effect in the oxidative coupling of methane on hydroxyapatites with incorporated lead

The introduction of small quantities of lead into calcium hydroxyapatite catalysts produces marked increases in the selectivity to C₂₊ hydrocarbons, while the conversion of methane remains relatively constant. Small surface concentrations of lead are sufficient to achieve C₂₊ selectivities of 80 and 90%, with oxygen and nitrous oxide, respectively, in contrast with 18 and 46%, respectively, obtained in the absence of lead. Since surface concentration of lead species sufficient to stabilize pairs of methyl radicals in close proximity to each other would be expected to facilitate the formation of C₂ hydrocarbons, an ensemble effect appears to be extant.     

Microporous carbons prepared from cationic surfactant-resorcinol/formaldehyde composites

Microporous carbons have been synthesized by the carbonization of cationic surfactant-resorcinol/formaldehyde (RF) composites, which were themselves formed by electrostatic organic-organic interaction. The porous structure produced by the decomposition of the surfactant plays an important role for the gasification of the RF polymer at higher temperatures. The pore size of the carbon prepared from tetrapropylammonium bromide (TPAB)-RF, cetyltrimethylammonium bromide (C₁₆TAB)-RF and decyltrimethylammonium bromide (C₁₀TAB)-RF mixtures can be estimated as 0.53 nm from the Horvath-Kawazoe method using N₂ adsorption isotherms. Their pore size distributions were very narrow, showing that the microporous carbons derived from surfactant-RF mixture may have promise as adsorbents and membrane materials.     

Recoverable shear strain of liquid crystal‐forming concentrated hydroxypropyl cellulose solutions

The recoverable shear strain (S_R) for the liquid crystal‐forming hydroxypropyl cellulose solutions was determined by means of a concentric cylinder rotational apparatus as functions of shear stress prior to recovery and concentration of the solutions at 30°C. S_R greatly depended on shear stress and concentration; the phase of the solution (the single phase or biphase) governed the dependences of S_R on stress and concentration. S_R increased with increasing stress for the single phase and decreased for the biphase. S_R seemed to be related to the die swell (B): S_R ∝ Bⁿ. S_R exhibited a maximum and a minimum with respect to concentration. S_R for the cellulosic cholesteric liquid crystalline solutions was greater than that for the isotropic solutions. A model was proposed for explaining the greater S_R. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 865–872, 2002     

Influence of the nigrosine dye on the thermal behavior of polyamide 66

To reveal the effect of the nigrosine dye, that the addition of the dye lowers the crystallization point (T_c) of molten polyamide resins with substantially no shift in the melting point (T_m), thus suppressing the crystallization enhancement of the crystalline nucleation agents, the characteristics of polyamide 66 (PA‐66) containing nigrosine dye EX (N‐EX) were investigated. Differential scanning calorimetry (DSC) analysis showed that the addition of N‐EX reduced the crystallization rate and T_c of molten PA‐66 with substantially no shift in T_m, and the crystallization enthalpy per unit of weight of PA‐66 was substantially constant. T_c of molten PA‐66 was lowered with an increase in the amount of N‐EX and reached its maximum at 13 wt % N‐EX. Dynamic mechanical analysis showed that the glass‐transition temperature and the secondary glass‐transition temperature increased with an increasing amount of the dye. On the other hand, the DSC and X‐ray diffraction results indicated that no dye molecule was present in the crystal structure of PA‐66. This effect of the nigrosine dye on PA‐66 is in contrast to those of crystalline nucleation agents, plasticizers, and antiplasticizers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3270–3274, 2006     

Polymerization of macromers

Summary The possibility of group transfer polymerization of methyl methacrylate-terminated polystyrene macromer (MA-PSt) was explored by using 1-methoxy-1-(trimethylsiloxy)-2-methyl-1-propene and tris(dimethylamino)sulfonium difluorotrimethylsilicate as initiator and catalyst, respectively. The results obtained at the polymerization temperature of 0°C were undesirable. However, the oligomerization at -78°C gave almost quantitatively oligo(MA-PSt) of which the degree of polymerization was in good agreement with the mole ratio of macromer to initiator. The GPC curve of oligo(MA-PSt) was sharp and symmetrical. In addition, it was shown by the copolymerization with methyl methacrylate that the polymerizability of the macromer was markedly enhanced in the presence of methyl methacrylate comonomer.     

Structural characterization of 1,2-polybutadiene by 13C-n.m.r. spectroscopy: 2. Sequence distribution of 1,2-unit in hydrogenated polybutadienes

The configurational sequences of 1,2-unit in a series of hydrogenated syndiotactic 1,2-polybutadienes were determined in relation to the sequence distribution of 1,2- and 1,4-units on the basis of the ¹³C-n.m.r. signal assignment of the methyl carbons. The observed triad distributions of 1,2- and 1,4-units and configurational distributions of the 1,2-unit are in good agreement with the calculated distributions from transition probabilities. The number average sequence lengths of the 1,2-unit and the 1,2-unit in the racemic addition are 5.7 to 8.0 and 4.1 to 5.4, respectively. From the extrapolation of the plot of the number average sequence length against the crystallinity of the starting 1,2-polybutadienes, the minimum sequence length for crystallization is estimated to be 3.7 for the 1,2-unit in the racemic addition.     

Anode‐voltage‐control circuit for compensation of luminance deterioration

Abstract— An external driving circuit that has realized long lifetime, power‐consumption control, and peak luminance for organic light‐emitting diode (OLED) displays have been developed. This circuit realizes an effective method for constant‐anode‐voltage (CV) driving refered to as clamped inverter (CI) driving. The feature of CV driving is to achieve low‐power consumption compared with constant‐anode‐current (CC) driving and to control the power consumption and peak luminance according to the image because display luminance can be easily changed by controlling the anode voltage. On the other hand, CV driving has the problem that luminance deterioration appears to be serious compared with that of CC driving because the current of the OLED element decreases according to usage time. To cope with this, a lifetime compensation circuit that has increased the anode voltage so that it compensates for the luminance deterioration has been developed. This circuit can compensate not only the decrease in current but also the decrease in luminance at a constant current that CC driving cannot. However, increasing the anode voltage causes an increase in stress on the OLED element. The influence of stress on OLED lifetime was verified. As a result, it was confirmed that this circuit can extend the lifetime by 32% even if the anode voltage is increased, causing stress on the OLED structure.     

Cooperative manipulation of a floating object by some space robots with joint velocity controllers: application of a tracking control method using the transpose of the generalized Jacobian matrix

We have studied the cooperative manipulation of floating object by several space robots. For these cooperative motions, we have reported that a tracking control method using the transpose of the generalized Jacobian matrix (GJM) can be utilized for robots with joint torque controllers. For cooperative motions by some robots with joint velocity controllers, we proposed a tracking control method using the transpose of the GJM. Simulation results show the effectiveness of the proposed control method.