The large thermal cross section of cadmium makes it ideal for many practical applications where screening of thermal neutrons is desired. For example, in non-destructive assay techniques, or for astrophysical studies of the s-process. All such applications require precise knowledge of the neutron-capture cross section on cadmium. Although there are some data on neutron-capture cross sections particularly at thermal energies and at energies relevant for astrophysics, there is very little data at most other energies. Further, the evaluated cross sections from the ENDF and JENDL databases disagree at high energies. Therefore, there is a critical need for precise knowledge of the 114Cd(n, gamma)115Cd cross section over a large range of incident neutron energies. We performed a direct measurement of the neutron-capture cross section at the Los Alamos Neutron Science Center (LANSCE) using the Detector for Advanced Neutron Capture Experiments (DANCE). A highly enriched (∼$99%), 100 mg pressed metallic pellet sample of 114Cd was used to perform the neutron-capture measurements in the range of 1 eV to 300 keV using the white neutron source available at LANSCE. Additional neutron capture data were also taken on highly enriched samples of 112Cd and 113Cd to enable careful background subtraction of even the small contaminants found in the 114Cd sample. We used a large energy sum windows around the Q-value to circumvent any complication that may arise from populating the 180 keV isomeric (T1/2 = 44.56d) state in 115Cd.

Defected wheel are one the major reasons endangered state of railroad vehicles safety statue, due to vehicle derailment and worsen the quality of freight and passenger transportation. Therefore, timely defect detection for monitoring and detecting the state of defects is highly critical. This thesis presents a passive non-contact acoustic structural health monitoring approach using ultrasonic acoustic emissions (UAE) to detect certain defects on different structures, as well as, classifying the type of the defect on them. The acoustic emission signals used in this study are in the ultrasonic range (18-120 kHz), which is significantly higher than the majority of the research in this area thus far. For the proposed method, an impulse excitation, such as a hammer strike, is applied to the structure. In addition, ultrasound techniques have higher sensitivity to both surface and subsurface defects, which make the defect detection more accurate. Three structures considered for this study are: 1) a longitudinal beam, 2) a lifting weight, 3) an actual rail-wheel. A longitudinal beam was used at the first step for a better understanding of physics of the ultrasound propagation from the defect, as well, develop a method for extracting the signature response of the defect. Besides, the inherent directionality of the ultrasound microphone increases the signal to noise ratio (SNR) and could be useful in the noisy areas. Next, by considering the ultimate goal of the project, lifting weight was chosen, due to its similarity to the ultimate goal of this project that is a rail-wheel. A detection method and metric were developed by using the lifting weight and two type of synthetic defects were classified on this structure. Also, by using same extracted features, the same types of defects were detected and classified on an actual rail-wheel. / Master of Science

Portland cement concrete (PCC) structures deteriorate with age and need to be maintained or replaced. Early detection of deterioration in PCC (e.g., alkali-silica reaction, freeze/thaw damage, or chloride presence) can lead to significant reductions in maintenance costs. However, it is often too late to perform low-cost preventative maintenance by the time deterioration becomes evident. Non-destructive evaluation (NDE) methods are potentially among the most useful techniques developed for assessing constructed facilities. They are noninvasive and can be performed rapidly. Portland cement concrete can be nondestructively evaluated by electrically characterizing its complex dielectric constant. The real part of the dielectric constant depicts the velocity of electromagnetic waves in PCC. The imaginary part describes the conductivity of PCC and the attenuation of electromagnetic waves, and hence the losses within the PCC media. Dielectric properties of PCC have been investigated in a laboratory setting using a parallel plate capacitor operating in the frequency range of 0.1MHz to about 40MHz. This capacitor set-up consists of two horizontal-parallel plates with an adjustable separation for insertion of a dielectric specimen (PCC). While useful in research, this approach is not practical for field implementation In this research, a capacitance probe has been developed for field application. The probe consists of two planar conducting plates and is made of flexible materials for placement on exposed surfaces of the specimens to be tested. The calibration method of both capacitive systems has been extensively studied to minimize systematic errors in the measurement process. These two measurement systems will be discussed and compared to one another on the basis of sensitivity and measurement repeatability. / Master of Science

