Acoustic emission (AE) is potentially an ideal technique for health monitoring of large structures due to the small number of sensors required and its high sensitivity. There has been much research ...conducted to characterize and provide qualitative understanding of the AE process in small specimens. Unfortunately, it is difficult to extend these results to real structures as the experimental data is dominated by geometric effects due to the small size of the specimens. The aim of this work is to provide a characterization of elastic waves emanating from fatigue cracks in plate-like structures. Fatigue crack growth was initiated in large 6082 T6 aluminium alloy plate specimens subjected to cyclic loading in the laboratory. A large specimen was used to eliminate signal reflections from the specimen edges and to enable signals from different wave modes to be separated in time. The signals were recorded using both resonant and non-resonant transducers attached to the surface of the specimens. Large numbers of AE signals were detected due to active fatigue crack propagation during the experiment. Analysis of experimental results from multiple crack growth events was used to characterize the modal and angular distributions of the radiated elastic waves. Experimental results are compared with finite element predictions to examine the mechanism of AE generation at the crack tip.
Modern reheating furnace control systems currently use limited measurements of the furnace temperature coupled with simple empirical mathematical models to predict and following regulate stock ...temperatures. However existing measurement data capture only a small amount of information about the operating state of the furnace. In addition, the mathematical models used in existing reheating furnace control systems are relatively crude so that predictions of process parameters have only limited accuracy and the precision of the supervisory process control system is compromised. Therefore furnace operation will be improved using these advanced measurements and dynamic modelling for improved furnace operation and control. In the completed research, the specifications for different advanced furnace measurements and modelling were determined. Beyond the analysis of the state-of-the-art in furnace measurements and modelling the collection of the requirements for advanced furnace measurements was completed. This covered stock and gas temperature measurements, furnace atmosphere measurements and radiometric imaging. Such measurement technologies were installed and operated in different types of reheating furnaces. The resulting information was used for the development of improved furnace models. The necessary data for each of the furnaces selected was collected to allow the development of the “virtual furnace” model by a well-documented zone modelling approach. The virtual furnace models were adapted to the specific situation in industrial facilities. General conclusions regarding new measurement approaches, reheating furnace models and furnace control were collected.
Conventional manual placement for decoupling capacitance (decap) is very time consuming and may lead to unavoidable human errors. In VLSI design environments there is a critical need to have an ...automated way via CAD tools, particularly to ensure quick turn-around times in the face of strong time-to-market pressures. Unfortunately, existing placer algorithms work best on rectangle placement regions, but are less efficient when working on polygon placement regions with more than 4 vertices. Therefore, in this paper, we present and propose a decap placer using new placement algorithm named Size and Level oriented algorithm (SL). This decap placer is implemented with routing and area consideration which works efficiently on not only rectangle but polygon placement regions as well. Furthermore, different placement orientations are implemented also in this decap placer for better decaps placement coverage.
The human immunodeficiency virus (HIV) epidemic in the US increasingly involves urban heterosexual adults, particularly women, belonging to ethnic minority groups. An understanding of gender-based ...differences in HIV risk behaviors within these groups would be of value in the ongoing struggle to limit HIV transmission in metropolitan centers.
This was a prospective study of demographic and historical characteristics and HIV risk behaviors. The study utilized a structured interview format, which was administered to all patients treated by participating emergency department physicians.
On univariate analysis of data obtained from 1,460 patients who had neither a known HIV infection nor a chief complaint or final emergency department diagnosis associated with HIV risk behaviors, men were more likely to be older, homeless, to have ever injected drugs, used crack, engaged in same-gender sex, paid for sex, been incarcerated, or had syphilis or gonorrhea. Women were more likely to report prior chlamydia infection or to report that their sole sex partners had other partners within the past year. On multivariate analysis, variables independently associated with male gender included homelessness, injection drug use, crack use, any prior sexually transmitted disease (in subjects 35 years of age or older), and sex with prostitutes. In a separate analysis of patients admitting to drug use, the male predominance of other risk behaviors was not observed; the only significant differences between genders were a higher rate of prostitution among women and a higher rate of sexual contact with a prostitute among men.
In patients visiting an inner-city emergency department in the Bronx, HIV risk behaviors are generally more common in men, but rates of risk behaviors among male and female drug users are comparable.
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