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In recent years, high speed data communications over twisted pair cables has gained tremendous demand. Asymmetric Digital Subscriber Line (ADSL) was standardized for use over twisted pair cables. A critical component in ADSL system is the echo canceller which is intended to discriminate unwanted echo signals caused by twisted pair interface circuit called the hybrid. An echo signal is characterized by the hybrid and the line type the hybrid is connected to. Recently, there has been a great concern that the echo signal displays wide variations when the twisted pair cable is shared with a telephone. The amount of echo signal present in the receiver will directly influence the ADSL system performance. Hence, high performance echo canceller with good tracking capability is required. In this thesis, a new adaptation scheme called Modified Conjugate Gradient method is proposed and applied to ADSL echo canceller. It is shown that superior tracking capability is obtained compared to previously proposed echo canceller using Least Mean Square (LMS) method while compromising small amount of computational complexity. / Graduation date: 1999

Using a novel paradigm, we provide direct evidence for the role of inhibition during semantic interference resolution in memory. In Experiment 1, target words were primed via a naming task. Then, a cue word prompted participants to generate either a meaningfully related or unrelated word. Producing an unrelated word should require suppression of the cue's closest associates, which were the primed targets. Finally, participants read a list of words including the suppressed targets. Participants were slower to name targets in the unrelated condition than in the related condition, indicating that generating an unrelated word required suppression of competitors. Experiment 2 eliminated the initial priming phase, and a robust suppression effect was observed. Both studies showed that naming targets in the unrelated condition was even slower than controls. These results reflect that resolving semantic competition entails suppression of rejected competitors to below baseline levels, supporting an inhibitory account of interference resolution.

Using a novel paradigm, we provide direct evidence for the role of inhibition during semantic interference resolution in memory. In Experiment 1, target words were primed via a naming task. Then, a cue word prompted participants to generate either a meaningfully related or unrelated word. Producing an unrelated word should require suppression of the cue's closest associates, which were the primed targets. Finally, participants read a list of words including the suppressed targets. Participants were slower to name targets in the unrelated condition than in the related condition, indicating that generating an unrelated word required suppression of competitors. Experiment 2 eliminated the initial priming phase, and a robust suppression effect was observed. Both studies showed that naming targets in the unrelated condition was even slower than controls. These results reflect that resolving semantic competition entails suppression of rejected competitors to below baseline levels, supporting an inhibitory account of interference resolution.

Full-scale experiments are conducted to study the effects of different water-based indirect and combination initial attack methods on the compartment environment and firefighter during compartment fire suppression, with an aim toward improving manual fire suppression effectiveness and firefighter safety. Hot layer temperatures typical of room fire conditions are developed in the test compartment using wood cribs. Five suppression methods including straight stream, penciling, continuous wide and narrow fog, and a wide angle burst method are examined for two different spray angles and nozzle pressures. Temperatures, heat flux, gas velocity, and gas concentrations are monitored for the duration of each experiment in the fire compartment, along with temperatures and gas concentrations in the area of the firefighter, just outside the compartment. Realistic fire conditions are repeatedly established in the test compartment, with each fuel load allowing up to nine suppression applications per fire. The repeatability of the compartment temperatures are demonstrated by the consistent hot layer temperature stratification in the room, along with the uniformity of the hot layer throughout a test, and the consistency of the temperature from test to test. The repeatability of each suppression method is also demonstrated by comparing results of compartment cooling achieved in repeat tests. Differences in average compartment temperature before and during suppression indicate that penciling tactics provide little cooling of the compartment. In narrow fog attacks, the hot layer is pushed toward the floor, resulting in increased temperatures in the lower layer, generally an undesired result. Wide angle fog methods may have greater impact on compartment temperature as compared to straight stream or narrow fog methods, however, they also result in large increases in temperature at the firefighter. Wide angle burst tactics less effectively cool the compartment gases than continuous methods, but also lead to less impact on the firefighter. Greater numbers of bursts increase cooling of the compartment, but at the expense of increased impact on the firefighter. Including impact on the firefighter, continuous straight stream methods, at a nozzle discharge pressure of 700 kPa and aimed to the top of the rear compartment wall, appear the best choice for initial attack on the fire developed in these experiments. Due to variability between real fire scenarios and experiments such as these, significantly more study of the various suppression tactics is required before the most effective methods of suppression can be determined for a given set of fire scenarios.

