2,980 research outputs found
Constitutional Law - Conscientious Objectors - First Amendment Religion Clauses Require Grant of Exemption from Draft Based on Personal Moral Objection to Service in Vietnam. United States v. Sisson (D. Mass. 1969)
This recent case discusses United States v. Sisson (D. Mass. 1969)
Analysis and design of a capsule landing system and surface vehicle control system for Mars exploration
Problems related to the design and control of an autonomous rover for the purpose of unmanned exploration of the planets were considered. Building on the basis of prior studies, a four wheeled rover of unusual mobility and maneuverability was further refined and tested under both laboratory and field conditions. A second major effort was made to develop autonomous guidance. Path selection systems capable of dealing with relatively formidable hazard and terrains involving various short range (1.0-3.0 meters), hazard detection systems using a triangulation detection concept were simulated and evaluated. The mechanical/electronic systems required to implement such a scheme were constructed and tested. These systems include: laser transmitter, photodetectors, the necessary data handling/controlling systems and a scanning mast. In addition, a telemetry system to interface the vehicle, the off-board computer and a remote control module for operator intervention were developed. Software for the autonomous control concept was written. All of the systems required for complete autonomous control were shown to be satisfactory except for that portion of the software relating to the handling of interrupt commands
Analysis and design of a capsule landing system and surface vehicle control system for Mars exploration
Problems related to the design and control of a mobile planetary vehicle to implement a systematic plan for the exploration of Mars are reported. Problem areas include: vehicle configuration, control, dynamics, systems and propulsion; systems analysis, terrain modeling and path selection; and chemical analysis of specimens. These tasks are summarized: vehicle model design, mathematical model of vehicle dynamics, experimental vehicle dynamics, obstacle negotiation, electrochemical controls, remote control, collapsibility and deployment, construction of a wheel tester, wheel analysis, payload design, system design optimization, effect of design assumptions, accessory optimal design, on-board computer subsystem, laser range measurement, discrete obstacle detection, obstacle detection systems, terrain modeling, path selection system simulation and evaluation, gas chromatograph/mass spectrometer system concepts, and chromatograph model evaluation and improvement
Using scientific machine learning for experimental bifurcation analysis of dynamic systems
Augmenting mechanistic ordinary differential equation (ODE) models with
machine-learnable structures is an novel approach to create highly accurate,
low-dimensional models of engineering systems incorporating both expert
knowledge and reality through measurement data. Our exploratory study focuses
on training universal differential equation (UDE) models for physical nonlinear
dynamical systems with limit cycles: an aerofoil undergoing flutter
oscillations and an electrodynamic nonlinear oscillator. We consider examples
where training data is generated by numerical simulations, whereas we also
employ the proposed modelling concept to physical experiments allowing us to
investigate problems with a wide range of complexity. To collect the training
data, the method of control-based continuation is used as it captures not just
the stable but also the unstable limit cycles of the observed system. This
feature makes it possible to extract more information about the observed system
than the standard, open-loop approach would allow. We use both neural networks
and Gaussian processes as universal approximators alongside the mechanistic
models to give a critical assessment of the accuracy and robustness of the UDE
modelling approach. We also highlight the potential issues one may run into
during the training procedure indicating the limits of the current modelling
framework.Comment: 16 pages, 15 figure
Polymeric alkali fullerides are stable in air
Infrared transmission, electron spin resonance, and X-ray diffraction
measurements show unambiguously that RbC and KC are stable in
air, in contrast to RbC which decomposes rapidly upon exposure.
The specimens studied transform into pure C and other byproducts when
heated above 100\dd C, approximately the temperature of the orthorhombic-fcc
phase transition. The stability of these compounds raises the possibility of
applying them as protective layers for the superconducting fullerides.Comment: Scheduled for publication in Appl. Phys. Lett. 66, 20 Feb. 1995,
typeset in REVTEX v3.0 in LaTeX. Postscript file including all figures is
available on WWW http://insti.physics.sunysb.edu/~mmartin/ under my list of
publications, or will be e-mailed by request
Mechanochemistry with Metallosupramolecular Polymers
The transduction of mechanical force into useful chemical reactions is an emerging design approach to impart soft materials with new functions. Here, we report that mechanochemical transductions can be achieved in metallo-supramolecular polymers. We show that both reversible and irreversible reactions are possible and useful to create me-chanically responsive materials that display new functions. The metallopolymer studied was a crosslinked network assembled from a europium salt and a telechelic poly(ethylene-co-butylene) with 2,6-bis(1′- methylbenzimidazolyl)pyridine (Mebip) ligands at the termini. The Eu3+ complexes serve both as mechanically responsive binding motifs and built-in optical probes that can monitor the extent of (dis)assembly due to their characteristic photoluminescent properties. Indeed, dose-dependent and reversible metal-ligand dissociation occurs upon exposure to ultrasound in solution. The absence of ultrasound-induced dissociation of a low-molecular weight model complex and in-depth studies of temperature effects confirm that the dissociation is indeed the result of mechanical activation. The influence of the strength of the metal-ligand interactions on the mechanically induced dissociation was also explored. Metallopolymers in which the Mebip ligands were substituted with more strongly coordinating dipicolinate (dpa) ligands do not dissociate upon exposure to ultrasound. Finally we show that mechanochemical transduction in metallosupramolecular polymers is also possible in the solid state. We demonstrate mending of damaged objects through ultrasound as well as mechanochromic behavior based on metal-exchange reactions in metallopolymers imbibed with an auxiliary metal salt
Orbital Migration of Interacting Stellar Mass Black Holes in Disks around Supermassive Black Holes
The merger rate of stellar-mass black hole binaries (sBHBs) inferred by the
Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) suggests
the need for an efficient source of sBHB formation. Active galactic nucleus
(AGN) disks are a promising location for the formation of these sBHBs, as well
as binaries of other compact objects, because of powerful torques exerted by
the gas disk. These gas torques cause orbiting compact objects to migrate
towards regions in the disk where inward and outward torques cancel, known as
migration traps. We simulate the migration of stellar mass black holes in an
example of a model AGN disk, using an augmented N-body code that includes
analytic approximations to migration torques, stochastic gravitational forces
exerted by turbulent density fluctuations in the disk, and inclination and
eccentricity dampening produced by passages through the gas disk, in addition
to the standard gravitational forces between objects. We find that sBHBs form
rapidly in our model disk as stellar-mass black holes migrate towards the
migration trap. These sBHBs are likely to subsequently merge on short
time-scales. The process continues, leading to the build-up of a population of
over-massive stellar-mass black holes. The formation of sBHBs in AGN disks
could contribute significantly to the sBHB merger rate inferred by LIGO.Comment: 18 pages, 13 figures, Accepted to Ap
3-Amino-5-bromo-2-iodoÂpyridine
The reaction of 3-amino-5-bromoÂpyridine with N-iodoÂsuccinimide in the presence of acetic acid produces the title compound, C5H4BrIN, with an iodo substituent in position 2 of the pyridine ring. The crystal structure features rather weak interÂmolecular N—H⋯N hydrogen bonds linking the molÂecules into chains along the z axis of the crystal
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