Showing papers by "Birla Institute of Technology and Science published in 1997"

Real-time navigation of a mobile robot using Kohonen's topology conserving neural network

Abstract: This paper proposes a real-time sensor based navigation method using Kohonen's topology conserving network for navigation of a mobile robot in any uncertain environment. The sensory information including target location with respect to current location of the mobile robot, have been discretely conserved using a two dimensional Kohonen lattice. Reinforcement learning based on a stochastic real valued technique have been implemented to compute the action space for this Kohonen lattice. The proposed scheme learns the input and output weight space of the Kohonen lattice which is generalized to any workspace. The effectiveness of the proposed scheme has been established by simulation where the complete domain of the input-space is quantized based on experience on sensory data encountered in real-time. The input-output mapping conserved by the Kohonen lattice during simulation was used to guide a mobile robot in a real-time environment. Successful navigation of the mobile robot without further training confirms the robustness of the proposed scheme.

Simultaneous determination of metoprolol-hydrochlorothiazide and propranolol-hydrochlorothiazide in combined formulations by derivative spectroscopy

Abstract: A derivative spectrophotometric procedure was established for simultaneous determination of propranolol HCl (PP) with hydrochlorothlazide (HTZ) and metoprolol tartrate (MTP) with HTZ in tablet preparations. The method uses first- and second-derivative spectra of tablet extract in 0.01N NaOH solution. Ratios of analyte concentrations in the mixture were determined by the compensation technique. The zero-crossing point (ZCP) was also used to estimate the amounts of PP and HTZ In the formulations, and results were compared with those from the compensation technique. The results were found to be precise and free from interferences.

Simultaneous Determination of Tinidazole‐Clotrimazole and Tinidazole‐Norfloxacin in Combined Tablet Preparations by Derivative Spectroscopy

Abstract: A derivative spectrophotometric procedure has been developed for the simultaneous determination of tinidazole, with either clotrimazole or norfloxacin, in combined tablet preparations. Tablet extracts of tinidazole and clotrimazole, and tinidazole and norfloxacin were prepared in 0.01 M NaOH. The zero crossing point technique and the compensation technique were used to estimate the amount of each drug in the combined formulations, and were compared. The results were found to be accurate and free from interferences.

Low complexity fractal-based image compression technique

Abstract: A fast image compression technique as well as its progressive image transmission (PIT) version using fractals is presented which uses a small pool of domains extracted using visually significant patterns. The affine transformations for an edge block are obtained by using its edge characteristics instead of the minimum mean square error criterion. Simulation studies demonstrate that this method is computationally simple, gives faster encoding speed and achieves good fidelity at relatively higher compression ratios than other fractal based techniques.

Quantitative Structure-Activity Relationship Studies on Some Acyclouridine Derivatives Acting as Anti-HIV-1 Drugs

Abstract: The anti-HIV-1 activity of some derivatives of 1-[2-hydroxyethoxy]-6-(phenylthio)thymine(HEPT) is analyzed in relation to their physicochemical and molecular properties. The activities of the compounds are found to be significantly correlated with hydrophobic constant π and the van der Waals volume Vw. The results are found to be useful in discussing the mechanism of drug-receptor interaction.

Quantitative Structure-Activity Relationship Studies on Some Viral Reverse Transcriptase Inhibitors Acting as Anti-Hiv-1 Agents

Abstract: The anti-HIV-1 and cytotoxic activities of some viral reverse transcriptase inhibitors, namely the analogues of [1-[2′,5′-bis-O-(tert-butyldimethylsilyl)-β-D-xylo-and-ribofuranosyl]]-3′-spiro-5″-[4″-amino-1″.2″-oxathiole 2″,2″-dioxide] (TSAO) pyrimidine and pyrimidine modified-nucleosides, are analysed in relation to their physicochemical and molecular properties. The antiviral activities of the compounds are found to be significantly correlated with hydrophobic and electronic properties of the molecules, but no physicochemical parameters were found to be correlated with the cytotoxic effects of the compounds. This difference is exploited to improve the selectivity of the compounds. It is observed that TSAO can provide potent anti-HIV-1 drugs with a disubstituted thymine ring, in which a substituent may be at the N3-position. The disubstitution reduces the cytotoxicity, and substituents' hydrophobicity and electron donating character enhance the antiviral activity.

