Optimal Trajectories for Near-Earth-Objects Using Solar Electric Propulsion (SEP) and Gravity Assisted Maneuver

The future interplanetary missions will probably use the conventional chemical rockets to leave the sphere of influence of the Earth, and solar electric propulsion (SEP) to accomplish the other maneuvers of the mission. In this work the optimization of interplanetary missions using solar electric propulsion and Gravity Assisted Maneuver to reduce the costs of the mission, is considered. The high specific impulse of electric propulsion makes a Gravity Assisted Maneuver 1 year after departure convenient. Missions for several Near Earth Asteroids will be considered. The analysis suggests criteria for the definition of initial solutions demanded for the process of optimization of trajectories. Trajectories for the asteroid 2002TC70 are analyzed. Direct trajectories, trajectories with 1 gravity assisted from the Earth and with 2 gravity assisted from the Earth and either Mars are present. An indirect optimization method will be used in the simulations

Mars Sample Return Mission: Mars Ascent Vehicle Propulsion Design

The aim of this research is to analyze a potential Mars Sample Return (MSR) mission through the study of an optimized design of the Mars Ascent Vehicle (MAV) propulsion system. The main goal of the MSR mission is to return to Earth samples of rocks and dust collected by a rover operating on the surface of Mars, and conveyed to the MAV into an Orbit Sample (OS) canister. The MAV must accomplish an initial ascent phase from the Mars surface to a circular Low Mars Orbit (LMO) with a radius of 500 Km and 30° inclination, and then with its second stage it must circularize into the target LMO where it releases the OS payload. A combination of the MAV and a second vehicle, the Mars Earth Return Vehicle (MERV) orbiter, is required to fulfill the final return phase from Mars to the Earth. After completing three different phases of rendezvous operations, with a final Hohmann Transfer the MERV is able to bring the OS to Earth with its payload. A spreadsheet model enables the evaluation of two different MAV architecture: a two-stage solid rocket, and a two-stage hybrid rocket. The study is based on the main rocket science equations, including the Tsiolkovsky Rocket Equation that calculates the change in velocity Delta V for the two stages of the MAV and the amount of propellant needed for both stages. From the analysis it can be noted that the two-stage hybrid design has significant advantages, firstly in terms of Gross Lift Off Mass GLOM (270 Kg) when compared to the solid solution (355 Kg). The hybrid rocket also has lower mass by up to 60 Kg since it does not require a thermal igloo. Finally, the mass fractions for both stages are comparable, and the required Delta V for the hybrid stages are less than those needed for the solid, allowing considerable fuel savings. The hybrid solution is ultimately preferred, considering the best performance related to the thermal fuel properties enabling the MAV to safely operated in the harsh Martian environment

Deep learning for knowledge tracing in learning analytics: An overview

Learning Analytics (LA) is a recent research branch that refers to methods for measuring, collecting, analyzing, and reporting learners’ data, in order to better understand and optimize the processes and the environments. Knowledge Tracing (KT) deals with the modeling of the evolution, during the time, of the students’ learning process. Particularly its aim is to predict students’ outcomes in order to avoid failures and to support both students and teachers. Recently, KT has been tackled by exploiting Deep Learning (DL) models and generating a new, ongoing, research line that is known as Deep Knowledge Tracing (DKT). This was made possible by the digitalization process that has simplified the gathering of educational data from many different sources such as online learning platforms, intelligent objects, and mainstream IT-based systems for education. DKT predicts the student’s performances by using the information embedded in the collected data. Moreover, it has been shown to be able to outperform the state-of-the-art models for KT. In this paper, we briefly describe the most promising DL models, by focusing on their prominent contribution in solving the KT task

Framing automatic grading techniques for open-ended questionnaires responses. A short survey

The assessment of students' performances is one of the essential components of teaching activities, and it poses different challenges to teachers and instructors, especially when considering the grading of responses to open-ended questions (i.e., short-answers or essays). Open-ended tasks allow a more in-depth assessment of students' learning levels, but their evaluation and grading are time-consuming and prone to subjective bias. For these reasons, automatic grading techniques have been studied for a long time, focusing mainly on short-answers rather than long essays. Given the growing popularity of Massive Online Open Courses and the shifting from physical to virtual classrooms environments due to the Covid-19 pandemic, the adoption of questionnaires for evaluating learning performances has rapidly increased. Hence, it is of particular interest to analyze the recent effort of researchers in the development of techniques designed to grade students' responses to open-ended questions. In our work, we consider a systematic literature review focusing on automatic grading of open-ended written assignments. The study encompasses 488 articles published from 1984 to 2021 and aims at understanding the research trends and the techniques to tackle essay automatic grading. Lastly, inferences and recommendations are given for future works in the Learning Analytics field

Spending per Medicare Beneficiary Is Higher in Hospital‐Owned Small‐ and Medium‐Sized Physician Practices

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/145215/1/hesr12765.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/145215/2/hesr12765-sup-0001-AppendixSA1.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/145215/3/hesr12765_am.pd

Osteopontin plasma levels and accelerated atherosclerosis in patients with CAD undergoing PCI: a prospective clinical study.

