A Value-Focused Thinking Model for the Selection of the Best Rigid Pavement, Partial-Depth Spall Repair Material

Concrete spalls on airfield pavements generate foreign object debris (FOD) that is damaging to aircraft engines, and may damage landing gear by roughening of the pavement surface. Repairing spalled concrete on aging and deteriorating airfields is essential for its safe operational use. Picking the best repair material from many products on the commercial market is difficult. There is wide variation on material properties, and good performance on certain criteria is critical to constructing long lasting repairs. Since there is currently no procedure for Air Force decision-makers to select the best rigid-pavement repair material, a model was created using Value-Focused Thinking (VFT) to evaluate repair material alternatives. Fourteen products were compared against each other. Each was scored using fourteen evaluation measures that were identified as important to the repair material selection process. Pavemend EX-H was found to be the best choice for repairs conducted during conventional, steady-state operations. VFT was shown to be an effective methodology for objectively ranking repair products, while providing a systematic process that can be tailored for future circumstances

The influence of geothermal sources on deep ocean temperature, salinity, and flow fields

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution May 1988This thesis is a study of the effect of geothermal sources on the deep circulation, temperature and salinity fields. In Chapter 1 background material is given on the strength and distribution of geothermal heating. In Chapter 2 evidence for the influence of a hydrothermal system in the rift valley of the Mid-Atlantic Ridge on nearby property fields and a model of the flow around such a heat source are presented, with an analysis of a larger-scale effect. Results of an analytical model for a heat source on a β-plane in Chapter 3 show how the response far from the source can have a structure different from the forcing because of its dependence on two parameters: a Peclet number (the ratio of horizontal advection and vertical diffusion), and a Froude-number-like parameter (the ratio of long wave phase speed to background flow speed) which control the relative amount of damping and advection of different vertical scales. The solutions emphasize the different behavior of a dynamical field like temperature compared to tracers introduced at the source. These ideas are useful for interpreting more complicated solutions from a numerical model presented in the final chapter.This study was supported by the National Science Foundation grants OCE8515642 to T. Joyce and OCE82-13967 to B. Warren, and by the WHOI-MIT Joint Program Ocean Ventures Fund

Location of the Lee-Yang zeros and absence of phase transitions in some Ising spin systems

We consider a class of Ising spin systems on a set \Lambda of sites. The sites are grouped into units with the property that each site belongs to either one or two units, and the total internal energy of the system is the sum of the energies of the individual units, which in turn depend only on the number of up spins in the unit. We show that under suitable conditions on these interactions none of the |\Lambda| Lee-Yang zeros in the complex z = exp{2\beta h} plane, where \beta is the inverse temperature and h the uniform magnetic field, touch the positive real axis, at least for large values of \beta. In some cases one obtains, in an appropriately taken \beta to infinity limit, a gas of hard objects on a set \Lambda'; the fugacity for the limiting system is a rescaling of z and the Lee-Yang zeros of the new partition function also avoid the positive real axis. For certain forms of the energies of the individual units the Lee-Yang zeros of both the finite- and zero-temperature systems lie on the negative real axis for all \beta. One zero-temperature limit of this type, for example, is a monomer-dimer system; our results thus generalize, to finite \beta, a well-known result of Heilmann and Lieb that the Lee-Yang zeros of monomer-dimer systems are real and negative.Comment: Plain TeX. Seventeen pages, five figures from .eps files. Version 2 corrects minor errors in version

An off-shell I.R. regularization strategy in the analysis of collinear divergences

We present a method for the analysis of singularities of Feynman amplitudes based on the Speer sector decomposition of the Schwinger parametric integrals combined with the Mellin-Barnes transform. The sector decomposition method is described in some details. We suggest the idea of applying the method to the analysis of collinear singularities in inclusive QCD cross sections in the mass-less limit regularizing the forward amplitudes by an off-shell choice of the initial particle momenta. It is shown how the suggested strategy works in the well known case of the one loop corrections to Deep Inelastic Scattering.Comment: 25 pages, 3 figure

