Formal verification of AI software

The application of formal verification techniques to Artificial Intelligence (AI) software, particularly expert systems, is investigated. Constraint satisfaction and model inversion are identified as two formal specification paradigms for different classes of expert systems. A formal definition of consistency is developed, and the notion of approximate semantics is introduced. Examples are given of how these ideas can be applied in both declarative and imperative forms

Sediment transport and erosion in the Fourchon area of Lafourche parish

NASA aerial photography in the form of color infrared and color positive transparencies is used as an aid in evaluating the rate and effect of erosion and sediment transport in Bay Champagne Louisiana

IR Monitoring of the Microquasar GRS 1915+105: Detection of Orbital and Superhump Signatures

We present the results of seven years of K-band monitoring of the low-mass X-ray binary GRS 1915+105. Positive correlations between the infrared flux and the X-ray flux and X-ray hardness are demonstrated. Analysis of the frequency spectrum shows that the orbital period of the system is $P_{orb}= 30.8 \pm 0.2$ days. The phase and amplitude of the orbital modulation suggests that the modulation is due to the heating of the face of the secondary star. We also report another periodic signature between 31.2 and 31.6 days, most likely due to a superhump resonance. From the superhump period we then obtain a range on the mass ratio of the system, $0.05 < q < 0.12$.Comment: 16 pages, 6 figures; v2: minor change

Little Holes to Hide In : Civil Defense and the Public Backlash Against Home Fallout Shelters, 1957-1963

Throughout the 1950s, U.S. policymakers actively encouraged Americans to participate in civil defense through a variety of policies. In 1958, amidst confusion concerning which of these policies were most efficient, President Eisenhower established the National Shelter Plan and a new civil defense agency titled The Office of Civil and Defense Mobilization. This agency urged homeowners to build private fallout shelters through print media. In response, Americans used newspapers, magazines, and science fiction novels to contest civil defense and the foreign and domestic policies that it was based upon, including nuclear strategy. Many Americans remained unconvinced of the viability of civil defense or feared its psychological impacts on society. Eventually, these criticisms were able to weaken civil defense efforts and even alter nuclear defense strategy and missile defense technology

Gas dynamics for accretion disk simulations

The behavior of accretion disks can largely be understood in terms of the basic physical processes of mass, energy, and momentum conservation. Despite this, detailed modeling of these systems using modern computational techniques is challenging and controversial. Disturbing differences exist between methods used widely in astrophysics, namely Eulerian finite-difference techniques and particle codes such as SPH. Therefore neither technique is fully satisfactory for accretion disk simulations. This paper describes a new fully Lagrangian method designed to resolve these difficulties

Remote sensing as an aid to route evaluation for relocated Louisiana Highway 1

NASA aerial photography in the form of color infrared and color positive transparencies is used as an aid for evaluation of the route proposed for relocated Louisiana Highway 1, between LaRose and Golden Meadow, in South Louisiana

The Orbital Period of the Ultracompact Low-Mass X-Ray Binary 4U 1543--624

We report the discovery of the orbital period of the ultracompact low-mass X-ray binary (LMXB) 4U 1543-624 using time-resolved optical photometry taken with the 6.5-m Clay (Magellan II) telescope in Chile. The light curve in the Sloan r' band clearly shows a periodic, sinusoidal modulation at 18.2+-0.1 min with a fractional semiamplitude of 8%, which we identify as the binary period. This is the second shortest orbital period among all the known LMXBs, and it verifies the earlier suggestion of 4U 1543-624 as an ultracompact binary based on X-ray spectroscopic properties. The sinusoidal shape of the optical modulation suggests that it arises from X-ray heating of the mass donor in a relatively low-inclination binary, although it could also be a superhump oscillation in which case the orbital period is slightly shorter. If the donor is a C-O white dwarf as previously suggested, its likely mass and radius are around 0.03 M_sun and 0.03 R_sun, respectively. For conservative mass transfer onto a neutron star and driven by gravitational radiation, this implies an X-ray luminosity of 6.5X10^36 erg/s and a source distance of 7 kpc. We also discuss optical photometry of another LMXB, the candidate ultracompact binary 4U 1822-000. We detected significant optical variability on a time scale of about 90 min, but it is not yet clear whether this was due to a periodic modulation.Comment: 4 pages, accepted for publication in ApJ Letter

Evidence for Superhumps in the Radio Light Curve of Algol and a New Model for Magnetic Activity in Algol Systems

Extensive radio data of two Algol systems and two RS CVn binaries were re-analyzed. We found evidence for a new periodicity that we interpret as a superhump in Algol, in which it may have been expected according to its semi-detached nature and low binary mass ratio. This is the first detection of the superhump phenomenon in the radio and the first observation of superhumps in Algol systems. According to our result, the accretion disk in Algol precesses in spite of its non-Keplerian nature and therefore this phenomenon is not restricted to the classical Keplerian disks in compact binaries.We propose that in Algol systems with short orbital periods, the disk is magnetically active as well as the secondary star. The magnetic field in the disk originates from amplification of the seed field in the magnetized material transferred from the secondary. The disk and stellar fields interact with each other, with reconnection of the field lines causing flares and particle acceleration. Relativistic particles are trapped in the field and directed toward the polar regions of the secondary star because of the dipole structure of its magnetic field. Our proposed model for the magnetic activity in Algol systems provides a simple explanation to the observed properties of Algol in the radio wavelengths, and to the presence of quiescent gyrosynchrotron emission near the polar region of the secondary star, where electrons are difficult to be confined if the field lines are open as in normal single magnetic stars. We propose that the superhump variation in the radio is generated by enhanced reconnection when the elongated side of the elliptic disk is the closest to the cool star. This leads to flares and enhancement in particle acceleration and is manifested as stronger gyrosynchrotron radiation.Comment: 8 pages, 5 figures, ApJ, accepted, uses apjfonts.sty and emulateapj5.sty, full abstract in pape