The transmission line is an underappreciated style of loudspeaker enclosure characterized by an acoustic labyrinth stemming from the rear of the speaker driver. In practice, the transmission line enclosure produces airy sound uncharacteristic of other styles, at the cost of more pronounced resonant peaks. The most important practical drawback of this loudspeaker enclosure design is the difficulty of properly applying damping to these enclosures. Ideally, this difficulty can be mitigated using an analytical model that accurately predicts the SPL frequency response of a transmission line loudspeaker system for a given geometry and mass of damping material. This research takes the first step towards establishing such a model by developing a limited model for a simple enclosure geometry. Through the application of a modal analysis, this research predicts the frequency response of the enclosure for the first five modes, discusses the effect damping has on this response, and experimentally verifies the produced outputs. For the simplified transmission line enclosure, the developed model successfully predicts the target portion of the frequency response. The model produces accurate results for a range of damping levels using experimentally derived damping ratios for the first five modes. The resulting curves for each modal damping ratio allow for a set of novel damping ratios to be produced from an input mass of damping material. Through this process, an input mass of damping material produces the predicted frequency response for a straight, non-tapered transmission line enclosure. This prediction can make damping a transmission line enclosure much more efficient, allowing for transmission line loudspeakers to be more widely available.

Comme plusieurs pays du monde, Madagascar a fait rentrer dans sa politique de santé, l’utilisation des médicaments génériques, de moindre coût, pour faciliter l’accès aux soins de la population. La promotion des médicaments génériques impose de garantir leur qualité par rapport aux médicaments de référence. Une étude a été menée pour contribuer à l’amélioration des pratiques du système de réglementation et des contrôles pharmaceutiques de Madagascar. Pour cela, l’environnement pharmaceutique et le système d’enregistrement des médicaments de ce pays sont présentés en regard de ceux existants dans d’autres pays. Ensuite, des contrôles de qualité englobant des essais physico-chimiques, pharmaco-techniques et pharmacologiques, sont réalisés sur vingt-deux médicaments antihypertenseurs dont quatre spécialités de références et dix-huit spécialités considérées comme leurs génériques, échantillonnés à Madagascar. L’augmentation incessante du nombre de malades atteints d’hypertension artérielle, couplée avec la difficulté de son traitement, sont à l’origine du choix de la famille thérapeutique étudiée. Pour les dix-huit spécialités considérées comme génériques, des non conformités aux référentiels ont été révélées. Seulement une spécialité considérée comme générique a présenté des caractéristiques, dont la cinétique de dissolution et les résultats pharmacologiques, similaires à celles de la référence. Des préconisations impliquant tous les acteurs du domaine pharmaceutiques ont pu être dégagées à partir de l’étude. / Like many countries in the world, Madagascar has returned in its health policy, the use of generic drugs, because of their lower cost, to facilitate access to health care of the population. The promotion of generic drugs needs to ensure their quality compared to reference drugs. A study was conducted to contribute to the improvement of practices and drug regulatory system in Madagascar . For this, the pharmaceutical environment and the registration of generic drugs in this country with those of other countries are presented. Then quality control tests were performed on twenty two antihypertensive drugs including four referent specialties and eighteen specialties considered as their generic, sampled in Madagascar . The choice of this therapeutic family was governed by the constant increase in the number of patients suffering from hypertension, associated with the difficulty of treatment. For the eighteen specialties considered as generics, non-compliances with standards were recorded at the end of the physicochemical and pharmacotechnical tests and pharmacological studies. Only one specialty was shown to present similar characteristics, including dissolution kinetics and pharmacological results, as the reference. Recommendations involving all stakeholders of the pharmaceutical field have been brought from the study.

Teleoperation of ground/aerial vehicle extends operator's ability (e.g. expertise, strength, mobility) into the remote environment, and haptic feedback enhances the human operator's perception of the slave environment. In my thesis, two cases are studied: wheeled mobile robot (MWR) haptic tele-driving over the Internet and unmanned aerial vehicle (UAV) haptic teleoperation over the Internet. We propose novel control frameworks for both dynamic WMR and kinematic WMR in various tele-driving modes, and for a "mixed" UAV with translational dynamics and attitude kinematics. The recently proposed passive set-position modulation (PSPM) framework is extended to guarantee the passivity and/or stability of the closed-loop system with time-varying/packet-loss in the communication; and proved performance in steady state is shown by theoretical measurements.For UAV teleoperation, we also derive a backstepping trajectory tracking control with robustness analysis. Experimental results for dynamic/kinematic WMR and an indoor quadrotor-type UAV are presented to show the efficacy of the proposed control framework.

