Equivalence relations between learnability,output-dissipativity and strict positive realness

This paper was originally motivated by aiming at explicating why a simple iterative learning control scheme for complicated robot dynamics with strong non-linearities works well in acquiring any given desired motion over a finite or infinite time duration or any periodic motion. To gain a physical insight into the problem, a class of linear dynamical systems with specified input and output of the same dimension is treated by defining two properties: output-dissipativity and learnability. It is then shown that the former implies the latter and furthermore, for a class of linear systems with single input and single output, they are equivalent to each other and each of them is also equivalent to strict positive realness of input-output transfer function. For a class of MIMO (multiple inputs and multiple outputs) systems, it is possible to prove that each of these properties is equivalent to strict positive realness of the input-output transfer function matrix if it is strictly proper or otherwise its direct term from input to output satisfies an extra condtion.     

Static and dynamic properties of McKibben pneumatic actuator for self-stability of legged-robot motion

A McKibben-type pneumatic actuator is widely used for utilization of its self-stabilization characteristics with a simple actuator model and a simple control method. However, how its characteristics act on the stability of robot motion have not been sufficiently discussed. The purpose of the paper is to analyze how various characteristics of McKibben pneumatic actuator (MPA) influence the stability of movements generated by MPA. In this paper, at first, we introduced two static models of the MPA which were proposed in the previous research and verified the models through validation experiments. The models of MPA form as simply as possible for a stability analysis. Next, we showed that the tension of MPA monotonically decreased according to the contraction velocity through validation experiments. Finally, the model was applied to a same simple robot model with the previous study and the stability of motions generated by the actuators was analyzed based on control theory. From the stability analysis, it was verified that the stability of the constant posture was achieved by the relatively simple static MPA model, the verified tension–velocity dependency of actuator, and the interaction with the properties of the actuator and the mechanical structure of the robot. This result suggests that the properties of MPA, particularly the verified velocity-dependent property, can contribute to the self-stability of a robot generated by the actuators, and it is important to consider the interaction between the mechanical structure and the actuator.     

Analgesic Mechanisms of Steroid Ointment against Oral Ulcerative Mucositis in a Rat Model

Despite the long history of use of steroid ointments for oral mucositis, the analgesic mechanism has not been fully elucidated. In this study, we examined the effects of triamcinolone acetonide (Tmc) on oral ulcerative mucositis-induced pain in conscious rats by our proprietary assay system. Based on evaluations of the physical properties and retention periods in the oral mucosa of human volunteers and rats, we selected TRAFUL^® ointment as a long-lasting base. In oral ulcerative mucositis model rats, TRAFUL^® with Tmc suppressed cyclooxygenase-dependent inflammatory responses with upregulations of glucocorticoid receptor-induced anti-inflammatory genes and inhibited spontaneous nociceptive behavior. When an ointment with a shorter residual period was used, the effects of Tmc were not elicited or were induced to a lesser extent. Importantly, TRAFUL^® with Tmc also improved oral ulcerative mucositis-induced mechanical allodynia, which has been reported to be independent of cyclooxygenase. Ca²⁺ imaging in dissociated trigeminal ganglion neurons showed that long-term preincubation with Tmc inhibited the hypertonic stimulation-induced Ca²⁺ response. These results suggest that the representative steroid Tmc suppresses oral ulcerative mucositis-induced pain by general anti-inflammatory actions and inhibits mechanical sensitivity in peripheral nerves. For drug delivery, long-lasting ointments such as TRAFUL^® are needed to sufficiently induce the therapeutic effects.     

Experimental set-up for simultaneously measuring changes in LD temperature and flying height of HAMR-HGA

Heat-assisted magnetic recording (HAMR) is a promising technology for overcoming the performance limit of the conventional magnetic head in a hard disk drive. The HAMR-HGA consists of a HAMR-head slider, a suspension, and a laser diode (LD) mounted on the slider. An optical near-field transducer (NFT) and a waveguide are near the write-pole in the head slider. During the HAMR process, current is applied to an LD, and the laser beam is coupled into the waveguide and delivered to the NFT. The NFT further concentrate the focused optical spot and the optical spot locally heats the recording medium, thereby reducing the media coercivity. The temperature of the LD and the slider, however, increases. The slider is, moreover, locally deformed, and the flying-height (FH) changes. Therefore, an experimental set-up to simultaneously evaluate the FH change and LD temperature of the HAMR-HGA was required to develop the HAMR technology. We developed a novel experimental set-up for simultaneously evaluating laser characteristics (power, voltage, and wavelength), the increase in LD temperature, and the FH change of a HAMR-HGA. By using this set-up to measure these characteristics of our prototype, the HAMR-HGA showed that the FH decreased as the LD temperature increased. The LD temperature is directly related to the laser characteristics. The change in laser characteristics affects the read-write performance of HAMR. The FH change also affects the performance. Therefore, the developed experimental set-up should be useful in improving HAMR-HGA.     

