Associate Professor of Zoology
Raja Narendra Lal Khan Women's College ( Autonomous)
Teaching experience( UG & PG)-22 years, Research Experience -35 years( 7 years as Post Doc Fellow in the form of Young Scientist of DST, Govt. of India & Pool Scientist from CSIR, Govt. of India, PhD produced-08, ongoing PhD students-07, Member of Governing Body of the college
Soil Ecotoxicology, Nutritional Ecology, Soil Microbiology
Usefulness of some enzyme of selected species of earth worm as biomarker to detect heavy metals pollution in soil
Usefulness of some molecular biological technique of Porcelio laevis ( Isopoda) as biomarker to detect heavy metals pollution in soil
Utility of earthworm gut containing bacteria in degradation of polythene & polypopeline
Sudipta Das, Pragnan Chakravorty, and Durbadal Mandal Springer Singapore
In this work, the problem of low sidelobe phased array synthesis is taken up, and variants of particle swarm optimization (PSO), like Grey PSO and Novel PSO, are adopted for dealing with this problem. For simplicity, periodic linear array geometries are considered. Effect of position regulation and inertia control strategies on the convergence of PSO variants is studied in this regard. Results reflect the impacts of position regulation and inertia control strategies on the convergence of the algorithms for the problem instance considered. Without the influence of position regulation Grey PSO and Novel PSO have been able to suppress interference levels for a 20-element linear array to \\(-21.31\\) and \\(-31.23\\) dB, respectively. Under the influence of the position regulation, their respective values got improved to \\(-27.90\\) and \\(-43.35\\) dB.
Vrushali Wasnik, Vijay Dahake, and Pragnan Chakravorty IEEE
Designs of modern antennas have been inevitably computational intensive tasks. Here, we present a stacked dielectric resonator antenna (DRA), where its bandwidth has been enhanced upto 189%, ranging from 0.5 GHz to 18.1 GHz. The effect of various parameters on antenna design has been investigated. This antenna configuration has monopole -type radiation pattern, operating beyond ultra wideband response.
Pragnan Chakravorty Institute of Electrical and Electronics Engineers (IEEE)
After decades of advances in signal processing, this article goes back to square one, when the word signal was defined. Here we investigate if everything is all right with this stepping stone of defining a signal.
Pragnan Chakravorty, Durbadal Mandal, Alessandro Polo, and Federico Viani IEEE
The information and communication technology (ICT) backbone of any smart city system should be essentially a wireless sensor network (WSN) for it to be smart in any sense. It goes beyond doubt that such a system is extremely hungry in terms of information and resources. The vital resources like frequency spectrum, power of transmission, number of trans-receivers etc. have their own set of limitations in terms of feasibility, availability, safety, reliability and cost-effectiveness. Here, major limitations of a wireless communication network are discussed. A strategy of smart integrated network service (SINS), using directive antennas and phased arrays is proposed to do away with most of these problems.
Pragnan Chakravorty and Durbadal Mandal Institute of Electrical and Electronics Engineers (IEEE)
Mutual coupling in antenna arrays has been a deterrent issue for design accuracy and predictions. Several techniques for calculation, reduction, and compensation of mutual coupling were proposed in the past; the techniques include both analytical and numerical approaches. However, the methods of mutual coupling mitigation in context of radiation pattern correction had been very few. Here, mutual impedances are calculated through a conventional technique and is used to form a set of network equations whose parameters are assimilated with those of a desired radiation pattern; the proposed technique directly leads to the calculation of feed currents, required in the antennas, for restoring the mutual coupling affected radiation pattern to the desired pattern. The technique is accurate with lesser computational complexity compared with the extant methods.
Pragnan Chakravorty and Durbadal Mandal Wiley
Bandpass filters with wide pass-band are an essential requirement in various equipments of satellite and defence communication sectors. Here a method of split-path interactions is proposed to approximately predict the resonant frequency and topology of bandpass filters which otherwise fall under the category of heuristic designs. Curved transmission lines are often required to make filter structures physically compact; however, curvature effects create errors in the theoretical design prediction of resonant or central frequencies for bandpass filter design. Earlier propositions on curvature corrections had been considerably precise, but recent design standards demand even higher accuracies. The prime feature of this work is the use of a meta-heuristic optimization i.e. Particle Swarm Optimization technique in curvature corrections for the first time which brings accuracies of over 99% in the corrected results. The split paths used in this design are suitably curved, with the proposed optimized curvature correction technique, so as to attain a compact size of the filter. The resulting filter has a low insertion loss of around -1.00dB and a sharp stopband cut-off. Fabrication was done on a FR4 microstrip substrate with a good agreement between measured and simulated results. Copyright © 2015 John Wiley & Sons, Ltd.
