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Optimal output‐constrained control of medium‐voltage DC shipboard power systems for pulsed power load accommodation
No full textFor pulsed power load (PPL) accommodation in a medium‐voltage DC (MVDC) shipboard power system (SPS), the charging control of energy storage systems (ESSs) and the generation control of distributed generators (DGs) need to be properly coordinated. Targeting the important but not well‐studied problem, an optimal output‐constrained control algorithm for the offline PPL accommodation strategy is presented. Three control objectives including realising the generation and charging control references, maintaining the DC bus and supercapacitor voltages within the safe operating ranges, and minimising the total generation cost of DGs, are fulfilled concurrently. First, an SPS model with multiple DGs, a supercapacitor ESS, and regular loads is developed. By restricting the DC bus and supercapacitor voltages within pre‐defined constraints, both the transient‐ and steady‐state performances of the SPS are guaranteed. Furthermore, by incorporating the cost minimisation objective into designed virtual control signals, the third control objective on energy efficiency is realised. The stability of the presented algorithm is rigorously proven based on the Lyapunov method. Finally, detailed case studies are conducted to validate the performance of the designed algorithm
Neutrophil Granulopoiesis Optimized Through Ex Vivo Expansion of Hematopoietic Progenitors in Engineered 3D Gelatin Methacrylate Hydrogels
No full textNeutrophils are the first line of defense of the innate immune system. In response to methicillin‐resistant Staphylococcus aureus infection in the skin, hematopoietic stem, and progenitor cells (HSPCs) traffic to wounds and undergo extramedullary granulopoiesis, producing neutrophils necessary to resolve the infection. This prompted the engineering of a gelatin methacrylate (GelMA) hydrogel that encapsulates HSPCs within a matrix amenable to subcutaneous delivery. The authors study the influence of hydrogel mechanical properties to produce an artificial niche for granulocyte‐monocyte progenitors (GMPs) to efficiently expand into functional neutrophils that can populate infected tissue. Lin‐cKIT+ HSPCs, harvested from fluorescent neutrophil reporter mice, are encapsulated in GelMA hydrogels of varying polymer concentration and UV‐crosslinked to produce HSPC‐laden gels of specific stiffness and mesh sizes. Softer 5% GelMA gels yield the most viable progenitors and effective cell‐matrix interactions. Compared to suspension culture, 5% GelMA results in a twofold expansion of mature neutrophils that retain antimicrobial functions including degranulation, phagocytosis, and ROS production. When implanted dermally in C57BL/6J mice, luciferase‐expressing neutrophils expanded in GelMA hydrogels are visualized at the site of implantation for over 5 days. They demonstrate the potential of GelMA hydrogels for delivering HSPCs directly to the site of skin infection to promote local granulopoiesis
Mentalistic and normative frameworks in children\u27s explanations of others\u27 behaviors
No full textAs they learn to navigate the social world, children construct frameworks to interpret others\u27 behavior. The present studies examined two such frameworks: a mentalistic framework, which construes behavior as driven by internal mental states; and a normative framework, which presumes people act in accordance with social norms. Participants included 101 children (ages 4, 7, and 10; 81% White; 41% female) and 35 adults (66% female) tested in the northeastern United States from 2019 to 2021. Children and adults utilized both mentalistic and normative frameworks to explain others\u27 behaviors. Framework use depended on features of the behavior being explained. Minimal developmental differences were observed. The relative independence and the utility of the mentalistic and normative frameworks for naïve reasoning about behavior are considered
JNK2 silencing lipid nanoparticles for elastic matrix repair
No full textThe over‐expression of c‐Jun N‐terminal kinase (JNK2), a stress activated mitogen kinase, in the aortic wall plays a critical role in the formation and progression of abdominal aortic aneurysm (AAA). This triggers chronic downstream upregulation of elastolytic matrix metalloproteinases (MMPs), MMPs2 and 9 to cause progressive proteolytic breakdown of the wall elastic matrix. We have previously shown that siNRA knockdown of JNK2 gene expression in an AAA culture model stimulates downstream elastin gene expression, elastic fiber formation, crosslinking and reduces elastolytic MMPs2 and 9. Since naked siRNA poorly routes to intracellular targets, has poor stability in blood, and could be potentially toxic and immunogenic, this project is aimed to develop PEGylated lipid nanoparticles (LNPs) for delivery of JNK siRNA and to generate evidence of successful JNK2 knockdown and downstream attenuation of MMP2 gene and protein expressions. LNPs were formulated using thin‐film hydration technique and had the size of 100–200 nm with zeta‐potential ranging between 30 and 40 mV. JNK siRNA loaded PEGylated LNPs successfully knocked down JNK2 in cytokine‐activated rat aneurysmal smooth muscle (EaRASMC) cultures. This resulted in a downstream decrease in MMP2 gene and protein expression and an upward trend in expression of genes for proteins critical for elastic fiber assembly such as elastin ( ELN) and lysyl oxidase ( LOX ). Our result indicates cationic LNPs to be potential carriers for JNK siRNA delivery improving potency for elastin homeostasis required for AAA repair which could possibly provide benefits in preventing the progression of small AAAs
Multiple baseline and multiple probe design studies targeting academic skills
