Showing papers by "National Institute of Advanced Industrial Science and Technology published in 1993"

An approach to artificial muscle using polymer gels formed by micro-phase separation

Abstract: Polymer gels react to diverse stimulations such as chemical, thermal, electrical and photonic excitation by deformation, volume change, hardening/softening and permeability changes. This paper presents advances made in chemomechanical energy conversion by polymer gels aiming to produce artificial muscle. Porous gel films made from poly(vinyl alcohol), poly(acrylic acid) and poly(allylamine) mixed solutions by subjecting them to freezing and thawing generate a mechanical power density close to skeletal muscle by changing the solvent from water to acetone. Porous gel fibers made from poly(vinyl methyl ether) solution crosslinked by γ-ray irradiation shrink as fast as skeletal muscle when the temperature is raised above 37°C. These polymer gels swell and shrink reversibly by chemical or thermal stimulations by means of mainly solubility phase transition of polymers. Those advances can be attained by producing porous structures by micro-phase separation.

Infrared study of vibrational property and polymerization of C60 and C70 under pressure

Abstract: Infrared spectra were measured for solid C[sub 60] and C[sub 70] to 7 GPa under hydrostatic or quasi-hydrostatic pressure at room temperature. Some vibrational modes showed negative or insensitive dependence of frequency on pressure, suggesting destabilization of C[sub 60] and C[sub 70] molecules by compression. In solid C[sub 60] new absorption bands gradually grew with increasing pressure in association with an intensity decrease of the original bands. These spectral changes were interpreted in terms of polymerization of C[sub 60] molecules. Polymerized molecules recovered at ambient pressure were converted back to the monomer by thermal annealing at 473 K. 16 refs., 4 figs., 2 tabs.

Dynamic control of a manipulator with passive joints in operational space

Abstract: A method for controlling a manipulator with passive joints, which have no actuators, in operational space is presented. The equation of motion is described in terms of operational coordinates. The coordinates are separated into active and passive components. The acceleration of the active components can be arbitrarily adjusted by using the coupling characteristics of manipulator dynamics. This method is also extended to path tracking control of a manipulator with passive joints. A desired path is geometrically specified in operational space. The position of the manipulator is controlled to follow the path. In this method, a path coordinate system based on the path is defined in operational space. The path coordinates consist of a component parallel to the path and components normal to the path. The acceleration of the components normal to the path is controlled according to feedback based on tracking error by using the dynamic coupling among the components. This in turn keeps the manipulator on the path. The effectiveness of the method is verified by experiments using a two-degree-of-freedom manipulator with a passive joint. >

Pressure effects on the aggregation of poly(N-isopropylacrylamide) and poly(N-isopropylacrylamide-co-acrylic acid) in aqueous solutions

Abstract: Pressure effects on the phase separation of aqueous solutions of poly(N-isopropylacrylamide) (pNIPA) and poly(N-isopropylacrylamide-co-acrylic acid) (pNIPA/AAc) were examined at pressures up to 250 MPa. The cloud point temperature first increased and then decreased as the pressure was raised. The copolymer solutions had higher maximum temperature and pressure than the pNIPA solutions. Though the cloud point curve of pNIPA solutions had no concentration dependence, the cloud point curve of pNIPA/AAc solutions shifted toward higher temperature and pressure with decreasing concentration

Excitation of high frequency surface acoustic waves by phase velocity scanning of a laser interference fringe

Abstract: We present a novel method for generating 100 MHz band surface acoustic wave (SAW) by using a scanning interference fringe at the phase velocity of the SAW. The scanning interference fringe is obtained by intersecting two laser beams with different frequencies, and used as a thermoelastic source. The principle of this method is described, and experimentally demonstrated in the 110 MHz Rayleigh waves on an aluminum specimen generated by a long‐pulse (140 ns) Q‐switched Nd:YAG laser.

Faradaic charge transfer with double-layer charging and/or adsorption-related charging at polymer-modified electrodes as observed by color impedance spectroscopy

Abstract: The interfacial processes at polymer-modified electrodes are investigated using electrochemical impedance and color impedance (electromodulated optical transmittance) spectroscopies. Direct in situ evidence for faradaic charge transfer with double-layer charging is obtained for polypyrrole/polystyrenwulfonate (PPy/PSS - ) composite films in 1 M aqueous LiCl, NaCl, KCl, CsCl, and Me 4 NCl. On the other hand, the high-frequency charging is found to be coupled with adsorption-related (faradaic) charging for the film in 1 M aqueous Bu 4 NCl. Thwe results are modeled with an equivalent circuit taking into account both the double-layer and adsorption-related capacitances at the film/solution interface

Effects of growth pressure and temperature on Fatty Acid composition of a barotolerant deep-sea bacterium.

