Policy Driven Management for Distributed Systems

Separating management policy from the automated managers which interpret the policy facilitates the dynamic change of behavior of a distributed management system. This permits it to adapt to evolutionary changes in the system being managed and to new application requirements. Changing the behavior of automated managers can be achieved by changing the policy without having to reimplement them—this permits the reuse of the managers in different environments. It is also useful to have a clear specification of the policy applying to human managers in an enterprise. This paper describes the work on policy which has come out of two related ESPRIT funded projects, SysMan and IDSM. Two classes of policy are elaborated—authorization policies define what a manager is permitted to do and obligation policies define what a manager must do. Policies are specified as objects which define a relationship between subjects (managers) and targets (managed objects). Domains are used to group the objects to which a policy applies. Policy objects also have attributes specifying the action to be performed and constraints limiting the applicability of the policy. We show how a number of example policies can be modeled using these objects and briefly mention issues relating to policy hierarchy and conflicts between overlapping policies. © 1994, Plenum Publishing Corporation. All rights reserved.Accepted versio

Phase Lags in the Optical-Infrared Light Curves of AGB Stars

To search for phase lags in the optical-infrared light curves of asymptotic giant branch stars, we have compared infrared data from the COBE DIRBE satellite with optical light curves from the AAVSO and other sources. We found 17 examples of phase lags in the time of maximum in the infrared vs. that in the optical, and 4 stars with no observed lags. There is a clear difference between the Mira variables and the semi-regulars in the sample, with the maximum in the optical preceding that in the near-infrared in the Miras, while in most of the semi-regulars no lags are observed. Comparison to published theoretical models indicates that the phase lags in the Miras are due to strong titanium oxide absorption in the visual at stellar maximum, and suggests that Miras pulsate in the fundamental mode, while at least some semi-regulars are first overtone pulsators. There is a clear optical-near-infrared phase lag in the carbon-rich Mira V CrB; this is likely due to C2 and CN absorption variations in the optical.Comment: AJ, in pres

Measurement of vortex velocities over a wide range of vortex age, downstream distance and free stream velocity

A wind tunnel test was conducted to obtain vortex velocity signatures over a wide parameter range encompassing the data conditions of several previous researchers while maintaining a common instrumentation and test facility. The generating wing panel was configured with both a revolved airfoil tip shape and a square tip shape and had a semispan aspect of 4.05/1.0 with a 121.9 cm span. Free stream velocity was varied from 6.1 m/sec to 76.2 m/sec and the vortex core velocities were measured at locations 3, 6, 12, 24 and 48 chordlengths downstream of the wing trailing edge, yielding vortex ages up to 2.0 seconds. Wing pitch angles of 6, 8, 9 and 12 deg were investigated. Detailed surface pressure distributions and wing force measurements were obtained for each wing tip configuration. Correlation with vortex velocity data taken in previous experiments is good. During the rollup process, vortex core parameters appear to be dependent primarily on vortex age. Trending in the plateau and decay regions is more complex and the machanisms appear to be more unstable

Nonperiodic Optical Flickering In Hz Herculis

NASA NGR 44-012-209NSF GP-25901, GP-41796Astronom

Extended Ultraviolet Disks and Ultraviolet-bright Disks in Low-mass E/S0 Galaxies

We have identified 15 extended ultraviolet (XUV) disks in a largely field sample of 38 E/S0 galaxies that have stellar masses primarily below ~4 × 10^(10) M_☉ and comparable numbers on the red and blue sequences. We use a new purely quantitative XUV-disk definition designed with reference to the "Type 1" XUV-disk definition found in the literature, requiring UV extension relative to a UV-defined star formation threshold radius. The 39% ± 9% XUV-disk frequency for these E/S0s is roughly twice the ~20% reported for late-type galaxies (although differences in XUV-disk criteria complicate the comparison), possibly indicating that XUV disks are preferentially associated with galaxies experiencing weak or inefficient star formation. Consistent with this interpretation, we find that the XUV disks in our sample do not correlate with enhanced outer-disk star formation as traced by blue optical outer-disk colors. However, UV-Bright (UV-B) disk galaxies with blue UV colors outside their optical 50% light radii do display enhanced optical outer-disk star formation as well as enhanced atomic gas content. UV-B disks occur in our E/S0s with a 42^(+9)_–8% frequency and need not coincide with XUV disks; thus their combined frequency is 61% ± 9%. For both XUV and UV-B disks, UV colors typically imply <1 Gyr ages, and most such disks extend beyond the optical R_(25) radius. XUV disks occur over the full sample mass range and on both the red and blue sequences, suggesting an association with galaxy interactions or another similarly general evolutionary process. In contrast, UV-B disks favor the blue sequence and may also prefer low masses, perhaps reflecting the onset of cold-mode gas accretion or another mass-dependent evolutionary process. Virtually all blue E/S0s in the gas-rich regime below stellar mass M_t ~ 5 × 10^9 M_☉ (the "gas-richness threshold mass") display UV-B disks, supporting the previously suggested association of this population with active disk growth

A search for X-rays from UV Ceti flare stars

A search of MIT/OSO-7 data was made for evidence of X-ray emission from flares of UV Ceti flare stars. Observations from McDonald Observatory were used to identify the times of optical flares. The only instance of coincident coverage occurred on 1974 January 21 UT at 03:43:26 GMT for delta m(u)=0.86 flare of YZ CMi. No radio coverage of this particular event was obtained. Upper limits (3 sigma) of 0.8, 1.0, and 0.7 photons/sq cm-sec on the observed X-ray flux were set for the energy ranges greater than or approximately equal to 15, greater than or approximately equal to 3, and 1-10 keV, respectively