Search results
(21 - 40 of 124)
Pages
- Title
- MATHEMATICAL-MODELS OF COCURRENT SPRAY-DRYING
- Creator
- Negiz, A., Lagergren, E. S., Cinar, A.
- Date
- 1995-10
- Publisher
- AMER CHEMICAL SOC
- Description
-
A steady state mathematical model for a cocurrent spray dryer-is developed. The model includes the mass, momentum, and energy balances for a...
Show moreA steady state mathematical model for a cocurrent spray dryer-is developed. The model includes the mass, momentum, and energy balances for a single drying droplet as well as the total energy and mass balances of the drying medium. A log normal droplet size distribution is assumed to hold at the exit of the twin-fluid atomizer located at the top of the drying chamber. The discretization of this log normal distribution with a certain number of bins yields a system of nonlinear coupled first-order differential equations as a function of the axial distance of the drying chamber. This system of equations is used to compute the axial changes in droplet diameter, density, velocity, moisture, and temperature for the droplets at each representative bin. Furthermore, the distributions of important process parameters such as droplet moisture content, diameter, density, and temperature are also obtainable along the length of the chamber. On the basis of the developed model, a constrained nonlinear optimization problem is solved, where the exit particle moisture content is minimized with respect to the process inputs subjected to a fixed mean particle diameter at the chamber exit. Response surface studies based on empirical models are also performed to illustrate the effectiveness of these techniques in achieving the optimal solution when an a priori model is not available. The structure of empirical models obtained from the model is shown to be in agreement with the structure of the empirical models obtained from the experimental studies.
Endnote format citation
Show less
- Title
- NUMERICAL SINGULARITY ANALYSIS
- Creator
- Adomaitis, R. A., Cinar, A.
- Date
- 1991
- Publisher
- PERGAMON-ELSEVIER SCIENCE LTD
- Description
-
A numerical scheme is presented for classifying the different static bifurcation behaviors exhibited by a nonlinear system in its remaining...
Show moreA numerical scheme is presented for classifying the different static bifurcation behaviors exhibited by a nonlinear system in its remaining parameter space. This numerical technique differs from previously published schemes in that the application of singularity theory is done numerically and requires no explicit differentiations of the system in question. It also does not require the reduction of the mathematical model to a scalar equation. The utility of this multivariable scheme will be demonstrated through an application to a seven PDE tubular packed-bed reactor model.
Endnote format citation
Show less
- Title
- Control of complex distributed systems with distributed intelligent agents
- Creator
- Tatara, Eric, Cinar, Ali, Teymour, Fouad
- Date
- 2007-06
- Publisher
- ELSEVIER SCI LTD
- Description
-
Control of spatially distributed systems is a challenging problem because of their complex nature, nonlinearity, and generally high order. The...
Show moreControl of spatially distributed systems is a challenging problem because of their complex nature, nonlinearity, and generally high order. The lack of accurate and computationally efficient model-based techniques for large, spatially distributed systems leads to challenges in controlling the system. Agent-based control structures provide a powerful tool to manago distributed systems by utilizing (organizing) local and global information obtained from the system. A hierarchical, agent-based system with local and global controller agents is developed to control networks of interconnected chemical reactors (CSTRs). The global controller agent dynamically updates local controller agent's objectives as the reactor network conditions change. One challenge posed is control of the spatial distribution of autocatalytic species in a network of reactors hosting multiple species. The multi-agent control system is able to intelligently manipulate the network flow rates such that the desired spatial distribution of species is achieved. Furthermore, the robustness and flexibility of the agent-based control system is illustrated through examples of disturbance rejection and scalability with respect to the size of the network.
Endnote format citation for DOI:10.1016/j.jprocont.2006.06.008
Show less
- Title
- Online batch/fed-batch process performance monitoring, quality prediction, and variable-contribution analysis for diagnosis
- Creator
- Undey, C., Ertunc, S., Cinar, A.
