Navier–Stokes solvers in European aircraft design

The paper gives a broad perspective of the progress made during the last 10 years in solving the Navier–Stokes equations and traces how this simulation technique went from being a specialized research topic to a practical engineering tool that design engineers use on a routine basis.

The scope is limited to Navier–Stokes solvers applied to industrial design of airframes with attention focused particularly on developments in Europe. An overview of the different Navier–Stokes codes used in Europe is given, and on-going developments are outlined.

The current state of progress is illustrated by computed steady and unsteady solutions to industrial problems, ranging from airfoil characteristics, flow around an isolated wing, to full aircraft configurations.

A discussion on the future industrial design environment is given, and developments in Europe towards a more integrated design approach with underlying concepts like ‘concurrent engineering (CE)’ and the ‘virtual product (VP)’ are summarized. The paper concludes with a discussion on future challenging applications.     

Solution numérique du problème de Képler

A numerical solution of the Kepler problem. Requiring a six-decimal accuracy, the Kepler problem can be solved with four iterations at most, even for an eccentricity close to 1, provided that a new initial approximation be introduced in this last case.     

A Program Plan for Earth Orbital Space Astronomy

Manned space flight offers the opportunity to couple the astronaut /scientist's ability to select and process data and to calibrate, modify, and repair instruments with the vantage point for astronomical observations provided by a platformlocated above the Earth's atmosphere. The role which manned space flight may play in the 1970-1990 time period in meeting astronomy research needs is examined. The instruments and facilities that appear feasible for that period are described.     

Analysis of long duration flares

Yohkoh has observed many long duration events permitting a statistical study of the properties of these interesting events. We have selected ten flares for analysis which have durations between 5 and 20 hours, and size ranging from C to X GOES class. Employing the Soft X-ray Telescope, the Bragg Crystal Spectrometer, GOES spacecraft, and ground-based H data, we examine the morphology, temperature, emission measure, location of the hard X-ray source, non-thermal velocities and upflows of the plasma at different stages in the flare development. Our results are used to address the question of the energy source that maintains the hot plasma at temperatures of several million degrees for many hours.     

Performance comparisons of modified SMI and GLR algorithms

Adaptive filtering for signal detection in colored interference of unknown statistics is addressed. The detection performance of a modified version of the well-known sample matrix inversion (SMI) algorithm, called the modified SMI (MSMI), is compared with that of the generalized likelihood ratio (GLR) algorithm in colored Gaussian interference. The performance sensitivity of the MSMI and GLR in colored Weibull and log-normal interference is studied via simulation. It is found that there is almost no need to use the more complicated GLR algorithm in Gaussian interference, while in Weibull or log-normal interference the GLR should be preferable to the MSMI     

Solar maximum mission experiment: Early results of the hard X-ray imaging experiment

We have selected four widely different flares from the early period of operations of the Hard X-Ray Imaging Spectrometer (HXIS) on SMM to illustrate the characteristic imaging properties of this experiment. For the small flare of April 4, 1980, we demonstrate the instrument's capability for locating a compact source. In the weak, but extensive, flare of April 6 we show how well the instrument can display spatial structure, and also the low level of the instrument background. In the 1B flare of April 7 we are able to locate positions of the X-ray emission in the soft and hard channels, and estimate the positional variations of the emission patches. Finally, in the IN flare of April 10, which produced the strongest hard X-ray burst we have seen so far, we repeat some of the studies made for the April 7 event, and also demonstrate the capability of the HXIS instrument to study the development, with high time resolution, of individual 8″ × 8″ elements of the flare.     

Dynamic Effects of Signal Normalizing on Adaptive Algorithms

A method is shown for suppressing the adaptive switching transient that arises in complex adaptive (LMS and stochastic approximation) algorithms due to signal normalization with controlled switched gains. The method involves rescaling of the adaptive weights with the normalizing gains just prior to the first adaptation with the new gains. In addition, an effective method of rescaling the adaptive gain factor based on the maximum eigenvalues of the respective covariance matrices is shown.     

Comparison of Bit Synchronization Schemes Using AM and Summed Clocks

This paper considers bit synchronization through the use of a separate clock signal which is either amplitude modulated onto or summed with the data signal. For continuous data transmission, such schemes are known to be inferior, in the sense of efficient use of power, to schemes which derive synchronization directly from the data signal. However, these techniques have application in burst systems such as spacecraft command systems, and in systems where receiver simplicity is more important than power conservation. For systems in which the composite data-clock signal subsequently modulates an RF carrier, it is shown that the summed clock signal performs slightly better than the AM clock signal, and that for both signal types, the optimum allocation of power between data and clock is approximately 9:1.     

Infrared Systems: I. Accuracy of Angle Measurement

In this paper expressions are derived for the error in position measurement for the problem of estimating the position of an infrared target in a random background and the combined prob lem when white detector noise is also affecting the estimation. Space filters performing linear scanning, nutation, and rotation are considered. A linear scanning infrared system is then considered in greater detail. The noise on the error signal is calculated, taking into account both the estimation error, as discussed in the first part, and "false alarms" occurring in the scan area far from the target.     

Plasma resonance stimulation in space plasmas

Relaxation sounders proved to work very well in dilute plasmas far from the Earth. They provide a very powerful diagnostic tool. In the solar wind and magnetosheath, they give a sure and precise measurement of the electron density. In the magnetosphere, where detailed measurements on the f_Q resonances are possible, they provide, in addition, a determination of the electron temperature and drift velocity. Moreover, the possibility of oblique echoes in this region gives the perspective of obtaining even more information on the medium by detailed interpretation of the signals.