Abhishek Pathak | Indian Institute of Technology Delhi (original) (raw)
Papers by Abhishek Pathak
2009 Annual IEEE India Conference, 2009
This paper presents RLC equivalent model of power plane for power distribution network (PDN) in h... more This paper presents RLC equivalent model of power plane for power distribution network (PDN) in high speed VLSI system consisting of package, board, and voltage regulator module. The frequency independent RLC equivalent model can be easily integrated in any SPICE compatible circuit simulator. SPICE simulation results of the proposed RLC models for regular and irregular power-ground plane pair have been extensively verified with full wave EM simulation results. The model shows good matching when compared with EM simulation results. The proposed SPICE model substantially reduces the CPU run time that requires only few seconds for which the EM solver would have taken several hours. Effects of different geometry and material of power plane on self-impedance profile have been analyzed.
IEEE India Conference, 2009
This paper presents RLC equivalent model of power plane for power distribution network (PDN) in h... more This paper presents RLC equivalent model of power plane for power distribution network (PDN) in high speed VLSI system consisting of package, board, and voltage regulator module. The frequency independent RLC equivalent model can be easily integrated in any SPICE compatible circuit simulator. SPICE simulation results of the proposed RLC models for regular and irregular power-ground plane pair have been extensively verified with full wave EM simulation results. The model shows good matching when compared with EM simulation results. The proposed SPICE model substantially reduces the CPU run time that requires only few seconds for which the EM solver would have taken several hours. Effects of different geometry and material of power plane on self-impedance profile have been analyzed.
Polymer-plastics Technology and Engineering, 2008
Journal of Applied Polymer Science, 2009
The present study explores the possibilities of using chitosan-magnetite (CM) nanocomposites for ... more The present study explores the possibilities of using chitosan-magnetite (CM) nanocomposites for removal of urea in blood serum. The CM nanocomposites, with an average diameter in the range of 12–33 nm, were characterized by transmission electron microscopic and selected area electron diffraction analysis. The particles demonstrate fair ability to remove urea in human blood serum. The maximum removal efficiency was nearly 26%, when 200 mg of CM nanocomposites were allowed to agitate with 25 mL of urea solution of concentration 100 mg/dL. The CM nanocomposites could be easily removed by applying moderate magnetic field. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Journal of Macromolecular Science, Part A, 2007
The study describes the preparation of Cu(II)-immobilized copolymer(CIC) under optimum conditions... more The study describes the preparation of Cu(II)-immobilized copolymer(CIC) under optimum conditions for the effective removal of urea. The copolymeric hydrogels, synthesized by free-radical aqueous copolymerization of monomers acrylamide and sodium acrylate, have been analyzed for ...
Polymer-Plastics Technology and Engineering, 2008
Physical Review A, 2012
Bessel beams possess a nondiffractive property that makes them suitable for propagating optical e... more Bessel beams possess a nondiffractive property that makes them suitable for propagating optical energy over long distances. We have utilized an axicon-generated Bessel beam to carry out a systematic study of the physics that governs propagation of intense, femtosecond-long pulses in a transparent crystal (barium fluoride). Filamentation and supercontinuum generation have been studied using axicon lenses of different cone angles. Emission induced by six-photon absorption of 800-nm photons is utilized to visualize the filaments within the crystal. Our results show that higher incident energy, E in ( 600 μJ), is required to generate filaments inside the crystal when an axicon is used, as compared to a spherical lens (6 μJ). Increase in cone angles increases the value of E in for filament formation. The size of the filaments is found to be independent of whether an axicon or a spherical lens is used. For a given axicon cone angle, variation of the input energy enables us to observe the transition from steady Bessel filamentation to a nonlinear, unbalanced, Bessel regime. Varying the separation distance between the axicon and the crystal enables differences in periodicity (distance between two focusing-refocusing events) in the filaments to be quantified. Supercontinuum generation is also probed as a function of distance of sample from the tip of the axicon and with different incident beam sizes. The input beam diameter is shown to have a distinct effect on axicon-generated white light.
Journal of Macromolecular Science, Part A, 2007
The study describes the preparation of Cu(II)-immobilized copolymer(CIC) under optimum conditions... more The study describes the preparation of Cu(II)-immobilized copolymer(CIC) under optimum conditions for the effective removal of urea. The copolymeric hydrogels, synthesized by free-radical aqueous copolymerization of monomers acrylamide and sodium acrylate, have been analyzed for ...
