Abstract:
In this paper, we consider a satellite orbiting in a Manev gravitational potential under the influence of an atmospheric drag force that varies with the square of velocity. Using an exponential atmosphere that varies with the orbital altitude of the satellite, we examine a circular orbit scenario. In particular, we derive expressions for the change in satellite radial distance as a function of the drag force parameters and obtain numerical results. The Manev potential is an alternative to the Newtonian potential that has a wide variety of applications, in astronomy, astrophysics, space dynamics, classical physics, mechanics, and even atomic physics.

Abstract:
An integral quantity is presented that relates the wake of a body in nominally two-dimensional flow to its drag, for Reynolds numbers ranging from 9,000 to 144,000. It is defined as the ratio of the kinetic energy to the vorticity in the fluid boundary and, for the special case of laminar flow, is proportional to the angular momentum in the wake bubble. The new quantity is useful for correlating drag data for circular and rectangular cylinders, wedges, v-gutters, and normal flat plates with and without splitter plates. The correlation indicates that the drag force is proportional to the flow speed and the mass flow rate stored in the boundary of the fluid, where the fluid boundary is defined so as to include the wake bubble. Order-of-magnitude arguments indicate that, absent any quantization of vortex size, this mass flow rate, and hence the drag force, can become unbounded as the vortices contained in the wake becomes finer.

Abstract:
The Yukawa correction to the Newtonian gravitational force is accepted as a parameterization of deviations from the inverse-square law of gravity which might be caused by new physics beyond the standard model of particles and the general theory of relativity. We investigate these effects on the clock onboard a drag-free satellite: dynamics of the satellite and influence on the time transfer link. We find the Yukawa signal in the time transfer is much harder to detect with current state of clocks than those effects on the dynamics, especially the secular change of periastron, by laser ranging in the case of an artificial Earth satellite carrying a frequency standard with an orbit of $a=10^7$\,m and $e=0.01$.

Abstract:
A long Gamma-Ray Burst (GRB) was detected with the instruments on board the INTEGRAL satellite on January 31 2003. Although most of the GRB, which lasted $\sim$150 seconds, occurred during a satellite slew, the automatic software of the INTEGRAL Burst Alert System was able to detect it in near-real time. Here we report the results obtained with the IBIS instrument, which detected GRB 030131 in the 15 keV - 200 keV energy range, and ESO/VLT observations of its optical transient. The burst displays a complex time profile with numerous peaks. The peak spectrum can be described by a single power law with photon index $\Gamma\simeq$1.7 and has a flux of $\sim$2 photons cm$^{-2}$ s$^{-1}$ in the 20-200 keV energy band. The high sensitivity of IBIS has made it possible for the first time to perform detailed time-resolved spectroscopy of a GRB with a fluence of 7$\times10^{-6}$ erg cm$^{-2}$ (20-200 keV).

Abstract:
The drag free technique is used to force a proof mass to follow a geodesic motion. The mass is protected from perturbations by a cage, and the motion of the latter is actively controlled to follow the motion of the proof mass. We present a theoretical analysis of the effects of quantum fluctuations for this technique. We show that a perfect drag free operation is in principle possible at the quantum level, in spite of the back action exerted on the mass by the position sensor.

Abstract:
We present a broad overview of the principal processes and astrophysical sites of gamma-ray line production and review the main pre-INTEGRAL satellite observations to set the stage to the next European era of gamma-ray line astronomy.

Abstract:
This paper studies the law of any power of the integral of geometric Brownian motion over any finite time interval. As its main results, two integral representations for this law are derived. This is by enhancing the Laplace transform ansatz of Yor (1992) with complex analytic methods, which is the main methodological contribution of the paper. The one of our integrals has a similar structure to that obtained by Yor, while the other is in terms of Hermite functions as those of Dufresne (2001). Performing or not performing a certain Girsanov transformation is identified as the source of these two forms of the laws. While our results specialize for exponents equal to 1 to those obtained by Yor, they yield on specialization representations for the exponent equal to minus 1 laws which are markedly different from those obtained by Dufresne.

Abstract:
The turbulent fluid flow through the sudden expansion passage is of scientific and industrial significance. The numerical analysis of the turbulent fluid flow through an axi-symmetric sudden expansion passage has been carried out by using modified

Abstract:
An experimental setup with computer based measurements is introduced. It is possible to observe the object’s motionduring the fall and see how the limiting speed is reached. Due to the air drag, the motion changes from a constantaccelerated motion to a motion with constant velocity. Measurements of the motion of a falling object are done with agraphing calculator and an attached data analyzer. Time-position and time-velocity diagrams of the falling motion areproduced to determine the air drag’s influence.

Abstract:
The density distribution function of the integral of the exponential Brownian motion is determined explicitly in the form of a rapidly convergent series.