Pragnan Chakravorty, Sudipta Das, Durbadal Mandal, and Ragini Lanjewar IEEE
To demonstrate the importance of feed line topology in the design of filter with coupled resonators, a pseudo interdigital bandpass filter is designed here. In the conventional approach the feedlines are of coupled type when the filter is designed over a substrate of RT/Duroid (εr = 10.8); however, when the filter is designed over FR4 (εr = 4.3) substrate, the coupled feed lines are unable to produce the desired filter response. To comply with the filter prototypes a tapped feedline structure is then implemented to produce the desired results. Therefore it may be deduced that feedline layout is not a matter of choice but an inevitable design requirement. An explicit design procedure and measured/simulated results are presented here.
Gopi Ram, P. Chakravorty, Durbadal Mandal, Rajib Kar, Sakti Prasad Ghoshal, and S. Banerjee IEEE
In this paper radiation pattern synthesis of time modulated circular antenna array is dealt with. Optimal switching time sequence and optimal uniform inter element spacing is used as variable to control the radiation pattern of the array. The optimal value of controlled parameter can be obtained by the evolutionary optimization technique. Three algorithms real coded algorithm (RGA), particle swarm optimization (PSO), and bacteria foraging optimization (BFO) has been used and compared with their performance. The numerical results have been carried out by taking three array set of 12-, 18-, and 25-elements. Simulation results show better side lobe performance with respect to the uniform circular antenna array.
Pragnan Chakravorty, Gopi Ram, Durbadal Mandal, and Sudipta Banerjee IEEE
Boundary conditions in particle swarm optimizers are an important algorithmic part which can constrain the particles within the solution space which increases their scope of participation in solution finding process. Usually, velocities of the particles are regulated to bring them back to solution space; Here the basic approach of regulating the position of particles is different than the conventional approaches, particles which go out of solution place are relocated inside by maintaining symmetry about the boundary. A twelve element linear antenna array is taken as the optimization target for the reduction of side lobes in the radiation pattern without increase in the mainlobe beamwidth. Results of the proposed boundary condition show better performance in terms of better global solution and quicker convergence compare to the other established boundary algorithms.
Pragnan Chakravorty and Durbadal Mandal Institute of Electrical and Electronics Engineers (IEEE)
Antenna arrays with interelement spacing as integral multiple of wavelength λ have been absent in practical implementations despite their highly directive main lobe; the disuse is primarily attributed to the presence of grating lobes. This letter proposes a modification in a linear antenna array whereby the grating lobes are suppressed by up to 100% with an additional improvement in the directivity of main-lobe and reduction in other sidelobe levels. A new array factor is synthesized by replacing the individual elements in a linear array with a pair of elements called discrete dipole elements (DDEs); a background theory of spatial hard windowing is proposed for the synthesis of array factor. Array factors of linear array made of eight DDEs are compared to those of an eight-element linear isotropic array to validate the claims. The proposed DDE array is then fabricated using monopole antennas; a good agreement between measured, simulated, and analytical results is seen.
Pragnan Chakravorty and Durbadal Mandal IEEE
Attainment of global optimal solution and reduction of computational time and resources have always been a trade off issue in formulation of nature inspired algorithms, this trade off challenge has brought in a deluge of new algorithms proposing their efficacy over one another. Particle swarm optimization (PSO) algorithm and its variants are quite popular in optimizing antenna designs particularly due to their algorithmic simplicity and fast convergence rates. However, as a matter of the ever present trade off, fast convergence often leads to sub optimal solutions. In some recent researches it has been shown that a class of boundary handling algorithms of PSO, known as position regulated boundary conditions (PRBCs), can minimize the trade off between fast convergence and accomplishment of global optimal solution, here, the performance of these boundary algorithms are compared with that of other established ones over three different optimization targets of antenna design namely, "Multi target optimization in linear antenna arrays", "Inset feed position optimization of rectangular patch antennas" and "Edge feed position optimization of rectangular patch antennas". Results show that the use of PRBCs in PSO leads to impressive improvement in the optimization efficiency in terms of lesser computational time and attainment of global optimal solution.
