Novel methods and apparatus used to measure high-speed state of polarization changes are developed. Knowledge of the effects of mechanical impacts on the state of polarization will benefit the reliability of optical communication systems. The impact creates a high-speed but continuous motion of the state of polarization over the Poincar´e sphere. The maximum speed at which the state of polarization changes due to an impact is shown to be higher than what has been reported previously. The investigation into the state of polarization changes led to the discovery of the repeatability and elasticity of state of polarization changes due to mechanical impacts. The repeatability and elasticity allow novel measurements of important polarization effects in optical fibres such as high-speed polarization mode dispersion and rotation vector measurements.

Novel methods and apparatus used to measure high-speed state of polarization changes are developed. Knowledge of the effects of mechanical impacts on the state of polarization will benefit the reliability of optical communication systems. The impact creates a high-speed but continuous motion of the state of polarization over the Poincar´e sphere. The maximum speed at which the state of polarization changes due to an impact is shown to be higher than what has been reported previously. The investigation into the state of polarization changes led to the discovery of the repeatability and elasticity of state of polarization changes due to mechanical impacts. The repeatability and elasticity allow novel measurements of important polarization effects in optical fibres such as high-speed polarization mode dispersion and rotation vector measurements.

This thesis looks at the effects of flexible working arrangements on workers' labour market outcomes. The particular type of flexible working arrangement analysed in this thesis is called "flexitime". This is an arrangement which gives workers the freedom to choose when to start and end their work. Flexitime provides workers with a new way to cater to their domestic responsibilities and in turn may reduce the costs of participating in the labour market. Therefore, it is closely connected with workers' compensation structure, human capital accumulation process, labour supply and job mobility. The effects of flexitime on workers' labour market outcomes are analysed from three aspects: wage, labour supply, and job mobility. The first chapter gives an introduction and overview of the thesis. The second chapter is a study on the compensating wage differentials associated with flexitime. In general I do not find convincing evidence showing the existence of compensating wage differentials associated with flexitime. One possible reason might be that flexitime brings additional benefits to firms (such as increased productivity and reduced turnover rate) so that firms may not necessarily need to reduce actual wages in exchange for flexitime provision. In the third chapter, I develop a model describing how flexitime may affect workers' labour supply decisions. The main finding of the model is that flexitime will increase workers' labour supply when the benefit associated with flexitime (increased child care production efficiency) is high relative to the cost of wage reduction (prediction 1). Meanwhile, the model also predicts that flexitime causes high human capital workers to increase their labour supply more than low human capital workers (prediction 2). Empirical findings show that flexitime is positively associated with working mothers' labour market hours, which confirms model prediction 1. However, there is arguably insufficient empirical evidence verifying model prediction 2. The fourth chapter considers the relationship between flexitime and workers' job satisfaction and job mobility. Flexitime is associated with high job satisfaction levels for both male and female workers. It also reduces the probability of quitting for female workers with young children. Male workers' job mobility decisions are not significantly affected by flexitime. The fifth chapter gives the conclusion of the thesis.

By applying the theory of compensating differentials on a self-compiled data set on the 67 sites in Sweden that offer medical internships, I seek to identify the factors of an internship that determine its salary. Because prospective interns tend to queue for popular internships, I use an estimated equilibrium salary that incorporates the opportunity cost of delaying the internship. I find a significant independent correlation between the travel time to the nearest major city and salary that is suggestive of a compensating differential. The results imply that a larger salary differentiation can mitigate the widespread phenomena of maldistribution of physicians.

<p>The aim of this essay is to examine how students in 6-9 grade with reading and writing difficulties are treated and supported by teachers and staff at Ideskolan, a community school north of Stockholm. I have chosen to answer the following question:</p><p>- How does Ideskolan cope with and support students with reading and writing difficulties</p><p>This has in turn generated the following questions:</p><p>- How is special education organized at Ideskolan?</p><p>- Is a diagnose always needed in order to deploy extra support?</p><p>The method I have employed is observation while participating, together with informal talks and interviews. I have visited Ideskolan twice, one week at the time. The material that the visits have generated is the foundation of the essay, supported by previous research in the field.</p><p>The essay clarifies what right to special support students have according to law, regulations, curriculum and teaching plans and what they look like in reality at Ideskolan. This paper questions why schools focus on the individual student in these matters instead on the schools organisation and way of working. It might not automatically be the students’ difficulties with reading and writing that limits their continued learning, but rather the schools attitude towards students with special needs. Some ways of working might minimize the difficulties while some can increase them. If so, perhaps a change is in order?</p><p>The essay also discusses the role of the special teacher – should she be supporting the students or her colleagues, or both. It also discusses if the teacher training should evolve to better suite the need to handle students with reading and writing difficulties.</p><p>Even though Ideskolan recognizes the fact that two – three students in each class suffers with reading and writing difficulties the support to these students are inadequate. The school can excuse it self by saying that there is no “right way to go”, for each student with reading and writing difficulties are unique and there for require different support.</p>

