Dissertations / Theses on the topic 'Non linear device'

Vibration-based energy harvesting devices have received much attention over the past few years due to the need to power wireless devices in remote or hostile environments. To date, resonant linear generators have been the most common type of generators used in harvesting energy for such devices. Simple tuning and modelling methods make it a more favourable solution theoretically if not practically. This thesis considers the limitations of resonant linear devices and investigates two non-linear generators to see if they can outperform the linear devices in certain situations. So far, in most of the literature, the energy harvester is assumed to be very small dynamically compared to the source so the source is not aected by the presence of the device. This thesis considers how the dynamics of the source is aected by the device if its impedance is signicant compared to the source. A tuning condition for maximum power transfer from the source to the device is derived. This tuning condition converges to the one presented in most of the literature when the impedance of the device is assumed to be very small compared to that of the source i.e. tuned so that the natural frequency of the device equals the excitation frequency. For the case when the impedance of the device has a negligible eect on the source, the performance of the device is only limited to a narrow frequency band and drops o rapidly if mistuned. To accommodate the mistuning limitations, new types of generators are proposed mainly by using a non-linear mechanism. These mechanisms are made up of a non-linear spring connected together with a mass and a linear viscous damper i.e. the energy harvesting component. The analysis of the fundamental performance limit of any non-linear device compared to that of a tuned linear device is carried out using the principal of conservation of energy. The analysis reveals that the performance of a non-linear device in terms of the power harvested is at most 4= greater than that of a tuned linear system and is strongly dependent upon the type of the non-linearity used. Two types of non-linear mechanisms are studied in this thesis. The rst one is a non-linear bi-stable mechanism termed a snap-through mechanism which rapidly moves the mass between two stable states. The aim is to steepen the displacement response curve as a function of time which results in the increase of velocity for a given excitation, thus increasing the amount of power harvested. This study reveals that the performance of the mechanism is better than a linear system when the natural frequency of the system is much higher than the excitation frequency. The study also shows that the power harvested by this mechanism rolls o at a slower rate compared to that of the linear system. Another non-linear mechanism described in this thesis uses a hardening-type spring. The aim of this mechanism is to provide a wider bandwidth over which the power can be harvested. This thesis presents numerical solutions and approximate analytical solutions for the bandwidth and eective viscous damping of a non-linear device employing a hardening-type stiness. Unlike the linear system, in which the bandwidth is only dependent on the damping ratio, it is found that the bandwidth of the nonlinear device depends on both the strength of the nonlinearity and the damping ratio. Experimental results are presented to validate the theoretical results. This thesis also investigates the benets of the non-linear device for a low frequency and high amplitude application using the measured vibration inputs from human motion such as walking and running. The eect of harmonics on the power harvested is also studied. Numerical simulations are carried out using measured input vibrations from human motion to study the best placement of the natural frequency of the device across the range of harmonics.

Recent technological developments have implemented the use of proportional control in prosthetic hands, giving rise to the importance of appropriate myoelectric control. EMG models in the past have assumed a linear proportionality to simplify the EMG-force relationships. However, it has been shown that a non-linear EMG-force relationship may be a more effective model. This study focused on evaluating three different control algorithms for a novel myoelectric training device, consisting of a toy car controlled by EMG signals from the distal muscles in the arm. Sixteen healthy adult subjects (5 male and 11 female) with an average age of 23.6 years (SD = 2.7) were asked to drive the car through a slalom course. Completion times as well as number of errors (wall hits, cone hits, and reversals) were recorded to evaluate performance. The NASA TLX was administered to evaluate psychometrics such as mental demand, physical demand, frustration, and overall workload. The average total errors per trial on the final day of testing using the linear proportional algorithm was found to be statistically significantly (p < 0.05) lower than digital and non-linear proportional. The average course completion time per trial and overall workload using the non-linear proportional algorithm was found to be statistically significantly (p < 0.05) lower than digital and linear proportional. These results suggest that a non-linear algorithm would be most appropriate for myoelectric control in prosthetic hands.

In this thesis, three years are enclosed of research activity in the topic of non linear characterization and modelling of microwave devices. I investigated various issues related to those topics which are closely related. In fact, to obtain good predictions, empirical models require accurate measurements. This aspect is particularly important when we want to predict the behavior of devices in nonlinear regime. More and more applications take advantage of devices operation in non-linear regime. For such a reason, non linear characterization is an hot topic and research activities have focused particular attention on the need of characterize the nonlinear behaviour of electron devices to obtain more accurate model prediction under actual operating conditions. The importance of this theme can be clearly understood by considering how, in recent years, microwave technologies have become attractive for communication applications and a number of commercial devices which are largely used in everyday life (e.g., cell phone, GPS, wireless communication and so on). In the first chapter the most important properties of devices and technologies used in microwave electronics circuits will be dealt with. Particular attention is devoted to the comparison between two III-V semiconductors for the fabrication of these devices: GaAs, proven technology and used for years, and GaN, a youngest technology still being tested. After this some of the most interesting issues related to III-V electron devices, are discussed, such as low frequency dispersion. Finally a brief look will be given at the non linear models for these devices. In the second Chapter the most important microwave measurement systems exploited to characterize the non linear dynamic behaviour of electron devices will be discussed: pulsed setups, load / source-pull measurement systems, and Large Signal time domain characterization systems. In particular, for each measurement technique, it has been described the principle of operation and the application they are used for. In chapter III an alternative, technology-independent large-signal measurement setup, developed during the PhD studies, is proposed for the experimental investigation on the low frequency dispersion of current/voltage characteristics in micro- and millimetre-wave electron devices and for their modeling. The proposed measurement technique will be presented describing its hardware and software implementations and showing different experimental examples. In Chapter IV a new modeling approach will be presented accounting for the nonlinear description of low-frequency dispersive effects (due to thermal phenomena and traps) affecting electron devices. The model will be identified by exploiting measurements carried out with the measurement system described in chapter III. In the last Chapter a new, low-cost technique will be described for drawing “load-pull contours” which are a powerful tool for power amplifier design. By exploiting the lowfrequency measurement system described in chapter III and conventional descriptions of device parasitic elements and nonlinear reactive effects, the proposed approach allows to obtain the same information gathered by expensive highfrequency load pull measurement systems.

This research revolves around the concept design and theoretical validation of a new type of wave energy converter (WEC), comprising a pitching floater integrated with a resonant U-tank (RUT) and a Wells turbine as power take-off (PTO). Theoretical formulation of a fully coupled multi-body dynamic system, incorporating the thermodynamic processes of the RUT air chamber, its interaction with the PTO dynamics and their coupling with the floater is presented. Inaccuracies of the dynamic modeling of RUT based on Lloyd's low order model, which assumes constant hydrodynamic parameters irrespective of the frequency, are demonstrated by a series of high fidelity CFD simulations. These simulations are a systematic series of fully viscous turbulent simulations, using unsteady RANSE solvers, of the water sloshing at different frequencies of oscillation. Calibration of Lloyd’s model with CFD results evidenced that the RUT hydrodynamic parameters are not invariant to frequency. A numerical model was developed based on Simulink WEC-Sim libraries to solve the non-linear thermo-hydrodynamic equations of the device in time domain. For power assessment, parametric investigations are conducted by varying the main dimensions of the RUT and power RAOs were computed for each iteration. Performance in irregular sea state are assessed using a statistical approach with the assumption of linear wave theory. By superimposing spectrum energy density from two resource sites with RAO, mean annual energy production (MEAP) are computed. The predicted MEAP favorably compares with other existing devices, confirming the superior efficiency of the new proposed device over a larger range of incident wave frequency.
M.S.
This study present results of an investigation into a new type of wave energy converter which can be deployed in ocean and by its pitch response motion, it can harvest wave energy and convert it to electrical energy. This device consist of a floater, a U-tank (resonant U-tank) with sloshing water free to oscillate in response to the floater motion and a pneumatic turbine which produces power as air is forced to travel across it. The pneumatic turbine is used as the power take-off (PTO) device. A medium fidelity approach was taken to carry out this study by applying Lloyd’s model which describes the motion of the sloshing water in a resonant U-tank. Computational fluid dynamics (CFD) studies were carried out to calibrate the hydrodynamic parameters of the resonant U-tank as described by Lloyd and it was discovered that these parameters are frequency dependent, therefore Lloyd’s model was modelled to be frequency dependent. The mathematical formulation coupling the thermodynamic evolution of air in the resonant U-tank chamber, modified Lloyd’s sloshing water equation, floater dynamics and PTO were presented for the integrated system. These set of thermo-hydrodynamic equations were solved with a numerical model developed using MATLAB/Simulink WEC-Sim Libraries in time domain in other to capture the non-linearity arising from the coupled dynamics. To assess the annual energy productivity of the device, wave statistical data from two resource sites, Western Hawaii and Eel River were selected and used to carrying out computations on different iterations of the device by varying the tank’s main dimensions. This results were promising with the most performing device iteration yielding mean annual energy production of 579 MWh for Western Hawaii.

