Certain attributes of an architect or engineer (AE) may be used to predict his performance. These attributes may be categorized as "hard" or "soft" attributes. Hard attributes include an AE's c...
详细信息
Certain attributes of an architect or engineer (AE) may be used to predict his performance. These attributes may be categorized as "hard" or "soft" attributes. Hard attributes include an AE's cognitive ability, job knowledge, task proficiency, and job experience. Soft attributes include an AE's conscientiousness, initiative, social skills, controllability, and commitment. The purpose of this study is to identify those attributes that affect an AE's performance, and to construct a model to predict his performance in design build (DB) projects. Twenty five attributes were generated using the hierarchy tree. The importance of these attributes was tested with designer/ builders who select and hire AEs, using a standard questionnaire. A statistical test showed that 24 of these attributes are significantly important. Thirty AEs were evaluated by experienced designer[builders (experts) who have worked with them in completed DB projects. Besides giving a global performance score of the AE (dependent variable), each expert also evaluated the AE on the degree to which they exhibited the important attributes (independent variables). Based on these ratings, an optimum multiple regression performance prediction model was obtained. To validate the model, another group of experts used the optimum model to evaluate 18 other AEs. The resulting performance score as calculated by the model was compared to the global performance scores awarded by the designer/builders. This validation process showed the model to be robust. The results of the study reveal that an AE's performance can be predicted by using just three attributes: AE's problem solving ability and project approach, AE's speed in producing design drawings, and the AE's level of enthusiasm in tackling a difficult assignment.
Radical copolymerization of N-vinylpyrrolidone with N-(p-acetoxy)phenylmaleimide and its oxime in the bulk and in a dimethylformamide solution was studied. Irrespective of the medium, copolymerization of N-vinylpyrrol...
详细信息
Radical copolymerization of N-vinylpyrrolidone with N-(p-acetoxy)phenylmaleimide and its oxime in the bulk and in a dimethylformamide solution was studied. Irrespective of the medium, copolymerization of N-vinylpyrrolidone with N-(p-acetoxy)phenylmaleimide yields copolymers with high tendency of comonomer units to alternation. Copolymerization of N-vinylpyrrolidone with N-(p-acetoxy)phenylmaleimide oxime in the bulk yields random copolymers. In the curve of the copolymer composition vs. the initial monomer mixture composition, there is an azeotropic point in the region of 45 mol % oxime. The kinetic relationships of the reactions were studied, and the structure of the copolymers obtained was determined. The ability of the copolymers to take up Cu(II) and Ni(II) ions from acidic and alkaline solutions was studied. The copolymers quantitatively take up Ni(II) and Cu(II) from ammonia solutions and can find use as sorbents for wastewater treatment to remove copper and nickel ions.
Recent developments in admixture technology have made significant progress to control the hydration of cement. This control has enabled concrete producers and users to stop cement hydration for a desired period and be...
详细信息
Recent developments in admixture technology have made significant progress to control the hydration of cement. This control has enabled concrete producers and users to stop cement hydration for a desired period and be able to restart it at any time, allowing the concrete to set normally, without sacrificing any of the properties of the hardened material. These types of admixtures, defined as extended-set control admixtures,' not only have a significant influence on the production, transportation, and placement of concrete, but have also had a positive impact on the environment. With this technology, in fact, if is possible to eliminate or greatly reduce the amount of waste in the production and use of concrete. The control of the hydration is currently achieved by the use of two admixtures, one defined as 'Stabilizer' is capable of stopping or stabilizing the hydration of cement, when it is mixed in the concrete, while the second named 'Activator,' is used to restart or activate the hydration. The extended set-control admixtures were originally developed for overnight and weekend stabilization of returned plastic concrete, for the long-haul stabilization of concrete that has to be placed at long distances from the batching plant and for overnight or weekend stabilization of concrete wash water from truck drums. The use of this system for the above mentioned applications allows a sensible reduction, or even an elimination of the waste in the production and use of concrete, and as a consequence a cost reduction for the producers and users of concrete. Other potential uses induce in Roller Compacted Concrete (RCC) applications and in shotcrete. This paper deals with an overview of the chemistry and mechanisms of action of these admixtures, their main practical uses, the effects of the use of extended set-control admixtures on the properties and durability of concrete in comparison with reference concrete, and with an overview of some other applications where this syste
暂无评论