High strength and high modulus poly(vinyl alcohol) by the gel ageing method

The gel ageing method was proposed for producing high strength and high modulus poly(vinyl alcohol) (PVA) materials. The PVA gel prepared from a solution in a mixed solvent of dimethylsulfoxide water (v/v)=8020 at -34 °C was moulded into a gel sheet and then aged in water at 10 °C for several months. The gel sheet was dried and then drawn at 200 °C. The tensile strength and the modulus of the drawn film were 2.8 and 72 GPa, respectively. These excellent properties are discussed in relation to the structures of the aged gel, the dried gel (namely the film) and the drawn film using the results from X-ray diffraction, differential scanning calorimetry and birefringence measurements. As a result, the most important process was shown to be the ageing process. If the crystallites with relatively low melting temperatures, which were called the B and C crystallites, were grown in the aged gel, the mechanical properties of the drawn film from it were as high as those described above. The orientation of the crystallites mildly caused during drying of the gel sheet was also shown to be a key structure which facilitated the high extension of the chain in the subsequent drawing process.     

Effects of O,Se, and Te on the rate of nitrogen dissolution in molten iron

The effects of oxygen, selenium, and tellurium on the rate of nitrogen dissolution into molten iron have been investigated at 1973 K using an isotope-exchange reaction and the results are summarized as follows. The rate constant of nitrogen dissolution measured at lower oxygen concentration ([mass pct O] < 0.015) is larger than previously reported ones under an atmospheric pressure and agrees well with the value from desorption rate under reduced pressures. Selenium and tellurium retard the nitrogen dissolution into liquid iron more significantly than oxygen, and the degree of the retarding effect is in the order of tellurium, selenium, and oxygen. The adsorption coefficients are calculated to be K_O = 144, K_Se = 1120, and K_Te = 1640 with respect to [1 mass pct solute] from present results. A model that surface active elements and nitrogen are adsorbed on the same site at the interface and the dissociation reaction of nitrogen molecule on the site represented by the equation is the rate-determining step reasonably expresses the retarding effect of the surface active elements on the reaction rate on the assumption that all sites at the metal surface have a uniform adsorption energy for each solute.     

Kinetics of association processes of d-fructose dehydrogenase onto liposome surfaces

Summary Association processes of D-fructose dehydrogenase (FDH) onto surfaces of liposomes which were composed of N-(5-dimethylamino-1-naphthalenesulfonyl)-L--dimyristoylphosphatidylethanolamide and L--dimyristoylphosphatidylcholine or L--dimyristoylphosphatidylglycerol (1:9) were investigated by the fluorescence stopped-flow technique. The association processes were divided into two relaxation processes: the faster process whose apparent rate constant monotonously increased with the concentration of FDH, and the slower process whose rate constant showed a saturation behavior. Taking the number of binding sites on the liposome surface into consideration, the corrected association rate constant of the faster process was 4.4% of the theoretical value for a binary collision, probably due to a disadvantageous surface-searching and dehydration processes on the liposome and protein surfaces. The Arrhenius plots of the rate constants both for the faster and slower steps showed a discontinuous change around the gel to liquid-crystal phase transition temperature of the liposomes. Strong influences of deformability of liposomes, and state of hydrating water molecules around polar heads, on the rate of association processes were suggested.     

Layered‐Herringbone Polymorphs and Alkyl‐Chain Ordering in Molecular Bilayer Organic Semiconductors

Production and control of 2D self‐organized layers of π‐conjugated molecules is a fundamental issue in organic electronics devices. This study reports that an intralayer polymorphic transformation is apparently observed in a bilayer‐type layered‐herringbone packing of a series of 2‐mono‐alkylated‐benzothieno[3,2‐b][1]benzothiophenes (mono‐C_n‐BTBTs) with the change in the substituted alkyl‐chain length, n. Slight variation in the intermolecular arrangement in the single‐crystal films is investigated with reasonable sensitivity via polarized optical absorption spectroscopy through the excitonic interactions between neighboring π‐electron cores. A clear polymorphic transition is observed based on the features of the in‐plane optical anisotropy with the change in the chain length between n = 7 (or less) and 8 (or more). A unique phase separation of the polymorphs is also observed in the films produced using a mixed solution with molecules having different n: the respective polymorphic phases appear separately, either as single molecular bilayers or multibilayer‐stacked films owing to geometrical frustration. The results indicate that the intralayer packing motif is predetermined by the competition and balance between the intermolecular core–core and chain–chain interactions. These findings pave the way for rational designing of organic molecules with considerably high layered crystallinity, and thus, of efficient carrier transport in organic thin‐film transistors.     

