1,606 research outputs found
Modal Test of the NASA Mobile Launcher at Kennedy Space Center
The NASA Mobile Launcher (ML), located at Kennedy Space Center (KSC), has recently been modified to support the launch of the new NASA Space Launch System (SLS). The ML is a massive structureconsisting of a 345-foot tall tower attached to a two-story base, weighing approximately 10.5 million poundsthat will secure the SLS vehicle as it rolls to the launch pad on a Crawler Transporter, as well as provide a launch platform at the pad. The ML will also provide the boundary condition for an upcoming SLS Integrated Modal Test (IMT). To help correlate the ML math models prior to this modal test, and allow focus to remain on updating SLS vehicle models during the IMT, a ML-only experimental modal test was performed in June 2019. Excitation of the tower and platform was provided by five uniquely-designed test fixtures, each enclosing a hydraulic shaker, capable of exerting thousands of pounds of force into the structure. For modes not that were not sufficiently excited by the test fixture shakers, a specially-designed mobile drop tower provided impact excitation at additional locations of interest. The response of the ML was measured with a total of 361 accelerometers. Following the random vibration, sine sweep vibration, and modal impact testing, frequency response functions were calculated and modes were extracted for three different configurations of the ML in 0 Hz to 12 Hz frequency range. This paper will provide a case study in performing modal tests on large structures by discussing the Mobile Launcher, the test strategy, an overview of the test results, and recommendations for meeting a tight test schedule for a large-scale modal test
Early childhood lung function is a stronger predictor of adolescent lung function in cystic fibrosis than early Pseudomonas aeruginosa infection
Pseudomonas aeruginosa has been suggested as a major determinant of poor pulmonary outcomes in cystic fibrosis (CF), although other factors play a role. Our objective was to investigate the association of early childhood Pseudomonas infection on differences in lung function in adolescence with CF
Solving Einstein's Equations With Dual Coordinate Frames
A method is introduced for solving Einstein's equations using two distinct
coordinate systems. The coordinate basis vectors associated with one system are
used to project out components of the metric and other fields, in analogy with
the way fields are projected onto an orthonormal tetrad basis. These field
components are then determined as functions of a second independent coordinate
system. The transformation to the second coordinate system can be thought of as
a mapping from the original ``inertial'' coordinate system to the computational
domain. This dual-coordinate method is used to perform stable numerical
evolutions of a black-hole spacetime using the generalized harmonic form of
Einstein's equations in coordinates that rotate with respect to the inertial
frame at infinity; such evolutions are found to be generically unstable using a
single rotating coordinate frame. The dual-coordinate method is also used here
to evolve binary black-hole spacetimes for several orbits. The great
flexibility of this method allows comoving coordinates to be adjusted with a
feedback control system that keeps the excision boundaries of the holes within
their respective apparent horizons.Comment: Updated to agree with published versio
An ISS Small-Gain Theorem for General Networks
We provide a generalized version of the nonlinear small-gain theorem for the
case of more than two coupled input-to-state stable (ISS) systems. For this
result the interconnection gains are described in a nonlinear gain matrix and
the small-gain condition requires bounds on the image of this gain matrix. The
condition may be interpreted as a nonlinear generalization of the requirement
that the spectral radius of the gain matrix is less than one. We give some
interpretations of the condition in special cases covering two subsystems,
linear gains, linear systems and an associated artificial dynamical system.Comment: 26 pages, 3 figures, submitted to Mathematics of Control, Signals,
and Systems (MCSS
A Characterization of Scale Invariant Responses in Enzymatic Networks
An ubiquitous property of biological sensory systems is adaptation: a step
increase in stimulus triggers an initial change in a biochemical or
physiological response, followed by a more gradual relaxation toward a basal,
pre-stimulus level. Adaptation helps maintain essential variables within
acceptable bounds and allows organisms to readjust themselves to an optimum and
non-saturating sensitivity range when faced with a prolonged change in their
environment. Recently, it was shown theoretically and experimentally that many
adapting systems, both at the organism and single-cell level, enjoy a
remarkable additional feature: scale invariance, meaning that the initial,
transient behavior remains (approximately) the same even when the background
signal level is scaled. In this work, we set out to investigate under what
conditions a broadly used model of biochemical enzymatic networks will exhibit
scale-invariant behavior. An exhaustive computational study led us to discover
a new property of surprising simplicity and generality, uniform linearizations
with fast output (ULFO), whose validity we show is both necessary and
sufficient for scale invariance of enzymatic networks. Based on this study, we
go on to develop a mathematical explanation of how ULFO results in scale
invariance. Our work provides a surprisingly consistent, simple, and general
framework for understanding this phenomenon, and results in concrete
experimental predictions
A hisztériával kapcsolatos diskurzusok tanulságai a szomatizációs jelenségek és a betegségmagatartás megértéséhez = The relevance of discourses about hysteria in the understanding of somatization phenomena and illness behaviour
Napjainkban a magatartástudományok kĂ©pviselĹ‘inek egyszerre kell számolniuk a betegsĂ©gekkel kapcsolatos bizonyosság Ă©s tudás konfliktusait elĹ‘hĂvĂł medikalizáciĂłs-technicizáciĂłs orvostudományi tendenciákkal Ă©s a társadalomtudományok ezekre reflektálĂł, kritikai Ă©s „posztmodern” megközelĂtĂ©seivel. EbbĹ‘l adĂłdĂłan igen fontos kihĂváskĂ©nt jelentkezik az interdiszciplináris megközelĂtĂ©s szĂĽksĂ©gessĂ©ge. KĂĽlönösen Ăgy van ez a nehezen definiálhatĂł betegsĂ©gek - a szomatizáciĂłs Ă©s pszichoszomatikus zavarok - esetĂ©ben, ahol a betegsĂ©gmagatartás gyakorlati problĂ©mái, továbbá a tĂĽnetek, a diagnĂłzisok Ă©s a szenvedĂ©s „valĂłdiságának” episztemolĂłgiai kĂ©rdĂ©sei egyszerre vannak jelen. Az utĂłbbi másfĂ©l Ă©vtized kritikai társadalomtudományi kutatásaiban rendkĂvĂĽli figyelmet kapott a szomatizáciĂłs zavarok Ă©s a klasszikus pszichoszomatikus kĂłrkĂ©pek elĹ‘djĂ©nek számĂtĂł hisztĂ©ria kĂ©rdĂ©sköre. A tanulmány a szakmai Ă©s laikus szĂłhasználatban nem hivatalosan máig tovább Ă©lĹ‘ betegsĂ©ggel kapcsolatos társadalomtudományi Ă©s orvosi megközelĂtĂ©sek közĂĽl azokat mutatja be, amelyek szempontokkal szolgálhatnak a szomatizáciĂłs Ă©s pszichoszomatikus kĂłrkĂ©pek, valamint a velĂĽk kapcsolatos Ă©rzelmi Ă©s viselkedĂ©ses reakciĂłk elemzĂ©sĂ©hez Ă©s megĂ©rtĂ©sĂ©hez
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