Correlations between GPS and USNO Master Clock time

The U.S. Naval Observatory Master Clock is used to steer the Global Positioning System (GPS) time. Time transfer data consisting of the difference between the Master Clock and GPS time has been acquired from all satellites in the GPS constellation covering a time period from 10 October 1995 to 12 December 1995. A Fourier analysis of the data shows a distinct peak in the Fourier spectrum corresponding to approximately a one day period. In order to determine this period more accurately, correlations are computed between successive days of the data, and an average of twenty five correlation functions shows that there exists a correlation equal to 0.52 at delay time 23 h 56 min, which corresponds to twice the average GPS satellite period. This correlation indicates that GPS time, as measured by the U.S. Naval Observatory, is periodic with respect to the Master Clock, with a period of 23 h and 56 min. An autocorrelation of a five day segment of data indicates that these correlations persist for four successive days     

Optimal time-varying load sharing for divisible loads

A load sharing problem involving the optimal load allocation of divisible loads in a distributed computing system consisting of N processors interconnected through a bus-oriented network is investigated. For a divisible lend, the workload is infinitely divisible so that each fraction of the workload can be distributed and independently computed on each processor. For the first time in divisible load theory, an analysis is provided in the case when the processor speed and the channel speed are time varying due to background jobs submitted to the distributed system with nonnegligible communication delays. A numerical method to calculate the average of the time-varying processor speed and the channel speed and an algorithm to find the optimal allocation of the workload to minimize the total processing finish time are proposed via a deterministic analysis. A stochastic analysis which makes use of Markovian queueing theory is introduced for the case when arrival and departure times of the background jobs are not known     

Low altitude dose measurements from APEX, CRRES and DMSP

Dosimeter data taken on the APEX (1994–1996), CRRES (1990–1991) and DMSP (1984–1987) satellites have been used to study the low altitude (down to 350 km) radiation environment. Of special concern has been the inner edge of the inner radiation belt due to its steep gradient. We have constructed dose models of the inner edge of the belt from all three spacecraft and put them into a personal computer utility, called APEXRAD, that calculates dose for user-selected orbits. The variation of dose for low altitude, circular orbits is given as a function of altitude, inclination and particle type. Dose-depth curves show that shielding greater than 1/4 in Al is largely ineffectual for low altitude orbits. The contribution of outer zone electrons to low altitude dose is shown to be important only for thin shields and to have significant variation with magnetic activity and solar cycle.     

Characterization of the near Earth radiation environment by Liulin type spectrometers

Comprehensive study of the dose, flux and deposited energy spectra shape data obtained by Liulin type spectrometers on spacecraft (five different experiments) and aircraft since 2001 is performed with the aim of understanding how well these parameters can characterize the type of predominant particles and their energy in the near Earth radiation environment. Three different methods for characterisation of the incoming radiation from Liulin spectrometers are described. The results revealed that the most informative one is by the shape of the deposited energy spectra. Spectra generated by Galactic Cosmic Rays (GCR) protons and their secondaries are with linear falling shape in the coordinates deposited energy/deposited per channel dose rate. The position of the maximum of the deposited energy spectra inside the South Atlantic Anomaly (SAA) region depends on the incident energy of the incoming protons. Spectra generated by relativistic electrons in the outer radiation belt have a maximum in the first channels. For higher energy depositions these spectra are similar to the GCR spectra. Mixed radiation by protons and electrons and/or bremsstrahlung is characterized by spectra with 2 maxima. All type of spectra has a knee close to 6.2 MeV deposited energy, which correspond to the stopping energy of protons in the detector. Dose to flux ratio known also as specific dose is another high information parameter, which is given by experimentally obtained formulae [Heffner, J. Nuclear radiation and safety in space. M. Atomizdat. 115, 1971 (in Russian)] connecting the dose to flux ratio and the incident energy of the particles.     

Optimization of efficient order service by information unmanned aerial vehicles

We propose a mathematical model and the numerical method for an optimal choice of unmanned aerial vehicles (UAVs) from those being in flight to fulfill a newly received order for monitoring (reconnaissance) of a new region. Examples of using the approach being proposed and main lines of its realization in promising information unmanned aircraft complexes (UAC) are presented.     

Investigation of helicopter maneuverability by the power balance method

The algorithms for calculating available overloads and maneuvers are presented. Nesterov’s loop maneuver is analyzed.     

On application of the theory of face seals with microgrooves to high-speed FV engine rotors

With allowance made for thermoelasticity of working surfaces and inertia forces on the lubricant coat, a hydrodynamic problem is solved for the noncontacting face seals with microgrooves in the high-speed rotors of FV engines. Also shown are the initiation of surface waviness in the zone of lubricant coat fracture and the influence of its amplitude upon the seal characteristics.     

Parametric navigation system synthesis on the basis of a magneto-inertial course transmitter

A technique for the parametric synthesis of the navigation system on the basis of the magneto-inertial course transmitter is proposed; the technique makes it possible to minimize the error scatter in determining the ground speed components, to analyze a nature of the error scatter variation in determining the location coordinates in time, to simulate and further choose regular intervals of using additional data obtained from the radionavigational satellite system.     

Metal creep model with the initial strain discontinuity and functional material constants

It is proposed that curves of metal creep be approximated by the time-relative linear law with the initial creep strain discontinuity; as a result, the solution of initial boundary value rheological problems is considerably simplified and is characterized by the adequate precision with a large service life. The labor intensity of computations is similar to the steady-state creep law. The introduction of functional material constants makes it possible to perform calculations of creep under the action of temperature that is different from the specified one in the basic experiments as well as calculations of nonuniformly heated structure elements.     

Jovian periodicities (∼10 h, ∼40 min) on Ulysses’ Distant Jupiter Encounter observations around the Halloween CIR events

We analyzed data from four different instruments (HI-SCALE, URAP, SWOOPS, VHM/FGM) onboard Ulysses spacecraft (s/c) and we searched for possible evidence of Jovian emissions when the s/c approached Jupiter during the times of Halloween events (closest time approach/position to Jupiter: February 5, 2004/R = 1683 R_J,θ = ∼49°). In particular, we analyzed extensively the low energy ion measurements obtained by the HI-SCALE experiment in order to examine whether low energy ion/electron emissions show a symmetry, and whether they are observed at north high latitudes upstream from the jovian bow shock, as is known to occur in the region upstream from the south bow shock as well ( Marhavilas et al., 2001). We studied the period from October 2003 to March 2004, as Ulysses moved at distances 0.8–1.2 AU from the planet at north Jovicentric latitudes <75°, and we present here an example of characteristic Jovian periodicities in the measurements around a CIR observed by Ulysses on days ∼348–349/2003 (R = 1894 R_J,θ = 72°). We show that Ulysses observed low energy ion (∼0.055–4.7 MeV) and electron (>∼40 keV) flux and/or spectral modulation with the Jupiter rotation period (∼10 h) as well as variations with the same period in solar wind parameters, radio and magnetic field directional data. In addition, characteristic strong ∼40 min periodic variations were found superimposed on the ∼10 h ion spectral modulation. Both the ∼10 h and ∼40 min ion periodicities in HI-SCALE measurements were present in several cases during the whole period examined (October 2003 to March 2004) and were found to be more evident during some special conditions, for instance during enhanced fluxes around the start (forward shock) and the end (reverse shock) of CIRs. We infer that the Jovian magnetosphere was triggered by the impact of the CIRs, after the Halloween events, and it was (a) a principal source of forward and reverse shock-associated ion flux structures and (b) the cause of generation of ∼10 h quasi-periodic magnetic field and plasma modulation observed by Ulysses at those times.