The calibration and flight test performance of the space shuttle orbiter air data system

The Space Shuttle air data system (ADS) is used by the guidance, navigation and control system (GN&C) to guide the vehicle to a safe landing. In addition, postflight aerodynamic analysis requires a precise knowledge of flight conditions. Since the orbiter is essentially an unpowered vehicle, the conventional methods of obtaining the ADS calibration were not available; therefore, the calibration was derived using a unique and extensive wind tunnel test program. This test program included subsonic tests with a 0.36-scale orbiter model, transonic and supersonic tests with a smaller 0.2-scale model, and numerous ADS probe-alone tests. The wind tunnel calibration was further refined with subsonic results from the approach and landing test (ALT) program, thus producing the ADS calibration for the orbital flight test (OFT) program. The calibration of the Space Shuttle ADS and its performance during flight are discussed in this paper. A brief description of the system is followed by a discussion of the calibration methodology, and then by a review of the wind tunnel and flight test programs. Finally, the flight results are presented, including an evaluation of the system performance for on-board systems use and a description of the calibration refinements developed to provide the best possible air data for postflight analysis work

Tapping Thermodynamics of the One Dimensional Ising Model

We analyse the steady state regime of a one dimensional Ising model under a tapping dynamics recently introduced by analogy with the dynamics of mechanically perturbed granular media. The idea that the steady state regime may be described by a flat measure over metastable states of fixed energy is tested by comparing various steady state time averaged quantities in extensive numerical simulations with the corresponding ensemble averages computed analytically with this flat measure. The agreement between the two averages is excellent in all the cases examined, showing that a static approach is capable of predicting certain measurable properties of the steady state regime.Comment: 11 pages, 5 figure

Effective diffusion constant in a two dimensional medium of charged point scatterers

We obtain exact results for the effective diffusion constant of a two dimensional Langevin tracer particle in the force field generated by charged point scatterers with quenched positions. We show that if the point scatterers have a screened Coulomb (Yukawa) potential and are uniformly and independently distributed then the effective diffusion constant obeys the Volgel-Fulcher-Tammann law where it vanishes. Exact results are also obtained for pure Coulomb scatterers frozen in an equilibrium configuration of the same temperature as that of the tracer.Comment: 9 pages IOP LaTex, no figure

Perturbation theory for the effective diffusion constant in a medium of random scatterer

We develop perturbation theory and physically motivated resummations of the perturbation theory for the problem of a tracer particle diffusing in a random media. The random media contains point scatterers of density $\rho$ uniformly distributed through out the material. The tracer is a Langevin particle subjected to the quenched random force generated by the scatterers. Via our perturbative analysis we determine when the random potential can be approximated by a Gaussian random potential. We also develop a self-similar renormalisation group approach based on thinning out the scatterers, this scheme is similar to that used with success for diffusion in Gaussian random potentials and agrees with known exact results. To assess the accuracy of this approximation scheme its predictions are confronted with results obtained by numerical simulation.Comment: 22 pages, 6 figures, IOP (J. Phys. A. style

The Central Symbiosis of Molecular Biology: Molecules in Mutualism.

As illustrated by the mitochondrion and the eukaryotic cell, little in biology makes sense except in light of mutualism. Mutualisms are persistent, intimate, and reciprocal exchanges; an organism proficient in obtaining certain benefits confers those on a partner, which reciprocates by conferring different benefits. Mutualisms (i) increase fitness, (ii) inspire robustness, (iii) are resilient and resistant to change, (iv) sponsor co-evolution, (v) foster innovation, and (vi) involve partners that are distantly related with contrasting yet complementary proficiencies. Previous to this work, mutualisms were understood to operate on levels of cells, organisms, ecosystems, and even societies and economies. Here, the concepts of mutualism are extended to molecules and are seen to apply to the relationship between RNA and protein. Polynucleotide and polypeptide are Molecules in Mutualism. RNA synthesizes protein in the ribosome and protein synthesizes RNA in polymerases. RNA and protein are codependent, and trade proficiencies. Protein has proficiency in folding into complex three-dimensional states, contributing enzymes, fibers, adhesives, pumps, pores, switches, and receptors. RNA has proficiency in direct molecular recognition, achieved by complementary base pairing interactions, which allow it to maintain, record, and transduce information. The large phylogenetic distance that characterizes partnerships in organismal mutualism has close analogy with large distance in chemical space between RNA and protein. The RNA backbone is anionic and self-repulsive and cannot form hydrophobic structural cores. The protein backbone is neutral and cohesive and commonly forms hydrophobic cores. Molecules in Mutualism extends beyond RNA and protein. A cell is a consortium of molecules in which nucleic acids, proteins, polysaccharides, phospholipids, and other molecules form a mutualism consortium that drives metabolism and replication. Analogies are found in systems such as stromatolites, which are large consortia of symbiotic organisms. It seems reasonable to suggest that 'polymers in mutualism relationships' is a useful and predictive definition of life

