Remarriages account for about one third of all marriages in the United States, however the research on remarried couple outcomes is limited, particularly with regard to finances and financial conflict. The family economic stress model theorizes that economic hardship promotes economic strain, which in turn promotes emotional distress and conflict patterns that have negative impacts on relationship satisfaction and relationship stability. This study used secondary cross-sectional dyadic data to conduct an actor-partner interdependence path analysis of 158 remarried couples to examine the direct and indirect effects of each spouse's perception of economic strain on their own marital satisfaction and stability, as well as on their spouse's marital satisfaction and stability, with financial conflict as an intermediary variable. Tests for indirect effects indicated that financial conflict strongly influences the relationship between economic strain and the marital outcomes (i.e., satisfaction and stability); none of the direct paths between economic strain and the marital outcomes were significant when accounting for financial conflict as a mechanism. Results indicated that, in the context of a remarriage, a person's perception of how much they have conflict about finances is a key mechanism that explains the association between that person's perception of economic strain and their marital satisfaction and stability, regardless of household income and marriage length. Clinicians who lack specific training in financial management but work with remarried couples experiencing economic strain and financial conflict may still be able to intervene effectively to improve relationship quality by helping spouses reduce interpersonal conflict. / Master of Science / Remarriages account for about one third of all marriages in the United States, however the research on the satisfaction (overall relationship quality) and stability (propensity for divorce) of remarried couples is limited, particularly with regard to disagreements about their finances (financial conflict). This study analyzed data from 158 remarried couples to examine the possible effects of each spouse's views of their perceived inability to meet their financial demands (economic strain) on their own, as well as their spouse's, marital satisfaction and stability (marital outcomes), with their perceived financial conflict acting as a mediating variable between economic strain and marital outcomes. Results indicated that, in the context of a remarriage, financial conflict strongly influenced the relationship between economic strain and marital outcomes, regardless of household income and marriage length, such that even though there is still a relationship between economic strain and marital outcomes apart from financial conflict, it is weaker than when financial conflict is included. In other words, risk of dissatisfaction and divorce are less about how financially strained a remarried couple perceives they are, and more about how frequently the couple perceives they have conflict about finances. Therefore, the results of this study indicated financial conflict frequency is an important mechanism for understanding how economic strain can influence remarital outcomes for both spouses. Clinicians working with remarried couples to improve their relationships, but lack specific training in financial management, may still be able to intervene effectively around the financial conflict.

