Hearing loss has a negative effect on the daily life of 10-15% of the world’s population. One of the most common ways to treat a hearing loss is to fit hearing aids which increases audibility by providing amplification. Hearing aids thus improve speech reception in quiet, but listening in noise is nevertheless often difficult and stressful. Individual differences in cognitive capacity have been shown to be linked to differences in speech recognition performance in noise. An individual’s cognitive capacity is limited and is gradually consumed by increasing demands when listening in noise. Thus, fewer cognitive resources are left to interpret and process the information conveyed by the speech. Listening effort can therefore be explained by the amount of cognitive resources occupied with speech recognition. A well fitted hearing aid improves speech reception and leads to less listening effort, therefore an objective measure of listening effort would be a useful tool in the hearing aid fitting process. In this thesis the Auditory Inference Span Test (AIST) was developed to assess listening effort by measuring an individual’s cognitive spare capacity, the remaining cognitive resources available to interpret and encode linguistic content of incoming speech input while speech understanding takes place. The AIST is a dual-task hearing-innoise test, combining auditory and memory processing, and requires executive processing of speech at different memory load levels. The AIST was administered to young adults with normal hearing and older adults with hearing impairment. The aims were 1) to develop the AIST; 2) to investigate how different signal-to-noise ratios (SNRs) affect memory performance for perceived speech; 3) to explore if this performance would interact with cognitive capacity; 4) to test if different background noise types would interact differently with memory performance for young adults with normal hearing; and 5) to examine if these relationships would generalize to older adults with hearing impairment. The AIST is a new test of cognitive spare capacity which uses existing speech material that is available in several countries, and manipulates simultaneously cognitive load and SNR. Thus, the design of AIST pinpoints potential interactions between auditory and cognitive factors. The main finding of this thesis was the interaction between noise type and SNR showing that decreased SNR reduced cognitive spare capacity more in speech-like noise compared to speech-shaped noise, even though speech intelligibility levels were similar between noise types. This finding applied to young adults with normal hearing but there was a similar effect for older adults with hearing impairment with the addition of background noise compared to no background noise. Task demands, MLLs, interacted with cognitive capacity, thus, individuals with less cognitive capacity were more sensitive to increased cognitive load. However, MLLs did not interact with noise type or with SNR, which shows that different memory load levels were not affected differently in different noise types or in different SNRs. This suggests that different cognitive mechanisms come into play for storage and processing of speech information in AIST and for listening to speech in noise. Thus, the results suggested that a test of cognitive spare capacity seems to be a useful way to assess listening effort, even though the AIST, in the design used in this thesis, might be too cognitively demanding to provide reliable results for all individuals.

Capacity pooling in production systems, in the form of production capacity or inventory pooling, has been extensively studied in the literature. While production capacity pooling has been proven to be beneficial, the impact of inventory pooling has been less significant. These results cannot be easily extended to repairable systems due to fundamental differences between repairable and production systems. For one thing, in repairable systems, the demand rate is a function of the number of operational machines, whereas it is exogenous and constant in production systems. In this Thesis, to serve different fleets of machines possibly at different locations, we study whether repair shop pooling is more cost effective than having dedicated on-site repair shops for each fleet. In the first model, we consider transportation delays and related costs, which have been traditionally ignored in the literature. We include on-site spare-part inventories that operate according to a continuous-review base-stock policy. Our numerical findings indicate that when transportation costs are reasonable, repair shop pooling is a better alternative. Next, we model a pooled repair shop that fixes failed components from different k-out-of-n:G systems. We permit a shared spare parts inventory serving all systems and/or reserved spare parts inventories for each system; we call this a hybrid model. The destination for a repaired component can be chosen either on a first-come-first-served basis or by following a static priority rule. Our findings show that both hybrid policies are more cost effective than having separate repair shops and inventories for each system. We propose implementing the multilevel rationing (MR) policy in systems with shared inventory. The MR policy prioritizes classes, and stops serving a class from inventory if the inventory level is below the inventory threshold identified for that class. When there is no inventory, the repaired component is sent to the highest priority class among those with down machines. To approximate the cost of the MR policy, we study an M/G/1//N queueing system serving multiple classes of customers with an unreliable server. Our numerical findings indicate that the MR policy performs as well as the epsilon-optimal policy and outperforms the hybrid policies.

