50 research outputs found
Permanent and Dynamic Behaviours of Self-excited Induction Generator In balanced mode
Due to its various advantages over the synchronous generator, the induction machine (IM) can be used as a generator in remote and rural areas. It be haves as a generator when its rotor is driven above its asynchronous speed. The required reactive power is provided by a local capacitors bank connected to the stator of the IM. Both permanent and transient modes of the self excited induction generator (SEIG) are studied. In both cases (loaded and no-loaded), the evolution of the output voltage for different values of the excitation capacitor and speed is presented. We analyze also, the influence of the capacitors and speed values on start-up of the SEIG. A comparison between laboratory tests and simulation results is done, that demonstrate the effectiveness of the proposed modelDue to its various advantages over the synchronous generator, the induction machine (IM) can be used as a generator in remote and rural areas. It be haves as a generator when its rotor is driven above its asynchronous speed. The required reactive power is provided by a local capacitors bank connected to the stator of the IM. Both permanent and transient modes of the self excited induction generator (SEIG) are studied. In both cases (loaded and no-loaded), the evolution of the output voltage for different values of the excitation capacitor and speed is presented. We analyze also, the influence of the capacitors and speed values on start-up of the SEIG. A comparison between laboratory tests and simulation results is done, that demonstrate the effectiveness of the proposed model
Layered LiNi0.5Co0.5O2 cathode materials grown by soft-chemistry via various solution methods
[Abstract] The lithiated nickelâcobalt oxide LiNi0.5Co0.5O2 used as cathode material was grown at low-temperature using different aqueous solution methods. The wet chemistry involved the mixture of metal salts (acetates or nitrates) with various carboxylic acid-based aqueous solutions. Physicochemical and electrochemical properties of LiNi0.5Co0.5O2 products calcined at 400â600°C were extensively investigated. The four methods used involved complexing agents such as either citric, oxalic, aminoacetic (glycine), or succinic acid in aqueous medium which functioned as a fuel, decomposed the metal complexes at low temperature, and yielded the free impurity LiNi0.5Co0.5O2 compounds. Thermal (TGâDTA) analyses and XRD data show that powders grown with a layered structure ( space group) have been obtained at temperatures below 400°C by the acidification reaction of the aqueous solutions. The local structure of synthesized products was characterized by Fourier transform infrared (FTIR) spectroscopy. The electrochemical properties of the synthesized products were evaluated in rechargeable Li cells using a non-aqueous organic electrolyte (1 M LiClO4 in propylene carbonate, PC). The LiNi0.5Co0.5O2 positive electrodes fired at 600°C exhibited good cycling behavior
NC Calabi-Yau Manifolds in Toric Varieties with NC Torus fibration
Using the algebraic geometry method of Berenstein and Leigh (BL),
hep-th/0009209 and hep-th/0105229), and considering singular toric varieties
with NC irrational torus fibration, we construct NC extensions
of complex d dimension Calabi-Yau (CY) manifolds embedded
in . We give realizations of the NC toric group, derive the constraint eqs for NC Calabi-Yau (NCCY) manifolds
embedded in and work out solutions for
their generators. We study fractional branes at singularities and show
that, due to the complete reducibility property of group
representations, there is an infinite number of non compact fractional branes
at fixed points of the NC toric group.Comment: 12 pages, LaTex, no figur
Removal Efficiency of Textile Dyes from Aqueous Solutions Using Calcined Waste of Eggshells as Eco-friendly Adsorbent: Kinetic and Thermodynamic Studies
This research investigates the removal of textile dyes (Rhodamine B and Alizarin Red S) from aqueous solution by a low-cost adsorbent prepared from eggshell waste.
Batch adsorption experiments were conducted in order to determine the effect of different parameters such as pH, dye concentration, contact time, adsorbent dosage, particle size, and temperature. The best correlation was found by Langmuir model, and the maximum adsorption capacity was 175.58 mg gâ1 for Rhodamine B and 156.56 mg gâ1 for Alizarin Red S. Thermodynamic studies showed that the adsorption of Rhodamine B and Alizarin Red S were feasible, spontaneous, and exothermic in nature. Regeneration study conducted to test the reusability (five cycles) and comparison of adsorption capacities of Rhodamine B and Alizarin Red S showed that calcined eggshell adsorbent could potentially be used for the removal of dyes from aqueous solutions.
