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This thesis investigated the potential advantages and disadvantages of high performance structures by comparing the financial and environmental impacts of a performance based four-story office building to one designed to meet minimum code-level requirements. To generate a comparison, the lateral system of a four-story structure utilizing buckling restrained braced frames was designed to meet code-level requirements per the American Society of Civil Engineers’ Minimum Design Loads for Buildings and Other Structures (ASCE 7-05) and again to meet the immediate occupancy criteria defined by ASCE 41-06 Seismic Rehabilitation of Existing Buildings. The following was then performed: Test the structural performance of both buildings using simulated code-level and maximum considered earthquakes Develop construction costs of both structures using RSMeans Square Foot Cost and Construction Cost Data Determine the financial benefit associated with the upgraded structure by subjecting both structures to a suite of earthquakes Calculate the carbon footprint generated during each building’s construction. The final project costs for the code level and immediate occupancy structures were $27.43 million and $27.93 million respectively, resulting in an upgrade cost of $500,000 or roughly 1.8% of the overall project cost. The upgrade cost was then input in FEMA’s Benefit-Cost Analysis, where it found the upgrade cost resulted in an annual savings ranging from $43,000 to $98,000 over the building’s 50-year life cycle. The carbon footprints were generated using BuildingScope, which relies on volumetric quantities of construction materials. The final models resulted in a carbon footprint of 7890 CO2 eq and 7940 CO2 eq for the code level and immediate occupancy structures respectively, showing favor for the structure utilizing fewer materials. Although the additional materials used in the immediate occupancy structure resulted in a slightly larger carbon footprint, the added capacity will decrease damages, resulting in an overall reduction of energy generated during the building’s life cycle.

The rise of organometal halide perovskite materials with extremely intriguing properties have opened a new horizon in the design of high speed and low price optoelectronic devices. The bandgap in the crystalline structure of these materials can be easily tuned for various applications and their dominant non-excitonic dynamics eliminate the requirement of a bulk or heterostructure for charge carrier separation. These unique properties increase the photo-sensitivity of perovskite-based optoelectronics and provide them with a low time constant, resulting in high precision fast devices. Realization of perovskite-based devices translates directly to inexpensive and simplified architectures of optoelectronic systems. In perovskite-based devices, costly silicon or wide bandgap semiconductor fabrication technology is largely replaced by solution processable methods. Their bandgap tunability allows the reduction of the required optical accessories and interconnects in optoelectronic components. For instance, a tuned perovskite-based detector can substitute a narrowband detecting system consisting of a conventional detector and its required optical accessories such as lenses and color filters. These properties of perovskite-based devices lead to the realization of inexpensive, low power and high-performance optoelectronic systems. In this work, the design of a narrowband, low noise, high performance and stable photodetector based on organic-inorganic hybrid perovskite structure is proposed. The full width at half maximum (FWHM) of the device would be in the nanometer range. The response of the device can be tuned using either different ratios of the lead salts or synthetic dyes (macromolecules) in the crystalline structure for color discrimination in machine vision and imaging applications. Non-excitonic photocarrier generation, tunability of the optical bandgap and low voltage requirements for charge carrier generation are the keys to the utility of this optoelectronic device. The goals of this project were to identify the required functional materials (lead salts and synthetic dyes based on their molecular structures) and optimize their performance; the study of their effect on the charge collection narrowing mechanism and bandwidth specifications defined for detectivity, linear dynamic range (LDR) and photoresponse speed. To achieve these goals, it was proposed to study the light detection properties as well as spectroscopic and semiconductor parameter characteristics of fabricated devices. The design considerations of such devices are versatile and may be modulated for different applications.

