BESSA, Vagner Henrique Loiola. Osciladores log-periódicos e tipo Caldirola-Kanai. 2012. 66 f. Dissertação (Mestrado em Física) - Programa de Pós-Graduação em Física, Departamento de Física, Centro de Ciências, Universidade Federal do Ceará, Fortaleza, 2012. / Submitted by Edvander Pires (edvanderpires@gmail.com) on 2015-10-19T18:23:14Z No. of bitstreams: 1 2012_dis_vhlbessa.pdf: 26350485 bytes, checksum: 4eb844c05187fb66d3b274a9f8d1b0ed (MD5) / Approved for entry into archive by Edvander Pires(edvanderpires@gmail.com) on 2015-10-20T20:53:49Z (GMT) No. of bitstreams: 1 2012_dis_vhlbessa.pdf: 26350485 bytes, checksum: 4eb844c05187fb66d3b274a9f8d1b0ed (MD5) / Made available in DSpace on 2015-10-20T20:53:49Z (GMT). No. of bitstreams: 1 2012_dis_vhlbessa.pdf: 26350485 bytes, checksum: 4eb844c05187fb66d3b274a9f8d1b0ed (MD5) Previous issue date: 2012 / In this work we present the classical and quantum solutions of two classes of time-dependent harmonic oscillators, namely: (a) the log-periodic and (b) the Caldirola-Kanai-type oscillators. For class (a) we study the following oscillators: (I) $m(t)=m_0frac{t}{t_0}$, (II) $m(t)=m_0$ and (III) $m(t)=m_0ajust{frac{t}{t_0}}^2$. In all three cases $omega(t)=omega_0frac{t_0}{t}$. For class (b) we study the Caldirola-Kanai oscillator (IV)where $omega(t)=omega_0$ and $m(t)=m_0 ext{exp}ajust{gamma t}$ and the oscillator with $omega(t)=omega_0$ and $m(t)=m_0ajust{1+frac{t}{t_0}}^alpha$, for $alpha=2$ (V) and $alpha=4$ (VI). To obtain the classical solution for each oscillator we solve the respective equation of motion and analyze the behavior of $q(t)$, $p(t)$ as well as the phase diagram $q(t)$ vs $p(t)$. To obtain the quantum solutions we use a unitary transformation and the Lewis and Riesenfeld quantum invariant method. The wave functions obtained are written in terms of a function ($ ho$) which is solution of the Milne-Pinney equation. Futhermore, for each system we solve the respective Milne-Pinney equation and discuss how the uncertainty product evolves with time. / Nesse trabalho apresentamos as soluções clássicas e quânticas de duas classes de osciladores harmônicos dependentes de tempo, a saber: (a) o oscilador log-periódico e (b) o oscilador tipo Caldirola-Kanai. Para a classe (a) estudamos os seguintes osciladores: (I) $m(t)=m_0frac{t}{t_0}$, (II) $m(t)=m_0$ e (III) $m(t)=m_0ajust{frac{t}{t_0}}^2$. Nesses três casos $omega(t)=omega_0frac{t_0}{t}$. Para a classe (b) estudamos o oscilador (IV) de Caldirola-Kanai onde $omega(t)=omega_0$ e $m(t)=m_0 ext{Exp}ajust{gamma t}$ e osciladores com $omega(t)=omega_0$ e $m(t)=m_0ajust{1+frac{t}{t_0}}^alpha$, para (V) $alpha=2$ e (VI) $alpha=4$. Para obter as soluções clássicas de cada oscilador resolvemos suas respectivas equações de movimento e analisamos o comportamento de $q(t)$, $p(t)$ assim como do diagrama de fase $q(t)$ vs $p(t)$. Para obter as soluções quânticas usamos uma transformação unitária e o método dos invariantes quânticos de Lewis e Riesenfeld. A função de onda obtida é escrita em termos de uma função $ ho$, que é solução da equação de Milne-Pinney. Ainda, para cada sistema resolvemos a respectiva equação de Milne-Pinney e discutimos como o produto da incerteza evolui no tempo.

