Deb K.,Michigan State University |
Jain H.,Indian Institute of Technology Delhi
IEEE Transactions on Evolutionary Computation | Year: 2014
Having developed multiobjective optimization algorithms using evolutionary optimization methods and demonstrated their niche on various practical problems involving mostly two and three objectives, there is now a growing need for developing evolutionary multiobjective optimization (EMO) algorithms for handling many-objective (having four or more objectives) optimization problems. In this paper, we recognize a few recent efforts and discuss a number of viable directions for developing a potential EMO algorithm for solving many-objective optimization problems. Thereafter, we suggest a reference-point-based many-objective evolutionary algorithm following NSGA-II framework (we call it NSGA-III) that emphasizes population members that are nondominated, yet close to a set of supplied reference points. The proposed NSGA-III is applied to a number of many-objective test problems with three to 15 objectives and compared with two versions of a recently suggested EMO algorithm (MOEA/D). While each of the two MOEA/D methods works well on different classes of problems, the proposed NSGA-III is found to produce satisfactory results on all problems considered in this paper. This paper presents results on unconstrained problems, and the sequel paper considers constrained and other specialties in handling many-objective optimization problems. © 1997-2012 IEEE.
Mummadi V.,Indian Institute of Technology Delhi
IEEE Transactions on Industrial Electronics | Year: 2011
In this paper, a robust digital proportionalintegralderivative (PID) controller is proposed for the H-bridge soft-switching boost converter (HSBC). This digital PID controller is designed to ensure load voltage regulation as well as to give robust performance with step loads and source rejection. The mathematical models of the H-bridge boost converter are formulated, using the system identification tool, and then used in digital PID design. Here, this compensator is designed in the direct digital domain according to a pole placement approach that uses sensitivity function shaping in order to ensure closed-loop converter system stability as well as robust performance against converter parameter uncertainties. To confirm this, design simulations have been carried out on a 60-W 2442-V HSBC. The experimental results are provided to validate the robust controller design concept. © 2006 IEEE.
Bishnoi S.,Indian Institute of Technology Delhi
Cement and Concrete Research | Year: 2013
The nucleation and growth process is known to control the kinetics of many important phase transformation processes. However, models of this process are often applied to systems, such as cements, which are different from the ones for which the models were originally developed. The applicability of the assumptions used in the development of these models to such systems has been questioned. One of the most common assumptions in nucleation and growth models is that the impingement between growing nuclei is proportional to the fraction of the untransformed volume. Through numerical simulations, this study investigates the validity of this assumption for various systems, including multiphase systems, different dimensionalities of growth and nucleation on boundaries of spherical particles. It is shown that although in some cases the models can be easily adapted for use in more complex systems, other systems are too complicated to be accurately represented by this simple rule. © 2013 Elsevier Ltd. All rights reserved.
Subramanian K.A.,Indian Institute of Technology Delhi
Energy Conversion and Management | Year: 2011
Experiments were conducted to compare the effects of water-diesel emulsion and water injection into the intake manifold on performance, combustion and emission characteristics of a DI diesel engine under similar operating conditions. The water to diesel ratio for the emulsion was 0.4:1 by mass. The same water-diesel ratio was maintained for water injection method in order to assess both potential benefits. All tests were done at the constant speed of 1500 rpm at different outputs. The static injection timing of 23° BTDC was kept as constant for all experimental tests. In the first phase, experiments were carried out to asses the performance, combustion and emission characteristics of the engine using the water-diesel emulsion. The emulsion was prepared using the surfactant of HLB:7. The emulsion was injected using the conventional injection system during the compression stroke. The second phase of work was that water was injected into the intake manifold of the engine using an auxiliary injector during the suction stroke. An electronic control unit (ECU) was developed to control the injector operation such as start of injection and water injection duration with respect to the desired crank angle. The experimental result indicates the both methods (emulsion and injection) could reduce NO emission drastically in diesel engines. At full load, NO emission decreased drastically from 1034 ppm with base diesel to 645 ppm with emulsion and 643 ppm with injection. But, NO emission reduction is lesser with injection than emulsion at part loads. Smoke emission is lower with the emulsion (2.7 BSU) than with water injection (3.2 BSU) as compared to base diesel (3.6 BSU). However, CO and HC levels were higher with emulsion than water injection. As regards NO and smoke reduction, the emulsion was superior to injection at all loads. Peak pressure, ignition delay and maximum rate of pressure rise were lesser with water injection as compared to the emulsion. It is well demonstrated through this comparative study that the emulsion method has higher potential of simultaneous reduction of NO and smoke emissions at all loads than injection method. © 2010 Elsevier Ltd. All rights reserved.
Jain S.,Indian Institute of Technology Delhi
Nanoscale | Year: 2013
Novel, size controlled fluorescent polymeric nanoparticles (FPNP) were synthesized having acetoacetoxy functionality on the surface for immobilization of biomolecules which can be utilized as biomarkers and labels in fluoroimmunoassays. Core-shell nanoparticles of poly(styrene, St-methyl methacrylate, MMA-acetoacetoxy ethyl methacrylate, AAEM), stabilized by various concentrations of surfactant, sodium lauryl sulphate (SLS), were obtained by facile miniemulsion co-polymerization encapsulated with pyrene molecules in their hydrophobic core. Analytical, spectroscopic and imaging characterization techniques revealed the formation of stable, monodisperse, spherical nano sized particles exhibiting high luminescence properties. Particles with 1% SLS (S1) showed good dispersion stability and fluorescence intensity and were chosen as ideal candidates for further immobilization studies. Steady state fluorescence studies showed 10 times higher fluorescence intensity of S1 nanoparticles than that of pyrene solution in solvent-toluene at the same concentration. Environmental factors such as pH, ionic strength and time were found to have no effect on fluorescence intensity of FPNPs. Surface β-di-ketone groups were utilized for the covalent immobilization of enzyme conjugated antibodies without any activation or pre-treatment of nanoparticles.