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Dandapathak M.,Hooghly Mohsin College | Sarkar S.,Burdwan Raj College | Sarkar B.C.,University of Burdwan
Optik | Year: 2014

The dynamics of an optical phase locked loop (OPLL) with first order loop filter having inherent loop time delay is investigated. In the presence of delay, the system is modeled as a third order autonomous system. In the out of lock condition or during the process of locking, the dynamics of the system is highly nonlinear and different nonlinear phenomena, like limit cycle oscillation, period doubling, chaotic oscillations etc., may be observed with the variation of design parameters. Applying the techniques of the nonlinear dynamics, we have calculated the effects of the inherent loop time delay in determining the state of the loop. The analytical results predicting the parameter values for stable and unstable region of operation are obtained using the quasi-linear Routh-Hurwitz method. The parameter range required for the onset of chaotic oscillations is estimated by Melnikov's global perturbation method. The predicted results are in agreement with those obtained by numerical integration of system equations. © 2014 Elsevier GmbH. All rights reserved.

Sarkar B.C.,University of Burdwan | Dandapathak M.,Hooghly Mohsin College | Sarkar S.,Burdwan Raj College | Banerjee T.,University of Burdwan
Progress In Electromagnetics Research M | Year: 2013

Dynamical stability of a system of bilaterally coupled periodic Gunn oscillators (BCPGO) has been studied employing Melnikov's global perturbation technique. In the BCPGO system, a fractional part of the output signal of one oscillator is injected into the other through a coupling network. The injected signal is considered as a perturbation on the free running dynamics of the receiving oscillator and the amount of perturbation is quantified by a parameter named coupling factor (CF). The limiting values of CFs leading to chaotic dynamics of the BCPGO system are predicted analytically by calculating the Melnikov functions (MFs) in the respective cases. Also the effect of the frequency detuning (FD) between the Gunn Oscillators (GOs) on the computed values of MFs has been examined. A thorough numerical simulation of the BCPGO dynamics has been done by solving the system equations. The obtained results are in qualitative agreement with the analytically predicted observations regarding the roles of the system parameters like CF and FD.

Sarkar B.C.,University of Burdwan | Sarkar D.,Jadavpur University | Sarkar S.,Burdwan Raj College | Chakraborty J.,University of Burdwan
Progress In Electromagnetics Research B | Year: 2011

The dynamics of a system comprising of two bilaterally coupled Gunn oscillators (BCGOs) has been examined using a circuit theoretic model of the Gunn oscillator (GO). The effects of coupling factors (kij) between i-th and j-th oscillators on the frequency-range of synchronized operation and the magnitude of common frequency of oscillation have been examined semi-analytically and by numerical solution of the system equations. The occurrence of chaotic oscillations at the verge of synchronization bands is observed in numerical simulation. The experimental response of the BCGO operating in the X-band is obtained and the results are found to be qualitatively similar to the analytical and numerical predictions.

Nath Das S.,Burdwan Raj College | Nath Das S.,Yonsei University | Patra S.,Burdwan Raj College | Prakash Kar J.,National Institute of Technology Tiruchirappalli | And 4 more authors.
Materials Letters | Year: 2013

The Mg-doped GaN nanowires with very high aspect ratio grew by the Vapor-Liquid-Solid method onto Si substrates using Ni as catalyst and Mg 3N2 powder as Mg source. Structural and optical characterizations of un-doped and Mg-doped GaN nanowires were investigated. The XRD shows that the relative intensities of other peaks [in comparison to (100)] increases with the incorporation of Mg. It indicates that Mg changes the preferential growth direction of nanowires. PL studies revealed that without doped samples a few donor levels rose due to structural defects. The incorporation of Mg produces a few additional donor levels (arising due to structural defects) as well as acceptor levels (arising due to Mg doping). These Mg-doped nanowires may be used as p-type nanowire. © 2013 Elsevier B.V.

Sarkar B.C.,University of Burdwan | Sarkar S.,Burdwan Raj College | Guin A.K.,University of Burdwan | Koley C.,NIT Mizoram
International Journal of Bifurcation and Chaos | Year: 2015

We have studied the performance of a Gunn oscillator (GO) based angle modulator-demodulator system in transmitting chaotic signals in the X-band microwave frequency channel. The principle of bias tuning of a GO is employed to implement the angle modulator used in the transmitter. The said GO is operated in a free running condition and then in a frequency synchronized condition to an external microwave signal, thus generating frequency modulated (FM) and phase modulated (PM) signals, respectively. The demodulator circuit is implemented with a GO phase synchronized to the incoming modulated signal, followed by a microwave mixer multiplying the input and the output signals of the GO and a low pass filter. The response of the system is analytically established, numerically examined and experimentally verified. The obtained results confirm that in the limit of low modulation index and in the linear range of operation of the bias tuned modulator and the phase synchronized detector, a chaos signal can be transmitted and recovered through a microwave channel using the technique of angle modulation. © 2015 World Scientific Publishing Company.

