This thesis presents two studies related to head injury. The study presented in Chapter 1 reviewed findings of cranial movement in animal and human specimens and evaluate the validity of cranial movement due to manual manipulation in humans through engineering analysis. The study had two parts. In Part I, the literature was reviewed to determine the cranial motion in animals and humans. Engineering analysis was done in Part II to determine the amount of force necessary to cause cranial motion in the studies from Part I using skull stiffness values from published studies. Chapter 2 explored data collection methodologies used in frontal sled tests. Several data collection methodologies exist for collecting kinematic data, such as Vicon motion analysis, video analysis, and sensors. Head trajectories from motion data and accelerometer data were plotted up to maximum forward excursion of the head for eight frontal sled tests, four conducted at Virginia Tech and four at the University of Virginia. In addition, the percent difference between maximum forward excursion values from sensor and motion data were calculated. Finally, Chapter 3 discusses the literary contributions of each study and to which journals they will be submitted. / Master of Science

An enhanced demand for lightweight materials in automotive applications has resulted in the growth of the use of injection molded discontinuous fiber-reinforced thermoplastics. During the intensive injection molding process, severe fiber breakage arises in the plasticating stage leading to a broad fiber length distribution. Fiber orientation distribution (FOD) is another highly anisotropic feature of the final injection molded parts induced by the mold filling process. The mechanical and other properties can be highly dependent on the fiber length distribution and fiber orientation distribution. The residual fiber length in the final part is of great significance determining the mechanical performances of injection molded discontinuous fiber reinforced thermoplastic composites. One goal of this research is to develop a fiber length characterization method with reproducible sampling procedure in a timely manner is described. In this work is also proposed an automatic fiber length measurement algorithm supported by Matlab®. The accuracy of this automatic algorithm is evaluated by comparing the measured results using this in-house developed tool with the manual measurement and good agreement between the two methods is observed. Accurate predictions of fiber orientation are also important for the improvement of mold design and processing parameters to optimize mechanical performances of fiber-reinforced thermoplastics. In various fiber orientation models, a strain reduction factor is usually applied to match the slower fiber orientation evolution observed experimentally. In this research, a variable strain reduction factor is determined locally by the corresponding local flow-type and used in fiber orientation simulation. The application of the variable strain reduction factor in fiber orientation simulations for both non-lubricated squeeze flow and injection molded center-gated disk, allows the simulated fiber re-orient rate to be dependent on the local flow-type. This empirical variable strain reduction factor might help to improve the fiber orientation predictions especially in complex flow, because it can reflect the different rates at which fibers orient during different flow conditions. Finally, the stiffness of injection-molded long-fiber thermoplastics is investigated by micro-mechanical methods: the Halpin-Tsai (HT) model and the Mori-Tanaka model based on Eshelby's equivalent inclusion (EMT). We proposed an empirical model to evaluate the effective fibers aspect ratio in the computation for the fiber bundles under high fiber content in the as-formed fiber composites. After the correction, the analytical predictions had good agreement with the experimental stiffness values from tensile tests on the composites. Our analysis shows that it is essential to incorporate the effect of the presence of fiber bundles to accurately predict the composite properties. / PHD / An enhanced demand for lightweight materials in automotive applications has resulted in the growth of the use of injection molded discontinuous fiber-reinforced thermoplastics. The injection molding process results in fiber length and fiber orientation distributions in the final parts. The mechanical and other properties can be highly dependent on the fiber length distribution and fiber orientation distribution. This work focuses on the process-structure-property relationship of fiber-thermoplastic composites. A novel fiber length measurement procedure and an automatic fiber length measurement tool were developed to improve the accuracy of fiber length measurement. The existing fiber orientation models have been improved by integration of the flow-type dependent fiber orientation kinetics. To improve the stiffness predictions, an empirical model has been developed to include the effects of fiber clumping on the elastic properties of injection molded fiber composites.