Η ευαισθησία των συστημάτων είναι ένα σημαντικό θέμα της Θεωρίας Συστημάτων, το οποίο καλύπτεται σε εισαγωγικό επίπεδο με αυτή την εργασία. Η ευαισθησία αφορά τις διαφορές ανάμεσα στο πραγματικό σύστημα και στο μαθηματικό μοντέλο: αν κάποιες παράμετροι διαφέρουν αρκετά ανάμεσα στο πραγματικό σύστημα και στο μαθηματικό μοντέλο και η συμπεριφορά του συστήματος εξαρτάται κατά μεγάλο βαθμό από αυτές τις παραμέτρους, τότε η χρησιμότητα του μαθηματικού μοντέλου θα είναι πολύ μικρή αν δεν γνωρίζουμε ταυτόχρονα την παραμετρική ευαισθησία του συστήματος, δηλαδή την επίδραση των μεταβολών των παραμέτρων πάνω στην δυναμική συμπεριφορά του συστήματος. Βασικό ρόλο παίζει η προσομοίωση των εξισώσεων ευαισθησίας κατάστασης. Καθορίζουμε αρχικά τις εξισώσεις ευαισθησίας κατάστασης για παραμέτρους τύπου α και δείχνουμε ότι οι συναρτήσεις ευαισθησίας κατάστασης ενός συνεχούς συστήματος με χρονικά αμετάβλητες παραμέτρους καθορίζονται πάντα από ένα γραμμικό σύστημα διαφορικών εξισώσεων με μηδενικές αρχικές συνθήκες. Στην συνέχεια θα επεκταθούμε και στην εύρεση των συναρτήσεων ευαισθησίας κατάστασης για την περίπτωση που έχουμε παραμέτρους τύπου β και θα δούμε ότι και εδώ οι εξισώσεις ευαισθησίας κατάστασης είναι πάντα γραμμικές και οι αρχικές συνθήκες είναι ή μηδέν ή μονάδα. Στη συνέχεια προχωράμε στην εύρεση των συναρτήσεων ευαισθησίας κατάστασης για την περίπτωση που έχουμε παραμέτρους τύπου λ, αφού δούμε πρώτα το πότε μπορούμε να χρησιμοποιήσουμε το μειωμένο ονομαστικό μοντέλο. Επί πλέον, εξετάζουμε εν συντομία και τον καθορισμό των εξισώσεων ευαισθησίας εξόδου. Για την περίπτωση που έχουμε να μελετήσουμε και να συγκρίνουμε την παραμετρική ευαισθησία συστημάτων ανοικτού και κλειστού βρόχου καθώς επίσης και στην σύνθεση συστημάτων "αναίσθητων" σε παραμετρικές μεταβολές, είναι αναγκαίο να έχουμε έναν ορισμό ευαισθησίας που να είναι ανεξάρτητος από την μορφή του σήματος εισόδου, αλλά να εξαρτάται μόνο από την δομή του συστήματος. Αυτή η απαίτηση ικανοποιείται με τους ορισμούς ευαισθησίας στο πεδίο συχνότητας, οι οποίοι βασίζονται στην συνάρτηση μεταφοράς ή στον πίνακα μεταφοράς του συστήματος. Εξετάζουμε τη συνάρτηση ευαισθησίας του Bode, τη συνάρτηση ευαισθησίας του Horowitz και τη συγκριτική συνάρτηση ευαισθησίας των Perkins και Cruz. Η τελευταία μπορεί να γενικευθεί και σε μη γραμμικά, χρονικά μεταβαλλόμενα συστήματα. / The sensitivity of systems is an important theme of Systems Theory, which is covered to an introductory level in this work. The sensitivity concerns differences between the real system and the mathematical model: if some parameters are quite different between the real system and the mathematical model and the behavior of the system depends strongly on these parameters, the utility of the mathematical model will be very little if we do not know both the parametric sensitivity of the system, i.e. the effect of changes in parameters on the dynamic behavior of the system. A key role is played by simulating the state sensitivity equations. First we determine the state of sensitivity equations for parameters of type a and show that the state of sensitivity functions of a continuous system with time invariant parameters are always determined by a linear system of differential equations with zero initial conditions. Then we expand and find the state sensitivity functions for the case where we have parameters of type b and we see that here the situation sensitivity equations are always linear and the initial conditions are zero. Then we move on finding state sensitivity functions for the type lambda parameters, after we look when the reduced nominal model can use. Moreover, we look briefly at the output sensitivity equations. In case we have to study and compare the parametric sensitivity of open and closed-loop systems as well as in the synthesis systems "unconscious" to parametric changes, it is necessary to have a definition of sensitivity that is independent of the input signal format, but can depend only on the structure of the system. This requirement is satisfied by the definitions of sensitivity in the frequency domain, which are based on the transfer function or the system operator panel. We examine the sensitivity function of Bode, the sensitivity function of Horowitz and the comparative context sensitivity of Perkins and Cruz. The latter can be generalized to nonlinear, time-varying systems.