- Date
- 2003-10-01
- Publisher
- AMER CHEMICAL SOC
- Description
-
An integrated online multivariate statistical process monitoring (MSPM), quality prediction, and fault diagnosis framework is developed for...
Show moreAn integrated online multivariate statistical process monitoring (MSPM), quality prediction, and fault diagnosis framework is developed for batch processes. Batch data from I batches, with J process variables measured at K time points generate a three-way array of size I x K x J. Unfolding this three-way array into a two-way matrix of size IK x J by preserving the variable direction is advantageous for developing online MSPM methods because it does not require estimation of future portions of new batches. Two different multiway partial least squares (MPLS) models are developed. The first model (MPLSV) is developed between the data matrix (IK x J) and the local batch time (or an indicator variable) for online MSPM. The second model (MPLSB) is developed between the rearranged data matrix in the batch direction (I x KJ) and the final quality matrix for online prediction of end-of-batch quality. The problem of discontinuity in process variable measurements due to operation switching (or moving to a different phase) that causes problems in alignment and modeling is addressed. Control limits on variable contribution plots are used to improve fault diagnosis capabilities of the MSPM framework. Case studies from a simulated fed-batch penicillin fermentation illustrate the implementation of the methodology.
Endnote format citation for DOI:10.1021/ie0208218
Show less
- Title
- Estimation of Future Glucose Concentrations with Subject-Specific Recursive Linear Models
- Creator
- Eren-oruklu, Meriyan, Cinar, Ali, Quinn, Lauretta, Smith, Donald
- Date
- 2009-04
- Publisher
- MARY ANN LIEBERT INC
- Description
-
Background: Estimation of future glucose concentrations is a crucial task for diabetes management. Predicted glucose values can be used for...
Show moreBackground: Estimation of future glucose concentrations is a crucial task for diabetes management. Predicted glucose values can be used for early hypoglycemic/hyperglycemic alarms or for adjustment of insulin injections or insulin infusion rates of manual or automated pumps. Continuous glucose monitoring (CGM) technologies provide glucose readings at a high frequency and consequently detailed insight into the subject's glucose variations. The objective of this research is to develop reliable subject-specific glucose prediction models using CGM data. Methods: Two separate patient databases collected under hospitalized (disturbance-free) and normal daily life conditions are used for validation of the proposed glucose prediction algorithm. Both databases consist of glucose concentration data collected at 5-min intervals using a CGM device. Using time-series analysis, low-order linear models are developed from patients' own CGM data. The time-series models are integrated with recursive identification and change detection methods, which enables dynamic adaptation of the model to inter-/intra-subject variability and glycemic disturbances. Prediction performance is evaluated in terms of glucose prediction error and Clarke Error Grid analysis (CG-EGA). Results: Prediction errors are significantly reduced with recursive identification of the models, and predictions are further improved with inclusion of a parameter change detection method. CG-EGA analysis results in accurate readings of 90% or more. Conclusions: Subject-specific glucose prediction strategy has been developed. Including a change detection method to the recursive algorithm improves the prediction accuracy. The proposed modeling algorithm with small number of parameters is a good candidate for installation in portable devices for early hypoglycemic/hyperglycemic alarms and for closing the glucose regulation loop with an insulin pump.
Endnote format citation
Show less
- Title
- Learning the Lingo? Gender, Prestige and Linguistic Adaptation in Review Communities
- Creator
- Hemphill, Libby, Otterbacher, Jahna
- Date
- 2011-11-19, 2012-02
- Publisher
- ACM Press
- Description
-
Women and men communicate differently in both face-to- face and computer-mediated environments. We study linguistic patterns considered...
Show moreWomen and men communicate differently in both face-to- face and computer-mediated environments. We study linguistic patterns considered gendered in reviews contributed to the Internet Movie Database. IMDb has been described as a male-majority community, in which females contribute fewer reviews and enjoy less prestige than males. Analyzing reviews posted by prolific males and females, we hypothesize that females adjust their communication styles to be in sync with their male counterparts. We find evidence that while certain characteristics of “female language” persevere over time (e.g., frequent use of pronouns) others (e.g., hedging) decrease with time. Surprisingly, we also find that males often increase their use of “female” features. Our results indicate, that even when they resemble men’s reviews linguistically, women’s reviews still enjoy less prestige and smaller audiences.
