Beam scanning of array using ferroelectric phase shifters

The beam scanning characteristics of a two-element array utilising a ferroelectric phase shifter are presented for the first time. Applying a DC voltage across the ferroelectric material changes the velocity of the input signal, a beam scan of 26° being achieved. The S₁₁ performance and the radiation patterns of the array at two frequencies are presented     

VDNet: an infrastructure‐less UAV‐assisted sparse VANET system with vehicle location prediction

Vehicular Ad Hoc Network (VANET) has been a hot topic in the past few years. Compared with vehicular networks where vehicles are densely distributed, sparse VANET have more realistic significance. The first challenge of a sparse VANET system is that the network suffers from frequent disconnections. The second challenge is to adapt the transmission route to the dynamic mobility pattern of the vehicles. Also, some infrastructural requirements are hard to meet when deploying a VANET widely. Facing these challenges, we devise an infrastructure‐less unmanned aerial vehicle (UAV) assisted VANET system called V ehicle‐D rone hybrid vehicular ad hoc Net work (VDNet), which utilizes UAVs, particularly quadrotor drones, to boost vehicle‐to‐vehicle data message transmission under instructions conducted by our distributed vehicle location prediction algorithm. VDNet takes the geographic information into consideration. Vehicles in VDNet observe the location information of other vehicles to construct a transmission route and predict the location of a destination vehicle. Some vehicles in VDNet equips an on‐board UAV, which can deliver data message directly to destination, relay messages in a multi‐hop route, and collect location information while flying above the traffic. The performance evaluation shows that VDNet achieves high efficiency and low end‐to‐end delay with controlled communication overhead. Copyright © 2016 John Wiley & Sons, Ltd.     

Novel cobweb-topology WDM access network architecture featuring ultra-high reliability and easy scalability

A wavelength division multiplexing access network architecture with cobweb topology is proposed in this paper. It can be a candidate for metro access network with high reliability in the future. This architecture can provide two protection methods. The protection strategy which can maximize the protected traffic is elaborated in the context. Mathematical models of system performance such as network scale and link reliability are established and analyzed in this paper.     

Texture gradient studies of a Cu‐tube by the robot at STRESS‐SPEC

The handling of larger samples for texture studies is limited when we using the Eulerian cradle. The robot Stäubli RX160 installed at STRESS‐SPEC offers much more freedom in sample manipulation on one hand to perform pole figure scanning and on the other hand to position the sample for a texture mapping. A key problem is that slit systems cannot be positioned close to large samples due to safety reasons which makes corrections more important. A very simple solution was tested to correct the scattered intensity for each pole figure point for constant volume and anisotropic absorption. A simple method to make these corrections is needed because engineering samples such as semi‐finished products have a large variety of shapes and weights and an ideal slit system is only seldomly available. The test sample was a Cu‐tube of 140 mm in diameter with an average wall thickness of 10 mm. To compare the corrections three kind of samples were measured, first a cube of 10 × 10 × 11 mm³ without any correction, second an 11 mm long tube segment and third a tube segment of 250 mm (12 kg weight) in length. Orientation Distribution Function (ODF) analysis of the average texture over the tube wall by the iterative series expansion method has shown that sufficient intensity corrections can be done to describe the texture gradient around the circumference of the Cu‐tube related to low ovality and eccentricity of the Cu‐tube.     

Chemoselectivity in the Oxidation of unsymmetrical Thioureas with NBS/sulfuric Acid: Benzothiazoles vs. 1,2,4-Thiadiazoles

Exclusive formation of 2-heteroarylaminobenzothiazoles is observed when N-aryl-N′-heteroarylthioureas are treated with NBS/H₂SO₄. A possible explanation to account for the lack of 1,2,4-thiadiazole formation is offered, and a previous report³ concerning the oxidation of N-phenyl-N′-(2-pyridyl)thiourea is shown to be erroneous.     

Existence of a smooth Lyapunov function for any smooth planar dynamical system with one limit cycle

Nonlinear Dynamics - The existence of a smooth Lyapunov function for any smooth planar dynamical system with one limit cycle is proved, which is based on a novel decomposition of the dynamical...     

Giant magnetorefractive effect in La<Subscript>0.7</Subscript>Ca<Subscript>0.3</Subscript>MnO<Subscript>3</Subscript> films

Complex experimental investigations of the structural, optical, and magneto-optical properties (magnetotransmission, magnetoreflection, and transversal Kerr effect, as well as the magnetoresistance, of La_0.7Ca_0.3MnO₃ epitaxial films indicate that magnetoreflection and magnetotransmission in manganite films can reach giant values and depend strongly on the magnetic and charge homogeneity of the films, their thickness, and spectral range under investigation. It has been shown that the optical enhancement of the magnetorefractive effect occurs in thin films as compared to manganite crystals. In the region of the minimum of the reflectance near the first phonon band, the resonance-like magnetorefractive effect has been observed, which is accompanied by change of the sign of the magnetoreflection. A model based on the theory of the magnetorefractive effect has been proposed to qualitatively explain this behavior.     

Experimental demonstration of probabilistic quantum cloning

The method of quantum cloning is divided into two main categories: approximate and probabilistic quantum cloning. The former method is used to approximate an unknown quantum state deterministically, and the latter can be used to faithfully copy the state probabilistically. Thus far, many approximate cloning machines have been experimentally demonstrated, but probabilistic cloning remains an experimental challenge, as it requires more complicated networks and a higher level of precision control. In this work, we design an efficient quantum network with a limited amount of resources and perform the first experimental demonstration of probabilistic quantum cloning in a NMR quantum computer. In our experiment, the optimal cloning efficiency proposed by Duan and Guo [Phys. Rev. Lett. 80, 4999 (1998)] is achieved.     

Efficient surface plasmon amplification from gain-assisted gold nanorods

We report on the efficient surface plasmon amplification by stimulated emission of radiation (spaser) from a gold nanorod coated with proper gain media. Numerical simulations show that the threshold of the nanorod-based spaser is nearly 1 order of magnitude lower than that of the core-shell nanosphere, which is verified by analysis with electrostatic theory. Furthermore, it is found that the nanorod-based nanosystem possesses unique optical properties such as wavelength tunability and polarization sensitivity.