Nanoindentation has brought in many features of research over the past decade. This novel technique is capable of producing insights into the small ranges of deformation. This special point has brought a lot of focus in understanding the deformation behavior under the indenter. Nickel, iron, tungsten and copper-niobium alloy system were considered for a surface deformation study. All the samples exhibited a spectrum of residual deformation. The change in behavior with indentation and the materials responses to deformation at low and high loads is addressed in this study. A study on indenter geometry, which has a huge influence on the contact area and subsequently the hardness and modulus value, has been attempted. Deformation mechanisms that govern the plastic flow in materials at low loads of indentation and their sensitivity to the rate of strain imparted has been studied. A transition to elastic, plastic kind of a tendency to an elasto-plastic tendency was seen with an increase in the strain rate. All samples exhibited the same kind of behavior and a special focus is drawn in comparing the FCC nickel with BCC tungsten and iron where the persistence of the elastic, plastic response was addressed. However there is no absolute reason for the inconsistencies in the mechanical properties observed in preliminary testing, more insights can be provided with advanced microscopy techniques where the study can be focused more to understand the deformation behavior under the indenter. These experiments demonstrate that there is a wealth of information in the initial stages of indentation and has led to much more insights into the incipient stages of plasticity.

The thesis deals with the design and implementation of broadband and narrowband antennas and their applications in practical environment. In this thesis, a new concept for designing the UWB antenna is proposed based on the CRLH metamaterials and this UWB antenna covers a frequency range from 2.45 GHz to 11.6 GHz. Based on the design of the UWB antenna, another antenna is developed that can cover a very wide bandwidth i.e from 0.66 GHz to 120 GHz. This antenna can not only be used for UWB applications but also for other communication systems working below the UWB spectrum such as GSM, GPS, PCS and Bluetooth. The proposed antenna covering the bandwidth from 0.66 GHz to 120 GHz is by far the largest bandwidth antenna developed based on metamaterials. Wide band antennas are not preferred for sensing purpose as it is difficult to differentiate the received signals. A multiband antenna which can be used as a strain sensor for structural health monitoring is proposed. The idea is to correlate the strain applied along the length or width with the multiple resonant frequencies. This gives the advantage of detecting the strain applied along any direction (either length or width), thus increasing the sensing accuracy. Design and application of a narrow-band antenna as a temperature sensor is also presented. This sensor can be used to detect very high temperature changes (>10000C). This sensor does not require a battery, can be probed wirelessly, simple and can be easily fabricated, can withstand harsh environmental conditions.

Employee turnover is a complex problem with many intertwining contributors. In general newly hired employees at an organization have a higher risk of injury. However, few studies have explored occupational injury as a predictor of employment duration. In this study we hypothesized that employees who sustained an injury during the early stages of employment were prone to higher turnover rates. All employees hired from 2012-2016 were identified using a large Midwestern manufacturing facilities human resources database (n=3765). Corresponding occupational injury information from the same time period was extracted from the onsite occupational health center. Employment duration was the dependent variable which was dichotomized as (i) working < 60 days or (ii) working ≥60 days. The 60-day threshold was based on the employer’s internal estimation of the duration of employment required to recover training costs. The primary independent variable was a first-time visit to the occupational health center within the first 60 days of employment, categorized as (i) no visit, (ii) a visit within 1-20 days, or (iii) a visit within 21-60 days. A secondary independent variable incorporated the nature of injury, classified as repetitive strain, acute sprain/strain, or other occupational injury types. Covariates included demographics (e.g., age, gender, and race/ethnicity), shift placement (e.g. first, second, third), and nature of assigned job (e.g., assembly, fabrication, maintenance). Incidence rates of first-time visits were calculated (i) across the full study period and (ii) for a reduced period that included only the first 60 days of employment. Logistic regression was used to estimate adjusted associations between the primary/secondary independent variables and the dependent variable. Of the 3765 employees, 1184 (31.5%) worked less than 60 days. About two-thirds were male, about half were white/Caucasian, and the overall mean age was 33.8±10.8 years. Between 2012 and 2016, 1105 first-time visits to the occupational health center were recorded for all new hires with an overall incidence rate (IR) of 47/100 person-years (PY). The IR for repetitive strain was 18/100PY. Of the 1105 first-time visits, 408 occurred within the first 60 days of employment with an overall IR of 85/100PY and an IR for repetitive strain of 36/100PY. Employees who visited the occupational health center in the first 20 days of employment were more likely to terminate prior to the 60-day threshold (adjusted odds ratio: 1.7; 95% confidence interval: 1.3-2.4). Elevated associations were seen for all nature of injury categories which occurred within 20 days when compared to non-injured employees. Overall, the results suggest that experiencing an occupational injury (in particular, a repetitive strain injury) within the first 20 days of employment is associated with termination before 60 days. Our results may not be generalizable to all manufacturing enterprises, and we do not make a distinction between voluntary and involuntary termination. However, the results indicate that employers should examine policies and practices to minimize the burden of injury among new employees and reduce turnover. In the case of the study facility, an extended or modified work hardening program could maximize new employees’ adaptation to the physical demands of manufacturing work.

