<p> Tuned Liquid Dampers (TLDs) are increasingly being used to suppress the dynamic vibration of tall buildings. An equivalent mechanical model is essential for rapid analysis and design of a TLD. The most common TLD tank geometries are circular, annular and rectangular. Rectangular tanks are utilized for 1-D and 2-D TLDs, whereas circular and annular are usually applied to axisymmetric structures. The amount of fluid that participates in the sloshing motion is directly influenced by the tank geometry. Although not commonly used, a TLD having a curved-bottom tank is expected to perform more effectively due to its relatively large value of effective mass. The main objective of this study is to develop mechanical models for seven TLDs with different tank geometries including the curved-bottom case, and to theoretically investigate the performance of rectangular, vertical-cylindrical and horizontal-cylindrical TLDs.</p> <p> Potential flow theory, linear long wave theory, Lagrange's equations and virtual work method are employed to develop the equivalent mechanical model parameters of TLDs with rectangular, vertical-cylindrical, horizontal-cylindrical, hyperboloid, triangular, sloped-bottom, and parabolic tank geometries. A rectangular, vertical-cylindrical and horizontal-cylindrical TLD are selected for further study using a single-degree-of-freedom (SDOF) model and a two degree of freedom structure-TLD system model applying the derived equivalent mechanical parameters.</p> <p> The dynamic characteristics of the TLDs as a SDOF system are investigated. The mechanical model is verified by comparing calculated values with experimental results for a rectangular TLD. The free surface motion, sloshing force and energy dissipation are found to be dependent upon the excitation amplitude. Analytical results also indicate that the horizontal-cylindrical TLD possesses the greatest normalized sloshing force and energy dissipation among the TLDs considered.</p> <p> The performances of various TLDs installed in a structure are studied in terms of effective damping, efficiency and robustness. Tuning ratio, structural response amplitude, mass ratio and liquid depth are adjusted to investigate their affect on the performance of the studied TLDs. Performance charts are developed and subsequently used to present the results. It is found that small liquid depth ratio and large mass ratio can lead to a robust structure-TLD system with small relative motion ratio between the structure and the vibration absorber. Comparisons of performance between the three TLDs are made and it can be concluded that the horizontal-cylindrical TLD is the most robust and effective device with the smallest relative motion ratio.</p> / Thesis / Master of Applied Science (MASc)

Doctor of Philosophy / Department of Civil Engineering / Hayder Rasheed / Recent applications in reinforced concrete columns, including strengthening and extreme loading events, necessitate the development of specialized nonlinear analysis methods to predict the confined interaction domain of axial force, shear, and bending moment in square and slightly rectangular concrete columns. Fiber-reinforced polymer (FRP) materials are commonly used in strengthening applications due to their superior properties such as high strength-to-weight ratio, high energy absorption and excellent corrosion resistance. FRP wrapping of concrete columns is done to enhance the ultimate strength due to the confinement effect, which is normally induced by steel ties. The existence of the two confinement systems changes the nature of the problem. Existing research focused on a single confinement system. Also, very limited research on rectangular sections was found in the literature. In this research, a model to estimate the combined behavior of the two systems in rectangular columns is proposed. The calculation of the effective lateral pressure is based on Lam and Teng model and Mander model for FRP wraps and steel ties, respectively. The proposed model introduces load eccentricity as a parameter that affects the compression zone size, and in turn the level of confinement engagement. Full confinement corresponds to zero eccentricity, while unconfined behavior corresponds to infinite eccentricity. The model then generates curves for eccentricities within these boundaries. The numerical approach developed has then been extended to account for shear interaction using the simplified modified compression field theory adopted by AASHTO LRFD Bridge Design Specifications 2014. Comparisons were then performed against experimental data and Response-2000, an analytical analysis tool based on AASHTO 1999 in order to validate the interaction domain generated. Finally, the developed models were implemented in the confined analysis software “KDOT Column Expert” to add FRP confinement effect and shear interaction.

