T-matrix formulation of real-space dynamical mean-field theory and the Friedel sum rule for correlated lattice fermions

We formulate real-space dynamical mean-field theory within scattering theory. Thereby the Friedel sum rule is derived for interacting lattice fermions at zero temperature.Comment: 7 pages, no figures, extended and corrected versio

Kinetic market models with single commodity having price fluctuations

We study here numerically the behavior of an ideal gas like model of markets having only one non-consumable commodity. We investigate the behavior of the steady-state distributions of money, commodity and total wealth, as the dynamics of trading or exchange of money and commodity proceeds, with local (in time) fluctuations in the price of the commodity. These distributions are studied in markets with agents having uniform and random saving factors. The self-organizing features in money distribution are similar to the cases without any commodity (or with consumable commodities), while the commodity distribution shows an exponential decay. The wealth distribution shows interesting behavior: Gamma like distribution for uniform saving propensity and has the same power-law tail, as that of the money distribution, for a market with agents having random saving propensity.Comment: RevTeX4, 6 pages, 5 eps figures, accepted in Eur. Phys. J.

Cost-Effective Quality Refractories for Ferro-Alloy Smelting Furnaces

Ferro-alloy smelting furnaces are electrothermic in nature where various alloys are produced. Lining of these furnaces with cost-effective quality refractories is an important factor for attaining longer campaigns, better productivity and lower cost as well. Selection of refractories for the lining of these furnaces is based on the methodology of smelting practice, the characteristics of slag and alloy compositions. The development of these refractories for lining of ferro-alloy smelting furnaces has been rather very sluggish as compared to blast furnaces and steel making vessels. Most of the ferro-alloy smelting furnaces use conventional refractory lining used about three to four decades ago. The main reason with respect to this is that furnace loads were relatively low as compared to the dimensions of the furnace. At present, the need for increased furnace availability has forced the refractory manufacturers to develop cost-effective quality refractories. In this paper, an attempt has been made to highlight the R&D work carried out at NML regarding high alumina refractories and carbon bricks from indigenous raw materials. Super duty fire clay bricks or high alumina and alusite bricks are presently used in the side lining which is prone to alkali attack and carbon monoxide disintegration . The hearth bottom, hearth walls are invariably lined with carbon bricks and blocks, due to their properties suiting the operation of the furnace. The refracton,sub-hearth which is below the bottom hearth and plays a very important role in the campaign life of the furnace is lined with 80-90% alumina bricks. Refractories for lining tap hole, runner and plug for smooth production offerro alloys have also been described in this paper

Refractory Practices in Ferro-alloy Smelting Furnaces

Ferro-alloy furnaces are basically electrothermic furnaces where various ironalloys viz. Fe-Si, Fe-Mn, Fe-Cr etc., are produced. In the production of these alloys, the furnace inside acts as a receptacle. Lining therefore plays an important role. The choice of refractories for the furnace lining is determined by the technology of smelting, the character of the slag and alloy composition as well. The ferro-alloy furnace lining is distinguished by the considerable thickness of the hearth which ensures greater thermal inertia and stability of temper-ature in the smelting zone of a furnace during short idling periods. Further, a fact common to all ferro-alloy furnaces is that the actual working layer of the furnace lining is the so called coating i.e., acretion formed by burden, components, lining fragments and smelted alloys

Oxidation Phenomena in Carbon containing Refractories and their Protection

This paper highlights the various mechanisms of oxidation reaction of the carbon-bearing refractories in different atmospheres with special emphasis to IMO-C and A1203-C refractory composites. Kinetics of oxidation of the graphite phase in alumina-carbon refractdries have been discussed in detail along with various models. In case of IVIgO-C refractories: besides oxidation reaction, reduction of MgO by carbon present in the composite and the effect of various atmospheres/gases thereupon have also been discussed. This paper also discusses the effects of pore-structure, service-temperature, graphite-content, flake-size and purity of graphite and binders used (tar, pitch, resin etc.) on the oxidation behaviour of alumina-carbon and magnesia-carbon refractories. The reaction kinetics at lower temperatures are controlled largely by chemical rate and partly by pore diffusion, while at higher temp-erature the reaction kineticis controlled by diffusion of oxidising gases; initially through the stationary surface gas film and then throtigh the pore-structure of the de-carbonized layer. The protective measures to be taken to reduce the oxidation of carbon-bearing refractory composites in different atmospheres have also been dealt with. The addition of silicon, magnesium, aluminium, sili-con-aluminium alloy, silicon carbide, boron carbide etc. has been found to increase the oxidation resistance and thus resulting in longer lining lives. The paper thus contributes to the understanding of the effects of vari-ous parameters on the oxidation reaction in carbon containing refractories and also the remedial measures to be taken to enhance the oxidation resistance

Performance Analysis of Maximum Power Point Tracking Algorithms Under Varying Irradiation

Photovoltaic (PV) system is one of the reliable alternative sources of energy and its contribution in energy sector is growing rapidly. The performance of PV system depends upon the solar insolation, which will be varying throughout the day, season and year. The biggest challenge is to obtain the maximum power from PV array at varying insolation levels. The maximum power point tracking (MPPT) controller, in association with tracking algorithm will act as a principal element in driving the PV system at maximum power point (MPP). In this paper, the simulation model has been developed and the results were compared for perturb and observe, incremental conductance, extremum seeking control and fuzzy logic controller based MPPT algorithms at different irradiation levels on a 10 KW PV array. The results obtained were analysed in terms of convergence rate and their efficiency to track the MPP.Keywords: Photovoltaic system, MPPT algorithms, perturb and observe, incremental conductance, scalar gradient extremum seeking control, fuzzy logic controller.Article History: Received 3rd Oct 2016; Received in revised form 6th January 2017; Accepted 10th February 2017; Available onlineHow to Cite This Article: Naick, B. K., Chatterjee, T. K. & Chatterjee, K. (2017) Performance Analysis of Maximum Power Point Tracking Algorithms Under Varying Irradiation. Int Journal of Renewable Energy Development, 6(1), 65-74.http://dx.doi.org/10.14710/ijred.6.1.65-7