OBJECTIVES: Growing evidence supports the role played by inflammation in atherosclerosis. Identifying sensitive biomarkers is useful in predicting accelerated atherosclerosis. We investigated prospectively the relationship between plasma levels of inflammatory biomarkers [osteopontin, C-reactive protein (CRP), interleukin-6 (IL-6)] and instent restenosis, and rapid coronary plaque progression in patients with coronary artery disease (CAD) undergoing percutaneous coronary intervention (PCI). METHODS: We studied 77 patients with CAD: 45 affected by unstable angina/non-ST elevation myocardial infarction [acute coronary syndrome (ACS)], and 32 by chronic coronary syndrome (CCS). Plasma osteopontin, IL-6, and CRP levels were measured before intervention in all patients; measurements were carried out on the basis of the following time course at 1,15, 30, 90, and 180 days follow-up in a subgroup of 39 consenting patients. Clinical and biohumoral data were correlated with baseline and 6-month PCI follow-up angiography. RESULTS: Osteopontin, IL-6, and CRP were higher in patients with ACS than in those with CCS (analysis of variance: P<0.001, 0.05, and 0.05, respectively). Baseline osteopontin levels proved to be associated with rapid coronary plaque progression (P=0.005) and instent restenosis (P=0.05). The highest osteopontin levels were found in patients with CAD with both rapid plaque progression and instent restenosis (P=0.003). PCI increased inflammatory markers acutely, and osteopontin remained elevated in patients with ACS. Patients with ACS showed a higher percentage (74%) of rapid plaque progression than those with CCS (26%) (P<0.05). CONCLUSION: The study prospectively shows the link between inflammatory status and accelerated atherosclerosis in patients with CAD undergoing PCI. The baseline and persistent rise of osteopontin is an expression of its contribution to the accelerated plaque progression, and therefore osteopontin may be a useful prognostic biomarker

Has VZV epidemiology changed in Italy? Results of a seroprevalence study

The aim of the study was to evaluate if and how varicella prevalence has changed in Italy. In particular a seroprevalence study was performed, comparing it to similar surveys conducted in pre-immunization era. During 2013–2014, sera obtained from blood samples taken for diagnostic purposes or routine investigations were collected in collaboration with at least one laboratory/center for each region, following the approval of the Ethics Committee. Data were stratified by sex and age. All samples were processed in a national reference laboratory by an immunoassay with high sensitivity and specificity. Statutory notifications, national hospital discharge database and mortality data related to VZV infection were analyzed as well. A total of 3707 sera were collected and tested. In the studied period both incidence and hospitalization rates decreased and about 5 deaths per year have been registered. The seroprevalence decreased in the first year of life in subjects passively protected by their mother, followed by an increase in the following age classes. The overall antibody prevalence was 84%. The comparison with surveys conducted with the same methodology in 1996–1997 and 2003–2004 showed significant differences in age groups 1–19&nbsp;y. The study confirms that in Italy VZV infection typically occurs in children. The impact of varicella on Italian population is changing. The comparison between studies performed in different periods shows a significant increase of seropositivity in age class 1–4&nbsp;years, expression of vaccine interventions already adopted in some regions

Public sector marketing : adjustment processes by taking the example of the city Hamburg an the event Hafengeburtstag

Stadtmarketing basiert auf der Philosophie der Kundenorientierung und wird als Fundament der zielgerichteten Gestaltung und Vermarktung einer Stadt definiert. Diese Bachelorarbeit analysiert die Anpassungsprozesse des Stadtmarketings am Beispiel der Stadt Hamburg und dem traditionellen Hamburger Event Hafengeburtstag

New perspectives in silicon micro and nanophotonics

In the last two decades, there has been growing interest in silicon-based photonic devices for many optical applications: telecommunications, interconnects and biosensors. In this work, an advance overview of our results in this field is presented. Proposed devices allow overcoming silicon intrinsic drawbacks limiting its application as a photonic substrate. Taking advantages of both non-linear and linear effects, size reduction at nanometric scale and new two-dimensional emerging materials, we have obtained a progressive increase in device performance along the last years. In this work we show that a suitable design of a thin photonic crystal slab realized in silicon nitride can exhibit a very strong field enhancement. This result is very promising for all photonic silicon devices based on nonlinear phenomena. Moreover we report on the fabrication and characterization of silicon photodetectors working at near-infrared wavelengths based on the internal photoemission absorption in a Schottky junction. We show as an increase in device performance can be obtained by coupling light into both micro-resonant cavity and waveguiding structures. In addition, replacing metal with graphene in a Schottky junction, a further improve in PD performance can be achieved. Finally, silicon-based microarray for biomedical applications, are reported. Microarray of porous silicon Bragg reflectors on a crystalline silicon substrate have been realized using a technological process based on standard photolithography and electrochemical anodization of the silicon. Our insights show that silicon is a promising platform for the integration of various optical functionalities on the same chip opening new frontiers in the field of low-cost silicon micro and nanophotonics