Modelling of the robotic Powerball®: a nonholonomic,underactuated and variable structure-type system

The Powerball® is the commercial name for a gyroscopic device that is marketed as a wrist exerciser. The device has a rotor with two underactuated degrees of freedom, which can be actuated by the appropriate motion of human or robot wrist axes. After the initial spin, applying the appropriate motion and torques to the housing leads to a spin-up of the rotor. Finding these torques intuitively is an easy task for human operators, but a complex task for a technical consideration, for example, in robotics.

This article's main contribution is a novel dynamic model that considers friction effects. The presented model includes all three working principles of the device: free rotor mode and both modes of rotor rolling in the housing. The work introduces models with one and two degrees of freedom actuation, both of which are suitable for laboratory control experiments. An estimation of the friction is discussed, and both the simulation and the experimental results are presented to evaluate the models.     

Suppression of Decoherence by Periodic Forcing

We consider a finite-dimensional quantum system coupled to a thermal reservoir and subject to a time-periodic, energy conserving forcing. We show that, if a certain dynamical decoupling condition is fulfilled, then the periodic forcing counteracts the decoherence induced by the reservoir: for small system–reservoir coupling $\lambda $ and small forcing period $T$ , the system dynamics is approximated by an energy conserving and non-dissipative dynamics, which preserves coherences. For times up to order $(\lambda T)^{-1}$ , the difference between the true and approximated dynamics is of size $\lambda +T$ . Our approach is rigorous and combines Floquet and spectral deformation theory. We illustrate our results on the spin-fermion model and recover previously known, heuristically obtained results.     

Numerical simulation of NQR/NMR: Applications in quantum computing

A numerical simulation program able to simulate nuclear quadrupole resonance (NQR) as well as nuclear magnetic resonance (NMR) experiments is presented, written using the Mathematica package, aiming especially applications in quantum computing. The program makes use of the interaction picture to compute the effect of the relevant nuclear spin interactions, without any assumption about the relative size of each interaction. This makes the program flexible and versatile, being useful in a wide range of experimental situations, going from NQR (at zero or under small applied magnetic field) to high-field NMR experiments. Some conditions specifically required for quantum computing applications are implemented in the program, such as the possibility of use of elliptically polarized radiofrequency and the inclusion of first- and second-order terms in the average Hamiltonian expansion. A number of examples dealing with simple NQR and quadrupole-perturbed NMR experiments are presented, along with the proposal of experiments to create quantum pseudopure states and logic gates using NQR. The program and the various application examples are freely available through the link http://www.profanderson.net/files/nmr_nqr.php.     

Ultrasound-promoted synthesis of 3-trichloromethyl-5-alkyl(aryl)-1,2,4-oxadiazoles

The alternative synthesis of 12 1,2,4-oxadiazoles using ultrasound irradiation from trichloroacetoamidoxime and acyl chlorides is reported. Seven of them are novel compounds. The 3-trichloromethyl-5alkyl(aryl)-1,2,4-oxadiazoles have been synthesised in better yields and shorter reaction times compared to the conventional method. This protocol can be applicable for preparation of 1,2,4-oxadiazoles containing aryl or alkyl groups attached at their C-5 side-chain.     

Incipient crystallization of transition-metal tungstates under microwaves probed by Raman scattering and transmission electron microscopy

Microwave synthesis was used to produce nanosized transition-metal tungstates in environmentally friendly conditions not yet reported by the literature: 110 and 150 °C, for times of 10 and 20 min. X-ray diffraction evidenced incipient crystallized materials, while transmission electron microscopy indicates nanostructured regions of about 2–5 nm inside an amorphous matrix. Raman spectroscopy was used to probe short-range ordering in the achieved samples and also to obtain a reliable set of spectra containing all the Raman-active bands predicted by group-theory calculations. The vibrational spectra showed no extra feature, indicating that the microwave processing was able to produce short-range ordered materials without tetrahedral distortions. These distortions are frequently reported when commercially modified kitchen microwave units are employed. In this work, the syntheses were conducted in a commercial apparatus especially designed for fully controlled temperature–time–pressure conditions.     

One-pot approach to synthesize PPy@S core–shell nanocomposite cathode for Li/S batteries

Journal of Nanoparticle Research - Graphene and graphene oxide are potential candidates as nanofluids for thermal management applications. Here, we investigate the rheological properties and...     

Investigation on miscibility,thermal, crystallographic diffraction and dynamic-mechanical properties of poly(vinyl alcohol)/poly(vinylpyrrolidone)/zirconium phosphate nanocomposites

Journal of Thermal Analysis and Calorimetry - This work approaches the effects of a synthetic nanofiller on poly(vinyl alcohol)/poly(vinylpyrrolidone)/zirconium phosphate (PVA/PVP/ZrP)...     

The Effects of an Impurity in an Ising‐XXZ Diamond Chain on Thermal Entanglement,on Quantum Coherence,and on Quantum Teleportation

The effects of an impurity plaquette on the thermal quantum correlations measurement by the concurrence, on quantum coherence quantified by the recently proposed l₁‐norm of coherence and on quantum teleportation in a Ising‐ $XXZ$ diamond chain are discussed. Such an impurity is formed by the $XXZ$ interaction between the interstitial Heisenberg dimers and the nearest‐neighbor Ising coupling between the nodal and interstitial spins. All the interaction parameters are different from those of the rest of the chain. By tailoring them, quantum entanglement and quantum coherence can be controlled and tuned. Therefore, the quantum resources—thermal entanglement and quantum coherence—of the model exhibit a clear performance improvement in comparison to the original model without impurities. It is demonstrated that quantum teleportation can be tuned by its inclusion. Thermal teleportation is modified in a significant way as well, and a strong increase in the average fidelity is observed. The exact solution is furnished by the use of the transfer‐matrix method.     

Analysis of Pre-Columbian objetcs from Cupisnique, one of the oldest culture from Perú, using a portable X-ray fluorescence equipment

Cupisnique (2000–200 BC) is one of the first complex societies that developed in the Jetequepeque valley in the “Formative period.” It includes several settlements: Puémape on the coast, Limoncarro in middle valley, Montegrande and Tembladera in the upper valley, and Kuntur Wasi in San Pablo. Currently the valley comprises two provinces, Pacasmayo and Chepen in the La Libertad region, north of Lima. Consideration should be given to cupisniques as premetallurgical culture, and the only used metal was gold, which is present in the native state, on the soil surface or shallow, and attracted attention because of color, brightness, weight, ductility, and inalterability. We analyzed three Cupisnique metal objects belonging to the Larco Museum of Lima designated with No. 4 (pectoral), No. 7 (pendant), and No. 12 (bracelet), using a portable energy-dispersive X-ray fluorescence equipment. Mean value for the pectoral were Au (62 %), Ag (23 %), Cu (15 %); for the pendant, Au (81 %), Ag (16.5 %), Cu (2.5 %); and for the bracelet, Au (69.1 %), Ag (20 %), and Cu (10.9 %).     

Rising damp in building walls: the wall base ventilation system

This work intends to validate a new system for treating rising damp in historic buildings walls. The results of laboratory experiments show that an efficient way of treating rising damp is by ventilating the wall base, using the HUMIVENT technique. The analytical model presented describes very well the observed features of rising damp in walls, verified by laboratory tests, who contributed for a simple sizing of the wall base ventilation system that will be implemented in historic buildings.