Effect of pigmentation on organic coating characteristics

The paper reviews the effects of pigmentation, i.e. type of pigment and pigment volume concentration, on organic coating characteristics, such as curing and film formation, mechanical properties, thermal expansion coefficient, glass transition temperature, stress development, physical ageing and water transport. The main families of pigments used in the fabrication of organic coatings and the effect of nanopigments incorporation in binders are also discussed.     

A review of transparent insulation systems and the evaluation of payback period for building applications

Research and development of transparent insulation systems (TI-systems) has been ongoing for 20 years with transparent insulation materials (TIMs) used to replace standard opaque insulation materials. TIM not only performs similar functions to opaque insulation, reducing heat losses and controlling indoor temperatures, but allows solar transmittance of more than 50%. With a thickness of less than 20 cm, it can provide a financial return to building occupants when applied to building facades, maximising occupiable and sellable spaces in urban areas, without compromising thermal comfort within buildings.In this review of TI-systems for building applications, drawbacks to previous applications, cost trends, and analysis of the limitation in information from previous studies are discussed. A major drawback in the development of TI-systems identified is the lack of cost information; the payback periods for TI-systems used in previous renovation projects are virtually unknown. Simple payback period calculations were undertaken based on information available from a demonstration project documented by the Solar Heating and Cooling (SHC) Programme of the International Energy Agency (IEA) Task 20 “Solar Energy in Building Renovation”. The calculations indicated an encouraging 5–8-year payback period for this particular case study. It was concluded that the simple payback period calculation may be used for feasibility studies to indicate the time required to recoup investment when installing TI-systems and to provide initial guidance for building designers when evaluating the potential application of TI-systems in their buildings.     

Removal of Sulfate,Phosphate and Colored Substances in Wastewater Effluents using Feldspar

Feldspar, among many natural substances such as termitemount-clay, saw-dust, kaolinite and dolomite, offers asignificant removal ability for sulfate, phosphate, and coloredsubstances. Optimization of experimental parameters such assolution pH and flow rate reveals, that the maximum efficiency forremoval of phosphate, sulfate, and colored substances is about42, 52, and 73% respectively. X-ray diffraction, adsorptionisotherm and recovery studies suggest, that the removal processof anions occurs via ion exchange in conjunction with surfaceadsorption. Furthermore, reaction rate studies indicate thatthe removal of the selected pollutants by feldspar follows first-order kinetics. Although the percent removal, under the optimized conditions, is higher for laboratory prepared solutions, efficiency is a little less for industrial effluentsdue to interferent effects.     

Strut-and-tie modelling of reinforced concrete beams using genetic algorithms optimization

This paper presents a method for automatically producing optimal strut-and-tie models for the design of reinforced concrete beams. The optimal model is generated by means of an optimization problem solved by using genetic algorithms. The basic idea developed here is that from an initial random generation of possible configurations of the strut-and-tie model for the beam subjected to study, new populations of possible configurations may be generated in an iterative way by using genetic operators until reaching an optimum solution for the studied problem which corresponds to the strut-and-tie configuration which minimizes the total strain energy. In the optimal configuration, compressive struts are not enforced to be parallel, which allows representing more consistently the physical reality of the flow of forces. Furthermore, the method is more simple and easier to apply than the methods based on the concepts of evolutionary structural optimization.     

Structural crack detection without updated baseline model by single and multiobjective optimization

Identification, localization and quantification of structural damage can be performed through a model-updating procedure. Model-updating methods require a baseline finite element (FE) model of the undamaged structure, which imposes a restriction on their applicability and can become very problematic especially for large and complex civil structures. Modeling errors in the baseline model whose effects exceed the modal sensitivity to damage are critical and make an accurate estimation of damage impossible. This paper presents an identification algorithm using modal data for assessing structural damage that is based on FE-updating procedures and takes modeling error into account. To overcome its influence, differences of mode shapes and frequencies before and after damage for both numerical model and experimental measurements are used instead of the mode shapes and frequencies themselves. To formulate the objective function, two different approaches have been considered taking into account how these differences are grouped: a single-objective approach and a multiobjective approach. The effectiveness of both approaches is verified against numerical and experimental results.     

Phenol recovery with tributyl phosphate in a hollow fiber membrane contactor: Experimental and model analysis

The extraction and stripping of phenol using a solution of tributyl phosphate in kerosene in a hydrophobic polypropylene hollow fiber membrane contactor has been studied. The effect of the aqueous and the organic phase flow rates on the overall mass transfer coefficient for both extraction and stripping steps was investigated. Experimental values of the overall mass transfer coefficient were determined and compared with predicted values from the resistance in series model. Results showed that the overall mass transfer coefficients for extraction were about one order of magnitude greater than those measured during the stripping process. The experimental values were in good agreement with the predicted values for the extraction module. However, the predicted values were slightly overestimated for the stripping module. The individual mass transfer resistances were analyzed and the rate-controlling steps of mass transfer were also identified in both extraction and stripping modules. The major resistance in extraction and stripping was in the aqueous phase and in the membrane phase, respectively.     

Epoxidation of natural rubber studied by nmr spectroscopy

Epoxidation of natural rubber with peroxyacids in homogeneous solution (CHCl₃, benzene) and in latex occurs without main chain fission or isomerization of the cis configuration. There are two possible modes of addition of oxygen to the double bond, which gives rise to diastereoisomers in dyad structures, as shown by the occurrence of splitting of ¹³C NMR resonances in 100% epoxidized rubber. In partially epoxidized rubber the ¹³C NMR resonances of the methylene carbon atoms have been fully assigned using pulse sequences and lanthanide shift reagents, in terms of triad sequences. Resonances in the olefinic region of the spectrum require assignment in terms of pentad sequences whereas those from the oxirane region are much more closely spaced and are assigned using triads. Intensity measurements on the methylene carbon NMR resonances show that the epoxidation reaction is a random process in both homogeneous solution and in latex particles.     

Fast isolation of faults in transmission systems using current transients

This paper presents a protection scheme that is capable of very fast isolation of faults in high voltage transmission systems. Proposed scheme comprises set of relays connected through a telecommunication network, located at different nodes of the system. Relays use wavelet coefficients of current signals to identify the fault directions relative to their location. Fault directions identified at different locations in the system can be combined to determine the faulted line (or busbar) and isolate it. A robust single ended traveling wave based fault distance estimation approach is proposed as a backup in case of communication failure. Investigations were carried out using time domain simulations in PSCAD/EMTDC for a high voltage transmission system.     

Maximum quasi-likelihood estimation for the near(2) model

Abstract.  Maximum quasi-likelihood estimation is investigated for the NEAR(2) model, an autoregressive time series model with marginal exponential distributions. In certain regions of the parameter space, simulations indicate that maximum quasi-likelihood estimators perform better than two-stage conditional least squares estimators in terms of the per cent of estimates falling in the parameter space. The problem of out-of-range estimates is shown to be caused by the lack of information in the data rather than the characteristics of the method of estimation.