This study looks at one hundred cases of siblicide committed across the United States. Cases are analyzed for criminality patterns which are used by the author to determine offender typologies. The goal of this research is to determine why this type of crime is committed, this question is answered by analyzing offenders and the crimes themselves. This research is important because this type of crime dates back to biblical times with the story of Cane and Able, and it has remained a problem within society. Though this type of crime has been investigated in the past it is necessary to reanalyze similar crimes to remain current on data, over time society changes and with it so does the method and rational for crime. By analyzing crimes of this nature and identifying typologies it will begin to paint a picture of why such crimes occur and can assist those who investigate similar crimes today. To conduct this research one hundred cases of siblicide were collected from across the United States in qualitative form. These cases were found online from reputable news sources that reported on them. They were then compiled into a grid and broken down by date, state, ethnicity and age of offenders and victims. The grid also contains data on weapon used, rational for killing, and a description of the crime that occurred. After the cases were collected, the author picked through the details and began to identify patterns within the cases. From these cases typologies can be created based on similar patterns between the cases. Once typologies are made the data is looked at through a theoretical lens using strain theory to determine if stress could potentially be a leading cause in this crime. The data compiled for this research is still being examined and a conclusion has not yet been made, though the author does expect to see a high level of stressors for those who commit this type of crime. This is expected due to the displacement that can occur with the presence of a sibling. It is expected that in a number of cases factors such as conflict, jealousy and financial stress will be the root cause of the violence that occurs. As for cases of younger children involved in cases the author expects to see a high level of accidental shootings paired with parental neglect. In conclusion this research will shed more light on a crime that has been occurring for thousands of years, and will allow one to understand siblicide in a modern context, by discussing why and how it occurs in today’s society. If it is found that stressor are not the predominant cause of this type of crime it would mean that there is a separate issue to address within this type of crime, and this research would help to identify what it is that truly causes siblicide to occur.

Motor vehicle collisions (MVCs) are a leading cause of injuries and injury-related fatalities in the United States. The National Highway Traffic Safety Administration (NHTSA) reported over 21,250 vehicle occupant fatalities in 2011, with 1,240,000 injuries sustained by passenger car occupants alone. MVCs are a common cause of blunt abdominal injuries. It has been reported that approximately 9,000 front seat occupants sustain moderate to severe abdominal injuries in frontal MVCs in the United States each year. A detailed understanding of the occurrence and mechanisms of abdominal injuries, as well as knowledge of the biomechanical response and tolerance of the abdomen in crash-specific loading modes, could benefit the reduction of abdominal organ injury incidence in MVCs. Therefore, the objective of the research presented in this dissertation was to characterize abdominal injury mechanisms, tissue failure thresholds, and internal organ response to blunt impacts of the abdomen. Field accident data from the Crash Injury Research and Engineering Network (CIREN) database were analyzed to determine the occupant and crash characteristics associated with crash-induced hollow abdominal organ injuries. Dynamic equibiaxial tension tests were conducted on tissue samples obtained from the human post-mortem stomach, small intestine, and colon to characterize the material properties and failure tolerance of these tissues. The effects of cadaver orientation on the relative position of the abdominal organs of two cadavers were quantified, and high-speed biplane x-ray imaging was used to investigate the relative kinematics of the thoracic and abdominal organs of four cadavers in response to crash-specific loading modes. Test configurations included blunt abdominal and thoracic impacts and driver-shoulder seatbelt loading. The motivation for this research was to advance efforts toward abdominal organ injury mitigation in MVCs, with each aspect of this research generating novel injury biomechanics data with applications for future experimental testing and finite element modeling. / Ph. D.

