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Wyszukujesz frazę "Singh, B. K." wg kryterium: Autor


Tytuł:
Effect of van Hove Singularity on T$\text{}_{c}$ in Rb doped C$\text{}_{60}$
Autorzy:
Agrawal, B. K.
Agrawal, S.
Yadav, P. S.
Srivastava, P.
Srivastava, R.
Singh, S.
Powiązania:
https://bibliotekanauki.pl/articles/2035748.pdf
Data publikacji:
2003-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.25.Jb
74.62.Fj
74.70.Wz
Opis:
In the present study we investigate the role of van Hove singularity on the optimization of T$\text{}_{c}$ in Rb doped fullerenes C$\text{}_{60}$ Rb$\text{}_{3}$. A first principles self-consistent full potential linear muffin-tin orbital method using density functional theory in local density approximation was employed. The doped Rb atoms are of two types occupying the tetrahedral and interstitial positions in the fcc lattice. The added Rb atoms fill the t$\text{}_{1u}$ band of the undoped fullerenes C$\text{}_{60}$ up to half which makes C$\text{}_{60}$Rb$\text{}_{3}$ conducting. Saddle points leading to van Hove singularities are observed in the neighbourhood of the symmetry point L. The shifting of the van Hove singularity with the volume of the lattice is investigated. We observe a saddle point just at the Fermi level for a lattice constant of 14.435Å. The highest value of T$\text{}_{c}$ should thus be observed at the above lattice constant. This result is in excellent agreement with the observed high value of T$\text{}_{c}$ measured in C$\text{}_{60}$Rb$\text{}_{3}$ for a lattice constant of 14.435Å.
Źródło:
Acta Physica Polonica A; 2003, 103, 5; 477-482
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Chaotic convection of viscoelastic fluid in porous medium under G-jitter
Autorzy:
Bhadauria, B. S.
Singh, A.
Singh, M. K.
Powiązania:
https://bibliotekanauki.pl/articles/265559.pdf
Data publikacji:
2019
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
teoria nieliniowa
grawitacja
konwekcja
non-linear theory
gravity modulation
chaotic convection
Opis:
The present article aims at investigating the effect of gravity modulation on chaotic convection of a viscoelastic fluid in porous media. For this, the problem is reduced into Lorenz system (non-autonomous) by employing the truncated Galerkin expansion method. The system shows transitions from periodic to chaotic behavior on increasing the scaled Rayleigh number R. The amplitude of modulation advances the chaotic nature in the system while the frequency of modulation has a tendency to delay the chaotic behavior which is in good agreement with the results due to [1]. The behavior of the scaled relaxation and retardation parameter on the system is also studied. The phase portrait and time domain diagrams of the Lorenz system for suitable parameter values have been used to analyze the system.
Źródło:
International Journal of Applied Mechanics and Engineering; 2019, 24, 1; 37-51
1734-4492
2353-9003
Pojawia się w:
International Journal of Applied Mechanics and Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Stability analysis and internal heating effect on oscillatory convection in a viscoelastic fluid saturated porous medium under gravity modulation
Autorzy:
Bhadauria, B. S.
Singh, M. K.
Singh, A.
Singh, B. K.
Kiran, P.
Powiązania:
https://bibliotekanauki.pl/articles/265014.pdf
Data publikacji:
2016
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
analiza stabilności
grawitacja
ciecz lepkosprężysta
nonlinear stability analysis
complex Ginzburg-Landau equation
gravity modulation
internal heating
bifurcation
Opis:
In this paper, we investigate the combined effect of internal heating and time periodic gravity modulation in a viscoelastic fluid saturated porous medium by reducing the problem into a complex non-autonomous Ginzgburg-Landau equation. Weak nonlinear stability analysis has been performed by using power series expansion in terms of the amplitude of gravity modulation, which is assumed to be small. The Nusselt number is obtained in terms of the amplitude for oscillatory mode of convection. The influence of viscoelastic parameters on heat transfer has been discussed. Gravity modulation is found to have a destabilizing effect at low frequencies and a stabilizing effect at high frequencies. Finally, it is found that overstability advances the onset of convection, more with internal heating. The conditions for which the complex Ginzgburg-Landau equation undergoes Hopf bifurcation and the amplitude equation undergoes supercritical pitchfork bifurcation are studied.
