Showing papers by "Techno India published in 1997"

Synthesis of single-resistance-controlled oscillators using CFOAs: simple state-variable approach

Abstract: A simple state-variable synthesis approach has been presented which makes it possible to evolve current feedback op-amp (CFOA)-based single-resistance-controlled oscillators (SRCO) systematically. Synthesised SRCOs possess several novel features and their workability has been confirmed experimentally as well as through SPICE simulations using commercially available AD844 CFOAs.

Thermodynamic nature of phase transitions in Pb(Zr x Ti1−x )O3 ceramics near the morphotropic phase boundary. I. Structural studies

Abstract: The room-temperature structures of Pb(Zr x Ti1−x )O3 ceramics are shown to be tetragonal for x ≤ 0·52 and rhombohedral for x ≥ 0·530 while both the rhombohedral phase (R-phase) and the tetragonal phase (T-phase) coexist at x = 0·525 corresponding to the morphotropic phase boundary (MPB). Ceramics with x = 0·530 and 0·535 undergo the following sequence of phase transitions with increasing temperature R → R + T → T → cubic (C). For x = 0·525, the sequence is R + T → T → C while, for x = 0·520, the T-phase directly transforms into C. The T-to-C-phase transitions for all the compositions is shown to be discontinuous. The phase transition sequence for x > 0·525 confirms that the MPB consists of a two-phase region and that it is tilted towards the Zr-rich end.

Independent global snapshots in large distributed systems

Abstract: Distributed systems depend on consistent global snapshots for process recovery and garbage collection activity. We provide exact conditions for an arbitrary checkpoint based on independent dependency tracking within clusters of nodes. The method permits nodes (within clusters) to independently compute dependency information based on available (local) information. The existing models of global snapshot computations provide the necessary and sufficient conditions. But, these require expensive global computations. The proposed computations can be performed by a node to identify existing global checkpoints. The nodes can also compute conditions to make a checkpoint, or conditions, such that a collection of checkpoints, can belong to a global snapshot.

Relevance of birth month in respiratory allergy.

Abstract: was just below the theoretical value, and intradaily variabihty was not significant (<20%); methachohne challenge revealed unchanged bronchial hyperreactivity; PD2oFEVi = 103 ng. Our patient's sensitization to grass pollen suggested the possibihty that the positivity to black henna could have been due to a cross-reacting immunoglobulin directed at grass pollen. However, no such cross-reactivity has been reported in the literature; moreover, the absence of seasonal allergic symptoms suggested that grass pollen sensitization was not clinically significant in our patient. To our knowledge, this is the first report of occupational asthma due to black henna in an herbal shop worker. This case is further distinguished from previous reports of sensitization to henna by the detection of IgE antibodies to the black variant of henna, /. argentea, and not the more common form of henna, L. inermis, used by hairdressers. The different botanic origin of the two plants is the most likely explanation of the unique sensitization to the species belonging to the genus Indigofera.

Shifting paradigms in education and their relevance to training in EMC design

Abstract: Public opinion in general has expressed unhappiness over the conduct and relevance of the university educational system. The Indian educational system has been trying hard to keep pace with the changing demands. This paper attempts to analyse the shifting paradigms in education technology and usage of information technology tools in the field of engineering education. Adopting these techniques can make EMC education more relevant to changing needs. A case study, where usage of IT tools in EM education has helped in creating interest in the subject is also presented.

Numerically calculated Q-switched laser output characteristics of high-power diode-laser-pumped Nd:YAG laser

Abstract: A numerical model for high power diode laser-pumped Q-switched Nd:YAG laser is presented. Number of models based on analytical methods for describing the performance effects of diode-pumped solid-state (DPSS) lasers have appeared in the literature. But very few numerical models have so far been reported. Our model based on the numerical method takes into account all operational characteristics of pump laser diode at 808 nm, all opto-geometric and spectroscopic parameters of Nd:YAG crystal, the cavity parameters and various losses including Q-switch loss. Only the thermal lensing effect is excluded in the model. The model has been described to be simple, flexible with on-line graphics facility. It has been tested in case of Q-switched Nd:YAG laser experimental results of which are in close agreement with those predicted by the model. The model can efficiently and accurately compute the Q- switched pulse energy, energy stored in the gain medium, pulse width, etc. Efforts are now being made to generalize and improve the predictive capability of the model so that it can be extended to other solid-state laser crystals optically pumped by laser diodes. It is expected that generalized mathematical model will be highly proficient and interactive to accurately predict the laser output.