Deductive efficiency,belief revision and acting

Abstract

The SNePS inference engine is optimized for deductive efficiency, i.e. all beliefs acquired via inference are added to the agent's beliefs so that future queries may be answered by a retrieval rather than rederivation. An assumption-based truth maintenance system keeps track of the derivation histories of derived beliefs. We show how such an architecture simplifies the ontology of prepositional representations of plans; acts; preconditions, and effects of actions. In addition, the deductive efficiency of the basic system automatically extends itself to efficient search of plans, and hierarchical plan decompositions.     

Aged rare earth doped silicates as optoelectronic material

Samples of various concentrations were prepared and kept unsintered for a period of three years to study the consistency of composition prepared and structural evolution of glass. The expanded peaks in the Raman spectra arise due to thermal agitation, and a Boltzmann type of distribution was expected in the silicate gels. The behavior of the gels during the dehydroxylation and dehydration is conditioned by its microstructure, which depends upon the physical conditions, I.e., pH, and drying conditions.     

Assessment of sand dune change detection in Rajasthan (Thar) Desert,India

Landsat MSS digital data provide an important means for the study of sand dune morphology and distribution, land cover change and desertification monitoring. Two images, one each of Landsat-l and Landsat-5 MSS were used to determine sand dunes, their change and desertification by human activities from 1973 to 1986. Five dune classes were observed: parabolic, barchan, longitudinal, transverse and sand sheet. Parabolic dunes and sand sheet are widely distributed and are dominant classes in this area. Other classes of land cover observed were canal, saline area, salt lake and protected plantation.

Various changes in dune structure are observed due to human activities followed by wind erosion which indicates that desertification is enhancing severely. But there was no major shift in previous dune boundaries from 1973 to 1986 in the study area. Excavation of parabolic dunes for a canal also affected the dune patterns in the Bikaner district. Recent salinization in the vicinity of the Indira Ghandhi Canal further accentuated the land degradation which is quite apparent in the Landsat image of 1986. A further study would be essential to know the present extent of sand dune morphodynamics and desertification.     

FUNCTION-BASED CANDIDATE DISCRIMINATION DURING MODEL-BASED DIAGNOSIS

We propose function for candidate discrimination, i.e., suspect ordering during model-based diagnosis. Function offers advantages over structure and fault probabilities currently being used for candidate discrimination. It is readily available from device design, unlike fault probabilities, which are hard to obtain. Function-based discrimination is not dependent on the topology of the device, unlike structure-based discrimination. We propose classes as a scheme for representation of function. As part of classes, we define a set of function primitives and provide a framework for identifying the functions of components and subsystems of a device. The representation scheme is domain independent. We propose a function-based technique for candidate discrimination called the default order technique, and outline a diagnosis algorithm that applies the technique to the class model of a device. Function-based diagnosis is in addition to and as a supplement for model-based diagnosis based on behavior and structure. We demonstrate by qualitative analysis that function-based discrimination is at least as effective as fault probabilities for candidate discrimination of simple devices. In complex devices, function facilitates explanation generation based on causality, which is a desirable feature of diagnosis systems. Our discrimination technique provides a functional basis for partitioning components in the practicable version of the minimum entropy technique proposed by deKleer.     

Continued fraction expansion and inversion by ‘rearranged’ Routh tables

The Routh algorithm is known to be the simplest method for continued fraction expansion and inversion but it faces a serious limitation when the first column entry of any row of the Routh table becomes zero (but not a zero row). In this paper a remedy for such situations is proposed by rearranging the coefficients of the row in which zero entry has occurred in the first column of the Routh table. All possible cases, where the first column entry of the Routh table may become zero, are discussed for Cauer's first and second forms and are illustrated by numerical examples. The coefficients of the rearranged Routh table are also calculated by the usual Routh algorithm, hence it is equally suitable for digital computation.     

Synthesis of sub-optimal feedback controls for a class of distributed parameter systems†

Technique are derived for the synthesis of sub-optimal feedback controls for parabolic and first-order hyperbolic systems. An explicit result for the time-invariant gain of a specified controller is obtained by a least square approximation of the closed-loop control to the optimal open-loop control. If a least square approximation of the state trajectories is used, a parameter search is shown to give the time-invariant gain. A time-varying gain can be obtained by a re-definition of the original optimal control problem, again with the controller functionality specified. The only require-mont in the closed-loop synthesis is that an optimal open-loop solution exists and is computable.     

Recursive least-squares parameter estimation in SISO systems via Poisson moment functionals Part 1. Open–loop systems

A recursive least-squares parameter estimation algorithm based on the Poisson moment functional (PMF) approach for S1SO systems in open-loop is presented in this paper. The proposed algorithm is suitable for on-line parameter estimation of real-world problems. Normalized PMFs are used to improve the performance of the algorithm in noisy conditions.     

Dielectric and Ferroelectric Properties of Ceramics in the Pb(Zn 1/3Nb2/3)O3-BaTiO3-PbTiO3 System

The use of Pb(Zn_1/3Nb_2/3)O₃ ceramics is restricted by the formation of a pyrochlore phase detrimental to both dielectric and piezoelectric properties. Recently it has been shown that a 6 mol% addition of BaTiO₃ to PZN suppresses the formation of pyrochlore phase. Phase relations and dielectric properties of ceramics in the PZN-BT-PT system are reported here. Compositions with the perovskite structure, having high dielectric constant and low temperature coefficient of capacitance, have been identified.