A method of atmospheric density measurements during space shuttle entry using ultraviolet-laser Rayleigh scattering

An analytical study and its experimental verification are described which show the performance capabilities and the hardware requirements of a method for measuring atmospheric density along the Space Shuttle flightpath during entry. Using onboard instrumentation, the technique relies on Rayleigh scattering of light from a pulsed ArF excimer laser operating at a wavelength of 193 nm. The method is shown to be capable of providing density measurements with an uncertainty of less than 1 percent and with a spatial resolution along the flightpath of 1 km, over an altitude range from 50 to 90 km. Experimental verification of the signal linearity and the expected signal-to-noise ratios is demonstrated in a simulation facility at conditions that duplicate the signal levels of the flight environment

Laser-spectroscopic measurement techniques for hypersonic, turbulent wind tunnel flows

A review is given of the nature, present status, and capabilities of two laser spectroscopic methods for the simultaneous measurement of temperature, density, and their fluctuations owing to turbulence in high speed wind tunnel flows. One method is based on the two frequency excitation of nitric oxide seeded into a nitrogen flow, using tunable dye lasers. The second, more recent method relies on the excitation of oxygen in air flows using a tunable, ArF excimer laser. Signal are obtained from both the laser induced fluorescence and from Raman scattering of the same laser pulse. Measurements are demonstrated in the turbulent boundary layer of a Mach-2 channel flow

The performance of arm locking in LISA

For the laser interferometer space antenna (LISA) to reach it's design sensitivity, the coupling of the free running laser frequency noise to the signal readout must be reduced by more than 14 orders of magnitude. One technique employed to reduce the laser frequency noise will be arm locking, where the laser frequency is locked to the LISA arm length. This paper details an implementation of arm locking, studies orbital effects, the impact of errors in the Doppler knowledge, and noise limits. The noise performance of arm locking is calculated with the inclusion of the dominant expected noise sources: ultra stable oscillator (clock) noise, spacecraft motion, and shot noise. Studying these issues reveals that although dual arm locking [A. Sutton & D. A Shaddock, Phys. Rev. D 78, 082001 (2008).] has advantages over single (or common) arm locking in terms of allowing high gain, it has disadvantages in both laser frequency pulling and noise performance. We address this by proposing a hybrid sensor, retaining the benefits of common and dual arm locking sensors. We present a detailed design of an arm locking controller and perform an analysis of the expected performance when used with and without laser pre-stabilization. We observe that the sensor phase changes beneficially near unity-gain frequencies of the arm-locking controller, allowing a factor of 10 more gain than previously believed, without degrading stability. We show that the LISA frequency noise goal can be realized with arm locking and Time-Delay Interferometry only, without any form of pre-stabilization.Comment: 28 pages, 36 figure

The complex and rapidly changing sociolinguistic position of the English language in Japan: a summary of English language contact and use

This paper investigates the role of English in Japan, outlining its current status and use. The paper begins with a critical review of the World Englishes model as it relates to the categorization of Japan within the expanding circle of English use and continues with a brief history of English language contact with the country. It then examines the changing role of English in the Japanese education system and media. This is followed by a discussion of the influence of English on the Japanese language as well as the role which the English language plays within the discourses of nihonjinron and kokusaika. The paper concludes with a call for empirical research to be conducted investigating the spread, acquisition and attitudes towards English in Japa

A Separate Civil War: Communities in Conflict in the Appalachian South

Appalachia\u27s Civil War The War\u27s Impact on Communities More often than not, historians of the Civil War have acted as if the Confederacy\u27s Appalachian areas did not exist. It is hard to blame them. The southern mountains have such an irritating way of frustrating facile general...

Rediscovering the "Farmless" Farm Population: The Nineteenth-Century Census and the Postbellum Reorganization of Agriculture in the U.S. South, 1860-1900

Historical analysis of the reorganization of agriculture in the postbellum American South has tended to exclude a sizable proportion of the region's free farm population. This "farmless farm population" consisted of household heads who reported a farm occupation on the 1860 and 1880 population censuses but who did not appear in the list of farm operators in the corresponding agricultural schedules. Using cross-sectional census datafrom 1860, 1880, and 1900 for eight counties in Tennessee, the author attempts to determine as precisely as possible the numerical importance of the farmless farm population and to demonstrate this group's corresponding capacity to distort analysis of such structural questions as the distribution of wealth, the extent of landlessness, or the prevalence of economic independence.L'analyse historique de la réorganisation de l'agriculture dans le Sud des États-Unis d'après guerre a eu tendance à exclure une partie assez importante de la population emphytéote. Ces « paysans sans ferme » comprenaient des chefs de ménage qui déclarèrent une profession agricole aux recensements de la population de 1860 et de 1880, mais dont les noms ne figuraient pas dans les listes d'exploitants agricoles des registres agricoles correspondants. À l'aide de données transversales des recensements de 1860, de 1880 et de 1900 pour huit comtés de l'État du Tennessee, l'auteur tente de déterminer aussi précisément que possible le nombre de paysans sans ferme et de démontrer la capacité correspondante de ce groupe de fausser l'analyse de questions telles que la répartition de la richesse, l'ampleur de la paysannerie sans terre ou la prévalence de la dépendance économique

Experiential Education and Civic Learning

not only demands experiential education; civic learning reinforces for us the nature of experiential education. To explore the relationship between the two, we must understand a number of factors: the nature of the contemporary challenges to civic learning; the relationship of the purposes that educational institutions choose to that civic challenge; the pedagogical choices available for learning civically; and the relationship of learning theory to the centrality of choice that lies at the core of civic learning. At the end of this investigation, we will find some important guiding principles that civic learning suggests for how we engage in experiential education

Houston Muslim Study

The purpose of the Houston Muslim Study is to provide an in-depth and policy-relevant study, through a non-security lens, about American Muslims at the local level in Houston, Texas. The study offers fresh insights and helps shape a discussion about American Muslims that is data-driven and moves beyond the generalizations, prejudices, and fear that too often surround public and policy discourses about Muslim communities in America

Experiential Education and Civic Learning

The nature of civic learning not only demands experiential education; civic learning reinforces for us the nature of experiential education. To explore the relationship between the two, we must understand a number of factors: the nature of the contemporary challenges to civic learning; the relationship of the purposes that educational institutions choose to that civic challenge; the pedagogical choices available for learning civically; and the relationship of learning theory to the centrality of choice that lies at the core of civic learning. At the end of this investigation, we will find some important guiding principles that civic learning suggests for how we engage in experiential education

The language of suffering: Media discourse and public attitudes towards the MH17 air tragedy in Malaysia and the UK

‘If it bleeds, it leads’, events characterised by fatalities, are likely to attract high levels of media coverage. This study adopts a multidisciplinary approach to investigate public discourses on the MH17 tragedy in Malaysia and the United Kingdom. First, corpus-based discourse analysis was employed to explore the construction of the Malaysian Airlines tragedy MH17 in four selected Malaysian and British newspapers. In addition, an attitudinal study examining 50 Malaysian and 50 UK nationals’ perceptions of the tragedy was conducted. Keywords analysis revealed an overall tendency for the news media to construct the air tragedy through classifications between ‘us’ and ‘others’. Specifically, important ‘Us’ (Malaysian elites) and non-important ‘Other’ (non-Malaysian) in the Malaysian newspapers, versus good ‘Us’ (the West) and evil ‘Others’ (Russia) in the British newspapers. The attitudinal analysis shows, for both the Malaysian and the UK respondents, the most salient associations with the MH17 tragedy related to ‘conflicts’