Java applets are developed to assist in the learning of basic structural analysis concepts. In order for these programs to be easily available over the Internet, they are written in the object-oriented Java programming language. The Java programs known as applets are embedded in HTML documents. The HTML documents, part of a series of instructional units, present the topics demonstrated by the applets. The applets include truss and frame determinacy applets; a three-hinged arch bridge applet; determinate and indeterminate truss analysis applets; determinate and indeterminate frame analysis applets and an influence line analysis applet. These programs are available to any student or instructor with Internet access. The applets provide good examples of the application of object-oriented programming and the development of software for a graphical user interface. They also serve as excellent tools that facilitate the understanding of structural engineering concepts utilizing a medium that allows independent learning at an individual pace. / Master of Science

Down syndrome (DS) is the most common genetic condition caused by an extra copy of chromosome 21. Adults with DS have cardiovascular and metabolic alteration, which may lead to an increased number of cardiovascular disease risk factors in this population. Such impairments may affect their ability to exercise and perform moderate-to-vigorous physical activity (MVPA). Moreover, MVPA may affect arterial health differently in adults with DS due to endothelial dysfunction and sympathetic impairment. The purpose of this dissertation was to investigate differences in cardiovascular health and physical activity (PA) profiles between adults with and without DS. Specific aims of this dissertation were to determine whether traditional cardiovascular disease risk factors predict arterial stiffness in adults with and without DS, investigate differences in PA and sedentary behavior (SB) levels and patterns using population-specific activity intensity cut-points in adults with and without DS, and to investigate whether DS moderates the relationship between SB and MVPA levels and arterial stiffness. Results from stepwise linear regression indicated that age, DS, and waist circumference significantly predicted arterial stiffness for the entire sample, and that many of the risk factors that predict arterial stiffness in adults without DS – body composition, blood pressure, and MVPA – do not predict arterial stiffness in adults with DS. Results from mixed-model ANOVA indicated that adults with DS had less sedentary time but greater MVPA than adults without DS and that adults with DS performed greater number of sedentary and MVPA bouts than adults without DS; however, these bouts were of shorter duration. Lastly, results from moderation analysis indicated that DS moderated the relationship between MVPA and arterial stiffness; however, the effect of age was greater than MVPA or DS on arterial stiffness. Adults with DS have greater number of cardiovascular disease risk factors than adults without DS; however, this does not appear to increase arterial stiffness. Furthermore, adults with DS may have better PA and SB profiles than adults without DS; however, MVPA levels do not affect arterial stiffness in this population. Therefore, differences in cardiovascular health and PA profiles may identify disparities in health between adults with and without DS.

Wood pallets are heavily used throughout the United States and the World to transport, store, and protect goods. During a lifecycle, pallets typically experience various stresses from warehouse storage racks, materials handling equipment, and floor stacking situations. The components within the pallet interact to withstand load and impact forces. Every year product damage and human injury/death result from improperly designed pallets, non-reliable packaging systems, and careless materials handling methods. In use wood pallets are exposed to a variety of loads and support conditions. This research investigates the effect of different pallet designs and support conditions on pallet stiffness. Uniform loads were applied to pallet designs containing thick or thin components and three, four, or five non-notched and notched stringers. The pallets were supported using racked across the length, racked across the width, fork truck tine, and floor stack support conditions. Structural analysis was used to determine the test loads for each pallet bending test. Pallet deflections were measured in specific locations for each bending test. Pallet test results indicated that heavy duty pallets are 6.5 times stiffer than light duty pallets tested in the racked across width (RAW) support condition. Non-notched pallets tested are 51% stiffer than notched pallets in the racked across length (RAL) support condition. Test results also indicated that a wider fork tine support span decreases average pallet stiffness by 29% and 49% for 4 and 5 stringer pallets, compared to 3 stringer. The heavy duty pallets tested are, on average, 48.3% stiffer than light duty pallets in the fork tine support condition. For the notched fork tine support condition, the average pallet stiffness decreased by 29% and 3% for four and five stringer pallets, compared to three stringer. Pallet joints were tested to measure joint stiffness. Joint rotation tests were conducted to determine rotation modulus and joint withdrawal tests were conducted to determine joint withdrawal stiffness. The joint stiffness measurements were used as spring constants in structural analysis based on semi-rigid joint performance. Heavy duty pallet joints were approximately half as stiff (6758 in-lbs/radian) in rotation as light duty pallet joints (12907 in-lbs/radian). Light duty pallet joints were less stiff (44008 lbs/in) in withdrawal than heavy duty pallet joints (57823 in/lbs). The results from this research were used to compare with results from ANSYS (Version 11) structural model estimates. The average predicted error for all pallet bending tests was 13% (heavy duty) and 3% (light duty). / Master of Science

