Kinetic and rheokinetic study of dicarboxylic fatty acid chain extension using a dioxazoline coupling agent

A kinetic and rheokinetic study of the condensation reaction of a dicarboxylic fatty acid, Pripol®1009 (C36), and a dioxazoline coupling agent (1,3‐Phenylene)‐bis(2‐Oxazoline) (OO) was made. The kinetic study showed a similar reactivity of the two acid groups of C36 and also a similar reactivity of the two oxazoline groups of OO. The reaction kinetics can be described using a second‐order kinetic model. A kinetic constant k = 16.1 × 10⁻⁴ mol⁻¹ s⁻¹ at 156°C with an activation energy E_a = 80.6 kJ mol⁻¹ was calculated. A rheological evaluation of the reactants and the obtained polymers showed that the reactive system had Newtonian behavior during all the reaction times for shear rates lower than 100 s⁻¹. Using this kinetic modeling and measured viscosity evolution of the reactive system at different temperatures, rheokinetic models were proposed for viscosity evolution with the molar mass evolution of the synthesized polymer and the reaction time and conversion. Viscosity evolution of the reactive system during the first 10 min, corresponding to a typical mean residence time in reactive extrusion, were calculated using the proposed rheokinetic model. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1017–1024, 1999     

The concept of conversion distribution in reactive processing

A new concept of conversion distribution applied to the continuous chemical modification and polymerization of polymers in a twin screw extruder was discussed. The kinetics and the residence time distribution function (RTD) are two undissociable parameters in reactive extrusion because their combination reflects the degree of homogeneity of the modified polymer at the die die exit of the extruder. A function G defining the distribution of the modification rate allowed us to evaluate the distribution of the extent of the conversion around the mean conversion. This study has underlined the predominant role of the kinetics on the structural homogeneity of the modified product. This new concept was developed, within a framework of reactive processing, from previous works on chemical modification of polymers and polycondensation in corotating twin screw extruder. © 1996 John Wiley & Sons, Inc.     

Effect of Some Heterocyclic Derivatives on the Removal of Copper Ions from Wastewater by Cementation

Removal of copper ions from copper sulphate solutions on a rotating zinc rod in absence and in presence of 3(2H)-furanones and 4H-pyran-4-one derivatives was investigated experimentally. Variables studied were initial copper ions concentration, rotational speed of the zinc rod, temperature and concentration of organic additives. It was found that cementation reaction is first order in presence and in absence of additives. Increasing concentration of initial copper ions, rotational speed of the zinc rod and temperature were found to increase the rate of cementation. In presence of organic additives an enhancement of the rate was observed, except in presence of methoxyfuranone the rate was found to decrease by an amount ranging from 11.74% to 33.79%. Rate acceleration or inhibition is associated mainly with changes in the structure of the additives as well as its concentration. The apparent activation energy for the cementation process in presence of different additives was estimated and was found to be r     

Utilization of pico hydro generation in domestic and commercial loads

Pico hydro is a term used to distinguish very small-scale hydropower with a maximum electrical output of five kilowatts (5 kW). It is a good technique of providing electricity to the off-grid remote and isolated regions that suffer energy deficit. Typical pico hydro generator is designed and supported by electrical converting system, batteries and safety equipment so that it can be installed at the residential water pipeline. In pico hydro generation, the environmental impact is negligible since large dams are not involved, and the schemes can be managed and maintained by the consumer. This paper is reviewing the application of hydro generation and particularly focusing on the implementation of pico hydro generation system in University Malaysia Pahang (UMP) Campus-Pekan. This system was designed and simulated using the Matalb simulink blocks. The pico hydro generator has been tested in a real application with a pelton turbine design which utilizes a high pressure of water flowing from the main tank into the faculties. The speed of the turbine and alternator depend on the pressure of the water. In this work, a 1.05 kW alternator is used to charge the battery and the DC power output from a battery is converted into 220 V, 50 Hz.     