Abstract: The effects of pressure and temperature on the fatty acid composition in a barotolerant deep-sea bacterium that had branched-chain fatty acids were examined. The major fatty acids of the strain at atmospheric pressure were iso-C(15:0), C(16:1), iso-C(17:0), and iso-C(17:1). As the growth pressure increased, the proportion of unsaturated fatty acid increased because of an increase in the proportion of iso-C(17:1). On the other hand, as the growth temperature decreased, the proportion of unsaturated fatty acid increased because of the increase in the proportion of C(16:1) and C(18:1).

Analysis of excitation and coherent amplitude enhancement of surface acoustic waves by the phase velocity scanning method

Abstract: We present a general theoretical formulation for the characteristics of surface acoustic waves (SAW) generated by the phase velocity scanning (PVS) method that employs a scanning single laser beam (SSB) or a scanning interference fringes (SIF). In the SSB approach, a broad band SAW pulse is generated and its amplitude is coherently enhanced when the laser scanning velocity V is equal to the phase velocity upsilon(R) of the SAW. The amplitude of the SAW follows a resonance curve represented by a sinc function of the scanning velocity V, but different spatial frequency components in the SSB significantly suppress the side lobes of the resonance curve. In the SIF approach, the scanning velocity upsilon(f) of the fringes is determined by the intersection angle and the frequency difference omega(a) of the laser beams. A narrow band tone burst of SAW with frequencies higher than 100 MHz can be excited. The SAW frequency omega depends upon a characteristic time t*, defined as a propagation time of the SAW across the laser beam spot. The SAW frequency omega is identical to the frequency difference omega(a) when the laser pulse width T is longer than the characteristic time t*. But, the SAW frequency omega is determined as a product k(f)upsilon(R) of the wave number of the SIF and the SAW velocity when the laser pulse width is shorter than the characteristic time. Precise frequency measurement provided by the amplitude enhancement effect and the narrow frequency bandwidth in the SIF approach make the PVS method particularly promising for the noncontact SAW velocity measurement.

Shape-selective isopropylation of biphenyl over a highly dealuminated mordenite: effect of propylene pressure

Abstract: A highly dealuminated H-mordenite (H-M) catalyzed the selective isopropylation of biphenyl to 4,4′-diisopropylbiphenyl (4,4′-DIPB). The high selectivity is ascribed to the shape-selective catalysis in mordenite pores. The selectivity of 4,4′-DIPB decreased during the isopropylation of biphenyl due to isomerization of 4,4′-DIPB under low propylene pressure. The increase of propylene pressure suppressed the isomerization in the isopropylation. 4,4′-DIPB itself was isomerized over highly dealuminated H-M under low propylene pressure.

Ion-beam-induced recrystallization in Si(100) studied with slow positron annihilation and Rutherford backscattering and channeling.

Abstract: Ion-beam-induced crystallization in silicon preamorphized by Ge-ion implantation was studied by combined means of Rutherford backscattering and channeling, and positron annihilation. The epitaxial regrowth of amorphous surface layers in a 〈100〉 Si substrate has been studied with irradiation of 400-keV ${\mathrm{Ar}}^{+}$ ions at the temperature of 400 \ifmmode^\circ\else\textdegree\fi{}C. The ion-beam-induced epitaxy was found to result in a drastic increase in the positron lifetime to a maximum value of 400 psec in the recrystallized silicon layer. It is demonstrated that vacancy migration is promoted during the epitaxial recrystallization to form defect complexes like trivacancies and/or quadrivacancies.

The Resistivity Measurements of HgBa2Ca2Cu3O8+x and HgBa2Ca3Cu4O10+x Superconductors under High Pressure

Abstract: The superconductivity of the HgBa2Ca2Cu3O8+x (1223) and HgBa2Ca3Cu4O10+x (1234) phases was studied by resistivity measurements under high pressure The highest onset Tc (Tco) was 156 K at 25 GPa for a 1223 and 1234 mixed-phase sample and 140 K at 13 GPa for a 1223-phase sample The Tco decreased after the maximum point with the increase of pressure

Chemical Potential Diagrams for Fe‐Cr‐Li‐K‐C‐O System: Thermodynamic Analysis on Reaction Profiles Between Alloys and Alkali Carbonates

