Computer program to assess impact of fatigue and fracture criteria on weight and cost of transport aircraft

A preliminary design analysis tool for rapidly performing trade-off studies involving fatigue, fracture, static strength, weight, and cost is presented. Analysis subprograms were developed for fatigue life, crack growth life, and residual strength; and linked to a structural synthesis module which in turn was integrated into a computer program. The part definition module of a cost and weight analysis program was expanded to be compatible with the upgraded structural synthesis capability. The resultant vehicle design and evaluation program is named VDEP-2. It is an accurate and useful tool for estimating purposes at the preliminary design stage of airframe development. A sample case along with an explanation of program applications and input preparation is presented

Investigation of the enhanced spatial density of submicron lunar ejecta between L values 1.2 and 3.0 in the earth's magnetosphere: Theory

Initial results from the measurement conducted by the dust particle experiment on the lunar orbiting satellite Lunar Explorer 35 (LE 35) were reported with the data interpreted as indicating that the moon is a significant source of micrometeroids. Primary sporadic and stream meteoroids impacting the surface of the moon at hypervelocity was proposed as the source of micron and submicron particles that leave the lunar craters with velocities sufficient to escape the moon's gravitational sphere of influence. No enhanced flux of lunar ejecta with masses greater than a nanogram was detected by LE 35 or the Lunar Orbiters. Hypervelocity meteoroid simulation experiments concentrating on ejecta production combined with extensive analyses of the orbital dynamics of micron and submicron lunar ejecta in selenocentric, cislunar, and geocentric space have shown that a pulse of these lunar ejecta, with a time correlation relative to the position of the moon relative to the earth, intercepts the earth's magnetopause surface (EMPs). As shown, a strong reason exists for expecting a significant enhancement of submicron dust particles in the region of the magnetosphere between L values of 1.2 and 3.0. This is the basis for the proposal of a series of experiments to investigate the enhancement or even trapping of submicron lunar ejecta in this region. The subsequent interaction of this mass with the upper-lower atmosphere of the earth and possible geophysical effects can then be studied

Analysis of a distributed fiber-optic temperature sensor using single-photon detectors

We demonstrate a high-accuracy distributed fiber-optic temperature sensor using superconducting nanowire single-photon detectors and single-photon counting techniques. Our demonstration uses inexpensive single-mode fiber at standard telecommunications wavelengths as the sensing fiber, which enables extremely low-loss experiments and compatibility with existing fiber networks. We show that the uncertainty of the temperature measurement decreases with longer integration periods, but is ultimately limited by the calibration uncertainty. Temperature uncertainty on the order of 3 K is possible with spatial resolution of the order of 1 cm and integration period as small as 60 seconds. Also, we show that the measurement is subject to systematic uncertainties, such as polarization fading, which can be reduced with a polarization diversity receiver

Optical conductivity for a dimer in the Dynamic Hubbard model

The Dynamic Hubbard Model represents the physics of a multi-band Hubbard model by using a pseudo-spin degree of freedom to dynamically modify the on-site Coulomb interaction. Here we use a dimer system to obtain analytical results for this model. The spectral function and the optical conductivity are calculated analytically for any number of electrons, and the distribution of optical spectral weight is analyzed in great detail. The impact of polaron-like effects due to overlaps between pseudo-spin states on the optical spectral weight distribution is derived analytically. Our conclusions support results obtained previously with different models and techniques: holes are less mobile than electrons.Comment: 11 pages, 4 figure

Engage D2.1 Communication plan, website, and visual identity material

The purpose of this document, Deliverable 2.1, is to describe the dissemination plan, dissemination policy and initial dissemination products of the SESAR 2020 Exploratory Research action Engage, taking into account its specifications and the target audience. The following pages document the corresponding tasks involved in D2.1

Coordination of passive systems under quantized measurements

In this paper we investigate a passivity approach to collective coordination and synchronization problems in the presence of quantized measurements and show that coordination tasks can be achieved in a practical sense for a large class of passive systems.Comment: 40 pages, 1 figure, submitted to journal, second round of revie

Investigation of infrared phonon modes in multiferroic single-crystal FeTe2_{2}O5_{5}Br

Reflection and transmission as a function of temperature (5--300 K) have been measured on single crystals of the multiferroic compound FeTe$_{2}$O$_{5}$Br utilizing light spanning the far infrared to the visible portions of the electromagnetic spectrum. The complex dielectric function and optical properties were obtained via Kramers-Kronig analysis and by fits to a Drude-Lortentz model. Analysis of the anisotropic excitation spectra via Drude-Lorentz fitting and lattice dynamical calculations have lead to the observation of all 52 IR-active modes predicted in the $ac$ plane and 43 or the 53 modes predicted along the b axis of the monoclinic cell. Assignments to groups (clusters) of phonons have been made and trends within them are discussed in light of our calculated displacement patterns.Comment: 9 pages, 7 figure

Phonon anomaly at the charge ordering transition in 1T-TaS2

The infrared reflectance of the transition metal chalcogenide 1T-TaS2 has been measured at temperatures from 30K to 360K over 30-45,000cm^-1 (4meV-5.5eV). The optical conductivity was obtained by Kramers-Kronig analysis. At 360K only modest traces of the phonon lines are noticeable. The phonon modes are followed by a pseudogap-like increase of the optical conductivity, with direct optical transitions observed at frequencies above 1eV. As the temperature decreases, the low frequency conductivity also decreases, phonon modes become more pronounced and pseudogap develops into a gap at 800cm^-1 (100meV). We observe an anomalous frequency dependence of the 208cm^-1 infrared-active phonon mode. This mode demonstrates softening as the temperature decreases below the 180K metal-to-insulator transition. The same mode demonstrates strong hysteresis of the frequency and linewidth changes, similar in its temperature behavior to the hysteresis in the dc-resistivity. We discuss a possible relation of the observed softening of the mode to the structural changes associated with the metal-to-insulator transition.Comment: 7 pages, 4 figures, 1 table; corrected typo