The master’s thesis deals with issues belonging to the field of dental biomechanics, specifically the mechanical interaction of dental implants with the bone tissue of the mandible. The thesis focuses on the stress-strain analysis of the mandible with the implant inserted in different positions, with a different angle relative to the occlusal plane. The solution is performed by computational modeling using the finite element method. The geometry model of mandible was created based on CT images. The aim of the master’s thesis was also to compare the influence of the choice of the material model of cancellous bone tissue on the resulting stress-strain states of the mandible with the dental implant. Three material models of cancellous bone tissue were created - two homogeneous material model and a heterogeneous material model, which was based on CT image data. The work also investigates the effect of rotation (+5° or -5°) of implants in basic positions on the resulting stress-strain states. The stress-strain analysis showed that position and rotation has a greater effect on the stress and strain of bone tissue and implant than the chosen material model of cancellous bone tissue.

MSCAGR (Animal Science) / Department of Animal Science / The aim of the study was to investigate the effects of feed withdrawal and strain on laying performance and egg quality of White and Brown Hy-line layers. Fifty four hens for each strain (White Hy-Line and Brown Hy-line) aged 18 weeks (point of laying stage) were used in the investigation. Feed withdrawal had no effect (P>0.05) on laying performance, mortality rate, egg internal and external quality, but significantly affected (P<0.01) average feed intake, body weight, small and extra-large eggs percentages. Hens under ad libitum consumed more feed than hens under four hours and eight hours feed withdrawal. High body weight was observed on ad libitum fed hens, intermediate on eight hours feed withdrawn hens and lower at four hours feed withdrawn hens. High percentage of small graded eggs was observed on four hours feed withdrawn hens, intermediate on eight hours feed withdrawn hens and lower on ad libitum fed hens. High percentage of extra-large graded eggs was observed on ad libitum fed hens, intermediate on eight hours feed withdrawn hens and lower four hours feed withdrawn hens. Strain had a significant effect on average egg weight, median egg weight, albumen weight, extra-small, small, medium and large graded eggs percentages (P<0.01) and on body weight, egg height , egg width, average egg shell colour (P<0.05). Strain did not affect (P>0.05) average feed intake, body weight change, egg output, feed conversion ratio, mortality rate, egg shell breaking force, albumen height, yolk height, yolk weight, extra-large and jumbo graded eggs percentage. Brown Hy-Line layers had high average egg weight, median egg weight, egg height, egg width, and average egg shell colour and albumen weight than White Hy-Line layers. Small sized eggs percentage and body weight were high on White Hy-Line layers compared to Brown Hy-Line layers. Medium and large sized eggs were high on Brown Hy-Line layers than White Hy-Lines. Feed withdrawal by strain interaction effect was observed on body weight, average egg weight and median egg weight, albumen weight and egg height, percentage of small, medium and large graded eggs (P<0.05). Brown Hy-Line hens under eight hours feed withdrawal had high egg weight, median egg weight, egg height, albumen weight and under eight hours feed withdrawn White Hy-Line hens had lower albumen height compared to other interactions. In all interactions White Hy-Line had high percentage of small graded eggs whereas Brown Hy-line had high percentage of large and medium graded eggs. / NRF

