On the fundamental acoustic mode in variable area,low Mach number nozzles

We consider the propagation of sound in nozzles of substantially varying cross-section, taking into account reflections from the tapering walls and non-uniform convection by the axially accelerated or decelerated mean flow. Exact solutions of the acoustic equations are obtained for the simplest case of the fundamental longitudinal mode in quasi-one-dimensional, low Mach number nozzle flow. The effects of non-uniform mean flow on sound are demonstrated by comparing horns with nozzles, and 15 properties (stated in italics and labelled P1, P2 ... P15 in the text) are proved and discussed, viz. concerning (1) relations between acoustic pressure and velocity; (2) equipartition or biasing of kinetic and compression energies; (3) conservation or evolution of wave action; (4) existence of elementary or special solutions and (5) cut-off frequencies, and amplitude and phase laws. We conclude with a simple formula for the approximate calculation of the acoustic fields; the formula can be made more accurate by using a correction factor for amplitude and phase, which is plotted against area ratio for propagation upstream or downstream in diffusers and convergent nozzles.     

Service Orientation Principles in Integrated Communication Environments

Today, every modern organization aspires to improve its performance through better use of information technology. As communication technology improves, organizations can operate over wider distances and can even assemble operational components on an ad-hoc basis to meet requirements of a specific objective. Future air traffic communication studies are already discussing whether to operate IP networks that are combining voice and data transport. The problem is that although voice and data are using a common infrastructure, they remain separate at the application level. Probably, some service providers have already enjoyed reduced network infrastructure and operational costs by merging voice and data transport, but the majority may have failed to realize the significant cost, productivity, and service differentiation capabilities that converged, collaborative applications could bring. This elaborates mechanisms needed for a robust and globally interconnected network environment (including infrastructure, systems, processes, and people) in which data is shared timely and seamlessly among users, applications, and platforms. Such an environment enables substantially improved situational awareness and shortened decision-making cycles. Stepping ahead, our contribution discusses standards making application or service convergence a reality.     

Relativistic electrons high doses at International Space Station and Foton M2/M3 satellites

The paper presents observation of relativistic electrons. Data are collected by the Radiation Risk Radiometer-Dosimeters (R3D) B2/B3 modifications during the flights of Foton M2/M3 satellites in 2005 and 2007 as well as by the R3DE instrument at the European Technology Exposure Facility (EuTEF) on the Columbus External Payload Adaptor at the International Space Station (ISS) in the period February 20 – April 28, 2008. On the Foton M2/M3 satellites relativistic electrons are observed more frequently than on the ISS because of higher (62.8°) inclination of the orbit. At both Foton satellites the usual duration of the observations are a few minutes long. On the ISS the duration usually is about 1 min or less. The places of observations of high doses due to relativistic electrons are distributed mainly at latitudes above 50° geographic latitude in both hemispheres on Foton M2/M3 satellites. A very high maximum is found in the southern hemisphere at longitudinal range 0°–60°E. At the ISS the maximums are observed between 45° and 52° geographic latitude in both hemispheres mainly at longitudes equatorward from the magnetic poles. The measured absolute maximums of dose rates generated by relativistic electrons are found to be as follows: 304 μGy h⁻¹ behind 1.75 g cm⁻² shielding at Foton M2, 2314 μGy h⁻¹ behind 0.71 g cm⁻² shielding at Foton M3 and 19,195 μGy h⁻¹ (Flux is 8363 cm⁻² s⁻¹) behind les than 0.4 g cm⁻² shielding at ISS.     

Experiences in Managing the Prometheus Project

Congress authorized NASA's Prometheus Project in February 2003, with the first Prometheus mission slated to explore the icy moons of Jupiter. The project had two major objectives: 1) to develop a nuclear reactor that would provide unprecedented levels of power and show that it could be processed safely and operated reliably in space for long-duration, deep-space exploration; and 2) to explore the three icy moons of Jupiter - Callisto, Ganymede, and Europa - and return science data that would meet the scientific goals as set forth in the Decadal Survey Report of the National Academy of Sciences. Early in project planning, it was determined that the development of the Prometheus nuclear-powered spaceship would be complex and require the intellectual knowledge residing at numerous organizations across the country. In addition, because of the complex nature of the project and the multiple partners, approaches beyond those successfully used to manage a typical JPL project would be needed. This describes the key experiences in managing Prometheus, which should prove useful for future projects of similar scope and magnitude.     

Pressure and Ionization Balances in the Circum-Heliospheric Interstellar Medium and the Local Bubble

A disconcerting mismatch of thermal pressures for two media in contact with each other, (1) the warm, Circum-Heliospheric Interstellar Medium (CHISM) and (2) the very hot material within a much larger region called the Local Bubble (LB), has troubled astronomers for over two decades. A possible resolution of this problem, at least in part, now seems possible. We now understand that earlier estimates for the average electron density in the very hot LB plasma were inflated by an unrecognized foreground contamination to the low energy diffuse X-ray background measurements. This foreground illumination arises from photons emitted by charge exchange reactions between solar wind ions and neutral atoms from the interstellar medium that enter into the heliosphere. However, with the resolution of this problem comes a new one. The high ionization fraction of helium in the CHISM, relative to that of hydrogen, could be understood in terms of the effects from a strong flux of EUV and X-ray radiation coming from both the Local Bubble and a conductive interface around the CHISM. A revision of this interpretation may now be in order, now that the photoionization rate from radiation emitted by hot gas the Local Bubble is lower than previously assumed.     

Evolution of the periodicities in 2S 0114+650

We have analysed 9 years of data from the All Sky Monitor on the Rossi X-ray Timing Explorer for 2S 0114+650 to study the evolution of its spin, binary, and super-orbital periods. The spin history of the neutron star in this system exhibits torque reversals lasting 1 year. The newly discovered super-orbital period has remained stable over the 9-year span, making 2S 0114+650 the fourth known system to exhibit stable super-orbital modulation. We compare its super-orbital period evolution with those of the other three such systems.     

The role of repair in the survival of mammalian cells from heavy ion irradiation: approximation to the ideal case of target theory.

Theories of cellular radiation sensitivity that preclude a significant role for cellular repair processes in the final biological expression of cellular damage induced by ionizing radiation are unsound. Experiments are discussed here in which the cell-cycle dependency of the repair deficiency of the S/S variant, of the L5178Y murine leukemic lymphoblast was examined by treatment with the heavy ions, 20Ne, 28Si, 40Ar, 56Fe and 93Nb. Evidence from those studies, which will be described in detail elsewhere, provide support for the notion that as the linear energy transfer (LET infinity) of the incident radiation increases the ability of the S/S cell to repair radiation damage decreases until effectively it is eliminated around 500 keV/micrometer. In the region of the latter LET infinity value, the behavior of the S/S cell approximates the ideal case of target theory where post-irradiation metabolism (repair) does not influence cell survival. The expression of this phenomenon among different cell types and tissues will depend upon the actual repair systems involved and other considerations.     

Energy-efficient intensifiers of laminar heat transfer

In this paper, calculations of some thermo-hydraulic parameters of different intensified channels have been carried out and a grooved channel that is optimal in mass and energy expenditure is determined. A new variant of the intensified channel is proposed and recommendations for engineers are presented.