scholarly journals FABRIKASI MIKROSFIR UO2 MENGGUNAKAN TEKNIK AERASI

2016 ◽  
Vol 22 (2) ◽  
Author(s):  
Meniek Rachmawati ◽  
Etty Mutiara ◽  
Tri Yulianto
Keyword(s):  
Sol Gel ◽  
Gaseous Mixture ◽  
Reduction Process ◽  
Free Fall ◽  
Heating Process ◽  
Low Density ◽  
High Production Rate ◽  
Tap Density ◽  
Electromagnetic Vibrator ◽  
High Production

FABRIKASI MIKROSFIR UO2 MENGGUNAKAN TEKNIK AERASI. Telah dikembangkan proses fabrikasi mikrosfir UO2 berdensitas rendah untuk umpan langsung proses peletisasi bahan bakar reaktor PHWR maju. Fabrikasi mikrosfir UO2 berdensitas rendah dilakukan dengan cara sol-gel menggunakan teknik aerasi pada sol/broth dengan metode eksternal dan tiga variasi cara gelasi. Pada teknik aerasi, broth disiapkan langsung digelasi tanpa didiamkan selama satu malam. Teknik aerasi merupakan kebalikan dari teknik deaerasi yang digunakan pada fabrikasi mikrosfir bahan bakar HTGR. Broth yang telah disiapkan dengan perbandingan mol NO3−/U antara 1,5 hingga 1,7 dengan pH larutan 1,6 dan viskositas antara 630-660cP langsung digelasi dengan tiga cara gelasi. Proses gelasi cara 1 dan cara 2 dilakukan dengan melewatkan broth pada dispersion nozzle berdiameter 1mm yang digetarkan dengan electromagnetic vibrator pada 150 Hz dengan media untuk droplet jatuh bebas yang berbeda sebelum masuk ke dalam larutan NH4OH, sedangkan gelasi dengan cara 3 dilakukan secara manual. Mikrosfir UO2 basah yang diperoleh dari ketiga cara gelasi di atas mendapat perlakuan panas yang sama yaitu dikeringkan pada temperatur 85 ºC dan 220 ºC masing-masing selama selama 1jam, dilanjutkan dengan proses kalsinasi mikrosfir UO2 selama 1 jam pada temperatur 500 ºC dalam media gas O2 dan direduksi pada temperatur 600 ºC dalam media campuran gas N2 dan H2 selama 1 jam. Mikrosfir UO2 hasil gelasi dengan cara 3 dipilih untuk disortir dan dikarakterisasi. Hasil karakterisasi memberikan data karakteristik mikrosfir UO2 berupa data diameter mikrosfir sebesar 900 µm, tap density 1,90 g/cm3 dan luas muka spesifik sebesar 6 m2/g. Hasil analisis dan hasil karakterisasi kemudian dibandingkan dengan data penelitian lain sehingga dapat disimpulkan bahwa penggunaan teknik aerasi pada broth menghasilkan mikrosfir UO2 berdensitas rendah yang memenuhi kriteria sebagai umpan langsung proses peletisasi bahan bakar PHWR maju dan PWR maju. Fabrikasi menggunakan teknik aerasi dengan gelasi cara 2 mempunyai peluang yang paling besar untuk menghasilkan mikrosfir UO2 dengan laju produksi yang tinggi dan karakteristik tertentu jika dilakukan pengaturan ulang pada laju dispersi dan durasi droplet jatuh bebas.Kata kunci: UO2, bahan bakar, sol-gel, mikrosfir, aerasi. UO2 MICROSPHERE FABRICATION USING AERATION TECHNIQUE. It has been developed a fabrication process of low density UO2 microspheres for direct feed in pelletization process of PHWR advanced reactor fuel. The fabrication has been implemented by a sol-gel method using aeration technique on the sol / broth with external methods and three variations of gelation. In the aeration technique, broth is directly prepared in gelation mode without one night settling time. The aeration technique is the opposite of the deaeration technique, which is used in fabricating microspheres HTGR fuel. The broth which has been prepared with a mole ratio of NO3 / U between 1.5 to 1.7 with pH solution of 1.6 and viscosity between 630-660 cP directly to be gelated in three ways of gelation. The process of both gelation method 1 and method 2 is implemented by passing through the broth to a dispersion nozzle with 1 mm of diameter which is vibrated by an electromagnetic vibrator at 150 Hz with medium for free fall droplet differently before entering into a solution of NH4OH, while the gelation method 3 implemented manually. The wet UO2 microspheres derived from the three ways of gelation above are treated by heating process at the same way that is dried at a temperature of 85 ºC and 220 ºC each respectively for 1 hour, followed by a calcination process of microspheres UO2 for 1 hour at a temperature of 500 ºC in gaseous medium of O2 and a reduction process at a temperature of 600 ºC in gaseous mixture of N2 and H2 medium for 1 hour. The UO2 microspheres gelation of method 3 are chosen to be sorted and characterized. The characterization results provide the characteristics data of UO2 microspheres in the form of microspheres diameter of 900 μm, tap density of 1.90 g/cm3 and specific surface area of 6 m2/g. The results of the analysis and characterization are then compared to other data of other research so that it can be concluded that the use of such an aeration technique on the broth can produce low density UO2 microspheres that qualify as direct feed for fuel pelletization process of the advanced PHWR and advanced PWR. The fabrication using the aeration technique with gelation method 2 has the greatest opportunity to produce UO2 microspheres with a high production rate and certain characteristics if it is implemented by resetting the rate of dispersion and the free fall droplet duration.Keywords: UO2 , fuel, sol-gel, microsphere, aeration.

