http://nopr.niscair.res.in/handle/123456789/8221 Search the Channel search http://nopr.niscair.res.in/simple-search http://nopr.niscair.res.in/handle/123456789/8326 Title: Variation of width of the hysteresis loop with temperature in an emitter-coupled Schmitt trigger <br/> <br/>Authors: Barua, A Gohain; Tiru, Banty <br/> <br/>Abstract: Schmitt trigger circuits are designed with <i style="">pnp</i> transistors: the first circuit with two 2SB324 germanium transistors, and the second one with two U188 silicon transistors. At certain collector resistances in the second stage- or the driven- transistor, the variations of the hysteresis loop width in temperature range –95-75°C for the first circuit, and 100-150°C for the second one have been observed. The increase in the loop width with temperature is shown. <br/> <br/>Page(s): 482-485 Mon, 29 May 2006 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/8325 Title: <smarttagtype namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="country-region"><smarttagtype namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="place"> Traceability of 100 kV <i style="">dc </i>high voltage measurements at NPL, India </smarttagtype></smarttagtype> <br/> <br/>Authors: Mahajan, S K; Ravat, K B; Kothari, P C <br/> <br/>Abstract: Recently, <i style="">dc</i> high voltage laboratory has been established at National Physical Laboratory, India (NPLI) for calibration of high voltage (HV) equipment. High Voltage resistive divider is the heart of <i style="">dc</i> high voltage measurements. The traceability of HV measurements is directly related to divider’s traceability to Josphson voltage standard, which is the primary standard of <i style="">dc</i> voltage. In-house calibration of HV divider using traceable <i style="">dc</i> calibrator and 10 V reference standard has been discussed in the present paper. The overall uncertainty of measurement has also been calculated and is about 10 ppm. <br/> <br/>Page(s): 478-481 Mon, 29 May 2006 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/8324 Title: Study of optical absorption and optical band gap determination of thin amorphous TeO₂-V₂O₅-MoO₃ blown films <br/> <br/>Authors: Elahi, Mohammad; Souri, Dariush <br/> <br/>Abstract: The optical absorption coefficient of amorphous 40TeO₂-(60-<i style="">x</i>) V₂O₅-<i style="">x</i>MoO₃ thin films was determined in a spectral range 190-1100 nm at room temperature. The fundamental optical absorption edge was sharp. The optical gap generally increases as the proportion of MoO₃ in the mixed films increases. The width of the tail of the localized states in the band gap was determined for different compositions, which is because of the lack of long range order. The results of the usual density-of-state models of amorphous materials are presented in this paper. <br/> <br/>Page(s): 468-472 Mon, 29 May 2006 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/8323 Title: Synthesis of MgB₂ from magnesium rich powders <br/> <br/>Authors: Rajput, Suchitra; Chaudhary, Sujeet; Kashyap, Subhash C <br/> <br/>Abstract: Superconducting bulk MgB₂ samples have been synthesized by employing a modified heat treatment without using any additional process steps generally undertaken in view of the substantial loss of Mg during sintering owing to its high vapour pressure at the processing temperature. Starting with Mg rich powder mixtures having different atomic ratios of Mg:B (as against the nominally required 1:2 ratio), we have obtained superconducting MgB₂ samples showing a transition temperature (<i style="">T</i>_c) in the range 40.4-40.7K when synthesized at sintering temperatures in the range 720-900°C. Typically, a MgB₂ sample (<i style="">T</i>_c= 40.5K) obtained from heat treating Mg and B in the ratio of 2:2 at 870°C for 1h duration exhibited critical current density in excess of 1×10⁷ A/m² at ≈38K. Our results further show that MgO is not detrimental to superconductivity. <br/> <br/>Page(s): 461-467 Mon, 29 May 2006 22:58:59 GMT