2,742 research outputs found
The Problem of Adhesion Methods and Locomotion Mechanism Development for Wall-Climbing Robots
This review considers a problem in the development of mobile robot adhesion
methods with vertical surfaces and the appropriate locomotion mechanism design.
The evolution of adhesion methods for wall-climbing robots (based on friction,
magnetic forces, air pressure, electrostatic adhesion, molecular forces,
rheological properties of fluids and their combinations) and their locomotion
principles (wheeled, tracked, walking, sliding framed and hybrid) is studied.
Wall-climbing robots are classified according to the applications, adhesion
methods and locomotion mechanisms. The advantages and disadvantages of various
adhesion methods and locomotion mechanisms are analyzed in terms of mobility,
noiselessness, autonomy and energy efficiency. Focus is placed on the physical
and technical aspects of the adhesion methods and the possibility of combining
adhesion and locomotion methods
Giant Magnetoresistance Oscillations Induced by Microwave Radiation and a Zero-Resistance State in a 2D Electron System with a Moderate Mobility
The effect of a microwave field in the frequency range from 54 to 140
on the magnetotransport in a GaAs quantum well with AlAs/GaAs
superlattice barriers and with an electron mobility no higher than
is investigated. In the given two-dimensional system under
the effect of microwave radiation, giant resistance oscillations are observed
with their positions in magnetic field being determined by the ratio of the
radiation frequency to the cyclotron frequency. Earlier, such oscillations had
only been observed in GaAs/AlGaAs heterostructures with much higher mobilities.
When the samples under study are irradiated with a 140- microwave
field, the resistance corresponding to the main oscillation minimum, which
occurs near the cyclotron resonance, appears to be close to zero. The results
of the study suggest that a mobility value lower than
does not prevent the formation of zero-resistance states in magnetic field in a
two-dimensional system under the effect of microwave radiation.Comment: 4 pages, 2 figur
CRIMINAL LAW—GIVE ME FREEDOM!: HOW AMBIGUOUS FEDERAL SUPERVISED RELEASE CONDITIONS UNDERMINE THE PURPOSE OF THE SENTENCING REFORM ACT
Vagueness, as the word suggests, is inherently uncertain. This Note addresses the issues of vagueness presented by unclear supervised release conditions, as well as discusses the split of authority pertaining thereto. Specifically, the condition discussed throughout the Note prohibits defendants from frequenting places where controlled substances are illegally present. Because federal appellate courts differ as to the condition’s meaning and its application, the existing circuit split will be thoroughly discussed. The main issues with the condition demonstrate a lack of attentiveness and forethought of the sentencing judges that ultimately impose undue hardships onto the defendants wishing to enter back into society. Furthermore, due to the lack of clarity of the proscribed terms, defendants may be uncertain as to what behavior is permitted and what act may result in re-incarceration. Since the proscribed terms are subject to varying interpretations, the defendants subject to this condition may find it difficult to obey. This Note will argue that the imposition of vague supervised release conditions is contradictory to the rehabilitative purpose of supervised release, and will urge the sentencing courts to exercise greater caution when imposing terms of federal supervision. This will ensure that defendants are not subject to unclear terms that may be unintentionally violated
Anisotropic positive magnetoresistance of a nonplanar 2D electron gas in a parallel magnetic field
We study the transport properties of a 2D electron gas in narrow GaAs quantum
wells with AlAs/GaAs superlattice barriers. It is shown that the anisotropic
positive magnetoresistance observed in selectively doped semiconductor
structures in a parallel magnetic field is caused by the spatial modulation of
the 2D electron gas.Comment: 4 pages, 3 figure
Size effects in radiospectroscopy spectra of ferroelectric nanopowders
The theoretical and experimental investigation of ferroelectric nanopowders
is performed. The manifestation in radiospectroscopy spectra of size driven
ferroelectric-paraelectric phase transition at some critical particle average
size was the main goal of the consideration. In theoretical part the size
effect for the materials with ferroelectric tetragonal phase and cubic
paraelectric phase was considered allowing for the spontaneous polarization
inhomogeneity inside a particle and distribution of particle sizes. In ESR the
transformation of the spectra from tetragonal symmetry to cubic symmetry with
decreasing of nanoparticle sizes was calculated. Measurements of Fe3+ ESR
spectra in nanopowder of BaTiO3 were carried out at room temperature. The
decrease of intensity of tetragonal symmetry ESR lines of Fe3+ and appearance
of cubic symmetry line with asymmetry of the shoulders was observed with the
average sizes decrease with complete disappearance of tetragonal spectrum at
average size less or equal 40 nm. The comparison of the theory with experiment
was carried out. The value of critical size Rc = 40 nm was extracted from ESR
data. The asymmetry and broadening of right hand side shoulder of ESR cubic
symmetry line was shown to be related to contribution of paramagnetic centers
in the vicinity of the particles surface. The deconvolution of the cubic line
allowed to show, that this region size is about 3 nm.Comment: 10 pages, 8 figure
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