Time delayed control of classically damped structural systems

The effects of time delays on collocated as well as non-collocated point control of classically damped discrete dynamic systems have been examined. Controllers of PID type nave been considered. Analytical estimates of time delays to maintain/obtain stability for small gains have been given. Several new results dealing with the effect of time delays on collocated and non-collocated control designs are obtained. It is shown that undamped structural systems cannot be stabilized with pure velocity (or integral) feedback without time delays while using a controller that is not collocated with the sensor, when the mass matrix is diagonal. However, with the appropriate choice of time delays, for certain classes of commonly occurring structural systems, stable non-collocated control can be achieved. Analytical results providing the upper bound on the controller's gain necessary for stability have been presented. The theoretical results obtained are illustrated and verified with numerical examples.     

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.     

Effect of fuzzification on the plosive cognition system

Fuzzy algorithms provide a simpler and more powerful approach than statistical decision methods for describing non-ideal (fuzzy) environments in which there exists no precise boundary between the categories due to inherent vagueness rather than randomness. This paper attempts to demonstrate the effectiveness of such an algorithm when applied to the computer recognition of patterns of biological origin such as Telugu unaspirated plosives in initial position of large number of utterances in CVC context. A multieategorizer is described in which the fuzzy processor embodies a fuzzy property extractor and a similarity matrix generator. A provision fur controlling fuzziness in property sets had been made by keeping two parameters. ‘exponential’ and ‘denominational’ fuzzifiers, in the components of property matrices ; their effect on recognition score is also studied.

Machines’ performances are explained by plotting curves and through confusion matrices when transition, duration and slope of transition from the point of transient release of stop closure to the steady state of only first two formants were used as input features. Voiced stops are differentiated more easily than unvoiced stops, with the maximum overall recognition score ranging from 60% for dentals to 85% for bilabials. The fuzzy hedge ‘ slightly ’ when applied to property sets reduces the confusion from that of the hedge ‘ very ’ and consecutive utilizations of the operations ‘CONT’, ‘ OIL’ and ‘INT’ resulted in a wide variation of about 20 to 25% in the recognition score. Such a variation is found to be insignificant beyond an optimum value of the exponential fuzzifier’.     

Competing risk theory approach to the nature of the outcome of conception

An attempt has been made to obtain the probabilities of pregnancy termination by live birth, still birth and abortion, in any particular order, assuming that the termination of pregnancy is associated with three competing ‘risks’, i.e. live birth, still birth and abortion, which need not necessarily operate at the same point of time. A probability model has been constructed to obtain the conditional probability of live birth/still birth/abortion given that the previous pregnancy has been terminated by a particular one of the three. The correlation coefficient between the outcomes of two particular consecutive pregnancy terminations, viz. live birth and reproductive wastage (which includes both abortion and still birth), has also been obtained. Given data pertaining to sample correlation coefficients between the nature of consecutive orders of the outcomes of conception from first to sixth, an exercise has been undertaken to estimate parameters relating to the ‘hazard’ rates of live births, still birth and abortion. The exercise further enables one to test the well-known demographic hypothesis that reproductive wastages follow each other in succession over consecutive orders of the outcomes of conception.     

OPTIMIZATION OF KREIS TEST FOR EDIBLE OILS

Quality evaluation of edible oils is tested by different methods. Among the chemical methods, Kreis test is a promising one for early detection of rancidity, particularly aldehydes with a characteristic odor impact. Positive relationship of these breakdown products with perceived deterioration in quality evoked interest in re-examining the Kreis test. The color development in the test is critical and requires optimization. In continuation of studies in edible oils, the present investigation deals with sunflower and mustard oils. Through central composite rotatable design, response surface was fit as a function of oil quantity (0.3–3.3 mL) 1% phloroglucinol (0.08 mol) in acetic acid (0.3–3.3 mL) and incubation period (10–90 min). The polynomial fits were excellent with multiple correlation of >0.90. Optimized conditions were obtained for the two oils. Thus, use of 1 mL oil, 1 mL of 1% phloroglucinol, incubation time of 20 min and absorbance readings at 545 nm is derived and found applicable to all edible oils for routine tests.     

Raman spectra of Bi–Sr–Ca–Cu–O high temperature superconductors

Two high-temperature superconducting BiSrCaCuO compounds were fabricated as Bi_2.1Sr₄Ca₄Cu₃O_10+δ and Bi₂Sr₂Ca₂Cu₃O_10+δ. The X-ray diffraction patterns of both the compounds show that Bi_2.1Sr₄Ca₄Cu₃O_10+δ contains predominantly the high T_c 2223 phase, and Bi₂Sr₂Ca₂Cu₃O_10+δ the low T_c 2212 and high T_c 2223 phases, in equal amounts. The Raman spectra of these samples exhibit broad bands in the 430–512 cm^-1 region, as in the lead-substituted 2212 phase. Change in configuration due to the presence of the 2223 phase in the sample is indicated by the broadening of the 465 cm^-1 line. New bands at 611 and 678 cm^-1 are observed. Peaks in the 430–512 cm^-1 region exhibit a softening when the temperature is reduced to 93 K. This revised version was published online in November 2006 with corrections to the Cover Date.     

SWELLING STRESS AND HYDROSTATIC COMPRESSIBILITY OF GROUND CORN AND ITS CONSTITUENTS

Swelling stresses and hydrostatic compressibilities of ground whole corn, endosperm and germ were determined by using the theory of swelling stresses in gels. The ground corn and its constituents were considered as gels. The magnitude of swelling stresses in the ground corn materials was in order of several thousand pounds per square inch at low equilibrium moisture contents, when subjected to increased vapor pressure. The hydrostatic compressibility for ground whole corn, endosperm and germ increased with an increase of moisture content.