Źródło:
International Journal of Applied Mechanics and Engineering; 2016, 21, 4; 785-803
1734-4492
2353-9003
Pojawia się w:
International Journal of Applied Mechanics and Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Natural convection in a hydrodynamically and thermally anisotropic non-rectangular porous cavity: effect of internal heat generation/absorption
Autorzy:
Chandran, P.
Sacheti, N. C.
Bhadauria, B. S.
Singh, A. K.
Powiązania:
https://bibliotekanauki.pl/articles/264468.pdf
Data publikacji:
2018
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
konwekcja naturalna
materiały porowate
przepuszczalność
dyfuzyjność cieplna
źródło ciepła
natural convection
trapezoidal cavity
porous medium
permeability
thermal diffusivity
Darcy's law
heat source/sink
Opis:
Laminar natural convection in a trapezoidal porous vertical cavity has been investigated in this work. It is assumed that the porous enclosure is filled up with a permeable material subject to hydrodynamic and thermal anisotropy, the flow being governed by the Darcy law as applicable to a non-isotropic medium. It is further assumed that (i) there is heating at the left vertical wall and cooling at the right wall of the enclosure and (ii) the flow domain is subject to the presence of heat source or heat sink. The partial differential equations governing the resulting free convection have been solved numerically in the non-dimensional forms. There arises a number of parameters relating to buoyancy, internal heating, cavity aspect ratio and inclination of the upper surface to the horizontal. The influence of these parameters has been illustrated and analyzed through contours of streamlines and isotherms. We have also discussed the role of internal heating as well as anisotropy on the heat transfer characteristics.
Źródło:
International Journal of Applied Mechanics and Engineering; 2018, 23, 3; 595-609
1734-4492
2353-9003
Pojawia się w:
International Journal of Applied Mechanics and Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Class of Chain Ratio-Cum-Dual to Ratio Type Estimator with Two Auxiliary Characters Under Double Sampling in Sample Surveys
Autorzy:
Choudhury, S.
Singh, B. K.
Powiązania:
https://bibliotekanauki.pl/articles/465944.pdf
Data publikacji:
2012
Wydawca:
Główny Urząd Statystyczny
Tematy:
auxiliary variate
double sampling
chain ratio-cum-dual to ratio estimator
bias
variance
efficiency
Opis:
This paper considers a chain ratio-cum-dual to ratio type estimator for estimating population mean of the study variate using two auxiliary variates under double (two-phase) sampling procedure, when the information on another additional auxiliary variate is available along with the main auxiliary variate. The asymptotically optimum estimators (AOEs) in the class are identified in two different cases with their bias and variances. The optimum values of the first phase and second phase sample sizes have been obtained for the fixed cost of survey. Theoretical and empirical studies have also been done to demonstrate the efficiency of the proposed estimator with respect to strategies which utilized the information on two auxiliary variates.
Źródło:
Statistics in Transition new series; 2012, 13, 3; 519-536
1234-7655
Pojawia się w:
Statistics in Transition new series
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of organic inputs on strength and stability of soil aggregates under rice-wheat rotation
Autorzy:
Das, B.
Chakraborty, D.
Singh, V.K.
Aggarwal, P.
Singh, R.
Dwivedi, B.S.
