A theoretical and experimental study of the ionosphere using radio signals from earth satellites progress report no. 9, 1 jan. - 30 jun. 1964

Morphology of ionosphere using radio signals from earth satellite

Nonlinear Unsteady Motions and NOx Production in Gas Turbine Combustors

Chiefly for improved efficiency, the trend to increasing use of gas turbine engines in stationary powerplants has been firmly established. The requirement for minimum NOx production has motivated operation as close as practically possible near the lean flammability limit, to reduce flame temperatures and consequently reduce formation of nitrogen oxides via the Zeldovich thermal mechanism. However, experience has shown that under these conditions, stability of the chamber is compromised, often leading to the presence of sustained oscillations in the combustor. That possibility raises the problem of the influence of oscillatory motions on the production of nitrogen oxides. Numerically calculating these influences for a complex geometry gas turbine combustor is too computationally expensive at this ?me. Nonlinear analytical methods making use of these influences are a promising direction for simplei ways to design and develop operational gas turbine combustors. However, this analysis needs results on which to base unsteady models of the interaction between nonlinear oscillations and species production within a gas turbine combustor. In this paper, two methods are explored briefly as an initial step. The first is based on a configuration of perfectly stirred and plug flow reactors to approximate the flow in a combustion chamber. A complete representation of the chemical processes is accommodated, but the geometry is simplified. The second is a full numerical simulation for a realistic geometry, but at this stage the chemistry is simplified

NASA-FAA helicopter Microwave Landing System curved path flight test

An ongoing series of joint NASA/FAA helicopter Microwave Landing System (MLS) flight tests was conducted at Ames Research Center. This paper deals with tests done from the spring through the fall of 1983. This flight test investigated and developed solutions to the problem of manually flying curved-path and steep glide slope approaches into the terminal area using the MLS and flight director guidance. An MLS-equipped Bell UH-1H helicopter flown by NASA test pilots was used to develop approaches and procedures for flying these approaches. The approaches took the form of Straight-in, U-turn, and S-turn flightpaths with glide slopes of 6 deg, 9 deg, and 12 deg. These procedures were evaluated by 18 pilots from various elements of the helicopter community, flying a total of 221 hooded instrument approaches. Flying these curved path and steep glide slopes was found to be operationally acceptable with flight director guidance using the MLS

Laboratory investigation of visible shuttle glow mechanisms

Laboratory experiments designed to uncover mechanistic information about the spectral and spatial characteristics of shuttle glow were conducted. The luminescence was created when a pulse of O atoms traveling at orbital velocities was directed toward NO molecules previously adsorbed to aluminum, nickel, and Z306 Chemglaz (a common baffle black) coated surfaces held at various temperatures. Spectral and spatial measurements were made using a CCD imaging spectrometer. Corroborative spectral information was recorded in separate measurements using a scanning monochromator and gated photomultiplier arrangement. The e-folding distance at several temperatures was calculated from images of the surface glow using the photometrics image processing capability of the imaging spectrometer. The e-folding distance was not altered as a function of incoming O beam velocity. The results are presented and the observations provide direct evidence that the visible shuttle glow results from recombination of oxygen atoms and surface bound NO

AN ECONOMIC ANALYSIS OF THE NORTH DAKOTA CATTLE INDUSTRY

The analysis was conducted to evaluate the impacts of both the Federal Agricultural Improvement and Reform Act of 1996 (FAIR) and the cattle cycle on the livestock enterprises. The North Dakota Representative Farm and Ranch Model, which uses the Food and Agricultural Policy Research Institute price projections as an input, was developed and used for this analysis. Net farm income and farm debt-to-asset ratios for the average and large beef cattle farms were analyzed. The U.S. cattle industry has been characterized by cyclical variations in production and prices. It appears that the current cattle cycle is in the final stages of expansion. Cattle numbers continued to increase during 1995, but at a slow rate. Industry estimates are that the bottom of cattle prices will occur in late 1996 or 1997. Price recovery is projected to start sometime in 1998 as inventory numbers decline. Prices are forecast to rise through 2002. Net farm income for the representative beef cattle farms is projected to follow the cattle cycle with the lowest net incomes during 1997- 1999. Net farm income for most representative beef cattle farms recovers by 2002-2003. The debt-to-asset ratios for the representative beef cattle farms will likely rise throughout the forecast period. FAPRI Note: Figures are not included in the machine readable copy--contact the authors for more information.livestock, representative farms, cattle cycle, Production Economics,

Effectiveness of a Slurry Cutoff Wall at Loeffel Site

In recent years slurry cutoff walls have been successfully employed to mitigate seepage and isolate liquid waste and leachate in the groundwater environment. However , a success of the slurry cutoff wall depends on the hydrological condition of the site. A post construction and pre-construction groundwater budget analysis can demonstrate the effectiveness of a slurry cutoff wall. In this paper, a detailed groundwater budget analysis of Loeffel site in the Southwestern Rensselaer County of New York is discussed. The analysis shows that the use of a slurry cutoff wall effectively mitigates the release of contaminated groundwater from the site