The objective of this study was to evaluate the effects of sex, loading rate, and age on the tensile and compressive material properties of human rib cortical bone over a wide range of subject demographics. Tension coupons were tested from sixty-one (n = 61) subjects (M = 32, F = 29) ranging in age from 17 to 99 years of age (Avg. = 56.4 +/- 26.2 yrs.). Compression samples were tested from thirty (n = 30) subjects (M = 19, F = 11) ranging in age from 18 to 95 years of age (Avg. = 49.0 +/- 23.9 yrs.). For each subject, one coupon/sample was tested to failure on a material testing system at a targeted strain rate of 0.005 strain/s, while a second coupon/sample was tested at 0.5 strain/s. A load cell was used to measure axial load for both the tension coupons and compression samples. An extensometer was used to measure displacement within the gage length of the tension coupons and a deflectometer was used to measure displacement of the compression samples. Tension data were obtained from fifty-eight (n = 58) coupons at 0.005 strain/s and fifty-eight (n = 58) coupons at 0.5 strain/s, with fifty-five (n = 55) matched pairs. Compression data were obtained from thirty (n = 30) compression samples at 0.005 strain/s and thirty (n = 30) samples at 0.5 strain/s. The elastic modulus, yield stress, yield strain, ultimate stress, elastic strain energy density (SED), plastic SED, and total SED were then calculated for each tensile and compression test. In addition, failure stress and failure strain were calculated for each tension test. There were no significant differences in the tensile material properties between sexes and no significant interactions between age and sex for either method of loading. In regard to the differences in tensile material properties with respect to loading rate, yield stress, yield strain, failure stress, ultimate stress, elastic SED, plastic SED, and total SED were significantly lower at 0.005 strain/s compared to 0.5 strain/s. All material properties were significantly lower at 0.005 strain/s compared to 0.5 strain/s in compression. Spearman correlation analyses showed that all tensile material properties had significant negative correlations with age at 0.005 strain/s except modulus. At 0.5 strain/s, all tensile material properties except yield strain had significant negative correlations with age. No significant correlations were observed in material properties with respect to advanced age in compression at either loading rate. Although the results revealed that the tensile material properties of human rib cortical bone varied significantly with respect to chronological age, the R2 values only ranged from 0.15 - 0.62, indicating that there may be other underlying variables that better account for the variance within a given population. Overall, this is the first study to analyze the effects of sex, loading rate, and age on tensile material properties of human rib cortical bone using a reasonably large sample size and the first study to test the compressive material properties of human rib cortical bone. The results of this study provide data that allows FEMs to better assess thoracic injury risk for all vehicle occupants. Additionally, this study provides the necessary data to more accurately model and assess differences in the material response of the rib cage for nearly all vehicle occupants of driving age. / Master of Science / The thorax is one of the most frequently injured body regions in motor vehicle collisions (MVCs), and severe thoracic injuries have been shown to increase mortality risk. Finite element models (FEMs) of the human body are frequently used to evaluate thoracic injury risk. However, the accuracy of these models is dependent on the biomechanical data used to validate them. Although the material properties of bone have been shown to vary with respect to age and loading rate, previous studies that have evaluated the material properties of human rib cortical bone were limited to a small number of subjects, a narrow age range, one loading rate, and one loading mode (tension). Therefore, the purpose of this study was to evaluate the effects of sex, age, and loading rate on the tensile and compressive material properties of rib cortical bone over a wide range of subject demographics. Tension coupons were tested from sixty-one (n = 61) subjects (M = 32, F = 29) ranging in age from 17 to 99 years (Avg. = 56.4 ± 26.2 years). Compression samples were tested from thirty (n = 30) subjects (M = 19, F = 11) ranging in age from 18 to 95 years (Avg. = 49.0 ± 23.9 years). For each subject, one coupon/sample was tested to failure on a material testing system at a targeted strain rate of 0.005 strain/s, while the other coupon was tested at 0.5 strain/s. A load cell was used to measure axial load for both the tension coupons and compression samples. An extensometer was used to measure displacement within the gage length of the tension coupons and a deflectometer was used to measure displacement of the compression samples. There were no significant differences in material properties between sexes and no significant interactions between age and sex for either method of loading. In regard to the differences in tensile material properties with respect to loading rate, yield stress, yield strain, failure stress, ultimate stress, elastic SED, plastic SED, and total SED were significantly lower at 0.005 strain/s compared to 0.5 strain/s. All material properties were significantly lower at 0.005 strain/s compared to 0.5 strain/s in compression. In regard to the effect of age, all tensile material properties had significant negative correlations with age at except the modulus at 0.005 strain/s and yield strain at 0.5 strain/s. No significant correlations were observed in material properties with respect to advanced age in compression at either loading rate. Overall, this is the first study to provide the tension and compression data needed to more accurately model and assess differences in the material response of the rib cage for nearly all vehicle occupants of driving age.

Strain-mediated magnetoelastic composite materials are being considered for communication in lossy environments. Their consideration is attributable to predictions stating order of magnitude improvements over current antenna technology. The magnetic antenna design considered herein consists of three layers: 1) a piezoelectric layer, 2) a linear elastic layer, and 3) a magnetoelastic layer. The antenna operates by mediating strain through the device in a resonant bending mode. The magnetoelastic layer is stressed which results in a changing magnetization ultimately leading to a changing magnetostatic field in free space which acts as a signal for information transfer. In order to prove the efficacy of this approach finite element models have been developed to aid in the design and optimization process. Where these models fall short is in their overall run-time to fully resolve the coupled dynamics. It is for this reason that the work presented in this thesis focuses on the development of a figure of merit capable of predicting optimal bias conditions and geometries needing only the data from a static bias study from FEA. The material level magnetomechanical coupling factor is chosen as the foundation for the figure of merit. The figure of merit is then augmented to include structure level information regarding the demagnetizing field and the non-uniform stress distribution. The main results presented are the effects of including demagnetization and stress distributions, and most importantly the ability of the metric to predict the change in magnetization of the device. It is shown that for aspect ratios greater than roughly 2.5 the metric trends the same as the change in magnetization predicted by finite element simulations. The region of disagreement between the metric and the fully resolved finite element simulation is explained by tying back to underlying assumptions made during the formulation of the magnetometric demagnetization factor used in the analysis. The case is made for the figure of merit to be included in the analysis of strain-mediated antennas for its ability to find optimum designs while reducing the overall simulation run-time by an order of magnitude. / Master of Science / Many communication devices are readily available however there are a few key gaps in communication technology that are yet to be filled. Notably, communication in lossy environments using small scale, low frequency, devices has proven difficult due to the fundamental limits of antennas (a cell phone cannot communicate into a mine shaft for search and rescue operations, nor can they communicate underwater to submarines or divers for instance). A promising new approach of communication using smart magnetic materials is under consideration in this thesis. Specifically, the goal herein is to develop an analysis tool capable of predicting device performance without having to run computationally expensive/time consuming finite element simulations. In this thesis it is shown that the analysis tool is capable of predicting device performance while reducing the necessary simulation run-time by an order of magnitude. Using this tool, researches will be able to design better prototypes; moving one step closer to portable communication in lossy environments.

