We have investigated the crystallization characteristics of melt compounded nanocomposites of poly(ethylene terephthalate) (PET) and single
walled carbon nanotubes (SWNTs). Differential scanning calorimetry studies showed that SWNTs at weight fractions as low as 0.03 wt% enhance
the rate of crystallization in PET, as the cooling nanocomposite melt crystallizes at a temperature 10 °C higher as compared to neat PET.
Isothermal crystallization studies also revealed that SWNTs significantly accelerate the crystallization process. WAXD showed oriented
crystallization of PET induced by oriented SWNTs in a randomized PET melt, indicating the role of SWNTs as nucleating sites.
Rani, Joseph(Wiley InterScience, October 22, 2006)
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Abstract:
Poly(ethylene terephthalate) (PET) nanocomposites
with single-walled carbon nanotubes (SWNTs) have
been prepared by a simple melt compounding method. With
increasing concentration (0-3 wt %) of SWNTs, the mechanical
and dynamic mechanical properties improved, corresponding
to effective reinforcement. Melt rheological characterization
indicated the effective entanglements provided by SWNTs in
the melt state as well. Thermogravimetric analysis suggested no influence of SWNTs on the thermal stability of PET. Electrical
conductivity measurements on the composite films pointed
out that the melt compounded SWNTs can result in electrical
percolation albeit at concentrations exceeding 2 wt %.
Sugunan, S; Suja, H; Deepa, C S; Sreejarani, K; Ouseph, M V(Indian Journal of Chemistry, November , 2002)
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Abstract:
Surface acidity of phosphate modified La2O3,CeO2 and SnO2 has been estimated by titrimetric Method using Hammett Indicators.Mixed Oxides of tin and lanthanum have also been prepared and subjected to phosphate modification.Surface characterizartion of the samples has been carried out using XRD, surface area,thermal analysis and IR spectroscopy.
Phosphate content in the samples has been chemically estimated. The catalytic activity for benzylation and esterification reaction has also been investigated.
Sugunan, S; Renuka, N K(Indian Journal of Chemistry, February , 2001)
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Abstract:
Vapour phase methylation of phenol is carried out over La2O3 supported vanadia systems of various composition. The structural features and physico chemical characterisation of the catalysts are investigated. Orthovanadates are formed in addition to surface vanadyl species on the metal oxide support. No V2O5 crystallites are detected. The acid base properties of the oxides are studied by Hammett indicator method and decomposition of cyclohexanol.The data are correlated with the catalytic activity and selectivity of the products. Ring alkylation is found to be predominant over these catalysts.
Sugunan, S; Sherly, K B(Indian Journal of Chemistry, October , 1994)
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Abstract:
Lanthanum oxide, La2O3 has been found to be an effective
catalyst for the liquid phase reduction of cyclohexanone.
The catalytic activities of La2O3 activated
at 300, 500 and 800·C and its mixed oxides with
alumina for the reduction of cyclohexanone with
2-propanol have been determined and the data parallel
that of the electron donating properties of the catalysts.
The electron donating properties of the catalysts have
been determined from the adsorption of electron acceptors
of different electron affinities on the surface of
these oxides.
The catalytic activity of some of the ABO3 (A = La, Pr
and Sm, B= Cr, Mn, Fe, Co and Ni) perovskite-type oxides
for the liquid phase reduction of ketone and oxidation of
alcohol in 2-propanol medium has been studied. The data
have been correlated with the surface electron donor
properties of these oxides. The surface electron donor
properties have been determined from the adsorption of
electron acceptors of varying electron affinities on the
oxide surface.
Spinel systems with the composition of Cu 1−x Zn x Cr 2 O 4 [x = 0 CCr, x = 0.25 CZCr-1, x = 0.5 CZCr-2, x = 0.75 CZCr-3 and x = 1 ZCr] were prepared by homogeneous co-precipitation method and were characterized by X-ray diffraction (XRD) and FT-IR spectroscopy. Elemental analysis was done by EDX, and surface area measurements by the BET method. The redox behavior of these catalysts in cyclohexane oxidation at 243 K using TBHP as oxidant was examined. Cyclohexanone was the major product over all catalysts with some cyclohexanol. 69.2% selectivity to cyclohexanol and cyclohexanone at 23% conversion of cyclohexane was realized over zinc chromite spinels in 10 h.
