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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.
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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.
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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.
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Title: Cessation of Screech in Underexpanded Jets
Creator: Raman, G.
Date: 1997-04-10
Publisher: Cambridge Univ Press
Description: In significantly underexpanded jets, screech inherently ceases to exist. This paper studies screech cessation in a supersonic rectangular jet...
Show moreIn significantly underexpanded jets, screech inherently ceases to exist. This paper studies screech cessation in a supersonic rectangular jet and provides an explanation for its occurrence. Experimental data are presented for fully expanded Mach numbers, M-j, ranging from 1.1 to 1.9. Screech becomes unsteady beyond M-j = 1.65 and ceases to exist beyond M-j = 1.75. The reason for this cessation has remained a mystery, and this paper examines three suspects: (i) the theory of a frequency mismatch between screech tones and the band of the most-amplified jet instability waves, (ii) the notion that Mach disk formation disrupts the shock-cell structure and weakens the screech-producing shocks, and (iii) the idea that acoustic feedback and receptivity diminish at high levels of underexpansion. A thorough interrogation of experimental data shows that (i) is not the main cause of screech cessation here, (ii) plays an insignificant role, and (iii) appears to have been largely responsible for screech cessation. Cessation occurs because feedback to the jet lip is diminished due to excessive expansion of the jet boundary. Further, since the jet lip now reflects and scatters low intensity sound, the end result is poor receptivity at the initial shear layer. This theory is substantiated by the re-activation of screech when the nozzle lip thickness is made larger than the expanded jet boundary. Finally, increasing lip thickness is seen to produce a systematic shift (to higher M-j) of the onset of cessation. The results of this study are of direct relevance to the sonic fatigue problem in aircraft structures, because understanding screech helps prevent such damage.
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Title: HACCP with multivariate process monitoring and fault diagnosis techniques: application to a food pasteurization process
Creator: Tokatli, F., Cinar, A., Schlesser, J. E.
Date: 2005-06
Publisher: ELSEVIER SCI LTD
Description: Multivariate statistical process monitoring (SPM), and fault detection and diagnosis (FDD) methods are developed to monitor the critical...
Show moreMultivariate statistical process monitoring (SPM), and fault detection and diagnosis (FDD) methods are developed to monitor the critical control points (CCPs) in a continuous food pasteurization process. Multivariate SPM techniques effectively use information from all process variables to detect abnormal process behavior. Fault diagnosis techniques isolate the source cause of the deviation in process variable(s). The methods developed are illustrated by implementing them to monitor the critical control points and diagnose causes of abnormal operation of a high temperature short time (HTST) pasteurization pilot plant. The detection power of multivariate SPM and FDD techniques over univariate SPM techniques is shown and their integrated use to ensure the product safety and quality in food processes is demonstrated.
Endnote format citation for DOI:10.1016/j.foodcont.2004.04.008
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Title: Jet-cavity Interaction Tones
Creator: Raman, G., Bencic, Tj, Envia, E.
Date: 2002-08
Publisher: American Inst Aeronaut Astronaut
Description: A fundamental study of resonant tones produced by jet-cavity interaction over a wide range of flow conditions covering both subsonic and...
Show moreA fundamental study of resonant tones produced by jet-cavity interaction over a wide range of flow conditions covering both subsonic and supersonic speeds is described. Two significant findings emerge. For the jet-cavity configurations investigated, a suitably defined reduced frequency parameter allows for a global classification of all jet-cavity tones into two main types. For the first type, the reduced frequency depends on the jet Mach number, whereas for the second type, the reduced frequency is independent of the jet Mach number. We propose simple correlations for the frequency of both types of tones. Based on earlier research, we had expected that the traditional classifications of cavity flows into the open, transitional, or closed variety would be insensitive to small changes in Mach number and would depend primarily on the cavity's LID ratio. However, use of the novel high-resolution photoluminescent pressure sensitive paint shows that these classifications are actually quite sensitive to the jet Mach number for jet-cavity interactions. However, these classifications provide no guidance for determining tone type, amplitude, or frequency.
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Title: Controller performance assessment by frequency domain techniques
Creator: Kendra, S. J., Cinar, A.
Date: 1997-06
Publisher: ELSEVIER SCI LTD
Description: A system identification based method for assessing the performance of closed-loop systems is proposed, utilizing measures which coincide...