Knowledge of geotechnical soil properties in the upper meter of the seabed is important for challenges such as scour around submerged structures, management of unexploded ordnances, and generally issues associated with active sediment transport and deposition. Portable free fall penetrometers have been previously used to provide initial information on sediment type, strength, and stratification, but challenges with the calibration of empirical parameters such as the cone factor and strain rate factor hampered the derivation of geotechnical design parameters such as undrained shear strength. This challenge applies particularly in areas of more rare seabed soil conditions such as very soft estuarine sediments. This study aims to advance the analysis procedure of portable free fall penetrometers (PFFP) in soft subaquatic fine-grained soils with natural water contents greater than the liquid limit by estimating the undrained shear strength (su). The logarithmic and power law methods for strain rate correction were investigated at sites in the York River Estuary and yielded a match to vane shear results at a logarithmic multiplier of k=0.1-0.3 and a power law rate exponent of β=0.01-0.03, indicating minimal strain rate effects. Resulting representative cone factors based on sediment strength and profile groupings ranged from 7 to 12 for logarithmic, power law, and no strain correction, and were tested at sites in the Potomac River with similar sediment properties. The PFFP su compared well with mini-vane shear measurements with differences of less than ± 0.5 kPa. Additionally, the PFFP su showed inappreciable differences in strength with or without strain rate application. Therefore, these high water content soils that exhibit little strain rate effects within a soil behavior context, can be better understood through rheological studies. Rheological studies were conducted, and the storage and loss modulus were observed to remain constant when the soil is tested over a range of frequencies. This indicates that the sediment strength is not affected by the rate of soil testing. The outcome of this study is the advanced the use of the PFFP by quantifying the strain rate effects and defining the applicable cone factors for use in estimating the undrained shear strength of soft estuarine marine soils. Furthermore, the understanding of soil behavior of these soils has been explored from rheological context. / Master of Science / Presence of unexploded munitions (UXO) in waterways and coastal environments poses a danger to the populace. UXOs located proud on the seabed can be moved by hydrodynamic forces such as waves and currents to habited areas. This has prompted the need to understand how UXOs interact with the seabed regarding erosion, burial, as well as sinking. Current methods used to detect munitions can lack accuracy from unknown seabed soil conditions. Portable free fall penetrometers (PFFP) are rapid and economical tools that are used to obtain soil information in the seabed. However, the interpretation of the penetrometer data needs to be advanced to get more accurate results of soil strength. In this research, physical soil samples were retrieved and tested in the laboratory. The laboratory results were used to calibrate the PFFP to improve the estimation of soil strength from PFFP. The estuarine soil tested exhibited high water contents raising the question of whether to describe its behavior rather as soil or suspension. Further tests were carried out to study how this soil deforms and flows when a load is applied. The results from this research enable the measuring of strength of the seabed more accurately and improves the understanding of very soft estuarine soil behavior.

Modern engineering structures often incorporate new materials and complex designs for which existing techniques for nondestructive evaluation prove inadequate, especially for dynamic and in-service measurements. At the same time, optical fiber sensors have been identified as an ideal candidate for embedded and attached measurements of material parameters such as strain, temperature, or state of damage. In particular, sensors based on optical fiber modal interference phenomena have been shown to be capable of highly sensitive detection of static and dynamic strain. This work reviews known applications of modal domain sensing to measurement science to date, and discusses the principles behind the method. A general expression for the intensity distribution emerging from a multimode fiber is formulated, covering both few mode and highly multimode fibers, and new expressions for their sensitivity to both radial and axial strain are derived. Optimized multimode fibers are seen to show an intrinsic phase sensitivity which rivals or even surpasses that of the single mode interferometer, especially in the case of applied radial strain. The use of modal domain sensors for real-time ultrasonic wave transduction is described as a particular application to NDE, with experimental results being presented with regard to acoustic emission monitoring as well as the detection and analysis of shock waves due to impact. Finally, optimization schemes and alternatives for such sensors are addressed, and recommendations for future work are raised. / Ph. D.

