Path planning for an autonomous mobile robot considering a region with a velocity constraint in a real environment

Recently, many research projects and competitions have attempted to find an autonomous mobile robot that can drive in the real world. In this article, we consider a path-planning method for an autonomous mobile robot that would be safe in a real environment. In such a case, it is very important for the robot to be able to identify its own position and orientation in real time. Therefore, we applied a localization method based on a particle filter. Moreover, in order to improve the safety of such autonomous locomotion, we improved the path-planning algorithm and the generation of the trajectory so that it can consider a region with a limited maximum velocity. In order to demonstrate the validity of the proposed method, we participated in the Real World Robot Challenge 2010. The experimental results are given.     

Bifurcation mechanism underlying echelon-mode formation

This paper presents a theory on the underlying mathematical mechanism of the echelon mode (a series of parallel short wrinkles that looks like a flight of stairs or wild geese arranged in formation) which has been observed ubiquitously with uniform materials, but which has long denied successful numerical simulations. It is shown by means of the group-theoretic bifurcation theory that the echelon mode formation can be explained as a recursive (secondary, tertiary, …) symmetry-breaking bifurcation if O(2) × O(2) is chosen as the underlying symmetry to model the local uniformity of materials. This implies, for example, that the use of periodic boundaries is essential to successfully realize the oblique stripe patterns and the subsequent echelon mode formation in numerical simulations. In fact, a recursive bifurcation analysis of a rectangular domain with periodic boundaries subject to uniform uniaxial compression yields various kinds of patterns, such as diamond, stripe and echelon modes, which are often observed for materials under shear.     

System reliability of suspension bridges

Provisions for the design of existing suspension bridges often rely on a deterministic basis. Consequently, the reliability of these bridges cannot be assessed if current provisions are applied. In order to develop cost-effective design and maintenance strategies for suspension bridges a system reliability-based approach has to be used. This is accomplished by a probabilistic finite element geometrically nonlinear analysis approach. This study forms part of an investigation into the system reliability evaluation of geometrically nonlinear large span bridges recently undertaken at the University of Colorado. A brief review of reliability analysis of geometrically nonlinear elastic structures allows for the determination of its relevance to the assessment of suspension bridges. A probabilistic finite element geometrically nonlinear elastic code is used for system reliability evaluation of suspension structures. The allowable stress design procedures used by the Honshu Shikoku Bridge Authority for the design of suspension bridges are presented along with their application to the design of an existing bridge. This bridge is studied from a system reliability viewpoint to evaluate its reliability under different loading and damage scenarios. Such information calls attention to the fact that the reliability of cables, hanger ropes and girders are very different. Therefore, optimal maintenance decisions for suspension bridges designed according to allowable stress method are not consistent with those based on equal component reliability values.     

Mechanical properties of an aromatic polyamide-imide composite film reinforced with an aromatic polyamide fiber cloth at high temperature

An aromatic polyamide-imide (PAI) film was reinforced with a plain cloth of aromatic polyamide fiber (Du Pont, Kevlar 49). The mechanical properties of the composite film were investigated by examination of the temperature dependencies of tensile dynamic mechanical properties, stress relaxation, and tensile stress-strain behaviors. The softening temperature of the composite film was lower than that of a homogeneous PAI film. At a high temperature, Kevlar fibers may act as a thermal conductor and lower the softening point of the PAI composite. The mechanical properties of the composite film at a high temperature are mostly controlled by the PAI matrix.     

Estimation of Shape Parameter of GGD Function by Negentropy Matching

In this paper we present a novel method for the estimation of the shape parameter of the Generalized Gaussian Distribution (GGD) function for the leptokurtic and Gaussian signals by matching negentropy of GGD function and that of data approximated by some non-polynomial functions. The negentropy of GGD function is monotonic function of its shape parameter for values corresponding to super-Gaussian and Gaussian distribution family. The simulation results have been compared with those obtained by existing methods such as Mallat’s method and Kurtosis matching method. It has been found that the proposed method is effective and useful in the cases where we have a few observation samples and distribution is highly spiky.     