Sudipta Das, Gopi Ram Hardel, Pragnan Chakravorty, Durbadal Mandal, Rajib Kar, and Dr. Sakti Prasad Ghoshal IEEE
One of the most striking aspects of nature inspired algorithms is their capability of reaching a pare to front, for a set number of objectives, with much lesser computational cost than the classical ones, this is primarily due to the intrinsic intelligence that they inherit from nature. In this paper, as a first example, optimization of linear antenna arrays with dipole element pattern is exemplified for side lobe (SLL) reduction with fixed main-lobe beam width using real coded genetic algorithm (RGA), though multi goal optimization seems to be possible with proper cost/fitness function formulation in linear arrays, such a task becomes extremely difficult when it comes to planar arrays, this calls for the use of multi objective variants of an algorithm to reach the pare to objectivity, as a second example non-dominated sorting genetic algorithm II (NSGA2) is considered as the optimization algorithm for SLL reduction and fixed main-lobe directivity for concentric regular hexagonal antenna arrays (CRHAA). The results show good outcome with respect to side lobe reduction and directivity.
Gopi Ram, Pragnan Chakravorty, Durbadal Mandal, Rajib Kar, and Sakti Prasad Ghoshal IEEE
In this paper, a new evolutionary optimization algorithm named gravitational search algorithm with wavelet mutation (GSAWM) is adopted for optimal design of hyper beam pattern of linear antenna arrays. Hyper beam is derived from sum and difference beam patterns associated with hyper beam exponent parameter for the array. In GSAWM, particles are considered as objects and their performances are measured by their masses. All these objects attract each other by gravity forces, and these forces produce global movements of all objects towards the objects with heavier masses. GSAWM guarantees the exploitation step of the algorithm and it is apparently free from premature convergence. Extensive simulation results justify superior optimization capability of GSAWM over the aforementioned optimization techniques. By optimization of current excitation weights and uniform inter-element spacing, GSAWM achieves optimized hyper beam with much greater reduction in side lobe level (SLL), improved directivity and much more improved first null beam width (FNBW), keeping the same value of hyper beam exponent. The whole simulation experiment has been performed for 10-, 14-, and 20-element linear antenna arrays.
Pragnan Chakravorty and Durbadal Mandal IEEE
In the research of past one decade it has been quite convincingly shown that the boundary conditions in particle swarm optimizers are an important algorithmic part which restricts the particles within the solution space thereby increasing their scope of participation in solution finding process. Usually, velocities of the particles are regulated to bring them back to solution space; here a different fundamental approach of regulating the position of particles is taken, particles which go out of solution place are relocated inside by maintaining symmetry about the boundary. A six element linear antenna array is taken as the optimization target for the placement of nulls in some specified angles and an overall reduction of side lobes in the radiation pattern. Results show better performance of this boundary condition over other established ones in terms of quicker convergence and obtaining better optimization solution.
Pragnan Chakravorty and Durbadal Mandal Elsevier BV
Abstract Boundary conditions in particle swarm optimizers have been, quite convincingly, shown as an important algorithmic part which restricts the particles within the solution space thereby increasing their scope of participation in solution finding process. As a common practice, velocities of the particles are regulated to bring them back to solution space; however, a different fundamental approach of regulating the position of particles is taken here, particles which go out of solution place are relocated to a position where it was in its past (i.e. hysteretic position) iterative cycle inside the boundary. A six element linear antenna array is taken as the optimization target for the reduction of side lobes in the radiation pattern. Results show better performance of this boundary condition over other established ones in terms of quicker convergence and obtaining better optimization solution.
Pragnan Chakravorty and Durbadal Mandal Springer India
It has been descriptively shown in the past that the boundary conditions in particle swarm optimizers are an important algorithmic part which restricts the particles within the solution space, thereby increasing their scope of participation in solution finding process. Usually, velocities of the particles are regulated to bring them back to solution space; here, a different fundamental approach of regulating the position of particles is taken; particles which go out of solution place are relocated inside by maintaining symmetry about the boundary. A three concentric ring circular antenna array is taken as the optimization target for the reduction of side lobes in the radiation pattern. Results show better performance of this boundary condition over other established ones in terms of quicker convergence and obtaining better optimization solution.