MACEDO, Diego Ximenes. Osciladores harmônicos acoplados dependentes do tempo. 2012. 65 f. Dissertação (Mestrado em Física) - Programa de Pós-Graduação em Física, Departamento de Física, Centro de Ciências, Universidade Federal do Ceará, Fortaleza, 2012. / Submitted by Edvander Pires (edvanderpires@gmail.com) on 2015-10-16T21:48:15Z No. of bitstreams: 1 2012_dis_dxmacedo.pdf: 1228459 bytes, checksum: 6d71730075dc0a642cfe80de6f3c9b6d (MD5) / Approved for entry into archive by Fabíola Bezerra(fabbezerra@yahoo.com.br) on 2016-01-20T14:38:07Z (GMT) No. of bitstreams: 1 2012_dis_dxmacedo.pdf: 1228459 bytes, checksum: 6d71730075dc0a642cfe80de6f3c9b6d (MD5) / Made available in DSpace on 2016-01-20T14:38:07Z (GMT). No. of bitstreams: 1 2012_dis_dxmacedo.pdf: 1228459 bytes, checksum: 6d71730075dc0a642cfe80de6f3c9b6d (MD5) Previous issue date: 2012 / In this work we present the classical and quantum solutions of time-dependent coupled harmonic oscillators. In these systems the masses, frequencies and coupling parameter (k) are functions of time. Four systems are investigated. To obtain the classical solutions we use a coordinate and momentum transformations along with a canonical transformation to write the original Hamiltonian as the sum of two Hamiltonians of uncoupled harmonic oscillators with modified time-dependent frequencies and unitary masses. We find the analytical expression for position and velocity of each oscillator of the systems. To obtain the exact quantum solutions we use a unitary transformation and the Lewis and Riesenfeld invariant method. The wave functions obtained are written in terms of a c-number quantity () which is solution of the Milne-Pinney equation. For each system we solve the respective Milne-Pinney equation and discuss how the quantum fluctuations and the uncertainty product evolve with time. / Neste trabalho apresentamos soluções clássicas e quânticas de osciladores harmônicos acoplados dependentes do tempo. Nesses sistemas as massas, frequências e o parâmetro de acoplamento são funções do tempo. Quatro sistemas são investigados. Para obter as soluções clássicas usamos uma transformação de coordenada e momento juntamente com uma transformação canônica para escrever o Hamiltoniano original como a soma de dois Hamiltonianos de osciladores harmônicos desacoplados dependentes do tempo com frequências modificadas dependentes do tempo e massas unitárias. Encontramos soluções analíticas para a posição e a velocidade para cada oscilador de todos os sistemas. Para obter as soluções quânticas exatas usamos uma transformação unitária e o método invariante de Lewis e Riesenfeld. As funções de onda são escritas em termos de uma quantidade escalar a qual é solução da equação de Milne-Pinney. Para cada sistema resolvemos a respectiva equação de Milne-Pinney e discutimos como as flutuações quânticas e o produto de incerteza evoluem no tempo.

Doctor of Philosophy / Department of Chemistry / Christine M. Aikens / The remarkable optical and luminescence properties of noble metal nanoparticles (with diameters < 2 nm) attract researchers due to potential applications in biomedicine, photocatalysis, and optoelectronics. Extensive experimental investigations on luminescence properties of thiolate-protected gold and silver nanoclusters during the past decade have failed to unravel their exact photoluminescence mechanism. Herein, density functional and time-dependent density functional theory (DFT and TDDFT) calculations are performed to elucidate electronic-level details of several such systems upon photoexcitation. Multiple excited states are found to be involved in photoemission from Au₂₅(SR)₁₈– nanoclusters, and their energies agree well with experimental emission energies. The Au₁₃ core-based excitations arising due to electrons excited from superatom P orbitals into the lowest two superatom D orbitals are responsible for all of these states. The large Stokes shift is attributed to significant geometrical and electronic structure changes in the excited state. The origin of photoluminescence of Ag₂₅(SR)₁₈– nanoclusters is analogous to their gold counterparts and heteroatom doping of each cluster with silver and gold correspondingly does not affect their luminescence mechanism. Other systems have been examined in this work to determine how widespread these observations are. We observe a very small Stokes shift for Au₃₈(SH)₂₄ that correlates with a relatively rigid structure with small bond length changes in its Au₂₃ core and a large Stokes shift for Au₂₂(SH)₁₈ with a large degree of structural flexibility in its Au₇ core. This suggests a relationship between the Stokes shift of gold−thiolate nanoparticles and their structural flexibility upon photoexcitation. The effect of ligands on the geometric structure and optical properties of the Au₂₀(SR)₁₆ nanocluster is explored. Comparison of the relative stability and optical absorption spectra suggests that this system prefers the [Au₇(Au₈SR₈)(Au₃SR₄)(AuSR₂)₂] structure regardless of whether aliphatic or aromatic ligands are employed. The real-time (RT) TDDFT method is rapidly gaining prominence as an alternative approach to capture optical properties of molecular systems. A systematic benchmark study is performed to demonstrate the consistency of linear-response (LR) and RT-TDDFT methods for calculating the optical absorption spectra of a variety of bare gold and silver nanoparticles with different sizes and shapes.