Το θέμα της παρούσας εργασίας είναι η μελέτη της ροής ύδατος εντός ανοιχτού αγωγού ορθογωνικής διατομής κατά την περίπτωση όπου έχουμε υπερχειλιστή λεπτής στέψης και ανάντη αυτού παρουσιάζεται ανισοκατανεμημένη παροχή. / Flow study in the downstream of one spillway with thin top, inside an rectangular open channel, in cases of uneven supply upstream of spillway.

Novel integral-equation methods for efficiently solving electromagnetic problems that involve more than a single length scale of interest in complex backgrounds are presented. Such multi-scale electromagnetic problems arise because of the interplay of two distinct factors: the structure under study and the background medium. Both can contain material properties (wavelengths/skin depths) and geometrical features at different length scales, which gives rise to four types of multi-scale problems: (1) twoscale, (2) multi-scale structure, (3) multi-scale background, and (4) multi-scale-squared problems, where a single-scale structure resides in a different single-scale background, a multi-scale structure resides in a single-scale background, a single-scale structure resides in a multi-scale background, and a multi-scale structure resides in a multi-scale background, respectively. Electromagnetic problems can be further categorized in terms of the relative values of the length scales that characterize the structure and the background medium as (a) high-frequency, (b) low-frequency, and (c) mixed-frequency problems, where the wavelengths/skin depths in the background medium, the structure’s geometrical features or internal wavelengths/skin depths, and a combination of these three factors dictate the field variations on/in the structure, respectively. This dissertation presents several problems arising from geophysical exploration and microwave chemistry that demonstrate the different types of multi-scale problems encountered in electromagnetic analysis and the computational challenges they pose. It also presents novel frequency-domain integral-equation methods with proper Green function kernels for solving these multi-scale problems. These methods avoid meshing the background medium and finding fields in an extended computational domain outside the structure, thereby resolving important complications encountered in type 3 and 4 multi-scale problems that limit alternative methods. Nevertheless, they have been of limited practical use because of their high computational costs and because most of the existing ‘fast integral-equation algorithms’ are not applicable to complex Green function kernels. This dissertation introduces novel FFT, multigrid, and FFT-truncated multigrid algorithms that reduce the computational costs of frequency-domain integral-equation methods for complex backgrounds and enable the solution of unprecedented type 3 and 4 multi-scale problems. The proposed algorithms are formulated in detail, their computational costs are analyzed theoretically, and their features are demonstrated by solving benchmark and challenging multi-scale problems. / text

Rectangular collimation is used in dentistry to reduce radiation by restricting the x-ray beam to approximately the size of a number 2 intraoral film (3.2X4.1 cm). However, this restricted beam size can lead to exposure errors. The aim of this study was to retrospectively evaluate the number of radiographs exposed and the presence of technical errors by the use of traditional circular or rectangular collimators during endodontic therapy on simulated teeth in manikins. A total of 1475 digital radiographs of 84 teeth exposed by 60 dental students were evaluated. Evaluation was done by a board certified endodontist, an endodontic resident, and a dental student. Analysis of the different raters showed no significant differences among the three. Radiographs were randomized and blindly renamed. Repeated-measures mixed-model ANOVA was used to compare the number of radiographs exposed using the different collimators. Although not statistically significant (P<.05), there were 15% more radiographs taken with the rectangular collimator when compared to the circular collimator. Using a repeated-measures logistic regression, there was a significant difference of the proportion of radiographs with cone cuts (P = .0003) taken with a rectangular collimator (59%) compared to radiographs taken with a circular collimator (19%). There was no significant evidence for a collimator difference when considering missed apex (P = .0986) or missed apex due to a cone cut (P = .0631). In order to expose high quality radiographs avoiding cone cuts, a traditional circular collimator may be indicated for use during endodontic therapy.

