SUMMARYParticle Swarm Optimization (PSO) is a search method which utilizes a set of agents that move through the search space to find the global minimum of an objective function. The trajectory of each particle is determined by a simple rule incorporating the current particle velocity and exploration histories of the particle and its neighbors. Since its introduction by Kennedy and Eberhart in 1995, PSO has attracted many researchers due to its search efficiency even for a high dimensional objective function with multiple local optima. The dynamics of PSO search has been investigated and numerous variants for improvements have been proposed. This paper reviews the progress of PSO research so far, and the recent achievements for application to large-scale optimization problems. key words: particle swarm optimization, swarm intelligence

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A new nondestructive method to estimate the stress distribution in a metal is proposed. It is based on the use of nonlinear dependence of ultrasound velocity on stress in metals. First, the dependence of ultrasound velocity on stress in an aluminum alloy is observed, and it is confirmed that the relation is nonlinear and that its derivative changes monotonically in the stress range of interest. Hence, if a certain stress perturbation is given to the observing region in a metal and the change of ultrasound velocity due to the perturbation is measured, the stress in that region can be estimated. This is the basic idea of the measurement of stress in a metal. Now, the field to give the stress perturbation is scanned along the probing ultrasonic beam and a set of data of phase change due to the velocity change is acquired. Then a matrix inversion technique is applied to them by taking account of the spatial distribution of the stress perturbation to obtain a precise stress distribution along the probing beam. The applicability of the proposed method is confirmed by computer simulations. Then a measuring system is constructed which consists of an electromagnetic transducer as the stress perturbation generator which gives approximately 0.4 MPa of perturbation, and a 50-MHz ultrasonic probing wave transmitter/receiver to detect the phase change. Finally, the stress distribution along a line in a specific aluminum alloy block is estimated by using the constructed system. The estimated stress distribution showed good agreement with the expected one. ¸

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Sixty of 128 (46.9%) residents of a nursing home were immunized with two doses of the trivalent split influenza vaccine. They developed 7.4-11.5-fold antibody increases, with a 69-82% protection rate, presenting good immune response rates to the influenza vaccine. Two outbreaks of influenza A (H3N2) occurred. There were no significant antigenic differences among the vaccine strain and the strains isolated from both outbreaks in haemagglutination-inhibition tests, suggesting that the second might have been a reoccurrence. There were no residents who were infected in both outbreaks. The vaccine efficacy against clinical illness in the first outbreak of typical influenza-like-illness (ILI) was 51% (relative risk: 0.49), and the febrile period was reduced significantly by vaccination. In the second outbreak, however, in which all patients had atypical ILI with a high fever but not respiratory symptoms, vaccine efficacy was not apparent for unknown reason.

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We introduce a statistical shape descriptor for Sketch-Based Image Retrieval. The proposed descriptor combines feature information in near and far support regions defined for each sketch point. Two feature values are extracted from each point, corresponding to near and far support regions from the point's perspective, and used to populate a 2-D histogram representing the shape features of the sketch image. The boundary between the support regions is calculated accordingly to each sketch point, which makes the approach scale invariant. We report results of objective evaluation of the proposed approach regarding robustness against noise, and comparative evaluation with three state-of-the-art methods, using an image database of scanned handwritten alphabets, digits, mathematical symbols and expressions. Experimental results show that the proposed method has competitive distinctiveness and robustness against noise.