Yoshikatsu Ohta

A New Parallel Closed Condition for Church-Rossser of Left-Linear Term Rewriting Systems

G.Huet (1980) showed that a left-linear term-rewriting system (TRS) is Church-Rosser (CR) if for every critical pair where is a parallel reduction from P to Q. But, it remains open whether it is CR when for every critical pair . In this paper, we give a partial solution to this problem, that is, a left-linear TRS is CR if for every critical pair where is a parallel reduction with the set W of redex occurrences satisfying that if the critical pair is generated from two rules overlapping at an occurrence u, then the length ¦w¦≤¦u¦ for every w∈W. Furthermore, a left-linear TRS is CR if or \(P\xrightarrow{\varepsilon }Q\)for every critical pair where W satisfies the same condition as the above and \(P\xrightarrow{\varepsilon }Q\) is a reduction whose redex occurrence is e (i.e., the root).

Opportunistic collaboration in participatory sensing environments

The proliferation of networked mobile devices that can capture and communicate various kinds of data provides an opportunity to design novel man-machine sensing environments of which this paper considers participatory sensing. To achieve energy efficiency and reduce data redundancy, we propose Aquiba protocol that exploits opportunistic collaboration of pedestrians. Sensing activity is reduced according to the number of available pedestrians in nearby area. The paper investigates the benefit of opportunistic collaboration in large-scale scenarios through simulation studies. To take microscopic interaction of social crowds into consideration, we adapt the social force model and include it as one of three mobility models applied in our studies. Though the simulation results depend on mobility models, they validate the benefit of opportunistic collaboration employed by Aquiba protocol.

The Unification Problem for Confluent Right-Ground Term Rewriting Systems

The unification problem for term rewriting systems(TRSs) is the problem of deciding, for a given TRS R and two terms M and N, whether there exists a substitution θ such that Mθ and Nθ are congruent modulo R (i.e., Mθ ↔R* Nθ). In this paper, the unification problem for confluent right-ground TRSs is shown to be decidable. To show this, the notion of minimal terms is introduced and a new unification algorithm of obtaining a substitution whose range is in minimal terms is proposed. Our result extends the decidability of unification for canonical (i.e., confluent and terminating) right-ground TRSs given by Hullot (1980) in the sense that the termination condition can be omitted. It is also exemplified that Hullots narrowing technique does not work in this case. Our result is compared with the undecidability of the word (and also unification) problem for terminating right-ground TRSs.

The Joinability and Unification Problems for Confluent Semi-constructor TRSs

The unification problem for term rewriting systems (TRSs) is the problem of deciding, for a TRS R and two terms s and t, whether s and t are unifiable modulo R. Mitsuhashi et al. have shown that the problem is decidable for confluent simple TRSs. Here, a TRS is simple if the right-hand side of every rewrite rule is a ground term or a variable. In this paper, we extend this result and show that the unification problem for confluent semi-constructor TRSs is decidable. Here, a semi-constructor TRS is such a TRS that every subterm of the right-hand side of each rewrite rule is ground if its root is a defined symbol. We first show the decidability of joinability for confluent semi-constructor TRSs. Then, using the decision algorithm for joinability, we obtain a unification algorithm for confluent semi-constructor TRSs.

Exploring analysis of football actions considering correlation of joints in the body

When beginners learn football skills, they need relevant guidance by a coach. However, it is difficult for them to find a good coach. When the beginners practice repeatedly to master the skills by themselves, they often do it in wrong and inefficient manners. In addition, it takes variation in time for each beginner to acquire embodied knowledge of football skill. In this paper, we analyze a football players action by using motion capture so as to quantify the difference between experts and beginners. Based on correlation of joints in the body, we present a method to analyze football skills by using a cross-correlation function.

A design of software adaptive to estimated user's mental state using pulse wave analysis

Recent study has shown that the pulse wave signal of human includes much information of humans mental condition. To get such information, measuring finger pulse wave is a non-invasive and convenient method. Then we analyze the measured pulse wave in frequency domain to investigate low- and high-frequency components whose the ratio can be used to estimate mental condition. We design and implement an API to retrieve users mental state easily and adaptively control a mobile phones software based on mental condition. To validate the benefit of API, we develop a mail filtering app on an Android phone and perform an experiment.