Title Comperating and compensating exercises for water skiers Synopsis The goal of my thesis "Comperating and compensating exercises for water skiers" is to create a summary of exercises, which will be part of sports preparation for water skiers during their main training season. In the first part, I characterize theoretical aspects of water skier's sports training including their training units, comperating exercise specifics and types of exercise needed in correction of muscle dysbalance. In the second part, I demonstrate current training unit using structural observation of chosen sample of athletes. In my questionnaire, I appraise results of current inclusion of balance exercise during training units in the main training season of competitors in the age group of 9 - 35 years of age. Furthermore, I describe an experiment concerned with muscle dysbalance of this group of water skiers. Based on the results, I propose exercises compensating this dysbalance. Finally, I review the influence of applied comperating exercise on chosen research sample. I describe results of individual investigation and further propose possible solutions to improve our current situation. Keywords Comperating and compensating exercises, muscle dysbalance, training unit

Este projeto de pesquisa foi desenvolvido visando quantificar possíveis distúrbios de vazão em emissores do tipo gotejador (irrigação localizada) submetidos à aplicação de cloro livre e acidificação em condições estática e dinâmica de fluxo de água no sistema. O experimento foi realizado no período de setembro de 2005 a junho de 2006, utilizando-se 14 modelos de gotejadores autocompensantes com suas respectivas linhas gotejadoras montadas em uma bancada de ensaios em estrutura metálica. Os tratamentos utilizados no experimento foram: a) aplicação dinâmica de 100 mg L-1 de cloro livre com pH na faixa de 5,5 a 6,0; b) aplicação estática de 100 mg L-1 de cloro livre com pH na faixa de 5,5 a 6,0; c) aplicação de ácido nítrico com pH na faixa de 2,0 a 3,0 durante &#189; h (sistema pressurizado); d) aplicação de ácido nítrico com pH na faixa de 2,0 a 3,0 durante 12 h (sistema pressurizado). Foram realizadas curvas vazão versus pressão para cada tratamento em três diferentes temperaturas da água (15, 25 e 40° C). O delineamento experimental utilizado foi o inteiramente aleatorizado em esquema fatorial, com utilização dos testes ?F? para análise de variância e Tuckey, a 5% de significância, para comparação de médias e análise de regressão. Os resultados obtidos mostram que para o tratamento da água com 100 mg L-1 de cloro livre em condição dinâmica, ocorreu um decréscimo de 10 a 20% em média da vazão (L h-1) para alguns modelos de gotejadores mais sensíveis aos produtos químicos, sendo que o modelo I apresentou redução drástica de vazão na ordem de 100% em virtude do bloqueio total do labirinto do emissor, em decorrência do aumento de 112% do volume da membrana após 2688 h de aplicação contínua de cloro. Os tratamentos estáticos não apresentaram variações acentuadas de vazão média (L h-1), coeficiente de variação (%), uniformidade de distribuição (%), Vazão Relativa (%) e Grau de Entupimento (%). Verificou-se relação linear entre a vazão e a temperatura da água para os gotejadores novos, sendo que após a aplicação dos diferentes tratamentos, as curvas vazão versus pressão para cada modelo de gotejador sofreram influência tanto da pressão quanto da temperatura de maneira distinta. / This research project was developed to quantify possible flow rate variation in emitters (drip irrigation) submitted to the application of free chlorine and acidification under static and dynamics conditions of water flow. The experiment was accomplished in the period of September, 2005 to June, 2006, being analyzed 14 models of pressure compensating emitters set up in a metallic bench. The treatments used in the experiment were the following ones: a) dynamic application of 100 mg L-1 of free chlorine with pH 5,5 to 6,0; b) static application of 100 mg L-1 of free chlorine with pH 5,5 to 6,0; c) application of acid nitric with pH 2,0 to 3,0 during &#189; h (pressurized system); d) application of acid nitric with pH 2,0 to 3,0 during 12 h (pressurized system). The operating pressures and emitter model combination were: 50, 100, 200, 300, 400 kPa for emitters A to N, in three different water temperatures (15, 25 and 40° C). The obtained values of flow rate were used to calculate the CUD, CV, relative flow rate, the percentage of drippers in each flow rate range, and the number of the drippers completely clogged. The statistical analysis of the treatments were accomplished by Tukey test at 5% probability. The obtained results show that for the treatment of the water with 100 mg L-1 of free chlorine in dynamic condition, a reduction from 10 to 20% of the flow rate (L h-1) occurred for some models more sensitive to chemical products. Model I presented drastic reduction of flow rate in the order of 100% by total blockade of the labyrinth of the emitter, due to the increase of 112% of the volume of the membrane after 2688 h of continuous application of 100 mg L-1 of chlorine free with pH 5,5 to 6,0. The static treatments didn\'t present accentuated variations of medium flow rate (L h-1), variation coefficient (%), distribution uniformity (%), relative flow rate (%) and degree of blockage (%). For pressure compensating emitters, where the discharge sensitivity to temperature is insignificant, after the application of the different treatments, the measured discharge/pressure relationship for each emitter model was sensitive to pressure as well to temperature.