The effect of damage and creep interaction on the behaviour of masonry columns including interface debonding and cracking

Creep can produce significant effects on the structural behaviour of composite quasi-brittle systems, such as masonry, by altering the stress distribution between and within structural elements. The failure of a masonry element can be accelerated through damage incurred by weathering or degradation from creep effects. In this study, a three-dimensional finite element model of a grouted masonry column is used to evaluate the significance of the interaction of creep and damage on the structural behaviour of the column. The effects of Poisson??s ratio in producing differential out-of-plane constraint stresses can be simulated using this model. By utilizing a cracking criterion and incorporating a cohesive zone material (CZM) model for the brickwork-grout interface, the sequence and the patterns of cracking of the masonry column, debonding of the interface and local failure are examined. It is shown that debonding of the brickwork-grout interface occurs prior to cracking of the outer shell of brickwork. Case studies are presented to demonstrate the significance of the interaction of creep and damage on local failure, cracking and debonding. It is shown that cracking and debonding can result in a stability failure of a masonry column that was originally in a stable condition. Further work on local buckling and post-buckling analysis seems crucial to explain composite masonry behaviour.     

Recent developments in microgrids and example cases around the world—A review

Climate change concerns due to the rising amounts of the carbon gas in the atmosphere have in the last decade or so initiated a fast pace of technological advances in the renewable energy industry. Such developments in technology and the move towards cleaner sources of energy have made distributed generation (DG) from renewable resources more desirable. However, it is a known fact that rising penetrations of DG can have adverse impacts on the grid structure and its operation. The microgrid concept is a solution proposed to control the impact of DG and make conventional grids more suitable for large scale deployments of DG. Covering many aspects of the power systems and power electronics fields, microgrids have become a very popular research field. This paper reviews the background and the concept of a microgrid, the current status of the literature, on-going research projects, and the relevant standards. It also presents a review of the microgrid pilot projects around the world in further detail and discusses the potential avenues for further research.     

Effect of Nitrogen and Niobium on the Structure and Secondary Hardening of Super Hard High Speed Tool Steel

High‐speed steels have been used mostly for multi‐point cutting tools and for plastic working tools. High speed steels are ferrous based alloys of the Fe‐C‐X multi‐component system where X represents a group of alloying elements comprising mainly Cr, W or Mo, V, and Co. The properties of these steels can be improved by modifying their chemical composition or the technology of their production. One of the new trends in modifying the tool steels chemical composition consists in the addition of niobium and nitrogen. In this work, the effects of niobium and nitrogen on morphology of carbides and secondary hardening temperature of investigated high speed tool steels were studied. This experimental work shows that, the conventional ingots have many types of carbides of different shapes and sizes precipitate on the boundary together with thick needle like carbides. On the contrary, for nitrogen steel, the nitrogen alloying leads to form dense, fine and well distributed microstructure. While, on the case of niobium alloying, single carbide (MC), and different types of eutectic carbides were precipitated which have a major effect on the secondary hardening temperature.     

Centrifugal casting of an Al-12Si-2Mg/Al2O3-particulate MMC. Part II: Evaluation of soundness and structure

A technique for the preparation of an MMC using centrifugal casting has been developed and tested for its feasibility in preparing Al-12Si-2Mg/Al₂O₃- particulate composites. The process is evaluated by observing the structure, measuring the homogeneity in the distribution of the ceramic particles, the porosity type and distribution, and by analysing the metal/ceramic interface for possible reactions.

The different processing conditions applied are: rotational frequency 16, 22.7 and 33.3 Hz (960, 1360 and 2000 rpm), Al₂O₃ particle size 30, 47, 60 and 89 μn, melt superheat 20, 100 and 150°C, specimen radius of rotation from 145 to 180 mm.

Because the ceramic particles are close packed, a uniform particle distribution with no agglomeration is obtained, and the interparticle distance depends only on the alumina particle size. The metal/ceramic interface was sharp with no reaction. Microporosity is observed in some locations due to incomplete infiltration between the alumina particles. Increasing rotational speed, particle size, superheat, and radius of rotation help to decrease the microporosity. The macrostructure along the composite length showed columnar grains followed by equiaxed grains. The type and size of the structure depend mainly on the composition of the matrix and not on the presence of the alumina particles.