No full textSingle‐case design (SCD) is a quantitative experimental technique in which participants serve as their own control. The use of an effect size in SCD allows evaluation of outcomes as well as comparison of outcomes via meta‐analyses. Characteristics of SCD research make the selection of an appropriate effect size complicated. Additionally, there are a number of factors that complicate the use of SCDs as a means to improve academic skills. The purpose of this study was to examine patterns by which SCD effect sizes are used to quantify outcomes from academic interventions. To do so, a descriptive analysis of an extant database of SCD studies was conducted. The authors created frequency tables for each effect size identified in the database as well as graphs to show the extent to which the use of effect sizes changed over time. The authors also determined whether the most frequently used effect sizes were appropriate for summarizing changes in academic outcomes. Although many effect sizes have been developed, only a small number are routinely used in SCD research for academic skills. The most frequently used effect sizes were those that come from standardized statistics, compared with those that utilized principles of regression or Bayesian analysis. , Practitioner Points Using an effect size in single‐case design allows for the empirical evaluation of outcomes. Although many effect sizes have been developed, only a few are routinely used in single‐case design research for academic skills. Practitioners should strive to use concrete and methodologically sound effect sizes when utilizing single‐case design for academic skills problems
Twisting two-dimensional iron sulfide layers into coincident site superlattices <i>via</i> intercalation chemistry
No full textTEM Electron diffraction analysis of twisted coincident site superstructures in intercalated tetragonal iron sulfide.</jats:p
PWHT-Free Cast Stainless Steels
No full textStandard specifications set forth by the American Society for Testing and Materials (ASTM) for the production of stainless steel castings require the castings to be heat treated after welding. The post weld heat treatment (PWHT) is designed to dissolve chromium-rich carbides that may form during welding. Chromium-rich carbides can precipitate on grain boundaries in the heat affected zone (HAZ), depleting their immediate surroundings of chromium, which is an essential element for corrosion resistance. This phenomenon is known as sensitization. Even though sensitization-resistant grades have been developed that mitigate this problem, the PWHT requirements in the ASTM standards do not distinguish between improved and susceptible compositions, leading to potentially redundant heat treatments. It has become necessary to investigate the possibility of waiving the PWHT requirement for grades that may not need it. Two groups of cast stainless steel (CF and CN grades) and their associated weld metals were investigated under different welding conditions to determine their sensitization resistance using thermodynamic simulation, HAZ simulation, electrochemical corrosion tests, and energy dispersive spectroscopy (EDS) in the scanning electron microscope (SEM) and transmission electron microscope (TEM). The alloys, which comprised CF3, CF8C, CF3MN, CF8, CN3MCu and CN7M, were selected to include sensitization-resistant grades. The results showed that the high carbon grades CN7M and CF8 together with their weld metals were strongly sensitized as expected and therefore need the post-weld solution anneal. The low carbon grades (CF3 and CN3MCu) and the niobium-stabilized grade (CF8C) were only mildly sensitized. Their degree of sensitization (DOS) values were low enough to potentially permit use in the as-welded state for applications where corrosive attack is not severe. It was however recommended that the PWHT requirement be maintained for them to pre-empt serious attack in more corrosive environments. Although not sensitized, the as-deposited welds for CF3 and CF8C (made with E308L and E347 filler metals respectively) experienced boundary dissolution, which was eliminated after the PWHT. It was concluded that the change in ferrite morphology and amount caused by the post-weld solution anneal contributed to mitigating the corrosion earlier observed. The CN3MCu welds (made with E320LR) had excellent resistance to sensitization. Results from thermodynamic and kinetic modelling suggest that adding nitrogen to CN3MCu can potentially improve its sensitization resistance to levels that would permit the CN3MCu/E320LR base metal/weld pair to be used without PWHT. The nitrogen-bearing CF3MN and its weld metal E316L showed the best resistance to intergranular corrosion without PWHT. None of their samples reactivated in the corrosion tests nor showed any boundary dissolution. Further tests are recommended for this base metal/weld metal pair to generate more comprehensive data on sensitization resistance before the PWHT requirement is completely removed
The Women in the Principal\u27s Office: A Mixed Methods Study of Principal Time Use and the Gendered Division of Household Labor
No full textOver a century of research on K-12 public school principal time use (PTU) illustrates that principals spend time on professional tasks beyond the instructional hours of their school days. Similarly, a century of research on the division of household labor suggests that women spend more time on household labor than men daily. However, no prior PTU study has recognized this gendered imbalance of household labor. The purpose of this study was to collect PTU data and household labor time use data from female and male principals, assistant principals, and aspiring principals to explore how the additional time demands of household labor may be impacting the disproportionate number of female principals to female teachers. Twenty principal pipeline participants (PPPs), composed of ten women and men from two northeastern states, completed a 24-hour electronic time diary for seven consecutive days to record their professional and household tasks in phase one of the explanatory sequential mixed methods study. For phase two of the study, two women and two men from each PPP group participated in semi-structured interviews based on their quantitative time diary data. The final connected quantitative and qualitative results indicated that women in the present study spent more time on their professional tasks as they advanced along the principal pipeline, and this time was more likely to be marked by multitasking and blurring professional and household boundaries to manage their competing demands than their male counterparts. Female assistant principals were the only PPP group of women who recorded more time spent on household tasks than their male counterparts. Additionally, women and men in the present study valued convenience and proximity to home when considering their current professional roles and possible advancement along the principal pipeline. Recommendations for future research are offered and implications for practitioners and policymakers are discussed
