Interrelationships between spinal and pelvic angles and hip muscle indices and their implications for workspace design

The shape of the lumbar and thoracic spinal curves in healthy subjects, when standing and when adopting a variety of working positions, was investigated using angular measures. The hypothesis that spinal and pelvic posture is determined by body position was supported. The mechanism by which body position influences spinal and pelvic posture was investigated using angular indices of the lengths of the hip flexors and extensors. The hypothesis that hamstring stretch determines postural adaptation to sitting positions was not supported. A multivariate analysis revealed that an index of iliopsoas length was the best predictor of posterior pelvic tilt in a variety of sitting positions. A supplementary investigation was carried out using data on the range of motion of the pelvis in the different body positions and its relationship to the muscle length indices. The role of the hamstring muscles in sitting posture was clarified. Some electromyographic data is presented to further illustrate the effect of body position on the role of the hip and trunk muscles in posture. A replication of the main findings and an investigation of some of the practical implications of the work were carried out drawing attention to some mechanisms of postural stress, potential problems of increased lumbar lordosis and their cost-effective alleviation through workspace design. The provision of a footrest, for example, was found to have significant effects on lumbar and pelvic angles in standing as well as in sitting. Further research into standing posture in the workplace is indicated by these findings. Some hypotheses for future investigation are presented

Reaction to 1-Bromo-2, 3-Epoxybutane with phenol in the presence of boron trifluoride

It is the purpose of this investigation to study the reaction of phenol with 1-bromo-2,3-epoxybutane in the presence of boron trifluoride and to identify the reaction products in order to gain information which will be helpful in understanding the mechanism of the reaction --Introduction, page 3

Package Bidding for Spectrum Licenses

The FCC was an innovator in adopting the rules of the simultaneous ascending-price auction for its sales of spectrum licenses. While these rules have performed well in the auctions conducted so far (and would perform even better with the design improvements suggested in our first report), there are two inherent limitations in any design that seeks to assign and price the licenses individually. First, such designs create strategic incentives for bidders interested in multiple licenses that are substitutes to reduce their demands for some of the licenses in order to reduce the final prices of the others; this is the demand reduction problem. Second, even if bidders behave non-strategically, there is a fundamental problem with the basic concept of individual-license pricing when licenses are complementary. In simultaneous ascending-price auctions, from a bidder's perspective this is the exposure problem. A bidder who is unsuccessful in bidding for a large package of licenses may be left with a partial package whose total price cannot be justified in the absence of those complementary licenses it failed to win. This problem is present in any auction mechanism that sells licenses individually, with no opportunity to bid on packages. In this report our task is confined to analyses of the merits of package bidding and the practical problems of implementation. In our next report, we will outline proposals for the details of the procedural rules and other aspects of implementing a practical design, as well as the software development that would be necessary.Auctions; Spectrum Auctions; Multiple-Round Auctions; Efficiency

Auction Design Enhancements for Non-Combinatorial Auctions

We evaluate a number of possible enhancements to the FCC auctions. We consider only changes to the current auction rules that stay within the basic format of the simultaneous multiple round auction for individual licenses. This report summarizes and extends our e-mail exchanges with FCC staff on this topic. A subsequent report will cover auctions with combination bids. Overall, the FCC spectrum auctions have been an enormous success. However, there are two design goals in the auction where important improvement can be achieved within the basic rules structure. These are restricting collusion among bidders and reducing the time taken to complete the auction. This report focuses on enhancements that help to achieve these two goals. Some of the suggested changes also streamline the auction process so large auctions can be conducted more quickly without sacrificing efficiency.Auctions; Spectrum Auctions; Multiple-Round Auctions; Efficiency

Mars Characterization for Future Missions

Annual simulations of Mars' atmosphere made with the NASA Ames Mars General Circulation Model have been used to extract and generate products to provide statistical products that detail the variability of Mars' atmosphere on fairly short time scales. These products are needed for the creation of a new version of Mars-GRAM, due for completion in June, 1999. The updated Mars-Gram, in turn, will provide guidance for forthcoming aerobraking and aerocapture activities. We have created files containing zonally-averaged fields (temperatures, densities, pressures, and winds, all on z-surfaces), as well as zonally-averaged diurnal and semidiurnal tidal amplitudes and phases. All fields represent a time averaged state (over either 5 or 30 sols), and all fields are available at each of 12 seasons for a Mars year (the seasons being 30deg of Ls apart). Files for low and moderate dust loading cases are liable via anonymous ftp. Files for a high dust case will be in place shortly

