Decoupling properties of singular LQ regulation problem

Some properties of a limiting solution derived from a standard LQ regulator problem are discussed in the case where the input weighting matrix tends to zero, for a discrete time system. The explicit limiting solution is given in some literature. It is shown that the limiting solution is closely connected with a disturbance decoupling problem. Moreover it is pointed out that the limiting feedback gain with the help of feedforward gain constructs the decoupled system with the maximum number of blocks.     

The formation of graphene–titania hybrid films and their resistance change under ultraviolet irradiation

We report the fabrication of hybrid films of graphene and monolayer titania using a simple electrostatic self-assembly method. Ultraviolet (UV) responses of the hybrid films based on the graphene–titania structure were investigated. We observed that the resistance of the graphene–titania hybrid increased exponentially with UV irradiation time and decreased exponentially when UV was turned off. Time constants of the order of hundreds of seconds were identified and found to be sensitive to the gas environment of graphene. The UV response as well as the time constant is tunable by varying the number of titania layers. Our results confirmed that UV irradiation played a significant role in the resistance modulation of graphene as well as graphene–titania hybrid films.     

BSCCO Superconductors: Hole-Like Fermi Surface and Doping Dependence of the Gap Function

We use the gradient of the energy-integrated angle resolved photoemission (ARPES) intensity in order to define precisely the Fermi surface (FS) in BSCCO superconductors. We show that, independent of the photon energy, the FS is a hole barrel centered at (, ). Then, the superconducting gap along the FS is precisely determined from ARPES measurements on overdoped and underdoped samples of Bi2212. As the doping decreases, the maximum gap increases, but the slope of the gap near the nodes decreases. Though consistent with d-wave symmetry, the gap with underdoping cannot be fit by the simple cos(k _x) – cos(k _y) form. A comparison of our ARPES results with available penetration depth data indicates that the renormalization of the linear T suppression of the superfluid density at low temperatures due to quasiparticle excitations around the d-wave nodes is large and doping dependent.     

Syntheses and properties of B-C-N and BN nanostructures

The current status of research on boron-carbon-nitrogen (B-C-N) and boron nitride (BN) nanotubes is presented. The latest achievements in syntheses, analyses and property measurements of these nanoscale tubular architectures are reviewed. The characteristic features of B-C-N and BN nanotubes, compared with conventional C nanotubes, are paid special attention. In particular, the latest breakthroughs in the chemical vapour deposition synthesis of BN nanotubes and an insight into their unique structures are highlighted. A wide range of potential applications is also envisaged, based on the recent progress, which includes pioneering results in BN nanocable fabrication, gas adsorption, electron transport and field emission measurements.     

Sellmeier dispersion for phase-matched terahertz generation in ZnGeP2

A Sellmeier dispersion of zinc germanium diphosphide (ZnGeP2) crystal has been formulated to determine the phase-matching characteristics of the crystal for the generation of coherent tunable terahertz radiation by difference-frequency mixing techniques. The results computed with the formulated Sellmeier dispersion provide an excellent fit to the experimental data.     

An Approximation for the Production Efficiency of Automatic Transfer Lines with In-Process Storages

This paper considers the production efficiency of automatic transfer lines where in-process storages are provided for stochastic station breakdowns. A simple approximation method is developed in order to readily obtain the production efficiency and show the benefit of providing storages even for long lines. Additionally, the optimal partitioning of the line and the method of allocating capacities for storages are numerically investigated.     

Specific Heat of the Surface Layers on the Amorphous Substrate in Solid and Liquid 3He

We have observed an excess heat capacity in liquid and bcc solid ³He at low temperatures. The heat capacity in the normal fluid is found to be the sum of the heat capacity of bulk normal fluid and a temperature-independent heat capacity C due to amorphous solid layers on the silver sinter surface, where C=7.3±6.8 JK^–1m^–2 corresponds to 1.6±0.6 amorphous solid layers. The heat capacity for bcc solid ³He is the sum of the heat capacity originating from the multiple-exchange interaction and a temperature independent heat capacity. The excess heat capacity C=12.1±3.1 JK^–1m^–2 for bcc solid corresponds to 1.9±0.3 amorphous solid layers. Our result indicates that the amorphous solid layers on an amorphous substrate yield a universal C in unit area throughout liquid, solid and adsorbed ³He.     

Performance Improvement of Current Source Inverter-Fed Induction Motor Drives

A high performance variable speed drive system using current source inverter fed induction motor is described. The principle of the drive control is based on the field-orientation method, where the stator current is used as the vector quantity. To improve the system response and to operate smoothly at low speed, a current pulsewidth modulation (PWM) control is provided by means of a feedback loop. This system operates stably and shows a high dynamic performance in a wide range, from zero to rated speed. Dual current source inverter is applied to this drive system which results in a remarkably low copper loss of the motor, even in PWM operation.