Effects of forced power transfer on high speed generator-loadsystems

A computer-aided method for investigating disturbances due to the forced paralleling of out of phase high speed salient pole AC generator systems feeding isolated loads is presented. The method is used to predict the system performance including the reverse voltage across the rotating bridge rectifier of the field exciter. This paper presents the fundamentals and the modeling approach used in the development of this method. In addition, the results of using this approach to compute the machine parameters under different load conditions including saturation effects due to magnetic material nonlinearities and space harmonics effects due to machine geometry and winding layouts are presented. The computed parameters are validated by comparison to test data. These parameters form the main data for simulating the forced paralleling of out of phase high speed salient pole AC generator systems feeding isolated loads. Further, the results of using this modeling approach in a case study to predict the system performance due to forced power transfer are summarized and are shown to be in good agreement with test data     

Vessel wall detection and blood noise reduction in intravascularultrasound imaging

Scattering from blood limits the contrast between the vessel wall and the lumen in intravascular ultrasound imaging. This makes it difficult to localize the vessel wall, especially on still images. This paper presents a method for automatic detection of vessel walls and reduction of blood noise based on correlation of the RF-signal between adjacent frames. The ultrasound RF-signal is quadrature demodulated, digitized, stored in memory, and transferred to a computer for processing and analysis. The absolute value of the cross-correlation coefficient between two adjacent frames is used to differentiate between stationary and fluctuating signals. Models and numerical calculations presented in this work indicate that the cross-correlation coefficient obtained from a radially dilating vessel wall will be larger than 0.8 under standard 20 MHz imaging conditions. The corresponding value from blood is less than 0.2 for blood velocities exceeding 0.5 cm s^-1 . The blood-noise filter is based on detecting this difference in correlation and displays vessel wall regions with no modifications, while regions detected as blood are rejected. A simplified vessel-wall detector that is suitable for real-time implementation is proposed. The performance of this detector and the blood noise filter are demonstrated by in vitro experiments     

Instron texture profile of buffalo milk cheddar cheese as influenced by composition and ripening changes

Buffalo milk Cheddar cheese samples of different ages were analysed for compositional attributes (CA), ripening indices (RI) and Instron Textural Profile (ITP). All samples were compositionally alike, except for pH and salt-in-moisture (SM) contents. RI showed significant variations. CA and RI showed highly significant correlations within themselves and with each other, except for moisture with pH, SM with moisture, MNFS, Fat and FDM and Fat with MNFS. The ITPs of cheeses showed significant variations and had highly significant intercorrelations indicating their interdependence. CA (except moisture and MNFS) and RI showed a highly significant correlationship with ITPs. Moisture content showed a highly significant correlationship with all ITPs, except cohesiveness and springiness, where it was significant. MNFS content showed significant correlations only with hardness and brittleness. Stepwise regression analysis revealed that MI was the most predominant factor influencing cheese texture, followed by pH, SM, FDM and TVFA. Knowing Ca and RI, the textural properties of cheeses can be forecast through mathematical equations. Similarly the age of cheese can also be predicted if RI and/or textural properties are known.     

Aromatic nitrations by mixed acid. Slow liquid-liquid reaction regime

Aromatic nitrations by mixed acid have been selected as a specific case of a heterogeneous liquid-liquid reaction. An extensive experimental programme has been followed using adiabatic and heat-flow calorimetry and pilot reactor experiments, supported by chemical analysis. A series of nitration experiments has been carried out to study the influences of different initial and operating conditions such as temperature, stirring speed and sulphuric acid concentration. In parallel, a mathematical model to predict the overall conversion rate has been developed. In this paper the mathematical modelling and the implementation and experimental validation for benzene, toluene and chlorobenzene mononitration in the kinetic control regime (slow liquid-liquid reaction) are presented and discussed.     

Electro-optic sampling system for the testing of high-speedintegrated circuits using a free running solid-state laser

This paper deals with the indirect electro-optic sampling technique for the low-invasive detection of periodical voltage waveforms on lines in high-speed integrated circuits. The system introduced here is based on a passive mode-coupled Ti:Sapphire-Laser as light source for generating optical pulses in the subpicosecond regime. Therefore, we have to synchronize the resulting electric measurement signal and its external trigger onto the pulse repetition rate of this free running solid-state laser. The multi user function of the laser system forces us to transmit the pulses via a single-mode fiber into the measurement setup. For that purpose we developed a special optical arrangement to minimize the widening of the pulses in the time domain. The system's high-temporal resolution of nearly 10 ps in combination with its high-voltage sensitivity of about 800 μV/√(Hz) is demonstrated by measurements of an integrated microwave frequency divider     

Clinical applications of cytokines in pediatrics

The use of adjuvants for immunopotentiation has been investigated since the 1920s and a number of comprehensive reviews and monographs have been published on this subject. A recent trend in immunopotentiation has been the use of delivery systems which allow for sustained or controlled release of antigens and which induce prolonged immunity following a single dose. This concept has been termed either single-step or single-shot immunization. The delivery system has been modulated to potentiate the immune response either by delivering the antigen (and perhaps an adjuvant or adjuvants) either over a prolonged period of time or in a predetermined sequence or by incorporating substances with immunoadjuvant properties (e.g., lecithin and certain biodegradable polymers) as carriers within the delivery system. This Review focuses on the progress made in the design of delivery systems for immunopotentiation. Particular emphasis is given to delivery systems designed to achieve single-step immunization.     

High fibre bread containing brewer's spent grains and its effect on lipid metabolism in rats

Bread samples containing milled brewer's spent grain (BSG) at levels of 10–25% were prepared. The protein content of the bread ws found to be 15.4, 16.3 and 18.8%, when BSG was added at levels of 10, 20 and 25%, respectively. Fibre content however was 4.9, 6.4 and 7.5%, repectively. Amino acid pattern of the bread samples revealed that most of the essential amino acids were found in considerable amounts compared to the FAO provisional pattern with exception to lysine, threonine and tryptophan which showed deficiencies. The bread samples were fed to rats for 28 days, after which total lipids and cholesterol were measured. The results indicated impaired growth weight (7.1–10.0%) compared with the control. Total lipids as well as total cholesterol were also reduced by 5.7–8.0% and 6.0–8.3%, respectively. Sensory evaluations of prepared bread showed high score acceptance for fino bread, rolls and baton salie amounted to 70.0, 63.0 and 62.7%, respectively.