Toward improved boron removal in RO by membrane modification: feasibility and challenges

Membrane modification by concentration polarization (CP)-enhanced radical graft polymerization using a dilute aqueous solution of appropriate monomer was examined as a method for increasing rejection of boric acid by reverse osmosis (RO) membranes. On the basis of suggested physicochemical rationales a number of monomers were examined in order to determine those with the lowest affinity toward boric acid as compared to water. The improvement in the modified membrane performance was mainly attributed to sealing less selective areas ("defects") inherently present in the original low pressure RO (LPRO) membranes. However, the effect clearly differed for different monomers. Among the examined monomers glycidyl methacrylate (GMA) exhibited the lowest affinity and the largest improvement in removal of boric acid along with a moderate loss of permeability and slightly improved NaCl rejection. Modification of LPRO membrane thus resulted in a membrane with a permeability in the brackish water RO (BWRO) range but with removal of boric acid and salt superior to those reported for most commercial BWRO membranes.     

Design Instruments of Service in the Era of Connection

The move towards digital connectivity demands a major rethink of processes, professional obligations and value propositions in architecture. Here, Phillip G Bernstein – architect, educator, technologist, and a vice-president of Autodesk, Inc – examines how digital modelling is destroying the barriers between design and execution. He considers what impact this has on liabilities and copyright, and investigates the possibilities for architects and builders to be financially rewarded for the performance promises that the new technology makes possible.     

Failure dynamics of the IGBT during turn-off for unclampedinductive loading conditions

The internal failure dynamics of the insulated gate bipolar transistor (IGBT) for unclamped inductive switching (UIS) conditions are studied using simulations and measurements. The UIS measurements are made using a unique, automated nondestructive reverse-bias safe operation area test system. Simulations are performed with an advanced IGBT circuit simulator model for UIS conditions to predict the mechanisms and conditions for failure. It is shown that the conditions for UIS failure and the shape of the anode voltage avalanche-sustaining waveforms during turn-off vary with the IGBT temperature, and turn-off current level. Evidence of single- and multiple-filament formation is presented and supported with both measurements and simulations     

Low-noise MEMS vibration sensor for geophysical applications

The need exists for high-sensitivity, low-noise vibration sensors for various applications, such as geophysical data collection, tracking vehicles, intrusion detectors, and underwater pressure gradient detection. In general, these sensors differ from classical accelerometers in that they require no direct current response, but must have a very low noise floor over a required bandwidth. Theory indicates a capacitive micromachined silicon vibration sensor can have a noise floor on the order of 100 ng/√Hz over 1 kHz bandwidth, while reducing size and weight tenfold compared to existing magnetic geophones. With early prototypes, we have demonstrated Brownian-limited noise floor at 1.0 μg/Hz, orders of magnitude more sensitive than surface micromachined devices such as the industry standard ADXL05     

Global stabilization of systems containing a double integrator using a saturated linear controller

In this paper, we present a Lyapunov function for systems containing a double integrator and with controller saturation. This Lyapunov function is composed of a positive-semidefinite quadratic term and an integral term. The main result provides a sufficient condition that guarantees a system with a double integrator can be globally stabilized by a saturating linear controller. For a triple-integrator system the saturated linear controller does not satisfy the sufficient condition, which agrees with the known result. Copyright © 1999 John Wiley & Sons, Ltd.