Prediction of the transient intermodulation performance of operational amplifiers

Closed-form expressions are obtained for the THD, THD-20 and MIM tests used to characterize the TIM performance of operational amplifiers and circuits of similar topology. Good agreement is observed between measured and calculated results. Using approximate formulae for Bessel functions, the calculations can be performed by using small programmable calculators.     

Phototransients in 30 mol% CdO-70 mol% P2O5 glass

Phototransients produced when radiation of wavelength 240 nm is switched on have been studied in (30 mol% CdO-70 mol% P²O⁵ glass at various applied voltages. The phototransients show a linear rise with field, while their decay time (time taken by the photocurrent to attain its steady value) tends to saturate at higher fields. For shorter times ΔIα exp (? t/r), while for longer times there is a departure from the exponential behaviour. These phototransients may be due to trapping of photo-excited charges by ionized donors and space charge effects.     

Prediction of carrier to intermodulation performance

Closed-form expressions correlating the carrier to intermodulation performance, of two SCPC systems, with the simple two-carrier measurements are obtained. It is assumed that the high power amplifiers are exhibiting both amplitude non-linearity and AM/PM conversion characteristics. The high power amplifier is modelled by a quadrature model, which is mathematically represented by two sets of sine functions. Special eases are considered where curve fitting techniques, usually used to find the parameters of the sine function representations, can be totally avoided.     

Brief communication Modelling the static emitter characteristics of unijunction transistors

An empirical formula is presented for the static emitter characteristic of the unijunction transistor (UJT). The three parameters of the formula can be calculated easily from separate regions in the device characteristic using manual calculations.     

Harmonic and intennodulation performance of wideband memoryless non-linear amplifiers

By using a different, but equivalent, representation for the general Fourier -series representation, it in shown that the available computer programs, originally designed for in term ovulation analysis of memoryless bandpass nonlinear amplifiers, are adaptable to wideband amplifiers after very minor modifications.     

ANTIOXIDANT POTENTIAL OF DESI CHICKPEA VARIETIES COMMONLY CONSUMED IN PAKISTAN

Antioxidant potential of four Desi chickpeas ( Cicer arietinum L.) varieties indigenous to Pakistan, namely Balksar 2000, CM98, Dasht and Winhar 2000, was evaluated. All studied varieties exhibited appreciable total phenolic content (0.92–1.12 mg gallic acid equivalents/g), total flavonoid content (0.79–0.99 mg catechin equivalent [CAE]/g) and condensed tannin content (0.58–0.69 mg CAE/g). In addition, antioxidant activities were tested using 2,2-diphenyl-1-picrylhydrazyl radical (1.05–1.24 µmol trolox/g), 2,2 ' -azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (37.24–45.32 µmol trolox/g), ferric-reducing antioxidant power (0.73–0.90 mmol Fe^{2 +} equivalents/100 g) and oxygen radical-absorbing capacity (8.58–11.4 µmol trolox/g). All varieties exhibited appreciable antioxidant potential and significant differences ( P <  0.05) were observed among the varieties in different systems of antioxidant activity evaluation. The results of the present analytical study showed Desi chickpea ( C. arietinum L.) indigenous to Pakistan to be a potentially valuable legume crop with high antioxidant potential.

PRACTICAL APPLICATIONS

The analytical findings of this study provide a regional database for this valuable legume crop, which has not been explored so far. The data obtained will be useful to both producers and consumers. Chickpeas may be used as functional ingredients for processing into health foods in the food industry.     

一种CSCW环境下群组自动机树同步模型

给出一种在协同环境下的基于群组自动机的动态树同步模型,模型对操作同步和状态同步都给出了能够具体到实际过程每一步的描述。在考察状态同步时,把它限制在引起更新冲突的系统最小局部进行,效率得到了保证;由于模型在描述系统时采用递归性质的算法,极适合于描述动态系统。     

MWCNTs/SWCNTs Nanofluid Thin Film Flow over a Nonlinear Extending Disc: OHAM Solution

The aim of this research is the improvement towards the consumption of energy in the field of engineering and industry. The efforts have been paid to the enhancement of heat transmission and cooling process through a nanofluid coating of a nonlinear stretching disc. The combination of Water(H2 O) and multiple walled carbon nanotubes(MWCNT)/single walled carbon nanotubes(SWCNT) have been used as a nanofluid. The spreading of a thin nano-layer with variable thickness over a nonlinear and radially stretching surface has been considered. The estimated results of the problem have been accomplished using the Optimal Homotopy Analysis Method(OHAM). The residual errors of the OHAM method have been shown physically and numerically. The important physical parameters of skin friction and Nusselt number have been calculated and discussed. The other embedding parameters like generalized magnetic parameter, Prantl number, nanofluid volume fraction and Eckert number have been intended and discussed. The obtained results have been compared with the Numerical(ND-Solve) method for both sorts of CNTs. The closed agreement of both methods has been achieved.     

Computation of characteristic weighting patterns and vectors of discrete multivariable systems

This paper presents a new incremental algorithm for the computation of characteristic (weighting) patterns and vectors of discrete convolution systems. The method first approximates the system by a real characteristic dyadic form. Considerable savings in computation time are made if this is a good approximation. If not, the estimates are incremented at each instant to find the actual characteristic patterns and dynamic vectors. Numerical examples are given for real dyadic and non-dyadic forms.     

On the optimal characteristics of a memoryless power amplifier system

The performance of the piecewise linear limiter with multi-carrier input signal with arbitrary carrier amplitudes is analysed by using a simple, accurate and general approach. The limiter characteristic is expanded as an infinite Fourier series and convergent series expressions are obtained for the output carriers and intermodu-lation products. The special case of an input consisting of two equal-amplitude carriers is considered in detail and the results are found to be very accurate. This result will help in deciding whether the piecewise linear limiter will produce optimal or suboptimal results under specific traffic and criterion of optimality.