THERMOPHYSICAL PROPERTIES OF FRESH AND ROASTED COFFEE POWDERS1

The present work deals with experimental determination of bulk specific heat, bulk thermal conductivity, bulk and true density and moisture content of Columbian and Mexican coffee bean powders. Specific heat was determined by DSC, thermal conductivity by modified Fitch apparatus, density by stereopycnometer and moisture contents by standard vacuum oven method. Specific heat values showed marginal rise over the temperature range (45 to 150C) studied. Thermal conductivity values, determined in the temperature range of 20–60C were not found to have any definite trend with rise in moisture in the experimental range of 4.8 to 9.8% moisture (dry basis). Bulk density of powders varied appreciably (1.298 to 0.882 g.cm^?3), while the change was negligible for true density (1.361 to 1.092 g.cm^?3) with the degree of roasting. Statistical analysis of the data shows the reliability of the experimental determinations. Suitable correlations were developed to determine bulk specific heat and bulk density.     

System dynamics simulation of Hopfield neural networks

Hopfield networks are a class of neural network models where non-linear graded response neurons organized into networks with effectively symmetric synaptic connections are able to implement interesting algorithms, thereby introducing the concept of information storage in the stable states of dynamical systems. In addition to opening up the possibility of using system dynamics as a vehicle to gain potentially useful insights into the behaviour of such networks, especially in the field or nonelectrical engineering, we study the dynamics of the state-space trajectory as well as time domain evolution of sensitivities of the states with respect to circuit parameters.     

Sliding wear characteristics of solid lubricant coating on titanium alloy surface modified by laser texturing and ternary hard coatings

Titanium alloys are poor in wear resistance and it is not suitable under sliding conditions even with lubrication because of its severe adhesive wear tendency. The surface modifications through texturing and surface coating were used to enhance the surface properties of the titanium alloy substrate. Hard and wear resistant coatings such as TiAlN and AlCrN were applied over textured titanium alloy surfaces with chromium as interlayer. To improve the friction and wear resisting performance of hard coatings further, solid lubricant, molybdenum disulphide (MoS2), was deposited on dimples made over hard coatings. Unidirectional sliding wear tests were performed with pin on disc contact geometry, to evaluate the tribological performance of coated substrates. The tests were performed under three different normal loads for a period of 40 min at sliding velocity of 2 m/s. The tribological behaviours of multi-layer coatings such as coating structure, friction coefficient and specific wear rate were investigated and analyzed. The lower friction coefficient of approximately 0.1 was found at the early sliding stage, which reduces the material transfer and increases the wear life. Although, the friction coefficient increased to high values after MoS₂ coating was partially removed, substrate was still protected against wear by underlying hard composite layer.     

Energy modelling for the national economy — generalized model based on a physical systems theory approach

This paper presents an approach to the study of the energy related issues of the national economy using physical systems theory concepts for economic and real life systems. The main issues are: the efficiency of various energy conversion and utilization processes in terms of the macro-level technological coefficients; the direct and indirect energy wastes as calculated on the basis of technological coefficients; the effect of energy wastes on the unit cost of energy available to the consumers; the consumption of natural resources based on the final and intermediate demands of various sectors; and the amount of environmental pollution due to energy wastes disposed of to nature. A model is developed for a simplified two-sector national economy which is later extended to a generalized multi-sector model in a branchchord framework. This generalization is a step forward in simplifying the solution methodology for the multi-sector models through substitution, thus avoiding the necessity of drawing a complex system graph or solving large matrices required in the solution methodology.     

Influence of curing regimes on compressive strength of ultra high performance concrete

The present paper is aimed to identify an efficient curing regime for ultra high performance concrete (UHPC), to achieve a target compressive strength more than 150 MPa, using indigenous materials. The thermal regime plays a vital role due to the limited fineness of ingredients and low water/binder ratio. By activation of the reaction kinetics, the effectiveness of the binder is enhanced which leads to improvements in mechanical as well as durability properties. The curing cycle employed are ambient air curing, water curing and hot air curing. The specimens were exposed to thermal regime at (90°C/150°C/200°C) for duration of 24, 48 or 72 hours at the age of 3rd and 7th day followed with air curing or water curing till 28 days. The results showed a marked difference in compressive strength ranging from 217 to 142 MPa with change in curing regimes. The samples when thermally cured at the age of 3rd and 7th day produced an average ultimate strength of 217–152 MPa and 196–150 MPa, respectively.     

A cost model for optimal mix of balanced stochastic assembly line and the modular assembly system for a customer oriented production system

A coat model is presented in this paper for balancing a stochastic assembly line where the incompletions on the line are handled on the basis of a modular assembly concept. The model proposed is a modification of the approach by Kottas and Lau and incorporates the provision of task times being greater than the cycle time for a customer oriented production system offering structural variations in the product. The assembly line was simulated using the balance obtained by the proposed model for estimation of in-process-atorage capacity for physical layout and design of the assembly line.     

Generalization of I-O-W model for waste management policy analysis and national planning

The generalization of the input-output-waste (I-O-W) model for different types of resources is presented in this paper as a new paradigm of national consistency modelling. This incorporates waste management (WM) policy analysis in a national planning context. The I-O-W model is an extension of the input-output model that formulates the waste aspects explicitly. The systematic analysis of intersectoral flow of different resources and wastes is important at the macro level for preparing resource plans that can be further integrated to frame overall economic plans. The paper briefly overviews the I-O-W model and generalizes it for five basic resources, i.e. material, energy, manpower, capital and services. The resource balance has been established by treating input to be equal to output plus waste for each resource independently as well as for the overall flow. The inputs required and the possible outputs for the generalized I-O-W model are listed. An illustrative example has been given that works out the direct, indirect and total energy. flows for a hypothetical economy. The scheme of integration is presented for overall WM policy analysis and national planning.     

Magnetic resonance in superparamagnetic zinc ferrite

In the present work, we have synthesized zinc ferrite nanoparticles by nitrate method. Presence of almost zero value of coercivity and remanence in the hysteresis of these samples shows the superparamagnetic nature at room temperature. Electron paramagnetic resonance spectroscopy performed on these samples in the temperature range 120–300 K indicates the systematic variation of the line-shapes of the spectra with temperature. Both g-value and peak-to-peak linewidth decrease with increase in temperature. The variation of g-values and peak-to-peak linewidth with temperature has been fitted with existing models and we observed different values of activation energies of the spins for both the samples.