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Predicting sediment transport at sandy beaches is a significant challenge in civil engineering owing to the variability in hydrodynamic, morphological, and geotechnical properties within a site and across multiple sites. Additionally, there are difficulties in measuring in-situ properties, and challenges in identifying and quantifying the different relevant driving and resisting forces. These challenges are further exacerbated in the intertidal zone where the addition of infiltration-exfiltration, wave run-up and run-down, bore collapse, cyclic emergence and submergence of sediments, interactions between standing waves and incident bores, and other processes must be considered. Among these many processes, pore pressure gradients within sandy beach sediments affect sediment transport by reducing the sediment's effective stress to zero (this process is called liquefaction). Despite the known importance of these pressure gradients with respect to sediment transport, there has been little field evidence of the role that these pore pressure gradients have on sediment transport, how they relate to the hydrodynamic properties, and their inclusion into predictive sediment transport equations. This study is based on field measurements of hydrodynamic and geotechnical properties, as well as pore pressure gradients during storm and non-storm conditions at sandy beaches in the intertidal zone. From the analysis of these field measurements, it was found that (1) liquefying pressure gradients are likely to develop in sediments that are rapidly inundated during storm conditions; (2) the magnitude of pore pressure gradients is related to the asymmetry of the pressure gradient and can occur with shoreward-directed near bed velocities; and (3) during non-storm conditions, pressure gradients that often do not exceed liquefaction criteria occurred more (less) frequently during a time period where erosion occurred in large (small) quantities, indicating that small non-liquefying pore pressure gradients may facilitate sediment transport. The results of this study demonstrate that current methods of scour calculations must include effects of pore pressure gradients to reduce error. Additionally, from this work it was found that sediment transport can be directed shoreward under momentary liquefaction. Finally, the results of this study show that sediment pore pressure gradients are related to wave skewness, spatial group steepness, and temporal group steepness which may aid modelling of pore pressure gradients. / Doctor of Philosophy / The transport of sediment particles (in this case, sand grains at beaches) is difficult to predict because of the many different governing processes that can be hard to measure, may be hard to relate to erosion or sediment accumulation specifically, and the variability in sediment and flow properties (grain size, fluid velocity, and others) at a specific location and across different locations. Storms, like hurricanes, tropical storms, and tsunamis, can drastically change the expected water properties (like water depth, wave height, and wave period), and the effects of water pressure within the sand bed. When a wave moves across the sand it causes a change in the water pressure that is within the sand. This water pressure is not the same throughout the sand with depth. When the gradient, or the difference between the water pressure at two different vertical locations, is large enough, the sand behaves like a fluid (like quicksand) and becomes easier to move, this process is called liquefaction. Even though previous work has shown that these pressure gradients (and the resulting liquefaction) is important for sediment transport, there have been few field measurements demonstrating their impact on sediment transport and how these gradients (and the resulting liquefaction) relate to wave and sand properties. This study presents field measurements of pressure gradients, wave and sediment properties, and sediment transport events during both storm and non-storm conditions. From these field measurements, it was shown that (1) during an extreme storm event, pressure gradients that liquefy the sediment are likely to occur on sediments that are not normally subjected to waves; (2) liquefying pressure gradients can occur when waves arrive at the beach, which may cause sediment to be moved shoreward; and (3) during non-storm conditions, pressure gradients that do not liquefy the sand occurred frequently during a sediment transport event, suggesting that these smaller pressure gradients may contribute to sediment transport by reducing the effective weight of the sediment. This work can be used to further understand the behavior of sediment pore pressure gradients, their relation to hydrodynamic properties, and how they influence sediment transport allowing for better predictions of sediment transport, beach nourishment calculations, and the design of coastal structures.