L'objectif principal de cette thèse est de concevoir, fabriquer et caractériser les dispositifs plasmoniques basés sur les cavités métalliques bidimensionnelles monocristallines pour le transfert d'information et la réalisation d'opérations logiques. Les fonctionnalités ciblées émergent de l'ingénierie spatiale et spectrale de résonances plasmon d'ordre supérieur supportées par ces cavités prismatiques. Les nouveaux éléments étudiés dans cette thèse ouvrent la voie à de nouvelles stratégies de transfert et de traitement de l'information en optique intégrée et miniaturisée. Dans un premier temps, nous caractérisons la réponse optique des nanoplaquettes d'or ultra-fines et de taille submicronique (400 à 900 nm) par spectroscopie en champ sombre. La dispersion des résonances plasmoniques d'ordre supérieur de ces cavités est mesurée et comparée avec un bon accord aux simulations obtenues par la méthode des dyades de Green (GDM). En outre, nous présentons une analyse par décomposition lorentzienne des réponses spectrales de ces nanoprismes déposés sur des minces substrats métalliques. Nous avons, par ailleurs systématiquement étudié les effets qui pourraient modifier les résonances plasmoniques par microscopie de luminescence non-linéaire, qui s'est avérée un outil efficace pour observer la densité d'états locale des plasmons de surface (SPLDOS). En particulier, nous montrons que les caractéristiques spectrale et spatiale des résonances plasmoniques d'ordre supérieur peuvent être modulées par la modification du substrat (diélectrique ou métallique), par l'insertion contrôlée d'un défaut dans la cavité ou par le couplage électromagnétique, même faible, entre les deux cavités. L'ingénierie rationnelle de la répartition spatiale des résonances confinées 2D a été appliquée à la conception de dispositifs à transmittance accordable entre deux cavités connectées. Les géométries particulières sont produites par gravure au faisceau d'ions focalisé sur des plaquettes cristallines d'or. Les dispositifs sont caractérisés par cartographie de luminescence non-linéaire en microscopie confocale et en microscopie de fuites. Cette dernière méthode offre un moyen unique d'observer la propagation du signal plasmon dans la cavité. Nous démontrons la dépendance en polarisation de la transmission plasmonique dans les composants à symétrie et géométrie adéquates. Les résultats sont fidèlement reproduits par notre outil de simulation GDM adapté à la configuration de transmission. Enfin, notre approche est appliquée à la conception et à la fabrication d'une porte logique reconfigurable avec plusieurs entrées et sorties. Nous démontrons que dix des douze portes logiques possibles à 2 entrées et 1 sortie sont activable sur une même structure en choisissant les trois points d'entrée et de sortie et en ajustant le seuil de luminescence non-linéaire pour le signal de sortie
The main objective of this PhD work is to design, fabricate and characterize plasmonic devices based on highly crystalline metallic cavities for the two-dimensional information transfer and logic gate operations. First, we thoroughly characterize the optical response of ultra-thin gold colloidal cavities of sub-micronic size (400 to 900 nm) by dark- field spectroscopy (Fig. 1a). The dispersion of the high order plasmonic resonances of the cavities is measured and compared with a good agreement to simulations obtained with a numerical based on the Green Dyadic Method (GDM). We further extend our experiments to systematically tune the spectral responses of these colloidal nanoprisms in vicinity of metallic thin film substrates. A comprehensive study of these sub-micronic size cavity in bowtie antenna configuration is performed. We show a polarization-dependent field enhancement and a nanoscale field confinement at specific locations in these bowtie antennas. We systematically study the effects that could potentially affect the plasmonic resonances by non-linear photon luminescence microscopy, which has proved to be an efficient tool to observe the surface plasmon local density of states (SPLDOS). Inparticular, we show that an effective spatially and spectrally tuning of the high order plasmonic resonances can be achieved by the modification of the substrate (dielectric or metallic), by the controlled insertion of a defect inside a cavity or by the weak electromagnetic coupling between two adjacent cavities. The rational tailoring of the spatial distribution of the 2D confined resonances was applied to the design of devices with tunable plasmon transmittance between two connected cavities. The specific geometries are produced by focused ion milling crystalline gold platelets. The devices are characterized by non-linear luminescence mapping in confocal and leakage radiation microscopy techniques. The latter offers a unique way to observe propagating SPP signal over a 2D plasmonic cavity. We demonstrate the polarization-dependent mode-mediated transmittance for devices withadequate symmetry. The results are faithfully reproduced with our simulation tool based on Green dyadic method. Finally, we extend our approach to the design and fabrication of a reconfigurable logic gate device with multiple inputs and outputs. We demonstrate that 10 out of the possible 12 2-input 1-output logic gates can be implemented on the same structure by choosing the two input and the one output points. We also demonstrate reconfiguration of the device by changing polarization of the incident beam, set of input locations and threshold of the non-linear luminescence readout signal

Le Chauffage Cyclotron Ionique (ICRH) par des ondes dans la gamme 30-80MHz est couramment utilisé dans les plasmas de fusion magnétique. Excitées par par des réseaux phasés de rubans de courant à la périphérie du plasma, ces ondes existent sous deux polarisations. L’onde rapide traverse le bord ténu du plasma par effet tunnel puis se propage à son centre où elle est absorbée. L’onde lente, émise de façon parasite, existe seulement à proximité des antennes. Quelle puissance peut être couplée au centre avec 1A de courant sur les rubans? Comment les champs radiofréquence (RF) proches et lointains émis interagissent-ils avec le plasma de bord par rectification de gaine RF à l’interface plasma-paroi? Pour répondre simultanément à ces deux questions, en géométrie réaliste sur l’échelle spatiale des antennes ICRH, cette thèse a amélioré et testé le code numérique SSWICH (Self-consitent Sheaths and Waves for ICH). SSWICH couple de manière auto-cohérente la propagation des ondes RF et la polarisation continue (DC) du plasma via des conditions aux limites non-linéaires de type gaine (SBC) appliquées à l’interface plasma / paroi. La nouvelle version SSWICH-FW est pleine onde et a été développée en deux dimensions (toroïdale/radiale). De nouvelles SBCs couplant les deux polarisations d’ondes ont été obtenues et mises en œuvre le long de parois courbes inclinées par rapport au champ magnétique de confinement. Avec ce nouvel outil en l'absence de SBCs, nous avons étudié l'impact d'une densité décroissant continûment à l'intérieur de la boîte d'antenne en traversant la résonance hybride basse (LH). Dans les limites mémoire de notre poste de travail, les champs RF au-dessous de la résonance LH ont changé avec la taille de maille. Par contre spectre de puissance couplée n’a que très peu évolué, et n’était que faiblement influencé par la densité à l'intérieur de l'antenne. En présence de SBCs, les simulations SSWICH-FW ont identifié le rôle de l'onde rapide sur l’excitation de gaines RF et reproduit certaines observations expérimentales clés. SSWICH-FW a finalement été adapté pour réaliser les premières simulations 2D électromagnétiques et de gaine-RF de la machine plasma cylindrique magnétisée ALINE
Ion Cyclotron Resonant Heating (ICRH) by waves in 30-80MHz range is currently used in magnetic fusion plasmas. Excited by phased arrays of current straps at the plasma periphery, these waves exist under two polarizations. The Fast Wave tunnels through the tenuous plasma edge and propagates to its center where it is absorbed. The parasitically emitted Slow Wave only exists close to the launchers. How much power can be coupled to the center with 1A current on the straps? How do the emitted radiofrequency (RF) near and far fields interact parasitically with the edge plasma via RF sheath rectification at plasma-wall interfaces? To address these two issues simultaneously, in realistic geometry over the size of ICRH antennas, this thesis upgraded and tested the Self-consistent Sheaths and Waves for ICH (SSWICH) code. SSWICH couples self-consistently RF wave propagation and Direct Current (DC) plasma biasing via non-linear RF and DC sheath boundary conditions (SBCs) at plasma/wall interfaces. Its upgrade is full wave and was implemented in two dimensions (toroidal/radial). New SBCs coupling the two polarizations were derived and implemented along shaped walls tilted with respect to the confinement magnetic field. Using this new tool in the absence of SBCs, we studied the impact of a density decaying continuously inside the antenna box and across the Lower Hybrid (LH) resonance. Up to the memory limits of our workstation, the RF fields below the LH resonance changed with the grid size. However the coupled power spectrum hardly evolved and was only weakly affected by the density inside the box. In presence of SBCs, SSWICH-FW simulations have identified the role of the fast wave on RF sheath excitation and reproduced some key experimental observations. SSWICH-FW was finally adapted to conduct the first electromagnetic and RF-sheath 2D simulations of the cylindrical magnetized plasma device ALINE

Dans le cadre de cette thèse on s'est intéressé à l'étude, par simulation, du fonctionnement des systèmes électriques en régime non-sinusoïdal, ainsi qu'aux effets de la pollution harmonique sur les éléments du système. Nous avons tout d'abord révisé les principaux paramètres du régime non-sinusoïdal (en proposant en complément les facteurs de distorsion intégratifs et dérivatifs) et la théorie de la puissance. Ensuite nous avons étudié la modélisation des principaux types de sources d'harmoniques, en adaptant des modèles existants ou en développant de nouveaux (pour les convertisseurs et les TCRs). Nous avons continué avec les éléments linéaires en choisissant parmi leurs modèles ceux appropriés à l'étude du régime non-sinusoïdal ou en proposant des modèles personnels, comme pour les transformateurs de puissance. On a toujours mis en évidence la caractéristique fréquentielle des paramètres des modèles. Après avoir évalué les principes potentiellement utilisables pour la modélisation du fonctionnement du système en régime non-sinusoïdal, nous avons choisi l'analyse harmonique itérative pour des études localisées, dont nous avons amélioré la convergence. Pour les études portant sur l'ensemble du système, nous avons développé un logiciel reposant sur la méthode dichotomique et la représentation hybride (temporelle et fréquentielle) des éléments non-linéaires. Les résultats des simulations réalisées dans le réseau IEEE 14 noeuds modifié, ont été utilisés dans l'analyse des interactions entre les sources harmoniques (principalement à l'aide de la puissance harmonique active totale). Dans la dernière partie, nous avons étudié les principaux types d'effets de la pollution harmonique et nous les avons détaillé pour différentes composantes du système
This thesis deals with the study, by simulation, of power Systems in non-sinusoidal situations including harmonie pollution effects. First the principal parameters of non-sinusoidal wave shapes and working conditions and some éléments of power theory were reviewed. Novel complementary intégrais and derivatives harmonie distortion factors were proposed as well. Secondly, the modelling of the main types of harmonie sources was studied, either by adapting existing models where possible or by designing new models, such for power converters or TCRs. The linear parts of the System where then treated by the appropriated models or making new proposais (as for power transformers). After evaluating the simulation principles of the power Systems operating in non-sinusoidal conditions, itérative harmonie analysis was selected for localised studies, where its convergence properties were improved. For mil scale system studies, a software program was developed based on the dichotomous method, where the hybrid modelling, in both time and frequency domains, of non-linear éléments is assumed. The results of simulations conducted on the IEEE 14-bus modified test network were used in order to analyse the interactions between the harmonie sources, mainly by using the individual and total harmonie active powers. Finally, the principal types of harmonie pollution effects hâve been studied and detailed for several System constituents

This thesis aims to investigate electrospun structures by means their production process and morpho-mechanical characterization. Considering the results obtained, the electrospun devices developed, will be useful for tendon and ligament tissue applications.

This doctoral project aims to contribute to advancement of the research in the field of innovative and resilient timber buildings with high seismic performance and minimum environmental impact in a green and sustainable way. Recent seismic events have raised questions about the adequacy of the current seismic design in code provisions. In modern seismic codes, the performance objectives are expressed in terms of life safety of the occupants and according to capacity design rules a certain damage level of structures is accepted under strong earthquakes. The resultant seismic damages are often difficult and financially prohibitive to repair. In order to significantly reduce structural and non-structural damage and avoid high economic loss, in the last decades research studies focused on the development of low damage design and technologies. In this thesis, seismic design and performance of multi-storey post-tensioned timber framed buildings with different dissipative systems have been investigated in order to develop new low-damage construction systems for high seismic areas. An extensive experimental campaign was performed at the structural laboratory of the University of Basilicata (Italy), in collaboration with the University of Canterbury (New Zealand), considering a three-dimensional, two-third scale, three-storey, post-tensioned glulam timber frame building. Different testing configurations were considered: i) the bare timber frame with post-tensioning only at the beam-column connections (free rocking); ii) the post-tensioned timber frame with dissipative devices at the beam-column and column-foundation connections (dissipative rocking); and iii) the post-tensioned timber frame with dissipative bracing systems at all storey (dissipative bracing). The seismic response of test specimen was investigated through unidirectional shaking table tests under consecutive ground motions at increasing PGA intensities, while the cyclic behaviour of hysteretic dampers was characterized by means of quasi-static tests. In particular, the testing configuration with dissipative bracing, which had not been previously implemented in post-tensioned glulam timber structures, has been deeply investigated in this research. The estimation of equivalent viscous damping has been proposed in order to optimize the displacement-based design procedure for sizing the hysteretic dissipative devices of the bracing systems. The experimental seismic response of the braced model is evaluated in terms of global and local behaviour and nonlinear numerical analysis have been carried out within two different FEM software (Sap 2000 and OpenSees). The comparison of the results obtained from all configurations demonstrated that the dissipative bracing system improved the seismic performance of post-tensioned timber buildings reducing inter-storey drift with full re-centring capability. During all seismic tests no damages were observed to structural elements, only localized breakage of external replaceable devices occurred during the test with strongest earthquake. More than one hundred inelastic cycles were experimentally recorded from dynamic tests before the failure of devices. The reliability of quasi-static testing procedures proposed by current seismic and guidelines codes for type tests and factory production control tests was also investigated. The number of cycles estimated from shaking table tests and non-linear dynamic analyses shows a decreasing trend with the increase of ductility demand in line with American standards testing requirements.

