Globally linearized control on diabatic continuous stirred tank reactor: a case study

This paper focuses on the promise of globally linearized control (GLC) structure in the realm of strongly nonlinear reactor system control. The proposed nonlinear control strategy is comprised of: (i) an input-output linearizing state feedback law (transformer), (ii) a state observer, and (iii) an external linear controller. The synthesis of discrete-time GLC controller for single-input single-output diabatic continuous stirred tank reactor (DCSTR) has been studied first, followed by the synthesis of feedforward/feedback controller for the same reactor having dead time in process as well as in disturbance. Subsequently, the multivariable GLC structure has been designed and then applied on multi-input multi-output DCSTR system. The simulation study shows high quality performance of the derived nonlinear controllers. The better-performed GLC in conjunction with reduced-order observer has been compared with the conventional proportional integral controller on the example reactor and superior performance has been achieved by the proposed GLC control scheme.     

Openness and Technology Diffusion in Payment Systems: The Case of NAFTA

We study the relationship between openness and payment system development. In particular, we analyze how the existence of technology diffusion from a more developed country fosters a transformation of payment choice in a less developed country. We apply our analysis to Mexico. Economic growth in Mexico was not high enough to cause a transformation of payment choice observed in the data after 2001. We argue that the switch towards electronic payments can be attributed to openness and related payment technology spillovers from the US in the context of NAFTA.     

A multi-criteria decision analysis framework for evaluating point-of-use water treatment alternatives

Despite significant progress on meeting global water targets, the lack of access to safe drinking water remains a significant problem in today’s world. Statistics from health agencies indicate that waterborne diseases are among the leading causes of health-related mortalities, particularly in developing nations. This paper examines the performance and applicability of various point-of-use (POU) water treatment alternatives, namely (i) solar disinfection; (ii) boiling of water; (iii) chlorination; (iv) disinfection–flocculation with a natural coagulant (powdered Moringa seeds); (v) filtration with ceramic pots; and (vi) biosand filtration. We evaluated the efficacy of each alternative using a set of criteria based on environmental sustainability, technological performance, financial viability, and social acceptability. We also integrated several multi-criteria decision analysis (MCDA) approaches to determine the most suitable water treatment method for a given community. The analytic hierarchy process (AHP) was implemented to elicit various preference structures and to generate the weights for the criteria. Subsequent ranking of the POU alternatives was then performed using the technique for order preference by similarity to ideal solutions (TOPSIS) method. Sensitivity analysis and visualization charts were developed to evaluate the impact of changes in preference ratings of each alternative with respect to the criteria. A case study was implemented in a rural area in the Philippines to determine the optimal POU alternatives given variations in AHP and TOPSIS input data. The resulting MCDA framework is flexible and can accommodate the inclusion of other alternatives and criteria, and it can also be generalized for other regions and applications.     

Design optimization of deep groove ball bearings using crowding distance particle swarm optimization

This paper presents a crowding distance particle swarm optimization technique to optimize the design parameters of deep groove ball bearings. The design optimization problem is multi-objective in nature. The considered objectives are maximizing dynamic and static load bearing capacities and minimizing elasto-hydrodynamic film thickness. The technique is applied to bearings used in transmission system of a tractor for the purpose of farming. Pareto optimal solutions are obtained using the proposed technique. The results obtained from the technique are found to be superior compared with NSGA-II and catalogue values.     

Reticulated Porous Foam Ceramics with Different Surface Chemistries

The aim of this study was to discuss the influence of different filter surface chemistries on the properties of foam filters. For reliable results, it is essential to ensure comparable structural properties (cell size and strut thickness) for all different surface chemistries (Al₂O₃, MgAl₂O₄, 3Al₂O₃·2SiO₂, SiO₂, and TiO₂) possess the same structural properties (cell size and strut thickness). Filters made of 100% of the investigated materials and alumina skeletons coated with the investigated materials were prepared. The coated alumina samples were sintered in one and two steps. The processing route with two sintering steps resulted in improved mechanical properties and comparable shrinkage and strut thickness. The 100% bulk foams possessed different pore sizes due to the differences of the material shrinkage. In this study, a comparison of the experimental investigated properties of the ceramic foam filters and the theoretically calculated values for foam materials derived from the bulk material properties is established.     

Availability and cost-centered preventive maintenance scheduling of continuous operating series systems using multi-objective genetic algorithm: A case study

This article presents a multi-objective (maximization of availability and minimization of maintenance cost) preventive maintenance (PM) scheduling model for a continuous operating series system (COSS) which do not provide an off-working period for PM. The objective functions are optimized by using a Multi-Objective Genetic Algorithm (MOGA). The effectiveness of the model is demonstrated through a coal-fired boiler-tube. The case study shows that the model can improve the availability along with profound reduction of the maintenance cost, i.e., increases the profit of the plant.     

Microstructural design of neodymium-doped lanthanum–magnesium hexaaluminate synthesized by aqueous sol–gel process

Aqueous sol–gel processing was used to synthesize neodymium-doped magnesium hexaaluminate (La_1?x Nd _x MgAl₁₁O₁₉; x = 0, 0.3, 0.4, 0.5) ceramic powder and subsequently calcined at 1450 and 1600 °C for 2 h. Randomly grown platelets of lanthanum–magnesium hexaaluminate formed a porous interlocking structure. Presence of various percentages of neodymium oxide significantly modifies the porous interlocking microstructure into self-reinforced, card-house-like microstructure. Platelets of rare earth-rich magnesium hexaaluminate were grown preferentially more than the stoichiometric rare earth magnesium hexaaluminate at elevated temperature greater than 1450 °C. Rare earth-rich magnesium hexaaluminate platelets form the skeleton of a card-house structure and the tiny platelets of stoichiometric rare earth magnesium hexaaluminate fill the house. The specific heat capacities, micro-hardness, and fracture toughness were studied in details.