Each year there is an increasing incidence of slip and fall accidents, especially among the elderly population. Existing evidence has identified several aging effects related to slip and fall accidents, yet, the causes of these accidents with advancing age are still little known. The objective of this research was to investigate the factors influencing the initial phase of unexpected slips and falls in younger and older individuals. More specifically, the relationship between ankle strength, the ankle joint power to transfer the whole body center-of-mass during normal gait, and the likelihood of slip-induced falls was identified. The walking experiment and the ankle strength tests were conducted in the Locomotion Research Laboratory, Virginia Tech. Fourteen old (67-79 years old) and 14 young (19-35 years old) individuals participated in this study (7 male and 7 female for each age group).Within a subsequent 20-minute session of natural walking on a linear track, kinematic and kinetic data were collected synchronously. A slippery surface was introduced to the participant on the purpose of unexpected slip event. The ankle strength tests were performed using a dynamometer. The results indicated that ankle strength degradation in older individuals was related to the outcome of slips (i.e., higher frequency of falls). The results also indicated that older individuals' RCOF was less than their younger counterparts. However, older individuals fell more often than younger individuals. It is concluded that friction demand characteristics may not be a total deterministic factor of fall accidents. Thus, the further research should focus not only on the dynamic of slips, but also on the dynamics of falls.</p> / Master of Science

Free-Fall Penetrometer (FFP) testing is an easy and rapid test procedure for seabed sediment characterization favorable to conventional geotechnical testing mainly due to its cost-effectiveness. Yet, FFP testing results are interpreted using empirical correlations, but difficulties arise to understand soil behavior under the high-strain rate (HSR) loading effects during rapid FFP penetration. The numerical simulation of FFP-soil interaction is also challenging. This study aims to numerically analyze FFP testing of saturated loose sands using the particle-based Material Point Method (MPM). The numerical analysis was conducted by simulating calibration chamber FFP tests on saturated loose quartz sand. The numerical results using quasi-static properties resulted in a reaction of the sand softer than the actual calibration chamber test. This implied the necessity of considering HSR effects. After performing parametric analyses, it was concluded that dilation plays an important role in the response of sand-water mixtures. Comparison of dry and saturated simulations showed that FFP penetration increases when the soil is dry and tends to develop a general bearing capacity failure mechanism. This is because the pore water increases the stiffness of the system and due to the increased strength that develops in saturated dilative sands when negative pore pressures develop. Local bearing failure mechanism is observed in all saturated simulations. Finally, numerical CPT (quasi-static) and FFP tests were used to examine the strain rate coefficient used in practice (K); and a consistent range between 1 to 1.5 was obtained. / Master of Science / Accurate characterization of seabed sediments is crucial to understand sediment mobilization processes and to solve nearshore engineering problems such as scouring around offshore structures. Its portability, low testing effort, and repeatability make FreeFall Penetrometer (FFP) testing a highly cost-effective sediment characterization test. Nevertheless, due to the complex penetration mechanism of FFPs in soils (e.g., high-strain rate effects due to rapid FFP loading), converting FFP output into practical information is complicated, and it heavily relies on empirical correlations. This thesis presents a numerical analysis of FFP testing on saturated sand using the Material Point Method. First, the simulation results were compared with laboratory tests. Later, a parametric study was performed to understand the effect of different material parameters on the FFP response and to highlight in a simplified manner the effects of rapid loading on the sand behavior. Additional simulations in dry sand (without water) revealed that dry conditions provide larger FFP penetrations than saturated ones for the same material parameters. Lastly, the strain rate coefficient, which is a parameter required in one of the most common empirical methods for converting FFP output into geotechnical parameters, was back-calculated. The results were consistent with values used in practice for similar conditions.

