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1.
R.?Venkata Krishnan K.?NagarajanEmail author S.?Clement Ravichandar T.?V.?Prabhu G.?Ravisankar K.?V.?Kasiviswanathan 《Journal of Sol-Gel Science and Technology》2011,59(3):394-403
Sol–gel based fuel fabrication processes have the potential to be the nuclear fuel fabrication processes in the future. Hence
development of sol–gel technology for nuclear fuel fabrication is being the pursued in the Department of Atomic Energy in
India. As a part of the efforts, a laboratory scale facility for fabrication of test fuel pins for irradiation in the Fast
Breeder Reactor (FBTR), Kalpakkam has been set up at the Indira Gandhi Centre for Atomic Research, Kalpakkam, India. These
fuel pins will be vibropacked with sol–gel derived microspheres or stacked with pellets obtained by compaction of sol–gel
derived microspheres. The facility is aimed at demonstration of the remote operation of the fuel pin fabrication process through
the sol–gel route. A capsule containing three test pins from this facility will be irradiated in FBTR. The design features
of the facility and the test fuel pins are described in this paper. 相似文献
2.
Vijay Sundaram Kasiviswanathan Muthukumarappan Stephen Gent 《Applied biochemistry and biotechnology》2017,181(3):1060-1079
Lignocellulosic feedstocks corn stover, prairie cord grass, and switchgrass were subjected to ammonia fiber expansion (AFEX?) pretreatment and densified using extrusion pelleting and ComPAKco densification technique. The effects of AFEX? pretreatment and densification were studied on the fast pyrolysis product yields. Feedstocks were milled in a hammer mill using three different screen sizes (2, 4, and 8 mm) and were subjected to AFEX? pretreatment. The untreated and AFEX?-pretreated feedstocks were moisture adjusted at three levels (5, 10, and 15 % wb) and were extruded using a lab-scale single screw extruder. The barrel temperature of the extruder was maintained at 75, 100, and 125 °C. Durability of the extruded pellets made from AFEX?-pretreated corn stover, prairie cord grass, and switchgrass varied from 94.5 to 99.2, 94.3 to 98.7, and 90.1 to 97.5 %, respectively. Results of the thermogravimetric analysis showed the decrease in the decomposition temperature of the all the feedstocks after AFEX? pretreatment indicating the increase in thermal stability. Loose and densified feedstocks were subjected to fast pyrolysis in a lab-scale reactor, and the yields (bio-oil and bio-char) were measured. Bio-char obtained from the AFEX?-pretreated feedstocks exhibited increased bulk and particle density compared to the untreated feedstocks. The properties of the bio-oil were statistically similar for the untreated, AFEX?-pretreated, and AFEX?-pretreated densified feedstocks. Based on the bio-char and bio-oil yields, the AFEX?-pretreated feedstocks and the densified AFEX?-pretreated feedstocks (pellets and PAKs) exhibited similar behavior. Hence, it can be concluded that densifying the AFEX?-pretreated feedstocks could be a viable option in the biomass-processing depots to reduce the transportation costs and the logistical impediments without affecting the product yields. 相似文献
3.
