A survey of psychologists at health maintenance organizations and community mental health centers.

Conducted a national survey of psychologists at health maintenance organizations (HMOs) and a comparison group of psychologists at community mental health centers. Activities and attitudes, and overall staffing patterns are examined. Recommendations are made for increasing the involvement of psychologists at HMOs. (5 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Simultaneous design and control of processes under uncertainty: A robust modelling approach

This paper presents a new methodology to integrate process design and control. The key idea in this method is to represent the system’s closed-loop nonlinear behaviour as a linear state space model complemented with uncertain model parameters. Then, robust control tools are applied to calculate bounds on the process stability, the process feasibility and the worst-case scenario. The new methodology was applied to the simultaneous design and control of a mixing tank process. The resulting design avoids the solution of computationally intensive dynamic optimizations since the integration of design and control problem is reduced to a nonlinear constrained optimization problem.     

Adaptive control of a CSTR with a neural network model

An adaptive control algorithm with a neural network model, previously proposed in the literature for the control of mechanical manipulators, is applied to a CSTR (Continuous Stirred Tank Reactor). The neural network model uses either radial Gaussian or “Mexican hat” wavelets as basis functions. This work shows that the addition of linear functions to the networks significantly improves the error convergence when the CSTR is operated for long periods of time in a neighborhood of one operating point, a common scenario in chemical process control. Then, a quantitative comparative study based on output errors and control efforts is conducted where adaptive controllers using wavelets or Gaussian basis functions and PID controllers (IMC tuning with fixed parameters and self tuning PID) are compared. From this comparative study, the practicality and advantages of the adaptive controllers over fixed or adaptive PID control is assessed.     

Control of a nonadiabatic packed bed reactor under periodic flow reversal

A full parametric study of the open-loop behavior of a packed bed reactor-recuperator system operating under periodic flow reversal produced a series of parametric maps which slow regions of operating conditions for which the system exhibits runaway, stable operation or extinction of the reaction. The reaction is CO oxidation over a Pt/alumina catalyst. A set of optimal operating conditions in terms of cycle time and heat transfer coefficient can be directly extracted from the parametric maps. A preliminary study on the control of periodic flow reversal tested and compared two strategies. 1) feedback PID control of the exit CO concentration and 2) model based feedforward control.     

On line estimation of matte grade in a copper smelter

This study deals with the design of an inferential estimator to predict matte grade in a copper smelter. A novel mathematical model for the dynamics of the smelter is presented and used as the basis of the on-line estimators. Two different types of estimators are proposed: an estimator with fixed parameters and an estimator with parameters which adapt in time based on infrequent process measurements. Several configurations of the adaptive and fixed estimators, based on different combinations of parameters and measurements, have been designed and compared to plant data. Conclusions are drawn regarding the most accurate configuration.     

Comparative study of black-box and hybrid estimation methods in fed-batch fermentation

A neural network based softsensor is proposed for a PHB fed-batch fermentation process. The softsensor is designed to estimate the biomass concentration on-line. The design is based on the following model structures: 1. a feedforward neural network, 2. a RBFN (radial basis function neural network) and 3. hybrid models composed of either feedforward or RBFN neural network and the a priori known dilution term of the mass balance equations. The different designs are experimentally implemented and compared using Alcaligenes eutrophus as a model fed-batch system. Additionally, the possibility of directly inferring the substrate (glucose) concentration from the estimated biomass was investigated by assessing the variability of the corresponding yield coefficient. The combination of the neural network model and mechanistic differential equation provided the best results. Because of the variability in the yield coefficient, substrate concentration could not be inferred directly.     

Behavioral health care dot-com and beyond: Computer-mediated communications in mental health and substance abuse treatment.

Computer-mediated communications (CMC) such as e-mail, websites, and CD-ROM and DVD programs, both on and off the Internet, will play an ever larger role in the future of behavioral health care. This address describes the current rapid expansion of CMC and some profound changes that are likely in the future. The reasons for using such CMC programs are addressed, and an example of a new multimedia version of the Addiction Severity Index is described. Issues and concerns about future uses of CMC are raised, as are possible implications for psychology. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Temperature excursions in packed bed reactors with an axial variation of catalyst activity

Research appears to be growing on a type of structured reactor in which catalyst activity varies or in which different catalysts are arranged in the reactant flow direction. These reactors offer improved selectivity for some classes of complex reactions under non-isothermal conditions or when composition modulation is employed. Our examination of the rather extreme case of alternating layers of inert and active catalyst indicate that this reactor structure accentuates wrong-way temperature excursions after a step-change in temperature and amplifies periodic input temperature disturbances. Experiments used a near adiabatic 2.5 cm diameter reactor packed with 3 mm particles of 0.2 wt.% Pt/Al₂O₃. Inert layers were just the 3 mm alumina particles. Step and triangular wave inputs of constant amplitude were used. Temperature response in the bed was measured by an axial array of computer-monitored thermocouples. Measurements were compared to those made on a homogeneous mixture of catalyst and support under identical input conditions. Simulation studies show that accentuation of the temperature excursions depends on layer thickness. Even first-order reaction kinetics show accentuated temperature excursions when layered beds are used.     

BOD5 estimation for pulp and paper mill effluent using UV absorbance

A novel method based on UV absorbance, is presented for estimating the BOD5 in pulp and paper mill effluent. This method could eventually be incorporated into an on-line sensor for BOD5 that is suitable for process control applications. Two streams, the reactor entrance and the final effluent, from two different mills were studied. One mill employed the Kraft pulping process, while the second mill was a thermo-mechanical one. The absorbance over the range 200-350 nm showed significant differences between the two mills. Because the two mills use very distinct processes, separate correlations were used to relate the absorbance to the BOD5 for both the mills. Results indicate that prediction of reactor entrance BOD5 was reasonable, whereas prediction of final effluent BOD5 was inaccurate, for both mills. Also studied was the effect of aeration on BOD5 results obtained at low BOD5 values for the Kraft mill.     

Decay of transmitted light during fiber breaks-implications forbreak location

The accuracy of a bit-counting method for locating fiber breaks in an optical communication system proposed by Rosher et al. is limited in part by the decay time of the transmitted light during fiber failure. In order to understand the nature of this limitation, decay times were measured for individual fibers using a variety of failure mechanisms. The mechanics of the break processes were considered and the implications for break location using the bit-counting technique were assessed. The fastest decay times (≈14 ns) occurred when fibers broke catastrophically under stress levels greater than 0.7×109 N/m². The decay times in this case implied a small break-location uncertainty of 3 m when employing the bit-counting scheme. Since the strength members of fiber cable break at much greater tensions, decay times for cable failures (for example, caused by a backhoe) should not significantly limit the break-location accuracy assuming that the fibers do not bend severely before breaking. For stresses below 0.7×109 N/m² the decay times increase as the stress decreases, attributable to a corresponding decrease in the speed with which the cores of the broken fiber sections tilt with respect to each other and/or separate