PYRITE PARTICLE SIZE DISTRIBUTION AND PYRITIC SULFUR REDUCTION IN CRUSHED COALS: A PRELIMINARY REPORT

ABSTRACT

Six bituminous coals were ground to 28, 100, and 400 mesh x 0, and examined by optical automated image analysis (AIA) to estimate their pyrite particle size distributions and degree of liberation (DOL). These data were used to determine the feasibility of estimating specific-gravity-based pyritic sulfur reduction by AIA methods. Preliminary results indicate that further research is warranted. A review of the progress is presented.     

MATHEMATICAL PROGRAMMING IN SEWER NETWORK DESIGN

This paper addresses itself to the question of obtaining the minimum cost design for a wastewater collection network. It first presents an empirical cost function for a single sewer line. The concept of optimization is then explored with respect lo sewer networks. The design problems of selecting an optimal mix of pipe diameters and slopes, given a set of economic and technological inputs as well as a network layout is then presented in three alternative mathematical programming formulations: separable convex, dynamic and geometric programming. These formulations guarantee the generation of global optimal solutions. Numerical solutions can be obtained using presently available computer capabilities. The paper concludes with an evaluation of the proposed formulations and their implications for both design practice and overall cost reduction in the area of wastewater collection.     

Consortium Developments Ltd and the failure of ‘new country towns’ in Mrs Thatcher’s Britain

This article examines the attempt by Britain’s biggest house builders to launch a privately‐initiated programme of ‘new country towns’ during the 1980s. It was their response to the policy changes of the Thatcher governments, shrinking the state sector and deregulating private enterprise. Consortium Developments Ltd (CDL) was established in 1983, intending to develop up to 15 new country towns in the prosperous region around London, where housing demand was high but local planning very restrictive of developers. Each town would comprise around 5000 dwellings with social and physical infrastructure largely provided by CDL. The concept was a novel one in twentieth century Britain, where new settlements had been developed previously by philanthropic companies or by government agencies. Advised by planners associated with Milton Keynes, CDL effectively updated the Garden City–New Town tradition for the Thatcher era. However, despite pushing four proposals through the planning process, all failed. This largely reflected opposition of the government’s own party supporters, who did not want Thatcherism shaping their own areas. In the face of this, Thatcher’s ministers were ultimately unwilling to support CDL. Combined with the effects of the 1990s property slump, the volume builders withdrew and CDL was dissolved. Its failure partly reflects wider fracture lines in Thatcherism, compounded by the aggressive and very public campaigning style of its own operations which gave each proposal a very wide political resonance. Thatcherism gave way to a more restrictive planning climate in the 1990s. Paradoxically, a Labour government is now, from 2003, creating massive new opportunities for private house building and town development around London.     

THE BULK AND SURFACE STRUCTURE OF γ-ALUMINA

This paper presents the real-time application of the learning control theory to the control of a chemical pilot plant: a pulsed liquid-liquid extraction column.

The behaviour of an agitated liquid-liquid extraction column can be related to random mechanisms such as the phenomena of droplets breakage and coalescence. Previous studies on hydrodynamic and mass transfer aspects showed that a pulsed liquid-liquid extraction column had an optimal behaviour for operating conditions close to flooding. These results led to choose the following strategy to control the column in its optimal behaviour zone:

- the measure of the conductivity of the liquid medium below the distributor which gives a good information about flooding, is the controlled variable

-the pulse frequency is the control action.

The learning control algorithm is based on a multilevel system of automata which operates in a random environment. By means of an evaluation unit of the performances of the column which generates either penalty (inaction) or reward on the basis of heuristic rules, the automaton chooses a value of the pulse frequency. This approach is essentially connected to artificial intelligence in so far as human knowledge on the plant is included in these rules.

This algorithm has been implemented on a microcomputer for control purposes. The experimental results presented show the good performances of the approach.     

Part I-Smith form and common divisor of polynomial matrices

Polynomial matrices play an important part in linear system calculations. New computational procedures are given for calculation of the Smith normal form and the greatest common right divisor of polynomial matrices. It is shown how suitable transformation matrices can be determined for the calculation of the Smith normal form, and how a set of polynomial matrix multipliers can be calculated for the greatest common right divisor problem. Neither of these algorithms relies on explicit calculation of the greate3t common divisor of polynomials. Limited numerical experience has shown that the3e algorithms are both fast and accurate.     

Flash Tube Seal Dynamics in 30 mm Ammunition

Certain 30 mm ammunitions use a flash tube to augment the primer and to provide an ignition source for the propellant. The flash tube must provide abundant hot gases/particles and pressurize the propellant bed sufficiently so that the initial burn rate of the propellant is high enough to propel the projectile to the muzzle within the few milliseconds that constitute the action time of the cannon. Rupture of the seal at differing rupture pressures was shown to affect the initial pressure in the chamber enclosing the propellant bed, as well as the amount of burning particles released into the bed.     

ETHYLENE CAPSULE PROMOTES EARLY RIPENING OF 'd'ANJOU' PEARS PACKED IN MODIFIED ATMOSPHERE BAGS

‘d'Anjou’ pears (Pyrus communis, L.) harvested commercially with flesh firmness of 64.5 N were incapable of ripening normally at 20C within 60 days of air storage at ‐1C (denoted as “under‐chilled” fruits). When under‐chilled ‘d'Anjou’ fruits (8 fruits, total fruit weight of 1.8 kg) were packed in a 3.8‐liter perforated bag inserted with an ethylene capsule, fruit would ripen normally at 20C. The ethylene concentration in the packed bag maintained no less than 100 ppm after 4 days at 20C, and declined to about 25 ppm on day 7. Regardless of the storage length, ripened fruit induced by the ethylene capsule developed high buttery and juicy texture. If ‘d’ Anjou’ fruit had been stored at ‐1C for less than 30 days, ripened fruit lacked high flavor quality. Flavor quality of ripened fruit improved rapidly when the fruit had been stored for longer than 30 days.