Abstract: A chemical thermodynamic analysis has been made on reactions between Fe-Cr alloys and mixed alkali carbonates with a local equilibrium approximation using various kinds of chemical potential diagrams for the Fe-Cr-Li-K-C-O system. The compounds stable in the presence of carbonates have been shown in a log P(O{sub 2}) vs. log P(CO{sub 2}) plot; their stabilities depend on the valence stability of the transition metal ions and the stabilization energy of double oxides. A log [a(Li)/a(M)] vs. log [a(K)/a(M)] diagram for the M-Li-K-C-O (M = Fe, Cr) systems visualizes which double oxides can be formed sequentially between the alkali carbonates and the transition metal oxides. A log [a(Cr)/a(Fe)] vs. log P(O{sub 2}) plot for the Fe-Cr-Li-K-C-O system under conditions of a(Li{sub 2}CO{sub 3}) = 0.34, a(K{sub 2}CO{sub 3}) = 0.14, and P(O{sub 2}) = 1 bar can be compared with experimental results on multilayered oxide scale on 310 and 316 stainless steels which were tested as separators in molten carbonate fuel cells. Reaction paths connecting the reaction products in the respective oxide scales formed on 310 and 316 can be represented on chemical potential diagrams. The activities of Cr and Fe in the alloys are the main factor of determining themore » oxide scales.« less

Photocatalytic reactions of acetic acid on platinum-loaded TiO2: ESR evidence of radical intermediates in the photo-Kolbe reaction

Abstract: Two elusive radical intermediates; a methyl radical (·CH3) and a carboxymethyl radical (·CH2CO2H), have been confirmed for the first time by direct observation of their ESR absorptions at room temperature on the photocatalytic reactions of acetic acid and metal (platinum)-loaded titanium dioxide (Pt/TiO2) in aqueous solution.

Optimal approach velocity of an end-effector to the environment

Abstract: This paper presents a new method of generating an optimal approach velocity to control the collision forces between a manipulator and its environment. First, an analysis of the contact motion shows the necessity to control the contact not only after the collision, as shown in previous studies, but also before the collision. Next, using a model of the force-controlled end-effector and its environntent, the forces generated at the contact are formulated as outputs of an autonomous system. In this system, the initial condition is determined by the approach velocity. The optimal approach velocity is defined as the velocity that minimizes the perfonnance index: the integral of the square deviation of the contact forces from the equilibrium force in the control of contact forces. A proportional relation between the optimal approach velocity and the contact force reference is derived analytically based on a mass-damper-spring model of the force-controlled end-effector and its environment. The results of the simu...

Preparation and Optical Properties of Gold-Dispersed BaTiO3 Thin Films

Abstract: Gold-dispersed BaTiO3 thin films and gold-dispersed SiO2 thin films were prepared by r. f. magnetron sputtering method. The as-deposited films were heat-treated in air at temperature ranging from 700 to 900°C for 1h, and were compared to the optical properties of these films. For the SiO2 matrix, an absorption peak position shifted toward longer wavelength from 520 to 535nm as the volume fraction of gold increases, and gold fine particles were spherical and were uniformly dispersed in the films. In contrast, for the BaTiO3 matrix, an absorption peak position shifted from 580 to 640nm. The matrix had substantially crystallized, and the size of matrix grain and the gold particle size varied widely. The nonlinear optical property of these thin films was measured by the degenerate four-wave mixing (DFWM) method using a frequency-doubled Nd: YAG laser with 7ns pulse duration. Third-order nonlinear susceptibility χ(3) of gold-dispersed BaTiO3 films increased with increasing the heat-treating temperature, volume fraction of gold in these films and the mean particle size of gold. The values of χ(3)/α532 of BaTiO3 films were much larger than those of SiO2 films. It seemed that BaTiO3 matrix contributes to increase the value of χ(3)/α532. The resulting maximum value of gold-dispersed BaTiO3 films was 3×10-6esu. The large χ(3) may be ascribed to the high dielectric constant of the films.

Low energy (100 eV) C+ ion doping into GaAs using combined ion beam and molecular beam epitaxial technology

Abstract: Low‐energy (100 eV) carbon ion (C+) irradiation during molecular beam epitaxy of GaAs was carried out using combined ion beam and molecular beam epitaxy (CIBMBE) technology for the growth temperature (Tg) range between 500 and 590 °C. Carbon incorporation was identified by both low‐temperature (2 K) photoluminescence and Hall effect measurements. In the PL spectra, two well‐established specific emissions, ‘‘g’’ and [g‐g], which are closely related to acceptor impurities, were observed for the above Tg range. The results indicate that carbon was both optically and electrically well activated as an acceptor even at Tg as low as 500 °C. Maximum net hole concentration, ‖NA‐ND‖, as high as 3×1018 cm−3 was obtained with no appreciable radiation damages and undesired impurity contamination.

