Probabilistic study of a dynamical system

This paper investigates the relation between a branching process and a non-linear dynamical system in C2. This idea has previously been fruitful in many investigations, including that of the FKPP equation by McKean, Neveu, Bramson, and others. Our concerns here are somewhat different from those in other work: we wish to elucidate those features of the dynamical system which correspond to the long-term behaviour of the random process. In particular, we are interested in how the dimension of the global attractor corresponds to that of the tail {sigma}-algebra of the process. The Poincaré–Dulac operator which (locally) intertwines the non-linear system with its linearization may sometimes be exhibited as a Fourier–Laplace transform of tail-measurable random variables; but things change markedly when parameters cross values giving the ‘primary resonance’ in the Poincaré–Dulac sense. Probability proves effective in establishing global properties amongst which is a clear description of the global convergence to the attractor. Several of our probabilistic results are analogues of ones obtained by Kesten and Stigum, and by Athreya and Ney, for discrete branching processes. Our simpler context allows the use of Itô calculus. Because the paper bridges two subjects, dynamical-system theory and probability theory, we take considerable care with the exposition of both aspects. For probabilist readers, we provide a brief guide to Poincaré–Dulac theory; and we take the view that in a paper which we hope will be read by analysts, it would be wrong to fudge any details of rigour in our probabilistic arguments

Monolayers of 3He on the Surface of Bulk Superfluid 4He

We have used quantum evaporation to investigate the two-dimensional fermion system that forms at the free surface of (initially isotopically pure) 4He when small quantities of 3He are added to it. By measuring the first-arrival times of the evaporated atoms, we have determined that the 3He-3He potential in this system is V_3S/k_B=(0.23+/-0.02) K nm^2 (repulsive) and estimated a value of m_3S=(1.53+/-0.02)m_3 for the zero-coverage effective mass. We have also observed the predicted second layer-state which becomes occupied once the first layer-state density exceeds about 0.6 monolayers.Comment: 2 pages, 3 figures. Submitted to Proc. LT-22 (1999) to appear in Physica

Relative Evaporation Probabilities of 3He and 4He from the Surface of Superfluid 4He

We report a preliminary experiment which demonstrates that 3He atoms in Andreev states are evaporated by high-energy (E/k_B ~ 10.2 K) phonons in a quantum evaporation process similar to that which occurs in pure 4He. Under conditions of low 3He coverage, high-energy phonons appear to evaporate 3He and 4He atoms with equal probability. However, we have not managed to detect any 3He atoms that have been evaporated by rotons, and conclude that the probability of a roton evaporating a 3He atom is less than 2% of the probability that it evaporates a 4He atom.Comment: 2 pages, 3 figures. Submitted to Proc. LT-22 (1999) Physica

A conceptual design methodology for evaluation of alternate propulsion system modifications on small aircraft

Conceptual design is often considered to be the most important step in the design of a new product or the modification of an existing product. The important steps in this conceptual design phase is the synthesis of potential solutions into concepts, the evaluation of these concepts within a repeatable and robust design methodology framework and analysis to identify and characterise the preferred solution concept. This research has arisen from problems associated with developing aircraft-based design modification concepts and predicting the impact of these changes as they propagate or flow down through the various aircraft subsystems, impacting engineering design, and leading to certification and operations challenges. This research problem is particularly evident in highly integrated systems such as high-performance military aircraft, helicopters, and complex civil aircraft. To illustrate this methodology the author has selected two case studies which apply two different alternate propulsion system technologies to small aircraft. These case studies were selected to provide a diverse design modification space encompassing differing aircraft roles and mission types, differing technologies and subsystems integration scope, and different data sources collection and analysis methods. In order to combine the elements of design synthesis, evaluation of concept alternatives and analysis of outputs, this thesis has formulated a matrix-based conceptual design methodology. This methodology extends current knowledge by implementing the concepts of design synthesis, evaluation and analysis as an iterative process, and building and linking together existing techniques. This new methodology combined various techniques and methods such as Quality Function Deployment (QFD), quantified morphological matrices (QMM), Pugh’s decision matrices, change options Multiple-Domain Matrices (MDM), and has adapted the Change Propagation Method (CPM). The second extension to current knowledge in this area was the development of Engineering and Certification Domain Mapping Matrix (DMM) techniques based on Design Structure Matrices (DSM). This extension into engineering and certification domain was undertaken to ensure that important modification-related risks and costs were incorporated into the early stages of design. The extension adopted existing DSM and DMM-based techniques and tools to evaluate the impact of changes to subsystems and hence impact of risks and costs resulting from aircraft modifications using change propagation method analysis techniques. The validation of this conceptual design methodology was achieved by verifying and assessing the adequacy of its application through an analysis process which examined (1) coverage of the design space attributes; (2) validation of the methodology against accepted scientific and industry conceptual design frameworks; and (3) confirmation of the existing techniques, structures and tools applied within the methodology

