Reactive Visual Navigation Based on Omnidirectional Sensing – Path Following and Collision Avoidance

Described here is a visual navigation method for navigating a mobile robot along a man-made route such as a corridor or a street. We have proposed an image sensor, named HyperOmni Vision, with a hyperboloidal mirror for vision-based navigation of the mobile robot. This sensing system can acquire an omnidirectional view around the robot in real time. In the case of the man-made route, road boundaries between the ground plane and wall appear as a close-looped curve in the image. By making use of this optical characteristic, the robot can avoid obstacles and move along the corridor by tracking the close-looped curve with an active contour model. Experiments that have been done in a real environment are described.     

Living metathesis polymerization of (p-n-butyl-o,o,m,m-tetrafluorophenyl)acetylene by MoOcl4-n-Bu4Sn-EtOH (1:1:1)

Summary Possibility of living metathesis polymerization by Mo catalysts was examined for (p-n-butyl-o,o,m,m-tetrafluorophenyl)acetylene, which has two fluorine atoms at both ortho positions. The MoOCl₄-n-Bu₄Sn-EtOH (1:1:1) catalyst yielded a polymer with narrow molecular weight distribution ( ), but the corresponding MoCl₅-based catalyst did not formed such a polymer. With the former catalyst, the number-average molecular weight of polymer increased in direct proportion to monomer conversion, while the molecular weight distribution remained narrow; this proves the livingness of the polymerization. The optimal conditions for the living polymerization were [n-Bu₄Sn]/[MoOCl₄]=∼1.0, [EtOH]/[MoOCl₄]=0.5–1.5, and temperature≤30 °C. n-Butyl acetate and acetone as well as EtOH were effective as third catalyst components.     

Magnetic torque of κ-(BEDT-TTF)2Cu(NCS)2 single crystals

The magnetic torque ofκ-(BEDT-TFF)₂Cu(NCS)₂ was measured as a function of field directionθ with respect to thea ^*-axis under constant magnetic fields,H, up to 8 kOe in the temperature range from 1.3 to 8 K. A sharp cusp, C₁, in the irreversible region was found atθ _c1 near theH∥bc-plane between 1.3 and 7 K. In addition, extra cusps, C₂ and C₃, were observed atθ _c2 andθ _c3, respectively, between 2.5 and 6 K. At each temperature, the perpendicular component ofH giving each cusp is kept constant as $H\cos \theta _{cn} = const \equiv H_{cp_n } (n = 1,2,3),$ i.e., cusps C₁, C₂, and C₃ are ruled by the characteristic field perpendicular to thebc-planeH _cp1,H _cp2, andH _cp3, respectively. These behaviors are almost the same as those we found in the oxide superconductor Bi₂Sr₂CaCu₂O₈. These results suggest that the cusps are intrinsic for irreversible vortex states of these layered superconductors.     

Preparation of NbN fibres by nitridation of sol-gel derived Nb2O5 fibres

Nbn fibres were prepared by nitriding sol-gel-derived Nb₂O₅ fibres. Precursor niobium-oxide-gel fibres were obtained by spinning viscous sots prepared through acid-catalysed hydrolysis of niobium penta-ethoxide, Nb(OC₂H₅)₅. It was found that the spinnability of the sols depended on the water/alkoxide and the acid/alkoxide ratios. The niobium-oxide-gel fibres thus obtained were converted to niobium nitride by heat-treatment in a NH₃ gas above 800°C. Characterization of these fibres was carried out using X-ray powder diffraction, Auger electron spectroscopy and scanning electron microscopy. The nitride fibres obtained at 1050°C were mostly of stoichiometric -NbN phase, and they showed a transition to a superconducting state at around 11 K.     

Distraction detection of lectures in e-learning using machine learning based on human facial features and postural information

Artificial Life and Robotics - While e-learning lectures allow students to learn at their own pace, it is difficult to manage students’ concentration, which prevents them from receiving...     