Geotechnical sediment properties such as moisture content, relative density, bearing capacity, and undrained shear strength have been discussed in the context of coastal sediment dynamics. However, these properties have rarely been assessed in their respective relevance or quantitatively related to sediment transport and erodibility. Also, to date there is no framework available for collecting direct measurements of these properties for estimating initiation of motion and erosion rates. Here, it is postulated that improving the ability to measure geotechnical sediment properties in energetic foreshore environments can improve our ability to predict coastal response to climate change. Through a series of field measurements, the research presented here (1) provides a framework for conducting geotechnical measurements of beaches, (2) advances portable free fall penetrometer (PFFP) data analysis in intertidal environments through the introduction of an impact velocity dependent strain-rate correction factor, (3) relates textural and sediment strength properties derived from PFFP measurements to an erosion rate parameter and hydrodynamically driven bed-level change, and (4) uses PFFP measurements to develop a sediment classification scheme in terms of soil behavior and erosion behavior for a mixed sediment type Arctic environment. Relationships between sediment properties other than grain size, most significantly void ratio, and erodibility parameters highlight the relevance of these measurements in geomorphodynamically active sandy beach environments. For the cohesive sediments in the Arctic, undrained shear strength was also related to an erosion rate parameter, allowing for a categorical framework for erodibility classification to be developed. The cohesive framework was combined with the relationships developed for sandy sediments and used to highlight areas of active sediment transport in the context of local morphodynamic and ice gouging processes. Finally, a simple case study showed how implementing in-situ erodibility parameters was important for long-term morphological modelling. The results represent a step forward in our ability to predict and mitigate climate change related issues from coastal erosion. / Doctor of Philosophy / Climate change driven impacts on coastal environments include increasing frequency and severity of storms, coastal erosion, and inundation of populated areas. Specifically for Arctic environments, warming has caused more sediment to be introduced into coastal waters as well as accelerated rates of permafrost melting and shoreline retreat and decreases in sea ice. One aspect of understanding how these changes will continue to affect coastal communities and our ability to predict climate change effects is understanding the role of sediment properties on sediment erosion and shoreline change. Physical and geomechanical (strength) properties of coastal sediments are important for a variety of coastal applications but have rarely been investigated in the context of quantifying, predicting, and assessing erosion, specifically in the context of field measurements. Towards this end, a series of field surveys were conducted along the coast of North Carolina at a sandy beach, and in Harrison Bay, Alaska, an Arctic coastal zone with both sandy and muddy sediments. Tools for taking physical samples of the beach and seabed, measuring the sediment strength, among other properties in place were used to characterize the local sediments. Once a framework was developed for characterizing the type of sediment, the measured properties were then related to measurements of erosion rate from a series of laboratory experiments performed on physical samples taken from the sites. Finally, one of the instruments for measuring sediment strength both on land and in the water was used to develop classification schemes for seabed sediments in terms of their erodibility. The results of this work highlight the importance of geotechnical properties for coastal sediment transport processes, reveal new relationships between sediment properties and properties quantifying erosion behavior, and offer a framework for future research to classify erodibility of coastal environments in the field with a single piece of equipment. Overall, the work presented here contributes to our ability to measure, quantify, and predict coastal response to climate change.

This thesis examines representations of the French educational system in Senegal as presented in L'aventure ambiguë and L'appel des arènes. Each unfolding respectively within a colonial and postcolonial Senegalese context, the novels problematize the French school system by incorporating representations of its failures. As this thesis will argue, analyzing each author's educational discourse will unmask a Senegalese perspective on a French institution, showcase various ways that Senegalese students internalized their educational experience and provide representations of the ways in which French education could be, and was, utilized by its pupils. Using two African novels in French to interpret historical experience will facilitate understanding of the French educational system from a Senegalese perspective. The first chapters create a foundation for analysis: Chapter two explains French goals and objectives when implementing a formal educational system in West Africa, while chapter three explores the form and function of the African novel in order to present it as a useful historical tool. Having defined the African novel in French as a viable means to interpret historical experience, chapter four focuses analysis on revealing how a system that was meant to procure French dominance, was ultimately transformed into a tool for Senegalese advantage. / Master of Arts

