The theorem of the complement for nested subpfaffian sets

Let R be an o-minimal expansion of the real field, and let L(R) be the language consisting of all nested Rolle leaves over R. We call a set nested subpfaffian over R if it is the projection of a boolean combination of definable sets and nested Rolle leaves over R. Assuming that R admits analytic cell decomposition, we prove that the complement of a nested subpfaffian set over R is again a nested subpfaffian set over R. As a corollary, we obtain that if R admits analytic cell decomposition, then the pfaffian closure P(R) of R is obtained by adding to R all nested Rolle leaves over R, a one-stage process, and that P(R) is model complete in the language L(R).Comment: final version before publicatio

Water Quality Studies in Malacca River Basin Using Geographic Information Systems (GIS)

Malacca Straits is recognized worldwide due to its importance as the busiest waterway in the world. The environmental profile of the Malacca Straits points to certain stresses in the ecosystem due to pollution load. Pollutants from land-based sources are probably the most pressing environmental problem. Wastes from agricultural, industrial, and domestic source discharge directly into the Straits or indirectly via rivers, which flow into the Straits. As far as land based pollution is concerned, study on river basin is important. The Malacca River basin is of the rivers flowing into the Straits of Malacca. Geographic information System (GIS) was used to map the water pollution scenario due to its ability to analyze spatial and temporal data. Beside that, correlation coefficient method was used to determine the relationship and variation between rainfall and water quality parameters. Six parameters selected for this study. namely. Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Ammoniacal Nitrogen. pH, Suspended Solid (SS), and Dissolved Oxygen (DO). The output of this study consists of water quality database. maps, and graphs on the water quality variations. The important of this study is the application of GIS technology in monitoring water quality. Technology plays an important role for effective environmental management

Towards an analytical theory of the third-body problem for highly elliptical orbits

When dealing with satellites orbiting a central body on a highly elliptical orbit, it is necessary to consider the effect of gravitational perturbations due to external bodies. Indeed, these perturbations can become very important as soon as the altitude of the satellite becomes high, which is the case around the apocentre of this type of orbit. For several reasons, the traditional tools of celestial mechanics are not well adapted to the particular dynamic of highly elliptical orbits. On the one hand, analytical solutions are quite generally expanded into power series of the eccentricity and therefore limited to quasi-circular orbits [17, 25]. On the other hand, the time-dependency due to the motion of the third-body is often neglected. We propose several tools to overcome these limitations. Firstly, we have expanded the disturbing function into a finite polynomial using Fourier expansions of elliptic motion functions in multiple of the satellite's eccentric anomaly (instead of the mean anomaly) and involving Hansen-like coefficients. Next, we show how to perform a normalization of the expanded Hamiltonian by means of a time-dependent Lie transformation which aims to eliminate periodic terms. The difficulty lies in the fact that the generator of the transformation must be computed by solving a partial differential equation involving variables which are linear with time and the eccentric anomaly which is not time linear. We propose to solve this equation by means of an iterative process.Comment: Proceedings of the International Symposium on Orbit Propagation and Determination - Challenges for Orbit Determination and the Dynamics of Artificial Celestial Bodies and Space Debris, Lille, France, 201

Coherent events and spectral shape at ion kinetic scales in the fast solar wind turbulence

In this paper we investigate spectral and phase coherence properties of magnetic fluctuations in the vicinity of the spectral transition from large, magnetohydrodynamic (MHD) to sub-ion scales using in-situ measurements of the Wind spacecraft in a fast stream. For the time interval investigated by Leamon et al. (1998) the phase-coherence analysis shows the presence of sporadic quasi-parallel Alfv\'en Ion Cyclotron (AIC) waves as well as coherent structures in the form of large-amplitude, quasi-perpendicular Alfv\'en vortex-like structures and current sheets. These waves and structures importantly contribute to the observed power spectrum of magnetic fluctuations around ion scales; AIC waves contribute to the spectrum in a narrow frequency range whereas the coherent structures contribute to the spectrum over a wide frequency band from the inertial range to the sub-ion frequency range. We conclude that a particular combination of waves and coherent structures determines the spectral shape of the magnetic field spectrum around ion scales. This phenomenon provides a possible explanation for a high variability of the magnetic power spectra around ion scales observed in the solar wind

Aerospace systems and mission analysis research Status report, 1 Apr. - 31 Dec. 1966

Systems and mission analysis of solar electric propulsion for solar system exploratio

Safety Evaluation of Critical Applications Distributed on TDMA-Based Networks

Critical embedded systems have to provide a high level of dependability. In automotive domain, for example, TDMA protocols are largely recommended because of their deterministic behavior. Nevertheless, under the transient environmental perturbations, the loss of communication cycles may occur with a certain probability and, consequently, the system may fail. This paper analyzes the impact of the transient perturbations (especially due to Electromagnetic Interferences) on the dependability of systems distributed on TDMA-based networks. The dependability of such system is modeled as that of "consecutive-k-out-of-n:F" systems and we provide a efficient way for its evaluation

Solar electric space mission analysis Progress report, 1 Jun. - 31 Dec. 1966

Characteristics and trajectory analysis of solar electric propulsion space missions - Mars orbiter and Jupiter flyb