There currently exists no reliable, non-destructive method for measuring stress in railroads and other similar structures without the need for a calibration measurement. Major limitations which have hindered previous techniques include sensitivity to boundary conditions, insensitivity to stress, and intolerance for material and geometry uncertainty. In this work, a technique is developed which seeks to solve these challenges by extracting the spectrum relation, or dispersion curve, of a waveguide from dispersive wave propagation meaasurements. The technique is based on spectral analysis of waves in structures modeled as beams, and as such is based on relatively low frequency vibrations, as opposed to other techniques which use nonlinear elastic modeling of structures at ultrasonic frequencies. The major contribution of this work is the development of a frequency-domain based signal processing technique which is capable of compensating for the dispersive, long wavelength reflections which have limited the ability of previous techniques to go low enough in frequency to achieve high stress sensitivity. By compensating for reflections, the present work is able to automate the process of analyzing wave propagation signals such that the entire dispersion curve can be extracted, enabling the identification of various parameters including stress, stiffness, density, and other material and geometry properties. This in turn enables measuring stress, performing model-updating for material and geometry uncertainty, and being indifferent to boundary conditions. The theory and algorithmic implementation is presented, along with simulations and experimental validation on a rectangular beam. / Master of Science / The ability to detect damage or the potential for damage in structures is highly desirable, especially in industries such as civil infrastructure in which failure can be incredibly costly and dangerous. In particular, non-destructive techniques which can predict failure without interfering with the operations of a structure are particularly sought after. In this work, a technique for non-intrusively and non-destructively measuring stress is developed, with the primary application being for measuring stress in railroads. The technique seeks to advance the state-of-the-art in wave-propagation-based techniques by adding the capability to automatically identify reflected waves. With this new capability, the method is able to quickly and efficiently analyze a large set of vibration measurements to extract information about the structure's material, geometry, and loading characteristics which enables solving for stress even when the structures material, geometry, and boundary conditions are not precisely known. The technique is demonstrated on both simulated and experimental data, in which a rectangular beam is tensioned and the stress is then identified.

<p dir="ltr">Terahertz Time Domain Spectroscopy (THz-TDS) is a powerful non-destructive, non-ionizing spectroscopic technique utilized for evaluating the optical properties of materials within the terahertz frequency range, spanning from 0.1 to 10 terahertz or wavelengths of 300 micron to 3000 micron. It effectively bridges the gap between microwave and infrared regions on the electromagnetic spectrum and its high resolution which avoiding scattering can quantify small changes in dielectric properties of media. It has high transmission through visibly opaque polymers and its ability to record both magnitude and phase information makes it a strong spectroscopic technique with applications in security, chemistry, electronics and telecommunication and non-destructive evaluation methods for solid mechanics.</p><p><br></p><p dir="ltr">This work introduces a polarization-dependent analytical model employing THz-TDS for computing strain in materials. The model establishes a correlation between volumetric strain and the change in time of arrival for a THz pulse, leveraging dielectrostrictive properties, variations in doping particle density, and changes in sample thickness due to Poisson’s effects. Validation of the analytical model is achieved through strain mapping of polydimethylsiloxane doped with highly dielectrostrictive strontium titanate (STO). Two experiments, including open-hole tensile and circular edge-notch specimens, demonstrate the efficacy of the model. Additionally, the study accounts for stress relaxation behavior to ensure measurement accuracy. Comparison of THz strain mapping results with finite element model (FEM) and surface strain measurements using digital image correlation (DIC) method highlights the technique's sensitivity to material features such as particle clumping and edge effects, while showcasing strong agreement with FEM and DIC results.</p><p><br></p><p dir="ltr">This analytical model is further expanded for experimentally mapping subsurface stress and strain in the adhesive layer of a single lap shear test. This in-situ non-destructive testing method pioneers the use of THz-TDS for stress estimation in the adhesive layer. Validation through strain mapping of STO doped Araldite 2011 epoxy adhesive with the analytical formulation is presented.</p><p dir="ltr">Finally, THz-TDS is applied for fracture front mapping in a double cantilever beam test with high-density polyethylene bonded with STO doped Araldite 2011. The phase-dependent model for mapping fracture fronts in the sub-surface adhesive layer involves analyzing convoluted waves due to interface resonances in a multi-layer structure using THz-TDS in transmission mode. The technique evaluates changes in dielectrostrictive properties and degree of separation to delineate fracture fronts. THz image enhancement algorithms facilitate crack front delineation. Error analysis on measured crack thickness is conducted to evaluate signal-to-noise ratio for THz-TDS. Additionally, an approach employing THz-TDS measured fracture propagation information for determining sub-surface stress maps in the adhesive layer and computing fracture toughness (G_Ic) is proposed. This work highlights the versatility and efficacy of THz-TDS in material characterization and stress/strain mapping in solid mechanics applications.</p>