Active-head slider with piezoelectric actuator using shear-mode deformation

The active-head slider technology for hard disk drive is one of the most promising means to decrease flying height. This paper describes a piezoelectric flying height control slider which has a faster dynamic response compared with conventional active-head sliders. This slider can be also adapted to the conventional slider-fabrication process. PZT layer located near the magnetic head has shear mode deformation by applying electric voltage between the upper and lower electrodes when the flying height of magnetic head needs to be decreased or increased. We fabricated a prototype with single crystal Si substrate for feasibility study. Our evaluation of the prototype revealed that the piezoelectric constant of the shear mode deformation was 0.88 nm/V, and the dynamic response was 50 kHz. The shape of the air bearing surface was optimized by simulations using a robust design method. We found that the stroke was 8 nm for an applied voltage of 11 V if the flying height was 11 nm with no deformation in PZT.     

A push–pull multi-layered piggyback PZT actuator

 To increase the recording density of hard disk drives (HDDs), we developed a push–pull multi-layered piggyback PZT actuator that enables fine positioning by a dual-stage servo system. This PZT actuator consists of 31-mode push–pull multi-layered PZT strips and a head suspension. It generates a 1.4-μm effective radial head displacement at 5 V. This displacement is twice that of conventional piggyback actuators. The main resonance frequency of the actuator is higher than 9 kHz, its lifetime is longer than five years, and it has a self-latch property. These features mean that the developed actuator can meet all the requirements for implementation in HDD servo systems, including a track density of 100 kTPI (kilo-tracks per inch). The actuator was implemented in two types of HDDs (A-type and B-type), which reduced the repeatable and non-repeatable positioning errors (by 40 to 45% and 28 to 34%, respectively). Received: 25 July 2001/Accepted: 11 December 2001     

Corrections and further comments to 'Equivalence relations between learnability,output-dissipativity and strict positive realness'

This correspondence presents corrections and further comments to our previous paper titled 'Equivalence relations between learnability, output-dissipativity and strict positive realness' (Arimoto and Naniwa 2000). It corrects (1) the previous definition of input?output 'invertibility' by assuming an additional continuity property of the system inverse operator, redefines exactly (2) the 'output-dissipativity' by adding a condition of invertibility, and presents (3) a further comment on the proof of Lemma 1. A diagram is given in order to clearly show interrelationships between these concepts.     

Modelling citation age data with right censoring

Summary Klaus Fuchs, during his years in England as an immigrant, has written 20 scientific papers. One of these papers, published in 1938, became a fundamental text in solid state physics and for the development of microelectronics in succeeding decades. It was cited more than 1200 times in the period from 1945 until 2003. It appears to be a typical case of delayed recognition in science. Pioneering papers simultaneously written by Hahn & Straßmann and by Meitner & Frisch on the discovery of nuclear fission are considered for comparison.     

Analysis of the unique gait mechanism of locusts focusing on the difference in leg length

The various types of gaits shown by insects are very interesting, and many studies have been conducted to investigate the mechanism of these gaits. In nature, there are many insects with apparent differences in the length of each leg, and it seems that the difference in leg length may affect the resultant gait of insects. However, there has not been much discussion about the influence of these differences in leg length on the gait. In this research, in order to investigate the influence of the difference in leg length on gait, we focus on locusts, whose hind legs are considerably longer than the other legs and shows a unique gait not seen in other insects. First, we measure the kinematics of gait of some insects, including locusts, and analyze the unique gait specific to locusts. Next, we reproduce this unique gait via numerical dynamical simulation. By conducting some simulations while changing the length of the legs, we investigate the mechanism of the unique gait of locusts and the influence of difference in leg length on walking. As a result, it is confirmed that the unique gait of locusts can be reproduced with a combination of long hind legs (compared to the front and middle legs) and the adjustment of the stroke and period of the hind leg based on horizontal ground reaction force.