2,948 research outputs found
Design and mathematical analysis of a three-mirror X-ray telescope based on ATM S-056 X-ray telescope hardware
The mathematical design of the aspheric third mirror for the three-mirror X-ray telescope (TMXRT) is presented, along with the imaging characteristics of the telescope obtained by a ray trace analysis. The present design effort has been directed entirely toward obtaining an aspheric third mirror which will be compatible with existing S-056 paraboloidal-hyperboloidal mirrors. This compatability will facilitate the construction of a prototype model of the TMXRT, since it will only be necessary to fabricate one new mirror in order to obtain a working model
Vignetting characteristics of the S-056 X-ray telescope
A ray trace analysis of the vignetting characteristics of the S-056 X ray telescope is presented. The relative energy is calculated in the spot formed in the focal plane of the S-056 X ray telescope by an off axis point source at infinity for off axis angles of 0, 1, 2, ..., 35 arc minutes. At each off axis angle, the relative energies are evaluated using theoretical X ray reflectivity curves for wavelengths of 8.34 A, 17.57 A, and 27.39 A, and also using an experimental X ray reflectivity curve for 8.34 A. The effects of vignetting due purely to the geometry of the S-056 optical system are evaluated separately, as well as jointly with the effects of mirror reflectivity
Ray-trace analysis of glancing-incidence X-ray optical systems
The results of a ray-trace analysis of several glancing-incidence X-ray optical systems are presented. The object of the study was threefold. First, the vignetting characteristics of the S-056 X-ray telescope were calculated using experimental data to determine mirror reflectivities. Second, a small Wolter Type I X-ray telescope intended for possible use in the Geostationary Operational Environmental Satellite program was designed and ray traced. Finally, a ray-trace program was developed for a Wolter-Schwarzschild X-ray telescope
MSFC holographic correlation techniques facility study
The basic theory of the holographic correlation system is illustrated. The effect of translating the object distribution in the object plane when the hologram is illuminated is investigated. The effect of translating the object along the optical axis is discussed and preliminary results presented
Quadratic response theory for spin-orbit coupling in semiconductor heterostructures
This paper examines the properties of the self-energy operator in
lattice-matched semiconductor heterostructures, focusing on nonanalytic
behavior at small values of the crystal momentum, which gives rise to
long-range Coulomb potentials. A nonlinear response theory is developed for
nonlocal spin-dependent perturbing potentials. The ionic pseudopotential of the
heterostructure is treated as a perturbation of a bulk reference crystal, and
the self-energy is derived to second order in the perturbation. If spin-orbit
coupling is neglected outside the atomic cores, the problem can be analyzed as
if the perturbation were a local spin scalar, since the nonlocal spin-dependent
part of the pseudopotential merely renormalizes the results obtained from a
local perturbation. The spin-dependent terms in the self-energy therefore fall
into two classes: short-range potentials that are analytic in momentum space,
and long-range nonanalytic terms that arise from the screened Coulomb potential
multiplied by a spin-dependent vertex function. For an insulator at zero
temperature, it is shown that the electronic charge induced by a given
perturbation is exactly linearly proportional to the charge of the perturbing
potential. These results are used in a subsequent paper to develop a
first-principles effective-mass theory with generalized Rashba spin-orbit
coupling.Comment: 20 pages, no figures, RevTeX4; v2: final published versio
Orion Spacecraft MMOD Protection Design and Assessment
The Orion spacecraft will replace the Space Shuttle Orbiter for American and international partner access to the International Space Station by 2015 and, afterwards, for access to the moon for initial sorties and later for extended outpost visits as part of the Constellation Exploration Initiative. This work describes some of the efforts being undertaken to ensure that the Constellation Program, Orion Crew Exploration Vehicle design will meet or exceed the stringent micrometeoroid and orbital debris (MMOD) requirements set out by NASA when exposed to the environments encountered with these missions. This paper will provide a brief overview of the approaches being used to provide MMOD protection to the Orion vehicle and to assess the spacecraft for compliance to the Constellation Program s MMOD requirements
Biaxial strength characteristics of selected alloys in a cryogenic environment Final engineering report, 6 Jan. 1965 - 6 May 1966
Uniaxial and biaxial strength characteristics and mechanical properties of metallic sheet materials at cryogenic temperature
You Can’t Always Get What You Want: Using “Broken Lotteries” to Check the Validity of Charter School Evaluations using Matching Designs
We consider situations in which public charter school lotteries are neither universally conducted nor consistently documented. Such lotteries produce “broken” Randomized Control Trials, but provide opportunities to assess the internal validity of quasi-experimental research designs. Here, we present the results of a statewide charter school evaluation using a broad-based student matching evaluation design, and run two additional analyses using the charter application wait-lists as robustness checks. Our additional models, which address concerns of self-selection by using only charter applicants as matched comparison students, yield similar effect estimates and thus provide support for the use of matching designs in charter school evaluations
Wean Dairy Calves Early
Dairy calves can be weaned from milk at 1 month of age by feeding a palatable, nutritious starter. Here\u27s more about the early weaning program\u27s secret - getting the calves on starter at an early age
Crystal structures of two one-dimensional coordination polymers constructed from Mn2+ ions, chelating hexafluoro-acetylacetonate anions, and flexible bipyridyl bridging ligands
Original Russian Text © 2016 M. J. Plater, B. M. De Silva, M. R. St. J. Foreman, W. T. A. Harrison. The text was submitted by the authors in English. Zhurnal Strukturnoi Khimii, Vol. 57, No. 6, pp. 1230-1235, July-August, 2016.Peer reviewedPostprin
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