On shift register realization of sequential machines

This paper deals with the modular realization of sequential machines using shift registers as the modules. For a given minimal machine, the minimum number of modules required for its realization has been determined. It is well known that the number of modules required to realize a given machine can sometimes be reduced by realizing a non-minimal machine equivalent to the given minimal one, i.e. by assigning multiple codes to the states of the given minimal machine. This case is dealt with in the second part of the paper.     

Sintering of ZnO: I,Densification and Grain Growth*

Densification and grain growth rates at the intermediate stage of the sintering of pressed zinc oxide pellets were measured in air and oxygen. Application of a lattice diffusion model to the results gave calculated diffusion coefficients in good agreement with directly measured diffusion coefficients for zinc. The change of atmosphere from air to oxygen resulted in lowering of grain size and calculated diffusivity; the diffusion decrease is consistent with lattice diffusivity of zinc occurring by an interstitial mechanism. The results can be expressed by the relations: in air, and in oxygen, from 900° to 100°C.     

A STUDY OF SPINLINE DYNAMICS USING ORTHOGONAL COLLOCATION

Previous work on slow flow of non-Newtonian fluids past particles assemblages has been reviewed. Using a combination of Happel's free surface model and variational principles, bounds on the drag have been obtained for the creeping flow of a Carreau Model fluid past an assemblage of rigid spheres. The bounds are related to friction factor for flow through fixed beds of spherical particles. Numerical results covering a wide range of model parameters and bed voidages are presented.

Theoretical predictions are validated by comparing with experimental results reported in the literature that involve viscoelastic fluids. Arithmetic averages of the two bounds compare well for 182 data points with an average error of 12%. It is demonstrated that the present analysis, though based on a purely viscous model, can predict creeping flow behaviour in rigid particles assemblage for both inelastic and viscoelastic fluids.     

Workload allocation in multi-product, multi-facility production systems with setup times

In this article, we model the problem of assigning work to M heterogeneous servers (machines), which arises from exogenous demands for N products, in the presence of nonzero setup times. We seek a workload allocation which minimizes the total expected Work-in-Progress (WIP) inventory. Demands are assumed to arrive according to independent Poisson processes, but the setup and the processing times can have arbitrary distributions. Whenever a machine produces more than one product type, production batch sizes are determined by a group scheduling policy; which is also known as the cyclic-exhaustive polling policy. We formulate the workload allocation problem as a nonlinear optimization problem and then provide several insights gleaned from first order necessary conditions, from numerical examples, and from a close examination of the objective function. For example, we show that increasing either the load or the number of products assigned to a machine, or both, does not necessarily increase its contribution to total WIP. These insights are then used to devise a heuristic workload allocation as well as a lower bound. The heuristic allocation is further refined using a nonlinear optimization algorithm.     

ESAP: Efficient and secure authentication protocol for roaming user in mobile communication networks

The Global System for Mobile communication (GSM) network is proposed to mitigate the security problems and vulnerabilities observed in the mobile telecommunication system. However, the GSM network is vulnerable to different kinds of attacks such as redirection attack, impersonation attack and Man in-the Middle (MiTM) attack. The possibility of these attacks makes the wireless mobile system vulnerable to fraudulent access and eavesdropping. Different authentication protocols of GSM were proposed to overcome the drawbacks but many of them lead to network signalling overload and increases the call set-up time. In this paper, an efficient and secure authentication and key agreement protocol (ESAP-AKA) is proposed to overcome the flaws of existing authentication protocol for roaming users in the GSM network. The formal verification of the proposed protocol is presented by BAN logic and the security analysis is shown using the AVISPA tool. The security analysis shows that the proposed protocol avoids the different possible attacks on the communication network. The performance analysis based on the fluid flow mobility model shows that the proposed protocol reduces the communication overhead of the network by reducing a number of messages. On an average, the protocol reduces 60% of network signalling congestion overhead as compared with other existing GSM-AKA protocols. Moreover, the protocol not only removes the drawbacks of existing protocols but also accomplishes the needs of roaming users.     

Investigation of Al Schottky junction on n-type CdS film deposited on polymer substrate

A systematic study has been made on the behavior of Al/n-CdS thin film junction on flexible polymer substrate (polyethylene terephthalate, PET) grown using thermal evaporation method. Temperature dependence of I-V measurements for this junction has been done which closely follow the equations of Schottky barrier junction dominated by thermionic emission mechanism. Intrinsic and contact properties such as barrier height, ideality factor and series resistance have been calculated from I-V characteristics. The barrier height of Al/n-CdS junction is found to increase with increase in temperature whereas ideality factor and series resistance decrease with increase in temperature.     

DISPERSION OF MATTER IN FLOW OF A BINGHAM PLASTIC IN A TUBE

The paper is concerned with the dispersion of a solute in a Bingham plastic fluid flowing in a pipe or a parallel plate channel. For pipe flow, the dispersion coefficient K ₂ first increases with ξ₀ (the dimensionless radius of the plug flow region), reaches a maximum and then decreases. But in a channel flow, K ₂ decreases monotonically with increasing ξ₀. Further K ₂ for channel flow is found to be larger than that for pipe flow for all values of ξ₀ except 0.8≤ξ₀≤1.