Generation of 100-mhz-band rayleigh waves by phase velocity scanning of a laser interference fringe

Abstract: We investigated the thermoelastic generation of Rayleigh waves in the 100 MHz frequency range using a scanning interference fringe (SIF) obtained by intersecting two laser beams with different frequencies. A long-pulse (140 ns) Q-switched Nd:YAG laser was used to generate Rayleigh waves on an aluminum specimen at various scanning velocities controlled by the intersection angle of the laser beams. It was found that the amplitude of the generated tone burst of Rayleigh waves followed a sinc function dependence over the scanning velocity with a peak at the Rayleigh wave velocity. The center frequency of the tone burst followed a linear dependence. Implications of these findings in the quantitative nondestructive evaluation of microdevice components are discussed.

Conditions for the formation of defect‐induced bound exciton emissions in GaAs grown by molecular beam epitaxy

Abstract: Conditions for the formation of defect‐induced bound exciton (DIBE) emissions in GaAs were investigated by molecular beam epitaxial method. Growth was made on both A‐ and B‐polarity substrates with (321), (221), and (211) orientations. For A‐polarity samples, (321)A and (211)A presented pronounced DIBE emissions. (221)A, however, exhibited no DIBE emission, instead it presented a dominant carbon donor‐carbon acceptor pair emission together with a small hump due to carbon donor‐related bound exciton emissions. For B‐polarity specimens, DIBE was completely vanished in all the three samples. It was theoretically demonstrated that DIBE is formed only when double‐handed Ga adatom site is existing.

Numerical calculation of flow orientation effects in the Langmuir–Blodgett deposition process

Abstract: The angular distribution function of rodlike particles in Langmuir–Blodgett (LB) films is numerically analyzed. The calculation is based on the integral form of the rotatory diffusion equation and, in contrast with previous analyses, does not assume an instantaneous thermal equilibrium. As each particle keeps memory of the flow history on the water surface, the final distribution function is dependent on the initial conditions of the particle. However, when the initial point is so far from the substrate that the memory of initial point is almost lost, the final distribution function is approximately determined by the dimensionless number C=(ζ’G+τ0)/2kBT, where ζ’ is the rotational friction coefficient, τ0 the Bingham yield value, a the substrate width, and vd the dipping velocity of the substrate. The presence of a meniscus region around the substrate should be taken into account. The streamlines between the water surface and the substrate surface are smoothly connected, while assuming a cylindrical shape...

Determination of the crystal orientation of CuInSe2 by Raman spectroscopy

Abstract: We have developed a new method for the determination of the crystal orientation of CuInSe2 by Raman spectroscopy. The single crystal of CuInSe2 has a (112) natural surface. On this surface we often observe slip lines, which construct a triangular shape. However, it is difficult to identify which corner is the projection of the c axis. We established a new method to identify the c direction by using Raman spectroscopy. This method is also effective for small single crystals down to the size of 1 μm.

Microscale evaluation of the viscoelastic properties of polymer gel for artificial muscles using transmission acoustic microscopy

Abstract: Local viscoelastic properties and a micromechanical structure of polymer hydrogel were studied using transmission acoustic microscopy (AM) with a spatial resolution up to 5 μm. Utilizing various amplitude, phase, and pulse techniques provided by the transmission AM, a velocity and an attenuation of the acoustic wave in the local point of the polymer sample as well as a frequency dependence (dispersion) of these values were evaluated in the frequency range from 30 to 320 MHz. Using these facilities a poly(vinylalcohol) polymer hydrogel for the artificial muscle was studied at the succeeding steps of its manufacturing process of cyclic freezing–thawing. It was found that synchronously, with the increase of the compressional elasticity and acoustic attenuation, a micromechanical nonuniformity of the gel also profoundly enhances it. Fiber‐like structures of 10–50 μm width possessing higher elastic modulus appear in the gel which can play a significant role in the macroscopic mechanical properties of the gel.

Electronic Structure of Stoichiometric and Reduced SrTiO3(100) Surfaces: A Photoemission Study

Abstract: We have performed angle-resolved photoemission and X-ray photoemission studies for Stoichiometric and reduced SrTiO3(100) surfaces. In the empirical band structure of the O2p valence bands along the whole Δ line in the bulk Brillouin zone, there is no essential difference between the Stoichiometric and reduced surfaces. Our results are in excellent agreement with the calculation. In addition to the O2p valence band structure, two new states at ~1 eV and ~11 eV below Fermi level appear for the reduced surface (but not for the stoichiometric surface). We show that both of these states are closely connected with oxygen vacancies near the surface.