418 research outputs found
Crossing the Boundaries: STEM Students in Four-Year and Community Colleges
No full textIn this paper we consider the role of community colleges for four-year STEM students as they move through their educational careers. We examine a student cohort who began their freshman year at a four-year college and the pathways that lead them to coursetaking or degrees at a community college. We identify three distinct roles of community colleges as used by four-year college students: (1) reverse transfer; (2) supplemental course taking while pursuing a four-year degree; (3) post-graduate community college coursetaking and/or enrollment. There are other variations on these three basic patterns but limited data and sample size constrain our analysis to these broader patternsArticle commissioned by the National Academy of Sciences, Engineering, and Medicine, Board on Science Education, for the project, "Barriers and Opportunities in Completing Two and Four-Year STEM Degrees".Peer reviewe
Cooperative ankle-exoskeleton control can reduce effort to recover balance after unexpected disturbances during walking
Get PDFBACKGROUND: In the last two decades, lower-limb exoskeletons have been developed to assist human standing and locomotion. One of the ongoing challenges is the cooperation between the exoskeleton balance support and the wearer control. Here we present a cooperative ankle-exoskeleton control strategy to assist in balance recovery after unexpected disturbances during walking, which is inspired on human balance responses. METHODS: We evaluated the novel controller in ten able-bodied participants wearing the ankle modules of the Symbitron exoskeleton. During walking, participants received unexpected forward pushes with different timing and magnitude at the pelvis level, while being supported (Exo-Assistance) or not (Exo-NoAssistance) by the robotic assistance provided by the controller. The effectiveness of the assistive strategy was assessed in terms of (1) controller performance (Detection Delay, Joint Angles, and Exerted Ankle Torques), (2) analysis of effort (integral of normalized Muscle Activity after perturbation onset); and (3) Analysis of center of mass COM kinematics (relative maximum COM Motion, Recovery Time and Margin of Stability) and spatio-temporal parameters (Step Length and Swing Time). RESULTS: In general, the results show that when the controller was active, it was able to reduce participants' effort while keeping similar ability to counteract and withstand the balance disturbances. Significant reductions were found for soleus and gastrocnemius medialis activity of the stance leg when comparing Exo-Assistance and Exo-NoAssistance walking conditions. CONCLUSIONS: The proposed controller was able to cooperate with the able-bodied participants in counteracting perturbations, contributing to the state-of-the-art of bio-inspired cooperative ankle exoskeleton controllers for supporting dynamic balance. In the future, this control strategy may be used in exoskeletons to support and improve balance control in users with motor disabilities.Biomechatronics & Human-Machine Contro
Recovering linear and angular momentum during walking
Get PDFFor most individuals maintaining balance during walking goes natural. We are not continuously thinking of how to maintain balance, and still we usually do not fall. However, maintaining balance is not a given for everyone. Both aging and various neuromuscular disorders affect the ability to maintain balance, resulting in an increased incidence of falls and the associated consequences. Also, in the situation of someone walking with an assistive device such as a powered lower-limb exoskeleton, for example due to a spinal cord injury (SCI), maintaining balance may be challenging. To provide better care and training programs and to improve balance support with assistive devices, a better understanding is needed of human balance recovery. Previous research often focused on the recovery of linear perturbations disturbing the body's linear momentum. However, in daily life we also encounter perturbations resulting in a rotational effect, disturbing the body's angular momentum. The aim of this work was to gain insights in the use of human balance strategies to recover whole-body linear and angular momentum. To provoke balance recovery responses we performed experiments in which perturbations were applied during standing and treadmill walking. These studies were performed with healthy participants, since they can serve as a source of inspiration for how balance recovery strategies are being used successfully. Perturbations of the linear and/or angular momentum were induced by the application of forces to the body at shoulder and/or pelvis height, provided by a haptic robot. This allowed for a controlled duration, magnitude and onset of the perturbations. Thereafter we analyzed how modulations of the ground reaction force and its point of application were used in order to maintain balance. We studied this in 1) situations that are relevant for SCI individuals walking with a powered lower limb exoskeleton and 2) situations that have not extensively been studied before, and therefore fill a gap in the current knowledge on human balance