Capacity pooling in production systems, in the form of production capacity or inventory pooling, has been extensively studied in the literature. While production capacity pooling has been proven to be beneficial, the impact of inventory pooling has been less significant. These results cannot be easily extended to repairable systems due to fundamental differences between repairable and production systems. For one thing, in repairable systems, the demand rate is a function of the number of operational machines, whereas it is exogenous and constant in production systems. In this Thesis, to serve different fleets of machines possibly at different locations, we study whether repair shop pooling is more cost effective than having dedicated on-site repair shops for each fleet. In the first model, we consider transportation delays and related costs, which have been traditionally ignored in the literature. We include on-site spare-part inventories that operate according to a continuous-review base-stock policy. Our numerical findings indicate that when transportation costs are reasonable, repair shop pooling is a better alternative. Next, we model a pooled repair shop that fixes failed components from different k-out-of-n:G systems. We permit a shared spare parts inventory serving all systems and/or reserved spare parts inventories for each system; we call this a hybrid model. The destination for a repaired component can be chosen either on a first-come-first-served basis or by following a static priority rule. Our findings show that both hybrid policies are more cost effective than having separate repair shops and inventories for each system. We propose implementing the multilevel rationing (MR) policy in systems with shared inventory. The MR policy prioritizes classes, and stops serving a class from inventory if the inventory level is below the inventory threshold identified for that class. When there is no inventory, the repaired component is sent to the highest priority class among those with down machines. To approximate the cost of the MR policy, we study an M/G/1//N queueing system serving multiple classes of customers with an unreliable server. Our numerical findings indicate that the MR policy performs as well as the epsilon-optimal policy and outperforms the hybrid policies.

The Dual Failure Restorability (DFR) problems involve the design of network topology to be restorable in the event of single and dual failures scenarios. We developed new integer linear programming (ILP) models to optimally design mesh topology networks with various survivability schemes; span restoration, p-cycle, DSP and path restoration to achieve any specified level of dual failure restorability in the networks. The first variation of the ILP models applies specified dual failure restorability limit to each pair of spans in the network, and the second applies the limit to average dual failure restorability in the entire network. We used 137 test-case networks, consisting of four network families; 10-node, 12-node, 15-node, and 18-node network families. The results show that the capacity cost increases as the specified levels of dual failure restorability increases, and the relative increase in capacity cost in sparsely connected networks is much higher compare to densely connected networks. / Engineering Management

Dissertation (Ph.D.) -- Worcester Polytechnic Institute. / Keywords: Computer aided manufacturing planning; Object-oriented systems analysis (OSA); Feature; manufacturing resource capability; setup planning; multi-part fixture Includes bibliographical references (p.146-154).

En kvalitativ studie har gjorts på åtta sistaårs gymnasieelever i södra Sverige. Studiens syfte var att undersöka self-efficacy bland eleverna. Två forskningsfrågor undersöktes: Vad upplever sistaårs gymnasieelever påverkar deras akademiska self-efficacy i samband med studier? Hur upplever sistaårs gymnasieelever att deras akademiska self-efficacy påverkar dem på deras fritid? Resultatet av en tematisk innehållsanalysvisade att positiv respons från tidigare erfarenhet hade ett positivt inflytande på elevernasself-efficacy och deras akademiska prestationer. Andras erfarenheter hade ofta en negativ inverkan på elevernas self-efficacy, deras fysiologiska och emotionella tillstånd påverkade dem olika. De som gjorde någon fysisk aktivitet underveckan kände sig mer lättad och fokuserade bättre på studierna jämfört med dem som inte gjorde någon form av fysisk aktivitet, dessa studenter kände ofta frustration eller stress påsin fritid och i deras akademiska prestation. Studien hoppas bidra till en större bild på målgruppen och ge en allmän bild på gymnasieelevers akademiska self-efficacy.

[pt] O dinamismo dos mercados vem se intensificando, em face da globalização, dos avanços tecnológicos e das mudanças sociais. Consequentemente, as empresas necessitam se adaptar tempestivamente para se manter competitivas, ou podem vir a desaparecer. Neste contexto, inovações disruptivas são cada vez mais frequentes. Assim é o caso da manufatura aditiva, conhecida popularmente por impressão 3D. Tratam-se de tecnologias com potencial disruptivo que vai além do paradigma de produção, influenciando a logística, a sociedade, os mercados e múltiplos setores, tais quais o de saúde, o de defesa, o automotivo, o de construção civil e até mesmo o de alimentos. Nesta vertente, o presente trabalho busca verificar o potencial disruptivo das tecnologias de manufatura aditiva, iniciando pelo aprofundamento no conhecimento sobre estas tecnologias. Em seguida, é feita análise sobre a gestão das cadeias de suprimentos atual e as implicações das tecnologias de manufatura aditiva sobre a gestão das cadeias de suprimentos. Por fim, o estudo confronta o potencial disruptivo da manufatura aditiva com a cadeia de suprimentos de sobressalentes da Marinha do Brasil, no intuito de aprimorar aquela cadeia de suprimentos, buscando, naquelas tecnologias, solução para as dificuldades enfrentadas pela Esquadra do Brasil. / [en] The dynamism of markets has been intensifying by the globalization, the technological advances and the social changes. Consequently, companies need to adapt timely to remain competitive, or may disappear. In this context, disruptive innovations are becoming more frequent. This is the case of additive manufacturing, popularly known as 3D printing. These are technologies with disruptive potential that goes beyond the production paradigm, influencing logistics, society, markets and multiple sectors, such as health, defense, automotive, civil construction and even food. From this point, this work seeks to verify the disruptive potential of additive manufacturing technologies, starting with the deepening of the knowledge about these technologies. Next, it is analyzed the management of current supply chains and the implications of additive manufacturing technologies on supply chain management. Finally, the study confronts the disruptive potential of additive manufacturing with the Brazilian Navy s supply chain of spare parts, in order to improve that supply chain, searching solutions to the difficulties faced by the Brazilian Fleet in those technologies.