The major cause of cracking in bridge decks, concrete pavements, as well as slabs on grade, is restrained shrinkage of the concrete. The resulting steel corrosion problem causes tremendous increase of maintenance and replacement cost. Shrinkage-compensating concrete (SHCC) and fiber-reinforced polymer (FRP) are explored to develop a hybrid slab system as one possible method of delaying the cracking and eliminating corrosion. To achieve the objective, a hybrid FRP reinforced SHCC structural system was developmed, and short-term and long-term behavior of this hybrid FRP-SHCC beams were investigated in this dissertation. In the first-stage development, a series of “coffee can” tests were carried out to measure and compare the expansion of SHCC from two candidate materials which were ettringite-system SHCC and lime-system SHCC. The selected SHCC candidate mix was then optimized to get the maximum expansion as well as a reasonable concrete strength. The optimized SHCC mix was used to make FRP-SHCC beams. The expansion of the concrete was measured through strain gauges on the FRP composite sheets during curing. Both glass FRP (GFRP) composite sheets and carbon FRP (CFRP) composite sheets were used for comparison. A series of third-point loading experiments were conducted to study the behavior of the proposed hybrid FRP-SHCC beams. In the second-stage development, long term prestress loss and static structural test of the proposed beams are investigated. Test results were evaluated based on maximum expansion strain, cracking load, crack width, load-deflection and ultimate load.The results indicate that the proposed system is promising in terms of its ability to develop a residual pre-stressing effect. Tests also show that the pre-stressing effect from the expansion of SHCC increases as the axial stiffness of the FRP reinforcement increases. A lime-system SHCC structural system shows higher prestress strain and less prestress loss than an ettringite-system SHCC system over the long term.