Reducibility of operation symbols in term rewriting systems and its application to behavioral specifications

In this paper, we propose the notion of reducibility of symbols in term rewriting systems (TRSs). For a given algebraic specification, operation symbols can be classified on the basis of their denotations: the operation symbols for functions and those for constructors. In a model, each term constructed by using only constructors should denote an element, and functions are defined on sets formed by these elements. A term rewriting system provides operational semantics to an algebraic specification. Given a TRS, a term is called reducible if some rewrite rule can be applied to it. An irreducible term can be regarded as an answer in a sense. In this paper, we define the reducibility of operation symbols as follows: an operation symbol is reducible if any term containing the operation symbol is reducible. Non-trivial properties of context-sensitive rewriting, which is a simple restriction of rewriting, can be obtained by restricting the terms on the basis of variable occurrences, its sort, etc. We confirm the usefulness of the reducibility of operation symbols by applying them to behavioral specifications for proving the behavioral coherence property.     

Generating and analyzing hierarchical interaction in a flock of robotic swarms

One of the popular approaches for the self-organized flocking of artificial agents is based on a computer animation model called Boid. This model reproduces flocking motion using three simple behavioral rules: repulsion, attraction, and alignment. However, the flocking performance largely depends on how these rules are configured, and no general guideline exists for the configuration. This paper introduces hierarchical interaction-based flocking by employing individuals that can switch their roles. Robots can move as leaders or followers depending on the situation. The flocking performance is evaluated, and the swarming behavior is analyzed in a scenario where robots travel alternately between two landmarks.     

Tricycle-style operation interface for children to control a telepresence robot

Telepresence robots will provide significant value to childhood education. They will offer children opportunities to join remote classrooms and to communicate with speakers of different languages in more enriched ways than are available by conventional video conferencing. However, the introduction of child-operated telepresence robots has yet to be tested. The design of the operation interface presents a particular challenge. In this study, we report the development of a tricycle-style operation interface based on requirements identified through classroom field observations. It was designed for intuitive use, even by young children, without the need of detailed instruction. The usability of the interface was tested in a field experiment involving 20 participants (4–8 years old). The participants were asked to perform six elementary tasks using a telepresence robot system controlled either by the tricycle-style interface or a standard video-game controller. The operational performance of the tricycle-style interface was found to be superior to that of the standard controller. The advantages and disadvantages of both interfaces are discussed.     

Prevention of accomplishing synchronous multi-modal human–robot cooperation by using visual rhythms

Effective rhythm expression (ERE) from a robot to a human performing a multi-modal physical-cooperation (MMPC) task was accomplished. During MMPC, the participant and the robot can exchange various rhythms between themselves. To accomplish ERE, it is important to appropriately select the modalities in which the robot expresses its desired rhythm. Accordingly, a hypothesis that selecting the visual rhythm for RE prevents MMPC was tested and confirmed. This hypothesis was preliminarily confirmed in regard to MMPC between two humans. Moreover, to confirm the hypothesis in regard to human–robot cooperation, an experimental system (including a rope-turning robot) was developed. This experimental system allowed experimenters to evaluate the synchronization during MMPC between a human and a robot by measuring the norm of angular velocities. The results of several experiments (namely, a comparison of norms), in which several combinations of visual and auditory rhythmic stimuli were presented to the subjects, strongly supported the hypothesis.     

Motion control of wearable-type walking support system based on the spring-mass model

Many systems and control methods have been proposed as mobility supports for the physically disabled and elderly individuals. In this research, we focus on a wearable-type system that supports the elderly with their walking. Different from typical control methods of wearable-type walking support systems, we propose a simple control method based on the spring–mass model. As a walking aid that does not require additional motions, such as sit-to-stand, this simple system is beneficial for two reasons. First, it reduces the calculation cost of deriving the support joint torque of the user; second, the wearable device hardware can be simply constructed from low-power actuators and springs rather than high-power actuators. In stance phase support mode, our motion control method compensates for a part of the force applied to the upper body as a leg muscle support. During the swing phase, walking is supported by a trajectory-following method using the impedance control as well as the spring–mass model. The proposed methods are applied to a prototype of a wearable-type walking support system, and evaluated in a series of experiments on human subjects.     

Estimating energy consumption from night-time DMPS/OLS imagery after correcting for saturation effects

A methodology is presented to accurately estimate electric power consumption from saturated night-time Defense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS) imagery using a stable light correction. An area correction for the stable light image of DMSP/OLS for the year 1999 was performed and the build-up area rate data were used to clarify the intensity distribution characteristics of the stable light. Based on the spatial distribution characteristics of the stable light, the saturation light of the electric power supply area of Japan was corrected using a cubic regression equation. The regression between the correction calculations by the cubic regression equation and the statistical electric power consumption data was applied in Japan and also in China, India and 10 other Asian countries. The correction method was then evaluated. This study confirms that electric power consumption can be estimated with high precision from the stable light.