A biped static balance control and torque pattern learning under unknown periodic external forces

This paper addresses a biped balancing task in which an unknown external force is exerted, using the so-called ‘ankle strategy’ model. When an external force is periodic, a human adaptively maintains the balance, next learns how much force should be produced at the ankle joint from its repeatability, and finally memorized it as a motion pattern. To acquire motion patterns with balancing, we propose a control and learning method: as the control method, we adopt ground reaction force feedback to cope with an uncertain external force, while, as the learning method, we introduce a motion pattern generator that memorizes the torque pattern of the ankle joint by use of Fourier series expansion. In this learning process, the period estimation of the external force is crucial; this estimation is achieved based on local autocorrelation of joint trajectories. Computer simulations and robot experiments show effective control and learning results with respect to unknown periodic external forces.     

Damage to seagrass and seaweed beds in Matsushima Bay,Japan, caused by the huge tsunami of the Great East Japan Earthquake on 11 March 2011

Damage to seagrass and seaweed beds caused by the huge tsunami of the Great East Japan Earthquake on 11 March 2011 was investigated in Matsushima Bay, Miyagi Prefecture, Japan, by comparing satellite images taken before the tsunami in November 2009 and after the tsunami in May 2011. The results showed that the tsunami destroyed 220 ha of seagrass and seaweed beds, from 320 ha in 2009 to 100 ha just after the tsunami. Zostera marina beds on the sandy and muddy bottom were rather severely damaged compared with brown seaweed beds of Sargassum horneri on the rocky substrate. Substrates of the beds and directions of the tsunami seem to be responsible for the magnitude of the damage to the beds. Maps of the spatial distributions of the beds before and after the tsunami can provide information for the restoration of seagrass and seaweed beds as natural infrastructures of coastal fisheries resources.     

Probabilistic nearest neighbor query processing on distributed uncertain data

A nearest neighbor (NN) query, which returns the most similar object to a user-specified query object, plays an important role in a wide range of applications and hence has received considerable attention. In many such applications, e.g., sensor data collection and location-based services, objects are inherently uncertain. Furthermore, due to the ever increasing generation of massive datasets, the importance of distributed databases, which deal with such data objects, has been growing. One emerging challenge is to efficiently process probabilistic NN queries over distributed uncertain databases. The straightforward approach, that each local site forwards its own database to the central server, is communication-expensive, so we have to minimize communication cost for the NN object retrieval. In this paper, we focus on two important queries, namely top-k probable NN queries and probabilistic star queries, and propose efficient algorithms to process them over distributed uncertain databases. Extensive experiments on both real and synthetic data have demonstrated that our algorithms significantly reduce communication cost.     

Fatigue striation in a wide range of crack propagation rates up to 70 μm/cycle in a ductile structural steel

The relationship between striation spacing and fatigue crack propagation rate up to 70 m/cycle was investigated for a ductile structural steel, qualified as JIS SM58Q. A modified compact-type specimen 400 mm wide and a centre-cracked specimen 200 mm wide were tested at a stress ratio, R, of 0 and 0.8. The fracture surface of the specimen was examined in detail under a scanning electron microscope. The crack propagation rate was expressed by a power function of the range of stress intensity factor from 0.1 to 70 m/cycle for R=0 and to 0.5 m/cycle for R=0.8. The striation spacing coincided with the fatigue crack propagation rate over the range 0.1 to 70 m/cycle. The profile of striation was found to be a ridge and valley type, and the ridges on one fracture surface coincided with those on the matching surface. It is suggested that the striation is formed by a plastic blunting mechanism.     

Experience with radio isotope myelography from neurosurgical aspects (author's transl)

Experience with Radio Isotope Myelography is reported here. 169Yb-DTPA as a tracer was intrathecally injected at lumbar region in twenty three patients with various spinal cord lesions. The first scanning is perfomed after comfirming by gamma-camera that the tracer reaches to the lesion, the second and the third scannings are done according to the ascending rate of the tracer. (I) Normal scintimyelogram (A) In normal case, the shape of the Radio Isotope Myelogram well corresponds the shape of anatomical subarachnoid space. (B) In normal adult cases, the tracer comes up to the cisterna magna in 20-25 minutes after the lumbar injection. Therefore, the scintimyelographic diagnosis should be made not only by the shape but also by the ascending rapidity of the tracer. (II) Abnormal scintimyelogram Abnormal scintimyelograms could be summarized as following three categories. (A) "Delay": It means delay of the ascending of the tracer. Besides, "Transient delay" found in a case of Arnord-Chiari's malformation was proposed. (B) "Partial block": It meas a defect at the level of the lesion. This "Partial block" were observed in cases of spinal cord angioma, cervical spondylosis and spinal cord tumor etc. (C) "Complete block": It means the stagnation of the tracer below the lesion. To sum up, Rario Isotope Myelography, especially in partial block, can more easily and more sensitively represent the maximum extent of the spinal cord lesion than other myelographic study or angiographic one. On the other hand, we can not qualitatively diagnose about the lesions by its indistinct border.     

Hydrothermal preparation of tailored hydroxyapatite

Hydrothermal vapor treatment method was applied for preparation of ceramic biomaterials. Hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂; HA) ceramics prepared by sintering with random crystal surface have already been used as bone-repairing materials which can directly bond to natural bones. If materials of HA could have the tailored specific crystal surface, they should have the advantage of adsorptive activity and osteoconductivity in comparison with the sintered HA. In the present study, porous HA sheets of about 50 μm to 1 mm in thickness and porous HA granules of about 50 μm to 1 mm in size with tailored crystal surface were prepared by the hydrothermal vapor exposure method at temperatures below 200°C. Porous sheets and porous granules of HA with controlled crystal surface should be suitable for scaffold of cultured bone, for bone graft material and for drug delivery system (DDS).     

Surface modification of biodegradable plastics by ion beams

Biodegradable plastics can be used as conventional plastics, while on disposal they decompose to water and carbon dioxide by microorganisms existing in natural environment. Products using biodegradable plastics have recently been developed in many companies pursuing ecology. In this study, surface modification of biodegradable plastics was carried out by inert ion beams for improvement of photo deterioration under an ultraviolet ray. The hardness of biodegradable plastics tended generally to decrease with irradiation of an ultraviolet ray. In this method, the hardness of ion-bombarded biodegradable plastics was kept at an initial value under an ultraviolet ray, because the modified layer by ion bombardment intercepted an ultraviolet ray. The hardness of He⁺ ion-bombarded biodegradable plastics showed larger value than that of Ar⁺ ion bombardment. He⁺ ion bombardment at ion energy of 10 keV produced the suitable property with both of high transmittance of a visible ray and high interception of an ultraviolet ray in a surface layer of biodegradable plastics.     

Construction of ULT-MRI cryostat for ultra low temperature physics

No Heading We have constructed an Ultra Low Temperature cryostat for Magnetic Resonance Imaging (ULT-MRI) applicable for various condensed phases of ³He at ultra low temperature, such as Nuclear Ordered Solid ³He or superfluid ³He. In contrast to conventional MRI for general use, where a pulsed-field gradient method is commonly used, we used a steady-field gradient method to avoid eddy current heating to metal parts at ultra low temperature. To avoid nonlinear response from the nuclear ordered spin system, which contradicts a principle of conventional MRI, we employed Free Induction Decay (FID) after a small tipping angle RF pulse to obtain the spectrum.PACS numbers: 07.20Mc, 67.57.Lm, 67.80.Jd, 76.60.Pc, 83.85.Fg