The changes occuring to cashew
kernels during storage at two humidity
levels - 80% to 20% with respect
to organoleptic characteristics,
protein content, carbohydrate content,
oil content, iodine and peroxide
values were studied. From the
present study it is concluded that
organoleptic characteristics of
cashew kernels deteriorates with increase
in humidity. Decrease in protein
and carbohydrate content of
stored cashew kernel is dependent
on humidity. Humidity increased
oxidative rancidification.
Binu, G S; Poulose Jacob, K(International Journal of Computer Science and Network Security, July , 2010)
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Abstract:
In Wireless Sensor Networks (WSN), neglecting the
effects of varying channel quality can lead to an
unnecessary wastage of precious battery resources and in
turn can result in the rapid depletion of sensor energy and
the partitioning of the network. Fairness is a critical issue
when accessing a shared wireless channel and fair
scheduling must be employed to provide the proper flow
of information in a WSN. In this paper, we develop a
channel adaptive MAC protocol with a traffic-aware
dynamic power management algorithm for efficient packet
scheduling and queuing in a sensor network, with time
varying characteristics of the wireless channel also taken
into consideration. The proposed protocol calculates a
combined weight value based on the channel state and link
quality. Then transmission is allowed only for those nodes
with weights greater than a minimum quality threshold
and nodes attempting to access the wireless medium with a
low weight will be allowed to transmit only when their
weight becomes high. This results in many poor quality
nodes being deprived of transmission for a considerable
amount of time. To avoid the buffer overflow and to
achieve fairness for the poor quality nodes, we design a
Load prediction algorithm. We also design a traffic aware
dynamic power management scheme to minimize the
energy consumption by continuously turning off the radio
interface of all the unnecessary nodes that are not included
in the routing path. By Simulation results, we show that
our proposed protocol achieves a higher throughput and
fairness besides reducing the delay.
This paper is a review of the work done on the dynamics of modulated logistic systems.
Three different problems are treated, viz, the modulated logistic map, the parametrically perturbed
logistic map and the combination map obtained by combining two maps of the quadratic family.
Many of the interesting features displayed by these systems are discussed.
Nandakumaran, V M; Bindu M, Krishna; Manu P, John(Cochin University of Science & Technology, 2004)
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Abstract:
Chaotic dynamics of directly modulated semiconductor lasers have been
studied extensively over the last two decades because of their application in secure
optical communication. However, chaos is generally suppressed in such systems when
the nonlinear gain reduction factor is above 0.01 which is very much smaller than
the reported values in semiconductors like InGaAsP. In this paper we show that by
giving an optoelectronic feedback with appropriate delay one can increase the range
of the values of the gain reduction factor for which chaos can be observed. Numerical
studies show that negative feedback is more efficient in producing chaotic dynamics.
Iron and mixed iron aluminium pillared montrnorillonites prepared by partial hydrolysis method were subjected to room temperature
exchange with transition metals of the first series. The resulting materials were characterised by different spectroscopic techniques
and surface area measurements. About 1-3% transition metals were incorporated into the porous network. The structural
stability of the porous network was not affected by exchange. XRD and AI NMR spectroscopy evidenced the presence of iron
substituted Al13 like polymers in FeAl pillared systems. Acidity and basicity benefited much as a result of metal exchange. Acidity
and basicity were quantified by model reactions, viz., cumene cracking and cyclohexanol decomposition respectively. The presence
of basic sites in otherwise acidic pillared clays, though diminutive in amount can be of much importance in acid base catalysed
reactions.
Mridula,S; Sreedevi,Menon K; Mohanan,K; Bijumon,P V(Microwave and Optical Technology Letters, February 20, 2004)
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Abstract:
The radiation characteristics of a microstrip-line-excited rectangular dielectric resonator antenna (DRA) are studied experimentally.The radiation charactristics and excitation of different modes are highly influenced by the orientation of the DR,feed line parameters ,and finite size of the ground plane
Padmaja, G; Ravi Kumar, A V; Vidyalal, V; Radhakrishnan, P; Nampoori, V P N; Vallabhan, C P G(Springer, June , 1991)
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Abstract:
The spectroscopic analysis of the emission from the plasma produced by irradiating a highT c superconducting GdBa2Cu3O7 target with a high power Nd:YAG laser beam shows the existence of the bands from different oxides in addition to the lines from neutrals and ions of the constituent elements. The spectral emissions by oxide species in laser-induced plasma show considerable time delays as compared to those from neutral and ionic species. Recombination processes taking place during the cooling of the hot plasma, rather than the plasma expansion velocities, have been found to be responsible for the observed time delays in this case. The decays of emission intensities from various species are found to be non-exponential.