abstract: The absorption spectra of metal-centered phthalocyanines (MPc's) have been investigated since the early 1960's. With improved experimental techniques to characterize this class of molecules the band assignments have advanced. The characterization remains difficult with historic disagreements. A new push for characterization came with a wave of interest in using these molecules for absorption/donor molecules in organic photovoltaics. The use of zinc phthalocyanine (ZnPc) became of particular interest, in addition to novel research being done for azaporphyrin analogs of ZnPc. A theoretical approach is taken to research the excited states of these molecules using time-dependent density functional theory (TDDFT). Most theoretical results for the first excited state in ZnPc are in only limited agreement with experiment (errors near 0.1 eV or higher). This research investigates ZnPc and 10 additional porphyrin analogs. Excited-state properties are predicted for 8 of these molecules using ab initio computational methods and symmetry breaking for accurate time- dependent self-consistent optimization. Franck-Condon analysis is used to predict the Q-band absorption spectra for all 8 of these molecules. This is the first time that Franck-Condon analysis has been reported in absolute units for any of these molecules. The first excited-state energy for ZnPc is found to be the closest to experiment thus far using a range-separated meta-GGA hybrid functional. The theoretical results are used to find a trend in the novel design of new porphyrin analog molecules. / Dissertation/Thesis / Doctoral Dissertation Materials Science and Engineering 2014

abstract: The need for sustainability in construction has encouraged scientists to develop novel environmentally friendly materials. The use of supplementary cementitious materials was one such initiative which aided in enhancing the fresh and hardened concrete properties. This thesis aims to explore the understanding of the early age rheological properties of such cementitious systems. The first phase of the work investigates the influence of supplementary cementitious materials (SCM) in combination with ordinary Portland cement (OPC) on the rheological properties of fresh paste with and without the effect of superplasticizers. Yield stress, plastic viscosity and storage modulus are the rheological parameters which were evaluated for all the design mixtures to fundamentally understand the synergistic effects of the SCM. A time-dependent study was conducted on these blends to explore the structure formation at various time intervals which explains the effect of hydration in conjecture to its physical stiffening. The second phase focuses on the rheological characterization of novel iron powder based binder system. The results of this work indicate that the rheological characteristics of cementitious suspensions are complex, and strongly dependent on several key parameters including: the solid loading, inter-particle forces, shape of the particle, particle size distribution of the particles, and rheological nature of the media in which the particles are suspended. Chemical composition and reactivity of the material play an important role in the time-dependent rheological study. A stress plateau method is utilized for the determination of rheological properties of concentrated suspensions, as it better predicts the apparent yield stress and is shown to correlate well with other viscoelastic properties of the suspensions. Plastic viscosity is obtained by calculating the slope of the stress-strain rate curve of ramp down values of shear rates. In oscillatory stress measurements the plateau obtained within the linear visco-elastic region was considered to be the value for storage modulus. Between the different types of fly ash, class F fly ash indicated a reduction in the rheological parameters as opposed to class C fly ash that is attributable to the enhanced ettringite formation in the latter. Use of superplasticizer led to a huge influence on yield stress and storage modulus of the paste due to the steric hindrance effect. In the study of iron based binder systems, metakaolin had comparatively higher influence than fly ash on the rheology due to its tendency to agglomerate as opposed to the ball bearing effect observed in the latter. Iron increment above 60% resulted in a decrease in all the parameters of rheology discussed in this thesis. In the OPC-iron binder, the iron behaved as reinforcements yielding higher yield stress and plastic viscosity. / Dissertation/Thesis / Masters Thesis Civil Engineering 2016

