We statistically examine long time sequences of Brownian motion for a nonequilibrium version of the Rayleigh piston model and confirm that the third cumulant of a long-time displacement for the nonequilibrium Brownian motion linearly increases with the observation time interval. We identify a multiplicative Langevin equation that can reproduce the cumulants of the long-time displacement up to at least the third order, as well as its mean, variance and skewness. The identified Langevin equation involves a velocity-dependent friction coefficient that breaks the time-reversibility and may act as a generator of the directionality. Our method to find the Langevin equation is not specific to the Rayleigh piston model but may be applied to a general time sequence in various fields.
We are facing security threats over the Internet that users are not aware of, such as malware infection as well as unauthorized access. We look into user interfaces which cause discomfort so that users can be more aware of security risks. Despite of our efforts on security protections, risk to encounter dangers is increasing by use of smartphones. This paper reports our research progress on discomfort factors with use of smartphones; we conducted a questionnaire survey and found factors that are supposed to cause discomfort when using smartphones obtained from the results of exploratory factor analysis. Through exploratory factor analysis, we came up with five factors that contribute to the discomfort feeling. In addition, we describe the verification results of the difference for each factor according to smartphone OSs (iOS/Android) and the smartphone usage period.
Heel raise repetitions and the maximum step length of elderly subjects were compared, and their differences as indices of fall history were investigated. [Subjects and Methods] The subjects were 80 persons over 65 years of age who could walk independently. The number of heel raises performed in 10 seconds, and the maximum step length, the greatest possible forward step distance, were measured and compared between subjects with and without a history of falls. [Results] The number of heel raises and maximum step length of the falls group were significantly less than those of the no-falls group, and their correlation coefficient was r=0.539. Also, the cutoff value for heel raises between the falls and no-falls groups was 10.5 (sensitivity, 80.9%; specificity, 72.7%). [Conclusion] The results show that the heel raise number correlated well with maximum step length, and because it was significantly lower in the falls group, there is a possibility that it is a useful predictor of falls.
Making users aware of the risk by giving them a sense of discomfort and helping them not to access dangerous sites is crucial. Thus, we focus on developing a warning interface, causing discomfort, allowing smartphone users to be aware of danger and risks. We studied discomfort feelings while using smartphones and extracted five discomfort factors from a questionnaire survey and factor analysis. We implemented a prototype of warning interfaces for web browsing on a smartphone considering five factors. In the experiments, we have found that three factors out of the five, namely, "Unintended operation or display," "Sudden changes," and "Understanding of the application," are significant for risk awareness, while the other two are not. This paper reports on the findings of the study.
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