Powiązania:
https://bibliotekanauki.pl/articles/25472.pdf
Data publikacji:
2014
Wydawca:
Polska Akademia Nauk. Instytut Agrofizyki PAN
Tematy:
tensile strength
stability
soil aggregate
rice
wheat
cereal crop rotation
Opis:
The study aims to elucidate the impact of organic inputs on strength and structural stability of aggregates in a sandy loam soil. Tensile strength, friability and water stability of aggregates, and the carbon contents in bulk soil and in large macro (>2 mm), small macro (0.25-2 mm), micro (0.053-0.25 mm) and silt+clay size (<0.053) aggregates were evaluated in soils from a long-term experiment with rice-wheat rotation at Modipuram, India, with different sources and amounts of organic C inputs as partial substitution of N fertilizer. Addition of organic substrates significantly improved soil organic C contents, but the type and source of inputs had different impacts. Tensile strength of aggregates decreased and friability increased through organic inputs, with a maximum effect under green gram residue (rice)-farmyard manure (wheat) substitution. Higher macroaggregates in the crop residue- and farmyard manure-treated soils resulted in a higher aggregate mean weight diameter, which also had higher soil organic C contents. The bulk soil organic C had a strong relation with the mean weight diameter of aggregates, but the soil organic C content in all aggregate fractions was not necessarily effective for aggregate stability. The soil organic C content in large macroaggregates (2-8 mm) had a significant positive effect on aggregate stability, although a reverse effect was observed for aggregates <0.25 mm. Partial substitution of nitrogen by organic substrates improved aggregate properties and the soil organic C content in bulk soil and aggregate fractions, although the relative effect varied with the source and amount of the organic inputs.
Źródło:
International Agrophysics; 2014, 28, 2
0236-8722
Pojawia się w:
International Agrophysics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Intranasal (IN) COVID-19 vaccines - a breakthrough
Autorzy:
Gambhir, R.S.
Kaur, K.
Matariya, R.
Singh, B.
Sood, R.
Singh, J.
Powiązania:
https://bibliotekanauki.pl/articles/28765534.pdf
Data publikacji:
2023
Wydawca:
Narodowy Instytut Zdrowia Publicznego. Państwowy Zakład Higieny
Opis:
Emerging variants of COVID-19 have threatened the effectiveness of intramuscular (IM) vaccines since that are made to target only the spike protein. Development of Intranasal (IN) vaccination has been proven to provide both the mucosal and systemic immune responses for broader and long lasting protection. Many IN vaccine candidates (virus-vectored vaccines, recombinant subunit vaccines and live attenuated vaccines) are in different phases of clinical trials and in near future many companies would be releasing their vaccines into the drug market. Potential advantages of IN vaccination over IM vaccination makes them ideal to be administered in children and developing populations of the world. This paper focuses on the very recent developments in intranasal vaccination with a spotlight on their safety and efficacy concerns. IN vaccination can prove to be game-changer in handling COVID-19 and potential viral contagious diseases in future.
Źródło:
Roczniki Państwowego Zakładu Higieny; 2023, 74, 1; 15-18
0035-7715
Pojawia się w:
Roczniki Państwowego Zakładu Higieny
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Oscillatory MHD convective flow of second order fluid through porous medium in a vertical rotating channel in slip-flow regime with heat radiation
Autorzy:
Garg, B. P.
Singh, K. D.
Bansal, A. K.
Powiązania:
https://bibliotekanauki.pl/articles/264392.pdf
Data publikacji:
2015
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
slip flow
convective
porous medium
rotating
oscillatory
radiation
second order fluid
porowatość
promieniowanie
magnetohydrodynamika
Opis:
An analysis of an oscillatory magnetohydrodynamic (MHD) convective flow of a second order (viscoelastic), incompressible, and electrically conducting fluid through a porous medium bounded by two infinite vertical parallel porous plates is presented. The two porous plates with slip-flow condition and the no-slip condition are subjected respectively to a constant injection and suction velocity. The pressure gradient in the channel varies periodically with time. A magnetic field of uniform strength is applied in the direction perpendicular to the planes of the plates. The induced magnetic field is neglected due to the assumption of a small magnetic Reynolds number. The temperature of the plate with no-slip condition is non-uniform and oscillates periodically with time and the temperature difference of the two plates is assumed high enough to induce heat radiation. The entire system rotates in unison about the axis perpendicular to the planes of the plates. Adopting complex variable notations, a closed form solution of the problem is obtained. The analytical results are evaluated numerically and then presented graphically to discuss in detail the effects of different parameters of the problem. The velocity, temperature and the skin-friction in terms of its amplitude and phase angle have been shown graphically to observe the effects of the viscoelastic parameter γ, rotation parameter Ω, suction parameter […], Grashof number Gr, Hartmann number M, the pressure A, Prandtl number Pr, radiation parameter N and the frequency of oscillation […].