Doctor of Philosophy / Department of Chemistry / Christine M. Aikens / Gold and silver particles with dimensions less than a nanometer possess unique characteristics and properties that are different from the properties of the bulk. They demonstrate a non–zero HOMO–LUMO gap that can reach up to 3.0 eV. These differences arise from size quantization effects in the metal core due to the small number of atoms. These nanoparticles have attracted great interest for decades both in fundamental and applied research. Small gold clusters protected by various types of ligands are of interest because ligands allow obtaining gold nanoclusters with given sizes, shapes and properties. Three main families of organic ligands are usually used for stabilization of gold nanoclusters: phosphine ligands, thiolate ligands and DNA. Usually, optical properties of these NPs are studied using optical absorption spectroscopy. Unfortunately, sometimes this type of spectrum is poorly resolved and tends to appear very similar for different complexes. In these cases, circular dichroism (CD) and magnetic circular dichroism (MCD) spectroscopy can be applied. However, the interpretation of experimental CD and MCD spectra is a complicated process. In this thesis, theoretically simulated CD and MCD spectra were combined with optical absorption spectra to study optical activity for octa– and nona– and undecanuclear gold clusters protected by mono– and bidentate phosphine ligands. Additionally, optical properties of bare and DNA protected silver NPs were studied. Theoretical CD spectra were examined to learn more about the origin of chirality in chiral organometallic complexes, and to contribute to the understanding of the difference in chiroptical activity of gold clusters stabilized by different phosphine ligands and DNA–stabilized silver clusters. Furthermore, optical properties of the small centered gold clusters Au₈(PPh₃)₈²⁺ and Au₉(PPh₃)₈³⁺ were examined by optical absorption and MCD spectra using TDDFT. Theoretical MCD spectra were also used to identify the plasmonic behavior of silver nanoparticles. These results showed that CD and MCD spectroscopy yield more detailed information about optical properties and electronic structure of the different chemical systems than optical absorption spectroscopy alone. Theoretical simulation of the CD and MCD spectra together with optical absorption spectra can be used to assist in the understanding of empirically measured CD and MCD and provide useful information about optical properties and electronic structure.

Doctor of Philosophy / Department of Civil Engineering / Robert J. Peterman / Results of an extensive experimental program conducted to determine the material, bond characteristics, and time-dependent deformations of a proposed self-consolidating concrete (SCC) mixture for bridge girders are presented. This research program was completed in a three-step process. The first phase consisted of 15 full-scale, pretensioned SCC flexural specimens that were tested to evaluate their transfer and development lengths. These specimens included both single-strand and multiple-strand beams, as well as specimens designed to evaluate the so-called “top-strand" effect. The top-strand specimens, with more than 20 inches of concrete below the strand, were tested to evaluate the current American Association of State Highway Officials requirement of a 30% increase development length when the concrete below the strand is more than 12 inches. Strand end-slip measurements, used to estimate transfer lengths, indicated the proposed SCC mixture meets ACI and AASHTO requirements. In addition, flexural tests confirmed the proposed SCC mixture also meets current code requirements for development length. The second step was to evaluate the elastic shortening, creep, and shrinkage properties of the proposed SCC mixture for bridge girders. Four bridge girders with an inverted-T profile were used to measure these time-dependent deformations. In two of the specimens, the strands were tensioned to 75% of ultimate tensile strength (representing a girder that would be put into service). Strands of the other two specimens were left untensioned to evaluate shrinkage effect of the concrete alone. The shrinkage was then subtracted from the fully tensioned specimens and elastic shortening and creep were isolated after relaxation losses were calculated from code expressions. In addition, the fully tensioned specimens were used to determine transfer lengths of the prestressing strand. The final step in the program was to record strain measurements in actual bridge girders used in the field. Elastic shortening, creep, and shrinkage prestress loss results of the proposed SCC mixture were compared with current design equations. Instrumentation of seven pretensioned girders in a five-span bridge located in Cowley County, Kansas, was used to measure time-dependent deformations. Three of these girders utilized SCC, while the other four were cast with conventional concrete.

Tissue engineering offers a paradigm shift in the treatment of back pain. Engineered intervertebral discs could replace degenerated tissue and overcome the limitations of current treatments that disrupt the biomechanics of the spine. New materials, which exhibit sophisticated mechanical responses, are needed to provide templates for tissue regeneration. These behaviours include time-dependent deformation---facilitating shock absorption and nutrient transfer---and strong material anisotropy and tensile-compressive nonlinearities---providing flexibility in controlled directions. In this work, frameworks for the design of materials with controllable structure-property relationships are developed. The time-dependent mechanical properties of composites of agar, alginate and gelatin hydrogels are investigated. It is shown that the time-dependent responses of the composites can be tuned over a wide range. It is then demonstrated that materials mimicking the fibre-reinforced nature of natural tissues can be developed by infiltrating thick electrospun fibre networks with alginate. These fibre-reinforced hydrogels have tensile and compressive properties that can be separately altered. To better understand the mechanical behaviour of these hydrogel-based materials, improved methods for characterising poroelastic and poroviscoelastic time-dependent material properties using indentation are developed. It is shown that poroviscoelastic relaxation is the product of separate poroelastic and viscoelastic relaxation responses. The techniques developed here provide a methodology to rapidly characterise the properties of time-dependent materials and to create materials with complex structure-property relationships similar to those found in natural tissues; they present a framework for biomimetic materials design. The work in this thesis can be used to inform the design of clinically relevant tissue engineering treatments and help the quarter of a million people each year who undergo spinal surgery to reduce back pain.