This work is licensed under a Creative Commons Attribution 4.0 International License
Salinité et pollution par les nitrates des eaux souterraines de la plaine des Triffa
Les eaux souterraines de la plaine des Triffa (Basse Moulouya) deviennent de plus en plus polluĂ©es. Les rĂ©sultats analytiques montrent que la plupart des puits sont chargĂ©s en sels et en nitrates, donc impropres Ă la consommation humaine et peuvent avoir un effet nĂ©gatif sur les cultures maraĂźchĂšres de la rĂ©gion. Dans la zone Ă©tudiĂ©e, des teneurs de 2,32 Ă 174,70 mg/l de NO3-, de 134 Ă 3614 mg/l de Cl- et de 103 Ă 1518 mg/l de Na+ ne sont pas exceptionnelles. Elles dĂ©passent largement les normes fixĂ©es par lâOMS et la CEE (50 mg/l pour les NO3 -, de 250 mg/l pour Cl- et de 175 mg/l pour Na+). Lâintensification de lâagriculture dans la plaine, notamment dans les pĂ©rimĂštres irriguĂ©s, lâĂ©pandage excessif des engrais, les applications rĂ©pĂ©tĂ©es, et Ă quantitĂ©s fortes, de fumiers, lâirrigation, les prĂ©cipitations et la remontĂ©e de la nappe dans certaines rĂ©gions ont engendrĂ© une pollution croissante des ressources en eau
NC Effective Gauge Model for Multilayer FQH States
We develop an effective field model for describing FQH states with rational
filling factors that are not of Laughlin type. These kinds of systems, which
concern single layer hierarchical states and multilayer ones, were observed
experimentally; but have not yet a satisfactory non commutative effective field
description like in the case of Susskind model. Using brane analysis and
fiber bundle techniques, we first classify such states in terms of
representations characterized, amongst others, by the filling factor of the
layers; but also by proper subgroups of the underlying gauge symmetry.
Multilayer states in the lowest Landau level are interpreted in terms of
systems of branes; but hierarchical ones are realized as Fiber bundles on
which we construct explicitly. In this picture, Jain and Haldane series
are recovered as special cases and have a remarkable interpretation in terms of
Fiber bundles with specific intersection matrices. We also derive the general
NC commutative effective field and matrix models for FQH states, extending
Susskind theory, and give the general expression of the rational filling
factors as well as their non abelian gauge symmetries.Comment: 54 pages 11 figures, LaTe
Finite-dimensional Lie algebras of order F
Lie algebras are natural generalisations of Lie algebras (F=1) and Lie
superalgebras (F=2). When not many finite-dimensional examples are known.
In this paper we construct finite-dimensional Lie algebras by an
inductive process starting from Lie algebras and Lie superalgebras. Matrix
realisations of Lie algebras constructed in this way from
and
, are given. We obtain non-trivial
extensions of the Poincar\'e algebra by In\"on\"u-Wigner contraction of certain
Lie algebras with .Comment: 20 pages, Late
Empirical investigation to explore potential gains from the amalgamation of Phase Changing Materials (PCMs) and wood shavings
The reduction of gained heat, heat peak shifting and the mitigation of air temperature fluctuations are some desirable properties that are sought after in any thermal insulation system. It cannot be overstated that these factors, in addition to others, govern the performance of such systems thus their effect on indoor ambient conditions. The effect of such systems extends also to Heating, Ventilation and Air-conditioning (HVAC) systems that are set up to operate optimally in certain conditions. Where literature shows that PCMs and natural materials such as wood-shavings can provide efficient passive insulation for buildings, it is evident that such approaches utilise methods that are of a degree of intricacy which requires specialist knowledge and complex techniques, such as micro-encapsulation for instance. With technical and economic aspects in mind, an amalgam of PCM and wood-shavings has been created for the purpose of being utilised as a feasible thermal insulation. The amalgamation was performed in the simplest of methods, through submerging the wood shavings in PCM. An experimental procedure was devised to test the thermal performance of the amalgam and compare this to the performance of the same un-amalgamated materials. Comparative analysis revealed that no significant thermal gains would be expected from such amalgamation. However, significant reduction in the total weight of the insulation system would be achieved that, in this case, shown to be up to 20.94%. Thus, further reducing possible strains on structural elements due to the application of insulation on buildings. This can be especially beneficial in vernacular architectural approaches where considerably large amounts and thicknesses of insulations are used. In addition, cost reduction could be attained as wood shavings are significantly cheaper compared to the cost of PCMs