Computer image generation: Reconfigurability as a strategy in high fidelity space applications

The demand for realistic, high fidelity, computer image generation systems to support space simulation is well established. However, as the number and diversity of space applications increase, the complexity and cost of computer image generation systems also increase. One strategy used to harmonize cost with varied requirements is establishment of a reconfigurable image generation system that can be adapted rapidly and easily to meet new and changing requirements. The reconfigurability strategy through the life cycle of system conception, specification, design, implementation, operation, and support for high fidelity computer image generation systems are discussed. The discussion is limited to those issues directly associated with reconfigurability and adaptability of a specialized scene generation system in a multi-faceted space applications environment. Examples and insights gained through the recent development and installation of the Improved Multi-function Scene Generation System at Johnson Space Center, Systems Engineering Simulator are reviewed and compared with current simulator industry practices. The results are clear; the strategy of reconfigurability applied to space simulation requirements provides a viable path to supporting diverse applications with an adaptable computer image generation system

A general multivariate latent growth model with applications in student careers Data warehouses

The evaluation of the formative process in the University system has been assuming an ever increasing importance in the European countries. Within this context the analysis of student performance and capabilities plays a fundamental role. In this work we propose a multivariate latent growth model for studying the performances of a cohort of students of the University of Bologna. The model proposed is innovative since it is composed by: (1) multivariate growth models that allow to capture the different dynamics of student performance indicators over time and (2) a factor model that allows to measure the general latent student capability. The flexibility of the model proposed allows its applications in several fields such as socio-economic settings in which personal behaviours are studied by using panel data.Comment: 20 page

Evaluation of revegetation techniques used on degraded agricultural land in the Central Avon Catchment, Western Australia

The agricultural region in the central Avon catchment is declining in both arable land and native vegetation. This decline has been due to the clearance of large tracts of native vegetation and its subsequent replacement by exotic crops and pasture species. The loss of vegetation has led to regional land degradation in the form of soil erosion and land salinisation. Therefore, changes in land management practices are required to make agricultural production more compatible with land conservation. Revegetation using native plants is the only management solution that integrates both land and ecological conservation with agricultural productivity. The continuation of current agricultural land use will therefore depend on the development of effective methods of revegetation. The land manager predominantly has a choice between directly sowing seeds and or planting nursery seedlings as methods of revegetation on degraded land. The widespread problem of land degradation in the Avon catchment dictates that the revegetation method chosen must be effective in terms of both seedling establishment and cost on a broad scale. To determine which method is most effective in revegetation, a series of laboratory and field trials were conducted. A trial was conducted in seed germination incubators to determine the relative importance of genetic and environmental influences on seed viability. The genetics of the seed stock had a significant influence on germination between different biolocalities. Similarly, environmental factors such as different temperature regimes also had a significant influence on seed germination. Consequently, a relationship was established between optimum germination temperature and the average mean winter temperature of the biolocality where the seed was collected. This suggests that temperature may influence seed genetics and subsequent germination, which varied according to the biolocality. The identification of environmental parameters that influenced seed germination provided a basis for comparison between direct seeding versus planted nursery seedlings in the field. The number of seedlings established in the second and third year at York was greater for direct seeding than from planted nursery seedlings with the exception of two species belonging to the Leguminosae family. However, the failure of seedlings from either method to become established in the field at Tammin emphasised the need to employ a post-sowing and planting management programme. The costs of seedling establishment using the direct seeding method was approximately one sixth the cost of nursery seedlings with the exception of Kennedia prostrata. The cost and time invested in revegetation programmes necessitates that the optimum seed biolocality should be selected in order to produce the most effective plant establishment from direct seeding in the field. Biolocality selection based on geographical distance alone did not produce conclusive criteria for effective revegetation. However, the matching of biogeographical regions and climatic conditions with the site of revegetation produced the most effective plant establishment. This predominantly resulted in the selection of a local species but in some situations biolocalities from further afield with a similar climate, also proved effective. The invasion of weeds at both the York and Tammin trial sites emphasise the potential effects on the establishment of native vegetation. The growth (height & stem width) of nursery seedlings was significantly reduced while the growth height decreased and the mortality of direct seeded seedlings increased when subjected to weed competition. Reversing the trend in land and ecological degradation within the central Avon catchment can only be achieved through a revegetation programme that integrates nature conservation with agricultural productivity. Direct seeding is a cost effective method of plant establishment provided that adequate attention is given to pre-seed treatment, seed quality testing, selection of the optimum seed biolocality, soil contour and profile preparation and post sowing control of both weed and predators. However, revegetation of degraded land using nursery seedlings can be just as effective when the cost of seed is expensive and difficult to germinate. If the central Avon wheatbelt is to continue to function as the \u27bread bowl\u27 of Western Australia then the establishment of native vegetation can only be achieved through the use of direct seeding methods on a broad scale. Current land management practises and the conservation of the remaining remnant vegetation will not maintain a sustainable agricultural based economy or adequately represent existing biodiversity in the central Avon catchment