Master thesis is based on a doctor thesis dealing with the behavior of reinforced concrete elements stressed shear by the author Ing. Stanislav Martinec, Ph.D. Author master thesis has the task create a spatial finally element model loading testing construction and researched the wall element. Defined finally elements model is mainly to provide proper interaction test device steel frame with the test wall element. Need for sufficiently detailed numerical analysis is necessary to define the non-linear concrete material model, that is researched element, using the extensions multiPlas for calculation software Ansys. The key output parameters, for comparison with the results of load tests, are total bevel and maximum level of applied force on the wall element. The goal is assess the effect of a steel frame, contained in finally element model, to output parameters for by non-linear numerical analysis.

Reported in this thesis are advances in glass poling, a technique which produces second-order optical nonlinearity in glass. Poling of glass has drawn much attention because frequency conversion and electro-optic modulation, operations which are typically restricted to crystals, becomes feasible in glass fibres and waveguides which are widely spread media in photonics thanks to their excellent optical properties and mature manufacturing technology. Poled silica glass, despite showing about 10 times lower second-order nonlinearity than nonlinear crystals, can be competitive with them because longer interaction lengths are possible in glass fibres, owing to the lower chromatic dispersion. -gratings in fibres. This technology led to the first demonstration of an all-fibre frequency doubler of a fibre laser. Milliwatts of red light in the fundamental mode were produced by frequency doubling in a quasi-phase matched periodically poled silica fibre which was directly spliced to the output of the laser source. Efficiency up to 2.5% has been demonstrated in 11.5 cm long device with only about 100W of pump power, which means that 50% conversion efficiency is expected for a 2kW input power.

Materials have always had a large impact on society over the different ages. Piezoelectric materials are the often ‘invisible’ materials which find widespread use, unknown to the general public by large. Mobile electronics, automotive systems, medical and industrial systems are few of the key areas where ‘piezoelectricity’ is indispensable. The parking sensor of our car uses the effect and even the echo to image an unborn baby in a womb requires the exploitation of the piezoelectric effect. The work presented in this thesis investigates the piezoelectric effect in semiconductors, namely in III V, III N and II VI materials to have a better understanding and design potential applications in light emitting diodes (LEDs) and other electronic devices. The current work focuses on the non-linear behaviour in the strain of the piezo effect, which is manifested by the generation of electric field under crystal deformation. Previous works have already confirmed the reports of the existence of non-linear piezoelectric effects in zincblende III V semiconductors. Here, the same semiempirical approach using Density Functional Theory has been utilized to investigate the strain dependent elastic and dielectric properties of wurtzite III N materials. While we report the strong non-linear strain induced piezoelectric behaviour with second order coefficients, all spontaneous polarization terms are substantially smaller than the previously proposed values. We show that, unlike existing models, our calculated piezoelectric coefficients and nonlinear model provide a close match to the internal piezoelectric fields of quantum well and superlattice structures. Also, pressure dependence of the piezoelectric field in InGaN based LEDs predicts a significant improvement of the spontaneous emission rate can be achieved as a result of a reduction of the internal field. The LED devices using the proposed structures including a metamorphic layer under the active region of the device are expected to increase their light output power by up to 10%. We also explored the impact of the non-linear piezo effect in nanowires and present a further theoretical computational study of single photon sources optimization in InGaN based wurtzite single quantum dots. We observed the light emission can be made by those single photon sources covering the entire visible spectrum through suitable change in the alloy composition.

La rencontre de l'optique et des microondes a donne naissance a un nouveau domaine : l'optomicroonde qui permet le traitement optique du signal microonde ou le controle optique de composants microondes. Cette these s'inscrit dans ce dernier axe. Lorsque l'on expose un semi-conducteur a une source optique dont les photons ont une energie suffisante, il y a creation dans le materiau de paires electron-trou modifiant la permittivite et la conductivite du substrat. Nous avons mis a profit ce principe pour realiser une charge adaptee accordable. L'extremite ouverte d'un stub depose sur une plaquette de silicium est illuminee par un signal optique et une tension continue ajoutee au signal microonde est appliquee dans le meme temps. Cette double commande optique et electrique nous permet de regler la frequence de rejection du stub sur une plage de plus de 60% en dessous de la frequence propre en dehors de toute illumination. Nous pouvons de plus ajuster le niveau de rejection entre 5 et 50 db. Apres des observations experimentales a deux longueurs d'onde optique differentes, nous nous sommes attaches a la modelisation de la charge photo-induite. Un modele intuitif a ete developpe sous la forme d'une resistance en serie avec une capacite. Il a ensuite ete verifie par des simulations electriques. Enfin, la resolution des equations de distribution des electrons et des trous a permis une approche plus fine du phenomene. Le role de chaque commande a ete mise en lumiere ce qui permet de mieux comprendre leur influence sur la repartition des charges dans le plasma photo-induit. Ainsi, nous avons mis en evidence l'influence de la diffusion laterale sur l'impedance de la charge photo-induite. D'autre part, les simulations ont montre l'importance de la duree de vie des porteurs et du dopage sur le modele. Finalement, la charge photo-induite sur un substrat de silicium a ete utilisee pour ses proprietes non-lineaires, dans le cadre du melange de deux signaux microondes. Les premieres simulations ont permis d'identifier les elements responsables de la generation des produits d'intermodulation. Ces travaux ouvrent de nombreuses perspectives d'utilisation de la charge photo-induite et de nouveaux horizons pour le controle optique de composants microondes.

El RbTiOPO4 és un cristall de òptica no lineal amb alts coeficients electró-òptics i un llindar de dany òptic elevat, això el converteix en un material potencial per aplicacions electro-òptiques. Actualment hi ha un interès en el desenvolupament de components òptics basats en materials dielèctrics, identificat com un tema de recerca punter per Europa Horitzó 2020. La finalitat d’aquesta tesis és explorar el RTP com a plataforma dielèctrica per dispositius fotònics, que tenen aplicacions en les telecomunicacions i en el sensat biològic. En aquesta tesis s’han crescut materials monocristal•lins en volum de RTP, K:RTP i Na:KTP pel mètode de Top seeded solution growth. Els cristalls obtinguts són òptims per ser utilitzats com a plataforma per fabricar guies d’ona i com a substrats pel creixement de capes epitaxials. Capes epitaxials de (Yb,Nb):RTP sobre RTP(001), RTP sobre K:RTP(001) i K.:RTP(100), i KTP sobre Na:KTP(001) s’han crescut per la metodologia de liquid phase epitaxy. Aquesta metodologia ha permès obtenir capes monocristal•lines amb una interfase d’alta qualitat cristal•lina La fabricació de guies d’ona ha esta realitzada per RIE i ICP-RIE. Es reporta en aquesta tesis, un avanç en el coneixement del procés de etching del RTP. El mètode d’intercanvi iònic, amb Cs+ com ió, s’ha utilitzat per produir guies rectes, corbes i MZ. Degut a l’alta conductivitat iònica del RTP al llarg de la direcció c cristal•logràfica, l’ intercanvi iònic és altament factible i gairebé unidireccional. S’ha obtingut exitosament el procés de guiat de llum en totes les guies d’ona fabricades. Pels Y-splitters i els MZ fabricats sobre els cristalls RTP/(Yb,Nb):RTP/RTP(001) estructurats amb RIE sobre la capa activa o bé el substrat, la guia obtinguda és monomode amb polarització TM a 1550 nm. Les pèrdues de propagació són de 3.5 dB/cm. Per les guies d’ona rectes fabricades sobre RTP/(Yb,Nb):RTP/RTP(001) per estructuració del recobriment per ICP-RIE, les pèrdues de propagació són 0.376 dB/cm a 1550 nm.
El RbTiOPO4 es un cristal de óptica no-lineal con altos coeficientes electro ópticos y un límite de daño óptico elevado, eso lo convierte en una potencial material para aplicaciones electrópticas. Actualmente existe un gran interés en el desarrollo de componentes ópticos basados en materiales dieléctricos, esto ha sido identificado como un tema puntero de investigación por Europa Horizonte 2020. La finalidad de esta tesis es explorar el RTP cómo plataforma dieléctrica para dispositivos fotónicos, que tienen aplicaciones en les telecomunicaciones y en el sensado biológico. En esta tesis, se han crecido materiales monocristalinos en volumen de RTP, K:RTP y Na:KTP por el método de Top seeded solution growth. Los cristales crecidos son óptimos para ser utilizados como plataforma para fabricar guías de onda y como sustratos para el crecimiento de capas epitaxiales. Capas epitaxiales de (Yb,Nb):RTP sobre RTP(001), RTP sobre K:RTP(001) yK.:RTP(100), i KTP sobre Na:KTP(001) se han crecido mediante la metodología de liquid phase epitaxy. Esta metodología ha permitido obtener capes monocristalinas con una interfase de alta calidad cristalina. La fabricación de guías de onda se ha hecho por RIE y ICP-RIE: Se reporta en esta tesis un avance en el conocimiento del proceso de etching en el RTP. El método de intercambio iónico, con Cs+ como ion, se ha utilizado para producir guías de onda rectas, curvas y MZ. Debido a la alta conductividad iónica del RTP a lo largo de la dirección c cristalográfica, el intercambio iónico es altamente factible y casi unidireccional. Se ha obtenido el guiado con éxito en todas las guías de onda fabricadas. En los Y-Splitters y MZ fabricados sobre los cristales RTP/(Yb,Nb):RTP/RTP(001) estructurados con RIE sobre la capa activa o bien el sustrato, la guía obtenida es monomodo con la polarización TM a 1550 nm. Las pérdidas de propagación son de 3.5 dB/cm. Para las guías de onda rectes fabricadas sobre RTP/(Yb,Nb):RTP/RTP(001) por estructuración del recubrimiento por ICP-RIE, las pérdidas por propagación son de 0.376 dB/cm a 1550 nm.
RbTiOPO4 is a non-linear optical crystal with high electro-optic coefficients and high optical damage threshold, which makes it suitable for electro-optic applications. There’s a current interest in developing dielectric based photonic components for integrated optics, identified as a topic of research by the Europe Horizon 2020. The aim of this thesis is to explore RTP for dielectric based photonic platforms, which have applications in telecommunications and biosensing. In this thesis is reported the successful grow of bulk single crystals of RTP, K:RTP and Na:RTP by Top Seeded Solution Growth technique. The crystals obtained are suitable to be used as platforms to fabricate optical waveguides and for substrates for growth of epitaxial layers. Epitaxial layers of (Yb,Nb):RTP were grown on RTP(001), RTP was grown on K:RTP(001) and K:RTP(100) and KTP was grown on Na:KTP(001) by Liquid phase epitaxy. This methodology allows obtaining a single crystalline layer, with high quality crystalline interface. Waveguide fabrication was performed by RIE and ICP-RIE. Advancement in this etching process on RTP is reported in this thesis. Cs+ ion exchange method was used to produce straight, bends and MZ waveguides. Due to the RTP high ionic conductivity along the c crystallographic direction, ion exchange is highly feasible and almost unidirectional. Waveguiding of the fabricated channel waveguides has been successful. For the Y-Splitter and MZ waveguides fabricated on the RTP/(Yb,Nb):RTP/RTP(001) crystals, by structuring the active layer or the substrate by RIE, the waveguides obtained were single mode in TM polarization at 1550 nm. The propagation loss was 3.5 dB/cm. For straight waveguides fabricated on the RTP/(Yb,Nb):RTP/RTP(001), by structuring the cladding by ICP-RIE, the propagation losses were 0.376 dB/cm at 1550 nm. The waveguides fabricated by Cs+ ion exchange have larger losses due to inhomogeneity on the Cs exchange among different ferroelectric domains present in the structure.

