A failure diagnosis and impact assessment prototype for Space Station Freedom

NASA is investigating the use of advanced automation to enhance crew productivity for Space Station Freedom in numerous areas, one being failure management. A prototype is described that diagnoses failure sources and assesses the future impacts of those failures on other Freedom entities

The Mechanical Properties And Deformation Behavior Of Heat Treated Versus As-Received Inconel X-750

X-750 is a nickel-chromium based super alloy of usefulness in a wide variety of applications such as gas turbines, rocket engines, nuclear reactors, pressure vessels, tooling, and aircraft structures. Its good mechanical properties are due to the strengthening from precipitation of γ′ particles upon prior ageing heat treatment. In this work, the effect of such heat treatment on the mechanical properties, tensile behavior, and fracture mechanisms of X-750 was studied at various temperatures by comparing it with a non-aged, solution annealed X-750. Tensile tests were conducted from room temperatures up to 900 °C at three separate strain rates (10-3, 10-4, 10-5 s-1); tested samples were analyzed by means of SEM observations. In addition, the microstructure of both aged and solution annealed materials were studied using SEM and TEM, both on as received and on tested specimens. Serrated flow was observed for a range of temperatures referred to as the Portevin Le Chatelier (PLC) regime (interaction of solutes with dislocations causing stress serrations) in both heat treated (HT) and non-heat treated (NHT) samples. There is a different level of prominence in the Normal and Inverse PLC effect between HT and NHT X-750. Sinusoidal stress serrations are observed for both HT and NHT material at high temperatures, and dynamic recrystallization becomes a dominant deformation mechanism. Vacuum effects were observed to be relevant for mechanical properties, flow behavior, and dynamic recrystallization. v When tested between room temperatures and 650 °C, the fracture surface of HT material evolves from purely intergranular to purely transgranular due to the thermal activation of dislocation mobility that relieves the stress at the grain boundaries, while the rupture of the NHT material is due to the coalescence of voids induced by decohesion at the MC (one metallic element with one carbon atom) carbides/matrix interface. At higher temperatures, precipitation of γ’ particles upon testing of the NHT material leads to a temperature-dependent increase in both yield strength and ultimate tensile strength. At the same time, an overall decrease of the HT material mechanical properties is observed. Minimum ductility was observed at 750 °C for both solution annealed and aged specimen, due to the oxidation of grain boundaries leading to an environmentally-induced fracture mechanism. At higher temperatures, dynamic recovery and dynamic recrystallization occur which prevents such a rupture mechanism, but finally leads to rupture by grain boundary slipping at 900 °C

Motion Pictures, Social Theory and Contemporary Film: A Thematic Content Analysis of Values.

A content analysis of the ten top-grossing films of 1993 was conducted examining the depiction of the family, the portrayal of violence, and the representation of religion. The results were compared with the rhetorical vision of popular motion pictures by film critic Michael Medved. Medved\u27s 1992 Hollywood VS America attacked the entertainment industry for its anti­ family, pro-violence, and anti-religious messages in film. A thematic comparison indicated that, across the three categories, Medved\u27s criticisms were supported about half of the time by the film sample. A deeper look at the results shows that Medved\u27s criticisms regarding the depiction of the family and the portrayal of violence were largely unsupported by the sample. His observations about anti-family messages were not found in any of the seven films evaluated for family content. The pro-violence content was reported in two of the six films studied for violence. Medved\u27s contention that religion is not represented in popular film was strongly supported, showing agreement in nine of the ten films in the sample. The thesis concludes that, in the areas of family and violence, his criticisms focus on the film content outside of their narrative context. That is, actual anti family and pro-violence issues are present in the films, but are treated in such a way as to reaffirm the traditional values of contemporary society. It is concluded that, overall, this reflection of accepted ideals is validated by the top-grossing box office status of the films. That popular motion picture content may be an indication of current social standards is discussed. Future areas of research and criticism within the context of social responsibility are considered

Feasibility testing for SalSA neutrino astrophysics project

Research is presented that was performed to determine possible locations for a full scale Salt Dome Shower Array (SalSA) neutrino telescope sensitive to energies from TeV ($10^{12}$ eV), PeV ($10^{15}$ eV), and EeV ($10^{18}$ eV) neutrinos. A detector to test possible site locations was designed around a half-Watt Ham radio to transmit short pulses of 145.500 MHz radiation. The research began by designing the system. Several phases of design took place as the system was refined and calibrated. Once finished, it was taken into a field and tested. The objective was to determine how the signals depended on distance. In principle, there should have been a linear relationship between distance and voltage. After successful testing, the system will be taken to a salt mine to accurately determine the index of refraction and attenuation length of that particular mine\u27s salt

Implications of mountain shading on calculating energy for snowmelt using unstructured triangular meshes