Corrosion of reinforcing bars is the major cause of deterioration of reinforced concrete (RC) structures in North America, Europe, the Middle East, and many coastal regions around the world. This deterioration leads to a loss of serviceability and functionality and ultimately affects the structural safety. The objective of this research is to formulate and implement a general stochastic finite element analysis (SFEA) framework for the time-dependent reliability analysis of RC beams with corroding flexural reinforcement. The framework is based on the integration of nonlinear finite element and reliability analyses through an iterative response surface methodology (RSM). Corrosion-induced damage is modelled through the combined effects of gradual loss of the cross-sectional area of the steel reinforcement and the reduction bond between steel and concrete for increasing levels of corrosion. Uncertainties in corrosion rate, material properties, and imposed actions are modelled as random variables. Effective implementation of the framework is achieved by the coupling of commercial finite element and reliability software. Application of the software is demonstrated through a case study of a simply-supported RC girder with tension reinforcement subjected to the effects of uniform (general) corrosion, in which two limit states are considered: (i) a deflection serviceability limit state and (ii) flexural strength ultimate limit state. The results of the case study show that general corrosion leads to a very significant decrease in the reliability of the RC beam both in terms of flexural strength and maximum deflections. The loss of strength and serviceability was shown to be predominantly caused by the loss of bond strength, whereas the gradual reduction of the cross-sectional area of tension reinforcement was found to be insignificant. The load-deflection response is also significantly affected by the deterioration of bond strength (flexural strength and stiffness). The probability of failure at the end of service life, due to the effects of uniform corrosion-induced degradation, is observed to be approximately an order of magnitude higher than in the absence of corrosion. Furthermore, the results suggest that flexural resistance of corroded RC beams is controlled by the anchorage (bond) of the bars and not by the yielding of fully bonded tensile reinforcement at failure. This is significant since the end regions can be severely corroded due to chloride, moisture, and oxygen access at connections and expansion joints. The research strongly suggests that bond damage must be considered in the assessment of the time-dependent reliability of RC beams subjected to general corrosion.

abstract: Short-notice disasters such as hurricanes involve uncertainties in many facets, from the time of its occurrence to its impacts’ magnitude. Failure to incorporate these uncertainties can affect the effectiveness of the emergency responses. In the case of a hurricane event, uncertainties and corresponding impacts during a storm event can quickly cascade. Over the past decades, various storm forecast models have been developed to predict the storm uncertainties; however, access to the usage of these models is limited. Hence, as the first part of this research, a data-driven simulation model is developed with aim to generate spatial-temporal storm predicted hazards for each possible hurricane track modeled. The simulation model identifies a means to represent uncertainty in storm’s movement and its associated potential hazards in the form of probabilistic scenarios tree where each branch is associated with scenario-level storm track and weather profile. Storm hazards, such as strong winds, torrential rain, and storm surges, can inflict significant damage on the road network and affect the population’s ability to move during the storm event. A cascading network failure algorithm is introduced in the second part of the research. The algorithm takes the scenario-level storm hazards to predict uncertainties in mobility states over the storm event. In the third part of the research, a methodology is proposed to generate a sequence of actions that simultaneously solve the evacuation flow scheduling and suggested routes which minimize the total flow time, or the makespan, for the evacuation process from origins to destinations in the resulting stochastic time-dependent network. The methodology is implemented for the 2017 Hurricane Irma case study to recommend an evacuation policy for Manatee County, FL. The results are compared with evacuation plans for assumed scenarios; the research suggests that evacuation recommendations that are based on single scenarios reduce the effectiveness of the evacuation procedure. The overall contributions of the research presented here are new methodologies to: (1) predict and visualize the spatial-temporal impacts of an oncoming storm event, (2) predict uncertainties in the impacts to transportation infrastructure and mobility, and (3) determine the quickest evacuation schedule and routes under the uncertainties within the resulting stochastic transportation networks. / Dissertation/Thesis / Doctoral Dissertation Industrial Engineering 2020