Browsing by Author "S.K. Kak"

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Automatic Voltage Regulation of DC Shunt Generators
(1973) Vimal Singh; S.K. Kak; Srinivasan Rangarajan
In a dc shunt generator, as the load increases the terminal voltage falls, giving a drooping characteristic. The regulation of voltage involves the adjustment of field excitation. A simple method of voltage regulation by automatic adjustment of field excitation making use of transistor circuitry is discussed. The added advantage of this method is that by the simple adjustment of circuit parameters, the characteristics of a compound generator can be achieved. Experimental results prove the effectiveness of the method. Copyright © 1973 by The Institute of Electrical and Electronics Engineers, Inc.
NEW ADAPTIVE DELTA MODULATOR SCHEME.
(1986) S.K. Kak; Anand Mohan
A new scheme for implementing a 4-bit memory adaptive delta modulator (ADM) is proposed. The prototype constructed has offered more than 20 db improvement in the dynamic range while maintaining the peak snr. Experimental results obtained from the prototype are similar to those reported by Schindler, Chakravorty and Faruqui and Jayant.
NOVEL THRESHOLD SENSING SWITCHED FILTER.
(1986) S.K. Kak; H.K. Gupta
A frequency selective switch is required in many applications such as FSK, voice operated relay and multitone dialing. A scheme for implementing such a switch using a tunable band pass filter has been proposed and evaluated. The pass band of the proposed scheme can be controlled with the help of a reference voltage. The prototype developed has offered a minimum of 2. 0 Hz bandwidth over audio frequency range. However, the principle can be extended to any frequency band.
Optical fiber array surface roughness sensor
(Society of Photo-Optical Instrumentation Engineers, 1999) Sarit Pal; S.K. Kak
The paper discusses the technique of sensing the roughness of a surface in terms of slope of its microelements, based on reflection and scattering of electromagnetic wave from such elements of the continuous surface. An array of fibers collects the optical power reflected from the surface due to illuminating optical energy launched onto it through the central fiber of the array. The tilt and orientation of the illuminated pixel can be estimated from the measurement of reflected and scattered power captured by different fibers in the array. Theoretical developments to compute the tilt and orientation of the illuminated area - by the shape of the illuminated spot of the incident beam, analyzing the reflected or scattered beam, and the reflected beam intensity available at different fibers of the array - is presented. The intensity profile so derived shows close agreement to that obtained experimentally. A number of different types of array packing structures have been suggested and analyzed to evaluate their comparative efficiencies. The results obtained demonstrate that such a sensor can be used to measure surface roughness over a wide range, by employing different techniques like analyzing total integrated scattering (TIS), angle resolved light scattering (ARLS), specular reflection etc.
Preparation of nearly single phase 2223 in Bi1.6Pb0.4Sr2Ca2Cu3Oy composition by a semi-wet route using Pb0.2SrCa(CO3)2.2 precursor
(1991) Dhananjai Pandey; R. Mahesh; A.K. Singh; V.S. Tiwari; S.K. Kak
A new method for the synthesis of nearly single phase 2223 in Bi1.6Pb0.4Sr2Ca2Cu3Oy composition within 72 h of total heat treatment, using coprecipitates of (1) 0.2 Pb, Ca, Sr as carbonates and (2) 1.6 Bi, 3 Cu as oxalate, is reported. Samples prepared have been characterized by their crystal structure using XRD, microstructure using SEM and electrical resistivity. © 1991.
Speed and voltage regulation of d.c. shunt machines using power transistor in field circuit
(1974) Vimal Singh; S.K. Kak
A simple method for speed and voltage regulation of d.c. shunt machines is presented. The method is based on the use of a power transistor circuit which automatically adjusts the field current Such that the Speed or output voltage, as the case may be, is maintained constant with increasing load on the machine. An added advantage of this inothod is that, by the simple adjustment of circuit parameters, the characteristics of a compound generator can be achieved from a shunt generator without using a series field winding. Experimental results prove the effectiveness of the method. © 1974 Taylor & Francis Ltd.
Zero resistivity at 122 K in Bi-Pb-Sr-Ca-Cu-O system
(1990) Dhananjai Pandey; R. Mahesh; V.S. Tiwari; A.K. Singh; S.K. Kak
Zero resistivity at 122 K in samples of nominal composition Bi1.6Pb0.535Sr2.675Su3Oy prepared via a semi-wet route using Pb0.2SrCa(CO3)2.2 precursors is reported. Possible reasons for the 10 K enhancement of Tc(R=0) over the commonly reported values are suggested. © 1990.