Yes / Tumor progression alters the composition and physical properties of the extracellular matrix. Particularly, increased matrix stiffness has profound effects on tumor growth and metastasis. While endothelial cells are key players in cancer progression, the influence of tumor stiffness on the endothelium and the impact on metastasis is unknown. Through quantitative mass spectrometry, we find that the matricellular protein CCN1/CYR61 is highly regulated by stiffness in endothelial cells. We show that stiffness-induced CCN1 activates β-catenin nuclear translocation and signaling and that this contributes to upregulate N-cadherin levels on the surface of the endothelium, in vitro This facilitates N-cadherin-dependent cancer cell-endothelium interaction. Using intravital imaging, we show that knockout of Ccn1 in endothelial cells inhibits melanoma cancer cell binding to the blood vessels, a critical step in cancer cell transit through the vasculature to metastasize. Targeting stiffness-induced changes in the vasculature, such as CCN1, is therefore a potential yet unappreciated mechanism to impair metastasis. / Cancer Research UK (CRUK Beatson Institute C596/A17196, CRUK Glasgow Centre C596/A18076 and S.Z. C596/A12935)

Active Magnetic Bearings (AMB) are a relatively recent innovation in bearing technology. Unlike conventional bearings, which rely on mechanical forces originating from fluid films or physical contact to support bearing loads, AMB systems utilize magnetic fields to levitate and support a shaft in an air-gap within the bearing stator. This design has many benefits over conventional bearings. The potential capabilities that AMB systems offer are allowing this new technology to be considered for use in state-of-the-art applications. For example, AMB systems are being considered for use in jet engines, submarine propulsion systems, energy storage flywheels, hybrid electric vehicles and a multitude of high performance space applications. Many of the benefits that AMB systems have over conventional bearings makes them ideal for use in these types of vehicular applications. However, these applications present a greater challenge to the AMB system designer because the AMB-rotor system may be subjected to external vibrations originating from the vehicle's motion and operation. Therefore these AMB systems must be designed to handle the aggregate vibration of both the internal rotor dynamic vibrations and the external vibrations that these applications will produce. This paper will focus on the effects of direct base excitation to an AMB/rotor system because base excitation is highly possible to occur in vehicular applications. This type of excitation has been known to de-stabilize AMB/rotor systems therefore this aspect of AMB system operation needs to be examined. The goal of this research was to design, build and test a test rig that has the ability to excite an AMB system with large amplitude base excitation. Results obtained from this test rig will be compared to predictions obtained from linear models commonly used for AMB analysis and determine the limits of these models. / Master of Science

Subsurface volume loss takes place in many geotechnical situations, and it is inherently accompanied by complex stress and displacement fields that may influence the performance of engineered geosystems. This research is a deformation-centered analysis, it depends on soil compressibility and it is implemented using finite elements. Soil stiffness plays a central role in predicting ground deformation. First, an enhanced Terzaghi’s soil compressibility model is proposed to satisfy asymptotic conditions at low and high stress levels with a small number of physically meaningful parameters. Then, the difference between small and large strain stiffness is explored using published small and large-strain stress-strain data. Typically, emphasis is placed on the laboratory-measured stiffness or compressibility; however, there are pronounced differences between laboratory measurements and field values, in part due to seating effects that prevail in small-thickness oedometer specimens. Many geosystems are subjected to repetitive loads; volumetric strains induced by drained repetitive ko-loads are experimentally investigated to identify shakedown and associated terminal density. The finite element numerical simulation environment is used to explore the effect of localized subsurface mass loss on free-surface deformation and shallow foundations settlement and bearing capacity. A stress relaxation module is developed to reproduce the change in stress associated to dissolution features and soft zone formation. The comprehensive parametric study is summarized in terms of dimensionless ratios that can be readily used for engineering applications. Field settlement data gathered at the Savannah River Site SRS are back-analyzed to compare measured values with predictions based on in situ shear wave velocity and strain-dependent stiffness reduction. The calibrated model is used to estimate additional settlements due to the pre-existing cavities, new cavities, and potential seismic events during the design life of the facility.