Show less
- Title
- Agent-based control of spatially distributed chemical reactor networks
- Creator
- Tatara, Eric, North, Michael, Hood, Cindy, Teymour, Fouad, Cinar, Ali
- Date
- 2005
- Publisher
- SPRINGER-VERLAG BERLIN
- Description
-
Large-scale spatially distributed systems provide a unique and difficult control challenge because of their nonlinearity, spatialdistribution...
Show moreLarge-scale spatially distributed systems provide a unique and difficult control challenge because of their nonlinearity, spatialdistribution and generally high order. The control structure for these systems tend to be both discrete and distributed as well and contain discrete and continuous elements. A layered control structure interfaced with complex arrays of sensors and actuators provides a flexible supervision and control system that can deal with local and global challenges. An adaptive agent-based control structure is presented whereby local control objectives may be changed in order to achieve the global control objective. Information is shared through a global knowledge environment that promotes the distribution of ideas through reinforcement. The performance of the agent-based control approach is illustrated in a case study where the interaction front between two competing autocatalytic species is moved from one spatial configuration to another. The multi-agent control system is able to effectively explore the parameter space of the network and intelligently manipulate the network flow rates such that the desired spatial distribution of species is achieved.
Endnote format citation
Show less
- Title
- Asian American Chicago Network: A Case Study of Facebook Group Use By Immigrant Groups
- Creator
- Rao, Xi, Hemphill, Libby
- Date
- 2016, 2016
- Publisher
- ACM
- Description
-
Through analyzing data from posts and about users, we describe how one particular Facebook group helps immigrants to the U.S. use social media...
Show moreThrough analyzing data from posts and about users, we describe how one particular Facebook group helps immigrants to the U.S. use social media to build a local community. As a preliminary study in intercultural communication through social media, we analyze one case, the Asian American Chicago Network (AACN) Facebook group, and uncover common topics users discuss and relationships between user tenure and various indicators of leadership and interaction. Our small finalized results from this preliminary project suggest that members of AACN likely use it (1) to build a professional network in the U.S.A., and (2) to reinforce and affirm their Asian culture and identities.
Sponsorship: National Science Foundation Award Number 1525662
Rao, X., & Hemphill, L. (2016). Asian American Chicago Network: A Case Study of Facebook Group Use By Immigrant Groups. In Proceedings of the 19th ACM Conference on Computer Supported Cooperative Work and Social Computing Companion (pp. 381–384). New York, NY, USA: ACM. http://doi.org/10.1145/2818052.2869077
Show less
- Title
- Automated control and monitoring of thermal processing using high temperature, short time pasteurization
- Creator
- Schlesser, J. E., Armstrong, D. J., Cinar, A., Ramanauskas, P., Negiz, A.
- Date
- 1997-10
- Publisher
- AMER DAIRY SCIENCE ASSOC
- Description
-
High temperature, short time pasteurization was used to evaluate a computer-based system for controlling the pasteurization process, acquiring...
Show moreHigh temperature, short time pasteurization was used to evaluate a computer-based system for controlling the pasteurization process, acquiring data, and monitoring records. Software was used for the control of hot water temperature, flow rate through the centrifugal timing pump, and diversion of under-processed product. Three types of control strategies were conducted: single loop, cascade, and multivariable. The single loop control strategy showed the most rapid responses to temperature changes, but the temperature response curve was slowest to return to its set point. The cascade control strategy showed slower recoveries to temperature changes, but the temperature response curve was smoother. The multivariable control strategy responded slightly faster than the cascade control strategy, and the temperature response curve was slightly smoother than the cascade control strategy. The multivariable control strategy was able to control the flow diversion valve by the use of a lethality controller. The data acquisition system, used to monitor the data obtained from the high temperature, short-time pasteurization system, was within +/- 0.1 degrees C of the temperature recorded by the safety thermal limit recorder. Reliability was determined by examining the changes in the position of the flow diversion valve to identify process deviations and by comparing the changes to the event marker on circular charts. The data acquisition system was an effective alternative for monitoring the completeness of data.