Esta dissertação tem como objetivo desenvolver uma sistemática de auxílio à tomada de decisão na definição das estratégias de suprimento de peças sobressalentes no âmbito da manutenção industrial. Para atingir este objetivo, inicialmente, foram realizadas revisões da literatura para identificar os critérios utilizados na definição das estratégias de suprimento e, também, as variáveis de decisão utilizadas na definição dessas estratégias. Essas variáveis foram divididas em quatro classes: sistema/equipamento, peça, suprimento e estocagem. Em seguida foram elaborados dois questionários fechados, o primeiro a respeito das características e o segundo a respeito das variáveis de decisão de suprimento das peças sobressalentes. Estes questionários foram aplicados na caracterização das peças de dois equipamentos instalados em uma planta petroquímica. As respostas do questionário de critérios foram avaliadas possibilitando a identificação de lacunas existentes na estratégia atualmente adotada pela empresa em relação a algumas peças, além de apontar algumas oportunidades de otimização de estoques. / This essay aims to develop a systematic to support spare parts provision decisionmaking in industrial maintenance. To achieve this goal, initially, literature reviews were conducted to identify the criteria used in the definition of supply strategies and also the decision variables used in the definition of these strategies. These variables were divided into four classes: system / equipment, spare part, supply and storage. Two closed questionnaires were developed. The first one was about the characteristics and the second one was about the decision variables of spare parts supply. These questionnaires were applied to characterize the parts of two equipment installed in a petrochemical plant. The characteristics questionnaire answers were evaluated, enabling the identification of gaps in the strategy currently adopted by the company for some parts, while pointing out some inventory optimization opportunities.

A competição global e a necessidade de otimização dos sistemas de produção e logística têm levado à necessidade de sistemas de manutenção mais eficientes. A habilidade de prever a ocorrência de falhas, através de Sistemas de Manutenção Inteligentes (Intelligent Maintenance Systems - IMS), pode evitar paradas não programadas e constituir uma grande vantagem competitiva. Além disso, um planejamento de demanda mais preciso em Cadeias de Suprimento de Peças de Reposição (Spare Parts Supply Chain - SPSC) resulta na disponibilidade de peças e serviços quando eles são necessários no chão de fábrica, evitando interrupções na produção. Uma integração adequada de ambos domínios é de grande importância neste contexto. Alguns dos desafios relativos a esta integração vêm das diferenças semânticas entre as áreas com diferentes vocabulários e conceitos. Este trabalho pretende propor uma modelagem semântica dos domínios através da criação de uma ontologia, provendo um vocabulário comum e uma integração semântica apropriada entre as áreas, como base para a construção futura de sistemas de informação para integrar IMS e SPSC. / Global competition and the need for logistic and production systems optimization has been leading to the need of more eficiente maintenance systems. Ability to forecast failures, through Intelligent Maintenance Systems (IMS), can avoid breakdowns and be a competitive advantage. Moreover, a more precise demand planning in Spare Parts Supply Chains (SPSC) results in the availability of parts and services when they are needed at shop floor, avoiding production interruptions. A proper integration of both domains is of utmost importance in this context. Some of the challenges related to this integration come from the semantic differences between areas with such a diversity of vocabulary and concepts. This work intends to propose a semantic modelling through the creation of an ontology, providing a common vocabulary and proper semantic integration, as basis for a future implementation of an integration information system between IMS and SPSC.

Abstract Purpose: The purpose of the study is to develop a model that will facilitate the choice of maintenance strategy within the Swedish pulp and paper industry. Without compromising system availability, the model aims to reduce inventory holding costs. Methodology: At first, a literary research was conducted to create a holistic view over the chosen topic, in time it developed into a literature framework. Secondly, a case study was conducted in order to obtain empirical data. The data were obtained through interviews and archival records. The literature framework and the empirical data were then cross-analyzed with each other. Findings: In this thesis, a model has been developed based on previously applied and accepted methods. The methods have been identified and described in order to provide a strategy in which the inventory levels- and value could be lowered. The findings indicate that the organization must seek to assign ABC-classified and VED-analyzed components different maintenance actions in order to reduce the total cost. Theoretical contribution: This thesis contributes to a methodology development regarding spare parts management. It aims to add knowledge to the existing gap regarding spare parts order point and batch size. The thesis provides a procedure in which systems including critical and expensive components are evaluated in order to assign them the appropriate maintenance. Practical relevance: The model has only been exemplified by using a system position from Stora Enso Skutskär, the numerical values are examples. The model must be tested with real values and the risk analysis must be carried out with a group of employees with great insight regarding the selected component and system position. Limitations: This thesis is delimited to spare parts management and inventory management. The study only involves one Swedish organization, whereas the organization and its spare parts management illustrates the complexity concerning spares. The model will not be verified as the focus is to highlight the research gap and to develop the model.