Pragnan Chakravorty Informa UK Limited
In the design of bandpass filters, the use of λ/2 stubs of shunt configuration had been mostly unacceptable due to their effect of narrow stopband bandwidths in the ensuing filters. The design of bandpass filter presented in this article introduces 360° series transmission line segments to increase the stopband bandwidths to an acceptable level without affecting the wide passband. This designed filter has low insertion loss of less than –1.98 dB and a fractional bandwidth of 50% at 6 GHz mid-band frequency. A sharp rejection in the stopband is observed. To further widen the bandwidth of stopbands, a series capacitor and a shunt stub are used. The transmission line model of the filter is in good agreement with measured results. The filter is planar and is fabricated on FR-4 substrate which makes it cost-effective and easy to fabricate.
A. H. Abdelhafiz, P. Chakravorty, S. Gupta, A. Haque, and A. J. Sinclair Wiley
To the Editor: The interposition of the computer screen between patient and physician as a tangible ‘third party’ in the encounter may turn into a double-edged sword. On one hand, it is an indispensable tool for scrutinising the full patient’s records and test results as well as for communication, test-ordering, prescribing, reminders, patient instruction and reducing medical errors – not to mention its role in clinical decision support and consulting databases. On the other hand, patients report and video-based studies confirm that physicians are now often immersed in their screens, gazing, keyboarding and hardly able to separate, or connect to them (1,2). This applies not only to primary care since increasing numbers of hospitals are using portable computers and electronic medical records on ward rounds. The increasing dominance of the computer threatens the patient–provider relationship (PPR) – a core attribute of a successful clinical encounter (3). To reconcile the distractions of the quintessential screen with the crucial delivery of personal, patient-centred and empathic care (4), the following ‘five Commandments’ of PPR in the computer era are suggested:
Rupa Dasgupta, Partha P. Chakravorty, and Anilava Kaviraj Informa UK Limited
Effects of sub-lethal doses of carbaryl (1-Naphthyl-methylcarbamate), chlorpyrifos (O,O-diethyl O-3,5,6-trichloro-2-pyridinyl-phosphorothioate) and endosulfan (6,7,8,9,10,10-Hexachloro-1,5,5a,6,9,9a-hexahydro-6,9-methano-2,4,3-benzodioxathiepin-3-oxide), respectively a carbamate, an organophosphate and an organochlorine insecticide on growth, reproduction and respiration of the tropical earthworm, Perionyx excavatus (Perrier) were investigated under laboratory conditions. The results showed significant reduction in biomass, production and hatching of cocoon and production of juveniles of the worms exposed to 0.75 to 3.03 mg/kg soil of carbaryl, 0.91 to 3.65 mg/kg soil of chlorpyrifos and 3.75 to 15.0 μg/kg soil of endosulfan corresponding to 12.5 to 50 % of LC50 value of the respective insecticide for P. excavatus. Endosulfan was found most dangerous among the three insecticides followed by carbaryl and chlorpyrifos. There was no hatching of the worms at endosulfan treatment 5.0 μg/kg soil (25 % LC50) or above while the highest dose of carbaryl and chlorpyrifos (50 % of LC50) rendered respectively 87.13 and 24.84 % reductions in hatching as compared to control. Chlorpyrifos produced no change in respiration of the worms except at the highest dose, while the worms showed an increase in evolution of CO2 at all doses of carbaryl and endosulfan. Based on the recommended agricultural dose of each insecticide, it was concluded that application of endosulfan and carbaryl was potentially dangerous to earthworms.
A. Haque, R. Das Gupta, and P. P. Chakravorty Springer Science and Business Media LLC
Xenylla welchi was used to evaluate toxicity of two herbicide formulations, pretilachlor (50 EC) and pendimethalin (30 EC) under laboratory conditions. Twenty four hours LC50 value of pretilachlor and pendimethalin formulations on Xenylla welchi were 72.7 and 190.0 g a.i/ha respectively which were less than their corresponding recommended agricultural doses. Again pretilachlor attained fastest LT50 (110 min) followed by pendimethalin (140 min). Significant reductions in hatching success were noted with the application of both the herbicide formulations at all doses excepting 1/8 and 1/10th of LC50 (9.1, 7.3 and 23.8, 19.0 g a.i/ha for pretilachlor and pendimethalin, respectively). Hatching success of the test specimens recorded 44.1 and 63.3% reduction from control for the highest applied dose (½ of LC50) of pretilachlor and pendimethalin, respectively. Juveniles of Xenylla welchi exposed to 1/6, 1/8 and 1/10th LC50 for pretilachlor (12.1, 9.1, 7.3 g a.i/ha) and 1/8 and 1/10th LC50 for pendimethalin (23.8, 19.0 g ai/ha) survived and exhibited increased moulting frequency (7 moultings in 28 days in both the herbicide treatments) in comparison to control (8 moulting in 42 days). Test specimens required 26.0 ± 1.2 and 28.1 ± 2.1 days to attain sexual maturity exposed to pretilachlor and pendamethalin respectively which was significantly less than control (42 ± 2.6 days).
