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.     

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.     

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.     

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.     

A general gradient estimation based identification algorithm

A discrete recursive time-domain identification algorithm based on gradient estimation approach is proposed for linear time-invariant lumped-parameter systems. The scheme is quite general. Without invoking the strictly positive real lemma, Landau's proportional plus integral algorithms are shown to be the special cases of the proposed algorithm. Other gradient estimation based algorithms are also shown to be the special cases. The convergence of the scheme is proved using the second method of Lyapunov.     

EFFECT of POLYPHENOL OXIDASE and ITS INHIBITORS ON ANTHOCYANIN CHANGES IN PLUM JUICE

Total phenolics and chlorogenic acid in different plum cultivars ranged from 262 to 922 μ/g and 33 to 103, μg/g, respectively. Stanley plums had the highest polyphenol oxidase (PPO) activity and chlorogenic acid to total phenolics ratio as compared to all other cultivars. Degradation of anthocyanins in the juice made from Stanley plums was directly related to the level of PPO in the juice. Among PPO inhibitors, L-cysteine and sodium metabisulfite (at 0.5 and 1.0 mM) were effective in minimizing degradation of anthocyanins. Anthocyanins in the juice samples were heat stable and pasteurized juice showed acceptable microbial quality.     

Investigation of nonionic diazo dye-doped polymer dispersed liquid crystal film

Sudan black B (SBB) was used to investigate as the nonionic diazo dye-doped in polymer dispersed liquid crystal (PDLC) display, by polymerization-induced phase separation (PIPS) method. The maximum absorbance, contrast ratio, dichroic ratio and the order parameter of nonionic diazo dye in nemetic host (TL203) were investigated using UV?CVis polarized spectroscopy. The orientation of the dye molecules was controlled by electric field, which enabled the contrast ratio of the dye to be obtained by electrically switching. The change occurring on droplet morphologies and electro-optical properties of PDLC film with the change in contents of Sudan black dye and liquid crystals (LC) contents was investigated. We found an increase in LC droplet sizes with the increase of diazo dye and LC contents. Moreover the addition of small amount of nonionic diazo dye reduced the threshold voltage (V $_{\boldsymbol{\rm th}})$ , increased off-state transmittance, enhanced the contrast ratio and decreased the response time of dye-doped PDLC. Additionally the change in transition temperature of LC and changes in LC droplet morphologies with the addition of dye were also observed. Such changes were observed with the images taken by polarized optical microscope (POM). The detail discussions on such behaviours were also made.     

石墨烯纳米片增强铝基复合材料的制备与性能

采用高能球磨、放电等离子烧结以及热挤压工艺制备含量为5.0%(体积分数)的石墨烯增强铝基复合材料。分别采用X射线光电子能谱、透射电镜及拉伸试验研究挤压态复合材料的显微组织与力学性能,发现5.0%(体积分数)的石墨烯分散在铝晶界上,并且未与铝基体发生界面反应。最终,挤压态复合材料的屈服强度和抗拉强度高达462 MPa和479 MPa,分别比挤压态铝基体提高62%和60%。断口分析表明,在断裂过程中复合材料中分散的石墨烯起到明显的载荷传递的作用。上述结果表明,采用高能球磨、放电等离子烧结以及热挤压制备工艺可将高含量石墨烯分散于铝合金中,且能控制石墨烯和铝基体之间的界面反应。     

Modelling the current—voltage characteristic of a fluorescent lamp for computer-aided design

An empirical formula is presented for the voltage-current characteristics of a fluorescent lamp. The three parameters of the formula can easily be obtained from the measured characteristics of the fluorescent lamp without recourse to conventional curve-fitting techniques. By using this formula the analytical study of electronic circuits incorporating fluorescent lamps can be simplified.