Two studies examined the hypothesis that acceptance and control-based interventions for pain have specific self-regulatory costs and benefits. Both studies consisted of volunteers from a sample derived from the pool of psychology students at the University of Manitoba. Relative to control-based coping, acceptance was predicted to be associated with: 1) Normalization of time distortion; 2) Faster post-stimulus pain recovery 3) Preservation of self-regulatory energy required for acts of self-control; 4) Stronger pain coping self-efficacy beliefs, relative to two control-based coping strategies: suppression and distraction, and 5) improved pain tolerance. Study I (N=180) showed no group differences for pain tolerance, retrospective duration judgments or self-efficacy ratings, and weak evidence of differential pain recovery effects. As predicted, temporal speed ratings were slower for the suppression condition relative to the distraction condition. In Study II the pattern of condition effects for temporal speed was replicated though the statistical main effect only approached significance. In Study II (N=190), between-group differences were detected for pain tolerance, pain recovery, retrospective duration judgments and self-efficacy belief variables. As predicted the distraction group showed higher pain tolerance than the suppression group. Contrary to prediction, the difference between distraction and acceptance for pain tolerance was not significant. Contrary to predictions the greatest normalization of retrospective duration distortion occurred in the distraction condition. As predicted, post-intervention self-efficacy ratings were higher for acceptance than suppression but the difference between acceptance and distraction was not significant. Predicted pain recovery effects were also detected in Study II such that pain ratings for the suppression and distraction conditions were higher than for the acceptance condition at 60 and 120 seconds post-tolerance. Hypothesized between-group differences for self-regulatory-strength depletion were not confirmed. Possible reasons for lack of difference between acceptance and distraction on pain tolerance ratings and ego depletion measures, as well as possible future research directions were discussed.

Two studies examined the hypothesis that acceptance and control-based interventions for pain have specific self-regulatory costs and benefits. Both studies consisted of volunteers from a sample derived from the pool of psychology students at the University of Manitoba. Relative to control-based coping, acceptance was predicted to be associated with: 1) Normalization of time distortion; 2) Faster post-stimulus pain recovery 3) Preservation of self-regulatory energy required for acts of self-control; 4) Stronger pain coping self-efficacy beliefs, relative to two control-based coping strategies: suppression and distraction, and 5) improved pain tolerance. Study I (N=180) showed no group differences for pain tolerance, retrospective duration judgments or self-efficacy ratings, and weak evidence of differential pain recovery effects. As predicted, temporal speed ratings were slower for the suppression condition relative to the distraction condition. In Study II the pattern of condition effects for temporal speed was replicated though the statistical main effect only approached significance. In Study II (N=190), between-group differences were detected for pain tolerance, pain recovery, retrospective duration judgments and self-efficacy belief variables. As predicted the distraction group showed higher pain tolerance than the suppression group. Contrary to prediction, the difference between distraction and acceptance for pain tolerance was not significant. Contrary to predictions the greatest normalization of retrospective duration distortion occurred in the distraction condition. As predicted, post-intervention self-efficacy ratings were higher for acceptance than suppression but the difference between acceptance and distraction was not significant. Predicted pain recovery effects were also detected in Study II such that pain ratings for the suppression and distraction conditions were higher than for the acceptance condition at 60 and 120 seconds post-tolerance. Hypothesized between-group differences for self-regulatory-strength depletion were not confirmed. Possible reasons for lack of difference between acceptance and distraction on pain tolerance ratings and ego depletion measures, as well as possible future research directions were discussed.

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