The Chemist in the shipyard

This paper is intended to illustrate the role that the chemist has to play in the maintenance of ships, and the scope of the work that a Dockyard Laboratory has to carry out. A number of specific problems are discussed and certain modern laboratory techniques are outline

Corrosion in Boilers & Water Circulation Systems with Special Reference to Marine Installations

Several different types of corrosion may be found to occur in boilers, especially - marine boilers, in addition to ordinary fatigue effects. There may be a more or less uniform and widespread attack upon all the metal surfaces of the boiler ; secondly , various forms of pitting are met with ;caustic embrittlement, or caustic cracking , may occur ; and lastly there will almost certainly be external corrosion on the fire side of the generating system. Of these, pitting is probably the commonest internal form of corrosion

Corrosion and the Failure of Metals

Corrosion is one of the greatest single factors in the failure of metals; no broad discussion of this topic could possibly be complete without reference to corros- ion phenomena. The mechanical failures encountered in practice can often be ascribed to causes such as the faulty design of components, or the unreasonable stress-ing of parts, or the use of wrong or impure materials or of those which have received faulty metallurgical treat-ment, or to the incorrect operation of machinery or equipment; the metal may well he less to blame than the man who manufactures it or uses it.But a tendency towards corrosion, on the other hand, is an inherent character-istic of many metals,including those most widely in use, and often contributes indirectly to, or intensifies, the other forms of failure to which metals are susceptible. No excuse is needed, therefore, for introducing a review of the subject into this Symposiu

The influence of process gas type on the enamel surface condition of a high power diode laser generated single-stage ceramic tile grout seal

Almost all laser materials processing operations require the simultaneous use of an process or assist gas. This paper examines the use of O2, Ar, N2 and He as process gasses during the firing of a vitreous enamel to form a single-stage ceramic tile grout seal with a high power diode laser (HPDL) and the effects thereof on the surface condition of the glaze. The findings revealed marked differences in the surface condition of the HPDL generated enamel glaze depending upon the process gas used. The use of O2 as the process gas was seen to result in glazes with far fewer microcracks and porosities than those generated with any of the other three gasses, particularly He. Such differences were found to be due to the ability of the smaller O2 gas molecules to dissolve molecularly into the open structure of the HPDL generated enamel glaze and also, the inherent reactiveness of O2 which consequently effects exothermic reactions when it is used as a process gas. Both occurrences were seen, in turn, to affect the cooling rate and therefore the tendency of the molten glaze to generate microcracks when cooled

A comparative investigation of the wear characteristics of a high power diode laser generated single-stage tile grout and commercial epoxy tile grout

A comparative study of a single-stage ceramic tile grout, generated using a 60 W high power diode laser (HPDL), and a commercially available tile grout has determined the wear characteristics of the two materials. Within both normal and corrosive environmental conditions, the single-stage ceramic tile grout proved to have a superior wear rate over the epoxy tile grout, 0.9 mg/cm2/h compared with 125 mg/cm2/h when in an HNO3 environment respectively. Likewise, life assessment testing revealed that the single-stage ceramic tile grout gave an increase in wear life of 4 to 42 times over the commercially available epoxy tile grout, depending upon the corrosive environment. It is believed that the economic and material benefits to be gained from the deployment of such an effective and efficient means of sealing ceramic tiles could be significant

Typical properties of optimal growth in the Von Neumann expanding model for large random economies

We calculate the optimal solutions of the fully heterogeneous Von Neumann expansion problem with $N$ processes and $P$ goods in the limit $N\to\infty$. This model provides an elementary description of the growth of a production economy in the long run. The system turns from a contracting to an expanding phase as $N$ increases beyond $P$. The solution is characterized by a universal behavior, independent of the parameters of the disorder statistics. Associating technological innovation to an increase of $N$, we find that while such an increase has a large positive impact on long term growth when $N\ll P$, its effect on technologically advanced economies ($N\gg P$) is very weak.Comment: 8 pages, 1 figur

CONCENTRATION ISSUES IN THE U.S. BEEF SUBSECTOR

Industrial Organization, Livestock Production/Industries,

Modeling Stable Matching Problems with Answer Set Programming

The Stable Marriage Problem (SMP) is a well-known matching problem first introduced and solved by Gale and Shapley (1962). Several variants and extensions to this problem have since been investigated to cover a wider set of applications. Each time a new variant is considered, however, a new algorithm needs to be developed and implemented. As an alternative, in this paper we propose an encoding of the SMP using Answer Set Programming (ASP). Our encoding can easily be extended and adapted to the needs of specific applications. As an illustration we show how stable matchings can be found when individuals may designate unacceptable partners and ties between preferences are allowed. Subsequently, we show how our ASP based encoding naturally allows us to select specific stable matchings which are optimal according to a given criterion. Each time, we can rely on generic and efficient off-the-shelf answer set solvers to find (optimal) stable matchings.Comment: 26 page

Low mass dimuons within a hybrid approach

We analyse dilepton emission from hot and dense hadronic matter using a hybrid approach based on the Ultrarelativistic Quantum Molecular Dynamics (UrQMD) transport model with an intermediate hydrodynamic stage for the description of heavy-ion collisions at relativistic energies. Focusing on the enhancement with respect to the contribution from long-lived hadron decays after freeze-out observed at the SPS in the low mass region of the dilepton spectra (often referred to as "the excess"), the relative importance of the emission from the equilibrium and the non-equilibrium stages is discussed.Comment: Proceedings of Hot Quarks 2010, 21-26 June 2010 Las Londe Les Maures; v2: Corrected typos and added a commen