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There are many human-robot interaction (HRI) tasks that are highly structured and follow a certain temporal sequence. Learning such tasks from demonstrations requires understanding the underlying rules governing the interactions. This involves identifying and generalizing the key spatial and temporal features of the task and capturing the high-level relationships among them. Despite its crucial role in sequential task learning, temporal reasoning is often ignored in existing learning from demonstration (LFD) research. This paper proposes a holistic LFD framework that learns the underlying temporal structure of sequential HRI tasks. The proposed Temporal-Reasoning-based LFD (TR-LFD) framework relies on an automated spatial reasoning layer to identify and generalize relevant spatial features, and a temporal reasoning layer to analyze and learn the high-level temporal structure of a HRI task. We evaluate the performance of this framework by learning a well-explored task in HRI research: robot-mediated autism intervention. The source code for this implementation is available at https://github.com/AssistiveRoboticsUNH/TR-LFD.

Self-supporting foils of aluminum oxide in the thickness range 100 to 300 nm were prepared by anodic oxidation of aluminum foil and subsequent dissolution of the unreacted aluminum. The foil thicknesses were measured by scanning electron microscopy. Using these foils, stopping cross sections of aluminum oxide for protons and deuterons were measured for particles in the energy range 0.90 to 2.50 MeV. These measured stopping cross sections are compared to other literature results and to the theoretical values as predicted by Bragg's Rule.

A new sample support film for small spot XRF analysis has been developed that improves detection limits by a factor of 10 over traditional polymer supports. The surface characteristics of this new film are excellent for retaining drops of sample solution in one place and allowing the solution to dry into a single spot A dimpling technique was developed to further aid in concentrating the evaporated samples to the prescribed spot size and position. The film showed good resistance to chemical attacfc from the solution, even some strong acids and bases. The detection limits achieved using micro sample XRF with the ultra thin sample support were sufficient to be a comparable alternative to ICP-MS and GFAAS for elemental analysis.

Widespread interest in light element analysis using XRF has stimulated the development of thin x-ray tube windows. Thinner windows enhance the soft x-ray output of the tube, which more efficiently excite the light elements in the sample. A computer program that calculates the effect of window thickness on light element sample fluorescence has been developed. The code uses an NIST algorithm to calculate the x-ray tube spectrum given various tube parameters such as beryllium window thickness, operating voyage, anode composition, and take-off angle. The interaction of the tube radiation with the sample matrix is modelled to provide the primary and secondary fluorescence from the sample. For x-rays in the energy region 30 - 1000 eV the mass attenuation coefficients were interpolated from the photo absorption data compilation of Henke, et al. The code also calculates the x-ray background due to coherent and incoherent scatter from the sample, as well as the contribution of such scatter to the sample fluorescence. Given the sample fluorescence and background the effect of tube window thickness on detection limits for light elements can be predicted.

A set of spectral analytic instruments has been developed for absolute intensity measurements in a spectral range of 1 - 600 a: (1) several modifications of grazing incidence spectrographs; (2) EUV monochromator- spectrometer with a constant angle of deviation; (3) focusing crystal von Hamos spectrometer using cylindrical mica and pyrolytic graphite crystals and a CCD linear array as a detector. These instruments are useful for plasma diagnostics, x-ray and EUV spectroscopy of laser-generated plasmas and capillary discharge plasmas, x-ray and EUV reflectometry, radiometry and x-ray fluorescence application.