Continuum Derrida Approach to Drift and Diffusivity in Random Media

By means of rather general arguments, based on an approach due to Derrida that makes use of samples of finite size, we analyse the effective diffusivity and drift tensors in certain types of random medium in which the motion of the particles is controlled by molecular diffusion and a local flow field with known statistical properties. The power of the Derrida method is that it uses the equilibrium probability distribution, that exists for each {\em finite} sample, to compute asymptotic behaviour at large times in the {\em infinite} medium. In certain cases, where this equilibrium situation is associated with a vanishing microcurrent, our results demonstrate the equality of the renormalization processes for the effective drift and diffusivity tensors. This establishes, for those cases, a Ward identity previously verified only to two-loop order in perturbation theory in certain models. The technique can be applied also to media in which the diffusivity exhibits spatial fluctuations. We derive a simple relationship between the effective diffusivity in this case and that for an associated gradient drift problem that provides an interesting constraint on previously conjectured results.Comment: 18 pages, Latex, DAMTP-96-8

Dynamic Matrix Factorization with Priors on Unknown Values

Advanced and effective collaborative filtering methods based on explicit feedback assume that unknown ratings do not follow the same model as the observed ones (\emph{not missing at random}). In this work, we build on this assumption, and introduce a novel dynamic matrix factorization framework that allows to set an explicit prior on unknown values. When new ratings, users, or items enter the system, we can update the factorization in time independent of the size of data (number of users, items and ratings). Hence, we can quickly recommend items even to very recent users. We test our methods on three large datasets, including two very sparse ones, in static and dynamic conditions. In each case, we outrank state-of-the-art matrix factorization methods that do not use a prior on unknown ratings.Comment: in the Proceedings of 21st ACM SIGKDD Conference on Knowledge Discovery and Data Mining 201

Tapping Spin Glasses

We consider a tapping dynamics, analogous to that in experiments on granular media, on spin glasses and ferromagnets on random thin graphs. Between taps, zero temperature single spin flip dynamics takes the system to a metastable state. Tapping, corresponds to flipping simultaneously any spin with probability $p$. This dynamics leads to a stationary regime with a steady state energy $E(p)$. We analytically solve this dynamics for the one dimensional ferromagnet and $\pm J$ spin glass. Numerical simulations for spin glasses and ferromagnets of higher connectivity are carried out, in particular we find a novel first order transition for the ferromagnetic systems.Comment: 5 pages, 3 figures, RevTe

IMPEDIMENTS TO CONTROLLING LEAFY SPURGE IN THE NORTHERN GREAT PLAINS

Leafy spurge is an invasive noxious weed, which by definition means it is inordinately difficult to control. The objective of this report is to present the results of focus group meetings and personal interviews with ranchers, local decision makers, and public land managers to discover strategies to improve leafy spurge management. Participants in the interviews and focus group meetings managed property in Fallon, Carter, and Wibaux Counties of Montana; Golden Valley, Bowman, Billings, and Slope Counties of North Dakota; Harding County of South Dakota; and Crook County of Wyoming. Ranchers and local decision makers believe that leafy spurge control must become more proactive rather than reactive; current strategies are largely reactive. Interviews with ranchers and local decision makers revealed that a considerable gap in understanding how to control leafy spurge exists between researchers and those attempting to combat the weed. Interviewers often mentioned that they have been unable to eradicate leafy spurge, which indicates that the current mind set of ranchers and land managers needs to change to one focusing more on controlling and managing leafy spurge rather than eradication. Specific recommendations would include 1) reducing the current levels of herbicide application rates - which are often two to three times higher than rates recommended by weed scientists, 2) must appreciate that herbicides are but one tool in the battle against leafy spurge, 3) must understand that in many cases eradication of leafy spurge will not be possible - the goal should be trying to control it, and 4) rangeland rental rates need to reflect current levels of weed infestations. Records of weed infestations (e.g., acreage, location, rate of spread, attempts at control) on public lands are woefully inadequate. Cooperation between ranchers, county weed boards, and public land agencies could be improved to enhance the effectiveness of existing control programs. Weed control regardless of land ownership is important for ranchers, absentee landowners, and public agencies to effectively control leafy spurge. In general, ranchers and land managers need to generate a broader base of support for control of leafy spurge, since the weed attacks the entire ecosystem and is not just an agricultural problem.leafy spurge management, ranchers, county weed boards, public land managers, policy makers, Farm Management, Production Economics,

CONTRIBUTION OF THE BISON INDUSTRY TO THE NORTH DAKOTA ECONOMY

The commercial bison industry is relatively new to North Dakota. There were an estimated 23,000 head of bison in North Dakota in 1998, and these animals were found in 47 of 53 counties. The purpose of this study was to estimate the economic contribution of the bison industry to the North Dakota economy. A survey of North Dakota bison producers and processors was conducted to provide estimates of direct impacts of bison activities within the state. Secondary economic impacts were determined using the North Dakota Input-Output Model. The direct impact of production and processing of bison in North Dakota in 1998 was estimated at $23 million. The$23 million in direct impacts generated an additional $47 million in secondary impacts within the state. The North Dakota bison industry supported a total of 757 secondary full- time equivalent (FTE) jobs within the state. Total economic activity generated within the state was estimated at$70 million, including $27 million in personal income and nearly$18 million in retail sales. In addition, the bison industry generated 4 million in tax revenue (including property, personal income, sales & use, and corporate income taxes). The direct impact of bison production in 1998 ranked fourth in North Dakota's livestock industry; below cattle and calves, dairy products, and hogs, and above turkey and sheep. The average direct impact generated for every bison in the state was 1,000. Total economic activity generated per bison in 1998 was $3,100 (includes direct and secondary impacts from production and processing). For every 30 head of bison an additional secondary FTE job was supported.bison industry, bison production, bison processing, North Dakota, economic impact, Agribusiness, Production Economics,