CMOS current feedback op amp-based chaos generators using novel active nonlinear voltage controlled resistors with odd symmetrical characteristics

Novel grounded and floating CMOS active nonlinear resistors with odd symmetrical characteristics are designed. The nonlinear resistors are then incorporated into two chaotic oscillator circuits based on a CMOS current feedback op amp (CFOA). The slopes of both the negative and positive segments of the nonlinear characteristics are voltage controlled, allowing for a wide range of dynamic behaviour to be observed and easily tuned in a period doubling route to chaos. Nonlinear current–voltage characteristics are derived in a piecewise-linear form and shown possibly to be modelled using a cubic polynomial approximation. PSPICE simulations using a standard 2.0 μm technology file and numerical simulations of the derived chaotic mathematical models are included.     

Comparison of estimates using record statistics from Weibull model: Bayesian and non-Bayesian approaches

This paper develops a Bayesian analysis in the context of record statistics values from the two-parameter Weibull distribution. The ML and the Bayes estimates based on record values are derived for the two unknown parameters and some survival time parameters e.g. reliability and hazard functions. The Bayes estimates are obtained based on a conjugate prior for the scale parameter and a discrete prior for the shape parameter of this model. This is done with respect to both symmetric loss function (squared error loss), and asymmetric loss function (linear-exponential (LINEX)) loss function. The maximum likelihood and the different Bayes estimates are compared via a Monte Carlo simulation study. A practical example consisting of real record values using the data from an accelerated test on insulating fluid reported by Nelson was used for illustration and comparison. Finally, Bayesian predictive density function, which is necessary to obtain bounds for predictive interval of future record is derived and discussed using a numerical example. The results may be of interest in a situation where only record values are stored.     

New CMOS Fully‐Differential Transconductor and Application to a Fully‐Differential Gm‐C Filter

A new CMOS voltage‐controlled fully‐differential transconductor is presented. The basic structure of the proposed transconductor is based on a four‐MOS transistor cell operating in the triode or saturation region. It achieves a high linearity range of ± 1 V at a 1.5 V supply voltage. The proposed transconductor is used to realize a new fully‐differential Gm‐C low‐pass filter with a minimum number of transconductors and grounded capacitors. PSpice simulation results for the transconductor circuit and its filter application indicating the linearity range and verifying the analytical results using 0.35 μm technology are also given.     

Current Operational Amplifier (COA): CMOS Realization and Active Compensation

A methodology for analysis and synthesis of lowpass sigma-delta () converters is presented in this paper. This method permits the synthesis of modulators employing continuous-time filters from discrete-time topologies. The analysis method is based on the discretization of a continuous-time model and using a discrete simulator, which is more efficient than an analog simulator. In our analysis approach, the influence of the sample and hold block and non-idealities of the feedback DAC can be systematically modeled by discrete-time systems. Finally, a realistic design of a second-order modulator with a compensation of the non-ideal behavior of the DAC is given. Moreover, simulation results show a good agreement with the theoretical predictions.     

A new active rc configuration for realizing nonminimum phase transfer functions

A new active RC configuration for realizing a second order nonminimum phase transfer function having a unity gain factor is given. The circuit has the advantages of being canonic, is always stable and is capable of realizing a high pole Q. The ω₀ and the pole Q sensitivities to all passive and active circuit components are derived. The effect of the limited frequency response of the OA is examined.     