Show moreA system identification based method for assessing the performance of closed-loop systems is proposed, utilizing measures which coincide naturally with classical and modern frequency domain design specifications. Standard robust control system design methodologies seek to maximize closed-loop performance, subject to strict robustness requirements and include specifications for bandwidth and peak magnitude of the sensitivity and complementary sensitivity functions. Estimates of these transfer functions can be obtained by exciting the reference input with a zero mean, pseudo random binary sequence, observing the process output and error response, and developing a closed-loop model. Performance assessment is based on the comparison between the observed frequency response characteristics and the design specifications. Selection of appropriate model structures, experiment design, and model validation which will ensure reasonable estimates of the closed-loop transfer functions are considered in this paper. A case study involving the performance assessment of a packed bed tubular reactor control system is presented.
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Title: Resonant interaction of a linear array of supersonic rectangular jets: An experimental study
Creator: Raman, G, Taghavi, R
Date: 1996-11-10
Publisher: CAMBRIDGE UNIV PRESS

Title: Easy Access, Early Exit? The Internet and the FDLP (preprint)
Creator: Griffin, Luke A., Ahrens, Aric G.
Date: 2004-07
Description: The article presents information on Federal Depository Library Program (FDLP). The majority of the twentieth century saw a marked growth in...
Show moreThe article presents information on Federal Depository Library Program (FDLP). The majority of the twentieth century saw a marked growth in the number of libraries participating in FDLP. The FDLP was established by Congressional resolution on December 27, 1813. On December 1, 1814, the American Antiquarian Society of Worcester, Massachusetts received the first documents distributed to a non-governmental body and became the first depository library. The primary purpose of the program was preservation of the historical record, not dissemination. Staff and funding issues and the availability of resources via the Internet points to the weight that libraries may be placing on the ability to provide information via the Internet on their decisions to remain in or to leave the FDLP. In today's work environment, in which increased productivity is expected and doing more with less is essential, the Internet can be an obvious alternative to physical collections, which require space and greater staff time and resources. In the last decade, the essential association between the ability to provide access to government information and participation in the FDLP has broken down.
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Title: Static and dynamic behavior of autocatalytic replicators in reactor networks
Creator: Tatara, E., Birol, I., Teymour, F., Cinar, A.
Date: 2004-07-07
Publisher: AMER CHEMICAL SOC
Description: The static and dynamic behavior of the autocatalytic reaction R + 2P --> 3P with decay P --> D is studied in networks of coupled continuous...
Show moreThe static and dynamic behavior of the autocatalytic reaction R + 2P --> 3P with decay P --> D is studied in networks of coupled continuous stirred tank reactors (CSTRs). Numerical bifurcation studies of the system are performed, resulting in rich steady-state bifurcation structures with multiple steady states and isolas. The heterogeneity of the networks is influenced by the number of reactors as well as the network topology. It is shown that the number of steady states of the network increases with heterogeneity, thereby allowing those autocatalytic species to exist in the network that would normally not exist in the homogeneous environment of a single CSTR. Spatial patterns of stable steady states are evident in reactor networks. Dynamic simulation studies are performed to illustrate the transition from one stable state configuration to another or from stable steady states to periodic regimes.
Endnote format citation for DOI:10.1021/ie030802d
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Title: Flow characteristics of a rectangular multielement supersonic mixer-ejector
Creator: Taghavi, R, Raman, G
Date: 1996-10
Publisher: AMER INST AERONAUT ASTRONAUT

Title: Jet Thrust Vectoring Using a Miniature Fluidic Oscillator
Creator: Raman, G., Packiarajan, S., Papadopoulos, G.
Date: 2005-03
Publisher: Royal Aeronautical Soc
Description: This paper presents a new approach to vectoring jet thrust using a miniature fluidic actuator that provided spatially distributed mass...
Show moreThis paper presents a new approach to vectoring jet thrust using a miniature fluidic actuator that provided spatially distributed mass addition. The fluidic actuators used had no moving parts and produced oscillatory flow with a square wave form at frequencies up to 1(.)6kHz. A subsonic jet with an exit diameter of 3(.)81cm was controlled using single and dual fluidic actuators, each with an equivalent circular diameter of 1(.)06mm. The fluidic nozzle was operated at pressures between 20(.)68 and 165(.)47kPa. The objectives of the present work included documentation of the actuation characteristics of fluidic devices, assessment of the effectiveness of fluidic devices for jet thrust vectoring, and evaluation of mass flow requirements for vectoring under various conditions. Measurements were made in the flow field using a pitot probe for the vectored and unvectored cases. Some acoustic measurements were made using microphones in the near-field and for selected cases particle image velocimetry (PIV) measurements were made. Thrust vectoring was obtained in low speed jets by momentum effects with fluidic device mass flow rates of only 2 x 10(-4) kg/sec (0-6% of main jet mass flow per fluidic oscillator). Although a single fluidic device produced vectoring of the primary jet, the dual fluidic device configuration (with two fluidic devices on either side of the jet exit) produced mass flux enhancement of 28% with no vectoring. Our results indicate that fluidic actuators have the potential for use in thrust vectoring, flow mixing and industrial flow deflection applications.