Yes / The near-trapping effects on wave-induced dynamic seabed response and liquefaction close to a multi-cylinder foundation in storm wave conditions are examined. Momentary liquefaction near multi-cylinder structures is simulated using an integrated wave-structure-seabed interaction model. The proposed model is firstly validated for the case of interaction of wave and a four-cylinder structure, with a good agreement with available experimental measurements. The validated model is then applied to investigate the seabed response around a four-cylinder structure at 0° and 45° incident angles. The comparison of liquefaction potential around individual cylinders in an array shows that downstream cylinder is well protected from liquefaction by upstream cylinders. For a range of incident wave parameters, the comparison with the results for a single pile shows the amplification of pressure within the seabed induced by progressive wave. This phenomenon is similar to the near-trapping phenomenon of free surface elevation within a cylinder array. / Energy Technology Partnership (ETP), Wood Group

Yes / Stability and safety of offshore wind turbines with mono-pile foundations, affected by nonlinear wave effect and dynamic seabed response, are the primary concerns in offshore foundation design. In order to address these problems, the nonlinear wave effect on dynamic seabed response in the vicinity of mono-pile foundation is investigated using an integrated model, developed using OpenFOAM, which incorporates both wave model (waves2Foam) and Biot’s poro-elastic model. The present model was validated against several laboratory experiments and promising agreements were obtained. Special attention was paid to the systematic analysis of pore water pressure as well as the momentary liquefaction in the proximity of mono-pile induced by nonlinear wave effects. Various embedment depths of mono-pile relevant for practical engineering design were studied in order to attain the insights into nonlinear wave effect around and underneath the mono-pile foundation. By comparing time-series of water surface elevation, inline force, and wave-induced pore water pressure at the front, lateral, and lee side of mono-pile, the distinct nonlinear wave effect on pore water pressure was shown. Simulated results confirmed that the presence of mono-pile foundation in a porous seabed had evident blocking effect on the vertical and horizontal development of pore water pressure. Increasing embedment depth enhances the blockage of vertical pore pressure development and hence results in somewhat reduced momentary liquefaction depth of the soil around the mono-pile foundation. / Energy Technology Partnership (ETP), Wood Group Kenny, and University of Aberdeen; the National Science Fund for Distinguished Young Scholars (51425901) and the 111 project (B12032).

Studies suggest that sleep disturbance may be an important etiological factor in the development of comorbid anxiety and depressive disorders, whereby anxiety leads to sleep difficulties, which in turn increase the vulnerability for depression. The primary aim of this study was to determine whether the sequential comorbidity patterns observed at the disorder level (i.e., where anxiety disorders most often precede insomnia, and insomnia most often precedes depression) were also present in daily fluctuations of symptoms. The secondary aim was to explore possible moderators of any observed temporal associations. Participants were 15 patients with generalized anxiety disorder (GAD; mean age = 28.9 years, SD = 9.8) and 15 good sleeper controls (mean age = 27.1 years, SD = 8.3) who were comparable in female:male ratio (73% female vs. 67% female). For 14 days, participants wore an actigraph to objectively assess sleep quality (sleep onset latency, total sleep time, wake after sleep onset, sleep efficiency) and completed daily symptom ratings multiple times each day using their smartphones to assess symptoms of anxiety, depressed mood, and subjective sleep quality. Study aims were assessed using multilevel modeling, with daily symptoms nested within individuals. Many of the analyses were lagged such that the time-varying predictor variable preceded the time-varying outcome variable temporally. Consistent with hypotheses, results demonstrated that anxious mood was predictive of later subjective and objective sleep disturbance in individuals with GAD, and this effect was strongest among individuals with higher levels of neuroticism, negative affect, and dysfunctional beliefs about sleep. Anxious mood was not associated with later subsequent sleep disturbance in healthy controls. In the GAD group, subjective and objective sleep disturbance predicted later depressed mood; this effect was moderated by temperament and dysfunctional beliefs about sleep. For the control group, the effect of subjective sleep disturbance on later depressed mood was moderated by neuroticism and the effect of objective sleep disturbance was moderated by dysfunctional beliefs about sleep, suggesting that sleep disturbance may increase vulnerability for depressed mood even in healthy individuals. These results suggest that explicitly targeting sleep disturbance during the treatment of GAD may attenuate the experience of depressive symptoms.

