A ’Millipede’ scanner model - Energy consumption and performance

This short report (1) describes an energy model for the seek and read/write operations in a mass-balanced Y-scanner for parallel-probe storage by IBM [1] and (2) updates the settings of the MEMS model in DiskSim with recent published figures from this XY-scanner. To speedup system simulations, a straight forward second-order model is used without control loop. Read/write operation is modeled by quasi-static calculations. To approximate seek behavior, ’bang-bang’ control is assumed; the result is close to the actual behavior with control loop [2]. Unfortunately, no energy measurements were available to validate the model. Using the proposed energy model, we are able to study the energy consumption of a MEMS-based storage device for different application areas and file systems

Design, Modeling, and Geometric Control on SE(3) of a Fully-Actuated Hexarotor for Aerial Interaction

In this work we present the optimization-based design and control of a fully-actuated omnidirectional hexarotor. The tilt angles of the propellers are designed by maximizing the control wrench applied by the propellers. This maximizes (a) the agility of the UAV, (b) the maximum payload the UAV can hover with at any orientation, and (c) the interaction wrench that the UAV can apply to the environment in physical contact. It is shown that only axial tilting of the propellers with respect to the UAV's body yields optimal results. Unlike the conventional hexarotor, the proposed hexarotor can generate at least 1.9 times the maximum thrust of one rotor in any direction, in addition to the higher control torque around the vehicle's upward axis. A geometric controller on SE(3) is proposed for the trajectory tracking problem for the class of fully actuated UAVs. The proposed controller avoids singularities and complexities that arise when using local parametrizations, in addition to being invariant to a change of inertial coordinate frame. The performance of the controller is validated in simulation.Comment: 9 pages, 9 figures, ICRA201

Optimized comb drive finger shape for shock-resistant actuation

This work presents the analytical solution, realization and measurement of a comb drive with finger shapes optimized for shock-resistant actuation. The available force for actuating an external load determines how large shock forces can be compensated for. An analytical expression is presented for the finger shape that provides a constant large available force over the actuation range. The finger shape is asymmetric, resulting in a 20% smaller unit cell width compared to a symmetric shape. This finger shape provides 4 times more available force than the standard straight finger shape

Compact Laser Communication Terminal Architecture and In-Orbit Demonstration

Satellites are generating more data than ever due to more demanding payloads, although communications Down To Earth (DTE) have not experienced the same growth in data rates. Compact Laser Communication Terminals are a promising technology that will increase bandwidths (10 Gbit+) and pave the way for larger data volumes to be transmitted which will increase the relevance of small and CubeSats in space data as service offerings. The in-orbit demonstrator is targeting a downlink data rate of 1 Gbit/s with a range of up to 1000km. A downlink wavelength of 1545nm is used while 1590nm is used for the ground station beacon. PRBS23 sequences will be transmitted from the in-orbit terminal to a ground station in the Netherlands. During in-orbit experimentation, attempts will be made to acquire payload data from other onboard payloads and to forward this data down to earth. This will provide valuable insight into possible future enhancements. The goal is to use the lessons learned from the in-orbit demonstration and results to drive the development of future iterations of the terminal. Lessons learned during the development phase, market feedback and test results are already being used to shape the architecture and design of the system. The following learnings are anticipated: robust fast data storage does add value; higher down and upload speeds are required; throughput enhancement using adjustable data rates will be worth the investment and enhancing error correction allows for more efficient transfers

Care and support for youth living with HIV/AIDS in secondary schools : perspectives of school stakeholders in western Uganda

Background: Although schools have been identified as significant settings in the response to the HIV/AIDS pandemic, limited research is available on how they can accommodate Youth Living with HIV/AIDS (YLWHA), especially in resource limited countries. In this study, we explored strategies by school stakeholders (school staff, parents/caretakers, and students) in western Uganda to care for and support YLWHA in their schools. Methods: The article utilizes data collected between May and October, 2019 from a qualitative inquiry based on focus group discussions and interviews with 88 school stakeholders purposively selected from 3 secondary schools in western Uganda. Textual data was analyzed thematically involving both inductive and deductive coding. Results: We identified 7 overarching interrelated themes in which participants reported strategies to care for and support YLWHA: counselling and guidance; social support networks and linkages; knowledge and skills; anti-stigma and anti-discrimination measures; disclosure of HIV status; treatment and management of HIV/AIDS; and affirmative actions for YLWHA. Stakeholders' strategies often differed regarding what was considered appropriate, the approach and who to take lead in supporting YLWHA. Conclusions: Despite the limited care and support strategies specific for YLWHA currently available in schools, our study points to optimism and high potential given stakeholders' identified avenues for improvement. We posit that promoting HIV/AIDS-care and support in schools is a gradual process requiring each school to develop a strong knowledge base about HIV/AIDS and support needs of YLWHA, develop a coherent and school-wide approach, and collaborate extensively with external stakeholders who are significant in supporting YLWHA

