Sequential tripping strategy for a transmission network back-upprotection expert system

This paper describes a sequential tripping strategy used in a wide area back-up protection expert system (BPES) to combat situations in which protection relays have maloperated or information is missing. The BPES is an innovative back-up protection scheme designed to prevent the occurrence of widespread blackouts. The BPES evaluates the certainty that transmission lines are likely to be affected by the fault and uses a sequential tripping strategy to isolate the fault if a firm decision is not available due to maloperated relays and/or missing information. The mode of analysis and the sequential tripping strategy ensures that the BPES will clear a fault at minimum risk to the network. An example is included to demonstrate how the certainty factor based sequential tripping strategy is employed by the BPES to clear a fault which occurred on the South Western part of the UK National Grid System     

Microprocessor-Based Control of an Ion Beam Deposition System

A microprocessor-based system with 32 A/D, 24 D/A, and 16 ac load controllers, has been designed and built to monitor and control an ion beam thin-film deposition system. The A/D and D/A channels have electrical isolation of 7.5 kV between channels and between input and output. The microprocessor system keeps the ion beam deposition parameters stable for extended periods of operation and it is proposed as a means to greatly simplify switching from one deposition species to another to grow thin multilayer or alloy films.     

Bonding in cotton fiber from formaldehyde-free crosslinks

Cotton fabric was crosslinked with five agents, three of which were prepared form formaldehyde and two of which were formaldehyde-free. The formaldehyde-free agents produced less bonding between layers in the laminated microstructure of the cotton fiber. One agent, 4,5-dihydroxy-1,3-dimethyl-2-imidazolidinone, gave no evidence of any interlayer bonding. All five agents gave the same relationship between wrinkle recovery angle and molar substitution on the cotton up to moderate recovery angles, but only agents based on formaldehyde gave higher wrinkle recovery angles with additional reaction. Intralayer crosslinking did not reduce absorptivity, as shown by moisture regain and dye receptivity, but did restrict swelling in cupriethylenediamine hydroxide to the same extent as combined interlayer and intralayer crosslinking. The decrease in extensibility of treated fabric with increasing wrinkle recovery angle was the same with all agents. These results indicate the regions of the fiber that are important for each of these properties.     

New natural 2-acetoxy fatty acids using chemical ionization and electron impact mass spectrometry

The phospholipids of the spongePolymastia gleneni contain saturated long chain (C_22–30)-acetoxy fatty acids. Their structures were assigned based on chromatographic and spectrometric data as well as comparison with a synthetic sample. The use of capillary gas chromatography combined with chemical ionization and electron impact mass spectrometry was instrumental in the eludication of structures, since only a very small amount of crude lipids was available. Part 10 of “Phospholipids in Marine Organisms.” For Part 9 in this series, see reference 12.     

Intramolecular crosslinking of poly(vinyl alcohol)

Poly(vinyl alcohol) is crosslinked in dilute solution (c=0.1 wt%) with glutaraldehyde. The reaction product is characterized by viscometry and gel permeation chromatography (g.p.c.). The intrinsic viscosity decreases with increasing degree of crosslinking and does not depend on temperature. G.p.c. reveals that the reaction product is not homogeneous, but consists of a mixture of particles with different sizes, possibly both intra- and intermolecularly crosslinked molecules. The intramolecularly crosslinked molecules are smaller in size than the initial polymer molecules and their size depends on the degree of crosslinking. They possess a narrow particle size distribution even if the initial polymer sample had a broad molecular weight distribution.     

Laboratory accreditation in the UK

Two complementary national laboratory accreditation schemes are run by the National Physical Laboratory (NPL) to provide official recognition of competent British laboratories and an assurance of quality to their customers. The first of these, the British Calibration Service (BCS), was set up in 1966 to accredit laboratories to calibrate instruments, gauges and reference materials. In 1981 the National Testing Laboratory Accreditation Scheme (NATLAS) was formed to extend the service to all kinds of testing. Both BCS and NATLAS form an integral part of the UK national measurement system and were combined to form the National Measurement Accreditation Service on 1 October 1985.     

PCR-based procedures in detection and DNA-fingerprinting of Salmonella from samples of animal origin

The usefulness of selected PCR-protocols for the detection of Salmonella in 117 samples of animal origin (17 raw minced meat, 27 raw chicken meat, 8 raw sausages, and 25 egg samples, as well as 18 poultry faecal, and caecal swabs samples) and DNA-fingerprinting typing is shown. To establish an accurate PCR-procedure for Salmonella detection the following parameters were evaluated: two pre-PCR concentration procedures, centrifugation and immunomagnetic separation (IMS) using Dynabeads anti- Salmonella; the specificity and sensitivity of 10 sets of primers; and different conditions of the amplification reaction. In light of the results obtained from the use of PCR-based procedures alone or in combination with conventional methods, the following findings can be underlined: First, IMS is more efficient than centrifugation in the recovery of Salmonella. Second, the selected IMS/PCR-detection protocol is less time-consuming (45 h) than the IMS/culture procedure (90 h), and a good concordance between them was found when the Kappa coefficient was calculated (0·87). Third, PCR-ribotyping technique showed a very low discrimination power, being able to differentiate only three profiles. Fourth, RAPD technique using specific primers supports previous works in which it was proposed as a simple and useful tool for discriminating isolates between and within serotypes. Fifth, The efficiency, rapidity, and flexibility of the PCR-protocols applied were high, and they can be performed using two PCR-programs and the same basic equipment.     

Shallow Linear Action Graphs and their Embeddings

Action calculi, which generalise process calculi such as Petri nets, π-calculusand ambient calculus, have been presented in terms of action graphs. We here offer linear action graphs as a primitive basis for action calculi. This paper presents the category of embeddings of undirected linear action graphs without nesting, using a novel form of graphical reasoning which simplifies some otherwise complex manipulations in regular algebra. The results are adapted in a few lines to directed graphs. This work is part of a long-term search for a uniform behavioural theory for process calculi. Received October 2000 / Accepted in revised form April 2001