Endnote format citation
Show less
- Title
- Agent-based control of autocatalytic replicators in networks of reactors
- Creator
- Tatara, E., Birol, I., Teymour, F., Cinar, A.
- Date
- 2005-03-15
- Publisher
- PERGAMON-ELSEVIER SCIENCE LTD
- Description
-
Spatially distributed systems such as reactor networks hosting multiple autocatalytic species demonstrate a rich spectrum of complex behavior....
Show moreSpatially distributed systems such as reactor networks hosting multiple autocatalytic species demonstrate a rich spectrum of complex behavior. From a control systems perspective, spatially distributed systems offer a difficult control challenge because of their distributed nature, nonlinearity, and high order. Furthermore, manipulation of the network states may require simultaneous control actions in different parts of the system and may need transients through several operating regimes to achieve the desired operation. The lack of accurate and computationally efficient model-based techniques for large, spatially distributed systems results in complications in controlling the system, either in disturbance rejection or changing the operational regimes of the system. A hierarchical, agent-based control structure is presented whereby local control objectives may be changed in order to achieve the global control objective. The performance of the control system is demonstrated for several global objectives. The challenge posed is to control the spatial distribution of autocatalytic species in a network of five reactors hosting two species using the interaction flow rates as the manipulated variables. The multi-agent control system is able to effectively explore the parameter space of the network and intelligently manipulate the network flow rates such that the desired spatial distribution of species is achieved.
Endnote format citation for DOI:10.1016/j.compchemeng.2004.09.022
Show less
- Title
- Cavity Resonance Suppression Using Miniature Fluidic Oscillators
- Creator
- Raman, G., Raghu, S.
- Date
- 2004-12
- Publisher
- American Inst Aeronaut Astronaut
- Title
- Nonlinear Interactions as Precursors to Mode Jumps in Resonant Acoustics
- Creator
- Panickar, P., Srinivasan, K., Raman, G.
- Date
- 2005-09
- Publisher
- American Inst Physics
- Description
-
This paper examines instability mode switching in various supersonic jet configurations that involve resonant acoustics. Resonant acoustics...
Show moreThis paper examines instability mode switching in various supersonic jet configurations that involve resonant acoustics. Resonant acoustics includes situations where flow instabilities are enhanced by feedback. The pressure spectra in such situations are rich in multiple modes, and mode switching can occur rather unpredictably. Our experiments reveal that mode switching and the number of nonlinear interactions are interconnected and this number increases just prior to a mode switch. We quantified nonlinear interactions by counting the number of such interactions occurring over a threshold level in the nonlinear cross-bicoherence spectrum and confirmed that nonlinear interactions are precursors to mode jumps. Further, this result was found to be independent of the threshold level. Moreover, if more than one instability mode coexisted, the decay of one and the persistence of the other caused a similar increase in nonlinearities. On the other hand, if there was no mode switch, the nonlinearities remained at comparable limits over the entire operating range. The latter part of the work focused on why difference interactions significantly outnumbered sum interactions in the spectra of shock-containing resonant flows. Using linear stability calculations it is shown that most of the difference interactions that occurred had a positive spatial growth rate and were, hence, unstable. In contrast, a majority of the sum interactions lay outside the amplified region which indicated that they tend to decay spatially. (c) 2005 American Institute of Physics.
http://dx.doi.org/10.1063/1.2008995
Show less
- Title
- Mixer-ejector Wall Pressure and Temperature Measurements Based on Photoluminescence
- Creator
- Taghavi, R.r., Raman, G., Bencic, Tj
- Date
- 2002-04
- Publisher
- American Inst Aeronaut Astronaut
- Description
-
Ejector side-wall pressure distribution is a key indicator of supersonic jet-mixer-ejector performance. When documenting pressure patterns on...