Mars Characterization for Future Missions

The purpose of this research project was to create statistical products which could of use to the engineering and scientific communities planning future missions to Mars. This has been accomplished. Using simulations of Mars' atmosphere under a variety of conditions, we have created statistical databases quantifying the behavior of Mars' atmosphere under a variety of conditions expected to be encountered on forthcoming missions. These data are now being incorporated into a new version of Mars-GRAM

Surface Lander Missions to Mars: Support via Analysis of the NASA Ames Mars General Circulation Model

We have characterized the near-surface martian wind environment as calculated with a set of numerical simulations carried out with the NASA Ames Mars General Circulation Model (Mars GCM). These wind environments are intended to offer future spacecraft missions to the martian surface a data base from which to choose those locations which meet the mission's criteria for minimal near surface winds to enable a successful landing. We also became involved in the development and testing of the wind sensor which is currently onboard the Mars-bound Pathfinder lander. We began this effort with a comparison of Mars GCM produced winds with those measured by the Viking landers during their descent through the martian atmosphere and their surface wind measurements during the 3+ martian year lifetime of the mission. Unexpected technical difficulties in implementing the sophisticated Planetary Boundary Layer (PBL) scheme of Haberle et al. (1993) within the Mars GCM precluded our carrying out this investigation with the desired improvement to the model's treatment of the PBL. Thus, our results from this effort are not as conclusive as we had anticipated. As it turns out, similar difficulties have been experienced by other Mars modelling groups in attempting to implement very similar PBL routines into their GCMs (Mars General Circulation Model Intercomparison Workshop, held at Oxford University, United Kingdom, July 22-24, 1996; organized by J. Murphy, J. Hollingsworth, M. Joshi). These problems, which arise due to the nature of the time stepping in each of the models, are near to being resolved at the present. The model discussions which follow herein are based upon results using the existing, less sophisticated PBL routine. We fully anticipate implementing the tools we have developed in the present effort to investigate GCM results with the new PBL scheme implemented, and thereafter producing the technical document detailing results from the analysis tools developed during this effort. Producing such a document now would be premature

Mars Global Surveyor: Aerobraking and Observations Support Using a Mars Global Circulation Model

This is a Final Report for a Joint Research Interchange (JRI) between NASA Ames Research Center and San Jose State University, Department of Meteorology. Using a global atmospheric circulation model for Mars, the focus of this JRI has been to provide support for the Mars Global Surveyor (MGS) spacecraft aerobraking activities and interpretation guidance of preliminary observations. ne primary atmospheric model applied in this investigation has been a high-top version of the NASA Ames Mars general circulation model (MGCM). Comparisons with an atmospheric model designed primarily for engineering purposes (Mars-GRAM) has also been carried out. From a suite of MGCM simulations, we have assessed plausible spatial and temporal variability in atmospheric density at high altitudes (e.g., 70-110 km) for seasonal dates and locations during Phase 1 aerobraking. Diagnostic tools have been developed to analyze circulation fields from the MGCM simulations, and these tools have been applied in the creation of a Mars climate catalogue database. Throughout Phase 1 aerobraking activities, analysis products have been provided to the MGS aerobraking atmospheric advisory group (AAG). Analyses of circulation variability at the coupling level between the MGCM and a Mars thermospheric global circulation model (MTGCM) has also been assessed. Finally, using a quasi-geostrophic dynamical formulation with the MGCM simulations, diagnosis of breaking planetary (Rossby) waves in Mars' middle atmosphere has been carried out. Titles of papers presented at scientific workshops and seminars, and a publication in the scientific literature are provided

The Martian Dust Cycle: Investigation of the Surface Lifting Component

We have investigated the nature of the annual cycle of suspended dust in the martian atmosphere. This has been undertaken to understand the dynamical processes responsible for lifting dust from the surface, locations where dust is preferentially lifted, and preferred sites for dust deposition upon the surface. Our efforts have involved carrying out a number of numerical simulations with the Ames Mars General Circulation Model (GCM) interactively coupled with an aerosol transport/ micro-physical model. The model generates an annual dust cycle similar to that observed. Various feedbacks are present in the atmosphere/ surface system which enter into the generation of the cycle. Several locations are primary surface sources of dust, while much of the remaining planet's surface acts a sink for suspended dust