On the use of observers in finite-time optimal regulator problems†

When a compatible dynamical observer is employod to construct the estimates of the inaccessible states of the system, an increase in the value of the performance index of a finite-time optimal regulator is in general encountered. An expression for this increase in the value is derived. The conditions for zero increase in the cost are discussed.     

Optimal maintenance policy for equipment subject to random deterioration and random failure A modern control theory approach

The stochastic version of Pontryagin's maximum principle is applied to determine an optimal maintenance policy of equipment subject to random deterioration. The deterioration of the equipment with age is modelled as a random process. Next the model is generalized to include random catastrophic failure of the equipment. The optimal maintenance policy is derived for two special probability distributions of time to failure of the equipment, namely, exponential and Weibull distributions Both the salvage value and deterioration rate of the equipment are treated as state variables and the maintenance as a control variable. The result is illustrated by an example.     

Textural pattern classification for oral squamous cell carcinoma

Despite being an area of cancer with highest worldwide incidence, oral cancer yet remains to be widely researched. Studies on computer‐aided analysis of pathological slides of oral cancer contribute a lot to the diagnosis and treatment of the disease. Some researches in this direction have been carried out on oral submucous fibrosis. In this work an approach for analysing abnormality based on textural features present in squamous cell carcinoma histological slides have been considered. Histogram and grey‐level co‐occurrence matrix approaches for extraction of textural features from biopsy images with normal and malignant cells are used here. Further, we have used linear support vector machine classifier for automated diagnosis of the oral cancer, which gives 100% accuracy.     

Multilayer capacitor ceramics in the PMN-PT-BT system: effect of MgO and 4PbO·B2O3 additions

Coexistence of pyrochlore phase is one of the major problems in the preparation of lead magnesium niobate (PMN) based perovskites as it leads to deterioration of the dielectric and piezoelectric properties. Although the columbite precursor method substantially reduces the formation of pyrochlore phase, the success of this process depends on various process conditions such as reactivity of MgO, level of mixing or grinding, control of PbO volatility and reversibility of the reaction. Compositions in the system (1−x)[(1−y)PMN yPT]x BT (where PT = PbTiO₃ and BT = BaTiO₃) were prepared by the columbite route. Results show that addition of excess MgO and 4PbO·B₂O₃ glass before sintering not only eliminates the pyrochlore phase completely but also produces a series of ceramics with low firing temperature, very high dielectric constant, low dissipation factor, high d.c. resistivity and extremely low temperature coefficient of capacitance (TCC). The unusually low TCC values make these high K dielectrics suitable for application in multilayer ceramic capacitors having EIA specifications Y5P, Y5R and Y5S. This revised version was published online in July 2006 with corrections to the Cover Date.     

HEAT TRANSFER DURING EVAPORATION of MILK to HIGH SOLIDS IN THIN FILM SCRAPED SURFACE HEAT EXCHANGER

Thermal performance of thin film scraped surface heat exchanger was evaluated for concentration of milk to high solids with process variables such as mass flow rate, steam condensing, temperature, etc. Appropriate dimensionless groups were formulated and fitted in Cobb-Douglas model to obtain a correlation. This relationship which is in the form of a Nusselt equation will be useful in predicting the scraped film coefficient during milk concentration to high solids. the effect of process variables on scraped film coefficient were discussed.     

INACTIVATION of PROTEASES and LIPASE IN MILK IN THIN FILM SCRAPED SURFACE HEAT EXCHANGER

A cascade thin film scraped surface heat exchangers, having sterilizer, regenerator and cooler sections was designed and fabricated. It was employed for inactivation of thermostable proteases and lipases in milk. Buffalo milk was sterilized in the temperature range: 143–152°C for holding times of 0.75, 1.0 and 1.25 s. Samples collected aseptically were stored at 37°C to study the proteolytic and lypolytic activities. the study established that activity of enzymes in milk subjected to higher temperature was far less than that of milk processed at lower temperature for same holding time. the effect of longer holding times was similar.     

Effect of prior cold work on mechanical properties and structure of an age-hardened Cu–1.5wt% Ti alloy

The effects of prior cold work on hardness, tensile properties, electrical conductivity and microstructure of an aged Cu–1.5 wt% Ti alloy have been studied by employing hardness and resistivity measurements, tensile tests and scanning and transmission electron microscopy. The hardness increased from 80 VHN in the solution-treated condition, to 210 VHN on peak ageing and 280 VHN with prior cold work followed by ageing. While a similar trend has been observed in yield and tensile strengths, the ductility (percentage elongation) decreased from 45% to 9%. The electrical conductivity of the alloy also increased up to 26% International annealed copper standard upon ageing the cold-worked alloy. Maximum strengthening of the alloy was associated with the precipitation of metastable, coherent and ordered Cu4 Ti, phase having body-centred tetragonal structure. The differences in the properties and microstructural evolution between low and high titanium alloys (for example, the absence of composition modulations and deformation twins in Cu–1.5 Ti alloy, while they are present in Cu–4.5 Ti alloy) have been discussed. Prior cold work did not change the fracture mode of microvoid coalescence.     

Minimal realization of arbitrary switching functions with 2-level networks of isodistinct and isobaric threshold gates

This paper deals with the synthesis of 2-level networks of threshold logic elements for realizing non-linearly separable switching functions. Gate minimality has been ensured for the types of gates used. The method is straightforward and can be programmed in a computer.     

(S,s) inventory policy for single replenishment channel—Part 2

A model for (S, s) inventory policy with a single replenishment channel and single server has already been developed. The method is extended to the situation where the inventory is replenished after the completion of two operations in tandem.