Modeling of Ultrasonic Signals from Weak Inclusions

Recent research efforts aimed at improving the detection of hard-alpha inclusions have emphasized the need for accurately modeling the responses from such weakly-reflecting inclusions. The need arises because of the rare natural occurrence of hard-alpha inclusions, and consequently, the lacks of suitable experimental samples. These difficulties lend impetus to the application of signal modeling to augment and extend the experimental data in assessing detectability. Currently, a new approach is being developed for the purpose of predicting time-domain echoes from inclusions of specified morphology. This work is the continuation of our previous study of flat-bottomed holes [1–2] in constructing a methodology for estimating the probability of detection of flaws in titanium alloys based on a combination of physical and statistical models

An approximation algorithm for bounded length tree linear broadcast routing

The high-strength alloys used in the aerospace industry today are inspected ultrasonically for material anomalies which may have resulted from the manufacturing process. These materials, such as titanium alloys, often have a large macro-grain structure which limits the sensitivity of the ultrasonic inspection to material anomalies. As a result, there has been much work directed towards developing inspection techniques which minimize the level of the reflections from the macro-grains and enhance the reflections from the material anomalies. In particular, the affect of transducers parameters such as transducer bandwidth, focus, and frequency on the signal-to-noise ratio of synthetic anomalies in titanium alloys has been investigated [1–3]. This investigation showed that the level of the grain noise relative to a known calibration target decreases in Ti-A16-V4 (Ti6-4) and Ti-A15-Sn2-Zr2-Mo4-Cr4 (Ti17) and the signal-to-noise ratio of synthetic anomalies with planar geometries in Ti6-4 increases as the volume of the ultrasonic pulse in the material decreases. This paper will extend these results to planar synthetic anomalies in Ti17 and non-planar synthetic anomalies in Ti6-4. In addition, a transducer design methodology for high sensitivity inspection based on managing the size of the ultrasonic pulse volume is presented and the implications of using this method for production inspections are described

Stage-specific and culture-specific coping strategies used by Mainland Chinese immigrants during resettlement in Hong Kong: A qualitative analysis

A qualitative study was undertaken to explore the stage-specific and culture-specific coping strategies used by Mainland Chinese immigrants in Hong Kong to handle psychosocial stressors experienced during the resettlement stage of the migration process. While direct action coping strategies of problem-solving and compromise were used by immigrants to deal with recurring, daily resettlement difficulties, cognitive strategies of positive comparisons and positive and optimistic thinking were utilized to change the meanings of these difficulties. Emotion-focused coping of acceptance and avoidance strategies were culture-specific, and were useful in reducing the stress associated with the resettlement difficulties encountered. It was also found that strategies such as acceptance, compromise and avoidance might have deleterious effects on the longer-term adjustment of immigrants. Implications for services and counseling for the immigrants were suggested. © 2002 by The Haworth Press, Inc. All rights reserved.link_to_subscribed_fulltex