Assessment of durability of recycled aggregate concrete produced by two-stage mixing approach

As more than 50% construction and demolition (C&D) wastes are composed of concrete debris in Hong Kong, recycling this debris into Recycled Aggregate (RA) for production of Recycled Aggregate Concrete (RAC) is an efficient way to alleviate the burden on landfill areas. Since RA is generated from concrete debris which has undergone years of services, the resulting RAC bears the weaknesses of lower density, higher water absorption, and higher porosity that limit them to lower-grade applications. Pinpointing to these weaknesses, Tam et al. [2005, Cement Concrete Res 35(6):1195–1203] developed the Two-Stage Mixing Approach (TSMA) for improving the strength of RAC, leading to the possibility in applying RAC for higher-grade applications. While the improvement in strength by TSMA has been proven in Tam et al.’s work [2005, Cement Concrete Res 35(6):1195–1203], the durability, in terms of deformation (shrinkage and creep) and permeability (water, air and chloride permeability), remains to be verified. In this paper, 0%, 20% and 100% of RA substitutions have been experimented to compare the durability performance of the Normal Mixing Approach (NMA) and the TSMA. Experiment results highlight that: (i) the higher the substitutions of RA, the weaker the performance of RAC; and (ii) the deformation and permeability of RAC can be enhanced when adopting TSMA. Therefore, it demonstrates that TSMA can help to improve the durability of RAC, on top of the previously verified strength improvement, and thus opening up wider applications of RAC.     

A genetic algorithm for railway scheduling with environmental considerations

A genetic algorithm is a randomized optimization technique that draws its inspiration from the biological sciences. Specifically, it uses the idea that genetics determines the evolution of any species in the natural world. Integer strings are used to encode an optimization problem and these strings are subject to combinatorial operations called reproduction, crossover and mutation, which improve these strings and cause them to ‘evolve’ to an optimal or nearly optimal solution. In this paper, the general machinations of genetic algorithms are described and a performance-enhanced algorithm is proposed for solving the important practical problem of railway scheduling. The problem under consideration involves moving a number of trains carrying mineral deposits across a long haul railway line with both single and double tracks in either direction. Collisions can only be avoided in sections of the line with double tracks. Constraints reflecting practical requirements to reduce environmental impacts from mineral transport, such as avoidance of loaded trains traversing populated areas during certain time slots, have to be satisfied. This is an NP-hard problem, which usually requires enumerative, as opposed to constructive, algorithms. For this reason, an ‘educated’ random search procedure like the genetic algorithm is an alternative and effective technique. The genetic algorithm is given difficult test problems to solve and the algorithm was able to generate feasible solutions in all cases.     

Factor analysis of the Marital Interaction Coding System (MICS).

A significant source of confusion in the marital observation area is the proliferation of systems for collapsing microbehavioral codes into categories. This study used an archival data set of 995 couples' videotaped conflict negotiations coded with the Marital Interaction Coding System-IV (MICS). A factor analysis was conducted to provide some empirically based guidance for the formation of coding categories. Four factors emerged for both men and women: Hostility, Constructive Problem Discussion, Humor, and Responsibility Discussion. Suggestions are made for category formation with MICS codes and for the development of a new coding system based on these results. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Business sans frontieres? Cultural diversity and the engineer inEurope

Business relationships between people of differing cultures, even within the confines of Europe, are fraught with opportunities for misunderstanding. The UK engineer doing business with mainland Europe is likely to be confronted with many differences in business customs, conventions and etiquette. Many of these are cultural. Indeed, it is said that about 20% of a business relationship is based on cultural human and interpersonal aspects. This 20% can make a negotiation succeed or fail. Time is one of these aspects. Will the British engineer be able to organise his/her business and schedule appointments in the same way as at home? The Spanish or French business partner may well have a completely different perception of time and working style. In many respects the cultural divergence corresponds to the geographic north/south divide in Europe. The author concentrates on a number of the social, cultural and linguistic factors, and offer some conclusions and solutions for the engineer     

Crystallization embrittlement of Ni-Ti-B glasses

While metallic glasses have excellent toughness and ductility in the as-cast and unrelaxed state, the process of crystallization leads to a nearly continuous and significant embrittlement. This change is examined on three Ni-Ti-B glasses and related to the morphology and distribution of the crystals obtained. For the partially crystallized materials, failure still occurs after intense shear on one well-defined shear plane, and it is shown how the crystals act as stress and strain incompatibilities causing localized crack or cavity formation. The relationships between sample mechanical properties, fracture surface characteristics and crystal distributions allow an analysis of cavity nucleation and growth rates, and thereby make it possible to suggest microstructures which may maintain reasonable toughness.     

Early, full weightbearing with flexible fixation delays fracture healing

Secondary fracture healing is known to be accelerated by the process of periosteal callus formation that can be induced by flexible fracture fixation in connection with loading of the injured extremity. The purpose of this study was to compare the healing of experimental fractures of long bones in sheep under early weightbearing with that of fractures under delayed, steadily increasing weightbearing. Differences in the quality of fracture healing were described by biomechanical (rigidity of fracture, indentation stiffness of callus) and histologic methods. Prevention from early, full weightbearing resulted in a higher flexural rigidity of the fracture, an increased mechanical stiffness of the callus tissue, and an enhanced bone formation at the healing front. Although early loading of a fresh fracture initiated an enormous amount of periosteal callus, the healing of the osteotomy was significantly delayed, and the quality of the newly formed tissue was reduced as compared with fractures with a reduced loading situation. A reduction of load transfer by delaying full weightbearing is advantageous for the healing of fractures stabilized with flexible fixation systems.     

13C n.m.r. study of solvation mechanisms in the radiation-induced polymerization of vinyl ethers

A ¹³C n.m.r. study of the microstructure of ethyl vinyl ether (EVE) and isopropyl vinyl ether (IPVE) polymers prepared under various experimental conditions and using chemical or γ-ray initiation has been made. Long stereo-sequence assignments were conducted for poly EVE allowing determination of the configurational statistic of propagation in the radiation-induced polymerization of EVE in low polar solvents. Stereo-sequence intensities are found in good agreement with the Markovian model. The results are considered as further support for the occurence of a specific interaction between the growing active centres and the polymer chains. In the case of IPVE polymers much more important overlappings of the resonance patterns are observed thus preventing any similar detailed study.     

Dynamics of social interactive behavior: A computerized procedure for analyzing trends, patterns, and sequences.

Describes procedures that use detailed and sequential observations of monkey mother-infant interactive behavior to make a coordinated analysis of development. Computer programs provide for (1) organizing the behavioral data into frequency tables and developmental curves, (2) making analyses of variance and trends comparing groups of Ss, and (3) determining statistically the patterns of simultaneous behavior and the sequences of patterns that characterize individual Ss and groups. This treatment of a large volume of data is economically feasible. The computer programs have been generalized for application in various kinds of behavioral research. Analyses provide bases in concrete behavioral terms for deriving hypotheses about the dynamics of social behavior and development. This approach promises a more complete and developmental view of complex interactive processes. Greater sophistication in the use of computer capabilities and in the application of mathematical models and treatments can increase its effectiveness. (19 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)