17,785 research outputs found
Design method for minimizing RF voltage breakdown
Research study was conducted and results were published. Using principles of similarity and minimum of experimental data, a number of universal curves have been constructed covering wide range of experimental parameters. Gases other than air, such as argon and carbon dioxide, also are included in study
Method for remotely sensing turbulence of planetary atmospheres
Based on variances of log-amplitude and phase fluctuations of radio occultation data received from orbital and fly-by missions, structure constant for Venusian planetary atmosphere has been estimated with high-confidence factor. Analysis indicates that effects of inhomogeneity, finite size, and superrefractivity of atmospheric turbulence cannot be ignored
Low loss dichroic plate
A low loss dichroic plate is disclosed for passing radiation within a particular frequency band and reflecting radiation outside of that frequency band. The dichroic plate is comprised of a configuration of dipole elements defined by slots formed in a conductive plate. The slots are dimensioned so as to pass radiation of a selected frequency and are shaped so as to minimize the relationship between that frequency and the tilt angle of the plate relative to the direction of radiation. The slots are arranged so as to minimize signal power loss due to cross polarization effects
Low-loss, circularly-polarized dichroic plate
Dichroic plate has orthogonally-disposed, loaded dipole apertures with their orientations arranged so as to cancel cross-coupling effects which would otherwise result in power loss to circularly polarized signal
Effects of turbulence in the atmosphere of Venus on Pioneer Venus radio, phase 2
Two problems related to the effects of turbulence in the atmosphere of Venus on the Pioneer entry probe radio link were studied. In the first problem, the cross correlation between the log amplitude and phase fluctuations of the Pioneer Venus communications link is examined. Data show that for fluctuation frequencies above approximately 1 Hz there is little or no correlation. For frequencies below this region the correlation is weak and the square root of the coherence has a peak value close to 0.65. The second problem consists of interferring turbulence characteristics of the Venus atmosphere from the Mariner 5 phase fluctuations. Data show that with the data processing techniques developed and currently available, the phase error due to oscillator drift, assumed trajectory delay, and spline curve fit exceed the turbulence induced fluctuations. Results show that it is not possible to interfere with the turbulence characteristics from Mariner 5 phase fluctuations
Evaluation of Half-metallic Antiferromagnetism in CrFeO ({}=La, Sr
The nearly well-ordered double perovskite LaCrFeO has been
synthesized recently. Contrary to previous theoretical predictions, but in
agreement with experimental observations, our first principle calculations
indicate an insulating ferrimagnet LaCrFeO with antialigned S=3/2
Cr and S=5/2 Fe ions,using the local spin density approximation
(LSDA), a correlated band theory LDA+U, and a semilocal functional modified
Becke-Johnson method. Additionally, we investigated the double perovskite
SrCrFeO, which is as yet unsynthesized. In LSDA calculations, this
system shows formally tetravalent Cr and Fe ions both having antialigned =1
moments, but is a simple metal. Once applying on-site Coulomb repulsion U on
both Cr and Fe ions, this system becomes half-metallic and the moment of Fe is
substantially reduced, resulting in zero net moment. These results are
consistent with our fixed spin moment studies. Our results suggest a precisely
compensated half-metallic SrCrFeO.Comment: 7 page
Plane-stress, elastic-plastic states in the vicinity of crack tips
Plane stress analysis of elastic-plastic states in vicinity of straight crack tip in thin plat
Closing the Wedge: Search Strategies for Extended Higgs Sectors with Heavy Flavor Final States
We consider search strategies for an extended Higgs sector at the
high-luminosity LHC14 utilizing multi-top final states. In the framework of a
Two Higgs Doublet Model, the purely top final states () are
important channels for heavy Higgs bosons with masses in the wedge above
and at low values of , while a final state is most
relevant at moderate values of . We find, in the
channel, with , that both single and 3 lepton final
states can provide statistically significant constraints at low values of for as high as GeV. When systematics on the
background are taken into account, however, the 3 lepton final state is more
powerful, though the precise constraint depends fairly sensitively on lepton
fake rates. We also find that neither nor final states
provide constraints on additional heavy Higgs bosons with couplings to tops
smaller than the top Yukawa due to expected systematic uncertainties in the background.Comment: Added a Fig. and updated references. Matches journal version. 31
pages, 11 figure
Scattering of Pruppacher-Pitter raindrops at 30 GHz
Optimum design of modern ground-satellite communication systems requires the knowledge of rain-induced differential attenuation, differential phase shift, and cross polarization factors. Different available analytical techniques for raindrop scattering problems were assessed. These include: (1) geometrical theory of diffraction; (2) method of moment; (3) perturbation method; (4) point matching methods; (5) extended boundary condition method; and (6) global-local finite element method. The advantages and disadvantages of each are listed. The extended boundary condition method, which was determined to yield the most scattering results, is summarized. The scattered fields for Pruppacher-Pitter raindrops with sizes ranging from 0.5 mm to 3.5 mm at 20 C and at 30 GHz for several incidence angles are tabulated
Modeling of composite beams and plates for static and dynamic analysis
A rigorous theory and corresponding computational algorithms was developed for a variety of problems regarding the analysis of composite beams and plates. The modeling approach is intended to be applicable to both static and dynamic analysis of generally anisotropic, nonhomogeneous beams and plates. Development of a theory for analysis of the local deformation of plates was the major focus. Some work was performed on global deformation of beams. Because of the strong parallel between beams and plates, the two were treated together as thin bodies, especially in cases where it will clarify the meaning of certain terminology and the motivation behind certain mathematical operations
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