High-speed and energy-efficient collisionless walking of underactuated rimless wheel

This paper discusses a method for achieving high-speed collisionless walking of a point-footed walker. First, we introduce a model of an underactuated rimless wheel with an internal reaction wheel for analysis, and develop two controllers for the single-limb support and double-limb support phases so that they minimize the corresponding control period based on the principle of the minimum-time control. The former is determined under the unilateral constraint condition, whereas the latter is determined under the constraint condition of the zero-moment point for maintaining double-limb support, respectively. Second, we extend the results obtained for generation of the highest speed collisionless walking gait without including double-limb support phases by appropriately setting the initial angular velocity of the reaction wheel. The approximate analytical solution of the target initial angular velocity is derived using the linearized model, and that of the nonlinear model is numerically obtained using a bisection method. The validity of the proposed methods is investigated through numerical simulations.     

Synthesis of rigid polyimides containing pendant norbornadiene moieties and their valence isomerization between norbornadiene and quadricyclane

Polymers having pendant norbornadiene (NBD) moieties and rigid main chains were prepared from reactions in DMF of pendant bromomethyl groups present in polyimides with a potassium carboxylate or phenolate derivatives of NBD using a phase transfer catalyst. The substitution was quantitative using tetrabutylammonium bromide at room temperature. The photochemical valence isomerization of pendant NBD to quadricyclane (QC) moieties occurred in films upon irradiation with 365 nm light. NBD polyimide (P-1a) prepared from hex afluoroisopropylidene-2-bis(phthalic anhydride) and 2,2-bis(3-amino-4-methylphenyl)hexafluoropropane showed a higher photochemical reactivity than the other NBD polyimides when the polymers were irradiated with 365 nm light. While usual polyimides have absorptions around 365 nm that hinder the photo-isomerization of NBD and also cause the polymer to decompose because of the irradiation, the P-1a matrix has no absorption at wavelengths above 340 nm and irradiation hardly affected the rate of isomerization. When the irradiated NBD polymers were heated, the reversion isomerization of the QC moieties to the original NBD moieties occurred easily concurrent with their decomposition. The rigid polyimide structure stabilizes the QC moieties and protects them from degradation during cyclic isomerization between NBD and QC. For example, the half-life of a pendant QC moiety in a polyimide is estimated to be 6 years at 25°C.     

Interfacial properties of polyelectrolyte-cellulose systems. IV. Electrokinetic properties of carboxymethylcellulose fibers with adsorbed multilayers of cationic polyelectrolyte

Zeta potential measurements by the streaming current method were performed on carboxymethylcellulose (CMC) with and without irreversibly adsorbed multilayers of cationic polyelectrolyte. Factors affecting the electrokinetic properties such as the amount of adsorbed polymer, polymer molecular weights (M_n 50,000 and 200,000), ionic strength (10^?5 ～ 10^?2M KCl), and pH of the streaming medium (KCl solutions) were examined. The negative zeta potential of CMC decreased to the point of monolayer formation and increased from that point to the saturated multilayer formation. The polarity of the zeta potential was negative throughout every adsorption stage. The negative zeta potential increase was attributed to: (a) binding of anions (Cl^? and OH^?) to the outermost layer of the multilayer from KCl solutions and (b) change in chemical potentials of counterions in a diffuse double layer due to expansion of the double layer in the presence of the adsorbed multilayer on CMC. The results suggest that the carboxyl groups under the monolayer are undetectable electrokinetically; however, the negative charge, due to unneutralized carboxyl groups under the monolayer, appears to cause further adsorption forming a saturated multilayer. When the effect of unneutralized carboxyls of CMC are shielded at higher levels of adsorption, the outermost layer of the multilayer becomes a potential-determining layer.     

The effect of water hardness on the solubilizing activity of linear alkylbenzene sulfonate

The behavior of linear alkylbenzene sulfonate in hard water has been studied by solubilization, transmittance and pH. Maximum solubilization is reported at specific water hardnesses on the basis of the change in the micellar properties of the detergent. The water hardness at maximum solubilization increases as the concentration of the detergent or of sodium tripolyphosphate (STPP), sodium nitrilo triacetic acid (NTA) or sodium ethylene diamine tetra acetic acid (EDTA) increases, while it decreases with an increase in the alkyl chain length of the detergent. A linear relationship between the detergent concentration and the water hardness at maximum solubilization or transmittance was found. It seems that the effect of STPP, NTA and EDTA on solubilization of anionic detergent was mainly due to water softening.     

