The application of Discrete-Event Systems (DES) theory to the problem of guar- anteeably enforcing concurrency constraints in multi-threaded applications has been studied under certain assumptions, namely, the assumption of a static pool of pre- existing instantiated threads, whose creation and termination are not modelled. This work proposes an extension of this case to handle dynamically instantiated and termi- nated threads using a Petri net formalism and an online limited-lookahead state-space search technique. / Thesis (Master, Computing) -- Queen's University, 2010-05-27 17:00:15.99

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This project has proved conclusively that discrete event simulation techniques can be used to simulate, on computer, a complex stochastic materials handling system. The packing, automatic palletising and warehousing departments of a large powders manufacturing factory was used as an example to investigate the capabilities of computer simulation. The company intends to increase the number of packing machines from seven to eleven, and has embarked on productivity improvement projects that aims to increase the average packing efficiency from the current 50%, to 60% with a long term goal of 70%. Due to the stochastic nature of the run and stop durations of the packing machines, it was impossible to predict the effect of the increased throughput on the palletising system by conventional means. The system was modelled on computer using the SIMAN simulation language. Extensive research was initially carried out in order to determine the operating parameters of the system. The generation of cases from the packing machines in the program was verified against actual production runs. Various alternatives were analyzed to assist in decision making on the expansion of the palletising system in order to accommodate the increased throughput expected from the packing floor. The simulation was therefore used to increase the capacity of the automatic palletising system at minimal cost while meeting demands from the packing floor. It was established that the only capital expenditure required would be about R500 000 to increase the capacity of a palletiser and to provide a pallet conveyor to transport 40% of the pallets to direct despatch. / Thesis (M.Eng.)-University of Durban-Westville, 1989.

Discrete-trials teaching (DTT) is one of the principal techniques used in Applied Behaviour Analysis programs for children with autism. Although the demand for training individuals to implement DTT is high, published studies on strategies to do so are few. I conducted two experiments to investigate a training package for teaching individuals to implement DTT. In Experiment 1, I used a modified multiple-baseline design to evaluate the training package for teaching five university students to implement DTT to teach three tasks to a confederate role-playing a child with autism. Also, in an AB within-subject design with each participant, I compared two components of the training package, a Self-Instructional Manual and Feedback plus Demonstration. Experiment 2 was a systematic replication of Experiment 1, with 2 teaching assistants, a resource teacher, and 3 parents of children with autism as participants. In both experiments I assessed the generalization (G1) of participants’ ability to implement DTT (while teaching the confederate) to teach tasks not targeted for Feedback plus Demonstration, as well as generalization (G2) of DTT while teaching a child with autism. After an average of approximately 3 hours to master the self-instructional manual, participants’ DTT accuracy in both experiments improved from an average of 34% in Baseline to an average of 61% following the Self-Instructional Manual. Results appeared to be due to the Self-Instructional Manual phase for 9 of the 11 participants. Following an average of 35 minutes of Feedback plus Demonstration of DTT of one task, participants’ DTT accuracy improved to an average of 91% while teaching a confederate. The improvement appeared to be due to the intervention with 10 of the 11 participants. The participants’ DTT accuracy averaged 90% during G1 and 86% during G2. These results demonstrate that this training package has considerable potential for teaching DTT to tutors, educational assistants, and parents of children with autism.

A widely used instructional method for teaching children with autism is Applied Behaviour Analysis (ABA), and a main component of ABA programming is discrete-trials teaching (DTT). DTT is made up of a series of brief teaching trials, with each trial including an antecedent (e.g., an instruction from the teacher), a response from the child, and an immediate consequence (e.g., a reinforcer provided for a correct response). Using a modified multiple-baseline design across participants, Experiment 1 assessed the effectiveness of a DTT self-instructional package (Fazzio & Martin, 2007) for teaching 4 pairs of newly-hired ABA tutors how to apply 21 components of DTT to teach 3 tasks to a confederate role-playing a child with autism. In Experiment 2, a group of 8 additional tutors were each independently presented with the same procedure. In both experiments, in Phase 1(baseline), tutors attempted to teach the 3 tasks to the confederate. In Phase 2 (manual), tutors mastered a 37-page self-instructional manual and once again attempted to teach the same 3 tasks to the confederate. Phase 3 was a within-subject AB design component. That is, if tutors did not meet a DTT mastery criterion of 80% after studying the manual in Phase 2, then they watched a brief video demonstration of a DTT expert teaching a task to a child role-playing a child with autism (Fazzio, 2007), and then once again attempted to teach the 3 tasks to the confederate. Across both experiments: a) The 16 tutors averaged 4.6 hours to master the self-instructional manual, and showed an average improvement in DTT accuracy of 32.2% from baseline; b) For the 13 tutors who did not meet the mastery criterion after reading the manual, their average DTT performance improved an additional 12% after watching the video; c) 13 of the 16 participants met mastery (3 after the manual and 10 after the manual plus video), and the other 3 tutors were very close to mastery. The results suggest that the training package is a practical, economical and efficient method of instructing newly-hired tutors in ABA programs for children with autism.

Appointment scheduling involves picking a strategy for sequencing patient appointments such that the wait time per patient is minimized and the idle time and overtime for the doctor are minimized. The goal of this project is to increase the number of scans per day at the echocardiogram clinic in the Hospital for Sick Children. The objectives were realized by performing simulations of the workflow of the echo clinic using simulation software. The simulation model did not precisely reflect the echo clinic, and the disparity was attributed to limitations in the simulation model. Nevertheless, the user accepted the model and six different policy change scenarios were explored. All six scenarios yielded significant increases in average scans per day per sonographer. Scenario IV, which eliminated the use of sonographer schedules, was recommended to be implemented due to ease of implementation and lack of negative effect on patient wait time and sonographer overtime.

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