A study of the lunisolar secular resonance 2ω˙+Ω˙=02\dot{\omega}+\dot{\Omega}=0

The dynamics of small bodies around the Earth has gained a renewed interest, since the awareness of the problems that space debris can cause in the nearby future. A relevant role in space debris is played by lunisolar secular resonances, which might contribute to an increase of the orbital elements, typically of the eccentricity. We concentrate our attention on the lunisolar secular resonance described by the relation $2\dot{\omega}+\dot{\Omega}=0$, where $\omega$ and $\Omega$ denote the argument of perigee and the longitude of the ascending node of the space debris. We introduce three different models with increasing complexity. We show that the growth in eccentricity, as observed in space debris located in the MEO region at the inclination about equal to $56^\circ$, can be explained as a natural effect of the secular resonance $2\dot{\omega}+\dot{\Omega}=0$, while the chaotic variations of the orbital parameters are the result of interaction and overlapping of nearby resonances.Comment: 15 pages, 8 figure

A study of the main resonances outside the geostationary ring

We investigate the dynamics of satellites and space debris in external resonances, namely in the region outside the geostationary ring. Precisely, we focus on the 1:2, 1:3, 2:3 resonances, which are located at about 66 931.4 km, 87 705.0 km, 55 250.7 km, respectively. Some of these resonances have been already exploited in space missions, like XMM-Newton and Integral. Our study is mainly based on a Hamiltonian approach, which allows us to get fast and reliable information on the dynamics in the resonant regions. Significative results are obtained even by considering just the effect of the geopotential in the Hamiltonian formulation. For objects (typically space debris) with high area-to-mass ratio the Hamiltonian includes also the effect of the solar radiation pressure. In addition, we perform a comparison with the numerical integration in Cartesian variables, including the geopotential, the gravitational attraction of Sun and Moon, and the solar radiation pressure. We implement some simple mathematical tools that allows us to get information on the terms which are dominant in the Fourier series expansion of the Hamiltonian around a given resonance, on the amplitude of the resonant islands and on the location of the equilibrium points. We also compute the Fast Lyapunov Indicators, which provide a cartography of the resonant regions, yielding the main dynamical features associated to the external resonances. We apply these techniques to analyze the 1:2, 1:3, 2:3 resonances; we consider also the case of objects with large area-to-mass ratio and we provide an application to the case studies given by XMM-Newton and Integral.Comment: 30 pages, 10 figure

The storage of hydrogen in the form of metal hydrides: An application to thermal engines

The possibility of using LaNi56, FeTiH2, or MgH2 as metal hydride storage sytems for hydrogen fueled automobile engines is discussed. Magnesium copper and magnesium nickel hydrides studies indicate that they provide more stable storage systems than pure magnesium hydrides. Several test engines employing hydrogen fuel have been developed: a single cylinder motor originally designed for use with air gasoline mixture; a four-cylinder engine modified to run on an air hydrogen mixture; and a gas turbine

INVESTIGATION OF INNER AND OUTER SUBSHELLS VIA TRANSFER REACTIONS

Transfer reactions, investigated a high incident energy (from 100 to 300 MeV), have considerably increased our knowledge of the nuclear response function to a particular simple mode of excitation of the nucleus. These reactions are particularly well suited to the study of high spin inner and outer subshells. The advantages of such approach are illustrated using few characteristic examples. a) Strong selectivity in angular momentum transfer, determination of the spin J of the inner hole state using polarized protonbeam in the case of one nucleon pick-up reaction. b) New experimental results via the (α, 6He) reaction at 218 MeV incident energy are obtained on the two-nucleon strength distributions in medium-heavy nuclei. c) First evidence of proton and neutron single-particle strengths at high excitation energy (5 to 15 MeV) in heavy nuclei are reported using the (α, t) (α, 3He) and (3He, d) stripping reactions. The experimental results will be compared to the predictions of nuclear models which take into account explicitly the coupling between single-particle and collective states in order to explain the observed fragmentation and spreading of the single-particle strength

Social media as intelligence in disaster response: eyewitness classification using community detection

