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41.
PLA/functionalized‐gum arabic based bionanocomposite films for high gas barrier applications 下载免费PDF全文
The present work focuses on the microwave synthesis of lactic acid‐grafted‐gum arabic (LA‐g‐GA) by polycondensation reaction and its influence as an additive to improve the gas barrier properties of poly(lactic acid) (PLA) films, prepared by solution casting method. It is observed that during the synthesis of LA‐g‐GA, hydrophilic gum is converted into hydrophobic due to grafting of in situ grown hydrophobic oligo‐(lactic acid). Subsequently, PLA/LA‐g‐GA bionanocomposite films are fabricated and characterized for structural, thermal, mechanical and gas barrier properties. Path breaking reduction in oxygen permeability (OP) of ~10 folds is achieved in case of PLA films containing LA‐g‐GA as filler. However, water vapor transmission rate (WVTR) is reduced up to 27% after 5 wt % addition of filler. Reduction in OP of this order of magnitude enables the PLA to compete with PET in term of enhancing shelf life and maintaining the food quality. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43458. 相似文献
42.
Synchronization of processes is one of the major performance bottlenecks in a distributed system. The synchronization is usually achieved via message passing. There are two basic types of overhead in such a synchronization: the rate of message exchange, and the blocking probabilities of processes. In this paper we consider two processes synchronizing via message passing and study their performance behavior on the basis of the above-mentioned overheads. A number of protocols for message exchange are analyzed. The model gives rise to a three-dimensional Markov chain. An algorithm to solve the model and numerical results are presented to compare the various protocols. 相似文献
43.
S. Chaurasia D.S. Munda S. Tripathi N.K. Gupta L.J. Dhareshwar G.J. Tallents 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2009,267(23-24):3611-3616
X-ray and ion emission from gold plasma produced by a sub-nanosecond Nd:glass laser has been studies as a function of distance of the target from the best focus position. Thermal ion (kinetic energy <19 keV) signals and soft X-ray flux (photon energy >0.7 keV) measurements decrease as the target is moved closer to the best focus position in spite of an increase in laser intensity. We observe simultaneously a strong correlation between the onset of this drop in the flux of soft X-ray and the growth of harder X-ray (photon energy 3–5 keV), alongside a growth in fast ion (energy >67 keV) numbers. This is indicative of the onset of non-linear processes at the higher irradiances (~1014 W/cm2) associated with the best focus position. Our results show that when using laser plasmas as X-ray or ion sources, X-ray and ion emission in a desired spectral range can be optimized by adjusting the focusing on the target. 相似文献
44.
Pavan Gangwar Rajiv Singh Ravi Pratap Tripathi Ashutosh Kumar Singh 《Energy Sources, Part A: Recovery, Utilization, and Environmental Effects》2019,41(15):1828-1837
Solar irradiance being considered as one of the most important alternative sources of energy can be harnessed in the form of electrical power using photovoltaic panels erected under the sun. Optimum conversion of power from solar panels can be obtained by using Maximum Power Point Tracking (MPPT), which involves continuously adjusting the angle of panels according to the change in the angle of falling irradiance. These trackers, however, use some amount of power for operation of MPPT equipment. Various techniques for arranging the solar panels in three dimensions have been suggested for optimizing the output power from them. The inspiration behind arranging the panels are often drawn from the natural trees where the branches and the leaves follow a particular pattern called phyllotaxy which is directly analogous to the Fibonacci number and Golden ratio. In this research work, the power output from two solar tree models based on 3/8 and 2/5 phyllotaxy pattern and solar conventional panel compared under similar irradiance conditions. There are so many phyllotaxy patterns like 1/3, 2/5, 3/8, etc. When the solar panels aligned in different phyllotaxies, then the orientation direction of solar panels are distinct. Each solar panel connected in solar trees is in a different direction, so that they received the maximum amount of sunlight throughout the day as compared to conventional panels which is oriented unidirectional. 相似文献
45.
S. L. Agrawal Markandey Singh Mridula Tripathi Mrigank Mauli Dwivedi Kamlesh Pandey 《Journal of Materials Science》2009,44(22):6060-6068
Present work deals with findings on dielectric relaxation behaviour and a.c. conduction in a SiO2-doped polymer nanocomposite electrolyte system, namely, [(100 − x)PEO + xSiO2]:yNH4SCN. The formation of nanocomposite has been ascertained by XRD measurements. The effect of salt and filler (SiO2) on conductivity response of PEO-based nanocomposite polymer electrolyte has been investigated by impedance spectroscopy.
The variation of dielectric permittivity, dielectric loss and modulus spectra with frequency and temperature was carried out
from impedance spectroscopy data. The a.c. conductivity seems to follow the universal power law. 相似文献
46.
