Analysis of axially dispersed systems with general boundary conditions—I: Formulation

Transient analysis in the past of finite axially dispersed systems with or without a rate process has been subject to the use of the Danckwerts boundar conditions. We present here a formulation which suggests a general set of boundary conditions from which the Danckwerts conditions arise as a special case. The resulting boundary value problems neatly fit the mold of self-adjoint operator theory. An integral transform approach is outlined for those not familiar with operator theory. Discussion of actual solutions to different cases is deferred to two other papers which appear as Parts II and III.     

A CMOS low noise amplifier based on common source technique for ISM band application

In this paper a 2.45 GHz narrowband low noise amplifier (LNA) for wireless communication system is enunciated. The proposed CMOS Low Noise amplifier has been verified through cadence spectre RF simulation in standard UMC 90 nm CMOS process. The proposed LNA is designed by cascoding of two transistors; that is the common source transistor drives a common gate transistor. To achieve better power gain along with low noise figure, cascoding of two transistor and source degeneration technique is used and for low power consumption, the MOS transistors are biased in subthreshold region. At 2.45 GHz frequency, it exhibits power gain 31.53 dB. The S11, S22 and S12 of the circuit is ?9.14, ?9.22 and ?38.03 dB respectively. The 1 dB compression point of the circuit is ?16.89 dBm and IIP3 is ?5.70 dBm. The noise figure is 2.34 dB, input/output match of ?9.14 dB/?9.22 dB and power consumption 8.5 mW at 1.2 V.     

Influence of Ar plasma treatment on the wetting behavior of pharmaceutical powders

In this study, corn starch and ibuprofen are treated in Argon (Ar) plasma to enhance the wettability of the powders without using any additive or guest particle. The powder and pellets were exposed to the Ar plasma for different time intervals (5–20?min) at optimized pressure and voltage. While the morphological changes due to plasma exposure are captured by SEM, the AFM measurement shows the variations in surface roughness for both corn starch and ibuprofen powders. The XPS and surface energy results confirm that the surface groups change is dominating under initial exposure, but longer exposure creates more damaging effect than building the new active sites at the surface. The contact angle (CA) measurement shows that with increase in treatment time, the CA decrease from 48° to 33° for corn starch and 69° to 51° for ibuprofen. A comparison of experimentally obtained CA and that of theoretically calculated CA shows that there exists some difference. This may be attributed to the absence of surface group contribution in the Wenzel model. The present study shows that short exposure is sufficient enough to improve the wetting where the surface group plays a dominant role over surface roughness.     

A filter for on-line estimation of spectral content

A robust filter algorithm to extract, a posteriori, the rational signal model from a noisy measurement, with little a priori information, is proposed. The spectrum and the statistics of the signal and of the corrupting noise are assumed unknown, except that the signal is assumed to have a rational spectrum. An algorithm based on system and signal theory is derived to select a set of frequencies where the signal-to-noise ratio (SNR) is high from a given measurement spectrum. The density of selected frequencies weights the importance of the measurement as a function of frequency, An estimate of the signal model is obtained from the best weighted least-squares fit to the measurement spectrum at the selected frequencies. The proposed filter has applications to control and signal processing, and a wide variety of applications are presented. Applications include: system identification of a dc motor and a two-link manipulator, extraction of a myo-electric signal from a noisy measurement, the assignment of a rational model to a vegetation tissue's impedance, and to the number density profile of atmospheric oxygen     

Autonomous control systems: monitoring, diagnosis and tuning

A systematic and unified approach which accomplishes performance monitoring, performance improvement and fault prediction in control systems is proposed. The feature vector which is a vector formed of the coefficients of the estimate of the sensitivity function and the influence matrix which is the Jacobian of the feature vector with respect to the physical parameter are shown to contain the relevant information to realize an autonomous control system. The feature vector is estimated using a robust, accurate and reliable linear predictive coding algorithm. The influence matrix is computed by perturbing the physical parameters one at a time and estimating the feature vectors for each case. The proposed scheme is evaluated both on simulated as well as on actual control systems     

Nonlinear Stochastic Simulation of Stirred Tank Reactors

An algorithm for solving nonlinear stochastic differential equations due to the authors has been used for simulating the behaviour of stirred tank reactors subject to random parametric fluctuations. Two examples have been chosen from the literature derived from the works of Pell and Aris, and Aris and Amundson who approached these problems through linearization techniques. The limitations of linearization, qualitatively pointed out by these authors, have been evaluated in quantitative terms in this work. Several interesting predictions reveal that while linearization provides an effective technique in some situations, in several other instances, powerful limitations exist necessitating direct analysis of the nonlinear equations.     

Reliable Hydraulic Turbine Governor Based on Identification and Adaptive Filtering

A scheme for improving reliable operation of a PID governor of a hydraulic turbine generating unit is proposed. The parameters of governor and actuators are identified on-line to, a) detect their anomalous behaviours, b) facilitate the calibration of the proportional integral and derivative gain settings. An adaptive filter is used to detect the lightly damped oscillations of the system. The proposed scheme was verified via simulation on the real data obtained from one of Mactaquac hydro-generating units of New Brunswick Electrical Power Commission. The simulation results show that the proposed scheme can indeed provide an accurate and rapid detection of the abnormal system operations.     

Measures of overshoot, speed of response and robustness

Performance measures for a linear multivariable system with nonlinear perturbations are defined in terms of the eigenvalues and the eigenvectors of the linearized system matrix, and an interactive computer-aided design of controller parameters is given. The overshoot and the speed of response are the parameters of an exponential envelope constraining the norm of the states under initial condition perturbations. The robustness is shown to be related to these measures, and is bounded by their ratio.