In this dissertation we proposed two generalizations of the Second-Order Least Squares (SLS) approach in two popular dynamic econometrics models. The first one is the regression model with time varying nonlinear mean function and autoregressive conditionally heteroskedastic (ARCH) disturbances. The second one is a linear dynamic panel data model. We used a semiparametric framework in both models where the SLS approach is based only on the first two conditional moments of response variable given the explanatory variables. There is no need to specify the distribution of the error components in both models. For the ARCH model under the assumption of strong-mixing process with finite moments of some order, we established the strong consistency and asymptotic normality of the SLS estimator. It is shown that the optimal SLS estimator, which makes use of the additional information inherent in the conditional skewness and kurtosis of the process, is superior to the commonly used quasi-MLE, and the efficiency gain is significant when the underlying distribution is asymmetric. Moreover, our large scale simulation studies showed that the optimal SLSE behaves better than the corresponding estimating function estimator in finite sample situation. The practical usefulness of the optimal SLSE was tested by an empirical example on the U.K. Inflation. For the linear dynamic panel data model, we showed that the SLS estimator is consistent and asymptotically normal for large N and finite T under fairly general regularity conditions. Moreover, we showed that the optimal SLS estimator reaches a semiparametric efficiency bound. A specification test was developed for the first time to be used whenever the SLS is applied to real data. Our Monte Carlo simulations showed that the optimal SLS estimator performs satisfactorily in finite sample situations compared to the first-differenced GMM and the random effects pseudo ML estimators. The results apply under stationary/nonstationary process and wih/out exogenous regressors. The performance of the optimal SLS is robust under near-unit root case. Finally, the practical usefulness of the optimal SLSE was examined by an empirical study on the U.S. airfares.

abstract: Lower-limb wearable assistive robots could alter the users gait kinematics by inputting external power, which can be interpreted as mechanical perturbation to subject normal gait. The change in kinematics may affect the dynamic stability. This work attempts to understand the effects of different physical assistance from these robots on the gait dynamic stability. A knee exoskeleton and ankle assistive device (Robotic Shoe) are developed and used to provide walking assistance. The knee exoskeleton provides personalized knee joint assistive torque during the stance phase. The robotic shoe is a light-weighted mechanism that can store the potential energy at heel strike and release it by using an active locking mechanism at the terminal stance phase to provide push-up ankle torque and assist the toe-off. Lower-limb Kinematic time series data are collected for subjects wearing these devices in the passive and active mode. The changes of kinematics with and without these devices on lower-limb motion are first studied. Orbital stability, as one of the commonly used measure to quantify gait stability through calculating Floquet Multipliers (FM), is employed to asses the effects of these wearable devices on gait stability. It is shown that wearing the passive knee exoskeleton causes less orbitally stable gait for users, while the knee joint active assistance improves the orbital stability compared to passive mode. The robotic shoe only affects the targeted joint (right ankle) kinematics, and wearing the passive mechanism significantly increases the ankle joint FM values, which indicates less walking orbital stability. More analysis is done on a mechanically perturbed walking public data set, to show that orbital stability can quantify the effects of external mechanical perturbation on gait dynamic stability. This method can further be used as a control design tool to ensure gait stability for users of lower-limb assistive devices. / Dissertation/Thesis / Masters Thesis Mechanical Engineering 2018

