Biography:

In the past S.M. Seltzer has collaborated on articles with M.J. Berger and K.C. Duvall. One of their most recent publications is Bremsstrahlung in the atmosphere☆. Which was published in journal Journal of Atmospheric and Terrestrial Physics.

More information about S.M. Seltzer research including statistics on their citations can be found on their Copernicus Academic profile page.

S.M. Seltzer's Articles: (8)

Bremsstrahlung in the atmosphere☆

AbstractCalculations are described pertaining to the emission of bremsstrahlung by electrons in the upper atmosphere and the penetration of this radiation to atmospheric depths of 3–10 g cm−2 where it can be measured by balloon-borne detectors. The calculations take into account the multiple scattering and slowing down of electrons, and the multiple Compton scattering and photoelectric absorption of bremsstrahlung photons. Numerical data have been generated for electron beams incident onto the atmosphere with energies between 20 keV and 2 MeV, assuming wide-area precipitation and an incident angular distribution isotropic over the downward hemisphere. The results relate the number and energy spectrum of the incident electrons to the bremsstrahlung flux spectrum at balloon heights. The interpretation of some observed bremsstrahlung flux spectra is attempted.

Enhancing simulation efficiency with analytical tools☆

AbstractSome means of combining both computer simulation and analytical techniques are described to mutually enhance their efficiency as design tools and to motivate those involved in engineering design. To consider using such combinations in the included example, the parameter plane stability analysis technique is described briefly and extended beyond that reported in the literature. To increase its utility (through a simple set of recursive formulas) and its applicability (through the portrayal of the effect of varying the sampling period of the computer), the numerical values that were rapidly selected by analysis were needed. This obviated the need for “cut-and-try” methods to choose the numerical values, thereby saving both time and computer utilization.

The development of a 6 to 7 MeV photon field for instrument calibration☆

AbstractA photon source has been developed at the National Bureau of Standards to measure the response of radiological survey instruments to high-energy photons. The 19F(p, αγ)16 O reaction has been used to produce a 6 to 7 MeV photon field with a fairly uniform photon flux density of approximately 3 × 103 cm−2 s−1 at one meter from the source. The photon flux density is obtained from measurements with a 3 × 3 inch2 Nal detector whose absolute response has been determined by a Monte Carlo calculation. The spectral characteristics of the high-energy photons have been determined from measurements with a large volume high purity germanium detector. The absorbed dose rate to water was measured with LiF thermoluminescent dosimeters (TLDs) at several depths in a 30 × 30 × 30 cm3 Lucite phantom. It is planned to compare absorbed dose determinations from the TLD measurements with those computed from spectral measurements. The response of six commercial radiological survey instruments has been measured behind various thicknesses of plastic absorber. The results indicate that approximately 2.5 cm of plastic in front of these instruments is sufficient to discriminate against the associated high-energy electron contamination.

DYNAMICS AND CONTROL OF FLEXIBLE AEROSPACE STRUCTURES

AbstractThe dynamics and control of flexible aerospace structures exercises many of the engineering disciplines. This plenary paper sets forth the importance of clearly establishing the mission and performance requirements of the flexible aerospace structure. Means of developing a system model are described, along with model reduction techniques. Several control system design methods are then discussed. Techniques for estimating and verifying system performance are described. Examples of existing techniques and facilities are set forth.

A POINTING AND CONTROL ARCHITECTURE FOR LARGE OPTICAL AEROSPACE SYSTEMS

AbstractImportant new advances in laser optics and recent space pointing demonstrations have enabled the United States Strategic Defense Initiative Organization (SDIO) to propose control strategies for large space based laser systems which utilize existing technologies and approaches. System performance, which has always been stressing from a control perspective, is now apparently within the state-of-the-art. The objective of this paper is to explain the nature of the technology advances and examine the control system implications for improving the feasibility and performance of systems such as large Space Based Laser platforms.

Images of soft materials: a 3D visualization of interior of the sample in terms of attenuation coefficient

AbstractImages of soft materials are obtained using image intensifier based X-ray system (Rao et al., Nucl. Instr. and Meth. A 437 (1999) 141). The interior of the soft material is visualized using the novel software in order to know the distribution of attenuation coefficient in terms of density. The novel software is based mainly on graphical library and applicable to several operating systems without any change. It can be applied to several applications starting from biomedical to industries, for example, quality control. The results for walnut and brew tooth are presented as a set of images from the internal parts of the sample. A description of the principal parameters required for tomographic visualization is given and some results based on this technique are reported and discussed.

A Pointing and Control Architecture for Large Optical Aerospace Systems

AbstractImportant new advances in laser optics and recent space pointing demonstrations have enabled the United States Strategic Defense Initiative Organization (SDIO) to propose control strategies for large space based laser systems which utilize existing technologies and approaches. System performance, which has always been stressing from a control perspective, is now apparently within the state-of-the-art. The objective of this paper is to explain the nature of the technology advances and examine the control system implications for improving the feasibility and performance of systems such as large Space Based Laser platforms.

Stabilizing a Spinning Skylab

AbstractThis paper presents the results of a study of the dynamics of a spinning Skylab space station. The stability of motion of several simplified models with flexible appendages was investigated. A digital simulation model that more accurately portrays the complex Skylab vehicle is described, and simulation results are compared with analytically derived results.

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