Alpha, Betti and the Megaparsec Universe: on the Topology of the Cosmic Web

We study the topology of the Megaparsec Cosmic Web in terms of the scale-dependent Betti numbers, which formalize the topological information content of the cosmic mass distribution. While the Betti numbers do not fully quantify topology, they extend the information beyond conventional cosmological studies of topology in terms of genus and Euler characteristic. The richer information content of Betti numbers goes along the availability of fast algorithms to compute them. For continuous density fields, we determine the scale-dependence of Betti numbers by invoking the cosmologically familiar filtration of sublevel or superlevel sets defined by density thresholds. For the discrete galaxy distribution, however, the analysis is based on the alpha shapes of the particles. These simplicial complexes constitute an ordered sequence of nested subsets of the Delaunay tessellation, a filtration defined by the scale parameter, $\alpha$. As they are homotopy equivalent to the sublevel sets of the distance field, they are an excellent tool for assessing the topological structure of a discrete point distribution. In order to develop an intuitive understanding for the behavior of Betti numbers as a function of $\alpha$, and their relation to the morphological patterns in the Cosmic Web, we first study them within the context of simple heuristic Voronoi clustering models. Subsequently, we address the topology of structures emerging in the standard LCDM scenario and in cosmological scenarios with alternative dark energy content. The evolution and scale-dependence of the Betti numbers is shown to reflect the hierarchical evolution of the Cosmic Web and yields a promising measure of cosmological parameters. We also discuss the expected Betti numbers as a function of the density threshold for superlevel sets of a Gaussian random field.Comment: 42 pages, 14 figure

Experiences and effects of HIV-related stigma among youth living with HIV/AIDS in Western Uganda : a photovoice study

HIV-related stigma has been identified as a significant stressor affecting Quality of Life of Youth Living With HIV/AIDS (YLWHA). Gaining a contextualized understanding of how this stigma is experienced by YLWHA in Western Uganda is crucial in addressing it in this group and setting. In this study, we explored the lived experiences of YLWHA with HIV-related stigma. Photovoice was used to gain insight into the lived experiences of HIV-related stigma in 11 YLWHA (15-19 years), purposively selected from a hospital-based peer support group. Group interview transcripts, notes and photographs were subjected to phenomenological hermeneutic analysis. Encounters with enacted, anticipated and internalized stigmas and their myriad sequels were prevalent in the photos and narratives of participants. Our findings were categorized and presented in 5 main themes that were identified through the analysis: being devalued, experiencing fear, experiencing injustices, feeling lonely, and lacking future perspectives. HIV-related stigmas were experienced in various socio-ecological domains but predominantly in homes and schools that ought to be supportive surroundings for youths. A multilevel approach, targeting the entire society where the root causes of stigma can be found and specific contexts like schools and homes where youth are confronted with stigma on a daily basis is proposed for a wholistic intervention

Experiences and perceptions of youth living with HIV in Western Uganda on school attendance : barriers and facilitators

Background: The globally recognized socio-economic benefits of education have stirred many countries in Sub-Saharan Africa like Uganda to promote universal access to schooling by removing fiscal barricades for those in primary and secondary schools. However, the proportion of Youth Living With HIV/AIDS (YLWHA) missing school, studying with difficulties and dropping out of school in Uganda has been observed to be higher than that of other youth. This study aimed at understanding the barriers and facilitators for YLWHA in Uganda to attend school. Methods: We conducted a qualitative inquiry with 35 purposively selected YLWHA aged 12 to 19 years, including 16 females at three accredited Antiretroviral Therapy (ART) treatment centres in Kabarole district in Western Uganda. Individual semi-structured interviews were tape-recorded, transcribed verbatim and subjected to thematic inductive analysis. Results: We identified five main themes in which barriers to attend school were reported and four main themes in which facilitators were reported by participants. The main themes for barriers were: 1) management of ART and illnesses, 2) fear, negative thoughts and self-devaluation, 3) lack of meaningful and supportive relationships, 4) reactionary attitudes and behaviours from others at school, 5) financial challenges. The main themes for facilitators were: 1) practical support at school, home and community, 2) counselling, encouragement and spirituality, 3) individual coping strategies, 4) hopes, dreams and opportunities for the future. Conclusion: Most of the barriers reported arose from HIV-related stigma and financial challenges whose genesis transcends school boundaries. While YLWHA reported measures to cope, and support from other people, these were non-sustainable and on a limited scale due to disclosure apprehension at school and the indiscretion of those who learnt about their status. To promote supportive school environments for YLWHA, integrated curricular and extracurricular interventions are necessary to increase HIV knowledge, dispel misconceptions about HIV and consequently transform the school community from a stigmatizing one to a supportive one