Showing papers by "Shantanu Das published in 2010"

Design of a Fractional Order Phase Shaper for Iso-Damped Control of a PHWR Under Step-Back Condition

Abstract: Phase shaping using fractional order (FO) phase shapers has been proposed by many contemporary researchers as a means of producing systems with iso-damped closed loop response due to a stepped variation in input. Such systems, with the closed loop damping remaining invariant to gain changes can be used to produce dead-beat step response with only rise time varying with gain. This technique is used to achieve an active step-back in a Pressurized Heavy Water Reactor (PHWR) where it is desired to change the reactor power to a pre-determined value within a short interval keeping the power undershoot as low as possible. This paper puts forward an approach as an alternative for the present day practice of a passive step-back mechanism where the control rods are allowed to drop during a step-back action by gravity, with release of electromagnetic clutches. The reactor under a step-back condition is identified as a system using practical test data and a suitable Proportional plus Integral plus Derivative (PID) controller is designed for it. Then the combined plant is augmented with a phase shaper to achieve a dead-beat response in terms of power drop. The fact that the identified static gain of the system depends on the initial power level at which a step-back is initiated, makes this application particularly suited for using a FO phase shaper. In this paper, a model of a nuclear reactor is developed for a control rod drop scenario involving rapid power reduction in a 500 MWe Canadian Deuterium Uranium (CANDU) reactor using AutoRegressive Exogenous (ARX) algorithm. The system identification and reduced order modeling are developed from practical test data. For closed loop active control of the identified reactor model, the fractional order phase shaper along with a PID controller is shown to perform better than the present Reactor Regulating System (RRS) due to its iso-damped nature.

Genetic variability, character association and path analysis in Jatropha curcas.

Abstract: Sixteen Jatropha curcas genotypes collected from four states were grown in randomized block design and evaluated for 12 characters. The genotypes showed significant differences in most component traits and seed yield, excepting primary branches/plant, fruits/bunch and seeds/fruit. The genotypes Utkal nursery, Phule1, IST 1, Jodhpur1 and Chhatrapati had above average (>84.7 g) seed yield/plant. Phenotypic coefficient of variation (PCV) & genotypic coefficient of variation (GCV) estimates were high for seed yield/plant followed by flowering bunches/plant, fruits/plant and secondary branches/plant. Heritability was high (>80%) for plant height, fruits/plant and 100 seed weight. Genetic advance (GA) was high (>50%) for seed yield/plant, fruits/plant and flowering bunches/plant. Moderate to high heritability accompanied with high genetic advance for seed yield/plant, fruits/plant and flowering bunches/plant indicated additive gene action and selection for these characters would be effective. Fruits/plant, flowering branches and bunches/plant, collar diameter and secondary branches/plant had high positive correlation with seed yield/plant. Flowering bunches/plant and fruits/plant had high positive direct effect on yield and indirect positive effect via these two traits greatly influenced positive association of other traits with yield. Seeds/fruit and 100 seed weight had moderate positive direct effect on yield. The remaining seven component traits had very low direct effect on yield. The character association and path analysis study revealed that selection for flowering bunches/plant and fruits/plant would be highly effective in bringing out improvement in yield. Selection for seeds/fruit and 100 seed weight would result in some improvement in yield. Thus, the ideotype to achieve high yield in Jatropha should have more number of flowering bunches/plant and fruits per plant and moderate to high value for seeds/fruit and 100- seed weight.

Fractional order phase shaper design with Bode's integral for iso-damped control system.

Abstract: The phase curve of an open loop system is flat in nature if the derivative of its phase with respect to frequency is zero. With a flat-phase curve, the corresponding closed loop system exhibits an iso-damped property i.e. maintains constant overshoot with the change of gain. This implies enhanced parametric robustness e.g. to variation in system gain. In the recent past, fractional order (FO) phase shapers have been proposed by contemporary researchers to achieve enhanced parametric robustness. In this paper, a simple methodology is proposed to design an appropriate FO phase shaper to achieve phase flattening in a control loop, comprising a plant controlled by a classical Proportional Integral Derivative (PID) controller. The methodology is demonstrated with MATLAB simulation of representative plants and accompanying PID controllers.

