In this study, the linear elastic fracture mechanics (LEFM) approach, including use of the equivalent initial flaw size (EIFS) concept and fatigue crack propagation (FCP) rates, da/dN, as a function of either DK or DK eff , was used to predict the fatigue life of a porosity-containing 319-T7 specimen. The uniaxial fatigue tests were conducted on a 319-T7 specimen at a stress ratio (R) of À1. For the LEFM-based fatigue life prediction, da/dN-DK data were obtained for the 319-T7 specimen at R = 0.1. The shape and the size of the porosity were analyzed based on the fractographic and the micrographic analyses for each fatigued specimen. The LEFM concept, including the use of the EIFS value, back-calculated by using da/dN-DK eff data, successfully predicts the porosity-affected stress vs the number of cycles to failure (S-N) fatigue behavior of cast 319-T7 specimens. The LEFM models presently available for predicting the fatigue life of porosity-containing alloys were evaluated and a simple modification was proposed based on extensive fractographic analysis results.

This paper generally relates to the field of wireless local area networks(WLANs), and more particularly, to AP selection and association methods for the performance of a station. In these days, IEEE 802.11 WLAN is widely deployed and used as an emerging service to connect high-speed Internet in the public wireless environment. But, if there are many users in hot spot area, they suffer a severe decrease of performance. Thus it needs an association and access control mechanism especially when it is used in the public environment. In this paper, we suggest an efficient association method using Beacon or Probe Response frames based IEEE 802.11 and analyze the performance of stations(STAs). Station selects AP using the information of the capability region in a Beacon or a Probe Response frame. According to the present paper, an association method for a public WLAN service, which includes a WLAN user terminal and an AP for relaying WLAN communications to and from the user terminal, includes the steps of the user terminal asking the AP's states to access with a radio channel; and the station selects and associates with the AP. Further, it is possible to improve the efficiency of network management.

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SUMMARYWe propose and demonstrate an Ethernet transport system that can support hard real-time traffics with guaranteed throughput and very low jitter performance even in the presence of asynchronous traffics. The superframe structure-based Ethernet system first synchronizes all the nodes in a network by using the IEEE 1588-compliant boundary clock scheme and then reserves the traffic channels for synchronous traffics before accommodating both synchronous and asynchronous traffics in the superframe. Our experimental demonstration performed on field-programmable gate array-enabled Gigabit Ethernet test benches shows that the proposed scheme not only guarantees the throughput of the synchronous frames but also substantially reduces the jitter of the synchronous frames less than 110 ns after seven-hop transmission.

Object-oriented programming has emerged as one of the most promising paradigms for developing sobware and it has gained wide acceptance from sopware erzgineers in diverse disciplines. Recent release of CLIPS, the C Language Integrated Production System developed by NASA S Johnson Space Center, includes an object-oriented language called COOL which is an acronym for CLIPS Object-Oriented Language. This paper evahrates COOL as an object-oriented programming language and shows an object-oriented approach to develop a large engineering sofhvare using CLIPS. A CLIPS implementation of an algorithm for a space structure's optimal sensor placement is given as an examplc.