The simulation of ionospheric conditions for space vehicles

Plasma wind tunnel to simulate ionospheric conditions for space vehicle

Techniques for the realization of ultrareliable spaceborne computers Interim scientific report

Error-free ultrareliable spaceborne computer

The spectral-curvature parameter: an alternative tool for the analysis of synchrotron spectra

The so-called Spectral Curvature Parameter(SCP), when plotted versus the high-frequency spectral index ($alpha_{high}$) of synchrotron sources, provides crucial parameters on the continuum spectrum of synchrotron radiation without the more complex modeling of spectral ageing scenarios. An important merit of the SCP-$alpha$ diagram is the enhanced reliability of extracting multiple injection spectra, $alpha_{inj}$. Different from the colour-colour diagram, tracks of different $alpha_{inj}$s, especially when the synchrotron particles are young, exhibit less overlap and less smearing in the SCP-$alpha$ diagram. Three giant radio galaxies(GRGs) and a sample of Compact steep spectrum(CSS) souces are presented. GRGs exhibit asymmetries of their injection spectral indices $alpha_{inj}$ in the SCP-$alpha_{high}$ diagram. The obtained $alpha_{inj}$s and the trends in the sources are cross-checked with the literature and show remarkable confidence. Besides the spectral steepening, spectral flattening is prominent in the radio lobes. The spectral flattening is a clue to efficient re-acceleration processes in the lobes. It implies interaction with the surrounding intergalactic or intra-cluster medium is an important characteristic of GRGs. In the SW lobe of DA240, there is a clear sign of CI and KP/JP bifurcation at the source extremity. This indicates a highly relativistic energy transportation from the core or in situ acceleration in this typical FR I lobe. Our analysis proves, if exists, KP spectra imply the existence of strong $B_{sync}$ field with $B_{sync} > B_{CMB}$. In the CSS sources, our result confirms the CI model and $B_{sync} >> B_{CMB}$. The synchrotron self-absorption is significant in the CSS sample.Comment: to be published in A&

Virtual acoustics displays

The real time acoustic display capabilities are described which were developed for the Virtual Environment Workstation (VIEW) Project at NASA-Ames. The acoustic display is capable of generating localized acoustic cues in real time over headphones. An auditory symbology, a related collection of representational auditory 'objects' or 'icons', can be designed using ACE (Auditory Cue Editor), which links both discrete and continuously varying acoustic parameters with information or events in the display. During a given display scenario, the symbology can be dynamically coordinated in real time with 3-D visual objects, speech, and gestural displays. The types of displays feasible with the system range from simple warnings and alarms to the acoustic representation of multidimensional data or events

Steady-state Ab Initio Laser Theory: Generalizations and Analytic Results

We improve the steady-state ab initio laser theory (SALT) of Tureci et al. by expressing its fundamental self-consistent equation in a basis set of threshold constant flux states that contains the exact threshold lasing mode. For cavities with non-uniform index and/or non-uniform gain, the new basis set allows the steady-state lasing properties to be computed with much greater efficiency. This formulation of the SALT can be solved in the single-pole approximation, which gives the intensities and thresholds, including the effects of nonlinear hole-burning interactions to all orders, with negligible computational effort. The approximation yields a number of analytic predictions, including a "gain-clamping" transition at which strong modal interactions suppress all higher modes. We show that the single-pole approximation agrees well with exact SALT calculations, particularly for high-Q cavities. Within this range of validity, it provides an extraordinarily efficient technique for modeling realistic and complex lasers.Comment: 17 pages, 11 figure

Curvature suppresses the Rayleigh-Taylor instability

The dynamics of a thin liquid film on the underside of a curved cylindrical substrate is studied. The evolution of the liquid layer is investigated as the film thickness and the radius of curvature of the substrate are varied. A dimensionless parameter (a modified Bond number) that incorporates both geometric parameters, gravity, and surface tension is identified, and allows the observations to be classified according to three different flow regimes: stable films, films with transient growth of perturbations followed by decay, and unstable films. Experiments and theory confirm that, below a critical value of the Bond number, curvature of the substrate suppresses the Rayleigh-Taylor instability

