Ultra light-weight and high-resolution X-ray mirrors using DRIE and X-ray LIGA techniques for space X-ray telescopes

We are developing novel ultra light-weight and high-resolution X-ray micro pore optics for space X-ray telescopes. In our method, curvilinear micro pore structures are firstly fabricated by silicon deep reactive ion etching (DRIE) or X-ray LIGA processes. Secondly, side walls of the micro structures are smoothed by magnetic field assisted finishing and/or hydrogen annealing techniques for high reflectivity mirrors. Thirdly, to focus parallel X-ray lights from astronomical objects, these structures are elastically or plastically bent into a spherical shape. Fourthly, the bent structures are stacked to form a multi-stage X-ray telescope. In this paper, we report on fabrication and X-ray reflection tests of silicon and nickel X-ray mirrors using the DRIE and LIGA processes, respectively. For the first time, X-ray reflections were confirmed on both of the mirrors. Estimated rms roughnesses were 5 nm and 3 nm for the silicon and nickel mirrors, respectively.     

Prediction of Human Behavior in Human--Robot Interaction Using Psychological Scales for Anxiety and Negative Attitudes Toward Robots

When people interact with communication robots in daily life, their attitudes and emotions toward the robots affect their behavior. From the perspective of robotics design, we need to investigate the influences of these attitudes and emotions on human-robot interaction. This paper reports our empirical study on the relationships between people's attitudes and emotions, and their behavior toward a robot. In particular, we focused on negative attitudes, anxiety, and communication avoidance behavior, which have important implications for robotics design. For this purpose, we used two psychological scales that we had developed: negative attitudes toward robots scale (NARS) and robot anxiety scale (RAS). In the experiment, subjects and a humanoid robot are engaged in simple interactions including scenes of meeting, greeting, self-disclosure, and physical contact. Experimental results indicated that there is a relationship between negative attitudes and emotions, and communication avoidance behavior. A gender effect was also suggested.     

Technique for anisotropic extension of organic crystals: application to temperature dependence of electrical resistance

We have developed a technique for the anisotropic extension of fragile molecular crystals. The pressure medium and the instrument, which extends the pressure medium, are both made from epoxy resin. Since the thermal contraction of our instrument is identical to that of the pressure medium, the strain applied to the pressure medium has no temperature dependence down to 2 K. Therefore, the degree of extension applied to the single crystal at low temperatures is uniquely determined from the degree of extension in the pressure medium and thermal contractions of the epoxy resin and the single crystal at ambient pressure. Using this novel instrument, we have measured the temperature dependence of the electrical resistance of metallic, superconducting, and insulating materials. The experimental results are discussed from the viewpoint of the extension (compression) of the lattice constants along the parallel (perpendicular) direction.     

Isolation of penicillin-resistant Streptococcus pneumoniae in Saga Medical School Hospital

A recent nationwide increase in beta-lactams-resistant Streptococcus pneumoniae has attracted a great deal of attention. We studied the drug sensitivity of S. pneumoniae isolated from various clinical specimens in Saga Medical School Hospital between April 1988 and December 1991. To determine the drug sensitivity of the strains, we used a micro-dilution method and determined the MIC. Drug resistance was evaluated using MIC of ampicillin (ABPC) as a reference MIC, and the results were roughly classified into the following three groups: sensitive (< or = 0.1 microgram/ml), moderately resistant (0.2-3.13 micrograms/ml) and highly resistant (> or = 6.25 micrograms/ml). The isolation frequency was calculated on the basis of one strain from one patient. No strain of S. pneumoniae with high resistance against ABPC was found in 1988 (94 strains of S. pneumoniae were isolated) and 1990 (115 strains isolated), but one such strain (0.8%) was found among 129 strains isolated in 1989, and 2 such strains (2.4%) among 84 strains isolated in 1991. Moderately resistant strains were isolated at the frequencies of 12.8%, 15.5%, 22.6%, and 21.4% respectively, in 1988, 1989, 1990, and 1991. A sum of the frequencies of "moderately resistant" and "highly resistant" (2.4%) strains was 23.8% in 1991. The frequency of resistant strains is increasing and the intensity of resistance is also being elevated.     