Application of Surface Acoustic Wave Sensors for Liquid Helium-4 and Helium-3

A surface acoustic wave (SAW) sensor can be used to determine the acoustic properties of liquid He. We applied this sensor for liquid ³He and liquid ⁴He. Two kinds of SAW were used in this experiment, Rayleigh-SAW and shear horizontal SAW. The damping of Rayleigh-SAW was measured in liquid ⁴He. The results agreed well with the reported values of the acoustic impedance, and the superfluid transition was clearly seen. The damping and the phase shift of shear horizontal SAW were measured in the normal liquid ³He. Temperature dependence of the damping and the phase shift was analyzed by the viscoelastic model, and the results were compared with the transverse acoustic impedance in the normal ³He.     

Superconductivity and Ferromagnetism of the Ru-1232 Compounds in the (Ru1−x Nb x )Sr2(GdCe1.8Sr0.2)Cu2O z System

The Ru-1232 compounds have been synthesized in the (Ru_1?xNb _x )Sr₂(GdCe_1.8Sr_0.2)Cu₂O _z system, and effects of Nb substitution for Ru on superconductivity and ferromagnetism of the Ru-1232 compounds have been investigated. First, X-ray powder diffraction study shows that nearly the single 1232 phase samples can be obtained in the x composition range from 0.0 to 0.3. Then, from the electrical resistivity study, it is found that each of the samples shows resistivity dropping phenomenon at two temperatures of T _c ^l and T _c ^h, which originates from superconductivity of the Ru-1232 phase and the Ru-1222 one, respectively. Both of the starting temperatures are lowering with increasing Nb content x. Lastly, from the magnetic susceptibility study, it is found that superconducting transition temperature T _c is 20 K for the Ru-1232 sample with x = 0.0 and the ferromagnetic transition temperature T _m is about 90 K. This study also shows that both of the values of T _c and T _m become low with increasing x from 0.0 to 0.3.     

Effects of Flexibility on Rocking Impedance of Deeply Embedded Foundation

This paper presents a detailed investigation of the influence on the rocking impedance of flexible sidewalls in embedded foundations. The study focuses on vertical and cylindrical foundations embedded in a homogeneous elastic stratum. In order to anticipate the effects of the flexibility, closed-form formulae for rocking impedance are derived based on three-dimensional wave propagation theory and superposition of both the rocking and flexural movements on a single model by assuming complete bonding conditions between the soil and foundations. A function representing the effect of the flexibility is identified from the closed-form formulae, in terms of the height to radius ratio of the foundations and the ratio of the stiffnesses of the ground and foundations. The rocking impedance for a flexible sidewall differs from those evaluated under the assumption of a rigid sidewall. The applicable range of rocking impedance evaluated under the assumption of a rigid sidewall is assessed, and contours to assist in the estimation of the dynamic response of deeply embedded foundations are presented.     

Recognition of camera-captured low-quality characters using motion blur information

Camera-based character recognition has gained attention with the growing use of camera-equipped portable devices. One of the most challenging problems in recognizing characters with hand-held cameras is that captured images undergo motion blur due to the vibration of the hand. Since it is difficult to remove the motion blur from small characters via image restoration, we propose a recognition method without de-blurring. The proposed method includes a generative learning method in the training step to simulate blurred images by controlling blur parameters. The method consists of two steps. The first step recognizes the blurred characters based on the subspace method, and the second one reclassifies structurally similar characters using blur parameters estimated from the camera motion. We have experimentally proved that the effective use of motion blur improves the recognition accuracy of camera-captured characters.     

Synthesis of two-dimensional IIR digital filters with desired spatial domain specifications and no overflow oscillations

A design technique of two-dimensional (2D) recursive infinite-area impulse response (IIR) digital filters (DFs) which approximates desired spatial-domain specifications and guarantees no overflow oscillations is proposed in this paper. First, it is shown that the balanced approximation is not optimal for l₂ model reduction. From this point of view, a new design technique of 2D separable-denominator (SD) digital filters is studied using reduced-dimensional decomposition and the l₂ model reduction methods based on balanced gains. This result is used as a starting point of a design algorithm for 2D non-separable ND DFs. Second, a design problem of 2D ND DFs is formulated as a nonlinear minimization problem with equality and inequality constraints, and the Broyden-Fletcher-Goldfarb-Shanno algorithm is applied to solve it. Finally, two examples are given to show the effectiveness of the proposed design technique.