Predictive optimisation of high-power IGBT switching under Active Voltage Control

Active Voltage Control (AVC) is an implementation of classic Proportional-Derivative (PD) control and multi-loop feedback control to force IGBT to follow a pre-set switching trajectory. The initial objective of AVC was mainly to synchronise the switching of IGBTs connected in series so as to realise voltage balancing between devices. For a single IGBT switching, the AVC reference needs further optimisation. Thus, a predictive manner of AVC reference generation is required to cope with the nonlinear IGBT switching parameters while performing low loss switching. In this paper, an improved AVC structure is adopted along with a revised reference which accommodates the IGBT nonlinearity during switching and is predictive based on current being switched. Experimental and simulation results show that close control of a single IGBT switching is realised. It is concluded that good performance can be obtained, but the proposed method needs careful stability analysis for parameter choice. © 2013 IEEE.

Cell surface display of functionally active lipases from Yarrowia lipolytica in Pichia pastoris

The lipase genes of Yarrowia lipolytica, LIPY7 and LIPY8, fused with FLO-flocculation domain sequence from Saccharomyces cerevisiae at their N-termini, were expressed in Pichia pastoris KM71. Following the induction with methanol, the recombinant proteins were displayed on the cell surface of P. pastoris, as confirmed by the confocal laser scanning microscopy. The LipY7p and LipY8p were anchored on P. pastoris via the flocculation functional domain of Flo 1 p. The surface-displayed lipases were characterized for their application as the whole-cell biocatalyst. These lipases can also be cleaved off from their anchor by enterokinase treatment to yield functionally active proteins in the supernatant offering an alternative purification method for LipY7p and LipY8p. (c) 2007 Elsevier Inc. All rights reserved.

Active control of normal shock wave/turbulent boundary layer interaction using "Smart" piezoelectric flap actuators

This paper looks at active control of the normal shock wave/turbulent boundary layer interaction (SBLI) using smart flap actuators. The actuators are manufactured by bonding piezoelectric material to an inert substrate to control the bleed/suction rate through a plenum chamber. The cavity provides communication of signals across the shock, allowing rapid thickening of the boundary layer approaching the shock, which splits into a series of weaker shocks forming a lambda shock foot, reducing wave drag. Active control allows optimum control of the interaction, as it would be capable of positioning the control region around the original shock position and control the rate of mass transfer. © 2004 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

Dense active appearance models using a bounded diameter minimum spanning tree

We present a method for producing dense Active Appearance Models (AAMs), suitable for video-realistic synthesis. To this end we estimate a joint alignment of all training images using a set of pairwise registrations and ensure that these pairwise registrations are only calculated between similar images. This is achieved by defining a graph on the image set whose edge weights correspond to registration errors and computing a bounded diameter minimum spanning tree (BDMST). Dense optical flow is used to compute pairwise registration and we introduce a flow refinement method to align small scale texture. Once registration between training images has been established we propose a method to add vertices to the AAM in a way that minimises error between the observed flow fields and a flow field interpolated between the AAM mesh points. We demonstrate a significant improvement in model compactness using the proposed method and show it dealing with cases that are problematic for current state-of-the-art approaches.

Novel regrowth-free vertical active-passive integration scheme with improved fabrication tolerance

We present a novel vertically-coupled active-passive integration architecture that provides an order of magnitude reduction in coupling coefficient variation between misaligned waveguides when compared with a conventional vertically-coupled structure. © 2005 Optical Society of America.

Novel regrowth-free vertical active-passive integration scheme with improved fabrication tolerance

We present a novel vertically-coupled active-passive integration architecture that provides an order of magnitude reduction in coupling coefficient variation between misaligned waveguides when compared with a conventional vertically-coupled structure. © 2005 Optical Society of America.

Novel regrowth-free vertical active-passive integration scheme with improved fabrication tolerance

We present a novel vertically-coupled active-passive integration architecture that provides an order of magnitude reduction in coupling coefficient variation between misaligned waveguides when compared with a conventional vertically-coupled structure. © 2005 Optical Society of America.

Carbon nanotube forests growth using catalysts from atomic layer deposition

We have grown carbon nanotubes using Fe and Ni catalyst films deposited by atomic layer deposition. Both metals lead to catalytically active nanoparticles for growing vertically aligned nanotube forests or carbon fibres, depending on the growth conditions and whether the substrate is alumina or silica. The resulting nanotubes have narrow diameter and wall number distributions that are as narrow as those grown from sputtered catalysts. The state of the catalyst is studied by in-situ and ex-situ X-ray photoemission spectroscopy. We demonstrate multi-directional nanotube growth on a porous alumina foam coated with Fe prepared by atomic layer deposition. This deposition technique can be useful for nanotube applications in microelectronics, filter technology, and energy storage. © 2014 AIP Publishing LLC.

Active sensing system with in situ adjustable sensor morphology.

