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A B S T R A C T High speed steels, such as the alloy H-13, when used as forging dies are subjected to both wear and cyclic loading, and both of these factors can affect the useful life of such dies. It follows that it is of some importance to determine the fatigue characteristics of such steels. However, fatigue studies of such alloys are limited, especially with respect to fatigue crack propagation (FCP) behaviour as a function of mean stress, and therefore more detailed studies are necessary.In the present study, the fatigue lifetimes and the crack propagation behaviour of a high speed steel were experimentally investigated in laboratory air under different stress ratios, R. A modified linear-elastic fracture mechanics (LEFM) approach was applied to analyze the experimentally-obtained FCP behaviour. The predicted S-N curves and crack growth behaviour for a wide range of R ratios agree well with the experimental data, and the modified LEFM approach is therefore considered to be useful for evaluation of the fatigue behaviour of this class of high strength steels. A = Material-environmental constant a = Half crack length da/dN = Rate of crack propagation F = Elastic-plastic correction factor f = Stress frequency K = Stress intensity factor K T = Stress concentration factor K max = Maximum stress intensity factor K max th = Threshold maximum stress intensity factor K min = Minimum stress intensity factor K op = Crack-opening stress intensity factor K op max = Maximum crack-opening stress intensity factor K = Stress intensity factor range K eff = Effective stress intensity factor range K eff th = Threshold effective stress intensity factor range k = Material constant M = A modified linear elastic fracture mechanics parameter N = Number of cycles N f = Number of cycles to failure N/N f = Fatigue life ratio Correspondence: S. Ishihara.

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In this paper, we present an implementation of a se mantic associative search space for medical document databases.We have implemented a semantic associative search space for the medical field by using encyclopedias which describe not only word definitions but also word explana tions.This implementation realizes a medical semantic asso ciative search space by using a medical encyclopedia which includes explicit word explanations.We have created an actual medical semantic associative search space which consists of 149 dimensions computed from the 217x219 matrix consisting of medical data.By using this actual medical space, we show several ex perimental results of semantic associative search space cre ation and medical document retrieval for clarifyingfeasibil ity of our implementation method.

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