We discuss various aspects of the post-Newtonian approximation in general relativity. After presenting the foundation based on the Newtonian limit, we show a method to derive post-Newtonian equations of motion for relativistic compact binaries based on a surface integral approach and the strong field point particle limit. As an application we derive third post-Newtonian equations of motion for ...

Some years ago Stephani derived the general solution of Einstein's eld equations for a conformally at perfect uid. In these metrics the spacelike hypersurfaces orthogonal to the uid ow have constant curvature. The metrics with non-zero expansion involve ve arbitrary functions a, b, c 1 , c 2 and c 3 of time t. It is shown that any Killing vectors must be tangent to the constant curvature hypers...

An asymptotic study of two spectral models which appear in uid-solid vibrations is presented in this paper. These two models are derived under the assumption that the uid is slightly compressible or viscous respectively. In the rst case, min-max estimations and a limit process in the variational formulation of the corresponding model are used to show that the spectrum of the compressible case t...

Access control in Unix systems is mainly based on user IDs, yet the system calls that modify user IDs (uid-setting system calls), such as setuid, are poorly designed, insufficiently documented, and widely misunderstood and misused. This has caused many security vulnerabilities in application programs. We propose to make progress on the setuid mystery through two approaches. First, we study kern...

Many types of animals use appendages bearing arrays of hair-like structures to capture molecules (e.g. olfactory antennae, gills) or particles (e.g. suspension-feeding appendages) from the surrounding water or air, and to locomote or move <uid past themselves. The performance of these functions depends on how much of the <uid encountered by the array of hairs <ows through the gaps between the h...

In this paper we present a novel approach to estimate and analyze 3D uid structure and motion of clouds from multi-spectrum 2D cloud image sequences. Accurate cloud-top structure and motion are very important for a host of meteorological and climate applications. However, due to the extremely complex nature of cloud uid motion, classical nonrigid motion analysis methods will be insuucient to so...

On one hand we present below some examples of uid networks control which illustrate the general method for optimally emptying networks with linear holding costs proposed in Avram, Bertsimas and Ricard(95). On the other hand we attempt to study the changes in the optimal policies for uid models caused by stochasticity e ects. In the case of the usual expected total emptying cost objective, we fo...

The eeects of ow induced by a random acceleration eld (g-jitter) are considered in two related situations that are of interest for microgravity uid experiments: the random motion of isolated buoyant particles, and diiusion driven coarsening of a solid-liquid mixture. We start by analyzing in detail actual accelerometer data gathered during a recent microgravity mission, and obtain the values of...

We describe some approaches to the synthesis of optimal policies for multiclass queueing network models based upon the close connection between stability of queueing networks and their associated uid limit models. It is found that there is also a close connection between optimization of the network and optimal control of the far simpler uid network model. This observation leads to a new class o...

We point out the existence of a new type of growing transverse mode in the gravitational instability. This appears as a post-Newtonian effect to Newtonian dynamics. We demonstrate this existence by formulating the Lagrangian perturbation theory in the framework of the cosmological post-Newtonian approximation in general relativity. Such post-Newtonian order effects might produce characteristic ...