recovery. In several chapters we address the topic of balance recovery during very slow walking, since this is a relevant speed for walking with a lower limb exoskeleton. Walking very slowly increases the time spent in the double support phase. Studying the responses to perturbations of the whole-body linear momentum (WBLM) while standing in a static double support phase, also called a staggered stance posture, provided insights in the coupling between the frontal- and sagittal-plane. A large base of support (BoS) enables opportunities for centre of pressure (CoP) modulation. Therefore, the large dimension of the BoS in the anteroposterior direction during staggered stance could also be used in the recovery from perturbations that were perpendicular to this direction. Focusing on the double support phase, with simulations based on a simple linear inverted pendulum model, we showed the effects of modulations of the CoP trajectory on the control of the centre of mass position and velocity. Comparing the simulated opportunities with the strategies that healthy individuals used, it turned out that we do not fully exploit the available options for a quick balance recovery. A specific type of perturbation that we used for several studies is a perturbation of the whole-body angular momentum (WBAM). This was obtained by applying two perturbations at the same time in opposite direction on the pelvis and upper body respectively. The responses to these perturbations revealed a high priority in recovery of the WBAM. This was done even at the expense of the WBLM. The WBAM recovery comprised a modulation of the horizontal ground reaction force, affecting the WBLM while this was not perturbed initially. This effect was independent of the instant of the gait cycle at which the perturbation was given and holds for very slow and normal walking speeds. The results emphasize the importance and prioritization of WBAM regulation in balance recovery. To conclude, the studies presented in this thesis provide insights into the human balance strategies used to recover from perturbations of the WBLM and WBAM during walking at very low and normal speeds. These insights can be considered in the development of controllers to assist balance or to improve balance training for those experiencing difficulties with balance control. Finally, the recorded data itself is valuable for validating whether proposed recovery strategies are human-like
Balance recovery following pelvis perturbations during very slow walking
No full textBACKGROUND AND AIM: Healthy humans have the ability to handle balance perturbations during walking very well. The ankle moment, as well as the foot placement location and timing are altered to counteract the perturbations and maintain balance.[1] Previously, healthy subjects have shown a strong linear relation between the body´s centre of mass (COM) velocity at heel contact (HC), and both the foot placement location and centre of pressure (COP) at subsequent toe off (TO) during laterally perturbed walking.[2] The walking speeds were 0.63 and 1.25 m/s.[2] In this study, it is questioned whether this relation also exist during very slow walking, because there will be more time during the double support phase to alter the balance recovery strategy. Therefore, we investigated the relation between the body´s COM velocity, and both the foot placement location and COP during a very slow walking speed. METHODS: Mediolateral (ML) pelvis perturbations were applied to 10 healthy subjects, during very slow (0.36 m/s) and normal (1.25 m/s) treadmill walking at TO of the right foot. An active optical motion capture system was used to record the body kinematics. Ground reaction forces were measured with the built-in force plates in the treadmill. The data was analysed to obtain COM velocities at HC right, foot placement location at HC right, COP locations at TO left and phase durations. RESULTS: Figure 1 presents the durations of the double and single support phases for the different perturbation magnitudes. The ML perturbations significantly affected the double and single support durations during very slow walking, while these durations were not affected during normal walking. Additionally, the COM velocity at HC right showed to have a high predictive value for the foot placement of the leading foot during the normal walking speed, whereas this was considerable lower during the very slow walking speed. The predictive value of the COM velocity was present for the COP location at the subsequent TO for both the normal and very slow walking speed. CONCLUSIONS: The results showed altered recovery strategies in the frontal plane during very slow walking compared to the normal walking speed. These differences were potentially caused by the longer double support phase duration, in which subjects used other strategies to control the distance between the COM and COP. REFERENCES:[1] A. L. Hof, R. M. van Bockel, T. Schoppen, and K. Postema, "Control of lateral balance in walking. Experimental findings in normal subjects and above-knee amputees," Gait Posture, vol. 25, no. 2, pp. 250-258, 2007. [2] M. Vlutters, E. H. F. van Asseldonk, and H. van der Kooij, "Center of mass velocity-based predictions in balance recovery following pelvis perturbations during human walking," J. Exp. Biol., vol. 219, no. 10, pp. 1514-1523,2016