Industrial demands for higher productivity rates and more stringent part tolerances require faster production machines that can produce, assemble, or manipulate parts at higher speeds and with better accuracy than ever before. In a majority of production machines, such as machine tools, ball screw drives are used as the primary motion delivery mechanism due to their reasonably high accuracy, high mechanical stiffness, and low cost. This brings the motivation for the research in this thesis, which has been to develop new control techniques that can achieve high bandwidths near the structural frequencies of ball screw drives, and also compensate for various imperfections in their motion delivery, so that better tool positioning accuracy can be achieved at high speeds. A precision ball screw drive has been designed and built for this study. Detailed dynamic modeling and identification has been performed, considering rigid body dynamics, nonlinear friction, torque ripples, axial and torsional vibrations, lead errors, and elastic deformations. Adaptive Sliding Mode Controller (ASMC) is designed based on the rigid body dynamics and notch filters are used to attenuate the effect of structural resonances. Feedforward friction compensation is also added to improve the tracking accuracy at velocity reversals. A bandwidth of 223 Hz was achieved while controlling the rotational motion of the ball screw, leading to a servo error equivalent to 1.6 um of translational motion. The motor and mechanical torque ripples were also modeled and compensated in the control law. This improved the motion smoothness and accuracy, especially at low speeds and low control bandwidths. The performance improvement was also noticeable when higher speeds and control bandwidths were used. By adding on the torque ripple compensation, the rotational tracking accuracy was improved to 0.95 um while executing feed motions with 1 m/sec velocity and 1 g acceleration. As one of the main contributions in this thesis, the dynamics of the 1st axial mode (at 132 Hz) were actively compensated using ASMC, which resulted in a command tracking bandwidth of 208 Hz. The mode compensating ASMC (MC-ASMC) was also shown to improve the dynamic stiffness of the drive system, around the axial resonance, by injecting additional damping at this mode. After compensating for the lead errors as well, a translational tracking accuracy of 2.6 um was realized while executing 1 m/sec feed motions with 0.5 g acceleration transients. In terms of bandwidth, speed, and accuracy, these results surpass the performance of most ball screw driven machine tools by 4-5 times. As the second main contribution in this thesis, the elastic deformations (ED) of the ball screw drive were modeled and compensated using a robust strategy. The robustness originates from using the real-time feedback control signal to monitor the effect of any potential perturbations on the load side, such as mass variations or cutting forces, which can lead to additional elastic deformations. In experimental results, it is shown that this compensation scheme can accurately estimate and correct for the elastic deformation, even when there is 130% variation in the translating table mass. The ED compensation strategy has resulted in 4.1 um of translational accuracy while executing at 1 m/sec feed motion with 0.5 g acceleration transients, without using a linear encoder. This result is especially significant for low-cost CNC (Computer Numerically Controlled) machine tools that have only rotary encoders on their motors. Such machines can benefit from the significant accuracy improvement provided by this compensation scheme, without the need for an additional linear encoder.

Industrial demands for higher productivity rates and more stringent part tolerances require faster production machines that can produce, assemble, or manipulate parts at higher speeds and with better accuracy than ever before. In a majority of production machines, such as machine tools, ball screw drives are used as the primary motion delivery mechanism due to their reasonably high accuracy, high mechanical stiffness, and low cost. This brings the motivation for the research in this thesis, which has been to develop new control techniques that can achieve high bandwidths near the structural frequencies of ball screw drives, and also compensate for various imperfections in their motion delivery, so that better tool positioning accuracy can be achieved at high speeds. A precision ball screw drive has been designed and built for this study. Detailed dynamic modeling and identification has been performed, considering rigid body dynamics, nonlinear friction, torque ripples, axial and torsional vibrations, lead errors, and elastic deformations. Adaptive Sliding Mode Controller (ASMC) is designed based on the rigid body dynamics and notch filters are used to attenuate the effect of structural resonances. Feedforward friction compensation is also added to improve the tracking accuracy at velocity reversals. A bandwidth of 223 Hz was achieved while controlling the rotational motion of the ball screw, leading to a servo error equivalent to 1.6 um of translational motion. The motor and mechanical torque ripples were also modeled and compensated in the control law. This improved the motion smoothness and accuracy, especially at low speeds and low control bandwidths. The performance improvement was also noticeable when higher speeds and control bandwidths were used. By adding on the torque ripple compensation, the rotational tracking accuracy was improved to 0.95 um while executing feed motions with 1 m/sec velocity and 1 g acceleration. As one of the main contributions in this thesis, the dynamics of the 1st axial mode (at 132 Hz) were actively compensated using ASMC, which resulted in a command tracking bandwidth of 208 Hz. The mode compensating ASMC (MC-ASMC) was also shown to improve the dynamic stiffness of the drive system, around the axial resonance, by injecting additional damping at this mode. After compensating for the lead errors as well, a translational tracking accuracy of 2.6 um was realized while executing 1 m/sec feed motions with 0.5 g acceleration transients. In terms of bandwidth, speed, and accuracy, these results surpass the performance of most ball screw driven machine tools by 4-5 times. As the second main contribution in this thesis, the elastic deformations (ED) of the ball screw drive were modeled and compensated using a robust strategy. The robustness originates from using the real-time feedback control signal to monitor the effect of any potential perturbations on the load side, such as mass variations or cutting forces, which can lead to additional elastic deformations. In experimental results, it is shown that this compensation scheme can accurately estimate and correct for the elastic deformation, even when there is 130% variation in the translating table mass. The ED compensation strategy has resulted in 4.1 um of translational accuracy while executing at 1 m/sec feed motion with 0.5 g acceleration transients, without using a linear encoder. This result is especially significant for low-cost CNC (Computer Numerically Controlled) machine tools that have only rotary encoders on their motors. Such machines can benefit from the significant accuracy improvement provided by this compensation scheme, without the need for an additional linear encoder.