Lagrangian statistics in unforced barotropic flows

We consider the dispersion of particles in potential vorticity (PV)-conserving flows. Because particle drift is preferentially along the mean PV contours, Lagrangian dispersion is strongly anisotropic. If the mean PV field moreover is spatially variable, as when there is topography, the anisotropy is more clearly visible in the dispersion of displacements along and across the mean PV field itself. We examine several numerical examples of unforced barotropic flows; in all cases, this projected dispersion is more anisotropic than that in cartesian (x, y) coordinates. What differs is the rate at which spreading occurs, both along and across contours. The method is applicable to real data, as is illustrated with float data from the deep North Atlantic. The results suggest a preferential spreading along contours of (barotropic) f/H

Representativeness of meridional hydrographic sections in the western South Atlantic

Many studies of the oceanic circulation are based on data collected during quasi-synoptic hydrographic surveys. After spatial averaging, to filter out the effects of mesoscale variability, it is often explicitly or implicitly assumed that the synoptic hydrographic gradients are representative of a quasi-steady mean state. Climatological tracer fields and float data at the depth of the North Atlantic Deep Water in the western South Atlantic (Brazil Basin) support the notion of a quasi-steady mean circulation characterized by alternating bands of primarily zonal flow with meridional scales of several hundreds of km. Visually, the mean circulation appears to dominate three samples of the large-scale meridional-density-gradient field taken between 1983 and 1994. A quantitative comparison reveals, however, that the baroclinic temporal variability of the zonal velocities is of the same magnitude as the mean and is associated with similar spatial scales. The synoptic geostrophic flow field is, therefore, only marginally representative of the mean state. Thus, the data do not support one of the central assumptions of reference-velocity methods, such as linear box-inverse models and the β-spiral, because baroclinic temporal variability renders the equation systems underlying these methods inconsistent. A modal decomposition of the temporally varying baroclinic zonal velocity field in the Brazil Basin indicates that the first two dynamical modes dominate, accounting for ≈90% of the rms velocities. The residual flow field that remains after removing the first two baroclinic modes from the three synoptic samples is dominated by the mean circulation. However, its magnitude is not sufficient to account for the float and tracer observations. Therefore, it is necessary to determine the projection of the mean zonal velocities onto the barotropic and the first two baroclinic modes in order to diagnose fully the mean zonal circulation in the western South Atlantic. There is evidence that the representativeness of synoptic hydrographic sections in other regions may be similarly marginal

Multiple Zonal Jets in a Differentially Heated Rotating Annulus

A laboratory experiment of multiple baroclinic zonal jets is described, thought to be dynamically similar to flow observed in the Antarctic Circumpolar Current. Differential heating sets the overall temperature difference and drives unstable baroclinic flow, but the circulation is free to determine its own structure and local stratification; experiments were run to a stationary state and extend the dynamical regime of previous experiments. Atopographic analog to the planetary β effect is imposed by the gradient of fluid depth with radius supplied by a sloping bottom and a parabolic free surface. New regimes of a low thermal Rossby number (RoT ~ 10-3) and high Taylor number (Ta ~ 1011) are explored such that the deformation radius Lp is much smaller than the annulus gap width L and similar to the Rhines length. Multiple jets emerge in rough proportion to the smallness of the Rhines scale, relatively insensitive to the Taylor number; a regime diagram taking the β effect into account better reflects the emergence of the jets. Eddy momentum fluxes are consistent with an active role in maintaining the jets, and jet development appears to follow the Vallis and Maltrud phenomenology of anisotropic wave-turbulence interaction on a ß plane. Intermittency and episodes of coherent meridional jet migration occur, especially during spinup

Spontaneous symmetry breaking: exact results for a biased random walk model of an exclusion process

