Influence of nitrate, ascorbic acid, and nitrate reductase microorganisms on N-nitrosamine formation during Korean-style soysauce fermentation.

Traditional Korean soysauce samples were collected from households in Chinju, Gyeongnam, Korea and analysed for volatile N-nitrosamines. Five of 24 samples contained NDMA (range = 1.6-10.4 micrograms/l) which was the only volatile N-nitroso compound found. Soysauce made from well water contained NDMA more often (4 of 6 samples) than soysauce made from tap water (1 of 18). This suggests that the water source is a determinate in the NDMA content of soysauce, probably due to a higher nitrate content of well water. The source of salt used did not clearly influence NDMA content. Soysauce was prepared in the laboratory using traditional methods but with 0 to 400 mg/l nitrate and in some cases made 6.5 to 65 mM in ascorbic acid and fermented for 120 days. The NDMA content of the samples was positively correlated with increasing nitrate concentration. Nitrate at 400 mg/l resulted in an NDMA content of 203 micrograms/l. Ascorbic acid substantially inhibited NDMA formation. All samples contained large numbers of nitrate reductase-containing organisms (greater than 1 x 10(7) CFU/ml).     

Extremum-seeking with variable gain control for intensifying biogas production in anaerobic fermentation.

A state-dependent variable-gain control system is implemented to follow the characteristics of a laboratory-scale up-flow anaerobic fixed-bed reactor dynamically. The transition from one state to another is determined on an hourly basis, depending on difference between the setpoint of the reactor pH and its true value. Considerable improvement of the process stability--reduction of oscillation in both the reactor pH and biogas production rate during high-rate operation, has been achieved, although the control structure is simple and intuitive.     

Precision winding of fiber optic filament. II. Winding control

For pt.I see ibid., vol.39, no.3, p.258-67 (1992). The winding of fiber optic filament in the hoop, or precision, pattern is considered. Various automatic control options that have been designed and tested are described. The controllers are designed to regulate the fiber lag angle, which is the angle at which the feed filament approaches the take-up spool. Successful, flawless winding is directly related to accurate lag regulation. The contributions are distinguished by the fact that the automatic winding rate is 10 to 30 times greater than that achieved before by operator-assisted winding     

Effects of measurement errors on microwave antenna holography

The effects of measurement errors appearing during the implementation of the microwave holographic technique are investigated in detail, and many representative results are presented based on computer simulations. The numerical results are tailored for cases applicable to the utilization of the holographic technique for the NASA's Deep Space Network antennas, although the methodology of analysis is applicable to any antenna. Many system measurement topics are presented and summarized     

Catching the wave [gravity wave communication]

In 1873, when James Clerk Maxwell published his treatise unifying electromagnetic theory, he stated that light was electromagnetic in nature and he predicted that electromagnetic waves of greater length might exist. A dozen years later, Heinrich Hertz constructed apparatus with which he generated and received these longer waves, and he demonstrated that their behavior was identical to that of light. In the century following Hertz, these longer waves, which we now call radio waves, have been utilized to provide a vast worldwide communication system. In his theory of general relativity, published in 1915, Albert Einstein postulated the existence of gravity waves that propagate at the speed of light. If these waves could be used for communication purposes, they would open a whole new spectrum for exploitation, independent of the electromagnetic spectrum. Why is it that today, three quarters of a century later, we don't have gravity-wave transmitting and receiving stations? The article examines the reasons for this and then determines quantitatively how far we are from adding gravity waves to our communications repertoire     

Vector-controlled induction motor drive with a self-commissioningscheme

Different vector-controlled structures are discussed, and their suitability for an economical and reliable industrial drive system is explored. From this, the design of a compact control hardware is derived, composed of an 80196 microcontroller and an ASIC (application-specific integrated circuit) for the generation of the pulsewidth modulation (PWM) signals. The drive system can be configured from a host computer or a hand-held servicing unit through a serial data link. Monitoring and diagnostic functions are included. A self-commissioning scheme permits the setting of the parameters for optimum dynamic performance of the induction motor. Various oscillograms demonstrate the behavior of the vector controller operating a 25-kVA PWM inverter     

Autonomous system expansion planning considering renewable energysources-a computer package

The authors describe the interactive package ASP (Autonomous System Planning), which determines the optimal expansion plan of an autonomous generation system including diesel units, wind generators, and photovoltaic generators. Utilizing meteorological data, load demand data and estimated economical parameters, the package finds the optimal system expansion policy for a period of N years. The solution algorithms implemented in the package recognize planning and operational constraints and take into consideration the stochastic nature of the meteorological conditions, loads, and the availability of the diesel units     

New results in spectral estimation of decimated processes

The aim of this letter is to derive the spectral density of decimated processes, and to establish their model when they are generated from ARMA processes. The optimal conditions of decimation are also discussed.<>