Psychological flexibility (PF) is defined as one’s ability to pursue valued activities despite distress. PF is a critical process of change in evidence-based treatments, and is associated with psychosocial health and functioning. Although PF is considered context-dependent, previous research often measures PF as a static construct, often by administering the Acceptance and Action Questionnaire, which may not fully capture the construct of PF and limits understanding of how PF may change over time. One approach for measuring individual dynamics over time is ecological momentary assessment (EMA), which has been applied to numerous psychological constructs, including PF recently. This study investigated the dynamic relationship between PF, affect, and stress in a clinical sample of 39 individuals. Six items from the Process Based Assessment Tool were used to measure PF in terms of experiential avoidance and values-promoting processes. Participants completed a two-week EMA phase which included answering daily self-report items, and collecting smartphone and wearable technology data on screen time, steps, sleep quality, distance traveled, and activity. I hypothesized that PF would vary within and across time and context to predict affect and stress and expected that indicators of psychosocial health and measures of psychological processes would influence PF, affect, and stress. Results revealed significant associations such that flexibility was generally related to higher positive affect, lower negative affect, and lower stress. Some PF-items were associated with better day-quality ratings. PF interacted with context (conflict or valued action) and type of situation, with greater PF generally associated with valued-actions. Measures of psychological and attentional processed differentially interacted with PF to predict affect and stress. Step count interacted with PF in several models. Screen time was associated with affect and stress at a given timepoint. Heart-rate variability was differentially related to stress, affect, and PF within and across time. Activity, GPS, and sleep quality data were not significant. Overall, this study supports evidence that PF is highly idiographic and related to indicators of psychosocial wellbeing over time, generally supporting my hypotheses.

Non-suicidal self-injury (NSSI), the deliberate and direct damage of one’s body tissue without suicidal intent, is a pervasive public health concern often leading to clinically significant long-term consequences (e.g., permanent scarring, hospitalization) that is theorized to be facilitated by negative affect and emotion dysregulation. The Emotional Cascade Model proposes that NSSI partially functions to disrupt the reciprocal and rapid amplification of negative affect driven by rumination. However, limited research has focused on state rumination and the distinct contribution of maladaptive and adaptive rumination subtypes, as well as the role of positive affect within this framework. Thus, the purpose of the current study was to replicate and explore the independent influences of overall and momentary (1) positive and negative affect and (2) rumination on NSSI acts and urges, as well as (3) the extent to which rumination moderates the relationship between affect and NSSI. To do so, rumination, affect, and NSSI urges and acts were assessed 4 times daily via ecological momentary assessment for 21-days among thirty undergraduate participants with past month NSSI. Our results partially replicated existing literature, such that overall negative affect was associated with greater overall NSSI urge strength and momentary negative affect and rumination predicted stronger NSSI urges at the next alert, with increased momentary rumination strengthening the relationship between momentary negative affect and NSSI urge. Exploratory investigations of overall and momentary positive affect showed some negative associations with NSSI urges and behaviors, with no moderating effect of rumination. Data did not support the independent examination of maladaptive and adaptive rumination subtypes. Taken together, this study highlighted the importance of exploring state rumination (in addition to trait) and affect in understanding NSSI thoughts and behaviors, and calls for future studies to further investigate distinct properties of rumination to understand its impact on specific emotions that maintain NSSI engagement. / Psychology