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Title: Statistical Monitoring of Complex Chemical Processes Using Agent-Based Systems
Creator: Perk, Sinem, Teymour, Fouad, Cinar, Ali
Date: 2010-06-02
Publisher: AMER CHEMICAL SOC
Description: It is highly desirable to have a statistical process monitoring (SPM) system that detects the abnormalities in process operations quickly with...
Show moreIt is highly desirable to have a statistical process monitoring (SPM) system that detects the abnormalities in process operations quickly with as few missed and false alarms as possible while the process operates under various operating conditions An agent-based combined monitoring and fault detection framework is proposed in this study. In this framework, different SPM techniques compete with and complement each other to enhance detection speed and accuracy. SPM techniques from literature such as principal component analysis (PCA), multiblock PCA (MBPCA), and dynamic PCA (DPCA) techniques are implemented in this agent-based process supervision system An agent performance assessment and agent management layer provides dynamic adaptation of the supervision system and improves the performance of SPM The statistical information coming from each of the statistical techniques is summarized through a consensus mechanism The performance of the agent-based consensus mechanism using different consensus criteria is tested for system disturbances of various magnitudes The effectiveness of the proposed agent-based framework with different consensus criteria is evaluated based on fault detection times and missed alarm rates and the adaptation of the supervision system is illustrated
Endnote format citation for DOI:10.1021/ie901368j
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Title: Integration of multivariate SPM and FDD by parity space technique for a food pasteurization process
Creator: Kosebalaban, F., Cinar, A.
Date: 2001-03-15
Publisher: PERGAMON-ELSEVIER SCIENCE LTD
Description: Multivariate statistical process monitoring (MSPM), contribution plots, and parity space fault diagnosis (FD) techniques are used to detect...
Show moreMultivariate statistical process monitoring (MSPM), contribution plots, and parity space fault diagnosis (FD) techniques are used to detect abnormal operation of dynamic processes and diagnose sensor and actuator faults. The methods are illustrated by monitoring the critical control points (CCP) and diagnosing causes of abnormal operation of a pilot pasteurization plant. An empirical model of the process is developed by using subspace state space system identification methods and normal process data. The process data collected under the influence of different magnitude and duration of faults in sensors and actuators are used to validate the MSPM and FD techniques. T-2 and squared prediction error (SPEN) charts are used as MSPM charts. A parity space technique for dynamic stochastic systems and dynamic trends in contribution plots of T-2 and SPEN statistics are used for FD. The detection and FD by these techniques show significant improvements over univariate methods.
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Title: Diagnosis of process disturbances by statistical distance and angle measures
Creator: Raich, A., Cinar, A.
Date: 1997
Publisher: PERGAMON-ELSEVIER SCIENCE LTD
Description: Disturbance and fault diagnosis techniques that rely on statistical methods traditionally utilize distance based discrimination functions....
Show moreDisturbance and fault diagnosis techniques that rely on statistical methods traditionally utilize distance based discrimination functions. Complementary information is contained in the angular relations between data clusters representing process operations under various disturbances. A novel disturbance diagnosis approach is presented based on angle discriminants. The diagnosis method is successful in cases where distance based discrimination is not very accurate. The methodology is illustrated by diagnosing various disturbances in the Tennessee Eastman process and compared with the diagnosis utilizing distance based algorithms.
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Title: Shock-induced Flow Resonance in Supersonic Jets of Complex Geometry
Creator: Raman, G.
Date: 1999-03
Publisher: American Inst Physics
Description: Jets with complex shock-cell structures exist in numerous technological applications. This paper describes a fundamental study of shock...