Źródło:
International Journal of Applied Mechanics and Engineering; 2015, 20, 1; 33-52
1734-4492
2353-9003
Pojawia się w:
International Journal of Applied Mechanics and Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Experimental Studies on Advanced Sheet Explosive Formulations Based on 2,4,6,8,10,12-Hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) and Hydroxyl Terminated Polybutadiene (HTPB), and Comparison with a RDX-based System
Autorzy:
Jangid, S. K.
Talawar, M. B.
Singh, M. K.
Nath, T.
Sinha, R. K.
Powiązania:
https://bibliotekanauki.pl/articles/358055.pdf
Data publikacji:
2016
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Tematy:
hazardous materials
sheet explosive
explosive reactive armour (ERA)
CL-20
RDX
Opis:
The present investigation reports the use of 2,4,6,8,10,12-hexanitro2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) in sheet explosive formulations. In this study, hydroxyl terminated polybutadiene (HTPB) based sheet explosives were prepared incorporating the powerful explosive CL-20 as a partial replacement for hexahydro-1,3,5-trinitro-1,3,5-triazine(RDX). The effects of incorporating CL-20 on the performance, sensitivity, thermal and mechanical properties of the sheet explosive compositions are reported. Sheet explosive formulation containing 80% of RDX and 20% of HTPB-binder was studied as control sample. HTPBbinder consisted of 12% HTPB, 2.9% dioctyl adipate (DOA) and 5.1% dioctyl phthalate (DOP). HTPB was cured with 4,4’-methylene diphenyl di-isocyanate (MDI) to form urethane linkages. The incorporation of 20% of CL-20 in place of RDX led to a remarkable increase in the velocity of detonation (VOD), of the order of 7680 m/s, and to better mechanical properties in terms of tensile strength (1.14 MPa) compared to the control formulation [RDX /HTPB-binder (80/20)]. The 20% CL-20 incorporated sheet explosive formulation also showed remarkable increases in impact and shock sensitivity. Thermal analysis of the sheet explosive compositions has also been carried out using differential scanning calorimetry (DSC).
Źródło:
Central European Journal of Energetic Materials; 2016, 13, 1; 135-147
1733-7178
Pojawia się w:
Central European Journal of Energetic Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Passerine birds supporting cross pollination in Erythrina stricta Roxb.
Autorzy:
Khanduri, V.P.
Kumar, K.S.
Sharma, C.M.
Riyal, M.K.
Kar, K.
Singh, B.
Sukumaran, A.
Powiązania:
https://bibliotekanauki.pl/articles/2078260.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Instytut Dendrologii PAN
Tematy:
Ornithophily
pollination
mating system
geitonogamy
pollen grains
Opis:
Erythina stricta is an ecologically important tree species in the rainforests of India and its nectar within the flowers contributes to birds’ diet and survival. Reports on the pollination of this species have not been published so far. We therefore explore the reproductive system of this tree species which has great significance to its ecosystem. Birds have an important role in the reproduction of trees through pollination particularly in tropical areas where reproductive success mostly depends on animal pollinator interactions. Study of visitation and nectar feeding behaviour of birds alongwith breeding system assessment of Erythina stricta. Birds visiting and foraging behaviour was observed during Erythrina stricta flowering season in an indian tropical rainforest. Reproductive system was assessed through controlled pollination experiments. Thirteen bird species were recorded visiting and foraging nectar from the flowers of Erythrina stricta. The maximum numbers of visits recorded were from the Red-vented Bulbul (Pycnonotus cafer, Pycnonotidae). The nectar feeding birds were, either (i) potential pollinator with long bills (e.g. Pycnonotus spp., Chloropsis aurifrons, and Dicrurus spp.) or (ii) nectar robbers with comparatively shorter bills (e.g. Zosterops palpebrosa, Stachyris ruficeps, Macronous gularis, Heterophasia glaciris). Controlled pollination experiments revealed high degree of cross pollination (xenogamy) and self-incompatibility in E. stricta. Birds were more frequent in early mornings and their foraging activity was also observed during evening hours; the frequency however, declined with respect to nectar availability. Long corolla tubes of E. stricta could restrict access to nectar collecting bees
Źródło:
Dendrobiology; 2021, 85; 117-126
1641-1307
Pojawia się w:
Dendrobiology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Between local connectedness and sum connectedness
Autorzy:
Kohli, J.K.