Análises estruturais de tamanho e diversidade em florestas tropicais, fornecem informações preciosas para o conhecimento e entendimento da comunidade. Uma maneira de analisar estruturalmente essas áreas são por meio de padrões ou análises comportamentais de atributos, os quais auxiliam na explicação da organização e funcionamento dessas comunidades. No decorrer do trabalho, foram analisados atributos quantitativos, como densidade de estande, área basal, diâmetro médio e diâmetro médio quadrático, tanto em valores absolutos como em relações gráficas abordando estruturalmente comunidades quanto ao seu tamanho e diversidade. O primeiro objetivo foi analisar os atributos quantitativos e verificar se por meio desses é possível discriminar a fitofisionomia da área em questão. Para isso, foram analisadas cinco parcelas permanentes abrangendo três fitofisionomias (cerradão, estacional e ombrófila) e concluiu-se que os padrões/comportamentos gerados pelos atributos nas áreas de mesma fitofisionomia nem sempre foram semelhantes. Contudo, a fitofisionomia classificada como cerradão, na maioria das vezes, gerou um comportamento distinto, se destacando e se diferenciando das demais. Já o segundo objetivo foi avaliar a influência de diferentes tipos de unidades amostrais na análise de atributos quantitativos em florestas tropicais nativas. Assim, foram analisados dados correspondentes a três tipos de unidades amostrais (pontos de Bitterlich, parcela circular e parcela retangular), em diferentes fitofisionomias: cerradão (Assis), ombrófila (Carlos Botelho) e estacional (Caetetus). Diante das análises feitas com esses dados, viu-se que para alguns atributos quantitativos, o tipo de unidade amostral influenciou nos resultados. A amostragem por Bitterlich, por exemplo estima com precisão a área basal e volume, mas tende a gerar estimativas enviesadas quando se trata de áreas com presença de muitas árvores pequenas, como no caso da área do cerradão. Na maioria das vezes, as parcelas de área fixa, como as parcelas circulares e retangulares, geraram padrões semelhantes, sendo que quaisquer diferenças podem ser devido à distribuição espacial das espécies, fatores não controlados ou ao acaso. Já a amostragem por pontos de Bitterlich, gerou resultados distintos, principalmente quando a área basal foi utilizada como medida de avaliação. Assim, dependendo da variável de interesse e da fitofisionomia amostrada, é preciso ser cauteloso na escolha do tipo de unidades amostral, pois dependendo destes fatores, os atributos quantitativos poderão gerar comportamentos e respostas diferenciadas. / Structural analyzes of size and diversity in tropical forests provide valuable information for knowledge and community understanding. One way of analyzing these areas structurally is by patterns or behavioral analyzes of attributes which help in explaining the organization and functioning of these communities. In the study quantitative attributes such as stand density, basal area, mean diameter and mean square diameter were analyzed both in absolute values and in graphical relations, structurally approaching communities as to their size and diversity. The first objective was to analyze the quantitative attributes and verify if it is possible to discriminate the phytophysiognomy of the area in question. For this, five permanent plots were analyzed covering three phytophysiognomies (cerradão, seasonal and ombrophilous) and it was concluded that the patterns/behaviors generated by the attributes in the areas of the same phytophysiognomy were not always similar. However, the phytophysiognomy classified as cerradão, in most cases, generated a distinct behavior standing out and differentiating itself from the others. The second objective was to evaluate the influence of different types of sample units on the analysis of quantitative attributes in native tropical forests. Thus, data corresponding to three types of sampling units (Bitterlich points, circular plot and rectangular plot) were analyzed in different phytophysiognomies: cerradão (Assis), ombrophilous (Carlos Botelho) and seasonal (Caetetus). Considering the analyzes made was observed that for some quantitative attributes the sample unit type influenced the results. Bitterlich sampling, for example, precisely estimates basal area and volume but tends to generate biased estimates when dealing with areas with presence of many small trees as in the case of the cerradão area. Most often, fixed-area plots such as circular and rectangular plots have generated similar patterns and any differences may be due to spatial distribution of species, uncontrolled or random factors. The Bitterlich point sampling generated different results from fixed-area plots, especially when the basal area was used as an evaluation measure. Thus, depending interest parameterand the phytophysiognomy sampled it is necessary to be cautious in choosing the type of sample units because depending on these factors the quantitative attributes may generate different behaviors and responses.