Journal of Applied Polymer Science, 2009
The goal of dialysis for patients with chronic renal failure is to remove nitrogenous end-product... more The goal of dialysis for patients with chronic renal failure is to remove nitrogenous end-products of catabolism and to restore the composition of the body's fluid environment toward normal.1 With renal failure of any cause, toxic end products of nitrogen metabolism (urea, uric acid, ...
Designed Monomers &# 38; Polymers, 2009
This work focuses on the investigation of antibacterial and biocompatible properties of a porous ... more This work focuses on the investigation of antibacterial and biocompatible properties of a porous Cu(II)-cross-linked chitosan membrane (CCCM). The membrane shows fair biocidal action against the model bacterium Escherichia coli. The total protein and HSA adsorbed was found to be 263 and 75 μg/cm. Finally, the 'diffusion cell model' was used to study adsorptive removal of urea from aqueous solutions.
Ferroelectrics Letters Section, 2010
Samples with representative formula Pb(1–1.5x)Smx(Zr0.7Sn0.3)0.938Ti0.062O3 (PSmZST) with x = 0.0... more Samples with representative formula Pb(1–1.5x)Smx(Zr0.7Sn0.3)0.938Ti0.062O3 (PSmZST) with x = 0.0, 0.01, 0.02 and 0.04 were synthesized using conventional solid state ceramic route. Dielectric properties were studied as a function of frequency and temperature. Dielectric constant curves show a hump before the paraelectric transition. Dielectric loss measurements show noticeable changes as compare to the unmodified composition. ac conductivity measurements show that conductivity of samples increases with increase of samarium (Sm) content.
Physica B-condensed Matter, 2009
Unmodified lead zirconate titanate stannate (PZST) system with compositional formula Pb [(Zr0.7Sn... more Unmodified lead zirconate titanate stannate (PZST) system with compositional formula Pb [(Zr0.7Sn0.3)xTi(1−x)]O3, where 0.92≤x≤0.94 has been studied at Morphotropic phase boundary (MPB) for dielectric, ferroelectric and shape memory effect. Field-induced strain measurements are presented to show that ∼0.08% remnant strain pertaining to shape memory can be observed in PZST ceramics at near-exact MPB.
Physica B: Condensed Matter, 2009
Unmodified lead zirconate titanate stannate (PZST) system with compositional formula Pb [(Zr 0.7 ... more Unmodified lead zirconate titanate stannate (PZST) system with compositional formula Pb [(Zr 0.7 Sn 0.3 ) x Ti (1Àx) ]O 3 , where 0.92rxr0.94 has been studied at Morphotropic phase boundary (MPB) for dielectric, ferroelectric and shape memory effect. Field-induced strain measurements are presented to show that $0.08% remnant strain pertaining to shape memory can be observed in PZST ceramics at near-exact MPB.
Electromagnetic Materials - Proceedings of the Symposium R, ICMAT 2005, 2005
The effects of stannate doping on the phase transition, P-E electrical hysteresis and shape memor... more The effects of stannate doping on the phase transition, P-E electrical hysteresis and shape memory behaviors of yttrium modified lead zirconate titanate stannate (with Ti=0.085) were examined. The increasing Sn/Zr ratios were investigated experimentally for their effect on obtaining the antiferroelectric phase at room temperature. It is observed that although the strain increases with increasing Sn/Zr ratio, all the samples (except x=0.4 and 0.5) are ferroelectric at room temperature. The sample with x=0.4 that was reported [Ref.2] to be antiferroelectric at 40°C, shows paraelectric or compensated AFE behavior at room temperature.
Ferroelectrics Letters Section - FERROELECTRICS LETT SECT, 2010
Samples with representative formula Pb(1–1.5x)Smx(Zr0.7Sn0.3)0.938Ti0.062O3 (PSmZST) with x = 0.0... more Samples with representative formula Pb(1–1.5x)Smx(Zr0.7Sn0.3)0.938Ti0.062O3 (PSmZST) with x = 0.0, 0.01, 0.02 and 0.04 were synthesized using conventional solid state ceramic route. Dielectric properties were studied as a function of frequency and temperature. Dielectric constant curves show a hump before the paraelectric transition. Dielectric loss measurements show noticeable changes as compare to the unmodified composition. ac conductivity measurements show that conductivity of samples increases with increase of samarium (Sm) content.
Materials Chemistry and Physics, 2010
Samples with representative formula (1 − y)[Pb(Zr 0.7 Sn 0.3 ) 0.938 Ti 0.062 O 3 ] (PZST)y(PbMg... more Samples with representative formula (1 − y)[Pb(Zr 0.7 Sn 0.3 ) 0.938 Ti 0.062 O 3 ] (PZST)y(PbMg 1/3 Nb 2/3 O 3 ) (PMN), with y = 0.01, 0.02, 0.05 and 0.07, were synthesized using conventional solid state ceramic route. Detailed studies on structural, dielectric, ...