Singh, D.
Tyagi, B.K.
Powiązania:
https://bibliotekanauki.pl/articles/746732.pdf
Data publikacji:
2013
Wydawca:
Polskie Towarzystwo Matematyczne
Tematy:
Z-locally connected space, almost (quasi, pseudo) locally connected space, sum connected space, regular open set, regular $F_\sigma$-set, $\theta$-open set, cl-supercontinuous function, mono-coreflective subcategory
Opis:
A new generalization of local connectedness called Z-local connectedness is introduced. Basic properties of Z-locally connected spaces are studied and their place in the hierarchy of variants of local connectedness, which already exist in the literature, is elaborated. The class of Z-locally connected spaces lies strictly between the classes of pseudo locally connected spaces (Commentations Math. 50(2)(2010),183-199) and sum connected spaces ($\equiv$ weakly locally connected spaces) (Math. Nachrichten 82(1978), 121-129; Ann. Acad. Sci. Fenn. AI Math. 3(1977), 185-205) and so contains all quasi locally connected spaces which in their turn contain all almost locally connected spaces introduced by Mancuso (J. Austral. Math. Soc. 31(1981), 421-428). Formulations of product and subspace theorems for Z-locally connected spaces are suggested. Their preservation under mappings and their interplay with mappings are discussed. Change of topology of a Z-locally connected space is considered so that it is simply a locally connected space in the coarser topology. It turns out that the full subcategory of Z-locally connected spaces provides another example of a mono-coreflective subcategory of TOP which properly contains all almost locally connected spaces.
Źródło:
Commentationes Mathematicae; 2013, 53, 1
0373-8299
Pojawia się w:
Commentationes Mathematicae
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Quasi Locally Connected Spaces and Pseudo Locally Connected Spaces
Autorzy:
Kohli, J.K.
Singh, D.
Tyagi, B. K.
Powiązania:
https://bibliotekanauki.pl/articles/746262.pdf
Data publikacji:
2010
Wydawca:
Polskie Towarzystwo Matematyczne
Tematy:
almost (quasi, pseudo) locally connected space
regular open set
regular \(F_\sigma\)-set
\(\theta\)-open set
\(D_\delta\)-completely regular space
quasi \(\theta\)-continuous function
coreflective subcategory
Opis:
Two new generalizations of locally connected spaces called ‘quasi locally connected spaces’ and ‘pseudo locally connected spaces’ are introduced and their basic properties are studied. The class of quasi locally connected spaces properly contains the class of almost locally connected spaces (J. Austral. Math. Soc. 31(1981), 421–428) and is strictly contained in the class of pseudo locally connected spaces which in its turn is properly contained in the class of sum connected spaces (Math. Nachrichten 82(1978), 121-129; Ann. Acad. Sci. Fenn. A I Math. 3(1977), 185–205). Product and subspace theorems for quasi (pseudo) locally connected spaces are discussed. Their preservation under mappings and their interplay with mappings are outlined. Function spaces of quasi (pseudo) locally connected spaces are considered. Change of topology of a quasi (pseudo) locally connected space is considered so that it is simply a locally connected space in the coarser topology. In contradistinction with almost locally connected spaces, quasi (pseudo) locally connected spaces constitute a coreflective subcategory of TOP.
Źródło:
Commentationes Mathematicae; 2010, 50, 2
0373-8299
Pojawia się w:
Commentationes Mathematicae
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Closure of municipal solid waste dumps. Site rating for odor impact
Autorzy:
Kumar, A.
Datta, M.
Nema, A. K.
Singh, R. K.
Gurjar, B. R.