Show moreJets with complex shock-cell structures exist in numerous technological applications. This paper describes a fundamental study of shock-induced flow resonance (commonly referred to as "jet screech") in supersonic jets with spanwise nonuniform shock-cell structures. Experiments that involve flow visualization and detailed mapping of the near field reveal unsteady aspects of shock-induced flow resonances, mode transitions, and directivity of the radiated noise. The following important results about the role of spanwise nonuniform shock-cells emerged: (1) It is possible to have two coexisting, independent feedback loops at nonharmonically related frequencies and different spanwise modes. (2) The same type of spanwise asymmetric mode was produced by two entirely different source configurations. (3) Nozzle geometry significantly altered the intensity and directivity of screech and broadband shock noise. The results presented here provide considerable insight into the fluid dynamics and acoustics of jets with spanwise oblique shock-cell structures and provide grounds for believing that shock-induced noise can be controlled by tailoring nozzle geometry. (C) 1999 American Institute of Physics. [S1070-6631(99)00103-8].
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Title: Resonant interaction of a linear array of supersonic rectangular jets: An experimental study
Creator: Raman, G, Taghavi, R
Date: 1996-11-10
Publisher: CAMBRIDGE UNIV PRESS

Title: INITIAL TURBULENCE EFFECT ON JET EVOLUTION WITH AND WITHOUT TONAL EXCITATION
Creator: Raman, G, Zaman, Kbmq, Rice, Ej
Date: 1989-07
Publisher: AMER INST PHYSICS

Title: Powered Resonance Tubes: Resonance Characteristics and Actuation Signal Directivity
Creator: Sarpotdar, S., Raman, G., Cain, A. B.
Date: 2005-12
Publisher: Springer
Description: The powered resonance tube (PRT) actuator and its variants are new developments in active flow control (AFC) technology. The PRT is attractive...
Show moreThe powered resonance tube (PRT) actuator and its variants are new developments in active flow control (AFC) technology. The PRT is attractive because it has no moving parts and can produce acoustic tones that have amplitudes greater than 150 dB over a large frequency bandwidth. The first part of this paper deals with the resonance characteristics of the PRT as a function of the operating parameters such as jet-to-tube spacing (Sp), tube depth (d), and nozzle pressure ratio (NPR). It was found that: (1) at low NPR (3.33), the PRT resonates at discrete combinations of spacing and depth. (2) Using theoretical estimates for predicting shock cell lengths, one could observe a correlation between the theoretical prediction for shock cell length and the spacing at which the PRT resonates. (3) At high NPR (4.29), for a fixed depth, the PRT resonates at virtually all spacings. (4) The frequency at which the PRT resonates remains approximately constant, regardless of spacing. The second part of the study focused on examining the directivity of the acoustic radiation from the PRT-significant for developing orientation strategies of the PRT with respect to the target flow in the end application. The directivity of the fundamental PRT tone and that of its harmonics were studied for a variety of resonance frequencies, both separately as well as cumulatively. It was found that the fundamental part of the actuation signal radiated predominantly in the downstream direction of the jet for low resonance frequencies. As the resonance frequency was increased from 3 to 12 kHz, the directivity changed from downstream of the jet to vertically upward, and finally upstream of the jet at the higher frequencies.
http://dx.doi.org/10.1007/s00348-005-0041-5
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Title: Intelligent real-time performance monitoring and quality prediction for batch/fed-batch cultivations
Creator: Undey, C., Tatara, E., Cinar, A.
Date: 2004-02-19
Publisher: ELSEVIER SCIENCE BV
Description: Supervision of batch bioprocess operations in real-time during the progress of a batch run offers many advantages over end-of-batch quality...
Show moreSupervision of batch bioprocess operations in real-time during the progress of a batch run offers many advantages over end-of-batch quality control. Multivariate statistical techniques such as multiway partial least squares (MPLS) provide an efficient modeling and supervision framework. A new type of MPLS modeling technique that is especially suitable for online real-time process monitoring and the multivariate monitoring charts are presented. This online process monitoring technique is also extended to include predictions of end-of-batch quality measurements during the progress of a batch run. Process monitoring, quality estimation and fault diagnosis activities are automated and supervised by embedding them into a real-time knowledge-based system (RTKBS). Interpretation of multivariate charts is also automated through a generic rule-base for efficient alarm handling. The integrated RTKBS and the implementation of MPLS-based process monitoring and quality control are illustrated using a fed-batch penicillin production benchmark process simulator.
Endnote format citation for DOI:10.1016/j.jbiotec.2003.10.004
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