sj-pdf-1-jcb-10.1177_0271678X231169579 - Supplemental material for Hemoglobin and cerebral hypoxic vasodilation in humans: Evidence for nitric oxide-dependent and <i>S</i>-nitrosothiol mediated signal transduction
No full textSupplemental material, sj-pdf-1-jcb-10.1177_0271678X231169579 for Hemoglobin and cerebral hypoxic vasodilation in humans: Evidence for nitric oxide-dependent and S-nitrosothiol mediated signal transduction by Ryan L Hoiland, David B MacLeod, Benjamin S Stacey, Hannah G Caldwell, Connor A Howe, Daniela Nowak-Flück, Jay MJR Carr, Michael M Tymko, Geoff B Coombs, Alexander Patrician, Joshua C Tremblay, Michelle Van Mierlo, Chris Gasho, Mike Stembridge, Mypinder S Sekhon, Damian M Bailey and Philip N Ainslie in Journal of Cerebral Blood Flow & Metabolism</p
Balance recovery in the double support during perturbed walking
No full textI. INTRODUCTION Exoskeleton walking increases the relative time spent in the double support phase (DSP). It is therefore crucial to control balance when both feet are on the ground. Healthy humans have excellent balance capabilities to avoid falling. The centre of pressure (CoP) describes the control of the centre of mass (CoM) movement [1]. The range of possible CoP locations in the DSP is determined by the foot placement at the end of the preceding single support phase. This study focuses on the CoP modulation during the DSP in the control of the CoM state. II. METHODS CoP trajectories in response to pelvis perturbations were extracted from an existing data set by Vlutters et al [2]. Anteroposterior and mediolateral perturbations with magnitudes up to 16% of the body weight were given at the moment of toe off. Parameterized CoP trajectories were generated with a spline function based on the experimental CoP trajectories, examples are shown in figure 1. Parameterization was done as a function of 1) the duration of the DSP, 2) the amplitude of the CoP, and 3) percentage of the amplitude reached halfway the DSP (= midpoint). The parameters were varied within a range equal to the standard deviation around the mean value obtained from the experimental data. The generated trajectories were used in model simulations of the CoM during the first DSP following the perturbation. A simple inverted pendulum model, relating the horizontal distance between the CoP and CoM to CoM acceleration, was used to assess the effectiveness of the CoP modulation in counteracting perturbation induced CoM velocity changes [3]. III. RESULTS The model outcome corresponds with the experimental data, figure 1. All the three CoP parameters are linearly related to the change in CoM velocity over the DSP, in both the experimental and modelled data. Changes of the midpoint resulted in larger variations in the modelled Δ CoM velocity, compared to those resulting from changes in the duration or amplitude, see figure 2. IV. DISCUSSION A simple inverted pendulum model was able to model representative CoM trajectories from the generated CoP trajectories as input. To control the CoM velocity after a perturbation, subjects used all CoP parameters. However, in the experimental data these parameters were also related with each other. When uncoupling the effect of these parameters in the model, the shape of the CoP trajectory, represented by the CoP shift that is reached halfway the DSP, had the largest influence on the changes of the CoM velocity during the DSP. Shifting the load earlier or later to the leading leg helps in increasing or decreasing the CoM velocity. This will help in counteracting the effect of the perturbation and returning to the baseline CoM velocity. REFERENCES [1] H. Reimann, T. D. Fettrow, E. D. Thompson, P. Agada, B. J. McFadyen, and J. J. Jeka, “Complementary mechanisms for upright balance during walking,” PLoS One, vol. 12, no. 2, pp. 1–16, 2017. [2] M. Vlutters, E. H. F. van Asseldonk, and H. van der Kooij, “Center of mass velocity-based predictions in balance recovery following pelvis perturbations during human walking,” J. Exp. Biol., vol. 219, no. 10, pp. 1514–1523, 2016. [3] Y. Jian, D. Winter, M. Ishac, and L. Gilchrist, “Trajectory of the body COG and COP during initiation and termination of gait,” Gait Posture, vol. 1, no. 1, pp. 9–2
The Good, the Bad, and the Ugly: An Autoethnographic Journey on Doing Participatory Action Research as a Graduate Student
No full textThe lead author documents the promises and pitfalls of doing critical participatory action research (PAR) as a graduate student within traditional institutions. This autoethnographic essay captures the vulnerabilities of the first author as she reflects on the human work that draws her to PAR, details the tensions that surfaced in the daily practices of doing PAR with youth, and addresses unforeseen hurdles that emerged from the ethics review board and the university–school partnership. The piece concludes with an epilogue from Dr. Michelle Fine, a senior scholar in the field of critical PAR, as she responds to the concerns raised in this essay.</jats:p
Communities of decoding : using the Decoding the Disciplines paradigm to create faculty learning communities on three continents.