Electric strength of epoxide resins and its relation to the structure

Epoxide resins having various ratios of ether and ester bonds were investigated as to the relation between electric strength and polymer characteristics. The electric strength over a wide range of temperature is presented here. A marked reduction of strength characteristics of the epoxide resins occurs at a critical temperature indistinguishable from the glass transition temperature T_g, which is related to the free volume and molecular relaxation process. At temperatures exceeding T_g, the electric strength has a strong dependence on polymer structure, film thickness, and applied pulse width. This behavior is considered to obey the thermal breakdown mechanism, and it is assumed that the ion is important in the precursory region of electric breakdown.     

Application of accelerators for the research and development of scintillators

We introduce experimental systems which use accelerators to evaluate scintillation properties such as scintillation intensity, wavelength, and lifetime. A single crystal of good optical quality is often unavailable during early stages in the research and development (R&D) of new scintillator materials. Because of their beams' high excitation power and/or low penetration depth, accelerators facilitate estimation of the properties of early samples which may only be available as powders, thin films, and very small crystals. We constructed a scintillation spectrum measurement system that uses a Van de Graaff accelerator and an optical multichannel analyzer to estimate the relative scintillation intensity. In addition, we constructed a scintillation time profile measurement system that uses an electron linear accelerator and a femtosecond streak camera or a microchannel plate photomultiplier tube followed by a digital oscilloscope to determine the scintillation lifetimes. The time resolution is approximately 10 ps. The scintillation spectra or time profiles can be obtained in a significantly shorter acquisition time in comparison with that required by conventional measuring systems. The advantages of the systems described in this study can significantly promote the R&D of novel scintillator materials.     

Evaluation of two-dimensional strain distribution by STEM/NBD

We proposed a strain mapping technique by Nano Beam electron Diffraction (NBD) combined with an energy filter (EF) and a scanning transmission electron microscopy (STEM) function. The STEM function improves the accuracy of a position where a diffraction pattern is acquired. The EF excludes inelastic scattering and enables novel numerical processing for the appropriate measurement of distances between diffraction disks. Using this technique, strain distributions were measured for two different types of p-MOSFETs, i.e., source/drain regions of each MOSFET is composed of different types of silicide, and the difference of their strain distributions in the channel region was confirmed. The proposed method was able to clarify that the strain distributions are quite different depending on the silicide materials even if the exterior of the MOSFETs was almost identical.     

Structural study of nanometer-sized iron crystallites in single crystalline iron–mgo composite films

Single crystalline composite films of iron and MgO are prepared by a simultaneous vacuum deposition technique. The structures of the composite films, especially of the iron crystallites embedded, are studied by high-resolution electron microscopy and nanometer-area electron diffraction. The α-iron (b.c.c.) crystallites of 1 nm in size are epitaxially embedded in single crystalline MgO films, the orientation being (011 )[100]_Fe/(001)[100]_Mgo and (001)[11 0]_Fe//(001)[100]_Mgo. A heat treatment of the as-grown films at 500–1,000°C brings about a phase transformation of the crystallites from α-iron to γ-iron (f.c.c.), followed by a grain growth of α-iron and finally the growth of the spinel, MgFe₂O₄. The γ-iron crystallites transformed are circular plates and have strains at the periphery to accommodate the surrounding MgO-matrix. The magnetic property of the composite films is also reported.     

Voltammetric potentials of polyaniline varying with electric percolation

The reduction of the emeraldine form of polyaniline film into leucoemeraldine, which corresponds to the conversion of an electric conductor into an insulator, shifted in the positive direction with increasing scan rate and film thickness. Similar dependence was found in the diffusion-controlled voltammograms of dispersed polyaniline latex particles with eight diameters ranging from 0.2 to 7.5 μm. The particles were synthesized by coating dispersed polystyrene latex with polyaniline. These variations were explained in terms of electric percolation of the conducting species to the electrode. The theoretical expression for the Nernst equation was derived on the assumption that the percolated and the un-percolated conducting species took inner potentials of the electrode and the solution phase, respectively. The conducting species does not participate in the determination of the equilibrium potential, though it participates in the Faradaic current. The cathodic peak potential shifted in the negative direction with an increase in particle size, solution viscosity, and film thickness, as predicted from the derived Nernst equation.     

Influence of Oil Viscosity,Chemical Oil Structure,and Chemical Additives on Friction Loss of Spur Gears (Concerning the Influence of Synthetic Oil and Mineral Oil)

The friction loss of gears and its quantitative estimation are important problems because of their relevance to energy conservation and load-carrying capacity. Recent research results do not provide satisfactory estimates of friction loss of spur gears. Therefore, the authors carried out experiments to study the influences of lubricating oil viscosity and additives, as well as base oil type and load and rotational speed on friction loss of spur gears. Base oil types used were paraffin mineral, poly-α-olefin, and polyglycol with several oil viscosities. An EP and a mild EP additive were studied in these oils. Finally, the temperature rise of teeth of gears as a function of friction power loss was investigated, and an empirical formula for calculating the temperature rise of the spur gear teeth was derived.