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 $\mathrm{GHz}$ on the magnetotransport in a GaAs quantum well with AlAs/GaAs superlattice barriers and with an electron mobility no higher than $10^6$ $\mathrm{cm^2/Vs}$ 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-$\mathrm{GHz}$ 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 $10^6$ $\mathrm{cm^2/Vs}$ 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

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

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

Directed electron transport through ballistic quantum dot under microwave radiation

Rectification of microwave radiation by asymmetric, ballistic quantum dot is observed. The directed transport is studied at different frequency (1-40 GHz) temperatures (0.3K-6K)and magnetic field. Dramatic reduction of the rectification is found in magnetic fields at which the cyclotron (Larmor) radius of the electron orbits at Fermi level is smaller than the size of the quantum dot. It strongly suggests the ballistic nature of the observed nonlinear phenomena. Both symmetric and anti-symmetric with respect to the magnetic field contributions to the directed transport are presented. We have found that the behavior of the symmetric part of the rectified voltage with the magnetic field is different significantly for microwaves with different frequencies. A ballistic model of the directed transport is proposed.Comment: 5 pages, 3 figure

Nonequilibrium stationary states with ratchet effect

An ensemble of particles in thermal equilibrium at temperature $T$, modeled by Nos\`e-Hoover dynamics, moves on a triangular lattice of oriented semi-disk elastic scatterers. Despite the scatterer asymmetry a directed transport is clearly ruled out by the second law of thermodynamics. Introduction of a polarized zero mean monochromatic field creates a directed stationary flow with nontrivial dependence on temperature and field parameters. We give a theoretical estimate of directed current induced by a microwave field in an antidot superlattice in semiconductor heterostructures.Comment: 4 pages, 5 figures (small changes added