This thesis presents decentralized model reference adaptive control techniques for systems with full-state feedback and systems with output feedback. The controllers are strictly decentralized, that is, each local controller uses feedback from only local subsystems and no information is shared between local controllers. The full-state feedback decentralized controller is effective for multi-input systems, where the dynamics matrix and control-input matrix are unknown. The decentralized controller achieves asymptotic stabilization and command following in the presence of sinusoidal disturbances with known spectrum. We present a construction technique of the reference-model dynamics such that the decentralized controller is effective for systems with arbitrarily large subsystem interconnections. The output-feedback decentralized controller is effective for single-input single-output subsystems that are minimum phase and relative degree one. The decentralized controller achieves asymptotic stabilization and disturbance rejection in the presence of an unknown disturbance, which is generated by an unknown Lyapunov-stable linear system.

Audit firm tenure impacts the quality of audit work and the disclosure of material internal control weaknesses. Public firms are required by the Sarbanes Oxley Act of 2002 (SOX) Section 302 to disclose material internal control weaknesses. Researchers debate whether audit firm rotation is necessary for improving audit quality (Chen, Lin, & Lin, 2008). Generally, an auditor needs sufficient time to become familiar with a client's business in order to enhance effective controls and financial reporting. However, long tenure may diminish auditor independence, and in turn reduce the quality of audit work and encourage a client to violate SOX disclosure requirements. Therefore, it is expected that the disclosure of material internal control weaknesses is less likely given long audit tenure. Prior studies consider many variables that impact the disclosure of control weaknesses, except audit tenure. Further, prior studies do not address the issue of whether familiarity or independence explains non-disclosure. This dissertation investigates the role of audit firm tenure and concludes that the disclosure of material internal control weaknesses is more likely given short tenure. Further, familiarity with the client's business, which is associated with long tenure, explains non-disclosure and not the lack of independence. Therefore, audit firm rotation may not be necessary.

Plannings systems which can be considered as modules of an Enterprise Resource Planning system play a vital role in different types of organizations. The effects of the planning systems towards the Management Control Systems and organizational performance are less investigated in the context of not-for-profit/service providing organizations. This study sheds light on the effects of the planning systems on informal management controls and non-financial organizational performance by investigating the Swedish university sector through a case study performed at the Royal Institute of technology where the data were gathered using semi-structured interviews from different administrators using the planning systems. The study presents the effects of ten planning systems towards personnel controls, cultural controls and planning & decision making controls. It further examines how the planning systems affect the personnel development, workplace relationships, employee satisfaction and other type of organizational performance measures. In this endeavour, the results of this study shows how the personnel controls affects the personnel development, cultural controls affects the workplace relationships and planning & decision making controls affects the employee satisfaction, all in the light of different planning systems. Furthermore, it was also found out how different planning systems affect different organizational performance measures, namely, quality and efficiency of processes, quality of staff, employee health & safety, gender equality, premises and infrastructure, student attractiveness, quality assurance, research & education and external professional relationships. Finally this study generalizes the results found through investigating each planning system, which can be applied to the university sector/not-for-profit organizational sector in Sweden. / ME200X

In this paper, a roll stability controller (RSC) is presented based on an eight degree of freedom dynamic vehicle model. The controller is designed for and tested on a scaled vehicle performing obstacle avoidance maneuvers on a populated test track. A rapidly-exploring random tree (RRT) algorithm is used for the vehicle to execute a trajectory around an obstacle, and examines the geographic, non-homonymic, and dynamic constraints to maneuver around the obstacle. A model predictive controller (MPC) uses information about the vehicle state and, based on a weighted performance measure, generates an optimal trajectory around the obstacle. The RSC uses the standard vehicle state sensors: four wheel mounted encoders, a steering angle sensor, and a six degree of freedom inertial measurement unit (IMU). An emphasis is placed on the mitigation of rollover and spin-out, however if a safe maneuver is not found and a collision is inevitable, the program will run a brake command to reduce the vehicle speed before impact. The trajectory is updated at a rate of 20 Hz, providing improved stability and maneuverability for speeds up to 10 ft/s and turn angles of up to 20°.