Joint inhomogeneity in dissimilar friction stir welded martensitic and nanostructured ferritic steels

Dissimilar welding between oxide dispersion strengthened ferritic (ODS) steel and reduced activation martensitic steel would be required for constructing the advanced blanket of progressive fusion reactors. In this study, we achieved dissimilar joints by friction stir welding, and aimed to characterise and ameliorate joint inhomogeneity. Main results reveal that the joint inhomogeneity is generated from discrepant microstructural evolutions within the martensitic and ODS ferritic steels. The ODS steel achieves evolution by the dynamic recrystallisation, while the martensitic steel undergoes phase transformation that drastically hardens the stir zone. By a proper post-weld heat treatment, the joint inhomogeneity can be effectively ameliorated due to carbide reprecipitation and stress relief in the joint.     

Geometrically nonlinear finite element reliability analysis of structural systems. II: applications

This is the second part of an investigation on finite element reliability analysis of geometrically nonlinear elastic structures (GNS). This study concentrates on applications. The linkage code RELSYS-FEAP presented in the companion paper is used for finding both component and system reliabilities of GNS. Structural reliabilities are evaluated for both geometrically linear and nonlinear elastic behaviors. Two geometrically nonlinear applications are presented, including a truss and a suspended structure. The stress and displacement reliabilities of the truss are computed considering both geometrically linear and nonlinear elastic behaviors. The system reliability of a geometrically nonlinear suspended structure is evaluated. The structure is modeled as a series of parallel subsystems according to three system failure criteria. The effects of correlation between loads, correlation between resistances, and material behavior (brittle or ductile) are evaluated and discussed. Finally, displacement reliability indices of the suspended structure are computed.     

Neutron irradiation hardening and microstructure changes in Fe-Mn binary alloys

Irradiation hardening and microstructure changes in Fe-Mn binary alloys were investigated after neutron irradiation at 290 °C and up to 0.13 dpa. Significant irradiation hardening comparable to that of Fe-1 at.%Cu alloy was observed in Fe-1 at.%Mn alloy. Manganese increases the number density of dislocation loops, which contributed to the observed irradiation hardening. Manganese serves as a nucleus of the loop by trapping interstitial atoms and clusters, preventing 1D motion of the loops.     

Reactivity and structural change of coal char during steam gasification

This study is intended to clarify the relationship among the reactivity of coal char with steam, structural change in residual carbon, and ash behavior. Steam gasification of various coal chars and demineralized chars was carried out in a fixed-bed reactor. After gasification, the reacted char was analyzed using laser raman spectroscope (LRS), and scanning electron microscope, energy dispersive X-ray spectroscope (SEM/EDX) mapping. Results of SEM images and EDX-mappings revealed that novel parallel analysis of cross correlation between EDX-mapping and LRS-mapping was found to be very effective for the comprehensive evaluation of ash behavior and carbonaceous structure. As the gasification reaction proceeds, the reactivity of the char was varied; existence of Si and Al seemed to suffocate the char reactivity.     

Site-directed mutagenesis in hemoglobin: test of functional homology of the F9 amino acid residues of hemoglobin {alpha} and {beta} chains

The cysteine residue at F9(93) of the human hemoglobin (Hb A)ß chain, conserved in mammalian and avian hemoglobins,is located near the functionally important 1–ß2interface and C-terminal region of the ß chain and isreactive to sulfhydryl reagents. The functional roles of thisresidue are still unclear, although regulation of local bloodflow through allosteric S-nitrosylation of this residue is proposed.To clarify the role of this residue and its functional homologyto F9(88) of the chain, we measured oxygen equilibrium curves,UV-region derivative spectra, Soret-band absorption spectra,the number of titratable -SH groups with p-mercuribenzoate andthe rate of reaction of these groups with 4,4'-dipyridine disulfidefor three recombinant mutant Hbs with single amino acid substitutions:AlaCys at 88 (rHb A88C), CysAla at 93ß (rHb C93ßA)and CysThr at 93ß (rHb C93ßT). These Hbs showedincreased oxygen affinities and impaired allosteric effects.The spectral data indicated that the R to T transition upondeoxygenation was partially restricted in these Hbs. The numberof titratable -SH groups of liganded form was 3.2–3.5for rHb A88C compared with 2.2 for Hb A, whereas those for rHbC93ßA and rHb C93ßT were negligibly small. The reductionof rate of reaction with 4,4'-dipyridine disulfide upon deoxygenationin rHb A88C was smaller than that in Hb A. Our experimentaldata have shown that the residues at 88 and 93ß have definiteroles but they have no functional homology. Structure–functionrelationships in our mutant Hbs are discussed.