68,967 research outputs found
Simulation and assimilation of satellite altimeter data at the oceanic mesoscale
An improved "objective analysis' technique is used along with an altimeter signal statistical model, an altimeter noise statistical model, an orbital model, and synoptic surface current maps in the POLYMODE-SDE area, to evaluate the performance of various observational strategies in catching the mesoscale variability at mid-latitudes. In particular, simulated repetitive nominal orbits of ERS-1, TOPEX, and SPOT/POSEIDON are examined. Results show the critical importance of existence of a subcycle, scanning in either direction. Moreover, long repeat cycles ( 20 days) and short cross-track distances ( 300 km) seem preferable, since they match mesoscale statistics. Another goal of the study is to prepare and discuss sea-surface height (SSH) assimilation in quasigeostrophic models. Restored SSH maps are shown to meet that purpose, if an efficient extrapolation method or deep in-situ data (floats) are used on the vertical to start and update the model
X-ray Variability and Period Determinations in the Eclipsing Polar DP Leo
An analysis of ROSAT observations for the eclipsing magnetic cataclysmic
binary DP Leo provides constraints on the origin, size, temperature,
variability and structure of the soft X-ray emission region on the surface of
the white dwarf. These data, when combined with prior observations, show a
progression of approximately 2 degrees per year in the impact position of the
accretion stream onto the white dwarf. One explanation for the observed drift
in stream position is that a magnetic activity cycle on the secondary produces
orbital period oscillations. These oscillations result in an orbital period
which cycles above and below the rotational period of the nearly synchronous
white dwarf. The accretion stream and X-ray emission regions are modeled to fit
the observational data. A distance to the system is also calculated. [An
erroneous value for the cyclotron luminosity, included in an earlier paper
version of the preprint, is corrected here.]Comment: uuencoded PostScript file (25 pages) + 8 figures available by
anonymous ftp to ftp.astro.psu.edu (in the directory /pub/robinson), to
appear in ApJ, PSU preprint 1994-1
Decay of fidelity in terms of correlation functions
We consider, within the algebraic formalism, the time dependence of fidelity
for qubits encoded into an open physical system. We relate the decay of
fidelity to the evolution of correlation functions and, in the particular case
of a Markovian dynamics, to the spectral gap of the generator of the semigroup.
The results are applicable to the analysis of models of quantum memories.Comment: 9 pages, no figure
What are we waiting for? [guest editorial]
The clinical education of Australia's aged care nurses can no longer be treated as the Cinderella of nursing's specialities. It is urgent that ways be agreed and measures taken to bring this branch of the profession, and residential aged care nursing in particular, into mainstream health care services. There should be no need to describe again the evolving shape of Australia's demographic profile between now and the middle of this century; and no need to prove here that the ageing bulge is already placing a severe strain on staffmg in the sector. A substantial percentage of the aged care nursing workforce is nearing retirement and the ratio of departures to recruits seems set to worsen at the same time as demand for high quality nursing care escalates. Important indicators - the number of the most highly dependent residents has doubled in the past seven years; compounding co-morbidities are increasingly common and an estimated 60-80% of residents in residential aged care facilities (RACFs) have a dementing illness - reveal the rapidly rising levels of frailty and dependency in the RACF population....
Study of fast response thermocouple measurement of temperatures in cryogenic gases
Thermocouples fabricated from uninsulated small diameter wire have fast reproducible response times. The thermocouple is thermally isolated from its supports by making the leads of sufficient length so that the heat conduction down the leads is small and assuming that the leads adjacent to the junction are subjected to the same thermal conditions
Polynomial Cointegration among Stationary Processes with Long Memory
n this paper we consider polynomial cointegrating relationships among
stationary processes with long range dependence. We express the regression
functions in terms of Hermite polynomials and we consider a form of spectral
regression around frequency zero. For these estimates, we establish consistency
by means of a more general result on continuously averaged estimates of the
spectral density matrix at frequency zeroComment: 25 pages, 7 figures. Submitted in August 200
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