A atividade humana tem contribuído com as emissões de gases de efeito estufa (GEE) associadas, principalmente, com queima de combustíveis fósseis e mudanças no uso da terra. Assim, se faz necessário que sejam adotadas medidas visando o retardamento dos efeitos das mudanças climáticas. As florestas exercem papel essencial no balanço de carbono principalmente por funcionarem como sumidouros de CO2. Por outro lado, se desmatadas, promovem emissões e liberam parte do carbono estocado. A quantidade de biomassa florestal e o teor de carbono podem variar em função do tipo florestal, bem como de sua localização. Entretanto, fator importante diz respeito à confiabilidade dos dados mensurados neste tipo de pesquisa. A biomassa e o carbono da parte aérea podem ser determinados via método destrutivo, ou estimados via método não destrutivo. A construção do Rodoanel Mário Covas trecho norte e a supressão de uma área de Mata Atlântica possibilitou a realização de estudo de biomassa da parte aérea via método destrutivo. O objetivo deste trabalho foi estudar o tamanho e forma de parcelas, a intensidade amostral, quantificar a biomassa e o carbono na parte aérea, comparar métodos destrutivos e não destrutivos para a quantificação de biomassa e carbono na parte aérea, estudar a variação da densidade básica da madeira das espécies nas diferentes classes de DAP e grupos sucessionais e comparar as medidas de altura total e DAP obtidas a campo no inventário com as medidas coletadas após o corte. O tamanho mais conveniente de parcela foi 400 m 2, com forma retangular e dimensão de 10 x 40 m. A intensidade amostral variou entre 39 e 75 unidades amostrais. A biomassa da parte aérea obtida, via método destrutivo, foi de 188,3 Mg ha-1 e o carbono, 85,1 Mg ha-1. A biomassa estimada por equações alométricas da literatura foi subestimada, quando comparada ao valor real, obtido via método destrutivo. As menores classes de DAP apresentaram as maiores densidades básicas da madeira. A densidade básica foi 0,488 g cm-3 na média das espécies. A porcentagem de carbono contida nos troncos e galhos não diferiu entre as classes de DAP. O teor de carbono foi 45,41%, na média dos troncos e galhos. Espécies pioneiras acumularam maior quantidade de biomassa e carbono nos galhos e apresentaram maior densidade básica que as não pioneiras. A utilização dos dados coletados na fase de inventário e após o corte não afetaram os valores de biomassa estimados. / Human activity has contributed to the emission of greenhouse gases associated mainly with burning fossil fuels and changes in land use. Thus, it is necessary that measures be adopted to delay the effects of climate change. Forests play an essential role in the carbon balance mainly acting as CO2 sinks. On the other hand, if they are deforested, they will promote emissions and release some of the stocked carbon. The amount of forest biomass and the carbon content may vary depending on the forest type and its location. However, an important factor is about the reliability of the data measured in this type of research. Aboveground biomass and carbon can be determined via destructive method or estimated by non-destructive method. The construction of the north extension of Mário Covas Road and the suppression of an Atlantic forest area made it possible to carry out study of the aboveground biomass via destructive method. The goal of this work was to study the size and shape of plots, the sampling intensity, their aboveground biomass and carbon, compare destructive and non-destructive methods for the quantification of biomass and carbon, study the variation of wood basic density in the species in different classes of diameter of trunk at breast height (DBH) and successional groups and compare the total height and DBH measures obtained on field in the inventory with the measures taken after the cut. The most convenient plot size is 400 m2, with rectangular shape and size of 10 x 40 m. The sampling intensity varied between 39 and 75 sample units. The aboveground biomass obtained, via destructive method, was 188.3 Mg ha-1 and carbon, 85.1 Mg ha-1. The biomass estimated by allometric equations of the literature was underestimated compared to the real value obtained via destructive method. Smaller DBH classes had the highest wood basic density. The basic density was 0.488 g cm-3 in average of the species. The percentage of carbon contained in the trunks and branches did not differ between the DBH classes. The carbon content was 45.41%, in the average of the trunks and branches. Pioneer species accumulated higher amount of biomass and carbon in the branches and had a higher wood basic density than non pioneers species. The utilization of data collected in the inventory phase and after the cut did not affect the estimated biomass values.