Effectiveness of a Slurry Cutoff Wall at Loeffel Site

In recent years slurry cutoff walls have been successfully employed to mitigate seepage and isolate liquid waste and leachate in the groundwater environment. However , a success of the slurry cutoff wall depends on the hydrological condition of the site. A post construction and pre-construction groundwater budget analysis can demonstrate the effectiveness of a slurry cutoff wall. In this paper, a detailed groundwater budget analysis of Loeffel site in the Southwestern Rensselaer County of New York is discussed. The analysis shows that the use of a slurry cutoff wall effectively mitigates the release of contaminated groundwater from the site

Species-time-area and phylogenetic-time-area relationships in tropical tree communities

The species-area relationship (SAR) has proven to be one of the few strong generalities in ecology. The temporal analog of the SAR, the species-time relationship (STR), has received considerably less attention. Recent work primarily from the temperate zone has aimed to merge the SAR and the STR into a synthetic and unified species-time-area relationship (STAR) as originally envisioned by Preston (1960). Here we test this framework using two tropical tree communities and extend it by deriving a phylogenetic-time-area relationship (PTAR). The work finds some support for Preston's prediction that diversity-time relationships, both species and phylogenetic, are sensitive to the spatial scale of the sampling. Contrary to the Preston's predictions we find a decoupling of diversity-area and diversity-time relationships in both forests as the time period used to quantify the diversity-area relationship changes. In particular, diversity-area and diversity-time relationships are positively correlated using the initial census to quantify the diversity-area relationship, but weakly or even negatively correlated when using the most recent census. Thus, diversity-area relationships could forecast the temporal accumulation of biodiversity of the forests, but they failed to back-cast the temporal accumulation of biodiversity suggesting a decoupling of space and time

Approximating Weighted Duo-Preservation in Comparative Genomics

Motivated by comparative genomics, Chen et al. [9] introduced the Maximum Duo-preservation String Mapping (MDSM) problem in which we are given two strings $s_1$ and $s_2$ from the same alphabet and the goal is to find a mapping $\pi$ between them so as to maximize the number of duos preserved. A duo is any two consecutive characters in a string and it is preserved in the mapping if its two consecutive characters in $s_1$ are mapped to same two consecutive characters in $s_2$. The MDSM problem is known to be NP-hard and there are approximation algorithms for this problem [3, 5, 13], but all of them consider only the "unweighted" version of the problem in the sense that a duo from $s_1$ is preserved by mapping to any same duo in $s_2$ regardless of their positions in the respective strings. However, it is well-desired in comparative genomics to find mappings that consider preserving duos that are "closer" to each other under some distance measure [19]. In this paper, we introduce a generalized version of the problem, called the Maximum-Weight Duo-preservation String Mapping (MWDSM) problem that captures both duos-preservation and duos-distance measures in the sense that mapping a duo from $s_1$ to each preserved duo in $s_2$ has a weight, indicating the "closeness" of the two duos. The objective of the MWDSM problem is to find a mapping so as to maximize the total weight of preserved duos. In this paper, we give a polynomial-time 6-approximation algorithm for this problem.Comment: Appeared in proceedings of the 23rd International Computing and Combinatorics Conference (COCOON 2017

A Well-Resolved Phylogeny of the Trees of Puerto Rico Based on DNA Barcode Sequence Data

Background: The use of phylogenetic information in community ecology and conservation has grown in recent years. Two key issues for community phylogenetics studies, however, are (i) low terminal phylogenetic resolution and (ii) arbitrarilydefined species pools. Methodology/principal findings: We used three DNA barcodes (plastid DNA regions rbcL, matK, and trnH-psbA) to infer a phylogeny for 527 native and naturalized trees of Puerto Rico, representing the vast majority of the entire tree flora of the island (89%). We used a maximum likelihood (ML) approach with and without a constraint tree that enforced monophyly of recognized plant orders. Based on 50% consensus trees, the ML analyses improved phylogenetic resolution relative to a comparable phylogeny generated with PHYLOMATIC (proportion of internal nodes resolved:constrained ML = 74%, unconstrained ML = 68%, PHYLOMATIC = 52%). We quantified the phylogenetic composition of 15 protected forests in Puerto Rico using the constrained ML and PHYLOMATIC phylogenies. We found some evidence that tree communities in areas of high water stress were relatively phylogenetically clustered. Reducing the scale at which the species pool was defined (from island to soil types) changed some of our results depending on which phylogeny (ML vs. PHYLOMATIC) was used. Overall, the increased terminal resolution provided by the ML phylogeny revealed additional patterns that were not observed with a less-resolved phylogeny. Conclusions/significance: With the DNA barcode phylogeny presented here (based on an island-wide species pool), we show that a more fully resolved phylogeny increases power to detect nonrandom patterns of community composition in several Puerto Rican tree communities. Especially if combined with additional information on species functional traits and geographic distributions, this phylogeny will (i) facilitate stronger inferences about the role of historical processes in governing the assembly and composition of Puerto Rican forests, (ii) provide insight into Caribbean biogeography, and (iii) aid in incorporating evolutionary history into conservation planning