Fibre reinforced polymers (FRP) are finding increasing use in structures subjected to high rate loading such as blast or impact. Proper design of such structures requires thorough characterisation of the material behaviour over a range of loading rates from quasi-static to impact. This thesis investigated the quasi-static and impact response of Glass Fibre Polypropylene (GFPP) in compression, bending and delamination. The bending and delamination response of Fibre Metal Laminates (FMLs) based on GFPP and aluminium was also investigated at quasi-static and impact rates. High strain rate (5x10^2 to 10^3 /s) compression tests were conducted on GFPP using a compressive Split Hopkinson Pressure Bar (SHPB) and a Direct Impact Hopkinson Pressure Bar (DIHPB), in the through-thickness and in-plane directions. In both loading directions, the peak stress of GFPP increased linearly with the logarithm of strain rate. For in-plane loading, the failure modes were dominated by localised fibre buckling and kink bands, leading to delamination. The through thickness loading produced macroscopic shear and spreading failure modes. However, both of these failure modes are linked to in-ply fibre failures, due to through thickness compression causing transverse tensile strain. Previous studies of similar materials have not explicitly stated the link between through thickness compression and fibre failure associated with transverse tensile strain. A novel test rig was developed for Three Point bend testing at impact rates. The specimen was supported at the outer points on a rigid impacter and accelerated towards a single output Hopkinson Pressure Bar (HPB), which impacted the specimen at its midspan. Previous impact bend test rigs based on HPBs were limited to testing specimens with deflections to failure up to approximately 1mm, whereas the rig implemented herein measured deflections up to approximately 10 mm. This configuration permits the output HPB to be chosen purely on the magnitude of the expected impact force, which resulted in superior force resolution to configurations used in other studies. The HPB Impact Bend rig was used to test GFPP and aluminium-GFPP FML specimens, at impact velocities ranging from 5 to 12 m/s. The flexural strength of GFPP increased with strain rate, while the flexural response of the FML specimens was relatively insensitive to strain rate. v Several candidate delamination test geometries were investigated at quasi-static displacement rates (1 mm/min), and the Single Leg Bend (SLB) test was identified as suitable for adaptation to higher rate testing. Single Leg Bend delamination tests of both GFPP and FML specimens were performed using the HPB Impact Bend rig, at impact velocities of 6 to 8 m=s. The shape of the force displacement response for the high rate testswas markedly different from the quasi-static tests, for both the GFPP and FML specimens. Finite element (FE) simulation of the quasi-static and impact rate SLB tests on GFPP indicated that the difference was probably due to the interaction of flexural vibrations and stress waves in the specimen and the impacter cross member. The experimental results and FE analysis suggest that the delamination fracture toughness of GFPP decreases slightly as strain rate increases. High rate delamination tests on FML specimens resulted in unstable crack growth.

Thesis advisor: Udayan Mohanty / The high surface area and atomic-level tunability offered by nanoparticles has defined their promise as heterogeneous catalysts. While initial studies began with nanoparticles of a single metal assuming thermodynamic shapes, modern work has focused on using nanoparticle composition and geometry to optimize nanocatalysts for a wide variety of reactions. Further optimization of these refined nanocatalysts remains difficult, however, as the factors that determine catalytic activity are intertwined and a fundamental understanding of each remains elusive. In this work, precise synthetic methods are used to tune a number of factors, including composition, strain, metal-to-metal charge transfer, atomic order, and surface faceting, and understand their impact on catalysis. The first chapter focuses on current achievements and challenges in the synthesis of intermetallic nanocatalysts, which offer long-range order that allows for total control of surface structure. A particular focus is given to the impact of the synthetic approach on the activity of the resulting nanoparticles. In the second chapter, multilayered Pd-(Ni-Pt)x nanoparticles serve as a controlled arena for the study of metallic mixing and order formation on the nanoscale. The third chapter controls the shell thickness of Au@PdPt core-alloyed shell nanoparticles on a nanometer scale to isolate strain at the nanoparticle surface. In the fourth chapter, the synthetic approaches of chapters two and three are applied to catalysis. In totality, the work presented here represents a brick in the foundation of understanding and exploiting structure-function relationships on the nanoscale, with an eye toward the rational design of tailored nanocatalysts. / Thesis (PhD) — Boston College, 2020. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

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