Fabrication of test structures for 4×4 InP/InGaAsP integrated optical matrix

A novel optical switching matrix measuring 1×2 mm2 in size is fabricated. The switching matrix is composed of waveguides, four 1×4 multimode interference (MMI) splitters, 32 total internal refraction mirrors and four 4×1 MMI combiners with the extremely compact size of 1×2 mm2. This integrated device are assessed and loss contribution measured from test structure is presented.

Process development on the monolithic fabrication of an ultra-compact 4×4 optical switch matrix on InP/InGaAsP material

We have fabricated an ultra-compact 4×4 optical matrix on InP/InGaAsP material. 1×4 MMI couplers and TIR mirrors are employed to produce a compact 1×2 mm2 device. A CH4/H2/O2 RIE dry etch process has been used to realize two-level dry etching: deep-etch for both the MMI couplers and the mirrors and shallow-etch for the rest of the routing waveguides. It was found that a metal/dielectric bilayer mask is essential for multi-dry-etch processes and high profile verticality. We have found a Ti intermediate mask for the deep-etch process which is removable by SF6 dry-etch before the following shallow process. Dry-etch removal of the intermediate mask is necessary to protect the deep-etched mirror sidewall.

LES and hybrid LES/RANS simulations for conjugate heat transfer over a matrix of cubes

Large Eddy Simulation (LES) and a novel k -l based hybrid LES/RANS approach have been applied to simulate a conjugate heat transfer problem involving flow over a matrix of surface mounted cubes. In order to assess the capability and reliability of the newly developed k -l based hybrid LES/RANS, numerical results are compared with new LES and existing RANS results. Comparisons include mean velocity profiles, Reynolds stresses and conjugate heat transfer. As well as for hybrid LES/RANS validation purposes, the LES results are used to gain insights into the complex flow physics and heat transfer mechanisms. Numerical simulations show that the hybrid LES/RANS approach is effective. Mean and instantaneous fluid temperatures adjacent to the cube surface are found to strongly correlate with flow structure. Although the LES captures more mean velocity field complexities, broadly time averaged wake temperature fields are found similar for the LES and hybrid LES/RANS. Copyright © 2005 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

A fully integrated 660 MHz low-swing energy-recycling DC-DC converter

A fully integrated 0.18 μm DC-DC buck converter using a low-swing "stacked driver" configuration is reported in this paper. A high switching frequency of 660 MHz reduces filter components to fit on chip, but this suffers from high switching losses. These losses are reduced using: 1) low-swing drivers; 2) supply stacking; and 3) introducing a charge transfer path to deliver excess charge from the positive metal-oxide semiconductor drive chain to the load, thereby recycling the charge. The working prototype circuit converts 2.2 to 0.75-1.0 V at 40-55 mA. Design and simulation of an improved circuit is also included that further improves the efficiency by enhancing the charge recycling path, providing automated zero voltage switching (ZVS) operation, and synchronizing the half-swing gating signals. © 2009 IEEE.

Modular risk modeling and management of water infrastructure disaster incidents

Water supply and wastewater control are critical elements of society's infrastructure. The objective of this study will be to provide a generic risk assessment tool to provide municipalities and the nation as a whole with a quantifiable assessment of their vulnerability to water infrastructure threats. The approach will prioritize countermeasures and identify where research and development is required to further minimize risk. This paper outlines the current context, primary concerns and state-of-the art in critical infrastructure risk management for the water sector and proposes a novel approach to resolve existing questions in the field. The proposed approach is based on a modular framework that derives a quantitative risk index for varied domains of interest. The approach methodology is scaleable and based on formal definitions of event probability and severity. The framework is equally applicable to natural and human-induced hazard types and can be used for analysis of compound risk events.

Modular distributed manufacturing systems and the implications for integrated control

Driven by the need for more responsive manufacturing processes and as a consequence of increasing complexity in products and production systems, this short paper introduces a number of developments in the area of modular, distributed manufacturing systems. Requirements for the development of such systems are addressed and, in particular, the relevance to current and future integrated control systems is examined. One of the key issues for integrated control systems in the future is the need to provide support for distributed decision-making in addition to existing distributed control capabilities.

SoC energy savings = reduce+reuse+recycle: A case study using a 660MHz DC-DC converter with integrated output filter

This paper advocates 'reduce, reuse, recycle' as a complete energy savings strategy. While reduction has been common to date, there is growing need to emphasize reuse and recycling as well. We design a DC-DC buck converter to demonstrate the 3 techniques: reduce with low-swing and zero voltage switching (ZVS), reuse with supply stacking, and recycle with regulated delivery of excess energy to the output load. The efficiency gained from these 3 techniques helps offset the loss of operating drivers at very high switching frequencies which are needed to move the output filter completely on-chip. A prototype was fabricated in 0.18μm CMOS, operates at 660MHz, and converts 2.2V to 0.75-1.0V at ∼50mA.1 © 2008 IEEE.

A 660MHz ZVS DC-DC converter using gate-driver charge-recycling in 0.18μm CMOS with an integrated output filter

The design and manufacture of a prototype chip level power supply is described, with both simulated and experimental results. Of particular interest is the inclusion of a fully integrated on-chip LC filter. A high switching frequency of 660MHz and the design of a device drive circuit reduce losses by supply stacking, low-swing signaling and charge recycling. The paper demonstrates that a chip level converter operating at high frequency can be built and shows how this can be achieved, using zero voltage switching techniques similar to those commonly used in larger converters. Both simulations and experimental data from a fabricated circuit in 0.18μm CMOS are included. The circuit converts 2.2V to 0.75∼1.0V at ∼55mA. ©2008 IEEE.