Quantitative structure-activity relationship studies on some anti-human-immunodeficiency-virus-1 (anti-HIV-1) drugs: viral reverse transcriptase inhibitors.

Abstract: The anti-HIV-1 activity of some 3-[(benzoxazol-2-ylmethyl)amino]-, 3-[(benzoxazol-2-yl)ethyl]-, 3-[N-(phthalimidomethyl)amino]-and 3-[N-(phthalimido)ethyl]-5-ethyl-6-methyl pyridin-2(1H)-one derivatives, that have been found to elicit their action through the allosteric inhibition of the enzyme viral reverse transcriptase (VRT), have been analysed in relation to the physicochemical properties of the molecules. Significant correlations were obtained between the activity and the hydrophobic and electronic constants of substituents and van der Waals' volume of the linker chain. Based on these findings the mechanism of action of these drugs is discussed.

Quantitative Structure–Activity Relationship Studies on Some Nonbenzodiazepines Binding to Benzodiazepine Receptor

Abstract: Quantitative structure–activity relationship (QSAR) studies are made on some nonbenzodiazepine ligands of benzodiazepine receptor (BZR), namely a series of 6-arylpyrrolo[2,1-d][1,5]benzo-thiazepines, a series of pyrido[1,2-a]benzimidazoles, and a series of some fused imidazopyridines. A Fujita-Ban approach adopted for the first series led to the suggestion that the most advantageous substituents in the series were only 4-Cl and 7-OCON(CH3)2. All other substituents were found to have negative contributions to the binding of the compounds with the BZR. In the case of pyrido[1,2-a]benzimidazoles, the 8-CONHR group was found to play an important role in the binding. The activity was found to be significantly correlated with the hydrophobic property of the R moiety and the electron-withdrawing ability of the ortho substituents in it. In the case of imidazopyridines, the Fujita-Ban approach revealed only the negative effects of the substituents that really mattered. By Hansch analysis these negative effects were accounted for by steric parameters.

Network inversion based neural controller for robot manipulations

Abstract: This paper proposes an indirect adaptive control scheme using the concept of network inversion. The neural model of the robot manipulator was obtained by training a radial basis function network from the input-output data generated from the plant. A query based learning algorithm has been proposed to improve the model prediction which uses an extended Kalman filtering based network inversion technique. A control scheme is designed incorporating the network inversion technique. The controller ensures Lyapunov stability of the dynamic system. The proposed control scheme is implemented on a two-link manipulator through simulation. Simulation results indicate that the control scheme is robust and stable and corresponding trajectory tracking is accurate.

Effect of the Core Size on the Higher Order Modes of a Chirofiber Filled with Different Core and Cladding Chiralities

Abstract: The present paper discusses the properties of higher order modes (i.e. modes corresponding to a non-zero first modal index v ≠ 0) for a chirofiber filled with different chiralities in the core and the cladding. The variation of the propagation constant s with the core radius shows a fluctuating nature for all these modes confirming and extending a previously reported result corresponding to v = 0. The presence of chirality has the general effect of increasing the number of propagating modes that can be sustained.

An efficient lapped orthogonal transform image coding technique

Abstract: A fast and computationally less complex coding technique is described which uses partial-lapped orthogonal transform (LOT) computation algorithm and efficiently discards perceptually insignificant high frequency transform coefficients. The coding process involves activity class energy classification, human visual system weighted normalization and quantization. The values of normalization factors are image independent and governed only by the bit-rate and activity index of the image blocks. Zones of various shapes and sizes are chosen for each activity class to perform zonal sampling which efficiently discards high frequency coefficients having zero values. A progressive transmission version of the proposed technique is also given. This technique gives better performance at comparable bit-rate than that obtained by using LOT/CVQ and LOT/VQ schemes.