Show moreEjector side-wall pressure distribution is a key indicator of supersonic jet-mixer-ejector performance. When documenting pressure patterns on an ejector wall using pressure-sensitive paint (PSP), one has to consider temperature variations caused by the supersonic jet flow within the ejector because these can cause significant local errors in the PSP results. If the temperature sensitivity of PSP is not corrected for in complex internal supersonic flows, large localized errors could contaminate the results. In the present work, temperature-sensitive paint maps the temperature distribution on the ejector wall and corrects PSP results point-by-point for temperature sensitivity. The experiments were conducted on multijet supersonic mixer-ejector configurations with straight, convergent (6-deg), and divergent (6-deg) side walls. A comparison of corrected and uncorrected PSP readings shows that at M-j = 1.55, the error with respect to true data from static pressure ports can be reduced from 4.98 to 2.84% for the case of a simple ejector with parallel walls. For the complex 6-deg convergent ejector at M-j = 1.39, the error reduces by almost an order of magnitude (from 20.83 to 2.66%). Our results indicate that the use of this correction technique can significantly reduce PSP errors in complex internal supersonic flow situations.
Show less
- Title
- Empirical modeling of systems with output multiplicities by multivariate additive NARX models
- Creator
- Decicco, J., Cinar, A.
- Date
- 2000-06
- Publisher
- AMER CHEMICAL SOC
- Description
-
Multivariable additive NARX (nonlinear autoregressive with exogenous inputs) modeling of process systems is presented. The model structure is...
Show moreMultivariable additive NARX (nonlinear autoregressive with exogenous inputs) modeling of process systems is presented. The model structure is similar to that of a generalized additive model (GAM) and is estimated with a nonlinear canonical variate analysis (CVA) algorithm called CANALS. The system is modeled by partitioning the data into two groups of variables. The first is a collection of future outputs, and the second is a collection of past input and outputs and future inputs. This approach is similar to linear subspace state-space modeling. An illustrative example of modeling is presented on the basis of a simulated continuous chemical reactor that exhibits multiple steady states in the outputs for a fixed level of the input.
Endnote format citation for DOI:10.1021/ie9906464
Show less
- Title
- Development of High Bandwidth Powered Resonance Tube Actuators with Feedback Control
- Creator
- Raman, G., Khanafseh, S., Cain, A. B., Kerschen, E.
- Date
- 2004-01-22
- Publisher
- Academic Press Ltd Elsevier Science Ltd
- Description
-
A high bandwidth powered resonance tube (PRT) actuator potentially useful for noise and flow control applications was developed. High...
Show moreA high bandwidth powered resonance tube (PRT) actuator potentially useful for noise and flow control applications was developed. High bandwidth allows use of the same actuator at various locations on an aircraft and over a range of flight speeds. The actuator selected for bandwidth enhancement was the PRT actuator, which is an adaptation of the Hartmann whistle. The device is capable of producing high-frequency and high-amplitude pressure and velocity perturbations for active flow control applications. Our detailed experiments aimed at understanding the PRT phenomenon are complemented by an improved analytical model and direct numerical simulations. We provide a detailed characterization of the unsteady pressures in the nearfield of the actuator using phase averaged pressure measurements. The measurements revealed that propagating fluctuations at 9 kHz were biased towards the upstream direction (relative to the supply jet). A complementary computational study validated by our experiments was useful in simulating the details in the region between the supply jet and the resonance tube where it was difficult to gather experimental data. High bandwidth was obtained by varying the depth of the resonance tube that determines the frequency produced by the device. Our actuator could produce frequencies ranging from 1600 to 15,000 Hz at amplitudes as high as 160 dB near the source. The frequency variation with depth is predicted well by the quarter wavelength formula for deep tubes but the formula becomes increasingly inaccurate as the tube depth is decreased. An improved analytical model was developed, in which the compliance and mass of the fluid in the integration slot is incorporated into the prediction of resonance frequencies of the system. Finally a feedback controller that varied both the resonance tube depth and spacing to converge on a desired frequency was developed and demonstrated. We are optimistic that numerous potential applications exist for such high bandwidth high dynamic range actuators. (C) 2003 Published by Elsevier Science Ltd.