Sarkar B.C.,University of Burdwan | Koley C.,University of Burdwan | Guin A.K.,University of Burdwan | Sarkar S.,Burdwan Raj College
Progress In Electromagnetics Research B | Year: 2012

The dynamics of a system of two bilaterally coupled chaotically oscillating X-band Gunn oscillators (GOs) has been studied by numerical simulation and by hardware experiment. The effect of variation of the coupling strengths between two oscillators in two paths has been explored. The chaotic oscillations in two GOs have become synchronized in most of the cases when coupling factors (CFs) are around 20% or more. However, the transformation of chaotic states of the GOs to quasi-periodic ones has been observed for some values of CFs. A detailed numerical analysis on the instantaneous error parameters of the GO state variables is presented to identify different steady state dynamical conditions of the system. Experimental observations of the GO output frequency power spectra and the averaged product of the two GO outputs in the coupled mode con-rm the occurrence of synchronization as well as quenching of chaotic oscillations for different values of CFs.

Sarkar B.C.,University of Burdwan | Koley C.,University of Burdwan | Guin A.K.,University of Burdwan | Sarkar S.,Burdwan Raj College
Progress In Electromagnetics Research B | Year: 2012

The dynamics of the onset of oscillations in a wave guide cavity based Gunn Oscillator (GO) has been critically examined through numerical simulations and experimental studies. The transition of the GO from a non-oscillatory to an oscillatory state and the same in the reverse direction occurs at different critical values of the dc bias voltage applied to the GO. In presence of a weak RF field in GO cavity, oscillations with broad band continuous spectrum and multiple discrete line spectrum are observed at the GO output for different values of dc bias below the above mentioned critical values. Analysing the numerically obtained time series data, chaos quantifiers have been obtained to prove the occurrence of the chaotic oscillations in the GO. Experimental results and observations of numerical simulation show good qualitative agreement.

Roy D.,University of Burdwan | Khan D.,Burdwan Raj College
International Journal of Industrial Engineering Computations | Year: 2010

In this paper, we address the optimization of an integrated line balancing process with workstation inventory management. While doing so, we have studied the interconnection between line balancing and its conversion process. Almost each and every moderate to large manufacturing industry depends on a long and integrated supply chain, consisting of inbound logistic, conversion process and outbound logistic. In this sense an approach addresses a very general problem of integrated line balancing. Research works reported in the literature so far mainly deals with minimization of cost for inbound and outbound logistic subsystems. In most of the cases conversion process has been ignored. We suggest a generic approach for linking the balancing of the line of production in the conversion area with the customers' rate of demand in the market and for configuring the related stock chambers. Thus, the main aim of this paper is to translate the underlying problem in the form of mixed nonlinear programming problem and design the optimum supply chain so that the total inventory cost and the cost of balancing loss of the conversion process is jointly minimized and ideal cycle time of the production process is determined along with ideal sizes of the stock chambers. A numerical example has been added to demonstrate the suitability of our approach. © 2010 Growing Science Ltd. All rights reserved.

Senthil Kumar M.,St Xaviers College | Nandi S.C.,Burdwan Raj College
Journal of Genetic Engineering and Biotechnology | Year: 2015

Asteracantha longifolia Nees is an ayurvedic medicinal herb. The internode explants of this plant were used for high frequency plant regeneration on Murashige and Skoog (MS) medium supplemented with various plant growth regulators (PGRs) in different concentrations. Apical meristem and leaf primordium formations were confirmed through microscopic analysis of histological sections of the organogenic callus tissues. The synergistic effect of α-naphthaleneacetic acid (NAA) 0.5 mg/l with N6 benzyladenine (BA) 0.25 mg/l increased the percentage of explants response for callus induction while comparing other treatments. Various concentrations of NAA were also found to be best for explants response to callus induction than 2,4-dichlorophenoxyacetic acid (2,4-D). The callus morphology (color and texture) was different according to the growth regulators and their concentrations. The highest percentage of response per culture for shoot bud regeneration was noted for the concentration of NAA 0.5 mg/l with BA 2.0 mg/l, the same concentration effectively increased the number of shoots per culture. Different concentrations of indol-3-butyric acid (IBA) and NAA were used in half strength MS medium for in vitro rooting of regenerated shoots. The maximum percentage of shoot response for rooting and the highest number of root formations per shoot were observed on the medium containing 0.5 mg/l of IBA. The survival rate (86.7%) of the regenerated plants was noted after 20 days of transplantation. © 2015.

Sarkar B.C.,University of Burdwan | Sarkar S.,Burdwan Raj College | Koley C.,University of Burdwan | Guin A.K.,University of Burdwan | Banerjee T.,University of Burdwan
International Journal of Bifurcation and Chaos | Year: 2013

Two X-band microwave Gunn oscillators have been separately operated with «below threshold» dc bias voltages under the influence of an injected weak RF field in their respective cavities to generate chaotic oscillations. The output of one such chaotic Gunn oscillator is injected into the other through a controllable coupling network to explore the possibility of synchronization between two oscillators. We establish through numerical simulation that (i) two oscillators with identical design parameters attain a state of complete synchronization and (ii) two oscillators with slightly different design parameters attain a state of generalized synchronization for reasonable value of coupling strengths. The occurrence of generalized synchronization has been proved through the «auxiliary» slave system approach of nonlinear analysis. Results of hardware experiments are incorporated to qualitatively support the observations made through numerical simulation. © 2013 World Scientific Publishing Company.

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