With this research, we work towards the overall objective of customizing polymer molecules in terms of their molecular structure to optimize processing performance. The work includes analysis of the rheology in shear and shear-free flows for sparsely long-chain branched, LCB, polyethylene, PE, resins; determination of the consistency of the molecular based constitutive model, the pom-pom model; for these flows, and evaluation of the same PE resins in film-casting. As we progress towards molecular systems with defined molecular structural characteristics, we transition from a linear low density polyethylene, LLDPE, based series of PE resins to a high density polyethylene, HDPE, based series of PE resins, each with materials of varying degrees of sparse LCB. Evaluation of the shear step-strain rheology for the series of LLDPE-based PE resins allows for the assessment of any inadequacies associated with the step-strain experiments and the ability of the K-BKZ analog of the pom-pom constitutive model to predict step-strain rheological behavior. Finite rise time and wall slip are addressed to ensure the accuracy of the experimental step-strain measurements and eliminated as factors contributing to the stress relaxation moduli response. Analysis of the K-BKZ analog of the pom-pom constitutive model includes comparisons between experimental stress relaxation moduli and predictions from the model using pom-pom model parameters determined from extensional rheology. The results show inconsistencies in the model predictions, where the predictions fail to capture the short time behavior and accurately dampen at larger strains. Pom-pom model parameters are determined using the K-BKZ analog of the pom-pom constitutive model and fitting the stress relaxation moduli. These results are qualitatively consistent indicating that branching occurs on the longest backbone segments, but the values appear to be unrealistic with respect to the molecular theory. Analysis of film-width reduction or necking during film-casting for the series of LLDPE-based resins determines whether uniaxial extensional rheological characteristics, in particular strain-hardening, that are a result of LCB influence the film-necking properties. At the lowest drawdown ratio necking is observed to be reduced with increasing LCB, and thus strain-hardening characteristics. At the higher drawdown ratios it is observed that LCB no longer reduces necking and the curves merge to the results found for linear PE, except in the case of LDPE, which shows reduced necking at all drawdown ratios. Furthermore, comparisons of film necking are also made to separate the effects of molecular weight distribution, MWD, and LCB. The results indicate that both broadening the MWD and the addition of sparse LCB reduce the degree of necking observed. It is established that film necking is more significantly reduced by LCB than by broadening the MWD. Analysis of the uniaxial extensional and dynamic shear rheology with the pom-pom constitutive model reveals that a distribution of branches along shorter relaxation time modes is important in reducing necking at higher drawdown ratios. Factors such as shear viscosity effects, extrudate swell, and non-isothermal behavior were eliminated as contributing factors because of the similar shear viscosity curves, N1 curves, and activation energies among the sparsely LCB PE resins. The same experimental concepts have been extended to the series of HDPE-based resins, but the lack of adequate uniaxial extensional data prevents a thorough analysis with respect to uniaxial extensional characteristics. Regardless, in the context of step-strain rheology, the results were found to be similar with those of the LLDPE-based series of resins, where a distinctive shape at short times was observed for any of the PE resins possessing some level of LCB that was not apparent in the linear PE resins. Film-casting revealed similar results to those of the LLDPE-based materials as well, but a broader spectrum of drawdown ratios revealed greater insight into how the distribution of branching controls the film-casting response. At low drawdown ratios all materials exhibit the same necking behavior. At intermediate drawdown ratios separation occurs where the linear PE resins experiences the most drastic necking, the sparsely LCB PE resins show reduced necking, and the LDPE shows an even greater reduction in necking. Progression then to the higher drawdown ratios results in similar necking behavior for the linear and sparsely LCB PE resins and greatly reduced necking for the LDPE. These results support the idea that to reduce necking the backbone segments that dominate the film-casting behavior must contain some level of LCB. / Ph. D.

