10,657 research outputs found
Benefits of VTOL aircraft in offshore petroleum logistics support
The mission suitability and potential economic benefits of advanced VTOL aircraft were investigated for logistics support of petroleum operations in the North Sea and the Gulf of Mexico. Concepts such as the tilt rotor and lift/cruise fan are promising for future operations beyond 150 miles offshore, where their high cruise efficiency provides savings in trip time, fuel consumption, and capital investment. Depending upon mission requirements, the aircraft operating costs are reduced by as much as 20 percent to 50 percent from those of current helicopters
On pricing kernels, information and risk
We discuss the finding that cross-sectional characteristic based models have
yielded portfolios with higher excess monthly returns but lower risk than their
arbitrage pricing theory counterparts in an analysis of equity returns of
stocks listed on the JSE. Under the assumption of general no-arbitrage
conditions, we argue that evidence in favour of characteristic based pricing
implies that information is more likely assimilated by means of nonlinear
pricing kernels for the markets considered.Comment: 20 pages, 3 figures, 1 tabl
Discrete ordinates-Monte Carlo coupling: A comparison of techniques in NERVA radiation analysis
In the radiation analysis of the NERVA nuclear rocket system, two-dimensional discrete ordinates calculations are sufficient to provide detail in the pressure vessel and reactor assembly. Other parts of the system, however, require three-dimensional Monte Carlo analyses. To use these two methods in a single analysis, a means of coupling was developed whereby the results of a discrete ordinates calculation can be used to produce source data for a Monte Carlo calculation. Several techniques for producing source detail were investigated. Results of calculations on the NERVA system are compared and limitations and advantages of the coupling techniques discussed
Cost and schedule management on the quiet short-haul research aircraft project
The Quiet Short-Haul Research Aircraft (QSRA) Project, one of the largest aeronautical programs undertaken by NASA to date, achieved a significant cost underrun. This is attributed to numerous factors, not the least of which were the contractual arrangement and the system of cost and schedule management employed by the contractor. This paper summarizes that system and the methods used for cost/performance measurement by the contractor and by the NASA project management. Recommendations are made for the use of some of these concepts in particular for future programs of a similar nature
Cosmological constant and Euclidean space from nonperturbative quantum torsion
Heisenberg's nonperturbative quantization technique is applied to the
nonpertrubative quantization of gravity. An infinite set of equations for all
Green's functions is obtained. An approximation is considered where: (a) the
metric remains as a classical field; (b) the affine connection can be
decomposed into classical and quantum parts; (c) the classical part of the
affine connection are the Christoffel symbols; (d) the quantum part is the
torsion. Using a scalar and vector fields approximation it is shown that
nonperturbative quantum effects gives rise to a cosmological constant and an
Euclidean solution.Comment: title is changed. arXiv admin note: text overlap with arXiv:1201.106
How Leading International Dairy Companies Adjusted to Changes in World Markets
This Discussion Paper focuses on strategic adjustments made by leading international dairy firms in response to world market developments in the late 1990s and early 2000s. Firms whose strategies were analyzed include Fonterra, Nestle, selected other Western European companies (including the Kerry Group and Parmalat), Kraft Foods, Dairy Farmers of America, and Land O'Lakes. In part, the paper describes dairy industry success stories that have implications for a broader group of dairy companies. It also shows how even successful dairy firms have pursued strategies that expose the companies to significant risks. Strategic alliances entered into by the companies received emphasis in the study.International Dairy Companies, Business Strategies, Agribusiness, Demand and Price Analysis, Financial Economics, Industrial Organization, International Relations/Trade, Marketing, Risk and Uncertainty,
Some Evidence on Finite Sample Behavior of an Instrumental Variables Estimator of the Linear Quadtratic Inventory Model
We evaluate some aspects of the finite sample distribution of an instrumental variables estimator of a first order condition of the Holt et al. (1960) linear quadratic inventory model. We find that for some but not all empirically relevant data generating processes and sample sizes, asymptotic theory predicts a wide dispersion of parameter estimates, with a substantial finite sample probability of estimates with incorrect signs. For such data generating processes, simulation evidence suggests that different choices of left hand side variables often produce parameter estimates of an opposite sign. More generally, while the asymptotic theory often provides a good approximation to the finite sample distribution, sometimes it does not
Quiet propulsive lift for commuter airlines
The performance of STOL or RTOL aircraft and NASA's research program to provide options for future design and certification of quiet propulsive-life transports is described
Computation of turbulent boundary layers on curved surfaces, 1 June 1975 - 31 January 1976
An accurate method was developed for predicting effects of streamline curvature and coordinate system rotation on turbulent boundary layers. A new two-equation model of turbulence was developed which serves as the basis of the study. In developing the new model, physical reasoning is combined with singular perturbation methods to develop a rational, physically-based set of equations which are, on the one hand, as accurate as mixing-length theory for equilibrium boundary layers and, on the other hand, suitable for computing effects of curvature and rotation. The equations are solved numerically for several boundary layer flows over plane and curved surfaces. For incompressible boundary layers, results of the computations are generally within 10% of corresponding experimental data. Somewhat larger discrepancies are noted for compressible applications
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