Yes / Ice cover formed on an alluvial channel can significantly alter the flow characteristics, such as the vertical distributions of streamwise velocity and shear stress, and hence the water and sediment transport process. The vertical profile of the suspended sediment concentration in the ice-covered alluvial channels with steady uniform flows is investigated in this study. To calculate the suspended sediment concentration, we are based on the Schmidt O’Brien equation and deduce an analytical model that employs an existing eddy viscosity model and a modified formula of the sediment fall velocity considering the common effects of the upper and lower boundaries. The proposed analytical model is then validated by using available experimental data reported in the literature. The predicted accuracy of the proposed model is evaluated through error statistics by comparing to previous modeled results. The relative concentration profiles of the suspended sediment are subsequently simulated by applying the validated analytical model with different characteristic parameters. Results show that the relative concentration decreases with the increase of both the ice cover roughness and the sediment fall velocity. The uniformity of the relative concentration distribution is closely related to the value of the proportionality parameter σ, revealing the physical mechanism that the more prominent the turbulent diffusion effect is, the more uniform the relative concentration profile is. / This work was supported by the National Natural Science Foundation of China (grant 604 numbers 52020105006 and 11872285) and the Open Funding of State Key Laboratory of Water Resources and Hydropower Engineering Science (WRHES), Wuhan University (Project number 2018HLG01).

SAMMANFATTNING Bakgrund: Personer med demenssjukdom har en dubbelt så hög fallrisk i jämförelse med kognitivt friska i samma ålder. Det är viktigt att systematiskt arbeta preventivt med fallrisk. Syfte: Syftet med studien var att undersöka förekomst och utveckling av antal fallhändelser och planerade fallpreventiva åtgärder för personer boende på demensboende i Sverige. Syftet var även att undersöka förekomst och utveckling av träningsinriktade fallpreventiva åtgärder och studera samband mellan fallhändelser, genomförda riskbedömningar och träningsinriktade fallpreventiva åtgärder. Detta för åren 2016–2022. Metod: Studien genomfördes som en ekologisk studie med registerdata från det nationella kvalitetsregistret Senior Alert. Trendberäkningar utfördes med Jonckheere-Terpstra Test och beräkning av Kendall´s Tau. För sambandsanalyserna genomfördes korrelationsanalyser, samt enkla och multivariata regressionsanalyser. Resultat: Det fanns en fallande trend avseende antal fallhändelser mellan åren 2016–2022. De vanligaste planerade fallpreventiva åtgärderna var larm, läkemedelsgenomgång och assistans vid förflyttning. Träningsinriktade fallpreventiva åtgärder planerades in i mycket låg utsträckning. Samband sågs mellan minskat antal fallhändelser och planering av träningsinriktade fallpreventiva åtgärder, främst balans-, muskelfunktions- och styrketräning. Samband sågs även mellan fall och genomförda riskbedömningar för fall. Metodologiska svagheter har uppmärksammats varför generaliserbarheten till hela målpopulationen är svag. Konklusion: Sammanfattningsvis visar resultaten en fallande trend med färre antal fall på svenska demensboenden under åren 2016–2022. Om fler individer skulle fallriskbedömas och fler träningsinriktade fallpreventiva åtgärder skulle planeras in finns möjligheten att förebygga ännu fler fall. Fysioterapeuter bör involveras i det fallpreventiva arbetet för att initiera balans-, muskelfunktions- och styrketräningsinsatser. För att öka tillförlitligheten till resultaten behövs framtida studier som undersöker samband mellan fall och planerade samt genomförda fallpreventiva åtgärder på individnivå.

Italian ryegrass (Lolium perenne) is one of the most troublesome weeds of rice in Mississippi. Its resistance to multiple modes of action has made it more difficult to control in recent years. The most effective and economical management strategy to control Italian ryegrass is fall-applied residual herbicides; however, the most effective products are not labeled for use in the fall prior to rice seeding. Therefore, research was conducted in Stoneville, MS, to evaluate the effect of fall-applied residual herbicides on rice growth and development. Acetochlor should not be applied in fall targeting Italian ryegrass in fields where rice is scheduled for seeding the following spring. Clomazone remains the only viable treatment as a fall-applied residual herbicide in rice areas.

