Application of a multi-channel system for continuous monitoring and an early warning system.

A multi-channel continuous toxicity monitoring system developed in our laboratory, based on two-stage mini-bioreactors, was successfully implemented in the form of computer-based data acquisition. The multi-channel system consists of a series of a two-stage minibioreactor systems connected by a fiber optic probe to a luminometer, and uses genetically engineered bioluminescent bacteria for the detection of the potential toxicity from the soluble chemicals. This system can be stably and continuously operated due to the separation of the culture reactor from the test reactor and accomplish easy and long-term monitoring without system shut down by abrupt inflows of severe polluting chemicals. Four different recombinant bioluminescent bacteria were used in different channels so that the modes of the samples toxicities can be reasonably identified and evaluated based upon the response signature of each channel. The bioluminescent signatures were delivered from four channels by switching one at once, while the data is automatically logged to an IBM compatible computer. We also achieved the enhancement of the system through the manipulation of the dilution rate and the use of thermo-lux fusion strains. Finally, this system is now being implemented to a drinking water reservoir and river for remote sensing as an early warning system.     

A single-chip storage LSI for home networks

Network direct attached storage (NDAS) is a network storage architecture that allows direct attachment of existing ATA/ATAPI devices to Ethernet without a separate server. Unlike other architectures such as NAS, SAN, and USB mass storage, no server computer intervenes between the storage and the client hosts. We describe an NDAS disk controller (NDC) amenable to low-cost single-chip implementation that processes a simplified L3/L4 protocol and converts commands between ATA/ATAPI and Ethernet, while the remaining complex tasks are performed by remote hosts. Unlike NAS architectures that use TCP/IP, NDAS uses a TCP-like lean protocol that lends itself well to high-performance hardware realization. Thanks to the simple NDAS architecture and protocol, an NDC implemented on a single 4 mm /spl times/ 4 mm chip in 0.18 /spl mu/m CMOS technology achieves a maximum throughput of 55 Mbytes/s on gigabit Ethernet, which is comparable to that of a high-performance disk locally attached to a host computer.     

Direct adaptive control of nonminimum phase systems using integralaction

A direct adaptive control scheme is proposed for nonminimum-phase systems in which controller parameters are estimated from the recursive least-squares algorithm and additional auxiliary parameters are obtained from the proposed polynomial identity. A local convergence is guaranteed without any extra condition. Integral action is incorporated into the adaptive controller to eliminate the steady-state error and to satisfy a condition of the unique solution for the polynomial identity. The control law used in this scheme is based on the set-point-on-I-only proportional-integral-derivative (PID) structure     

Using ion implantation to adjust the transition temperature of superconducting films

We summarize a continuing investigation into using ion implantation to alter the transition temperature of superconducting thin films. The primary motivation for the work presented here was to study the feasibility of using magnetic ion doping to replace the bi-layer T_c control process currently used for certain cryogenic detector applications at National Institute for Standards and Technology. The results from work with various ion species implanted into aluminum, molybdenum, titanium and tungsten host films are presented.     

Synthesis of LiFePO4 with fine particle by co-precipitation method

LiFePO₄ is a potential candidate for the cathode material of the lithium secondary batteries. A co-precipitation method was adopted to prepare LiFePO₄ because it is simple and cheap. Nitrogen gas was needed to prevent oxidation of Fe²⁺ in the aqueous solution. The co-precipitated precursor shows the high reactivity with the reductive gas, and the single phase of LiFePO₄ is successfully synthesized with the aid of carbon under less reductive conditions. LiFePO₄ fine powder prepared by co-precipitation method shows high rate capability, impressive specific capacity and cycle property.     

Physical modeling of gas/liquid mass transfer in a gas stirred ladle

The absorption of gas through the plume eye and of an injected gas in a steelmaking ladle process was investigated, using a physical model of CO₂ absorption into a NaOH solution. The results show that the inert gas escaping through the plume eye is ineffective in protecting the bath from the atmosphere, and placing an oil layer (simulated slag) decreases the absorption rate significantly. Increasing the flow rate of the inert gas not only exposes more of the liquid surface to the CO₂ atmosphere, but also increases the mass transfer coefficient at the surface. The overall mass transfer between an injected CO₂ gas and NaOH solution includes the mass transfer through the surface of the bath as well as the mass transfer in the bubble dispersion zone. The difference between the mass transfer in the bubble dispersion zone and the overall mass transfer was found to be significant for relatively low gas flow rates. The mass transfer coefficient of CO₂ in the bubble dispersion zone was estimated using available information regarding the bubble size and velocity. Mass transfer coefficient estimated for the constant bubble frequency regime shows a dependence on gas flow rate. However, if a constant characteristic size of bubbles is assumed as an alternative approach, the mass transfer coefficient is independent of the gas flow rate.     

Pulse stabilisation in harmonically FM modelocked erbium fibre ring laser with DFBLD

A new pulse stabilisation scheme for a harmonically frequency modulated (FM) modelocked erbium fibre ring laser using a distributed feedback laser diode (DFBLD) is presented. More than 65 dB supermode noise suppression in the RF spectrum was obtained with the proposed method. Effective reduction of supermode noise can be accomplished as the DFBLD in the fibre laser acts not only as a fast-gain saturated medium but also as an optical bandpass filter for suppressing supermode noise in a harmonically modelocked laser system.     

High dielectric constant thin film EBG power/ground network for broad-band suppression of SSN and radiated emissions

We experimentally demonstrated the great advantages of a high dielectric constant thin film electromagnetic bandgap (EBG) power distribution network (PDN) for the suppression of power/ground noises and radiated emissions in high-performance multilayer digital printed circuit boards (PCBs). Five-layer test PCBs were fabricated and their scattering parameters measured. The power plane noise and radiated emissions were measured, investigated and related to the PDN impedance. This successfully demonstrated that the bandgap of the EBG was extended more than three times, covering a range of hundreds of MHz using a 1-cm /spl times/ 1-cm EBG cell, the SSN was reduced from 170 mV to 10 mV and the radiated emission was suppressed by 22 dB because of the high dielectric constant thin film EBG power/ground network.