BACKGROUND: Despite the widespread use of sensors in engineering systems like robots and automation systems, the common paradigm is to have fixed sensor morphology tailored to fulfill a specific application. On the other hand, robotic systems are expected to operate in ever more uncertain environments. In order to cope with the challenge, it is worthy of note that biological systems show the importance of suitable sensor morphology and active sensing capability to handle different kinds of sensing tasks with particular requirements. METHODOLOGY: This paper presents a robotics active sensing system which is able to adjust its sensor morphology in situ in order to sense different physical quantities with desirable sensing characteristics. The approach taken is to use thermoplastic adhesive material, i.e. Hot Melt Adhesive (HMA). It will be shown that the thermoplastic and thermoadhesive nature of HMA enables the system to repeatedly fabricate, attach and detach mechanical structures with a variety of shape and size to the robot end effector for sensing purposes. Via active sensing capability, the robotic system utilizes the structure to physically probe an unknown target object with suitable motion and transduce the arising physical stimuli into information usable by a camera as its only built-in sensor. CONCLUSIONS/SIGNIFICANCE: The efficacy of the proposed system is verified based on two results. Firstly, it is confirmed that suitable sensor morphology and active sensing capability enables the system to sense different physical quantities, i.e. softness and temperature, with desirable sensing characteristics. Secondly, given tasks of discriminating two visually indistinguishable objects with respect to softness and temperature, it is confirmed that the proposed robotic system is able to autonomously accomplish them. The way the results motivate new research directions which focus on in situ adjustment of sensor morphology will also be discussed.

Strength and hydration products of reactive MgO-silica pastes

The reaction between MgO and microsilica has been studied by many researchers, who confirmed the formation of magnesium silicate hydrate. The blend was reported to have the potential as a novel material for construction and environment purposes. However, the characteristics of MgO vary significantly, e.g., reactivity and purity, which would have an effect on the hydration process of MgO-silica blend. This paper investigated the strength and hydration products of reactive MgO and silica blend at room temperature up to 90 days. The existence of magnesium silicate hydrate after 7 days' curing was confirmed with the help of infrared spectroscopy, thermogravimetric analysis and X-ray diffraction. The microstructural and elemental analysis of the resulting magnesium silicate hydrate was conducted using scanning electron microscopy and energy dispersive spectroscopy. In addition, the effect of characteristics of MgO on the hydration process was discussed. It was found that the synthesis of magnesium silicate hydrate was highly dependent on the reactivity of the precursors. MgO and silica with higher reactivity resulted in higher formation rate of magnesium silicate hydrate. In addition, the impurity in the MgO affects the pH value of the blends, which in turn determines the solubility of silica and the formation of magnesium silicate hydrate. © 2014 Elsevier Ltd. All rights reserved.

Cloning of biologically active genomes from a Helicoverpa armigera single-nucleocapsid nucleopolyhedrovirus isolate by using a bacterial artificial chromosome

Purification of genotypes from baculovirus isolates provides understanding of the diversity of baculoviruses and may lead to the development of better pesticides. Here, we report the cloning of different genotypes from an isolate of Helicoverpa armigera single-nucleocapsid nucleopolyhedrovirus (HaSNPV) by using a bacterial artificial chromosome (BAC). A transfer vector (pHZB10) was constructed which contained an Escherichia coli mini-F replicon cassette within the upstream and downstream arms of HaSNPV polyhedrin gene. Hz2e5 cells were co-transfected with wild-type HaSNPV DNA and pHZB10 to generate recombinant viruses by homologous recombination. The DNA of budded viruses (BVs) was used to transform E. coli. One of the bacmid colonies, HaBacHZ8, has restriction enzyme digestion profiles similar to an in vivo cloned strain HaSNPV-G4, the genome of which has been completely sequenced. For testing the oral infectivity, the polyhedrin gene of HaSNPV was reintroduced into HaBacHZ8 to generate the recombinant bacmid HaBacDF6. The results of one-step growth curves, electron microscopic examination, protein expression analysis and bioassays indicated that HaBacDF6 replicated as well as HaSNPV-G4 in vitro and in vivo. The biologically functional HaSNPV bacmids obtained in this research will facilitate future studies on the function genomics and genetic modification of HaSNPV. (C) 2003 Elsevier B.V. All rights reserved.

OCCURRENCE AND DISTRIBUTION OF SILICA-SCALED CHRYSOPHYTES IN ZHEJIANG, JIANGSU, HUBEI, YUNNAN AND SHANDONG PROVINCES, CHINA

Fifty-one phytoplankton samples were collected from different ecological environments in five provinces located in the central, eastern and southwestern parts of China. 41 taxa of silica-scaled chrysophytes, 8 of them belonging to the Chrysophyceae and 33 to the Synurophyceae, have been identified by means of electron microscopy. Among them, Mallomonas parvula, M. calceolus, M. cyathellata (?), M. costata, M. crassisquama, and Synura echinulata are new to China. The silica-scaled chrysophyte flora and its geographical distribution in this region are analysed and discussed.

Low threshold lasing of GaN-based vertical cavity surface emitting lasers with an asymmetric coupled quantum well active region

We have fabricated and characterized GaN-based vertical cavity surface emitting lasers (VCSELs) with a unique active region structure, in which three sets of InGaN asymmetric coupled quantum wells are placed in a half-wavelength (0.5 lambda) length. Lasing action was achieved under optical pumping at room temperature with a threshold pumping energy density of about 6.5 mJ/cm(2). The laser emitted a blue light at 449.5 nm with a narrow linewidth below 0.1 nm and had a high spontaneous emission factor of about 3.0x10(-2). The results indicate that this active region structure is useful in reducing the process difficulties and improving the threshold characteristics of GaN-based VCSELs.