The intention of the work presented is to provide novel, accurate and time-efficient way of designing multi-sines stimulus signal to replace real-life modulated signals prevailing within telecommunication networks, hence providing a novel tool for the development of modern RF measurement and design solution. The work demonstrated that with 50 tones, the multi-sines stimulus excites almost the same level of nonlinearity as real modulated signals do. For this conclusion the investigation of nonlinear behaviour mechanism was taken and a real DUT was measured under designed multi-siness and various types of modulated signals. It is also demonstrated that this multi-sines stimulus is compatible with the advanced RF measurement systems which are capable of measuring the complete RF waveform including the harmonic and base-band frequencies but demanding a periodical stimulus signal. Furthermore, a novel and quick sub-sampling algorithm was proposed to efficiently use the memory of Sampling Oscilloscope and therefore allows for accurate multi-sines capturing. An averaging algorithm for multi-sines stimulus was proposed to “stabilize” the captured waveform and a PCA based phase compensating algorithm was also proposed to tackle the problem of frequency shift under multi-sines excitation.

Thesis (S.M. and S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.
Includes bibliographical references (leaf 72).
Polymeric self-resettable circuit protection devices have been manufactured for many years with an extrusion based process. These devices add negligible resistance to a circuit at normal power operating conditions but increases in resistance by several orders of magnitude at a pre-determined level of power in order to protect the circuit from over- current or over-voltage conditions. After the electrical surge stops, and power returns to a normal level, the resistance of the device drops, and the circuit may resume its normal operation. These devices are used in computers, cell-phones, and other consumer and industrial electronic devices where normal fuses are not convenient or practical. The current manufacturing process extrudes long sheets of 2-mm thick polymer lined with 0.05-mm thick foil on both sides. This foil-polymer-foil structure, called plaque, is punched into 13 mm x 8 mm x 2 mm rectangles, called chips. The chips undergo heat treatment and radioactive cross-linking steps before wire leads are soldered onto them for easy electrical connection to either test or circuit boards. Though effective, this process produces more waste and remains less flexible than an injection-compression (IC) molding process. With this new process, devices are made individually in a multi- cavity mold, skipping the punching and soldering steps. This thesis explores IC molding and its benefits and drawbacks for manufacturing circuit protection devices. IC molded devices were manufactured, tested, and compared to standard devices, produced by the extrusion process, in the areas of physical and electrical performance.
(cont.) Budget considerations prevented the study of individually IC molded devices and instead a 150 mm x 75 mm mold cavity was used to create an IC molded plaque from which chips could be punched and wire leads attached. In this way, any electrical variations across the IC molded plaque, produced by flow or thermal properties of the new process, could be studied with electrical tests, and physical variations across the IC molded plaque could be examined with a peel test. Cycle life data and data comparing device resistance to device temperature show that the new manufacturing process has potential to create equal or better performing devices than the existing extrusion process.
by Joseph T. Hardy.
S.M.and S.B.

This thesis describes a new algorithm for the harmonic analysis of power systems. Existing non-linear models are incorporated into a structure that allows very general configurations that are linked by linear ac and dc systems. A three phase loadflow is included at the power frequency and the steady-state is solved iteratively using a real-valued, positive frequency, full Newton technique. This structure allows electrical and non-electrical variables to be solved simultaneously. The resultant process is fast, robust and shows excellent comparison with time domain simulation. The harmonic characteristics of large power conversion installations such as HVdc and high-pulse LVdc are investigated. The effects of system operation on the harmonic transfer through an HVdc link are investigated using the multiple run feature of the algorithm. Also, the representation of bipolar HVdc links is investigated and justifications for accurate dc system representation shown. The harmonic domain converter has been generalised, and a representation of the zigzag transformer developed. Using this the effects of outage conditions of a high-pulse installation are modelled, and a proposal is given for the minimisation of low order harmonic generation during this condition. Finally, a fast numerical technique for the accurate calculation of non-linear device impedances is described. This is used in conjunction with simplified converter models to assess the impact of the converter on the linear ac system impedance. A comparison is made between the different methods of harmonic analysis and a quantitative assessment of their accuracy given.

Unconventional computing paradigms are subject of increasing interest for the design and the development of computing systems that aim to overcome the limitations of standard digital technologies related to low power efficiency and intrinsic integration limits in the fabrication processes. Networks of nano-objects fabricated exploiting the self-assembling of their building blocks at the nanoscale, are promising physical substrate for the fabrication of neuromorphic devices thanks to their non-linear electrical properties and dynamic behavior in response to external applied voltage. Recently, cluster-assembled metallic films showed resistive switching properties under the application of an external electrical films and the possibility to fabricate multi-electrode device capable to implement information processing systems [9, 10]. Here I studied the non local and correlated electrical behaviour of multi-electrode cluster-assembeld gold films and I proposed a device that exploits the coduction porperties of these systems to implement efficient and autonomous data processing.

L’amélioration du confort des usagers ainsi que l’augmentation du niveau de sécurité des structures requièrent le développement de techniques permettant de limiter efficacement les vibrations. Dans cette optique, les travaux exposés ici proposent le développement et l’analyse de méthodes de contrôle vibratoire pour des structures de faibles dimensions et utilisant peu d’énergie. Afin de satisfaire à ces deux critères, il est ici proposé d’utiliser des éléments piézoélectriques électriquement interfacés de manière non-linéaire et périodiquement distribués sur la structure-cible à contrôler. Ainsi, l’approche proposée permet de bénéficier à la fois des avantages des techniques de contrôle non-linéaires appliquées aux matériaux intelligents de type piézoélectrique, offrant des performances remarquables tout en étant peu consommatrices d’énergie, avec ceux des structures périodiques exhibant des bandes fréquentielles interdites présentant de fortes atténuations de la propagation d’onde. Plus particulièrement, ce mémoire s’intéresse à différentes architectures d’interconnexion des interfaces électriques non-linéaires permettant un bon compromis entre la bande fréquentielle contrôlée et les performances en termes d’atténuation des vibrations. Ainsi, trois architectures principales sont proposées, allant de structures totalement périodiques, tant au niveau mécanique qu’électrique (interconnexions), à des structures présentant un certain degré d’apériodicité sur le plan électrique (entrelacement), impactant ainsi la propagation de l’onde acoustique en élargissant la bande de contrôle, pour enfin proposer une architecture hybride entre interconnexion et entrelacement conduisant à des systèmes large bande performants
For ameliorating vibration reduction systems in engineering applications, miscellaneous vibration control methods, including vibration damping systems, have been developed in recent years. As one of intelligent vibration damping systems, nonlinear electronic damping system using smart materials (e.g., piezoelectric materials), is more likely to achieve multimodal vibration control. With the development of meta-structures (a structure based upon metamaterial concepts), electronic vibration damping shunts, such as linear resonant damping or negative capacitance shunts, have been introduced and integrated abundantly in the electromechanical meta-structure design for wave attenuation and vibration reduction control. Herein, semi-passive Synchronized Switch Damping on the Inductor (SSDI) technique (which belongs to nonlinear electronic damping techniques), is combined with smart meta-structure (also called smart periodic structure) concept for broadband wave attenuation and vibration reduction control, especially for low frequency applications. More precisely, smart periodic structure with nonlinear SSDI electrical networks is investigated from the following four aspects, including three new techniques for limiting vibrations: First, in order to dispose of a tool allowing the evaluation of the proposed approaches, previous finite element (FE) modeling methods for piezoelectric beam structures are summarized and a new voltage-based FE modeling method, based on Timoshenko beam theory, is proposed for investigating smart beam structure with complex interconnected electrical networks; then, the first developed technique lies in smart periodic structure with nonlinear SSDI interconnected electrical networks, which involves wave propagation interaction between continuous mechanical and continuous nonlinear electrical media; the second proposed topology lies in smart periodic structures with nonlinear SSDI interleaved / Tri-interleaved electrical networks involving wave propagation interaction between the continuous mechanical medium and the discrete nonlinear electrical medium. Due to unique electrical interleaved configuration and nonlinear SSDI electrical features, electrical irregularities are induced and simultaneously mechanical irregularities are also generated within an investigated periodic cell; the last architecture consists in smart periodic structures with SSDI multilevel interleaved-interconnected electrical networks, involving wave propagation interaction between the continuous mechanical medium and the multilevel continuous nonlinear electrical medium. Compared with the SSDI interconnected case, more resonant-type band gaps in the primitive pass bands of purely mechanical periodic structures can be induced, and the number of such band-gaps are closely related to the interconnection / interleaved level. Finally, the main works and perspectives of the thesis are summarized in the last chapter

Linear springs with variable stiffnesses find some key roles in robotic applications. They are implemented into robotic devices for two main reasons, to increase energy efficiency of walking-running robots and prosthesis, and to get safe human-robot interaction at industrial robots. Being inspired from the human actuation system, a mathematical method to get mechanically adjustable linear springs is noted in the literature
antagonistically working two quadratic springs method. But the proposed solution requires two non-linear springs with quadratic spring characteristics and they are not readily available. Several solutions have been noted in the literature for the acquisition of such non-linear springs. At this thesis work, the solution is realized with a string wrapping around cam mechanism. Two different prototypes were designed and constructed and the second one was physically tested to validate the linear spring behavior. The results displayed good linear spring characteristics with different levels of adjustable spring stiffness. Beside the antagonistically working two quadratic springs method, three novel methods to get mechanically adjustable linear springs are introduced at this thesis. They are based on using hanging weights, an exponential characteristic spring and a linear translation spring respectively. The real prototypes were not manufactured but sample designs using string wrapping around cam mechanisms are made.