R. Das Gupta, P.P. Chakravorty, and A. Kaviraj Elsevier BV
Ecotoxicological risks of agricultural application of six insecticides to soil organisms were evaluated by acute toxicity tests under laboratory condition following OECD guidelines using the epigeic earthworm Eisenia fetida as the test organism. The organochlorine insecticide endosulfan (LC(50) - 0.002 mg kg(-1)) and the carbamate insecticides aldicarb (LC(50) - 9.42 mg kg(-1)) and carbaryl (LC(50) - 14.81 mg kg(-1)) were found ecologically most dangerous because LC(50) values of these insecticides were lower than the respective recommended agricultural dose (RAD). Although E. fetida was found highly susceptible to the pyrethroid insecticide cypermethrin (LC(50) - 0.054 mg kg(-1)), the value was higher than its RAD. The organophosphate insecticides chlorpyrifos (LC(50) - 28.58 mg kg(-1)), and monocrotophos (LC(50) - 39.75 mg kg(-1)) were found less toxic and ecologically safe because the LC(50) values were much higher than their respective RAD.
R. Das Gupta, P. P. Chakravorty, and A. Kaviraj Springer Science and Business Media LLC
The 96 h LC50 values of six insecticides were determined on a non-target epigeic earthworm Perionyx excavatus under laboratory conditions. Cypermethrin was found most toxic to P. excavatus (LC50-0.008 mg/kg), followed by endosulfan (LC50-0.03 mg/kg), carbaryl (LC50-6.07 mg/kg), chlorpyrifos (LC50-7.3 mg/kg), aldicarb (LC50-10.63 mg/kg) and monocrotophos (LC50-13.04 mg/kg). When these LC50 values were compared with their respective recommended agricultural doses, aldicarb and carbaryl appeared more dangerous than other pesticides because of their lower LC50 values than their respective recommended agricultural dose. Mean lethal time to cause 50% mortality at recommended agricultural dose (LT50) also indicated that aldicarb achieved the fastest LT50 (26 h) followed by endosulfan (38 h) and carbaryl (44 h) indicating the danger of these pesticides to P. excavatus.
Name of the Investigator Title of the project and duration Amount
Sanctioned/ completed/ongoing Funding Agency
Dr. P. P. Chakravorty (PI) Ecophysiological---Soil microarthropod 3 years
Dr. P. P. Chakravorty (PI) Bioassay of insecticides—soil collembola
Dr. P. P. Chakravorty (PI) Use of vermicompost—lateritic soil management 0,000/-
( W. B.)
Dr. P. P. Chakravorty (PI) Bioassay of insecticide pollution---soil
microarthropods. 2 years Rs.
Dr. P. P.Chakravorty (PI) &
R. Dasgupta (Co PI) Ecotoxicological & Biochemical --- Epigeic earthworm fauna. 2 years Rs.
Dr. P. P.Chakravorty (PI),
Dr. R. Dasgupta & Dr.T.
D as (Co PI) Studies on the usefulness of some-- pollution in agro ecosystem Rs.
Dr. P.P.Chakravorty ( PI) Studies on the role of selected ---ecosystems
ongoing DST W.B.
Recommendation of tree species in afforestation programme with respect to soil health, Establishment of ecologically safe insecticides for general agricultural practices
Research collaboration has been initiated between myself and Dr. Yuji Sakai, Kokaguin University, Tokyo, Japan
Start up my carrier as an Assistant Professor of Zoology on 19/04/2000, at present i am attached to my Institution as an Associate Professor
• Membership of Academic Societies---
1. Life Member Society of Soil Biology & Ecology, Bangalore.
2.Life Member National Environmental science academy, New Delhi
3. Life Member Physiological society of India, Kolkata
4. Life Member Zoological society of India, Kolkata.
5. Member Society for Conservation of Biology, Baltimore, Maryland, USA
6. Member of ISEIS ( International Society for Environmental Information sciences), Canada.
7. Life Member The Academy of Environmental Biology, ITRC, Lucknow.
8. Member International Society of Tropical Ecology, JNU
9. Life member Asian Biological Research Foundation