One of the most important prerequisites in the drug development is to attain a reproducible and robust product in terms of its nature, and its chemical and physical properties. This can be challenging, since the crystalline form of drugs and excipients can be directly transformed into the amorphous one during normal pharmaceutical processing, referred to as process-induced amorphisation or process-induced disorder. The intention of this thesis was to address the mechanisms causing disorder during powder flow and milling and, in association with this, to evaluate, the ability of Raman spectroscopy and atomic force microscopy (AFM) to quantify and characterize process-induced disorder. The amorphisation mechanisms were controlled by stress energy distribution during processing, which in turn was regulated by a series of process parameters. Compression and shearing stress caused by sliding were stress types that acted on the particles during powder flow and ball milling process. However, sliding was the most important inter-particulate contact process giving rise to amorphisation and the transformation was proposed to be caused by vitrification. The plastic stiffness and elastic stiffness of the milling-induced particles were similar to a two-state particle model, however the moisture sorption characteristics of these particles were different. Thus the milled particles could not be described solely by a two-state particle model with amorphous and crystalline domains.  Raman spectroscopy proved to be an appropriate and effective technique in the quantification of the apparent amorphous content of milled lactose powder. The disordered content below 1% could be quantified with Raman spectroscopy. AFM was a useful approach to characterize disorder on the particle surfaces. In summary, this thesis has provided insight into the mechanisms involved in process-induced amorphisation of pharmaceutical powders and presented new approaches for quantification and characterization of disordered content by Raman spectroscopy and atomic force microscopy.

A rigidez a pequenas deformações e sua respectiva degradação são informações cruciais para se determinar parâmetros de projeto mais precisos. Apesar de sua importância, estas propriedades não são usualmente investigadas. Assim, o objetivo do presente trabalho foi de estudar a degradação da rigidez da areia de Osório artificialmente cimentada por meio de diferentes métodos de laboratório. A escolha por um material cimentado ocorreu baseada em apelos ambientais, econômicos e técnicos. O presente estudo também objetiva desenvolver e validar um sistema de Bender Elements (BE), que forneça resultados confiáveis na avaliação da degradação do solo. Pares de BE foram construídos para serem utilizados em testes de bancada e ensaios triaxiais. Além disso, um amplificador de sinal, assim como scripts foram desenvolvidos especialmente para a interpretação dos dados no domínio do tempo. O aumento da rigidez durante o processo de cura foi avaliado por meio da velocidade de onda cisalhante, medida pelos BE e por um equipamento de ondas ultrassônicas (UPV), sob condições de pressão atmosférica. Ensaios de degradação da rigidez, por sua vez, foram conduzidos em uma câmara triaxial especialmente modificada para a instalação dos BE Após sete dias de cura atmosférica, os corpos-de-prova foram cisalhados no equipamento triaxial modificado enquanto mudanças de rigidez eram obtidas por meio de testes de BE e instrumentação interna. Os resultados demonstraram que o sistema BE desenvolvido foi bem sucedido na avaliação da rigidez do solo estudado. A comparação entre os resultados do BE e UPV não foi conclusiva no que se refere à dependência do solo à frequência. A degradação do módulo obtida por ambas as metodologias apresentou uma adequada concordância para o corpo-deprova com menor quantidade de cimento. Módulos obtidos por BE foram pouco maiores que os obtidos por medidas internas. Ainda, a interpretação no domínio do tempo dos resultados de BE para corpos-de-prova cimentados, especialmente durante ensaios triaxiais, foi difícil de ser executada, reforçando a necessidade de se combinar diferentes métodos de interpretação quando BE forem utilizados. / Stiffness at small strains and its respective degradation are crucial information to determine more precise design parameters. Despite their importance, these properties are not usually investigated. Thus, the objective of the present work was to study the stiffness degradation of artificially cemented Osorio sand by means of different laboratory methods. The choice for a cemented material was based on environmental, economic, and technical appeals. The present study also aimed to develop and validate a Bender Elements (BE) system that can provide reliable results in the evaluation of soil degradation. BE pairs were built for bench and triaxial tests. In addition, a signal amplifier, as well as scripts were specially developed for the interpretation of data in the time domain. Increase in stiffness during the curing process was evaluated by shear wave velocity measured by BE and an ultrasonic pulse wave velocity (UPV) equipment under atmospheric pressure conditions. Stiffness degradation tests were conducted in a specially modified triaxial chamber for BE installation After seven days of atmospheric curing, specimens were sheared in the modified triaxial equipment, while stiffness changes were obtained by BE tests and internal instrumentation. The results showed that the developed BE system was capable of successfully evaluating the studied soil. The comparison between BE and UPV results was not conclusive regarding soil dependence on frequency. Shear module degradation obtained with the two methodologies presented an adequate agreement for the specimen with the smaller amount of cement. Shear moduli obtained with BE were slightly larger than those obtained with internal measurements. Also, BE results interpretation in the time domain for cemented specimens, especially in the triaxial tests, was difficult to perform, reinforcing the need to combine different interpretation methods when BE are used.