Disasters cause widespread devastation to both physical infrastructure and the lives of individuals residing in large geographic areas. The disruption caused by disaster events is further compounded by high levels of uncertainty and information scarcity, presenting significant challenges to disaster response organisations and impeding the effectiveness of coordinated response efforts. The increasing use of digital technologies, such as social media, presents valuable sources of information that are available in real-time from geographically-distributed networks of ‘humans as sensors’. The data generated by these technologies can supplement traditional sources of intelligence to build models of situational awareness and inform decision-making, resulting in more effective disaster response operations. This thesis proposes a method of curating social media data to enhance its usefulness as a source of intelligence for disaster response organisations during crisis events. The research was conducted in four phases: (i) An ethnographic study developed a conceptual framework of the values and challenges of social media intelligence as perceived by disaster response practitioners. High data volume and low rates of relevance were established as key factors impeding integration with existing intelligence sources. (ii) Empirical studies of Twitter discourse were conducted during eight disaster events to identify patterns of online behaviour and establish the informative potential of social media data as a rich source of eyewitness reports. (iii) Geoproximate preferential attachment (homophily) was identified in the structure of Twitter relationship networks. An eyewitness classification model integrated relationship features for data curation. The model was evaluated on temporally-partitioned subgraphs and shown to be effective in real-time environments. (iv) The classification model was validated in simulated disaster response scenarios conducted with emergency service practitioners. Feedback from participants confirmed the effectiveness of the approach to improving the practical value of social media data as a source of intelligence during disaster response operations

Effects of Poverty Funding on Literacy Achievement Over Time in Arkansas Schools

This dissertation provides additional background to the limited research regarding the effectiveness of the use of state categorical money on literacy achievement measured by the Arkansas Literacy Benchmark Exam for a cohort of third through sixth grade students and a cohort of fifth through eighth grade students in Arkansas school districts. Using a non-experimental design, the researcher tested two hypotheses using a mixed factorial analysis of variance (ANOVA). The independent variables for the two hypotheses were change over time with two levels measured in school years (2008 versus 2009 versus 2010 versus 2011) and the two NSLA funding levels. The dependent variables were literacy achievement measured by the scaled scores from the 2009-2012 Arkansas Benchmark Examination for the students in the sample. Using descriptive statistics, the researcher also asked two research questions to determine how program expenditures were allocated among six researcher-defined categories by districts assigned to two categories, and the researcher sought to determine how the additional moneys were expended. The researcher established four cohorts and used a stratified random sampling selection process to choose 320 participants for the study from six school districts. Two cohorts of students in each group who were consecutively enrolled for all years during Grades 3 through 6 (Hypothesis 1) and Grades 5 through 8 (Hypothesis 2) were selected. The selected districts were stratified into two groups: (a) changed NSLA funding level and (b) unchanged NSLA funding level. Stratifying the participants was needed since the main purpose of the study was to observe differences between changed and unchanged NSLA funding level groups. The results of this study showed no significant interaction between the independent variable of NSLA funding and the dependent variable literacy achievement scores. However, there was a significant interaction between the independent variable of change over time and the dependent variable literacy achievement scores. For the main effect of time, a significant difference on literacy achievement was observed over time. More NSLA funding was spent on non-literacy categories than literacy categories. This observation was true for both the changed and unchanged NSLA funding level groups

Effects of Pressurization on Aluminum 319 and A356.2 Alloy Castings

Castings made of aluminum 319 and A356.2 alloy were examined to determine the effectiveness of using pressure application during solidification to reduce porosity levels. Pyknometry was the method chosen to measure porosity. It was determined that the porosity of castings poured in both alloys was reduced in some instances. During the study, the surfaces of these castings were also examined and some were found to have defects present. After the porosity was evaluated, specimens of castings poured in both alloys were tested to determine whether or not the surface intrusions affected the castings. The defects were found to reduce the strength of the castings poured in aluminum 319. The castings poured in A356.2 did not have surface intrusions or any significant decreases in strength. Therefore it was concluded that of the two alloys tested, A356.2 alloy is most suited for using pressurization as a method of reducing porosity