The use of model-based test requirements throughout the productlife cycle

Test requirements, which are generally collected in multiple disparate formats throughout the life cycle of an electronic product, could be used in various applications that reduce test and development cycle times and increase the confidence in the final test program. Unfortunately, test requirements are seldom captured in a consistent format that may be processed by a computer, thus eliminating the possibility of using such requirements in an engineering application. Additionally, such an approach disallows test requirements captured in one segment of the product life cycle to be reused in subsequent life cycle stages. This paper describes a model-based methodology, specifically the Test Requirements Model (TeRM), which can be shown to facilitate the transfer of test-related product information between various stages of the life cycle. This transportability, in conjunction with an exchange format that can be processed by a computer, permits test requirement information to support value-added applications in the engineering process throughout the life cycle of a product     

The high-LET radiation component measured during the EUROMIR-94 mission.

Stacks of CR-39 plastic nuclear track detectors were mounted inside the MIR-station during the EUROMIR-94-mission. We present LET-spectra determined separately for long range cosmic ray heavy ions and for short range target fragments produced in nuclear interactions of cosmic rays and measured charge distributions for relativistic and stopping particles.     

Pade approximations to matched filter amplitude probabilityfunctions

Performance analysis of echolocation systems requires the probability density function (pdf) or survival function of a matched filter output. A method is presented to derive approximations to these functions using a Pade approximation to their associated characteristic function (CF). The method is based on the Hankel transform. It allows computation of detection probabilities when the matched filter responses to clutter and a target are separately known. Several numerical examples are presented     

Source processes in the high-latitude ionosphere

Space Science Reviews -     

Plasma transfer processes at the magnetopause

Space Science Reviews -     

A robust exponential mixture detector applied to radar

Exponential mixture probability density functions (pdfs) are shown to be useful models of radar sea clutter. The variability of certain parameters leads to estimation error and degradation in the performance of detection algorithms derived from this model. Robust implementations are introduced by assuming that parameters are known within certain intervals and selecting values to prevent an excessive number of false alarms. An empirical study demonstrates an average 6-9 dB gain in comparison with a constant false-alarm rate (CFAR) processor     

Velocity Shear Induced Phenomena in Solar Atmosphere

We present a brief overview of the probable velocity-shear induced phenomena in solar plasma flows. Shear-driven MHD wave oscillations may be the needed mechanism for the generation of solar Alfvén waves, for the transmission of fast waves through the transition region, and for the acceleration of the solar wind. This revised version was published online in June 2006 with corrections to the Cover Date.     

The Extinct Radionuclide Timescale of the Early Solar System

The tendency of iodine to be mobilised during secondary processing is reflected both in the presence of ¹²⁹Xe_XS in secondary minerals and in the bulk ¹²⁹Xe_XS/I ratios in meteorites. Comparison of absolute ages derived through calibration of chronometers based on ¹²⁹Xe, ⁵³Mn and ²⁶Al against the Pb-Pb system yields a plausible timescale for the early solar system. In this system, the earliest chondrule ages are most readily interpreted as representing formation after the beginning of parent body processing. This revised version was published online in June 2006 with corrections to the Cover Date.     

Microwave Azimuth Measuring System

A breadboard microwave pointing device (ElectroTransit) has been designed, fabricated, and tested. The device and accompanying RF sources comprise a portable, battery-operated, azimuth angle measuring system with application in surveying, mapping, and geodesy, and for conducting basic research in tropospheric propagation and turbulence studies. The angle measuring sensor combines a Ka-band interferometer with an optical theodolite to provide two modes of pointing. Azimuth angle can be read directly to 0.1 arc-second. Preliminary tests on the interferometer show a pointing repeatability on the order of two arc-seconds, three sigma, when tropospheric turbulence is minimum and a mean absolute error of less than 10 arc-seconds, three sigma, compared with first-order optical standards. This paper describes the design, fabrication, and testing of this extremely precise instrumentation.     

Utilization of CAM,CAF, MAX,and FAX for space radiation analyses using HZETRN

To estimate astronaut health risk due to space radiation, one must have the ability to calculate various exposure-related quantities that are averaged over specific organs and tissue types. Such calculations require computational models of the ambient space radiation environment, particle transport, nuclear and atomic physics, and the human body. While significant efforts have been made to verify, validate, and quantify the uncertainties associated with many of these models and tools, relatively little work has focused on the uncertainties associated with the representation and utilization of the human phantoms. In this study, we first examine the anatomical properties of the Computerized Anatomical Man (CAM), Computerized Anatomical Female (CAF), Male Adult voXel (MAX), and Female Adult voXel (FAX) models by comparing the masses of various model tissues used to calculate effective dose to the reference values specified by the International Commission on Radiological Protection (ICRP). The MAX and FAX tissue masses are found to be in good agreement with the reference data, while major discrepancies are found between the CAM and CAF tissue masses and the reference data for almost all of the effective dose tissues. We next examine the distribution of target points used with the deterministic transport code HZETRN (High charge (Z) and Energy TRaNsport) to compute mass averaged exposure quantities. A numerical algorithm is presented and used to generate multiple point distributions of varying fidelity for many of the effective dose tissues identified in CAM, CAF, MAX, and FAX. The point distributions are used to compute mass averaged dose equivalent values under both a galactic cosmic ray (GCR) and solar particle event (SPE) environment impinging isotropically on three spherical aluminum shells with areal densities of 0.4 g/cm², 2.0 g/cm², and 10.0 g/cm². The dose equivalent values are examined to identify a recommended set of target points for each of the tissues and to further assess the differences between CAM, CAF, MAX, and FAX. It is concluded that the previously published CAM and CAF point distributions were significantly under-sampled and that the set of point distributions presented here should be adequate for future studies involving CAM, CAF, MAX, or FAX. It is also found that the errors associated with the mass and location of certain tissues in CAM and CAF have a significant impact on the mass averaged dose equivalent values, and it is concluded that MAX and FAX are more accurate than CAM and CAF for space radiation analyses.