L’amortissement de vibrations mécaniques trouve de nombreuses applications dans le domaine du contrôle acoustique ou de la réduction de contraintes dans l’industrie (machine outil), le génie civil (structure autoportée), ou encore l’aéronautique (réduction de contrainte lors des manoeuvres). Les recherches actuelles tendent principalement vers des méthodes utilisant des matériaux piézoélectriques collés à la surface des structures à traiter. Une technique prometteuse, développée au LGEF à l’INSA de Lyon, est l’amortissement de vibration d’une structure mécanique par méthode SSDI (pour Synchronized Switch Damping on an Inductor). Cette technique d’amortissement semi-active exploite un procédé non-linéaire de traitement de la tension aux bornes d’un élément piézoélectrique, capteur et actionneur à la fois. L’objectif de ce travail est de réaliser l’intégration de l’électronique de traitement de la tension aux bornes des éléments piézoélectriques en technologie microélectronique, afin de pouvoir l’embarquer sur le patch piézoélectrique à terme. Une analyse des techniques d’amortissement publiées permet d’y situer ce travail et de définir les points clés de la technique SSDI. Au deuxième chapitre, un certain nombre de modèles sont développés pour comparer et guider les choix de conception, et pour aboutir à des arbitrages architecturaux. Le troisième chapitre développe la conception d’un ASIC dans une technologie avec option haute tension, comprenant une fonction haute-tension de traitement du signal piézoélectrique et une chaine basse-tension d’analyse, de décision et de commande. La première réalise l’inversion de la tension piézoélectrique à l’aide d’un circuit RLC passif de conversion de l’énergie. La seconde s’attache à la détection des extremums de manière à optimiser l’amortissement. Un diviseur de tension auto-adaptatif avec protection contre les surtensions ainsi qu’un détecteur de pic de tension permettent de réaliser cette opération. Ces fonctions sont caractérisées en simulations et mesures. Le fonctionnement de l’ASIC est ensuite testé sur une structure mécanique, et les performances sont décrites et interprétées au chapitre 4. Le comportement multi-mode et la grande dynamique des signaux mécaniques traités sont des avancées par rapport à la bibliographie
Mechanical vibration damping has many applications in industry (machine tools), civil engineering (bridge construction), or aeronautics (stress during maneuvers). Current research tends mainly to use piezoelectric materials based methods. A promising technique from the LGEF of INSA Lyon is the vibration damping of mechanical structure by so-called SSDI method (for Synchronized Switch Damping on an Inductor). This semi-active damping technique uses a non-linear process to invert the voltage across a piezoelectric element. The element is used as sensor and actuator at a time. The aim of this work is to achieve an integration of the electronic process with the SSDI voltage inversion in a microelectronic technology. It has ultimately to embed the electronic controller on the piezoelectric patch. The analysis of published damping techniques can situate this work and identify key points of the SSDI technique. In the second chapter, several models are developed to compare and decide of the best architectural design choice. The third chapter presents an ASIC design in a technology with high voltage option. The ASIC consists of a high-voltage piezoelectric signal processing part and a low-voltage control part. The first function performs piezoelectric voltage reversing by mean of a passive RLC energy conversion circuit. The second function focuses on the extremum voltage detection circuit in order to optimize damping efficiency. A self-tuning voltage divider with over-voltage protection and a peak voltage detector can perform this operation. These functions are characterized by simulations and measurements. The ASIC operation is then tested with mechanical structures, and damping performances are described and interpreted in Chapter 4. The multimodal behavior and the mechanical signals high-dynamic are new contribution as regard in the bibliography

Orientador: Milton Dias Junior
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
Made available in DSpace on 2018-08-17T18:54:27Z (GMT). No. of bitstreams: 1 Miyasato_HugoHeidy_M.pdf: 3357683 bytes, checksum: 9fcd8bd237500580084498c606879165 (MD5) Previous issue date: 2011
Resumo: Fenômenos de ruído, vibração e sua severidade (NVH) são uma grande preocupação da indústria automotiva desde o século 20. A fim de atingir uma vantagem competitiva, as montadoras têm se focado na melhora do desempenho de NVH dos seus produtos para lidar com um cenário de mercado global competitivo. No intuito de verificar o comportamento do sistema durante o processo de desenvolvimento, métodos computacionais são aplicados para encontrar melhores abordagens e na previsão de problemas, economizando tempo e orçamento da empresa gastos na construção de protótipos e testes. Nesse trabalho, gear rattle, um ruído induzido por impacto cuja causa são as engrenagens sem carga da transmissão, será modelado e simulado. É diagnosticado com maior intensidade em veículos com motores diesel em marcha lenta e excitado especificamente quando uma faixa de frequências que causa grande amplitude de vibração nos elementos internos da caixa de câmbio é alcançada. Modelos lineares do trem de potência em ponto morto ou em tração serão estudados, compreendendo as suas características básicas, tais como frequências naturais e modos associados que podem ser representativos do fenômeno. Esse sistema possui elementos com fortes não-linearidades, tais como a rigidez estratificada com histerese da embreagem e a folga entre os dentes dos engrenamentos. Uma caracterização mais realista será incluída no modelo com uma rigidez variante no tempo para o engrenamento helicoidal, utilizado em todas transmissões manuais, com uma componente dissipativa adequada aos impactos. Para verificar condições de operação que podem somente ser avaliadas segundo formulação não-linear, simulações serão realizadas para verificar a eficácia de orientações de solução e propostas de modificação encontradas na literatura
Abstract: Noise, Vibration and Harshness (NVH) phenomena are a great concern of the automotive industry since the twentieth century. In order to achieve a commercial advantage, manufacturers have focused on improving the NVH performance of their products to cope with a competitive global market scenario. To verify the behavior of the system during the design process, computational methods are applied to find a better approach and foresee problems, saving company budget and time spent in prototypes and tests. In this work, gear rattle, a impact-induced noise caused by the unloaded gear teeth inside the gearbox, will be modeled and simulated. It is diagnosed with a higher intensity in diesel vehicle engines at idle speed and in a more specific way excited when a range of frequency that causes large amplitude of vibration in the internal elements of the gearbox is reached. Linear models of the powertrain operating in idle and traction will be studied, in order to understand its basic characteristics, such as natural frequencies and associated vibration modes that could be representative to this phenomena. This system has elements with strong nonlinearities such as the stratified stiffness with hysteresis of the clutch and the backlash between the gear teeth. A more realistic feature will be included in the model with a time variable stiffness for the helical gear mesh, used in all manual transmissions, with a suitable dissipative component for the impacts. To verify operational conditions which can only be evaluated with nonlinear formulation, simulations will be made to verify the effectiveness of solution guidelines and modification procedures found in literature
Mestrado
Mecanica dos Sólidos e Projeto Mecanico
Mestre em Engenharia Mecânica

Abstract: Highway bridges have great values in a country because in case of any natural disaster they may serve as lines to save people’s lives. Being vulnerable under significant seismic loads, different methods can be considered to design resistant highway bridges and rehabilitate the existing ones. In this study, base isolation has been considered as one efficient method in this regards which in some cases reduces significantly the seismic load effects on the structure. By reducing the ductility demand on the structure without a notable increase of strength, the structure is designed to remain elastic under seismic loads. The problem associated with the isolated bridges, especially with elastomeric bearings, can be their excessive displacements under service and seismic loads. This can defy the purpose of using elastomeric bearings for small to medium span typical bridges where expansion joints and clearances may result in significant increase of initial and maintenance cost. Thus, supplementing the structure with dampers with some stiffness can serve as a solution which in turn, however, may increase the structure base shear. The main objective of this thesis is to provide a simplified method for the evaluation of optimal parameters for dampers in isolated bridges. Firstly, performing a parametric study, some directions are given for the use of simple isolation devices such as elastomeric bearings to rehabilitate existing bridges with high importance. Parameters like geometry of the bridge, code provisions and the type of soil on which the structure is constructed have been introduced to a typical two span bridge. It is concluded that the stiffness of the substructure, soil type and special provisions in the code can determine the employment of base isolation for retrofitting of bridges. Secondly, based on the elastic response coefficient of isolated bridges, a simplified design method of dampers for seismically isolated regular highway bridges has been presented in this study. By setting objectives for reduction of displacement and base shear variation, the required stiffness and damping of a hysteretic damper can be determined. By modelling a typical two span bridge, numerical analyses have followed to verify the effectiveness of the method. The method has been used to identify equivalent linear parameters and subsequently, nonlinear parameters of hysteretic damper for various designated scenarios of displacement and base shear requirements. Comparison of the results of the nonlinear numerical model without damper and with damper has shown that the method is sufficiently accurate. Finally, an innovative and simple hysteretic steel damper was designed. Five specimens were fabricated from two steel grades and were tested accompanying a real scale elastomeric isolator in the structural laboratory of the Université de Sherbrooke. The test procedure was to characterize the specimens by cyclic displacement controlled tests and subsequently to test them by real-time dynamic substructuring (RTDS) method. The test results were then used to establish a numerical model of the system which went through nonlinear time history analyses under several earthquakes. The outcome of the experimental and numerical showed an acceptable conformity with the simplified method.
Résumé: Les ponts routiers ont une grande valeur dans un pays parce qu’en cas de catastrophe naturelle, ils peuvent servir comme des lignes pour sauver des vies. Étant vulnérable sous des charges sismiques importantes, on peut considérer différentes méthodes pour concevoir des ponts routiers résistants et également pour réhabiliter des ponts existants. Dans cette étude, l'isolation de la base a été considérée comme une méthode efficace qui peut réduire significativement les effets des charges sismiques sur la structure. En réduisant la demande en ductilité sur la structure sans une augmentation notable de force, la structure est conçue pour rester élastique sous des charges sismiques. Le problème associé aux ponts isolés, particulièrement avec des appuis en élastomère, peut être leurs déplacements excessifs sous les charges de service et de séisme. Ceci peut défier l’objectif d'utiliser des appuis en élastomère pour les ponts typiques de petite portée où les joints de dilatation et les dégagements peuvent aboutir à une augmentation significative des frais d'exploitation et de maintenance. Ainsi, supplémenter la structure avec des amortisseurs d’une certaine rigidité peut servir de solution, ce qui peut cependant augmenter l’effort tranchant transmis à la sous-structure. Cette étude a pour but de fournir une méthode simplifiée afin d’évaluer les paramètres optimaux des amortisseurs dans les ponts isolés. Dans cette thèse, premièrement, basé sur une étude paramétrique, quelques directions sont données pour l'utilisation de dispositifs d'isolation simples, dont les appuis en élastomère, afin de réhabiliter des ponts existant avec une haute importance. Les paramètres comme la géométrie du pont, les clauses des normes et le type de sol sur lequel la structure est construite ont été appliqués sur un pont typique de deux portées. Il est conclu que les paramètres mentionnés peuvent déterminer l'emploi d'isolement de la base des ponts routiers. À la deuxième phase, basé sur le coefficient de réponse élastique des ponts isolés, une méthode de conception simplifiée d’amortisseur pour des ponts routiers réguliers isolés à la base a été présentée dans cette étude. En sélectionnant des objectifs pour la réduction du déplacement et la variation de l’effort tranchant, la rigidité et l'amortissement exigés d'un amortisseur hystérétique peuvent être déterminés. L’étude s’est poursuivie par une modélisation numérique d’un pont à deux portées pour vérifier l'efficacité de la méthode. Pour un modèle numérique d'un pont isolé typique, la méthode a été utilisée pour identifier des paramètres linéaires équivalents pour un certain déplacement et effort tranchant désigné. Par la suite, assumant un amortisseur de type hystérétique, les paramètres non linéaires de l’amortisseur ont été calculés et utilisés. La comparaison des résultats du modèle numérique sans amortisseur et avec l'amortisseur a démontré que la méthode proposée est suffisamment précise. Par la suite, un nouvel amortisseur hystérétique simple en acier a été conçu. Cinq spécimens ont été fabriqués de deux différents grades d’acier et ont été testés en combinaison avec un isolateur à l’échelle réelle dans le laboratoire de structures de l'Université de Sherbrooke. La procédure comprenait la caractérisation des spécimens par des tests cycliques en contrôle de déplacement et par la suite la réalisation d’essais par la méthode de sous-structuration dynamique en temps réel. Les résultats des essais ont été utilisés pour établir un modèle numérique du système qui a subi des analyses temporelles non linéaires sous plusieurs séismes. Le résultat des essais expérimentaux et numériques montrent une conformité acceptable avec la méthode simplifiée.