In-situ geotechnical testing of surficial sediment layers in areas of active sediment dynamics can provide essential information about physical and geotechnical variations of sediment properties with regards to active sediment remobilization processes. For example, portable free fall penetrometers (PFFPs) can assist with the detection of mobile sediment layers. They are easy to deploy, and can provide a large spatial coverage in a time- and cost-effective manner. However, they often struggle to provide more detailed information about the properties of mobile sediment layers due to a lack of calibration and validation in existing data sets. Currently, existing sediment samplers often disturb, or ignore the uppermost sediment layers. Simultaneous sediment sampling and geotechnical profiling is needed to fill this gap, and to drive data interpretation forward. A field investigation of surficial sediments was conducted in the wetland waterways of coastal Louisiana in 2014. In-situ tests were conducted using PFFP, and disturbed sediment samples were collected in selected locations. The results allowed us to map changes in sediment strength and stratification, and correlate the geotechnical results to local site characteristics. However, the need for high quality sediment samples for calibration and validation was emphasized by the results. Three different sediment sampler add-on units targeting mobile layers were designed and manufactured based on lessons-learned from the literature. The designs were tested in the laboratory and in the field (Yakutat, Alaska and York River, Virginia) in 2017. The samples were analyzed to understand the influence of different sampler characteristics on collected sample quality, and, to define mobile layer sampler characteristics that enable simultaneous geotechnical testing and the collection of high quality samples. Following field survey campaigns in the York River, Virginia in 2016 allowed to assess surficial sediment layer characteristics and behavior based on a coupled analysis of geotechnical data from in-situ PFFP tests and the sedimentological data collected using box cores and the novel sediment sampler. In summary, novel strategies and instrumentation to carry out simultaneous sediment sampling and geotechnical profiling of seabed surface layers were tested, and new pathways for geotechnical data analysis for the investigation of mobile seabed layers were presented. / PHD / Coastal erosion and evolution, marine slope stability, river bank stability, maintenance of navigable water depth, or the stability of offshore structures are some of the modern challenges impacted by subaqueous sediment dynamics. Although, numerous researchers have investigated this issue for decades, some gaps in knowledge still prevail due to its interdisciplinary and complex nature. One of the most intriguing questions related to seabed soil behavior is the characterization of the sediment layers and textures at the seafloor surface being directly involved in sediment transport processes and local geomorphodynamics. These layers are often characterized by a most recent sediment deposition history, and a loose particle arrangements. Accordingly, these sediment layers show almost no resistance to accommodate loads (the sediment strength), and are highly erodible. The strength of surficial layers can be evaluated using portable free fall penetrometers (PFFPs) which are rapid and economic geotechnical site investigation tools designed to geomechanically test seabed surface layers. Nevertheless, there is a lack of data from areas of active sediment dynamics leading to gaps in understanding regarding sediment strength variations affected by active sediment transport processes. This research widens the use of PFFPs into wetland waterways (e.g. channels, lakes, and strait). Moreover, first attempts to quantify the influence of wave forces on sediment beds were also made and promising results were obtained which can open paths to new interdisciplinary. However, the PFFPs are challenged by a lack of physical sediment samples to groundtruth and verify the collected data. Thus, the sampling of such sediment layers is a currently missing part in the framework of in-situ investigations. This dissertation aimed to develop a novel field sampling technology in terms of an add-on unit that can be attached to portable dynamic penetrometers for deployment in areas of active sediment dynamics. Thus, the data to measure sediment strength can be collected simultaneously with physical seabed samples. Different sampler designs were tested and evaluated, and new pathways for joint geotechnical and sedimentological data analysis demonstrated. The results of this research can therefore contribute to the current understanding of seabed sediment behavior.

