Satellite altimeters after Skylab and GEOS-C - should they utilize a single transmitter or an array of pulsed amplifiers?

An attempt was made to determine if future satellite altimeters, operating at K-band, should use a single transmitter or an array of pulsed amplifiers. The two systems were compared as a function of reliability, power, service life, system requirements, and weight. Preliminary results indicate the modular system to be superior in service life and reliability although it requires more power and is substantially heavier than the single system. No concrete conclusions were reached as to which system should be used

Partnership in practice

This paper examines human resource management practices adopted in a group of eight case study firms and their tendencies towards versus away from partnership. The analysis is based on data collected during interviews with 124 employees (75 in organisations tending towards partnership and 49 in organisations tending away from partnership) and senior managers, conducted in 1997-1998 for the Job Insecurity and Work Intensification Survey (JIWIS). Drawing on the perspectives of senior managers and employees, we examine the tendency of firms towards and away from partnership in employment relations; and in keeping with the JIWIS methodology (Burchell et.al., 2001) we combine quantitative and qualitative evidence in our analysis. Specifically, we are interested in what partnership looks like in these different contexts, the reasons it is pursued (or not), the degree to which companies have been successful in achieving their partnership objectives (from the perspective of both management and employees), and the conditions that have either facilitated or impeded partnership in relationships with employees

The collisional drift mode in a partially ionized plasma

The structure of the drift instability was examined in several density regimes. Let sub e be the total electron mean free path, k sub z the wave-vector component along the magnetic field, and the ratio of perpendicular ion diffusion to parallel electron streaming rates. At low densities (k sub z lambda 1) the drift mode is isothermal and should be treated kineticly. In the finite heat conduction regime square root of m/M k sub z Lambda sub 1) the drift instability threshold is reduced at low densities and increased at high densities as compared to the isothermal threshold. Finally, in the energy transfer limit (k sub z kambda sub e square root of m/M) the drift instability behaves adiabatically in a fully ionized plasma and isothermally in a partially ionized plasma for an ion-neutral to Coulomb collision frequency ratio

Stratospheric CCN sampling program

Two one liter grab samples of stratospheric aerosol were returned from each of six U-2 sampling missions. Cloud condensation nuclei (CCN) spectra from each sample were obtained. Interest was centered on the effects of volcanic activity. Spurious particle generation was found to be a serious problem in container 9 LFT and a much smaller problem in container 9 RT. Initial studies of an option for improved sample containers and values were completed. A CCN spectrometer, able to operate at an internal pressure of 300 mb, was designed

Quantifying Acetaldehyde in Astronomical Ices and Laboratory Analogues: IR Spectra, Intensities, 13C Shifts, and Radiation Chemistry

Acetaldehyde is of interest to astrochemists for its relevance to both interstellar and cometary chemistry, but little infrared (IR) spectral data have been published for the solid phases of this compound. Here we present IR spectra of three forms of solid acetaldehyde, with spectra for one form being published for the first time. Direct measurements of band strengths and absorption coefficients also are reported for the first time for amorphous aldehyde, the form of greatest interest for astrochemical work. An acetaldehyde band strength at 1350 cm1 that has been used as a reference for about 20 yr is seen to be in error by about 80 per cent when compared to the direct measurements presented here. Spectra and peak positions also are presented for H13C(O)13CH3, and then used for the first identification of ketene as a radiation product of solid acetaldehyde

The electromagnetic interchange mode in a partially ionized collisional plasma

A collisional electromagnetic dispersion relation is derived from two-fluid theory for the interchange mode coupled to the Alfven, acoustic, drift and entropy modes in a partially ionized plasma. The fundamental electromagnetic nature of the interchange model is noted; coupling to the intermediate Alfven mode is strongly stabilizing for finite k sub z. Both ion viscous and ion-neutral stabilization are included, and it was found that collisions destroy the ion finite Larmor radius cutoff at short perpendicular wavelengths

High density constraint on the entropy instability

The entropy instability squared is a nonisothermal effect which is eliminated by parallel ion pressure at high densities (k sub z lambda sub e 1/2 sq root of m/M), reducing previous growth rate estimates and the range of unstable parameters

The correlation between soft and hard X-rays component in flares: from the Sun to the stars

In this work we study the correlation between the soft (1.6--12.4 keV, mostly thermal) and the hard (20--40 and 60--80 keV, mostly non-thermal) X-ray emission in solar flares up to the most energetic events, spanning about 4 orders of magnitude in peak flux, establishing a general scaling law and extending it to the most intense stellar flaring events observed to date. We used the data from the Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) spacecraft, a NASA Small Explorer launched in February 2002. RHESSI has good spectral resolution (~1 keV in the X-ray range) and broad energy coverage (3 keV--20 MeV), which makes it well suited to distinguish the thermal from non-thermal emission in solar flares. Our study is based on the detailed analysis of 45 flares ranging from the GOES C-class, to the strongest X-class events, using the peak photon fluxes in the GOES 1.6--12.4 keV and in two bands selected from RHESSI data, i.e.20--40 keV and 60--80 keV. We find a significant correlation between the soft and hard peak X-ray fluxes spanning the complete sample studied. The resulting scaling law has been extrapolated to the case of the most intense stellar flares observed, comparing it with the stellar observations. Our results show that an extrapolation of the scaling law derived for solar flares to the most active stellar events is compatible with the available observations of intense stellar flares in hard X-rays.Comment: 9 pages, 10 figures. To be published in Astronomy and Astrophysic

Some High Temperature Diffusion Studies on Materials of Thermionic Interest

High temperature diffusion studies between uranium materials and refractory metals and alloys - thermionic emission propertie