A Unique Hybrid Propulsion System Design for Large Space Boosters

A study was made of the application of hybrid rocket propulsion technology to large space boosters. Safety, reliability, cost, and performance comprised the evaluation criteria, in order of relative importance, for this study. The effort considered the so called classic hybrid design approach versus a novel approach which utilizes a fuel-rich gas generator for the fuel source. Other trades included various fuel/oxidizer combinations, pressure-fed versus pump fed oxidizer delivery systems, and reusable versus expandable booster systems. Following this initial trade study, a point design was generated. A gas generated-type fuel grain with pump fed liquid oxygen comprised the basis of this point design. This design study provided a mechanism for considering the means of implementing the gas generator approach for further defining details of the design. Subsequently, a system trade study was performed which determined the sensitivity of the design to various design parameters and predicted optimum values for these same parameters. The study concluded that a gas generator hybrid booster design offers enhanced safety and reliability over current of proposed solid booster designs while providing equal or greater performance levels. These improvements can be accomplished at considerably lower cost than for the liquid booster designs of equivalent capability

Diophantine networks

We introduce a new class of deterministic networks by associating networks with Diophantine equations, thus relating network topology to algebraic properties. The network is formed by rep- resenting integers as vertices and by drawing cliques between M vertices every time that M dis- tinct integers satisfy the equation. We analyse the network generated by the Pythagorean equation x2+y2 = z2 showing that its degree distribution is well approximated by a power law with exponen- tial cut-o®. We also show that the properties of this network di®er considerably from the features of scale-free networks generated through preferential attachment. Remarkably we also recover a power law for the clustering coe±cient. We then study the network associated with the equation x2 + y2 = z showing that the degree distribution is consistent with a power-law for several decades of values of k and that, after having reached a minimum, the distribution begins rising again. The power law exponent, in this case, is given by ° » 4:5 We then analyse clustering and ageing and compare our results to the ones obtained in the Pythagorean case

Mediapolis: an introduction

The organisation of this workshop has been prompted by concerns with the way media so often seem to get left out of writing on cities and urban politics (rather than vice-versa). We agree with Iveson’s (2007) argument that urban and media studies have much more in the way of shared concerns when it comes to politics than is conventionally thought to be the case. As a result, we are hoping this workshop will create an occasion for urban scholars to meet those studying media, to explore what difference it makes to explicitly consider the place of media practices in making a politics of cities, and conversely, to consider what is left out when such practices are relegated to the background. In certain ways, we are suggesting a contemporary return to something like Robert Park’s inclination in relation to cities and media. In his seminal essay on the natural history of the newspaper, for example (Park, 1925), Park exhibits a style which does not generally seem to distinguish between or oppose the urban and the media when studying politics and democracy. This surely has something to do with Park’s own intellectual period, and the absence of established disciplines in media or urban studies. Yet this is also precisely the point of the workshop: an opportunity for engagement and discussion through a similar sort of pre-disciplinary spirit

Cockpit Resource Management (CRM) for part 91 and 135 operations

Every flight is characterized by constant change. It is the way each individual crew responds to that change that determines how effectively they will be able to manage their flight deck. The concepts of Flight Deck Management (FDM) is presented. The principles dealt with are applicable to every flight, and the occurrence of change in the conduct of every flight is given. Nothing remains as it is initially perceived. It is then shown how SimuFlite accomplishes training in these concepts. Finally the challenges which are faced as an industry to make FDM more effective are discussed

Towards Coordination-Intensive Visualization Software

Most coordination realizations in current visualization systems are ''last-minute'' ad-hoc and rely on the richness of the chosen implementation language. Moreover, very few visualization models implicitly consider coordination. If coordination is contemplated from the design point of view, it is usually only regarded as part of the communication protocol and is generally dealt with within that restricted domain. Coordinated multiple views are beneficial and a flexible model for coordination will ensure easy embedding of coordination in such exploratory environments. This paper compares different approaches to coordination in exploratory visualization (EV). We recognize the need for a coordination model and for that we formalize aspects of coordination in EV. Furthermore, our work draws on the findings of the interdisciplinary study of coordination by various researchers