Enhanced Plasma Profile Estimation and Control in Tokamaks via Machine Learning
No full textThe tokamak concept is currently one of the most promising avenues to achieve energy generation through nuclear fusion, a feat that would enable the world to produce nearly limitless clean electricity. Unfortunately, no tokamak to date has ever achieved the conditions that would allow more energy to be generated from fusion reactions than it takes to sustain a plasma in that state. In order to produce and maintain a plasma that is both favorable for fusion reactions to occur and stable, a large number of different plasma properties must be carefully controlled. These plasma properties are all closely interconnected and display highly nonlinear behavior. In addition, a limited number of actuators are available that each produce multiple different effects, making it virtually impossible to design separate controllers for each plasma property that can operate independently. Instead, control solutions need to be developed that consider the interconnectedness of the system and use the same actuators to regulate multiple different plasma properties simultaneously. In order to quantify the interconnectedness of the system, model-based control techniques can be used that rely on predictive models to describe the plasma evolution.A number of different factors determine if a predictive model is suitable for control applications. The most important requirement of these models is usually the ability to run fast enough for the relevant application; the calculation speed requirement is often on the order of milliseconds. In order to achieve these calculation speeds, many physics-based control-oriented models make simplifying assumptions, sacrificing some of their accuracy. Empirical models can achieve very high levels of accuracy at fast enough calculation speeds, but can be limited in the range of plasma scenarios they are valid for. Machine learning offers a solution to these trade-offs: by training a machine learning algorithm to replicate the calculations of a slow, high fidelity physics-oriented code, a model can be developed that runs fast enough to be useful for control applications while retaining most of the accuracy of the high fidelity code and validity across a wide range of plasma scenarios. In this dissertation, two neural network surrogate models are trained to replicate the results of physics-oriented codes: NubeamNet predicts the effects of neutral beam injection on the plasma, and MMMnet predicts the turbulent diffusivity coefficients. These neural network surrogates are integrated with conventional models to improve the fidelity of the control-oriented predictive simulation code COTSIM. This combination of machine learning-based and conventional models are then applied to a number of different model-based control applications. A feedforward optimization scheme that uses COTSIM including neural networks as its predictive model is developed to aid in scenario planning activities. An observer algorithm is devised to estimate the state of the electron temperature profile in real time, and has been validated in real time on the DIII-D tokamak. A feedback controller is designed to actively regulate the electron temperature profile, and is shown to successfully track a temperature profile target in experiment. Another controller is developed to actively track both the electron temperature profile and the safety factor profile simultaneously
A Mixed-Methods Approach to Understanding Teacher Stress and Psychological Help-Seeking During the COVID-19 Pandemic
No full textDuring the coronavirus-19 (COVID-19) pandemic, teachers experienced significant and unique stressors. While many of these stressors were new and directly related to the pandemic, teaching has long been understood as a high-stress profession, with teachers reporting higher incidence of stress than almost any other field. Teachers also experience high rates of adverse professional quality of life outcomes such as compassion fatigue. Because teacher stress predicts adverse teacher outcomes as well as adverse student outcomes, there is a need to understand how teachers cope with their stressors and to identify environmental factors or interventions which may mitigate the relationships between stress and adverse outcomes.The relationships between teacher stress, coping resources including self-care and administrative support, professional quality of life, and job satisfaction and motivation to persist were examined in this study. A convergent parallel mixed-methods approach, including structural equation modeling and thematic analysis of semi-structured interviews, was utilized to gain depth of insight and integrate teacher voice. It was hypothesized that administrative support and self-care during the pandemic would mediate the relationships between teacher stress, professional quality of life, and job satisfaction and motivation to persist, and that significant differences in these relationships would exist between teachers who sought psychological care during the pandemic and those who did not. Due to the lack of existing research on teacher psychological help-seeking, exploratory thematic analysis of semi-structured interviews was used to gain insight into teachers\u27 actual psychological help-seeking behavior. Results indicated that the hypothesized model approximately fit the data, and that the relationship between teacher stress and self-care was significantly different across groups. Qualitative interview data was integrated to gain depth of insight into teacher perceptions of their stress and coping at the individual and school levels, as well as their experiences of seeking and engaging with mental health services. Implications for practice include ways for mental health professionals, school administrators, and teachers, to continue to support teacher mental health and well-being. Future research directions are also provided