Shuttle system ascent aerodynamic and plume heating

The shuttle program provided a challenge to the aerothermodynamicist due to the complexity of the flow field around the vehicle during ascent, since the configuration causes multiple shock interactions between the elements. Wind tunnel tests provided data for the prediction of the ascent design heating environment which involves both plume and aerodynamic heating phenomena. The approach for the heating methodology based on ground test firings and the use of the wind tunnel data to formulate the math models is discussed

Semiclassical description of the kinematically complete experiments

Based on the semiclassical, impact parameter method a theoretical model is constructed to calculate totally differential cross sections for single ionization of helium by impact with fast C$^{6+}$ ions. Good agreement with the experiment is achieved in the scattering plane, while in the perpendicular plane a similar structure to that observed experimentally is obtained. The contribution of different partial waves to the cross section is also investigated.Comment: 9 pages, 6 figure

QAnon Propaganda on Twitter as Information Warfare: Influencers, Networks, and Narratives

QAnon refers to a set of far-right, conspiratorial ideologies that have risen in popularity in the U.S. since their initial promotion in 2017 on the 4chan internet message board. A central narrative element of QAnon is that a powerful group of elite, liberal members of the Democratic Party engage in morally reprehensible practices, but that former U.S. President Donald J. Trump was prosecuting them. Five studies investigated the influence and network connectivity of accounts promoting QAnon on Twitter from August, 2020 through January, 2021. Selection of Twitter accounts emphasized on-line influencers and "persons of interest" known or suspected of participation in QAnon propaganda promotion activities. Evidence of large-scale coordination among accounts promoting QAnon was observed, demonstrating rigorous, quantitative evidence of "astroturfing" in QAnon propaganda promotion on Twitter, as opposed to strictly "grassroots" activities of citizens acting independently. Further, evidence was obtained supporting that networks of extreme far-right adherents engaged in organized QAnon propaganda promotion, as revealed by network overlap among accounts promoting far-right extremist (e.g., anti-Semitic) content and insurrectionist themes; New Age, occult, and "esoteric" themes; and internet puzzle games like Cicada 3301 and other "alternate reality games." Based on well-grounded theories and findings from the social sciences, it is argued that QAnon propaganda on Twitter in the months circa the 2020 U.S. Presidential election likely reflected joint participation of multiple actors, including nation-states like Russia, in innovative misuse of social media toward undermining democratic processes by promoting "magical" thinking, ostracism of Democrats and liberals, and salience of White extinction narratives common among otherwise ideologically diverse groups on the extreme far-right.Comment: 60 pages, 14 figure

A study to explore the use of orbital remote sensing to determine native arid plant distribution

The author has identified the following significant results. It is possible to determine, from ERTS imagery, native arid plant distribution. Using techniques of multispectral masking and extensive fieldwork, three native vegetation communities were defined and mapped in the Avra Valley study area. A map was made of the Yuma area with the aid of ground truth correlations between areas of desert pavement visible on ERTS images and unique vegetation types. With the exception of the Yuma soil-vegetation correlation phenomena, only very gross differentiations of desert vegetation communities can be made from ERTS data. Vegetation communities with obvious vegetation density differences such as saguaro-paloverde, creosote bush, and riparian vegetation can be separated on the Avra Valley imagery while more similar communities such as creosote bush and saltbush could not be differentiated. It is suggested that large differences in vegetation density are needed before the signatures of two different vegetation types can be differentiated on ERTS imagery. This is due to the relatively insignificant contribution of vegetation to the total radiometric signature of a given desert scene. Where more detailed information concerning the vegetation of arid regions is required, large scale imagery is appropriate

Effect of heuristics on serendipity in path-based storytelling with linked data

Path-based storytelling with Linked Data on the Web provides users the ability to discover concepts in an entertaining and educational way. Given a query context, many state-of-the-art pathfinding approaches aim at telling a story that coincides with the user's expectations by investigating paths over Linked Data on the Web. By taking into account serendipity in storytelling, we aim at improving and tailoring existing approaches towards better fitting user expectations so that users are able to discover interesting knowledge without feeling unsure or even lost in the story facts. To this end, we propose to optimize the link estimation between - and the selection of facts in a story by increasing the consistency and relevancy of links between facts through additional domain delineation and refinement steps. In order to address multiple aspects of serendipity, we propose and investigate combinations of weights and heuristics in paths forming the essential building blocks for each story. Our experimental findings with stories based on DBpedia indicate the improvements when applying the optimized algorithm

Correlations of record events as a test for heavy-tailed distributions

A record is an entry in a time series that is larger or smaller than all previous entries. If the time series consists of independent, identically distributed random variables with a superimposed linear trend, record events are positively (negatively) correlated when the tail of the distribution is heavier (lighter) than exponential. Here we use these correlations to detect heavy-tailed behavior in small sets of independent random variables. The method consists of converting random subsets of the data into time series with a tunable linear drift and computing the resulting record correlations.Comment: Revised version, to appear in Physical Review Letter

Evaluation of nonmetallic thermal protection materials for the manned space shuttle. Volume 1, task 1: Assessment of technical risks associated with utilization of nonmetallic thermal protection system

Technical problems of design and flight qualification of the proposed classes of surface insulation materials and leading edge materials were reviewed. A screening test plan, a preliminary design data test plan and a design data test plan were outlined. This program defined the apparent critical differences between the surface insulators and the leading edge materials, structuring specialized screening test plans for each of these two classes of materials. Unique testing techniques were shown to be important in evaluating the structural interaction aspects of the surface insulators and a separate task was defined to validate the test plan. In addition, a compilation was made of available information on proposed material (including metallic TPS), previous shuttle programs, pertinent test procedures, and other national programs of merit. This material was collected and summarized in an informally structured workbook