Novel model reference adaptive control laws for improved transient dynamics and guaranteed saturation constraints

In classical model reference adaptive control (MRAC), the adaptive rates must be tuned to meet multiple competing objectives. Large adaptive rates guarantee rapid convergence of the trajectory tracking error to zero. However, large adaptive rates may also induce saturation of the actuators and excessive overshoots of the closed-loop system’s trajectory tracking error. Conversely, low adaptive rates may produce unsatisfactory trajectory tracking performances. To overcome these limitations, in the classical MRAC framework, the adaptive rates must be tuned through an iterative process. Alternative approaches require to modify the plant’s reference model or the reference command input. This paper presents the first MRAC laws for nonlinear dynamical systems affected by matched and parametric uncertainties that constrain both the closed-loop system’s trajectory tracking error and the control input at all times within user-defined bounds, and enforce a user-defined rate of convergence on the trajectory tracking error. By applying the proposed MRAC laws, the adaptive rates can be set arbitrarily large and both the plant’s reference model and the reference command input can be chosen arbitrarily. The user-defined rate of convergence of the closed-loop plant’s trajectory is enforced by introducing a user-defined auxiliary reference model, which converges to the trajectory tracking error obtained by applying the classical MRAC laws before its transient dynamics has decayed, and steering the trajectory tracking error to the auxiliary reference model at a rate of convergence that is higher than the rate of convergence of the plant’s reference model. The ability of the proposed MRAC laws to prescribe the performance of the closed-loop system’s trajectory tracking error and control input is guaranteed by barrier Lyapunov functions. Numerical simulations illustrate both the applicability of our theoretical results and their effectiveness compared to other techniques such as prescribed performance control, which allows to constrain both the rate of convergence and the maximum overshoot on the trajectory tracking error of uncertain systems.     

Association of Oxidative Stress with Disease Activity and Damage in Systemic Lupus Erythematosus: A Cross Sectional Study from a Tertiary Care Centre in Southern India

To study oxidative stress in systemic lupus erythematosus (SLE) by estimating serum oxidised LDL (OxLDL), 8-hydroxy-2′-deoxyguanosine (8-OHdG), malondialdehyde (MDA), and total anti-oxidant status and to correlate with SLE disease activity and disease damage. Eighty SLE patients satisfying the Systemic Lupus International Collaborating Clinics/American College of Rheumatology (SLICC/ACR) 2012 criteria and 80 healthy controls were studied. Exclusion criteria were infections, renal insufficiency, other connective tissue diseases, drug-induced lupus, smoking, alcohol consumption. Disease activity was measured by SLE disease activity index-2 K (SLEDAI), disease damage was quantified by SLICC-Damage Index (SDI). Sera was tested for OxLDL, 8-OHdG, and total antioxidant status (TAS) by double-antibody sandwich ELISA; MDA measured by Colorimetric assay. Oxidative stress markers were compared between group1- controls, group 2-mildly active SLE (SLEDAI ≤ 5), group 3- moderate to highly active SLE (SLEDAI ≥ 6). SLE patients had significantly higher MDA, 8-OHdG and lower TAS when compared to healthy controls, while OxLDL was similar in the three groups. MDA, 8-OHdG were significantly higher, TAS lower in group 3 compared to group 2. MDA had positive correlation with SLEDAI, TAS negatively correlated with SLEDAI. SLE with neuropsychiatric manifestations, vasculitis, anti-sdDNA antibodies had higher MDA, MDA/TAS ratio. SLE patients with thrombocytopenia, and vasculitis had higher OxLDL. Only OxLDL was significantly higher in those patients who have SDI > 1. SLE patients have increased oxidative stress measured by increases in MDA, 8-OHdG, and lower total antioxidant status that was associated with disease activity and some disease manifestations. However only OxLDL was associated with damage.     

Applying a principle of explicability to AI research in Africa: should we do it?

Ethics and Information Technology - Developing and implementing artificial intelligence (AI) systems in an ethical manner faces several challenges specific to the kind of technology at hand,...     

大学教学发展中心的效益评估——以密歇根大学学习与教学研究中心为例

评估大学教学发展中心的工作效果有助于高等教育质量的改善。本文首先对教师发展工作的相关研究做了文献述评,随后介绍了密歇根大学学习与教学研究中心开发的项目综合评估模型,并结合具体的项目与服务案例展示了该中心如何记录并评估教师的教学发展工作以及如何借助这些评估结果来改善自身实践。文章最后为中国大学教学中心的建设提供了一些建议。     

The Viability of Combining Academic and Career Pathways: A Study of Linked Learning

In an attempt to reform high schools and prepare students with the knowledge and skills needed for the 21st century, educators and policymakers have turned to programs that combine career and academic pathways. One such program, Linked Learning, has taken up the reform challenge by relying on technical adjustments, rearranging students’ schedules, and integrating career technical education (CTE) with a set of courses that support students’ eligibility for their state and university college system. Linked Learning has attempted to avoid the pitfalls often associated with an earlier vocational education model. This article reports findings from a year-long study of eight schools in five districts whose district leaders and principals have placed Linked Learning at the core of their platform for school reform. Interviews with these educators reveal that while changing the structure of students’ course schedules offered some advantages for students, school principals were challenged to keep their academic and career promises. This qualitative investigation has shown that to understand reform challenges it is essential to examine the broader school, district, and state context in which the reform is embedded. Both structural and cultural considerations must be addressed if high school reform is to more effectively support students.     

Mathematics for teaching and deep subject knowledge: voices of Mathematics Enhancement Course students in England

This article reports an investigation into how students of a mathematics course for prospective secondary mathematics teachers in England talk about the notion of ‘understanding mathematics in depth’, which was an explicit goal of the course. We interviewed eighteen students of the course. Through our social practice frame and in the light of a review of the literature on mathematical knowledge for teaching, we describe three themes that weave through the students’ talk: reasoning, connectedness and being mathematical. We argue that these themes illuminate privileged messages in the course, as well as the boundary and relationship between mathematical and pedagogic content knowledge in secondary mathematics teacher education practice.     

Why Is This So Hard?: Ideologies of Endangerment,Passive Language Learning Approaches,and Ojibwe in the United States

This paper describes 3 language learning approaches common in many urban and rural Ojibwe communities, as well as the ideologies of endangerment that drive and sustain them. Drawing from collaborative language revitalization work with teachers, learners, and community leaders, we analyze some of the teaching and learning practices that lead to the common mismatch between language learner goals and expectations, on the one hand, and the outcomes of language learning, on the other. We outline how these 3 approaches to language learning relate to cultural identities and place-based notions of authenticity as well as to current findings in the field of second language acquisition. We then profile 2 speakers who have learned Ojibwe successfully as adults to illustrate how their success was possible largely because they were able to engage with the Ojibwe language in interactive ways that run counter to common language learning approaches. We suggest that for language revitalization efforts, and individual learners, to experience higher levels of success, greater attention needs to be paid to how ideologies of endangerment impact language learning approaches.