S. V. Ingale P. B. Wagh A. K. Tripathi V. S. Kamble Ratanesh Kumar Satish C. Gupta 《Journal of Porous Materials》2011,18(5):567-572
In the present work, results on the physico-chemical properties of the silica aerogels prepared by sol–gel process using mixtures
of TMOS and MTMS as precursor are reported. The wide range of precursor mixture was studied with ratio of MTMS/TMOS in precursor
mixtures as 0:100, 25:75, 50:50, 75:25, and 100:0 by volume. The gels with these precursor mixtures were successfully prepared
using two step acid–base catalysis for gelation. Acetic acid (0.001 M) and NH4OH (1.5 M) were used for catalysis and resulting alcogels were subsequently dried by supercritical solvent extraction method.
FTIR spectroscopy revealed that the aerogels show more intense peak at 1,260 and 790 cm−1 attributed to Si–CH3 resulting in more hydrophobic nature and these results were concurrent with adsorbed water content measurements made using
Karl Fischer’s titration technique. The resulted aerogels were characterized using differential thermal analysis, thermo gravimetric
analysis and surface area measurements. The surface area measurements showed an interesting trend that the surface area increased
from 395 to 1,037 m2/g with increase in MTMS content in the precursor mixture from 0 to 50% and then again decreased to 512 m2/g for further increase in MTMS content from 50 to 100% in the precursor mixture. It was observed from our studies that silica
aerogels prepared using a starting mixture of 50% TMOS and 50% MTMS resulted in high moisture resistance (adsorbed water content
of 0.721% w/w), low density of 90 kg/m3 and the highest surface area of 1,037 m2/g, which has great potential for catalysis support applications. 相似文献
47.
48.
Lei Yao Khan R. Chodavarapu V.P. Tripathi V.S. Bright F.V. 《IEEE transactions on biomedical circuits and systems》2009,3(5):304-311
We present the design and implementation of a phase luminometry sensor system with improved and tunable detection sensitivity achieved using a complementary metal-oxide semiconductor (CMOS) integrated circuit. We use sol-gel derived xerogel thin films as an immobilization media to house oxygen (O2) responsive luminescent molecules. The sensor operates on the principal of phase luminometry wherein a sinusoidal modulation signal is used to excite the luminophores encapsulated in the porous xerogel films and the corresponding phase shift of the emission signals is monitored. The phase shift is directly related to excited state lifetimes of the luminophores which in turn are related to the concentration of the target analyte species present in the vicinity of the luminophores. The CMOS IC, which consists of a 16 times 16 high-gain phototransistor array, current-to-voltage converter, amplifier and tunable phase shift detector, consumes an average power of 14 mW with 5-V power supply operating at a 38-kHz modulation frequency. The output of the IC is a dc voltage that corresponds to the detected luminescence phase shift with respect to the excitation signal. As a prototype, we demonstrate an oxygen sensor system by encapsulating the luminophore tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) within the xerogel matrices. The sensor system showed a fast response on the order of few seconds and we obtained a detection sensitivity of 118 mV per 1% change in O2 concentration. The system demonstrates a novel concept to tune and improve the detection sensitivity for specific concentrations of the target analyte in many biomedical monitoring applications. 相似文献
49.
Amit Kumar Rajendra Prasad Badoni Shailey Singhal Shilpi Agarwal Amitabh Raj Tripathi 《Chemical Engineering Communications》2018,205(1):92-101
Sulfated zirconia is a very strong solid acid catalyst which can be utilized for various reactions. The present study focuses on synthesis of zirconia-based catalyst with high acidity and high surface area, particularly for isomerization reaction. Sulfated zirconia has been obtained by sulfation of zirconia prepared by hydrothermal route. The catalyst was developed by impregnating tungstophosphoric acid on sulfated zirconia by wet incipient method. The catalyst was characterized through Brunauer–Emmett–Teller (BET) surface area, temperature-programmed desorption of ammonia, temperature program reduction of hydrogen, Fourier transmission infrared spectroscopy, and thermogravimetric analysis. The results revealed that the catalyst is crystalline in nature with surface area 190–225?m2 g?1 and acidity 0.135–0.558?mmol?g?1. Twenty-five percent conversion was obtained (as confirmed by gas chromatography) at 225°C using n-hexane as model hydrocarbon in fixed-bed microreactor. 相似文献
50.
Raghunath R Tripathi RM Mahapatra S Sadasivan S 《The Science of the total environment》2002,285(1-3):21-27
Selenium (Se) levels in whole blood, serum, urine, muscle and saliva of Mumbai adults have been estimated by differential pulse cathodic stripping voltammetry (DPCSV); the detection limit of Se is 0.05 ng ml(-1). The reliability of estimation is further assessed through the analysis of Standard Reference Materials. The Se levels in whole blood (n = 35) and blood serum (n = 201) of the Mumbai adult population is 99.6 and 100 ng ml(-1); approximately 34.8% of the population have serum Se levels between 80 and 100 ng ml(-1). The blood serum levels of Se for Mumbai adults are comparable to those of whole blood. The mean concentration of Se in urine on a 24-h basis is 5.2 ng ml(-1). Muscle and saliva of the Mumbai adult population contain 195.4 ng g(-1) and 2 ng ml(-1) of Se, respectively. A good correlation between serum Se and dietary Se is observed with a correlation coefficient of 0.89. 相似文献