<p>Hydraulic systems are commonly used for actuation and manipulation of heavy loads. They are found in a variety of different industries, such as in automotive, manufacturing, robotics, construction, and aerospace. Conventional hydraulic systems use a centralized constant pressure supply system. Pressurized fluid is then channeled to actuators using servo-valves. The advantages of these systems are their high torque to mass ratio, and the ability to control speed and direction with relative precision. However, there are also disadvantages such as the requirement of a bulky centralized supply, leakage, noise, and reduced energy efficiency due to orifice flow and the requirement for maintaining a constant supply pressure.</p> <p>Electro-Hydrostatic Actuation systems (EHA) alleviate many of the above mentioned shortcomings of servo-valve controlled hydraulic systems. In the EHA position control is achieved by regulating the pumping action. Here, a fixed or a variable displacement pump can be used to move oil from one chamber of the actuator to the other. In these actuators, the presence of nonlinearities associated with pump/motor static friction and backlash, pressure drop in the piping system, and nonlinear friction at the load have a significant effect on the performance and positional precision of the system.</p> <p>This research will focus on developing a multiple inner-loop control strategy by implementing multiple inner-loops that utilize the differential pump/load position and velocity. The main goal will be to decrease the effect of the pump backlash as well as the nonlinear friction at the load; both of which negatively impact positional precision. Therefore, the main benefit of this method is an improvement in trajectory tracking precision, which is particularly important for high precision hydrostatic systems. Furthermore, a sliding mode control strategy will be incorporated into the design to suppress load oscillations reported in precision trajectory tracking applications. The research hypothesis states that sliding mode control in conjunction with multiple inner-loops, will improve the trajectory tracking performance of a hydrostatic actuation system by partially compensating the effects of static friction at the load. Theoretical analysis, simulation supported by experimental results are presented to demonstrate the effectiveness of the newly developed methods in suppressing the effects of nonlinearities on the EHA performance, with the downside of an increased complexity due to the increased number of controller parameters.</p> / Doctor of Philosophy (PhD)

<p>Sampled-data supervisory control deals with timed discrete event systems (TDES) where the supervisors are to be implemented as sampled-data controllers. A sampled-data controller views the system as a series of inputs and outputs and is controlled by a periodic clock. It samples its inputs, changes state, and updates its outputs on each clock edge (the tick event). The sampled-data supervisory control framework provides a set of conditions that the TDES system must satisfy to ensure its correct behaviour in order to be implemented as sampled data controllers. A serious limitation for automatic verification of systems is the size of the system's synchronous product. To overcome this limitation, we propose the use of a compositional approach to the verification of sampled-data supervisory control. In this approach, first we recast the required conditions for sampled-data supervisory control in terms of other properties such as language inclusion, nonblocking or controllability, which already have existing compositional methods and algorithms. This makes the sampled-data properties suitable for compositional verification, considerably increasing the size of systems that can be handled using sampled-data supervisory control. We also develop and implement a set of algorithms for the compositional verification of these sampled-data properties. We provide an example of the SD Controlled Flexible Manufacturing System to test our algorithms.</p> / Master of Science (MSc)

<p>This thesis investigates the effect of different passive suppression techniques of different configurations on the flow-excited acoustic resonance of an internal axisymmetric cavity. This type of acoustic resonance is observed in many practical applications such as valves installed in steam pipe lines, and gas transport system. An experimental setup of a cavity-duct system has been altered to facilitate the study of the suppression and/or delay of resonance over the range of Mach number of 0.07-0.4. Three different cavity depths have been studied d=12.5 mm, 25 mm, and 50 mm deep. For each depth, the cavity length is changed from L=25 mm to 50 mm. The investigation matrix includes the study of two rounding radii, two chamfer geometries and three different types of spoilers, all located at the leading edge of the cavity. A reference case of no suppression seat installed for each of the examined cavity geometries is tested. Rounding off cavity edges for both radii has increased the acoustic pressure level, yet delayed the onset of resonance. Chamfering the upstream edge of the cavity delayed the onset of resonance as a result of increasing the cavity characteristic length which delays the coupling of the shear layer perturbations and the acoustic field. The delay and the suppression of resonance achieved by the chamfer depend on the size of the cavity. All spoiler configurations have proven effectiveness in delaying and suppressing resonance for all cavities. The choice of spoiler configuration would depend on cavity size and robustness/strength of acoustic resonance.</p> / Master of Science (MSc)