Journal of the American Ceramic Society, 2014
ABSTRACT The study set out to investigate the compositional inconsistency in lanthanum zirconate ... more ABSTRACT The study set out to investigate the compositional inconsistency in lanthanum zirconate system revealed the presence of nonstoichiometry in lanthanum zirconate powders when synthesized by coprecipitation route. X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) investigations confirmed the depletion of La3+ ions in the system. Analysis using Vegard's law showed the La/Zr mole ratio in the sample to be around 0.45. An extra step of ultrasonication, introduced during the washing stage followed by the coprecipitation reaction, ensured the formation of stoichiometric La2Zr2O7. Noteworthy is also the difference between crystal sizes in the samples prepared by with and without ultrasonication step. This difference has been explained in light of the formation of individual nuclei and their scope of growth within the precipitate core. The differential scanning calorimetry (DSC) analyses revealed that optimum pH for the synthesis of La2Zr2O7 is about 11. The ultrasonication step was pivotal in assuring consistency in mixing and composition for the lanthanum zirconate powders.
Chemical Communications, 2011
Confluence of a modular design approach and self-assembly with a 'steroid-D-p-A' module generates... more Confluence of a modular design approach and self-assembly with a 'steroid-D-p-A' module generates spontaneous polarization in solids and for the first time in nano-architectures constituted from organogels, at room temperature (RT).
Ceramics International, 2010
A modified lead zirconate stannate titanate system (PZST) has been studied for shape memory effec... more A modified lead zirconate stannate titanate system (PZST) has been studied for shape memory effect. Addition of magnesium niobate (MN) slows down the dipole relaxation process, leading to increased ($3-fold improvement) remnant strain in the PZST system (0.99PZST-0.01PMN). Room temperature X-ray diffraction patterns before poling (antiferroelectric (AFE) tetragonal) and after poling (ferroelectric (FE) rhombohedral), clearly demonstrate that the transition to the ferroelectric phase is stable even in the absence of any electric field. A small applied electric field ($1.7 kV/cm) in the opposite direction was required to bring the sample back to its original shape. Field-induced strain butterfly loops taken at 50 Hz show that the material response time is quite small. #
2009 Annual IEEE India Conference, 2009
This paper presents RLC equivalent model of power plane for power distribution network (PDN) in h... more This paper presents RLC equivalent model of power plane for power distribution network (PDN) in high speed VLSI system consisting of package, board, and voltage regulator module. The frequency independent RLC equivalent model can be easily integrated in any SPICE compatible circuit simulator. SPICE simulation results of the proposed RLC models for regular and irregular power-ground plane pair have been extensively verified with full wave EM simulation results. The model shows good matching when compared with EM simulation results. The proposed SPICE model substantially reduces the CPU run time that requires only few seconds for which the EM solver would have taken several hours. Effects of different geometry and material of power plane on self-impedance profile have been analyzed.
IEEE India Conference, 2009
This paper presents RLC equivalent model of power plane for power distribution network (PDN) in h... more This paper presents RLC equivalent model of power plane for power distribution network (PDN) in high speed VLSI system consisting of package, board, and voltage regulator module. The frequency independent RLC equivalent model can be easily integrated in any SPICE compatible circuit simulator. SPICE simulation results of the proposed RLC models for regular and irregular power-ground plane pair have been extensively verified with full wave EM simulation results. The model shows good matching when compared with EM simulation results. The proposed SPICE model substantially reduces the CPU run time that requires only few seconds for which the EM solver would have taken several hours. Effects of different geometry and material of power plane on self-impedance profile have been analyzed.
Polymer-plastics Technology and Engineering, 2008
Journal of Applied Polymer Science, 2009
The present study explores the possibilities of using chitosan-magnetite (CM) nanocomposites for ... more The present study explores the possibilities of using chitosan-magnetite (CM) nanocomposites for removal of urea in blood serum. The CM nanocomposites, with an average diameter in the range of 12–33 nm, were characterized by transmission electron microscopic and selected area electron diffraction analysis. The particles demonstrate fair ability to remove urea in human blood serum. The maximum removal efficiency was nearly 26%, when 200 mg of CM nanocomposites were allowed to agitate with 25 mL of urea solution of concentration 100 mg/dL. The CM nanocomposites could be easily removed by applying moderate magnetic field. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Journal of Macromolecular Science, Part A, 2007
The study describes the preparation of Cu(II)-immobilized copolymer(CIC) under optimum conditions... more The study describes the preparation of Cu(II)-immobilized copolymer(CIC) under optimum conditions for the effective removal of urea. The copolymeric hydrogels, synthesized by free-radical aqueous copolymerization of monomers acrylamide and sodium acrylate, have been analyzed for ...