Powiązania:
https://bibliotekanauki.pl/articles/208306.pdf
Data publikacji:
2018
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
population statistics
waste dumps
odour nuisance
statystyki ludności
składowiska odpadów
uciążliwość zapachowa
Opis:
More than 60% of the waste dumps in India are within 500 m from the communities. The odor impact from these sites may be the sole criterion to prioritize these sites for closure/remediation. The existing rating systems do not consider odor impact in their assessment. A new system, proposed in the study, employs seven parameters derived from the literature review and selects their ratings based on data obtained from a survey of waste dumps in Indian cities having population more than one million and expert judgment. Application of the new system to the waste sites with continuously varying characteristics shows that the scores are spread over the full range of 0–1000 and have minimum clustering. The sensitivity analysis of the new system shows that the system exhibits medium to high sensitivity to five out of seven parameters employed in the system. The odor impact ratings for the fifteen waste dumps from the new system prioritize these dumps into three categories for remedial action and help suggesting a particular cover alternative for these dumps.
Źródło:
Environment Protection Engineering; 2018, 44, 2; 37-56
0324-8828
Pojawia się w:
Environment Protection Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Study of temperature of black holes in terms of Chandrasekhar limit
Autorzy:
Mahto, D.
Jha, B. K.
Singh, K.M.
Ram, M.
Powiązania:
https://bibliotekanauki.pl/articles/412044.pdf
Data publikacji:
2015
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
black holes
formula for the temperature
Hawking
Einstein
Opis:
Stephen Hawking gave the formula for the temperature for the black holes as[wzór] . In the present research article, we have converted this formula in terms of Chandrasekhar limit [Mch] and also calculated their values for different test black holes existing in XRBs and AGN. [wzór] Kelvin.
Źródło:
International Letters of Chemistry, Physics and Astronomy; 2015, 40; 43-50
2299-3843
Pojawia się w:
International Letters of Chemistry, Physics and Astronomy
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Optimization of Ammonium Sulfamate Nitration for the Preparation of Ammonium Dinitramide
Autorzy:
Mandal, A. K.
Kunjir, G. M.
Singh, J.
Adhav, S. S.
Singh, S. K.
Pandey, R. K.
Bhattacharya, B.
Lakshmi Kantam, M.
Powiązania:
https://bibliotekanauki.pl/articles/358022.pdf
Data publikacji:
2014
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Opis:
The reaction kinetics for the preparation of ammonium dinitramide (ADN) is described. ADN is the ammonium salt of the dinitramide anion, and belongs to the group of inorganic oxidizers, mainly useful for energetic rocket propellant formulations, particularly for underwater applications. It is also a potential candidate to replace ammonium perchlorate (AP), in order to develop chlorine-free, green propellants. At HEMRL, ADN is prepared by the nitration of ammonium sulfamate (AS) using mixed acid, followed by hydrolysis, neutralization with ammonia (g) and rectification using solvent. The nitration of ammonium sulfamate (AS) is carried out at a subzero temperature of -40 ±1 °C. The yield of ADN is reliant on the formation of dinitramidic acid, an intermediate product formed during the hydrolysis step, and its stability is predominantly dependent upon the level of acidity and temperature of the reaction medium. Prior to these kinetics studies, process optimization of the nitration of ammonium sulfamate (AS) was performed and gave the final mole ratio of AS:HNO3:H2SO4. Since the nitration of AS is sensitive to temperature, the rate of reaction was studied at fixed temperatures with variation of time, keeping all of the other parameters, such as vessel volume, agitator speed, feed rate etc., constant. During these studies, predetermined quantities of ammonium sulfamate (AS) and mixed acid were allowed to react at a fixed temperature (-40 ±1 °C) for different reaction periods to generate the concentration profile of AS. Using this concentration profile, the reaction order and reaction rate constant were evaluated. In order to find the effect of temperature on the reaction rate and yield, experiments were conducted at other temperatures such as -30 and -50 °C. In the present studies, it was found that the optimum temperature of nitration is -40 ±1 °C and that the rate of reaction follows a pseudo second order process with rate constant 0.01113 (min-1)•(mol/L)-1. The reaction time evaluated for 55 to 60% conversion is about 70-80 minutes at -40 ±1 °C, based on this kinetics. The activation energy of AS nitration was found to be -4.6 kcal/mol, using the reaction kinetic data based on the temperature dependent rate equation derived from Arrhenius’s law.
Źródło:
Central European Journal of Energetic Materials; 2014, 11, 1; 83-97
1733-7178
Pojawia się w:
Central European Journal of Energetic Materials
Dostawca treści:
Biblioteka Nauki
Artykuł

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