Moshe Sidi. / Bibliography: p. 25. / "June 1984" / "NSF-ECS-8310698"

Description based on: 2nd, Dec.20, 1977. Prepared on NASA Grant NSG 1312, MIT OSP no.84371. Submitted to NASA Langley Research Center, Theoretical Mechanics Branch. Prepared by: 1977- , G. Stein and M. Athans.

Charles E. Rohrs, Lena Valavani, Michael Athans, Gunter Stein. / "June 1983" / Bibliography: p. 14. / "NASA/NGL-22-009-124" "ONR/N00014-82-K-0582 (NR 606-003) "NSF/ECS-8210960" "NSF/ECS-8206495"

A permutation array, represented by PA(n, d), is a subset of Sn such that any two distinct elements have a distance of at least d where d is the number of differing positions. We analyze the upper and lower bounds of permutation codes with distance equal to 4. An optimization problem on Young diagrams is used to improve the upper bound for almost all n while the lower bound is improved for small values of n by means of recursive construction methods.

A permutation array, represented by PA(n, d), is a subset of Sn such that any two distinct elements have a distance of at least d where d is the number of differing positions. We analyze the upper and lower bounds of permutation codes with distance equal to 4. An optimization problem on Young diagrams is used to improve the upper bound for almost all n while the lower bound is improved for small values of n by means of recursive construction methods.

Treatment integrity is an important component of behavioural interventions, however few studies have examined methods to teach supervisors to evaluate the treatment integrity of such interventions applied by front-line staff. The purpose of the current study was to evaluate the effectiveness of a self-instructional package to teach individuals to evaluate the treatment integrity of discrete-trials teaching (DTT) sessions using the Discrete-Trials Teaching Evaluation Form (DTTEF). Participants consisted of six staff from the St.Amant Autism Programs. In a modified multiple-baseline design across a pair of participants, and replicated across two more pairs, at Baseline, a participant observed a confederate who role-played an instructor teaching three tasks to a confederate who role-played a child with autism spectrum disorder (ASD). Each participant was required to evaluate sessions taught with (a) low integrity, (b) moderate integrity, or (c) high integrity. During training, participants studied a self-instructional package. At Post-training, participants were assessed on the same tasks as during Baseline. During Generalization, participants were assessed evaluating the treatment integrity of three videos of an Autism Tutor administering DTT to a child with ASD. Finally, during a seven-month Follow-up, four participants were available and were assessed evaluating the treatment integrity of a confederate instructor teach a confederate child with low, moderate, and high integrity. Results demonstrated that after an average of 1 hour and 16 minutes of training, there was an immediate increase in accuracy across all participants. Specifically, mean accuracy increased from 47.6% in Baseline to 84.7% at the Post-training assessment (a 37.1% increase). All participants showed excellent generalization results, and three of the four participants who were available at the Follow-up assessment performed at a high level. These results suggest that the training package has potential to be used as an effective method to train staff who work with children with ASD to evaluate the treatment integrity of DTT sessions. / February 2016