Cette thèse porte sur la caractérisation non destructive de structures 2D magnéto-diélectriques inhomogènes complexes. L’ensemble des étapes allant de l’expérience au traitement du problème inverse est traité. Dans un premier temps, un modèle direct reliant le champ diffusé aux propriétés électromagnétiques du matériau a été mis en place. Ce modèle requiert des calculs par éléments finis de la propagation de l’onde électromagnétique, en présence de l’objet observé lorsque celui-ci est positionné sur un support métallique. Une validation expérimentale a été réalisée via la mise en place d'un banc de mesure multi statique. Différentes étapes d'ajustements et d'étalonnages ont permis la réduction du bruit de mesure ainsi que des biais. L’inversion est traitée principalement par une approche linéaire, avec un choix attentif de la valeur des hyper paramètres qui y sont associés. Une fois les outils mis en place, six études ont été réalisées pour la validation de notre système d’imagerie 2D des propriétés électromagnétiques de matériaux magnéto-diélectriques inhomogènes. Cela comprend l’évaluation des incertitudes de mesure, de la résolution spatiale, la mesure de différents matériaux magnétiques et l’utilisation de différents supports à géométries variées. L’ensemble des résultats expérimentaux réalisés se place dans une hypothèse de géométrie 2D. C’est pourquoi, nous avons ensuite orienté nos travaux vers la recherche d’un design innovant permettant de faire évoluer le banc de mesure en un dispositif d’imagerie 3D. Dans cette perspective, une source secondaire vient se déplacer proche de la cible pour acquérir de l’information selon la troisième dimension. / The subject of this thesis is the non-destructive characterization of complex inhomogeneous magneto-dielectric structures. Successively, the experimental developments, the modelling and the data treatments stages are addressed. A forward model that links the scattered field to the electromagnetic properties is established. This model requires some finite element computations in order to estimate the propagation of the electromagnetic wave in presence of the magneto-dielectric object which is glued on a metallic support. A multistatic bench has been designed and constructed in order to collect measured scattered fields. Several adjustments and calibration procedures have been carried out to reduce the measurement noise and biases. Next, the inverse problem has been dealt with, in order to retrieve the electromagnetic properties of the samples, from the measured scattered field. The inverse problem is mainly solved with a linear approach, with a careful selection of the hyperparameters. Once the system has been fine tuned, six studies have been realized to validate our 2D imaging system. The assessment of the measurement uncertainty, the evaluation of the spatial resolution, the characterization of various magnetics materials and the use of different supports with variable geometries have been performed. So far, all the developments were done under a 2D hypothesis. That is why, we have then focused our research on the design of a 3D innovative imaging setup. To this end, a secondary source moving close to the target has been added in order to gain information in the third direction. A numerical study has been performed to assess the expected performances of this new setup.