Get PDFDavid Pace1, Janice Miller-Young2, Michelle Yeo2, Manie Moolman3, Jennifer Clark4, Adrian Jones5, Anette Wilkinson3, Deirdre van Jaarsveldt3
1 Indiana University
2 Mount Royal University
3 University of the Free State
4 University of New England, NSW
5 La Trobe University
Decoding the Disciplines is being used to increase learning in at least nine countries on four continents, and the model has been enriched, as scholars of teaching and learning have
adapted the paradigm to the needs of their institutions. This session will begin with a very brief introduction to the Decoding model, followed by presentations showing how teams in Canada, South Africa, and Australia are putting Decoding to use on their campuses:
David Pace (Indiana University), co-founder of Decoding, will briefly describe the paradigm and its development.
Dr’s Janice Miller-Young and Michelle Yeo at Mount Royal University will provide examples and evidence of the various ways in which the Decoding framework is being used on their
campus. Since 2013 a faculty learning community at Mount Royal has used Decoding for professional development, curriculum design, and research purposes. They will explore
some of the common themes that have emerged from these projects, connect the learning to practical applications for teachers in higher education, and make recommendations for
further work.
Dr Manie Moolman (Teaching and Learning Director: of the Faculty of Law), Prof. Annette Wilkinson (Professor Researcher, at the Centre for Teaching and Learning), and Dr Deirdre van
Jaarsveldt, Lecturer Researcher, from the University of the Free State, South Africa will describe the Decoding Learning in Law project. This 17-member learning community has focused on a
crucial bottleneck to learning in their discipline — reading case law and applying the law to a set of facts - and has used an ‘adapted’ version of the Decoding model that specifically provides for group participation and interaction within a specific discipline. They will provide evidence and reflect on the implementation and will explain that the Decoding model is not only efficient in solving bottlenecks, but that it can also be used as a means for deep reflection and professional development; curriculum design; and the identification of other bottlenecks that could hinder student learning in the faculty.
Adrian Jones (La Trobe University) and Jennifer Clark (University of New England) will describe how Australian-based scholars have used ‘Decoding’ to kick start cross-university conversations about the curriculum priorities for the first-year of tertiary study in five Humanities and Social Sciences disciplines. Each national Threshold Learning Outcome was addressed, and a good practice guide was drawn up, all focused on the crucial first-year. History is discussed as a case
study.
Participants will discuss how Decoding can be put to use on their campuses.
David Pace and Joan Middendorf, Decoding the Disciplines: Helping Students Learn Disciplinary Ways of Thinking (New Directions in Teaching and Learning, Vol. 98 (Fall 2004).
Arlene Díaz, Joan Middendorf, David Pace, and Leah Shopkow, ‘The History Learning Project ‘Decodes’ a Discipline’ in Kathleen McKinney, Ebbs, Flows, and Rips: The Scholarship of Teaching and Learning In and Across the Disciplines (Indiana University Press, 2013)
Decoding the Disciplines Website —
http://decodingthedisciplines.org/
Interim website for the ‘In the Beginning’ project funded by the [Australian] Office of Learning and Teaching -
http://www.firstyearlearningthresholds.edu.au/.