http://dx.doi.org/10.1016/S0022-460X(03)00212-8
Show less
- Title
- Aeroacoustic Features of Coupled Twin Jets with Spanwise Oblique Shock-Cells
- Creator
- Panickar, P., Srinivasan, K., Raman, G.
- Date
- 2004-11-22
- Publisher
- Academic Press Ltd Elsevier Science Ltd
- Description
-
This paper experimentally investigates the aeroacoustics of coupled twin jets of complex geometry. The study was motivated by the fact that...
Show moreThis paper experimentally investigates the aeroacoustics of coupled twin jets of complex geometry. The study was motivated by the fact that twin jet configurations that are commonly used in aircraft propulsion systems can undergo unpredictable resonant coupling resulting in structural damage. Further, nozzles with spanwise oblique exits are increasingly being considered for their aerodynamic and acoustic advantages, as well as stealth benefits. Although several studies have examined aspects of twin jet coupling, very little data is available on the coupling of jets from nozzles of complex geometry. Our study focuses on twin convergent nozzles with an aspect ratio of 7 with spanwise oblique exits operated over the fully expanded Mach number range from 1.3 to 1.6. The inter-nozzle spacing (s/h) was varied from 7.4 to 13.5. However, the focus remained on the lower spacing that is more representative of aircraft applications. Several interesting results have emerged from this study: (1) Coupling of twin nozzles with a beveled exit was observed only when the beveled edges faced each other and the nozzles formed a 'V' shape in the inter-nozzle region. Specifically, if the two beveled edges were oriented away from each other to form an arrowhead (W) shape no coupling was observed. (2) Despite the presence of spanwise antisymmetric, spanwise symmetric and spanwise oblique modes for the single nozzles, only the first two modes were evident in the coupling. (3) The symmetric coupling produced unsteady pressures in the inter-nozzle region that were up to 7.5 dB higher than the antisymmetrically coupled case. (4) Dynamic tests conducted by moving the nozzles apart while they were operating or by continuously changing the stagnation pressure at fixed inter-nozzle spacing revealed that coupling modes could co-exist at non-harmonically related frequencies. These dynamic tests reproduced the static test data. (5) The frequency of both coupling modes agrees with the higher order waveguide modes based on Tam's theory. (6) Differences in broadband shock noise between the 'V' and 'A' configurations were also documented. Our results provide an understanding of complex twin jet coupling and will serve as benchmark data for validating computational models. (C) 2003 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.jsv.2003.10.011
Show less
- Title
- Using Controlled Unsteady Fluid Mass Addition to Enhance Jet Mixing
- Creator
- Raman, G.
- Date
- 1997-04
- Publisher
- American Inst Aeronaut Astronaut
- Description
-
A rectangular jet was excited by controlled unsteady fluid mass addition using two miniature fluidic jets placed on either side of its narrow...
Show moreA rectangular jet was excited by controlled unsteady fluid mass addition using two miniature fluidic jets placed on either side of its narrow dimension. The subharmonic of the primary's preferred jet column frequency [St(D-e) = fD(e)/U-J = 0.15] was forced in the antisymmetric mode because such forcing persists for longer downstream distances than the fundamental. Details of the phase-averaged flowfield, velocity gradient terms, velocity spectra, and the mean and fluctuating flowfields were documented. The fluidically excited mode grew and persisted in the flow beyond the potential core region. Unsteady fluid mass addition of 12% (4% momentum addition) per fluidic jet resulted in a 35% reduction of the potential core length and about a 60% increase in the normalized mass flux (percentages are with reference to the primary unforced jet). On the basis of the results, it appears that fluidic devices have the potential for use in shear flow control applications.