Ce travail de cette thèse propose une conception et une réalisation d’un banc intégré de caractérisation temporelle des dispositifs RF non-linéaires conçu avec des récepteurs de type THA. Ce banc est une version miniaturisée, moins onéreuse et à performances comparables d’un banc similaire « éclaté » et développé au sein d’XLIM. Le banc intégré développé dans ce travail est entièrement étalonné. Il est versatile vis-à-vis des techniques de sous échantillonnage mis en œuvre pour mesurer des signaux RF sur des temps d’acquisition très différents (<50 µs ou < quelques ms). La technique CIS est utilisée pour l’acquisition périodiques de signaux RF périodiques de durée courtes. La technique DQD est utilisée pour l’acquisition périodiques ou apériodique de signaux RF périodiques ou apériodiques. Cet outil a été utilisé pour extraire, à partir des formes d’ondes temporelles mesurées à leurs accès, plusieurs paramètres caractéristiques (AM/AM- AM/PM, EVM) d’amplificateurs GaN de gamme 10 à 50 W soumis à des excitations simples ou à des signaux modulés. Ce manuscrit décrit aussi la mise en œuvre le développement, parallèlement au travail précédent, d’une plateforme de laboratoire de travaux pratiques à distance pour le projet européen TEMPUS EOLES
This work proposes the design and the realization of a 4-channel integrated and calibrated time-domain characterization system for the characterization of non-linear microwave devices. This integrated measurement system uses THA based receivers. This is a miniaturized, less expensive and comparable version of a similar laboratory available tool developed within XLIM. The integrated instrument developed in this work is fully calibrated. It is versatile with respect to sub-sampling techniques used to measure RF signals over very different acquisition times (<50 µs or < few ms). The CIS technique is used for the periodic acquisition of periodic short duration RF signals. The DQD technique is used for the periodic or aperiodic acquisition of periodic or aperiodic RF signals. This tool was used to extract, from the measured time-domain waveforms at their ports, several characteristic parameters (AM/AM-AM/PM, EVM) of GaN amplifiers operating in the 10 to 50 W range and excited with simple or modulated signals. This manuscript also describes the implementation, and the development, performed along with the previous work, of a laboratory platform for remote practical works in the context of the European project TEMPUS EOLES

Despite significant efforts have been directed toward reducing waste generation and encouraging alternative waste management strategies, landfills still remain the main option for Municipal Solid Waste (MSW) disposal in many countries. Hence, landfills and related impacts on the surroundings are still current issues throughout the world. Actually, the major concerns are related to the potential emissions of leachate and landfill gas into the environment, that pose a threat to public health, surface and groundwater pollution, soil contamination and global warming effects. To ensure environmental protection and enhance landfill sustainability, modern sanitary landfills are equipped with several engineered systems with different functions. For instance, the installation of containment systems, such as bottom liner and multi-layers capping systems, is aimed at reducing leachate seepage and water infiltration into the landfill body as well as gas migration, while eventually mitigating methane emissions through the placement of active oxidation layers (biocovers). Leachate collection and removal systems are designed to minimize water head forming on the bottom section of the landfill and consequent seepages through the liner system. Finally, gas extraction and utilization systems, allow to recover energy from landfill gas while reducing explosion and fire risks associated with methane accumulation, even though much depends on gas collection efficiency achieved in the field (range: 60-90% Spokas et al., 2006; Huitric and Kong, 2006). Hence, impacts on the surrounding environment caused by the polluting substances released from the deposited waste through liquid and gas emissions can be potentially mitigated by a proper design of technical barriers and collection/extraction systems at the landfill site. Nevertheless, the long-term performance of containment systems to limit the landfill emissions is highly uncertain and is strongly dependent on site-specific conditions such as climate, vegetative covers, containment systems, leachate quality and applied stress. Furthermore, the design and operation of leachate collection and treatment systems, of landfill gas extraction and utilization projects, as well as the assessment of appropriate methane reduction strategies (biocovers), require reliable emission forecasts for the assessment of system feasibility and to ensure environmental compliance. To this end, landfill simulation models can represent an useful supporting tool for a better design of leachate/gas collection and treatment systems and can provide valuable information for the evaluation of best options for containment systems depending on their performances under the site-specific conditions. The capability in predicting future emissions levels at a landfill site can also be improved by combining simulation models with field observations at full-scale landfills and/or with experimental studies resembling landfill conditions. Indeed, this kind of data may allow to identify the main parameters and processes governing leachate and gas generation and can provide useful information for model refinement. In view of such need, the present research study was initially addressed to develop a new landfill screening model that, based on simplified mathematical and empirical equations, provides quantitative estimation of leachate and gas production over time, taking into account for site-specific conditions, waste properties and main landfill characteristics and processes. In order to evaluate the applicability of the developed model and the accuracy of emissions forecast, several simulations on four full-scale landfills, currently in operative management stage, were carried out. The results of these case studies showed a good correspondence of leachate estimations with monthly trend observed in the field and revealed that the reliability of model predictions is strongly influenced by the quality of input data. In particular, the initial waste moisture content and the waste compression index, which are usually data not available from a standard characterisation, were identified as the key unknown parameters affecting leachate production. Furthermore, the applicability of the model to closed landfills was evaluated by simulating different alternative capping systems and by comparing the results with those returned by the Hydrological Evaluation of Landfill Performance (HELP), which is the most worldwide used model for comparative analysis of composite liner systems. Despite the simplified approach of the developed model, simulated values of infiltration and leakage rates through the analysed cover systems were in line with those of HELP. However, it should be highlighted that the developed model provides an assessment of leachate and biogas production only from a quantitative point of view. The leachate and biogas composition was indeed not included in the forecast model, as strongly linked to the type of waste that makes the prediction in a screening phase poorly representative of what could be expected in the field. Hence, for a qualitative analysis of leachate and gas emissions over time, a laboratory methodology including different type of lab-scale tests was applied to a particular waste material. Specifically, the research was focused on mechanically biologically treated (MBT) wastes which, after the introduction of the European Landfill Directive 1999/31/EC (European Commission, 1999) that imposes member states to dispose of in landfills only wastes that have been preliminary subjected to treatment, are becoming the main flow waste landfilled in new Italian facilities. However, due to the relatively recent introduction of the MBT plants within the waste management system, very few data on leachate and gas emissions from MBT waste in landfills are available and, hence, the current knowledge mainly results from laboratory studies. Nevertheless, the assessment of the leaching characteristics of MBT materials and the evaluation of how the environmental conditions may affect the heavy metals mobility are still poorly investigated in literature. To gain deeper insight on the fundamental mechanisms governing the constituents release from MBT wastes, several leaching experiments were performed on MBT samples collected from an Italian MBT plant and the experimental results were modelled to obtain information on the long-term leachate emissions. Namely, a combination of experimental leaching tests were performed on fully-characterized MBT waste samples and the effect of different parameters, mainly pH and liquid to solid ratio (L/S,) on the compounds release was investigated by combining pH static-batch test, pH dependent tests and dynamic up-flow column percolation experiments. The obtained results showed that, even though MBT wastes were characterized by relatively high heavy metals content, only a limited amount was actually soluble and thus bioavailable. Furthermore, the information provided by the different tests highlighted the existence of a strong linear correlation between the release pattern of dissolved organic carbon (DOC) and several metals (Co, Cr, Cu, Ni, V, Zn), suggesting that complexation to DOC is the leaching controlling mechanism of these elements. Thus, combining the results of batch and up-flow column percolation tests, partition coefficients between DOC and metals concentration were derived. These data, coupled with a simplified screening model for DOC release, allowed to get a very good prediction of metal release during the experiments and may provide useful indications for the evaluation of long-term emissions from this type of waste in a landfill disposal scenario. In order to complete the study on the MBT waste environmental behaviour, gas emissions from MBT waste were examined by performing different anaerobic tests. The main purpose of this study was to evaluate the potential gas generation capacity of wastes and to assess possible implications on gas generation resulting from the different environmental conditions expected in the field. To this end, anaerobic batch tests were performed at a wide range of water contents (26-43 %w/w up to 75 %w/w on wet weight) and temperatures (from 20-25 °C up to 55 °C) in order to simulate different landfill management options (dry tomb or bioreactor landfills). In nearly all test conditions, a quite long lag-phase was observed (several months) due to the inhibition effects resulting from high concentrations of volatile fatty acids (VFAs) and ammonia that highlighted a poor stability degree of the analysed material. Furthermore, experimental results showed that the initial waste water content is the key factor limiting the anaerobic biological process. Indeed, when the waste moisture was lower than 32 %w/w the methanogenic microbial activity was completely inhibited. Overall, the obtained results indicated that the operative conditions drastically affect the gas generation from MBT waste, in terms of both gas yield and generation rate. This suggests that particular caution should be paid when using the results of lab-scale tests for the evaluation of long-term behaviour expected in the field, where the boundary conditions change continuously and vary significantly depending on the climate, the landfill operative management strategies in place (e.g. leachate recirculation, waste disposal methods), the hydraulic characteristics of buried waste, the presence and type of temporary and final cover systems.