Made available in DSpace on 2014-06-11T19:30:51Z (GMT). No. of bitstreams: 0 Previous issue date: 2005-02-01Bitstream added on 2014-06-13T20:00:56Z : No. of bitstreams: 1 duarte_maq_dr_ilha.pdf: 2208096 bytes, checksum: 7daf91683010b0f39c715c9cc1ded5d8 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Neste trabalho é feito um estudo sobre os métodos de redução de ruído aditivo em sinais de voz baseados em wavelets e, através deste estudo, propõe-se um novo método de redução de ruído em sinais de voz no domínio wavelet. O princípio básico da maioria dos métodos de redução de ruído baseados em wavelets é a determinação e aplicação de um limiar, que permite bons resultados para sinais contaminados por ruído branco, mas não são eficientes no processamento de sinais contaminados por ruído colorido, que é o tipo de ruído mais comum em situações reais. Nesses métodos, o limiar, geralmente, é calculado nos intervalos de silêncio e aplicado em todo o sinal. Os coeficientes no domínio wavelet são comparados com este limiar e aqueles que estão abaixo deste valor são eliminados, fazendo assim uma aplicação linear deste limiar. Esta eliminação acaba causando descontinuidades no tempo e na freqüência no sinal processado. Além disso, a forma com que o limiar é calculado pode degradar os trechos de voz do sinal processado, principalmente nos casos em que o limiar depende fortemente da última janela do último trecho de silêncio. O método proposto neste trabalho também é baseado em corte por limiar, mas em vez de uma aplicação linear do limiar, ele faz uma aplicação não-linear, o que evita as descontinuidades causadas por outros algoritmos. O limiar é calculado nos trechos de silêncio e não depende apenas da última janela do último trecho de silêncio, mas sim de todas as janelas, já que este limiar é uma média de todos os limiares calculados neste trecho. Isto faz com que a redução do ruído seja mais uniforme e introduza menos distorções no sinal processado. Além disso, nos trechos de voz ainda é calculado um novo limiar que também será usado, em conjunto com o limiar calculado no silêncio. Isto faz com que a energia da janela que... . / In this work a study of additive noise reduction in speech based on wavelets is presented and, based on this study a new noise reduction method in speech in the wavelet domain is proposed. The basic idea of most methods of noise reduction based on wavelets is the determination and application of a threshold, that produces good results for signals contaminated by white noise, but they are not very efficient in processing signals contaminated by colored noise, which is more common in real situations. In those methods, the threshold, generally, is calculated in the silence intervals and applied to the whole signal. The coefficients in the wavelet domain are compared with this threshold and those that are below this value are eliminated, making a linear application of this threshold. This elimination causes discontinuities in time and frequency of the processed signal. Besides, the way that the threshold is computed can degrade the voice segments of the processed signal, principally when the threshold depends strongly on the last window of the last silence segment. The proposed method in this work is also based in thresholding, but, instead of a linear application of the threshold, it makes a non-linear application, which avoids the discontinuities caused by other algorithms. The threshold is calculated in the silence segments and is not dependent only on the last window of the last silence segment, but of all the windows, since this threshold is an average of all thresholds calculated in this segment. It makes noise reduction more uniform and introduces less distortion in the processed signal. Besides, in the voice segments a new threshold is calculated that will be also used with the threshold calculated in the silence. It makes that the energy of the window that is being processed is also considered. This way, it is... (Complete abstract, click electronic address below).

The economic wellbeing, physical and mental health of the ageing population in the United Kingdom is associated with continued participation in the labour force. Encouraging later life employment is therefore a key policy issue. Research into older person's employment trajectories is concentrated on male working patterns, and often takes an individualistic approach that does not account for the domestic context. Previous research on women's labour force participation has been informed by small scale qualitative studies that do consider the household domain but these findings cannot be generalized to the wider population. This research investigates the factors associated with the continued employment of women aged 50 to 59 using data from the English Longitudinal Study of Ageing (ELSA). Transition rates out of employment between 2001 and 2011 are modeled using multilevel discrete time event history specifications that permit the inclusion of time varying covariates. Retirement is characterized as an ageing process which allows the impact of predictors on transition rates to be assessed and measured as women approach state pension age. Alternative time structures are considered, with parameter estimates from an age baseline model compared with those from a time on study specification. Results illustrate the sensitivity of parameter estimates in discrete time event history models to the measurement of time, and emphasize the importance of adopting a time metric that is commensurate with the theoretical representation of retirement as a dynamic ageing process. The domestic context is realised as sampled women and their male partners are positionedwithin a household structure, and asymmetric effects of predictors on the transition rate of each gender are considered. Own poor health, caring responsibilities and a retired or inactive spouse accelerate labour market exit for women whilst high levels of accrued pension wealth predict earlier transitions for their male partners. The age of employment exit for females is independent of pension wealth, but pension resources do predict the retirement pathway taken following any transition that does occur. Women residing in the wealthiest households are more likely to report as voluntary retired prior to state pension age whilst those in the poorest of couples are at higher risk of following an involuntary pathway into an alternative inactive state. These findings emphasize the importance of conducting research into later life employment trajectories on a household, rather than individual, basis.