scholarly journals Characterization and optimization of extracellular enzymes production by Aspergillus niger strains isolated from date by-products

2021 ◽  
Vol 19 (1) ◽  
Author(s):  
Reda Bellaouchi ◽  
Houssam Abouloifa ◽  
Yahya Rokni ◽  
Amina Hasnaoui ◽  
Nabil Ghabbour ◽  
...  
Keyword(s):  
Aspergillus Niger ◽  
Culture Medium ◽  
Extracellular Enzymes ◽  
Enzyme Expression ◽  
Specific Enzyme ◽  
Enzymatic Production ◽  
High Production Rate ◽  
High Production ◽  
Incubation Temperatures ◽  
By Products

Abstract Background This work aims to study the optimal conditions of the fermentation culture medium used for the production of extracellular enzymes (amylase, cellulase, lipase, and protease) from previously isolated Aspergillus niger strains in date by-products. Results The five most powerful isolates selected based on the zone of degradation formed on Petri plates by the substrate were subjected to the quantitative evaluation of their enzymatic production. All five strains showed almost similar API-ZYM profiles, with minor variations observed at the level of some specific enzyme expression. The production of cellulase and amylase was depending on pH and incubation temperatures. ASP2 strain demonstrated the high production rate of amylase (at pH 5 and 30 °C) and cellulase (at pH 6 and 30 °C) for 96 h of incubation. Conclusion The A. niger showed the ability to produce several extracellular enzymes and can be used in the valorization of different agroindustrial residues.

scholarly journals Isotope separation of 176Lu a precursor to 177Lu medical isotope using broadband lasers

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
M. V. Suryanarayana
Keyword(s):  
Production Rate ◽  
Isotope Separation ◽  
Medical Applications ◽  
Optimum Conditions ◽  
High Production Rate ◽  
Laser Isotope Separation ◽  
High Production ◽  
System Requirements ◽  
Medical Isotope ◽  
Rhodamine Dye

AbstractA new photoionization scheme accessible by Rhodamine dye lasers is proposed for the isotope separation of 176Lu.$$5d6s^{2}\,{^{2}D_{{3/2}}} (0.0\, {\text{cm}}^{{ - 1}} )\mathop{\longrightarrow}\limits^{{573.8130\, {\text{nm}}}}5d6s6p\,{^{4}F_{{3/2}}^{o}} \left( {17427.28\, {\text{cm}}^{{ - 1}} } \right)\mathop{\longrightarrow}\limits^{{560.3114\, {\text{nm}}}}$$ 5 d 6 s 2 2 D 3 / 2 ( 0.0 cm - 1 ) ⟶ 573.8130 nm 5 d 6 s 6 p 4 F 3 / 2 o 17427.28 cm - 1 ⟶ 560.3114 nm $$6s{6p}^{2}\,{^{4}{P}_{5/2}}\left(35274.5 \,{\text{cm}}^{-1}\right){\to } Autoionization\, State {\to }{Lu}^{+}$$ 6 s 6 p 2 4 P 5 / 2 35274.5 cm - 1 → A u t o i o n i z a t i o n S t a t e → Lu + Optimum conditions for the laser isotope separation have been theoretically computed and compared with the previously reported work. The enrichment of ~ 63% can be obtained with > 22 mg/h production rate even when broadband lasers with bandwidth of 500 MHz are employed for the two step excitation. The simplified system requirements for the photoionization scheme combined with a high production rate of 176Lu than previously reported is expected to reduce the global shortage of 176Lu isotope for medical applications.