This dissertation hypothesizes,

"It is possible to design a self-assembled, nanoscale, high-speed, resonance energy transfer device exhibiting non-linear gain with a few molecules."

The report recognizes DNA self-assembly, a relatively inexpensive and a massively parallel fabrication process, as a strong candidate for self-assembled RET systems. It successfully investigates into the design and simulations of a novel sequential self-assembly process employed to realize the goal of creating large, scalable, fully-addressable DNA nanostructure-substrate for future molecular circuitry.

As a pre-cursor to the final device modeling various RET wire designs for interconnecting nanocircuits are presented and their modeling and simulation results are discussed. A chromophore RET system using a biomolecular sensor as a proof-of-concept argument that shows it is possible to model and characterize chromophore systems as a first step towards device modeling is also discussed.

Finally, the thesis report describes in detail the design, modeling, characterization, and fabrication of the Closed-Diffusive Exciton Valve: a self-assembled, nanoscale (area of 17.34 nm2), high-speed (3.5 ps to 6 ps) resonance energy transfer device exhibiting non-linear gain using only 10 molecules, thus confirming the hypothesis. It also recognized improvements that can be made in the future to facilitate better device operation and suggested various applications.

Dissertation

D.Ing. (Electrical and Electronic Engineering)
The non-linear resonant pole (NLRP) inverter is part of the family of soft switching topologies based on resonant phenomena. The sequence of commutation that occurs between the semiconductors of a conventional voltage source inverter is modified through the mechanisms of energy exchange between added passive energy storage components. The NLRP inverter, through its psuedo resonant behaviour (resonant transition), gives rise to zero voltage and zero current turn-on of the switching devices as well as soft turn-off. The switching device voltage stresses are around 1 p.u, while the current stresses are reduced to around 1.3 p.u, by feeding back a portion of the load current. The rms current flowing through the inductor and switches is greatly reduced by driving the inductor into saturation (non-linear mode of operation). The advantages of soft switching, such as high switching frequency which allows greater dynamic response and higher power densities, along with reduced EMI, are achieved with this topology. Detailed analysis at multi- and sub-cycle levels is carried out, resulting in circuit equations and the criteria for commutation success. The commutation boundaries of the inverter are defined and methods discussed on how to extend them. The modulation of the NLRP inverter and some aspects regarding its use as part of both low and high performance induction motor drives are presented.

Pour une exploitation technologique possible en ingénierie électromécanique, nous considérons dans cette thèse l'étude dynamique et la synchronisation des dispositifs électromécaniques non-linéaires décrits par le système couplé constitué de l'oscillateur électrique de Duffing couplé magnétiquement et paramètriquement aux oscillateurs mécaniques linéaires en série et en parallèle. L'intérêt porté sur ces dispositifs électromécaniques revêt un caractère technologique indéniable, dû à sa présence dans plusieurs branches de l'ingénierie électromécanique. Nous étudions le comportement de ces dispositifs à travers les études analytique et numérique, et montrons que les phénomènes non-linéaires tels que: les phénomènes de résonances, d'anti-résonances, d'hystérésis et de multi-stabilité, les oscillations sous et super harmoniques, et le chaos peuvent être utilisé pour améliorer les perfectionnements à des taches industrielles. Le problème de synchronisation des états régulier et chaotique de ces dispositifs est aussi d'un grand intérêt pour des applications en ingénierie électromécanique.

The objective of this thesis is to study of optical effects, arising in the form of non-uniform waveguide structure, complicated refractive index profiles or due to pulse propagation in dense wavelength division multiplexing (DWDM) optical communication systems. These effects are important and critically influence the performance of DWDM optical systems. A comprehensive survey of current literature on optical effects due to nonuniform optical structure and nonlinear optical effects is first done, showing their advantages and disadvantage in optical communication systems. A survey on methods of optical waveguide analysis is also done. The main contribution has been made to three main aspects of the problem : Accurate analysis of uniform/non-uniform optical waveguides with arbitary refractive index profiles Pulse propagation and distortion in DWDM Raman amplification systems. Use of non-uniform FBG to compensate for pulse distortion We study several existing analytical techniques developed so far for analyzing the mode of non-uniform optical waveguide structures. Later, we verify the analytical results by finite element method (FEM). The convergence study is also carried out. A new computational technique is proposed modifying the finite element method to analyze complex refractive index profiles required for the analysis, namely single mode step index profile, multi clad fiber, W -profile, chirp profile etc. An accuracy of 10−4 in the calculation of propagation constant/eigen-value is demonstrated. Dispersion characteristics of optical fibers w.r.t. different profile parameters is evaluated. A modification to scalar BPM is proposed and applied to study the effects of inhomogeneities along the propagation direction. The applicability and accuracy of the method is tested using integrated optic waveguide devices, namely, graded index slab waveguide. The proposed BPM uses Fourier decomposition of the transverse field. Coupled mode theory (CMT) of optical waveguides in non-homogeneous optical medium is applied to study the interaction of lightwaves propagation together such as in a DWDM system. The BPM results is verified by CMT. The inhomogeneous waveguide theory is extended to study pulse propagation in DWDM optical communication system. Nonlinear optical effects are an important aspects of DWDM systems with fiber Raman amplifier. Finite difference time domain (FDTD) method is necessary to study these nonlinear optical effects as other conventional methods are not suitable here. Here, we discuss DWDM optical communication systems due to nonlinearity in the form of SRS effect. In case of FRA, we study the various kinds of fiber profile design parameters, for the purpose to achieve and extend the flat gain bandwidth over the EDFA window. We also propose and study, a new bi-directional optical fiber transmission scheme with various constraints, using Raman amplification process with and without pump depletion. Our scheme, provides an advantage like high SNR, low pump induced noise, for long-haul communication link. We find that, there is a quite significant crosstalk and power coupling among the dense DWDM channels but earlier discussed BPM fails to account for possible interference effects among the channels. To reduce the harmful nonlinear optical effects like four wave mixing (FWM), we need to deploy a high chromatic dispersion fiber, which will ultimately lead to high pulse walk-off rate among the DWDM channels; hence for high bit rate long haul systems, walk-off effect can not be ignored. Application of FDTD provided an improved insight into the effect of GVD on stimulated Raman scattering crosstalk than different modulation techniques and line codes. It is shown through analysis that pulse walk-off phenomena may distort the data asymmetrically; especially for case of wide-band DWDM transmission system. Hence, the pulse walk-off effect should be considered in future systems containing optical amplifier. It is shown, that large walk-off rate may reduce the crosstalk among DWDM channels but tends to increase the asymmetric pulse distortion. Data may lose due to high walk-off effect. We also investigate channel addition/removal process in DWDM fiber Raman amplifier. We also demonstrate that the pulse walk-off effect tends to lead significantly to positive chirp for higher frequency channels. This feature can be exploited to overcome the chromatic dispersion effects in DWDM transmission systems. Pulse walk-off induced chirp, can be compensated by using the nonuniform fiber Bragg grating (NUFBG). The CMT due to periodic perturbation of the circular cylindrical waveguide structures is applied here. Here, we discuss the function of fiber Bragg grating as a transmission versus reflecting grating filter. We also discuss, FBG application to gain flattening of an EDFA window as well as how the group velocity dispersion (GVD) will be affected with bandwidth and coupling coefficient. We develop a new analytical technique to estimate the bandwidth of FBG based optical system. Finally, we investigate the dispersion compensation properties, pulse distortion, peak reflectivity analysis in uniform/non-uniform FBG due to an uniform/non-uniform incoming signal. More complicated refractive index profile can significantly reduce the GVD as well as side lobes intensity. Dispersion characteristic due to an arbitrary refractive index profile is discussed in details for the case of non-uniform FBG. Thus, we concluded that wide band DWDM optical communication system need to closely take into account various inhomogeneities and nonlinearities of optical fibers w.r.t. wave and pulse propagation.

The objective of this thesis is to study of optical effects, arising in the form of non-uniform waveguide structure, complicated refractive index profiles or due to pulse propagation in dense wavelength division multiplexing (DWDM) optical communication systems. These effects are important and critically influence the performance of DWDM optical systems. A comprehensive survey of current literature on optical effects due to nonuniform optical structure and nonlinear optical effects is first done, showing their advantages and disadvantage in optical communication systems. A survey on methods of optical waveguide analysis is also done. The main contribution has been made to three main aspects of the problem : Accurate analysis of uniform/non-uniform optical waveguides with arbitary refractive index profiles Pulse propagation and distortion in DWDM Raman amplification systems. Use of non-uniform FBG to compensate for pulse distortion We study several existing analytical techniques developed so far for analyzing the mode of non-uniform optical waveguide structures. Later, we verify the analytical results by finite element method (FEM). The convergence study is also carried out. A new computational technique is proposed modifying the finite element method to analyze complex refractive index profiles required for the analysis, namely single mode step index profile, multi clad fiber, W -profile, chirp profile etc. An accuracy of 10−4 in the calculation of propagation constant/eigen-value is demonstrated. Dispersion characteristics of optical fibers w.r.t. different profile parameters is evaluated. A modification to scalar BPM is proposed and applied to study the effects of inhomogeneities along the propagation direction. The applicability and accuracy of the method is tested using integrated optic waveguide devices, namely, graded index slab waveguide. The proposed BPM uses Fourier decomposition of the transverse field. Coupled mode theory (CMT) of optical waveguides in non-homogeneous optical medium is applied to study the interaction of lightwaves propagation together such as in a DWDM system. The BPM results is verified by CMT. The inhomogeneous waveguide theory is extended to study pulse propagation in DWDM optical communication system. Nonlinear optical effects are an important aspects of DWDM systems with fiber Raman amplifier. Finite difference time domain (FDTD) method is necessary to study these nonlinear optical effects as other conventional methods are not suitable here. Here, we discuss DWDM optical communication systems due to nonlinearity in the form of SRS effect. In case of FRA, we study the various kinds of fiber profile design parameters, for the purpose to achieve and extend the flat gain bandwidth over the EDFA window. We also propose and study, a new bi-directional optical fiber transmission scheme with various constraints, using Raman amplification process with and without pump depletion. Our scheme, provides an advantage like high SNR, low pump induced noise, for long-haul communication link. We find that, there is a quite significant crosstalk and power coupling among the dense DWDM channels but earlier discussed BPM fails to account for possible interference effects among the channels. To reduce the harmful nonlinear optical effects like four wave mixing (FWM), we need to deploy a high chromatic dispersion fiber, which will ultimately lead to high pulse walk-off rate among the DWDM channels; hence for high bit rate long haul systems, walk-off effect can not be ignored. Application of FDTD provided an improved insight into the effect of GVD on stimulated Raman scattering crosstalk than different modulation techniques and line codes. It is shown through analysis that pulse walk-off phenomena may distort the data asymmetrically; especially for case of wide-band DWDM transmission system. Hence, the pulse walk-off effect should be considered in future systems containing optical amplifier. It is shown, that large walk-off rate may reduce the crosstalk among DWDM channels but tends to increase the asymmetric pulse distortion. Data may lose due to high walk-off effect. We also investigate channel addition/removal process in DWDM fiber Raman amplifier. We also demonstrate that the pulse walk-off effect tends to lead significantly to positive chirp for higher frequency channels. This feature can be exploited to overcome the chromatic dispersion effects in DWDM transmission systems. Pulse walk-off induced chirp, can be compensated by using the nonuniform fiber Bragg grating (NUFBG). The CMT due to periodic perturbation of the circular cylindrical waveguide structures is applied here. Here, we discuss the function of fiber Bragg grating as a transmission versus reflecting grating filter. We also discuss, FBG application to gain flattening of an EDFA window as well as how the group velocity dispersion (GVD) will be affected with bandwidth and coupling coefficient. We develop a new analytical technique to estimate the bandwidth of FBG based optical system. Finally, we investigate the dispersion compensation properties, pulse distortion, peak reflectivity analysis in uniform/non-uniform FBG due to an uniform/non-uniform incoming signal. More complicated refractive index profile can significantly reduce the GVD as well as side lobes intensity. Dispersion characteristic due to an arbitrary refractive index profile is discussed in details for the case of non-uniform FBG. Thus, we concluded that wide band DWDM optical communication system need to closely take into account various inhomogeneities and nonlinearities of optical fibers w.r.t. wave and pulse propagation.

