Stimulus-response Method Research Articles

Application of Raman Spectroscopy for Determining Residence Time Distributions in Extruder Reactors

The time that a polymeric material spends in the barrel of an extruder is known as its residence time. In an ideal plug flow reactor, all elements of the fluid travel at the same velocity, and the residence time of each fluid element is the same. However, the velocity profile developed in twin-screw extruders is nonideal because of back-mixing, as well as the slow exchange of bulk material to and from a polymer film on the barrel wall or screw surfaces. Consequently, a distribution of residence times is produced for the polymer, and this distribution is known as the exit age distribution or residence time distribution (RTD). The measurement of the RTD in an extruder usually involves a stimulus-response method. The extrusion process is subjected to a pulse input of a tracer at the feed port. The concentration of the tracer in the extrudate is then recorded as a function of time. A graphical plot of the tracer concentration against extrusion time produces the RTD curve. Some tracers which have been employed in the literature and the relevant property measured are given in Table I.

A new approach to continuous emulsion polymerization

AbstractThe application of a continuous Couette‐Taylor vortex reactor to continuous emulsion polymerization was studied. First, the mixing characteristics of the reactor were examined by the stimulus‐response method. It was found that the reactor performance was similar to that of a continuous flow reactor consisting of more than 60 well‐stirred tanks in series if the reactor was properly designed and operated near the critical Taylor number. It was also demonstrated by a comparison of the particle size distributions of the latexes produced in a batch reactor and in the continuous Couette‐Taylor vortex reactor that the continuous reactor could produce latex particles with fairly narrow size distribution. Furthermore, since no stirrer is involved, this continuous reactor is suited for the purpose of avoiding coagulation of latex particles that are very sensitive to mechanical shear.

Residence time distribution of gas in the fluidized bed in a rotating drum.

When a tumbling particle bed in a horizontal rotating drum is aerated, the particle bed can be considered as a gas fluidized bed, which may be called a fluidized bed in rotating drum (FBRD).Measurement of the residence time distribution (RTD) of gas in an FBRD of coarse particles was carried out by the stimulus-response method using a bench-scale rig. The concentration change of nonadsorbing tracer gas (methane) in the exit stream, as the response to a pulse input, was measured by a flame ionization detector connected with PC data acquisition system.The results of the experiments revealed that the RTD of gas was affected by the parameter ξ, which included aeration rate and rotation speed of drum, and aeration angle. Backmixing of gas was found for large ξ. The reactor efficiency, calculated from the real RTD functions, was close to that of the packed bed and was distinctly higher than that of the conventional bubbling fluidized bed for small ξ. Finally, the reactor efficiency of the FBRD was represented in terms of parameter ξ.

Analysis of relationships between symptoms and environmental factors over time

Weekly respiratory symptom information was obtained on a random population of 3800 whites in Tucson. We asked weekly about 14 symptoms representing acute respiratory illnesses (ARI), rhinitis (Rh), and other conditions. The denominator for each week was about 80 randomly chosen subjects from the study population. Interactions of the air pollutants total suspended particulate, oxidants, carbon monoxide, nitrogen oxides for the basin, meteorological information, and aero-allergens were examined. The temporal and spatial interactions between the weekly symptoms and the environmental factors were tested utilizing multivariate methods such as Fourier analyses, multiple regression, and the stimulus-response method, adjusting for lags and controlling for season. Multiple regressions with a smoothing function (using fourier or other methods) yield significant correlations between symptoms and the environmental factors, and separate the ARI's from the Rh's and the miscellaneous symptoms.

Feedback modification in instrumental conditioning of articulation.