Role of frustration in quasi 1D conductor — Charge ordering and/or CDW in (R1,R2-DCNQI)2M (M=Ag, Li, Cu) system —

Synchrotron X-ray high-resolution measurements have been performed to investigate the nature of the insulating state of a quarter-filled quasi-one-dimensional conductor (DI-DCNQI)₂Ag and the π-d interacted conductor (DBr-DCNQI)₂Cu. The two-fold structure in the ground state of (DI-DCNQI)₂Ag system consists of not only charge ordering columns but also monotonic charge dimerized columns caused by frustration among DCNQI columns. On the other hand, Cu salt in the insulating phase realizes a commensurate structure where the Cu charge ordering is coupled with the 3c-CDW in the insulator phase. The frustration among charged columns is restrained by the charge ordering of the Cu ions.     

Application of functionally graded material for solid insulator in gaseous insulation system

Functionally graded materials (FGM) have spatial distribution of a material property in order to achieve efficient stress control. An application of the FGM to a solid insulator (spacer) for a gaseous insulation system, like gas insulated switchgear, is expected to improve electric field (E-field) distribution around the spacer. In this paper, we describe the applicability of the FGM spacer to gas insulated power equipment. In the FGM spacer, we gave spatial distribution of dielectric permittivity to control the E-field distribution inside and outside the spacer. This paper includes following key results for the applications of the FGM. Firstly, E-field simulation results when applying the FGM by a finite element method are presented, in which we show the effective reduction of the maximum field strength by applying the FGM. Next, a fabrication technique of the FGM spacer sample with not only step-by-step but also continuous changes of permittivity is presented by use of centrifugal force. Finally, dielectric breakdown tests using FGM samples which are accurately controlled the spatial distribution of permittivity are carried out under lightning impulse voltage applications. The test result indicates the increase of breakdown voltage (BDV). From these results, we verified the applicability and the fabrication technique of FGM spacer for improvement of the dielectric strength in the gaseous insulation system.     

Constant-ratio-coupled multi-grain digital synchronizer with flexible input-output delay selection for versatility in low-power applications

The constant-ratio-coupled multi-grain digital synchronizer (CRC-MGsynchronizer) is proposed as a means for making high-speed connections with very low power consumption, both among multiple chips such as processors, controllers, and storage devices, and among on-chip modules. The synchronizer not only provides a wide range of operating frequencies, but is fast locking and only occupies a small area on chip. Therefore, it contributes to large reductions in power consumption and costs. It is suitable for use in various low-power systems (e.g., battery-hungry mobile appliances and low-cost consumer electronic products). Three major techniques were applied to the design: 1)a multi-grain structure for the delay elements, which greatly reduces the number of gates while facilitating locking in a very small number of clock cycles;2) constant-ratio-coupled (CRC) delay lines (measurement versus generation)for flexible selection of the input-output delay; and 3) a new lock stage decision circuit (LSDC) scheme, conferring excellent testability. Moreover,the architecture is all-digital, and thus it has high process portability. By applying these techniques to a DDR memory interface circuit for a mobile application processor fabricated in 130-nm technology, we were able to reduce power consumption by 42% and chip area by 65% compared with a conventional implementation. Furthermore, the novel design spans a frequency range covering 12 times the minimum frequency.     

Statistical analysis for multiplicatively modulated nonlinear autoregressive model and its applications to electrophysiological signal analysis in humans

Modulating the dynamics of a nonlinear autoregressive model with a radial basis function (RBF) of exogenous variables is known to reduce the prediction error. Here, RBF is a function that decays to zero exponentially if the deviation between the exogenous variables and a center location becomes large. This paper introduces a class of RBF-based multiplicatively modulated nonlinear autoregressive (mmNAR) models. First, we establish the local asymptotic normality (LAN) for vector conditional heteroscedastic autoregressive nonlinear (CHARN) models, which include the mmNAR and many other well-known time-series models as special cases. Asymptotic optimality for estimation and testing is described in terms of LAN properties. The mmNAR model indicates goodness-of-fit for surface electromyograms (EMG) using electrocorticograms (ECoG) as the exogenous variables. Concretely, it is found that the negative potential of the motor cortex forces change in the frequency of EMG, which is reasonable from a physiological point of view. The proposed mmNAR model fitting is both useful and efficient as a signal-processing technique for extracting information on the action potential, which is associated with the postsynaptic potential.