C. Karunanithy K. Muthukumarappan W. R. Gibbons 《Applied biochemistry and biotechnology》2014,172(7):3656-3669
Pretreatment is one of the biggest challenges in utilizing lignocellulosic feedstocks to meet the mandatory requirements for biofuels around the world. Earlier researchers evaluated extrusion and ozone pretreatment separately and found that sugar recovery can be improved significantly from 15–20 to 40–75 % for different feedstocks. To further improve sugar recoveries, extrusion-ozone sequential pretreatment was explored. Accordingly, optimal extruded switchgrass (176?°C, 155 rpm, 20 % moisture, and 8 mm) and big bluestem (180?°C, 155 rpm, 20 % moisture, and 8 mm) at 25–75 % moisture content were exposed to an ozone flow rate of 37–365 mg/h for 2.5 to 10 min. Pretreated samples were then subjected to enzymatic hydrolysis to determine sugar recovery. Statistical analyses confirmed significant effects of the independent variables and their interactions on sugar recoveries for both feedstocks. Maximum glucose, xylose, and total sugar recovery of 66.4, 82.3, and 70.4 %, respectively, were obtained when a low-moisture (25 %) extruded switchgrass was ozonated for 2.5 min at a flow rate of 37 mg/h. Respectively, this represents increases of 3.42, 5.01, and 3.42 times that of the control. When big bluestem at 25 % moisture was extruded and then ozonated for 2.5 min at a flow rate of 365 mg/h, resulting glucose, xylose, and total sugar recoveries of 90.8, 92.2, and 87.5 %, respectively, were obtained. These represent increases of 4.5, 2.7, and 3.9 times than that of the control. It is also noteworthy that furfural and hydroxymethyl furfural were not detected in any of the pretreatments, and only low levels (0.14–0.18 g/l) of acetic acid were measured. The results show that sequential pretreatment using extrusion and ozone is an efficient way to improve sugar recovery from herbaceous biomass feedstocks. 相似文献
4.
R. Srinivasan V. Sankaranarayanan C. K. Subramaniam Prakash Fortunata Rajam S. Kasiviswanathan Vijayashree Radhakrishnan 《Phase Transitions》2013,86(1-3):87-95
Abstract Resistance and thermopower measurements have been made on a series of compounds, YBa2Cu3- x Zn x O7-y, with x = 0.025, 0.05, 0.1, 0.15 and 0.2. The superconducting transition temperature decreases as the zinc concentration increases. In a range of temperatures below TM , the mid point of the transition, the resistance shows an exponential temperature dependence fitting the phenomenological formula proposed by Ausloos et al. From the plot of logarithm of resistivity vs. (TM ? T) 1/2/T, one deduces a value of the average dimension of the Josephson junction to be a few tens of Å, suggesting the microtwin boundaries to be the location of the junctions. The thermopower shows a peak always just above Tc . This conclusively shows that phonon drag is not the cause of the peak. The temperature dependence of the thermopower appears to resemble closely the earlier observations of Srinivasan et al. on yttrium barium copper oxide. Single-particle tunneling measurements carried out for two concentrations, x = 0 and 0.05, appear to indicate that the energy gap parameter scales with Tc , and 2Δ/kTc has an approximate value of 5.5. 相似文献
5.
Dr. Bhaskar Chandra Mohanty P. Malar Thomas Osipowicz B. S. Murty Shikha Varma Dr. S. Kasiviswanathan 《Surface and interface analysis : SIA》2009,41(3):170-178
Thermal stability of silver selenide thin films formed from the solid‐state reaction of Ag‐Se diffusion couples on Si substrates covered with a thin Cr film, is investigated. Glancing angle X‐ray diffraction (GXRD), XPS, atomic force microscopy (AFM) and Rutherford backscattering spectrometry (RBS) are used to characterize the as‐deposited films and those annealed at 100, 200, 300, and 400 °C. The results reveal the formation of polycrystalline orthorhombic silver selenide films that remain stable without compositional change upon thermal annealing, in marked contrast to the agglomeration exhibited by silver selenide films deposited on Si without Cr film. The improvement in the thermal stability is attributed to compressive stress relief by a grainy morphology with large surface area, the formation of which is promoted by partially oxidized Cr adhesion film. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
6.
Flodman HR Boyer EJ Muthukumarappan A Noureddini H 《Applied biochemistry and biotechnology》2012,166(4):1070-1081
The feasibility of using coproducts from dry grind corn ethanol production as a substrate for the production of soluble fiber
was examined. Acid- and base-catalyzed hydrolysis experiments were performed using sulfuric acid and sodium hydroxide to partially
hydrolyze hemicellulose content of whole stillage, a precursor to distillers' grains, to soluble fiber. The influences of
temperature, reaction time, and hydrolyzing agent concentration on the formation of soluble fiber were studied. Soluble fiber
was recovered by precipitation in a 95% ethanol solution. Results indicate that appreciable quantities of soluble fiber may
be extracted using either acid- or base-catalyzed reactions. The highest yield of soluble fibers was 13.2 g per 100 g-db of
treated whole stillage using one weight percent sodium hydroxide at 80oC for 1 h. HPLC analysis was used to quantify the amount
of monomeric sugars which were formed during the hydrolysis procedures. 相似文献
7.
