Anderson Localization in Disordered Vibrating Rods

We study, both experimentally and numerically, the Anderson localization phenomenon in torsional waves of a disordered elastic rod, which consists of a cylinder with randomly spaced notches. We find that the normal-mode wave amplitudes are exponentially localized as occurs in disordered solids. The localization length is measured using these wave amplitudes and it is shown to decrease as a function of frequency. The normal-mode spectrum is also measured as well as computed, so its level statistics can be analyzed. Fitting the nearest-neighbor spacing distribution a level repulsion parameter is defined that also varies with frequency. The localization length can then be expressed as a function of the repulsion parameter. There exists a range in which the localization length is a linear function of the repulsion parameter, which is consistent with Random Matrix Theory. However, at low values of the repulsion parameter the linear dependence does not hold.Comment: 10 pages, 6 figure

Six Sigma: From a goal-theoretic perspective to shared-vision development

Purpose: The purpose of this paper is to extend understanding of the success of Six Sigma quality management initiative by investigating the effects of Six Sigma teamwork and statistical process control (SPC) on organizational shared vision.Design/methodology/approach: The information used comes from a larger study, the data for which were collected from a random sample of 237 European firms. Of these 237 organizations, 58 are Six Sigma organizations. Structural Equation Modelling (SEM) was used to test the hypotheses.Findings: The main findings show that Six Sigma teamwork and SPC positively affect the development of organizational shared vision. A positive but not significant influence is also observed between shared vision and organizational performance.Research limitations/implications: Positive effects found in this study should be investigated further employing a larger sample of Six Sigma firms and including other variables such as organizational learning. Further, the effects of these variables on performance should be measured with real results from firms to test possible direct and indirect influence on performance.Practical implications: The findings of this study offer a justification of Six Sigma implementation in firms. This study provides us with an in-depth understanding of some structural elements that characterize the Six Sigma methodology, enabling us to provide an explanation for its success.Originality/value: There is little empirical research on the positive effects of Six Sigma implementation and even less that explains the success of Six Sigma initiatives. Our paper contributes to filling this gap. It also contributes to emerging literature on how the development of shared vision affects organizational performance

Learning force patterns with a multimodal system using contextual cues

Previous studies on learning force patterns (fine motor skills) have focused on providing “punctual information”, which means users only receive information about their performance at the current time step. This work proposes a new approach based on “contextual information”, in which users receive information not only about the current time step, but also about the past (how the target force has changed over time) and the future (how the target force will change). A test was run to compare the performance of the contextual approach in relation to the punctual information, in which each participant had to memorize and then reproduce a pattern of force after training with a multimodal system. The findings suggest that the contextual approach is a useful strategy for force pattern learning. The advantage of the contextual information approach over the punctual information approach is that users receive information about the evolution of their performance (helping to correct the errors), and they also receive information about the next forces to be exerted (providing them with a better understanding of the target force profile). Finally, the contextual approach could be implemented in medical training platforms or surgical robots to extend the capabilities of these systems