Recessive Robinow syndrome: with emphasis on endocrine functions

We present the characteristic features of 14 children with the recessive form of Robinow syndrome and the growth hormone (GH) response to provocation with clonidine and the serum insulin-like growth factor-I (IGF-I) concentration in 12 of these children. The gonadotropin (luteinizing hormone [LH] and follicle-stimulating hormone [FSH]) response to gonadotropin-releasing hormone (GnRH) was evaluated in early pubertal and pubertal patients, and the testosterone response to human chorionic gonadotropin (HCG) was evaluated in males. Children with Robinow syndrome, born at full-term, were short at birth (length, 41.4+/-2.1 cm) and had markedly slow growth velocity (GV) during the first year (13.1+/-2.1 cm/yr); consequently, they were significantly short at the end of the first year of life (length, 54.4+/-2.9 cm). This intrauterine and early extrauterine growth delay reflected low growth potential. During childhood, the GV standard deviation score (GVSDS) remained low (-2.17+/-0.83). Despite the presence of empty sella in all of the patients, they had an adequate GH response to clonidine provocation (peak, 19.3+/-5.8 microg/L) and a normal serum IGF-I concentration (309+/-142 ng/mL) for their age. During childhood and early adolescence, boys with Robinow syndrome had low basal testosterone and a low testosterone response to HCG stimulation (3,000 IU/m2/d intramuscularly [IM] for 3 days). However, their basal and GnRH-stimulated FSH concentrations were normal. Two girls (Tanner II breast development) had a normal serum estradiol (E2) concentration but high LH and FSH responses to GnRH stimulation. This suggested either defective feedback of E2 on the hypothalamic-pituitary axis or hyporesponsiveness of the ovaries to gonadotropin. Four weeks of HCG therapy (2,500 IU/m2 IM twice weekly) in three boys with Robinow syndrome increased the penile length and testicular volume, denoting a significant Leydig cell response to prolonged HCG stimulation and the presence of functioning androgen receptors. It is suggested that HCG and/or testosterone therapy during infancy may improve the severe micropenis in these patients.     

The stability of fixed bed catalytic reactors

A proper control design for safe and economic operation of industrial catalytic reactors requires a detailed study of transient and steady state behaviour. The present paper discusses contributions in this area with an emphasis on the stability problem. In addition, an attempt has been made to relate the stability of a fixed bed catalytic reactor to that of individual catalyst particles. Sufficient conditions for local stability of a two-dimensional and a one dimensional model for the reactor are obtained using the extension of Lyapunov stability theory to distributed parameter systems. For the two-dimensional model, the sufficient conditions are in the form of inequalities which require steady-state information. For the one dimensional model, the reactor is locally stable if and only if the slope of the heat removal line is greater than the slope of the heat generation curve at the steady state for small perturbations in temperature and concentration.     

A kinetic model for the hydrochloric acid leaching of kaolinite clay in the presence of fluoride ions

The dissolution of kaolinite clay in hydrochloric acid solutions has been carried out in the presence of fluoride ions. Leaching in the presence of fluoride ions activates the clay for leaching, making higher extractions possible at lower roasting and leaching temperatures. The activation energy for the leaching of clay calcined at 540°C is decreased from 71 kJ/mol to 23 kJ/mol in the presence of fluoride ions. Dissolution in the presence of fluoride appears to fit a second-order reaction mechanism.     

Evaluation of malonanilides as new stabilizers for double-base propellants

Five malonanilide derivatives (M1-M5) were prepared by the reaction of ethyl malonate with aniline derivatives. These compounds were investigated as new stabilizers for double-base propellants (DBPs). The evaluation process has been performed through thermal stability tests, thermal analyses measurements (TGA and DSC) and kinetic parameters calculations (E(a)). The results of the new stabilizers were compared with the results of the classical stabilizer N, N-diethyldiphenyl urea. It has been found that o- and p-dinitromalonanilides, in particular, showed better stability effect for DBPs than the classical one.     

Fully differential CMOS CCII based on differential difference transconductor

This paper presents a new CMOS fully differential second-generation current conveyor (FDCCII). The proposed FDCCII is based on a fully differential difference transconductor as an input stage and two class AB output stages. Besides the proposed FDCCII circuit is operating at supply voltages of ±1.5 V, it has a total standby current of 380 μA. The application of the FDCCII to realize variable gain amplifier, fully differential integrator, and fully differential second order bandpass filter are given. The proposed FDCII and its applications are simulated using CMOS 0.35 μm technology.