The present work mainly focuses on the estimation of various components and the extraction of microcrystalline cellulose(MCC)from non-wood sources like Country Almond/Badam shell through acid hydrolysis.This hydrolyze...The present work mainly focuses on the estimation of various components and the extraction of microcrystalline cellulose(MCC)from non-wood sources like Country Almond/Badam shell through acid hydrolysis.This hydrolyzed MCC was successfully used as reinforcement for development of biocomposites.Country Almond/Badam trees are found all over Kerala,India and they give nuts once in a year.Usually the nut shells are discarded and are becoming one of the sources of agricultural waste.During this investigation various components were isolated from the Country Almond shells and they were characterised using different spectral and analytical techniques thereby the composition of Country Almond shells was successfully determined for the first time.The properties of MCC especially the crystalline nature depends on the source from which is isolated.FT-IR spectra give evidence for the chemical structure of MCC.Morphology of MCC was evidenced from scanning electron microscopy.Transmission electron microscopy and atomic force microscopy reveal the agglomerated bundles of particles and rough surface of MCC.The extracted MCC was found to contain Cellulose I and Cellulose II polymorphs,and this was confirmed from the X-ray diffraction(XRD)studies.The MCC extracted from Country Almond shells has reasonably good thermal stability.Solution casting method was adopted for the development of green composite of Poly(vinyl alcohol)reinforced with MCC extracted from Country Almond shell.The mechanical property of developed composites has been enhanced by the addition of MCC.The dispersion of MCC in the PVA matrix and flocculation of MCC significantly influence the mechanical strength.展开更多
We report the transient effects in Erbium Doped Fiber Amplifier (EDFA) systems for pulsed signals with different duty-cycles. The work includes the analysis using three different duty-cycles, 10%, 20% and 50%. A curve...We report the transient effects in Erbium Doped Fiber Amplifier (EDFA) systems for pulsed signals with different duty-cycles. The work includes the analysis using three different duty-cycles, 10%, 20% and 50%. A curve fitting technique is also proposed to predict the transients of any lesser duty-cycled pulse, once the transients of a larger duty-cycled pulse is known. Mathematical evaluation confirms the double exponential shape of transient distorted signal. Further, EDFA transient effect is experimentally verified on a Wavelength Division Multiplexed (WDM) link by multiplexing high and low bitrate modulated optical signals. We conclude the paper by proposing a transient suppression technique for variable dutycycle signals and analyzing its effectiveness with different wavelength spacing.展开更多
Active phased array antennas enhances the performance of modern radars by using multiple low power transmit/receive modules in place of a high power transmitter in conventional radars. Fully distributed phased array r...Active phased array antennas enhances the performance of modern radars by using multiple low power transmit/receive modules in place of a high power transmitter in conventional radars. Fully distributed phased array radars demand the distribution of various signals in radio frequency(RF) and digital domain for real time operation. This is normally achieved through complex and bulky coaxial distribution networks. In this work, we intend to tap the inherent advantages of fiber links with wavelength division multiplexed(WDM) technology and a feasibility study to adapt these links for radar applications is carried out. This is done by analysing various parameters like amplitude, delay, frequency and phase variation response of various radar waveforms over WDM links. This also includes performance evaluation of non-linear frequency modulation(NLFM) signals, known for better signal to noise ratio(SNR) to specific side lobe levels. NLFM waveforms are further analysed using pulse compression(PC) technique. Link evaluation is also carried out using a standard simulation environment and is then experimentally verified with other waveforms like RF continuous wave(CW), pulsed RF and digital signals. Synchronization signals are generated from this variable duty cycle digital signals during real time radar operation. During evaluation of digital signals, variable transient effects for different duty cycles are observed from an amplifier configuration. A suppression method is proposed to eliminate this transient effects. Further, the link delay response is investigated using different lengths of fiber spools. It can be inferred from the experimental results that WDM links are capable of handling various signals significant to radar applications.展开更多
文摘The present work mainly focuses on the estimation of various components and the extraction of microcrystalline cellulose(MCC)from non-wood sources like Country Almond/Badam shell through acid hydrolysis.This hydrolyzed MCC was successfully used as reinforcement for development of biocomposites.Country Almond/Badam trees are found all over Kerala,India and they give nuts once in a year.Usually the nut shells are discarded and are becoming one of the sources of agricultural waste.During this investigation various components were isolated from the Country Almond shells and they were characterised using different spectral and analytical techniques thereby the composition of Country Almond shells was successfully determined for the first time.The properties of MCC especially the crystalline nature depends on the source from which is isolated.FT-IR spectra give evidence for the chemical structure of MCC.Morphology of MCC was evidenced from scanning electron microscopy.Transmission electron microscopy and atomic force microscopy reveal the agglomerated bundles of particles and rough surface of MCC.The extracted MCC was found to contain Cellulose I and Cellulose II polymorphs,and this was confirmed from the X-ray diffraction(XRD)studies.The MCC extracted from Country Almond shells has reasonably good thermal stability.Solution casting method was adopted for the development of green composite of Poly(vinyl alcohol)reinforced with MCC extracted from Country Almond shell.The mechanical property of developed composites has been enhanced by the addition of MCC.The dispersion of MCC in the PVA matrix and flocculation of MCC significantly influence the mechanical strength.
文摘We report the transient effects in Erbium Doped Fiber Amplifier (EDFA) systems for pulsed signals with different duty-cycles. The work includes the analysis using three different duty-cycles, 10%, 20% and 50%. A curve fitting technique is also proposed to predict the transients of any lesser duty-cycled pulse, once the transients of a larger duty-cycled pulse is known. Mathematical evaluation confirms the double exponential shape of transient distorted signal. Further, EDFA transient effect is experimentally verified on a Wavelength Division Multiplexed (WDM) link by multiplexing high and low bitrate modulated optical signals. We conclude the paper by proposing a transient suppression technique for variable dutycycle signals and analyzing its effectiveness with different wavelength spacing.
文摘Active phased array antennas enhances the performance of modern radars by using multiple low power transmit/receive modules in place of a high power transmitter in conventional radars. Fully distributed phased array radars demand the distribution of various signals in radio frequency(RF) and digital domain for real time operation. This is normally achieved through complex and bulky coaxial distribution networks. In this work, we intend to tap the inherent advantages of fiber links with wavelength division multiplexed(WDM) technology and a feasibility study to adapt these links for radar applications is carried out. This is done by analysing various parameters like amplitude, delay, frequency and phase variation response of various radar waveforms over WDM links. This also includes performance evaluation of non-linear frequency modulation(NLFM) signals, known for better signal to noise ratio(SNR) to specific side lobe levels. NLFM waveforms are further analysed using pulse compression(PC) technique. Link evaluation is also carried out using a standard simulation environment and is then experimentally verified with other waveforms like RF continuous wave(CW), pulsed RF and digital signals. Synchronization signals are generated from this variable duty cycle digital signals during real time radar operation. During evaluation of digital signals, variable transient effects for different duty cycles are observed from an amplifier configuration. A suppression method is proposed to eliminate this transient effects. Further, the link delay response is investigated using different lengths of fiber spools. It can be inferred from the experimental results that WDM links are capable of handling various signals significant to radar applications.