Show less
- Title
- NONLINEAR PREDICTIVE CONTROL OF PERIODICALLY FORCED CHEMICAL REACTORS
- Creator
- Ozgulsen, F., Kendra, S. J., Cinar, A.
- Date
- 1993-04
- Publisher
- AMER INST CHEMICAL ENGINEERS
- Description
-
A nonlinear model-predictive control strategy is developed to maintain the superior-to-steady-state performance of a periodically forced...
Show moreA nonlinear model-predictive control strategy is developed to maintain the superior-to-steady-state performance of a periodically forced chemical reactor. The performance of the predictive con troller is investigated in the presence of measurement disturbances and parametric uncertainty. It is also shown that statistically inferred input-output models can be a substitute whenever detailed fundamental models are not available. A nonlinear autoregressive polynomial model based on observed plant data is built and incorporated into the control scheme. The catalytic oxidation of ethylene in a periodically-forced, continuous stirred-tank reactor is considered as the test case.
Endnote format citation
Show less
- Title
- Modeling, monitoring and control strategies for high temperature short time pasteurization systems - 2. Lethality-based control
- Creator
- Negiz, A., Ramanauskas, P., Cinar, A., Schlesser, J. E., Armstrong, D. J.
- Date
- 1998-02
- Publisher
- ELSEVIER SCI LTD
- Description
-
A lethality-based control system was designed to provide accurate control of a high temperature shout time (HTST) pasteurizer and to process...
Show moreA lethality-based control system was designed to provide accurate control of a high temperature shout time (HTST) pasteurizer and to process milk products with a lethality equivalent of 161 degrees F (71.67 degrees C) or above for 15 s. This control system provides significant flexibility in operating the process and optimizing functional properties of the food components. Multivariable control of an HTST pasteurizer is implemented by using product total lethality to determine the controller set-points. The equation that relates the temperature and flow rate combinations to the product total lethality, 161 degrees F (71.67 degrees C), 15 s, was modified to permit overprocessing levels specified by plant personnel. By using this equation and the set-point value selected for the other variable, set-point values for the temperature or the flow rate controller were computed. The flow and temperature controllers are integrated into a real-time monitoring and control system. The monitoring and control system includes the multivariable controller, the lethality rate calculation module, statistical monitoring of the total lethality, product flow rate, hot wafer outlet temperature, and holding tube exit temperature measurements, and the display screens for visual inspection of the monitoring tools. This study attempted to achieve compliance of the HTST process operation with the recommended Pasteurized Milk Ordinance by providing a margin between the alarm limits of the monitoring chart and the safety limits.
Endnote format citation
Show less
- Title
- Statistical monitoring of multivariable dynamic processes with state-space models
- Creator
- Negiz, A., Cinar, A.
- Date
- 1997-08
- Publisher
- AMER INST CHEMICAL ENGINEERS
- Description
-
Industrial continuous processes may have a large number of process variables and are usually operated for extended periods at fixed operating...
Show moreIndustrial continuous processes may have a large number of process variables and are usually operated for extended periods at fixed operating points under closed-loop control, yielding process measurements that are autocorrelated, cross-correlated and collinear. A statistical process monitoring (SPM) method based on multivariate statistics and system theory is introduced to monitor the variability of such processes. The statistical model that describes the in-control variability is based on a canonical-variate (CV) stare-space model that is an equivalent representation of a vector autoregressive moving-average rime-series model. The CV state variables obtained from the state-space model are linear combinations of the past process measurements that explain the variability of the future measurements the most. Because of this distinctive feature, the CV state variables are regarded as the principal dynamic directions A T-2 statistic based on the CV state variables is used for developing an SPM procedure. Simple examples based on simulated data and an experimental application based on a high-temperature short-time milk pasteurization process illustrate advantages of the proposed SPM method.
Show less