Effects of an embedding bulk fluid on phase separation dynamics in a thin liquid film

Using dissipative particle dynamics simulations, we study the effects of an embedding bulk fluid on the phase separation dynamics in a thin planar liquid film. The domain growth exponent is altered from 2D to 3D behavior upon the addition of a bulk fluid, even though the phase separation occurs in 2D geometry. Correlated diffusion measurements in the film show that the presence of bulk fluid changes the nature of the longitudinal coupling diffusion coefficient from logarithmic to algebraic dependence of 1/s, where s is the distance between the two particles. This result, along with the scaling exponents, suggests that the phase separation takes place through the Brownian coagulation process.Comment: 6 pages, 5 figures. Accepted for publication in Europhys. Let

Information criteria for efficient quantum state estimation

Recently several more efficient versions of quantum state tomography have been proposed, with the purpose of making tomography feasible even for many-qubit states. The number of state parameters to be estimated is reduced by tentatively introducing certain simplifying assumptions on the form of the quantum state, and subsequently using the data to rigorously verify these assumptions. The simplifying assumptions considered so far were (i) the state can be well approximated to be of low rank, or (ii) the state can be well approximated as a matrix product state. We add one more method in that same spirit: we allow in principle any model for the state, using any (small) number of parameters (which can, e.g., be chosen to have a clear physical meaning), and the data are used to verify the model. The proof that this method is valid cannot be as strict as in above-mentioned cases, but is based on well-established statistical methods that go under the name of "information criteria." We exploit here, in particular, the Akaike Information Criterion (AIC). We illustrate the method by simulating experiments on (noisy) Dicke states

Disciplinary processes and the management of poor performance among UK nurses: bad apple or systemic failure? A scoping study

The rise of managerialism within healthcare systems has been noted globally. This paper uses the findings of a scoping study to investigate the management of poor performance among nurses and midwives in the United Kingdom within this context. The management of poor performance among clinicians in the NHS has been seen as a significant policy problem. There has been a profound shift in the distribution of power between professional and managerial groups in many health systems globally. We examined literature published between 2000 and 10 to explore aspects of poor performance and its management. We used Web of Science, CINAHL, MEDLINE, British Nursing Index, HMIC, Cochrane Library and PubMed. Empirical data are limited but indicate that nurses and midwives are the clinical groups most likely to be suspended and that poor performance is often represented as an individual deficit. A focus on the individual as a source of trouble can serve as a distraction from more complex systematic problems

Time-dependent density functional theory calculation of van der Waals coefficient of sodium clusters

In this paper we employ all-electron \textit{ab-initio} time-dependent density functional theory based method to calculate the long range dipole-dipole dispersion coefficient (van der Waals coefficient) $C_{6}$ of sodium atom clusters containing even number of atoms ranging from 2 to 20 atoms. The dispersion coefficients are obtained via Casimir-Polder relation. The calculations are carried out with two different exchange-correlation potentials: (i) the asymptotically correct statistical average of orbital potential (SAOP) and (ii) Vosko-Wilk-Nusair representation of exchange-correlation potential within local density approximation. A comparison with the other theoretical results has been performed. We also present the results for the static polarizabilities of sodium clusters and also compare them with other theoretical and experimental results. These comparisons reveal that the SAOP results for C_{6} and static polarizability are quite accurate and very close to the experimental results. We examine the relationship between volume of the cluster and van der Waals coefficient and find that to a very high degree of correlation C_{6} scales as square of the volume. We also present the results for van der Waals coefficient corresponding to cluster-Ar atom and cluster-N_{2} molecule interactions.Comment: 22 pages including 6 figures. To be published in Journal of Chemical Physic