Solar dynamic heat rejection technology. Task 1: System concept development

The results are presented of a concept development study of heat rejection systems for Space Station solar dynamic power systems. The heat rejection concepts are based on recent developments in high thermal transport capacity heat pipe radiators. The thermal performance and weights of each of the heat rejection subsystems is addressed in detail, and critical technologies which require development tests and evaluation for successful demonstration are assessed and identified. Baseline and several alternate heat rejection system configurations and optimum designs are developed for both Brayton and Rankine cycles. The thermal performance, mass properties, assembly requirements, reliability, maintenance requirements and life cycle cost are determined for each configuration. A specific design was then selected for each configuration which represents an optimum design for that configuration. The final recommendations of heat rejection system configuration for either the Brayton or Rankine cycles depend on the priorities established for the evaluation criteria

Measurement of Birefringence of Low-Loss, High-Reflectance Coating of M-Axis Sapphire

The birefringence of a low-loss, high-reflectance coating applied to an 8-cm-diameter sapphire crystal grown in the m-axis direction has been mapped. By monitoring the transmission of a high-finesse Fabry-Perot cavity as a function of the polarization of the input light, we find an upper limit for the magnitude of the birefringence of 2.5 x 10^-4 rad and an upper limit in the variation in direction of the birefringence of 10 deg. These values are sufficiently small to allow consideration of m-axis sapphire as a substrate material for the optics of the advanced detector at the Laser Interferometer Gravitational Wave Observatory

Perceptual impact of environmental factors in sighted and visually impaired individuals

To a visually impaired individual the physical world presents many challenges. For a person with impaired sight, wayfinding through a complex environment is fraught with dangers, both actual and imagined. The current generation of mobility aids have the possibility of addressing a broad range of physical issues through technological solutions. The perception of difficulty however, can mean that many visually impaired individuals are fearful or uncomfortable about independent mobility or travel. In this context it becomes necessary to discover exactly what environments, environmental factors or items constitute a ‘perception of difficulty’ in the individuals mental landscape and may trigger a negative response before they interact with the physical environment. This paper reports on research, which sought to ascertain what levels of perceptual difficulties specific environments and factors presented to individuals. The research was conducted with both visually impaired and sighted groups and compared differences and similarities in perceptual difficulty between these two groups

An Early Pliocene North American Deer: Bretzia pseudalces, Its Osteology, Biology, and Place in Cervid History

82 pagesThe cervid genus Bretzia was fi rst described in 1974 from antler and skull material found in the White Bluffs local fauna of the Pliocene Ringold Formation in south-central Washington. Cervid specimens from the Ringold deposits had been mentioned in published reports in 1917 and 1953, but not until a series of specimens was collected by Willis E. Fry and donated to the Burke Museum in Seattle, about 1970, was the evidence adequate to provide a preliminary diagnosis of Bretzia. The basis of the genus was a series of shed antlers and a portion of the skull of a male individual. Although statements have been made generally characterizing the dentition and postcranial skeleton as similar to Odocoileus, the detailed descriptions of these elements have not previously been published.Bretzia was similar in size to modern O. hemionus (mule deer) but differed in antler morphology and details of the skull, teeth, and postcranial skeleton. The antler pedicles are more widely separated than in most Cer-vidae. The antlers are distinctive, with a single anterior tine and a posterior beam which in adult individuals forms a large palmate structure. Enough antlers are known to present a developmental series including juvenile, adolescent, adult, and senescent forms. Numerous details of the dentition and postcranial skeleton, including the metacarpals show that Bretzia pseudalces was a telemetacarpal deer (subfamily Capreolinae). The relationship of Bretzia to the living tribes (Alcini, Capreolini, and Rangiferini) is uncertain. Bretzia was one of three known genera (Bretzia, Odocoileus, and Eocoileus) in an early Pliocene (ca. 5 Ma) evolutionary radiation of cervids after the initial immigration from Asia into North America around the time of the Miocene-Pliocene boundary. The Ringold Formation deposits in which the cervid sample was found date to the early Blancan (early Pliocene), probably between 5.0 and 4.8 Ma. The White Bluffs cervid sample largely consists of seasonal (winter and spring) accumulations of bones, antlers, and teeth, which were scattered, weathered, and then buried by spring fl oods. The proximal environment was a level fl oodplain with the streams bordered by forest and brush, and surrounded by marsh, small lakes, and grassland. The climate was seasonal but somewhat milder and wetter than at present

Effectiveness of Forest Management Strategies to Mitigate Effects of Global Change in South-Central Siberia

We investigated questions about the ability of broad silvicultural strategies to achieve multiple objectives (reduce disturbance losses, maintain the abundance of preferred species, mitigate fragmentation and loss of age-class diversity, and sequester aboveground carbon) under future climate conditions in Siberia. We conducted a factorial experiment using the LANDIS-II landscape disturbance and succession model. Treatments included varying the size and amount of areas cut and the cutting method (selective or clearcut). Simultaneously, the model simulated natural disturbances (fire, wind, insect out-breaks) and forest succession under projected future climate conditions as predicted by an ensemble of global circulation models. The cutting method and cutting rate treatments generally had a large effect on species and age-class composition, residual living biomass, and susceptibility to disturbance, whereas cutblock size had no effect. Cutblock size affected only measures of fragmentation, but cutting method and cutting rate often had an even greater effect. Based on the results, we simulated a “recommended” strategy and compared it with the current forest management practice. The recommended strat-egy resulted in greater forest biomass, increased abundance of favored species, and reduced fragmentation, but it did not sig-nificantly reduce losses by disturbance. No single strategy appears able to achieve all possible forest management objectives