La Dépression Post-AVC (DPAVC) constitue une des complications psychiatriques les plus fréquentes dans les suites d’un Accident Vasculaire Cérébral (AVC) avec des conséquences majeures en termes de récupération fonctionnelle et de qualité de vie. Il est nécessaire de disposer de critères permettant une identification précoce des patients à risque afin de leur proposer des aides adaptées. L’objectif de ce travail de thèse est d’étudier certains facteurs de risque et de protection de la DPAVC avec une approche en vie quotidienne chez des patients présentant un AVC peu invalidant. Dans une première partie, nous présentons l’étude du rôle exercé par le soutien social et la routinisation sur la sévérité des symptômes dépressifs trois mois après l’AVC par la méthode « Ecological Momentary Assessment ». Dans une seconde partie, nous explorons le rôle de la voix comme marqueur précoce de la DPAVC. Nous avons mis en évidence que la perception du soutien social initial influence l’intensité des symptômes dépressifs et les activités trois mois après. D’autre part, nous avons observé une dynamique temporelle unidirectionnelle entre l’augmentation des routines et la survenue de symptômes dépressifs plus intenses. Enfin, les analyses vocales nous ont permis d’identifier des marqueurs de DPAVC avec des modifications longitudinales de la fréquence fondamentale ainsi que des marqueurs précoces (shimmer et ruptures de voisement). Au-delà des facteurs cliniques traditionnellement reconnus, ce travail a mis en évidence de façon écologique de nouveaux marqueurs de risque de DPAVC dont la détection pourrait permettre d’élaborer de nouvelles stratégies de prévention et de prise en charge / Post-stroke depression (PSD) is one of the most common psychiatric complications following stroke with detrimental consequences in terms of functional recovery and quality of life. Its identification and treatment at the earliest stages of care remains a clinical challenge. The aim of this thesis is to study risk and protective factors for PSD based on data collected in the contexts of daily life. In the first section, we present a study of the role played by social support and routinization on the severity of depressive symptoms three months after stroke by Ecological Momentary Assessment (EMA). In the second section, we examine the voice as an early marker of PSD. We observed that patient perceptions of better support quality, and not quantity, immediately following mild stroke, are associated with better behavioral and emotional outcomes three months later. In addition, we observed a unidirectional pattern of association between mood and routines, whereby the occurrence of routines was associated with a higher level of depressive symptomatology over subsequent hours. Finally, voice analysis allowed us to identify PSD markers with longitudinal changes in fundamental voice frequency and discriminant analysis demonstrated that initial voice breaks coupled with shimmer are strongly predictive of subsequent PSD. Beyond commonly-recognized clinical risk factors such as stroke severity, these ecological investigations identified new markers for PSD whose detection could lead to new strategies for prevention and care

The focus of this research is on identification, location, interruption, characterization and overall management of faults in conventional AC distribution systems as well as isolated MVDC power systems. The primary focus in AC distributions systems is on identifying and locating underground cable faults using voltage and current waveforms as the input data. Cable failure process is gradual and is characterized by a series of single-phase sub-cycle incipient faults with high arc voltage. They often go undetected and eventually result in a permanent fault in the same phase. In order to locate such incipient cable faults, a robust yet practical algorithm is developed taking into account the fault arc voltage. The algorithm is implemented in the time-domain and utilizes power quality monitor data to estimate the distance to the fault in terms of the line impedance. It can be applied to locate both sub-cycle as well as permanent faults. The proposed algorithm is evaluated and proved out using field data collected from utility distribution circuits. Furthermore, this algorithm is extended to locate evolving faults on overhead distribution lines. Evolving faults are faults beginning in one phase of a distribution circuit and spreading to another phase after a few cycles. The algorithm is divided into two parts, namely, the single line-to-ground portion of the fault and the line-to-line-to-ground portion of the fault. For the single line-to-ground portion of the fault, the distance to the fault is estimated in terms of the loop or self-reactance between the monitor and the fault. On the other hand, for the line-to-line-to-ground and line-to-line portion of the fault the distance is estimated in terms of the positive-sequence reactance. The secondary focus of fault management in AC distribution systems is on identifying fault cause employing voltage and current waveform data as well as meteorological information. As the first step, unique characteristics of cable faults are examined along with methods to identify such faults with suitable accuracy. These characteristics are also used to distinguish underground cable faults from other overhead distribution line faults. The overhead line faults include tree contact, animal contact and lightning induced faults. Waveform signature analysis, wavelet transforms and arc voltages during the fault event are used for fault cause identification and classification. A statistical based classification methodology to identify fault cause is developed by utilizing promising characteristics. Unlike the AC system infrastructure which is already in place, the DC system considered in this document is that of a notional electric ship. The nature of DC current, with the absence of a current zero as well as the presence of power electronic devices influencing the current behavior, makes interrupting DC fault currents challenging. As a part of this research an innovative DC fault interruption scheme is proposed for rectifier- fed MVDC systems. A fault at the terminals of a phase-controlled rectifier results in a high magnitude current impulse caused by the filter capacitor discharging into the fault resistance. It is proposed to use a series inductor to limit the magnitude of this current impulse. The addition of the inductor results in an underdamped series RLC circuit at the output terminals of the rectifier which causes the fault current to oscillate about zero. Furthermore, it is proposed to utilize a conventional AC circuit breaker to interrupt this fault current by exploiting the zero crossings resulting from the oscillations. Using the proposed scheme for the example case, the peak fault current magnitude as well as the interruption time is significantly reduced. / text