Reji, Philip; Sathy, P; Nampoori, V P N; Jacob, Philip; Vallabhan, C P G(IOP, 1992)
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Abstract:
Two-photon absorption in methanol solutions of Rhodamine 6G is investigated by photoacoustics using the second harmonic of a pulsed Nd:YAG laser. Competition between one-photon and two-photon processes is observed, depending critically on the sample concentration and input light flux.
Mohammed Yusuff, K K; Sridevi, N; Pearly Sebastian, C(Wiley InterScience, January 9, 2007)
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Abstract:
Ruthenium(III) complexes of the Schiff bases
formed by the condensation of polymer bound aldehyde and
the amines, such as 1,2-phenylenediamine (PS-opd), 2-aminophenol
(PS-ap), and 2-aminobenzimidazole (PS-ab) have been
prepared. The magnetic moment, EPR and electronic spectra
suggest an octahedral structure for the complexes. The complexes
of PS-opd, PS-ap, and PS-ab have been assigned the
formula [PS-opdRuCl3(H2O)], [PS-apRuCl2(H2O)2], [PS-ab-
RuCl3(H2O)2], respectively. These complexes catalyze oxidation
of catechol using H2O2 selectively to o-benzoquinone. The catalytic activity of the complexes is in the order [PS-ab-
RuCl3(H2O)2] . [PS-opdRuCl3(H2O)] [PS-apRuCl2(H2O)2].
Mechanism of the catalytic oxidation of catechol by ruthenium(
III) complex is suggested to take place through the formation
of a ruthenium(II) complex and its subsequent oxidation
by H2O2 to the ruthenium(III) complex.
Jayaraj, M K(American Institute of Physics, January 4, 2006)
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Abstract:
The radio frequency plasma generated during the sputtering of Indium Tin Oxide target using Argon
was analyzed by Langmuir probe and optical-emission spectroscopy. The basic plasma parameters
such as electron temperature and ion density were evaluated. These studies were carried out by
varying the RF power from 20 to 50 W. A linear increase in ion density and an exponential decrease
in electron temperature with rf power were observed. The measured plasma parameters were then
correlated with the properties of ITO thin films deposited under similar plasma conditions.
Rajesh, M; Geetha, K; Sheeba, M; Radhakrishnan, P; Nampoori, V P N; Vallabhan, C P G(Society of Photo-Optical Instrumentation Engineers, July , 2006)
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Abstract:
The length-dependent tuning of the fluorescence spectra of a dye doped polymer fiber is reported. The fiber is pumped sideways and the fluorescence is measured from one of the ends. The excitation of a finite length of dye doped fiber is done by a diode pumped solid state laser at a wavelength of 532 nm. The fluorescence emission is measured at various positions of the fiber starting from a position closer to the pumping region and then progressing toward the other end of the fiber. We observe that the optical loss coefficients for shorter and longer distances of propagation through the dye doped fiber are different. At longer distances of propagation, a decrease in optical loss coefficient is observed. The fluorescence peaks exhibit a redshift of 12 nm from 589 to 610 nm as the point of illumination progresses toward the detector end. This is attributed to the self-absorption and re-emission of the laser dye in the fiber.
Sunil K Narayanankutty(Taylor & Francis LLC, 2005)
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Abstract:
The thermal degradation of short nylon-6 fiber reinforced acrylonitrile
butadiene rubber (NBR) composites with and without epoxy-based bonding
agent has been studied by thermogravimetric analysis (TGA). It was found that
the onset of degradation shifted from 330.5 to 336.1°C in the presence of short
nylon fiber, the optimum fiber loading being 20 phr. The maximum rate of degradation
of the composites was lower than that of the unfilled rubber compound,
and it decreased with increase in fiber concentration. The presence of epoxy
resin-based bonding agent in the virgin elastomer and the composites improved
the thermal stability. Results of kinetic studies showed that the degradation of
NBR and the short nylon fiber reinforced composites followed first-order
kinetics.