Effect of Altitude on Short Term Memory

Previous work has documented that cognitive deficits were observed in subjects tested at high altitudes (15,000 ft to 25,000 ft). Controversy remains as to whether cognitive deficits are observed at altitudes below 15,000 ft. The present study focused on this controversy, looking at the effects of moderate altitudes, 12,500 ft and 15,000 ft, on short term memory and compared them to a control altitude of 2,000 ft. Subjects were 72 students and instructors from the Department of Aviation Sciences at the University of North Dakota. After a series of pretests, including the Vocabulary Subtest of the Wechsler Adult Intelligence Scale-Revised, the Digit Span subtest from the Wechsler Memory Scale-Revised, the Vandenbcrg Mental Rotation Test, the Digit Symbol subtest of the Wechsler Adult Intelligence Scale-Revised, and the near-contrast sensitivity portion of the Vistech VCTS 6000 chart, subjects were assigned to one of three altitude groups and spent an hour and a half at their designated altitude for cognitive testing. One of the tasks administered was the Sternberg (Salthouse & Somberg, 1982) memory task. The second task was a dual attention task in which subjects performed a 30 min vigilance task while simultaneously listening to an audio tape with instructions to recall and read back a radio call prefaced by their assigned call sign. The audio tape of the radio calls contained four different call signs and half of the radio calls were high memory loads (at least 4 pieces of information) and half were low memory loads (no more than 2 pieces of information). Analysis of variance was used to analyze the data. No consistent and interpretable effects were found in the Sternberg task. No effects of altitude were found in the vigilance task. The analysis of the readbacks revealed no significant difference for readbacks with low memory loads. However, for recall of readbacks with high memory loads, significant deficits in recall observed at 12,500 ft and 15,000 ft

Self-determination theory and diminished functioning: the role of interpersonal control and psychological need thwarting

Drawing from self-determination theory (Ryan & Deci, 2002), three studies explored the social-environmental conditions that satisfy versus thwart psychological needs and, in turn, impact psychological functioning and well/ill-being. In cross-sectional Studies 1 and 2, structural equation modeling analyses supported latent factor models in which need satisfaction was predicted by athletes’ perceptions of autonomy support and need thwarting was better predicted by perceived coach control. Athletes’ perceptions of need satisfaction predicted positive outcomes associated with sport participation (vitality and positive affect) whereas perceptions of need thwarting more consistently predicted maladaptive outcomes (disordered eating, burnout, depression, negative affect, and physical symptoms). In addition, athletes’ perceptions of psychological need thwarting were significantly associated with perturbed physiological arousal (elevated levels of secretory immunoglobulin A) prior to training. The final study involved the completion of a diary and supported the relations observed in the cross-sectional studies at a daily level. These findings have important implications for the operationalization and measurement of interpersonal styles and psychological needs

The observation of photon echoes from evanescently coupled rare-earth ions in a planar waveguide

We report the measurement of the inhomogeneous linewidth, homogeneous linewidth and spin state lifetime of Pr3+ ions in a novel waveguide architecture. The TeO2 slab waveguide deposited on a bulk Pr3+:Y2SiO5 crystal allows the 3H4 - 1D2 transition of Pr3+ ions to be probed by the optical evanescent field that extends into the substrate. The 2 GHz inhomogeneous linewidth, the optical coherence time of 70 +- 5 us, and the spin state lifetime of 9.8 +- 0.3 s indicate that the properties of ions interacting with the waveguide mode are consistent with those of bulk ions. This result establishes the foundation for large, integrated and high performance rare-earth-ion quantum systems based on a waveguide platform.Comment: 5 pages, 5 figure

AAP-1A launch vehicle performance and preliminary range safety analyses. Volume 2 - Range safety

Range safety data with trajectories, impact, and casualty probability for Saturn 1B/AAP-1A launch vehicl