Propagation of “small fatigue crack” initiated from notch-root

Recently, early stage of initiated fatigue crack propagation, so-called, “small crack” propagation behavior from notch-root is becoming more and more important for the developement of improved prediction of fatigue life of structural components. In the present paper, fine-grid-method which was already presented in the previous paper was applied to this problem. Special attention was given to the crack-tip strain changes of “small crack” engulfed in the plastic field of the notch. The relationship between fatigue crack propagation rate, $\text{da}\text{dN}$, and stress intensity factor range, ΔK, as well as local crack-tip strain range, Δ?^T, which was previously proposed by the authors were investigated.     

Grammatical inference in bioinformatics

Bioinformatics is an active research area aimed at developing intelligent systems for analyses of molecular biology. Many methods based on formal language theory, statistical theory, and learning theory have been developed for modeling and analyzing biological sequences such as DNA, RNA, and proteins. Especially, grammatical inference methods are expected to find some grammatical structures hidden in biological sequences. In this article, we give an overview of a series of our grammatical approaches to biological sequence analyses and related researches and focus on learning stochastic grammars from biological sequences and predicting their functions based on learned stochastic grammars.     

On case-based learnability of languages

Case-based reasoning is deemed an important technology to alleviate the bottleneck of knowledge acquisition in Artificial Intelligence (AI). In case-based reasoning, knowledge is represented in the form of particular cases with an appropriate similarity measure rather than any form of rules. The case-based reasoning paradigm adopts the view that an Al system is dynamically changing during its life-cycle which immediately leads to learning considerations. Within the present paper, we investigate the problem of case-based learning of indexable classes of formal languages. Prior to learning considerations, we study the problem of case-based representability and show that every indexable class is case-based representable with respect to a fixed similarity measure. Next, we investigate several models of case-based learning and systematically analyze their strengths as well as their limitations. Finally, the general approach to case-based learnability of indexable classes of formal languages is prototypically applied to so-called containmet decision lists, since they seem particularly tailored to case-based knowledge processing.     

Learning context-free grammars using tabular representations

We present a novel algorithm using new hypothesis representations for learning context-free grammars from a finite set of positive and negative examples. We propose an efficient hypothesis representation method which consists of a table-like data structure similar to the parse table used in efficient parsing algorithms for context-free grammars such as Cocke-Younger-Kasami algorithm. By employing this representation method, the problem of learning context-free grammars from examples can be reduced to the problem of partitioning the set of nonterminals. We use genetic algorithms for solving this partitioning problem. Further, we incorporate partially structured examples to improve the efficiency of our learning algorithm, where a structured example is represented by a string with some parentheses inserted to indicate the shape of the derivation tree of the unknown grammar. We demonstrate some experimental results using these algorithms and theoretically analyse the completeness of the search space using the tabular method for context-free grammars.     

Parameter of local cyclic strain distribution

The local cyclic strain distribution near the crack tip was investigated by the Computer Aided Fine Grid Method. This method makes it possible to measure continuously every in-plane component of local cyclic strain distribution. It was found that the magnitude of the local cyclic strain distribution near the crack tip was varied by the applied cyclic load level and the material, but the shape of the local cyclic strain distribution near the crack tip was experimentally scarcely altered.

The local cyclic strain field near the crack tip could be written as the following equation. Δε_eq(r, θ) = ΔA · f(θ) · r⁻¹ A single parameter ΔA, which characterizes the local cyclic strain field near the crack tip, was newly proposed by authors.     

Combinatorial search of thermoelastic shape-memory alloys with extremely small hysteresis width

Reversibility of structural phase transformations has profound technological implications in a wide range of applications from fatigue life in shape-memory alloys (SMAs) to magnetism in multiferroic oxides. The geometric nonlinear theory of martensite universally applicable to all structural transitions has been developed. It predicts the reversibility of the transitions as manifested in the hysteresis behaviour based solely on crystal symmetry and geometric compatibilities between phases. In this article, we report on the verification of the theory using the high-throughput approach. The thin-film composition-spread technique was devised to rapidly map the lattice parameters and the thermal hysteresis of ternary alloy systems. A clear relationship between the hysteresis and the middle eigenvalue of the transformation stretch tensor as predicted by the theory was observed for the first time. We have also identified a new composition region of titanium-rich SMAs with potential for improved control of SMA properties.