scholarly journals Can Frequency Account for the Grammatical Choices of Children and Adults in Nominal Modification Contexts? Evidence from Elicited Production and Child-Directed Speech

Languages ◽  
2021 ◽  
Vol 6 (1) ◽  
pp. 35
Author(s):  
Emanuela Sanfelici ◽  
Petra Schulz
Keyword(s):  
Language Acquisition ◽  
Production Rate ◽  
Relative Clauses ◽  
Language Use ◽  
Spontaneous Speech ◽  
Production Task ◽  
Specific Context ◽  
High Production Rate ◽  
High Production ◽  
Acquisition Order

There is consensus that languages possess several grammatical variants satisfying the same conversational function. Nevertheless, it is a matter of debate which principles guide the adult speaker’s choice and the child’s acquisition order of these variants. Various proposals have suggested that frequency shapes adult language use and language acquisition. Taking the domain of nominal modification as its testing ground, this paper explores in two studies the role that frequency of structures plays for adults’ and children’s structural choices in German. In Study 1, 133 three- to six-year-old children and 21 adults were tested with an elicited production task prompting participants to identify an agent or a patient referent among a set of alternatives. Study 2 analyzed a corpus of child-directed speech to examine the frequency of passive relative clauses, which children, similar to adults, produced very often in Study 1. Importantly, passive relatives were found to be infrequent in the child input. These two results show that the high production rate of rare structures, such as passive relatives, is difficult to account for with frequency. We claim that the relation between frequency in natural speech and use of a given variant in a specific context is indirect: speakers may opt for the less grammatically complex computation rather than for the variant most frequently used in spontaneous speech.

Experimental Study of DRA for Vertical Two-Phase Annular Flow

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
R. L. J. Fernandes ◽  
B. A. Fleck ◽  
T. R. Heidrick ◽  
L. Torres ◽  
M. G. Rodriguez
Keyword(s):  
Pressure Gradient ◽  
Drag Reduction ◽  
Production Rate ◽  
Annular Flow ◽  
Liquid Holdup ◽  
Two Phase ◽  
High Production Rate ◽  
High Production ◽  
Feasibility Test ◽  
Main Effects

Experimental investigation of drag reduction in vertical two-phase annular flow is presented. The work is a feasibility test for applying drag reducing additives (DRAs) in high production-rate gas-condensate wells where friction in the production tubing limits the production rate. The DRAs are intended to reduce the overall pressure gradient and thereby increase the production rate. Since such wells typically operate in the annular-entrained flow regime, the gas and liquid velocities were chosen such that the experiments were in a vertical two-phase annular flow. The drag reducers had two main effects on the flow. As expected, they reduced the frictional component of the pressure gradient by up to 74%. However, they also resulted in a significant increase in the liquid holdup by up to 27%. This phenomenon is identified as “DRA-induced flooding.” Since the flow was vertical, the increase in the liquid holdup increased the hydrostatic component of the pressure gradient by up to 25%, offsetting some of reduction in the frictional component of the pressure gradient. The DRA-induced flooding was most pronounced at the lowest gas velocities. However, the results show that in the annular flow the net effect will generally be a reduction in the overall pressure gradient by up to 82%. The findings here help to establish an envelope of operations for the application of multiphase drag reduction in vertical flows and indicate the conditions where a significant net reduction of the pressure gradient may be expected.