Polymer-Plastics Technology and Engineering, 2008
Physical Review A, 2012
Bessel beams possess a nondiffractive property that makes them suitable for propagating optical e... more Bessel beams possess a nondiffractive property that makes them suitable for propagating optical energy over long distances. We have utilized an axicon-generated Bessel beam to carry out a systematic study of the physics that governs propagation of intense, femtosecond-long pulses in a transparent crystal (barium fluoride). Filamentation and supercontinuum generation have been studied using axicon lenses of different cone angles. Emission induced by six-photon absorption of 800-nm photons is utilized to visualize the filaments within the crystal. Our results show that higher incident energy, E in ( 600 μJ), is required to generate filaments inside the crystal when an axicon is used, as compared to a spherical lens (6 μJ). Increase in cone angles increases the value of E in for filament formation. The size of the filaments is found to be independent of whether an axicon or a spherical lens is used. For a given axicon cone angle, variation of the input energy enables us to observe the transition from steady Bessel filamentation to a nonlinear, unbalanced, Bessel regime. Varying the separation distance between the axicon and the crystal enables differences in periodicity (distance between two focusing-refocusing events) in the filaments to be quantified. Supercontinuum generation is also probed as a function of distance of sample from the tip of the axicon and with different incident beam sizes. The input beam diameter is shown to have a distinct effect on axicon-generated white light.
Journal of Macromolecular Science, Part A, 2007
The study describes the preparation of Cu(II)-immobilized copolymer(CIC) under optimum conditions... more The study describes the preparation of Cu(II)-immobilized copolymer(CIC) under optimum conditions for the effective removal of urea. The copolymeric hydrogels, synthesized by free-radical aqueous copolymerization of monomers acrylamide and sodium acrylate, have been analyzed for ...
Journal of Applied Polymer Science, 2009
The goal of dialysis for patients with chronic renal failure is to remove nitrogenous end-product... more The goal of dialysis for patients with chronic renal failure is to remove nitrogenous end-products of catabolism and to restore the composition of the body's fluid environment toward normal.1 With renal failure of any cause, toxic end products of nitrogen metabolism (urea, uric acid, ...
Designed Monomers &# 38; Polymers, 2009
This work focuses on the investigation of antibacterial and biocompatible properties of a porous ... more This work focuses on the investigation of antibacterial and biocompatible properties of a porous Cu(II)-cross-linked chitosan membrane (CCCM). The membrane shows fair biocidal action against the model bacterium Escherichia coli. The total protein and HSA adsorbed was found to be 263 and 75 μg/cm. Finally, the 'diffusion cell model' was used to study adsorptive removal of urea from aqueous solutions.
Ferroelectrics Letters Section, 2010
Samples with representative formula Pb(1–1.5x)Smx(Zr0.7Sn0.3)0.938Ti0.062O3 (PSmZST) with x = 0.0... more Samples with representative formula Pb(1–1.5x)Smx(Zr0.7Sn0.3)0.938Ti0.062O3 (PSmZST) with x = 0.0, 0.01, 0.02 and 0.04 were synthesized using conventional solid state ceramic route. Dielectric properties were studied as a function of frequency and temperature. Dielectric constant curves show a hump before the paraelectric transition. Dielectric loss measurements show noticeable changes as compare to the unmodified composition. ac conductivity measurements show that conductivity of samples increases with increase of samarium (Sm) content.
Physica B-condensed Matter, 2009
Unmodified lead zirconate titanate stannate (PZST) system with compositional formula Pb [(Zr0.7Sn... more Unmodified lead zirconate titanate stannate (PZST) system with compositional formula Pb [(Zr0.7Sn0.3)xTi(1−x)]O3, where 0.92≤x≤0.94 has been studied at Morphotropic phase boundary (MPB) for dielectric, ferroelectric and shape memory effect. Field-induced strain measurements are presented to show that ∼0.08% remnant strain pertaining to shape memory can be observed in PZST ceramics at near-exact MPB.
