38,220 research outputs found
Analysis of Satellite-to-Satellite Tracking (SST) and altimetry data from GEOS-C
Radar altimetry and satellite-to-satellite (SST) range and range rate tracking measurements were used to infer the exterior gravitational field of the earth and the structure of the geoid from GEOS-C metric data. Under the SST analysis, a direct point-by-point estimate of gravity disturbance by means of a recursive filter with backward smoothing was attempted but had to be forsaken because of poor convergence. The adopted representation consists of a more or less uniform grid of discrete masses at a depth of approximately 400 km from the earth's surface. The layer is superimposed on a spherical harmonics model. The procedure for smoothing the altimetry and inferring the fine-structured gravity field over the Atlantic test area is described. The local disturbances are represented by means of a density layer. The altimeter height biases were first estimated by a least squares adjustment at orbital crossover points. After taking out the bias, long wavelength contributions from GEM-6 as well as a calibration correction were subtracted. The residual heights were then represented by a mass distribution beneath the earth's surface
Experimental investigation of a large-scale, two-dimensional, mixed-compression inlet system: Internal performance and drag at transonic conditions, free stream Mach equals 0.6 to 1.28
A large scale, variable-geometry inlet system with a design Mach number of 3.0 was tested at Mach numbers from 0.6 to 1.28. Variable features for off-design operation are an adjustable-height ramp system and a translating cowl. Experimental results are presented for transonic ramp and cowl positions showing the effect of throat boundary layer bleed and vortex generators on engine-face performance. Detailed pressure and force-balance data are used to evaluate transonic drag characteristics
The universal functorial equivariant Lefschetz invariant
We introduce the universal functorial equivariant Lefschetz invariant for
endomorphisms of finite proper G-CW-complexes, where G is a discrete group. We
use K_0 of the category of "phi-endomorphisms of finitely generated free
RPi(G,X)-modules". We derive results about fixed points of equivariant
endomorphisms of cocompact proper smooth G-manifolds.Comment: 33 pages; shortened version of the author's PhD thesis, supervised by
Wolfgang Lueck, Westfaelische Wilhelms-Universitaet Muenster, 200
Theories of risk: testing investor behaviour on the Taiwan stock and stock index futures markets
This paper considers four utility functions - concave, convex, S-shaped, and reverse S-shaped - to analyze the behavior of different types of investors on the Taiwan stock index and its corresponding index futures. Using stochastic dominance (SD) rules, we show that the existence of all four investor types is plausible. Risk averters prefer spot to futures, whereas risk seekers prefer futures to spot. Investors with S-shaped utility functions prefer spot (futures) to futures (spot) when markets move upward (downward). Investors with reverse S-shaped utility functions prefer futures (spot) to spot (futures) when markets move upward (downward). We show that both spot and futures markets can exist when only risk averters are present, but futures can dominate spot only if there is some risk seeking behavior. These results are robust with respect to sub-periods, spot returns including dividends and diversification
Effects of Diversity on Multi-agent Systems: Minority Games
We consider a version of large population games whose agents compete for
resources using strategies with adaptable preferences. The games can be used to
model economic markets, ecosystems or distributed control. Diversity of initial
preferences of strategies is introduced by randomly assigning biases to the
strategies of different agents. We find that diversity among the agents reduces
their maladaptive behavior. We find interesting scaling relations with
diversity for the variance and other parameters such as the convergence time,
the fraction of fickle agents, and the variance of wealth, illustrating their
dynamical origin. When diversity increases, the scaling dynamics is modified by
kinetic sampling and waiting effects. Analyses yield excellent agreement with
simulations.Comment: 41 pages, 16 figures; minor improvements in content, added
references; to be published in Physical Review
Behavior of shell-model configuration moments
An important input into reaction theory is the density of states or the level
density. Spectral distribution theory (also known as nuclear statistical
spectroscopy) characterizes the secular behavior of the density of states
through moments of the Hamiltonian. One particular approach is to partition the
model space into subspaces and find the moments in those subspaces; a
convenient choice of subspaces are spherical shell-model configurations. We
revisit these configuration moments and find, for complete
many-body spaces, the following behaviors: (a) the configuration width is
nearly constant for all configurations; (b) the configuration asymmetry or
third moment is strongly correlated with the configuration centroid; (c) the
configuration fourth moment, or excess is linearly related to the square to the
configuration asymmetry. Such universal behavior may allow for more efficient
modeling of the density of states in a shell-model framework.Comment: 12 pages, 8 figure
Could mergers become more sustainable? A study of the stock exchange mergers of NASDAQ and OMX
This study investigates whether the merger of NASDAQ and OMX could reduce the portfolio diversification possibilities for stock market investors and whether it is necessary to implement national policies and international treaties for the sustainable development of financial markets. Our study is very important because some players in the stock markets have not yet realized that stock exchanges, during the last decades, have moved from government-owned or mutually-owned organizations to private companies, and, with several mergers having occurred, the market is tending gradually to behave like a monopoly. From our analysis, we conclude that increased volatility and reduced diversification opportunities are the results of an increase in the long-run comovement between each pair of indices in Nordic and Baltic stock markets (Denmark, Sweden, Finland, Estonia, Latvia, and Lithuania) and NASDAQ after the merger. We also find that the merger tends to improve the error-correction mechanism for NASDAQ so that it Granger-causes OMX, but OMX loses predictive power on NASDAQ after the merger. We conclude that the merger of NASDAQ and OMX reduces the diversification possibilities for stock market investors and our findings provide evidence to support the argument that it is important to implement national policies and international treaties for the sustainable development of financial markets
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