因有數學式子，所以無法編輯。 / 因有數學式子，所以無法編輯。

O trabalho trata da formulação e implementação numérica de um modelo de dano para o concreto. O objetivo é o de reproduzir laços de histerese observados experimentalmente em diagramas de tensão-deformação uniaxiais quando, a partir de um certo nível de solicitação, e dano correspondente, passam-se a realizar ciclos de descarregamento e recarregamento. O modelo propõe que os laços de histerese resultam da dissipação conjunta decorrente do dano evolutivo e do fenômeno de fricção interna nas faces das fissuras. O fenômeno de fricção interna está relacionado à suposição de que as fissuras não se abrem simplesmente por separação formando faces com superfícies lisas, mas tendem a combinar modos de separação e deslizamento segundo superfícies com uma certa rugosidade. O deslizamento entre as faces das fissuras dá origem a uma deformação por escorregamento, assumida como responsável por um comportamento plástico com encruamento cinemático não-linear. A abordagem termodinâmica considerada no sentido de contemplar a danificação e a fricção interna leva à dedução de que a tensão total num ponto do meio com dano resulta dividida em uma parcela dita tensão elasto-danificada e em uma outra denominada tensão de escorregamento, também dependente do nível de danificação da estrutura. Dois tipos básicos de aplicações são realizadas: as primeiras visam avaliar a influência das variáveis de estado e dos parâmetros do material na forma dos diagramas de tensão-deformação. As outras aplicações são dedicadas à utilização do modelo na análise do comportamento dinâmico de uma viga em concreto armado submetida à vibração forçada. Destaca-se o efeito dos laços de histerese sobre o amortecimento estrutural. Mostra-se que a utilização deste modelo de dano leva à geração de um amortecimento estrutural que com os modelos de dano usuais somente poderia ser obtido a partir da utilização do modelo de amortecimento de Rayleigh, por exemplo, na equação do movimento. / This work deals with numerical formulation and implementation of a damage model to concrete. The aim is to reproduce hysteresis loops observed experimentally in uniaxial stress-strain diagram when cycles of unloading and reloading are produced. The model proposes that the hysteresis loops are due to the coupling between the dissipation of damage process and the internal friction phenomenon between the faces of crack lips. The phenomenon of internal friction is related to the supposition that the crack doesn\'t open itself by separation mode creating plane lips, but there is a tendency to combine opening and sliding modes across irregular surfaces. The sliding between the crack surfaces generates a sliding strain, which is assumed as responsible by a plastic behaviour with non-linear kinematics hardening. The thermodynamic approach considering damage and internal friction leads to the deduction that the total stress at a point is composted by one component named elasto-damage stress and another named sliding stress, both dependent of the structure damage level. Two basic kinds of simulation are performed: the first one aims to evaluate the influence of the state variables and the material parameters over the stress-strain diagrams. The following simulations are dedicated to the use of the model in dynamic analysis of a reinforced concrete beam subjected to vibration. It is emphasized the effect of the structural damping from hysteresis loops. It is showed that the present damage model generates structural damping that could only be obtained with conventional damage model by using the Rayleigh damping approach in the equation of motion.

This master's thesis deals with the control design method called Non-linear Dynamic Inversion (NDI) and how it can be applied to Unmanned Aerial Vehicles (UAVs). In this thesis, simulations are conducted using a model for the unmanned aerial vehicle SHARC (Swedish Highly Advanced Research Configuration), which Saab AB is developing. The idea with NDI is to cancel the non-linear dynamics and then the system can be controlled as a linear system. This design method needs much information about the system, or the output will not be as desired. Since it is impossible to know the exact mathematical model of a system, some kind of robust control theory is needed. In this thesis integral action is used. A problem with NDI is that the mathematical model of a system is often very complex, which means that the controller also will be complex. Therefore, a controller that uses pure NDI is only discussed, and the simulations are instead based on approximations that use a cascaded NDI. Two such methods are investigated. One that uses much information from aerodata tables, and one that uses the derivatives of some measured outputs. Both methods generate satisfying results. The outputs from the second method are more oscillatory but the method is found to be more robust. If the signals are noisy, indications are that method one will be better.