In many parts of the world, the snowmelt energy balance is dominated by net solar shortwave radiation. This is the case in the Canadian Rocky Mountains, where clear skies dominate the winter and spring. In mountainous regions, solar irradiance at the snow surface is not only affected by solar angles, atmospheric transmittance, and the slope and aspect of immediate topography, but also by shadows from surrounding terrain. Many hydrological models do not consider such horizon-shadows. The accumulation of errors in estimating solar irradiance by neglecting horizon-shadows can lead to significant errors in calculating the timing and rate of snowmelt due to the seasonal storage of internal energy in the snowpack. A common approach to representing the landscape is through structured meshes. However, such representations introduce errors due to the rigid nature of the mesh, creating artefacts and other constraints. Unstructured triangular meshes are more efficient in their representation of the terrain by allowing for a variable resolution. These meshes do not suffer from the artefact problems of a structured mesh. This thesis demonstrates the increased accuracy of using a horizon-shading model with an unstructured mesh versus standard self-shading algorithms in Marmot Creek Research Basin (MCRB), Alberta, Canada. A systematic basin-wide over-prediction (basin mean expressed as phase change mass: 14 mm, maximum: 200 mm) in net shortwave is observed when only self-shadows are considered. The horizon-shadow model was run at a point scale at three sites throughout MCRB to investigate the effects of scale on the model results. It was found that small triangles were best suited for this topographic region and that shadow patterns were captured accurately. Large triangles were found to be too easily shaded by the model, created many disjointed regions. As well, model results were compared to measurements of mountain shadows by timelapse digital cameras. These images were orthorectified and the shadow regions extracted allowing for a quantitative comparison. It was found that the horizon-model produced results within 10 m of the measured shadows, and properly captured shadow transits. A point-scale energy balance model SNOBAL was run via The Cold Regions Hydrological Model, an HRU based hydrologic model. It was found that in the highly shaded valleys, snowpack ablation could be incorrect by approximately 4 days. Although MCRB was generally not significantly impacted by the over-estimation in irradiance in this study, insight into the horizon-shadowing process was possible as a result of the existing network of radiometers and other meteorological stations at MCRB. Because down-stream processes such as flooding depend on correct headwater snowmelt predictions, quantitative results demonstrating inaccuracies in a modelled component of the surface energy balance can help improve snowmelt modelling

The Laureate English Program: Taking a research informed approach to blended learning

The aim of this case study is to describe the implementation of the Laureate English Program (LEP), the consequent decision to roll out blended learning across the network, and the Laureate-Cambridge University Press research partnership. Phase 1 of the research was completed in September 2012. The goal of this first phase was to gain a general understanding of student profile, computer literacy and competence, student levels of achievement, and student feedback on their blended learning experience. Six hundred and forty-eight students and 35 teachers responded to a questionnaire, which included multiple choice questions and open ended questions requiring extended comment. The questionnaires revealed that less than 25% of the Laureate student group had ever learned a language online before, which impacted significantly on student perception and use of online learning content. Furthermore, the first phase of research has revealed the impact that a complex interplay of different factors has on the relative effectiveness of these blended programs, and it has acknowledged that research is central to informed decision making in order to provide for effective blended learning.DOI: 10.18870/hlrc.v3i1.10

Blended language learning: An effective solution but not without its challenges

The study discussed in this investigation is part of a larger collaborative initiative between Laureate Education and Cambridge University Press (LEP-CUP collaboration). This second phase of the research, completed in 2013, aimed to further explore the conclusions from phase 1 and set out to identify effective and appropriate best practice blended learning models within the network. A study was set up with 36 teachers, all experienced ELT teachers with differing levels of experience in blended language teaching, who took part in extended focus groups discussions sessions prompted by a series of questions. Responses from these groups of teachers indicated that a flipped classroom model is beginning to develop. The authors of this study found evidence of changing approaches to language teaching, changes that are not without their challenges, but for a number of the teachers who participated in this research sample these changes are bringing considerable benefit to their teaching experience. This study offered teachers another opportunity to become change managers for students who need to acquire the autonomous, life-long learning skills of the 21st as they transition into professional life. The scope of this study cannot address and solve all of the issues involved in this process, but it provides a step towards that end. DOI: 10.18870/hlrc.v4i3.21

A PC based fault diagnosis expert system

The Integrated Status Assessment (ISA) prototype expert system performs system level fault diagnosis using rules and models created by the user. The ISA evolved from concepts to a stand-alone demonstration prototype using OPS5 on a LISP Machine. The LISP based prototype was rewritten in C and the C Language Integrated Production System (CLIPS) to run on a Personal Computer (PC) and a graphics workstation. The ISA prototype has been used to demonstrate fault diagnosis functions of Space Station Freedom's Operation Management System (OMS). This paper describes the development of the ISA prototype from early concepts to the current PC/workstation version used today and describes future areas of development for the prototype

A failure management prototype: DR/Rx

This failure management prototype performs failure diagnosis and recovery management of hierarchical, distributed systems. The prototype, which evolved from a series of previous prototypes following a spiral model for development, focuses on two functions: (1) the diagnostic reasoner (DR) performs integrated failure diagnosis in distributed systems; and (2) the recovery expert (Rx) develops plans to recover from the failure. Issues related to expert system prototype design and the previous history of this prototype are discussed. The architecture of the current prototype is described in terms of the knowledge representation and functionality of its components