Essa dissertação aborda o tema de propagação de ondas de tensão em hastes metálicas retangulares. Este tipo de onda pode ser utilizada como base na verificação da integridade estrutural através de um ensaio não destrutivo (END). A propagação de ondas elásticas em sólidos apresenta muito potencial quando se deseja estimar a integridade de determinada estrutura. Porém para transformar esse fenômeno físico em uma técnica aplicável na detecção de danos, alguns passos devem ser seguidos, dentre eles: a compreensão das características de propagação da estrutura em estudo, in teração das ondas elásticas com defeitos, aten uação das ondas propagadoras devido a fontes de amortecimento e dispersão. Neste contexto o presente trabalho tem o principal foco no desenvolvimento de uma metodologia eficiente para a investigação da propagação de ondas de tensão em hastes retangulares metálicas, abordando o tema por diversos aspectos. No decorrer do mesmo são calcu ladas as curvas de dispersão de uma haste retangular com seção transversal de 15 x5 [rum], para uma faixa de frequência determinada [0,100 kHz], utilizando três metodologias distintas e realizando a comparação crítica entre elas. São realizadas investigações teóricas, de forma analítica e numérica (via análise explícita empregando elementos finitos) e uma inves tigação experimental das características de propagação da geometria referida. Também os efeitos da aten uação das ondas na geometria é estudado. Os resulta dos obtidos são discutidos procurando mostrar sua coerência e enfatizando a informação sobre o comportamento mecânico das ondas de tensão nesse tipo de estrutura, observando aspectos relevantes à concepção de técnicas de END que possi bilitem a avaliação da integridade dessas estruturas. / This dissertation addresses the issue of propagation of stress waves in metallic rectangular rods. This type of wave can be used as the integrity check structural integrity through a non-destructive test (NDT). The propagation of elastic waves in solids has a lot of potential when estimating the given structure integrity. But to turn this physical phenomenon in an applicable technique for the detection of damage, some steps should be taken, including: understanding of propagating characteristics of the structure under study, interaction of elastic waves with defects, attenuation of the propagating waves due to sources of damping and dispersion. In this context, the present work is the main focus in developing an effective methodology for investigating the propagation of stress waves in rectangular metal rods, addressing the issue by several aspects. During the same are calculated dispersion curves of a rod with rectangular cross section 15 x5 [mm], for a given frequency range [0,100 kHz], using three different methodologies and performing the critical comparison between them. Are performed theoretical investigations, in analytical and numerical form (via explicit analysis using finite element) and an experimental investigation of the propagation features said geometry. Also the effects of attenuation of the waves on geometry is studied. The results are discussed trying to show their consistency and emphasizing information about the mechanical behavior of stress waves in this type of structure, observing relevant aspects to the design of NDT techniques to enable the assessment of the integrity of these structures.

The explosion of internet traffic, advent of social media sites such as Facebook and Twitter, and increased availability of digital cameras has saturated life with images and videos. Never before has it been so important to sift quickly through large amounts of digital information. Salient Object Detection (SOD) is a computer vision topic that finds methods to locate important objects in pictures. SOD has proven to be helpful in numerous applications such as image forgery detection and traffic sign recognition. In this thesis, I outline a novel SOD technique to automatically isolate important objects from the background in images.

This paper describes recent progress in a continuing program to develop and apply RM³ (recess mounting with monolithic metallization) technologies for heterogeneous integration. Particular emphasis is placed on the applicability of RM³ integration to in-plane geometries for on-chip optical clock and signal distribution and on the suitability of commercially processed IC wafers for use as substrates for rectangular dielectric waveguides. / Singapore-MIT Alliance (SMA)

The objective of current study was to numerically investigate the flow and heat transfer characteristics in a stationary one pass rectangular channel (AR=4:1) with circular and elliptical pin fin arrays. Two types of elliptical pin fins (a SEF and an N fin whose minor axis length is equal to the diameter of the circular fin) were used. The analysis was performed with an array of six rows of staggered pin fins in the streamwise direction for Reynolds numbers (Re) of 10,000, 20,000, 30,000, 40,000 and 50,000. 3-D, steady simulations were performed using the low Reynolds number k-omega SST turbulence model in the FLUENT CFD code. The data predicted by the current numerical model showed favorable agreement with the experiments in the validation study. It was observed that SEF array produces minimum pressure loss and the highest thermal performance. It was also observed that N fin array produces minimum hot spots and the highest channel averaged Nusselt number ratio values.