It has been recently suggested that a totally asymmetric exclusion process with two species on an open chain could exhibit spontaneous symmetry breaking in some range of the parameters defining its dynamics. The symmetry breaking is manifested by the existence of a phase in which the densities of the two species are not equal. In order to provide a more rigorous basis to these observations we consider the limit of the process when the rate at which particles leave the system goes to zero. In this limit the process reduces to a biased random walk in the positive quarter plane, with specific boundary conditions. The stationary probability measure of the position of the walker in the plane is shown to be concentrated around two symmetrically located points, one on each axis, corresponding to the fact that the system is typically in one of the two states of broken symmetry in the exclusion process. We compute the average time for the walker to traverse the quarter plane from one axis to the other, which corresponds to the average time separating two flips between states of broken symmetry in the exclusion process. This time is shown to diverge exponentially with the size of the chain.Comment: 42 page

Beach changes at Nauset Inlet, Cape Cod, Massachusetts, 1670-1981

A historical study of barrier beach and inlet changes for the Nauset Inlet region, Cape Cod, Massachusetts, was performed to document patterns of beach and inlet change as a preliminary to designing and carrying out ffeld studies of inlet sediment transport. 120 historical charts from 1670 and 125 sets of aerial photographs from 1938 formed the basis for this study. Specific aspects of barrier beach and inlet change addressed include onshore barrier beach movement, longshore tidal inlet migration, and longshore sand bypassing past the inlet. In an effort to correlate forcing events with barrier changes, an exhaustive study of the local storm climate was performed. Detailed treatment of the specific mechanisms responsible for Nauset Inlet migration episodes in a direction opposite the dominant littoral drift are treated in a companion paper by Aubrey, Speer, and Ruder (1982). Documentation of the data base available for the Nauset Area is presented herein as appendices.Prepared for NOAA, 0ffice of Sea Gnant under Grant NA 80-AA-D- 00077 (R/B-21) and for the U.S. Army Research 0ffice under Grant DAAG29-81-K-0004

Proteção de camundongos atímicos BALB/c (Nu/Nu) contra Plasmodium berghei por esplenócitos oriundos de camundongos normais BALB/c (Nu/+)

Camundongos atímicos BALB/c (Nu/Nu) sucumbem entre 7-13 dias após a inoculação (DAI) da cepa NK65 de Plasmodium berghei. Todavia, seus singenêicos heterozigotos (Nu/+) morrem em 7-8 DAI. Camundongos nude (Nu/Nu) reconstituídos com 2xl0(7) esplenócitos de camundongos heterozigotos singenêicos normais não infectados (Nu/+) 20 dias antes da inoculação a (DBI) do parasita, sucumbem 2 dias antes que os animais controles. Camundongos nude reconstituídos 10 ou 2 DBI, vivem 2-4 dias a mais que os animais controles e alguns deles sobrevivem. Esses achados indicam que a cepa NK65 de P. berghei induz, no mínimo, dois imunofenômenos dependentes de linfócitos T; um supressivo e outro estimulatório. A reconstituição de camundongos nude com células T de camundongos BALB/c (Nu/+) parece reduzir ou "By-pass" a atividade supressora das células T, o qual leva à formação de uma resposta imune protetora por alguns dos camundongos nude.Athymic BALB/c (Nu/Nu) mice died at 7-13 days after inoculation (DAI) of Plasmodium berghei NK65, whereas their heterozygous (Nu/+) littermates died at 7-8 DAI. Nude (Nu/Nu) mice, reconstituted with 2 x 10(7) splenocytes from uninfected heterozygous (Nu/+) littermates at 20 days before parasite inoculation (DBI), died about 2 days earlier than control nude mice; nude mice reconstituted at 10 or 2 DBI lived 2 to 4 days longer than control nudes; and nude mice reconstituted 2 DAI lived even longer and some survived. These findings indicate that P. berghei NK65 induces at least two T-cell dependent immune phenomena, one suppressive and the other stimulatory. Reconstitution of nude mice with T-cells from BALB/c (Nu/+) mice appeared to reduce or bypass suppressive T-cell activities which allowed the formation of a protective immune response by some of the nude mice