The National Highway Traffic Safety Administration (NHTSA) reported that in 2008 there were a total of 37,261 automotive related fatalities, 26,689 of which were vehicle occupants. It has been reported that in automotive collisions chest injuries rank second only to head injuries in overall number of fatalities and serious injuries. In frontal collisions, chest injuries constitute 37.6% of all AIS 3+ injuries, 46.3% of all AIS 4+ injuries, and 43.3% of all AIS 5+ injuries. In side impact collisions, it has been reported that thoracic injuries are the most common type of serious injury (AIS≥3) to vehicle occupants in both near side and far side crashes which do not involve a rollover. In addition, rib fractures are the most frequent type of thoracic injury observed in both frontal and side impact automotive collisions. Anthropomorphic test devices (ATDs), i.e. crash test dummies, and finite element models (FEMs) have proved to be integral tools in the assessment and mitigation of thoracic injury risk. However, the validation of both of these tools is contingent on the availability of relevant biomechanical data. In order to develop and validate FEMs and ATDs with improved thoracic injury risk assessment capabilities, it is necessary to generate biomechanical data currently not presented in the literature. Therefore, the purpose of this dissertation is to present novel material, structural, and global thoracic skeletal response data as well as quantify thoracic injury timing in both frontal belt loading and side impact tests using cadaveric specimens. / Ph. D.

The initiation and propagation of adiabatic shear bands is analyzed numerically for an impulsively loaded thick-walled steel tube. A circumferential V-notch located at the outer surface of the center of the tube provides a stress concentration. The material is modeled as strain hardening, strain-rate hardening and thermal softening. The dynamic loading conditions considered are pure torsion, axial pressure combined with torsion, and internal pressure combined with torsion. Because of the stress concentration, a shear band will first initiate in an element adjoining the notch tip and propagate radially inwards through the thickness of the tube. The speed of propagation and the amount of energy required to drive a shear band through the material are calculated. The effects of the pressure preload and the depth of the notch are studied. Also, the influence of thermal softening is investigated by modeling it after a relation proposed by Zhou et al. <i>[Vita removed July 18, 2008 CK/GMc 2/2/2012]<i> / Master of Science

This study adds to current understandings of the relationship between socioeconomic conditions and health by examining the influence of work-family strain on health in the context of the recent Great Recession and the preceding and following years in the United States. Analyses used data from the 2002 and 2008 National Survey of the Changing Workforce (NSCW) and 2002, 2006 and 2010 General Social Survey's Quality of Working Life modules. Findings suggest that work-family strain in general increased during the Great Recession compared to non-recessionary periods, that people who experience lower levels of work-family strain enjoy better health, and that health tends to be better during non-recessionary periods compared to recessionary periods. Work-family strain was shown to mediate a small portion of the impact of macroeconomic condition on health. While work-family strain does not appear to be a primary mediator of the relationship macroeconomic condition and health it remains significant and also a very alterable condition. Findings suggest that positive workplace environments can significantly lessen the negative impacts of work-family strain on health of employees. Improvements of workplace environments and conscious efforts to reduce work-family strain for employees could have significant impact on the health of the working US population with minimal costs during both recessionary and non-recessionary periods. / Ph. D.

Sensing has been essential for the investigation, understanding, exploitation, and utilization of physical phenomena. Traditional single-point sensing methods are being challenged by the multi-point or distributed sensing capabilities afforded by optical fiber sensors. A powerful technique available for distributed sensing involves the use of the Optical Frequency Domain Reflectometry (OFDR). This work focuses on using OFDR as a means of obtaining distributed vibration measurements using the Rayleigh scatter along a single-mode optical fiber. The effort begins by discussing various distributed measurement techniques currently in use before discussing the OFDR technique. Next, a thorough discussion on how high spatially resolved Rayleigh measurements are acquired and how such measurements can be used to make static strain measurements is presented. A new algorithm to resolve strain at regions of high spatial gradient is developed. This results in enhanced measurement performance of systems using the Rayleigh scatter to determine static strain or temperature measurements by improving measurement fidelity at the high gradient locations. Next, discussions on how dynamic strain (vibration) couples to optical fiber in a single point and in a distributed setting are presented. Lessons learned are then used to develop a new and unique distributed vibration measurement algorithm. Various consequential benefits are then reviewed before concluding remarks are stated. A simulation model was developed and used to supplement this investigation in every step of the discussion. The model was used to gain insight on how various physical phenomena interact with the optical fiber. The simulation was also used to develop and optimize the high gradient and vibration algorithms developed herein. Simple experiments were then used to validate the theory and the simulation models. / Ph. D.