C. Karunanithy K. Muthukumarappan W. R. Gibbons 《Applied biochemistry and biotechnology》2012,167(1):81-99
Pretreatment is the first step to open up lignocellulose structure in the conversion of biomass to biofuels. Extrusion can be a viable pretreatment method due to its ability to simultaneously expose biomass to a range of disruptive conditions in a continuous flow process. Extruder screw speed, barrel temperature, and feedstock moisture content are important factors that can influence sugar recovery from biomass. Hence, the current study was undertaken to investigate the effects of these parameters on extrusion pretreatment of pine wood chips. Pine wood chip at 25, 35, and 45?% wb moisture content were pretreated at various barrel temperatures (100, 140, and 180?°C) and screw speeds (100, 150, and 200?rpm) using a screw with compression ratios of 3:1. The pretreated pine wood chips were subjected to standard enzymatic hydrolysis followed by sugar and byproducts quantification. Statistical analyses revealed the existence of significant differences in sugar recovery due to independent variables based on comparing the mean of main effects and interaction effects. Pine wood chips pretreated at a screw speed of 150?rpm and a barrel temperature of 180?°C with a moisture content of 25?% resulted in a maximum cellulose, hemicellulose, and total sugar recoveries of 65.8, 65.6, and 66.1?%, respectively, which was about 6.7, 7.9, and 6.8 fold higher than the control (unpretreated pine chips). Furthermore, potential fermentation inhibitors such as furfural, hydroxyl methyl furfural, and acetic acid were not found in any of the treatment combinations. 相似文献
8.
Anahita Dehkhoda Eckard Kasiviswanathan Muthukumarappan William Gibbons 《Applied biochemistry and biotechnology》2012,167(2):377-393
Extrusion processing has shown potential to be used as a pretreatment method for second-generation bioethanol production. Furthermore, surfactants have been shown to reduce enzyme deactivation and increase the efficiency of hydrolysis. Therefore, a sequential pretreatment technique was developed for corn stover (CS) and prairie cordgrass (PCG) in which a single screw extruder was used for the first pretreatment according to a previously optimized condition using 70?C180?°C for feed, barrel, and die zones with 65?C155?rpm screw speed. The second pretreatment was optimized in this study at 45?C55?°C, 1?C4?h, 0.15?C0.6?g Tween 20/g glucan according to response surface methodology. Optimization of surfactant pretreatment facilitated the estimation of interaction and higher-order effects for major factors involved in surfactant treatment (temperature, time, surfactant loading). Using 8.6?FPU/g glucan cellulase, the optimum conditions found by fitting appropriate quadratic models to the data increased glucose and xylose yield by 27.5 and 33?% for CS and by 21.5 and 27?% for PCG, respectively. Tween 20 concentrations and pretreatment temperature were the most significant factors affecting sugar yield (p value <0.05). Studies of SDS concentration at and beyond critical micelle concentration (5.2?C100?mM) demonstrated a decrease in sugar yield compared to control. 相似文献
9.
S. Kasiviswanathan G. Rangarajan 《Physica C: Superconductivity and its Applications》1992,200(3-4):301-306
Tunneling measurements were performed at 4.2 K on well-characterized NdBa2Cu3O7−y samples using a sandwich configuration with an artificially grown barrier layer (sputtered indium oxide) and Pb0.5In0.5 counter electrode. The conductance spectra exhibited well-defined structures characteristic of gap opening. Fitting the data to a life-time broadened BCS density of states function yielded the following values: 20 meV for the energy gap Δ, 1.5 meV for the line width Γ and 5.3 for 2Δ/kBTc. 相似文献
10.