The use of bent crystals with high integrated reflectivity in focusing crystal spectrometers (Johann and von Hamos schemes) is considered. It is shown that in a von Hamos scheme mosaic focusing takes place. Thus a mosaic crystal simultaneously provides high spectral resolution and high efficiency. Expressions for the mosaic focusing are obtained. Focusing mica and graphite crystal von Hamos spectrometers (radius of crystal curvature is 20 mm) are investigated: spectral and spatial resolution and absolute efficiency are measured in a spectral range of 2 - 2.6 angstroms using laser-produced plasma and iron isotope x-ray sources. The mica crystal spectrometer showed high spatial (up to 10 micrometers ) and spectral ((lambda) /(delta) (lambda) approximately 1000) resolution, whereas the graphite spectrometer showed very high efficiency (30 - 70 times higher than the mica crystal) and moderate spectral resolution ((lambda) /(delta) (lambda) approximately 500 - 750). In the latter case mosaic focusing is observed: spectral resolution is 10 - 15 times higher than spectral resolution determined by the mosaic spread of the crystal ((lambda) /(delta) (lambda) approximately 50). The results allow one to estimate a maximum efficiency for focusing crystal spectrometers. Prospects for using the von Hamos spectrometers for x-ray spectroscopy and x-ray fluorescence are considered.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Widespread interest in light element analysis using XRF has stimulated the development of thin x-ray tube windows. Thinner windows enhance the soft x-ray output of the tube, which more efficiently excite the light elements in the sample. A computer program that calculates the effect of window thickness on light element sample fluorescence has been developed. The code uses an NIST algorithm to calculate the x-ray tube spectrum given various tube parameters such as beryllium window thickness, operating voltage, anode composition, and take-off angle. The interaction of the tube radiation with the sample matrix is modelled to provide the primary and secondary fluorescence from the sample. For x-rays in the energy region 30 - 1000 eV the mass attenuation coefficients were interpolated from the photoabsorption data compilation of Henke, el al. The code also calculates the x-ray background due to coherent and incoherent scatter from the sample, as well as the contribution of such scatter to the sample fluorescence. Given the sample fluorescence and background the effect of tube window thickness on detection limits for light elements can be predicted. 17 refs., 3 figs., 2 tabs.

The electron field-emission properties of carbon nanotubes enable the fabrication of cold cathodes for a variety of vacuum device applications. The utilization of these cathodes is an attractive alternative for the replacement of thermionic or hot cathodes for generating X-rays. Miniature X-ray tubes have been fabricated using triode-style carbon nanotube- based cathodes. In this paper we report the results of characterization studies, such as beam current dependence on the control gate voltage. Also, results on focal spot measurements and electron-beam modeling allow the possibility of reducing focused spot sizes. Driving gate voltages below 1000 volts for easy pulsing has been achieved, and the extended lifetime data suggests that a regulated power supply would be ideal for a constant AC operation mode. The 1mm focal spot size achieved so far is suitable for most XRF applications.

An X-ray shielded test chamber has been designed and built that includes a CCD-pinhole camera and energy-dispersive silicon PIN-diode detector for spectrum collection. The use of this chamber is an innovative approach that allows rapid imaging of the electron beam spot on the anode, as well as the spectral characterization of the tube. The beamspot dimensions and location can be measured at several high-voltage settings to ensure stability. This setup allows monitoring spectral contamination lines, total output flux, and net target-peak intensity at the anode line. To ensure tube X-ray output stability a spotstability test is performed. Relative standard deviations of less than 1% are typical. Leakage current must be very low since operating conditions are typically less than 10 µA of emission current. In the case of arcing tubes the measurement of leakage current is problematic, as arcing will damage the measuring equipment. By using a resistor string and measuring the voltage drop across this string, it is possible to achieve a very sensitive current measurement while protecting the meter from high-voltage transients. Finally, the filament impedance is monitored as an indicator of the tube vacuum integrity and/or the tube high internal pressure.

This year, the National Institute of Mental Health (NIMH) launched a modest but potentially significant pilot program titled the Community Support Program (CSP). CSP is designed to improve services for one particularly vulnerable population—adult psychiatric patients whose disabilities are severe and persistent but for whom long-term skilled or semiskilled nursing care is inappropriate. Specifically, CSP involves contracts (not grants) between NIMH and State mental health agencies, many of whom will subcontract with local agencies for demonstration projects. To date, 19 States have been awarded CSP contracts amounting to a total of approximately $3.5 million for the first year's activities. Although the program is so new that little has been published about it, interpretations are beginning to appear in the press and the professional literature. The New York Times (February 7, 1978), for example, while emphasizing the need for Federal leadership to improve services to chronic patients, referred to the CSP initiative in an editorial as "belatedly pulled together" and "meager." Professional literature has viewed it more positively. A recent article in the Scientific American (Bassuk and Gerson 1978, p. 53), for example, highlighted the importance of the program in "the acknowledgment of the specific needs of the chronic severely disabled person," and "the willingness of the Federal government to accept more responsibility for the mentally ill." The APA Monitor (Herbert 1977, p. 4)

A multifaceted network of opportunities and services is required by mentally disabled adults living in the community; the challenge is to assure that client and community needs are comprehensively met, without interfering with individual rights or perpetuating needless dependence on formal services.