碩士
國立中正大學
化學暨生物化學研究所
99
Microfluidic systems have various bio-analytical advantages such as minimum simple and reagent consumption, reduced analysis time, and assay cost effectiveness, as well as less development efforts to integrate into portable equipments. However, in biomedical applications because assayed sample often contains only ultra-trace amount of analytes, without pretreatment steps to concentrate sample, quantitative determination is problematic. Therefore there remains a need to develop miniaturized concentration unit in microfluidic device. Our previous work using an ion exchange resin granule to concentrate acidic fluorescence dyes when this resin granule is placed in a moderate electric field (100 V/cm). The concentration factor of dyes using this device is enomorous 10^5 to 10^6. In this study we firstly study the effects of dye dissociation in concentration factor to conclude that the concentration factor reaches the maximum when the concentrated dye becomes fully dissociated at the pH condition of pKa + 2 or higher. Similarly when protein is trapped using this granule device, protein has higher concentration factor at pH condition to obtain higher charge state. In other words, the suitable pH value to concentrate each protein is dependent on protein isoelectric point, pI value. When buffer pH is adjusted, selective protein trapping can be accomplished. We use fluorescein-tagged BSA and Texas red-tagged avidin to demonstrate selective trapping of these two proteins at different pH conditions. The red emission of tagged avidin cannot be seen at pH 8.01 while clear concentration observed with the intensified green emission of labeled BSA. Under this buffer basicity at pH 8.01, only BSA of which pI is 4.8 is highly charged but avidin of which pI is 10.5 is almost neutral. When buffer is adjusted to pH 11 to fully protonated both proteins, the emission of both tagged fluorescence labels of BSA and advidin is clearly intensified to confirm successful concentration effects. Inevitable long mixing time in micro-channel due to fluid irrotationality in small scale conduits also constrains the utility of micro-fluidic devices. Our group previously has developed a miniaturized mixing device applying external high frequency AC field to achieve highly efficient mixing. We use the dielectric materials to fabricate micro-mixing reservoir with the sharp curvature at the corners, and we apply the high-frequency ac electric field to generate the nonlinear vortex electro-osmotic flow via building up induced charges when the field lines penetrate through the sharp corners. This device has been proven to speed up the contacts of glucose with the glucose oxidase-entrapped sol-gel particles to accelerate the formation of hydrogen peroxide. Under the mixing acceleration, more hydrogen peroxide products react with luminol and ferric ions than the amount of hydrogen peroxide produced without mixing. As a consequence, chemiluminescence emitted with lumino reactions becomes more intense under mixing. In this study we conduct preliminary studies using this device to develop chemiluminescence-based miniaturized enzymatic assays to determine glucose.

Ogni azienda che si riconosca socialmente responsabile deve occuparsi dello sviluppo delle carriere dei propri dipendenti da due punti di vista: quello individuale e personale e quello professionale. La carriera all’interno di un’azienda coinvolge, infatti, la persona in quanto individuo con un proprio carattere e una precisa identità e la persona in quanto lavoratore con un bagaglio specifico di conoscenze e competenze. L’azienda ha, quindi, il compito di promuovere carriere professionalmente stimolanti che si sviluppino in linea con i suoi stessi valori, la sua visione e la sua missione. Nel panorama moderno, aziende che sviluppano la propria idea di business nel rispetto dei lavoratori proponendo loro un percorso di crescita, si mostrano senza dubbio lungimiranti. Un tale approccio, però, non basta a far sì che vengano definite socialmente responsabili. I fattori della Responsabilità Sociale d’Impresa sono infatti numerosi e, ad oggi, uno dei problemi principali da affrontare è quello del progressivo invecchiamento della popolazione. Dal momento che la forza lavoro mondiale sta invecchiando e che si sta rispondendo al problema spostando la linea del pensionamento, tutte le aziende sono obbligate a mantenere le persone il più a lungo possibile attive e motivate a lavoro. L’età è spesso visto come un fattore di diversità e di discriminazione, ma nello sviluppare la mia argomentazione, cercherò di dimostrare che una politica del lavoro che supporti l’idea dell’invecchiamento attivo può trasformare questo fattore da limite in opportunità. Il rispetto degli esseri umani, a prescindere dalle differenze legate all’età, dovrebbe essere uno dei valori fondanti di ogni impresa. Nel primo capitolo della tesi, svilupperò il tema della dignità umana così come è stato concepito a partire dalla filosofia greca fino alla modernità. La dignità intesa come valore ontologico, legato all’essenza dell’uomo, diventerà con Kant il fattore di uguaglianza tra tutti gli esseri viventi, la giustificazione del rispetto reciproco. Il concetto di dignità verrà, poi, definito nel secondo capitolo come il principale valore che deve ispirare l’azione sociale delle imprese, come l’elemento che garantisce il rispetto di ogni dipendente che prima ancora di essere un lavoratore è un essere umano. La dignità è ciò che rende l’essere umano degno di essere considerato un fine in se stesso piuttosto che un mezzo per il raggiungimento di un fine esterno. Nell’era della globalizzazione, dove il denaro è il valore principale, gli esseri umani rischiano di diventare un mezzo al servizio dell’economia. A questo punto, il rispetto della dignità deve divenire il fondamento di un ambiente di lavoro che promuove la crescita e la fioritura dell’essere umano. Nel secondo capitolo cercherò quindi di dimostrare come l’idea di dignità possa promuovere un management “umanistico” centrato sul rispetto dell’essere umano. Un’impresa socialmente responsabile può promuovere il rispetto di ogni lavoratore se fa propri i valori di dignità e uguaglianza. Attraverso la teoria dello Humanistic Management che veicola tali valori, il lavoro diventa un luogo in cui l’uomo può esprimere se stesso, la sua identità, le sue conoscenze e competenze. Inoltre, dal momento che la popolazione sta invecchiando, le aziende devono farsi carico della forza lavoro più anziana, come è emerso sopra. A questo punto, nel terzo capitolo, il concetto della Responsabilità Sociale d’Impresa sarà analizzato nel suo legame con i temi dell’invecchiamento attivo e della diversità sul posto di lavoro. Conosciamo diverse ragioni di differenza a lavoro: genere, cultura, etnia, competenze, ma qui ci concentreremo sul fattore età. È naturale che i lavoratori anziani abbiano un’idea di lavoro diversa da quella dei giovani e che le loro abilità siano differenti. Ma questa diversità non deve essere valutata come migliore o peggiore: essa dipende da fattori che analizzeremo e che l’impresa socialmente responsabile conosce e valorizza per creare un ambiente di lavoro stimolante e collaborativo, eliminando possibili conflitti intergenerazionali. Alcune delle teorie che permettono di raggiungere tali obiettivi sono il Diversity Management e l’Age Management: ogni impresa può promuovere pratiche per valorizzare gli anziani, permettendo loro di rimanere più a lungo attivi e proattivi a lavoro e di condividere le proprie conoscenze e competenze. L’ultimo capitolo della tesi si concentrerà su un caso di azienda italiana che ha sviluppato uno strumento di valorizzazione di collaboratori over 65. Sto parlando della Loccioni, presso cui ho svolto la ricerca applicata e che promuove il progetto Silverzone, un network di persone in pensione che hanno conosciuto l’azienda nel corso della loro carriera e che continuano a collaborare con essa ancora dopo il pensionamento. Per capire l’impatto qualitativo e quantitativo che il progetto ha sull’azienda, ho portato avanti un’analisi qualitativa dei dati ottenuti grazie a due tipi di questionari. Il primo ha visto il coinvolgimento dei 16 managers della Loccioni a cui sono state sottoposte le seguenti domande: 1. Chi sono i silver nella tua area di business? Quali i progetti in cui essi sono coinvolti? 2. Qual è il valore del loro supporto per l’azienda? E, allo stesso tempo, quali sono le difficoltà che possono incontrarsi durante queste collaborazioni? 3. Qual è la frequenza degli incontri con i silver? 4. Perché l’azienda ha bisogno di questo network? Successivamente, ho sottoposto un altro questionario agli 81 silver della rete. Di seguito i dettagli: 1. Qual è il tuo nome? 2. Dove sei nato? 3. Dove vivi? 4. Qual è stato il tuo percorso formativo? 5. Qual è stata la tua carriera professionale? 6. Come e con chi è avvenuto il primo contatto Loccioni? 7. Come sei venuto a conoscenza del progetto Silverzone? 8. Con quali dei collaboratori Loccioni stai lavorando? 9. In quali progetti sei coinvolto? 10. Potresti descrivere il progetto in tre parole? 11. Che significato ha per te fare parte di questa rete? 12. Nella tua opinione, come deve essere il Silver? 13. Che tipo di relazioni hai con i collaboratori Loccioni? 14. Quali dimensioni umane (dono, relazione, comunità, rispetto) e professionali (innovazione, tecnologia, rete) emergono lavorando in questo progetto? Il progetto Silverzone è sicuramente una buona pratica di Age Management per mantenere più a lungo attivi i lavoratori over 65. I progetti in cui i Silver sono coinvolti hanno un importante impatto economico sull’impresa, in termini di investimento ma anche di guadagno. Ad ogni modo, qui la necessità di fare profitto, stando a quanto è emerso dai risultati delle interviste, è subordinata al più alto valore del rispetto dei bisogni umani che diventa garante di un posto di lavoro comfortable, dove si riesce a stringere relazioni piacevoli, collaborative e produttive.