Solution of extraordinary differential equations with physical reasoning by obtaining modal reaction series

Abstract: Mathematical modeling of many engineering and physics problem leads to extraordinary differential equations like Nonlinear, Delayed, and Fractional Order. An effective method is required to analyze the mathematical model which provides solutions conforming to physical reality. A Fractional Differential Equation (FDE), where the leading differential operator is Riemann-Liouvelli (RL) type requires fractional order initial states which are sometimes hard to physically relate. Therefore, we must be able to solve these extraordinary systems, in space, time, frequency, area, volume, with physical reality conserved. Extra Ordinary Differential equation Systems and its solution, with Physical Principle, of action-reaction and equivalent mathematical decomposition method, are obtained as an aid for Physicists and Engineers to tackle the process dynamics with ease. This reactions-chain generates internal modes from zeroth mode reaction to first mode second mode and to infinite modes; instantaneously in parallel time or space-scales; and the sum of all these modes gives entire system reaction. This modal reaction as explained by physics theory exactly matches the principle of Adomian Decomposition Method (ADM). Fractional Differential Equation (FDE) with Riemann-Liouvelli formulation linear and non-linear is solved as per ADM. In this formulation of FDE by RL method it is found that there is no need to worry about the fractional initial states; instead one can use integer order initial states (the conventional ones) to arrive at solution of FDE. This new finding too is highlighted in this paper-along with several other problems to give physical insight to the solution of extraordinary differential equation systems. This way one gets insight to Physics of General Differential Equation Systems-and its solution-by Physical Principle and equivalent mathematical decomposition method. This facilitates ease in modeling.

Genetic variability, character association and path analysis in Jatropha curcas.

Abstract: Sixteen Jatropha curcas genotypes collected from four states were grown in randomized block design and evaluated for 12 characters. The genotypes showed significant differences in most component traits and seed yield, excepting primary branches/plant, fruits/bunch and seeds/fruit. The genotypes Utkal nursery, Phule1, IST 1, Jodhpur1 and Chhatrapati had above average (>84.7 g) seed yield/plant. Phenotypic coefficient of variation (PCV) & genotypic coefficient of variation (GCV) estimates were high for seed yield/plant followed by flowering bunches/plant, fruits/plant and secondary branches/plant. Heritability was high (>80%) for plant height, fruits/plant and 100 seed weight. Genetic advance (GA) was high (>50%) for seed yield/plant, fruits/plant and flowering bunches/plant. Moderate to high heritability accompanied with high genetic advance for seed yield/plant, fruits/plant and flowering bunches/plant indicated additive gene action and selection for these characters would be effective. Fruits/plant, flowering branches and bunches/plant, collar diameter and secondary branches/plant had high positive correlation with seed yield/plant. Flowering bunches/plant and fruits/plant had high positive direct effect on yield and indirect positive effect via these two traits greatly influenced positive association of other traits with yield. Seeds/fruit and 100 seed weight had moderate positive direct effect on yield. The remaining seven component traits had very low direct effect on yield. The character association and path analysis study revealed that selection for flowering bunches/plant and fruits/plant would be highly effective in bringing out improvement in yield. Selection for seeds/fruit and 100 seed weight would result in some improvement in yield. Thus, the ideotype to achieve high yield in Jatropha should have more number of flowering bunches/plant and fruits per plant and moderate to high value for seeds/fruit and 100- seed weight.

Quenching the conducted emission hazards for heliborne time domain electromagnetic exploration system

Abstract: Noise limits set by regulatory agencies make solutions to common mode EMI a necessary consideration in the manufacture and use of electronic equipment. Common mode filters are generally relied upon to suppress line conducted common mode interference. These filters successfully and reliably reduce common mode noise. However, successful design of common mode filters requires foresight into the non ideal character of filter components - the inductor in particular. It is the aim of this paper to provide filter designers the knowledge required to identify those characteristics critical to desired filter performance.

A hardwire technique developed for sub-criticality annunciation for PHWR

Abstract: “Sub criticality” is a parameter of common interest and usage in reactor operation A hardwired circuit for real time measurement of sub criticality is presented and it does not involve any data acquisition or estimation technique The circuit was tested with different test inputs and the outputs were compared against the analytical solutions of reactor kinetic equation for the same This reactivity meter is made for Indian PHWRs (Pressurized Heavy Water Reactor) for multi-decade operation from 10−8 Full Power to final decade of power operation through 8 and half decades However it can be tuned to use for any other reactor where flux shape can be considered as stationary The scheme is very robust as its response to different kinds of test inputs are in very close agreement with analytical solutions This system will aid reactor operator's confidence and add to plant reliability and maintainability The aim of this work is to have the system's performance evaluated for multi-decade operation with single group solution, with the innovative electronic technique developed; subsequently the multi-group circuit enhancement is possible

Oscillatory Spreading and Surface Instability of a Non-Newtonian Fluid under Compression

Abstract: Starch solutions, which are strongly non-Newtonian, show a surface instability, when subjected to a load. A droplet of the fluid is sandwiched between two glass plates and a weight varying from 1 to 5 kgs. is placed on the top plate. The area of contact between the fluid and plate increases in an oscillatory manner, unlike Newtonian fluids in a similar situation. The periphery moreover, develops a viscous fingering like instability, which is not expected under compression. We attempt to model the non-Newtonian nature of the fluid through a visco-elastic model incorporating generalized calculus. This is shown to exhibit a qualitatively similar oscillatory variation in the surface strain.