Monitoring tropical cyclone intensity using wind fields derived from short-interval satellite images

Rapid scan visible images from the Visible Infrared Spin Scan Radiometer sensor on board SMS-2 and GOES-1 were used to derive high resolution upper and lower tropospheric environmental wind fields around three western Atlantic tropical cyclones (1975-78). These wind fields were used to derive upper and lower tropospheric areal mean relative vorticity and their differences, the net relative angular momentum balance and upper tropospheric mass outflow. These kinematic parameters were shown by studies using composite rawinsonde data to be strongly related to tropical cyclone formation and intensity changes. Also, the role of forced synoptic scale subsidence in tropical cyclone formation was examined. The studies showed that satellite-derived lower and upper tropospheric wind fields can be used to monitor and possibly predict tropical cyclone formation and intensity changes. These kinematic analyses showed that future changes in tropical cyclone intensity are mainly related to the "spin-up" of the storms by the net horizontal transport of relative angular momentum caused by convergence of cyclonic vorticity in the lower troposphere and to a lesser extent the divergence of anticyclone vorticity in the upper troposphere

Pediatric Oncology Nurses’ Perceptions of Prognosis-Related Communication

Background Disclosure of prognosis-related information is an essential aspect of communication with pediatric patients with cancer and their families. The nurse is believed to play an important role in this process, but nurse perceptions and experiences have not been well-described. Purpose Provide an exploration of pediatric oncology nurses’ experiences with prognosis-related communication (PRC). Method Mixed-methods, multiphase design. This paper highlights the qualitative portion of the study. Findings Three themes were identified: Importance of collaboration, impact of PRC, and delivery of prognostic information. Discussion Collaboration is a critical element of PRC. Nurses are often not included in the disclosure process, which limits the ability of nurses to fully function in their roles, compromising patient, family, and nurse outcomes. A paradigm shift is required to empower nurses to be more active participants. More education of physicians and nurses is necessary to consistently engage nurses in PRC and prepare nurses for critical conversations

The relation between cholesterol and haemorrhagic or ischaemic stroke in the Renfrew/Paisley study

Studies have found little association between cholesterol and overall stroke risk, but this could be attributable to different relations for haemorrhagic and ischaemic stroke. Stroke mortality data from prospective studies cannot usually be divided into stroke subtypes. We have therefore analysed stroke based on hospital admissions, obtained by computerised linkage with acute hospital discharges in Scotland for a large prospective cohort study

Numerical Simulation of Baroclinic Jovian Vortices

We examine the evolution of baroclinic vortices in a time-dependent, nonlinear numerical model of a Jovian atmosphere. The model uses a normal-mode expansion in the vertical, using the barotropic and first two baroclinic modes. Results for the stability of baroclinic vortices on an f plane in the absence of a mean zonal flow are similar to results of Earth vortex models, although the presence of a fluid interior on the Jovian planets shifts the stability boundaries to smaller length scales. The presence of a barotropic mean zonal flow in the interior stabilizes vortices against instability and significantly modifies the finite amplitude form of baroclinic instabilities. The effect of a zonal flow on a form of barotropic instability produces periodic oscillations in the latitude and longitude of the vortex as observed at the level of the cloud tops. This instability may explain some, but not all, observations of longitudinal oscillations of vortices on the outer planets. Oscillations in aspect ratio and orientation of stable vortices in a zonal shear flow are observed in this baroclinic model, as in simpler twodimensional models. Such oscillations are also observed in the atmospheres of Jupiter and Neptune. The meridional propagation and decay of vortices on a β plane is inhibited by the presence of a mean zonal flow. The direction of propagation of a vortex relative to the mean zonal flow depends upon the sign of the meridional potential vorticity gradient; combined with observations of vortex drift rates, this may provide a constraint on model assumption for the flow in the deep interior of the Jovian planets