A cadeia da construção civil é uma grande causadora de impactos ambientais, pois além do alto consumo de recursos naturais gera também grandes quantidades de resíduos. Isto traz elevados custos à sociedade pela necessidade de remoção e destinação dos resíduos, normalmente depositados em aterros. A reciclagem tem sido uma alternativa para redução do volume de resíduos finais. Estudos utilizando agregados reciclados de Resíduos de Construção e Demolição (RCD) para a produção de concreto têm sido realizados por vários pesquisadores indicando viabilidade técnica da sua aplicação. No entanto, há dúvidas que dificultam a implementação do uso de resíduos reciclados dada a grande variabilidade das suas propriedades devido à variação de sua constituição que é muito influenciada pela origem dos mesmos. Assim, alguns tratamentos são propostos com a intenção de otimizar o desempenho do concreto produzido com estes agregados reciclados. A presente dissertação tem como objetivo avaliar a influência dessas variabilidades dos agregados de RCD reciclados nas propriedades do concreto estrutural. Esses agregados foram provenientes das cidades de Macaé e São Paulo, ambos submetidos aos mesmos tipos de tratamento: (a) britagem e (b) britagem e separação densitária (jigue), atendendo a mesma faixa granulométrica de -19+4,8 mm. No programa experimental, foi utilizada a metodologia de dosagem convencional para a avaliação do comportamento mecânico do concreto reciclado. Neste estudo, os agregados foram utilizados sem pré-saturação, o que possibilitou o preenchimento de parte dos poros dos agregados pela pasta de cimento. Tal procedimento contribuiu para uma menor diferença relativa de desempenho do concreto convencional em relação ao produzido com agregados reciclados, principalmente para os concretos com maior relação água/cimento. Foram analisados os resultados de resistência à compressão, resistência à tração por compressão diametral, módulo de elasticidade, absorção de água, índice Binder Intensity e ensaio de ultra-som. Comprovou-se que a porosidade dos agregados é o fator principal de influência no comportamento do concreto. Já a origem dos agregados foi um fator secundário dado que os mesmos apresentavam diferentes porosidades em função da cidade onde foram obtidos. A separação densitária possibilitou a aproximação do comportamento dos agregados de diferentes origens por aproximar a porosidade dos mesmos. / The civil construction industry is a great producer of environment impacts. It also generates great amounts of residues, further the high consumption of natural resources. This fact brings high costs to society due to the need of residues removing and disposal, which typically occurs in landfills. Recycling has been an alternative to reduce the volume of residues. Studies using recycled aggregates from Construction and Demolition Waste (CDW) to produce concrete have been carried out by several researchers, indicating that is technically feasible in terms of application. However, there are questions that turns difficult the implementation of the use of recycled residues, due to the great variability of their properties as a result of the variation of their constitution, which is strongly influenced by their origin. Thus, a few treatments are proposed, aiming at optimizing the performance of these recycled aggregates to produce concrete. The present work aims at assessing the influence of the recycled CDW aggregates on the properties of structural concrete. These aggregates originated from the cities of Macaé and São Paulo, and both were submitted to the same type of treatment: (a) crushing and (b) crushing and density separation (jig), complying with the same granulometric range of -19+4.8 mm. The conventional mix design methodology was used in the experimental program to assess the concrete behavior and the influence of the recycled material. The aggregates were used in this study without being pre-saturated, which allowed filling up part the pores of the aggregates with cement paste. Such procedure contributed for a smaller relative difference on the performance of the conventional concrete and that one produced with recycled aggregates, especially the concrete with a higher water/cement ratio. The compressive strength, split tensile strength, elastic modulus, water absorption, Binder Intensity index and measuring of ultrasonic testing were analyzed. The porosity of the aggregate was proved to be a prevalent factor influencing the behavior of the concrete. The origin of the aggregates was a secondary factor because they had different porosities according to the city where they were obtained. The density separation allowed the reduction of the difference in behavior between the concretes produced with aggregates from different origins by approaching their porosity.

The purpose of this project was to examine the predictors of risky sexual behaviors and poor eating behaviors for women who experienced childhood sexual abuse, including family hardiness, and depression in a structural equation model. A second group of those who had not been sexually abused as children was also tested using the same structural equation model.

Un « mode de coordination » est un concept qui définit l’interaction entre les rapports sociaux et l’économie. Celle-ci, qui ne peut pas être séparée du politique, se développe grâce au fonctionnement des différentes formes institutionnelles. Plusieurs modes de coordination ont été identifiés par la littérature, à savoir, le « mode de coordination par le marché », le « mode de coordination éthique » et le « mode de coordination bureaucratique ». Vahabi (2010) a introduit un nouveau type de coordination qu’il a nommé : « mode de coordination destructive ». Celui-ci privilège la violence et les moyens coercitifs dans les relations sociales et assure une allocation appropriative des ressources. Vahabi présente la République iranienne comme un exemple-type du « mode de coordination destructive » étant donné son capitalisme rentier et la corruption de son système politique dans la gestion des ressources. Nous nous intéressons, dans ce travail de recherche, à étudier dans quelle mesure le cas du Liban peut être analysé à la lumière de ce mode de coordination destructive. / A « mode of coordination » is a concept that define the interaction between social relations and economy. The latter, which cannot be separated from politics, develops through the functioning of different institutional forms. Several methods of coordination have been identified in the literature, namely, the « market mode of coordination », the « ethics mode of coordination » and the « bureaucratic mode coordination mode ». Vahabi (2010) introduced a new type of coordination that he called it: the "destructive mode of coordination." This mode privilege violence and coercive means in social relations and provides an appropriate allocation of resources. Vahabi present Iranian Republic as a typical example of "destructive mode of coordination" because of the nature of its capitalism and corruption of its political system in the management of resources. We are interested in this research, to examine to what extent the case of Lebanon can be analyzed as a destructive mode of coordination.