The far field diffraction pattern for corner reflectors with complex reflection coefficients

The far field diffraction pattern of a geometrically perfect corner reflector is examined analytically for normally incident monochromatic light. The states of polarization and the complex amplitudes of the emerging light are expressed through transformation matrices in terms of those of the original incident light for each sextant of the face in a single coordinate system. The analytic expression of the total diffraction pattern is obtained for a circular face. This expression consists of three component functions in addition to the basic Airy function. The coefficient of each function is expressed in terms of complex coefficients of reflectance of the reflecting surface. Some numerical results for different reflecting surfaces, including total internal reflection, are presented. The iso-intensity contours of the diffraction pattern evaluated from the analytical expressions for an uncoated solid corner reflector are also presented along with the photographs of the pattern

Shuttle time and frequency transfer experiment

A proposed space shuttle experiment to demonstrate techniques for global high precision comparison of clocks and primary frequency standards is described. The experiment, using transmitted microwave and pulsed laser signals, compared a hydrogen maser clock onboard the space shuttle with a clock in a ground station in order to demonstrate time transfer with accuracies of 1 nsec or better and frequency comparison at the 10 to the -14th power accuracy level

Identification Decisions: Who is the Most Consistent?

This research was published by the KU Center for Research on Learning, formerly known as the University of Kansas Institute for Research in Learning Disabilities.This study was designed to: (a) examine the type of judgments on LD characteristics rendered by multidisciplinary team members and (b) explore which of the groups typically represented on a staffing team was most homogeneous in making decisions on LD students. The consistency of judgment among groups were comparable when making judgments on LD and non-LD characteristics. Thus, the findings were supportive of the multidisciplinary approach to identification and evaluation of LD children and youth

The Homogeneity of Identifaction Decisions by Different Groups on LD Adolescents

This research was published by the KU Center for Research on Learning, formerly known as the University of Kansas Institute for Research in Learning Disabilities.Three related studies were designed to address some key issues confronting the learning disability field concerning the identification of learning disabled adolescents. The first study (Research Report No. 9) addressed the question of which group(s) of professionals or parents make the most homogeneous identification decisions on learning disabilities' criteria. In the second study, (Research Report No. 10) the temporal and interscorer reliability as well as the construct and content validity of the Modified Component Disability Instrument was investigated. The reliability and validity of the Modified Component Disability Checklist and Secondary Test battery were investigated in the third study (Research Report No. 11)

Identification of Learning Disabled Adolescents: A Bayesian Approach

This research was published by the KU Center for Research on Learning, formerly known as the University of Kansas Institute for Research in Learning Disabilities.The identification of learning disabled adolescents for program placement is a major concern of school personnel. The identification model discussed in this article addresses an array of problems associated with identification of LD populations. The Bayesian approach is an alternative to traditional methods that rely primarily on psychometric data or classroom/clinical observation for identification decisions

Bayesian Screening Procedure for Identification of Learning Disabled Adolescents: Administration, Scoring, and Interpretation

This research was published by the KU Center for Research on Learning, formerly known as the University of Kansas Institute for Research in Learning Disabilities.The Secondary Learning Disabilities Form of the Screening Procedure is described, and procedures for administration and scoring are detailed. In addition, interpretation guidelines are presented. Both the Revised Checklist of Academic Problems (Teacher Checklist) and the Self-Bating Student Checklist are discussed

Twin Ice Cores from Greenland Reveal History of Climate Change, More

Two projects conducted from 1989 to 1993 collected parallel ice cores—just 30 km apart— from the central part of the Greenland ice sheet. Each core is more than 3 km deep and extends back 110,000 years. In short, the ice cores tell a clear story: humans came of age agriculturally and industrially during the most stable climatic regime recorded in the cores. Change—large, rapid, and global—is more characteristic of the Earth\u27s climate than is stasis

High-accuracy global time and frequency transfer with a space-borne hydrogen maser clock

A proposed system for high-accuracy global time and frequency transfer using a hydrogen maser clock in a space vehicle is discussed. Direct frequency transfer with a accuracy of 10 to the minus 14th power and time transfer with an estimated accuracy of 1 nsec are provided by a 3-link microwave system. A short pulse laser system is included for subnanosecond time transfer and system calibration. The results of studies including operational aspects, error sources, data flow, system configuration, and implementation requirements for an initial demonstration experiment using the Space Shuttle are discussed

A continuum model (PSUMEL1) of ice mélange and its role during retreat of the Antarctic Ice Sheet

Rapidly retreating thick ice fronts can generate large amounts of mélange (floating ice debris), which may affect episodes of rapid retreat of Antarctic marine ice. In modern Greenland fjords, mélange provides substantial back pressure on calving ice faces, which slows ice front calving rates. On the much larger scales of West Antarctica, it is unknown if mélange could clog seaways and provide enough back pressure to act as a negative feedback slowing retreat. Here we describe a new mélange model, using a continuum-mechanical formulation that is computationally feasible for long-term continental Antarctic applications. It is tested in an idealized rectangular channel and calibrated very basically using observed modern conditions in Jakobshavn fjord, West Greenland. The model is then applied to drastic retreat of Antarctic ice in response to warm mid-Pliocene climate. With mélange parameter values that yield reasonable modern Jakobshavn results, Antarctic marine ice still retreats drastically in the Pliocene simulations, with little slowdown despite the huge amounts of mélange generated. This holds both for the rapid early collapse of West Antarctica and for later retreat into major East Antarctic basins. If parameter values are changed to make the mélange much more resistive to flow, far outside the range for reasonable Jakobshavn results, West Antarctica still collapses and retreat is slowed or prevented only in a few East Antarctic basins.</p

Evaluation of thermal data for geologic applications

Sensitivity studies using thermal models indicated sources of errors in the determination of thermal inertia from HCMM data. Apparent thermal inertia, with only simple atmospheric radiance corrections to the measured surface temperature, would be sufficient for most operational requirements for surface thermal inertia. Thermal data does have additional information about the nature of surface material that is not available in visible and near infrared reflectance data. Color composites of daytime temperature, nighttime temperature, and albedo were often more useful than thermal inertia images alone for discrimination of lithologic boundaries. A modeling study, using the annual heating cycle, indicated the feasibility of looking for geologic features buried under as much as a meter of alluvial material. The spatial resolution of HCMM data is a major limiting factor in the usefulness of the data for geologic applications. Future thermal infrared satellite sensors should provide spatial resolution comparable to that of the LANDSAT data