Stress Development in Low Dielectric Constant Silica Films During Drying and Heating Process

1999 ◽  
Vol 594 ◽  
Author(s):  
Mengcheng Lu ◽  
C. Jeffrey Brinker
Keyword(s):  
Dielectric Constant ◽  
Tensile Stress ◽  
Sol Gel ◽  
Low Dielectric Constant ◽  
Heating Process ◽  
Residual Tensile Stress ◽  
Silica Films ◽  
Stress Development ◽  
Low Dielectric

AbstractLow dielectric constant silica films are made using a surfactant templated sol-gel process (K∼2.5) or an ambient temperature and pressure aerogel process (K∼1.5). This paper will present the in-situ measurement and analysis of stress development during the making of these films, from the onset of drying till the end of heating. The drying stress is measured by a cantilever beam technique; the thermal stress is measured by monitoring the wafer curvature using a laser deflection method. During the course of drying, the surfactant templated films experience a low drying stress due to the influence of the surfactant on surface tension and extent of siloxane condensation. The aerogel films first develop a biaxial tensile stress due to solidification and initial drying. At the final stage of drying where the drying stress vanishes, dilation of the film recreates the porosity of the wet gel state, reducing the residual stress to zero. For the surfactant templated films, very small residual tensile stress remains after the heat treatment is finished (∼30MPa). Aerogel film has almost no measurable stress developed in the calcination process. In situ spectroscopic ellipsometry analysis during drying and heating, and TGA/DTA are all used to help understand the stress development.

Microstructure of Porous V2O-CeO2-SiO2 Catalyst for SCR of NO with NH3 at Low Temperature

2014 ◽  
Vol 875-877 ◽  
pp. 213-217 ◽  
Author(s):  
Mohd Razali Sohot ◽  
Umi Sarah Jais ◽  
Muhd Rosli Sulaiman
Keyword(s):  
Catalytic Activity ◽  
Low Temperature ◽  
Catalytic Reduction ◽  
Sol Gel ◽  
Reduction Process ◽  
No Emission ◽  
Scr Of No ◽  
Before And After ◽  
The Right ◽  
Proven Method

Selective catalytic reduction (SCR) is a well-proven method to reduce NO emission. However, to choose the right catalyst that provides a surface for reaction between NO and ammonia at low temperatures is a challenging task for a catalysts developers. In an earlier study, we prepared V2O5-CeO2-SiO2 catalyst with increasing V2O5 content by sol-gel route and found that the catalytic activity improved with increasing the V2O5 loading up to 0.5%. The catalytic activity, however, dropped when V2O5 loading was about 1% and increased back when the loading of V2O5 was about 5%. In this study, we looked into the microstructural relationship to explain these findings. The microstructures of the catalysts before and after exposure to NO gas revealed that the catalysts with 0.2% and 0.5% V2O5 were more porous after the reduction process possibly due to improved breakdown of (NH4)HCO3 to NH3 by the possible interaction with the V2O5 and CeO2-containing catalysts which consequently resulted in a more efficient NO reduction to N2 and H2O at low temperature. The microstructure of the catalyst with 1% V2O5 content to 5%, improved back the efficiency although clogging by CeVO4 phase still possible due to its presence based on XRD. The well-ordered micropores before exposure to NO and the more efficient breakdown of (NH4)HCO3 could have contributed to increase back the catalytic activity at low temperature.

scholarly journals Rapid Turnover and High Production Rate of Myeloid Cells in Adult Rhesus Macaques with Compensations during Aging

2018 ◽  
Vol 200 (12) ◽  
pp. 4059-4067 ◽  
Author(s):  
Ziyuan He ◽  
Carolina Allers ◽  
Chie Sugimoto ◽  
Nursarat Ahmed ◽  
Hideki Fujioka ◽  
...  
Keyword(s):  
Production Rate ◽  
Rhesus Macaques ◽  
Myeloid Cells ◽  
Rapid Turnover ◽  
High Production Rate ◽  
High Production

Booming Then, Sputtering Now

2021 ◽  
Vol 103 (3) ◽  
pp. 281-308
Author(s):  
Michael Woo
Keyword(s):  
World War Ii ◽  
Los Angeles ◽  
Low Income ◽  
Home Ownership ◽  
Homeless Population ◽  
World War ◽  
Housing Shortage ◽  
High Production Rate ◽  
Racial Barriers ◽  
High Production

This article reviews the post-World War II mass production of houses in Los Angeles and the roots of today’s housing shortage. Even with a high production rate, minorities and low-income Angelenos have experienced racial barriers and displacement. Today, L.A.’s homeless population is disproportionally Black, while home ownership is disproportionally white. The article concludes with four proposals for responding to today’s shortage of affordable and racially equitable housing.

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