The number of multi-robot systems deployed in field applications has risen dramatically over the years. Nevertheless, supervising and operating multiple robots at once is a difficult task for a single operator to execute. In this paper we propose a novel approach for utilizing advising automated agents when assisting an operator to better manage a team of multiple robots in complex environments. We introduce the Myopic Advice Optimization (MYAO) Problem and exemplify its implementation using an agent for the Search And Rescue (SAR) task. Our intelligent advising agent was evaluated through extensive field trials, with 44 non-expert human operators and 10 low-cost mobile robots, in simulation and physical deployment, and showed a significant improvement in both team performance and the operator's satisfaction.

We demonstrate the exchange coupling of a ferromagnetic semiconductor (Ga 1-x Mn x As) with an overgrown antiferromagnet (MnO). Unlike most conventional exchange biased systems, the blocking temperature of the antiferromagnet (T B = 48 ± 2 K) and the Curie temperature of the ferromagnet (T C = 55.1 ± 0.2 K) are comparable. The resulting exchange bias manifests itself as a clear shift in the magnetization hysteresis loop when the bilayer is cooled in the presence of an applied magnetic field and an enhancement of the coercive field. * nsamarth@phys.psu.edu

We propose a simplified version of the one-bond two-mode percolation model originally developed for the long wave phonons related to the stiff Be–VI bond in (Zn, Be) chalcogenides, which open the class of random mixed crystals with contrast in the bond stiffness. This is deduced from the comparison between the Raman responses from the stiff Be–VI bond and the soft Zn–VI one in these systems. The simplified version is tested on (Ga, In)As, made of soft-like bonds only and taken here as a representative challenging system. This results in a successful reinterpretation of the puzzling multi-phonon behaviour in the Raman/infrared spectra of this alloy, that has been a subject of debate. The discussion is supported by contour modelling of the TO and LO Raman lineshapes by applying the Hon and Faust treatment to a version of the modified-random-element-isodisplacement model generalized to multi-oscillators. Also, the assignment of the long wave phonons in (Ga, In)As is supported by atomistic calculations of the bond length distributions of the minority bond species in large (Ga, In)As supercells corresponding to alloy compositions close to the In–As (In ∼0.19) and Ga–As (In ∼0.81) bond percolation thresholds. The configurations are analysed to distinguish between isolated and connected bonds, not in the usual terms of next nearest neighbours.

We have investigated the growth and optical properties of a set of BexZn1−xTe epitaxial layers having different composition, with x ranging from 0–0.7. Comparison of the reflectivity and the photoluminescence spectra allowed us to locate the direct-to-indirect band gap crossover for this alloy at x≈0.28. The Γ→Γ direct band gap exhibits a linear dependence on composition over the entire compositional range and can be fitted to the equation EgΓ(x)=2.26*(1−x)+4.1*x. It increases linearly with BeTe content at a rate of 18 meV for a change of 1% in BeTe content. The Γ→X indirect band gap for BexZn1−xTe can be fitted to the equation EgX(x)=3.05*(1−x)+2.8*x−0.5*x*(1−x), suggesting that the energy of the indirect Γ→X transition for ZnTe is about 3.05 eV.

We report the observation of anomalies in the longitudinal magnetoresistance of tensile-strained Ga 1−x Mn x As epilayers with perpendicular magnetic anisotropy. Magnetoresistance measurements carried out in the planar geometry (magnetic field parallel to the current density) reveal "spikes" that are antisymmetric with respect to the direction of the magnetic field. These anomalies always occur during magnetization reversal, as indicated by a simultaneous change in sign of the anomalous Hall effect. The data suggest that the antisymmetric anomalies originate in anomalous Hall effect contributions to the longitudinal resistance when domain walls are located between the voltage probes. This interpretation is reinforced by carrying out angular sweeps of H, revealing an antisymmetric dependence on the helicity of the field sweep.

Zone-center longitudinal (LO) and transverse (TO) optical phonons of Zn1−xBexTe epilayers are identified by Raman spectroscopy. On top of the expected BeTe- and ZnTe-like modes, which obey the modified-random-element-isodisplacement model, we observe an extra BeTe-like (TO, LO) doublet at intermediate x values. It has the same atypical characteristics as its BeSe-like counterpart in ZnBeSe alloy. Its activation validates our percolative picture for multimode description in Be–chalcogenide alloys that open the attractive class of mixed crystals with a sharp contrast in the bond stiffness. Also, the local modes of Be in ZnTe and of Zn in BeTe are identified at 411 cm−1 and 195 cm−1, respectively.

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Using a rotating analyzer spectroscopic ellipsometer, we have investigated the complex dielectric function of a series of ternary BexZn1−xTe thin films in the energy range between 0.7 and 6.5 eV for alloy concentrations between x=0.0 and x=0.52. After determining the alloy concentrations using x-ray diffraction and photoluminescence techniques, a standard inversion technique was used to obtain the optical constants from the measured ellipsometric spectra. Analyzing the second derivative of both the real and the imaginary parts of the dielectric constant, we have deduced the critical point parameters corresponding to the electronic transitions in the Brillouin zone. We find that the energy of the critical points with respect to Be concentration does not show any bowing effects unlike many other II–VI semiconductor ternary alloys.