This thesis presents an empirical research that aims to explore insight generation in discrete-event simulation (DES) studies. It is often claimed that simulation is useful for generating insights. There is, however, almost no empirical evidence to support this claim. The factors of a simulation intervention that affect the occurrence of insight are not clear. A specific claim is that watching the animated display of a simulation model is more helpful in making better decisions than relying on the statistical outcomes generated from simulation runs; but again, there is very limited evidence to support this. To address this dearth of evidence, two studies are implemented: a quantitative and a qualitative study. In the former, a laboratory-based experimental study is used, where undergraduate students were placed in three separate groups and given a task to solve using a model with only animation, a model with only statistical results, or using no model at all. In the qualitative study, semi-structured interviews with simulation consultants were carried out, where participants were requested to account examples of projects in which clients change their problem understanding and generate more effective ideas. The two separated parts of the study found different types of evidence to support that simulation generates insight. The experimental study suggests that insights are generated more rapidly from statistical results than the use of animation. Research outcomes from the interviews include descriptions of: the phase of a simulation study where insight emerges; the role of different methods applied and means used in discovering and overcoming discontinuity in thinking (for instance, the role of consultant s influence in problem understanding); how some factors of a simulation intervention are associated with the processes of uncovering and overcoming discontinuity in thinking (for example, the role of clients team in the selection of methods used to communicate results); and the role of the model and consultant in generating new ideas. This thesis contributes to the limited existing literature by providing a more in depth understanding of insight in the context of simulation and empirical evidence on the insight-enabling benefits of simulation based on an operational definition. The findings of the study provide new insights into the factors of simulation that support fast and creative problem solving.

Most firms are still failing to think strategically and systematically about managing supply disruption risk and most of the supply chain management efforts are focused on reducing supply chain operation costs rather than managing disruption. Some innovative firms have taken steps to implement supply chain risk management (SCRM). Inventory management is part of SCRM because supply disruptions negatively affect the reliability of deliveries from suppliers and the costs associated with the ordering process. The complexity of existing inventory models makes it challenging to combine the management of the supply process and inventory in a single model due, for example, to the difficulty of including the characteristics of the disruption process in the supply chain network structure. Therefore, there is a need for a simple flexible model that can incorporate the key elements of supply disruption in an inventory model. This thesis presents a series of models that investigate the importance of information on disruption discovery and recovery for a firm’s supply and inventory management. A simple two-echelon supply chain with one firm and two suppliers (i.e., referred to as the onshore and offshore suppliers) in a single product/component setting has been considered in this thesis for the purpose of experimental analyses. The sourcing decisions that the firm faces during periods of supply disruption are examined leading to an assessment of how information about the risk and length of disruption and recovery can be used to facilitate the firm’s sourcing decisions and monitor the performance of stock control during the disruption. The first part of this thesis analyses basic ordering models (Model 1 and Model 2 respectively) without the risk of supply disruption and with the risk of supply disruption. The second part analyses the value of supply disruption information, using a model with advance information on the length of disruption (Model 3) and a model with learning about the length of disruption (Model 4). The third part explores a quantitative recovery model and the analyses in this part consider of three models. Model 5 assumes a basic phased recovery model, Model 6 assumes advance information about the phased recovery process and Model 7 assumes learning about the phased recovery process. The last part of this thesis investigates the order pressure scenario that exists in the firm’s supply chain. Under this scenario, disruption to one part of the supply chain network increases demand on the remainder resulting in a lower service levels than normal. This scenario is applied to all the previous models apart from Model 1. The models in this thesis are examined under finite and infinite planning horizons and with constant and stochastic demand. The objective of the models is to minimise the expected inventory cost and optimise the order quantity from the suppliers given the different assumptions with respect to the length of supply disruption and information about the recovery process. The models have been developed using the discrete time Markov decision process (DTMDP) technique and implemented using the Java programming language. The findings of this thesis could be used to help a firm that is facing the risk supply disruption to develop its SCRM program. The findings highlight the importance of considering quantitative measures of the disruption and recovery processes, something which is still not popular within SCRM in some organisations.