Portable Free Fall Penetrometers (PFFPs) are lightweight tools used for rapid and economic characterization of surficial subaqueous sediments. PFFPs vary in weight, shape and size with options for using add-on units. The different configurations enable deployments in various environments and water depths, including the nearshore zone where conventional methods are challenged by energetic hydrodynamics and limited navigable depth. Moreover, PFFPs offer an opportunity to reduce the high site investigation costs associated with conventional offshore geotechnical site investigation methods. These costs are often a major obstacle for small projects serving remote communities or testing novel renewable energy harvesting machines. However, PFFPs still face issues regarding data analysis and interpretation, particularly in energetic sandy nearshore areas. This includes a lack of data and accepted analysis methods for such environments. Therefore, the goal of this research was to advance data interpretation and sediments characterization methods using PFFPs with emphasis on deployments in energetic nearshore environments. PFFP tests were conducted in the nearshore areas of: Yakutat Bay, AK; Cannon Beach, AK; and the U.S. Army Corps of Engineers' Field Research Facility's beach, Duck, NC. From the measurements, the research goal was addressed by: (1) introducing a methodology to create a regional sediment classification scheme utilizing the PFFP deceleration and pore pressure measurements, sediment traces on the probe upon retrieval, and previous literature; (2) investigating the effect of wave forcing on the sediments' behavior through correlating variations in sediment strength to wave climate, sandbar migration, and depth of closure, as well as identifying areas of significant sediment mobilization processes; and (3) estimating the relative density and friction angle of sand in energetic nearshore areas from PFFP measurements. For the latter, the field data was supported by vacuum triaxial tests and PFFP deployments under controlled laboratory conditions on sand samples prepared at different relative densities. The research outcomes address gaps in knowledge with regard to the limited studies available that investigate the sand geotechnical properties in energetic nearshore areas. More specifically, the research contributes to the understanding of surficial sediment geotechnical properties in energetic nearshore areas and the enhancement of sediment characterization and interpretation methods. / PHD / The increasing demand for energy, fluctuations of oil prices, and the expected reduction in the world’s oil production in addition to concerns associated to the global climate change drive the search for renewable energy sources. Out of the different sources of renewable energy, the reliable availability of waves is an advantage over other sources like solar and wind. However, different challenges are still facing the advancement of generating energy from waves. One important challenge is the reliability of the anchoring or foundation system, and the associated site characterization and data collection. The stability of the systems depends on the sediment strength (ability accommodate loads), sediments susceptibility to scour (removal of the sediments around the foundations), and local morphodynamics (changes in the seabed shape). In fact, the stability of the foundations in the seabed represents a major concern for many nearshore and offshore structures. Accordingly, the site characterization stage of any project is essential to mitigate the risks of failures, as well as to achieve cost-effective designs. Portable Free fall penetrometers (PFFPs) are rapid and economical tools used to characterize uppermost seabed sediments. The variability of such devices in weight, shape and size enables the use in different environments and water depths. However, data of PFFPs in sandy sediments is still limited which contradicts the fact that sand represents the most common soil type on the beaches worldwide. Accordingly, the aim of this research is to investigate the sediment behavior in energetic wave areas, and to advance the methods of interpreting the PFFP data in sandy nearshore zones. A PFFP was used to characterize the sediments in three main areas: Yakutat Bay, AK, Cannon Beach, AK and the U.S. Army Corps of Engineers’ Field Research Facility’s beach, Duck, NC. The results were utilized to introduce a sediment classification scheme and complete an existing sediment distribution map for Yakutat Bay, AK; study the effect of storms on the seabed sediment strength; and to determine sand strength parameters using PFFP measurements. The results of this research will contribute to improve the sediment characterization methods and to understand topmost sediment layers’ properties.

The taphonomy and paleoecology of a well-preserved mosasaur (DSM 10716) are reported from Oktibbeha County, Mississippi. The mosasaur was recovered from the Prairie Bluff Chalk, the exact stratigraphic position and age confirmed using established foraminiferal zonation for the Late Cretaceous of the U. S. Gulf Coastal Plain. A species identification of Mosasaurus cf. hoffmanni Mantell is given using shape and structure of the quadrate and jugal, as well as tooth counts for the dentary, maxilla, and pterygoid. DSM 10716 exhibits well-preserved trace fossils including feeding traces and the remains of encrusting bivalves. The associated fossils are probed for similar phenomena to modern whale falls and other ancient carcass falls. Based on associated fossils present on DSM 10716, evidence for a mobile scavenger stage, a possible enrichment opportunist stage, and a reef stage is established. No chemosynthetic organisms were detected to suggest the existence of a sulfophilic stage.