Especially the ‘History’ button, and then ‘Developing Students’ Skills’.Institute for Scholarship of Teaching and Learning, Academic Development Centr
Sur l'histoire des femmes en France
No full textWomen's history has been very recent in France. This study deals with the historiographical reasons of this lateness and those of its emerging. Without any pretense at thoroughness, the author tries to point out the major directions of research (family, education, work, women's fights...) and the groups, centers, publications connected with it, especially at university level. It tries to make out the contemporary specifications of this history, its aims and limits, and its relations with the place of women in the French society.L'histoire des femmes est, en France, très récente. Cet article s'interroge sur les raisons historiographiques de son retard et sur celles de son émergence. Sans prétendre à l'exhaustivité, il s'efforce d'indiquer les principales directions de recherche (famille, éducation, travail, luttes des femmes...) et de signaler les groupes, centres, périodiques qui la soutiennent, notamment dans le domaine universitaire. Il tente de dégager les spécificités actuelles de cette histoire, ses objectifs et ses limites, en liaison avec la place des femmes dans la société française.De gesciedschrijving over vrouwen is in Frankrijk zeer recent. In dit artikel gaat Michelle Perrot in op de oorzaken van deze vertraging. Zonder naar volledigheid te streven vermeldt zij een aantal studiegebieden (familie, opvoeding, werk, vrouwenstrijd enz) en een aantal groepen, centra, tijdschriften die op universitair niveau deze beweging steunen. Men poogt de hedendaagse eigenheid van deze geschiedenis naar voor te brengen, alsook de objektieven en de beperkingen ervan, steeds in relatie met de plaats van de vrouw in de Franse gemeenschap.Perrot Michelle. Sur l'histoire des femmes en France. In: Revue du Nord, tome 63, n°250, Juillet-septembre 1981. pp. 569-579
Peak Shaving the Electrical Power Demand of Ship-to-shore Cranes: Developing operational policies to maintain productivity under increasingly restrictive peak power limitations
No full textElectrification of numerous end-users is a worldwide trend to address climate change, according to the International Energy Agency. This trend has also reached container terminal operators. Currently most of the ship-to-shore cranes employed are electrified, leading to an increase in the required electrical power demand and to an increase in the volatility of the electrical power demand of container terminals. As a result, the contractual power demand charged by the grid operator, based on the maximum required power demand (peak power) at any moment in time, is upscaled, leading to additional costs for the container terminal operator. However, the highest required power demand values occur infrequently, leading to significant expenses for a resource that is rarely utilised. By implementing a peak shaving strategy, the peak power can be reduced, leading to a decrease in the contractual power demand related costs. Nevertheless, it is crucial to minimise the impact of the specific peak shaving strategy on the productivity of a container terminal to actually derive economic benefits from its implementation. The aim of this study is to develop operational policies that effectively maintain productivity for a cluster of six ship-to-shore cranes under increasingly restrictive peak power limitations. A discrete event simulation approach was employed for evaluating the operational and economic impact. In total four policies were developed, two according to the `who fits is served' approach (policy 0 and policy 1) and two according to the `priority based' approach (policy 2 and policy 3). In the first approach the initiation of a movement only depends on the power availability, while for the second approach the initiation of a movement depends on the power availability and the urgency of the movement in terms of productivity. Moreover, for both approaches one policy allows only one kinematic profile (policy 0 and policy 2) and one policy allows varying kinematic profiles (policy 1 and policy 3). A metaheuristic was employed to find near-optimal adapted kinematic profiles. The findings of this study suggest that the established `priority based' approach is more effective than the `who fits is served' approach in maintaining productivity under increasingly restrictive peak power limitations. When combined with the allowance of adapted kinematic profiles (policy 3), this strategy achieves the most cost savings. Policy 3, has been shown to reduce the contractual power demand related costs by 53\% compared to the baseline scenario, which is the greatest recorded reduction of all created policies without adversely affecting the ship-to-shore cranes' productivity. Mechanical Engineering | Multi-Machine Engineerin
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