Although the self-hearing of a child with defective articulation often has been altered in traditional methods of therapy (Van Riper & Irwin, 1958) , such practices have received little empirical verification. The present experiment was designed to investigate through an operant conditioning paradigm the differences between normal and modified auditory feedback in a sound-learning task for children with defective articulation of the / r / sound. The use of the stimulus-response method within an operant conditioning paradigm permitted consideration of the latency period between stimulus and response. Forty children with the consistent misarticulation of the / r / sound were assigned on the basis of age to one of four cypes of training sessions based on normal or modified feedback; 0to 3-sec. stimulus-response latency period. Each training procedure included 1 0 Ss equally divided between younger children ( 6 through 8 ) and older children (9 through 1 1 ) . During the training sessions a Uher recorder was used to present the taped stimuli consisting of the / r / sound in the prevocalic and posrvocalic positions in the following words: work, worry, far, and run. Each child completed 42 stimulus-response trials in approximately 25 min. During the normal feedback condition, the child heard his own responses without alteration in auditory feedback. During the modified feedback condition, the child heard his own sound production through earphones at a slightly increased intensity level. A lightbulb representing a clown's nose signalled the child's response immediately or 3 sec. following the stimulus. Reinforcement, based on the method of successive approximation, consisted of cereal bits delivered through the mouth of the clown whenever the investigator perceived a change in the child's response closer to that of the stimulus. A panel of 5 clinicians (reliability. 3 9 ) evaluated the recorded responses of each child before and after training on a three-point equal-appearing interval scale. Analysis of variance was used to examine effects of feedback, age, and latency. Mean difference scores show (Fig. 1 ) modified feedback (combined mean difference score, 9.7; SD, 9.3) was more successful than normal feedback (combined mean difference score, -.04; SD. 11.3) in eliciting standard productions of the /r / sound. N o significant differences were found between the conditions of 0-sec. latency and 3-sec. latency, nor bew e e n rhe older and younger children. The results agree with those of Arnold ( 1956) who

Effects of varying latencies in the stimulus-response paradigm of speech therapy.

Effects of varying latencies upon articulatory productions in the stimulus-response paradigm were studied. Zero latency was compared to latency equal to stimuli and to latency with silent rehearsal of muscular movements. 30 children with misarticulated /r/ from kindergarten, first, and second grades participated as Ss in each of 3 latency conditions. Stimulus /ra/ was recorded on tape to provide 30 stimulations per S. Tape I contained stimuli with no latency; Tape II had stimuli with latency; and Tape III contained stimuli with latency and conditioning for muscular practice. Responses 1, 10, 20, and 30 of each S were judged. Only the responses following zero latency yielded significantly improved reponses after 30 stimulus-response trials. No significant differences were found among conditions after 30 trials. When change scores between Trials 1 and 30 were compared, the zero-latency condition was significantly better than the latency condition. When individuals were studied, however, some improved under a given condition whereas others did not or may even have regressed. It appears desirable to continue to use the stimulus-response method with latencies adapted to the individual S.

The effects of sulfur dioxide and A 2 influenza virus on pneumonia and weight reduction in mice: An analysis of stimulus-response relationships

Using a mouse-influenza model, mice were exposed in exposure chambers to various doses of influenza A 2 virus and sulfur dioxide, each alone and in combination. Temperature, relative humidity and length of exposure were all controlled. Control animals were in the same setting, but did not have influenza virus or sulfur dioxide exposure. The two responses measured were: the amount of pneumonia produced and the amount of weight reduction produced by the exposure stimuli. A stimulus-response method of analysis was utilized. Virus exposure produced pneumonia even at low dose. Sulfur dioxide produced pneumonia at higher doses, but appeared to have an inverse effect at lower doses when compared to control animals. The two combined produced more pneumonia than either one did separately. Sulfur dioxide produced more weight reduction than influenza virus, and combination exposures produced more weight reduction than either stimulus did separately. Dosage effects (correlations) were seen in both the production of pneumonia and the production of weight reduction. The stimulus-response method clarified and quantified the relationships found.

A comparative analysis of the stimulus-response relationship between mortality and air pollution-weather

A comparative analysis of the relationship between mortality and air pollution-weather was performed for three U. S. cities: New York, Philadelphia and Los Angeles. Analysis was performed in the same manner for each city for similar periods in time. Corrections were made for such factors as day-of-week and seasonal effects. Comparative analyses between cities and within cities (by season) permitted evaluation of reliability and validity of the findings. Using regression analysis, mortality was found to be related in time to air pollution and weather. A new method of analysis, the stimulus response method, was then utilized to show the relationship of environmental and health events as they are related in time.

Stimulus-response method for flows and volumes in slightly perturbed constant parameter systems.

The area and the first time moment of tracer kinetic data on steady state systems contains information on flows and volumes of distribution in the system. A simple and general method of obtaining such information is given. The method consists of equating the ratio of the time integrals of appropriate stimulus function and response function in an actually performed finite amount tracer experiment to the ratio of stimulus and response that would exist in the tracer steady state. The generality of the method is illustrated by deriving the volume of osmotically exchangeable water in an organ from measurement of its transient bulk water exchange during a small osmotic perturbation.

A Stimulus Response Method for the Analysis of Environmental and Health Events Related in Time

(1971). A Stimulus Response Method for the Analysis of Environmental and Health Events Related in Time. Environmental Letters: Vol. 2, No. 1, pp. 23-34.