Physica B: Condensed Matter, 2009
Unmodified lead zirconate titanate stannate (PZST) system with compositional formula Pb [(Zr 0.7 ... more Unmodified lead zirconate titanate stannate (PZST) system with compositional formula Pb [(Zr 0.7 Sn 0.3 ) x Ti (1Àx) ]O 3 , where 0.92rxr0.94 has been studied at Morphotropic phase boundary (MPB) for dielectric, ferroelectric and shape memory effect. Field-induced strain measurements are presented to show that $0.08% remnant strain pertaining to shape memory can be observed in PZST ceramics at near-exact MPB.
Electromagnetic Materials - Proceedings of the Symposium R, ICMAT 2005, 2005
The effects of stannate doping on the phase transition, P-E electrical hysteresis and shape memor... more The effects of stannate doping on the phase transition, P-E electrical hysteresis and shape memory behaviors of yttrium modified lead zirconate titanate stannate (with Ti=0.085) were examined. The increasing Sn/Zr ratios were investigated experimentally for their effect on obtaining the antiferroelectric phase at room temperature. It is observed that although the strain increases with increasing Sn/Zr ratio, all the samples (except x=0.4 and 0.5) are ferroelectric at room temperature. The sample with x=0.4 that was reported [Ref.2] to be antiferroelectric at 40°C, shows paraelectric or compensated AFE behavior at room temperature.
Ferroelectrics Letters Section - FERROELECTRICS LETT SECT, 2010
Samples with representative formula Pb(1–1.5x)Smx(Zr0.7Sn0.3)0.938Ti0.062O3 (PSmZST) with x = 0.0... more Samples with representative formula Pb(1–1.5x)Smx(Zr0.7Sn0.3)0.938Ti0.062O3 (PSmZST) with x = 0.0, 0.01, 0.02 and 0.04 were synthesized using conventional solid state ceramic route. Dielectric properties were studied as a function of frequency and temperature. Dielectric constant curves show a hump before the paraelectric transition. Dielectric loss measurements show noticeable changes as compare to the unmodified composition. ac conductivity measurements show that conductivity of samples increases with increase of samarium (Sm) content.
Materials Chemistry and Physics, 2010
Samples with representative formula (1 − y)[Pb(Zr 0.7 Sn 0.3 ) 0.938 Ti 0.062 O 3 ] (PZST)y(PbMg... more Samples with representative formula (1 − y)[Pb(Zr 0.7 Sn 0.3 ) 0.938 Ti 0.062 O 3 ] (PZST)y(PbMg 1/3 Nb 2/3 O 3 ) (PMN), with y = 0.01, 0.02, 0.05 and 0.07, were synthesized using conventional solid state ceramic route. Detailed studies on structural, dielectric, ...
Journal of the American Ceramic Society, 2014
ABSTRACT The study set out to investigate the compositional inconsistency in lanthanum zirconate ... more ABSTRACT The study set out to investigate the compositional inconsistency in lanthanum zirconate system revealed the presence of nonstoichiometry in lanthanum zirconate powders when synthesized by coprecipitation route. X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) investigations confirmed the depletion of La3+ ions in the system. Analysis using Vegard's law showed the La/Zr mole ratio in the sample to be around 0.45. An extra step of ultrasonication, introduced during the washing stage followed by the coprecipitation reaction, ensured the formation of stoichiometric La2Zr2O7. Noteworthy is also the difference between crystal sizes in the samples prepared by with and without ultrasonication step. This difference has been explained in light of the formation of individual nuclei and their scope of growth within the precipitate core. The differential scanning calorimetry (DSC) analyses revealed that optimum pH for the synthesis of La2Zr2O7 is about 11. The ultrasonication step was pivotal in assuring consistency in mixing and composition for the lanthanum zirconate powders.
Chemical Communications, 2011
Confluence of a modular design approach and self-assembly with a 'steroid-D-p-A' module generates... more Confluence of a modular design approach and self-assembly with a 'steroid-D-p-A' module generates spontaneous polarization in solids and for the first time in nano-architectures constituted from organogels, at room temperature (RT).
Ceramics International, 2010
A modified lead zirconate stannate titanate system (PZST) has been studied for shape memory effec... more A modified lead zirconate stannate titanate system (PZST) has been studied for shape memory effect. Addition of magnesium niobate (MN) slows down the dipole relaxation process, leading to increased ($3-fold improvement) remnant strain in the PZST system (0.99PZST-0.01PMN). Room temperature X-ray diffraction patterns before poling (antiferroelectric (AFE) tetragonal) and after poling (ferroelectric (FE) rhombohedral), clearly demonstrate that the transition to the ferroelectric phase is stable even in the absence of any electric field. A small applied electric field ($1.7 kV/cm) in the opposite direction was required to bring the sample back to its original shape. Field-induced strain butterfly loops taken at 50 Hz show that the material response time is quite small. #