Hinode/Extreme-Ultraviolet Imaging Spectrometer Observations of the Temperature Structure of the Quiet Corona

We present a Differential Emission Measure (DEM) analysis of the quiet solar corona on disk using data obtained by the Extreme-ultraviolet Imaging Spectrometer (EIS) on {\it Hinode}. We show that the expected quiet Sun DEM distribution can be recovered from judiciously selected lines, and that their average intensities can be reproduced to within 30%. We present a subset of these selected lines spanning the temperature range $\log$ T = 5.6 to 6.4 K that can be used to derive the DEM distribution reliably. The subset can be used without the need for extensive measurements and the observed intensities can be reproduced to within the estimated uncertainty in the pre-launch calibration of EIS. Furthermore, using this subset, we also demonstrate that the quiet coronal DEM distribution can be recovered on size scales down to the spatial resolution of the instrument (1$"$ pixels). The subset will therefore be useful for studies of small-scale spatial inhomogeneities in the coronal temperature structure, for example, in addition to studies requiring multiple DEM derivations in space or time. We apply the subset to 45 quiet Sun datasets taken in the period 2007 January to April, and show that although the absolute magnitude of the coronal DEM may scale with the amount of released energy, the shape of the distribution is very similar up to at least $\log$ T $\sim$ 6.2 K in all cases. This result is consistent with the view that the {\it shape} of the quiet Sun DEM is mainly a function of the radiating and conducting properties of the plasma and is fairly insensitive to the location and rate of energy deposition. This {\it universal} DEM may be sensitive to other factors such as loop geometry, flows, and the heating mechanism, but if so they cannot vary significantly from quiet Sun region to region.Comment: Version accepted by ApJ and published in ApJ 705. Abridged abstrac

Reducing Uncertainty: A Student Perspective on an Introductory Communication Course

This assessment examines the Cal Poly Communication Studies (COMS) Department’s organizational needs and obstacles to effectively educating students in the major. We also propose a research question and method in order to provide the COMS department with insight into their organizational needs. Specifically, we have identified issues in overall educational effectiveness in correspondence with the needs and perspectives of their students. We will look into this issue through interviews, surveying, and analyzing the current COMS curriculum

Observations of Active Region Loops with the EUV Imaging Spectrometer on Hinode

Previous solar observations have shown that coronal loops near 1 MK are difficult to reconcile with simple heating models. These loops have lifetimes that are long relative to a radiative cooling time, suggesting quasi-steady heating. The electron densities in these loops, however, are too high to be consistent with thermodynamic equilibrium. Models proposed to explain these properties generally rely on the existence of smaller scale filaments within the loop that are in various stages of heating and cooling. Such a framework implies that there should be a distribution of temperatures within a coronal loop. In this paper we analyze new observations from the EUV Imaging Spectrometer (EIS) on \textit{Hinode}. EIS is capable of observing active regions over a wide range of temperatures (\ion{Fe}{8}--\ion{Fe}{17}) at relatively high spatial resolution (1\arcsec). We find that most isolated coronal loops that are bright in \ion{Fe}{12} generally have very narrow temperature distributions ($\sigma_T \lesssim 3\times10^5$ K), but are not isothermal. We also derive volumetric filling factors in these loops of approximately 10%. Both results lend support to the filament models.Comment: Submitted to ApJ

Interspecific Hybridisation between \u3cem\u3eTrifolium repens\u3c/em\u3e and \u3cem\u3eT. occidentale\u3c/em\u3e for the Improvement of Drought Tolerance in White Clover

Trifolium repens (white clover) is one of the most important forage legumes in temperate region of the world. Phylogenetically it is an allotetraploid between T. pallescens and T. occidentale (Williams et al., 2012). Stands of white clover, although a perennial, often decline significantly by drought stress (Van Den Bosch et al., 1993). T. occidentale is a diploid (2n=2x=16) stoloniferous perennial clover that grows naturally in saline, dry habitats and as such may be a useful source of genes to improve the drought tolerance of white clover cultivars (Hussain and Williams, 2013). Although white clover has been successfully hybridised with various annual and perennial Trifolium species (Williams, 1987), the resulting F1 hybrids have not been effectively utilised as useful genetic material for the improvement of white clover cultivars. The objective of our current research was to evaluate F1 and BC1 hybrids between T. repen and T. occidentale for drought tolerance

Personality, Gender and Careers in Information Technology

The downturn in information technology enrollment numbers in colleges and universities has spurred a stream of research focusing on identifying factors that inhibit students’ interest in information technology. Most of these studies measure individuals’ perceptions and beliefs. We argue that the profession is composed of multiple occupations and those occupations have different characteristics concerning the work performed, the opportunities available, and the people who are employed in those occupations. We investigate the relationship between personality and the intent of students to pursue careers in the information technology field. Last, we examine if there is a gender personality profile for students who decide to pursue careers in information technology. Our findings can be used by researchers and practitioners to better describe to students the specific opportunities and career paths available within the IT profession