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Certain aspects relating to cost control in large research and development projects are discussed. The ideas presented will be of special interest to the scientists and the engineers working as project leaders or project managers.Certain typical characteristics of an R & D project make the conventional cost control techniques like the variance analysis quite dysfunctional during the initial phase of the project. As the project work progresses, new budgets, incorporating finer details of the activities should be prepared which become more functional for the control purposes. A considerable saving in cost can be effected by determining an optimum cost-time relationship and the pattern of expenditure. Finally, certain behavioural aspects which are considered to be of immense importance for the success of any control System are discussed.

In adaptive control systems the controller parameters are to be adjusted in real time in accordance with the information received from the measurements on system dynamics. A special purpose or general purpose digital computer is often necessary for generating the signals for controller parameter adjustments. In this paper we describe a few electronic devices whose parameters are directly under the control of digital signals. These devices will be of great use for many applications including adaptive control. The devices described in this paper are, digitally controlled variable gain amplifier, digitally controlled compensating network and digitally controlled variable frequency sampler.

An adaptive model for a human operator has been proposed in this paper. This model takes into account the structure of the nervous system and its information processing capabilities. The central nervous system as proposed by McCulIoch and Pitts is assumed to be a large scale system composed of neurons which is considered to be a threshold element. In the proposed model, a quasi-linear model as proposed by McRuer and Krendel has been taken as a basic transfer function of the human operator. It has some adjustable parameters which are adjusted by the human operator as the situation demands. The adaptive loop operates to make discrete time adjustments in the human operator's parameters through a decision unit.

Sequential logic circuits are described for adjusting the parameters of the controller in a linear control system operating in time varying environments. The adaptive loop operates to make discrete-time adjustments in the adjustable controller parameters, while the basic control system operates in continuous time. The adjustable controller parameters can have only discrete values instead of continuous range of values. The value of the parameters at a particular instant depends upon the control inputs which are the outputs of the sequential logic circuit. The sequential logic circuit described here utilizes the information/signals obtained by identifying certain characteristic of the control system. The system performance always tends towards the optimum response despite the variations in the system dynamics.

The importance of computers in medical research has been long recognized. With the availability of many medical instruments and recording devices, enormous amount of data is available in various forms. The analysis of physiological signals like electrocardiogram (ECG) and Electro-encephalogram (EEG) is very useful from the clinical point of view. These signals possess a large amount of hidden information about the physiological conditions of the related organs. ECG and EEG produce different types of patterns that the eye of the physician has empirically correlated with the important aspects of health. The computers use these relations and perform the analysis automatically with greater precision and accuracy.The acquisition, reduction and analysis of data which lead to final interpretation should be treated as a single information processing task. Also since there is immense amount of physiological data which is to be analysed on-line within a short time, special purpose computers serve very useful purpos...

Frequency domain analysis of EEG signals is highly useful for biofeedback and detecting various sleep stages. A simple spectrum analyser circuit has been described in this paper to display the autospectra on a CRO or an X-Y recorder.The circuit uses a digitally controlled band-pass filter whose centre frequency is variable by digital signals. Output of band-pass filter is fullwave rectified and filtered to give absolute value of amplitude of the frequency component present at a particular moment. The instrument covers whole of the low frequency spectrum of EEG signals (0.2 Hz to 28 Hz). This instrument has hold facility also, which enables one to note time variations of the amplitude of a particular frequency.

In a lightly damped control system rise time is small but large overshoot and prolonged oscillations present in the output are unwanted. If such a system is required to produce dead beat response, input is to be modified suitably by a prefilter or controller which is generally called possicast controller. Posicast control technique first proposed by O. J. M. Smith in 1957 for producing dead response with the help of delay lines was found satisfactory for second order systems. Zaborszky in 1958 on the same lines proposed a simple nonlinearized system using relays. This too was suitable for second order systems only. By changing system dynamics suitably it is possible to get dead beat response for third order and higher order systems also. A detailed study of posicast control system by N. G. Nath and A. K. Choudhury (1969) have shown that it is possible to apply posicast principle to higher order systems also. For even order systems a positive casting of the system input is required, while for odd order sys...

In a transistor astable multivibrator, the frequency is given by the simple formula In this paper the variation of frequency with the change in the collector and base voltage have been experimentally investigated for both germanium and silicon transistors. The effect of the variation of the base resistance on the slope of the voltage frequency variation has also been studied.It has been observed that a linear voltage controlled oscillator can be obtained by variation of base voltage, keeping the collector voltage constant. It has been found that the experimental change of frequency with base and collector voltage are not covered by theory.

Voltage and temperature compensation of transistor free running multi-vibrators, using both germanium and Silicon transistors has been achieved by use of Zener diodes and thermistors.For a nominal frequency of fifty, a voltage change of 50 per cent, or temperature change of 25°C., above and below room temperature, did not change the frequency beyond 0·5 cycles.

The class of short circuit conductance matrices realizable as n-port resistive networks is extended in this paper using generalized tree terminal graphs. In Part I, the realization is done in terms of PL tree terminal graphs. Necessary and sufficient conditions are given so that the tree terminal graph corresponding to a given short circuit conductance matrix is a PL tree. These conditions are based entirely on the sign pattern of the entries of the short circuit conductance matrix. Also the necessary and sufficient conditions for the realizability are stated.In Part II, the general question of realizability, determination of an appropriate tree terminal graph and the complete realization of a short circuit conductance matrix are discussed. No tree transformations are used in the realization procedure.

A wide band directional loudspeaker system with a nearly constant beam width of 30° in the vertical plane and 120° in the horizontal plane has been described here. Systems using straight line columns of speakers satisfy the directivity requirements over a limited frequency range. A uniform directivity over a wide range of frequency is achieved if radiators are arranged in a curve (arc of a circle). Vertical directivity was achieved by placing the seven speakers along a 60° arc of a circle of radius 5½ ft. and for horizontal directivity three such columns were placed in a 120° arc of a circle of radius 1¼ ft. The directivity remained substantially constant between 200 c/s. and 8 Kc/s. The system was tested in SWP hanger of Roorkee University having floor section of 166 × 142 ft. and metallic parabolic roof 34 ft. high. A considerable improvement in articulation index was achieved.

Power-supply interference is often associated with the measurements of electrical and non-electrical quantities specially with the recording of electro-physiological signals. This paper describes a novel filter circuit to suppress power-supply interference. The circuit described here uses digital techniques and has following special characteristics: (i) The rejection-filter circuit possesses a high value of Q. (ii) The filter eliminates harmonic frequencies also. This property helps in eliminating power supply interference still further because in most cases the waveform of the supply is not pure sinusoidal. (iii) The filter has tracking characteristics and any variation in power-supply frequency is automatically taken care of i.e., tuning of the filter is not required.

The response of a distributed RC network due to sine and cosine forcing functions have been obtained. The response for any other forcing function can be obtained by building up the corresponding Fourier series. An example of a pulse train has been included.

A digitally controlled automatic gain control (AGC) system is described in this paper using analogue and digital integrated circuits to accomplish the automatic gain control on physiological signals, widely varying in amplitude. Digitally controlled devices have been described by Jain and Chatterjee for the purpose of adaptive control. The principle of adaptive control has been used in the design of this AGC system.AGC system described in this paper is suitable to obtain almost constant amplitude signals from signals with wide amplitude variations. This scheme has been successfully used in arrhythmia monitoring system of Jain and Kabisatpathy.