Stabilization and passification of distributed-order fractional linear systems using methods of preservation

This paper studies the stabilization and passification of a class of distributed-order linear time-invariant systems, by using methods of preservation in the frequency domain. Results about preservation of stability and passivity of classical linear time-invariant systems are extended to one more general family of matrix functions. Based on these results, a new approach to the problems of stabilization and passification of distributed-order linear time-invariant systems is presented. Also a result that extends the known techniques for pole placement of classical linear time-invariant systems to the new class of distributed-order linear time-invariant systems is given. Examples are given to show the validity of theoretical results.     

‘Strong mothers make strong children’: sports,eugenics and nationalism in Brazil at the beginning of the twentieth century

Based on post-structural feminist and gender studies, the present article analyses the importance given to the practice of physical education, sports and exercise as part of the national policy to strengthen the Caucasian-Brazilian population at the beginning of the twentieth century, emphasising the priority made of the White female body as the most important instrument in strengthening the so called ‘White race’. All the editions of the Revista Educação Physica, the first magazine published specifically for physical education and sport in Brazil, was the primary research source. Other books, manuals, reviews from scientific congresses and official publications from the Brazilian Government at the time were also examined. Via the technical analysis of the contents of the aforementioned publications, it was possible to conclude that the Brazilian nationalist discourse at the time sought what was called the ‘refinement of the White race’ by strengthening its women while, at the same time, systematically ignoring Black women.     

Is passive drag dependent on the interaction of kayak design and paddler weight in flat-water kayaking?

Abstract

Drag is one of the major factors that influences kayaking performance. To focus on the drag of the kayak’s hull shape and the paddlers’ weight per se, the passive drag (D_p) was measured on a flat-water sprint course for one paddler with added weights. D_p was measured by an electromechanical towing device using a load cell, at incremental and constant velocities from 2.78 to 5.56 m/s. Three kayaks of different sizes and shapes (Nelo® K1 Quattro-M, ML, and L) were used and the paddlers’ body weight was adjusted with weights so the total paddler weight in the kayak was 65, 75, and 85 kg. The mean D_p increased by the power function of D = kvⁿ (mean R² = .990; SD .006). The D_p went from 21.37?±?1.29 N at 2.78 m/s to 89.32?±?6.43 N at 5.56 m/s. For the two lighter weighted kayaks (65 and 75 kg), the lowest D_p was observed with different kayak sizes (M, ML, or L) depending on the target velocity. The manufacturers suggest that paddlers should select a kayak size according to their body weight to minimise drag; however, the results of this study suggest that target velocities, and thus competition distance should also be factored into kayak selection.     

Why do students consider dropping out of doctoral degrees? Institutional and personal factors

Despite the increasing popularity of doctoral education, many students do not complete their studies, and very little information is available about them. Understanding why some students consider that they do not want to, or cannot, continue with their studies is essential to reduce dropout rates and to improve the overall quality of doctoral programmes. This study focuses on the motives students give for considering dropping out of their doctoral degree. Participants were 724 social sciences doctoral students from 56 Spanish universities, who responded to a questionnaire containing doctoral degree conditions questions and an open-ended question on motives for dropping out. Results showed that a third of the sample, mainly the youngest, female and part time students, stated that they had intended to drop out. The most frequent motives for considering dropping out were difficulties in achieving a balance between work, personal life and doctoral studies and problems with socialization. Overall, results offer a complex picture that has implications for the design of doctoral programmes, such as the conditions and demands of part-time doctoral studies or the implementation of educational proposals that facilitate students’ academic and personal integration into the scientific community in order to prevent the development of a culture of institutional neglect.     

Resisting Erasure and Developing Networks of Solidarity: Testimonios of Two Puerto Rican Scholars in the Academy

In this article, we share findings from a critical qualitative study aimed at better understanding the ways that language, history, and geography mediate our work and identities as educational researchers. As scholars whose particular sociocultural and political histories are often absent in scholarly discussions about language and education, we use the intergenerational sharing of testimonios as both methodology and narrative development to gain a deeper understanding of experiences involving the learning and use of English that influence our academic careers. We theorize our experiences as resisting erasure and contribute to Latina epistemology scholarship and critical educational research about Puerto Ricans in the United States. Moreover, we forward the concept of funds of knowledge as a professional practice. Telling our stories and developing mentoring networks is necessary for our individual and collective functioning and well-being as scholars; it cultivates solidarity as a means of thriving in the academy.     

A developmental perspective on full- versus part-day kindergarten and children's academic trajectories through fifth grade

Children's kindergarten experiences are increasingly taking place in full- versus part-day programs, yet important questions remain about whether there are significant and meaningful benefits to full-day kindergarten. Using the Early Childhood Longitudinal Study's Kindergarten Cohort ( N = 13,776), this study takes a developmental approach to examining associations between kindergarten program type and academic trajectories from kindergarten (ages 4–6 years) through 5th grade (ages 9–12 years). Full-day kindergarten was associated with greater growth of reading and math skills from fall until spring of kindergarten. Initial academic benefits diminished soon after kindergarten. The fade-out of the full-day advantage is in part explained by differences in the children who attend part- and full-day kindergarten as well as school characteristics.