A model for the creep of concrete

Porosity and density changes were measured for a series of mortar specimens and a series of cement paste specimens subjected to various compressive stress histories during desorption and sorption cycles.

It was found that hydration is inhibited by compressive stress. Under normal basic and drying creep, the effect of compressive stress is to reduce the porosity and increass the interlayer volume with a corresponding increase in the weight of water retained in the interlayer spaces. For specimens completely dried under load the interlayer volume decreases with load. A model for the creep of concrete is advanced in which, under sustained stress, interlayer volume increases as a result of physical distortion of the solid sheets of cement hydrate.     

Interfuel substitution in the primary metals industries

This paper applies a translog price possibility frontier to a pooled sample in order to measure the extent of interfuel substitution effects in the primary metals industries. The results clearly indicate that relative changes in fuel prices across primary metals industries have significant effects on energy consumption. This, in turn, has important implications for public policy. In particular, the market system appears better able to deal with exogenous shifts in energy supplies than has frequently been assumed in the formulation of public policies toward the energy crisis.     

Synthesis and mesomorphic properties of a new thermotropic liquid-crystalline ‘backbone’ copolyester

Details of the thermal behaviour of the following liquid-crystalline ‘backbone’ copolyester are reported: — [OCC₆O]_0.6+[OOCC₆H₄OCH₂CH₂OC₂H₄COOCH₂CH₂]_0.4? Between 218° and 337°C, observations using a polarizing microscope indicate the formation of a birefringent melt that exhibits a Schlieren texture. From the observation of disclinations of strength $\text{±}\text{1}\text{2}$, the mesophase can be identified as a nematic phase. The isobaric phase diagram of mixtures of copolyester and N,N′-di-(ρ-methoxy benzylidene)-α,α′-bi-ρ-toluidine and X-ray diffraction patterns provide definite proof as to the nematic structure of the birefringent melt. Addition of a chiral compound to the copolyester in the nematic state causes the formation of the typical textures of cholesterics. The temperature dependence of the order parameter has been determined from FTi.r. polarized spectra. At high temperature S is found to be 0.3. Such a result confirms the recent theory of Ronca and Yoon: the isotropic-nematic transition of semiflexible polymers does not entail a very high degree of order in the resultant nematic phase.     

Issues in Distributed it Management

The implementation and management problems facing today's IT operations managers and administrators working with distributed systems and networks are well known. No simple solution exists. Success requires the enterprise to define clearly and explicitly both the problem to be solved and the goal of the project.