Optimised IGBT turn-off under active voltage control in PEBB applications

Active Voltage Control (AVC) is an implementation of classic Proportional-Derivative (PD) control and multi-loop feedback control to force an IGBT to follow a pre-set switching trajectory. Previously, AVC was mainly used for controlling series-connected IGBTs in order to enable voltage balance between IGBTs. In this paper, the nonlinear IGBT turn-off transient is further discussed and the turnoff of a single IGBT under AVC is further optimised in order to meet the demand of Power Electronic Building Block (PEBB) applications. © 2013 IEEE.

Shaping pulse transitions by active voltage control for reduced EMI generation

High-performance power switching devices (IGBT/MOSFET) realise high-performance power converters. Unfortunately, with a high switching speed of the IGBT or MOSFET freewheel diode chopper cell, the circuit has intrinsic sources of high-level EMI. Therefore, costly EMI filters or shielding are normally demanded on the load and supply side. Although an S-shaped voltage transient with a high order of derivation eliminates the discontinuity and could suppress HF spectrum of EMI emissions, a practical control scheme is still under development. In this paper, Active Voltage Control (AVC) is applied to successfully define IGBT switching dynamics with a smoothed Gaussian waveform so a reduced EMI can be achieved without extra EMI suppression devices. © 2013 IEEE.

Generating Options for Active Risk Control (GO-ARC): introducing a novel technique.

BACKGROUND: After investing significant amounts of time and money in conducting formal risk assessments, such as root cause analysis (RCA) or failure mode and effects analysis (FMEA), healthcare workers are left to their own devices in generating high-quality risk control options. They often experience difficulty in doing so, and tend toward an overreliance on administrative controls (the weakest category in the hierarchy of risk controls). This has important implications for patient safety and the cost effectiveness of risk management operations. This paper describes a before and after pilot study of the Generating Options for Active Risk Control (GO-ARC) technique, a novel tool to improve the quality of the risk control options generation process. OUTCOME MEASURES: The quantity, quality (using the three-tiered hierarchy of risk controls), variety, and novelty of risk controls generated. RESULTS: Use of the GO-ARC technique was associated with improvement on all measures. CONCLUSIONS: While this pilot study has some notable limitations, it appears that the GO-ARC technique improved the risk control options generation process. Further research is needed to confirm this finding. It is also important to note that improved risk control options are a necessary, but not sufficient, step toward the implementation of more robust risk controls.

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.

Androgen receptor targets NFKB and TSPI to suppress prostate tumor growth in vivo

The androgen role in the maintenance of prostate epithelium is subject to conflicting opinions. While androgen ablation drives the regression of normal and cancerous prostate, testosterone may cause both proliferation and apoptosis. Several investigators note decreased proliferation and stronger response to chemotherapy of the prostate cancer cells stably expressing androgen receptor (AR), however no mechanistic explanation was offered. In this paper we demonstrate in vivo anti-tumor effect of the AR on prostate cancer growth and identify its molecular mediators. We analyzed the effect of AR on the tumorigenicity of prostate cancer cells. Unexpectedly, the AR-expressing cells formed tumors in male mice at a much lower rate than the AR-negative controls. Moreover, the AR-expressing tumors showed decreased vascularity and massive apoptosis. AR expression lowered the angiogenic potential of cancer cells, by increasing secretion of an anti-angiogenic protein, thrombospondin-1. AR activation caused a decrease in RelA, a subunit of the pro-survival transcription factor NF kappa B, reduced its nuclear localization and transcriptional activity. This, in turn, diminished the expression of its anti-apoptotic targets, Bcl-2 and IL-6. Increased apoptosis within AR-expressing tumors was likely due to the NF kappa B suppression, since it was restricted to the cells lacking nuclear (active) NF kappa B. Thus we for the first time identified combined decrease of NF kappa B and increased TSP1 as molecular events underlying the AR anti-tumor activity in vivo. Our data indicate that intermittent androgen ablation is preferable to continuous withdrawal, a standard treatment for early-stage prostate cancer. (C) 2007 Wiley-Liss, Inc.

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.

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.